MEE09:57 BLEKINGE TEKNISKA  HÖGSKOLA ‐ BTH  A COMPARATIVE STUDYOF

MEE09:57 BLEKINGE TEKNISKA  HÖGSKOLA ‐ BTH  A COMPARATIVE STUDYOF

MEE09:57

A COMPARATIVE STUDYOF

UMTS/WCDMA AND WiMAX

TECHNOLOGIES

MASTER THESIS REPORT BY

: MUHAMMAD UMAIR ASLAM, ARIF HUSSAIN, SALAHUDDIN

BLEKINGE TEKNISKA 

HÖGSKOLA ‐ BTH 

 

A COMPARATIVE STUDY OF UMTS/WCDMA AND

WIMAX TECHNOLOGIES

 

This thesis is submitted to the Department of Telecommunications, 

School of Engineering at Blekinge Institute of Technology in partial  fulfillment of the requirements for the degree of Master of Science in 

Electrical Engineering  

 

MUHAMMAD UMAIR ASLAM 

ARIF HUSSAIN 

SALAHUDDIN 

   

Blekinge Institute of Technology 

June 2009 

 

 

Blekinge Institute of Technology 

School of Engineering 

Department of Telecommunications   

Examiner:   

Prof. Dr. Adrian Popescu

Supervisor

: Dr.Alexandru Popescu

ii 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

iii 

 

 

                                    ABSTRACT 

 

 

 

The field  of mobile  broadband in wireless communication systems  is  increasingly  facing  the  challenges  of  the  provision  of  high  data  rates,  improved  seamless  connectivity  and  broadband  internet  services.  UMTS/WCDMDA  which  is  a  third  generation wireless mobile cellular technology has been adopted in most parts of  the world and now undergoing a phase of evolution and will be emerged soon as 

LTE.  On  the  other  hand,  WiMAX  which  is  also  some  times  called  as  fourth  generation mobile broadband technology is likely to be accepted in many places. 

With higher data rates for transmission, adaptive modulation and coding, OFDMA  based  physical  layer  and  a  very  flexible  architecture,  WiMAX  appears  to  be  suppressing UMTS soon. However, the Long Term Evolution (LTE) of 3G or UMTS is  likely  to  compete  the  WiMAX  both  technically  and  economically.  This  research  provides a comparative interpretation of architecture, salient features, robustness,  physical layer, mobility, capacity and coverage aspects of the both UMTS/WCDMA  and  WiMAX  broadband  technologies.  It  also  explains  the  error  probabilities  in  transmission  for  modulation  techniques  employed  in  both  technologies.  MATLAB  simulations are provided in the simulation part of this report to further elaborate  the differences in the two technologies in some respects. Simulation results show  that the more suitability and effectively of performance for WiMAX.  This research  helps developing a better understanding for operators and users to make a choice  in  preferring  any  of  the  technologies  regarding  different  features.  Based  on  the  study and simulation results of the key features related to capacity and fading of  both  technologies,  we    investigate  the  more  suitability  of  any  of  the  two 

 

 

 

 

 

 

 

 

technologies in terms of better quality and lower error rate in all IP environments. 

iv 

 

 

 

 

 

 

ACKNOWLEGEMENTS 

 

 

Praise and glory be to ALLAH, the Lord, benefactor and cherisher of the entire world. We are grateful to over Almighty ALLAH for providing us with the knowledge, skills and capability to complete this research successfully.

Our knowledge of the field has been raised significantly and remarkably during the whole course of this Master Thesis completion. It has indeed motivated us to explore more facts and obtain increased knowledge in the field of Telecommunications and we would like to continue the research in future. The role of the university and the department has been very important and helpful for us during the whole period of research. All faculty members especially Mr.

MikaelAsman, the program manager of Electrical Engineering Program, have always been kind and cooperative to us for which we are really very thank full.

We would like express our especial gratitude and regards to Mr.Alexandru Popescu our project supervisor for his tremendous support and guidance. He has always been a source of inspiration for us.

We are also very thankful to all of our friends and family members for their continuous and everlasting love, attention and moral support. We are also very grateful to all fellows at BTH who helped us morally and academically in every hour of need.

Muhammad Umair Aslam, Arif Hussain & Salahuddin

 

 

Table of Contents 

BLEKINGE TEKNISKA HÖGSKOLA ‐ BTH ...................................................................................................... i 

A COMPARATIVE STUDY OF UMTS/WCDMA AND WIMAX TECHNOLOGIES.............................. ii 

ABSTRACT................................................................................................................................................. iv 

ACKNOWLEGEMENTS ............................................................................................................................... v 

LIST OF FIGURES...................................................................................................................................... xii 

LIST OF TABLES........................................................................................................................................ xv 

Chapter1 ...........................................................................................................................................1 

INTRODUCTION......................................................................................................................................... 1 

1.1 Thesis Layout and Short Description of Chapters ........................................................................... 5 

1.1.1 Chapter 2...................................................................................................................................... 5 

1.1.2 Chapter 3...................................................................................................................................... 5 

1.1.3 Chapter 4...................................................................................................................................... 5 

1.1.4 Chapter 5...................................................................................................................................... 5 

1.1.5 Chapter 6...................................................................................................................................... 6 

Chapter 2 ......................................................................................................................................... 7 

UNIVERSAL MOBILE TELECOMMUNICATIONS SYSTEM (UMTS) ............................................................... 7 

2.1 Introduction .................................................................................................................................... 7 

2.2 Why UMTS ...................................................................................................................................... 8 

2.3 Evolution of UMTS/WCDMA ........................................................................................................... 8 

2.3.1 System Evolution.......................................................................................................................... 9 

2.4 WCDMA......................................................................................................................................... 10 

Chapter 2 ..........................................................................................................................................1 

2.4.1 Some Significant characteristics of WCDMA ............................................................................. 11 

2.5 Architecture of UMTS Network..................................................................................................... 12 

2.5.1 User Equipment Domain............................................................................................................ 13  vi 

 

2.5.2 Mobile Equipment (ME)............................................................................................................. 13 

2.5.4 Infrastructure Domain ............................................................................................................... 13 

2.5.4.1 Home Network (HN) ............................................................................................................... 14 

2.5.4.2 Service Network (SN) .............................................................................................................. 14 

2.5.4.3 Transit Network (TN)............................................................................................................... 14 

2.6 Universal Terrestrial Radio Access Network (UTRAN) .................................................................. 14 

2.6.1 Operation Mode of UTRAN........................................................................................................ 14 

2.6.1.1 UTRAN FDD (Frequency Division Duplex) ............................................................................... 15 

2.6.1.2 UTRAN TDD (Time division Duplex) ........................................................................................ 15 

2.7 Core Network ................................................................................................................................ 16 

2.7.1 CS Domain .................................................................................................................................. 16 

2.7.2 PS Domain .................................................................................................................................. 16 

2.7.3. Mobile Switching Centre (MSC): ............................................................................................... 18 

2.7.4. Mobile Station (MS) .................................................................................................................. 18 

2.7.5. Home Location Register (HLR) .................................................................................................. 18 

2.7.6. Visitor Location Register (VLR):................................................................................................. 18 

2.7.7. Authentication Center (AuC)..................................................................................................... 18 

2.7.8. Gateway MSc (GMSC) ............................................................................................................... 18 

2.7.9. Serving GPRS Support Node...................................................................................................... 19 

2.7.10. Gateway GPRS Support Node ................................................................................................. 19 

2.8 Description of UMTS Radio Interface............................................................................................ 19 

2.8.1 Logical channels ......................................................................................................................... 20 

2.8.1.1 Control logical channels .......................................................................................................... 20 

2.8.1.2 Traffic logical channels............................................................................................................ 21 

2.8.2. Transport Channels ................................................................................................................... 21 

2.9 Physical Layer................................................................................................................................ 24 

2.9.1 Spread Spectrum........................................................................................................................ 24 

2.9.1.1Channelization ......................................................................................................................... 25 

2.9.1.2 Scrambling............................................................................................................................... 25 

2.9.2 Cell Structure ............................................................................................................................. 25 

2.9.3. Cell State ................................................................................................................................... 27  vii 

 

2.9.4. Capacity..................................................................................................................................... 27 

2.9.5. Duplex Method ......................................................................................................................... 27 

2.9.6. Multipath diversity.................................................................................................................... 27 

2.9.7 Power Control ............................................................................................................................ 28 

2.10. UMTS MAC Layer ....................................................................................................................... 30 

2.11UMTS RLC Layer ........................................................................................................................... 30 

2.12 Handovers in UMTS..................................................................................................................... 31 

2.13.1. Types of Handovers in UMTS .................................................................................................. 32 

2.13.1.1. Vertical Handovers:.............................................................................................................. 32 

2.13.1.2. Horizontal Handovers: ......................................................................................................... 32 

2.13.1.3. Intra‐System Handovers: ..................................................................................................... 32 

2.13.1.4. Inter‐System Handovers: ..................................................................................................... 32 

2.13.1.5. Hard Handovers: .................................................................................................................. 33 

2.13.1.6. Soft Handovers:.................................................................................................................... 33 

2.13.1.7. Softer Handovers: ................................................................................................................ 34 

2.14 UMTS Services............................................................................................................................. 35 

Chapter 3 ....................................................................................................................................... 36 

WiMAX .................................................................................................................................................... 36 

3.1 Introduction .................................................................................................................................. 36 

3.2 Background ................................................................................................................................... 36 

3.3 Evolution of WiMAX...................................................................................................................... 37 

3.3.1 IEEE802.16‐2001 ........................................................................................................................ 37 

3.3.2 IEEE802.16a‐2003 ...................................................................................................................... 38 

3.3.3 IEEE802.16c‐2002....................................................................................................................... 38 

3.3.4 IEEE802.16d‐2004 ...................................................................................................................... 38 

3.3.5 IEEE 802.16e‐2005 ..................................................................................................................... 39 

3.4 Some Significant Features of WiMAX ........................................................................................... 40 

3.4.1 OFDM Based Physical Layer ....................................................................................................... 40 

3.4.2 Adaptive Modulation and Coding (AMC) ................................................................................... 40 

3.4.3 TDD and FDD Support ................................................................................................................ 40  viii 

 

3.4.4 per User Resource Allocation..................................................................................................... 40 

3.4.5 Quality of Service (QoS) ............................................................................................................. 40 

3.4.6 Advance Antenna Techniques Adaptation................................................................................. 40 

3.4.7 Link layer Retransmission .......................................................................................................... 41 

3.4.8 Mobility ...................................................................................................................................... 41 

3.4.9 Scalability ................................................................................................................................... 41 

3.4.10 High Data Rate ......................................................................................................................... 41 

3.4.11 Security .................................................................................................................................... 41 

3.4.12 IP based Architecture............................................................................................................... 41 

3.5 Technological Aspects of WiMAX ................................................................................................. 42 

3.5.1 Fixed WiMAX.............................................................................................................................. 43 

3.5.1.1 PHY Layer ................................................................................................................................ 43 

3.5.1.2 MAC LAYER.............................................................................................................................. 44 

3.5.2 Mobile WiMAX ........................................................................................................................... 44 

3.5.2.1 PHY Layer ................................................................................................................................ 44 

3.3.2.2 MAC Layer ............................................................................................................................... 45 

3.6 Architecture of Mobile WiMAX..................................................................................................... 46 

3.7 Mobility in WiMAX ........................................................................................................................ 49 

3.8 Handovers in WiMAX .................................................................................................................... 49 

3.8.1. Hard Handover (HHO) ............................................................................................................... 50 

3.8.2. Fast Base Station Switching (FBSS) ........................................................................................... 50 

3.8.3. Macro Diversity Handover (MDHO).......................................................................................... 51 

3.9 WiMAX System Components ........................................................................................................ 52 

3.9.1. WiMAX Base Station (BS) .......................................................................................................... 52 

3.9.2. WiMAX Receiver or Customer Premise Equipment (CPE) ........................................................ 52 

3.9.3. BACKHAUL................................................................................................................................. 52 

3.10 WiMAX   Working........................................................................................................................ 53 

3.10.1 Advanced Working Features for WiMAX ................................................................................. 54 

Chapter 4 ....................................................................................................................................... 56 

COMPARATIVE ANALYSIS ........................................................................................................................ 56  ix 

 

4.1 Comparison of Physical Layer Access Techniques ........................................................................ 56 

4.1.1. OFDMA for WiMAX ................................................................................................................... 57 

4.1.2. WCDMA..................................................................................................................................... 58 

4.1.2.1. Frequency Division Multiple Access. (FDMA) ........................................................................ 59 

4.1.2.2. Time Division Multiple Access (TDMA) .................................................................................. 59 

4.1.2.3. Code Division Multiple Access (CDMA).................................................................................. 60 

4.1.2.4. Description ............................................................................................................................. 60 

4.1.3. Comparison (WCDMA and OFDMA) ......................................................................................... 63 

4.2 Comparison of Modulation Schemes............................................................................................ 65 

4.2.1Binary Phase Shift Keying (BPSK): ............................................................................................... 66 

4.2.2. Quadrature‐Phase Shift Keying (QPSK)..................................................................................... 68 

4.2.3. Quadrature Amplitude Modulation (QAM) .............................................................................. 68 

4.3 Comparison of Handovers ............................................................................................................ 70 

4.4 Comparison of Channel Impairment and Equalization ................................................................. 70 

4.5 Comparison of Architecture.......................................................................................................... 71 

4.6 Capacity and Coverage Comparison ............................................................................................. 75 

4.6.1 for WCDMA ................................................................................................................................ 75 

4.6.1.1. Coverage and Cell Range in WCDMA..................................................................................... 76 

4.6.2 FOR WiMAX................................................................................................................................ 77 

4.6.3. Capacity Estimation for WiMAX and WCDMA .......................................................................... 79 

4.7 Spectral Efficiency ......................................................................................................................... 81 

Chapter 5 ....................................................................................................................................... 83 

SIMULATIONS.......................................................................................................................................... 83 

5.1 Simulations Using AWGN Channel Model .................................................................................... 83 

5.2 BPSK .............................................................................................................................................. 84 

5.3 QPSK.............................................................................................................................................. 85 

5.4 16‐QAM......................................................................................................................................... 86 

5.5 64‐QAM......................................................................................................................................... 88 

5.6 Simulations using Rayleigh Fading Channel Model....................................................................... 90 

Chapter 6 ....................................................................................................................................... 95  x 

 

 

 

 

 

CONCLUSIONS......................................................................................................................................... 95 

6.1 Conclusions ................................................................................................................................... 95 

6.2 Future Work .................................................................................................................................. 96 

REFRENCES .............................................................................................................................................. 97 

APPENDIX A........................................................................................................................................... 102 

Abbreviations and Acronyms ................................................................................................................ 102 

APPENDIX B ........................................................................................................................................... 109 

Matlab Simulation code ........................................................................................................................ 109  xi 

 

 

 

                                   

LIST OF FIGURES 

Figure2. 1 Standardization and commercial operation schedule for WCDMA and its evolution [4]

………..8

Figure2. 2

 

Peak data rate evolution for WCDMA [4]

…………………………………………………………………………………… 9 

Figure2. 3

 

System evolutions [4]…………………………………………………………………………....9

Figure2. 4 Direct Spread…………………………………………………………………………...............11

Figure2. 5 General UMTS Architecture [2]……………………………………………………………….13

 

Figure 2. 6  UTRAN Architecture [2]…………………………………………………………………..…15

Figure2. 7

 

Architecture of Umts Core Network (Release 99) [2]…………………………………………17

Figure2. 8 UMTS Architecture Release 99[9]…………………………………………………………….19

Figure2. 9 UMTS Protocol Layer [2, 70]

…………………………………………………….…..

20

Figure2. 10

 

UMTS Channel Mapping [13]…………………………………………………………..……23

 Figure2. 11

 

Spreading and Scrambling [4]……………………………………………………………….25

Figure2. 12 UMTS cell structure [2] [14]…………………………………………………………………26

Figure2. 13 Power Control to Resolve Near Far Field Effect [8]………………………………………....28 

Figure2. 14

 

Inner and outer Loop Power Control [2]……………………………………………………...29

Figure2. 15 UMTS MAC Layer [10]……………………………………………………………………...30 

 

 

Figure2. 16 Radio Link Control Layers [10]………………………………………………………………31

Figure2. 17

 

Hard Handover [20]…………………………………………………………………………..33

 Figure2. 18

 

Soft handover [20]……………………………………………………………………………34

Figure2. 19

 

Softer Handover

[20]………………………………………………………………….34

 

xii 

 

Figure 3.1 WiMAX Standard [23]............................................................................................................... 39 

Figure 3.2 Representing WiMAX as subset of IEEE802.16 [31] ............................................................... 42 

Figure 3.3 MAC layer of WiMAX [28] ...................................................................................................... 44 

Figure  3.4  Mobile WIMAX Reference Model [23]................................................................................... 47 

Figure 3.5 WiMAX network architecture [28]............................................................................................ 49 

Figure 3.6 Fast Base Station Switching [43] ............................................................................................... 50 

Figure   3.7 Macro Diversity Handover [43] ............................................................................................... 51 

Figure  3.8 Backhaul (WiMAX) [45] .......................................................................................................... 53 

Figure   3.9 WIMAX working [23] ............................................................................................................. 54 

Figure 4.1FDMA [50] ................................................................................................................................. 59 

Figure 4.2 TDMA [50] ................................................................................................................................ 59 

Figure  4.3 CDMA [50] ............................................................................................................................... 60 

Figure  4.4 WCDMA Frequency band ........................................................................................................ 61 

Figure  4.5 Spreading and Despreading [9]................................................................................................. 62 

Figure  4.6 Block Scheme of WiMAX Signal Transmission from OFDM Based TX to Rx [53]............... 65 

Figure 4.7 QPSK constellation .................................................................................................................... 68 

Figure 4.8 constellation 16QAM, 64 QAM................................................................................................. 69 

Figure 4.9  WIMAX Architecture [57]........................................................................................................ 72 

Figure 4.10 UMTS Integration.................................................................................................................... 73 

Figure 4.11 Network Architecture for UMTS and Mobile WiMAX [57]................................................... 74 

Figure 4.12 UMTS Cell Structure [61]........................................................................................................ 76 

Figure 4.13 Data Rate of Impact Modulation in WIMAX Network [62].................................................... 78 

Figure 5.1 Simulations Model with AWGN Channel ................................................................................. 83 

Figure 5.2 .................................................................................................................................................... 85 

Figure 5.3 .................................................................................................................................................... 86  xiii 

 

 

 

 

 

 

 

 

 

 

 

 

Figure  5.4 ................................................................................................................................................... 87 

Figure 5.5 .................................................................................................................................................... 88 

 

 

Figure 5.6 .................................................................................................................................................... 89 

Figure  5.7 ................................................................................................................................................... 89 

Figure 5.8 Reflection, Diffraction and Scattering........................................................................................ 91 

Figure 5.9 Refraction................................................................................................................................... 91 

Figure 5.10 Multipath Propagation of radio waves. ................................................................................... 92 

 Figure 5.11

 

Simulation Model with Rayleigh Fading Channel…………………………..……………….93 

 

 

Figure 5.12……………………………………………………………………………………………………………………………………………93 

Figure 5.13……………………………………………………………………………………………………………………………………………94  xiv 

 

 

 

 

                                       LIST OF 

TABLES

 

 

Table 1.1: Cellular Network Generations [1] ................................................................................................ 5 

Table 2.2 UMTS Services ........................................................................................................................... 35 

Table 3.1 Comparing Physical Layer in Mobile and Fixed WiMAX [39].................................................. 45 

Table 4.1 Technology Comparison [46]...................................................................................................... 56 

Table  4.2 Different Parameters in WiMAX [51]........................................................................................ 58 

 

 

Table  4.3  Comparison of WCDMA and OFDM [71]................................................................................ 65 

Table 4.4 

Main Parameters OF UMTS and WIMAX IEEE 802.16e [53]

....................................... 560 

Table  4.5 

UMTS cell coverage comparison

.......................................................................................... 77 

Table  4.6 WiMAX

Different Coverage Range [62]

................................................................................ 80 

Table  4.7

Spectral Efficiency Comparison [69]

.................................................................................... 83  xv 

 

 

Chapter1                                                            

INTRODUCTION

 

T elecommunication world has undergone tremendous changes during the past ten years. Both technical and political factors have contributed towards the evolution of telecommunication systems, especially in the development of mobile broadband. In the world of telecommunications, most of the telephone and radio networks involved are wireless in nature. Also various television networks and internet are used to be wireless in nature. Cellular networks are also use to be wireless, with an improved level of Quality of Service (QoS) and better mobility. While studying the advancement in the field of mobile communications and cellular networks, we come across various generations, which were introduced successively.

In the first generation (1G), portable devices of large sizes employing analog communication systems were introduced. Advance Mobile Phone System (AMPS) was introduced in 1976 in USA.

Total Access Communication System (TACS) was adopted by Europe, England, Hong-Kong and

Japan using 900MHz frequency band and Extended Access Communication System (ETACS) which is an enhanced form of TACS which uses greater number of communication system subscribers and was adopted in United Kingdom, are the example of 1G standard.

In second generation (2G), a shift from analog to digital communication systems took place and cellular networks also adopted digital communication systems. In mobile telephony, the major 2G standards are Global System for Mobile communication (GSM) with 900MHz and 1800 MHz frequency bands in Europe and United States. Code Division Multiple Access (CDMA) in which signals are spreaded over a large range of frequencies employing a spread spectrum technique and

Time Division Multiple Access (TDMA) was adopted in America and New Zealand. TDMA involves time division for the channels resulting in higher transmission data rate.

The 3 rd

generation of mobile communication can rightly be termed as the generation enabling mobile broadband i.e. it has attained the capability of wireless use of internet or work over an IP network.

Mobile broadband has now been remarkably adopted world wide and attempts are being made to achieve even faster data rates up to several 100 Mbps. Two different standards have been embraced by the industry to attain such high speeds and move into the next generation and those standards are

UMTS employing Wideband Code Division Multiple Access (W-CDMA) and World

Interoperability for Microwave Access (WiMAX) employing Orthogonal Frequency Division

Multiple Access (OFDMA).In third generation (3G), Universal Mobile Telecommunication System

(UMTS) was introduced and adopted in Europe and some other parts of the world. UMTS enabled very high throughput and data rates. UMTS employed Wideband Code Division Multiple Access

(WCDMA) for a wide frequency range of packet data services for users. UMTS offered variable bit rate and a very large variety of traffic on air interface.

Our research is aimed at the comparison of standards, services, architecture and various features including physical layer of UMTS and WiMAX. Worldwide Interoperability for Microwave Access

(WiMAX) refers to a compatible system of equipment being devised for American IEEE 802.16 standard and European Telecommunication Standard Institute (ETSI) HiperMAN standard. It has a range of fifty kilometers and hypothetical data rate of 100 Mbps. The efforts are being made to converge and develop an inter-working between IEEE 802.16 standard and the HiperMAN standard of ETSI.

WiMAX delivers some outstanding features including support for all 2G and 3G networks, offering very high quality of video streaming and conferencing and also high quality voice over IP (VoIP).

Specification

1G NETWORKS

2 G networks

2.5G networks

2.75G networks

Protocol

AMPS

Data TAC

FDMA

Mobitex

NMT

TACS

CDMA

GSM iDEN

PCS

TDMA

CDMA 2000 1xRTT

GPRS

HSCSD

EDGE

WiDEN

EGPRS 2

Speed

N/A

Features

Voice service only (analog)

No data service

Up to 20Kbps

Up to 144Kbps

Up to 114 kbps

Up to 64kbps

Up to 384kbps

Up to 100kbps

473kbps(uplink)

1.2 Mbps(down link

Digital voice service

Push-to-talk(PTT)

Short massage service(SMS)

Conference calling

Caller ID

Voice mail

Simple data application such email and web browsing

All 2G features plus:

• MMS (Multimedia

Message Service)

• Web browsing

• Real-time location-based services such as directions

Basic multimedia, including support for short audio and video clips, games and images

Better performance for all

2/2.5G services

LTE

3G networks

3.5G networks

4G Networks

CDMA 2000EVDO

CDMA 2000 EVDO (

Voice and data)

UMTS/WCDMA

CDMA 2000/EVDO

Rev A

HSDPA

CDMA 2000

EVDO Rev B

WiMAX

UMB

Up to 2.4 Mbps

Up to 2.4 Mbps

Up to 2 Mbps

Up to 3.1 Mbps

Up to 14.4 Mbps

Up to 46 Mbps

Support for all 2G and

2.5G features plus:

• Full motion video

• Streaming music

• 3D gaming

• Faster Web browsing

Support for all 2/2.5/3G features plus:

• On-demand video

• Video conferencing

• Faster Web browsing

(especially graphics intensive sites)

Support for all prior 2G/3G features plus:

• High quality streaming video

                                                              Table 1.1: 

Cellular Network Generations

 [1]

1.1 Thesis Layout and Short Description of Chapters

1.1.1 Chapter 2

In this chapter, background, development history, standards, capacity and coverage aspects, detailed description of architecture with emphasis on Radio Access Network (RAN), Physical layer and

MAC layer description, handover strategies and other multiple features of UMTS are explained in depth. Also specification and feature of WCDMA, which is employed in UMTS as a radio access technique, are taken into special consideration. UMTS/WCDMA is discussed in technical as well as physical aspects comprehensively.

 

1.1.2 Chapter 3

This chapter involves all the technical specifications and features of WiMAX along with the description of its architecture. The IEEE standard for WiMAX is IEEE 802.16. This WiMAX standard is classified further into two for fixed WiMAX with 802.16d and mobile WiMAX with

802.16e standards. The air interface for WiMAX is considered to be very robust and flexible.

Physical layer of WiMAX includes orthogonal frequency division multiplexing (OFDM). This feature of WiMAX increases its effectiveness and elegance. The flexibility of WiMAX MAC layer enables a variety of traffic to be accommodated i.e. voice, video multimedia .this chapter covers all the aspects related to WiMAX network architecture, Quality of service (QoS), mobility management, its multiple techniques Orthogonal Frequency Division Multiplexing (OFDM) based physical layer including modulation techniques (adaptive) and other features.

 

1.1.3 Chapter 4

In this chapter, the two technologies i.e. UMTS and WiMAX are compared in detail. Physical layers of both the technologies with their radio access techniques are discussed and compared. Merits and demerits of both technologies are discussed while mutually comparing those with respect to coverage, capacity, mobility and handovers, equipment and architecture complexity.

 

1.1.4 Chapter 5

Simulation is done in MATLAB for modulation techniques of both technologies i.e. BPSK, QPSK,

16QAM and 64QAM. Two simulation models i.e. AWGN and Rayleigh Fading Channel models are adopted the results are compared and discussed with respect to signal power and error rates.

 

1.1.5 Chapter 6

This chapter includes the final interpretation of the comparison of the UMTS and WiMAX and an interworking architecture for both the technologies is suggested to be worked out as future work.

Chapter 2  

UNIVERSAL MOBILE 

TELECOMMUNICATIONS SYSTEM 

(UMTS) 

2.1 Introduction

I n mobile communication, the three different generations have been emerged throughout the world.

First generation of mobile communication systems was deployed in early 1990s which included the analog transmission. 1G was established in Nordic Mobile Telephone (NMT) system and

American Mobile Phone System (AMPS). The increasing number of users of mobile systems and correspondingly increasing service demands initiated the development of different communication systems globally. Hence Group Special Mobile (GSM) which later named as Global System for

Mobile communications (GSM) was launched worldwide which is called Second Generation

(2G).Second generation of mobile communication is based on digital networks which provided advance mobility, voice oriented wireless communication system. There were different standards in different regions due to which 2G could not be successfully deployed all over the world.2G still exists in some regions of the world.3G,the third generation of mobile communications was developed based on GSM networks. Third generation (3G) which is recognized as Universal Mobile

Telecommunications System (UMTS) has been launched in most regions of the world. UMTS is also being developed under the International Telecommunication Union-Telecom Sector (ITU-TS) whose general name is International Mobile Telecommunication-2000(IMT-2000) which is a subgroup of

ITU, also fulfills the requirements of 3G Systems. UMTS is one of the 3G mobile broad band systems which are being developed into 4G.Presently UMTS system uses WCDMA for radio transmission. UMTS is a 3G technology known as next wave of mobile broadband which offers data rates up to 2 Mbps [2].

UMTS offers a reliable service for mobile users residing in any place of the world. UMTS is mainly based on GSM standards. Due to its well organized standards for mobile users, UMTS now exists throughout the world and geographically mobile users are capable to continuously access the internet

service with roaming facility when they are traveling. Users are capable to access UMTS system through terrestrial and satellite transmission.

2.2 Why UMTS

Third generation standard presented by European Mobile Telecommunication system in collaboration with Japanese standardization group which proposed UMTS.UMTS is also included in those number of standards which have been approved by International Telecommunication Union-

Telecommunication Standardization Sector (ITU-T) under the protection of international mobile telephony 2000(IMT 2000) [3].

2.3 Evolution of UMTS/WCDMA

Evolution is the most general terms which is used in the background of Universal Mobile

Telecommunication (UMTS).The research work on WCDMA started by European research projects CODIT and FRAMS in 1990s.Intialy this project was developed to evaluate the link performance and basic understanding of WCDMA standardization ETSI , A European standardize body decided in 1998 that WCDMA will be the third generation air interface[4].A comprehensive standardization work has been accomplished as main part of 3GPP.First completed standardization set ended in 1999 which is called Release 99.

3GPP Schedule

3GPP R99  3GPP R5  3GPPR6  3GPP R7 R8

2000 2001 2002 2003 200

4

2005 2006

Commercially 3GPP R99 3GPP R5 3GPPR6 3GPPR7 RGPPR8

2007 2008 2009 2010

          Figure2. 20 

Standardization and commercial operation schedule for WCDMA and its evolution

[4]

   

Third generation developed a new radio access method which was WCDMA and commercially it started work during 2001 in Japan. In Europe it started work in a testing phase in 2002 but commercially it was used during 2003.HSDPA was commercially launched in 2005 and HSUPA was used during 2007. Further HSPA Evolution moved to 3GPP (Release7) and now its deployment has been taken in hand commercially. Currently HSPA Evolution which is recognized as HSPA+ is under consideration. Now a day 3GPP is also working over Long Term Evolution (LTE).

3GPP Schedule 3GPP R99 3GPP R5 3GPP R6 3GPP R7 3GPP R8

Down link peak rate

0.4Mbps

0.4Mbps

14.0Mbps

0.4Mpbs

14Mbps

5.7Mbps

28Mbps

11Mbps

LTE

16OMbps

HSPA 42 mBPS

LTE 50

Mbps

Uplink peak data

 

                                               Figure2. 21 

Peak data rate evolution for WCDMA [4] 

 

 

 

 

   

2.3.1 System Evolution

Global System for Mobile communication (GSM) and WCDMA has a joint account where they have

80 to 90 % global mobile subscription. WCDMA is compatible with other systems like GSM in seamless handovers and dual mode hand set. Mostly WCDMA networks are deployed where GSM networks have already been established .However, GSM and EDGE are deployed in parallel with

WCDMA. On the same path GSM and WCDMA are also compatible with Long Term Evolution

(LTE).The market share has been declined since 2004 when CDMA 2000 moved to GSM /WCDMA to get a number of benefits currently more then 10 %. Maximum operators of CDMA moved to

GSM/WCDMA for their open ecosystem and low cost mobile devices. Evolution Data Only

(EVDO) is commercially launched now a day. To improve data rates further some operators are seeking to deploy HSPA or WiMAX and LTE in the long run [4].

GSM    EDGE           EDGE evolution 

WCDMA          HSPA evolution 

     

LTE 

 

  

                                                             Figure2. 22 

System evolutions [4] 

 

2.4 WCDMA

Wideband Code Division Multiple Access (WCDMA) is a radio access technology which has been currently deployed in UMTS mobile networks.

Channel bandwidth 5MHz

Duplex mode FDD and TDD

 

Downlink RF channel structure Direct spread

Chip rate 3.84 Mbps

 

Frame length 10 ms

 

Balanced QPSK (Downlink)

 

Spreading modulation Dual-channel QPSK (Uplink)

Data modulation

Channel coding

Complex spreading circuit

QPSK (Downlink)

BPSK (Uplink)

Convolution and Turbo codes

Coherent detection

Channel multiplexing in downlink

User dedicated time multiplexed pilot ( downlink and uplink), common pilot in the downlink

Data and control channels time multiplexed

Control and pilot channel time multiplexed

Channel multiplexing in uplink

I&Q multiplexing for data and control channel

MultiMate Variable spreading and multimode

Spreading factors 4-256 (uplink) and 4-512(uplink)

Power control Open and fast closed loop (1.6 kHz)

Spreading (downlink)

OVSF sequences for channel separation

Gold sequences 218-1 for cell and user separation

(truncated cycle 10 ms)

Handover

Soft hand over inter-frequency handover

  Table 2.1:  

Parameters of WCDMA [6]

ETSI alpha group designed this radio access technique which was completed in 1999.WCDMA fulfills the need of high data rate and multiuser access to the network at the same time .The concept of design of WCDMA air interface was developed to support several services with different Quality of service (QoS) to achieve the target of high data rates up to 2Mbps. [5]

Underlying technique like direct sequence spread spectrum (DSSS) is used in WCDMA where transmitted bits by the users are spread through a wider bandwidth than the real information. Two types of duplex methods are used in WCDMA/UMTS networks. First one is frequency Division

Duplex FDD) and the second is Time Division Duplex (TDD). FDD is used for paired band and

TDD is used for unpaired band [7].

2.4.1 Some Significant characteristics of WCDMA

The key characteristics of WCDMA are described below.

Nominal bandwidth

The WCDMA standard was developed for 5MHz as an operation channel bandwidth [8].

WCDMA

Direct spread (DS)

         Direct Spread 

 

 

(3.84Mcps

  

5MHZ

     

                                                                          Figure2. 23 

Direct Spread

Chip Rate

3.84Mcps was selected as chip rate for WCDMA, Which is larger than CDMA 2000.

Synchronization of Network

In WCDMA environment base station perform their task asynchronously. There is no need to synchronize base station timing with satellite base timing. However these base stations are also capable to work in synchronous timing [8].

Core Network

WCDMA is capable of interfacing with GSM-MAP core network. Basically it was developed in favor of GSM network [8].

High Degree of Services

WCDMA provides support for a variety of services like up to 2Mbps data rates and also capable of performing several parallel tasks in the same link [8].

 

 

2.5 Architecture of UMTS Network

The development in 3G networks is based on the evolution of GSM/GPRS networks.3G networks support all types of services such like data, video and voice conversations. Internet Protocol (IP) is introduced as a driving technology. GPRS presented IP backbone into mobile core network

[3].UMTS introduced a new radio access technology which is totally based on radio access network without bringing any change into the core network. After implementation of successive releases of

UMTS, a major change such as Internet Protocol (IP) is introduced in core network [2].

The general architecture of UMTS physically consists of two main domains i.e. User Equipment

(UE) and infrastructure domain. Each planned domain characterizes a maximum level group of physical bodies. The reference points are assigned between each domain. Further the function of both domains is described as below.

• User Equipment domain(UE)

In User Equipment domain users acquire the services of UMTS.

• Infrastructure domain principle

In UMTS, infrastructure domain includes physical nodes which are responsible to terminate the radio interface in order to provide end to end service to the user.

 

The main part of Universal Terrestrial Radio Access Network (UTRAN) consists of controller, transceiver and antenna. It establishes a link between base station and mobile station. The main role of Core Network (CN) is switching and routing in network. Core network and UTRAN are connected through IU interface. There are two main interfaces as shown, first one is IU-PS, which is an interface between CS and RNC and secondly IU-CS i.e. an interface between circuit domain and core network. The function of reference point Uu which separates both domains called as radio interface [2].

User Equipment (UE) Domain 

                                                                   

                                                                   

                                   

 

UMTS

Uu

Identity

Mobile

                                                                   

(USIM) (ME)

 

 

 

 

 

 

Infrastructure domain                                                                       

 

 

 

Home

Network (HN) domain

[                  

Network (AN) domain

 

  [Zu]       

Serving

 

                               [Yu]            

Network (SN)

 

Network (TN)  domain 

Core Network (CN) domain 

                                                                   Figure2. 24 

General UMTS Architecture [2]

2.5.1 User Equipment Domain

EU is referred to as the terminal where users use all services with help of radio interface. In UMTS, general architecture it divided further in two parts.

2.5.2 Mobile Equipment (ME)

User Equipment comprising a physical structure like a handset is termed as mobile equipment. It is divided further in two parts i.e. mobile terminal(TM) and terminal equipment. The main role of mobile terminal is to maintain radio transmission and that of terminal Equipment is to control the application. Both entities are physically situated in same card.

2.5.3 UMTS Subscriber Identity Module (USIM)

It is a removable smart card which is assign to each user which allows the usage of all services in a protected way where encryption and authentication process in any case of ME i.e. used [2

]. 

2.5.4 Infrastructure Domain

This part contains physical body which is used to terminate the radio interface which provides end to end service for User Equipment. Functionally, Infrastructure domain is further categorised in two part i.e. Access network (UTRAN) and Core Network (CN)

Regarding core network there are three different sub domains characterised in different situations where users communicate with each other in different types of network like fixed or mobile network.

The three different sub domains are described below. 

2.5.4.1 Home Network (HN)

The service profiles of user along with parameters for secure identification are contained in HN and are required to be in coordination with the parameters of USIM at UE.

2.5.4.2 Service Network (SN)

Actually SN is responsible to transfer user’s data from source to destination.

2.5.4.3 Transit Network (TN)

It establishes a link between SN and remote party because this core network is placed in transmission path.

2.6 Universal Terrestrial Radio Access Network (UTRAN)

The main function of UTRAN is to make and maintain a Radio Access Bears (RABs) for reliable transmission between user Equipment and core network. It establishes a connection between mobile terminal and core network. In the figure (2.5) it is stated that Radio Network Subsystem (RNSs) is connected to core network with IU interface which is a reference point in UMTS architecture model.

In a UMTS cell every RNS is responsible to receive and deliver the information .UE and RNS develop connection through Uu which is also called radio interface. UTRAN also contain a number of radio network subsystems. There is only one radio network controller (RNC) and a number of

Node B or base stations are present.RNC are connected with each other through lur interface while node B or base stations are connected with Iub .Node A and Nodes B are break points between air interface and network and further one or more sectors are generated [2] [9].RNC performs several logical functions as below.

• Controlling RNC(CRNC)..................it work regarding node B

• Serving RNC (SRNC)....................... it function occurring with UE

• Drift RNC......................................it perform in soft handover with respect to UE

2.6.1 Operation Mode of UTRAN

Two operation modes have been regulated for UTRN Radio interface.

 

 

 

 

 

 

 

2.6.1.1 UTRAN FDD (Frequency Division Duplex)

• WCDMA is used as access technique during uplink and downlink transmission in a network.

• These are capable to use pair band.

 

                                                                                                         

UTRAN

                     NODE B                                                                  RNS 

 

 

 

 

 

                          Iub 

             

RNC 

 

 

 

  NODE B    Iub 

 

                                                                                        Iur 

 

   

CN 

          

 

                      Iub    

              

Lu 

 

 

                                                                                                                          Iur‐g                                           

 

                 

 

 

 

 

                                                                                               Lur‐g                             lu 

GERAN BSS

                    

                                                                  Figure2. 25  

UTRAN Architecture [2]

2.6.1.2 UTRAN TDD (Time division Duplex)

• TDMA and CDMA are used at the same as an access technique during uplink and downlink transmission.

• They are able to use unpaired band.

2.7 Core Network

Core network of UMTS provides all services to its subscribers thus it is known as fundamental stage in the communication network. Core network is recognized as a long rang network which transfers one user’s information to its relevant destination .Core network is the main part of infrastructure domain where it covers all aspects which don’t have a direct link to radio access network. As a result there is a chance to merge different network architectures with different radio access technologies. Connection management, session management and mobility management are main examples of its functionalities. In new releases of UMTS, some main changes were introduced in core network of architecture, after which the Radio access part became stable and moved towards the IP based network [2][10].

There are two main domains in UMTS core network and they are categorized regarding to user traffic aspect [2].

2.7.1 CS Domain

In UMTS network the role of CS domain is to provide support for traffic control.

The services performed by CS are

• To maintain the user location information.

• To manage the network characteristic. the core network performs various switching functions for CS through Mobile switching canter

(MSC) and Gateway MSC , home location centre (HLC),visitor location register(VLR).

2.7.2 PS Domain

PS domain depends on serving GPRS nodes (SGSN) and gateway GPRS support node (GGSN), both perform their duties as a router and gateway(online book performance). They are also involved in the session management and mobility management. In some cases, mobility management is achieved by combining CS and PS through collaboration of SGSN, GGSN. VLR,

HLR, MSC [2]. A brief description of core network elements here a brief description of the elements in a core network of UMTS is given

                                                                                                                          

 

 

 

 

 

                             

                                                                                         CORE NETWORK 

 

                                                                                  CS domain 

MSC 

                               B                                               NC                                                       

 

Iu_CS 

 

 

      E                                                                                                                                    

    VLR

                                      G                               NC                                                               

   MSC 

     GMSC 

                                 B                                      

 

 

     Iu_CS 

 

                 F                                                                                             C                          

VLR

                                                                 D  

 

 

                                

 

  Gs 

 

                                                                                       H 

 

E I

I R

 AuC 

                                                                                           

HLR 

 

 

UTRAN 

 

 

                                                                                                                                            

Iu_PS 

                GF                Gr                                                                  Gc                            

 

 

 

                                                                  Gn/GP                                                              

SGSN  GGSN 

 

                                                        PS domain

 

 

 

                                                                                                                

                                               Figure2. 26 

Architecture of UMTS Core Network (Release 99) [2]

 

2.7.3. Mobile Switching Centre (MSC):

MSC can actually be defined as a central signaling and switching functions performing unit in

UMTS. Iu CS interface is used by the MSC for the interaction with RAN. Also, CS services are provided or handled by the MSC. The additional feature of MSC in UMTS is its capability and capacity of managing handovers and other mobility related functionalities like position registering procedures.

2.7.4. Mobile Station (MS)

It is referred to as user equipment which has mobile equipment and identification card for UMTS

(USIM).

2.7.5. Home Location Register (HLR)

The information of the subscribers is contained by the HLR for a particular network. It also includes the service profiles. Its core responsibility is the management of mobile users.

2.7.6. Visitor Location Register (VLR):

VLR is responsible to manage the roaming of MS within the boundary of MSC. VLR has particular location information regarding the users. On many occasions it accomplishes specific tasks with out any interaction with HLR. If mobile users enter in any new region of MSC then the area which cover the MSC, sends a notice for registry and then transfer to VLR, where a mobile station is placed.

Meanwhile if MS is not able to register, the VLR and HLR share their information to accept the new call [2].

2.7.7. Authentication Center (AuC)

Authentication procedure is basically set to operate on challenge and response principle in UMTS networks for communication. A3 algorithm is employed for the calculation of SRES parameters from random numbers of 128 bits along with the authentication key Ki. Values of SRES are compared thereafter [11].

2.7.8. Gateway MSc (GMSC)

Basically it is a particular MSC that offers CS services between core network and external network and also responsible for all incoming / out going calls to the external network.

2.7.9. Serving GPRS Support Node

It works in packet domain similar to VLR and MSC working in CS domain. SGSN is responsible for three main functions which are security task, access control and mobility management.

2.7.10. Gateway GPRS Support Node

A communication is established between UMTS network and external network through GGSN interface .It works in packet domain same as GMSC works in CS domain .GGSN also maintains the session, mobility and accounting/billing management.

 

 

 

UE 

 

 

 

 

 

To other  networks 

PLMN, ISDN 

To other  packet  switched  networks  

                                                

Figure2. 27

 

UMTS Architecture Release 99[9]

2.8 Description of UMTS Radio Interface

WCDMA has been acknowledged and adopted as an air interface technology for UMTS networks.

Because this is a quite deferent technology as compare to GSM/TDMA. It is very essential to know the fundamental characteristics of UMTS radio interface network.

UMTS architecture provides three types of channels in accordance with the protocol layer which are categorized as Logical channels, Transport channels, and Physical channels

 

                  Logical Channels

                  Transport Channels

       Physical Channels

                                                                            Figure2. 28 

UMTS Protocol Layer [2, 70]

By means of this division of channels, the radio interface adopts different configurations which farther facilitate a variable Quality of service.

2.8.1 Logical channels

Depending upon the information which is being communicated, logical channels carryout the transfer of the information between the MAC layer and RLC layer for user traffic transfer and control information transfer, these channels are used to be mapped over transport channels

[2].Logical channel are further divided into two parts, control logical channels and traffic logical channels.

2.8.1.1 Control logical channels

Control logical channel transmits information regarding channel control [2] [12]

Broad Cast Control Channel (BCCH)

• Defined in down link direction only

• Contains cell specific information

• Contains carrier control information

Paging Control Channel (PCCH)

• Used for notification of incoming message.

• It is also defined in downlink.

Common Control Channel (CCCH)

• It is a point to point bidirectional channel.

• Transports signaling information.

Dedicated Control Channel (DCCH)

• It is a Point to point bi directional channel.

• Responsible for transferring data regarding dedicated control.

Shared Channel Control Channel (SHCCH)

• Carries initialization massage transmitted by UE.

2.8.1.2 Traffic logical channels

Logical traffic channels are responsible to deliver the information regarding user aspect

Dedicated Traffic Channel (DTCH)

• It is defined in user plane.

• It is bidirectional with respect to user’s traffic.

Common Traffic Channel (CTCH)

• It transfers specific user information to more than one user and group.

• It is a unidirectional point to point channel.

2.8.2. Transport Channels

Transport channels are defined between MAC and physical layer. Their main function is to specify the way of the transfer of information to radio interface from logical channel. Format of the data

transmission regarding bit error rate, coding of the channel and interleaving is defined by transport logical channel. Logical channels are being mapped on to the transport channels according to the system configuration. These channels are defined as [12] [2].

Dedicated Transport Channel (DDC)

• It is defined as bidirectional dedicated channel specific for user Equipment

Broadcast Channel (BCH)

• A broadcast channel which has information about user equipment within cell and also intended to receive information from UE.

Forward Access Channel (FACH)

• Defined in down link direction only and also specific for UE.

• Supposed to deliver the data.

Paging Channel (PCH)

• It is specified for down link

• Carries information regarding incoming call, data session.

• It can receive information by any EU throughout the cell.

Random Access Channel (RACH)

• It is defined for uplink only.

• This channel provides support to carry the request of user Equipment which is intended to access the network [12].

Uplink Common Packet Channel (CPCH)

• It is defined in uplink direction only.

• It is used in support of fast power controlling.

Downlink Shared Channel (DSCH)

• It is defined downlink only.

• There a number of users can participate at the same time to access the information in this channel [2].

                                                  

  Figure2. 29

 

UMTS Channel Mapping [13]

2.9 Physical Layer

In the physical layer of UMTS, WCDMA is adopted as a radio access technology. The basic role of physical layer is to transform the data information into radio signals (physical) which have been received from different transport channels. Procedures of different types are performed in the physical layer in order to produce the radio signals to be sent to the antennas for transmission from the received transport block. Where as the reveres process is carried out for theses radio signals at the receiver end to recover the transport block and farther transported to the MAC layer. A number of key functions are performed by the physical layer in UMTS /WCDMA.

It has to carry out and handover procedures , detection of error , channel multiplexing , mapping of transport channels to physical channels, power control, synchronization of frequency and time and a number of other functionalities regarding transmission and reception of the radio (physical) signals are also executed in the physical layer in addition to the above tasks[2]. Now we shall discuss some important characteristic features and functionalities to be covered by radio (physical) layer. A special type of modulation system where spread spectrum (modulated) signal bandwidth is larger than the actual signal bandwidth. This spectral spreading is completed through a code which is free from the information signal and also this code is again reused at receiver end to dispread the signal [4].

2.9.1 Spread Spectrum

All CDMA systems are referred to as spread spectrum systems including WCDMA. Spread spectrum systems utilize a greater bandwidth as compared to the normal for the data transmission.

The level of interference is reduced in these spread spectrum systems as a result of decrease in average power spectral density. Simply viewing, the spreading means the increase in the bandwidth of signals. The same frequency band is utilized by all the users to transmit data simultaneously. The users are distinguished from each other on the basis of different spreading codes which are allocated to each user which also facilitates the dispreading process for data retrieval even at lower levels of transmitter power.

All spread spectrum techniques are known for the efficient utilization of available frequencies based on the concept of frequency reuse. Frequency Hoping (FH) and Direct Sequence (DS) are the two widely adopted schemes for spreading a data signal. In UMTS, air interface employees DS technique due to following merits of the technique [4].

9 Susceptibility performance of broad band interface.

9 Greater power efficiency.

9 Multipath signal combining capability.

9 Built in redundancy.

9 Processing gain is achieved during dispreading process.

Channelization code scrambling code

DATA Chip rate Chip rate

Modulator

 

                                                        Figure2. 30

 

Spreading and Scrambling [4]

A carrier bandwidth of about 5MHz is provided in UMTS radio networks with a fixed 3.84Mcps chip rate which is a remarkable increase in WCDMA unlike other systems with a bandwidth of

1MHz.As the fig (2.11) shows, the spreading process consists of two operations.

2.9.1.1Channelization

The bandwidth of signal is increased in this operation and orthogonal codes are used for encoding the data which are obtained from Orthogonal Variable Spreading Factor (OVSF) code family. With the help of OVSF codes the orthogonality can be maintained even after using different spreading factors (lengths). Hence using OVSF codes in channelization enables different data rates for different users.

2.9.1.2 Scrambling

Scrambling involves the usage of pseudo noise codes for encoding data after channelization process and has nothing to do with the bandwidth of the signal. In this process, the bit order is rearranged according to a specific sequence of codes. For uplink, scrambling provides distinction between different terminals and for downlink, it is important for distinguishing different cells of a single base station. By applying scrambling process the coordination of code between base station and different terminals does not remain necessary. For scrambling codes are selected from the Gold family of codes. Specification for codes in scrambling are as follows [4].

Code length ................................. 10 ms

Code chip length........................... 38400 chips

Chip Rate...................................... 3.84 Mcps

2.9.2 Cell Structure

UMTS adopted the WCDMA hierarchal cell structure to resolve the performance and cost related issues. In such a system a mobile user can easily handover. Hence after deployment of WCDMA the

mobile communication atmosphere accepted such a Hierarchal Cell Structure (HCS).WCDMA hierarchal cell structure has two types of cell which provided two types of services regarding coverage and users. These are micro and macro cells. Macro cells cover large areas and less populated areas while micro cells have smaller coverage area and are used for the coverage of densely populated areas. Farther hierarchal layer structure is installed to provide global roaming and coverage for UMTS systems.

There are two categories in layer division. The highest layer which is specified for planet and satellite coverage and the other layer which provides support for terrestrial radio access network

UTRAN. Hence both layers establish cells to follow the criteria i.e. lower layer has smaller area which made small cells and higher layer has large area which is specified for large cells. So smaller cells have been selected for more populated area with respect to users. Micro cells support large area jointly with macro cells to enhance the capacity in most populated areas. And Pico cells are installed in such important places where there is a need for high capacity (airport). Hence these two famous standards are deployed in cellular networks. Small cells increase the capacity geographically and grater cells improve the coverage in same geographical region [2][14].

 

 

   

                                                                 

Figure2. 31

 

UMTS cell structure [2] [14]

2.9.3. Cell State

There are two modes in UTRAN, which are connecting mode and idle model. In idle mode UTRAN is unable to access the UE to get any information but on the other side idle mobile terminal remains in active position and can be adjusted with the control channel of specific cell. When mobile terminal is turned on it chooses a suitable cell in accordance with the characteristic of synchronization and broad cast channel. Idle mode is authorized only for transmission as an initial massage which is sent by RACH transport channel to start the RRC connection. RRC connection is also activated through network by using this massage which is coming from NAS. This paging massage is broadcasted to the user in the cell. In radio resource management users are able to control different functionality of control channel. Connecting mode there are for RCC states and UE can switch between theses states. These states are comprised of Cell DCEH, Cell FACH, Cell PCH and

URA PCH [2] [15].

2.9.4. Capacity

Capacity and coverage play an important role in wireless communication networks. The next generation is aiming at providing high speed data, large bandwidth and voice conversation. Actually radio access network of UMTS which is based on CDMA is already launched in the most parts of the world. So aim of UMTS is to overcome the basic necessity of users and also provide a high speed channel where multimedia massaging like services is available. Radio interface of CDMA cellular system has some complicated issues regarding exchange between capacity and coverage. In

UMTS network, every new user creates some extra interference for already existing users with in the cell which affects the whole network. Raising the capacity and increasing load cause the cell size to be reduced. This shrinking cell is covered by the nearest cell. In WCDMA the mechanism is also referred to as soft capacity [16].

2.9.5. Duplex Method

WCDMA system involves two duplexing methods such as time division duplexing and frequency division multiplexing.FDD needs pair band in both direction (uplink and downlink). Both duplexing techniques are same regarding performance however; there are some differences between the two. In

TDD mode there is no propagation delay between a base station and mobile station. As a result collision can occur between transmitting and receiving time slots [16]. Due to small propagation delay TDD systems are more suitable for any environment.TDD mode is also responsible to allocate the Pico cell. One of the big advantages of TDD is its symmetric data flow in both directions.

2.9.6. Multipath diversity

Usually all CDMA systems have multipath diversity property but WCDMA is the only system which exhibits multipath diversity for small cells [2].In wireless systems there are some multipath effects which usually cause problems.

One of the main features of DSSS system is its received signal through different multipath channels which cause performance improvement. A received signal has different variations due to some reflection from obstacles. Multipath can take place due to reflection, diffraction and scattering. The principle which is used in rake receiver called multipath diversity principle in which a number of corealtors are used .Rake receiver is used to identify the powerful multipath element. The main components of rake receiver block are match filter, code generator, co-realtor, channel estimator, phase rotator delay equalizer and combiner. Phase rotator is responsible for adjusting timing in every figure of the symbol. Based on support of rotator and equalizer, it is easy to divide its energy in several parts and also phase and amplitude changed by channel estimation .Hence at the end by compensating its signal strength and also time delay of different elements jointly increase its signal quality. This procedure is known as Maximum Ratio Combining (MRC).Here it needs to know the exact information of SNR and also phase of signal(diversity)[2][16].

2.9.7 Power Control

Power control process is very important for WCDMA atmosphere. When a number of users which are located “near “and “far” tend to communicate in a single seem BS, then due to near-far field effect causes problems in WCDMA system. It is very important to overcome the received power at the base station due to near far effects where all mobile terminals send signals at same frequency [8].

                                      Figure2. 32 

Power Control to Resolve Near Far Field Effect [8]

So the purpose of development of power control is to provide support for air interface physical layer.

WCDMA systems contain three main power control algorithms which are close (inner) loop, open loop and outer loop control algorithms. In open loop power control, UE is capable to fix a particular value which is most suitable for receiver. This algorithm is used in initial stage where transmission power is needed to be set in the uplink direction only. Due to path loss, SIR Interference in cell and broadcast channel (BCH) it is easy to calculate desired power level.

Power control outer loop function is calculated with significant value such as block error (BLER) into a suitable value of SNR and interference. This value depends on features of physical channels and some atmospheric changes such as line of sight (LOS), Non line of sight (NLOS).

ULSIR Target adjustment

TX POWER SIR UL

DL SIR Target adjustment PT.DL BLER UL

PT.UL

BLER DL

DL OUTER LOOP INNER LOOP UL OUTER LOOP

POWER CONTROL POWER CONTROL POWER CONTROL

                                                   

                                                          Figure2. 33 

Inner and outer Loop Power Control [2]

Outer loop power control is carried out in the direction of uplink at RNC where UTRAN is responsible to fix the BLER standard which is executed in down link direction by mobile terminal.

Inner loop power control is also responsible to compensate the suitable transmission power in relation to achieve the SIR target. Inner loop power control works for both open loop and closed loop.

Open loop power control works only in that environment where there is no availability of feed back channels in opposite way [2] [4].

Closed loop power control provides better solution in case of slow fading where some changes occur in different channels like RACH and FACH in both directions.

2.10. UMTS MAC Layer

The main function of the Mac layer is to coordinate the transmission of data to the medium

(physical). In the MAC layer, the different steams of data are housed in the form of queues. Actually decision for sending data packet (next) is being carried out in the MAC layer. Following tasks are also performed by the MAC layer.

Providing information of current state to RRC sub layer.

Encryption of the data in transparent RLC mode.

Multiplexing of data streams in the logical channel to the transport channel.

ƒ Provisioning of logical channels.

ƒ Mapping of logical channels to transport channels.

ƒ Selecting of appropriate Transport Format (TF).

ƒ Priority handling/scheduling.

ƒ Monitoring of the traffic volume.

ƒ Ciphering (if transparent RLC- mode is used.

ƒ If common channel are used, identification of by UE by the

ƒ No segmentation of data

Tasks that are related to the data multiplexing of logical channels to  transport channels 

 

                                            Figure2. 34 

UMTS MAC Layer [10]

2.11UMTS RLC Layer

Radio Link Control (RLC) sub layer guards data streams of different types from errors to be induced. It has three modes for operation.

In acknowledge mode this RLC layer requests for detection of error for data blocks. In this mode the

RLC layer ensures error free transmission of data in correct sequence.

In unacknowledged mode, error correction does not take place rather the data packets with error are simply rejected.

In transparent mode the data is forwarded to the MAC layer without adding the separate header to it this mode is very useful for transmission of audio and video data stream[10].

THE RADIO LINK CONTROL LAYER

ƒ 3 transfer modes.

ƒ Acknowledged mode transfer (ARQ error handling ,order, singleness)

ƒ Unacknowledged mode transfer (error-free, singleness, contemporary)

ƒ Transparent mode transfer.(no error protection)

ƒ Segmentation/reassembly.

ƒ Flow control.

ƒ Ciphering (only non-transparent services)

Tasks that are related to the protected transmission of data.

 

                                              Figure2. 35 

Radio Link Control Layers [10]

2.12 Handovers in UMTS

Handover can be defined as procedure or strategy by which an ongoing call is maintained or held in session without dropping or any discontinuity when the mobile user is moving at a high speed and crosses the boundary of a cell and enters a new cell. It can rightly be termed as criteria of mobility of a user moving in cellular networks.

An efficient and effective handover mechanism is required in UMTS networks to ensure advanced mobility, provision of continuity of services and maintainability of QoS. Moreover, balancing of load within different cells, the facility of roaming between different networks and reduction in interference by providing strong connectivity to the BS is amongst the desired outcomes of handovers in UMTS.

Actually, the switching of mobile user to another different channel without interruption is referred to as the handover process. The need of handover for an ongoing call emerges due to following reasons

[17].

i) The user moves from area of one cell to another cell. ii) Number of users in a particular cell increases in a case when already a call is in progress in that cell. iii) When a mobile user changes its position such that it enters an area with a service or network other than UMTS.

2.13.1. Types of Handovers in UMTS

Different types of handovers in UMTS are discussed below.

2.13.1.1. Vertical Handovers:

When a user with ongoing call is required to enter an area of coverage of the different access technology than that it is already subscribing, then in order to retain the session of call, the type of handover used is called vertical handover. Hence a vertical handover can be explained as a transfer of call between two different access technologies for example UMTS to WLAN or GSM.

2.13.1.2. Horizontal Handovers:

Unlike vertical handovers, a horizontal handover is the one in which transfer of call takes place from one channel to another and the access technology for both the channels is same and both the channels belong to same core network.

2.13.1.3. Intra-System Handovers:

Intra-System handovers are those which occur in a single system only [18]. Intra-System handovers can be observed in FDD-TDD dual mode terminals where handover takes place from FDD to TDD techniques. If the intra-system handover takes place within the cells with similar carrier frequency in

WCDMA system, it is also referred to as Intra-frequency handover while for the cells with difference of the values of WCDMA carrier frequencies, the handover is said to be Inter-frequency handover.

2.13.1.4. Inter-System Handovers:

This is the type of handovers which takes place within the cells of different Radio Access

Techniques (RAT) or in other way different Radio Access Mode (RAM). Commonly an example for this type of handovers can be a handover between WCDMA and GSM. When the handover takes place within different CDMA systems, it is also referred to as Inter-System handover.

2.13.1.5. Hard Handovers:

It is a break before make type handover i.e. the connection in the source cell is disconnected first and the connection in the target cell is made after that. If it occurs as a seamless handover, the mobile user does not get affected. A short disconnection takes place in type of handover regarding real-timebearer whereas its occurrence remains lossless for non real-time-bearers. Hard handovers can occur either as inter-frequency or intra-frequency handovers.

In hard handovers, more than one channel at a time cannot be retained by a user that means that the complexity of hardware for mobile is reduced as it would have been in the case of receiving two channels at a time. This characteristic can be viewed as an advantage of hard handover. On the other hand, call dropping probability is much higher for hard handovers [19].

                                                                                 Figure2. 36 

Hard Handover [20]

2.13.1.6. Soft Handovers:

It is a make before break type of handovers which was actually adopted in CDMA systems. The connection to the target cell is made before disconnecting from the source cell i.e. the connection to the source cell is retained for some time even after acquiring the channel from the target cell.

Soft handovers give lower call dropping probability and reduced interference [21] which can be considered an advantage of this handover and the disadvantages of this type include comparatively complex hardware and increased overhead because of simultaneous connection to more than one cells( using more than one channel at a time). In UMTS/WCDMA systems, soft handovers are widely adopted.

 

                                                            Figure2. 37 

Soft handover [20]

2.13.1.7. Softer Handovers:

In case of multipath effects when more than one signal (multiple copies of signals) are received by a single base station, the type of handover is called softer handover. It can be treated as an interfrequency handover as it uses the one carrier frequency. Another feature of this type of handover is that only one power control loop works in it actively [16].

 

 

                                                                       Figure2. 38 

Softer Handover [20]

 

2.14 UMTS Services

Here we shall discuss some important services offered by UMTS network in including voice communication, text, and bearer services in order to enable the transfer of information among different access point .UMTS offer s connectionless as well as connection oriented services in case of PPT and PT to multiple connections. In UMTS, different data rates offered are given the table below [22].

Services Data rate in kbps

Satellite and Rural Outdoor

Urban Outdoor

144 Kbits/s

384 Kbits/s

Indoor and low range out door 2048 Kbits/s

                                                                         Table

 2.2

 

UMTS Services

 

Chapter 3  

WiMAX 

3.1 Introduction

W orldwide Interpretability for Microwave Access is commonly abbreviated and known as

WiMAX. Wireless Metropolitan Area Networking (WMAN) provides the basis for the development of WiMAX technology whereas WMAN standard is based on IEEE 802.16 .The deployment of WiMAX technology has made high throughput possible over longer distance i.e. all over the world. It has the capacity of providing "Last Mile" broadband wireless access (BWA) instead of cable and DSL.

3.2 Background

Typically, point-to-point radios(a broadband wireless technology) which is a well known service providing class technique for the connection of long haul networks has remained in use for a considerable long period of time. Due to economy, higher flexibility and capability of covering larger geographical areas with broadband services, a higher attention and priority of usage has been given to point-to-multipoint technologies by the wireless network operators for a long time.

In early generations of broadband, discrepancies like less serviceability with higher costs were present and faced by the industry. Also, dissatisfaction was there in industrial circles as there was no healthy competition due to a number of reasons. The difference in the regulations of different countries regarding frequency allocation and usage pulled the manufacturers of equipment towards the adaptation of proprietary air interface technologies. All these factors were held responsible for the lack of the economies of scale in broadband as compared to other technologies. The shortcomings and deficiencies of previous technologies are attempted to be addressed in WiMAX in following aspects. [23]

™ CPE and BS cost

™ Shared bandwidth up to 100Mbps

™ Licensed and unlicensed frequency spectrum

™ Cellular network similar coverage

™ Independent of line of sight

™ Large scale operation and interpretability

With economy and precision, WiMAX will make the delivery of broadband data, video and voice traffic to different kind of users and customers possible for the service providers. As the equipment

employed in WiMAX is based on standards and interoperable hence the goal of achieving low costs and using precise frequency bands will become possible ensuring the economy of scale.

3.3 Evolution of WiMAX

WiMAX is entirely based on the IEEE 802.16 standard .it contain all the necessary features of IEEE

802.16 standards and can rightly be termed as a subset of IEEE 802.16.

By the end of 1990’s, a number of the equipment manufacturers for telecommunication industry

started to develop and introduce devices and equipment for broadband wireless access. In this scenario, the issue of unavailability of any interoperable standard for linkage and operation between the equipment of different manufacturers aroused and faced by the industry. in order to discuss and eradicate the problem, a meeting was summoned by The National Wireless Electronic Systems Test bed (N-WEST) in the United States of America's the National Institute of Standard and Technology

(NIST) in 1998.[24].An IEEE 802 working group was established as a result and it was decided to solve the problem with in IEEE 802.The efforts have been made by the working group in order to specify the standards for fix and mobile broadband wireless access .All the related amendments and associated standards for 1EEE 802.16 and wireless MAN air interface are being developed and regulated by this working group .

In the first version of IEEE 802.16-2001[25] standard which was approved in 2001, the information about the specifications of both physical (PHY) and medium access control (MAC) layers for broadband wireless access (BWA).With the passage of time many changes and amendments were introduced into this version because of new features and utilizations. IEEE 802.16-2004 [24] is the present version of this standard was approved in 2004 and combines all previous versions. The main feature of this standard was its specification of the air interface for fixed type broadband systems.

This specification also provided support for multimedia services both in licensed and license exempt frequency bands[24].an amendment was introduce to IEEE 802.16-2004 known as IEEE 802.16e

2005[26] and it got approved by the working group IEEE 802 in 2006.A detailed overview of the evolution of the standard is stated below.

3.3.1 IEEE802.16-2001

In point to point and point to multipoint communication [25], for fixed BWA, specifications are assigned for physical layer and MAC layer in this firstly issued standard. Single carrier modulation

(SC) in 10 - 66 GHz band of frequency is adopted in physical layer.

QPSK, 16 QAM and 64 QAM modulation techniques are used in this standard. The support for both

Frequency Division Duplexing (FDD) and Time Division Duplexing (TDD) is provided in this standard. Provision of differential Quality of Service (QoS) for MAC layer is a significant feature of this standard. QoS check is carried through a service flow ID. Parameters like maximum latency and tolerated jitter [27] are specified by service flows and their corresponding QoS parameters.

3.3.2 IEEE802.16a-2003

The IEEE 802.16-2001 standard was amended by this standard and improvement was introduced to the Medium Access Control layer to support extra and multiple specifications of the physical layer.

The IEEE 802.16 working group approved it in 2003[25]. Support for 2-11 GHz frequency band was provided as a result of this amendment for licensed and license exempt frequency band.

Geographical coverage capacity of the network was enhanced due to Inclusion of less than 11GHz range which made Non Line of Sight (NLOS) function possible. The standard suffered from multipath propagation problem which was addressed by adding features like advanced power management technique and adaptive antenna arrays [25]. By making a number of privacy layer features compulsory in this standard unlike 802.16-2001 where those were optional, the security was enhanced. More ever this standard provided an option for support to mesh topology along with point to multipoint topology. Along with single carrier modulation (SC), this standard provides an option of using Orthogonal Frequency Division Multiplexing (OFDM).

 

3.3.3 IEEE802.16c-2002

IEEE802 The discrepancies and errors in the first version of the standard were removed and corrected in the.16c standard in 2002 [24].this standard provides system profile for 10-66 GHz frequency band in detail.

3.3.4 IEEE802.16d-2004

In 2004, all the previous version of the standard were combine and consolidated in a new standard named IEEE 802.16-2004.All the specifications provided by previous versions were endorsed and approved. It is also known as fixed WiMAX standard. Providing 72Mbits/s, this standard enables the delivery of last mile. Wireless broadband access as an alternative of Digital Subscriber Line (DSL).

Connectivity is also provided in it along with Line of sight connectivity

.

          8 0 2 .

.

1 6    

Fixed broadband wireless air interfaces 10-66GHZ

          ( ( 2 0 0 1 ) )                        

802.16 amendment fixed broadband wireless MAC and

PHY 2-11 GHZ

8 0 2 .

.

1 6 a

 

 

(

( 2 0 0 3

)

)

                                      802.16 revision par 802.16, 802.16a  

8 0 2 .

.

1

6  

 

                                       Fixed broadband wireless system              

2 0 0

4

                                       Profile errata for 2‐11 GHZ                          

                                       (Formerly 802.16a REVd   

Korea, China and European  standards coverage to 802.16 

 

Korea: WiBro

China: CCSA

 

Europe: ETSI HiperMAN

 

 

8 0 2 .

.

1 6 e  

 

(

( 2 H 2 0 0 5 )

                                        Broad band at vehicular speed in  

                                                               Figure 3.1 

WiMAX Standard [23]

 

3.3.5 IEEE 802.16e-2005

It is also known as mobile WiMAX. Mobile WiMAX is covered by 802.16e standard or IEEE

802.16-2005, this is the amendment of 802.16-2004. IEEE 802.16e standard includes better support for quality of service and uses Scalable Orthogonal Frequency Division Multiple Access

(SOFDMA). It is used for ground up for the HiperMAN giving longer range in Bits /Hz/Sec with higher throughput. It is optimized for dynamic mobile radio channels and wider ranges of unlicensed bands which offer higher throughput than 802.16d products. On the bases of these modifications, it provides full support for mobility.

 

3.4 Some Significant Features of WiMAX

WiMAX can rightly be viewed as an emerging wireless broadband access technique which contains a higher degree of flexibility regarding deployment and operational usage. WiMAX has the capability to support different systems of architecture i.e. point to point, point to multipoint and

Ubiquitous. Significance of WiMAX is elaborated in some of its following distinguishing features.

[28, 29, 30]

3.4.1 OFDM Based Physical Layer

The principle of orthogonality provides the basis for the operation of WiMAX in physical layer i.e.

Orthogonal Frequency Division Multiplexing (OFDM), which has a characteristic property to avoid multipath and enabling operation in NLOS environment [28] is adopted.

3.4.2 Adaptive Modulation and Coding (AMC)

Connection to the increased number of users is attained in the WiMAX using adaptive modulation and Forward Error Correction (FEC) coding scheme [24].

Employing AMC throughput can effectively be increased. With higher data rate and low signal to noise ratio, adaptive modulation and coding scheme requires highest and advance modulation techniques.

3.4.3 TDD and FDD Support

Both Time Division Duplexing (TDD) and Frequency Division Duplexing (FDD) along with a half duplex FDD [24] is supported in WiMAX. Due to flexibility and low complexity TDD is mostly preferred.

3.4.4 per User Resource Allocation

In WiMAX, a very flexible and dynamic method for resource allocation is adopted for each user depending upon the requirement or demand of the user. It is actually executed and controlled in the base station by a scheduler. TDM scheme is employed to share capacity among multiple users in accordance their demand. The method of resource allocation is very flexible and provides frame by frame based information [28, 29].

3.4.5 Quality of Service (QoS)

In WiMAX architecture the MAC layer is responsible for QoS [28]. End to end QoS can be achieved by using sub channelization and multiple or different coding methods. QoS can be improved and increased by flexible scheduling and using data rates in higher degrees.

3.4.6 Advance Antenna Techniques Adaptation

Multiple input and multiple output (MIMO) is strongly supported by WiMAX which permits adaptation of multiple antenna topologies and schemes like space time encoding, beam forming and spatial multiplexing. Using MIMO systems of antenna deployment at transmitter and receiver

spectral efficiency and overall capacity of the system is improved as the above mention schemes are employed.

3.4.7 Link layer Retransmission

Link layer of WiMAX supports Automatic Retransmission Requests (ARQ) in order to achieve increased reliability [24]. The transmitted packed is required to be acknowledged at the receiver and in case of packet lost no acknowledgement is received from the receiver and the transmitted packet is used to be retransmitted automatically. Hybrid-ARQ i.e. a mixture of FEC and ARQ can also be supported in WiMAX if required.

3.4.8 Mobility

Support for the seamless handovers in delay tolerant mobility applications like VoIP is provided in mobile WiMAX. Mobile applications of WiMAX also support

• Power saving mechanisms

• Frequent channel estimation

• Power control

• Sub channelization for uplink

3.4.9 Scalability

In WiMAX the scalable architecture of physical layer enables the data rates to be easily scaled according to available bandwidth of channel .in OFDMA, the fast Fourier transform (FFT) size can be scaled with respect to available bandwidth [27,28] and hence scalability for bandwidth and data rate in WiMAX is fully supported.

3.4.10 High Data Rate

Remarkably high peak data rate are supported in WiMAX such as 74 Mbps at 20 MHz [28].TDD is scheme is used in 10 MHz spectrum in a ration of 3:1 downlink to uplink.

3.4.11 Security

The mechanism of security adopted in WiMAX is very robust. Advanced Encryption Standard

(AES) is used for supporting strong encryption with robust privacy and key management protocol.

Extensible Authentication Protocol (EAP) is selected for a flexible authentication [27.28].

3.4.12 IP based Architecture

The network architecture of WiMAX is completely based on IP platform. IP architecture is used to provide all end to end services which depend on IP protocol for QoS, mobility, session management and security.

 

3.5 Technological Aspects of WiMAX

WiMAX is a guarantee mark for products that pass compliance and operability test for the IEEE

802.16 standard [31]. It is a technology, enabling the delivery of last mile wireless broadband access

(BWA) as an alternative to cable and DSL. It is a point-to-multipoint architecture, which resembles very much to the traditional mobile telephone system, though it differs in specifications and properties. Mainly, WiMAX defines an all-IP based architecture, which provides support for high throughput over long distances. Two layers in the OSI-stack are defined by WiMAX, which are the

Physical and the Medium Access Control (MAC) layer.

The preposition that WiMAX is all-IP, means that a common IP network core is used, where the circuit core network is absent in favour of the IP packet network. Also, it reduces the complexity and overhead by employing a single protocol. Due to this reason WiMAX is well suited for IP-services like VoIP, IPTV, streaming applications and Internet surfing. This means that services which are already available at the internet will be available for use over WiMAX.

IEEE 802.16 standard provides the basis for WiMAX. All mandatory features in 802.16 are also mandatory in WiMAX, and optional features in IEEE 802.16 may be optional, mandatory or not included. Hence, WiMAX can be known as a subset of the IEEE 802.16 standard as illustrated in Fig

3.2.

 

                   

IEEE 802.16

 

      

 

                                

                    

     WiMAX

 

                                                         Figure 3.2 

Representing WiMAX as subset of IEEE802.16 [31]

 

WiMAX Forum [32], an organization of leading operators of communications components and equipment companies, describes the interoperability and compatibility specifications and standards.

WiMAX systems implemented by various vendors with different equipment will interoperate. The common platform will lower the costs and enhance performance, thus the market will adopt the technology faster and more widely. A parallel can be drawn to the success of WiFi, a Wireless Local

Area Network (WLAN) system, specified by the WiFi Alliance [33] based on the standard 802.11b/g

[34, 35].

The IEEE 802.16 Air Interface Specification explains options for a number of physical layers for different frequency bands and according to region by region frequency regulatory rules. In order to achieve interoperability, WiMAX has undertaken the development of System Profiles specifying which options are to be utilized. Testing Specifications are developed to verify these specific profiles, and Certification Labs are used to permit vendors to prove that their equipment meets these profiles. WiMAX Forum arranges meetings called plug fests, where vendors meet for validation and verification of interoperability with other vendor’s equipment [36].

Two system profiles are defined for WiMAX. Fixed WiMAX was first specified and later mobile

WiMAX which adds mobility to WiMAX. These profiles are based on the specifications of IEEE

802.16d and IEEE 802.16e respectively. An overview will be given for both system profiles.

3.5.1 Fixed WiMAX

The fixed WiMAX profile, based on the IEEE 802.16d specification, is mainly aimed at the fixed wireless access and can support nomadic and portable access too in some cases.

3.5.1.1 PHY Layer

In the physical layer of fixed WiMAX, the performance of the system is increased and complexity is reduced. IEEE 802.16d is capable to support multiple accesses for uplink transmission. Where as multicarrier modulation is utilized to manage the signal for both time and frequency domains [29].

WiMAX physical layer is based on OFDM based multiplexing techniques which are used to deliver high data rate over a multiple number of specifically spaced shorter subcarriers, where each subcarrier utilizes a separate frequency which decreases the interference and also reduces crosstalk.

In short, we can say that a channel bandwidth is further divided into several sub channels where by utilizing different frequencies information on each channel, transmission can take place [28].

In fixed WiMAX, FFT size is 256 which is fixed where 192 subcarrier are used to carry the information. Eight pilot subscribers are allocated for channel estimation and synchronization and 56 are used for guard band. 3.5 MHz bandwidth channel is assigned for fixed WiMAX however; it varies some times regarding subcarrier spacing. When subcarrier spacing is enlarged than symbol time is reduced also which is caused by delay spread. By the above phenomena it is concluded that number of subcarrier is directly proportional to channel bandwidth. [28]

Performance as well as the range of fixed WiMAX can be improved by employing subchannelization (limited) in the uplink direction. It consequently improves the link budget characteristic and also the range. The IEEE 802.16d standard for fixed WiMAX include advanced features like flexible channel bandwidth , AMC, forward error correction and advanced antenna systems.[28]

 

3.5.1.2 MAC LAYER

The MAC layer provides an interface for physical layer and transport layer.MAC layer gets packet from the higher layer named as MAC service data unit (MSDUSs). It enables MAC protocol data unit (MPDU) to be delivered through air interface. For reception purpose, MAC layer also provides support as well. WiMAX MAC layer has also introduced a sub layer named as converges sub layer which is capable of interfacing with other higher layer protocol like ATM, Internet , IP etc. Due to compatibility with higher layer the convergence layer decreases the overhead for higher layers by reducing the MPDU header. In order to maintain the efficient transmission, MAC layer of WiMAX utilizes variable length MPDUs. [28]

 

Service Specific convergence sub layer

M

A

MAC common part sub layer

Security Sub layer

 

                                                                      Figure 3.3  

MAC layer of WiMAX [28]

3.5.2 Mobile WiMAX

The required functionality has been introduced by IEEE 802.16e specification in order to support mobility. Currently, mobile WiMAX follows the IEEE 802.16e specification of 802.16 standards

[37].Mobile WiMAX uses Orthogonal Frequency Division Multiple Access (OFDMA) in the air interface for improved performance in mobile multi path NLOS environments. Scalable OFDMA

(SOFDMA) is adopted for scalable channel bandwidths [38]. Enhanced and new techniques to better support mobility are added to both the PHY and MAC layers, which will be addressed in the following sub-sections.

3.5.2.1 PHY Layer

Many of the parameters from the Fixed WiMAX part is kept in mobile WiMAX, but enhancements are done as listed in Table 3.

 

Multiplexing 

FFT size 

Duplexing mode 

Modulation 

Channel Bandwidth 

Fixed WiMAX 

OFDM 

256 

TDD, FDD, HFDD 

BPSK, QPSK, 16, 64‐QAM 

3.5,7,10 MHz 

    Mobile WiMAX 

SOFDMA 

512,1024 

TDD 

QPSK, 16 , 64‐QAM 

5,7,8.75,10 MHZ 

Frequency 

2GHz to 11GHZ  2.3GHZ to 2.5 GHZ 

                                                

                                       Table 3.2 

Comparing Physical Layer in Mobile and Fixed WiMAX [39]

As elaborated from the table, BPSK is removed as an alternative for modulation. TDD is the only choice of duplexing. OFDM has been enhanced by the OFDMA multiplexing technique. Two FFT sizes are decided for use in S-OFDMA. The enhanced multiplexing technique adds sub channelization.

The two key smart antenna methods favoured by the WiMAX Forum, MIMO and AAS or beam forming, could increase coverage from two to nine kilometres radius for an urban base station having mobile support, a 20-fold increase in the capacity of subscriber [39].

For the mobile part lower frequencies are used due to improving deployment in a mobile channel, where Doppler effects and Multipath fading are frequent. Radio signals penetrate better and the

NLOS requirement is possible to overcome at lower frequencies.

Other advanced features in mobile WiMAX are Adaptive Modulation and Coding (AMC), Hybrid

Automatic Repeat Request (H-ARQ) and Fast Channel Feedback (CQICH). These were introduced with mobile WiMAX to enhance coverage and capacity for WiMAX in mobile applications.

3.3.2.2 MAC Layer

The Media Access Control (MAC) sub layer has been enhanced especially with the need to support mobility. This includes power management and handover between base stations. Mobile WiMAX has the same support for QoS as the fixed profile with the addition of the QoS profile enhanced real time-Polling Service. It was mainly introduced to support variable sized packets for VoIP. The scheduler is more advanced due to more varying conditions caused by the mobile environment.

Available resources are scheduled in response to busty data traffic and time varying channel conditions. Fast channel feedback is provided by the CQICH channel, and the adaptive modulation and coding (AMC) combined with Hybrid Auto Repeat Request (H-ARQ) provide robust transmission over the time-varying channel. As in the fixed part, scheduling is performed for both

Downlink and uplink traffic. Dynamic Resource Allocation is supported, where resource allocation may be changed on a frame-by-frame basis in response to traffic and channel conditions. Frequency selective scheduling is also supported, where mobile users with fixed resource demands are allocated to the strongest sub-channels that are composed of the best sub carriers.

Battery is a critical subject in mobile devices, and should be spared as much as possible for longer duration. Two modes for power efficient operation are therefore added. The first is idle mode, where the mobile station (MS) on the move only is available for DL broadcast traffic messages without registration to a specific BS. Handoff management will therefore not be considered if the MS is in idle mode. The second is sleep mode, where pre-negotiated periods of absence are announced from the MS to the BS. Power usage and radio resources are minimized. Handover must to be supported to obtain mobility. Three mobility modes are supported. The first and only mandatory is Hard

Handover, where the connection with the BS is ended first before the MS switches to another BS

(break-before-make). The second and optional is Fast Base Station Switching (FBSS) where the BS and MS maintain an active set, which is a list of Base stations involved in the FBSS. The MS monitors the active set, and performs handover based on the signal strength from the CQI channel

(make-before break). Thirdly an optional Macro Diversity Handover (MDHO) method may be used, where an active set is kept in the MS and Base stations and transmissions are performed from the

MS to all the Base stations and vice versa. A MDHO starts when a MS decides to transmit or receive unicast messages and traffic from multiple Base stations in the same time interval [33].

 

3.6 Architecture of Mobile WiMAX

Based on the standard IEEE 802.16e, mobile WiMAX is specifying a system that will support mobility. The IEEE 802.16e specifies the MAC and PHY layers, but specification for network layer functionality is needed to support true mobility. Aspects such as inter-network and inter vendor interoperability for roaming, multi-vendor access networks and inter-company billing [40] are required to be viewed seriously.

 

 

 

 

SS/

MS 

WiMAX forum have therefore formed two additional working groups for these purposes. WiMAX

Forum Network Working Group creates higher level networking specifications for fixed, nomadic, portable and mobile WiMAX systems beyond the standards specifications. The other one is a

Service Provider Working Group which links service provider participation within WiMAX

[41].Several aspects are considered, which roughly summarized are mobility and handover, QoS, security and multi-vendor interoperability. A logical representation of the network architecture can be identified by the Network Reference Model (NRM) as shown in Figure 3.4

 

        R2 

    R2 

 

 

 

 

 ASN 

 

                  R4 

                  R8    

Another    

ASN 

 

Visited NSP  

 

     CSN  

ASP Network  or Internet 

 

Home NSP  

 

    CSN 

ASP Network  or Internet 

 

                                                            Figure  3.4  

Mobile WIMAX Reference Model [23]

A Mobile Station (MS) is connected with an Access Service Network (ASN) consisting of base stations and one or several ASN Gateways. Interface R1, between MS and ASN, involves Medium

Access Control (MAC) functions for station-locating, paging, Radio Resource Management (RRC) and mobility between base stations. ASNs are located within a Network Access Provider (NAP).

Several ASNs may be located within a NAP. ASNs manage the radio links, whereas the NAPs are logical business entities which controls and deploy the ASNs. Layer-2 connectivity is provided within the ASN, before the control is handled to a Connectivity Service Network (CSN) which provides IP connectivity (L3). Connection to internet through gateways and routing is kept at this level. Authentication, Accounting and Authorization (AAA) is administrated in this entity by servers and proxies. Gateways for interworking with other networks and Mobile IP Home Agents (MIP-HA) may also be present in a CSN. Content services as well as IMS services, support systems for billing and operation will be important. The logical entity maintaining the CSN is a Network Service

Provider (NSP), where the amount and type of provided functionality will differ in various Network

Service Providers. Mobility and handovers will be widely supported in the network architecture.

Handover-support between WiMAX Network Service Providers as well as with other technologies as for instance WiFi and 3G systems will be provided. Mobility is a requirement and may be supported for IPv4 or IPv6.QoS will emerge to be an important subject in future and present networks. Extensive QoS support is offered in the WiMAX radio access domain, both per MS and per service flow for the Mobile Stations. Services are differentiated and will have the ability to be supported throughout the network by QoS mechanisms as for instance Differentiated Services (Diff-

Serve). Bandwidth management and admission control is addressed. Policies regarding QoS, as defined by different Network Service Providers, will be implemented through Service Level

Agreements (SLA).

Interoperability of equipment from multiple different vendors, within and across ASNs, is a key aspect for system diffusion. Operators will have a scalable, extensible operation and flexibility in selection of network architecture. For instance how to design the network with Pico, micro and macro base-stations. Options for which backhauling technology to use will be flexible, for instance with options for wire line and/or wireless technologies with different quality

 

                                                                  Figure 3.5 

WiMAX network architecture [28]

3.7 Mobility in WiMAX

The IEEE 802.16e standard provides the specifications for Mobile Wireless Broadband Services

(MWBS) in WiMAX. It enables the provision of mobility(seamless) to end users while stationary or in moving positions anywhere .An all IP based mobile broadband technology i.e. mobile WiMAX has benefited the mobile end users in accordance with the IP-specific optimizations of 802.16[42].It has an built in capacity to manage handovers at higher speeds . Now WiMAX Forum has provided some specifications which describe a node for mobility support and termed as ASN Gateway

[42].Mobile WiMAX has made the high quality video downloading and video conferencing like features possibly available for mobile end users.

3.8 Handovers in WiMAX

IEEE 802.16e gives support for three methods of handovers in mobile WiMAX namely,

1. Hard Hanover (HHO) which is mandatory.

2. Fast Base Station Switching (FBSS) which is optional.

3. Macro Diversity Handover (MDHO) which is also optional.

3.8.1. Hard Handover (HHO)

This is a compulsory method of handover and is applied at the initial stage of handovers in mobile

WiMAX. During HHO, a quick connection transfer takes place between two base stations. Mobile

Station (MS) provides measurements based on which the decision for handover can be made either by BS, Ms or any other unit. The quality of the signal of closely located base stations is determined by the MS with the help of repeated radio frequency (RF) scans done at regular intervals. The base station provides time slots called scanning intervals during which the MS carries out scanning.MS can connect to one or more than one base stations during this time and can execute initial ranging

[28]. Synchronization with the target base station is started by the MS when the handover decision has been made and the connection with the previous base station is disconnected [28

].

3.8.2. Fast Base Station Switching (FBSS)

In FBSS, a connection is retained by the MS with more than one base station at the same time.MS holds the active set in FBSS which is actually the information of those base stations which have an involvement in handover procedure. Ranging is performed by the MS and a valid ID for connection with each base station is preserved by it. Anchor BS [28] is the only base station which communicates with the MS. The connection is shifted from one anchor BS to another when desired in such a way that no explicit handoff signalling is required to do so. New adopted anchor BS is reported to CQICH by the MS [28]

 

Area of neighbor BS

 

Figure 3.6 

Fast Base Station Switching [43]

3.8.3. Macro Diversity Handover (MDHO)

This method is very much similar to FBSS. It has a diversity set which consists of all the base stations which are being communicated at uplink and downlink at the same time. With the help of selection diversity, the MS chooses the best uplink to send data to various base stations. Whereas in the downlink, employing a diversity combining technique the MS combines the received multiple copies.

FBSS and MDHO are better than HHO. For both, the synchronization of base stations and usage of same carrier frequency is required.

 

Area of neighbor BS

 

Figure   3.7 

Macro Diversity Handover [43]

3.9 WiMAX System Components

A typical WiMAX system is constituted by following two components, a) WiMAX Base Station (BS). b) WiMAX Receiver or Customer Premise Equipment (CPE).

Whereas by means of backhaul the system is connected to the core network. A backhaul itself is not considered to be an incorporated component of the WiMAX system.

3.9.1. WiMAX Base Station (BS)

Base station is referred to as a point from where WiMAX signals are used to be broadcasted. It includes a WiMAX tower and electronic devices [23]. The theoretical coverage range of a BS is 50

Km or 30 Miles but due to geographical limitations it is in reality limited up to 10 Km or 6 Miles radius of area. Any wireless device can be connected to internet if it is located in this area. The area of coverage of each base station is known as a cell with the maximum radius of 10 Km or 6 Miles in reality. Antennas in a base station can generate circular cells if those are supposed to be Omnidirectional or can generate even other linear shapes of cells in case of point to point communication.

WiMAX base station provides the frequency bandwidth to the users according to their demand by using MAC layer as per the standard and ensures interoperability of networks. All these functions are performed on real time basis.

3.9.2. WiMAX Receiver or Customer Premise Equipment (CPE)

It can be referred to as a device which receives the signals from a BS and by virtue of which a connection to the WiMAX networks is made. It may be a

Personal Computer Mobile Computer Interface Card (PCMCIA) card or a stand alone antenna

[44].The procedure for connection to a WiMAX network resembles to that of a procedure in WiFi where connections to the access points area made. WiMAX has an edge over WiFi that its area of coverage is considerably larger.

3.9.3. BACKHAUL

Backhaul can be defined as a high speed link (microwave) which connects WiMAX base stations to many other base stations. It provides roaming facility and ensures better mobility by maintaining connections in case of moving subscriber. Backhaul encapsulates both types of connections i.e. from user to service provider and provider to the core WiMAX network. Any technology can be supported for the deployment by the backhaul regarding system connection to the backbone of network.

Figure  3.8 

Backhaul (WiMAX) [45]

 

3.10 WiMAX Working

IEEE 802.16 specification defines the working parameters for fixed and mobile WiMAX which can serve the purpose of MIMO based wireless communications for a large number of users or subscribers. Schematically, WiMAX working principle resembles largely to that of a point-tomultipoint pattern of communication in cellular networks. IEEE 802.16e, which provides an extension in the original 802.16 specification for enhanced mobility, has made seamless communication possible between different base stations unlike IEEE 802.16d (fixed WiMAX).

For ideal case, point-to-point antennas are referred to as backhaul, must be employed by WiMAX for connection within subscriber sites and with base stations which are located distantly. In special cases like a mesh network, point-to-multipoint pattern is also adopted to serve as a backhaul.

Customer Premise Equipment (CPE) are provided with the point-to-multipoint connectivity by the base stations either by employing LOS or NLOS methodology also known as Last Mile [23]. In an ideal consideration for WiMAX point-to-multipoint antennas topology is suggested for end users connectivity to base stations in a non line of sight environment.

  

Figure   3.9 

WIMAX working [23]

3.10.1 Advanced Working Features for WiMAX

9 The WiMAX architecture is capable of performing coordination centrally with increased security and encryption.

9 The architecture is built so that it can eliminate PP client communication.

9 NLOS operation is achieved employing robust radio interfaces.

9 OFDM PHY is supported by the architecture and for end users, facility of self installation is provided.

9 High speed IP services in WiMAX are capable to provide 110 Mbps in 3.5MHz band of frequency and up to 3550 Mbps with greater number of channels (1420 MHz) [23].

9 WiMAX is capable of providing 2 nd

generation IP QoS which can support real time features.

9 Radio interface with less delays are provided in WiMAX for VoIP and internet gaming like applications which are considered to be latency and jitter sensitive.

Chapter 4  

 COMPARATIVE ANALYSIS 

 

 

 

 

I n this chapter we will give a comparative interpretation for the two technologies already discussed in detail in the previous two chapters, regarding some important aspects. This comparative study is aimed at highlighting the pros and cons of both the technologies both technically and with respect to applications.

Technology comparison

Peak Data Rate

WiMAX

DL:70 Mbps

UMTS

DL:2 Mbps

UL:70 Mbps UL:2 Mbps

Band width 5-6 GHz 5MHZ

Multiple access

Duplex

Mobility

Coverage standardization

Target market

OFDM/OFDMA

CDMA

TDD FDD

Low

Mid

High

Large

802.16 3GPP

Home /Enterprise Public

Table 4.1

Technology Comparison [46]

4.1 Comparison of Physical Layer Access Techniques

First of all we will compare the multiple access techniques used in WiMAX and UMTS which are

Orthogonal Frequency Division Multiple Access (OFDMA) and Wideband Code Division Multiple

Access (WCDMA) respectively for both technologies.

The physical layer is considered to be the most basic layer in a network. Mainly it provides the radio interface for the physical transmission. It is also responsible for functions like data coding, flow control, multiplexing and bit synchronization [47].

4.1.1. OFDMA for WiMAX

In the physical layer of WiMAX the technique adopted for radio access is OFDMA which is based on OFDM multiplexing technique. In OFDM separate orthogonal subcarriers are used for modulation and transmission of sub streams of input data with lower data rates obtained by the division of main input data stream. Due to reduced data rate robustness is increased for OFDM as it increases the duration of symbols and decreases delays in spread spectrum. Orthogonality eliminates the possibility of cross talk between subcarriers even if they overlap. Hence increased bandwidth efficiency is obtained by permitting the overlapping which reduces the requirement for more spectrums. Inverse Fast Fourier Transform (IFFT) is used to produce OFDM signals. IFFT has lower level of complexity and enables up to 2048 subcarriers which is a large number. OFDM uses OFDM symbols in time domain and subcarriers in frequency domain. Individual users are all provided with time and frequency resources in sub channels [48].

In OFDMA, the multiple access technique for WiMAX, the channel is divided in a manner that it can be shared by many users. Simultaneous use of the same channel for all users is made possible in

OFDMA by assigning a single subcarrier or a group of subcarriers to them [49].

OFDMA can also be referred to as multicarrier OFDM version with a feature of assigning subcarriers for different users. A feature that is comparable to CDMA for assigning spread codes with different data rates to different users, in OFDMA is that of assigning different number of subcarriers to users depends upon their demands and channel conditions. The mobile WiMAX adopts S-OFDMA as multiple access technique. It has been opted in order to address the issue of difference in channel sizes country wise. Scalability enables the mobile WiMAX standard IEEE

802.16e-2005 to support 1.25 MHz to 20MHz range of channel sizes. It is achieved with the help of fixed frequency spacing of 10.94 KHz and by the adjustment of FFT according to bandwidth or channel size.

Two types of sub channel permutations are used in S-OFDMA i.e. diversity permutation and contiguous permutations for sub channelization. The former is more suitable for mobile user applications and the second one for fixed and portable applications.

Parameter 

FFT size 

Fixed WiMAX OFDM 

256        

Number  of  used  data  subcarriers 

192         

Number of pilot subcarriers  8         

Mobile  WiMAX  Scalable 

OFDMA 

128              512                1024  

2048 

72            360                720   

1440 

12       60        120      240 

Number  of  null/guard  band  subcarriers 

56          44       92        184      368 

Cyclic  prefix  or  guard  time 

(Tg/Tb) 

1/32        

Oversampling rate (Fs/BW) 

1/16       1/8        ¼ 

Depends  on  bandwidth:  7/6  for  256  OFDM,  8/7  for  multiples of 1.75MHz, and 28/25 for multiples of  

1.25MHz, 1.5MHz, 2MHz, or 2.75MHz. 

Channel bandwidth (MHz)  3.5          1.25       5        10      20 

10.94  Subcarrier  frequency  spacing 

(kHz) 

15.625                    

Useful symbol time (ms)  64                    

Guard  time  assuming  12.5% 

(ms) 

8                    

OFDM symbol duration (ms)  72                   

91.4 

11.4 

102.9 

Number of OFDM symbols in 5  ms frame 

69                    

 

48.0 

Table 4.2 

Different Parameters in WiMAX [51]

 

4.1.2. WCDMA

The physical layer of UMTS is based on WCDMA which is also referred to as the multiple access technique employed in UMTS .WCDMA can be explained describing the three fundamental access

technologies: frequency division, multiplexing (FDMA),Time division multiplexing (TDMA),Code division multiplexing (CDMA) are referred to as air interface technologies.

4.1.2.1. Frequency Division Multiple Access. (FDMA)

In FDMA, the available frequency range is divided into smaller bandwidth and provided to the users.

This provides every user with a unique frequency space for operation. This bandwidth is further subdivided for voice transmission and reception purposes .it implies that FDMA uses duplex mode of communication. FDMA is adopted in most cellular networks.

POWER  

TIME 

  

                                                       FREQUENCY      

Figure 4.1 

FDMA [50]

 

4.1.2.2. Time Division Multiple Access (TDMA)

In TDMA, The frequency is dived in different time slots. It enables the provision of the usage of the same frequency by multiple users at the same time. In TDMA, the capacity of the network is increased

Power

Time

Frequency

 

Figure 4.2 

TDMA [50]

                                   

4.1.2.3. Code Division Multiple Access (CDMA)

In CDMA, each user is assigned a spreading code for coding and decoding of the massage signal. In

CDMA each user has the provision of using the whole bandwidth of the system for whole the time.

At base station each user’s unique scrambling code helps in its detection.

Figure 4.3 

CDMA [50]

 

For WCDMA, some up gradations were introduced in CDMA. 5 MHz bandwidth is used in frequency domain to transmit the information. The significant feature in WCDMA is the decrease in the transmission power to deliver the information through spreading in accordance with the frequency band .A frequency band of 4.5 to 5 MHz is assigned to WCDMA.

4.1.2.4. Description

In UMTS networks, power and spreading factors are considered as a variable. WCDMA provides full support for duplex communication so two modes are defined for WCDMA transmission channel.

• TDD (time division duplex)

• FDD( frequency division duplex)

In FDD mode the entire radio spectrum was divided into pair band for the range 60MHz. in

WCDM, 12 channels are dedicated for uplink and downlink for FDD mode. A total of 5 MHz channel bandwidth where 7 channels are fixed for uplink and remaining channels are used in downlink (fig).TDD System is utilized for unpaired band and FDD system for pair band.

The total bandwidth in WCDMA is 5MHz but operating bandwidth is 3.84MHZ. There are 5 MHz guard band between its neighboring channels which reduce the interference

 

 

Frequency

                                                                                                                                                                                            

                                   

Effective Bandwidth 3.84MHZ 

                WCDMA Channel Bandwidth 5 MHZ         

                                                   Channel bandwidth  

Figure 4.4 

WCDMA Frequency band

WCDMA uses two basic method of spreading in a given frequency band. One of these methods is frequency hopping (FH).Frequency hopping is utilized in spread spectrum to transmit the signal.

Due to spreading code the transmitted data is varied quickly. The variation is due to carrier frequency through a delivered time, where data creates spread bandwidth. By supporting the spreading code, carrier is hopped to a further frequency band in a given time. Further it has two types of modulation which is represented as fast FH and slow FH. In fast frequency hopping rate of hopping is always greater than symbol rate while in Slow FH the rate of hopping is smaller than the symbol rate. [4, 9] 

The other method is direct sequence (DS).Where data is transferred through unique frequency band.

In this scenario, data is spread by the support of the whole bandwidth of a dedicated radio channel.

Where usually frequency reuse factor is always kept equal to one. Hence, all users use similar frequency to deliver the data. Multi carrier (MC) spreading is another type of spreading. Where different carriers are utilized in a given frequency band.

Direct Sequence Wideband Code Division Multiple Access Duplex Frequency Division Duplex

(DS-WCDMA-FDD) is assigned for UMTS network previously While Direct Sequence Wideband

Code Division Multiple Access Time Division Duplex (DS-WCDMA-TDD) and MC-CDMA will be adopted in evolution of UMTS [9].

                               

Wide band spreaded  signal   

Original narrow  band signal   

Wide band spreaded    signal  

Received narrow  band signal  

 

Wide band spreaded  signal   

 

Figure 4.5 

Spreading and Dispreading [9]

Wide band spreaded  signal   

The main factor which is used in WCDMA communication channel to access the number of users and regarding security are called code. Based on above theory of WCDMA, there should be one code only but practically there are a number of codes that are used to decrease the drawbacks which create some limitation in radio channel. Two types of codes are used in WCDMA .First one is channelization code and second one is scrambling code. Physical data is divided by channelization code in the uplink direction. It is also responsible to control the channel. Partition of the terminal is taken into account in the direction of uplink while cell partition is possible in the direction of downlink.

At the end spreading code is achieved by multiplying these two types (scrambling and channelization). Both codes are capable to examine such a noise in WCDMA signal through spreading code. Both codes are considered as an orthogonal code in such series. Here the actual idea gets developed in accordance with the aim of getting the user data form noise which is referred to as wideband signal. By using properties, the product of orthogonal codes will be zero.

The product of original baseband and wideband signals are characterized as a code in WCDMA signal based on the following parameters.

• One bit base band signal as assigned for payload

• Chip is also represented one of code signal

• Transmission speed is called chip rate

• Signal chip rate which is equal to 3.84million chip/sec

Figure (34) depicts the actual process of Spreading, dispreading and transmission by using a Uu interface. Here the original narrowband signal as input is multiplied by spreading code (wideband signal) over the air interface .and for dispreading needs to be multiplied by similar spread code [4,9].

WCDMA uses 3.84MHz as operating bandwidth; the original bandwidth of transmitted signal is smaller than the entire bandwidth of WCDMA Channel. It means the original bandwidth of transmitted signal is same as the spreading code bandwidth.

4.1.3. Comparison (WCDMA and OFDMA)

The above stated facts clear the procedural and operational details and characteristics (differences and similarities) of radio access techniques’ used in both technologies i.e. is UMTS and WIMAX.

Now some key distinguishing features of OFDMA and WCDMA are discussed and compared as follow.

• Due to Orthogonality maintenance by the sub channels in OFDMA, the performance of system is not affected by multipath component in OFDMA, therefore OFDMA is more tolerant to multipath and self interference as compared to WCDMA.

• OFDMA systems have better scalability option as compared to WCDMA. Different parts of channels are assigned to the users in OFDMA whereas; in CDMA systems the whole channel or entire channel bandwidth is utilized by each user for transmission.

• OFDMA based systems are free of Multipath Access Interference(MAI) with reference to multipath users but WCDMA systems contain interference as asynchronous CDMA is adopted in WCDMA for uplink transmission.

• QoS can be improved in OFDMA based system due to frequency selective scheduling which is not applicable for CDMA based systems such as WCDMA.

• OFDMA has ability to fully support the advanced and smart antenna technologies whereas

CDMA based systems have a limited support for this technology, as CDMA signal requires the entire bandwidth of the channel and for smart antenna technologies, complexity of the system is scalable to the bandwidth of the channel.

Deeply analyzing, it becomes clear that OFDMA is of greater advantages as compared to WCDMA however, the future evolution of UMTS like long term evolution (LTE) will also be adopting

OFDMA based multipath access technique [52].The following two block diagrams will further elaborate the difference and a comparative interpretation of the signal transmission mechanisms for the two technologies.

 

 

 

Bits 

Channel  coding        

(CC‐ TC) 

Rate 

Matching 

 

                                  Transmitting path

 

       RF       

Front‐ end 

Interleaver 

       DAC 

Data 

Mapping 

(QPSK) 

Channel            

(AWGN) 

Channelization  coding 

Scrambling  coding 

 

 

 

                                   

Receiving path 

       RF       

Front‐ end 

    ADC 

Path 

Analyzer 

Channelization  coding 

Scrambling  coding 

Bits 

 

 

 

 

 

  Decoder 

Receiving path  

De multiplexing 

RF       

Front‐end 

   DAC 

De Interleave r

Cyclic  prefix 

Rake  combiner 

 

 

 

Figure 35 

Block Scheme of UMTS Signal Transmission from WCDMA based TX to RX [53]

                Bits 

Channel 

Coding 

(Rs‐Cc) 

Matching 

(Puncturing) 

Interleaver

Mapping 

(QPSK 16, 

64 QAM) 

S/P QAM  to OFDM 

FFT (256, 512, 

1024, 2048)

 

Channel 

(AWGN) 

RF       

Front‐end 

 ADC 

Cyclic  prefix

FFT (256, 

512, 1024, 

2048)

    Bits 

Decode  viterbi

 

Channel 

Estimation and  correction 

De Interleaver De Mapping 

(QPSK 16, 64 

QAM) 

P/S OFDM  to QAM 

Figure  4.6 

Block Scheme of WiMAX Signal Transmission from OFDM Based TX to Rx [53]

 

PARAMETERS

Frequency bandwidth

Frame duration

Duplexing

Data rate

Variable data rate

Data modulation

Coding

Maximum transmit power of BS/Rs

BS antenna gain

MS antenna gain

WCDMA

2GHz

10ms

2Mbps

Variable SF, Multicode

QPSK and BPSK

6Mbps to 48Mbps

BPSK, QPSK, 16-

QAM and 64-QAM

Micro cell (4W)and macro cell 20W

Macro 17.5 dBi and micro 11dBi

0.0dBi

OFDMA

3.5GHz

20ms concatenated w9th reed

Solomon

100 mW

14dBi

0.0dBi

Table 4.3 Comparison

of WCDMA and OFDM [71]

 

 

4.2 Comparison of Modulation Schemes

Modulation is defined as a procedure in which a baseband signal, typically of low frequency is multiplied or associated with a signal of higher frequency called carrier frequency, in order to transmit the signal successfully over long distances. In all types of wireless communications, different modulation schemes are adopted depending on the network conditions. The employment of a suitable and efficient modulation scheme for the signal transmission is of great use to achieve better utilization of the radio spectrum and to minimize the transmission-reception errors. Typically,

a carrier signal is referred to as a high frequency sinusoidal signal. Modulation used in this case can either be analog or digital.

Here we shall describe and compare the merits and limitations of different modulation schemes adopted and UMTS/WCDMA and WiMAX technologies. In UMTS/WCDMA, BPSK and QPSK are employed as modulation schemes in the physical layer whereas WiMAX employs BPSK, QPSK,

16QAM and 64QAM [23] depending upon the physical requirements of the network. WiMAX has an edge over UMTS/WCDMA regarding selection and application of a modulation scheme for the transmission of radio signals that it can adopt a low level modulation technique in case of lower signal to noise ratio scenarios which have lower data rates and in case of a transmission scenario with higher signal-to-noise ratio (SNR), a high level modulation technique can be adopted for transmission. This phenomenon is termed as adaptive modulation and in some cases it is also referred to as link adaptation. In case of multipath fading and other variations in the link the concept of adaptive modulation enables the selection of a suitable modulation scheme automatically. In

WiMAX, an advantage of the concept is the uninterrupted and the continues availability of real time services like video or voice [54] It is also in accordance with one of the OFDM features that signals of different frequencies can be transmitted by employing different modulation schemes in OFDM.

The following figure will demonstrate the scenario of adaptive modulation scheme in WiMAX.

We will discuss some details of the above listed modulation schemes:

4.2.1Binary Phase Shift Keying (BPSK):

BPSK is the special type of phase shift keying technique which uses two phases that are 180° out of phase. It is considered as the most robust technique because it requires more distortion to reach an incorrect decision. However, the modulation rate is limited to only 1 bit/symbol and by employing this technique it is difficult to achieve higher data-rate where bandwidth is limited.

Q

01  00

I

Figure 4.7 

BPSK Constellations

 

 

 

 

    

   

 

 

 

 

 

   

                  

 

64 –QAM

21.33

Mbps SNR =

22 dB

 

 

 

 

 

 

Base Station

 

16-QAM 10.67 Mbps

SNR 16 dB

SNR 9dB

QPSK 5.33 Mbps

BPSK 2.01 Mbps

SNR

6dB

Figure 4.8 

Adaptive Modulation Scheme in WiMAX Cell [23]

4.2.2. Quadrature-Phase Shift Keying (QPSK)

QPSK uses four signals to represent four phases as depicted from signal space diagram

(constellation) which are 90 degrees out of phase. It can encode 2 bits/symbol which are twice as compared to BPSK with half the bandwidth needed but requires more transmitting energy and can not resist the noise as well as BPSK can. The general equation of QPSK is written as

S

QPSK

(t)=

E

S

Cos

⎢⎣

( )

π

2

⎥⎦

φ

( )

E

S

sin

⎢⎣

( )

π

2

⎥⎦

φ

( )

i

=

1 , 2 , 3 , 4

01 

00 

11

10

Figure 4.7 

QPSK constellation

 

4.2.3. Quadrature Amplitude Modulation (QAM)

With the phase difference of 180 degree QAM uses two different carrier frequency signals with varying amplitudes QAM is among one the schemes adopted in WIMAX .Depending upon number of bit used for each symbol this modulation scheme has different types or arrays .the IEEE standard

802.16 includes 16-QAM with 4 bits for each modulation symbol and 64 QAM with 6 bit for each modulation symbol for WiMAX. 64 QAM is Viewed as the modulation schemes with highest efficiency among all the schemes used in WiMAX .QPSK and 4-QAM with 4 bits per modulation symbols are considered to be similar.

16 QAM 

Q

64 QAM 

Figure 4.8  

Constellation 16QAM, 64 QAM

It can be concluded from the above description that the WiMAX has an edge over the

UMTS/WCDMA with respect to efficiency and effectiveness by virtue of the feature of adaptive modulation. However, the UMTS/WCDMA evolution i.e. HSDPA, includes the feature of adaptive modulation. Moreover, the variation is possible in WiMAX with adaptive modulation in spectral efficiency and also in the data throughputs which is associated to the variation in modulation scheme and data transmitted for each signal. As 64-QAM gives very high throughput as compared to QPSK, we can say that in WIMAX higher throughput is achieved than in the UMTS/WCDMA. Similarly,

WIMAX gives higher data rates with 16-QAM and 64-QAM as compared to UMTS/WCDMA with

BPSK or QPSK which have lower data rates comparatively. Other aspects related to the modulation schemes such as bit error rate (BER) and SNR will be discussed in chapter number 5.

     PARAMETERS      CODING 

 

           UMTS 

 

   CC.TC 

 

     QPSK 

MAPPING 

 

       WiMAX 

 

   RS‐CC 

 

QPSK,16QAM,64QAM 

 

SIGNAL DIVISION 

Spreading  by  OVSF  and 

Pseudo noise  

 

  Sequence code 

FFT:265,512,1024,2048 

Table 4.4 Main

Parameters OF UMTS and WIMAX IEEE 802.16e [53]

 

 

4.3 Comparison of Handovers

The handover procedures for WiMAX and UMTS have been described in detail in previous chapters. Here we shall take into account a comparative interpretation of handovers for both technologies .Originally, the UMTS technology was introduced for the mobile networks. Whereas the initial versions of WiMAX did not support and included any features for mobility. However some features for users mobility support were included in the later version of WiMAX i.e. IEEE

802.16e.

The first type of handover i.e. the hard handover is included in both the technologies and its function is very much similar for both WiMAX and UMTS. In case of WiMAX, the MS which is known as

UE (user equipment) in case of UMTS is linked up to only one base station. Low mobility or mobility at lower speeds is given by hard handovers only which can also be termed as portability. To attain full mobility or mobility at high speed, the WiMAX standard was provided with FBSS and

MDHO Handovers.

If MS in WIMAX and UE in UMTS have the capability of communication with all the base stations, and in UMTS case called Node Bs lying in active set, the type of hand over in WiMAX is called

MDHO which is similar in function to that in UMTS and called as softer handover. Diversity combining for the signals received in uplink and down link is possible for base station in this type of handovers.

A latest type of handover introduced in WiMAX is FBSS which unlike MDHO do not include diversity combining while it can communicate with all base stations in the active set. For FBSS the signals are processed only in the base station serving as the anchor base station. In case of change of anchor base station it doesn’t employ explicit massages for handover signalling which can be viewed as at advantage of FBSS in WiMAX [20].

Generally UMTS and 3G Technology support soft handover in mobile network where as the

WiMAX technology supports network optimized hard handovers. As this method of handover in

WiMAX makes it more bandwidth efficient for handover as compare to UMTS because soft handover maintain a simultaneous connection with more than one base station but the advantage of soft handover is that the delay for handover is reduced in it [38].

 

4.4 Comparison of Channel Impairment and Equalization

When we talk about Vehicle-to-Vehicle (V2V) communication in broadband wireless technologies like WCDMA and WIMAX, the Inter Symbol Interference (ISI) introduces high level of errors in reception at high vehicular speeds.

In order to minimize the effects caused by ISI remarkably, the method of adaptive equalization is adapted[55].Equalization enables error free reception of data by creating an ideal channel temporarily (channel).WCDMA and WIMAX have included different method of equalization as channel variation depending on the physical environment condition and also for both technologies.

Based on multipath diversity principle WCDMA employ Rake receiver for equalization [56] Rake receiver has the ability to rejoin the components of multipath for the improvement of SNR, whereas

WiMAX is based on OFDMA technique to tackle multipath fading, in order to reduce ISI and maintain orthogonality, cyclic prefix (CP) in WIMAX LMS equalization is employed for estimation of channel [56].

As compared to WiMAX which uses LMS Equalizer, WCDMA with Rake receiver has a great capability to maintain high SNR effectively because in OFDMA systems like WiMAX the channel estimation becomes more complicated and difficult in case of higher delay spread when multipath channel exceeds the CP length (channel). CDMA systems like WCDMA make the integrity of data guaranteed while moving at high speeds.

 

4.5 Comparison of Architecture

The architectures of both technologies i.e. WiMAX and UMTS/WCDMA will be compared in this section. The IEEE 802.16 is referred to as mobile WiMAX famous commercially among the broadband wireless access technologies, which is a challenge for future of UMTS/3G networks( 2 arch of 3g/WiMAX).Mobile WiMAX is able to provide at least 15 Mbps data rate with full mobility with in a radius of 4km and is also considered better alternative to the fully launched UMTS/3G networks with respect to its voice quality and narrow band signals .WiMAX forum has recently developed its mobile architecture to provide end to end services beyond air interface.

WiMAX mobile system model is consists of the following elements. Mobile user terminal, access service network (ASN), connectivity service network (CSN), user terminal application agent and

Mobile Subscriber Station (MSS) fig (4.11) Mobile Host (MH) and base station transceivers are responsible to maintain the traffic through air interface because both are situated at the same network edge .Further ASN, BTS and CSN are linked up with whole IP core network.ASN contains many

BTSs and Numerous ASN gateways .ASN has several responsibilities such as Quality of services, security, mobility, and MS access. Core network functionality is carried out by (CSN), where it has a number of tasks to be accomplished like call admission control, assigning the IP address and billing.

One of the (CSN) responsibilities is to establish a link between WiMAX and 3G networks through roaming.

Figure 4.9  

WiMAX Architecture [57]

On the other side, UMTS architecture provides support for packet related traffic. Architecturally, it contains three main parts. User Equipment, UTRAN and Core Network (CN). UTRAN is comprised of two main parts, node B and RNC. Core network is composed of SGSN and GGSN where GSSN is responsible to provide link with external packet switched data while SGSN is capable to link up with RNS through IuPS interface and Uu interface is able to connect the UE and UTRAN.

 

 

UE                   NODE B            RNC              SGSN        GGSN 

EXTERNAL IP NETWORK 

              

Figure 4.10

UMTS Integration

WiMAX is one of the all IP based technologies which further based on OFDM. It has been deployed globally. IEEE 802.16e, which is most pioneering standard of the WiMAX, focuses on its radio link especially on physical and MAC layers. (Networking Group)WiMAX NWG has provided three main stages for end to end architecture of WiMAX .Stage one provides service requirements regarding service provider working group. Stage two is focused on architecture and a stage three explains its architecture.

  

The network architecture working Group (NWG) of WiMAX forum has designed particular architecture and protocol which support mobility. The basic architecture of the two networks is illustrated in the figure below.

Figure 4.11 

Network Architecture for UMTS and Mobile WiMAX [57]

At higher levels both architectures are same but different protocols are used at every interface. One of the key factors of designing architecture of WiMAX network is to provide internetworking between 3GPP and WiMAX networks. The network architecture of WiMAX can rightly be interpreted as an all IP network without any involvement of circuit telephony. The all IP network gives higher operational efficiency and a reduced cost of operation with high scalability. The network architecture of WiMAX is based on packet switched structure. The network architecture of

WiMAX also supports modularity and flexibility to adjust a large range of deployment [58] the end to end architecture of WiMAX supports multimedia services, voice over IP, and also IP broad cast and multicast services.

Some basic differences between the network specifications of WiMAX and those of UMTS will be discussed on comparative basis. Mobility is handled at intra-RNC inter-RNC, intra SGSN and inter

GGSN level [58] in 3G cellular system.

This multilevel mobility support adds complexity to network architecture in UMTS. Whereas

WiMAX is considered to include a simplified and seamless mobility features which can accommodate different configuration of ASN.

The latency Issues are greater for a network with multiple control points as in UMTS architecture and convergence of different application like data, voice and video become more complex while mobile WiMAX network architecture has less number of control points and a simplified design of architecture helps in decreasing the level of latency in WiMAX network architecture .

The 3G (UMTS ) network architecture suffers from overlap in functionalities like authentication for security purpose and end-to-end Quality of service for admission control whereas the WiMAX network architecture do not suffer from such complexities and difficulties[59].

4.6 Capacity and Coverage Comparison

Here, capacity and coverage aspects for both the technologies will be discussed and compared.

4.6.1 for WCDMA

In WCDMA, Capacity is referred to as the capacity of a single cell in WCDMA network. Capacity can be described as the maximum amount of bits that can be communicated or the maximum number of simultaneous calls (services) which a cell can support.

In WCDMA, capacity is viewed as a three dimensional entity which is interconnected to the coverage and QoS mutually. Cell capacity in WCDMA network can also be defined as the number of maximum DPCHs which can be assigned simultaneously in a cell in WCDMA network. The radio access network control the transmit power at each DPCH in order to maintain Eb/Nt (energy per bit to noise spectrum density ratio) constant for having a required QoS [60].The Radio access network of WCDMA in accordance with the changing channel conditions has the ability to adjust the power transmitted for every PDCHs in order to maintain signal to noise ratio (Eb/Nt) constant. The cell capacity is also effected by data rate(Rb).An increased interference is observed when the data rate is high because transmission power becomes high for high data rate and as a result capacity in decreased. The cell capacity in WCDMA depends on mobility of channel, its application types and requirement of QoS.

According to UMTS release 99, the data rate of voice service radio channel is selected as 12.2Kbps.

A data rate of 64Kbps is selected in UMTS for circuit switched data whereas for packet switched data, UMTS services employ 384Kbps data rate. In WCDMA system the cell coverage is found to be highly dependent upon the nature of service used and the extent of loading of the cell [60].

The core objective of capacity planning is to provide the support for users with less delay and no blocking of traffic and the coverage for cellular networks is referred to as the mobility of service for the whole (entire) network area.

 

  WORLD CELL 

 

  ZONE   4 

 

  ZONE   3 

 

ZONE 2 

 

                                      

 

PICO CELL

Figure 4.12 

UMTS Cell Structure [61]

 

Cell 

Pico Cell 

Micro CELL 

Macro Cell 

World cell  coverage 

2Mbps 

384Kbps 

188Kbps 

Un defined  

Table 4.5 

UMTS cell coverage comparison

4.6.1.1. Coverage and Cell Range in WCDMA

The range of cell or coverage of cell in WCDMA is determined in following steps:

• Calculation of propagation loss.

• Determination and calculation of link budget for radio wave propagation.

As a secondary step after selecting cell range, the cell coverage is determined by using any of the propagation models like, okurama-Hata, Walfish-ikegamiete by using relation.

S=K

The area of coverage for a cell with hexagonal configuration is calculated where

S = Coverage Area

R = Maximum Cell Range (It also explain that sectored cells are not in hexagonal shape).

K= Constant

4.6.2 FOR WiMAX

For WiMAX and any other cellular system the term capacity is referred to as the measure of data which can be communicated to and from the users. For any channel a limit exists that how much amount of data can be transferred reliably? Capacity of a WiMAX system can be determined by calculating the data rate for every unit of frequency bandwidth which the system can support to deliver. The capacity can also be determined by quantification of the numbers of users which the system or a sector or a channel can support.

WiMAX system simultaneously facilitates all the users to subscribe to the services such as browsing

Emailing, Downloading, videos and files. However the system performance is changed regarding its demand. Due to different functionality there might be high data rate on downloading then up loading. In other way the capacity maintains the load when distinct users exist on a system and it also specify the actual point where load exceeds the ability to deliver of every sector.

WiMAX holds the capability of changing the modulation techniques automatically and dynamically depending upon the location of users in order to increase and improve the coverage and its range.QAM modulation is used for the devices which are located nearer to the base transceiver stations(BTS).QAM is consider to most efficient modulation scheme with higher value of spectral efficiency .on the other hand, for the users located at the edge areas of the cell or at indoor location,

QPSK is used which has less spectrum efficiency. Only 20% of maximum data rate throughput of

QAM 5/6 can be achieved when using QPSK 1/2[60].

Figure 4.13 

Data Rate of Impact Modulation in WIMAX Network [62]

The data rate is a random variable which depends on user's type and modulation technique used.

Special consideration is given to frequency reuse factor in every channel. The system capacity in

WiMAX is improved by the use of adaptive modulation. In WiMAX therefore a base station should necessarily be placed in the area with high concentration of users, which provides efficiency in adaptation of modulation types.

Location or distribution of users and kind of service which they require are the factor upon which the capacity of WiMAX system is dependent. In WiMAX capacity depends upon C/I ratio because greater spectral efficiency can be achieved using high constellation modulation. [62].

.

The WiMAX network architecture supports the concept of macro BTSs (multi sector) in order to attain and effective outdoor coverage with a fixed number of BTSs. The use of micro cells and Pico cells in the outdoor or extended residential coverage with Femto-cell is possible as illustrated below table

Sector

Macro cell

Usually

Range

( Urban area)

500-1,000m

Average sector capacity (10

MHZ channel)

10-15Mbps

Target cost

High

Site requirements

High

Micro cell

1-3

300-500m

10-15 Mbps

Medium

Medium

Pico cell

1

150-300m

10-20 Mbps

Low

Low

Pico cell

1

Indoor enterprise, public areas

10-25 Mbps

Low

Low

Femto cell

1

Indoor residential

10-25Mbps

Very low

None

 

Table 4.6   

WiMAX Different Coverage Range [62]

 

WiMAX provide 50km coverage for LOS and 8km for NLOS situation. But however in practical it support 7 to 10 km in fixed broadband access and at least 200m to 7 km for portable [62].

4.6.3. Capacity Estimation for WiMAX and WCDMA

Here some estimation is given for the capacity of WCDMA and WiMAX. Receiver sensitivity of spread spectrum which is defined through this equation [63]

P rss

=

F

+

KTW

+

E

N

0

b

W

R

(4.1)

In above equation parameters represent

F= Noise figure in dB

K=Boltzmann's constant which is equal to 1.381

w ⁄ HZ ⁄ K

T= Temperature which is equal to 290K

W= refer to WCDMA chip rate

EЬ ⁄ N₀= bit energy to noise spectral density in dB

R = bit rate in Kbps

In WiMAX receiver sensitivity is given as [64]

  

P r

, min

=

SNR rx

+

10 log

10

(

W

)

+

N

0

(4.2)

Where SNR is the signal to noise ratio and W is the effective signal bandwidth and F is 12dB

It shows that the procedure of sampling and channelization is occurring due to band utilization, by resulting there is no share of total bandwidth during the transmission of information .so there is needed to rewrite the equation where W show the useable bandwidth of subcarrier umber which is illustrated by the following figures.

Nυsed =192 which applicable for all subcarriers

Nғғт =256 which represent number of sub channel

Number of sub channel shows N sub channel and sampling frequency Fs (MHz) and sampling factor shown the given equation [65,66]

P rmim

=

SNR rx

+

10 log

10

⎜⎜

F s

N used

N subchan

16

N

FFT

⎟⎟

(4.3)

Fs

=

8000nW

800

E b j

.

Rj

.

Vj

N

0

In the above equation ’i’ represents other-to-own cell interference. For WCDMA,

T

WCDMA

=

1

BLER

⎜⎜

E b

N

0

⎟⎟

E b

W

N

0

Throughput for WiMAX is given by

+

R

i

1

+

1

η

(4.4)

T

WiMAX

=

Fs

C r

G

E f

+

1

N

N used

FFT

(4.5)

Where

E f

represent number bit/ symbol of modulation technique

Cr represents Coding rate,

G is rate of Guard period Tg to the bit period Tb and

G=1/ x is equal to 1 to 5

So

T s

=

T b

+

T g

(4.6)

It can be concluded from all the above discussion regarding capacity and coverage of the two technologies that is WCDMA and WiMAX that as compare to WCDMA, WIMAX is capable of supporting high throughput and therefore can be viewed as a technology with better capacity then

WCDMA. High data rate transmission depends on the location of subscriber. The distance of the subscriber of the base station determines the transmission data rate to be adopted as a result of implying Adaptive Modulation and Coding (AMC) in WiMAX.

4.7 Spectral Efficiency

Spectral efficiency can be defined as the amount of traffic which a system can transmit for a particular spectrum. A higher system spectral efficiency offers high quality of service to the end client for particular traffic load. Some factors are necessary to achieve efficient spectrum which are directivity of antennas, sharing the frequency, time distribution, environmental spacing and orthogonal frequency .Spectral efficiency is one of the key factors to attain high cell capacity. [67]

Spectral efficiencies of WiMAX and UMTS/WCDMA will be studied in this section. In WCDMA system a large frequency i.e. of 5MHz is specified for channels 5MHz. Each call is compressed to the maximum range of 8500 bit/s and also there are 100 simultaneously calls are possible in same cell. Due to spread spectrum it is possible to have the minimum frequency reuse factor as 1[68].

If we talk about WIMAX there are 2.5GHz or 3.5GHz licensed spectrum selected for it.3.5 GHz band is basically of vital practical importance in the given range of 3.3 to 3.8GHz.

In mobile WiMAX as referred to IEEE802.16e, it has not been finalized for its specifications yet however it provides 37 Mbps as good performance.5MHz WiMAX offer the speed of 18.7Mbps which is already similar to UMTS release 5 HSDPA with speed of 14.4 Mbps [68].

WiMAX provides a high spectral efficiency then WCDMA. In some scenarios, the given range 2 .5 or 3.5 licensed band where spectrum availability limits the deployment of WiMAX with higher frequency. These bands do not have good performance as compare to 1.8, 1.9 and 2 GHz band due to its RP propagation. In fact, WiMAX has greater RF performance as compared to 3G because of its wide spectrum. If we compare WiMAX at 3.5GHz with WCDMA at 2.0GHz in IM 2000 band then

WiMAX' s enhance performance agrees to present a feasible subscriber performance. Although

there will be a poor propagation with high frequency. Spectral efficiency of WiMAX also allows the operator to provide advanced standard performance as compared to WCDMA.

 

Standard 

 

 

 

Net bit rate R   frequency channel 

Mbit/s

 

Bandwidth  B  /frequency  channel(MHZ) 

 

Link spectral efficiency R/B 

(Bit/s) Hz 

WiMAX

 

IEEE 802.16‐2004 

 

 

                                96

 

 

20(1.75, 3.5, 7…..)

 

 

4.8

 

 

 

Frequency reuse factor I/K 

 

System spectral efficiency 

(Bits/s)Hz/site 

UMTS/WCDMA

 

WCDMA    FDD

 

1/4 

 

 

1.2

 

 

 

 

MAX 0.384/mobile 

 

 

 

 

0.077/mobile 

 

                              1 

                           

 

 

0.51 

 

Table 4.7   

Spectral Efficiency Comparison [69]

Chapter 5

SIMULATIONS 

 

I n this chapter, simulation results will be discussed. As discussed in the previous chapters that adaptive modulation is used in WiMAX. WiMAX utilizes BPSK, QPSK, 16-QAM and 64-QAM while WCDMA uses QPSK and 16-QAM as transmission techniques. Here in this chapter, a comparison of all these modulation schemes will be done.

5.1 Simulations Using AWGN Channel Model

In our simulations, we will calculate the Symbol Error Rate (SER) of each modulation scheme and plot it against Eb / No Where SER is the bit error rate while Eb / No is the energy per bit per noise.

There will be a comparison of theoretical calculated values of BER and simulated values of BER depending upon our simulation model. SER and Eb / No are very important parameters in communication system. The overall efficiency of the system depends on the values of SER and for very small values of SER the system is said to be efficient. Eb / No give information about the signal power and if a relation is found between these parameters then it is of great important.

 

 

                       

Random bits 

Generation 

Modulation AWGN 

Channel

Demodulati0n 

     

Comparison of Theoretical  and practical Results

 

Figure 5.1 

Simulations Model with AWGN Channel 

 

 

Above is the block diagram of our simulation model and it will be implemented in Matlab. This model will be used for all the above discussed modulation schemes. In our simulation model, first

we generate random bits. In our simulation we are generating one million random bits. After that symbols are made using these bits. The length of these symbols can vary in different modulation schemes e.g. in case of BPSK one bit is used to represent one symbol but in QPSK two bits represents one symbol. That’s why we are taking 1 million bits. With these one million bits the execution time of our program is around 5 minutes and if we generate more bits then the program will take much more time.

Then these bits are modulated using different modulation schemes. First BPSK will be used then

QPSK, 16-QAM and 64-QAM. After modulation, the signal is passed through Additive White

Gaussian Noise (AWGN) channel so that random noise can be added to the signal. Then the signal is demodulated and a graph between the SER and Eb / No is plotted which shows the simulated results.

Also a graph containing theoretical values of SER and Eb / No is plotted to get an idea about the difference between our simulated results and theoretical results. Here we will discuss all our simulated plots.

 

5.2 BPSK

In BPSK one bit is used to describe one symbol so BER is equal to the SER. The theoretical formula for the calculation of BER of BPSK is

P b

=

1

2

E b

N o

 

 

 

 

 

 

In the above graph the theoretical and simulated SER of BPSK is depicted. SER is plotted against different values of Eb/No. The blue curve is showing the theoretical values and pink graph is showing the simulated values. From the graph, it is clear that the theoretical and simulates values of

SER are almost the same. There is only a little difference when the value of Eb/No is near to 10 dB.

Symbol error probability curve for BPSK modulation theory simulation

10

-3

10

-4

10

-1

10

-2

10

-5

-2 0 2 4

Eb/No, dB

6 8 10

 

 

                                                                                               Figure 5.2

 

5.3 QPSK

QPSK is also known as 4-QAM. In QPSK two bits are used to represent one symbol. BER is not equal to the SER. The theoretical formula for the calculation of SER in QPS is  

 

P e

erfc

E

2

N o

 

But QPSK system shows two bit /symbol so transmitted signal/symbol energy is twice the signal energy / bit i.e. E=2E

b

In term of

E b

N

0 the average probability of symbol error is equal to

p

erfc

E b

N

0

 

10

0

S

QPSK

(t) =

E

S

Cos

⎢⎣

( )

π

2

⎥⎦

φ

( )

E

S

sin

⎢⎣

( )

π

2

⎥⎦

φ

( )

i

=

1 , 2 , 3 , 4

 

Symbol error probability curve for QPSK(4-QAM) theory-QPSK simulation-QPSK

10

-1

10

-2

10

-3

10

-4

10

-5

-2 0 2 4 6

Es/No, dB

8 10 12 14

 

                                                                                                      Figure 5.3

 

This graph is showing the theoretical and simulated values of SER for QPSK. The theoretical and simulated values are the same but after 12 dB there is a slight difference between the values.

 

5.4 16-QAM

In 16-QAM, four bits are used to represent one symbol. The theoretical formula for the calculation of SER in 16-QAM is

p e

2

1

1

M

erfc

2

3

E

(

M

av

1

)

No

 

Where

M

=

 

For practical purpose M-ary QAM is given by

p e

2

1

1

M

erfc

E

N o o

 

10

0

Symbol error probability curve for 16-QAM modulation theory simulation

10

-1

10

-2

10

-3

10

-4

 

10

-5

0 2 4 6 8 10

Es/No, dB

12 14 16 18 20

 

                                                                                                    Figure  5.4

 

In the above figure both the theoretical and simulated values of SER for 16-QAM are shown. There is a slight difference in values when Eb / No are less than 10 dB but after that the values are almost the same.

5.5 64-QAM

In 64-QAM, 8 bits are used to represent one symbol. The theoretical formula for the calculation of

SER in 64-QAM is

p e

2

1

1

M

erfc

2

3

E

(

M

av

1

)

No

 

10

0

Symbol error probability curve for 64-QAM modulation theory simulation

10

-1

10

-2

10

-3

10

-4

10

-5

0 5 10 15

Es/No, dB

20 25 30

 

Figure 5.5

 

The theoretical and simulated values of SER are almost the same for 64-QAM as shown in the above figure.

10

-3

10

-4

10

0

10

-1

Theoatical Symbol error probability for different modulation schemes

BPSK

QPSK

16-QAM

64-QAM

10

-2

10

-3

10

-4

10

-5

0

10

-5

0 5 10 15

Eb/No, dB

20 25 30

Figure 5.6

 

10

0

10

-1

Simulated Symbol error probability for different modulation schemes

BPSK

QPSK

16-QAM

64-QAM

10

-2

 

5 25 30 10 15

Eb/No, dB

Figure 5.7

 

20

 

The above two figures show the theoretical and simulated results for all of the four modulation schemes. Form the above figures it is clear that the theoretical and simulated results for all the modulation schemes are almost the same. This shows that the simulation model is quite efficient.

From the graphs it is also visible that BPSK has the least SER when compared to all the other modulation schemes. QPSK is the also very efficient but it has higher SER as compared to BPSK.

16-QAM and 64-QAM are less efficient in terms of SER when compared to QPSK and BPSK. But

64-QAM has the highest data rates. When the channels conditions are very good means the value of

Eb / No is high then 64-QAM can be used to provide high data rates. 16-QAM has relatively less data rates when compared with 64-QAM while QPSK and BPSK have even less data rates than 16-

QAM.

 

5.6 Simulations using Rayleigh Fading Channel Model

In the previous model, AWGN channel was used for transmission. In this new model we will use

Rayleigh fading channel for transmission. By the introduction of Rayleigh fading channel in our transmission model, there is a need of using OFDM as a transmission technique in WiMAX and

WCDMA in case of UMTS. Rayleigh fading in normally caused by the multipath interference in the transmission channel when we have Non-Line of Sight (NLOS) between the transmitter and the receiver. In most of the cellular networks there is NLOS path between the transmitter and the receiver so Rayleigh fading is essential in all these networks. As it is discussed earlier that Rayleigh fading is caused by the multipath propagation of radio waves in free space. Due to reflection, refraction, diffraction and scattering phenomena’s multiple copies of the same transmitted signal are received at the receiver with different time intervals.

Reflection

When radio waves collide with an object which has higher length then the wavelengths of radio waves then the radio waves come back by making the same angle at which they collided with the object.

Diffraction

This happens when radio waves collide with the edge of an object which has higher length as compared to the wavelength of the radio wave. The radio waves bends after striking to the edge of that object.

Scattering

When radio waves strike with an object that has same or less length as compared to the wavelength of the radio waves then this wave is divided into all direction by making different weaker radio waves. All these phenomena’s are shown in the figure below.

 

                                           Figure 5.8

Reflection, Diffraction and Scattering [72]

Refraction

This phenomena occurs when radio waves enter from one medium to another medium. For example when they travel from air and enter in water, there is a slight change in the propagation path and they just bend by making some angle of incident.

                                                         

Figure 5.9

:

Refraction [72]

 

 

                                                

Figure 5.10

Multipath Propagation of radio waves. [73]

In the above figure multipath propagation of radio waves is shown. It is clear from the figure that multiple copies of the same signal are arriving at the receiver. These copies come at the receiver on different time intervals. This make very difficult for the receiver to recognize the original signal as multiple bits are there for a single bit. These bits are different from each other due to their different time of arrival. These different signals are causing Inter Symbol Interference (ISI) at the receiver end as the receiver is unable to identify the original signal. To overcome this problem OFDM is used as a transmission technique.

Our new simulation model is shown in the figure below. In this model, Rayleigh fading channel is used as a transmission medium. First random bits are generated, and then theses bits are modulated using OFDM. After that these bits are passed through a Rayleigh fading channel. At the receiver end the received signal is modulated and the original signal is recovered from it and then we perform a comparison between our theoretical and practical results.

 

 

 

 

 

 

                                                                                                                                                                             

  

Random  OFDM  Demodulation 

Rayleigh 

Fading 

Channel 

                

Comparison of Theoretical and practical Results

Figure 5.11 

Simulation Model with Rayleigh Fading Channel 

10

0

10

-1

BPSK Mod

QPSK Mod

16QAM Mod

64QAM Mod

10

-2

10

-3

10

-4

0 5 10 15 20 25

SNR dB

30 35 40 45 50

Figure 5.12 theoretical value of SER in OFDM 

 

10

0

10

-1

10

-2

10

-3

10

-4

BPSK Mod

QPSK Mod

16QAM Mod

64QAM Mod

 

0 5 10 15

SNR dB

20 25 30

 

Figure 5.13 probability of error in term of SNR 

In M-ary psk probability of error can calculate by using this formula.

p e

erfc

E

N

O

S

sin

π

M

Probability of error for M ary QAM has been calculated by following formula.

P e

2

⎜⎜

1

1

M

⎟⎟

erfc

2

(

M

3

E

1

S

)

N

O

In the above figures, theoratical values of SER for BPSK, QPSK, 16QAM and 64 QAM by using

Rayleigh fading channel and OFDM are depicted. From the graph it is clear that by using Ralyeigh fading we are having high values of SER against SNR. This is due to the multipath interfernce. And in figure 5.13, we observed that BPSK is most efficient to achieve same probaility of error in term of SNR with other modulation techniques.

Chapter 6

  

    CONCLUSIONS 

6.1 Conclusions

T here exists an environment of hard competition between WiMAX and 3G cellular systems such as UMTS and other CDMA systems in the field of mobile broadband. After discussing various features of both the technologies including architecture, radio access techniques, mobility, robustness and physical layer parameters in detail, we can conclude that not a single technology of the two can be declared completely suppressing the other.

WiMAX has a tendency to become a complementary wireless board band technology to UMTS

(3G). Initially the 3G and the UMTS networks were designed as a network for the transmission of the voice but afterwards, it was upgraded to include data transmission capability as well. Whereas

WiMAX was aimed at complementing the 3G networks with capability of high speed data services.

With extended broadband capability, distance service capability and an effective QoS for voice support, WiMAX is becoming a great threat to UMTS.

The WiMAX technology encircles some dominating features of advantage over UMTS. For single carrier and multicarrier operation, WiMAX can support both FDD and TDD. Advance quality of service, scalability, higher support for mobility, very flexible architecture with high data rate and advance security features are also the highlighting features of WiMAX technology. The air interface of WiMAX is considered to be highly robust and flexible. OFDM is employed in the physical layer of WiMAX which deploys features like cyclic prefix (CP) and Inverse Fast Fourier Transform

(IFFT) which helps in cooping with multipath effect and reducing ISI. Mobile WiMAX gives better performance as it employs OFDMA as multiple access technique. Adaptive modulation and coding, sub channelization and multiuser diversity are among distinguishing features of OFDMA. WiMAX includes strong and a very effective error coding in the Physical Layer. MAC Layer of WiMAX provides support for power saving operation and its architecture has the capability for different types of QoS support. More ever it’s PDU construction, ARQ mechanism and power full authentication and string encryption. Techniques provide better security in user data transmission. Due to flexible architecture it provides support for its handling model such as fixed, mobile and also nomadic. One of the features of reference model is providing interoperability between the networks. The network support paging for the base station and also inactive mode operation.

Here we will discuss UMTS which employs WCDMA as radio access technology, which mainly employs QPSKP as modulation technique and DSCDMA (Direct Sequence Code Division Multiple

Access) for signal spreading. UMTS is capable of offering packet switch and circuit switch services by employing ATM technology. In the WCDMA is under going a process of evolution at the time and all IP core based network is provided in specifications of WCDMA RELEASE 2000 with effective IP support. However, the up coming 3GPP releases are supposed to provide higher data rates and work is in progress over High Speed Packet Access (HSPA) which may include feature like adoptive modulation and coding, Hybrid Automatic Repeat Request (HARQ), and reduced from size. It is also expected to include a fast cells side selection mechanism and uplink DCH Associated with Access Control Channel (ACCH).

It can be observed by comparing WiMAX and UMTS features that generally WIMAX is capable offering better services then UMTS. It provided solution for some of the technical complexity and flaws cellular networks like UMTS. It has been found more spectrally efferent and flexible .both

LOS and NLOS data transmission are supported in WiMAX with increased security mechanism and higher bandwidth. WiMAX is soon expected to provide the facility of high speed connectivity to internet for all users any time and at any place in static and moving position.

 

6.2 Future Work

In future architecture can be proposed for the interworking of the both technologies. WIMAX and

UMTS employing IP as a common interconnection protocol the seamless connection of mobiles becomes possible to the different networks (internetworking).

The said internetworking architecture for UMTS and WiMAX may possible is based on 3GPP standard. The so called internetworking model should address the issues of architecture, IP address management, seamless handover procedure i.e. handover from access network of WiMAX to

UTRAN (UTMS) and handovers from UTRAN to WiMAX access network efficiently and affectively. UMTS and WiMAX interworking architecture should promised reduced losses due to switching between the networks i.e. low packet loss and reduced time of interruption. In future mobile broad band user can be facilitated if the proper 3GPP WiMAX interworking architecture is provided with lower handover latency and reduced packet loss. A roaming architecture and efficient mobility scheme is needed in future regarding multiple operator environments.

                                 

REFRENCES 

[1] http://www.motorola.com/staticfiles/Business/Products/Mobile%20Computers/Handheld%20

Computers/_Documents/staticfile/3G_Whitepaper_0608.pdf

[2] P.R Jordi, S.Orial and A.Ramon,”Radio resource management strategies in UMTS”. John

Wiley& Sons, Ltd 2005

[3] J. Bannister, P. Mather & S. Coop "Convergence technology for 3G networks IP, UMTS,

EGPRS, and ATM ", p.3, John Wily & Sons, Ltd 2004.

[4] H. Holma & A. Toskala”WCDMA for UMTS – Radio Access for Third

[5] G. Mikeal, “Third generation radio access “Ericson research, Munich, 1999.

[6] William Stallings, “Wireless Communications and Networking”, Prentice Hall, 2003.

[7] http://www.symatech.net/wcdma

[8] Qualcomm, commonalities between CDMA and WCDMA technologies: Qualcomm incorporated http://www.qualcomm.com/common/documents/white_papers/Commonalities_CDMA2000_WCD

MA_wp.pdf (Jan, 2009)

[9] Heikki Kaaranen, Ari Ahtiainen, Lauri Laitinen, Siamäk Naghian,Valtteri Niemi: UMTS

Networks Architecture, Mobility and Services, John Wiley & Sons, Ltd 2005.

[10] B.Walke, P.Seidenberg and M.P.Althoff, “UMTS the Fundamentals”, John Wiley & Son, Ltd

2001.

[11] http://www.freepatentsonline.com/5991407.html authentication center

[12] http://www.umtsworld.com/technology/UMTSChannels.htm

[13] http://www.scribd.com/doc/7072747/UMTS-Physical-Layer

[14] UMTS, UMTS/IMT-2000 “Assessing Global Requirements for the Next

Century”, Report No. 6, UMTS Forum, London, UK, 1999

[15] http://www.umtsworld.com/technology/RCC_states.htm

[16] Stijn N. P. Van Cauwenberge; "Study of Soft Handover in UMTS", Technical University of

Denmark, University of Gent, Belgium, July 31, 2003.DTU

[17] http://www.3g4g.co.uk/Tutorial/ZG/zg_handover.html

[18]Jussi Laukkanen “UMTS Quality of service concept and Architecture”, University of Helsinki,

4-5-2000

[19] UMTS, UMTS/IMT-2000 “Assessing Global Requirements for the Next

[20] Z.Becvar, J.Zelenka, R Bestak,” comparison of handovers in UMTS and WiMAX” Czech technical university in Prague, department of telecommunication Engineering.

[21] http://www.umtsworld.com/technology/handover.htm

[22] http://sabyasachi.tripod.com/publications/3Gdata.pdf

[23] D. Pareek, the Business of WiMAX, John Wiley, 2006.

[24] “IEEE Standard 802.16 for Global Broadband Wireless Access,”

http://ieee802.org/16/docs/03/C8021603_14.pdf” last accessed 15.05.09

[25]IEEE STD 802.162001,”IEEE Std. 802.162001” IEEE Standard for Local and

Metropolitan area networks Part 16: Air Interface for Fixed Broadband Wireless Access

Systems”, December 2001

[26] IEEE Std 802.16e2005 and IEEE Std 802.162004/Cor 12005(Amendment and Corrigendum to

IEEE Std 802.162004),”IEEE Standard for Local and metropolitan area networks Part 16: Air

Interface for Fixed and Mobile Broadband Wireless Access Systems Amendment 2: Physical and

Medium Access Control Layers for Combined Fixed and Mobile Operation in Licensed Bands and

Corrigendum 1”, February 2006

[27] Derrick D. Boom, “Denial Of Service Vulnerabilities In IEEE 802.16 Wireless

Networks”, Master’s Thesis at Naval Postgraduate School Monterey, California, USA,

2004

[28]A.G.Jeffrey, G.A runabha and M.Rias,”Fundamentle of wimax: Understanding Broadband

Wireless networking, prentice Hall, Fubruary 2007

[29] Syed Ahson, Mohammad Ilyas, “WiMAX Technologies: Performance Analysis and QoS”, CRC

Press, 2007

[30] WiMAX Forum, “Documentation, Technology Whitepapers”, [Online]. Available at WiMAX

Forum.org: http://www.wimaxforum.org/resources/documents [Accessed: Feb 20, 2009]

[31]IEEE802.16, IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems IEEE Standards 802.16-2004 (Revision of IEEE

Standards 802.16-2001). 2004.

[32] www.wimaxforum.org.

[33] www.wifi.org.

 

[34]1IEEE802.11, IEEE Std 802.11g-2003 [Amendment to IEEE Std 802.11, 1999 Edition (Reaff

2003) as amended by IEEE Standards 802.11a-1999, 802.11b-1999/Core 1-2001, and 802.11d-

2001], Amendment 4: Further Higher Data Rate Extension in the 2.4 GHz Band. 2003.

[35]IEEE802.11, IEEE Standard for Information Technology-Telecommunications and information exchange between systems-Local and metropolitan area networks-Specific requirements-Part 11:

Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications. 1999.

[36]Maya Ayache,E.A., Milan Zoric, Jose de La Plaza, Mobile WiMAX Plug fest Whitepaper. 2006:

WiMAX Forum. p. 1-14.

[37]Group, W., IEEE Standards 802.16e-2005 and IEEE Standards 802.16-2004/Core 1-2005, Part

16: Air Interface for Fixed and Mobile Broadband Wireless Access Systems. 2006. p. 1-864.

[38]Douglas, Mobile WiMAX - Part 2: Comparative Analysis. 2006. p. 47.

[39]Rethink, Evolution path for fixed WiMAX sought as mobile standard ratified. Wireless Watch,

2006.

[40]Douglas, Mobile WiMAX - Part 1: A Technical Overview and Performance Evaluation. 2006: p.

1-53.

[41]Demcgrew, WiMAX Service Provider Working Group Final. 2004, WiMAX Forum: WiMAX

Forum. p. 1-9.

[42] Abdul. R Usmani, Mobile WiMAX, Wateen Telecom Available online:

http://abdul.usmani.googlepages.com/Mobile-WiMAX-V1.0170207.pdf

,[43] http://fireworks.intranet.gr/Publications/Fireworks_6CTUPB008a.pdf

[44] WiMAX and wireless network, [online].Available www.wifinotes.com/wimax/how-wimaxworks.html [Accessed: March. 2.2009].

[45] http://www.althosbooks.com/into80wi.html

[46]K.AktAul,”Comparative analysis of WLAN, WiMAX and UMTS technologies” PIERS proceedings; Department of Electronics & Communication Engineering

Electrical and Electronics Faculty, dildiz Technical University, Istanbul, turkey, 2007.

PIERS Proceedings, August 27-30, Prague, Czech Republic, 2007

Comparative Analysis of WLAN, WiMAX and UMTS Technologies

[47] Wikipedia contributors, "Physical layer," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Physical_layer&oldid=211090774

Last accessed March. 2009

[48] WiMAX Forum website, “Mobile WiMAX – Part I: A Technical Overview and

Performance Evaluation”, 2006.

[49] Lars Ahlin, Jens Zander, Ben Slimane, Principles of Wireless Communication,

Student literature 2006.

[50] http://www.safecomprogram.gov/NR/rdonlyres/695E6803-4D9C-40FD-8E57-

FE57C273E48A/0/SIAR_Multiple_Access_Techniques.pdf

[51] J. G. Andrews, A. Ghosh, R. Muhammad, Fundamentals of WiMAX Understanding Broadband

Wireless Networking, Chapter 2, Prentice Hall, 2007.

[52] 3GPP Technical Report, 25.899, HSDPA Enhancements; Release 5, version 6.0.0.

June 2004

[53] S. Claudio, Z. Olga, OBJECT-ORIENTED MODEL OF SDR LIBRARY FOR

WIMAX/UMTS SYSTEM BASEBAND LEVEL Technical Report # DIT-07-039

[54] Rony Kowalski, “The Benefits of Dynamic Adaptive Modulation for High Capacity

Wireless Backhaul Solutions”, Ceragon Networks, [Online]. Available: http://www.ceragon.com/files/The%20Benefits%20of%20Dynamic%20Adaptive%20Mo dulation.pdf [Accessed: Feb 21, 2009]

[55] Simon R. Saunders and A. Aarago’n-Zavala “ANTENNAS AND

PROPAGATION FOR WIRELESS COMMUNICATION SYSTEMS” Second

Edition, John Wiley & Sons Ltd, 2007.

[56] B. Rabindranath,S.Sanjib et al., “Wi-Fi, WiMAX and WCDMA, a comparative study based on

Channel Impairments and Equalization method used” Sikkim Maniple Institute of Technology,

Sikkim Manipal University, majitar, rangpo, East Sikkim 737132.

[57] Timo Smura,” COMPETITION BETWEEN EMERGING WIRELESS NETWORK

TECHNOLOGIES: CASE HSPA VS. WIMAX IN EUROPE” Helsinki University of Technology /

Networking Laboratory HUT, FINLAND

[58] Sanida Omerovic, WiMAX Overview Faculty of Electrical Engineering, University of

Ljubljana, Sloveni Faculty of Electrical

[59] Kwang-Cheng Chen Mobile WiMAX Edited by National Taiwan University, Taiwan J.

Roberto B. de Marca Pontifical Catholic University, Brazil

[60] QUALCOMM, Air interface cell capacity of WCDMA SYSTEMS: Qualcomm incorporated

Aug2006.http://www.qualcomm.com/common/documents/white_papers/Air_Interface_Cell_Capacit y_of_WCDMA_Systems.pdf

[61] http://www.three-g.net/3g_umts_spectrum.pdf

[62] http://www.senzafiliconsulting.com/downloads/SenzaFili_IndoorCoverageSurvey.Pdf

[63] J. S. Lee et al. CDMA Systems Engineering Handbook. Artech House Publishers, 1998.

[64] F. Figueiredo et al., “Coverage Prediction and Performance Evaluation of Wireless Metropolitan Area Networks based on IEEE 802.16”. Journal of

[65] E. J. B. Rodriguez “Uplink Throughput Enhancements and Delay

Reductions in 3G WCDMA Systems Using 3.5G Enhanced Uplink

Techniques”. IEEE International Symposium on Spread Spectrum Techniques

And Applications, ISSSTA. Manaus, Amazon. pp. 223-227. Aug. 2006.

[66] J. B. R Eduardo, C.A. Gustavo and S.C. Jefferson “Capacity Analysis and Coverage

Comparison” for IMT-2000 Systems in Brazilian Cities IEEE2008

[67] SPECTRAL EFFICIENCY FOR MOBILE TELECOM SERVICES http://www.tec.gov.in/what%20new_files/TECreport%20on%20spectral%20efficiency/Annex%20II

-%20Concept%20Paper%20on%20Spectrum%20Efficiency.pdf

[68]The Promise of WiMAX Paul Sergeant, Senior Manager, Alternative Access Networks http://www.motorola.com/networkoperators/pdfs/Wi4-the-promise-article.pdf

[69] http://en.wikipedia.org/wiki/Spectral_efficiency

 

 

 

 

 

 

[70]http://www.comlab.hut.fi/opetus/238/lecture7_RadioInterfaceProtcols.pdf

 

[71] N. Quoc-Thinh.F.Lionel Fiat, and A.Nazim, “architecture for UMTS-WiMAX internetworking”,

 

First International IEEE workshop, University of Evry, France, April 2006.

[72] W. Stallings, Wireless Communication and Networking, Pearson Education, 2006.

[73]http://194.7.80.153/website/book.asp?menuid=15&vs=3&page=vol2-sup2%2Fch02s02.html

 

 

 

                                        APPENDIX A 

 

Abbreviations and Acronyms 

WLAN Wireless Local Area Network

Mobile Systems

EDGE Enhanced Data rates for GSM Evolution

OFDM Orthogonal Frequency Division Multiplexing

2G Second Generation

IP Internet Protocol

SOFDMA Scalable Orthogonal Frequency Division Multiple Access

DOCSIS Data over Cable Service Interface Specification to Ratio

WCDMA Wideband Code Division Multiple Access

TDMA Time Division Multiple Access

BPSK Binary Phase Shift keying

Quadrature keying

MIMO Multiple Input Multiple Output

ETACS

VOIP

CN

UTRAN

Extended Access Communication System

ITU-TS Telecommunication

CODIT Compartmentalization of Decay in Trees

HSUPA High-Speed

Long Evolution

HSPA Access

EVDO

Universal Terrestrial Radio Access Network

AUC

GMSC

RNC

PCCH

CCCH

SHCCH

DDC

HN

TN

IU

CRNC

VLR

Service Node

Gateway Node

FBSS

Shared Channel Control Channel

CTCH

FACH

PCH

DSCH

FH

DS

Maximum Combining

NLOS

TF

TDD

Transport Format

RAM

WMAN Wireless Metropolitan Area Networking

DSL

Time

EAP

WLAN

AMC

Wireless Local Area Network

FBSS

H-ARQ

Hybrid Automatic Repeat Request

MDHO Macro

ASN

MS

NAP

MC

Service Agreement

Media Center

DS-WCDMA-FDD

DSWCDMA-TDD

Direct Sequence Wideband Code Division Multiple Access FDD

Direct Sequence Wideband Code Division Multiple Access TDD

16QAM 16Quadrature

V2V

CP Cyclic Prefix

MH Mobile Host

SER

ATM

PCMCIA Personal Computer Memory Card

 

 

                                        APPENDIX B 

 

Matlab Simulation code 

%-------------------------------------------------------------------------%

% this code is written by

% Arif Hussain email: [email protected]

% Salahuddin email: [email protected]

% M.Umair Aslam email:[email protected]

%--------------------------------------------------------------------------%

% Code for BPSK

clear all close all

N = 10^6; % number of bits or symbols rand('state',100); % initializing the rand() function randn('state',200); % initializing the randn() function

% Transmitter ip = rand(1,N)>0.5; % generating 0,1 with equal probability s = 2*ip-1; % BPSK modulation 0 -> -1; 1 -> 0 n = 1/sqrt(2)*[randn(1,N) + j*randn(1,N)]; % white gaussian noise, 0dB variance

Eb_N0_dB = [-3:10]; % multiple Eb/N0 values for ii = 1:length(Eb_N0_dB)

% Noise addition

y = s + 10^(-Eb_N0_dB(ii)/20)*n; % additive white gaussian noise

% receiver - hard decision decoding

ipHat = real(y)>0;

% counting the errors nErr(ii) = size(find([ip- ipHat]),2); end simBer = nErr/N; % simulated ber theoryBer = 0.5*erfc(sqrt(10.^(Eb_N0_dB/10))); % theoretical ber figure; semilogy(Eb_N0_dB,theoryBer,'b.-'); hold on semilogy(Eb_N0_dB,simBer,'mx-'); axis([-3 10 10^-5 0.5]) grid on legend('theory', 'simulation'); xlabel('Eb/No, dB'); ylabel('Symbol Error Rate'); title('Symbol error probability curve for BPSK modulation');

%code for QPSK

N = 10^5; % number of symbols

Es_N0_dB = [-3:20]; % multiple Eb/N0 values ipHat = zeros(1,N); for ii = 1:length(Es_N0_dB)

ip = (2*(rand(1,N)>0.5)-1) + j*(2*(rand(1,N)>0.5)-1); % s = (1/sqrt(2))*ip; % normalization of energy to 1 n = 1/sqrt(2)*[randn(1,N) + j*randn(1,N)]; % white guassian noise, 0dB variance y = s + 10^(-Es_N0_dB(ii)/20)*n; % additive white gaussian noise

% demodulation y_re = real(y); % real y_im = imag(y); % imaginary ipHat(find(y_re < 0 & y_im < 0)) = -1 + -1*j; ipHat(find(y_re >= 0 & y_im > 0)) = 1 + 1*j; ipHat(find(y_re < 0 & y_im >= 0)) = -1 + 1*j; ipHat(find(y_re >= 0 & y_im < 0)) = 1 - 1*j; nErr(ii) = size(find([ip- ipHat]),2); % couting the number of errors end simSer_QPSK = nErr/N; theorySer_QPSK = erfc(sqrt(0.5*(10.^(Es_N0_dB/10)))) -

(1/4)*(erfc(sqrt(0.5*(10.^(Es_N0_dB/10))))).^2; close all figure semilogy(Es_N0_dB,theorySer_QPSK,'b.-'); hold on semilogy(Es_N0_dB,simSer_QPSK,'mx-'); axis([-3 15 10^-5 1]) grid on legend('theory-QPSK', 'simulation-QPSK'); xlabel('Es/No, dB')

ylabel('Symbol Error Rate') title('Symbol error probability curve for QPSK(4-QAM)')

% 16-QAM modulation clear

N = 10^6; % number of symbols alpha16qam = [-3 -1 1 3]; % 16-QAM alphabets

Es_N0_dB = [0:20]; % multiple Es/N0 values ipHat = zeros(1,N); for ii = 1:length(Es_N0_dB)

ip = randsrc(1,N,alpha16qam) + j*randsrc(1,N,alpha16qam);

s = (1/sqrt(10))*ip; % normalization of energy to 1

n = 1/sqrt(2)*[randn(1,N) + j*randn(1,N)]; % white guassian noise, 0dB variance

y = s + 10^(-Es_N0_dB(ii)/20)*n; % additive white gaussian noise

% demodulation

y_re = real(y); % real part

y_im = imag(y); % imaginary part

ipHat_re(find(y_re< -2/sqrt(10))) = -3;

ipHat_re(find(y_re > 2/sqrt(10))) = 3;

ipHat_re(find(y_re>-2/sqrt(10) & y_re<=0)) = -1;

ipHat_re(find(y_re>0 & y_re<=2/sqrt(10))) = 1;

ipHat_im(find(y_im< -2/sqrt(10))) = -3;

ipHat_im(find(y_im > 2/sqrt(10))) = 3;

ipHat_im(find(y_im>-2/sqrt(10) & y_im<=0)) = -1;

ipHat_im(find(y_im>0 & y_im<=2/sqrt(10))) = 1;

ipHat = ipHat_re + j*ipHat_im;

nErr(ii) = size(find([ip- ipHat]),2); % couting the number of errors end simBer = nErr/N; theoryBer = 3/2*erfc(sqrt(0.1*(10.^(Es_N0_dB/10)))); close all figure semilogy(Es_N0_dB,theoryBer,'b.-','LineWidth',2); hold on semilogy(Es_N0_dB,simBer,'mx-','Linewidth',2); axis([0 20 10^-5 1]) grid on legend('theory', 'simulation'); xlabel('Es/No, dB') ylabel('Symbol Error Rate') title('Symbol error probability curve for 16-QAM modulation')

% 64-QAM modulation

clear all close all

N = 10^3; % number of symbols

M = 64; % number of constellation points

k = sqrt(1/((2/3)*(M-1))); % normalizing factor m = [1:sqrt(M)/2]; % alphabets alphaMqam = [-(2*m-1) 2*m-1];

Es_N0_dB = [0:30]; % multiple Es/N0 values ipHat = zeros(1,N); % init for ii = 1:length(Es_N0_dB)

ip = randsrc(1,N,alphaMqam) + j*randsrc(1,N,alphaMqam);

s = k*ip; % normalization of energy to 1

n = 1/sqrt(2)*[randn(1,N) + j*randn(1,N)]; % white guassian noise, 0dB variance y = s + 10^(-Es_N0_dB(ii)/20)*n; % additive white gaussian noise

% demodulation

y_re = real(y)/k; % real part

y_im = imag(y)/k; % imaginary part

% rounding to the nearest alphabet

% 0 to 2 --> 1

% 2 to 4 --> 3

% 4 to 6 --> 5 etc

ipHat_re = 2*floor(y_re/2)+1;

ipHat_re(find(ipHat_re>max(alphaMqam))) = max(alphaMqam);

ipHat_re(find(ipHat_re<min(alphaMqam))) = min(alphaMqam);

% rounding to the nearest alphabet

% 0 to 2 --> 1

% 2 to 4 --> 3

% 4 to 6 --> 5 etc

ipHat_im = 2*floor(y_im/2)+1;

ipHat_im(find(ipHat_im>max(alphaMqam))) = max(alphaMqam);

ipHat_im(find(ipHat_im<min(alphaMqam))) = min(alphaMqam);

ipHat = ipHat_re + j*ipHat_im;

nErr(ii) = size(find([ip- ipHat]),2); % counting the number of errors end simSer = nErr/N; theorySer = 2*(1-1/sqrt(M))*erfc(k*sqrt((10.^(Es_N0_dB/10)))) ...

- (1-2/sqrt(M) + 1/M)*(erfc(k*sqrt((10.^(Es_N0_dB/10))))).^2; close all figure semilogy(Es_N0_dB,theorySer,'bs-','LineWidth',2); hold on semilogy(Es_N0_dB,simSer,'m*-','Linewidth',1); axis([0 30 10^-5 1]) grid on legend('theory', 'simulation'); xlabel('Es/No, dB') ylabel('Symbol Error Rate') title('Symbol error probability curve for 64-QAM modulation')

%simulted and theoratical symbol error rate probability for diffrent modulation scheme

% Code for BPSK clear all close all

clc

N = 10^6; % number of bits or symbols rand('state',100); % initializing the rand() function randn('state',200); % initializing the randn() function

% Transmitter ip = rand(1,N)>0.5; % generating 0,1 with equal probability s = 2*ip-1; % BPSK modulation 0 -> -1; 1 -> 0 n = 1/sqrt(2)*[randn(1,N) + j*randn(1,N)]; % white gaussian noise, 0dB variance

Es_N0_dB1 = [-3:10]; % multiple Eb/N0 values for ii = 1:length(Es_N0_dB1)

% Noise addition

y = s + 10^(-Es_N0_dB1(ii)/20)*n; % additive white gaussian noise

% receiver - hard decision decoding

ipHat = real(y)>0;

% counting the errors

nErr1(ii) = size(find([ip- ipHat]),2); end simSer1 = nErr1/N; % simulated ber theorySer1 = 0.5*erfc(sqrt(10.^(Es_N0_dB1/10))); % theoretical ber

% figure;

% semilogy(Eb_N0_dB,theoryBer,'b.-');

% hold on

% semilogy(Eb_N0_dB,simBer,'mx-');

% axis([-3 10 10^-5 0.5])

% grid on

% legend('theory', 'simulation');

% xlabel('Eb/No, dB');

% ylabel('Symbol Error Rate');

% title('Symbol error probability curve for BPSK modulation');

% QPSK

% N = 10^5; % number of symbols

Es_N0_dB2 = [-3:20]; % multiple Eb/N0 values ipHat = zeros(1,N); for ii = 1:length(Es_N0_dB2) ip = (2*(rand(1,N)>0.5)-1) + j*(2*(rand(1,N)>0.5)-1); % s = (1/sqrt(2))*ip; % normalization of energy to 1 n = 1/sqrt(2)*[randn(1,N) + j*randn(1,N)]; % white guassian noise, 0dB variance y = s + 10^(-Es_N0_dB2(ii)/20)*n; % additive white gaussian noise

% demodulation y_re = real(y); % real y_im = imag(y); % imaginary ipHat(find(y_re < 0 & y_im < 0)) = -1 + -1*j; ipHat(find(y_re >= 0 & y_im > 0)) = 1 + 1*j; ipHat(find(y_re < 0 & y_im >= 0)) = -1 + 1*j; ipHat(find(y_re >= 0 & y_im < 0)) = 1 - 1*j; nErr2(ii) = size(find([ip- ipHat]),2); % couting the number of errors end simSer_QPSK = nErr2/N;

theorySer_QPSK = erfc(sqrt(0.5*(10.^(Es_N0_dB2/10)))) -

(1/4)*(erfc(sqrt(0.5*(10.^(Es_N0_dB2/10))))).^2;

% figure;

% semilogy(Es_N0_dB,theorySer_QPSK,'b.-');

% hold on

% semilogy(Es_N0_dB,simSer_QPSK,'mx-');

% axis([-3 15 10^-5 1])

% grid on

% legend('theory-QPSK', 'simulation-QPSK');

% xlabel('Es/No, dB')

% ylabel('Symbol Error Rate')

% title('Symbol error probability curve for QPSK(4-QAM)')

% 16-QAM modulation

% N = 2*10^5; % number of symbols alpha16qam = [-3 -1 1 3]; % 16-QAM alphabets

Es_N0_dB3 = [0:20]; % multiple Es/N0 values ipHat = zeros(1,N); for ii = 1:length(Es_N0_dB3)

ip = randsrc(1,N,alpha16qam) + j*randsrc(1,N,alpha16qam);

s = (1/sqrt(10))*ip; % normalization of energy to 1

n = 1/sqrt(2)*[randn(1,N) + j*randn(1,N)]; % white guassian noise, 0dB variance

y = s + 10^(-Es_N0_dB3(ii)/20)*n; % additive white gaussian noise

% demodulation

y_re = real(y); % real part

y_im = imag(y); % imaginary part

ipHat_re(find(y_re< -2/sqrt(10))) = -3;

ipHat_re(find(y_re > 2/sqrt(10))) = 3;

ipHat_re(find(y_re>-2/sqrt(10) & y_re<=0)) = -1;

ipHat_re(find(y_re>0 & y_re<=2/sqrt(10))) = 1;

ipHat_im(find(y_im< -2/sqrt(10))) = -3;

ipHat_im(find(y_im > 2/sqrt(10))) = 3;

ipHat_im(find(y_im>-2/sqrt(10) & y_im<=0)) = -1;

ipHat_im(find(y_im>0 & y_im<=2/sqrt(10))) = 1;

ipHat = ipHat_re + j*ipHat_im;

nErr3(ii) = size(find([ip- ipHat]),2); % couting the number of errors end simSer3 = nErr3/N; theorySer3 = 3/2*erfc(sqrt(0.1*(10.^(Es_N0_dB3/10))));

% figure;

% semilogy(Es_N0_dB,theoryBer,'b.-','LineWidth',2);

% hold on

% semilogy(Es_N0_dB,simBer,'mx-','Linewidth',2);

% axis([0 20 10^-5 1])

% grid on

% legend('theory', 'simulation');

% xlabel('Es/No, dB')

% ylabel('Symbol Error Rate')

% title('Symbol error probability curve for 16-QAM modulation')

% 64-QAM modulation

% N = 7*10^5; % number of symbols

M = 64; % number of constellation points k = sqrt(1/((2/3)*(M-1))); % normalizing factor m = [1:sqrt(M)/2]; % alphabets alphaMqam = [-(2*m-1) 2*m-1];

Es_N0_dB4 = [0:30]; % multiple Es/N0 values ipHat = zeros(1,N); % init for ii = 1:length(Es_N0_dB4)

ip = randsrc(1,N,alphaMqam) + j*randsrc(1,N,alphaMqam);

s = k*ip; % normalization of energy to 1

n = 1/sqrt(2)*[randn(1,N) + j*randn(1,N)]; % white guassian noise, 0dB variance

y = s + 10^(-Es_N0_dB4(ii)/20)*n; % additive white gaussian noise

% demodulation

y_re = real(y)/k; % real part

y_im = imag(y)/k; % imaginary part

% rounding to the nearest alphabet

% 0 to 2 --> 1

% 2 to 4 --> 3

% 4 to 6 --> 5 etc

ipHat_re = 2*floor(y_re/2)+1;

ipHat_re(find(ipHat_re>max(alphaMqam))) = max(alphaMqam);

ipHat_re(find(ipHat_re<min(alphaMqam))) = min(alphaMqam);

% rounding to the nearest alphabet

% 0 to 2 --> 1

% 2 to 4 --> 3

% 4 to 6 --> 5 etc

ipHat_im = 2*floor(y_im/2)+1;

ipHat_im(find(ipHat_im>max(alphaMqam))) = max(alphaMqam);

ipHat_im(find(ipHat_im<min(alphaMqam))) = min(alphaMqam);

ipHat = ipHat_re + j*ipHat_im;

nErr4(ii) = size(find([ip- ipHat]),2); % counting the number of errors end simSer4 = nErr4/N; theorySer4 = 2*(1-1/sqrt(M))*erfc(k*sqrt((10.^(Es_N0_dB4/10)))) ...

- (1-2/sqrt(M) + 1/M)*(erfc(k*sqrt((10.^(Es_N0_dB4/10))))).^2;

% theoratical figure; semilogy(Es_N0_dB1,theorySer1,'r+-','LineWidth',1.5); axis([0 30 10^-5 1]) grid on xlabel('Eb/No, dB') ylabel('Symbol Error Rate') title('Theoatical Symbol error probability for different modulation schemes') hold on semilogy(Es_N0_dB2,theorySer_QPSK,'g+-','LineWidth',1.5); hold on semilogy(Es_N0_dB3,theorySer3,'b+-','LineWidth',1.5); hold on semilogy(Es_N0_dB4,theorySer4,'k+-','LineWidth',1.5);

legend('BPSK','QPSK','16-QAM','64-QAM');

% simulated figure; semilogy(Es_N0_dB1,simSer1,'r+-','LineWidth',1.5); axis([0 30 10^-5 1]) grid on xlabel('Eb/No, dB') ylabel('Symbol Error Rate') title('Simulated Symbol error probability for different modulation schemes') hold on semilogy(Es_N0_dB2,simSer_QPSK,'g+-','LineWidth',1.5); hold on semilogy(Es_N0_dB3,simSer3,'b+-','LineWidth',1.5); hold on semilogy(Es_N0_dB4,simSer4,'k+-','LineWidth',1.5); legend('BPSK','QPSK','16-QAM','64-QAM');

% simulation code for different modulation scheme with Rayleigh fading channel

close all clear all clc

% No. of Subcarriers

N_of_sub = 1000;

% Input Data

X1 = rand(1,N_of_sub)>0.5;

% trellis = poly2trellis(7,[171 133]);

% code = convenc(x,trellis); % Encode a string of ones.

% Serial to Parallel Conversion of Input data par = series2parallel(X1,N_of_sub);

% M-ary PSK Modulation alphabet_M = 2; % Alphabet size

X2 = 0; for count1 = 2:1:6; alphabet_M = alphabet_M + X2;

% Use M-ary modulation to produce modulated signal y_mod. if(alphabet_M<=8)

y_mod=modulate(modem.pskmod(alphabet_M),par); else

y_mod=modulate(modem.qammod(alphabet_M),par); end

% Apply IFFT operation ifft_y_mod = ifft(y_mod);

% Add Cyclic Prefix cyc_pr(count1,:) = cyclicpad(ifft_y_mod,256); %#ok<AGROW> len_cyc_pr = length(cyc_pr);

% Parallel to Serial out = reshape(cyc_pr(count1,:),1,len_cyc_pr);

% Transmit signal through an AWGN channel. y_AWGN = awgn(out,100,'measured');

% Rayleigh Fading Channel

R_fading_ch = rayleighchan(1/1000,100,[0 2e-5],[0 -9]); rf = filter(R_fading_ch,y_AWGN); % Pass signal through channel.

R_fading_ch % Display all properties of the channel object.

% Serial to Parallel par2 = series2parallel(rf,len_cyc_pr); re_par = real(par2);

% Remove cyclic prefix r_cyc_pr(count1,:) = decyclicpad(par2,256); len_rcp = length(r_cyc_pr);

% FFT fft_y_mod = fft(r_cyc_pr(count1,:));

% Demodulate fft signal at Rxer. if (alphabet_M<=8)

y_demod=demodulate(modem.pskdemod(alphabet_M),fft_y_mod); else

y_demod=demodulate(modem.qamdemod(alphabet_M),fft_y_mod); end

% Parallel to Serial xdash = reshape(fft_y_mod,1,N_of_sub); error = 0 ; for a = 1:1:N_of_sub; if (xdash(:,a) == X1(:,a))

error = 0;

else

error = error+1; end end terror(count1,:) = error;

EbNo = 0:1:N_of_sub-1; if(alphabet_M<=8)

S_err(count1,:) = berawgn(0.9*EbNo,'psk',alphabet_M,'nondiff');

SERtheory(count1,:) = berfading(EbNo,'psk',alphabet_M,1);

Pr_err(count1,:) = erfc(sqrt(0.9*EbNo)*sin(pi/alphabet_M)); else

S_err(count1,:) = berawgn(0.9*EbNo,'qam',alphabet_M);

SERtheory(count1,:) = berfading(EbNo,'qam',alphabet_M,1);

Pr_err(count1,:) = 2*((1-(1/sqrt(alphabet_M)))*erfc(sqrt((1.5*EbNo)/(alphabet_M-1)))); end alphabet_M= 2^count1; end

%tb = 2; % Traceback length for decoding

%decoded = vitdec(xdash,trellis,tb,'trunc','soft',128); figure() semilogy(EbNo,S_err(2,:),'+c',EbNo,S_err(3,:),'-b',EbNo,S_err(5,:),'*-r',EbNo,S_err(6,:),'*-k'); axis([0 25 0.00001 1]); grid on xlabel('SNR dB') ylabel('Symbol Error Probability')

legend('BPSK','QPSK','16QAM','64QAM') figure() semilogy(EbNo,SERtheory(2,:),'+c',EbNo,SERtheory(3,:),'-b',EbNo,SERtheory(5,:),'*r',EbNo,SERtheory(6,:),'*-k'); axis([0 50 0.00001 1]); grid on xlabel('SNR dB') ylabel('Theoritical Value of SER') legend('BPSK Mod','QPSK Mod','16QAM Mod','64QAM Mod') figure() semilogy(EbNo,Pr_err(2,:),'-c',EbNo,Pr_err(3,:),'-b',EbNo,Pr_err(5,:),'*-r',EbNo,Pr_err(6,:),'*-k'); axis([0 30 0.00001 1]); grid on xlabel('SNR dB') ylabel('Probability of Error') legend('BPSK Mod','QPSK Mod','16QAM Mod','64QAM Mod')

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