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1

Introduction

Without doubt, both cellular phones and the Internet have had a great impact on our lives. Since their introduction in the late 1970s and the early 1980s, the demand for cell phones has had a steady growth in terms of usage and popularity. Initially aimed at “mobilizing” telephony service, mobile communications have gone from bettering voice quality, to adding basic exchanges, to the currently witnessed proliferation of delivering fully fledged multimedia services. This latter evolution was motivated, and made feasible, by the exponential popularity that the Internet has undergone since its introduction to the general public in the mid 1990s. Indeed, the Internet has evolved much since then, and has managed to span the introduction of various multimedia services, ranging from emails and file transfers, to live voice and video streams. By the end of the 1990s, extending Internet services to mobile telecommunications was foreseen as a natural evolution. The many efforts made at the time pursuing such extension – both in the industrial and research sectors can already be seen in today’s widely deployed Third Generation (3G) networks. The popularity of today’s 3G networks was further strengthened by the introduction of truly smart cellular phones, or smart phones, which featured highly usable interfaces and ease of installation of software applications and packages. Figure 1.1 shows the 3G coverage in the some countries, as calculated by the Organization for Economic

Cooperation and Development (OECD) [1].

The advent of a capable mobile Internet has made possible many new services

COPYRIGHTED MATERIAL

interact live and through both voice and video with their friends and partners. At the same time, sharing services and social networks resulted in multitudes of text, voice and video statuses and snapshots being constantly uploaded. Users are also able to access their work and financial documents on the go, and connect to their working stations that reside either at their offices or in the Internet cloud, greatly enhancing their productivity over the air. Meanwhile, doctors and caregivers are

LTE, LTE-Advanced and WiMAX: Towards IMT-Advanced Networks, First Edition.

Abd-Elhamid M. Taha, Najah Abu Ali and Hossam S. Hassanein.

© 2012 John Wiley & Sons, Ltd. Published 2012 by John Wiley & Sons, Ltd.

2

100

90

80

70

60

50

40

30

20

10

0

LTE, LTE-Advanced and WiMAX: Towards IMT-Advanced Networks

Figure 1.1

3G penetration in various countries up to 2009, per OECD. Note that the average penetration in the surveyed countries is 81 %.

able to monitor the vitals and the state of their patients remotely, immensely reducing costs incurred for commuting and hospital stays costs and improving the patients’ overall wellbeing. Third generation networks have also enabled location based services, already being utilized by various targeted advertisements and reward-based credit cards. Such location based services are also enabling the tracking of vehicles, cargo trucks and products nationwide and in real time.

Indeed, much of the above services – and more – can already be witnessed.

Despite such possibilities, the increasing demand and popularity of mobile applications and services, in addition to the growing dependence on Internet applications and services in the various sectors (government, commerce, industry, personal, etc.) is calling for a more reliable broadband connectivity that can be made anytime and anywhere. In addition, and as will be noted below, the elemental characteristics of 3G networks hindered their capability of handling this increased demand. Hence, the International Telecommunications

Union – Radiocommunications Sector (ITU-R) sought in 2006 to initiate efforts towards realizing more capable networks. The resulting network would mark a substantial improvement over current networks, and facilitate a smooth transition in next generation networks. Such improvements would inevitably include enhancements to both the access network, that is, the Radio Interface Technologies (RITs), and the core network, that is, network management interface.

The intention of this book is to provide an overview of the two Radio Interface

Technologies (RITs) that were presented by the Third Generation Partnership

Project (3GPP) and the Institute for Electrical and Electronics Engineer (IEEE) in response the ITU-R requirements letter for Fourth Generation (4G), or IMT-

Advanced networks. The letter, issued in 2008, identified the target performance criteria in which the candidate technologies must outperform 3G networks.

Both candidate technologies, namely 3GPP’s Long Term Evolution – Advanced

Introduction

3

(LTE-Advanced) and IEEE’s 802.16m, were approved by the ITU-R Working

Party 5D in October 2010 as initially satisfying the basic requirements.

The objective of this chapter is to elaborate on the motivation for IMT-

Advanced networks. The following section summarizes the evolution of the wireless generations, indicating the great advances that have thus far been achieved in wireless communications in general. We next elaborate on the exact motivations for IMT-Advanced. Section 1.3 describes the expected features of

IMT-Advanced systems, and the elements of performance used to specify their requirements. Section 1.4 then introduces the two RIT that have been recently approved as satisfying the ITU-R requirements. Finally, Section 1.5 details an overview of the book.

1.1

Evolution of Wireless Networks

Table 1.1. summarizes the history of cellular networks. Through the generations, emphases have been made on different design objectives, ones that best served the requirements of the time.

Interest in the First Generation (1G) cellular, for example, focused on mobilizing landline telephony. The outcome networks, Advanced Mobile Phone

Systems (AMPS) and Total Access Communication Systems (TACS), were circuit switched with analog voice transmission over the air. A definite drawback of analog transmission was a generally degraded quality and an extreme sensitivity to basic mobility and medium conditions. Hence, the main design objective in Second Generation (2G) cellular networks was to enhance voice quality. The standards responded by replacing analog voice transmission with digital encoding and transmission, immensely improving voice communication.

Improvements to the network core also facilitated the introduction of basic digital messaging services, such as the Short Messaging Service (SMS). The two main

Table 1.1

Generations of cellular technologies [2]

Generation Year Network Technology

1G

2G

2.5G

3G

4G

Early 1980s Circuit switched

Early 1990s D-AMPS, GSM,

CDMA (IS-95)

1996 Circuit switched or

2000

2012

Packet switched

Non-IP Packet switched/Circuit switched

IP based, Packet switched core network

TACS, AMPS

D-AMPS, GSM,

CDMA

GPRS, EDGE,

EVDO, EVDV

WCDMA,

CDMA2000

Not finalized

Data

Analog Voice

Digital Voice

Digital Voice

+ Data

Digital Voice

+ High speed Data

+ video

Digital Voice, High speed Data,

Multimedia,

Security

4

LTE, LTE-Advanced and WiMAX: Towards IMT-Advanced Networks standards comprising 2G networks were Global System for Mobile Communications (GSM) and Interim Standard 95 (IS-95), commercially called (cdmaOne).

GSM relied mostly on Time Division Multiple Access (TDMA) techniques, while cdmaOne, as the name suggests, utilized Code Division Multiple Access

(CDMA). Such division, in addition to variation in the spectrum bands utilized for deployments in different regions, would mark a characteristic interoperability problem that was to be witnessed for a substantial period of time afterwards.

The introduction and the increasing popularity of the 2G technologies coincided with the early years of the Internet. As the Internet experienced an exponential growth in usage, interest in having digital and data services of wireless and mobile devices began to materialize. Evolutions for the two main 2G technologies, GSM into General Packet Radio Services (GPRS) and Enhanced Data Rates for GSM Evolution (EDGE) and cdmaOne into cdmaTwo (IS-95b), enhanced the network cores to be able to handle simple data transfers. For example, GPRS introduced two components, the GPRS Support Node (SGSN) and the Gateway

GPRS Support Node (GGSN). The objectives of these components was to augment the existing GSM infrastructure to facilitate data access at the RIT level

(SGSN), and to facilitate interconnecting the GPRS network with other data networks, including the Internet (GGSN). Basic email and mobile web access were enabled, but the sophistication of the general mobile Internet experience did not allow popular access, and restricted its usage to the enterprise.

In 1999, the ITU approved five radio interfaces comprising the IMT-2000 technologies.

These were the EDGE, cdma2000, Universal Mobile

Telecommunication System (UMTS) (Wideband – CDMA (W-CDMA), Time-

Division – CDMA (TD-CDMA) and Time Division-Synchronous CDMA

(TD-SCDMA)) and Digital Enhanced Cordless Telecommunications (DECT).

In 2007, Worldwide Interoperability for Microwave Access (WiMAX) was also recognized as an IMT-2000 technology. These technologies make up the 3G networks. In their design, great emphasis was given to enhance the support for voice services, expand and enhance the support for data services, and enable multimedia to the mobile handset. 3G technologies are sometimes classified based on their nature, with EDGE and CDMA2000 recognized as being evolutionary technologies, that is, enhancing their 2G predecessor technologies, and UMTS and WiMAX as revolutionary, that is, based on completely new radio interfaces. In the case of UMTS, it was WCDMA, while WiMAX relied on Orthogonal Frequency Multiple Access (OFDMA). As will be illustrated in the next chapter, the viability of sub-carrier allocation facilitated by OFDMA has made it the multiple access technique of choice in 4G networks.

3G technologies displayed, and still display, that Internet access through a mobile handset can provide users with a rich experience. The recent widespread of smart phones and pads offered by various vendors indicates the strong demand for such services. However, 3G technologies have faced certain challenges in accommodating the increasing demand. These include deteriorating quality of indoor coverage, unsustainable data rates at different mobility levels, roaming difficulties

(incoherent spectrum allocation between different countries), and infrastructure

Introduction

5

complexity. While some of these challenges could be efficiently mitigated by denser deployments, the associated cost and complexity made this an unattractive solution. As for network performance, signaling overhead in 3G networks has been observed to consume substantial bandwidths – even more than the requirements of the multimedia being transferred.

The latter revolutions in 3G technology, namely the LTE from 3GPP and the WiMAX 1.5 from the WiMAX Forum, directly addressed these and other issues. Parting away from the RITs that have been used in 2G and early 3G technologies (TDMA and W-CDMA), LTE and WiMAX are based on OFDMA.

This facilitated delivering high data rates while being robust to varying mobility levels and channel conditions. The two networks also introduced other technologies, such as using advanced antenna techniques, simplified network core, the usage of intelligent wireless-relay network components, and others.

In early 2008, the ITU-R issued a circular letter initiating the proposal process for candidates for IMT-Advanced technologies. The requirements set for IMT-

Advanced were made to address the outstanding issues faced by operators, vendors and users in 3G networks, and were made to accommodate the expanding demand for mobile broadband services. The requirements were set with the general framework of the IMT objectives (i.e., per Recommendation ITU-R M.1645

[3]), which set the desired objectives for users, manufactures, application developers, network operators, content providers, and services providers. Both the

3GPP and IEEE responded with candidate proposals in October 2009, the 3GPP with LTE-Advanced, an evolution of LTE, and the IEEE with the WirelessMAN-

Advanced air interface (IEEE 802.16m). Currently, deployments of LTE and

WiMAX have already started. The Global mobile Suppliers Association (GSA) indicates commitments by 128 operators in 52 countries [4] in addition to 52 pre-commitments (trial or test) deployments [5]. Meanwhile, the WiMAX forum in its most recent Industry Research Report (IRR) indicates that there are currently

582 WiMAX deployments in 150 countries [6, 7]. Note that these deployments are not IMT-Advanced, that is, are not 4G networks. However, given the ease of upgrade from LTE to LTE-Advanced and from WiMAX 1.5 to WiMAX 2.0, these deployments are indicative of how future deployments will play out.

The initial timeline set by the ITU-R Working Party 5D, the party overseeing

IMT-Advanced systems, is shown in Figure 1.2. At the moment, the standardization of both technologies has passed Step 7 which entails the consideration of evaluation results in addition to consensus building and decision. The working party met in October 2010 to decide on the successful candidates and decide on future steps. Both LTE-Advanced and WirelessMAN-Advanced have been recognized as IMT-Advanced technologies. Both standardization bodies are now in Step 8, which entails the development of the radio interface recommendations.

1.2

Why IMT-Advanced

3G networks faced elemental issues in trying to accommodate the projected demand for mobile Internet service. One such issue is the high cost of either

6

LTE, LTE-Advanced and WiMAX: Towards IMT-Advanced Networks

WP 5D meetings

2008

No.1

No.2

(0)

No.3

No.4

2009

No.5

No.6

No.7

Step1 and 2

(20 months)

Step 3

(8 months)

(1)

Step 4

(16 months)

Step 5, 6 and 7

(20 months)

2010

No.8

(2)

No.9

(3)

Step 8

(12 months)

2011

No.10

(4)

Figure 1.2

IMT-Advanced Timeline.

expanding the network or the network operation in general. Such costs became a substantial consideration when addressing the 3G network performance in densely populated areas or when trying to overcome coverage deadspots. Of particular importance is the performance at the cell-edge, that is, connection quality at overlaps between the coverage areas of neighboring cells, which have been repeatedly remarked to be low in 3G networks. Such problems would usually be addressed by increasing the deployment of Base Stations (BS), which in addition to their high costs entail additional interconnection and frequency optimization challenges.

Certain performance aspects of 3G networks were also expected to be more pronounced. Some aspects were due to the scaling properties of the 3G networks, for example, delay performance due to increased traffic demand. The general support for different levels of mobility also suffered greatly in WCDMA-based networks. Perhaps most critical was the indoors and deadspot performance of

3G networks, especially when various studies have indicated that the bulk of network usage is made while being at either the office or at home.

Combined, the above issues made it cumbersome for operators to respond to the ever increasing demand. Meanwhile, handling specific heterogeneities have made it harder for both operators and user equipment vendors to maintain homogeneous and streamlined service and production structures. For example, the spectrum mismatch between even neighboring countries in 3G deployments prevented users from roaming between different networks – and at times even requiring the user to utilize (and synchronize between) different handsets. At the same time, despite the availability of multi-modal user equipment for a long time, it has thus far been difficult to maintain handovers across the different technologies.

1.3

The ITU-R Requirements for IMT-Advanced Networks

The general requirements for IMT-Advanced surpass the performance levels of

3G networks. Enhanced support of basic services (i.e., conversational, interactive, streaming and background) is expected. Figure 1.3 shows the famous

Introduction

7

8

LTE, LTE-Advanced and WiMAX: Towards IMT-Advanced Networks

“Van diagram” which illustrates the relationship between the IMT-Advanced requirements and previous generations. The figure shows the serving area, with one axis being the sustainable data rate supported, while the other shows the mobility level at which that rate can be supported. For example, high mobility

(>120 km/h) could only be supported up to

∼15Mbit/s in Enhanced IMT-2000.

The expectation, per the van diagram, is that the technologies will enable the support of data rates that are at least an order of magnitude higher. For stationary to low mobility (<10 km/h) it is foreseen that data rates surpassing 1Gbit/s can be sustained, while >100 Mbit/s are projected for high mobility levels.

While the data rates are perhaps a key defining characteristics of IMT-

Advanced networks, the requirements in general will enable such networks to exhibit other important features, including the following [6].

A high degree of commonality of functionality worldwide with flexibility to support

a wide range of services and applications in a cost efficient manner. Emphasis here is on service easiness and application distribution and deployment.

Compatibility of services within IMT and with fixed networks. In other words,

IMT-Advanced should fully realize extending broadband Internet activity over wireless and on the move.

Capability of interworking with other radio access systems. An advantage for both operators and users, as it expands the viability of using the RIT most appropriate for a certain location, traffic and mobility. It also strengthens the economic stance of the users.

High quality mobile services. Emphasis here is not just on high data rates, but sustainable high data rates, that is, connection performance that overcomes both mobility and medium challenges.

User equipment suitable for worldwide use. A clear emphasis on eliminating, as much as possible, handset and user equipment incompatibility across the different regions.

User-friendly applications, services and equipment. Ease and clarity of use in both the physical and the virtual interfaces.

Worldwide roaming capability. An emphasis on exploiting harmonized spectrum allocations.

Enhanced peak data rates to support advanced services and applications

(100 Mbit/s for high mobility and 1 Gbit/s for low mobility). Such values are to be considered as the minimum supported rates, with high rates encouraged to be sought by the contending candidates.

The ITU-R Report M.2134, entitled “Requirements related to technical performance for IMT-Advanced radio interface(s)” [8], comprises the following elements in specifying the characteristics of future networks.

• Cell spectral efficiency

• Peak spectral efficiency

Introduction

9

• Bandwidth

• Cell edge user spectral efficiency

• Latency

• Control plane latency

• User plane latency

• Mobility

• Handover Interruption Time

• Voice Over Internet Protocol (VoIP) capacity

• Spectrum

Sustaining a specific rate is more viable at lower speeds than at higher speeds.

This is due to the characteristics of the wireless channels and the mobility effects on the quality of the received signal at both sides of the communication link.

There are also matters related to sustaining a certain performance level for mobile users during handovers. Accordingly, the IMT-Advanced requirements document indicates the different classes of mobility for which the requirements are defined in order to clarify ITU’s expectations. The following classes of mobility are defined.

• Stationary: 0 km/h

• Pedestrian: >0 km/h to 10 km/h

• Vehicular: 10 to 120 km/h

• High speed vehicular: 120 to 350 km/h

The document also identifies the test environments for IMT-Advanced, and the mobility levels supported in each test environment. These are shown in Table 1.2.

It should be noted that most of the values required below are defined assuming antenna configurations of downlink 4

× 2 and uplink 2 × 4. For example, a 4 × 2 arrangement in the downlink means that 4 antennas would be utilized at the base station and two antennas would be utilized at the user equipment or mobile station. Similarly, a 2

× 4 arrangement in the uplink means that two antennas are utilized for transmission at the user equipment and four antennas at the base station. We elaborate on such advanced antennas setup in Chapter 2.

Table 1.2

Test environments and the supported mobility levels

Indoor

Test Environments

Microcellular Base coverage urban

Mobility classes supported

Stationary, pedestrian

Stationary, pedestrian,

Vehicular

Stationary, pedestrian, vehicular

High speed

Vehicular, High speed vehicular

10

LTE, LTE-Advanced and WiMAX: Towards IMT-Advanced Networks

Table 1.3

The required cell spectral efficiencies in the different environments in IMT-Advanced

Test environment

Downlink

(bit/s/Hz/cell)

Uplink

(bit/s/Hz/cell)

Indoor

Microcellular

Base coverage urban

High speed

3

2.6

2.2

1.1

2.25

1.80

1.4

0.7

1.3.1 Cell Spectral Efficiency

A cell’s spectral efficiency is the aggregate throughput for all users in that cell divided by the nominal channel bandwidth (computed by multiplying the effective bandwidth by the reuse factor), all divided by the number of cells. Table 1.3 shows the requirements values for cell spectral efficiency at different mobility levels.

1.3.2 Peak Spectral Efficiency

The peak spectral efficiency is the highest theoretical data rate (normalized by bandwidth) that can be delivered to a single Mobile Station (MS) when all available radio resources for the corresponding link direction are utilized. The minimum requirements for peak spectral efficiency are 15 bit/s/Hz for downlink and 6.75 bit/s/Hz for uplink. These values are defined assuming antenna configuration of 4

× 2 for downlink and 2 × 4 for uplink.

1.3.3 Bandwidth

The candidate technology shall operate with scalable bandwidth allocations using either single or multiple RF carriers, up to and including 40 MHz. Supporting wider bandwidths (e.g., up to 100 MHz) is encouraged by the proponents.

1.3.4 Cell Edge User Spectral Efficiency

The cell edge user spectral efficiency is the average user throughput over a certain period of time, divided by the channel bandwidth. Table 1.4 details the required cell edge user spectral efficiency in the different test environments.

1.3.5 Latency

The requirements specify latencies at both the control plane (C-Plane) and user plane (i.e., transport delay). C-plane latency is defined as the transition time between different connection modes, and is required to be less than 100 ms for

Introduction

Table 1.4

The required cell edge user spectral efficiency in different test environments in IMT-Advanced

Test environment

Downlink

(bit/s/Hz)

Uplink

(bit/s/Hz)

Indoor

Microcellular

Base coverage urban

High speed

0.1

0.075

0.06

0.04

0.07

0.05

0.03

0.015

11

idle to active transition. On the other hand, user plane latency describes the time it takes an IP packet that is ready to be transmitted at one end of the access link

(i.e., base station or mobile station) to be ready for processing by the IP layer at the end of the access link (i.e., respectively the mobile station or the base station). The delay latency includes delay introduced by associated protocols and control signaling assuming the user terminal is in the active state. The latency is required to be less than 10 ms in unloaded conditions for small IP packets (e.g.,

0 byte payload

+ IP header) for both downlink and uplink

1.3.6 Rates per Mobility Class

Table 1.5 specifies the expected average spectral efficiencies for mobile users travelling at different speeds. For instance, users traveling at 10km/hr the user can expect a spectral efficiency of 1 (Bits/s/Hz). This translates into a sustained

40 Mb/s given an allocation of 40 MHz.

1.3.7 Handover Interruption Time

Handover interruption time is perhaps one of the most critical requirements in the

ITU requirements documents. This is the time in which a mobile handset loses all effective communication (back and forth) as it is in the middle of disassociating with the serving BS and associating with the target BS. Naturally, the duration

Table 1.5

The required rates to be sustained at the different mobility levels in IMT-Advanced

Test environment Bit/s/Hz Speed (km/h)

Indoor

Microcellular

Base coverage urban

High speed

1.0

0.75

0.55

0.25

10

30

120

350

12

LTE, LTE-Advanced and WiMAX: Towards IMT-Advanced Networks has a significant impact on the quality of voice (e.g., VoIP) and video (e.g., video streaming or video conferences) communication. To achieve a requested system throughput increase, the Medium Access Control (MAC) management overhead caused by handovers has to be decreased as well. This reduction can be achieved by changing the MAC management message structure and by changing the MAC message exchange scheme.

For handovers performed while the MS maintains frequency and band – the expected norm for handovers – the interruption time shall not exceed 27.5 ms.

If the frequency is not maintained, but the handover is performed with the same band, and an additional 12.5 ms are allowed for frequency assignment. Creating a total bound of 40 ms. If both frequency and band are changed, a 60 ms bound is set.

IMT-Advanced are also expected to support inter-technology handovers to the full extent (both interworking, and across different operators, as applicable).

By support, it is expected that sufficient abstractions would be provided by the management functionalities to allow the MS or the operators of the different technologies to facilitate an inter-technology handover. Extending the emphasis to full coexistence; the support should accommodate handovers between IMT-

Advanced technologies, in addition to handovers between IMT-Advanced and some selected legacy technologies, namely 2G, IMT-2000, and WiFi. It should be noted, however, that no fixed bounds were made regarding the handover interruption times for inter-technology handovers.

1.3.8 VoIP Capacity

The requirements document defines the VoIP capacity as the minimum of the calculated capacity for either link direction divided by the effective bandwidth in the respective link direction. The values shown in Table 1.6 are derived assuming

12.2 kb/s codec with a 50 % activity factor such that the percentage of users in outage (<98 % packet delivery success within a 50 ms delay bound) is less than 2 %.

Table 1.6

The required voice capacity (in terms of VoIP) calls for different test environments in IMT-Advanced

Test environment Min VoIP capacity

(Active users/sector/MHz)

Indoor

Microcellular

Base coverage urban

High speed

50

40

40

30

Introduction

13

1.3.9 Spectrum

A first step in realizing the aforementioned features is to establish, as much as possible, common frequency bands dedicated to IMT and/or IMT-Advanced. The following frequency bands have been recognized by the ITU as ones that can be harmonized across the different regions.

• 450–470 MHz

• 698–960 MHz

• 1710–2025 MHz

• 2110–2200 MHz

• 2300–2400 MHz

• 2500–2690 MHz

• 3400–3600 MHz

1.4

IMT-Advanced Networks

1.4.1 LTE-Advanced

The 3GPP Technical Report (TR) 36.913 [9] details the requirements for

LTE-Advanced to satisfy. The document stressed backward compatibility with

LTE in targeting IMT-Advanced. It does, however, also indicate that support for non-backward compatible entities will be made if substantial gains can be achieved. Minimizing complexity and cost and enhanced service delivery are strongly emphasized.

The objective of reduced complexity is an involved one, but it includes minimizing system complexity in order to stabilize the system and inter-operability in earlier stages and decreases the cost of terminal and core network elements.

For these requirements, the standard will seek to minimize the number of deployment options, abandon redundant mandatory features and reduce the number of necessary test cases. The latter can be a result of reducing the number of states of protocols, minimizing the number of procedures, and offering appropriate parameter range and granularity. Similarly, a low operational complexity of the

UE can be achieved through supporting different RIT, minimizing mandatory and optional features and ensuring no redundant operational states.

Enhanced service delivery, with special care to Multimedia Broadcast/Multicast Service (MBMS), will be made. MBMS is aimed at realizing

TV broadcast over the cellular infrastructure. It is expected, however, that such services will be undersubscribed in 3G networks. It is hence very critical to enhance MBMS services for 4G networks as it will be a key differentiating and attractive service.

LTE-Advanced will feature several operational features. These include relaying, where different levels of wireless multihop relay will be applied,

14

LTE, LTE-Advanced and WiMAX: Towards IMT-Advanced Networks and synchronization between various network elements without relying on dedicated synchronization sources. Enabling co-deployment (joint LTE and

LTE-Advanced) and co-existence (with other IMT-Advanced technologies) is also to be supported. Facilitating self-organization/healing/optimization will facilitate plug-n-play addition of infrastructure components, especially in the case of relay and in-door BS. The use of femtocells, very short-range coverage

BSs, will enhance indoors service delivery. Finally, LTE-Advanced systems will also feature facilitating advanced radio resource management functionalities, with special emphasis on flexibility and opportunism, and advanced antenna techniques, where multiple antennas and multi-cell MIMO techniques will be applied.

LTE-Advanced will support peak data rates of 1 Gbps for the downlink, and a minimum of 100 Mbps for the uplink. The target uplink data rate, however, is

500 Mbps. For latencies, the requirements are 50 ms for idle to connected and

10 ms for dormant to connected. The system will be optimized for 0– 190 km/h mobility, and will support up to 500 km/h, depending on operating band. For spectral efficiency, LTE-Advanced requirements generally exceed those of IMT-

Advanced, for example, the system targets a peak of 30 bps/Hz for the downlink and 15 bps/Hz for the uplink, while average spectrum efficiency (bps/Hz/cell) are expected to reach 3.7 (4

× 4 configuration) for the downlink and 2.0 (2 × 4 configuration) for the uplink. Support for both TDD and FDD, including half duplex FDD, will be made possible. The following spectrum bands are targeted.

• 450–470 MHz

• 698–862 MHz

• 790–862 MHz (*)

• 2300–2400 MHz

• 3400–4200 MHz

• 4400–4990 MHz (*)

The (*) marked bands are not within the requirements of the IMT-Advanced requirements, and some IMT-Advanced may not be supported by LTE-Advanced.

These bands are the 1710– 2025, 2110– 2200 and the 2500– 2690 MHz bands.

1.4.2 IEEE 802.16m

As a minimum, the requirements for the IEEE 802.16m [10] entail full support for the IMT-Advanced requirements. This is in addition to backward compatibility with legacy or 802.16-2009 systems. There is also the requirement to enhance service delivery to the mobile users, which involves two objectives. The first is to enhance WiMAX 1.5’s Multicast Broadcast Services (MBS), which is similar to

3GPP’s MBMS; the second is to utilize Location Based Services (LBS), which are aimed at supporting context-based service delivery. As for the operational features supported IEEE 802.16m, they are similar to those for LTE-Advanced.

Introduction

15

Most of the requirements of IEEE 802.16m match those of the IMT-Advanced, including operating in the spectrums set by the ITU-R report. Similar to LTE-

Advanced, the IEEE 802.16m is intended to support both duplexing schemes, including half duplex FDD. The standard will also support flexible bandwidth allocations, up to 40 MHz.

1.5

Book Overview

This book is about IMT-Advanced access networks. It begins with two introductory chapters. This chapter provides a brief history and motivation for

IMT-Advanced networks, and establishes the requirements for IMT-Advanced networks – as set by the ITU-R. The next chapter, Chapter 2, introduces the physical layer technologies and networking advances that are collectively enabling both IEEE and 3GPP to satisfy the IUT-R requirements in their

IMT-Advancements, respectively the IEEE 802.16m amendment and 3GPP’S

Release 10. The chapter covers the multi-carrier access technologies utilized in

IMT-Advanced networks and their immediate predecessors, including OFDMA and SC-FDMA. It also reviews notions of diversity, adaptive modulation and coding, and frequency reuse, in addition to how wideband transmissions

(<20 MHz) are made possible using carrier aggregation techniques. Advanced antenna techniques, including MIMO, CoMP, and inter-cell MIMO are also introduced. Finally, the chapter discusses the use of small cells through wireless multihop relaying and femtocells, in addition to access composites will be utilized in IMT-Advanced networks.

The remainder of the book is divided into three parts. The first discusses

WiMAX or IEEE 802.16 networks based on the amalgamated IEEE 802.16-

2009 documents, which includes the IEEE 802.16j amendment for multihop relay

WiMAX networks, in addition to the IEEE 802.16m amendment. The second Part discusses LTE and LTE-Advanced documents based on Release 9 and Release

10 recommendations. The third and last part of the book, “The Road Ahead”, offers a multi-faceted comparison of the two technologies, provides a view of the

IMT-Advanced market and identifies the future outlook for this next generation cellular networks.

Part I consists of Chapters 3 to 8. Chapter 3 introduces the WiMAX network, its air interface and its network architecture. In doing so, it identifies the differences between the IEEE 802.16-2009 and its m amendment. The chapter also provides a brief overview of the functionalities discussed in the remainder of the part, which is organized as follows.

Chapter 4 describes the WiMAX frame structure, in addition to how addressing and identification are performed. The chapter discusses both the TDD and

FDD options, how relay stations are accommodated in WiMAX and new frame structure for IEEE 802.16m better suits the ITU-R requirements. It then discusses how addressing and connections identifications are performed in the two generations. Chapter 5 discusses network entry, connection initialization and ranging.

Chapter 6 details WiMAX’s quality of service classes, initially defined in IEEE

16

LTE, LTE-Advanced and WiMAX: Towards IMT-Advanced Networks

802.16-2009, in addition to how bandwidth requests, reservations and grants are communicated in the network. Meanwhile, Chapter 7 delves into the details of mobility management in the IEEE 802.16 access networks, including the management between legacy and Advanced WiMax and between WiMAX and other access technologies. Finally, the security aspects of the IEEE technologies are introduced in Chapter 8.

Part II, comprising Chapters 9 to 14, discusses LTE and LTE-Advanced and follows the outline of the first part. In Chapter 9, LTE’s air interface and architecture is introduced, including 3GPP’s support for femtocells and relay stations LTE-

Advanced. The chapter also briefs the reader on the contents of the remainder of the part, which is organized as follows.

Chapter 10 delves into the descriptions of the frame structures utilized in both

LTE and LTE-Advanced. It also summarizes how 3GPP network elements are identified. Chapter 11 describes the states and state transition of user equipment, describing the processes for both the idle and connected states, and connection establishment and tear down. As well, the chapter describes the state mapping between access and core signaling. In Chapter 12, quality of service handling and connection management is explained, while Chapter 13 describes intra-network and intra-network mobility management and signaling. Additionally, Chapter 13 gives an overview of LTE-Advanced mobility management for femtocells and relay stations. The last chapter in Part II, Chapter 14, discussed security in 3GPP.

Chapters 15 to 19 make up Part III of book. Chapter 15 offers a comparison between the two standards based on how they satisfy the ITU-R requirements, their functionalities, and their individual use of the enabling technologies described in Chapter 2. Meanwhile, Chapter 16 goes into how each technology attends to the ITU-R coexistence and inter-technology handover requirements.

Chapter 17 goes into the quality of service aspects of the IMT-Advanced networks. Specifically, the chapter looks at the two technologies’ QoS definitions and handling. A market view of the IMT-Advnaced is provided in Chapter 18, and a future outlook is offered in Chapter 19.

A reader interested in a thorough understanding of the two IMT-Advanced networks and their current and future standing is invited to read all the chapters in their given sequence. Readers interested in any of the individual technologies need only to read the respective part. A head-to-head comparison can be made by reading the relevant chapters, for example, Chapters 10 and 16 for frame structure and network identification; Chapters 13 and 18 for mobility management; and so on. Meanwhile, a reader interested into the comparative analysis of the technologies’ current and future status can jump right ahead to Part III.

References

[1] 3G Coverage (up to 2009), available at OECD Broadband Portal, http://www.

oecd.org/document/36/0,3746,en_2649_33703_38690102_1_1_1_1,00.html.

Introduction

17

[2] HSPA to LTE-Advanced, a whitepaper by RYSAV Research, available at 3G Americas, http://www.3gamericas.org/documents/3G_Americas_RysavyResearch_HSPA-LTE_

Advanced_Sept2009.pdf.

[3] Recommendation ITU-R M.1645, “Framework and overall objectives of the future development of IMT-2000 and systems beyond IMT-2000”, http://www.itu.int/rec/R-REC-M.1645-0-

200306-I/en.

[4] Global LTE Commitments, available at GSA Statistics, http://www.gsacom.com/news/ statistics.php4.

[5] LTE Global Map, available at GSA Statistics http://www.gsacom.com/news/statistics.php4.

[6] WiMAX Forum, Industry Research Report, March 2011, http://www.wimaxforum.org/ resources/research-archive.

[7] WiMAX Deployments, http://wimaxmaps.org/.

[8] Report ITU-R M.2134, “Requirements related to the technical performance for IMT-Advanced radio interface(s),” http://www.itu.int/pub/R-REP-M.2134-2008/en.

[9] 3GPP Technical Report 36.913, “Requirements for further advancements for Evolved Universal Terrestial Radio Access (E-UTRA) (LTE-Advanced),” http://ftp.3gpp.org/specs/html-info/

36913.htm.

[10] IEEE 802.16 Broadband Wireless Access Working Group, “IEEE 802.16m Requirements,” http://www.wirelessman.org/tgm/core.html#07_002.

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