LTE and LTE advanced
LTE and LTE advanced
IMT and IMT-Advanced Technologies
• LTE, LTE Advanced and Wireless MAN-Advanced, are
designed to enable high speed Internet/Broadband at
anytime, anywhere, with higher level of user-level
• As per ITU for IMT-Advanced technologies, the targeted
peak data rates are up to 100 Mbit/s for high mobility and
up to 1 Gbit/s for low mobility scenario. Scalable
bandwidths up to at least 40 MHz should be provided
• key technologies:
– Orthogonal Frequency Division Multiplex (OFDMA)
– Multiple Input Multiple Output (MIMO) and
– System Architecture Evolution (SAE)
MIMO Multiple Input Multiple Output
• Uses multiple transmitter and receiver antennas, which
allow independent channels to be created in space.
• Various Approaches for MIMO:
– Space diversity:- to improve the communication reliability by
decreasing the sensitivity to fading by picking up multiple
copies of the same signal at different locations in space.
– Beamforming:- antenna elements are used to adjust the
strength of the transmitted and received signals, based on
their direction for focusing of energy.
– Spatial Multiplexing:- Increased capacity, reliability,
coverage, reduction in power requirement by introducing
additional spatial channels that are exploited by using spacetime coding
OFDMA Orthogonal Frequency Division Multiple Access
• Based on the idea of dividing a given high-bitrate data stream into several parallel lower bitrate streams and modulating each stream on
separate carrier – often called sub-carriers or
• Multi-carrier modulation scheme minimize
inter-symbol interference (ISI) by making the
symbol time large enough so that the channelinduced delays are an insignificant (<10%)
fraction of the symbol duration.
OFDMA Orthogonal Frequency Division Multiple Access
• OFDM is a spectrally efficient version of multi-carrier
modulation where sub-carriers are selected such that
they are all orthogonal to one another over the symbol
duration, thereby avoiding the need to have non
overlapping sub-carrier channels to eliminate intercarrier interference .
• Guard intervals are used between OFDM symbols. By
making the guard intervals larger than the expected
multi-path delay spread, Inter Symbol Interference
(ISI) can be completely eliminated
OFDMA Orthogonal Frequency Division Multiple Access
• OFDMA can be used as a multi-access scheme, where
the available sub-carriers may be divided into several
groups of sub-carriers called sub-channels. Different
sub channels may be allocated to different users as a
multiple access mechanism. This type of multi access
scheme is called OFDMA.
• OFDMA is essentially a hybrid of FDMA and TDMA.
Users are dynamically assigned sub-carriers (FDMA)
in different time slots (TDMA).
• OFDMA is a flexible multiple access technique that
can accommodate many users with widely varying
applications, data rates and QoS requirements.
LTE Long Term Evolution
• Capabilities:– Scalable bandwidth up to 20 MHz, covering 1.4, 3, 5, 10, 15,
and 20 MHz
– Up/Downlink peak data rates up to 86.4/326 Mbps with 20
MHz bandwidth
– Operation in both TDD and FDD modes
– Reduced latency, up to 10 ms round-trip times between user
equipment and the base station, and up to less than 100 ms
transition times from inactive to active
LTE Specifications and speed
Peak downlink speed with 64QAM in Mbps
Peak uplink speeds(Mbps)
Data type
Channel bandwidth (MHz)
Duplex schemes
Spectral efficiency
Access schemes
Modulation types supported
100 (SISO), 172 (2x2 MIMO), 326 (4x4 MIMO)
50 (QPSK), 57 (16QAM), 86 (64QAM)
All packet switched data (voice and data). No
circuit switched.
1.4, 3, 5, 10, 15, 20
0 - 15 km/h (optimised),
15 - 120 km/h (high performance)
Idle to active less than 100ms
Small packets ~10 ms
Downlink: 3 - 4 times Rel 6 HSDPA
Uplink: 2 -3 x Rel 6 HSUPA
OFDMA (Downlink)
SC-FDMA (Uplink)
QPSK, 16QAM, 64QAM (Uplink and
LTE Advanced: Key features
• Features:– Compatibility of services
– Enhanced peak data rates to support advanced
services and applications (100 Mbit/s for high
and 1 Gbit/s for low mobility).
– Spectrum efficiency: 3 times greater than LTE.
– Peak spectrum efficiency: downlink – 30
bps/Hz; uplink – 6.75 bps/Hz.
– Spectrum use: ability to support scalable
bandwidth use and spectrum aggregation when
non-contiguous spectrum needs to be used.
3GPP specification releases
1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
GSM/GPRS/EDGE enhancements
Release 99
Release 4
1.28Mcps TDD
Release 5 HSDPA, IMS
Release 6
Release 7 HSPA+ (MIMO, HOM etc.)
ITU-R M.1457
IMT-2000 Recommendations
Release 8
Release 9
Release 10 LTE-Advanced
LTE-Advanced 주요 표준 동향 및 요소 기술
Comparison chart
Max downlink speed( bps) 384 k
14 M
28 M
Max uplink speed (bps) 128 k
5.7 M
11 M
75 M
500 M
Latency round trip time 150 ms
100 ms
~10 ms
less than 5
3GPP releases
Rel 99/4
Rel 5 / 6
Rel 7
Rel 8
Rel 10
Access methodology
LTE User Equipment categories
• The LTE UE (User Equipment) categories or UE
classes are needed:
– to ensure that the base station (eNodeB) can communicate
correctly with the user equipment.
– So the base station is able to determine the performance of
the UE and communicate with it accordingly.
• Five different LTE UE categories defined with a wide
range in the supported parameters and performance
e.g. LTE category 1 does not support MIMO, but LTE
UE category five supports 4x4 MIMO.
The Second meeting of SATRC Working Group on Spectrum
12-13 December 2011 Colombo, Sri Lanka
LTE User Equipment categories
LTE UE category data rates
LTE UE category modulation formats supported
Requirements for LTE-Advanced [1]
General requirement
 LTE-Advanced
is an evolution of LTE
 LTE-Advanced shall meet or exceed IMTAdvanced requirements within the ITU-R time
 Extended LTE-Advanced targets are adopted
LTE-Advanced 주요 표준 동향 및 요소 기술
Requirements for LTE-Advanced [2]
Comparison between IMT-Advanced and LTE-Advanced
 LTE-Advanced should at least fulfill or exceed IMTAdvanced requirements
ITU Requirement
Peak data rates
3GPP Requirement
1Gbps in DL 500Mbps in UL
40MHz (scalable BW)
Up to 100MHz
User plane latency
Improved compared to LTE
Control plane latency
Active   Active dormant(<10ms) Camped  Active (<50ms)
Peak spectrum efficiency
15bps/Hz in DL 6.75bps/Hz in UL
Average spectrum efficiency
30bps/Hz in DL 15bps/Hz in UL
Set for four scenarios and several antenna configurations See next slide for case 1 requirement
Cell edge spectrum effciency
VoIP capacity
Up to200 UEs per 5MHz
LTE-Advanced 주요 표준 동향 및 요소 기술
Improved compared to LTE
Requirements for LTE-Advanced [3]
System performance requirements for IMT-Advanced
ITU system performance requirement
Spectrum Efficiency
DL (4x2 MIMO)
UL (2x4 MIMO)
DL (4x2 MIMO)
UL (2x4 MIMO)
LTE-Advanced 주요 표준 동향 및 요소 기술
Base coverage Urban
Rural/ High speed
Requirements for LTE-Advanced [4]
System Performance Requirements from TR 36.913
Peak Spectral Efficiency:
 DL
30bits/Hz (8x8 MIMO), UL 15bps/Hz (4x4 MIMO)
Seem to be easily achievable by means of extended utilization of # of antennas
Average Spectral Efficiency (SE) and Edge Spectral Efficiency for LTE Case-1
 System
performances of LTE Rel-8 are about 30% ~ 70% lower than 3GPP target
What would be key enabling technologies to fill up the gap between two?
Antena LTE
Cell Avg. SE Cell Avg. SE Cell Edge SE Cell Edge SE [bps/Hz/cell] (3GPP [bps/Hz/cell] (3GPP [bps/Hz/user] (3GPP [bps/Hz/user] (3GPP R1‐072580)
LTE-Advanced 주요 표준 동향 및 요소 기술
Performance issues
Peak data rate
Average sector throughput
Quality of Service (QoS)
• Peak data rates are often perceived as actual data rates a
subscriber will experience on a wireless network; this is
however far from the reality.
• Peak data rates do not take into account factors like traffic
load, fading, attenuation loss and the signal to noise ratio
that have an impact on the end subscriber data rate in a
fixed line environment, and an even greater impact in
wireless networks.
• In wireless, additional factors such as the surrounding
environment and atmospheric conditions also affect the
achievable data rates. This results in a real world data rate
that is well below the theoretical peak data rate obtained in
laboratory environments
• Many different ways to measure performance of
wireless technologies which take into account
various conditions and scenarios. These include:
– peak throughput,
– average sector throughput,
– cell edge throughput and
– subscriber data rate
• To accurately predict realistic live LTE network
capacity and achievable subscriber experience,
operators need to understand the different
performance measurements.
Radio transmission is broadcast via a radio base station, this
equipment transmits the radio signals which are received by end user
equipment (UE).
Radio signal quality affected by several factors, such as the signal
path loss; this is essentially the reduction in power density of the
signal as it moves through the environment in which it is traveling.
Other factors that affect the signal strength include free space loss
which affects the subscriber’s signal as he moves away from the
transmitting base station. The signal also suffers if its path is
obstructed by a factor known as diffraction or if the signal is reflected
and reaches the receiver via a number of different paths. This results
in performance degradation known as multipath.
In effect, the less path loss and susceptibility to interference, the better
the signal strength a UE experiences. The better the quality of signal
received, the better the performance and throughput achieved by the
effects of signal path loss suffered by radio signals due to factors such as
free space loss, multipath, buildings and vegetation, diffraction and the
general atmosphere.
Performance issues
• new adaptive modulation schemes and techniques
compensate for environmental factors, delivering more
capacity and better range in an inherently noisy
environment full of obstacles
• One example is adaptive modulation
provides tradeoff between delivered bit rate
and robustness of digital encoding, in order
to balance throughput with error resilience.
In areas where signal strength is good,
modulation switches to a higher bit rate
with less robust encoding, while in areas
where signal strength is poor or there are a
lot of multi-path reflections, the modulation
switches to a lower bit rate with more
robust encoding to minimize errors.
Thus highest throughput occurs closer to tower
Performance issues
• Several factors impact the
practical throughput in RF
– additional overhead added by
adaptive modulation and error
correction coding affect actual data
rate experienced by a user,
significantly lowering the user
experienced data rate compared to
the physical layer peak data rates
measured in the lab.
Performance issues
• LTE technology is spectrally efficient hence gets
more bits per second over a fixed bandwidth than
previous technologies and as a result, if you take
into account a reasonable error rate coding, you
reach a peak data rate that is more realistic for
commercial deployment.
Antenna Technology
Channel Bandwidth and Data Rates
Channel Bandwidth and Data Rates
Table 1a – LTE Peak Data Rates
(Mbps) – no error rate coding
Antenna Technology
Table 1b – LTE Peak Data Rates (Mbps) –
5/6 error rate coding
Performance issues
Figure 5 – LTE Sector Throughput compares the average sector throughput
capacity of various cellular radio technologies
LTE provides a significant improvement in Average Sector Throughput
capacity across all channel bandwidths when compared to other 3GGP
technologies by leveraging 2X2 MIMO and OFDM.
Performance issues
Note Conditions - LTE is based on 2.6GHz and UMTS is 2.1GHz showing realistic performance in the field
Comparing LTE and HSPA+ performance across entire cell area
Performance issues
• With LTE’s all IP, flat architecture, the initial data
packet connection is much faster, typically 50 ms,
and then between 12-15 ms roundtrip latency
• The low latency of LTE, combined with its high
average sector throughput, makes it an ideal
platform for demanding services like video,
gaming, and VoIP.
Performance issues
• QoS classes ensure network can prioritize certain types of
packet for immediate and secured delivery; can provide
differentiated types of service, with potential for offering
creative new billing models while offering subscribers a
guaranteed level of service.
• The class of QoS and Guaranteed Bit Rate (GBR) are
significantly dependent on the level of latency (delays in
packet transmission), jitter (variation in latency), and
dropped packets that occur in the network.
• Without a QoS implementation on a loaded network,
subscribers will experience choppy videos, echo and
delays in voice resulting in poor audio quality on voice
Performance issues
• Realistic average subscriber data rate
UMTS LTE a technology
Lawrence Harte
Althos Publishing
Also see
• standard for wireless data communications technology
and an evolution of the GSM/UMTS standards.
• goal of LTE was to increase the capacity and speed of
wireless data networks using new DSP (digital signal
processing) techniques and modulations that were
developed around the turn of the millennium.
• A further goal was the redesign and simplification of the
network architecture to an IP-based system with
significantly reduced transfer latency compared to the 3G
• The LTE wireless interface is incompatible with 2G and 3G
networks, so that it must be operated on a separate
wireless spectrum.
• Universal mobile telecommunications
system - UMTS - Long Term Evolution LTE
– set of projected improvements to the 3rd generation
wireless systems - 3G, including
– 100 Mbps+ data transmission (peak) rates,
– reduced transmission delays (reduced latency),
– increased system capacity and
– shorter transmission latency times.
– Commonly referred to as nearly 4G (even though it is
not a ‘true’ 4G technology for which true 4G is
sometimes used for LTE Advanced)
• allows cellular carriers to offer a very efficient
(more subscribers per cell site) mix of
multimedia services (voice, data, and video)
for existing (mobile telephone) and new
(Internet and television) customers.
• designed to permit advanced and reliable
services including media streaming and large
file transfers.
– new services offer potential of higher average revenue per user
than existing 1st and 2nd generation mobile customers.
– for existing mobile carriers that upgrade to LTE, marketing is
geared towards acquiring new data-only and mobile television
LTE specification
provides downlink peak rates of 300 Mbit/s, uplink peak rates of 75
Mbit/s and QoS provisions permitting a transfer latency of less than 5
ms in the radio access network.
can manage fast-moving mobiles and supports multi-cast and
broadcast streams.
supports scalable carrier bandwidths, from 1.4 MHz to 20 MHz and
supports both frequency division duplexing (FDD) and time-division
duplexing (TDD).
IP-based network architecture, called the Evolved Packet Core (EPC)
and designed to replace the GPRS Core Network, supports seamless
handovers for both voice and data to cell towers with older network
technology such as GSM, UMTS and CDMA2000.
simpler architecture results in lower operating costs (for example, each EUTRA cell will support up to four times the data and voice capacity supported by HSPA)
natural evolution of 3GPP GSM and UMTS WCDMA networks.
Since LTE provides services above the original 3rd generation (3G)
requirements, but does not provide service levels for 4th generation
(4G) requirements, it is sometimes called “Beyond 3G”.
key attributes include a variable bandwidth (1.4 MHz up to 20
MHz) OFDM radio channel, the co-existence of multiple physical
channels on the same frequency using channel codes, many
logical (transport) channels, separate signaling channels,
multiple service QoS types, multi-system operation, and other
advanced operational features.
Each wide (20 MHz) LTE RF channel can have more than 800
simultaneous communication channels. Some of the channels are
used for control purposes, while others are used for voice (audio)
and user data transmission.
Recall: what is UMTS
Mobile Communication System - Universal Mobile Telephone System - UMTS - is
a wide area broadband wireless communications system that uses digital radio
transmission to provide voice, data, and multimedia communication services.
Recall: What is UMTS?
A UMTS system coordinates communication between mobile devices (user
equipment), radio access radio sites (UTRAN), and uses a packet switching core
network to connect UMTS devices to other devices or networks.
Digital Media Formats - LTE is designed to transfer digital information in packet
data format.
Functional Sections - The LTE system is composed of three key
– - User Equipment (UE) - A device that converts media to and from UMTS LTE radio
- UMTS Terrestrial Radio Access Network (UTRAN) - Assemblies that convert digital
signals to radio signals that can be sent to mobile devices and receive radio signals
that can be converted back to their digital form.
- UTRAN is divided into enhanced node B base stations - eNB - parts that are
located at the cell site and radio network controllers - RNC - that coordinate the
distribution and reception of communication connections.
- Core Network (CN) - The CN performs the interconnection between the base
station parts and other networks such as the public switched telephone network
- PSTN - and public Internet. The core network is composed of high speed
packet data switches, databases, and administrative control services.
LTE key features
LTE key features
LTE key features include high speed data transmission, low latency packet
data transmission, flexible frequency allocation, self-configuration capability,
all IP core network, and multibeam transmission.UMTS LTE data
transmission rates can reach up to 100 Mbps for the downlink and up to
50 Mbps for the uplink.
UMTS LTE packet data transmission is significantly low allowing for low
latency applications (such as VoIP Internet Telephony).
The UMTS LTE system can use a mix of radio channel frequency
bandwidths and duplex transmission types allowing for UMTS to be
deployed in small amounts of spectrum.
The UMTS LTE system was designed for automatic configuration and
radio transmission optimization reducing the operational complexity and
The UMTS LTE switching system (the core network) only uses IP
connections between network components simplifying design and
deployment. This standardizes the equipment and service requirements
simplifying design complexity and lowering support costs.
UMTS LTE can use multibeam transmission to increase distance,
reliability, and provide more capacity.
LTE: UMTS evolution
LTE: UMTS evolution
UMTS LTE natural evolution of 3GPP GSM and UMTS WCDMA
networks. Because LTE provides services above the original 3rd
generation (3G) requirements but does not provide service levels for 4th
generation (4G) requirements, it is sometimes called “Beyond 3G.”
0G - Mobile Telephone before cellular
1G - Analog Cellular
2G - Digital Cellular
2.5G - High Speed Packet Data
3G UMTS WCDMA - Multimedia
3G UMTS LTE - Ultra Broadband Packet Data
(cellular) mobile communication evolved from single user per radio
channel (analog) to shared high-speed multimedia broadband channels.
One key benefit of evolution is ability of a mobile carrier to provide more
services in same amount of radio channel bandwidth. If carrier upgrades
system radio equipment and adds customers with new mobile
technologies (and eventually gets rid of the old), they lower service costs
(or make more money).
LTE services
LTE services
GSM voice service started as a full rate voice service that allowed 8
users per GSM radio channel. The original design allowed for the use of
a half rate voice service (lower quality audio) to incrase the number of
simultaneous GSM voice users to 16 per radio channel.
GSM Data services started as low speed circuit switched data (9.6
kbps). The GSM system evolved to allow the combination of multiple
circuit switched data connections to provide high speed circuit
switched data services - HSCSD.
GSM short messaging service - SMS messaging service for extremely
short text messages (140 characters). SMS evolved into executable
messages that allow for advanced two-way messaging features.
GSM Multicast - GSM has capabilities of one to many type services
such as group call (dispatch type services) and voice broadcast (such
as traffic alerts).
GSM Packet Data - GPRS - The GSM system evolved allowing users to
dynamically share packet data resources on one or more GSM channels
for services such as Internet browsing.
LTE devices
LTE devices
UMTS LTE devices range from fixed adapters (e.g. home network
termination units) to network termination adapters that allow a mix of
device types to connecto the UMTS LTE system.
– UMTS LTE mobile telephones may include the capability to use UMTS LTE
radio channels and other types of radio signals (such as WCDMA, GSM,
CDMA2000, and WiMAX).
– Multimode UMTS LTE mobile device allows service providers to gradually
migrate users in their systems to areas that can provide UMTS LTE radio
Mobile Telephones - Portable devices that can be used for voice
PCMCIA Air Cards - Cards that can slide into computers to provide data
Embedded Radio Modules - Radio assemblies that can be built-in or
installed in devices such as laptop computers, video cameras, or digital
signage displays.
LTE devices
External Radio Modems - Assemblies that can be connected to other
devices through USB, Ethernet, or other connection types to provide
data services.
Network Termination Units (NTUs) - A receiver assembly that can
produce one or more outputs that can be connected to devices such as
home telephones, computers, or television sets.
Media Players - Portable devices that can receive and display
Location Devices - Devices that can capture and/or display position
location information.
LTE Radio
LTE Radio
LTE radio is the transmission of control and user
information in packet data format through a wide RF
channel which usually operate on frequency bands around
the world ranging from 800 MHz to 2 GHz.
LTE was designed as a Multimode system which allows
mobile devices to transfer between the LTE system and
other types of systems such as GSM, WCDMA, or even
Multiple Types of Modulation - The LTE system can
transmit using different types of modulation - QPSK and QAM
- to allow the system to increase the data transmission rate
when low distortion radio conditions exist.
LTE Radio
Multiple Input Multiple Output (MIMO) - UMTS systems can use
multiple transmission paths to increase the distance and reliability of
radio transmission.
Variable Channel Bandwidth - The RF channel bandwidth can be
dynamically assigned to allow the UMTS flexibility for bandwidth
assignment (narrow channels) and increasing data transmission rates
when bandwidth is available.
FDD or TDD Operation - UMTS system can used paired frequencies
- FDD - or shared single frequencies - TDD to allow UMTS systems to
operate in a mix of frequency bands.
The LTE system can use multiple types of modulation. The lowest
level modulation type (and most robust) is Quadrature Phase Shift
Keying - QPSK modulation. When radio conditions permit, 16-QAM can
be used to increase transmission capacity. If radio conditions permit,
64-QAM may be used. Complexity and cost of 64-QAM, mobile devices
may not include a 64-QAM transmission option.
LTE modulation types
figure shows that amplitude and phase
modulation - QAM - can be combined to
form an efficient modulation system.
In this example, one digital signal
changes the phase and another digital
signal changes the amplitude. This allows
a much higher data transfer rate as
compared to a single modulation type.
LTE MIMO radio transmission
LTE system can use multiple input multiple output - MIMO - radio transmission
to provide increased transmission reliability and higher data transmission
A multiple input multiple output (MIMO) transmission system transmits signals over
multiple paths to a receiver where they are combined to produce a higher quality
example shows that a single beam transmission signal can have deep signal fade
levels. When two or more beams are used, the signal fades are minimized,
resulting in a more even (error free) signal.
LTE dynamic bandwidth
LTE system can dynamically change its transmission bandwidth up to 20 MHz by
adding or removing sub-carrier channels.
Figure shows how LTE system can dynamically assign bandwidth through the
allocation of sub-carriers. This diagram shows that the RF channel bandwidth can be
up to 20 MHz wide. The RF channel can be divided into 15 kHz sub-channels and
bandwidth configuration (allocated sub-carriers) is a portion of the RF channel.
LTE system
The key parts of a LTE system include:
user equipment (UE), User equipment - can be many types
of devices ranging from simple mobile telephones to digital
evolved node B (eNB), radio access part of the LTE system.
evolved packet core (EPC), uses an IP packet system
which can connect to other types of networks such as the
public switched telephone network - PSTN through the use
of gateway - GW - devices.
LTE system
simplified diagram of an LTE system: includes mobile communication
devices (user equipment - UE) that can communicate through an evolved
node B (eNB), enhanced packet core (EPC) packet switching system.
LTE system is compatible with both the new variable width LTE channels, 5 MHz
wide WCDMA radio channels, and narrow 200 kHz GSM channels.
This example also shows that the LTE system can provide broadcast video,
multimedia (mixed data), and voice services.
LTE evolved Node B (eNB)
An evolved Node B - eNB - is the radio
access part of the LTE system.
Each eNB contains at least one radio
transmitter, receiver, control section and
power supply.
In addition to radio transmitters, and
receivers, eNBs contain resource
management and logic control functions
that have been traditionally separated into
base station controllers (BSCs) or radio
network controllers (RNCs).
This added capability allows eNBs to
directly communicate with each other,
eliminating the need for mobile switching
systems (MSCs) or controllers (BSCs or
LTE evolved Node B (eNB)
eNB functions include radio resource management - RRM,
radio bearer control, radio admission control - access control,
connection mobility management, resource scheduling
between UEs and eNB radios, header compression, link
encryption of user data stream, packet routing of user data
towards its destination (usually to EPC or other eNBs),
scheduling and transmitting paging messages (incoming calls
and connection requests), broadcast information
coordination (system information), and measurement
reporting (to assist in handover decisions).
Each eNB is composed of an antenna system (typically a radio tower),
building, and base station radio equipment. Base station radio equipment
consists of RF equipment (transceivers and antenna interface equipment),
controllers, and power supplies.
LTE Gateways
LTE gateways are devices that adapts media
transmission between the LTE system and other systems
such as the Internet or the public switched telephone
network - PSTN.
LTE Gateways
LTE system uses serving gateways - S-GW and packet
gateways - P-GW
A serving gateway, S-GW is a device or assembly that coordinates the
control and adapts data transmission between a device and a system.
• may adapt communication processes and underlying data to access method
used by device or system with which it is communicating.
• also functions as a mobility anchor point (fixed connection route during a
communication session) for handovers between eNBs (inter-eNB
handovers), and an anchor point for inter-3GPP mobility.
A packet gateway is a device or assembly that coordinates the control and
adapts packet data transmission between a communication connection and
another system.
• may adapt data formats and communication processes to the system that it
is communicating with.
• may allocate IP addresses or filter packets (deep packet inspection).
LTE Mobile management entity (MME)
A mobile management entity - MME - is a processing element within the
LTE. Can be used to help find, route, and maintain and transfer
communication connections to e.g. WiMAX wireless devices.
The MME can perform end to end connection signaling and security
services between core networks (Inter CN node signaling). It can perform
mode access control to the UE when it is not connected.
The MME can maintain location information about devices and determine
which gateway will be used to connect mobile devices to other networks.
LTE Evolved Packet Core (EPC)
The LTE system uses two basic types of network
elements; enhanced node B - eNB base stations and
media gateways.
No switch is needed as network elements can communicate
with each other to setup connections and connection
transfers (handovers).
The LTE system uses an evolved packet core - EPC - to
receive, process, and forward packets towards their
destinations. The use of an EPC allows for the rapid
processing of packets, which increases data throughput
while reducing packet delays.
LTE Evolved Packet Core-EPC
Figure shows the key functional parts of an evolved packet core - EPC - system.
Example shows several types of packet flows (voice, Internet browsing, and
video) that are transferred to a user equipment device in a UMTS LTE system.
The serving gateway categorizes each incoming packet and routes it to a
mobility tunnel that reaches the eNB (base station). The eNB maps and
manages the data transmission to the UE on appropriate radio bearer channels.
LTE network architecture
key network elements include
user equipment (UE)
base stations (eNBs)
Evolved Packet Core-EPC
serving gateway (S-GW) and mobile management entity (MME)
subscriber databases (HSS) and packet gateway (P-GW).
UEs communicate with eNBs (base stations) through the Uu radio interface.
eNBs can directly communicate with each other using an X2 interface or with
MMEs using the S1 interface.
MME sets up and manages mobile connections using information from HSS.
Calls are controlled by an S-GW and the call or session event information from
the S-GW is provided to a policy control and charging function (PCRF) which
translates the information into billing records.
The S-GW can also link to a serving general packet radio service support node
(SGSN) to allow the UMTS system to interoperate with other mobile
communication systems including GSM, GPRS, and WCDMA.
LTE network architecture
The LTE network architecture uses a modular system
design called the system architecture evolution SAE, which is composed of separate components that
may be added, removed, or connected together to
evolve or improve the capabilities of an existing system.
The LTE system uses an SAE to transition from a voice
centric switched network to a universal broadband
communications access system.
LTE protocol architecture
LTE can use use multiple protocols that are divided into processing
layers. Each protocol layer performs specific functions. Each protocol
layer may also use one or more protocols. The layered approach
simplifies for the adding of new functions without requiring significant
changes to the system.
Radio resource control - RRC - is a protocol is used to coordinate the
operation (control) of the radio.
Packet data convergence protocol - PDCP - ensures that all the
packets are transferred and placed in correct order.
The radio link control - RLC - layer is concerned with maintaining the
radio link between the mobile device and the base station.
Medium access control layer - MAC - coordinates access requests
and assignment from the system.
Broadcast and multicast control - BMC -is responsible for receiving and
processing broadcast messages.
LTE protocol layers
Figure shows how the protocol layers of the LTE system can link the radio
device, through the evolved node B (eNB) base station.
The LTE radio link is divided into layers where each layer performs its specific
function and passes its data on to the next layer above or below.
Physical Layer - The physical layer converts digital bits to and from RF packets that
are sent between the UMTS LTE device and the access point.
MAC Layer - The medium access control layer (MAC) is the process used to request
and coordinate access to the system.
RLC Layer - The radio link control layer is concerned with maintaining the radio link
between the mobile device and the base station.
PDCP Layer - Ensures that all packets are transferred and placed in correct order.
LTE network interfaces
LTE network interfaces
This figure shows key LTE network elements and how they interface with
each other. LTE network interfaces define the characteristics and processes
that are used to connect network elements to each other or to other
Uu Interface - User equipment - UE - communicate with evolved node B
(eNB) using the Uu interface.
S1 Interface - is used to eNBs to the serving gateway (S-GW).
X2 Interface - allows eNBs to directly connect with each other.
S6 Interface - allows mobile management entity (MME) to connect with
customer database (HSS).
S3 Interface - is used to link to existing systems (such as GSM, GPRS,
and WCDMA) to the LTE system.
S5 Interface - connects the LTE system to packet data networks such as
the Internet.
S7 Interface - connects the LTE system to operations and support
LTE system operation
LTE system operates by coordinating connections with mobile devices,
managing connection transfers (mobility), setting up and managing service
sessions, keeping track of the location of mobile devices, and coordinating
the distribution of signals to groups (multicast) or to geographic areas
Connection States - The LTE must identify and control the mode of each
wireless device that is operating in its system.
Connection Transfers (Mobility) - the LTE system coordinates the transfer of
connections as wireless devices move to different radio coverage areas.
Session Management (IMS) - The LTE system sets up, initializes, and
manages communication services such as voice, data, and video.
Location Based Services (LBS) - LTE systems maintain position location
information for commercial services, system management, and emergency
Muticasting and Broadcasting - LTE systems coordinate the distribution of
signals to groups of users (multicast) or to geographic regions (broadcast).
LTE mobility states
Mobility states are the status conditions of a mobile device as it relates to a
communication network. Mobility states include detached (unknown), active
(communicating), and idle (awaiting actions).
This figure that LTE device starts in the detached (unknown status) state
when it is turned on. After it registers with the system, it changes into the
active state. If the device is inactive for a period of time (does not transfer
information), it may be moved into the idle mode. If there is data to be
transferred, the mode may be changed back to the active state. When a
device is powered off, it informs the system (deregisters) and detaches.
LTE handover (HO)
LTE Handover is performed by the user equipment devices connecting
directly to each other through the eNBs. No switching equipment is
required for LTE handovers to other devices in the LTE system.
Can handover within a system (intra-system), to other systems (intersystem), and to systems that use other radio access technologies (Inter-RAT
LTE handover (HO)
This figure shows the basic handover process that occurs in the LTE
system where the system has determined that the signal strength and
quality of the radio channel it is receiving and the serving eNB (source
eNB) is below desired levels and handover is preferred.
Process starts when the source eNB commands the UE to start measuring the
radio channel quality from a nearby base station (target eNB). Using the
information from the mobile, it is determined that the adjacent cell site is a
candidate for the handover and the direct transfer process starts.
The source eNB informs the target eNB using the X2 interface that a handoff
request has been initiated. During the handover process, the source eNB
forwards the user data to the target eNB. When the UE has successfully
connected to the target eNB, the connection is transferred and the target
eNB updates the MME of the transfer completion.
The MME then informs the serving gateway to change the user’s media path
(path change) from the source eNB to the target eNB.
IP Multimedia Subsystem (IMS)
IP Multimedia Subsystem (IMS)
IP multimedia subsystem - IMS - is set of session based protocols that can be
used to provide services using Internet protocol (IP) based. IMS has evolved
from its first use in 3rd generation mobile telephone standards that to other
types of networks including voice over Internet protocol (VoIP) and IP television
(IPTV). IMS can integrate devices and services across multiple types of
networks.Set of Session Control Protocols - IMS defines the use of session
control protocols (existing and tested protocols such as SIP) to negotiate and
initialize protocols that are used for communication sessions.
Integrates Systems and Services - The IMS system can be used to integrate
different systems and services that can be addressed using IP connetions.
IP Multimedia Subsystem (IMS)
Started with 3GPP and Evolved to VoIP and IPTV - IMS protocols are so
flexible that they have been used in other types of sytsems such as Internet
telephony and Internet protocol Television - IPTV.
This figure shows the basic functions of the IMS system. This diagram
shows that a user equipment device (a mobile phone in this example) is
calling another device (a landline telephone). The UE sends its connection
request (an invite) to the proxy call session control function (P-CSCF). The
P-CSCF needs to find the call server so it sends a request to the
interrogatory call session control sever (I-CSCF). The I-CSCF contacts the
home subscriber server (HSS) which contains the service profile of the user
and the location of the serving call session control function (S-CSCF). The
S-CSCF will then manage the communication session with the UE through
the P-CSCF. The IMS system can then connect a call through a media
gateway (signaling processes not shown) so the connection can reach the
landline telephone.
Location based Services (LBS)
LTE can provide location information using different types positioning
systems including the system itself (network positioning) or through the use of
global positioning system - GPS.
Location based Services (LBS)
LTE location services include:
Commercial Location Services (Commercial LCS) - Value added services that
are performed using location determination equipment and services such as
mapping and advertising.
Internal Location Services (Internal LCS) - Position discovery activities and data
that are used for network or service operation (find and page the subscriber).
Emergency Location Services (Emergency LCS) - Discovery and transfer device
location information to emergency facilities or services. Emergency LCS provide
agencies with the identification and location of a device that has dialed an
emergency services number (such as 112 or 911).
This figure shows how mobile communication systems can use GPS signals to
provide location information. A mobile telephone has both mobile communication
and GPS reception capability. When the user dials an emergency number, the GPS
information can is sent to the public safety access point to allow emergency services
to the location of the user’s mobile telephone.
Lawful Intercept Location Services (Lawful Intercept LCS) – Provides
identification and location information of a device to an authorized public safety
Evolved MBMS
LTE was designed to allow for shared (multicast) types of services
such as digital broadcast radio and digital video broadcast.
The eMBMS feature can simultaneously transmit the same media
signals using LTE eNBs to multiple recipients in the same
geographic region.
In addition to the shared transmission capability, the two-way
capabiltiy of the MBMS system allows users to dynamically interact
with the broadcast network. This means that the MBMS system can
provide one-way bearer services (multicasting and broadcasting
media) and user controlled media streaming.
Evolved MBMS
This figure shows how the MBMS system can be used to provide radio and television
broadcast services.
A television station (a or a video subscription channel) is broadcast to all the cells
within the LTE system area. Each TV subscription viewer must use a key (previously
provided) so they can receive and decode the television signal. A audio broadcast
(local radio station) is also connected to some of the LTE cells. Voice broadcast
(traffic alerts) are connected to a cells in the system area.
LTE summary
LTE summary
LTE was designed to simultaneously provide a mix of services
ranging from real time voice to high-speed Internet browsing.
The use of a single IP type of interconnection simplifies
deployment, maintenance, and reduces equipment cost.
Base stations (eNBs) can directly connect to each other with
eliminates the need for a switching system.
The radio structure is flexible (bandwidth, duplex types) which
allows LTE to be deployed in different spectrums.
IP Multimedia Subsystem - IMS - is used to setup and manage
multimedia sessions with devices in and outside of the LTE
Multiple types of location based services are integrated into the
LTE system.
LTE is an evolution of GSM, GPRS, and WCDMA.
• See SLIDES BY Toskala
• IEEE Tutorial
Orthogonal frequency-division
multiplexing (OFDM)
• method of encoding digital data on multiple carrier
• developed into a popular scheme for wideband
digital communication, whether wireless or over
copper wires, used in applications such as digital
television and audio broadcasting, DSL
broadband internet access, wireless networks,
and 4G mobile communications.
Orthogonal frequency-division
multiplexing (OFDM)
• is a frequency-division multiplexing (FDM)
scheme used as a digital multi-carrier modulation
method. A large number of closely spaced
orthogonal sub-carrier signals are used to carry
data. The data is divided into several parallel data
streams or channels, one for each sub-carrier.
Each sub-carrier is modulated with a conventional
modulation scheme (such as quadrature
amplitude modulation or phase-shift keying) at a
low symbol rate, maintaining total data rates
similar to conventional single-carrier modulation
schemes in the same bandwidth.
Orthogonal frequency-division
multiplexing (OFDM)
• primary advantage of OFDM over single-carrier
schemes is
– ability to cope with severe channel conditions (for example,
attenuation of high frequencies in a long copper wire, narrowband
interference and frequency-selective fading due to multipath)
without complex equalization filters.
– low symbol rate makes use of a guard interval between symbols
affordable, making it possible to eliminate intersymbol interference
(ISI) and utilize echoes and time-spreading (that shows up as
ghosting on analogue TV) to achieve a diversity gain, i.e. a signalto-noise ratio improvement. This mechanism also facilitates the
design of single frequency networks (SFNs), where several
adjacent transmitters send the same signal simultaneously at the
same frequency, as the signals from multiple distant transmitters
may be combined constructively, rather than interfering as would
typically occur in a traditional single-carrier system.
Supplementary slides
based on ieee tutorial
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