LTE System Overview

LTE/SAE System Overview

Training Manual Contents

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Copyright © Huawei Technologies Co., Ltd

i

Contents

1 Network Architecture ................................................................................................................ 1-1

1.1 Evolution of Cellular Networks .................................................................................................................... 1-2

1.1.1 First Generation Mobile Systems ......................................................................................................... 1-2

1.1.2 Second Generation Mobile Systems .................................................................................................... 1-2

1.1.3 Third Generation Mobile Systems ....................................................................................................... 1-3

1.1.4 Fourth Generation Mobile Systems ..................................................................................................... 1-5

1.2 3GPP Releases ............................................................................................................................................... 1-6

1.2.1 Pre-Release 99 ..................................................................................................................................... 1-6

1.2.2 Release 99 ............................................................................................................................................ 1-6

1.2.3 Release 4 .............................................................................................................................................. 1-6

1.2.4 Release 5 .............................................................................................................................................. 1-7

1.2.5 Release 6 .............................................................................................................................................. 1-7

1.2.6 Release 7 .............................................................................................................................................. 1-8

1.2.7 Release 8 .............................................................................................................................................. 1-9

1.2.8 Release 9 and Beyond .......................................................................................................................... 1-9

1.3 E-UTRAN Architecture ............................................................................................................................... 1-10

1.3.1 User Equipment ................................................................................................................................. 1-10

1.3.2 Evolved Node B ................................................................................................................................. 1-12

1.3.3 Femto Cells ........................................................................................................................................ 1-13

1.4 E-UTRAN Interfaces and Protocols ............................................................................................................ 1-14

1.4.1 Uu Interface ....................................................................................................................................... 1-14

1.4.2 X2 Interface ....................................................................................................................................... 1-16

1.4.3 S1 Interface ........................................................................................................................................ 1-18

1.5 EPC Architecture ......................................................................................................................................... 1-19

1.5.1 Mobility Management Entity ............................................................................................................. 1-19

1.5.2 Serving - Gateway .............................................................................................................................. 1-20

1.5.3 Packet Data Network - Gateway ........................................................................................................ 1-21

1.6 EPC Interfaces and Protocols ...................................................................................................................... 1-21

1.6.1 S11 Interface ...................................................................................................................................... 1-21

1.6.2 S5/S8 Interface ................................................................................................................................... 1-22

1.6.3 S10 Interface ...................................................................................................................................... 1-23

1.6.4 SGi Interface ...................................................................................................................................... 1-23

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1.6.5 Additional Network Elements and Interfaces ..................................................................................... 1-24

2 LTE Air Interface Principles .................................................................................................... 2-1

2.1 Radio Interface Techniques ........................................................................................................................... 2-2

2.1.1 Frequency Division Multiple Access ................................................................................................... 2-2

2.1.2 Time Division Multiple Access ............................................................................................................ 2-3

2.1.3 Code Division Multiple Access ............................................................................................................ 2-3

2.1.4 Orthogonal Frequency Division Multiple Access ................................................................................ 2-4

2.1.5 Transmission Modes ............................................................................................................................ 2-4

2.2 Principles of OFDM ...................................................................................................................................... 2-5

2.2.1 Frequency Division Multiplexing ........................................................................................................ 2-6

2.2.2 OFDM Subcarriers ............................................................................................................................... 2-6

2.2.3 Fast Fourier Transforms ....................................................................................................................... 2-7

2.2.4 LTE FFT Sizes ..................................................................................................................................... 2-8

2.2.5 OFDM Symbol Mapping ..................................................................................................................... 2-8

2.2.6 Time Domain Interference ................................................................................................................... 2-9

2.2.7 OFDM Advantages and Disadvantages.............................................................................................. 2-11

2.3 LTE Channel Structures .............................................................................................................................. 2-12

2.3.1 Logical Channels ............................................................................................................................... 2-12

2.3.2 Transport Channels ............................................................................................................................ 2-14

2.3.3 Physical Channels .............................................................................................................................. 2-14

2.3.4 Radio Channels .................................................................................................................................. 2-15

2.3.5 Channel Mapping ............................................................................................................................... 2-16

2.4 LTE Frame Structure ................................................................................................................................... 2-17

2.4.1 Type 1 Radio Frames, Slots and Subframes ....................................................................................... 2-17

2.4.2 Type 2 Radio Frames, Slots and Subframes ....................................................................................... 2-19

2.5 Downlink OFDMA ..................................................................................................................................... 2-20

2.5.1 General OFDMA Structure ................................................................................................................ 2-20

2.5.2 Physical Resource Blocks and Resource Elements ............................................................................ 2-20

2.5.3 LTE Physical Signals ......................................................................................................................... 2-22

2.5.4 Downlink Reference Signals .............................................................................................................. 2-23

2.6 Uplink SC-FDMA ....................................................................................................................................... 2-24

2.6.1 SC-FDMA Signal Generation ............................................................................................................ 2-24

2.6.2 OFDMA Verses SC-FDMA ............................................................................................................... 2-26

2.7 Multiple Input Multiple Output ................................................................................................................... 2-26

2.7.1 Spatial Multiplexing ........................................................................................................................... 2-27

2.7.2 Space Time Coding ............................................................................................................................ 2-28

2.7.3 Adaptive MIMO Switch ..................................................................................................................... 2-28

2.8 Multimedia Broadcast Multicast Service .................................................................................................... 2-28

2.8.1 MBMS Logical Architecture .............................................................................................................. 2-29

2.8.2 MBMS Cell Configuration ................................................................................................................. 2-30

3 eNB Product Overview ............................................................................................................. 3-1


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3.1 The Huawei eNB Family ............................................................................................................................... 3-2

3.1.1 BTS3900(A) LTE ................................................................................................................................. 3-2

3.1.2 DBS3900 LTE ...................................................................................................................................... 3-3

3.2 Products and Application Scenarios .............................................................................................................. 3-5

3.2.1 BTS3900(A) LTE ................................................................................................................................. 3-5

3.2.2 DBS3900 LTE ...................................................................................................................................... 3-5

3.3 Operation and Maintenance .......................................................................................................................... 3-5

3.3.1 The Operations and Maintenance System ............................................................................................ 3-5

3.3.2 Benefits ................................................................................................................................................ 3-6

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Training Manual Figures



v

Figures

Figure 1-1 Evolution of Cellular Networks ........................................................................................................ 1-2

Figure 1-2 Second Generation Mobile Systems ................................................................................................. 1-3

Figure 1-3 Third Generation Mobile Systems .................................................................................................... 1-4

Figure 1-4 Fourth Generation Mobile Systems .................................................................................................. 1-5

Figure 1-5 3GPP Releases .................................................................................................................................. 1-6

Figure 1-6 HSDPA (Release 5) ........................................................................................................................... 1-7

Figure 1-7 HSUPA (Release 6) ........................................................................................................................... 1-8

Figure 1-8 HSPA+ (Release 7) ........................................................................................................................... 1-8

Figure 1-9 Release 8 HSPA+ and LTE ............................................................................................................... 1-9

Figure 1-10 Release 9 and Beyond ................................................................................................................... 1-10

Figure 1-11 LTE Reference Architecture .......................................................................................................... 1-10

Figure 1-12 User Equipment Functional Elements .......................................................................................... 1-11

Figure 1-13 Evolved Node B Functional Elements .......................................................................................... 1-13

Figure 1-14 E-UTRAN Interfaces .................................................................................................................... 1-14

Figure 1-15 Uu Interface Protocols .................................................................................................................. 1-15

Figure 1-16 X2 Interface Protocols .................................................................................................................. 1-17

Figure 1-17 S1 Interface Protocols ................................................................................................................... 1-18

Figure 1-18 EPC Architecture and Interfaces ................................................................................................... 1-19

Figure 1-19 MME Functional Elements ........................................................................................................... 1-20

Figure 1-20 S-GW Functional Elements .......................................................................................................... 1-20

Figure 1-21 PDN-GW Functional Elements ..................................................................................................... 1-21

Figure 1-22 S11 Interface Protocols ................................................................................................................. 1-22

Figure 1-23 S5/S8 Interface Protocols.............................................................................................................. 1-23

Figure 1-24 S10 Interface Protocols ................................................................................................................. 1-23

Figure 1-25 SGi Interface Protocols ................................................................................................................. 1-24

Figure 1-26 Additional Network Elements and Interfaces ............................................................................... 1-24

Figures


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Figure 2-1 Radio Interface Techniques ............................................................................................................... 2-2

Figure 2-2 Frequency Division Multiple Access ................................................................................................ 2-2

Figure 2-3 Time Division Multiple Access ......................................................................................................... 2-3

Figure 2-4 Code Division Multiple Access ........................................................................................................ 2-3

Figure 2-5 Orthogonal Frequency Division Multiple Access ............................................................................. 2-4

Figure 2-6 Frequency Division Duplex .............................................................................................................. 2-4

Figure 2-7 Time Division Duplex ....................................................................................................................... 2-5

Figure 2-8 Use of OFDM in LTE ....................................................................................................................... 2-5

Figure 2-9 FDM Carriers .................................................................................................................................... 2-6

Figure 2-10 OFDM Subcarriers .......................................................................................................................... 2-7

Figure 2-11 Inverse Fast Fourier Transform ....................................................................................................... 2-7

Figure 2-12 Fast Fourier Transform ................................................................................................................... 2-8

Figure 2-13 OFDM Symbol Mapping ................................................................................................................ 2-9

Figure 2-14 OFDM PAPR (Peak to Average Power Ratio) ................................................................................ 2-9

Figure 2-15 Delay Spread ................................................................................................................................. 2-10

Figure 2-16 Inter Symbol Interference ............................................................................................................. 2-10

Figure 2-17 Cyclic Prefix ................................................................................................................................. 2-11

Figure 2-18 LTE Channels ............................................................................................................................... 2-12

Figure 2-19 Location of Channels .................................................................................................................... 2-12

Figure 2-20 BCCH and PCH Logical Channels ............................................................................................... 2-13

Figure 2-21 CCCH and DCCH Signaling ........................................................................................................ 2-13

Figure 2-22 Dedicated Traffic Channel ............................................................................................................ 2-13

Figure 2-23 LTE Release 8 Transport Channels ............................................................................................... 2-14

Figure 2-24 Radio Channel .............................................................................................................................. 2-15

Figure 2-25 Downlink Channel Mapping ......................................................................................................... 2-16

Figure 2-26 Uplink Channel Mapping .............................................................................................................. 2-17

Figure 2-27 LTE Frame Structure..................................................................................................................... 2-18

Figure 2-28 Normal and Extended Cyclic Prefix ............................................................................................. 2-18

Figure 2-29 Type 2 TDD Radio Frame ............................................................................................................. 2-19

Figure 2-30 OFDMA in LTE ............................................................................................................................ 2-20

Figure 2-31 Physical Resource Block and Resource Element .......................................................................... 2-21

Figure 2-32 Downlink Cell ID ......................................................................................................................... 2-22

Figure 2-33 PSS and SSS Location for FDD ................................................................................................... 2-22


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Figure 2-34 PSS and SSS Location for TDD ................................................................................................... 2-23

Figure 2-35 SC-FDMA Subcarrier Mapping Concept ...................................................................................... 2-24

Figure 2-36 SC-FDMA Signal Generation ....................................................................................................... 2-25

Figure 2-37 SC-FDMA and the eNB ................................................................................................................ 2-26

Figure 2-38 SU-MIMO and MU-MIMO .......................................................................................................... 2-27

Figure 2-39 MIMO Spatial Multiplexing ......................................................................................................... 2-27

Figure 2-40 Spatial Multiplexing Interference Issues ...................................................................................... 2-27

Figure 2-41 MIMO Space Time Coding ........................................................................................................... 2-28

Figure 2-42 Adaptive MIMO Switch................................................................................................................ 2-28

Figure 2-43 MBMS Logical Architecture ........................................................................................................ 2-29

Figure 2-44 MBSFN Synchronization Areas .................................................................................................... 2-30

Figure 2-45 MBMS Cell Configuration ........................................................................................................... 2-30

Figure 3-1 BTS3900(A) LTE Architecture ......................................................................................................... 3-2

Figure 3-2 BBU3900 .......................................................................................................................................... 3-2

Figure 3-3 LRFU ................................................................................................................................................ 3-3

Figure 3-4 DBS3900 LTE Architecture .............................................................................................................. 3-4

Figure 3-5 RRU .................................................................................................................................................. 3-4

Figure 3-6 O&M System .................................................................................................................................... 3-6

Figures


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Training Manual Tables



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Tables

Table 1-1 2G, 2.5G and 2.75G GSM/GPRS Systems ......................................................................................... 1-3

Table 1-2 IMT Advanced Features ..................................................................................................................... 1-5

Table 1-3 UE Categories ................................................................................................................................... 1-12

Table 2-1 LTE Channel and FFT Sizes ............................................................................................................... 2-8

Table 2-2 Type 2 Radio Frame Switching Points.............................................................................................. 2-19

Table 2-3 Downlink PRB Parameters ............................................................................................................... 2-21

Table 2-4 SC-FDMA verses OFDMA .............................................................................................................. 2-26

Tables


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Training Manual 1 Network Architecture



1-1

1 Network Architecture

Objectives

On completion of this section the participants will be able to:

1.1 Describe the evolution of cellular networks.

1.2 Summarize the evolution of 3GPP releases, from Release 99 to Release 9 and beyond.

1.3 Explain the logical architecture of the E-UTRAN.

1.4 Describe the interfaces and associated protocols within the E-UTRAN.

1.5 Explain the logical architecture of the EPC.

1.6 Describe the interfaces and associated protocols within the EPC.



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1.1 Evolution of Cellular Networks

Cellular mobile networks have been evolving for many years. The initial systems, which are

referred to as “First Generation”, have now been replaced with “Second Generation” and

“Third Generation” solutions. However today, 4G or “Fourth Generation” systems are now

being deployed.

Figure 1-1 Evolution of Cellular Networks

1G (First

Generation)

2G (Second

Generation)

3G (Third

Generation)

4G (Fourth

Generation)

1.1.1 First Generation Mobile Systems

The 1G (First Generation) mobile systems were not digital, i.e. they utilized analogue

modulation techniques. The main systems included:

AMPS (Advanced Mobile Telephone System) - This first appeared in 1976 in the United

States and was mainly implemented in the Americas, Russia and Asia. Various issues

including weak security features made the system prone to hacking and handset cloning.

TACS (Total Access Communications System) - This was the European version of

AMPS but with slight modifications including the operation on different frequency

bands. It was mainly used in the United Kingdom, as well as parts of Asia.

ETACS ((Extended Total Access Communication System) - This provided an improved

version of TACS. It enabled a greater number of channels and therefore facilitated more

users.

These analogue systems were all proprietary based FM (Frequency Modulation) systems and

therefore they all lacked security, any meaningful data service and international roaming

capability.

1.1.2 Second Generation Mobile Systems

2G (Second Generation) systems utilize digital multiple access technology, such as TDMA

(Time Division Multiple Access) and CDMA (Code Division Multiple Access). Figure 1-2

illustrates some of the different 2G mobile systems including:

GSM (Global System for Mobile communications) - this is the most successful of all 2G

technologies. It was initially developed by ETSI (European Telecommunications

Standards Institute) for Europe and designed to operate on the 900MHz and 1800MHz

frequency bands. It now has world-wide support and is available for deployment on

many other frequency bands, such as 850MHz and 1900MHz. A mobile described as tri

band or quad band indicates support for multiple frequency bands on the same device.

GSM utilizes TDMA and as such, it employs 8 timeslots on a 200kHz radio carrier.

cdmaOne - this is a CDMA (Code Division Multiple Access) system based on the IS-95

(Interim Standard 95). It uses a spread spectrum technique which incorporates a mixture

of codes and timing to identify cells and channels. The system bandwidth is 1.25MHz.

D-AMPS (Digital - Advanced Mobile Phone System) - this is based on the IS-136

(Interim Standard 136) and is effectively an enhancement to AMPS. Supporting a TDMA





1-3

access technique, D-AMPS is primarily used on the North American continent, as well as

in New Zealand and parts of the Asia-Pacific region.

Figure 1-2 Second Generation Mobile Systems

2G (Second

Generation)

GSM

cdmaOne

(IS-95)

D-AMPS

(IS-136)

Other

In addition to being digital, with the associated improvements in capacity and security, these

2G digital systems also offer enhanced services such as SMS (Short Message Service) and

circuit switched data.

2.5G Systems

Most 2G systems have now been evolved. For example, GSM was extended with GPRS

(General Packet Radio System) to support efficient packet data services, as well as increasing

the data rates.

As this feature does not meet 3G requirements, GPRS is therefore often referred to as 2.5G. A

comparison been 2G and 2.5G systems is illustrated in Table 1-1.

2.75G Systems

GSM/GPRS systems also added EDGE (Enhanced Data Rates for Global Evolution). This

nearly quadruples the throughput of GPRS. The theoretical data rate of 473.6kbit/s enables

service providers to efficiently offer multimedia services. Like that of GPRS, EDGE is

usually categorized as 2.75G as it does not fulfill all the requirements of a 3G system.

Table 1-1 2G, 2.5G and 2.75G GSM/GPRS Systems

System Service Theoretical Data Rate Typical Data Rate

2G GSM Circuit Switched 9.6kbit/s or 14.4kbit/s 9.6kbit/s or 14.4kbit/s

2.5G GPRS Packet Switched 171.2kbit/s 4kbit/s to 50kbit/s

2.75G EDGE Packet Switched 473.6kbit/s 120kbit/s

1.1.3 Third Generation Mobile Systems

3G (Third Generation) systems, which are defined by IMT2000 (International Mobile

Telecommunications - 2000), state that they should be capable of providing higher



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transmission rates, for example: 2Mbit/s for stationary or nomadic use and 348kbit/s in a

moving vehicle.

The main 3G technologies are illustrated in Figure 1-3.These include:

W-CDMA (Wideband CDMA) - This was developed by the 3GPP (Third Generation

Partnership Project). There are numerous variations on this standard, including

TD-CDMA and TD-SCDMA. W-CDMA is the main evolutionary path from GSM/GPRS

networks. It is a FDD (Frequency Division Duplex) based system and occupies a 5MHz

carrier. Current deployments are mainly at 2.1GHz, however deployments at lower

frequencies are also being seen, e.g. UMTS1900, UMTS900, UMTS850 etc. W-CDMA

supports voice and multimedia services with an initial theoretical rate of 2Mbit/s

however, most service providers were initially offering 384kbit/s per user. This

technology is continuing to evolve and later 3GPP releases have increased the rates to in

excess of 40Mbit/s.

TD-CDMA (Time Division CDMA) - This is typically referred to as UMTS TDD (Time

Division Duplex) and is part of the UMTS specifications, however it has only limited

support. The system utilizes a combination of CDMA and TDMA to enable efficient

allocation of resources.

TD-SCDMA (Time Division Synchronous CDMA) - This was jointly developed by

Siemens and the CATT (China Academy of Telecommunications Technology).

TD-SCDMA has links to the UMTS specifications and is often identified as UMTS-TDD

LCR (Low Chip Rate). Like TD-CDMA, it is also best suited to low mobility scenarios

in micro or pico cells.

CDMA2000 - This is a multi-carrier technology standard which uses CDMA.

CDMA2000 is actually a set of standards including CDMA2000 EV-DO

(Evolution-Data Optimized) which has various “revisions”. It is worth noting that

CDMA2000 is backward compatible with cdmaOne.

Figure 1-3 Third Generation Mobile Systems

UMTS

W-CDMA

TD-SCDMA

CDMA2000

Other

UMTS

TD-CDMA

3G (Third

Generation)

WiMAX (Worldwide Interoperability for Microwave Access) - This is another wireless

technology which satisfies IMT2000 3G requirements. The air interface is part of the

IEEE (Institute of Electrical and Electronics Engineers) 802.16 standard which originally

defined PTP (Point-To-Point) and PTM (Point-To-Multipoint) systems. This was later

enhanced to provide mobility and greater flexibility. The success of WiMAX is mainly

down to the “WiMAX Forum”, an organization formed to promote conformity and

interoperability between vendors.





1-5

1.1.4 Fourth Generation Mobile Systems

4G (Fourth Generation) cellular wireless systems need to meet the requirements set out by the

ITU (International Telecommunication Union) as part of IMT Advanced (International Mobile

Telecommunications Advanced). Illustrated in Table 1-2, these features enable IMT Advanced

to address evolving user needs.

Table 1-2 IMT Advanced Features

Key IMT Advanced Features

A high degree of common functionality worldwide while retaining the flexibility to support

a wide range of services and applications in a cost efficient manner.

Compatibility of services within IMT and with fixed networks.

Capability of interworking with other radio access systems.

High quality mobile services.

User equipment suitable for worldwide use.

User-friendly applications, services and equipment.

Worldwide roaming capability.

Enhanced peak data rates to support advanced services and applications (100Mbit/s for high

and 1Gbit/s for low mobility were identified as targets).

The three main 4G systems include:

LTE Advanced - LTE (Long Term Evolution) is part of 3GPP family of specifications,

however it does not meet all IMT Advanced features, as such it is sometimes referred to

as 3.99G. In contrast, LTE Advanced is part of a later 3GPP Release and this has been

designed specifically to meet 4G requirements.

WiMAX 802.16m - The IEEE and the WiMAX Forum have identified 802.16m as their

offering for a 4G system.

UMB (Ultra Mobile Broadband) - This is identified as EV-DO Rev C. It is part of 3GPP2

however most vendors and service providers have decided to promote LTE instead.

Figure 1-4 Fourth Generation Mobile Systems

LTE

Advanced

UMB

(EV-DO Rev C)

WiMAX

802.16m

4G (Fourth

Generation)



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1.2 3GPP Releases

The development of GSM, GPRS, EDGE, UMTS, HSPA and LTE is in stages known as 3GPP

Releases. Hardware vendors and software developers use these releases as part of their

development roadmap. Figure 1-5 illustrates the main 3GPP Releases that included key

enhancements of the radio interface.

Figure 1-5 3GPP Releases

GSM

9.6kbit/s

GPRS

171.2kbit/s

EDGE

473.6kbit/s

UMTS

2Mbit/s

HSDPA

14.4Mbit/s

HSUPA

5.76Mbit/s

HSPA+

28.8Mbit/s

42Mbit/s

LTE

+300Mbit/s

Phase 1

Phase 2+

(Release 97)

Release 99

Release 99

Release 5

Release 6

Release 7/8

Release 8

Release 9/10

LTE Advanced

3GPP Releases enhance various aspects of the network and not just the radio interface. For

example, Release 5 started the introduction of the IMS (IP Multimedia Subsystem) in the core

network.

1.2.1 Pre-Release 99

Pre-Release 99 saw the introduction of GSM, as well as the addition of GPRS. The main

GSM Phases and 3GPP Releases include:

GSM Phase 1.

GSM Phase 2.

GSM Phase 2+ (Release 96).



1.2.2 Release 99

3GPP Release 99 saw the introduction of UMTS, as well as the EDGE enhancement to GPRS.

UMTS contains all the features needed to meet the IMT-2000 requirements as those defined

by the ITU. It is able to support CS (Circuit Switched) voice and video services, as well as PS

(Packet Switched) data services over common and dedicated bearers. Initial data rates for

UMTS were 64kbit/s, 128kbit/s and 384kbit/s. Note that the theoretical maximum was

2Mbit/s.

1.2.3 Release 4

Release 4 included enhancements to the core network and in particular the notion of it being

bearer independent. Thus the concept of “All IP Networks” was included and service





1-7

providers were able to deploy Soft Switch based networks, i.e. the MSC (Mobile Switching

Centre) was replaced by the MSC Server and MGW (Media Gateways). This improved

network utilization in addition to consolidating engineering knowledge and increasing vendor

competition.

1.2.4 Release 5

Release 5 introduces the first major addition to the UMTS air interface by specifying HSDPA

(High Speed Downlink Packet Access) in order to improve both capacity and spectral

efficiency. Figure 1-6 illustrates some of the main features associated with Release 5 and

these include:

Adaptive Modulation - In addition to the original UMTS modulation scheme of QPSK

(Quadrature Phase Shift Keying), HSDPA also includes support for 16 QAM

(Quadrature Amplitude Modulation).

Flexible Coding - Based on fast feedback from the mobile in the form of a CQI (Channel

Quality Indicator), the UMTS base station, i.e. the Node B, is able to modify the

effective coding rate and thus increase system efficiency.

Fast Scheduling - HSDPA includes a 2ms TTI (Time Transmission Interval) which

enables the Node B scheduler to quickly and efficiently allocate resources to mobiles.

HARQ (Hybrid Automatic Repeat Request) - In the event a packet does not get through

to the UE (User Equipment) successfully, the system employs HARQ. This improves the

retransmission timing, thus requiring less reliance on the RNC (Radio Network

Controller).

Figure 1-6 HSDPA (Release 5)

HSDPA

Adaptive Modulation

Flexible Coding

Fast Scheduling (2ms)

HARQ

UE

UTRAN

RNCNode B

Iub

1.2.5 Release 6

Release 6 adds various features, with HSUPA (High Speed Uplink Packet Data) being of most

interest to RAN development. Even though the term HSUPA is widespread, this 3GPP

enhancement also goes under the term “Enhanced Uplink”. It is also worth noting that

HSDPA and HSUPA work in tandem and thus the term HSPA (High Speed Packet Access) is

now in common use.

HSUPA, like HSDPA adds functionality to improve packet data. Figure 1-7 illustrates the

three main enhancements which include:

Flexible Coding - HSUPA has the ability to dynamically change the coding and therefore

improve the efficiency of the system.

Fast Power Scheduling - A key fact of HSUPA is that it provides a method to schedule

the power from different mobiles. This scheduling can use either a 2ms or 10ms TTI.



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HARQ - Like HSDPA, HSUPA also utilizes HARQ. The main difference is the timing

relationship for retransmissions.

Figure 1-7 HSUPA (Release 6)

HSUPA

Flexible Coding

Fast Power Scheduling

HARQ

UE

UTRAN

RNCNode B

Iub

Enhancements introduced in Release 6 are not limited to HSUPA. For example, GAN

(Generic Access Network) technologies are also included which enables alternative radio

access technologies such as Wi-Fi (Wireless Fidelity) to be used yet still support true

interworking.

Although no longer the correct terminology, UMA (Unlicensed Mobile Access) is still in common use to

describe the 3GPP’s GAN technology.

1.2.6 Release 7

The main RAN based feature of Release 7 is HSPA+. This, like HSDPA and HSUPA,

provides various enhancements to improve packet switched data delivery. Figure 1-8

illustrates the main features which include:

64 QAM - This is available in the DL (Downlink) and enables HSPA+ to operate at a

theoretical rate of 21.6Mbit/s.

16 QAM - This is available in the UL (Uplink) and enables the uplink to theoretically

achieve 11.76Mbit/s.

MIMO (Multiple Input Multiple Output) Operation - this is added to HSPA+ Release 7

and offers various benefits including the ability to offer a theoretical 28.8Mbits/s in the

downlink.

Figure 1-8 HSPA+ (Release 7)

HSPA+

64 QAM (DL)

16 QAM (UL)

MIMO Operation (DL)

Power Enhancements (DL)

Less Overhead (DL)

UE

UTRAN

RNCNode B

Iub

Power Enhancements -Various enhancements such as CPC (Continuous Packet

Connectivity) have been included. This includes DTX (Discontinuous Transmission),





1-9

DRX (Discontinuous Reception) and HS-SCCH (High Speed - Shared Control Channel)

Less Operation etc. Collectively these improve the mobiles battery consumption.

Less Overhead - The downlink includes an enhancement to the MAC (Medium Access

Control) layer which effectively means that fewer headers are required. This in turn

reduces overhead and thus improves the system efficiency.

1.2.7 Release 8

There are many additions to the RAN functionality in Release 8, such as an enhancement to

HSPA+. However the main aspect is the inclusion of LTE (Long Term Evolution). Figure 1-9

illustrates some of the main features for Release 8 HSPA+ and LTE.

Release 8 HSPA+ enables various key enhancements, these include:

64 QAM and MIMO - Release 8 enables the combination of 64 QAM and MIMO, thus

quoting a theoretical rate of 42Mbit/s, i.e. 2 x 21.6Mbit/s.

Dual Cell Operation - DC-HSDPA (Dual Cell - HSDPA) is a Release 8 feature which is

further enhanced in Release 9 and Release 10. It enables a mobile to effectively utilize

two 5MHz UMTS carriers. Assuming both are using 64 QAM (21.6Mbit/s), the

theoretical maximum is 42Mbps. Note that in Release 8, a mobile is not able to combine

MIMO and DC-HSDPA.

Less Uplink Overhead - In a similar way to Release 7 in the downlink, the Release 8

uplink has also been enhanced to reduce overhead.

Figure 1-9 Release 8 HSPA+ and LTE

HSPA+

64 QAM + MIMO (DL)

Dual Cell Operation

Less Overhead (UL)

UE

UTRAN

RNCNode B

Iub

eNB

E-UTRAN

LTE

Enhanced Techniques

Flexible Bandwidth

Flexible Spectrum Options

High Data Rates

Very Fast Scheduling

Improved Latency

LTE provides a new radio access technique, as well as enhancements in the E-UTRAN

(Evolved - Universal Terrestrial Radio Access Network). These enhancements are further

discussed as part of this course.

1.2.8 Release 9 and Beyond

Even though LTE is a Release 8 system, it is yet further enhanced in Release 9. There are a

huge number of features in Release 9. One of the most important is the support of additional

frequency bands.



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Figure 1-10 Release 9 and Beyond

LTE

Release 8

LTE

Release 9

LTE Advanced

Release 10

Release 10 includes the standardization of LTE Advanced, i.e. the 3GPP’s 4G offering. As

such, it includes the modification of the LTE system to facilitate 4G services.

1.3 E-UTRAN Architecture

In contrast to the 2G and 3G networks defined by the 3GPP, LTE can be simply divided into a

flat IP based bearer network and a service enabling network. The former can be further

subdivided into the E-UTRAN (Evolved - Universal Terrestrial Radio Access Network) and

the EPC (Evolved Packet Core) where as support for service delivery lies in the IMS (IP

Multimedia Subsystem). This reference architecture can be seen in Figure 1-11.

Figure 1-11 LTE Reference Architecture

UEeNB

E-UTRAN EPC

S-GW

MME

PDN-GW

IMS

HSS Video ASCSCF

eNB

Whilst UMTS is based upon W-CDMA technology, the 3GPP developed new specifications

for the LTE air interface based upon OFDMA (Orthogonal Frequency Division Multiple

Access) in the downlink and SC-FDMA (Single Carrier - Frequency Division Multiple Access)

in the uplink. This new air interface is termed the E-UTRA (Evolved - Universal Terrestrial

Radio Access).

1.3.1 User Equipment

Like that of UMTS, the mobile device in LTE is termed the UE (User Equipment) and is

comprised of two distinct elements; the USIM (Universal Subscriber Identity Module) and the

ME (Mobile Equipment).

The ME supports a number of functional entities including:





1-11

RR (Radio Resource) - this supports both the Control Plane and User Plane and in so

doing, is responsible for all low level protocols including RRC (Radio Resource Control),

PDCP (Packet Data Convergence Protocol), RLC (Radio Link Control), MAC (Medium

Access Control) and the Phy (Physical) Layer.

EMM (EPS Mobility Management) - is a Control Plane entity which manages the

mobility management states the UE can exist in; LTE Idle, LTE Active and LTE

Detached. Transactions within these states include procedures such as TAU (Tracking

Area Update) and handovers.

ESM (EPS Session Management) - is a Control Plane activity which manages the

activation, modification and deactivation of EPS bearer contexts. These can either be

default EPS bearer contexts or dedicated EPS bearer contexts.

Figure 1-12 User Equipment Functional Elements

UE

EPS Mobility & EPS

Session Management

IP Adaptation

FunctionRadio Resource

Control

Plane

User

Plane

EPS Session Management

Bearer Activation

Bearer Modification

Bearer Deactivation

Radio Resource

RRC, PDCP, RLC, MAC &

Phy Layer Protocols

EPS Mobility Management

Registration

Tracking Area Update

Handover

In terms of the Phy layer, the capabilities of the UE may be defined in terms of the

frequencies and data rates supported. Devices may also be capable of supporting adaptive

modulation including QPSK (Quadrature Phase Shift Keying), 16QAM (16 Quadrature

Amplitude Modulation) and 64QAM (Quadrature Amplitude Modulation).

In terms of the radio spectrum, the UE is able to support several scalable channels including;

1.4MHz, 3MHz, 5MHz, 10MHz, 15MHz and 20MHz whilst operating in FDD (Frequency

Division Duplex) and/or TDD (Time Division Duplex). Furthermore, the UE may also

support advanced antenna features such as MIMO (Multiple Input Multiple Output) which is

discussed in at 2.7 .



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Table 1-3 UE Categories

UE Category Maximum Downlink Data Rate

Number of Downlink Data Streams

Maximum Uplink Data Rate

Support for Uplink 64QAM

1 10.3Mbit/s 1 5.2Mbit/s No




5 302.8Mbit/s 4 75.4Mbit/s Yes

UE Identities

An LTE capable UE will be allocated / utilize a number of identities during operation within

the network. These include:

IMSI (International Mobile Subscriber Identity) - this complies with the standard 3GPP

format and is comprised of the MCC (Mobile Country Code), MNC (Mobile Network

Code) and the MSIN (Mobile Subscriber Identity Number). This uniquely identifies a

subscriber from within the family of 3GPP technologies - GSM, GPRS, UMTS etc.

IMEI (International Mobile Equipment Identity) - is used to uniquely identify the ME. It

can be further subdivided into a TAC (Type Approval Code), FAC (Final Assembly Code)

and SNR (Serial Number).

GUTI (Globally Unique Temporary Identity) - is allocated to the UE by the MME

(Mobility Management Entity) and identifies a device to a specific MME. The identity is

comprised of a GUMMEI (Globally Unique MME Identity) and an M-TMSI (MME -

Temporary Mobile Subscriber Identity).

S-TMSI (Serving - Temporary Mobile Subscriber Identity) - is used to protect a

subscriber’s IMSI during NAS (Non Access Stratum) signaling between the UE and

MME as well as identifying the MME from within a MME pool. The S-TMSI is

comprised of the MMEC (MME Code) and the M-TMSI.

IP Address - the UE requires a routable IP address from the PDN (Packet Data Network)

from which it is receiving higher layer services. This may either be an IPv4 or IPv6

address.

1.3.2 Evolved Node B

In addition to the new air interface, a new base station has also be specified by the 3GPP and

is referred to as an eNB (Evolved Node B). These, along with their associated interfaces form

the E-UTRAN and in so doing, are responsible for:

RRM (Radio Resource Management) - this involves the allocation to the UE of the

physical resources on the uplink and downlink, access control and mobility control.

Date Compression - is performed in both the eNB and the UE in order to maximize the

amount of user data that can be transferred on the allocated resource. This process is

undertaken by PDCP.

Data Protection - is performed at the eNB and the UE in order to encrypt and integrity

protect RRC signaling and encrypt user data on the air interface.





1-13

Routing - this involves the forwarding of Control Plane signaling to the MME and User

Plane traffic to the S-GW (Serving - Gateway).

Packet Classification and QoS Policy Enforcement - this involves the “marking” of

uplink packets based upon subscription information or local service provider policy. QoS

(Quality of Service) policy enforcement is then responsible for ensuring such policy is

enforced at the network edge.

Figure 1-13 Evolved Node B Functional Elements

eNB

Radio Resource

Management

Data

Compression

Data ProtectionRouting

Packet

Classification

and QoS Policy

Enforcement

Security in LTE is not solely limited to encryption and integrity protection of information passing across

the air interface but instead, NAS encryption and integrity protection between the UE and MME also takes

place. In addition, IPSec may also be used to protect user data within both the E-UTRAN and EPC.

eNB Identities

In addition to the UE identities already discussed, there are a number of specific identities

associated with the eNB. These include:

TAI (Tracking Area Identity) - is a logical group of neighboring cells defined by the

service provider in which an LTE idle UE is able to move within without needing to

update the network. As such, it is similar to a RAI (Routing Area Identity) used in 2G

and 3G packet switched networks.

ECGI (Evolved Cell Global Identity) - is comprised of the MCC, MNC and ECI

(Evolved Cell Identity), the later being coded by each service provider.

1.3.3 Femto Cells

In order to improve both network coverage and capacity, the 3GPP have developed a new type

of base station to operate within the home or small business environment. Termed the HeNB

(Home Evolved Node B), this network element forms part of the E-UTRAN and in so doing

supports the standard E-UTRAN interfaces. However, it must be stated that HeNBs do not

support the X2 interface.

The architecture may include an HeNB-GW (Home Evolved Node B - Gateway) which

resides between the HeNB in the E-UTRAN and the MME / S-GW in the EPC in order to

scale and support large numbers of base station deployments.



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HeNB Identities

To aid in the efficient operation of both the UE and the network, there are a number of

additional identities which have been introduced by the 3GPP for femto cell operation. These

are:

CSG (Closed Subscriber Group) Identity - this is used by a UE to determine whether it is

permitted to use the HeNB. The CSG Identity is broadcast in SI (System Information)

messages.

HeNB Name - is a free text human readable name broadcast by the HeNB to advise

subscribers of the identity of the HeNB they are, or are about to register with.

1.4 E-UTRAN Interfaces and Protocols

As with all 3GPP technologies, it is the actual interfaces which are defined in terms of the

protocols they support and the associated signaling messages and user traffic that traverse

them.

Figure 1-14 E-UTRAN Interfaces

E-UTRAN EPC

X2

Uu

S-GW

MMEeNB

eNB

S1-MME

S1-MME

S1-U

S1-U

1.4.1 Uu Interface

The Uu Interface supports both a Control Plane and a User plane and spans the link between

the UE and the eNB / HeNB. The principle Control Plane protocol is RRC while the User

Plane is designed to carry IP datagrams. However, both Control and User Planes utilize the

services of PDCP, RLC and MAC.

Radio Resource Control

RRC deals with all the signaling between the UE and the E-UTRAN in addition to

transporting NAS signaling between the UE and the MME. It also provides the main

configuration and parameters to the lower layer protocols. For example, the Phy Layer will

receive information from RRC on how to configure certain of its aspects. Key responsibilities

of RRC include:

System Information.





1-15

PLMN and Cell Selection.

Admission Control.

Security Management.

Cell Reselection.

Measurement Reporting.

Handovers and Mobility.

NAS Transport.

Radio Resource Management.

Packet Data Convergence Protocol

PDCP operates on both the Control Plane and User Plane. In addition to IP header

compression and sequencing / duplicate packet detection, PDCP is also responsible for

security on the air interface. As such, its key responsibilities include:

Encryption - Control Plane and User Plane.

Integrity Checking - Control Plane.

IP Header Compression - User Plane.

Sequencing and Duplicate Detection - User Plane.

Figure 1-15 Uu Interface Protocols

RLC

MAC

PHY

PDCP

RRC

RLC

MAC

PHY

PDCP

IP

Control Plane User Plane

eNBUE

Uu

Radio Link Control

As the name would suggest, RLC provides “radio link” control in the UE and eNB and in so

doing, it provides three delivery services to the higher layers. These are:

TM (Transparent Mode) - this provides a connectionless service and is utilized for some

of the air interface channels e.g. broadcast and paging.

UM (Unacknowledged Mode) - like that of TM, this also provides a connectionless

service but with additional functionality incorporating sequencing, segmentation and

concatenation.



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AM (Acknowledged Mode) - this supports ARQ (Automatic Repeat Request) thereby

operating in a connection orientated mode.

Medium Access Control

MAC provides the interface between the E-UTRA protocols and the Phy Layer and supports

the following services:

Mapping - this is the “mapping” of information between the logical and transport

channels.

Multiplexing - in order to increase system efficiency, information from different Radio

Bearers is multiplexed into the same TB (Transport Block).

HARQ (Hybrid Automatic Repeat Request) - provides error correction services over the

air interface. This requires close interworking with the Physical Layer.

Radio Resource Allocation - this is the scheduling of traffic and signaling to users based

upon QoS.

Physical

The Physical Layer incorporates a number of functions. These include:

Error Detection.

FEC (Forward Error Correction) Encoding / Decoding.

Rate Matching.

Physical Channel Mapping.

Power Weighting.

RF (Radio Frequency) Modulation and Demodulation.

Frequency and Time Synchronization.

Radio Measurements.

MIMO Processing.

Transmit Diversity.

Beamforming.

RF Processing.

1.4.2 X2 Interface

The X2 Interface interconnects two eNBs and in so doing supports both a Control Plane and

User Plane. It also extends the S1 Interface when two or more eNBs lie between the UE and

the EPC. The X2AP (X2 Application Protocol) Control Plane protocol resides on SCTP

(Stream Control Transmission Protocol) where as the IP is transferred over the User Plane

using the services of GTP-U (GPRS Tunneling Protocol - User) and UDP (User Datagram

Protocol).

X2 Application Protocol

The X2AP is responsible for the following functions:

Mobility Management - this enables the serving eNB to move the responsibility of a

specified UE to a target eNB. This includes Forwarding the User Plane, Status Transfer

and UE Context Release functions.





1-17

Load Management - this function enables eNBs to communicate with each other in order

to report resource status, overload indications and current traffic loading.

Error Reporting - this allows for the reporting of general error situations for which

specific error reporting mechanism have not been defined.

Setting / Resetting X2 - this provides a means by which the X2 interface can be setup /

reset by exchanging the necessary information between the eNBs.

Configuration Update - this allows the updating of application level data which is needed

for two eNBs to interoperate over the X2 interface.

Figure 1-16 X2 Interface Protocols

eNB

IP

Layer 2

Layer 1

SCTP

X2AP

IP

Layer 2

Layer 1

UDP

GTP-U


eNB

X2

Stream Control Transmission Protocol

Defined by the IETF (Internet Engineering Task Force) rather than the 3GPP, SCTP was

developed to overcome the shortfalls in TCP (Transmission Control Protocol) and UDP when

transferring signaling information over an IP bearer. Functions provided by SCTP include:

Reliable Delivery of Higher Layer Payloads.

Sequential Delivery of Higher Layer Payloads.

Improved resilience through Multihoming.

Flow Control.

Improved Security.

SCTP is also found on the S1-MME Interface which links the eNB to the MME.

GPRS Tunneling Protocol - User

GTP-U tunnels are used to carry encapsulated PDU (Protocol Data Unit) and signaling

messages between endpoints or in the case of the X2 interface. Numerous GTP-U tunnels may

exist in order to differentiate between EPS bearer contexts and these are identified through a

TEID (Tunnel Endpoint Identifier).

GTP-U is also found on the S1-U Interface which links the eNB to the S-GW and may also be used on the

S5 Interface linking the S-GW to the PDN-GW.



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1.4.3 S1 Interface

The S1 Interface can be subdivided into the S1-MME interface supporting Control Plane

signaling between the eNB and the MME and the S1-U Interface supporting User Plane traffic

between the eNB and the S-GW.

Figure 1-17 S1 Interface Protocols

eNB

IP

Layer 2

Layer 1

SCTP

S1AP

IP

Layer 2

Layer 1

UDP

GTP-U


S1-MME

MME eNB

S1-U

S-GW

S1 Application Protocol

The S1AP spans the S1-MME Interface and in so doing, supports the following functions:

E-RAB (Evolved - Radio Access Bearer) Management - this incorporates the setting up,

modifying and releasing of the E-RABs by the MME.

Initial Context Transfer - is used to establish an S1UE context in the eNB, setup the

default IP connectivity and transfer NAS related signaling.

UE Capability Information Indication - is used to inform the MME of the UE Capability

Information.

Mobility - this incorporates mobility features to support a change in eNB or change in

RAT.

Paging.

S1 Interface Management - this incorporates a number of sub functions dealing with

resets, load balancing and system setup etc.

NAS Signaling Transport - the transport of NAS related signaling over the S1-MME

Interface.

UE Context Modification and Release - this allows for the modification and release of

the established UE Context in the eNB and MME respectively.

Location Reporting - this enables the MME to be made aware of the UE’s current

location within the network.





1-19

1.5 EPC Architecture

In addition to LTE, the 3GPP also defined the SAE (System Architecture Evolution) as part of

the Release 8 framework for an evolution or migration of core network to provide a packet

optimized architecture supporting higher data rates, lower latency and multi RAT connectivity.

Within this architecture, the functionally of the core network is made much “flatter” with

much of the intelligence required to support service delivery being placed within domains

such as the IMS. In essence, this removes much of the call / session control from the core.

Figure 1-18 illustrates the fundamental architecture of the EPC and in so doing identifies the

key interfaces which exist between the network elements. It should be stated however that

there exists additional interfaces which link the EPC with the IMS and legacy 3GPP / Non

3GPP architectures.

Figure 1-18 EPC Architecture and Interfaces

EPC

S1-MME

S1-U

S11

S5/S8

S-GW

SGi

PDN-GW

MME

MME

S10

1.5.1 Mobility Management Entity

The MME is the Control Plane entity within the EPC and as such is responsible for the

following functions:

NAS Signaling and Security - this incorporates both EMM (Evolved Mobility

Management) and ESM (Evolved Session Management) and thus includes procedures

such as Tracking Area Updates and EPS Bearer Management. The MME is also

responsible for NAS security.

S-GW and PDN-GW Selection - upon receipt of a request from the UE to allocate a

bearer resource, the MME will select the most appropriate S-GW and PDN-GW. This

selection criterion is based on the location of the UE in addition to current load

conditions within the network.

Tracking Area List Management and Paging - whilst in the LTE Idle state, the UE is

tracked by the MME to the granularity of a Tracking Area. Whilst UEs remain within the

Tracking Areas provided to them in the form of a Tracking Area List, there is no

requirement for them to notify the MME. The MME is also responsible for initiating the

paging procedure.

Inter MME Mobility - if a handover involves changing the point of attachment within the

EPC, it may be necessary to involve an inter MME handover. In this situation, the

serving MME will select a target MME with which to conduct this process.



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Authentication - this involves interworking with the subscriber’s HSS (Home Subscriber

Server) in order to obtain AAA (Access Authorization and Accounting) information with

which to authenticate the subscriber. Like that of other 3GPP system, authentication is

based on AKA (Authentication and Key Agreement).

Figure 1-19 MME Functional Elements

NAS Signaling

and Security

S-GW and

PDN-GW

Selection

Tracking Area List

Management and

Paging

Inter MME

Mobility

Authentication

MME

1.5.2 Serving - Gateway

Figure 1-20 S-GW Functional Elements

Mobility Anchor

Downlink

Packet

Buffering

Packet Routing

and Forwarding

Lawful

Interception

GTP/PMIP

Support

S-GW

The S-GW terminates the S1-U Interface from the E-UTRAN and in so doing, provides the

following functions:

Mobility Anchor - for inter eNB handovers, the S-GW acts as an anchor point for the

User Plane. Furthermore, it also acts as an anchor for inter 3GPP handovers to legacy

networks - GPRS and UMTS.

Downlink Packet Buffering - when traffic arrives for a UE at the S-GW, it may need to

be buffered in order to allow time for the MME to page the UE and for it to enter the

LTE Active state.

Packet Routing and Forwarding - traffic must be routed to the correct eNB on the

downlink and the specified PDN-GW on the uplink.

Lawful Interception - this incorporates the monitoring of VoIP (Voice over IP) and other

packet services.





1-21

GTP/PMIP Support - if PMIP (Proxy Mobile IP) is used on the S5/S8 Interfaces, the

S-GW must support MAG (Mobile Access Gateway) functionality. Furthermore, support

for GTP/PMIP chaining may also be required.

1.5.3 Packet Data Network - Gateway

The PDN-GW is the network element which terminates the SGi Interface towards the PDN

(Packet Data Network). If a UE is accessing multiple PDNs, there may be a requirement for

multiple PDN-GWs to be involved. Functions associated with the PDN-GW include:

Packet Filtering - this incorporates the deep packet inspection of IP datagrams arriving

from the PDN in order to determine which TFT (Traffic Flow Template) they are to be

associated with.

Lawful Interception - as with the S-GW, the PDN-GW may also monitor traffic as it

passes across it.

IP Address Allocation - IP addresses may be allocated to the UE by the PDN-GW. This is

included as part of the initial bearer establishment phase or when UEs roam between

different access technologies.

Transport Level Packet Marking - this involves the marking of uplink and downlink

packets with the appropriate tag e.g. DSCP (Differentiated Services Code Point) based

on the QCI (QoS Class Identifier) of the associated EPS bearer.

Accounting - through interaction with a PCRF (Policy Rules and Charging Function), the

PDN-GW will monitor traffic volumes and types.

Figure 1-21 PDN-GW Functional Elements

Packet Filtering

Lawful

Interception

IP Address

Allocation

Transport

Level Packet

Marking

Accounting

PDN-GW

1.6 EPC Interfaces and Protocols

1.6.1 S11 Interface

The S11 Interface links the MME with the S-GW in order to support Control Plane signaling.

In so doing, it utilizes GTPv2-C (GPRS Tunneling Protocol version 2 - Control) which, like

all other interfaces which use variants of GTP use the services of UDP and IP.



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GPRS Tunneling Protocol version 2 - Control

GTPv2-C supports the transfer of signaling messages between the MME and the S-GW and as

such is responsible for the exchange of the following message types:

Path Management - this incorporates Echo Request and Echo Response messages to

ensure ongoing connectivity across the link.

Tunnel Management - these messages are used to activate, modify and delete the EPS

bearers and sessions spanning the network.

Mobility Management - these messages ensure mobility is supported through a

combination of relocation and notification procedures.

CS (Circuit Switched) Fallback - this incorporates suspend and resume procedures

during fallback to circuit switched operation.

Non 3GPP Access - these messages support the establishment of tunnels to forward

packet data between the 3GPP and Non 3GPP networks.


IP

Layer 2

Layer 1

UDP

GTPv2-C

Control Plane

S11

MME S-GW

GTPv2-C is also found on the S5/S8 Interface between the S-GW and PDN-GW and the S10 Interface

between MMEs. Furthermore, it can also be found on the S3 and S4 interfaces when interconnecting with

an SGSN (Serving GPRS Support Node).

1.6.2 S5/S8 Interface

The S5/S8 Interface links the S-GW with the PDN-GW and supports both a Control Plane and

User Plane. The term S5 is used when these elements reside within the same PLMN (Public

Land Mobile Network) and S8 when the interface spans a HPLMN (Home Public Land

Mobile) / VPLMN (Visited Public Land Mobile network).

The GTPv2-C protocol operates on the Control Plane for both of these interfaces whereas

GTP-U or PMIP is used on the User Plane.

Proxy Mobile IP

Defined by the IETF, PMIP supports mobility when a UE moves from one S-GW to another

during a handover procedure. Data is tunneled between the PDN-GW, which supports HA

(Home Agent) functionality and the S-GW, which acts as the FA (Foreign Agent).





1-23

It is anticipated that PMIP will be used by 3GPP2 based networks migrating to LTE as they

already utilize PMIP within their 3G architectures. 3GPP based networks however are

expected to use GTP-U instead.

Figure 1-23 S5/S8 Interface Protocols

IP

Layer 2

Layer 1

UDP

GTPv2-C

IP

Layer 2

Layer 1

UDP

GTP-U / PMIP


S5/S8

S-GW PDN-GW

1.6.3 S10 Interface

The S10 Interface links two MMEs in order to pass Control Plane signaling. In so doing, it

uses the services of GTPv2-C.


IP

Layer 2

Layer 1

UDP

GTPv2-C

Control Plane

S10

MME MME

1.6.4 SGi Interface

The SGi Interface connects the PDN-GW to an external PDN. This could be the public

Internet, Corporate Intranets or a service provider’s network supporting services such as the

IMS. Although defined by the 3GPP, the protocols which operate over the SGi Interface are

defined by the IETF and include TCP, UDP in addition to a host of application specific

protocols.



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Figure 1-25 SGi Interface Protocols

IP

Layer 2

Layer 1

TCP / UDP

Applications

SGi

PDN-GW

1.6.5 Additional Network Elements and Interfaces

In addition to the network elements, interfaces and associated protocols discussed so far, the

EPC connects with numerous other nodes and networks. These are illustrated in Figure 1-26.

Figure 1-26 Additional Network Elements and Interfaces

EPC

S11

S5/S8

S10

MME

MME

SGSN

RNC

PCRF

HSS

EIR

S6a

S101

S2a

Gx

ePDG

S2bS103

S12

S4

S3

S13

CDMA

2000

CDMA

2000

Trusted

Non 3GPP

IP Access

Untrusted

Non 3GPP

IP Access

PDN-GW

Wn

S-GW





1-25

These include, but are not limited to the:

HSS (Home Subscriber Server) - this can be considered a “master” database within the

PLMN. Although logically it is considered as one entity, the HSS in practice is made up

of several physical databases depending upon subscriber numbers and redundancy

requirements. The HSS holds variables and identities for the support, establishment and

maintenance of calls and sessions made by subscribers. It is connected to the MME via

the S6a Interface which uses the protocol Diameter.

PCRF (Policy and Charging Rules Function) - this supports functionality for policy

control through the PDF (Policy Decision Function) and charging control through the

CRF (Charging Rules Function). As such, it provides bearer network control in terms of

QoS and the allocation of the associated charging vectors. The PCRF downloads this

information over the Gx Interface using the Diameter protocol.

ePDG (evolved Packet Data Gateway) - which is used when connecting to Untrusted

Non 3GPP IP Access networks. It provides functionality to allocate IP addresses in

addition to encapsulating / de-encapsulating IPSec (IP Security) and PMIP tunnels. It

connects to the PDN-GW via the S2b Interface.

RNC (Radio Network Controller) - which forms part of the 3GPPs UTRAN (Universal

Terrestrial Radio Access Network), the RNC connects to the S-GW to support the

tunneling of User Plane traffic using GTP-U. The interface linking these network

elements is the S12 Interface.

SGSN (Serving GPRS Support Node) - this forms part of the 3GPPs 2G and 3G packet

switched core domain. It connects to both the MME and S-GW in order to support

packet switched mobility and uses the GTPv2-C and GTP-U protocols respectively. The

SGSN connects to the MME via the S3 Interface and the S-GW via the S4 Interface.

EIR (Equipment Identity Register) - this database enables service providers to validate a

particular IMEI (International Mobile Equipment identity) against stored lists. It

connects to the MME via the S13 Interface and uses the Diameter protocol for message

transfer.



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Training Manual 2 LTE Air Interface Principles



2-1

2 LTE Air Interface Principles

Objectives


2.1 Describe the radio interface techniques used in the uplink and downlink.

2.2 Describe the principles of OFDM.

2.3 Describe the channel structure of the air interface.

2.4 Detail the time-domain structure in the radio interface in uplink and downlink for both

FDD and TDD mode.

2.5 Have a good understanding of the OFDMA principles used in the downlink.

2.6 Have a good understanding of the SC-FDMA principles used in the uplink.

2.7 Describe MIMO.

2.8 Describe briefly the role of MBMS within LTE.



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2.1 Radio Interface Techniques

In wireless cellular systems, mobiles have to share a common medium for transmission. There

are several categories of assignment but the main four are: FDMA (Frequency Division

Multiple Access), TDMA (Time Division Multiple Access), CDMA (Code Division Multiple

Access) and OFDMA (Orthogonal Frequency Division Multiple Access).

Figure 2-1 Radio Interface Techniques

FDMA

TDMA CDMA

OFDMA

Radio Interface

Techniques

2.1.1 Frequency Division Multiple Access

In order to accommodate various devices on the same wireless network, FDMA divides the

available spectrum into subbands or channels. The concept of FDMA is illustrated in Figure

2-2. Using this technique a dedicated channel can be allocated to a user, whilst other users

occupy other channels, i.e. frequencies.

In a cellular system, mobiles typically occupy two channels, one for the downlink and one for

the uplink. This does however make FDMA less efficient since most data applications are

downlink biased.

Figure 2-2 Frequency Division Multiple Access

Frequency

Power Time

FDMA

Each user allocated a

different subband/

channel.

FDMA channels also suffer since they cannot be too “close together” as the energy from one

channel affects the adjacent/neighboring channels. To combat this, additional guard bands

between channels are required which reduces the systems spectral efficiency.





2-3

2.1.2 Time Division Multiple Access

In TDMA systems, the channel bandwidth is shared in the time domain. Figure 2-3 illustrates

the concept of TDMA. This illustrates how each device is allocated a time on the channel,

referred to as a “timeslot”. These are then grouped into a TDMA frame. The number of

timeslots in a TDMA frame is dependent on the system; for example GSM utilizes eight

timeslots.

Figure 2-3 Time Division Multiple Access

Frequency

PowerTime

TDMA


different time on the

channel.

Devices must be allocated a timeslot; therefore it is usual to have one or more timeslots

reserved for common control and system access.

TDMA systems are typically digital and therefore offer additional features such a ciphering

and integrity protection. In addition, they can employ enhanced error detection and correction

schemes such as FEC (Forward Error Correction). This enables the system to be more

resilient to noise and interference and therefore, they tend to offer greater spectral efficiency

when compared to FDMA systems.

2.1.3 Code Division Multiple Access

The concept of CDMA is slightly different to that of FDMA and TDMA. Instead of sharing

resources in the time or frequency domain, CDMA devices operate on the same frequency

band at the same time. This is possible due to the fact that each transmission is separated

using a unique code.

Figure 2-4 Code Division Multiple Access

Frequency

PowerTime

CDMA


different code on the

channel.

There are two main types of CDMA, FHSS (Frequency Hopping Spread Spectrum) and DSSS

(Direct Sequence Spread Spectrum) however all the current major cellular systems utilize

DSSS.



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In DSSS, the narrowband signal is spread with a wideband code prior to transmission. The

receivers are designed to extract the encoded signal (with the correct code) and reject

everything else as noise.

UMTS, cdmaOne and CDMA2000 all use CDMA. However the implementation of the codes

and the bandwidths used is different. For example UMTS utilizes a 5MHz channel bandwidth,

whereas cdmaOne uses only 1.25MHz.

2.1.4 Orthogonal Frequency Division Multiple Access

OFDMA (Orthogonal Frequency Division Multiple Access) is the latest addition to cellular

systems. It provides a multiple access technique based on OFDM (Orthogonal Frequency

Division Multiplexing). Figure 2-5 illustrates the basic view of OFDMA. Here it can be seen

that the bandwidth is broken down to smaller units known as “subcarriers”. These are grouped

together and allocated as a resource to a device. It can also be seen that a device can be

allocated different resources in both the time and frequency domain.

Additional detail on OFDM and OFDMA is provided later in this section.

Figure 2-5 Orthogonal Frequency Division Multiple Access

Frequency

PowerTime

OFDMA


different resource

which can vary in

time and frequency.

2.1.5 Transmission Modes

Cellular systems can be designed to operate in two main transmission modes, namely FDD

(Frequency Division Duplex) and TDD (Time Division Duplex).

Frequency Division Duplex

The concept of FDD is illustrated in Figure 2-6. A separate uplink and downlink channel are

utilized enabling a device to transmit and receive data at the same time (assuming the device

incorporates a duplexer). The spacing between the uplink and downlink channel is referred to

as the duplex spacing.

Figure 2-6 Frequency Division Duplex

Uplink Downlink

Duplex Spacing

Frequency

Channel

Bandwidth

Channel

Bandwidth





2-5

Normally the uplink channel (mobile transmit) operates on the lower frequency. This is done

because higher frequencies suffer greater attenuation than lower frequencies and therefore it

enables the mobile to utilize lower transmit power levels.

Some systems also offer half-duplex FDD mode, where two frequencies are utilized, however

the mobile can only transmit or receive, i.e. not transmit and receive at the same time. This

allows for reduced mobile complexity since no duplex filter is required.

Time Division Duplex

TDD mode enables full duplex operation using a single frequency band with time division

multiplexing for the uplink and downlink signals. One advantage of TDD is its ability to

provide asymmetric uplink and downlink allocations. Depending on the system, other

advantages include dynamic allocation, increased spectral efficiency, and improved use of

beamforming techniques. The later being due to the carrier having the same uplink and

downlink frequency characteristics.

Figure 2-7 Time Division Duplex

TDDFrequency

Downlink Uplink Downlink Uplink

TDD Frame TDD Frame

Time

Asymmetric

Allocation

Downlink

and Uplink

2.2 Principles of OFDM

The LTE air interface utilizes two different multiple access techniques, both of which are

based on OFDM (Orthogonal Frequency Division Multiplexing). These are:

OFDMA (Orthogonal Frequency Division Multiple Access) - used on the downlink.

SC-FDMA (Single Carrier - Frequency Division Multiple Access) - used on the uplink.

Figure 2-8 Use of OFDM in LTE

eNB

UE

OFDM

(OFDMA)

OFDM

(SC-FDMA)



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The concept of OFDM is not new and is currently being used on various systems such as

Wi-Fi (Wireless Fidelity) and WiMAX (Worldwide Interoperability for Microwave Access).

Furthermore, it was even considered for UMTS back in 1998. One of the main reasons why it

was not chosen at the time however was the handsets limited processer power and the poor

battery capabilities.

LTE was able to choose an OFDM based access due to the fact mobile handset processing

capabilities and battery performance have both significantly improved over the intervening

years. In addition, there is continual pressure to produce ever more spectrally efficient

systems.

2.2.1 Frequency Division Multiplexing

OFDM is based on FDM (Frequency Division Multiplexing) and is a method whereby

multiple frequencies are used to simultaneously transmit information. Figure 2-9 illustrates an

example of FDM with four subcarriers. These can be used to carry different information and

to ensure that each subcarrier does not interfere with the adjacent subcarrier, a guard band is

utilized. In addition, each subcarrier has slightly different radio characteristics and this may be

used to provide diversity.

Figure 2-9 FDM Carriers

Frequency

Guard Band

Channel

Bandwidth

Subcarrier

FDM systems are not that spectrally efficiency (when compared to other systems) since

multiple guard bands are required.

2.2.2 OFDM Subcarriers

OFDM follows the same concept as FDM but it drastically increases spectral efficiency by

reducing the spacing between the subcarriers. Figure 2-10 illustrates how the subcarriers can

overlap due to their orthogonally with the other subcarriers, i.e. the subcarriers are

mathematically perpendicular to each other. As such, when a subcarrier is at its maximum, the

two adjacent subcarriers are passing through zero. Furthermore, OFDM systems still employ

guard bands. These are however located at the upper and lower parts of the channel in order to

reduce adjacent channel interference.





2-7

Figure 2-10 OFDM Subcarriers

Frequency

Channel

Bandwidth

Orthogonal

Subcarriers

Centre Subcarrier

Not Orthogonal

The centre subcarrier, known as the DC (Direct Current) subcarrier, is not typically used in OFDM

systems due to its lack of orthogonality.

2.2.3 Fast Fourier Transforms

OFDM subcarriers are generated and decoded using mathematical functions called FFT (Fast

Fourier Transform) and IFFT (Inverse Fast Fourier Transform). The IFFT is used in the

transmitter to generate the waveform. Figure 2-11 illustrates how the coded data is first

mapped to parallel streams before being modulated and processed by the IFFT.

Figure 2-11 Inverse Fast Fourier Transform

Coded

BitsIFFT

Serial

to

Parallel

Subcarrier

Modulation

RF

Inverse Fast

Fourier

Transform

Complex

Waveform

At the receiver side, this signal is passed to the FFT which analyses the complex/combined

waveform to generate the original streams. Figure 2-12 illustrates the FFT process.



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Figure 2-12 Fast Fourier Transform

Coded

Bits

Parallel

to

Serial

FFT

Subcarrier

Demodulation

Receiver

Fast Fourier

Transform

2.2.4 LTE FFT Sizes

Fast Fourier Transforms and Inverse Fast Fourier Transforms both have a defining size. For

example, an FFT size of 512 indicates that there are 512 subcarriers. In reality, not all 512

subcarriers can be utilized for data transfer due to the channel guard bands and the fact that a

DC (Direct Current) subcarrier is also required.

Table 2-1 illustrates the channel bandwidth options available to LTE, as well as the FFT size

and associated sampling rate. Using the sampling rate and the FFT size, the subcarrier spacing

can be calculated, e.g. 7.68MHz/512 = 15kHz.

Table 2-1 LTE Channel and FFT Sizes

Channel Bandwidth

FFT Size Subcarrier Bandwidth

Sampling Rate

1.4MHz 128

15kHz

1.92MHz

3MHz 256 3.84MHz

5MHz 512 7.68MHz

10MHz 1024 15.36MHz

15MHz 1536 23.04MHz

20MHz 2048 30.72MHz

The subcarrier spacing of 15kHz is also used to identify the OFDM symbol duration.

2.2.5 OFDM Symbol Mapping

The mapping of OFDM symbols to subcarriers is dependent on the system design. The first

12 modulated OFDM symbols are mapped to 12 subcarriers, i.e. they are transmitted at the

same time but using different subcarriers. The next 12 subcarriers are then mapped to the next

OFDM symbol period. In addition, a CP (Cyclic Prefix) is added between the symbols.





2-9

Figure 2-13 OFDM Symbol Mapping

Time

Frequency

Amplitude

OFDM

Symbol

Cyclic

Prefix

Modulated

OFDM

Symbol

LTE allocates resources in groups of 12 subcarriers. This is referred to as a PRB (Physical Resource

Block).

In the previous example, 12 different modulated OFDM symbols were transmitted

simultaneously. Figure 2-14 illustrates how the combined energy from this will result in either

constructive peaks (when the symbols are the same) or destructive nulls (when the symbols

are different).

Figure 2-14 OFDM PAPR (Peak to Average Power Ratio)

Amplitude

Time

OFDM

Symbol

PAPR (Peak to Average

Power Ratio) Issue

2.2.6 Time Domain Interference

The OFDM signal provides some protection in the frequency domain due to the orthogonality

of the subcarriers. The main issue to overcome however is delay spread, i.e. multipath

interference.

Figure 2-15 illustrates two of the main multipath effects, namely delay and attenuation. The

delayed signal can manifest itself as ISI (Inter Symbol Interference), whereby one symbol

impacts the next.



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Figure 2-15 Delay Spread

Energy

Time

Delay Spread

ISI is typically combated with “equalizers”. However for the equalizer to be effective, a

known bit pattern or “training sequence” is required. This reduces the system capacity, as well

as impacting on the processing required within the device. Instead, OFDM systems employ a

CP (Cyclic Prefix).

Figure 2-16 Inter Symbol Interference

1st Received

SignalDelayed

Signal

Interference

Caused

Cyclic Prefix

A Cyclic Prefix is utilized in most OFDM systems to combat multipath delays. It effectively

provides a guard period for each OFDM symbol. Figure 2-17 illustrates the Cyclic Prefix and

identifies its location in the OFDM Symbol. Notice that the Cyclic Prefix is effectively a copy

from the back of the original symbol which is then placed in front to make the OFDM symbol

(Ts).





2-11

Figure 2-17 Cyclic Prefix

Symbol Period T(s)T(g)

CP

CP

CP

CP

CP

CP

CP

CP

CP

CP

CP

CP

Frequency

TimeSymbol Period T(s)

Bit Period T(b)Cyclic Prefix

LTE has two defined Cyclic Prefix sizes, normal and extended. The extended Cyclic Prefix is designed for

larger cells.

The size of the Cyclic Prefix relates to the maximum delay spread the system can tolerate. As

such, systems designed for macro coverage, i.e. large cell radius, should have a large CP. This

does however impact on system capacity as the number of symbols per second is will be

reduced.

2.2.7 OFDM Advantages and Disadvantages

OFDM Advantages

OFDM systems typically have a number of advantages:

OFDM is almost completely resistant to multi-path interference due to its very long

symbol duration.

Higher spectral efficiency for wideband channels - 5MHz and above.

Flexible spectrum utilization.

Relatively simple implementation using FFT and IFFT.

OFDM Disadvantages

OFDM also has some disadvantages:

Frequency errors and phase noise can cause issues.

Doppler shift impacts subcarrier orthogonality.



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Some OFDM systems can suffer from high PAPR (Peak to Average Power Ratio).

Accurate frequency and time synchronization.

2.3 LTE Channel Structures

The concept of “channels” is not new. Both GSM and UMTS defined various channel

categories, however LTE terminology is closer to UMTS. Broadly there are four categories of

channel.

Figure 2-18 LTE Channels

Logical

Channels

Transport

Channels

Physical

Channels

Radio

Channels

2.3.1 Logical Channels

In order to describe Logical Channels it is best to first identify where logical channels are

located in relationship to the LTE protocols and the other channel types. Figure 2-19

illustrates the Logical Channels located between the RLC (Radio Link Control) and the MAC

(Medium Access Control) layers.

Figure 2-19 Location of Channels

RLC

MAC

PHY

Logical

ChannelsTransport

Channels

Physical

Channels Radio

Channel

Logical Channels are classified as either Control Logical Channels, which carry control data

such as RRC (Radio Resource Control) signaling, or Traffic Logical Channels which carry

User Plane data.

Control Logical Channels

The various forms of these Control Logical Channels include the:

BCCH (Broadcast Control Channel) - this is a downlink channel used to send of SI

(System Information) messages from the eNB (Evolved Node B). These are defined by

RRC.

PCCH (Paging Control Channel) - this is a downlink channel used by the eNB to

broadcast paging information.





2-13

Figure 2-20 BCCH and PCH Logical Channels

BCCH

eNBUE

PCCH

System Information

Messages

Paging

Devices

CCCH (Common Control Channel) - this is used to establish an RRC Connection or

specifically a SRB (Signaling Radio Bearer). It is also used for re-establishment

procedures. Note, SRB 0 maps to the CCCH.

DCCH (Dedicated Control Channel) - this provides a bi-directional channel for signaling.

Logically there are two DCCH activated:

− SRB 1 - is used for RRC messages, as well as RRC messages which carry high

priority NAS signaling.

− SRB 2 - is used for RRC carrying low priority NAS signaling. Prior to its

establishment, low priority signaling is sent on SRB1.

Figure 2-21 CCCH and DCCH Signaling

CCCH

eNBUE

CCCH

DCCH

DCCH

SRB 0

SRB 0

SRB 1

SRB 2

Low Priority

NAS Signalling

Traffic Logical Channels

3GPP Release 8 LTE has one type of Logical Channel carrying traffic, namely the DTCH

(Dedicated Traffic Channel). This is used to carry DRB (Dedicated Radio Bearer) information,

i.e. IP datagrams.

Figure 2-22 Dedicated Traffic Channel

eNBUE

DTCHDRB

Carries AM or UM

RLC Traffic



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The DTCH is a bi-directional channel that can operate in either RLC AM (Acknowledged

Mode) or UM (Unacknowledged Mode). This is configured by RRC and is based on the QoS

(Quality of Service) applied to the E-RAB (EPS Radio Access Bearer).

2.3.2 Transport Channels

Historically, transport channels were split between common and dedicated channels. However,

LTE has moved away from dedicated channels in favor of the common/shared channels

approach due to the associated efficiencies this provides. The main 3GPP Release 8 Transport

Channels include the:

BCH (Broadcast Channel) - this is a fixed format channel which occurs once per frame

and it is used to carry the MIB (Master Information Block). Note that the majority of

system information messages are carried on the DL-SCH (Downlink - Shared Channel).

PCH (Paging Channel) - which is used to carry the PCCH, i.e. paging messages. It also

utilizes DRX (Discontinuous Reception) to improve UE battery life.

DL-SCH (Downlink - Shared Channel) - is the main downlink channel for data and

signaling. It supports dynamic scheduling, as well as dynamic link adaptation. In

addition, it utilizes HARQ (Hybrid Automatic Repeat Request) operation to improve

performance. As previously indicated, it also facilitates the sending of system

information messages.

RACH (Random Access Channel) - carries limited information and is used in

conjunction with Physical Channels and preambles to provide contention resolution

procedures.

UL-SCH (Uplink Shared Channel) - similar to the DL-SCH, this channel supports

dynamic scheduling (eNB controlled) and dynamic link adaptation by varying the

modulation and coding. In addition, it too supports HARQ (Hybrid Automatic Repeat

Request) operation to improve system performance.

Figure 2-23 LTE Release 8 Transport Channels

BCH

eNBUE

PCH

DL-SCH

RACH

UL-SCH

2.3.3 Physical Channels

The Phy (Physical) Layer facilitates transportation of MAC Transport Channels, as well as

providing scheduling, formatting and control indicators.

Downlink Physical Channels

Physical Channels on the downlink include the :

PBCH (Physical Broadcast Channel) - used to carry the BCH.

PCFICH (Physical Control Format Indicator Channel) - is used to indicate the number of

OFDM symbols used for the PDCCH.





2-15

PDCCH (Physical Downlink Control Channel) - used for resource allocation.

PHICH (Physical Hybrid ARQ Indicator Channel) - used as part of the HARQ process.

PDSCH (Physical Downlink Shared Channel) - used to carry the DL-SCH.

Uplink Physical Channels

There are a number of Uplink Physical Channels in LTE. These include the:

PRACH (Physical Random Access Channel) - this channel carries the Random Access

Preamble. The location of the PRACH is defined by higher layer signaling, i.e. RRC.

PUCCH (Physical Uplink Control Channel) - this carries uplink control and feedback. It

can also carry scheduling requests to the eNB.

PUSCH (Physical Uplink Shared Channel) - which is the main uplink channel and is

used to carry the UL-SCH. It carries both signaling and user data, in addition to uplink

control. It is worth noting that the UE is not allowed to transmit the PUCCH and PUSCH

at the same time.

2.3.4 Radio Channels

The term “Radio Channel” is typically used to describe the overall channel, i.e. the downlink

and uplink carriers for FDD operation and the carrier for TDD operation.

Figure 2-24 Radio Channel

eNB

UE

Radio

Channel

Radio

Channel

UE

FDD

TDD



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2.3.5 Channel Mapping

There are various options for multiplexing multiple bearers together such that Logical

Channels may be mapped to one or more Transport Channels. These in turn are mapped into

Physical Channels.

Figure 2-25 Downlink Channel Mapping

DL-SCH

Physical Layer

MAC Layer

RLC Layer

PDCP Layer

RRC Layer

Physical

Channels

Transport

Channels

Logical

Channels

PDSCHPDCCHPHICHPCFICHPBCH

BCH PCH

BCCH PCCH CCCH DCCH DTCH

TM TM TM UM/AM UM/AM

Ciphering

Integrity

Ciphering

ROHC

RRC

ESM EMM IPNAS Layer





2-17

Figure 2-26 Uplink Channel Mapping

Physical Layer

MAC Layer

RLC Layer

PDCP Layer

RRC Layer

Physical

Channels

Transport

Channels

Logical

Channels

PUSCHPUCCHPRACH

RACH

CCCH

TM UM/AM UM/AM

Ciphering

Integrity

Ciphering

ROHC

RRC

ESM EMM IPNAS Layer

UL-SCH

DCCH DTCH

In order to facilitate the multiplexing of Logical Channels to Transport Channels, the MAC

Layer typically adds a LCID (Logical Channel Identifier).

2.4 LTE Frame Structure

In LTE, devices are allocated blocks of subcarriers for a period of time. These are referred to

as a PRB (Physical Resource Block). The resource blocks are contained within the LTE

generic frame structure of which two types are defined; Type 1 and Type 2 radio frames.

2.4.1 Type 1 Radio Frames, Slots and Subframes

The Type 1 radio frame structure is used for FDD and is 10ms in duration. It consists of 20

slots, each lasting 0.5ms. Two adjacent slots form one subframe. For FDD operation, 10

subframes are available for downlink transmission and 10 subframes are available for uplink

transmission, with each transmission separated in the frequency domain.

Figure 2-27 illustrates the FDD frame structure, as well as highlighting the slots and subframe

concept. In addition, it illustrates how the slots are numbered 0 to 19.



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Figure 2-27 LTE Frame Structure

Slot (0.5ms)

Radio Frame Tf = 307200 x Ts = 10ms

Subframe (1ms)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Ts = 1/(15000x2048)

= 32.552083ns

Tslot = 15360 x Ts

LTE Time Unit

The LTE time unit is identified as Ts and is calculated as 1/(15000×2048) which equates to

approximately 32.552083ns. Various aspects of LTE utilize this parameter, or multiples of it,

to identify timing and configuration information.

Cyclic Prefix Options

The concept of a CP (Cyclic Prefix) within OFDM systems has already been discussed. In

LTE, two different cyclic prefix sizes, namely “Normal” and “Extended” were selected. In

order to facilitate these, two different slot formats are required. Figure 2-28 illustrates the

seven and six ODFM symbol options. Obviously, to facilitate a larger cyclic prefix, one of the

symbols is sacrificed, thus the symbol rate is reduced.

Figure 2-28 Normal and Extended Cyclic Prefix

Radio Frame = 10ms

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

7 OFDM

Symbols (Normal

Cyclic Prefix)

6 OFDM Symbols

(Extended Cyclic

Prefix)

0 1 2 3 4 5 6

0 1 2 3 4 5

CP (Cyclic

Prefix)

Ts

Ts

The use of the extended cyclic prefix is intended for scenarios where the range of the cell

needs to be extended, e.g. for coverage planning purposes or when multicast services are

being employed in the cell.





2-19

2.4.2 Type 2 Radio Frames, Slots and Subframes

The Type 2 radio frame structure is used for TDD. One key addition to the TDD frame

structure is the concept of “special subframes”. This includes a DwPTS (Downlink Pilot Time

Slot), GP (Guard Period) and UpPTS (Uplink Pilot Time Slot). These have configurable

individual lengths and a combined total length of 1ms.

For TDD operation, the ten subframes are shared between the uplink and the downlink. Both

5ms and 10ms switch-point periodicity is supported however subframes 0 and 5 must be

allocated to the downlink as these contain the PSS (Primary Synchronization Signal) and SSS

(Secondary Synchronization Signal), as well as the broadcast information in subframe 0.

Figure 2-29 Type 2 TDD Radio Frame

Type 2 Radio Frame Tf = 307200 x Ts = 10ms

0

Special

Subframe

2 3 4 5 7 8 9

DwPTS (Downlink

Pilot Time Slot)

GP (Guard Period)

UpPTS (Uplink

Pilot Time Slot)

There are various frame configuration options available for TDD operation. Table 2-2

illustrates these different options. Configuration options 0, 1, 2 and 6 have a 5ms switching

point and therefore require two special subframes. The remainder are based on a 10ms

switching point. In the table, the letter “D” is reserved for downlink transmissions, “U” uplink

transmissions and “S” denotes a special subframe with the three fields DwPTS, GP and

UpPTS.

Table 2-2 Type 2 Radio Frame Switching Points

Configuration Switching Point Periodicity

Subframe Number

0 1 2 3 4 5 6 7 8 9

0 5ms D S U U U D S U U U

1 5ms D S U U D D S U U D

2 5ms D S U D D D S U D D

3 10ms D S U U U D D D D D

4 10ms D S U U D D D D D D

5 10ms D S U D D D D D D D

6 5ms D S U U U D S U U D

The DwPTS and UpPTS in a special frame can be used to carry information. For example the DwPTS can

include scheduling information and the UpPTS can be configured to facilitate random access bursts.



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2.5 Downlink OFDMA

2.5.1 General OFDMA Structure

The E-UTRA downlink is based on OFDMA. As such, multiple devices are able to receive

information at the same time but on different portions of the radio channel. In most OFDMA

systems, this is referred to as a “Subchannel”, i.e. a collection of subcarriers. However, in

E-UTRA, the term “Subchannel” is replaced with the term PRB (Physical Resource Block).

Figure 2-30 illustrates the concept of OFDMA, whereby different users are allocated one or

more resource blocks in the time and frequency domain thereby enabling the efficient

scheduling of the available resources.

Figure 2-30 OFDMA in LTE

Frequency

Channel

Bandwidth

E.g. 3MHz

Time

Device is allocated one

or more PRB (Physical

Resource Blocks)

PRB consists of 12

subcarriers for 0.5ms

OFDMA

It is also worth noting that a device is typically allocated 1ms of time, i.e. a subframe, and not

an individual PRB.

2.5.2 Physical Resource Blocks and Resource Elements

A PRB (Physical Resource Block) consists of 12 consecutive subcarriers and lasts for one slot,

i.e. 0.5ms.

Figure 2-31 illustrates the size of a PRB. The NRBDL

parameter is used to define the number of

RB (Resource Block) used in the DL (Downlink). This is dependent on the channel bandwidth.





2-21

In contrast, NRBUL

is used to identify the number of resource blocks in the UL (Uplink). Each

Resource Block consists of NSCRB

subcarriers, which for standard operation is set to 12. In

addition, another configuration is available when using MBSFN (Multimedia Broadcast

Multicast Service Single Frequency Network) and a 7.5kHz subcarrier spacing.

The PRB is used to identify an allocation. It typically includes six or seven symbols,

depending on whether an extended or normal cyclic prefix is configured.

The term RE (Resource Element) is used to describe one subcarrier lasting one symbol. This

can then be assigned to carry modulated information, reference information or nothing.

Figure 2-31 Physical Resource Block and Resource Element

Radio Frame = 10ms

0 2 3 4 5 7 8 9

Slot 8 Slot 9

NRBDL

NSC

RB S

ub

carr

iers

= 1

2

61

Physical Resource

Block

Resource

Element

Subframe

The different configurations for the downlink E-UTRA PRB are illustrated in Table 2-3.

Table 2-3 Downlink PRB Parameters

Configuration NSCRB NSymb

DL

Normal Cyclic Prefix ∆f = 15kHz 12

7

Extended Cyclic

Prefix

∆f = 15kHz 6

∆f = 7.5kHz 24 3

The Uplink PRB configuration is similar to that shown; however the 7.5kHz option is not available.



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2.5.3 LTE Physical Signals

In order for the UE to be able to access the network, the eNB must broadcast various

downlink signals. As the downlink is scalable from 1.4MHz to 20MHz and the device may

not be aware of the eNB configuration, the method of finding the system needs to be

consistent. Consequently synchronization and cell identity information must appear on the

downlink in a fixed location irrespective of the radio spectrum configuration. Figure 2-32

illustrates the structure of the NIDcell

(Cell Identity).

Figure 2-32 Downlink Cell ID

cell (1) (2)

(1)

(2)

Downlink Synchronization Signals

eNB

UEWhere:

NID = 3NID + NID

NID = 0,…..167

NID = 0, 1, or 2

In LTE, there are two synchronization sequences. These are referred to as the PSS (Primary

Synchronization Signal) and the SSS (Secondary Synchronization Signal). The location of

these is dependent on the transmission mode, i.e. FDD or TDD, as well as the use of the

normal or extended cyclic prefix.

Figure 2-33 PSS and SSS Location for FDD

Radio Frame

Slots

0 1 2 3 4 5 6

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Bandwidth

72

Subcarriers

PSS (Primary

Synchronization

Sequence)

Repeated in

slots 0 and 10

SSS (Secondary

Synchronization

Sequence)

0 1 2 3 4 5

Bandwidth

Normal CP

Extended CP

62





2-23

Figure 2-34 PSS and SSS Location for TDD

Radio Frame

Slots

0 1 2 3 4 5 6

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Bandwidth

0 1 2 3 4 5

Bandwidth

Normal CP

Extended CP

0 1 2 3 4 5 6

0 1 2 3 4 5

Primary Synchronization Signal

The PSS provides downlink synchronization information for the UE. The signal sent is one of

three ZC (Zadoff-Chu) sequences. This provides a pseudo noise pattern which devices can

correlate, whilst at the same time enabling adjacent cells/sectors on the eNB to utilize

different synchronization signals. The NID (0,1 or 2) is mapped to a Zadoff-Chu root index

which is used in the sequence generation process

Secondary Synchronization Signal

The SSS is generated from the interleaved concatenation of two 31 bit binary sequences

which are cyclic shifted based on the value of NID.

2.5.4 Downlink Reference Signals

Unlike other systems, the LTE air interface does not employ a frame preamble. Instead it

utilizes various RS (Reference Signal) to facilitate coherent demodulation, channel estimation,

channel quality measurements and timing synchronization etc. Fundamentally there are three

types of downlink reference signals:

Cell Specific (non-MBSFN).

MBSFN (Multimedia Broadcast Multicast Service Single Frequency Network).

UE Specific.

Cell Specific Reference Signals

In LTE, the cell-specific reference signals are arranged in a two dimensional lattice of time

and frequency. This has been done so that they are equidistant and therefore provides a

minimum mean squared error estimate for the channel. In addition, the timing between the



Training Manual



Issue 01 (2010-05-01)

reference symbols is an important factor for channel estimation and relates to the maximum

doppler spread supported, i.e. speed. In LTE, this works out at two reference symbols per slot.

The spacing in frequency domain is also an important factor, as this relates to the expected

coherence bandwidth and delay spread of the channel. In LTE there is a six subcarrier

separation of reference signals, however these are staggered in time such that they appear

every three subcarriers.

MBSFN Reference Signals

The LTE system also defines a set of reference signals for MBSFN. These are only present

when the PMCH (Physical Multicast Channel) is present and uses the extended cyclic prefix.

UE Specific Reference Signals

UE Specific Reference Signals are supported for single antenna port transmission on the

PDSCH and are transmitted on antenna port 5. It is typically used for beamforming when

non-codebook based pre-coding is applied.

2.6 Uplink SC-FDMA

The uplink in LTE, as previously mentioned, is based on SC-FDMA (Signal Carrier -

Frequency Division Multiple Access). This was chosen for its low PAPR (Peak to Average

Power Ratio) and flexibility which reduced complexity in the UE and improved power

performance and battery life. SC-FDMA tries to combine the best characteristics of single

carrier systems such as low peak-to-average power ratio, with the advantages of multi carrier

OFDM and as such, is well suited to the LTE uplink.

2.6.1 SC-FDMA Signal Generation

Figure 2-35 SC-FDMA Subcarrier Mapping Concept

Subcarrier

MappingDFT IDFT

Symbols

Time Domain Frequency Domain Time Domain

0

0

0

0

0

0

0

CP

Insertion

The basic transmitter and receiver architecture is very similar (nearly identical) to OFDM, and

it offers the same degree of multipath protection. Importantly, because the underlying





2-25

waveform is essentially a single carrier, the PAPR is lower. It is quite difficult to visually

represent SC-FDMA in the time and frequency domain however this section aims to illustrate

the concept.

In Figure 2-35, the SC-FDMA signal generation process starts by creating a time domain

waveform of the data symbols to be transmitted. This is then converted into the frequency

domain, using a DFT (Discrete Fourier Transform). DFT length and sampling rate are chosen

so that the signal is fully represented, as well as being spaced 15kHz apart. Each subcarrier

will have its own fixed amplitude and phase for the duration of the SC-FDMA symbol. Next

the signal is shifted to the desired place in the channel bandwidth using the zero insertion

concept, i.e. subcarrier mapping. The signal is then converted to a single carrier waveform

using an IDFT (Inverse Discrete Fourier Transform) in addition to other functions. Finally a

cyclic prefix can be added. Note that additional functions such as S-P (Serial to Parallel) and

P-S (Parallel to Serial) converters are also required as part of a detailed functional description.

Figure 2-36 illustrates the concept of the DFT, such that a group of N symbols map to N

subcarriers. However depending on the combination of the N symbols into the DFT, the

output will vary. As such, the actual amplitude and phase of the N subcarriers is more like a

“code word”.

Figure 2-36 SC-FDMA Signal Generation

DFT

N symbols sequence

produces N subcarriers

Different input sequence

produces different output

N Symbols

DFT Output

Modulated and

Coded Symbols

DFT

N Symbols

At the eNB, the receiver takes the N subcarriers and reverses the process. This is achieved

using an IDFT (Inverse Discrete Fourier Transform) which effectively reproduces the original

N symbols. Figure 2-37 illustrates the basic view of how the subcarriers received at the eNB

are converted back into the original signals.

Note that the SC-FDMA symbols have a constant amplitude and phase and like ODFMA, a

CP (Cyclic Prefix) is still required.



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Issue 01 (2010-05-01)

Figure 2-37 SC-FDMA and the eNB

N Subcarriers

Time

Power

IDFT

IDFT

Cyclic

Prefix First N Symbols

Second N Symbols

2.6.2 OFDMA Verses SC-FDMA

The main reason SC-FDMA was specified for the uplink was because of its PA (Power

Amplifier) characteristics. Typically, the SC-FDMA signal will operate with a 2-3 dB lower

PAPR. This makes the system more efficient, thus increasing the UE’s battery life. SC-FDMA

also performs better when in larger cells.

It must be noted that OFDMA is better in a number of areas, such as Inter-symbol

orthogonality and the ability to provide a more flexible frequency domain scheduling

mechanism. This increases the system performance. In addition, OFDMA is more suitable for

uplink MIMO (Multiple Input Multiple Output) operation and its associated high date rate

services.

Table 2-4 highlights three main features and indicates which technology is best suited.

Table 2-4 SC-FDMA verses OFDMA

Feature SC-FDMA OFDMA

Low PAPR Y X

Performance X Y

Uplink MIMO X Y

2.7 Multiple Input Multiple Output

MIMO relates to the use of multiple antennas at both the transmitter (Multiple Input) and

receiver (Multiple Output). The terminology and methods used in MIMO can differ from

system to system, however most fall into one of two categories:

SU-MIMO (Single User - Multiple Input Multiple Output) - this utilizes MIMO

technology to improve the performance towards a single user.

MU-MIMO (Multi User - Multiple Input Multiple Output) - this enables multiple users

to be served through the use of spatial multiplexing techniques.





2-27

Figure 2-38 SU-MIMO and MU-MIMO

SU-MIMO

MU-MIMO

eNB

UE

Increases capacity since a

single user benefits from

multiple data streams.

eNBUE

UE

Increases sector

capacity by allowing

users to share streams.

2.7.1 Spatial Multiplexing

The most common MIMO category is referred to as SM (Spatial Multiplexing). This enables

multiple modulation symbol streams to be sent to a single UE using the same time and

frequency parameters. The differentiation of signals is achieved by the different reference

signals which were sent as part of the PRB (Physical Resource Block). Figure 2-39 illustrates

the concept of Spatial Multiplexing using a 2×2 MIMO system.

Figure 2-39 MIMO Spatial Multiplexing

eNB

UE

Port 0

Port 1TB

TB

MIMO

TB

TB

2x2 SM (Spatial

Multiplexing)

The main issue with Spatial Multiplexing in a cellular system is the high levels of interference

which may be experienced, especially at the cell edge. Unfortunately, this can affect both

spatial streams thereby introducing twice as many errors. For this reason, Spatial Multiplexing

is typically used close to the eNB, i.e. not at the cell edge.

Figure 2-40 Spatial Multiplexing Interference Issues

eNB

UE

Port 0

Port 1TB

TB

MIMO

TB

TB

Interference

causes twice

as may errors

Interference



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Issue 01 (2010-05-01)

2.7.2 Space Time Coding

If a UE was at the cell edge it could still benefit from MIMO. However it would rely on

different implementations, such as STC (Space Time Coding). Figure 2-41Figure 2-41

illustrates the basic concept of STC in a MIMO system.

Figure 2-41 MIMO Space Time Coding

eNB

UE

Port 0

Port 1

MIMO TB

Interference

TB

1 2 3 4 5 6

1 2 3 4 5 6

123 456

Form of

STC

TB Still

Recoverable

Increased

Robustness

2.7.3 Adaptive MIMO Switch

To truly optimize the channel efficiency, some systems offer the ability to support AMS

(Adaptive MIMO Switch). Figure 2-42Figure 2-42 illustrates how a system could utilize a

mixture of Spatial Multiplexing and Space Time Coding, to optimize the eNB performance.

Figure 2-42 Adaptive MIMO Switch

Space Time

Coding

Spatial

Multiplexing

High SNRLow SNR

Effic

ien

cy

UE

eNB

AMS Point

2.8 Multimedia Broadcast Multicast Service

MBMS (Multimedia Broadcast Multicast Service) is a point-to-multipoint service in which

data is transmitted from a single source to multiple recipients. This provides a more efficient

mechanism for the delivery of services such as Mobile TV and text streams etc.





2-29

2.8.1 MBMS Logical Architecture

To support MBMS, a number of additional functions are required within the LTE architecture.

This includes:

BM-SC (Broadcast Multicast - Service Centre) - provides functions for the MBMS user

service provisioning and delivery. In may be used as an entry point for external content

providers in addition to authorizing and initiating MBMS bearer services etc.

MBMS-GW (Multimedia Broadcast Multicast Service - Gateway) - supports the transfer

of Control Plane and User Plane information from the BM-SC to the MME and eNB

respectively. It also allocates an IP multicast address to the eNB which should be used to

receive the MBMS data.

Figure 2-43 MBMS Logical Architecture

M3UE

UE

eNB

MME

MBMS-GW

BM-SCSm SGmb

SGi-mb

M1

MCE (Multi-cell / multicast Coordination Entity) - this function is responsible for

admission control and the allocation of the radio resources used be the eNBs in the

MBSFN (MBMS over Single Frequency Network) area. Although the specifications do

not preclude the positioning of the MCE in any network element, it is envisaged that it

will form part of the eNB.

If the MCE does not form part of the eNB, the M2 Interface will be present to link the MCE with the eNB.

The M3 Interface will still exist between the MME and the MCE.

In addition to the network elements and associated functions already discussed, MBMS also

utilizes a number of “areas”. These include the:

MBSFN Synchronization Area - this is an area within the network where all eNBs can be

synchronized and perform MBSFN transmissions. These transmissions can further be

defined as a simulcast transmission of identical waveforms at the same time from

multiple cells. As such, these are seen as a single transmission with respect to the UE.

MBSFN Synchronization Areas are capable of supporting one or more MBSFN Areas.

MBSFN Area - this consists of a group of cells within an MBSFN Synchronization Area

which are coordinated to achieve an MBSFN transmission. A cell within a MBSFN

Synchronization Area can only belong to one MBSFN Area.

MBSFN Area Restricted Cell - this is a cell within the MBSFN Area which does not

contribute to the MBSFN transmission. It may be able to transmit for other services but

this will be at a reduced power and the resource allocated for the MBSFN transmission.



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Issue 01 (2010-05-01)

Figure 2-44 MBSFN Synchronization Areas

eNB eNB eNBeNB eNB

MBSFN AreaMBSFN

Area

MBSFN

Area

MBSFN Synchronization Area

UEMBSFN Transmission

MBSFN Area

Reserved Cell

User data flow synchronization on the air interface is achieved using the SYNC protocol on

the M1 Interface. As part of these procedures, the BM-SC includes a timestamp alongside the

SYNV PDU packets which is used to ensure all the eNBs within the MBSFN Synchronization

Area use a common reference.

2.8.2 MBMS Cell Configuration

In accordance with the 3GPP’s Release 9 specifications, MBMS dedicated cell is now void

and as such, support for MBMS services will only be present on carriers alongside unicast

traffic. MBMS is not supported however in HeNB (Home Evolved Node B). Furthermore,

single cell MBMS transmission is no longer supported which restricts MBMS operation to

multi cell mode only. This concept is illustrated in Figure 2-45.

Figure 2-45 MBMS Cell Configuration

eNB eNB

UE

UE UE

MBMS/Unicast Mixed Cell

Multi-cell MBMS Transmission

Unicast

Transmission

MBSFN Reference Signals are only transmitted when the PMCH (Physical Multicast Channel) is present.

Furthermore, these reference signals are defined for the Extended Cyclic prefix only.


Training Manual 3 eNB Product Overview



3-1

3 eNB Product Overview

Objectives


3.1 Describe the Huawei eNB product family.

3.2 Describe the Huawei eNB products and application scenarios.

3.3 Describe the Huawei eNB operation and maintenance system.



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Issue 01 (2010-05-01)

3.1 The Huawei eNB Family

The Huawei eNB (Evolved Node B) product family consists of two core products; the

BTS3900(A) LTE and the DBS3900 LTE which focus on customer innovations. The former

comes in two versions, the BTS3900 LTE is a compact indoor macro eNB where as the

BTS3900A LTE is an outdoor version. The DBS3900 however has a distributed architecture

enabling the radio unit to be installed at the mast head close to the antennas thereby reducing

feeder loss and improving system coverage.

3.1.1 BTS3900(A) LTE

The BTS3900(A) LTE features a distributed architecture and consists of two basic modules;

the BBU3900 (Baseband control Unit) and the LRUF (LTE Radio Frequency Unit). These are

interconnected through a CPRI (Common Public Radio Interface) using electrical cables.

Flexible combinations of these two basic modules and auxiliary devices, provides diverse site

solutions that are applicable in different scenarios.

Figure 3-1 BTS3900(A) LTE Architecture

Cabinets

BBU3900

(BaseBand control Unit)

LRFU

(LTE Radio Frequency

Unit)CPRI

RF Antenna

Baseband Control Unit

Figure 3-2 BBU3900

The BBU3900 performs the following functions:

It provides support for connection between the eNB and the MME (Mobility

Management Entity) or S-GW (Serving Gateway).





3-3

It provides CPRI ports for communication with the LRFU and processes uplink and

downlink signals.

It performs centralized management of the entire BTS3900(A) LTE and DBS3900 LTE

in terms of O&M (Operations and Maintenance) and signaling processing.

It provides an O&M channel for connection to LMT (Local Maintenance Terminal) or

iManager M2000.

It provides the clock port, alarm monitoring port and USB (Universal Serial Bus) port.

LTE Radio Frequency Unit

The LRFU performs modulation, demodulation, data processing and combining and dividing

for baseband signals and RF signals. The LRFU supports double feeders (2Tx + 2Rx) as well

as four feeders (4Tx + 4Rx) through a combined installation of two LRFUs.

Figure 3-3 LRFU

Cabinets

The indoor macro cabinet BTS3900 LTE houses the BBU3900 and up to six LRFUs. In

addition, it also provides functions such as power distribution, heat dissipation and surge

protection.

The outdoor separated macro cabinet BTS3900A LTE consists of the RFC (Radio Frequency

Cabinet) and APM30H (Advanced Power Module with Heat exchanger cooling) which are

installed in stack mode.

Other configurations are available according to customer requirements.

3.1.2 DBS3900 LTE

The DBS3900 LTE features a distributed architecture. The two basic modules of the

DBS3900 LTE consist of the BBU3900 and RRU3201 (Remote Radio Unit) These are

interconnected through a standardized CPRI using optical cables.



Training Manual



Issue 01 (2010-05-01)

Figure 3-4 DBS3900 LTE Architecture

BBU3900

(BaseBand control Unit)RRU3201

(Radio Remote Unit)CPRI

RF Antenna

Auxiliary Devices

APM30H / IBBS200D&T / TMC11H

The Auxiliary Devices are the supporting elements to the BBU3900 and RMU3201. These

provide installation space for the BBU3900 and supply power to the BBU3900 and RRU3201.

Examples of auxiliary devices include the AMP30H, IBBS200D (Integrated Battery Backup

System with direct cooler), IBBS200T (Integrated Battery Backup System with TEC cooler)

and TMC11H (Transmission Cabinet with heat exchanger cooler).

Remote Radio Unit

Figure 3-5 RRU

The RRU3201 is a remote radio unit which performs modulation, demodulation, data

processing and combining and dividing for baseband signals and RF signals. The RRU3201

supports double feeders (2Tx + 2RX) and can also support four feeders (4Tx + 4Rx) through

combined installation of two RRU3201s. It can support a maximum of three cascading levels,

thus meeting the fast capacity expansion requirements of service providers.

Auxiliary Devices

The auxiliary devices provided by Huawei can be combined with the basic modules in a

flexible manner to support device installation scenarios. Examples include the:

AMP30H - this is a power system for outdoor applications including power supply and

battery backup. It also provides space to house the BBU3900.





3-5

IBBS200D&T - this is a long duration integrated battery backup system.

TMC11H - used when greater space is required for transmission equipment. It is utilized

in outdoor environments and can house both the BBU3900 and transmission equipment.

3.2 Products and Application Scenarios

With continuous capacity expansion required with mobile networks, site selection for the eNB

has turned into a bottleneck during network deployment. Site selection becomes increasingly

complex to implement and requires additional investment in network deployment.

3.2.1 BTS3900(A) LTE

The BTS3900(A) LTE is a compact indoor / outdoor macro eNB providing the following

features:

The BBU3900 and LRFU are installed in the BTS3900 LTE in a centralized mode which

helps to reduce the cost of maintenance on the tower.

The BTS3900 LTE is low weight and compact in size yet provides excellent scalability

in that it supports stack installation of two BTS3900s.

The BTS3900 family (LTE, UMTS and GSM) can share one indoor macro cabinet which

saves installation space and facilitates smooth technology evolution.

3.2.2 DBS3900 LTE

The DBS3900 LTE is characterized by its small footprint, easy installation and low power

consumption thus enabling it to be installed in the spare space at an existing cell site. The

RRU is also compact and light allowing it to be installed close to the antenna to reduce feeder

loss and thus improve system coverage. Thus the DBS3900 LTE enables service providers to

efficiently deploy a high performance LTE network with a low TCO (Total Cost of Ownership)

by minimizing the investment in power, space and manpower.

3.3 Operation and Maintenance

The BTS3900(A) LTE and DBS3900 LTE has the same O&M functions and thus is supported

by the same O&M system.

3.3.1 The Operations and Maintenance System

The O&M System consists of the LMT (Local Maintenance Terminal) and the iManager

M2000. The LMT is used to maintain a single eNB via an Ethernet cable for local

maintenance or via an IP network when remote maintenance is required. The iManager

M2000 is used to remotely maintain multiple eNBs with different software versions. O&M

functions thus include:

LMT performs data configuration, alarm monitoring, commissioning and software

upgrades.

The iManager M2000 performs data configuration, alarm monitoring, performance

monitoring and software upgrades



Training Manual



Issue 01 (2010-05-01)

Figure 3-6 O&M System

iManager M2000

LMTeNB

LMT

IP

Network

3.3.2 Benefits

The O&M system from Huawei offers the following benefits:

Configuration Management

Configuration management of the eNB encompasses a number of key features. These include

easy accessibility through the user friendly GUI which provides scenario specific

configuration wizards. Furthermore, service providers using the Huawei network planning

tool iPlan are able to import data thus lowering the time needed by network planners and site

optimization engineers.

High reliability is also ensured through a number of key features. These support data

configuration, query, export backup and restoration in addition to being able to rollback in

batches.

Finally, configuration management is also supported through a “northbound” NMS (Network

Management System) with the ability to add, modify and remove eNB configurations through

MML (Man Machine Language) commands.

Fault Management

Fault management within the eNB provides easy fault localization, high reliability in addition

to various tracing and monitoring methods.

Easy fault localization is supported through a number of features including alarm handling

suggestions and alarm correlation. This ensures KPI (Key Performance Indicator) service

level failures can be rectified quickly and accurately.

High reliability is also ensured through the inclusion of a comprehensive fault detection

system which operates over all aspects of the eNB; hardware, software, antenna, transmission

etc. Moreover, fault detection also extends to door status control, smoke, water damage and

temperature.





3-7

The eNB supports various tracing functions to check the compatibility of the interfaces. It also

supports real-time performance monitoring in GUI mode thus enabling the engineers to locate

performance failures quickly.

Performance Management

Performance management features multiple monitoring and reporting periods, and the

appropriate measurement point allocation. For example, the eNB can collect performance

counters every 15 or 60 minutes in addition to supporting real-time monitoring of KPIs for a

duration of one minute.

With regards point allocation, the eNB can support performance measurement at system level

or cell level, of neighbor cells, on interfaces and device usage. This aids the engineer in fault

finding.

Security Management

Security management supports both network level and user level security services. These

include; encryption of key information regarding the user, user account management and

authentication, access right control and support for industry standard security protocols - sFTP

(Secure File Transfer Protocol), SSL (Secure Socket Layer) and IPSec (IP Security).

Software Management

Software management within the eNB encompasses a number of key features. These include

easy accessibility, high efficiency and the minimizing of disruption to services during

software upgrades.

Deployment Management

The eNB deployment solution consists of automatic identification of the eNB through GPS

binding and unique binding and initial configuration through a USB drive. In addition, local

commissioning is not required as this function can be carried out remotely at the NMC.

Equipment / Inventory Management

The equipment management function incorporates a number of functions such as inventory

reporting for the main equipment (mechanical and electrical) through the iManager M2000.



Training Manual



Issue 01 (2010-05-01)


Training Manual 4 Glossary



4-1

4 Glossary

Numerics

16 QAM (Quadrature Amplitude

Modulation

2G (Second Generation)

3G (Third Generation)

3GPP (Third Generation

Partnership Project)

4G (Fourth Generation)

A

ACK (Acknowledgement)

AM (Acknowledged Mode)

AMPS (Advanced Mobile

Telephone System)

AMS (Adaptive MIMO

Switching)

APN (access Point Name)

ARQ (Automatic Repeat Request)

AS (Access Stratum)

AWS (Advanced Wireless

Services)

B

BCCH (Broadcast Control

Channel)

BCH (Broadcast Channel)

C

CATT (China Academy of

Telecommunications Technology)

CC (Chase Combining)

CCCH (Common Control

Channel)

CCE (Control Channel Element)

CDD (Cyclic Delay Diversity)

CDMA (Code Division Multiple

Access)

CFI (Control Format Indicator)

CP (Cyclic Prefix)

CPC (Continuous Packet

Connectivity)

CQI (Channel Quality Indicator)

CRC (Cyclic Redundancy Check)

C-RNTI (Cell - Radio Network

Temporary Identifier)

CS (Circuit Switched)

CS (Cyclic Shift)

CSG (Closed Subscriber Group)

D

DAI (Downlink Assignment

Index)

D-AMPS (Digital - Advanced

Mobile Phone System)

DC (Direct Current)

DCCH (Dedicated Control

Channel)

DC-HSDPA (Dual Cell - HSDPA)

DCI (Downlink Control

Information)

DCS (Digital Cellular Service)

DFT (Discrete Fourier Transform)

DL (Downlink)

DL-SCH (Downlink - Shared

Channel)

DL-SCH (Downlink Shared

Channel)

DRB (Dedicated Radio Bearer)

DRS (Demodulation Reference

Signal)

DRX (Discontinuous Reception)

DSSS (Direct Sequence Spread

Spectrum)

DTCH (Dedicated Traffic

Channel)

DTX (Discontinuous

Transmission)

DwPTS (Downlink Pilot Time

Slot)

4 Glossary


Training Manual



Issue 01 (2010-05-01)

E

EARFCN (E-UTRA Absolute

Radio Frequency Channel

Number)

EDGE (Enhanced Data Rates for

Global Evolution)

E-GSM (Extended GSM)

EMM (EPS Mobility

Management)

eNB (Evolved Node B)

EPC (Evolved Packet Core)

EPLMN (Equivalent HPLMN)

EPS (Evolved Packet System)

E-RAB (EPS Radio Access

Bearer)

ESM (EPS Session Management)

ETACS (Extended Total Access

Communication System)

ETSI (European

Telecommunications Standards

Institute)

E-UTRA (Evolved - Universal

Terrestrial Radio Access)

E-UTRAN (Evolved - Universal

Terrestrial Radio Access

Network)

EV-DO (Evolution-Data

Optimized)

F

FDD (Frequency Division

Duplex)

FDM (Frequency Division

Multiplexing)

FDMA (Frequency Division

Multiple Access)

FEC (Forward Error Correction)

FFT (Fast Fourier Transform)

FHSS (Frequency Hopping

Spread Spectrum)

FM (Frequency Modulation)

FSTD (Frequency Shift Time

Diversity)

G

GF(2) (Galois Field (2))

GP (Guard Period)

GPRS (General Packet Radio

System)

GSM (Global System for Mobile

communications)

GSMA (GSM Association)

GUTI (Globally Unique

Temporary Identifier)

H

HARQ (Hybrid ARQ)

HARQ (Hybrid Automatic Repeat

Request)

HeNB (Home eNB)

HI (HARQ Indicator)

HPLMN (Home PLMN)

HSDPA (High Speed Downlink

Packet Access)

HSPA (High Speed Packet

Access)

HS-SCCH (High Speed - Shared

Control Channel)

HSUPA (High Speed Uplink

Packet Data)

I

IDFT (Inverse Discrete Fourier

Transform)

IEEE (Institute of Electrical and

Electronics Engineers)

IFFT (Inverse Fast Fourier

Transform)

IMEI (International Mobile

Equipment Identity)

IMS (IP Multimedia Subsystem)

IMSI (International Mobile

Subscriber Identity)

IMT Advanced (International

Mobile Telecommunications

Advanced)

IMT2000 (International Mobile

Telecommunications - 2000)

IP (Internet Protocol)

IR (Incremental Redundancy)

IS-136 (Interim Standard 136)

ISI (Inter Symbol Interference)

ITU (International

Telecommunication Union)

L

LCID (Logical Channel

Identifier)

LCR (Low Chip Rate)

LTE (Long Term Evolution)

M

MAC (Medium Access Control)

MBSFN (MBMS over Single

Frequency Network)

MCS (Modulation and Coding

Scheme)

MGW (Media Gateways)

MIB (Master Information Block)





4-3

MIMO (Multiple Input Multiple

Output)

MME (Mobility Management

Entity)

MSC (Mobile Switching Centre)

Msg3 (Higher Layer Message)

MU-MIMO (Multi User - MIMO)

N

NACK (Negative

Acknowledgement)

NAS (Non Access Stratum)

NDI (New Data Indicator)

O

OFDM (Orthogonal Frequency

Division Multiplexing)

OFDMA (Orthogonal Frequency

Division Multiple Access)

P

PAPR (Peak to Average Power

Ratio)

PBCH (Physical Broadcast

Channel)

PCCH (Paging Control Channel)

PCFICH (Physical Control

Format Indicator Channel)

PCH (Paging Channel)

PCS (Personal Communications

Service)

PDCCH (Physical Downlink

Control Channel)

PDCP (Packet Data Convergence

Protocol)

PDN-GW (Packet Data Network -

Gateway)

PDSCH (Physical Downlink

Shared Channel),

PF (Paging Frame)

P-GSM (Primary GSM)

PH (Power Headroom),

PHICH (Physical Hybrid ARQ

Indicator Channel)

PHR (Power Headroom Report),

2-85

PHY (Physical Layer)

PL (Pathloss)

PLMN (Public Land Mobile

Network)

PMI (Precoding Matrix Indicator)

PO (Paging Occasion)

PRACH (Physical Random

Access Channel)

PRB (Physical Resource Block)

PS (Packet Switched)

P-S (Parallel to Serial)

PSS (Primary Synchronization

Signal)

PTM (Point-To-Multipoint)

PTP (Point-To-Point)

PUCCH (Physical Uplink Control

Channel)

PUSCH (Physical Uplink Shared

Channel)

Q

QoS (Quality of Service)

QPP (Quadratic Permutation

Polynomial)

QPSK (Quadrature Phase Shift

Keying)

R

R (Cell Ranking)

RA (Random Access)

RACH (Random Access Channel)

RAN (Radio Access Network)

RAPID (Random Access

Preamble Identifier)

RA-RNTI (Random Access -

RNTI)

RB (Radio Bearer)

RB (Resource Block)

RBG (Resource Block Groups)

RE (Resource Element)

REG (Resource Element Group)

R-GSM (Railways GSM)

RI (Rank Indication)

RIV (Resource Indication Value)

RLC (Radio Link Control)

RNC (Radio Network Controller)

RRC (Radio Resource Control)

RS (Reference Signals)

RSRP (Reference Signal Received

Power)

RSRQ (Reference Signal

Received Quality)

RSSI (Received Signal Strength

Indicator)

RV (Redundancy Version)

S

S (Cell Selection)

SAW (Stop And Wait)

SC-FDMA (Single Carrier -

Frequency Division Multiple

Access)

4 Glossary


Training Manual



Issue 01 (2010-05-01)

SFBC (Space Frequency Block

Coding)

SFN (System Frame Number),

S-GW (Serving Gateway)

SI (System Information)

SIB (System Information Block)

SIB 1 (System Information Block

Type1)

SI-RNTI (System Information -

Radio Network Temporary

Identifier)

SM (Spatial Multiplexing)

SMS (Short Message Service)

S-P (Serial to Parallel)

SR (Scheduling Request)

SRB (Signaling Radio Bearer)

SRS (Sounding Reference Signal)

SSS (Secondary Synchronization

Signal)

STC (Space Time Coding)

SU-MIMO (Single User - MIMO)

T

TA (Timing Alignment)

TAC (Tracking Area Code)

TACS (Total Access

Communications System)

TAI (Tracking Area Identity)

TB (Transport Block)

TBS (Transport Block Set)

TBS (Transport Blok Size)

TD (Transmit Diversity)

TD-CDMA (Time Division

CDMA)

TDD (Time Division Duplex)

TDMA (Time Division Multiple

Access)

TD-SCDMA (Time Division

Synchronous CDMA)

TF (Transport Format)

TFT (Traffic Flow Template)

TM (Transparent Mode)

TPC (Transmit Power Control)

TPMI (Transmitted Precoding

Matrix Indicator)

TTI (Time Transmission Interval)

TX (Transmit)

U

UCI (Uplink Control Information)

UE (User Equipment)

UL (Uplink)

UL-SCH (Uplink Shared

Channel)

UM (Unacknowledged Mode)

UMB (Ultra Mobile Broadband)

UpPTS (Uplink Pilot Time Slot)

USIM (Universal Subscriber

Identity Module)

V

VRB (Virtual Resource Block)

W

WCDMA (Wideband CDMA)

WiMAX (Worldwide

Interoperability for Microwave

Access)

Z

ZC (Zadoff-Chu)





4-1

LTE System Overview

Documents

Transcript of LTE System Overview