For Huke LTE Air Interface ISSUE 1.03

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Training Manual Contents

Issue 01 (2010-05-01) Huawei Proprietary and Confidential

Copyright Huawei Technologies Co., Ltd

i

Contents

1 The Air Interface ........................................................................................................................ 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 ....................... ................................................................. ............... 1-4

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 .................................................................................................................. .......................... 1-7

1.2.3 Release 4 .................................................................................................................... .......................... 1-7

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 ................................................................ ........................................................ 1-10

1.3 Radio Interface Techniques ........................................................................... .............................................. 1-10

1.3.1 Frequency Division Multiple Access .................................................................................... ............. 1-10

1.3.2 Time Division Multiple Access ............................................................ .............................................. 1-11

1.3.3 Code Division Multiple Access ............................................................ .............................................. 1-11

1.3.4 Orthogonal Frequency Division Multiple Access .............................................................................. 1-12

1.4 Transmission Modes ...................................................... ................................................................. ............. 1-12

1.4.1 Frequency Division Duplex ............................................................................ ................................... 1-13

1.4.2 Time Division Duplex ................................................................ ........................................................ 1-13

1.5 Spectrum Usage .............................. .............................................................. .............................................. 1-14

1.5.1 Frequency Bands ............................................................. ................................................................. .. 1-14

1.5.2 Existing Mobile Deployment ................................................................ ............................................. 1-16

1.5.3 LTE Release 8 Bands ...................................................... ................................................................. .. 1-17

1.6 Channel Coding in LTE ............................................................ ................................................................. .. 1-20

1.6.1 Transport Block CRC ................................................................ ......................................................... 1-20

1.6.2 Code Block Segmentation and CRC Attachment ....................................................... ........................ 1-21

1.6.3 Channel Coding ........................................ ................................................................. ........................ 1-23

1.6.4 Rate Matching ...................................................... ................................................................. ............. 1-28


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1.6.5 Code Block Concatenation ......................................................... ........................................................ 1-29

1.7 Principles of OFDM ...................................................... ................................................................. ............. 1-30

1.7.2 Frequency Division Multiplexing .............................................................................. ........................ 1-30

1.7.1 OFDM Subcarriers ................................................................................................................ ............. 1-31

1.7.2 Fast Fourier Transforms ................................................................................................................ ..... 1-31

1.7.3 LTE FFT Sizes ..................................................... ................................................................. ............. 1-32

1.7.4 OFDM Symbol Mapping ..................................................................... .............................................. 1-32

1.7.5 Time Domain Interference .............................................................................. ................................... 1-33

1.7.6 OFDM Advantages and Disadvantages................ ................................................................. ............. 1-35

2 LTE Physical Layer..................................................................................................................... 2-1

2.1 The Uu Interface.............................. .............................................................. ................................................ 2-3

2.2 LTE Radio Interface Protocols ............................................................................................ .......................... 2-3

2.2.1 Control and User Plane Protocols .............................................................................. .......................... 2-4

2.2.2 Non Access Stratum ........................................................ ................................................................. .... 2-4

2.2.3 RRC .......................................................... ................................................................. .......................... 2-7

2.2.4 PDCP ............................................. ................................................................. ..................................... 2-7

2.2.5 RLC ........................................................... ................................................................. .......................... 2-8

2.2.6 MAC .................................................................... .............................................................. .................. 2-9

2.2.7 Physical ...................................................................................... .......................................................... 2-9

2.3 LTE Channel Structure ............................................................. ................................................................. .. 2-10

2.3.1 Logical Channels ........................... ................................................................. ................................... 2-10

2.3.2 Transport Channels .............................................. ................................................................. ............. 2-12

2.3.3 Physical Channels ........................................................... ................................................................. .. 2-13

2.3.4 Radio Channels ..................................................................................................................... ............. 2-13

2.3.5 Channel Mapping ............................................................ ................................................................. .. 2-14

2.4 LTE Frame Structure .......................................................................... ......................................................... 2-15

2.4.1 Type 1 Radio Frames, Slots and Subframes ....................................................................................... 2-15

2.4.2 Type 2 Radio Frames, Slots and Subframes ....................................................................................... 2-17

2.5 OFDM Signal Generation .................................. ................................................................. ........................ 2-18

2.5.1 Codewords, Layers and Antenna Ports ........................... ................................................................. .. 2-19

2.5.2 Scrambling ................................................................................ ......................................................... 2-20

2.5.3 Modulation Mapper................................... ................................................................. ........................ 2-21

2.5.4 Layer Mapper ....................................................... ................................................................. ............. 2-22

2.5.5 Precoding ............................................................. ................................................................. ............. 2-23

2.5.6 Resource Element Mapper .............................................................................. ................................... 2-26

2.5.7 OFDM Signal Generation .................................................................................................. ................ 2-26

2.6 Downlink OFDMA ............................................ ................................................................. ........................ 2-26

2.6.1 General OFDMA Structure ........................................................................................................... ..... 2-26

2.6.2 Physical Resource Blocks and Resource Elements ............................................................... ............. 2-27

2.7 LTE Physical Signals................................ ................................................................ ................................... 2-28

2.8 Downlink Reference Signals ....................................................................................................... ................ 2-31


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2.8.1 Cell Specific Reference Signals ...................................................................... ................................... 2-31

2.8.2 MBSFN Reference Signals ................................................................................................ ................ 2-33

2.8.3 UE Specific Reference Signals ............................ ................................................................. ............. 2-34

2.9 Downlink LTE Physical Channels ................................................................. .............................................. 2-34

2.9.1 PBCH (Physical Broadcast Channel) .............................................................. ................................... 2-34

2.9.2 PCFICH (Physical Control Format Indicator Channel) ..................................................................... 2-35

2.9.3 PDCCH (Physical Downlink Control Channel) ......................................................... ........................ 2-37

2.9.4 PHICH (Physical Hybrid ARQ Indicator Channel) ....... ............................................................... ..... 2-40

2.9.5 PDSCH (Physical Downlink Shared Channel) .................................................................. ................ 2-41

2.10 Downlink Control Signaling ............................ ................................................................. ........................ 2-42

2.10.1 DCI Format 0 ................................................................................................ ................................... 2-42

2.10.2 DCI Format 1 ................................................................................................ ................................... 2-43

2.10.3 DCI Format 1A .................................................. ................................................................. ............. 2-43

2.10.4 DCI Format 1B ...... ................................................................. ......................................................... 2-44

2.10.5 DCI Format 1C ...... ................................................................. ......................................................... 2-44

2.10.6 DCI Format 1D .................................................. ................................................................. ............. 2-45

2.10.7 DCI Format 2 ................................................................................................ ................................... 2-45

2.10.8 DCI Format 2A .................................................. ................................................................. ............. 2-46

2.10.9 DCI Format 3 ................................................................................................ ................................... 2-46

2.10.10 DCI Format 3A ................................................ ................................................................. ............. 2-46

2.11 LTE Cell Search Procedure ................... ................................................................. ................................... 2-47

2.11.1 Cell Search ................................................................... ............................................................... ..... 2-47

2.11.2 PSS Correlation ............................................................. ................................................................. .. 2-48

2.11.3 SSS Correlation ............................................................. ................................................................. .. 2-49

2.11.4 Master Information Block ........................................................................................ ........................ 2-50

2.11.5 System Information Messages ................ ................................................................. ........................ 2-50

2.11.6 PLMN Selection ............................................................ ................................................................. .. 2-55

2.11.7 Cell Selection ................................................................ ................................................................ ... 2-57

2.12 Uplink Transmission Technique ........................................................................................................... ..... 2-58

2.12.1 SC-FDMA Signal Generation ............................ ................................................................. ............. 2-58

2.13 OFDMA Verses SC-FDMA ............................................................... ........................................................ 2-61

2.14 Uplink LTE Physical Channels .. ................................................................. .............................................. 2-61

2.14.1 PRACH (Physical Random Access Channel) .......................................................... ........................ 2-62

2.14.2 PUSCH (Physical Uplink Shared Channel) ............................. ........................................................ 2-66

2.14.3 PUCCH (Physical Uplink Control Channel) ............................................................ ........................ 2-68

2.15 Timing Relationships................................................... ................................................................. ............. 2-69

2.16 Uplink Reference Signals ................................................................. ......................................................... 2-70

2.16.1 Demodulation Reference Signal ........................................................ .............................................. 2-71

2.16.2 Sounding Reference Signal ......................................................................................................... ..... 2-72

2.17 Uplink Control Signaling ............................................................................ .............................................. 2-75

2.17.1 PUCCH Format 1 .......................................................... ................................................................. .. 2-75

2.17.2 PUCCH Format 1a and 1b ....................................................................................... ........................ 2-76


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2.18 LTE Random Access Procedure ........................................................ ........................................................ 2-78

2.18.1 RRC Connection ................................................ ................................................................. ............. 2-78

2.18.2 PRACH Preambles ........................................................ ................................................................. .. 2-79

2.18.3 Random Access Procedure Initialization....................................................... ................................... 2-80

2.18.4 Random Access Response Window .................................................................................... ............. 2-82

2.18.5 Random Access Response ........................................................................................................... ..... 2-82

2.18.6 Uplink Transmission .......................................... .............................................................. ................ 2-83

2.19 Uplink Power Control ...................................... ................................................................. ........................ 2-84

2.19.1 PUSCH Power Control ...................................... .............................................................. ................ 2-84

2.19.2 PUCCH Power Control ............................................................................................................... ..... 2-85

2.19.3 PRACH Power Control ............................................................................................................... ..... 2-86

2.20 Paging Procedures ....................................................... ................................................................. ............. 2-86

2.20.1 Discontinuous Reception for Paging ............................................................. ................................... 2-86

2.20.2 Paging Frame .......................................... ................................................................. ........................ 2-87

2.21 HARQ Operation .................................. ................................................................. ................................... 2-88

2.21.1 Retransmission Types ............................................................... ........................................................ 2-88

2.21.2 HARQ Methods ...................................... ................................................................. ........................ 2-88

2.21.3 HARQ in LTE ..................................................................................................................... ............. 2-90

2.21.4 HARQ In the Downlink ................................................................................ ................................... 2-91

2.21.5 HARQ In the Uplink ........................................................................................................ ................ 2-91

2.21.6 ACK NACK Timing...................................................... ................................................................. .. 2-92

2.22 Diversity Options ........................................................ ................................................................. ............. 2-94

2.22.1 SU-MIMO and MU-MIMO ................................................................................................ ............. 2-94

2.22.2 MIMO and Transmission Options ................................................................. ................................... 2-94

2.22.3 MIMO Modes ................................ ............................................................... ................................... 2-95

2.22.4 Spatial Multiplexing in LTE ................................................................ ............................................. 2-96

2.22.5 Feedback Reporting ........................................... ................................................................. ............. 2-98

3 Dynamic Resource Allocation ..................................................Error! Bookmark not defined.

3.1 Scheduling Principles and Signaling ...............................................................Error! Bookmark not defined.

3.1.1 QoS in Packet Switched Networks ........................................................Error! Bookmark not defined.

3.1.2 Key Factors Influencing Scheduling ......................................................Error! Bookmark not defined.

3.1.3 Scheduling Methods ........................................................ .......................Error! Bookmark not defined.

3.1.4 Downlink Scheduling ................................................................ .............Error! Bookmark not defined.

3.1.5 PDSCH Resource Allocation .................................................................Error! Bookmark not defined.

3.1.6 Modulation and Coding Scheme .......................................................... ..Error! Bookmark not defined.

3.1.7 Uplink Scheduling .................................................................................Error! Bookmark not defined.

3.2 Scheduler Interaction.......................................................................................Error! Bookmark not defined.

3.2.1 Radio Bearers ....................................................... ..................................Error! Bookmark not defined.

3.2.2 Scheduler Interaction with Layer 2 and Layer 1 ....................................Error! Bookmark not defined.

3.3 Dynamic and Semi-persistent Scheduling .......................................................Error! Bookmark not defined.

3.3.1 Dynamic Scheduling ................................................................. .............Error! Bookmark not defined.


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3.3.2 Downlink Semi-persistent Scheduling ...................................................Error! Bookmark not defined.

3.3.3 Uplink Semi-persistent Scheduling ........................................................Error! Bookmark not defined.

4 Intra LTE Mobility ......................................................................Error! Bookmark not defined.

4.1 Intra-LTE Mobility ........................................................ ..................................Error! Bookmark not defined.

4.1.1 Idle State - Cell Reselection ................................................................. ..Error! Bookmark not defined.

4.1.2 Active State Mobility .............................................................................Error! Bookmark not defined.

4.1.3 Handover Procedure ........................................................ .......................Error! Bookmark not defined.

4.2 Reporting Options ...........................................................................................Error! Bookmark not defined.

4.2.1 Measurement Configuration Parameter .................................................Error! Bookmark not defined.

4.2.2 Report Configuration Parameter ............................................................Error! Bookmark not defined.

4.3 Mobility Measurements...................................................................................Error! Bookmark not defined.

4.3.1 Measurement Gaps .......................................................... .......................Error! Bookmark not defined.

4.3.2 Gap Configuration .................................................................................Error! Bookmark not defined.

4.3.3 UE Measurements ........................................................... .......................Error! Bookmark not defined.

5 Glossary ....................................................................................................................................... 3-1


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Figures

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

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

Figure 1-3Third Generation Mobile Systems ..................................................................................... ............... 1-5

Figure 1-4Forth Generation Mobile System ................................................................. ..................................... 1-6

Figure 1-53GPP Releases ............................................................. ................................................................. .... 1-6

Figure 1-6HSDPA ....................................................................... ............................................................... ....... 1-7

Figure 1-7HSUPA ....................................................................... ............................................................... ....... 1-8

Figure 1-8HSPA+ (Release 7) ................................................................ ........................................................... 1-9

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

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

Figure 1-11Radio Interface Techniques ............................................................. .............................................. 1-10

Figure 1-12Frequency Division Multiple Access ............................................................................................ 1-11

Figure 1-13Time Division Multiple Access ....................................................... .............................................. 1-11

Figure 1-14Code Division Multiple Access ................................................................. ................................... 1-12

Figure 1-15Orthogonal Frequency Division Multiple Access ......................................................................... 1-12

Figure 1-16Frequency Division Duplex .......................................................................................................... 1-13

Figure 1-17Time Division Duplex ........................................................... ........................................................ 1-13

Figure 1-18GSM Deployments ................... ................................................................. ................................... 1-16

Figure 1-19Key UMTS Deployment Bands ................................................................. ................................... 1-17

Figure 1-20EARFCN Calculation ................................................ .............................................................. ..... 1-19

Figure 1-21Example Downlink EARFCN Calculation ................................................ ................................... 1-19

Figure 1-22Summary of LTE Transport Channel Processing .......................................................................... 1-20

Figure 1-23Cyclic Redundancy Check Concept ........................................................... ................................... 1-21

Figure 1-24CRC Parity Bits .............................................. ................................................................. ............. 1-21

Figure 1-25Code Block Segmentation and CRC Attachment ...................................... ................................... 1-22

Figure 1-26Example Calculation for Segmentation and Filler Bits................... .............................................. 1-22


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Figure 1-27Repetition Coding of the HI ............................................................ .............................................. 1-24

Figure 1-28Basic Rate Convolutional Coder ............................................................ ................................... 1-25

Figure 1-29Convolutional Coding Trellis .......................................................... .............................................. 1-25

Figure 1-30Example of Viterbi Decoding ................................... ............................................................... ..... 1-26

Figure 1-31Initializing Tail Biting Convolutional Coding ...................... ........................................................ 1-27

Figure 1-32LTE 1/3 Rate Tail Biting Convolutional Coding............................. .............................................. 1-27

Figure 1-33LTE Turbo Coding .......................................................................... .............................................. 1-28

Figure 1-34LTE Rate Matching .................................................................................................................. ..... 1-28

Figure 1-35Code Block Concatenation .............................................................................................. ............. 1-29

Figure 1-36Use of OFDM in LTE ................................................................................................... ................ 1-30

Figure 1-37FDM Carriers ............................................................. ................................................................. .. 1-30

Figure 1-38OFDM Subcarriers ................................................................ ........................................................ 1-31

Figure 1-39Inverse Fast Fourier Transform ....................................................... .............................................. 1-31

Figure 1-40Fast Fourier Transform ......................................................................................... ........................ 1-32

Figure 1-41OFDM Symbol Mapping ................................................................................................ .............. 1-33

Figure 1-42OFDM PAPR (Peak to Average Power Ratio) ................................................................ .............. 1-33

Figure 1-43Delay Spread .............................................................. ................................................................. .. 1-34

Figure 1-44Inter Symbol Interference ............................................................................................................. 1-34

Figure 1-45Cyclic Prefix .................................................................................................................... ............. 1-35

Figure 2-1The LTE Air Interface ............................................................. .......................................................... 2-3

Figure 2-2LTE Control Plane and User Plane ................................................... ................................................ 2-3

Figure 2-3E-UTRA Protocols ................................................................. ........................................................... 2-4

Figure 2-4NAS Signaling ............................................................. ................................................................. .... 2-4

Figure 2-5Main RRC Functions .............................................................................................. .......................... 2-7

Figure 2-6PDCP Functions ........................................................... ................................................................. .... 2-8

Figure 2-7RLC Modes and Functions ................................................................................................ ............... 2-8

Figure 2-8Medium Access Control Functions ................................................................................................... 2-9

Figure 2-9Physical Layer Functions ........................................................ ........................................................ 2-10

Figure 2-10LTE Channels ...................................... ................................................................. ........................ 2-10

Figure 2-11Location of Channels .................................................................................................... ................ 2-10

Figure 2-12BCCH and PCCH Logical Channels ................................... ......................................................... 2-11

Figure 2-13CCCH and DCCH Signaling .......................................................... .............................................. 2-11

Figure 2-14Dedicated Traffic Channel ....................................................................................................... ..... 2-12


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Figure 2-15LTE Release 8 Transport Channels ............................................................ ................................... 2-13

Figure 2-16Radio Channel .......................... ................................................................. ................................... 2-14

Figure 2-17Downlink Channel Mapping ........................................................... .............................................. 2-14

Figure 2-18Uplink Channel Mapping................................ ................................................................ .............. 2-15

Figure 2-19LTE Frame Structure ................ ................................................................. ................................... 2-16

Figure 2-20Normal and Extended Cyclic Prefix .................................... ......................................................... 2-16

Figure 2-21Normal CP Configuration ............................................................................................................. 2-17

Figure 2-22Type 2 TDD Radio Frame ................................................................ ............................................. 2-18

Figure 2-23Downlink Physical Layer Processing ............. ................................................................. ............. 2-19

Figure 2-24Codeword, Layer and Antenna Port Mapping ................................ .............................................. 2-19

Figure 2-25Scrambling in LTE ................................................................ ........................................................ 2-20

Figure 2-26LTE Scrambling Code Generation .............................................................................................. .. 2-20

Figure 2-27BPSK, QPSK and 16QAM Modulation Mapper ..................................................................... ..... 2-21

Figure 2-2864QAM Modulation Mapper ................................................................................ ........................ 2-21

Figure 2-29LTE Precoding Options.............................................. .............................................................. ..... 2-24

Figure 2-30Example of the Downlink Signal Generation Equation ................................................................ 2-26

Figure 2-31OFDMA in LTE ......................................................................................... ................................... 2-27

Figure 2-32Physical Resource Block and Resource Element .......................................................................... 2-28

Figure 2-33Downlink Cell ID ..................... ................................................................. ................................... 2-29

Figure 2-34PSS and SSS Location for FDD...................... ................................................................. ............. 2-29

Figure 2-35PSS and SSS Location for TDD .......................................... ......................................................... 2-30

Figure 2-36SSS Scrambling ............................................................................................................... ............. 2-31

Figure 2-37Reference Signals - One Antenna Port....................................................... ................................... 2-32

Figure 2-38Reference Signal Physical Cell ID Offset ..................................................................................... 2-32

Figure 2-39Reference Signals - Two Antenna Ports (Normal CP) .................................................................. 2-32

Figure 2-40Reference Signals - Four Antenna Ports (Normal CP)............................... ................................... 2-33

Figure 2-41MBSFN Reference Signals ............................................................. .............................................. 2-34

Figure 2-42UE Specific Reference Signals ................................................................................................ ..... 2-34

Figure 2-43Broadcast Signaling .............................................................. ........................................................ 2-35

Figure 2-44MIB to PBCH Mapping (FDD and Normal CP) .............................................................. ............. 2-35

Figure 2-45CFI to PCFICH Mapping ................................................................ .............................................. 2-36

Figure 2-46FDD Downlink Control Region ................................................................. ................................... 2-37

Figure 2-47REG to CCE and PDCCH Mapping .......................................................... ................................... 2-38


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Figure 2-48PDCCH to Control Region Mapping ............................................................................... ............. 2-38

Figure 2-49CCE Allocation Levels ............. ................................................................. ................................... 2-39

Figure 2-50Common and UE-Specific Search Spaces ................................................. ................................... 2-39

Figure 2-51PHICH Mapping ........................................................ ................................................................. .. 2-40

Figure 2-52Extended PHICH Example ........................................................................ ................................... 2-41

Figure 2-53Generic PDSCH Mapping .............................. ................................................................. ............. 2-41

Figure 2-54Initial Procedures ................................................................. ......................................................... 2-47

Figure 2-55PSS and SSS for Cell Search (FDD Mode) .................................................................. ................ 2-47

Figure 2-56Physical Cell Identities ................................................................... .............................................. 2-48

Figure 2-57PSS Correlation ................................... ................................................................. ........................ 2-48

Figure 2-58SSS Correlation Example ................................................................ ............................................. 2-49

Figure 2-59PBCH and the Master Information Block ............................................................. ........................ 2-50

Figure 2-60System Information Block Type 1 ....................................... ......................................................... 2-51

Figure 2-61Example of SI Mapping ................................................................................................ ................ 2-52









Figure 2-70PLMN Selection ....................... ................................................................. ................................... 2-55

Figure 2-71LTE Cell Selection ................................................................................................ ........................ 2-57

Figure 2-72SC-FDMA Subcarrier Mapping Concept .............................................................. ........................ 2-59

Figure 2-73SC-FDMA Signal Generation ......................................................... .............................................. 2-60

Figure 2-74SC-FDMA and the eNB ................................................................................................ ................ 2-60

Figure 2-75Example of the Uplink Signal Generation Equation ..................................................................... 2-61

Figure 2-76Release 8 Uplink Physical Channels .......................................................... ................................... 2-62

Figure 2-77PRACH Preamble ................................................................ ......................................................... 2-62

Figure 2-78PRACH Guard Period ........................................................... ........................................................ 2-63

Figure 2-79PRACH FDD Formats .......................................................... ........................................................ 2-64

Figure 2-80PRACH Configuration .......................................................... ........................................................ 2-64


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Figure 2-81PRACH Configuration and Preamble Sequences Per Cell ........................................................... 2-66

Figure 2-82PUSCH Mapping ................................................................. ......................................................... 2-67

Figure 2-83Multiplexing Control Signaling ............................................................................ ........................ 2-67

Figure 2-84Mapping to Physical Resource Blocks for PUCCH ......................................................... ............. 2-68

Figure 2-85FDD Timing ............................................................... ................................................................. .. 2-69

Figure 2-86Example of TDD Configuration 2 ....... ................................................................. ........................ 2-70

Figure 2-87Uplink Reference Signals ......... ................................................................. ................................... 2-70

Figure 2-88DRS Sequence Group Selection ........................................................................... ........................ 2-71

Figure 2-89Uplink Demodulation Reference Signal (Normal CP) ................................................................ .. 2-72

Figure 2-90Uplink Demodulation Reference Signal (Extended CP) ............................................................. .. 2-72

Figure 2-91Requirement for SRS ............................................................ ........................................................ 2-73

Figure 2-92Example of SRS Frequency Hopping .............................................................................. ............. 2-73

Figure 2-93Example SRS Allocation ................................ ................................................................ .............. 2-74

Figure 2-94PUCCH Format 1a and 1b (Normal CP) ................................................... ................................... 2-76

Figure 2-95PUCCH Format 2 (Normal CP) .................................................................................................... 2-77

Figure 2-96PUCCH Format 2 (Extended CP) .................................................................................... ............. 2-77

Figure 2-97PUCCH Format 2a and 2b ACK/NACK Coding .......................................................................... 2-78

Figure 2-98Overall Random Access Procedure ............................................................ ................................... 2-78

Figure 2-99Random Access RRC Signaling Procedure .......................................................... ........................ 2-79

Figure 2-100PRACH Probing ................................ ................................................................. ........................ 2-79

Figure 2-101Allocating Preambles to Group A and Group B ............................................................. ............. 2-81

Figure 2-102Random Access Response Window ............................................................................................ 2-82

Figure 2-103MAC Random Access Response ....... ................................................................. ........................ 2-82

Figure 2-104Random Access - Assigned UL-SCH ................................................................. ........................ 2-83

Figure 2-105MAC Contention Resolution ........................ ................................................................. ............. 2-84

Figure 2-106Uplink Power Control ......................................................... ........................................................ 2-84

Figure 2-107Paging Issues .......................... ................................................................. ................................... 2-86

Figure 2-108System with DRX Reception of Paging .............................................................. ........................ 2-87

Figure 2-109ARQ Verses HARQ ........................... ................................................................. ........................ 2-88

Figure 2-110Basic Concept of SAW........................................................................................ ........................ 2-89

Figure 2-111HARQ Parallel Processes .............................................................. .............................................. 2-89

Figure 2-112HARQ Methods ............................................ ................................................................. ............. 2-89

Figure 2-113Example of Redundancy Versions and Soft Bits ............................................................ ............. 2-90


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Figure 2-114FDD HARQ Processes ........................................................ ........................................................ 2-91

Figure 2-115Downlink FDD HARQ Timing ................................................................ ................................... 2-93

Figure 2-116Uplink FDD HARQ Timing .......................................................... .............................................. 2-93

Figure 2-117SU-MIMO and MU-MIMO ........................................................................................... ............. 2-94

Figure 2-118Spatial Multiplexing MIMO .............. ................................................................. ........................ 2-95

Figure 2-119Spatial Multiplexing Interference Issues ............................................................. ........................ 2-95

Figure 2-120MIMO Space Time Coding ........................................................... .............................................. 2-96

Figure 2-121AMS Concept................................................ ................................................................. ............. 2-96

Figure 2-122PDSCH Processing ............................................................................................. ........................ 2-97

Figure 2-123Feedback Reporting ............................................................................................................... ..... 2-98

Figure 2-1244-bit CQI Table ........................................................ ................................................................. .. 2-98

Figure 3-1IP Scheduling ............................................................... .......................Error! Bookmark not defined.

Figure 3-2Basic Scheduling in a Cell ................................................................ ..Error! Bookmark not defined.

Figure 3-3Packet Classifier and Packet Scheduler ..............................................Error! Bookmark not defined.

Figure 3-4Key Factors Influencing Scheduling ...................................................Error! Bookmark not defined.

Figure 3-5Possible Scheduling Method ............................................................. ..Error! Bookmark not defined.

Figure 3-6Type 0 Resource Allocation ................................................................Error! Bookmark not defined.



Figure 3-9Using the TBS Size ................................................................ .............Error! Bookmark not defined.

Figure 3-10Scheduler Interaction ............................................................ ............Error! Bookmark not defined.

Figure 3-11Dynamic Scheduling .........................................................................Error! Bookmark not defined.

Figure 3-12Semi Persistent Scheduling ............................................................. ..Error! Bookmark not defined.

Figure 4-1Intra-LTE Mobility .............................................................................Error! Bookmark not defined.

Figure 4-2Intra-Frequency and Inter-frequency ..................................................Error! Bookmark not defined.

Figure 4-3SintrasearchParameter .............................................................................Error! Bookmark not defined.

Figure 4-4Impact to Treselection ............................................................. ............Error! Bookmark not defined.

Figure 4-5Ranking Equation ...............................................................................Error! Bookmark not defined.

Figure 4-6Intra-LTE Mobility .............................................................................Error! Bookmark not defined.

Figure 4-7LTE Handover Procedure ....................................................... ............Error! Bookmark not defined.

Figure 4-8Measurement Configuration Parameters .............................................Error! Bookmark not defined.

Figure 4-9Report Configuration Parameters .......................................................Error! Bookmark not defined.

Figure 4-10Periodic and Event Reporting ...........................................................Error! Bookmark not defined.


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Figure 4-11Non Gap Assisted ................................................................. .............Error! Bookmark not defined.

Figure 4-12Gap Assisted .....................................................................................Error! Bookmark not defined.

Figure 4-13Gap Configuration ............................................................................Error! Bookmark not defined.


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xv

Tables

Table 1-12.5G and 2.75G GSM/GPRS Systems ........................................................... ..................................... 1-3

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

Table 1-3GSM Frequency Bands ............................................................. ........................................................ 1-14

Table 1-4UMTS FDD Frequency Bands ................................................................................. ........................ 1-15

Table 1-5UMTS TDD Frequency Bands ...................................................................... ................................... 1-15

Table 1-6LTE Release 8 Frequency Bands .............................................................................. ........................ 1-18

Table 1-7Transport Channel Coding Options .................... ................................................................. ............. 1-23

Table 1-8Control Information Coding Options ............................................................. ................................... 1-23

Table 1-9CFI Encoding.................................................................................................................................... 1-24

Table 1-10Convolutional Coding Example ....................... ................................................................. ............. 1-25

Table 1-11Standard Convolutional Coding Verses Tail Biting Convolutional Coding .................................... 1-27

Table 1-12LTE Sub-block Interleaver ................................................................ .............................................. 1-29

Table 1-13LTE Channel and FFT Sizes .............................................................................................. ............. 1-32

Table 2-1NAS EMM and ESM Procedures ....................................................... ................................................ 2-5

Table 2-2Downlink CP Parameters .......................................................... ........................................................ 2-17

Table 2-3Type 2 Radio Frame Switching Points........................... ................................................................. .. 2-18

Table 2-4Layer Mapper Configuration ............................................................................................................ 2-22

Table 2-5Codeword to Layer Mapping for Spatial Multiplexing ...................... .............................................. 2-22

Table 2-6Codeword to Layer Mapping for Transmit Diversity .......................................................... ............. 2-23

Table 2-7Codebook for Transmission for Two Antenna Ports ......................................................................... 2-25

Table 2-8Downlink PRB Parameters ................................................................................................ ............... 2-28

Table 2-9Example of SSS Indices .......................... ................................................................. ........................ 2-30

Table 2-10CFI Mapping ...................... .............................................................. .............................................. 2-36

Table 2-11CFI Codewords ............................................................ ................................................................. .. 2-37

Table 2-12DCI Formats ..................................................... ................................................................. ............. 2-42

Table 2-13DCI Ambiguous Sizes of Information Bits ..................................................................................... 2-43


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Table 2-14Precoding Information Field for 4 Antenna Ports (Open Loop) .................. ................................... 2-46

Table 2-15Cell Selection Parameters .......................................................................................................... ..... 2-57

Table 2-16SC-FDMA verses OFDMA .............................. ................................................................. ............. 2-61

Table 2-17Random Access Preamble Parameters .......................................................................................... .. 2-63

Table 2-18PRACH Configuration Index ........................... ................................................................. ............. 2-65

Table 2-19K Values for TDD Configurations............................................................ ................................... 2-69

Table 2-20PUCCH Formats .......................................................... ................................................................. .. 2-75

Table 2-21Parameters for Random Access ...................................................................................................... 2-80

Table 2-22FDD Subframe Patterns .......................................................... ........................................................ 2-87

Table 2-23TDD Subframe Patterns .......................................................... ........................................................ 2-88

Table 2-24TDD HARQ Processes ........................................................................................... ........................ 2-91

Table 2-25UL HARQ Operation .............................................................. ........................................................ 2-92

Table 2-26Codebook Precoding......................................... .............................................................. ................ 2-97

Table 3-1Modulation and TBS index table for PDSCH.......................................Error! Bookmark not defined.


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1-1

1 The Air InterfaceObjectives

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 8.

1.3 Describe radio interface techniques.

1.4 Explain the difference between FDD and TDD mode.

1.5 Describe flexible spectrum usage.

1.6 Explain the concepts of channel coding and FEC (Forward Error Correction).

1.7 Describe the principles for OFDM.


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1.1 Evolution of Cellular Networks

Cellular mobile networks have been evolving for many years. The initial networks arereferred to as First Generation. These have now been replaced with Second Generation

and Third Generation networks.It is only now that 4G or Fourth Generationsystems arebeing deployed.

Figure 1-1Evolution 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. It was mainly implemented in the Americas, Russia and Asia. Various issuesincluding weak security features made the system prone to hacking and handset cloning.

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

AMPS with slight modifications, as well as operating in 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 moreusers.

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, these include:

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

technologies. It was initially developed by ETSI (European TelecommunicationsStandards Institute) for Europe and designed to operate in the 900MHz and 1800MHz

frequency bands. It now has world-wide support and is available for deployment onmany other frequency bands, such as 850MHz and 1900MHz. A mobile described astri-band or quad-band indicates support for multiple frequency bands on the same device.

GSM is TDMA, such that it employs 8 timeslots on a 200kHz radio carrier.

cdmaOne - this is a CDMA (Code Division Multiple Access) system based on IS-95(Interim Standard 95). It uses a spread spectrum technique and utilizes a mixture of

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


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D-AMPS (Digital - Advanced Mobile Phone System) - this is based on IS-136 (InterimStandard 136) and is effectively an enhancement to AMPS which provides a TDMA

access technique. It has been primarily used on the North American continent, as well as

in New Zealand and parts of Asia-Pacific.

Figure 1-2

Second Generation Mobile Systems

2G (Second

Generation)

GSM

cdmaOne

(IS-95)

D-AMPS

(IS-136)

Other

In addition to being digital, as well as improving capacity and security, these 2G digital

systems also offer enhanced services such as SMS (Short Message Service) and circuitswitched data.

2.5G Systems

Most 2G systems are being evolved. For example, GSM was extended with GPRS (GeneralPacket Radio System) to support efficient packet data services, as well as increasing the data

rates.

As this feature does not meet 3G requirements, GRPS is often referred to as 2.5G. Acomparison between 2G and 2.5G systems is illustrated inTable 1-1.

2.75G Systems

GSM/GPRS systems also added EDGE (Enhanced Data Rates for Global Evolution). Thisnearly quadruples the throughput of GPRS. The theoretical data rate of 473.6kbit/s enables

service providers to efficiently offer multimedia services. Like GPRS, since it does notcomply with all the features of a 3G system, EDGE is usually categorized as 2.75G.

Table 1-12.5G and 2.75G GSM/GPRS Systems

System Service Theoretical DataRate

Typical Data Rate

2G GSM Circuit Switched

Data Service

9.6kbit/s or

14.4kbit/s

9.6kbit/s or

14.4kbit/s


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2.5G GPRS Packet Switched

Data171.2kbit/s 4kbit/s to 50kbit/s

2.75G EDGE Packet Switched

Data473.6kbit/s 120kbit/s

1.1.3 Third Generation Mobile Systems

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

Telecommunications - 2000). IMT2000 defines that a 3G system should provide highertransmission rates, for example: 2Mbit/s for stationary or nomadic use and 348kbit/s in amoving vehicle.

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

WCDMA (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. WCDMA is the main evolutionary path from GSM/GPRSnetworks. It is a FDD (Frequency Division Duplex) based system and occupies a 5MHz

carrier. Current deployments are mainly at 2.1GHz, however deployments at lowerfrequencies are also being seen, e.g. UMTS1900, UMTS850, UMTS900 etc. WCDMAsupports voice and multimedia services with an initial theoretical rate of 2Mbit/s, with

most service providers initially offering 384kbit/s per user. However, this technology iscontinuing 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 (TimeDivision Duplex) and is part of the UMTS specifications, however it has only limitedsupport. 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 bySiemens 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 scenariosin 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.

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 originallydefined PTP (Point-To-Point) and PTM (Point-To-Multipoint) systems. This was laterenhanced to provide mobility and greater flexibility. The success of WiMAX is mainly

down to the WiMAX Forum, which is an organization formed to promote conformity

and interoperability between vendors.


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Figure 1-3Third Generation Mobile Systems

UMTS

WCDMA

TD-SCDMA

CDMA2000

WiMAX

UMTS

TD-CDMA

3G (Third

Generation)

1.1.4 Fourth Generation Mobile Systems4G (Fourth Generation) cellular wireless systems need to meet the requirements set by the

ITU (International Telecommunication Union) as part of IMT Advanced (International MobileTelecommunications Advanced). These features are illustrated inTable 1-2 and enable IMT

Advanced to address evolving user needs.

Table 1-2IMT Advanced Features

Key IMT Advanced Features

A high degree of commonality of 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 main three 4G systems include:

LTE Advanced - LTE (Long Term Evolution) is part of 3GPP, however it does not meetall 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 has been designed specifically to meet 4G

requirements.

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


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Figure 1-4Forth Generation Mobile System

LTEAdvanced

UMB(EV-DO Rev C)

WiMAX

802.16m

4G (Fourth

Generation)

1.2 3GPP ReleasesThe 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 enhance the radiointerface.

Figure 1-53GPP 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, 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).



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1.2.2 Release 99

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

UMTS contains all features needed to meet the IMT-2000 requirements as defined by theITU. It is able to support both CS (Circuit Switched) voice and video services, as well PS

(Packet Switched) data services over common and dedicated bearers. Initial data rates forUMTS were 64kbit/s, 128kbit/s and 384kbit/s. Note that the theoretical maximum was2Mbit/s.

1.2.3 Release 4

Release 4 included enhancements to the core network. The concept of All IP Networkswasincluded and service providers were able to deploy Soft Switch based networks, i.e. the MSC

(Mobile Switching Centre) was replaced by MSC Servers and MGW (Media Gateways).

1.2.4 Release 5Release 5 is the first major addition to the UMTS air interface. It adds HSDPA (High Speed

Downlink Packet Access) which improves capacity and spectral efficiency.Figure 1-6illustrates some of the main features which include:

Adaptive Modulation - In addition to the original UMTS modulation scheme, 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 (ChannelQuality 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), whichenables 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 throughto the UE (User Equipment) successfully, the system employs HARQ (Hybrid Automatic

Repeat Request). This improves the retransmission timing, thus requiring less reliance onthe RNC (Radio Network Controller).

Figure 1-6HSDPA

HSDPA

Adaptive Modulation

Flexible CodingFast 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 mostinterest 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


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

HSUPA, like HSDPA adds functionality to improve packet data. Figure 1-7 illustrates thethree main enhancements which include:

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

HARQ - Like HSDPA, HSUPA also utilizes HARQ. The main difference is the timingrelationship for the retransmission.

Figure 1-7HSUPA

HSUPA

Flexible CodingFast Power Scheduling

HARQ

UE

UTRAN

RNCNode B

Iub

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 1-8illustrates the main features which include:

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

theoretical rate of 21.6Mbit/s.

16 QAM - This is added to the UL (Uplink) and enables the uplink to theoreticallyachieve 11.76Mbit/s.

MIMO (Multiple Input Multiple Output) Operation - this is added to HSPA+ Release 7and offers various benefits including the ability to offer a theoretical 28.8Mbits/s in the

downlink.

Power Enhancements -Various enhancements such as CPC (Continuous Packet

Connectivity) have been included. Thus enabling DTX (Discontinuous Transmission),

DRX (Discontinuous Reception) and HS-SCCH (High Speed - Shared Control Channel)Less Operation. Collectively these improve the mobiles battery consumption.

Less Overhead - The downlink includes an enhancement to the MAC (Medium AccessControl) layer which effectively means that fewer headers are required. This in turnimproves the system efficiency.


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Figure 1-8HSPA+ (Release 7)

HSPA+

64 QAM (DL)

16 QAM (UL)MIMO Operation (DL)

Power Enhancements (DL)

Less Overhead (DL)

UE

UTRAN

RNCNode B

Iub

1.2.7 Release 8

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

HSPA+. However the main aspect is the inclusion of LTE (Long Term Evolution). Figure 1-9illustrates 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, thusquoting 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 utilizetwo 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 combineMIMO and DC-HSDPA.

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

uplink has been enhanced to reduce overhead.

Figure 1-9Release 8 HSPA+ and LTE

HSPA+

64 QAM + MIMO (DL)

Dual Cell Operation

Less Overhead (UL)

UE

UTRAN

RNCNode B

Iub

eNB

E-UTRAN

LTEEnhanced 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.


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1.2.8 Release 9 and Beyond

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

number of features in Release 9. One of the most important is the support of additionalfrequency bands.

Figure 1-10Release 9 and Beyond

LTE

Release 8

LTE

Release 9

LTE Advanced

Release 10

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

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

1.3 Radio Interface Techniques

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

are various categories of assignment, the main four include: FDMA (Frequency DivisionMultiple Access), TDMA (Time Division Multiple Access), CDMA (Code Division Multiple

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

Figure 1-11Radio Interface Techniques

FDMA

TDMA CDMA

OFDMA

Radio Interface

Techniques

1.3.1 Frequency Division Multiple Access

In order to accommodate various devices on the same wireless network, FDMA divides theavailable spectrum into sub-bands or channels. The concept of FDMA is illustrated inFigure

1-12.Using this technique a dedicated channel can be allocated to a user, whilst other usersoccupy other channels, i.e. frequencies.

In a cellular system mobiles typically occupy multiple channels; one for the downlink and onefor the uplink. This does however make FDMA less efficient since most data applications are

downlink intensive.


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Figure 1-12Frequency Division Multiple Access

Frequency

Power Time

FDMA

Each user allocated a

different subband/

channel.

FDMA channels also suffer since they cannot be close together due to the energy from onetransmission affecting the adjacent/neighboring channels. To combat this, additional guard

bands between channels are required, which also reduces the systems spectral efficiency.

1.3.2 Time Division Multiple AccessIn TDMA systems the channel bandwidth is shared in the time domain.Figure 1-13 illustratesthe concept of TDMA. It shows how each device is allocated a time on the channel, known as

a timeslot.These are then grouped into a TDMA frame. The number of timeslots in aTDMA frame is dependent on the system, for example GSM utilizes 8 timeslots.

Figure 1-13

Time Division Multiple Access

Frequency

PowerTime

TDMA

Each user allocated adifferent 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 normally digital and therefore offer additional features such as ciphering

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

including FEC (Forward Error Correction). This enables the system to be more resilient tonoise and interference and therefore they have a greater spectral efficiency when compared toFDMA systems.

1.3.3 Code Division Multiple Access

The concept of CDMA is slightly different to that of FDMA and TDMA. Instead of sharingresources in the time or frequency domain, the devices are able to use the system at the same

time and using the same frequency/bandwidth. This is possible due to the fact that each

transmission is separated using a unique code.

There are two ma

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