OEA000101 LTE Air Interface ISSUE 1.00.pdf

LTE Air Interface

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

Contents

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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 .................................................................................................................................................... 2-8

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

2.3 LTE Channel Structure .................................................................................................................................. 2-9

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

2.3.2 Transport Channels ............................................................................................................................ 2-11

2.3.3 Physical Channels .............................................................................................................................. 2-12

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

2.3.5 Channel Mapping ............................................................................................................................... 2-13

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 ................................................................................................. 3-1

3.1 Scheduling Principles and Signaling ............................................................................................................. 3-2

3.1.1 QoS in Packet Switched Networks ...................................................................................................... 3-3

3.1.2 Key Factors Influencing Scheduling .................................................................................................... 3-4

3.1.3 Scheduling Methods ............................................................................................................................. 3-4

3.1.4 Downlink Scheduling ........................................................................................................................... 3-5

3.1.5 PDSCH Resource Allocation ............................................................................................................... 3-6

3.1.6 Modulation and Coding Scheme .......................................................................................................... 3-7

3.1.7 Uplink Scheduling ............................................................................................................................... 3-9

3.2 Scheduler Interaction..................................................................................................................................... 3-9

3.2.1 Radio Bearers ....................................................................................................................................... 3-9

3.2.2 Scheduler Interaction with Layer 2 and Layer 1 .................................................................................. 3-9

3.3 Dynamic and Semi-persistent Scheduling ................................................................................................... 3-10

3.3.1 Dynamic Scheduling .......................................................................................................................... 3-11

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3.3.2 Downlink Semi-persistent Scheduling ............................................................................................... 3-11

3.3.3 Uplink Semi-persistent Scheduling .................................................................................................... 3-12

4 Intra LTE Mobility ..................................................................................................................... 4-1

4.1 Intra-LTE Mobility ........................................................................................................................................ 4-2

4.1.1 Idle State - Cell Reselection ................................................................................................................. 4-2

4.1.2 Active State Mobility ........................................................................................................................... 4-4

4.1.3 Handover Procedure ............................................................................................................................. 4-5

4.2 Reporting Options ......................................................................................................................................... 4-6

4.2.1 Measurement Configuration Parameter ............................................................................................... 4-6

4.2.2 Report Configuration Parameter .......................................................................................................... 4-7

4.3 Mobility Measurements ................................................................................................................................. 4-8

4.3.1 Measurement Gaps ............................................................................................................................... 4-8

4.3.2 Gap Configuration ............................................................................................................................... 4-9

4.3.3 UE Measurements ................................................................................................................................ 4-9

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

Contents

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Training Manual

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Issue 01 (2010-05-01)

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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 .................................................................................................... 1-5

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Figure 2-6 PDCP Functions ................................................................................................................................ 2-7

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

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

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

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

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

Figure 2-12 BCCH and PCCH Logical Channels ............................................................................................ 2-10

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

Figure 2-14 Dedicated Traffic Channel ............................................................................................................ 2-11

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Figure 2-15 LTE Release 8 Transport Channels ............................................................................................... 2-12

Figure 2-16 Radio Channel .............................................................................................................................. 2-13

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

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

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

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

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

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

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

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

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

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

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

Figure 2-28 64QAM Modulation Mapper ........................................................................................................ 2-21

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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









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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Figure 2-124 4-bit CQI Table ........................................................................................................................... 2-98

Figure 3-1 IP Scheduling .................................................................................................................................... 3-2

Figure 3-2 Basic Scheduling in a Cell ................................................................................................................ 3-2

Figure 3-3 Packet Classifier and Packet Scheduler ............................................................................................ 3-3

Figure 3-4 Key Factors Influencing Scheduling ................................................................................................. 3-4

Figure 3-5 Possible Scheduling Method ............................................................................................................. 3-4

Figure 3-6 Type 0 Resource Allocation .............................................................................................................. 3-6



Figure 3-9 Using the TBS Size ........................................................................................................................... 3-8

Figure 3-10 Scheduler Interaction .................................................................................................................... 3-10

Figure 3-11 Dynamic Scheduling ..................................................................................................................... 3-11

Figure 3-12 Semi Persistent Scheduling ........................................................................................................... 3-12

Figure 4-1 Intra-LTE Mobility ........................................................................................................................... 4-2

Figure 4-2 Intra-Frequency and Inter-frequency ................................................................................................ 4-2

Figure 4-3 Sintrasearch Parameter ........................................................................................................................... 4-3

Figure 4-4 Impact to Treselection ....................................................................................................................... 4-4

Figure 4-5 Ranking Equation ............................................................................................................................. 4-4

Figure 4-6 Intra-LTE Mobility ........................................................................................................................... 4-5

Figure 4-7 LTE Handover Procedure ................................................................................................................. 4-5

Figure 4-8 Measurement Configuration Parameters ........................................................................................... 4-6

Figure 4-9 Report Configuration Parameters ..................................................................................................... 4-7

Figure 4-10 Periodic and Event Reporting ......................................................................................................... 4-8

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Figure 4-11 Non Gap Assisted ............................................................................................................................ 4-8

Figure 4-12 Gap Assisted ................................................................................................................................... 4-9

Figure 4-13 Gap Configuration .......................................................................................................................... 4-9

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Tables

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Tables

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

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

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

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

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

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

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

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

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

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

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

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

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

Table 3-1 Modulation and TBS index table for PDSCH ..................................................................................... 3-7

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Training Manual 1 The Air Interface



1-1

1 The Air Interface 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 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 are

referred to as First Generation. These have now been replaced with Second Generation and Third Generation networks. It is only now that 4G or Fourth Generation systems are 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. It 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 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 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, these include:

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 in 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 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 (Interim

Standard 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 circuit

switched data.

2.5G Systems

Most 2G systems are being 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, GRPS is often referred to as 2.5G. A

comparison between 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 GPRS, since it does not

comply with all the features of a 3G system, EDGE is usually categorized as 2.75G.

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

System Service Theoretical Data Rate

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

Data

171.2kbit/s 4kbit/s to 50kbit/s

2.75G EDGE Packet Switched

Data

473.6kbit/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 higher

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:

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/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, UMTS850, UMTS900 etc. WCDMA

supports 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 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.

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, which is an organization formed to promote conformity and interoperability between vendors.

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Figure 1-3 Third Generation Mobile Systems

UMTS

WCDMA

TD-SCDMA

CDMA2000

WiMAX

UMTS

TD-CDMA

3G (Third

Generation)

1.1.4 Fourth Generation Mobile Systems

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

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

Telecommunications Advanced). These features are illustrated in Table 1-2 and enable IMT

Advanced to address evolving user needs.

Table 1-2 IMT 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 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 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.

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Figure 1-4 Forth Generation Mobile System

LTE

Advanced

UMB

(EV-DO Rev C)

WiMAX

802.16m

4G (Fourth

Generation)

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 enhance 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, 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 the ITU.

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 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. The concept of All IP Networks was included 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 5

Release 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 1-6

illustrates 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 (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 (Hybrid Automatic

Repeat Request). This improves the retransmission timing, thus requiring less reliance on

the RNC (Radio Network Controller).

Figure 1-6 HSDPA

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

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

used.

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.

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

relationship for the retransmission.

Figure 1-7 HSUPA

HSUPA

Flexible Coding

Fast 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 1-8

illustrates 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 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.

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 Access

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

improves the system efficiency.

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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

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 1-9

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 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.

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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 additional

frequency bands.

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 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 Division

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

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

Figure 1-11 Radio 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 the

available spectrum into sub-bands or channels. The concept of FDMA is illustrated in Figure

1-12. 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 multiple channels; one for the downlink and one

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

downlink intensive.

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Figure 1-12 Frequency 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 one

transmission 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 Access

In TDMA systems the channel bandwidth is shared in the time domain. Figure 1-13 illustrates

the 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 a TDMA 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 a

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 normally digital and therefore offer additional features such as ciphering

and integrity. In a

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