Inacon LTE from a z

UMTS Universal Mobile Telecommunication System IP Internet Protocol RFC 791 WCDMA Wide-band Code Division Multiple Access OFDMA Orthogonal Frequency Division Multiple Access Principles a

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LTE from A-Z

Technology and Concepts of

-the 4G 3GPP Standard

INACON GmbH Kriegsstrasse 154

76133 Karlsruhe

Germany www.inacon.com e-mail: inacon@inacon.de

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Cover design by Stefan Kohler

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Foreword of the Publisher:

Dear Reader:

Note that this book is primarily a training document because the primary business of INACON GmbH is the training and consulting market for mobile communications As such, we are proud to providing high-end training courses to many clients worldwide, among them operators like Cingular, Mobilkom Austria, SWISSCOM, T-MOBILE or VSNL (India) and equipment suppliers like ALCATEL-LUCENT, ERICSSON and SONY-ERICSSON, MOTOROLA, NOKIA-SIEMENS and RIM

INACON GmbH is not one of the old-fashioned publishers With respect to market, form-factor, homogenous quality over all books and most importantly with respect to after-sales support, INACON GmbH is moving into a new direction Therefore, INACON GmbH does not leave you alone with your issues and this book but we offer you to contact the author directly through e-mail (inacon@inacon.de), if you have any questions All our authors are employees of INACON GmbH and all of them are proven experts in their area with usually many years of practical experience

time-to-The most important assets and features of the book in front of you are:

• Extensive and detailed index to allow instant access to information about virtually every parameter, timer and detail of this technology.

• If applicable, incorporation of examples from our practical field experiences and real life recordings.

virtually every page.

Finally, we again like to congratulate you to the purchase of this book and we like to wish you success in using it during your daily work

Sincerely,

Gunnar Heine / President & CEO of INACON GmbH

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Table of Content

Principles and Motivation of LTE 1

1.1 Mobile Radio: Comparison between 3G and 4G 2

1.1.1 Performance and Mobility Management related Issues 2

1.1.2 Architecture related Issues 4

1.1.3 Procedure and Radio related Issues 6

1.2 Requirements on LTE 8

1.2.1 General Requirements 8

1.2.1.1 Support of Enhanced Quadruple Play Services 10

1.2.1.2 Very High Data Rates @ flexible bandwidth deployment ((1.25) 5 – 20 MHz) 10

1.2.1.3 AIPN and PS services only 10

1.2.2 Important Characteristics of LTE Physical Layer 12

1.2.2.1 General Physical Layer Characteristics 12

1.2.2.1.1 OFDM 12

1.2.2.1.2 Scalable Bandwidth 13

1.2.2.1.3 Smart Antenna Technology 14

1.2.2.1.4 Fast scheduling and AMC 14

1.2.2.1.5 No Soft(er) handover 14

1.2.3.2 OFDM/OFDMA 16

1.2.3.2.1 Traditional narrowband communication 16

1.2.3.2.2 Problems for wideband signals 17

1.2.3.2.3 OFDM 17

1.2.3.2.4 OFDM and OFDMA 17

1.2.3.2.5 LTE and OFDM 17

1.2.3.3 Smart Antenna Technology in LTE 18

1.2.3.3.1 Categorization of Smart Antenna Technologies 18

1.2.3.3.1.1 SISO 18

1.2.3.3.1.2 SIMO 18

1.2.3.3.1.3 MISO 19

1.2.3.3.1.4 MIMO 19

1.2.3.3.2 Multiple Input Multiple Output (MIMO) 20

1.2.3.3.2.1 Multiple carrier technology 21

1.2.3.3.2.2 MIMO 21

1.2.3.3.3 Adaptive Antenna Systems (AAS) 22

1.2.3.3.3.1 Signal generation 23

1.2.3.3.3.2 Constructive superimposition at the intended receiver 23 1.2.3.3.3.3 Destructive superimposition at the not intended receiver .23

1.2.3.3.3.4 Generation of signals for multiple UE’s 23

1.2.3.4 Macro Diversity exploitation by SFN 24

1.2.3.4.1 Requirements for MBMS services 24

1.2.3.4.2 MBMS operation with a SFN 24

1.2.3.4.3 SFN for point to point services 25

1.2.3.5 The Frequency Bands Intended for LTE 26

1.2.3.5.1 Exclusive usage 27

1.2.3.5.2 Refarming 27

1.2.3.5.3 Licensed operation 27

1.2.3.5.4 Unlicensed operation 27

1.2.3.6 Flexible Bandwidths, Parameters 28

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-1.2.3.6.1 Fixed subcarrier separation 28

1.2.3.6.2 Usage of carriers in the middle of the bandwidth for PBCH and synchronization signals 29

1.2.3.6.3 Deployment Scenarios 30

1.2.4 Important Characteristics of the LTE Layer 2 and 3 32

1.2.4.1 Support of the new LTE L1 32

1.2.4.2 Simple IP centric protocols supporting AIPN 32

1.2.4.3 Support of various inter RAT handovers (GSM, UTRA, etc.) 33

1.3 LTE and System Architecture Evolution (SAE) 34

1.3.1 Overview 34

1.3.1.1 Missing RNC 34

1.3.1.2 Interconnected eNB’s 35

1.3.1.3 Separate entities for user plane and control plane in the EPC 36

1.3.1.4 Combined Serving Gateway and MME 36

1.3.1.5 Combined Serving and PDN Gateways 36

1.3.1.6 S1-flex 36

1.3.1.7 Used legacy elements 36

1.3.1.8 Roaming case 36

1.3.1.9 Direct Tunnel 36

1.3.1.10 EPS, EPC, E-UTRAN & LTE, SAE 36

1.3.2 The eNB 38

1.3.2.1 Selection of MME at attachment 39

1.3.2.2 Scheduling of paging messages 39

1.3.2.3 Routing of user plane data to Serving GW 40

1.3.2.4 PDCP 40

1.3.2.5 RRM/RRC 40

1.3.2.6 RLC 40

1.3.2.7 MAC 40

1.3.2.8 Complete L1 functionality 40

1.3.3 The MME 42

1.3.3.1 NAS signalling 42

1.3.3.2 Inter CN node signaling (3GPP networks) 42

1.3.3.3 Security management 42

1.3.4 The Serving GW 44

1.3.4.1 Termination of U-plane packets for paging reasons 44

1.3.4.2 Support of UE mobility anchoring by switching U-plane during inter eNB handover 44

1.3.4.3 Transport Packet Marking According to QCI 45

1.3.4.4 Mobility anchoring for inter-3GPP mobility 45

1.3.4.5 Packet routing and forwarding 45

1.3.4.6 Charging support 45

1.3.4.7 Lawful interception 45

1.3.5 The PDN GW 46

1.3.5.1 Termination towards of PDN’s 46

1.3.5.2 Policy enforcement 46

1.3.5.3 Charging support 46

1.3.5.4 DHCPv4 and DHCPv6 functions 47

1.3.6 Identifiers of the UE and the Network Elements 48

1.3.6.1 PLMN ID 50

1.3.6.2 EPS Bearer ID 50

1.3.6.3 MMEI 50

1.3.6.4 GUMMEI 50

1.3.6.5 Physical Cell ID 50

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-1.3.6.6 eNB/cell ID 50

1.3.6.7 TAI 50

1.3.6.8 C-RNTI 50

1.3.6.9 RA-RNTI 50

1.3.6.10 SI-RNTI 50

1.3.6.11 P-RNTI 50

1.3.6.12 Random Value 50

1.3.6.13 IMSI, S-TMSI, and IMEI 52

1.3.6.14 GUTI 52

1.3.6.15 eNB S1-AP UE ID and MME S1-AP UE ID 52

1.4 The E-UTRAN Protocol Stack 54

1.4.1 Control Plane Protocol Stack 54

1.4.1.1 Air Interface protocols 55

1.4.1.2 NAS protocols 56

1.4.2 User Plane Protocol Stack 58

1.4.2.1 Air Interface protocols 58

1.4.2.2 S1 protocol 58

1.4.3 X2 Interface Control Plane Protocol Stack 60

1.4.4 X2 User Plane Protocol Stack 62

1.5 Overview Channels of E-UTRAN 64

1.5.1 Channel Types 64

1.5.1.1 Logical Channels 64

1.5.1.2 Transport Channels 64

1.5.1.3 Physical Channels 65

1.5.2 Logical Channels of E-UTRAN 66

1.5.2.1 BCCH 66

1.5.2.2 PCCH 66

1.5.2.3 CCCH 66

1.5.2.4 MCCH 66

1.5.2.5 DCCH 67

1.5.2.6 DTCH 67

1.5.2.7 MTCH 67

1.5.3 Transport Channels of E-UTRAN 68

1.5.3.1 RACH 68

1.5.3.2 UL-SCH 68

1.5.3.3 BCH 68

1.5.3.4 PCH 68

1.5.3.5 MCH 69

1.5.3.6 DL-SCH 69

1.5.4 Physical Channels of E-UTRAN 70

1.5.4.1 PBCH 70

1.5.4.2 PDCCH 70

1.5.4.3 PCFICH 71

1.5.4.4 PUCCH 71

1.5.4.5 PRACH 71

1.5.4.6 PHICH 72

1.5.4.7 PDSCH 72

1.5.4.8 PMCH 72

1.5.4.9 PUSCH 72

1.5.4.10 Downlink reference signal 72

1.5.4.11 Primary and secondary synchronization signal 72

1.5.4.12 Uplink reference signal or UL pilot symbol 72

1.5.4.13 Uplink sounding signal 72

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-1.5.4.14 Random Access Preamble 72

1.5.5 Mapping of Channels in E-UTRAN 74

1.6 Key Development Trends manifested in LTE 76

1.6.1 Mapping of User Plane Packets to the Resources 76

1.6.1.1 Method 1: Fast resource allocation on optimum resources 77

1.6.1.2 Method 2: Slow resource allocation on suboptimum resources 78

1.6.1.3 GSM 78

1.6.1.4 WCDMA 78

1.6.1.5 HSPA 78

1.6.1.6 LTE 78

1.6.1.7 General trend 78

1.6.2 All IP Network and Simple Packet Service Driven Protocols 80

1.6.2.1 Reduced User Plane Latency 82

1.6.2.1 Reduced Control Plane Latency 84

1.7 LTE Key Feature Summary 86

1.7.1 Air Interface Technology 86

1.7.2 System Architecture 87

1.7.3 Service Aspects 87

Key Technologies of the LTE Physical Layer 89

2.1 Introduction OFDM Technology 90

2.1.1 Impact of Orthogonality in the Frequency Domain – 3 Steps 90

2.1.2 Practical Exercise: Physical Basics of OFDM / OFDMA 96

2.1.3 Practical Exercise: Scaling of OFDM / OFDMA-Systems 98

2.1.4 The In-Phase – Quadrature (I/Q) Presentation 100

2.1.5 OFDM / OFDMA and IFFT 102

2.1.5.1 Considering the Discrete Oscillator Array Option 103

2.1.5.2 Details of the IFFT Option 103

2.1.5.3 Why is it called F a s t Fourier Transformation? 103

2.1.6 Modulation Scheme Overview 104

2.1.8 Tackling Inter-Symbol Interference (ISI) 108

2.1.8.1 Introduction 108

2.1.8.1.1 Delay Spread 108

2.1.8.2 Cyclic Prefix 110

2.1.8.2.1 Variable Duration and other Assets of the Cyclic Prefix 111

2.1.8.2.2 Cyclic Prefix in OFDMA in LTE 111

2.1.9 Layout of a Typical OFDM System 112

2.1.9.1 Remarks on the Brick Wall Image 113

2.1.9.2 Subchannelization 113

2.1.9.3 Pilot Subcarriers 113

2.1.9.4 Null Subcarriers 113

2.2 Introduction to MIMO Technology 114

2.2.1 The Basics: Signal Fading Physics between TX and RX 114

2.2.2 Multiplexing Dimensions 116

2.2.2 Multiplexing Dimensions 118

2.2.3 The Multipath Dimension 120

2.2.6 MIMO General Operation 122

The Physical Layer of E-UTRAN 125

3.1 The Use of OFDM/OFDMA in LTE 126

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-3.1.1 Frame Structure 126

3.1.1.1 The generic frame structure 126

3.1.1.2 The downlink slots 127

3.1.1.3 The uplink slots 127

3.1.1.4 The frame structure type 2 127

3.1.2 LTE Parameters 128

3.1.2.1 The normal configuration 128

3.1.2.2 The extended configuration with 15 kHz subcarrier separation 128

3.1.2.3 The extended configuration with 7.5 kHz subcarrier separation 129

3.1.2 Resource Element and Resource Block Definition 130

3.1.2.1 Definition Resource Element 130

3.1.2.2 Definition Resource Block 130

3.1.2.3 Definition Subframe 130

3.1.2.4 Number of resource blocks in a given bandwidth 131

3.1.3 Choice of the UL Transmission Scheme (UL Data Symbols only) 132

3.1.3.1 What would happen if OFDM would be used in the UL 133

3.1.3.2 SC-FDMA is used for the UL 133

3.1.4 FDD and TDD Operation in E-UTRAN 134

3.1.4.1 Reciprocity 134

3.1.4.1.1 Reciprocity of the mobile radio channel 134

3.1.4.1.2 Speed of scheduling decisions 135

3.1.4.2 UL / DL Asymmetry and Others 136

3.1.4.2.1 UL/DL symmetry 136

3.1.4.2.2 Interference scenarios 136

3.1.4.2.3 TRX architecture 137

3.1.4.2.4 Deployment in a given frequency band 137

3.1.4.3 Summary FDD vs TDD 138

3.2 The DL Physical Channels and their Frame Structures .140 3.2.1 Allocation of DL Physical Channels to Resource Elements 140

3.2.1.1 Not used subcarriers 142

3.2.1.2 Primary Synchronization Signal 142

3.2.1.3 Secondary Synchronization Signal 142

3.2.1.4 Pilot or Reference Signal 142

3.2.1.5 PBCH 142

3.2.1.6 PCFICH 142

3.2.1.7 PHICH 142

3.2.1.8 PDCCH 142

3.2.1.9 PDSCH (and PMCH) 142

3.2.2 System Information on PBCH and PDSCH 144

3.2.2.1 Split of the BCH on the PBCH and the PDSCH 144

3.2.3 PCFICH, PDCCH, and PHICH 146

3.2.3.1 The PCFICH 147

3.2.3.2 The PDCCH 148

3.2.3.3 The PHICH 148

3.2.4 The Downlink Processing Chain 150

3.2.4.1 Encoded transport block bits 150

3.2.4.2 Scrambling 150

3.2.4.3 Modulator 152

3.2.4.4 Layer Mapper 152

3.2.4.5 Precoding 152

3.2.4.6 OFDM signal generation 152

3.2.4.7 CP and IFFT 152

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-3.3 The UL Physical Channels and their Frame Structures .154

3.3.1 Overview UL Physical Channels (RRC_CONNECTED) 154

3.3.1.1 Scheduling Request (SR) on the PUCCH 154

3.3.1.2 Small amount of L1 information on the PUCCH 155

3.3.1.3 Big amount of L1 information on the PUSCH 155

3.3.1.4 L1 information on the PUSCH multiplexed with the TrCH data 155

3.3.1.5 Sounding reference symbols PUSCH resources 155

3.3.2 Overview PUCCH 156

3.3.3 PUCCH Mapping for ACK/NACK only and Scheduling Request 158

3.3.3.1 Usage of Zadoff-Chu sequences 158

3.3.3.2 Spreading of repeated data Zadoff-Chu symbols 160

3.3.3.3 Spreading of reference Zadoff-Chu symbols 160

3.3.3.3 PUCCH Format 1 160

3.3.3.4 PUCCH Formats 1a and 1b 160

3.3.3.5 Shortened PUCCH Formats 1a and 1b 160

3.3.3.6 Multiple access of the PUCCH 160

3.3.4 Shared usage of Resources with CAZAC Sequences 162

3.3.4.1 Zadoff-Chu sequences are CAZAC sequences 163

3.3.4.2 Separation of different UE’s with cyclic shifted Zadoff-Chu sequences 163

3.3.5.1 PUCCH Format 2 164

3.3.5.2 PUCCH Formats 2a and 2b 165

3.3.6 The Uplink Processing Chain 166

3.3.6.1 Transport block bits 166

3.3.6.2 Scrambling 166

3.3.6.3 Modulator 166

3.3.6.4 DFT pre-coder 166

3.3.6.5 Demultiplexing of signals other than data 167

3.3.6.6 Resource element mapper 167

3.3.6.7 IFFT 167

3.3.6.7 CP 167

3.4 Overview all Physical Channels 168

3.4.1 Special usage of the 6 RB around the DC carrier 169

3.4.2 Multiplexing of the PCFICH, PDCCH and the PDSCH/PMCH in the normal DL subframe 170

3.4.3 Sounding reference signal 170

3.4.4 Modulation of the physical channels 170

3.4.5 Channel coding 170

3.5 Physical Layer Procedures 172

3.5.1 Timing Advance Control 174

3.5.1.1 Principle 174

3.5.1.2 Procedure 178

3.5.1.2.1 TA while the UE is not synchronized to the eNB 178

3.5.1.2.2 TA while the UE is synchronized to the eNB 179

3.5.2 Channel Estimation DL 180

3.5.2.1 Channel Estimation Principle of LTE 180

3.5.2.1.1 The description of the mobile radio channel 180

3.5.2.1.2 Coping with a frequency selective mobile radio channel 182

3.5.2.2 Channel Estimation Downlink 184

3.5.2.2.1 Normal configuration with 4 TX antennas 184

3.5.2.2.2 Normal configuration with less than 4 TX antennas 185

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-3.5.2.2.3 Extended configuration with 15 kHz subcarrier spacing 185

3.5.2.2.4 Extended configuration with 15 kHz subcarrier spacing for MBSFN 185

3.5.2.2.5 Extended configuration with 7.5 kHz subcarrier spacing for MBSFN 185

3.5.3 Power Control Principle (PUSCH) 186

3.5.4.1 The Transmission Diversity Problem 188

3.5.4.1.1 Receive diversity 188

3.5.4.1.2 Unsuccessful transmit diversity 189

3.5.4.2 AAS in LTE 190

3.5.4.2.1 Practical Exercise: Draw the Antenna Diagram of AAS 192

3.5.4.3 CDD 194

3.5.4.3.1 Delay diversity 194

3.5.4.3.2 Cyclic delay diversity 194

3.5.4.3.3 Cyclic delay diversity and MIMO 195

3.5.4.4 SFBC 196

3.5.4.4.1 Space Frequency Block Codes 197

3.5.4.4.2 Space Time Block Codes 197

3.5.4.5 MIMO 198

3.5.4.5.1 MIMO and AAS combined = multiple rank beamforming 199

3.5.4.5.2 When MIMO fails 199

3.5.4.6 The Codebook 200

3.5.4.6.1 Optimum beamforming weights 201

3.5.4.6.2 Signaling of sub-optimum beamforming weights 201

3.5.5 Initial Cell Search 202

3.5.5.1 Primary and Secondary Synchronization Signals 202

3.5.5.2 Procedure 204

3.5.6 Random Access 206

3.5.6.1 PRACH Structure Format 0 206

3.5.6.2 Random Access Procedure 208

3.5.7 Inter Cell Interference Mitigation 210

3.5.7.1 Traditional frequency reuse in LTE 210

3.5.7.1.1 Frequency reuse bigger than 1 211

3.5.7.1.2 Frequency reuse 1 with low initial load 211

3.5.7.1.3 Frequency reuse 1 strongly increased load 211

3.5.7.1.4 Frequency reuse 1 after “the party” 211

3.5.7.2 Fractional Frequency Reuse with Intercell Interference Coordination 212

3.6 UE Classes 214

3.6.1 Overview 214

3.6.1.1 Classes 1-4 214

3.6.1.2 UE class 5 215

3.6.2 Calculation of the DL Peak Throughput for LTE UE Class 5 216

The Higher Layers of E-UTRAN 219

4.1 Overview 220

4.1.1 E-UTRAN Architecture Control Plane 220

4.1.2 E-UTRAN Architecture User Plane 222

4.2 Features of MAC 224

4.2.1 Overview 224

4.2.1.1 Data transfer logical channels ←→ transport channels 224

4.2.1.2 Radio resource allocation 224

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-4.2.2 MAC Random Access Procedure 226

4.2.2.1 Contention based random access procedure 226

4.2.2.2 Non-contention based random access procedure 227

4.2.3 Structure of MAC-PDU 228

4.2.3.1 MAC control element 229

4.2.3.2 Normal MAC SDU 229

4.2.4 MAC Control Elements 230

4.2.4.1 Contention resolution ID 231

4.2.4.2 Timing Advance 231

4.2.4.3 DRX 231

4.2.4.4 Padding 231

4.2.4.5 Short, long and truncated buffer status reports 231

4.3 Features of RLC 232

4.3.1 Overview 232

4.3.1.1 Data transfer 232

4.3.1.2 Error detection and recovery 232

4.3.1.3 Reset 233

4.3.2 Structure of RLC PDU 234

4.3.3 Structure of RLC AM with PDCP PDU Segments 236

4.4 Features of PDCP 238

4.4.1 Overview 238

4.4.1.1 RoHC 238

4.4.1.2 Numbering of PDCP PDU’s 238

4.4.1.3 In-sequence delivery of PDU’s 238

4.4.1.4 Duplicate deletion 238

4.4.1.5 Encryption 239

4.4.1.6 Integrity Protection 239

4.4.2 Structure of PDCP PDU 240

4.5 Features of RRC 242

4.5.1 Overview 242

4.5.1.1 Transmission of broadcast information 243

4.5.1.2 Establish and maintain services 243

4.5.1.3 QoS control 243

4.5.1.4 Transfer of dedicated control information 243

4.5.2 State Characteristics of RRC 244

4.5.2.1 RRC_IDLE 244

4.5.2.2 RRC_CONNECTED 244

4.6 NAS Protocol States and Transitions 246

4.6.1 EMM-DEREGISTERED & ECM-IDLE 246

4.6.2 EMM-REGISTERED & ECM-IDLE 246

4.6.3 EMM-REGISTERED & ECM-CONNECTED 247

4.7 Mobility 248

4.7.1 Mobility Management in the EMM-DEREGISTERED & ECM-IDLE State 248

4.7.2 Mobility Management in the EMM-REGISTERED & ECM-IDLE State 250

4.7.3 Mobility Management in the EMM-REGISTERED & ECM-CONNECTED State 252

4.7.4 Inter RAT Mobility Management 254

4.7.4.1 Cell Reselection (EMM-REGISTERED & ECM-IDLE) 255

4.7.4.2 Handover (EMM-REGISTERED & ECM-CONNECTED) 255

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-4.8 QoS in LTE 256

4.8.1 Bearer Architecture 256

4.8.2 QoS Parameters 258

4.8.2.1 ARP 259

4.8.2.2 Label 259

4.8.2.3 GBR 259

4.8.2.4 MBR 259

4.8.2.5 AMBR 259

4.8.3 QoS Classes Identifier 260

4.9 Security in LTE 262

Selected E-UTRAN Scenarios 265

5.1 Initial Context Setup Procedure 266

5.2 Tracking Area Update 268

5.1.1 Inter MME tracking area update 268

5.1.2 Intra MME tracking area update 269

5.3 PDP Context Establishment 270

5.4 Intra MME Handover 274

5.4.1 Practical Exercise: Intra eNB Handover 278

5.5 Inter MME Handover 280

5.6 How a TCP/IP MTU is reaching the UE / the Internet 284

5.6.1 TCP/IP layer 284

5.6.2 PDCP layer 284

5.6.3 RLC layer 284

5.6.4 MAC layer 285

5.6.5 PHY layer 285

Solutions for Practical Exercises 287

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-LTE from A-Z

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-Chapter 1:

Principles and Motivation of LTE

Objectives

Some of your questions that will be answered during this session…

of UMTS?

radio network look like?

like?

What key development trends are manifested in LTE?

Principles and Motivation of LTE

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1.1 Mobile Radio: Comparison between 3G and 4G

1.1.1 Performance and Mobility Management related Issues

The objective of this section is to list the most important performance and mobility management related differences between 3G and 4G mobile radio.

Key points of this section are:

1 4G mobile radio will be strongly focusing on the provision of IP-based bearer services This will also require IP-based mobility management mechanisms.

2 4G mobile radio services will not be able to provide IP-based real-time end-to-end services without QoS-aware IP backbone networks This is an important, yet usually unconsidered constraint.

Use only for participants of NSN LTE from A-Z Training LTE from A-Z

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Room for your Notes

• Abbreviations of this Section: 3G 3rd Generation MOBIKE IKEv2 Mobility and Multihoming Protocol (RFC 4555) 4G 4th Generation QoS Quality of Service GMM GPRS Mobility Management RAN Radio Access Network IKEv2 Internet Key Exchange protocol / version 2 (RFC 4306) RAT Radio Access Technology (e.g GERAN, UTRAN, )

IP Internet Protocol (RFC 791) SIP Session Initiation Protocol (RFC

3261)

MM Mobility Management

1

3

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1.1.2 Architecture related Issues

The objective of this section is to list the most important architecture related differences between 3G and 4G mobile radio.

1 The independence between core and access network is the basic means

to provide for FMC.

2 Many 4G handsets will be multipurpose devices that are not limited to mobile access networks To a large degree, these handsets will have at least the functionality of today’s PDA’s.

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3G 3rd Generation IP Internet Protocol (RFC 791)

4G 4th Generation PDA Personal Digital Assistant

FMC Fixed Mobile Convergence

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1.1.3 Procedure and Radio related Issues

The objective of this section is to list the most important procedure and radio related differences between 3G and 4G mobile radio.

1 The most impressive increased spectral efficiency of 4G mobile radio.

2 The transition away from an access network specific protocol architecture towards an IP-based architecture.

Spectral efficiency is not relating to the peak throughput directly but is giving average usage of the spectrum in the cells The true unit is bit/s/Hz/cell

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3G 3rd Generation SIP Session Initiation Protocol (RFC

3261)

4G 4th Generation UMTS Universal Mobile Telecommunication

System

IP Internet Protocol (RFC 791) WCDMA Wide-band Code Division Multiple

Access

OFDMA Orthogonal Frequency Division

Multiple Access

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1.2 Requirements on LTE

1.2.1 General Requirements

The objective of this section is to provide the key requirements on LTE.

Key points of this section are that LTE is designed for AIPN and for PS services only from the start and that the requirements are very similar to those of WiMAX.

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AIPN All IP Network MHz Mega Hertz (106 Hertz)

DL Downlink PS Packet Switched

E-UTRAN Evolved UMTS (Universal Mobile

LTE Long Term Evolution (of UMTS) WiMAX Worldwide Interoperability for

Microwave Access (IEEE 802.16)

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1.2.1.1 Support of Enhanced Quadruple Play Services

Quadruple play services have not only to be followed - also the (quality) enhancements being standardized in 3GPP and the other standardization bodies have to be followed, e.g conversational QoS VoIP, fast gaming, enhanced MBMS etc For the UE Mobility speeds of up to 250 km/h should be supported In a special case implementation up to 500 km/h should be possible

1.2.1.2 Very High Data Rates @ flexible bandwidth deployment ((1.25) 5 – 20 MHz)

Very high data rates are necessary in order to keep up with the fixed network developments and the other 4G mobile radio standards Flexible bandwidth is easing the deployment because not everywhere the biggest bandwidth deployment is reasonable or possible It is open whether 1.25 MHz will be implemented This is a compatibility issue with LCR LCR and 1.25 MHz apply for China

1.2.1.3 AIPN and PS services only

The AIPN will make the infrastructure deployment a lot cheaper and easier Naturally,

to use only PS services in an AIPN is the best choice However, in order to have the same high QoS standards as known from CS services, both the network architecture and the latency requirements in the PS user plane need to be changed As well an efficient operation of PS service including fast wake up of the UE in RRC_IDLE mode

is requiring low latency times in the control plane as well

[3GTR 25.912 (13.2, 13.3), 3GTR 25.814 (7.1.2.4.3), 3GTR 26.913 (5, 7.5), 3GTR 25.912 (7.1.1.4)]

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3GPP Third Generation Partnership Project

(Collaboration between different

standardization organizations (e.g

ARIB, ETSI) to define advanced

mobile communications standards,

responsible for UMTS)

MHz Mega Hertz (106 Hertz)

3GTR 3rd Generation Technical Report PS Packet Switched

4G 4th Generation QoS Quality of Service

AIPN All IP Network RRC_ID

LE RRC state

CS Circuit Switched UE User Equipment

LCR Low Chip Rate TDD VoIP Voice over IP

MBMS Multimedia Broadcast / Multicast

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1.2.2 Important Characteristics of LTE Physical Layer

1.2.2.1 General Physical Layer Characteristics

The objectives of this section are to list the key characteristics of the physical layer and to provide understanding about how they relate to the requirements on LTE.

Key point of this section is that the LTE layer 1 is dominated by flexibility in all aspects.

1.2.2.1.1 OFDM

OFDM is enabling an efficient and low complexity usage of high data rate transmission in a frequency selective channel In a broadband single carrier system AMC is the less efficient the more bandwidth is used

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1.2.2.1.2 Scalable Bandwidth

It is for further study what operating bandwidths are used for TDD below 5 MHz 1.6

and 3.2 MHz will not be used for FDD

3GTR 3rd Generation Technical Report MIMO Multiple In / Multiple Out (antenna

system)

3GTS 3rd Generation Technical

Specification OFDM Orthogonal Frequency Division Multiplexing

AAS Adaptive Antenna Systems OFDMA Orthogonal Frequency Division

Multiple Access

AMC Adaptive Modulation and Coding SC-FDMA Single Carrier Frequency Division

Multiple Access

DL Downlink TDD Time Division Duplex

E-UTRAN Evolved UMTS (Universal Mobile

Telecommunication System)

Terrestrial Radio Access Network

UE User Equipment

FDD Frequency Division Duplex UL Uplink

LTE Long Term Evolution (of UMTS) UTRAN UMTS (Universal Mobile

Telecommunication System) Terrestrial Radio Access Network

Service eNB Enhanced Node B

MHz Mega Hertz (106 Hertz)

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13

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1.2.2.1.3 Smart Antenna Technology

Especially MIMO Technologies and SDMA (beam forming) technology have to be mentioned here These technologies are allowing reuse of the transmission capacity

of the given radio channel several times and are the preconditions for very high data rates

[3GTR 25.912 (5.3.3, 5.3.4)]

1.2.2.1.4 Fast scheduling and AMC

As known from HSPA, LTE will also perform fast scheduling and HARQ The difference with respect to HSPA will be that these processes run much faster LTE offers a HARQ RTT of only 5 ms AMC will be used for both UL and DL with more variants of modulation schemes than HSPA In contrast to HSPA a shared channel is used in the UL

[3GTR 25.912 (7.1.2)]

1.2.2.1.5 No Soft(er) handover

Since there will be no RNC’s, currently no soft handover will be used for LTE Instead

of the soft handover the eNB’s coordinate their interference amongst each other In order to reach the same benefits as the missing soft handover this interference coordination will be utilized in a self organizing network such that the interference amongst the eNB’s is kept at a minimum

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3GTR 3rd Generation Technical Report MIMO Multiple In / Multiple Out (antenna

system)

AMC Adaptive Modulation and Coding RNC Radio Network Controller

DL Downlink RTT Round Trip Time

HARQ Hybrid ARQ SDMA Space Division Multiple Access

HSPA High Speed Packet Access (operation

of HSDPA and HSUPA) UL Uplink

LTE Long Term Evolution (of UMTS) eNB Enhanced Node B

1

15

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1.2.3.2 OFDM/OFDMA

The objective of this section is to show how OFDM technology is combining the benefits of narrowband systems with the benefits of wideband systems

by means of orthogonal frequency multiplexing technology.

Key point of this section is that OFDM is combining the advantages of narrowband systems – simple receiver – with the advantage of wideband systems – high

1.2.3.2.1 Traditional narrowband communication

All mobile radio signals experience distortions at the boundaries of their symbols This is due various delayed versions of the transmitted signal that are received with different delays and are thus overlapping at the symbol boundaries

The nature of traditional narrowband communication is that the symbols are very long compared to the distortion zone in-between their symbols In the useful time of the received symbol the modulated content of the symbol can be demodulated The advantage of this scheme is that no complex equalizer is needed in order to detect these narrowband signals

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1.2.3.2.2 Problems for wideband signals

Unfortunately this scheme cannot be used for wideband signals directly since then

the symbol duration is limited by the maximum expected length of the distortion zone

1.2.3.2.3 OFDM

OFDM is a wideband system using many orthogonal narrowband carries in order to

perform a simple receive processing on each of these carriers Orthogonality is

achieved by means of having an equal distance in-between the individual carriers

This frequency spacing is the inverse useful symbol duration Thus OFDM can allow

for both a wideband signal for high data rate transmission and an easy detection

mechanism In the picture Orthogonality can be seen by the fact that at the position

of the main lobe of each subcarriers spectrum there is a zero crossing of the other

subcarriers’ spectra

1.2.3.2.4 OFDM and OFDMA

Both OFDM and OFDMA are using OFDM technology The difference is:

OFDMA

The OFDMA transmitter is mapping signals dedicated to more than one receiver on

the OFDM carriers

OFDM

OFDM alone is using all the transmitted carriers for a single receiver

1.2.3.2.5 LTE and OFDM

LTE is using OFDMA technology in the DL and single carrier technology in the UL

However the UL signals look like OFDM signals This method is allowing an easy

equalization in the frequency domain before the UL signals are demodulated in the

time domain

[3GTR 25.912 (7.1, 7.2)]

3GTR 3rd Generation Technical Report OFDM Orthogonal Frequency Division

Multiplexing

DL Downlink OFDMA Orthogonal Frequency Division

Multiple Access

LTE Long Term Evolution (of UMTS) UL Uplink

1

17

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1.2.3.3 Smart Antenna Technology in LTE

1.2.3.3.1 Categorization of Smart Antenna Technologies

The objective of this section is to clarify the different terms which are used in the context of multiple antenna techniques

Key point of this section is that the terms “single in / out” or “multiple-in / out” have to be interpreted from the perspective of the channel between TX and

RX Therefore, a system with two RX-antennas and one TX-antenna is a SIMO

SIMO and MIMO have to be distinguished

1.2.3.3.1.1 SISO

SISO-systems do not really belong in this section but need to be mentioned for completeness SISO-systems deploy only one TX- and one RX-antenna which excludes them from the group of “multiple antennas” techniques with their enhanced capabilities

1.2.3.3.1.2 SIMO

• SIMO-systems have been around for quite some time SIMO-systems apply receive diversity schemes and typically soft decision and maximum ratio combining (MRC) to counteract poor multipath conditions at a single antenna

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• One important implementation example for a receive diversity scheme is the

GSM-uplink receive diversity: The MS uses a single TX-antenna but typically, the

BS has two receive antennas

1.2.3.3.1.3 MISO

TX-antennas are used to apply transmit diversity schemes towards a single

RX-antenna One important implementation example for a transmit diversity scheme

is Space-Time-Coding (STC) which will be represented in a later section.

more detail in a later section

1.2.3.3.1.4 MIMO

MIMO-systems are characterized by deploying both: Two or more TX-antennas and

two or more RX-antennas

MIMO-systems may or may not incorporate the receive and transmit diversity

schemes of SIMO- and MISO-systems, respectively

BS Base Station (IEEE 802.16) RX Receive

GSM Global System for Mobile

Communication SIMO Single In / Multiple Out (antenna system)

MIMO Multiple In / Multiple Out (antenna

system) SISO Single In / Single Out (antenna system)

MISO Multiple In / Single Out (antenna

system) STC Space Time Coding

MRC Maximum Ratio Combining TX Transmit

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1.2.3.3.2 Multiple Input Multiple Output (MIMO)

The objective of this section to visualize the key features of MIMO technology in a very simple way.

Key points of this section are the efficiency of MIMO comes with the expense

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• Green and red bits are symbolizing the two data streams at the transmitter.

• The pipes are symbolizing the mobile radio channels of the two carriers

• The buckets are symbolizing the output of the initial detector at the receiver

1.2.3.3.2.1 Multiple carrier technology

For the multiple carrier transmission scheme the input data need first to be separated

to two data streams Each of the data streams could be able to completely occupy

the individual carrier Each of the shown two carriers is treated individually as if only

one carrier would be transmitted Multiple carrier technology is known for a very long

time even though the digital signal processing is very simple the challenge of multiple

carrier technology lies in the RF This is why these days not that much multiple

carrier technology is implemented (except for OFDM systems of course)

1.2.3.3.2.2 MIMO

MIMO is as well using a serial to parallel converter in order to create separate data

streams The difference here is that not multiple carriers but multiple antennas are

used in TX and RX in order to create more max throughput or signals for more

users With e.g N antennas for TX and N antennas for RX (N x N) the data rate could

be enhanced by N times Since each receive antenna is receiving the signals from

both transmitters in the general case the mobile radio channel is mixing up the two

data streams This means that the receiver has to separate these mixed data

streams from each other Since N data streams have to be separated the receiver

has to receive N different versions of the N data stream signals This is why N

receive antennas are needed This data separation might add quite significant effort

in the receiver’s digital signal processing Since with MIMO now the data rate on a

single carrier is multiplied, it becomes very tempting for 4G to implement MIMO

nevertheless

MIMO add a new dimension to mobile radio: Instead of frequency space is used

4G 4th Generation RF Radio Frequency

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1.2.3.3.3 Adaptive Antenna Systems (AAS)

The objective of this section to show key features and key benefits of AAS.

Key point of this section is that AAS is both improving the signal quality and

is reducing the interference in the system by means of weighing various TX antennas’ signals with different antenna weights.

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1.2.3.3.3.1 Signal generation

In the upper part the physical setup the signal generation is shown At first the user

signal is created as if there were no AAS

Then the signal is copied two times (once for each antenna) and is then multiplied

with a user dependent weighing factor for each antenna In the case of this picture

the two weighing factors are both 1 In an AAS system the antennas are usually very

close together: Typically half the wave length is chosen in order to perform

beamforming

1.2.3.3.3.2 Constructive superimposition at the intended receiver

In the picture the weighing coefficients are chosen in a way that the two antennas

radio signals are superimposing constructively at the position of the UE One benefit

of the AAS is that the TX energy is bundled in the direction of the UE’s the signal is

intended for

For realistic AAS more than 2 antennas are situated in a line (linear antenna array) or

on a circle (circular antenna array)

1.2.3.3.3.3 Destructive superimposition at the not intended receiver

UE2 is located below the two antennas Here the signal of antenna 1 has traveled

exactly half a wavelength longer than the signal of antenna 2 This has the

consequence that it always has a phase shift of 180 degrees compared with the

signal of antenna 2

This leads to a complete destruction of the two antennas signals Here the benefit of

AAS of interference reduction is shown very well

What would happen once one of the two antennas is switched off?

How to achieve that that the AAS is radiating the signal towards UE2?

1.2.3.3.3.4 Generation of signals for multiple UE’s

Each UE will have its own signal generated with its own weighing factors After the

weighing process for each UE the signals are added up before they reach the TX

antennas This feature is very important for AAS’s application in modern mobile radio

systems where multiple signals for multiple UE’s are transmitted on the individual

radio carrier

Room for your Note

AAS Adaptive Antenna Systems UE User Equipment

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1.2.3.4 Macro Diversity exploitation by SFN

The objective of this section is to illustrate how the SFN basically works.

Key point of this section is that SFN transmitting the same signals synchronously by multiple eNB’s in order to provide macro diversity.

Image Description

the eNB’s are the choir members, and the UE’s are the audience

1.2.3.4.1 Requirements for MBMS services

Since the signals for MBMS are multicast it is difficult to direct or tune them to the individual UE’s mobile radio channels They have to be broadcast Even though here MIMO is applicable many other methods like power control, AAS, etc cannot be applied This is why it would be very advantageous if some kind of macro diversity could be exploited in order to enhance the quality of MBMS to a similar level as for the point to point services

1.2.3.4.2 MBMS operation with a SFN

Like in a choir the core network is distributing the same piece of data to a multitude of eNB’s The eNB’s are drawn as choir members In a choir all the members have to sing synchronously and with the same voice In an OFDM system SFN can be applied easily provided that all the eNB’s are synchronized and that they are transmitting exactly the same bits on exactly the same subcarriers Then the UE’s cannot distinguish whether the signal is coming from one or from several eNB’s and macro diversity is exploited automatically

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This benefit, however, comes at a price: Like the conductor does with the choir, the

mobile radio network needs to coordinate precisely within the eNB’s

1.2.3.4.3 SFN for point to point services

Imagine an individual person is listening to a choir presentation alone Then the ticket

would be quite expensive In the same way the aforementioned coordination

overhead is limiting the use of SFN for point to point services Features like soft

handover are not intended by LTE – especially this can be seen from the network

AAS Adaptive Antenna Systems OFDM Orthogonal Frequency Division

Multiplexing

LTE Long Term Evolution (of UMTS) SFN Single Frequency Network

Service UE User Equipment

system) eNB Enhanced Node B

1

25

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1.2.3.5 The Frequency Bands Intended for LTE

The objective of this section is to show how LTE will use the available frequency bands

Key point of this section is that LTE and UTRA compete for the same frequency bands.

Table Description

purpose they are identical to the frequency bands for UMTS - UTRA

Since of the frequency bands are also foreseen for other standards e.g band 7 and

12 might/will also be used for WiMAX, LTE is both competing with other standards and with UTRA about the frequency bands

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