LTE air interface

LTE Air Interface Training Manual

Contents Content s

Contents 1 The Air Interface Inter face ............................................................................................. ............................................................................................................................. ................................ 1-1 1.1 Ev E volution of Cellular Networks Networks ....................... ............................................................ ................................. 1-2 1.1.1 First F irst Generation Mobile System S ystemss .................................................................................. ....................... 1-2 1.1.2 Second S econd Generation Generation Mobile Systems................. Systems................. ............................................................. ....................... 1-2 1.1.3 Third Generation Mobile Systems Systems ............................................................ ........................................... 1-4 1.1.4 Fourth Generation 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 Interface Techniques .......................................................................................... ............................... 1-10 1-10 1.3.1 Freque F requency ncy Division Multiple Access ... ............................................................. ................................. 1-10 1.3.2 Time Di vision Multiple Access Access .......................................... ............................................................. ... 1-11 1.3.3 Code Division Division Multiple Access Access ....................................................................................................... ... 1-11 1.3.4 Orthogonal Orthogonal Frequency Frequency Division Multiple Access ............................ .................................................. 1-12 1-12 1.4 Transmission Modes............................................................. ............................................................. .......... 1-12 1-12 1.4.1 Freque F requency ncy Division Duplex ........ ............................................................ ........................................... 1-13 1-13 1.4.2 Time Di vision Duplex ........................................................... ............................................................ . 1-13 1.5 Spectrum Usage................................................................ ................................................................ ........... 1-14 1.5.1 Frequency Frequency Bands ............................................................................ .................................................... 1-14 1.5.2 Existing Mobile Deployment Deployment ............................. ............................................................ .................... 1-16 1.5.3 LTE LTE Release 8 Bands ................................................ ............................................................. ............ 1-17 1.6 Channel Coding i n LTE ........................................................ ............................................................. .......... 1-20 1.6.1 Transport Transport Block CRC ............................................................ ............................................................ . 1-20 1.6.2 Code C ode Block Segmentation Segmentation and CRC Attachment Attachment ............................................................................... 1-21 1-21 1.6.3 Channel Coding........................................................... Coding........................................................... ............................................................. .......... 1-23 1.6.4 Rate R ate Matching ............................................................................................................... ..................... 1-28

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1.6.5 Code Block Concatenation............................................................... .................................................. 1-29 1-29 1.7 Principles of OFDM OFDM ............................................................. ............................................................. .......... 1-30 1.7.2 Freque F requency ncy Division Multiplexing ...................................... ............................................................. ... 1-30 1.7.1 OFDM Subcarriers ...................................................... ........................................................... ............ 1-31 1.7.2 Fast Fourier F ourier Transform Transformss .............. ............................................................ ........................................... 1-31 1-31 1.7.3 LTE LTE FFT F FT Sizes ............................................................ ............................................................. .......... 1-32 1.7.4 OFDM Symbol Symbol Mapping ........................................................................ ........................................... 1-32 1-32 1.7.5 Time Domain Interference Interference ...................... ............................................................ ............................... 1-33 1.7.6 OFDM Advantages Advantages and Disadvantages Disadvantages ................................................................ .............................. 1-35 1-35

2 LTE LT E Physical Phys ical Layer .............................................................................................. ......................................................................................................................... ........................... 2-1 2.1 The Uu Interface................................. Interface................................. ............................................................... ............................................ 2-3 2.2 LTE Radio Interface Interface Protocols ................................................................................................ ...................... 2-3 2.2.1 Control and User User Plane Protocols ................................................................................. ....................... 2-4 2.2.2 Non Access S tratum ............................................................................................................... .............. 2-4 2.2.3 RRC................................................................ ................................................................ ...................... 2-7 2.2.4 PDCP......................................................................... ............................................................. .............. 2-7 2.2.5 RLC......................................................... ............................................................ ................................. 2 2-8 -8 2.2.6 MAC ................................................................ .............................................................. ...................... 2-8 2.2.7 Physica P hysicall ................................................................................. ............................................................ ... 2-9 2.3 LTE Channel Structure ......................................................... ............................................................. ............ 2-9 2.3.1 Logical Channels.............................................. ............................................................. ..................... 2-10 2.3.2 Transport Transport Channels...................................................... Channels...................................................... ........................................................... ............ 2-11 2-11 2.3.3 Physical C hannels ....................................................... ............................................................. .......... 2-12 2.3.4 Radio Channels ............................................................................................................. ..................... 2-13 2.3.5 Channel Mapping ........................................................ ............................................................. .......... 2-13 2.4 LTE Frame Structure .................................................................................................. ................................. 2 2-15 -15 2.4.1 Type Type 1 Radio Frames, Frames, Slots and Subframes Subframes ................................................................ ....................... 2-15 2.4.2 Type Type 2 Radio Frames, Frames, Slots and Subframes Subframes ................................................................ ....................... 2-17 2.5 OFDM Signa Si gnall Generation Generation ................................ ............................................................ ............................... 2-18 2.5.1 Codew C odewords, ords, Layers and Antenna Antenna Ports................................................................ P orts................................................................ ............................... 2-19 2.5.2 Scrambling Scrambling ................................ ................................................................ ......................................... 2-20 2-20 2.5.3 Modulation Modulation Mapper Mapper................................................................ ........................................................... . 2-21 2.5.4 Layer Layer Mapper .............................................................. ............................................................. .......... 2-22 2.5.5 Precoding ................................................................ ................................................................ ........... 2-23 2.5.6 Resourc R esourcee Element Element Mapper ..................................................................................................... ............ 2-26 2.5.7 OFDM Signal Generation ....................................................................... ........................................... 2-26 2-26 2.6 Downlink OFDMA .............................................................. ............................................................. .......... 2-26 2.6.1 General General OFDMA Structure Structure ....................................... ............................................................. ............ 2-26 2.6.2 Physica P hysicall Resource Blocks and Resource Elements ............................................................................ 2-27 2-27 2.7 LTE Physical Signals................................................................... Si gnals................................................................... ............................................................. ... 2-28 2.8 Downlink Downlink Reference Reference Signals S ignals ................................................................................................ ....................... 2-31

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1.6.5 Code Block Concatenation............................................................... .................................................. 1-29 1-29 1.7 Principles of OFDM OFDM ............................................................. ............................................................. .......... 1-30 1.7.2 Freque F requency ncy Division Multiplexing ...................................... ............................................................. ... 1-30 1.7.1 OFDM Subcarriers ...................................................... ........................................................... ............ 1-31 1.7.2 Fast Fourier F ourier Transform Transformss .............. ............................................................ ........................................... 1-31 1-31 1.7.3 LTE LTE FFT F FT Sizes ............................................................ ............................................................. .......... 1-32 1.7.4 OFDM Symbol Symbol Mapping ........................................................................ ........................................... 1-32 1-32 1.7.5 Time Domain Interference Interference ...................... ............................................................ ............................... 1-33 1.7.6 OFDM Advantages Advantages and Disadvantages Disadvantages ................................................................ .............................. 1-35 1-35

2 LTE LT E Physical Phys ical Layer .............................................................................................. ......................................................................................................................... ........................... 2-1 2.1 The Uu Interface................................. Interface................................. ............................................................... ............................................ 2-3 2.2 LTE Radio Interface Interface Protocols ................................................................................................ ...................... 2-3 2.2.1 Control and User User Plane Protocols ................................................................................. ....................... 2-4 2.2.2 Non Access S tratum ............................................................................................................... .............. 2-4 2.2.3 RRC................................................................ ................................................................ ...................... 2-7 2.2.4 PDCP......................................................................... ............................................................. .............. 2-7 2.2.5 RLC......................................................... ............................................................ ................................. 2 2-8 -8 2.2.6 MAC ................................................................ .............................................................. ...................... 2-8 2.2.7 Physica P hysicall ................................................................................. ............................................................ ... 2-9 2.3 LTE Channel Structure ......................................................... ............................................................. ............ 2-9 2.3.1 Logical Channels.............................................. ............................................................. ..................... 2-10 2.3.2 Transport Transport Channels...................................................... Channels...................................................... ........................................................... ............ 2-11 2-11 2.3.3 Physical C hannels ....................................................... ............................................................. .......... 2-12 2.3.4 Radio Channels ............................................................................................................. ..................... 2-13 2.3.5 Channel Mapping ........................................................ ............................................................. .......... 2-13 2.4 LTE Frame Structure .................................................................................................. ................................. 2 2-15 -15 2.4.1 Type Type 1 Radio Frames, Frames, Slots and Subframes Subframes ................................................................ ....................... 2-15 2.4.2 Type Type 2 Radio Frames, Frames, Slots and Subframes Subframes ................................................................ ....................... 2-17 2.5 OFDM Signa Si gnall Generation Generation ................................ ............................................................ ............................... 2-18 2.5.1 Codew C odewords, ords, Layers and Antenna Antenna Ports................................................................ P orts................................................................ ............................... 2-19 2.5.2 Scrambling Scrambling ................................ ................................................................ ......................................... 2-20 2-20 2.5.3 Modulation Modulation Mapper Mapper................................................................ ........................................................... . 2-21 2.5.4 Layer Layer Mapper .............................................................. ............................................................. .......... 2-22 2.5.5 Precoding ................................................................ ................................................................ ........... 2-23 2.5.6 Resourc R esourcee Element Element Mapper ..................................................................................................... ............ 2-26 2.5.7 OFDM Signal Generation ....................................................................... ........................................... 2-26 2-26 2.6 Downlink OFDMA .............................................................. ............................................................. .......... 2-26 2.6.1 General General OFDMA Structure Structure ....................................... ............................................................. ............ 2-26 2.6.2 Physica P hysicall Resource Blocks and Resource Elements ............................................................................ 2-27 2-27 2.7 LTE Physical Signals................................................................... Si gnals................................................................... ............................................................. ... 2-28 2.8 Downlink Downlink Reference Reference Signals S ignals ................................................................................................ ....................... 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 Downlink LTE Physica P hysicall Channels............................................................. .................................................. 2-34 2.9.1 PBCH (Physical (Physical Broadcast Broadcast Channel) ........................................................ ......................................... 2-34 2-34 2.9.2 PCFICH (Physical Control Format Format Indicator Indicator Channel) ........................................................... .......... 2-35 2.9.3 PDCCH (Physical Downlink Control Channel) ............................................................. .................... 2-37 2.9.4 PHI P HICH CH (Physical (Physical Hybrid Hybrid ARQ Indicator Indicator Channel).......................... .................................................. 2-40 2-40 2.9.5 PDSCH P DSCH (Physical (Physical Downlink 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 LTE Cell Search Procedure 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 Information Block Bl ock ................................................................................. ............................... 2-50 2-50 2.11.5 System Information Messages...................................................... .................................................... 2-50 2-50 2.11.6 PLMN Selection........................................................ ............................................................. .......... 2-55 2.11.7 Cell Selection ................................................. ............................................................. ..................... 2-57 2.12 Uplink Transmission Transmission Technique ............................................................................................ .................... 2-58 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.............................................................................................. C hannels.............................................................................................. .................... 2-61 2.14.1 PRACH (Physical Random Access Access Channel)................................................................................... 2-62 2-62 2.14.2 PUSCH (Physical Uplink Shared Channel) ............ ............................................................. ............ 2-66 2.14.3 PUCCH P UCCH (Physical (Physical Uplink Control Channel)................................................................ .................... 2-68 2.15 Timing Relationships............................................................................. .................................................... 2-69 2-69 2.16 Uplink Reference Signals .................................................................................................. ........................ 2-70 2.16.1 Demodulation Demodulation Reference Reference Signal................................................... .................................................... 2-71 2-71 2.16.2 Sound S ounding ing Reference Signal .............................. ............................................................ .................... 2-72 2.17 Uplink C ontrol Signaling .............................................................................................................. ............ 2-75 2.17.1 PUCCH F ormat ormat 1 ................................................................................................ ............................. 2-75 2.17.2 PUCCH Format 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

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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 ½ 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 Po wer 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 2-62 System Information Block Type 2 ....................................................... ......................................... 2-53 Figure 2-63 System Information Block Type 3 ....................................................... ......................................... 2-53 Figure 2-64 System Information Block Type 4 ....................................................... ......................................... 2-53 Figure 2-65 System Information Block Type 5 ....................................................... ......................................... 2-54 Figure 2-66 System Information Block Type 6 ....................................................... ......................................... 2-54 Figure 2-67 System Information Block Type 7 ....................................................... ......................................... 2-54 Figure 2-68 System Information Block Type 8 ....................................................... ......................................... 2-55 Figure 2-69 System Information Block Type 9 ....................................................... ......................................... 2-55 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 Si gnal (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 3-7 Type 1 Resource Allocation ................................................................................................ .............. 3-7 Figure 3-8 Type 2 Resource Allocation ................................................................................................ .............. 3-7 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 Di versity ................... .................................................... 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

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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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The Air Interface

Objectives On completion of this section the p articipants 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 s ystems were not digital, i.e. the y utilized analogue modulation techniques. The main systems in cluded: 

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 tec hnology, 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:

1-2



GSM (Global System for Mobile communications) - this is the most successful of all 2G technologies. It was initi ally 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 e nhancement 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

Other

cdmaOne (IS-95)

D-AMPS (IS-136)

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 i llustrated in Table 1-1.

2.75G Systems GSM/GPRS systems also added EDGE (E nhanced 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 M obile Telecommunications - 2000). IMT2000 defines th at 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:

1-4



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. Ho wever, 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 sce narios in micro or pico cells.



CDMA2000 - This is a multi-carrier te chnology standard which uses CDM A. 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 Mi crowave Access) - This is another wireless technology which satisfies IMT2000 3G requirements. The air interf ace 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

3G (Third Generation)

UMTS TD-CDMA

WiMAX

CDMA2000 TD-SCDMA

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 m anner. Compatibility of services within IMT and with fixed networks. Capability of interworking with other radi o 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 t heir offering for a 4G system.



UMB (Ultra Mobile Broadband) - This is identified as EV-DO Rev C. It is part of 3GP P2 however most vendors and service providers have decided to promote LTE instead.

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Figure 1-4 Forth Generation Mobile System

4G (Fourth Generation) LTE Advanced

UMB (EV-DO Rev C)

WiMAX 802.16m

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

Phase 2+ (Release 97)

Release 99

Release 6

Release 8

GPRS 171.2kbit/s

UMTS 2Mbit/s

HSUPA 5.76Mbit/s

LTE +300Mbit/s

Release 9/10 LTE Advanced

GSM 9.6kbit/s

EDGE 473.6kbit/s

HSDPA 14.4Mbit/s

Phase 1

Release 99

Release 5

HSPA+ 28.8Mbit/s 42Mbit/s Release 7/8

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:

1-6



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 spectr al efficiency. Figure 1-6 illustrates some of the main features which include: 

Adaptive Modulation - In addition to the origin al UMTS modulation scheme, QPSK (Quadrature Phase Shift Keying), HSDPA also includes support for 16 QAM (Quadrature Amplitude Modulation).



Flexible Coding - Based on fast fee dback 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), whi ch enables the Node B scheduler to quickly and efficiently allocate resources to mobiles.



HARQ (Hybrid Automatic Repeat Request) - I n the event a packet does not get t hrough 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

UTRAN

Iub Node B

RNC

UE

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 ter m HSUPA is widespread, this 3GPP enhancement also goes under the term “Enhanced Uplink”. It i s also worth not ing that

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HSDPA and HSUPA work in t andem and thus t he term HSPA (High S peed 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 there fore 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 eithe r 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

UTRAN

HSUPA Flexible Coding Fast Power Scheduling HARQ

Iub Node B

RNC

UE

1.2.6 Release 7 The main RAN based feature of Release 7 is HSPA+. This, like HSDPA and HSUPA, provides various enhancements to im prove packet switched data delivery. Figure 1-8 illustrates the main features which include:

1-8



64 QAM - This is added to the D L (Downlink) and enables HSPA+ to operate at a theoretical rate of 21.6Mbit/s.



16 QAM - This is added to the U L (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 o ffer a theoretical 28.8Mbits/s in the downlink.



Power Enhancements -Various enhancements such as CPC ( Continuous Packet Connectivity) have been included. Thus en abling DTX (Discontinuous Transmission), DRX (Discontinuous Reception) and HS-SCCH (High Speed - Shared Control Channel) Less Operation. Collectively these improve the mobile’s battery consumption.



Less Overhead - The downlink includes an enhancement to the MA C (Medium Access Control) layer which effectively means that fewer headers are required. This in turn improves the s ystem 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)

UTRAN

Iub Node B

RNC

UE

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 e ffectively 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

UTRAN

HSPA+ 64 QAM + MIMO (DL) Dual Cell Operation Less Overhead (UL)

Iub Node B LTE Enhanced Techniques Flexible Bandwidth Flexible Spectrum Options High Data Rates Very Fast Scheduling Improved Latency

RNC

UE E-UTRAN

eNB

LTE provides a new radio access technique, as well as enhancements in the E-UTRAN (Evolved - Universal Terrestrial Radio Access Network). These enhancements are furthe r 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 3GPP’s 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 c ommon medium for transmission. There are various categories of assignment, t he 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

Radio Interface Techniques FDMA

OFDMA

TDMA

CDMA

1.3.1 Frequency Division Multiple Access In order to accommodate various de vices on the same wireless net work, FDMA divides the available spectrum into sub-bands or cha nnels. 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 fo r 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

Power

Time FDMA Each user allocated a different subband/ channel.

Frequency FDMA channels also suffer suffer since they cannot be close together t ogether 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 system’ system ’s spectral efficiency. 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 e ach device is allocated a time on the channel, known as int o a TDMA frame. frame. The number of timeslots in a a “timeslot”. These are then grouped into TDMA frame is dependent on the system, for example GSM utilizes 8 ti meslots. Figure 1-13 Time Division Multiple Access

Power

Time TDMA Each user allocated a different time on the channel.

Frequency Devices must be allocated a timeslot; therefore it is usual to have one or more timeslots reserved for common control and system access. TDMA systems are normally digital and therefore offer additional features such as ciphering and integrity. In addition, they ca n employ enhanced error detection and correction schemes including FEC (Forward Error Correction). This enables the system to be more resilient to noise and interference and therefore they have a greater spectral efficiency when compared to FDMA systems.

1.3.3 Code Division Multiple Access The concept of CDMA is slightly different to that of FDM A and TDMA. Instead In stead of sharing resources in the time or frequency domain, the devices are able to use the system at the same time and using the same frequency/bandwidth. This is possible due t o the fact that ea ch transmission is separated using a unique code. There are two main types of CDMA, FHSS (Frequency Hopping Spread Spectrum) and DSSS (Direct Sequence Spread Spectrum), with all the current cellular systems utilizing DSSS.

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Figure 1-14 illustrates the basic concept of CDMA. The narrowband signals are spread with a wideband code and then transmitted. The receivers are designed to extract the encoded signal (with the correct code) and reject everything else as noise. Figure 1-14 Code Division Multiple Access

Time

Power

CDMA Each user allocated a different code on the channel.

Frequency UMTS, cdmaOne and CDMA2000 all use CDMA. However the implementation of the codes and the bandwidths used is different. For exam ple UMTS utilizes a 5MHz channel bandwidth, whereas cdmaOne uses only 1.25MHz.

1.3.4 Orthogonal Frequency Division Multiple Access OFDMA (Orthogonal Frequency Division Multiple Access) Access) is the latest addition to cellular cell ular systems. It provides a multiple access technique based on OFDM (Orthogonal Frequency Division Multiplexing). Figure 1-15 illustrates the basic view of OFDMA. It can be seen that the bandwidth the bandwidth is broken down to smaller units known as “subcarriers”. These are grouped together and allocated as a resource to a device. It can also be seen that a device can be allocated different resources in both the time and frequency domain. Additional detail on OFDM and OFDM A is provided in Se ction 1.7 and and 2.6 . Figure 1-15 Orthogonal Orthogonal Frequency Division Multiple Access

Time

Power

OFDMA Each user allocated a different resource which can vary in time and frequency.

Frequency

1.4 Transmission Modes Cellular systems can be designed to operate in two main transmission modes, namely FDD (Frequency Division Duplex) and TDD (Time Division Duplex).

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1.4.1 Frequency Division Duplex The concept of FDD is illustrated illustr ated in Figure 1-16. A separate separate uplink and downlink channel are utilized, enabling a device to transmit a nd receive data at the same time (assuming the device incorporates a duplexer). The spacing between the uplink and downlink channel is referred to as the duplex spacing. Figure 1-16 Frequency Division Duplex

Channel Bandwidth

Channel Bandwidth

Uplink

Downlink

Frequency

Duplex Spacing Normally the uplink channel (mobile t ransmit) operates on the lower lowe r frequency. This This is done because higher frequencies suffer greater attenuation than lower frequencies and therefore it enables the mobile to utilize lower transmit levels. Some systems also offer half-duplex FDD mode, where two frequencies are utilized, however the mobile can only transmit or receive, i.e. not transmit and receive at the same time. This allows for reduced mobile complexity complexity since no duplex filter filte r is required.

1.4.2 Time Division Duplex TDD mode enables full duplex operation using a sin gle frequency band and time ti me division multiplexing the uplink and downlink signals. One advantage of TDD i s its ability to provide asymmetrical uplink and downlink allocation. Depending on the s ystem, other advantages include dynamic allocation, increased spectral e fficiency, fficiency, as well as the t he improved impr oved use of beamforming techniques - this is due t o having the same uplink and downlink frequency characteristics. Figure 1-17 Time Division Duplex

Downlink and Uplink

Downlink TDD Frame

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TDD

Asymmetric Allocation

Uplink

Downlink

Uplink

Time

TDD Frame


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1.5 Spectrum Usage One of the main factors in any cellular system is the frequency of deployment. Most 2G, 3G and 4G systems offer multiple options. For e xample, GSM can be deployed at v arious bands including: 900MHz, 1800MHz, 1900MHz, 850MHz etc.

1.5.1 Frequency Bands Each cellular system defines its own set of frequency bands it is able to operate on. In order to identify possible LTE bands it is worth noting the bands used by other technologies such as GSM, UMTS etc.

GSM Bands Table 1-3 illustrates the main frequency bands defined for GSM. However, this does not guarantee that the spectrum is available since there may be regulatory issues, as well as limitations in some handsets and base stations. The initial GSM band was referred to as P-GSM (Primary GSM). This was mainly defined to replace the TACS system which was also i n the 900MHz band. Other 900MHz ban ds which were added include E-GSM (Extended GSM) and R-GSM (Railways GSM) bands, providing more channels and support of a railway based variant. Finally, other bands away f rom the 900MHz band are also available; however the support for 450MHz and 480MHz is limited. The terms DCS (Digital Cellular Service) and PCS (Personal Communications Service) are typically used in Europe and North America respectively to identify the higher frequency deployment options. It was expected that these frequencies would offer a better re-use in built up areas and theref ore provide additional capacity. Table 1-3 GSM Frequency Bands

Operating Band

Frequency Band

Uplink Frequency (MHz)

Downlink Frequency (MHz)

GSM 400

450

450.4 - 457.6

460.4 - 467.6

GSM 400

480

478.8 - 486.0

488.8 - 496.0

GSM 850

850

824.0 - 849.0

869.0 - 894.0

GSM 900 (P-GSM)

900

890.0 - 915.0

935.0 - 960.0

GSM 900 (E-GSM)

900

880.0 - 915.0

925.0 - 960.0

GSM-R (R-GSM)

900

876.0 - 880.0

921.0 - 925.0

DCS 1800

1800

1710.0 - 1785.0

1805.0 - 1880.0

PCS 1900

1900

1850.0 - 1910.0

1930.0 - 1990.0

UMTS Bands UMTS, like GSM, has a number of f requency bands defined. These are identifie d by an “Operating Band” number which is illustrated in Table 1-4, along with the associated Uplink and downlink frequency ranges.

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Table 1-4 UMTS FDD Frequency Bands

Operating Band

Frequency Band

Uplink Frequency (MHz)

Downlink Frequency (MHz)

I

2100

1920 - 1980

2110 - 2170

II

1900

1850 - 1910

1930 - 1990

III

1800

1710 - 1785

1805 - 1880

IV

1700

1710 - 1755

2110 - 2155

V

850

824 - 849

869 - 894

VI

800

830 - 840

875 - 885

VII

2600

2500 - 2570

2620 - 2690

VIII

900

880 - 915

925 - 960

IX

1700

1749.9 - 1784.9

1844.9 - 1879.9

X

1700

1710 - 1770

2110 - 2170

XI

1500

1427.9 - 1452.9

1475.9 - 1500.9

XII

700

698 - 716

728 - 746

XIII

700

777 - 787

746 - 756

XIV

700

788 - 798

758 - 768

In addition to the previous UMTS FDD b ands, various UMTS TDD bands are also defined. Table 1-5 illustrates the main TDD bands, however the majority of these have never been implemented. Table 1-5 UMTS TDD Frequency Bands

Frequency Band 1900 - 1920 2010 - 2025 1850 - 1910 1930 - 1990 1910 - 1930 2570 - 2620

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1.5.2 Existing Mobile Deployment The list of current mobile service providers is constantly increasing. The latest list of GSM/UMTS and LTE operators is maintained by the GSMA (GSM Association).

GSM Deployments Figure 1-18 summarizes the main GSM deployment bands. It can be seen that GSM 9 00 and GSM 1800 are used in most parts of the world, i.e. Europe, Middle East, Africa a nd most of Asia/Pacific. In contrast, GSM 850 and GSM 1900 are mainly used in North America and Canada, as well as many other l ocations. Finally, the lower fre quency bands, i.e. GSM 400/450 has limited support. Figure 1-18 GSM Deployments

Europe, Middle East, Africa, and most of Asia/Pacific.

United States, Canada, and many other countries in the Americas.

GSM 900 GSM 1800

This has limited support.

GSM 850 GSM 1900

GSM 400

Main UMTS Deployments The main UMTS deployment bands are illustrated in Figure 1-19, these include: 

Band I (WCDMA 2100) - This is mainly used in Europe, Africa, Asia, Australia, New Zealand and Brazil.



Band II (WCDMA 1900) - This is used in North and South America.



Band IV (WCDMA 1700) - This is typically referred to as the AWS ( Advanced Wireless Services) band. Certain service providers in North America and Canada have access to this band.



Band V (WCDMA 850) - This is found mainly in North and South America, as well as Australia, New Zealand, Canada, Israel, Poland and Asia.



Band VIII (WCDMA 900) - This is now being found in Europe, Asia, Australia, New Zealand and Venezuela. This list and usage of ban ds is not exclusive. As such other countries, as well as oth er cellular systems may exist.

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Figure 1-19 Key UMTS Deployment Bands

Band II (WCDMA 1900)

Band I (WCDMA 2100)

Band IV (WCDMA 1700)

Main UMTS Deployments

Band V (WCDMA 850)

Band VIII (WCDMA 900)

1.5.3 LTE Release 8 Bands The LTE Radio interface, namely the E-UTRA (Evolved - Uni versal Terrestrial Radio Access), is able to operate in many different radio bands. Table 1-6 illustrates the Release 8 frequency bands as well as other parameters which are used to identify centre frequencies. FDD requires two centre frequencies, one for the downlink and one for the uplink. These carrier frequencies are each given an EARFCN (E-UTRA Absolute Radio Frequency Channel Number) which ranges from 0 to 65535. In contrast, TDD onl y has one EARFCN. The parameters re quired to calculate the EARFCN(s) include: 

FDL_low - This is the lower frequency of the downlink band.



FDL_high - This is the higher frequency of the downlink band.



NOffs-DL - This is a parameter used as part of the downlink EARFCN calculation.



NDL - This is the actual downlink EARFCN number.



FUL_low - This is the lower frequency of the uplink band.



FUL_high - This is the higher frequency of the uplink band.



NOffs-UL - This is a parameter used as part of the uplink EARFCN calculation.



NUL - This is the actual uplink EARFCN number.

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