WCDMA Physical Layer Design

A. ChockalingamAssistant Professor

Indian Institute of Science, Bangalore-12

[email protected]://ece.iisc.ernet.in/~achockal

2

Outline

WCDMA Network ArchitectureWCDMA Network Architecture

WCDMA Physical LayerWCDMA Physical Layer

– Physical / Transport / Logical Channels Physical / Transport / Logical Channels

– UplinkUplink» Spreading - Channelisation / ScramblingSpreading - Channelisation / Scrambling» Transport Formats and ConfigurationTransport Formats and Configuration» Multiplexing and Channel CodingMultiplexing and Channel Coding

– DownlinkDownlink» Spreading / Scrambling / ChannelisationSpreading / Scrambling / Channelisation» Multiplexing and Channel CodingMultiplexing and Channel Coding

3

2G to 3G Evolution

IS-95AIS-95A IS-95BIS-95B cdma2000cdma2000

IMT2000IMT2000

IMT2000: ITU’s Standardization Effort towards 3GIMT2000: ITU’s Standardization Effort towards 3G (IMT-2000 previously termed as FPLMTS)UMTS:UMTS: European Effort (Specified by 3G Partnership Project 3GPP)

GSMGSM GPRSGPRS

WCDMAWCDMA

EDGEEDGE

DDAATTAA

IISS9999

4

UMTS NW Model

USIMMobile

Equipment

Access Network

Serving Network

PS/CS

Transit Network

CuCu UuUu IuIu YuYu

User EquipmentUser Equipment Access NetworkAccess Network Core NetworkCore Network

InfrastructureInfrastructure

Home Network

Access StratumAccess Stratum(Protocols between UE and Access NW)

Non-access StratumNon-access Stratum(Protocols between UE and Core NW)

ZuZu

Stratum: Stratum: Refers to a way of grouping protocols handling activities

5

UMTS NW Architecture

Node B

UE

UE

UE

Node B

Node B

Node B

RNC

RNC

UTRAN

RNS

RNS

CN

CN (CS Domain)

CN (PS Domain)

SGSN GGSN

Registers

HLR/AuC/EIR(Home Network)

3G MSC/ VLR

3G GMSC

UuUu IuIu

IurIur

IubIub

6

WCDMA System Features

UTRA FDD mode and TDD modeUTRA FDD mode and TDD mode

UTRA FDD featuresUTRA FDD features– Multiple Access:Multiple Access: CDMACDMA

– Channel Spacing:Channel Spacing: 5 MHz5 MHz

– Chip Rate:Chip Rate: 3.84 Mcps3.84 Mcps

– Frame Length:Frame Length: 10 msec10 msec

– Time Slots:Time Slots: 15 slots per 10 msec frame 15 slots per 10 msec frame

– Spreading Factor:Spreading Factor: 4 to 5124 to 512

– Multi-rate:Multi-rate: Through Multi-code orThrough Multi-code or Orthogonal Variable Spreading Orthogonal Variable Spreading

7

UTRA FDD Features

– FEC Codes:FEC Codes: Rate 1/2, 1/3 convolutional code Rate 1/2, 1/3 convolutional code with constraint length K = 9with constraint length K = 9

Rate 1/3, 8-state Turbo Rate 1/3, 8-state Turbo codingcoding

– Interleaving:Interleaving: Intra- or Inter-frame interleaving Intra- or Inter-frame interleaving (10, 20 40, 80 msec)(10, 20 40, 80 msec)– Modulation:Modulation: QPSKQPSK– Detection:Detection: Coherent based on pilot symbolsCoherent based on pilot symbols– Micro diversity:Micro diversity: RAKE in BS and UERAKE in BS and UE

– Power Control:Power Control: Fast closed-loop at 1500 Hz rateFast closed-loop at 1500 Hz rate– Intra-frequency HO: Soft / Softer HandoverIntra-frequency HO: Soft / Softer Handover– Inter-frequency HO: Hard HandoverInter-frequency HO: Hard Handover– Interference Cancellation: Support for multiuser detectionInterference Cancellation: Support for multiuser detection

8

Radio Interface Protocol Model

PHYPHY

MACMAC

RLCRLC

Transport ChannelsTransport Channels

Logical ChannelsLogical Channels

User PlaneUser PlaneRadio BearersRadio Bearers

Signalling Signalling Radio BearersRadio Bearers

PDCPPDCPBMCBMC

RRCRRC

USER PLANEUSER PLANECONTROL PLANECONTROL PLANE

ControlControl

L1L1(Radio Physical Layer)(Radio Physical Layer)

L2L2(Radio Link Layer)(Radio Link Layer)

L3L3(Radio Network Layer)(Radio Network Layer)U-Plane Radio BearersU-Plane Radio Bearers

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WCDMA Radio Channels

Physical ChannelsPhysical Channels– Transmission media. Transmission media. – Two types of physical channels defined in L1; FDD and TDD. Two types of physical channels defined in L1; FDD and TDD. – FDD is characterized by frequency, code, I/Q phaseFDD is characterized by frequency, code, I/Q phase– Follow a layered structure of “radio frames” and “time slots”Follow a layered structure of “radio frames” and “time slots”

Transport ChannelsTransport Channels– describes the way information is transferred over the radio interfacedescribes the way information is transferred over the radio interface

Logical ChannelsLogical Channels– the type of information transferred characterizes a logical channelthe type of information transferred characterizes a logical channel

UE BS RNC

Logical ChannelsLogical Channels

Transport ChannelsTransport Channels

Physical ChannelsPhysical Channels

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Physical Channels

Corresponds to a specific carrier frequency, Corresponds to a specific carrier frequency, code, relative phase in I and Q branchescode, relative phase in I and Q branches

Dedicated and Common Physical ChannelsDedicated and Common Physical Channels Layered structure of radio frames and time slots Layered structure of radio frames and time slots A radio frame = 10 msec = 15 slots/frame A radio frame = 10 msec = 15 slots/frame 1 frame = 38400 chips, 1 slot = 2560 chips1 frame = 38400 chips, 1 slot = 2560 chips Slot configuration varies depending on the Slot configuration varies depending on the

channel bit rate of the physical channelchannel bit rate of the physical channel– # bits/slot different for different physical channels# bits/slot different for different physical channels– may vary with time (on a frame by frame basis)may vary with time (on a frame by frame basis)

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U/L Physical Channels

Dedicated U/L ChannelsDedicated U/L Channels– DPDCHDPDCH– DPCCHDPCCH

Common U/L ChannelsCommon U/L Channels– PRACHPRACH

» Preamble partPreamble part» Message partMessage part

– PCPCHPCPCH

» Preamble partPreamble part» Message partMessage part

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Dedicated U/L Physical Channels

Two typesTwo types– Dedicated Physical Data CHannel (DPDCH)Dedicated Physical Data CHannel (DPDCH)– Dedicated Physical Control CHannel (DPCCH)Dedicated Physical Control CHannel (DPCCH)– Both are I/Q code multiplexed within each radio frameBoth are I/Q code multiplexed within each radio frame

U/L DPDCH carries the DCH transport channelU/L DPDCH carries the DCH transport channel U/L DPCCH carries L1 control bits such asU/L DPCCH carries L1 control bits such as

– Pilot bitsPilot bits (to enable channel estimation for coherent detection at BS)(to enable channel estimation for coherent detection at BS)

– Transmit power control (TPC)Transmit power control (TPC) commands commands– Feedback Information (FBI)Feedback Information (FBI)

» used for CL transmit diversity and Site Selection Diversity used for CL transmit diversity and Site Selection Diversity Transmission (SDTC)Transmission (SDTC)

– Transport Format Combination Indicator (TFCI)Transport Format Combination Indicator (TFCI)» for several simultaneous services. Informs the rx of the transport for several simultaneous services. Informs the rx of the transport

format combination of the transport channels mapped to DPDCHformat combination of the transport channels mapped to DPDCH

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U/L Frame Structure

There is only one U/L DPCCH on each radio linkThere is only one U/L DPCCH on each radio link There can be 0, 1, or several DPDCHs on each radio linkThere can be 0, 1, or several DPDCHs on each radio link

10 msec frames divided into 15 slots10 msec frames divided into 15 slots

S0S0 S1S1 S2S2 S3S3 S13S13 S14S14

1 Frame = 15 slots = 10 msec1 Frame = 15 slots = 10 msec

DATADATA

1 time slot = 2/3 msec1 time slot = 2/3 msecDPDCHDPDCH

(on I-Chl)(on I-Chl)

PilotPilotDPCCHDPCCH(on Q-Chl)(on Q-Chl)

TFCITFCI FBIFBI TPCTPC

10 bits = 2560 chips => SF = 25610 bits = 2560 chips => SF = 256

(N(Ndatadata bits) bits)

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I, Q Spreading for DPDCH, DPCCH

DPDCH-1DPDCH-1

DPDCH-3DPDCH-3

CCd,1d,1

CCd,3d,3 BBdd

BBddII

DPDCH-2DPDCH-2

DPCCH-2DPCCH-2

CCd,2d,2

CCcc BBcc

BBddQQ

I+jQI+jQ

SSdpch,ndpch,n

CCc, c, CCd,n: d,n: Channelization codesChannelization codesSdpch,n: Scrambling codeSdpch,n: Scrambling codeBBd, d, BBc: c: Gain factorsGain factors

Up to 6 DPDCHs in parallelUp to 6 DPDCHs in parallel

jj

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WCDMA Transmission Rates (U/L)

System Chip Rate : 3.84 McpsSystem Chip Rate : 3.84 Mcps

Symbol Rates on UplinkSymbol Rates on Uplink– Chl Symb RateChl Symb Rate Chl Bit Rate Chl Bit Rate SF Bits/frame N SF Bits/frame Ndatadata

15 Ks/s15 Ks/s 15 Kb/s 256 15 Kb/s 256 150 150

10 10

30 Ks/s30 Ks/s 30 Kb/s 128 30 Kb/s 128 300 300

20 20

60 Ks/s 60 Kb/s60 Ks/s 60 Kb/s 64 600 40 64 600 40

120 Ks/s 120 Kb/s120 Ks/s 120 Kb/s 32 1200 80 32 1200 80

240 Ks/s 240 Kb/s 240 Ks/s 240 Kb/s 16 2400 16 2400

160 160

480 Ks/s 480 Kb/s 480 Ks/s 480 Kb/s 8 4800 8 4800

320 320

960 Ks/s 960 Kb/s 4 9600 640 960 Ks/s 960 Kb/s 4 9600 640

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WCDMA Channelisation Codes

Orthogonal codesOrthogonal codes

Used for channel separation both in U/L and D/L Used for channel separation both in U/L and D/L

directionsdirections

Can have different spreading factor values (thus Can have different spreading factor values (thus

support different symbol rates)support different symbol rates)

CCch,SF,kch,SF,k : SF - Spreading Factor, k is the code : SF - Spreading Factor, k is the code

number 0<=k<= SF-1number 0<=k<= SF-1

Spreading factor value indicates how many bits of Spreading factor value indicates how many bits of

those codes are used in a connectionthose codes are used in a connection

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U/L Channelization Codes

Orthogonal Variable Spreading Factor (OVSF) Orthogonal Variable Spreading Factor (OVSF) channelization codeschannelization codes Separates data / control channels from same UESeparates data / control channels from same UE Preserves orthogonality between these channelsPreserves orthogonality between these channels

(1)(1)(1,1)(1,1)

(1,-1)(1,-1)

(1,1,1,1)(1,1,1,1)

(1,1,-1,-1)(1,1,-1,-1)

(1,-1,1,-1)(1,-1,1,-1)

(1,-1,-1,1)(1,-1,-1,1)

SF=1SF=1SF=2SF=2

SF=4SF=4

C(SF,k)C(SF,k)

SF: Spreading FactorSF: Spreading Factork: code number 0<k<=SF-1k: code number 0<k<=SF-1

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U/L Scrambling Codes

Use complex valued scrambling code Use complex valued scrambling code

Long scrambling sequences (2^24)Long scrambling sequences (2^24)

– Gold sequences (linear combination of two m-sequences)Gold sequences (linear combination of two m-sequences)

Short scrambling sequences (2^24)Short scrambling sequences (2^24)– from a family sequence of periodically extended S(2) from a family sequence of periodically extended S(2)

codescodes

Long or short sequences for DPCCH / DPDCH Long or short sequences for DPCCH / DPDCH

Only long sequences for message parts of PRACH Only long sequences for message parts of PRACH

and PCPCHand PCPCH

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WCDMA Code Types

Scrambling Codes, Channelisation CodesScrambling Codes, Channelisation Codes

UplinkUplink Downlink Downlink

Scrambling codesScrambling codes User separationUser separation Cell separationCell separation

ChannelisationChannelisation Data and ControlData and Control Users within aUsers within acodescodes channels from thechannels from the cell cell same terminalsame terminal

Spreading code = Scrambling code x Channelisation codeSpreading code = Scrambling code x Channelisation code

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Common U/L Physical Channels

Two TypesTwo Types– Physical Random Access CHannel (PRACH)Physical Random Access CHannel (PRACH)– Physical Common Packet CHannel (PCPCH)Physical Common Packet CHannel (PCPCH)

Physical Random Access CHannel (PRACH)Physical Random Access CHannel (PRACH)– carries RACHcarries RACH– Uses S-ALOHA technique with fast Acquisition Indication Uses S-ALOHA technique with fast Acquisition Indication – Access slots (15 access slots per 2 frames) Access slots (15 access slots per 2 frames) – RA transmission consists of RA transmission consists of

» several 4096 chip preambles (uses 256 repetitions of 16 chips several 4096 chip preambles (uses 256 repetitions of 16 chips signature sequence) and 1or 2 frame messagesignature sequence) and 1or 2 frame message

PreamblePreamble Message Part (1 or 2 frames)Message Part (1 or 2 frames)

4096 Chips4096 Chips

PreamblePreamble

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Random Access

UEUE BSBS

PRACH: Preamble sent (initial access)PRACH: Preamble sent (initial access)

No detection on AICHNo detection on AICH

PRACH: Preamble sent (initial access)PRACH: Preamble sent (initial access)

AICH: Preamble sent detectedAICH: Preamble sent detected

PRACH: Random Access Info sentPRACH: Random Access Info sent

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Common U/L Physical Channels

Physical Common Packet CHannel (PCPCH)Physical Common Packet CHannel (PCPCH)– Carries CPCHCarries CPCH– CPCH is based on DSMA-CD technique with fast CPCH is based on DSMA-CD technique with fast

Acquisition IndicationAcquisition Indication– Access slot timing and structure are identical to those Access slot timing and structure are identical to those

defined for RACHdefined for RACH– Transmission consists ofTransmission consists of

» Access preamble(s) - one or several each 4096 chipsAccess preamble(s) - one or several each 4096 chips» Collision Detection preambleCollision Detection preamble» DPCCH Power Control Preamble (0 or 8 slots)DPCCH Power Control Preamble (0 or 8 slots)» Message of variable length (Nx10 msec)Message of variable length (Nx10 msec)

– PCPCH good for carrying small sized bursty data PCPCH good for carrying small sized bursty data

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Transport Formats / Configurations

Transport Block Transport Block (TB)(TB)» Basic unit of data exchanged between L1 & MAC for L1 Basic unit of data exchanged between L1 & MAC for L1

processingprocessing

Transport Block Size: Transport Block Size: Number of bits in a TB. Number of bits in a TB.

Transport Block Set Transport Block Set (TBS)(TBS)» A set of TBs exchanged between L1 and MAC at the same A set of TBs exchanged between L1 and MAC at the same

time instant using the same transport channeltime instant using the same transport channel

Transport Block Set Size:Transport Block Set Size: Number of bits in a TBSNumber of bits in a TBS

Transmission Time Interval Transmission Time Interval (TTI)(TTI)» Periodicity at which a TBS is transferred by the physical Periodicity at which a TBS is transferred by the physical

layer on to the radio interface - {10, 20, 40, 80 ms}layer on to the radio interface - {10, 20, 40, 80 ms}» MAC delivers one TBS to the physical layer every TTI MAC delivers one TBS to the physical layer every TTI

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Transport Format Transport Format (TF)(TF)– Format offered by L1 to MAC (and vice versa) for the delivery of aFormat offered by L1 to MAC (and vice versa) for the delivery of a TBS during a TTI on a given transport channel (TrCH)TBS during a TTI on a given transport channel (TrCH)– Dynamic part (TB size, TBS size)Dynamic part (TB size, TBS size)– Semi-static part (TTI, type/rate of coding,size of CRC)Semi-static part (TTI, type/rate of coding,size of CRC)

– TB size, TBS size, TTI define the TrCH bit rateTB size, TBS size, TTI define the TrCH bit rate before L1 processing before L1 processing» e.g., TB size = 336 bits (320 bit payload + 16 bits RLC header)e.g., TB size = 336 bits (320 bit payload + 16 bits RLC header)

» TBS size = 2 TBs per TTI, TTI = 10 msTBS size = 2 TBs per TTI, TTI = 10 ms

» DCH Bit rate (with RLC header) = 336*2/10 = 67.2 KbpsDCH Bit rate (with RLC header) = 336*2/10 = 67.2 Kbps

» User Bit rate (without RLC header) = 320*2/10 = 64 KbpsUser Bit rate (without RLC header) = 320*2/10 = 64 Kbps– Variable bit rate can be achieved by changing (Variable bit rate can be achieved by changing (between TTIsbetween TTIs) ) either the TBS size only, or both the TB size and TBS Sizeeither the TBS size only, or both the TB size and TBS Size

Transport Format Set Transport Format Set (TFS)(TFS)– a set of TFs associated with a TrCHa set of TFs associated with a TrCH– semi-static part of all TFs in a TFS is the samesemi-static part of all TFs in a TFS is the same

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Transport Format Combination Transport Format Combination (TFC)(TFC)» Multiple TrCHs each having a TFMultiple TrCHs each having a TF» Authorized combination of the currently valid TFs that can be Authorized combination of the currently valid TFs that can be

submitted to L1 on a submitted to L1 on a CCTrCHCCTrCH, containing one TF from each TrCH, containing one TF from each TrCH Transport Format Combination Set Transport Format Combination Set (TFCS)(TFCS)

» A set of TFCs on a CCTrCH. Produced by RNCA set of TFCs on a CCTrCH. Produced by RNC

» TFCS is given to MAC by L3 for controlTFCS is given to MAC by L3 for control

» MAC chooses between the different TFCs specified in the TFCSMAC chooses between the different TFCs specified in the TFCS

» MAC has control over only the dynamic part of the TFs. Semi-static part MAC has control over only the dynamic part of the TFs. Semi-static part relates to QoS (e.g., quality) and is controlled by RNC admission controlrelates to QoS (e.g., quality) and is controlled by RNC admission control

» Bit rate can be changed quickly by MAC with no need to L3 signalingBit rate can be changed quickly by MAC with no need to L3 signaling

Transport Format Indicator Transport Format Indicator (TFI)(TFI)» A label for a specific TF within a TFS. Used between MAC and L1A label for a specific TF within a TFS. Used between MAC and L1

Transport Format Combination Indicator Transport Format Combination Indicator (TFCI)(TFCI)» Used to inform the receiving side of the currently valid TFCUsed to inform the receiving side of the currently valid TFC

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TTITTI TTITTI TTITTI

TTITTI TTITTI TTITTI

TBTBDCH1DCH1

DCH2DCH2

TBTB TBTB

TBTB TBTB TBTB

TBTB

Transport Block SetTransport Block Set(TBS)(TBS)

TBTB

TBTB

Transport Format (TF)Transport Format (TF)Transport Format Transport Format

Set (TFS)Set (TFS)

Transport FormatTransport FormatCombination (TFC)Combination (TFC)

Transport FormatTransport FormatCombination SetCombination Set

(TFCS)(TFCS)

27

TFI and TFCI (Transmitter)

Transport Chl 1 Transport Chl 1 Transport Chl 2 Transport Chl 2

Transport Transport BlockBlock



Transport Transport BlockBlockTFITFI TFITFI

TFCITFCICoding and Coding and MultiplexingMultiplexing

Physical Physical LayerLayer

Higher Higher LayerLayer

DPCCH (Q-Chl) DPCCH (Q-Chl) DPDCH (I-Chl)DPDCH (I-Chl)

Physical Physical Control ChlControl Chl

Physical Physical Data ChlData Chl

E.g: Two transport channels mapped to a single physical channelE.g: Two transport channels mapped to a single physical channel

This dotted lineThis dotted linerepresents the Iur interface represents the Iur interface in case of NW sidein case of NW side

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TFI and TFCI (Receiver)

Transport Chl 1 Transport Chl 1 Transport Chl 2 Transport Chl 2

Transport Transport Block & EIBlock & EI



Transport Transport Block & EIBlock & EITFITFI TFITFI

TFCITFCIDecodeDecode

Decoding and Decoding and DemultiplexingDemultiplexing

Physical Physical LayerLayer

Higher Higher LayerLayer

DPCCH (Q-Chl)DPCCH (Q-Chl) DPDCH (I-Chl)DPDCH (I-Chl)

EI: Error EI: Error IndicationIndication

Physical Physical Control ChlControl Chl

Physical Physical Data ChlData Chl

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TFI and TFCI

Each transport channel is accompanied by a Each transport channel is accompanied by a TFITFI at each at each time event at which data is expected to arrive from HLtime event at which data is expected to arrive from HL

Physical layer combines the TFI info from different Physical layer combines the TFI info from different transport channels to the TFCItransport channels to the TFCI

TFCI is sent on the DPCCH to inform the receiver about TFCI is sent on the DPCCH to inform the receiver about the instantaneous the instantaneous transport format combinationtransport format combination of the of the transport channels mapped to the U/L DPDCH transport channels mapped to the U/L DPDCH transmitted simultaneouslytransmitted simultaneously

30

Transport Format (e.g., Speech)

Conversational Speech (12 Kbps)Conversational Speech (12 Kbps)

– 12.2 Kbps max.12.2 Kbps max.

– TTI: 20 msecTTI: 20 msec

– Transport Formats (TF) available:Transport Formats (TF) available:

TF RAB1 RAB2 RAB3TF RAB1 RAB2 RAB3

TF0v 0 x 81 0 x 103 0 x 60 (e.g., silence)TF0v 0 x 81 0 x 103 0 x 60 (e.g., silence)

TF1v 1 x 81 1 x 103 1 x 60 (e.g, active voice)TF1v 1 x 81 1 x 103 1 x 60 (e.g, active voice)

two other formats too (see Stds. Doc.)two other formats too (see Stds. Doc.)

– TFC: (TF0, TF0, TF0) e.g., during silenceTFC: (TF0, TF0, TF0) e.g., during silence

(TF1, TF1, TF1) e.g., during active voice periods(TF1, TF1, TF1) e.g., during active voice periods

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Transport Format (e.g., Data)

Interactive/Background Data (64 Kbps)Interactive/Background Data (64 Kbps)

– 64 Kbps max.64 Kbps max.

– TTI: 20 msecTTI: 20 msec

– Transport Block (TB) size = 336 bitsTransport Block (TB) size = 336 bits

– Transport Formats (TF) available:Transport Formats (TF) available:

» TF0 - 0 x 336TF0 - 0 x 336

» TF1 - 1 x 336TF1 - 1 x 336

» TF2 - 2 x 336TF2 - 2 x 336

» TF3 - 3 x 336TF3 - 3 x 336

» TF4 - 4 x 336 TF4 - 4 x 336

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Transport Format (Speech + Data)

Conversational speech (12 Kbps) + Conversational speech (12 Kbps) + Interactive/Background Data (64 Kbps)Interactive/Background Data (64 Kbps)

Voice TrCH Data TrCHVoice TrCH Data TrCH

TFC1: (TF0v, TF0v, TF0v) TF0dTFC1: (TF0v, TF0v, TF0v) TF0dTFC2: (TF0v, TF0v, TF0v) TF1dTFC2: (TF0v, TF0v, TF0v) TF1d

TFC3: (TF0v, TF0v, TF0v) TF2d TFC3: (TF0v, TF0v, TF0v) TF2d

TFC4: (TF0v, TF0v, TF0v) TF3dTFC4: (TF0v, TF0v, TF0v) TF3d







33

Multiplexing & Channel Coding

Data arrives at the coding/mux unit in transport block sets, Data arrives at the coding/mux unit in transport block sets, once every transmission time interval (TTI) once every transmission time interval (TTI)

TTI depends on the transport channel; {10, 20, 40, 80 ms})TTI depends on the transport channel; {10, 20, 40, 80 ms}) Main steps Main steps

– Add CRC to each blockAdd CRC to each block– transport block concatenation and block segmentationtransport block concatenation and block segmentation– channel codingchannel coding– first interleaving (per TTI)first interleaving (per TTI)– radio frame segmentation (when TTI > 10 ms)radio frame segmentation (when TTI > 10 ms)– rate matching (repetition or puncturing) rate matching (repetition or puncturing) – multiplexing of transport channels (CCTrCH)multiplexing of transport channels (CCTrCH)– insertion of DTX indication bitsinsertion of DTX indication bits– physical channel segmentationphysical channel segmentation– second interleaving (per radio frame, ie., among bits in 1 radio frame)second interleaving (per radio frame, ie., among bits in 1 radio frame)– mapping to physical channelmapping to physical channel

34

Multiplexing & Channel Coding (U/L)

CRC AttachmentTrBk Concatenation/

Code Block Segmentation

Channel Coding

Radio Frame Equalization

1st Interleaving

Radio Frame Segmentation

Rate Matching

CCTrCHCCTrCH



Channel Coding

Radio Frame Equalization

1st Interleaving


Rate Matching

TrCH-2TrCH-2

TrCH Multiplexing

Physical Channel Segmentation

2nd interleaving

TrCH-1TrCH-1

Physical Channel Mapping

PhCH#2PhCH#2 PhCH#1PhCH#1

35

Multiplexing & Channel Coding (..cntd)

Applicable to DCH, RACH, CPCH, DSCH, BCH, Applicable to DCH, RACH, CPCH, DSCH, BCH, FACH, PCHFACH, PCH

CRCCRC– add CRC to each transport block for error detectionadd CRC to each transport block for error detection

– CRC calculated on entire transport blockCRC calculated on entire transport block

– Size of CRC: 24, 16, 12, 8, 0 bitsSize of CRC: 24, 16, 12, 8, 0 bits

– what CRC size is used for each TrCH is signaled from what CRC size is used for each TrCH is signaled from higher layershigher layers

36


TrBk Concatenation & Code Block SegmentationTrBk Concatenation & Code Block Segmentation– all transport blocks in a TTI are concatenated all transport blocks in a TTI are concatenated

– if no. of bits in a TTI after concatenation (X) is greater than if no. of bits in a TTI after concatenation (X) is greater than the maximum size of the code block (in the channel coding the maximum size of the code block (in the channel coding block), then code block segmentation is done block), then code block segmentation is done

– max. size of the code block (Z) depends on whether max. size of the code block (Z) depends on whether » Convolutional code ( Z = 504 bits) orConvolutional code ( Z = 504 bits) or

» Turbo code ( Z = 5114 bits) is used for the TrCHTurbo code ( Z = 5114 bits) is used for the TrCH

– Code blocks after segmentation are of the same sizeCode blocks after segmentation are of the same size

– Filler bits (zeros) added to 1st coded block toFiller bits (zeros) added to 1st coded block to» to make integer number of code blocks, orto make integer number of code blocks, or» if X < 40 bits when Turbo code is usedif X < 40 bits when Turbo code is used

37


Channel CodingChannel Coding

Coding SchemeCoding Scheme Coding RateCoding RateType of TrCHType of TrCH

BCHBCH

PCHPCH

RACHRACH

DPCH, DCH, DPCH, DCH, DSCH, FACHDSCH, FACH

Convolutional Convolutional CodingCoding(constraint (constraint length = 9)length = 9)

Turbo CodingTurbo Coding 1/31/3

1/3, 1/21/3, 1/2

1/21/2

If number of coded blocks is greater than 1, they are If number of coded blocks is greater than 1, they are serially concatenatedserially concatenated

38


Radio Frame EqualizationRadio Frame Equalization– padding the input bit sequence in order to ensure that padding the input bit sequence in order to ensure that

the output can be segmented into data segments of the output can be segmented into data segments of equal sizeequal size

– I.e., number of bits per segment is same after radio I.e., number of bits per segment is same after radio frame equalization frame equalization

– performed only on the U/Lperformed only on the U/L

1st Interleaving1st Interleaving – block interleaver block interleaver

– among bits in a TTIamong bits in a TTI

39


Radio Frame SegmentationRadio Frame Segmentation– when TTI > 10 msec, input bit sequence is segmented when TTI > 10 msec, input bit sequence is segmented

and mapped on to Fi consecutive radio framesand mapped on to Fi consecutive radio frames

Rate MatchingRate Matching– means that bits on a transport channel are repeated or means that bits on a transport channel are repeated or

punctured punctured to ensure that the total bit rate after TrCH to ensure that the total bit rate after TrCH multiplexing is identical to the total channelmultiplexing is identical to the total channel bit rate bit rate of the allocated dedicated physical channels of the allocated dedicated physical channels

– higher layers assign a rate-matching (semi-static) higher layers assign a rate-matching (semi-static) attribute for each transport channelattribute for each transport channel

– this attribute is used to calculate the number of bits to this attribute is used to calculate the number of bits to repeat or puncture, spreading factor, number of PhCHs repeat or puncture, spreading factor, number of PhCHs needed, rate matching patternneeded, rate matching pattern

40


TrCH Multiplexing TrCH Multiplexing – every 10 msec, one radio frame from each TrCH is every 10 msec, one radio frame from each TrCH is

delivered to the TrCH multiplexingdelivered to the TrCH multiplexing

– these radio frames are serially concatenated into a these radio frames are serially concatenated into a coded composite transport channelcoded composite transport channel (CCTrCH) (CCTrCH)

Physical Channel SegmentationPhysical Channel Segmentation– when more than once PhCH is used, the physical when more than once PhCH is used, the physical

channel segmentation divides the bits among different channel segmentation divides the bits among different PhCHsPhCHs

2nd Interleaving2nd Interleaving– among bits within a radio frameamong bits within a radio frame

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Insertion of Discontinuous Transmission (DTX) Insertion of Discontinuous Transmission (DTX) Indication BitsIndication Bits– only on the D/Lonly on the D/L

– used to fill up the radio frame with bitsused to fill up the radio frame with bits

– insertion point depends on whether insertion point depends on whether fixed positions fixed positions (1st (1st Insertion)Insertion) or or flexible positions flexible positions (2nd Insertion)(2nd Insertion) of the of the TrCHs in the radio frame are usedTrCHs in the radio frame are used

– During connection setup, NW decides if fixed or flexible During connection setup, NW decides if fixed or flexible position is used for each CCTrCHposition is used for each CCTrCH

– DTX Indication bits are not transmitted; they only tell DTX Indication bits are not transmitted; they only tell when the Tx must be turned offwhen the Tx must be turned off

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Transport Format DetectionTransport Format Detection– TFCI Based DetectionTFCI Based Detection

– Explicit Blind DetectionExplicit Blind Detection» using receive power ratiousing receive power ratio

» by use of channel decoding and CRC checkby use of channel decoding and CRC check

– Guided DetectionGuided Detection» Explicit blind detection used on Guiding TrCHExplicit blind detection used on Guiding TrCH

» Guiding TrCH has the same TTI as the TrCH under Guiding TrCH has the same TTI as the TrCH under considerationconsideration

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Blind Transport Format DetectionBlind Transport Format Detection

– Using Received Power Ratio (for the case of 2 TFs)Using Received Power Ratio (for the case of 2 TFs)» Ratio of the power received on DPDCH (Pd) and DPCCH (Pc)Ratio of the power received on DPDCH (Pd) and DPCCH (Pc)

» Full Rate TF: if ratio Pd/Pc > threshold Full Rate TF: if ratio Pd/Pc > threshold

» Zero rate TF: if ratio Pd/Pc < thresholdZero rate TF: if ratio Pd/Pc < threshold

– Using CRC (for the case of multiple TFs)Using CRC (for the case of multiple TFs)

» Receiver knows only the possible TFs or end bit (thru’ L3 signaling) Receiver knows only the possible TFs or end bit (thru’ L3 signaling)

» Receiver performs FEC (Viterbi) decodingReceiver performs FEC (Viterbi) decoding

» path metric selection among the surviving paths in the decodingpath metric selection among the surviving paths in the decoding

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D/L Physical Channels

Dedicated D/L ChannelsDedicated D/L Channels– DPDCHDPDCH– DPCCHDPCCH

Common D/L ChannelsCommon D/L Channels– Common PIlot CHannel (CPICH)Common PIlot CHannel (CPICH)

» Primary CPICH Primary CPICH » Secondary CPICHSecondary CPICH

– Common Control Physical CHannel (CCPCH)Common Control Physical CHannel (CCPCH)» Primary CCPCH,Primary CCPCH,» Secondary CCPCHSecondary CCPCH

– Synchronization CHannel (SCH)Synchronization CHannel (SCH)» Primary SCH,Primary SCH,» Secondary SCHSecondary SCH

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Dedicated D/L Physical Channels

Dedicated Physical CHannel (D/L DPCH)Dedicated Physical CHannel (D/L DPCH)– transmits dedicated data generated at L2 and abovetransmits dedicated data generated at L2 and above– time-multiplexes with L1 control bits (Pilot, TPC, time-multiplexes with L1 control bits (Pilot, TPC,

TFCI)TFCI)

D/L DPCH D/L DPCH – Time-multiplex of a D/L DPDCH and a D/L DPCCHTime-multiplex of a D/L DPDCH and a D/L DPCCH

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DL Frame Structure

S0S0

10 msec frames divided into 15 slots10 msec frames divided into 15 slots

No. of bits in different DPDCH field (Npilot, Ntpc, Ntfci, Ndata1, No. of bits in different DPDCH field (Npilot, Ntpc, Ntfci, Ndata1,

Ndata2) are given in tablesNdata2) are given in tables

Which slot format to use is configured (and reconfigured) by Which slot format to use is configured (and reconfigured) by

higher layershigher layers

S1S1 S2S2 S3S3 S13S13 S14S14

1 Frame = 15 slots = 10 msec1 Frame = 15 slots = 10 msec

DATA 1DATA 1

1 time slot = 2/3 msec1 time slot = 2/3 msec

DPDCHDPDCH

PilotPilot

DPCCHDPCCH

TFCITFCITPCTPC DATA 2DATA 2

DPDCHDPDCH DPCCHDPCCH

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D/L Transmission

Multicode Transmission on D/LMulticode Transmission on D/L– Multicode transmission can be employed on the D/LMulticode transmission can be employed on the D/L– I.e., CCTrCH is mapped on to several parallel D/L I.e., CCTrCH is mapped on to several parallel D/L

DPCHs using the same spreading factorDPCHs using the same spreading factor– In this case, L1 control information is sent only on the In this case, L1 control information is sent only on the

first downlink DPCHfirst downlink DPCH

Multiple CCTrCHsMultiple CCTrCHs– In case there are several CCTrCHs mapped to different In case there are several CCTrCHs mapped to different

DPCHs transmitted to the same UE, different spreading DPCHs transmitted to the same UE, different spreading factors can be used on DPCHsfactors can be used on DPCHs

– multiple CCTrCHs feature for future releasemultiple CCTrCHs feature for future release

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WCDMA Transmission Rates (D/L)

System Chip Rate : 3.84 McpsSystem Chip Rate : 3.84 Mcps

Symbol Rates on DownlinkSymbol Rates on Downlink– Symb RateSymb Rate Chl bit rateChl bit rate SFSF

7.5 Ks/s7.5 Ks/s 15 Kb/s 512 15 Kb/s 512

15 Ks/s15 Ks/s 30 Kb/s 256 30 Kb/s 256

30 Ks/s30 Ks/s 60 Kb/s 128 60 Kb/s 128

60 Ks/s 120 Kb/s 64 60 Ks/s 120 Kb/s 64

120 Ks/s 240 Kb/s 32120 Ks/s 240 Kb/s 32

240 Ks/s 480 Kb/s 16 240 Ks/s 480 Kb/s 16

480 Ks/s 960 Kb/s 8 480 Ks/s 960 Kb/s 8

960 Ks/s 1920 Kb/s 4 960 Ks/s 1920 Kb/s 4

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Common D/L Physical Channels

Common Pilot CHannel (CPICH)Common Pilot CHannel (CPICH)– 30 Kbps fixed rate channel (SF = 256)30 Kbps fixed rate channel (SF = 256)– Primary CPICHPrimary CPICH

» Always uses the same channelization codeAlways uses the same channelization code» Scrambled by primary scrambling codeScrambled by primary scrambling code» There is one and only one P-CPICH per cellThere is one and only one P-CPICH per cell» Broadcast over the entire cellBroadcast over the entire cell» Provides a phase reference for several D/L channelsProvides a phase reference for several D/L channels

– Secondary CPICHSecondary CPICH» Uses an arbitrary channelization code of SF=256Uses an arbitrary channelization code of SF=256» Scrambled either by the primary or a secondary scrambling codeScrambled either by the primary or a secondary scrambling code» A cell may contain 0,1, or several S-CPICHA cell may contain 0,1, or several S-CPICH» Broadcast over entire OR part of a cellBroadcast over entire OR part of a cell» A S-CPICH can be a phase reference to some D/L channels A S-CPICH can be a phase reference to some D/L channels

(which is communicated to the UE thru’ higher layer signaling) (which is communicated to the UE thru’ higher layer signaling)

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Common Control Physical CHannel (CCPCH)Common Control Physical CHannel (CCPCH)– Primary CCPCH (P-CCPCH)Primary CCPCH (P-CCPCH)

» 30 Kbps fixed rate channel with SF=25630 Kbps fixed rate channel with SF=256» Carries BCH transport channel Carries BCH transport channel » No TPC, TFCI, pilot bits are sentNo TPC, TFCI, pilot bits are sent» the transport channel mapped to P-CCPCH (I.e., BCH) can the transport channel mapped to P-CCPCH (I.e., BCH) can

only have a fixed predefined TFC only have a fixed predefined TFC

– Secondary CCPCH (S-CCPCH)Secondary CCPCH (S-CCPCH)» Carries FACH and PCHCarries FACH and PCH» S-CCPCH can be with TFCI and without TFCI S-CCPCH can be with TFCI and without TFCI » NW decides if TFCI has to be sentNW decides if TFCI has to be sent» So UE should be (mandatory) capable of receiving with or So UE should be (mandatory) capable of receiving with or

without TFCI (i.e., blind)without TFCI (i.e., blind)» S-CCPCH can support multiple TFCs using TFCIS-CCPCH can support multiple TFCs using TFCI

– Main difference between CCPCHs and Dedicated Physical Main difference between CCPCHs and Dedicated Physical Channels : a CCPCH is NOT inner loop Power ControlledChannels : a CCPCH is NOT inner loop Power Controlled

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Synchronization CHannel (SCH)Synchronization CHannel (SCH)– Downlink signal used for cell searchDownlink signal used for cell search– Consists of Primary and Secondary subchannelsConsists of Primary and Secondary subchannels

– Primary SCHPrimary SCH» Uses Primary Sychronization Code (PSC), TX Uses Primary Sychronization Code (PSC), TX

once every slotonce every slot» PSC is the same for every cell in the systemPSC is the same for every cell in the system

– Secondary SCHSecondary SCH» Tx in parallel with Primary SCHTx in parallel with Primary SCH

» SSC indicates which of the code groups (64 SSC indicates which of the code groups (64 groups) the cell’s DL scrambling code belongs to groups) the cell’s DL scrambling code belongs to

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D/L Spreading

DL PhysicalDL PhysicalChannel dataChannel data CCd,SF,md,SF,m

Serial toSerial to ParallelParallelConv.Conv.

II

QQ

I+jQI+jQ

SSdl,ndl,n

jj

Channelisation code: - Differentiate users in a cellChannelisation code: - Differentiate users in a cell - OVSF- OVSF - UTRAN assigns channelisation codes to diff. phy. chls- UTRAN assigns channelisation codes to diff. phy. chlsScrambling Code: Differentiate cells Scrambling Code: Differentiate cells

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Scrambling Codes

# possible D/L scrambling codes = 2**18 -1 = 262143 # possible D/L scrambling codes = 2**18 -1 = 262143

Scrambling codes divided into 512 setsScrambling codes divided into 512 sets– 1 primary scrambling code and 15 secondary scrambling codes1 primary scrambling code and 15 secondary scrambling codes

– So, there are 512 x 16 = 8192 codes So, there are 512 x 16 = 8192 codes

Each cell is allocated one and only primary scrambling code Each cell is allocated one and only primary scrambling code – The primary CCPCH (Common Control Physical CHannel) is Tx The primary CCPCH (Common Control Physical CHannel) is Tx

always using this primary scrambling codealways using this primary scrambling code

– Other D/L physical channels can be Tx with either the PSC or SSC Other D/L physical channels can be Tx with either the PSC or SSC

from the set associated with the PSC of the cellfrom the set associated with the PSC of the cell

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Multiplexing & Channel Coding (D/L)



Channel Coding

Rate Matching

1st Insertion of DTX Indication

1st Interleaving


CCTrCHCCTrCH



Channel Coding

Rate Matching

1st Insertion of DTX Indication

1st Interleaving


TrCH-2TrCH-2

TrCH Multiplexing

Physical Channel Segmentation

2nd interleaving

TrCH-1TrCH-1

Physical Channel Mapping

PhCH#2PhCH#2 PhCH#1PhCH#1

2nd Insertion of DTX Indication

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Physical Channel MappingPhysical Channel Mapping

– on U/L: PhCHs are either completely filled or not on U/L: PhCHs are either completely filled or not used at all used at all

– on D/L: No bits in locations with DTX indication on D/L: No bits in locations with DTX indication » in compressed mode, no bits are mapped to certain slots in compressed mode, no bits are mapped to certain slots

in a PhCH. Reducing the SF by a factor of 2, 7.5 slots in a PhCH. Reducing the SF by a factor of 2, 7.5 slots per frame is used in compressed modeper frame is used in compressed mode

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Insertion of Discontinuous Transmission (DTX) Insertion of Discontinuous Transmission (DTX) Indication BitsIndication Bits– only on the D/Lonly on the D/L

– used to fill up the radio frame with bitsused to fill up the radio frame with bits

– insertion point depends on whether insertion point depends on whether fixed positions fixed positions (1st (1st Insertion)Insertion) or or flexible positions flexible positions (2nd Insertion)(2nd Insertion) of the of the TrCHs in the radio frame are usedTrCHs in the radio frame are used

– During connection setup, NW decides if fixed or flexible During connection setup, NW decides if fixed or flexible position is used for each CCTrCHposition is used for each CCTrCH

– DTX Indication bits are not transmitted; they only tell DTX Indication bits are not transmitted; they only tell when the Tx must be turned offwhen the Tx must be turned off

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WCDMA Physical Channels

P-CCPCHP-CCPCHS-CCPCHS-CCPCH

DPDCHDPDCH

DPCCHDPCCHPDSCHPDSCHPCPCHPCPCHPRACHPRACH BSBSUEUE

AICHAICHP-SCHP-SCH

S-SCHS-SCHCSICHCSICH

CPICHCPICHPICHPICH

CD/CA-ICHCD/CA-ICH

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Channel Mapping on the U/L

CCCH DTCH DCCH

RACH DCH CPCH

PRACH DPDCH DPCCH PCPCH

LogicalLogicalChannelsChannels

TransportTransportChannelsChannels

PhysicalPhysicalChannelsChannels

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Channel Mapping on the D/L

BCCH PCCH CTCH CCCH DCCH DTCH

BCH PCH FACH DCH DSCH

P-CCPCH S-CCPCH DPDCH DPCCH PDSCH

LogicalLogicalChannelsChannels

TransportTransportChannelsChannels

PhysicalPhysicalChannelsChannels

WCDMA Physical Layer Design

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