Wcdma physical layer

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  • 1. WCDMA Physical Layer Design A. Chockalingam Assistant Professor Indian Institute of Science, Bangalore-12 [email_address] http://ece.iisc.ernet.in/~achockal
  • 2. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Outline
    • WCDMA Network Architecture
    • WCDMA Physical Layer
      • Physical / Transport / Logical Channels
      • Uplink
        • Spreading - Channelisation / Scrambling
        • Transport Formats and Configuration
        • Multiplexing and Channel Coding
      • Downlink
        • Spreading / Scrambling / Channelisation
        • Multiplexing and Channel Coding
  • 3. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore 2G to 3G Evolution IS-95A IS-95B cdma2000 IMT2000 IMT2000: ITU’s Standardization Effort towards 3G (IMT-2000 previously termed as FPLMTS) UMTS: European Effort (Specified by 3G Partnership Project 3GPP) GSM GPRS WCDMA EDGE D A T A I S 9 9
  • 4. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore UMTS NW Model USIM Mobile Equipment Access Network Serving Network PS/CS Transit Network Cu Uu Iu Yu User Equipment Access Network Core Network Infrastructure Home Network Access Stratum (Protocols between UE and Access NW) Non-access Stratum (Protocols between UE and Core NW) Zu Stratum: Refers to a way of grouping protocols handling activities
  • 5. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore 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 Uu Iu Iur Iub
  • 6. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore WCDMA System Features
    • UTRA FDD mode and TDD mode
    • UTRA FDD features
      • Multiple Access: CDMA
      • Channel Spacing: 5 MHz
      • Chip Rate: 3.84 Mcps
      • Frame Length: 10 msec
      • Time Slots: 15 slots per 10 msec frame
      • Spreading Factor: 4 to 512
      • Multi-rate: Through Multi-code or
      • Orthogonal Variable Spreading
  • 7. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore UTRA FDD Features
      • FEC Codes: Rate 1/2, 1/3 convolutional code
      • with constraint length K = 9
      • Rate 1/3, 8-state Turbo coding
      • Interleaving: Intra- or Inter-frame interleaving
      • (10, 20 40, 80 msec)
      • Modulation: QPSK
      • Detection: Coherent based on pilot symbols
      • Micro diversity: RAKE in BS and UE
      • Power Control: Fast closed-loop at 1500 Hz rate
      • Intra-frequency HO: Soft / Softer Handover
      • Inter-frequency HO: Hard Handover
      • Interference Cancellation: Support for multiuser detection
  • 8. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Radio Interface Protocol Model PHY MAC RLC Transport Channels Logical Channels User Plane Radio Bearers Signalling Radio Bearers PDCP BMC RRC USER PLANE CONTROL PLANE Control L1 (Radio Physical Layer) L2 (Radio Link Layer) L3 (Radio Network Layer) U-Plane Radio Bearers
  • 9. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore WCDMA Radio Channels
    • Physical Channels
      • Transmission media.
      • Two types of physical channels defined in L1; FDD and TDD.
      • FDD is characterized by frequency, code, I/Q phase
      • Follow a layered structure of “radio frames” and “time slots”
    • Transport Channels
      • describes the way information is transferred over the radio interface
    • Logical Channels
      • the type of information transferred characterizes a logical channel
    UE BS RNC Logical Channels Transport Channels Physical Channels
  • 10. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Physical Channels
    • Corresponds to a specific carrier frequency, code, relative phase in I and Q branches
    • Dedicated and Common Physical Channels
    • Layered structure of radio frames and time slots
    • A radio frame = 10 msec = 15 slots/frame
    • 1 frame = 38400 chips, 1 slot = 2560 chips
    • Slot configuration varies depending on the channel bit rate of the physical channel
      • # bits/slot different for different physical channels
      • may vary with time (on a frame by frame basis)
  • 11. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore U/L Physical Channels
    • Dedicated U/L Channels
      • DPDCH
      • DPCCH
    • Common U/L Channels
      • PRACH
        • Preamble part
        • Message part
      • PCPCH
        • Preamble part
        • Message part
  • 12. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Dedicated U/L Physical Channels
    • Two types
      • Dedicated Physical Data CHannel (DPDCH)
      • Dedicated Physical Control CHannel (DPCCH)
      • Both are I/Q code multiplexed within each radio frame
    • U/L DPDCH carries the DCH transport channel
    • U/L DPCCH carries L1 control bits such as
      • Pilot bits (to enable channel estimation for coherent detection at BS)
      • Transmit power control (TPC) commands
      • Feedback Information (FBI)
        • used for CL transmit diversity and Site Selection Diversity Transmission (SDTC)
      • Transport Format Combination Indicator (TFCI)
        • for several simultaneous services. Informs the rx of the transport format combination of the transport channels mapped to DPDCH
  • 13. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore U/L Frame Structure
    • There is only one U/L DPCCH on each radio link
    • There can be 0, 1, or several DPDCHs on each radio link
    • 10 msec frames divided into 15 slots
    S0 S1 S2 S3 S13 S14 1 Frame = 15 slots = 10 msec DATA 1 time slot = 2/3 msec DPDCH (on I-Chl) Pilot DPCCH (on Q-Chl) TFCI FBI TPC 10 bits = 2560 chips => SF = 256 (N data bits)
  • 14. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore I, Q Spreading for DPDCH, DPCCH DPDCH-1 DPDCH-3 C d,1 C d,3 B d B d I DPDCH-2 DPCCH-2 C d,2 C c B c B d Q I+jQ S dpch,n C c, C d,n: Channelization codes Sdpch,n: Scrambling code B d, B c: Gain factors Up to 6 DPDCHs in parallel j
  • 15. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore WCDMA Transmission Rates (U/L)
    • System Chip Rate : 3.84 Mcps
    • Symbol Rates on Uplink
      • Chl Symb Rate Chl Bit Rate SF Bits/frame N data
      • 15 Ks/s 15 Kb/s 256 150 10
      • 30 Ks/s 30 Kb/s 128 300 20
      • 60 Ks/s 60 Kb/s 64 600 40
      • 120 Ks/s 120 Kb/s 32 1200 80
      • 240 Ks/s 240 Kb/s 16 2400 160
      • 480 Ks/s 480 Kb/s 8 4800 320
      • 960 Ks/s 960 Kb/s 4 9600 640
  • 16. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore WCDMA Channelisation Codes
    • Orthogonal codes
    • Used for channel separation both in U/L and D/L directions
    • Can have different spreading factor values (thus support different symbol rates)
    • C ch,SF,k : SF - Spreading Factor, k is the code number 0<=k<= SF-1
    • Spreading factor value indicates how many bits of those codes are used in a connection
  • 17. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore U/L Channelization Codes
    • Orthogonal Variable Spreading Factor (OVSF)
    • channelization codes
    • Separates data / control channels from same UE
    • Preserves 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) SF=1 SF=2 SF=4 C(SF,k) SF: Spreading Factor k: code number 0<k<=SF-1
  • 18. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore U/L Scrambling Codes
    • Use complex valued scrambling code
    • Long scrambling sequences (2^24)
      • Gold sequences (linear combination of two m-sequences)
    • Short scrambling sequences (2^24)
      • from a family sequence of periodically extended S(2) codes
    • Long or short sequences for DPCCH / DPDCH
    • Only long sequences for message parts of PRACH and PCPCH
  • 19. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore WCDMA Code Types
    • Scrambling Codes, Channelisation Codes
    • Uplink Downlink
    • Scrambling codes User separation Cell separation
    • Channelisation Data and Control Users within a
    • codes channels from the cell
    • same terminal
    • Spreading code = Scrambling code x Channelisation code
  • 20. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Common U/L Physical Channels
    • Two Types
      • Physical Random Access CHannel (PRACH)
      • Physical Common Packet CHannel (PCPCH)
    • Physical Random Access CHannel (PRACH)
      • carries RACH
      • Uses S-ALOHA technique with fast Acquisition Indication
      • Access slots (15 access slots per 2 frames)
      • RA transmission consists of
        • several 4096 chip preambles (uses 256 repetitions of 16 chips signature sequence) and 1or 2 frame message
    Preamble Message Part (1 or 2 frames) 4096 Chips Preamble
  • 21. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Random Access UE BS PRACH: Preamble sent (initial access) No detection on AICH PRACH: Preamble sent (initial access) AICH: Preamble sent detected PRACH: Random Access Info sent
  • 22. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Common U/L Physical Channels
    • Physical Common Packet CHannel (PCPCH)
      • Carries CPCH
      • CPCH is based on DSMA-CD technique with fast Acquisition Indication
      • Access slot timing and structure are identical to those defined for RACH
      • Transmission consists of
        • Access preamble(s) - one or several each 4096 chips
        • Collision Detection preamble
        • DPCCH Power Control Preamble (0 or 8 slots)
        • Message of variable length (Nx10 msec)
      • PCPCH good for carrying small sized bursty data
  • 23. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Transport Formats / Configurations
    • Transport Block (TB)
        • Basic unit of data exchanged between L1 & MAC for L1 processing
    • Transport Block Size: Number of bits in a TB.
    • Transport Block Set (TBS)
        • A set of TBs exchanged between L1 and MAC at the same time instant using the same transport channel
    • Transport Block Set Size: Number of bits in a TBS
    • Transmission Time Interval (TTI)
        • Periodicity at which a TBS is transferred by the physical layer on to the radio interface - {10, 20, 40, 80 ms}
        • MAC delivers one TBS to the physical layer every TTI
  • 24. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Transport Formats / Configurations
    • Transport Format (TF)
      • Format offered by L1 to MAC (and vice versa) for the delivery of a
      • TBS during a TTI on a given transport channel (TrCH)
      • Dynamic part (TB size, TBS size)
      • Semi-static part (TTI, type/rate of coding,size of CRC)
      • TB size, TBS size, TTI define the TrCH bit rate before L1 processing
        • e.g., TB size = 336 bits (320 bit payload + 16 bits RLC header)
        • TBS size = 2 TBs per TTI, TTI = 10 ms
        • DCH Bit rate (with RLC header) = 336*2/10 = 67.2 Kbps
        • User Bit rate (without RLC header) = 320*2/10 = 64 Kbps
      • Variable bit rate can be achieved by changing ( between TTIs )
      • either the TBS size only, or both the TB size and TBS Size
    • Transport Format Set (TFS)
      • a set of TFs associated with a TrCH
      • semi-static part of all TFs in a TFS is the same
  • 25. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Transport Formats / Configurations
    • Transport Format Combination (TFC)
        • Multiple TrCHs each having a TF
        • Authorized combination of the currently valid TFs that can be submitted to L1 on a CCTrCH , containing one TF from each TrCH
    • Transport Format Combination Set (TFCS)
        • A set of TFCs on a CCTrCH. Produced by RNC
        • TFCS is given to MAC by L3 for control
        • MAC chooses between the different TFCs specified in the TFCS
        • 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 control
        • Bit rate can be changed quickly by MAC with no need to L3 signaling
    • Transport Format Indicator (TFI)
        • A label for a specific TF within a TFS. Used between MAC and L1
    • Transport Format Combination Indicator (TFCI)
        • Used to inform the receiving side of the currently valid TFC
  • 26. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Transport Formats / Configurations TTI TTI TTI TTI TTI TTI TB DCH1 DCH2 TB TB TB TB TB TB Transport Block Set (TBS) TB TB Transport Format (TF) Transport Format Set (TFS) Transport Format Combination (TFC) Transport Format Combination Set (TFCS)
  • 27. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore TFI and TFCI (Transmitter) Transport Chl 1 Transport Chl 2 Transport Block Transport Block Transport Block Transport Block TFI TFI TFCI Coding and Multiplexing Physical Layer Higher Layer DPCCH (Q-Chl) DPDCH (I-Chl) Physical Control Chl Physical Data Chl E.g: Two transport channels mapped to a single physical channel This dotted line represents the Iur interface in case of NW side
  • 28. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore TFI and TFCI (Receiver) Transport Chl 1 Transport Chl 2 Transport Block & EI Transport Block & EI Transport Block & EI Transport Block & EI TFI TFI TFCI Decode Decoding and Demultiplexing Physical Layer Higher Layer DPCCH (Q-Chl) DPDCH (I-Chl) EI: Error Indication Physical Control Chl Physical Data Chl
  • 29. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore TFI and TFCI
    • Each transport channel is accompanied by a TFI at each time event at which data is expected to arrive from HL
    • Physical layer combines the TFI info from different
    • transport channels to the TFCI
    • TFCI is sent on the DPCCH to inform the receiver about
    • the instantaneous transport format combination of the
    • transport channels mapped to the U/L DPDCH
    • transmitted simultaneously
  • 30. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Transport Format (e.g., Speech)
    • Conversational Speech (12 Kbps)
      • 12.2 Kbps max.
      • TTI: 20 msec
      • Transport Formats (TF) available:
      • TF RAB1 RAB2 RAB3
      • 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)
      • two other formats too (see Stds. Doc.)
      • TFC: (TF0, TF0, TF0) e.g., during silence
      • (TF1, TF1, TF1) e.g., during active voice periods
  • 31. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Transport Format (e.g., Data)
    • Interactive/Background Data (64 Kbps)
      • 64 Kbps max.
      • TTI: 20 msec
      • Transport Block (TB) size = 336 bits
      • Transport Formats (TF) available:
        • TF0 - 0 x 336
        • TF1 - 1 x 336
        • TF2 - 2 x 336
        • TF3 - 3 x 336
        • TF4 - 4 x 336
  • 32. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Transport Format (Speech + Data)
    • Conversational speech (12 Kbps) + Interactive/Background Data (64 Kbps)
      • Voice TrCH Data TrCH
      • TFC1: (TF0v, TF0v, TF0v) TF0d
      • TFC2: (TF0v, TF0v, TF0v) TF1d
      • TFC3: (TF0v, TF0v, TF0v) TF2d
      • TFC4: (TF0v, TF0v, TF0v) TF3d
      • TFC5: (TF0v, TF0v, TF0v) TF4d
      • TFC6: (TF1v, TF1v, TF1v) TF0d
      • TFC7: (TF1v, TF1v, TF1v) TF1d
      • TFC8: (TF1v, TF1v, TF1v) TF2d
      • TFC9: (TF1v, TF1v, TF1v) TF3d
      • TFC10: (TF1v, TF1v, TF1v) TF4d
  • 33. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Multiplexing & Channel Coding
    • Data arrives at the coding/mux unit in transport block sets, once every transmission time interval (TTI)
    • TTI depends on the transport channel; {10, 20, 40, 80 ms})
    • Main steps
      • Add CRC to each block
      • transport block concatenation and block segmentation
      • channel coding
      • first interleaving (per TTI)
      • radio frame segmentation (when TTI > 10 ms)
      • rate matching (repetition or puncturing)
      • multiplexing of transport channels (CCTrCH)
      • insertion of DTX indication bits
      • physical channel segmentation
      • second interleaving (per radio frame, ie., among bits in 1 radio frame)
      • mapping to physical channel
  • 34. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Multiplexing & Channel Coding (U/L) CRC Attachment TrBk Concatenation/ Code Block Segmentation Channel Coding Radio Frame Equalization 1st Interleaving Radio Frame Segmentation Rate Matching CCTrCH CRC Attachment TrBk Concatenation/ Code Block Segmentation Channel Coding Radio Frame Equalization 1st Interleaving Radio Frame Segmentation Rate Matching TrCH-2 TrCH Multiplexing Physical Channel Segmentation 2nd interleaving TrCH-1 Physical Channel Mapping PhCH#2 PhCH#1
  • 35. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Multiplexing & Channel Coding (..cntd)
    • Applicable to DCH, RACH, CPCH, DSCH, BCH, FACH, PCH
    • CRC
      • add CRC to each transport block for error detection
      • CRC calculated on entire transport block
      • Size of CRC: 24, 16, 12, 8, 0 bits
      • what CRC size is used for each TrCH is signaled from higher layers
  • 36. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Multiplexing & Channel Coding (..cntd)
    • TrBk Concatenation & Code Block Segmentation
      • all transport blocks in a TTI are concatenated
      • if no. of bits in a TTI after concatenation (X) is greater than the maximum size of the code block (in the channel coding block), then code block segmentation is done
      • max. size of the code block (Z) depends on whether
        • Convolutional code ( Z = 504 bits) or
        • Turbo code ( Z = 5114 bits) is used for the TrCH
      • Code blocks after segmentation are of the same size
      • Filler bits (zeros) added to 1st coded block to
        • to make integer number of code blocks, or
        • if X < 40 bits when Turbo code is used
  • 37. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Multiplexing & Channel Coding (..cntd)
    • Channel Coding
    Coding Scheme Coding Rate Type of TrCH BCH PCH RACH DPCH, DCH, DSCH, FACH Convolutional Coding (constraint length = 9) Turbo Coding 1/3 1/3, 1/2 1/2 If number of coded blocks is greater than 1, they are serially concatenated
  • 38. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Multiplexing & Channel Coding (..cntd)
    • Radio Frame Equalization
      • padding the input bit sequence in order to ensure that the output can be segmented into data segments of equal size
      • I.e., number of bits per segment is same after radio frame equalization
      • performed only on the U/L
    • 1st Interleaving
      • block interleaver
      • among bits in a TTI
  • 39. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Multiplexing & Channel Coding (..cntd)
    • Radio Frame Segmentation
      • when TTI > 10 msec, input bit sequence is segmented and mapped on to Fi consecutive radio frames
    • Rate Matching
      • means that bits on a transport channel are repeated or punctured to ensure that the total bit rate after TrCH multiplexing is identical to the total channel bit rate of the allocated dedicated physical channels
      • higher layers assign a rate-matching (semi-static) attribute for each transport channel
      • this attribute is used to calculate the number of bits to repeat or puncture, spreading factor, number of PhCHs needed, rate matching pattern
  • 40. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Multiplexing & Channel Coding (..cntd)
    • TrCH Multiplexing
      • every 10 msec, one radio frame from each TrCH is delivered to the TrCH multiplexing
      • these radio frames are serially concatenated into a coded composite transport channel (CCTrCH)
    • Physical Channel Segmentation
      • when more than once PhCH is used, the physical channel segmentation divides the bits among different PhCHs
    • 2nd Interleaving
      • among bits within a radio frame
  • 41. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Multiplexing & Channel Coding (..cntd)
    • Insertion of Discontinuous Transmission (DTX) Indication Bits
      • only on the D/L
      • used to fill up the radio frame with bits
      • insertion point depends on whether fixed positions (1st Insertion) or flexible positions (2nd Insertion) of the TrCHs in the radio frame are used
      • During connection setup, NW decides if fixed or flexible position is used for each CCTrCH
      • DTX Indication bits are not transmitted; they only tell when the Tx must be turned off
  • 42. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Multiplexing & Channel Coding (..cntd)
    • Transport Format Detection
      • TFCI Based Detection
      • Explicit Blind Detection
        • using receive power ratio
        • by use of channel decoding and CRC check
      • Guided Detection
        • Explicit blind detection used on Guiding TrCH
        • Guiding TrCH has the same TTI as the TrCH under consideration
  • 43. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Multiplexing & Channel Coding (..cntd)
    • Blind Transport Format Detection
      • Using Received Power Ratio (for the case of 2 TFs)
        • Ratio of the power received on DPDCH (Pd) and DPCCH (Pc)
        • Full Rate TF: if ratio Pd/Pc > threshold
        • Zero rate TF: if ratio Pd/Pc < threshold
      • Using CRC (for the case of multiple TFs)
        • Receiver knows only the possible TFs or end bit (thru’ L3 signaling)
        • Receiver performs FEC (Viterbi) decoding
        • path metric selection among the surviving paths in the decoding
  • 44. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore D/L Physical Channels
    • Dedicated D/L Channels
      • DPDCH
      • DPCCH
    • Common D/L Channels
      • Common PIlot CHannel (CPICH)
        • Primary CPICH
        • Secondary CPICH
      • Common Control Physical CHannel (CCPCH)
        • Primary CCPCH,
        • Secondary CCPCH
      • Synchronization CHannel (SCH)
        • Primary SCH,
        • Secondary SCH
  • 45. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Dedicated D/L Physical Channels
    • Dedicated Physical CHannel (D/L DPCH)
      • transmits dedicated data generated at L2 and above
      • time-multiplexes with L1 control bits (Pilot, TPC, TFCI)
    • D/L DPCH
      • Time-multiplex of a D/L DPDCH and a D/L DPCCH
  • 46. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore DL Frame Structure S0
    • 10 msec frames divided into 15 slots
    • No. of bits in different DPDCH field (Npilot, Ntpc, Ntfci, Ndata1, Ndata2) are given in tables
    • Which slot format to use is configured (and reconfigured) by higher layers
    S1 S2 S3 S13 S14 1 Frame = 15 slots = 10 msec DATA 1 1 time slot = 2/3 msec DPDCH Pilot DPCCH TFCI TPC DATA 2 DPDCH DPCCH
  • 47. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore D/L Transmission
    • Multicode Transmission on D/L
      • Multicode transmission can be employed on the D/L
      • I.e., CCTrCH is mapped on to several parallel D/L DPCHs using the same spreading factor
      • In this case, L1 control information is sent only on the first downlink DPCH
    • Multiple CCTrCHs
      • In case there are several CCTrCHs mapped to different DPCHs transmitted to the same UE, different spreading factors can be used on DPCHs
      • multiple CCTrCHs feature for future release
  • 48. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore WCDMA Transmission Rates (D/L)
    • System Chip Rate : 3.84 Mcps
    • Symbol Rates on Downlink
      • Symb Rate Chl bit rate SF
      • 7.5 Ks/s 15 Kb/s 512
      • 15 Ks/s 30 Kb/s 256
      • 30 Ks/s 60 Kb/s 128
      • 60 Ks/s 120 Kb/s 64
      • 120 Ks/s 240 Kb/s 32
      • 240 Ks/s 480 Kb/s 16
      • 480 Ks/s 960 Kb/s 8
      • 960 Ks/s 1920 Kb/s 4
  • 49. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Common D/L Physical Channels
    • Common Pilot CHannel (CPICH)
      • 30 Kbps fixed rate channel (SF = 256)
      • Primary CPICH
        • Always uses the same channelization code
        • Scrambled by primary scrambling code
        • There is one and only one P-CPICH per cell
        • Broadcast over the entire cell
        • Provides a phase reference for several D/L channels
      • Secondary CPICH
        • Uses an arbitrary channelization code of SF=256
        • Scrambled either by the primary or a secondary scrambling code
        • A cell may contain 0,1, or several S-CPICH
        • Broadcast over entire OR part of a cell
        • A S-CPICH can be a phase reference to some D/L channels (which is communicated to the UE thru’ higher layer signaling)
  • 50. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Common D/L Physical Channels
    • Common Control Physical CHannel (CCPCH)
      • Primary CCPCH (P-CCPCH)
        • 30 Kbps fixed rate channel with SF=256
        • Carries BCH transport channel
        • No TPC, TFCI, pilot bits are sent
        • the transport channel mapped to P-CCPCH (I.e., BCH) can only have a fixed predefined TFC
      • Secondary CCPCH (S-CCPCH)
        • Carries FACH and PCH
        • S-CCPCH can be with TFCI and without TFCI
        • NW decides if TFCI has to be sent
        • So UE should be (mandatory) capable of receiving with or without TFCI (i.e., blind)
        • S-CCPCH can support multiple TFCs using TFCI
      • Main difference between CCPCHs and Dedicated Physical Channels : a CCPCH is NOT inner loop Power Controlled
  • 51. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Common D/L Physical Channels
    • Synchronization CHannel (SCH)
      • Downlink signal used for cell search
      • Consists of Primary and Secondary subchannels
      • Primary SCH
        • Uses Primary Sychronization Code (PSC), TX once every slot
        • PSC is the same for every cell in the system
      • Secondary SCH
        • Tx in parallel with Primary SCH
        • SSC indicates which of the code groups (64 groups) the cell’s DL scrambling code belongs to
  • 52. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore D/L Spreading DL Physical Channel data C d,SF,m Serial to Parallel Conv. I Q I+jQ S dl,n j Channelisation code: - Differentiate users in a cell - OVSF - UTRAN assigns channelisation codes to diff. phy. chls Scrambling Code: Differentiate cells
  • 53. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Scrambling Codes
    • # possible D/L scrambling codes = 2**18 -1 = 262143
    • Scrambling codes divided into 512 sets
      • 1 primary scrambling code and 15 secondary scrambling codes
      • So, there are 512 x 16 = 8192 codes
    • Each cell is allocated one and only primary scrambling code
      • The primary CCPCH (Common Control Physical CHannel) is Tx always using this primary scrambling code
      • Other D/L physical channels can be Tx with either the PSC or SSC from the set associated with the PSC of the cell
  • 54. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Multiplexing & Channel Coding (D/L) CRC Attachment TrBk Concatenation/ Code Block Segmentation Channel Coding Rate Matching 1st Insertion of DTX Indication 1st Interleaving Radio Frame Segmentation CCTrCH CRC Attachment TrBk Concatenation/ Code Block Segmentation Channel Coding Rate Matching 1st Insertion of DTX Indication 1st Interleaving Radio Frame Segmentation TrCH-2 TrCH Multiplexing Physical Channel Segmentation 2nd interleaving TrCH-1 Physical Channel Mapping PhCH#2 PhCH#1 2nd Insertion of DTX Indication
  • 55. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Multiplexing & Channel Coding (..cntd)
    • Physical Channel Mapping
      • on U/L: PhCHs are either completely filled or not
      • used at all
      • on D/L: No bits in locations with DTX indication
        • in compressed mode, no bits are mapped to certain slots in a PhCH. Reducing the SF by a factor of 2, 7.5 slots per frame is used in compressed mode
  • 56. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Multiplexing & Channel Coding (..cntd)
    • Insertion of Discontinuous Transmission (DTX) Indication Bits
      • only on the D/L
      • used to fill up the radio frame with bits
      • insertion point depends on whether fixed positions (1st Insertion) or flexible positions (2nd Insertion) of the TrCHs in the radio frame are used
      • During connection setup, NW decides if fixed or flexible position is used for each CCTrCH
      • DTX Indication bits are not transmitted; they only tell when the Tx must be turned off
  • 57. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore WCDMA Physical Channels P-CCPCH S-CCPCH DPDCH DPCCH PDSCH PCPCH PRACH BS UE AICH P-SCH S-SCH CSICH CPICH PICH CD/CA-ICH
  • 58. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Channel Mapping on the U/L CCCH DTCH DCCH RACH DCH CPCH PRACH DPDCH DPCCH PCPCH Logical Channels Transport Channels Physical Channels
  • 59. Dr. A. Chockalingam Dept of ECE, IISc, Bangalore Channel Mapping on the D/L BCCH PCCH CTCH CCCH DCCH DTCH BCH PCH FACH DCH DSCH P-CCPCH S-CCPCH DPDCH DPCCH PDSCH Logical Channels Transport Channels Physical Channels