Introductions to WCDMA FDD Mode Physical Layer

Transcription

1 Wireless Information Transmission System Lab. Introductions to WCDMA FDD Mode Physical Layer Institute of Communications Engineering National Sun Yat-sen University

2 Table of Contents Traditional Sequential ASIC Design Flow WCDMA Network Architecture Physical Layer General Description Multiplexing and Channel Coding (MCC) WCDMA Uplink Physical Layer WCDMA Downlink Physical Layer Compressed Mode Site Selection Transmit Diversity 2

3 References 3GPP Technical Specification (Release 999, 25 Series) WCDMA for UMTS Radio Access For Third Generation Mobile Communications -- by Harri Holma and Antti Toskala, Artech House, 2 Wireless Communications - Principles & Practice -- by Theodore S. Rappaport, Prentice Hall, 2nd Edition, Dec. 3, 2 WCDMA Requirements and Practical Design -- by Rudolf Tanner and Jason Woodard, John Wiley & Sons, Ltd, March 25. 3

4 Communications Hardware Design Flow System Specifications Floating Point Simulation Fixed Point Simulation RTL Coding Function Verification. Perfect Receiver 2. Synchronization 3. Channel Estimation 4. Channel Decoding 5. De-Interleaving 6. Performance should meet system requirements.. Hardware cost limits precision of received signal. 2. Hardware architecture should be considered. 3. Performance is worse than floating point simulation.. RTL:Register Transfer Level 2. Verilog/VHDL 4

5 Wireless Information Transmission System Lab. WCDMA Network Architecture Institute of Communications Engineering National Sun Yat-sen University

6 Network Elements in a WCDMA PLMN Uu Iu Node B USIM RNC MSC/VLR GMSC PLMN, PSTN ISDN, etc. Node B Cu Iub Iur HLR Node B ME RNC SGSN GGSN Internet Node B UE UTRAN Core Network External Networks PLMN: Public Land Mobile Network. One PLMN is operated by a single operator. 6

7 User Equipment (UE) The UE consists of two parts: The Mobile Equipment (ME) is the radio terminal used for radio communication over the Uu interface. The UMTS Subscriber Identity Module (USIM) is a smartcard that holds the subscriber identity, performs authentication algorithms, and stores authentication and encryption keys and some subscription information that is needed at the terminal. UTRAN consists of two distinct elements: The Node B converts the data flow between the Iub and Uu interfaces. It also participates in radio resource management. The Radio Network Controller (RNC) owns and controls the radio resources in its domain (the Node Bs connected to it). RNC is the service access point for all services UTRAN provides the core network (CN). 7

8 WCDMA System Architecture UMTS system utilizes the same well-known architecture that has been used by all main 2nd generation systems. The network elements are grouped into: The Radio Access Network (RAN, UMTS Terrestrial RAN = UTRAN) that handles all radio-related functionality. The Core Network (CN) which is responsible for switching and routing calls and data connections to external networks. Both User Equipment (UE) and UTRAN consist of completely new protocols, which is based on the new WCDMA radio technology. The definition of CN is adopted from GSM. 8

9 Main Elements of the GSM Core Network HLR (Home Location Register) is a database located in the user s home system that stores the master copy of the user s service profile. The service profile consists of, for example, information on allowed services, forbidden roaming areas, and Supplementary Service information such as status of call forwarding and the call forwarding number. It is created when a new user subscribes to the system. HLR stores the UE location on the level of MSC/VLR and/or SGSN. 9

10 Main Elements of the GSM Core Network MSC/VLR (Mobile Services Switching Center / Visitor Location Register) is the switch (MSC) and database (VLR) that serves the UE in its current location for circuit switched services. The MSC function is used to switch the CS transactions. The VLR function holds a copy of the visiting user s service profile, as well as more precise information on the UE s location within the serving system.

11 Main Elements of the GSM Core Network GMSC (Gateway MSC) is the switch at the point where UMTS PLMN is connected to external CS networks. All incoming and outgoing circuit switched connections go through GMSC. SGSN (Serving GPRS (General Packet Radio Service) Support Node) functionality is similar to that of MSC/VLR, but is typically used for Packet Switched (PS) services. GGSN (Gateway GPRS Support Node) functionality is close to that of GMSC but is in relation to PS services.

12 Interfaces Cu Interface: this is the electrical interface between the USIM smartcard and the ME. The interface follows a standard format for smartcards. Uu Interface: this is the WCDMA radio interface, which is the subject of the main part of WCDMA technology. This is also the most important open interface in UMTS. Iu Interface: this connects UTRAN to the CN. Iur Interface: the open Iur interface allows soft handover between RNCs from different manufacturers. Iub Interface: the Iub connects a Node B and an RNC. UMTS is the first commercial mobile telephony system where the Controller-Base Station interface is standardized as a fully open interface. 2

13 Wireless Information Transmission System Lab. WCDMA Physical Layer General Description (3G TS 25.2) Institute of Communications Engineering National Sun Yat-sen University

14 3GPP RAN Specifications TS 25.2 Physical Layer general description Describes the contents of the layer documents (TS 25.2 series); where to find information; a general description of layer. TS 25.2 Physical channels and mapping of transport channels onto physical channels (FDD) Establishes the characteristics of the layer- transport channels and physical channels in the FDD mode, and specifies: Transport channels Physical channels and their structure Relative timing between different physical channels in the same link, and relative timing between uplink and downlink; Mapping of transport channels onto the physical channels. 4

15 3GPP RAN Specifications TS TS Multiplexing and Channel Coding (FDD) Spreading and Modulation (FDD) Describes multiplexing, channel coding, and interleaving in the FDD mode and specifies: Coding and multiplexing of transport channels; Channel coding alternatives; Coding for layer control information; Different interleavers; Rate matching; Physical channel segmentation and mapping; Establishes the characteristics of the spreading and modulation in the FDD mode, and specifies: Spreading; Generation of channelization and scrambling codes; Generation of random access preamble codes; Generation of synchronization codes; Modulation; 5

16 3GPP RAN Specifications TS Physical Layer Procedures (FDD) Establishes the characteristics of the physical layer procedures in the FDD mode, and specifies: Cell search procedures; Power control procedures; Random access procedure. TS Physical Layer Measurements (FDD) Establishes the characteristics of the physical layer measurements in the FDD mode, and specifies: The measurements performance by layer ; Reporting of measurements to higher layers and network; Handover measurements and idle-mode measurements. 6

17 General Protocol Architecture Radio interface means the Uu point between User Equipment (UE) and network. The radio interface is composed of Layers, 2 and 3. Layer 3 Radio Resource Control (RRC) Layer 2 Control / Measurements Medium Access Control Logical channels Transport channels Layer Physical layer 7

18 General Protocol Architecture The circles between different layer/sub-layers indicate Service Access Points (SAPs). The physical layer offers different Transport channels to MAC. A transport channel is characterized by how the information is transferred over the radio interface. MAC offers different Logical channels to the Radio Link Control (RLC) sub-layer of Layer 2. A logical channel is characterized by the type of information transferred. 8

19 General Protocol Architecture Physical channels are defined in the physical layer. There are two duplex modes: Frequency Division Duplex (FDD) and Time Division Duplex (TDD). In the FDD mode a physical channel is characterized by the code, frequency and in the uplink the relative phase (I/Q). In the TDD mode the physical channels is also characterized by the timeslot. The physical layer is controlled by RRC. 9

20 Service Provided to Higher Layer The physical layer offers data transport services to higher layers. The access to these services is through the use of transport channels via the MAC sub-layer. The physical layer is expected to perform the following functions in order to provide the data transport service:. Macrodiversity distribution/combining and soft handover execution. 2. Error detection on transport channels and indication to higher layers. 3. FEC encoding/decoding of transport channels. 4. Multiplexing of transport channels and demultiplexing of coded composite transport channels (CCTrCHs). 2

21 Service Provided to Higher Layer 5. Rate matching of coded transport channels to physical channels. 6. Mapping of coded composite transport channels on physical channels. 7. Power weighting and combining of physical channels. 8. Modulation and spreading/demodulation and despreading of physical channels. 9. Frequency and time (chip, bit, slot, frame) synchronisation.. Radio characteristics measurements including FER, SIR, Interference Power, etc., and indication to higher layers.. Inner - loop power control. 2. RF processing. 2

22 Multiple Access UTRA has two modes, FDD (Frequency Division Duplex) & TDD (Time Division Duplex), for operating with paired and unpaired bands respectively. FDD: A pair of frequency bands which have specified separation shall be assigned for the system. TDD: A duplex method whereby uplink and downlink transmissions are carried over same radio frequency by using synchronised time intervals. In the TDD, time slots in a physical channel are divided into transmission and reception part. 22

23 Physical Layer Measurements Radio characteristics including FER, SIR, Interference power, etc., are measured and reported to higher layers and network. Such measurements are:. Handover measurements for handover within UTRA. Specific features being determined in addition to the relative strength of the cell, for the FDD mode the timing relation between cells for support of asynchronous soft handover. 2. The measurement procedures for preparation for handover to GSM9/GSM8. 3. The measurement procedures for UE before random access process. 23

24 Transport Channels Transport channels are services offered by Layer to the higher layers. A transport channel is defined by how and with what characteristics data is transferred over the air interface. Two groups of transport channels: Dedicated Transport Channels Common Transport Channels 24

25 Dedicated Transport Channels Transport Channels DCH Dedicated Channel (only one type) Common Transport Channels divided between all or a group of users in a cell (no soft handover, but some of them can have fast power control) BCH: Broadcast Channel FACH: Forward Access Channel PCH: Paging Channel RACH: Random Access Channel CPCH: Common Packet Channel DSCH: DL Shared Channel 25

26 Dedicated Transport Channels There exists only one type of dedicated transport channel, the Dedicated Channel (DCH) The Dedicated Channel (DCH) is a downlink or uplink transport channel. The DCH is transmitted over the entire cell or over only a part of the cell using e.g. beam-forming antennas. DCH carries both the service data, such as speech frames, and higher layer control information, such as handover commands or measurement reports from the terminal. 26

27 Dedicated Transport Channels The content of the information carried on the DCH is not visible to the physical layer, thus higher layer control information and user data are treated in the same way. The physical layer parameters set by UTRAN may vary between control and data. Possibility of fast rate change (every ms) Support of fast power control. Support of soft handover. 27

28 Common Transport Channel Broadcast Channel (BCH) -- mandatory BCH is a downlink transport channel that is used to broadcast system and cell specific information. BCH is always transmitted over the entire cell. The most typical data needed in every network is the available random access codes and access slots in the cell, or the types of transmit diversity. BCH is transmitted with relatively high power. Single transport format a low and fixed data rate for the UTRA broadcast channel to support low-end terminals. 28

29 Common Transport Channel Paging Channel (PCH) -- mandatory PCH is a downlink transport channel. PCH is always transmitted over the entire cell. PCH carries data relevant to the paging procedure, that is, when the network wants to initiate communication with the terminal. The identical paging message can be transmitted in a single cell or in up to a few hundreds of cells, depending on the system configuration. 29

30 Common Transport Channel Random Access Channel (RACH) -- mandatory RACH is an uplink transport channel. RACH is intended to be used to carry control information from the terminal, such as requests to set up a connection. RACH can also be used to send small amounts of packet data from the terminal to the network. The RACH is always received from the entire cell. The RACH is characterized by a collision risk. RACH is transmitted using open loop power control. 3

31 Common Transport Channel Forward Access Channel (FACH) -- mandatory FACH is a downlink transport channel. FACH is transmitted over the entire cell or over only a part of the cell using e.g. beam-forming antennas. FACH can carry control information; for example, after a random access message has been received by the base station. FACH can also transmit packet data. FACH does not use fast power control. FACH can be transmitted using slow power control. There can be more than one FACH in a cell. The messages transmitted need to include in-band identification information. 3

32 Common Transport Channel Common Packet Channel (CPCH) -- optional CPCH is an uplink transport channel. CPCH is an extension to the RACH channel that is intended to carry packet-based user data. CPCH is associated with a dedicated channel on the downlink which provides power control and CPCH Control Commands (e.g. Emergency Stop) for the uplink CPCH. The CPCH is characterised by initial collision risk and by being transmitted using inner loop power control. CPCH may last several frames. 32

33 Common Transport Channel Downlink Shared Channel (DSCH) -- optional DSCH is a downlink transport channel shared by several UEs to carry dedicated user data and/or control information. The DSCH is always associated with one or several downlink DCH. The DSCH is transmitted over the entire cell or over only a part of the cell using e.g. beam-forming antennas. DSCH supports fast power control as well as variable bit rate on a frame-by-frame basis. 33

34 Transport Channel Dedicated Common Channel Shared Channels Channel DCH FACH RACH CPCH DSCH USCH Uplink/ Downlink Both Downlink Uplink Uplink Downlink Uplink, only in TDD. Code Usage According to maximum bit rate. Fixed codes per cell. Fixed codes per cell. Fixed codes per cell. Shared between users. Shared between users. Fast Power Yes No No Yes Yes Yes Control Soft Handover Yes No No No No No Suited for: Medium or large data amount. Small data amounts. Small data amounts. Small or medium data amounts. Medium or large data amounts. Medium or large data amounts. Suited for bursty data? No Yes Yes Yes Yes Yes 34

35 Mapping of Transport Channels onto Physical Channels Transport Channels DCH Physical Channels Dedicated Physical Data Channel (DPDCH) Dedicated Physical Control Channel (DPCCH) RACH CPCH BCH FACH PCH DSCH Unmapped Physical Random Access Channel (PRACH) Physical Common Packet Channel (PCPCH) Primary Common Control Physical Channel (P-CCPCH) Secondary Common Control Physical Channel (S-CCPCH) Physical Downlink Shared Channel (PDSCH) Common Pilot Channel (CPICH) Synchronization Channel (SCH) Acquisition Indicator Channel (AICH) Access Preamble Acquisition Indicator Channel (AP-AICH) Paging Indicator Channel (PICH) CPCH Status Indicator Channel (CSICH) Collision-Detection/Channel-Assignment Indicator Channel (CD/CA-ICH) 35

36 Interface Between Higher Layers and the Physical Layer Transport Ch Transport Ch 2 Transport Ch Transport Ch 2 Transport Block Transport Block Transport Block & Error Indication Transport Block & Error Indication TFI Transport Block TFI Transport Block TFI Transport Block & Error Indication TFI Transport Block & Error Indication Higher Layer Physical Layer TFCI Coding & Multiplexing TFCI Decoding & Demultiplexing Physical Control Channel Physical Data Channel Physical Control Channel Physical Data Channel 36

37 Transport Format Indicator (TFI) The TFI is a label for a specific transport format within a transport format set. It is used in the inter-layer communication between MAC and L each time a transport block set is exchanged between the two layers on a transport channel. When the DSCH is associated with a DCH, the TFI of the DSCH also indicates the physical channel (i.e. the channelisation code) of the DSCH that has to be listened to by the UE. 37

38 Transport Format Combination Indicator (TFCI) This is a representation of the current Transport Format Combination. The TFCI is used in order to inform the receiving side of the currently valid Transport Format Combination, and hence how to decode, de-multiplex and deliver the received data on the appropriate Transport Channels. There is a one-to-one correspondence between a certain value of the TFCI and a certain Transport Format Combination. MAC indicates the TFI to Layer at each delivery of Transport Block Sets on each Transport Channel. Layer then builds the TFCI from the TFIs of all parallel transport channels of the UE, processes the Transport Blocks appropriately and appends the TFCI to the physical control signalling. Through the detection of the TFCI the receiving side is able to identify the Transport Format Combination. 38

39 Mapping of Transport Channel to Physical Channel In UTRA, the data generated at higher layers is carried over the air with transport channels, which are mapped in the physical layer to different physical channels. The physical layer is required to support variable bit rate transport channels to offer bandwidth-ondemand services, and to be able to multiplex several services to one connection. The transport channels may have a different number of blocks. Each transport channel is accompanied by the Transport Format Indicator (TFI). 39

40 Mapping of Transport Channel to Physical Channel The physical layer combines the TFI information from different transport channels to the Transport Format Combination Indicator (TFCI). TFCI is transmitted in the physical control channel. At any moment, not all the transport channels are necessarily active. One physical control channel and one or more physical data channels form a single Coded Composite Transport Channel (CCTrCh). 4

41 Wireless Information Transmission System Lab. Multiplexing and Channel Coding ( 3G TS ) Institute of Communications Engineering National Sun Yat-sen University

42 Table of Contents Overview of MCC Transport channel related terminologies UL-MCC DL-MCC Some examples 42

43 Overview of MCC MCC multiplexing and channel coding Encoding data stream from MAC and higher layers to offer transport services over the radio transmission link Map transport block data into physical channel data Operations performed in MCC CRC attachment Channel coding Interleaving Radio frame equalization/segmentation Rate matching Transport channel multiplexing Mapping to physical channels 43

44 Overview of MCC Multiplexing and channel coding (MCC) is a key procedure in 3GPP PHY to support QoS requirements from upper layers MCC interfaces with the 3GPP MAC layer by transport channels (TrCHs) Different QoS requirements may assign to different transport channels Transport channels are processed and multiplexed into one or more physical channels (PhCHs) by MCC 44

45 UL Multiplexing and Channel Coding 45

46 DL Multiplexing and Channel Coding 46

47 Transport block Transport block set Transport block size Transport block set size Transmission time interval (TTI) Transport format Transport format set Transport Channel Related Terminologies Transport format combination Transport format combination set 47

48 Transport block A basic unit exchanged between L and MAC Transport block set Transport Channel Related Terminologies A set of transport block exchanged between L and MAC at the same time instance in the same transport channel Transport block size Size of transport block Transport block set size Size of transport block set Transport block Transport block Transport block Transport block Transport block Transport block TrCH 48

49 Transport Channel Related Terminologies Transport format Format of definition for the delivery of transport block set during a TTI (transmission time interval) Format contains Dynamic part Transport block size Transport block set size Static part Transmission time interval Error protection Channel coding type (/2,/3convolutional, turbo,no cc) Rate matching parameter CRC size (8bit, 2bit, 6bit, 24bit, no CRC) Ex:{32bits, 64bits}, { ms, ½ convolutional code, rate matching parameter =, 8bits CRC } 49

50 Transport format set Ex: Transport Channel Related Terminologies The set of transport formats associated to a transport channel Transport block set size and transport block size can be different in a transport format set All other parameters are fixed in a transport format set { 4bits, 4bits }, { 8bits, 8bits }, { 6bits, 6bits } { ms, ½ convolutional code, rate matching parameter =, 8bits CRC } 5

51 Transport format combination L multiplexes several transport channels into one physical channel Transport format is a combination of currently valid transport formats of different transport channel Examples: Transport Channel Related Terminologies DCH: {2bits, 2bits}, {ms, ½ convolutional code, rm=2} DCH2: {32bits, 28bits}, {ms, turbo code, rm = 3} DCH3: {32bits, 32bits}, {4ms, ½ convolutional code, rm = } 5

52 Transport format combination set Ex: A set of transport format combination Combination DCH{2bits, 2bits}, DCH2{32bits, 28bits} DCH3{32bits,32bits} Combination 2 DCH{4bits, 4bits}, DCH2{32bits, 28bits} DCH3{32bits,32bits} Combination 3 DCH{6bits, 6bits}, DCH2{32bits, 32bits} DCH3{32bits,32bits} Static part Transport Channel Related Terminologies DCH: {ms, ½ convolutional code, rm=2} DCH2: {ms, turbo code, rm = 3} DCH3: {4ms, ½ convolutional code, rm = } 52

53 AMR TFCS example Transport Channel Related Terminologies N TRCHa =8 N TRCHb =3 N TRCHc =6 N TRCHa =39 N TRCHb = N TRCHc = N TRCHa = N TRCHb = N TRCHc = N TRCHd =48 N TRCHd =48 N TRCHd =48 Transport format combination Transport format combination 2 Transport format combination 3 CRC = 2 bits CC = /3 TTI = 2ms No CRC CC = /3 TTI = 2ms No CRC CC = /2 TTI = 2ms CRC = 6bits CC = /3 TTI = 4ms Transport format set a Transport format set c Transport format set b Transport format set d 53

54 TFCS is defined every radio link setup Each TF can change every TTI indicated by higher layer Receiver will be noted via TFCI bits in DPCCH DPDCH Transport Channel Related Terminologies Data N data bits T slot = 256 chips, N data = *2 k bits (k=..6) DPCCH Pilot N pilot bits TFCI N TFCI bits FBI N FBI bits TPC N TPC bits T slot = 256 chips, bits Slot # Slot # Slot #i Slot #4 radio frame: T f = ms 54

55 UL-MCC CRC attachment TrBk concatenation / code block segmentation Channel coding Radio frame equalization st interleaving Radio frame segmentation Rate matching TrCH multiplexing Physical channel segmentation 2 nd interleaving Physical channel mapping 55

56 CRC-attachment UL-MCC For error detection g CRC24 (D) = D 24 + D 23 + D 6 + D 5 + D + g CRC6 (D) = D 6 + D 2 + D 5 + g CRC2 (D) = D 2 + D + D 3 + D 2 + D + g CRC8 (D) = D 8 + D 7 + D 4 + D 3 + D + TrBk TrBk 56

57 UL-MCC TrBk concatenation TrBk TrBk CRC CRC TrBk CRC TrBk CRC Code block segmentation Input block size of channel encoder is limited convolutional coding : 54 bit max turbo coding : 54 bit max The whole input block is segmented into the same smaller size. Filler bits are added to the last block 2 filler bits 498 bits 5 bits 5 bits 498 bits 57

58 Channel coding For error correction Turbo-code UL-MCC Higher error correction capability, long decoding latency Rate = /3 Convolutional code Lower error correction capability, short decoding latency Rate = /2 or /3 58

59 UL-MCC Usage of coding scheme and coding rate Type of TrCH BCH PCH RACH CPCH, DCH, DSCH, FACH Coding scheme Convolutional coding Turbo coding No coding Coding rate /2 /3, /2 /3 59

60 Convolutional Coding in WCDMA Input D D D D D D D D (a) Rate /2 convolutional coder Output G = 56 (octal) Output G = 753 (octal) Input D D D D D D D D (b) Rate /3 convolutional coder Output G = 557 (octal) Output G = 663 (octal) Output 2 G 2 = 7 (octal) 6

61 Turbo Coder in WCDMA xk st constituent encoder zk Input xk D D D Input Turbo code internal interleaver Output 2nd constituent encoder z k Output x k D D D x k 6

62 UL-MCC Concatenation of encoded blocks Radio frame size equalization Code block After CC, rate /2 Concatenation Of encoded blocks Radio frame size equalization Assume TTI=8, 236/8 = 54.5, So we add 4 to let it can be divided by 8 62

63 UL-MCC st interleaving is an inter-frame interleaving scheme Interleaving period is one TTI, 2, 4, 8 ms =>, 2, 4, 8 columns in the interleaving matrix st interleaving including three steps write input bits into the matrix row by row perform inter-column permutation based on pre-defined patterns (according to the TTI) read output bits from the matrix column by column 63

64 UL-MCC st interleaving: Input bits 2 3 STEP Write input bits row by row STEP 2 Inter-column permutation STEP 3 Read output bits column by column 64

65 65 Rate Matching Rate matching performs after radio frame segmentation (per ms data) N ij : number of bits in a radio frame before RM on TrCH i N data,j : total number of bits that are available for the CCTrCH RM i : rate matching attribute for transport channel i ΔN i,j :number of bits that should be repeated/punctured in each radio frame on TrCH i = = = I m j m m j data i m j m m j i N RM N N RM Z,,,, I N Z Z N j i j i j i j i,..., i for all,,,, = = Δ

66 Rate Matching Example Assume 3 TrCH N = 3, RM = N =, RM = 2 N 2 = 2, RM = 3 If N data = 8 Z = floor(3*8/76) = 3 : Δ= Z2 = floor((3+2)*8/76) = 53 : ΔN = 23 Z3 = floor((3+2+26)*8/76) = 8 : ΔN 2 = 7 If N data = 3 Z = floor(3*3/76) = 22 : ΔN = -8 Z2 = floor((3+2)*3/76) = : ΔN = -2 Z3 = floor((3+2+26)*3/76) = 3 : ΔN 2 = - 66

67 Rate Matching How could we decide which bits should be punctured/repeated? Determine of e ini, e plus, e minus e = e ini m = do while m < Xi (input bit length before RM) e = e e minus if e <= then -- update error -- check if bit m be punctured/ repeated end do Repeat or puncture x m e = e + e plus end if m = m + -- update error -- next bit 67

68 Rate Matching Example: e ini =3, e minus =2, e plus =5 (Puncturing case) Variable e: Input bits: Output bits: X X X X RM 68

69 UL-MCC TrCH multiplexing Serially multiplex different transport channels into a coded composite transport channel (CCTrCH) Physical Channel Segmentation If more than one physical channel (spreading code) is used, physical channel segmentation is used. 2 nd interleaving Intra-frame interleaving Similar with st interleaving, but with C2 = 3 Physical channel mapping Map CCTrCH to one or multiple physical channels 69

70 TrCH TTI=2 UL-MCC TTI=2 TrCH2 TTI=4 TrCH3 Radio frame segmentation TrCH TrCH TrCH2 TrCH2 TrCH3 TrCH3 TrCH3 TrCH3 Rate matching TrCH TrCH TrCH2 TrCH2 TrCH3 TrCH3 TrCH3 TrCH3 TrCH multiplexing TrCH TrCH2 TrCH3 2 nd interleaving Physical channel mapping CCTrCH PhCH PhCH 7 c c2

71 . CRC attachment DL-MCC 2. TrBk concatenation / code block segmentation 3. Channel coding 4. Rate matching 5. st insertion of DTX indication 6. st interleaving 7. Radio frame segmentation 8. TrCH multiplexing 9. 2 nd insertion of DTX indication. Physical channel segmentation. 2 nd interleaving 2. Physical channel mapping 7

72 Rate Matching Since DL rate matching is performed before TrCH multiplexing, the RM does not know TF of other transport channel TrCH TrCH2 TrCH3 TrCH?? TrCH TrCH2 TrCH3? PhCH size PhCH size RM in UL case RM in DL case 72

73 2 solutions in DL-RM Fixed position Rate Matching Use the maximum N i in TFS i for all i as the data size before RM Calculate for ΔN i as in UL case Flexible position Find maximum RM i *N i,j for all combination j Calculate for ΔN i 73

74 TFCS example Rate Matching Combination : DCH{2bits, 2bits}, DCH2{32bits, 28bits} DCH3{32bits,32bits} Combination 2: DCH{4bits, 4bits}, DCH2{32bits, 28bits} DCH3{32bits,32bits} Combination 3: DCH{6bits, 6bits}, DCH2{32bits, 32bits} DCH3{32bits,32bits} Assume RM = RM2 = RM3 = (same importance) Fixed position Choose N =6, N 2 =28, N 3 =32 to calculate for ΔN i Flexible position Choose N =4, N 2 =28, N 3 =32 to calculate for ΔN i (combination 2) 74

75 Normal mode Rate Matching For frames not overlapping with transmission gap Compressed mode Frames overlapping with transmission gap Frame structure of type A Slot # (N first - ) transmission gap Slot # (N last + ) Data T P C TF CI Data2 PL PL Data T P C TF CI Data2 PL Frame structure of type B Slot # (N first - ) transmission gap Slot # (N last + ) Data T P C TF CI Data2 PL T P C PL Data T P C TF CI Data2 PL 75

76 Rate Matching Compressed mode by puncturing Use rate matching algorithm to generate available space for transmission gap We insert p-bits corresponding to the transmission gap length and will be removed later Using slot format A Compressed mode by reducing the spreading factor by 2 Using slot format B (reduce spreading factor by 2) to increase available transmission bits Compressed mode by higher layer scheduling Higher layer schedule the transmission data Using slot format A 76

77 DTX Insertion Since the rate matching output is to match the maximum bit number of each TrCH, DTX (discontinuous transmission bits) should be inserted to match the real bit number after TrCH multiplexing Before RM TrCH TrCH2 TrCH3 After RM TrCH TrCH2 TrCH3 TrCH MUX TrCH TrCH2 TrCH3 DTX PhCH size 77

78 Physical Channel Mapping TPC N TPC bits T slot = 256 chips, *2 k bits (k=..7) DPDCH Data2 N data2 bits DPDCH DPCCH DPCCH Data N data bits TFCI N TFCI bits Pilot N pilot bits Slot # Slot # Slot #i Slot #4 One radio frame, T f = ms 78

79 Detail Issues in MCC Why RM is done after st interleaving and radio frame segmentation in UL? Although transport format for the individual TrCH changes only once per TTI, combination of TrCHs may be different in each frame Rate matching shall be done on a frame-by-frame basis to dynamically assign PhCH resources Therefore, radio frame segmentation is performed before rate matching 79

80 Detail Issues in MCC But, why RM is done before st interleaving and radio frame segmentation in DL? PhCH resources are pre-assigned by the upper layers in DL Rate matching must be done before st interleaving since DTX insertion of fixed position shall be performed after rate matching and before st interleaving Rate matching parameters are still calculated on a radio frame basis 8

81 Some Examples UL DCH example UL 2.2 kbps data UL 64/28/44 kbps packet data UL 384 kbps packet data TrCH multiplexing 2.2 kbps data kbps data 64 kbps data kbps data DL DCH example DL 2.2 kbps data DL 64/28/44 kbps packet data TrCH multiplexing 2.2 kbps data kbps data 8

82 UL 2.2 kbps data Transport block TrCh#a TrCh#b TrCh#c CRC attachment* N TrCHa N TrCHb N TrCHc CRC Tail bit attachm ent* N TrCHa 2 N TrCHb N TrCHc Convolutional coding R=/3, /2 N TrCHa+2 Tail 8 N TrCHb Tail 8*N TrCHb/3 N TrCHc Tail 8*N TrCHc/6 Radio frame equalization 3*( N TrCHa+2) 3*( N TrCHb+8*N TrCHb/3) 2*( N TrCHc+8*N TrCHc/6) st interleaving 3*( N TrCHa+2) 3*( N TrCHb+8*N TrCHb/3) 2*( N TrCHc+8*N TrCHc/6) Radio frame segm entation R ate m atching 3*( N TrCHa+2)+* 3*( N TrCHa /8 N TrCHb+8*N TrCHb/3)+*N TrC #a #2b #b #2b 2*( N TrCHc+8*N TrCHc/6) #c #2c N RFa N RFa N RFb N RFb N RFc N RFc #a #2b #b #2b #c #2c N RFa+N RM _a N RFa+N RM_2b N RFb+N RM_b N RFb+N RM_2b N RFc+N RM _ c N RFc+N RM_ 2c To TrC h M ultiplexing N RFa=[3*( N TrCHa+2)+* N TrCHa /8 ]/2 N RFb=[3*( N TrCHb+8*N TrCHb/3)+*N TrCHb/3]/2 N RFc= N TrCHc+8*N TrCHc/6 * C R C and tail bits for TrC H #a is attached even if N TrCha = bits since CRC parity bit attachment for bit transport block is applied. 82

83 UL 64/28/44 kbps data Transport block CRC attachment 336 CRC TrBk concatenation B TrBks (B=,, 2, 4, 8, 9) Turbo coding R=/3 352* B Tail bit attachm ent 56* B st interleaving 56* B Tail 2* B/9 Radio frame segm entation R ate m atching 56* B +2* B/9 # #2 (56* B +2* B/9 )/2 (56* B +2* B/9 )/2 # #2 (56* B +2* B/9 )/2+N RM (56* B +2* B/9 )/2+N RM2 To TrC h M ultiplexing 83

84 UL 384 kbps data Transport block CRC attachment 336 CRC TrB k concatenation B TrBks (B=,, 2, 4, 8, 2, 24) Code block segm entatio n 352* B Turbo coding R=/3 76* B 76* B Tail b it attach m en t 528* B 528* B st in terleaving Tail Tail 528* B 2* B/24 528* B 2* B/24 R adio fram e segm entatio n Rate matching 56* B +24* B/24 # #2 (56* B +24* B/24 )/2 (56* B +24* B/24 )/2 # #2 (56* B +24* B/24 )/2+ N RM (56* B +24* B/24 )/2+ N RM 2 To TrCh M ultiplexing 84

85 2.2 kbps kbps data 2.2 kbps data 2.2 kbps data 3.4 kbps data TrCH multiplexing #a #2a #b #2b #c #2c #a #2a #b #2b #c #2c # #2 #3 #4 #a #b #c # #2a #2b #2c #2 #a #b #c #3 #2a #2b #2c #4 2 nd interleaving Physical channel mapping 6 ksps DPDCH CFN=4N CFN=4N+ CFN=4N+2 CFN=4N+3 85

86 64 kbps kbps data 64 kbps data 3.4 kbps data TrCH multiplexing # #2 #3 #4 # #2 #3 #4 # # #2 #2 #3 #3 #4 #4 2 nd interleaving Physical channel mapping 24 ksps DPDCH CFN=4N CFN=4N+ CFN=4N+2 CFN=4N+3 86

87 DL 2.2 kbps data Transport block TrCh#a TrCh#b TrCh#c CRC attachment* N TrCHa N TrCHb N TrCHc CRC Tail bit attachm ent* N TrCHa 2 N TrCHb N TrCHc Convolutional coding R=/3, /2 N TrCHa+2 Tail 8 N TrCHb Tail 8*N TrCHb/ 3 N TrCHc Tail 8* N TrCHc/6 R ate m atch in g 3*(N TrCHa+2) 3*(N TrCHb+8* N TrCHb/3) 2*(N TrCHc+8* N TrCHc/6 ) Insertion of D T X indication 3*(N TrCHa+2)+N RM a 3*(N TrCHb+8* N TrCHb/ 3 )+ N RM b 2*(N TrCHc+8* N TrCHc/6 )+ N RM c st in terleavin g 3*(N TrCHa+2)+N RM a+n DI 3*(N TrCHb+8* N TrCHb/ 3 )+ N RM b+n DIb 2*(N TrCHc+8* N TrCHc/6)+N RM c+n DIc Radio frame segm entation 3*(N TrCHa+2)+N RM a+n DI #a #2a 3*(N TrCHb+8* N TrCHb/ 3 )+ N RM b+n DIb #b #2b 2*(N TrCHc+8* N TrCHc/6)+N RM c+n DIc #c #2c N RFa N RFa N RFb N RFb N RFc N RFc To TrCh M ultiplexing N RFa = [3*(N TrCHa+2) +N RM a+n DIa]/2 N RFb = [3*(N TrCHb+8* N TrCHb/3)+ N RM b+n DIb]/2 N RFc = [2*(N TrCHc+8* N TrCHc/6 )+ N RM c+n DIc]/2 * C R C and tail bits for TrC H #a is attached even if N TrCha = bits since C R C parity bit attachm ent for bit transport block is applied. 87

88 DL 64/28/44 kbps data Transport block C R C attachm ent 336 CRC TrB k concatenation B TrBks (B=,, 2, 4, 8, 9) Turbo coding R=/3 352* B Tail bit attachm ent 56*B R ate m atch in g 56*B Tail 2* B/9 st in terleav in g 56* B+2* B/9 +N RM Radio fram e segm entation 56* B +2* B/9 +N RM # #2 ( 5 6 * B + 2 * B/9 +N RM )/2 (56* B +2* B/9 +N RM )/2 T o T rc h M u ltip lex in g 88

89 2.2 kbps kbps data 2.2 kbps data 2.2 kbps data 3.4 kbps data TrCH multiplexing #a #2a #b #2b #c #2c #a #2a #b #2b #c #2c # #2 #3 #4 #a #b #c # #2a #2b #2c #2 #a #b #c #3 #2a #2b #2c #4 2 nd interleaving Physical channel mapping ksps DPCH slot CFN=4N slot CFN=4N+ slot CFN=4N+2 slot CFN=4N+3 Pilot symbol TPC 89

90 Wireless Information Transmission System Lab. WCDMA Uplink Physical Layer Institute of Communications Engineering National Sun Yat-sen University

91 Table of Contents Overview Uplink Physical Layer Dedicated Uplink Physical Channels Uplink Dedicated Physical Data Channel (UL DPDCH) Uplink Dedicated Physical Control Channel (UL DPCCH) Common Uplink Physical Channels Physical Random Access Channel (PRACH) Physical Common Packet Channel (PCPCH) Uplink Physical Layer Modulation 9

92 Configuration Overview Radio frame A radio frame is a processing unit which consists of 5 slots. The length of a radio frame corresponds to 384 chips. Time slot A time slot is a unit which consists of fields containing bits. The length of a slot corresponds to 256 chips. Spreading Modulation: QPSK. Data Modulation: BPSK. Spreading Two-level spreading processes 92

93 Spreading (cont.) Channelization operation OVSF codes. Overview Transform every data symbol into a number of chips. Increase the bandwidth of the signal. The number of chips per data symbol is called the Spreading Factor. Data symbols on I- and Q-branches are independently multiplied with an OVSF code. Scrambling operation Long or short Gold codes. Applied to the spread signals. Randomize the codes Spread signal is further multiplied by complex-valued scrambling 93

94 Uplink Physical Channels Dedicated Uplink Physical Channels Uplink Dedicated Physical Data Channel (UL DPDCH) Uplink Dedicated Physical Control Channel (UL DPCCH) Common Uplink Physical Channels Physical Random Access Channel (PRACH) Physical Common Packet Channel (PCPCH) 94

95 Dedicated Uplink Physical Channels UL Dedicated Physical Data Channel (UL DPDCH) Carry the DCH transport channel (generated at Layer 2 and above). There may be zero, one, or several uplink DPDCHs on each radio link. UL Dedicated Physical Control Channel (UL DPCCH) Carry control information generated at Layer One and only one UL DPCCH on each radio link. 95

96 Frame Structure for UL DPDCH/DPCCH DPDCH Data N data bits T slot = 256 chips, N data = *2 k bits (k=,,,6) DPCCH Pilot N pilot bits TFCI N TFCI bits FBI N FBI bits TPC N TPC bits T slot = 256 chips, bits One Power Control Period Slot # Slot # Slot #i Slot #4 radio frame: T f = ms = 384 chips 96

97 UL DPDCH The parameter k determines the number of bits per uplink DPDCH slot. It is related to the spreading factor SF of the DPDCH as SF = 256/2 k. The DPDCH spreading factor ranges from 256 down to 4. Slot Format #i Channel Bit Rate (kbps) Channel Symbol Rate (ksps) SF Bits/ Frame Bits/ Slot N data

98 UL DPCCH - Layer Control Information The spreading factor of the uplink DPCCH is always equal to 256, i.e. there are bits per uplink DPCCH slot. Slot Form at #i A B 2 2A 2B A 5B Channel Bit Rate (kbps) Channel Symbol Rate (ksps) SF Bits/ Frame Bits/ Slot N pilot N TPC N TFCI N FBI Transmitted slots per radio frame

99 UL DPCCH - Layer Control Information Pilot Bits. Support channel estimation for coherent detection. Frame Synchronization Word (FSW) can be sued to confirm frame synchronizaton. Transmit Power Control (TPC) command. Inner loop power control commands. Feedback Information (FBI). Support of close loop transmit diversity. Site Selection Diversity Transmission (SSDT) Transport-Format Combination Indicator (TFCI) optional TFCI informs the receiver about the instantaneous transport format combination of the transport channels. 99

100 Pilot Bit Patterns with N pilot =3,4,5,6 Slot # Bit # N pilot = 6 N pilot = 5 N pilot = 4 N pilot = 3 Shadowed column is defined as FSW (Frame Synchronization Word).

101 Pilot Bit Patterns with N pilot =7,8 Shadowed column is defined as FSW (Frame Synchronization Word). Slot # Bit # N pilot = 8 N pilot = 7

102 FBI Bits The FBI bits are used to support techniques requiring feedback from the UE to the UTRAN Access Point, including closed loop mode transmit diversity and site selection diversity transmission (SSDT). S field D field N FBI The S field is used for SSDT signalling, while the D field is used for closed loop mode transmit diversity signalling. The S field consists of,, or 2 bits. The D field consists of or bit. Simultaneous use of SSDT power control and closed loop mode transmit diversity requires that the S field consists of bit. 2

103 TFCI Bits There are two types of uplink dedicated physical channels: those that include TFCI (e.g. for several simultaneous services) those that do not include TFCI (e.g. for fixed-rate services). It is the UTRAN that determines if a TFCI should be transmitted and it is mandatory for all UEs to support the use of TFCI in the uplink. In compressed mode, DPCCH slot formats with TFCI fields are changed. There are two possible compressed slot formats for each normal slot format. 3

104 TPC Bit Patterns TPC Bit Pattern N TPC = N TPC = 2 Transmitter power control command 4

105 Spreading of UL DPCH c d, β d DPDCH DPDCH 3 c d,3 β d Σ I c d,5 β d DPDCH 5 S lo n g,n or S short,n I+ jq c d,2 β d DPDCH 2 c d,4 β d DPDCH 4 DPDCH 6 c d,6 β d Σ Q c c β c j DPCCH 5

106 Spreading of UL DPCH The binary DPCCH and DPDCHs to be spread are represented by real-valued sequences, i.e. the binary value "" is mapped to the real value +, while the binary value "" is mapped to the real value. The DPCCH is spread to the chip rate by the channelization code c c, while the n:th DPDCH called DPDCHn is spread to the chip rate by the channelization code c d,n. One DPCCH and up to six parallel DPDCHs can be transmitted simultaneously, i.e. n 6. 6

107 Channelization Codes Each CDMA channel is distinguished via a unique spreading code. These spreading codes should have low crosscorrelation values. In 3GPP W-CDMA, Orthogonal Variable Spreading Factor (OVSF) codes are used. Preserve the orthogonality between a user s different physical channels. Scrambling is used on top of spreading. 7

108 Code-tree for Generation of Orthogonal Variable Spreading Factor (OVSF) Codes C ch,4, =(,,,) C ch,2, = (,) C ch,4, = (,,-,-) C ch,, = () C ch,4,2 = (,-,,-) C ch,2, = (,-) C ch,4,3 = (,-,-,) SF = SF = 2 SF = 4 The channelization codes are uniquely described as C ch,sf,k, where SF is the spreading factor of the code and k is the code number, k SF-. 8

109 Channelization Codes As the chip rate is already achieved in the spreading by the channelization codes, the symbol rate is not affected by the scrambling. Another physical channel may use a certain code in the tree if no other physical channel to be transmitted using the same code three is using a code that is on an underlying branch, i.e. using a higher spreading factor code generated from the intended spreading code to be used. Neither can a smaller spreading factor code on the path to the root of the tree be used. 9

110 Channelization Codes The downlink orthogonal codes within each base station are managed by the radio network controller (RNC) in the network. The definition for the same code tree means that for transmission from a single source, from either a terminal or a base station. One code tree is used with one scrambling code on top of the tree. Different terminals and different base stations may operate their code trees independently of each other.

111 Generation of Channelization Codes C ch,, = = =,,,,,,,,,2,,2, ch ch ch ch ch ch C C C C C C ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) = ,2,2,2,2,2,2,2,2,,2,,2,,2,,2,,2,,2,,2,,2,2,2 2,2,2,3,2,2,2,,2,,2 : : : n n ch n n ch n n ch n n ch n ch n ch n ch n ch n ch n ch n ch n ch n n ch n n ch n ch n ch n ch n ch C C C C C C C C C C C C C C C C C C

112 OVSF Code Allocation for UL DPCH DPCCH is always spread by c c = C ch,256, When there is only one DPDCH DPDCH is spread by c d, = C ch,sf,k (k= SF / 4) When there are more than one DPDCH All DPDCHs have SF=4 DPDCH n is spread by the the code c d,n = C ch,4,k k = if n {, 2}, k = 3 if n {3, 4} and k = 2 if n {5, 6} 2

113 Gain of UL DPCH After channelization, the real-valued spread signals are weighted by gain factors, β c for DPCCH and β d for all DPDCHs. At every instant in time, at least one of the values β c and β d has the amplitude.. The β-values are quantized into 4 bit words. After the weighting, the stream of real-valued chips on the I- and Q-branches are then summed and treated as a complex-valued stream of chips. This complex-valued signal is then scrambled by the complexvalued scrambling code S dpch,n. 3

114 Gain of UL DPCH Signaling values for β c and β d 4 Quantized amplitude ratios β c and β d Switch off

115 Long scrambling code allocation The n-th UL long scrambling code S dpch,n (i) = C long,n (i), i =,,, C i i i) = c long,, n( i) + j( ) clong,2 n(2 ) 2 long, n(, Short scrambling code allocation The n-th UL short scrambling code S dpch,n (i) = C short,n (i), i =,,, C short, n Scrambling Codes of UL DPCH i ( i) = cshort,, n( i mod256) + j( ) cshort,2, 5 n i mod

116 Configuration of Uplink Scrambling Sequence Generator MSB LSB x c long,,n y c long,2,n 6

117 Uplink Long Scrambling Codes Two elementary codes: c long,,n and c long,2,n. c long,,n and c long,2,n are constructed from position wise modulo 2 sum of 384 chip segments of two binary m-sequences, x and y. x and y are originated from two generator polynomials of degree 25. x sequence: generator polynomial: X 25 +X 3 + y sequence: generator polynomial: y 25 +y 3 +y 2 +y+ The sequence c long,2,n is a chip shifted version of the sequence c long,,n. c long,,n and c long,2,n are Gold codes. 7

118 For code number, n Uplink Long Scrambling Codes n=[n 23 n ], with n being the LSB Let x n (i)andy(i) denote the i -th chip of the sequence x n and y. Initial conditions x n ()=n, x n ()=n,, x n (22)=n 22, x n (23)=n 23, x n (24)= y()=y()= =y(23)= y(24)= 8

119 Uplink Long Scrambling Codes Recursive formulation, i=,, x n (i+25) =x n (i+3) + x n (i) modulo 2 y(i+25) = y(i+3)+y(i+2) +y(i+)+y(i) modulo 2 Gold sequence z n z n (i ) = x n (i ) + y (i ) modulo 2, i =,, 2,, Z n ( i) + if zn( i) = = for i =,,,2 if zn( i) =

120 Uplink Long Scrambling Codes c long,,n (i ) = Z n (i ), i =,, 2,, c long,2,n is a chip shifted version of the sequence c long,,n c long,2,n (i ) = Z n ((i ) modulo (2 25 )), i =,, 2,, C i i i) = c long,, n( i) + j( ) clong,2 n(2 ) 2 long, n(, 2

121 Uplink Short Scrambling Sequence Generator for 255 Chip Sequence d(i) mod mod n addition multiplication mod 2 b(i) mod 4 + z n (i) Mapper c short,,n (i) c short,2,n (i) a(i) mod

122 Uplink Short Scrambling Codes Two elementary codes: c short,,n and c short,2,n 256 chips Generation From the family of periodically extended S(2) codes The n:th quaternary S(2) sequence z n (i ), n , is obtained by modulo 4 addition of three sequences One quaternary sequence a (i ) Two binary sequences b (i ) and d (i ) 22

123 Uplink Short Scrambling Codes z n (i ) = a(i ) + 2b(i ) + 2d (i ) modulo 4 (i =.. 254) Given a code number n =[n 23 n 22 n ] quaternary sequence a (i ): g (x)= x 8 +x 5 +3x 3 +x 2 +2x+ Initial conditions a () = 2n + modulo 4 a (i) = 2n i modulo 4, i =, 2,, 7, Recursive formulation a (i) = 3a (i-3) + a (i-5) + 3a (i-6) + 2a (i-7) + 3a (i-8) modulo 4, i = 8, 9,,

124 Uplink Short Scrambling Codes Binary sequence b(i): g (x)= x 8 +x 7 +x 5 +x+ Initial conditions B (i ) = n 8+i modulo 2, i =,,, 7, Recursive formulation b (i) = b (i-) + b (i-3) + b (i-7) + b (i-8) modulo 2, i = 8, 9,,

125 Uplink Short Scrambling Codes Binary sequence d (i ): g 2 (x)= x 8 +x 7 +x 5 +x 4 + Initial conditions d (i ) = n 6+i modulo 2, i =,,, 7 Recursive formulation d (i ) = d (i-) + d (i-3) + d (i-4) + d (i-8) modulo 2, i = 8, 9,, 254 z n (i) = a (i) + 2b (i) + 2d (i) modulo 4 (i =.. 254) 25

126 Uplink Short Scrambling Codes z n (i) is extended to length 256 chips z n (255) = z n () Mapping C short, n is C i) = c z n (i) c short,,n (i) c short,2,n (i) ( i mod256) + j( ) i short, n( short,, n short,2, n c i mod

127 Physical Random Access Channel (PRACH) PRACH is used to carry the RACH. The random access transmission is based on a Slotted ALOHA approach with fast acquisition indication. The UE can start the random-access transmission at the beginning of a number of well-defined time intervals, denoted access slots. There are 5 access slots per two frames and they are spaced 52 chips apart. Information on what access slots are available for random-access transmission is given by higher layers. 27

128 PRACH Access Slot Numbers and Their Spacing radio frame: ms radio frame: ms 52 chips # # #2 #3 #4 #5 #6 #7 #8 #9 # # #2 #3 #4 Access slot # Access slot # Random Access Transmission Random Access Transmission Access slot #7 Access slot #8 Random Access Transmission Random Access Transmission Access slot #4 28

129 Structure of the Random-Access Transmission The random-access transmission consists of one or several preambles of length 496 chips and a message of length ms or 2 ms. Preamble Preamble Preamble Message part 496 chips ms (one radio frame) Preamble Preamble Preamble Message part 496 chips 2 ms (two radio frames) 29

130 RACH Preamble Code Construction Each preamble is of length 496 chips and consists of 256 repetitions of a signature of length 6 chips. There are a maximum of 6 available signatures. The random access preamble code C pre,n, is a complex valued sequence. It is built from a preamble scrambling code S r-pre,n and a preamble signature C sig,s as follows: C pre, n, s ( k) = S r pre, n ( k) C sig, s ( k) e π π j( + k ) 4 2 where k= corresponds to the chip transmitted first in time., k =,,2,,495 3

131 PRACH Preamble Scrambling Code The scrambling code for the PRACH preamble part is constructed from the long scrambling sequences. There are 892 PRACH preamble scrambling codes in total. The n:th preamble scrambling code, n =,,, 89, is defined as: S r-pre,n (i ) = c long,,n (i ), i =,,, 495; 3