WCDMA Day 1

WCDMA PrinciplesDAY - 1

ContentsChapter 1 Introduction

Chapter 2 WCDMA Network Structure

Chapter 3 WCDMA Technologies

Chapter 4 WCDMA RNC Area

Mobile Network Evolution

Network Spectrum

3G Service AreaUplinkDownlinkMumbai1959-1964 MHz2149-2154 MHzDelhi1974-1979 MHz2164-2169 MHzKolkata1974-1979 MHz2164-2169 MHzPunjab1964-1969 MHz2154-2159 MHzRajasthan1959-1964 MHz2149-2154 MHzMadhya Pradesh1969-1974 MHz2159-2164 MHzWest Bengal1964-1969 MHz2154-2159 MHzHimachal Pradesh1974-1979 MHz2164-2169 MHzBihar1969-1974 MHz2159-2164 MHzOrissa1974-1979 MHz2164-2169 MHzAssam1959-1964 MHz2149-2154 MHzNorth East1974-1979 MHz2164-2169 MHzJammu & Kashmir1969-1974 MHz2159-2164 MHz

Target of IMT2000Global uniform frequency band and standard, global seamless coverage

High efficient spectrum utility

High quality of service, high security

Easy for evolution from 2G system

Providing multimedia serviceCar speed environment: 144kbpsWalk speed environment: 384kbpsIndoor environment: 2048kbps

WCDMA FDD

WCDMA FDDMultiple access methodDS-CDMADuplex MethodFrequency DivisionFrequency BandUplink : 1920-1980MHz, Downlink : 2110-2170MHzBase Station SynchronizationAsynchronous/Synchronous operationChip Rate3.84McpsFrame Length10msService multiplexingMultiple Services with different QoS are multiplexed on a single connectionMulti-user detection, smart antennasSupported by standard, optional in implementationPower ControlFast Power Control, 1.5KHzHandoverSofter, Soft & Hard HandoverTransmit DiversityOpen & Closed LoopVoice CodingAMR Voice Coding, rate 4.75kb 12.2kbps

WCDMA Voice EvolutionAdopt AMR voice coding, and support voice quality of 4.75Kbps ~ 12.2Kbps

Adopt soft handover and transmit diversity to improve system capacity

Provide high fidelity voice mode

Fast power control

Data Service Evolution of WCDMASupport maximum 2Mbps data service

Support packet switch

Adopt ATM platform currently

Provide QoS

Common Packet Channel(CPCH) and Downlink Share Channel(DSCH) can support Internet packet services better

Provide high-quality support for uplink-downlink symmetric data service, such as voice, video phone, conference TV

ContentsChapter 1 Introduction




GSM /GPRS BSSBTSBSCPCUSS7SCPSMSSCEPSTN/other PLMNInternet,IntranetMSC/VLRGMSCHLR/AUCSGSNCGBGGGSNOther PLMNCS domainPS domainAGbWCDMA Network Structure

GSMBSSWCDMA Interfaces

Chapter 1 Introduction




Contents


Section 1 - WCDMA Transmission Block Diagram

Section 2 - Power Control - Handover - Diversity

Source codingChannel codingSpreadingModulationSource decodingChannel decodingDespreadingDemodulationRadio channelBlock Diagram of WCDMA System

Common Technical TermsBit, Symbol, Chip:A bit is the input data which contain informationA symbol is the output of the convolution, encoder, and the block interleavingA chip is the output of spreading

Processing Gain:Processing gain is the ratio of chip rate to the bit rate. Closely related to spreading factor, SF.

Forward direction/ Downlink : Information path from base station to mobile stationReverse direction/ Uplink : Information path from mobile station to base station

WCDMA SystemSource CodingVoice : Adaptive multirate technique with rate 4.75kbps 12.2kbps

Channel CodingCRC Attachment.Check for error during transmission.Voice : CRC check returns error, discard informationData : CRC check returns error; ask for retransmission

Convolutional or Turbo CodingConvolution coding for voice and low speed signalingTurbo Coding for large data transmission. Better performance than convolutional coding

Interleaving Distribute error over data transmitted

Rate MatchingMatch symbol rate to that accepted by spreadingRate matching technique : Repeat or puncturing

WCDMA SystemSpreadingSpreading (OVSF code)SF 4 512, depends on data rate

Scrambling (Gold Code)

ModulationQPSK


Section 1 - WCDMA Transmission Block Diagram

Section 2 - Power Control - Handover - Diversity

Power ControlOpen Loop Power ControlSet initial power for transmission of PRACH

Closed Loop Power Control

Inner Loop Power ControlUplink : Controls power of NodeB. Downlink : Ensures all power received at NodeB are just enough to maintain satisfactory connection Fast Power Control : 1.5khz

Outer Loop Power Control Set SIRthreshold based on BER/BLER

System information :CPICH power, UL interference & constantPRACH Tx powerOpen Loop Power ControlControlled by UE. Determine UE initial transmission power for random access procedure. Not in use when inner loop power control running. UE obtain information from network on: CPICH power Uplink interference level Constant value (Default = 2dB)

UE Initial Power = CPICH power CPICH_RSCP + UL interference + Constant

Power Control Bit Located in UE & NodeB

Controls power of dedicated physical channels

Power controls occurs at 1500Hz, thus known as fast power control

NodeB and UE continuously measure and compare SIRmeasured with SIRthreshold value, and inform each other to increase /reduce its power accordingly.With Optimum Power ControlReceived power at NodeB(SIR)measuredNodeBUE2UE3UE1UE4SIR thresholdInner Closed Loop Power Control

BER/BLER ValueChange in (SIR)thresholdRNCSIR thresholdOuter Closed Loop Power ControlAdjust SIR for every user

Needed to keep track of changes in radio environment

Aims to provide required quality

If SIRthreshold reaches its maximum, system has to perform inter-frequency/inter-system handover RRC connection release

Softer handover Handover between intra-frequency cells under the control of the same BTS Radio link connection to new target cell is created before existing connection being deleted.

Soft handover Handover between intra-frequency cells under the control of the different BTSs

Hard handover Condition of hard handover:Intra-frequency handover, cells controlled by different RNCs and no Iur interface between themInter-frequency handoverInter-system handover

Interruption in voice or data communication occurs but this interruption does not effect the user communicationHandover

Selection combination in the RNC during soft handoff Maximum ratio combination in the NodeB during softer handoffsSoft/Softer Handover

Space Time transmit Diversity (STTD)Restoring data streamTransmission Diversity : STTD

Time Switch transmit Diversity (TSTD)Used in synchronization physical channel ( SCH)Transmission Diversity : TSTD

UMTS Radio Interface Physical Layer

ContentsChapter 1 : Physical Layer Overview

Chapter 2 : Physical Layer Key Technology

Chapter 3 : Physical Layer Procedures

Chapter 4 : Transmit Diversity on Physical Channel

UTRAN Protocol Structure

Core Network

RNS

RNS

RNC

RNC

Node B

Node B

Node B

Node B

Iu

Iu

Iur

Iub

Iub

Iub

Iub

Spreading TechnologySpreading consists of 2 stepsChannelization operation: Transforms data symbols into chips. Thus increasing the bandwidth of the signal. The number of chips per data symbol is called the Spreading FactorSF.The operation is done through multiplication with OVSF code.Scrambling operation is applied to the spreading signal.

Channelization CodeOVSF code is used as channelization code The channelization codes are uniquely described as Cch,SF,k, where SF is the spreading factor of the code and k is the code number, 0 k SF-1.

SF = 1

SF = 2

SF = 4

Cch,1,0 = (1)

Cch,2,0 = (1,1)

Cch,2,1 = (1,-1)

Cch,4,0 =(1,1,1,1)

Cch,4,1 = (1,1,-1,-1)

Cch,4,2 = (1,-1,1,-1)

Cch,4,3 = (1,-1,-1,1)

Scrambling CodeScrambling code GOLD sequence.Scrambling code period : 10ms ,or 38400 chips.The code used for scrambling of uplink DPCCH/DPDCH may be of either long or short type, There are 224 long and 224 short uplink scrambling codes. Uplink scrambling codes are assigned by higher layers.For downlink physical channels, a total of 218-1 = 262,143 scrambling codes can be generated. Only scrambling codes k = 0, 1, , 8191 are used.

Primary Scrambling Code

Group 0Group1Group 63512 primary scrambling codes64 primary scrambling code groupsEach group consists of 8 primary scrambling codesPrimary scrambling codes for downlink physical channelsPrimary scrambling code 0Primary scrambling code 1Primary scrambling code 7Primary scrambling code 8*63Primary scrambling code 63*87Primary Scrambling Code Group

ContentsChapter 1 : Physical Layer Overview



Chapter 4 : Transmit Diversity on Physical Channel

ContentsChapter 2 : Physical Layer Key Technology

Section 1 Physical Channel Structure and Function

Section 2 Channel Mapping

WCDMA Radio Interface3GPP protocol defined WCDMA radio interface into three channels: Physical channel, transport channel and logical channel.

Logical channel: Carrying user services. Divided into 2 types, based on services it carried: Control channel and service channel. Transport channel: Between radio interface layer 2 and physical layer. Services provided by physical layer for MAC layer. Based on information transported, can be divided into dedicated channel and common channel.

Physical channel: It is the ultimate embodiment of all kinds of information when they are transmitted on radio interfaces. Each channel that uses dedicated carrier frequency, code (spreading code and scramble) and carrier phase can be regarded as a dedicated channel.

Traffic channelControl channelDedicated traffic channel DTCHCommon traffic channel CTCHBroadcast control channel BCCHPaging control channel PCCHDedicate control channel DCCHCommon control channel (CCCHLogical channel

Broadcast channel (BCH)Forward access channel (FACH)Paging channel (PCH)Random access channel (RACH)

BCH, FACH & PCH are downlink channels.Only RACH is common uplink channel

Dedicated Channel (DCH)Dedicated Channel (DCH) exists on uplink or downlink channel. Dedicated transport channelTransport channel

A physical channel is defined by a specific carrier frequency, code (scrambling code, spreading code) and relative phase. In UMTS system, the different code (scrambling code or spreading code) can distinguish the channels. Most channels consist of radio frames and time slots, and each radio frame consists of 15 time slots.Two types of physical channel: UL and DLPhysical Channel

Downlink Common Physical Channel Common Pilot Channel (CPICH) Synchronization Channel (SCH) Common Control Physical Channel (CCPCH) Paging Indicator Channel (PICH) Acquisition Indicator Channel (AICH)Downlink Dedicated Physical Channel Downlink DPCHDownlink Physical ChannelDownlink Physical Channel

DCH dataDPDCHDPCCHProvide control data for DPDCH ,such as demodulation, power control,etc.Data bearer at physical layerDCH data Functions of Downlink DPDCH/DPCCH

Common Pilot Channel(CPICH)Common Pilot Channel (CPICH)Carries pre-defined sequence.Fixed rate 30Kbps SF=256Can use STTD on this channel

Common Pilot Channel (CPICH)Primary CPICHUses OVSF code -Cch, 256,0Scrambled by the primary scrambling codeOnly one CPICH per cellBroadcast over the entire cellThe P-CPICH is a phase reference for SCH, Primary CCPCH, AICH, PICH. By default, it is also a phase reference for downlink DPCH.

Secondary CPICHAn arbitrary channel code of SF=256 is used for S-CPICHS-CPICH is scrambled by either the primary or a secondary scrambling codeThere may be zero, one , or several secondary CPICH.S-CPICH may be transmitted over part of the cellS-CPICH may be a phase reference for S-CCPCH and downlink DPCH.

Synchronization Channel (SCH)Used for cell searchTwo sub channels: P-SCH and S-SCH. SCH is transmitted at the first 256 chips of every time slot.PSC is transmitted repeatedly in each time slot.SSC specifies the scrambling code groups of the cell.SSC is chosen from a set of 16 different codes of length 256, there are altogether 64 primary scrambling code groups.

acsi,0

acsi,14

acp

acsi,1

acp

One 10 ms SCH radio frame

Slot #14

Slot #1

SecondarySCH

Slot #0

PrimarySCH

acp

256 chips

2560 chips

Primary Common Control Physical Channel (PCCPCH)Fixed rate30kbpsSF=256, 1Carry BCH transport channelNot transmitted during the first 256 chips of each time slot.Only data partSTTD transmit diversity may be used

Data18 bits

1 radio frame: Tf = 10 ms

Tslot = 2560 chips , 20 bits

Slot #0

Slot #1

Slot #i

Slot #14

(Tx OFF)

256 chips

Secondary Common Control Physical Channel (SCCPCH)Carry FACH and PCH. Two types of SCCPCH: with or without TFCI. UTRAN decides if a TFCI should be transmitted, UE must support TFCI.Possible rates are the same as that of downlink DPCHSF =256 - 4. FACH and PCH can be mapped to the same or separate SCCPCHs. If mapped to the same S-CCPCH, they can be mapped to the same frame.

DataNdata bits

Pilot Npilot bits

1 radio frame: Tf = 10 ms

TFCI NTFCI bits

Tslot = 2560 chips, 20*2k bits (k=0..6)

Slot #0

Slot #1

Slot #i

Slot #14

Paging Indicator Channel (PICH)Fixed-rate (SF=256, 3), used to carry the Paging Indicators (PI).PICH is always associated with an S-CCPCH to which a PCH transport channel is mapped to. N paging indicators {PI0, , PIN-1} in each PICH frame, N=18, 36, 72, or 144. If a paging indicator in a certain frame is set to 1, it indicates that UEs associated with this paging indicator should read the corresponding frame of the associated S-CCPCH.

b299

b288

b0

b1

b287

One radio frame (10 ms)

12 bits (undefined)

288 bits for paging indication

Acquisition Indicator Channel (AICH)Frame structure of AICHtwo frames, 20 ms consists of a repeated sequence of 15 consecutive AS, each of length 20 symbols(5120 chips). Each time slot consists of two partsan Acquisition-Indicator(AI) and a part of duration 1024chips with no transmission.Acquisition-Indicator AI have 16 kinds of Signature. CPICH is the phase reference of AICH.

20 ms

Unused part

AI part

a39

a38

a33

a30

a32

a31

a0

a2

a1

AS #0

AS #14

AS #i

AS #1

AS #0

AS #14

Uplink Common Physical Channel Physical Random Access Channel (PRACH)Uplink Dedicated Physical Channel Uplink Dedicated Physical Data Channel (Uplink DPDCH) Uplink Dedicated Physical Control Channel (Uplink DPCCH)Uplink Physical ChannelUplink Physical Channel

Physical Random Access Channel (PRACH)The PRACH consist of 2 parts:Preambleone or several preamble. Each preamble is of length 4096chips and consists of 256 repetitions of a signature whose length is 16 chips. Total of 16 signaturesSF : 256Message part : Two type, 10 or 20ms message partSF : 256 - 32

Which signature is available and the length of message part are determined by higher layer

PRACH Transmission Structure

Preamble

Preamble

20 ms (two radio frames)

4096 chips

Preamble

Message part

Preamble

Preamble

10 ms (one radio frame)

4096 chips

Preamble

Message part

Function of physical channel


Section 1 Physical Channel Structure and Function

Section 2 Channel MappingContents

Channel Mapping

Chapter 1 : Physical Layer Overview



Chapter 4 : Transmit Diversity on Physical ChannelContents

Chapter 3 : Physical Layer Procedure

Section 1 Synchronisation Procedure ( Cell Search)

Section 2 Random Access ProcedureContents

Slot synchronizationFrame synchronization and code-group identificationScrambling-code identificationUE uses PSC to acquire slot synchronization to a cellUE uses SSC to find frame synchronization and identify the code group of the cell found in the first stepUE determines the primary scrambling code through correlation over the CPICH with all codes within the identified group, and then detects the P-CCPCH and reads BCH information1. Synchronization ProcedureCell Search

Chapter 3 : Physical Layer Procedure

Section 1 Synchronisation Procedure ( Cell Search)

Section 2 Random Access ProcedureContents

2. Random Access ProcedureRACHPhysical random access procedure

UE decoded BCH to find out the available RACH sub-channel, its scrambling code and available signature.

Randomly select one of the RACH sub-channels from the group its access class allows to use. Signature also selected randomly from among the available signatures.

Set Preamble Retransmission Counter to Preamble_ Retrans_ Max

Set Preamble Initial Power

Transmit a preamble using the selected uplink access slot, signature, and preamble transmission power

2. Random Access ProcedureRACH

If no Acquisition Indicator received for the corresponding signature in the downlink access slot :

Select the next available access slot in the set of available RACH sub-channels within the given access service class (ASC)

Select a signature

Increase the Commanded Preamble Power

Decrease the Preamble Retransmission Counter by one. If the Preamble Retransmission Counter > 0 then repeat from step 6. Otherwise exit the physical random access procedure.

2. Random Access ProcedureRACHIf Negative Acquisition Indicator corresponding to the selected signature is detected in the downlink access slot corresponding to the selected uplink access slot, exit the physical random access procedure

If a Positive Acquisition Indicator corresponding to the selected signature is detected, Transmit the random access message three or four uplink access slots after the uplink access slot of the last transmitted preamble

Exit physical random access procedure

Chapter : Call Flow

Contents

Chapter : Key Performance Indicator

Accessibility

Retainability

IntegrityContents

Accessibility

Retainibility

Cases for Handoff and Call Drop Analysis

Cases for Call Drop AnalysisUplink interference

Chapter : Extra

Contents

Thank You!!

**WCDMA benefits :1) Soft handover reduce probability of drop call2) Processing Gain wide transmission bandwidth compared to user data, less power needed or transmission3) RRM for admission control & packet scheduling4) Multipath Signal Processing combine power for increase signal integrity

***How Wireless technology evolves?1G- the beginning/birth of commercial mobile network. Since then, there has been tremendous effort in developing mobile network equipment to further enhance the performance of the system.

1G: Purpose to enable wireless communication. (FDMA) Voice quality & capacity limitation. NMT,TACS-systems for analogue wireless phone2G: Aim for wireless high quality voice service. High quality, that is compatible with fixed line quality.3G: Provide for high quality multimedia service. Subscribers demand, operator needs for new source of revenue.Data service were available for wired connection, thus crippled the mobility of mobile device like laptop.NMT : Nordic Mobile Telephone, the first international standardization group (Denmark, Finland, Iceland, Norway & Sweden).TACS : Total Access Communication System (Europe & China)AMPS : Advanced Mobile Phone Systems (USA)TDMA (D-AMPS) digital advanced mobile phone system.PDC: Personal Digital Cellular (Japan)GPRS: General Packet Radio Service. - Hardware (eg BTS: PCU, GPRS)EDGE : Enhance data rate for global evolution.-Provide higher data rates than GPRS. Can co-exist with GPRS. When used with GPRS, its called EGPRS.-New transcoder in BTS and software upgrade in both BTS and BSC.Before: Voice, SMS, E-mail3G: Voice, Video, SMS, WAP, Email, Web, MMS, StreamingNeed reliable and high speed access to email, data & application.Provide LAN like connectivity on the road, enable user to work as if they never leave the office, thus enhance productivity.

In the past 20 years, there have been tremendous effort being put in, to provide better services. Now, this bring us to a question, as to what are the driving factors that influence/shape the development/future of mobile communication?

*************Block diagram for digital communcation.Coding scheme voice: AMR , 8 rates(4.75 12.2kbps)CRC attachmentTo check, if error then retransmit.But if just use error checking mechanism, too much retransmission, then reduce total throughput.So, introduce more powerful/effective mechanism, called FEC, by introducing redundant bits.

Channel coding:Purpose: for data protection/error correction1. Convolution coding ( , 1/3 rate). Introduce redundancy bits. For voice & low speed signaling. or Turbo coding (data encoding)2. Interleaving : distribute error over data transmitted3. Rate matching : match symbol rate to that accepted by spreading

Spreading:Spreading : OVSF codesScramblingDifferent codes for different purpose in downlink and uplink.

**The processing gain is calculated as follows: 10*log10128=21db

**AMR rate: bit rate controlled by RNC. As users increases, RNC can dynamically reduces user AMR rate;Depending on air interface load and speech quality on the connection.

CRC attachmentTo check, if error then retransmit.But if just use error checking mechanism, too much retransmission, then reduce total throughput.So, introduce more powerful/effective mechanism, called FEC, by introducing redundant bitsChannel coding:Purpose: for data protection/error correction1. Convolution coding ( , 1/3 rate). Introduce redundancy bits. For voice & low speed signaling. or Turbo coding (data encoding)2. Interleaving : distribute error over data transmitted3. Rate matching : match symbol rate to that accepted by spreading

Spreading:Spreading : OVSF codesScramblingDifferent codes for different purpose in downlink and uplink.

*****Power Control:-Control interference level. UE/NodeB tx at very optimum power level. By control power, lower interference, can increase capacity.Radio link quality is maintain during connectionOvercome near-far effect, shadowing & fast fading.

**RSCP received signal code power**Located in BTS & UE.Controls power of dedicated physical channels.

Inner loop power controlThe base station compares the measured Eb/Nt with the corresponding objective and the mobile station will be ordered to decrease the transmission power if the measured Eb/Nt exceeds the objective. Otherwise, the mobile station will be ordered to increase the transmission power. The adjustment frequency is 1500HZ.Outer loop power controlEstimate Eb/Nt objective based on the measured Frame Error Rate(FER) Eb/Nt=bit energy/density of interference power spectrum, similar to signal-to-noise ratio.

****Soft handoff means that during the handoff of a mobile station at the coverage edge areas of two or multiple base stations, the mobile station receives the signals from multiple base stations (two in most cases) at the same time and the base stations receive the signals from this mobile station at the same time. The mobile station will not disconnect from the original base station until some conditions are satisfied. The reasons for soft handoff are as follows: 1. CDMA system can implement the frequency multiplexing of adjacent cells with the same frequency. 2. For each channel, the mobile station and base station adopt multiple RAKE receivers to receive multi-path signals at the same time. In the course of soft handoff, the signals from various base stations, for a mobile station, are equal to multi-path signals and the receiving of these signals by the mobile station is equal to a kind of space diversity. This soft handoff or softer handoff can improve the quality of service during the handoff in a real sense. That is to say, the conversation quality at the coverage edge is improved and the call dropping rate greatly reduced. This is not common commercial propagation, but a fundamental solution because call dropping in a GSM system mostly takes place during the handoff.

******UTRAN:UMTS Terrestrial Radio Access Network.The UTRAN consists of a set of Radio Network Subsystems connected to the Core Network through the Iu.A RNS consists of a Radio Network Controller and one or more NodeBs. A Node B is connected to the RNC through the Iub interface. Inside the UTRAN, the RNCs of the Radio Network Subsystems can be interconnected together through the Iur. Iu(s) and Iur are logical interfaces. Iur can be conveyed over direct physical connection between RNCs or virtual networks using any suitable transport network.

**Spreading is applied to the physical channels. It consists of two operations. The first is the channelization operation, which transforms every data symbol into a number of chips, thus increasing the bandwidth of the signal. The number of chips per data symbol is called the Spreading Factor (SF). The second operation is the scrambling operation, where a scrambling code is applied to the spread signal.

**The channelization codes of figure are Orthogonal Variable Spreading Factor (OVSF) codes that preserve the orthogonality between a users different physical channels. The OVSF codes can be defined using the code tree of the figure.

***********Now we will begin to discuss the physical channel. Physical channel is the most important and complex channel. A physical channel is defined by a specific carrier frequency,code and relative phase. In CDMA system, the different code (scrambling code or spreading code) can distinguish the channel. Most channels consist of radio frames and time slots, and each radio frame consist of 15 time slots. There are two types of physical channel:UL and DL. Lets look at the uplink physical channel first.

****The transmit diversity is STTD.SF256,0*****The Secondary CCPCH is used to carry the FACH and PCH. There are two types of Secondary CCPCH: those that include TFCI and those that do not include TFCI. It is the UTRAN that determines if a TFCI should be transmitted, hence making it mandatory for all UEs to support the use of TFCI. The set of possible rates for the Secondary CCPCH is the same as for the downlink DPCH

System default : SF 64, 1

TFCI : support variable service rate. But rate for 1 radio frame is fixed.No TFCI : fixed rate service

**This is the structure of paging indicator channel.In a 10ms radio frame, 288bits are used to carry paging indicators and the remain 12 bits are undefined.

**AS:access slot.The AICH is a fixed rate physical channel (SF 256) used to indicate in the cell the reception by the base station of PRACH preambles(signatures). Once the base station has received a preamble, the same signature that has been detected on the PRACH preamble is then sent back to the UE using this channel.

**Uplink physical channel is divided into uplink dedicated physical channel and uplink common physical channel. Uplink dedicated physical channel is divided into uplink dedicated physical data channel(UL DPDCH) and uplink dedicated physical common channel(UL DPCCH). Uplink common physical channel includes physical random access channel(PRACH) and physical common packet channel(PCPCH).

*********During the cell search, the UE searches for a cell and determines the downlink scrambling code and frame synchronisation of that cell. The cell search is typically carried out in three steps:Step 1: Slot synchronisationDuring the first step of the cell search procedure the UE uses the SCHs primary synchronisation code to acquire slot synchronisation to a cell. This is typically done with a single matched filter (or any similar device) matched to the primary synchronisation code which is common to all cells. The slot timing of the cell can be obtained by detecting peaks in the matched filter output.Step 2: Frame synchronisation and code-group identificationDuring the second step of the cell search procedure, the UE uses the SCHs secondary synchronisation code to find frame synchronisation and identify the code group of the cell found in the first step. This is done by correlating the received signal with all possible secondary synchronisation code sequences, and identifying the maximum correlation value. Since the cyclic shifts of the sequences are unique the code group as well as the frame synchronisation is determined.Step 3: Scrambling-code identificationDuring the third and last step of the cell search procedure, the UE determines the exact primary scrambling code used by the found cell. The primary scrambling code is typically identified through symbol-by-symbol correlation over the CPICH with all codes within the code group identified in the second step. After the primary scrambling code has been identified, the Primary CCPCH can be detected.And the system- and cell specific BCH information can be read.If the UE has received information about which scrambling codes to search for, steps 2 and 3 above can be simplified.

***ASC:access service class.The physical random access procedure described in this subclause is initiated upon request from the MAC sublayer .Before the physical random-access procedure can be initiated, Layer 1 shall receive the following information from the higher layers (RRC):-The preamble scrambling code.-The message length in time, either 10 or 20 ms.-The AICH_Transmission_Timing parameter [0 or 1].-The set of available signatures and the set of available RACH sub-channels for each Access Service Class (ASC). Sub-channels are defined in subclause 6.1.1.-The power-ramping factor Power Ramp Step [integer > 0].-The parameter Preamble Retrans Max [integer > 0].-The initial preamble power Preamble_Initial_Power.-The Power offset P p-m = Pmessage-control Ppreamble, measured in dB, between the power of the last transmitted preamble and the control part of the random-access message.-The set of Transport Format parameters. This includes the power offset between the data part and the control part of the random-access message for each Transport Format.Note that the above parameters may be updated from higher layers before each physical random access procedure is initiated.At each initiation of the physical random access procedure, Layer 1 shall receive the following information from the higher layers (MAC):-The Transport Format to be used for the PRACH message part.-The ASC of the PRACH transmission.-The data to be transmitted (Transport Block Set).The physical random-access procedure shall be performed as follows:1Derive the available uplink access slots, in the next full access slot set, for the set of available RACH sub-channels within the given ASC. Randomly select one access slot among the ones previously determined. If there is no access slot available in the selected set, randomly select one uplink access slot corresponding to the set of available RACH sub-channels within the given ASC from the next access slot set. The random function shall be such that each of the allowed selections is chosen with equal probability.2Randomly select a signature from the set of available signatures within the given ASC. The random function shall be such that each of the allowed selections is chosen with equal probability.3Set the Preamble Retransmission Counter to Preamble Retrans Max.4Set the parameter Commanded Preamble Power to Preamble_Initial_Power.5In the case that the Commanded Preamble Power exceeds the maximum allowed value, set the preamble transmission power to the maximum allowed power. In the case that the Commanded Preamble Power is below the minimum level required in [7], set the preamble transmission power to a value, which shall be at or above the Commanded Preamble Power and at or below the required minimum power specified in [7]. Otherwise set the preamble transmission power to the Commanded Preamble Power. Transmit a preamble using the selected uplink access slot, signature, and preamble transmission power.6If no positive or negative acquisition indicator (AI +1 nor 1) corresponding to the selected signature is detected in the downlink access slot corresponding to the selected uplink access slot:6.1Select the next available access slot in the set of available RACH sub-channels within the given ASC.6.2Randomly select a new signature from the set of available signatures within the given ASC. The random function shall be such that each of the allowed selections is chosen with equal probability.6.3Increase the Commanded Preamble Power by DP0 = Power Ramp Step [dB]. If the Commanded Preamble Power exceeds the maximum allowed power by 6dB, the UE may pass L1 status ("No ack on AICH") to the higher layers (MAC) and exit the physical random access procedure.6.4Decrease the Preamble Retransmission Counter by one.6.5If the Preamble Retransmission Counter > 0 then repeat from step 5. Otherwise pass L1 status ("No ack on AICH") to the higher layers (MAC) and exit the physical random access procedure.7If a negative acquisition indicator corresponding to the selected signature is detected in the downlink access slot corresponding to the selected uplink access slot, pass L1 status ("Nack on AICH received") to the higher layers (MAC) and exit the physical random access procedure. 8Transmit the random access message three or four uplink access slots after the uplink access slot of the last transmitted preamble depending on the AICH transmission timing parameter. Transmission power of the control part of the random access message should be P p-m [dB] higher than the power of the last transmitted preamble. Transmission power of the data part of the random access message is set according to subclause 5.1.1.2.9Pass L1 status "RACH message transmitted" to the higher layers and exit the physical random access procedure.

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WCDMA Day 1

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