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WCDMA Channels

Copyright 2010 MobileComm Technologies India Pvt. Ltd. All rights reserved MobileComm is committed to providing our customers with quality instructor ledTelecommunications Training.This documentation is protected by copyright. No part of the contents of thisdocumentation may be reproduced in any form, or by any means, without the prior written consent of MobileComm Technologies .Document Number: RK/CT/3/2010This manual prepared by: MobileComm Technologies MobileComm Technologies(India)Pvt. Ltd.424, First Floor, Udyog Vihar Phase -4, Gurgaon-122002 Headquarter:MobileComm Professionals Inc.1255 West 15th Street, Suite 440Plano, TX, 75075Tel: (972) 633-5100Fax: (972) 633-5106

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Section 1 Physical Channel Structure and Function

Section 2 Channel Mapping

Content

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WCDMA Radio InterfaceWCDMA Radio Interface

3GPP 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.

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Logical channelLogical channel

Traffic channel

Control channel

Dedicated traffic channel （ DTCH）Common traffic channel （ CTCH）

Broadcast control channel （ BCCH）Paging control channel （ PCCH）Dedicate control channel （ DCCH）Common control channel (CCCH）

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Transport channelTransport 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 channel

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Physical ChannelPhysical 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 DL

Physical Channel

Frequency,code,phase

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Downlink Physical ChannelDownlink Physical 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 DPCH

Downlink Physical Channel

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Functions of Downlink DPDCH/DPCCH Functions of Downlink DPDCH/DPCCH

DCH data

DPDCH

DPCCH

Provide control data for DPDCH ,such as demodulation, power control,etc.

Data bearer at physical layer

DCH data

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Common Pilot Channel(CPICH)Common Pilot Channel(CPICH)

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

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Common Pilot Channel (CPICH) Common Pilot Channel (CPICH)

Primary CPICH Uses OVSF code -Cch, 256,0 Scrambled by the primary scrambling code Only one CPICH per cell Broadcast over the entire cell The P-CPICH is a phase reference for SCH, Primary CCPCH,

AICH, PICH. By default, it is also a phase reference for downlink DPCH.

Secondary CPICH An arbitrary channel code of SF=256 is used for S-CPICH S-CPICH is scrambled by either the primary or a secondary

scrambling code There may be zero, one , or several secondary CPICH. S-CPICH may be transmitted over part of the cell S-CPICH may be a phase reference for S-CCPCH and downlink

DPCH.

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Synchronization Channel (SCH)Synchronization Channel (SCH)

Used for cell search Two 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.

Primary SCH

Secondary SCH

256 chips

2560 chips

One 10 ms SCH radio frame

acsi,0

acp

acsi,1

acp

acsi,14

acp

Slot #0 Slot #1 Slot #14

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Primary Common Control Physical Channel (PCCPCH)Primary Common Control Physical Channel (PCCPCH)

Fixed rate（ 30kbps， SF=256, 1） Carry BCH transport channel Not transmitted during the first 256 chips of each time slot. Only data part STTD transmit diversity may be used

Data 18 bits

Slot #0 Slot #1 Slot #i Slot #14

Tslot = 2560 chips , 20 bits

1 radio frame: Tf = 10 ms

(Tx OFF)

256 chips

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Secondary Common Control Physical Channel (SCCPCH)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 DPCH

SF =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.

Slot #0 Slot #1 Slot #i Slot #14

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

Pilot Npilot bits

Data Ndata bits

1 radio frame: Tf = 10 ms

TFCI NTFCI bits

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Paging Indicator Channel (PICH) Paging Indicator Channel (PICH)

One radio frame (10 ms)

b1 b0

288 bits for paging indication 12 bits (undefined)

b287 b288 b299

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.

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Acquisition Indicator Channel (AICH)Acquisition Indicator Channel (AICH)

Frame structure of AICH： two 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 parts， an 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.

AS #14 AS #0 AS #1 AS #i AS #14 AS #0

a1 a2a0 a31 a32a30 a33 a38 a39

AI part Unused part

20 ms

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Uplink Physical Channel Uplink Physical Channel

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 Channel

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Physical Random Access Channel (PRACH) Physical Random Access Channel (PRACH)

The PRACH consist of 2 parts: Preamble

one 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 signatures

SF : 256 Message part :

Two type, 10 or 20ms message part SF : 256 - 32

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

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PRACH Transmission StructurePRACH Transmission Structure

Message part Preamble

4096 chips 10 ms (one radio frame)

Preamble Preamble

Message part Preamble

4096 chips 20 ms (two radio frames)

Preamble Preamble

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Function of physical channel

P-CCPCH-Primary common control physical channel

SCH- Synchronisation Channel

P-CPICH-Primary common pilot channel S-CPICH-secondary common pilot channel

Cell broadcast channels

DPDCH-dedicated physical data channel

DPCCH-dedicated physical control channel

Dedicated channels

Paging channels

PICH-paging Indicator Channel

S-CCPCH-Secondary common control physical channel

PRACH-Physical random access channel

AICH-Acquisition Indicator Channel

Random access channels

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Channel Mapping

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Cell search procedure

(P-SCH) Primary SCH

(S-SCH) Secondary SCH

CPICH

P-CCPCH P-CCPCH

Slot synchronisation to

a cell

10 ms

The Primary CCPCH is detected using the identified primary scrambling code After the cell search, system and cell specific BCH information can be read.

Frame synchronisation and identification of the cell code

group

Determination of the exact primary scrambling code

used by the found cell

Phase 1

Phase 2

Phase 3

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Cell search procedure

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15

scramblingcode group

group 00

group 01

group 02

group 03

group 05

group 04

group 62

group 63

1 1 2 8 9 10 15 8 10 16 2 7 15 7 16

1 1 5 16 7 3 14 16 3 10 5 12 14 12 10

1 2 1 15 5 5 12 16 6 11 2 16 11 12

1 2 3 1 8 6 5 2 5 8 4 4 6 3 7

1 2 16 6 6 11 5 12 1 15 12 16 11 2

1 3 4 7 4 1 5 5 3 6 2 8 7 6 8

9 11 12 15 12 9 13 13 11 14 10 16 15 14 16

9 12 10 15 13 14 9 14 15 11 11 13 12 16 10

slot number0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

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11 11

11 11

11 11

11 11

15

15

15

15 15

15

15

15 15

15 15

5

5

SSC Allocation for S-SCH

I monitor the S-SCH

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Call procedures

Power OFF

PLMN selection

IDLE mode

CONNECTED mode

Cell search

Cell selection

System information (BCH)

Power ON

Location registration

Cell reselection

RACH procedure

RACH procedure

RRC Connection

Paging

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Paging procedure (2/2)

• A cell can have configured more than one S-CCPCH + PICH for paging. The configuration type is specified in SIB 1 and SIB 5.

UE reads System info (SIB 5)

UE evaluates which S-CCPCH

UE evaluates how often to check PI from PICH

UE evaluates when to check PI from

PICHUE evaluates which PI

to check

Paging procedure

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Random access procedure

UE

RRC: System Information (BCCH / BCH /

PCCPCH)

1. PRACH Preamble (P1)

2. PRACH Preamble (P2=P1

+P0)

3. AICH: Acquisition Indication

4. RRC : RRC Connection Request

(RACH / PRACH Message (P3=P2

+Pm-p)) WBTS

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Random access procedure

UE

•Location Update•Authentication•Security Mode Setup•Paging•Call Setup

1. Location Update

Request

2. Authentication and Security Mode

Setup

3. Location Update Accept

4. Paging

5. Call Setup

MSC / VLR

WBTS

Ciphering and Integrity Protection

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DEDICATED CHANNEL PROCEDURE

Figure :Dedicated channel establishment-mobile terminated call

UE in Idle Mode

1. PI on the PICH

2. PCH message on the S-CCPCH

3. UE ramps up the power by sending preambles

4. Node B responds on the AICH

5. UE sends the RACH message

6. FACH message on S-CCPCH

7. DL-DPCH ramp up

8. UE sends UL-DPCH

DPCH established

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MOC Call Setup