02- OWA200003 WCDMA Radio Interface Physical Layer

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WCDMA Radio Interface Physical Layer

ISSUE 1.0


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, for example Modulation and

spreading/demodulation and despreading, Inner -

loop power control etc.


References

TS 25.104 UTRA (BS) FDD Radio Transmission and Re

ception

TS 25.201 Physical layer-general description

TS 25.211 Physical channels and mapping of

transport channels onto physical channels (FDD)

TS 25.212 Multiplexing and channel coding (FDD)

TS 25.213 Spreading and modulation (FDD)

TS 25.214 Physical layer procedures (FDD)

TS 25.308 UTRA High Speed Downlink Packet Access

(HSDPA); Overall description; Stage 2

TR 25.877 High Speed Downlink Packet Acces (HSDPA) -

Iub/Iur Protocol Aspects

TR 25.858 Physical layer aspects of UTRA High Speed D

ownlink Packet Access


Upon completion of this course, you will be

able to:

Outline radio interface protocol

Architecture

Describe key technology of UMTS

physical layer

Describe UMTS physical layer procedures


Chapter 1 Physical Layer OverviewChapter 1 Physical Layer Overview

Chapter 2 Physical Layer Key Technology Chapter 2 Physical Layer Key Technology

Chapter 3 Physical Layer ProceduresChapter 3 Physical Layer Procedures


UTRAN Protocol Structure

RNS

RNC

RNS

RNC

Core Network

NodeB NodeB NodeB NodeB

Iu Iu

Iur

Iub IubIub Iub


Radio Interface Protocol Structure

L3

con

tro

l

con

tro

l

con

tro

l

con

tro

l

Logical Channels

Transport Channels

C-plane signaling U-plane information

PHY

L2/MAC

L1

RLC

DCNtGC

L2/RLC

MAC

RLCRLC

RLCRLC

RLCRLCRLC

Duplication avoidance

UuS boundary

BMC L2/BMC

control

PDCPPDCP L2/PDCP

DCNtGC

Radio Bearers

RRC


Spreading Technology Spreading consists of 2 steps ：

Channelization operation, which transforms data symbols into chips. Thus increasing the bandwidth of the signal, The number of chips per data symbol is called the Spreading Factor （ SF ） .The operation is done by multiplying with OVSF code.

Scrambling operation is applied to the spreading signal .

Data bit

OVSF code

Scrambling code

Chips after spreading


Channelization Code

OVSF 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 Code

Scrambling code: GOLD sequence.

Scrambling code period: 10ms ,or 38400 chips.

The code used for scrambling of the 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. scrambling codes k = 0, 1, …, 8191 are used.


Scrambling codes for downlink physical channels

Set 0

Set 1

…

Set 511

Primary scrambling code 0

……

Secondary scrambling code 1

Secondary scrambling code 15

Primary scrambling code

511×16

……

Secondary scrambling code 511×1

6＋ 15

8192 scrambling codes

512 sets

Primary Scrambling Code

……

A primary scrambling code and 15 secondary scrambling codes are

included in a set.


Primary Scrambling Code Group

Primary scrambling codes for downlink physical channels

Group 0

…


……

Primary scrambling code

8*63

……

Primary scrambling code 63*8＋

7

512 primary scrambling codes

……

Group 1

Group 63



64 primary scrambling code groups

Each group consists of 8 primary scrambling codes



Chapter 2 Physical Layer Key TechnologyChapter 2 Physical Layer Key Technology




Section 1 Physical ChannelSection 1 Physical Channel Structure and FunctionsStructure and Functions

Section 2 Channel MappingSection 2 Channel Mapping


WCDMA radio interface has three kinds of channels

In terms of protocol layer, the WCDMA radio interface has three channels: Physical channel, transport channel and logical channel.

Logical channel: Carrying user services directly. According to the types of the carried services, it is divided into two types: Control channel and service channel.

Transport channel: It is the interface of radio interface layer 2 and physical layer, and is the service provided for MAC layer by the physical layer. According to whether the information transported is dedicated information for a user or common information for all users, it is 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 kind of channel which uses dedicated carrier frequency, code (spreading code and scramble) and carrier phase (I or Q) can be regarded as a dedicated channel.


Control channel

Traffic 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)

Logical Channel

HUAWEI TECHNOLOGIES CO., LTD. Page 18All rights reserved

Dedicated Channel (DCH)

-DCH is an uplink or downlink channel

Broadcast channel (BCH)

Forward access channel (FACH)

Paging channel (PCH)

Random access channel (RACH)

High-speed downlink shared channel

(HS-DSCH)

Common transport channel

Dedicated transport channel

Transport Channel


Physical 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


Downlink Physical Channel

Downlink Dedicated Physical Channel

(Downlink DPCH)

Downlink Common Physical Channel

Common Control Physical Channel (CCPCH)

Synchronization Channel (SCH)

Paging Indicator Channel (PICH)

Acquisition Indicator Channel (AICH)

Common Pilot Channel (CPICH)

High-Speed Packet Downlink Shared Channel (HS-PDSCH)

High-Speed Shared Control Channel (HS-SCCH)

Downlink Physical Channel


Uplink Physical Channel

Uplink Dedicated Physical Channel

Uplink Dedicated Physical Data Channel (Uplink DPDCH)

Uplink Dedicated Physical Control Channel (Uplink DPCCH)

High-Speed Dedicated Physical Channel (HS-DPCCH)

Uplink Common Physical Channel

Physical Random Access Channel

(PRACH)

Uplink Physical Channel


Function of physical channel

Node B UE

P-CCPCH-Primary Common Control Physical ChannelSCH- Synchronisation Channel

P-CCPCH-Primary Common Control Physical ChannelSCH- Synchronisation Channel

P-CPICH-Primary Common Pilot Channel S-CPICH-Secondary Common Pilot ChannelP-CPICH-Primary Common Pilot Channel S-CPICH-Secondary Common Pilot Channel

Cell broadcast channels

DPDCH-Dedicated Physical Data ChannelDPDCH-Dedicated Physical Data Channel

DPCCH-Dedicated Physical Control ChannelDPCCH-Dedicated Physical Control Channel

Dedicated channels

Paging channels

PICH-Paging Indicator ChannelPICH-Paging Indicator Channel

S-CCPCH-Secondary Common Control Physical ChannelS-CCPCH-Secondary Common Control Physical Channel

PRACH-Physical Random Access ChannelPRACH-Physical Random Access Channel

AICH-Acquisition Indicator ChannelAICH-Acquisition Indicator Channel

Random access channels

HS-DPCCH-High Speed Dedicated Physical Control ChannelHS-DPCCH-High Speed Dedicated Physical Control Channel

HS-SCCH-High Speed Share Control Channel HS-SCCH-High Speed Share Control Channel

HS-PDSCH-High Speed Physical Downlink Share ChannelHS-PDSCH-High Speed Physical Downlink Share Channel

High speed downlink share channels


Primary Synchronization Channel (P-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, and there are altogether 64 SSC sequences correspond to 64 primary scrambling code groups.

Primary SCH

Secondary SCH

Slot #0 Slot #1 Slot #14

acsi,0

pac pac pac

acsi,1 acs

i,14

256 chips

2560 chips

One 10 ms SCH radio frame


slot number Scrambling Code Group #0 #1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 #13 #14

Group 0 1 1 2 8 9 10 15 8 10 16 2 7 15 7 16

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

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

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

Group 4 1 2 16 6 6 11 15 5 12 1 15 12 16 11 2

…

Group 61 9 10 13 10 11 15 15 9 16 12 14 13 16 14 11

Group 62 9 11 12 15 12 9 13 13 11 14 10 16 15 14 16

Group 63 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10

Secondary Synchronization Channel (S-SCH)

……..

2560 chips

acp

Slot # ?

P-SCH acp

Slot #?

16 6S-SCH

acp

Slot #?

11 Group 2Slot 7, 8, 9

256 chips


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

Carries pre-defined sequence.

Fixed rate 30Kbps ， SF=256

Primary CPICH

Uses the fixed channel 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.

Pre-defined symbol sequence

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

Tslot = 2560 chips , 20 bits

1 radio frame: Tr = 10 ms


Primary Common Control Physical Channel (PCCPCH) Fixed rate, fixed OVSF code （ 30kbps ， Cch,256,1 ） Carry BCH transport channel The PCCPCH is not transmitted during the first 256 chips of each time slot. Only data part STTD transmit diversity may be used

PCCPCH Data

18 bits

Slot #0

1 radio frame: T f = 10 ms

Slot #1 Slot #i

256 chips

Slot #14

T slot = 2560 chips,20 bits

SCH


Paging Indicator Channel (PICH) PICH is a fixed-rate (SF=256) physical channel used to carry the Paging Indicators (PI). Frame structure of PICH: one frame of length 10ms consists of 300 bits of which 288 bits

are used to carry paging indicators and the remaining 12 bits are not defined. 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.

One radio frame (10 ms)

b1 b0

288 bits for paging indication

12 bits (undefined)

b287 b288 b299


Secondary Common Control Physical Channel (SCCPCH) Carry FACH and PCH. Two kinds 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 fame.

DataN bits

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

1 radio frame: T f = 10 ms

T slot = 2560 chips,

Data

PilotN bitsPilotN bits

TFCITFCI

20*2 k bits (k=0..6)


Physical Random Access Channel (PRACH) The random-access transmission data consists of two parts:

One or several preambles ： each preamble is of length 4096chips and consists of 256 repetitions of a signature whose length is 16 chips ， 16 available signatures totally

10 or 20ms message part

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

Message partPreamble

4096 chips10 ms (one radio frame)

Preamble Preamble

Message partPreamble

4096 chips 20 ms (two radio frames)

Preamble Preamble


PRACH Access Timeslot Structure

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

5120 chips

radio frame: 10 ms radio frame: 10 ms

Access slot #0 Random Access Transmission

Access slot #1

Access slot #7

Access slot #14

Random Access Transmission

Random Access Transmission

Random Access TransmissionAccess slot #8


PRACH Message Structure

PilotN bits

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

Message part radio frame TRACH = 10 ms

Tslot = 2560 chips, 10*2

Pilot

TFCI

N bitsTFCI

DataN data bitsData

Control

k bits (k=0..3)


Acquisition Indicator Channel (AICH) Frame structure of AICH ： two frames, 20 ms ， consists of a repeated

sequence of 15 consecutive AS, each of length 40 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


Uplink Dedicated Physical Channel (DPDCH&DPCCH)

DPDCH and DPCCH are I/Q code multiplexed within each radio frame

DPDCH carries data generated at Layer 2 and higher layer

DPCCH carries control information generated at Layer 1

Each frame is 10ms and consists of 15 time slots, each time slot

consists of 2560 chips

The spreading factor of DPDCH is from 4 to 256

The spreading factor of DPDCH and DPCCH can be different in the

same Layer 1 connection

Each DPCCH time slot consists of Pilot, TFCI ， FBI ， TPC


Frame Structure of Uplink DPDCH/DPCCH

Pilot Npilot bits

TPC NTPC bits

DataNdata bits


Tslot = 2560 chips, 10*2 k bits (k=0..6)

1 radio frame: T = 10 msf

DPDCH

DPCCHFBI

NFBI bitsTFCI

NTFCI bits


Downlink Dedicated Physical Channel (DPDCH+DPCCH)

DCH consists of dedicated data and control information.

Control information includes ： Pilot 、 TPC 、 TFCI(optional).

The spreading factor of DCH can be from 512 to 4,and can be changed during connection

DPDCH and DPCCH is time multiplexed.


Frame Structure of Downlink DPCH

One radio frame, Tf = 10 ms


Tslot = 2560 chips, 10*2 k bits (k=0..7)

Data2Ndata2 bits

DPDCH

TFCI NTFCI bits

Pilot Npilot bits

Data1Ndata1 bits

DPDCH DPCCH DPCCH

TPC NTPC bits


High-Speed Physical Downlink Shared Channel (HS-PDSCH)

Bear service data and layer2 overhead bits mapped from the transport

channel

SF=16, can be configured several channels to increase data service

Slot #0 Slot#1 Slot #2

T slot = 2560 chips, M*10*2k bits (k=4)

DataN Data 1 bits

1 subframe: Tf = 2 ms


High-Speed Shared Control Channel (HS-SCCH)

Carries physical layer signalling to a single UE ,such as modulation scheme (1 bit) ,channelization code set (7 bit), transport Block size (6bit),HARQ process number (3bit), redundancy version (3bit), new data indicator (1bit), Ue identity (16bit)

HS-SCCH is a fixed rate (60 kbps, SF=128) downlink physical channel used to carry downlink signalling related to HS-DSCH transmission

Slot #0 Slot#1 Slot #2

T slot= 2560 chips, 40 bits

DataN Data 1 bits

1 subframe: T f = 2 ms


High-Speed Dedicated Physical Control Channel (HS-DPCCH )

HS-DPCCH carries information to acknowledge downlink transport

blocks and feedback information to the system for scheduling and link

adaptation of transport block

CQI and ACK/NACK

Physical Channel ,Uplink, SF=256,power control

Subframe #0 Subframe # i Subframe #4

HARQ-ACK CQI

One radio frame T f = 10 ms

One HS-DPCCH subframe (2 ms)

2 T slot = 5120 chips T slot = 2560 chips


Chapter 2 Physical Layer Key Technology Chapter 2 Physical Layer Key Technology

Section 1 Physical Channel Structure and FunctionsSection 1 Physical Channel Structure and Functions

Section 2 Channel MappingSection 2 Channel Mapping


Mapping Between ChannelsLogical channels Transport channels Physical channels

BCCH BCH P-CCPCH

FACH S-CCPCH

PCCH PCH S-CCPCH

CCCH RACH PRACH

FACH S-CCPCH

CTCH FACH S-CCPCH

DCCH, DTCH DCH DPDCH

HS-DSCH HS-PDSCH

RACH, FACH PRACH, S-CCPCH


Synchronization Procedure—Cell Search

Frame synchronization and code-group identification

Scrambling-code identification

UE uses SSC to find frame synchronization and identify the code group of the cell found in the first step

UE 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 information。

Slot synchronizationUE uses PSC to acquire slot synchronization to a cell


Synchronization Procedure— Channel Timing Relationship

AICH access slo ts

Secondary SCH

Primary SCH

S-CCPCH,k

10 ms

PICH

#0 #1 #2 #3 #14 #13 #12 #11 #10 #9 #8 #7 #6 #5 #4

P -CCPCH, (SFN modulo 2) = 0 P -CCPCH, (SFN modulo 2) = 1

Any CPICH

k:th S -CCPCH

PICH for k:th S -CCPCH

n:th DPCH DPCH,n


Random Access Procedure START

Choose a RACH sub channel fromavailable ones

Get available signatures

Set Preamble Retrans Max

Set Preamble _Initial _ Power

Send a preamble

Check the corresponding AI

Increase message part power by p-m based on preamble power

Set physical status to be RACH message transmitted Set physical status to be Nack

on AICH received

Choose a access slot again

Counter> 0 & Preamble power-maximum allowed power<6 dB

Choose a signature and increase preamble transmit power

Set physical status to be Nack on AICH received

Get negative AI

No AI

Report the physical status to MAC

END

Get positive AI

The counter of preamble retransmit Subtract-1, Commanded preamble power

increased by Power Ramp Step

N

Y

Send the corresponding message part


Random Access Procedure—RACH

Physical random access procedure

1. Derive 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 ；

2. Randomly select a signature from the set of available signatures within the given ASC. ；

3. Set the Preamble Retransmission Counter to Preamble_ Retrans_ Max



4. Set the parameter Commanded Preamble Power to Preamble_Initial_Power

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

6. If 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:

− A: Select the next available access slot in the set of available RACH sub-channels within the given ASC;

− B: select a signature;

− C: Increase the Commanded Preamble Power;

− D: 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.



7. If a 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 Signature

8. 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

9. exit the physical random access procedure


Transmit diversity Mode

Application of Tx diversity modes on downlink Application of Tx diversity modes on downlink physical channelphysical channel

Physical channel type Open loop mode Closed loop mode

TSTD STTD Mode 1 Mode 2

P-CCPCH – applied – –

SCH applied – – –

S-CCPCH – applied – –

DPCH – applied applied applied

PICH – applied – –

HS-PDSCH – applied applied –

HS-SCCH – applied – –

AICH – applied – –


Transmit Diversity-STTD

Space time block coding based transmit antenna diversity(STTD ） 4 consecutive bits b0, b1, b2, b3 using STTD coding

b0 b1 b2 b3

b0 b1 b2 b3

-b2 b3 b0 -b1

Antenna 1

Antenna 2Channel bits

STTD encoded channel bitsfor antenna 1 and antenna 2.


Transmit Diversity-TSTD

Time switching transmit diversity (TSTD) is used Time switching transmit diversity (TSTD) is used only on SCH channel.only on SCH channel.

Antenna 1

Antenna 2

ac si,0

acp

acsi,1

acp

acsi,14

acp

Slot #0 Slot #1 Slot #14

acsi,2

acp

Slot #2

(Tx OFF)

(Tx OFF)(Tx OFF)

(Tx OFF)

(Tx OFF)

(Tx OFF)(Tx OFF)(Tx OFF)


Transmit Diversity － Closed Loop Mode Closed loop mode transmit diversity

Used in DPCH and PDSCH ； Channel coding, interleaving and spreading are done as in non-

diversity mode. The spread complex valued signal is fed to both TX

antenna branches, and weighted with antenna specific weight

factors w1 and w2.

The weight factors are determined by the UE, and signalled to the

UTRAN access point (=cell transceiver) using the D-bits of the FBI

field of uplink DPCCH.

The calculation of weight factor is the key point of closed loop Tx di

versity.there are two modes with different calculation methods of w

eight factor ：

− 1 、 mode 1 uses phase adjustment ； the dedicated pilot sym

bols of two antennas are different(orthogonal)

− 2 、 mode 2 uses phase/amplitude adjustment ； the dedicate

d pilot symbols of two antennas are the same.


Summary

This course mainly introduces the basic concept,

key technology and procedures of WCDMA phy

sical layer.

This is very helpful for comprehension of Uu int

erface features and further study .

www.huawei.com

Thank You

02- OWA200003 WCDMA Radio Interface Physical Layer

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