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OWA200003 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 Reception

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 Downlink Packet Access


Upon completion of this course, you

will be able to:

Understand radio interface

protocol Architecture

Understand key technology of

UMTS physical layer

Understand 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

Node B Node B Node B Node B

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


Data Processing at Physical Layer

Data from MAC Layer（ TB）

Channel coding and multiplexing

Spreading and modulation


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 =

262143 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 Channel Structure and FunctionsSection 1 Physical Channel Structure 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


Dedicated Channel (DCH)

-The Dedicated Channel (DCH) is an

uplink or downlink channel.

Broadcast channel (BCH)

Forward access channel (FACH)

Paging channel (PCH)

Random access channel (RACH)

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 DL shared Channel

Downlink Physical Channel


Uplink Physical Channel

Uplink Dedicated Physical Channel

Uplink Dedicated Physical Data

Channel (Uplink DPDCH)

Uplink Dedicated Physical Control

Channel (Uplink 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


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

Slot #0 Slot #1 Slot #14

acsi,0

pac pac pac

acsi,1 acs

i,14

256 chips2560 chips

One 10 ms SCH radio frame


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

Carries pre-defined sequence.

Fixed rate 30Kbps ， SF=256

The CPICH uses the same channel and scrambling code but different sequences in the case transmit diversity is used on downlink channel

slot #1

Frame#i+1Frame#i

slot #14

A A A A A A A A A A A A A A A A A A A A A A A A

-A -A A A -A -A A A -A A -A -A A A -A -A A A -A -A A A -A -AAntenna 2

Antenna 1

slot #0

Frame Boundary


Common Pilot Channel (CPICH) Primary CPICH

Uses the same 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. 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.


Primary Common Control Physical Channel (PCCPCH) Fixed rate （ 30kbps ， SF=256 ） 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

Data

18 bits

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

1 radio frame: Tf = 10 ms

256 chips

T slot = 2560 chips,20 bits

(Tx OFF)


Paging Indicator Channel (PICH)

PICH is a fixed-rate (SF=256) physical channel used to carry the Paging Indicators (PI).

PICH is always associated with an S-CCPCH to which a PCH transport channel is mapped.

Frame structure of PICH ： one frame of length 10ms consists of 300 bits of which 288 bits a

re 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 p

aging 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.

Data

N bits



T slot = 2560 chips,

Data

PilotN bitsPilotN bits

TFCI

TFCI

20*2k 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


PRACH Transmission Structure

Message part Preamble

4096 chips 10 ms (one radio frame)

Preamble Preamble

Message part

Preamble

4096 chips 20 ms (two radio frames)

PreamblePreamble


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

Data

N data bits Data

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 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


Uplink Dedicated Physical Channel

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

Data Ndata bits


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


DPDCH

DPCCH FBI

NFBI bits TFCI

NTFCI bits


Functions of Uplink DPDCH/DPCCH

DCH Data

DPDCHDPDCH

DPCCHDPCCH

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

Data bearer Data bearer at physical layerat physical layer


Downlink Dedicated Physical Channel

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.

Multi-code transmission within one CCTrCH uses the same

spreading factor. In this case, the DPCH control information is

transmitted only on the first downlink DPCH.

Different CCTrCH can use different spreading factors in the

case there are several CCTrCHs for one UE. In this case

information of only one DPCCH needs to be transmitted.


Frame Structure of Downlink DPCH

One radio frame, Tf = 10 ms


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

Data2 Ndata2 bits

DPDCH

TFCI NTFCI bits

Pilot Npilot bits

Data1 Ndata1 bits

DPDCH DPCCH DPCCH

TPC NTPC bits


DCH data

DPDCHDPDCH

DPCCHDPCCH

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

Data bearer Data bearer at physical layerat physical layer

DCH data

Functions of Downlink DPDCH/DPCCH



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

Section 2 Channel MappingSection 2 Channel Mapping


{XOR}

Transport Channels

(L1 Characteristics Dependent) PCH BCH FACH RACH DCH

S-CCPCHP-CCPCHPhysical

ChannelsPRACH DPDCH

Logical Channels

(Data Dependent)PCCH

DCCH

DTCH

DecicatedLogicalChannel

CipherOn

BCCH CCCH CTCH

Higher Layer data

PagingPaging

SystemInfoSystem

InfoSignaling

Signaling

CellBroadcast

Service

CellBroadcast

Service

Signalingand

User data

Signalingand

User data

DTCHDTCH

Channel Mapping


Synchronization Procedure—Cell Search

Slot synchronization

Frame synchronization and code-group identification

Scrambling-code identification

UE uses PSC to acquire slot synchronization to a cell

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。


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

Any PDSCH


Synchronization Procedure—Common Channe Synchronization

Common Channel Synchronization

The following physical channels have the same frame timing ： SCH(Primary and secondary)

CPICH(Primary and secondary)

P-CCPCH

PDSCH

P-CCPCH’s radio frame timing is acquired by cell search （ The P-CCPCH on which the cell SFN is transmitted is used as timing reference for all the physical channels ）


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 powermaximum 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 Commanded preamble power

increased by Power Ramp Step1;

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-TSTDTime switching transmit diversity (TSTD) is Time switching transmit diversity (TSTD) is used only on SCH channel.used 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 diversity.there are two modes with different calculation methods of weight factor ：

− 1 、 mode 1 uses phase adjustment ； the dedicated pilot symbols of two antennas are different(orthogonal)

− 2 、 mode 2 uses phase/amplitude adjustment ； the dedicated pilot symbols of two antennas are the same.

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