01 wcdma radio interface physical layer

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WCDMA Radio Interface Physical Layer

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Foreword

l The physical layer offers data transport services to higher layers.

l The access to these services is through the use of transport channels

via the MAC sub-layer.

l The physical layer is expected to perform the following functions in

order to provide the data transport service, for example: spreading,

modulation and demodulation, despreading, Inner-loop power

control and etc.




Objectives

l Upon completion of this course, you will be able to:

p Outline radio interface protocol Architecture

p Describe key technology of UMTS physical layer

p Describe UMTS physical layer procedures




Contents

1. Physical Layer Overview

2. Physical Layer Key Technology

3. Physical Layer Procedure




UTRAN Protocol Structure

RNS

RNCRNC

RNS

RNCRNC

Core Network

NodeBNodeB NodeBNodeB NodeBNodeB NodeBNodeB

IuIu IuIu

IurIur

IubIub IubIubIubIub IubIub

UTRAN

User Equipment




Radio Interface Protocol Structure

L3co

ntro

l

cont

rol

cont

rol

cont

rol

Logical Channels

Transport Channels

C-plane signaling U-plane information

PHY

L2/MAC

L1

RLC

DCNtGC

L2/RLC

MAC

RLCRLCRLC

Duplication avoidance

UuS boundary

L2/BMC

control

PDCPPDCP L2/PDCP

DCNtGC

Radio Bearers

RRC

RLCRLCRLC

RLC

BMC




Spreading Technology

l Spreading consists of 2 steps

p Channelization operation, which transforms data symbols into chips

p Scrambling operation is applied to the spreading signal

Data bit

OVSF code

Scrambling code

Chips after spreading




Spreading Technology

l OVSF code is used as channelization code

l 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

l Scrambling code: GOLD sequence.

l Scrambling code period: 10ms ,or 38400 chips.

l 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.

l For downlink physical channels, a total of 218-1 = 262,143 scrambling

codes can be generated. scrambling codes k = 0, 1, …, 8191 are used.




Primary Scrambling Code

A primary scrambling code and 15 secondary scrambling codes are included in a set.

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

511×16＋15

8192 scrambling

codes512 sets

……




Primary Scrambling Code Group

Primary scrambling codes for downlink physical channels

Group 0

…


……


8*63

……


63*8＋7512 primary scrambling

codes

……

Group 1

Group 63



15

64 primary scrambling code

groupsEach group consists of 8

primary scrambling codes




Contents







Contents


2.1 Physical Channel Structure and Functions

2.2 Channel Mapping




WCDMA Radio Interface Channel Definition

l Logical Channel = information container

p Defined by <What type of information> is transferred

l Transport Channel = characteristics of transmission

p Described by <How> and with <What characteristics> data is

transmitted over the radio interface

l Physical Channel = specification of the information global

content

p providing the real transmission resource, maybe a frequency , a

specific set of codes and phase




Logical Channel

Control channel

Traffic channelDedicated traffic channel (DTCH)

Common traffic channel (CTCH)

Broadcast control channel (BCCH)

Paging control channel (PCCH)

Dedicate control channel (DCCH)

Common control channel (CCCH)




Transport Channel

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




Physical Channel

l A physical channel is defined by a specific carrier frequency, code

(scrambling code, spreading code) and relative phase.

l In UMTS system, the different code (scrambling code or spreading

code) can distinguish the channels.

l Most channels consist of radio frames and time slots, and each radio

frame consists of 15 time slots.

l Two types of physical channel: UL and DL

Physical Channel

Frequency, Code, Phase




Downlink Physical Channel

l Downlink Dedicated Physical Channel (Downlink DPCH)

l Downlink Common Physical Channel

p Primary Common Control Physical Channel (P-CCPCH)

p Secondary Common Control Physical Channel (S-CCPCH)

p Synchronization Channel (SCH)

p Paging Indicator Channel (PICH)

p Acquisition Indicator Channel (AICH)

p Common Pilot Channel (CPICH)

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

p High-Speed Shared Control Channel (HS-SCCH)

Downlink Physical Channel




Uplink Physical Channel

l Uplink Dedicated Physical Channel

p Uplink Dedicated Physical Data Channel

(Uplink DPDCH)

p Uplink Dedicated Physical Control Channel

(Uplink DPCCH)

p High-Speed Dedicated Physical Channel

(HS-DPCCH)

l Uplink Common Physical Channel

p Physical Random Access Channel (PRACH)

Uplink Physical Channel




Function of Physical Channel

Node B UE

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

P-CPICH-Primary Common Pilot ChannelP-CPICH-Primary 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 Channels (P-SCH & S-SCH)

l Used for cell search

l Two sub channels: P-SCH and S-SCH

l SCH is transmitted at the first 256 chips

of every time slot

l PSC is transmitted repeatedly in each

time slot

l SSC specifies the scrambling code

groups of the cell

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




Secondary Synchronization Channel (S-SCH)

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

l……..acp

Slot # ?

PP--SCHSCH acp

Slot #?

16 6SS--SCHSCH

acp

Slot #?

11 Group 2Group 2Slot 7, 8, 9Slot 7, 8, 9

256 chips




Primary Common Pilot Channel (PCPICH)

l Primary CPICH

p Carrying pre-defined sequence

p Fixed channel code: Cch, 256, 0, Fixed rate 30Kbps

p Scrambled by the primary scrambling code

p Broadcast over the entire cell

p A phase reference for SCH, Primary CCPCH, AICH, PICH and downlink

DPCH, Only one CPICH per cell

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)

l Carrying BCH transport channel

l Fixed rate, fixed OVSF code (30kbps，Cch, 256, 1)

l The PCCPCH is not transmitted during the first 256 chips of each time

slot

PCCPCH Data18 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)

l Carrying Paging Indicators (PI)

l Fixed rate (30kbps), SF = 256

l N paging indicators {PI0, …, PIN-1} in each PICH frame, N=18, 36, 72,

or 144

One radio frame (10 ms)

b1b0

288 bits for paging indication 12 bits (undefined)

b287 b288 b299




Secondary Common Control Physical Channel (SCCPCH)

l Carrying FACH and PCH, SF = 256 - 4

p Pilot: used for demodulation

p TFCI: Transport Format Control Indication, used for describe data format

DataN bits

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

1 radio frame: T f = 10 ms

T slot = 2560 chips,

DataPilot

N bitsPilotN bitsTFCITFCI

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




Physical Random Access Channel (PRACH)

l Carrying uplink signaling and data, consist of two parts:

p One or several preambles: 16 kinds of available preambles

p 10 or 20ms message part

Message partPreamble

4096 chips10 ms (one radio frame)

Preamble Preamble

Message partPreamble

4096 chips 20 ms (two radio frames)

Preamble Preamble




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

TFCIN bitsTFCI

DataN data bitsData

Control

kbits (k=0..3)




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




Acquisition Indicator Channel (AICH)

l Carrying the Acquisition Indicators (AI), SF = 256

p There are 16 kinds of Signature to generate AI

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)

l Uplink DPDCH and DPCCH are I/Q code division multiplexed

(CDM) within each radio frame

l DPDCH carries data generated at Layer 2 and higher layer, the

OVSF code is Cch,SF,SF/4, where SF is from 256 to 4

l DPCCH carries control information generated at Layer 1, the

OVSF code is Cch,256,0




Uplink Dedicated Physical Channel (DPDCH&DPCCH)

l Frame Structure of Uplink DPDCH/DPCCH

PilotNpilot bits

TPCNTPC bits

DataNdata bits


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

1 radio frame: Tf = 10 ms

DPDCH

DPCCH FBINFBI bits

TFCINTFCI bits




Downlink Dedicated Physical Channel (DPDCH+DPCCH)

l Downlink DPDCH and DPCCH is time division multiplexing

(TDM).

l DPDCH carries data generated at Layer 2 and higher layer

l DPCCH carries control information generated at Layer 1

l The OVSF code is Cch,SF,n, where SF is from 512 to 4, and n is

from 0 to SF-1.




Downlink Dedicated Physical Channel (DPDCH+DPCCH)

l Frame Structure of Downlink DPCH (DPDCH+DPCCH)

One radio frame, Tf = 10 ms


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

Data2Ndata2 bits

DPDCH

TFCINTFCI bits

PilotNpilot bits

Data1Ndata1 bits

DPDCH DPCCH DPCCH

TPCNTPC bits




High-Speed Physical Downlink Shared Channel (HS-PDSCH)l Bearing service data and layer2 overhead bits mapped from the

transport channel

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

Slot #0 Slot#1 Slot #2

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

DataNdata1 bits

1 subframe: Tf = 2 ms




High-Speed Shared Control Channel (HS-SCCH)

l 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)

l 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

Tslot = 2560 chips, 40 bits

DataNdata1 bits

1 subframe: Tf = 2 ms




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

l Carrying information to acknowledge downlink transport blocks and

feedback information to the system for scheduling and link

adaptation of transport block

p CQI and ACK/NACK

l Physical Channel, Uplink, SF=256

Subframe #0 Subframe #i Subframe #n

One HS-DPCCH subframe ( 2ms )

HARQ

1 radio frame: Tf = 10 ms

CQI

Tslot = 2560 chips 2 × Tslot = 5120 chips




Contents


2.1 Physical Channel Structure and Functions

2.2 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




Contents







Synchronization Procedure - Cell Search

Frame synchronization & 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 Synchronization

UE uses PSC to acquire slot synchronization to a cell




Synchronization Procedure - Channel Timing Relationship

AICH access slots

Secondary SCH

Primary SCH

τ S-CCPCH,k

10 ms

t PICH

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

P-CCPCH (SFN mod 2 = 0) P-CCPCH (SFN mod 2 = 1)

Any CPICH

K:th S-CCPCH

PICH for k:th S-CCPCH

n:th DPCHτDPCH,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 RACHmessage transmitted Set physical status to be Nack

on AICH received

Choose a access slot again

Counter> 0 & Preamble power < maximum allowed power

Choose a signature and increase preamble transmit power

Set physical status to be Nackon 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




Transmit diversity Mode

l Application of Tx diversity modes on downlink physical channel

––applied–AICH

––applied–HS-SCCH

–appliedapplied–HS-PDSCH

––applied–PICH

appliedappliedapplied–DPCH

––applied–S-CCPCH

–––appliedSCH

––applied–P-CCPCH

Mode 2Mode 1STTDTSTD

Closed loop modeOpen loop modePhysical channel type




Transmit Diversity - STTD

l Space time block coding based transmit antenna diversity (STTD)

p 4 consecutive bits b0, b1, b2, b3 using STTD coding

b0 b1 b2 b3 Antenna 1

Antenna 2Channel bits

STTD encoded channel bitsfor antenna 1 and antenna 2.

b0 b1 b2 b3

-b2 b3 b0 -b1




Transmit Diversity - TSTD

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

channel

Antenna 1

Antenna 2

i,0

i,1

acsi,14

Slot #0 Slot #1 Slot #14

i,2

acp

Slot #2

(Tx OFF)

(Tx OFF)

(Tx OFF)

(Tx OFF)

(Tx OFF)

(Tx OFF)

(Tx OFF)

acp acp

acsacs

acp

acs(Tx OFF)




Closed Loop Mode

l Used in DPCH and HS-PDSCH




References

l TS 25.104 UTRA (BS) FDD Radio Transmission and Reception

l TS 25.201 Physical layer-general description

l TS 25.211 Physical channels and mapping of transport channels onto physical

channels (FDD)

l TS 25.212 Multiplexing and channel coding (FDD)

l TS 25.213 Spreading and modulation (FDD)

l TS 25.214 Physical layer procedures (FDD)

l TS 25.308 UTRA High Speed Downlink Packet Access (HSDPA)

l TR 25.877 High Speed Downlink Packet Access (HSDPA) - Iub/Iur Protocol Aspects

l TR 25.858 Physical layer aspects of UTRA High Speed Downlink Packet Access




l This course mainly introduces the basic concept, key

technology and procedures of WCDMA physical layer.

l These knowledge is very important for understanding Uu

interface and further study.

Summary



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01 wcdma radio interface physical layer

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