WPO-03 WCDMA Radio Channel Structure

WCDMA Radio Channel Structure

ZTE University

Objectives

At the end of this course, you will be able to ：– Master system channel types

– Master function of the channels

Content

Type of System Channel

Function of the Channels

RNS RNS

NodeB NodeBNodeB NodeB

RNC

CN

RNC

Iu Iu

Iur

Iub IubIub Iub

UTRAN System Structure

Channel Types （ UTRAN）

Physical

Channel

Transpor

tation

Channel

Logical

Channel

Node B RNC

Physical channel

Transportation channel

Logical channel

UE

UTRAN Radio Interface Protocol

L3

co

ntr

ol

co

ntr

ol

co

ntr

ol

co

ntr

ol

LogicalChannels

TransportChannels

C-plane signalling U-plane information

PHY

L2/MAC

L1

RLC

DCNtGC

L2/RLC

MAC

RLCRLC

RLCRLC

RLCRLC

RLC

Duplication avoidance

UuS boundary

BMC L2/BMC

control

PDCPPDCP L2/PDCP

DCNtGC

RadioBearers

RRC

Channel Types

For the radio interfaces in WCDMA system, according to different protocol layer, channels that carry user businesses are divided into:

Logical Channel ： Directly carry user business ； according to the business that

carried is of control side or user side, it is divided into two categories, control channel and business channel.

Transportation Channel ： Describe how data is transmitted at air interface; it is the interface

between radio interface 2 and physical layer, and the services that physical layer provided to MAC layer; Transportation channel is divided into private channel and public channel, which are respectively used to transmit private information to single user and public information to all users.

Physical Channel ： The ultimate forms when all kinds of information are transmitted at

radio interface, with each form using a specific carrier frequency, code (spreading code and scrambling code) and relative carrier phase. All these can be considered as a specific channel.

Channels

PHY layer

MAC layer

RLC layer

Transportation channel

Physical channel

Logical channel

L1

L2

Business and Functions of L1

L1 is mainly to provide data transmission service to MAC and higher layers ；

Functions of L1 ： Error detection for transportation channel Interleaving and deinterleaving of transportation channel Multiplexing and demultiplexing from transportation channel

to CCTrCH Encoded transportation channel speed adapted to physical

channel CCTrCH reflection to physical channel Weighing and combination of physical channel Modulation/demodulation, spreading/despreading of

physical channel Frequency and time synchronization Radio features measurement （ FER 、 SIR ） Close loop power control RF processing

Business and Functions of MAC

MAC business is expressed by logical channel. MAC Functions ：

Reflection of logical channel and transportation channel Select proper transportation format according to real-time

speed Priority adjustment to the data flow of a same UE Inter-UE priority adjustment Multiplexing and demultiplexing of the last session data

being transported at public or private transportation channels

Business flow monitoring Type switching and encryption of transportation channel Business level selection while RACH launching

Business and Functions of RLC

Businesses that RLC provided to upper layer ： Establishment/Release of RLC connection, transparent

data transmission, no-answer data transmission, answered data transmission, unrecoverable error notifications, etc.

RLC Functions ： Segmentation and Reassembly Serial connection, and PADDING Transmission of user data Error detection PDU sequential delivery Repeat detection Flow control Serial number detection Protocol error detection and recovery Data information encryption Hang up and recovery of data transmission

RLC Working Mode

Transparent Mode ： No protocol overhead is added to RLC before SDU. Incorrect PDU

will be discarded or marked as error. Transparent mode is generally used for real-time or streaming

business. No-answer mode

No retransmission mechanism, the accuracy of data transmission cannot be ensured. While receiving, incorrect PDU will be discarded or marked as error. At sending end, discarding will be performed based on time, the data timed out during sending will be discarded.

Typical no-answer mode application is VOIP and cell broadcast. Answered Mode

In answered mode, ARQ is used to ensure the accuracy of data transmission. RLC is two-way in answered mode. Information need to be exchanged on the two direction to judge the accurate receiving of the data, thus data will be retransmitted while failure or notification will be given to identify if data was successfully received.

Typical answered mode business is group business, such as WEB browsing, mail downloading, etc.

PDCP Functions

Reflect network PDU from network protocol to RLC protocol ；

Header compression/decompression, to reduce the redundancy control message in upper layer data, and improve the efficiency of air interface ； TCP/IP ——Non-real time IP RTP/UDP/IP in Rel4——Real time IP （ e.g. VOIP ）

Cache, retransmit upper layer data

Note ： PDCP exists only in PS

RRC Functions Broadcast management of system information ； Paging/notification ； RRC connection management (establishment,

reestablishment, maintenance and release) ； Radio carrier management (establishment,

reconfiguration and release) to provide service to NAS ； Mobile management of RRC connection ； Initial cell selection ； Requested Qos control and reflection to different

resources in access layer Management and control of radio resources ； UE measurement control and measurement report.

High Layer PDU

RLC SDU

High Layer PDU

RLC

Header

RLC

Header

MAC SDU MAC SDUMAC

Header

MAC

Header

Transport Block Transport Block

CRC CRC

RLC SDU

……

……

……

……

……

High Layer

L2 RLC

（ Non-transparent mode ）

L2 MAC

(Non-transparent mode)

L1

Segmentation

and cascadingReassembly

Data Flow at Uu Interface

Physical Channel

Dedicated Physical Channel (DPCH)

Physical Random Access Channel (PRACH)

Physical Common Packet Channel (PCPCH)

Uplink Physical Channels

Secondary Common Control Physical Channel (S-CCPCH)

Common Pilot Channel (CPICH)

Primary Common Control Physical Channel (P-CCPCH)

Synchronisation Channel (SCH)

Physical Downlink Shared Channel (PDSCH)

Downlink Physical Channels

Acquisition Indication Channel (AICH)

Page Indication Channel (PICH)

Dedicated Physical Channel (DPCH)

Transportation Channel

Random Access Channel (RACH)

Broadcast Channel (BCH)

Paging Channel (PCH)

Forward Access Channel (FACH)

Common Packet Channel (CPCH)

Common Transport Channels

Dedicated Transport Channels

Downlink Shared Channel (DSCH)

Dedicated Channel (DCH)

Logical Channel

B r o a d c a s t C o n t r o l C h a n n e l ( B C C H )

P a g i n g C o n t r o l C h a n n e l ( P C C H )

D e d i c a t e d C o n t r o l C h a n n e l ( D C C H )

C o m m o n C o n t r o l C h a n n e l ( C C C H )

C o n t r o l C h a n n e l ( C C H )

D e d i c a t e d T r a f f i c C h a n n e l ( D T C H )T r a f f i c C h a n n e l ( T C H )

C o m m o n T r a f f i c C h a n n e l ( C T C H )

Reflection of Transportation Channel and Physical Channel

Content


Functions of the Channel

Physical Channel


Uplink Physical Channel

Two dedicated uplink physical channels (DPDCH and DPCCH)

Two public physical channels (PRACH and PCPCH)

DPCCH

PRACH

PCPCH

DPCCH

uplink physical channels

public physical channels

Uplink Dedicated Physical Channel Structure

DPCCH contains 4 domains ： Pilot ： used for channel estimation of base station receiver and frame

synchronization ； TFCI ： determine different TrCHS transmission format while multiplexing

to a same CCTrCH ； FBI ： used for downlink closed loop emission classifications ； TPC ： used for the power control instructions in downlink closed loop

power control

Pilot N pilot bits

TPC N TPC bits

DataN data bits

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

T slot = 2560 chips, 10 bits

1 radio frame: T f = 10 ms

DPDCH

DPCCHFBI

N FBI bitsTFCI

N TFCI bits

T slot = 2560 chips, N data = 10*2 k bits (k=0..6)

Uplink Dedicated Physical Channel

Data side and control side of uplink dedicated physical channel are I/Q multiplexing, which means DPDCH and DPCCH are I/Q code multiplexing in every radio frame.

For a connection, no matter how many the data channel is, there is but only one control channel. In every wireless connection, there can be 0, 1, or several uplink DPDCHs.

Uplink DPDCH is used to transmit DCH. Uplink DPCCH is used to transmit the control information

generated by L1. Control information of L1 contains ： Known pilot bit that support channel estimation for related

detection TPC FBI An optional TFCI (TFCI transfers the real-time parameters

of different transmission channels that multiplexed on uplink DPDCH, and meanwhile, correspondent with data that will be transmit in the same frame 。 There is but only one uplink DPCCH in one connection for each layer.)

PRACH

PRACH Data channel and control channel of PRACH message are

also I/Q multiplexing, and the minimum spreading factor of its data channel is 32, with 4 time slot formats. While control channel has only one time slot format, with two domains: Pilot domain and TFCI domain.

Pilot

N pilot bits

Data

Ndata

bits


T slot = 2560 chips, 10*2 k bits (k=0..3)

Message part radio frame T RACH = 10 ms

Data

ControlTFCI

N TFCI bits

Time slot structure of PRACH message

PRACH

PRACH PRACH is made up of prefix part and message part.

Following is the structure of random access emission. Random access emission contains one or more 4096-

chip-length prefixes and one message part of 10 or 20ms.

Message partPreamble

4096 chips 10 ms (one radio frame)

Preamble Preamble

Message partPreamble

4096 chips 20 ms (two radio frames)

Preamble Preamble

Structure of PRACH access emission

Downlink Physical Channel

Downlink physical channel contains dedicated downlink physical channel, one shared physical channel and 5 public control physical channels:

DPCH

SCH

CPICH

PICH

AICH

CCPCH

PDSCH

public control physical channels

Dedicated Downlink Physical Channel

DL DPCH DPCCH and DPDCH in downlink is time division

multiplexing, and DL DPCCH contains 3 domains ：TPC domain, TFCI domain and PLIOT domain, the SF of DL DPDCH can be arranged from 4 to 512.

One radio frame, Tf = 10 ms

TPC

NTPC

bits


Tslot

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

Data2

Ndata2

bits

DPDCH

TFCI

NTFCI

bits

Pilot

Npilot

bits

Data1

Ndata1

bits

DPDCH DPCCH DPCCH

Frame structure of DL DPCH

Public Downlink Physical Channel

CPICH CPICH is a downlink physical channel with fixed

speed (30kbps ， SF ＝ 256), which is used to transmit predefined bit/symbol sequence. The function of CPICH is to assist UE to perform channel estimation for DCH. Modulation format of CPICH ：

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

CPICH

Divided into P-CPICH and S-CPICH ； Non-encoded channel ； P-CPICH uses fixed spreading factor (Cch,256,0), has

fixed bit rate of 30kbit/s ； Each cell has but only one P-CPICH which uses the

primary scrambling code ； Used for the searching of cell primary scrambling code ； S-CPICH can use any of the SF=256 channel codes ； Used to assist UE to perform estimation for dedicated or

public channels ； P-CPICH provides phase and power benchmark for other

channels ； P-CPICH is mainly used for measurement and estimation

while handover, cell selection and cell reselection ； Adjust the transmission power of P-CPICH to balance the

load of different cells, determine cell coverage and cell respirations ；

P-CPICH broadcast to the whole cell ；

P-CCPCH

Public control physical channel is made up of P-CCPCH and S-CCPCH.

P-CCPCH is a downlink physical channel with fixed speed (30kbps ， SF=256), which is to transmit BCH ， and uses the primary scrambling code of the cell.

In the first 256chips of every time slot, CCPCH performs not emission. During this period, primary SCH and secondary SCH will be transmitted, but with no Pilot/TPC/TFC domain.

Data18 bits


Tslot = 2560 chips , 20 bits

1 radio frame: Tf = 10 ms

(Tx OFF)

256 chips

Frame structure of P-CCPCH

S-CCPCH

S-CCPCH carries PCH and FACH, and has the following characteristics ：

Each cell has at least one S-CCPCH with low transmission speed ；

The difference between P-CCPCHS-CCPCH is that, P-CCPCH only has fixed and pre-defined transmission format, but S-CCPCH can use TFCI to support more transmission formats.


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

Pilot Npilot bits

DataNdata bits

1 radio frame: Tf = 10 ms

TFCI NTFCI bits

Frame structure of S-CCPCH

SCH

SCH Divided into P-SCH and S-SCH ； Non-spreading and non-scrambling channel ； Downlink signal used for cell searching, to provide chip

synchronization, time slot synchronization and frame synchronization for users ；

The first 256 chips of each slot is used to transmit synchronization code.

PrimarySCH

SecondarySCH

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

SCH

P-SCH contains one 256chips-length modulation code and PSC

PSC is repeatedly transmitted in each slot to transfer the completely known sequence ；

PSC of every cell in the system is the same ； S-SCH repeatedly transmit a 15-sequence modulation code,

with length of each code is 256chips. SSC is transmitted spontaneously with SCH ；

SSC is identified with csi, k, and i=0 ， 1 ，……， 63,which is the sequence number of scrambling code group; k=0 ， 1 ， 2……, which is the time slot number.

Each SSC is selected from one of the 16 different codes with length of 256 ；

SSC contains scrambling code group information, which can be used to determine the scrambling code group that being used in the cell..

PICH

PICH carries PI (Page Indication), whose SF=256, radio frame length is 10ms, contains 300bits, among which 288 bits carries PI, and the other12 bits are Tx Off.

PICH is always connected with one S-CCPCH, which is transmitting a PCH.

In each PICH frame, Np PI were transmitted {P0, …, PNp-1}, and here Np=18, 36, 72, or 144. If the Pli of one frame is set to 1, this means the UE that correspondent with Pii should adjust the frame that related to S-CCPCH.

b1b0

288 bits for paging indication12 bits (transmission

off)

One radio frame (10 ms)

b287 b288 b299

Frame structure of PICH

Content


Functions of the Channel

Physical Channel


Dedicated Transportation Channel

DCH (UL/DL) DCH is either an uplink or downlink channel. DCH

does not care what carried is actual user data or high-layer control information, as its content is invisible in physical layer.

DCH has the following characteristics ： Fast power control ； Quick speed change frame by frame ； Soft handover

Public Transportation Channel － BCH

BCH (DL) BCH is a downlink transportation channel, which is used to

broadcast specific system or cell information, such as the random accessing code, accessing slot, or the transmission diversity method being used by other channels in the cell.

BCH is always transmitted in the whole cell with an independent transmission format. Data rate of BCH is low and fixed.

If UE cannot correctly decode BCH, it will not be able to register in the cell. Therefore, the transmission power of BCH is relatively higher, in order that all the UEs in the cell coverage can receive it.

BCH is carried by P-CCPCH

Functions of FACH

FACH (DL) FACH is a downlink public transportation channel,

which can carry either control information, or a small portion of group data.

FACH has the following characteristics ： Open loop power control is used, but not closed loop. At least one FACH is transmitting to the whole cell at

low speed.. Physical channel that carries FACH is S-CCPCH

Functions of RACH

RACH (UL) RACH is an uplink transportation channel, carries the

control information transmitted by UE, such as connection request, registration, location update, and it also send a small portion of group data. No matter which position in the cell, base station should be able to receive RACH that carries control information.

RACH has the following characteristics ： Uses open loop power control.

Physical channel that carries RACH is PRACH

Functions of PCH

PCH (DL) PCH is a downlink transportation channel that carries

related paging data. Based on different system configuration, same paging information can be sent to one single cell or even several hundred cells. The design of paging channel directly affects the power loss of UE when it is idle.

Physical channel that carries PCH is S-CCPCH

WPO-03 WCDMA Radio Channel Structure

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