2- Channel Structure and Function 26

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Channel Structure andfunction

Version 3.00

ZTE CORPORATIONZTE Plaza, Keji Road South,Hi-Tech Industrial Park,Nanshan District, Shenzhen,P. R. China518057 Tel: (86) 755 26771900 800-9830-9830Fax: (86) 755 26772236URL:http://support.zte.com.cnE-mail: [email protected]
http://support.zte.com.cn/http://support.zte.com.cn/mailto:[email protected]:[email protected]://support.zte.com.cn/


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Contents

Chapter 1..................................................................1

Chanel structure........................................................1

Channels of UTRAN...........................................................1

Logical channels....................................................................2

Transport channels ...............................................................3

Physical channels .................................................................5

Channel Mapping.................................................................18

Physical layer porcedure..................................................20

Cell search procedure...........................................................20

Random Access Procedure....................................................20


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C h a p t e r 1

Chanel structure

No flammables:

mapping of logical channels onto transport channels

mapping of transport channels and physical channels

physical layer procedure

Channels of UTRANChannels of UTRAN are divided into

logical channels

transport channels

physical channels

In air interface protocol modele of UTRAN, MAC layer accomplishthe mapping of logical channels onto transport channels, PHY

layer accomplish the mapping of transport channels ontophysical channels. Figure 1 shows the position of logicalchannels and transport channels

Confidential and Proprietary Information of ZTE CORPORATION 1


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Channel Structure and function

F I G U R E 1 L O G I C A L C H A N N E L S A N D T R A N S P O R T C H A N N E L S

Du p l i c a t i o n Av o id a n c e

G C N t D C

G C N t D C

R L CR L C

R L CR L C

R L CR L C

R L CR L C

B M C

P D C PP D C P

C -p la n e s ig na llin g U -p lan e in fo rm a tio nU u S b o u n d a r

control

control

control

control

L 3

R a d io

B e a r e r s

L 2 / P D C P

L 2 / B M C

L 2 / R L C

L o g ic a l

C h a n n e l s

L 2 / M A C

T r a n sp o r tC h a n n e l s

L 1

c o n t r o lR R C

M A C

P H Y

Logical channels

MAC layer implement the mapping between logical channel andtransport channel and provide data transport service for logical.

Logical channels are divided into control channel and traffic

channel. Fig illustrates the structure of logical channels:

2 Confidential and Proprietary Information of ZTE CORPORATION


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Chapter 1 Chanel structure

F I G U R E 2 LO G I C A L C H A N N E L S T R U C T U R E

Control channels only used to transport control planeinformation. Including BCCH,PCCH,CCCH,DCCH,SHCCH.

Traffic channels only used to transport user plane information.Inculuding DTCH,CTCH.

Transport channels

Transport channels are services offered by Layer 1 to the higher

layersA transport channel is defined by how and with whatcharacteristics data is transferred over the air interface. A

general classification of transport channels is into two groups:

Dedicated channel: used by dedicated user.

Common channel: used by all users within one cell.

Show as Figure 3



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F I G U R E 3 T R A N S P O R T C H A N N E L S

B C H

P C H

F A C H

D S C H

R A C H

C P C H

D C H

D C H

There exists only one type of dedicated transport channel, theDedicated Channel (DCH). The Dedicated Channel (DCH) is adownlink or uplink transport channel. The DCH is transmittedover the entire cell or over only a part of the cell using e.g.

beam-forming antennas.

There are six types of common transport channels: BCH, FACH,PCH, RACH, CPCH and DSCH.

Broadcast Channel -BCH

The Broadcast Channel (BCH) is a downlink transport channelthat is used to broadcast system- and cell-specific information.

The BCH is always transmitted over the entire cell and has asingle transport format.

Forward Access Channel -FACH

The Forward Access Channel (FACH) is a downlink transport

channel. The FACH is transmitted over the entire cell. It isused to transmit control imformation after Basestation havereceived the random access requirement sent by UE. FACH isalso can be used to send paket data.

There is one or several FACH within one cell. One of them

must has low datarate so all terminals in this cell can receiveit. The others can have high datarate.

Paging Channel - PCH

The Paging Channel (PCH) is a downlink transport channel.The PCH is always transmitted over the entire cell. Thetransmission of the PCH is associated with the transmissionof physical-layer generated Paging Indicators, to support

efficient sleep-mode procedures.

Random Access Channel - RACH

The Random Access Channel (RACH) is an uplink transport

channel. The RACH is always received from the entire cell. It



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is used to carry control information (such as call setuprequest) sent by UE.The RACH is characterized by a collisionrisk and by being transmitted using open loop power control.

Commnon Packet Channel - CPCH

The Common Packet Channel (CPCH) is an uplink transport

channel. CPCH is associated with a dedicated channel on thedownlink which provides power control and CPCH Control

Commands (e.g. Emergency Stop) for the uplink CPCH. TheCPCH is characterised by initial collision risk and by being

transmitted using inner loop power control.

Downlink Shared Channel - DSCH

The Downlink Shared Channel (DSCH) is a downlinktransport channel shared by several UEs The DSCH isassociated with one or several downlink DCH. The DSCH istransmitted over the entire cell or over only a part of the cellusing e.g. beam-forming antennas.

Physical channels

Physical channels are defined by a specific carrier frequency,scrambling code, channelization code (optional), time start &stop (giving a duration) and, on the uplink, relative phase (0 or

/2). There is 2 types of physical channel. Uplink physical anddownlink physical.

Uplink physical channels

There are 2 types of uplink dedicated physical channels(UplinkDedicated Physical Data Channel and Uplink Dedicated PhysicalControl Channel) and 2 types of uplink common physicalchannels( Physical Random Access Channel and PhysicalCommon Packet Channel) illustrate as Figure 4

F I G U R E 4 U P L I N K P H Y S I C A L C H A N N E L S

Uplink dedicated physical channels



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There are two types of uplink dedicated physical channels, theuplink Dedicated Physical Data Channel (uplink DPDCH) and theuplink Dedicated Physical Control Channel (uplink DPCCH).TheDPDCH and the DPCCH are I/Q code multiplexed within each

radio frameThe uplink DPDCH is used to carry the DCH transport channel.There may be zero, one, or several uplink DPDCHs on each radiolink.

The uplink DPCCH is used to carry control information generated

at Layer 1. The Layer 1 control information consists of knownpilot bits to support channel estimation for coherent detection,transmit power-control (TPC) commands, feedback information(FBI), and an optional transport-format combination indicator(TFCI). The transport-format combination indicator informs thereceiver about the instantaneous transport format combination

of the transport channels mapped to the simultaneouslytransmitted uplink DPDCH radio frame. There is one and only

one uplink DPCCH on each radio link.

Figure 5 shows the frame structure of the uplink dedicatedphysical channels. Each radio frame of length 10 ms is split into15 slots, each of length Tslot = 2560 chips, corresponding to one

power-control period.

F I G U R E 5 F R A M E S T R U C T U R E O F U P L I N K D E D I C A T E D P H Y S I C A L C H A N N E L

The parameter k in figure determines the number of bits peruplink DPDCH slot. It is related to the spreading factor SF of theDPDCH as SF = 256/2k. The DPDCH spreading factor may rangefrom 256 down to 4. The spreading factor of the uplink DPCCH isalways equal to 256, i.e. there are 10 bits per uplink DPCCHslot.

The exact number of bits of the uplink DPDCH and the differentuplink DPCCH fields (Npilot, NTFCI, NFBI, and NTPC) is configured byhigher layers and can also be reconfigured by higher layers.

The FBI bits are used to support techniques requiring feedback

from the UE to the UTRAN Access Point, including closed loop



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mode transmit diversity and site selection diversity transmission(SSDT).

There are two types of uplink dedicated physical channels; those

that include TFCI (e.g. for several simultaneous services) and

those that do not include TFCI (e.g. for fixed-rate services). It isthe UTRAN that determines if a TFCI should be transmitted andit is mandatory for all UEs to support the use of TFCI in theuplink.

Npilot34567and 8The shadowed column part of pilotbit pattern is defined as FSW and FSWs can be used to confirm

frame synchronization. (The value of the pilot bit pattern otherthan FSWs shall be "1".)

TPC is corresponding to power contrl command.

Multi-code operation is possible for the uplink dedicated physicalchannels. When multi-code transmission is used, several parallelDPDCH are transmitted using different channelization codes.However, there is only one DPCCH per radio link.

Uplink common physical channels

Physical Random Access Channel (PRACH)

The random-access transmission is based on a Slotted

ALOHA approach with fast acquisition indication. The UE canstart the random-access transmission at the beginning of anumber of well-defined time intervals, denoted access slots.There are 15 access slots per two frames and they arespaced 5120 chips apart Information on what access slots

are available for random-access transmission is given byhigher layers.The random-access transmission consists ofone or several preambles of length 4096 chips and a

message of length 10 ms or 20 ms.

F I G U R E 6 F R A M E S T R U C T U R E O F R A N D O M A C C E S S C H A N N E L



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Pilot

Npilot bits

Data

Ndata bits

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

Tslot = 2560 chips, 10*2kbits (k=0..3)

Message part radio frame TRACH = 10 ms

Data

ControlTFCI

NTFCI bits

Each preamble is of length 4096 chips and consists of 256repetitions of a signature of length 16 chips. There are amaximum of 16 available signatures.

The 10 ms message part radio frame is split into 15 slots, eachof length Tslot = 2560 chips. Each slot consists of two parts, adata part to which the RACH transport channel is mapped and acontrol part that carries Layer 1 control information. The dataand control parts are transmitted in parallel.

A 10 ms message part consists of one message part radio

frame, while a 20 ms message part consists of two consecutive10 ms message part radio frames. The message part length isequal to the Transmission Time Interval of the RACH Transportchannel in use. This TTI length is configured by higher layers.

The data part consists of 10*2k bits, where k=0,1,2,3. Thiscorresponds to a spreading factor of 256, 128, 64, and 32respectively for the message data part.

The control part consists of 8 known pilot bits to support channel

estimation for coherent detection and 2 TFCI bits. Thiscorresponds to a spreading factor of 256 for the message control

part. The pilot bit pattern is described in table 8. The totalnumber of TFCI bits in the random-access message is 15*2 =30. The TFCI of a radio frame indicates the transport format ofthe RACH transport channel mapped to the simultaneouslytransmitted message part radio frame. In case of a 20 msPRACH message part, the TFCI is repeated in the second radio

frame. Physical Common Packet ChannelPCPCH

The Physical Common Packet Channel (PCPCH) is used tocarry the CPC. The CPCH transmission is based on DSMA-CD

approach with fast acquisition indication. The UE can starttransmission at the beginning of a number of well-defined

time-intervals, relative to the frame boundary of the receivedBCH of the current cell.

The PCPCH access transmission consists of one or severalAccess Preambles [A-P] of length 4096 chips, one Collision

Detection Preamble (CD-P) of length 4096 chips, a DPCCH

Power Control Preamble (PC-P) which is either 0 slots or 8



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slots in length, and a message of variable length Nx10 ms.

F I G U R E 7 F R A M E S T R U C T U R E O F CPCH

Pilot

Npilot bits

TP C

NTPC bits

Data

Ndata bits


Tslot = 2560 chips, 10*2k

bits (k=0..6)

1 radio frame: Tf = 10 ms

Data

ControlFBI

NFBI bitsTFCI

NTFCI bits

CPCH access preamble part

Similar to RACH preamble part. The RACH preamble signaturesequences are used. The number of sequences used could be

less than the ones used in the RACH preamble. The scramblingcode could either be chosen to be a different code segment of

the Gold code used to form the scrambling code of the RACHpreambles or could be the same scrambling code in case the

signature set is shared.

CPCH collision detection preamble partSimilar to RACH preamble part. The RACH preamble signaturesequences are used. The scrambling code is chosen to be adifferent code segment of the Gold code used to form thescrambling code for the RACH and CPCH preambles

CPCH power control preamble part

The power control preamble segment is called the CPCH PowerControl Preamble (PC-P) part. The Power Control Preamblelength is a higher layer parameter, Lpc-preamble, which shall take

the value 0 or 8 slots. The TFCI field is filled with "1" bits.

CPCH message part



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Similar to uplink dedicated channel, Each 10 ms frame is splitinto 15 slots, each of length Tslot = 2560 chips. Each slot consistsof two parts, a data part that carries higher layer informationand a control part that carries Layer 1 control information. The

data and control parts are transmitted in parallel. The sf ofCPCH message part is 256

Downlink physical channel

Downlink physical channels include Detedicated physical channel\ one Shared Physical Channel\ five Commnon Control Channel

downlink Detedicated physical channel -DPCH

primary and secondary Commnon Pilot Channel - CPICH

primary and secondary Common Control Physicl Channel -CCPCH

Synchronous Channel - SCH

Physical Downlink Shared Channel - DSCH

Acquisition Indication Channel - AICH

Paging Indication Channel - PICH

downlink physical are illustrated as Figure 8

F I G U R E 8 D O W N L I N K P H Y S I C A L C H A N N E L S

There is only one type of downlink dedicated physical channel,the Downlink Dedicated Physical Channel (downlink DPCH).

Within one downlink DPCH, dedicated data generated at Layer 2and above, i.e. the dedicated transport channel (DCH), istransmitted in time-multiplex with control information generatedat Layer 1 (known pilot bits, TPC commands, and an optionalTFCI). The downlink DPCH can thus be seen as a time multiplexof a downlink DPDCH and a downlink DPCCH.

Each frame of length 10 ms is split into 15 slots, each of length


Downlink DedicatedPhysical Channel


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Tslot = 2560 chips, corresponding to one power-control period.

F I G U R E 9 F R A M E S T R U C T U R E O F DL DPCH

The parameter k in figure 9 determines the total number of bitsper downlink DPCH slot. It is related to the spreading factor SFof the physical channel as SF = 512/2k. The spreading factormay thus range from 512 down to 4.

The exact number of bits of the different downlink DPCH fields

(Npilot, NTPC, NTFCI, Ndata1 and Ndata2) is given in table 11. What slotformat to use is configured by higher layers and can also bereconfigured by higher layers.

There are basically two types of downlink Dedicated Physical

Channels; those that include TFCI (e.g. for several simultaneous

services) and those that do not include TFCI (e.g. for fixed-rateservices). It is the UTRAN that determines if a TFCI should betransmitted and it is mandatory for all UEs to support the use ofTFCI in the downlink.

Npilot248 & 16

TPC symbol is corresponding to transimission power controlcommand T 0or1

Downlink Common Physical Channel

Common Pilot Channel (CPICH)

The CPICH is a fixed rate (30 kbps, SF=256) downlink physical

channel that carries a pre-defined bit sequence. There are twotypes of Common pilot channels, the Primary and Secondary

CPICH. They differ in their use and the limitations placed ontheir physical features.Fig show the frame structure of CPICH.



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Pre-defined bit sequence


Tslot = 2560 chips , 20 b it

1 radio frame: = 10 ms

s l o t #1

F r a m e # i + 1F r a m e # i

s l o t #14

A n t e n n a 2

A n t e n n a 1

s l o t #0

F r a m e B o u n d a r y

0 0 0 0 0 0 0 0 0 0 0 00 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 00 0 0 0 0 00 0 0 0 0 0 0 0 0 0 0 0

1 1 1 1 0 0 0 0 1 1 1 10 0 0 0 1 1 0 0 1 1 1 1 0 0 0 0 1 11 1 0 0 0 01 1 1 1 0 0 0 0 1 1 1 1

The Primary Common Pilot Channel (P-CPICH) has the following

characteristics:

- The same channelization code is always used for the P-CPICH, see [4];

- The P-CPICH is scrambled by the primary scrambling

code, see [4];- There is one and only one P-CPICH per cell;

- The P-CPICH is broadcast over the entire cell.

The Primary CPICH is a phase reference for the followingdownlink channels: SCH, Primary CCPCH, AICH, PICH AP-AICH,CD/CA-ICH, CSICH, DL-DPCCH for CPCH and the S-CCPCH. Bydefault, the Primary CPICH is also a phase reference fordownlink DPCH and any associated PDSCH. The UE is informed

by higher layer signalling if the P-CPICH is not a phase referencefor a downlink DPCH and any associated PDSCH.The Primary

CPICH is always a phase reference for a downlink physical

channel using closed loop TX diversity.

A Secondary Common Pilot Channel (S-CPICH) has the followingcharacteristics:

- An arbitrary channelization code of SF=256 is used for theS-CPICH, see [4];

- A S-CPICH is scrambled by either the primary or asecondary scrambling code,

- There may be zero, one, or several S-CPICH per cell;

- A S-CPICH may be transmitted over the entire cell or onlyover a part of the cell;



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

Pilot

Npilot bits

Data

Ndata1 bits

1 radio frame: Tf = 10 ms

TFCI

NTFCI bits

The parameter k in figure 17 determines the total number of bitsper downlink Secondary CCPCH slot. It is related to thespreading factor SF of the physical channel as SF = 256/2k. Thespreading factor range is from 256 down to 4. The FACH and

PCH can be mapped to the same or to separate Secondary

CCPCHs.

If FACH and PCH are mapped to the same Secondary CCPCH,they can be mapped to the same frame. The main differencebetween a CCPCH and a downlink dedicated physical channel isthat a CCPCH is not inner-loop power controlled. The main

difference between the Primary and Secondary CCPCH is thatthe transport channel mapped to the Primary CCPCH (BCH) can

only have a fixed predefined transport format combination, whilethe Secondary CCPCH support multiple transport format

combinations using TFCI.

Synchronous Channel (SCH)

The Synchronisation Channel (SCH) is a downlink signal used forcell search. The SCH consists of two sub channels, the Primary

and Secondary SCH. The 10 ms radio frames of the Primary andSecondary SCH are divided into 15 slots, each of length 2560chips. Figure illustrates the structure of the SCH radio frame.

PrimarySCH

SecondarySCH

256 chips

2560 chips

One 10 ms SCH radio frame

acs,

acp

acs,

acp

acs,

acp

Slot #0 Slot #1 Slot #14

The Primary SCH consists of a modulated code of length 256chips, the Primary Synchronisation Code (PSC) denoted cp infigure , transmitted once every slot. The PSC is the same for

every cell in the system.

The Secondary SCH consists of repeatedly transmitting a length15 sequence of modulated codes of length 256 chips, theSecondary Synchronisation Codes (SSC), transmitted in parallelwith the Primary SCH. The SSC is denoted cs

i,k in figure , where i

= 0, 1, , 63 is the number of the scrambling code group, and k



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= 0, 1, , 14 is the slot number. Each SSC is chosen from a setof 16 different codes of length 256. This sequence on theSecondary SCH indicates which of the code groups the cell'sdownlink scrambling code belongs to.

Physical Downlink Shared Channel (PDSCH)

The Physical Downlink Shared Channel (PDSCH) is used to carrythe Downlink Shared Channel (DSCH).

A PDSCH corresponds to a channelisation code below or at aPDSCH root channelisation code. A PDSCH is allocated on a radioframe basis to a single UE. Within one radio frame, UTRAN mayallocate different PDSCHs under the same PDSCH rootchannelisation code to different UEs based on code multiplexing.Within the same radio frame, multiple parallel PDSCHs, with thesame spreading factor, may be allocated to a single UE. This is aspecial case of multicode transmission. All the PDSCHs are

operated with radio frame synchronisation.

PDSCHs allocated to the same UE on different radio frames mayhave different spreading factors.

The frame and slot structure of the PDSCH are shown on figure .


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

Data

Ndata1 bits

1 radio frame: Tf= 10 ms

For each radio frame, each PDSCH is associated with one

downlink DPCH. The PDSCH and associated DPCH do notnecessarily have the same spreading factors and are not

necessarily frame aligned.

All relevant Layer 1 control information is transmitted on the

DPCCH part of the associated DPCH, i.e. the PDSCH does notcarry Layer 1 information. To indicate for UE that there is data

to decode on the DSCH, the TFCI field of the associated DPCH

shall be used.The TFCI informs the UE of the instantaneous transport formatparameters related to the PDSCH as well as the channelisation

code of the PDSCH.

Acqusition Indication Channel(AICH)

The Acquisition Indicator channel (AICH) is a fixed rate(SF=256) physical channel used to carry Acquisition Indicators

(AI). Acquisition Indicator AIs corresponds to signature s on thePRACH.

Figure illustrates the structure of the AICH. The AICH consists

of a repeated sequence of 15 consecutive access slots (AS),



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each of length 5120 chips. Each access slot consists of twoparts, an Acquisition-Indicator (AI) part consisting of 32 real-valued symbols a0, , a31 and a part of duration 1024 chips withno transmission that is not formally part of the AICH. The part of

the slot with no transmission is reserved for possible use byCSICH or possible future use by other physical channels.

The spreading factor (SF) used for channelisation of the AICH is256.

The phase reference for the AICH is the Primary CPICH.

1024 chips

Transmission Of

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

a1 a2a0 a31a30

AI part =4096 chips, 32 real-valued symbo

20 ms

CPCH Access Preamble Acqusition IndicationChannel (AP-AICH)

The Access Preamble Acquisition Indicator channel (AP-AICH) isa fixed rate (SF=256) physical channel used to carry APacquisition indicators (API) of CPCH. AP acquisition indicator APIscorresponds to AP signature s transmitted by UE.

AP-AICH and AICH may use the same or different channelisationcodes. The phase reference for the AP-AICH is the Primary

CPICH. Figure illustrates the structure of AP-AICH.

1024 chips

Transmission Off

AS #1 A S #0 AS # 1 AS #i AS #1 A S #0

a1 a2a0 a31a30

API part =4096 chips, 32 real-valued sym

20 ms

The AP-AICH has a part of duration 4096 chips where the APacquisition indicator (API) is transmitted, followed by a part ofduration 1024chips with no transmission that is not formally partof the AP-AICH. The part of the slot with no transmission isreserved for possible use by CSICH or possible future use byother physical channels.

CPCH Collision Detection/Channel Assignment Indicator

Channel (CD/CA -ICH)

The Collision Detection Channel Assignment Indicator

channel (CD/CA-ICH) is a fixed rate (SF=256) physical



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channel used to carry CD Indicator (CDI) only if the CA is notactive, or CD Indicator/CA Indicator (CDI/CAI) at the sametime if the CA is active. The structure of CD/CA-ICH is shownin figure .

1024 chips

Transmission Of

AS #1 AS #0 AS #1 AS #i AS #1 A S #0

a1 a2a0 a31a30

CDI/CAIpart =4096 chips, 32 real-valued sy

20 ms

CD/CA-ICH and AP-AICH may use the same or different

channelisation codes.

The CD/CA-ICH has a part of duration of 4096chips where theCDI/CAI is transmitted, followed by a part of duration 1024chipswith no transmission that is not formally part of the CD/CA-ICH.

The part of the slot with no transmission is reserved for possibleuse by CSICH or possible future use by other physical channels.

The spreading factor (SF) used for channelisation of the CD/CA-ICH is 256.

Paging Indication Channel (PICH)

The Paging Indicator Channel (PICH) is a fixed rate (SF=256)

physical channel used to carry the paging indicators. The PICH isalways associated with an S-CCPCH to which a PCH transportchannel is mapped.

Figure 24 illustrates the frame structure of the PICH. One PICH

radio frame of length 10 ms consists of 300 bits (b0, b1, , b299).Of these, 288 bits (b0, b1, , b287) are used to carry pagingindicators. The remaining 12 bits are not formally part of thePICH and shall not be transmitted (DTX). The part of the framewith no transmission is reserved for possible future use.

b1b0

288 b i ts for paging indication12 b i ts ( t ransmissi

off)

One radio f rame (10 ms)

b28 7b28 8 b29 9

In each PICH frame, Np paging indicators {P0, , PNp-1} are

transmitted, where Np=18, 36, 72, or 144.

The PI calculated by higher layers for use for a certain UE, isassociated to the paging indicator Pq, where q is computed as afunction of the PI computed by higher layers, the SFN of the P-

CCPCH radio frame during which the start of the PICH radio



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frame occurs, and the number of paging indicators per frame(Np):

( )( )( ) NpNp

SFNSFNSFNSFNPIq mod144

144mod512/64/8/18

++++=

Further, the PI calculated by higher layers is associated with the

value of the paging indicator Pq. If a paging indicator in a certainframe is set to "1" it is an indication that UEs associated with

this paging indicator and PI should read the corresponding frameof the associated S-CCPCH.

The PI bitmap in the PCH data frames over Iub containsindication values for all higher layer PI values possible. Each bit

in the bitmap indicates if the paging indicator associated withthat particular PI shall be set to 0 or 1. Hence, the calculation in

the formula above is to be performed in Node B to make theassociation between PI and Pq..The mapping from {P0, , PNp-1}

to the PICH bits {b0, , b287} are according to Table 1

TA B L E 1 M A P P I N G O F P A G I N G I N D I C A T O R S P Q T O PICH B I T S

Number of paging

indicators perframe (Np)

Pq = 1 Pq = 0

Np=18{b16q, , b16q+15} ={1, 1,, 1}

{b16q, , b16q+15} ={0, 0,, 0}

Np=36{b8q, , b8q+7} = {1,1,, 1}

{b8q, , b8q+7} = {0,0,, 0}

Np=72 {b4q, , b4q+3} = {1,1,, 1} {b4q, , b4q+3} = {0,0,, 0}

Np=144 {b2q, b2q+1} = {1, 1} {b2q, b2q+1} = {0, 0}

Channel Mapping

Mapping between logical channels and transportchannels

Figure 10 illustrates the mapping between logical channel andtransport channels.



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F I G U R E 10 M A P P I N G B E T W E E N L O G I C A L C H A N N E L A N D T R A N S P O R T C H A N N E L S

Figure 11illustrates the mapping between transport channel and

physical channels.

F I G U R E 11 M A P P I N G B E T W E E N T R A N S P O R T C H A N N E L A N D P H Y S I C A L C H A N N E L S .

In addition to the transport channels introduced earlier, there

exist physical channels tocarry only information relevant tophysical layer procedures. The Synchronisation Channel(SCH),the Common Pilot Channel (CPICH) and the Acquisition

Indication Channel (AICH)are not directly visible to higher layersand are mandatory from the system function point ofview, to be

transmitted from every base station. The CPCH Status IndicationChannel(CSICH) and the Collision Detection/Channel Assignment

Indication Channel (CD/CA-ICH) are needed if CPCH is used.



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Physical layer porcedure

Cell search procedure

During the cell search, the UE searches for a cell and determinesthe downlink scrambling code and frame synchronisation of thatcell. The cell search is typically carried out in three steps:

Step 1: slot synchronous

During the first step of the cell search procedure the UE uses the

SCHs primary synchronisation code to acquire slotsynchronisation to a cell. This is typically done with a single

matched filter (or any similar device) matched to the primary

synchronisation code which is common to all cells. The slottiming of the cell can be obtained by detecting peaks in thematched filter output.

Step 2: frame synchronous and code-group identification

During the second step of the cell search procedure, the UE usesthe SCHs secondary synchronisation code to find framesynchronisation and identify the code group of the cell found inthe first step. This is done by correlating the received signal withall possible secondary synchronisation code sequences, and

identifying the maximum correlation value. Since the cyclic shiftsof the sequences are unique the code group as well as the frame

synchronisation is determined.Step 3: scrambling-code identification

During the third and last step of the cell search procedure, theUE determines the exact primary scrambling code used by thefound cell. The primary scrambling code is typically identifiedthrough symbol-by-symbol correlation over the CPICH with allcodes within the code group identified in the second step. Afterthe primary scrambling code has been identified, the Primary

CCPCH can be detected.And the system- and cell specific BCHinformation can be read.

Random Access Procedure

At each initiation of the physical random access procedure,Layer 1 shall receive the following information from the higherlayers (MAC):

The Transport Format to be used for the PRACH messagepart.

The ASC of the PRACH transmission.

The data to be transmitted (Transport Block Set).

The physical random-access procedure shall be performed as



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follows:

1. Derive the available uplink access slots, in the next fullaccess slot set, for the set of available RACH sub-channels

within the ASC Randomly select one access slot among the

ones previously determined. If there is no access slotavailable in the selected set, randomly select one uplinkaccess 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 allowedselections is chosen with equal probability.

2. Randomly select a signature from the set of availablesignatures within the given ASC. The random function shallbe such that each of the allowed selections is chosen withequal probability.

3. Set the Preamble Retransmission Counter to Preamble

Retrans Max.

4. Set the parameter Commanded Preamble Power to

Preamble_Initial_Power.

5. In the case that the Commanded Preamble Power exceedsthe maximum allowed value, set the preamble transmissionpower to the maximum allowed power. In the case that the

Commanded Preamble Power is below the minimum levelrequired in [7], set the preamble transmission power to a

value, which shall be at or above the Commanded PreamblePower and at or below the required minimum power specified

in [7]. Otherwise set the preamble transmission power to the

Commanded Preamble Power. Transmit a preamble using theselected uplink access slot, signature, and preambletransmission power.

6. If no positive or negative acquisition indicator (AI +1nor 1) corresponding to the selected signature isdetected in the downlink access slot corresponding to theselected uplink access slot:

1) Select the next available access slot in the set of available

RACH sub-channels within the given ASC.

2) Randomly select a new signature from the set of availablesignatures within the given ASC. The random function shall

be such that each of the allowed selections is chosen withequal probability.

3) Increase the Commanded Preamble Power by P0 = PowerRamp Step [dB]. If the Commanded Preamble Powerexceeds the maximum allowed power by 6dB, the UE maypass L1 status ("No ack on AICH") to the higher layers (MAC)

and exit the physical random access procedure.

4) Decrease the Preamble Retransmission Counter by one.

5) If the Preamble Retransmission Counter > 0 then repeatfrom step 5. Otherwise pass L1 status ("No ack on AICH") to

the higher layers (MAC) and exit the physical random access



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procedure.

7. If a negative acquisition indicator corresponding to theselected signature is detected in the downlink access slot

corresponding to the selected uplink access slot, pass L1

status ("Nack on AICH received") to the higher layers (MAC)and exit the physical random access procedure.

8. Transmit the random access message three or four uplink

access slots after the uplink access slot of the lasttransmitted preamble depending on the AICH transmission

timing parameter. Transmission power of the control part of

the random access message should be P p-m [dB] higherthan the power of the last transmitted preamble.

9. Pass L1 status "RACH message transmitted" to the higherlayers and exit the physical random access procedure.


GSM 1800

Documents

2- Channel Structure and Function 26