5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface Part 5: 1 of 34 WCDMA Air Interface Training...

Part 5: 1 of 345/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface

WCDMA Air Interface Training

Part 5 WCDMA Acquisition,

Synchronization,and Handover


WCDMA Physical Layer Procedures

• Physical Layer Timing and procedures

BS Downlink timing

Fast Synchronization Codes

Synchronization Code 1 (PSC)

Synchronization Code 2 (SSCi)

Downlink Scrambling Codes

Used by UE to distinguish desired Base Station

8192 possible codes, 64 Scrambling Code Groups

Slot Synchronization

Frame Synchronization

System Timing Synchronization

Soft Handover

Random Access protocol

Packet Access protocol

Inter-Frequency Handover


Downlink Transmission Timing

Secondary SCH

Primary SCH

S-CCPCH,k

10 ms Frame

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

CPICH (Common Pilot Channel)

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

Any PDSCH

PICH

DPCH,n

Common PilotChannel

Primary CCPCH(Broadcast Data)

Secondary CCPCH(Paging, Signaling)

Paging Indication Channel

SCH (PSC+SSC)P-CCPCHS-CCPCHPICHAICHPDSCHDPCH

S-CCPCH,k = N x 256 chips

DPCH,n = N x 256 chips

PICH = 7680 chips (3 slots)

3GPP TS 25.211 ¶ 7.03GPP TS 25.211 ¶ 7.0

k:th S-CCPCH

PICH for n:th S-CCPCH

n:th DPCCH/DCDPH

Downlink Shared Channel

Dedicated PhysicalControl/Data Channel


Downlink Scrambling Codes• Downlink Scrambling Codes

Used to distinguish Base Station transmissions on Downlink Each Cell is assigned one and only one Primary Scrambling Code

The Cell always uses the assigned Primary Scrambling Code for the Primary and Secondary CCPCH’s

Secondary Scrambling Codes may be used over part of a cell, or for other data channels

Primary SC0

Secondary Scrambling

Codes

(15)


Codes

(15)


Codes

(15)


Codes

(15)

Code Group #1 Code Group #64

8192 Downlink Scrambling CodesEach code is 38,400 chips of a 218 - 1 (262,143 chip) Gold Sequence

3GPP TS 25.213 ¶ 5.2.23GPP TS 25.213 ¶ 5.2.2

Primary SC7 Primary SC504Primary SC511


Downlink Scrambling Codes• Downlink Scrambling Code Generation

10 mSec Gold Code formed by Modulo-2 Addition of 38,400 chips from two m-sequences

Initial Conditions:

x(0) =1; X(1)... X(17) = 0y(0) ... Y(17) = 1

I

Q

1

1 0

02

2

3

3

4

4

5

5

6

6

7

7

8

8

9

9

17

17

16

16

15

15

14

14

13

13

12

12

11

11

10

10

X

Y

3GPP TS 25.213 ¶ 5.2.23GPP TS 25.213 ¶ 5.2.2

Primary Scrambling code i (where i = 0,...,511) is generatedby offsetting the X sequence by (16*i) clock cycles from the Y sequence

Primary Scrambling code i (where i = 0,...,511) is generatedby offsetting the X sequence by (16*i) clock cycles from the Y sequence


Synchronization Codes• Synchronization Codes (PSC, SSC)

Broadcast by BS

First 256 chips of every SCH time slot

Allows UE to achieve fast synchronization in an asynchronous system

Primary Synchronization Code (PSC)

Fixed 256-chip sequence with base period of 16 chips

Provides fast positive indication of a WCDMA system

Allows fast asynchronous slot synchronization

Secondary Synchronization Codes (SSC)

A set of 16 codes, each 256 bits long

Codes are arranged into one of 64 unique permutations

Specific arrangement of SSC codes provide UE with frame timing, BS “code group”

P-CCPCH

(PSC + SSC + BCH)2304 Chips256 Chips

3GPP TS 25.213 ¶ 5.2.33GPP TS 25.213 ¶ 5.2.3

Broadcast Data (18 bits)SSCi

PSC


Primary Synchronization Code

• Primary Synchronization Code (PSC)

let a = <1, 1, 1, 1, 1, 1, -1, -1, 1, -1, 1, -1, 1, -1, -1, 1>

PSC(1...256) = < a, a, a, -a, -a, a, -a, -a, a, a, a, -a, a, -a, a, a >

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

1 Frame = 15 slots = 10 mSec

Note: PSC is transmitted “Clear” (Without scrambling)

3GPP TS 25.213 ¶ 5.2.33GPP TS 25.213 ¶ 5.2.3

Broadcast Data (18 bits)SSCi

2304 Chips256 ChipsSCH BCH

PSC


Secondary Synchronization Code Group

• 16 Fixed 256-bit Codes; Codes arranged into one of 64 patterns

slot number Scrambling Code Group

#1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 #13 #14 #15

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

Group 2 1 1 5 16 7 3 14 16 3 10 5 12 14 12 10

Group 3 1 2 1 15 5 5 12 16 6 11 2 16 11 15 12

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

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

Group 64 9 12 10 15 13 14 9 14 15 11 11 13 12 16 10

Note:

The SSC patterns positively identify one and only one of the 64 Scrambling Code Groups.

This is possible because no cyclic shift of any SSC is equivalent to any cyclic shift of any other SSC.

3GPP TS 25.213 ¶ 5.2.33GPP TS 25.213 ¶ 5.2.3

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15


SSC1 SSC2 SSC3 SSC4 SSC5 SSC6 SSC7 SSC8 SSC9 SSC10 SSC11 SSC12 SSC13 SSC14 SSC15 SSC16

SSCi

SSC1 SSC15


Slot Synchronization

• Slot Synchronization using Primary Synchronization Code

BCH Data

PSC[1]

BCH Data

PSC[2]

BCH Data

PSC[3]

BCH Data

PSC[4]

BCH Data

PSC[15]

Matched Filter(Matched to PSC)

10 mSec Frame (15 slots x 666.666 uSec)

MatchedFilterOutput

time

P-CCPCH

(PSC)

3GPP TS 25.214 Annex C3GPP TS 25.214 Annex C


Frame Synchronization, SCG ID

• Frame Synchronization using Secondary Synchronization Code

BCH Data

SSC[1]

BCH Data

SSC[2]

BCH Data

SSC[3]

BCH Data

SSC[4]

BCH Data

SSC[15]

Matched Filter

Matched to SSC code group pattern

10 mSec Frame (15 slots x 666.666 uSec)

MatchedFilterOutput

time

SSC[2]

SSC[3]

SSC[4]

SSC[1]

SSC[6]

SSC[7]

SSC[8]

SSC[5]

SSC[10]

SSC[11]

SSC[12]

SSC[9]

SSC[14]

SSC[15]

SSC[13]

SSC Code Group Pattern provides

• Frame Synchronization

• Positive ID of Scrambling Code Group

Remember, no cyclic shift of any SSC is equal to any other SSC

3GPP TS 25.214 Annex C3GPP TS 25.214 Annex C


Random Access

• Random Access Attempt and AICH Indication

Pre-amble

Pre-amble

Pre-amble

AICH

RACH

NoInd.

NoInd.

Acq.Ind.

RACH

message part(UE Identification)UE

BS

3GPP TS 25.211 ¶ 7.33GPP TS 25.211 ¶ 7.3

4096 chips(1.066 msec)


Random Access Procedure

• Prior to initiating a Random Access attempt, the UE receives:

The preamble spreading code for this cell

The available random access signatures

The available spreading factors for the message part

The message length (10 ms or 20 ms)

Initial preamble transmit power

Power ramping factor

The AICH transmission timing parameter

The power offset DPp-m between preamble and the message part.

Transport Format parameters

3GPP TS 25.214 ¶ 6.13GPP TS 25.214 ¶ 6.1


Random Access Preamble Signatures

Random Access Preamble Signature Symbols

Signature P0 P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 P12 P13 P14 P15

0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 -1 1 -1 1 -1 1 -1 1 -1 1 -1 1 -1 1 -1 2 1 1 -1 -1 1 1 -1 -1 1 1 -1 -1 1 1 -1 -1 3 1 -1 -1 1 1 -1 -1 1 1 -1 -1 1 1 -1 -1 1 4 1 1 1 1 -1 -1 -1 -1 1 1 1 1 -1 -1 -1 -1 5 1 -1 1 -1 -1 1 -1 1 1 -1 1 -1 -1 1 -1 1 6 1 1 -1 -1 -1 -1 1 1 1 1 -1 -1 -1 -1 1 1 7 1 -1 -1 1 -1 1 1 -1 1 -1 -1 1 -1 1 1 -1 8 1 1 1 1 1 1 1 1 -1 -1 -1 -1 -1 -1 -1 -1 9 1 -1 1 -1 1 -1 1 -1 -1 1 -1 1 -1 1 -1 1 10 1 1 -1 -1 1 1 -1 -1 -1 -1 1 1 -1 -1 1 1 11 1 -1 -1 1 1 -1 -1 1 -1 1 1 -1 -1 1 1 -1 12 1 1 1 1 -1 -1 -1 -1 -1 -1 -1 -1 1 1 1 1 13 1 -1 1 -1 -1 1 -1 1 -1 1 -1 1 1 -1 1 -1 14 1 1 -1 -1 -1 -1 1 1 -1 -1 1 1 1 1 -1 -1 15 1 -1 -1 1 -1 1 1 -1 -1 1 1 -1 1 -1 -1 1

• Preamble codes are 16-long Orthogonal Walsh Codes.

• Preamble = [ P0, P1, … P15 ] repeated 256 times (4096 chips total).

• Preamble codes help the BS distinguish between UE making simultaneous Random Access Attempts.

3GPP TS 25.213 ¶ 4.3.3.33GPP TS 25.213 ¶ 4.3.3.3


Random Access Scrambling Codes

• Random Access Preamble Scrambling Codes

Preamble Scrambling Code is a 4096-chip segment of a 225-long Gold Code

The UE targets one BS by using the BS’s indicated preamble scrambling code

“All UE accessing this cell shall use Random Access Preamble Spreading Code

n2 ”

“All UE accessing this cell shall use Random Access Preamble Spreading Code

n1 ”

3GPP TS 25.213 ¶ 4.3.33GPP TS 25.213 ¶ 4.3.3


Acquisition Indication Channel

• Acquisition Indication Channel (AICH)

Transmits Acquisition Indicators in response to UE Access Attempts

AI’s are derived from the UE’s Access Preamble Signature

Identifies the UE which is the target of the AICH response

1024 chips

AS #0 AS #1 AS #i AS #14

a1 a2a0 a31a30

AI part

20 ms

AS #14 AS #0

(Transmission Off)

15

0,

sjssj bAIa

3GPP TS 25.211¶ 5.3.3.63GPP TS 25.211¶ 5.3.3.6


Random Access Message

• Random Access Message

Sent only after positive AICH indication

3GPP TS 25.211¶ 5.2.23GPP TS 25.211¶ 5.2.2

Random Access Message (10, 20, 40, or 80 bits per slot)

RACH Data Slot (0.666 mSec)

Pilot (8 bits)

RACH Message Slot (0.666 mSec)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15


I

QTFCI (2 bits)


Random Access Offset Timing• Random Access Procedure

Available RACH time slots determined by upper layers, sent over BCHUE selects slot based on pseudo-random algorithm

#0 #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

P PP Message

= Random Access Transmission

3GPP TS 25.211 ¶ 5.2.2.1.13GPP TS 25.211 ¶ 5.2.2.1.1


Acquisition and Synchronization

• Physical Layer Procedures

1) UE Acquisition and Synchronization

Initiate Cell Synchronization

P-CCPCH

(PSC + SSC + BCH)

UE Monitors Primary SCH code, detects peak in matched filter output

Slot Synchronization Determined ------>

UE Monitors Secondary SCH code, detects SCG and frame start time offset

Frame Synchronization and Code Group Determined ------>

UE Determines Scrambling Code by correlating all possible codes in group

Scrambling Code Determined ------>

UE Monitors and decodes BCH data

BCH data, Super-frame synchronization determined ------>

Cell Synchronization Complete

UE adjusts transmit timing to match timing of BS + 1.5 Chips


Random Access


2) UE Requests System Access and Registration

Cell Synchronization Complete

P-CCPCH

(PSC + SSC + BCH)

UE Reads Random Access parameters from BS;Calculates Random Access probe power

Initiate Random Access Attempt; Respond to Authentication challenge

When system Registration is complete, UE enters Idle mode


Establishing a Dedicated Channel


3) Establishing a Dedicated Channel

UE in Idle Mode

BS Begins transmission of downlink DPCCH/DPDCH

UE Establishes chip and frame sync to UTRAN

UE begins transmission of Reverse Link Channel,Responds to TPC bits from BS

UTRAN establishes Reverse Link chip and frame sync,Responds to TPC bits from UE

UE and BS notify upper layers that synchronization is complete

Dedicated Channel Established

3GPP TS 25.214 ¶ 4.3.23GPP TS 25.214 ¶ 4.3.2


Packet Channel AccessAICHDPCCH

3GPP TS 25.211 ¶ 7.43GPP TS 25.211 ¶ 7.4

CCCTFCITPC Pilot

FBITFCI TPCPilot

DPDCH (Data); SF 4 to 256

DL-DPCCH Slot (SF=256)

DPCCH Slot (SF=256)

CPCHDPCCHDPDCH

CCC (CPCH Control Commands)e.g., Start-of-Message , Emergency-Stop

PCPCHUplink Data Packet

‘N’ x 10 msec FramesPower Control

Preamble(0 or 8 slots)

FBITFCI TPCPilot

PCPH PC-Preamble Slot (SF=256)

CSICH

APAP

AP-AICH CD/CA-ICH

CDP


Packet Channel Access

• Prior to Packet Access, the UE receives from the UTRAN:

UL Access Preamble (AP) scrambling code.

UL Access Preamble signature set.

The Access preamble slot sub-channels group.

AP- AICH preamble Channelization code.

UL Collision Detection(CD) preamble scrambling code.

CD Preamble signature set.

CD preamble slot sub-channels group.

CD-AICH preamble Channelization code.

CPCH UL scrambling code.

DPCCH DL Channelization code.([512] chip).

CSICH/CA message indicating channel availability

3GPP TS 25.211 ¶ 7.43GPP TS 25.211 ¶ 7.4


CPCH Status Indication Channel

• CPCH Status Indication Channel (CSICH)

Transmits Indicators to convey PCPH Channel Availability

1024 chips8 bits/slotSF = 256

AS #0 AS #1 AS #i AS #14

b1 b2b0

4096 chips

20 ms

AS #14 AS #0

(Transmission Off)

3GPP TS 25.211¶ 5.3.3.63GPP TS 25.211¶ 5.3.3.6

b4 b5b3 b7b6

Higher layers provide mapping of status indicators to availability of CPCH resources


Access Preamble Indication Channel

• Access Preamble Indication Channel (AP-AICH)

Transmits Indicators in response to UE CPCH Access Attempt

API’s are derived from the UE’s CPCH Access Preamble Signature

Identifies the UE which is the target of the AP-AICH response

1024 chips

AS #0 AS #1 AS #i AS #14

a1 a2a0 a31a30

20 ms

AS #14 AS #0

(Transmission Off)

15

0,

sjssj bAPIa

3GPP TS 25.211¶ 5.3.3.63GPP TS 25.211¶ 5.3.3.6


CD/CA Indication Channel

• Collision Detection/Channel Assignment Indication Channel

Transmits Acquisition Indicators in response to UE CD preambles

CDI’s are derived from the UE’s CD Preamble Signature

Optionally may transmit CPCH Channel Assignment Indicators

1024 chips

AS #0 AS #1 AS #i AS #14

a1 a2a0 a31a30

20 ms

AS #14 AS #0

(Transmission Off)

15

0,

15

0,

sjss

sjssj bCAIbCDIa

3GPP TS 25.211¶ 5.3.3.63GPP TS 25.211¶ 5.3.3.6


WCDMA Soft Handover

Destination BSOriginating BS SC5 SC6

SC1

SC4SC7 SC8

• Each cell uses a different Scrambling Code

• Each cell has an independent time reference

• CPICH and System Frame timing between cells is arbitrary


The WCDMA Soft Handover Problem...

• WCDMA Base Stations have Asynchronous timing references IS-95/cdma2000 BS’s are synchronized to GPS!

Data 2TFCIData 1 TPC

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Pilot

CPICH 2CPICH 2CPICH 2


DPCCH/DPDCHDPCCH/DPDCHDPCCH/DPDCH

CPICH 2

CPICH 1

DPCCH/DPDCH

Toffset

10 msecframe

BS 1

BS 2

DPCCH/DPDCHDPCCH/DPDCHDPCCH/DPDCH DPCCH/DPDCH

10 msec DPCCH/DPDCH frame

0.666 msec DPCCH/DPDCH slot


WCDMA Handover Scenarios

RNS

RNC

RNS

RNC

Node B Node B Node B Node B

Iu Iu

Iur

Iub IubIub Iub

Inter-Node(Hard or Soft)

Intra-Node(Softer)

Inter-RNS(Soft with Iur;

Hard with no Iur)

UTRAN

Core Network

3GPP TS 25.8323GPP TS 25.832


WCDMA Soft Handover

• To facilitate asynchronous handover, timing adjustments are made by the UE, the RNC, and the Core Network

TimeAlignment

Transport ChannelFrame Alignment

RadioSynchronization

RNS

UTRAN

Core Network

UE

RNS

Node B

Node B

Node B

Vocoder

Node B

Node B

Node B

RNCRNC

3GPP TS 25.401 ¶ 9.03GPP TS 25.401 ¶ 9.0


WCDMA Soft Handover• Soft Handover Initiation

(2)

UE measures CPICH power and time delay

from adjacent cells

(3)

UE Reports measurements to UTRAN

(1)

UTRAN informs UE of neighboring cell

information

(4)

UTRAN decides the handover

strategy




CPICH 2

CPICH 1

DPCCH/DPDCH

Toffset

10 msecframe

BS 1

BS 2

UTRAN

UE Reports Toffset

to UTRAN


WCDMA Soft Handover

(6)

UE Rake Receiver Synchronizes to BS2

DPCCH/DPDCH

(7)

UE in soft handover with BS1 and BS2 DPCCH/DPDCH’s

(5)

UTRAN Commands BS2 to adjust DPCH timing by

Toffset

(8)

When BS2 sufficiently strong, drop BS1.

(Handover complete)



CPICH 2CPICH 2CPICH 2CPICH 2

CPICH 1

DPCCH/DPDCH

Toffset

10 msecframe

BS 1

BS 2

UTRAN

UE Reports Toffset

to UTRAN

UTRAN Commands BS2to adjust DPCH timing

by Toffset

DPCCH/DPDCHDPCCH/DPDCHDPCCH/DPDCH DPCCH/DPDCH

Toffset

• Soft Handover Execution


Inter-Frequency Handover

• Inter-frequency Handover

To allow inter-frequency measurements, data is compressed in time so that some of the 10 mSec frame is available for measurements.

8 to 14 slots per frame may be used

Data compression can be accomplished by:

Decreasing the Spreading Factor by 2:1

– Increases Data Rate so bits get through twice as fast!

Puncturing bits

– weakens FEC coding

Higher layer scheduling

– Reduces available timeslots for user traffic


Compressed Mode Operation• 1 to 7 slots per frame diverted for hard handover processes

3GPP TS 25.212 ¶ 4.4.33GPP TS 25.212 ¶ 4.4.3

1 2 3 4 5 6 7 8 9 10 11 12 13 14 151 2 3 4 511 12 13 14 15 6

1 2 3 4 5 11 12 13 14 151 2 3 4 511 12 13 14 15 6

1 2 3 4 5 6 7 8 9 10 11 12 4 511 12 13 14 15 6

10 mSec Frames (15 slots)

Normal Operation

Compressed-Mode; single-frame method

Compressed-Mode; double-frame method

Transmission Gap

Transmission Gap

The complete TFCI word must be transmitted every frame, even in Compressed Mode.Compressed Mode Slot formats (A,B) contain higher proportion of TFCI bits per slot compared with normal slots.


Handover to/from GSM

• Handover to/from GSM

GSM handover is an explicit requirement in WCDMA

Facilitated by commonality of multi-frame structures

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

T T T T T T T T T T T S T T T T T T T T T T T T T I

12 WCDMA 10 mSec Frames (120 ms)

GSM 26-frame TCH multiframe (120 ms)

T = Traffic FrameS = SACCH FrameI = Idle Frame

5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface Part 5: 1 of 34 WCDMA Air Interface Training...

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Transcript of 5/038 13 - EN/LZU 108 5306 Rev A WCDMA Air Interface Part 5: 1 of 34 WCDMA Air Interface Training...