Cell Search,Paging And Uplink Access In Cdma Systems

Cell search,paging and uplink access in CDMA systems

Song Pengpeng

Presentation Title — 2 All rights reserved © 2004

Contents

> Cell search in cdma2000 and WCDMA• Acquisition in cdma2000• Cell search in WCDMA

> Paging in cdma2000 and WCDMA• Paging channels in cdma2000• Paging channels in WCDMA

> Random access in cdma2000 and WCDMA• Random access in cdma2000• Random access in WCDMA


Acquisition in CDMA2000

> Pilot channel

> Pilot Channel is effectively the PN sequences itself and contains no information.

> Pilot channel provides the mobile with timing and phase reference.

> Pilot symbol strength is a key measurement in soft handoff.

S(t)

BasebandFi l ter

BasebandFi l ter

Al l 0s

I -Channel PN sequence1. 2288Mcps

Q-Channel PN sequence1. 2288Mcps

I (t)

Q(t)

tfc2cos

tfc2sin

W0

(Al l 0s at 1. 2288Mcps)



> The Sync Channel carries baseband information at 1.2 kbps and is spread by Walsh function 32.

BasebandFi l ter

BasebandFi l ter

Syncchannel

bi ts

Wal sh 32Sequence at1. 2288Mcps

I -Channel PN sequence1. 2288Mcps

Q-Channel PN sequence1. 2288Mcps

B

b

Bl ockI nterl eaver

Symbolrepeti t i on

Conv.EncoderR=1/ 2

1. 2 kbps 2. 4 kbps 4. 8 kbps1. 2288M cps

Sync channel super f rame (96 bi ts) Sync channel super f rame (96 bi ts)

Sync channelf rame (32

bi ts)


bi ts)


bi ts)


bi ts)


bi ts)


bi ts)

Pi l ot PNsequence

Pi l ot PNsequence

Pi l ot PNsequence

Pi l ot PNsequence

SOMSync channel f rame body (31 bi ts)

Sync channel message capsul e: 31*6=186 bi ts

80 ms



> Pilot channel for short code acquisition--- search window of 26.66ms

> Decoding Sync channel --- data rate@2kbps

““Handoff between asynchronous and synchronous systems”, Handoff between asynchronous and synchronous systems”, [email protected] , IEEE VTC2000 , IEEE VTC2000““Handoff between asynchronous and synchronous systems”, Handoff between asynchronous and synchronous systems”, [email protected] , IEEE VTC2000 , IEEE VTC2000

mailto:[email protected]




> Ec/No @-21dB at cell boundary;

> The sync channel can be reliably decoded in 240ms;

> Maximal boot_up time for cdma2000 system is 325ms !““Handoff between asynchronous and synchronous systems”, Handoff between asynchronous and synchronous systems”, [email protected] , IEEE VTC2000 , IEEE VTC2000““Handoff between asynchronous and synchronous systems”, Handoff between asynchronous and synchronous systems”, [email protected] , IEEE VTC2000 , IEEE VTC2000




Cell search in WCDMA

> cell search---to resolve code ,time and frequency ambiguity.• Power on---for initial cell search• Idle mode---for identifying new camping cells• Active mode---for identifying handover candidates

> Cell search procedures

““Cell search in WCDMA”, Yi-Pin Wang, Tony Ottosson, IEEE joural on selected areas in communications,Cell search in WCDMA”, Yi-Pin Wang, Tony Ottosson, IEEE joural on selected areas in communications,Vol18,No8, August 2000Vol18,No8, August 2000

““Handoff between asynchronous and synchronous systems”, Handoff between asynchronous and synchronous systems”, [email protected] , IEEE VTC2000 , IEEE VTC2000


““Handoff between asynchronous and synchronous systems”, Handoff between asynchronous and synchronous systems”, [email protected] , IEEE VTC2000 , IEEE VTC2000

Sl otsynchroni zati on

Code groupi denti fi cati on

and f ramesysnchroni zati on

Scrambl i ngcode

i denti fi cati on

Frequencysynchroni zati on

Decodi ng BCHchannel

Target cel l search

i ni t i al cel l search





> Sync channels in a cell search for WCDMA

““ cell searching in WCDMA”,Sanat Kamal Bahl, IEEE Potential 2003; 3gpp TS 25.211~214cell searching in WCDMA”,Sanat Kamal Bahl, IEEE Potential 2003; 3gpp TS 25.211~214““ cell searching in WCDMA”,Sanat Kamal Bahl, IEEE Potential 2003; 3gpp TS 25.211~214cell searching in WCDMA”,Sanat Kamal Bahl, IEEE Potential 2003; 3gpp TS 25.211~214

Unmodulated orthogonal

gold code --- Cp

Unmodulated orthogonal

gold code --- Cp

Cs*DjCs*DjCs*DjCs*Dj

Cell Cell specific specific

ScramblinScrambling codeg code

Cell Cell specific specific

ScramblinScrambling codeg code



> Stage 1: Slot synchronization by PSC

Autocorrelation function over the full PN periodAutocorrelation function over the full PN periodAutocorrelation function over the full PN periodAutocorrelation function over the full PN period

Slot synchronization using the matched filterSlot synchronization using the matched filterSlot synchronization using the matched filterSlot synchronization using the matched filter

““Initital cell search procedure in WCDMA---an imporved algorithm for FDD”,Initital cell search procedure in WCDMA---an imporved algorithm for FDD”,[email protected],IEEE [email protected],IEEE 2003




> Stage 2: frame synchronization and GI(Group Indicator) identification

Ful l correl at i ond1, d2, . . . d16

Cs * Dj



threshol d(Cs, Dj )

Cs, 1

Cs, 2

Cs, 16…





> Stage 3: scrambling code identification---symbol-wise correlation over CPICH with all scrambling

codes within the code group identified in step 2.



> False alarm probability and detection threshold





> Initial Cell search procedures

30 ms30 ms

20 ms20 ms

10 ms10 ms

Stage 2

Stage 3

Stage 4

Stage 1

Stage 2 . . . Stage 2 Stage 2

Stage 3 Stage 3 … Stage 3 Stage 3

Stage 1 . . . Stage 1 Stage 1

start Stage 3rej ects

candi dates

Stage 3accepts

candi dates

Frequencyacqui si t i on

achi eved

Nt sl ots

Nf sl ots



> It can be seen that for a 90% reliability, the acquisition time is around 500ms at the cell boundary of –21dB !

WCDMA acquisition time in AWGN channelWCDMA acquisition time in AWGN channelWCDMA acquisition time in AWGN channelWCDMA acquisition time in AWGN channel WCDMA acquisition time in fading channelWCDMA acquisition time in fading channelWCDMA acquisition time in fading channelWCDMA acquisition time in fading channel

““Handoff between asynchronous and synchronous systems”, Handoff between asynchronous and synchronous systems”, [email protected] , IEEE VTC2000 , IEEE VTC2000““Handoff between asynchronous and synchronous systems”, Handoff between asynchronous and synchronous systems”, [email protected] , IEEE VTC2000 , IEEE VTC2000

> Synchronization time : Ts=Tc/(1-Pe)

Where





> Average acquisition time with different radio configuration parameter




Paging channel in CDMA2000

> QPCH, BCCH and CCCH replace the paging channel in IS95.• Enabling Access Probe Handoff(APHO) and Access Handoff

(AHO)• BCCH---cell specific broadcasting information• CCCH---BS responds to MS• QPCH---to improve mobile phone standby time

– Single bit messages twice per 80ms slot to direct slotted-mode MS

– Pilot aided coherent OOK detection– Tri-valued decision:0,1 or Erasure

““The paging channel in cdma2000”,[email protected], IEEE 2000The paging channel in cdma2000”,[email protected], IEEE 2000““Phone standby time in cdma2000:the quick paging channel in soft Phone standby time in cdma2000:the quick paging channel in soft

handoff”,__,IEEE handoff”,__,IEEE transactions on vehicular technology,vol 50,No5,Sept 2001.transactions on vehicular technology,vol 50,No5,Sept 2001.

““soft handoff on the quick paging channel”,__,Globalcomm’99soft handoff on the quick paging channel”,__,Globalcomm’99““Cdma2000:battery life improvement techniques”,__,IEEE 2000Cdma2000:battery life improvement techniques”,__,IEEE 2000

““The paging channel in cdma2000”,[email protected], IEEE 2000The paging channel in cdma2000”,[email protected], IEEE 2000““Phone standby time in cdma2000:the quick paging channel in soft Phone standby time in cdma2000:the quick paging channel in soft

handoff”,__,IEEE handoff”,__,IEEE transactions on vehicular technology,vol 50,No5,Sept 2001.transactions on vehicular technology,vol 50,No5,Sept 2001.

““soft handoff on the quick paging channel”,__,Globalcomm’99soft handoff on the quick paging channel”,__,Globalcomm’99““Cdma2000:battery life improvement techniques”,__,IEEE 2000Cdma2000:battery life improvement techniques”,__,IEEE 2000


Paging channel in WCDMA

> PCH+FCCHSecondary Common Control Channel

> PICH: to carry the paging indicators.• A PICH is always associated with an S-CCPCH to which a

PCH transport channel is mapped.

b1b0

288 bits for paging indication12 bits (transmission

off)

One radio frame (10 ms)

b287 b288 b299

3GPP physical layer specification 25.2113GPP physical layer specification 25.2113GPP physical layer specification 25.2113GPP physical layer specification 25.211

Structure of Paging Indicator Channel (PICH)Structure of Paging Indicator Channel (PICH) Structure of Paging Indicator Channel (PICH)Structure of Paging Indicator Channel (PICH)


Enhanced random access in CDMA2000

> IS95 access mode: slotted ALOHA mode

> New features in CDMA2000 reverse access:• Faster capture feedback: an access header containing

request ID and access type• Fast congestion and overload control:periodically

broadcasting a fast access inhibit indicator bit (ISMA)• Support of variable-size/rate packets• Closed loop power control • Shortened access probe• Soft handoff capability• Discontinuous /gated-off preamble

““Enhanced Random Access and Reservation Scheme in CDMA2000”, kamran etemad, Enhanced Random Access and Reservation Scheme in CDMA2000”, kamran etemad, IEEE Personal Communications. April 2001IEEE Personal Communications. April 2001

3GPP2 C.S00002-A,”physical layer standard for cdma2000 spread spectrum systems”, Release A3GPP2 C.S00002-A,”physical layer standard for cdma2000 spread spectrum systems”, Release A


3GPP2 C.S00002-A,”physical layer standard for cdma2000 spread spectrum systems”, Release A3GPP2 C.S00002-A,”physical layer standard for cdma2000 spread spectrum systems”, Release A



> REACH: Basic Access mode

…Message data

Preambl e

REACH

> Involved channels:• REACH: distinguished by its long codes• RCCCH: only be used based on a reservation mode• FCPCH(forward common power control channel)• FCACH(forward common channel assignment

channel): to provide a fast feedback or response mechanism

• FCCCH:





> REACH: Power control access mode

…Message data

Preambl e

REACH header

FCPCH

Earl y ACK

Accessmessage

ACK

…

Preambl e

REACH header

Earl y ACKti me out

(a): a successful probe

(b): a fai l ed probe





> REACH: reservation access mode

A reservation access probe followed by data transmission on RCCCHA reservation access probe followed by data transmission on RCCCHA reservation access probe followed by data transmission on RCCCHA reservation access probe followed by data transmission on RCCCH



…

Preambl e

REACH header

FCPCH

RCCCHassi gnment

Accessmessage

ACK

RCCCH data



> Enhanced access procedures

Cel lsel ecti on

Modesel ecti on

Formi ngthe

AccessProbes

Accessi nhi bi tcheck

Accessprobi ng

Powercontrol(except

BAmode)

Sof thandoff(RA mode

onl y)

Monitors Monitors the Ec/Iothe Ec/IoMonitors Monitors the Ec/Iothe Ec/Io

RA mode for long RA mode for long data burst;data burst;

BA or PCA mode for BA or PCA mode for short signaling and short signaling and

MAC messagesMAC messages

RA mode for long RA mode for long data burst;data burst;

BA or PCA mode for BA or PCA mode for short signaling and short signaling and

MAC messagesMAC messages

…

TA RT

I ni t i alpower

Power i ncrement

Access probe

Access probe sequence

Check the Check the busy/idle busy/idle status or status or

inhibit flaginhibit flag

Check the Check the busy/idle busy/idle status or status or

inhibit flaginhibit flag

RandomlRandomly selects y selects a ERACHa ERACH

RandomlRandomly selects y selects a ERACHa ERACH




Random access scheme in WCDMA

> Initial access scheme proposed in [*]• In use of Orthogonal signatures ;preamble and data both

transmitted in I&Q branches

> Access scheme proposed by ARIB[**]• Data on I branch;preamble and pilot on Q branch

> Access scheme for UTRA• Power ramping method• Guard period for frame alignment• Avoid the drawbacks of above schemes

[*] [*] Esmailzadeh.R,Gustafsson,M. “A novel random access method for CDMA systems”,ICUPC’97,San Diego,CA,USAEsmailzadeh.R,Gustafsson,M. “A novel random access method for CDMA systems”,ICUPC’97,San Diego,CA,USA[**]ARIB,”specification of Air Interface for the 3G Mobile System”,ARIB report of IMT-2000 Radio Transmission [**]ARIB,”specification of Air Interface for the 3G Mobile System”,ARIB report of IMT-2000 Radio Transmission

Technology Special Group,Vol 3Technology Special Group,Vol 3Frank.G,Weber G,”random access scheme for the ETSI/UTRA WCDMA”,IEEE VTC99Frank.G,Weber G,”random access scheme for the ETSI/UTRA WCDMA”,IEEE VTC99

[*] [*] Esmailzadeh.R,Gustafsson,M. “A novel random access method for CDMA systems”,ICUPC’97,San Diego,CA,USAEsmailzadeh.R,Gustafsson,M. “A novel random access method for CDMA systems”,ICUPC’97,San Diego,CA,USA[**]ARIB,”specification of Air Interface for the 3G Mobile System”,ARIB report of IMT-2000 Radio Transmission [**]ARIB,”specification of Air Interface for the 3G Mobile System”,ARIB report of IMT-2000 Radio Transmission

Technology Special Group,Vol 3Technology Special Group,Vol 3Frank.G,Weber G,”random access scheme for the ETSI/UTRA WCDMA”,IEEE VTC99Frank.G,Weber G,”random access scheme for the ETSI/UTRA WCDMA”,IEEE VTC99



> RACH access: acknowledged by AICH• Minimized buffer requirements;• Minimized processing delay;• Frame structure compatibility with dedicated physical

channels

data

256chi ps

256*16=4096 chi ps

. . .

preambl e preambl e

data

Pi l otbi ts

TFCI

preambl e

1 radi o f rame=10 ms

Frank.G,Weber G,”random access scheme for the ETSI/UTRA WCDMA”,IEEE VTC99Frank.G,Weber G,”random access scheme for the ETSI/UTRA WCDMA”,IEEE VTC993GPP physical layer specification TS 25.11~2143GPP physical layer specification TS 25.11~214

Frank.G,Weber G,”random access scheme for the ETSI/UTRA WCDMA”,IEEE VTC99Frank.G,Weber G,”random access scheme for the ETSI/UTRA WCDMA”,IEEE VTC993GPP physical layer specification TS 25.11~2143GPP physical layer specification TS 25.11~214



> CPCH access scheme: acknowledged by AP-AICH and CD/CA-ICH• DSMA/CR(digital sense multiple access/collision

resolution)

““an overview of Common Packet Channel(CPCH), an opitmum wireless Internet Mechanism in an overview of Common Packet Channel(CPCH), an opitmum wireless Internet Mechanism in 3GPP WCDMA system and comparison of various UMTS Non Real Time data deployment opitons”, Dr. Kourosh Parsa,3GPP WCDMA system and comparison of various UMTS Non Real Time data deployment opitons”, Dr. Kourosh Parsa,


DL-PCpreambl e

Downl i nk DPCCH

UL-PCpreambl e

Upl i nk DPCCH

Downl i nk

Upl i nk

Downl i nkacknowl edge: AP-AI CH

Contenti on resol uti onacknowl edgement ondownl i nk: CD/ CA- I CH

Access Phase: powerrampi ng of preambl es

Contenti on resol uti onpreambl e: CD



> RACH---for fast access and short/medium packets• High rate RACH---suited for packet transmissions of

medium size• Low rate RACH--- only used for very short packet

transmissions

> CPCH--- the most efficient approach to bursty packet access• Do not need multiple control channels running to support

the circuit operation• A factor of 4 and 26 higher spectrum efficiency in

downlink and uplink as compared to use of dedicated channels.

• Four –fold efficiency as compared to RACH““an overview of Common Packet Channel(CPCH), an opitmum wireless Internet Mechanism in an overview of Common Packet Channel(CPCH), an opitmum wireless Internet Mechanism in

3GPP WCDMA system and comparison of various UMTS Non Real Time data deployment opitons”, Dr. Kourosh Parsa,3GPP WCDMA system and comparison of various UMTS Non Real Time data deployment opitons”, Dr. Kourosh Parsa,““Performance of a common channel packet access in WCDMA”,Farooq Khan,Performance of a common channel packet access in WCDMA”,Farooq Khan,

Christiaan Roobol and Johan Larsson, IEEE 1998Christiaan Roobol and Johan Larsson, IEEE 1998


““Performance of a common channel packet access in WCDMA”,Farooq Khan,Performance of a common channel packet access in WCDMA”,Farooq Khan,Christiaan Roobol and Johan Larsson, IEEE 1998Christiaan Roobol and Johan Larsson, IEEE 1998

Thank you!