cell update fach state transfer 1205

HUAWEI TECHNOLOGIES CO., LTD.

www.huawei.com

Huawei Confidential

Security Level:

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23/4/26

Cell update & FACH Transfer

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Content

• UE Working Modes and States• Cell Update and FHHO Scenarios• Main Reason for CDR Increase in FACH• Problem and Solutions

HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential

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UE Working Modes and States

Idle Mode Connected Mode

CELL_DCH CELL_FACH CELL_PCH URA_PCH





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Idle Mode The UE has no relation to UTRAN, only to CN. Any data

transfer, a signalling connection should have to be established.

UE camps on a cell It enables the UE to receive system information from the PLMN UE can monitor PICH of a cell for paging

The idle mode tasks can be divided into three processes: PLMN selection and reselection Cell selection and reselection Location registration





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Connected Mode When UE is in connected mode

The UE position can be known on different levels: Cell level (CELL_DCH/CELL_FACH/CELL_PCH) UTRAN Registration Area (URA) level (URA_PCH)

The UE can use different types of channels in connected mode Dedicated transport channels (CELL_DCH) Common transport channels (CELL_FACH)





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Connected Mode Cell-DCH

In active state Communicating via its dedicated channels UTRAN knows which cell UE stays in





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Connected Mode Cell-FACH

In active state Few data to be transmitted both in uplink and in downlink. There

is no need to allocate dedicated channel for this UE Downlink uses FACH and uplink uses RACH UE needs to monitor the FACH for its information UTRAN knows which cell the UE stays in





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Connected Mode Cell-PCH

No data to be transmitted or received Monitor PICH, to receive its paging UTRAN knows which cell the UE stays in UTRAN has to update cell information of UE when UE roams to

another cell Lower the power consumption of UE





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Connected Mode URA-PCH

No data to be transmitted or received Monitor PICH, to receive its paging UTRAN only knows which URA (which consists of multiple cells)

that UE stays UTRAN updates UE information only after UE has roamed to other

URA A better way to reduce the resource occupancy and signaling

transmission





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UE Working Modes and States

CELL_DCH CELL_FACH

CELL_PCHURA_PCH

IDLE

DEAD - Scan networks (PLMN)- Camp on a cell

- Monitor paging channel- Cell re-selection

- Dedicated channel- Common service,

such as voice

- Reduce activity, DRX, and save powerRRC Connection

- Common channel- PS service with few

data to transmit

- Reduce activity further- Avoid unnecessary

signaling





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FHHO ： Forward Hard Handover

FHHO used to monitor the RRC connection state on common channel, which process the mobility of UE on Common Channel

FHHO also contains the RRC connection rebuilt in DCH.

FHHO including Cell UPDATE and URA UPDATE(only occurs in URA_PCH)





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FHHO Function （ CELL_DCH） RLC Un-recovery Error: recover the RL when UE cannot

normal communicate with UTRAN equaled RLC layer using AM mode

RL failure: using in RRC connection rebuilt, when all the RLs loss of synchronization, UE try to rebuilt the RRC connection with UTRAN





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Relation between FHHO and RRC StateRRC Connection state Realizable FHHO Function （ update cause）CELL_DCH Cell Update (RLC ERR 、 RL FAIL)

CELL_FACH Cell Update (Periodical Cell update, Cell reselection, Re-enter Serving Cell, RLC ERR)

CELL_PCH Cell Update (Periodical Cell update, Cell reselection, Re-enter Serving Cell, Paging Response, UL Data Transmit)

URA_PCH Cell Update (Paging Response, UL Data Transmit), URA Update (Periodical URA update, URA reselection)





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Cell Update Function Periodical Cell update: UE moving within one cell ， majority

way to monitor RRC connection Cell reselection: UE mobility state cross different cells, major

way of UE keep RRC connection with UTRAN serving in Common Channel.

Re-enter Service Area: another way to keep RRC connection when move, T305 expired

RLC Un-recovery Error: recover the RL when UE cannot normal communicate with UTRAN equaled RLC layer using AM mode

Paging Response ： response to paging type 1 from UTRAN when RRC connection exist

UL Data Transmit ： UE inform UTRAN needing data transmit





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URA Update Function Periodical URA update: URA ID contained in Cell system info

with UE mobility URA reselection: URA ID not in the system info when UE move





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Cell Update Signaling Flow





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Current state on Global network: PS CDR increase a lot PS HSPA CDR Close FACH Open FACH

Brazil Claro 0.44% 0.72%SA Vodacom 0.80% 3.50%Brazil VIVO 0.73% 4.24%Greess VDF 0.52% 2%

Gemanny O2 0.76% 3.70%Turkey VDF 0.88% 2.54%





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Main reasons for the CDR increase on FACH

PS call drop after H2F RB Reconfig failure PS call drop by TRB/SRB reset on FACH state PS call drop due to the procedure flow crossed

by F2H RB Reconfig and Cellupdate PS call drop by SRB rebuilt during P2F phase





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Reason and SolutionsReason No power control on FACH No SoftHO on FACH The state not consistent between UE and RAN

Solutions Decrease Users on the FACH state by decrease H2F

volume threshold Configure longer H2F timer than the PS inactivate

timer, let non-throughput user fast transfer to idle Decrease the time from FACH to PCH or idle state.

Thank Youwww.huawei.com





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RNTI - Radio Network Temporary Identifier Five types of RNTI exist

Serving RNC RNTI (S-RNTI) Drift RNC RNTI (D-RNTI) Cell RNTI (C-RNTI) UTRAN RNTI (U-RNTI) HS-DSCH RNTI (H-RNTI)

xujin

From ProtocolThe cell RNTI (C-RNTI) identifies a UE having a RRC connection within a cell.The U-RNTI (UTRAN Radio Network Temporary Identity) is allocated to a UE having a RRC connection and identifies the UE within UTRAN.The H-RNTI identifies an UE having a HS-PDSCH assignment within a cell.





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Cell update flow （ P->F）UE RRM RR FMR SIG

DLCCCH:Cell update confirm

Apply radio resource

ULCCCH:Cell update request

If MACC/MACD in different board ， built AAL2 connection

Built MACC and MACD logical channel

ULDCCH:Physical channal re-configuration

completeCell update and UE state

indicate

RLC restore





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Cell update with relocation （ PS）SourceRNC TargetRNCCN

Rel ocati on Reqi red

Rel ocati on RequsetRANAP RANAP

RANAP RANAP

RANAP RANAPRel ocati on Requset Ack

RANAP RANAPRel ocati on Cmd

Rel ocati on Commi tRNSAP RNSAP

RANAP RANAPI U Rel Cmd

RANAP RANAPI U Rel Compl ete

RNSAP RNSAPRel ocati on Detect

UE

RRCRRC Cel l Update Conf

RRCRRC UTRAN Mobi l i ty I nfo Conf

RRCRRC Cell UpdateRNSAP RNSAPUL Si g Trans I nd





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Cell update with relocation （ PS）SourceRNC TargetRNCCN

Rel ocat i on Reqi red

Rel ocati on Requset

RANAP RANAP

RANAP RANAP

Est Req

Est Conf

Q.AAL2

Q.AAL2

Q.AAL2

Q.AAL2

RANAP RANAPRel ocati on Requset Ack

RANAP RANAPRel ocati on Cmd

Rel ocati on Commi tRNSAP RNSAP

RANAP RANAPI U Rel Cmd

RANAP RANAPI U Rel Compl ete

RNSAP RNSAPRel ocati on Detect

UE

RRCRRC Cel l Update Conf

RRCRRC UTRAN Mobi l i ty I nfo Conf

AAL2 Rel Conf

AAL2 Rel Req Q.AAL2

Q.AAL2

Q.AAL2

Q.AAL2

RA Update





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25

UE DRNCSource

DRNCTarget

SRNC

RNSAP RNSAP8. Common Transp. Channel Resources Release

RNSAPRNSAP

2. Uplink Signalling TransferIndication

RNSAP

3. Common Transp. Channel ResourcesInitialization Request

RNSAP

RRC 1. CCCH: Cell UpdateRRC-relay

RRC6. DCCH: Cell Update Confirm

RRC

RRC7. DCCH: RNTI Relocation Complete

RRC

RNSAPRNSAP

4. Common Transp. Channel Resourcesinitialization Response

5. ALCAP Iur bearer setup

FHHO （ Cell Update crossing IUR）





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UETargetRNC

5.CCCH: URA Update Confirm

SourceRNC

2.Uplink Signalling Transfer Indication

ServingRNC

[ new C-RNTI,D-RNTI, UL message]

1.CCCH: URA Update

[U-RNTI, URA update cause]RRC-relayRRC

3. Decision Not toperform SRNS

relocation

RRC RRC-relay

RNSAP

RNSAP

4. Downlink Signalling Transfer Request

RNSAP

RNSAP

FHHO （ URA update）





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FHHO FlowUE RNS

Cell Update

Cell Update Confirm

UE RNSCell Update

Cell Update ConfirmUTRAN Mobility Info Confirm

UE RNSCell Update

Cell Update ConfirmRB Release Complete

Cell update procedure with radio bearer release

Cell update procedure with update of UTRAN mobility information

Cell update procedure with radio bearer release

UE RNSCell Update

Cell Update ConfirmRB recfg complete

Cell update procedure with radio bearer reconfiguration

UE RNSURA Update

UAR Update ConfirmURA update procedure, basic flow

UE RNSURA Update

UAR Update ConfirmUTRAN Mobility Info Confirm

URA update procedure with update of UTRAN mobility information

cell update fach state transfer 1205

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