Cell Reselection

WCDMA L1 Tutoria Tutoriall

Cell Reselection Overview

2

WCDMA Layer 1 Tutorial

4/13/2011

Cell Reselection

Introduction •

Process by which a UE detects, evaluates, and camps on a better neighbor when already camped on a cell – –

•

Idle Mode, CELL_PCH, URA_PCH URA_PCH CELL_FACH

Suggested Reading – – – –

TS 25.304 TS 25.133 TS 25.331 Systems Memos by Messay Amerga •

•

http://lvcrpprd.qualcomm.com/livelink/li http://lvcrpprd.qualcomm.c om/livelink/livelink?func=ll velink?func=ll&objId=2572252 &objId=25722527&objAction=brow 7&objAction=browse&sort=name se&sort=name

Deviation from Specification is highlighted in Red

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4/13/2011

Cell Reselection

Introduction •

Process by which a UE detects, evaluates, and camps on a better neighbor when already camped on a cell – –

•

Idle Mode, CELL_PCH, URA_PCH URA_PCH CELL_FACH

Suggested Reading – – – –

TS 25.304 TS 25.133 TS 25.331 Systems Memos by Messay Amerga •

•

http://lvcrpprd.qualcomm.com/livelink/li http://lvcrpprd.qualcomm.c om/livelink/livelink?func=ll velink?func=ll&objId=2572252 &objId=25722527&objAction=brow 7&objAction=browse&sort=name se&sort=name

Deviation from Specification is highlighted in Red

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Cell Reselection

Message Flow Diagram RRC

L1 CHY_ACQ_REQ

ACQ Procedures Procedures CPHY_ACQ_CNF (success)

l1m_state = ACQ CPHY_SETUP_REQ (BCH/PCCPCH) CPHY_SETUP_CNF (success)

l1m_state = BCH CPHY_CELL_SELECTION_REQ

Evaluate Cell Selection Criteria (S Values) CPHY_CELL_SELECTION_CNF CPHY_CELL_TRANS (cell camp on cell 0) CPHY_CELL_TRANS_CNF (success) CPHY_SETUP_REQ (SCCPCH)

l1m_state = PCH/FACH CPHY_SETUP_CNF (success) CPHY_CELL_PARM_REQ

Cell selection/cell reselection parameters CPHY_CELL_MEAS_REQ

SIB parms, neighbor cell list CPHY_DRX_REQ

l1m_state = PCH_SLEEP (Cell Selection/Reselection Selection/Reselection Evaluation every DRX Cycle) Pilot Dies/Neighbor Cell becomes stronger CPHY_CELL_RESELECTION_IND (cell 1) CPHY_SETUP_REQ (PCCPCH_N/BCH_N) CPHY_SETUP_CNF (success)

Read SIBs CPHY_CELL_TRANSITION_REQ (reselection success)

l1m_state = PCH Set up SCCPCH on new Cell CPHY_CELL_TRANS_CNF (success) CPHY_CELL_PARM_REQ CPHY_CELL_MEAS_REQ CPHY_DRX_REQ

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Cell Reselection

S Criteria •

Squal > 0 AND Srxlev > 0 to camp on a cell

•

Squal = Ec/Io – Qqualmin – – –

•

Ec/Io > Qqualmin to camp Ec/Io is measured by UE Qqualmin is from SIB3

Srxlev = RSCP – Qrxlevmin – max(UE_TXPWR_MAX_RACH – P_MAX, 0) – –

– –

RSCP should be greater than a minimum RSSI When RF output power of the t he UE is less than what the UE may use in the cell, then UE should be closer to NodeB RSCP is measured by UE Qrxlevmin and UE_TXPWR_MAX_RACH is from SIB3

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Cell Reselection

SIB3 Parameters •

Sintrasrch (optional) – –

•

Sintersrch (optional) – –

•

–

Used in ranking serving cell based on Ec/Io.

Qqualmin –

•

Used in ranking serving cell based on RSCP

Qhyst2s –

•

Measure inter-RAT neighbor cells when Squal <= SsearchRAT Always measure inter-RAT neighbor cells when not specified

Qhyst1s –

•

Measure inter-frequency neighbor cells when Squal <= Sintersrch Always measure inter-frequency neighbor cells when not specified

SsearchRAT (optional) –

•

Measure intra-frequency neighbor cells when Squal <= Sintrasrch Always measure intra-frequency neighbor cells when not specified

Minimum required quality measure based on Ec/Io

Qrxlevmin –

Minimum required quality measure based on RSCP

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Cell Reselection

SIB3 Parameters •

UE_TXPWR_MAX_RACH –

•

Treselection –

•

Maximum allowed UL TX power

Time for which the neighbor cell should meet cell reselection criteria for UE to reselect

Cell Selection and Reselection Quality Measure – –

Ec/Io or RSCP Specifies which measurement quantity ranking should be based on

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Cell Reselection

SIB11 Parameters •

Neighbor List –

•

Qoffset1s,n –

•

Maximum allowed UL TX Power for neighbour cell

Qqualmin –

•

Quality Offset used to rank cell based on Ec/Io

UE_TXPWR_MAX_RACH –

•

Quality Offset used to rank cell based on RSCP

Qoffset2s,n –

•

UE will also detect neighbors not specified in the list and reselect to it (FACH) • Idle Mode support for detected cells still under discussion

Minimum required quality measure based on Ec/Io

Qrxlevmin –

Minimum required quality measure based on RSCP

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Cell Reselection

Serving Cell Ranking •

RSCP Ranking –

•

UE implementation same as specified in 25.304 • Rank_s = RSCP + Qhyst1

Ec/Io Ranking –

UE implementation same as specified in 25.304 • Rank_s = Ec/Io + Qhyst2

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Cell Reselection

Neighbor Cell Ranking (RSCP) •

FDD cells –

•

GSM cells –

–

•

Rank_n = RSCP – Qoffset1 • UE implementation same as specified in 25.304

Rank_n = Filtered RSSI – Qoffset1 • Filtered RSSI is running average of 4 samples • UE follows specification if serving cell S criteria meets Rank_n = Filtered RSSI – MIN( 10, Qoffset1 ) • UE deviates from specification when Serving Cell fails S criteria • Prevents UE from staying on bad 3G cell when network setting, Qoffset1, is unreasonably high

If Inter-frequency or GSM neighbors are present – –

Always perform RSCP ranking first, irrespective of measurement quantity If RSCP ranking yields FDD cell as best cell, re-rank FDD cells based on Ec/Io if measurement quantity is set to Ec/Io

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Cell Reselection

Neighbor Cell Ranking (Ec/Io) •

FDD Cells – –

Deviates from specification (Rank_n = Ec/Io – Qoffset2) Rank_n = Ec/Io – MAX( Qoffset2 + Qhyst2, Qhyst2_add ) + Qhyst2 • Qhyst2_add (additional hysteresis) based on serving cell Ec/Io if Ec/Io < -12dB • Qhyst2_add = 2 dB, = (14+Ec/Io) dB, if -12dB < Ec/Io < -10dB = 4dB,

•

if Ec/Io > -10dB

For more information: –

“Suppressing Idle Mode Re -selections based on CPICH measurements,” by Messay Amerga

–

Discusses why hysteresis is applied based on observed signal strength

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Cell Reselection

Reselection Criteria (GSM) •

When Serving Cell Meets S criteria – –

•

Rn > Rs, and Srxlev > 0, for Treselection Choose cell that meets above condition for evaluation with other cells

When Serving Cell Fails S criteria – –

Neighbor cell Srxlev > 0 for Treselection Choose cell that meets above condition for evaluation with other cells

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Cell Reselection

Reselection Criteria (FDD) •

When Serving Cell meets S criteria –

–

•

RSCP Ranking and Measurement Quantity is RSCP • Rn > Rs, and neighbor cell meets S criteria for Treselection • Choose cell that meets above condition for evaluation with other cells RSCP Ranking and Measurement Quantity is Ec/Io • Rn > Rs, and neighbor cell meets S criteria • Choose cell that meets above condition for evaluation with other cells • Treselection is incremented during Ec/Io re-ranking

When Serving Cell fails S criteria –

–

RSCP Ranking and Measurement Quantity is RSCP • Neighbor cell meets S criteria for Treselection • Choose cell that meets above condition for evaluation with other cells RSCP Ranking and Measurement Quantity is Ec/Io • Neighbor cell meets S criteria • Choose cell that meets above condition for evaluation with other cells • Treselection is incremented during Ec/Io re-ranking

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Cell Reselection

Choosing Best Cell •

RSCP Ranking and Measurement Quantity is RSCP –

•

RSCP Ranking and Measurement Quantity is Ec/Io – –

•

Choose best ranked cell from cells selected for reselection evaluation

Choose best ranked cell from cells selected for reselection evaluation If best cell is FDD cell, re-rank based on Ec/Io and choose best cell

GSM Cell – –

–

If BSIC of best cell not verified, verify BSIC If BSIC has changed, check to see if is in neighbor list • Reselect only to cells in neighbor list If above conditions fail, choose next best GSM cell to reselect

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Cell Reselection

Out Of Service •

Idle Mode –

•

FACH –

•

Serving cell fails S criteria continuously for 12s

Serving cell fails S criteria continuously for 4s

CPHY_OUT_OF_SERVICE_INDICATION sent to RRC –

RRC performs Cell Selection • If UE was in Idle Mode, enter Idle mode on new cell • If UE in CELL_FACH enter CELL_FACH on new cell –

•

RRC performs Cell Update on new cell

Deviation from specification –

–

OOS timer is not incremented when RRC is reading SIBs of neighbor cell • May cause OOS timer to expire later than 12s Reselection given priority over OOS

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Cell Reselection

Reacquisition Algorithm during DRX •

In Idle Mode, UE wakes up and reacquires serving cell

•

If Reacquisition fails – –

UE performs a modified cell reselection algorithm Treselection not taken into consideration to save time of missed pages

Wake up Perform Reacq List Search

No

Intra-f Nbrs Present?

Yes

Serving Cell Reacquired?

Search Intra-f nbrs and rank

No

Perform Normal Cell Reselection Procedure

Yes

Best nbr meet S criteria?

Yes

No

Step 1/2/3 (Full) Search on serv frequency Serv Cell Found? No Inter-f nbrs present?

Yes

Rank any intra-f nbrs found


Yes

No Yes

Perform inter-f searches

No


Yes

No

GSM nbrs present?

Yes

Perform GSM meas and rank

No

Best nbr meet S criteria? No

OOS Timer Expired? Yes

Send OOS

No

Increment OOS Timer

Go To Sleep

Yes

Reselect to Neighbor

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Cell Reselection

Cell Reselection Algorithm Has Cell Selection failed for N DRX cycles?

Determine if Active set meets cell selection

Perform Active set search

Yes

no

RRC indication No Cell reselection needed

Have measurement conditions been met?

no

yes

Use CPICH RSCP and GSM RSSI meas to compute Qmeas,n

Cell reselection indication to RRC

yes

no bc=next ranked cell

no

meas quality set to Ec/Io and multiple frequencies in Monitored list?

n=0

Are Squal,n and S rxlev,n > 0?

no Is bc serving cell?

no

no

yes

Is bc GSM cell?

Clear Tsr,n exclude n from ranked list

yes

yes

Qmeas computed using RSCP?

Increment Tsr,n

Any other neighbors?

For the Active cell compute: Rs = Q meas,s + Qhyst

bc=best cell

n++ no

no

no

Is bc serving cell?

For each searched cell, compute on : R = Qmeas,n -Qoffset n

Use CPICH Ec/Io and to compute Q meas,n

yes

yes

Tsr,BC > Treselection?

Search all scheduled intra-freq, inter-freq and inter-RAT monitored cells

rank all cells according to Rs for serving cell and Rn for neighbor cells

yes

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Cell Reselection

Full Search Timer •

Step 1/2/3 is also called Full Search – –

•

Idle Mode – – – –

•

Searches entire PN space (10ms) to get cell position Used to discover timing and energy of ASYNC cells

Done when Serving Cell and all Neighbor Cells < -16 dB Every 30s for intra-frequency and Squal < Sintrasrch Every 30s for inter-frequency and Squal < Sintersrch Done when serving cell Squal falls below Sthreshold for the first time and there are only ASYNC neighbors present

FACH –

Every 360ms

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Cell Reselection

Measurement Rules (Idle Mode) •

Measurements are started when Squal <= Sthreshold –

•

Measurements are started when S criteria fails for Nserv DRX cycles –

•

Sthreshold is Sintrasrch, Sintrasrch, and SsrchRAT,m for intra-frequency, inter-frequency and inter-RAT searches

In this case, the above measurement rule is ignored

Measurements are also started when reacquisition fails –

Treselection is also not taken into account in this case

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Cell Reselection

W2G Reselection (Idle Mode) •

When reacquisition fails –

•

Delay reselection to GSM by 2 DRX cycles

Reselect if serv cell ECIO < -20 dB or RxAGC < -95 dBm –

In Idle Mode, S criteria of serving cell must fail for 5s

•

Optimizations featurized (FEATURE_DELAY_3G_TO_2G)

•

UE can handle BSIC mismatches –

•

Reselects to cell with same ARFCN but different BSIC, if specified in SIB11

Only one cell is BSIC reconfirmed –

Spec specifies 4 cells to be reconfirmed

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Cell Reselection

Measurements in FACH •

UE always performs measurements – –

•

UE checks if Squal < Sthreshold before reselecting –

•

Makes sure we don’t reselect if Squal > Sthreshold

Intra-frequency cells measurements done every 80ms – –

•

Without regard to Sintrasrch, Sintersrch or SsearchRAT Spec compliant, since according to 25.304 • If Sx > SsearchRAT m, UE need not perform measurements on cells of RAT "m".

Can be pre-empted by FACH measurement occasions Step 1/2/3 search can stretch timing

Inter-frequency and GSM measurements are done during FACH measurement occasions – –

Inter-frequency and GSM measurements alternate RACH transmissions and Intra-frequency search can reserve FACH measurement occasions •

•

Causes UE to “lose” FACH measurement occasions

UE can detect and reselect to cells not specified in SIB11 –

Reselection parameters defaulted to use serving cell values

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Cell Reselection

Barred Cells Support •

Implementation is 25.304 Compliant

•

SIB 3 parameters (Cell Access Restriction IE) – – – –

•

Cell Barred Intraf reselection Indicator T-barred value Cell Reservation

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Cell Reselection

Barred Cell Suport in IDLE Mode •

Serving Cell Barred – – – – –

•

Trigger Immediate reselection by simulating reacq failure Ignore S-thresholds Ignore reselection timer Serving cell not considered for ranking and hence reselection is triggered if a neighbor is suitable. If no neighbor is suitable for reselection trigger OOS

Neighbor Cell Barred – – –

Measurements are not made as long as the neighbor is barred. Neighbor barred cell is excluded from reselection ranking. If the frequency is barred, all cells in the frequency not considered for measurements and reselection ranking.

• Acquistion –

Acquistions (except those for Handovers) are not allowed on barred cells.

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Cell Reselection

FACH Mode Barred

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Cell Reselection

Software Flow Chart (Idle Mode) Wake Up srchzz_prepare_for_wake_up() - restore fingers - start aset srch

srchzz_aset_srch_done() - calculate serviing cell eng

Serving Cell max_eng[0] > path_thresh?

NO

YES srchzz_declare_reacq_status_drx(TRUE, TRUE) - send reacq success status to DRX

Do DRX PICH Processing and call srchcr_start_cell_reselection_eval()

Do Aset Evaluation Check if neighbor measurements required srchcr_aset_cell_select_reselect_eval()

Perform reacquisition failure algorithm srchcr_start_nset_srch_cmd( SRCHCR_REACQ_FAIL_CR_SRCH)

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Cell Reselection

Software Flow Chart (FACH Mode) srchfach_proc_srch_ops() - Handle search heartbeat events - ASET 20ms, NSET 80ms

Aset search timer expired?

srch_fing_triage_due = TRUE

NO

YES

Any search in progress?

NO

YES srch_aset_srch_due = TRUE

YES Triage due timer expired?

NO

Perform aset search

Nset search timer expired?

srchcr_aset_srch_done() - get aset results

srchfach_next_srch_cmd() - check if step 1/2/3 due - check if triage due

YES YES srch_cell_resel_eval_due = TRUE

Any search in progress?

NO

srch_cell_resel_eval_ due = TRUE?

YES

srchcr_aset_cell_select_reselect_eval() - Perform aset eval - perform intra-f neighbor searching and evaluation

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Cell Reselection

Software Flow Chart (Idle Mode) srch_aset_cell_select_reselect_eval() -Perform aset eval

srchcr_det_neigh_srch() -Determines if nbr search needed -Intra, inter or GSM

srchcr_prepare_srched_cells() -initialise cells for search

srchcr_start_n_srch() initialise cells for search

G

NO

YES srchcr_start_intra_f_srch()

Intra search reqd?

Inter search reqd?

NO InterRAT reqd? YES NO

YES NO

NO

Is fiull search condition met()?

Need full search?

YES A

lim_put_local_cmd() -Sets nset srch done

YES B

C

D

F

E

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Cell Reselection

Software Flow Chart (Idle Mode) A

B

D

Do Step1,2 & 3 search

srchcr_start_inter_f_srch()

srchcr_nset_srch_cmd() - Pick strongest and rem cells and do list search.

srchcr_inter_f_nset_srch_cmd() -Pick strongest & rem cells and do list search

Send meas cmd to DSP

C

E

srchcr_start_gsm_srch() -GSM search

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Cell Reselection

Software Flow Chart (Idle Mode) srchcr_nset_list_srch_done() - Called when list srch results from dsp are available only for intra-f

srchcr_intra_f_post_list_srch_dump() -Cal Ecio for the rslts

srchcr_reset_proc_start_n_srch() -Process rslts, determine new search

Is intra-f srch in progress?

NO

Is Inter-f srch in progress?

YES

NO

YES

srchcr_proc_intra_f_srch() -Process rslts of intra-f

srchcr_proc_inter_f_srch() -Process rslts of inter-f

srchcr_sort_nset() - Sort the results by energy

srchcr_sort_inter_f_nset() - Sort the results by energy

srchcr_nset_intra_f_cell_reselect_eval() - Evaluate the rank of s-cell and n-cells and increment or reset Tresel accordingly

srchcr_nset_inter_f_cell_reselect_eval() - Evaluate the rank of s-cell and n-cells and increment or reset Tresel accordingly

G

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Cell Reselection

Files List File

Description

Srchcr.h

Function prototypes, data structures, and enums

Srchcr.c

Cell Reselection main implementation

Srchzz.c

Search wake up and sleep functions (Idle Mode)

Srchfach.c

Search kickoff point in FACH. FACH measurement occasion implementation

Srchcrgsm.h

Cell Reselection GSM measurements (Idle) related declarations

Srchcrgsm.c

Cell Reselection GSM measurements (Idle) related implementation. Command functions and callback functions to read results.

Srchgsmdrv.h srchgsmdrv.c

Scheduler for GSM measurements. Wrapper for GL1.

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Cell Reselection

F3 Messages •

Start Cell Reselection –

•

srchcr.c 06824 Start Cell Reselection...

Idle Mode •

Reacquisition (after DRX wake up) –

•

Reacquisition succeeds –

•

srchcr.c 07296 CR srch due Intra 1 Inter 0 GSM 1

Serving cell rank based on RSCP –

•

srchcr.c 07294 CR Start:2*squal=25,srxlev=36,sintr_int=16

Intra-f and GSM searches are due –

•

srchcr.c 07249 CR Aset Eval:freq 10689 PSC 8 tot_eng 105824

Start Cell Reselection Evaluation (conditions for measurements met) –

•

srchzz.c 01921 Reacq list search failed 4496 6464

Start Aset Evaluation –

•

srchzz.c 01662 [18399] srch rsp DRX:stat 1 (slew -2)

Reacquisition fails –

•

srchzz.c 01860 <---- Reacq: eng(105824)pos(289021)psc(8)----->

srchcr.c 07353 CR RANK:(RSCP) rank_s -53,PSC 8,2*rscp -126

Serving cell rank based on ECIO –

srchcr.c 07362 CR RANK:(ECIO) 2*rank_s -7,PSC 8,2*ecio-15

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Cell Reselection

F3 Messages •

Idle Mode (Continued) •

Cell Reselection not evaluated (conditions not met) –

•

Rank of neighbor cell based on RSCP – –

•

srchcr.c 02595 CR RANK IF:(ECIO) 2*rank_n -63,PSC 27,2*ecio-63

Rank of GSM neighbor cell (based on RSSI) –

•

srchcr.c 02519 CR RANK:(ECIO) 2*rank_n -63,PSC 27,2*ecio-63

Rank of neighbor cell based on ECIO for Inter-frequency –

•

srchcr.c 03299 FDD rerank returned NULL

Rank of neighbor cell based on ECIO –

•

srchcr.c 03273 Rerank FDD cell based on ECIO

FDD reranking did not find any best cells –

•

srchcr.c 04357 CR RANK:(RSCP) 2*RSCP -168,PSC 27,qoff1 0 srchcr.c 04360 CR RANK:(RSCP) rank_n -84,2*sq_n -63,srxlv_n -84

Rerank FDD cells based on ECIO –

•

srchcr.c 07383 CR not eval:2*squal=21,Nserv=0,sintr_int=10

srchcr.c 06346 GSM rank -72, s_rxlev_n 43 arfcn 13

TmeasureGSM expired –

srchcr.c 05943 CR:TmeasGSM xpired, sinterrat 20

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Cell Reselection

F3 Messages •

Idle Mode (continued) •

Treselection started on neighbor cell – –

•

Treselection reset on neighbor cell – –

•

–

srchcr.c 06490 Start BSIC identification

End of GSM BSIC Identification –

•

srchcr.c 03400 No best cell found srchcr.c 09179 Did not find suitable ncell to reselect

Start GSM Cell BSIC Identification –

•

srchcr.c 06100 CR EVAL nbr searching done

No best cell found during this evaluation –

•

srchcr.c 04427 CR:Inc Tresel on PSC=8 t=256 frames Tresel=5

Cell Reselection Evaluation done –

•

srchcr.c 02571 CR:Reset Tresel on PSC 27 srchcr.c 06398 CR:Reset Tresel on ARFCN 90

Treselection Incremented on neighbor cell –

•

srchcr.c 04407 CR:Start Tresel on PSC 9 srchcr.c 06366 CR:Start Tresel on ARFCN 13

srchcrgsm.c 00620 GSM ACQ clnp done:cur_gfn=45

Cell Reselection Indication – –

srchcr.c 09069 CEL RESEL IND:GSM BSIC ncc0 bcc 0 ARFCN 13 srchcr.c 08999 CEL RESEL IND:Fr 10689 psc 9

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Cell Reselection

F3 Messages •

FACH •

Serving cell evaluation started – –

•

CRNTI is valid for FACH Measurement Occasions –

•

srchfach.c 03556 FACH meas oksn SW due at 1520 for Inter-freq to meas at 1521

FACH inter-frequency measurement (step 1) –

•

srchfach.c 02753 FACH meas oksn: Ntti 1, M_REP 16, C_RNTI 1

FACH inter-frequency measurement due –

•

rrcllcoc.c 09264 Valid C-RNTI in CC

FACH Measurement Occasion parameters –

•

srchcr.c 07249 CR Aset Eval:freq 10689 PSC 8 tot_eng 110976 srchcr.c 07294 CR Start:2*squal=25,srxlev=41,sintr_int=16

srchcmmeas.c 01999 Starting interF 10830 step1

FACH inter-frequency results (step 1) – – –

srchcmdrv.c 00930 SRCHCM:Step1 peak 0 egy 48932 pos 1160 srchcmmeas.c 02697 Step1Done #Peak 13 NoCell 13 RSSI -69 dBm srchcmmeas.c 01490 Selecting PSCpeak 0 posCx8 1160 egy 48932

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Cell Reselection

F3 Messages •

FACH (continued) •

FACH inter-frequency measurements (list search) –

•

FACH inter-frequency measurements (reconfirmation) – –

•

srchcrgsm.c 02868 FACH GSM meas proceed with RSSI

FACH GSM BSIC Identification –

•

srchfach.c 03545 FACH meas oksn SW due at 1534 for GSM to meas at 1537

FACH GSM RSSI measurement –

•

srchcmmeas.c 02155 Starting ReconfListSrch srchcmmeas.c 03272 Cell->DETECTED SCR 144 posCx8 83080 egy 66768

FACH GSM measurement due –

•

srchcmmeas.c 02124 Starting PSCACQlistSrch F 10830 SCR 144

srchcrgsm.c 03468 FACH GSM meas proceed with BSIC Id

FACH GSM BSIC verified or not –

srchcr.c 10882 BSIC verified?: 0

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Cell Reselection

F3 Messages •

FACH (continued) •

FACH GSM rank –

•

FACH inter-frequency rank based on RSCP – –

•

srchcr.c 10878 FACH GSM rank -110, s_rxlev_n -9 arfcn 90 srchcr.c 02905 CR RANK:(RSCP) 2*RSCP -156,PSC 9,qoff1 0 srchcr.c 02908 CR RANK:(RSCP) rank_n -78,2*sq_n 21,srxlv_n 21

FACH inter-frequency rank based on ECIO – –

srchcr.c 02505 CR RANK:(ECIO) 2*rank_s -6,PSC 8,2*ecio-14 srchcr.c 02595 CR RANK IF:(ECIO) 2*rank_n -19,PSC 9,2*ecio-19

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F3 MESSAGES •

Step1 Peak Elimination •

Eliminates same Step1 Peaks from Step1 srch result and (ASET or NSET) cells – –

•

Sorting – Intra frequency •

Number of sorted intra frequency cells –

•

srchcr.c 09311 Sorted 2 cells

Interfreq messages •

Cell reselection not evaluated – reason : CR not enabled or inter-f cells not present –

•

•

srchcr.c Inter-f Nset not evaled

Cell reselection evaluated –

srchcr.c Inter-f NSET eval for cell resel

When sorting entire Inter-f set – –

l

srchcr.c 1661 Stp1 cnt: before Elimination 25 srchcr.c 1679 Stp1 cnt: after Elimination 20

srchcr.c Sorting Inter-freq NSET cnt= srchcr.c Sorting Inter-f NSET

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Cell Reselection

F3 MESSAGES •

Inter-f messages continued •

If any sorted cells have 0 energy, they are indicated via this message – –

•

srchcr.c Netwk sync nbr fr not found srchcr.c Sorted cells freq f_idx

Cell reselection indications •

Found better cell than the present serving cell –

•

Reselection indication given to RRC with the Freq and PSC value – –

•

srchcr.c Found next best ranked cell srchcr.c CEL RESEL IND:Fr psc srchcr.c CEL RESEL IND:GSM BSIC =2,3 ARFCN 12

Reselection indication given for a GSM cell with ARFCN and ncc & bcc –

srchcr.c Did not find next best GSM cell

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4/13/2011

Cell Reselection

F3 MESSAGES •

Neigbhour searches evaluations •

To do full inter-f search with sync and async cells –

•

In FACH mode – if aset or all sync neigbhours have less than -16dB or no nbrs –

•

srchcr.c Do inter-f full srch sync async srchcr.c Full Srch tmr exp, do Full Srch

In Idle mode – if aset or all sync neigbhours have less than -16dB or no nbrs –

srchcr.c Cells weak, do step 1/2/3

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4/13/2011

Cell Reselection

F3 MESSAGES •

GSM –

•

search for BSIC id aborted due to cell being weak –

•

srchcr.c Sorting GSM nset cells srchcr.c ARFCN %d too weak for BSIC id

Wait for timer expiry before GSM timing is slammed after waking up –

srchcr.c waiting for GSM time ready

–

srchcr.c No GSM nbr cells srchcr.c Pending resel: No GSM search srchcr.c No GSM neighbors to search srchcr.c CR:TmeasGSM xpired, sinterrat srchcr.c BSIC verif tmr xpired, sinterrat srchcr.c aset srch going on. Not making it inactive srchcr.c CR Res for ARFCN srchcr.c GSM PScan: idx= burst= rssi/16=

– – – – – – –

40


4/13/2011

Cell Reselection

F3 MESSAGES

•

Rudimentary messages – – – –

srchcr.c sync nset async nset uset srchcr.c Start Cell Reselection... srchcr.c Cell trans in prog, no cell resel eval srchcr.c Inc num drx= last gsm srch=

Cell Reselection

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