04 3G RPLS2_RU10_Cell Selection and Reselection

1 © Nokia Siemens Networks 3G RPLS / AA / 10/2008I insert classification level

Cell Selection and Reselection

3GRPLS (RN3155) – Section 4

6 © Nokia Siemens Networks 3G RPLS / AA / 10/2008 Soc Classification level

CM requestsNAS controlradio

measurements

PLMNselected

PLMNavailable

registrationarea changes

locationregistration

response

indicationto user

manual mode

locationregistration

cell selectionand reselection

PLMN selectionand reselection

automatic mode

RRC tasks:

• PLMN selection & reselection;

• Cell selection & reselection;

• Location registration LR.

if the UE is in the RRC idle mode

if the UE is in the RRC connected modestates:• CELL_FACH,• CELL_PCH &• URA_PCH

Cell Selection and Reselection: Motivation

TS 25.304:Idle mode task

subdivided into 3 processes:


PLMN search

Search PLMNs

UTRA:

If RSCP > -95 dBm

GSM:

If RSSI > -85 dBm

High qualityPLMNs

Other foundPLMNs

PLMN IdPLMN Id+ RSCP/RSSI

UE AS

UE NAS

TS 25.304 & TS 43.022


Operator controlled PLMN list

User controlled PLMN list

Last registered PLMN

Home PLMN

Other high quality PLMN‘s in random

order

Switch onin automatic PLMN selection operation mode

HPLMN Search Period Timer6 .. 480 minutesDefault: 60 minutes

PLMN Selection

Other PLMN‘s in decreasing signal

quality order


Cell- acceptable (limited services*)- suitable (full service set)- barred- reserved#

Access Class barred:(UE access classes 0..9 and 11..15)

BCCH SIB3/4: Cell Access Restriction

Cell status and special reservations

* e.g. Emergency Call (Access Class = 10) in Network w/o Roaming Agreement# e.g. for operator use

Cell status &special reservations: Access Control


Cell Barred Cell reservedfor operator

Cell reservedfor future extension

Case

1

2

3

4

not barred

not barred

not barred

barred

not reserved not reserved

not reserved reserved

reserved ---

--- ---

suitable for selection and reselection

suitable for AC 11 or 15 in HPLMN otherwise “barred”

Cell “barred”

Not suitable – not even for emergency call

Cell status and special reservations


UE RRC idle

I ignore all Access Class related cell

access restrictions when selecting a cell

to camp on

UE RRC connected

Access Class only relevant for access

(from RRC IDLE)

Access Class irrelevantfor access

suitable cell

suitable cell

Access Control

Access Control normallyused for load reasons:

Overload Control feature


• WCEL: CellBarred•Defines whether the cell is barred or not. •A barred cell is a cell where a UE is not allowed to camp on. •This parameter is part of SIB 3.•0 (Barred), 1 (Not barred); default: 1.

• WCEL: TBarred•If the UE does not select another cell, and the barred cell remains to be the “best” one, the UE shall after expiry of the time interval Tbarred again check whether the status of the barred cell has changed.•This parameter is part of SIB 3.•[10, 20, 40, 80, 160, 320, 640, and 1280] seconds; default: 40 seconds.

• WCEL: Cell_Reserved•Defines whether the cell is reserved for operator use. •This parameter is part of SIB 3.•0 (Reserved), 1 (Not reserved); default: 1.

• WCEL: IntraFreq_Cell_Reselect_Ind•Defines whether intra-frequency cell re-selection is allowed when the cell is barred.•This parameter is part of SIB 3/4.•0 (Allowed), 1 (Not allowed); default: 0.

NSN Parameters for Cell Reservations and Restrictions


Cell Selection Process

NAS controls

AS controlscorrespondentprocedures

NAS:

PLMNselection

• RAT(s) information associated with the selected PLMN• forbidden registration areas• list of equivalent PLMNs

UE CN

AS:attempts to find suitable cells

States and State Transition in the RRC Idle Mode

suitablecell

found

campednormally

campedon any cell

all networkservices available

limited servicese.g. Emergency Call

YES

NO

acceptable cell


1

Initial Cell Selection

Camped normally

Cell Reselection Evaluation

Process

no cell information stored for the PLMN

cell information stored for the PLMN

go here whenever a new PLMN is selected

no suitable cell found

suitable cell found suitable cell found

Connected Mode

suitable cell found


no suitable

cell found

Stored Information

Cell Selection

trigger

suitable cell selected


Cell Selection when leaving

connected mode

leave idle mode

return to idle mode

NAS registration

rejected

(adopted from TS 25.304)



Camped on Any Cell

Any Cell Selection

Connected Mode

(Emergency calls only)

return to idle mode

go here when no USIM in the UE

USIM inserted 1

leave idle mode

no acceptable cell found

an acceptable cell found

Cell Selection when leaving

connected mode

acceptable cell found

suitable cell found 1

Cell Reselection Evaluation

Process

trigger

acceptable cell selected

no acceptable cell found

(adopted from TS 25.304)



Qqualmeas (dB)(CPICH Ec/N0)

Qrxlevmeas (dBm)CPICH RSCP

Qrxlevmin

Srxlev > 0

Pcompensation

Squal > 0S-Criterion

fulfilledSqual >0 AND

Srxlev > 0

suitable

cell?

Cell Selection Criterion S (in the FDD mode)

Squal =CPICH Ec/No – QqualMin

Srxlev =Qrxlevmeas – Qrxlevmin– Pcompensation

QqualMin:-24...0; def.: -18 dB

SIB 11/12

AdjsQrxlevmin:-115...-25; def.:-115 dB

SIB 11/12


Cell Selection Criterion S

Pcompensation= max(UE_TXPWR_MAX_RACH – P_MAX, 0)

Cell size defining parameters:• Qrxlevmin• Qqualmin

I am outsid

e

I am inside, but have not

enough power

-50 .. 33 dBm

UEtxPowerMaxPRACH-50..33 dBm; 21 dBm

SIB3/4

AdjsQrxlevmin:-115...-25; def.: -115 dB

Srxlev = Qrxlevmeas – Qrxlevmin– Pcompensation


Initial Cell Selection(scan RF channel)

Stored Information Cell Selection

carrier, even Scr.Code may be stored in UE

or

I have to find a suitable

cell

Squal = Qqualmeas – Qqualmin > 0Srxlev = Qrxlevmeas – Qrxlevmin – Pcompensation > 0

Once a suitable cell is found this cell is selected

(Initial) Cell Selection Process


• Active Set cells as candidates for cell selections; if not suitable, then

• Stored information cell selection Squal > 0Srxlev > 0

Cell Selection When Leaving the RRC Connected Mode


• WCEL: QrxlevMin •The minimum required RX level in the cell. •This parameter is part of SIB 3.•[-119 ... –25] dBm, step 2 dBm; default: -115 dBm.

• WCEL: QqualMin•The minimum required quality level in the cell (Ec/No). •This parameter is part of SIB 3.•[-24 ... 0] dB, step 1 dB, default: -18 dB.

• WCEL: UEtxPowerMaxPRACH•This parameter defines the maximum transmission power level a UE can use on PRACH. •The value of the parameter also effects the cell selection and reselection procedures. •The value of the parameter is sent to UE in the Cell selection and re-selection of SIB 3 and 4 of the serving cell.[..]

NSN Parameters for Cell Selection


S-Criterionfulfilled

cells with highest HCSPriorities &H > 0

measurementthresholds

cells with lower HCS

priority than in serving cell

If No Cellwith H>0accept allneighbours

HCS in use: HCS not in use:



H-Criterionfor fast

moving UEsfor slow

moving UEs

R-Criterioncell ranking



Cell Reselection in the RRC Idle and RRC Connected Mode


Hierarchical Cell Structures

3

3

3

33

3

1

2

2

2

Normally, different layers are created using different frequencies

Priority


Cell reselection without HCS

• Normal re-selection process (without HCS) follows simplified procedure

• Measurement criteria without HCS

• S-criteria

• R-criteria

Without HCS


Cell reselection without HCS

Measuredneighbours

Neighbour listfrom BCCH

Best ranked cell

Measurement criteria

S – criteriaSuitable

neighbours

R – criteria

Re-selection if not serving cell

Without HCS


SintrasearchSintersearchSsearchRAT m

No need to measure

neighbour cells

Intra- frequency

Sx=Squal (in FDD mode)

Intra-frequencyInter-frequency

serving cell

Example: NSN Qqualmin = -18 dB, Sintrasearch = 10dB, Sintersearch = 8dB,Ssearch_RAT = 4dB

When to perform measurements

Intra-frequency

Inter-freqencyInter-RAT

Cell Reselection: Measurement RulesWithout HCS

-8 dB-10 dB-14 dBEC/N0 =

SinterSearch:0...20; def.: 8 dB

SintraSearch:0...20; def.: 10 dB

Ssearch_RAT:0...20; def.: 4 dB


Squal =CPICH Ec/No

-qQualMin


Rs = Qmeas,s + Qhysts

Rn = Qmeas,n - Qoffsets,n

Qmeas,n

Qmeas,s

Qm

eas

Rs

Rn

Qoffsets,n

Qhysts

Rn > Rs =>“cell reselection“

Treselection

Cell Reselection: R-CriterionWithout HCS

Qmeas = Ec/No or RSCPEc/No Qhyst2 /RSCP Qhyst1Rs / Rn: Serving / Neighbouring cell value

Qhyst20.. 40; def.: 2 dB

AdjisQoffset2-50.. 50; def.: 0 dB

FDD cells & Ec/No:2nd Ranking

Adjg,s,iQoffset1-50.. 50; def.: 0 dBQhyst1

0.. 40; def.: 0 dB

WCDMA & GSM cells; RxLev:

1st Ranking


• WCEL: UseOfHCS•This parameter indicates whether the serving cell belongs to a Hierarchical Cell Structure (HCS). •This parameter is part of SIB 11/12.•0 (HCS not used), 1 (HCS in use); default: 0.

• WCEL: Sintrasearch•The threshold for intra-frequency measurements, and for the HCS measurement rules.•This parameter is part of SIB 3.•[0 ... 20] dB, step 2 dB, default: 10 dB.

• WCEL: Sintersearch•The threshold for inter-frequency measurements, and for the HCS measurement rules.•This parameter is part of SIB 3.•[0 ... 20] dB, step 2 dB, default: 8 dB.

• WCEL: Ssearch_RAT•The RAT-specific threshold for inter-RAT measurement rules. •This parameter is part of SIB 3.•[0 ... 20] dB, step 2 dB, default: 4 dB.

NSN Parameters for Cell Reselection (Part I)


Cell reselection with HCS

• Normal re-selection process (without HCS) follows procedure

• Measurement criteria without HCS

• S-criteria

• H-criteria

• R-criteria

• HCS specific H-criteria defines whether priorities are applied in re-selection

With HCS


Cell reselection with HCS

Measuredneighbours

Neighbour listfrom BCCH

Best ranked cell

Measurement criteriawith HCS

S – criteria

Neighboursto rank

R – criteria

Re-selection if not serving cell

With HCS

Suitableneighbours

H – criteria

Prioritizedneighbours

UseOfHCS0 (not used), 1 (used)

SIB 11/12

HCS_PRIO0 (lowest) ..

7(highest); step: 1SIB 11/12


Higher HCS priority



Equal &higher HCS

priorityIntra-

frequencyInter-

frequency

Example: NSN Sintrasearch = 10 dB, Sintersearch = 8 dB,Ssearch_RAT = 4 dB,SsearchHCS = -1 dB

Cell Reselection: Measurement RulesWith HCS

SintrasearchSintersearchSsearchRAT mSlimitsearchRAT m

Sx=Squal (in FDD mode)if Srxlevs > SsearchHCS

BCCH SI: HCS is used

-8 dB-10 dB-14 dBEC/N0 =

Srxlevs ≤ SsearchHCSif SsearchHCS

-1..91; def.: -1 dB*SIB3

AdjsQrxlevmin:-115...-25; def.: -115 dB

SIB 11/12

Srxlev =Qrxlevmeas – Qrxlevmin

-115 dBmRSCP =

*negative values are set to 0 by UE

Srxlevs ≤ SsearchHCS OR Squal ≤ Sintersearch

Squal =CPICH Ec/No

- QqualMin


SIB 11/12


Example: NSN Sintrasearch = 10 dB, Sintersearch = 8 dB,Ssearch_RAT = 4 dB, Slimit, searchRAT = 2 dB SsearchHCS = -1dB, SHCS_RAT = -1dB

Cell Reselection: Measurement RulesWith HCS

or

SintrasearchSintersearchSsearchRAT m

Higher HCS priority


SlimitsearchRAT m


Intra-frequency

Inter-freqencyInter-RAT

Intra-frequency,

Inter-frequency, &

Equal and higher HCS priority inter

RAT

Equal &higher HCS

priorityIntra-

frequencyInter-

frequency

Sx=Squal (in FDD mode)

if Srxlevs ≤ SHCS,RATm measure on allInter-RAT cells

if Srxlevs > SHCS,RATm

HCS; Inter-RAT measurements?

-14 dBEC/N0 =

Slimit,SearchRAT0..20; def.: 2 dB

SIB3

-16 dB

SHCS_RAT-1..91; def.:-1 dB*

SIB3

AdjsQrxlevmin:-115...-25; def:. -115 dB

SIB 11/12

Srxlev =Qrxlevmeas – Qrxlevmin

-115 dBmRSCP ≤

*negative values are set to 0 by UE


• WCEL: SHCS_RAT•The RAT specific threshold for inter-RAT measurement rules. •This parameter is part of SIB 3.•[-1 ... 91] dB, step 2 dB, default: -1 dB (UE sets this value to 0).

• WCEL: Slimit_SearchRAT•Threshold for skipping inter-RAT measurement rules in HCS. •Above this RAT specific threshold in the serving UTRA cell, the UE does not need to perform any inter-RATm measurements. •This parameter is part of SIB 3.•[0 ... 20] dB, step 2 dB, default: 2 dB.

• WCEL: SsearchHCS•Threshold for intra- and inter-frequency measurement rules in HCS. •Below this limit in the serving cell, the UE initiates measurements of all intra and inter-frequency neighbouring cells of the serving cell. •This parameter is part of SIB 3.•[-1 ... 91] dB, step 2 dB, default: -1 dB (UE sets this value to 0).

NSN Parameters for Cell Reselection (Part II)


Measurement Rules with HCS and fast moving UEsWith HCS

NCR = cell reselections threshold (default: 8)TCRmax = time period

NCR/TCRmax

fast moving UE

time

TCrmaxHyst

measurement rule for fast moving UEs

measures neighbouring cells with equal or lower HCS priority

priorizes cells with lower HCS priority for re-selection

Example: NSN NCr: 1..16; def.: 8; SIB3TCrmax: not used, 30, 60, 120, 180, 240 s; def.: 60s; SIB3TCrmaxhyst: not used; 10..70; 10; SIB3

measurement rules forslow moving UEs

measurement rules forslow moving UEs


• WCEL: NCr•This parameter defines the maximum number of cell reselections.•If the number of cell reselections during the TCrmax time period exceeds the value of NCr, high mobility has been detected. •Not used if TCrmax equals 'not used’.•This parameter is part of SIB 3.•[1 ... 16], default: 8.

• WCEL: TCrmax•The duration for evaluating the allowed amount of cell reselections. •If the number of cell reselections during the time period defined by Tcrmax exceeds Ncr, high mobility has been detected. •This parameter is part of SIB 3.•[0 (= not used), 30, 60, 120, 180, 240] seconds, default: 60 seconds.

• WCEL: TCrmaxHyst•Cell reselection hysteresis for reverting from UE high-mobility measurements.•The additional time period before UE reverts to low-mobility measurements.•This parameter is part of SIB 3.•[0 (= not used), 10, 20, 30, 40, 50, 60, 70] seconds, default: 0 seconds.

NSN Parameters for Cell Reselection (Part III)


Cell Reselection: H-Criterion (slow moving UE)With HCS

HCS is in use:Candidates

for cell re-selection? H-Criterion !


only cells with

highest HCSpriorities &

H > 0


cells with lower HCS

priority than in serving cell

H-Criterionfor fast

moving UEsfor slow

moving UEs

R-Criterioncell ranking R-Criterion

cell ranking

Hs = Qmeas,s – Qhcss

Hn = Qmeas,n - Qhcsn – TOn * Ln

accept allNeighbours*

cells withH>0


no cells withH>0

Qhcs#: -24..0; def.: -24 dB

* id. to HCS not in use

TOn: temporary Offset during Penalty Time;3, 6, 9, 12, 15, 18, 21, 100 dB; Infinity; def: 3

#AdjgHCSthreshold:-110..-37; def.: -110 dB


Cell Reselection: H-Criterion (slow moving UE) and TOn

Qmeas,n - Qhcsn

0time

TOnTOn

PENALTY_TIMEn PENALTY_TIMEn

TOn = 0 TOn = 0

StartTn

StartTn

StopTn

Hs = Qmeas,s – Qhcss

Hn = Qmeas,n - Qhcsn – TOn * Ln

Example:HCS_PRIOn <> HCS_PRIOs

=> Ln = 1

TOn = TEMP_OFFSETn * W(PENALTY_TIMEn – Tn)

temp. offset used only when neighbour has different priority thanserving cell

TOn: temporary Offset during Penalty Time;Adji/g/sTempOffset1

3, 6, 9, 12, 15, 18, 21, 100 dB; Infinity

Ln = 0, if HCS_Prion = HCS_Prios

= 1, if HCS_Prion ≠ HCS_Prios

Penalty_Timen : 0..60; def.: 0s

H-Criterion:H>0


• WCEL: HCS_PRIO•This parameter defines the HCS priority level for a cell. •Value 0 indicates the lowest HCS priority and value 7 indicates the highest HCS priority.•[0 ... 7], default: 0.

• WCEL: QHCS•Quality threshold level for applying prioritised hierarchical cell re-selection for a cell. •Part of HCS Serving cell information (Qhcss). •This parameter is part of SIB 3. •[-24 ... 0] dB, step 0.5 dB, default: -24 dB.

• HOPS: AdjsHCSthreshold•Defines the threshold level which must be exceeded by the CPICH Ec/No of the intra-frequency neighbouring cell before the hierarchical cell re-selection becomes possible (Qhcsn).•[-24 ... 0] dB, step 0.5 dB, default: -24 dB.

• HOPI: AdjiHCSthreshold: •[-24 ... 0] dB, step 0.5 dB, default: -24 dB.

• HOPG: AdjgHCSthreshold: •[-110 ... -37] dBm, step 1 dBm, default: -110 dBm.

NSN Parameters for Cell Reselection (Part IV)


• HOPS: AdjsTempOffset1•This parameter is used in the cell ranking between cells when the intra-frequency neighbour cell has the same HCS priority level as the serving cell. •[3, 6, 9, 12, 15, 18, 21, 100 (Infinity)] dB, default: 3 dB. •HOPI: AdjiTempOffset1, •HOPG: AdjgTempOffset1

• HOPS: AdjsTempOffset2•This parameter is used in the cell ranking between WCDMA cells when the intra-frequency neighbour cell has the same HCS priority level as the serving cell. •[2, 3, 4, 6, 8, 10, 12, 100 (Infinity)] dB, default: 2 dB. •HOPI: AdjiTempOffset2

• HOPS: AdjsPenaltyTime•Defines the time period during which the Temporary Offset 1/2 is applied in the cell re-selection procedure for the intra-frequency neighbour cell in question.•[0 ... 60] seconds, step 10 seconds, default: 0.•HOPI: AdjiPenaltyTime, •HOPG: AdjgPenaltyTime

NSN Parameters for Cell Reselection (Part IV)


Qmeas,n – Qoffsets,n

PENALTY_TIMEn PENALTY_TIMEn

TOn = 0 TOn=0

StartTn

StartTn

StopTn


Rn = Qmeas,n - Qoffsets,n - TOn * (1 – Ls)

Example:HCS_PRIOn = HCS_PRIOs

=> Ln = 0 TOn = TEMP_OFFSETn * W(PENALTY_TIMEn – Tn)

Qmeas,s

temp. offset used only when neighbour has same priority thanserving cell

TOn

TOn

Cell Reselection: R-Criterion and TOnWith HCS


Cell Reselection: R-CriterionWith HCS


Rn = Qmeas,n - Qoffsets,n - TOn * (1 – Ls)

Qmeas,n

Qmeas,s

Qm

eas

Rs

Rn

Qoffsets,n

Qhysts

Example: HCS_PRIOn <> HCS_PRIOs => Ln = 1

Treselection: 0..31; default: 2s

Adjg,s,iQoffset-50.. 50; def.: 0 dB

Qhyst10.. 40; def.: 0 dB

Qhyst20.. 40; def.: 2 dBAdji&sQoffset2

-50.. 50; def.: 0 dBFDD cells & Ec/No:

2nd Ranking

WCDMA &GSM; RxLev:1st Ranking

Rn > Rs => “cell reselection“


• WCEL: Qhyst1 (Qhyst2) • Qhyst1 is used for TDD and GSM cells, and for FDD cells when cell selection and re-

selection quality measure is set to CPICH RSCP (CPICH Ec/No) (Qhyst1s/ Qhyst2s). • This parameter is part of SIB 3.• [0 ... 40] dB, step 2 dB, default: Qhyst1 = 0 dB, Qhyst2 = 2 dB.

• HOPS: AdjsQoffset1 (AdjsQoffset2) • This parameter is used in the cell re-selection and ranking between WCDMA cells. • The value of this parameter is subtracted from the measured CPICH RSCP (CPICH Ec/No)

of the intra-frequency neighbour cell before the UE compares the quality measure with the cell re-selection/ranking criteria.

• [-50 ... 50] dB, default: 0 dB. • HOPS: AdjsQoffset1 (AdjsQoffset2), HOPG: AdjgQoffset1

• WCELL: Treselection• The UE triggers the reselection of a new cell if the cell reselection criteria are fulfilled during

the time interval Treselection.• This parameter is part of SIB 3.• [0 ... 31] seconds, default: 2 seconds.

• The remaining parameters were already specified under NSN Parameters for Cell Reselection (Part IV).

NSN Parameters for Cell Reselection (Part V)


DRXcycle

Nserv

S

S

S S

start measurement on all neighbouring cells

12 seconds

if still no suitable cells

UE initiates cell selection procedures for the

selected PLMN

UE “out of service area”At least one• CPICH Ec/Io

measurement• CPICH RSCP

measurement• S criterion evaluation

DRX cycle

if UE RRC idle

if UE in CELL_FACH, CELL_PCH or URA_PCH

Cell Reselection: Measurement Requirements – Serving Cell


At least one• CPICH Ec/Io measurement, or

CPICH RSCP measurement

TmeasureFDD cycle

3 dB

Serving cellIntra-frequency cell

time

UE is capable of evaluating that an intra-frequencycell has become better ranked (if Treselection = 0)

within TevaluateFDD

Cell Reselection: Measurement – Intra-frequency Cells


At least one• CPICH Ec/Io measurement or

CPICH RSCP measurement

(Ncarrier-1) * TmeasureFDD cycle

3 dB for CPICH Ec/Io 5 dB for CPICH RSCP

Serving cellInter-frequency cell

time

UE is capable of evaluating that an inter-frequencycell has become better ranked (if Treselection = 0)

within (Ncarrier -1) * TmeasureFDD

Cell Reselection: Measurement– Inter-frequency Cells


DRX cyclelength [s]

Nserv [number ofDRX cycles]

TmeasureFDD [s](number of

DRX cycles)

TevaluateFDD [s](number of

DRX cycles)

TmeasureGSM [s](number of

DRX cycles)0.08 4 0.64 (8 DRX cycles) 2.56 (32 DRX cycl) 2.56 (32 DRX cycl)

0.16 4 0.64 (4) 2.56 (16) 2.56 (16)

0.32 4 1.28 (4) 5.12 (16) 5.12 (16)

0.64 4 1.28 (2) 5.12 (8) 5.12 (8)

1.28 2 1.28 (1) 6.4 (5) 6.4 (5)

2.56 2 2.56 (1) 7.68 (3) 7.68 (3)

5.12 1 5.12 (1) 10.24 (2) 10.24 (2)

In idle mode, UE supports DRX cycles lengths 0.64, 1.28, 2.56 and 5.12 s

Each GSM neighbour• GSM BCCH carrier RSSI

TmeasureGSM

BSIC at least every 30 seconds for each of the 4 strongest GSM BCCH carriers

30 seconds

+

(DRX cycle length table source: TS 25.133 V3.11.0 chap. 4.2.2.1)

Cell Reselection: Measurement Requirements + GSM Cells


50 ms

50 ms

50 ms

TSI

TBCCH

intra-frequency

inter-frequency

inter-RAT

Cell Reselection: Maximum Interruption in Paging Reception

Documents

04 3G RPLS2_RU10_Cell Selection and Reselection