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Cell selection & Reselection

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Cell Selection

Procedure

A : Camped normallyB : Any cell selectionC : Camped on any cellD : Connected mode

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The cell selection criterion S is fulfilledwhen: S rxlev > 0 and S qual > 0,

Where:

S qual = Q qualmeas - Q qualmin S rxlev = Q rxlevmeas - Q rxlevmin - P compensation

Cell Selection Criteria (Criteria S)

Parameter Description

S qual Cell selection quality value (dB) Applicable only to FDD cells

S rxlev Cell selection RX level value (dB)

Qqualmeas Measured cell quality valueQuality of the received signal indicated in average CPICH Ec/No (dB) for FDD cells

Applicable only to FDD cells

Q rxlevmeas Measured cell Rx level valueCPICH RSCP of received signal for FDD cells (dBm).P-CCPCH RSCP of received signal for TDD cells (dBm)

Qqualmin Qqualmin , required minimum quality levelQ rxlevmin Qrxlevmin , required minimum RX level

P compensation

Max ( MaxAl lowedUlTxPower -MaxUEPower, 0) (dB)where,l MaxAl lowedUlTxPower , maximum allowed UE UL TX power.l MaxUEPower: maximum RF output power of the UE (dBm)MaxAl lowedUlTxPower is set by the network according to the designed cell coverage.When the maximum UE power is lower than the value, the effective cell coverage for this UEis actually reduced by P compensation .

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Cell Selection Criteria (Criteria S) The cell selection criterion S is fulfilled

when: S rxlev > 0 and S qual > 0,Where:

S qual = Q qualmeas - Q qualmin S rxlev = Q rxlevmeas - Q rxlevmin - P compensation

Parameter ID Parameter Name Default Value GUI Value Range Actual Value Range Unit

QqualminMin quality level -18 -24~0 -24~0 dB

Qrxlevmin Min Rx level -58 (-115 dB) -58~-13 -115~-25 2 dB

MaxAllowedUlTxPower Max allowed UE UL TX power 24 -50~33 -50~33 dBm

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• Criterion H• Criterion R

• S Criteria

Cell Reselection Process

Cell Reselection

• Measurement Start Criteria with HCS Disabled• Measurement Start Criteria for Slow UE in HCS• Measurement Start Criteria for Fast UE in HCS

Measurement Start Criteria

Cell Reselection Criteria

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Cell Reselection Process

3. UE selects a suitable cell to camp

The cells are queued according to the measurement results,Suitable cell is select by reselection criteria

2. UE decides intra-frequency, inter-frequency or inter-RAT

start the intra-frequency, inter-frequency or inter-RAT measurementaccording to the Sx and Movement State

1. The UE calculates the serving cell S X

S qual = Q qualmeas - Q qualmin S rxlev = Q rxlevmeas - Q rxlevmin – P compensation

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Measurement Start CriteriaMeasurement Start Criteria with HCS DisabledIn tra-f requency m easurem ent

S qual = Q qualmeas - Q qualmin

If S qual > S in t rasearch or Q qualmeas > S in t rasearch + Q qua lminthe UE does not need to start the intra-frequency measurement.

If S qual

≤ S in t rasearch

or Q qualmeas

≤ S in t rasearch +

Q qua lmin

the UE needs to start the intra-frequency measurement.

If system messages do not contain S intrasearch ,the UE always needs to start the intra-frequencymeasurement.

S in t rasearch is set through IdleSintrasearch or ConnSintrasearch on the RNC side .

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Measurement Start CriteriaMeasurement Start Criteria with HCS DisabledIn ter-f requency m easurem ent

S qual = Q qualmeas - Q qualmin

If S qual > S intersearch or Q qualmeas > S intersearch + Q qualmin

the UE does not need to start the inter-frequency measurement.

If S qual ≤ S intersearch or Q qualmeas ≤ S intersearch + Q qualmin

the UE needs to start the inter-frequency measurement.

If system messages do not contain S intersearch ,the UE always needs to start the inter-frequencymeasurement.

S in tersearch is set through IdleSintersearch or ConnSin tersearch on the RNC side.

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Measurement Start CriteriaMeasurement Start Criteria with HCS DisabledInter-RAT m easurem ent

S qual = Q qualmeas - Q qualmin

If S qual > S searchRATm or Q qualmeas > S searchRATm + Q qualmin

the UE does not need to start the inter-RAT measurement.

If S qual ≤ S searchRATm or Q qualmeas ≤ S searchRATm + Q qualmin

the UE needs to start the inter-RAT measurement.

If system messages do not contain S searchRATm ,the UE always needs to start the inter-RATmeasurement.

S searchRATm is set through SsearchRat on the RNC side.

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Measurement start criteria for cell reselection with HCS disabled

Parameter ID Parameter Name Default Value GUI Value Range Actual Value Range Unit IdleSintrasearch Intra-freq cell reselection threshold for idle mode 5 (10 dB) -16~10;127 -32~20, 127 2 dBIdleSintersearch Inter-freq cell reselection threshold for idle mode 4 (8 dB) -16~10;127 -32~20, 127 2 dB

SsearchRat Inter-RAT cell reselection threshold 2 (4dB) -16~10;127 -32~20, 127 2 dB

-8 dB -10 dB -14 dB -18 dB

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Measurement start criteria for cell reselection with HCS disabled

Measurement Start Criteria with HCS Disabled

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Measurement Start Criteria with HCS EnabledUE Speed Estimation

The criteria with HCS enabled needs to consider the UE speed.

When the UE is in the s low m ovement s ta teIf # cell reselection within a period TCRmax > CRMaxNum , or the RNC

notify that UE is in fast movement, the UE is in the fast movement state.

When the UE is in the fas t mo vementIf # cell reselection within a period TCRmax < CRMaxNum , the UE keeps

in the fast movement state for a hysteresis period ( TCrmaxHyst ).

During the hysteresis period, even if the conditions for fast movement are not met,the UE still stay in the fast movement state until the hysteresis period expires.

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Measurement Start Criteria for Slow UE in HCS

Intra-frequency and inter-frequency measurement criteria for the UE in slow movement

Measurement Start Criteria with HCS Enabled

Condition ResultS rxlev ≤ S searchHCS or S qual ≤ S intersearch or S searchHCS not deliveredor S intersearch not delivered

All intra-frequency and inter-frequency cells are measured.S searchHCS is set through SsearchHCS on the RNC side.

S qual ≤ S intrasearch Intra-frequency and inter-frequency cells with their HCS level no lower

than that of the current cell are measuredS qual > S intrasearch Intra-frequency and inter-frequency cells with their HCS level higher than

that of the current cell are measured.S intrasearch not delivered All intra-frequency cells are measured.

Inter-frequency cells with their HCS level higher than that of the currentcell are measured.

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Measurement Start Criteria for Slow UE in HCS

Inter-RAT measurement criteria for UE in slow movement

Measurement Start Criteria with HCS Enabled

Condition ResultS rxlev ≤ S HCS,RATm or S qual ≤

S SearchRATm Inter-RAT cells are measured.S HCS,RATm is set through SHCSRat on the RNC side.

S qual ≤ S limit,SearchRATm Inter-RAT cells are measured when the HCS level of inter-RAT cells ishigher than or equal to that of the current cell.S limit,SearchRATm is set through SlimitSearchRat on the RNC side.

S qual > S limit,SearchRATm The UE need not measure inter-RAT cells.S HCS,RATm not delivered Inter-RAT cells are measured.

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Measurement Start Criteria for Fast UE in HCS

Intra-frequency and inter-frequency measurement criteria for the UE in fast movement

Measurement Start Criteria with HCS Enabled

Inter-RAT measurement criteria for the UE in fast movement

Condition ResultS rxlev ≤ S searchHCS or S qual ≤ S intersearch or S searchHCS not deliveredor S intersearch not delivered

All intra-frequency and inter-frequency cells aremeasured.

Others (such as S rxlev and S qual are good) All intra-frequency and inter-frequency cells with

their HCS level no higher than that of the current cell

are measured

Condition ResultS rxlev ≤ S HCS,RATm or S qual ≤ S SearchRATm Inter-RAT cells are measured.

S HCS,RATm or S SearchRATm not delivered Inter-RAT cells are measured.Others (such as S rxlev and S qual are good) All inter-RAT cells are measured when the HCS level

of inter-RAT cells is lower than or equal to that of thecurrent cell.

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Cell Reselection CriteriaDefinition of Criterion H

Criterion DefinitionCriterion H Hs= Qmeas, s - Qhcs s

Hn= Qmeas, n - Qhcs n - TOn x Lnl Hs is for the serving cell.l Hn is for the neighboring cell.l Qmeas, s is the measurement result of the serving cell.l Qhcs s is set through the parameter Qhcs for the serving celll Qmeas, n is the measurement result of the neighboring cell.l Qhcs n is set through the parameter Qhcs for the neighboring cell.l

Qhcs n is set through the following way:− If the parameter Adj sQhcsSwi t ch is set to ON, Qhcs n is set through the parameterIn te rFreqAdjsQhcs or In te rRatAdjsQhcs for the neighboring cell.l If the parameter Adj sQhcsSwi t ch is set to OFF, Qhcs n is set through theparameter Qhcs for the neighboring cell.

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Criterion DefinitionCriterion R Rs=Qmeas, s + Qhyst s

Rn=Qmeas, n -Qoffset s, n - TOn x (1-Ln)l Rs is for the serving cell.l Rn is for the neighboring cell.l Qmeas, s is the measurement result of the serving cell.l Qhyst s is set through the parameter IdleQhyst1s (RSCP) or IdleQhyst2s (Ec/No)for the serving cell.l Qmeas, n is the measurement result of the neighboring cell.l Qoffset s, n is set through the parameter IdleQoffset1sn (RSCP) or IdleQoffset2sn

(Ec/No).

Cell Reselection CriteriaDefinition of Criterion R

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Cell reselection parameter

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Cell Reselection Procedure

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SummaryCell selection• Criteria SMeasurement start criteria

• Measurement start criteria with HCS disabled• Measurement start criteria with HCS enabled

Cell reselection• Cell reselection procedure• Criteria H• Criteria R

Reference• HedExLite RAN feature documentation “UE behaviors in idle” • 3GPP TS 25.304

Measurement Start Criteria for Slow UE in HCSMeasurement Start Criteria for Fast UE in HCS

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Thank you!

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Scenario 3G2100: Cell-Reselection

EPLMN: Equivalent Public Mobile Network EPLMN software MSS (MSC Soft Switch)

LA, CI, IMSI

MSS MNC network network g

2G900

3G900

3G2100

MNC = 03

MNC = 01

2G900

3G900

3G2100

MNC-03 and MNC-01

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2G900

3G9003G2100

MNC = 03 MNC = 01

2G900

3G900

3G2100

MNC-03 and MNC -01

SearchingNo service modeLA & RA update

Cell ReselectionService modeLA & RA update

Scenario 3G2100: Cell-Reselection

Advantage:

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2G900

3G900

3G2100Reserve

not Allow roaming Allow roaming

* SIM 3G2100

Scenario 3G2100: Cell-Reselection

not Reserve

Cell reserve

Allow roamingnot Allowroaming

Cell not reserve

Available

Available2G900

3G900

3G2100

Theory:Same Coverage

Actual:Not same Coverage