wo_nast3008_e01_0 umts cell selection and reselection

UMTS Cell Selection and Reselection

Contents

1 Strategy of Cell Selection and Reselection...............................................................................................1

2 States and State Transitions in Idle Mode................................................................................................1

2.1 Cell selection process overview........................................................................................................2

2.2 Camped normally state overview......................................................................................................2

2.3 Connected mode state overview........................................................................................................2

2.4 Any cell selection state overview......................................................................................................3

2.5 Camped on any cell state overview...................................................................................................3

3 Cell Selection Process.................................................................................................................................1

3.1 Initial cell selection...........................................................................................................................1

3.2 Stored Information cell selection.......................................................................................................1

3.3 Cell selection criteria.........................................................................................................................1

4 Rules of Cell Reselection Measurement....................................................................................................1

4.1 Measurement rules for cell re-selection when HCS is not used........................................................1

4.2 High mobility state when HCS is not used........................................................................................2

4.3 Measurement rules for cell re-selection when HCS is used..............................................................3

4.4 Measurement rules for inter-frequency and inter-RAT cell reselection when absolute priorities are

used.........................................................................................................................................................6

4.5 Highest ranked cells with cell reservations, access restrictions or unsuitable...................................7

4.6 Rules of Cell Reselection Measurement for UE in CELL_FACH State............................................8

4.7 Cell reselection criteria......................................................................................................................8

4.8 Absolute priority based criteria for inter-frequency and inter-RAT cell reselection........................14

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1 Strategy of Cell Selection and Reselection

Different types of measurements are used in different RATs and modes for the cell

selection and reselection.

The NAS can control the RAT(s) in which the cell selection should be performed, for

instance by indicating RAT(s) associated with the selected PLMN, and by maintaining

a list of forbidden registration area(s) and a list of NAS-specified service area in

priority order. The UE will select a suitable cell and the radio access mode based on

measurements and cell selection criteria.

In order to speed up the cell selection process, stored information for several RATs may

be available in the UE.

When camped on a cell, the UE will regularly search for a better cell according to the

cell reselection criteria. If a better cell is found, that cell is selected. The change of cell

may imply a change of RAT (that is, cell reselection between different systems).

For normal service, the UE has to camp on a suitable cell, tune to that cell's control

channel(s) so that the UE can:

Receive system information from the PLMN;

Receive registration area information from the PLMN, e.g., location area and

routing area; and

Identify to which service area as specified by NAS that the serving cell belongs.

Receive other AS and NAS Information;

Receive paging and notification messages from the PLMN; and

Initiate call setup for outgoing calls or other actions from the UE.

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2 States and State Transitions in Idle Mode

Fig 2.1-1 shows the states and procedures of cell selection and reselection in Idle

Mode.

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Fig 2.1-1 Idle Mode Cell Selection and Reselection

In any state, a new PLMN selection causes an exit to number 1

2.1 Cell selection process overview

Whenever a PLMN has been selected by NAS, the UE will attempt to find a suitable

cell to camp on. The NAS may control the cell selection by:

Providing information on RAT(s) associated with the selected PLMN;

Maintaining lists of forbidden registration areas;

Providing a list of equivalent PLMNs.

One or several RATs may be associated with the selected PLMN. It depends on the UE

capability and PLMN plan.

If a suitable cell is found, the UE will select this cell to camp on, and report this event

to NAS so that the necessary NAS registration procedures can be performed. When the

registration is successful, the UE enters in state Camped normally in order to obtain

normal service.

2.2 Camped normally state overview

If after a Cell reselection evaluation process a better cell is found, the Cell reselection

procedure is performed. If no suitable cell is found, the UE will enter the state Any cell

selection.

When UE leaves idle mode in order to enter the state Connected mode, the UE shall

attempt to access the current serving cell. If the access attempt to the serving cell fails,

the UE will use the Cell reselection evaluation procedure.

2.3 Connected mode state overview

When returning to idle mode, the UE shall use the procedure Cell selection when

leaving connected mode in order to find a suitable cell to camp on and enter state

Camped normally. If a suitable cell is found, then the UE reports this event to NAS to

be capable to perform necessary NAS registration procedures. If no suitable cell is

found, the Stored information cell selection procedure will be used by the UE.

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Chapter 2 States and State Transitions in Idle Mode

If no suitable cell is found in cell reselection evaluation process, the UE enters the state

Any cell selection.

2.4 Any cell selection state overview

The state Any cell selection is also entered if the NAS indicates that a location

registration is rejected or there is no SIM/USIM in the UE.

If an acceptable cell is found, the UE will inform the NAS and camp on this cell and

obtain limited service, state Camped on any cell.

2.5 Camped on any cell state overview

In this state the UE obtains limited service. The UE will regularly attempt to find a

suitable cell, trying all RATs that are supported by the UE. If a suitable cell is found,

this causes an exit to number 2 in Figure 3.

NOTE: The 'PLMN selection and reselection' process may select a new PLMN at any

time in idle mode, which in Figure 3 causes an exit to number 1.

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3 Cell Selection Process

The UE will use one of the following two search procedures:

3.1 Initial cell selection

This procedure requires no prior knowledge of which RF channels are UTRA carriers.

The UE will scan all RF channels in the UTRA/GSM bands to find a suitable cell in the

chosen PLMN. On each carrier, the UE need only search for the strongest cell. Once a

suitable cell is found this cell shall be selected.

3.2 Stored Information cell selection

This procedure requires stored information of carrier frequencies and optionally also

information on cell parameters, e.g. scrambling codes, from previously received

measurement control information elements. Once the UE has found a suitable cell the

UE shall select it. If no suitable cell is found the Initial cell selection procedure will be

started.

3.3 Cell selection criteria

The cell selection criterion S is fulfilled when:

Where,

Qqualmeas: Measured cell quality value. Applicable only for FDD cells. The quality of

the received signal expressed in CPICH Ec/N0 (dB).

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Qrxlevmeas: Measured cell RX level value. This is received signal, CPICH RSCP for

FDD cells (dBm), P-CCPCH RSCP for TDD cells (dBm) and RXLEV for GSM cells

(dBm).

Qqualmin: Minimum required quality level in the cell (dB). Applicable only for FDD

cells. (For serving cell: the parameter is indicated by Qqualmin; for neighbour cell with

absolute priority configuration, the parameter is indicated by QqualminFDD.)

Qrxlevmin: Minimum required RX level in the cell (dBm). (For serving cell: If

DltaQRxLevMin is broadcast, Qrxlevmin =QrxLevMin+DltaQRxLevMin. If

DltaQRxLevMin is not broadcast, Qrxlevmin +QRxLevMin. Whether to broadcast

DltaQRxLevMin or not is controlled by DltaQRxLevMinPr. For neighbor cell: In Idle

mode or SIB12 is not broadcast, if DtQrxLvMnSib11 is not broadcast, Qrxlevmin

=QrxLevMin. In Idle mode or SIB12 is not broadcast, if DtQrxLvMnSib11 is broadcast,

Qrxlevmin =QrxLevMin+DtQrxLvMnSib11. In connected mode and SIB12 is

broadcast, if DtQrxLvMnSib12 is not broadcast, Qrxlevmin =QRxLevMin. If

DtQrxLvMnSib12 is broadcast, Qrxlevmin =QrxLevMin+DtQrxLvMnSib12. Whether

to broadcast DtQrxLvMnSib11 or not is controlled by DtQrxLvMnSib11Pr. Whether to

broadcast DtQrxLvMnSib12 or not is controlled by DtQrxLvMnSib12Pr. For neighbor

cell with absolute priority configuration, the parameters for UTRAN/GSM/EUTRAN

are independently indicated by QrxlevminFDD/QrxlevminGSM/QrxlevminEUTRA)

Notes: Whether to broadcast SIB12 is controlled by SIB12Ind

QqualminOffset(QqualminOffset): Offset to the signalled Qqualmin taken into account

in the Squal evaluation. The parameter is available only for FDD cells and SIB3.

Whether to broadcast QqualminOffset is controlled by parameter QqulmnOffstPre.

QrxlevminOffset(QrxlevminOffset): Offset to the signalled Qrxlevmin taken into

account in the Srxlev evaluation. The parameter is available only for SIB3. Whether to

broadcast QrxlevminOffset is controlled by parameter QrxlvmnOffstPre.

UE_TXPWR_MAX_RACH: Maximum TX power level MaxRACHTxPwr on RACH

(read in system information) (dBm) (for cells under the RNC, it is the max value of

MaxRACHTxPwr (Prach); for cells under other RNC, it is the value of

MaxRACHTxPwr (externalUtranCell)).

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P_MAX: Maximum RF output power of the UE (dBm)

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4 Rules of Cell Reselection Measurement

Different rules apply for cell reselection measurement when HCS is used and when

HCS is not used.

4.1 Measurement rules for cell re-selection when HCS is not used

When the serving cell does not use HCS (UseOfHCS(utranCell)), the measurement

rules for cell reselection are:

In the following rules, the UE uses Squal for FDD cells and Srxlev for TDD cells for

Sx:

1. If Sx > SIntraSearch, UE may choose to not perform intra-frequency measurements.

If Sx <= Sintrasearch, UE performs intra-frequency measurements.

If Sintrasearch, is not sent, UE performs intra-frequency measurements. Whether to

broadcast Sintrasearch or not is controlled by SintrasearchPre.

2. The UE may choose to not perform inter-frequency measurements when the

following conditions are satisfied:

MBMS preferred frequency layer is not configured (FreqPLInd), or MBMS

preferred frequency layer is configured but the current serving cell belongs to the

MBMS preferred frequency layer.

Sx> Sintersearch

If SsearchHCS is broadcast and Srxlev > SsearchHCS

The UE needs to perform inter-frequency measurements at least for the MBMS

preferred frequency layer when the following conditions are satisfied:

MBMS preferred frequency layer is configured and the current serving cell does

not belong to the MBMS preferred frequency layer.

Sx > Sintersearch

If SsearchHCS is broadcast and Srxlev > SsearchHCS.

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The UE needs to perform inter-frequency measurements when any one of the following

conditions is satisfied:

Sx <= Sintersearch

IF SsearchHCS is broadcast and Srxlev <= SsearchHCS.

If SinterSearch is not broadcast, the UE performs inter-frequency measurement. Whether to

broadcast SinterSearch or not is controlled by SInterSearchPre.

3. If Sx > SSearchRat, UE does not need to measure quality of inter-RAT neighbor cells.

If Sx <= SSearchRat, the UE performs inter-RAT cell quality measurement.

If SsearchRat is not broadcast, the UE performs inter-RAT neighbor cell quality

measurement. Whether to broadcast SsearchRat or not is controlled by

OtherRATInfoPre.

If HCS is not used and the UE receives SLimitRat, the UE will ignore the

parameter.

4.2 High mobility state when HCS is not used

In non-HCS environment, if the parameters NoHcsTCrMax, NoHcsNCr and

NoHcsTCrMaxHyst are sent on the system information broadcast, it is necessary to

start the UE high mobility state detection mechanism so that the cell reselection criteria

decision can be made with the reselection timer multiplied by the scaling factor or not.

If in non-HCS environment the number of cell reselections during time period

NoHcsTCRMax exceeds NoHcsNCr, or if the network (via RRC release, RB re-

configuration) has ordered the UE to consider itself to be in high-mobility state, then

high-mobility state is triggered.

When the number of cell reselections during time period NoHcsTCRMax no longer

exceeds NoHcsNCr, the UE will:

Continue in high-mobility state.

If the number of cell reselections during time period NoHcsTCRHyst does not

exceed NoHcsNCr and also the network does not order the UE to stay in high-

mobility state, then the UE exits high-mobility state.

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4.3 Measurement rules for cell re-selection when HCS is used

When the serving cell uses HCS (UseOfHCS (utranCell) ), the measurement rules of

cell reselection are:

IF an MBMS PL (preferred layer) is used then,

If the UE is in HCS low mobility state, for serving cell and neighbour cells

belonging to the MBMS PL set the HCS priority = HcsPrio + HcsOffMbms.

If the UE is in HCS high mobility state, for serving cell and neighbour cells

belonging to the MBMS PL set the HCS priority = HcsPrio.

For serving cell and neighbour cells not belonging to the MBMS PL, set the HCS

priority = HcsPrio

IF an MBMS PL is not used, then HCS priority = HcsPrio

Where: HcsPrio is the parameters configured by cells. The HcsPrio of the current RNC

cell takes the value of HcsPrio (utranCell). The HcsPrio of the neighbor RNC cell takes

the value of HcsPrio (externalUtranCell). The HcsPrio of the GSM cell takes the value

of (externalGsmCell).

In the following rules, the UE uses Squal for FDD cells and Srxlev for TDD cells for

Sx:

1. For intra-frequency and inter-frequency measurement rules for UEs not in high-

mobility

IF (Srxlev <= SsearchHCS) or (if FDD and Sx <= Sintersearch) THEN

<UE measure on all intra-frequency and inter-frequency cells.>

ELSE

IF (Sx > Sintrasearch) THEN

< UE measure on all intra-frequency and inter-frequency cells, which have higher

HCS priority level than the serving cell. >

ELSE

<UE measure on all intra-frequency and inter-frequency cells, which have equal

or higher HCS priority level than the serving cell >

ENDIF

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IF Sintrasearch is not sent for the serving cell, THEN

<UE measure on all intra-frequency cells. Fast-moving UEs may also use this

rule. UE measure on all inter-frequency cells, which have higher HCS priority level

than the serving cell unless measurement rules for fast-moving UEs are triggered.>

ENDIF

ENDIF

Whether to broadcast Sintrasearch or not is controlled by SintraSearchPre.

If HCS(UseOfHCS (utranCell)) is used and if SsearchHCS or Sintersearch (FDD) is not sent for

the serving cell, UE will measure on all intra-frequency and inter-frequency cells.

Whether to broadcast SsearchHCS or not is controlled by SSearchHCSPre. Whether to

broadcast SinterSearch or not is controlled by SInterSearchPre.

2. For intra-frequency and inter-frequency measurement rules for fast-moving UEs:

This measurement rule applies when the HCS is used and the UE is in fast-moving

state and also the UE receives the broadcast message of NoHcsTCrMax, NoHcsNCr

and NoHcsTCrMaxHyst.

If the number of cell reselections during time period TCrMax exceeds NCr, or if the

network (via signaling of RRC release, RB re-configuration) has ordered the UE to

consider itself in high mobility state, the UE is triggered to enter fast-moving state.

In this high-mobility state, UE will

IF(Srxlevs <= SsearchHCS) or (if FDD and Sx <= Sintersearch) or SsearchHCS or Sintersearch (FDD)

are not sent, THEN

<UE measure on all intra-frequency and inter-frequency cells.>

ELSE

<UE measure intra-frequency and inter-frequency neighbour cells, which have equal or

lower HCS priority than serving cell. >

ENDIF

When the number of cell reselections during time period TCRmax no longer exceeds

NCr, the UE will:

UE continues in high-mobility state.

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If the number of cell reselections during time period TCrmaxHyst does not exceed

NCr and also the network does not order the UE to stay in high-mobility state,

then the UE exits high-mobility state.

When serving cell belongs to a hierarchical cell structure, the UE will follow these

rules for Inter-RAT measurements:

The UE uses Squal for FDD cells and Srxlev for TDD cells for Sx in the following

rules.

3. Inter-system threshold-based measurement rules for UEs not in high-mobility

IF (Srxlevs <= SHCSRat) or (if FDD and Squal <= SSearchRat) THEN

<UE measure on all neighbour cells of other RAT >

ELSE

IF (Sx > SLimitRat) THEN

<UE may choose not to perform inter-RAT measurement>

ELSE

< UE measure on all neighbour cells between systems, which have equal or higher

HCS priority level than the serving cell. >

ENDIF

ENDIF

If HCS is used and if SHCSRat is not sent for the serving cell, the UE will measure on

all inter-RAT cells. Whether to broadcast SHCSRat or not is controlled by

SHCSRatPre.

4. Inter-system measurement rules for fast-moving UEs

If the number of cell reselections during time period TCrMax exceeds NCr, or if the

network (via signaling of RRC release, RB re-configuration) has ordered the UE to

consider itself in high mobility state, the UE is triggered to enter fast-moving state.

In this high-mobility state, UE will

IF (Srxlev <= SHCSRat) or (if FDD and Squal <= SSearchRat), or SHCSRat or SsearchRat are not

sent, THEN

< UE measure on all intra-system cells >

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ELSE

< UE measure inter-RAT neighbour cells, which have equal or lower HCS priority than

serving cell. >

ENDIF

Remarks: Whether to broadcast SHCSRat or not is controlled by SHCSRatPre. Whether to

broadcast SsearchRat or not is controlled by OtherRATInfoPre.

When the number of cell reselections during time period TCRmax no longer exceeds

NCr, the UE will

Continues in high-mobility state.

If the number of cell reselections during time period TCrmaxHyst does not exceed

NCr and also the network does not order the UE to stay in high-mobility state,

then the UE exits high-mobility state.

4.4 Measurement rules for inter-frequency and inter-RAT cell reselection when absolute priorities are used

If the UE has received absolute priority information for inter-frequency layers

(AbsPriReselSwch(utranCell)), the UE shall follow these rules:

The UE shall perform measurements of inter-frequency layers with a priority

higher than the priority of the current serving layer.

For inter-frequency layers with a priority equal or lower than the priority of

the current serving layer:

- If SrxlevServingCell>Sprioritysearch1 and SqualServingCell > Sprioritysearch2 the UE may choose

not to perform measurements of inter-frequency layers of equal or lower

priority.

- If SrxlevServingCell<=Sprioritysearch1 or SqualServingCell<=Sprioritysearch2 the UE shall

perform measurements of inter-frequency layers of equal or lower priority.

The UE shall not perform measurements of inter-frequency layers for which

the UE has no absolute priority.

If the UE has received absolute priority information for inter-RAT layers

(AbsPriReselSwch(utranCell)), the UE shall follow these rules:

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The UE shall perform measurements of inter-RAT layers with a priority

higher than the priority of the current serving cell.

For inter-RAT layers with a priority lower than the priority of the current

serving cell:

- If SrxlevServingCell>Sprioritysearch1 and SqualServingCell>Sprioritysearch2 the UE may choose

not to perform measurements of inter-RAT layers of lower priority.

- If SrxlevServingCell<=Sprioritysearch1 or SqualServingCell<=Sprioritysearch2 the UE shall

perform measurements of inter-RAT layers of lower priority.

The absolute priority of current serving cell: ServCelPriority;

The absolute priority of inter-frequency layers in UTRAN:

UtranPriority[MAX_NUM_UTRAN_FREQ];

The absolute priority of inter-RAT layers in EUTRAN:

EutranPriority[MAX_NUM_UTRAN_FREQ];

The absolute priority of inter-RAT layers in GERAN:

GeranPriority[MAX_NUM_GERAN_CELL_GROUP].

4.5 Highest ranked cells with cell reservations, access restrictions or unsuitable

Rank the cells according to cell reselection ranking criteria. The UE will detect whether

the highest ranked cells are with cell reservations, access restrictions or in other state

unsuitable for camping. If yes, the cells will be excluded from the candidate list for cell

reselection (This limitation is judged again when the highest ranked cell changes.).

If the highest ranked cell is an intra-frequency or inter-frequency cell which is not

suitable due to being part of the "list of forbidden LAs " or belonging to a PLMN

which is not indicated as being equivalent to the registered PLMN, the UE will not

consider this cell and other cells on the same frequency, as candidates for reselection

within 300s. If the UE has to perform an any cell selection procedure any limitation

will be removed.

If the highest ranked cell is an inter-RAT cell which is not suitable due to being part of

the "list of forbidden LAs " or belonging to a PLMN which is not indicated as being

equivalent to the registered PLMN, the UE will not consider this cell as a candidate for

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reselection within 300s. If the UE has to perform an any cell selection procedure any

limitation will be removed.

4.6 Rules of Cell Reselection Measurement for UE in CELL_FACH State

For UE in CELL_FACH state

If parameter “UE Inter-frequency FDD Measurement Indicator

(FDDInterFMeasInd)” is set to “False”, UE shall neither perform measurements

nor evaluate cell re-selection criteria on inter-frequency FDD cells.

If parameter “UE Inter-RAT Measurement Indicator (InterRatMIndPre)” is set to

“False”, UE shall not perform Inter-RAT Measurement.

If parameter “UE Inter-frequency FDD Measurement Indicator

(FDDInterFMeasInd)” or “UE Inter-RAT Measurement Indicator

(InterRatMIndPre)” is set to “True”, UE shall perform Inter-frequency or Inter-

RAT Measurement only in FACH measurement occasion, other occasion shall be

used to transmit user data. The FACH measurement occasion is decided by

parameter “FACH Measurement Occasion Cycle Length Coefficient

(FachMeasK)” which is described in 3gpp 25.331 “FACH measurement occasion

info”.

4.7 Cell reselection criteria

The following cell re-selection criteria are used for intra-frequency cells, inter-

frequency cells if no absolute priority information for any inter-frequency layer is

available to the UE, and inter-RAT cells if no absolute priority information for any

inter-RAT layer is available to the UE for that RAT. For inter-frequency and inter-RAT

layers in a RAT for which absolute priorities are defined.

If the serving cell uses the HCS (UseOfHCS (utranCell)) structure, the following cell

reselection rule H is used for quality ranking in cell reselection.

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If the cell does not use the HCS structure, the following cell reselection rule R is used

for quality ranking in cell reselection.

Where,

Qmeas,s: Quality measurement result of serving cell.

Connected mode: When SIB4 is not broadcast, the parameter values are taken as in the

case of Idle mode; when SIB4 is broadcast, the value of QHcsEcNo (SIB4) is taken if

Ec/No is used as the quality measure, and the value of QHcsRSCP (SIB4) is taken if

RSCP is used as the quality measure.} Whether to broadcast SIB4 is controlled by

SIB4Ind. Whether Ec/No or RSCP is used as the quality measure is controlled by

QualMeas.

Qmeas,n: Quality measurement result of neighbor cell.

Qhcs,n: This specifies the quality threshold levels of neighbor cells for applying

prioritised hierarchical HCS cell re-selection (Idle mode: If Ec/No is used as the quality

measure, the value of QhcsEcN0Sib11 is taken; if RSCP is used as the quality measure,

the value of QhcsRscpSib11 is taken. Connected mode: When SIB12 is not broadcast,

the parameter values are taken as in the case of Idle mode; when SIB12 is broadcast,

the value of QhcsEcN0Sib12 is taken if Ec/No is used as the quality measure, and the

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value of QhcsRscpSib12 is taken if RSCP is used as the quality measure. Whether to

broadcast SIB12 is controlled by SIB12Ind

Connected mode: When SIB4 is not broadcast, the parameter values are taken as in the

case of Idle mode; when SIB4 is broadcast, the value of QHyst1SPch is taken if RSCP

is used as the URA_PCH state reselection quality measure, and the value of

QHyst2SFach is taken if Ec/No is used as the CELL_FACH state reselection quality

measure. Whether to broadcast SIB4 is controlled by SIB4Ind.

Qoffmbms: This specifies the offset added to cells belonging to the MBMS PL when a

decision of HCS cell R reselection rule is being made.

Connected mode: When SIB12 is not broadcast, the parameter values are taken as in

the case of Idle mode; when SIB12 is broadcast, the value of Qoffset1SNSib12 is taken

if RSCP is used as the reselection quality measure, and the value of Qoffset2SNSib12 is

taken if Ec/No is used as the reselection quality measure. Whether SIB12 is broadcast

controlled by SIB12Ind

Tn: The timer used after cell reselection. The rules to start Tn are as follows:

Tn is implemented for each neighbour cell. Tn will be started from zero when one

of the following conditions becomes true:

If HCS_PRIOn <> HCS_PRIOs and Qmeas,n > Qhcsn

or

If HCS_PRIOn = HCS_PRIOs and

- for serving FDD and neighbour FDD cells if the quality measure for cell selection

and reselection is set to CPICH RSCP in the serving cell, and Qmeas,n > Qmeas,s +

Qoffset1s,n

or

- for serving FDD and neighbour FDD cells if the quality measure for cell selection

and reselection is set to CPICH Ec/No in the serving cell, and Qmeas,n > Qmeas,s +

Qoffset2s,n

or

- for all other serving and neighbour cells:

Qmeas,n > Qmeas,s + Qoffset1s,n

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Tn for the associated cell will be stopped as soon as any of the above conditions

are no longer fulfilled.. Any value calculated for TOn is valid only if the associated

timer Tn is still running otherwise TOn will be set to zero.

At cell-reselection, a timer Tn is stopped only if the corresponding cell is not a

neighbour cell of the new serving cell, or if the criteria given above for starting

timer Tn for the corresponding cell is no longer fulfilled with the parameters of the

new serving cell. On cell re-selection, timer Tn will be continued to be run for the

corresponding cells but the criteria given above will be evaluated with parameters

broadcast in the new serving cell if the corresponding cells are neighbours of the

new serving cell.

Connected mode: When SIB12 is not broadcast, the parameter values are taken as in

the case of Idle mode; when SIB12 is broadcast, the value of TempOffset1Sib12 is

taken if RSCP is used as the reselection quality measure and the value of

TempOffset2Sib12 is taken if Ec/No is used as the reselection quality measure. Whether

to broadcast SIB12 is controlled by SIB12Ind)}. If HCS (UseOfHCS (utranCell) ) is

used, TEMP_OFFSETn is used to calculate TOn. If HCS (UseOfHCS (utranCell) ) is

not used, TEMP_OFFSETn is not applied when calculating Rn.

HCS_PRIOn: This specifies the HCS priority level for neighbour cells (non-HCS cell:

The HcsPrio of the current RNC cell takes the value of HcsPrio(utranCell). The

HcsPrio of the neighbor RNC cell takes the value of HcsPrio (externalUtranCell). The

HcsPrio of the GSM cell takes the value of HcsPrio (externalGsmCell). If not

configured, it is 0 default. For value of HCS cells, refer to Value of “HCS Priority” in

“Cell reselection measurement rule when the hierarchical cell structure (HCS) is used.

HCS_PRIOs: This specifies the HCS priority level for serving cell. (non-HCS cell: The

HcsPrio of the current RNC cell takes the value of HcsPrio(utranCell). The HcsPrio of

the neighbor RNC cell takes the value of HcsPrio (externalUtranCell). The HcsPrio of

the GSM cell takes the value of HcsPrio (externalGsmCell). For value of HCS cells,

refer to Value of “HCS Priority” in “Cell reselection measurement rule when the

hierarchical cell structure (HCS) is used.

The cell are ranked by quality according to the above defined R or H criteria using

CPICH RSCP (for FDD), P-CCPCH RSCP (for TDD) and the measurement result of

averaged received signal level (for GSM) as the calculation quantity of Qmeasn,

Qmeass, R or H. The best ranked cell is the cell with the highest R or H value.

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For the cell selection and reselection parameters: Whether Qhcs, TCrmax, NCR and

TCrmaxHyst are configured is controlled by HcsSrvCelInfoPre. Whether the HCS-related

parameters in neighbor cell such as HCS_PRIO, Qhcs, Penalty_time,

Temporary_offset1 and Temporary_offset2 are configured is controlled by UseOfHCS

(utranRelation) and UseOfHCS (gsmRelation).

If a TDD or GSM cell is ranked as the best cell, then the UE will perform cell re-

selection to that TDD or GSM cell and camps on the chosen cell.

If an FDD cell is ranked as the best cell and the quality measurement for cell selection

and re-selection is set to CPICH RSCP, the UE will perform cell re-selection to that

FDD cell and and camps on the chosen cell (If this cell is found to be not suitable, the

UE will behave according to “Highest ranked cells with cell reservations, access

restrictions or unsuitable for normal camping”).

If an FDD cell is ranked as the best cell and the quality measure for cell selection and

re-selection is set to CPICH Ec/No, the UE shall perform a second ranking of the FDD

cells according to the R criteria specified above, but using the quality measure CPICH

Ec/No for deriving the Qmeas,n and Qmeas,s and calculating the R values of the FDD cells

(If this cell is found to be not suitable, the UE will behave according to “Highest

ranked cells with cell reservations, access restrictions or unsuitable for normal

camping”).

In all cases, the UE will reselect the new cell, only if the following conditions are met:

The new cell is better ranked than the serving cell during a time interval

Treselection according to the R or H criteria. If Treselections,PCH is provided in

SIB4, the URA_PCH state timer takes the value of TreselectionPch; if

Treselections,FACH is provided in SIB4, the CELL_FCH state timer takes the value

of TreselectionFach. For hierarchical cell structures when high mobility state has

not been detected, if according to the HCS rules the serving cell is not ranked then

all the ranked cells are considered to be better ranked than the serving cell. In case

the UE reselects a cell on an MBMS preferred frequency to receive an MBMS

service not available on the current frequency, the UE may reduce interval

TreselectionS, TreselectionS, PCH and TreselectionS, FACH. (Whether to configure SIB4

is controlled by SIB4Ind).

More than 1 second has elapsed since the UE camped on the current serving cell.

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The timers Treselection, TReselectionPch and TReselectionFach will be

multiplied by scaling factor if the following conditions are satisfied:

The high mobility state of cell is detected and "Speed dependent ScalingFactor

for_Treselection" (SpSf) is broadcast on system information (whether broadcast is

controlled by SpSfPre), then TreselectionS, TReselectionPch and

TReselectionFach will be multiplied by the scaling factor SpSf in intra-frequency

measurement and the result is the actually used TreselectionS, TReselectionPch

and TReselectionFach.

The high mobility state of cell is not detected and " Inter-Frequency ScalingFactor

for Treselection" (InterFreqSf) is broadcast on system information (whether

broadcast is controlled by InterFreqSfPre), then Treselection, TReselectionPch

and TReselectionFach will be multiplied by the scaling factor InterFreqSf in inter-

frequency measurement and the result is the actually used TreselectionS,

TReselectionPch and TReselectionFach.


for_Treselection" (SpSf) and "Inter-Frequency ScalingFactor for Treselection

" (InterFreqSf) are broadcast on system information, then Treselection,

TReselectionPch and TReselectionFach will be multiplied by the scaling factors

SpSf and InterFreqSf in inter-frequency measurement and the result is the actually

used TreselectionS, TReselectionPch and TReselectionFach.

The high mobility state of cell is not detected and "Inter-RAT ScalingFactor for

Treselection" (InterRatSf) is broadcast on system information (whether broadcast

is controlled by InterRatSfPre), then Treselection, TReselectionPch and

TReselectionFach will be multiplied by the scaling factor InterRatSf in inter-RAT

measurement and the result is the actually used Treselection, TreselectionPch and

TReselectionFach.


for_Treselection" (SpSf) and "Inter-RAT ScalingFactor for Treselection "

(InterRatSf) are broadcast on system information, then TreselectionS,

TReselectionPch and TReselectionFach will be multiplied by the scaling factors

SpSf and InterRatSf in inter-RAT measurement and the result is the actually used

Treselection, TReselectionPch and TReselectionFach.

In case scaling is applied to Treselection or TReselectionPch, the UE will round

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up the Treselection or TReselectionPch after all scalings to the nearest second. In

case scaling is applied to TReselectionFach, the UE will round up the result after

all scalings to the nearest 0.2 seconds.

4.8 Absolute priority based criteria for inter-frequency and inter-RAT cell reselection

Absolute priority based inter-frequency and inter-RAT cell reselection is controlled by

AbsPriReselSwch. When this switch is “on”, SIB 19 will be broadcast. RNC configures

related frequency information (EutranInterFNum/DlEARFCN/AllowMeasBand/

GsmBandIndicator/GsmCellGroupNum/StartARFCN/UtranInterFNum/UtranUARFCN

), and serving cell priority (ServCelPriority), frequency priority (UtranPriority) and

other RAT priority (EutranPriority/ GeranPriority) to UE in SIB19.

In the above description, EutranInterFNum is the number of neighbor EUTRAN center

frequencies. DlEARFCN is the IE “EARFCN” of each EUTRAN center frequency,

which means the Downlink EUTRAN Absolute Radio Frequency Channel Number.

AllowMeasBand is the IE “Measurement Bandwidth” of each EUTRAN center

frequency. It indicates the number of resource blocks over which the UE could measure

in each EUTRAN frequency in idle mode. These parameters inform UE about the

information of EUTRAN network.

GsmCellGroupNum is the Number of neighbor GSM Frequency Groups.

GsmBandIndicator is the IE “Band Indicator” of each GSM frequency group.

StartARFCN is the IE “Starting ARFCN” of each GSM frequency group. These

parameters inform UE about the information of GSM network.

UtranInterFNum is the number of neighboring UTRAN FDD Frequencies.

UtranUARFCN is the IE “UARFCN” of each UTRAN FDD Frequency. These

parameters inform UE about the information of UTRAN inter-frequency network.

The following criteria are used for inter-frequency cells if absolute priority information

for inter-frequency is available to the UE, and inter-RAT cells if absolute priority

information for inter-RAT is available to the UE.

If System Information Block 18 with UTRAN information is provided then the UE

shall apply inter-frequency priority rules below only to UTRAN cells of the selected

PLMN or equivalent PLMNs. If System Information Block 18 is not provided, or is

provided but contains no information for UTRAN, then the rules below apply for the

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entire UTRAN RAT.

If System Information Block 18 with GERAN information is provided then the UE

shall apply the GERAN RAT priority rules below only to GERAN cells of the selected

PLMN or equivalent PLMNs. If System Information Block 18 is not provided, or is

provided but contains no information for GERAN, then the rules below apply for the

entire GERAN RAT.

If priority information is provided for any inter-frequency layers, cells belonging to

inter-frequency layers for which no priority or no threshold is assigned shall not be

considered for reselection.

If priority information is provided for any inter-RAT layers in a RAT, cells belonging to

layers in that RAT for which no priority or no threshold is assigned shall not be

considered for reselection.

If the UE has received absolute priority information for inter-frequency layers, the UE

shall follow these rules:

The UE shall perform measurements of inter-frequency layers with a priority

higher than the priority of the current serving layer.

For inter-frequency layers with a priority equal or lower than the priority of

the current serving layer:

- If SrxlevServingCell > Sprioritysearch1 and SqualServingCell > Sprioritysearch2 the UE may choose

not to perform measurements of inter-frequency layers of equal or lower priority.

- If SrxlevServingCell <= Sprioritysearch1 or SqualServingCell <= Sprioritysearch2 the UE shall perform

measurements of inter-frequency layers of equal or lower priority.

If the UE has received absolute priority information for inter-RAT layers, the UE shall

follow these rules:

The UE shall perform measurements of inter-RAT layers with a priority higher

than the priority of the current serving cell.

For inter-RAT layers with a priority lower than the priority of the current serving

cell:

- If SrxlevServingCell > Sprioritysearch1 and SqualServingCell > Sprioritysearch2 the UE may choose not

to perform measurements of inter-RAT layers of lower priority.

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- If SrxlevServingCell <= Sprioritysearch1 or SqualServingCell <= Sprioritysearch2 the UE shall perform

measurements of inter-RAT layers of lower priority.

Where,

Sprioritysearch1,,CPICH RSCP Measurement Trigger Threshold for Absolute Priority

Reselection Criteria, SPrioritySearch1

Sprioritysearch2,, CPICH EcN0 Measurement Trigger Threshold for Absolute Priority

Reselection Criteria, SprioritySearch2

The following definitions apply

- Criterion 1: the SrxlevnonServingCell,x of a cell on an evaluated higher absolute priority

is greater than Threshx,high during a time interval Treselection;

- Criterion 2: SrxlevServingCell < Threshserving,low or SqualServingCell<0 and the

SrxlevnonServingCell,x of a inter-frequency cell on an evaluated equal absolute priority

layer is greater than Threshx,low during a time interval Treselection;

- Criterion 3: SrxlevServingCell<Threshserving,low or SqualServingCell<0 and the

SrxlevnonServingCell,x of a cell on an evaluated lower absolute priority layer is greater

than Threshx,low during a time interval Treselection;

where,

Threshx,high, an Srxlev based threshold used by the UE for cell reslection towards a

higher absolute priority layer. For UTRAN, it is

UtranHighThresh[MAX_NUM_UTRAN_FREQ]; for EUTRAN, it is

EutranHighThresh[MAX_NUM_EUTRAN_FREQ]; for GERAN, it is

GeranHighThresh[MAX_NUM_GERAN_CELL_GROUP].

Threshx,low, an Srxlev based threshold used by the UE for cell reselection towards an

equal or lower absolute priority layer. For UTRAN, it is

UtranLowThresh[MAX_NUM_UTRAN_FREQ]; for EUTRAN, it is

EutranLowThresh[MAX_NUM_EUTRAN_FREQ]; for GERAN, it is

GeranLowThresh[MAX_NUM_GERAN_CELL_GROUP];

Threshserving,low, the limit for Srxlev in the serving cell below which the UE may perform

cell reselection to a cell on a lower absolute priority layer. ThreshServingLow

Cell reselection to a cell on a higher absolute priority layer than the camped frequency

shall be performed if criterion 1 is fulfilled.

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Cell reselection to an inter-frequency cell on an equal absolute priority layer to the

camped frequency shall be performed if criterion 2 is fulfilled.

Cell reselection to a cell on a lower absolute priority layer than the camped frequency

shall be performed if criterion 3 is fulfilled.

If more than one cell meets the above criteria, the UE shall reselect the cell with the

highest SrxlevnonServingCell,x among the cells meeting the criteria on the highest absolute

priority layer.

The UE shall not perform cell reselection to cells for which the cell selection criterion

S is not fulfilled.

The UE shall not perform cell reselection until more than 1 second has elapsed since

the UE camped on the current serving cell.

SIB19 also broadcasts Qrxlevmin of UTRAN for Cell Reselection (QrxlevminFDD),

Qqualmin of UTRAN for Cell Reselection (QqualminFDD), Qrxlevmin of EUTRAN

for Cell Reselection (QrxlevminEUTRA) and Qrxlevmin of GSM for Cell Reselection

(QrxlevminGSM)

In all the above criteria the values of Treselections, Treselections,PCH or Treselections,FACH

apply for Treselection and are scaled according to the UE mobility state and target

RAT.

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wo_nast3008_e01_0 umts cell selection and reselection

Documents

suitable cell

cell selection criteria

change of cell

better cell

cell reselection

cell reservations

serving cell

initial cell selection