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

i

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.

1

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.

go here whenever a new PLMN is selected

cell information stored for the PLMN

Stored information Cell Selection no suitable cell found

no cell information stored for the PLMN

1

Initial Cell Selection

no suitable cell found

2

suitable cell found

suitable cell found no suitable cell found

Cell Selection when leaving connected mode

return to idle mode

suitable cell found

Camped normally

NAS indicates that registration on selected PLMN is rejected (except with cause #14 or #15 [5][16])

trigger

leave idle mode

suitable cell found

Connected mode

Cell Reselection Evaluation Process

no suitable cell found

Any Cell Selection

no acceptable cell found

go here when no USIM in the UE

USIM inserted acceptable cell found

Cell Selection when leaving connected mode

return to idle mode

acceptable cell found

Camped on any cell

2

trigger

leave idle mode

acceptable cell found

Connected mode (Emergency calls only)

Cell Reselection Evaluation Process

Fig 2.1-1

suitable cell found

1

no acceptable cell found

Idle Mode Cell Selection and Reselection 1


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. If no suitable cell is found in cell reselection evaluation process, the UE enters the state Any cell selection. 2

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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:

for FDD cells:

Srxlev > 0 AND Squal > 0

for TDD cells:

Srxlev > 0

Where,

Squal = Qqualmeas – (Qqualmin + QqualminOffset) Srxlev = Qrxlevmeas – (Qrxlevmin + QrxlevminOffset) – Pcompensation

Qqualmeas: Measured cell quality value. Applicable only for FDD cells. The quality of the received signal expressed in CPICH Ec/N0 (dB).

1


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. Pcompensation ＝ max(UE_TXPWR_MAX_RACH – P_MAX, 0)

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)). P_MAX: Maximum RF output power of the UE (dBm) 2

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.

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

1


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.

2


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 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 ENDIF 3


IF Sintrasearch is not sent for the serving cell, THEN 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 ELSE ENDIF When the number of cell reselections during time period TCRmax no longer exceeds NCr, the UE will: 

UE continues in high-mobility state.

4




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 ELSE IF (Sx > SLimitRat) THEN 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 > 5


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:

6


 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 7


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

(FDDInterFMeasInd)”

Inter-frequency or

“UE

FDD

Measurement

Indicator

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.

Hs = Qmeas,s - Qhcss Hn = Qmeas,n - Qhcsn – TOn * Ln

8


If the cell does not use the HCS structure, the following cell reselection rule R is used for quality ranking in cell reselection.

Rs = Qmeas,s + Qhysts + Qoffmbms Rn = Qmeas,n - Qoffsets,n + Qoffmbms - TOn * (1 – Ln) Where, TOn = TEMP_OFFSETn * W(PENALTY_TIMEn – Tn) Ln = 0 Ln = 1

if HCS_PRIOn = HCS_PRIOs if HCS_PRIOn <> HCS_PRIOs

W(x) = 0 W(x) = 1

for x < 0 for x >= 0

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 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 9


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



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 10


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. 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). 11


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.



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 12


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.



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



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

13


4.8 Absolute priority based inter-RAT cell reselection

criteria

for

inter-frequency

and

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 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 14


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.

-

If SrxlevServingCell <= Sprioritysearch1 or SqualServingCell <= Sprioritysearch2 the UE shall perform measurements of inter-RAT layers of lower priority.

Where, 15


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
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

UtranHighThresh[MAX_NUM_UTRAN_FREQ];

UTRAN,

for

EutranHighThresh[MAX_NUM_EUTRAN_FREQ];

for

it

is

EUTRAN,

it

is

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.

UtranLowThresh[MAX_NUM_UTRAN_FREQ]; EutranLowThresh[MAX_NUM_EUTRAN_FREQ];

For

for for

UTRAN,

it

is

EUTRAN,

it

is

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. 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 16


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.

17

Umts Cell Selection and Reselection

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