6 Idle mode tasks

05.083GPPRadio subsystem link controlTS

6.1 Introduction

Whilst in idle mode, an MS shall implement the cell selection and re‑selection procedures described in 3GPP TS 03.22. These procedures make use of measurements and sub‑procedures described in this subclause.

The procedures ensure that the MS is camped on a cell from which it can reliably decode downlink data and with which it has a high probability of communications on the uplink. Once the MS is camped on a cell, access to the network is allowed.

This clause makes use of terms defined in 3GPP TS 03.22.

The MS shall not use the discontinuous reception (DRX) mode of operation (i.e. powering itself down when it is not expecting paging messages from the network) while performing the cell selection algorithm defined in 3GPP TS 03.22. However use of powering down is permitted at all other times in idle mode.

For the purpose of cell selection and reselection, the MS shall be capable of detecting and synchronizing to a BCCH carrier and read the BCCH data at reference sensitivity level and reference interference levels as specified in 3GPP TS 05.05. An MS in idle mode shall always fulfil the performance requirement specified in 3GPP TS 05.05 at levels down to reference sensitivity level or reference interference level. The allowed error rates (see 3GPP TS 05.05) might impact the cell selection and reselection procedure, e.g. trigger cell reselection. Moreover, one consequence of the allowed error rates is that in the case of no frequency hopping and a TU3 (TU6 for GSM 400, TU1.5 for DCS 1 800 and PCS 1 900) propagation profile it can not be expected that an MS will respond to paging unless the received signal level is 2 dB higher than the specified reference level.

For the purposes of cell selection and reselection, the MS is required to maintain an average of received signal levels for all monitored frequencies. These quantities termed the "received level averages" (RLA_C), shall be unweighted averages of the received signal levels measured in dBm. The accuracy of the received signal level measurements for idle mode tasks shall be the same as for radio link measurements (see subclause 8.1.2).

The times given in subclauses 6.2, 6.3 and 6.6 refer to internal processes in the MS required to ensure that the MS camps as quickly as possible to the most appropriate cell.

For the cell selection, the MS shall be able to select the correct (fourth strongest) cell and be able to respond to paging on that cell within 30 seconds of switch on, when the three strongest cells are not suitable. This assumes a valid SIM with PIN disabled and ideal radio conditions. This requirement is not applicable for multi-RAT mobile stations.

The tolerance on all the timing requirements in clause 6 is ± 10 %, except for PENALTY_TIME where it is ± 2 s.

6.2 Measurements for normal cell selection

The measurements of this clause shall be performed by an MS which has no prior knowledge of which RF channels are BCCH carriers.

The MS shall search all RF channels within its bands of operation, take readings of received RF signal level on each RF channel, and calculate the RLA_C for each. The averaging is based on at least five measurement samples per RF carrier spread over 3 to 5 s, the measurement samples from the different RF carriers being spread evenly during this period.

A multi band MS shall search all channels within its bands of operation as specified above. The number of channels searched will be the sum of channels on each band of operation.

BCCH carriers can be identified by, for example, searching for frequency correction bursts. On finding a BCCH carrier, the MS shall attempt to synchronize to it and read the BCCH data.

The maximum time allowed for synchronization to a BCCH carrier is 0.5 s, and the maximum time allowed to read the BCCH data, when being synchronized to a BCCH carrier, is 1.9 s or equal to the scheduling period for the BCCH data, whichever is greater (see 3GPP TS 05.02). The MS is allowed to camp on a cell and access the cell after decoding all relevant BCCH data.

6.3 Measurements for stored list cell selection

The MS may include optional storage of BCCH carrier information when switched off as detailed in 3GPP TS 03.22. For example, the MS may store the BCCH carriers in use by the PLMN selected when it was last active in network. The BCCH list may include BCCH carriers from more than one band in a multi band operation PLMN. A MS may also store BCCH carriers for more than one PLMN which it has selected previously (e.g. at national borders or when more than one PLMN serves a country), in which case the BCCH carrier lists must be kept quite separate.

The stored BCCH carrier information used by the MS may be derived by a variety of different methods. The MS may use the BA_RANGE information element, which, if transmitted in the channel release message (see 3GPP TS 04.18), indicates ranges of carriers which include the BCCH carriers in use over a wide area or even the whole PLMN. It should be noted that the BA(BCCH) list might only contain carriers in use in the vicinity of the cell on which it was broadcast, and therefore might not be appropriate if the MS is switched off and moved to a new location.

The BA_RANGE information element contains the Number of Ranges parameter (defined as NR) as well as NR sets of parameters RANGEi_LOWER and RANGEi_HIGHER. The MS should interpret these to mean that all the BCCH carriers of the network have ARFCNs in the following ranges:

Range1 = ARFCN(RANGE1_LOWER) to ARFCN(RANGE1_HIGHER);
Range2 = ARFCN(RANGE2_LOWER) to ARFCN(RANGE2_HIGHER);
RangeNR = ARFCN(RANGENR_LOWER) to ARFCN(RANGENR_HIGHER).

If RANGEi_LOWER is greater than RANGEi_HIGHER, the range shall be considered cyclic and encompasses carriers with ARFCN from range RANGEi_LOWER to 1 023 and from 0 to RANGEi_HIGHER. If RANGEi_LOWER equals RANGEi_HIGHER then the range shall only consist of the carrier whose ARFCN is RANGEi_LOWER.

If an MS includes a stored BCCH carrier list of the selected PLMN it shall perform the same measurements as in subclause 6.2 except that only the BCCH carriers in the list need to be measured.

NOTE: If the selected PLMN is equal to one of the equivalent PLMNs, then stored list cell selection applies to all equivalent PLMNs.

If stored list cell selection is not successful, then as defined in 3GPP TS 03.22, normal cell selection shall take place. Since information concerning a number of channels is already known to the MS, it may assign high priority to measurements on the strongest carriers from which it has not previously made attempts to obtain BCCH information, and omit repeated measurements on the known ones.

6.4 Criteria for cell selection and reselection

The path loss criterion parameter C1 used for cell selection and reselection is defined by:

C1 = (A ‑ Max(B,0))

where

A = RLA_C ‑ RXLEV_ACCESS_MIN
B = MS_TXPWR_MAX_CCH ‑ P

except for the class 3 DCS 1 800 MS where:

B = MS_TXPWR_MAX_CCH + POWER OFFSET ‑ P
RXLEV_ACCESS_MIN = Minimum received signal level at the MS required for access to the system.
MS_TXPWR_MAX_CCH = Maximum TX power level an MS may use when accessing the system until otherwise commanded.

POWER OFFSET = The power offset to be used in conjunction with the MS TXPWR
MAX CCH parameter by the class 3 DCS 1 800 MS.
P = Maximum RF output power of the MS.

All values are expressed in dBm.

The path loss criterion (3GPP TS 03.22) is satisfied if C1 > 0.

The reselection criterion C2 is used for cell reselection only and is defined by:

C2 = C1 + CELL_RESELECT_OFFSET ‑ TEMPORARY OFFSET * H(PENALTY_TIME ‑ T) for
PENALTY_TIME <> 11111
C2 = C1 ‑ CELL_RESELECT_OFFSET for PENALTY_TIME = 11111

where

For non‑serving cells:

H(x) = 0 for x < 0
= 1 for x 0

For serving cells:
H(x) = 0

T is a timer implemented for each cell in the list of strongest carriers (see subclause 6.6.1). T shall be started from zero at the time the cell is placed by the MS on the list of strongest carriers, except when the previous serving cell is placed on the list of strongest carriers at cell reselection. In this, case, T shall be set to the value of PENALTY_TIME (i.e. expired).

CELL_RESELECT_OFFSET applies an offset to the C2 reselection criterion for that cell.

NOTE: CELL_RESELECT_OFFSET may be used to give different priorities to different bands when multiband operation is used.

TEMPORARY_OFFSET applies a negative offset to C2 for the duration of PENALTY_TIME after the timer T has started for that cell.

PENALTY_TIME is the duration for which TEMPORARY_OFFSET applies. The all ones bit pattern on the PENALTY_TIME parameter is reserved to change the sign of CELL_RESELECT_OFFSET and the value of TEMPORARY_OFFSET is ignored as indicated by the equation defining C2.

CELL_RESELECT_OFFSET, TEMPORARY_OFFSET, PENALTY_TIME and CELL_BAR_QUALIFY (see table 1a) are optionally broadcast on the BCCH of the cell. If not broadcast, the default values are CELL_BAR_QUALIFY = 0, and C2 = C1. The use of C2 is described in 3GPP TS 03.22.

These parameters are used to ensure that the MS is camped on the cell with which it has the highest probability of successful communication on uplink and downlink.

The signal strength threshold criterion parameter C4 is used to determine whether prioritised LSA cell reselection shall apply and is defined by:

C4 = A – PRIO_THR

where

A is defined as above and PRIO_THR is the signal threshold for applying LSA reselection. PRIO_THR is broadcast on the BCCH. If the idle mode support is disabled for the LSA (see 3GPP TS 11.11) or if the cell does not belong to any LSA to which the MS is subscribed or if no PRIO_THR parameter is broadcast, PRIO_THR shall be set to .

6.5 Downlink signalling failure

The downlink signalling failure criterion is based on the downlink signalling failure counter DSC. When the MS camps on a cell, DSC shall be initialized to a value equal to the nearest integer to 90/N where N is the BS_PA_MFRMS parameter for that cell (see 3GPP TS 05.02). Thereafter, whenever the MS attempts to decode a message in its paging subchannel; if a message is successfully decoded (BFI = 0) DSC is increased by 1, however never beyond the initial value, otherwise DSC is decreased by 4. When DSC  0, a downlink signalling failure shall be declared.

For GPRS, an MS in packet idle mode shall follow the same procedure. The counter DSC shall be initialized each time the MS leaves packet transfer mode. In case DRX period split is supported, DSC shall be initialized to a value equal to the nearest integer to max(10, 90* NDRX), where NDRX is the average number of monitored blocks per multiframe according to its paging group (see 3GPP TS 05.02). In non-DRX mode, the MS shall only increment/decrement DSC for one block per DRX period according to its paging group. The exact position of these blocks is not essential, only the average rate.

NOTE: The network sends the paging subchannel for a given MS every BS_PA_MFRMS multiframes or, in case DRX period split is supported, every 1/NDRX multiframes. The requirement for network transmission on the paging subchannel is specified in 3GPP TS 04.18 or 3GPP TS 04.60. The MS is required to attempt to decode a message every time its paging subchannel is sent.

A downlink signalling failure shall result in cell reselection.

6.6 Measurements for Cell Reselection

Upon completion of cell selection and when starting the cell reselection tasks, the MS shall synchronize to and read the BCCH information for the 6 strongest non‑serving carriers (in the BA) as quickly as possible within the times specified in subclause 6.6.1. For multi band MSs the strongest non‑serving carriers may belong to different frequency bands. If system information message type 2 ter or 2 quater is used in the serving cell, and the MS has decoded all relevant serving cell BCCH data, except system information message 2 ter and/or 2 quater, then the MS shall start cell reselection measurements based on the know part of the BA, until system information message 2 ter and/or 2 quater is decoded and the full BA can be used.

MSs supporting SoLSA with SoLSA subscription shall perform cell re-selection according to subclause 6.6.3. Other MSs shall perform cell re-selection according to subclause 6.6.2.

MSs supporting other radio access technologies shall also perform measurements and cell-reselection according to subclauses 6.6.4 and 6.6.5

6.6.1 Monitoring of received signal level and BCCH data

Whilst in idle mode an MS shall continue to monitor all BCCH carriers as indicated by the BCCH allocation (BA ‑ See table 1). A running average of received signal level (RLA_C) in the preceding 5 to:

Max {5 , ((5 * N + 6) DIV 7) * BS_PA_MFRMS / 4}

seconds shall be maintained for each carrier in the BCCH allocation. N is the number of non‑serving cell BCCH carriers in BA and the parameter BS_PA_MFRMS is defined in 3GPP TS 05.02.

The same number of measurement samples shall be taken for all non‑serving cell BCCH carriers of the BA list, and the samples allocated to each carrier shall as far as possible be uniformly distributed over each evaluation period. At least 5 received signal level measurement samples are required per RLA_C value. New sets of RLA_C values shall be calculated as often as possible.

For the serving cell, received signal level measurement samples shall be taken at least for each paging block of the MS. The RLA_C shall be a running average determined using samples collected over a period of 5 s to Max {5s, five consecutive paging blocks of that MS}. The samples shall as far as possible be uniformly distributed over each evaluation period. At least 5 received signal level measurement samples are required per RLA_C value. New RLA_C values shall be calculated as often as possible.

The list of the 6 strongest non‑serving carriers shall be updated at least as often as the duration of the running average defined for measurements on the BCCH allocation and may be updated more frequently.

In order to minimize power consumption, MS that employ DRX (i.e. power down when paging blocks are not due) should monitor the received signal levels of non‑serving cell BCCH carriers during the frames of the paging block that they are required to listen to. The MS shall include the BCCH carrier of the current serving cell (i.e. the cell the MS is camped on) in this measurement routine. Received signal level measurement samples can thus be taken on several non‑serving cell BCCH carriers and on the serving carrier during each paging block.

The MS shall attempt to decode the full BCCH data of the serving cell at least every 30 seconds or at least as often as possible in the case that system information scheduling period exceeds 30 seconds.

If SI13 is broadcast, the MS supporting change mark in SI13 (See 3GPP TS 04.18) is only required to confirm system information on the BCCH of the serving cell if indicated by change mark in SI13.

The MS shall attempt to decode the BCCH data block that contains the parameters affecting cell reselection for each of the 6 strongest non‑serving cell BCCH carriers at least every 5 minutes. When the MS recognizes that a new BCCH carrier has become one of the 6 strongest, the BCCH data shall be decoded for the new carrier within 30 seconds.

The MS shall attempt to check the BSIC for each of the 6 strongest non‑serving cell BCCH carriers at least every 30 seconds, to confirm that it is monitoring the same cell. If a change of BSIC is detected then the carrier shall be treated as a new carrier and the BCCH data re-determined.

In addition, an MS supporting SoLSA with SoLSA subscription shall attempt to decode BSIC and the BCCH data blocks that contain the parameters affecting SoLSA cell reselection for the 6 strongest carriers, which are included both in the BCCH allocation and in the BA_PREF as received in the latest CHANNEL RELEASE message (see 04.18). At least one carrier shall be searched every 5 minutes, one after another. In the case the MS has been able to decode the BCCH data blocks, the rules described in subclause 6.6.3 shall be followed.

When requested by the user, the MS shall determine which PLMNs are available (Manual Mode) or available and allowable (Automatic Mode) (see 3GPP TS 03.22) within 10 seconds (for GSM 450), 10 seconds (for GSM 480), 15 seconds (for GSM 850 and GSM 900) or 20 seconds (for DCS 1 800 and PCS 1 900). A multi band MS shall perform the same procedures in all bands of operation within the sum of time constraints in the respective band of operation.

In both cases, this monitoring shall be done so as to minimize interruptions to the monitoring of the PCH.

The maximum time allowed for synchronization to a BCCH carrier is 0,5 s, and the maximum time allowed to read the BCCH data, when being synchronized to a BCCH carrier, is 1,9 s or equal to the scheduling period for the BCCH data, whichever is greater (see 3GPP TS 05.02).

6.6.2 Path loss criteria and timings for cell re‑selection

The MS is required to perform the following measurements (see 3GPP TS 03.22) to ensure that the path loss criterion to the serving cell is acceptable.

At least every 5 s the MS shall calculate the value of C1 and C2 for the serving cell and re‑calculate C1 and C2 values for non-serving cells (if necessary). The MS shall then check whether:

i) The path loss criterion (C1) for current serving cell falls below zero for a period of 5 seconds. This indicates that the path loss to the cell has become too high.

ii) The calculated value of C2 for a non‑serving suitable cell exceeds the value of C2 for the serving cell for a period of 5 seconds, except;

a) in the case of the new cell being in a different location area or, for a GPRS MS, in a different routing area or always for a GPRS MS in ready state in which case the C2 value for the new cell shall exceed the C2 value of the serving cell by at least CELL_RESELECT_HYSTERESIS dB as defined by the BCCH data from the current serving cell, for a period of 5 seconds; or

b) in case of a cell reselection occurring within the previous 15 seconds in which case the C2 value for the new cell shall exceed the C2 value of the serving cell by at least 5 dB for a period of 5 seconds.

This indicates that it is a better cell.

Cell reselection for any other reason (see 3GPP TS 03.22) shall take place immediately, but the cell that the MS was camped on shall not be returned to within 5 seconds if another suitable cell can be found. If valid RLA_C values are not available, the MS shall wait until these values are available and then perform the cell reselection if it is still required. The MS may accelerate the measurement procedure within the requirements in subclause 6.6.1 to minimize the cell reselection delay.

If no suitable cell is found within 10 seconds, the cell selection algorithm of 3GPP TS 03.22 shall be performed. Since information concerning a number of channels is already known to the MS, it may assign high priority to measurements on the strongest carriers from which it has not previously made attempts to obtain BCCH information, and omit repeated measurements on the known ones.

6.6.3 Cell reselection algorithm for SoLSA

At least for every new sample or every second, whichever is the greatest, the MS calculate the value of C1, C2 and C4 for the serving cell and the non‑serving cells. The MS shall make a cell reselection if:

i) The path loss criterion parameter (C1) for the serving cell falls below zero for a period of 5 seconds.

ii) A non‑serving suitable cell (see 3GPP TS 03.22) is evaluated to be better than the serving cell for a period of 5 seconds. The best cell is

– the cell with the highest value of C2 + LSA_OFFSET among those cells that have highest LSA priority among those that fulfil the criteria C4  0, or

– the cell with the highest value of C2 among all cells, if no cell fulfil the criterion C4  0.

LSA_OFFSET and LSA ID(s) are broadcast on BCCH. LSA priority is defined by the list of LSAs for the subscriber stored on the SIM (see 3GPP TS 11.11). Cells with no LSA priority, eg non-LSA cells, are given LSA priority lower than 0. If no LSA_OFFSET parameter is broadcast, LSA_OFFSET shall be set to 0.

When evaluating the best cell, the following hysteresis values shall be subtracted from the C2 value for the neighbour cells:

– if the new cell is in the same location area: 0;

– if the new cell is in a different location area:
CELL_RESELECT_HYSTERESIS, which is broadcast on BCCH of the serving cell.

– in case of a cell reselection occurred within the previous 15 seconds: 5 dB.

Cell reselection for any other reason (see 3GPP TS 03.22) shall take place immediately, but the cell that the MS was camped on shall not be returned to within 5 seconds if another suitable cell can be found. If valid receive level averages are not available, the MS shall wait until these values are available and then perform the cell reselection if it is still required. The MS may accelerate the measurement procedure within the requirements in subclause 6.6.1 to minimise the cell reselection delay.

If no suitable cell is found within 10 seconds, the cell selection algorithm of 3GPP TS 03.22 shall be performed. Since information concerning a number of channels is already known to the MS, it may assign high priority to measurements on the strongest carriers from which it has not previously made attempts to obtain BCCH information, and omit repeated measurements on the known ones.

6.6.4 Measurements on cells of other radio access technologies

For a multi-RAT MS, cells or frequencies with other radio access technologies may be included in 3G Cell Reselection list (see 3GPP TS 04.18). The network controls the measurements for reselection of these cells by the parameter Qsearch_I broadcast on BCCH. Qsearch_I defines a threshold and also indicates whether these measurements shall be performed when RLA_C (see subclause 6.6.1) of the serving cell is below or above the threshold. These measurements may be performed less frequently than measurements of GSM cells as described in subclause 6.6.1, in order to conserve MS power.

The MS shall be able to identify and select a new best UTRAN cell on a frequency, which is part of the 3G Cell Reselection list, within 30 seconds after it has been activated under the condition that there is only one UTRAN frequency in the list and under good radio conditions. For test purposes the following radio conditions can be used: Serving GSM cell at RXLEV= -70 dBm, with 6 GSM neighbours at RXLEV= -75 dBm. Then either an UTRAN FDD neighbour cell or an UTRAN TDD neighbour cell is switched on. The radio conditions for the UTRAN FDD cell are as follows (see TS 25.101 for definitions):

Parameter

Unit

UTRAN FDD Cell

CPICH_Ec/Ior

dB

-10

PCCPCH_Ec/Ior

dB

-12

SCH_Ec/Ior

dB

-12

PICH_Ec/Ior

dB

-15

DPCH_Ec/Ior

dB

-

OCNS_Ec/Ior

dB

-0.94

dB

10

dBm/3.84 MHz

-70

CPICH_Ec/Io

dB

-10.4

CPICH RSCP

dBm

-70

FDD_Qoffset

integer

5 (-12dB)

FDD_Qmin

integer

7 (-12 dB)

Qsearch_I

integer

7 (search always)

Propagation Condition

AWGN

The radio conditions for the UTRAN TDD cell (3.84 Mcps) are as follows (see 3GPP TS 25.123 for definitions and for the values of the remaining configuration parameters):

Parameter

Unit

UTRA TDD Cell

(3.84 Mcps)

Timeslot Number

0

8

P-CCPCH_Ec/Ior

dB

-3

SCH_Ec/Ior

dB

-9

-9

SCH_toffset

integer

0

0

PICH_Ec/Ior

dB

-3

OCNS_Ec/Ior

dB

-3.12

-3.12

PCCPCH RSCP

dBm

-70

-70

TDD_Qoffset

integer

5 (-12 dB)

Qsearch_I

integer

7 (search always)

Propagation Condition

AWGN

NOTE: On timeslot 8 the P-CCPCH is not transmitted; on that timeslot, the PCCPCH RSCP defines the power level of the beacon channel.

The allowed time is increased by 30 seconds for each additional UTRAN frequency in the 3G Cell Reselection list. However, multiple UTRAN cells on the same frequency in the list does not increase the allowed time.

A multi-RAT MS shall be able to monitor 64 UTRAN cells, divided into (depending on the MS capability):

– FDD cells on up to 3 FDD frequencies, with a maximum of 32 cells per frequency; and/or
– TDD cells on up to 3 TDD frequencies with a maximum of 32 cells per frequency.

The MS shall attempt to read and store UTRAN predefined configurations using the rules defined in 3GPP TS 25.331 with the following exceptions:

– The MS shall build a list of at most 16 predefined configurations, read from the BCCH of the identified UTRAN cells of equivalent PLMNs.

– After PLMN selection (see 3GPP TS 23.122), the MS shall delete any old list of predefined configurations and as soon as possible attempt to read the predefined configurations from one identified UTRAN cell of the selected PLMN or of an equivalent PLMN.

– The MS shall attempt to update the list of predefined configurations every 60 minutes.

In case of a conflict with GSM tasks, the GSM tasks take precedence.

NOTE: Instead of reading new predefined configurations from a PLMN, the MS may use previously received predefined configurations for that PLMN according to the rules in 3GPP TS 25.331.

The MS shall report the list of predefined configurations in the UTRAN CLASSMARK CHANGE message (see 3GPP TS 04.18).

6.6.5 Algorithm for cell re‑selection from GSM to UTRAN

If the 3G Cell Reselection list includes UTRAN frequencies, the MS shall, at least every 5 s update the value RLA_C for the serving cell and each of the at least 6 strongest non-serving GSM cells.

The MS shall then reselect a suitable (see TS 25.304) UTRAN cell if:

– for a TDD cell the measured RSCP value exceeds the value of RLA_C for the serving cell and all of the suitable (see 3GPP TS 03.22) non-serving GSM cells by the value XXX_Qoffset for a period of 5 s and

– for an FDD cell the following criteria are all met for a period of 5 s:

  1. its measured RSCP value exceeds the value of RLA_C for the serving cell and all of the suitable (see 3GPP TS 03.22) non-serving GSM cells by the value XXX_Qoffset,
  2. its measured Ec/No value is equal or greater than the value FDD_Qmin, and
  3. its measured RSCP value is equal to or greater than FDD_RSCP_threshold, if supported by the MS.

In case of a cell reselection occurring within the previous 15 seconds, XXX_Qoffset is increased by 5 dB.

where

– Ec/No and RSCP are the measured quantities, see subclause 8.1.5.

– FDD_RSCP_threshold equals Qrxlevmin + Pcompensation + 10 dB, if these parameters are available, otherwise - (criterion not effective).

– Qrxlevmin is the minimum required RX level in the UTRAN FDD cell (dBm), see 3GPP TS 25.304.

– Pcompensation is max(UE_TXPWR_MAX_RACH – P_MAX, 0) (dB), see 3GPP TS 25.304.

– UE_TXPWR_MAX_RACH is the maximum TX power level an MS may use when accessing the UTRAN FDD cell on RACH (dBm), see 3GPP TS 25.304.

– P_MAX is the maximum RF output power of the MS (dBm) in UTRAN FDD mode, see 3GPP TS 25.304.

– FDD_Qmin and XXX_Qoffset are broadcast on BCCH of the serving cell. XXX indicates other radio access technology/mode.

Note: The parameters required to determine if the UTRAN cell is suitable are broadcast on BCCH of the UTRAN cell. An MS may start reselection towards the UTRAN cell before decoding the BCCH of the UTRAN cell, leading to a short interruption of service if the UTRAN cell is not suitable.

The MS may store the UTRAN cell RSCP suitability criterion parameters above, whenever decoded from a UTRAN FDD cell of an equivalent PLMN. The most recently decoded parameters are valid reselection criteria towards all UTRAN FDD cells. This list of parameters shall be cleared after PLMN selection (see 3GPP TS 23.122).

Cell reselection to UTRAN shall not occur within 5 seconds after the MS has reselected a GSM cell from an UTRAN cell if a suitable GSM cell can be found.

If more than one UTRAN cell fulfils the above criteria, the MS shall select the cell with the greatest RSCP value.

6.7 Release of TCH and SDCCH

6.7.1 Normal case

When the MS releases all TCHs or SDCCH and returns to idle mode or packet idle mode, it shall, as quickly as possible, camp on the cell whose channel has just been released. If the full (P)BCCH data for that cell was not decoded in the preceding 30s, the MS shall then attempt to decode the full (P)BCCH data. Until the MS has decoded the (P)BCCH data required for determining the paging group, it shall also monitor all paging blocks on timeslot 0 of the BCCH carrier or, for GPRS if PCCCH exists, on the PDCH indicated on BCCH for possible paging messages that might address it. If the MS receives a page before having decoded the full (P)BCCH data for the cell, the MS shall store the page and respond once the relevant (P)BCCH data has been decoded, provided that the cell is not barred and the MS’s access class is allowed. Reception of full BCCH(BA) information is not required before responding to the page.

If at the release of the connection the MS has the knowledge that the cell whose channel is being released is not suitable (see 3GPP TS 03.22), the MS is allowed to camp on any suitable cell.

NOTE: The received signal level measurements on surrounding cells made during the last 5 seconds on the TCH or SDCCH may be averaged and used, where possible, to speed up the process. However, it should be noted that the received signal level monitoring while on the TCH or SDCCH is on carriers in BA (SACCH), while the carriers to be monitored for cell reselection are in BA (BCCH) or BA (GPRS).

After decoding the relevant (P)BCCH data the MS shall perform cell reselection as specified in 3GPP TS 03.22.

6.7.2 Call re‑establishment

In the event of a radio link failure, call re‑establishment may be attempted (according to the procedure in 3GPP TS 04.18). The MS shall perform the following algorithm to determine which cell to use for the call re‑establishment attempt.

i) The received signal level measurement samples taken on the carriers indicated in the BA (SACCH) received on the serving cell and on the serving cell BCCH carrier in the last 5 seconds shall be averaged, and the carrier with the highest average received signal level with a permitted NCC as indicated on the SACCH of the serving cell (see subclause 7.2) shall be taken.

ii) On this carrier the MS shall attempt to decode the BCCH data block containing the parameters affecting cell selection.

iii) If the cell is suitable (see 3GPP TS 03.22) and call re‑establishment is allowed, call re‑establishment shall be attempted on this cell.

iv) If the MS is unable to decode the BCCH data block or if the conditions in iii) are not met, the carrier with the next highest average received signal level with a permitted NCC shall be taken, and the MS shall repeat steps ii) and iii) above.

v) If the cells with the 6 strongest average received signal level values with a permitted NCC have been tried but cannot be used, the call re‑establishment attempt shall be abandoned, and the algorithm of subclause 6.7.1 shall be performed.

The MS is under no circumstances allowed to access a cell to attempt call re‑establishment later than 20 seconds after the detection within the MS of the radio link failure causing the call re‑establishment attempt. In the case where the 20 seconds elapses without a successful call re‑establishment the call re‑establishment attempt shall be abandoned, and the algorithm of subclause 6.7.1 shall be performed.

Call re‑establishment shall not be applied for voice group calls.

6.8 Abnormal cases and emergency calls

When in the limited service state (see 3GPP TS 03.22) the aim is to gain normal service rapidly and the following tasks shall be performed, depending on the conditions, as given in the table below:

a) The MS shall monitor the received signal level of all RF channels within its bands of operation, and search for a BCCH carrier which has C1 > 0 and which is not barred. When such a carrier is found, the MS shall camp on that cell, irrespective of the PLMN identity.

b) The MS shall search the strongest RF channels to determine which PLMNs are available (Manual Mode) or available and allowable (Automatic Mode). This information shall be processed according to the PLMN selection algorithm defined in 3GPP TS 03.22.

c) The MS shall perform cell reselection at least among the cells of the PLMN of the cell on which the MS has camped, according to the algorithm of 3GPP TS 03.22, except that a zero value of CELL_RESELECT_HYSTERESIS shall be used.

Condition

Tasks to be performed as a minimum:

SIM Present

Other

MS camped on a cell

a)

b)

c)

X

X

No

Yes

No

No

No

X

Yes

No

No

Yes

Yes

"IMSI Unknown", "illegal MS"

Yes

No

No

Yes

Yes

No suitable cell of selected PLMN

or "PLMN not allowed"

Yes

No

Yes

Yes

NOTE: X = "Don’t care state".

In this mode, only emergency calls may be made (and these may only be made if task c) was being performed). Powering down of the MS is permitted.