4.3.33 Support for Multi-USIM UE

23.4013GPPGeneral Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) accessRelease 18TS

4.3.33.1 General

A network and a Multi-USIM UE may support one or more of the following features for Multi-USIM UE operation:

– Connection Release, as described in clause 4.3.33.2.

– Paging Cause Indication for Voice Service, as described in clause 4.3.33.3.

– Reject Paging Request, as described in clause 4.3.33.4.

– Paging Timing Collision Control, as described in clause 4.3.33.5.

– Paging Restriction, as described in clause 4.3.33.6.

In the Attach procedure (as specified in clause 5.3.2.1), or in the Tracking Area Update procedure (as specified clause 5.3.3), when a Multi-USIM UE has more than one USIM active, supports and intends to use one or more Multi-USIM specific features, it indicates to the MME the corresponding Multi-USIM feature(s) are supported. Based on the received indication of supported Multi-USIM features from the UE, the MME shall indicate to the UE the support of the Multi-USIM features based on the Multi-USIM features supported by network and any preference policy by the network, if available. When a UE returns to having only one USIM active from a Multi-USIM UE that previously indicated to the network it supported Multi-USIM feature(s), the UE shall indicate all the Multi-USIM features are not supported to the network for that USIM. The MME shall only indicate the support of Paging Restriction feature together with the support of either Connection Release feature or Reject Paging Request feature.

The Multi-USIM UE includes the support of individual features for Connection Release, Paging Cause Indication for Voice Service, Reject Paging Request and Paging Restrictions as specified in clause 5.11.3.

The network shall not indicate support for any Multi-USIM feature to the UE as part of the Emergency Attach procedure or as part of Tracking Area Update for Emergency attached UE.

A Multi-USIM UE shall use a separate IMEI for each USIM when it registers with the network.

4.3.33.2 Connection Release

A Multi-USIM UE may request to be released to ECM-IDLE state for a USIM due to activity on another USIM if both the UE and the network indicate to each other the Connection Release feature is supported. A Multi-USIM UE indicates that it requests to be released to ECM-IDLE state for the USIM by initiating the Service Request procedure (using Extended Service Request message) or a Tracking Area Update procedure if the UE needs to perform Tracking Area Update at the same time with this network (including the case where the Tracking Area Update is performed due to mobility to a Tracking Area outside the current Tracking Area List, i.e. before detecting whether the network supports the feature in the new Tracking Area, provided that the network has already indicated support for Connection Release feature in the current Tracking Area List), by including a Release Request indication. If supported by the UE and network, the UE may also provide, together with the Release Request indication, Paging Restriction Information, as specified in clause 4.3.33.6, which requests the network to restrict paging.

NOTE: When there is no PLMN-wide support for the Connection Release feature, it can occur that upon tracking area update with Release Request indication the UE is not released by the network. The UE behaviour, when it detects that the network does not support the feature in a new TA, is outside the scope of this specification.

4.3.33.3 Paging Cause Indication for Voice Service

A Multi-USIM UE and the network may support the Paging Cause Indication for Voice Service feature.

The MME that supports Paging Cause Indication for Voice Service feature should provide a Voice Service Indication in the S1AP Paging message for the MMTel voice service, only if the UE indicates the Paging Cause Indication for Voice Service feature is supported. The MME determines the downlink data triggering the paging is related to a MMTel voice service based on the Paging Policy Indicator as specified in clause 4.9 for MMTel voice.

NOTE: The indication of CS voice in the CN domain indication in S1AP paging message and Uu paging message is not modified by the Paging Cause Indication for Voice Service feature.

Upon reception of the Voice Service Indication in S1AP Paging Message, an eNodeB that supports the Paging Cause Indication for Voice Service should include the Voice Service Indication the Uu Paging message to the UE.

A UE that supports the Paging Cause Indication for Voice Service feature is capable of differentiation between Paging from a network that does not support the Paging Cause Indication for Voice Service feature and Uu Paging without the Voice Service Indication. How the UE distinguishes the Paging from a RAN that does not support the Paging Cause Indication for Voice Service feature and Paging without the Voice Service Indication is defined in TS 36.331 [37]. The UE determines whether the Paging Cause Indication for Voice Service feature is supported in the current Tracking Area by EPC based on the MUSIM capability exchange with the MME, see clause 4.3.33.1. The UE determines that the Paging Cause Indication for Voice Service feature is supported if it is supported by both the RAN, as indicated in the received Uu Paging message, and by EPC, as indicated in the MUSIM capability exchange with the MME.

The UE uses the Paging Cause Indication for Voice Service as described in TS 24.301 [46] and TS 36.331 [37].

4.3.33.4 Reject Paging Request

A Multi-USIM UE may respond to a page for a USIM with an indication to the MME that the UE does not accept the paging and requests to be released to ECM-IDLE state after sending this response, if both UE and network indicate to each other the Reject Paging Request feature is supported.

Upon being paged, the Multi-USIM UE attempts to send an Extended Service Request message to the paging network including the Reject Paging Indication as the response to the paging, unless it is unable to do so, e.g. due to UE implementation constraints. In addition to the Reject Paging Indication, the UE may include Paging Restriction Information as specified in clause 4.3.33.6 in the Extended Service Request message, if the Paging Restrictions are supported by UE and network.

4.3.33.5 Paging Timing Collision Control

To avoid possible paging occasion collision and to enhance the likelihood that paging is received successfully for different USIMs, a Multi-USIM UE may provide, for at least one USIM, a Requested IMSI Offset value that is used for the determination of paging occasions. Upon reception of a Requested IMSI Offset value from UE in Attach Request or Tracking Area Update Request, a supporting MME provides an Accepted IMSI Offset value to the UE in the Attach Accept or Tracking Area Update Accept message to acknowledge it supports the feature and provide the accepted value. The Accepted IMSI Offset Value may be different from the Requested IMSI Offset provided by the UE. The Alternative IMSI value, determined as below, is stored in the UE context in the MME. If the UE does not provide any Requested IMSI Offset value in Attach Request or Tracking Area Request, the MME removes any stored Alternative IMSI value in the UE context. The UE and the network use the Accepted IMSI Offset to determine the paging occasion. The UE and MME use the Accepted IMSI Offset value to calculate the Alternative IMSI value that is determined based on UE’s IMSI as follows:

Alternative IMSI value = [MCC] [MNC] [(MSIN value + Accepted IMSI Offset) mod (MSIN address space)]

where: the MCC, MNC and MSIN value are the fields of the UE’s IMSI as defined in TS 23.003 [9].

The MME uses the Alternative IMSI value to compute the UE Identity Index Value. The MME sends the UE Identity Index Value to RAN in the Paging message (see TS 36.413 [36]) for RAN to derive the paging occasions according to TS 36.304 [34].

The UE uses the Alternative IMSI value for the determination of paging occasions as specified in TS 36.304 [34].

NOTE 1: It is recommended to avoid excessive signalling load from UE due to this procedure.

NOTE 2: The MME does not remove Alternative IMSI value if the Tracking Area Update Request is for periodic Tracking Area Update.

4.3.33.6 Paging Restriction

A Multi-USIM UE and the network may support Paging Restriction. A Multi-USIM UE, if the MME indicates that the network supports Paging Restriction feature, may indicate Paging Restriction Information in an Extended Service Request or a Tracking Area Update Request (including the case where the Tracking Area Update is performed due to mobility to a Tracking Area outside the current Tracking Area List, i.e. before detecting whether the network supports the feature in the new Tracking Area, provided that the network has already indicated support for Paging Restrictions in the current Tracking Area List), as specified in clauses 4.3.33.2 and 4.3.33.4.

The MME may accept or reject the Paging Restriction Information requested by the UE. If the MME accepts the Paging Restriction Information from the UE, the MME stores the Paging Restriction Information from the UE in the UE context. If the MME rejects the Paging Restriction Information the MME removes any stored Paging Restriction Information from the UE context and discards the UEs requested Paging Restriction Information. The MME informs the UE about the acceptance/rejection of the requested Paging Restriction Information in the Tracking Area Update Accept or Service Accept message.

If the UE does not provide Paging Restriction Information in the Extended Service Request message or the Tracking Area Update Request message, or if the UE initiates the Service Request procedure, the MME removes any stored Paging Restriction Information from the UE context.

The Paging Restriction Information may indicate any of the following:

a) all paging is restricted, or

b) all paging is restricted, except paging for voice service (MMTel voice or CS domain voice), or

c) all paging is restricted, except for certain PDN Connection(s), or

d) all paging is restricted, except for certain PDN Connection(s) and voice service (MMTel voice or CS domain voice).

NOTE 1: The UE expects not to be paged for any purpose in case a). The UE expects to be paged only for voice service in case b). The UE expects to be paged only for certain PDN Connection(s) in case c). The UE expects be paged for voice service and certain PDN Connection(s) in case d). The MME can page the UE for mobile terminated signalling based on local policy considering the stored Paging Restriction Information, except for case a). In this case, to comply with UE provided Paging Restriction Information, the MME can trigger S1 release procedure as soon as possible after the mobile terminated signalling procedure is executed.

NOTE 2: In the case of roaming, the paging restrictions for voice service implied by bullet b) and d) depends on the existence of an agreement with the HPLMN to support voice service via IMS. Hence the support of paging restrictions in bullets b) and d) takes the IMS voice service agreement into consideration.

NOTE 3: When there is no PLMN-wide support for the Paging Restriction feature, it can occur that upon Tracking Area Update due to mobility with Paging Restriction Information the UE detects the network does not support the feature. If so, the UE assumes that no Paging Restriction is applied.