Improvements in and relating to multi-USIM operation in a user equipment

Abstract

A method of operating a User Equipment, UE, with Multi-Universal Subscriber Identity Module, Multi-USIM, capability, wherein if the UE is in a non-allowed area and encounters or receives a trigger for

Description

The present invention relates to improvements in the configuration and operation of a mobile device or User Equipment, UE, which has Multi-USIM capability. USIM is a UMTS Subscriber Identify Module, effectively a module within a UE which serves as an identifier of the UE. A Multi-USIM, MUSIM, UE is a UE that supports more than one USIM and hence can be simultaneously registered to multiple Public Land Mobile Networks, PLMNs. When this is the case, the multiple registrations can lead to the UE switching between the PLMNs for the purpose of getting a particular service e.g. voice service. The UE can send some information to a serving network (e.g. the Access and Mobility Management Function, AMF, of the network) which helps determine the UE’s preferences with respect to MUSIM operations. For example, the UE may send a so called ‘paging restriction’ to inform the network about whether the UE would prefer to be paged, or whether paging should be restricted for all or some services, etc. The description of some relevant MUSIM features is shown below from 3GPP TR 23.752 VO.5.0: “5.38 Support for Multi-USIM UE 5.38.1 General A network and a UE may support one or more of the following enhancements for Multi-USIM UE operation: Connection release as described in clause 5.38.2; Paging Cause Indication for Voice Service, as described in clause 5.38.3; Reject paging request, as described in clause 5.38.4; Paging Restriction, as described in clause 5.38.5. In the Registration procedure (as specified in clause 4.2.2.2.2), 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 AMF the corresponding Multi-USIM feature(s) are supported. Based on the received indication of supported Multi-USIM features from the UE, the AMF 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 turns to have only one USIM active from a Multi-USIM UE that previously indicated to the network for the USIM with supported Multi-USIM feature(s), the UE shall indicate all the Multi-USIM features are not supported to the network for the USIM. The AMF shall indicate the support of Paging Restriction feature together with the support of either Connection Release feature or Reject Paging feature. The Multi-MUSIM UE includes the support of individual features for Connection release, Paging Cause Indication for Voice Service, Reject paging request and Paging Restriction as specified in clause 5.4.4a. A Multi-USIM UE shall use a separate PEI for each USIM when it registers to the network. 5.38.2 Connection release A Multi-USIM UE may request the network to release the UE from RRC-CONNECTED state for a USIM due to activity on another USIM, if both UE and network indicate this feature is supported to each other. The UE indicates that it requests to be released from RRC-CONNECTED state, by initiating either a Service Request procedure or a Registration procedure (in case the UE needs to perform Registration Update at the same time with this network), including a Release Indication. If supported by the UE, the UE may also provide, only together with the Release Indication, a Paging Restriction Information, as specified in clause 5.38.5, which requests the network to restrict paging. The Paging Restriction Information from the UE is stored in the UE context in the AMF. If no Paging Restriction Information is provided in the Service Request or the Registration Request, any stored Paging Restriction Information in the UE context is removed. When the UE initiates a Service Request procedure or Registration procedure without providing a Release Indication, the network removes any stored Paging Restriction Information. NOTE: When there is no PLMN-wide support for the Connection Release feature, it can occur that upon mobility update with Connection Release request 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 RA, is outside the scope of this specification. Editor's note: It is FFS if the connection release is performed via AS procedure for NR connects to 5GC. 5.38.3 Paging cause indication for voice service The UE and the network may support Paging Cause Indication for Voice Service feature. The network that supports Paging Cause Indication for Voice Service feature shall provide a Voice Service Indication for IMS voice service in the Paging message, only if the UE indicates the Paging Cause Indication for Voice Service feature is supported to the network. The network determines the IMS voice service based on the Paging Policy Indicator as specified in clause 5.4.3.2. Upon reception of the Voice Service Indication in NGAP Paging Message from AMF, the NG-RAN supporting Paging Cause Indication for Voice Service should include the Voice Service Indication in the Uu Paging message to the UE. When the UE context indicates Paging Cause Indication for Voice Service feature is supported, in order to require NG RAN to deliver the Voice Service Indication in RAN paging for UE in RRC-lnactive state, the AMF provides an indication indicating the Paging Cause Indication for Voice Service feature is supported to the NG-RAN. Upon reception the indication, the NG-RAN supporting the Paging Cause Indication for Voice Service indication feature stores it into the UE context. For a UE in RRC-lnactive, the NG-RAN should provide the Voice Service Indication in the RAN Paging message only when there is Paging Cause Indication for Voice Service indication in the UE context and detects the downlink data which triggers the RAN Paging message is related to voice service based on the Paging Policy Indicator, in the header of the received downlink data, as specified in clause 5.4.3.2. 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 Paging without the Voice Service Indication. Editor's note: How the UE can distinguish the Paging from a network that does not support the Paging Cause Indication for Voice Service feature and Paging without the Voice Service Indication depends upon RAN's decision. 5.38.4 Reject paging request A Multi-USIM UE may setup connection to respond to a page with a Reject Paging Indication to the network indicating that the UE does not accept the paging and requests to return to CM-IDLE state after sending this response, if both UE and network indicate this feature is supported to each other. Upon being paged by the network, the Multi-USIM UE in CM-IDLE state attempts to send a Service Request message to this network including the Reject Paging Indication, 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 5.38.5 in the Service Request message, if supported by UE. 5.38.5 Paging restriction The UE and the network may support Paging Restriction. The UE, if the AMF indicates that the network supports Paging Restriction feature, may indicate Paging Restriction Information in the Service Request or Registration Request message as specified in clauses 5.38.2 and 5.38.4. 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 (IMS voice); or c) all paging is restricted, except for certain PDU Session(s); or d) all paging is restricted, except paging for voice service (IMS voice) and certain PDU session(s). 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 PDU Session(s) in case c). The UE expects to be paged for voice service and certain PDU session(s) in case d). 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.” Other details regarding the UE behaviour with respect to the MUSIM feature can be found in TS 24.501. The detailed UE behaviour when it is in a restricted service area is shown below from 3GPP TS 23.501: “The service area restrictions consist of tracking areas forming either an allowed area, or a non-allowed area. The tracking areas belong to either the registered PLMN or its equivalent PLMNs in the registration area. The allowed area can contain up to 16 tracking areas or include all tracking areas in the registered PLMN and its equivalent PLMN(s) in the registration area. The non-allowed area can contain up to 16 tracking areas. The network conveys the service area restrictions to the UE by including either an allowed area, or a non-allowed area, but not both, in the Service area list IE of a REGISTRATION ACCEPT message or a CONFIGURATION UPDATE COMMAND message. If the network does not convey the service area restrictions to the UE in the Service area list IE of a REGISTRATION ACCEPT message, the UE shall treat all tracking areas in the registered PLMN and its equivalent PLMN(s) in the registration area as allowed area and delete the stored list of "allowed tracking areas" or the stored list of "non-allowed tracking areas". When the UE receives a Service area list IE with an allowed area indication during a registration procedure or a generic UE configuration update procedure: a) if the "Type of list" included in the Service area list IE does not indicate "all TAIs belonging to the PLMNs in the registration area are allowed area", the UE shall delete the old list of "allowed tracking areas" and store the tracking areas in the allowed area as the list of "allowed tracking areas". If the UE has a stored list of "non-allowed tracking areas", the UE shall delete that list; or b) if the "Type of list" included in the Service area list IE indicates "all TAIs belonging to the PLMNs in the registration area are allowed area", the UE shall treat all tracking areas in the registered PLMN and its equivalent PLMN(s) as allowed area and delete the stored list of "allowed tracking areas" or the stored list of "non-allowed tracking areas". When the UE receives a Service area list IE with a non-allowed area indication during a registration procedure or a generic UE configuration update procedure, the UE shall delete the old list of "non-allowed tracking areas" and store the tracking areas in the nonallowed area as the list of "non-allowed tracking areas". If the UE has a stored list of "allowed tracking areas", the UE shall delete that list. If the UE is successfully registered to a PLMN and has a stored list of "allowed tracking areas": a) while camped on a cell whose TAI is in the list of "allowed tracking areas", the UE shall stay in, or enter, the state 5GMM-REGISTERED.NORMAL-SERVICE and is allowed to initiate any 5GMM and 5GSM procedures; and b) while camped on a cell which is in the registered PLMN or a PLMN from the list of equivalent PLMNs and whose TAI is not in the list of "allowed tracking areas", the UE shall enter the state 5GMM-REGISTERED.NON-ALLOWED-SERVICE, and: 1) if the UE is in 5GMM-IDLE mode or 5GMM-IDLE mode with suspend indication over3GPP access, the UE: i) shall not include the Uplink data status IE in the registration procedure for mobility and periodic registration update except for emergency services or for high priority access; ii) shall not perform the registration procedure for mobility and periodic registration update with Follow-on request indicator set to "Follow-on request pending", except for: emergency services; high priority access; indicating a change of 3GPP PS data off UE status; sending an SOR transparent container; sending a UE policy container; or sending a UE parameters update transparent container; iii) shall not initiate a service request procedure or request the lower layers to resume a suspended connection, except for: emergency services; emergency services fallback; high priority access; responding to paging; responding to notification received over non-3GPP access; indicating a change of 3GPP PS data off UE status; sending an SOR transparent container; sending a UE policy container; or sending a UE parameters update transparent container; and 2) if the UE is in 5GMM-CONNECTED mode or 5GMM-CONNECTED mode with RRC inactive indication over 3GPP access, the UE: i) shall not perform the registration procedure for mobility and periodic registration update with Uplink data status IE except for emergency services or for high priority access; ii) shall not initiate a service request procedure except for: emergency services; emergency services fallback; high priority access; responding to paging or responding to notification received over non-3GPP access; iii) shall not initiate a 5GSM procedure except for: emergency services; high priority access; or indicating a change of 3GPP PS data off UE status; and iv) shall not perform the NAS transport procedure except for the sending: SMS; an LPP message; a location services message; an SOR transparent container; a UE policy container; a UE parameters update transparent container; or a CloT user data container. NOTE 1: The contents of CloT user data container can be data that is not for exception reports, or data that is for exception reports if allowed for the UE (see subclause 6.2.13). If the UE is successfully registered to a PLMN and has a stored list of "non-allowed tracking areas": a) while camped on a cell which is in the registered PLMN or a PLMN from the list of equivalent PLMNs and whose TAI is not in the list of "non-allowed tracking areas", the UE shall stay in, or enter, the state 5GMM-REGISTERED.NORMAL-SERVICE and is allowed to initiate any 5GMM and 5GSM procedures; and b) while camped on a cell whose TAI is in the list of "non-allowed tracking areas", the UE shall enter the state 5GMM-REGISTERED.NON-ALLOWED-SERVICE, and: 1) if the UE is in 5GMM-IDLE mode or 5GMM-IDLE mode with suspend indication over 3GPP access, the UE: i) shall not include the Uplink data status IE in the registration procedure for mobility and periodic registration update except for emergency services or for high priority access; ii) shall not perform the registration procedure for mobility and periodic registration update with Follow-on request indicator set to "Follow-on request pending", except for: emergency services; high priority access; indicating a change of 3GPP PS data off UE status; sending an SOR transparent container; sending a UE policy container; or sending a UE parameters update transparent container; and iii) shall not initiate a service request procedure or request the lower layers to resume a suspended connection, except for: emergency services; emergency services fallback; high priority access; responding to paging; responding to notification received over non-3GPP access; indicating a change of 3GPP PS data off UE status; sending an SOR transparent container; sending a UE policy container; or sending a UE parameters update transparent container; and 2) if the UE is in 5GMM-CONNECTED mode or 5GMM-CONNECTED mode with RRC inactive indication over 3GPP access, the UE: i) shall not perform the registration procedure for mobility and registration update with the Uplink data status IE except for emergency services or for high priority access; ii) shall not initiate a service request procedure or request the lower layers to resume a suspended connection, except for: emergency services; emergency services fallback; high priority access; or responding to paging or responding to notification received over non-3GPP access; iii) shall not initiate a 5GSM procedure except for: emergency services; high priority access; or indicating a change of 3GPP PS data off UE status; and iv) shall not perform the NAS transport procedure except for the sending: SMS; an LPP message; a location services message; an SOR transparent container; a LJE policy container; a UE parameters update transparent container; or a CloT user data container. NOTE 2: The contents of CloT user data container can be data that is not for exception reports, or data that is for exception reports if allowed for the UE (see subclause 6.2.13). The list of "allowed tracking areas", as well as the list of "non-allowed tracking areas" shall be erased when: a) the UE is switched off; and b) the UICC containing the USIM is removed or an entry of the "list of subscriber data" with the SNPN identity of the SNPN is updated. When a tracking area is added to the list of "5GS forbidden tracking areas for roaming" or to the list of "5GS forbidden tracking areas for regional provision of service" as specified in the subclauses 5.5.1.2.5 or 5.5.1.3.5, the tracking area shall be removed from the list of "allowed tracking areas" if the tracking area is already present in the list of "allowed tracking areas" and from the list of "non-allowed tracking areas" if the tracking area is already present in the list of "non-allowed tracking areas".” As can be seen from the above, the UE in a non-allowed area is restricted from initiating a service request procedure except in response to paging, or for emergency services, or if the UE is a high priority UE. The specification in 3GPP TS 23.501 defines the handling of NAS congestion at both the mobility management and the session management levels. The following is specified in 3GPP TS 23.501 about congestion handling on the mobility management level: “5.3. 9 Handling of NAS level mobility management congestion control The AMF may detect 5GMM signalling congestion and perform general NAS level congestion control. Under the 5GMM signalling congestion conditions the AMF may reject 5GMM signalling requests from UEs as specified in 3GPP TS 23.501 [8], The AMF should not reject the following: a) requests for emergency services; b) requests for emergency services fallback; c) requests from UEs configured for high priority access in selected PLMN; d) DEREGISTRATION REQUEST message; e) requests for mobile terminated services, triggered by paging or a notification procedure; and f) requests for initial registration or mobility and periodic registration update, when emergency is indicated by lower layers. When general NAS level congestion control is active, the AMF may include a value for the mobility management back-off timer T3346 in the reject messages. The UE starts the timer T3346 with the value received in the 5GMM reject messages. To avoid that large numbers of UEs simultaneously initiate deferred requests, the AMF should select the value for the timer T3346 for the rejected UEs so that timeouts are not synchronised. If the UE is registered in the same PLMN over the 3GPP access and non-3GPP access, and the UE receives the timer T3346 from the AMF, the timer T3346 shall apply to both 3GPP access and non-3GPP access. If the UE receives the paging message or NOTIFICATION message when timer T3346 is running and the UE is registered to the same PLMN over 3GPP access and non-3GPP access, the UE shall stop the timer T3346 for both accesses and respond to the paging message or NOTIFICATION message as specified in subclause 5.6.2 and subclause 5.6.3. NOTE 1: As an implementation option, MUSIM-capable UE is allowed to not respond to paging based on the information available in the paging message, e.g. voice service indication. If the timer T3346 is running when the UE enters state 5GMM-DEREGISTERED, the UE remains switched on, and the USIM in the UE remains the same, then the timer T3346 is kept running until it expires or it is stopped. If the UE is switched off when the timer T3346 is running, the UE shall behave as follows when the UE is switched on and the USIM in the UE remains the same: let t1 be the time remaining for T3346 timeout at switch off and let t be the time elapsed between switch off and switch on. Ift1 is greater than t, then the timer shall be restarted with the value t1 -1. If t1 is equal to or less than t, then the timer need not be restarted. If the UE is not capable of determining t, then the UE shall restart the timer with the value t1. If the UE enters a new PLMN while timer T3346 is running, and the new PLMN is not equivalent to the PLMN where the UE started timer T3346, the UE shall stop timer T3346 when initiating 5GMM procedures in the new PLMN. After a change in registration area, if the timer T3346 is running and 5GS update status is 5U1 UPDATED then the UE shall set the 5GS update status to 5U2 NOT UPDATED and enter state 5GMM-REGISTERED.ATTEMPTING-REGISTRATION-UPDATE. If timer T3346 is running or is deactivated, and the UE is a UE configured for high priority access in selected PLMN, or the UE needs to initiate signalling for emergency services or emergency services fallback, then the UE is allowed to initiate 5GMM procedures. NOTE 2: UE can, based on implementation, restrict lower layers of non-3GPP access from establishing access stratum connection on a registered PLMN when timer T3346 is running for the same PLMN.” When the NAS back-off (BO) timer is running, the UE is not allowed to initiate a procedure e.g. service request, unless if the procedure is triggered by certain events such as a need to request emergency services. Service gap control is (SGC) is a feature that enables the network to control the frequency of mobile originated (MO) requests forthe purpose of sending data. The network uses a SGC timer which determines the duration of time between consecutive MO requests. For example, after the UE registers with the network, the network may provide a SGC timer to the UE. The UE starts the timer after it transitions from 5GMM-CONNECTED mode to 5GMM-IDLE mode, after which the UE is not permitted to perform MO requests except for certain exceptions. However, when the timer expires, the UE can transition from 5GMM-IDLE mode to 5GMM-CONNECTED mode for MO data transfer. The following is specified in 3GPP TS 23.501 about SGC: “Service gap control (SGC) only applies to 3GPP access. The network may control the frequency with which UEs can transition from 5GMM-IDLE mode to 5GMM-CONNECTED mode via the SGC as specified in 3GPP TS 23.501 [8] and 3GPP TS 23.502 [9], If the network supports SGC and the service gap time value i.e. T3447 value is available in the 5GMM context of the UE, the AMF shall consider SGC as active for the UE. The UE and the network negotiate usage of SGC during the registration procedure for initial registration and registration procedure for mobility and periodic registration update: the UE supporting SGC indicates its support in the REGISTRATION REQUEST message. If the UE supports SGC and the SGC is active for the UE, the AMF includes T3447 value IE in the REGISTRATION ACCEPT message (see subclause 5.5.1.2 and subclause 5.5.1.3). The UE stores the T3447 value; and for UEs that do not support SGC when the network rejects mobility management signalling requests because SGC is active in the network, the mechanism for general NAS level mobility management congestion control as specified in subclause 5.3.9 applies. The network can provide a new T3447 value to the UE to be used next time it is started or stop timer T3447 in the UE if running with the Generic UE configuration update procedure as specified in subclause 5.4.4. The UE shall start timer T3447 when the N1 NAS signalling connection is released and if: the UE supports SGC, and the T3447 value is available in the UE and does not indicate zero; and the N1 NAS signalling connection released was not established for: paging; registration procedure for initial registration with Follow-on request indicator set to "No follow-on request pending"; registration procedure for mobility and periodic registration update with Follow-on request indicator set to "No follow-on request pending" and without Uplink data status IE included; requests for emergency services; or requests for exception data reporting. If the SGC is active in the network, after the UE transitions from 5GMM-CONNECTED mode to 5GMM-IDLE mode except when the UE was in 5GMM-CONNECTED mode due to: paging; registration procedure for initial registration with Follow-on request indicator set to "No follow-on request pending"; registration procedure for mobility and periodic registration update with Follow-on request indicator set to "No follow-on request pending" and without Uplink data status IE included, requests for emergency services; or requests for exception data reporting, the network shall start timer T3447 if not already running: with the T3447 value available in the 5GMM context minus 4 minutes, if the UE supports SGC and the T3447 value has been sent to the UE with a non-zero value; or with the T3447 value available in the 5GMM context if the UE does not support SGC. When timer T3447 is running, the network allows: requests for emergency service; requests for emergency services fallback; requests for high priority access; requests for exception data reporting; registration procedure for initial registration with Follow-on request indicator set to "No follow-on request pending"; registration procedure for mobility and periodic registration update without Uplink data status IE included and with Follow-on request indicator set to "No follow-on request pending"; or service request procedure or registration procedure for mobility and periodic registration update triggered by paging and subsequent MO signalling or MO data, if any, until the UE enters 5GMM-IDLE mode. The UE or the network with a running T3447 timer keeps the timer running when the UE transits from 5GMM-IDLE mode to 5GMM-CONNECTED mode.” From the above, it can be concluded that when the SGC timer (i.e. T3447) expires and the UE goes to connected mode for MO data or signalling, the UE will start T3447 upon transition to idle mode again. A first issue with the prior art relates to the MUSIM feature due to the UE’s presence in a restricted service area. This MUSIM feature requires the UE to communicate with the network for its correct operations. For example, the UE sends the Service Request message to set the desired paging restrictions which directly impact paging and hence the user’s experience and service delays. As such, it is important for the UE to be able to communicate the necessary parameters, as soon as they become available e.g. based on the user’s preferences, with the network so that the services can be obtained as required with minimal impacts to the user’s experience and minimal service delays. The problem may be set out as follows. When the UE is in a restricted area, the UE is currently restricted from initiating a service request procedure except for emergency services, etc. As the current exceptions do not include the MUSIM feature, the UE will not be able to set its preferred paging restrictions or delete the stored paging restrictions (also referred to as paging restriction information) and this will negatively impact the user’s experience when the UE is in a restricted service area. A second issue with the prior art is related to the MUSIM feature due to NAS congestion. The UE may have a 5GMM back-off (BO) time running due to congestion in the network. While the timer is running, the UE is prohibited from sending NAS messages to the network except if there is a need to request emergency services. However, this will also negatively impact the user’s experience, since there is no exception that has been defined for MUSIM i.e. when the 5GMM BO timer is running, the UE will not be able to set its preferences for MUSIM or delete the stored paging restrictions (also referred to as paging restriction information) and this can have negative impacts to the user’s experience. A third issue with the prior art relates to the MUSIM feature due to Service Gap Control. The UE with a running service gap control (SGC) timer will be allowed to perform certain procedures as listed earlier i.e. the AMF will allow some procedures that are initiated by the UE even though the SGC timer is running. However, the list of procedures that are not to be rejected by the AMF does not include the service request procedure, or the registration procedure, with MUSIM related parameters. As such, if the UE with a SGC timer attempts to e.g. provide a new paging restriction information or to delete the stored paging restrictions (also referred to as paging restriction information), then the AMF will reject the request from the UE. This will negatively impact the user’s experience, as mobile terminated requests will be impacted since the UE’s most up to date paging restrictions cannot be provided or deleted from the network. It is an aim of embodiments of the present invention to address these and other issues in the prior art, whether mentioned herein or not. According to the present invention there is provided an apparatus and method as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows. According to a first aspect of the present invention, there is provided a method of operating a User Equipment, UE, with MUSIM capability, wherein if the UE is in a non-allowed area and encounters or receives a trigger for a Network Access Stratum, NAS procedure related to a MUSIM feature, then the UE performs a Registration procedure with respect to a connected telecommunication network. In an embodiment, the UE additionally verifies it a timer is running which is intended to block the Registration procedure if not related to MUSIM and if it is so verified, the timer is disregarded and, if it is not so verified, than the Registration procedure is blocked by the UE. In an embodiment, the timer is one of a Back Off, BO, timer, T3446, and a Service Gap Control, SGC, timer, T3447. In an embodiment, being in a non-allowed area corresponds with the UE being in a 5GMM-REGISTERED.NON-ALLOWED-SERVICE state. In an embodiment, the MUSIM feature is one of: Connection release, Paging Cause Indication, Reject paging request, Paging Restriction and delete stored paging restrictions information. In an embodiment, if the UE is in a non-allowed area, then a request for a MUSIM feature is treated as a trigger for the Registration procedure. In an embodiment, the UE is in a non-allowed area if it is located in a specifically non-allowed area or if it not located in an allowed area. According to a second aspect of the present invention, there is provided method of operating a User Equipment, UE, with MUSIM capability, wherein if the UE encounters or receives a trigger for a Network Access Stratum, NAS procedure related to a MUSIM feature, but there is a timer running which is intended to block the NAS procedure if not related to MUSIM and if it is so verified, the timer is disregarded and the procedure is initiated, and if it is not so verified, then the NAS procedure is blocked by the UE. In an embodiment, the NAS procedure is a Service Request procedure. In an embodiment, the timer is one of a Back Off, BO, timer, T3446, and a Service Gap Control, SGC, timer, T3447. In an embodiment, the MUSIM feature is one of: Connection release, Paging Cause Indication, Reject paging request, Paging Restriction and delete stored paging restrictions information. In an embodiment, the UE is S1 and or N1 mode. According to a third aspect of the present invention, there is provided UE operable to perform the method of any preceding aspect. When in a restricted service area, the UE can / should verify if the trigger for a NAS procedure is related to at least one MUSIM feature (e.g. to provide paging restrictions, or delete stored paging restrictions information etc). If yes, the UE determines to allow procedure and hence send the necessary NAS message such as (but not limited to) the Service Request message or the Registration Request message. When the UE has a BO timer that is running, the UE can / should verify if the trigger for a NAS procedure is related to at least one MUSIM feature (e.g. to provide paging restrictions or delete stored paging restrictions information, etc). If yes, the UE determines to allow procedure and hence send the necessary NAS message such as (but not limited to) the Service Request message. The network should not reject the NAS message from the UE, or the rejection and providing the BO timer should be considered (optionally by the UE) as implicit acceptance of removal of stored paging restrictions information at the network NF. e.g. AMF. When the UE has a service gap control timer that is running, the UE can / should verify if the trigger for a NAS procedure is related to at least one MUSIM feature (e.g. to provide paging restrictions, etc). If yes, the UE determines to allow procedure and hence send the necessary NAS message such as (but not limited to) the Service Request message. The network should not reject the NAS message from the UE. Although a few preferred embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims. For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example only, to the accompanying diagrammatic drawings in which: Figure 1 shows a flowchart illustrating operation of a UE in a restricted service areaaccording to an embodiment of the invention; Figure 2 shows a flowchart illustrating operation of a UE with a running Back Off timer according to an embodiment of the invention; and Figure 3 shows a flowchart illustrating operation of a network (MME or AMF) with a UE context having a running BO timer according to an embodiment of the invention. Note that throughout this application, the term “MUSIM feature” can be related to, or can refer to, any of the following: connection release (e.g. for MUSIM), paging cause indication (e.g. for MUSIM), reject paging request (e.g. for MUSIM), or paging restriction (e.g. for MUSIM), or any combination of these features. Note that the detailed embodiments herein can be applied in any combination and in any order. They can also be applied to the UE in S1 mode (if possible) or N1 mode, or both (if possible). Note that S1 mode may refer to EPS, and N1 mode may refer to 5GS and as such the network may refer to one or more nodes such as the MME (in EPS) or the AMF (in 5GS). In a first embodiment, the UE verifies for a new condition based on which a service request procedure can be initiated while in a restricted service area. Note that, here, a UE that is in restricted service area can mean e.g. the UE is not in an allowed area, or the UE is in a non-allowed area. The UE may be configured, e.g. either pre-configured (e.g. in the USIM and / or mobile equipment) or configured by the network using any NAS signalling (e.g. Registration Accept message, or Configuration Update Command message, or any other NAS message that may be existing or may be newly defined), with rules regarding whether or not to allow a certain NAS procedure that is triggered by, or for the purpose of, a MUSIM feature. The configuration may be e.g. that the UE: is to allow one or more NAS procedures if the procedure is related to one (or more, ora subset of the) MUSIM features; oris not to allow one or more NAS procedures if the procedure is related to one (or more, or a subset of the) MUSIM features. The configuration is stored in the UE until a new / updated configuration is received and thereby the UE considers the new received configuration (as explained above) is the most valid or most recent configurations and thereby the UE may delete and / or update any previous configured that was stored. Note that details regarding the UE being configured as explained above, and optionally regarding the UE verifying the configuration in order to determine an action (or to not take an action) can be applied to all the procedures detailed herein. When the UE is in a restricted service area, the UE may detect (or receive or be faced with) a trigger to perform a service request procedure. The UE should verify if the trigger is for at least one MUSIM feature. If the trigger is related to at least one MUSIM feature, the UE should verify if the procedure is to be permitted or not e.g. based on a configuration that is stored in the UE as described above. If the UE determines (e.g. as explained above) that the UE should permit the procedure, then the UE should initiate the NAS procedure and send the necessary NAS message e.g. a Service Request message, Registration Request message, etc. Note that the UE may do this either when in 5GMM-IDLE mode, or5GMM-CONNECTED mode, or5GMM-CONNECTED mode with RRC inactive indication. For example, if the UE has sent a service request message without including paging restrictions (PRs), the network should delete any stored PRs (e.g. that is in the UE’s context) and send back the NAS response message like Service accept or Service reject or Registration Accept / Reject message, in this case the AMF and the UE should optionally treat that the PRs are deleted at the UE and network side, and optionally that any new PR(s) that was sent by the UE is to be considered the most up to date or the most valid PR(s). Moreover, if the UE is in 5GMM-IDLE mode with suspend indication, then the UE may take the same actions as set out above. In this case, if the UE determines to initiate a NAS procedure e.g. due to a trigger that is related to at least one MUSIM feature (and optionally if permitted based on the configurations of the UE as explained earlier), then the UE may first request the lower layers to resume the connection. The UE may then send a NAS message after the lower layers indicate that the RRC connection has been resumed. When sending the NAS message as described above, the UE should optionally not include the Uplink data status IE (or optionally not include the Allowed PDU session status IE) so as to not request the establishment of User Plane, UP, resources except if the UE requires resources for an emergency PDU session or if the UE is a high priority access UE. Similarly, the AMF should not reject a NAS message from the UE which is in a restricted area if the NAS message contains information (e.g. one or more information elements) that is related to at least one MUSIM feature. Note that the steps of the procedure above can be applied in any combination or order. Moreover, a NAS message (that may be sent by the UE) can be any NAS message such as, but not limited to, a Service Request message, Control Plane Service Request message, Registration Request message, etc. Figure 1 shows steps in a procedure for UE behaviour based on the description above, noting that this is an example only and not intended to be limiting. At step S1, the UE is in a restricted service area and has a trigger to initiate a NAS procedure. At step S2, the UE verifies if the trigger is related to at least one MUSIM feature. If not, at S3, the UE blocks the procedure and flow returns to S1. If the verification as S2 is yes, then the UE, at step S4, allows or initiates the procedure and sends the necessary NAS message. The NAS message may be a Service request procedure or, preferably, a registration procedure. This step may optionally involve requesting a lower layer to resume a connection. Note that the steps above can be arranged in any order and in any combination. Note that for all of the procedures herein, the UE may first determine what action to take based on a configuration that is stored in the UE, where this configuration is received in the UE as described earlier. This can apply to all the procedures herein. Optionally, when sending a NAS message in S1 mode, e.g. a Control Plane Service Request (CPSR) message or a Tracking Area Update (TAU) Request message, the UE should not set any bit in the message such that the bit indicates a request to setup user plane resources. The bit may be the “Active flag” bit and, as such, the UE should not set the bit such that the value of the bit indicates that radio bearer resources are required / requested. As such, the bit should be set to a value that indicates that no user plane resources, or no bearer resources are required / requested. Note that this procedure can be always applied by the UE when sending the CPSR or the TAU Request message in S1 mode. Optionally this may apply anytime the UE sends the indicated NAS message when the NAS message includes any IE that is related to a MUSIM feature e.g. when the UE request type IE is included and optionally when the value of the IE indicates that the NAS signalling release is required (or the value indicates “NAS signalling connection release”) or the IE indicates “Rejection of paging”. Note that the procedure above can always be applicable in S1 mode noting that this is not related to a restricted service area. In a second embodiment, when the UE has a running back-off (BO) timer e.g. a mobility management BO timer, the UE may get a request from upper layers which is a trigger for a NAS procedure (e.g. service request procedure or a registration procedure). The UE should verify if the request is related to at least one MUSIM feature. If this is the case, then the UE should allow the procedure and hence initiate the related procedure by sending the appropriate NAS message (e.g. Service Request message or Registration Request message). Note that the determination in the UE may be done based on a configuration that the UE has as explained earlier. As such, if the trigger is related to at least one MUSIM feature, (optionally if the configuration in the UE allows the procedure) then the UE should permit the procedure and send the corresponding NAS message, whereas, otherwise, the UE does not initiate the procedure (e.g. the UE blocks the procedure) if the trigger is not deemed to be an exception to the running BO timer. As such, a trigger that is related to at least one MUSIM feature should be considered, by the UE (and optionally the network), to be an exception to a running BO timer. Also, the network should not reject a NAS message (e.g. due to congestion) when the NAS message (and / or NAS procedure) includes at least one indication or information element that is related to at least one MUSIM feature, or providing a BO timer should be treated (e.g. by the UE and / or the network) as an implicit indication of (e.g. a successful) completion of the procedure. For example if the UE has sent a service request message without including paging restrictions (PRs), the network should delete any stored PRs (e.g. that is in the UE’s context) and send back the NAS response message like Service accept or Service reject or Registration Accept / Reject message, in this case the AMF and the UE should optionally treat that the PRs are deleted at the UE and network side, and optionally that any new PR(s) that was sent by the UE is to be considered the most up to date or the most valid PR(s). Therefore, in summary, a trigger for a service that is related to at least one MUSIM feature should be considered by the UE and / or the network (e.g. AMF) to be an exception to a running BO timer (e.g. the mobility management BO timer). Thus, the UE with a running BO timer should allow a related NAS procedure (and hence send a corresponding NAS message) when the trigger for the procedure is for at least one MUSIM feature. Similarly, the network (e.g. AMF or MME) should not reject a request from a UE that is related to at least one MUSIM feature. Note that the procedure above applies to a UE that operates in S1 mode (i.e. EPS) and / or N1 mode (i.e. 5GS) and hence the network can refer to an AMF and / or an MME. The steps above can apply in any combination or order. Moreover, the NAS message can be any of a: Service Request, Control Plane Service Request, Tracking Area Update Request, Registration Request, or any other NAS message that is existing or that may be new and that is used in either S1 mode or N1 mode. Note that the BO timer in question may be a BO timer that is related to the NAS protocol in S1 mode or the NAS protocol in N1 mode or both. Figure 2 shows steps in a procedure for UE behaviour based on the description above, noting that this is an example only and not intended to be limiting. At step S11, the UE has a running BO timer and has a trigger to initiate a NAS procedure. At step S12, the UE verifies if the trigger is related to at least one MUSIM feature. If not, at S13, the UE blocks the procedure and flow returns to S1. If the verification as S12 is yes, then the UE, at step S14 allows or initiates the procedure and sends the necessary NAS message. This step may optionally involve requesting a lower layer to resume a connection. Note that the steps above can be arranged in any order and in any combination. Figure 3 shows a flowchart more aligned with the network operation, where the network (MME to AMF) with a UE context having a running BO timer. Note that in Figure 3, the network providing a BO timer to the UE may mean that the BO timer is also running in the network. At step S21, the network has provided the UE with a BO timer. The network receives a NAS message from the UE. At step S22, the network verifies if the NAS message is related to at least one MUSIM feature. If not, at S23, the network rejects the message and flow returns to S21. If the verification as S22 is yes, then the network, at step S24 accepts or processes (i.e. does not reject) the NAS message and sends a response to the UE. Flow optionally returns to step S21. When the UE with or having a service gap control (SGC) timer (T3447) that is running, the UE may get a request from upper layer which is a trigger for a NAS procedure (e.g. service request procedure or a registration procedure). The UE should verify if the request is related to at least one MUSIM feature. If this is the case, then the UE should allow the procedure (optionally after verifying a configuration in the UE as described earlier), and hence initiate the related procedure by sending the appropriate NAS message (e.g. Service Request message or Registration Request message, Control Plane Service Request message, etc). As such, if the trigger is related to at least one MUSIM feature, then the UE should permit the procedure and send the corresponding NAS message, whereas otherwise the UE does not initiate the procedure (e.g. the UE blocks the procedure) if the trigger is not deemed to be an exception to the running SGC timer. As such, a trigger that is related to at least one MUSIM feature should be considered, by the UE (and optionally the network), to be an exception to a SGC timer. Also, the network should not reject a NAS message, from a UE for which there is a running SGC timer, when the NAS message (and / or NAS procedure) includes at least one indication or information element that is related to at least one MUSIM feature. Optionally, the UE and / or the network does not start the SGC timer after the NAS connection is released (i.e. after transitioning from 5GMM-CONNECTED mode to 5GMM-IDLE mode in N1 mode, or from EMM-CONNECTED mode to EMM-IDLE mode in S1 mode) if the NAS connection with a the NAS message that was sent by the UE such that the message included any information and / or indication that is related to at least one MUSIM feature. Note that the procedures set out above apply to a UE that operates in S1 mode (i.e. EPS) and / or N1 mode (i.e. 5GS) and hence the network can referto an AMF and / or an MME. The procedures above can apply in any combination or order. Moreover, the NAS message can be any of a: Service Request, Control Plane Service Request, Tracking Area Update Request, Attach Request, Registration Request, or any other NAS message that is existing or that may be new and that is used in either S1 mode or N1 mode. Note that the SGC timer may be a timer that is related to the NAS protocol in S1 mode or the NAS protocol in N1 mode or both. Note that the Figure 2 and Figure 3 can also be applicable for the UE and the network, respectively, as described above, where for example the BO timer in these figures can be replaced with the SGC timer. The proposals herein enable the UE to provide the necessary information regarding operation with MUSIM which reduces both delays and negative impacts to the UE / user experiences and services. At least some of the example embodiments described herein may be constructed, partially or wholly, using dedicated special-purpose hardware. Terms such as ‘component’, ‘module’ or‘unit’ used herein may include, but are not limited to, a hardware device, such as circuitry in the form of discrete or integrated components, a Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC), which performs certain tasks or provides the associated functionality. In some embodiments, the described elements may be configured to reside on a tangible, persistent, addressable storage medium and may be configured to execute on one or more processors. These functional elements may in some embodiments include, by way of example, components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. Although the example embodiments have been described with reference to the components, modules and units discussed herein, such functional elements may be combined into fewer elements or separated into additional elements. Various combinations of optional features have been described herein, and it will be appreciated that described features may be combined in any suitable combination. In particular, the features of any one example embodiment may be combined with features of any other embodiment, as appropriate, except where such combinations are mutually exclusive. Throughout this specification, the term “comprising” or “comprises” means including the components) specified but not to the exclusion of the presence of others. Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. 25

Claims

1. A method of operating a User Equipment, UE, with Multi-UMTS Subscriber Identify Module, MUSIM, capability, wherein if the UE is in a non-allowed area and encounters or 5 receives a trigger for a Network Access Stratum, NAS procedure related to a MUSIM feature, then the UE performs a Registration procedure with respect to a connected telecommunication network.

2. The method of claim 1 wherein the UE additionally verifies it a timer is running which is 10 intended to block the Registration procedure if not related to MUSIM and if it is so verified, the timer is disregarded and, if it is not so verified, than the Registration procedure is blocked by the UE.

3. The method of claim 2 wherein the timer is one of a Back Off, BO, timer, T3446, and a 15 Service Gap Control, SGC, timer, T3447.

4. The method of any preceding claim wherein being in a non-allowed area corresponds with C\l the UE being in a 5GMM-REGISTERED.NON-ALLOWED-SERVICE state.20 5. The method of any preceding claim wherein the MUSIM feature is one of: Connectionrelease, Paging Cause Indication, Reject paging request, Paging Restriction and delete stored paging restrictions information.

6. The method of any preceding claim wherein if the UE is in a non-allowed area, then a 25 request for a MUSIM feature is treated as a trigger for the Registration procedure.

7. The method of any preceding claim wherein the UE is in a non-allowed area if it is located in a specifically non-allowed area or if it not located in an allowed area.

308. A UE operable to perform the method of any preceding claim.

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