Handling cell selection or reselection of a cell associated with a TAI in a wireless communication system

Abstract

Embodiments herein provide a method and system for handling cell selection or reselection of a cell associated with a TAI in a wireless communication system. The method includes initiating a first NAS request message on a first RAT within a first PLMN. Further, the method includes receiving a first NAS message on the first RAT. The first NAS message includes a reject cause #15 stating 'no suitable cells in tracking area'. Further, the method includes detecting whether the first NAS message includes an ATUCI mentioning that access to the first RAT is restricted. Further, the method includes skipping storing of the first TAI in a list of forbidden tracking areas for roaming when the first NAS message includes the ATUCI. Further, the method includes initiating a registration of the UE (100) on a second RAT when the first TAI is not stored in the list of forbidden tracking areas.

Description

HANDLING CELL SELECTION OR RESELECTION OF A CELL ASSOCIATED WITH A TAI IN A WIRELESS COMMUNICATION SYSTEM

[0001] This application is based on and derives the benefit of Indian Provisional Applications 202441084747 filed on 5thNovember 2024 and 202441086657 filed on 11thNovember 2024 the contents of which are incorporated herein by reference. The present disclosure is related to the field of wireless communication. More particularly, the present disclosure is related to a method and system for handling cell selection or reselection of a cell associated with a tracking area identity (TAI) in a wireless communication system.

[0002] In wireless communication systems, national roaming services are vital for ensuring seamless connectivity, especially in areas where the primary network operator lacks coverage. Allowing unrestricted use of radio access technologies (RAT) for national roamers can result in technical challenges including interoperability issues, quality of service concerns and network congestion concerns.

[0003] As per CP-241298 and C4-242303, enhancements are being made to evolved packet system (EPS) and 5thgeneration system (5GS), focusing on the delivery of RAT utilization restriction information (also referred as access technology utilization control information) to the UE, along with the associated UE behavior (e.g., Whether access technology is restricted or not restricted).. There may be an update to the access restriction data in the home location register (HLR) to facilitate the limitation of RAT utilization at the serving GRPS servicing node (SGSN). Additionally, a potential update to the access restriction data in the home subscriber server (HSS) is being considered to allow for the limitation of RAT utilization at the mobility management entity (MME). Furthermore, there could be an update to the access restriction data in the unified data management (UDM) / unified data repository (UDR) to support the limitation of RAT utilization at the access and mobility management function (AMF).

[0004] When a core network wants to restrict the user equipment (UE) to avail service on certain RAT(s), it may send reject cause #15 along with RAT Utilization Control Information IE in any of the NAS messages (for example, Registration Reject, UE Configuration Update or UCU, UE Parameters Update or UPU etc.). In addition, #15 cause code includes the TAI(s) in which the UE is restricted to use the mentioned RAT(s) i.e., the TAI(s) to be included in Forbidden Tracking Area list or FTAI List (for example, "forbidden tracking areas due to RAT Restriction"). The UE then adds the TAI(s) in the FTAI list. Network decides to allow the RAT(s) and thus indicates "RAT is no more restricted" to UE as part of RAT Utilization Control Information in any of the NAS messages (for example, Registration Reject, UCU, UPU etc.). But, in this scenario, TAI(s) is / are still part of FTAI list, thus UE cannot access / register on those TAI(s). This results in UE not getting the intended service on the desired RAT(s).

[0005] The Network Function (NF) for e.g. UDM / PCF / AMF decides to restrict the UE to avail service on certain RAT(s) & sends reject cause #15 along with RAT utilization control information in any of the NAS messages (for example, Registration Reject, UCU, UPU etc.). #15 optionally includes the TAI#15 optionally includes the TAI(s) in which the UE is restricted to use the mentioned RAT(s).

[0006] The UE shall add the TAI(s) received in #15 along with RAT Utilization Control Information, in the FTAI list. NF for e.g. UDM / PCF / AMF decides to allow the UE to avail service on the previously restricted RAT(s) and updates the RAT Restriction Information to in any of the NAS messages (for example, UCU, UPU, Steering Of Roaming or SOR Update etc., registration accept). Since TAI(s) is / are still part of FTAI list, UE cannot access / register on those TAI(s).

[0007] Hence, is desirable to address the above mentioned problems and disadvantages or at least provide a useful alternative.

[0008] The principal object of the embodiments herein is to provide a method and system for handling cell selection or reselection of a cell associated with a TAI in a wireless communication system.

[0009] Another object of the embodiments herein is to provide a framework for handling a TAI list received along with RAT utilization control information

[0010] Yet another object of the embodiments herein is to provide a framework for handling forbidden Tracking Area identity(FTAI) in the Satellite access.

[0011] In an aspect, the objectives are achieved by providing a method for handling cell selection or reselection of a cell associated with a TAI in a wireless communication system. The method includes initiating a first NAS request message on a first RAT within a first PLMN. The first NAS request message is camped on a cell belonging to a first TAI. Further, the method includes receiving a first NAS message on the first RAT upon initiation of the first NAS request message. The first NAS message includes a reject cause #15 stating 'no suitable cells in tracking area'. Further, the method includes detecting whether the first NAS message includes UE access technology utilization control information (ATUCI). The ATUCI mentions that access to the first RAT is restricted. Further, the method includes skips storing of the first TAI in a list of forbidden tracking areas for roaming when the first NAS message received includes the ATUCI. Further, the method includes initiating a registration of the UE on a second RAT within the first PLMN, when the first TAI is not stored in the list of forbidden tracking areas for roaming.

[0012] In another aspect, the objectives are achieved by providing a method for handling cell selection or reselection of a cell associated with a TAI in a wireless communication system. Further, the method includes initiating a first NAS request message on a first RAT within a first PLMN. The first NAS request message is camped on a cell belonging to a first TAI. Further, the method includes receiving a first NAS message on the first RAT upon initiation of the first NAS request message. The first NAS message includes a reject cause #15 stating 'no suitable cells in tracking area'. Further, the method includes detecting whether the first NAS message includes an extended cause code stating "Satellite next generation radio access network (NG-RAN) not allowed in PLMN". Further, the method includes skipping storing of the first TAI in a list of forbidden tracking areas for roaming when the first NAS message includes the extended cause code stating "Satellite NG-RAN not allowed in PLMN". Further, the method includes starting a timer associated with the UE upon detection of the extended cause code stating "Satellite NG-RAN not allowed in PLMN". A capability of the satellite NG-RAN is disabled during a duration of the timer. Further, the method includes initiating a registration of the UE on the first RAT belonging to the first PLMN upon an expiry of the timer.

[0013] In another aspect, the objectives are achieved by providing a UE for handling cell selection or reselection of a cell associated with a TAI in a wireless communication system. The UE includes a processor, a memory coupled to the processor, and an ATUCI handling controller communicatively coupled to the processor and the memory. The ATUCI handling controller initiates a first NAS request message on a first RAT within a first PLMN. The first NAS request message is camped on a cell belonging to a first TAI. Further, the ATUCI handling controller receives a first NAS message on the first RAT upon initiation of the first NAS request message. The first NAS message includes a reject cause #15 stating 'no suitable cells in tracking area'. Further, the ATUCI handling controller detects whether the first NAS message includes UE ATUCI. The ATUCI mentions that access to the first RAT is restricted. Further, the ATUCI handling controller skips storing of the first TAI in a list of forbidden tracking areas for roaming when the first NAS message received includes the ATUCI. Further, the ATUCI handling controller initiates a registration of the UE on a second RAT within the first PLMN, when the first TAI is not stored in the list of forbidden tracking areas for roaming.

[0014] The UE further includes satellite handling controller communicatively coupled to the processor and the memory. The satellite handling controller initiates a first NAS request message on a first RAT within a first PLMN. The first NAS request message is camped on a cell belonging to a first TAI. Further, the satellite handling controller receives a first NAS message on the first RAT upon initiation of the first NAS request message. The first NAS message includes a reject cause #15 stating 'no suitable cells in tracking area'. Further, the satellite handling controller detects whether the first NAS message includes an extended cause code stating "Satellite next generation radio access network (NG-RAN) not allowed in PLMN". Further, the satellite handling controller skips storing of the first TAI in a list of forbidden tracking areas for roaming when the first NAS message includes the extended cause code stating "Satellite NG-RAN not allowed in PLMN". Further, the satellite handling controller starts a timer associated with the UE upon detection of the extended cause code stating "Satellite NG-RAN not allowed in PLMN". A capability of the satellite NG-RAN is disabled during a duration of the timer. Further, the satellite handling controller initiates a registration of the UE on the first RAT belonging to the first PLMN upon an expiry of the timer.

[0015] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications be made within the scope of the embodiments herein.

[0016] These and other features, aspects, and advantages of the present embodiments are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:

[0017] Fig. 1 is a sequence diagram that illustrates a process where a UE is restricted from using certain RAT(s) in specific TAI(s) according to the prior art.

[0018] Fig. 2 is a sequence diagram that illustrates a process of RAT restriction management and TAI handling for a UE in a mobile network according to the prior art.

[0019] Fig. 3 is a sequence diagram that illustrates a scenario of the UE not receiving a service according to the prior art.

[0020] Fig. 4 is a schematic diagram that illustrates a schematic of the UE implemented to carry out the disclosed subject matter according to an embodiment as disclosed herein.

[0021] Fig. 5 is a sequence diagram that illustrates a process of RAT restriction management and TAI handling for the UE in a mobile network according to an embodiment as disclosed herein.

[0022] Fig. 6 is a sequence diagram that illustrates a process of RAT restriction, TAI management, and registration handling for the UE according to an embodiment as disclosed herein.

[0023] Fig. 7 is a sequence diagram that illustrates a scenario of the UE receiving the service according to an embodiment as disclosed herein.

[0024] Fig. 8 is a flow diagram that illustrates a method for handling cell selection or reselection of a cell associated with a TAI associated with an ATUCI according to an embodiment as disclosed herein.

[0025] Fig. 9 is a flow diagram that illustrates that illustrates a method for handling cell selection or reselection of a cell associated with a TAI associated with a satellite NG-RAN according to an embodiment as disclosed herein.

[0026] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. Also, the various embodiments described herein are not necessarily mutuallyexclusive, as some embodiments can be combined with a plurality of other embodiments to form new embodiments. The term "or" as used herein, refers to a non-exclusive or, unless otherwise indicated. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein can be practiced and to further enable those skilled in the art to practice the embodiments herein. Accordingly, the examples are not be construed as limiting the scope of the embodiments herein.

[0027] As is existing in the field, embodiments are described and illustrated in terms of blocks that carry out a described function or functions.　These blocks, which referred to herein as managers, units, modules, hardware components or the like, are physically implemented by analog and / or digital circuits such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits, and the like, and optionally be driven by firmware and software. The circuits, for example, be embodied in a plurality of semiconductor chips, or on substrate supports such as printed circuit boards, and the like.　The circuits constituting a block be implemented by dedicated hardware, or by a processor (for example, a plurality of programmed microprocessors and associated circuitry), or by a combination of dedicated hardware to perform some functions of the block and a processor to perform other functions of the block.Eachblock of the embodiments be physically separated into two or more interacting and discrete blocks without departing from the scope of the proposed method.　Likewise, the blocks of the embodiments be physically combined into more complex blockswithoutdeparting from the scope of the proposed method.

[0028] The accompanying drawings are used to help easily understand various technical features and it is understood that the embodiments presented herein are not limited by the accompanying drawings. As such, the proposed method is construed to extend to any alterations, equivalents and substitutes in addition to those which are particularly set out in the accompanying drawings. Although the terms first, second, etc. used herein to describe various elements, these elements are not be limited by these terms. These terms are generally used to distinguish one element from another.

[0029] The terms Rat-Type and RAT, AT (access technology) are used interchangeably and have the same meaning and they represent at least one of the below:

[0030] ≫ 5G(N1 mode), 4G(S1 mode), 3G, 2G

[0031] ≫ EPS, 5GS

[0032] ≫ NR

[0033] ≫ NR in unlicensed bands

[0034] ≫ NR(LEO) satellite access

[0035] ≫ NR(MEO) satellite access

[0036] ≫ NR(GEO) satellite access

[0037] ≫ NR(OTHERSAT) satellite access

[0038] ≫ NR RedCap

[0039] ≫ NG-RAN

[0040] ≫ Satellite NG-RAN

[0041] ≫ E-UTRA / E-UTRAN

[0042] ≫ Satellite E-UTRAN

[0043] ≫ E-UTRA in unlicensed bands

[0044] ≫ NB-IoT or NB-S1

[0045] ≫ WB-IoT

[0046] ≫ LTE-M

[0047] In the embodiment, the RAT indicates the Radio access technology defined in 3GPP TS 36.304 and 3GPP TS 38.304, respectively.

[0048] Fig. 1 is a sequence diagram that illustrates a process where a UE (100) is restricted from using certain RAT(s) in specific TAI(s) according to the prior art. Fig. 1 focuses on management of RAT restrictions and Forbidden Tracking Area (FTAI) list updates for the UE (100) in a mobile network, focusing on the process where the UE (100) is initially restricted from using certain (RAT(s)) in specific TAIs. Issues arise when the restriction is lifted but the FTAI list is not updated. As shown, the sequence diagram includes the UE (100), a RAT-1 (102A), an AMF-1 (104A), a RAT-2 (102B), a MME-1 (106), and a network function (NF) (108) in communication with each other.

[0049] In this context, when the NF (108) (for example, UDM / PCF / AMF) decides to restrict the UE (100) to avail service on certain RAT(s) & sends reject cause #15 along with RAT Utilization Control Information in any of the NAS messages (for example, Registration Reject, UCU, UPU etc.). #15 optionally includes the TAI#15 optionally includes the TAI(s) in which the UE (100) is restricted to use the mentioned RAT(s). The UE (100) shall add the TAI(s) received in #15 along with RAT Utilization Control Information, in the FTAI list. When the NF (108) decides to allow the UE (100) to avail service on the previously restricted RAT(s) and updates the RAT Restriction Information to in any of the NAS messages (for example, UCU, UPU, SOR Update etc.). Since TAI(s) is / are still part of FTAI list, the UE (100) cannot access / register on those TAI(s).

[0050] This can be solved by the following embodiments when the NF (108) imposes the RAT Restriction for a certain RAT(s) for the UE (100) and indicates the same to the UE (100) in RAT Utilization Control Information along with TAI(s) on which the RAT is restricted along with the #15 cause code, the UE (100) shall a) Not add TAI as part of the Forbidden Tracking Area list or FTAI list (for example, "forbidden tracking areas due to RAT Restriction") b) Memorize the TAI(s) received for RAT Restriction and remove the TAI(s) from FTAI list once the RAT restrictions are removed by the NF (108). Alternatively, the UE (100) need not memorize the TAI(s) and shall try to access / register on these once the RAT Restriction is removed and the NF (108) shall reject the Current TAI if it is not allowed or accept the Current TAI if it is allowed.

[0051] Fig. 2 is a sequence diagram that illustrates a process of RAT restriction management and TAI handling for the UE (100) in a mobile network according to the prior art. As shown, the sequence diagram includes the UE (100), the RAT-1 (102A), the AMF-1 (104A), the RAT-2 (102B), the MME-1 (106), and the NF (108) in communication with each other.

[0052] The UE (100) does not add TAI as part of the Forbidden Tracking Area list or FTAI list (for example, "forbidden tracking areas due to RAT Restriction"), according to embodiments as disclosed herein. When the NF (108) decides to restrict the UE (100) to avail service on certain RAT(s) & sends reject cause #15 along with RAT Utilization Control Information in any of the NAS messages (for example, Registration Reject, UCU, UPU etc.). #15 optionally includes the TAI#15 optionally includes the TAI(s) in which the UE (100) is restricted to use the mentioned RAT(s). The UE (100) shall not add the FTAI(s) received in NAS message (e.g in the Forbidden TAI(s) for the list of "5GS forbidden tracking areas for roaming" IE) or the current TAI where a NAS message is received with cause code #15 or any other cause along with RAT Utilization Control Information, in the FTAI list. The UE (100) shall add the TAI(s)(received as part of NAS message or the current TAI) in the FTAI list if the RAT Utilization Control Information Element (IE) is not included as part of the NAS message or Extended EMM cause IE is not included. The NF (108) decides to allow the UE (100) to avail service on the previously restricted RAT(s) and updates the RAT Restriction Information to the UE (100) in any of the NAS messages (for example, UCU, UPU, SOR Update etc.). Since TAI(s) is / are not part of FTAI list, the UE (100) can access / register on those TAI(s).

[0053] Fig. 3 is a sequence diagram that illustrates a scenario of the UE (100) not receiving a service according to the prior art. As shown in the sequence diagram, the UE (100) and a PLMN (302) are in communication with each other. Each step is explained in further detail below.

[0054] At step 1, the UE (100) send uplink NAS message (for example, registration message or tracking area update request or service request). The UE (100) receives NAS message (for example, registration reject, tracking area update reject or network initiated detach) including 5GMM cause #15 and extended 5GMM cause IE with value "Satellite NG-RAN not allowed in the PLMN (302)" or EMM cause value #15 and extended EMM cause IE with value "Satellite E-UTRAN not allowed in the PLMN (302)" as illustrated in the step 2.

[0055] At step 3, the UE (100) shall store the current TAI (for example, TAI-1) in the list of FTAI list optionally for the respective access technology (Satellite E-UTRAN or Satellite NG-RAN ) where the NAS message in step-2 is received.

[0056] At step 4, MS disables its satellite NG-RAN capability on the PLMN (302) (for example, PLMN-1) due to Satellite NG-RAN not allowed in PLMN. Start TS timer or MS disables its satellite E-UTRAN capability on the PLMN (302) due to Satellite E-UTRAN not allowed in the PLMN (302). Further the TL timer is started.

[0057] Further at step 5, After TS or TL timer expiry, the UE (100) deletes the stored information in the "PLMNs with satellite NG-RAN not allowed" list / "PLMNs with satellite E-UTRAN not allowed" list. Suppose, the UE (100) is in the TAI-1, then the UE (100) will not get the service until the TAI-1 is removed from FTAI list. The FTAI list is cleared at 12 to 24 hours, as illustrated in step 6.

[0058] 3GPP has introduced "Satellite NG-RAN not allowed in the PLMN (302)" value in the "Extended 5GMM cause" IE, in conjunction with 5GMM cause #15. The main purpose of this mechanism is that there are scenarios where the not allowed satellite service is not localized in the PLMN (302), but rather the PLMN (302) does not allow the UE (100) to access the network via a satellite cell while it is allowed to access via non-satellite or terrestrial cells.

[0059] Similarly, 3GPP has introduced "Satellite E-UTRAN not allowed in the PLMN (302)" value in the "Extended GMM cause" IE, in conjunction with GMM cause #15. The main purpose of this mechanism is that there are scenarios where the not allowed satellite service is not localized in the PLMN (302), but rather the PLMN (302) does not allow the UE (100) to access the network via a satellite cell while it is allowed to access via non-satellite or terrestrial cells.

[0060] So, when the UE (100) supports the extended 5GMM cause or GMM cause as below:

[0061] #15 (No suitable cells in tracking area).

[0062] 1. if the Extended 5GMM cause IE with value "Satellite NG-RAN not allowed in the PLMN (302)" is included in the REGISTRATION REJECT message,

[0063] i. the message has been successfully integrity checked by the NAS; and the UE (100) is configured for "Satellite Disabling Allowed for 5GMM cause #15" as specified in 3GPP　TS　24.368

[0017] or 3GPP　TS　31.102

[0022] , then the UE (100) shall disable satellite NG-RAN capability; or

[0064] ii. otherwise, the UE (100) shall ignore the Extended 5GMM cause IE; and

[0065] 2. Search for a suitable cell in another tracking area according to 3GPP　TS　38.304

[0028] or 3GPP　TS　36.304　[25C].

[0066] The FTAI list in the current TAI is as below:

[0067] If the satellite NG-RAN capability was not disabled as above, and:

[0068] 1. The UE (100) is not operating in SNPN access operation mode and the Forbidden TAI(s) for the list of "5GS forbidden tracking areas for roaming" IE is not included in the REGISTRATION REJECT message, the UE (100) shall store the current TAI in the list of "5GS forbidden tracking areas for roaming" and enter the state 5GMM-DEREGISTERED.LIMITED-SERVICE. If the REGISTRATION REJECT message is not integrity protected, the UE (100) shall memorize the current TAI was stored in the list of "5GS forbidden tracking areas for roaming" for non-integrity protected NAS reject message; or

[0069] 2. The UE (100) is operating in SNPN access operation mode, the UE (100) shall store the current TAI in the list of "5GS forbidden tracking areas for roaming" for the current SNPN and the selected entry of the "list of subscriber data" or the PLMN (302) subscription selected, and enter the state 5GMM-DEREGISTERED.LIMITED-SERVICE. If the REGISTRATION REJECT message is not integrity protected, the UE (100) shall memorize the current TAI was stored in the list of "5GS forbidden tracking areas for roaming" for the current SNPN and the selected entry of the "list of subscriber data" or the PLMN (302) subscription selected, for non-integrity protected NAS reject message.

[0070] Similar behaviour is specified to E-UTRAN satellite as well.

[0071] The MS may support "Satellite Disabling Allowed for 5GMM cause #15" as specified in 3GPP　TS　24.501

[0064] . If the MS supports "Satellite Disabling Allowed for 5GMM cause #15" and the "Satellite Disabling Allowed for 5GMM cause #15" parameter as specified in 3GPP　TS　24.368

[0050] or 3GPP　TS　31.102

[0040] is present and set to enabled:

[0072] ≫ the MS shall maintain a list of "PLMNs with satellite NG-RAN not allowed";

[0073] ≫ when the MS disables its satellite NG-RAN capability on the PLMN (302) due to Satellite NG-RAN not allowed in the PLMN (302), it shall add the PLMN (302) to the "PLMNs with satellite NG-RAN not allowed" list, and start timer TS if timer TS is not already running;

[0074] ≫ the number of PLMNs that the MS can store in the "PLMNs with satellite NG-RAN not allowed" list is implementation specific, but it shall be at least one;

[0075] ≫ the value of timer TS is MS implementation specific, but it shall not exceed the maximum possible value of 24 hours;

[0076] ≫ in automatic PLMN selection the MS shall not consider PLMNs included in the "PLMNs with satellite NG-RAN not allowed" list as the PLMN (302) selection candidates for satellite NG-RAN access technology, unless no other PLMN (302) is available. This does not prevent selection of the PLMN (302) if it is available in another RAT; and

[0077] ≫ the MS shall delete stored information in the "PLMNs with satellite NG-RAN not allowed" list when the MS is switched off, the USIM is removed or timer TS expires.

[0078] The expiry of timer TS does not cause the removal of the PLMNs from the list of PLMNs where N1 mode is not allowed for 3GPP access or from the list of PLMNs where voice service was not possible in N1 mode, if any.

[0079] The MS may support "Satellite Disabling Allowed for EMM cause #15" as specified in 3GPP　TS　24.301　[23A]. If the MS supports "Satellite Disabling Allowed for EMM cause #15" and the "Satellite Disabling Allowed for EMM cause #15" parameter as specified in 3GPP　TS　24.368

[0050] or 3GPP　TS　31.102

[0040] is present and set to enabled:

[0080] ≫ the MS shall maintain a list of "PLMNs with satellite E-UTRAN not allowed";

[0081] ≫ when the MS disables its satellite E-UTRAN capability on the PLMN (302) due to Satellite E-UTRAN not allowed in the PLMN (302), it shall add the PLMN (302) to the "PLMNs with satellite E-UTRAN not allowed" list, and start timer TL if timer TL is not already running;

[0082] ≫ the number of PLMNs that the MS can store in the "PLMNs with satellite E-UTRAN not allowed" list is implementation specific, but it shall be at least one;

[0083] ≫ the value of timer TL is MS implementation specific, but it shall not exceed the maximum possible value of 24 hours;

[0084] ≫ in automatic PLMN selection the MS shall not consider PLMNs included in the "PLMNs with satellite E-UTRAN not allowed" list as the PLMN (302) selection candidates for satellite E-UTRAN access technology, unless no other PLMN (302) is available. This does not prevent selection of the PLMN (302) if it is available in another RAT; and

[0085] ≫ the MS shall delete stored information in the "PLMNs with satellite E-UTRAN not allowed" list when the MS is switched off, the USIM is removed or timer TL expires.

[0086] That means when TL / TS timer expires, the MS shall delete stored information in the "PLMNs with satellite E-UTRAN not allowed" and the "PLMNs with satellite NG-RAN not allowed" list respectively for which timer expired as above.

[0087] NAS message is specified in TS 24.501 or TS 24.301. Some NAS message, but not limited to the list shown below,

[0088] a) IDENTITY REQUEST;

[0089] b) AUTHENTICATION REQUEST;

[0090] c) AUTHENTICATION RESULT;

[0091] d) AUTHENTICATION REJECT;

[0092] e) REGISTRATION REJECT

[0093] f) DEREGISTRATION ACCEPT

[0094] g) SERVICE REJECT

[0095] h) REGISTRATION REQUEST;

[0096] i) IDENTITY RESPONSE (if requested identification parameter is SUCI);

[0097] j) AUTHENTICATION RESPONSE;

[0098] k) AUTHENTICATION FAILURE;

[0099] l) SECURITY MODE REJECT;

[0100] m) DEREGISTRATION REQUEST; and

[0101] n) DEREGISTRATION ACCEPT;

[0102] p) UCU- UE CONFIGURATION UPDATE COMMAND

[0103] q) UPU

[0104] Further some NAS messages described in TS 24.301 are: ATTACH REQUEST; - IDENTITY RESPONSE (if requested identification parameter is IMSI); - AUTHENTICATION RESPONSE; - AUTHENTICATION FAILURE; - SECURITY MODE REJECT; - DETACH REQUEST; - DETACH ACCEPT; - TRACKING AREA UPDATE REQUEST, - ATTACH REQUEST; - IDENTITY RESPONSE; - AUTHENTICATION RESPONSE; - AUTHENTICATION FAILURE; - SECURITY MODE REJECT; - DETACH REQUEST; - DETACH ACCEPT; - TRACKING AREA UPDATE REQUEST; - SERVICE REQUEST; - EXTENDED SERVICE REQUEST; - CONTROL PLANE SERVICE REQUEST, TRACKING AREA UPDATE REJECT, ATTACH REJECT, GUTI RELLOACTION COMMAND.

[0105] In an embodiment, FTAI list is at-least one of the following:

[0106] ≫ "5GS forbidden tracking areas for roaming"

[0107] ≫ "5GS forbidden tracking areas for regional provision of service"

[0108] When the message is received on NG-RAN (N1 mode) or

[0109] FTAI list is at-least one of the following

[0110] ≫ "forbidden tracking areas for roaming"

[0111] ≫ "forbidden tracking areas for regional provision of service"

[0112] When the message is received on E-UTRAN (S1 mode)

[0113] FTAI list is at-least one of the following (FTAI(s) received in NAS message)

[0114] ≫ the Forbidden TAI(s) for the list of "5GS forbidden tracking areas for roaming" IE; or

[0115] ≫ the Forbidden TAI(s) for the list of "5GS forbidden tracking areas for regional provision of service" IE; or

[0116] FTAI list is at-least one of the following (FTAI(s) received in NAS message)

[0117] ≫ the Forbidden TAI(s) for the list of " forbidden tracking areas for roaming" IE; or

[0118] ≫ the Forbidden TAI(s) for the list of " forbidden tracking areas for regional provision of service" IE;

[0119] Currently, when the UE (100) receives 5GMM or EMM cause #15 or cause#13 which is non integrity protected and the the Forbidden TAI(s) for the list of "5GS forbidden tracking areas for roaming" IE or TAI(s) for the list of "5GS forbidden tracking areas for regional provision of serve" IE or both included. The UE (100) doesn't add the current TAI into the FTAI list.

[0120] In an embodiment, when the UE (100) receives 5GMM or EMM cause #15 or cause#13 which is non integrity protected and the Forbidden TAI(s) for the list of "5GS forbidden tracking areas for roaming" IE or TAI(s) for the list of "5GS forbidden tracking areas for regional provision of serve" IE or both included. The UE (100) adds the current TAI into the FTAI list if not already included in FTAI list (optionally when the Current TAI is in the FTAI list but not stored for the non-integrity protected message).

[0121] Embodiments disclosed herein provides a method and system for handling forbidden Tracking Area ID (TAI) in the Satellite access. The present disclosure specifically addresses the challenges related to forbidden TAI. In an embodiment, a method and system is described to not store current TAI in the list of FTAI list. As the current TAI is not in the FTAI list, the UE (100) will receive the service even if it is in the current TAI.

[0122] In an embodiment, a method is described to store the TAI into FTAI list and optionally memorize that the UE (100) stored the current TAI into the FTAI list and after the TS or TL timer expiry, MS delete stored information in the "PLMNs with satellite NG-RAN not allowed" list / "PLMNs with satellite E-UTRAN not allowed" list. The UE (100) additionally deletes the TAI from FTAI list stored for the satellite E-UTRAN or satellite NG-RAN access. Further as the current TAI is not in the FTAI list, the UE (100) will receive the service even if it is in the current TAI.

[0123] Fig. 4 is a block diagram that illustrates a schematic of the UE (100) implemented to carry out the disclosed subject matter according to anembodimentas disclosed herein. Examples of the UE (100) can include, but are not limited to, Consumer Electronics (such as Mobile Phones and Smartphones), Tablets, Wearable Devices, Computing Devices (such as Laptops, Notebooks, Desktops, Workstations, etc.), IoT Devices, Automotive Systems (such as connected cars, Autonomous Vehicles, Vehicle-to-Everything (V2X) communication devices, etc.), Enterprise Devices such as robotics, Specialized Equipment (such as Medical Devices, Public Safety Devices, etc.), Media Devices (such as Gaming Consoles, Streaming Devices, etc.).

[0124] In an embodiment, in Fig. 4, the UE (100) includes a processor (402), a memory (404), an I / O interface (406), an ATUCI handling controller (408), and a satellite handling controller (410) coupled to the processor (402) and the first memory (404). The components are explained in further detail below.

[0125] The processor (402) communicate with the memory (404), the I / O interface (406), and the ATUCI handling controller (408), and the satellite handling controller (410). The processor (402) is configured to execute instructions stored in the memory (404) and to perform various processes. The processor (402) includes one or a plurality of processors, is a general-purpose processor such as the CPU, an application processor (AP), or the like, a graphics-only processing unit such as a graphics processing unit (GPU), a visual processing unit (VPU), and / or an Artificial Intelligence (AI) dedicated processor such as a neural processing unit (NPU).

[0126] The memory (404) includes storage locations to be addressable through the processor (402). The memory (404) stores the first NAS message received including the reject cause code #15, the list of forbidden tracking areas, and the like. The memory (404) is not limited to a volatile memory and / or a non-volatile memory. Further, the memory (404) includes a plurality of computer-readable storage media. The memory (404) includes non-volatile storage elements. For example, non-volatile storage elements include magnetic hard disks, optical disks, floppy disks, flash memories, or forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories. In addition, the memory may, in some examples, be considered a non-transitory storage medium. The term "non-transitory" may indicate that the storage medium is not embodied in a carrier wave or a propagated signal. However, the term "non-transitory" should not be interpreted that the memory is non-movable. In some examples, the memory is configured to store larger amounts of information. In certain examples, a non-transitory storage medium may store data that can, over time, change (e.g., in Random Access Memory (RAM) or cache).

[0127] The I / O interface (406) transmits the information between the memory (404) and external peripheral devices. The peripheral devices are the input-output devices associated with the UE (100). Further, the ATUCI handling controller (408) and the satellite handling controller (410) communicate with the I / O interface (406) and the memory (404). The ATUCI handling controller (408) and the satellite handling controller (410) are coupled to the memory (404) and the processor (402). This coupling allows for efficient data transfer and communication between the components, ensuring that the ATUCI handling controller (408) can handle cell selection or reselection of a cell associated with a TAI in a wireless communication system, and the.

[0128] The ATUCI correlation controller (408) is an innovative integrated circuit that is implemented in the UE (100). In an embodiment, the structure of such innovative integrated circuit includes a multi-core architecture that enables handling cell selection or reselection of a cell associated with a TAI in a wireless communication system. Each core is optimized for specific tasks, such as receiving a first NAS message on a first RAT, detecting whether the first NAS message mentions that the first RAT is restricted, skipping storing of the first RAT in the list of forbidden tracking areas when the first RAT is restricted, and the like. The innovative integrated circuit for the above-mentioned points is made of a combination of analog and digital components designed to enable handling cell selection or reselection of a cell associated with a TAI in a wireless communication system. The analog components include a low-noise amplifier and a high-precision analog-to-digital converter to ensure accurate signal processing. The digital components consist of a microcontroller unit (MCU) and a digital signal processor (DSP) that work in tandem to enable handling cell selection or reselection of a cell associated with a TAI in a wireless communication system.

[0129] The satellite correlation controller (410) is an innovative integrated circuit that is implemented in the UE (100). In an embodiment, the structure of such innovative integrated circuit includes a multi-core architecture that enables handling cell selection or reselection of a cell associated with a TAI in a wireless communication system. Each core is optimized for specific tasks, such as receiving a first NAS message on a first RAT, detecting whether the first NAS message mentions that satellite NG-RAN is not allowed in the PLMN (302), skipping storing of the first RAT in the list of forbidden tracking areas when the satellite NG-RAN is not allowed in the PLMN (302), initiating a registration of the UE (100) on the first RAT based on a timer expiry, and the like. The innovative integrated circuit for the above-mentioned points is made of a combination of analog and digital components designed to enable handling cell selection or reselection of a cell associated with a TAI in a wireless communication system. The analog components include a low-noise amplifier and a high-precision analog-to-digital converter to ensure accurate signal processing. The digital components consist of a microcontroller unit (MCU) and a digital signal processor (DSP) that work in tandem to enable handling cell selection or reselection of a cell associated with a TAI in a wireless communication system.

[0130] Fig. 5 is a sequence diagram that illustrates a process of RAT restriction management and TAI handling for the UE (100) in a mobile network according to an embodiment as disclosed herein. As shown, the sequence diagram includes the UE (100), the RAT-1 (102A), the AMF-1 (104A), the RAT-2 (102B), the MME-1 (106), and the NF (108) in communication with each other. The UE (100) memorizes the TAI(s) received for RAT Restriction and remove the TAI(s) from FTAI list once the RAT restrictions are removed by the NF (108), according to embodiments as disclosed herein.

[0131] In an embodiment, when the NF (108) decides restrict the UE (100) to avail service on certain RAT(s) & sends reject cause #15 along with RAT Utilization Control Information in any of the NAS messages (for example, Registration Reject, UCU, UPU etc.). #15 optionally includes the TAI(s) in which the UE (100) is restricted to use the mentioned RAT(s). The proposed solution emphasizes that the UE (100) shall memorize the TAI(s)(TAI(s) received in NAS message or the current TAI where a NAS message is received with cause code #15 or any other cause) to be added in the FTAI list along with the RAT Utilization Control Information IE. The NF (108) decides to allow the UE (100) to avail service on the previously restricted RAT(s) and updates the RAT RAT Utilization Control Information to the UE (100) in any of the NAS messages (for example, UCU, UPU, SOR Update etc.). Remove the memorized TAI(s) added in the FTAI list due to RAT Restriction. Since TAI(s) is / are not part of FTAI list, the UE (100) can access / register on those TAI(s).

[0132] Fig. 6 is a sequence diagram that illustrates a process of RAT restriction, TAI management, and registration handling for the UE (100) according to an embodiment as disclosed herein. The UE (100) is initially restricted from using certain RATs in specific TAIs, but can later attempt to access those areas once the restriction is removed. The NF (108) plays a role in determining whether to accept or reject the registration of the UE (100) based on the current TAI, according to embodiments as disclosed herein.

[0133] In an embodiment, when the NF (108) decides to restrict the UE (100) to avail service on certain RAT(s) & sends reject cause #15 along with RAT utilization control information in any of the NAS messages (for example, Registration Reject, UCU, UPU etc.). #15 optionally includes the TAI(s) in which the UE (100) is restricted to use the mentioned RAT(s). The UE (100) shall add the TAI(s) received in #15 along with RAT Utilization Control Information, in the FTAI list. The NF (108) decides allow the UE (100) to avail service on the previously restricted RAT(s) and updates the RAT Restriction Information to in any of the NAS messages (for example, UCU, UPU, SOR Update etc.). The UE (100) shall try to access / register on the TAI(s) even if in FTAI list.

[0134] In an embodiment, the NF (108) shall accept the registration (i.e. provide registration accept message to the UE (100) along with RAT utilization control information IE) if the current TAI the UE (100) is camped on is allowed for the UE (100) or reject the registration if current TAI is not allowed (or forbidden for the UE (100) and provide registration reject message along with the RAT utilization control information IE.

[0135] In an embodiment, the NF (108) should indicate a cause code and include the RAT utilization control information. The UE (100) understands that one or more RATs are restricted based on the RAT utilization control information but the UE (100) will not add the TAI as part of the FTAI list. The cause code can be an existing cause code as described in TS 24.501 or it can be a new cause code. The cause code can be included as part of any NAS message e.g. registration accept message, registration reject message and the deregistration request message. The UE (100) may perform actions as described in this embodiment when the RAT utilization control information is received by the UE (100).

[0136] In an embodiment, reject or deregistration message without including any cause code and include RAT Utilization Control Information IE. #15 is used as an example in this embodiment. However, it can be any other cause code for e.g. 11,12,13,14, 16, the complete list of cause codes which can be received in a NAS message is described in TS 24.501. If the NAS message optionally including the cause code e.g. #15 or otherwise indicates to the UE (100) along with the RAT utilization control information and indicates Equivalent Public Land Mobile Network (EPLMN) is also restricted (Type of Operation Description(TOOD)), then the UE (100) shall add the TAIs of the EPLMN as part of the FTAI list. The UE (100) shall memorize that it has added the TAIs including of the EPLMN and when the RAT is no more restricted for the UE (100), the UE (100) shall remove the memorized TAIs which were added due to RAT utilization control information.

[0137] In an embodiment, the RAT restriction information / policy can be delivered to the UE (100) in such a way that at least one

[0138] of the below in any order / combination is used to determine if a given RAT is allowed (also referred as non-restricted access technology) or forbidden (also referred at restricted access technology) to the UE (100).

[0139] ≫ Per PLMN-ID: RAT can be restricted on a per PLMN (302)) basis. E.g. PLMN-1: Allowed: RAT-1,2, Forbidden RAT-3,4

[0140] ≫ Per TAI: RAT is restricted for a given TAI / RA or for a list of TAI / RA. E.g. TAI-1: Allowed: RAT-1,2, Forbidden RAT-3,4

[0141] ≫ Per cell: RAT can be restricted per PCI / ARFCN or per Global cell ID or for a list of cells. E.g. Cell-ID-1: Allowed: RAT-1,2, Forbidden RAT-3,4

[0142] ≫ Per area: Allowed area for a given RAT or forbidden Area for a given RAT.

[0143] ≫ Per time: E.g. LTE RAT optionally on the PLMN (302) X is forbidden from 9:00 AM to 6 PM or NR is forbidden on a list of TAIs for the next two hours. Or the time may start when a message or indication is received from the network till the duration expires

[0144] ≫ Per RAT type: This indicates the information on whether a given RAT is allowed or forbidden for the UE (100).

[0145] In an embodiment, if the RAT restriction policy is received from the NF (108), by means of signalling such as UCU, Attach / Registration / TAU accept or reject or Detach / Deregistration request, then, the policy is applied to the PLMN (302) only and if the RAT restriction policy is delivered by HSS / UDM by procedures such as SOR / UPU, then the HPLMN can also update the policy for other PLMNs.

[0146] In an embodiment of RAT restriction policy application, before the policy is exchanged between the UE (100) and NF (108), the UE (100) should have indicated the support for RAT restriction (i.e., Access technology utilization control supported) in the UE capability exchange (5GMM capability IE or UE network capability IE). Access technology utilization control Information Element (IE) is used to communicate the restricted access technologies (e.g., Satellite communication, next generation radio access network (NG-RAN), UMTS Terrestrial Radio Access Network (UTRAN), evolved-UTRAN (E-UTRAN), GSM / EDGE Radio Access Network (GERAN)) information to the UE or to indicate to the UE to remove the access technology utilization control information Once the UE (100) receives the RAT restriction policy, the existing policy, if any, will be replaced with the received policy. The RAT restriction policy does not apply to the UE (100) in Emergency mode or when a Disaster condition is detected or when the UE (100) is camped for Disaster roaming or when the UE (100) is in Manual mode. The RAT restriction policy shall not take effect if the RAT was earlier restricted for the UE (100) by means of a reject cause. If the UE (100) received a reject cause earlier (say #27) which restricted the UE (100) on a particular RAT and the new policy does not restrict that RAT for the UE (100), the UE (100) is still not allowed to access the RAT. The UE (100) shall follow the reject cause handling as per specification. If the UE (100) has restricted a RAT due to Voice not being available on that RAT, then, the RAT restriction policy does not take effect for that RAT. If the RAT restriction policy un-restricts a RAT that was not allowed as per the OPMNwAct list on SIM, then, the UE (100) shall ignore the RAT restriction policy and follow OPLMNwACT list. If all of the supported RAT of the UE (100) are restricted for the PLMN (302), it should be treated as a Forbidden PLMN (FPLMN) . The term area / location / geographical area are used in this embodiment may refer to any of cell / cell ID, TAC / TAI, PLMN (302), MCC / MNC, Latitude / longitude, CAG cell or any geographical location / coordinate.

[0147] In an embodiment, the term FTAI list used refers to the Forbidden Tracking Area list (as defined in the 3GPP TS 23.122). It can be any or at least of one of "forbidden location areas for roaming", "forbidden tracking areas for roaming", "5GS forbidden tracking areas for roaming", "forbidden location areas for regional provision of service", "forbidden tracking areas for regional provision of service", "5GS forbidden tracking areas for regional provision of service", "CAG information list", or "PLMNs not allowed to operate at the present location of the UE (100)". This can also include the Forbidden PLMN lists (as described in TS 23.122 / TS 24.501) wherein the list will include the PLMN IDs instead of TAI lists. The term FTAI list is used for illustration when TAI is forbidden but it can be any area. The term area / location / geographical area are used in this embodiment may refer to any of cell / cell ID, TAC / TAI, PLMN (302), MCC / MNC, Latitude / longitude, CAG cell or any geographical location / coordinate.

[0148] In an embodiment, the RAT (or AT) utilization control information can be included in any downlink NAS message with RAT restriction information (for example, GERAN is not restricted or GERAN is restricted etc.) is indicated to the UE (100). Additionally, the NF (108) can indicate to the UE (100) whether the RAT restriction is applied on the PLMN (302) equivalent.

[0149] ≫ RAT utilization control: The purpose of the RAT utilization control information element is for the network to communicate the restricted RAT(s) information (i.e RAT restriction policy) to the UE (100). (May indicate through Type of RAT utilization control set to the PLMN (302) and its equivalent PLMN(s))

[0150] ≫ The RAT utilization control information element is coded as shown in figure　9.9.3.3x.1 and table　9.9.3.3x.1.

[0151] ≫ The RAT utilization control is a type 4 information element.

[0152]

[0153] Table 1: RAT utilization control information element

[0154]

[0155] Table　2: RAT utilization control information element

[0156] In an embodiment, RAT utilization control Information is set to current PLMN and its equivalent PLMN(s) then the UE (100) deems that all TAI(s) for the equivalent PLMN(s) are forbidden TAI / LAI.

[0157] For example, suppose the UE (100) is registered on PLMN-1 and PLMN-2 is equivalent to the PLMN (302). If the RAT utilization control set to current PLMN and its equivalent PLMN(s)

[0158] ≫ case 1: The UE (100) deems that all LAI of PLMN-2 is forbidden LAI if the GERAN is restricted

[0159] ≫ case 2: The UE (100) deems that all TAI(s) of the PLMN-2 is forbidden TAI if the UTRAN is restricted

[0160] ≫ case 3: The UE (100) deems that all TAI(s) of the PLMN-2 is forbidden TAI if the NG-RAN is restricted

[0161] In these case, additionally the UE (100) memorizes that all Forbidden LAI (location area identifier), Forbidden TAI is due to RAT restriction.

[0162] When the RAT restriction is removed then the UE (100) additionally remove the forbidden TAI / forbidden LAI from the forbidden TAI / LAI list when corresponding RAT / access is not restricted (for example, UTRAN is not restricted, the forbidden TAI stored due to RAT restriction is removed).

[0163] In this embodiment, NAS message is specified in TS 24.501 or TS 24.301 as below. This is some of the NAS message but not limited to the listed below.

[0164] TS 24.501

[0165] a) IDENTITY REQUEST

[0166] b) AUTHENTICATION REQUEST;

[0167] c) AUTHENTICATION RESULT;

[0168] d) AUTHENTICATION REJECT;

[0169] e) REGISTRATION REJECT

[0170] f) DEREGISTRATION ACCEPT

[0171] g) SERVICE REJECT

[0172] h) REGISTRATION REQUEST;

[0173] i) IDENTITY RESPONSE (if requested identification parameter is SUCI);

[0174] j) AUTHENTICATION RESPONSE;

[0175] k) AUTHENTICATION FAILURE;

[0176] l) SECURITY MODE REJECT;

[0177] m) DEREGISTRATION REQUEST; and

[0178] n) DEREGISTRATION ACCEPT;

[0179] p) UCU- UE CONFIGURATION UPDATE COMMAND

[0180] q) UPU-UE parameter update

[0181] 24.301

[0182] ATTACH REQUEST; - IDENTITY RESPONSE (if requested identification parameter is IMSI); - AUTHENTICATION RESPONSE; - AUTHENTICATION FAILURE; - SECURITY MODE REJECT; - DETACH REQUEST; - DETACH ACCEPT; - TRACKING AREA UPDATE REQUEST, - ATTACH REQUEST; - IDENTITY RESPONSE; - AUTHENTICATION RESPONSE; - AUTHENTICATION FAILURE; - SECURITY MODE REJECT; - DETACH REQUEST; - DETACH ACCEPT; - TRACKING AREA UPDATE REQUEST; - SERVICE REQUEST; - EXTENDED SERVICE REQUEST; - CONTROL PLANE SERVICE REQUEST, TRACKING AREA UPDATE REJECT, ATTACH REJECT, GUTI RELLOACTION COMMAND

[0183] In an embodiment, if the UE (100) receives the NAS message (optionally with 5GMM or EMM cause value cause #15) and if the UE (100) is not operating in SNPN access operation mode and the Forbidden TAI(s) for the list of "5GS forbidden tracking areas for roaming" IE and the RAT utilization control IE is not included in the NAS message (for example, DEREGISTRATION REQUEST message), the UE (100) shall store the current TAI in the list of "5GS forbidden tracking areas for roaming". Otherwise, the UE (100) shall store the current TAI in the list of "5GS forbidden tracking areas for roaming" for the current SNPN and the selected entry of the "list of subscriber data" or the selected PLMN subscription.

[0184] In an embodiment, if the UE (100) receives the NAS message (optionally with 5GMM or EMM cause value e,g cause #15) and

[0185] ≫ if the UE (100) is in WB-S1 mode and the Extended EMM cause IE with value "E-UTRAN not allowed" is included in the ATTACH REJECT message, the UE (100) supports "E-UTRA Disabling for EMM cause #15", and the "E-UTRA Disabling Allowed for EMM cause #15" parameter as specified in 3GPP TS 24.368 [15A] or 3GPP TS 31.102

[0017] is present and set to enabled; then the UE (100) shall disable the E-UTRA capability as specified in subclause 4.5 and search for a suitable cell in GERAN or UTRAN or NG-RAN radio access technology.;

[0186] ≫ if the UE (100) is in NB-S1 mode and the Extended EMM cause IE with value "NB-IoT not allowed" is included in the ATTACH REJECT message, then the UE (100) may disable the NB-IoT capability as specified in subclause 4.9 and search for a suitable cell in E-UTRAN radio access technology; - otherwise, the UE (100) shall search for a suitable cell in E-UTRAN radio access technology.

[0187] Then, the UE (100) adds the current TAI in the list of "forbidden tracking areas for roaming" if the E-UTRA capability is not disabled due to extended EMM cause.

[0188] In an embodiment, if the UE (100) receives the NAS message (optionally with 5GMM or EMM cause value e,g cause #15) and

[0189] - if the UE (100) is in WB-S1 mode and RAT utilization control IE is included in the NAS message (for example, included in the ATTACH REJECT message), the UE (100) shall not add the current TAI in the list of "forbidden tracking areas for roaming",

[0190] - if the UE (100) is in NB-S1 mode and RAT utilization control IE is included in the NAS message (for example, included in the ATTACH REJECT message), the UE (100) shall not add the current TAI in the list of "forbidden tracking areas for roaming",

[0191] Then, the UE (100) adds the current TAI in the list of "forbidden tracking areas for roaming" if RAT utilization control IE is not included in the NAS message.

[0192] In an embodiment, when the UE (100) receives NAS message with the RAT utilization control information then the UE (100) can ignore the associated 5GMM cause value #x (specified in TS 24.501), EMM cause value #X(specified in TS 24.301), GMM cause value #x (optionally for the RAT / access which is restricted). e,g 5GMM cause #11, 12, 13, 15 etc.

[0193] In the embodiment, the terms RAT-Type and RAT or AT are used interchangeably and have the same meaning and they represent at least one of the following: 5G(N1 mode), 4G(S1 mode), 3G, 2G, Evolved Packet Service (EPS), 5GS,NR ,NR in unlicensed bands, NR(LEO) satellite access, NR(MEO) satellite access, NR(GEO) satellite access, NR(OTHERSAT) satellite access, NR RedCap, E-UTRA, E-UTRA in unlicensed bands, NB-IoT or NB-S1, WB-IoT, LTE-M., E-UTRAN, GERAN, satellite E-UTRAN, NG-RAN, satellite NG-RAN

[0194] In the embodiment, FTAI, forbidden TAI are used interchangeably and have the same meaning. Forbidden LAI is used for "forbidden location areas for regional provision of service" or the list of "forbidden location areas for roaming.

[0195] Fig. 7 is a sequence diagram that illustrates a scenario of the UE (100) receiving the service according to an embodiment as disclosed herein. As shown in the sequence diagram, the UE (100) and the PLMN (302) are in communication with each other. Each step is explained in further detail below.

[0196] At step 1, the UE (100) send uplink NAS message (for example, registration message or tracking area update request or service request).

[0197] At step 2, the UE (100) rece ive NAS message (for example, registration reject, tracking area update reject or network initiated detach) including 5GMM cause #15 and extended 5GMM cause IE with value "Satellite NG-RAN not allowed in the PLMN (302)"(over the Satellite NG-RAN) or EMM cause value #15 and extended EMM cause IE with value "Satellite E-UTRAN not allowed in the PLMN (302)"(over the Satellite E-UTRAN).

[0198] MS disables its satellite NG-RAN capability on the PLMN (302) (for example, PLMN-1) due to Satellite NG-RAN not allowed in the PLMN (302) (if NAS message received over the satellite NG-RAN). Start TS timer or MS disables its satellite E-UTRAN capability (if NAS message is received over Satellite E-UTRAN ) on the PLMN (302) (PLMN-1) due to Satellite E-UTRAN not allowed in the PLMN (302). Start TL timer, as illustrated in the step 3.

[0199] The UE (100) shall not store the current TAI (for example, TAI-1) in the list of FTAI list optionally for the respective access technology (Satellite E-UTRAN or Satellite NG-RAN ) where the NAS message in step 2 is received when the UE (100) disables its satellite NG-RAN capability / satellite E-UTRAN capability on the PLMN (302) (for example, TAI-1 is not stored into the FTAI list). The UE (100) stores the TAI-1 into the FTAI list only if the satellite NG-RAN capability / satellite E-UTRAN capability is not disabled due to step 3.

[0200] After TS or TL timer expiry, the UE (100) deletes the stored information in the "PLMNs with satellite NG-RAN not allowed" list or "PLMNs with satellite E-UTRAN not allowed" list as illustrated at the step 5.

[0201] As the TAI (TAI-1) is not in the FTAI list so if the UE (100) is in the TAI-1 location will receive the service.

[0202] Alternatively, in step 3 the UE (100) stores the TAI-1 into the FTAI list and optionally memorize that the UE (100) stored TAI-1 into the FTAI list is because of the step 2 (Satellite NG-RAN not allowed in the PLMN (302) or Satellite E-UTRAN not allowed in the PLMN (302)). After TS or TL timer expiry, MS delete stored information in the "PLMNs with satellite NG-RAN not allowed" list / "PLMNs with satellite E-UTRAN not allowed" list. The UE (100) additionally delete the TAI (optionally all TAI stored in the FTAI list have memorization that TAI was stored due to step-2) from FTAI list stored for the satellite E-UTRAN or satellite NG-RAN access.

[0203] Fig. 8 is a flow diagram that illustrates a method for handling cell selection or reselection of a cell associated with a TAI associated with an ATUCI according to an embodiment as disclosed herein. The method includes steps (802-816). Each step is explained in further detail below.

[0204] At step (802), the UE (100) initiates a first NAS request message on a first RAT within a first PLMN. The first NAS request message is camped on a cell belonging to a first TAI. The first NAS request message includes a registration request message, a deregistration request message, an attach request message, a detach request message, a tracking area update request message, a service request message, and the like.

[0205] At step (804), the UE (100) receives a first NAS message on the first RAT upon initiation of the first NAS request message. The first NAS message includes a reject cause #15 stating 'no suitable cells in tracking area'. At step (806), the UE (100) detects whether the first NAS message includes UE ATUCI. The ATUCI mentions that access to the first RAT is restricted. The first NAS message includes a registration reject message, a deregistration request message, an attach reject message, a detach request message, a tracking area update reject, service reject message, and the like.

[0206] At step (808), the UE (100) skips storing of the first TAI in a list of forbidden tracking areas for roaming when the first NAS message received includes the ATUCI. At step (810), the UE (100) initiates a registration on a second RAT within the first PLMN. This is initiated when the first TAI is not stored in the list of forbidden tracking areas for roaming.

[0207] At step (812) receives a second NAS message that mentions that the UE ATUCI mentioning that access to the first RAT is not restricted. At step (814), the UE (100) generates a second NAS request message on the first RAT belonging to a first TAI when the first RAT is not restricted. At step (816), the UE (100) initiates the registration of the UE (100) on the first RAT using the second NAS request message.

[0208] In an embodiment, the UE (100) detects whether it is not operating in a standalone non-public network (SNPN) access operation mode, whether forbidden TAI(s) for a list of forbidden tracking areas for roaming is not included in the registration reject message, and whether an ATUCI information element (IE) is not included in the registration reject message. The UE (100) then stores a first TAI belonging to a first RAT in the list of forbidden tracking areas for roaming when the UE (100) is not operating in the SNPN access operation mode.

[0209] In an embodiment, the UE (100) detects whether it is not operating in the SNPN access operation mode, whether forbidden TAI(s) for a list of forbidden tracking areas for roaming is not included in the deregistration request message, and whether an ATUCI IE is not included in the deregistration request message. The UE (100) stores a first TAI belonging to a first RAT in the list of forbidden tracking areas for roaming when the UE (100) is not operating in the SNPN access operation mode. Else, the UE (100) stores the first TAI belonging to the first RAT in the list of forbidden tracking areas for roaming associated with a first PLMN when the UE (100) is operating in the SNPN access operation mode.

[0210] In an embodiment, the UE (100) detects whether an ATUCI IE is not included in at least one of the attach reject message, the detach request message, and the tracking area update reject message, service reject. The UE (100) stores a first TAI belonging to a first RAT in a list of forbidden tracking areas for roaming when the ATUCI IE is not included in at least one of the attach reject message, the detach request message, and the tracking area update reject message.

[0211] In an embodiment, if the UE (100) receives the Forbidden TAI(s) for example, in NAS message) for the list of "FTAI" IE (forbidden tracking areas for roaming / 5GS forbidden tracking areas for roaming IE) and the ATUCI IE is not included in the REGISTRATION REJECT / SERVICE REJECT / ATTACH REJETC / TAU REJECT message, the UE (100) shall store the TAI(s) belonging to the serving PLMN or equivalent PLMN(s) and ignore the TAI(s) which do not belong to the serving PLMN or equivalent PLMN(s) included in the IE, if not already stored, into the list of "5GS forbidden tracking areas for roaming";

[0212] In an embodiment, if the UE (100) receive 5GMM cause #15 (No suitable cells in tracking area) in the NAS message (e.g. SERVICE REJECT, REGISTRATION REJECT) then

[0213] #15 (No suitable cells in tracking area).

[0214] i) the UE (100) is not operating in SNPN access operation mode;

[0215] ii) the Forbidden TAI(s) for the list of "5GS forbidden tracking areas for roaming" IE is not included in the SERVICE REJECT, REGISTRATION REJECT message; and

[0216] iii) the Access technology utilization control IE is not included in the SERVICE REJECT message or the SERVICE REJECT, REGISTRATION REJECT message is not integrity protected,

[0217] then the UE (100) shall store the current TAI in the list of "5GS forbidden tracking areas for roaming" and remove the current TAI from the stored TAI list if present.

[0218] In an embodiment, if the UE (100) is not operating in SNPN access operation mode, the Forbidden TAI(s) for the list of "5GS forbidden tracking areas for roaming" IE is not included in the DEREGISTRATION REQUEST message and Access technology utilization control IE is not included in the DEREGISTRATION REQUEST message, the UE (100) shall store the current TAI in the list of "5GS forbidden tracking areas for roaming".

[0219] If the UE (100) stores the current TAI in the list of "5GS forbidden tracking areas for roaming" and the SERVICE REJECT message is not integrity protected, the UE (100) shall memorize the current TAI was stored in the list of "5GS forbidden tracking areas for roaming" for non-integrity protected NAS reject message;

[0220] In an embodiment, if the UE (100) receives EMM cause #15 in the NAS message (for example, SERVICE REJECT, ATTACH REJECT, TRACKING AREA UPDATE REJECT) message and,

[0221] the Extended EMM cause IE with value "Satellite E-UTRAN not allowed in PLMN" is not included in the ATTACH REJECT / TRACKING AREA UPDATE REJECT / SERVICE REJECT message or the ATTACH REJECT / TRACKING AREA UPDATE REJECT / SERVICE REJECT message is not integrity protected; and

[0222] the Access technology utilization control IE is not included in the ATTACH REJECT / TRACKING AREA UPDATE REJECT / SERVICE REJECT message or the ATTACH REJECT / TRACKING AREA UPDATE REJECT / SERVICE REJECT message is not integrity protected,

[0223] then the UE (100) shall store the current TAI in the list of "forbidden tracking areas for roaming".

[0224] Fig. 9 is a flow diagram that illustrates that illustrates a method for handling cell selection or reselection of a cell associated with a TAI associated with a satellite NG-RAN according to an embodiment as disclosed herein. The method includes steps (902-912). Each step is explained in further detail below.

[0225] At step (902), the UE (100) initiates a first NAS request message on a first RAT within a first PLMN. The first NAS request message is camped on a cell belonging to a first TAI. The first NAS request message includes a registration request message, an attach request message, a tracking area update request message, and the like.

[0226] At step (904), the UE (100) receives a first NAS message on the first RAT upon initiation of the first NAS request message. The first NAS message comprises a reject cause #15 stating 'no suitable cells in tracking area'. The first NAS message includes a registration reject message, an attach reject message, a tracking area update reject message, and the like.

[0227] At step (906), the UE (100) detects whether the first NAS message includes an extended cause code stating "Satellite next generation radio access network (NG-RAN) not allowed in the PLMN (302)". At step (908), the UE (100) skips storing of the first TAI in a list of forbidden tracking areas for roaming when the first NAS message includes the extended cause code stating "Satellite NG-RAN not allowed in the PLMN (302)".

[0228] At step (910), the UE (100) starts a timer associated with the UE (100) upon detection of the extended cause code stating "Satellite NG-RAN not allowed in the PLMN (302)". A capability of the satellite NG-RAN is disabled during a duration of the timer. At step (912), the UE (100) initiates a registration of the UE (100) on the first RAT belonging to the first PLMN upon an expiry of the timer.

[0229] In an embodiment, the UE (100) detects whether an extended cause code stating "Satellite NG-RAN not allowed in the PLMN (302)" is not included in at least one of the registration reject message, the attach reject message, and the tracking area update reject message or whether at least one of the registration reject message, the attach reject message, and the tracking area update reject message is not integrity performed. The UE (100) stores a first TAI belonging to a first RAT in a list of forbidden tracking areas for roaming upon the detection.

[0230] According to embodiments, a method for handling cell selection or reselection of a cell associated with a tracking area identity (TAI) in a wireless communication system is provided. The method comprises initiating, by a user equipment (UE) (100), a first non-access stratum (NAS) request message on a first radio access technology (RAT) within a first public land mobile network (PLMN). The first NAS request message is camped on a cell belonging to a first TAI. The method comprises receiving, by the UE (100), a first NAS message on the first RAT upon initiation of the first NAS request message, wherein the first NAS message comprises a reject cause #15 stating 'no suitable cells in tracking area'; detecting, by the UE (100), whether the first NAS message includes UE access technology utilization control information (ATUCI), wherein the ATUCI mentions that access to the first RAT is restricted; skipping, by the UE (100), storing of the first TAI in a list of forbidden tracking areas for roaming when the first NAS message received includes the ATUCI; and initiating, by the UE (100), a registration of the UE (100) on a second RAT within the first PLMN, when the first TAI is not stored in the list of forbidden tracking areas for roaming.

[0231] For example, detecting, by the UE (100), whether the first NAS message includes UE ATUCI comprises receiving, by the UE (100), a second NAS message that comprises the UE ATUCI mentioning that access to the first RAT is not restricted; generating, by the UE (100), a second NAS request message on the first RAT belonging to a first TAI when the first RAT is not restricted; and initiating, by the UE (100), the registration of the UE (100) on the first RAT using the second NAS request message.

[0232] For example, the first NAS request message comprises at least one of a registration request message, a deregistration request message, an attach request message, a detach request message, a tracking area update request message, and a service request message.

[0233] For example, the first NAS message comprises at least one of a registration reject message, a deregistration request message, an attach reject message, a detach request message, a tracking area update reject, and a service reject message.

[0234] For example, the method comprises detecting, by the UE (100), whether the UE (100) is not operating in a standalone non-public network (SNPN) access operation mode, whether forbidden TAI(s) for a list of forbidden tracking areas for roaming is not included in the registration reject message, and whether an ATUCI information element (IE) is not included in the registration reject message; and storing, by the UE (100), a first TAI belonging to a first RAT in the list of forbidden tracking areas for roaming when the UE (100) is not operating in the SNPN access operation mode.

[0235] For example, the method comprises detecting, by the UE (100), whether the UE (100) is not operating in a SNPN access operation mode, whether forbidden TAI(s) for a list of forbidden tracking areas for roaming is not included in the deregistration request message, and whether an ATUCI IE is not included in the deregistration request message; performing, by the UE (100), one of: storing, by the UE (100), a first TAI belonging to a first RAT in the list of forbidden tracking areas for roaming when the UE (100) is not operating in the SNPN access operation mode; and storing, by the UE (100), the first TAI belonging to the first RAT in the list of forbidden tracking areas for roaming associated with a first PLMN when the UE (100) is operating in the SNPN access operation mode.

[0236] For example, the method comprises detecting, by the UE (100), whether an ATUCI IE is not included in at least one of the attach reject message, the detach request message, and the tracking area update reject message, service reject; and storing, by the UE (100), a first TAI belonging to a first RAT in a list of forbidden tracking areas for roaming when the ATUCI IE is not included in at least one of the attach reject message, the detach request message, and the tracking area update reject message.

[0237] According to embodiments, a method for handling cell selection or reselection of a cell associated with a TAI in a wireless communication system is provided. The method comprises: initiating, by a UE (100), a first NAS request message on a first RAT within a first PLMN, wherein the first NAS request message is camped on a cell belonging to a first TAI; receiving, by the UE (100), a first NAS message on the first RAT upon initiation of the first NAS request message, wherein the first NAS message comprises a reject cause #15 stating 'no suitable cells in tracking area'; detecting, by the UE (100), whether the first NAS message includes an extended cause code stating "Satellite next generation radio access network (NG-RAN) not allowed in a PLMN (302)"; skipping, by the UE (100), storing of the first TAI in a list of forbidden tracking areas for roaming when the first NAS message includes the extended cause code stating "Satellite NG-RAN not allowed in the PLMN (302)"; starting, by the UE (100), a timer associated with the UE (100) upon detection of the extended cause code stating "Satellite NG-RAN not allowed in the PLMN (302)", wherein a capability of the satellite NG-RAN is disabled during a duration of the timer; and initiating, by the UE (100), a registration of the UE (100) on the first RAT belonging to the first PLMN upon an expiry of the timer.

[0238] The method comprises the first NAS request message comprises at least one of a registration request message, an attach request message, and a tracking area update request message.

[0239] The method comprises the first NAS message comprises at least one of a registration reject message, an attach reject message, and a tracking area update reject message.

[0240] The method comprises detecting, by the UE (100), whether an extended cause code stating "Satellite NG-RAN not allowed in the PLMN (302)" is not included in at least one of the registration reject message, the attach reject message, and the tracking area update reject message or whether at least one of the registration reject message, the attach reject message, and the tracking area update reject message is not integrity performed; and storing, by the UE (100), a first TAI belonging to a first RAT in a list of forbidden tracking areas for roaming upon the detection.

[0241] According to embodiments, a UE (100) for handling cell selection or reselection of a cell associated with a TAI in a wireless communication system is provided. The UE comprise a processor (402); a memory (404) coupled to the processor (402); and an ATUCI handling controller (408) communicatively coupled to the processor (402) and the memory (404). The ATUCI handling controller (408) initiates a first NAS request message on a first RAT within a first PLMN, wherein the first NAS request message is camped on a cell belonging to a first TAI; receives a first NAS message on the first RAT upon initiation of the first NAS request message, wherein the first NAS message comprises a reject cause #15 stating 'no suitable cells in tracking area'; detects whether the first NAS message includes UE ATUCI, wherein the ATUCI mentions that access to the first RAT is restricted; skips storing of the first TAI in a list of forbidden tracking areas for roaming when the first NAS message includes the ATUCI; and initiates a registration of the UE (100) on a second RAT within the first PLMN, when the first TAI is not stored in the list of forbidden tracking areas for roaming. The UE comprises satellite handling controller (410) communicatively coupled to the processor (402) and the memory (404). The satellite handling controller (410) initiates first NAS request message on a first RAT within a first PLMN, wherein the first NAS request message is camped on a cell belonging to a first TAI; receives a first NAS message on the first RAT upon initiation of the first NAS request message, wherein the first NAS message comprises a reject cause #15 stating 'no suitable cells in tracking area'; detects whether the first NAS message includes an extended cause code stating "Satellite NG-RAN not allowed in a PLMN (302)"; skips storing of the first TAI in a list of forbidden tracking areas for roaming when the first NAS message includes the extended cause code stating "Satellite NG-RAN not allowed in the PLMN (302)"; starts a timer associated with the UE (100) upon detection of the extended cause code stating "Satellite NG-RAN not allowed in the PLMN (302)", wherein a capability of the satellite NG-RAN is disabled during a duration of the timer; and initiates a registration of the UE (100) on the first RAT belonging to the first PLMN upon an expiry of the timer.

[0242] For example, the first TAI is part of a current TAI or part of the list of forbidden tracking areas for roaming received in the first NAS message.

[0243] According to embodiments, a method performed by a user equipment (UE) in a wireless communication system is provided. The method comprises transmitting a first non-access stratum (NAS) request message to a network entity (e.g., MME, AMF) of a public land mobile network (PLMN), wherein the first NAS request message is camped on a cell belonging to a current tracking area identity (TAI); receiving a first NAS reject message upon initiation of the first NAS request message from the network entity (e.g., MME, AMF), wherein the first NAS reject message comprises a reject cause #15 indicating 'no suitable cells in tracking area'; determining whether the first NAS reject message includes access technology utilization control information or not; in accordance with a determination that the first NAS reject message include the access technology utilization control information, skipping storing of the current TAI in a list of forbidden tracking areas for roaming; and in accordance with a determination that the first NAS reject message does not include the access technology utilization control information, storing the current TAI in a list of forbidden tracking areas for roaming based on at least one condition.

[0244] For example, the method comprises determining whether the UE is operating in a standalone non-public network (SNPN) access operation mode or not; and determining whether at least one forbidden TAI for the list of forbidden tracking areas for roaming is included in the first NAS reject message. The current TAI is stored in a case that the UE is not operating in the SNPN access operation mode, the at least one forbidden TAI for the list of forbidden tracking areas for roaming is not included in the first NAS reject message, and the access technology utilization control information is not included in the first NAS reject message.

[0245] For example, the method comprises determining whether an extended cause code indicating "Satellite NG-RAN not allowed in PLMN" or "Satellite E-UTRAN not allowed in PLMN" is included in the first NAS reject message or not, and in accordance with a determination that the extended cause code indicating "Satellite NG-RAN not allowed in PLMN" or "Satellite E-UTRAN not allowed in PLMN" is included in the first NAS reject message, skipping storing of the current TAI in a list of forbidden tracking areas for roaming.

[0246] For example, the current TAI is stored in a case that the UE is not operating in the SNPN access operation mode, the at least one forbidden TAI for the list of forbidden tracking areas for roaming is not included in the first NAS reject message, the extended cause code indicating "Satellite NG-RAN not allowed in PLMN" or "Satellite E-UTRAN not allowed in PLMN" is not included in the first NAS reject message, and the access technology utilization control information is not included in the first NAS reject message.

[0247] For example, the method comprises receiving a second NAS message that comprises access technology utilization control information indicating that access to a first RAT is not restricted; generating a second NAS request message on the first RAT belonging to the current TAI in a case that the first RAT is not restricted; and initiating a registration of the UE on the first RAT using the second NAS request message.

[0248] For example, the first NAS request message comprises at least one of a registration request message, a deregistration request message, an attach request message, a detach request message, a tracking area update request message, or a service request message.

[0249] For example, the first NAS reject message comprises at least one of a registration reject message, a deregistration request message, an attach reject message, a detach request message, a tracking area update reject, or a service reject message.

[0250] According to embodiments, a user equipment (UE) in a wireless communication system is provided. The UE comprises at least one processor comprising processing circuitry; at least one transceiver comprising communication circuitry; and memory storing instructions that, when executed by the at least one processor, cause the at least one processor to transmit a first non-access stratum (NAS) request message to a network entity (e.g., MME, AMF) of a public land mobile network (PLMN) through the at least one transceiver, wherein the first NAS request message is camped on a cell belonging to a current tracking area identity (TAI); receive a first NAS reject message upon initiation of the first NAS request message from the network entity (e.g., MME, AMF) through the at least one transceiver, wherein the first NAS reject message comprises a reject cause #15 indicating 'no suitable cells in tracking area'; determine whether the first NAS reject message includes access technology utilization control information or not; in accordance with a determination that the first NAS reject message include the access technology utilization control information, skip storing of the current TAI in a list of forbidden tracking areas for roaming; and in accordance with a determination that the first NAS reject message does not include the access technology utilization control information, store the current TAI in a list of forbidden tracking areas for roaming based on at least one condition.

[0251] For example, the instructions, when executed by the at least one processor, cause the at least one processor to determine whether the UE is operating in a standalone non-public network (SNPN) access operation mode or not; and determine whether at least one forbidden TAI for the list of forbidden tracking areas for roaming is included in the first NAS reject message. The current TAI is stored in a case that the UE is not operating in the SNPN access operation mode, the at least one forbidden TAI for the list of forbidden tracking areas for roaming is not included in the first NAS reject message, and the access technology utilization control information is not included in the first NAS reject message.

[0252] For example, the instructions, when executed by the at least one processor, cause the at least one processor to determine whether an extended cause code indicating "Satellite NG-RAN not allowed in PLMN" or "Satellite E-UTRAN not allowed in PLMN" is included in the first NAS reject message or not, and in accordance with a determination that the extended cause code indicating "Satellite NG-RAN not allowed in PLMN" or "Satellite E-UTRAN not allowed in PLMN" is included in the first NAS reject message, skip storing of the current TAI in a list of forbidden tracking areas for roaming.

[0253] For example, the current TAI is stored in a case that the UE is not operating in the SNPN access operation mode, the at least one forbidden TAI for the list of forbidden tracking areas for roaming is not included in the first NAS reject message, the extended cause code indicating "Satellite NG-RAN not allowed in PLMN" or "Satellite E-UTRAN not allowed in PLMN" is not included in the first NAS reject message, and the access technology utilization control information is not included in the first NAS reject message.

[0254] For example, the instructions, when executed by the at least one processor, cause the at least one processor to receive a second NAS message that comprises access technology utilization control information indicating that access to a first RAT is not restricted; generate a second NAS request message on the first RAT belonging to a current TAI in a case that the first RAT is not restricted; and initiate a registration of the UE on the first RAT using the second NAS request message.

[0255] For example, the first NAS request message comprises at least one of a registration request message, a deregistration request message, an attach request message, a detach request message, a tracking area update request message, or a service request message.

[0256] For example, the first NAS reject message comprises at least one of a registration reject message, a deregistration request message, an attach reject message, a detach request message, a tracking area update reject, or a service reject message

[0257] According to embodiments, a non-transitory storage medium is provided. The non-transitory storage medium is configured to store one or more instructions that, when executed by at least one processor, cause a user equipment (UE) to perform operations including transmitting a first non-access stratum (NAS) request message to a network entity of a public land mobile network (PLMN), wherein the first NAS request message is camped on a cell belonging to a current tracking area identity (TAI); receiving a first NAS reject message upon initiation of the first NAS request message from the network entity, wherein the first NAS reject message comprises a reject cause #15 indicating 'no suitable cells in tracking area'; determining whether the first NAS reject message includes access technology utilization control information or not; in accordance with a determination that the first NAS reject message include the access technology utilization control information, skipping storing of the current TAI in a list of forbidden tracking areas for roaming; and in accordance with a determination that the first NAS reject message does not include the access technology utilization control information, storing the current TAI in a list of forbidden tracking areas for roaming based on at least one condition.

[0258] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the scope of the embodiments as described herein.

Claims

1.A method performed by a user equipment (UE) in a wireless communication system, the method comprising:transmitting a first non-access stratum (NAS) request message to a network entity of a public land mobile network (PLMN), wherein the first NAS request message is camped on a cell belonging to a current tracking area identity (TAI);receiving a first NAS reject message upon initiation of the first NAS request message from the network entity, wherein the first NAS reject message comprises a reject cause #15 indicating 'no suitable cells in tracking area';determining whether the first NAS reject message includes access technology utilization control information or not;in accordance with a determination that the first NAS reject message include the access technology utilization control information, skipping storing of the current TAI in a list of forbidden tracking areas for roaming; andin accordance with a determination that the first NAS reject message does not include the access technology utilization control information, storing the current TAI in a list of forbidden tracking areas for roaming based on at least one condition.2.The method of claim 1, further comprising:determining whether the UE is operating in a standalone non-public network (SNPN) access operation mode or not; anddetermining whether at least one forbidden TAI for the list of forbidden tracking areas for roaming is included in the first NAS reject message,wherein the current TAI is stored in a case that the UE is not operating in the SNPN access operation mode, the at least one forbidden TAI for the list of forbidden tracking areas for roaming is not included in the first NAS reject message, and the access technology utilization control information is not included in the first NAS reject message.3.The method of claim 2, further comprising:determining whether an extended cause code indicating "Satellite NG-RAN not allowed in PLMN" or "Satellite E-UTRAN not allowed in PLMN" is included in the first NAS reject message or not; andin accordance with a determination that the extended cause code indicating "Satellite NG-RAN not allowed in PLMN" or "Satellite E-UTRAN not allowed in PLMN" is included in the first NAS reject message, skipping storing of the current TAI in a list of forbidden tracking areas for roaming.4.The method of claim 3,wherein the current TAI is stored in a case that the UE is not operating in the SNPN access operation mode, the at least one forbidden TAI for the list of forbidden tracking areas for roaming is not included in the first NAS reject message, the extended cause code indicating "Satellite NG-RAN not allowed in PLMN" or "Satellite E-UTRAN not allowed in PLMN" is not included in the first NAS reject message, and the access technology utilization control information is not included in the first NAS reject message.5.The method of claim 1, further comprising:receiving a second NAS message that comprises access technology utilization control information indicating that access to a first RAT is not restricted;generating a second NAS request message on the first RAT belonging to the current TAI in a case that the first RAT is not restricted; andinitiating a registration of the UE on the first RAT using the second NAS request message.6.The method of claim 1, wherein the first NAS request message comprises at least one of a registration request message, a deregistration request message, an attach request message, a detach request message, a tracking area update request message, or a service request message.7.The method of claim 1, wherein the first NAS reject message comprises at least one of a registration reject message, a deregistration request message, an attach reject message, a detach request message, a tracking area update reject, or a service reject message.8.A user equipment (UE) in a wireless communication system, the UE comprising:at least one processor comprising processing circuitry;at least one transceiver comprising communication circuitry; andmemory storing instructions that, when executed by the at least one processor, cause the at least one processor to:transmit a first non-access stratum (NAS) request message to a network entity of a public land mobile network (PLMN) through the at least one transceiver, wherein the first NAS request message is camped on a cell belonging to a current tracking area identity (TAI);receive a first NAS reject message upon initiation of the first NAS request message from the network entity through the at least one transceiver, wherein the first NAS reject message comprises a reject cause #15 indicating 'no suitable cells in tracking area';determine whether the first NAS reject message includes access technology utilization control information or not;in accordance with a determination that the first NAS reject message include the access technology utilization control information, skip storing of the current TAI in a list of forbidden tracking areas for roaming; andin accordance with a determination that the first NAS reject message does not include the access technology utilization control information, store the current TAI in a list of forbidden tracking areas for roaming based on at least one condition.9.The UE of claim 8, wherein the instructions, when executed by the at least one processor, cause the at least one processor to:determine whether the UE is operating in a standalone non-public network (SNPN) access operation mode or not; anddetermine whether at least one forbidden TAI for the list of forbidden tracking areas for roaming is included in the first NAS reject message,wherein the current TAI is stored in a case that the UE is not operating in the SNPN access operation mode, the at least one forbidden TAI for the list of forbidden tracking areas for roaming is not included in the first NAS reject message, and the access technology utilization control information is not included in the first NAS reject message.10.The UE of claim 9, wherein the instructions, when executed by the at least one processor, cause the at least one processor to:determine whether an extended cause code indicating "Satellite NG-RAN not allowed in PLMN" or "Satellite E-UTRAN not allowed in PLMN" is included in the first NAS reject message or not; andin accordance with a determination that the extended cause code indicating "Satellite NG-RAN not allowed in PLMN" or "Satellite E-UTRAN not allowed in PLMN" is included in the first NAS reject message, skip storing of the current TAI in a list of forbidden tracking areas for roaming.11.The UE of claim 10,wherein the current TAI is stored in a case that the UE is not operating in the SNPN access operation mode, the at least one forbidden TAI for the list of forbidden tracking areas for roaming is not included in the first NAS reject message, the extended cause code indicating "Satellite NG-RAN not allowed in PLMN" or "Satellite E-UTRAN not allowed in PLMN" is not included in the first NAS reject message, and the access technology utilization control information is not included in the first NAS reject message.12.The UE of claim 8, wherein the instructions, when executed by the at least one processor, cause the at least one processor to:receive a second NAS message that comprises access technology utilization control information indicating that access to a first RAT is not restricted;generate a second NAS request message on the first RAT belonging to a current TAI in a case that the first RAT is not restricted; andinitiate a registration of the UE on the first RAT using the second NAS request message.13.The UE of claim 8, wherein the first NAS request message comprises at least one of a registration request message, a deregistration request message, an attach request message, a detach request message, a tracking area update request message, or a service request message.14.The UE of claim 8, wherein the first NAS reject message comprises at least one of a registration reject message, a deregistration request message, an attach reject message, a detach request message, a tracking area update reject, or a service reject message.15.A non-transitory storage medium configured to store one or more instructions that, when executed by at least one processor, cause a user equipment (UE) to perform operations including transmitting a first non-access stratum (NAS) request message to a network entity of a public land mobile network (PLMN), wherein the first NAS request message is camped on a cell belonging to a current tracking area identity (TAI);receiving a first NAS reject message upon initiation of the first NAS request message from the network entity, wherein the first NAS reject message comprises a reject cause #15 indicating 'no suitable cells in tracking area';determining whether the first NAS reject message includes access technology utilization control information or not;in accordance with a determination that the first NAS reject message include the access technology utilization control information, skipping storing of the current TAI in a list of forbidden tracking areas for roaming; andin accordance with a determination that the first NAS reject message does not include the access technology utilization control information, storing the current TAI in a list of forbidden tracking areas for roaming based on at least one condition.

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