Method and electronic device for wireless communication

Abstract

A method and an electronic device for wireless communication are provided. The method is applicable to the UE. A rejection cause # 62 (no network slice is available) is received from a message of the network. It is determined that there is an allowed NSSAI or a configured NSSAI in the message, all S-NSSAIs in the allowed NSSAI and the configured NSSAI are denied, and at least one S-NSSAI is denied due to "S-NSSAI is not available in the current registration area". And searching a proper cell in the other tracking area. According to the invention, wireless communication can be better carried out.

Description

Technical Field

[0001] The present invention generally relates to wireless communications, and more particularly to methods and electronic devices for recovering from a forbidden tracking area identity (FTAI) after no slices are available in the network. Background Art

[0002] When registration is rejected due to reason #62 and all single network slice selection assistance information (S-NSSAI) in the allowed network slice selection assistance information (NSSAI) and the configured NSSAI or the default configured NSSAI are rejected, and at least one S-NSSAI is rejected due to "S-NSSAI not available in a current registration area", the user equipment (UE) shall store the current tracking area identity (TAI) in the "5GS prohibited roaming tracking area" list, remember that the current TAI is stored in the "5GS prohibited roaming tracking area" list because it is rejected due to "S-NSSAI not available in a current registration area", and enter the 5GMM-DEREGISTERED.LIMITED-SERVICE state.

[0003] However, there is currently no defined recovery mechanism, such as whether the UE should stay in the current cell to obtain limited service, or whether the UE should perform a public land mobile network (PLMN) search procedure, or whether the UE should perform a cell selection procedure in another tracking area (TA). Summary of the invention

[0004] One embodiment of the present invention provides a method for recovering from a forbidden tracking area identifier (FTAI) after there are no available slices in the network. The method is applicable to a user equipment (UE). The method includes the following steps. A rejection reason #62 (no network slice available) is received from a message from the network. It is determined that there is an allowed NSSAI or a configured NSSAI in the message. All S-NSSAIs in the allowed NSSAI and the configured NSSAI are rejected, and at least one S-NSSAI is rejected due to "S-NSSAI is not available in the current registration area". Search for a suitable cell in another tracking area.

[0005] The method also includes not searching for a PLMN and staying at the same TAI to obtain limited services.

[0006] The method also includes searching for a suitable cell in a tracking area that is the same PLMN but is not on the "5GS prohibited roaming tracking area" list.

[0007] The method also includes the following steps: Supporting access to a stand-alone non-Public network (SNPN) using credentials from a credentials holder, an equivalent SNPN, or both, a selected "Subscriber Data List" entry, or a selected same PLMN subscription. Searching for a suitable cell in a tracking area that is the same PLMN but is not on the "5GS Prohibited Roaming Tracking Area" list.

[0008] The method further comprises the following steps: performing PLMN selection or SNPN selection for 3rd Generation Partnership Project (3GPP) access; performing network selection for non-3GPP access.

[0009] According to the above method, the message from the network is a registration rejection (REGISTRATION REJECT) message or a deregistration request (DEREGISTRATION REQUEST) message.

[0010] The method also includes entering the 5GMM-DEREGISTERED.LIMITED-SERVICE state.

[0011] One embodiment of the present invention also provides a method for recovering from a forbidden tracking area identifier (FTAI) after there are no available slices in the network. The method is applicable to a user equipment. The method comprises the following steps. A rejection reason #62 (no network slice available) is received from a message from the network. It is determined that there is neither an allowed NSSAI for the current PLMN nor a configured NSSAI for the current PLMN in the message. All S-NSSAIs in the default configured NSSAI are rejected, and at least one S-NSSAI is rejected due to "S-NSSAI is not available in the current registration area". A suitable cell is searched for in another tracking area.

[0012] An embodiment of the present invention also provides an electronic device, including a processor. The processor receives a rejection reason #62 (no network slice available) in a message from the network. The processor determines that there is an allowed NSSAI or a configured NSSAI in the message. All S-NSSAIs in the allowed NSSAI and the configured NSSAI are rejected, and at least one S-NSSAI is rejected because "S-NSSAI is not available in the current registration area". The processor searches for a suitable cell in another tracking area.

[0013] According to the above electronic device, the processor does not search for a PLMN and stays at the same TAI to obtain limited services.

[0014] According to the above electronic device, the processor searches for a suitable cell in a tracking area that is the same as the PLMN but is not on the “5GS prohibited roaming tracking area” list.

[0015] According to the above electronic device, the processor supports accessing the SNPN using credentials from a credential holder, an equivalent SNPN, or both, a selected "Subscriber Data List" entry, or a selected same PLMN subscription, and searching for a suitable cell in a tracking area that is the same PLMN but not on the "5GS Tracking Areas Prohibited Roaming" list.

[0016] According to the above electronic device, the processor performs PLMN selection or SNPN selection for 3GPP access, and performs network selection for non-3GPP access.

[0017] According to the above electronic device, the message from the network is a registration rejection message or a deregistration request message.

[0018] According to the above electronic device, the processor enters the 5GMM-DEREGISTERED.LIMITED-SERVICE state.

[0019] One embodiment of the present invention also provides an electronic device, comprising a processor. The processor receives a rejection reason #62 (no network slice available) in a message from the network. The processor determines that there is neither an allowed NSSAI for the current PLMN nor a configured NSSAI for the current PLMN in the message. All S-NSSAIs in the default configured NSSAI are rejected, and at least one S-NSSAI is rejected because "S-NSSAI is not available in the current registration area". The processor searches for a suitable cell in another tracking area.

[0020] By utilizing the present invention, wireless communication can be better performed. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention may be more fully understood by reading the following detailed description with reference to the accompanying drawings, in which:

[0022] Figure 1 A flow chart showing a method of recovering from FTAI after no slices are available in the network according to some embodiments of the present invention;

[0023] Figure 2 A flow chart showing a method of recovering from FTAI after no slices are available in the network according to some embodiments of the present invention;

[0024] Figure 3 A schematic diagram of a communication system 300 is shown according to some embodiments of the present invention. DETAILED DESCRIPTION

[0025] In order to make the above-mentioned purposes, features and advantages of some embodiments of the present invention more easily understood, they are described in detail below with reference to the accompanying drawings.

[0026] Certain terms are used throughout the specification and claims to refer to specific components. As will be appreciated by those skilled in the art, electronic equipment manufacturers may refer to the same component by different names. The present invention is not intended to distinguish between components that have different names but the same function. It should be understood that the words "include", "have" and "include" are used in an open-ended manner and should therefore be interpreted as "including, but not limited to...". Therefore, when the terms "include", "have" or "include" are used in the present invention to indicate the presence of specific technical features, values, method steps, operations, units or components, it does not exclude the possibility of adding more technical features, values, method steps, working processes, units, components or any combination of the above.

[0027] Directional terms used throughout the description and claims, such as "on", "upper", "above", "lower", "below", "front", "back", "rear", "left", "right", etc., refer only to the direction of the drawings. Therefore, the directional terms are used to explain and not to limit the present invention. With respect to the drawings, the drawings show the general characteristics of the methods, structures, or materials used in particular embodiments. However, the drawings should not be interpreted as defining or limiting the scope or properties encompassed by these embodiments. For example, the relative size, thickness, and position of each layer, each region, or each structure may be reduced or exaggerated for clarity.

[0028] When a corresponding component such as a layer or region is referred to as being "on another component", it may be directly on the other component, or other components may exist between them. On the other hand, when a component is referred to as being "directly on another component (or a variation thereof)", there are no components between them. In addition, when a corresponding component is referred to as being "on another component", the corresponding component and the other component have an arrangement relationship along the top view / vertical direction, the corresponding component may be below or above the other component, and the arrangement relationship along the top view / vertical direction is determined by the orientation of the device.

[0029] It should be understood that when a component or layer is referred to as being “connected to” another component or layer, it can be directly connected to the other component or layer, or intervening components or layers may exist. Conversely, when a component is referred to as being “directly connected to” another component or layer, there are no intervening components or layers.

[0030] The electrical connection or coupling described in the present invention may refer to direct connection or indirect connection. In the case of direct connection, the endpoints of the components on the two circuits are directly connected or connected through a wire segment, and in the case of indirect connection, there is a switch, a diode, a capacitor, an inductor, a resistor, other suitable components or a combination of the above components between the endpoints of the components on the two circuits, but the intermediate components are not limited thereto.

[0031] The terms "first", "second", "third", "fourth", "fifth" and "sixth" are used to describe components. They are not used to indicate priority or precedence, but only to distinguish components with the same name.

[0032] It should be noted that the technical features in the different embodiments described below may be replaced, recombined or mixed with each other to constitute another embodiment without departing from the spirit of the present invention.

[0033] Figure 1A flow chart of a method for recovering from FTAI after no slices are available in a network according to some embodiments of the present invention is shown. The method is applicable to a UE. In some embodiments, the UE may be a laptop, a tablet, or a smartphone, but the present invention is not limited thereto. In some embodiments, the UE is included in a communication system, which also includes a base station. The UE is able to access a network through the base station. The UE is connected to the base station through Radio Resource Control (RRC) signaling, but the present invention is not limited thereto. In some embodiments, the base station may be a gNB, but the present invention is not limited thereto.

[0034] like Figure 1 As shown, the method includes the following steps. A rejection reason #62 (no network slice available) is received from a message from the network (step S100). The message contains allowed network slice selection assistance information (NSSAI) or configured NSSAI. All single NSSAIs (S-NSSAI) in the allowed NSSAI and the configured NSSAI are rejected, and at least one S-NSSAI is rejected because "S-NSSAI is not available in the current registration area" (step S102). Search for a suitable cell in another tracking area (step S104). In some embodiments, in step S100, the registration is rejected, and the message contains a rejection reason #62 (i.e., no network slice is available). In some embodiments, the message in step S100 is a registration rejection message or a deregistration request message received from the network via a base station.

[0035] Subsequently, in step S102, the UE determines whether there is an allowed network slice selection assistance information (NSSAI) or a configured NSSAI in the message. All single NSSAIs (S-NSSAIs) in the allowed NSSAIs and the configured NSSAIs are rejected, and at least one S-NSSAI is rejected due to "S-NSSAI is not available in the current registration area". Next, in step S104, the UE searches for a suitable cell in another tracking area. In some embodiments, the UE searches for a suitable cell in another tracking area according to 3GPP TS 38.304

[28] or 3GPP TS 36.304[25C]. In some embodiments, for a UE not operating in SNPN access mode, a cell is considered suitable if the following conditions are met. First, the cell is part of a selected PLMN or a registered PLMN or a PLMN in the equivalent PLMN list. For this PLMN, either the PLMN-ID of the PLMN is broadcast by the cell and has no associated Closed Access Group I (CAG-ID) and the CAG-only indication (TS23.501

[10] ) for this PLMN in the UE does not exist or is false, or the allowed CAG list (TS23.501

[10] ) for this PLMN in the UE includes the CAG-ID broadcast by the cell for this PLMN. Secondly, the cell selection criteria are met. In some embodiments, the cell is considered suitable based on the latest information provided by the non-access stratum (NAS). For example, the cell is not barred. The cell is part of at least one tracking area (TA), where the tracking area is not in the "tracking areas prohibited from roaming" list (TS 22.011[8]).

[0036] In some embodiments, for a user equipment (UE) operating in SNPN access mode, a cell is considered suitable if the following conditions are met. First, the cell is part of the selected SNPN or the registered SNPN of the UE. Second, the cell selection criteria are met. In some embodiments, the cell is considered suitable based on the latest information provided by the NAS. For example, the cell is not prohibited. The cell is part of at least one TA that does not belong to the "Tracking Area Prohibited Roaming" list and the TA belongs to the selected SNPN or the registered SNPN of the UE.

[0037] In some embodiments, after executing steps S100 and S102, the UE does not search for PLMN. The UE stays in the same TAI to obtain limited service. In some embodiments, the UE enters the 5GMM-DEREGISTERED.LIMITED-SERVICE state. In some embodiments, after executing steps S100 and S102, the UE searches for a suitable cell in a tracking area that is the same PLMN but is not on the "5GS prohibited roaming tracking area" list.

[0038] In some embodiments, after performing steps S100 and S102, if the UE supports access to the SNPN using credentials from the credential holder, an equivalent SNPN, or both, a selected "Subscriber Data List" entry, or a selected same PLMN subscription, the UE searches for a suitable cell in a tracking area that is the same PLMN but is not on the "5GS Tracking Areas Prohibited Roaming" list.

[0039] In some embodiments, after performing steps S100 and S102, the UE performs PLMN selection or SNPN selection for a third generation partnership project (3GPP) access. The UE performs network selection for a non-3GPP access. In some embodiments, the UE performs PLMN selection or SNPN selection for a 3GPP access according to 3GPP TS23.122. The UE performs network selection for a non-3GPP access according to 3GPP TS24.502.

[0040] For example, for UE NAS in RRC_IDLE state and RRC_INACTIVE state, PLMN selection and SNPN selection can be completed by the following operations. For UEs not operating in SNPN access mode, the UE maintains a list of PLMNs in priority order according to TS23.122[9]. The UE selects the PLMN using the automatic or manual mode specified in TS23.122[9] and requests the UE access stratum (AS) to select a cell belonging to the PLMN. For each PLMN, the associated radio access technology (RAT) can be set. The UE evaluates the report of available PLMNs and any associated CAG-IDs from the AS for PLMN selection. The UE maintains a list of equivalent PLMN identities. The UE maintains a list of "PLMNs that are not allowed to operate at the current UE location". The UE maintains disaster roaming information applicable to available PLMNs, including potential disaster PLMNs for available PLMNs. To support manual CAG selection, the UE requests a search for available CAGs and evaluates the available CAG report from the AS for CAG selection.

[0041] For UEs operating in SNPN access mode, the UE maintains a SNPN list according to TS23.122[9]. The UE selects a SNPN using the automatic or manual mode specified in TS23.122[9] and requests the AS to select a cell belonging to that SNPN. The UE evaluates the available SNPN reports from the AS for SNPN selection.

[0042] In some embodiments, for UE AS in RRC_IDLE state and RRC_INACTIVE state, PLMN selection and SNPN selection can be completed by the following operations. For UEs not operating in SNPN access mode, the UE searches for available PLMNs. If relevant RATs are set for the PLMN, the UE searches for the PLMN in these RATs and other RATs specified in TS23.122[9]. For UEs operating in SNPN access mode, the UE only considers new radio (NR) cells to search for available SNPNs. The UE performs measurements to support PLMN / SNPN selection. The UE synchronizes to the broadcast channel to identify the found PLMN / SNPN. The UE reports the available PLMNs and any related CAG-IDs and related RATs to NAS upon request or automatically. The UE automatically reports disaster roaming information applicable to available PLMNs, including potential disaster PLMNs.

[0043] For UEs operating in SNPN access mode, the UE automatically reports available SNPNs to NAS. As specified in TS 38.331[3], the UE automatically reports to NAS the SNPN access information associated with different credential holder subscriptions, whether the network access indicator is enabled, and the list of supported GINs. To support manual CAG selection, the UE searches for cells broadcasting CAG-IDs. The UE reports the CAG-ID of the found cell and the associated manual CAG selection permission indicator, Human-Readable Network Name (HRNN) and PLMN to NAS. When NAS selects a CAG, the UE selects any acceptable or suitable cell belonging to the selected CAG and indicates to NAS that it can be accessed for the registration process. To support manual SNPN selection, the UE reports the available SNPNs and the associated HRNN (if any) to NAS upon NAS request.

[0044] Figure 2 A flow chart of a method for recovering from a forbidden tracking area identity (FTAI) after no slices are available in the network according to some embodiments of the present invention is shown. The method is also applicable to a UE. Figure 2As shown, the method includes the following steps. Rejection reason #62 (no network slice available) is received from a message of the network (step S200). There is neither an allowed NSSAI for the current PLMN nor a configured NSSAI for the current PLMN in the message. All S-NSSAIs in the default configured NSSAI are rejected, and at least one S-NSSAI is rejected due to "S-NSSAI is not available in the current registration area" (step S202). Search for a suitable cell in another tracking area (step S204). In some embodiments, the message in step S200 is a registration rejection message or a deregistration request message received from the network by a base station.

[0045] Thereafter, in step S202, the UE determines that there is neither an allowed NSSAI for the current PLMN nor a configured NSSAI for the current PLMN in the message. All S-NSSAIs in the default configured NSSAI are rejected, and at least one S-NSSAI is rejected due to "S-NSSAI is not available in the current registration area". Next, in step S204, the UE searches for a suitable cell in another tracking area. In some embodiments, the UE searches for a suitable cell in another tracking area according to 3GPP TS 38.304

[28] or 3GPP TS36.304[25C]. In some embodiments, for a UE not operating in SNPN access mode, a cell is considered suitable if the following conditions are met. First, the cell is part of a selected PLMN or a registered PLMN or a PLMN in the equivalent PLMN list. For this PLMN, either the PLMN-ID of the PLMN is broadcast by the cell and has no associated closed access group ID (CAG-ID) and the CAG-only indication (TS23.501

[10] ) for this PLMN in the UE does not exist or is false, or the allowed CAG list (TS23.501

[10] ) for this PLMN in the UE includes the CAG-ID broadcast by the cell. Secondly, the cell selection criteria are met. In some embodiments, the cell is considered suitable based on the latest information provided by the non-access stratum (NAS). For example, the cell is not barred. The cell is part of at least one tracking area that is not in the "Tracking Areas Prohibited Roaming" list (TS22.011[8]).

[0046] In some embodiments, for a UE operating in SNPN access mode, a cell is considered suitable if the following conditions are met. First, the cell is part of the selected SNPN or the SNPN to which the UE is registered. Second, the cell selection criteria are met. In some embodiments, the cell is considered suitable based on the latest information provided by the NAS. For example, the cell is not prohibited. The cell is part of at least one tracking area that is not in the "Tracking Areas Prohibited from Roaming" list, which tracking area belongs to the selected SNPN or the SNPN to which the UE is registered.

[0047] In some embodiments, after executing steps S200 and S202, the UE does not search for PLMN. The UE stays in the same TAI to obtain limited service. In some embodiments, the UE enters the 5GMM-DEREGISTERED.LIMITED-SERVICE state. In some embodiments, after executing steps S200 and S202, the UE searches for a suitable cell in a tracking area that is the same PLMN but is not on the "5GS prohibited roaming tracking area" list.

[0048] In some embodiments, after performing steps S200 and S202, if the UE supports access to the SNPN using credentials from the credential holder, an equivalent SNPN, or both, a selected "Subscriber Data List" entry, or a selected same PLMN subscription, the UE searches for a suitable cell in a tracking area that is the same PLMN but is not on the "5GS Tracking Areas Prohibited Roaming" list.

[0049] In some embodiments, after performing steps S200 and S202, the UE performs PLMN selection or SNPN selection for a third generation partnership project (3GPP) access. The UE performs network selection for a non-3GPP access. In some embodiments, the UE performs PLMN selection or SNPN selection for a 3GPP access according to 3GPP TS23.122. The UE performs network selection for a non-3GPP access according to 3GPP TS24.502.

[0050] Figure 3 Schematic diagram of a communication system 300 according to some embodiments of the present invention is shown. Figure 3 As shown, the communication system 300 includes a UE 302, a network 304, and a base station 306. In some embodiments, the UE 302 may be a laptop, a tablet, or a smart phone, but the present invention is not limited thereto. In some embodiments, the UE 302 can access the network 304 through the base station 306. The UE 302 is connected to the base station 306 through radio resource control (RRC) signaling, but the present invention is not limited thereto. In some embodiments, the base station 306 may be a gNB, but the present invention is not limited thereto.

[0051] In some embodiments, UE 302 includes an antenna 312, a transceiver 308, and a processor 310. The transceiver 308 is electrically connected between the antenna 312 and the processor 310. The processor 310 may be a modem, but the present invention is not limited thereto. In some embodiments, UE 302 also includes a memory (not shown) storing a plurality of codes. The processor 310 reads the code stored in the memory to perform the following steps. The processor 310 receives a rejection reason #62 (no network slice available) from a message of the network 304. In some embodiments, the message is a registration rejection message or a deregistration request message. The registration of UE 302 is rejected in the message due to reason #62 (i.e., no network slice available).

[0052] The processor 310 determines that there is an allowed NSSAI or a configured NSSAI in the message. All S-NSSAIs in the allowed NSSAI and the configured NSSAI are rejected, and at least one S-NSSAI is rejected because "S-NSSAI is not available in the current registration area". Then, the processor 310 searches for a suitable cell in another tracking area. In some embodiments, the processor 310 searches for a suitable cell in another tracking area according to 3GPP TS 38.304

[28] or 3GPP TS 36.304[25C]. In some embodiments, for a UE 302 not operating in SNPN access mode, a cell is considered suitable if the following conditions are met. First, the cell is part of a PLMN in a selected PLMN or a registered PLMN or an equivalent PLMN list. For this PLMN, either the PLMN-ID of the PLMN is broadcast by the cell and there are no closed access group IDs (CAG-IDs) associated with this PLMN in the UE 302 and the CAG-only indication (TS23.501

[10] ) is not present or is false, or the allowed CAG list in the UE (TS23.501

[10] ) includes the CAG-ID broadcast by the cell for this PLMN. Second, the cell selection criteria are met. In some embodiments, the cell is considered suitable based on the latest information provided by the non-access stratum (NAS). For example, the cell is not barred. The cell is part of at least one tracking area that is not in the "tracking areas prohibited from roaming" list (TS22.011[8]).

[0053] In some embodiments, for a user equipment (UE 302) operating in SNPN access mode, a cell is considered suitable if the following conditions are met. First, the cell is part of the selected SNPN or the registered SNPN of UE 302. Second, the cell selection criteria are met. In some embodiments, the cell is considered suitable based on the latest information provided by NAS. For example, the cell is not prohibited. The cell is part of at least one tracking area that does not belong to the "tracking area prohibited roaming" list, which tracking area belongs to the selected SNPN or the registered SNPN of UE 302.

[0054] In some embodiments, if the UE 302 determines that there is an allowed NSSAI or a configured NSSAI in the message, all S-NSSAIs in the allowed NSSAI and the configured NSSAI are rejected, and at least one S-NSSAI is rejected due to "S-NSSAI is not available in the current registration area", the UE 302 does not search for the PLMN. The UE 302 stays in the same TAI for limited service. In some embodiments, the UE 302 enters the 5GMM-DEREGISTERED.LIMITED-SERVICE state. In some embodiments, if the UE 302 determines that there is an allowed NSSAI or a configured NSSAI in the message, all S-NSSAIs in the allowed NSSAI and the configured NSSAI are rejected, and at least one S-NSSAI is rejected due to "S-NSSAI is not available in the current registration area", the UE 302 searches for a suitable cell in a tracking area that is the same PLMN but does not belong to the "5GS prohibited roaming tracking area" list.

[0055] In some embodiments, UE 302 determines that there is an allowed NSSAI or a configured NSSAI in the message. All S-NSSAIs in the allowed NSSAI and the configured NSSAI are rejected, and at least one S-NSSAI is rejected due to "S-NSSAI is not available in the current registration area". If UE 302 supports access to the SNPN using credentials from a credential holder, an equivalent SNPN, or both, a selected "Subscriber Data List" entry, or a selected same PLMN subscription, UE 302 searches for a suitable cell in a tracking area that is the same PLMN but not on the "5GS prohibited roaming tracking area" list.

[0056] In some embodiments, if the UE 302 determines that there is an allowed NSSAI or a configured NSSAI in the message, all S-NSSAIs in the allowed NSSAI and the configured NSSAI are rejected, and at least one S-NSSAI is rejected due to "S-NSSAI is not available in the current registration area", the UE 302 performs PLMN selection or SNPN selection for a third generation partnership project (3GPP) access. The UE 302 performs network selection for non-3GPP access. In some embodiments, the UE 302 performs PLMN selection or SNPN selection for 3GPP access according to 3GPP TS 23.122. The UE 302 performs network selection for non-3GPP access according to 3GPP TS 24.502.

[0057] In some embodiments, the processor 310 receives a rejection reason #62 (no network slice available) in a message from the network 304. In some embodiments, the rejection message is a registration rejection message or a deregistration request message. The registration of UE 302 is rejected in the message due to reason #62 (i.e., no network slice is available). The processor 310 determines that there is neither an allowed NSSAI for the current PLMN nor a configured NSSAI for the current PLMN in the message. All S-NSSAIs in the default configured NSSAI are rejected, and at least one S-NSSAI is rejected due to "S-NSSAI is not available in the current registration area". Then, the processor 310 searches for a suitable cell in another tracking area. In some embodiments, the processor 310 searches for a suitable cell in another tracking area according to 3GPP TS 38.304

[28] or 3GPP TS 36.304 [25C].

[0058] In some embodiments, if the UE 302 determines that there is neither an allowed NSSAI for the current PLMN nor a configured NSSAI for the current PLMN in the message, all S-NSSAIs in the default configured NSSAI are rejected, and at least one S-NSSAI is rejected due to "S-NSSAI is not available in the current registration area", the UE 302 does not search for the PLMN. The UE 302 stays in the same TAI for limited service. In some embodiments, the UE 302 enters the 5GMM-DEREGISTERED.LIMITED-SERVICE state. In some embodiments, if the UE 302 determines that there is neither an allowed NSSAI for the current PLMN nor a configured NSSAI for the current PLMN in the message, all S-NSSAIs in the default configured NSSAI are rejected, and at least one S-NSSAI is rejected due to "S-NSSAI is not available in the current registration area", the UE 302 searches for a suitable cell in a tracking area that is the same PLMN but does not belong to the "5GS prohibited roaming tracking area" list.

[0059] In some embodiments, the UE 302 determines that there is neither an allowed NSSAI nor a configured NSSAI for the current PLMN in the message, all S-NSSAIs in the default configured NSSAI are rejected, and at least one S-NSSAI is rejected due to "S-NSSAI is not available in the current registration area". If the UE 302 supports access to the SNPN using credentials from a credential holder, an equivalent SNPN, or both, a selected "Subscriber Data List" entry, or a selected same PLMN subscription, the UE 302 searches for a suitable cell in a tracking area that is the same PLMN but is not on the "5GS prohibited roaming tracking area" list.

[0060] In some embodiments, if UE 302 determines that there is neither an allowed NSSAI for the current PLMN nor a configured NSSAI for the current PLMN in the message, all S-NSSAIs in the default configured NSSAI are rejected, and at least one S-NSSAI is rejected due to "S-NSSAI is not available in the current registration area", UE 302 performs PLMN selection or SNPN selection for third generation partnership project (3GPP) access. UE 302 performs network selection for non-3GPP access. In some embodiments, UE 302 performs PLMN selection or SNPN selection for 3GPP access according to 3GPP TS23.122. UE 302 performs network selection for non-3GPP access according to 3GPP TS24.502.

[0061] Although the present invention has been described by preferred embodiments, it should be understood that the present invention is not limited to the disclosed embodiments. On the contrary, the present invention is intended to cover various modifications and similar arrangements (which are obvious to those skilled in the art). Therefore, the scope of the claims should be given the broadest interpretation to cover all such modifications and similar arrangements.

Claims

1. A method for wireless communication, the method being applicable to a user equipment, comprising: receiving a reject cause #62 from a message from the network, the reject cause #62 indicating that no network slice is available; determining that there is allowed network slice selection assistance information or configured network slice selection assistance information in the message, wherein all single network slice selection assistance information in the allowed network slice selection assistance information and the configured network slice selection assistance information are rejected, and at least one single network slice selection assistance information is rejected due to "the single network slice selection assistance information is not available in the current registration area"; as well as Search for a suitable cell in another tracking area.

2. The method for wireless communication according to claim 1, wherein: The message from the network is a registration rejection message or a deregistration request message.

3. The method for wireless communication according to claim 1, wherein: Further including: No search for public land mobile networks; as well as Stay in the same tracking area ID for limited service.

4. The method for wireless communication according to claim 1, wherein: Further including: Search for the suitable cell in the tracking areas of the same public land mobile network but not on the "5GS prohibited roaming tracking areas" list.

5. The method for wireless communication according to claim 1, wherein: Further including: Supports access to a standalone non-public network using credentials from a credential holder, an equivalent standalone non-public network, or both, a selected Subscriber Data List entry, or a selected subscription to the same public land mobile network; and Search for the suitable cell in the tracking areas of the same public land mobile network but not on the "5GS prohibited roaming tracking areas" list.

6. The method for wireless communication according to claim 1, wherein: Further including: Performing public land mobile network selection or standalone non-public network selection for 3GPP access; and Perform network selection for non-3GPP access.

7. The method for wireless communication according to claim 3, wherein: Further including: Enter 5GMM-DEREGISTERED.LIMITED-SERVICE state.

8. A method for wireless communication, the method being applicable to a user equipment, comprising: receiving a reject cause #62 from a message from the network, the reject cause #62 indicating that no network slice is available; determining that there is neither allowed network slice selection assistance information for the current public land mobile network nor configured network slice selection assistance information for the current public land mobile network in the message, wherein all single network slice selection assistance information in the default configured network slice selection assistance information are rejected, and at least one single network slice selection assistance information is rejected due to "single network slice selection assistance information is not available in the current registration area"; as well as Search for a suitable cell in another tracking area.

9. The method for wireless communication according to claim 8, wherein: The message from the network is a registration rejection message or a deregistration request message.

10. The method for wireless communication according to claim 8, wherein: Further including: not searching for the public land mobile network; as well as Stay within the same tracking area ID for limited service.

11. The method for wireless communication according to claim 8, wherein: Further including: Search for the suitable cell in the tracking areas of the same public land mobile network but not on the "5GS prohibited roaming tracking areas" list.

12. The method for wireless communication according to claim 8, wherein: Further including: Supports access to a standalone non-public network using credentials from a credential holder, an equivalent standalone non-public network, or both, a selected Subscriber Data List entry, or a selected subscription to the same public land mobile network; and Search for the suitable cell in the tracking areas of the same public land mobile network but not on the "5GS prohibited roaming tracking areas" list.

13. The method for wireless communication according to claim 8, wherein: Further including: Performing public land mobile network selection or standalone non-public network selection for 3GPP access; and Perform network selection for non-3GPP access.

14. The method for wireless communication according to claim 9, wherein: Further including: Enter 5GMM-DEREGISTERED.LIMITED-SERVICE state.

15. An electronic device for wireless communication, comprising: A processor configured to: receiving a reject cause #62 from a message from the network indicating that no network slice is available; determining that there is allowed network slice selection assistance information or configured network slice selection assistance information in the message, wherein all single network slice selection assistance information in the allowed network slice selection assistance information and the configured network slice selection assistance information are rejected, and at least one single network slice selection assistance information is rejected due to "the single network slice selection assistance information is not available in the current registration area"; as well as Search for a suitable cell in another tracking area.

16. The electronic device according to claim 14, wherein: The message from the network is a registration rejection message or a deregistration request message.

17. The electronic device according to claim 15, wherein: The processor does not search for a public land mobile network and stays in the same tracking area identification for limited service.

18. The electronic device according to claim 15, wherein: The processor searches for the suitable cell in a tracking area of ​​the same public land mobile network but not on the "5GS prohibited roaming tracking area" list.

19. The electronic device according to claim 15, wherein: The processor supports access to the independent non-public network using credentials from a credential holder, an equivalent independent non-public network, or both, a selected "Subscriber Data List" entry, or a selected subscription to the same public land mobile network; and Search for the suitable cell in the tracking area of ​​the same public land mobile network but not on the "5GS prohibited roaming tracking area" list.

20. The electronic device according to claim 15, wherein: The processor performs public land mobile network selection or independent non-public network selection for 3GPP access and performs network selection for non-3GPP access.

21. The electronic device according to claim 15, wherein: The processor enters the 5GMM-DEREGISTERED.LIMITED-SERVICE state.

22. An electronic device for wireless communication, comprising: A processor configured to: receiving a reject cause #62 from a message from the network indicating that no network slice is available; determining that there is neither allowed network slice selection assistance information for the current public land mobile network nor configured network slice selection assistance information for the current public land mobile network in the message, wherein all single network slice selection assistance information in the default configured network slice selection assistance information are rejected, and at least one single network slice selection assistance information is rejected due to "single network slice selection assistance information is not available in the current registration area"; as well as Search for a suitable cell in another tracking area.

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