Method for network slice admission control per access type

Abstract

A wireless communication method is disclosed for use in a radio network node, the method including transmitting to a wireless terminal a rejection reason associated with a first connection request and an indication of at least one access type associated with the rejection reason.

Description

[Technical Field]

[0001] This document relates generally to wireless communications and in particular to fifth generation (5G) th generation) relating to wireless communication. [Background technology]

[0002] In 5G networks, Network Slice Admission Control (NSAC) may be deployed to monitor and control the number of registered user equipment (UE) per network slice and the number of protocol data unit (PDU) sessions per network slice for network slices that are subject to NSAC. However, when access types are considered, there is a need to limit the number of PDU sessions per network slice and / or the number of UEs per network slice. NSAC How to support this is a topic to be discussed.

[0003] This document provides information on each access type. NSAC , especially for each access type in 5G systems NSAC The present invention relates to a method, system, and device for: Summary of the Invention [Means for solving the problem]

[0004] The present disclosure relates to a wireless communication method for use in a radio network node, the method comprising: transmitting to the wireless terminal a rejection reason associated with the first connection request and an indication of at least one access type associated with the rejection reason; Includes:

[0005] Various embodiments may preferably implement the following features. Preferably, the first connection request is a protocol data unit session establishment request or a packet data network connection request.

[0006] Preferably, the wireless communication method comprises: receiving, from the network slice admission control function, a network slice admission control result associated with the rejection of the first connection request; Further includes:

[0007] Preferably, the network slice admission control result is: The maximum number of wireless terminals associated with a network slice or a single network slice selection assistance information has been reached, or The maximum number of protocol data unit sessions associated with a network slice or a single network slice selection assistance information has been reached. At least one of the following is shown.

[0008] Preferably, the reason for rejection is: Lack of resources, The maximum number of wireless terminals associated with a network slice or a single network slice selection assistance information has been reached, or The maximum number of protocol data unit sessions associated with a network slice or a single network slice selection assistance information has been reached. At least one of the following is shown.

[0009] Preferably, at least one access type is 3GPP (3rd Generation Partnership Project) compliant. rd The first connection request may include at least one of a 3GPP (3rd Generation Partnership Project) access type, a non-3GPP access type, or a first access type associated with the first connection request.

[0010] Preferably, the at least one access type includes only a first access type associated with the first connection request, and the method includes: Further including receiving a second connection request from the wireless terminal via a second access type different from the first access type, wherein the first connection request and the second connection request are associated with the same single network slice selection assistance information or the same access point name.

[0011] Preferably, the reason for the refusal indicates a lack of resources, and the first connection request and the second connection request are associated with the same access point name.

[0012] Preferably, the at least one access type includes only a first access type associated with the first connection request, and the method includes: The method further includes receiving a second connection request from the wireless terminal via the first access type associated with the first connection request after the back-off timer expires, wherein the first connection request and the second connection request are associated with the same single network slice selection assistance information or the same access point name.

[0013] Preferably, the at least one access type includes a 3GPP access type and a non-3GPP access type, and the method includes: The method further includes receiving a second connection request from the wireless terminal via a 3GPP access type or a non-3GPP access type after the backoff timer expires, wherein the first connection request and the second connection request are associated with the same single network slice selection assistance information or the same access point name.

[0014] Preferably, the reason for the refusal indicates a lack of resources, and the first connection request and the second connection request are associated with the same access point name.

[0015] Preferably, the wireless communication method comprises: transmitting a back-off timer associated with the first connection request to the wireless terminal; Further includes:

[0016] Preferably, the radio network node comprises at least one of a session management function or a combined session management function and packet data network gateway control plane function node.

[0017] The present disclosure relates to a wireless communication method for use in a wireless terminal, the method comprising: receiving from the wireless network node a rejection reason associated with the first connection request and an indication of at least one access type associated with the rejection reason; Includes:

[0018] Various embodiments may preferably implement the following features. Preferably, the first connection request is a protocol data unit session establishment request or a packet data network connection request.

[0019] Preferably, the reason for rejection is: Lack of resources, The maximum number of wireless terminals associated with a network slice or a single network slice selection assistance information has been reached, or The maximum number of protocol data unit sessions associated with a network slice or a single network slice selection assistance information has been reached. At least one of the following is shown.

[0020] Preferably, the at least one access type includes at least one of a Third Generation Partnership Project (3GPP) access type, a non-3GPP access type, or a current access type associated with the first connection request.

[0021] Preferably, the wireless communication method comprises: and transmitting, to the wireless network node, a second connection request associated with the same single network slice selection assistance information or the same access point name as the first connection request based on at least one of the rejection reason or the indication. Further includes:

[0022] Preferably, the at least one access type includes only a first access type associated with the first connection request, and the method includes: sending a second connection request to the wireless network node via a second access type different from the first access type; and wherein the first connection request and the second connection request are associated with the same single network slice selection assistance information or the same access point name.

[0023] Preferably, the reason for the refusal indicates a lack of resources, and the first connection request and the second connection request are associated with the same access point name.

[0024] Preferably, the at least one access type includes only a first access type associated with the first connection request, and the method includes: Further included is sending a second connection request to the radio network node via the first access type associated with the first connection request after the back-off timer expires, wherein the first connection request and the second connection request are associated with the same single network slice selection assistance information or the same access point name.

[0025] Preferably, the at least one access type includes a 3GPP access type and a non-3GPP access type, and the method includes: The method further includes, after the back-off timer expires, sending a second connection request to the radio network node via a 3GPP access type or a non-3GPP access type, wherein the first connection request and the second connection request are associated with the same single network slice selection assistance information or the same access point name.

[0026] Preferably, the reason for the refusal indicates a lack of resources, and the first connection request and the second connection request are associated with the same access point name.

[0027] Preferably, the wireless communication method comprises receiving from the wireless network node a back-off timer associated with the first connection request. Further includes:

[0028] Preferably, the radio network node comprises at least one of a session management function or a combined session management function and packet data network gateway control plane function node.

[0029] The present disclosure relates to a radio network node, the radio network node comprising: a communication unit configured to transmit to the wireless terminal a rejection reason associated with the first connection request and an indication of at least one access type associated with the rejection reason; Equipped with.

[0030] Various embodiments may preferably implement the following features. Preferably, the radio network node further comprises a processor configured to perform any of the aforementioned wireless communication methods.

[0031] The present disclosure relates to a wireless terminal. a communication unit configured to receive from a wireless network node a rejection reason associated with the first connection request and an indication of at least one access type associated with the rejection reason; Equipped with.

[0032] Various embodiments may preferably implement the following features. Preferably, the wireless terminal further comprises a processor configured to perform any of the aforementioned wireless communication methods.

[0033] The present disclosure relates to a computer program product comprising a computer readable program medium code stored thereon, the code, when executed by a processor, causing the processor to implement a wireless communication method as set forth in any one of the preceding methods.

[0034] The exemplary embodiments disclosed herein are directed to providing features that will be readily apparent from reference to the following description in conjunction with the accompanying drawings. In accordance with various embodiments, exemplary systems, methods, devices, and computer program products are disclosed herein. It is understood, however, that these embodiments are presented by way of example and not limitation, and it will be apparent to those skilled in the art upon reading this disclosure that various modifications to the disclosed embodiments can be made while remaining within the scope of the present disclosure.

[0035] Thus, the present disclosure is not limited to the example embodiments and applications described and illustrated herein. Additionally, the specific order and / or hierarchy of steps in the methods disclosed herein is merely exemplary approaches. Based on design preferences, the specific order or hierarchy of steps in a disclosed method or process can be rearranged while remaining within the scope of the present disclosure. Thus, those skilled in the art will understand that the methods and techniques disclosed herein present various steps or operations in a sample order, and that the present disclosure is not limited to the specific order or hierarchy presented, unless otherwise stated.

[0036] These and other aspects and their implementations are described in more detail in the drawings, description, and claims. [Brief explanation of the drawings]

[0037] [Figure 1] 1 shows a schematic diagram of a network according to one embodiment of the present disclosure; [Figure 2]1 shows a schematic diagram of a procedure according to one embodiment of the present disclosure. [Figure 3] 1 shows a schematic diagram of a procedure according to one embodiment of the present disclosure. [Figure 4] 1 shows a schematic diagram of a procedure according to one embodiment of the present disclosure. [Figure 5] 1 illustrates an example of a schematic diagram of a wireless terminal according to one embodiment of the present disclosure. [Figure 6] 1 illustrates an example of a schematic diagram of a radio network node according to one embodiment of the present disclosure. [Figure 7] 1 shows a flowchart of a method according to one embodiment of the present disclosure. [Figure 8] 1 shows a flowchart of a method according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0038] In this disclosure, a network slice represents a logical network that provides specific network capabilities and network characteristics.

[0039] In this disclosure, a network slice instance represents a set of network function instances and required resources (e.g., computational, storage, and networking resources) that form a deployed network slice.

[0040] 1 illustrates a schematic diagram of a network system (e.g., a network architecture) according to an embodiment of the present disclosure. For example, the network system illustrated in FIG. 1 may be a 5G system (5GS). In FIG. 1, the network system includes the following network functions / entities:

[0041] 1) UE: User Equipment 2) RAN: Radio Access Network In this disclosure, a RAN may be equivalent to a RAN node or a next-generation RAN (NG-RAN) (node).

[0042] 3) AMF: Access and Mobility Management Function The AMF includes functions such as UE mobility management, reachability management, connection management, and registration management. The AMF terminates the RAN control plane (CP) interface N2, as well as the non-access stratum (NAS) interface N1, which is NAS encryption and integrity protection. The AMF also distributes session management (SM) NAS to the appropriate SMF via the N11 interface.

[0043] The AMF is configured with information indicating the network slices that are the subject of NSAC. The AMF triggers an availability check of the number of UEs per network slice and an update procedure to the Network Slice Admission Control Function (NSACF) to update the number of UEs registered in the network slice that is the subject of NSAC when this network slice is included in the authorized Network Slice Selection Assistance Information (NSSAI) for the UE (i.e., the AMF requests the UE to register in a single NSSAI (S-NSSAI)) or is removed from the authorized NSSAI (i.e., the AMF requests the UE to deregister from the S-NSSAI).

[0044] 4) SMF: Session Management Function The SMF includes functions such as session establishment, modification and release, UE IP address allocation and management, and selection and control of user plane (UP) functions.

[0045] The SMF is configured with information indicating the network slices that are the subject of the NSAC. The SMF that anchors the PDU sessions triggers an availability check and update procedure for the number of PDU sessions per network slice to the NSACF for the network slices that are the subject of the NSAC at the start of the PDU session establishment procedure (only for new PDU sessions) or as the last step of a successful PDU session release procedure.

[0046] 5) NSACF: Network Slice Admission Control Function The NSACF supports monitoring and control of the number of registered UEs per network slice and the number of established PDU sessions per network slice. The NSACF also supports event-based network slice status notification and reports to consumer NFs (e.g., network exposure functions (NEFs) or application functions (AFs)).

[0047] 6) NSSF: Network Slice Selection Function The NSSF supports the following functions: selecting the set of network slice instances that will serve the UE; determining the allowed NSSAIs and mapping them to a home public land mobile network (HPLMN) S-NSSAI, if necessary; determining the configured NSSAIs and mapping them to a HPLMN S-NSSAI, if necessary; determining the set of AMFs that will be used to serve the UE, or determining a list of candidate AMFs based on the configuration, possibly by querying a Network Repository Function (NRF).

[0048] 7) UPF: User Plane Function The UPF serves as an anchor point for intra- / inter-radio access technology (RAT) mobility and as an external PDU session point for interconnection to the Data Network (DN). The UPF also routes and forwards data packets according to indications from the SMF. The UPF also buffers downlink (DL) data when the UE is in idle mode.

[0049] 8) NEF: Network Exposure Function The NEF supports capability and event exposure. The AF can access NSACF services through the NEF if the AF is not trusted.

[0050] 9) AF: Application Function If the AF is untrusted, the AF may access the NSACF services through the NEF, or if the AF is trusted, the AF may access the NSACF services directly.

[0051] 2 shows a schematic diagram of a procedure for checking availability and updating the number of PDU sessions per network slice according to one embodiment of the present disclosure. The procedure for checking availability and updating the number of PDU sessions per network slice is used to update (e.g., increase or decrease) the number of PDU sessions established on an S-NSSAI (i.e., network slice) that is the subject of an NSAC. The SMF is configured with information indicating the network slice that is the subject of the NSAC.

[0052] In step 201, if the SMF does not know which NSACF it should communicate with, the SMF performs NSACF discovery. The SMF anchoring the PDU sessions triggers an availability check and update procedure to the NSACF of the number of PDU sessions per network slice for the network slices that are the subject of the NSAC at the start of the PDU session establishment procedure (only if a new PDU session is to be established) and / or as the last step of a successful PDU session release procedure.

[0053] In step 202, the SMF anchoring the PDU sessions sends an Nnsacf_NSAC_NumOfPDUsUpdate_Request message to the NSACF. The SMF includes in the message the UE identifier (ID), the PDU session ID, the S-NSSAI for which the number of PDU sessions per network slice needs to be updated, the access type, and an update flag indicating that the number of PDU sessions established on the S-NSSAI should be increased if the procedure is triggered at the beginning of a PDU session establishment procedure, or that the number of PDU sessions on the S-NSSAI should be decreased if the procedure is triggered at the end of a PDU session release procedure.

[0054] In step 203, the NSACF updates the current number of PDU sessions established on the S-NSSAI, i.e., increases or decreases the number of PDU sessions per network slice based on the information provided by the anchor SMF in the update flag parameter.

[0055] If the update flag parameter from the SMF that anchors the PDU session indicates an increase and the maximum number of PDU sessions established on the S-NSSAI has already been reached, the NSACF returns a result parameter indicating that the maximum number of PDU sessions per network slice has been reached. If the maximum number of PDU sessions established on the S-NSSAI has not been reached, the NSACF checks the UE ID. If the UE ID is identified, the NSACF stores the PDU session ID and increments the number of PDU sessions for that S-NSSAI. If the NSACF cannot identify the UE ID, the NSACF creates an entry for the UE ID, stores the PDU session ID, and increments the number of PDU sessions for that S-NSSAI.

[0056] If the update flag parameter from the SMF that anchors the PDU sessions indicates that the current number of PDU sessions per S-NSSAI should be decreased, the NSACF identifies the UE ID, decreases the number of PDU sessions for that S-NSSAI, and deletes the associated PDU session ID. If the UE ID has no more PDU sessions, after the decrease, the NSACF deletes the UE ID entry.

[0057] In one embodiment, the NSACF considers the access type to determine whether to increase or decrease the number of PDU sessions per S-NSSAI.

[0058] In step 204, the NSACF acknowledges the update to the anchor SMF via a Nnsacf_NSAC_NumOfPDUsUpdate_Response message. If the NSACF returns a maximum number of PDU sessions per S-NSSAI arrival result (i.e., the result indicates that the maximum number of PDU sessions registered on the S-NSSAI has been reached), the SMF rejects the PDU session establishment request with a rejection reason of "insufficient resources for the specific slice" and possibly a back-off timer. Under such conditions, the UE will not initiate another PDU session establishment procedure for the same S-NSSAI until the back-off timer expires.

[0059] During the availability check and update procedure for the number of PDU sessions per network slice, the NSACF may take the access type into account when increasing or decreasing the number of PDU sessions per S-NSSAI. However, it remains unknown how the NSACF increases or decreases the number of PDU sessions when taking the access type into account. The present disclosure provides embodiments that support and realize NSAC per access type for the number of PDU sessions per S-NSSAI, for example, during the availability check and update procedure for the number of PDU sessions per network slice.

[0060] In some embodiments, based on the network operator's policy, the NSACF may be configured to apply NSAC to the S-NSSAI only for 3rd Generation Partnership Project (3GPP) access types or non-3GPP access types. Note that the number of PDU sessions established via access types other than the currently applied access type is not counted. Under such conditions, if a PDU session establishment request is rejected on one access type, the UE may not initiate another PDU session establishment request with the same S-NSSAI via another access type. However, if a PDU session establishment request is rejected on one access type, the UE should be allowed to initiate a PDU session establishment request with the same S-NSSAI via another access type within 5GS. Therefore, how to support NSAC for the number of PDU sessions per network slice when access types are considered in 5GS (e.g., NSAC per access type) needs to be discussed. Similarly, in the case of an evolved packet system (EPS) (e.g., fourth generation (4G)), NSAC may be applied to the S-NSSAI only for 3rd Generation (4G) and 5GS. th It also needs to be discussed how to support NSAC per access type in terms of the number of UEs in a network slice and / or the number of PDU sessions per network slice.

[0061] In the present disclosure, a method is provided for supporting NSAC per access type per S-NSSAI in 5GS and / or EPS (e.g., an interworking network (architecture) that supports both 5GS and EPS).

[0062] Figure 3 shows a schematic diagram of a procedure according to one embodiment of the present disclosure, which is associated with NSAC per access type for number of PDU sessions per S-NSSAI (in 5GS) and includes the following steps:

[0063] Step 301 (UE to AMF): The UE initiates the UE request PDU session establishment procedure by sending a PDU session establishment request, which includes a PDU session ID, a requested (PDU session) type, an S-NSSAI, etc.

[0064] In one embodiment, the request type indicates "initial request" if the PDU session establishment request is a request to establish a new PDU session, or indicates "existing PDU session" if the PDU session establishment request is associated with an existing PDU session switch between 3GPP access and non-3GPP access, or a PDU session handover from an existing PDN connection within the EPS.

[0065] The UE includes the S-NSSAI from the authorized NSSAIs of the current access type in the PDU session establishment request. If the mapping of authorized NSSAIs has been provided to the UE, the UE provides both the S-NSSAI of the visited public land mobile network (VPLMN) from the authorized NSSAI and the corresponding S-NSSAI of the HPLMN from the mapping of authorized NSSAIs.

[0066] Step 302 (AMF to SMF): If the AMF does not have an association with the SMF for the PDU session ID provided by the UE (for example, if the request type indicates an "initial request"), the AMF invokes the Nsmf_PDUSession_CreateSMContext request.

[0067] In one embodiment, the AMF sends the S-NSSAI of the serving PLMN from the allowed NSSAI to the SMF. In a roaming scenario in local breakout (LBO), the AMF may also send the corresponding S-NSSAI of the HPLMN from the mapping of the allowed NSSAI to the SMF.

[0068] The AMF determines the access type and RAT type of the PDU session. Step 303 (SMF): The SMF that anchors the PDU session triggers an availability check and update procedure to the NSACF for the number of PDU sessions per network slice for the S-NSSAI that is the subject of NSAC at the start of the PDU session establishment procedure (only if a new PDU session is to be established). If the SMF does not know which NSACF to communicate with, it performs NSACF discovery.

[0069] Step 304 (SMF to NSACF): The SMF sends an Nnsacf_NSAC_NumOfPDUsUpdate_Request message to the NSACF. The SMF includes in the message the UE ID, the PDU session ID, the S-NSSAI for which the number of PDU sessions per network slice update is required, the access type, and an update flag. In one embodiment, the update flag indicates that the number of PDUs established on the S-NSSAI should be increased since the procedure is being triggered at the beginning of the PDU session establishment procedure.

[0070] Step 305 (NSACF): The NSACF is configured with information indicating which access type is specified for the S-NSSAI that is the subject of the NSAC (i.e., 3GPP access type, non-3GPP access type, or both 3GPP access type and non-3GPP access type).

[0071] In one embodiment, if per-access-type NSAC for the S-NSSAI is required (e.g., NSAC is configured to be applicable to the S-NSSAI only via 3GPP access, i.e., the number of PDU sessions established on the S-NSSAI via non-3GPP access is not controlled, or the number of PDU sessions established on the S-NSSAI via 3GPP access and non-3GPP access is counted separately using separate quotas), and the maximum number of PDU sessions established on the S-NSSAI via the current access type has already been reached, the NSACF returns a result parameter indicating that the maximum number of PDU sessions on the S-NSSAI over the current access type has been reached. In this embodiment, the result parameter applies only to the current access type, for example, included in the Nnsacf_NSAC_NumOfPDUsUpdate_Request message.

[0072] If NSAC per access type for the S-NSSAI is not required and the maximum number of PDU sessions established on the S-NSSAI has already been reached, the NSACF returns a result parameter indicating that the maximum number of PDU sessions on the S-NSSAI has been reached. In this embodiment, the result parameter applies to both 3GPP and non-3GPP access types.

[0073] Step 306 (NSACF to SMF): The NSACF acknowledges the update to the SMF via a Nnsacf_NSAC_NumOfPDUsUpdate_Response message.

[0074] Step 307 (SMF to AMF): In one embodiment, if the NSACF returns that the maximum number of PDU sessions established on the S-NSSAI via the current access type has already been reached, the SMF rejects the PDU session establishment request with a rejection reason that the maximum number of PDU sessions on the specific network slice has already been reached. In this embodiment, the result parameter applies only to the current access type. The SMF further sends an indication that in this embodiment, the rejection reason applies only to the current access type. Furthermore, the SMF may optionally send a back-off timer associated with the rejection reason.

[0075] In one embodiment, if the NSACF returns that the maximum number of PDU sessions established on the S-NSSAI has already been reached, the SMF rejects the PDU session establishment request with a rejection reason that the maximum number of PDU sessions on the specific slice has already been reached. In this embodiment, the result parameter applies only to both 3GPP and non-3GPP access types. The SMF sends an indication of the rejection reason that applies to both 3GPP and non-3GPP access types. Furthermore, the SMF may optionally send a back-off timer associated with the rejection reason.

[0076] In one embodiment, the SMF rejects the UE request via NAS SM signaling by responding to the AMF with an Nsmf_PDUSession_CreateSMContext Response. The SMF also indicates to the AMF that the PDU session ID should be considered released and that the PDU session establishment is stopped.

[0077] Step 308 (AMF to UE): The AMF forwards the NAS SM message to the UE. Step 309 (UE): In one embodiment, if the UE receives a rejection reason that the maximum number of PDU sessions on a particular slice has already been reached and an indication that the rejection reason applies only to the current access type, the UE may immediately initiate another PDU session establishment procedure to establish a PDU session with the same S-NSSAI on another access type (i.e., an access type different from the current access type included in the PDU session establishment request). Alternatively, the UE may initiate another PDU session establishment procedure to establish a PDU session with the same S-NSSAI via the current access type after the associated back-off timer expires. The UE may receive the associated back-off timer along with the rejection reason.

[0078] In one embodiment, if the UE receives a rejection reason that the maximum number of PDU sessions on a particular slice has already been reached and an indication that the rejection reason applies to both 3GPP and non-3GPP access types, the UE may initiate another PDU session establishment procedure to establish a PDU session with the same S-NSSAI over the current access type or over another access type after the associated back-off timer expires. The UE may receive the associated back-off timer along with the rejection reason.

[0079] Figure 4 shows a schematic diagram of a procedure according to one embodiment of the present disclosure. The procedure shown in Figure 4 is associated with NSAC per access type in an Evolved Packet System (EPS) or interworking network (architecture) that supports both 5GS and EPS, and includes the following steps:

[0080] Step 401 (UE to Mobility Management Entity (MME)): The UE initiates a UE request packet data network (PDN) procedure by sending a PDN connection request message, which includes access point name (APN), PDN type, Protocol Configuration Options (PCO), request type, PDU session ID, etc.

[0081] Step 402 (MME to SMF+PGW-C): The MME sends a create session request to the SMF+PGW-C.

[0082] Step 403 (SMF+PGW-C): The SMF+PGW-C is configured with information indicating which S-NSSAIs are subject to NSAC. In one embodiment, the SMF+PGW-C is configured with information indicating which S-NSSAIs are subject to NSAC in 5GS only.

[0083] In one embodiment, the SMF+PGW-C selects an S-NSSAI associated with a PDN connection. If the S-NSSAI selected by the SMF+PGW-C is subject to NSAC in both EPS and 5GS, the SMF+PGW-C triggers an interaction with the NSACF to check the availability of the S-NSSAI by invoking separate NSAC procedures, in order, for the number of UEs and the number of PDU sessions.

[0084] Step 404 (SMF+PGW-C to NSACF): The SMF+PGW-C sends an Nnsacf_NSAC_NumOfUEsUpdate_Request message to the NSACF. The SMF+PGW-C includes in the message the UE ID, access type, S-NSSAI, NF ID, and an update flag indicating that the number of UEs registered in the S-NSSAI should be increased.

[0085] Step 405 (NSACF): The NSACF is configured with information indicating which access type is specified for the S-NSSAI that is the subject of the NSAC (i.e., 3GPP access type, non-3GPP access type, or both 3GPP access type and non-3GPP access type).

[0086] In one embodiment, if per access type NSAC for the S-NSSAI is required and the maximum number of UEs registered in the S-NSSAI via the current access type has already been reached, the NSACF returns a result parameter indicating that the maximum number of UEs registered in the S-NSSAI via the current access type has been reached. In this embodiment, the result parameter applies only to the current access type.

[0087] In one embodiment, if per access type NSAC for the S-NSSAI is not required and the maximum number of UEs registered on the S-NSSAI has already been reached, the NSACF returns a result parameter indicating that the maximum number of UEs registered on the S-NSSAI has been reached. In this embodiment, the result parameter applies to both 3GPP and non-3GPP access types.

[0088] In one embodiment, if the maximum number of UEs registered in the S-NSSAI has not been reached, the NSACF records the registration and returns a success result.

[0089] Step 406 (NSACF to SMF+PGW-C): The NSACF acknowledges the update to the SMF+PGW-C with a Nnsacf_NSAC_NumOfUEsUpdate_Response message.

[0090] If the maximum number of UEs registered in the S-NSSAI has already been reached, the following steps 407-409 may be skipped. In one embodiment, if the NSACF returns a successful result (i.e., the maximum number of UEs registered in the S-NSSAI has not been reached), the following steps 407-409 are performed.

[0091] Step 407 (SMF+PGW-C to NSACF): The SMF+PGW-C sends an Nnsacf_NSAC_NumOfPDUsUpdate_Request message to the NSACF. The SMF+PGW-C includes in the message the UE ID, the PDU session ID, the S-NSSAI for which an update of the number of PDU sessions per network slice is required, the access type, and an update flag indicating that the number of PDUs established on the S-NSSAI should be increased.

[0092] Step 408 (NSACF): The NSACF is configured with information indicating which access type is specified for the S-NSSAI that is the subject of the NSAC (i.e., 3GPP access type, non-3GPP access type, or both 3GPP access type and non-3GPP access type).

[0093] In one embodiment, if a per-access-type NSAC for the S-NSSAI is required and the maximum number of PDU sessions established on the S-NSSAI via the current access type has already been reached, the NSACF returns a result parameter indicating that the maximum number of PDU sessions on the S-NSSAI via the current access type has been reached. Note that the result parameter applies only to the current access type.

[0094] In one embodiment, if per-access-type NSAC for the S-NSSAI is not required and the maximum number of PDU sessions established on the S-NSSAI has already been reached, the NSACF returns a result parameter indicating that the maximum number of PDU sessions on the S-NSSAI has been reached. In this embodiment, the result parameter applies to both 3GPP and non-3GPP access types.

[0095] Step 409 (NSACF to SMF+PGW-C): The NSACF acknowledges the update to the SMF+PGW-C with a Nnsacf_NSAC_NumOfPDUsUpdate_Response message.

[0096] In one embodiment, steps 407-409 may be interchanged with steps 404-406. That is, steps 407-409 may be performed before steps 404-406. In this embodiment, if the maximum number of PDU sessions established over the S-NSSAI has been reached, steps 404-406 may be omitted. In one embodiment, if the NSACF returns a successful result (i.e., the maximum number of PDU sessions established over the S-NSSAI has not been reached), steps 404-406 are performed.

[0097] Step 410 (SMF+PGW-C to MME): In one embodiment, if the NSACF returns that the maximum number of UEs or the maximum number of PDU sessions on the S-NSSAI over the current access type has already been reached, the SMF+PGW-C rejects the PDN connection establishment request with a rejection reason of "insufficient resources" or a rejection reason that the maximum number of UEs or the maximum number of PDU sessions on a particular network slice has already been reached. In this embodiment, the SMF+PGW-C further sends an indication that the rejection reason applies only to the current access type.

[0098] In one embodiment, if the NSACF returns that the maximum number of UEs or the maximum number of PDU sessions on the S-NSSAI has already been reached, the SMF+PGW-C rejects the PDN connection establishment request with a rejection reason of "insufficient resources" or a rejection reason that the maximum number of UEs or the maximum number of PDU sessions on a particular network slice has already been reached. In this embodiment, the SMF+PGW-C also sends an indication that the rejection reason applies to both 3GPP and non-3GPP access types.

[0099] In one embodiment, to avoid impact on the MME, an indication of the rejection reason that applies to both 3GPP and non-3GPP access types, or to the current access type only, is transmitted to the UE together with a PCO information element (IE) included in the PDN connection establishment reject message.

[0100] Step 411 (MME to UE): The MME rejects the PDN connection request and sends a rejection reason and a related indication to the UE.

[0101] Step 412 (UE): In one embodiment, if the UE receives a rejection reason of "insufficient resources" and an indication that the rejection reason applies only to the current access type, the UE may immediately initiate another PDN connection establishment procedure to establish a PDN connection with the same APN via another access type. Alternatively, the UE may initiate a PDN connection establishment procedure to establish a PDN connection with the same APN via the current access type after an associated back-off timer expires. The UE may receive the associated back-off timer along with the rejection reason and indication.

[0102] In one embodiment, if the UE receives a rejection reason indicating that the maximum number of UEs or the maximum number of PDU sessions on a particular network slice has already been reached and an indication that the rejection reason applies only to the current access type, the UE may immediately initiate another PDN connection establishment procedure to establish a PDN connection with the same APN via another access type. Alternatively, the UE may immediately initiate a PDU session establishment procedure to establish a PDN connection with the same S-NSSAI via the other access type. As another alternative, the UE may initiate another PDN connection establishment procedure to establish a PDN connection with the same APN via the current access type after an associated back-off timer expires. As yet another alternative, the UE may initiate another PDU session establishment procedure to establish a PDN connection with the same S-NSSAI via the current access type after an associated back-off timer expires. The UE may receive the associated back-off timer along with the rejection reason and the indication.

[0103] In one embodiment, if the UE receives a rejection reason of "insufficient resources" and an indication that the rejection reason applies to both 3GPP and non-3GPP access types, the UE may initiate another PDN connection establishment procedure to establish a PDN connection with the same APN via the current access type or another access type after an associated back-off timer expires. The UE may receive the associated back-off timer along with the rejection reason and the indication.

[0104] In one embodiment, if the UE receives a new rejection reason that the maximum number of UEs or the maximum number of PDU sessions on a particular network slice has already been reached and an indication that the rejection reason applies to both 3GPP and non-3GPP access types, the UE may initiate another PDN connection establishment procedure to establish a PDN connection with the same APN via the current access type or another access type after an associated back-off timer expires. Alternatively, the UE may initiate a PDU session establishment procedure to establish a PDU session with the same S-NSSAI via the current access type or another access type after an associated back-off timer expires. The UE may receive the associated back-off timer along with the rejection reason and the indication.

[0105] 5 relates to a schematic diagram of a wireless terminal 50 according to one embodiment of the present disclosure. The wireless terminal 50 may be, but is not limited to, a user equipment (UE), a mobile phone, a laptop, a tablet computer, an e-book reader, or a portable computer system. The wireless terminal 50 may include a processor 500, such as a microprocessor or an application specific integrated circuit (ASIC), a storage unit 510, and a communication unit 520. The storage unit 510 may be any data storage device that stores program code 512 that is accessed and executed by the processor 500. The storage unit 5105. Embodiments of the communication unit 520 include, but are not limited to, a subscriber identity module (SIM), a read-only memory (ROM), a flash memory, a random-access memory (RAM), a hard disk, and an optical data storage device. The communication unit 520 may be a transceiver and is used to transmit and receive signals (e.g., messages or packets) according to the processing results of the processor 500. In one embodiment, the communication unit 520 transmits and receives signals via at least one antenna 522 shown in FIG. 5.

[0106] In one embodiment, storage unit 510 and program code 512 may be omitted and processor 500 may include a storage unit having program code stored therein.

[0107] Processor 500 may implement any one of the steps in the illustrated embodiments on wireless terminal 50, for example, by executing program code 512.

[0108] The communication unit 520 may be a transceiver. Alternatively or additionally, the communication unit 520 may combine a transmitting unit and a receiving unit configured to transmit and receive signals, respectively, to and from a wireless network node (e.g., a base station).

[0109] 6 relates to a schematic diagram of a radio network node 60 according to one embodiment of the present disclosure. The radio network node 60 may be, but is not limited to, a satellite, a base station (BS), a network entity, a mobility management entity (MME), a serving gateway (S-GW), a packet data network (PDN) gateway (P-GW), a radio access network (RAN) node, a next-generation RAN (NG-RAN) node, a gNB, an eNB, a gNB central unit (gNB-CU), a gNB distributed unit (gNB-DU), a data network, a core network, or a radio network controller (RNC). Furthermore, the radio network node 60 may comprise (implement) at least one network function, such as an access and mobility management function (AMF), a session management function (SMF), a user place function (UPF), a policy control function (PCF), or an application function (AF). The radio network node 60 may include a processor 600, such as a microprocessor or an ASIC, a storage unit 610, and a communication unit 620. The storage unit 610 may be any data storage device that stores program code 612 that is accessed and executed by the processor 600. 610 Examples of the memory include, but are not limited to, a SIM, a ROM, a flash memory, a RAM, a hard disk, and an optical data storage device. The communication unit 620 may be a transceiver and is used to transmit and receive signals (e.g., messages or packets) according to the processing results of the processor 600. In one example, the communication unit 620 transmits and receives signals via at least one antenna 622 shown in FIG. 6.

[0110] In one embodiment, the storage unit 610 and the program code 612 may be omitted. The processor 600 may include a storage unit having the program code stored therein.

[0111] The processor 600 may implement any of the steps described in the illustrated embodiment on the radio network node 60, for example by executing the program code 612.

[0112] The communication unit 620 may be a transceiver. Alternatively, or in addition, the communication unit 620 may combine a transmitting unit and a receiving unit configured to transmit and receive signals, respectively, to a wireless terminal (e.g., user equipment or another wireless network node).

[0113] 7 shows a schematic diagram of a method according to one embodiment of the present disclosure. The method shown in FIG. 7 may be used in a radio network node (e.g., an SMF, an SMF+PGW-C, a radio network node including an SMF or an SMF+PGW-C, or a radio network node that performs all or at least part of the functionality of an SMF or an SMF+PGW-C), and includes the following steps:

[0114] Step 701: Send a rejection reason associated with a first connection request and an indication of at least one access type associated with the rejection reason to a wireless terminal (eg, UE).

[0115] 7, the radio network node transmits to the wireless terminal a rejection reason associated with the first connection request. In this embodiment, the radio network node transmits to the wireless terminal an indication associated with the rejection reason, the indication being for at least one access type associated with the rejection reason.

[0116] In one embodiment, the first connection request is a PDU establishment request or a PDN connection request. In one embodiment, the radio network node receives from the NSACF an NSAC result associated with the rejection of the first connection request, for example, the radio network node transmits a rejection reason and an indication in response to or based on the received NSAC result.

[0117] In one embodiment, the NSAC results are: The maximum number of wireless terminals associated with the network slice or S-NSSAI has been reached, or The maximum number of protocol data unit sessions associated with a network slice or S-NSSAI has been reached. At least one of the following is shown.

[0118] In one embodiment, the rejection reason is: Lack of resources, The maximum number of wireless terminals associated with the network slice or S-NSSAI has been reached, or The maximum number of protocol data unit sessions associated with a network slice or S-NSSAI has been reached. At least one of the following is shown.

[0119] In one embodiment, the at least one access type (e.g., indicated by or associated with the indication) includes at least one of a 3GPP access type, a non-3GPP access type, or a first access type associated with the first connection request (e.g., the current access type described above). For example, the indication may include / indicate the first access type (e.g., one of the 3GPP access type and the non-3GPP access type). Alternatively, the indication may include / indicate both the 3GPP access type and the non-3GPP access type.

[0120] In one embodiment, the at least one access type includes only the first access type associated with the first connection request. In this embodiment, the radio network node receives a second connection request from the wireless terminal via a second access type different from the first access type. Note that the first connection request and the second connection request are associated with the same S-NSSAI or the same APN. That is, the second connection request may be a PDU establishment request or a PDN connection request. For example, the rejection reason may indicate insufficient resources, and the first connection request and the second connection request are associated with the same APN (that is, both the first connection request and the second connection request are PDN connection requests).

[0121] In one embodiment, the at least one access type includes only the first access type associated with the first connection request. In this embodiment, the radio network node receives a second connection request from the wireless terminal via the first access type associated with the first connection request after the backoff timer expires, and the first connection request and the second connection request are associated with the same single network slice selection assistance information or the same access point name. Note that the first connection request and the second connection request are associated with the same S-NSSAI or the same APN. That is, the second connection request may be a PDU establishment request or a PDN connection request.

[0122] In one embodiment, the at least one access type includes a 3GPP access type and a non-3GPP access type. In this embodiment, the radio network node receives a second connection request from the radio terminal via the 3GPP access type or the non-3GPP access type after a back-off timer expires, and the first connection request and the second connection request are associated with the same S-NSSAI or the same APN. That is, the radio terminal may request to establish the same PDU session or the same PDN connection after the back-off timer expires. In this embodiment, the rejection reason may indicate insufficient resources, and the first connection request and the second connection request are associated with the same access point name.

[0123] In one embodiment, the radio network node may transmit to the wireless terminal a back-off timer associated with the first connection request.

[0124] In one embodiment, the radio network node is / includes at least one of an SMF or a combined SMF and PGW-C node (i.e., SMF+PGW-C).

[0125] 8 shows a flowchart of a method according to one embodiment of the present disclosure. The method shown in FIG. 8 may be used in a wireless terminal (e.g., a UE) and includes the following steps:

[0126] Step 801: Receive from a radio network node a rejection reason associated with a first connection request and an indication of at least one access type associated with the rejection reason.

[0127] 8, the wireless terminal receives a rejection reason associated with the first connection request from a radio network node (e.g., SMF or SMF+PGW-C). In this embodiment, the rejection reason is received along with an indication of at least one access type associated with the rejection reason. Based on the rejection reason and / or the indication, the wireless terminal determines when to send a second connection request to the radio network node, wherein the first connection request and the second connection request have the same S-NSSAI or the same APN.

[0128] In one embodiment, the first connection request is a PDU session establishment request or a PDN connection request. In one embodiment, the rejection reason is: Lack of resources, The maximum number of wireless terminals associated with the network slice or S-NSSAI has been reached, or The maximum number of protocol data unit sessions associated with a network slice or S-NSSAI has been reached. At least one of the following is shown.

[0129] In one embodiment, the at least one access type (e.g., indicated by or associated with the indication) includes at least one of a 3GPP access type, a non-3GPP access type, or a first access type associated with the first connection request (e.g., the current access type described above). For example, the indication may include / indicate the first access type (e.g., one of the 3GPP access type and the non-3GPP access type). Alternatively, the indication may include / indicate both the 3GPP access type and the non-3GPP access type.

[0130] In one embodiment, the at least one access type includes only the first access type associated with the first connection request. In this embodiment, the wireless terminal transmits the second connection request to the radio network node via a second access type different from the first access type, and the first connection request and the second connection request are associated with the same S-NSSAI (i.e., the same network slice) or the same APN. That is, the wireless terminal may transmit the second connection request immediately / after receiving, for example, a rejection reason and / or an indication, without waiting a certain period of time (e.g., until after a backoff timer expires). In this embodiment, the rejection reason may indicate insufficient resources, and the first connection request and the second connection request are associated with the same APN.

[0131] In one embodiment, the at least one access type includes only the first access type associated with the first connection request, wherein the wireless terminal transmits a second connection request to the wireless network node via the first access type associated with the first connection request after the back-off timer expires, and the first connection request and the second connection request are associated with the same S-NSSAI or the same APN.

[0132] In one embodiment, the at least one access type includes a 3GPP access type and a non-3GPP access type. In this embodiment, the wireless terminal transmits a second connection request to the radio network node via the 3GPP access type or the non-3GPP access type after the back-off timer expires, and the first connection request and the second connection request are associated with the same S-NSSAI or the same APN. In this embodiment, the rejection reason may indicate insufficient resources, and the first connection request and the second connection request may be associated with the same APN.

[0133] In one embodiment, the radio network node may receive a back-off timer associated with the first connection request from the radio network node.

[0134] In one embodiment, the radio network node is / includes at least one of an SMF or a combined SMF and PGW-C node (i.e., SMF+PGW-C).

[0135] While various embodiments of the present disclosure have been described above, it should be understood that they are presented by way of example only, and not by way of limitation. Similarly, various figures may depict example architectures or configurations provided to enable those skilled in the art to understand example features and functionality of the present disclosure. However, such persons will understand that the present disclosure is not limited to the example architectures or configurations shown, but can be implemented using a variety of alternative architectures and configurations. Moreover, as will be understood by those skilled in the art, one or more features of one embodiment can be combined with one or more features of another embodiment described herein. Thus, the breadth and scope of the present disclosure should not be limited by any of the above-described example embodiments.

[0136] It is also understood that any reference to elements herein using designations such as "first," "second," etc., generally does not limit the quantity or order of those elements. Rather, these designations may be used herein as a convenient means of distinguishing between two or more elements or instances of an element. Thus, a reference to a first and a second element does not imply that only two elements may be employed or that the first element must in any way precede the second element.

[0137] Additionally, those skilled in the art will understand that information and signals may be represented using any one of a variety of different technologies and techniques. For example, the data, instructions, commands, information, signals, bits, and symbols that may be referenced in the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0138] Those skilled in the art will further recognize that any one of the various illustrative logical blocks, units, processors, means, circuits, methods, and functions described in connection with the aspects disclosed herein may be implemented by electronic hardware (e.g., a digital implementation, an analog implementation, or a combination of the two), firmware, various forms of program or design code incorporating instructions (which may be referred to herein for convenience as "software" or "software units"), or any combination of these technologies.

[0139] To clearly illustrate this interchangeability of hardware, firmware, and software, various illustrative components, blocks, units, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware, firmware, or software, or a combination of these technologies, depends on the particular application and design constraints imposed on the overall system. Those skilled in the art may implement the described functionality in various ways for each particular application, and such implementation decisions do not depart from the scope of the present disclosure. According to various embodiments, a processor, device, component, circuit, structure, machine, unit, etc. may be configured to perform one or more of the functions described herein. The terms "configured to" or "configured for," as used herein with respect to a specified operation or function, refer to a processor, device, component, circuit, structure, machine, unit, etc. that is physically constructed, programmed, and / or arranged to perform the specified operation or function.

[0140] Furthermore, those skilled in the art will understand that the various example logical blocks, units, devices, components, and circuits described herein can be implemented in or by an integrated circuit (IC), which can include a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), or other programmable logic device, or any combination thereof. The logical blocks, units, and circuits can further include an antenna and / or transceiver for communicating with various components within a network or device. The general-purpose processor can be a microprocessor, although in the alternative, the processor can be any conventional processor, controller, or state machine. A processor can also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other suitable configuration for performing the functions described herein. If implemented in software, the functions can be stored as one or more instructions or code on a computer-readable medium. Thus, the steps of a method or algorithm disclosed herein can be implemented as software stored on a computer-readable medium.

[0141] Computer-readable media includes both computer storage media and communication media, including any medium that can enable a computer program or code to be transmitted from one place to another. Storage media can be any available medium that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer.

[0142] In this document, the term "unit" as used herein refers to software, firmware, hardware, and any combination of these elements for performing the associated functions described herein. Furthermore, for purposes of discussion, various units are described as individual units, but as will be apparent to one skilled in the art, two or more units may be combined to form a single unit that performs the associated functions according to embodiments of the present disclosure.

[0143] Additionally, memory or other storage devices, as well as communication components, may be employed in embodiments of the present disclosure. It will be appreciated that, for clarity, the above description has described embodiments of the present disclosure with reference to different functional units and processors. However, it will be apparent that any suitable distribution of functionality between different functional units, processing logic elements, or domains may be used without detracting from the present disclosure. For example, functionality illustrated as being performed by separate processing logic elements or controllers may be performed by the same processing logic element or controller. Accordingly, references to specific functional units do not refer to a strict logical or physical structure or organization, but merely to suitable means for providing the described functionality.

[0144] Various modifications to the implementations described in this disclosure will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other implementations without departing from the scope of the present disclosure. Thus, the present disclosure is not intended to be limited to the implementations shown herein but is to be accorded the widest scope consistent with the novel features and principles disclosed herein, as set forth in the following claims.

Claims

1. receiving, by the wireless terminal, from a radio network node, a rejection reason associated with a first protocol data unit (PDU) session establishment request and an indication that the rejection reason applies only to a current access type; Including, the indication indicates that the wireless terminal can initiate a second PDU session establishment request via another access type different from the current access type; A wireless communication method, wherein the first PDU session establishment request and the second PDU session establishment request are associated with the same single network slice selection assistance information (S-NSSAI).

2. The wireless communication method of claim 1 , wherein the reason for the rejection indicates a lack of resources.

3. The wireless communication method of claim 1 , wherein the current access type comprises a Third Generation Partnership Project (3GPP) access type or a non-3GPP access type.

4. and receiving a back-off timer by the wireless terminal; After the back-off timer expires, the wireless terminal may initiate the second PDU session establishment request via the current access type or the other access type. The wireless communication method according to claim 1 .

5. receiving from the radio network node a back-off timer associated with the first PDU session establishment request; further comprising Before the back-off timer expires, the wireless terminal may initiate a second PDU session establishment request via the other access type that is different from the current access type. The wireless communication method according to claim 1 .

6. The wireless communication method of claim 1 , wherein the radio network node comprises a session management function.

7. a radio network node, comprising: at least one processor; and a memory storing instructions that, when executed by the processor, cause the radio network node to: transmitting to the wireless terminal a rejection reason associated with the first protocol data unit (PDU) session establishment request and an indication that the rejection reason applies only to the current access type; the indication is used to indicate that the wireless terminal can initiate a second PDU session establishment request via another access type different from the current access type; A radio network node, wherein the first PDU session establishment request and the second PDU session establishment request are associated with the same single network slice selection assistance information (S-NSSAI).

8. The processor may cause the radio network node to: receiving, from a network slice admission control function, a network slice admission control result associated with a rejection of the first PDU session establishment request; 8. The radio network node of claim 7, wherein the network slice admission control result indicates that a maximum number of protocol data unit sessions associated with a network slice or a single network slice selection assistance information via the current access type has been reached.

9. The radio network node of claim 7 , wherein the reason for rejection indicates a lack of resources.

10. The current access type is the 3rd Generation Partnership Project (3GPP) rd 8. The radio network node of claim 7, comprising a 3GPP (3rd Generation Partnership Project) access type or a non-3GPP access type.

11. 8. The radio network node of claim 7, wherein the processor causes the radio network node to transmit a back-off timer to the radio terminal, and the indication is further used to indicate that the radio terminal can initiate the second PDU session establishment request via the current access type or the other access type after the back-off timer expires.

12. the processor causing the radio network node to transmit a back-off timer associated with the first PDU session establishment request to the wireless terminal; 8. The radio network node of claim 7, wherein the indication is used to indicate that the radio terminal can initiate a second PDU session establishment request via the other access type different from the current access type before the back-off timer expires.

13. A wireless terminal, an apparatus comprising at least one processor and a memory storing instructions, the instructions, when executed by the processor, causing the apparatus to: receiving from a radio network node a rejection reason associated with a first protocol data unit (PDU) session establishment request and an indication that the rejection reason applies only to a current access type; the indication indicates that the wireless terminal can initiate a second PDU session establishment request via another access type different from the current access type; A wireless terminal, wherein the first PDU session establishment request and the second PDU session establishment request are associated with the same single network slice selection assistance information (S-NSSAI).

14. The wireless terminal of claim 13 , wherein the reason for denial indicates a lack of resources.

15. The current access type is the 3rd Generation Partnership Project (3GPP) rd 14. The wireless terminal of claim 13, comprising a 3GPP (3rd Generation Partnership Project) access type or a non-3GPP access type.

16. 14. The wireless terminal of claim 13, wherein the processor causes the wireless terminal to receive a back-off timer, and after the back-off timer expires, the wireless terminal can initiate the second PDU session establishment request via the current access type or the other access type.

17. the processor causes the wireless terminal to receive from the radio network node a back-off timer associated with the first PDU session establishment request; 14. The wireless terminal of claim 13, wherein the wireless terminal can initiate a second PDU session establishment request via the other access type different from the current access type before the backoff timer expires.

18. The wireless terminal of claim 13 , wherein the radio network node comprises a session management function.

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