TWI758046B - Method of handling multi-access pdu session handover and user equipment thereof - Google Patents

Abstract

A method of handling multi-access (MA) Protocol data unit (PDU) session handover is proposed. An ATSSS-Supported UE first establishes a MA PDU Session on both 3GPP and non-3GPP access in a currently registered PLMN which is an ATSSS-Supported network. The UE then moves from the ATSSS-Supported network to an ATSSS-not-Supported network and finally reaches another ATSSS-Supported network. In one novel aspect, a solution is provided on how to handle the ongoing MA PDU Session with two accesses under handover scenarios between ATSSS-Supported and ATSSS-not-Supported networks. Furthermore, if the ongoing MA PDU Session cannot handover, a solution is provided on how to handle the MA PDU Session.

Description

Method for handling session switching of multiple access protocol data units and user equipment thereof

Embodiments of the present invention relate generally to wireless communications, and, more particularly, to handling multiple access (Multi-Access, MA) PDUs between different PLMNs and AMFs in a 5G New Radio (NR) communication network Session switching method.

Wireless communication networks have grown exponentially over the years. Long-Term Evolution (LTE) systems have higher peak data rates, lower latency, improved system capacity and lower operating costs due to simplified network architecture. LTE systems (also known as 4G systems) also provide seamless integration with legacy wireless networks such as GSM, CDMA, and Universal Mobile Telecommunication System (UMTS). In the LTE system, the evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of evolved mobile stations that communicate with a plurality of mobile stations called user equipment (UE). Node B (evolved Node-B, eNodeB or eNB). The 3rd generation partner project (The 3rd generation partner project, 3GPP) network usually includes the integration of 2G/3G/4G systems. The Next Generation Mobile Network (NGMN) committee has decided to focus future NGMN activities on defining the end-to-end requirements for 5G new radio (NR) systems.

In 5G/NR, a Protocol Data Unit (PDU) session defines the association between the UE and the data network that provides the PDU connection service. PDU session establishment is a parallel process of the packet data network (PDN) connection (bearer) process in 4G/LTE. Each PDU session is identified by a PDU session ID (PDU session ID, PSI), and may include a plurality of Quality of Service (Quality of Service, QoS) flows and QoS rules. Each PDU session may be established via a 5G access network (eg, a 3GPP radio access network (RAN) or via a non-3GPP RAN). The network or UE may initiate different PDU session processes, eg, PDU session establishment, PDU session modification and PDU session release. Due to new radio conditions, load balancing or due to specific services, different handover procedures and inter-system transitions are used to switch the UE from the source 5G access network to the target 5G access or target 4G access network.

Operators are looking for ways to balance data traffic between mobile networks and non-3GPP accesses in ways that are transparent to users and reduce congestion on mobile networks. In 5GS, UE can connect to both 3GPP accesses and non-3GPP accesses (using 3GPP NAS signaling) at the same time, so 5GS can take advantage of these multiple accesses to improve user experience and optimize traffic distribution across various accesses . Therefore, 3GPP introduced multiple access (Multi-Access, MA) PDU sessions in 5GS. The MA PDU session uses one 3GPP access network or one non-3GPP access network at a time, or both a 3GPP access network and a non-3GPP access network at the same time. In addition, the UE and network can support the Access Traffic Steering Switching and Splitting (ATSSS) function to distribute traffic for established MA PDU sessions using 3GPP access and non-3GPP access.

However, when transitioning from 5GS to EPS between systems, the UE behavior on how to handle MA PDU sessions is undefined.

ATSSS-supported UEs first establish MA PDU sessions on both 3GPP accesses and non-3GPP accesses in the currently registered public land mobile network (PLMN) where the currently registered PLMN is a network that supports ATSSS. The UE then moves from a network supporting ATSSS to an ATSSS-not-supported network and finally to another network supporting ATSSS. In a handover scenario between a network that supports ATSSS and a network that does not support ATSSS, it is not defined how the network and the UE handle the ongoing MA PDU session using the two accesses. Furthermore, if an ongoing MA PDU session cannot be handed over, it is undefined how the network and the UE handle the MA PDU session.

A method for handling MA PDU sessions in the case of inter-system transitions is proposed. The MA PDU session uses a 3GPP access network or a non-3GPP access network at a time, or uses a 3GPP access network and a non-3GPP access network at the same time. The UE and the network can support the ATSSS function to distribute traffic for established MA PDU sessions using 3GPP access and non-3GPP access. During intersystem transition from 5GS to EPS using 3GPP access, if interworking with EPS is supported, the 3GPP part of the MA PDU session will be transferred to the PDN connection and the non-3GPP part of the MA PDU session will be released. QoS flows for MA PDU sessions based on both 3GPP access types and non-3GPP access types are transferred into the EPS bearer context of the corresponding PDN connection. On the other hand, if interworking with EPS is not supported, MA PDU sessions based on non-3GPP access types in 5GS are reserved. Data traffic of MA PDU sessions based on 3GPP access type is transferred to non-3GPP access type.

In one embodiment, the UE performs registration in the 5G mobile communication network. The UE establishes a MA PDU session in 5GS. MA PDU sessions have PSI and are established with both the first RAT access type and the second RAT access type. The UE performs inter-system conversion from 5GS to EPS. In EPS, the UE switches the MA PDU session to the corresponding PDN connection based on the first RAT access type. The MA PDU session based on the first RAT access type is transferred to the PDN connection and the MA PDU session based on the second RAT access type is released.

In another embodiment, the UE performs registration in the 5G mobile communication network. The UE establishes a MA PDU session in 5GS. MA PDU sessions have PSI and are established with both the first RAT access type and the second RAT access type. The UE performs inter-system conversion from 5GS to EPS. The UE determines that the MA PDU session is not switched to the corresponding PDN connection in the EPS. Data traffic based on the first RAT access type in the MA PDU session is then transferred to the second RAT access type in the 5GS.

In one novel aspect, an ATSSS-capable UE first establishes MA PDUs on 3GPP accesses and non-3GPP accesses in a currently registered PLMN that is an ATSSS-capable network. The UE then moves from a network supporting ATSSS to a network not supporting ATSSS and finally to another network supporting ATSSS. In a novel aspect, a solution is provided on how to handle an ongoing MA PDU session with two accesses in a scenario of switching between an ATSSS-enabled network and a non-ATSSS-enabled network. In addition, if the ongoing MA PDU session cannot be switched, a solution on how to handle the MA PDU session is provided.

In one embodiment, the UE performs registration in the first PLMN connected to the first AMF supporting ATSSS. The UE establishes a MA PDU session in the first PLMN. The MA PDU session is established based on both the first RAT access type and the second RAT access type. When the UE moves from the first PLMN or the first AMF to the second PLMN or the second AMF that does not support the ATSSS, it is determined whether to maintain the MA PDU session. Based on the ATSSS not supported indicator received from the second PLMN or the AMF, the UE locally releases the MA PDU session based on the access part of the first RAT.

In another embodiment, the UE includes a registration module for performing registration in a first public land mobile network connected to one of the first access and mobility management functions supporting an incoming traffic steering handover and split . The UE also includes an AP data unit session and a packet data network connection processing circuit for establishing a multiple access protocol data unit session in the first public land mobile network, wherein the multiple access protocol data unit session is based on Both a first radio access technology access type and a second radio access technology access type are established. The UE further includes configuration and control circuitry for determining when to move from the first public land mobile network or the first access and mobility management function to a second common one that does not support the access traffic steering handover and split Whether to maintain the MAP session for terrestrial mobile network or a secondary access and mobility management function. wherein the UE locally releases the multiple access protocol based on an indicator received from the second public land mobile network or the second access and mobility management function that does not support access traffic steering switching and splitting The data unit session is based on the portion of the first radio access technology access type.

The present invention proposes a method for handling multiple access protocol data unit session switching and a user equipment thereof. In the switching scenario between a network that supports ATSSS and a network that does not support ATSSS, the UE locally releases the MA PDU session. The first RAT access part achieves the beneficial effects of optimizing MA PDU session processing and improving the utilization efficiency of network resources.

In a novel aspect, when a UE moves from a network that supports ATSSS to a network that does not support ATSSS, if the UE finds that an ATSSS-not-supported indicator is sent by the network or that the ATSSS-supported indicator is not received , the UE locally releases the first RAT access part of the MA PDU session established in the network supporting ATSSS, while the network supporting ATSSS also releases the first RAT access part of the established MA PDU session locally. The UE and the network supporting ATSSS do not need to exchange signaling to perform the release process of the MA PDU session, which can optimize the processing process of the entire MA PDU session and improve the efficiency of network resource use, for example, to avoid wasting resources between the UE and the network. Signaling exchange on the network side.

Other embodiments and benefits are set forth in the detailed description below. This summary is not intended to define the invention. The invention is defined by the scope of the claims.

Reference will now be made in detail to some embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

Figure 1 illustrates an exemplary 5G network 100 supporting MA PDU session management with inter-system translation in accordance with one novel aspect. 5G network 100 includes UE 101, 3GPP RAN 102, non-3GPP RAN 103, access and mobility Access and Mobility Management Function (AMF) 110, Session Management Function (SMF) 111, Non-3GPP Interworking Function (N3IWF) 112, User Plane Function (UPF) ) 113 and a 5G core (5G core, 5GC) or Evolved Packet core (EPC) data network 120. The AMF communicates with base stations, SMFs and UPFs for access and mobility management of radio access equipment in the 5G network 100 . The SMF is mainly used for interworking with the decoupled data plane, creating, updating and deleting PDU sessions, and managing the session context with the UPF. The N3IWF function of the 5G Core Network Control Plane Function Interface is responsible for routing messages out of the 5G RAN.

In an access layer (Access Stratum, AS), the RAN provides radio access for the UE 101 via a radio access technology (radio access technology, RAT). In the Non-Access Stratum (NAS) layer, AMF and SMF communicate with RAN and 5GC/EPC for access and mobility management of radio access equipment and PDU session management in 5G network 100 . 3GPP RAN 102 may include base stations (gNB or eNB) that provide radio access to UE 101 through various 3GPP RATs including 5G, 4G and 3G/2G. The non-3GPP RAN 103 may include an access point (AP) that provides radio access to the UE 101 via a non-3GPP RAT including WiFi. UE 101 may gain access to data network 120 through 3GPP RAN 102, AMF 110, SMF 111 and UPF 113. UE 101 may gain access to access network 120 through non-3GPP RAN 103, N3IWF 112, AMF 110, SMF 111 and UPF 113. The UE 101 may be equipped with a single radio frequency (RF) module or transceiver, or a plurality of RF modules or transceivers to perform services via different RAT/CNs. The UE 101 may be a smart phone, a wearable device, an Internet of Things (IoT) device, a tablet, and the like.

The 5GS network is a packet-switched (PS) Internet Protocol (IP) network. This means that the network passes all data traffic in IP packets and provides users with an always-on IP connection. When the UE joins the EPS network, a Packet Data Network (PDN) address (that is, an address that can be used on the PDN) is allocated to the UE to realize the connection between the UE and the PDN. In 4G, EPS defines a default EPS bearer to provide IP connectivity on an always-on line. In 5G, the PDU session establishment process is a parallel process of the PDN connection process in 4G. The PDU session defines the association between the UE and the data network that provides the PDU connection service. Each PDU Session is identified by a PDU Session ID and may include a plurality of QoS Flows and QoS Rules. In 5G networks, QoS flow is the best fine-grained QoS management to achieve more flexible QoS control. The concept of QoS flow in 5G is similar to EPS bearer in 4G.

Each PDU session can be established using the 3GPP RAN or at a non-3GPP RAN for radio access. 5G session management (5G Session management, 5GSM) based on both 3GPP access and non-3GPP access PDU sessions is managed by AMF and SMF through NAS signaling. Operators are looking for ways to balance data traffic between mobile networks and non-3GPP access in a way that is transparent to users and reduces congestion on the mobile network. In 5GS, the UE can connect to both 3GPP accesses and non-3GPP accesses (using 3GPP NAS signaling), so 5GS can take advantage of these multiple accesses to improve user experience and optimize traffic distribution across various accesses. Therefore, 3GPP introduced MA PDU session in 5GS. The MA PDU session uses one 3GPP access network or one non-3GPP access network at a time, or both a 3GPP access network and a non-3GPP access network at the same time. Additionally, the UE and the network can support ATSSS functionality to distribute traffic for established MA PDU sessions using 3GPP access and non-3GPP access.

When a MA PDU session is established in 5GS, a plurality of QoS flows are included in the non-NAS layer. Each QoS flow can be mapped to a corresponding EPS bearer. In addition, each QoS flow can use 3GPP access or non-3GPP access based on ATSSS rules. When adding a QoS flow, the network may provide the UE with a QoS flow description information element (IE) including a list of QoS flow descriptions. Each QoS flow description includes a QoS flow identifier (QoS flow identifier, QFI), a QoS flow operation code, a plurality of QoS flow parameters, and a QoS flow parameter list. Each parameter included in the parameter list consists of a parameter identifier that identifies the corresponding parameter. One of the parameter identifiers is EPS bearer identity (EPS bearer identity, EBI), and EBI is used to identify the EPS bearer mapped to or associated with the QoS flow. However, if the MA PDU session does not support interworking with EPS, there are no associated EPS Session Management (ESM) parameters, e.g. EBI, mapping, when transitioning from 5GS to EPS using 3GPP. The EPS bearer context.

After inter-system transition from N1 (5GS) mode to S1 (4G, EPS) mode, if interworking with EPS is supported, the PDU session in 5GS is transferred to the corresponding PDN connection in EPS, and the QoS flow of the PDU session is mapped to The associated EPS bearer. The default EPS bearer context includes PDU session identity (PSI), single network slice selection assistance information (S-NSSAI), aggregate maximum bit rate (Aggregate Maximum Bit Rate, AMBR) and configuration options IE or One or more QoS flow descriptions received in the extended agreement configuration option IE, or the preset EPS bearer context is associated with the PDU session identifier, S-NSSAI, session AMBR and one or more QoS flow descriptions. However, the UE behavior of how to handle MA PDU sessions when transitioning from 5GS to EPS is not defined, regardless of whether the system supports interworking with EPS.

According to a novel aspect, if interworking with EPS is supported, and if MA PDU sessions in 5GS are based on 3GPP and non-3GPP accesses (i.e., MA PDU sessions are established and MA PDU sessions are If the user plane resource is successfully established), when using 3GPP access to switch from 5GS to EPS, the 3GPP part of the PDU session is transferred to the PDN connection, and the non-3GPP part of the PDU session is released. QoS flows based on 3GPP access and non-3GPP access MA PDU sessions are transferred to the EPS bearer context of the corresponding PDN connection. As indicated by arrow 131, the MA PDU session with PSI=1 in 5GS is transferred to PDN connection #1 in EPS. All QoS flows with EBI allocated using 3GPP and non-3GPP accesses are transferred to PDN connection #1 in EPS. User plane resources based on non-3GPP access MA PDU sessions are released in 5GS via the PDU session release process, and ATSSS rules are released. On the other hand, if interworking with EPS is not supported, and if MA PDU sessions in 5GS are based on both 3GPP and non-3GPP accesses, when inter-system transitions from 5GS to EPS using 3GPP accesses, the 3GPP access MA PDU session, and transfer data traffic based on 3GPP access MA PDU session to non-3GPP access in 5GS. As indicated by arrow line 132, MA PDU sessions with PSI=1 in 5GS are maintained and are not transferred to any PDN connections in EPS. Optionally, the data traffic of the MA PDU session based on the 3GPP access is transferred to the non-3GPP access through the PDU session modification process initiated by the network or the UE. In some steering modes, the UE can transfer 3GPP traffic directly to a non-3GPP access without the need for a PDU session modification process.

Figure 2 shows a simplified block diagram of a wireless device (eg, UE 201 and network entity 211) in accordance with an embodiment of the present invention. The network entity 211 may be a base station and/or an AMF/SMF. The network entity 211 has an antenna 215 that transmits and receives radio signals. The radio frequency RF transceiver module 214 coupled to the antenna receives the RF signal from the antenna 215 , converts the RF signal to a baseband signal, and then sends the baseband signal to the processor 213 . The RF transceiver module 214 also converts baseband signals received from the processor 213 , converts the baseband signals to RF signals, and sends them to the antenna 215 . The processor 213 processes the received baseband signals and invokes different function modules to execute the functions in the base station 211 . The memory 212 stores data and program instructions 220 to control the operation of the base station 211 . The network entity 211 also includes a protocol stack 280 and a set of control function modules and circuits 290 . PDU session and PDN connection processing circuit 231 handles PDU/PDN establishment and modification procedures. QoS and EPS bearer management circuitry 232 creates, modifies and deletes QoS and EPS bearers for the UE. The configuration and control circuit 233 provides various parameters to configure and control related functions of the UE, including mobility management and PDU session management, and the switching module 234 handles switching between 5GS and EPS and switching between systems.

Similarly, UE 201 has memory 202 , processor 203 and RF transceiver module 204 . The RF transceiver module 204 is coupled to the antenna 205 , receives RF signals from the antenna 205 , converts the RF signals to baseband signals, and sends the baseband signals to the processor 203 . The RF transceiver module 204 also converts the received baseband signals from the processor 203 to RF signals and sends the RF signals to the antenna 205 . The processor 203 processes the received baseband signals, and invokes different functional modules and circuits to perform functions in the UE 201 . The memory 202 stores data and program instructions 210 executed by the processor to control the operation of the UE 201 . By way of example, suitable processors include special purpose processors, digital signal processors (DSPs), microprocessors, and DSP cores, controllers, microcontrollers, application specific integrated circuits One or more microprocessors and/or state machines associated with integrated circuits (ASIC), file programmable gate array (FPGA) circuits, and other types of integrated circuits (ICs). A processor associated with the software may be used to implement and configure features of the UE 201 .

The UE 201 also includes a set of functional modules and control circuits to perform functional tasks of the UE 201 . Protocol stack 260 includes a NAS layer for communicating with AMF/SMF/MME entities connected to the core network, a Radio Resource Control (RRC) layer for high-level configuration and control, a Packet Data Convergence Protocol (Packet) Data Convergence Protocol, PDCP)/Radio Link Control (Radio Link Control, RLC) layer, medium access control (Media Access Control, MAC) layer and physical (Physical, PHY) layer. System modules and circuits 270 may be implemented and configured through software, firmware, hardware, and/or combinations thereof. When executed by the processor via program instructions contained in memory, the functional modules and circuits interact with each other to allow the UE 201 to perform embodiments and functional tasks and features in the network.

In one example, system modules and circuits 270 include: PDU session and PDN connection processing circuitry 221 for performing PDU session and PDN connection establishment and modification procedures with the network; for managing, creating, modifying, and deleting QoS flows QoS flow and EPS bearer processing circuits 222 for mapping and mapped EPS bearer contexts; configuration and control circuits 223 for handling configuration and control parameters for mobility management and session management; handover module 224 for handling handovers and inter-system transitions ; and a registration module that performs registration with the network. Furthermore, the UE 201 also includes registration circuitry for performing registration in a network (eg, a 5G mobile communication network). In one example, if interworking is supported and if the MA PDU session is based on both 3GPP and non-3GPP access, then upon intersystem transition from 5GS to EPS with 3GPP access, the 3GPP portion of the PDU session is transferred to the PDN connection, And release the non-3GPP part of the PDU session. The QoS flow of the MA PDU session based on both 3GPP access and non-3GPP access is transferred to the EPS bearer context of the corresponding PDN connection. In another example, if interworking is not supported, and if the MA PDU session is based on both 3GPP and non-3GPP access, then when inter-system transition from 5GS to EPS using 3GPP access, the non-3GPP based access in 5GS is maintained The MA PDU session is connected, and the data traffic of the MA PDU session based on the 3GPP access is transferred to the non-3GPP access. In yet another example, when the UE moves from a PLMN or AMF that supports ATSSS to a PLMN or AMF that does not support ATSSS, when the UE receives the ATTSS support indicator and the PDU session status without a signaling exchange with the network , the UE locally releases the MA PDU session.

Figure 3 shows one embodiment of establishing a MA PDU session in 5GS after the UE has registered to the network through both 3GPP and non-3GPP access types belonging to the same PLMN. The UE 301 registers with the PLMN1 via the 3GPP base station gNB 302 using the 3GPP access type. The UE 301 also registers with the PLMN1 via the non-3GPP access point AP 303 with the non-3GPP access type. The UE 301 establishes the MA PDU session by initiating the PDU session establishment procedure with the network using the 3GPP or non-3GPP access type. The initiation of the MA PDU connection service refers to the establishment of user plane resources on both 3GPP accesses and non-3GPP accesses. Since the UE 301 has registered to the network with two RAT access types belonging to the same PLMN1, the MA PDU session with PSI=1 is established based on both the 3GPP and non-3GPP access types, and then the User plane resources are created on both.

Figure 4 shows one embodiment of establishing a MA PDU session in 5GS after the UE has registered to the network via 3GPP and non-3GPP access types belonging to different PLMNs. The UE 401 registers with the first PLMN1 via the 3GPP base station gNB 402 using the 3GPP access type. The UE 401 also registers with the second PLMN2 via the non-3GPP access point AP 403 using the 3GPP access type. The UE 401 establishes the MA PDU session by initiating a PDU session establishment procedure with the network using one of the access types (eg, 3GPP access type). For example, the UE 401 sends a PDU SESSION ESTABLISHMENT REQUEST message to the gNB 402, where the Request Type IE is set to "MA PDU request" and PSI=1. User plane resource establishment on 3GPP access. Then, the UE 401 sends another PDU SESSION ESTABLISHMENT REQUEST message to the AP 403, wherein the Request Type IE is set to "MA PDU request" and also PSI=1. User plane resource establishment on non-3GPP access. Since the UE 401 registers to the network using two RAT access types belonging to different PLMNs, in two separate steps, a MA PDU session with PSI=1 is first established using the 3GPP access type and then using the non-3GPP access type. Connection type is established.

Figure 5 shows another embodiment of establishing a MA PDU session in 5GS when the UE is registered to one RAT access type and then registered to another RAT access type of the same PLMN. The UE 501 registers with the first PLMN1 via the 3GPP base station gNB 502 using the 3GPP access type. UE 501 is not registered to PLMN1 with a non-3GPP access type. Then, the UE 501 establishes a MA PDU session by initiating a PDU session establishment procedure with the network using the 3GPP access type. For example, the UE 501 sends a PDU SESSION ESTABLISHMENT REQUEST message to the gNB 502, where the Request Type IE is set to "MA PDU request" and PSI=1. User plane resource establishment on 3GPP access. Later, the UE 501 registers with the same PLMN1 via the non-3GPP access point AP 503 with the non-3GPP access type. The UE 501 sends another PDU SESSION ESTABLISHMENT REQUEST message to the AP 503, wherein the Request Type IE is set to "MA PDU request" and also PSI=1. User plane resource establishment on non-3GPP access. Thus, in two separate steps, the UE 501 establishes a MA PDU session to the same PLMN1 with PSI=1 using both 3GPP access types and non-3GPP access types.

Figure 6 shows a simplified block diagram of a UE supporting MultiPath Transmission Control Protocol (MPTCP) functions operating above the IP layer and/or ATSSS functions operating below the IP layer as data exchange functions picture. The UE and the network may support one or more steering functions for the MA PDU session. The MPTCP function operates above the IP layer, while the ATSSS Low-Layer (ATSSS-LL) function operates below the IP layer as a data exchange function. As shown in Figure 6, in higher layers, the MPTCP function verifies the ATSSS rules, and MPTCP streams (Transmission Control Protocol (TCP) streams from applications that are allowed to use MPTCP) are split into bindings to the middle layer and subflows of different IPs (eg, IP stacks) in lower layers, then directed or switched to non-3GPP accesses or 3GPP accesses. For non-MPTCP streams (eg, User Datagram Protocol (UDP), TCP, Ethernet streams), in the lower layers, the ATSSS-LL function verifies the ATSSS rules and splits, directs, or splits the traffic. Switch to non-3GPP or 3GPP access.

In an ATSSS capable UE, the ATSSS-LL requirements are as follows. For the MA PDU session of the Ethernet PDU session type, the ATSSS-LL function must be used. For MA PDU sessions of IPv4, IPv6 or IPv4v6 PDU session type, if the UE does not support the MPTCP function, the ATSSS-LL function is mandatory. If the UE supports the MPTCP function, only the active-standby boot mode of the ATSSS-LL function is mandatory. All other boot modes are optional. The network provides ATSSS rules in 5GSM messages, eg, in PDU SESSION ESTABLISHMENT ACCEPT or PDU SESSION MODIFICATION COMMAND messages. Parameters of ATSSS rules include rule precedence which determines the order in which ATSSS rules are evaluated in the UE, traffic descriptor (descriptor), application description, IP description, access selection description, bootstrap mode (active/standby) used to identify the matching traffic , Minimum Latency, Load Balancing, Priority-Based), and identifies whether the MPTCP function or the ATSSS-LL function should be applied to the steering function matching traffic. Examples of ATSSS rules include: 1. "Traffic Description: UDP, DestAddr 1.2.3.4", "Boot Mode: Active-Standby, Master=3GPP, Slave=Non-3GPP" This rule means "Boot has destination IP address 1.2. 3.4 UDP traffic to the primary access (3GPP) (if available). If the primary access is not available, use the backup access (non-3GPP)". 2. "Traffic Description: TCP, DestPort 8080", "Guide Mode: Minimum Delay", the meaning of this rule is "Direct TCP traffic with destination port 8080 to the incoming connection with minimum delay." UE needs to be based on two incoming connections Round Trip Time (RTT) is measured to determine which access has the least delay. 3. "Traffic description: Application-1", "Guide mode: Load balancing, 3GPP=20%, non-3GPP=80%", "Guide function: MPTCP", the meaning of this rule is "By using the MPTCP function, the application- 1 out of 20% of traffic is sent to 3GPP accesses, and 80% of traffic is sent to non-3GPP accesses.”

Figure 7 illustrates one embodiment of inter-system transition from 5GS to EPS and QoS flow handling when converting MA PDU sessions to PDN connections. In 5GS, the UE establishes a MA PDU session with PSI=1 using 3GPP and non-3GPP access. The MA PDU session is configured with three QoS flows and some ATSSS rules for data traffic distribution. The granularity of the ATSSS steering function is per service data flow (SDF), not per QoS flow. The scope of the SDF is independent of QoS flows. A QoS flow may include one or more SDFs, and the SDFs may be distributed over one or more QoS flows. The ATSSS steering function determines which access is used (3GPP or non-3GPP) to send SDF traffic. During inter-system transition from 5GS to EPS, user plane resources based on 3GPP access MA PDU sessions are transferred to the corresponding PDN connections in EPS, and resources are released based on the user plane of non-3GPP access MA PDU sessions. All three QoS flows of the MA PDU session are transferred to the corresponding PDN connections in the EPS. PDN connection 1 in EPS includes two EPS bearers: a default EPS bearer with EBI=1 associated with QoS flow 1 and QoS flow 2, and a dedicated EPS bearer with EBI=2 associated with QoS flow 3.

Figure 8 shows the sequence flow between UE 801 and 5GS and EPS when the MA PDU session transitions to a PDN connection when transitioning from 5GS to EPS inter-system in accordance with one novel aspect. In step 811, the UE 801 registers with the 5GS network using the 3GPP access type. In step 812, the UE 801 registers with the 5GS network using the non-3GPP access type. The registered 5GS network belongs to the same PLMN. In step 821, the UE 801 initiates a PDU session establishment process by sending a PDU SESSION ESTABLISHMENT REQUEST message based on any access type to create a request type IE with set to "MA PDU request" and PSI= 1 of the MA PDU session. In step 822, the UE 801 receives a PDU session establishment accept (PDU SESSION ESTABLISHMENT ACCEPT) message from the network based on the corresponding access type, wherein the message carries the ATSSS rule. In step 831, a MA PDU session with PSI=1 is established between UE 801 and 5GS using both 3GPP and non-3GPP access types. ATSSS rules provide parameters for traffic steering, handover and segmentation functions between 3GPP and non-3GPP accesses. Note that the establishment of the MA PDU session may require multiple steps, eg if the UE is registered with a different RAT with a different PLMN.

In step 841, an inter-system transition occurs to switch the UE 801 from 5GS to EPS. When UE 801 moves from 5GS to EPS, for both idle mode and connected mode mobility, MA PDU session moves to corresponding PDN connection in EPS. The SMF triggers the PDU session release process to release the MA PDU session based on the non-3GPP access in 5GS, eg, the user plane resources of the MA PDU session on the non-3GPP access. In step 842, the network sends a PDU SESSION RELEASE COMMAND message to the UE 801, wherein the Access Type IE is set to "non-3GPP" and PSI=1. In step 843, the UE 801 sends a PDU SESSION RELEASE COMPLETE message to the network. Releases user plane resources for MA PDU sessions on non-3GPP accesses, and also releases ATSSS rules. Note that the PDU session release process of steps 842-843 may occur after step 851. Furthermore, the non-3GPP access portion of the MA PDU session can be released locally by the UE without performing the PDU session release procedure. In step 851, the MA PDU session based on the 3GPP access is converted to the PDN connection in the EPS for 3GPP access. Note that QoS flows with assigned EBIs for MA PDU sessions using 3GPP access and non-3GPP access are transferred into the EPS bearer context of the corresponding PDN connection using 3GPP access. The UE and SMF delete ATSSS related contexts, eg, ATSSS rules and measurement assistance information.

Figure 9 shows one embodiment of inter-system transition and QoS flow handling from 5GS to EPS when the MA PDU session is not transitioned to a PDN connection. In 5GS, the UE uses 3GPP and non-3GPP access to establish a MA PDU session with PSI=1. The MA PDU session is configured with three QoS flows and some ATSSS rules for data traffic distribution. QoS Flow 1 and QoS Flow 2 are created for 3GPP access, and QoS Flow 3 is created for non-3GPP access. However, the UE does not support MA PDU session interworking, eg, the QoS flow of the MA PDU session does not allocate the mapped EPS bearer of the corresponding PDN connection in the EPS. During inter-system transition from 5GS to EPS, the MA PDU session in 5GS is maintained and is not transferred to any PDN connection in EPS. The UE can move the data traffic of the MA PDU session from a 3GPP access to a non-3GPP access based on the bootstrapping mode of the ATSSS rules. For example, if the steering mode is active-standby, the UE may steer the SDF by using the active access (if available), or use the backup access to steer the SDF when the active access is unavailable. If the steering mode is minimum delay, the UE may use the access network with the minimum RTT to steer the SDF. If the steering mode is load balancing, the UE may steer the SDF across both 3GPP and non-3GPP accesses. If only one access (eg, non-3GPP) is available, the UE steers the SDF by using the available access. The network may also move the data traffic of the MA PDU session from the 3GPP access to the non-3GPP access via the PDU session modification process.

Figure 10 shows the sequence flow between the UE and the 5GS and EPS when the MA PDU session is not transitioned to a PDN connection when transitioning from 5GS to EPS intersystem according to a novel aspect. In step 1011, the UE 1001 registers with the 5GS network using the 3GPP access type. In step 1012, the UE 1001 registers with the 5GS network using the non-3GPP access type. The registered 5GS network belongs to the same PLMN. In step 1021, the UE 1001 initiates a PDU session establishment process by sending a PDU SESSION ESTABLISHMENT REQUEST message based on any access type to create a request type IE with set to "MA PDU request" and PSI= 1 of the MA PDU session. In step 1022, the UE 1001 receives a PDU session establishment accept (PDU SESSION ESTABLISHMENT ACCEPT) message from the network through the corresponding access type, wherein the message carries the ATSSS rule. In step 1031, a MA PDU session with PSI=1 is established between UE 1001 and 5GS using both 3GPP and non-3GPP access types. ATSSS rules provide parameters for traffic steering, handover and segmentation functions between 3GPP and non-3GPP accesses. Note that the establishment of the MA PDU session may require multiple steps, eg if the UE is registered with a different PLMN using a different RAT.

In step 1041, an inter-system transition occurs to switch the UE 1001 from 5GS to EPS. When UE 1001 moves from 5GS to EPS, the MA PDU session in 5GS is maintained with non-3GPP access for idle mode and connected mode mobility. In step 1042, the network sends a PDU SESSION MODIFICATION COMMAND message to the UE 1001. In step 1043, the UE 1001 sends a PDU SESSION MODIFICATION COMPLETE message to the network. Through the PDU session modification process, the network can modify the boot mode in the ATSSS rules, thereby shifting the data traffic of the MA PDU session from 3GPP access to non-3GPP access. Note that UE 1001 is able to transfer data traffic from 3GPP access to non-3GPP access without the PDU session modification process itself, eg, based on the bootstrap mode in the ATSSS rules.

11 is a flow diagram of a method of supporting MA PDU sessions with inter-system translation in accordance with a novel aspect of the present invention. In step 1101, the UE performs registration in the 5G mobile communication network. In step 1102, the UE establishes a MA PDU session in 5GS. MA PDU sessions have PSI and are established with both the first RAT access type and the second RAT access type. In step 1103, the UE performs inter-system conversion from 5GS to EPS. In step 1104, the UE converts the MA PDU session to the corresponding PDN connection in the EPS based on the first RAT access type. The MA PDU session based on the first RAT access type is transferred to the PDN connection and the MA PDU session based on the second RAT access type is released.

12 is a flow diagram of a method of supporting MA PDU sessions with inter-system translation in accordance with a novel aspect of the present invention. In step 1201, the UE performs registration in the 5G mobile communication network. In step 1202, the UE establishes a MA PDU session in 5GS. MA PDU sessions have PSI and are established with both the first RAT access type and the second RAT access type. In step 1203, the UE performs inter-system conversion from 5GS to EPS. In step 1204, the UE determines that the MA PDU session is not switched to the corresponding PDN connection in the EPS. The data traffic based on the first RAT access type in the MA PDU session is transferred to the second RAT access type in the 5GS.

MA PDU session handover between PLMN and AMF

When the ATSSS-capable core network supports MA PDU session establishment, the core network will provide the UE with an indicator to support MA PDU session establishment during the registration process. If the UE receives an indicator that supports establishment of MA PDU sessions in the currently registered PLMN, ie, an indicator that supports ATSSS, the UE may initiate the process of establishing MA PDU sessions if the UE supports ATSSS functionality. Otherwise, when the UE is registered to the PLMN, the UE may receive an indicator that ATSSS is not supported or may receive an indicator that is not related to ATSSS. The indicator can prevent the UE from triggering the establishment of a MA PDU session, and can avoid frequent signaling between the UE and the core network that does not support the ATSSS function. The ATSSS-capable UE first establishes MA PDU session support on both 3GPP and non-3GPP accesses in the currently registered PLMN, which is the ATSSS-capable network. Then, the UE moves from the network that supports ATSSS to the network that does not support ATSSS, and finally arrives at another network that supports ATSSS. In a novel aspect, a solution is provided on how to handle an ongoing MA PDU session with two accesses in a scenario of switching between an ATSSS-enabled network and a non-ATSSS-enabled network. In addition, if the ongoing MA PDU session cannot be handed over to the target network, a solution on how to handle the MA PDU session is provided.

Figure 13 illustrates, in accordance with one novel aspect, one embodiment of handling MA PDU session handover when a UE moves from a PLMN or AMF supporting ATSSS to a PLMN or AMF not supporting ATSSS. In the embodiment of Figure 13, the UE 1301 (UE-1) is ATSSS capable and consists of a first PLMN-1 comprising a first AMF 1303 (AMF-1) and a first SMF 1304 (SMF-1) The first base station gNB 1302 (gNB-1) provides service. Since AMF-1 supports ATSSS, AMF-1 sends an ATSSS support indicator to UE-1 during the registration process to support MA PDU session. Therefore, UE-1 sends a MA PDU session establishment request to SMF-1 and establishes a MA PDU session through both 3GPP and non-3GPP accesses. On the other hand, PLMN-2 includes a second base station gNB 1312 (gNB-2), a second AMF 1313 (AMF-2), and a second SMF 1314 (SMF-2). AMF-2 does not support ATSSS and does not support MA PDU sessions.

When UE-1 moves from PLMN-1 that supports ATSSS to PLMN-2 that does not support ATSSS, the target network (PLMN-2) can inform UE-1 whether the 3GPP access of the MA PDU session can be used in the registration process by using The ATSSS support indicator is switched from gNB-1 to gNB-2. Since the network can notify UE-1 of an indicator, eg, ATSSS supported indicator or ATSSS not supported indicator or no indicator, to inform UE-1 whether the target network PLMN-2 supports or not during the indication registration related process ATSSS function. If the target network PLMN-2 does not support ATSSS, UE-1 knows that PLMN-2/AMF-2 does not support ATSSS. There are two situations in this case.

In the first use case, the 3GPP access of the MA PDU session is transferred from PLMN-1 to PLMN-2, eg, from gNB-1 to gNB-2. There are two options in the first use case. Under the first alternative, the MA PDU session is not fully transferred to the target network (ie PLMN-2), ie the 3GPP and non-3GPP access of the MA PDU session is not used in PLMN-2 at the same time. Only the 3GPP incoming part of the MA PDU session can be transferred to the target network. The non-3GPP incoming portion of the MA PDU session is released locally by SMF-1 in PLMN-1. During handover, SMF-2 in the target network (ie PLMN-2) will establish user plane (UP) resources for the 3GPP access portion of the transferred MA PDU session. Under the second alternative, the 3GPP access part is transferred to PLMN-2 but the UE can still access non-3GPP access resources through PLMN-1, then the UE can still use the PDU session as a MA PDU session (which reuses the stored ATSSS rules).

In the second use case, the 3GPP access portion of the MA PDU session is not transferred to the target network. The AMF (AMF-1) of the source network informs the SMF (SMF-1) of the source network that the 3GPP access part of the MA PDU session is released by SMF-1 and marked as unavailable to UE-1. There are two alternatives in the second use case. Under the first alternative, if the non-3GPP access portion of the MA PDU session is still available after the handover, SMF-1 may direct traffic to the non-3GPP access of the MA PDU session. Under the second alternative, the MA PDU session is completely released by SMF-1. Note that in the example of Figure 13, AMF-1 and AMF-2 belong to two different PLMNs, PLMN-1 and PLMN-2, respectively. In another example, a similar MA PDU handover handling mechanism applies when AMF-1 and AMF-2 belong to the same PLMN as long as the UE moves from source AMF-1 that supports ATSSS to target AMF-2 that does not support ATSSS.

Figure 14 shows the sequence flow between the UE, the source network (that supports ATSSS) and the target network (that does not support ATSSS) for handover processing of MA PDU sessions, according to one novel aspect. In step 1411, UE 1401 establishes a MA PDU session in PLMN-1 through both 3GPP access and non-3GPP access. PLMN-1 includes AMF-1 (supporting ATSSS) and SMF-1. In step 1412, UE 1401 moves from source PLMN-1 or AMF-1 to target PLMN-2 or AMF-2, which includes AMF-2 (not supporting ATSSS) and SMF-2. UE 1401 triggers a registration request to PLMN-2 or AMF-2 (step 1421 ), and AMF-2 responds with an ATSSS support indicator and PDU session status in a registration accept message (step 1422 ). The UE 1401 determines, based on the ATSSS support indicator provided by the network, whether the established MA PDU session will be handed over to the target PLMN-2 via 3GPP access, and thus whether to maintain the MA PDU session. In the first use case, the 3GPP access portion of the MA PDU session is transferred to the target PLMN-2. In the second use case, the 3GPP access portion of the MA PDU session is not transferred to the target PLMN-2.

In the first use case, since the AMF-2 in PLMN-2 does not support ATSSS, the MA PDU session cannot be completely transferred to the target network PLMN-2, i.e. the 3GPP incoming part and the non-3GPP incoming part of the MA PDU session Cannot be used in PLMN-2 at the same time. However, in step 1431, the 3GPP access portion of the MA PDU session is handed over to the target network. The non-3GPP incoming portion of the MA PDU session may be released locally by SMF-1 in PLMN-1 (step 1433). During handover, SMF-2 in PLMN-2 will establish user plane resources for the 3GPP access portion of the transferred MA PDU session (step 1434). From the UE's perspective, since UE 1401 has received an ATSSS unsupported indicator or no indicator from the current network (eg, AMF-2 in PLMN-2) during registration, UE 1401 may The non-3GPP access portion of the MA PDU session is released locally based on the ATSSS support indicator (step 1432). Alternatively, the 3GPP access part is transferred to the new PLMN-2, while the UE 1401 can still access non-3GPP user plane resources through the original PLMN-1 and can reuse the stored ATSSS rules. In other words, data traffic can be communicated on the non-3GPP access part of the MA PDU session in the original PLMN-1, and can also be communicated on the 3GPP access part of the transfer of the MA PDU session in the new PLMN-2.

In the second use case, the 3GPP access portion of the MA PDU session is not transferred to the target PLMN-2. Therefore, after UE 1401 receives the ATSSS support indicator or PDU session status, UE 1401 may locally release the 3GPP access portion of the MA PDU session (step 1441). UE 1401 may maintain or release the non-3GPP access portion of the MA PDU session (step 1442). Furthermore, when the UE 1401 receives the ATSSS support indicator or the PDU session status, the UE 1401 may release the MA PDU session completely locally. In source PLMN-1, AMF-1 may notify SMF-1 that the MA PDU session is not handed over to target PLMN-2 (step 1443). Therefore, SMF-1 either releases the entire MA PDU, or directs data traffic on the 3GPP access portion of the MA PDU session to the non-3GPP access portion of the MA PDU session (step 1444). Note that when the UE 1401 receives the ATSSS support indicator and the PDU session status, no additional signaling exchange with the network is required, the UE 1410 releases the MA PDU session locally, and the network also releases the MA PDU session locally to reduce signaling overhead . It should also be noted that, as described in steps 1441 and 1442, the UE 1401 may locally release the 3GPP and non-3GPP accesses of the MA PDU session. Alternatively, UE 1401 may release the entire MA PDU session locally at once.

Figure 15 illustrates one of the handling of MA PDU session handovers when a UE moves from an ATSSS capable PLMN or AMF to a non-ATSSS capable PLMN or AMF and then to another ATSSS capable PLMN or AMF in accordance with a novel aspect Example. In the example of Figure 15, the UE is ATSSS capable, AMF-1 in PLMN-1 supports ATSSS, AMF-2 in PLMN-2 does not support ATSSS, and AMF-3 in PLMN-3 supports ATSSS. In step 1, the UE is served by gNB-1 and establishes a MA PDU session in PLMN-1. In step 2, the UE moves from AMF-1 which supports ATSSS in PLMN-1 to AMF-2 which does not support ATSSS in PLMN-2. In step 3, a handover occurs between PLMN-1 and PLMN-2, and the UE is served by gNB-2. The 3GPP access part of the MA PDU session can be transferred to PLMN-2. In step 4, if the UE cannot transfer the MA PDU session on the 3GPP access, if the non-3GPP access is still available after the handover, AMF-1 informs SMF-1 to move the traffic to the non-3GPP access of the MA PDU session. In step 5, the AMF-2 sends either an ATSSS unsupported indicator to the UE or no indicator to the UE during PLMN registration update. In step 6, if the 3GPP incoming PDU session has been transferred, the SMF-2 establishes user plane (UP) resources for the 3GPP incoming PDU session. In step 7, the UE maintains or locally releases the non-3GPP access part of the MA PDU session.

In step 8, the UE moves from a network that does not support ATSSS to another network that supports ATSSS, eg, the UE moves from PLMN-2 that does not support ATSSS to PLMN-3 that supports ATSSS. In step 9, a handover occurs between PLMN-2 and PLMN-3. Similarly, in step 10, the PLMN-3 or AMF-3 will notify the UE of the ATSSS support indicator during the PLMN registration update, and the UE will receive the ATSSS support indicator. In step 11, the SMF-3 may initiate a PDU session modification procedure to establish UP resources on the 3GPP access of the MA PDU session and assign the ATSSS rules to the UE. In step 12, after the UE registers with the non-3GPP access in PLMN-3, the UE may initiate a PDU session establishment procedure to establish UP resources on the non-3GPP access of the MA PDU session.

16 is a flow diagram of a method by which a UE handles MA PDU sessions between a PLMN or AMF that supports ATSSS and a PLMN or AMF that does not support ATSSS, in accordance with one novel aspect. In step 1601, the UE performs registration in the first PLMN connected to the first AMF supporting ATSSS. In step 1602, the UE establishes a MA PDU session in the first PLMN. MA PDU sessions are established with a first Radio Access Technology (RAT) access type and a second RAT access type. In step 1603, when the UE moves from the first PLMN or the first AMF to the second PLMN or the second AMF which does not support ATSSS, it is determined whether to maintain the MA PDU session. In step 1604, the UE locally releases the MA PDU session based on the access type part of the first RAT based on the ATSSS not supported indicator received from the second PLMN or the second AMF.

Although the present invention has been described in connection with specific embodiments for illustrative purposes, the invention is not limited thereto. Accordingly, various modifications, adaptations, and combinations of the various features of the described embodiments may be practiced without claiming the scope of the invention described in the Claims.

100:5G network 102: 3GPP RAN 103: Non-3GPP RAN 113: User leveling function 112: Non-3GPP interworking function 120: Data Network 131, 132: Arrow lines: 1001, 801, 501, 401, 301, 201, 101, 1301, 1401: User Equipment 211: Base Station 502, 302, 402, 1302, 1312: Next Generation Node Bs 110, 1303, 1313: Access and mobility management functions 111, 1304, 1314: Session management functions 260,280: Protocol Stack 203, 213: Processor 202, 212: Memory 210, 220: Data and Program Instructions 204,214: RF Transceiver Modules 221, 231: PDU session and PDN connection processing circuit 222, 232: QoS and EPS Bearer Management Circuits 223, 233: Configuration and Control Circuits 224, 234: Toggle Module 270,290: Control function modules and circuits 205, 215: Antenna 503, 403, 303: Incoming contacts 1201,1202,1203,1204,1101,1102,1103,1104,1011,1012,1021,1022,1031,1041,1042,1043,811,812,821,822,831,841,842,843,851,1411,1412,1421,1422,1431,1432,1433,1434, 1441, 1442, 1443, 1444, 1601, 1602, 1603, 1604: Steps

The drawings illustrate embodiments of the invention, wherein like numerals refer to like components. FIG. 1 illustrates an exemplary 5G network supporting multiple access protocol data unit session management with inter-system translation in accordance with one novel aspect. FIG. 2 shows a simplified block diagram of user equipment and network entities in accordance with an embodiment of the present invention. Figure 3 shows one embodiment of establishing a MA PDU session in 5GS after the UE has registered to the network via 3GPP and non-3GPP access types belonging to the same PLMN. Figure 4 shows one embodiment of establishing a MA PDU session in 5GS after the UE has registered to the network via 3GPP and non-3GPP access types belonging to different PLMNs. Figure 5 shows another embodiment of establishing a MA PDU session in 5GS when the UE is registered to one RAT access type and then registered to another RAT access type. Figure 6 shows a simplified block diagram of a UE supporting MPTCP functions operating above the IP layer and/or ATSSS functions operating below the IP layer as data exchange functions. Figure 7 illustrates one embodiment of the inter-system transition and QoS flow handling from 5GS to EPS when the MA PDU session is transferred to the PDN connection. Figure 8 shows the sequence flow between the UE and the 5GS and EPS when the MA PDU session is transferred to the PDN connection when transitioning from 5GS to EPS, according to a novel aspect. Figure 9 shows one embodiment of inter-system transition from 5GS to EPS and QoS flow handling when the MA PDU session is not transferred to the PDN connection. Figure 10 shows the sequence flow between the UE and the 5GS and EPS when the MA PDU session is not transferred to the PDN connection when transitioning from 5GS to EPS, according to a novel aspect. 11 is a flow diagram of a method of supporting MA PDU sessions with inter-system translation in accordance with a novel aspect of the present invention. 12 is a flow diagram of another method of supporting MA PDU sessions with inter-system translation in accordance with a novel aspect of the present invention. Figure 13 illustrates, in accordance with one novel aspect, one embodiment of handling MA PDU session handover when a UE moves from a PLMN or AMF supporting ATSSS to a PLMN or AMF not supporting ATSSS. Figure 14 shows the sequence flow between the UE, the source network (that supports ATSSS) and the target network (that does not support ATSSS) for handover processing of MA PDU sessions, according to one novel aspect. Figure 15 illustrates one of the handling of MA PDU session handovers when a UE moves from an ATSSS capable PLMN or AMF to a non-ATSSS capable PLMN or AMF and then to another ATSSS capable PLMN or AMF in accordance with a novel aspect Example. 16 is a flow diagram of a method by which a UE handles MA PDU sessions between a PLMN or AMF that supports ATSSS and a PLMN or AMF that does not support ATSSS, in accordance with one novel aspect.

1601, 1602, 1603, 1604: Steps

Claims (11)

A method of handling multiple access protocol data unit session handover, comprising: a user equipment connecting to a first public land mobile network that supports a first access and mobility management function that supports an incoming traffic steering handover and segmentation performing registration in the middle of the road; establishing an MAP data unit session in the first public land mobile network, wherein the MAP data unit session is based on a first radio access technology access type and a first Two radio access technology access types are both established; when moving from the first public land mobile network or the first access and mobility management function to one that does not support the access traffic steering handover and split the second when a public land mobile network or a second access and mobility management function, determine whether to maintain the multiple access protocol data unit session; and based on the second public land mobile network or the second access and mobility The management function receives an indicator that access traffic steering switching and splitting is not supported, the UE locally releases the portion of the MAP session based on the first RAT access type. The method for handling multiple access protocol data unit session handover as recited in claim 1, wherein the first radio access technology access type is a third generation partnership project access, and wherein the second radio access technology The type of access technology access is a non-third-generation partner program access. The method for handling MAP-DU session handover as claimed in claim 1, wherein the UE releases the MAP-DU session in the first public land mobile network based on the second radio User plane resources that are part of the technical access type. The method of handling MAP-DU session handover as claimed in claim 1, wherein the user equipment maintains the MAP-DU session in the first public land mobile network based on the second RAP user plane resources that are part of an access type, and wherein the multiple access protocol data unit session moves to the second radio access type based on data traffic of the first radio access type. The method of handling MAP data unit session handover as claimed in claim 1, wherein the MAP data unit session is handed over to the second public land mobile network, wherein the MAP data unit session is based on Portions of the first radio access technology access type are transferred to a protocol data unit session in the second public land mobile network. The method for handling MAP-DU session handover as claimed in claim 5, wherein the UE releases the MAP-DU session in the first public land mobile network based on the second RAP User plane resources that are part of the technology access type. The method for handling MAP-DU session handover as claimed in claim 5, wherein the user equipment maintains the MAP-DU session in the first public land mobile network based on the second RAP User plane resources that are part of a technology access type, and where the user equipment reuses stored access traffic steering switching and segmentation rules. The method for processing multiple access protocol data unit session switching as described in claim 1, further comprising: switching to a third access and mobility management function having a third access and mobility management function supporting the access traffic steering switching and segmentation three public land mobile networks; and upon handover, executing a protocol data unit session modification process to upgrade a protocol data unit session to a new multiple access protocol data unit session. The method for handling MAP-DU session switching as recited in claim 8, further comprising: initiating a protocol-data-unit session establishment process to initiate a non-third-party session in the new MAP-DU session On behalf of the partner program into the link to create user plane resources. The method for handling multiple access protocol data unit session switching as described in claim 1, further comprising: sending a registration request to the second public land mobile network or the second access and mobility management function request message; and receiving a registration accept message from the second public land mobile network or the second access and mobility management function, wherein the registration accept message includes the indicator of the unsupported access traffic steering switching and splitting and a protocol data unit session status or no indicator and protocol data unit session protocol data unit session status. A user equipment comprising: a registration module for performing registration in a first public land mobile network connected to a first access and mobility management function that supports an incoming traffic steering switching and splitting; a PAD session and packet data network connection processing circuit for establishing a multiple access protocol data unit session in the first public land mobile network, wherein the multiple access protocol data unit session is based on a first public land mobile network a radio access technology access type and a second radio access technology access type are both established; and a configuration and control circuit for determining when from the first public land mobile network or the first access and mobility management function to maintain the MAP session when a second public land mobile network or a second access and mobility management function does not support the access traffic steering handover and split, wherein , the UE locally releases the multiple access protocol data based on an indicator received from the second public land mobile network or the second access and mobility management function that does not support access traffic steering switching and splitting The cell session is based on the portion of the first radio access technology access type.

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