WO2023077381A1

WO2023077381A1 - Methods for session identifier management

Info

Publication number: WO2023077381A1
Application number: PCT/CN2021/128794
Authority: WO
Inventors: Zhendong Li; Jinguo Zhu
Original assignee: Zte Corporation
Priority date: 2021-11-04
Filing date: 2021-11-04
Publication date: 2023-05-11

Abstract

A wireless communication method for use in a first wireless network node is disclosure. The method comprises transmitting, to a second wireless network node, a protocol data unit, PDU, session identifier list comprising at least one PDU session identifier associated with a wireless terminal.

Description

METHODS FOR SESSION IDENTIFIER MANAGEMENT

This document is directed generally to wireless communications and in particular to 5 ^th generation (5G) wireless communications.

When a 5G system is designed, one feature of the 5G system is supporting interworking with an evolved packet system (EPS) (i.e. 4 ^th generation (4G) network) . In order to support the interworking with the EPS, a protocol data unit (PDU) session identifier (ID) is always assigned even if a user equipment (UE) accesses the network via the EPS. When the UE accesses the EPS and:

1) when the UE supports a 5G non-access stratum (NAS) , the PDU session ID is assigned by the UE and is sent to a session management function (SMF) + packet data network (PDN) gateway control plane (PGW-C) .

2) when the UE only supports a 4G NAS, the SMF+PGW-C creates the PDU session ID on behalf of the UE according to a default EPS bearer ID of a PDN connection of the UE.

In the 5G communications, the PDU session ID is unique among all PDU sessions for one UE. However, in the above case 2, the same PDU session ID may be reused for a single UE. That is, the PDU session ID may not be unique for one UE in some cases, which may result in a failure of establishing the PDN connection.

This document relates to methods, systems, and devices for PDU session ID management, in particular to methods, systems, and devices for PDU session ID management for a PDN connection.

The present disclosure relates to a wireless communication method for use in a first wireless network node. The method comprises:

transmitting, to a second wireless network node, a protocol data unit, PDU, session identifier list comprising at least one PDU session identifier associated with a wireless terminal.

Various embodiments may preferably implement the following features:

Preferably, the at least one PDU session identifier comprises at least one of:

at least one PDU session identifier associated with at least one existing packet session of the wireless terminal,

at least one PDU session identifier unused by any existing packet session of the wireless terminal, or

a PDU session identifier assigned for a packet session of the wireless terminal.

Preferably, the method further comprises receiving, from the second wireless network node, a request for at least one PDU session identifier of the wireless terminal.

Preferably, the method further comprises receiving, from the second wireless network node, a request for registering a packet session associated with the wireless terminal.

Preferably, the packet session is a packet data network, PDN, connection or a PDU session.

Preferably, the request comprises a PDU session identifier candidate, the at least one PDU session identifier comprises a PDU session identifier assigned for a packet session, and the PDU session identifier candidate is different from the PDU session identifier assigned for the packet session.

Preferably, the method further comprises receiving, from the second wireless network node, a subscription information request for the wireless terminal.

Preferably, the method further comprises receiving, from the second wireless network node, a request for registering a PDN connection of the wireless terminal, wherein the request comprises a PDU session identifier associated with the PDN connection.

Preferably, the first wireless network node comprises a user data management or a combination node of a user data management and a home subscription server.

Preferably, the second wireless network node comprises a session management function or a combination node of a session management function and a PDN gateway control plane.

The present disclosure relates to a wireless communication method for use in a second wireless network node, the method comprising:

receiving, from a first wireless network node, a protocol data unit, PDU, session identifier list comprising at least one PDU session identifier associated with a wireless terminal, and

determining a PDU session identifier associated with a packet data network, PDN, connection of the wireless terminal based on the PDU session identifier list.

Various embodiments may preferably implement the following features:

Preferably, the at least one PDU session identifier comprises at least one of:

at least one PDU session identifier associated with at least one existing PDN connection of the wireless terminal,

at least one PDU session identifier unused by any existing PDN connection of the wireless terminal, or

a PDU session identifier assigned by the first wireless network node.

Preferably, the wireless communication method further comprises transmitting, to the first wireless network node, a subscription information request for the wireless terminal.

Preferably, the wireless communication method further comprises transmitting, to the first wireless network node, a request for registering the PDN connection associated with the wireless terminal.

Preferably, the wireless communication method further comprises transmitting, to the first wireless network node, a request for at least one PDU session identifier of the wireless terminal.

Preferably, the request comprises a PDU session identifier candidate associated with the PDN connection, the at least one PDU session identifier comprises a PDU session identifier assigned for the PDN connection, and the PDU session identifier candidate is different from the PDU session identifier assigned for the PDN connection.

Preferably, the wireless communication method further comprises transmitting, to the first wireless network node, a registration request comprising the PDU session identifier associated with the PDN connection.

Preferably, the wireless communication method further comprises receiving, from a serving gateway, a create session request associated with the PDN connection.

Preferably, the first wireless network node comprises a user data management or a combination node of a user data management and a home subscription server

Preferably, the second wireless network node comprises a session management function or a combination node of a session management function and a PDN gateway control plane

The present disclosure relates to a first wireless network node. The first wireless network node comprises:

a communication unit, configured to transmit, to a second wireless network node, a protocol data unit, PDU, session identifier list comprising at least one PDU session identifier associated with a wireless terminal.

Various embodiments may preferably implement the following feature:

Preferably, the first wireless network node further comprises a processor configured to perform any of the aforementioned wireless communication methods.

The present disclosure relates to a second wireless network node. The second wireless network node comprises:

a communication unit, configured to receive, from a first wireless network node, a protocol data unit, PDU, session identifier list comprising at least one PDU session identifier associated with a wireless terminal, and

a processor, configured to determine a PDU session identifier associated with a packet data network, PDN, connection of the wireless terminal based on the PDU session ID list.

Various embodiments may preferably implement the following feature:

Preferably, the processor is further configured to perform any of the aforementioned wireless communication methods.

The present disclosure relates to a computer program product comprising a computer-readable program medium code stored thereupon, the code, when executed by a processor, causing the processor to implement a wireless communication method recited in any one of foregoing methods.

The exemplary embodiments disclosed herein are directed to providing features that will become readily apparent by reference to the following description when taken in conjunction with the accompany 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 of ordinary skill in the art who read the present disclosure that various modifications to the disclosed embodiments can be made while remaining within the scope of the present disclosure.

Thus, the present disclosure is not limited to the exemplary embodiments and applications described and illustrated herein. Additionally, the specific order and/or hierarchy of steps in the methods disclosed herein are merely exemplary approaches. Based upon design preferences, the specific order or hierarchy of steps of the disclosed methods or processes can be re-arranged while remaining within the scope of the present disclosure. Thus, those of ordinary skill in the art will understand that the methods and techniques disclosed herein present various steps or acts in a sample order, and the present disclosure is not limited to the specific order or hierarchy presented unless expressly stated otherwise.

The above and other aspects and their implementations are described in greater detail in the drawings, the descriptions, and the claims.

FIG. 1 shows a schematic diagram of a network according to an embodiment of the present disclosure.

FIG. 2 shows a schematic diagram of a procedure according to an embodiment of the present disclosure.

FIG. 3 shows a schematic diagram of a procedure according to an embodiment of the present disclosure.

FIG. 4 shows a schematic diagram of a procedure according to an embodiment of the present disclosure.

FIG. 5 shows a schematic diagram of a procedure according to an embodiment of the present disclosure.

FIG. 6 shows a schematic diagram of a procedure according to an embodiment of the present disclosure.

FIG. 7 shows an example of a schematic diagram of a wireless terminal according to an embodiment of the present disclosure.

FIG. 8 shows an example of a schematic diagram of a wireless network node according to an embodiment of the present disclosure.

FIG. 9 shows a flowchart of a method according to an embodiment of the present disclosure.

FIG. 10 shows a flowchart of a method according to an embodiment of the present disclosure.

FIG. 1 shows a schematic diagram of a network (architecture) according to an embodiment of the present disclosure. The network (architecture) shown in FIG. 1 supports mobility between a 5G system (5GS) and an EPS (i.e. an interworking network (architecture supporting the 5GS and the EPS) , and comprises the following network functions/entities:

1) UE: User equipment:

One UE accesses the EPC (4G network) via an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) , and interacts with a mobility management entity (MME) of the core network via non-access-stratum (NAS) signaling. The E-UTRAN is called 3GPP access. The UE also can access to the EPC via other access (e.g. Wifi, Fix network) , which are called non-3GPP access.

The UE (e.g. another UE) accesses the 5GS and obtains services via NextGen radio access network (NG-RAN) and interacts with an Access and Mobility Control Function (AMF) of the core network (e.g. 5G core network (5GC) ) via the NAS signaling. The NG-RAN is called 3GPP access. The UE also can access the 5GC via other access (e.g. Wifi, Fix network) , which is also called non-3GPP access.

2) eNB (Evolved Universal Terrestrial Radio Access Network (E-UTRAN) base station) :

The eNB is responsible for an air interface resource scheduling and an air interface connection management of a network which is accessed by the UE.

3) MME (Mobility management entity) :

The MME is a core network control plane entity and is mainly responsible for user authentication, authorization and subscription checking, user mobility management, packet data network (PDN) connection, bearer maintenance, paging triggering in a user IDLE state, and other functions.

4) S-GW (Serving gateway) :

The S-GW is a core network user plane function entity and is mainly responsible for an interaction with a PDN gateway (PGW) .

5) NG-RAN (Next-generation radio access network) :

The NG-RAN is responsible for the air interface resource scheduling and air interface connection management of a network which is accessed by the UE. In the present disclosure, the NG-RAN may be equal to NG-RAN node, RAN, RAN node or gNB.

6) AMF (Access and mobility management function) :

The AMF is a common control plane function in the core network. One UE can only access to one AMF. The AMF is responsible for mobility management and selecting an appropriate SMF when the UE initiates a PDU connection establishment, forwarding the NAS signaling between the UE and the SMF, and forwarding access stratum (AS) signaling between the base station and the SMF.

7) SMF+PGW-C (Session management function + PDN gateway control plane) :

The SMF+PGW-C is a combo node of the SMF and the PGW-C. It has functionalities of both the SMF in the 5GS and the PGW-C in the EPS.

8) UPF+PGW-U (User plane function + PDN gateway user plane) :

The UPF+PGW-U is a combo node of the UPF and the PGW-U. It has functionalities of both the UPF in the 5GS and the PGW-U in the EPS.

The P-GW is a core network user plane function entity in the EPS and an access point which is used for the UE to access the PDN connection, and is responsible for user Internet Protocol (IP) address allocation, network-triggered bearer establishment, modification and deletion, Quality of Service (QoS) control, charging and other functions. The P-GW is divided into two parts. One is a packet data network gateway control entity (PGW-Control, PGW-C) , and another one is a packet data network gateway user plane entity (PGW-User, PGW-U) . The PGW-C is responsible for signaling control and the PGW-U is responsible for IP data forwarding. Each PDN connection of the UE has a corresponding P-GW, and different PDN connections may have different P-GWs.

The SMF in the 5GS interacts with the UE, and is responsible for processing requests of user PDU session establishment, modification and deletion, selecting the UPF, establishing a user plane connection between the UE and the UPF, determining session QoS parameters together with a policy control function (PCF) , and the like. Each PDU session of the UE has a corresponding SMF, and different PDU sessions may have different SMFs.

The UPF provides user plane processing functions, including data forwarding and QoS execution. When users move, the UPF also provides user plane anchor points to ensure service continuity.

9) HSS+UDM (Home subscriber server + user data management)

The HSS+UDM is a combo node of the HSS and the UDM. It has functionalities of both the UDM in the 5GS and the HSS in the EPS. The HSS stores subscription information of the user (e.g. UE) in the EPS and the UDM stores subscription data of the user (e.g. UE) in the 5GS.

10) PCF (Policy control function) :

The PCF is responsible for resource authorization and provides Policy and Charging Control (PCC) rule (s) to the SMF+PGW-C.

Note that an N26 interface may be between the AMF and the MME and is used to transfer UE context between the EPS and the 5GS during mobility (e.g. handover and idle mobility) . In an embodiment, the N26 interface may be optional.

In the EPS, the UE is identified by an International Mobile Subscription Identity (IMSI) . In the 5GS, the UE is identified by a Subscription Permanent Identifier (SUPI) . When the UE accesses the EPS and the interworking architecture shown in FIG. 1 is applied, the SMF+PGW-C maps the UE IMSI to an IMSI-based SUPI and further uses this IMSI-based SUPI to interact with the PCF and the UDM/HSS.

In the 5GS, the UE establishes a PDU session to access the application service (s) . In the 4G system, the UE establishes a PDN connection to access the application service (s) . In the present disclosure, the PDU session and/or the PDN connection may be called packet session.

When the UE moves from the 5GS to the 4G system (i.e. EPS) , a PDU session established in the 5GS is converted to a PDN connection in the 4G system and the QoS flow in the PDU session is converted to an EPS bearer in the 4G system. In addition, when the UE moves from the 4G system to the 5GS, a PDN connection established in the 4G system is converted to a PDU session established in the 5GS and the EPS bearer in the PDN connection is converted to the QoS flow in the 5GS.

For every PDU session for the UE, there is one corresponding unique PDU session ID. The UE assigns the PDU session ID and sends it to the SMF during a PDU session establishment.

When the UE accesses the EPS, in order to support interworking with the 5GS, the PDU session ID is also assigned by the UE which sends it to the SMF+PGW-C via a Protocol Configuration Option (PCO) during a PDN connection establishment.

The PDU session ID is used by the SMF+PGW-C to interact with the PCF (when the UE accesses the network via the EPS or the 5GS) and the UDM (when the UE accesses the network via the 5GS) . The combination of the PDU session ID and the UE ID (e.g. SUPI) uniquely identifies the context of the PDU session or PDN connection of the UE in the PCF and the UDM/HSS.

In the present disclosure, a 5G-capable-UE may be equal to a 5G UE, a UE supporting a 5G NAS or the UE supporting an N1 NAS.

In the present disclosure, a 4G-capable-UE may be equal to a 4G UE, a UE supporting a 4G NAS or a UE supporting an S1 NAS.

When the UE only supports the 4G NAS (i.e. 4G capable only UE) and has a 5G subscription, the network/interworking architecture shown in the FIG. 1 may be used. In this scenario, the SMF+PGW-C creates the PDU session ID on behalf of the UE because the UE cannot assign and send the PDU session ID (which is always needed in the interworking architecture) to the SMF+PGW-C.

In order to distinguish the PDU session ID created by the UE and the SMF+GW-C, different address spaces are used. The PDU session ID assigned by the UE is always less than 63. The SMF+PGW-C map a default EPS bearer ID (i.e. Linked bearer ID) of the PDN connection to the PDU session ID. For example, the PDU session ID created by the SMF+PGW-C equals the default EPS bearer ID + 64 (i.e. PDU session ID = default EPS bearer ID + 64) .

FIG. 2 shows a schematic diagram of a PDN connection establishment procedure according to an embodiment of the present disclosure. In FIG. 2, the UE is a 4G-only-UE having a 5G subscription. The PDN connection establishment procedure comprises the following steps:

Step 201: The UE sends a PDN Connectivity Request (e.g. APN) to the MME.

Step 202: The MME selects a P-GW according to the APN and allocates a default EPS Bearer Id (e.g. the default EPS Bearer ID = 5) . The MME sends a Create Session Request message (e.g. comprising the IMSI, the PDN GW address, the EPS Bearer Id) to the S-GW.

Step 203: The S-GW sends the received Create Session Request message to the P-GW (i.e. the SMF+PGW-C) according to the P-GW address in the received message.

Step 204: The SMF+PGW-C retrieves Session Management Subscription data associated with the UE from the UDM/HSS by using a Nudm_SDM_Get (e.g. comprising a SUPI) . The SUPI is mapped from the received IMSI.

Step 205: Because the UE has 5G subscription and is the 4G-only-UE, the SMF+PGW-C creates the PDU session ID of the PDN connection on behalf of the UE. For example, the Linked EPS bearer ID in the Create Session Request is 5 and the PDU session ID is equal to 5 plus 64, i.e. 69.

Step 206: The SMF+PGW-C selects a PCF serving this session (e.g. PDN connection) .

Step 207: The SMF performs an SM Policy Association Establishment procedure by invoking an Npcf_SMPolicyControl_Create operation (e.g. comprising the SUPI, the PDU session ID, the IP address) to selected PCF. In an embodiment, the PDU session ID may be 69.

Step 208: The SMF+PGW-C sends a Create session Response to the S-GW. The Create session Response carries QoS parameter (s) for the PDN connection.

Step 209: The S-GW sends the Create session Response to the MME.

Step 210: According to the received QoS parameter (s) , the MME sends a Bearer Setup request to the eNB.

Step 211: The eNB allocates radio resource (s) for the EPS bearer.

Step 212: The eNB sends a Bearer Setup Response to the MME.

In some scenarios, the PDN connection establishment procedure shown in FIG. 2 may have a PDU session ID conflict issue. FIG. 3 shows a schematic diagram of a procedure according to an embodiment of the present disclosure. In the embodiment shown in FIG. 3, a PDU session ID conflict occurs.

Step 301: The UE establishes a PDN connection PDN1 via the procedure shown in FIG. 1. In this embodiment, the MME allocates a value 5 as the default EPS Bearer ID (i.e. Linked Bearer ID) . The SMF+PGW-C creates the PDU session ID according to the default EPS Bearer ID, i.e. PDU session ID = 5 plus 64 = 69. The SMF+PGW-C creates the SM Association with PCF using SUPI + PDU session ID (i.e. 69) .

Step 302: The UE initiates a PDN connection transfer to a non-3GPP access (e.g. Wifi, Fix network) . In this procedure, the MME releases all the allocated EPS bearer IDs assigned for this PDN Connection (whose EPS Bearer ID value is set as 5) . Note that the PDU session ID does not change in the SMF+PGW-C.

Step 303: The UE sends a PDN Connectivity Request (comprising an APN APN2) to the MME.

Step 304: The MME selects a P-GW according to the APN2 and allocates a default EPS Bearer ID. In this embodiment, the MME may allocate the value 5 as the default EPS bearer ID again. The MME sends a Create Session Request message (e.g. the IMSI, the PDN GW address, the EPS Bearer Id) to the S-GW. In some embodiments, the P-GW in step 304 may be different from the P-GW in step 301.

Step 305: The S-GW sends the received Create Session Request to the P-GW according to the P-GW address in the received message.

Step 306: The SMF+PGW-C retrieves Session Management Subscription data of the UE from the UDM/HSS by using a Nudm_SDM_Get (e.g. SUPI) . The SUPI is mapped from the received IMSI.

Step 307: Because the UE has the 5G subscription and is a 4G-only-UE, the SMF+PGW-C creates the PDU session ID on behalf of the UE. In this embodiment, the default EPS bearer ID value is 5. Thus, the PDU session ID equal to 5 plus 64, i.e. 69.

Step 308: The SMF+PGW-C selects a PCF serving this PDN connection.

Step 309: The SMF performs an SM Policy Association Establishment procedure by invoking Npcf_SMPolicyControl_Create operation (SUPI, PDU session ID (i.e. 69) , IP address) to the selected PCF.

Step 310: The PCF finds the same combination of SUPI + 69 has existed, resulting in a conflict error.

Step 311: The PCF responds to the SMF+PGW-C with an error cause value.

Step 312: The PDN Connection establishment fails.

The combination of SUPI and PDU session ID are unique in the PCF.

For the 4G-only-UE, the PDU session ID is created by using the default EPS bearer ID of corresponding PDN connection. Under such a condition, the same EPS bearer ID will create the same PDU session ID.

When the PDN connection of the UE is transferred to the non-3GPP access in EPS, the MME releases all the EPS bearer IDs allocated to this PDN connection.

When the UE requests to establish a new PDN connection, the MME allocates the EPS bearer ID for the default Bearer. If the default EPS Bearer ID value of the new PDN connection is the same as the default EPS Bearer ID once assigned to the previous PDN connection, the PDU session ID conflict occurs.

The present disclosure provides a method for avoiding the PDU session ID conflict. The method may be used for the 4G-only-UE in the interworking architecture shown in FIG. 1.

In an embodiment, the UDM returns a PDU session ID list to the SMF+PGW-C. The PDU session ID in the PDU session ID list may be/comprise at least one of:

- PDU session ID (s) for the existing PDN connection,

- PDU session ID (s) that are not used by the existing PDN connection, or

- A PDU session ID determined by the UDM.

In an embodiment, the UDM may return the PDU session ID list, when receiving, from the SMF+PGW-C:

- a Nudm_SDM_Get service operation, or

- a Nudm_UECM_Registration service operation, or

- a dedicated request for the PDU session ID list.

As an alternative or in addition, when the SMF+PGW-C invokes the Nudm_SDM_Get or the Nudm_UECM_Registration service operation, the SMF+PGW-C may indicate a request for obtaining the PDU session ID list. The PDU session ID list may be/comprise the PDU session ID (s) for the existing PDN connection of the UE or the PDU session ID (s) that are not used by the existing PDN connection (s) .

FIG. 4 shows a schematic diagram of a procedure according to an embodiment of the present disclosure. In FIG. 4, the UDM return the PDU session ID list when returning subscription data to the SMF+PGW-C. Note that the UE in this procedure is a 4G capable only UE.

Step 401: The UE sends a PDN Connectivity Request (e.g. APN) to the MME, to establish a PDN connection.

Step 402: The MME selects a P-GW according to the APN and allocates a default EPS Bearer ID. The MME sends a Create Session Request message (e.g. the IMSI, the PDN GW address, the EPS Bearer ID) to the S-GW.

Step 403: The S-GW sends the received Create Session Request to the P-GW (e.g. SMF+PGW-C) according to the P-GW address in the received message.

Step 404: The SMF+PGW-C retrieves Session Management Subscription data of the UE from the UDM/HSS by using a Nudm_SDM_Get (e.g. the SUPI) . The SUPI is mapped from the received IMSI. In an embodiment, the SMF+PGW-C may indicate a request for the PDU session ID associated with the PDN connection to the UDM and the UDM returns a PDU session ID list to the SMF+PGW-C. The PDU session ID in the PDU session ID list may be/comprise:

- The PDU session ID (s) for the existing PDN connection (s) , or

- The PDU session ID (s) that are not used by the existing PDN connection (s) .

Step 405: Because the UE has the 5G subscription and is the 4G-only-UE, the SMF+PGW-C determines the PDU session ID on behalf of the UE. The SMF+PGW-C determines the PDU session ID according to the default EPS Bearer ID and the PDU session ID list received from the UDM.

Step 406: The SMF+PGW-C selects a PCF serving this session.

Step 407: The SMF performs an SM Policy Association Establishment procedure by invoking a Npcf_SMPolicyControl_Create operation (e.g. the SUPI, the PDU session ID, the IP address) to selected PCF.

Step 408: SMF+PGW-C completes the PDN connection establishment (see, e.g., steps 208 to 212 in FIG. 2) .

Step 409: The SMF+PGW-C registers the PDN session information to the UDM by invoking a Nudm_UECM_Registration (e.g. the SUPI, the PDU session ID) to the UDM.

FIG. 5 shows a schematic diagram of a procedure according to an embodiment of the present disclosure. In FIG. 5, the UDM returns the PDU session ID list to the SMF+PGW-C when receiving a PDU session register request. Note that the UE in FIG. 5 is a 4G capable only UE.

Step 501: The UE sends a PDN Connectivity Request (e.g. APN) to the MME, to establish a PDN connection.

Step 502: The MME selects a P-GW according to the APN and allocates a default EPS Bearer ID for the PDN connection. The MME sends a Create Session Request message (e.g. IMSI, PDN GW address, EPS Bearer Id) to the S-GW.

Step 503: The S-GW sends the received Create Session Request message to the P-GW (e.g. SMF+PGW-C) according to the P-GW address in the received message.

Step 504: The SMF+PGW-C retrieves Session Management Subscription data of the UE from the UDM/HSS by using a Nudm_SDM_Get (e.g. comprising the SUPI) . The SUPI is mapped from the received IMSI.

Step 505: The SMF+PGW-C registers the PDN session information to the UDM by invoking a Nudm_UECM_Registration (e.g. the SUPI, the PDU session ID) to the UDM. In an embodiment, the SMF+PGW-C may indicate a request for the PDU session ID to the UDM.

In an embodiment, the UDM may reject the register request and return a PDU session ID list to the SMF+PGW-C. The PDU session ID in the PDU session ID list may be/comprise:

- PDU session ID (s) used for the existing PDN connection, or

- PDU session ID (s) that are not used by the existing PDN connection.

As an alternative or in addition, the UDM may accept the register request and return the PDU session ID determined by the UDM for the PDN connection.

Step 506: Because the UE has the 5G subscription and is the 4G-only-UE, the SMF+PGW-C determines the PDU session ID for the PDN connection on behalf of the UE. In this embodiment, the SMF+PGW-C determines the PDU session ID according to the default EPS Bearer ID and the PDU session ID list received from the UDM.

Step 507: The SMF+PGW-C registers the PDN session information to the UDM by invoking a Nudm_UECM_Registration (e.g. SUPI, PDU session ID) to the UDM. The step 507 may be performed at any time after step 506. If the registration request in step 505 is accepted by the UDM, the step 507 may be omitted.

Step 508: The SMF+PGW-C selects a PCF serving the PDN connection.

Step 509: The SMF performs an SM Policy Association Establishment procedure by invoking Npcf_SMPolicyControl_Create operation (e.g. the SUPI, the PDU session ID, the IP address) to the selected PCF.

Step 510: The SMF+PGW-C completes the PDN connection establishment procedure (see, e.g. steps 208 to 212 in FIG. 2) .

FIG. 6 shows a schematic diagram of a procedure according to an embodiment of the present disclosure. In FIG. 6, the UDM returns the PDU session ID list to the SMF+PGW-C when receiving a dedicated request for a PDU session ID of the UE. Note that the UE in FIG. 6 is a 4G capable only UE.

Step 601: The UE sends a PDN Connectivity Request (e.g. the APN) to the MME, to establish a PDN connection.

Step 602: The MME selects a P-GW according to the APN and allocates a default EPS Bearer ID for the PDN connection. The MME sends a Create Session Request message (e.g. the IMSI, the PDN GW address, the EPS Bearer ID) to the S-GW.

Step 603: The S-GW sends the received Create Session Request message to the P-GW (e.g. SMF+PGW-C) according to the P-GW address in the received message.

Step 604: The SMF+PGW-C retrieves Session Management Subscription data of the UE from the UDM/HSS by using a Nudm_SDM_Get message (e.g. the SUPI) . The SUPI is mapped from the received IMSI.

Step 605: The SMF+PGW-C sends a request to the UDM/USS for obtaining at least one PDU session ID, e.g., for the PDN connection. In an embodiment, the SMF+PGW-C may include a PDU session ID candidate for the PDN connection in the request. The UDM/USS returns the PDU session ID list to the SMF+PGW-C. In an embodiment, the PDU session ID in the list may be/comprise:

- PDU session ID (s) for the existing PDN connection (s) , or

- PDU session ID (s) that are not used by the existing PDN connection (s) , or

- A PDU session ID determined by the UDM for this PDN.

Step 606: Because the UE has 5G subscription and is the 4G-only-UE, the SMF+PGW-C determines the PDU session ID on behalf of the UE. The SMF+PGW-C determine the PDU session ID according to the default EPS Bearer ID and received PDU session ID list from the UDM.

Step 607: The SMF+PGW-C selects a PCF serving this PDN connection.

Step 608: The SMF performs an SM Policy Association Establishment procedure by invoking a Npcf_SMPolicyControl_Create (e.g. the SUPI, the PDU session ID, the IP address) to selected PCF.

Step 609: The SMF+PGW-C completes the PDN connection establishment (e.g. steps 208 to 212 in FIG. 2) .

Step 610: The SMF+PGW-C registers the PDN session information to the UDM by invoking a Nudm_UECM_Registration (e.g. the SUPI, the PDU session ID) to the UDM.

FIG. 7 relates to a schematic diagram of a wireless terminal 70 according to an embodiment of the present disclosure. The wireless terminal 70 may be a user equipment (UE) , a mobile phone, a laptop, a tablet computer, an electronic book or a portable computer system and is not limited herein. The wireless terminal 70 may include a processor 700 such as a microprocessor or Application Specific Integrated Circuit (ASIC) , a storage unit 710 and a communication unit 720. The storage unit 710 may be any data storage device that stores a program code 712, which is accessed and executed by the processor 700. Embodiments of the storage unit 712 include but are not limited to a subscriber identity module (SIM) , read-only memory (ROM) , flash memory, random-access memory (RAM) , hard-disk, and optical data storage device. The communication unit 720 may a transceiver and is used to transmit and receive signals (e.g. messages or packets) according to processing results of the processor 700. In an embodiment, the communication unit 720 transmits and receives the signals via at least one antenna 722 shown in FIG. 7.

In an embodiment, the storage unit 710 and the program code 712 may be omitted and the processor 700 may include a storage unit with stored program code.

The processor 700 may implement any one of the steps in exemplified embodiments on the wireless terminal 70, e.g., by executing the program code 712.

The communication unit 720 may be a transceiver. The communication unit 720 may as an alternative or in addition be combining a transmitting unit and a receiving unit configured to transmit and to receive, respectively, signals to and from a wireless network node (e.g. a base station) .

FIG. 8 relates to a schematic diagram of a wireless network node 80 according to an embodiment of the present disclosure. The wireless network node 80 may be a satellite, a base station (BS) , a network entity, a Mobility Management Entity (MME) , Serving Gateway (S-GW) , 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) , and is not limited herein. In addition, the wireless network node 80 may comprise (perform) 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) , an application function (AF) , etc. The wireless network node 80 may include a processor 800 such as a microprocessor or ASIC, a storage unit 810 and a communication unit 820. The storage unit 810 may be any data storage device that stores a program code 812, which is accessed and executed by the processor 800. Examples of the storage unit 812 include but are not limited to a SIM, ROM, flash memory, RAM, hard-disk, and optical data storage device. The communication unit 820 may be a transceiver and is used to transmit and receive signals (e.g. messages or packets) according to processing results of the processor 800. In an example, the communication unit 820 transmits and receives the signals via at least one antenna 822 shown in FIG. 8.

In an embodiment, the storage unit 810 and the program code 812 may be omitted. The processor 800 may include a storage unit with stored program code.

The processor 800 may implement any steps described in exemplified embodiments on the wireless network node 80, e.g., via executing the program code 812.

The communication unit 820 may be a transceiver. The communication unit 820 may as an alternative or in addition be combining a transmitting unit and a receiving unit configured to transmit and to receive, respectively, signals to and from a wireless terminal (e.g. a user equipment or another wireless network node) .

FIG. 9 shows a flowchart of a method according to an embodiment of the present disclosure. The method shown in FIG. 9 may be used in a first wireless network node (e.g. UDM/HSS, a wireless network node comprising UDM/HSS or a wireless network node performing at least part of functionalities of UDM/HSS) and comprises the following step:

Step 901: Transmit, to a second wireless network node, a PDU session ID list comprising at least one PDU session ID associated with a wireless terminal.

In FIG. 9, the first wireless network node transmits a PDU session ID list to a second wireless network node (e.g. SMF, SMF+PGW-C, a wireless network node comprising SMF or SMF+PGW-C, or a wireless network node performing at least part of functionalities of SMF or SMF+PGW-C) . In this embodiment, the PDU session ID list comprises at least one PDU session ID associated with a wireless terminal (e.g. UE) . Based on the PDU session ID list, the wireless terminal is able to determine a PDU session ID for a PDN connection. The PDU session ID conflict can be avoided, therefore.

In an embodiment, the at least one PDU session ID (or the PDU session ID list) comprises at least one of:

at least one PDU session ID associated with at least one existing packet session of the wireless terminal,

at least one PDU session ID unused by any existing packet session of the wireless terminal, or

a PDU session identifier ID for a packet session of the wireless terminal.

In an embodiment, the first wireless network node receives a request for at least one PDU session ID (of the wireless terminal) (e.g. the request in step 605) from the second wireless network node.

In an embodiment, the first wireless network node receives a request for registering a packet session associated with the wireless terminal (e.g. Nudm_UECM_Registration) from the second wireless network node.

In an embodiment, the packet session is a PDN connection or a PDU session.

In an embodiment, the request (e.g. Nudm_UECM_Registration in step 505 or the request in step 605) comprises a PDU session ID candidate. In this embodiment, the PDU session ID candidate may be rejected by the first wireless network node. Under such a condition, the first wireless network node may assign a PDU session ID for a packet session and transmits the assigned PDU session ID (in the PDU session ID list) to the second wireless network node. Note that, the assigned PDU session ID is different from the PDU session identifier candidate.

In an embodiment, the first wireless network node receives a subscription information request for the wireless terminal (e.g. Nudm_SDM_Get) from the second wireless network node.

In an embodiment, the first wireless network node receives, from the second wireless network node, a request for registering a PDN connection of the wireless terminal (e.g. Nudm_UECM_Registration in

step

409, 507 or 610) , wherein the request comprises a PDU session identifier associated with the PDN connection. That is, after the second wireless network node determines the PDU session ID for the PDN connection based on the PDU session ID list, the second wireless network node transmits the determined PDU session ID to the first wireless network node for registering the PDU session ID of the PDN connection. Note that this request may be omitted if the PDU session ID list comprises the PDU session ID assigned for a packet session (e.g. PDN connection) of the wireless terminal. In other words, this request may not be needed if the first wireless network node assigns the PDU session ID for the PDN connection and transmits the assigned PDU session ID to the second wireless network node in the PDU session ID list.

FIG. 10 shows a flowchart of a method according to an embodiment of the present disclosure. The method shown in FIG. 10 may be used in a second wireless network node (e.g. SMF, SMF+PGW-C, a wireless network node comprising SMF or SMF+PGW-C, or a wireless network node performing at least part of functionalities of SMF or SMF+PGW-C) and comprises the following steps:

Step 1001: Receive, from a first wireless network node, a PDU session ID list comprising at least one PDU session ID associated with a wireless terminal.

Step 1002: Determine a PDU session ID associated with a PDN connection of the wireless terminal based on the PDU session ID list.

In FIG. 10, the second wireless network node receives a PDU session ID list from a first wireless network node (e.g. UDM/HSS, a wireless network node comprising UDM/HSS or a wireless network node performing at least part of functionalities of UDM/HSS) . The PDU session ID list comprises at least one PDU session ID associated with a wireless terminal (e.g. UE) . According to/Based on the PDU session ID list, the second wireless network node determines a PDU session ID for a PDN connection of the wireless terminal.

a PDU session identifier assigned by the first wireless network node.

In an embodiment, the second wireless network node transmits a request for at least one PDU session ID (of the wireless terminal) (e.g. the request in step 605) to the first wireless network node. For example, the second wireless network node may transmit the request for obtaining/acquiring at least one PDU session ID for the PDN connection.

In an embodiment, the second wireless network node transmits a request for registering a packet session associated with the wireless terminal (e.g. Nudm_UECM_Registration) to the first wireless network node.

In an embodiment, the request (e.g. Nudm_UECM_Registration in step 505 or the request in step 605) comprises a PDU session ID candidate. In this embodiment, the PDU session ID candidate may be rejected by the first wireless network node. Under such a condition, the second wireless network node may receive a PDU session ID assigned by the first wireless network node in the PDU session ID list. Note that, the assigned PDU session ID is different from the PDU session identifier candidate.

In an embodiment, the second wireless network node transmits a subscription information request for the wireless terminal (e.g. Nudm_SDM_Get) to the first wireless network node.

In an embodiment, the second wireless network node transmits, to the first wireless network node, a request for registering a PDN connection of the wireless terminal (e.g. Nudm_UECM_Registration in

step

In an embodiment, the second wireless network node receives a create session request associated with the PDN connection from an S-GW.

While various embodiments of the present disclosure have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. Likewise, the various diagrams may depict an example architectural or configuration, which are provided to enable persons of ordinary skill in the art to understand exemplary features and functions of the present disclosure. Such persons would understand, however, that the present disclosure is not restricted to the illustrated example architectures or configurations, but can be implemented using a variety of alternative architectures and configurations. Additionally, as would be understood by persons of ordinary skill 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 one of the above-described exemplary embodiments.

It is also understood that any reference to an element herein using a designation such as "first, " "second, " and so forth does not generally limit the quantity or order of those elements. Rather, these designations can be used herein as a convenient means of distinguishing between two or more elements or instances of an element. Thus, a reference to first and second elements does not mean that only two elements can be employed, or that the first element must precede the second element in some manner.

Additionally, a person having ordinary skill in the art would understand that information and signals can be represented using any one of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits and symbols, for example, which may be referenced in the above description can be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

A skilled person would further appreciate that any one of the various illustrative logical blocks, units, processors, means, circuits, methods and functions described in connection with the aspects disclosed herein can 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 can be referred to herein, for convenience, as "software" or a "software unit” ) , or any combination of these techniques.

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 techniques, depends upon the particular application and design constraints imposed on the overall system. Skilled artisans can implement the described functionality in various ways for each particular application, but such implementation decisions do not cause a departure from the scope of the present disclosure. In accordance with various embodiments, a processor, device, component, circuit, structure, machine, unit, etc. can be configured to perform one or more of the functions described herein. The term “configured to” or “configured for” as used herein with respect to a specified operation or function refers 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.

Furthermore, a skilled person would understand that various illustrative logical blocks, units, devices, components and circuits described herein can be implemented within or performed by an integrated circuit (IC) that 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 antennas and/or transceivers to communicate with various components within the network or within the device. A general purpose processor can be a microprocessor, but 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, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other suitable configuration to perform 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.

Computer-readable media includes both computer storage media and communication media including any medium that can be enabled to transfer a computer program or code from one place to another. A storage media can be any available media 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.

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. Additionally, for purpose of discussion, the various units are described as discrete units; however, as would be apparent to one of ordinary skill in the art, two or more units may be combined to form a single unit that performs the associated functions according embodiments of the present disclosure.

Additionally, memory or other storage, as well as communication components, may be employed in embodiments of the present disclosure. It will be appreciated that, for clarity purposes, 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 to be performed by separate processing logic elements, or controllers, may be performed by the same processing logic element, or controller. Hence, references to specific functional units are only references to a suitable means for providing the described functionality, rather than indicative of a strict logical or physical structure or organization.

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 can be applied to other implementations without departing from the scope of this disclosure. Thus, the 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 recited in the claims below.

Claims

A wireless communication method for use in a first wireless network node, the method comprising:

transmitting, to a second wireless network node, a protocol data unit, PDU, session identifier list comprising at least one PDU session identifier associated with a wireless terminal.
The wireless communication method of claim 1, wherein the at least one PDU session identifier comprises at least one of:

at least one PDU session identifier associated with at least one existing packet session of the wireless terminal,

at least one PDU session identifier unused by any existing packet session of the wireless terminal, or

a PDU session identifier assigned for a packet session of the wireless terminal.
The wireless communication method any of claims 1 or 2, further comprising:

receiving, from the second wireless network node, a request for the at least one PDU session identifier of the wireless terminal.
The wireless communication method of claim 1 or 2, further comprising:

receiving, from the second wireless network node, a request for registering a packet session associated with the wireless terminal.
The wireless communication method of claim 2 or 4, wherein the packet session is a packet data network, PDN, connection or a PDU session.
The wireless communication method any of claims 3 to 5, wherein the request comprises a PDU session identifier candidate,

wherein the at least one PDU session identifier comprises a PDU session identifier assigned for a packet session,

wherein the PDU session identifier candidate is different from the PDU session identifier assigned for the packet session.
The wireless communication method of claim 1 or 2, further comprising:

receiving, from the second wireless network node, a subscription information request for the wireless terminal.
The wireless communication method any of claims 1 to 7, further comprising:

receiving, from the second wireless network node, a request for registering a PDN connection of the wireless terminal,

wherein the request comprises a PDU session identifier associated with the PDN connection.
The wireless communication method of any of claims 1 to 8, wherein the first wireless network node comprises a user data management or a combination node of a user data management and a home subscription server.
The wireless communication method of any of claims 1 to 9, wherein the second wireless network node comprises a session management function or a combination node of a session management function and a PDN gateway control plane.
A wireless communication method for use in a second wireless network node, the method comprising:

receiving, from a first wireless network node, a protocol data unit, PDU, session identifier list comprising at least one PDU session identifier associated with a wireless terminal, and

determining a PDU session identifier associated with a packet data network, PDN, connection of the wireless terminal based on the PDU session identifier list.
The wireless communication method of claim 11, wherein the at least one PDU session identifier comprises at least one of:

at least one PDU session identifier associated with at least one existing PDN connection of the wireless terminal,

at least one PDU session identifier unused by any existing PDN connection of the wireless terminal, or

a PDU session identifier assigned by the first wireless network node.
The wireless communication method of claim 11 or 12, further comprising:

transmitting, to the first wireless network node, a subscription information request for the wireless terminal.
The wireless communication method of claim 11 or 12, further comprising:

transmitting, to the first wireless network node, a request for registering the PDN connection associated with the wireless terminal.
The wireless communication method of claim 11 or 12, further comprising:

transmitting, to the first wireless network node, a request for the at least one PDU session identifier of the wireless terminal.
The wireless communication method of claim 14 or 15, wherein the request comprises a PDU session identifier candidate associated with the PDN connection,

wherein the at least one PDU session identifier comprises a PDU session identifier assigned for the PDN connection, and

wherein the PDU session identifier candidate is different from the PDU session identifier assigned for the PDN connection.
The wireless communication method any of claims 11 to 16, further comprising:

transmitting, to the first wireless network node, a registration request comprising the PDU session identifier associated with the PDN connection.
The wireless communication method any of claims 11 to 17, further comprising:

receiving, from a serving gateway, a create session request associated with the PDN connection.
The wireless communication method of any of claims 11 to 18, wherein the first wireless network node comprises a user data management or a combination node of a user data management and a home subscription server.
The wireless communication method of any of claims 11 to 19, wherein the second wireless network node comprises a session management function or a combination node of a session management function and a PDN gateway control plane.
A first wireless network node, comprising:

a communication unit, configured to transmit, to a second wireless network node, a protocol data unit, PDU, session identifier list comprising at least one PDU session identifier associated with a wireless terminal.
The first wireless network node of claim 21, further comprising:

a processor, configured to perform any of the wireless communication methods of claims 2 to 10.
A second wireless network node, comprising:

a communication unit, configured to receive, from a first wireless network node, a protocol data unit, PDU, session identifier list comprising at least one PDU session identifier associated with a wireless terminal, and

a processor, configured to determine a PDU session identifier associated with a packet data network, PDN, connection of the wireless terminal based on the PDU session ID list.
The second wireless network node of claim 23, wherein the processor is further configured to perform any of the wireless communication methods of claims 12 to 20.
A computer program product comprising a computer-readable program medium code stored thereupon, the code, when executed by a processor, causing the processor to implement a wireless communication method recited in any one of claims 1 to 20