CN117479255A - Method for executing intersystem change and user equipment - Google Patents

Abstract

Methods are presented to perform supporting an intersystem change without an N26 interface or without an N26 interface when a UE registers with the same or different networks through 3GPP and non-3GPP accesses. The UE registers with one or more PLMNs/SNPNs through 3GPP access and non-3GPP access. The UE receives a registration accept message over the 3GPP access, the message carrying a first 5GS network feature support IE indicating that interworking without an N26 interface is not supported. The UE also receives a registration accept message over the non-3GPP access, the message carrying a second 5GS network feature support IE indicating support for interworking without an N26 interface. The UE ignores the second indication received over the non-3GPP access and considers supporting the N26 interface for interworking. Thus, after an intersystem change from 5G to 4G, the UE triggers a TAU procedure on LTE in 4G EPS.

Description

Method for executing intersystem change and user equipment

Cross Reference to Related Applications

The subject matter of this application is incorporated herein by reference in accordance with 35U.S. c. ≡119 claiming priority from U.S. provisional application No. 63/369,669 entitled "Interworking without N26 interface support or not supported received in non-3GPP access" filed on day 28 of 7 of 2022.

Technical Field

The disclosed embodiments relate generally to wireless communications, and more particularly to performing inter-system changes and handling indications of supporting interworking without an N26 interface when received over non-3GPP access.

Background

Third generation partnership project (Third generation partnership project,3 GPP) and 5G New Radio (NR) mobile telecommunications systems provide high data rates, lower delays, and improved system performance. In 3GPP NR, a 5G terrestrial NR access network (comprising a plurality of base stations, e.g., a next generation node B (Next Generation Node-B, gNB) communicates with a plurality of mobile stations, referred to as User Equipment (UE). An orthogonal frequency division multiple Access (Orthogonal Frequency Division Multiple Access, OFDMA) is selected for an NR downlink radio access scheme due to its robustness to multipath fading, higher spectral efficiency and bandwidth scalability.

In 5GS, the UE may register and connect to both 3GPP and non-3GPP accesses (using NAS signaling), so the 5GS can utilize these multiple accesses to improve user experience and optimize traffic allocation across the various accesses. When the UE registers with 3GPP or non-3GPP access, the UE receives a registration accept (REGISTRATION ACCEPT) message carrying a 5GS network feature support IE, which in turn carries an indication of "support interworking without N26 interface" or "support interworking without N26 interface". In other words, the IWK N26 bit in the 5GS network feature support IE may be set to "support interworking without N26 interface" or "support interworking without N26 interface".

In the current protocol, if the UE registers with a first network having a first configuration including "support interworking without an N26 interface" or "support interworking without an N26 interface" through a 3GPP access and the UE registers with a second network having a second configuration through a non-3GPP access, the UE may consider using the second configuration in the first network, and the first network and the second network may be the same PLMN, or different PLMNs, the same SNPN, or different SNPNs. However, such UE behavior may be incorrect.

Disclosure of Invention

Methods are presented to perform supporting an intersystem change without an N26 interface or without an N26 interface when a UE registers with the same or different networks through 3GPP and non-3GPP accesses. The UE registers with one or more PLMNs/SNPNs through 3GPP access and non-3GPP access. The UE receives a registration accept message over the 3GPP access, the message carrying a first 5GS network feature support IE indicating that interworking without an N26 interface is not supported. The UE also receives a registration accept message over the non-3GPP access, the message carrying a second 5GS network feature support IE indicating support for interworking without an N26 interface. The UE ignores the second indication received over the non-3GPP access and considers supporting the N26 interface for interworking. Thus, after an intersystem change from 5G to 4G, the UE triggers a TAU procedure on LTE in 4G EPS.

In one embodiment, a UE maintains one or more protocol data unit (Protocol Data Unit, PDU) sessions in 5GS, wherein the UE registers with a first network via a first access type, and wherein the first network indicates that interworking without an N26 interface is supported. The UE receives a registration accept message from a second network over a second access type, wherein the second network indicates that interworking without an N26 interface is supported. The UE performs an intersystem change from 5GS to EPS. The UE triggers a tracking area update (tracking area update, TAU) procedure in the EPS.

Other embodiments and advantages are described in the detailed description that follows. This summary is not intended to define the invention. The invention is defined by the claims.

Drawings

The drawings illustrate embodiments of the invention, wherein like reference numerals refer to like parts throughout.

Fig. 1 illustrates an example 5G network and a method of performing supporting no N26 interface or supporting an intersystem change without an N26 interface when a UE registers with the same or different network through a 3GPP access and a non-3GPP access, according to one novel aspect.

Fig. 2 shows a simplified block diagram of a UE and a network entity according to an embodiment of the invention.

Fig. 3 shows the content of a registration accept message and a 5GS network feature support (5 GS NETWORK FEATURE SUPPORT) IE with an IWK N26 interface support indication.

Fig. 4 illustrates a sequence flow between a UE and a network entity for performing an intersystem change based on an indication received over a 3GPP or non-3GPP access that an N26 interface is not supported, in accordance with one novel aspect.

Fig. 5 is a flow chart of a method of performing support for an intersystem change without an N26 interface or without an N26 interface when a UE registers with the same or different networks through 3GPP and non-3GPP accesses, according to one novel aspect of the present invention.

Detailed Description

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

Fig. 1 illustrates an example 5G network and a method of performing supporting no N26 interface or supporting an intersystem change without an N26 interface when a UE registers with the same or different network through a 3GPP access and a non-3GPP access, according to one novel aspect. The 5G/4G network 100 includes a UE 101, a 3GPP access 102 (e.g., a 3GPP radio access network (E-UTRAN or NG-RAN)), a non-3GPP access 103 (e.g., non-3GPP WiFi), an access and mobility management function (access and mobility management function, AMF) 110 or mobility management entity (mobility management entity, MME) 130, a session management function (session management function, SMF) 111 or Serving Gateway (SGW) 131, a non-3GPP interworking function (non-3GPP interworking function,N3IWF) 112, a user plane function (user plane function, UPF) 113, and a user plane function (5 GC or EPC) data network 120. In 5G, AMF 110 communicates with base stations in 3GPP access 102, SMF 111, and UPF 113 for access and mobility management of wireless access devices in 5G network 100. The SMF 111 is primarily responsible for interacting with the decoupled data plane, creating, updating and removing PDU sessions, and managing session contexts with the UPF 113. The N3IWF 112 interfaces with 5G core network control plane functions and is responsible for routing messages outside the 5G RAN.

In the Access Stratum (AS) layer, the RAN provides radio Access to the UE 101 via a radio Access technology (radio Access technology, RAT). In the Non-Access Stratum (NAS) layer, the AMFs 110 and SMFs 111 communicate with RANs and 5 GCs for Access and mobility management of wireless Access devices and PDU session management in the 5G network 100. The 3GPP access 102 can include a base station (gNB or eNB) providing radio access for the UE 101 via various 3GPP RATs including 5G, 4G, and 3G/2G. The non-3GPP access 103 can include an Access Point (AP) that provides wireless access for the UE 101 via a non-3GPP RAT including WiFi. UE 101 may gain access to data network 120 through 3GPP access 102, AMF 110/MME 130, SMF 111/SGW 131, and UPF 113. The UE 101 may gain access to the data network 120 through non-3GPP access 103, N3IWF 112, AMF/MME, SMF/SGW, and UPF 113. The UE 101 may be equipped with a single Radio Frequency (RF) module or transceiver or multiple RF modules or transceivers for services via different RATs/CNs. In some examples, the UE 101 may be a smart phone, a wearable device, an internet of things (Internet of Things, ioT) device, a tablet computer, or the like.

In 5GS, a protocol data unit (protocol data unit, PDU) session defines an association between a UE and a data network providing PDU connectivity services. PDU session establishment is a parallel procedure to the PDN connection (bearer) procedure in 4G/LTE. An intersystem change from 5g N1 mode to 4g S1 mode may occur when the UE has at least one active PDU session, the intersystem change comprising an N26 interface: an interface between a mobility management entity (e.g., MME 130) in EPS and access and mobility management functions (e.g., AMF 110) in 5 GS.

When the UE registers with 3GPP or non-3GPP access, the UE receives a registration accept (REGISTRATION ACCEPT) message, where the message carries a 5GS network feature support IE, and the IE in turn carries an "support interworking without N26 interface" indication or an "support interworking without N26 interface" indication. In other words, the IWK N26 bit in the 5GS network feature support IE may be set to "support interworking without N26 interface" or "support interworking without N26 interface". In the current protocol, if the UE registers with a first network having a first configuration including "support interworking without an N26 interface" or "support interworking without an N26 interface" through a 3GPP access, and the UE registers with a second network having a second configuration through a non-3GPP access, the UE may consider to use the second configuration in the first network. However, such UE behaviour may be incorrect, in particular if the second configuration is associated with interworking function support received over a non-3GPP access type, since N26 is a 3GPP specific configuration and may be ignored when the UE receives relevant information over a non-3GPP access.

According to one novel aspect of the present invention, a method of performing support of an intersystem change without an N26 interface or without an N26 interface when a UE registers to the same or different networks through 3GPP and non-3GPP accesses is proposed. As shown in fig. 1, a UE registers with one or more Public Land Mobile Networks (PLMNs) or independent non-public networks (SNPNs) through a 3GPP access 102 and a non-3GPP access 103. The UE 101 receives a registration accept message over the 3GPP access, the message carrying a first 5GS network feature support IE indicating that interworking without an N26 interface is not supported (e.g., supporting an N26 interface for interworking). The UE 101 also receives a registration accept message over the non-3GPP access, the message carrying a second 5GS network feature support IE indicating that interworking without an N26 interface is supported (e.g., no N26 interface is supported for interworking). The UE 101 ignores the second indication received over the non-3GPP access and considers supporting the N26 interface for interworking. Thus, after an intersystem change from 5G to 4G, the UE 101 triggers a TAU procedure (non-attach procedure) on LTE in 4G EPS.

Fig. 2 shows a simplified block diagram of a wireless device (e.g., UE 201 and network entity 211) according to an embodiment of the invention. The network entity 211 may be a base station and/or an AMF/SMF. The network entity 211 has an antenna 215 that sends and receives radio signals. The radio frequency RF transceiver module 214 is coupled to the antenna, receives RF signals from the antenna 215, converts the RF signals to baseband signals and transmits the baseband signals to the processor 213. The RF transceiver 214 also converts the baseband signal received from the processor 213, converts the baseband signal into an RF signal, and transmits to the antenna 215. The processor 213 processes the received baseband signal and invokes different functional modules to perform features in the base station 211. Memory 212 includes volatile and nonvolatile computer-readable storage media that store program instructions and data 220 to control the operation of base station 211. In the example of fig. 2, the network entity 211 further comprises a protocol stack 280 and a set of control function modules and circuits 290. The protocol stack 280 includes a NAS layer in communication with AMF/SMF/MME entities connected to the core network, a radio resource control (Radio Resource Control, RRC) layer for higher layer configuration and control, a packet data convergence protocol/radio link control (Packet Data Convergence Protocol/Radio Link Control, PDCP/RLC) layer, a medium access control (Media Access Control, MAC) layer, and a Physical (PHY) layer. In one example, the control function module and circuitry 290 includes registration circuitry 291 that handles registration procedures, connection processing circuitry 292 that handles signaling connections, and configuration and control circuitry 293 that provides different parameters to configure and control UE including registration and paging related functions. The network entity 211 may be one 5GS network component or more than one 5GS network component (e.g. access network + AMF + N3IWF + SMF, etc.).

Similarly, UE 201 has memory 202, processor 203, and RF transceiver module 204. The RF transceiver 204 is coupled to the antenna 205, receives RF signals from the antenna 205, converts the RF signals to baseband signals, and transmits the baseband signals to the processor 203. The RF transceiver 204 also converts the baseband signal received from the processor 203, converts the baseband signal into an RF signal, and transmits the RF signal to the antenna 205. The processor 203 processes the received baseband signals and invokes various functional modules and circuits to perform the features in the UE 201. Memory 202 includes volatile and non-volatile computer readable storage media storing data and program instructions 210 to be executed by the processor to control the operation of UE 201. Suitable processors include, by way of example, a special purpose processor, a digital signal processor (digital signal processor, DSP), a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, a controller, a microcontroller, application specific integrated circuits (application specific integrated circuit, ASIC), field programmable gate array (file programmable gate array, FPGA) circuits, and other types of integrated circuits (integrated circuit, ICs), and/or a state machine. A processor associated with the software may be used to implement and configure features of the UE 201.

UE 201 also includes a protocol stack 260 and a set of control function modules and circuitry 270. The protocol stack 260 includes a NAS layer for communication with an AMF/SMF/MME entity connected to the core network, an RRC layer for higher layer configuration and control, a PDCP/RLC layer, a MAC layer, and a PHY layer. The control function modules and circuitry 270 may be implemented and configured by software, firmware, hardware, and/or combinations thereof. The control function modules and circuits, when executed by the processor via program instructions contained in the memory, interwork with each other to allow the UE 201 to perform the embodiments and functional tasks and features in the network. In one example, the control function module and circuitry 270 includes registration processing circuitry 271 that performs registration procedures with the network, connection processing circuitry 272 that processes RRC and NAS signaling connections, inter-system change processing circuitry 273 for performing inter-system changes, and configuration and control circuitry 274 that processes configuration and control parameters including obtaining and determining network feature support.

Fig. 3 shows the content of a registration accept message and a 5GS network feature support IE with an IWK N26 interface support indication. When the UE attempts to register with the network, the UE sends a registration request (REGISTRATION REQUEST) message to the network. In response, the UE receives a registration accept (REGISTRATION ACCEPT) message from the network. The registration accept message includes a plurality of information elements (information element, IE) including a 5GS network feature support IE as shown in table 510. The content of the 5GS network feature support IE is in turn carried by certain bits, each bit indicating whether a certain network feature is supported or not.

For example, bit 7 of the 5GS network feature support IE carries an IWK N26 indication indicating whether interworking without an N26 interface is supported or not supported. If IWK N26 (bit 7) = 0, it indicates that interworking without an N26 interface is not supported (e.g., interworking with an N26 interface is supported), and if IWK N26 (bit 7) = 1, it indicates that interworking without an N26 interface is supported (e.g., interworking with an N26 interface is not supported). Note that the N26 interface is an interface between the MME in EPS and the AMF in 5 GS. If an N26 interface is supported, then upon an intersystem change from 5GS to EPS, one or more PDU sessions in 5GS will be network transferred to the corresponding PDN connection and the UE need only initiate a tracking area update (tracking area update, TAU) procedure. On the other hand, if the N26 interface is not supported, upon an intersystem change from 5GS to EPS, the UE needs to transmit an ATTACH REQUEST (atach REQUEST) message containing a PDN connection REQUEST (PDN CONNECTIVITY REQUEST) message with a REQUEST type set to "handover" or "emergency bearer service handover" to transfer one or more PDU sessions from N1 mode to S1 mode. The UE also needs to initiate a PDN connection activation procedure for each respective PDU session.

Fig. 4 illustrates a sequence flow between a UE and a network entity for performing an intersystem change based on an indication received over a 3GPP or non-3GPP access that an N26 interface is not supported, in accordance with one novel aspect. In step 411, UE 401 registers with PLMN1 by sending a registration request message on 3GPP access 402, which carries the information requested by the UE. In step 412, UE 401 receives a registration accept message over the 3GPP access, the registration accept message carrying a list of IEs (e.g., 5GS network feature support IEs). For example, the 5GS network feature support IE carries a first IWK N26 indicator (e.g., bit 7= 0) to indicate that interworking without an N26 interface is not supported. In other words, PLMN1 indicates to the UE that interworking with an N26 interface is supported.

In step 421, UE 401 registers with PLMN2 by sending a registration request message on non-3GPP access 403, which carries the information requested by the UE. In step 422, UE 401 receives a registration accept message over the non-3GPP access, the registration accept message carrying a list of IEs (e.g., 5GS network feature support IEs). For example, the 5GS network feature support IE carries a second IWK N26 indicator (e.g., bit 7= 1) to indicate that interworking without an N26 interface is supported. In other words, PLMN2 indicates to the UE that interworking with the N26 interface is not supported. In general, the UE should update its configuration based on the newly received 5GS network feature support IE. However, because the second IWK N26 indicator is provided via a non-3GPP access and the N26 interface is a 3GPP specific configuration, the UE should ignore such an indication for an indication of an intersystem change from 5GS to EPS to switch PDU session to PDN connection.

Thus, in step 431, UE 401 performs an intersystem change from 5GS to EPS (N1 mode to S1 mode). In step 441, UE 401 ignores the second IWK N26 indicator provided from PLMN2 via non-3GPP access. As a result, UE 401 knows that the network supports interworking with an N26 interface, and that the PDU session in 5GS will be switched by the network to the corresponding PDN connection in EPS. In step 451, UE 401 triggers a TAU procedure (non-ATTACH (atach) procedure) in LTE to complete the intersystem change.

The benefit of triggering the TAU procedure is that the UE and the network can carry 5G registration information and 5G PDU sessions to 4G in a single TAU procedure. If the IWK N26 is not supported, the UE needs to perform multiple procedures, such as an ATTACH procedure and one or more PDN connection activation procedures, to complete the intersystem change. It should be noted that the first network PLMN1 and the second network PLMN2 may be the same PLMN or may be different PLMNs. In addition, the first network may be a SNPN1, the second network may be a SNPN2, and the SNPN1 and the SNPN2 may be the same SNPN or different SNPNs. In general, for configurations received from the first network and the second network through the 3GPP and the non-3GPP, if the first network and the second network are the same, the UE maintains a common configuration; if the first network and the second network are different, the UE maintains two independent configurations. In the case of IWK N26, since N26 is a 3GPP specific configuration, the UE should ignore the IWK N26 indicator received over the non-3GPP access.

Fig. 5 is a flow chart of a method of performing support for an intersystem change without an N26 interface or without an N26 interface when a UE registers with the same or different networks through 3GPP and non-3GPP accesses, according to one novel aspect of the present invention. In step 501, the UE maintains one or more PDU sessions in 5GS, wherein the UE registers with a first network via a first access type, and wherein the first network indicates that interworking without an N26 interface is not supported. In step 502, the UE receives a registration accept message from a second network over a second access type, wherein the second network indicates that interworking without an N26 interface is supported. In step 503, the UE performs an intersystem change from 5GS to EPS. In step 504, the UE triggers a TAU procedure in the EPS.

Although the present invention has been described in connection with certain specific embodiments for instructional purposes, the present invention is not limited thereto. Accordingly, various modifications, adaptations, and combinations of the various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims.

Claims (18)

1. A method of performing an intersystem change, comprising:

maintaining, by a User Equipment (UE), one or more Protocol Data Unit (PDU) sessions in 5GS, wherein the UE registers with a first network via a first access type, and wherein the first network indicates that interworking without an N26 interface is not supported;

receiving a registration accept message from a second network over a second access type, wherein the second network indicates support for interworking without an N26 interface;

performing an intersystem change from 5GS to EPS; and

a Tracking Area Update (TAU) procedure is triggered in the EPS.

2. The method of claim 1, wherein the first access type is a 3GPP access, and wherein the second access type is a non-3GPP access.

3. The method of claim 1, wherein the UE supports sending an attach request message to transfer the one or more PDU sessions from 5GS to EPS, and wherein the attach request message carries a PDN connection request message with a request type set to handover.

4. The method of claim 1, wherein the UE ignores the indication from the second network.

5. The method of claim 1, wherein the UE considers not supporting interworking without an N26 interface and not sending an attach request message to EPS.

6. The method of claim 1, wherein the registration accept message carries a 5GS network feature support IE with an IWK N26 indication.

7. The method of claim 1, wherein the first network and the second network belong to the same Public Land Mobile Network (PLMN) or the same independent non-public network (SNPN).

8. The method of claim 1, wherein the first network and the second network belong to different Public Land Mobile Networks (PLMNs) or different independent non-public networks (SNPNs).

9. A User Equipment (UE) that performs an intersystem change, comprising:

connection processing circuitry to maintain one or more Protocol Data Unit (PDU) sessions in 5GS, wherein a UE registers with a first network via a first access type, and wherein the first network indicates that interworking without an N26 interface is not supported;

a receiver for receiving a registration accept message from a second network over a second access type, wherein the second network indicates support for interworking without an N26 interface;

an inter-system change processing circuit for performing an inter-system change from 5GS to EPS; and

and a transmitter for transmitting a Tracking Area Update (TAU) request to trigger a TAU procedure in the EPS.

10. The UE of claim 9, wherein the first access type is a 3GPP access, and wherein the second access type is a non-3GPP access.

11. The UE of claim 9, wherein the UE supports sending an attach request message to transfer the one or more PDU sessions from 5GS to EPS, and wherein the attach request message carries a PDN connection request message with a request type set to handover.

12. The UE of claim 9, wherein the UE ignores the indication from the second network.

13. The UE of claim 9, wherein the UE considers that interworking without an N26 interface is not supported and does not send an attach request message to EPS.

14. The UE of claim 9, wherein the registration accept message carries a 5GS network feature support IE with an IWK N26 indication.

15. The UE of claim 9, wherein the first network and the second network belong to a same Public Land Mobile Network (PLMN) or a same independent non-public network (SNPN).

16. The UE of claim 9, wherein the first network and the second network belong to different Public Land Mobile Networks (PLMNs) or different independent non-public networks (SNPNs).

17. A User Equipment (UE) that performs an intersystem change, comprising:

a processor coupled to a memory, the memory storing program instructions and data that, when executed by the processor, cause the user equipment to perform the operations of the method of any of claims 1-8.

18. A non-transitory computer readable storage medium storing program instructions and data which, when executed by a processor of a user equipment performing an intersystem change, cause the user equipment to perform the operations of the method of any one of the preceding claims 1-8.