Method for handling session management timers after inter-system change

Abstract

A method of handling session management timers after inter-system change is presented. Upon inter-system change from S1 mode to N1 mode, the UE can perform deregistration when re-registration is needed. The UE stops all 5GSM non-congestion avoidance timers. In addition to 5GSM non-congestion avoidance timers, there can be ESM non-congestion avoidance timers running. The UE can consider RATC and EPLMN C indicators in the re-try indicators IE and stop all ESM non-congestion timers. Upon inter-system change from N1 mode to S1 mode, the UE can perform detach procedure when re-attachment is needed. The UE stops all ESM non-congestion avoidance timers. In addition to ESM non-congestion avoidance timers, there can be 5GSM non-congestion avoidance timers running. The UE can consider RATC and EPLMN C indicators in the re-try indicators IE and stop all 5GSM non-congestion timers.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Application No. 63 / 308,179, filed February 9, 2022, entitled "Handling of the Session Management Timer of the Other System," subject to which is incorporated herein by reference. (35 U.S.SC §119) Technical Field

[0003] The disclosed implementations generally relate to wireless communication, and more specifically, to a method for handling session management timers after switching between execution systems. Background Technology

[0004] Over the years, wireless communication networks have grown exponentially. Long-Term Evolution (LTE) systems offer high peak data rates, low latency, improved system capacity, and low operating costs due to a simplified network architecture. LTE systems (also known as 4G systems) also provide seamless integration with older wireless networks such as GSM, CDMA, and the Universal Mobile Telecommunication System (UMTS). In LTE systems, the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) comprises multiple evolved Node-Bs (eNodeBs / eNBs) that communicate with multiple mobile stations (called User Equipment (UE)). 3rd Generation Partner Project (3GPP) networks typically include a hybrid 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 (5GS).

[0005] In 4G Evolved Packet System (EPS), the Packet Data Network (PDN) connection procedure is an important procedure when the LTE communication system accesses a packet data network. The purpose of the PDN connection procedure is to establish a default EPS bearer between the UE and the packet data network. The Protocol Data Unit (PDU) session establishment in 5G is a parallel procedure to the PDN connection procedure in 4G. The PDU session defines an association between the UE and a data network that provides PDU connectivity services.

[0006] If the UE is registered in EPS, the UE can initiate the PDN connection procedure for PDN connection (S1 mode). If the connection procedure is rejected, the UE can be configured with certain non-congestion back-off timers. At inter-system change from S1 mode to N1 mode, the UE can perform de-registration when re-registration is needed. The UE stops all 5GSM non-congestion back-off timers. However, in addition to the 5GSM non-congestion back-off timers, there can be ESM non-congestion back-off timers running. Similarly, if the UE is registered in 5GS, the UE can initiate the PDU session establishment procedure for PDU session (N1 mode). If the establishment procedure is rejected, the UE can be configured with certain non-congestion back-off timers. At inter-system change from N1 mode to S1 mode, the UE can perform the detach procedure when re-attachment is needed. The UE stops all ESM non-congestion back-off timers. However, in addition to the ESM non-congestion back-off timers, there can be 5GSM non-congestion back-off timers running.

[0007] A solution is sought. SUMMARY

[0008] A method of handling session management timers at inter-system change is presented. At inter-system change from S1 mode to N1 mode, the UE can perform deregistration when re-registration is needed. The UE stops all 5GSM non-congestion back-off timers. In addition to 5GSM non-congestion back-off timers, there can be ESM non-congestion back-off timers running. The UE can consider RATC and EPLMN C indicators in the re-try indicator IE and stop all ESM non-congestion timers. At inter-system change from N1 mode to S1 mode, the UE can perform detach procedure when re-attachment is needed. The UE stops all ESM non-congestion back-off timers. In addition to ESM non-congestion back-off timers, there can be 5GSM non-congestion back-off timers running. The UE can consider RATC and EPLMN C indicators in the re-try indicator IE and stop all 5GSM non-congestion timers.

[0009] In one embodiment, a UE starts a back-off timer in a first mobile communication system, wherein the back-off timer is not related to congestion control. The UE performs inter-system change from the first system to a second system. The UE receives a non-access stratum (NAS) signaling message from the second system indicating that the UE needs to perform a re-registration procedure or a re-attachment procedure in the second system. The UE stops the back-off timer started in the first system upon receiving the NAS signaling message in the second system. In one embodiment, the first mobile communication system is EPS, and wherein the second mobile communication system is 5GS. The NAS signaling message is a deregistration request message from 5GS. In a second embodiment, the first mobile communication system is 5GS, and wherein the second mobile communication system is EPS. The NAS signaling message is a detach request message from EPS.

[0010] Other embodiments and advantages are described in the following detailed description. This summary is not intended to define the invention. The invention is defined by the claims. BRIEF DESCRIPTION OF DRAWINGS

[0011] The accompanying drawings illustrate embodiments of the present invention, wherein like numbers refer to like parts.

[0012] Figure 1 An exemplary mobile communication network for handling session management timers at inter-system change according to one novel aspect is illustrated.

[0013] Figure 2 A simplified block diagram of a user equipment (UE) and a network entity according to embodiments of the present invention is illustrated.

[0014] Figure 3 A first embodiment of handling session management timers at inter-system change from S1 mode to N1 mode is exemplified in one novel aspect.

[0015] Figure 4 A second embodiment of handling session management timers at inter-system change from N1 mode to S1 mode is exemplified in one novel aspect.

[0016] Figure 5 is a flowchart of a method of handling session management timers at inter-system change from S1 mode to N1 mode according to one novel aspect of the present application. DETAILED DESCRIPTION

[0017] Reference will now be made in detail to some embodiments of the application, examples of which are illustrated in the accompanying drawings.

[0018] Figure 1 An exemplary mobile communication network 100 for handling session management timers at inter-system change according to one novel aspect is exemplified. The mobile communication network 100 comprises a user equipment UE 101, a base station gNB / eNB 102, an Access and Mobility Management Function (AMF), a Session Management Function (SMF) or a Mobility Management Entity (MME) 103, and a 5G / 4G core network 5GC / EPC 104. In Figure 1 In the example of, the UE 101 and its serving base station gNB 102 belong to a part of a Radio Access Network RAN 120. In the Access Stratum (AS) layer, the RAN 120 provides radio access for the UE 101 via a Radio Access Technology (RAT). In the Non-Access Stratum (NAS) layer, the AMF / SMF / MME 103 communicates with the gNB 102 and the 5GC / EPC 104 for access and mobility management of wireless access devices in the network 100 and PDU session management. The UE 101 can be equipped with one Radio Frequency (RF) transceiver or multiple RF transceivers for different application services via different RATs / CNs. The UE 101 can be a smartphone, a wearable device, an Internet of Thing (IoT) device, and a tablet computer, etc.

[0019] An EPS network is a packet-switched (PS) Internet Protocol (IP) network. This means that the network delivers all data traffic in the form of IP packets and provides IP connectivity for users. When a UE joins a 5GS network, a Packet Data Network (PDN) address (i.e., an address that can be used on a PDN) is assigned to the UE for its connection with the PDN. In 4G, the PDN connectivity procedure is an important procedure to establish a default EPS bearer between the UE and the packet data network. EPS has defined a default EPS bearer to provide IP connectivity. The Protocol Data Unit (PDU) session establishment procedure in 5G is a parallel procedure to the PDN connectivity procedure in 4G. A PDU session defines an association between a UE and a data network that provides PDU connectivity service.

[0020] If the UE is registered in EPS, the UE can initiate a PDN connectivity procedure for PDN connectivity (S1 mode). If the connectivity procedure is rejected, the UE can be configured with certain non-congestion back-off timers. At inter-system change from S1 mode to N1 mode, the UE can perform deregistration when re-registration is needed. The UE stops all 5GSM non-congestion back-off timers. However, in addition to the 5GSM non-congestion back-off timers, there can be ESM non-congestion back-off timers that are running. Similarly, if the UE is registered in 5GS, the UE can initiate a PDU session establishment procedure for PDU session (N1 mode). If the establishment procedure is rejected, the UE can be configured with certain non-congestion back-off timers. At inter-system change from N1 mode to S1 mode, the UE can perform a detach procedure when re-attachment is needed. The UE stops all ESM non-congestion back-off timers. However, in addition to the ESM non-congestion back-off timers, there can be 5GSM non-congestion back-off timers that are running.

[0021] According to one novel aspect, a method of handling session management timers at inter-system change is proposed. At inter-system change from N1 mode to S1 mode (141), the UE 101 performs a detach procedure (151) in EPS when re-attachment is needed. The UE stops all ESM non-congestion back-off timers. The UE considers RATC and EPLMN C indicators in Re-attempt indicator IE and stops all 5GS M non-congestion timers (if running). At inter-system change from S1 mode to N1 mode (161), the UE 101 performs a deregistration (171) when re-registration is needed. The UE stops all 5GS M non-congestion back-off timers. The UE considers RATC and EPLMN C indicators in Re-attempt indicator IE and stops all ESM non-congestion timers (if running).

[0022] Figure 2 A simplified block diagram of a wireless device (e.g., UE 201) and network entity 211 according to embodiments of the application is illustrated. The network entity 211 can be a base station and / or an AMF / SMF / MME / SGSN / RAN. The network entity 211 has an antenna 215 to send and receive radio signals. A radio frequency (RF) transceiver module 214 coupled with the antenna 215 receives RF signals from the antenna 215, converts the RF signals to baseband signals and sends the baseband signals to the processor 213. The RF transceiver 214 also converts baseband signals received from the processor 213, converts the baseband signals to RF signals and sends the RF signals to the antenna 215. The processor 213 processes the received baseband signals and invokes different functional modules to perform the features in the base station 211. The memory 212 includes volatile and non-volatile computer readable storage media, storing program instructions and data 220 for controlling the operation of the base station 211. In Figure 2 In the example, the network entity 211 also includes a protocol stack 280 and a set of control functional modules and circuits 290. The PDU session, PDN connection and PDP context processing circuit 231 handles PDU / PDN / PDP establishment and modification procedures. The QoS and EPS bearer management circuit 232 creates, modifies and deletes QoS and EPS bearers for UEs. The configuration and control circuit 233 provides different parameters to configure and control the related features of UEs, including mobility and session management and PDU / PDN / PDP management.

[0023] Similarly, the UE 201 has a memory 202, a processor 203, and a radio frequency (RF) transceiver module 204. The RF transceiver 204 is coupled with an antenna 205, receives RF signals from the antenna 205, converts the RF signals into baseband signals, and sends the baseband signals to the processor 203. The RF transceiver 204 also converts baseband signals received from the processor 203 into 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 the functions in the UE 201. The memory 202 includes volatile and non-volatile computer readable storage media, which stores data and program instructions 210 to be executed by the processor to control the operations of the UE 201. As an example, suitable processors include: application specific processors, digital signal processors (DSPs), multiple microprocessors, one or more microprocessors in association with a DSP core, controllers, micro-controllers, application specific integrated circuits (ASICs), field programmable gate array (FPGA) circuits, and other types of integrated circuits (ICs) and / or state machines. The processor associated with software can be used to implement and configure the functions of the UE 201.

[0024] The UE 201 also includes a set of functional modules and control circuits to perform the functional tasks of the UE 201. The protocol stack 260 includes a non-access stratum (NAS) layer for communication with the AMF / SMF / MME / SGSN entities connected to the core network, a radio resource control (RRC) layer for high layer configuration and control, a packet data convergence protocol / radio link control (PDCP / RLC) layer, a media access control (MAC) layer, and a physical (PHY) layer. The system modules and circuits 270 can be implemented and configured by software, firmware, hardware, and / or combinations thereof. When executed by the processor via program instructions contained in the memory, the functional modules and circuits work with each other to allow the UE 201 to perform the functional tasks and functions in the embodiments and the network.

[0025] In one example, the system modules and circuitry 270 include PDU session, PDN connection, and PDP context handling circuitry 221 that performs PDU session and PDN connection establishment and modification procedures with the network; session and mobility management circuitry 222 that manages session and mobility parameters; inter-system handling circuitry 223 that handles inter-system handover functionality; and configuration and control circuitry 224 that handles configuration and control parameters for session and mobility management. In one novel aspect, upon inter-system handover from a first system to a second system, the UE 201 performs de-attachment or registration when re-attachment or re-registration is required. The UE stops all non-congestion back-off timers of the second system. The UE also considers the RATC and EPLMNC indicators in the re-try indicator IE and stops all non-congestion timers of the first system.

[0026] Figure 3 A first implementation of handling session management timers upon inter-system handover from S1 mode to N1 mode is illustrated in one novel aspect. In step 311, the UE 301 is registered in a first mobile communication system (e.g., EPS 302) (S1 mode). To establish a default EPS bearer between the UE and a packet data network, in step 312, the UE 301 initiates a PDN connection procedure by sending a PDN connection request message to the EPS 302. In step 313, the UE 301 receives a PDN connection reject message from the EPS 302 due to non-congestion related reasons. The PDN connection reject message includes a non-congestion back-off timer with a reject cause value (e.g., #8, #27, #32, #33). In the PDN connection reject message, the network can also include a RATC indicator in the re-try indicator IE sent to the UE 301 (321). The RATC indicator can indicate that the UE is not allowed to re-try the PDN connection procedure in A / Gb mode or Iu mode or N1 mode (322). In the PDN connection reject message, the network can also include an EPLMNC indicator in the re-try indicator IE sent to the UE 301 (323). The EPLMNC indicator can indicate that the UE is not allowed to re-try the PDN connection procedure in an Equivalent PLMN (EPLMN) (324).

[0027] In step 331, the UE 301 starts the ESM non-congestion back-off timer (as provided by the EPS network in step 313). Until the ESM back-off timer expires, the UE will not re-attempt the PDN connectivity procedure in the EPS. Later, in step 341, the UE 301 performs an inter-system change from the first mobile communication network EPS (S1 mode) to the second mobile communication network 5GS (N1 mode). In step 342, the UE 301 receives a de-registration request (DE-REGISTRATION REQUEST) message from the 5GS 303. Upon receiving the de-registration request message, if the de-registration request message indicates “re-registration required”, the UE shall stop the timers (e.g. T3346, T3396, T3584, T3585) and other 5GSM back-off timers not related to congestion control (if running). In step 351, if the UE 301 is operating in single-registration mode, the UE shall also stop all ESM back-off timers not related to congestion control (if running) (e.g. started in step 331).

[0028] The UE can consider the RATC indicator in the re-attempt indicator IE. For example, if the RATC indication received in S1 mode indicates “UE is not allowed to re-attempt the procedure in A / Gb mode or Iu mode or N1 mode”, the UE stops the ESM non-congestion back-off timer upon receiving a de-registration request message with “re-registration required” after the UE inter-system changes to N1 mode. The UE can consider the EPLMNC indicator in the re-attempt indicator IE. For example, if the EPLMNC indication received in S1 mode indicates “UE is not allowed to re-attempt the procedure in equivalent PLMN”, the UE stops the ESM non-congestion back-off timer upon receiving a de-registration request message with “re-registration required” after the UE inter-system changes to N1 mode and / or moves to an EPLMN.

[0029] Figure 4A second implementation of handling session management timers at inter-system change from N1 mode to S1 mode is illustrated in one novel aspect. In step 411, the UE 401 is registered in a first mobile communication system (e.g., 5GS 403). To associate the UE with a data network that provides PDU connectivity service, in step 412, the UE 401 initiates a PDU session establishment procedure by sending a PDU session establishment request message to the 5GS 403. In step 413, the UE 401 receives a PDU session establishment reject message from the 5GS 403 due to non-congestion related reasons. The PDU session establishment reject message includes a non-congestion back-off timer with a reject cause value (e.g., #8, #27, #32, #33, #70). In the PDU session establishment reject message, the network can also include a RATC indicator in the Retention Indicators IE sent to the UE 401 (421). The RATC indicator can indicate that the UE is not allowed to re-attempt the PDU session establishment procedure in S1 mode (422). In the PDU session establishment reject message, the network can also include an EPLMN C indicator in the Retention Indicators IE sent to the UE 401 (423). The EPLMN C indicator can indicate that the UE is not allowed to re-attempt the PDU session establishment procedure in an Equivalent PLMN (EPLMN) (424).

[0030] In step 431, the UE 401 starts the 5GSM non-congestion back-off timer (as provided by the 5GS network in step 413). The UE will not re-attempt the PDU session establishment procedure in the 5GS until the 5GSM back-off timer expires. Later, in step 441, the UE 401 performs an inter-system change from the first mobile communication network 5GS (N1 mode) to the second mobile communication network EPS (S1 mode). In step 442, the UE 401 receives a DETACH REQUEST message from the EPS 402. When receiving the DETACH REQUEST message and the Detach Type indication is “Need Reattach”, the UE shall also stop the timer (e.g., T3396) and other ESM back-off timers not related to congestion control (if running). In step 451, if the UE 401 is operating in single-registration mode, the UE shall also stop all 5GSM back-off timers not related to congestion control (if running) (e.g., started in step 431).

[0031] The UE can consider the RATC indicator in the re-attempt indicator IE. For example, if the RATC indication received in N1 mode indicates "UE is not allowed to re-attempt the procedure in S1 mode", the UE stops the 5GSM non-congestion back-off timer upon receiving a detach request message with "re-attach required" upon inter-system handover to S1 mode. The UE can consider the EPLMNC indicator in the re-attempt indicator IE. For example, if the EPLMNC indication received in N1 mode indicates "UE is not allowed to re-attempt the procedure in equivalent PLMN", the UE stops the 5GSM non-congestion back-off timer upon receiving a detach request message with "re-attach required" upon inter-system handover to S1 mode and / or moving to an EPLMN.

[0032] Figure 5 is a flowchart of a method of handling session management timers upon inter-system handover between S1 mode and N1 mode according to a novel aspect of the present application. In step 501, a UE starts a back-off timer in a first mobile communication system, wherein the back-off timer is not related to congestion control. In step 502, the UE performs inter-system handover from the first system to a second system. In step 503, the UE receives a NAS signaling message from the second system, the NAS signaling message indicating that the UE needs to perform a re-registration procedure or a re-attach procedure in the second system. In step 504, the UE stops the back-off timer started in the first system upon receiving the NAS signaling message in the second system. In one embodiment, the first mobile communication system is EPS, and wherein the second mobile communication system is 5GS. The NAS signaling message is a logoff request message from 5GS. In a second embodiment, the first mobile communication system is 5GS, and wherein the second mobile communication system is EPS. The NAS signaling message is a detach request message from EPS.

[0033] While the application has been described in connection with certain specified embodiments thereof, it is to be understood that this is by way of illustration and not by way of limitation. Accordingly, various modifications, adaptations and combinations of the features described herein are possible without departing from the scope of the application as set forth in the claims.

Claims

1. A method for managing a session timer after inter-system handover, the method comprising: A backoff timer is initiated by the user equipment (UE) in the first mobile communication system, wherein the backoff timer is not related to congestion control; Perform an inter-system handover from the first mobile communication system to the second mobile communication system; The UE receives a Non-Access Stratum (NAS) signaling message from the second mobile communication system, the NAS signaling message indicating that the UE needs to perform a re-registration or re-attachment process in the second mobile communication system; and When the NAS signaling message is received in the second mobile communication system, the backoff timer started in the first mobile communication system is stopped.

2. The method according to claim 1, wherein, The first mobile communication system is an evolved packet system (EPS), and the second mobile communication system is a 5G system (5GS).

3. The method according to claim 2, wherein, The NAS signaling message is a deregistration request message from 5GS.

4. The method according to claim 2, wherein, During the PDN connection process, the UE is configured with the backoff timer in the EPS.

5. The method according to claim 4, wherein, The UE receives an indicator in the EPS indicating that the UE is not allowed to retry the PDN connection procedure in N1 mode or the equivalent PLMN EPLMN.

6. The method according to claim 1, wherein, The first mobile communication system is a 5G system 5GS, and the second mobile communication system is an evolved packet system EPS.

7. The method according to claim 6, wherein, The NAS signaling message is a detach request message from EPS.

8. The method according to claim 6, wherein, During the PDU session establishment process, the UE is configured with the backoff timer in the 5GS.

9. The method according to claim 8, wherein, The UE receives an indicator in 5GS indicating that the UE is not allowed to retry the PDU session establishment process in S1 mode or equivalent PLMN EPLMN.

10. The method according to claim 1, wherein, The UE also stops all non-congestion backoff timers of the second mobile communication system.

11. A user equipment (UE) with a post-inter-system handover processing session management timer, the user equipment (UE) include: A backoff timer is initiated by the UE in the first mobile communication system, wherein the backoff timer is not related to congestion control; Inter-system processing circuitry for performing inter-system handover from the first mobile communication system to the second mobile communication system; and Receiver, configured to receive Non-Access Stratum (NAS) signaling messages from the second mobile communication system, the NAS signaling... The message indicates that the UE needs to perform a re-registration process or a re-attachment process in the second mobile communication system. In the process, when the UE receives the NAS signaling message from the second mobile communication system, it stops the process described in the first... The backoff timer started in a mobile communication system.

12. The UE according to claim 11, wherein, The first mobile communication system is an evolved packet system (EPS), and the second mobile communication system is a 5G system (5GS).

13. The UE according to claim 12, wherein, The NAS signaling message is a deregistration request from 5GS. Requesting information.

14. The UE according to claim 12, wherein, During the PDN connection process, the UE is configured with the backoff timer in the EPS.

15. The UE according to claim 14, wherein, The UE receives an indication in the EPS that the above is not allowed. An indicator that the UE will retry the PDN connection procedure in N1 mode or an equivalent PLMN (EPLMN).

16. The UE according to claim 11, wherein, The first mobile communication system is a 5G system 5GS, and the second mobile communication system is an evolved packet system EPS.

17. The UE according to claim 16, wherein, The NAS signaling message is a detach request message from EPS.

18. The UE according to claim 16, wherein, During the PDU session establishment process, the UE It is equipped with the backoff timer described in the 5GS.

19. The UE according to claim 18, wherein, The UE receives an indication in 5GS that it is not allowed to... An indicator for the UE to retry the PDU session establishment process in S1 mode or an equivalent PLMN (EPLMN).

20. The UE according to claim 11, wherein, The UE also stops all non-congestion backoff timers of the second mobile communication system.

21. A non-volatile computer-readable storage medium storing program instructions and data, wherein the program instructions and data are stored in a manner that allows the storage of program instructions and data to be accessed by the computer. When the data is used by the user equipment's processor to execute the session management timer after inter-system handover, it causes the user... The user equipment performs the operation of the method according to any one of claims 1 to 10.

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