Method for enhancing reception of service acceptance message and user equipment

Abstract

The present invention proposes a reception enhancement method and user equipment (UE) supporting a service accept message. In one embodiment, when the UE determines that a service request process has been successfully completed and no service acceptance is received during the process, a new timer is started. In another embodiment, an existing timer T3417 or T3417ext can be used to define an allowed time window for receiving a service accept message. When the timer is running, the UE regards the service accept message as being received successfully, and the message does not cause a protocol error.

Description

[0001] Cross-references

[0002] The present invention claims the following priority: U.S. Provisional Patent Application No. 62 / 571,346, filed on October 12, 2017, entitled “Allowed window for reception of standalone SERVICE ACCEPT”; U.S. Provisional Patent Application No. 62 / 573,712, filed on October 18, 2017, entitled “Allowed window for reception of standalone SERVICE ACCEPT”; U.S. Provisional Patent Application No. 62 / 635,641, filed on February 27, 2018, entitled “Allowed window for reception of standalone SERVICE ACCEPT”. The above U.S. patent applications are hereby incorporated by reference. Technical Field

[0003] Embodiments of the present invention relate generally to wireless communications and, more particularly, to methods for supporting reception of independent SERVICE ACCEPT messages. Background Art

[0004] Wireless communication networks have grown exponentially over the years. The Long-Term Evolution (LTE) system provides high peak data rates, low latency, improved system capacity, and low operating costs due to a simple network architecture. The LTE system, also known as the 4G system, also provides seamless integration with older networks such as the Global System For Mobile Communications (GSM), Code Division Multiple Access (CDMA), and Universal Mobile Telecommunications System (UMTS). In the LTE system, the evolved universal terrestrial radio access network (E-UTRAN) includes multiple evolved Node-Bs (eNodeBs or eNBs) that communicate with multiple mobile stations called user equipment (UE). The 3rd Generation Partnership Project (3GPP) is a non-profit organization dedicated to the development of 4G networks and the creation of new technologies for the mobile industry. rdThe 3rd generation partner project (3GPP) network usually includes a mixture of the second generation (2G) / third generation (3G) / fourth generation (4G) systems. With the optimization of network design, the development of various standards has improved a lot.

[0005] When the UE needs to establish a service connection, the UE sends a SERVICE REQUEST message to the mobility management entity (MME) through its serving eNB. The UE also establishes a user plane radio bearer for data communication. The service request procedure may be considered completed when 1) the UE receives a security-protected non-access stratum (NAS) message, such as a SECURITY MODE COMMAND message or a SERVICE ACCEPT message, or 2) the UE receives an indication from a lower layer that a user plane radio bearer has been established. If the service request procedure is considered to be completed in the UE and the UE subsequently receives a service accept message, a different approach is provided.

[0006] In Release 13 (Rel-13), the UE considers the Service Accept message to be received in the wrong protocol state. The network cannot always successfully send the Service Accept message to the UE along with the evolved packet system (EPS) bearer context state information element, and the bearer context state information element in the UE is not synchronized. In Release 14 (Rel-14), the UE is able to receive and process the Service Accept message after determining that the Service Request procedure has been successfully completed, that is, after the UE has received a Security Mode Command message or received an indication that a user plane radio bearer has been established. In this special case, the UE should consider the Service Accept message to have been received in the Service Request procedure, but in all other cases, the UE still considers the Service Accept message to be received in the wrong protocol state.

[0007] How long should the UE receive the service accept message after the service request procedure is completed, that is, what is the time window allowed for successful reception of the service accept message after the service request procedure is completed is undefined. A solution is needed. Summary of the invention

[0008] A method for strengthening reception of a service accept message supported by a UE is proposed. In one embodiment, when the UE determines that a service request process is successfully completed, for example, when the UE receives a SECURITY MODE COMMAND message or an indication of an established user plane radio bearer from a lower layer, and no service accept message is received during the process, a new timer is started. When the timer runs, the UE regards the service accept message as being received successfully, and the message does not cause a protocol error. In another embodiment, the existing timer T3417 or T3417ext can be used to define an allowed time window for receiving a service accept message. When the timer runs, the UE stays in the EPS mobility management (EMM)-service-request-initiation (EMM-SERVICE-REQUEST-INITIATED) state, and the service request process is considered to be incomplete. The UE is able to regard the service accept message as being received successfully, and the message does not cause a protocol error. When the timer expires, the UE leaves the EMM-SERVICE-REQUEST-INITIATED state and considers that the service request process has been successfully completed.

[0009] In one embodiment, the UE sends a service request message in a mobile communication network to initiate a service request process. The UE is in a SERVICE-REQUEST-INITIATED state. Before the service request process is completed and a service acceptance message is received from a mobile management entity (MME), the UE starts a timer. The UE receives a service acceptance message from the MME before the timer expires. The UE successfully accepts the service acceptance message. When the message is received after the timer expires, the UE rejects the service acceptance message from the MME. The UE sends an error status back to the MME.

[0010] In another embodiment, the UE sends a service request message in a mobile communication network to initiate a service request. The UE starts a timer and is in a service-request-initiating state. The UE completes the service request process and continues to run the timer. The UE receives a service accept message from a mobile management entity (MME). When the service accept message is received before the timer expires, the UE successfully accepts the service accept message. When the service accept message is received after the timer expires, the UE rejects the service accept message. The UE sends an error status back to the MME.

[0011] The service acceptance message reception enhancement method and user equipment of the present invention can use a timer to define an allowed time window for receiving the service acceptance message, thereby successfully receiving the service acceptance message without causing a protocol error.

[0012] 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings depict embodiments of the present invention, wherein like numerals refer to like parts.

[0014] Figure 1 A typical LTE / new radio (NR) network that novelly supports receiving independent service acceptance messages is described.

[0015] Figure 2 is a simplified block diagram of a user equipment (UE) implementing an embodiment of the present invention.

[0016] Figure 3 A novel first embodiment for receiving a service accept message using a new timer is described.

[0017] Figure 4 A novel second embodiment using a new timer for receiving a service accept message is described.

[0018] Figure 5 A first embodiment of a novel method of using an existing timer to receive a service accept message is described.

[0019] Figure 6 A novel second embodiment of using an existing timer to receive a service accept message is described.

[0020] Figure 7 A novel first embodiment for receiving a service accept message using a new timer or an existing timer is described.

[0021] Figure 8 A novel second embodiment for receiving a service accept message using a new timer or an existing timer is described.

[0022] Fig. 9 The invention is a flowchart of a novel method for receiving independent service acceptance messages using a new timer.

[0023] Fig.10 The invention is a flow chart of a novel method for receiving independent service acceptance message by using an existing timer. DETAILED DESCRIPTION

[0024] Reference will now be made in detail to some embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

[0025] Figure 1A typical LTE / NR network 100 that supports receiving a novel independent service acceptance message is described. The LTE / NR network 100 includes an application server including a server 111, wherein the server 111 provides various services by communicating with a plurality of user equipments (UEs) including a UE 114. Figure 1 In the LTE / NR network 100, a server 111 and a packet data network gateway (PDN-GW or P-GW) 113 are part of a core network (CN) 110. A UE 114 and its serving base station (BS) 115 are part of a radio access network (RAN) 120. The RAN 120 provides radio access to the UE 114 via a radio access technology (RAT). The server 111 communicates with the UE 114 via the PDN GW 113, the serving GW 116, and the BS 115. A mobility management entity (MME) 117 communicates with the BS 115, the serving GW 116, and the PDN GW 113 for mobility management of radio access devices in the LTE / NR network 100. The UE 114 is configured with one radio frequency (RF) transceiver or multiple RF transceivers to be served by different RAT / CNs. UE 114 may be a smart phone, a wearable device, an Internet of Things (IoT) device, a tablet computer, etc.

[0026] LTE and NR networks are packet-switched (PS) Internet Protocol (IP) networks. This means that the network provides all data traffic in the form of IP packets and provides users with always-on IP connections. When a UE joins an LTE / NR network, a packet data network (PDN) address (i.e., an address that can be used on a PDN) can be assigned to the UE to connect to the PDN. LTE / NR refers to the UE's "IP access connection" as an evolved packet system (EPS) bearer, which is a connection between the UE and the P-GW. The P-GW is the default gateway for the UE's IP access. LTE / NR has defined a default EPS bearer to provide always-on IP connectivity. The UE can establish an additional data radio bearer for data communication.

[0027] exist Figure 1In the present invention, when UE 114 needs to establish a service connection, the UE sends a service request message to MME 117 through its serving BS 115 to initiate a service request procedure and change its EPS mobility management (EMM) state. UE 114 can be considered to be in the EMM-SERVICE-REQUEST-INITIATED state. The service request procedure can be considered to be completed when 1) the UE receives a security-protected non-access stratum (NAS) message, such as a security mode command message or a service accept message, or 2) the UE receives an indication from a lower layer that a user plane radio bearer has been established. The UE then returns to the EMM-NORMAL-SERVICE state. If the service request procedure is considered to be completed in the UE and the UE subsequently receives a service accept message, it is undefined within how long the UE should accept the service accept message after the service request procedure is completed (i.e., what is the time window allowed for successful reception of the service accept message after the service request procedure is completed).

[0028] According to a novel aspect, a timer 140 is started when the UE determines that the service request process has been successfully completed, for example, when the UE receives a security mode command message or an indication of an established user plane radio bearer from a lower layer, and the UE does not receive a service accept message during the process. When the timer runs, the UE regards the service accept message 130 as being received successfully, and the message does not cause a protocol error. In another embodiment, an existing timer T3417 or T3417ext can be used to define an allowed time window for receiving the service accept message 130. When the timer runs, the UE stays in the EMM-Service-Request-Initiated state and considers the service request process to be incomplete. The UE is able to regard the service accept message 130 as being received successfully, and the message does not cause a protocol error. When the timer expires, the UE leaves the EMM-Service-Request-Initiated state and considers the service request process to be successfully completed.

[0029] Figure 2A simplified block diagram of a UE 201 that implements an embodiment of the present invention is described. The UE 201 has a memory 202, a processor 203, and a radio frequency (RF) transceiver 204. The RF transceiver 204 is coupled to an antenna 205, receives RF signals from the antenna 205, converts them to baseband signals, and sends them to the processor 203. The RF transceiver 204 also converts the baseband signals received from the processor 203, converts them to RF signals, and sends them to the antenna 205. The processor 203 processes the received baseband signals and calls different functional modules and circuits to perform functions in the UE 201. The memory 202 stores program instructions and data 210 to control the operation of the UE 201 by the processor. Suitable processors include, for example, special purpose processors, digital signal processors (DSP), multiple microprocessors, one or more microprocessors associated with a DSP core, controllers, microcontrollers, application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) circuits and other types of integrated circuits (IC) and / or state machines. The features of UE201 can be implemented and configured using a processor associated with software.

[0030] UE 201 also includes a set of protocol stacks 260 and control circuits, wherein the control circuits include various system modules and circuits 270 that perform the functional tasks of UE 201. The protocol stack 260 includes a NAS layer for communicating with an MME connected to the core network, a radio resource control (RRC) layer for higher 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 hardware, firmware, software, and any combination thereof. When the processor executes the functional modules and circuits through program instructions in the memory, they cooperate with each other to enable UE 201 to execute implementation plans and functional tasks and features in the network. In one example, the configuration circuit 206 receives various configurations from the network, the timer 207 is configured to help properly receive the service acceptance message, the connection and data radio bearer (DRB) processing circuit 208 handles the UE connection and DRB establishment, and the service status and error handling circuit 209 handles the correct EMM status and corresponding error status of the UE.

[0031] Figure 3 A first embodiment of a novel method for receiving a service acceptance message using a new timer is described. Figure 3 In an embodiment of the present invention, a new timer is introduced and a service acceptance message is successfully accepted. In step 311, UE 301 sends a service request message to MME 302. UE 301 starts timer T3417 and enters EMM-SERVICE-REQUEST-INITIATED state. In step 312, UE 301 and MME 302 establish and activate a user plane radio bearer. In step 321, UE 301 determines that the service request process is completed. UE 301 stops timer T3417 and returns to EMM-NORMAL-SERVICE state. When the UE receives a security mode command message or an indication of an established user plane radio bearer from a lower layer, it determines that the service request process is completed. Then UE 301 starts a new timer T SA When it is determined that the service request process has been completed and the UE has not received a service acceptance during the service request process, a new timer T is started. SA . It can be a timer T SA Configure a predefined value, for example, 5 seconds.

[0032] In step 322, MME 302 detects that the EPS bearer context state has changed. In step 323, MME 302 sends a service acceptance message together with an EPS bearer context state information element (IE) to UE 301. At this time, timer T SA Still running, for example, for 2.8 seconds. SA While still running, the UE regards the service acceptance message as being received successfully and the message will not cause a protocol error. Therefore, in step 331, the UE 301 successfully receives the service acceptance message and stops the timer T SA UE 301 can also update the EPS bearer context state and keep in sync with the network. In this embodiment, although MME 302 cannot send a service accept message before the service request process is completed, UE 301 can successfully receive the message and use the new timer T SA Update the EPS bearer context status.

[0033] Figure 4 A novel second embodiment using a new timer to receive a service acceptance message is described. Figure 4In an embodiment of the present invention, a new timer is introduced, but the service acceptance message cannot be successfully accepted due to expiration of the timer. In step 411, UE 401 sends a service request message to MME 402. UE 401 starts the T3417 timer and enters the EMM-SERVICE-REQUEST-INITIATED state. In step 412, UE 401 and MME 402 establish and activate a user plane radio bearer. In step 421, UE 401 determines that the service request process is completed. UE 401 stops timer T3417 and returns to the EMM-NORMAL-SERVICE state. When the UE receives a security mode command message or an indication of an established user plane radio bearer from a lower layer, it determines that the service request process is completed. Then UE 401 starts a new timer T SA When it is determined that the service request process has been completed and the UE has not received a service acceptance message during the service request process, a new timer T is started. SA . It can be a timer T SA Configure a predefined value, for example, 5 seconds.

[0034] In step 422, the timer T SA In step 423, MME 402 detects a reason to send a service acceptance message, such as a protocol error in MME. In step 424, MME 402 sends a service acceptance message to UE 401. At this time, timer T SA has expired. When the timer T SA After the expiration or when the timer T SA If the UE receives a service acceptance message when the service is stopped / no longer running, it is considered to be a message in an error protocol state. Please note that when a service acceptance message is received, or a security-protected EPS session management (ESM) message or a security-protected EMM message not related to the EMM common procedure is received, or when the UE starts a new service request procedure, the timer T SA Therefore, in step 431, UE 401 receives the service acceptance message in the error protocol state and causes a protocol error. In step 432, UE 401 sends an EMM error status to MME 402. In this embodiment, since MME 402 receives the service acceptance message in the error protocol state after the service request process is completed or the timer T SA After the expiration, MME 402 sends a service acceptance message, and UE 401 receives the message in an error protocol state.

[0035] Instead of relying on a new timer, the existing timer T3417 or T3417ext can be used to define an allowed time window for receiving a service acceptance message. Traditionally, timer T3417 is started when a service request process is initiated, and timer T3417 is stopped when the service request process is completed. When the timer expires, the service request process is terminated. The operation of timer T3417 can be modified to define an allowed time window for receiving a service acceptance message. Specifically, timer T3417 is not stopped when a security mode command message or an indication of an established user plane radio bearer from a lower layer is received. When timer T3417 is running, successfully receiving and processing a service acceptance message does not cause a protocol error. A predefined value, for example, 5 seconds, can be configured by the network for timer T3417 or T3417ext.

[0036] Figure 5 A novel first embodiment of receiving a service accept message using an existing timer is described. In step 511, UE 501 sends a service request message to MME 502. In step 512, timer T3417 starts and UE 501 enters the EMM-Service-Request-Initiated state. In step 513, UE 501 and MME 502 establish and activate a user plane radio bearer. In step 522, UE 501 determines that the service request process has been completed and transitions to the EMM-Regular-Service state. However, timer T3417 is not stopped (step 521) and remains running. In step 523, MME detects that the EPS bearer context state needs to be updated. In step 524, MME 502 sends a service accept message to UE 501 together with the EPS bearer context state IE. At this time, timer T3417 is still running, for example, for 3.4 seconds. When timer T3417 is still running, the UE regards the service accept message as successfully received and the message does not cause a protocol error. Therefore, in step 531, UE 501 successfully receives the service accept message. In step 532, UE 501 stops timer T3417.

[0037] Figure 6A novel second embodiment of receiving a service acceptance message using an existing timer is described. In step 611, UE 601 sends a service request message to MME 602. In step 612, timer T3417 starts and UE 601 enters the EMM-service-request-initiated state. In step 613, UE 601 and MME 602 establish and activate a user plane radio bearer. In step 622, UE 601 determines that the service request process has been completed and transitions to the EMM-regular-service state. However, timer T3417 is not stopped (step 621) and remains running. In step 623, timer T3417 expires. In step 624, MME 602 detects a reason to send a service acceptance message, such as a protocol error in the MME. In step 625, MME 602 sends a service acceptance message to UE 601. At this point, timer T3417 has expired. The service acceptance message received after timer T3417 expires triggers a protocol error. Therefore, in step 631, UE 601 receives the service accept message in the error protocol state and causes a protocol error. In step 632, UE 601 sends an EMM error state to MME 602.

[0038] Figure 7 A first embodiment of a novel use of a new timer or an existing timer for receiving a service accept message is described. Either the new timer or the modified timer T3417 defines an allowed time window for receiving a service accept message. Figure 7In step 711, the modified timer T3417 is described as an example. In step 712, the timer T3417 is started and the UE 701 enters the EMM-SERVICE-REQUEST-INITIATED state. In step 713, the UE 701 and the MME 702 establish and activate the user plane radio bearer. In step 721, the UE 701 receives a security mode command message or an indication from a lower layer that a user plane radio bearer has been established and the UE 701, and the UE 701 does not receive a service acceptance message during this process. However, the timer T3417 is not stopped, the UE 701 stays in the EMM-SERVICE-REQUEST-INITIATED state and considers that the service request process is not completed. If a new timer is defined, the new timer can be started. In step 722, the MME 702 detects that the EPS bearer context state needs to be updated. In step 723, MME 702 sends the service accept message together with the EPS bearer context status IE to UE 701. At this time, timer T3417 / new timer is still running, for example, for 3.4 seconds. When timer T3417 / new timer is still running, UE regards the service accept message as successfully received, and the message does not cause a protocol error. Therefore, in step 731, UE 701 successfully receives the service accept message. In step 732, UE 701 stops timer T3417 / new timer. The service request process is completed, and UE 701 returns to EMM-Normal-Service state.

[0039] Figure 8 A novel second embodiment using a new timer or an existing timer for receiving a service accept message is described. Either the new timer or the modified timer T3417 defines an allowed time window for receiving a service accept. Figure 8In step 811, the modified timer T3417 is described as an example. In step 812, the timer T3417 is started and the UE 801 enters the EMM-service-request-initiated state. In step 813, the UE 801 and the MME 802 establish and activate the user plane radio bearer. In step 821, the UE 801 receives a security mode command message or an indication of an established user plane radio bearer from a lower layer, and the UE 801 does not receive a service acceptance message during this process. However, the timer T3417 is not stopped, the UE 801 stays in the EMM-service-request-initiated state and considers that the service request process is not completed. If a new timer is defined, a new timer can be started. In step 822, the timer T3417 / new timer expires. When the timer T3417 / new timer expires, the UE 801 leaves the EMM-service-request-initiated state and considers that the service request process has been successfully completed. However, the service accept message received after the timer T3417 / new timer expires triggers a protocol error. In step 823, MME 802 detects a reason to send the service accept message, such as a protocol error in the MME. In step 824, MME 802 sends a service accept message to UE 801. At this point, timer T3417 / new timer has expired. Therefore, in step 831, UE 801 receives the service accept message in an error protocol state and causes a protocol error. In step 832, UE 801 sends an EMM error state to MME 802.

[0040] Fig. 9 Flow chart of a novel method for receiving an independent service acceptance message using a new timer. In step 901, the UE sends a service request message in a mobile communication network to initiate a service request process. The UE is in a service-request-initiating state. In step 902, when the service request process is completed and before a service acceptance message is received from the MME, the UE starts a timer. In step 903, the UE receives a service acceptance message from the MME before the timer expires. The UE successfully accepts the service acceptance message. In step 904, when the message is received after the timer expires, the UE rejects the service acceptance message from the MME. The UE sends an error status back to the MME.

[0041] Fig.10The invention is a flowchart of a novel method for receiving an independent service acceptance message using an existing timer. In step 1001, the UE sends a service request message in a mobile communication network to initiate a service request process. The UE starts the timer and is in a service-request-initiate state. In step 1002, the UE completes the service request process and continues to run the timer. In step 1003, the UE receives a service acceptance message from the MME. In step 1004, when the service acceptance message is received before the timer expires, the UE accepts the service acceptance message. In step 1005, when the service acceptance message is received after the timer expires, the UE rejects the service acceptance message. The UE sends an error status back to the MME.

[0042] Although the present invention has been described in conjunction with certain specific embodiments for instructional purposes, it is not limited thereto. Accordingly, various modifications, adaptations and combinations of the various features of the described embodiments may be effected without departing from the scope of the present invention as set forth in the claims.

Claims

1. A method for enhancing reception of a service acceptance message, comprising: The user equipment sends a service request to initiate a service request process in the mobile communication network; When the service request process is completed, start the timer; When a service acceptance message is received before the timer expires, accepting the service acceptance message from the mobility management entity; as well as When the service accept message is received after expiration of the timer, an error status is sent to the mobility management entity.

2. The method for enhancing reception of a service acceptance message according to claim 1, wherein: The service request procedure is completed when the user equipment receives a security protected non-access stratum message or an indication that a user plane radio bearer has been established.

3. The method for enhancing reception of a service acceptance message according to claim 1, further comprising: In response to receiving the E-P System bearer context state information element before the timer expires, accepting the E-P System bearer context state information element.

4. The method for enhancing reception of a service acceptance message according to claim 1, further comprising: When the service request process is completed, the system enters the Normal-Service state.

5. The method for enhancing reception of a service acceptance message according to claim 1, further comprising: After the service request process is completed and before receiving the service acceptance message, it stays in the service-request-initiated state.

6. The method for enhancing reception of a service acceptance message according to claim 5, further comprising: After receiving the service acceptance message, enter the normal-service state and stop the timer.

7. A user equipment for enhancing reception of a service acceptance message, characterized in that: include: a transmitter, sending a service request to initiate a service request process in a mobile communication network; A timer that starts when the service request process is completed; The receiver, when receiving the service acceptance message before the expiration of the timer, accepts the service acceptance message from the mobility management entity; as well as The service status and error handling circuit generates an error status and sends it to the mobility management entity when the service acceptance message is received after the timer expires.

8. The user equipment according to claim 7, characterized in that The service request procedure is completed when the user equipment receives a security protected non-access stratum message or an indication that a user plane radio bearer has been established.

9. The user equipment according to claim 7, characterized in that In response to receiving the E-P System bearer context state information element before the timer expires, accepting the E-P System bearer context state information element.

10. The user equipment according to claim 7, characterized in that When the service request process is completed, the user equipment enters the normal-service state.

11. The user equipment according to claim 7, characterized in that After the service request process is completed and before receiving the service acceptance message, the user equipment stays in the service-request-initiating state.

12. The user equipment according to claim 11, characterized in that After receiving the service acceptance message, the user equipment enters the normal-service state and stops the timer.

13. A method for enhancing reception of a service acceptance message, comprising: The user equipment sends a service request to initiate a service request process in the mobile communication network; receiving a security protected non-access stratum message or an indication that a user plane radio bearer has been established; When receiving the security protected non-access stratum message or the indication that a user plane radio bearer has been established, starting a timer; receiving a service acceptance message from a mobility management entity; When the service acceptance message is received before the timer expires, accepting the service acceptance message; as well as When the service accept message is received after expiration of the timer, an error status is sent to the mobility management entity.

14. The method for enhancing reception of a service acceptance message according to claim 13, further comprising: In response to receiving the E-P System bearer context state information element before the timer expires, accepting the E-P System bearer context state information element.

15. The method for enhancing reception of a service acceptance message according to claim 13, further comprising: When the service request process is completed, the system enters the Normal-Service state.

16. The method for enhancing reception of a service acceptance message according to claim 13, further comprising: After the service request process is completed and before receiving the service acceptance message, it stays in the service-request-initiated state.

17. The method for enhancing reception of a service acceptance message according to claim 16, further comprising: After receiving the service acceptance message, enter the normal-service state and stop the timer.

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