Access gateway reselection method and apparatus, communication device, and storage medium

Abstract

The present application relates to an access gateway (AGW) reselection method and apparatus, a communication device, a storage medium, and a computer program product. The method comprises: during establishment of an IP multimedia subsystem (IMS) session, executing an AGW reselection operation.

Description

Access gateway reselection method, device, communication equipment and storage medium

[0001] Related applications

[0002] This application claims priority to Chinese patent application number 2024103369647, filed on March 22, 2024, entitled “Access Gateway Reselection Method, Apparatus, Communication Equipment and Storage Medium,” the entire text of which is hereby incorporated by reference. Technical Field

[0003] The present application relates to the field of wireless communication technology, and in particular to an access gateway reselection method, apparatus, communication equipment, storage medium, and computer program product. Background Art

[0004] The current 3GPP (3rd Generation Partnership Project) standard only allows terminals to connect to terrestrial base stations via satellites operating in transparent mode to achieve seamless coverage. However, due to geographical constraints and other factors, gateway deployment is difficult in some areas, and communication services remain geographically restricted. To address this issue, a fusion of terrestrial base stations and satellites operating in regenerative mode has been proposed.

[0005] In traditional IMS (IP Multimedia Subsystem) voice communication services, signaling between calling and called users is primarily transmitted through ground-based AGWs (Access Gateways), enabling communication between the calling and called users.

[0006] However, in order to realize the communication service between UE-satellite-UE and to realize the IMS voice service support transcoding, security isolation from the IMS core network, lawful interception and data retention and other functions, the on-board AGW can be selected for users. Therefore, a method for reselecting the on-board access gateway AGW is urgently needed.

[0007] Summary of the Invention

[0008] Embodiments of the present application provide an access gateway reselection method, apparatus, communication device, storage medium, and computer program product.

[0009] In a first aspect, an embodiment of the present application provides a method for reselecting an access gateway, the method comprising:

[0010] During the multimedia subsystem IMS session establishment process, the AGW reselection operation is performed.

[0011] In one embodiment, the method further comprises:

[0012] Determine whether to execute the UE-satellite-UE service based on the acquired access information of the two call parties.

[0013] In one embodiment, the method further comprises:

[0014] Based on whether the UE-satellite-UE service is executed, it is determined whether to trigger the AGW reselection operation.

[0015] In one embodiment, when a terrestrial AGW is currently selected as a candidate AGW, determining whether to trigger an AGW reselection operation based on whether a UE-satellite-UE service is performed includes:

[0016] In response to not performing the UE-satellite-UE service, not triggering a reselection operation of the AGW; and

[0017] In response to the execution of the UE-satellite-UE service, an AGW reselection operation is triggered, the currently selected ground AGW is released and the onboard AGW is reselected as the candidate AGW.

[0018] In one embodiment, when an onboard AGW is currently selected as a candidate AGW, determining whether to trigger an AGW reselection operation based on whether a UE-satellite-UE service is performed includes:

[0019] In response to not performing the UE-satellite-UE service, triggering an AGW reselection operation, releasing the currently selected onboard AGW and reselecting a terrestrial AGW as the candidate AGW;

[0020] In response to the execution of the UE-satellite-UE service, no reselection operation of the AGW is triggered.

[0021] In one embodiment, the method further includes: determining one or more candidate AGWs based on satellite information and / or access information of both parties of the call.

[0022] In one embodiment, the access information of the two parties in the call includes at least one of satellite identification information, access type, and access cell identification of the two parties.

[0023] In one embodiment, the satellite information includes at least one of ephemeris information, orbit, and satellite identification.

[0024] In one embodiment, the method further comprises:

[0025] Send an interaction request to the 5GC network element; the interaction request is used to confirm whether the candidate AGW is available.

[0026] In one embodiment, the method further comprises:

[0027] An address allocation request message is sent to the candidate AGW network element; the address allocation request message is used to instruct the candidate AGW network element to send a response message to the P-CSCF after completing the address allocation; the response message carries the allocated address.

[0028] In one embodiment, the method further comprises:

[0029] receiving a first conference initialization protocol SIP message sent by a user terminal, and selecting a ground AGW for the user terminal; the ground AGW is used to allocate an output address to the user terminal; and

[0030] The first SIP message is forwarded to other IMS network elements, and the original address of the user terminal is replaced with the output address allocated to the user terminal by the ground AGW.

[0031] In one embodiment, the method further comprises:

[0032] In response to receiving the newly allocated address, a second Conference Initialization Protocol (SIP) message is sent to the user terminal; the second SIP message is used to inform the user terminal of the new address allocated to the user terminal by the candidate AGW.

[0033] In one embodiment, the method further comprises:

[0034] In response to receiving the newly allocated address, a third conference initialization protocol SIP message is sent to other IMS network elements; the third SIP message is used to notify the candidate AGW of the newly allocated address.

[0035] In one embodiment, the third SIP message carries identification information of the satellite where the candidate AGW is deployed.

[0036] In one embodiment, determining one or more candidate AGWs based on satellite information includes:

[0037] Based on the satellite information, selecting an AGW deployed on a regenerative mode satellite currently accessed by the user terminal as a candidate AGW; and / or,

[0038] The onboard AGW closest to the regenerative mode satellite accessed by the user terminal is selected as the candidate AGW.

[0039] In a second aspect, an embodiment of the present application provides an access gateway reselection device, which is applied to a P-CSCF, and includes:

[0040] The execution module is used to execute the AGW reselection operation during the multimedia subsystem IMS session establishment process.

[0041] In one embodiment, the apparatus further comprises:

[0042] The first determining module is configured to determine whether to execute the UE-satellite-UE service according to the acquired access information of the two call parties.

[0043] In one embodiment, the first determining module is further configured to determine whether to trigger an AGW reselection operation based on whether a UE-satellite-UE service is executed.

[0044] In one embodiment, when a terrestrial AGW is currently selected as a candidate AGW, the first determining module is further configured to: in response to not performing a UE-satellite-UE service, not trigger an AGW reselection operation; and

[0045] In response to the execution of the UE-satellite-UE service, an AGW reselection operation is triggered, the currently selected ground AGW is released and the onboard AGW is reselected as the candidate AGW.

[0046] In one embodiment, when the on-board AGW is currently selected as the candidate AGW, the first determining module is further configured to: in response to not performing the UE-satellite-UE service, trigger an AGW reselection operation, release the currently selected on-board AGW, and reselect a terrestrial AGW as the candidate AGW; and

[0047] In response to the execution of the UE-satellite-UE service, no reselection operation of the AGW is triggered.

[0048] In one embodiment, the apparatus further comprises:

[0049] The second determining module is configured to determine one or more candidate AGWs based on satellite information and / or access information of both parties of the call.

[0050] In one embodiment, the access information of the two parties in the call includes at least one of satellite identification information, access type, and access cell identification of the two parties.

[0051] In one embodiment, the satellite information includes at least one of ephemeris information, orbit, and satellite identification.

[0052] In one embodiment, the apparatus further comprises:

[0053] The first sending module is used to send an interaction request to the 5GC network element; the interaction request is used to confirm whether the candidate AGW is available.

[0054] In one embodiment, the apparatus further comprises:

[0055] The second sending module is used to send an address allocation request message to the candidate AGW network element; the address allocation request message is used to instruct the candidate AGW network element to send a response message to the P-CSCF after completing the address allocation; the response message carries the allocated address.

[0056] In one embodiment, the apparatus further comprises:

[0057] a receiving module, configured to receive a first conference initialization protocol SIP message sent by a user terminal, and select a ground AGW for the user terminal; the ground AGW is configured to allocate an output address to the user terminal; and

[0058] An updating module is configured to forward the first SIP message to other IMS network elements and replace the original address of the user terminal with the output address allocated by the ground AGW to the user terminal.

[0059] In one embodiment, the apparatus further comprises:

[0060] The third sending module is configured to send a second Conference Initialization Protocol (SIP) message to the user terminal in response to receiving the newly allocated address; the second SIP message is used to notify the user terminal of the new address allocated to the user terminal by the candidate AGW.

[0061] In one embodiment, the apparatus further comprises:

[0062] The fourth sending module is configured to send a third conference initialization protocol SIP message to other IMS network elements in response to receiving the newly allocated address; the third SIP message is used to notify the candidate AGW of the new address allocated.

[0063] In one embodiment, the third SIP message carries identification information of the satellite where the candidate AGW is deployed.

[0064] In one embodiment, the second determining module is specifically configured to select, based on the satellite information, an AGW deployed on a regenerative mode satellite currently accessed by the user terminal as a candidate AGW; and / or,

[0065] The onboard AGW closest to the regenerative mode satellite accessed by the user terminal is selected as the candidate AGW.

[0066] In a third aspect, an embodiment of the present application provides a computer-readable storage medium having a computer program stored thereon, which implements any one of the steps of the above-mentioned access gateway reselection method when executed by a processor.

[0067] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the following steps are implemented:

[0068] During the multimedia subsystem IMS session establishment process, the AGW reselection operation is performed.

[0069] In a fifth aspect, an embodiment of the present application provides a computer program product, including a computer program, which, when executed by a processor, implements the following steps:

[0070] During the multimedia subsystem IMS session establishment process, the AGW reselection operation is performed.

[0071] The details of one or more embodiments of the present application are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the disclosed drawings without any creative work.

[0073] FIG1 is a diagram illustrating an application environment of a method for reselecting an access gateway according to an embodiment of the present application;

[0074] FIG2 is a schematic diagram of an IMS media plane data path in one embodiment of the present application;

[0075] FIG3 is a flowchart illustrating steps for determining whether to trigger an AGW reselection operation in one embodiment of the present application;

[0076] FIG4 is a flowchart illustrating steps for determining whether to trigger an AGW reselection operation in another embodiment of the present application;

[0077] FIG5 is a schematic diagram of a flow chart of the steps of replacing a user terminal address in one embodiment of the present application;

[0078] FIG6 is a schematic diagram of a flow chart of a method for selecting an onboard AGW in one embodiment of the present application;

[0079] FIG7 is a flowchart illustrating a specific example of a method for reselecting an access gateway in an embodiment of the present application. DETAILED DESCRIPTION

[0080] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0081] Figure 1 is a schematic diagram of an application scenario for access gateway reselection provided by an embodiment of the present application. As shown in Figure 1 , this scenario includes a first user terminal 100 (not shown in Figure 1 ), a second user terminal 200, and an onboard access gateway (AGW) 300. Data is transmitted between the first user terminal 100 and the second user terminal 200 via a network, and data is transmitted between the first user terminal 100 and the onboard access gateway (AGW) 300 via a network.

[0082] The first user terminal 100 and the second user terminal 200 may be wireless terminals. A wireless terminal may be a device that provides voice and / or other service data connectivity to a user, or a handheld device with wireless connection capabilities, or other processing devices connected to a wireless modem. A wireless terminal may communicate with one or more core networks via a radio access network (RAN). A wireless terminal may be a mobile terminal, such as a mobile phone (or "cellular" phone) and a computer with a mobile terminal. For example, a mobile device may be portable, pocket-sized, handheld, built-in, or vehicle-mounted. These devices exchange voice and / or data with a radio access network. A wireless terminal may also be referred to as a system, subscriber unit, subscriber station, mobile station, mobile station, remote station, remote terminal, access terminal, user terminal, user agent, or user device or user equipment, without limitation herein.

[0083] Traditionally, voice communication services primarily utilize ground-based AGWs (Access Gateways) to transmit signaling between calling and called users, enabling communication between them. However, due to geographical or political constraints, gateway deployment is difficult in some areas, and therefore, communication services remain geographically restricted. Integrating ground-based base stations with regenerative satellites can address this issue and provide terminals with a range of value-added services. Specifically, as shown in Figure 1, UE-satellite-UE communication services allow user-plane data to be communicated between UEs within the coverage of one or more serving satellites without traversing the terrestrial network. This UE-satellite-UE communication service effectively eliminates reliance on ground-based gateways, reduces user-plane latency, and provides potential service scenarios for future space-based and ground-based services. To achieve this, UE-satellite-UE communication services and IMS voice services support transcoding, secure isolation from the IMS core network, lawful interception, and data retention. The embodiments of the present application provide an access gateway reselection method. After determining that the user meets the UE-satellite-UE communication conditions, the reselection operation from the ground AGW to the on-satellite AGW is completed. This effectively saves the signaling overhead during the user's establishment of an IMS voice session, shortens the call establishment delay, and ensures that limited on-satellite resources are effectively utilized, enabling the network to maintain efficient allocation when it has more heterogeneous resources.

[0084] It should be noted that the beneficial effects or technical problems solved by the embodiments of the present application are not limited to this one, but may also include other implicit or related problems. For details, please refer to the description of the following embodiments.

[0085] Before introducing the specific embodiments of the present invention, the professional terms involved in the present invention are explained:

[0086] P-CSCF: Proxy-Call Session Control Function, proxy call session control function;

[0087] SIP: Session Initiation Protocol, Session Initiation Protocol;

[0088] UE: User Equipment, user equipment, user terminal;

[0089] IMS: IP Multimedia Subsystem;

[0090] IMS-AGW: IMS Access Media Gateway;

[0091] RAT type: Radio Access Technology Type;

[0092] AMF: Access and Mobility Management Function;

[0093] N2 interface: reference point between (R)AN and AMF;

[0094] N4 interface: reference point between SMF and UPF.

[0095] The following specific embodiments describe in detail the technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0096] IMS voice services place clear demands on the deployment of AGWs in the UE's media path to support a range of critical functions, including but not limited to transcoding, secure isolation from the IMS core network, lawful interception, and data retention. Figure 2 shows the IMS media plane data path using AGWs. Therefore, to enable IMS voice services in the UE-satellite-UE communication mode, the network must be capable of deploying AGWs on satellites. Furthermore, the control plane of the IMS network needs to be further enhanced to support the selection of an on-satellite AGW for users when the IMS voice conditions in the UE-satellite-UE communication mode are met. Consequently, AGW reselection is required during IMS session establishment.

[0097] In one embodiment, a method for reselecting an access gateway is provided. The method is applied to a P-CSCF and includes the following steps:

[0098] During the multimedia subsystem IMS session establishment process, the AGW reselection operation is performed.

[0099] In practice, the P-CSCF performs access gateway reselection during the multimedia subsystem (IMS) session establishment process. For example, when both communicating users meet the UE-satellite-UE communication conditions, the P-CSCF can reselect the access gateway from the ground-based AGW to the satellite-based AGW. This effectively improves the performance of satellite voice services, enhances service availability and competitiveness, and reduces signaling overhead during IMS voice session establishment.

[0100] Optionally, the P-CSCF may also implement a reselection operation from the onboard AGW to the ground AGW. The embodiment of the present application does not limit the reselection operation of the P-CSCF.

[0101] In the aforementioned access gateway reselection method, the AGW reselection operation is performed during the multimedia subsystem (IMS) session establishment process. This method completes the reselection from the ground-based AGW to the satellite-based AGW after determining that the user meets the UE-satellite-UE communication conditions. This effectively reduces the signaling overhead during the user's IMS voice session establishment, shortens call establishment latency, and ensures that limited satellite resources are effectively utilized, enabling the network to maintain efficient allocation even when more heterogeneous resources are available.

[0102] In one embodiment, the method further comprises:

[0103] Determine whether to execute the UE-satellite-UE service based on the access information of the two call parties obtained;

[0104] During implementation, the P-CSCF can obtain access information for both parties in a call. Based on this information, the P-CSCF can determine whether to execute the UE-satellite-UE service. For example, the access information for both parties may include at least one of the satellite identification information, access type, and access cell identification of both parties. The P-CSCF uses this satellite identification information to determine whether the UE-satellite-UE service is available for both parties.

[0105] In one embodiment, the method further comprises:

[0106] Based on whether the UE-satellite-UE service is executed, it is determined whether to trigger the AGW reselection operation.

[0107] In implementation, whether to trigger AGW reselection is determined based on whether UE-satellite-UE services are available. For example, the access information of both parties in a call includes at least one of their satellite identification information, access type, and access cell identification. The P-CSCF uses this satellite identification information to determine whether the two parties in the call can perform UE-satellite-UE services. Furthermore, the P-CSCF uses this satellite identification information to identify a suitable AGW as a candidate AGW, completing the AGW reselection.

[0108] In this embodiment, the access information of both callers is used to determine whether to execute the UE-satellite-UE service. Furthermore, based on whether the UE-satellite-UE service is executed, it is determined whether to trigger AGW reselection. This ensures that limited on-board resources are effectively utilized, allowing the network to maintain efficient allocation even when it has more heterogeneous resources.

[0109] In one embodiment, as shown in FIG3 , when a terrestrial AGW is currently selected as a candidate AGW, determining whether to trigger an AGW reselection operation based on whether a UE-satellite-UE service is being performed includes:

[0110] Step 302: In response to not performing the UE-satellite-UE service, not triggering the AGW reselection operation; and

[0111] Step 304 : In response to the execution of the UE-satellite-UE service, an AGW reselection operation is triggered, the currently selected ground AGW is released, and the onboard AGW is reselected as a candidate AGW.

[0112] Specifically, if a terrestrial AGW is currently selected as a candidate AGW and UE-satellite-UE service is not being performed, AGW reselection is not triggered. That is, the on-satellite AGW is not used, and the currently selected terrestrial AGW is used as the candidate AGW. If a terrestrial AGW is currently selected as a candidate AGW and UE-satellite-UE service is being performed, AGW reselection is triggered. That is, the on-satellite AGW is used, the terrestrial AGW is released, and the on-satellite AGW is selected as the candidate AGW.

[0113] In one embodiment, as shown in FIG4 , when an onboard AGW is currently selected as a candidate AGW, determining whether to trigger an AGW reselection operation based on whether a UE-satellite-UE service is executed includes:

[0114] Step 402: In response to not performing the UE-satellite-UE service, triggering an AGW reselection operation, releasing the currently selected onboard AGW and reselecting a terrestrial AGW as a candidate AGW; and

[0115] Step 404: In response to executing the UE-satellite-UE service, the AGW reselection operation is not triggered.

[0116] Specifically, when the on-satellite AGW is currently selected as the candidate AGW, if the UE-satellite-UE service is not performed, the AGW reselection operation is triggered, that is, the currently selected on-satellite AGW is released and the ground AGW is selected as the candidate AGW; when the on-satellite AGW is currently selected as the candidate AGW, if the UE-satellite-UE service is performed, the AGW reselection operation is not triggered, that is, the currently selected on-satellite AGW is used or the currently selected on-satellite AGW is released and another on-satellite AGW is selected as the candidate AGW.

[0117] In one embodiment, the method further comprises:

[0118] One or more candidate AGWs are determined based on satellite information and / or access information of both parties in the call.

[0119] In implementation, the P-CSCF determines one or more candidate AGWs based on satellite information and / or access information of both parties. Satellite information includes, but is not limited to, ephemeris information, orbit information, and satellite identifiers. Access information of both parties may include, but is not limited to, satellite identifiers of both parties. Therefore, when determining to execute a UE-satellite-UE service, the P-CSCF can determine one or more suitable candidate AGWs based on either or a combination of the satellite information and the access information of both parties. For example, if, based on satellite information, it is determined that latency variations caused by satellite motion no longer meet service requirements, a candidate AGW reselection operation is triggered, i.e., one or more new suitable candidate AGWs are determined.

[0120] In this embodiment, one or more candidate AGWs are determined based on satellite information and / or access information of both parties in the call, thereby ensuring that limited on-board resources are effectively utilized and enabling the network to maintain efficient allocation when having more heterogeneous resources.

[0121] In one embodiment, the method further includes: sending an interaction request to a 5GC network element.

[0122] The interaction request is used to confirm whether the candidate AGW is available.

[0123] In implementation, after determining a suitable on-board AGW, the P-CSCF sends an interaction request to the 5GC network element to negotiate with the 5GC network element through the interaction message to confirm whether the on-board AGW can be applied.

[0124] In implementation, if it is determined through negotiation not to use the onboard AGW as the candidate AGW, for example, if the 5GC cannot provide a suitable onboard UPF (User Plane Function), the P-CSCF will still use the currently selected terrestrial AGW to complete the establishment of the terrestrial voice session between the two parties, that is, no AGW reselection will be performed.

[0125] If the onboard AGW is determined to be the candidate AGW through negotiation, the P-CSCF releases the terrestrial AGW and selects a suitable onboard AGW for the user terminal. The onboard AGW then allocates input and output addresses to the user terminals of both communicating parties. The process of determining whether to use the terrestrial AGW as the candidate AGW through negotiation is similar.

[0126] In this embodiment, by sending an interaction request to the 5GC network element to negotiate the availability of the candidate AGW, the reliability of the communication system can be ensured. After confirming the availability of the candidate AGW, the system can flexibly select the candidate AGW to use, thereby improving the stability and reliability of communication.

[0127] In one embodiment, the method further comprises:

[0128] An address allocation request message is sent to the candidate AGW network element; the address allocation request message is used to instruct the candidate AGW network element to send a response message to the P-CSCF after completing address allocation.

[0129] The response message carries the allocated address.

[0130] In practice, during the multimedia subsystem (IMS) session establishment process, the P-CSCF sends an address allocation request message to the candidate AGW network element. After completing the address allocation, the candidate AGW sends a response message to the P-CSCF. This response message carries the address assigned by the candidate AGW to the user terminal. The P-CSCF can update the stored original user terminal address based on the address received in the response message, thereby implementing the AGW reselection operation.

[0131] In this embodiment, during the IMS session establishment process, the P-CSCF sends an address allocation request message to the candidate AGW network element, which can implement address allocation for the user terminal and ensure the effectiveness and accuracy of address allocation through the candidate AGW network element. This helps manage network address resources, avoid address conflicts and confusion, and improve network stability and reliability.

[0132] In one embodiment, as shown in FIG5 , the method further includes:

[0133] Step 502: Receive a first conference initialization protocol SIP message sent by a user terminal, and select a ground AGW for the user terminal.

[0134] Among them, the ground AGW is used to allocate output addresses to user terminals

[0135] In practice, users typically use traditional terrestrial IMS voice services more frequently. Therefore, when the IMS network cannot determine whether the current user can be provided with IMS voice services in the UE-satellite-UE communication mode, or determines that IMS voice services in the UE-satellite-UE communication mode cannot be provided, the P-CSCF selects the terrestrial AGW to transmit signaling between the calling and called user terminals. Specifically, the P-CSCF receives a first session initialization protocol (SIP) message sent by the user terminal and selects a terrestrial AGW for the user terminal. The terrestrial AGW can allocate output and input addresses to the user terminals on both sides of the call.

[0136] Step 504: forward the first SIP message to other IMS network elements, and replace the original address of the user terminal with the output address allocated to the user terminal by the ground AGW.

[0137] During implementation, the P-CSCF forwards the first SIP message to other IMS network elements and replaces the original address of the user terminal stored locally with the output address assigned to the user terminal by the ground AGW. At the same time, the first SIP message is also used to instruct other IMS network elements participating in the call process to update the address of the user terminal (on the calling side) to the output address assigned to the user terminal by the ground AGW.

[0138] In this embodiment, by selecting a terrestrial AGW for the user terminal and replacing the original address of the user terminal with the allocated output address when receiving the first SIP message, an IMS session based on the terrestrial AGW can be established, thereby implementing an IMS voice call service.

[0139] In one embodiment, the method further comprises:

[0140] In response to receiving the newly allocated address, a second conference initialization protocol (SIP) message is sent to the user terminal.

[0141] In practice, during the AGW reselection process, the P-CSCF, in response to receiving the newly assigned address, sends a second Session Initiation Protocol (SIP) message to the user terminal. The second SIP message notifies the user terminal of the new address assigned by the candidate AGW, allowing the user terminal to replace its original address with the new address.

[0142] Optionally, the SIP message type may be SIP INVITE (SIP invitation), SIP Response (SIP response), or SIP Register (SIP registration), which is not limited in the embodiment of the present application.

[0143] In this embodiment, the user terminal is notified to update the address when the AGW is reselected through a SIP message, thereby achieving AGW reselection, which can effectively save the signaling overhead of the user terminal in establishing an IMS voice session and shorten the delay in establishing the call.

[0144] In one embodiment, the method further comprises:

[0145] In response to receiving the newly allocated address, a third conference initialization protocol SIP message is sent to the other IMS network element.

[0146] The third SIP message is used to notify the candidate AGW of the new address allocated.

[0147] In implementation, in response to receiving the newly allocated address, the P-CSCF sends a third conference initialization protocol SIP message to other IMS network elements participating in the communication session establishment process, and replaces the output address allocated by the original ground AGW for the user terminal UE stored in the IMS network element with the output address allocated by the onboard AGW for the user terminal, that is, the third SIP message is used to notify each IMS network element to update the address (for example, the output address of the user terminal on the calling side, or the input address of the user terminal on the called side) to the new address allocated by the candidate AGW.

[0148] Optionally, other IMS network elements include but are not limited to: a source P-CSCF (i.e., a P-CSCF used to trigger AGW reselection), a peer P-CSCF (capable of replacing the address assigned to the UE by the original AGW with the address assigned to the UE by the candidate AGW). The address of the user terminal includes but is not limited to the IP address, port number, etc. of the user terminal, and this embodiment of the present application does not limit this.

[0149] In this embodiment, other IMSs participating in the communication session are notified through SIP messages to update the locally stored user terminal address based on the new address assigned to the user terminal by the reselected AGW. This, in turn, enables the reselection of the AGW, ensuring that limited on-board resources are effectively utilized and enabling the network to maintain efficient allocation even when it has more heterogeneous resources.

[0150] In one embodiment, the third SIP message carries identification information of the satellite where the candidate AGW is deployed.

[0151] In this embodiment, the third SIP message sent by the P-CSCF to other IMS network elements also carries satellite identification information, thereby clarifying the satellite deployed by the onboard AGW, and further, enabling positioning and monitoring of the satellite.

[0152] In one embodiment, as shown in FIG6 , the satellite information includes at least one of ephemeris information, orbit, and satellite identification. Therefore, the specific process of determining one or more candidate AGWs based on the satellite information includes steps 602 to 604.

[0153] Step 602: Based on the satellite information, select an AGW deployed on the regenerative mode satellite currently accessed by the user terminal as a candidate AGW.

[0154] In practice, the P-CSCF selects one or more on-board AGWs from among the numerous on-board AGWs to provide communication session services based on satellite information, such as ephemeris, orbit, and satellite identifier. The selection principles include, but are not limited to, prioritizing the use of AGWs deployed on the regenerative-mode satellite currently accessed by the user terminal as the on-board AGW to improve on-board AGW handover efficiency.

[0155] And / or, in step 604, the onboard AGW closest to the regenerative mode satellite accessed by the user terminal is selected as the candidate AGW.

[0156] In implementation, the P-CSCF may select the on-board AGW based on the principle of selecting the on-board AGW closest to the regenerative mode satellite accessed by the user terminal. In addition to the selection principle in step 602 or step 604, the P-CSCF may also select the on-board AGW based on indicators such as on-board AGW performance, which is not limited in this embodiment of the present application.

[0157] In this embodiment, satellite information is used to select an onboard AGW, thereby selecting an AGW suitable for the current user terminal communication. By selecting an AGW deployed on the regenerative mode satellite currently connected to the user terminal or the nearest onboard AGW, latency can be reduced, network quality can be optimized, and energy can be saved, thereby improving the performance and efficiency of the communication system.

[0158] In one embodiment, as shown in FIG7 , a specific example of a method for reselecting an access gateway is provided. The example process includes:

[0159] Step 701: The user terminal sends a SIP message (first SIP message) to the P-CSCF.

[0160] Step 702: The P-CSCF selects a terrestrial AGW for the user terminal, wherein the terrestrial AGW is used to allocate an output address to the user terminal.

[0161] Step 703: forward the first SIP message to other IMS network elements (Other IMS Functions), and replace the original address of the user terminal with the output address allocated to the user terminal by the ground AGW.

[0162] In step 704, the P-CSCF determines whether to execute the UE-satellite-UE service based on the acquired access information of the call parties; and determines whether to trigger the AGW reselection operation based on whether the UE-satellite-UE service is executed.

[0163] Step 705: The P-CSCF sends an interaction request to the 5GC network element. The interaction request is used to negotiate and confirm whether the candidate AGW is available.

[0164] Step 706: When the on-board AGW is used, the P-CSCF releases the terrestrial AGW and selects the on-board AGW for the user terminal.

[0165] Step 707: The P-CSCF sends a second SIP message to the user terminal. The second SIP message is used to inform the user terminal of the new address allocated to the user terminal by the candidate AGW.

[0166] Step 708: In response to receiving the newly allocated address, the P-CSCF sends a third session initialization protocol (SIP) message to other IMS network elements, wherein the third SIP message is used to notify the candidate AGW of the newly allocated address.

[0167] In step 709, other IMS network elements replace the output address of the user terminal assigned by the ground AGW with the output address of the user terminal assigned by the onboard AGW.

[0168] In the embodiment of the present application, the access gateway reselection method is described by taking the P-CSCF on the calling side as an example. Optionally, the access gateway reselection method can also be applied to the P-CSCF on the called side. The processing process is similar to that of the P-CSCF on the calling side. The only difference is that when the P-CSCF on the called side allocates the address, the original address of the user terminal on the called side is replaced with the input address allocated by the onboard AGW.

[0169] It should be understood that although the various steps in the flow charts of Figures 3 to 7 are shown in sequence as indicated by the arrows, these steps are not necessarily performed in sequence in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be performed in other orders. Moreover, at least a portion of the steps in Figures 3 to 7 may include multiple steps or multiple stages, and these steps or stages are not necessarily performed at the same time, but can be performed at different times, and the execution order of these steps or stages is not necessarily performed in sequence, but can be performed in turn or alternately with other steps or at least a portion of the steps or stages in other steps.

[0170] In one embodiment, an access gateway reselection device is provided. The device is applied to a P-CSCF and includes:

[0171] The execution module is used to execute the AGW reselection operation during the multimedia subsystem IMS session establishment process.

[0172] In one embodiment, the apparatus further comprises:

[0173] The first determining module is configured to determine whether to execute the UE-satellite-UE service according to the acquired access information of the two call parties.

[0174] In one embodiment, the first determining module is further configured to determine whether to trigger an AGW reselection operation based on whether a UE-satellite-UE service is executed.

[0175] In one embodiment, when a terrestrial AGW is currently selected as a candidate AGW, the first determining module is further configured to: in response to not performing a UE-satellite-UE service, not trigger an AGW reselection operation; and

[0176] In response to the execution of the UE-satellite-UE service, an AGW reselection operation is triggered, the currently selected ground AGW is released and the onboard AGW is reselected as the candidate AGW.

[0177] In one embodiment, when the on-board AGW is currently selected as the candidate AGW, the first determining module is further configured to: in response to not performing the UE-satellite-UE service, trigger an AGW reselection operation, release the currently selected on-board AGW, and reselect the terrestrial AGW as the candidate AGW; and

[0178] In response to the execution of the UE-satellite-UE service, no reselection operation of the AGW is triggered.

[0179] In one embodiment, the apparatus further comprises:

[0180] The second determining module is configured to determine one or more candidate AGWs based on satellite information and / or access information of both parties of the call.

[0181] In one embodiment, the access information of both parties of the call includes at least one of satellite identification information, access type, and access cell identification of both parties of the communication.

[0182] In one embodiment, the satellite information includes at least one of ephemeris information, orbit, and satellite identification.

[0183] In one embodiment, the apparatus further comprises:

[0184] The first sending module is used to send an interaction request to the 5GC network element, where the interaction request is used to confirm whether the candidate AGW is available.

[0185] In one embodiment, the apparatus further comprises:

[0186] The second sending module is used to send an address allocation request message to the candidate AGW network element; the address allocation request message is used to instruct the candidate AGW network element to send a response message to the P-CSCF after completing the address allocation; the response message carries the allocated address.

[0187] In one embodiment, the apparatus further comprises:

[0188] A receiving module, configured to receive a first conference initialization protocol SIP message sent by a user terminal and select a ground AGW for the user terminal; the ground AGW is configured to allocate an output address to the user terminal; and

[0189] An updating module is configured to forward the first SIP message to other IMS network elements and replace the original address of the user terminal with the output address allocated by the ground AGW to the user terminal. In one embodiment, the apparatus further includes:

[0190] The third sending module is configured to send a second conference initialization protocol SIP message to the user terminal in response to receiving the newly allocated address; the second SIP message is used to notify the user terminal of the new address allocated to the user terminal by the candidate AGW.

[0191] In one embodiment, the apparatus further comprises:

[0192] The fourth sending module is configured to send a third conference initialization protocol SIP message to other IMS network elements in response to receiving the newly allocated address; the third SIP message is used to notify the candidate AGW of the new address allocated.

[0193] In one embodiment, the third SIP message carries identification information of the satellite where the candidate AGW is deployed.

[0194] In one embodiment, the second determining module is specifically configured to select, based on satellite information, an AGW deployed on a regenerative mode satellite currently accessed by the user terminal as a candidate AGW; and / or,

[0195] The onboard AGW closest to the regenerative mode satellite accessed by the user terminal is selected as the candidate AGW.

[0196] The specific limitations of the access gateway reselection device can be found in the limitations of the access gateway reselection method described above and will not be further elaborated here. Each module in the aforementioned access gateway reselection device may be implemented in whole or in part via software, hardware, or a combination thereof. Each of the aforementioned modules may be embedded in or independent of a processor in a computer device in hardware form, or may be stored in a memory in a computer device in software form, so that the processor can call and execute the corresponding operations of each of the aforementioned modules.

[0197] In one embodiment, a communication device is provided, including a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the following steps are implemented:

[0198] During the multimedia subsystem IMS session establishment process, the AGW reselection operation is performed.

[0199] In one embodiment, when the processor executes the computer program, the processor further implements the following steps:

[0200] Determine whether to execute the UE-satellite-UE service based on the acquired access information of the two call parties.

[0201] In one embodiment, when the processor executes the computer program, the processor further implements the following steps:

[0202] Based on whether the UE-satellite-UE service is executed, it is determined whether to trigger the AGW reselection operation.

[0203] In one embodiment, when a terrestrial AGW is currently selected as a candidate AGW, the processor determines whether to trigger an AGW reselection operation based on whether a UE-satellite-UE service is being performed, and further implements the following steps:

[0204] In response to not performing the UE-satellite-UE service, not triggering a reselection operation of the AGW; and

[0205] In response to the execution of the UE-satellite-UE service, an AGW reselection operation is triggered, the currently selected ground AGW is released and the onboard AGW is reselected as the candidate AGW.

[0206] In one embodiment, when an onboard AGW is currently selected as a candidate AGW, the processor determines whether to trigger an AGW reselection operation based on whether a UE-satellite-UE service is being performed, and further implements the following steps:

[0207] In response to not performing the UE-satellite-UE service, triggering an AGW reselection operation, releasing the currently selected onboard AGW and reselecting a terrestrial AGW as a candidate AGW;

[0208] In response to the execution of the UE-satellite-UE service, no reselection operation of the AGW is triggered.

[0209] In one embodiment, when the processor executes the computer program, it further implements the following steps: determining one or more candidate AGWs based on satellite information and / or access information of both parties of the call.

[0210] In one embodiment, the access information of both parties of the call includes at least one of satellite identification information, access type, and access cell identification of both parties of the communication.

[0211] In one embodiment, the satellite information includes at least one of ephemeris information, orbit, and satellite identification.

[0212] In one embodiment, when the processor executes the computer program, the processor further implements the following steps:

[0213] Send an interaction request to the 5GC network element to confirm whether the candidate AGW is available.

[0214] In one embodiment, when the processor executes the computer program, the processor further implements the following steps:

[0215] An address allocation request message is sent to the candidate AGW network element; the address allocation request message is used to instruct the candidate AGW network element to send a response message to the P-CSCF after completing the address allocation; the response message carries the allocated address.

[0216] In one embodiment, when the processor executes the computer program, the processor further implements the following steps:

[0217] receiving a first conference initialization protocol SIP message sent by a user terminal, and selecting a ground AGW for the user terminal; the ground AGW is used to allocate an output address to the user terminal; and

[0218] The first SIP message is forwarded to other IMS network elements, and the original address of the user terminal is replaced with the output address allocated to the user terminal by the ground AGW.

[0219] In one embodiment, when the processor executes the computer program, the processor further implements the following steps:

[0220] In response to receiving the newly allocated address, a second conference initialization protocol SIP message is sent to the user terminal; the second SIP message is used to inform the user terminal of the new address allocated to the user terminal by the candidate AGW.

[0221] In one embodiment, when the processor executes the computer program, the processor further implements the following steps:

[0222] In response to receiving the newly allocated address, a third conference initialization protocol SIP message is sent to other IMS network elements; the third SIP message is used to notify the candidate AGW of the newly allocated address.

[0223] In one embodiment, when the processor executes the computer program, the processor further implements the following steps:

[0224] Based on the satellite information, selecting an AGW deployed on a regenerative mode satellite currently accessed by the user terminal as a candidate AGW; and / or,

[0225] The onboard AGW closest to the regenerative mode satellite accessed by the user terminal is selected as the candidate AGW.

[0226] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the following steps are implemented:

[0227] During the multimedia subsystem IMS session establishment process, the AGW reselection operation is performed.

[0228] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0229] Determine whether to execute the UE-satellite-UE service based on the acquired access information of the two call parties.

[0230] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0231] Based on whether the UE-satellite-UE service is executed, it is determined whether to trigger the AGW reselection operation.

[0232] In one embodiment, when a terrestrial AGW is currently selected as a candidate AGW, a computer program executed by a processor determines whether to trigger an AGW reselection operation based on whether a UE-satellite-UE service is being performed, and further implements the following steps:

[0233] In response to not performing the UE-satellite-UE service, not triggering a reselection operation of the AGW; and

[0234] In response to the execution of the UE-satellite-UE service, an AGW reselection operation is triggered, the currently selected ground AGW is released and the onboard AGW is reselected as the candidate AGW.

[0235] In one embodiment, when an onboard AGW is currently selected as a candidate AGW, a computer program executed by a processor determines whether to trigger an AGW reselection operation based on whether a UE-satellite-UE service is being performed, and further implements the following steps:

[0236] In response to not performing the UE-satellite-UE service, triggering an AGW reselection operation, releasing the currently selected onboard AGW and reselecting a terrestrial AGW as a candidate AGW;

[0237] In response to the execution of the UE-satellite-UE service, no reselection operation of the AGW is triggered.

[0238] In one embodiment, when the computer program is executed by the processor, the computer program further implements the following steps: determining one or more candidate AGWs based on satellite information and / or access information of both parties of the call.

[0239] In one embodiment, the access information of both parties of the call includes at least one of satellite identification information, access type, and access cell identification of both parties of the communication.

[0240] In one embodiment, the satellite information includes at least one of ephemeris information, orbit, and satellite identification.

[0241] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0242] Send an interaction request to the 5GC network element to confirm whether the candidate AGW is available.

[0243] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0244] An address allocation request message is sent to the candidate AGW network element; the address allocation request message is used to instruct the candidate AGW network element to send a response message to the P-CSCF after completing the address allocation; the response message carries the allocated address.

[0245] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0246] receiving a first conference initialization protocol SIP message sent by a user terminal, and selecting a ground AGW for the user terminal; the ground AGW is used to allocate an output address to the user terminal; and

[0247] The first SIP message is forwarded to other IMS network elements, and the original address of the user terminal is replaced with the output address allocated to the user terminal by the ground AGW.

[0248] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0249] In response to receiving the newly allocated address, a second conference initialization protocol SIP message is sent to the user terminal; the second SIP message is used to inform the user terminal of the new address allocated to the user terminal by the candidate AGW.

[0250] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0251] In response to receiving the newly allocated address, a third conference initialization protocol SIP message is sent to other IMS network elements; the third SIP message is used to notify the candidate AGW of the newly allocated address.

[0252] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0253] Based on the satellite information, selecting an AGW deployed on a regenerative mode satellite currently accessed by the user terminal as a candidate AGW; and / or,

[0254] The onboard AGW closest to the regenerative mode satellite accessed by the user terminal is selected as the candidate AGW.

[0255] The present application also provides a computer program product comprising instructions, which, when executed on a computer, causes the computer to perform the following steps:

[0256] During the multimedia subsystem IMS session establishment process, the AGW reselection operation is performed.

[0257] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0258] Determine whether to execute the UE-satellite-UE service based on the acquired access information of the two call parties.

[0259] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0260] Based on whether the UE-satellite-UE service is executed, it is determined whether to trigger the AGW reselection operation.

[0261] In one embodiment, when a terrestrial AGW is currently selected as a candidate AGW, a computer program executed by a processor determines whether to trigger an AGW reselection operation based on whether a UE-satellite-UE service is being performed, and further implements the following steps:

[0262] In response to not performing the UE-satellite-UE service, not triggering a reselection operation of the AGW; and

[0263] In response to the execution of the UE-satellite-UE service, an AGW reselection operation is triggered, the currently selected ground AGW is released and the onboard AGW is reselected as the candidate AGW.

[0264] In one embodiment, when an onboard AGW is currently selected as a candidate AGW, a computer program executed by a processor determines whether to trigger an AGW reselection operation based on whether a UE-satellite-UE service is being performed, and further implements the following steps:

[0265] In response to not performing the UE-satellite-UE service, triggering an AGW reselection operation, releasing the currently selected onboard AGW and reselecting a terrestrial AGW as a candidate AGW;

[0266] In response to the execution of the UE-satellite-UE service, no reselection operation of the AGW is triggered.

[0267] In one embodiment, when the computer program is executed by the processor, the computer program further implements the following steps: determining one or more candidate AGWs based on satellite information and / or access information of both parties of the call.

[0268] In one embodiment, the access information of both parties of the call includes at least one of satellite identification information, access type, and access cell identification of both parties of the communication.

[0269] In one embodiment, the satellite information includes at least one of ephemeris information, orbit, and satellite identification.

[0270] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0271] Send an interaction request to the 5GC network element to confirm whether the candidate AGW is available.

[0272] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0273] An address allocation request message is sent to the candidate AGW network element; the address allocation request message is used to instruct the candidate AGW network element to send a response message to the P-CSCF after completing the address allocation; the response message carries the allocated address.

[0274] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0275] receiving a first conference initialization protocol SIP message sent by a user terminal, and selecting a ground AGW for the user terminal; the ground AGW is used to allocate an output address to the user terminal; and

[0276] The first SIP message is forwarded to other IMS network elements, and the original address of the user terminal is replaced with the output address allocated to the user terminal by the ground AGW.

[0277] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0278] In response to receiving the newly allocated address, a second conference initialization protocol SIP message is sent to the user terminal; the second SIP message is used to inform the user terminal of the new address allocated to the user terminal by the candidate AGW.

[0279] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0280] In response to receiving the newly allocated address, a third conference initialization protocol SIP message is sent to other IMS network elements; the third SIP message is used to notify the candidate AGW of the newly allocated address.

[0281] In one embodiment, when the computer program is executed by a processor, the following steps are further implemented:

[0282] Based on the satellite information, selecting an AGW deployed on a regenerative mode satellite currently accessed by the user terminal as a candidate AGW; and / or,

[0283] The onboard AGW closest to the regenerative mode satellite accessed by the user terminal is selected as the candidate AGW.

[0284] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory or optical memory, etc. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0285] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0286] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A method for reselecting an access gateway, the method being applied to a P-CSCF (Proxy-Call Session Control Function), the method comprising: During the multimedia subsystem IMS session establishment process, an AGW (Access Gateway) reselection operation is performed.

2. The method according to claim 1, wherein The method further comprises: Determine whether to execute the UE-satellite-UE service based on the acquired access information of the two call parties.

3. The method according to claim 2, further comprising: Based on whether the UE-satellite-UE service is executed, it is determined whether to trigger the AGW reselection operation.

4. The method according to claim 3, wherein: In a case where a terrestrial AGW is currently selected as a candidate AGW, determining whether to trigger an AGW reselection operation based on whether a UE-satellite-UE service is performed includes: In response to not performing the UE-satellite-UE service, not triggering a reselection operation of the AGW; and In response to the execution of the UE-satellite-UE service, an AGW reselection operation is triggered, the currently selected ground AGW is released and the onboard AGW is reselected as the candidate AGW.

5. The method according to claim 3, wherein In the case where the on-board AGW is currently selected as the candidate AGW, determining whether to trigger the AGW reselection operation based on whether the UE-satellite-UE service is performed includes: In response to not performing the UE-satellite-UE service, triggering an AGW reselection operation, releasing the currently selected onboard AGW and reselecting a terrestrial AGW as the candidate AGW; and In response to the execution of the UE-satellite-UE service, no reselection operation of the AGW is triggered.

6. The method according to claim 4 or 5, wherein: The method further comprises: One or more candidate AGWs are determined based on satellite information and / or access information of both parties of the call.

7. The method according to any one of claims 2 to 6, wherein: The access information of the two parties in the call includes at least one of satellite identification information, access type, and access cell identification of the two parties.

8. The method according to claim 6, wherein: The satellite information includes at least one of ephemeris information, orbit, and satellite identification.

9. The method according to claim 6, wherein: The method further comprises: Send an interaction request to the 5GC network element; the interaction request is used to confirm whether the candidate AGW is available.

10. The method according to claim 9, wherein: The method further comprises: An address allocation request message is sent to the candidate AGW network element; the address allocation request message is used to instruct the candidate AGW network element to send a response message to the P-CSCF after completing the address allocation; the response message carries the allocated address.

11. The method according to claim 1, wherein The method further comprises: receiving a first conference initialization protocol SIP message sent by a user terminal, and selecting a ground AGW for the user terminal; the ground AGW is used to allocate an output address to the user terminal; and The first SIP message is forwarded to other IMS network elements, and the original address of the user terminal is replaced with the output address allocated to the user terminal by the ground AGW.

12. The method according to claim 1 or 10, wherein: The method further comprises: In response to receiving the newly allocated address, a second Conference Initialization Protocol (SIP) message is sent to the user terminal; the second SIP message is used to inform the user terminal of the new address allocated to the user terminal by the candidate AGW.

13. The method according to claim 1 or 10, wherein: The method further comprises: In response to receiving the newly allocated address, a third conference initialization protocol SIP message is sent to other IMS network elements; the third SIP message is used to notify the candidate AGW of the newly allocated address.

14. The method according to claim 13, wherein The third SIP message carries identification information of the satellite deployed by the candidate AGW.

15. The method according to claim 6 or 8, wherein The determining one or more candidate AGWs based on satellite information includes: Based on the satellite information, selecting an AGW deployed on a regenerative mode satellite currently accessed by the user terminal as a candidate AGW; and / or, The onboard AGW closest to the regenerative mode satellite accessed by the user terminal is selected as the candidate AGW.

16. An access gateway reselection device, the device being applied to a P-CSCF, the device comprising: The execution module is used to execute the AGW reselection operation during the multimedia subsystem IMS session establishment process.

17. A communication device comprising a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method according to any one of claims 1 to 15 when executing the computer program.

18. A computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 15 are implemented.

19. A computer program product comprising a computer program, which, when executed by a processor, implements the steps of the method according to any one of claims 1 to 15.

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