Method and apparatus for multicast handover data transmission, and storage medium

Abstract

The disclosure provides a multicast switching data transmission method and device, and a storage medium, relates to the technical field of mobile communication, and can be applied to the scene that a source base station and a target base station both receive same multicast messages from a same MB-UPF. The multicast switching data transmission method comprises the following steps: receiving a switching request message sent by the source base station, wherein the switching request message comprises a terminal identifier of a first to-be-switched terminal, an MBS session ID and a multicast caching instruction; in response to the PDU having the MBS session ID, caching a multicast data packet corresponding to the MBS session ID based on the multicast caching instruction; and in response to being connected with the first to-be-switched terminal, sending the multicast data packet to the first to-be-switched terminal. The technical scheme of the embodiment of the disclosure can improve the network resource utilization rate and reduce the probability of data packet loss.

Description

Technical Field

[0001] This disclosure relates to the field of mobile communication technology, and more specifically, to a data transmission method for multicast switching, a data transmission apparatus for multicast switching, and a computer-readable storage medium. Background Technology

[0002] The 5G (5th Generation Mobile Communication Technology) standard within the 3GPP (3rd Generation Partnership Project) includes two data transfer methods for multicast session handover: Xn handover and N2 handover. Taking Xn handover as an example... Figure 1 The schematic diagram illustrates the principle of Xn switching in the related technology, such as... Figure 1 As shown, when terminal device 13 moves from the coverage area of ​​source base station 11 to the coverage area of ​​target base station 12, due to the handover, some data packets of terminal device 13 are transmitted from source base station 11 to target base station 12 for buffering. After terminal device 13 joins the multicast session of target base station 12 through target base station 12, target base station 12 then sends the buffered data packets to terminal device 13.

[0003] However, if both the source base station and the target base station receive the same multicast message from the same MB-UPF (Multicast Broadcast User Plane Function), the data packet transmitted from the source base station to the target base station has already been received by the target base station. This results in the duplicate transmission of data packets, wasting network resources.

[0004] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] The purpose of this disclosure is to provide a data transmission method, a data transmission device, and a computer-readable storage medium for multicast switching, thereby overcoming, to at least some extent, the problem of low network resource utilization in related technologies.

[0006] Other features and advantages of this disclosure will become apparent from the following detailed description, or may be learned in part from practice of this disclosure.

[0007] According to a first aspect of the present disclosure, a data transmission method for multicast handover is provided, applied to a target base station, the data transmission method comprising:

[0008] The system receives a handover request message sent by the source base station, the handover request message including the terminal identifier of the first terminal to be handed over, the multicast service MBS session identity identifier ID, and the multicast cache instruction;

[0009] In response to the existence of the MBS session ID in the Protocol Data Unit (PDU), the multicast data packet corresponding to the MBS session ID is cached based on the multicast caching instruction;

[0010] In response to connecting to the first terminal to be switched, the multicast data packet is sent to the first terminal to be switched.

[0011] In some example embodiments of this disclosure, based on the foregoing scheme, while caching the multicast data packets corresponding to the MBS session ID based on the multicast caching instruction, the data transmission method further includes:

[0012] Record the terminal identifier and first time of the first terminal to be switched, where the first time is the cache start time corresponding to the first terminal to be switched.

[0013] In some example embodiments of this disclosure, based on the foregoing scheme, in response to connecting to the first terminal to be switched, the data transmission method further includes:

[0014] Record a second time, which is the time when the first terminal to be switched successfully connects to the target base station;

[0015] Sending the multicast data packet to the first terminal to be switched includes:

[0016] The multicast data packets cached between the first time and the second time are sent to the first terminal to be switched.

[0017] In some example embodiments of this disclosure, based on the foregoing scheme, after sending the multicast data packet to the first terminal to be switched, the data transmission method further includes:

[0018] Identify the non-shared multicast data packets cached between the first time and the second time.

[0019] Delete the non-shared multicast data packet.

[0020] In some example embodiments of this disclosure, based on the foregoing scheme, determining the non-shared multicast data packets cached between the first time and the second time includes:

[0021] Obtain a third time, which is the time when the second terminal to be switched successfully connects to the target base station;

[0022] In response to the third time being greater than the first time and less than the second time, the multicast data packets cached between the first time and the third time are determined as the non-shared multicast data packets.

[0023] In some example embodiments of this disclosure, based on the foregoing scheme, in response to N2 handover, the receiving of the handover request message sent by the source base station includes:

[0024] The handover request message is received from the source base station sequentially through the source access and mobility management function unit (AMF) and the target AMF.

[0025] According to a second aspect of the present disclosure, a data transmission method for multicast handover is provided, applied to a source base station, the data transmission method comprising:

[0026] Obtain the measurement report of the first terminal to be switched;

[0027] In response to the measurement report indicating that a base station handover is required, a handover request message is sent to the target base station. The handover request message includes the terminal identifier of the first terminal to be handed over, the multicast service MBS session identity identifier ID, and the multicast cache instruction.

[0028] The handover request message is used to instruct the target base station to cache the multicast data packet corresponding to the MBS session ID based on the multicast caching instruction when the Protocol Data Unit (PDU) contains the MBS session ID, and to send the multicast data packet to the first terminal to be handed over in response to the connection with the first terminal to be handed over.

[0029] According to a third aspect of the present disclosure, a data transmission apparatus for multicast handover is provided, applied to a target base station, the data transmission apparatus comprising:

[0030] The receiving module is used to receive a handover request message sent by the source base station. The handover request message includes the terminal identifier of the first terminal to be handed over, the multicast service MBS session identity identifier ID, and the multicast buffer instruction.

[0031] The caching module is used to cache the multicast data packets corresponding to the MBS session ID based on the multicast caching instruction in response to the existence of the MBS session ID in the Protocol Data Unit (PDU).

[0032] The first sending module is configured to send the multicast data packet to the first terminal to be switched in response to a connection with the first terminal to be switched.

[0033] According to a fourth aspect of the present disclosure, a data transmission apparatus for multicast handover is provided, applied to a source base station, the data transmission apparatus comprising:

[0034] The acquisition module is used to acquire the measurement report of the first terminal to be switched.

[0035] The second sending module is used to send a handover request message to the target base station in response to the measurement report indicating that a base station handover is required. The handover request message includes the terminal identifier of the first terminal to be handed over, the multicast service MBS session identity identifier ID, and the multicast cache instruction.

[0036] The handover request message is used to instruct the target base station to cache the multicast data packet corresponding to the MBS session ID based on the multicast caching instruction when the Protocol Data Unit (PDU) contains the MBS session ID, and to send the multicast data packet to the first terminal to be handed over in response to the connection with the first terminal to be handed over.

[0037] According to a fifth aspect of the present disclosure, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the data transmission method for multicast switching according to any one of the preceding claims.

[0038] The multicast handover data transmission method, multicast handover data transmission device, and computer-readable storage medium provided in this disclosure embodiment include a target base station receiving a handover request message sent by a source base station. The handover request message includes a terminal identifier of the first terminal to be handed over, an MBS (Multicast Broadcast Service) session ID (Identity Document), and a multicast caching instruction. When the PDU (Protocol Data Unit) contains the MBS session ID, it can be determined that the target base station and the source base station are receiving the same multicast message from the same MB-UPF. At this time, the target base station can cache the multicast data packet corresponding to the MBS session ID based on the multicast caching instruction in the handover request message, and send the multicast data packet to the first terminal to be handed over after the target base station successfully connects with the first terminal to be handed over. On the one hand, when both the source base station and the target base station receive the same multicast message from the same MB-UPF, the source base station can notify the target base station to cache the same multicast data packets. After the terminal to be handed over successfully accesses the target base station, the source base station will transmit the cached multicast data packets to the terminal to be handed over. The source base station and the target base station will no longer transmit multicast data packets, thereby saving network resources and improving the utilization rate of network resources. On the other hand, since the multicast data packets are no longer transmitted from the source base station to the target base station, the probability of data packet loss caused by handover is greatly reduced, and out-of-order arrival of data packets due to transmission delay is also avoided, thus improving network handover performance.

[0039] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0040] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. In the drawings:

[0041] Figure 1 The schematic diagram illustrates the principle of Xn switching in the prior art;

[0042] Figure 2 The schematic diagram illustrates a data transmission method for multicast switching according to some embodiments of the present disclosure;

[0043] Figure 3 The illustration shows a schematic diagram of a data transmission method flow for multicast switching according to some embodiments of the present disclosure;

[0044] Figure 4 This schematic diagram illustrates the working principle of a target base station maintenance buffer according to some embodiments of the present disclosure;

[0045] Figure 5 A schematic diagram of a cache record table of a target base station according to some embodiments of the present disclosure is shown.

[0046] Figure 6 The illustration shows a schematic diagram of another data transmission method flow for multicast switching according to some embodiments of the present disclosure;

[0047] Figure 7 The illustration shows a schematic diagram of a data transmission method flow for multicast switching according to some embodiments of the present disclosure;

[0048] Figure 8 The illustration shows a schematic diagram of a data transmission method flow for multicast switching according to some embodiments of the present disclosure;

[0049] Figure 9 The schematic diagram illustrates the structure of a data transmission apparatus for multicast switching according to some embodiments of the present disclosure;

[0050] Figure 10 The schematic diagram illustrates the structure of a data transmission apparatus for multicast switching according to some embodiments of the present disclosure;

[0051] Figure 11A schematic diagram of a computer-readable storage medium according to some embodiments of the present disclosure is shown.

[0052] In the accompanying drawings, the same or corresponding reference numerals indicate the same or corresponding parts. Detailed Implementation

[0053] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be more thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art.

[0054] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0055] Furthermore, the accompanying drawings are for illustrative purposes only and are not necessarily drawn to scale. The block diagrams shown in the drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0056] In this embodiment of the disclosure, when both the source base station and the target base station receive the same multicast message from the same MB-UPF, the source base station can notify the target base station to cache the same multicast data packets through a handover request message. The target base station can serve multiple terminals that are switching simultaneously through an efficient caching mechanism, and finally transmit the cached data packets to the corresponding terminal after the handover.

[0057] Based on the inventive concept of this disclosure, all network elements, base stations and terminals in the network system must support multicast functionality. Moreover, during terminal handover, both the source base station and the target base station receive the same multicast message from the same MB-UPF, meaning that multiple terminals are distributed under the source base station and the target base station and simultaneously receive multicast messages.

[0058] For example, Figure 2 A schematic diagram illustrating a data transmission method for multicast switching according to some embodiments of the present disclosure is shown, with reference to... Figure 2As shown, the MB-UPF sends multicast data packets to the UPF (User Plane Function), which then forwards the multicast data packets to both the source base station 21 and the target base station 22. When terminal 23 moves from the source base station 21 to the target base station 22, if the source base station 21 determines, based on the measurement report reported by terminal 23, that a handover to the target base station 22 is necessary, it sends a handover request message to the target base station 22. This message carries the terminal identifier of terminal 23, the MBS session ID, and a multicast caching instruction to notify the target base station 22 to cache the same multicast data packets. When terminal 23 successfully connects to the target base station 22, the target base station 22 first sends the cached multicast data packets to terminal 23, and then continuously sends subsequent data from the UPF to terminal 23. During the base station handover process, the source base station 21 no longer transmits data packets to the target base station 22, conserving network resources.

[0059] In this example embodiment, a data transmission method for multicast handover is first provided, which can be applied to a target base station. Figure 3 The illustration schematically depicts a data transmission method flow for multicast switching according to some embodiments of the present disclosure. (Reference) Figure 3 As shown, the data transmission method for multicast switching may include the following steps:

[0060] Step S310: Receive a handover request message sent by the source base station. The handover request message includes the terminal identifier of the first terminal to be handed over, the MBS session ID, and the multicast buffer instruction.

[0061] Step S320: In response to the existence of MBS session ID in PDU, cache the multicast data packet corresponding to MBS session ID based on the multicast caching instruction;

[0062] In step S330, in response to connecting to the first terminal to be switched, a multicast data packet is sent to the first terminal to be switched.

[0063] According to the data transmission method for multicast handover in this example embodiment, when both the source base station and the target base station receive the same multicast message from the same MB-UPF, the source base station can notify the target base station to cache the same multicast data packets. After the terminal to be handed over successfully accesses the target base station, the source base station transmits the cached multicast data packets to the terminal to be handed over. The source base station and the target base station no longer transmit multicast data packets, thereby saving network resources and improving the utilization rate of network resources. On the other hand, since the multicast data packets are no longer transmitted from the source base station to the target base station, the probability of data packet loss caused by handover is greatly reduced, and out-of-order arrival of data packets due to transmission delay is also avoided, thus improving network handover performance.

[0064] The data transmission method for multicast switching in this example embodiment will be further explained below.

[0065] In step S310, a handover request message sent by the source base station is received.

[0066] The handover request message may include, but is not limited to, the terminal identifier of the first terminal to be handed over, the MBS session ID, and the multicast buffer instruction.

[0067] In one example embodiment, taking Xn handover as an example, when the first terminal to be handed over moves from the source base station to the target base station, the source base station determines that a base station handover is required based on the measurement report reported by the first terminal to be handed over. It can then send an Xn handover request message to the target base station, which carries the terminal identifier of the first terminal to be handed over, as well as the MBS session ID and multicast buffer instructions.

[0068] In one example embodiment, taking N2 handover as an example, the source base station initiates N2 handover when it determines that a base station handover is required based on the measurement report sent by the first terminal to be handed over. The target base station receives handover request messages sent sequentially by the source base station through the source AMF (Access and Mobility Management Function) and the target AMF.

[0069] Specifically, the source base station can send a Handover Required message to the source AMF. After receiving the message, the source AMF sends a Namf_Communication_CreateUEContext Request message to the target AMF to request the creation of terminal device context information. Based on this message, the target AMF updates the PDU session context of the SMF (Session Management Function). Then, the target AMF can send a Handover Request message to the target base station. The Handover Required message, Namf_Communication_CreateUEContext Request message, and Handover Request message carry the terminal identifier of the first terminal to be handed over, as well as the MBS session ID and multicast buffer instructions. In this way, the terminal identifier of the first terminal to be handed over, as well as the MBS session ID and multicast buffer instructions, are sequentially sent from the source base station to the target base station through signaling and messages in the source base station, source AMF, target AMF, and target base station. The target base station receives this information.

[0070] Step S320: In response to the existence of MBS session ID in the PDU, cache the multicast data packet corresponding to the MBS session ID based on the multicast caching instruction.

[0071] After receiving the terminal identifier of the first terminal to be handed over, along with the MBS session ID and multicast caching instruction, the target base station checks whether its PDU contains the MBS session ID. If it does, it returns a handover request success message to the source base station and begins caching the multicast data packets corresponding to the MBS session ID based on the multicast caching instruction. If it does not, it enters the standard Xn handover or X2 handover process and does not execute the subsequent processes of the scheme provided in this embodiment.

[0072] For example, for Xn handover, the target base station can directly reply with a handover request success message to the source base station. For N2 handover, the target base station can sequentially send the handover request success message from the target base station to the source base station through the target base station, the target AMF, the source AMF, and existing handover signaling or messages in the source base station.

[0073] In step S330, in response to connecting to the first terminal to be switched, a multicast data packet is sent to the first terminal to be switched.

[0074] Once the first terminal to be handed over moves to the target base station and successfully connects to the target base station, the target base station can send the cached multicast data packets to the first terminal to be handed over, and then continuously send subsequent data to the first terminal to be handed over, thus completing the handover of the first terminal to be handed over from the source base station to the target base station.

[0075] In one exemplary embodiment, while caching multicast data packets corresponding to the MBS session ID based on multicast caching instructions, the target base station may also record the terminal identifier and a first time of the first terminal to be handed over, wherein the first time is the caching start time corresponding to the first terminal to be handed over. The target base station is responsible for maintaining the cache area and cache records.

[0076] When the target base station successfully connects with the first terminal to be handed over, the target base station can record a second time, which is the time when the first terminal to be handed over successfully connects to the target base station. Correspondingly, the target base station sending multicast data packets to the first terminal to be handed over may include sending multicast data packets buffered between the first and second times to the first terminal to be handed over.

[0077] For example, after the target base station sends the multicast data packet to the first terminal to be handed over, it may also include the step of deleting the multicast data packet related to the first terminal to be handed over from the buffer. Specifically, it may include: determining the non-shared multicast data packet cached between the first time and the second time; and deleting the non-shared multicast data packet.

[0078] The process of determining the cached non-shared multicast data packets between the first time and the second time may include: obtaining a third time, which is the time when the second terminal to be switched successfully connects to the target base station; and in response to the third time being greater than the first time and less than the second time, determining the cached multicast data packets between the first time and the third time as non-shared multicast data packets.

[0079] For example, taking Xn switching as an example, combined with Figure 2 As shown, the MB-UPF sends the multicast data packet to the UPF, and the UPF simultaneously sends the multicast data packet to both the source base station 21 and the target base station 22.

[0080] Assuming that at time T0, terminal 23 moves from source base station 21 to target base station 22, source base station 21 obtains the measurement report of terminal 23 and determines that base station handover needs to be performed based on the measurement report. Then, during the handover preparation phase, source base station 21 sends a first Xn handover request message to target base station 22. The first Xn handover request message carries the terminal identifier U1 of terminal 23, as well as MBS session ID and first multicast buffer instruction, but is not limited to these.

[0081] Assuming that at time T1, the target base station 22 receives the first Xn handover request message, checks that it has the MBS session ID carried in the first Xn handover request message, then returns a handover request success message to the source base station 21, and at the same time starts caching any PDU session message in the multicast corresponding to the MBS session ID, and records the terminal identifier U1 and the time T1 when caching starts.

[0082] Assuming that at time T2, terminal 24 also moves from source base station 21 to target base station 22, source base station 21 obtains the measurement report of terminal 24 and determines that base station handover needs to be performed based on the measurement report. Then, during the handover preparation phase, source base station 21 sends a second Xn handover request message to target base station 22. The second Xn handover request message may carry the terminal identifier U2 of terminal 24, MBS session ID and second multicast buffer instruction, but is not limited to these.

[0083] Assuming that at time T3, the target base station 22 receives the second Xn handover request message, checks that it has the MBS session ID carried in the second Xn handover request message, and then returns a request success message to the source base station 21. The target base station 22 finds that it is caching multicast information at this time, so it continues the current caching process and records the terminal identifier U2 of the terminal 24 and the time T3 when the terminal 24 started caching.

[0084] Suppose that at time T4, terminal 23 accesses target base station 22. At this time, target base station 22 will send a copy of the multicast data packets cached during the time period T1 to T4 to terminal 23.

[0085] During the above process, the target base station 22 needs to maintain the cache area and cache records. Figure 4 This schematic diagram illustrates the working principle of a target base station maintenance buffer according to some embodiments of the present disclosure, such as... Figure 4 As shown, at time T3, the target base station 22 receives the second Xn handover request message. Based on this second Xn handover request message, it needs to start caching the corresponding multicast data packets for terminal 24 (terminal identifier denoted as U2). However, at this time, based on the movement of terminal 23 (terminal identifier denoted as U1), multicast data packets are already being cached, and terminal 24 and terminal 23 are receiving the same multicast data packets. At this time, it is only necessary to continue the current caching process, and there is no need to open a new cache area for terminal 24. Terminal 23 and terminal 24 can share the multicast data packets cached in the time period T3 to T4. This part of the multicast data packets can be called shared multicast data packets. Correspondingly, the multicast data packets cached in the time period T1 to T3 can be called non-shared multicast data packets.

[0086] Figure 5 A schematic diagram illustrating a cache record table of a target base station according to some embodiments of the present disclosure is shown, such as... Figure 5 As shown, this cache record table can record information such as the terminal identifier, MBS session ID, and cache start time of the terminal being served.

[0087] After sending a copy of the multicast data packets cached during time period T1 to T4 to terminal 23, target base station 22 can clear the multicast data packets cached during time period T1 to T3 and clear the cache records of terminal 23. The multicast data packets cached during time period T3 to T4 and subsequent cached multicast data packets can be used for handover of terminal 24. For example, if terminal 24 accesses target base station 22 at time T5, target base station 22 can send a copy of the multicast data packets cached during time period T3 to T5 to terminal 24.

[0088] This packet caching method can serve multiple terminals with minimal resource consumption. During multicast switching, if a terminal is in shared MBS traffic transmission mode, it also needs to enter independent MBS traffic transmission mode before switching. Therefore, this packet caching method can be applied to both independent MBS traffic transmission scenarios and shared MBS traffic transmission scenarios.

[0089] Based on the same inventive concept. Figure 6 This illustration schematically depicts another data transmission method for multicast handover according to some embodiments of the present disclosure, which can be applied to a source base station. For example... Figure 6 As shown, the method may include the following steps:

[0090] In step S610, the measurement report of the first terminal to be switched is obtained;

[0091] In step S620, in response to the measurement report indicating that a base station handover is required, a handover request message is sent to the target base station. The handover request message includes the terminal identifier of the first terminal to be handed over, the MBS session ID, and a multicast caching instruction. The handover request message is used to instruct the target base station to cache the multicast data packets corresponding to the MBS session ID based on the multicast caching instruction when the PDU has an MBS session ID, and in response to connecting with the first terminal to be handed over, to send the multicast data packets to the first terminal to be handed over.

[0092] Based on the above Figure 3 and Figure 6 The data transmission method for multicast switching in the corresponding embodiment will be further illustrated below using Xn switching and X2 switching as examples.

[0093] Figure 7 This illustration schematically depicts a data transmission method flow for multicast switching according to some embodiments of the present disclosure, with reference to... Figure 7 As shown, the data transmission method for multicast switching, taking Xn switching as an example, may include the following steps S701 to S711.

[0094] In step S701, the terminal sends a measurement report to the source base station.

[0095] The source base station receives a measurement report from terminal U1 and determines that a base station handover is required based on the measurement report. At this point, the handover preparation phase begins.

[0096] In step S702, the source base station sends an Xn handover request message to the target base station.

[0097] The source base station sends an Xn handover request message to the target base station. This Xn handover request message includes, but is not limited to, the terminal identifier of terminal U1, the MBS session ID, and the multicast buffer instruction. For example, the terminal identifier may be 5G-GUTI (Globally Unique Temporary UE Identity), the MBS session ID may be MBSSession ID = 1001, and the multicast buffer instruction may be Broadcast Buffer Indicator = true.

[0098] In step S703, the target base station, in response to the existence of the MBS session ID, caches the corresponding multicast data packets and records the cached data.

[0099] After receiving the Xn handover request message from the source base station, the target base station finds that its own PDU session's MBS session ID is the same as the MBS session ID carried in the Xn handover request message. For example, if it detects that the MBS session ID of PDU session ID = 101 is also 1001, it indicates that the target base station and the source base station are receiving the same multicast message from the same MB-UPF. At this time, the target base station immediately begins to copy subsequent messages of this session to the buffer and inserts a buffer record for terminal U1 into the buffer record table. This record can contain the terminal identifier, MBS session ID, and buffer start time of terminal U1. For example, the inserted buffer record might be: Terminal identifier 5G-GUTI1 = 4600312345678123456, MBS session ID1 = 1001, and buffer start time TimeStart1 = 10000. Simultaneously, the target base station replies to the source base station with a handover request success message. This success message includes, but is not limited to, the multicast buffer acknowledgment character Broadcast Buffer Ack, for example, Broadcast Buffer Ack = 1.

[0100] After the source base station receives the handover request success message returned by the target base station, it cancels the data transmission from the source base station to the target base station during the handover execution phase and stops transmitting data to the target base station. The handover process then proceeds to step S704.

[0101] In step S704, the target base station sends an N2 path switch request message to the AMF.

[0102] In step S705, the AMF sends an UpdateSMContext request message Nsmf_PDUSession_UpdateSMContext Request to the SMF.

[0103] In step S706, the SMF sends an N4 Session Modification Request to the UPF.

[0104] In step S707, the UPF confirms the N4 session modification request and returns an N4 session modification response message (N4Session Modification Response) to the SMF.

[0105] In step S708, after terminal U1 moves to the target base station and successfully connects, the target base station first sends the multicast data packet corresponding to terminal U1 in the buffer to terminal U1, and records the time when terminal U1 accesses the target base station, for example, this time is recorded as TimeEnd1 = 10005. Subsequently, the target base station can continuously send multicast data packets sent by UPF to terminal U1.

[0106] In step S709, the target base station identifies and deletes non-shared multicast data packets from the buffer.

[0107] For example, if the cache start time for terminal U1 is TimeStart1 = 10000 and the access time to the target base station is TimeEnd1 = 10005, after the target base station sends multicast data for the period from 10001 to 10005 to terminal U1, it determines the non-shared multicast data packets within that period. Suppose that at some point during the period from 10001 to 10005, such as at 10004, the target terminal receives an Xn handover request message from the source base station for terminal U2, and determines that the multicast data packets cached by terminal U2 are based on this Xn handover request message. Then, terminals U1 and U2 share the multicast data packets cached during the period from 10004 to 10005, and the multicast data packets cached during the period from 10001 to 10004 are non-shared multicast data packets. The target base station then deletes the non-shared multicast data packets from its cache.

[0108] In step S710, the SMF sends an UpdateSMContext Response message Nsmf_PDUSession_UpdateSMContext Response to the AMF.

[0109] In step S711, the AMF returns an N2 Path Switch RequestAck message to the target base station, completing the multicast Xn handover process.

[0110] Figure 8 This illustration schematically depicts a data transmission method flow for multicast switching according to some embodiments of the present disclosure, with reference to... Figure 8 As shown, the data transmission method for multicast switching, taking N2 switching as an example, may include the following steps S801 to S821.

[0111] In step S801, the source base station receives the measurement report sent by the terminal.

[0112] In step S802, when the source base station determines that a base station handover is required based on the measurement report, it initiates an N2 handover and sends a handover request message Handover Required to the source AMF.

[0113] In step S803, the source AMF sends a request message Namf_Communication_CreateUEContext Request to the target AMF to create terminal context information.

[0114] In step S804, the target AMF and SMF establish an update PDU session context channel Nsmf_PDUSession_UpdateSMContext.

[0115] In step S805, the target AMF sends a Handover Request message to the target base station.

[0116] The Handover Required message in step S802, the Namf_Communication_CreateUEContext Request message in step S803, and the Handover Request message in step S805 all carry the terminal identifier, MBS session ID, and multicast buffer instruction, but are not limited to these. For example, the terminal identifier could be 5G-GUTI = 4601012345678123456, the MBS session ID could be MBS Session ID = 1002, and the multicast buffer indicator could be Broadcast Buffer Indicator = true.

[0117] In step S806, the target base station, in response to the existence of the MBS session ID, caches the corresponding multicast data packets and records the cached data.

[0118] Upon receiving a Handover Request message, if the target base station detects that its own PDU session's MBS session ID is the same as the MBS session ID carried in the Handover Request (e.g., both are 1002), it immediately begins copying subsequent messages of that session to the cache and inserts a cache record for the terminal into the cache record table. This record can include the terminal identifier, MBS session ID, and cache start time. For example, the recorded cache record might be: Terminal Identifier 5G-GUTI = 4601012345678123456, MBS Session ID = 1002, Cache Start Time TimeStart2 = 20000. Simultaneously, the target base station replies with a handover request confirmation message to the source base station, which may include steps S807 to S814.

[0119] In step S807, the target base station sends a Handover Request Ack message to the target AMF.

[0120] In step S808, the target AMF sends an UpdateSMContext request message Nsmf_PDUSession_UpdateSMContext Request to the SMF.

[0121] In step S809, the SMF sends an N4 Session Modification Request to the UPF.

[0122] In step S810, the UPF confirms the N4 session modification request and returns an N4 session modification response message (N4Session Modification Response) to the SMF.

[0123] In step S811, the SMF sends an UpdateSMContext Response message Nsmf_PDUSession_UpdateSMContext Response to the target AMF.

[0124] In step S812, the target AMF sends a Namf_Communication_CreateUEContext Response message to the source AMF.

[0125] In step S813, the source AMF sends a handover command to the source base station.

[0126] In step S814, the source base station sends a Handover Command to the terminal.

[0127] The Handover Request Ack message in step S807, the Namf_Communication_CreateUEContext Response message in step S812, and the Handover Command instruction in step S813 include, but are not limited to, the multicast buffer acknowledgment character Broadcast Buffer Ack, such as Broadcast Buffer Ack = 1.

[0128] After the source base station receives the Handover Command and sends it to the terminal, the switching process proceeds to step S815, where the source base station no longer transmits data to the target base station, thus canceling the direct or indirect data transmission between the source base station and the target base station.

[0129] In step S815, after the terminal moves to the target base station and successfully connects, the terminal sends a Handover Confirm message to the target base station.

[0130] In step S816, the target base station sends a Handover Notify to the target AMF.

[0131] In step S817, the target AMF sends an UpdateSMContext request message Nsmf_PDUSession_UpdateSMContext Request to the SMF.

[0132] In step S818, the SMF requests the UPF to modify the N4 session, and the UPF replies to confirm the N4 session modification.

[0133] In step S819, the target base station first sends the multicast data packets corresponding to the terminal in the buffer to the terminal, and records the time when the terminal accesses the target base station, for example, this time is recorded as TimeEnd2 = 20005. Subsequently, the target base station can continuously send the multicast data packets subsequently sent by the UPF to the terminal.

[0134] In step S820, the target base station identifies and deletes non-shared multicast data packets from the buffer.

[0135] The target base station determines the non-shared multicast data packets between the terminal's buffer start time (TimeStart2) and the time when the terminal accesses the target base station (TimeEnd2), and then deletes these non-shared multicast data packets from the buffer. The method for determining non-shared multicast data packets can be found in [reference needed]. Figure 7 The description of step S709 in the corresponding embodiment will not be repeated here.

[0136] In step S821, the SMF sends an UpdateSMContext Response message (Nsmf_PDUSession_UpdateSMContext Response) to the target AMF, completing the multicast N2 handover process.

[0137] The multicast handover data transmission scheme provided in this disclosure is applied to scenarios where both the source base station and the target base station receive the same multicast message from the same MB-UPF. It effectively reduces the amount of data transmitted directly or indirectly between the source and target base stations during different types of handovers, conserving network resources while significantly reducing the probability of packet loss in data transmission between base stations. It also avoids out-of-order packet arrival due to transmission delays, thus improving network performance. Furthermore, the data packet caching method of the target base station in this disclosure can serve multiple terminals with minimal resource consumption. During multicast handover, if the terminal is in shared MBS traffic transmission mode, it needs to first enter independent MBS traffic transmission mode before handover. Therefore, this data packet caching method can be applied to both independent MBS traffic transmission scenarios and shared MBS traffic transmission scenarios.

[0138] Multicast services often serve a large number of terminals within a continuous area. In some demanding multicast scenarios, such as deterministic networks, URLLC (Ultra Reliable Low Latency Communication), and even multicast services in future 6G networks, the data transmission scheme for multicast handover provided in this disclosure can effectively improve the availability and reliability of data transmission during base station handover. Moreover, it can avoid problems such as incompatibility between base stations from different manufacturers and complex configurations, thus ensuring the normal operation of operator network services.

[0139] It should be noted that although the steps of the method in this disclosure are described in a specific order in the accompanying drawings, this does not require or imply that the steps must be performed in that specific order, or that all the steps shown must be performed to achieve the desired result. Additional or alternative steps may be omitted, multiple steps may be combined into one step, and / or a step may be broken down into multiple steps.

[0140] Furthermore, in the exemplary embodiments of this disclosure, a data transmission apparatus for multicast handover is also provided, which can be applied to a target base station. (Refer to...) Figure 9 As shown, the multicast switching data transmission device 900 may include a receiving module 910, a buffer module 920, and a first transmitting module 930. Wherein:

[0141] The receiving module 910 is used to receive a handover request message sent by the source base station. The handover request message includes the terminal identifier of the first terminal to be handed over, the MBS session ID, and the multicast buffer instruction.

[0142] The caching module 920 is used to cache the multicast data packets corresponding to the MBS session ID based on the multicast caching instruction in response to the existence of the MBS session ID in the PDU;

[0143] The first sending module 930 is used to send cached multicast data packets to the first terminal to be switched in response to a connection with the first terminal to be switched.

[0144] In an exemplary embodiment of this disclosure, based on the foregoing scheme, the data transmission device 900 for multicast switching may further include a first recording module, which may be used to record the terminal identifier and a first time of the first terminal to be switched, wherein the first time is the cache start time corresponding to the first terminal to be switched.

[0145] In an exemplary embodiment of this disclosure, based on the foregoing scheme, the data transmission device 900 for multicast handover may further include a second recording module, which may be used to record a second time in response to the connection between the target base station and the first terminal to be handed over, the second time being the time when the first terminal to be handed over successfully connects to the target base station;

[0146] The first sending module 930 can be specifically used to send the multicast data packets buffered between the first time and the second time to the first terminal to be switched.

[0147] In an exemplary embodiment of this disclosure, based on the foregoing scheme, the data transmission apparatus 900 for multicast switching may further include a determining module and a deleting module; wherein:

[0148] The determination module can be used to determine the non-shared multicast packets buffered between the first and second time points;

[0149] The delete module can be used to delete non-shared multicast packets.

[0150] In an exemplary embodiment of this disclosure, based on the foregoing scheme, the determining module can be specifically used to obtain a third time, and in response to the third time being greater than the first time and less than the second time, to determine the multicast data packets cached between the first time and the third time as non-shared multicast data packets, wherein the third time is the time when the second terminal to be switched successfully connects to the target base station.

[0151] In an exemplary embodiment of this disclosure, based on the foregoing scheme, in response to N2 handover, the receiving module 910 may be specifically used to receive handover request messages sent sequentially by the source base station through the source AMF and the target AMF.

[0152] In the exemplary embodiments of this disclosure, another data transmission apparatus for multicast handover is also provided, which can be applied to the source base station. (Refer to...) Figure 10 As shown, the multicast switching data transmission device 1000 may include an acquisition module 1010 and a second transmission module 1020. Wherein:

[0153] The acquisition module 1010 can be used to acquire the measurement report of the first terminal to be switched;

[0154] The second sending module 1020 can be used to send a handover request message to the target base station in response to the measurement report indicating that a base station handover is required. The handover request message includes the terminal identifier of the first terminal to be handed over, the MBS session ID, and a multicast caching instruction. The handover request message is used to instruct the target base station to cache the multicast data packets corresponding to the MBS session ID based on the multicast caching instruction when the PDU has an MBS session ID, and to send the multicast data packets to the first terminal to be handed over in response to the connection with the first terminal to be handed over.

[0155] The specific details of each module of the multicast switching data transmission device described in the above embodiments have been described in detail in the corresponding multicast switching data transmission methods, so they will not be repeated here.

[0156] It should be noted that although several modules or units of the data transmission apparatus for multicast switching have been mentioned in the detailed description above, this division is not mandatory. In fact, according to embodiments of this disclosure, the features and functions of two or more modules or units described above can be embodied in one module or unit. Conversely, the features and functions of one module or unit described above can be further divided and embodied by multiple modules or units.

[0157] Those skilled in the art will understand that various aspects of this disclosure can be implemented as a system, method, or program product. Therefore, various aspects of this disclosure can be embodied in the following forms: a completely hardware embodiment, a completely software embodiment (including firmware, microcode, etc.), or an embodiment combining hardware and software aspects, collectively referred to herein as a "circuit," "module," or "system."

[0158] Through the description of the above embodiments, those skilled in the art will readily understand that the exemplary embodiments of this disclosure can be implemented by software or by combining software with necessary hardware. Therefore, the technical solutions according to the embodiments of this disclosure can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (such as a CD-ROM, USB flash drive, external hard drive, etc.) or on a network, including several instructions to cause a computing device (such as a personal computer, server, terminal device, or network device, etc.) to execute the methods according to the embodiments of this disclosure.

[0159] In exemplary embodiments of this disclosure, a computer-readable storage medium is also provided, on which a program product capable of implementing the methods described above is stored. In some possible embodiments, various aspects of this disclosure may also be implemented as a program product including program code that, when the program product is run on a terminal device, causes the terminal device to perform the steps described in the "Exemplary Methods" section of this specification according to various exemplary embodiments of this disclosure.

[0160] refer to Figure 11As shown, a program product 1100 for implementing the data transmission method for multicast switching described above, according to an embodiment of the present disclosure, is described. This product may be a portable compact disc read-only memory (CD-ROM) and includes program code, and may run on a terminal device, such as a personal computer. However, the program product of the present disclosure is not limited thereto. In this document, a readable storage medium may be any tangible medium containing or storing a program that may be used by or in conjunction with an instruction execution system, apparatus, or device.

[0161] The program product may employ any combination of one or more readable media. A readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of readable storage media (a non-exhaustive list) include: an electrical connection having one or more wires, a portable disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination thereof.

[0162] Computer-readable signal media may include data signals propagated in baseband or as part of a carrier wave, carrying readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. A readable signal medium may also be any readable medium other than a readable storage medium, capable of sending, propagating, or transmitting programs for use by or in conjunction with an instruction execution system, apparatus, or device.

[0163] The program code contained on the readable medium may be transmitted using any suitable medium, including but not limited to wireless, wired, optical fiber, radio frequency (RF), or any suitable combination thereof.

[0164] Program code for performing the operations of this disclosure can be written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Java and C++, and conventional procedural programming languages ​​such as C or similar languages. The program code can execute entirely on the user's computing device, partially on the user's computing device, as a standalone software package, partially on the user's computing device and partially on a remote computing device, or entirely on a remote computing device or server. In cases involving remote computing devices, the remote computing device can be connected to the user's computing device via any type of network, including a local area network (LAN) or a wide area network (WAN), or it can be connected to an external computing device (e.g., via the Internet using an Internet service provider).

[0165] Furthermore, the above figures are merely illustrative of the processes included in the method according to exemplary embodiments of this disclosure and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0166] From the above description of the embodiments, those skilled in the art will readily understand that the exemplary embodiments described herein can be implemented by software or by combining software with necessary hardware. Therefore, the technical solutions according to the embodiments of this disclosure can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (such as a CD-ROM, USB flash drive, external hard drive, etc.) or on a network, including several instructions to cause a computing device (such as a personal computer, server, touch terminal, or network device, etc.) to execute the methods according to the embodiments of this disclosure.

[0167] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the claims.

[0168] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A data transmission method for multicast switching, characterized in that, Applied to a target base station, the data transmission method includes: The system receives a handover request message sent by the source base station, the handover request message including the terminal identifier of the first terminal to be handed over, the multicast service MBS session identity identifier ID, and the multicast cache instruction; In response to the existence of the MBS session ID in the Protocol Data Unit (PDU), the multicast data packet corresponding to the MBS session ID is cached based on the multicast caching instruction; In response to connecting with the first terminal to be switched, the multicast data packet is sent to the first terminal to be switched; the source base station and the target base station no longer transmit multicast data packets.

2. The data transmission method according to claim 1, characterized in that, While caching the multicast data packets corresponding to the MBS session ID based on the multicast caching instruction, the data transmission method further includes: Record the terminal identifier and first time of the first terminal to be switched, where the first time is the cache start time corresponding to the first terminal to be switched.

3. The data transmission method according to claim 2, characterized in that, In response to connecting to the first terminal to be switched, the data transmission method further includes: Record a second time, which is the time when the first terminal to be switched successfully connects to the target base station; Sending the multicast data packet to the first terminal to be switched includes: The multicast data packets cached between the first time and the second time are sent to the first terminal to be switched.

4. The data transmission method according to claim 3, characterized in that, After sending the multicast data packet to the first terminal to be switched, the data transmission method further includes: Identify the non-shared multicast data packets cached between the first time and the second time. Delete the non-shared multicast data packet.

5. The data transmission method according to claim 4, characterized in that, The step of determining the cached non-shared multicast data packets between the first time and the second time includes: Obtain a third time, which is the time when the second terminal to be switched successfully connects to the target base station; In response to the third time being greater than the first time and less than the second time, the multicast data packets cached between the first time and the third time are determined as the non-shared multicast data packets.

6. The data transmission method according to claim 1, characterized in that, In response to the N2 handover, the handover request message received from the source base station includes: The handover request message is received from the source base station sequentially through the source access and mobility management function unit (AMF) and the target AMF.

7. A data transmission method for multicast switching, characterized in that, Applied to the source base station, the data transmission method includes: Obtain the measurement report of the first terminal to be switched; In response to the measurement report indicating that a base station handover is required, a handover request message is sent to the target base station. The handover request message includes the terminal identifier of the first terminal to be handed over, the multicast service MBS session identity identifier ID, and the multicast cache instruction. The handover request message is used to instruct the target base station to cache the multicast data packet corresponding to the MBS session ID based on the multicast caching instruction when the protocol data unit (PDU) contains the MBS session ID, and to send the multicast data packet to the first terminal to be handed over in response to the connection; the source base station and the target base station no longer transmit multicast data packets.

8. A data transmission device for multicast switching, characterized in that, Applied to a target base station, the data transmission device includes: The receiving module is used to receive a handover request message sent by the source base station. The handover request message includes the terminal identifier of the first terminal to be handed over, the multicast service MBS session identity identifier ID, and the multicast buffer instruction. The caching module is used to cache the multicast data packets corresponding to the MBS session ID based on the multicast caching instruction in response to the existence of the MBS session ID in the Protocol Data Unit (PDU). The first sending module is configured to send the multicast data packet to the first terminal to be switched in response to a connection with the first terminal to be switched. In this case, multicast data packets are no longer transmitted between the source base station and the target base station.

9. A data transmission device for multicast switching, characterized in that, Applied to the source base station, the data transmission device includes: The acquisition module is used to acquire the measurement report of the first terminal to be switched. The second sending module is used to send a handover request message to the target base station in response to the measurement report indicating that a base station handover is required. The handover request message includes the terminal identifier of the first terminal to be handed over, the multicast service MBS session identity identifier ID, and the multicast cache instruction. The handover request message is used to instruct the target base station to cache the multicast data packet corresponding to the MBS session ID based on the multicast caching instruction when the Protocol Data Unit (PDU) contains the MBS session ID, and to send the multicast data packet to the first terminal to be handed over in response to the connection with the first terminal to be handed over. In this case, multicast data packets are no longer transmitted between the source base station and the target base station.

10. A computer-readable storage medium having a computer program stored thereon, the computer program, when executed by a processor, implementing the data transmission method for multicast switching as described in any one of claims 1 to 7.

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