Communication method and communication apparatus

Abstract

A communication method and a communication apparatus, which are capable of reducing the occupation of a communication link between a UPF network element and a base station, thereby improving data transmission performance. The method comprises: a UPF network element replicating received downlink data of a terminal to obtain a copy of the downlink data of the terminal, and respectively sending the downlink data of the terminal to a source access network device of the terminal and sending the copy of the downlink data of the terminal to a target access network device of the terminal.

Description

Communication methods and communication devices

[0001] This application claims priority to Chinese Patent Application No. 202510070413.5, filed on January 15, 2025, entitled "Communication Method and Communication Device", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of communications, and more particularly to communication methods and communication devices. Background Technology

[0003] In order to reduce the interruption delay caused by the handover during base station handover, dual active protocol stack (DAPS) handover is usually used.

[0004] During DAPS handover, the user plane function (UPF) network element sends downlink data to the source base station; after the source base station assigns a sequence number (SN) to the downlink data, it obtains the downlink data with the assigned SN; the source base station sends the downlink data with the assigned SN to the UPF network element, and the UPF network element forwards the downlink data to the target base station. That is, the communication link of downlink data involved in the handover process is UPF network element → source base station → UPF network element → target base station.

[0005] However, this method requires a large amount of communication link resources between the UPF network element and the base station, affecting the transmission performance of other data. Summary of the Invention

[0006] This application provides a communication method and a communication device that can reduce the occupancy of communication links between UPF network elements and base stations, and improve data transmission performance.

[0007] Firstly, a communication method is provided. This method can be executed by a UPF network element, a module applied to a UPF network element (e.g., a processor, chip, or chip system), or a logical node, logical module, or software capable of implementing all or part of the UPF network element functions. The method includes: receiving first data, the first data including downlink data from a terminal; sending the first data to a source access network device of the terminal; and sending a copy of the first data to a target access network device of the terminal.

[0008] Based on this scheme, the UPF network element can directly send a copy of the first data to the target access network device of the terminal, without the source access network device forwarding the data to the target access network device through the UPF network element. This allows the UPF network element to send the first data to the source access network device and the copy of the first data to the target access network device of the terminal respectively. In other words, the downlink data communication links involved in the handover process are UPF network element → source access network device and UPF network element → target access network device. Compared with the existing downlink data communication links, it can reduce the communication links used for downlink data transmission, that is, reduce the target access network device → UPF network element, and reduce the communication links used for downlink data transmission. This reduces the link overhead and communication link occupancy between the UPF network element and the access network device caused by forwarding during the handover process, reduces resource waste, and thus improves data transmission performance.

[0009] In one possible design, the method further includes: receiving second information, the second information being used to indicate a target access network device corresponding to the first data transmission channel, the first data transmission channel being used to transmit a copy of the first data.

[0010] Based on this design, the first data transmission channel can be used to transmit a copy of the first data to its corresponding target access network device. In other words, the second information can clearly indicate the target access network device to which the UPF network element sends the copy of the first data, making it easier for the UPF network element to find the correct peer when sending the copy of the first data and improving the accuracy of data transmission.

[0011] In one possible design, the method further includes: sending third information to the first core network element, the third information being used to indicate the UPF network element corresponding to the first data transmission channel.

[0012] Based on this design, the third information can clearly indicate the UPF network element corresponding to the copy used to send the first data, thereby facilitating the flexible management of the UPF network element corresponding to the first data transmission channel by the first core network element, enabling unified management of the first data transmission channel by the network, and improving the reliability of the communication system.

[0013] Secondly, a communication method is provided. This method can be executed by a first access network device, which is the source access network device of the terminal, or by a module (e.g., processor, chip, or chip system) applied to the first access network device, or by a logical node, logical module, or software capable of implementing all or part of the functions of the first access network device. The method includes: sending fourth information, which requests a UPF network element to send first data to the first access network device and to send a copy of the first data to the target access network device of the terminal.

[0014] In one possible design, the method further includes sending a fifth message and / or a sixth message, wherein the fifth message is used to indicate the sequence number of the copy of the first data, and the sixth message is used to instruct the UPF network element to begin sending a copy of the first data to the target access network device.

[0015] In one possible design, the method further includes receiving a seventh message, which indicates that the UPF network element is permitted to send a copy of the first data to the target access network device.

[0016] Thirdly, a communication method is provided. This method can be executed by a second access network device, which is the target access network device of the terminal; it can also be executed by a module (e.g., processor, chip, or chip system) applied to the second access network device; or it can be implemented by a logical node, logical module, or software capable of implementing all or part of the functions of the second access network device. The method includes: receiving a copy of first data, where the first data is downlink data of the terminal; and sending a copy of the first data to the terminal.

[0017] In one possible design, the method further includes: receiving fourth information, the fourth information being used to request the UPF network element to send first data to the first access network device and to send a copy of the first data to the target access network device of the terminal.

[0018] In one possible design, the method further includes: sending second information and / or seventh information, wherein the second information is used to indicate the target access network device corresponding to the first data transmission channel, the first data transmission channel is used to transmit a copy of the first data, and the seventh information is used to indicate that the UPF network element is allowed to send a copy of the first data to the target access network device.

[0019] In one possible design, the method further includes receiving fifth information, which indicates the sequence number of a copy of the first data.

[0020] Fourthly, this application provides a communication device. This communication device may include modules corresponding to the methods / operations / steps / actions described in the first aspect or any possible implementation of the first aspect. These modules may be hardware circuits, software, or a combination of hardware circuits and software.

[0021] In one design, the device may include a processing module and a communication module. The communication module is used to perform the sending and receiving actions in the method described in the first aspect or any possible implementation thereof, while the processing module is used to perform the processing actions involved in the method described in the first aspect or any possible implementation thereof.

[0022] Fifthly, this application provides a communication device. This communication device may include modules corresponding to the methods / operations / steps / actions described in the second aspect or any possible implementation thereof.

[0023] In one design, the device may include a processing module and a communication module. The communication module is used to perform the sending and receiving actions in the method described in the second aspect or any possible implementation thereof, while the processing module is used to perform the processing actions involved in the method described in the second aspect or any possible implementation thereof.

[0024] Sixthly, this application provides a communication device. This communication device may include modules corresponding to the methods / operations / steps / actions described in the third aspect or any possible implementation thereof.

[0025] In one design, the device may include a processing module and a communication module. The communication module is used to perform the sending and receiving actions in the method described in the third aspect or any possible implementation thereof, while the processing module is used to perform the processing actions involved in the method described in the third aspect or any possible implementation thereof.

[0026] A seventh aspect provides an apparatus including a processor, wherein instructions, when executed by the processor, cause a method as described in the first aspect or any possible implementation thereof to be implemented.

[0027] Optionally, the device may further include a storage medium that stores the instructions executed by the processor.

[0028] Eighthly, an apparatus is provided, including a processor, wherein instructions, when executed by the processor, cause a method as described in the second aspect or any possible implementation thereof to be implemented.

[0029] Optionally, the device may further include a storage medium that stores the instructions executed by the processor.

[0030] A ninth aspect provides an apparatus including a processor, wherein instructions, when executed by the processor, cause a method as described in the third aspect or any possible implementation thereof to be implemented.

[0031] Optionally, the device may further include a storage medium that stores the instructions executed by the processor.

[0032] In a tenth aspect, a chip is provided, including processing circuitry for running a program or instructions to cause the methods described in the first aspect or any possible implementation thereof to be implemented.

[0033] Optionally, the chip may further include a memory for storing programs or instructions.

[0034] Optionally, the chip may also include the transceiver circuit, or an input / output interface.

[0035] Eleventhly, a chip is provided, including processing circuitry for running programs or instructions to implement methods as described in the second aspect or any possible implementation thereof.

[0036] Optionally, the chip may further include a memory for storing programs or instructions.

[0037] Optionally, the chip may also include the transceiver circuit, or an input / output interface.

[0038] In a twelfth aspect, a chip is provided, including processing circuitry for running a program or instructions to implement a method as described in the third aspect or any possible implementation thereof.

[0039] Optionally, the chip may further include a memory for storing programs or instructions.

[0040] Optionally, the chip may also include the transceiver circuit, or an input / output interface.

[0041] In a thirteenth aspect, a computer-readable storage medium is provided, the computer-readable storage medium including instructions that, when executed by a processor, cause the method as described in the first aspect or any possible implementation thereof to be implemented.

[0042] In a fourteenth aspect, a computer-readable storage medium is provided, the computer-readable storage medium including instructions that, when executed by a processor, cause the method as described in the second aspect or any possible implementation thereof to be implemented.

[0043] In a fifteenth aspect, a computer-readable storage medium is provided, the computer-readable storage medium including instructions that, when executed by a processor, cause the method as described in the third aspect or any possible implementation thereof to be implemented.

[0044] In a sixteenth aspect, a computer program product is provided, the computer program product comprising computer program code or instructions that, when the computer program code or instructions are executed, cause the method as described in the first aspect or any possible implementation thereof to be implemented.

[0045] In a seventeenth aspect, a computer program product is provided, the computer program product comprising computer program code or instructions that, when the computer program code or instructions are executed, cause the method as described in the second aspect or any possible implementation thereof to be implemented.

[0046] Eighteenth aspect, a computer program product is provided, the computer program product including computer program code or instructions, which, when run, cause the method as described in the third aspect or any possible implementation thereof to be implemented.

[0047] Nineteenth aspect, a communication system is provided, the communication system comprising: means for performing the first aspect or any possible implementation thereof, means for performing the second aspect or any possible implementation thereof, and means for performing the third aspect or any possible implementation thereof.

[0048] It is understood that the technical effects of any of the second to nineteenth aspects of this application can be referred to the relevant content in the first aspect, and will not be repeated here. Attached Figure Description

[0049] Figure 1 is a schematic diagram of a quasi-fixed cell scenario according to an embodiment of this application;

[0050] Figure 2 is a schematic diagram of a mobile cell scenario according to an embodiment of this application;

[0051] Figure 3 is a flowchart of a contention-based four-step random access method according to an embodiment of this application;

[0052] Figure 4 is a flowchart of a non-contention-based four-step random access method according to an embodiment of this application;

[0053] Figure 5 is a flowchart of a contention-based two-step random access method according to an embodiment of this application;

[0054] Figure 6 is a flowchart of a non-contention-based two-step random access method according to an embodiment of this application;

[0055] Figure 7 is a flowchart of an embodiment of the random access-free method of this application;

[0056] Figure 8 is a flowchart of DAPS switching based on the NG port according to an embodiment of this application;

[0057] Figure 9 is a schematic diagram of DAPS switching according to an embodiment of this application;

[0058] Figure 10 is a schematic diagram of a wireless access network system based on transparent satellite according to an embodiment of this application;

[0059] Figure 11 is a schematic diagram of a regenerative satellite system with base station processing function but without inter-satellite links according to an embodiment of this application;

[0060] Figure 12 is a schematic diagram of a regenerative satellite system with inter-satellite links and base station processing function according to an embodiment of this application;

[0061] Figure 13 is a schematic diagram of a regenerative satellite system with DU processing function according to an embodiment of this application;

[0062] Figure 14 is a schematic diagram of the protocol layer architecture of CU-DU according to an embodiment of this application;

[0063] Figures 15-16 are flowcharts of communication methods according to various embodiments of this application;

[0064] Figure 17 is a schematic diagram of DAPS switching according to an embodiment of this application;

[0065] Figures 18 and 19 are schematic diagrams of the structure of communication devices according to various embodiments of this application. Detailed Implementation

[0066] In the description of this application, unless otherwise stated, " / " indicates that the objects before and after are in an "or" relationship. For example, A / B can mean A or B. "And / or" in this application is merely a description of the relationship between the related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. A and B can be singular or plural.

[0067] In the description of this application, unless otherwise stated, "multiple" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple.

[0068] Furthermore, to facilitate a clear description of the technical solutions in the embodiments of this application, the terms "first" and "second" are used in the embodiments of this application to distinguish identical or similar items with substantially the same function and effect. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and the terms "first" and "second" are not necessarily different.

[0069] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a specific manner to facilitate understanding.

[0070] It is understood that the term "embodiment" used throughout the specification means that a specific feature, structure, or characteristic related to an embodiment is included in at least one embodiment of this application. Therefore, various embodiments throughout the specification do not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. It is understood that in the various embodiments of this application, the sequence number of each process does not imply the order of execution; the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0071] It is understood that in this application, "...when" and "if" both refer to the corresponding processing that will be carried out under certain objective circumstances, and are not limited to a specific time, nor do they require a judgment action to be performed during implementation, nor do they imply any other limitations.

[0072] It is understood that some optional features in the embodiments of this application can be implemented independently in certain scenarios without relying on other features, such as the current solution on which they are based, to solve the corresponding technical problems and achieve the corresponding effects. Alternatively, they can be combined with other features as needed in certain scenarios. Correspondingly, the apparatus given in the embodiments of this application can also implement these features or functions, which will not be elaborated here.

[0073] In this application, unless otherwise specified, the same or similar parts between the various embodiments can be referred to each other. In the various embodiments of this application, unless otherwise specified or there is a logical conflict, the terminology and / or descriptions between different embodiments are consistent and can be mutually referenced. Technical features in different embodiments can be combined to form new embodiments based on their inherent logical relationships. The following descriptions of the embodiments of this application do not constitute a limitation on the scope of protection of this application.

[0074] A non-terrestrial network (NTN) refers to a radio frequency (RF) network or network segment used on satellite platforms, unmanned aircraft systems (UAS), or high-altitude platforms. A typical NTN provides communication services via satellite.

[0075] Satellite communication boasts advantages such as wide coverage, long communication distance, high reliability, high flexibility, and high throughput. Unaffected by geographical environment, weather conditions, or natural disasters, it has been widely applied in fields such as aviation, maritime, and military communications. Introducing satellite communication into future 5G mobile communication networks can provide communication services to areas difficult to cover by terrestrial networks, such as oceans and forests. This will enhance the reliability of 5G communication, providing users with more stable and higher-quality communication services, such as for users on trains and airplanes. It can also provide more data transmission resources and support a larger number of connections. Thanks to the current concept of "anytime, anywhere" communication, the status of satellite communication will be further enhanced in the future.

[0076] Generally speaking, the higher the satellite's orbit, the larger its coverage area, but the longer its communication latency. Satellites can be classified according to their orbital altitude into low Earth orbit (LEO), medium Earth orbit (MEO), and geostationary orbit (GEO). Non-geosynchronous orbit (NGSO) includes LEO (approximately 300 km to 1500 km) and MEO (approximately 7000 km to 25000 km).

[0077] NTN cells can be categorized into fixed cells (or stationary cells), quasi-fixed cells, and mobile cells. A fixed cell refers to a cell or beam that permanently covers a specific geographical area. A quasi-fixed cell refers to a cell or beam that covers one geographical area for a limited time and then covers a different geographical area at another time. Quasi-fixed cells can also be called quasi-Earth-fixed cells. Figure 1 is a schematic diagram of a quasi-fixed cell scenario according to an embodiment of this application. As shown in Figure 1, an NGSO satellite generates a steerable beam that covers a specific geographical area for a period of time. That is, the satellite covers the same geographical area from time T1 to T3. A mobile cell refers to a cell or beam that slides across the Earth's surface. Figure 2 is a schematic diagram of a mobile cell scenario according to an embodiment of this application. As shown in Figure 2, an NGSO satellite generates a fixed or non-steerable beam that covers an area that slides across the Earth's surface. That is, the satellite covers different geographical areas from time T1 to T3, covering geographical area 1 at time T1, geographical area 2 at time T2, and geographical area 3 at time T3.

[0078] When a terminal accesses a communication network via NTN, it needs NTN parameter information. This communication network could be a new radio (NR), long-term evolution (LTE), or another network. Since NTN networks primarily refer to satellite networks, NTN parameter information can also be called NTN-Config or satellite auxiliary information. This NTN parameter information includes satellite ephemeris information, timing advance (TA) parameters, epoch time parameters, synchronization validity period (ntn-UlSyncValidityDuration) parameters, kmac parameters, downlink (DL) polarization indication information, uplink (UL) polarization indication information, and TA report enable information, etc.

[0079] Among them, satellite ephemeris information is used to provide satellite ephemeris to indicate the satellite's position. The terminal can obtain and / or predict the satellite's position based on the satellite ephemeris information; common timing advance parameter information is the common timing advance value of network control, which can be used to characterize the round-trip transmission delay between the reference point and network equipment within the satellite coverage area. The terminal can obtain the common timing advance TA value based on the common timing advance parameter information. This common timing advance parameter information may also include the common timing advance value drift rate and the common timing advance value drift rate variation. The terminal can also predict and estimate future and past common timing advance values ​​based on this common timing advance parameter information; start time parameter information is used to indicate the start time of NTN parameter information; synchronization validity time parameter information is used to indicate the validity duration of NTN parameter information. Within this validity duration, the terminal can apply NTN parameter information without obtaining new NTN parameter information. The start time of this validity duration is the start time (epoch). The time corresponding to (time); the kmac parameter information refers to the scheduling offset provided by the network side when the timing of the downlink and uplink frames is misaligned at the base station. The value of this scheduling offset can be 0; the DL polarization indication information is used to indicate the polarization mode of the downlink, where the polarization mode can be right-handed circular polarization, left-handed circular polarization, linear polarization, etc.; the UL polarization indication information is used to indicate the polarization mode of the uplink, where the polarization mode can be right-handed circular polarization, left-handed circular polarization, linear polarization, etc.; the TA report enable information is used to instruct the terminal to send a TA report to the base station during or after random access.

[0080] In non-terrestrial networks, the round-trip time (RTT) between a terminal and a base station can be the sum of the terminal's common timing advance (TA) value and kmac parameter information. RTT can also be called the round-trip distance time. The RTT value between the terminal and the base station can be rounded according to actual needs, either by slot or subframe; or it can be left unrounded. In 4G networks, the RTT between the terminal and the base station can also be expressed as UE-eNB RTT; in 4G networks, the RTT between the terminal and the base station can also be expressed as UE-gNB RTT.

[0081] To enable terminals to access base stations, access methods can be divided into random access and non-random access.

[0082] Figure 3 is a flowchart of a contention-based four-step random access method according to an embodiment of this application. As shown in Figure 3, the specific process of the contention-based four-step random access method is as follows:

[0083] S301. The terminal sends a random access preamble, Msg1, to the base station.

[0084] Correspondingly, the base station receives the random access preamble, Msg1, from the terminal.

[0085] After the terminal and the base station perform downlink synchronization, the terminal determines the physical random access channel (PRACH) to send the random access preamble and sends the random access preamble to the base station.

[0086] In 4G systems, after the random access preamble ends in the subframe, the terminal waits for three subframes plus the UE-eNB RTT before opening the random access response window. The size (or duration) of the random access response window is configured by the base station. If the UE repeatedly sends the random access preamble multiple times, the opening time of the random access response window is based on the subframe ending the last sent random access preamble, waiting for three subframes plus the UE-eNB RTT before opening the random access response window. In 5G systems, after the random access preamble ends in the subframe, the terminal adds the UE-gNB RTT and then opens the random access response window. Unlike 4G systems, the waiting time in 5G systems does not necessarily need to be the fixed three subframes; it can be zero subframes or other numbers of subframes.

[0087] The terminal determines a random access radio network temporary identifier (RA-RNTI) to uniquely identify itself during the random access process. Within the random access response window, the terminal monitors the PDCCH scrambled based on the RA-RNTI. It should be noted that after sending the random access preamble, the terminal initiates a random access response window (RA-RNTI), continuously monitoring the PDCCH until the required random access response is obtained on the PDSCH channel. The terminal can determine the location of the PDSCH, such as the time-frequency resource location, based on information in the PDCCH.

[0088] S302, The base station sends a random access response, namely Msg2, to the terminal.

[0089] Correspondingly, the terminal receives a random access response from the base station, namely Msg2.

[0090] The base station determines the RA-RNTI and uses the RA-RNTI to scramble the PDCCH.

[0091] After receiving the random access preamble from the terminal, the base station obtains the uplink timing offset (TA) value of the terminal based on the random access preamble. The base station sends a random access response on the PDSCH via Msg2 to indicate that it has received the random access preamble. Msg2 carries the TA value and is sent to the terminal to adjust the terminal's transmission timing.

[0092] The information carried in the random access response also includes the random access preamble identifier (RA), uplink grant (ULgrant), and cell radio network temporary identifier (Temporary C-RNTI).

[0093] S303, The terminal sends an RRC connection establishment request, namely Msg3, to the base station.

[0094] Correspondingly, the base station receives an RRC connection establishment request from the terminal, namely Msg3.

[0095] After receiving Msg2, the terminal achieves uplink synchronization and can transmit Msg3 on the predetermined physical uplink shared channel (PUSCH). Msg3 carries the terminal's unique identifier (UE ID), which is used to distinguish different terminals, differentiate terminals involved in the transmission conflict in step S304, and resolve the conflict. If the terminal has previously connected to a cell, it uses the cell's radio network identifier C-RNTI as the UE ID, which is unique within that cell; otherwise, the terminal uses an identifier from the core network (S-TMSI or a random number).

[0096] It should be noted that after receiving the random access response, the terminal will stop the random access response window. In the first symbol or subframe after all Msg3 transmissions have ended plus the RTT between the terminal and the base station, the terminal starts or restarts the contention resolution timer, providing a time window for the terminal to wait for the contention resolution message. During the contention resolution timer's operation, the terminal monitors the PDCCH, such as a TC-RNTI or C-RNTI scrambled PDCCH.

[0097] S304, The base station sends a contention resolution message, namely Msg4, to the terminal.

[0098] Correspondingly, the terminal receives a contention resolution message from the base station, namely Msg4.

[0099] The base station assists the terminal in contention resolution by using C-RNTI on the PDCCH or UE Contention Resolution Identity on the PDSCH. Before the contention resolution timer expires, the terminal continuously monitors the PDCCH. If any of the following conditions are met, the terminal considers the contention resolution successful (i.e., the terminal has successfully accessed the network) and stops the contention resolution timer; otherwise, the timer is not stopped.

[0100] Scenario 1: The terminal detects its own C-RNTI on the PDCCH via Msg4. In this case, the terminal will stop contention-resolve the timer and discard the Temporary C-RNTI.

[0101] Scenario 2: The terminal detects its Temporary C-RNTI on the PDCCH via Msg4, and the UE Contention Resolution Identity contained in the MAC PDU received by the terminal from the PDSCH is the same as the UE Contention Resolution Identity carried in the Msg3 sent by the terminal (i.e., the MAC PDU is successfully decoded). At this time, the terminal stops the contention resolution timer and sets the Temporary C-RNTI to C-RNTI.

[0102] If the contention resolution timer times out, the terminal will discard the Temporary C-RNTI and consider the contention resolution to have failed.

[0103] Contention-based four-step random access can lead to contention risks. To address this issue, a contention-free four-step random access method is proposed. The key difference between contention-based and contention-based four-step random access methods is that the random access preamble is randomly selected by the terminal in contention-based methods, while it is allocated by the base station in contention-free methods. This reduces the contention resolution process. Aside from this, the other steps in the contention-free four-step random access method are the same as those in the contention-based method.

[0104] Figure 4 is a flowchart of a non-contention-based four-step random access method according to an embodiment of this application. As shown in Figure 4, the specific process of the non-contention-based four-step random access method is as follows:

[0105] S401. The base station sends the assigned random access preamble to the terminal.

[0106] Accordingly, the terminal receives a random access preamble allocated by the base station.

[0107] S402, The terminal sends a random access preamble, Msg1, to the base station.

[0108] Correspondingly, the base station receives the random access preamble, Msg1, from the terminal.

[0109] S403, The base station sends a random access response, namely Msg2, to the terminal.

[0110] Correspondingly, the terminal receives a random access response from the base station, namely Msg2.

[0111] S404. The terminal sends an RRC connection establishment request, namely Msg3, to the base station.

[0112] Correspondingly, the base station receives an RRC connection establishment request from the terminal, namely Msg3.

[0113] To simplify the random access process and reduce latency, in the contention-based four-step random access, the two Msg1 and Msg3 sent by the terminal are merged into a new MsgA and sent to the base station, and the two Msg2 and Msg4 sent by the base station are merged into a new MsgB and sent to the terminal. The entire random access process is simplified to only two steps, namely contention-based two-step random access.

[0114] Figure 5 is a flowchart of a contention-based two-step random access method according to an embodiment of this application. As shown in Figure 5, the specific process of the contention-based two-step random access method is as follows:

[0115] S501, The terminal sends MsgA to the base station.

[0116] Correspondingly, the base station receives MsgA from the terminal.

[0117] The transmission of MsgA can be divided into two parts: the transmission of the random access preamble and the transmission of the PUSCH payload, corresponding to Msg1 and Msg3 in the four-step random access process, respectively. This can be understood as follows: when the terminal receives the two-step random access configuration, it obtains both the information for sending the random access preamble on the PRACH and an authorization related to sending the random access preamble to transmit the content originally sent on Msg3 on the PUSCH. That is, MsgA is not a single message sent within the same transmission time interval (TTI), but rather two messages sent at different times: the random access preamble is sent at the first TTI, and then the PUSCH payload is sent on the corresponding biased PUSCH resource.

[0118] The terminal sends the PUSCH payload or the subframe, symbol, or time slot at the end of the random access preamble, plus the UE-gNB RTT, and then opens the random access response window (i.e., msgB-ResponseWindow). The size (or duration) of the random access response window is configured by the base station.

[0119] The terminal determines the msgB-RNTI and monitors the PDCCH within the random access response window to detect downlink control information scrambled by the msgB-RNTI and / or C-RNTI.

[0120] During contention-based two-step random access, the terminal carries its unique identifier (UE ID) in the PUSCH. This identifier is used for collision resolution in MsgB to distinguish the terminal that sent the conflicting message. If the terminal has previously connected to a cell, it uses the cell's C-RNTI as its UE ID, which is unique within that cell; otherwise, the terminal uses an identifier from the core network, such as the S-TMSI or a random number.

[0121] S502, The base station sends MsgB to the terminal.

[0122] Correspondingly, the terminal receives MsgB from the base station.

[0123] During the contention-based two-step random access process, the base station needs to parse both the random access preamble sent by the terminal and its associated PUCH payload. If both are successfully parsed, a contention resolution message (MsgB) is sent. This message can also include information about RRC connection establishment.

[0124] Contention-based two-step random access can lead to contention risks. To address this issue, a contention-free two-step random access method is proposed. The key difference between contention-based and contention-based two-step random access methods is that the random access preamble is randomly selected by the terminal in contention-based methods, while in contention-free methods, the preamble is allocated by the base station, which also allocates PUSCH resources to the terminal. This reduces the contention resolution process.

[0125] Figure 6 is a flowchart of a non-contention-based two-step random access method according to an embodiment of this application. As shown in Figure 6, the specific process of the non-contention-based two-step random access method is as follows:

[0126] S601. The base station sends the random access preamble and PUSCH resources allocated to the terminal to the terminal.

[0127] Accordingly, the terminal receives random access preamble and PUSCH resources allocated by the base station.

[0128] S602. The terminal sends MsgA to the base station based on the random access preamble and PUSCH resources allocated by the base station.

[0129] Correspondingly, the base station receives MsgA.

[0130] S603, The base station sends MsgB to the terminal.

[0131] Correspondingly, the terminal receives MsgB.

[0132] The process of the base station sending MsgA and the base station sending MsgB to the terminal can be referred to the process in S501 to S502 above.

[0133] To simplify access methods, reduce signaling overhead, and improve communication efficiency, a random access channel-less (RACH-less) approach is proposed. Figure 7 is a flowchart of a random access channel-less approach according to an embodiment of this application. As shown in Figure 7, the specific process of random access channel-less during base station handover is as follows:

[0134] S701. The source base station sends a handover request to the target base station. Correspondingly, the target base station receives the handover request.

[0135] S702. The target base station sends a handover request confirmation to the source base station. Correspondingly, the source base station receives the handover request confirmation.

[0136] S703: The source base station sends an RRC reconfiguration message to the terminal. Correspondingly, the terminal receives the RRC reconfiguration message.

[0137] RRC reconfiguration messages are also known as handover commands. RRC reconfiguration messages contain rach-less handover configurations. Additionally, RRC reconfiguration messages may include timed advance adjustment instructions and optional pre-allocated uplink grants, i.e., pre-configured resources.

[0138] When the terminal performs a handover, the terminal starts a timer (timing advance timer, TAT).

[0139] S704. The terminal sends an RRC connection reconfiguration complete message to the target base station. Correspondingly, the target base station receives the RRC connection reconfiguration complete message.

[0140] If the RRC reconfiguration message contains a periodic UL resource from the pre-configured resources, the terminal sends RRCReconfigurationComplete using that UL resource. Otherwise, the terminal monitors the PDCCH of the target cell to obtain UL scheduling and sends RRCReconfigurationComplete.

[0141] S705: The target base station sends a handover success message to the terminal. Correspondingly, the terminal receives the handover success message.

[0142] After a successful handover, the target base station sends a handover success message to the terminal. This message contains the UE contentionresolution identity MAC CE. Upon receiving this message, the terminal considers the handover successful and releases resources related to non-random access, such as pre-allocated uplink authorization.

[0143] In RACH-less handover, a handover technique that can skip the random access process is used.

[0144] In a 5G NR system, during the handover process, when a terminal receives an RRC reconfiguration message for a handover command, it immediately disconnects its user plane from the source cell. This prevents the terminal from transmitting data with any base station before establishing a connection with the target cell, resulting in a handover interruption delay.

[0145] To address handover interruption latency caused by base station handover, a dual active protocol stack (DAPS) handover method is proposed. DAPS handover is an enhancement of basic NR handover. Ideally, DAPS handover can achieve zero-millisecond user plane interruption latency during the handover process, hence it is also called "zero" interruption handover. During DAPS handover, the terminal maintains its user plane connection with the source cell and continues data transmission with the source cell until a connection is established with the target cell for data transmission. DAPS handover requires the terminal to be able to simultaneously receive and / or transmit data with both the source and target cells within a short period. That is, during base station handover, the terminal can continue to receive downlink user data from the source cell until the source cell is released, and the terminal continues to send uplink user data to the source cell until it successfully randomly accesses the target cell.

[0146] Figure 8 is a flowchart of DAPS handover based on the NG port according to an embodiment of this application. As shown in Figure 8, the specific process of DAPS handover based on the NG port is as follows:

[0147] S801, the source base station sends a handover request message to the target base station through the AMF network element.

[0148] The handover request message may include quality of service (QoS) flow information from the source base station proposing to perform downlink data forwarding.

[0149] A source base station can request a DAPS handover for one or more data radio bearers (DRBs). If a DAPS handover is requested for a DRB, all QoS flows mapped to the DRB should request downlink data forwarding. The handover request message may include the target cell identifier, the terminal's identifier at the source base station, and terminal capability information.

[0150] Accordingly, the target base station receives the handover request message.

[0151] S802. The target base station sends a handover request confirmation message to the source base station through the AMF network element.

[0152] The request confirmation message includes a DAPS acceptance message. The handover request confirmation message also includes information required for the terminal to access the target base station, such as the target cell identifier, the new cell radio network temporary identifier (C-RNTI), the target base station security algorithm identifier, dedicated RACH resources, the association between RACH resources and synchronization signal blocks (SSBs), the association between RACH resources and the terminal-specific channel state information reference signal (CSI-RS) configuration, public RACH resources, and system information of the target cell.

[0153] Correspondingly, the source base station receives the handover request confirmation message.

[0154] S803: The source base station sends an RRC reconfiguration message, i.e., a DAPS handover command, to the terminal.

[0155] The RRC reconfiguration message is used to trigger terminal handover. The RRC reconfiguration message contains information required to access the target cell, such as the target cell identifier, the new C-RNTI, the target base station security algorithm identifier, dedicated RACH resources, the association between RACH resources and SSB, the association between RACH resources and terminal-specific CSI-RS configuration, public RACH resources, and system information of the target cell.

[0156] In a DAPS handover scenario based on the NG port, the RRC reconfiguration message contains DRB information that allows the terminal to perform DAPS.

[0157] Correspondingly, the terminal receives the RRC reconfiguration message.

[0158] S804. The source base station sends an Early Status Transmission (EASTTRANSFER) message to the target base station via the AMF network element.

[0159] Specifically, S804a, the source base station sends an uplink RAN ​​Early Status Transmission (UL RAN Early STATUSTRANSFER) message to the AMF network element.

[0160] The S804b and AMF network elements send a downlink RAN ​​Early Status Transmission (DL RAN Early STATUS TRANSFER) message to the target base station.

[0161] The Early Status Transmission (EAST) message contains the count value of the first downlink SDU forwarded by the source base station to the target base station, or the count value of a downlink SDU that has been discarded for the corresponding DRB during DAPS handover. The count value consists of the high-order hyperframe number (HFN) and the low-order sequence number (SN), used to uniquely identify each SDU.

[0162] It should be noted that before step S809, the Early STATUS TRANSFER message can be sent once or multiple times. The first message contains the count value of the first downlink SDU forwarded by the source base station to the target base station. This message is used by the target base station to know from which SDU the source base station started forwarding to the target base station. Subsequent messages are used by the target base station to discard / clear the cached downlink SDUs that the source base station has successfully transmitted to the terminal, in order to free up memory.

[0163] S805: The source base station forwards downlink data to the target base station through the UPF network element.

[0164] Specifically, after receiving downlink data from the UPF network element, the source base station assigns a serial number (SN) to the downlink data, obtains the downlink data with the assigned SN, and then forwards the downlink data with the assigned SN to the target base station through the UPF network element. That is, the source base station can forward downlink PDCP SDUs with the SN assigned by the source base station to the target base station. Simultaneously, the source base station receives downlink data from the UPF and sends it to the terminal.

[0165] Correspondingly, the target base station receives downlink data.

[0166] S806. The terminal sends an RRC reconfiguration complete message, i.e., a handover complete message, to the target base station.

[0167] Correspondingly, the target base station receives the RRC reconfiguration complete message.

[0168] After the target base station receives the RRC reconfiguration complete message, the handover process is completed.

[0169] It should be noted that before step S806, the terminal may need to perform downlink synchronization with the target cell before proceeding with the random access procedure. After the terminal switches to the target cell, the target base station begins uplink scheduling for the terminal, and the terminal sends a new UL PDCP PDU to the target base station, meaning the terminal switches its UL data transmission to the target base station. However, even after switching its UL data transmission to the target base station, to ensure data consistency and reliability, the terminal will continue to send information to the source base station, such as UL Layer 1 CSI feedback, HARQ feedback, Layer 2 RLC feedback, ROHC feedback, HARQ data (re)transmission, and RLC data (re)transmission.

[0170] S807, The target base station sends a handover notification message to the AMF network element.

[0171] This handover notification message indicates that the terminal has successfully switched over.

[0172] Correspondingly, the AMF network element receives the handover notification message.

[0173] The S808 and AMF network elements send a handover success message to the source base station.

[0174] Correspondingly, the source base station receives the handover success message.

[0175] S809. The source base station sends a sequence number transmission status (SN STATUS TRANSFER) message to the target base station through the AMF network element.

[0176] After the source base station receives the terminal handover success message, it stops data transmission with the terminal. The source base station sends a Sequence Number Transmission Status (SN STATUS TRANSFER) message to the target base station through the AMF network element. This SN STATUS TRANSFER message contains the count value assigned to the next DL SDU without a SN in the data sent by the target base station to the terminal. This count value includes the PDCP-SN and the superframe number.

[0177] Correspondingly, the target base station receives the sequence number transmission status (SN STATUS TRANSFER) message.

[0178] S810, the target base station sends a source cell release message to the terminal.

[0179] Accordingly, the terminal receives the source cell release message. After receiving this message, the terminal releases the source cell configuration and stops receiving downlink data from the source base station.

[0180] While DAPS handover is not currently supported in NTN or satellite communication scenarios, future satellite communication systems may require zero service interruption during handover. Therefore, extending DASP handover to satellite communication scenarios could be considered.

[0181] In satellite communication systems, there is no direct interface (Xn interface) between base stations. For example, if the base station is on the ground, there is no Xn interface between base stations; or, if the base station is mounted on a satellite, there may be no inter-satellite link between satellites, resulting in no Xn interface between base stations. Therefore, DAPS handover based on the NG interface is required.

[0182] Figure 9 is a schematic diagram of DAPS handover according to an embodiment of this application. As shown in Figure 9, during the DAPS handover process, the UPF network element sends downlink data to the source base station; after the source base station allocates a serial number (SN) to the downlink data, it obtains the downlink data after the SN allocation; then, it splits into two paths. In one path, the source base station sends the data to the terminal; in the other path, the source base station sends the downlink data after the SN allocation to the UPF network element, and the UPF network element forwards the downlink data to the target base station. That is, the communication link of the downlink data involved in the handover process is UPF network element → source base station → UPF network element → target base station. However, this method will occupy the communication link resources between the UPF network element and the base station, resulting in resource waste. Furthermore, since the UPF network element and the base station transmit data through an interface in satellite communication, this problem is even more prominent.

[0183] Based on this, this application proposes a technical solution that can reduce the resource consumption of the communication link between the UPF network element and the base station. The technical solution provided in this application is described below with reference to the accompanying drawings.

[0184] The technical solutions of this application embodiment can be used in various communication systems, including third-generation partnership project (3GPP) communication systems, such as fourth-generation (4G) systems like long-term evolution (LTE), 5G systems like new radio (NR), hybrid LTE and 5G networks, non-terrestrial networks (NTN), or other future communication systems. The communication system can also be a non-3GPP communication system; there is no limitation on this.

[0185] It should be noted that the solutions in this application embodiment can also be applied to various NTN systems. The NTN system can be one of the five NTN-based next-generation radio access network (NG-RAN architectures) systems defined in 3GPP TR38.821.

[0186] 1) Radio Access Network (RAN) architecture with transparent satellite system

[0187] Figure 10 is a schematic diagram of a transparent satellite-based wireless access network system according to an embodiment of this application. As shown in Figure 10, the system includes a terminal, a satellite, a non-terrestrial network gateway (NTN-gateway), a terrestrial base station, and a core network. The terminal communicates with the terrestrial base station via the satellite. The satellite, acting as a relay node in the wireless access network, does not perform any signal processing, only radiofrequency filtering, frequency conversion, and amplification. In other words, the satellite is transparent in this system, primarily acting as an L1 relay, regenerating physical layer signals, and does not involve other higher protocol layers. The NTN-gateway supports all the functions required to forward NR Uu interface signals and is a key node connecting the satellite and the terrestrial network. The remote radio unit (RRU) can include both the satellite and the NTN-gateway.

[0188] 2) Regenerative satellite without inter-satellite link, but with base station processing capabilities (gNB processed payload)

[0189] Figure 11 is a schematic diagram of a regenerative satellite system with base station processing capabilities but without inter-satellite links, according to an embodiment of this application. As shown in Figure 11, the system includes a terminal, a satellite, a non-terrestrial network gateway (NTN-gateway), and a core network. The satellite not only performs radio frequency filtering, frequency conversion, and amplification, but also possesses base station processing capabilities; in this system, the satellite can be considered a base station. Data transmission between the satellite and the NTN-gateway occurs via the SRI air interface.

[0190] 3) Regenerative satellite with inter-satellite link and base station processing capabilities (gNB processed payload)

[0191] Figure 12 is a schematic diagram of a regenerative satellite system with inter-satellite links and base station processing capabilities according to an embodiment of this application. As shown in Figure 12, the system includes a terminal, a satellite, a non-terrestrial network gateway (NTN-gateway), and a core network. Unlike the system shown in Figure 11, the satellite in Figure 12 has an inter-satellite link (ISL).

[0192] 4) A regenerative satellite system with DU processing capabilities (NG-RAN with a regenerative satellite based on gNB-DU)

[0193] Figure 13 is a schematic diagram of a regenerative satellite system with DU processing function according to an embodiment of this application. As shown in Figure 13, the system includes a terminal, a satellite, a non-terrestrial network gateway (NTN-gateway), a ground base station, and a core network. The satellite not only performs radio frequency filtering, frequency conversion, and amplification, but the DU is also deployed on the satellite, or the satellite has DU functionality.

[0194] 5) Regenerative satellite systems with integrated access and backhaul (IAB) capabilities

[0195] In this system, the satellite not only performs wireless frequency filtering, frequency conversion, and amplification, but also has IAB (Infrastructure, Access, and Biotechnology) capabilities.

[0196] The communication systems described above are merely illustrative examples, and are not limited to those described herein. The communication systems provided in this application do not impose any limitations on the solutions described herein. This will be explained uniformly here and will not be repeated below.

[0197] In this application embodiment, the core network equipment in the core network (CN) can be equipment in the core network that provides service support to the terminal. For example, access and mobility management function (AMF) network elements, session management function (SMF) network elements, user plane function (UPF) network elements, etc. Of course, the core network may also include other core network equipment, without limitation.

[0198] The AMF (Access Default Mode) network element is primarily responsible for terminal access management and mobility management in the mobile network, such as user location updates, user network registration, and user handover. The SMF (Service Default Mode) network element is primarily responsible for session management in the mobile network, such as session establishment, modification, and release. The UPF (User Plane Functional Element) network element is responsible for connecting to external networks and processing user packets, such as forwarding and accounting.

[0199] It should be noted that in this application, network elements can also be referred to as entities or functional entities. For example, an AMF network element can also be referred to as an AMF entity or an AMF functional entity. Furthermore, the aforementioned SMF and UPF network elements may have other names in future communication systems, and this application does not impose specific limitations on them.

[0200] The access network equipment involved in this application can be a radio access network (RAN) node (or device) that connects a terminal to a wireless network. The access network equipment in the embodiments of this application can include various forms of base stations (BS), such as: evolved Node B (gNB), transmission reception point (TRP), evolved Node B (eNB), radio network controller (RNC), node B (NB), base station controller (BSC), base transceiver station (BTS), home-evolved Node B (or home Node B (HNB)), base band unit (BBU), or wireless fidelity (Wi-Fi) access point (AP), etc. This application does not specifically limit these features.

[0201] As one possible implementation, the access network equipment may include centralized unit (CU) nodes, distributed unit (DU) nodes, or RAN equipment including both CU and DU nodes. This RAN equipment, including CU and DU nodes, separates the protocol layer of the gNB in ​​the NR system. Some protocol layer functions are centrally controlled by the CU, while the remaining partial or complete protocol layer functions are distributed in the DU, which is centrally controlled by the CU.

[0202] In one example, the CU may include CU-CP and CU-UP. Figure 14 is a schematic diagram of the protocol layer architecture of CU-DU according to an embodiment of this application. In the protocol layer architecture of CU-DU shown in Figure 14, CU-CP can be understood as a logical node carrying the RRC layer and the PDCP control plane (control plane part of PDCP, PDCP-C), used to implement the control plane functions of the CU. PDCP-C is mainly responsible for the encryption and decryption of control plane data, integrity protection, data transmission, etc. CU-UP is responsible for user plane functions, mainly including SDAP and the PDCP corresponding to the user plane, namely PDCP-U. Among them, SDAP is mainly responsible for processing the core network data and mapping the flow to the bearer. PDCP-U is mainly responsible for the encryption and decryption of data plane, integrity protection, header compression, sequence number maintenance, data transmission, etc. DU can deploy the RLC layer, MAC layer and PHY layer, or in other words, DU can be understood as a logical node carrying the RLC layer, MAC layer and PHY layer, thus, DU has the processing capabilities of RLC, MAC and PHY layers. Of course, DU can also implement or carry other functions. CU-CP can communicate with CU-UP via the E1 interface. CU-CP represents the gNB connected to the core network via the NG interface. CU-CP can communicate with DU via F1-C. CU-UP can be understood as a logical node carrying the SDAP layer and PDCP user plane (PDCP user plane part of PDCP, PDCP-U), used to implement the CU's user plane functions. CU-UP can communicate with DU via F1-U.

[0203] CU-CP can interact with network elements in the core network used to implement control plane functions. These network elements can be access and mobility function network elements, such as the AMF network element in a 5G system. CU-UP can interact with network elements in the core network used to implement user plane functions. These network elements can be, for example, UPF network elements.

[0204] The functional division of CU and DU described above is merely an example and does not constitute a limitation on CU and DU. The functions of CU and DU can be configured as needed. For example, CU or DU can be configured as a node with more protocol layer functions, or as a node with partial protocol layer processing functions. For instance, some functions of the RLC layer and the protocol layer functions above the RLC layer can be placed in the CU, while the remaining functions of the RLC layer and the protocol layer functions below the RLC layer can be placed in the DU. Furthermore, the functions of CU or DU can be divided according to service type or other system requirements, such as by latency. Functions that require low latency can be placed in the DU, while functions that do not require low latency can be placed in the CU.

[0205] For example, in some examples, the CU may not carry the PDCP layer, i.e., it may only carry the RRC layer. CU-CP may not carry PDCP-C, CU-UP may not carry PDCP-U, or CU-UP may carry PDCP-C or may not exist at all. In other examples, the DU may not carry the RLC layer. Furthermore, it is also possible to have only the DU without a CU.

[0206] The terminal involved in the embodiments of this application can be a device that provides voice and / or data connectivity to users, and can also be referred to as terminal equipment, user equipment (UE), mobile station, mobile terminal, etc. The terminal can be widely used in various scenarios; for example, it can be deployed on land, including indoors or outdoors, handheld or vehicle-mounted; it can also be deployed on water (such as ships); and it can also be deployed in the air (such as airplanes, balloons, and satellites). The terminal can be a mobile phone, tablet computer, laptop computer, PDA, mobile internet device (MID), wearable device, virtual reality (VR) device, augmented reality (AR) device, wireless terminal in industrial control, wireless terminal in self-driving, wireless terminal in remote medical surgery, wireless terminal in smart grid, wireless terminal in transportation safety, wireless terminal in smart city, wireless terminal in smart home, etc. The embodiments of this application do not specifically limit this.

[0207] It should be noted that the communication system described in the embodiments of this application is for the purpose of more clearly illustrating the technical solutions of the embodiments of this application, and does not constitute a limitation on the technical solutions provided in the embodiments of this application. As those skilled in the art will know, with the evolution of network architecture and the emergence of new business scenarios, the technical solutions provided in the embodiments of this application are also applicable to similar technical problems.

[0208] The following description, using the aforementioned communication system as an example, illustrates the communication method provided in this application's embodiments, taking the interaction between a UPF network element, a first access network device, and a second access network device. It should be noted that in the following embodiments of this application, the message names, parameter names, or information names between the UPF network element, the first access network device, and the second access network device are merely examples; other names may exist in other embodiments, and the method provided in this application does not specifically limit these.

[0209] It is understood that in the embodiments of this application, the UPF network element, the first access network device, and the second access network device may execute some or all of the steps in the embodiments of this application. These steps or operations are merely examples, and the embodiments of this application may also execute other operations or variations thereof. Furthermore, the various steps may be executed in different orders as presented in the embodiments of this application, and it is not necessarily necessary to execute all the operations in the embodiments of this application.

[0210] It is understood that this application uses UPF network elements, the first access network device, and the second access network device as examples to illustrate the execution subjects of the interaction, but this application does not limit the execution subjects of the interaction. For example, the method executed by the UPF network element in this application can also be executed by a module (e.g., a chip, chip system, or processor) applied to the UPF network element, or by a logical node, logical module, or software that can implement all or part of the functions of the UPF network element; the method executed by the first access network device in this application can also be executed by a module (e.g., a chip, chip system, or processor) applied to the first access network device, or by a logical node, logical module, or software that can implement all or part of the functions of the first access network device; the method executed by the second access network device in this application can also be executed by a module (e.g., a chip, chip system, or processor) applied to the second access network device, or by a logical node, logical module, or software that can implement all or part of the functions of the second access network device.

[0211] Furthermore, in this application, "sending information" can be understood as one device sending information to another device, or it can also be understood as one logical module within a device sending information to another logical module. For example, "UPF network element sending information" can be understood as a UPF network element sending information to another device (such as the first access network device), or it can be understood as logical module 1 (such as the processing module) in the UPF network element sending information to logical module 2 (such as the communication module) in the UPF network element.

[0212] In this application, "receiving information" can be understood as one device receiving information from another device, or it can also be understood as a logical module within a device receiving information from another logical module. For example, "the first access network device receiving information" can be understood as the first access network device receiving information from another device (such as a UPF network element), or it can be understood as logical module 1 (such as a processing module) in the first access network device receiving information from logical module 2 (such as a communication module) in the first access network device.

[0213] In this application, the phrase "sending information to... (e.g., a second access network device)" or the related illustrations in the accompanying drawings can be understood as the destination of the information being the second access network device. This can include sending information directly or indirectly to the second access network device. Similarly, the phrases "receiving information from... (e.g., a UPF network element)," "receiving information from... (e.g., a UPF network element)," or "receiving information sent (e.g., by a UPF network element)," or the related illustrations in the accompanying drawings, can be understood as the source of the information being the UPF network element. This can include receiving information directly or indirectly from the UPF network element. Information may undergo necessary processing between the source and destination, such as format changes, but the destination can understand the valid information from the source. Similar expressions in this application can be interpreted similarly and will not be elaborated further here.

[0214] Figure 15 is a flowchart of a communication method according to an embodiment of this application, which may include the following steps:

[0215] S1501 and UPF network elements receive the first data, which includes the terminal's downlink data.

[0216] In one possible implementation, the data network sends first data to the UPF network element, and the corresponding UPF network element receives the first data. The downlink data of the terminal may include user plane data.

[0217] S1502, the UPF network element sends the first data to the source access network device of the terminal.

[0218] Correspondingly, the terminal's source access network device receives the first data.

[0219] S1503, the UPF network element sends a copy of the first data to the target access network device of the terminal.

[0220] Correspondingly, the target access network device of the terminal receives a copy of the first data.

[0221] In one possible implementation, the UPF network element stores the first data, and the UPF network element can copy the first data to obtain a copy of the first data, and then send the copy of the first data to the target access network device of the terminal.

[0222] It should be noted that the copy of the first data sent by the UPF network element to the target access network device of the terminal is not the downlink data of the terminal forwarded by the source access network device of the terminal through the UPF network element.

[0223] It should be noted that there is no strict order between the above steps S1502 and S1503. Step S1502 can be executed first and then step S1503, or step S1503 can be executed first and then step S1502, or steps S1502 and S1503 can be executed simultaneously. This application does not make any specific limitation in this regard.

[0224] As one possible implementation, the method further includes the UPF network element receiving second information, the second information being used to indicate the target access network device corresponding to the first data transmission channel, and the first data transmission channel being used to transmit a copy of the first data.

[0225] For example, each access network device has a unique access network device identifier to identify the access network device. The second information may include access network device identifier information. Based on this access network device identifier information, the second information can point to the target access network device corresponding to the first data transmission channel.

[0226] For example, the second information may include the data transmission channel address information and the channel identification information of the target access network device. Based on the data transmission channel address information and the channel identification information of the target access network device, the corresponding access network device can be uniquely identified; that is, the second information can indicate that the first data transmission channel corresponds to the target access network device.

[0227] In one possible implementation, the UPF network element can be a receiver of second information from the first core network element.

[0228] For example, the first core network element can be an SMF element or an AMF element.

[0229] As one possible implementation, the method further includes the UPF network element sending third information to the first core network element, the third information being used to indicate the UPF network element corresponding to the first data transmission channel.

[0230] For example, the third information may include the data transmission channel address information and the channel identification information of the UPF network element. Based on the data transmission channel address information and the channel identification information of the UPF network element, the corresponding UPF network element can be uniquely identified. In other words, the third information can indicate the UPF network element corresponding to the first data transmission channel.

[0231] As one possible implementation, the first access network device sends fourth information, which requests the UPF network element to send first data to the first access network device and to send a copy of the first data to the target access network device of the terminal.

[0232] For example, the fourth information can be explicit information, which may include dual-path transmission indication information or UPF to target base station data transmission request information. The dual-path transmission indication information or UPF to target base station data transmission request information is used to request the UPF network element to send the first data to the source base station and send a copy of the first data to the target base station, rather than the source base station forwarding the data to the target base station through the UPF network element.

[0233] For example, the fourth information can be implicit, meaning it does not include direct data forwarding information and / or indirect data forwarding information. Both direct and indirect data forwarding information are used to instruct the UPF network element to send data to the source base station, which then sends the data back to the UPF network element. Finally, the UPF network element forwards the data to the target base station. In other words, this data forwarding information is used to instruct the establishment of a communication link: UPF network element → source base station → UPF network element → target base station. The difference between direct and indirect data forwarding information is that direct data forwarding information is applied in scenarios where the source and target base stations have an Xn interface. In DAPS handover based on the Xn interface, the UPF network element sends data to the source base station, and the source base station sends the data to the target base station through the Xn interface. Indirect data forwarding information, on the other hand, is applied in scenarios where the source and target base stations do not have an Xn interface. In this scenario, during DAPS handover, the UPF network element sends data to the source base station, and the source base station then forwards the data to the target base station through the UPF network element.

[0234] As one possible implementation, the method further includes the first access network device sending fifth information and / or sixth information, wherein the fifth information is used to indicate the sequence number of the copy of the first data, and the sixth information is used to instruct the UPF network element to start sending a copy of the first data to the target access network device.

[0235] For example, the fifth information may include the sequence number of the first data in the copy of the first data. As another example, the fifth information may include the sequence number of the i-th data in the copy of the first data, where i is a positive integer. This allows the target access network device to know the sequence number of the copy of the first data and reduces the amount of information carried in the fifth information, thereby reducing data transmission overhead.

[0236] For example, the sixth information can be a pre-defined string, such as "data transmission". After the first access network device sends this string, it can instruct the UPF network element to begin sending a copy of the first data to the target access network device. For example, the sixth information may include a start dual-path transmission indication or a start UPF-to-target base station data transmission indication, which is used to instruct the UPF network element to begin sending a copy of the first data to the target access network device.

[0237] As one possible implementation, the method further includes the first access network device receiving seventh information, which is used to indicate that the UPF network element is allowed to send a copy of the first data to the target access network device.

[0238] For example, the seventh information may include data transmission indication information for the target base station, which allows the UPF network element to send a copy of the first data to the target base station, rather than the UPF network element forwarding the data received from the source base station to the target base station.

[0239] Following step S1503, the process further includes the target access network device of the terminal sending a copy of the first data to the terminal. Correspondingly, the terminal receives the copy of the first data.

[0240] As one possible implementation, the method further includes the second access network device receiving fourth information, the fourth information being used to request the UPF network element to send first data to the first access network device and to send a copy of the first data to the target access network device of the terminal.

[0241] As one possible implementation, the method further includes the second access network device sending second information and / or seventh information, wherein the second information is used to indicate the target access network device corresponding to the first data transmission channel, the first data transmission channel is used to transmit a copy of the first data, and the seventh information is used to indicate that the UPF network element is allowed to send a copy of the first data to the target access network device.

[0242] For example, the second access network device may send second information and / or seventh information to the second core network element. For instance, the second core network element may be an AMF element or an SMF element.

[0243] As one possible implementation, the method further includes the second access network device receiving fifth information, which is used to indicate the sequence number of the copy of the first data.

[0244] Based on the above scheme, the UPF network element can directly send a copy of the first data to the target access network device of the terminal, without the source access network device forwarding the data to the target access network device through the UPF network element. This enables the UPF network element to send the first data to the source access network device and the copy of the first data to the target access network device of the terminal respectively. In other words, the downlink data communication links involved in the handover process are UPF network element → source access network device and UPF network element → target access network device. Compared with the existing downlink data communication links, the communication links used for downlink data transmission can be reduced, that is, the target access network device → UPF network element can be reduced. This reduces the link overhead and communication link occupancy between the UPF network element and the access network device caused by forwarding during the handover process, reduces resource waste, and thus improves data transmission performance.

[0245] The following section provides a detailed explanation of the specific implementation of this communication method, using the first access network device as the source base station, the second access network device as the target base station, and DAPS handover based on the NG interface as an example.

[0246] Figure 16 is a flowchart of a communication method according to an embodiment of this application, which may include the following steps:

[0247] S1601, The source base station sends the fourth information to the AMF network element.

[0248] The fourth information is used to request the UPF network element to send the first data to the source base station and a copy of the first data to the target base station.

[0249] For example, the fourth piece of information can be carried in the handover request. This handover request may also include the target base station identifier (TargetID), the PDU session identifier (PDU Session ID), DAPS handover related information, etc.

[0250] The target base station identifier is used to uniquely identify a target base station, enabling AMF network elements to communicate with the corresponding target base station based on this identifier. The PDU session identifier indicates a specific PDU session. DAPS handover related information indicates the DRB information for which the source base station requests a DAPS handover, and can also indicate all QoS flow information mapped to the corresponding DRB, thus clearly specifying which DRBs or QoS requirements the UPF network element needs to send a copy of the first data to the target base station.

[0251] Correspondingly, the AMF network element receives the fourth information.

[0252] S1602 and AMF network elements send the fourth information to the target base station.

[0253] For example, the fourth piece of information can be carried in the handover request. This handover request may also include the target base station identifier (TargetID), the PDU session identifier (PDU Session ID), DAPS handover related information, etc.

[0254] Correspondingly, the target base station receives the fourth information.

[0255] S1603, The target base station sends the second and / or seventh information to the AMF network element.

[0256] For example, the second information may include the target base station's data transmission channel address information (N3UP address) and the target base station's channel identification information (Tunnel ID). Based on the target access network device's data transmission channel address information and the target access network device's channel identification information, the corresponding target base station can be uniquely identified; that is, the second information can indicate the target base station corresponding to the first data transmission channel. Furthermore, the target base station can provide a data transmission channel address for each data transmission channel to be established (e.g., PDUsession) for transmitting a copy of the first data.

[0257] For example, the seventh information may include data transmission indication information for the target base station, which allows the UPF network element to send a copy of the first data to the target base station, rather than the UPF network element forwarding the data received from the source base station to the target base station.

[0258] For example, the second and / or seventh information can be carried in the handover request confirmation. This handover request confirmation may also include a DAPS acceptance message, information required for the terminal to access the target base station, etc.

[0259] The information required for a terminal to access a target base station may include the target cell identifier, the new cell radionetwork temporary identifier (C-RNTI), the target base station security algorithm identifier, dedicated RACH resources, the association between RACH resources and synchronization signal blocks (SSBs), the association between RACH resources and terminal-specific channel state information reference signals (CSI-RS) configurations, public RACH resources, and system information of the target cell.

[0260] Correspondingly, the AMF network element receives the second and / or seventh information.

[0261] S1604, the AMF network element sends the second information to the SMF network element.

[0262] For example, the second information may include the data transmission channel address information (N3UP address) of the target base station and the channel identification information (Tunnel ID) of the target base station.

[0263] For example, the second information can be carried in the Update Session Management Context Request (Nsmf_PDUSession_UpdateSMContextRequest) message.

[0264] Optionally, the AMF network element can also send a seventh piece of information to the SMF network element. This seventh piece of information can be an explicit indication or an implicit indication. For example, an explicit indication could be that the seventh piece of information is carried in an Update Session Management Context Request (Nsmf_PDUSession_UpdateSMContext Request) message; an implicit indication could be that it is pre-agreed upon (e.g., protocol stipulations) and does not carry data forwarding indication information. This data forwarding indication information is used to indicate that the UPF network element is allowed to forward data from the source base station to the target base station.

[0265] Correspondingly, the SMF network element receives the second information.

[0266] S1605, the SMF network element sends the second information to the UPF network element.

[0267] For example, the second information may include the data transmission channel address information (N3UP address) of the target base station and the channel identification information (Tunnel ID) of the target base station.

[0268] For example, the second information can be carried in a Session Modification Request message.

[0269] Understandably, the AMF and SMF network elements act as relay devices, sending the second information to the UPF network element.

[0270] The SMF network element can also send an eighth message to the UPF network element. This eighth message can be used to request the UPF network element to allocate a channel for transmitting a copy of the first data. This eighth message can be an explicit or implicit indication. For example, an explicit indication can be carried in a Session Modification Request message; an implicit indication can be pre-agreed upon (e.g., protocol stipulations) and not include the data forwarding channel allocation indication information. This data forwarding channel allocation indication information is used to instruct the UPF network element to allocate a channel for forwarding data from the source base station.

[0271] SMF network elements can communicate with UPF network elements through the N4 interface.

[0272] Correspondingly, the UPF network element receives the second information.

[0273] S1606, UPF network element sends third information to SMF network element.

[0274] For example, the third information may include the data transmission channel address information (UPF N3 address) and the channel identification information (UPF N3 Tunnel ID) of the UPF network element. Based on the data transmission channel address information and the channel identification information of the UPF network element, the corresponding UPF network element can be uniquely identified. In other words, the third information can indicate the UPF network element corresponding to the first data transmission channel.

[0275] For example, third-party information can be carried in a Session Modification Response message.

[0276] Correspondingly, the SMF network element receives the third information.

[0277] S1607. The SMF network element sends an Update Session Management Context Response (Nsmf_PDUSession_UpdateSMContextResponse) message to the AMF network element.

[0278] This message indicates that the first data transmission channel has been successfully established.

[0279] Correspondingly, the AMF network element receives the Update Session Management Context Response (Nsmf_PDUSession_UpdateSMContext Response) message.

[0280] S1608 and AMF network elements send the seventh information to the source base station.

[0281] For example, this seventh piece of information can be an explicit or implicit indication. The information required for the terminal to access the target base station may be transparent to the source base station.

[0282] For example, the seventh piece of information can be carried in the handover request confirmation. This handover request confirmation may also include a DAPS acceptance message, information required for the terminal to access the target base station, etc.

[0283] After the source base station receives the handover request confirmation, the source base station does not need to perform downlink data forwarding. That is, the source base station does not need to forward the downlink data received by the UPF network element to the target base station through the UPF network element.

[0284] Correspondingly, the source base station receives the seventh information.

[0285] S1609. The source base station sends an RRC reconfiguration message, i.e., a DAPS handover command, to the terminal.

[0286] This RRC reconfiguration message can trigger a terminal handover. This message includes the information required to access the target cell.

[0287] S1610, The source base station sends the fifth and / or sixth information to the AMF network element.

[0288] For example, the fifth piece of information includes the count value of the first data in the copy of the first data, which indicates the sequence number of the first data in the copy of the first data.

[0289] For example, the fifth and / or sixth information may be carried in an Early STATUS TRANSFER message. The name of the Early STATUS TRANSFER message is only an example, and the message may also have other names, which are not limited in this application.

[0290] It should be noted that the fifth and sixth pieces of information mentioned above can be carried in one message or in two messages, and this application does not impose any restrictions on this.

[0291] Correspondingly, the AMF network element receives the fifth and / or sixth information.

[0292] S1611 and AMF network elements send the fifth information to the target base station.

[0293] For example, the fifth piece of information includes the count value of the first data in the copy of the first data, which indicates the sequence number of the first data in the copy of the first data.

[0294] Correspondingly, the target base station receives the fifth piece of information.

[0295] S1612, the AMF network element sends the ninth message to the SMF network element.

[0296] The ninth piece of information is used to instruct the UPF network element to begin sending a copy of the first data to the target base station. This information includes, for example, the PDU session ID, the transfer or transmission method, and channel identification information (e.g., Tunnel ID). The transfer or transmission method can be copying.

[0297] For example, the ninth piece of information can be carried in a PDU Session Modification Request message.

[0298] Correspondingly, the SMF network element receives the ninth message.

[0299] S1613, Session Modification is performed between SMF network elements and UPF network elements.

[0300] For example, a UPF network element can copy the first data to obtain a copy of the first data. For instance, the UPF network element can determine to copy the QoS flow corresponding to the PDU session or the data corresponding to the DRB based on the PDU session ID to obtain a copy of the corresponding QoS flow or the corresponding data.

[0301] S1614, the UPF network element sends the first data to the source base station and sends a copy of the first data to the target base station.

[0302] In one possible implementation, the UPF network element can communicate with the base station via the N3 interface. Data is transmitted through the user plane (UP).

[0303] Accordingly, the source base station receives the first data, and the target base station receives a copy of the first data.

[0304] S1615, The target base station sends a copy of the first data to the terminal.

[0305] Accordingly, the terminal receives a copy of the first data.

[0306] It should be noted that this application embodiment only uses one AMF network element as an example for illustration. The number of AMF network elements can be one or more, and this application embodiment does not limit this. Similarly, this application embodiment does not limit the number of SMF network elements and UPF network elements.

[0307] Figure 17 is a schematic diagram of DAPS handover according to an embodiment of this application. As shown in Figure 17, during the DAPS handover process, the UPF network element sends downlink data to the source base station and sends a copy of the downlink data to the target base station. The source base station allocates a serial number (SN) to the downlink data before sending the data to the terminal; wherein, the source base station sends the fifth information to the target base station via the AMF network element, and the target base station allocates a serial number (SN) for the copy of the downlink data based on the fifth information, thus obtaining a copy of the downlink data after the SN allocation. That is, during the DAPS handover process, the communication links for downlink data are UPF network element → source base station and UPF network element → target base station.

[0308] The method provided in this application has been described above. In addition, this application also provides a communication device for implementing the functions described in the above method embodiments.

[0309] It is understood that, in order to achieve the aforementioned functions, the communication device includes hardware structures and / or software modules corresponding to the execution of each function. Those skilled in the art should readily recognize that, based on the units and algorithm steps of the examples described in conjunction with the embodiments disclosed herein, this application can be implemented in hardware or a combination of hardware and computer software. Whether a function is executed in hardware or by computer software driving hardware depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0310] This application embodiment can divide the communication device into functional modules according to the above method embodiment. For example, each function can be divided into a separate functional module, or two or more functions can be integrated into one processing module. The integrated module can be implemented in hardware or as a software functional module. It should be noted that the module division in this application embodiment is illustrative and only represents one logical functional division. In actual implementation, there may be other division methods.

[0311] Figure 18 is a schematic diagram of the structure of a communication device 180 according to an embodiment of this application. The communication device 180 includes a communication module 1801. The communication device 180 can be used to implement the functions of the above-mentioned UPF network element, the first access network device, or the second access network device.

[0312] In some embodiments, the communication device 180 may further include a storage module (not shown in FIG18) for storing program instructions and data.

[0313] In some embodiments, the communication device 180 may further include a processing module (not shown in FIG18) for processing instructions and data.

[0314] In some embodiments, the communication module 1801, also known as a transceiver unit, is used to implement sending and / or receiving functions. The communication module 1801 may consist of a transceiver circuit, a transceiver, a transceiver unit, or a communication interface.

[0315] In some embodiments, the communication module 1801 may include a receiving module and a transmitting module, respectively used to perform the receiving and transmitting steps performed by the UPF network element, the first access network device, or the second access network device in the above method embodiments, and / or other processes to support the technology described herein.

[0316] In one possible implementation, when the communication device 180 is used to implement the function of a UPF network element:

[0317] The communication module 1801 is used to receive first data, which includes downlink data of the terminal; send the first data to the source access network device of the terminal; and send a copy of the first data to the target access network device of the terminal.

[0318] The communication module 1801 is also used to receive second information, which is used to indicate the target access network device corresponding to the first data transmission channel, and the first data transmission channel is used to transmit a copy of the first data.

[0319] The communication module 1801 is also used to send third information to the first core network element, the third information being used to indicate the UPF network element corresponding to the first data transmission channel.

[0320] When the communication device 180 is used to implement the function of the first access network device, and the first access network device is the source access network device of the terminal, in one possible implementation:

[0321] The communication module 1801 is used to send fourth information, which is used to request the UPF network element to send first data to the first access network device and to send a copy of the first data to the target access network device of the terminal.

[0322] The communication module 1801 is also used to send a fifth message and / or a sixth message, wherein the fifth message is used to indicate the sequence number of the copy of the first data, and the sixth message is used to instruct the UPF network element to start sending a copy of the first data to the target access network device.

[0323] The communication module 1801 is also used to receive seventh information, which is used to indicate that the UPF network element is allowed to send a copy of the first data to the target access network device.

[0324] When the communication device 180 is used to implement the function of the second access network device, and the second access network device is the target access network device of the terminal, in one possible implementation:

[0325] The communication module 1801 is used to receive a copy of the first data, which is the downlink data of the terminal; and to send a copy of the first data to the terminal.

[0326] The communication module 1801 is also used to receive fourth information, which is used to request the UPF network element to send first data to the first access network device and to send a copy of the first data to the target access network device of the terminal.

[0327] The communication module 1801 is also used to send second information and / or seventh information. The second information is used to indicate the target access network device corresponding to the first data transmission channel. The first data transmission channel is used to transmit a copy of the first data. The seventh information is used to indicate that the UPF network element is allowed to send a copy of the first data to the target access network device.

[0328] The communication module 1801 is also used to receive fifth information, which is used to indicate the sequence number of the copy of the first data.

[0329] All relevant content of each step involved in the above method embodiments can be referenced from the functional description of the corresponding functional module, and will not be repeated here.

[0330] In this application, the communication device 180 can be presented in an integrated manner by dividing it into various functional modules. Here, "module" can refer to an application-specific integrated circuit (ASIC), a circuit, a processor and memory that executes one or more software or firmware programs, integrated logic circuits, and / or other devices that can provide the above functions.

[0331] In some embodiments, when the communication device 180 in FIG18 is a chip or chip system, the function / implementation process of the communication module 1801 can be implemented through the input / output interface (or communication interface) of the chip or chip system.

[0332] Since the communication device 180 provided in this embodiment can execute the above method, the technical effects it can achieve can be referred to the above method embodiment, and will not be repeated here.

[0333] As a possible product form, the UPF network element, first access network device, or second access network device described in the embodiments of this application can be implemented using the following: one or more field programmable gate arrays (FPGAs), programmable logic devices (PLDs), controllers, state machines, gate logic, discrete hardware components, any other suitable circuits, or any combination of circuits capable of performing the various functions described throughout this application.

[0334] As another possible product form, the UPF network element, the first access network device, or the second access network device in this application can adopt the structure shown in FIG19, or include the components shown in FIG19. FIG19 is a schematic diagram of the structure of a communication device 1900 according to an embodiment of this application. The communication device 1900 can be a UPF network element or a chip or system-on-a-chip in the UPF network element; or, it can be a first access network device or a module, chip, or system-on-a-chip in the first access network device; or, it can be a second access network device or a module, chip, or system-on-a-chip in the second access network device.

[0335] As shown in Figure 19, the communication device 1900 includes at least one processor 1901 and at least one communication interface (Figure 19 is merely an example illustrating the inclusion of a communication interface 1904 and a processor 1901). Optionally, the communication device 1900 may also include a communication bus 1902 and a memory 1903.

[0336] Processor 1901 can be a general-purpose central processing unit (CPU), a general-purpose processor, a network processor (NP), a digital signal processor (DSP), a microprocessor, a microcontroller, a PLD, or any combination thereof. Processor 1901 can also be other devices with processing capabilities, such as circuits, devices, or software modules, without limitation.

[0337] Communication bus 1902 is used to connect different components in communication device 1900, enabling communication between them. Communication bus 1902 can be a peripheral component interconnect (PCI) bus or an extended industry standard architecture (EISA) bus, etc. This bus can be divided into address bus, data bus, control bus, etc. For ease of illustration, only one thick line is used in Figure 19, but this does not indicate that there is only one bus or one type of bus.

[0338] Communication interface 1904 is used for communicating with other devices or communication networks. Exemplarily, communication interface 1904 can be a module, circuit, transceiver, or any device capable of communication. Optionally, communication interface 1904 can also be an input / output interface located within processor 1901, used to implement signal input and signal output for the processor.

[0339] The memory 1903 can be a device with storage function, used to store instructions and / or data. The instructions can be computer programs.

[0340] For example, the memory 1903 may be a read-only memory (ROM) or other type of static storage device capable of storing static information and / or instructions; it may also be a random access memory (RAM) or other type of dynamic storage device capable of storing information and / or instructions; it may also be an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital universal optical discs, Blu-ray discs, etc.), magnetic disk storage media or other magnetic storage devices, etc., without limitation.

[0341] It should be noted that the memory 1903 can exist independently of the processor 1901, or it can be integrated with the processor 1901. The memory 1903 can be located inside or outside the communication device 1900, without limitation. The processor 1901 can be used to execute the instructions stored in the memory 1903 to implement the methods provided in the following embodiments of this application.

[0342] As an optional implementation, the communication device 1900 may also include an output device 1905 and an input device 1906. The output device 1905 communicates with the processor 1901 and can display information in various ways. For example, the output device 1905 may be a liquid crystal display (LCD), a light-emitting diode (LED) display device, a cathode ray tube (CRT) display device, or a projector, etc. The input device 1906 communicates with the processor 1901 and can receive user input in various ways. For example, the input device 1906 may be a mouse, keyboard, touchscreen device, or sensing device, etc.

[0343] In some embodiments, those skilled in the art will recognize that the communication device 180 shown in FIG18 can take the form of the communication device 1900 shown in FIG19 in terms of hardware implementation.

[0344] The function / implementation process of the communication module 1801 in Figure 18 can be realized through the communication interface 1904 in the communication device 1900 shown in Figure 19.

[0345] It should be noted that the structure shown in Figure 19 does not constitute a specific limitation on the UPF network element, the first access network device, or the second access network device. For example, in other embodiments of this application, the UPF network element, the first access network device, or the second access network device may include more or fewer components than shown in the figure, or combine some components, or split some components, or have different component arrangements. The components shown in the figure may be implemented in hardware, software, or a combination of software and hardware.

[0346] In some embodiments, this application also provides a communication device, which includes a processor for implementing the methods in any of the above method embodiments.

[0347] As one possible implementation, the communication device also includes a memory. This memory stores necessary computer programs and data. The computer program may include instructions, which a processor can invoke to instruct the communication device to execute the methods described in any of the above method embodiments. Alternatively, the memory may not be present in the communication device.

[0348] As another possible implementation, the communication device also includes an interface circuit, which is a code / data read / write interface circuit, used to receive computer execution instructions (which are stored in memory and may be read directly from memory or may be transmitted through other devices) and transmit them to the processor.

[0349] As another possible implementation, the communication device also includes a communication interface for communicating with modules outside the communication device.

[0350] It is understood that the communication device can be a chip or a chip system. When the communication device is a chip system, it can be composed of chips or may include chips and other discrete devices. This application does not specifically limit this.

[0351] This application also provides a computer-readable storage medium storing a computer program or instructions thereon, which, when executed by a computer, implements the functions implemented by the UPF network element in any of the above method embodiments.

[0352] This application also provides a computer-readable storage medium having a computer program or instructions stored thereon, which, when executed by a computer, implements the functions performed by the first access network device in any of the above method embodiments.

[0353] This application also provides a computer-readable storage medium having a computer program or instructions stored thereon, which, when executed by a computer, implements the functions performed by the second access network device in any of the above method embodiments.

[0354] This application also provides a computer program product that, when executed by a computer, implements the functions performed by the UPF network element in any of the above method embodiments.

[0355] This application also provides a computer program product that, when executed by a computer, implements the functions performed by the first access network device in any of the above method embodiments.

[0356] This application also provides a computer program product that, when executed by a computer, implements the functions performed by the second access network device in any of the above method embodiments.

[0357] This application also provides a communication system, including a UPF network element, a first access network device, and a second access network device.

[0358] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0359] It is understood that the systems, apparatuses, and methods described in this application can also be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the couplings or direct couplings or communication connections shown or discussed may be through some interfaces; indirect couplings or communication connections between devices or units may be electrical, mechanical, or other forms.

[0360] The units described as separate components may or may not be physically separate; that is, they may be located in one place or distributed across multiple network units. The components shown as units may or may not be physical units. Some or all of the units can be selected to achieve the purpose of this embodiment, depending on actual needs.

[0361] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0362] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented using software programs, implementation can be, in whole or in part, in the form of a computer program product. This computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium accessible to a computer or a data storage device containing one or more servers, data centers, etc., that can be integrated with the medium. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state drive (SSD)). In embodiments of this application, the computer may include the aforementioned apparatus.

[0363] Although this application has been described herein in conjunction with various embodiments, those skilled in the art, by reviewing the accompanying drawings, disclosure, and appended claims, will understand and implement other variations of the disclosed embodiments in carrying out the claimed application. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality. A single processor or other unit can implement several functions listed in the claims. While different dependent claims may recite certain measures, this does not mean that these measures cannot be combined to produce good results.

[0364] Although this application has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made thereto without departing from the scope of this application. Accordingly, this specification and drawings are merely illustrative descriptions of the application as defined by the appended claims, and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from its scope. Thus, if such modifications and modifications fall within the scope of the claims and their equivalents, this application is also intended to include such modifications and modifications.

Claims

1. A communication method, characterized in that, The method, applied to User Plane Function (UPF) network elements, includes: Receive first data, the first data including downlink data from the terminal; Send the first data to the source access network device of the terminal; A copy of the first data is sent to the target access network device of the terminal.

2. The method according to claim 1, characterized in that, The method further includes: Receive second information, the second information being used to indicate that the first data transmission channel corresponds to the target access network device, the first data transmission channel being used to transmit a copy of the first data.

3. The method according to claim 2, characterized in that, The method further includes: Send third information to the first core network element, the third information being used to indicate that the first data transmission channel corresponds to the UPF network element.

4. A communication method, characterized in that, Applied to a first access network device, wherein the first access network device is the source access network device of the terminal, the method includes: Send a fourth message, which is used to request the User Plane Function (UPF) network element to send the first data to the first access network device and to send a copy of the first data to the target access network device of the terminal.

5. The method according to claim 4, characterized in that, The method further includes: Send a fifth message and / or a sixth message, wherein the fifth message is used to indicate the sequence number of the copy of the first data, and the sixth message is used to instruct the UPF network element to start sending a copy of the first data to the target access network device.

6. The method according to claim 4, characterized in that, The method further includes: The seventh information is received, which is used to indicate that the UPF network element is allowed to send a copy of the first data to the target access network device.

7. A communication method, characterized in that, Applied to a second access network device, which is the target access network device of the terminal, the method includes: Receive a copy of the first data, which is the terminal's downlink data; Send a copy of the first data to the terminal.

8. The method according to claim 7, characterized in that, The method further includes: The fourth information is received, which is used to request the User Plane Function (UPF) network element to send the first data to the first access network device and to send a copy of the first data to the target access network device of the terminal.

9. The method according to claim 7, characterized in that, The method further includes: Send a second message and / or a seventh message, wherein the second message is used to indicate that the first data transmission channel corresponds to the target access network device, the first data transmission channel is used to transmit a copy of the first data, and the seventh message is used to indicate that the UPF network element is allowed to send a copy of the first data to the target access network device.

10. The method according to claim 7, characterized in that, The method further includes: Receive fifth information, which indicates the sequence number of the copy of the first data.

11. A communication device, characterized in that, The communication device includes a module for performing the method as described in any one of claims 1-3, or includes a module for performing the method as described in any one of claims 4-6, or includes a module for performing the method as described in any one of claims 7-10.

12. A communication device, characterized in that, The communication device includes a processor; the processor is configured to run a computer program or instructions to cause the communication device to perform the method as described in any one of claims 1-3, or to cause the communication device to perform the method as described in any one of claims 4-6, or to cause the communication device to perform the method as described in any one of claims 7-10.

13. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions or programs that, when executed on a computer, cause the method as described in any one of claims 1-3 to be performed, or cause the method as described in any one of claims 4-6 to be performed, or cause the method as described in any one of claims 7-10 to be performed.

14. A computer program product, characterized in that, The computer program product includes computer instructions; when some or all of the computer instructions are executed on a computer, they cause the method as described in any one of claims 1-3 to be performed, or cause the method as described in any one of claims 4-6 to be performed, or cause the method as described in any one of claims 7-10 to be performed.

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