Data retransmission method, related equipment and communication system

Abstract

The invention relates to the field of XR. The invention specifically relates to a data retransmission method, related equipment and a communication system. The method comprises: a UPF network element receiving a transmission result and a transmission sequence number of a downlink data packet from an RAN device, the transmission result of the downlink data packet being used for indicating whether the downlink data packet is successfully transmitted to a UE; and the UPF network element determines whether the downlink data packet needs to be retransmitted based on the transmission result and the transmission sequence number of the downlink data packet. By adopting the embodiment of the invention, the data packet retransmission efficiency can be improved.

Description

Technical Field

[0001] This application relates to the field of XR, and more particularly to a data retransmission method, related equipment and communication system. Background Technology

[0002] To address the reliability issues in end-to-end transmission, packet retransmission is a common solution. This involves retransmitting lost or corrupted data packets when packet loss or data corruption is detected, ensuring that the receiving end can receive them correctly.

[0003] After the application server transmits a data packet to the user equipment (UE), the UE application layer detects whether the data transmission was successful. If the data packet is not received within a preset time, the UE application layer determines that the data packet transmission failed, that is, the UE did not receive the data packet. The UE application layer reports the data packet transmission failure to the application server. Only then does the application server know that the UE did not receive the data packet. The application server then decides whether to retransmit the data packet.

[0004] The process from the UE's application layer sensing a data packet to determining whether the data packet was not received and whether the data packet was successfully transmitted takes a long time. If the application server decides to retransmit the data packet based on the UE's feedback information, it will lead to low efficiency in data packet retransmission. Summary of the Invention

[0005] This application provides a data retransmission method, related equipment, and communication system. Using this application's embodiments is beneficial for improving the efficiency of data packet retransmission.

[0006] Firstly, embodiments of this application provide a data retransmission method. This method should be applicable to user plane function (UPF) network elements.

[0007] The UPF network element receives the transmission result and sequence number of downlink data packets transmitted between the RAN device and the UE from the radio access network (RAN) device. The transmission result of the downlink data packets between the RAN device and the UE indicates whether the transmission of the downlink data packets to the UE was successful, and the sequence number of the downlink data packets identifies the downlink data packets. The UPF network element determines whether the downlink data packets need to be retransmitted based on the transmission result and sequence number of the downlink data packets between the RAN device and the UE.

[0008] It can be seen that, compared with the existing technology, the introduction of UPF network elements and RAN equipment between the UE and the application server allows the UPF network element to decide whether to retransmit downlink data packets based on the transmission results of downlink data packets determined by the RAN equipment. Since the UPF network element and RAN equipment are closer to the UE than the application server, the UPF network element can make a faster decision on whether to retransmit downlink data packets based directly on the transmission results of downlink data packets between the RAN equipment and the UE, thereby improving the efficiency of data packet retransmission.

[0009] In conjunction with the first aspect, in a feasible implementation, the UPF network element determines whether the downlink data packet needs to be retransmitted based on the transmission result of the downlink data packet transmission between the RAN device and the UE and the transmission sequence number of the downlink data packet, including:

[0010] If the transmission result of the downlink data packet between the RAN device and the UE indicates that the downlink data packet transmission failed, the UPF network element determines that the downlink data packet needs to be retransmitted. The UPF network element determines the downlink data packet based on its transmission sequence number.

[0011] In conjunction with the first aspect, in a feasible implementation, the method in this example also includes:

[0012] The UPF network element obtains the downlink data packet and determines whether the downlink data packet is a data packet that needs to be retransmitted after being lost. If the downlink data packet is a data packet that needs to be retransmitted after being lost, the UPF network element adds a transmission sequence number to the downlink data packet.

[0013] It can be seen that the UPF network element only adds a transmission sequence number to the downlink data packets that need to be retransmitted after packet loss. When the UPF network element receives the transmission result indicating that the downlink data packet transmission failed, it also receives the transmission sequence number of the downlink data packet. The UPF network element can directly decide whether to retransmit the downlink data packet based on the transmission sequence number without relying on other information, which improves decision-making efficiency and thus helps to improve the efficiency of retransmission.

[0014] In conjunction with the first aspect, in a feasible implementation, the UPF network element determines the sequence number to retransmit the downlink data packet based on the transmission sequence number of the downlink data packet, including:

[0015] UPF network elements determine the retransmission identifier of downlink data packets based on the transmission sequence number. The retransmission identifier of downlink data packets is used to indicate whether the downlink data packet needs to be retransmitted in the event of a transmission failure. If the retransmission identifier of a downlink data packet indicates that the downlink data packet needs to be retransmitted, then the UPF network element determines that the downlink data packet needs to be retransmitted.

[0016] It can be seen that the UPF network element directly decides whether to retransmit the downlink data packet by using the retransmission flag of the downlink data packet, without needing to rely on other information to make the decision, which improves decision-making efficiency and thus helps to improve retransmission efficiency.

[0017] In conjunction with the first aspect, in a feasible implementation, the method of this embodiment further includes:

[0018] The retransmission identifier for downlink data packets can come from the application server side, meaning that the application server adds a retransmission identifier to the downlink data packet when sending it to the UPF side; or, the retransmission identifier for the downlink data packet can be determined by the UPF network element itself, meaning that the UPF determines whether the downlink data packet needs to be retransmitted after packet loss. For example, the UPF network element can determine whether the downlink data packet needs to be retransmitted after packet loss based on the importance of the downlink data packet.

[0019] In conjunction with the first aspect, in a feasible implementation, the method of this embodiment further includes:

[0020] The UPF network element receives the estimated retransmission delay of downlink data packets from the RAN device. The estimated retransmission delay of the downlink data packets is the estimated time required to retransmit the downlink data packets to the UE. It then obtains a retransmission delay threshold for the downlink data packets. The estimated time required to retransmit the downlink data packets to the UE can be the estimated time required for the RAN device to retransmit the downlink data packets to the UE, or the estimated time required for the UPF network element to retransmit the downlink data packets to the UE via the RAN device after the RAN device notifies the UPF network element, or the estimated time required for the UPF network element to retransmit the downlink data packets to the UE via the RAN device. Correspondingly, the retransmission delay threshold for the downlink data packets can be the retransmission delay threshold for the RAN device to retransmit the downlink data packets to the UE, or the retransmission delay threshold for the UPF network element to retransmit the downlink data packets to the UE via the RAN device after the RAN device notifies the UPF network element, or the retransmission delay threshold for the UPF network element to retransmit the downlink data packets to the UE via the RAN device.

[0021] If the retransmission flag of the downlink data packet indicates that the downlink data packet needs to be retransmitted, the UPF network element determines that the downlink data packet needs to be retransmitted, including:

[0022] If the retransmission flag of the downlink data packet is used to indicate that the downlink data packet needs to be retransmitted, and the estimated retransmission delay of the downlink data packet is less than or equal to the retransmission delay threshold of the downlink data packet, then the UPF network element determines that the downlink data packet needs to be retransmitted.

[0023] It can be seen that when the UPF network element decides whether to retransmit downlink data packets based on the retransmission flag of the downlink data packets, it introduces a retransmission delay threshold for downlink data packets. Only when the retransmission flag indicates that the downlink data packets need to be retransmitted, and the estimated retransmission delay of the downlink data packets is less than or equal to the retransmission delay of the downlink data packets, is it determined that the downlink data packets need to be retransmitted. This avoids the situation where the retransmission delay does not meet the requirements after the downlink data packets are retransmitted.

[0024] In conjunction with the first aspect, in a feasible implementation, the UPF network element receives the estimated retransmission delay of the downlink data packet from the RAN device. The estimated retransmission delay of the downlink data packet is the estimated time required for the RAN device to retransmit the downlink data packet to the UE, or the estimated time required for the UPF network element to retransmit the downlink data packet to the UE through the RAN device after the RAN side notifies the UPF network element, or the estimated time required for the UPF network element to retransmit the downlink data packet to the UE through the RAN device.

[0025] UPF network elements determine the need to retransmit downlink data packets based on the sequence number of the downlink data packets, including:

[0026] The UPF network element determines the retransmission delay threshold of the downlink data packet based on the transmission sequence number of the downlink data packet; if the estimated retransmission delay of the downlink data packet is less than or equal to the retransmission delay threshold of the downlink data packet, the UPF network element determines that the downlink data packet needs to be retransmitted.

[0027] It can be seen that when the UPF network element decides whether to retransmit downlink data packets, it introduces a retransmission delay threshold for downlink data packets. Only when the estimated retransmission delay of the downlink data packet is less than or equal to the actual retransmission delay of the downlink data packet is it determined that the downlink data packet needs to be retransmitted, thus avoiding the situation where the retransmission delay does not meet the requirements after the downlink data packet is retransmitted.

[0028] In conjunction with the first aspect, in a feasible implementation, the retransmission delay threshold for downlink data packets is obtained by the UPF network element from its local configuration, or from the session management function (SMF) network element or a third-party application.

[0029] In conjunction with the first aspect, in a feasible implementation, the transmission result of downlink data packets between the RAN device and the UE is determined by the RAN device based on feedback information from the UE regarding the downlink data packets sent from the RAN device to the UE. Therefore, this method results in a more accurate determination of the transmission result; or;

[0030] The transmission result of downlink data packets between the RAN device and the UE is determined by the RAN device based on the transmission status of its media access (MAC) layer transport blocks when sending downlink data packets to the UE. In other words, it is not determined based on the UE's reception status. Therefore, this method allows for faster determination of the transmission result.

[0031] In conjunction with the first aspect, in a feasible implementation, the method of this embodiment further includes:

[0032] When a UPF network element determines that a downlink data packet needs to be retransmitted, it retransmits the downlink data packet to the UE.

[0033] In conjunction with the first aspect, in a feasible implementation, the method of this embodiment further includes:

[0034] The UPF network element receives the first information from the UE. The first information is sent by the UE to the application server after the UPF network element or RAN device retransmits the downlink data packet to the UE. The first information is used to indicate that the UE has not received the downlink data packet. The UPF network element discards or ignores the first information.

[0035] It can be seen that when the UPF network element receives the first information indicating that the UE has not received the downlink data packet after retransmitting the downlink data packet to the UE, it can directly ignore or discard the first information to reduce the workload of the UPF network element.

[0036] In conjunction with the first aspect, in a feasible implementation, the UPF network element caches the aforementioned downlink data packets, or the UPF network element is equipped with an application server.

[0037] Secondly, embodiments of this application provide a data retransmission method. This method should be applicable to RAN devices.

[0038] The RAN device receives downlink data packets and their sequence numbers from the UPF network element; the RAN device sends downlink data packets to the UE to determine the transmission result of the downlink data packets between the RAN device and the UE; the RAN device sends the transmission result and sequence number of the downlink data packets to the UPF network element, which are used to determine whether the downlink data packets need to be retransmitted.

[0039] It can be seen that, compared with the existing technology, the introduction of UPF network elements and RAN equipment between the UE and the application server allows the UPF network element to decide whether to retransmit downlink data packets based on the transmission results of downlink data packets determined by the RAN equipment. Since the UPF network element and RAN equipment are closer to the UE than the application server, the UPF network element can make a decision on whether to retransmit downlink data packets more quickly based on the transmission results of downlink data packets between the RAN equipment and the UE, thereby improving the efficiency of data packet retransmission.

[0040] In conjunction with the second aspect, in a feasible implementation, the RAN device determines the transmission result of the downlink data packet, including:

[0041] The RAN device determines the transmission delay of sending downlink data packets to the UE; if the transmission delay of the downlink data packets exceeds a first transmission delay threshold, the RAN device determines that the downlink data packet transmission has failed; wherein, the transmission result of the downlink data packets includes downlink data packet transmission failure.

[0042] In conjunction with the second aspect, in a feasible implementation, the RAN device determines the transmission result of the downlink data packet, including:

[0043] The RAN device determines the transmission result of downlink data packets based on the transmission status of the RAN device's MAC layer transport blocks.

[0044] It can be seen that the transmission result of the downlink data packet is determined by the RAN device based on the transmission delay of the downlink data packet, or based on the sending status of the MAC layer transport block, or based on the feedback message from the UE side, rather than based on the upper-layer feedback information between the UE and the application server. This allows the RAN device to quickly know the transmission result of the downlink data packet. The UPF network element then decides whether to retransmit the downlink data packet based on the transmission result determined by the RAN device. This enables the UPF network element to make a quick decision, which is beneficial to improving the efficiency of data packet retransmission.

[0045] In conjunction with the second aspect, in a feasible implementation, the method of this embodiment further includes:

[0046] After receiving the transmission sequence number of the downlink data packet, the RAN device records the correspondence between the transmission sequence number of the downlink data packet and the sequence number of the packet data convergence protocol (PDCP) layer of the downlink data packet;

[0047] The RAN equipment determines the transmission result of downlink data packets, including:

[0048] The RAN device receives a feedback message from the UE, which includes a transmission identifier and a PDCP layer sequence number. The transmission identifier is used to indicate whether the UE has received the downlink data packet. The RAN device determines the transmission result of the downlink data packet based on the correspondence between the PDCP layer sequence number and the transmission sequence number, the PDCP layer sequence number, and the transmission identifier.

[0049] As can be seen from the PDCP layer sequence number, the data interaction between the RAN device and the UE is achieved through the PDCP layer. Therefore, the feedback information received by the RAN device is generated by the UE's underlying layer sensing whether downlink data packets have been received, rather than by the UE's application layer sensing whether downlink data packets have been received. Since the UE's underlying layer can directly sense whether downlink data packets have been received, the RAN device can quickly obtain feedback information from the RAN's underlying layer regarding downlink data packets, and thus quickly determine the transmission result of the downlink data packets. This allows the UPF network element to quickly make a decision on whether to retransmit the downlink data packets based on the transmission result determined by the RAN device, which is beneficial to improving the efficiency of data packet retransmission. The UE's application layer can be the UE's transport layer or application layer, or other protocol layers above IP. The UE's underlying layer refers to the protocol layers between the UE and the RAN device, including but not limited to the physical layer, MAC layer, radio link control (RLC) layer, and PDCP layer.

[0050] In conjunction with the second aspect, in a feasible implementation, the method of this embodiment further includes:

[0051] The RAN device sends the estimated retransmission delay of the downlink data packet to the UPF network element. The estimated retransmission delay of the downlink data packet is used to determine whether the downlink data packet needs to be retransmitted. The estimated retransmission delay of the downlink data packet is the estimated time required for the RAN device to retransmit the downlink data packet to the UE, or the estimated time required for the UPF network element to retransmit the downlink data packet to the UE through the RAN device after the RAN device notifies the UPF network element, or the estimated time required for the UPF network element to retransmit the downlink data packet to the UE through the RAN device.

[0052] It can be seen that by sending the estimated retransmission delay of downlink data packets to the UPF network element, the UPF network element takes into account the estimated retransmission delay of downlink data packets when deciding whether to retransmit them. Only when the estimated retransmission delay of downlink data packets is less than or equal to the actual retransmission delay of downlink data packets is it determined that downlink data packets need to be retransmitted, thus avoiding the situation where the retransmission delay does not meet the requirements after retransmitting downlink data packets.

[0053] In conjunction with the second aspect, in a feasible implementation, the transmission result of the downlink data packet, the sequence number of the downlink data packet, and / or the estimated retransmission delay of the downlink data packet are carried in the user-plane general packet radio service tunneling protocol for user plane (GTP-U) layer of the uplink data packet. This uplink data packet can be a data packet sent by the UE to the server or an empty packet generated by the RAN side.

[0054] Thirdly, embodiments of this application provide a data retransmission method. This method should be applicable to RAN equipment.

[0055] The RAN device receives third information and downlink data packets from the application server. The third information is used to determine whether retransmission is required after the downlink data packet transmission fails. The RAN device sends downlink data packets to the UE. When the RAN device determines that the downlink data packet transmission has failed, the RAN device determines to retransmit the downlink data packet to the UE based on the third information.

[0056] As can be seen, compared with the existing technology, the introduction of RAN equipment between UE and application server allows RAN equipment to make decisions on whether to retransmit downlink data packets based on the transmission results of downlink data packets determined by RAN equipment and third-party information. Since RAN equipment is closer to UE than application server, it can make decisions on whether to retransmit downlink data packets more quickly based on the transmission results of downlink data packets between RAN equipment and UE, thereby improving the efficiency of data packet retransmission.

[0057] In conjunction with the third aspect, in a feasible implementation, the third information includes retransmission indication information for downlink data packets, which is used to indicate that downlink data packets need to be retransmitted in the event of transmission failure.

[0058] In conjunction with the third aspect, in a feasible implementation, the retransmission indication information includes the transmission sequence number of the downlink data packet or the retransmission identifier of the downlink data packet.

[0059] In conjunction with the third aspect, in a feasible implementation, the third information includes a downlink data packet retransmission delay threshold. The RAN device determines to retransmit the downlink data packet to the UE based on the third information, including:

[0060] The RAN device obtains the estimated retransmission delay of the downlink data packet; the estimated retransmission delay of the downlink data packet is the estimated time required for the RAN device to retransmit the downlink data packet to the UE; when the estimated retransmission delay of the downlink data packet is less than or equal to the retransmission delay threshold of the downlink data packet, the RAN device determines to retransmit the downlink data packet to the UE.

[0061] It can be seen that when deciding whether to retransmit downlink data packets, the RAN device considers the estimated retransmission delay of the downlink data packets. Only when the estimated retransmission delay of the downlink data packets is less than or equal to the actual retransmission delay of the downlink data packets is it determined that the downlink data packets need to be retransmitted, thus avoiding the situation where the retransmission delay does not meet the requirements after the downlink data packets are retransmitted.

[0062] In conjunction with the third aspect, in a feasible implementation, the method of this embodiment further includes:

[0063] The RAN device determines the transmission delay of sending downlink data packets to the UE; if the transmission delay of the downlink data packets exceeds a first transmission delay threshold, the RAN device determines that the downlink data packet transmission has failed, wherein the transmission result of the downlink data packets includes downlink data packet transmission failure.

[0064] In conjunction with the third aspect, in a feasible implementation, the method of this embodiment further includes:

[0065] The RAN device determines the transmission result of the downlink data packet based on the transmission status of the MAC layer transport block of the RAN device, and determines whether the downlink data packet transmission has failed based on the transmission result of the downlink data packet; or the RAN device determines the transmission result of the downlink data packet based on the feedback message of the PDCP layer on the UE side, and determines whether the downlink data packet transmission has failed based on the transmission result of the downlink data packet.

[0066] It can be seen that the transmission result of the downlink data packet is determined by the RAN device based on the transmission delay, or based on the sending status of the MAC layer transport block, or based on the feedback message from the UE side, rather than based on the upper-layer feedback information between the UE and the application server. This allows the RAN device to quickly know the transmission result of the downlink data packet. The RAN device decides whether to retransmit the downlink data packet based on the transmission result of the downlink data packet, which helps to improve the efficiency of data packet retransmission.

[0067] In conjunction with the third aspect, in a feasible implementation, the method of this embodiment further includes:

[0068] After receiving the transmission sequence number of the downlink data packet, the RAN device records the correspondence between the transmission sequence number of the downlink data packet and the PDCP layer sequence number of the downlink data packet;

[0069] The RAN device determines the transmission result of the downlink data packet, including:

[0070] The RAN device receives a feedback message from the RAN, which includes a transmission identifier and a PDCP layer sequence number. The transmission identifier of the downlink data packet is used to indicate whether the UE has received the downlink data packet. The RAN device determines whether the downlink data packet transmission has failed based on the correspondence between the PDCP layer sequence number and the transmission sequence number, the PDCP layer sequence number and the transmission identifier.

[0071] As can be seen from the PDCP layer sequence number, the data interaction between the RAN device and the UE is achieved through the PDCP layer. Therefore, the feedback information received by the RAN device is generated by the UE's underlying layer sensing whether downlink data packets have been received, rather than by the UE's application layer sensing whether downlink data packets have been received. Since the UE's underlying layer can directly sense whether downlink data packets have been received, the RAN device can quickly obtain feedback information from the RAN's physical layer regarding downlink data packets, and thus quickly determine the transmission result of the downlink data packets. This allows the RAN device to quickly make a decision on whether to retransmit the downlink data packets based on the transmission result determined by the RAN device, which is beneficial to improving the efficiency of data packet retransmission. Here, the UE's application layer can be the UE's transport layer or application layer, or other protocol layers above IP, while the UE's underlying layer refers to the protocol layers between the UE and the RAN, including but not limited to the physical layer, MAC layer, radio link layer (RLC layer), and PDCP layer.

[0072] In conjunction with the third aspect, in a feasible implementation, the method of this embodiment further includes:

[0073] After retransmitting the downlink data packet to the UE, the RAN device sends a second message to the UPF network element, which indicates that the downlink data packet has been retransmitted to the UE.

[0074] It can be seen that by sending the second information to the UPF network element to inform the UPF network element that the downlink data packet has been retransmitted to the UE, when the UPF network element subsequently receives the first information from the UE to the application server indicating that the downlink data packet has not been received, since the downlink data packet has been retransmitted to the UE, the UPF network element can directly ignore or discard the first information, thereby reducing the workload of the UPF network element.

[0075] In conjunction with the third aspect, in a feasible implementation, the method of this embodiment further includes:

[0076] After the RAN device retransmits the transmission result of the downlink data packet to the UE, if it receives the first information sent by the UE to the application server, and the first information indicates that the UE has not received the downlink data packet, then it discards or ignores the first information.

[0077] Since the downlink data packet has been retransmitted to the UE, but the first information fed back by the UE to the application server has been received, the RAN device can directly ignore or discard the first information to reduce the workload of the application server.

[0078] Fourthly, embodiments of this application provide a data retransmission method. This method should be applicable to UPF network elements.

[0079] The UPF network element acquires downlink data packets and obtains the third information of the downlink data packets. The third information is used to determine whether the downlink data packets need to be retransmitted after transmission failure. The UPF network element sends the downlink data packets and the third information to the RAN device.

[0080] Compared to existing technologies, this approach introduces a UPF network element and a RAN device between the UE and the application server. The UPF network element sends third information about the downlink data packets to the RAN device, which uses this third information to determine whether the downlink data packets need to be retransmitted. Because the RAN device is closer to the UE than the application server, it can make a faster decision on whether to retransmit the downlink data packets based on the transmission results between the RAN device and the UE, thereby improving the efficiency of data packet retransmission.

[0081] In conjunction with the fourth aspect, in a feasible implementation, the UPF network element obtains the third information of the downlink data packet, including:

[0082] UPF network elements add transmission sequence numbers to downlink data packets, and the third information includes the transmission sequence number.

[0083] Furthermore, after acquiring the downlink data packet, the UPF network element determines whether the downlink data packet is a data packet that needs to be retransmitted after being lost; if the downlink data packet is a data packet that needs to be retransmitted after being lost, the UPF network element adds a transmission sequence number to the downlink data packet.

[0084] Adding a sequence number to downlink data packets serves two purposes: firstly, it identifies the downlink data packet; secondly, when adding a sequence number only to downlink data packets that need to be retransmitted after packet loss, the sequence number is used to identify that the downlink data packet needs to be retransmitted after packet loss.

[0085] In conjunction with the fourth aspect, in a feasible implementation, the third information includes retransmission indication information for downlink data packets, which is used to indicate that downlink data packets need to be retransmitted to the UE in the event of transmission failure.

[0086] In conjunction with the fourth aspect, in a feasible implementation, the retransmission indication information includes the transmission sequence number of the downlink data packet or the retransmission identifier of the downlink data packet.

[0087] In conjunction with the fourth aspect, in a feasible implementation, the third information includes a downlink data packet retransmission delay threshold, which is used to determine whether downlink data packets need to be retransmitted to the UE.

[0088] By sending the retransmission delay threshold of downlink data packets to the RAN device, the RAN device considers the retransmission delay threshold when deciding whether to retransmit downlink data packets. Only when the estimated retransmission delay of the downlink data packet is less than or equal to the actual retransmission delay of the downlink data packet is it determined that the downlink data packet needs to be retransmitted, thus avoiding the situation where the retransmission delay does not meet the requirements after the downlink data packet is retransmitted.

[0089] In conjunction with the fourth aspect, in a feasible implementation, the third information can be carried in the GTP-U layer of the downlink data packet.

[0090] In conjunction with the fourth aspect, in a feasible implementation, the retransmission delay threshold for downlink data packets in the third information can be derived from the session management network element.

[0091] In conjunction with the fourth aspect, in a feasible implementation, the method of this embodiment also includes:

[0092] The UPF network element receives a second message from the RAN device, which indicates that the downlink data packet has been retransmitted to the UE.

[0093] In conjunction with the fourth aspect, in a feasible implementation, the method of this embodiment further includes:

[0094] After receiving the second information, the UPF network element receives the first information from the UE, which indicates that no downlink data packets have been received; or discards or ignores the first information.

[0095] It can be seen that after receiving the second information from the RAN device, the UPF network element receives the first information from the UE. The first information is an indication sent by the UE to the application server to indicate that the downlink data packet has not been received. Since the RAN device has retransmitted the downlink data packet to the UE, the UPF network element discards or ignores the first information to reduce the workload of the UPF network element and also avoids unnecessary retransmission by the application server.

[0096] Fifthly, embodiments of this application provide a data retransmission method. This method should be applicable to the application layer of the UE.

[0097] The UE's application layer receives the transmission result of the uplink data packet from the UE's underlying layer during transmission between the UE's underlying layer and the RAN device, as well as the transmission sequence number of the uplink data packet. Based on the transmission result and transmission sequence number of the uplink data packet during transmission between the UE's underlying layer and the RAN device, the UE's application layer determines whether to retransmit the uplink data packet by sequence number.

[0098] As can be seen, by introducing the UE's underlying layer between the UE's application layer and the application server, the UE's application layer determines whether to retransmit the uplink data packet based on the transmission result of the uplink data packet determined by the UE's underlying layer. Since the UE's underlying layer can quickly know the transmission result of the uplink data packet between the UE's underlying layer and the RAN device, it can make a faster decision on whether to retransmit the uplink data packet, thus improving the efficiency of data packet retransmission. Here, the UE's application layer can be the UE's transport layer or application layer, or other protocol layers above IP, while the UE's underlying layer refers to the protocol layer between the UE and the RAN, including but not limited to the physical layer, MAC layer, RLC layer, and PDCP layer.

[0099] In conjunction with the fifth aspect, in a feasible implementation, the method of this embodiment further includes:

[0100] The UE's application layer obtains the uplink data packet; the UE's application layer determines whether the uplink data packet is a data packet that needs to be retransmitted after being lost; if the uplink data packet is a data packet that needs to be retransmitted after being lost, the UE's application layer adds a transmission sequence number to the uplink data packet.

[0101] In conjunction with the fifth aspect, in a feasible implementation, the UE's application layer determines whether to retransmit the uplink data packet based on the transmission result of the uplink data packet between the UE's underlying layer and the RAN device and the transmission sequence number of the uplink data packet, including:

[0102] If the transmission result of the uplink data packet between the UE's underlying layer and the RAN device indicates that the uplink data packet transmission failed, the UE's application layer determines that the uplink data packet needs to be retransmitted.

[0103] It can be seen that the UE's application layer only adds a transmission sequence number to the uplink data packets that need to be retransmitted after packet loss. When the UE's application layer receives the transmission result indicating that the uplink data packet transmission has failed, it also receives the transmission sequence number of the uplink data packet. The UE's application layer can directly decide whether to retransmit the uplink data packet based on the transmission sequence number without relying on other information, which improves decision-making efficiency and thus helps to improve the efficiency of retransmission.

[0104] In conjunction with the fifth aspect, in a feasible implementation, the UE's application layer determines that uplink data packets need to be retransmitted, including:

[0105] The UE's application layer determines the retransmission identifier of the uplink data packet based on the transmission sequence number. The retransmission identifier of the uplink data packet is used to indicate whether the uplink data packet needs to be retransmitted in the event of a transmission failure. If the retransmission identifier of the uplink data packet indicates that the uplink data packet needs to be retransmitted, then the UE's application layer determines that the uplink data packet needs to be retransmitted. Alternatively, the UE's application layer determines whether the uplink data packet needs to be retransmitted based on the importance of the uplink data packet.

[0106] It can be seen that the UE's application layer directly decides whether to retransmit the uplink data packet by using the retransmission flag of the uplink data packet, which improves decision-making efficiency and thus helps to improve retransmission efficiency.

[0107] In conjunction with the fifth aspect, in a feasible implementation, the method of this embodiment further includes:

[0108] The UE's application layer receives the estimated retransmission delay of uplink data packets from the UE's underlying layer. The estimated retransmission delay of uplink data packets is the estimated time required to retransmit the uplink data packets to the RAN device. The UE's application layer obtains the retransmission delay threshold of uplink data packets. The UE's application layer can be the UE's transport layer or application layer, or a protocol layer on top of IP. The UE's underlying layer refers to the protocol layer between the UE and the RAN, including but not limited to the physical layer, MAC layer, RLC layer, PDCP layer, etc.

[0109] If the retransmission flag of the uplink data packet indicates that the uplink data packet needs to be retransmitted, the UE's application layer determines that the uplink data packet needs to be retransmitted, including:

[0110] If the retransmission flag of the uplink data packet is used to indicate that the uplink data packet needs to be retransmitted, and the estimated retransmission delay of the uplink data packet is less than or equal to the retransmission delay threshold of the uplink data packet, then the application layer of the UE determines that the uplink data packet needs to be retransmitted.

[0111] It can be seen that when the UE's application layer decides whether to retransmit the uplink data packet based on the retransmission flag of the uplink data packet, it introduces an uplink data packet retransmission delay threshold. Only when the uplink data packet retransmission flag indicates that the uplink data packet needs to be retransmitted, and the estimated retransmission delay of the uplink data packet is less than or equal to the retransmission delay of the uplink data packet, is it determined that the uplink data packet needs to be retransmitted. This avoids the situation where the retransmission delay does not meet the requirements after the uplink data packet is retransmitted.

[0112] In conjunction with the fifth aspect, in a feasible implementation, the method of this embodiment further includes:

[0113] The UE's application layer receives the estimated retransmission delay of the uplink data packet from the UE's underlying layer. The estimated retransmission delay of the uplink data packet is the estimated time required to retransmit the uplink data packet to the RAN device.

[0114] The UE's application layer determines that uplink data packets need to be retransmitted, including:

[0115] If the estimated retransmission delay of the uplink data packet is less than or equal to the retransmission delay threshold of the uplink data packet, the UE's application layer determines that the uplink data packet needs to be retransmitted.

[0116] It can be seen that when the UE's application layer decides whether to retransmit uplink data packets, it introduces a retransmission delay threshold for uplink data packets. Only when the estimated retransmission delay of the uplink data packet is less than or equal to the actual retransmission delay of the uplink data packet is it determined that the uplink data packet needs to be retransmitted, thus avoiding the situation where the retransmission delay does not meet the requirements after retransmitting the uplink data packet.

[0117] In conjunction with the fifth aspect, in a feasible implementation, the retransmission delay threshold for uplink data packets is obtained by the UE application layer from its local configuration, or from the SMF network element or a third-party application.

[0118] In conjunction with the fifth aspect, in a feasible implementation, the method of this embodiment further includes:

[0119] The UE's application layer receives a fourth message from the application server; the fourth message is sent by the RAN after the UE retransmits the uplink data packet to the RAN device at the UE's bottom layer, and the fourth message is used to indicate that the application server has not received the uplink data packet; the UE's application layer discards or ignores the fourth message.

[0120] As can be seen, since the uplink data packet has been retransmitted to the UE, when the fourth information indicating that the UE has not received the uplink data packet is received, the UE's application layer can directly ignore or discard the fourth information to reduce the workload of the UE's application layer.

[0121] Sixthly, embodiments of this application provide a data retransmission method. This method should be applicable to the underlying layer of the UE.

[0122] The UE's lower layer receives uplink data packets and their sequence numbers from the UE's application layer; the UE's lower layer sends uplink data packets to the RAN device; the UE's lower layer determines the transmission result of the uplink data packets; the UE's lower layer sends the transmission result and sequence number of the uplink data packets to the UE's application layer, which are used to determine whether the uplink data packets need to be retransmitted. Here, the UE's application layer can be the UE's transport layer or application layer, or other protocol layers above IP, while the UE's lower layer refers to the protocol layer between the UE and the RAN, including but not limited to the physical layer, MAC layer, RLC layer, and PDCP layer.

[0123] As can be seen, by introducing the UE's underlying layer between the UE's application layer and the application server, the UE's application layer can quickly decide whether to retransmit the uplink data packet based on the transmission result of the uplink data packet determined by the UE's underlying layer. Since the UE's underlying layer can quickly know the transmission result of the uplink data packet between the UE's underlying layer and the RAN device, the UE's application layer can make a decision on whether to retransmit the uplink data packet more quickly based on the transmission result, which is conducive to improving the efficiency of data packet retransmission.

[0124] In conjunction with the sixth aspect, in a feasible implementation, the UE's underlying layer determines the transmission result of the uplink data packet, including:

[0125] The UE's underlying layer determines the transmission delay of sending uplink data packets to the RAN device; if the transmission delay of uplink data packets exceeds the second transmission delay threshold, the UE's underlying layer determines that the uplink data packet transmission has failed, wherein the transmission result of uplink data packets includes uplink data packet transmission failure.

[0126] In conjunction with the sixth aspect, in a feasible implementation, the UE's underlying layer determines the transmission result of the uplink data packet, including:

[0127] The UE's underlying layer determines the transmission result of uplink data packets based on the transmission status of the UE's underlying transport blocks.

[0128] It can be seen that the transmission result of the uplink data packet is determined by the UE's underlying layer based on the transmission delay of the uplink data packet or based on the sending status of the underlying transport block, rather than based on feedback information from the application server. This allows the UE's underlying layer to quickly know the transmission result of the uplink data packet, and then decide whether to retransmit the uplink data packet based on the transmission result determined by the UE's underlying layer, which is beneficial to improving the efficiency of data packet retransmission.

[0129] In conjunction with the sixth aspect, in a feasible implementation, the method of this embodiment further includes:

[0130] After receiving the transmission sequence number of the uplink data packet, the UE's underlying layer records the correspondence between the transmission sequence number of the uplink data packet and the PDCP layer sequence number of the uplink data packet;

[0131] The underlying layer of the UE determines the transmission result of the uplink data packet, including:

[0132] The UE's underlying layer receives a feedback message from the RAN device, which includes a transmission identifier and a PDCP layer sequence number. The transmission identifier is used to indicate whether the RAN device has received the uplink data packet. The UE's underlying layer determines the transmission result of the uplink data packet based on the correspondence, the PDCP layer sequence number, and the transmission identifier.

[0133] In conjunction with the sixth aspect, in a feasible implementation, the method of this embodiment further includes:

[0134] The UE's underlying layer sends the estimated retransmission delay of the uplink data packet to the UE's application layer. The estimated retransmission delay of the uplink data packet is used to determine whether the uplink data packet needs to be retransmitted. The estimated retransmission delay of the uplink data packet is the estimated time required for the UE's underlying layer to retransmit the uplink data packet to the RAN device.

[0135] It can be seen that by sending the estimated retransmission delay of uplink data packets to the UE's application layer, the UE's application layer considers the estimated retransmission delay of uplink data packets when deciding whether to retransmit them. Only when the estimated retransmission delay of uplink data packets is less than or equal to the actual retransmission delay of uplink data packets is it determined that uplink data packets need to be retransmitted, thus avoiding the situation where the retransmission delay does not meet the requirements after retransmitting uplink data packets.

[0136] In conjunction with the sixth aspect, in a feasible implementation, the method of this embodiment further includes:

[0137] The UE's lower layer receives the fifth information sent by the UE's application layer, which indicates whether it is necessary to determine the transmission result of the uplink data packet; and sends the transmission result of the uplink data packet and the transmission sequence number of the uplink data packet to the UE's application layer.

[0138] In a seventh aspect, embodiments of this application provide a UPF network element, including units or modules for implementing the method provided in the first aspect or any possible implementation of the first aspect, or including units or modules for implementing the method provided in the fourth aspect or any possible implementation of the fourth aspect.

[0139] Eighthly, embodiments of this application provide a RAN device including units or modules for implementing the method provided in the second aspect or any possible implementation of the second aspect, or including units or modules for implementing the method provided in the third aspect or any possible implementation of the third aspect.

[0140] Ninthly, embodiments of this application provide a UE including units or modules for implementing the method provided in the fifth aspect or any possible implementation of the fifth aspect, or including units or modules for implementing the method provided in the sixth aspect or any possible implementation of the sixth aspect.

[0141] In a tenth aspect, embodiments of this application provide a UPF network element, including a processor and a memory. The memory is used to store program code. The processor is used to call the program code stored in the memory to execute the method provided in the first aspect or any possible implementation of the first aspect, or to include units or modules for implementing the method provided in the fourth aspect or any possible implementation of the fourth aspect.

[0142] Eleventhly, embodiments of this application provide a RAN device, including a processor and a memory. The memory is used to store program code. The processor is used to call the program code stored in the memory to execute the method provided in the second aspect or any possible implementation of the second aspect, or to include units or modules for implementing the method provided in the third aspect or any possible implementation of the third aspect.

[0143] In a twelfth aspect, embodiments of this application provide a UE, including a processor and a memory. The memory is used to store program code. The processor is used to invoke the program code stored in the memory to execute the method provided in the fifth aspect or any possible implementation of the fifth aspect, or to include units or modules for implementing the method provided in the sixth aspect or any possible implementation of the sixth aspect.

[0144] In a thirteenth aspect, embodiments of this application provide a computer storage medium including computer instructions that, when executed on an electronic device, cause the electronic device to perform a method provided by any possible implementation of the first aspect, or any possible implementation of the second aspect, or any possible implementation of the third aspect, or any possible implementation of the fourth aspect, or any possible implementation of the fifth aspect, or any possible implementation of the sixth aspect.

[0145] In a fourteenth aspect, embodiments of this application provide a computer program product that, when run on a computer, causes the computer to perform a method as provided in any of the possible implementations of the first aspect, or any of the possible implementations of the second aspect, or any of the possible implementations of the third aspect, or any of the possible implementations of the fourth aspect, or any of the possible implementations of the fifth aspect, or any of the possible implementations of the sixth aspect.

[0146] In a fifteenth aspect, embodiments of this application also provide a data retransmission method, which is applied to a communication system including a UE, a RAN device, and a UPF network element. The method includes:

[0147] The RAN device receives downlink data packets and their sequence numbers from the UPF network element.

[0148] The RAN device sends downlink data packets to the UE to determine the transmission result of the downlink data packets between the RAN device and the UE;

[0149] The RAN device sends the transmission result of the downlink data packet between the RAN device and the UE and the transmission sequence number of the downlink data packet to the UPF network element; wherein, the transmission result of the downlink data packet between the RAN device and the UE is used to indicate whether the transmission of the downlink data packet to the UE was successful.

[0150] UPF network elements determine whether downlink data packets need to be retransmitted based on the transmission result of downlink data packets between the RAN device and the UE and the transmission sequence number of the downlink data packets.

[0151] In a sixteenth aspect, embodiments of this application also provide a communication system, which includes a UE, a RAN device, and a UPF network element;

[0152] RAN equipment is used to receive downlink data packets and their sequence numbers from UPF network elements.

[0153] RAN equipment, used to send downlink data packets to UE;

[0154] RAN equipment is used to determine the transmission outcome of downlink data packets;

[0155] The RAN device is used to send the transmission result of the downlink data packet between the RAN device and the UE and the transmission sequence number of the downlink data packet to the UPF network element; wherein, the transmission result of the downlink data packet is used to indicate whether the transmission of the downlink data packet to the UE was successful.

[0156] The UPF network element is used to determine whether downlink data packets need to be retransmitted based on the transmission result of downlink data packets between the RAN device and the UE and the transmission sequence number of the downlink data packets.

[0157] In a seventeenth aspect, embodiments of this application also provide a data retransmission method, which is applied to a communication system including a UE, a RAN device, and a UPF network element. The method includes:

[0158] UPF network elements acquire downlink data packets and obtain the third information of the downlink data packets. The third information is used to determine whether the downlink data packets need to be retransmitted after transmission failure.

[0159] The UPF network element sends downlink data packets and the third information to the RAN device; wherein, the third information is used to determine whether retransmission is required after the downlink data packet transmission fails.

[0160] The RAN device sends downlink data packets to the UE;

[0161] When the RAN device determines that the downlink data packet transmission has failed, the RAN device determines to retransmit the downlink data packet to the UE based on third-party information.

[0162] In an eighteenth aspect, embodiments of this application also provide a communication system, which includes a UE, a RAN device, and a UPF network element;

[0163] UPF network elements are used to acquire downlink data packets and obtain the third information of the downlink data packets. The third information is used to determine whether the downlink data packets need to be retransmitted after a transmission failure.

[0164] UPF network elements are used to send downlink data packets and the third information to RAN devices;

[0165] RAN equipment, used to send downlink data packets to UE;

[0166] The RAN device is used to determine, based on third-party information, to retransmit downlink data packets to the UE when the RAN device determines that downlink data packet transmission has failed.

[0167] In a nineteenth aspect, embodiments of this application also provide a data retransmission method, which is applied to a communication system including a UE and a RAN device; the method includes:

[0168] The UE's underlying layer receives uplink data packets and their sequence numbers from the UE's application layer.

[0169] The UE's underlying layer sends uplink data packets to the RAN device;

[0170] The UE's underlying layer determines the transmission result of uplink data packets between the UE's underlying layer and the RAN device;

[0171] The transmission result and sequence number of the uplink data packet transmitted between the UE's underlying layer and the RAN device are sent from the UE's application layer to the uplink data packet transmission result.

[0172] The UE's application layer determines whether to retransmit the uplink data packet based on the transmission result of the uplink data packet between the UE's underlying layer and the RAN device and the transmission sequence number of the uplink data packet.

[0173] In a twentieth aspect, embodiments of this application also provide a communication system, which includes a UE and a RAN device;

[0174] The UE's underlying layer is used to receive uplink data packets and uplink data packet sequence numbers from the UE's application layer.

[0175] The underlying layer of the UE is used to send uplink data packets to the RAN device;

[0176] The UE's underlying layer is used to determine the transmission result of uplink data packets between the UE's underlying layer and the RAN device;

[0177] The UE's underlying layer is used to send uplink data packets to the UE's application layer, transmitting the transmission results and sequence numbers of the uplink data packets between the UE's underlying layer and the RAN device.

[0178] The UE's application layer is used to determine whether to retransmit the uplink data packet based on the transmission result of the uplink data packet transmission between the UE's underlying layer and the RAN device and the transmission sequence number of the uplink data packet.

[0179] It is understood that the beneficial effects of the embodiments described in the seventh to twentieth aspects can be referred to the beneficial effects of the methods described in the first to sixth aspects, and will not be repeated here. Attached Figure Description

[0180] Figure 1 A schematic diagram of a communication system architecture provided in an embodiment of this application;

[0181] Figure 2 A flowchart illustrating a data retransmission method provided in an embodiment of this application;

[0182] Figure 3 A flowchart illustrating another data retransmission method provided in an embodiment of this application;

[0183] Figure 4 A flowchart illustrating another data retransmission method provided in an embodiment of this application;

[0184] Figure 5 A flowchart illustrating another data retransmission method provided in an embodiment of this application;

[0185] Figure 6 A flowchart illustrating another data retransmission method provided in an embodiment of this application;

[0186] Figure 7 A flowchart illustrating another data retransmission method provided in an embodiment of this application;

[0187] Figure 8 An interactive flowchart illustrating a data retransmission method provided in an embodiment of this application;

[0188] Figure 9 An interactive flowchart illustrating another data retransmission method provided in this application embodiment;

[0189] Figure 10An interactive flowchart illustrating another data retransmission method provided in this application embodiment;

[0190] Figure 11 A schematic diagram of the structure of a UPF network element provided in an embodiment of this application;

[0191] Figure 12 This is a schematic diagram of the structure of a RAN device provided in an embodiment of this application;

[0192] Figure 13 A schematic diagram of the structure of a UE provided in an embodiment of this application;

[0193] Figure 14 This is a schematic diagram of the structure of a communication device provided in an embodiment of this application. Detailed Implementation

[0194] The terms “first,” “second,” “third,” and “fourth,” etc., used in the specification, claims, and drawings of this application are used to distinguish different objects, not to describe a specific order.

[0195] "Multiple" refers to two or more. "And / or" describes the relationship between related objects, indicating three possible relationships. For example, A and / or B means: A exists alone, A and B exist simultaneously, or B exists alone. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0196] The embodiments of this application will now be described with reference to the accompanying drawings.

[0197] See Figure 1 , Figure 1 This is a schematic diagram of a communication system architecture provided in an embodiment of this application. The communication system is a network architecture diagram of 5th Generation Mobile Networks (5G). It includes a radio access network (RAN), which can be represented as two parts: RAN equipment and a core network (CN). The RAN equipment provides network access functionality for authorized user equipment (UE) in a specific area and can use transmission tunnels of different qualities according to the UE's level and service requirements. For example, the RAN equipment can manage radio resources, provide access services to the UE, and thus complete the forwarding of control information and / or data information between the UE and the CN.

[0198] To facilitate understanding of the embodiments of this application, firstly, in conjunction with Figure 1 This application describes one application scenario in detail.

[0199] 1. User equipment (UE): This can be referred to as terminal equipment, terminal, access terminal, user unit, user station, mobile station, mobile station, remote station, remote terminal, mobile device, user terminal, wireless communication equipment, user agent, or user device. Terminal equipment can also be a cellular phone, cordless phone, session initiation protocol (SIP) phone, wireless local loop (WLL) station, personal digital assistant (PDA), handheld device with wireless communication capabilities, computing device or other processing device connected to a wireless modem, vehicle-mounted device, drone, wearable device, terminal equipment in a 5G network, or terminal equipment in an evolved public land mobile network (PLMN), etc., and this application embodiment does not limit this.

[0200] 2. Access Network (AN): Provides network access for authorized users in a specific area and can use transmission tunnels of different qualities depending on the user's level and service requirements. Access networks can employ different access technologies. Current access network technologies include: radio access network technologies used in 3G systems, radio access network technologies used in 4G systems, or next-generation radio access network (NG-RAN) technologies (such as those used in 5G systems).

[0201] An access network that uses wireless communication technology to implement access network functions can be called a radio access network (RAN). A RAN manages radio resources, provides access services to terminals, and facilitates the forwarding of control signals and user data between terminals and the core network.

[0202] Wireless access network equipment can be, for example, a base station (NodeB), an evolved NodeB (eNB or eNodeB), a next-generation Node base station (gNB) in a 5G mobile communication system, a base station in a future mobile communication system, or an access point (AP) in a Wi-Fi hotspot system. It can also be a wireless controller in a cloud radio access network (CRAN) scenario, or it can be a relay station, access point, vehicle-mounted equipment, drone, wearable device, or network equipment in a 5G network or an evolved PLMN. This application does not limit the specific technology or equipment form used in the wireless access network equipment.

[0203] 3. Access Management Network Element: Primarily used for mobility management and access management, responsible for transmitting user policies between user equipment and PCF network elements, etc. It can be used to implement other functions of the Mobile Management Entity (MME) besides session management. For example, access authorization (authentication) function.

[0204] In 5G communication systems, the access management network element can be an access and mobility management function (AMF) network element. In future communication systems, the access management network element can still be an AMF network element, or it can have other names; this application does not limit this.

[0205] 4. Session Management Network Element: Primarily used for session management, allocation and management of Internet Protocol (IP) addresses for user equipment, selection of endpoints for manageable user plane functions, policy control and billing function interfaces, and downlink data communication.

[0206] In 5G communication systems, the session management network element can be an SMF network element. In future communication systems, the session management network element can still be an SMF network element, or it can have other names; this application does not limit this.

[0207] 5. User plane network elements: used for packet routing and forwarding, QoS processing of user plane data, completion of user plane data forwarding, session / flow-level billing statistics, bandwidth limiting functions, etc.

[0208] In 5G communication systems, user plane network elements can be UPF network elements. In future communication systems, user plane network elements can still be UPF network elements, or they can have other names; this application does not limit this.

[0209] 6. Data network element: A network used to provide data transmission.

[0210] In 5G communication systems, data network elements can be data network (DN) elements. In future communication systems, data network elements can still be DN elements, or they can have other names; this application does not limit this.

[0211] 7. Policy control network element: A unified policy framework used to guide network behavior, providing policy rule information to control plane functional network elements (such as AMF, SMF, etc.).

[0212] In 4G communication systems, this policy control network element can be a Policy and Charging Rules Function (PCRF) network element. In 5G communication systems, this policy control network element can be a PCF network element. In future communication systems, this policy control network element can still be a PCF network element, or it can have other names; this application does not limit its scope.

[0213] 8. Data management network element: used to handle user equipment identification, access authentication, registration, and mobility management, etc.

[0214] In 5G communication systems, this data management network element can be a unified data management (UDM) network element; in 4G communication systems, this data management network element can be a home subscriber server (HSS) network element. In future communication systems, the data management network element can still be a UDM network element, or it can have other names; this application does not limit this.

[0215] 9. Network Exposure Function (NEF) Element: Used to securely expose services and capabilities provided by the 3rd Generation Partnership Project (3GPP) network functions to the outside world.

[0216] 10. Application Function (AF) Network Element: Provides a specific application layer service to the UE. When providing services to the UE, the AF has requirements for QoS and charging policies and needs to notify the network. Simultaneously, the AF also needs to obtain application-related information from the core network. The AF can possess all the functions defined in the technical specification (TS) 23.501R-15, as well as related functions for application services. That is, in the user plane architecture, the application server (AS) and the UE communicate in the user plane via the UE-RAN-UPF-AF path. The AF can also communicate with other network function (NF) network elements in the 5G core network (5GC) in the control plane architecture via the NEF. For example, it can communicate with the PCF network element via the NEF network element. If the AF is deployed by the 5GC operator, the AF network element can also communicate directly with other NF network elements in the 5GC in the control plane architecture without going through the NEF network element, such as directly communicating with the PCF network element.

[0217] 11. Network Data Analysis Function (NWDAF) Network Element: It can be used to collect data from network elements, AF and operation administration and maintenance (OAM) management system, and analyze the data through machine learning, artificial intelligence and other solutions, and feed it back to network elements, AF, etc. to optimize network or service configuration, thereby providing better network quality and service experience.

[0218] 12. Network Repository Function (NRF) Network Element: This element provides network element discovery functionality, offering network element information corresponding to the network element type based on requests from other network elements. NRF network elements also provide network element management services, such as network element registration, updates, deregistration, and network element status subscription and push notifications.

[0219] 13. Authentication server function (AUSF) network element: mainly responsible for authenticating users to determine whether to allow users or devices to access the network.

[0220] 14. Service Communication Proxy (SCP) element: It can be used for indirect communication between NFs. Service requests from NFs can be proxied by the SCP.

[0221] Figure 1 N1, N2, N3, N4, N6, N9, Nnwdaf, Nnef, Nnrf, Npcf, Nudm, Naf, Nausf, Namf, and Nsmf are interface sequence numbers. The meanings of these interface sequence numbers can be found in the definition of 3GPP TS 23.501.

[0222] It should be understood that the network architecture described above for the embodiments of this application is merely an example, and the network architecture applicable to the embodiments of this application is not limited thereto. Any network architecture capable of realizing the functions of the above-described network elements is applicable to the embodiments of this application.

[0223] It should also be understood that Figure 1 The AMF, SMF, UPF, NEF, PCF, UDM, NWDAF, NRF, AUSF, and SCP network elements shown can be understood as network elements in the core network used to implement different functions, such as network slices that can be combined as needed. These core network elements can be independent devices or integrated into the same device to implement different functions. This application does not limit the specific form of the above network elements.

[0224] It should also be understood that the above naming is defined solely for the purpose of distinguishing different functions and should not constitute any limitation on this application. This application does not preclude the possibility of using other naming conventions in 5G networks and other future networks. For example, in 6G networks, some or all of the aforementioned network terminology may be retained from 5G, or other names may be used. Figure 1 The interface names between the various network elements are merely examples; in actual implementations, the interface names may differ, and this application does not impose any specific limitations on them. Furthermore, the names of the messages (or signaling) transmitted between the aforementioned network elements are also merely examples and do not constitute any limitation on the function of the messages themselves.

[0225] See Figure 2 , Figure 2 This is a flowchart illustrating a data retransmission method provided in an embodiment of this application. The method is applied to... Figure 1 UPF network elements in the network. For example... Figure 2 As shown, the method includes:

[0226] S201, the UPF network element receives the transmission result of the downlink data packet transmitted between the RAN device and the UE and the transmission sequence number of the downlink data packet. The transmission result of the downlink data packet transmitted between the RAN device and the UE is used to indicate whether the RAN device successfully transmitted the downlink data packet to the UE.

[0227] In one feasible embodiment, the UPF network element obtains downlink data packets from the application server; when the application server is deployed on the UPF network element, the UPF network element generates downlink data packets itself.

[0228] After acquiring downlink data packets, UPF network elements have two processing methods for the downlink data packets:

[0229] Method 1: The UPF network element adds a first transmission sequence number to all acquired downlink data packets. This first transmission sequence number is used to identify the downlink data packet. Optionally, the UPF network element sets a retransmission delay threshold and / or a retransmission flag for the downlink data packet. The retransmission flag of the downlink data packet indicates whether the downlink data packet needs to be retransmitted in the event of transmission failure, and the retransmission delay threshold determines whether the downlink data packet needs to be retransmitted in the event of packet loss.

[0230] Specifically, when setting a retransmission flag for downlink data packets, the UPF network element determines whether a downlink data packet needs to be retransmitted after packet loss after acquiring each downlink data packet. That is, whether the downlink data packet needs to be retransmitted after packet loss. If the downlink data packet needs to be retransmitted after packet loss, the retransmission flag indicates that the downlink data packet needs to be retransmitted in the event of transmission failure; if the downlink data packet does not need to be retransmitted after packet loss, the retransmission flag indicates that the downlink data packet does not need to be retransmitted in the event of transmission failure. This retransmission flag is determined by the UPF network element. For example, the UPF network element can determine whether the downlink data packet needs to be retransmitted after packet loss based on information representing the importance of the downlink data packet carried in the downlink data packet sent by the application server; or, if the application server is deployed on the UPF network element, the UPF network element can determine whether the downlink data packet needs to be retransmitted after packet loss based on the importance of the downlink data packet.

[0231] It should be noted that the data packets that need to be retransmitted after packet loss are those that will affect the processing of subsequent data packets (such as encoding and decoding processing) after loss, or data packets corresponding to key frames.

[0232] When adding a retransmission delay threshold to acquired downlink data packets, the UPF network element can add a retransmission delay threshold to each acquired downlink data packet; however, multiple downlink data packets may have the same retransmission delay threshold. In the case where multiple downlink data packets may have the same retransmission delay threshold, the UPF network element can add the retransmission delay threshold to only one of these downlink data packets. When transmitting multiple downlink data packets with the same retransmission delay threshold to the RAN device, these multiple downlink data packets can be sent simultaneously or consecutively. The downlink data packet with the added retransmission delay threshold is the first among these multiple downlink data packets to be transmitted to the RAN device; alternatively, if the retransmission delay thresholds of the downlink data packets are the same or change slowly, the UPF network element can notify the RAN device of a fixed retransmission delay threshold through the SMF network element.

[0233] Method 2: After acquiring each downlink data packet, the UPF network element determines whether the downlink data packet is one that needs to be retransmitted after packet loss. If the downlink data packet is one that needs to be retransmitted after packet loss, the UPF network element adds a second transmission sequence number to the downlink data packet. If the downlink data packet is not one that needs to be retransmitted after packet loss, the UPF network element does not add a second transmission sequence number to the downlink data packet. In this case, the second transmission sequence number has two functions: first, it is used to identify the downlink data packet; second, it is used to indicate that the downlink data packet is one that needs to be retransmitted after packet loss, or it is used to trigger the RAN device to determine the transmission result of the downlink data packet and send the transmission result and transmission sequence number of the downlink data packet to the UPF network element. Optionally, when adding a retransmission delay threshold to the acquired downlink data packets, the UPF network element can add a retransmission delay threshold to each acquired downlink data packet.

[0234] It should be noted that the second transmission sequence number of the downlink data packet can be an existing identifier used to distinguish downlink data packets, such as the TCP identifier or the RTP identifier, or it can be newly generated.

[0235] Optionally, the UPF network element sends the downlink data packet retransmission delay threshold to the RAN device while sending the downlink data packet to the RAN device.

[0236] In some cases, multiple downlink data packets may have the same retransmission delay threshold. The UPF network element can add the retransmission delay threshold to only one of these downlink data packets. When transmitting multiple downlink data packets with the same retransmission delay threshold to the RAN device, these multiple downlink data packets can be sent simultaneously or consecutively. The downlink data packet with the added retransmission delay threshold is the first among these multiple downlink data packets to be transmitted to the RAN device. Alternatively, if the retransmission delay thresholds of the downlink data packets are the same or change slowly, the UPF network element can notify the RAN device of a fixed retransmission delay threshold through the SMF network element.

[0237] It should be noted that the retransmission delay threshold for downlink data packets can be sent directly from the SMF network element to the RAN device. In this case, the retransmission delay threshold for downlink data packets on the SMF network element can come from the UPF network element or a third-party application.

[0238] In one example, the SMF network element sends a retransmission delay threshold to the RAN device. The SMF network element can carry the retransmission delay threshold in the QoS parameters sent to the RAN device, meaning that the retransmission delay threshold for the downlink data packets corresponding to this QoS flow is the same, and they are all the same retransmission delay threshold.

[0239] In another example, after a third-party application generates a downlink data packet, it carries a retransmission delay threshold in the downlink data packet sent to the UPF network element.

[0240] After processing the downlink data packet as described above, the UPF network element sends the downlink data packet to the RAN device, so that the RAN device can send the downlink data packet to the UE. Optionally, if the downlink data packet has a corresponding sequence number (including a first sequence number or a second sequence number), the UPF network element also transmits the downlink data packet with the added sequence number to the RAN device.

[0241] After the RAN device sends a downlink data packet to the UE, the RAN device can obtain the transmission result of the downlink data packet and send the transmission result of the downlink data packet to the UPF network element. Optionally, if the downlink data packet has a corresponding transmission sequence number (including a first transmission sequence number or a second transmission sequence number), the RAN device also sends the transmission sequence number of the downlink data packet to the UPF network element.

[0242] S202. The UPF network element determines whether to retransmit the downlink data packet based on the transmission result of the downlink data packet between the RAN device and the UE and the transmission sequence number of the downlink data packet.

[0243] The aforementioned transmission sequence number includes either the first transmission sequence number or the second transmission sequence number.

[0244] In one feasible implementation, for the case where the UPF network element only adds a second transmission sequence number to downlink data packets that need to be retransmitted after packet loss, the UPF network element determines whether the downlink data packet was successfully transmitted based on the transmission result of the downlink data packet. If the transmission result of the downlink data packet indicates that the downlink data packet transmission failed, the UPF network element determines that the downlink data packet needs to be retransmitted based on the second transmission sequence number of the downlink data packet.

[0245] Optionally, if the downlink data packet transmission failure is determined based on the transmission result of the downlink data packet, the UPF network element determines whether the downlink data packet needs to be retransmitted based on the downlink data packet retransmission delay threshold and the estimated retransmission delay of the downlink data packet obtained from the RAN device. The estimated retransmission delay of the downlink data packet is the estimated time required to retransmit the downlink data packet to the UE. This time can be the time required for the downlink data packet to travel from the RAN device to the UE (i.e., RAN device -> UE) (i.e., the air interface transmission delay between the RAN device and the UE), or the sum of the time required for the RAN device to obtain the downlink data packet to be retransmitted from the UPF network element and the time required for the data packet to travel from the RAN device to the UE, i.e., the time from RAN device -> UPF network element -> RAN device -> UE. If the estimated retransmission delay of the downlink data packet is less than or equal to the downlink data packet retransmission delay threshold, the UPF network element determines that the downlink data packet needs to be retransmitted; if the estimated retransmission delay of the downlink data packet is greater than the downlink data packet retransmission delay threshold, the UPF network element determines that the downlink data packet does not need to be retransmitted.

[0246] It should be noted that the retransmission delay threshold for downlink data packets is obtained by the UPF network element from its local configuration, or from the SMF network element or a third-party application.

[0247] In one example, the SMF network element sends a retransmission delay threshold to the UPF network element. The SMF network element can carry the retransmission delay threshold in the N4 rule sent to the UPF network element, meaning that the retransmission delay threshold for the downlink data packets corresponding to this service flow is the same, and they are all the same retransmission delay threshold.

[0248] In another example, after a third-party application generates a downlink data packet, it carries a retransmission delay threshold in the downlink data packet sent to the UPF.

[0249] The process of RAN device -> UPF network element -> RAN device refers to the RAN device obtaining the downlink data packets that need to be retransmitted from the UPF network element. The transmission time between the RAN device and the UPF network element can also be called CN PDB, which can be determined based on the operator's configuration information.

[0250] In one feasible implementation, when the UPF network element adds a first transmission sequence number to each acquired downlink data packet, in one example, the UPF network element determines the retransmission identifier of the downlink data packet based on the first transmission sequence number of the downlink data packet. There is a correspondence between the first transmission sequence number of the downlink data packet and the retransmission identifier of the downlink data packet. If the retransmission identifier of the downlink data packet is used to indicate that the downlink data packet needs to be retransmitted in the event of transmission failure, then the UPF network element determines that the downlink data packet needs to be retransmitted; if the retransmission identifier of the downlink data packet is used to indicate that the downlink data packet does not need to be retransmitted in the event of transmission failure, then the UPF network element determines that the downlink data packet does not need to be retransmitted.

[0251] In another example, the UPF network element determines whether to retransmit a downlink data packet based on a downlink data packet retransmission delay threshold and the estimated retransmission delay obtained from the RAN device. The estimated retransmission delay is the estimated time required to retransmit the downlink data packet to the UE. If the estimated retransmission delay is less than or equal to the downlink data packet retransmission delay threshold, the UPF network element determines that the downlink data packet needs to be retransmitted; if the estimated retransmission delay is greater than the downlink data packet retransmission delay threshold, the UPF network element determines that the downlink data packet does not need to be retransmitted.

[0252] In another example, the UPF network element determines the retransmission delay threshold and retransmission identifier of the downlink data packet based on the first transmission sequence number of the downlink data packet. There is a correspondence between the first transmission sequence number of the downlink data packet and the retransmission delay threshold and retransmission identifier. The estimated retransmission delay of the downlink data packet is obtained from the RAN device. The estimated retransmission delay of the downlink data packet is the estimated time required to retransmit the downlink data packet to the UE. If the estimated retransmission delay of the downlink data packet is less than or equal to the retransmission delay threshold of the downlink data packet, and the retransmission identifier of the downlink data packet is used to indicate that the downlink data packet needs to be retransmitted in the event of transmission failure, then the UPF network element determines that the downlink data packet needs to be retransmitted. If the estimated retransmission delay of the downlink data packet is greater than the retransmission delay threshold of the downlink data packet, or the retransmission identifier of the downlink data packet is used to indicate that the downlink data packet does not need to be retransmitted in the event of transmission failure, then the UPF network element determines that the downlink data packet does not need to be retransmitted.

[0253] It should be noted that if the transmission result of the downlink data packet is sent when the RAN device determines that the estimated transmission delay of the downlink data packet is less than or equal to the retransmission delay threshold of the downlink data packet, then when the UPF decides whether to retransmit the downlink data packet, it only considers the second transmission sequence number of the downlink data packet, or only considers the second transmission sequence number and the retransmission identifier of the downlink data packet, and no longer considers the retransmission delay threshold of the downlink data packet.

[0254] The UPF network element is equipped with an application server. After determining whether the downlink data packet needs to be retransmitted, the UPF network element retransmits the downlink data packet to the UE. If the UPF network element determines that the downlink data packet does not need to be retransmitted, the UPF network element does not perform the operation of retransmitting the downlink data packet to the UE.

[0255] It should be noted that when the UPF network element determines to retransmit downlink data packets to the UE, it may optionally adjust the priority of the flow corresponding to the downlink data packet to ensure that the downlink data packet can be sent to the UE side quickly.

[0256] In one feasible implementation, the UPF network element receives first information from the UE. The first information is sent by the UE to the application server after the UPF network element or RAN device retransmits the downlink data packet to the UE, and the first information is used to indicate that the UE has not received the downlink data packet before the retransmission. The UPF network element discards or ignores the first information.

[0257] If the UPF network element determines that it has retransmitted the downlink data packet to the UE, but it has not yet reached the UE, and if it receives the UE's first information at this time, the UPF network element ignores or discards the first information.

[0258] As can be seen, compared with the prior art, the solution in this embodiment introduces a UPF network element and a RAN device between the UE and the application server. The UPF network element decides whether to retransmit the downlink data packet based on the transmission result of the downlink data packet determined by the RAN device. Since the UPF network element and RAN device are closer to the UE than the application server, the UPF network element can make a faster decision on whether to retransmit the downlink data packet based directly on the transmission result of the downlink data packet between the RAN device and the UE, thereby improving the efficiency of data packet retransmission. The UPF network element only adds a second transmission sequence number to the downlink data packet that needs to be retransmitted after packet loss. When the UPF network element receives the transmission result indicating that the downlink data packet transmission has failed, it also receives the second transmission sequence number of the downlink data packet. The UPF network element can directly decide whether to retransmit the downlink data packet based on the second transmission sequence number without relying on other information, improving decision-making efficiency and thus improving retransmission efficiency. When the UPF network element adds a first transmission sequence number to each acquired downlink data packet, it determines the retransmission identifier of the downlink data packet based on this first transmission sequence number. The UPF network element directly decides whether to retransmit the downlink data packet based solely on this retransmission identifier, without needing to rely on other information, thus improving decision-making efficiency and consequently improving retransmission efficiency. When deciding whether to retransmit a downlink data packet, the UPF network element introduces a downlink data packet retransmission delay threshold. Only when the estimated retransmission delay of the downlink data packet is less than or equal to its actual retransmission delay is the retransmission determined to be necessary, preventing situations where the retransmission delay does not meet the requirements after retransmission.

[0259] See Figure 3 , Figure 3 This is a flowchart illustrating another data retransmission method provided in an embodiment of this application. The method is applied to... Figure 1 RAN equipment in the system. For example... Figure 3 As shown, the method includes:

[0260] S301, the RAN device receives downlink data packets and their sequence numbers from the UPF network element.

[0261] It should be noted that the UPF network element has two processing methods when adding transmission sequence numbers to the acquired downlink data packets:

[0262] 1. The UPF network element adds a first transmission sequence number to all acquired downlink data packets. The first transmission sequence number is used to identify the downlink data packets.

[0263] 2. After acquiring each downlink data packet, the UPF network element determines whether the downlink data packet is a packet that needs to be retransmitted after being lost. If the downlink data packet is a packet that needs to be retransmitted after being lost, the UPF network element adds a second transmission sequence number to the downlink data packet. That is, this second transmission sequence number is used to trigger the RAN device to determine the transmission result of the downlink data packet and send the second transmission sequence number and the transmission result of the downlink data packet to the UPF network element. At this time, the transmission sequence number has two functions: one is to identify the downlink data packet, and the other is to indicate that the downlink data packet is a packet that needs to be retransmitted after being lost. In other words, for downlink data packets that do not need to be retransmitted, the UPF network element only needs to send the downlink data packet to the RAN device, and does not need to send the second transmission sequence number of the downlink data packet to the RAN device, nor does it need to instruct the RAN device to report the transmission result of the downlink data packet to the UPF network element.

[0264] S302. The RAN device sends downlink data packets to the UE and determines the transmission result of the downlink data packets between the RAN device and the UE.

[0265] In one feasible embodiment, when the RAN device receives a downlink data packet from a UPF network element, the RAN device assigns a PDCP layer sequence number to the downlink data packet. If it also receives the transmission sequence number of the downlink data packet, the RAN device records the correspondence between the PDCP layer sequence number assigned to the downlink data packet and the transmission sequence number of the downlink data packet. The RAN device sends the downlink data packet to the UE through the PDCP layer. This downlink data packet carries the assigned PDCP layer sequence number, meaning the RAN device can determine the transmission result of the downlink data packet based on the result of sending the PDCP layer data packet.

[0266] In a feasible implementation, the RAN device determines the transmission result of downlink data packets in two ways:

[0267] Method 1: The RAN device determines whether the downlink data packet was successfully transmitted based on the feedback information from the UE. For example, the information fed back by the UE includes the PDCP layer sequence number and transmission identifier of the downlink data packet. The RAN device determines that the transmission identifier is the transmission identifier of the downlink data packet based on the correspondence between the PDCP layer sequence number and the transmission sequence number. The transmission identifier of the downlink data packet is used to indicate whether the UE has received the downlink data packet or whether the downlink data packet has been lost. The RAN device determines whether the downlink data packet was successfully transmitted based on the transmission identifier of the downlink data packet.

[0268] It should be noted that if the RAN device queries the correspondence between the transmission sequence number and the PDCP layer sequence number based on the PDCP layer sequence number of the downlink data packet and fails to find the transmission sequence number corresponding to the PDCP layer sequence number of the downlink data packet, it means that the downlink data packet does not have a corresponding transmission sequence number. In other words, when the UPF network element adds a transmission sequence number to the downlink data packet, it only adds a transmission sequence number to the data packet that needs to be retransmitted after packet loss. That is to say, the downlink data packet without a transmission sequence number is the data packet that does not need to be retransmitted after packet loss. Therefore, the RAN device can ignore or discard the feedback information of the downlink data packet without a corresponding transmission sequence number.

[0269] In one example, the transmission identifier of the downlink data packet is NACK or ACK; when the transmission identifier of the downlink data packet is NACK, it means that the UE has not received the downlink data packet, that is, the downlink data packet transmission has failed; when the transmission identifier of the downlink data packet is ACK, it means that the UE has received the downlink data packet, that is, the downlink data packet transmission has been successful.

[0270] Method 2: The RAN device determines whether the downlink data packet was successfully transmitted based on its own information. For example, in RLCUM mode, the RAN device determines whether the downlink data packet was successfully transmitted based on the actual transmission status of the MAC layer transport blocks; or, the RAN device obtains the transmission duration of the downlink data packet to the UE, that is, the elapsed time of transmitting the downlink data packet to the UE. If the transmission duration exceeds the first transmission duration threshold, the RAN device determines that the downlink data packet transmission failed.

[0271] It should be noted that downlink data packet transmission failure includes cases where the RAN device fails to transmit data even after MAC layer retransmission between the RAN device and the UE; optionally, downlink data packet transmission failure also includes cases where the RAN device fails to transmit data even after MAC layer and RLC layer retransmission between the RAN device and the UE.

[0272] S303. The RAN device sends the transmission result of the downlink data packet between the RAN device and the UE and the transmission sequence number of the downlink data packet to the UPF network element. The transmission result of the downlink data packet between the RAN device and the UE and the transmission sequence number of the downlink data packet are used to determine whether the downlink data packet needs to be retransmitted.

[0273] Optionally, the RAN device also sends the estimated retransmission delay of the downlink data packet to the UPF network element. The estimated retransmission delay is the estimated time required for the RAN device to retransmit the downlink data packet to the UE, or the estimated time required for the UPF network element to retransmit the downlink data packet to the UE via the RAN device after notification, or the estimated time required for the UPF network element to retransmit the downlink data packet to the UE via the RAN device. The transmission result, sequence number, and / or estimated retransmission delay of the downlink data packet are carried in the GTP-U layer of the uplink data packet. Here, the uplink data packet is either a data packet from the UE or an empty packet generated by the RAN device and sent to the UPF network element.

[0274] Optionally, if the RAN device obtains the retransmission delay threshold for downlink data packets, the RAN device determines the estimated retransmission delay of the downlink data packets. If the estimated retransmission delay of the downlink data packets is less than or equal to the retransmission delay threshold, the RAN device sends the transmission result and sequence number of the downlink data packets to the UPF network element. The retransmission delay threshold for the downlink data packets can be obtained from the UPF network element, the SMF network element, or a third-party application.

[0275] During the process of the RAN device obtaining the retransmission delay threshold of downlink data packets, if multiple downlink data packets have the same retransmission delay threshold, and the UPF network element sends multiple downlink data packets to the RAN device simultaneously or continuously, and the first downlink data packet carries the retransmission delay threshold, the RAN device determines whether the retransmission delay threshold can be obtained from the downlink data packets. If the retransmission delay threshold can be obtained from the downlink data packets, then the retransmission delay threshold is determined to be the retransmission delay threshold of the downlink data packet; if the retransmission delay threshold cannot be determined from the downlink data packets, then the retransmission delay threshold of the downlink data packet is determined to be the same as the retransmission delay threshold of the previous downlink data packet.

[0276] It should be noted that when the UPF network element determines to retransmit downlink data packets to the UE, it may optionally adjust the priority of the flow corresponding to the downlink data packet to ensure that the downlink data packet can be sent to the UE side quickly.

[0277] In S302 and S303, the transmission sequence number of the downlink data packet includes either the first transmission sequence number or the second transmission sequence number.

[0278] As can be seen, compared with the prior art, the solution in this embodiment introduces a UPF network element and a RAN device between the UE and the application server. The UPF network element decides whether to retransmit the downlink data packet based on the transmission result of the downlink data packet determined by the RAN device. Since the UPF network element and RAN device are closer to the UE than the application server, the UPF network element can directly and quickly make a decision on whether to retransmit the downlink data packet based on the transmission result between the RAN and the UE, thereby improving the efficiency of data packet retransmission. The transmission result of the downlink data packet can be determined by the RAN device based on the transmission delay of the downlink data packet or based on the sending status of the MAC layer transport block, rather than based on the feedback information from the UE. This allows the RAN device to quickly know the transmission result of the downlink data packet. The UPF network element then makes a decision on whether to retransmit the downlink data packet based on the transmission result determined by the RAN device, enabling the UPF network element to make a rapid decision and improving the efficiency of data packet retransmission. By sending the estimated retransmission delay of downlink data packets to the UPF network element, the UPF network element considers the estimated retransmission delay of downlink data packets when deciding whether to retransmit them. Only when the estimated retransmission delay of downlink data packets is less than or equal to the actual retransmission delay of downlink data packets is it determined that downlink data packets need to be retransmitted, thus avoiding the situation where the retransmission delay does not meet the requirements after retransmitting downlink data packets.

[0279] See Figure 4 , Figure 4 This is a flowchart illustrating another data retransmission method provided in an embodiment of this application. The method is applied to... Figure 1 RAN equipment in the system. For example... Figure 4 As shown, the method includes:

[0280] S401, the RAN device receives third information and downlink data packets from the application server. The third information is used to determine whether retransmission is required after the downlink data packet transmission fails.

[0281] In one feasible implementation, the third information includes retransmission indication information for downlink data packets, which indicates that the downlink data packets need to be retransmitted in the event of a transmission failure.

[0282] Optionally, the retransmission indication information includes the second transmission sequence number of the downlink data packet, or the retransmission identifier of the downlink data packet.

[0283] It should be noted that the reason the retransmission indication information can be the second transmission sequence number of the downlink data packet is that after each downlink data packet is acquired, the UPF network element determines whether the downlink data packet is a lost packet that needs to be retransmitted. If the downlink data packet is a lost packet that needs to be retransmitted, the UPF network element adds a second transmission sequence number to the downlink data packet. In this case, the second transmission sequence number has two functions: first, to identify the downlink data packet; and second, to indicate that the downlink data packet is a lost packet that needs to be retransmitted. That is to say, for downlink data packets that do not need to be retransmitted, the UPF network element only needs to send the downlink data packet to the RAN device, and does not need to send the transmission sequence number of the downlink data packet to the RAN device.

[0284] The reason why retransmission indication information can be the retransmission identifier of downlink data packets is that the UPF network element adds a retransmission identifier to each acquired downlink data packet after acquiring it. Specifically, the UPF network element determines whether the downlink data packet is a packet that needs to be retransmitted after packet loss; if the downlink data packet is a packet that needs to be retransmitted after packet loss, the retransmission identifier indicates that the downlink data packet needs to be retransmitted in the event of transmission failure; if the downlink data packet is a packet that does not need to be retransmitted after packet loss, the retransmission identifier indicates that the downlink data packet does not need to be retransmitted in the event of transmission failure.

[0285] S402, the RAN device sends downlink data packets to the UE.

[0286] It should be noted that the specific implementation process of S402 can be found in the relevant description of S302, and will not be described here.

[0287] S403. When the RAN device determines that the downlink data packet transmission has failed, the RAN device determines to retransmit the downlink data packet to the UE based on third information.

[0288] It should be noted that the specific implementation process of "RAN device determines downlink data packet transmission failure" in S403 can be found in the relevant description in S302, and will not be described here.

[0289] In one feasible implementation, when the UPF network element adds a transmission sequence number to downlink data packets by only adding a second transmission sequence number to downlink data packets that require retransmission after packet loss, the RAN device can determine that the downlink data packet needs to be retransmitted based on the second transmission sequence number. In this case, the second transmission sequence number can simply be a retransmission identifier, meaning that there is no need to generate an additional transmission sequence number; the retransmission identifier can be used as the second transmission sequence number.

[0290] In another feasible implementation, the UPF network element adds a first transmission sequence number to the downlink data packet by adding a first transmission sequence number to each acquired downlink data packet to identify it, and simultaneously adding a retransmission flag to the downlink data packet. There is a correspondence between the first transmission sequence number and the retransmission flag of the downlink data packet. The RAN device determines the retransmission flag of the downlink data packet based on the third transmission sequence number of the downlink data packet. If the retransmission flag indicates that the downlink data packet needs to be retransmitted, the RAN device determines that the downlink data packet needs to be retransmitted; if the retransmission flag indicates that the downlink data packet does not need to be retransmitted, the RAN device determines that the downlink data packet does not need to be retransmitted.

[0291] In another feasible implementation, the third information includes a retransmission delay threshold for downlink data packets. The RAN device obtains the estimated retransmission delay of the downlink data packets, which is the estimated time required to retransmit the downlink data packets. The RAN device determines the retransmission delay threshold for the downlink data packets based on the transmission sequence number of the downlink data packets. If the estimated retransmission delay is less than or equal to the retransmission delay threshold, the RAN determines that the downlink data packets need to be retransmitted; if the estimated retransmission delay is greater than the retransmission delay threshold, the RAN determines that the downlink data packets do not need to be retransmitted. The retransmission delay threshold for downlink data packets can be sent from the UPF network element to the RAN device through the GTP-U layer of the downlink data packets, or it can be sent from the SMF network element to the RAN device. Specifically, the SMF network element sends the retransmission delay threshold to the RAN device. Optionally, the SMF network element can carry the retransmission delay threshold in the QoS parameters sent to the RAN device, meaning that the retransmission delay threshold for the downlink data packets corresponding to this QoS flow is the same, and is always the same retransmission delay threshold.

[0292] In another feasible implementation, the RAN device obtains the estimated retransmission delay of the downlink data packet; the RAN device determines the downlink data packet retransmission delay threshold and determines whether the downlink data packet needs to be retransmitted after packet loss; the RAN device determines whether the downlink data packet needs to be retransmitted based on the second transmission sequence number of the downlink data packet; if it is determined based on the second transmission sequence number that the downlink data packet needs to be retransmitted, and the estimated retransmission delay is less than or equal to the retransmission delay threshold, then the RAN device determines that the downlink data packet needs to be retransmitted; if it is determined based on the second transmission sequence number that the downlink data packet does not need to be retransmitted, and the estimated retransmission delay is less than or equal to the retransmission delay threshold, then the RAN device determines that the downlink data packet does not need to be retransmitted; if it is determined based on the second transmission sequence number that the downlink data packet needs to be retransmitted, and the estimated retransmission delay is greater than the retransmission delay threshold, then the RAN device determines that the downlink data packet does not need to be retransmitted.

[0293] In another feasible implementation, the RAN device obtains the estimated retransmission delay of the downlink data packet; the RAN device determines the downlink data packet retransmission delay threshold and whether the downlink data packet needs to be retransmitted after packet loss; the RAN device determines whether the downlink data packet needs to be retransmitted based on the first transmission sequence number and retransmission identifier of the downlink data packet; if it is determined that the downlink data packet needs to be retransmitted based on the first transmission sequence number and retransmission identifier, and the estimated retransmission delay is less than or equal to the retransmission delay threshold, then the RAN device determines that the downlink data packet needs to be retransmitted; if it is determined that the downlink data packet does not need to be retransmitted based on the first transmission sequence number and retransmission identifier, and the estimated retransmission delay is less than or equal to the retransmission delay threshold, then the RAN device determines that the downlink data packet does not need to be retransmitted; if it is determined that the downlink data packet needs to be retransmitted based on the first transmission sequence number and retransmission identifier, and the estimated retransmission delay is greater than the retransmission delay threshold, then the RAN device determines that the downlink data packet does not need to be retransmitted.

[0294] It should be noted that, in the process of the RAN device determining the retransmission delay threshold of downlink data packets, if multiple downlink data packets have the same retransmission delay threshold, and the UPF network element sends multiple downlink data packets to the RAN device simultaneously or continuously, and the first downlink data packet carries the retransmission delay threshold, the RAN device determines whether the retransmission delay threshold can be obtained from the downlink data packet. If the retransmission delay threshold can be obtained from the downlink data packet, then the retransmission delay threshold is determined to be the retransmission delay threshold of the downlink data packet; if the retransmission delay threshold cannot be determined from the downlink data packet, then the retransmission delay threshold of the downlink data packet is determined to be the same as the retransmission delay threshold of the previous downlink data packet.

[0295] When it is determined to retransmit a downlink data packet to the UE, the RAN device retransmits the downlink data packet to the UE. It should be noted that when the RAN device determines to retransmit a downlink data packet to the UE, it may optionally adjust the priority of the flow corresponding to the downlink data packet to ensure that the downlink data packet can be sent to the UE side quickly.

[0296] In one feasible implementation, after retransmitting the downlink data packet to the UE, the RAN device sends a second message to the UPF network element, the second message indicating that the downlink data packet has been retransmitted to the UE.

[0297] In one feasible implementation, after the RAN device retransmits the transmission result of the downlink data packet to the UE, if it receives the first information sent by the UE to the application server, and the first information indicates that the UE has not received the downlink data packet before the retransmission, the RAN device discards or ignores the first information to avoid unnecessary retransmission by the application server, since the RAN device has already retransmitted the downlink data packet to the UE.

[0298] As can be seen, compared with the prior art, this embodiment introduces a RAN device between the UE and the application server. The RAN device determines whether to retransmit the downlink data packet based on the transmission result of the downlink data packet determined by the RAN device and third-party information. Since the RAN device is closer to the UE than the application server, it can make a faster decision on whether to retransmit the downlink data packet based on the transmission result between the RAN device and the UE, thereby improving the efficiency of data packet retransmission. When deciding whether to retransmit the downlink data packet, the RAN device considers the estimated retransmission delay of the downlink data packet. It only determines that the downlink data packet needs to be retransmitted when the estimated retransmission delay is less than or equal to the actual retransmission delay, avoiding the situation where the retransmission delay does not meet the requirements after retransmission. The transmission result of the downlink data packet can be determined by the RAN device based on the transmission delay or the transmission status of the MAC layer transport block, rather than based on the feedback information from the UE. This allows the RAN device to quickly know the transmission result of the downlink data packet, and the RAN device's decision on whether to retransmit the downlink data packet based on the transmission result is beneficial to improving the efficiency of data packet retransmission. By sending a second message to the UPF network element to inform it that the downlink data packet has been retransmitted to the UE, when the UPF network element subsequently receives the first message from the UE to the application server indicating that the downlink data packet has not been received, since the downlink data packet has already been retransmitted to the UE, the UPF network element can directly ignore or discard the first message, thereby reducing the workload of the UPF network element and the application server.

[0299] See Figure 5 , Figure 5 This is a flowchart illustrating another data retransmission method provided in an embodiment of this application. The method is applied to... Figure 1 UPF network elements in the network. For example... Figure 5 As shown, the method includes:

[0300] The S501 and UPF network elements acquire downlink data packets and obtain the third information of the downlink data packets. The third information is used to determine whether the downlink data packets need to be retransmitted after transmission failure.

[0301] In one feasible implementation, the UPF network element obtains downlink data packets, either from the application server or by generating the downlink data packets itself when the application server is deployed on the UPF network element.

[0302] In one feasible implementation, the UPF network element adds a second transmission sequence number to the downlink data packet. The third information of the downlink data packet includes the second transmission sequence number of the downlink data packet, which is used to indicate whether the downlink data packet needs to be retransmitted after packet loss or transmission failure.

[0303] In one feasible implementation, the third information of the downlink data packet includes retransmission indication information for the downlink data packet, which is used to indicate that the downlink data packet needs to be retransmitted in the event of a transmission failure.

[0304] Optionally, the retransmission indication information includes the second transmission sequence number of the downlink data packet, or the retransmission identifier of the downlink data packet.

[0305] There are two ways for UPF network elements to add transmission sequence numbers to downlink data packets:

[0306] Method 1: The UPF network element adds a first transmission sequence number to all acquired downlink data packets to identify them. Simultaneously, the UPF network element adds a retransmission flag to each downlink data packet. The retransmission flag of the downlink data packet indicates whether retransmission is necessary in the event of a transmission failure. In this case, the retransmission indication information for the downlink data packet includes the retransmission flag.

[0307] Specifically, when setting a retransmission flag for downlink data packets, the UPF network element determines whether a downlink data packet needs to be retransmitted after packet loss after acquiring each downlink data packet. If the downlink data packet needs to be retransmitted after packet loss, the retransmission flag indicates that the downlink data packet needs to be retransmitted in the event of transmission failure. If the downlink data packet does not need to be retransmitted after packet loss, the retransmission flag indicates that the downlink data packet does not need to be retransmitted in the event of transmission failure. Specifically, if the application server is deployed in the UPF network element, the UPF determines whether the downlink data packet needs to be retransmitted after packet loss or transmission failure based on the importance of the downlink data packet, such as the impact of the downlink data packet loss on the service experience. If the application server is not deployed in the UPF network element, for example, the UPF network element determines whether the downlink data packet needs to be retransmitted after packet loss or transmission failure based on the information added by the application server to the downlink data packet to characterize the importance of the downlink data packet.

[0308] It should be noted that the data packets that need to be retransmitted after packet loss are those that will affect the processing of subsequent data packets (such as encoding and decoding processing) after loss, or data packets corresponding to key frames.

[0309] Method 2: After acquiring a downlink data packet, the UPF network element determines whether the downlink data packet is a packet that needs to be retransmitted after being lost. If the downlink data packet is a packet that needs to be retransmitted after being lost, the UPF network element adds a second transmission sequence number to the downlink data packet. In this case, the second transmission sequence number has two functions: first, to identify the downlink data packet; and second, to indicate that the downlink data packet is a packet that needs to be retransmitted after being lost. Optionally, when adding a retransmission delay threshold to the acquired downlink data packets, the UPF network element can add a retransmission delay threshold to each acquired downlink data packet.

[0310] Optionally, the UPF network element sends the downlink data packet retransmission delay threshold to the RAN device while sending the downlink data packet to the RAN device.

[0311] In some cases, multiple downlink data packets may have the same retransmission delay threshold. The UPF network element can add a retransmission delay threshold to only one of these downlink data packets. When transmitting multiple downlink data packets with the same retransmission delay threshold to the RAN device, these multiple downlink data packets can be sent simultaneously or consecutively. The downlink data packet with the added retransmission delay threshold is the first among these multiple downlink data packets to be transmitted to the RAN device. Alternatively, if the retransmission delay thresholds of the downlink data packets are the same or change slowly, the UPF network element can notify the RAN device of a fixed retransmission delay threshold through the SMF network element, meaning that multiple downlink data packets share a single retransmission delay threshold.

[0312] It should be noted that the retransmission delay threshold for downlink data packets can be sent directly from the SMF network element to the RAN device. In this case, the retransmission delay threshold for downlink data packets on the SMF network element can come from the UPF network element or a third-party application.

[0313] In one example, the SMF network element sends a retransmission delay threshold to the RAN device. The SMF network element can carry the retransmission delay threshold in the QoS parameters sent to the RAN device, meaning that the retransmission delay threshold for the downlink data packets corresponding to this QoS flow is the same, and they are all the same retransmission delay threshold.

[0314] In another example, after a third-party application generates a downlink data packet, it carries a retransmission delay threshold in the downlink data packet sent to the UPF network element.

[0315] In one feasible implementation, the UPF network element adds a retransmission delay threshold to each acquired downlink data packet. The downlink data packet retransmission delay threshold is used to determine whether the downlink data packet needs to be retransmitted to the UE. The third information of the downlink data packet includes the downlink data packet retransmission delay threshold.

[0316] The S502 and UPF network elements send downlink data packets and third-party information to the RAN equipment.

[0317] The third information of the downlink data packet is carried in the GTP-U layer of the downlink data packet.

[0318] In one feasible implementation, the third information includes the retransmission delay threshold of the downlink data packet; in other words, the UPF network element carries the retransmission delay threshold of the downlink data packet in the GTP-U layer of the downlink data packet sent to the RAN device.

[0319] In one feasible implementation, the retransmission delay threshold for downlink data packets comes from the SMF network element. That is, the retransmission delay threshold for downlink data packets of the RAN device is sent to the RAN device by the SMF network element, or the retransmission delay threshold for downlink data packets of the UPF network element is sent to the UPF network element by the SMF network element.

[0320] In one feasible implementation, the UPF network element receives second information from the RAN device, which indicates that the downlink data packet has been retransmitted to the UE.

[0321] In one feasible implementation, the method of this embodiment further includes:

[0322] After receiving the second information from the RAN device, the UPF network element receives the first information from the UE. The first information is an indication sent by the UE to the application server to indicate that the downlink data packet has not been received. Since the RAN device has retransmitted the downlink data packet to the UE, the UPF network element discards or ignores the first information to reduce the workload of the UPF network element and also avoids unnecessary retransmission by the application server.

[0323] As can be seen, compared with the prior art, the scheme of this embodiment introduces a UPF network element and a RAN device between the UE and the application server. The UPF network element sends third information of the downlink data packet to the RAN device, which is used by the RAN device to determine whether the downlink data packet needs to be retransmitted based on the third information. Since the RAN device is closer to the UE than the application server, it can make a decision on whether to retransmit the downlink data packet more quickly based on the transmission result of the downlink data packet between the RAN device and the UE, thereby improving the efficiency of data packet retransmission. By sending the downlink data packet retransmission delay threshold to the RAN device, the RAN device considers the downlink data packet retransmission delay threshold when deciding whether to retransmit the downlink data packet. It only determines that the downlink data packet needs to be retransmitted when the estimated retransmission delay is less than or equal to the actual retransmission delay, thus avoiding the situation where the retransmission delay does not meet the requirements after retransmitting the downlink data packet.

[0324] See Figure 6 , Figure 6This is a flowchart illustrating another data retransmission method provided in an embodiment of this application. The method is applied to... Figure 1 The application layer of the UE. For example... Figure 6 As shown, the method includes:

[0325] S601, The UE's application layer receives the transmission result and sequence number of the uplink data packet transmitted between the UE's underlying layer and the RAN device.

[0326] After the UE's application layer obtains the uplink data packets, it has two processing methods for the uplink data packets:

[0327] Method 1: The UE's application layer adds a third transmission sequence number to all acquired uplink data packets to identify them. Optionally, the UE's application layer determines a retransmission delay threshold and / or a retransmission flag for each uplink data packet. The retransmission flag indicates whether the uplink data packet needs to be retransmitted in the event of a transmission failure, and the uplink data packet retransmission delay threshold determines whether the uplink data packet needs to be retransmitted in the event of a transmission failure.

[0328] Specifically, when setting a retransmission flag for an uplink data packet, the UE's application layer determines whether the uplink data packet is one that needs to be retransmitted after packet loss after each uplink data packet is acquired. If the uplink data packet is one that needs to be retransmitted after packet loss, the retransmission flag of the uplink data packet indicates that the uplink data packet needs to be retransmitted in the event of transmission failure. If the uplink data packet is one that does not need to be retransmitted after packet loss, the retransmission flag of the uplink data packet indicates that the uplink data packet does not need to be retransmitted in the event of transmission failure.

[0329] It should be understood that the application layer obtaining an uplink data packet can be interpreted as the application layer generating an uplink data packet.

[0330] It should be noted that the data packets that need to be retransmitted after packet loss are those that will affect the processing of subsequent data packets (such as encoding and decoding processing) after loss, or data packets corresponding to key frames.

[0331] Specifically, when adding a retransmission delay threshold to the acquired uplink data packets, the UE's application layer can add a retransmission delay threshold to each acquired uplink data packet. For uplink data packets acquired by the UE's application layer, multiple uplink data packets may have the same retransmission delay threshold. Therefore, the UE's application layer can add a retransmission delay threshold to only one of these multiple uplink data packets. When transmitting uplink data packets to the UE's underlying layer, these multiple uplink data packets can be sent simultaneously or consecutively. Among these multiple uplink data packets, the uplink data packet with the added retransmission delay threshold is the first to be transmitted to the UE's underlying layer. Optionally, the uplink data packets have the same retransmission delay threshold. The UE's application layer can be the UE's transport layer or application layer, or a protocol layer above IP, while the UE's underlying layer refers to the protocol layer between the UE and the RAN device, including but not limited to the physical layer, MAC layer, RLC layer, and PDCP layer.

[0332] Method 2: After the UE's application layer acquires each uplink data packet, it determines whether the uplink data packet is a packet that needs to be retransmitted after packet loss. If the uplink data packet is a packet that needs to be retransmitted after packet loss, the UE's application layer adds a fourth transmission sequence number to the uplink data packet. At this time, the fourth transmission sequence number has two functions: first, it is used to identify the uplink data packet; second, it is used to instruct the UE's underlying layer to determine the transmission result of the uplink data packet, or to trigger the UE's underlying layer to determine the transmission result of the uplink data packet and send the transmission sequence number and transmission result of the uplink data packet to the application layer, as well as the fourth transmission sequence number and transmission result of the uplink data packet.

[0333] Optionally, when adding a retransmission delay threshold to the acquired uplink data packets, the UE's application layer can add a retransmission delay threshold to each acquired uplink data packet. For uplink data packets acquired by the UE's application layer, there may be multiple uplink data packets with the same retransmission delay threshold. Therefore, the UE's application layer can add a retransmission delay threshold to only one of these multiple uplink data packets. When transmitting uplink data packets to the UE's underlying layer, these multiple uplink data packets can be sent simultaneously or consecutively. Among these multiple uplink data packets, the uplink data packet with the added retransmission delay threshold is the first to be transmitted to the UE's underlying layer. The UE's application layer can be the UE's transport layer or application layer, or a protocol layer above IP. The UE's underlying layer refers to the protocol layer between the UE and the RAN, including but not limited to the physical layer, MAC layer, RLC layer, and PDCP layer.

[0334] After processing the uplink data packet as described above, the UE's application layer sends the uplink data packet to the UE's underlying layer, so that the UE's underlying layer can send the uplink data packet to the RAN device. Optionally, if the uplink data packet has a corresponding sequence number (including a third or fourth sequence number), the UE's application layer also transmits the sequence number of the uplink data packet to the UE's underlying layer.

[0335] After the UE's underlying layer sends an uplink data packet to the RAN device, the UE's underlying layer can determine the transmission result of the uplink data packet and send the transmission result of the uplink data packet to the UE's application layer. Optionally, if the uplink data packet has a corresponding transmission sequence number (including a third or fourth transmission sequence number), the UE's underlying layer also sends the transmission sequence number of the uplink data packet to the UE's application layer.

[0336] In one feasible implementation, the method of this embodiment further includes:

[0337] The UE's application layer sends a fifth message to the UE's underlying layer, which indicates whether it is necessary to determine the transmission result of the uplink data packet.

[0338] It should be noted that for the UE's application layer, the transmission results of some uplink data packets need to be monitored, such as uplink data packets that need to be retransmitted after packet loss or transmission failure. The transmission results of some uplink data packets do not need to be monitored. Therefore, the UE's application layer sends the fifth message to the UE's underlying layer to inform the UE's underlying layer whether it needs to provide feedback on the transmission results of uplink data packets.

[0339] S602. The UE's application layer determines whether to retransmit the uplink data packet based on the transmission result of the uplink data packet between the UE's underlying layer and the RAN device and the transmission sequence number of the uplink data packet.

[0340] In one feasible implementation, for the case where the UE's application layer only adds a fourth transmission sequence number to the uplink data packets that need to be retransmitted after packet loss, the UE's application layer determines whether the uplink data packet was successfully transmitted based on the transmission result of the uplink data packet. If the transmission result of the uplink data packet indicates that the uplink data packet transmission failed, the UE's application layer determines that the uplink data packet needs to be retransmitted based on the fourth transmission sequence number of the uplink data packet.

[0341] Optionally, if it is determined that the uplink data packet transmission failed based on the transmission result of the uplink data packet, the UE's application layer determines whether to retransmit the uplink data packet based on the retransmission delay threshold of the uplink data packet and the estimated retransmission delay of the uplink data packet obtained from the UE's underlying layer. The estimated retransmission delay of the uplink data packet is the estimated time required to retransmit the uplink data packet to the RAN device. This time can be the time required for the uplink data packet to be transmitted from the UE's underlying layer to the RAN device (i.e., UE's underlying layer -> RAN device) (i.e., the air interface transmission delay of UE's underlying layer -> RAN device), or the sum of the time required for the UE's underlying layer to obtain the uplink data packet that needs to be retransmitted from the UE's application layer and the time required for the data packet to be transmitted from the UE's underlying layer -> RAN device to the RAN device, i.e., the time from UE's underlying layer -> UE's application layer -> UE's underlying layer -> RAN device. If the estimated retransmission delay of the uplink data packet is less than or equal to the retransmission delay threshold of the uplink data packet, the UE's application layer determines that the uplink data packet needs to be retransmitted; if the estimated retransmission delay of the uplink data packet is greater than the retransmission delay threshold of the uplink data packet, the UE's application layer determines that the uplink data packet does not need to be retransmitted.

[0342] It should be noted that the uplink data packet retransmission delay threshold is obtained by the UE's application layer from its local configuration or from the SMF network element. The process of UE's lower layer -> UE's application layer -> UE's lower layer means that the UE's lower layer obtains the uplink data packets that need to be retransmitted from the UE's application layer.

[0343] In one feasible implementation, when the UE's application layer adds a third transmission sequence number to each acquired uplink data packet, in one example, the UE's application layer determines the retransmission identifier of the uplink data packet based on the third transmission sequence number. There is a correspondence between the third transmission sequence number and the retransmission identifier of the uplink data packet. If the retransmission identifier of the uplink data packet indicates that the uplink data packet needs to be retransmitted in the event of a transmission failure, then the UE's application layer determines that the uplink data packet needs to be retransmitted; if the retransmission identifier of the uplink data packet indicates that the uplink data packet does not need to be retransmitted in the event of a transmission failure, then the UE's application layer determines that the uplink data packet needs to be retransmitted; or the UE's application layer determines whether the uplink data packet needs to be retransmitted based on the importance of the uplink data packet itself, without relying on the retransmission identifier. In other words, the UE's application layer does not generate a retransmission identifier for the acquired uplink data packets.

[0344] In another example, the UE's application layer determines the uplink data packet retransmission delay threshold based on the third transmission sequence number of the uplink data packet, and there is a correspondence between the third transmission sequence number of the uplink data packet and the uplink data packet retransmission delay threshold. The estimated retransmission delay of the uplink data packet is obtained from the UE's underlying layer. The estimated retransmission delay of the uplink data packet is the estimated time required to retransmit the uplink data packet to the RAN device. If the estimated retransmission delay of the uplink data packet is less than or equal to the uplink data packet retransmission delay threshold, the UE's application layer determines that the uplink data packet needs to be retransmitted. If the estimated retransmission delay of the uplink data packet is greater than the uplink data packet retransmission delay threshold, the UE's application layer determines that the uplink data packet does not need to be retransmitted.

[0345] In another example, the UE's application layer determines the uplink data packet retransmission delay threshold and retransmission flag, and obtains the estimated retransmission delay of the uplink data packet from the UE's underlying layer. If the estimated retransmission delay of the uplink data packet is less than or equal to the uplink data packet retransmission delay threshold, and the uplink data packet retransmission flag is used to indicate that the uplink data packet needs to be retransmitted in the event of transmission failure, then the UE's application layer determines that the uplink data packet needs to be retransmitted. If the estimated retransmission delay of the uplink data packet is greater than the uplink data packet retransmission delay threshold, or the uplink data packet retransmission flag is used to indicate that the uplink data packet does not need to be retransmitted in the event of transmission failure, then the UE's application layer determines that the uplink data packet does not need to be retransmitted.

[0346] In one feasible implementation, the method of this embodiment further includes:

[0347] The UE's application layer receives the fourth information from the application server. The fourth information is sent after the UE's underlying layer retransmits the uplink data packet to the RAN. The fourth information is used to indicate that the application server has not received the uplink data packet. Since the UE's application layer has already retransmitted the uplink data packet to the application server, the UE's application layer discards or ignores the fourth information to avoid unnecessary retransmission.

[0348] As can be seen, by introducing the UE's underlying layer between the UE's application layer and the application server, the UE's application layer determines whether to retransmit the uplink data packet based on the transmission result of the uplink data packet determined by the UE's underlying layer. Since the UE's underlying layer can quickly know the transmission result of the uplink data packet compared to the UE's application layer, it can make a faster decision on whether to retransmit the uplink data packet based on the transmission result between the UE's underlying layer and the RAN device, thus improving the efficiency of data packet retransmission. The UE's application layer only adds a fourth transmission sequence number to uplink data packets that need to be retransmitted after packet loss. When the UE's application layer receives the transmission result indicating uplink data packet transmission failure, it also receives the fourth transmission sequence number of the uplink data packet. The UE's application layer can directly decide whether to retransmit the uplink data packet based on the fourth transmission sequence number without relying on other information, improving decision-making efficiency and thus improving retransmission efficiency. When the UE's application layer adds a sequence number and retransmission flag to each acquired uplink data packet, the application layer directly decides whether to retransmit the uplink data packet based on the retransmission flag, without relying on other information. This improves decision-making efficiency and, consequently, retransmission efficiency. Furthermore, when deciding whether to retransmit the uplink data packet, the UE's application layer introduces an uplink data packet retransmission delay threshold. Only when the estimated retransmission delay of the uplink data packet is less than or equal to its actual retransmission delay is it determined that the uplink data packet needs to be retransmitted. This avoids situations where the retransmission delay does not meet requirements after retransmission.

[0349] See Figure 7 , Figure 7 This is a flowchart illustrating another data retransmission method provided in an embodiment of this application. The method is applied to... Figure 1 The underlying layer of the UE. For example... Figure 7 As shown, the method includes:

[0350] S701, The UE's underlying layer receives uplink data packets and uplink data packet transmission sequence numbers from the UE's application layer.

[0351] It should be noted that the UE's application layer has two processing methods when adding transmission sequence numbers to the acquired uplink data packets:

[0352] 1. The UE's application layer adds a third transmission sequence number to all acquired uplink data packets. The third transmission sequence number is used to identify the uplink data packets.

[0353] 2. After acquiring each uplink data packet, the UE's application layer determines whether it is a data packet that needs to be retransmitted due to packet loss. If the uplink data packet is a data packet that needs to be retransmitted due to packet loss, the UE's application layer adds a fourth transmission sequence number to the uplink data packet. This fourth transmission sequence number serves two functions: first, it identifies the uplink data packet; second, it triggers the UE's lower layer to determine the transmission result of the uplink data packet and send the transmission sequence number and transmission result of the uplink data packet to the UE's application layer. In other words, the uplink data packet is a data packet that needs to be retransmitted due to packet loss or transmission failure. That is, for uplink data packets that do not need to be retransmitted, the UE's application layer only needs to send the uplink data packet to the UE's lower layer, and does not need to send the transmission sequence number of the uplink data packet to the UE's lower layer.

[0354] Note that the UE's application layer can be the UE's transport layer or application layer, or other protocol layers on top of IP, while the UE's bottom layer refers to the protocol layer between the UE and the RAN, including but not limited to the physical layer, MAC layer, RLC layer, PDCP layer, etc.

[0355] S702, The UE's lower layer sends an uplink data packet to the RAN device; The UE's lower layer determines the transmission result of the uplink data packet between the UE's lower layer and the RAN device.

[0356] In one feasible embodiment, when the UE's underlying layer receives an uplink data packet from the UE's application layer, the UE's underlying layer assigns a PDCP layer sequence number to the uplink data packet. If the transmission sequence number of the uplink data packet is also received simultaneously, the UE's underlying layer records the correspondence between the PDCP layer sequence number assigned to the uplink data packet and the transmission sequence number of the uplink data packet. The UE's underlying layer then sends the uplink data packet to the RAN device through the PDCP layer, and the uplink data packet carries the assigned PDCP layer sequence number.

[0357] In a feasible implementation, the UE's underlying layer determines the transmission result of the uplink data packet in two ways:

[0358] Method 1: The UE's underlying layer determines whether the uplink data packet was successfully transmitted based on feedback information from the RAN device. For example, the feedback information from the RAN device includes the PDCP layer sequence number and transmission identifier of the uplink data packet. The UE's underlying layer determines that the transmission identifier in the feedback information is the transmission identifier of the uplink data packet based on the PDCP layer sequence number of the uplink data packet and the correspondence between the transmission sequence number and the PDCP layer sequence number. The transmission identifier of the uplink data packet is used to indicate whether the RAN device has received the uplink data packet. The UE's underlying layer determines whether the uplink data packet was successfully transmitted based on the transmission identifier of the uplink data packet.

[0359] It should be noted that if the UE's underlying layer queries the correspondence between the transmission sequence number and the PDCP layer sequence number based on the PDCP layer sequence number of the uplink data packet and fails to find the corresponding transmission sequence number, it means that the uplink data packet does not have a corresponding transmission sequence number. In other words, when the UE's application layer adds a transmission sequence number to the uplink data packet, it only adds the transmission sequence number to the data packet that needs to be retransmitted after packet loss. That is to say, the uplink data packet without a transmission sequence number is the data packet that does not need to be retransmitted after packet loss. Therefore, the UE's underlying layer can ignore or discard the feedback information of the uplink data packet without a corresponding transmission sequence number.

[0360] In one example, the transmission identifier of the uplink data packet is NACK or ACK; when the transmission identifier of the uplink data packet is NACK, it means that the RAN device has not received the uplink data packet, that is, the uplink data packet transmission has failed; when the transmission identifier of the uplink data packet is ACK, it means that the RAN device has received the uplink data packet, that is, the uplink data packet transmission has been successful.

[0361] Method 2: The UE's underlying layer determines whether the uplink data packet was successfully transmitted based on its own information. For example, in RLCUM mode, the UE's underlying layer determines whether the uplink data packet was successfully transmitted based on the actual transmission status of the MAC layer transport block; or, the UE's underlying layer obtains the transmission duration of the uplink data packet to the RAN device, that is, the elapsed time of transmitting the uplink data packet to the RAN device. If the transmission duration exceeds the second transmission duration threshold, the UE's underlying layer determines that the uplink data packet transmission failed.

[0362] It should be noted that uplink data packet transmission failure includes cases where the UE fails to transmit data even after MAC layer retransmission between the UE's underlying layer and the RAN device; optionally, uplink data packet transmission failure also includes cases where the UE fails to transmit data even after MAC layer and RLC layer retransmission between the UE's underlying layer and the RAN device.

[0363] S703. The UE's underlying layer sends the transmission result of the uplink data packet between the UE's underlying layer and the RAN device and the transmission sequence number of the uplink data packet to the UE application layer. The transmission result of the uplink data packet between the UE's underlying layer and the RAN device and the transmission sequence number of the uplink data packet are used to determine whether the uplink data packet needs to be retransmitted.

[0364] In one feasible implementation, the UE's underlying layer also sends the estimated retransmission delay of the uplink data packet to the UE's application layer. The estimated retransmission delay of the uplink data packet is used to determine whether the uplink data packet needs to be retransmitted.

[0365] In one feasible implementation, the UE's lower layer receives the retransmission delay threshold of the uplink data packet from the UE's application layer. The UE's lower layer determines the estimated retransmission delay of the uplink data packet, i.e., the estimated delay for retransmitting the uplink data packet to the RAN device, and when the estimated retransmission delay of the uplink data packet is less than or equal to the retransmission delay threshold, it sends the transmission sequence number and transmission result of the uplink data packet to the UE's application layer.

[0366] During the process of obtaining the retransmission delay threshold of uplink data packets at the UE's underlying layer, if multiple uplink data packets have the same retransmission delay threshold, and the UE's application layer sends multiple uplink data packets to the UE's underlying layer simultaneously or continuously, and the first uplink data packet carries the retransmission delay threshold, the UE's underlying layer determines whether the retransmission delay threshold can be obtained from the uplink data packets. If the retransmission delay threshold can be obtained from the uplink data packets, then the retransmission delay threshold determined by the UE's underlying layer is the retransmission delay threshold of the uplink data packet; if the retransmission delay threshold cannot be determined from the uplink data packets, then the UE's underlying layer determines that the retransmission delay threshold of the uplink data packet is the same as the retransmission delay threshold of the previous uplink data packet.

[0367] In one feasible implementation, the UE's lower layer receives the fifth information sent by the UE's application layer, which indicates whether it is necessary to determine the transmission result of the uplink data packet; and sends the transmission result of the uplink data packet and the transmission sequence number of the uplink data packet to the UE's application layer.

[0368] Specifically, when the fifth information indicates that the transmission result of the uplink data packet needs to be determined, the UE's lower layer determines the transmission result of the uplink data packet according to the method described in S702, and sends the transmission result of the uplink data packet and the transmission sequence number of the uplink data packet to the UE's application layer; when the fifth information indicates that the transmission result of the uplink data packet does not need to be determined, the UE's lower layer does not perform the operation of determining the transmission result of the uplink data packet, nor does it need to send the transmission result of the uplink data packet and the transmission sequence number of the uplink data packet to the UE's application layer.

[0369] In S702 and S703, the transmission sequence number of the uplink data packet includes either the third transmission sequence number or the fourth transmission sequence number.

[0370] As can be seen, by introducing the UE's underlying layer between the UE's application layer and the application server, the UE's application layer quickly decides whether to retransmit the uplink data packet based on the transmission result of the uplink data packet determined by the UE's underlying layer. Since the UE's underlying layer can quickly know the transmission result of the uplink data packet between the UE's underlying layer and the RAN device, it can make a faster decision on whether to retransmit the uplink data packet, thus improving the efficiency of data packet retransmission. The transmission result of the uplink data packet is determined by the UE's underlying layer based on the transmission delay of the uplink data packet or based on the sending status of the underlying transport blocks, rather than based on feedback information from the application server. This allows the UE's application layer to quickly know the transmission result of the uplink data packet and further decide whether to retransmit the uplink data packet based on the transmission result determined by the UE's underlying layer, which helps to improve the efficiency of data packet retransmission. By sending the estimated retransmission delay of uplink data packets to the UE's application layer, the UE's application layer considers the estimated retransmission delay of uplink data packets when deciding whether to retransmit them. Only when the estimated retransmission delay of uplink data packets is less than or equal to the actual retransmission delay of uplink data packets is it determined that uplink data packets need to be retransmitted, thus avoiding the situation where the retransmission delay does not meet the requirements after retransmitting uplink data packets.

[0371] See Figure 8 , Figure 8 This is an interactive flowchart illustrating a data retransmission method provided in an embodiment of this application. The method is applied to... Figure 1 The system shown. (As shown in the image) Figure 8 As shown, the method includes:

[0372] S801, AF network element sends AF request to PCF network element.

[0373] In one example, the AF request includes a first indication and flow description information. The flow description information can be an IP triple, quintuple, or application identifier, etc. The first indication information indicates that the flow described by the flow description requires retransmission acceleration processing.

[0374] In another example, the AF request includes a first indication that the service flow corresponding to the AF request needs to be retransmitted and accelerated.

[0375] In one example, the AF network element interacts directly with the PCF network element through the API provided by the PCF network element, or the AF network element interacts with the NEF network element through the API provided by the NEF network element, and then the NEF network element interacts with the PCF network element. That is, the AF network element interacts with the PCF network element through the NEF network element.

[0376] It should be noted that S801 is optional.

[0377] S802, PCF network element sends PCC rules to SMF network element.

[0378] The PCC rule can be generated by the PCF network element during the subsequent PDU session establishment or modification process. The PCC rule is used to indicate the QoS policy for a specified service flow, and the PCC rule includes first indication information.

[0379] The PCF network element generates PCC rules based on its local configuration and / or information provided by the AF (as described in S801).

[0380] This step is optional.

[0381] S803, SMF network element sends N4 rule to UPF network element.

[0382] Specifically, the SMF network element sends an N4 rule to the UPF network element based on the PCC rule and / or local configuration information. The N4 rule includes a second indication information, which is used to instruct the UPF network element to enable the fast retransmission mechanism. That is, it instructs the UPF network element to add a transmission sequence number to the downlink data packet and decide whether to retransmit the downlink data packet based on the information fed back by the RAN device.

[0383] The S804 and SMF network elements send third instruction information to the RAN equipment.

[0384] Specifically, the SMF network element sends a third indication message to the RAN device based on PCC rules and / or local configuration information. This third indication message is used to instruct the RAN device to determine the first transmission result of the downlink data packet and to feed back the first transmission result of the downlink data packet to the UPF network element. The first transmission result of the downlink data packet is used to indicate whether the downlink data packet was successfully transmitted.

[0385] The S805 and UPF network elements add transmission sequence numbers to downlink data packets.

[0386] It should be noted that the downlink data packet is a data packet transmitted from the application server to the UE via the UPF network element and RAN equipment; or if the application server is deployed in the UPF network element, then the downlink data packet is a downlink data packet from the UPF network element itself.

[0387] Specifically, in one example, the UPF network element adds a first transmission sequence number to each received downlink data packet, which is used to identify the downlink data packet.

[0388] In another example, after receiving each downlink data packet, the UPF network element determines whether the downlink data packet is a packet that needs to be retransmitted after packet loss. A packet that needs to be retransmitted after packet loss may be one that would affect the processing of subsequent data packets (such as encoding / decoding), or it may be a data packet corresponding to a key frame, or it may have higher importance. If the downlink data packet is a packet that needs to be retransmitted after packet loss, the UPF network element adds a second transmission sequence number to the downlink data packet. In other words, the second transmission sequence number of the downlink data packet indicates that it needs to be retransmitted; that is, the second transmission sequence number of the downlink data packet is used to instruct the RAN device to determine the transmission result of the downlink data packet and report it back to the UPF network element.

[0389] In one example, the sequence number of the downlink packet is carried in the GTP-U layer of the downlink packet.

[0390] In one example, 8 bits are used to mark the sequence number of data packets. The sequence number of the first data packet (including the first or second sequence number) is 0, the sequence number of the second data packet is 1, and when the sequence number is 255, it starts marking again from 0.

[0391] The S806 and UPF network elements send downlink data packets and transmission sequence numbers to the RAN equipment.

[0392] Sending downlink data packets and sequence numbers can be understood as sending downlink data packets carrying sequence numbers.

[0393] S807, RAN equipment records the correspondence between the transmission sequence number of downlink data packets and the PDCP layer sequence number.

[0394] It should be noted that the RAN device can receive multiple downlink data packets, and correspondingly, multiple sequence numbers; furthermore, when the RAN device sends a downlink data packet to the UE, it simultaneously sends the PDCP layer sequence number of that downlink data packet to the UE. Therefore, after receiving multiple downlink data packets and their corresponding sequence numbers, the RAN device records the correspondence between the sequence numbers of the multiple downlink data packets and the PDCP layer sequence numbers. This step is optional.

[0395] S808, RAN equipment sends target downlink data packets to UE.

[0396] The target downlink data packet is one of the downlink data packets received by the RAN device. Specifically, the RAN device sends the target downlink data packet to the UE through the PDCP layer, and at the same time sends the PDCP layer sequence number of the target downlink data packet to the UE.

[0397] S809, UE sends feedback information to RAN equipment.

[0398] The feedback information includes the target PDCP sequence number and transmission identifier.

[0399] The transmission identifier is used to indicate whether the UE has received the target downlink data packet sent by the RAN device. In one example, the transmission identifier is ACK, which indicates that the UE has received the target downlink data packet from the RAN device, or that the RAN device has successfully transmitted the target downlink data packet to the UE; the transmission identifier is NACK, which indicates that the UE has not received the target downlink data packet from the RAN device, or that the RAN device has failed to transmit the target downlink data packet to the UE.

[0400] S809 is optional.

[0401] The S810 and RAN devices determine whether the target downlink data packets have been successfully transmitted.

[0402] Specifically, RAN devices determine whether target downlink data packets have been successfully transmitted in two ways;

[0403] Method 1: The RAN device determines whether the target downlink data packet was successfully transmitted based on the feedback information from the UE. For example, the information fed back by the UE includes the target PDCP layer sequence number and the transmission identifier. The RAN device determines the transmission identifier corresponding to the target PDCP layer sequence number based on the correspondence between the target PDCP layer sequence number and the transmission identifier and the PDCP layer sequence number. This transmission identifier is the transmission identifier of the target downlink data packet. Therefore, the RAN device can determine that the transmission identifier included in the feedback information is the transmission identifier of the target downlink data packet based on the transmission identifier corresponding to the target PDCP layer sequence number. This identifier is used to indicate whether the UE has received the target downlink data packet or whether the target downlink data packet has been lost. The RAN device determines whether the target downlink data packet was successfully transmitted based on the transmission identifier of the target downlink data packet.

[0404] It should be noted that if the RAN device queries the correspondence between the transmission sequence number and the PDCP layer sequence number based on the target PDCP layer sequence number and fails to find the corresponding transmission sequence number, it means that the downlink data packet corresponding to the target PDCP layer sequence number does not have a corresponding transmission sequence number. In other words, when the UPF network element adds a transmission sequence number to the downlink data packet, it only adds a transmission sequence number to the data packet that needs to be retransmitted after packet loss. That is to say, the downlink data packet without a transmission sequence number is the data packet that does not need to be retransmitted after packet loss. Therefore, the RAN device can ignore or discard the feedback information of the downlink data packet without a corresponding transmission sequence number.

[0405] In one example, the transmission identifier of the target downlink data packet is NACK or ACK; when the transmission identifier of the target downlink data packet is NACK, it means that the UE has not received the target downlink data packet, that is, the transmission of the target downlink data packet has failed; when the transmission identifier of the target downlink data packet is ACK, it means that the UE has received the target downlink data packet, that is, the transmission of the target downlink data packet has been successful.

[0406] Method 2: The RAN device determines whether the target downlink data packet was successfully transmitted based on its own information. For example, in RLC UM mode, the RAN device determines whether the target downlink data packet was successfully transmitted based on the actual transmission status of the MAC layer transport blocks; or, the RAN device obtains the transmission duration of the target downlink data packet to the UE, that is, the elapsed time of transmitting the target downlink data packet to the UE. If the transmission duration exceeds the first transmission duration threshold, the RAN device determines that the target downlink data packet transmission failed.

[0407] It should be noted that the failure of the target downlink data packet transmission includes the case where the transmission still fails after MAC layer retransmission between the RAN device and the UE; optionally, the failure of the target downlink data packet transmission also includes the case where the transmission still fails after MAC layer and RLC layer retransmission between the RAN device and the UE.

[0408] Optionally, if the RAN device determines that the target downlink data packet transmission was successful, the RAN device will not execute S811 and subsequent operations; if the RAN device determines that the target downlink data packet transmission failed, the RAN device will execute S811.

[0409] In S806-S810, the transmission sequence number of the downlink data packet includes either the first transmission sequence number or the second transmission sequence number.

[0410] The S811 and RAN devices determine the estimated retransmission delay of the target downlink data packet based on air interface resource information.

[0411] The estimated retransmission delay of the target downlink data packet is the time required for the target downlink data packet to be transmitted from the RAN device to the UE (i.e., RAN device -> UE) (i.e., the air interface transmission delay of RAN device -> UE), or the sum of the time required for the RAN device to obtain the target downlink data packet from the UPF network element and the time required for the data packet to be transmitted from the RAN device to the UE, i.e., the time from RAN device -> UPF network element -> RAN device -> UE.

[0412] It should be noted that the process of RAN device -> UPF network element -> RAN device refers to the RAN device obtaining the target downlink data packet that needs to be retransmitted from the UPF network element. The transmission time between the RAN device and the UPF network element can also be called the core network packet delay budget (CN PDB), which can be determined based on the operator's configuration information.

[0413] S811 is optional.

[0414] S812, RAN equipment sends the first transmission result to UPF network element.

[0415] The first transmission result includes the sequence number of the target downlink data packet and transmission status information of the target downlink data packet, which indicates whether the target downlink data packet was successfully transmitted. Optionally, the first transmission result also includes the estimated retransmission delay.

[0416] Optionally, the first transmission result is carried on an uplink data packet, which is an uplink data packet from the UE or an empty packet generated by the RAN device.

[0417] The S813 and UPF network elements determine whether the target downlink data packets need to be retransmitted.

[0418] In one example, if an application server, such as a media relay server node, is deployed in the UPF network element, the UPF network element determines whether the target downlink data packet needs to be retransmitted based on the first transmission result.

[0419] Specifically, if the transmission result of the target downlink data packet is determined to be successful based on the first transmission result of the target downlink data packet, then S814 is not executed. If the transmission identifier of the target downlink data packet is determined to be unsuccessful, then two cases are specified to determine whether the target downlink data packet needs to be retransmitted.

[0420] Scenario 1: The UPF network element adds a second sequence number only for downlink data packets that need to be retransmitted after packet loss. For Scenario 1, the UPF network element can determine whether to retransmit the target downlink data packet in two ways:

[0421] Method A1: If the first transmission result sent by the RAN device to the UPF network element includes the second transmission sequence number of the target downlink data packet, the UPF network element determines that the target downlink data packet needs to be retransmitted.

[0422] Method A2: If the first transmission result sent by the RAN device to the UPF network element includes the second transmission sequence number of the target downlink data packet and the estimated retransmission delay, and the estimated retransmission delay is less than or equal to the retransmission delay threshold, then the UPF network element determines that the target downlink data packet needs to be retransmitted; if the first transmission result sent by the RAN device to the UPF network element includes the second transmission sequence number of the target downlink data packet and the estimated retransmission delay, and the estimated retransmission delay is greater than the retransmission delay threshold, then the UPF network element determines that the target downlink data packet does not need to be retransmitted.

[0423] Scenario 2: The UPF network element adds a sequence number, assigning a first sequence number to each received downlink data packet. For Scenario 2, the UPF network element can determine whether to retransmit the target downlink data packet in two ways:

[0424] In Method B1, the UPF network element obtains the retransmission identifier of the target downlink data packet based on the first transmission sequence number of the target downlink data packet. There is a correspondence between the first transmission sequence number and the retransmission identifier. The retransmission identifier of the target downlink data packet is used to indicate whether the target downlink data packet needs to be retransmitted in the event of transmission failure. That is, the UPF network element determines whether the target downlink data packet needs to be retransmitted after packet loss or transmission failure based on the first transmission sequence number of the target downlink data packet. If the retransmission identifier of the target downlink data packet indicates that the target downlink data packet needs to be retransmitted in the event of transmission failure, the UPF network element determines that the target downlink data packet needs to be retransmitted. If the retransmission identifier of the target downlink data packet indicates that the target downlink data packet does not need to be retransmitted in the event of transmission failure, the UPF network element determines that the target downlink data packet does not need to be retransmitted.

[0425] In Method B2, the retransmission flag of the target downlink data packet is used to indicate that the target downlink data packet needs to be retransmitted in the event of a transmission failure. The UPF network element obtains the retransmission delay threshold of the target downlink data packet based on the first transmission sequence number of the target downlink data packet. There is a correspondence between the first transmission sequence number and the retransmission delay threshold. If the estimated retransmission delay of the target downlink data packet is less than or equal to the retransmission delay threshold, the UPF network element determines that the target downlink data packet needs to be retransmitted. If the estimated retransmission delay of the target downlink data packet is greater than the retransmission delay threshold, the UPF network element determines that the target downlink data packet does not need to be retransmitted.

[0426] In one example, if the UPF network element is not a relay network element, the UPF network element will forward the first transmission result to the proxy server or application server (AS).

[0427] S814, UPF network element retransmits target downlink data packets to UE.

[0428] When the UPF network element determines that the target downlink data packet needs to be retransmitted, the UPF network element retransmits the target downlink data packet to the UE.

[0429] S815, UE sends the first information to the UPF network element.

[0430] This step is optional.

[0431] The first message is sent by the UE after the UPF network element retransmits the target downlink data packet to the UE, and it is sent by the UE to the application server to indicate that the UE has not received the target downlink data packet before the retransmission. In one example, the first message is NACK.

[0432] S816 and UPF network elements ignore or discard the first information.

[0433] Specifically, if the UPF network element determines that it has retransmitted the target downlink data packet to the UE, and receives the first information from the UE, the UPF network element ignores or discards the first information.

[0434] It should be pointed out here that Figure 8 For a detailed description and beneficial effects of the illustrated embodiments, please refer to [link to relevant documentation]. Figure 2 and Figure 3 The relevant descriptions of the embodiments shown will not be repeated here.

[0435] See Figure 9 , Figure 9 An interactive flowchart illustrating another data retransmission method provided in this application embodiment. This method is applied to... Figure 1 The system shown. (As shown in the image) Figure 9 As shown, the method includes:

[0436] S901, AF network element sends AF request to PCF network element.

[0437] In one example, the AF request includes a first indication and flow description information. The flow description information can be an IP triple, quintuple, or application identifier, etc. The first indication information indicates that the flow described by the flow description requires retransmission acceleration processing.

[0438] In another example, the AF request includes a first indication that the service flow corresponding to the AF request needs to be retransmitted and accelerated.

[0439] In one example, the AF network element interacts directly with the PCF network element through the API provided by the PCF network element, or the AF network element interacts with the NEF network element through the API provided by the NEF network element, and then the NEF network element interacts with the PCF network element. That is, the AF network element interacts with the PCF network element through the NEF network element.

[0440] It should be noted that the S901 is optional.

[0441] S902, PCF network element sends PCC rules to SMF network element.

[0442] The PCC rule can be generated by the PCF network element during the subsequent PDU session establishment or modification process. The PCC rule is used to indicate the QoS policy for a specified service flow, and the PCC rule includes first indication information.

[0443] The PCF network element generates PCC rules based on its local configuration and / or information provided by the AF (as described in S901).

[0444] This step is optional.

[0445] S903, SMF network element sends N4 rule to UPF network element.

[0446] Specifically, the SMF network element sends an N4 rule to the UPF network element based on the PCC rule and / or local configuration information. The N4 rule includes a fourth indication information, which is used to instruct the UPF network element to enable the fast retransmission mechanism. That is, the UPF network element adds a transmission sequence number to the downlink data packet and optionally adds a retransmission delay threshold and / or a retransmission flag. The retransmission delay threshold is used by the RAN device to decide whether the downlink data packet that has failed to transmit needs to be retransmitted, and the retransmission flag is used to indicate whether the downlink data packet needs to be retransmitted in the event of a transmission failure.

[0447] S904 and SMF network elements send the fifth instruction information to the RAN equipment.

[0448] Specifically, the SMF network element sends a fifth indication message to the RAN device based on PCC rules and / or local configuration information. This fifth indication message is used to instruct the RAN device to decide whether to retransmit downlink data packets.

[0449] Optionally, the fifth indication information includes a retransmission delay threshold, which is used by the RAN device to decide whether downlink data packets that have failed to transmit need to be retransmitted.

[0450] In one example, the fifth instruction information instructs the RAN device to decide whether to retransmit the downlink data packet based on the transmission sequence number and transmission result of the downlink data packet.

[0451] In another example, the fifth instruction information instructs the RAN device to decide whether to retransmit the downlink data packet based on the transmission result, sequence number, and retransmission flag of the downlink data packet.

[0452] In another example, the fifth indication information instructs the RAN device to decide whether to retransmit the downlink data packet based on the transmission result, transmission sequence number, and retransmission delay threshold.

[0453] In another example, the fifth indication information instructs the RAN device to decide whether to retransmit the downlink data packet based on the transmission result, transmission sequence number, retransmission identifier, and retransmission delay threshold.

[0454] The S905 and UPF network elements add transmission sequence numbers to downlink data packets.

[0455] It should be noted that the downlink data packet is a data packet transmitted from the application server to the UE via the UPF network element and RAN equipment, or if the application server is deployed in the UPF network element, then the downlink data packet is a downlink data packet from the UPF network element itself.

[0456] Specifically, in one example, the UPF network element adds a first transmission sequence number to each received downlink data packet. Optionally, it also adds a retransmission flag to each received downlink data packet, indicating whether the downlink data packet needs to be retransmitted. In other words, when the UPF network element receives a downlink data packet, it determines whether the downlink data packet needs to be retransmitted after packet loss; the UPF adds a retransmission flag to the received downlink data packet based on the determination result. A data packet that needs to be retransmitted after packet loss is one that will affect the encoding and decoding of subsequent data packets, or it is a key frame, or it has higher importance. Optionally, the UPF network element adds a retransmission delay threshold to the downlink data packets. It should be noted that the UPF network element can add a retransmission delay threshold to each received downlink data packet. Since multiple downlink data packets have the same retransmission delay threshold, the UPF network element can add the retransmission delay threshold to only one of these multiple downlink data packets, such as adding the retransmission delay threshold to the first downlink data packet. When the UPF network element sends these multiple downlink data packets to the RAN, it can send them simultaneously or continuously.

[0457] In another example, after receiving each downlink data packet, the UPF network element determines whether the downlink data packet is one that needs to be retransmitted after packet loss. If the downlink data packet is one that needs to be retransmitted after packet loss, the UPF network element adds a second transmission sequence number to the downlink data packet. In this case, this second transmission sequence number can simply be a retransmission identifier; that is, there is no need to generate an additional second transmission sequence number, and the retransmission identifier is used as the second transmission sequence number. In other words, the second transmission sequence number of the downlink data packet indicates that the downlink data packet needs to be retransmitted. Optionally, the UPF network element adds a retransmission delay threshold to the downlink data packets that need to be retransmitted after packet loss.

[0458] The S906 and UPF network elements send downlink data packets and third-party information to the RAN equipment.

[0459] Sending downlink data packets and third information to the RAN device can be understood as sending downlink data packets carrying third information to the RAN device;

[0460] The third information is used to determine whether a downlink data packet needs to be retransmitted after a transmission failure. The third information includes a first retransmission indication, which indicates that a retransmission is required if a downlink data packet transmission fails.

[0461] In one example, the first retransmission indication information includes the second sequence number of the downlink data packet. In other words, the RAN device can determine that the downlink data packet needs to be retransmitted after being lost based on the second sequence number of the downlink data packet.

[0462] In another example, the first retransmission indication information includes a retransmission identifier for the downlink data packet; in other words, the retransmission identifier of the downlink data packet can be used to indicate that the downlink data packet needs to be retransmitted when transmission fails. In this case, the third information also includes the transmission sequence number of the downlink data packet, which the RAN device uses to determine the retransmission identifier of the downlink data packet when making a decision. Optionally, the third information also includes a retransmission delay threshold for the downlink data packet.

[0463] Optionally, the third information is carried in the GTP-U layer of the downlink data packet.

[0464] S907, RAN equipment records the correspondence between the transmission sequence number of downlink data packets and the PDCP layer sequence number of downlink data packets.

[0465] It should be noted that the RAN device receives multiple downlink data packets, and correspondingly, multiple pieces of third information; furthermore, when the RAN device sends a downlink data packet to the UE, it simultaneously sends the PDCP layer sequence number of that downlink data packet to the UE. Therefore, after receiving multiple downlink data packets and corresponding third information, the RAN device records the correspondence between the transmission sequence numbers of the multiple downlink data packets and the PDCP layer sequence numbers.

[0466] This step is optional.

[0467] S908, RAN equipment sends target downlink data packets to UE.

[0468] Specifically, the RAN device sends the target downlink data packet to the UE through the PDCP layer, and at the same time sends the PDCP layer sequence number of the target downlink data packet to the UE.

[0469] The S909 and RAN devices determine whether the target downlink data packets have been successfully transmitted.

[0470] Specifically, RAN devices determine whether the target downlink data packet has been successfully transmitted in two ways:

[0471] Method 1: The RAN device determines whether the target downlink data packet was successfully transmitted based on the feedback information from the UE. For example, the feedback information from the UE includes the target PDCP layer sequence number and the transmission identifier. The RAN device determines the transmission identifier corresponding to the target PDCP layer sequence number based on the correspondence between the target PDCP layer sequence number and the transmission identifier and the PDCP layer sequence number. This transmission identifier is the transmission identifier of the target downlink data packet. Therefore, the RAN device can determine that the transmission identifier included in the feedback information is the transmission identifier of the target downlink data packet based on the transmission identifier corresponding to the target PDCP layer sequence number. This identifier is used to indicate whether the UE has received the target downlink data packet. The RAN device determines whether the target downlink data packet was successfully transmitted based on the transmission identifier of the target downlink data packet.

[0472] It should be noted that if the RAN device queries the correspondence between the transmission sequence number and the PDCP layer sequence number based on the target PDCP layer sequence number and fails to find the corresponding transmission sequence number, it means that the downlink data packet corresponding to the target PDCP layer sequence number does not have a corresponding transmission sequence number. In other words, when the UPF network element adds a transmission sequence number to the downlink data packet, it only adds a transmission sequence number to the downlink data packet that needs to be retransmitted after packet loss. That is to say, the downlink data packet without a transmission sequence number is the data packet that does not need to be retransmitted after packet loss. Therefore, the RAN device can ignore or discard the feedback information of the downlink data packet without a corresponding transmission sequence number.

[0473] In one example, the transmission identifier of the target downlink data packet is NACK or ACK; when the transmission identifier of the target downlink data packet is NACK, it means that the UE has not received the target downlink data packet, that is, the transmission of the target downlink data packet has failed; when the transmission identifier of the target downlink data packet is ACK, it means that the UE has received the target downlink data packet, that is, the transmission of the target downlink data packet has been successful.

[0474] Method 2: The RAN device determines whether the target downlink data packet was successfully transmitted based on its own information. For example, in RLC UM mode, the RAN device determines whether the target downlink data packet was successfully transmitted based on the actual transmission status of the MAC layer transport blocks, or the RAN device obtains the transmission duration of the target downlink data packet to the UE, i.e., the elapsed time of transmitting the target downlink data packet to the UE. If the transmission duration exceeds the first transmission duration threshold, the RAN device determines that the target downlink data packet transmission failed.

[0475] If the RAN device determines that the target downlink data packet transmission was successful, the RAN device will not execute S910; if the RAN device determines that the target downlink data packet transmission failed, the RAN device will execute S910.

[0476] In S906-S909, the transmission sequence number of the downlink data packet includes either the first transmission sequence number or the second transmission sequence number.

[0477] The S910 and RAN devices determine whether the target downlink data packets need to be retransmitted.

[0478] In one feasible implementation, when the UPF network element adds a transmission sequence number to downlink data packets by only adding a second transmission sequence number to downlink data packets that require retransmission after packet loss, the RAN device determines that the target downlink data packet needs to be retransmitted based on the second transmission sequence number of the target downlink data packet. In this case, the second transmission sequence number can simply be a retransmission identifier, meaning that there is no need to generate an additional transmission sequence number; the retransmission identifier is used as the transmission sequence number.

[0479] In another feasible implementation, the RAN device determines whether the target downlink data packet needs to be retransmitted based on the retransmission identifier of the target data packet. Specifically, the RAN device determines the retransmission identifier of the target downlink data packet based on the first transmission sequence number of the target downlink data packet. There is a correspondence between the first transmission sequence number and the retransmission identifier. If the retransmission identifier indicates that the target downlink data packet needs to be retransmitted, the RAN device determines that the target downlink data packet needs to be retransmitted; if the retransmission identifier indicates that the target downlink data packet does not need to be retransmitted, the RAN device determines that the target downlink data packet does not need to be retransmitted.

[0480] In another feasible implementation, the RAN device obtains the estimated retransmission delay of the target downlink data packet. This estimated retransmission delay is the estimated time required to retransmit the target downlink data packet. This time can be the time required for the target downlink data packet to travel from the RAN device to the UE (i.e., RAN device -> UE) (i.e., the air interface transmission delay between the RAN device and the UE), or the sum of the time required for the RAN device to obtain the target downlink data packet from the UPF network element and the time required for the target downlink data packet to travel from the RAN device to the UE, i.e., the time from RAN device -> UPF network element -> RAN device -> UE. The RAN device decides whether to retransmit based on the retransmission delay threshold of the target downlink data packet and the estimated retransmission delay of the target downlink data packet. If the estimated retransmission delay is less than or equal to the retransmission delay threshold, the RAN determines that the target downlink data packet needs to be retransmitted; if the estimated retransmission delay is greater than the retransmission delay threshold, the RAN determines that the target downlink data packet does not need to be retransmitted. The retransmission delay threshold of the target downlink data packet can be either sent from the UPF network element to the RAN device through the GTP-U layer of the target downlink data packet, or sent from the SMF network element to the RAN device.

[0481] It should be noted that the process of RAN device -> UPF network element -> RAN device refers to the RAN device obtaining the target downlink data packet that needs to be retransmitted from the UPF network element. The transmission time between the RAN device and the UPF network element can also be called CN PDB, which can be determined based on the operator's configuration information.

[0482] In another feasible implementation, the RAN device obtains the estimated retransmission delay of the target downlink data packet; the RAN device determines the retransmission delay threshold of the target downlink data packet and determines whether the target downlink data packet needs to be retransmitted; if it is determined based on the second transmission sequence number that the target downlink data packet needs to be retransmitted, and the estimated retransmission delay is less than or equal to the retransmission delay threshold, then the RAN device determines that the target downlink data packet needs to be retransmitted; if it is determined based on the second transmission sequence number that the target downlink data packet does not need to be retransmitted, and the estimated retransmission delay is less than or equal to the retransmission delay threshold, then the RAN device determines that the target downlink data packet does not need to be retransmitted; if it is determined based on the retransmission identifier of the second transmission sequence number that the target downlink data packet needs to be retransmitted, and the estimated retransmission delay is greater than the retransmission delay threshold, then the RAN device determines that the target downlink data packet does not need to be retransmitted.

[0483] In another feasible implementation, the RAN device obtains the estimated retransmission delay of the target downlink data packet; the RAN device further determines whether the target downlink data packet needs to be retransmitted based on the retransmission identifier and retransmission delay threshold of the target downlink data packet; if it is determined that the target downlink data packet needs to be retransmitted based on the first transmission sequence number and retransmission identifier, and the estimated retransmission delay is less than or equal to the retransmission delay threshold, then the RAN device determines that the target downlink data packet needs to be retransmitted; if it is determined that the target downlink data packet does not need to be retransmitted based on the first transmission sequence number and retransmission identifier, and the estimated retransmission delay is less than or equal to the retransmission delay threshold, then the RAN device determines that the target downlink data packet does not need to be retransmitted; if it is determined that the target downlink data packet needs to be retransmitted based on the first transmission sequence number and retransmission identifier, and the estimated retransmission delay is greater than the retransmission delay threshold, then the RAN device determines that the target downlink data packet does not need to be retransmitted.

[0484] It should be noted that the RAN device executes S911 when it is determined that the target downlink data packet needs to be retransmitted; the RAN device does not execute S911 when it is determined that the target downlink data packet does not need to be retransmitted.

[0485] S911, RAN equipment retransmits target downlink data packets to UE.

[0486] Specifically, the RAN device retransmits the target downlink data packet to the UE through the PDCP layer.

[0487] S912, RAN equipment sends the second information to UPF network element.

[0488] This step is optional, and the second information includes the transmission sequence number of the target downlink data packet.

[0489] In one example, after retransmitting the target downlink data packet to the UE, the RAN device sends a second message to the UPF network element to notify the UPF network element that the RAN device has retransmitted the target downlink data packet to the UE. In other words, the second message is used to indicate that the RAN device has retransmitted the target downlink data packet to the UE.

[0490] In one example, the RAN device sends an uplink data packet to the UPF network element, and the GTP-U layer of this uplink data packet carries second information. Optionally, this uplink data packet can be a data packet from the UE, or an empty packet generated by the RAN device.

[0491] S913, UE sends the first information to the UPF network element.

[0492] Optionally, this step involves using the first information to indicate that the UE has not received the target downlink data packet. In one example, the second information is NACK.

[0493] S914 and UPF network elements ignore or discard the first information.

[0494] Specifically, this step is optional. Since the RAN device has already retransmitted the target downlink data packet to the UE, if the UPF network element receives the first information indicating that the UE has not received the target downlink data packet at this time, the UPF network element can ignore or discard the first information.

[0495] S915, UE sends the first information to RAN equipment.

[0496] This step is optional.

[0497] S916 RAN equipment ignores or discards the first information.

[0498] This step is optional. Since the RAN device has already retransmitted the target downlink data packet to the UE, if the RAN device receives the first information indicating that the UE has not received the target downlink data packet at this time, the RAN device may ignore or discard the first information.

[0499] It should be noted that S912-S914 and S915-S916 are parallel schemes, and only one of them can be implemented. Figure 9 For a detailed description and beneficial effects of the illustrated embodiments, please refer to [link to relevant documentation]. Figure 4 and Figure 5 The relevant descriptions of the embodiments shown will not be repeated here.

[0500] See Figure 10 , Figure 10An interactive flowchart illustrating another data retransmission method provided in this application embodiment. This method is applied to... Figure 1 UE in the example. Figure 10 As shown, the method includes:

[0501] S1001, AF network element sends AF request to PCF network element.

[0502] In one example, the AF request includes a first indication and flow description information. The flow description information can be an IP triple, quintuple, or application identifier, etc. The first indication information indicates that the flow described by the flow description requires retransmission acceleration processing.

[0503] In another example, the AF request includes a first indication that the service flow corresponding to the AF request needs to be retransmitted and accelerated.

[0504] In one example, the AF network element interacts directly with the PCF network element through the API provided by the PCF network element, or the AF network element interacts with the NEF network element through the API provided by the NEF network element, and then the NEF network element interacts with the PCF network element. That is, the AF network element interacts with the PCF network element through the NEF network element.

[0505] It should be noted that S1001 is optional.

[0506] S1002, PCF network element sends PCC rules to SMF network element.

[0507] The PCC rule is generated by the PCF network element during the subsequent PDU session establishment or modification process. The PCC rule is used to indicate the QoS policy for command service flows, and the PCC rule includes first indication information.

[0508] Among them, the PCF network element generates PCC rules based on local configuration and / or information provided by the AF network element (as described in S801).

[0509] This step is optional.

[0510] S1003, SMF network element sends the sixth instruction information to UE.

[0511] The sixth indication information is used to instruct the UE's underlying layer to determine the transmission result of the uplink data packet and send the transmission result to the UE's application layer to trigger the UE's application layer to decide whether the uplink data packet needs to be retransmitted.

[0512] The UE's application layer can be the UE's transport layer or application layer, or a protocol layer on top of IP. The UE's bottom layer refers to the protocol layer between the UE and the RAN, including but not limited to the physical layer, MAC layer, radio link layer (RLC), PDCP layer, etc.

[0513] In one feasible implementation, this step is optional: the UE's underlying layer triggers the UE's application layer to decide whether to retransmit the uplink data packet based on local configuration information or cross-layer indications from the UE's application layer.

[0514] S1004. The UE's application layer sends uplink data packets and uplink data packet identification information to the UE's underlying layer.

[0515] This step is performed after the PDU session establishment or modification process is completed or after the service is started.

[0516] Optionally, the identification information can be a sequence number added by the APP layer to the uplink data packet, or it can be a corresponding sequence number already present in the transport layer of the uplink data packet, such as a Transport Control Protocol (TCP) sequence number or a Real-Time Transport Protocol (RTP) sequence number; this is not limited here. In one example, the uplink data packet's sequence number is carried in the RTP or TCP layer of the uplink data packet.

[0517] In one example, 8 bits are used to mark the sequence number of data packets. The sequence number of the first data packet is 0, the sequence number of the second data packet is 1, and so on, incrementing by 1. When the sequence number reaches 255, it starts marking again from 0.

[0518] It should be noted that the following steps use the transmission sequence number as an example to illustrate the identification information. For the detailed implementation process of adding transmission sequence numbers to uplink data packets, please refer to [link to relevant documentation]. Figure 7 The relevant descriptions will not be repeated here.

[0519] S1005, The UE's underlying record establishes the correspondence between the transmission sequence number of the uplink data packet and the PDCP layer sequence number.

[0520] This step is optional.

[0521] It should be noted that the UE's underlying layer can receive multiple uplink data packets, and correspondingly, multiple sequence numbers; furthermore, when the UE's underlying layer sends an uplink data packet to the UE, it also sends the PDCP layer sequence number of that uplink data packet. Therefore, after receiving multiple uplink data packets and their corresponding sequence numbers, the UE's underlying layer records the correspondence between the sequence numbers of the multiple uplink data packets and the PDCP layer sequence numbers.

[0522] S1006, The UE's underlying layer sends the target uplink data packet to the RAN device.

[0523] The target uplink data packet is one of the uplink data packets received by the UE's underlying layer. The UE's underlying layer sends the target uplink data packet to the RAN device through the PDCP layer, and the target uplink data packet contains the PDCP layer sequence number.

[0524] S1007, The UE's underlying layer determines whether the target uplink data packet was successfully transmitted.

[0525] Specifically, the UE's underlying layer determines whether the target uplink data packet has been successfully transmitted in three ways:

[0526] Method 1: The UE's underlying layer determines whether the target uplink data packet was successfully transmitted based on feedback information from the RAN device. For example, the feedback information from the RAN device includes the target PDCP layer sequence number and the transmission identifier. The UE's underlying layer determines the transmission identifier corresponding to the target PDCP layer sequence number based on the correspondence between the target PDCP layer sequence number and the transmission identifier and the PDCP layer sequence number. This transmission identifier is the transmission identifier of the target uplink data packet. Therefore, the UE's underlying layer can determine that the transmission identifier included in the feedback information is the transmission identifier of the target uplink data packet based on the transmission identifier corresponding to the target PDCP layer sequence number. This identifier is used to indicate whether the RAN device has received the target uplink data packet. The UE's underlying layer determines whether the target uplink data packet was successfully transmitted based on the transmission identifier of the target uplink data packet.

[0527] It should be noted that if the UE's underlying layer queries the correspondence between the transmission sequence number and the PDCP layer sequence number based on the target PDCP layer sequence number and fails to find the corresponding transmission sequence number, it means that the uplink data packet corresponding to the target PDCP layer sequence number does not have a corresponding transmission sequence number. In other words, when the UE's application layer adds a transmission sequence number to the uplink data packet, it only adds a transmission sequence number to the uplink data packet that needs to be retransmitted after packet loss. That is to say, the uplink data packet without a transmission sequence number is the data packet that does not need to be retransmitted after packet loss. Therefore, the UE's underlying layer can ignore or discard the feedback information of the uplink data packet without a corresponding transmission sequence number.

[0528] In one example, the second transmission result of the target uplink data packet includes NACK or ACK; when the transmission result of the target uplink data packet includes NACK, it means that the RAN device has not received the target uplink data packet, that is, the transmission of the target uplink data packet has failed; when the transmission result of the target uplink data packet includes ACK, it means that the RAN device has received the target uplink data packet, that is, the transmission of the target uplink data packet has been successful.

[0529] Method 2: The UE determines whether the target uplink data packet was successfully transmitted based on its own information. For example, in RLCUM mode, the UE's underlying layer determines whether the uplink data packet was successfully transmitted based on the actual transmission status of the MAC layer transport block, or the UE's underlying layer obtains the transmission duration of the target uplink data packet to the RAN device, i.e., the elapsed time of transmitting the target uplink data packet to the RAN device. If the transmission duration exceeds the second transmission duration threshold, the UE's underlying layer determines that the target uplink data packet transmission failed.

[0530] S1008, The UE's underlying layer sends the transmission sequence number and second transmission result of the target uplink data packet to the UE's application layer.

[0531] It should be noted that the purpose of the UE's underlying layer sending the transmission sequence number of the uplink data packet to the UE's application layer at the same time as sending the second transmission result is to inform the application layer that the second transmission result is the second transmission result of the uplink data packet.

[0532] S1009. Does the UE's application layer need to retransmit the target uplink data packet based on the second transmission result of the target uplink data packet?

[0533] Specifically, if the target uplink data packet is successfully transmitted based on the second transmission result of the target uplink data packet, then S1010 is not executed. If the target uplink data packet is failed to be transmitted based on the transmission identifier of the target uplink data packet, then two specific cases are used to determine whether the target uplink data packet needs to be retransmitted.

[0534] Scenario 1: The UE's application layer adds a sequence number only for uplink data packets that need to be retransmitted after packet loss.

[0535] For scenario 1, the UE's application layer can determine whether to retransmit the target uplink data packet in two ways:

[0536] Method A1: If the second transmission result sent by the UE's underlying layer to the UE's application layer includes the fourth transmission sequence number of the target uplink data packet, the UE's application layer determines that the target uplink data packet needs to be retransmitted.

[0537] Method A2: If the second transmission result includes the fourth transmission sequence number and estimated retransmission delay of the target uplink data packet, and the estimated retransmission delay of the target uplink data packet is less than or equal to the retransmission delay threshold of the target uplink data packet, then the UE's application layer determines that the target uplink data packet needs to be retransmitted; if the second transmission result includes the fourth transmission sequence number and estimated retransmission delay of the target uplink data packet, and the estimated retransmission delay of the target uplink data packet is greater than the retransmission delay threshold of the target uplink data packet, then the UE's application layer determines that the target uplink data packet does not need to be retransmitted.

[0538] Scenario 2: The UE's application layer adds a third sequence number to each received uplink data packet. For Scenario 2, the UPF network element can determine whether to retransmit the target uplink data packet in two ways:

[0539] In method B1, the UE's application layer obtains the retransmission identifier of the target uplink data packet based on the third transmission sequence number. There is a correspondence between the third transmission sequence number and the retransmission identifier. The retransmission identifier of the target uplink data packet is used to indicate whether the target uplink data packet needs to be retransmitted in the event of transmission failure. If the retransmission identifier of the uplink data packet indicates that the target uplink data packet needs to be retransmitted in the event of transmission failure, the UE's application layer determines that the target uplink data packet needs to be retransmitted. If the retransmission identifier of the target uplink data packet indicates that the target uplink data packet does not need to be retransmitted in the event of transmission failure, the UE's application layer determines that the target uplink data packet does not need to be retransmitted.

[0540] Method B2: The target uplink data packet retransmission flag is used to indicate that the target uplink data packet needs to be retransmitted in the event of a transmission failure. The UE's application layer obtains the retransmission delay threshold of the target uplink data packet based on the third transmission sequence number. There is a correspondence between the third transmission sequence number and the retransmission delay threshold. If the estimated retransmission delay of the target uplink data packet is less than or equal to the retransmission delay threshold, the UE's application layer determines that the target uplink data packet needs to be retransmitted. If the estimated retransmission delay of the target uplink data packet is greater than the retransmission delay threshold, the UE's application layer determines that the target uplink data packet does not need to be retransmitted.

[0541] S1010, the UE's application layer retransmits the target uplink data packet to the application server.

[0542] S1011, The application server sends the fourth information to the application layer of the UE.

[0543] This step is optional.

[0544] The fourth message is sent by the application server after the UE's application layer retransmits the target uplink data packet to the application server, and it is used to indicate that the application server has not received the target uplink data packet. In one example, the fourth message is NACK.

[0545] S1012, The UE's application layer ignores or discards the fourth information.

[0546] This step is optional.

[0547] Specifically, if the UE's application layer determines that the target uplink data packet has been retransmitted to the application server, and if the fourth information is received from the application server at this time, the UE's application layer will ignore or discard the fourth information since the target uplink data packet has already been retransmitted to the application server.

[0548] It should be pointed out here that Figure 10 For a detailed description and beneficial effects of the illustrated embodiments, please refer to [link to relevant documentation]. Figure 6 and Figure 7 The relevant descriptions of the embodiments shown will not be repeated here.

[0549] Reference Figure 11 The diagram shown is a structural schematic of a UPF network element provided in an embodiment of this application. The UPF network element 1100 is... Figure 1 UPF network elements in the network. For example... Figure 11 As shown, the UPF network element 1100 includes: a transceiver unit 1101, a determination unit 1102, an acquisition unit 1103, and a processing unit 1104.

[0550] In one feasible embodiment, the transceiver unit 1101 is used to receive the transmission result of the downlink data packet transmitted between the RAN device and the UE and the transmission sequence number of the downlink data packet, wherein the transmission result of the downlink data packet transmitted between the RAN device and the UE is used to indicate whether the transmission of the downlink data packet to the UE was successful.

[0551] The determining unit 1102 is used to determine whether it is necessary to retransmit the downlink data packet based on the transmission result of the downlink data packet being transmitted between the RAN device and the UE and the transmission sequence number of the downlink data packet.

[0552] In one feasible implementation, the determining unit 1102 is specifically used for:

[0553] If the transmission result of the downlink data packet between the RAN device and the UE indicates that the downlink data packet transmission failed, then the downlink data packet needs to be retransmitted based on the transmission sequence number of the downlink data packet.

[0554] In one feasible implementation, the acquisition unit 1103 is used to acquire downlink data packets;

[0555] The determining unit 1102 is also used to determine whether the downlink data packet is a data packet that needs to be retransmitted after being lost. If the downlink data packet is a data packet that needs to be retransmitted after being lost, a transmission sequence number is added to the downlink data packet.

[0556] In one feasible implementation, the determining unit 1102 is specifically used for:

[0557] The retransmission identifier of the downlink data packet is determined based on the transmission sequence number. The retransmission identifier of the downlink data packet is used to indicate whether the downlink data packet needs to be retransmitted in the event of a transmission failure. If the retransmission identifier of the downlink data packet indicates that the downlink data packet needs to be retransmitted, then it is determined that the downlink data packet needs to be retransmitted.

[0558] In one feasible implementation, the transceiver unit 1101 is further configured to receive the estimated retransmission delay of the downlink data packet from the RAN device, wherein the estimated retransmission delay of the downlink data packet is the estimated time required to retransmit the downlink data packet to the UE.

[0559] The acquisition unit 1103 is also used to acquire the retransmission delay threshold of the downlink data packet based on the transmission sequence number of the downlink data packet;

[0560] The determining unit 1102 is specifically used to: if the retransmission flag of the downlink data packet is used to indicate that the downlink data packet needs to be retransmitted, and the estimated retransmission delay of the downlink data packet is less than or equal to the retransmission delay threshold of the downlink data packet, then it is determined that the downlink data packet needs to be retransmitted.

[0561] In one feasible implementation, the transceiver unit 1101 is further configured to receive the estimated retransmission delay of the downlink data packet from the RAN device, the estimated retransmission delay of the downlink data packet being the estimated time required to retransmit the downlink data packet to the UE.

[0562] The determining unit 1102 is specifically used to: determine the retransmission delay threshold of the downlink data packet based on the transmission sequence number of the downlink data packet; if the estimated retransmission delay of the downlink data packet is less than or equal to the retransmission delay threshold of the downlink data packet, then determine that the downlink data packet needs to be retransmitted.

[0563] In one feasible implementation, the retransmission delay threshold for downlink data packets is obtained by the UPF network element 1100 from its local configuration, or from the SMF network element or a third-party application.

[0564] In one feasible implementation, the transmission result of downlink data packets between the RAN device and the UE is determined by the RAN device based on the feedback information from the UE regarding the downlink data packets sent from the RAN device to the UE, or;

[0565] The transmission result of downlink data packets between the RAN device and the UE is determined by the RAN device based on the RAN device's MAC layer transport block transmission status when sending downlink data packets to the UE.

[0566] In one feasible implementation, the transceiver unit 1101 is also used to retransmit downlink data packets to the UE when it is determined that retransmission of downlink data packets is necessary.

[0567] In one feasible implementation, the transceiver unit 1101 is further configured to receive first information from the UE, which is sent by the UE after the UPF network element or RAN device retransmits the downlink data packet to the UE, and the first information is used to indicate that the UE has not received the downlink data packet.

[0568] The processing unit 1104 is used to discard or ignore the first information.

[0569] In one feasible implementation, the UPF network element caches downlink data packets, or an application server is deployed on the UPF network element.

[0570] In another possible embodiment, the acquisition unit 1103 is used to acquire downlink data packets and acquire third information of the downlink data packets, the third information being used to determine whether the downlink data packets need to be retransmitted after transmission failure.

[0571] The transceiver unit 1101 is used to send downlink data packets and third-party information to the RAN equipment.

[0572] In one feasible implementation, the acquisition unit 1103 is used to acquire third information of the downlink data packet, including:

[0573] Add a transmission sequence number to the downlink data packet; the third information includes the transmission sequence number.

[0574] In one feasible implementation, the determining unit 1102 is used to determine whether the downlink data packet is a data packet that needs to be retransmitted after being lost after the downlink data packet is acquired.

[0575] Acquisition unit 1103 is used to acquire third information of downlink data packets, including:

[0576] If the downlink data packet is a data packet that needs to be retransmitted after being lost, the UPF network element adds a transmission sequence number to the downlink data packet.

[0577] In one feasible implementation, the third information includes retransmission indication information for downlink data packets, which is used to indicate that downlink data packets need to be retransmitted to the UE in the event of transmission failure.

[0578] In one feasible implementation, the retransmission indication information includes the sequence number of the downlink data packet or the retransmission identifier of the downlink data packet.

[0579] In one feasible implementation, the third information includes a downlink data packet retransmission delay threshold, which is used to determine whether the downlink data packet needs to be retransmitted to the UE.

[0580] In one feasible implementation, the third information can be carried in the GTP-U layer of the downlink data packet.

[0581] In one feasible implementation, the transceiver unit 1101 is further configured to receive second information from the RAN device, the second information being used to indicate that the downlink data packet has been retransmitted to the UE.

[0582] In one feasible implementation, the transceiver unit 1101 is further configured to receive first information from the UE after receiving the second information, the first information being used to indicate that the UE has not received downlink data packets;

[0583] The processing unit 1104 is used to discard or ignore the first information.

[0584] It is worth noting that the specific functional implementation of the UPF network element 1100 can be found in [link to relevant documentation]. Figure 2 or Figure 3 The detailed description of the illustrated embodiment shows that each unit or module in the UPF network element 1100 can be individually or entirely merged into one or more other units or modules, or some of the units or modules can be further divided into multiple functionally smaller units or modules. This achieves the same operation without affecting the technical effects of the embodiments of this application. The above-mentioned units or modules are based on logical function division. In practical applications, the function of one unit (or module) is implemented by multiple units (or modules), or the function of multiple units (or modules) is implemented by one unit (or module).

[0585] Reference Figure 12 The diagram shown is a structural schematic of a RAN device provided in an embodiment of this application. The RAN device 1200 is... Figure 1 RAN equipment in the system. For example... Figure 12 As shown, the RAN device 1200 includes: a transceiver unit 1201, a determination unit 1202, and a processing unit 1203.

[0586] In one possible embodiment, the transceiver unit 1201 is configured to receive downlink data packets and the transmission sequence number of the downlink data packets from the UPF network element; and send downlink data packets to the UE.

[0587] The determining unit 1202 is used to determine the transmission result of the downlink data packet between the RAN device and the UE;

[0588] The transceiver unit 1201 is also used to send the transmission result and sequence number of the downlink data packet to the UPF network element. The transmission result and sequence number of the downlink data packet are used to determine whether the downlink data packet needs to be retransmitted.

[0589] In one feasible implementation, the determining unit 1202 is specifically used for:

[0590] The RAN device determines the transmission delay of the downlink data packet to be sent to the UE; if the transmission delay of the downlink data packet exceeds the first transmission delay threshold, the RAN device determines that the downlink data packet transmission has failed; wherein, the transmission result of the downlink data packet includes downlink data packet transmission failure.

[0591] In one feasible implementation, the determining unit 1202 is specifically used for:

[0592] The transmission result of downlink data packets is determined based on the transmission status of the MAC layer transport blocks of the RAN equipment.

[0593] In one feasible implementation, the processing unit 1203 is used to record the correspondence between the transmission sequence number of the downlink data packet and the PDCP layer sequence number of the downlink data packet after receiving the transmission sequence number of the downlink data packet.

[0594] The transceiver unit 1201 is also used to receive feedback messages from the UE. The feedback messages include a transmission identifier and a PDCP layer sequence number. The transmission identifier is used to indicate whether the UE has received the downlink data packet. The determination unit 1202 is specifically used to determine the transmission result of the downlink data packet based on the correspondence between the PDCP layer sequence number and the transmission sequence number, the PDCP layer sequence number and the transmission identifier.

[0595] In one feasible implementation, the transceiver unit 1201 is also used to send the estimated retransmission delay of the downlink data packet to the UPF network element. The estimated retransmission delay of the downlink data packet is used to determine whether the downlink data packet needs to be retransmitted. The estimated retransmission delay of the downlink data packet is the estimated time required for the RAN device to retransmit the downlink data packet to the UE.

[0596] In one feasible implementation, the transmission result of the downlink data packet, the transmission sequence number of the downlink data packet, and / or the estimated retransmission delay of the downlink data packet are carried in the GTP-U layer of the uplink data packet.

[0597] In another possible embodiment, the transceiver unit 1201 is configured to receive third information and downlink data packets from the application server, wherein the third information is used to determine whether retransmission is required after the downlink data packet transmission fails; and to send downlink data packets to the UE.

[0598] The determining unit 1202 is used to determine, based on third information, to retransmit the downlink data packet to the UE when it is determined that the downlink data packet transmission has failed.

[0599] In one feasible implementation, the third information includes retransmission indication information for downlink data packets, which indicates that the downlink data packets need to be retransmitted in the event of a transmission failure.

[0600] In one feasible implementation, the retransmission indication information includes the sequence number of the downlink data packet or the retransmission identifier of the downlink data packet.

[0601] In one feasible implementation, the third information includes the retransmission delay threshold for downlink data packets, and the determining unit 1202 is specifically used for:

[0602] Obtain the estimated retransmission delay of the downlink data packet; the estimated retransmission delay of the downlink data packet is the estimated time required to retransmit the downlink data packet to the UE; when the estimated retransmission delay of the downlink data packet is less than or equal to the retransmission delay threshold of the downlink data packet, determine to retransmit the downlink data packet to the UE.

[0603] In one feasible implementation, the determining unit 1202 is further used for:

[0604] Determine the transmission delay of sending downlink data packets to the UE; if the transmission delay of downlink data packets exceeds a first transmission delay threshold, then determine that the downlink data packet transmission has failed, wherein the transmission result of downlink data packets includes downlink data packet transmission failure.

[0605] In one feasible implementation, the determining unit 1202 is further used for:

[0606] The transmission result of the downlink data packet is determined based on the transmission status of the MAC layer transport block of the RAN device 1200, and the transmission result of the downlink data packet is used to determine whether the downlink data packet transmission failed.

[0607] In one feasible implementation, the processing unit 1203 is used to record the correspondence between the transmission sequence number of the downlink data packet and the PDCP layer sequence number of the downlink data packet after receiving the transmission sequence number of the downlink data packet.

[0608] The transceiver unit 1201 is also configured to receive a feedback message from the RAN, the feedback message including a transmission identifier and a PDCP layer sequence number, the transmission identifier of the downlink data packet being used to indicate whether the UE has received the downlink data packet;

[0609] The determining unit 1202 is also used to determine whether the downlink data packet transmission has failed based on the correspondence between the PDCP layer sequence number and the transmission sequence number, the PDCP layer sequence number and the transmission identifier.

[0610] In one feasible implementation, the transceiver unit 1201 is further configured to send second information to the UPF network element after retransmitting the downlink data packet to the UE, the second information being used to indicate that the downlink data packet has been retransmitted to the UE.

[0611] In one feasible implementation, the processing unit 1203 is configured to discard or ignore the first information if it receives the first information sent by the UE to the application server after retransmitting the transmission result of the downlink data packet to the UE, and the first information indicates that the UE has not received the downlink data packet.

[0612] It is worth noting that the specific functional implementation of RAN device 1200 is described above. Figure 3 or Figure 4The specific description of the illustrated embodiment is as follows. Each unit or module in the RAN device 1200 can be individually or entirely merged into one or more other units or modules, or some of these units or modules can be further divided into multiple functionally smaller units or modules. This achieves the same operation without affecting the technical effects of the embodiments of this application. The aforementioned units or modules are based on logical functional division. In practical applications, the function of one unit (or module) is implemented by multiple units (or modules), or the function of multiple units (or modules) is implemented by one unit (or module).

[0613] Reference Figure 13 The diagram shown is a structural schematic of a UE provided in an embodiment of this application. The UE1300 is... Figure 1 UE in the example. Figure 13 As shown, the UE1300 includes: a transceiver unit 1301, a determination unit 1302, an acquisition unit 1303, and a processing unit 1304.

[0614] In one possible embodiment, from the application layer perspective of UE1300:

[0615] The transceiver unit 1301 is used to receive the transmission result and the transmission sequence number of the uplink data packet transmitted between the UE's underlying layer and the RAN device from the UE's underlying layer.

[0616] The determining unit 1302 is used to determine whether to retransmit the uplink data packet based on the transmission result of the uplink data packet transmission between the UE's underlying layer and the RAN device and the transmission sequence number of the uplink data packet.

[0617] In one feasible implementation, the acquisition unit 1303 is used to acquire uplink data packets;

[0618] The determining unit 1302 is used to determine whether the uplink data packet is a data packet that needs to be retransmitted after being lost; if the uplink data packet is a data packet that needs to be retransmitted after being lost, a transmission sequence number is added to the uplink data packet.

[0619] In one feasible implementation, the determining unit 1302 is used to determine whether the uplink data packet needs to be retransmitted based on the transmission result and sequence number of the uplink data packet, including:

[0620] If the transmission result of the uplink data packet indicates that the uplink data packet transmission failed, then the uplink data packet needs to be retransmitted based on the transmission sequence number of the uplink data packet.

[0621] In one feasible implementation, the determining unit 1302 is used to determine the sequence number for retransmission of the uplink data packet based on the transmission sequence number of the uplink data packet, including:

[0622] The retransmission identifier of the uplink data packet is determined based on the transmission sequence number. The retransmission identifier of the uplink data packet is used to indicate whether the uplink data packet needs to be retransmitted in the event of a transmission failure. If the retransmission identifier of the uplink data packet indicates that the uplink data packet needs to be retransmitted, then it is determined that the uplink data packet needs to be retransmitted.

[0623] In one feasible implementation, the transceiver unit 1301 is also used to receive the estimated retransmission delay of the uplink data packet from the underlying layer of the UE, wherein the estimated retransmission delay of the uplink data packet is the estimated time required to retransmit the uplink data packet to the RAN device.

[0624] The acquisition unit 1303 is also used to acquire the retransmission delay threshold of the uplink data packet based on the transmission sequence number of the uplink data packet;

[0625] The determining unit 1302 is used to determine that an uplink data packet needs to be retransmitted if the retransmission flag of the uplink data packet indicates that the uplink data packet needs to be retransmitted, including:

[0626] If the retransmission flag of the uplink data packet is used to indicate that the uplink data packet needs to be retransmitted, and the estimated retransmission delay of the uplink data packet is less than or equal to the retransmission delay threshold of the uplink data packet, then it is determined that the uplink data packet needs to be retransmitted.

[0627] In one feasible implementation, the transceiver unit 1301 is also used to receive the estimated retransmission delay of the uplink data packet from the underlying layer of the UE, wherein the estimated retransmission delay of the uplink data packet is the estimated time required to retransmit the uplink data packet to the RAN device.

[0628] The UE's application layer determines which uplink data packets need to be retransmitted based on the sequence number of the uplink data packets, including:

[0629] The determining unit 1302 is used to determine the retransmission delay threshold of the uplink data packet based on the transmission sequence number of the uplink data packet; if the estimated retransmission delay of the uplink data packet is less than or equal to the retransmission delay threshold of the uplink data packet, it is determined that the uplink data packet needs to be retransmitted.

[0630] In one feasible implementation, the uplink data packet retransmission delay threshold is obtained from the local configuration of the UE application layer, or from the SMF network element or a third-party application.

[0631] In one feasible implementation, the transceiver unit 1301 is further configured to receive fourth information from the RAN device; the fourth information is sent by the RAN after the UE retransmits the uplink data packet to the RAN at the underlying layer, and the fourth information is used to indicate that the RAN device has not received the uplink data packet.

[0632] Processing unit 1304 is used to discard or ignore the fourth information.

[0633] In one feasible implementation, the transceiver unit 1301 is also used to send fifth information to the underlying layer of the UE, the fifth information being used to indicate whether it is necessary to determine the transmission result of the uplink data packet.

[0634] In one possible embodiment, the following is explained from the perspective of the underlying layer of UE1300:

[0635] The transceiver unit 1301 is used to receive uplink data packets and uplink data packet sequence numbers from the application layer of the UE; and to send uplink data packets to the RAN device.

[0636] The determining unit 1302 is used to determine the transmission result of the uplink data packet between the UE's underlying layer and the RAN device;

[0637] The transceiver unit 1301 is also used to send the transmission result and sequence number of the uplink data packet from the UE's lower layer to the UE's application layer. The transmission result and sequence number of the uplink data packet are used to determine whether the uplink data packet needs to be retransmitted.

[0638] In one feasible implementation, the determining unit 1302 is used to determine the transmission result of the uplink data packet, including:

[0639] Determine the transmission delay of sending uplink data packets to the RAN device; if the transmission delay of uplink data packets exceeds the second transmission delay threshold, then determine that the uplink data packet transmission has failed, wherein the transmission result of uplink data packets includes uplink data packet transmission failure.

[0640] In one feasible implementation, the determining unit 1302 is used to determine the transmission result of the uplink data packet, including:

[0641] The transmission result of uplink data packets is determined based on the transmission status of the underlying transport blocks of the UE.

[0642] In one feasible implementation, the processing unit 1304 is used to record the correspondence between the transmission sequence number of the uplink data packet and the PDCP layer sequence number of the uplink data packet after receiving the transmission sequence number of the uplink data packet.

[0643] The transceiver unit 1301 is also used to receive a feedback message from the RAN device, which includes a transmission identifier and a PDCP layer sequence number. The transmission identifier is used to indicate whether the RAN device has received an uplink data packet.

[0644] Determining unit 1302 is used to determine the transmission result of the uplink data packet, including:

[0645] The transmission result of the uplink data packet is determined based on the correspondence, PDCP layer sequence number, and transmission identifier.

[0646] In one feasible implementation, the transceiver unit 1301 is further configured to send the estimated retransmission delay of the uplink data packet to the application layer of the UE. The estimated retransmission delay of the uplink data packet is used to determine whether the uplink data packet needs to be retransmitted. The estimated retransmission delay of the uplink data packet is the estimated time required for the UE's underlying layer to retransmit the uplink data packet to the RAN device.

[0647] In conjunction with the sixth aspect, in a feasible implementation, the method of this embodiment further includes:

[0648] The transceiver unit 1301 is also used to receive the fifth information sent by the application layer of the UE, the fifth information being used to indicate whether it is necessary to determine the transmission result of the uplink data packet; and to send the transmission result of the uplink data packet and the transmission sequence number of the uplink data packet to the application layer of the UE.

[0649] It is worth noting that the specific functional implementation of UE1300 can be found above. Figure 6 or Figure 7 The specific description of the illustrated embodiment is as follows. Each unit or module in UE1300 can be individually or entirely merged into one or more other units or modules, or some of these units or modules can be further divided into multiple functionally smaller units or modules. This achieves the same operation without affecting the technical effects of the embodiments of this application. The aforementioned units or modules are based on logical functional division. In practical applications, the function of one unit (or module) is implemented by multiple units (or modules), or the function of multiple units (or modules) is implemented by one unit (or module).

[0650] It should be noted that, in this application, the transmission result of uplink data packets refers to the transmission result of uplink data packets between the UE's underlying layer and the RAN device, and the transmission result of downlink data packets refers to the transmission result of downlink data packets between the RAN device and the UE.

[0651] Based on the description of the above method embodiments and related device embodiments, please refer to... Figure 14 This application also provides a schematic diagram of the structure of a communication device 1400. The communication device 1400 can be... Figure 11 The UPF network element 1100 shown, or Figure 12 The RAN device 1200 shown, or Figure 13 The UE1300 shown. Figure 14 The communication device 1400 shown includes a memory 1401, a processor 1402, a communication interface 1403, and a bus 1404. The memory 1401, the processor 1402, and the communication interface 1403 are interconnected via the bus 1404.

[0652] Optionally, the memory 1401 may be a read-only memory (ROM), a static storage device, a dynamic storage device, or a random access memory (RAM).

[0653] Memory 1401 can store programs. When the program stored in memory 1401 is executed by processor 1402, processor 1402 and communication interface 1403 are used for execution. Figures 2-7 The various steps of the data retransmission method in the illustrated embodiment.

[0654] The processor 1402 employs a general-purpose central processing unit (CPU), microprocessor, application-specific integrated circuit (ASIC), graphics processing unit (GPU), or one or more integrated circuits to execute relevant programs to achieve the functions required by the units in the UPF network element 1100, RAN device 1200, or UE 1300 of this application embodiment, or to execute the functions required by this application. Figures 2-7 The data retransmission method of the illustrated embodiment.

[0655] The processor 1402 can also be an integrated circuit chip with signal processing capabilities. In its implementation, this application... Figures 2-7Each step of the data retransmission method shown can be completed by integrated logic circuits in the hardware of processor 1402 or by instructions in software form. Optionally, processor 1402 is a general-purpose processor, digital signal processor (DSP), ASIC, field programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic device, or discrete hardware component. Processor 1402 can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor is a microprocessor or any conventional processor, etc. The steps of the methods disclosed in the embodiments of this application can be directly embodied in the execution of a hardware decoding processor, or can be executed by a combination of hardware and software modules in the decoding processor. Optionally, the software modules are located in random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, or other mature storage media in the art. The storage medium is located in memory 1401. Processor 1402 reads the information in memory 1401 and, in conjunction with its hardware, performs the functions required by the units included in the UPF network element 1100, RAN device 1200, or UE 1300 in this embodiment of the application, or performs... Figures 2-7 The data retransmission method of the illustrated embodiment.

[0656] The communication interface 1403 uses transceiver devices, such as, but not limited to, transceivers, to enable communication between the communication device 1400 and other devices or communication networks.

[0657] Bus 1404 may include a pathway for transmitting information between various components of communication device 1400 (e.g., memory 1401, processor 1402, communication interface 1403).

[0658] It should be noted that, although Figure 14 The communication device 1400 shown only illustrates the memory, processor, and communication interface. However, those skilled in the art should understand that in specific implementations, the communication device 1400 may also include other components necessary for normal operation. Furthermore, depending on specific needs, those skilled in the art should understand that the communication device 1400 may also include hardware components for implementing other additional functions. Moreover, those skilled in the art should understand that the communication device 1400 may only include the components necessary for implementing the embodiments of this application, and may not necessarily include... Figure 14 All the devices shown.

[0659] This application also provides a chip, which includes a processor and a data interface. The processor reads instructions stored in the memory through the data interface to implement the data retransmission method of this application.

[0660] Optionally, as one implementation, the chip further includes a memory storing instructions, and the processor is used to execute the instructions stored in the memory. When the instructions are executed, the processor is used to execute the data retransmission method.

[0661] This application also provides a computer-readable storage medium storing instructions that, when executed on a computer or processor, cause the computer or processor to perform one or more steps of any of the above methods.

[0662] This application also provides a computer program product containing instructions. When the computer program product is run on a computer or processor, it causes the computer or processor to perform one or more steps of any of the methods described above.

[0663] Those skilled in the art will appreciate that the functionality described in conjunction with the various illustrative logic blocks, modules, and algorithmic steps disclosed herein can be implemented by hardware, software, firmware, or any combination thereof. If implemented in software, the functionality described by the various illustrative logic blocks, modules, and steps can be stored or transmitted as one or more instructions or codes on a computer-readable medium and executed by a hardware-based processing unit. The computer-readable medium may comprise a computer-readable storage medium, which corresponds to a tangible medium, such as a data storage medium, or a communication medium that includes any medium facilitating the transfer of a computer program from one place to another (e.g., based on a communication protocol). In this way, the computer-readable medium may substantially correspond to (1) a non-transitory tangible computer-readable storage medium, or (2) a communication medium, such as a signal or carrier wave. The data storage medium may be any available medium accessible by one or more computers or one or more processors to retrieve instructions, code, and / or data structures for implementing the techniques described in this application. A computer program product may comprise a computer-readable medium.

[0664] By way of example and not limitation, such computer-readable storage media includes RAM, ROM, EEPROM, CD-ROM or other optical disc storage devices, magnetic disk storage devices or other magnetic storage devices, flash memory, or any other media that can be used to store desired program code in the form of instructions or data structures and is accessible by a computer. Furthermore, any connection is properly referred to as computer-readable media. For example, if instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of media. However, it should be understood that the computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other temporary media, but are specifically referring to non-temporary tangible storage media. As used herein, disks and optical discs include Compact Discs (CDs), Laser Discs, Optical Discs, Digital Versatile Discs (DVDs), and Blu-ray Discs, where disks typically reproduce data magnetically, while optical discs reproduce data optically using lasers. Combinations of these should also be included within the scope of computer-readable media.

[0665] Instructions can be executed by one or more processors, such as one or more DSPs, general-purpose microprocessors, ASICs, FPGAs, or other equivalent integrated or discrete logic circuits. Therefore, the term "processor" as used herein can refer to any of the foregoing structures or any other structures suitable for implementing the techniques described herein. Furthermore, in some aspects, the functions described in the various illustrative logic blocks, modules, and steps described herein are provided within dedicated hardware and / or software modules configured for encoding and decoding, or incorporated into combined codecs. Moreover, the techniques can be fully implemented within one or more circuit or logic elements.

[0666] In the embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the division of units is merely a logical functional division, and in actual implementation, there may be other division methods. For instance, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Optionally, the coupling, direct coupling, or communication connection shown or discussed between them may be through some interfaces, indirect coupling or communication connection of devices or units, such as electrical, mechanical, or other forms.

[0667] Optionally, the units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, i.e., located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0668] 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, it can be implemented, in whole or in part, as a computer program product. This computer program product includes one or more computer instructions. When these computer program instructions are loaded and executed on a computer, all or part of the processes or functions according to the embodiments of this application are generated.

[0669] The above description is merely a specific implementation of the embodiments of this application, but the protection scope of the embodiments of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the embodiments of this application should be covered within the protection scope of the embodiments of this application. Therefore, the protection scope of the embodiments of this application should be determined by the protection scope of the claims.

Claims

1. A data retransmission method, characterized in that, The method includes: The User Plane Function (UPF) network element receives the transmission result and the sequence number of the downlink data packet transmitted between the RAN device and the User Equipment (UE) from the downlink data packet received from the Radio Access Network (RAN) device. The UPF network element determines whether the downlink data packet needs to be retransmitted based on the transmission result and the transmission sequence number.

2. The method according to claim 1, characterized in that, The UPF network element determines whether the downlink data packet needs to be retransmitted based on the transmission result and the transmission sequence number, including: If the transmission result of the downlink data packet indicates that the downlink data packet transmission failed, the UPF network element determines that the downlink data packet needs to be retransmitted based on the transmission sequence number of the downlink data packet.

3. The method according to claim 2, characterized in that, The UPF network element determines a sequence number to retransmit the downlink data packet based on the transmission sequence number of the downlink data packet, including: The UPF network element determines the retransmission identifier of the downlink data packet, which is used to characterize whether the downlink data packet needs to be retransmitted in the event of transmission failure. If the retransmission flag indicates that the downlink data packet needs to be retransmitted, then the UPF network element determines that the downlink data packet needs to be retransmitted.

4. The method according to claim 3, characterized in that, The method further includes: The UPF network element receives the estimated retransmission delay of the downlink data packet from the RAN device, and the estimated retransmission delay of the downlink data packet is the estimated time required to retransmit the downlink data packet to the user equipment (UE). The UPF network element obtains the retransmission delay threshold of the downlink data packet; If the retransmission flag indicates that the downlink data packet needs to be retransmitted, the UPF network element determines that the downlink data packet needs to be retransmitted, including: If the retransmission flag is used to indicate that the downlink data packet needs to be retransmitted, and the estimated retransmission delay is less than or equal to the retransmission delay threshold, then the UPF network element determines that the downlink data packet needs to be retransmitted.

5. The method according to claim 2, characterized in that, The method further includes: The UPF network element receives the estimated retransmission delay of the downlink data packet from the RAN device, where the estimated retransmission delay of the downlink data packet is the estimated time required to retransmit the downlink data packet to the UE. The UPF network element determines whether the downlink data packet needs to be retransmitted based on the transmission sequence number of the downlink data packet, including: The UPF network element determines the retransmission delay threshold of the downlink data packet; If the estimated retransmission delay is less than or equal to the retransmission delay threshold, the UPF network element determines that the downlink data packet needs to be retransmitted.

6. The method according to claim 4 or 5, characterized in that, The retransmission delay threshold is obtained by the UPF network element from its local configuration, or from the Session Management Function (SMF) network element or a third-party application.

7. The method according to claim 2, characterized in that, The method further includes: The UPF network element acquires the downlink data packet; The UPF network element determines whether the downlink data packet is a data packet that needs to be retransmitted after being lost; If the downlink data packet is a data packet that needs to be retransmitted after being lost, the UPF network element adds a transmission sequence number to the downlink data packet.

8. The method according to any one of claims 1-7, characterized in that, The transmission result is determined by the RAN device based on feedback information from the UE regarding the downlink data packets sent by the RAN device to the UE, or; The transmission result is determined by the RAN device based on the transmission status of the RAN device's Media Access MAC transport block when the RAN device sends the downlink data packet to the UE.

9. The method according to any one of claims 1-8, characterized in that, The method further includes: When it is determined that the downlink data packet needs to be retransmitted, the UPF network element retransmits the downlink data packet to the UE.

10. The method according to claim 9, characterized in that, The method further includes: The UPF network element receives first information from the UE; the first information is sent by the UE after the UPF network element or RAN device retransmits the downlink data packet to the UE, and the first information is used to indicate that the UE has not received the downlink data packet; The UPF network element discards or ignores the first information.

11. The method according to any one of claims 1-10, characterized in that, The UPF network element caches the downlink data packets, or an application server is deployed on the UPF network element.

12. A data retransmission method, characterized in that, The method includes: The Radio Access Network (RAN) device receives downlink data packets and the transmission sequence number of the downlink data packets from the User Plane Function (UPF) network element; The RAN device sends the downlink data packet to the user equipment (UE); the RAN device determines the transmission result of the downlink data packet; The RAN device sends the transmission result and sequence number of the downlink data packet to the UPF network element. The transmission result and sequence number of the downlink data packet are used to determine whether the downlink data packet needs to be retransmitted.

13. The method according to claim 12, characterized in that, The RAN device determines the transmission result of the downlink data packet, including: The RAN device determines the transmission delay for sending the downlink data packet to the UE; If the transmission delay exceeds a first transmission delay threshold, the RAN device determines that the downlink data packet transmission has failed, wherein the transmission result of the downlink data packet includes the downlink data packet transmission failure.

14. The method according to claim 12, characterized in that, The RAN device determines the transmission result of the downlink data packet, including: The RAN device determines the transmission result of the downlink data packet based on the transmission status of the MAC layer transport block of the radio access network RAN ​​device.

15. The method according to claim 12, characterized in that, The method further includes: After receiving the transmission sequence number of the downlink data packet, the RAN device records the correspondence between the transmission sequence number and the PDCP layer sequence number of the downlink data packet; The RAN device determines the transmission result of the downlink data packet, including: The RAN device receives a feedback message from the UE, the feedback message including a transmission identifier and a PDCP layer sequence number, the transmission identifier being used to indicate whether the UE has received the downlink data packet; The RAN device determines the transmission result of the downlink data packet based on the correspondence, the PDCP layer sequence number, and the transmission identifier.

16. The method according to any one of claims 12-15, characterized in that, The method further includes: The RAN device sends the estimated retransmission delay of the downlink data packet to the UPF network element. The estimated retransmission delay of the downlink data packet is used to determine whether the downlink data packet needs to be retransmitted. The estimated retransmission delay of the downlink data packet is the estimated time required for the RAN device to retransmit the downlink data packet to the UE.

17. The method according to claim 16, characterized in that, The transmission result of the downlink data packet, the transmission sequence number of the downlink data packet, and / or the estimated retransmission delay of the downlink data packet are carried in the User Layer General Packet Radio Service Tunneling Protocol (GTP-U) layer of the uplink data packet.

18. A data retransmission method, characterized in that, The method is applied to a communication system, which includes a user equipment (UE), a radio access network (RAN) device, and a user plane function (UPF) network element. The method further includes: The RAN device receives downlink data packets and the transmission sequence number of the downlink data packets from the UPF network element; The RAN device sends the downlink data packet to the UE and determines the transmission result of the downlink data packet between the RAN device and the UE; wherein, the transmission result is used to indicate whether the transmission of the downlink data packet to the UE was successful; The RAN device sends the transmission result and transmission sequence number to the UPF network element; The UPF network element determines whether the downlink data packet needs to be retransmitted based on the transmission result and the transmission sequence number.

19. A communication system, the communication system comprising a user equipment (UE), a radio access network (RAN) device, and a user plane function (UPF) network element, the method further comprising: The RAN device is used to receive downlink data packets and the transmission sequence number of the downlink data packets from the UPF network element; The RAN device is configured to send the downlink data packet to the UE and determine the transmission result of the downlink data packet between the RAN device and the UE; wherein the transmission result is used to indicate whether the transmission of the downlink data packet to the UE was successful. The RAN device is used to send the transmission result and sequence number of the downlink data packet to the UPF network element; The UPF network element is used to determine whether the downlink data packet needs to be retransmitted based on the transmission result and the transmission sequence number.

20. A user plane UPF network element, characterized in that, The UPF network element includes a unit or module that implements any one of claims 1-11.

21. A radio access network (RAN) device, characterized in that, The RAN device includes units or modules that implement any one of claims 12-17.

22. A user plane UPF network element, characterized in that, The method includes a processor and a memory, wherein the memory is used to store program code, and the processor is used to execute the program code to implement the method according to any one of claims 1 to 11.

23. A radio access network (RAN) device, characterized in that, The method includes a processor and a memory, wherein the memory is used to store program code, and the processor is used to execute the program code to implement the method of any one of claims 12 to 17.

24. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the method described in any one of claims 1-17.

25. A computer program product, characterized in that, When the computer program product is run on a computer, it causes the computer to perform the method as described in any one of claims 1-17.

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