Data retransmission method, related device, and communication system

Abstract

The present application relates to the field of XR, and in particular to a data retransmission method, a related device, and a communication system. The method comprises: a UPF network element receives a transmission result and a transmission sequence number of a downlink data packet from a RAN device, wherein the transmission result of the downlink data packet is used for indicating whether the downlink data packet has been successfully transmitted to a UE; and the UPF network element determines, on the basis of the transmission result and the transmission sequence number of the downlink data packet, whether the downlink data packet needs to be retransmitted. The embodiments of the present application facilitate improving the efficiency of data packet retransmission.

Description

Data retransmission method, related device and communication system

[0001] The present application claims priority to the Chinese patent application No. 202411093505.7, filed on August 8, 2024, and entitled “Data retransmission method, related device and communication system”, the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the field of XR, and in particular to a data retransmission method, related device and communication system. BACKGROUND

[0003] In order to solve the transmission reliability problem in the end-to-end transmission process, packet loss retransmission is a common solution, that is, when it is found that the packet is lost or damaged, the lost or damaged packet is retransmitted to ensure that the receiving end can correctly receive.

[0004] After the application server transmits the data packet to the user equipment (UE), the UE application layer perceives whether the data is successfully transmitted; if the data packet is not received within a preset time period, the UE application layer determines that the data packet transmission fails, that is, the UE does not receive the data packet, the UE application layer feeds back the transmission result of the data packet transmission failure to the application server, and thus the application server knows that the UE does not receive the data packet; the application server decides whether the data packet needs to be retransmitted.

[0005] The process of determining whether the data packet is successfully transmitted from the perception of the data packet to the determination that the data packet is not received by the UE application layer takes a long time, and if the application server decides to retransmit the data packet based on the feedback information of the UE, the efficiency of the data packet retransmission will be low. SUMMARY

[0006] The embodiments of the present application provide a data retransmission method, related device and communication system, which is beneficial to improve the efficiency of data packet retransmission.

[0007] In a first aspect, the embodiments of the present application provide a data retransmission method. The method can be applied to a user plane function (UPF) network element.

[0008] The UPF network element receives a transmission result of a downlink data packet transmitted between a radio access network (RAN) device and a UE and a 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 is successful, and the transmission sequence number of the downlink data packet is used to identify the downlink data packet; and the UPF network element determines whether the downlink data packet needs to be retransmitted based on 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.

[0009] It can be seen that, compared with the prior art, the UPF network element and the RAN device are introduced between the UE and the application server, and the UPF network element makes a decision on whether the downlink data packet needs to be retransmitted based on the transmission result of the downlink data packet determined by the RAN device. Since the UPF network element and the RAN device are closer to the UE than the application server, the UPF network element can make a decision on whether the downlink data packet needs to be retransmitted more quickly based on the transmission result of the downlink data packet transmitted between the RAN device and the UE, thereby facilitating improvement of the efficiency of data packet retransmission.

[0010] In combination with the first aspect, in a feasible implementation manner, the UPF network element determines whether the downlink data packet needs to be retransmitted based on 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, including:

[0011] If the transmission result of the downlink data packet transmitted between the RAN device and the UE indicates that the downlink data packet transmission fails, 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 the transmission sequence number of the downlink data packet.

[0012] In combination with the first aspect, in a feasible implementation manner, the method of the present example further includes:

[0013] The UPF network element obtains the downlink data packet, determines whether the downlink data packet is a data packet that needs to be retransmitted after being lost, and 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.

[0014] It can be seen that the UPF network element only adds a transmission sequence number to the downlink data packet that needs to be retransmitted after being lost. When the UPF network element receives the transmission result indicating that the downlink data packet transmission fails, the UPF network element also receives the transmission sequence number of the downlink data packet. The UPF network element can directly make a decision on whether the downlink data packet needs to be retransmitted based on the transmission sequence number, without the aid of other information, thereby improving the decision efficiency and facilitating improvement of the retransmission efficiency.

[0015] In combination with the first aspect, in a feasible implementation manner, the UPF network element determines the retransmission of the downlink data packet based on the transmission sequence number of the downlink data packet, including:

[0016] The UPF network element determines the retransmission identifier of the downlink data packet based on the transmission sequence number, and the retransmission identifier of the downlink data packet is used to indicate whether the downlink data packet needs to be retransmitted in the case of transmission failure; if the retransmission identifier 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.

[0017] It can be seen that the UPF network element directly decides whether the downlink data packet needs to be retransmitted through the retransmission identifier of the downlink data packet, without the need for other information to make the decision, thereby improving the decision efficiency and further improving the efficiency of retransmission.

[0018] In combination with the first aspect, in a feasible implementation manner, the method of the embodiment further includes:

[0019] The retransmission identifier of the downlink data packet can be from the application server side, that is, the application server adds the retransmission identifier of the downlink data packet when sending the downlink data packet to the UPF side; or, the retransmission identifier of the downlink data packet is determined by the UPF network element, that is, the UPF determines whether the downlink data packet needs to be retransmitted after packet loss occurs, and exemplarily, the UPF network element can determine whether the downlink data packet needs to be retransmitted after packet loss occurs according to the importance of the downlink data packet.

[0020] In combination with the first aspect, in a feasible implementation manner, the method of the embodiment further includes:

[0021] 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 being the estimated required time for retransmitting the downlink data packet to the UE; and acquires the retransmission delay threshold of the downlink data packet; wherein the estimated required time for retransmitting the downlink data packet to the UE can be the estimated required time for the RAN device to retransmit the downlink data packet to the UE, or the estimated required time 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 required time for the UPF network element to retransmit the downlink data packet to the UE through the RAN device. Correspondingly, the retransmission delay threshold of the downlink data packet can be the retransmission delay threshold of the RAN device for retransmitting the downlink data packet to the UE, or the retransmission delay threshold of the UPF network element for retransmitting the downlink data packet to the UE through the RAN device after the RAN device notifies the UPF network element, or the retransmission delay threshold of the UPF network element for retransmitting the downlink data packet to the UE through the RAN device.

[0022] If the retransmission identifier 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:

[0023] If the retransmission identifier of the downlink data packet indicates 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, the UPF network element determines that the downlink data packet needs to be retransmitted.

[0024] It can be seen that, when deciding whether to retransmit the downlink data packet based on the retransmission identifier of the downlink data packet, the UPF network element introduces the retransmission delay threshold of the downlink data packet, and only when the retransmission identifier indicates 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 of the downlink data packet, it is determined that the downlink data packet needs to be retransmitted, avoiding the situation that the retransmission delay does not meet the requirements after retransmitting the downlink data packet.

[0025] In combination with the first aspect, in a feasible implementation manner, the UPF network element receives the estimated retransmission delay of the downlink data packet from the RAN device, which is the time estimated by the RAN device to retransmit the downlink data packet to the UE, or is the time estimated by 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 is the time estimated by the UPF network element to retransmit the downlink data packet to the UE side;

[0026] 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, including:

[0027] 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, and 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.

[0028] It can be seen that, when deciding whether to retransmit the downlink data packet, the UPF network element introduces the retransmission delay threshold of the downlink data packet, and only when the estimated retransmission delay of the downlink data packet is less than or equal to the retransmission delay of the downlink data packet, it is determined that the downlink data packet needs to be retransmitted, avoiding the situation that the retransmission delay does not meet the requirements after retransmitting the downlink data packet.

[0029] In combination with the first aspect, in a feasible implementation manner, the retransmission delay threshold of the downlink data packet is obtained by the UPF network element from the local configuration of the UPF network element, or from a session management function (SMF) network element or a third-party application.

[0030] With reference to the first aspect, in a possible implementation manner, the transmission result of the downlink data packet between the RAN device and the UE is determined by the RAN device based on feedback information of the UE for the downlink data packet transmitted by the RAN device to the UE. Therefore, in this manner, the determination of the transmission result is more accurate; or

[0031] With reference to the first aspect, in a possible implementation manner, the transmission result of the downlink data packet between the RAN device and the UE is determined by the RAN device based on a sending condition of a media access (MAC) layer transport block of the RAN device when the RAN device sends the downlink data packet to the UE. That is, the transmission result is not determined according to the receiving condition of the UE. Therefore, in this manner, the transmission result can be determined more quickly.

[0032] With reference to the first aspect, in a possible implementation manner, the method of the embodiment further includes:

[0033] The UPF network element retransmits the downlink data packet to the UE when it is determined that the downlink data packet needs to be retransmitted.

[0034] With reference to the first aspect, in a possible implementation manner, the method of the embodiment further includes:

[0035] The UPF network element receives first information from the UE, the first information being sent by the UE to the application server after the UPF network element or the RAN device retransmits the downlink data packet to the UE, and the first information being used to indicate that the UE does not receive the downlink data packet; and the UPF network element discards or ignores the first information.

[0036] As can be seen, when the first information indicating that the UE does not receive the downlink data packet is received after the downlink data packet is retransmitted to the UE, the UPF network element can directly ignore or discard the first information, so as to reduce the workload of the UPF network element.

[0037] With reference to the first aspect, in a possible implementation manner, the UPF network element buffers the downlink data packet, or the UPF network element is deployed with the application server.

[0038] The second aspect, the embodiment of the application provides a data retransmission method. The method can be applied to the RAN device.

[0039] The RAN device receives a downlink data packet and a transmission sequence number of the downlink data packet from the UPF network element; the RAN device sends the downlink data packet to the UE and determines a transmission result of the downlink data packet between the RAN device and the UE; and the RAN device sends the transmission result of the downlink data packet and the transmission sequence number to the UPF network element, the transmission result of the downlink data packet and the transmission sequence number being used to determine whether the downlink data packet needs to be retransmitted.

[0040] It can be seen that, compared with the prior art, the UPF network element and the RAN device are introduced between the UE and the application server, the UPF network element determines the transmission result of the downlink data packet based on the determination of the RAN device, and decides whether the downlink data packet needs to be retransmitted. Since the UPF network element and the RAN device are closer to the UE than the application server, the UPF network element can make a decision on whether the downlink data packet needs to be retransmitted more quickly based on the transmission result of the downlink data packet transmitted between the RAN device and the UE, thereby facilitating improvement of the efficiency of data packet retransmission.

[0041] In combination with the second aspect, in a feasible implementation manner, the RAN device determines the transmission result of the downlink data packet, including:

[0042] The RAN device determines the transmission delay of the downlink data packet sent to the UE; if the transmission delay of the downlink data packet exceeds a first transmission delay threshold, the RAN device determines that the downlink data packet transmission fails; wherein the transmission result of the downlink data packet includes the downlink data packet transmission failure.

[0043] In combination with the second aspect, in a feasible implementation manner, the RAN device determines the transmission result of the downlink data packet, including:

[0044] The RAN device determines the transmission result of the downlink data packet based on the sending condition of the MAC layer transport block of the RAN device.

[0045] 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 condition of the MAC layer transport block, or based on the feedback message of the UE side bottom layer, but not based on the upper layer feedback information between the UE and the application server, so that the RAN device can quickly know the transmission result of the downlink data packet, and the UPF network element determines whether the downlink data packet needs to be retransmitted based on the transmission result of the downlink data packet determined by the RAN device, so that the UPF network element can quickly make a decision, thereby facilitating improvement of the efficiency of data packet retransmission.

[0046] In combination with the second aspect, in a feasible implementation manner, the method of the embodiment further includes:

[0047] The RAN device records the correspondence between the transmission sequence number of the downlink data packet and the packet data convergence protocol (PDCP) layer sequence number of the downlink data packet after receiving the transmission sequence number of the downlink data packet;

[0048] The RAN device determines the transmission result of the downlink data packet, including:

[0049] 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 receives the downlink data packet; and 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.

[0050] It can be seen that, according to the PDCP layer sequence number, the data interaction between the RAN device and the UE is implemented through the PDCP layer, and therefore the feedback information received by the RAN device is generated based on the bottom layer of the UE perceiving whether the downlink data packet is received, rather than the application layer of the UE perceiving whether the downlink data packet is received. Since the bottom layer of the UE can directly perceive whether the downlink data packet is received, the RAN device can quickly obtain the feedback information from the bottom layer of the RAN for the downlink data packet, and then determine the transmission result of the downlink data packet, so that the UPF network element can quickly make a decision on whether the downlink data packet needs to be retransmitted based on the transmission result of the downlink data packet determined by the RAN device, which is beneficial to improving the efficiency of data packet retransmission. The application layer of the UE can be a protocol layer above IP or IP, such as a transport layer or an application layer of the UE, and the bottom layer of the UE refers to the protocol layer between the UE and the RAN device, including but not limited to a physical layer, a MAC layer, a radio link control (RLC) layer, a PDCP layer, etc.

[0051] In combination with the second aspect, in a possible implementation manner, the method of the embodiment further includes:

[0052] The RAN device sends an estimated retransmission delay of the downlink data packet to the UPF network element, the estimated retransmission delay of the downlink data packet being used to determine whether the downlink data packet needs to be retransmitted, the estimated retransmission delay of the downlink data packet being an estimated time required for the RAN device to retransmit the downlink data packet to the UE, or an estimated time required for the UPF network element to retransmit the downlink data packet to the UE side through the RAN device after being notified by the RAN device, or an estimated time required for the UPF network element to retransmit the downlink data packet to the UE side through the RAN device.

[0053] It can be seen that, by sending the estimated retransmission delay of the downlink data packet to the UPF network element, the UPF network element considers the estimated retransmission delay of the downlink data packet when making a decision on whether the downlink data packet needs to be retransmitted, and only when the estimated retransmission delay of the downlink data packet is less than or equal to the retransmission delay of the downlink data packet, it is determined that the downlink data packet needs to be retransmitted, thereby avoiding the situation that the retransmission delay of the downlink data packet does not meet the requirements after the downlink data packet is retransmitted.

[0054] With reference to the second aspect, in a possible 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 a general packet radio service tunnelling protocol for user plane (GTP-U) layer of a user plane of the uplink data packet. The uplink data packet can be a data packet sent by the UE to the server or a null packet generated at the RAN side.

[0055] With reference to the third aspect, an embodiment of the present application provides a data retransmission method. The method can be applied to a RAN device.

[0056] The RAN device receives third information and a downlink data packet from an application server, where the third information is used to determine whether retransmission is needed after the downlink data packet fails to be transmitted; the RAN device sends the downlink data packet to a UE; and when the RAN device determines that the downlink data packet fails to be transmitted, the RAN device determines, based on the third information, whether to retransmit the downlink data packet to the UE.

[0057] It can be seen that, compared with the prior art, the RAN device is introduced between the UE and the application server, and the RAN device determines whether retransmission is needed based on the transmission result of the downlink data packet determined by the RAN device and the third information. Since the RAN device is closer to the UE than the application server, the RAN device can make a decision on whether retransmission is needed based on the transmission result of the downlink data packet between the RAN device and the UE more quickly, thereby facilitating improvement of the efficiency of data packet retransmission.

[0058] With reference to the third aspect, in a possible implementation, the third information includes retransmission indication information of the downlink data packet, where the retransmission indication information is used to indicate that the downlink data packet needs to be retransmitted in the case of transmission failure.

[0059] With reference to the third aspect, in a possible implementation, the retransmission indication information includes a transmission sequence number of the downlink data packet or a retransmission identifier of the downlink data packet.

[0060] With reference to the third aspect, in a possible implementation, the third information includes a retransmission delay threshold of the downlink data packet, and the RAN device determines, based on the third information, whether to retransmit the downlink data packet to the UE, including:

[0061] The RAN device obtains an estimated retransmission delay of the downlink data packet, where the estimated retransmission delay of the downlink data packet is an estimated time required by the RAN device to retransmit the downlink data packet to the UE; and 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.

[0062] It can be seen that the RAN device considers the estimated retransmission delay of the downlink data packet when deciding whether to retransmit the downlink data packet. When the estimated retransmission delay of the downlink data packet is less than or equal to the retransmission delay of the downlink data packet, it is determined that the downlink data packet needs to be retransmitted, thereby avoiding the situation that the retransmission delay does not meet the requirement after retransmitting the downlink data packet.

[0063] With reference to the third aspect, in a possible implementation, the method further includes:

[0064] The RAN device determines a transmission delay of the downlink data packet transmitted to the UE. If the transmission delay of the downlink data packet exceeds a first transmission delay threshold, the RAN device determines that the downlink data packet transmission fails, wherein the transmission result of the downlink data packet includes the downlink data packet transmission failure.

[0065] With reference to the third aspect, in a possible implementation, the method further includes:

[0066] The RAN device determines the transmission result of the downlink data packet based on the sending of the MAC layer transport block of the RAN device, and determines whether the downlink data packet transmission fails based on the transmission result of the downlink data packet. Alternatively, the RAN device determines the transmission result of the downlink data packet based on the feedback message of the UE-side PDCP layer, and determines whether the downlink data packet transmission fails based on the transmission result of the downlink data packet.

[0067] 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 of the MAC layer transport block, or based on the feedback message of the UE-side bottom layer, rather than based on the upper-layer feedback information between the UE and the application server. This enables the RAN device to quickly know the transmission result of the downlink data packet, and helps to improve the efficiency of data packet retransmission when the RAN device decides whether to retransmit the downlink data packet based on the transmission result of the downlink data packet.

[0068] With reference to the third aspect, in a possible implementation, the method further includes:

[0069] 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 after receiving the transmission sequence number of the downlink data packet.

[0070] The RAN device determines the transmission result of the downlink data packet, including:

[0071] The RAN device receives 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 receives the downlink data packet; and the RAN device determines whether the transmission of the downlink data packet fails based on a correspondence between the PDCP layer sequence number and the transmission sequence number, the PDCP layer sequence number and the transmission identifier.

[0072] It can be seen that, according to the PDCP layer sequence number, the data interaction between the RAN device and the UE is implemented through the PDCP layer, and therefore the feedback information received by the RAN device is generated based on the perception of the lower layer of the UE on whether the downlink data packet is received, rather than the perception of the application layer of the UE on whether the downlink data packet is received. Since the lower layer of the UE can directly perceive whether the downlink data packet is received, the RAN device can quickly obtain the feedback information from the RAN on the downlink data packet at the physical layer, and then quickly determine the transmission result of the downlink data packet, so that the RAN device can make a decision on whether the downlink data packet needs to be retransmitted based on the transmission result of the downlink data packet determined by the RAN device, which is beneficial to improving the efficiency of data packet retransmission. The application layer of the UE can be a transport layer or a protocol layer above IP of the UE, and the lower layer of the UE refers to the protocol layer between the UE and the RAN, including but not limited to the physical layer, the MAC layer, the radio link layer RLC layer, the PDCP layer, etc.

[0073] In combination with the third aspect, in a possible implementation manner, the method of the embodiment further includes:

[0074] After retransmitting the downlink data packet to the UE, the RAN device sends second information to the UPF network element, the second information being used to indicate that the downlink data packet has been retransmitted to the UE.

[0075] 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 is not received, the UPF network element can directly ignore or discard the first information, so as to reduce the workload of the UPF network element.

[0076] In combination with the third aspect, in a possible implementation manner, the method of the embodiment further includes:

[0077] After determining the transmission result of the downlink data packet, if the RAN device receives the first information from the UE to the application server, and the first information indicates that the UE does not receive the downlink data packet, the RAN device discards or ignores the first information.

[0078] Since the downlink data packet has been retransmitted to the UE, but the first information fed back by the UE to the application server is received, the RAN device can directly ignore or discard the first information to reduce the workload of the application server.

[0079] In a fourth aspect, the embodiments of the present application provide a data retransmission method. The method can be applied to a UPF network element.

[0080] The UPF network element obtains a downlink data packet and third information of the downlink data packet, the third information being used to determine whether the downlink data packet needs to be retransmitted after a transmission failure; and the UPF network element sends the downlink data packet and the third information to a RAN device.

[0081] Compared with the prior art, the UPF network element and the RAN device are introduced 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 for 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, the RAN device can make a decision on whether the downlink data packet needs to be retransmitted based on the transmission result between the RAN device and the UE, which is conducive to improving the efficiency of data packet retransmission.

[0082] In a feasible implementation manner in combination with the fourth aspect, the UPF network element obtains the third information of the downlink data packet, including:

[0083] The UPF network element adds a transmission serial number to the downlink data packet, and the third information includes the transmission serial number.

[0084] Further, after obtaining 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 serial number to the downlink data packet.

[0085] By adding the transmission serial number to the downlink data packet, one function is to identify the downlink data packet, and another function is to identify that the downlink data packet needs to be retransmitted after being lost when the transmission serial number is added to only the downlink data packet that needs to be retransmitted after being lost.

[0086] In a feasible implementation manner in combination with the fourth aspect, the third information includes retransmission indication information of the downlink data packet, and the retransmission indication information is used to indicate that the downlink data packet needs to be retransmitted to the UE in the case of a transmission failure.

[0087] In a feasible implementation manner in combination with the fourth aspect, the retransmission indication information includes a transmission serial number of the downlink data packet or a retransmission identifier of the downlink data packet.

[0088] In a possible implementation of the fourth aspect, the third information includes a retransmission delay threshold of the downlink data packet, and the retransmission delay threshold of the downlink data packet is used to determine whether the downlink data packet needs to be retransmitted to the UE.

[0089] By sending the retransmission delay threshold of the downlink data packet to the RAN device, the RAN device considers the retransmission delay threshold of the downlink data packet when deciding whether to retransmit the downlink data packet, and determines that the downlink data packet needs to be retransmitted only 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, thereby avoiding the situation that the retransmission delay does not meet the requirement after the downlink data packet is retransmitted.

[0090] In a possible implementation of the fourth aspect, the third information can be carried in a GTP-U layer of the downlink data packet.

[0091] In a possible implementation of the fourth aspect, the retransmission delay threshold of the downlink data packet in the third information can come from a session management network element.

[0092] In a possible implementation of the fourth aspect, the method further includes:

[0093] The UPF network element receives second information from the RAN device, and the second information is used to indicate that the downlink data packet has been retransmitted to the UE.

[0094] In a possible implementation of the fourth aspect, the method further includes:

[0095] After receiving the second information, the UPF network element receives first information from the UE, and the first information is used to indicate that the downlink data packet has not been received; and the first information is discarded or ignored.

[0096] It can be seen that, after receiving the second information from the RAN device, the UPF network element receives first information from the UE, and the first information is indication information sent by the UE to the application server and used 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, so as to reduce the workload of the UPF network element, and also avoid unnecessary retransmission of the application server.

[0097] In the fifth aspect, an embodiment of the present application provides a data retransmission method. The method can be applied to an application layer of a UE.

[0098] The application layer of the UE receives a transmission result of an uplink data packet transmitted between a lower layer of the UE and a RAN device and a transmission sequence number of the uplink data packet, and determines whether the uplink data packet needs to be retransmitted based on the transmission result and the transmission sequence number.

[0099] It can be seen that, between the application layer of the UE and the application server, by introducing the bottom layer of the UE, the application layer of the UE determines the transmission result of the uplink data packet based on the bottom layer of the UE, to decide whether the uplink data packet needs to be retransmitted. Since the bottom layer of the UE can quickly know the transmission result of the uplink data packet transmitted between the bottom layer of the UE and the RAN device, the application layer of the UE can make a decision on whether the uplink data packet needs to be retransmitted more quickly based on the transmission result, thereby facilitating improvement of the efficiency of data packet retransmission. The application layer of the UE can be a transport layer or an application layer or a protocol layer above IP or IP, and the bottom layer of the UE refers to a protocol layer between the UE and the RAN, including but not limited to a physical layer, a MAC layer, an RLC layer, a PDCP layer, and the like.

[0100] In combination with the fifth aspect, in a feasible implementation manner, the method of the embodiment further includes:

[0101] The application layer of the UE acquires the uplink data packet, determines whether the uplink data packet is a data packet that needs to be retransmitted after being lost, and adds a transmission sequence number to the uplink data packet if the uplink data packet is a data packet that needs to be retransmitted after being lost.

[0102] In combination with the fifth aspect, in a feasible implementation manner, the application layer of the UE determines whether the uplink data packet needs to be retransmitted based on the transmission result of the uplink data packet transmitted between the bottom layer of the UE and the RAN device and the transmission sequence number of the uplink data packet, including:

[0103] If the transmission result of the uplink data packet transmitted between the bottom layer of the UE and the RAN device indicates that the uplink data packet fails to be transmitted, the application layer of the UE determines that the uplink data packet needs to be retransmitted.

[0104] It can be seen that the application layer of the UE adds a transmission sequence number to only the uplink data packet that needs to be retransmitted after being lost. When the application layer of the UE receives the transmission result for indicating that the uplink data packet fails to be transmitted, the application layer of the UE also receives the transmission sequence number of the uplink data packet. The application layer of the UE can directly determine that the uplink data packet needs to be retransmitted based on the transmission sequence number, without the aid of other information, thereby improving the decision efficiency and facilitating improvement of the retransmission efficiency.

[0105] In combination with the fifth aspect, in a feasible implementation manner, the application layer of the UE determines that the uplink data packet needs to be retransmitted, including:

[0106] The application layer of the UE determines a retransmission identifier of the uplink data packet based on a transmission sequence number, the retransmission identifier of the uplink data packet being used to indicate whether the uplink data packet needs to be retransmitted in the case of a transmission failure; if the retransmission identifier of the uplink data packet indicates that the uplink data packet needs to be retransmitted, the application layer of the UE determines that the uplink data packet needs to be retransmitted; or, the application layer of the UE determines whether the uplink data packet needs to be retransmitted according to the importance of the uplink data packet.

[0107] It can be seen that the application layer of the UE directly decides whether the uplink data packet needs to be retransmitted through the retransmission identifier of the uplink data packet, which improves the decision efficiency and is conducive to improving the retransmission efficiency.

[0108] In combination with the fifth aspect, in a feasible implementation manner, the method of the embodiment further includes:

[0109] The application layer of the UE receives an estimated retransmission delay of the uplink data packet from a bottom layer of the UE, the estimated retransmission delay of the uplink data packet being an estimated required time for retransmitting the uplink data packet to the RAN device; the application layer of the UE acquires a retransmission delay threshold of the uplink data packet; wherein the application layer of the UE can be a transmission layer or an application layer or a protocol layer above IP of the UE, and the bottom layer of the UE refers to a protocol layer between the UE and the RAN, including but not limited to a physical layer, a MAC layer, an RLC layer, a PDCP layer, and the like.

[0110] If the retransmission identifier of the uplink data packet indicates that the uplink data packet needs to be retransmitted, the application layer of the UE determines that the uplink data packet needs to be retransmitted, including:

[0111] If the retransmission identifier 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, the application layer of the UE determines that the uplink data packet needs to be retransmitted.

[0112] It can be seen that the application layer of the UE introduces the retransmission delay threshold of the uplink data packet when deciding whether the uplink data packet needs to be retransmitted based on the retransmission identifier of the uplink data packet, and only determines that the uplink data packet needs to be retransmitted when the retransmission identifier of the uplink data packet 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, thereby avoiding the situation that the retransmission delay does not meet the requirements after the uplink data packet is retransmitted.

[0113] In combination with the fifth aspect, in a feasible implementation manner, the method of the embodiment further includes:

[0114] The application layer of the UE receives an estimated retransmission delay of the uplink data packet from a bottom layer of the UE, the estimated retransmission delay of the uplink data packet being an estimated required time for retransmitting the uplink data packet to the RAN device;

[0115] The application layer of the UE determines that the uplink data packet needs to be retransmitted, including:

[0116] 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 application layer of the UE determines that the uplink data packet needs to be retransmitted.

[0117] It can be seen that when the application layer of the UE decides whether to retransmit the uplink data packet, the retransmission delay threshold of the uplink data packet is introduced, and when the estimated retransmission delay of the uplink data packet is less than or equal to the retransmission delay of the uplink data packet, it is determined that the uplink data packet needs to be retransmitted, thereby avoiding the case that the retransmission delay does not meet the requirements after retransmitting the uplink data packet.

[0118] In combination with the fifth aspect, in a feasible implementation manner, the retransmission delay threshold of the uplink data packet is obtained by the application layer of the UE from the local configuration of the application layer of the UE, or from the SMF network element or a third-party application.

[0119] In combination with the fifth aspect, in a feasible implementation manner, the method of the embodiment further includes:

[0120] The application layer of the UE receives fourth information from the application server; the fourth information is sent by the RAN after the lower layer of the UE retransmits the uplink data packet to the RAN device, and the fourth information is used to indicate that the application server does not receive the uplink data packet; and the application layer of the UE discards or ignores the fourth information.

[0121] It can be seen that since the uplink data packet has been retransmitted to the UE, when the fourth information used to indicate that the UE does not receive the uplink data packet is received, the application layer of the UE can directly ignore or discard the fourth information, so as to reduce the workload of the application layer of the UE.

[0122] In the sixth aspect, the embodiment of the present application provides a data retransmission method. The method can be applied to the lower layer of the UE.

[0123] The lower layer of the UE receives the uplink data packet and the transmission sequence number of the uplink data packet from the application layer of the UE; the lower layer of the UE sends the uplink data packet to the RAN device; the lower layer of the UE determines the transmission result of the uplink data packet; and the lower layer of the UE sends 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, and the transmission result of the uplink data packet and the transmission sequence number of the uplink data packet are used to determine whether the uplink data packet needs to be retransmitted. The application layer of the UE can be a protocol layer above IP or IP, such as a transmission layer or an application layer, and the lower layer of the UE refers to the protocol layer between the UE and the RAN, including but not limited to a physical layer, a MAC layer, an RLC layer, a PDCP layer, and the like.

[0124] It can be seen that, between the application layer of the UE and the application server, by introducing the bottom layer of the UE, the application layer of the UE determines the transmission result of the uplink data packet based on the transmission result of the uplink data packet determined by the bottom layer of the UE, so as to quickly decide whether the uplink data packet needs to be retransmitted. Since the bottom layer of the UE can quickly know the transmission result of the uplink data packet transmitted between the bottom layer of the UE and the RAN device relative to the application layer of the UE, the application layer of the UE can make a decision on whether the uplink data packet needs to be retransmitted based on the transmission result more quickly, thereby facilitating to improve the efficiency of data packet retransmission.

[0125] In combination with the sixth aspect, in a feasible implementation manner, the bottom layer of the UE determines the transmission result of the uplink data packet, including:

[0126] The bottom layer of the UE determines the transmission delay of the uplink data packet transmitted to the RAN device; if the transmission delay of the uplink data packet exceeds a second transmission delay threshold, the bottom layer of the UE determines that the uplink data packet transmission fails, wherein the transmission result of the uplink data packet includes the uplink data packet transmission failure.

[0127] In combination with the sixth aspect, in a feasible implementation manner, the bottom layer of the UE determines the transmission result of the uplink data packet, including:

[0128] The bottom layer of the UE determines the transmission result of the uplink data packet based on the sending situation of the bottom layer transmission block.

[0129] It can be seen that, the transmission result of the uplink data packet is determined by the bottom layer of the UE based on the transmission delay of the uplink data packet or the sending situation of the bottom layer transmission block, instead of the feedback information from the application server, so that the bottom layer of the UE can quickly know the transmission result of the uplink data packet, thereby further deciding whether the uplink data packet needs to be retransmitted according to the transmission result of the uplink data packet determined by the bottom layer of the UE, and facilitating to improve the efficiency of data packet retransmission.

[0130] In combination with the sixth aspect, in a feasible implementation manner, the method of the embodiment further includes:

[0131] After receiving the transmission serial number of the uplink data packet, the bottom layer of the UE records the correspondence between the transmission serial number of the uplink data packet and the PDCP layer serial number of the uplink data packet;

[0132] The bottom layer of the UE determines the transmission result of the uplink data packet, including:

[0133] The bottom layer of the UE receives the feedback message from the RAN device, the feedback message including a transmission identifier and a PDCP layer serial number, the transmission identifier being used to indicate whether the RAN device receives the uplink data packet; the bottom layer of the UE determines the transmission result of the uplink data packet based on the correspondence, the PDCP layer serial number and the transmission identifier.

[0134] In conjunction with the sixth aspect, in a possible implementation manner, the method of the embodiment further includes:

[0135] The bottom layer of the UE sends the estimated retransmission time delay of the uplink data packet to the application layer of the UE, the estimated retransmission time delay of the uplink data packet is used to determine whether the uplink data packet needs to be retransmitted, and the estimated retransmission time delay of the uplink data packet is the estimated required time of the bottom layer of the UE for retransmitting the uplink data packet to the RAN device.

[0136] It can be seen that, by sending the estimated retransmission time delay of the uplink data packet to the application layer of the UE, the application layer of the UE considers the estimated retransmission time delay of the uplink data packet when deciding whether the uplink data packet needs to be retransmitted, and it is determined that the uplink data packet needs to be retransmitted only when the estimated retransmission time delay of the uplink data packet is less than or equal to the retransmission time delay of the uplink data packet, thereby avoiding the situation that the retransmission time delay does not meet the requirement after the uplink data packet is retransmitted.

[0137] In conjunction with the sixth aspect, in a possible implementation manner, the method of the embodiment further includes:

[0138] The bottom layer of the UE receives the fifth information sent by the application layer of the UE, the fifth information is used to indicate whether the transmission result of the uplink data packet needs to be determined, and sends the transmission result of the uplink data packet and the transmission serial number of the uplink data packet to the application layer of the UE.

[0139] In the seventh aspect, an embodiment of the present application provides a UPF network element, including units or modules for implementing the method provided by the first aspect or any possible implementation manner of the first aspect, or including units or modules for implementing the method provided by the fourth aspect or any possible implementation manner of the fourth aspect.

[0140] In the eighth aspect, an embodiment of the present application provides a RAN device, including units or modules for implementing the method provided by the second aspect or any possible implementation manner of the second aspect, or including units or modules for implementing the method provided by the third aspect or any possible implementation manner of the third aspect.

[0141] In the ninth aspect, an embodiment of the present application provides a UE, including units or modules for implementing the method provided by the fifth aspect or any possible implementation manner of the fifth aspect, or including units or modules for implementing the method provided by the sixth aspect or any possible implementation manner of the sixth aspect.

[0142] In a tenth aspect, an embodiment of the present application provides a UPF network element, comprising a processor and a memory. The memory is configured to store program codes. The processor is configured to invoke the program codes stored in the memory to execute the method provided in the first aspect or any possible implementation of the first aspect, or comprises units or modules for implementing the method provided in the fourth aspect or any possible implementation of the fourth aspect.

[0143] In an eleventh aspect, an embodiment of the present application provides a RAN device, comprising a processor and a memory. The memory is configured to store program codes. The processor is configured to invoke the program codes stored in the memory to execute the method provided in the second aspect or any possible implementation of the second aspect, or comprises units or modules for implementing the method provided in the third aspect or any possible implementation of the third aspect.

[0144] In a twelfth aspect, an embodiment of the present application provides a UE, comprising a processor and a memory. The memory is configured to store program codes. The processor is configured to invoke the program codes stored in the memory to execute the method provided in the fifth aspect or any possible implementation of the fifth aspect, or comprises units or modules for implementing the method provided in the sixth aspect or any possible implementation of the sixth aspect.

[0145] In a thirteenth aspect, an embodiment of the present application provides a computer storage medium, comprising computer instructions, when the computer instructions run on an electronic device, make the electronic device execute the method provided in any possible implementation of the first aspect, or the method provided in any possible implementation of the second aspect, or the method provided in any possible implementation of the third aspect, or the method provided in any possible implementation of the fourth aspect, or the method provided in any possible implementation of the fifth aspect, or the method provided in any possible implementation of the sixth aspect.

[0146] In a fourteenth aspect, an embodiment of the present application provides a computer program product, when the computer program product runs on a computer, makes the computer execute the method provided in any possible implementation of the first aspect, or the method provided in any possible implementation of the second aspect, or the method provided in any possible implementation of the third aspect, or the method provided in any possible implementation of the fourth aspect, or the method provided in any possible implementation of the fifth aspect, or the method provided in any possible implementation of the sixth aspect.

[0147] In a fifteenth aspect, an embodiment of the present application further provides a data retransmission method, the method is applied to a communication system, the communication system comprises a UE, a RAN device and a UPF network element, and the method comprises the following steps.

[0148] The RAN device receives a downlink data packet and a transmission sequence number of the downlink data packet from the UPF network element;

[0149] The RAN device transmits the downlink data packet to the UE and determines a transmission result of the downlink data packet transmitted between the RAN device and the UE;

[0150] The RAN device transmits 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 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 is successful;

[0151] The UPF network element determines whether the downlink data packet needs to be retransmitted based on 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.

[0152] In a sixteenth aspect, the embodiments of the present application further provide a communication system, which comprises a UE, a RAN device and a UPF network element;

[0153] The RAN device is configured to receive a downlink data packet and a transmission sequence number of the downlink data packet from the UPF network element;

[0154] The RAN device is configured to transmit the downlink data packet to the UE;

[0155] The RAN device is configured to determine a transmission result of the downlink data packet;

[0156] The RAN device is configured to transmit 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 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 is successful;

[0157] The UPF network element is configured to determine whether the downlink data packet needs to be retransmitted based on 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.

[0158] In a seventeenth aspect, the embodiments of the present application further provide a data retransmission method, which is applied to a communication system comprising a UE, a RAN device and a UPF network element, and the method comprises the following steps:

[0159] The UPF network element acquires a downlink data packet and third information of the downlink data packet, wherein the third information is used to determine whether the downlink data packet needs to be retransmitted after a transmission failure;

[0160] The UPF network element transmits the downlink data packet and the third information to the RAN device, wherein the third information is used to determine whether the downlink data packet needs to be retransmitted after a transmission failure;

[0161] The RAN device sends the downlink data packet to the UE.

[0162] When the RAN device determines that the downlink data packet transmission fails, the RAN device determines, based on the third information, whether to retransmit the downlink data packet to the UE.

[0163] In an eighteenth aspect, the embodiments of the present application further provide a communication system, which comprises a UE, a RAN device and a UPF network element.

[0164] The UPF network element is configured to acquire a downlink data packet and third information of the downlink data packet, wherein the third information is used to determine whether the downlink data packet needs to be retransmitted after transmission fails.

[0165] The UPF network element is configured to send the downlink data packet and the third information to the RAN device.

[0166] The RAN device is configured to send the downlink data packet to the UE.

[0167] The RAN device is configured to, when the RAN device determines that the downlink data packet transmission fails, determine, based on the third information, whether to retransmit the downlink data packet to the UE.

[0168] In a nineteenth aspect, the embodiments of the present application further provide a data retransmission method, which is applied to a communication system comprising a UE and a RAN device; the method comprises the following steps.

[0169] The bottom layer of the UE receives an uplink data packet and a transmission serial number of the uplink data packet from an application layer of the UE.

[0170] The bottom layer of the UE sends the uplink data packet to the RAN device.

[0171] The bottom layer of the UE determines a transmission result of the uplink data packet transmitted between the bottom layer of the UE and the RAN device.

[0172] The bottom layer of the UE sends, to the application layer of the UE, the transmission result of the uplink data packet transmitted between the bottom layer of the UE and the RAN device and the transmission serial number of the uplink data packet.

[0173] The application layer of the UE determines, based on the transmission result of the uplink data packet transmitted between the bottom layer of the UE and the RAN device and the transmission serial number of the uplink data packet, whether to retransmit the uplink data packet.

[0174] In a twentieth aspect, the embodiments of the present application further provide a communication system, which comprises a UE and a RAN device.

[0175] The bottom layer of the UE is configured to receive an uplink data packet and a transmission serial number of the uplink data packet from an application layer of the UE.

[0176] a bottom layer of the UE, configured to send the uplink data packet to the RAN device;

[0177] a bottom layer of the UE, configured to determine a transmission result of the uplink data packet transmitted between the bottom layer of the UE and the RAN device;

[0178] a bottom layer of the UE, configured to send the transmission result of the uplink data packet transmitted between the bottom layer of the UE and the RAN device and a transmission sequence number of the uplink data packet to an application layer of the UE;

[0179] an application layer of the UE, configured to determine whether to retransmit the uplink data packet based on the transmission result of the uplink data packet transmitted between the bottom layer of the UE and the RAN device and the transmission sequence number of the uplink data packet.

[0180] It can be understood that the beneficial effects of the embodiments of the seventh aspect to the twentieth aspect can refer to the beneficial effects of the methods of the first aspect to the sixth aspect, which will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0181] FIG. 1 is a schematic diagram of a communication system architecture provided by an embodiment of the present application;

[0182] FIG. 2 is a schematic diagram of a data retransmission method provided by an embodiment of the present application;

[0183] FIG. 3 is a schematic diagram of another data retransmission method provided by an embodiment of the present application;

[0184] FIG. 4 is a schematic diagram of another data retransmission method provided by an embodiment of the present application;

[0185] FIG. 5 is a schematic diagram of another data retransmission method provided by an embodiment of the present application;

[0186] FIG. 6 is a schematic diagram of another data retransmission method provided by an embodiment of the present application;

[0187] FIG. 7 is a schematic diagram of another data retransmission method provided by an embodiment of the present application;

[0188] FIG. 8 is an interactive schematic diagram of a data retransmission method provided by an embodiment of the present application;

[0189] FIG. 9 is an interactive schematic diagram of another data retransmission method provided by an embodiment of the present application;

[0190] FIG. 10 is an interactive schematic diagram of another data retransmission method provided by an embodiment of the present application;

[0191] FIG. 11 is a structural schematic diagram of a UPF network element provided by an embodiment of the present application;

[0192] FIG. 12 is a structural diagram of a RAN device according to an embodiment of the present application;

[0193] FIG. 13 is a structural diagram of a UE according to an embodiment of the present application;

[0194] FIG. 14 is a structural diagram of a communication device according to an embodiment of the present application. DETAILED DESCRIPTION

[0195] The terms "first", "second", "third", and "fourth" and the like in the description and claims of the present application and the accompanying drawings are used to distinguish between similar objects, and are not necessarily used to describe a particular sequential order.

[0196] "Multiple" means two or more. "And / or" describes the association relationship of the associated objects, which means that there are three relationships, for example, A and / or B means that there are three cases: A exists alone, A and B exist together, and B exists alone. The character " / " generally represents that the associated objects before and after it are in an "or" relationship.

[0197] Embodiments of the present application will be described below with reference to the accompanying drawings.

[0198] Referring to FIG. 1, FIG. 1 is a schematic diagram of a communication system architecture according to an embodiment of the present application. The communication system is a schematic diagram of a network architecture of the fifth generation mobile communication technology (5th Generation Mobile Networks, 5G). It includes a (radio) access network ((radio) access network, (R)AN, expressed as a RAN device and a core network (core network, CN) two parts. The RAN device is used to provide network access functions for authorized user equipment (User Equipment, UE) in a specific area, and can use different quality transmission tunnels according to the level of the UE, the demand of the service, etc. For example, the RAN device can manage radio resources to provide access services for the UE, and then complete the forwarding of control information and / or data information between the UE and the CN.

[0199] In order to facilitate understanding of the embodiments of the present application, first, an application scenario of the embodiments of the present application will be described in detail in combination with FIG. 1.

[0200] 1、User Equipment (UE): can be referred to as terminal device, terminal, access terminal, subscriber unit, subscriber station, mobile station, mobile, remote station, remote terminal, mobile device, user terminal, wireless communication device, user agent or user equipment. The terminal device can also be a cellular phone, a cordless phone, a session initiation protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a handheld device with wireless communication function, a computing device or other processing device connected to a wireless modem, an in-vehicle device, a drone, a wearable device, a terminal device in a 5G network, or a terminal device in an evolved public land mobile network (PLMN), etc., and the embodiments of the present application are not limited thereto.

[0201] 2、Access Network (AN): provides network access functions for authorized users in a specific area, and can use transmission tunnels of different qualities according to the level of users, the needs of services, etc. The access network can be an access network using different access technologies. Current access network technologies include: wireless access network technologies used in the 3rd generation (3G) system, wireless access network technologies used in the 4th generation (4G) system, or next generation radio access network (NG-RAN) technologies (such as wireless access technologies used in the 5G system, etc.).

[0202] The access network that realizes the access network function based on wireless communication technology can be referred to as a radio access network (RAN). The radio access network can manage wireless resources and provide access services for terminals, and then complete the forwarding of control signals and user data between terminals and core networks.

[0203] The radio access network device 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 wireless hotspot system, and can also be a radio controller in a cloud radio access network (CRAN) scenario, or can be a relay station, an access point, a vehicle-mounted device, a drone, a wearable device, a network device in a 5G network or an evolved PLMN, and the like. The embodiments of the present application do not limit the specific technology and specific device form adopted by the radio access network device.

[0204] 3. Access management network element: mainly used for mobility management and access management, responsible for transferring user policies between user equipment and PCF network elements, and can be used to implement other functions in addition to session management in the mobile management entity (MME) function. For example, the function of access authorization (authentication).

[0205] In the 5G communication system, the access management network element can be an access and mobility management function (AMF) network element. In the future communication system, the access management network element can still be an AMF network element, or can have other names, which are not limited in the present application.

[0206] 4. Session management network element: mainly used for session management, allocation and management of Internet protocol (IP) addresses of user equipment, selection of manageable user plane functions, termination of policy control and charging function interfaces, and downlink data communication.

[0207] In the 5G communication system, the session management network element can be an SMF network element. In the future communication system, the session management network element can still be an SMF network element, or can have other names, which are not limited in the present application.

[0208] 5. User plane network element: used for packet routing and forwarding, QoS processing of user plane data, completion of user plane data forwarding, session / stream level-based charging statistics, bandwidth limiting function, and the like.

[0209] In the 5G communication system, the user plane network element can be a UPF network element. In the future communication system, the user plane network element can still be a UPF network element, or can also have other names, which are not limited in the present application.

[0210] 6. Data network network element: a network for providing transmission of data.

[0211] In the 5G communication system, the data network network element can be a data network (DN) network element. In the future communication system, the data network network element can still be a DN network element, or can also have other names, which are not limited in the present application.

[0212] 7. Policy control network element: a unified policy framework for guiding network behavior, providing policy rule information, etc. for control plane function network elements (such as AMF, SMF network elements, etc.).

[0213] In the 4G communication system, the policy control network element can be a policy and charging rules function (PCRF) network element. In the 5G communication system, the policy control network element can be a PCF network element. In the future communication system, the policy control network element can still be a PCF network element, or can also have other names, which are not limited in the present application.

[0214] 8. Data management network element: for processing user equipment identification, access authentication, registration, and mobility management, etc.

[0215] In the 5G communication system, the data management network element can be a unified data management (UDM) network element; in the 4G communication system, the data management network element can be a home subscriber server (HSS) network element. In the future communication system, the data management network element can still be a UDM network element, or can also have other names, which are not limited in the present application.

[0216] 9. Network exposure function (NEF) network element: for securely exposing services and capabilities provided by 3rd generation partnership project (3GPP) network functions to the outside, etc.

[0217] 10、application function (AF) network element: provides certain application layer services to the UE, and the AF has requirements for QoS policy and charging policy when providing services to the UE, and needs to inform the network. At the same time, the AF also needs to obtain the information related to the application feedback by the core network. The AF can have all the functions of the AF defined in the technological specification (TS) 23.501 R-15 version, and have related functions for application services. That is, in the user plane architecture, the application server (AS) and the UE are in user plane communication through the path of UE-RAN-UPF-AF. The AF can also communicate with other network function (NF) network elements in the 5G core network (5GC) in the control plane architecture through the NEF. For example, communicate with the PCF through the NEF network element. If the AF is arranged by the operator of the 5GC, the AF network element can also directly communicate 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.

[0218] 11、network data analysis function (NWDAF) network element: can be used to collect data from network elements, AFs, and operation administration and maintenance (OAM) sides, and analyze the data through machine learning, artificial intelligence, etc. Scheme, and feedback to network elements, AFs, etc. Network or service configuration optimization, so as to provide better network quality and service experience.

[0219] 12、network repository function (NRF) network element: can be used to provide network element discovery function, and provide network element information corresponding to network element type based on the request of other network elements. The NRF network element also provides network element management services, such as network element registration, update, deregistration, and network element state subscription and push, etc.

[0220] 13、authentication server function (AUSF) network element: mainly responsible for authenticating users to determine whether to allow users or devices to access the network.

[0221] 14. Service communication proxy (SCP) network element: can be used for direct or indirect communication of NFs, service requests of NFs can be proxied by SCP.

[0222] N1, N2, N3, N4, N6, N9, Nnwdaf, Nnef, Nnrf, Npcf, Nudm, Naf, Nausf, Namf, and Nsmf in FIG. 1 are interface serial numbers. The meanings of these interface serial numbers can be referred to the meanings defined in 3GPP TS 23.501.

[0223] It should be understood that the network architecture applied to the embodiments of the present application is only illustrative, and the network architecture applicable to the embodiments of the present application is not limited thereto, and any network architecture capable of realizing the functions of the above-mentioned network elements is applicable to the embodiments of the present application.

[0224] It should also be understood that the AMF network element, SMF network element, UPF network element, NEF network element, PCF network element, UDM network element, NWDAF network element, NRF network element, AUSF network element, SCP network element, etc. shown in FIG. 1 can be understood as network elements in the core network for realizing different functions, for example, can be combined into a network slice as needed. These core network network elements can be independent devices or can be integrated into the same device to realize different functions, and the present application does not limit the specific form of the above-mentioned network elements.

[0225] It should also be understood that the above-mentioned naming is only defined for the purpose of distinguishing different functions, and should not constitute any limitation on the present application. The present application does not exclude the possibility of using other names in 5G networks and future other networks. For example, in a 6G network, part or all of the above-mentioned networks can use the terms in 5G, or other names, etc. The interface names between the network elements in FIG. 1 are only an example, and the names of the interfaces in the specific implementation can be other names, and the present application does not specifically limit this. In addition, the names of the messages (or signaling) transmitted between the above-mentioned network elements are also only an example, and do not constitute any limitation on the functions of the messages themselves.

[0226] Referring to FIG. 2, FIG. 2 is a flow diagram of a data retransmission method provided by the embodiments of the present application. The method is applied to the UPF network element in FIG. 1. As shown in FIG. 2, the method comprises:

[0227] S201, the UPF network element receives the transmission result of the downlink data packet of the RAN device transmitted between the RAN device and the UE and the transmission serial 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 RAN device successfully transmits the downlink data packet to the UE.

[0228] In one possible embodiment, the UPF network element acquires the downlink data packet, which can be acquired from the application server; when the application server is deployed on the UPF network element, the UPF network element itself generates the downlink data packet.

[0229] After the UPF network element acquires the downlink data packet, the UPF network element has two processing methods for the downlink data packet:

[0230] Method one: the UPF network element adds a first transmission serial number to all acquired downlink data packets, and the first transmission serial number is used to identify the downlink data packet. Optionally, the UPF network element sets a retransmission delay threshold and / or a retransmission identifier for the downlink data packet. The retransmission identifier of the downlink data packet is used to indicate whether the downlink data packet needs to be retransmitted in the case of transmission failure, and the retransmission delay threshold is used to determine whether the downlink data packet needs to be retransmitted in the case of packet loss.

[0231] Specifically, when setting the retransmission identifier for the downlink data packet, the UPF network element determines whether the downlink data packet is a data packet that 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 is a data packet that needs to be retransmitted after packet loss, the retransmission identifier of the downlink data packet indicates that the downlink data packet needs to be retransmitted in the case of transmission failure; if the downlink data packet is a data packet that does not need to be retransmitted after packet loss, the retransmission identifier of the downlink data packet indicates that the downlink data packet does not need to be retransmitted in the case of transmission failure. The retransmission identifier 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 according to the information carried in the downlink data packet sent by the application server, which represents the importance of the downlink data packet; 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 according to the importance of the downlink data packet.

[0232] It should be noted that the data packet that needs to be retransmitted after packet loss is a data packet that will affect the processing (such as encoding and decoding processing) of subsequent data packets after packet loss, or a data packet corresponding to a key frame.

[0233] In the case that the retransmission delay threshold is added to the obtained downlink data packet, the UPF network element can add the retransmission delay threshold to each obtained downlink data packet. In the case that the retransmission delay thresholds of multiple downlink data packets are the same, the UPF network element can add the retransmission delay threshold to only one of the downlink data packets. In the case that multiple downlink data packets with the same retransmission delay threshold are transmitted to the RAN device, the multiple downlink data packets can be transmitted simultaneously or consecutively. In the case that the downlink data packet with the added retransmission delay threshold is the first downlink data packet in the multiple downlink data packets transmitted to the RAN device. Alternatively, in the case that 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 the fixed retransmission delay threshold through the SMF network element.

[0234] In the case that the retransmission delay threshold is added to the obtained downlink data packet, the UPF network element can add the retransmission delay threshold to each obtained downlink data packet. In the case that the retransmission delay thresholds of multiple downlink data packets are the same, the UPF network element can add the retransmission delay threshold to only one of the downlink data packets. In the case that multiple downlink data packets with the same retransmission delay threshold are transmitted to the RAN device, the multiple downlink data packets can be transmitted simultaneously or consecutively. In the case that the downlink data packet with the added retransmission delay threshold is the first downlink data packet in the multiple downlink data packets transmitted to the RAN device. Alternatively, in the case that 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 the fixed retransmission delay threshold through the SMF network element.

[0235] It is to be noted that the second transmission sequence number of the downlink data packet can be the original identification of the downlink data packet, such as a TCP identification, an RTP identification, or the like, or can be newly generated.

[0236] Alternatively, the UPF network element can transmit the retransmission delay threshold of the downlink data packet to the RAN device at the same time as the downlink data packet.

[0237] In the case that the retransmission delay threshold is added to the obtained downlink data packet, the UPF network element can add the retransmission delay threshold to each obtained downlink data packet. In the case that the retransmission delay thresholds of multiple downlink data packets are the same, the UPF network element can add the retransmission delay threshold to only one of the downlink data packets. In the case that multiple downlink data packets with the same retransmission delay threshold are transmitted to the RAN device, the multiple downlink data packets can be transmitted simultaneously or consecutively. In the case that the downlink data packet with the added retransmission delay threshold is the first downlink data packet in the multiple downlink data packets transmitted to the RAN device. Alternatively, in the case that 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 the fixed retransmission delay threshold through the SMF network element.

[0238] It should be noted that the retransmission delay threshold of the downlink data packet can be directly sent by the SMF network element to the RAN device, at this time, the retransmission delay threshold of the downlink data packet on the SMF network element can be from the UPF network element or a third-party application.

[0239] In one example, the SMF network element sends the retransmission delay threshold to the RAN device. The SMF network element can carry the retransmission delay threshold in the QoS parameter sent to the RAN device, that is, the retransmission delay threshold of the downlink data packet corresponding to the QoS flow is the same, and is the retransmission delay threshold.

[0240] In another example, the third-party application generates the downlink data packet and carries the retransmission delay threshold in the downlink data packet sent to the UPF network element.

[0241] After the UPF network element performs the above processing on the downlink data packet, the UPF network element sends the downlink data packet to the RAN device to send the downlink data packet to the UE through the RAN device. 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 UPF network element also transmits the downlink data packet with the added transmission sequence number to the RAN device.

[0242] After the RAN device sends the 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.

[0243] S202, the UPF network element determines whether the downlink data packet needs to be retransmitted 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.

[0244] The above transmission sequence number includes a first transmission sequence number or a second transmission sequence number.

[0245] In one possible implementation, for the case where the UPF network element only adds a second transmission sequence number to the downlink data packet that needs to be retransmitted after packet loss, the UPF network element determines whether the downlink data packet is successfully transmitted based on the transmission result of the downlink data packet, and if it is determined that the downlink data packet is not successfully transmitted based on the transmission result of the downlink data packet, 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.

[0246] Optionally, if it is determined that the downlink data packet transmission fails based on the transmission result of the downlink data packet, the UPF network element determines whether the downlink data packet needs to be retransmitted according to the retransmission time delay threshold of the downlink data packet and the estimated retransmission time delay of the downlink data packet obtained from the RAN device. The estimated retransmission time delay of the downlink data packet is the estimated time required for retransmitting the downlink data packet to the UE. The time can be the time required for transmitting the downlink data packet from the RAN device to the UE (i.e., RAN device->UE), that is, the air interface transmission time delay of RAN device-UE, or the sum of the time required for the RAN device to obtain the downlink data packet that needs to be retransmitted from the UPF network element and the time required for transmitting the data packet from the RAN device to the UE, that is, the time of RAN device->UPF network element->RAN device->UE. If the estimated retransmission time delay of the downlink data packet is less than or equal to the retransmission time delay threshold of the downlink data packet, the UPF network element determines that the downlink data packet needs to be retransmitted. If the estimated retransmission time delay of the downlink data packet is greater than the retransmission time delay threshold of the downlink data packet, the UPF network element determines that the downlink data packet does not need to be retransmitted.

[0247] It should be noted that the retransmission time delay threshold of the downlink data packet is obtained from the local configuration of the UPF network element or from the SMF network element or a third-party application.

[0248] In one example, the SMF network element sends the retransmission time delay threshold to the UPF network element. The SMF network element can carry the retransmission time delay threshold in the N4 rule sent to the UPF network element, that is, the retransmission time delay threshold of the downlink data packet corresponding to the service flow is the same, and is the retransmission time delay threshold.

[0249] In another example, the third-party application generates the downlink data packet and carries the retransmission time delay threshold in the downlink data packet sent to the UPF.

[0250] The RAN device->UPF network element->RAN device process refers to the RAN device obtaining the downlink data packet that needs to be retransmitted from the UPF network element. The transmission time of the RAN device-UPF network element can also be referred to as CN PDB, which can be determined based on the operator configuration information.

[0251] In one feasible implementation, in the case that the UPF network element adds the first transmission sequence number to each obtained 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, the first transmission sequence number of the downlink data packet has a corresponding relationship with 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 case of transmission failure, 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 case of transmission failure, 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 whether to retransmit the downlink data packet based on the retransmission delay threshold of the downlink data packet 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 required time for retransmitting 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, 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, the UPF network element determines that the downlink data packet does not need to be retransmitted.

[0253] In another example, the UPF network element determines the retransmission delay threshold and the retransmission identifier of the downlink data packet based on the first transmission sequence number of the downlink data packet, the first transmission sequence number of the downlink data packet has a corresponding relationship with the retransmission delay threshold and the retransmission identifier of the downlink data packet. The UPF network element obtains the estimated retransmission delay of the downlink data packet from the RAN device, which is the estimated required time for retransmitting 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 case of transmission failure, 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 case of transmission failure, the UPF network element determines that the downlink data packet does not need to be retransmitted.

[0254] It is pointed out here that if the transmission result of the downlink data packet is sent in the case that the RAN device judges 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, the UPF 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 when deciding whether to retransmit the downlink data packet, and no longer considers the retransmission delay threshold of the downlink data packet.

[0255] The UPF network element is deployed with an application server, and after determining whether the downlink data packet needs to be retransmitted, the UPF network element retransmits the downlink data packet to the UE; when 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.

[0256] It should be pointed out here that when the UPF network element determines to retransmit the downlink data packet to the UE, the priority of the flow corresponding to the downlink data packet can be optionally adjusted in advance to ensure that the downlink data packet can be quickly sent to the UE side.

[0257] In a possible implementation, the UPF network element receives first information from the UE, the first information being sent by the UE to the application server after the UPF network element or the RAN device retransmits the downlink data packet to the UE, and the first information being used to indicate that the UE has not received the downlink data packet before retransmission; and the UPF network element discards or ignores the first information.

[0258] If the UPF network element determines that the downlink data packet has been retransmitted to the UE but has not arrived at the UE, if the first information of the UE is received at this time, the UPF network element ignores or discards the first information.

[0259] It can be seen that, compared with the prior art, the scheme of the embodiment introduces the UPF network element and the RAN device between the UE and the application server, and the UPF network element determines whether the downlink data packet needs to be retransmitted based on the transmission result of the downlink data packet determined by the RAN device. Since the UPF network element and the RAN device are closer to the UE than the application server, the UPF network element can make a decision on whether the downlink data packet needs to be retransmitted more quickly based on the transmission result of the downlink data packet between the RAN device and the UE, thereby facilitating improvement of the efficiency of data packet retransmission. The UPF network element adds the second transmission serial number to the downlink data packet that needs to be retransmitted after packet loss. When the UPF network element receives the transmission result for indicating the transmission failure of the downlink data packet, the UPF network element receives the second transmission serial number of the downlink data packet. The UPF network element can directly make a decision on whether the downlink data packet needs to be retransmitted based on the second transmission serial number without the aid of other information, thereby improving the decision efficiency and facilitating improvement of the retransmission efficiency. In the case where the UPF network element adds the first transmission serial number to each obtained downlink data packet, the UPF network element determines the retransmission identifier of the downlink data packet based on the first transmission serial number of the downlink data packet. The UPF network element directly makes a decision on whether the downlink data packet needs to be retransmitted based on the retransmission identifier of the downlink data packet without the aid of other information, thereby improving the decision efficiency and facilitating improvement of the retransmission efficiency. When the UPF network element makes a decision on whether the downlink data packet needs to be retransmitted, the UPF network element introduces the retransmission delay threshold of the downlink data packet. When the estimated retransmission delay of the downlink data packet is less than or equal to the retransmission delay of the downlink data packet, it is determined that the downlink data packet needs to be retransmitted, thereby avoiding the case where the retransmission delay does not meet the requirement after the downlink data packet is retransmitted.

[0260] Referring to FIG. 3, FIG. 3 is a flowchart of another data retransmission method provided by the embodiment of the application. The method is applied to the RAN device in FIG. 1. As shown in FIG. 3, the method comprises the following steps.

[0261] S301, the RAN device receives a downlink data packet and a transmission serial number of the downlink data packet from the UPF network element.

[0262] It should be noted that, when the UPF network element adds the transmission serial number to the obtained downlink data packet, there are two processing modes:

[0263] 1. The UPF network element adds the first transmission serial number to all obtained downlink data packets, and the first transmission serial number is used to identify the downlink data packet.

[0264] 2. After the UPF network element obtains each downlink data packet, it 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 second transmission sequence number to the downlink data packet. That is, the 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 data packet that needs to be retransmitted after being lost. That is, for a downlink data packet that does not need to be retransmitted, the UPF network element only needs to send the downlink data packet to the RAN device, does not need to send the second transmission sequence number of the downlink data packet to the RAN device, and does not need to instruct the RAN device to feed back the transmission result of the downlink data packet to the UPF network element.

[0265] S302. The RAN device sends the downlink data packet to the UE and determines the transmission result of the downlink data packet transmitted between the RAN device and the UE.

[0266] In a feasible embodiment, when the RAN device receives the downlink data packet from the UPF network element, the RAN device allocates a PDCP layer sequence number to the downlink data packet, and if the transmission sequence number of the downlink data packet is also received, the RAN device records the correspondence between the PDCP layer sequence number allocated 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, and the downlink data packet carries the allocated PDCP layer sequence number, that is, the RAN device can determine the transmission result of the downlink data packet according to the sending result of the PDCP layer data packet.

[0267] In a feasible implementation, the RAN device determines the transmission result of the downlink data packet in two ways:

[0268] Method one: the RAN device determines whether the downlink data packet is successfully transmitted based on the feedback information of the UE; for example, the feedback information of the UE includes the PDCP layer sequence number and the 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 of the downlink data packet, and the transmission identifier of the downlink data packet is used to indicate whether the UE receives the downlink data packet or whether the downlink data packet is lost, and the RAN device determines whether the downlink data packet is successfully transmitted based on the transmission identifier of the downlink data packet.

[0269] It is pointed out here that if the RAN device fails to find the transmission sequence number corresponding to the PDCP layer sequence number of the downlink data packet based on the correspondence between the PDCP layer sequence number of the downlink data packet and the transmission sequence number, it means that the downlink data packet does not have a corresponding transmission sequence number, in other words, the UPF network element adds a transmission sequence number only to the data packet that needs to be retransmitted after being lost when adding a transmission sequence number to the downlink data packet, that is, the downlink data packet without a transmission sequence number is a data packet that does not need to be retransmitted after being lost, therefore, the RAN device can ignore or discard the feedback information of the downlink data packet without a corresponding transmission sequence number.

[0270] In one example, the transmission identification of the downlink data packet is NACK or ACK; when the transmission identification of the downlink data packet is NACK, it means that the UE does not receive the downlink data packet, that is, the downlink data packet transmission fails; when the transmission identification of the downlink data packet is ACK, it means that the UE receives the downlink data packet, that is, the downlink data packet transmission succeeds.

[0271] Method two: the RAN device determines whether the downlink data packet is successfully transmitted based on its own information. For example, in the RLC UM mode, the RAN device determines whether the downlink data packet is successfully transmitted according to the actual sending situation of the MAC layer transport block; or the RAN device obtains the transmission duration of the downlink data packet transmitted to the UE, that is, the used duration of the downlink data packet transmitted to the UE, if the transmission duration exceeds the first transmission duration threshold, the RAN device determines that the downlink data packet transmission fails.

[0272] It is pointed out here that the downlink data packet transmission failure includes the case that the MAC layer retransmission between the RAN device and the UE still fails; optionally, the downlink data packet transmission failure also includes the case that the MAC layer and RLC layer retransmission between the RAN device and the UE still fails.

[0273] S303, the RAN device sends 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 to the UPF network element, and 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 are used to determine whether the downlink data packet needs to be retransmitted.

[0274] Optionally, the RAN device further sends the estimated retransmission delay of the downlink data packet to the UPF network element, the estimated retransmission delay of the downlink data packet being the time estimated to be needed by the RAN device to retransmit the downlink data packet to the UE, or the time estimated to be needed by the UPF network element to retransmit the downlink data packet to the UE through the RAN device, or the time estimated to be needed by the UPF network element to retransmit the downlink data packet to the UE through the RAN device. The transmission result, the transmission sequence number and / or the estimated retransmission delay of the downlink data packet are carried in the GTP-U layer of the uplink data packet. The uplink data packet here is a data packet from the UE or a null packet generated by the RAN device and sent to the UPF network element.

[0275] Optionally, if the RAN device acquires the retransmission delay threshold of the downlink data packet, the RAN device determines the estimated retransmission delay of the downlink data packet and sends the transmission result and the transmission sequence number of the downlink data packet to the UPF network element 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 retransmission delay threshold of the downlink data packet can be from the UPF network element or the SMF network element or a third-party application.

[0276] In the process of acquiring the retransmission delay threshold of the downlink data packet by the RAN device, the retransmission delay thresholds of multiple downlink data packets are the same, the UPF network element sends multiple downlink data packets to the RAN device at the same time or successively, and in the case that the first downlink data packet in the multiple downlink data packets carries the retransmission delay threshold, the RAN device determines whether the retransmission delay threshold is obtained from the downlink data packet, and if the retransmission delay threshold is obtained from the downlink data packet, determines that the retransmission delay threshold is the retransmission delay threshold of the downlink data packet; if the retransmission delay threshold is not obtained from the downlink data packet, determines that the retransmission delay threshold of the downlink data packet is the same as the retransmission delay threshold of the previous downlink data packet.

[0277] It is pointed out here that when the UPF network element determines to retransmit the downlink data packet to the UE, the UPF network element can optionally first adjust the priority of the flow corresponding to the downlink data packet to ensure that the downlink data packet can be quickly sent to the UE side.

[0278] The transmission sequence number of the downlink data packet in S302 and S303 includes the first transmission sequence number or the second transmission sequence number.

[0279] It can be seen that, compared with the prior art, the scheme of the embodiment introduces the UPF network element and the RAN device between the UE and the application server, and the UPF network element determines the transmission result of the downlink data packet based on the RAN device to decide whether the downlink data packet needs to be retransmitted. Since the UPF network element and the RAN device are closer to the UE than the application server, the UPF network element can make a decision on whether the downlink data packet needs to be retransmitted more quickly based on the transmission result of the downlink data packet between the RAN and the UE, thereby facilitating to improve 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 situation of the MAC layer transport block, rather than based on the feedback information of the UE, so that the RAN device can quickly know the transmission result of the downlink data packet, and the UPF network element makes a decision on whether the downlink data packet needs to be retransmitted based on the transmission result of the downlink data packet determined by the RAN device, so that the UPF network element can make a decision quickly, which is conducive to improving the efficiency of data packet retransmission. By sending the estimated retransmission delay of the downlink data packet to the UPF network element, the UPF network element considers the estimated retransmission delay of the downlink data packet when making a decision on whether the downlink data packet needs to be retransmitted, and only determines that the downlink data packet needs to be retransmitted when the estimated retransmission delay of the downlink data packet is less than or equal to the retransmission delay of the downlink data packet, thereby avoiding the situation that the retransmission delay does not meet the requirement after the downlink data packet is retransmitted.

[0280] Referring to FIG. 4, FIG. 4 is a flowchart of another data retransmission method provided by the embodiment of the application. The method is applied to the RAN device in FIG. 1. As shown in FIG. 4, the method comprises the following steps.

[0281] S401, the RAN device receives third information and a downlink data packet from an application server, wherein the third information is used to determine whether the downlink data packet needs to be retransmitted after transmission failure.

[0282] In a feasible implementation, the third information comprises retransmission indication information of the downlink data packet, and the retransmission indication information is used to indicate that the downlink data packet needs to be retransmitted in the case of transmission failure.

[0283] Optionally, the retransmission indication information comprises a second transmission sequence number of the downlink data packet or a retransmission identifier of the downlink data packet.

[0284] It is pointed out here that the reason why the retransmission indication information can be the second transmission sequence number of the downlink data packet is that the UPF network element needs to determine whether the downlink data packet is a data packet that needs to be retransmitted after being lost after obtaining each downlink data packet. If the downlink data packet is a data packet that needs to be retransmitted after being lost, the UPF network element adds a second transmission sequence number to the downlink data packet. At this time, the second 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 data packet that needs to be retransmitted after being lost. That is, for a downlink data packet that does 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.

[0285] The reason why the retransmission indication information can be the retransmission identifier of the downlink data packet is that the UPF network element adds a retransmission identifier to each obtained downlink data packet. Among them, 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 retransmission identifier of the downlink data packet indicates that the downlink data packet needs to be retransmitted in the case of transmission failure. If the downlink data packet is a data packet that does not need to be retransmitted after being lost, the retransmission identifier of the downlink data packet indicates that the downlink data packet does not need to be retransmitted in the case of transmission failure.

[0286] S402, the RAN device sends the downlink data packet to the UE.

[0287] It is pointed out here that the specific implementation process of S402 can be referred to the related description of S302, which will not be described here.

[0288] S403, when the RAN device determines that the downlink data packet transmission fails, the RAN device determines to retransmit the downlink data packet to the UE based on the third information.

[0289] It is pointed out here that the specific implementation process of "the RAN device determines that the downlink data packet transmission fails" in S403 can be referred to the related description of S302, which will not be described here.

[0290] In a feasible implementation manner, when the UPF network element adds the transmission sequence number to the downlink data packet in a manner of adding a second transmission sequence number only to the downlink data packet that needs to be retransmitted after being lost, the RAN device can determine that the downlink data packet needs to be retransmitted based on the second transmission sequence number of the downlink data packet. At this time, the second transmission sequence number can be only a retransmission identifier, that is, the retransmission identifier is taken as the second transmission sequence number without generating an additional transmission sequence number.

[0291] In another possible implementation, the manner in which the UPF network element adds the first transmission sequence number to the downlink data packet is that the first transmission sequence number for identifying the downlink data packet is added to each obtained downlink data packet, and meanwhile, the retransmission identifier is added to the downlink data packet, the first transmission sequence number of the downlink data packet and the retransmission identifier have a corresponding relationship, the RAN device determines the retransmission identifier of the downlink data packet based on the third transmission sequence number of the downlink data packet, and if the retransmission identifier 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 identifier 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.

[0292] In another possible implementation, the third information includes a retransmission delay threshold of the downlink data packet, the RAN device obtains an estimated retransmission delay of the downlink data packet, the estimated retransmission delay being an estimated required time for retransmitting the downlink data packet, and the RAN device 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 is less than or equal to the retransmission delay threshold, the RAN determines that the downlink data packet needs to be retransmitted; if the estimated retransmission delay is greater than the retransmission delay threshold, the RAN determines that the downlink data packet does not need to be retransmitted. The retransmission delay threshold of the downlink data packet can be sent by the UPF network element to the RAN device through the GTP-U layer of the downlink data packet, or sent by 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 parameter sent to the RAN device, that is, the retransmission delay thresholds of the downlink data packets corresponding to the QoS flow are the same, and are all the retransmission delay threshold.

[0293] In another possible implementation, the RAN device obtains an estimated retransmission delay of the downlink data packet, determines a retransmission delay threshold of the downlink data packet and determines whether the downlink data packet needs to be retransmitted after packet loss, determines whether the downlink data packet needs to be retransmitted based on the second transmission sequence number of the downlink data packet, 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 needs to be retransmitted and the estimated retransmission delay is less than or equal to the retransmission delay threshold, 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 does not need to be retransmitted and the estimated retransmission delay is less than or equal to the retransmission delay threshold, and 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.

[0294] In another possible implementation, the RAN device acquires an estimated retransmission delay of the downlink data packet; the RAN device determines a 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 a first transmission sequence number and a 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 the retransmission identifier, and the estimated retransmission delay is less than or equal to the retransmission delay threshold, 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 the retransmission identifier, and the estimated retransmission delay is less than or equal to the retransmission delay threshold, 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 the retransmission identifier, and the estimated retransmission delay is greater than the retransmission delay threshold, the RAN device determines that the downlink data packet does not need to be retransmitted.

[0295] It is to be noted that, in the process of determining the retransmission delay threshold of the downlink data packet by the RAN device, the retransmission delay thresholds of multiple downlink data packets are the same, the UPF network element simultaneously or continuously sends multiple downlink data packets to the RAN device, and in the case that the first downlink data packet in the multiple downlink data packets carries the retransmission delay threshold, the RAN device determines whether the retransmission delay threshold is obtained from the downlink data packet, if the retransmission delay threshold is obtained from the downlink data packet, it is determined that the retransmission delay threshold is the retransmission delay threshold of the downlink data packet; if the retransmission delay threshold cannot be determined from the downlink data packet, it is determined that the retransmission delay threshold of the downlink data packet is the same as the retransmission delay threshold of the previous downlink data packet.

[0296] In the process of determining to retransmit the downlink data packet to the UE, the RAN device retransmits the downlink data packet to the UE; it is to be noted that, in the process of determining to retransmit the downlink data packet to the UE, the RAN device may optionally adjust the priority of the flow corresponding to the downlink data packet in advance to ensure that the downlink data packet can be quickly sent to the UE side.

[0297] In one possible implementation, after the RAN device retransmits the downlink data packet to the UE, the RAN device sends second information to the UPF network element, the second information being used to indicate that the downlink data packet has been retransmitted to the UE.

[0298] In one possible implementation, after the RAN device retransmits the downlink data packet to the UE, if the RAN device 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 retransmission, since the RAN device has retransmitted the downlink data packet to the UE, the RAN device discards or ignores the first information to avoid unnecessary retransmission of the application server.

[0299] It can be seen that, compared with the prior art, the embodiment introduces the RAN device between the UE and the application server, and the RAN device makes a decision on whether the downlink data packet needs to be retransmitted based on the transmission result of the downlink data packet determined by the RAN device and the third information. Since the RAN device is closer to the UE than the application server, the RAN device can make a decision on whether the downlink data packet needs to be retransmitted more quickly based on the transmission result of the downlink data packet between the RAN device and the UE, thereby facilitating to improve the efficiency of data packet retransmission. When making a decision on whether the downlink data packet needs to be retransmitted, the RAN device considers the estimated retransmission delay of the downlink data packet, and only determines that the downlink data packet needs to be retransmitted when the estimated retransmission delay of the downlink data packet is less than or equal to the retransmission delay of the downlink data packet, thereby avoiding the situation that the retransmission delay does not meet the requirement after the downlink data packet is retransmitted. The transmission result of the downlink data packet can be determined by the RAN device based on the transmission delay or based on the sending situation of the MAC layer transport block, rather than based on the feedback information of the UE, so that the RAN device can quickly know the transmission result of the downlink data packet, and it is beneficial to provide the efficiency of data packet retransmission when the RAN device makes a decision on whether the downlink data packet needs to be retransmitted based on the transmission result of the downlink data packet. 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 and sent to the application server for indicating that the downlink data packet is not received, since the downlink data packet has been retransmitted to the UE, the UPF network element can directly ignore or discard the first information, so as to reduce the workload of the UPF network element and the application server.

[0300] Referring to FIG. 5, FIG. 5 is a flowchart of another data retransmission method provided by the embodiment of the application. The method is applied to the UPF network element in FIG. 1. As shown in FIG. 5, the method comprises the following steps:

[0301] S501, the UPF network element acquires a downlink data packet, and acquires third information of the downlink data packet, the third information being used to determine whether the downlink data packet needs to be retransmitted after transmission failure.

[0302] In a feasible implementation, the UPF network element acquires the downlink data packet, which can be acquired in the application server. When the application server is deployed on the UPF network element, the UPF network element itself generates the downlink data packet.

[0303] In a feasible implementation, the UPF network element adds a second transmission serial number to the downlink data packet, wherein the third information of the downlink data packet comprises the second transmission serial number of the downlink data packet, and the second transmission serial number is used to indicate whether the downlink data packet needs to be retransmitted after packet loss or transmission failure.

[0304] In a feasible implementation, the third information of the downlink data packet includes retransmission indication information of the downlink data packet, the retransmission indication information being used to indicate that the downlink data packet needs to be retransmitted in the case of transmission failure.

[0305] Optionally, the retransmission indication information includes a second transmission sequence number of the downlink data packet or a retransmission identifier of the downlink data packet.

[0306] There are two ways for the UPF network element to add the transmission sequence number to the downlink data packet:

[0307] In the first way, the UPF network element adds a first transmission sequence number to all obtained downlink data packets, which is used to identify the downlink data packet. Meanwhile, the UPF network element adds a retransmission identifier to the downlink data packet. The retransmission identifier of the downlink data packet is used to indicate whether the downlink data packet needs to be retransmitted in the case of transmission failure. At this time, the retransmission indication information of the downlink data packet includes the retransmission identifier of the downlink data packet.

[0308] Specifically, when setting the retransmission identifier of the downlink data packet, the UPF network element judges whether the downlink data packet is a data packet that needs to be retransmitted after packet loss after obtaining each downlink data packet. If the downlink data packet is a data packet that needs to be retransmitted after packet loss, the retransmission identifier of the downlink data packet indicates that the downlink data packet needs to be retransmitted in the case of transmission failure. If the downlink data packet is a data packet that does not need to be retransmitted after packet loss, the retransmission identifier of the downlink data packet indicates that the downlink data packet does not need to be retransmitted in the case 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 according to the importance of the downlink data packet, such as the degree of influence on service experience after the downlink data packet is lost. If the application server is not deployed in the UPF network element, the UPF network element determines whether the downlink data packet needs to be retransmitted after packet loss or transmission failure according to information added by the application server in the downlink data packet to represent the importance of the downlink data packet.

[0309] It should be noted that the data packet that needs to be retransmitted after packet loss is a data packet that will affect the processing (such as coding and decoding processing) of subsequent data packets after loss, or a data packet corresponding to a key frame.

[0310] The second transmission sequence number is added to the downlink data packet by the UPF network element. The second 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 data packet that needs to be retransmitted after being lost.

[0311] Optionally, the UPF network element sends the retransmission delay threshold of the downlink data packet to the RAN device at the same time as sending the downlink data packet to the RAN device.

[0312] Optionally, the UPF network element sends the retransmission delay threshold of the downlink data packet to the RAN device at the same time as sending the downlink data packet to the RAN device.

[0313] It should be noted that the retransmission delay threshold of the downlink data packet can be sent directly by the SMF network element to the RAN device. In this case, the retransmission delay threshold of the downlink data packet on the SMF network element can come from the UPF network element or a third-party application.

[0314] In one example, the SMF network element sends the retransmission delay threshold to the RAN device. The SMF network element can carry the retransmission delay threshold in the QoS parameter sent to the RAN device, that is, the retransmission delay thresholds of the downlink data packets corresponding to the QoS flow are the same, and are all the retransmission delay threshold.

[0315] In another example, the third-party application generates the downlink data packet and carries the retransmission delay threshold in the downlink data packet sent to the UPF network element.

[0316] In one possible implementation, the UPF network element adds a retransmission delay threshold to each obtained downlink data packet, and the retransmission delay threshold of the downlink data packet 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 retransmission delay threshold of the downlink data packet.

[0317] S502, the UPF network element sends the downlink data packet and the third information to the RAN device.

[0318] The third information of the downlink data packet is carried in a GTP-U layer of the downlink data packet.

[0319] In a possible implementation, the third information includes a 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.

[0320] In a possible implementation, the retransmission delay threshold of the downlink data packet is from the SMF network element, that is, the retransmission delay threshold of the downlink data packet of the RAN device is sent by the SMF network element to the RAN device, or the retransmission delay threshold of the downlink data packet of the UPF network element is sent by the SMF network element to the UPF network element.

[0321] In a possible implementation, the UPF network element receives second information from the RAN device, and the second information is used to indicate that the downlink data packet has been retransmitted to the UE.

[0322] In a possible implementation, the method of the embodiment further includes:

[0323] After receiving the second information from the RAN device, the UPF network element receives first information from the UE, and the first information is indication information sent by the UE to the application server and used to indicate that the downlink data packet is not received; since the RAN device has retransmitted the downlink data packet to the UE, the UPF network element discards or ignores the first information, so as to reduce the workload of the UPF network element, and also avoid unnecessary retransmission of the application server.

[0324] As can be seen, compared with the prior art, the scheme of the embodiment introduces the UPF network element and the 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, and the RAN device determines 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, the RAN device can make a decision on whether the downlink data packet needs to be retransmitted based on the transmission result of the downlink data packet between the RAN device and the UE, thereby facilitating improvement of the efficiency of data packet retransmission. By sending the retransmission delay threshold of the downlink data packet to the RAN device, the RAN device considers the retransmission delay threshold of the downlink data packet when making a decision on whether the downlink data packet needs to be retransmitted, and determines that the downlink data packet needs to be retransmitted only 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, thereby avoiding a situation where the retransmission delay does not meet the requirement after the downlink data packet is retransmitted.

[0325] Referring to FIG. 6, FIG. 6 is a flow diagram of another data retransmission method provided by the embodiments of the present application. The method is applied to the application layer of the UE in FIG. 1. As shown in FIG. 6, the method comprises the following steps.

[0326] S601, the application layer of the UE receives the transmission result of the uplink data packet transmitted between the bottom layer of the UE and the RAN device and the transmission sequence number of the uplink data packet.

[0327] After obtaining the uplink data packet, the application layer of the UE has two processing methods for the uplink data packet.

[0328] Method one: the application layer of the UE adds a third transmission sequence number to all obtained uplink data packets, which is used to identify the uplink data packet. Meanwhile, the application layer of the UE optionally determines the retransmission delay threshold and / or retransmission identifier for the uplink data packet. The retransmission identifier of the uplink data packet is used to indicate whether the uplink data packet needs to be retransmitted in the case of transmission failure, and the retransmission delay threshold of the uplink data packet is used to determine whether the uplink data packet needs to be retransmitted in the case of transmission failure.

[0329] Specifically, when setting the retransmission identifier for the uplink data packet, the application layer of the UE determines whether the uplink data packet is a data packet that needs to be retransmitted after packet loss after obtaining each uplink data packet; if the uplink data packet is a data packet that needs to be retransmitted after packet loss, the retransmission identifier of the uplink data packet indicates that the uplink data packet needs to be retransmitted in the case of transmission failure; if the uplink data packet is a data packet that does not need to be retransmitted after packet loss, the retransmission identifier of the uplink data packet indicates that the uplink data packet does not need to be retransmitted in the case of transmission failure.

[0330] It should be understood that obtaining an uplink data packet by the application layer can be understood as generating an uplink data packet by the application layer.

[0331] It should be noted that the data packet that needs to be retransmitted after packet loss is a data packet that will affect the processing (such as encoding and decoding processing) of subsequent data packets after packet loss, or a data packet corresponding to a key frame.

[0332] Specifically, when adding the retransmission delay threshold to the obtained uplink data packet, the application layer of the UE can add the retransmission delay threshold to each obtained uplink data packet; for the uplink data packet obtained by the application layer of the UE, there can be multiple uplink data packets with the same retransmission delay threshold, and therefore the application layer of the UE can add the retransmission delay threshold to only one of the multiple uplink data packets, and the multiple uplink data packets can be transmitted simultaneously or consecutively when the uplink data packets are transmitted to the bottom layer of the UE, wherein the uplink data packet to which the retransmission delay threshold is added is the first uplink data packet transmitted to the bottom layer of the UE among the multiple uplink data packets. Alternatively, the uplink data packets have the same retransmission delay threshold. The application layer of the UE can be a protocol layer above IP or IP, such as a transport layer or an application layer of the UE, and the bottom layer of the UE refers to a protocol layer between the UE and a RAN device, including but not limited to a physical layer, a MAC layer, an RLC layer, a PDCP layer, and the like.

[0333] In mode two, after the application layer of the UE obtains an uplink data packet, the application layer of the UE 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 application layer of the UE adds a fourth transmission sequence number to the uplink data packet. At this time, the fourth transmission sequence number has two functions, one is to identify the uplink data packet, and the other is to instruct the bottom layer of the UE to determine the transmission result of the uplink data packet, or to trigger the bottom layer of the UE to determine the transmission result of the uplink data packet, and to send the transmission sequence number and the transmission result of the uplink data packet to the application layer.

[0334] Alternatively, when adding the retransmission delay threshold to the obtained uplink data packet, the application layer of the UE can add the retransmission delay threshold to each obtained uplink data packet; for the uplink data packet obtained by the application layer of the UE, there can be multiple uplink data packets with the same retransmission delay threshold, and therefore the application layer of the UE can add the retransmission delay threshold to only one of the multiple uplink data packets, and the multiple uplink data packets can be transmitted simultaneously or consecutively when the uplink data packets are transmitted to the bottom layer of the UE, wherein the uplink data packet to which the retransmission delay threshold is added is the first uplink data packet transmitted to the bottom layer of the UE among the multiple uplink data packets. The application layer of the UE can be a protocol layer above IP or IP, such as a transport layer or an application layer of the UE, and the bottom layer of the UE refers to a protocol layer between the UE and a RAN device, including but not limited to a physical layer, a MAC layer, an RLC layer, a PDCP layer, and the like.

[0335] The application layer of the UE sends the uplink data packet to the bottom layer of the UE after the above processing, so as to send the uplink data packet to the RAN device through the bottom layer of the UE. Optionally, if the uplink data packet has a corresponding transmission serial number (including the third transmission serial number or the fourth transmission serial number), the application layer of the UE simultaneously transmits the transmission serial number of the uplink data packet to the bottom layer of the UE.

[0336] After the bottom layer of the UE sends the uplink data packet to the RAN device, the bottom layer of the UE can determine the transmission result of the uplink data packet and send the transmission result of the uplink data packet to the application layer of the UE. Optionally, if the uplink data packet has a corresponding transmission serial number (including the third transmission serial number or the fourth transmission serial number), the bottom layer of the UE simultaneously sends the transmission serial number of the uplink data packet to the application layer of the UE.

[0337] In a possible implementation, the method of the embodiment further includes:

[0338] The application layer of the UE sends fifth information to the bottom layer of the UE, where the fifth information is used to indicate whether the transmission result of the uplink data packet needs to be determined.

[0339] It is pointed out here that, for the application layer of the UE, the transmission result of some uplink data packets needs to be concerned, such as the uplink data packet that needs to be retransmitted after packet loss or transmission failure, and the transmission result of some uplink data packets does not need to be concerned. Therefore, the application layer of the UE sends the fifth information to the bottom layer of the UE to inform the bottom layer of the UE whether the transmission result of the uplink data packet needs to be fed back.

[0340] S602, the application layer of the UE determines whether the uplink data packet needs to be retransmitted based on the transmission result of the uplink data packet transmitted between the bottom layer of the UE and the RAN device and the transmission serial number of the uplink data packet.

[0341] In a possible implementation, for the case that the application layer of the UE adds the fourth transmission serial number only for the uplink data packet that needs to be retransmitted after packet loss, the application layer of the UE determines whether the uplink data packet is successfully transmitted based on the transmission result of the uplink data packet. If it is determined that the uplink data packet is unsuccessfully transmitted based on the transmission result of the uplink data packet, the application layer of the UE determines that the uplink data packet needs to be retransmitted based on the fourth transmission serial number of the uplink data packet.

[0342] Optionally, if it is determined that the uplink data packet fails to be transmitted based on the transmission result of the uplink data packet, the application layer of the UE determines whether to retransmit the uplink data packet based on the retransmission time delay threshold of the uplink data packet and the estimated retransmission time delay of the uplink data packet obtained from the bottom layer of the UE. The estimated retransmission time delay of the uplink data packet is the estimated time required for retransmitting the uplink data packet to the RAN device. The time can be the time required for transmitting the uplink data packet from the bottom layer of the UE to the RAN device (i.e., the air interface transmission time delay of UE's bottom layer -> RAN device), or the sum of the time required for the bottom layer of the UE to obtain the uplink data packet to be retransmitted from the application layer of the UE and the time required for transmitting the uplink data packet from the bottom layer of the UE to the RAN device (i.e., the time of UE's bottom layer -> UE's application layer -> UE's bottom layer -> RAN device). If the estimated retransmission time delay of the uplink data packet is less than or equal to the retransmission time delay threshold of the uplink data packet, the application layer of the UE determines that the uplink data packet needs to be retransmitted. If the estimated retransmission time delay of the uplink data packet is greater than the retransmission time delay threshold of the uplink data packet, the application layer of the UE determines that the uplink data packet does not need to be retransmitted.

[0343] It is pointed out here that the retransmission time delay threshold of the uplink data packet is obtained by the application layer of the UE from the local configuration or from the SMF network element. The process of UE's bottom layer -> UE's application layer -> UE's bottom layer means that the bottom layer of the UE obtains the uplink data packet to be retransmitted from the application layer of the UE.

[0344] In a feasible implementation, in the case where the application layer of the UE adds a third transmission serial number to each obtained uplink data packet, in an example, the application layer of the UE determines the retransmission identifier of the uplink data packet based on the third transmission serial number of the uplink data packet. The third transmission serial number of the uplink data packet and the retransmission identifier of the uplink data packet have a corresponding relationship. If the retransmission identifier of the uplink data packet indicates that the uplink data packet needs to be retransmitted in the case of transmission failure, the application layer of the UE 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 case of transmission failure, the application layer of the UE determines that the uplink data packet does not need to be retransmitted. Alternatively, the application layer of the UE determines whether the uplink data packet needs to be retransmitted based on the importance of the uplink data packet, without the help of the retransmission identifier, in other words, the application layer of the UE does not generate the retransmission identifier for the obtained uplink data packet.

[0345] In another example, the application layer of the UE determines a retransmission delay threshold of the uplink data packet based on a third transmission sequence number of the uplink data packet, the third transmission sequence number of the uplink data packet corresponding to the retransmission delay threshold of the uplink data packet; obtains an estimated retransmission delay of the uplink data packet from the bottom layer of the UE, the estimated retransmission delay of the uplink data packet being an estimated time required for retransmitting 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 retransmission delay threshold of the uplink data packet, the application layer of the UE determines that the uplink data packet needs to be retransmitted; and if the estimated retransmission delay of the uplink data packet is greater than the retransmission delay threshold of the uplink data packet, the application layer of the UE determines that the uplink data packet does not need to be retransmitted.

[0346] In another example, the application layer of the UE determines a retransmission delay threshold and a retransmission identifier of the uplink data packet, and obtains an estimated retransmission delay of the uplink data packet from the bottom layer of the UE; 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, and the retransmission identifier of the uplink data packet indicates that the uplink data packet needs to be retransmitted in the case of transmission failure, the application layer of the UE determines that the uplink data packet needs to be retransmitted; and if the estimated retransmission delay of the uplink data packet is greater than the retransmission delay threshold of the uplink data packet, or the retransmission identifier of the uplink data packet indicates that the uplink data packet does not need to be retransmitted in the case of transmission failure, the application layer of the UE determines that the uplink data packet does not need to be retransmitted.

[0347] In a possible implementation, the method of the present embodiment further includes:

[0348] The application layer of the UE receives fourth information from the application server; the fourth information is sent after the uplink data packet is retransmitted to the RAN by the bottom layer of the UE, and the fourth information indicates that the application server has not received the uplink data packet; and since the application layer of the UE has retransmitted the uplink data packet to the application server, the application layer of the UE discards or ignores the fourth information to avoid unnecessary retransmission.

[0349] It can be seen that, between the application layer of the UE and the application server, by introducing the bottom layer of the UE, the application layer of the UE determines the transmission result of the uplink data packet based on the bottom layer of the UE, to decide whether the uplink data packet needs to be retransmitted. Since the bottom layer of the UE can quickly know the transmission result of the uplink data packet relative to the application layer of the UE, the application layer of the UE can make a decision on whether the uplink data packet needs to be retransmitted based on the transmission result of the uplink data packet between the bottom layer of the UE and the RAN device more quickly, thereby facilitating to improve the efficiency of data packet retransmission. The application layer of the UE only adds the fourth transmission serial number to the uplink data packet that needs to be retransmitted after packet loss. When the application layer of the UE receives the transmission result indicating the transmission failure of the uplink data packet, the fourth transmission serial number of the uplink data packet is also received. The application layer of the UE can directly decide whether the uplink data packet needs to be retransmitted based on the fourth transmission serial number, without the aid of other information, thereby improving the decision efficiency and facilitating to improve the efficiency of retransmission. In the case that the application layer of the UE adds the transmission serial number and the retransmission identifier to each obtained uplink data packet, the application layer of the UE directly decides whether the uplink data packet needs to be retransmitted based on the retransmission identifier of the uplink data packet, without the aid of other information, thereby improving the decision efficiency and facilitating to improve the efficiency of retransmission. When the application layer of the UE decides whether the uplink data packet needs to be retransmitted, the retransmission delay threshold of the uplink data packet is introduced. When the estimated retransmission delay of the uplink data packet is less than or equal to the retransmission delay of the uplink data packet, it is determined that the uplink data packet needs to be retransmitted, thereby avoiding the case that the retransmission delay does not meet the requirement after the uplink data packet is retransmitted.

[0350] Referring to FIG. 7, FIG. 7 is a flowchart of another data retransmission method provided by the embodiment of the application. The method is applied to the bottom layer of the UE in FIG. 1. As shown in FIG. 7, the method comprises the following steps.

[0351] S701, the bottom layer of the UE receives the uplink data packet and the transmission serial number of the uplink data packet from the application layer of the UE.

[0352] It should be noted that, when the application layer of the UE adds the transmission serial number to the obtained uplink data packet, there are two processing methods:

[0353] 1. The application layer of the UE adds the third transmission serial number to all obtained uplink data packets, and the third transmission serial number is used to identify the uplink data packet.

[0354] 2. After the application layer of the UE acquires an uplink data packet, the 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 application layer of the UE adds a fourth transmission sequence number to the uplink data packet. At this time, the fourth transmission sequence number has two functions: one is to identify the uplink data packet, and the other is to trigger the UE bottom layer to determine the transmission result of the uplink data packet and send the transmission sequence number and the transmission result of the uplink data packet to the UE application layer, i.e., the uplink data packet is a data packet that needs to be retransmitted after being lost or transmission failure. That is, for uplink data packets that do not need to be retransmitted, the application layer of the UE only needs to send the uplink data packet to the bottom layer of the UE, and does not need to send the transmission sequence number of the uplink data packet to the bottom layer of the UE.

[0355] Note that the application layer of the UE can be a protocol layer above IP or IP, such as a transport layer or an application layer of the UE, and the bottom layer of the UE refers to the protocol layer between the UE and the RAN, including but not limited to the physical layer, the MAC layer, the RLC layer, the PDCP layer, etc.

[0356] S702, the bottom layer of the UE sends the uplink data packet to the RAN device; the bottom layer of the UE determines the transmission result of the uplink data packet transmitted between the bottom layer of the UE and the RAN device.

[0357] In a feasible embodiment, when the bottom layer of the UE receives the uplink data packet from the application layer of the UE, the bottom layer of the UE allocates a PDCP layer sequence number to the uplink data packet, and if the transmission sequence number of the uplink data packet is also received, the bottom layer of the UE records the correspondence between the PDCP layer sequence number allocated to the uplink data and the transmission sequence number of the uplink data packet. The bottom layer of the UE sends the uplink data packet to the RAN device through the PDCP layer, and the uplink data packet carries the allocated PDCP layer sequence number.

[0358] In a feasible implementation, the bottom layer of the UE determines the transmission result of the uplink data packet in two ways:

[0359] Method one: the bottom layer of the UE determines whether the uplink data packet is successfully transmitted based on the feedback information of the RAN device; for example, the feedback information of the RAN device includes the PDCP layer sequence number of the uplink data packet and the transmission identifier; the bottom layer of the UE determines that the transmission identifier in the feedback information is the transmission identifier of the uplink data packet based on the correspondence between the PDCP layer sequence number of the uplink data packet and the transmission sequence number and the PDCP layer sequence number, and the transmission identifier of the uplink data packet is used to indicate whether the RAN device receives the uplink data packet, and the bottom layer of the UE determines whether the uplink data packet is successfully transmitted based on the transmission identifier of the uplink data packet.

[0360] It is pointed out here that if the bottom layer of the UE fails to find the transmission sequence number corresponding to the PDCP layer sequence number of the uplink data packet based on the correspondence between the PDCP layer sequence number and the transmission sequence number of the uplink data packet, it means that the uplink data packet does not have a corresponding transmission sequence number, in other words, the application layer of the UE adds a transmission sequence number only to the data packet that needs to be retransmitted after being lost when adding a transmission sequence number to the uplink data packet, that is, the uplink data packet without a transmission sequence number is a data packet that does not need to be retransmitted after being lost, therefore, the feedback information of the uplink data packet without a corresponding transmission sequence number can be ignored or discarded by the bottom layer of the UE.

[0361] In one example, the transmission identification of the uplink data packet is NACK or ACK; when the transmission identification of the uplink data packet is NACK, it means that the RAN device does not receive the uplink data packet, that is, the uplink data packet transmission fails; when the transmission identification of the uplink data packet is ACK, it means that the RAN device receives the uplink data packet, that is, the uplink data packet transmission succeeds.

[0362] Method two: the bottom layer of the UE determines whether the uplink data packet is successfully transmitted based on its own information. For example, in the RLC UM mode, the bottom layer of the UE determines whether the uplink data packet is successfully transmitted according to the actual sending situation of the MAC layer transport block; or the bottom layer of the UE obtains the transmission duration of the uplink data packet transmitted to the RAN device, that is, the used duration of the uplink data packet transmitted to the RAN device, if the transmission duration exceeds the second transmission duration threshold, the bottom layer of the UE determines that the uplink data packet transmission fails.

[0363] It is pointed out here that the uplink data packet transmission failure includes the case that the MAC layer retransmission between the bottom layer of the UE and the RAN device still fails; optionally, the uplink data packet transmission failure also includes the case that the MAC layer and RLC layer retransmission between the bottom layer of the UE and the RAN device still fails.

[0364] S703, the bottom layer of the UE sends the transmission result of the uplink data packet transmitted between the bottom layer of the UE and the RAN device and the transmission sequence number of the uplink data packet to the application layer of the UE, the transmission result of the uplink data packet transmitted between the bottom layer of the UE 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.

[0365] In one possible implementation, the bottom layer of the UE also sends the estimated retransmission delay of the uplink data packet to the application layer of the UE, and the estimated retransmission delay of the uplink data packet is used to determine whether the uplink data packet needs to be retransmitted.

[0366] In a feasible implementation, the bottom layer of the UE receives a retransmission delay threshold of an uplink data packet from the application layer of the UE. The bottom layer of the UE determines an estimated retransmission delay of the uplink data packet, that is, an estimated delay for retransmitting the uplink data packet to the RAN device, and sends the transmission sequence number and the transmission result of the uplink data packet to the application layer of the UE when the estimated retransmission delay of the uplink data packet is less than or equal to the retransmission delay threshold.

[0367] In the process of obtaining the retransmission delay threshold of the uplink data packet by the bottom layer of the UE, the retransmission delay thresholds of a plurality of uplink data packets are the same, the application layer of the UE sends a plurality of uplink data packets to the bottom layer of the UE at the same time or successively, and in the case that the first uplink data packet in the plurality of uplink data packets carries the retransmission delay threshold, the bottom layer of the UE determines whether the retransmission delay threshold is obtained from the uplink data packet. If the retransmission delay threshold is obtained from the uplink data packet, the retransmission delay threshold determined by the bottom layer of the UE is the retransmission delay threshold of the uplink data packet. If the retransmission delay threshold cannot be determined from the uplink data packet, the bottom layer of the UE 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.

[0368] In a feasible implementation, the bottom layer of the UE receives fifth information sent by the application layer of the UE, the fifth information being used to indicate whether the transmission result of the uplink data packet needs to be determined, and sends 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.

[0369] Specifically, when the fifth information is used to indicate that the transmission result of the uplink data packet needs to be determined, the bottom layer of the UE 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 application layer of the UE. When the fifth information is used to indicate that the transmission result of the uplink data packet does not need to be determined, the bottom layer of the UE does not perform the operation of determining the transmission result of the uplink data packet, and does not need 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.

[0370] In S702 and S703, the transmission sequence number of the uplink data packet includes the third transmission sequence number or the fourth transmission sequence number.

[0371] It can be seen that, between the application layer of the UE and the application server, by introducing the bottom layer of the UE, the application layer of the UE determines the transmission result of the uplink data packet based on the bottom layer of the UE, so as to quickly decide whether the uplink data packet needs to be retransmitted. Since the bottom layer of the UE can quickly know the transmission result of the uplink data packet transmitted between the bottom layer of the UE and the RAN device relative to the application layer of the UE, the application layer of the UE can make a decision on whether the uplink data packet needs to be retransmitted based on the transmission result more quickly, thereby facilitating to improve the efficiency of data packet retransmission. The transmission result of the uplink data packet is determined by the bottom layer of the UE based on the transmission delay of the uplink data packet or based on the sending situation of the bottom layer transmission block, instead of based on the feedback information on the application server side, so that the application layer of the UE can quickly know the transmission result of the uplink data packet, thereby further deciding whether the uplink data packet needs to be retransmitted according to the transmission result of the uplink data packet determined by the UE bottom layer, and facilitating to provide the efficiency of data packet retransmission. By sending the estimated retransmission delay of the uplink data packet to the application layer of the UE, the application layer of the UE considers the estimated retransmission delay of the uplink data packet when deciding whether the uplink data packet needs to be retransmitted, and only determines that the uplink data packet needs to be retransmitted when the estimated retransmission delay of the uplink data packet is less than or equal to the retransmission delay of the uplink data packet, thereby avoiding the situation that the retransmission delay does not meet the requirement after the uplink data packet is retransmitted.

[0372] Referring to FIG. 8, FIG. 8 is an interactive flow diagram of a data retransmission method provided by an embodiment of the present application. The method is applied to the system shown in FIG. 1. As shown in FIG. 8, the method comprises the following steps.

[0373] S801, the AF network element sends an AF request to the PCF network element.

[0374] In one example, the AF request comprises first indication information and flow description information. The flow description information is IP triplets, five-tuple or application identifier and the like. The first indication information is used to indicate that the service flow indicated by the service flow description information needs to be processed by retransmission acceleration.

[0375] In another example, the AF request comprises first indication information, which is used to indicate that the service flow corresponding to the AF request needs to be processed by retransmission acceleration.

[0376] In one example, the AF network element directly interacts 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.

[0377] It should be noted that S801 is optional.

[0378] S802, the PCF network element sends a PCC rule to the SMF network element.

[0379] The PCC rule can be generated by the PCF network element in a subsequent PDU session establishment or modification process. The PCC rule is used to indicate a QoS policy for a specified service flow, wherein the PCC rule includes first indication information.

[0380] The PCF network element generates the PCC rule according to local configuration and / or information provided by the AF (as described in S801).

[0381] This step is optional.

[0382] S803, the SMF network element sends an N4 rule to the UPF network element.

[0383] Specifically, the SMF network element sends an N4 rule to the UPF network element based on the PCC rule and / or local configuration information, wherein the N4 rule includes second indication information, and the second indication information is used to instruct the UPF network element to start a fast retransmission mechanism, i.e., instruct the UPF network element to add a transmission sequence number to a downlink data packet and determine whether the downlink data packet needs to be retransmitted based on information fed back by the RAN device.

[0384] S804, the SMF network element sends third indication information to the RAN device.

[0385] Specifically, the SMF network element sends third indication information to the RAN device based on the PCC rule and / or local configuration information, and the third indication information is used to instruct the RAN device to determine a first transmission result of a downlink data packet and feed back the first transmission result of the downlink data packet to the UPF network element, wherein the first transmission result of the downlink data packet is used to indicate whether the downlink data packet is successfully transmitted.

[0386] S805, the UPF network element adds a transmission sequence number to a downlink data packet.

[0387] It should be noted that the downlink data packet is a data packet transmitted from an application server to a UE via the UPF network element and the RAN device; or the application server is deployed in the UPF network element, and the downlink data packet is a downlink data packet from the UPF network element itself.

[0388] Specifically, in one example, the UPF network element adds a first transmission sequence number to each received downlink data packet, and the first transmission sequence number is used to identify the downlink data packet.

[0389] In another example, the UPF network element determines, after receiving each downlink data packet, whether the downlink data packet is a data packet that needs to be retransmitted after packet loss; wherein the data packet that needs to be retransmitted after packet loss can be a data packet that will affect subsequent data packet processing (such as codec processing) after loss, or the data packet is a data packet corresponding to a key frame, or the data packet has a higher importance. If the downlink data packet is a data 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 represents the need to retransmit the downlink data packet, i.e. 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 feed back to the UPF network element.

[0390] In one example, the transmission sequence number of the downlink data packet is carried in the GTP-U layer of the downlink data packet.

[0391] In one example, 8 bits are used to mark the data packet transmission sequence number, the transmission sequence number of the first data packet (including the first transmission sequence number or the second transmission sequence number) is 0, the transmission sequence number of the second data packet is 1, and when the transmission sequence number is 255, it is marked again from 0.

[0392] S806, the UPF network element sends the downlink data packet and the transmission sequence number to the RAN device.

[0393] Wherein, sending the downlink data packet and the transmission sequence number can be understood as sending the downlink data packet carrying the transmission sequence number.

[0394] S807, the RAN device records the correspondence between the transmission sequence number of the downlink data packet and the PDCP layer sequence number.

[0395] It should be noted that the downlink data packet received by the RAN device can be multiple, and the corresponding transmission sequence number can also be multiple; and the RAN device sends the PDCP layer sequence number of the downlink data packet to the UE at the same time when sending the downlink data packet to the UE. Therefore, after receiving multiple downlink data packets and corresponding transmission sequence numbers, the RAN device records the correspondence between the transmission sequence number of the multiple downlink data packets and the PDCP layer sequence number. Wherein, this step is optional.

[0396] S808, the RAN device sends the target downlink data packet to the UE.

[0397] Wherein, 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 sends the PDCP layer sequence number of the target downlink data packet to the UE at the same time.

[0398] S809, the UE sends feedback information to the RAN device.

[0399] The feedback information includes a target PDCP sequence number and a transmission identifier.

[0400] The transmission identifier is used to indicate whether the UE receives the target downlink data packet sent by the RAN device. In one example, the transmission identifier is ACK, which is used to indicate that the UE receives the target downlink data packet from the RAN device, or to indicate that the RAN device successfully transmits the target downlink data packet to the UE; or the transmission identifier is NACK, which is used to indicate that the UE does not receive the target downlink data packet from the RAN device, or to indicate that the RAN device fails to transmit the target downlink data packet to the UE.

[0401] S809 is optional.

[0402] S810, the RAN device determines whether the target downlink data packet is successfully transmitted.

[0403] Specifically, the RAN device determines whether the target downlink data packet is successfully transmitted in two ways.

[0404] The first way: the RAN device determines whether the target downlink data packet is successfully transmitted based on the feedback information of the UE; for example, the feedback information of the UE includes a target PDCP sequence number and a transmission identifier; the RAN device determines the transmission sequence number corresponding to the target PDCP sequence number based on the correspondence between the transmission sequence number and the PDCP sequence number, and the transmission sequence number is the transmission sequence number 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, which is used to indicate whether the UE receives the target downlink data packet or whether the target downlink data packet is lost, and the RAN device determines whether the target downlink data packet is successfully transmitted based on the transmission identifier of the target downlink data packet.

[0405] It should be noted that if the RAN device queries the correspondence between the transmission sequence number and the PDCP sequence number based on the target PDCP sequence number and fails to find the transmission sequence number corresponding to the target PDCP sequence number, it means that the downlink data packet corresponding to the target PDCP sequence number does not have a corresponding transmission sequence number, in other words, the UPF network element only adds a transmission sequence number to the data packet that needs to be retransmitted after being lost when adding a transmission sequence number to the downlink data packet. That is, the downlink data packet without a transmission sequence number is a data packet that does not need to be retransmitted after being lost. Therefore, the RAN device can ignore or discard the feedback information of the downlink data packet without a corresponding transmission sequence number.

[0406] 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 indicates that the UE does not receive the target downlink data packet, i.e., the transmission of the target downlink data packet fails; when the transmission identifier of the target downlink data packet is ACK, it indicates that the UE receives the target downlink data packet, i.e., the transmission of the target downlink data packet succeeds.

[0407] Option 2: The RAN device determines whether the transmission of the target downlink data packet succeeds based on its own information. For example, in the RLC UM mode, the RAN device determines whether the transmission of the target downlink data packet succeeds according to the actual sending of the MAC layer transmission block; or the RAN device obtains the transmission duration of the target downlink data packet to the UE, i.e., the used duration of the target downlink data packet to the UE, and if the transmission duration exceeds a first transmission duration threshold, the RAN device determines that the transmission of the target downlink data packet fails.

[0408] It is pointed out here that the transmission failure of the target downlink data packet includes the case that the retransmission between the RAN device and the UE at the MAC layer still fails; optionally, the transmission failure of the target downlink data packet also includes the case that the retransmission between the RAN device and the UE at the MAC layer and the RLC layer still fails.

[0409] Optionally, if the RAN device determines that the transmission of the target downlink data packet succeeds, the RAN device does not perform S811 and the subsequent operations; if the RAN device determines that the transmission of the target downlink data packet fails, the RAN device performs S811.

[0410] In S806-S810, the transmission sequence number of the downlink data packet includes the first transmission sequence number or the second transmission sequence number.

[0411] In S811, the RAN device determines the estimated retransmission delay of the target downlink data packet based on the air interface resource information.

[0412] 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 of RAN device->UPF network element->RAN device->UE.

[0413] It should be noted that the RAN device->UPF network element->RAN device process refers to the RAN device obtaining the target downlink data packet that needs to be retransmitted from the UPF network element. The transmission time of the RAN device-UPF network element can also be referred to as a core network packet delay budget (CN PDB), which can be determined based on operator configuration information.

[0414] Optionally, S811 is performed.

[0415] S812, the RAN device sends the first transmission result to the UPF network element.

[0416] The first transmission result includes the transmission sequence number of the target downlink data packet and the transmission situation information of the target downlink data packet, and the transmission situation information is used to indicate whether the target downlink data packet is successfully transmitted. Optionally, the first transmission result further includes an estimated retransmission delay.

[0417] Optionally, the first transmission result is carried on an uplink data packet, which is an uplink data packet from the UE or a null packet generated by the RAN device.

[0418] S813, the UPF network element determines whether the target downlink data packet needs to be retransmitted.

[0419] 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.

[0420] Specifically, if it is determined based on the first transmission result of the target downlink data packet that the target downlink data packet is successfully transmitted, S814 is not performed. If it is determined based on the transmission identifier of the target downlink data packet that the target downlink data packet is unsuccessfully transmitted, two cases are described in detail to determine whether the target downlink data packet needs to be retransmitted.

[0421] Case 1: The UPF network element adds the transmission sequence number, and only adds the second transmission sequence number for the downlink data packet that needs to be retransmitted after packet loss. For case 1, the UPF network element can determine whether to retransmit the target downlink data packet in two ways:

[0422] 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.

[0423] 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, 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, the UPF network element determines that the target downlink data packet does not need to be retransmitted.

[0424] Case 2: The UPF network element adds the transmission sequence number, and adds the first transmission sequence number for each received downlink data packet. For case 2, the UPF network element can determine whether to retransmit the target downlink data packet in two ways:

[0425] 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, and there is a corresponding relationship 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 case 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 is used to indicate that the target downlink data packet needs to be retransmitted in the case 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 is used to indicate that the target downlink data packet does not need to be retransmitted in the case of transmission failure, the UPF network element determines that the target downlink data packet does not need to be retransmitted.

[0426] B2, the retransmission identifier of the target downlink data packet is used to indicate that the target downlink data packet needs to be retransmitted in the case of transmission failure, and 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, and there is a corresponding relationship 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 of the target downlink data packet, 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 of the target downlink data packet, the UPF network element determines that the target downlink data packet does not need to be retransmitted.

[0427] In one example, if the UPF network element is not a relay network element, the UPF network element forwards the first transmission result to a proxy server or an application server (AS).

[0428] S814, the UPF network element retransmits the target downlink data packet to the UE.

[0429] 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.

[0430] S815, the UE sends first information to the UPF network element.

[0431] This step is optional.

[0432] The first information is sent by the UE after the UPF network element retransmits the target downlink data packet to the UE, and the first information is used by the UE to indicate to the application server side that the UE has not received the target downlink data packet before retransmission. In one example, the first information is NACK.

[0433] S816, the UPF network element ignores or discards the first information.

[0434] Specifically, if the UPF network element determines that the target downlink data packet has been retransmitted to the UE, and the first information from the UE is received at this time, the UPF network element ignores or discards the first information.

[0435] It should be pointed out that the detailed description and benefits of the embodiment shown in FIG. 8 can be referred to the related description of the embodiments shown in FIGS. 2 and 3, which will not be described here.

[0436] Referring to FIG. 9, FIG. 9 is an interactive flow diagram of another data retransmission method provided by the embodiments of the present application. The method is applied to the system shown in FIG. 1. As shown in FIG. 9, the method comprises:

[0437] S901, the AF network element sends an AF request to the PCF network element.

[0438] In one example, the AF request comprises first indication information and flow description information. The flow description information is IP triple, quintuple or application identifier information. The first indication information is used to indicate that the service flow indicated by the service flow description information needs to be retransmitted and accelerated.

[0439] In another example, the AF request comprises first indication information, which is used to indicate that the service flow corresponding to the AF request needs to be retransmitted and accelerated.

[0440] In one example, the AF network element directly interacts 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.

[0441] It should be pointed out that S901 is optional.

[0442] S902, the PCF network element sends a PCC rule to the SMF network element.

[0443] The PCC rule can be generated by the PCF network element in a subsequent PDU session establishment or modification process. The PCC rule is used to indicate a QoS policy for a specified service flow, and the PCC rule includes first indication information.

[0444] The PCF network element generates the PCC rule according to local configuration and / or information provided by the AF (as described in S901).

[0445] This step is optional.

[0446] S903. The SMF network element sends N4 rules to the UPF network element.

[0447] Specifically, the SMF network element sends N4 rules to the UPF network element based on the PCC rule and / or local configuration information, wherein the N4 rules include fourth indication information, and the fourth indication information is used to instruct the UPF network element to start 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 identifier. The retransmission delay threshold is used to determine whether the downlink data packet that fails in transmission needs to be retransmitted by the RAN device. The retransmission identifier is used to indicate whether the downlink data packet needs to be retransmitted in the case of transmission failure.

[0448] S904. The SMF network element sends fifth indication information to the RAN device.

[0449] Specifically, the SMF network element sends fifth indication information to the RAN device based on the PCC rule and / or local configuration information, and the fifth indication information is used to instruct the RAN device to determine whether to retransmit the downlink data packet.

[0450] Optionally, the fifth indication information includes a retransmission delay threshold, which is used to determine whether the downlink data packet that fails in transmission needs to be retransmitted by the RAN device.

[0451] In one example, the fifth indication information instructs the RAN device to determine whether to retransmit the downlink data packet based on the transmission sequence number and the transmission result of the downlink data packet.

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

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

[0454] In another example, the fifth indication information indicates that the RAN device decides whether to retransmit the downlink data packet based on a transmission result, a transmission sequence number, a retransmission identifier and a retransmission time delay threshold of the downlink data packet.

[0455] S905, the UPF network element adds a transmission sequence number to the downlink data packet.

[0456] 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 the RAN device, or the application server is deployed in the UPF network element, and the downlink data packet is a downlink data packet from the UPF network element itself.

[0457] Specifically, in one example, the UPF network element adds a first transmission sequence number to each received downlink data packet, and optionally, also adds a retransmission identifier to each received downlink data packet, the retransmission identifier being used to indicate whether the downlink data packet needs to be retransmitted. In other words, the UPF network element judges whether the downlink data packet needs to be retransmitted after being lost after receiving each downlink data packet, and the UPF adds a retransmission identifier to the received downlink data packet based on the judgment result. Wherein, the data packet that needs to be retransmitted after being lost is a data packet that will affect the encoding and decoding of subsequent data packets, or is a key frame, or has a higher importance. Optionally, the UPF network element adds a retransmission time delay threshold to the downlink data packet. It should be noted that the UPF network element can add a retransmission time delay threshold to each received downlink data packet. Wherein, the retransmission time delay thresholds of multiple downlink data packets are the same, so the UPF network element can only add a retransmission time delay threshold to one of these multiple downlink data packets, such as the first downlink data packet of these multiple downlink data packets. The UPF network element can send these multiple downlink data packets simultaneously or continuously.

[0458] In another example, the UPF network element judges whether the downlink data packet needs to be retransmitted after being lost after receiving each downlink data packet, and if the downlink data packet needs to be retransmitted after being lost, the UPF network element adds a second transmission sequence number to the downlink data packet. At this time, the second transmission sequence number can only be a retransmission identifier, that is, the retransmission identifier is used as the second transmission sequence number without generating an additional second transmission sequence number. In other words, the second transmission sequence number of the downlink data packet represents that the downlink data packet needs to be retransmitted. Optionally, the UPF network element adds a retransmission time delay threshold to the downlink data packet that needs to be retransmitted after being lost.

[0459] S906, the UPF network element sends the downlink data packet and the third information to the RAN device.

[0460] The sending of the downlink data packet and the third information to the RAN device can be understood as the sending of the downlink data packet carrying the third information to the RAN device.

[0461] The third information is used to determine whether the downlink data packet needs to be retransmitted after a transmission failure. The third information includes first retransmission indication information, which is used to indicate that the downlink data packet needs to be retransmitted in the case of a transmission failure.

[0462] In one example, the first retransmission indication information includes a second transmission 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 a packet loss based on the second transmission sequence number of the downlink data packet.

[0463] In another example, the first retransmission indication information includes a retransmission identifier of the downlink data packet, that is, the retransmission identifier of the downlink data packet can be used to indicate that the downlink data packet needs to be retransmitted in the case of a transmission failure. In this case, the third information further includes a transmission sequence number of the downlink data packet, and the RAN device determines the retransmission identifier of the downlink data packet based on the transmission sequence number of the downlink data packet when making a decision. Optionally, the third information further includes a retransmission delay threshold of the downlink data packet.

[0464] Optionally, the third information is carried in the GTP-U layer of the downlink data packet.

[0465] S907, 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.

[0466] It should be noted that the RAN device receives multiple downlink data packets, and correspondingly, there are multiple third information. When the RAN device sends the downlink data packet to the UE, the RAN device also sends the PDCP layer sequence number of the downlink data packet to the UE. Therefore, after the RAN device receives multiple downlink data packets and corresponding third information, the RAN device records the correspondence between the transmission sequence number of the multiple downlink data packets and the PDCP layer sequence number.

[0467] This step is optional.

[0468] S908, the RAN device sends the target downlink data packet to the UE.

[0469] Specifically, the RAN device sends the target downlink data packet to the UE through the PDCP layer, and simultaneously sends the PDCP layer sequence number of the target downlink data packet to the UE.

[0470] S909, the RAN device determines whether the target downlink data packet is successfully transmitted.

[0471] Specifically, the RAN device determines whether the target downlink data packet is successfully transmitted in two ways:

[0472] In a first mode, the RAN device determines whether the target downlink data packet is successfully transmitted based on the feedback information of the UE. For example, the feedback information of the UE includes a target PDCP layer sequence number and a transmission identifier. The RAN device determines a transmission sequence number corresponding to the target PDCP layer sequence number based on the correspondence between the transmission sequence number and the PDCP layer sequence number, and the transmission sequence number is the transmission sequence number of the target downlink data packet. Therefore, the RAN device can determine, based on the transmission sequence number corresponding to the target PDCP layer sequence number, that the transmission identifier included in the feedback information is the transmission identifier of the target downlink data packet, which indicates whether the UE receives the target downlink data packet. The RAN device determines whether the target downlink data packet is successfully transmitted based on the transmission identifier of the target downlink data packet.

[0473] It should be noted that if the RAN device fails to find the transmission sequence number corresponding to the target PDCP layer sequence number based on the target PDCP layer 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, the UPF network element adds a transmission sequence number only to the downlink data packet that needs to be retransmitted after being lost when adding a transmission sequence number to the downlink data packet. In other words, the downlink data packet without a transmission sequence number is a data packet that does not need to be retransmitted after being lost. Therefore, the RAN device can ignore or discard the feedback information of the downlink data packet without a corresponding transmission sequence number.

[0474] In an 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 does not receive the target downlink data packet, i.e., the target downlink data packet is not successfully transmitted. When the transmission identifier of the target downlink data packet is ACK, it means that the UE receives the target downlink data packet, i.e., the target downlink data packet is successfully transmitted.

[0475] In a second mode, the RAN device determines whether the target downlink data packet is successfully transmitted based on its own information. For example, in the RLC UM mode, the RAN device determines whether the target downlink data packet is successfully transmitted according to the actual sending situation of the MAC layer transport block, or the RAN device acquires the transmission duration of the target downlink data packet transmitted to the UE, i.e., the used duration of the target downlink data packet transmitted to the UE. If the transmission duration exceeds a first transmission duration threshold, the RAN device determines that the target downlink data packet is not successfully transmitted.

[0476] If the RAN device determines that the target downlink data packet is successfully transmitted, the RAN device does not perform S910. If the RAN device determines that the target downlink data packet is not successfully transmitted, the RAN device performs S910.

[0477] The transmission sequence number of the downlink data packet in S906-S909 includes a first transmission sequence number or a second transmission sequence number.

[0478] S910, the RAN device determines whether the target downlink data packet needs to be retransmitted.

[0479] In a feasible implementation, when the UPF network element adds a transmission sequence number to the downlink data packet in the manner of adding a second transmission sequence number to only the downlink data packet that needs to be retransmitted, 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. At this time, the second transmission sequence number can be only a retransmission identifier, that is, the retransmission identifier is used as the transmission sequence number without generating an additional transmission sequence number.

[0480] In another feasible implementation, the RAN device determines whether the target downlink data packet needs to be retransmitted based on a retransmission identifier of the target data packet. Specifically, the RAN device determines the retransmission identifier of the target downlink data packet based on a first transmission sequence number of the target downlink data packet, and there is a corresponding relationship 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.

[0481] In another feasible implementation, the RAN device obtains an estimated retransmission delay of the target downlink data packet. The estimated retransmission delay is an estimated required time for retransmitting the target downlink data packet. The time can be a time required for transmitting the target downlink data packet from the RAN device to the UE (i.e., RAN device->UE), that is, an air interface transmission delay of the RAN device-UE, or a sum of a time required for the RAN device to obtain the target downlink data packet from the UPF network element and a time required for transmitting the target downlink data packet from the RAN device to the UE, that is, a time of RAN device->UPF network element->RAN device->UE. The RAN device determines whether to perform retransmission according to a 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 sent by the UPF network element to the RAN device through a GTP-U layer of the target downlink data packet, or sent by the SMF network element to the RAN device.

[0482] It should be noted that the process of RAN device -> UPF network element -> RAN device refers to that the RAN device obtains the target downlink data packet which needs to be retransmitted from the UPF network element. The transmission time of the RAN device-UPF network element can also be referred to as CN PDB, which can be determined based on the operator configuration information.

[0483] In another possible 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, 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, the RAN device determines that the target downlink data packet does not need to be retransmitted; if it is determined based on the second transmission sequence number retransmission identifier that the target downlink data packet needs to be retransmitted, and the estimated retransmission delay is greater than the retransmission delay threshold, the RAN device determines that the target downlink data packet does not need to be retransmitted.

[0484] In another possible implementation, the RAN device obtains the estimated retransmission delay of the target downlink data packet; the RAN device additionally determines whether the target downlink data packet needs to be retransmitted according to the retransmission identifier and the retransmission delay threshold of the target downlink data packet; if it is determined based on the first transmission sequence number and the retransmission identifier 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, the RAN device determines that the target downlink data packet needs to be retransmitted; if it is determined based on the first transmission sequence number and the retransmission identifier 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, the RAN device determines that the target downlink data packet does not need to be retransmitted; if it is determined based on the first transmission sequence number and the retransmission identifier that the target downlink data packet needs to be retransmitted, and the estimated retransmission delay is greater than the retransmission delay threshold, the RAN device determines that the target downlink data packet does not need to be retransmitted.

[0485] It should be noted that when it is determined that the target downlink data packet needs to be retransmitted, the RAN device performs S911; when it is determined that the target downlink data packet does not need to be retransmitted, the RAN device does not perform S911.

[0486] S911, the RAN device retransmits the target downlink data packet to the UE.

[0487] Specifically, the RAN device retransmits the target downlink data packet to the UE through the PDCP layer.

[0488] S912, the RAN device sends second information to the UPF network element.

[0489] The step is optional, and the second information includes a transmission sequence number of the target downlink data packet.

[0490] In one example, the RAN device sends the second information to the UPF network element after retransmitting the target downlink data packet to the UE, so as to inform the UPF network element that the RAN device has retransmitted the target downlink data packet to the UE. In other words, the second information is used to indicate that the RAN device has retransmitted the target downlink data packet to the UE.

[0491] In one example, the RAN device sends the uplink data packet to the UPF network element, and the GTP-U layer of the uplink data packet carries the second information. Optionally, the uplink data packet is a data packet from the UE or a null packet generated by the RAN device.

[0492] S913. The UE sends the first information to the UPF network element.

[0493] The step is optional, and the first information is used to indicate that the UE has not received the target downlink data packet. In one example, the first information is a NACK.

[0494] S914. The UPF network element ignores or discards the first information.

[0495] The step is optional. Since the RAN device has 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, the UPF network element can ignore or discard the first information.

[0496] S915. The UE sends the first information to the RAN device.

[0497] The step is optional.

[0498] S916. The RAN device ignores or discards the first information.

[0499] The step is optional. Since the RAN device has 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, the RAN device can ignore or discard the first information.

[0500] It is pointed out that S912-S914 and S915-S916 are parallel schemes, and the two schemes are executed alternatively. For details and advantages of the embodiment shown in FIG. 9, refer to the related description of the embodiments shown in FIG. 4 and FIG. 5, which are not described herein.

[0501] Referring to FIG. 10, FIG. 10 is an interactive flowchart of another data retransmission method provided by an embodiment of the present application. The method is applied to the UE in FIG. 1. As shown in FIG. 10, the method includes:

[0502] S1001, the AF network element sends an AF request to the PCF network element.

[0503] In one example, the AF request includes first indication information and flow description information. The flow description information is IP triplets, five-tuple, or application identifier, etc. The first indication information is used to indicate that the service flow indicated by the service flow description information needs to be processed by the retransmission acceleration.

[0504] In another example, the AF request includes first indication information, which is used to indicate that the service flow corresponding to the AF request needs to be processed by the retransmission acceleration.

[0505] In one example, the AF network element directly interacts 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.

[0506] It should be noted that S1001 is optional.

[0507] S1002, the PCF network element sends a PCC rule to the SMF network element.

[0508] The PCC rule is generated by the PCF network element in the subsequent PDU session establishment or modification process. The PCC rule is used to indicate the QoS policy for the instruction service flow, wherein the PCC rule includes first indication information.

[0509] The PCF network element generates the PCC rule according to the local configuration and / or the information provided by the AF network element (as described in S801).

[0510] This step is optional.

[0511] S1003, the SMF network element sends sixth indication information to the UE.

[0512] The sixth indication information is used to indicate the UE's bottom layer to determine the transmission result of the uplink data packet, and send the transmission result to the application layer of the UE to trigger the application layer of the UE to decide whether the uplink data packet needs to be retransmitted.

[0513] The application layer of the UE can be the protocol layer of the UE above IP or IP, and the bottom layer of the UE refers to the protocol layer between the UE and the RAN, including but not limited to the physical layer, the MAC layer, the radio link layer RLC layer, the PDCP layer, etc.

[0514] In one possible implementation, the step is optional, and the UE's underlying layer triggers the UE's application layer to decide whether the uplink data packet needs to be retransmitted according to the local configuration information or the cross-layer indication of the UE's application layer.

[0515] S1004. The UE's application layer sends the uplink data packet and the identification information of the uplink data packet to the UE's underlying layer.

[0516] The step is performed after the PDU session establishment or modification procedure is completed or after the service is started.

[0517] Optionally, the identification information can be a transmission sequence number added to the uplink data packet by the APP layer, or a corresponding sequence number of the transport layer of the uplink data packet, such as a transmission control protocol (TCP) sequence number or a real-time transport protocol (RTP) sequence number, which is not limited herein. In one example, the transmission sequence number of the uplink data packet is carried in the RTP layer or the TCP of the uplink data packet.

[0518] In one example, 8 bits are used to mark the transmission sequence number of the data packet, the transmission sequence number of the first data packet is 0, the transmission sequence number of the second data packet is 1, and the transmission sequence number is incremented by 1, and when the transmission sequence number is 255, the marking is restarted from 0.

[0519] It should be noted that the transmission sequence number is used as an example for description in the following steps. For a specific implementation process of adding the transmission sequence number to the uplink data packet, please refer to the related description of FIG. 7, which is not described herein.

[0520] S1005. The UE's underlying layer records the correspondence between the transmission sequence number of the uplink data packet and the PDCP layer sequence number.

[0521] The step is optional.

[0522] It should be noted that the UE's underlying layer can receive multiple uplink data packets, and correspondingly, there are multiple transmission sequence numbers. When the UE's underlying layer sends the uplink data packet to the UE, the PDCP layer sequence number of the uplink data packet is also sent to the UE. Therefore, after the UE's underlying layer receives multiple uplink data packets and corresponding transmission sequence numbers, the UE's underlying layer records the correspondence between the multiple transmission sequence numbers of the uplink data packets and the PDCP layer sequence numbers.

[0523] S1006. The UE's underlying layer sends the target uplink data packet to the RAN device.

[0524] The target uplink data packet is one of the uplink data packets received by the UE's bottom layer. The UE's bottom layer sends the target uplink data packet to the RAN device through the PDCP layer, and the target uplink data packet contains a PDCP layer sequence number.

[0525] S1007, The UE's bottom layer determines whether the target uplink data packet is successfully transmitted.

[0526] Specifically, the UE's bottom layer determines whether the target uplink data packet is successfully transmitted in three ways:

[0527] The first way: The UE's bottom layer determines whether the target uplink data packet is successfully transmitted based on the feedback information of the RAN device; for example, the feedback information of the RAN device includes a target PDCP layer sequence number and a transmission identifier; the UE's bottom layer determines the transmission sequence number corresponding to the target PDCP layer sequence number based on the correspondence between the transmission sequence number and the PDCP layer sequence number, and the transmission sequence number is the transmission sequence number of the target uplink data packet, so the UE's bottom layer can determine that the transmission identifier included in the feedback information is the transmission identifier of the target uplink data packet, which indicates whether the RAN device receives the target uplink data packet, and the UE's bottom layer determines whether the target uplink data packet is successfully transmitted based on the transmission identifier of the target uplink data packet.

[0528] It should be noted that if the UE's bottom 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 transmission sequence number corresponding to the target PDCP layer sequence number, it means that the uplink data packet corresponding to the target PDCP layer sequence number has no corresponding transmission sequence number, in other words, the application layer of the UE adds the transmission sequence number only to the uplink data packet that needs to be retransmitted after being lost, that is, the uplink data packet without the transmission sequence number is the data packet that does not need to be retransmitted after being lost, therefore, the feedback information of the uplink data packet without the corresponding transmission sequence number can be ignored or discarded by the UE's bottom layer.

[0529] 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 does not receive the target uplink data packet, i.e., the target uplink data packet fails to be transmitted; when the transmission result of the target uplink data packet includes ACK, it means that the RAN device receives the target uplink data packet, i.e., the target uplink data packet is successfully transmitted.

[0530] Mode two: the UE determines whether the target uplink data packet is successfully transmitted based on its own information. For example, in the RLC UM mode, the UE determines whether the target uplink data packet is successfully transmitted according to the actual sending situation of the MAC layer transmission block, or the UE obtains the transmission duration of the target uplink data packet transmitted to the RAN device, that is, the used duration of the target uplink data packet transmitted to the RAN device, and if the transmission duration exceeds a second transmission duration threshold, the UE determines that the target uplink data packet is unsuccessfully transmitted.

[0531] S1008, the bottom layer of the UE sends the transmission sequence number of the target uplink data packet and the second transmission result to the application layer of the UE.

[0532] It should be noted that the bottom layer of the UE sends the transmission sequence number of the uplink data packet to the application layer of the UE at the same time as sending the second transmission result to the application layer of the UE, and the purpose of sending the transmission sequence number of the uplink data packet to the application layer of the UE is to inform the application layer that the second transmission result is the second transmission result of the uplink data packet.

[0533] S1009, the application layer of the UE determines whether the target uplink data packet needs to be retransmitted based on the second transmission result of the target uplink data packet.

[0534] Specifically, if it is determined that the target uplink data packet is successfully transmitted based on the second transmission result of the target uplink data packet, S1010 is not performed, and if it is determined that the target uplink data packet is unsuccessfully transmitted based on the transmission identifier of the target uplink data packet, whether the target uplink data packet needs to be retransmitted is determined in two cases.

[0535] Case 1: the application layer of the UE adds the transmission sequence number, and only adds the first transmission sequence number for the uplink data packet that needs to be retransmitted after packet loss. For case 1, the application layer of the UE can determine whether to retransmit the target uplink data packet in two ways:

[0536] Mode A1: if the second transmission result sent by the bottom layer of the UE to the application layer of the UE includes the fourth transmission sequence number of the target uplink data packet, the application layer of the UE determines that the target uplink data packet needs to be retransmitted.

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

[0538] Case 2: the application layer of the UE adds the third transmission sequence number to each received uplink data packet. For case 2, the UPF network element can determine whether to retransmit the target uplink data packet in two ways:

[0539] Way B1: the application layer of the UE obtains the retransmission identifier of the target uplink data packet based on the third transmission sequence number, and the third transmission sequence number and the retransmission identifier have a corresponding relationship; 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 case 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 case of transmission failure, the application layer of the UE 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 case of transmission failure, the application layer of the UE determines that the target uplink data packet does not need to be retransmitted.

[0540] Way B2: the retransmission identifier of the target uplink data packet is used to indicate that the target uplink data packet needs to be retransmitted in the case of transmission failure, the application layer of the UE obtains the retransmission delay threshold of the target uplink data packet based on the third transmission sequence number, and the third transmission sequence number and the retransmission delay threshold have a corresponding relationship; if 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, the application layer of the UE 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 of the target uplink data packet, the application layer of the UE determines that the target uplink data packet does not need to be retransmitted.

[0541] S1010: The application layer of the UE retransmits the target uplink data packet to the application server.

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

[0543] This step is optional.

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

[0545] S1012: The application layer of the UE ignores or discards the fourth information.

[0546] This step is optional.

[0547] Specifically, if the application layer of the UE determines that the target uplink data packet has been retransmitted to the application server, and if the fourth information of the application server is received at this time, since the target uplink data packet has been retransmitted to the application server, the application layer of the UE ignores or discards the fourth information.

[0548] It should be noted that the detailed description and advantages of the embodiment shown in FIG. 10 can be referred to the related description of the embodiments shown in FIG. 6 and FIG. 7, which will not be described herein.

[0549] Referring to FIG. 11, a structure diagram of a UPF network element provided by an embodiment of the present application is shown. The UPF network element 1100 is the UPF network element in FIG. 1. As shown in FIG. 11, 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 a possible implementation, the transceiver unit 1101 is configured to receive a transmission result of a downlink data packet transmitted between a RAN device and a UE and a 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 is successful.

[0551] The determination unit 1102 is configured to determine whether the downlink data packet needs to be retransmitted based on 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.

[0552] In a possible implementation, the determination unit 1102 is specifically configured to:

[0553] If the transmission result of the downlink data packet transmitted between the RAN device and the UE indicates that the transmission of the downlink data packet fails, then the determination unit 1102 is configured to determine that the downlink data packet needs to be retransmitted based on the transmission sequence number of the downlink data packet.

[0554] In a possible implementation, the acquisition unit 1103 is configured to acquire the downlink data packet.

[0555] The determination unit 1102 is further configured to determine whether the downlink data packet is a data packet that needs to be retransmitted after being lost, and if the downlink data packet is the data packet that needs to be retransmitted after being lost, then the processing unit 1104 is configured to add the transmission sequence number to the downlink data packet.

[0556] In a possible implementation, the determination unit 1102 is specifically configured to:

[0557] The determination unit 1102 is further configured to determine a retransmission identifier of the downlink data packet based on the transmission sequence number, wherein the retransmission identifier of the downlink data packet is used to represent whether the downlink data packet needs to be retransmitted in the case of transmission failure, and if the retransmission identifier of the downlink data packet indicates that the downlink data packet needs to be retransmitted, then the determination unit 1102 is configured to determine that the downlink data packet needs to be retransmitted.

[0558] In a possible implementation, the transceiver unit 1101 is further configured to receive an estimated retransmission delay of the downlink data packet from the RAN device, wherein the estimated retransmission delay of the downlink data packet is an estimated time required for retransmitting the downlink data packet to the UE.

[0559] The obtaining unit 1103 is further configured to obtain the retransmission time 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 configured to determine that the downlink data packet needs to be retransmitted if the retransmission identifier of the downlink data packet indicates that the downlink data packet needs to be retransmitted and the estimated retransmission time delay of the downlink data packet is less than or equal to the retransmission time delay threshold of the downlink data packet.

[0561] In a possible implementation, the transceiving unit 1101 is further configured to receive, from the RAN device, the estimated retransmission time delay of the downlink data packet, the estimated retransmission time delay of the downlink data packet being an estimated required time for retransmitting the downlink data packet to the UE.

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

[0563] In a possible implementation, the retransmission time delay threshold of the downlink data packet is obtained by the UPF network element 1100 from a local configuration of the UPF network element 1100, or obtained from an SMF network element or a third-party application.

[0564] In a possible implementation, the transmission result of the downlink data packet between the RAN device and the UE is determined by the RAN device based on feedback information of the UE for the downlink data packet transmitted by the RAN device to the UE, or;

[0565] The transmission result of the downlink data packet between the RAN device and the UE is determined by the RAN device based on a sending situation of a MAC layer transport block of the RAN device when the RAN device sends the downlink data packet to the UE.

[0566] In a possible implementation, the transceiving unit 1101 is further configured to retransmit the downlink data packet to the UE when it is determined that the downlink data packet needs to be retransmitted.

[0567] In a possible implementation, the transceiving unit 1101 is further configured to receive first information from the UE, the first information being sent by the UE after the UPF network element or the RAN device retransmits the downlink data packet to the UE, and the first information being used to indicate that the UE does not receive the downlink data packet.

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

[0569] In a possible implementation, the UPF network element buffers the downlink data packet, or an application server is deployed on the UPF network element.

[0570] In another possible implementation, the obtaining unit 1103 is configured to obtain the downlink data packet and obtain third information of the downlink data packet, the third information being used to determine whether the downlink data packet needs to be retransmitted after a transmission failure;

[0571] The transceiver unit 1101 is configured to send the downlink data packet and the third information to the RAN device.

[0572] In a possible implementation, the obtaining unit 1103 is configured to obtain the third information of the downlink data packet, and the third information includes:

[0573] The downlink data packet is added with a transmission serial number, and the third information includes the transmission serial number.

[0574] In a possible implementation, the determining unit 1102 is configured to determine, after obtaining the downlink data packet, whether the downlink data packet is a data packet that needs to be retransmitted after a packet loss.

[0575] The obtaining unit 1103 is configured to obtain the third information of the downlink data packet, and the third information includes:

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

[0577] In a possible implementation, the third information includes retransmission indication information of the downlink data packet, and the retransmission indication information is used to indicate that the downlink data packet needs to be retransmitted to the UE in the case of a transmission failure.

[0578] In a possible implementation, the retransmission indication information includes a transmission serial number of the downlink data packet or a retransmission identifier of the downlink data packet.

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

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

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

[0582] In a possible implementation, the transceiver unit 1101 is further configured to receive, after receiving the second information, first information from the UE, and the first information is used to indicate that the UE has not received the downlink data packet.

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

[0584] It is worth pointing out that, in which the specific function implementation of UPF network element 1100 refers to the specific description of the embodiment shown in FIG. 2 or FIG. 3, each unit or module in the UPF network element 1100 can be combined into one or several other units or modules respectively or all, or some of the units or modules therein can be further split into a plurality of units or modules with smaller functions to constitute, which can achieve the same operation without affecting the implementation of the technical effects of the embodiments of the present application. The above-mentioned units or modules are divided based on logical functions. In actual application, the function of one unit (or module) is realized by a plurality of units (or modules), or the functions of a plurality of units (or modules) are realized by one unit (or module).

[0585] Referring to FIG. 12, a structure schematic diagram of a RAN device provided by an embodiment of the present application is shown. The RAN device 1200 is the RAN device in FIG. 1. As shown in FIG. 12, 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 a downlink data packet and a transmission sequence number of the downlink data packet from a UPF network element; and transmit the downlink data packet to a UE.

[0587] The determination unit 1202 is configured to determine a transmission result of the downlink data packet transmitted between the RAN device and the UE.

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

[0589] In one possible implementation, the determination unit 1202 is specifically configured to:

[0590] determine a transmission delay of the downlink data packet transmitted to the UE; if the transmission delay of the downlink data packet exceeds a first transmission delay threshold, the RAN device determines that the downlink data packet transmission fails; wherein the transmission result of the downlink data packet includes the downlink data packet transmission failure.

[0591] In one possible implementation, the determination unit 1202 is specifically configured to:

[0592] determine the transmission result of the downlink data packet based on the sending situation of the MAC layer transmission block of the RAN device.

[0593] In a possible implementation, the processing unit 1203 is configured to record a correspondence between the transmission sequence number of the downlink data packet and a 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 further configured to receive 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 receives the downlink data packet, and the determining unit 1202 is specifically configured to determine a 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 a possible implementation, the transceiver unit 1201 is further configured to send an estimated retransmission delay of the downlink data packet to the UPF network element, the estimated retransmission delay of the downlink data packet being used to determine whether the downlink data packet needs to be retransmitted, and the estimated retransmission delay of the downlink data packet being an estimated required time for the RAN device to retransmit the downlink data packet to the UE.

[0596] In a possible 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 a GTP-U layer of the uplink data packet.

[0597] In another possible embodiment, the transceiver unit 1201 is configured to receive third information and a downlink data packet from an application server, the third information being used to determine whether the downlink data packet needs to be retransmitted after a transmission failure of the downlink data packet, and to send the downlink data packet to the UE.

[0598] The determining unit 1202 is configured to determine, based on the third information, whether the downlink data packet needs to be retransmitted to the UE when it is determined that the downlink data packet fails to be transmitted.

[0599] In a possible implementation, the third information includes retransmission indication information of the downlink data packet, the retransmission indication information being used to indicate that the downlink data packet needs to be retransmitted in the case of a transmission failure.

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

[0601] In a possible implementation, the third information includes a retransmission delay threshold of the downlink data packet, and the determining unit 1202 is specifically configured to:

[0602] obtain an estimated retransmission delay of the downlink data packet, the estimated retransmission delay of the downlink data packet being an estimated required time for the downlink data packet to be retransmitted to the UE, and determine that the downlink data packet needs to be retransmitted 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.

[0603] In an implementation, the determining unit 1202 is further configured to:

[0604] determine a transmission delay of the downlink data packet to the UE, and determine that the downlink data packet fails to be transmitted if the transmission delay of the downlink data packet exceeds a first transmission delay threshold, wherein the transmission result of the downlink data packet comprises that the downlink data packet fails to be transmitted.

[0605] In an implementation, the determining unit 1202 is further configured to:

[0606] determine the transmission result of the downlink data packet based on a sending condition of a MAC layer transmission block of the RAN device 1200, and determine whether the downlink data packet fails to be transmitted based on the transmission result of the downlink data packet.

[0607] In an implementation, the processing unit 1203 is configured to record a correspondence between the transmission sequence number of the downlink data packet and a 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 further configured to receive a feedback message from the RAN, wherein the feedback message comprises a transmission identifier and a PDCP layer sequence number, and the transmission identifier of the downlink data packet is used to indicate whether the UE receives the downlink data packet.

[0609] The determining unit 1202 is further configured to determine whether the downlink data packet fails to be transmitted 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 an implementation, the transceiver unit 1201 is further configured to send second information to a UPF network element after retransmitting the downlink data packet to the UE, wherein the second information is used to indicate that the downlink data packet has been retransmitted to the UE.

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

[0612] It is worth pointing out that the specific function implementation of the RAN device 1200 is described in the specific description of the above-mentioned embodiments of FIG. 3 or FIG. 4. The various units or modules in the RAN device 1200 can be combined into one or several other units or modules respectively or all, or some of the units or modules can be further split into a plurality of units or modules that are functionally smaller to constitute, which can achieve the same operation without affecting the implementation of the technical effects of the embodiments of the present application. The above-mentioned units or modules are divided based on logical functions. In actual application, the function of one unit (or module) is implemented by a plurality of units (or modules), or the functions of a plurality of units (or modules) are implemented by one unit (or module).

[0613] Referring to FIG. 13, a structure diagram of a UE provided by an embodiment of the present application is shown. The UE 1300 is the UE in FIG. 1. As shown in FIG. 13, the UE 1300 includes a transceiver unit 1301, a determination unit 1302, an acquisition unit 1303, and a processing unit 1304.

[0614] In one possible embodiment, the description is from the application layer of the UE 1300:

[0615] The transceiver unit 1301 is configured to receive the transmission result of the uplink data packet transmitted between the bottom layer of the UE and the RAN device and the transmission sequence number of the uplink data packet.

[0616] The determination unit 1302 is configured to determine whether the uplink data packet needs to be retransmitted based on the transmission result of the uplink data packet transmitted between the bottom layer of the UE and the RAN device and the transmission sequence number of the uplink data packet.

[0617] In one possible implementation, the acquisition unit 1303 is configured to acquire the uplink data packet.

[0618] The determination unit 1302 is configured to determine whether the uplink data packet is a data packet that needs to be retransmitted after being lost, and add the transmission sequence number to the uplink data packet if the uplink data packet is the data packet that needs to be retransmitted after being lost.

[0619] In one possible implementation, the determination unit 1302 is configured to determine whether the uplink data packet needs to be retransmitted based on the transmission result of the uplink data packet and the transmission 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 fails, it is determined that the uplink data packet needs to be retransmitted based on the transmission sequence number of the uplink data packet.

[0621] In one possible implementation, the determination unit 1302 is configured to determine whether the uplink data packet needs to be retransmitted based on the transmission sequence number of the uplink data packet, including:

[0622] determining, by the UE, the retransmission identifier of the uplink data packet based on the transmission sequence number of the uplink data packet, the retransmission identifier of the uplink data packet being used to indicate whether the uplink data packet needs to be retransmitted in case of a transmission failure; and determining, by the UE, that the uplink data packet needs to be retransmitted if the retransmission identifier of the uplink data packet indicates that the uplink data packet needs to be retransmitted.

[0623] In a possible implementation, the transceiver 1301 is further configured to receive, from the UE, an estimated retransmission delay of the uplink data packet at the underlying layer, the estimated retransmission delay of the uplink data packet being an estimated time required for retransmitting the uplink data packet to the RAN device.

[0624] The obtaining unit 1303 is further configured to obtain 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 configured to determine that the uplink data packet needs to be retransmitted if the retransmission identifier of the uplink data packet indicates that the uplink data packet needs to be retransmitted.

[0626] The determining unit 1302 is configured to determine that the uplink data packet needs to be retransmitted if the retransmission identifier of the uplink data packet 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 threshold of the uplink data packet.

[0627] In a possible implementation, the transceiver 1301 is further configured to receive, from the UE, an estimated retransmission delay of the uplink data packet at the underlying layer, the estimated retransmission delay of the uplink data packet being an estimated time required for retransmitting the uplink data packet to the RAN device.

[0628] The application layer of the UE determines that the uplink data packet needs to be retransmitted based on the transmission sequence number of the uplink data packet, and includes the following steps.

[0629] The determining unit 1302 is configured to determine the retransmission delay threshold of the uplink data packet based on the transmission sequence number of the uplink data packet, and determine that the uplink data packet needs to be retransmitted 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.

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

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

[0632] The processing unit 1304 is configured to discard or ignore the fourth information.

[0633] In a possible implementation, the transceiver 1301 is further configured to send fifth information to the bottom layer of the UE, where the fifth information is used to indicate whether the transmission result of the uplink data packet needs to be determined.

[0634] In a possible implementation, the following is described from the perspective of the bottom layer of the UE 1300:

[0635] The transceiver 1301 is configured to receive the uplink data packet and the transmission sequence number of the uplink data packet from the application layer of the UE, and send the uplink data packet to the RAN device.

[0636] The determining unit 1302 is configured to determine the transmission result of the uplink data packet transmitted between the bottom layer of the UE and the RAN device.

[0637] The transceiver 1301 is further configured to send, by the bottom layer of the UE, 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, where the transmission result of the uplink data packet and the transmission sequence number of the uplink data packet are used to determine whether the uplink data packet needs to be retransmitted.

[0638] In a possible implementation, the determining unit 1302 is configured to determine the transmission result of the uplink data packet, including:

[0639] determining a transmission delay of the uplink data packet sent to the RAN device, and determining that the uplink data packet fails to be transmitted if the transmission delay of the uplink data packet exceeds a second transmission delay threshold, where the transmission result of the uplink data packet includes that the uplink data packet fails to be transmitted.

[0640] In a possible implementation, the determining unit 1302 is configured to determine the transmission result of the uplink data packet, including:

[0641] determining the transmission result of the uplink data packet based on a sending situation of a transport block of the bottom layer of the UE.

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

[0643] The transceiver 1301 is further configured to receive a feedback message from the RAN device, where the feedback message includes a transmission identifier and a PDCP layer sequence number, and the transmission identifier is used to indicate whether the RAN device receives the uplink data packet.

[0644] The determining unit 1302 is configured to determine the transmission result of the uplink data packet, including:

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

[0646] In a possible implementation, the transceiver 1301 is further configured to send, to the application layer of the UE, an estimated retransmission time delay of the uplink data packet, the estimated retransmission time delay of the uplink data packet being used to determine whether the uplink data packet needs to be retransmitted, and the estimated retransmission time delay of the uplink data packet being an estimated required time for the bottom layer of the UE to retransmit the uplink data packet to the RAN device.

[0647] With reference to the sixth aspect, in a possible implementation, the method further includes:

[0648] The transceiver 1301 is further configured to receive fifth information sent by the application layer of the UE, the fifth information being used to indicate whether the transmission result of the uplink data packet needs to be determined, and send, to the application layer of the UE, the transmission result of the uplink data packet and the transmission sequence number of the uplink data packet.

[0649] It should be noted that the specific implementation of the UE 1300 is described in the specific description of the embodiments shown in FIG. 6 or FIG. 7. Each unit or module in the UE 1300 can be combined into one or several other units or modules respectively or all, or some of the units or modules can be further split into a plurality of units or modules with smaller functions to constitute, which can realize the same operation, and does not affect the implementation of the technical effects of the embodiments of the present application. The above-mentioned units or modules are divided based on logical functions. In actual application, the function of one unit (or module) is implemented by a plurality of units (or modules), or the functions of a plurality of units (or modules) are implemented by one unit (or module).

[0650] It should be noted that, in the present application, the transmission result of the uplink data packet refers to the transmission result of the uplink data packet between the bottom layer of the UE and the RAN device, and the transmission result of the downlink data packet refers to the transmission result of the downlink data packet between the RAN device and the UE.

[0651] Based on the description of the above method embodiments and related device embodiments, referring to FIG. 14, the present application further provides a structural schematic diagram of a communication apparatus 1400. The communication apparatus 1400 can be the UPF network element 1100 shown in FIG. 11, or the RAN device 1200 shown in FIG. 12, or the UE 1300 shown in FIG. 13. The communication apparatus 1400 shown in FIG. 14 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 in communication connection with each other through the bus 1404.

[0652] Optionally, the memory 1401 is a Read Only Memory (ROM), a static storage device, a dynamic storage device or a Random Access Memory (RAM).

[0653] The memory 1401 can store programs, and when the programs stored in the memory 1401 are executed by the processor 1402, the processor 1402 and the communication interface 1403 are configured to perform various steps of the data retransmission method of the embodiments shown in FIGS. 2-7.

[0654] The processor 1402 is a general-purpose Central Processing Unit (CPU), a microprocessor, an Application Specific Integrated Circuit (ASIC), a graphics processing unit (GPU) or one or more integrated circuits, configured to execute related programs to implement the functions required by the units in the UPF network element 1100, the RAN device 1200 or the UE 1300 in the embodiments of the present application, or to perform the data retransmission method of the embodiments shown in FIGS. 2-7.

[0655] The processor 1402 can also be an integrated circuit chip and have a signal processing capability. In implementation, the various steps of the data retransmission method shown in FIGS. 2-7 can be completed by hardware integrated logic circuit or software form instructions in the processor 1402. Alternatively, the processor 1402 is a general purpose processor, a Digital Signal Processing (DSP), an ASIC, a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic device, discrete hardware component. The processor 1402 can implement or execute the various methods, steps and logic block diagrams disclosed in the embodiments of the present application. The general purpose processor is a microprocessor or any conventional processor. The steps of the method disclosed in conjunction with the embodiments of the present application can be directly embodied as a hardware code processor to execute, or be executed by a combination of hardware and software modules in the code processor. Alternatively, the software module is located in a random access memory, a flash memory, a read only memory, a programmable read only memory or an electrically erasable programmable memory, a register or other mature storage medium in the art. The storage medium is located in the memory 1401, and the processor 1402 reads the information in the memory 1401, and combines the hardware to complete the functions required by the units included in the UPF network element 1100, the RAN device 1200 or the UE 1300 in the embodiments of the present application, or executes the data retransmission method of the embodiments shown in FIGS. 2-7.

[0656] The communication interface 1403 uses a transceiver such as but not limited to a transceiver to realize the communication between the communication apparatus 1400 and other devices or communication networks.

[0657] The bus 1404 can include a path for transmitting information between the various components (e.g., the memory 1401, the processor 1402, the communication interface 1403) of the communication apparatus 1400.

[0658] It should be noted that although the communication apparatus 1400 shown in FIG. 14 only shows the memory, the processor, the communication interface, in the specific implementation, those skilled in the art should understand that the communication apparatus 1400 also includes other devices necessary for normal operation. At the same time, according to the specific needs, those skilled in the art should understand that the communication apparatus 1400 can also include hardware devices for realizing other additional functions. In addition, those skilled in the art should understand that the communication apparatus 1400 can also only include the devices necessary for the embodiments of the present application, and does not have to include all the devices shown in FIG. 14.

[0659] The embodiment of the present application further provides a chip, which comprises a processor and a data interface, and the processor reads instructions stored on a memory through the data interface to implement the data retransmission method of the embodiment of the present application.

[0660] Optionally, as an implementation manner, the chip further comprises a memory, and the memory stores instructions, and the processor is used for executing the instructions stored on the memory, and when the instructions are executed, the processor is used for executing the data retransmission method.

[0661] The embodiment of the present application further provides a computer readable storage medium, which stores instructions, and when the instructions are executed on a computer or a processor, the computer or the processor executes one or more steps in any one of the methods.

[0662] The embodiment of the present application further provides a computer program product comprising instructions, and when the computer program product is executed on a computer or a processor, the computer or the processor executes one or more steps in any one of the methods.

[0663] Those skilled in the art will appreciate that the functions described with respect to the various illustrative logical blocks, modules, and algorithm steps described in this specification can be implemented by hardware, software, firmware, or any combination thereof. If implemented in software, the functions described with respect to the various illustrative logical blocks, modules, and steps described in this specification can be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable media can include computer-readable storage media, which corresponds to a tangible medium such as data storage media, or communication media including any medium that facilitates transfer of a computer program from one place to another, e.g., according to a communication protocol. In this manner, computer-readable media generally can correspond to (1) tangible computer- readable storage media which is non-transitory or (2) a communication medium such as a signal or carrier wave. Data storage media can be any available media that can be accessed by one or more computers or one or more processors to retrieve instructions, code, and / or data structures for implementation of the techniques described in this specification. A computer program product can include a computer-readable medium.

[0664] By way of example, and not limitation, such computer-readable storage media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage, or other magnetic storage devices, flash memory, or any other storage medium that can be used to store desired program code means in the form of instructions or data structures and that can be accessed by a computer. Also, any

[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 circuitry. Accordingly, the term "processor," as used herein can refer to any of the foregoing structure or any other structure suitable for implementation of the techniques described herein. In addition, in some aspects, the functions described herein can be provided within dedicated hardware and / or software modules configured for encoding and decoding, or incorporated in a combined codec. Also, the techniques could be fully implemented in one or more circuits or logic elements.

[0666] In several embodiments provided in the present application, it should be understood that the disclosed system, apparatus, and method can be implemented in other ways. For example, the division of the units is only a logical function division. In actual implementation, there can be another division manner. For example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. Alternatively, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interfaces, 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 displayed as units may or may not be physical units, i.e., located in one place, or distributed to multiple network units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiment scheme.

[0668] In the above embodiments, all or part can be realized by software, hardware, firmware or any combination thereof. When realized by software, all or part can be realized in the form of a computer program product. The computer program product includes one or more computer instructions. When loaded and executed on a computer, the computer program instructions generate the processes or functions according to the embodiments of the present application, all or part.

[0669] The above is only a specific implementation of the embodiments of the present application, but the protection scope of the embodiments of the present application is not limited thereto, any change or replacement within the technical scope disclosed by the embodiments of the present application should be covered within the protection scope of the embodiments of the present application. Therefore, the protection scope of the embodiments of the present application should be subject to the protection scope of the claims.

Claims

1. A data retransmission method, characterized by, The method comprises: A user plane function (UPF) network element receives a transmission result of a downlink data packet transmitted between a radio access network (RAN) device and a user equipment (UE) and a transmission sequence number of the downlink data packet from the 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 of claim 1, wherein, The UPF network element determines whether the downlink data packet needs to be retransmitted based on the transmission result and the transmission sequence number, comprising: If the transmission result of the downlink data packet indicates that the downlink data packet fails to be transmitted, 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 of claim 2, wherein, 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, comprising: The UPF network element determines a retransmission identifier of the downlink data packet, wherein the retransmission identifier of the downlink data packet indicates whether the downlink data packet needs to be retransmitted in case of transmission failure; If the retransmission identifier indicates that the downlink data packet needs to be retransmitted, the UPF network element determines that the downlink data packet needs to be retransmitted.

4. The method of claim 3, wherein, The method further comprises: The UPF network element receives an estimated retransmission delay of the downlink data packet from the RAN device, wherein the estimated retransmission delay of the downlink data packet is an estimated time required for retransmitting the downlink data packet to the UE; The UPF network element acquires a retransmission delay threshold of the downlink data packet; If the retransmission identifier indicates that the downlink data packet needs to be retransmitted, and 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. The method further comprises:

5. The method of claim 2, wherein, The UPF network element receives an estimated retransmission delay of the downlink data packet from the RAN device, wherein the estimated retransmission delay of the downlink data packet is an estimated time required for retransmitting the downlink data packet to the UE; 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, comprising: The UPF network element determines a 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. The retransmission delay threshold is acquired by the UPF network element from a local configuration of the UPF network element, or from a session management function (SMF) network element or a third-party application.

6. The method according to claim 4 or 5, characterized in that, The method further comprises:

7. The method of claim 2, wherein, 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; The UPF network element adds a transmission sequence number to the downlink data packet if the downlink data packet is a data packet that needs to be retransmitted after being lost. The transmission result is determined by the RAN device based on feedback information of the UE for the RAN device to transmit a downlink data packet to the UE, or 8. The method according to any one of claims 1 to 7, characterized in that, ​ The transmission result is determined by the RAN device based on a sending condition of a MAC transmission block of the RAN device when the RAN device sends the downlink data packet to the UE.

9. The method according to any one of claims 1 to 8, characterized in that, The method further comprises: 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 of claim 9, wherein, The method further comprises: The UPF network element receives first information from the UE, wherein the first information is sent by the UE after the UPF network element or the RAN device retransmits the downlink data packet to the UE, and the first information is used to indicate that the UE does not receive the downlink data packet. The UPF network element discards or ignores the first information.

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

12. A data retransmission method, characterized by, The method comprises: A radio access network (RAN) device receives a downlink data packet and a transmission serial number of the downlink data packet from a user plane function (UPF) network element. The RAN device sends the downlink data packet to a user equipment (UE), and determines a transmission result of the downlink data packet. The RAN device sends the transmission result of the downlink data packet and the transmission serial number of the downlink data packet to the UPF network element, wherein the transmission result of the downlink data packet and the transmission serial number of the downlink data packet are used to determine whether the downlink data packet needs to be retransmitted.

13. The method of claim 12, wherein, The RAN device determines the transmission result of the downlink data packet, comprising: The RAN device determines a transmission delay of 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 fails to be transmitted, wherein the transmission result of the downlink data packet comprises that the downlink data packet fails to be transmitted.

14. The method of claim 12, wherein, The RAN device determines the transmission result of the downlink data packet, comprising: The RAN device determines the transmission result of the downlink data packet based on a sending condition of a MAC layer transmission block of the RAN device.

15. The method of claim 12, wherein, The method further comprises: After receiving the transmission serial number of the downlink data packet, the RAN device records a correspondence between the transmission serial number and a PDCP layer serial number of the downlink data packet. The RAN device determines the transmission result of the downlink data packet, comprising: The RAN device receives a feedback message from the UE, wherein the feedback message comprises a transmission identifier and a PDCP layer serial number, and the transmission identifier is used to indicate whether the UE receives the downlink data packet. The RAN device determines the transmission result of the downlink data packet based on the correspondence, the PDCP layer serial number and the transmission identifier.

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

17. The method of claim 16, wherein, 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 a general packet radio service tunneling protocol (GTP-U) layer at a user plane of an uplink data packet.

18. A data retransmission method, characterized by, The method is applied to a communication system comprising a user equipment (UE), a radio access network (RAN) device and a user plane function (UPF) network element, and further comprising: The RAN device receives a downlink data packet and a transmission sequence number of the downlink data packet from the UPF network element; The RAN device transmits the downlink data packet to the UE and determines a transmission result of the downlink data packet transmitted 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 is successful or not; The RAN device transmits the transmission result and the 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 comprising a user equipment (UE), a radio access network (RAN) device and a user plane function (UPF) network element, and further comprising: The RAN device receives a downlink data packet and a transmission sequence number of the downlink data packet from the UPF network element; The RAN device transmits the downlink data packet to the UE and determines a transmission result of the downlink data packet transmitted 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 is successful or not; The RAN device transmits the transmission result and the transmission sequence number of the downlink data packet 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.

20. A user plane UPF network element, characterized by, The UPF network element comprises units or modules for implementing any of claims 1-11.

21. A radio access network (RAN) device, comprising: The RAN device comprises units or modules for implementing any of claims 12-17.

22. A user plane UPF network element, characterized by, A processor and a memory are included, wherein the memory is configured to store program code, and the processor is configured to execute the program code to implement the method of any of claims 1-11.

23. A radio access network (RAN) device, comprising: A processor and a memory are included, wherein the memory is configured to store program code, and the processor is configured to execute the program code to implement the method of any of claims 12-17.

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

25. A computer program product, characterised in that, The computer program product, when running on a computer, causes the computer to perform the method of any of claims 1-17. The computer program product, when running on a computer, causes the computer to perform the method of any of claims 1-17.

Images