Reliable data distribution method based on segmented acknowledgement mechanism in satellite-ground integrated network

Abstract

The application provides a reliable data distribution method based on a segmented acknowledgement mechanism in a satellite-ground integrated network, and belongs to the field of satellite mobile communication.The application designs an extension function module, namely a reliable GTP-U module, in a GTP-U tunnel protocol module of a satellite gNB and a UPF.Through extension of the GTP-U tunnel protocol, the application realizes the functions of mobile service data message buffering, timeout retransmission and an acknowledgement mechanism, can monitor the receiving state of the data message in real time in a physical link of satellite communication in a segmented manner, and can quickly find packet loss and retransmit in the granularity of a link segment, so that the bandwidth utilization of satellite communication is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of satellite mobile communication, and specifically refers to a reliable data distribution method based on a segmented confirmation mechanism in a satellite-ground integrated network. Background Technology

[0002] Satellite mobile communication networks and terrestrial mobile communication networks have both achieved remarkable successes after more than 30 years of independent development, but they also have their own limitations. Satellite mobile communication networks can achieve global, all-weather coverage, but they are relatively closed and have high construction and operation costs. Terrestrial mobile communication systems have a high degree of standardization and a developed global industrial chain, but their global coverage is limited, currently covering less than 6% of the Earth's surface. With the emergence of new application scenarios and diverse services, the independent development of satellite and terrestrial networks will inevitably be broken, leading to deep integration and complementary advantages between satellite and terrestrial networks.

[0003] International standardization organizations and related alliances have conducted preliminary explorations into the architecture design and key technologies of satellite-terrestrial converged networks, but some significant technical challenges remain. One hot topic is how to meet the quality of service requirements of various mobile services under the conditions of long latency and high error rate satellite links. When service data passes through satellite links, the TCP end-to-end retransmission mechanism, which performs well in terrestrial networks, can experience severe performance degradation due to excessively high RTT (Round Trip Time). Existing research adds PEP (Protocol Enhancing Proxy) nodes between satellite and terrestrial networks to perform TCP spoofing, dividing the end-to-end TCP connection into several TCP segments. However, this approach is not suitable for converged space-ground networks for the following reasons: 1) Terrestrial mobile communication systems (such as 5G) use GTP-U (GPRS Tunneling Protocol-User Plane) tunnels to implement the N3 interface between base stations and UPF (User Plane Function) network elements, and the N9 / N19 interface between UPFs. User data (including TCP packets) is encapsulated in GTP-U packets, and the intermediate nodes of the GTP-U tunnel cannot see the inner TCP packets; 2) If it is necessary to parse the inner TCP packets in the GTP-U tunnel, it will not only greatly increase the complexity of processing, but also pose security risks.

[0004] GTP-U uses the UDP protocol at the transport layer, and UDP lacks an acknowledgment and retransmission mechanism. In terrestrial networks, this doesn't present a performance issue because terrestrial network links have good quality and low latency, and good performance can be achieved using the TCP retransmission mechanism at the end nodes. However, if the GTP-U protocol is used directly on satellites, TCP performance will degrade under long RTT conditions.

[0005] In order to achieve satellite-to-ground convergence using the technical standards of terrestrial mobile communication systems, the GTP-U protocol needs to be modified to add an acknowledgment and retransmission mechanism, so as to realize reliable transmission of inter-satellite and satellite-to-ground segmented acknowledgment and retransmission, and solve the performance problem of TCP end-to-end retransmission.

[0006] Based on the above analysis, implementing a reliable satellite transmission mechanism based on GTP-U is essential for ensuring the quality of service for diverse services in a space-ground converged network. Summary of the Invention

[0007] To meet the quality of service requirements of mobile services in satellite communication networks, this invention proposes a reliable data distribution method based on a segmented acknowledgment mechanism in a satellite-terrestrial converged network. This method enables reliable data distribution based on a segmented acknowledgment mechanism in scenarios where satellite and terrestrial mobile communication systems are integrated into a single network.

[0008] The technical solution adopted in this invention is as follows:

[0009] A reliable data distribution method based on segmented acknowledgment mechanism in a space-ground integrated network includes the following steps:

[0010] Step 1: Based on the planned network topology of the satellite mobile communication system, enable the reliable GTP-U extension function for gNBs and UPFs that require reliable tunnel transmission during network deployment;

[0011] Step 2: Based on the data received by gNB and UPF, determine whether to initiate reliable tunnel transmission. If initiated, proceed to step 3; otherwise, continue receiving data and repeat step 2.

[0012] Step 3: The gNB or UPF, acting as the reliable GTP-U transmission sender, constructs a PDU session container type extension header to carry the QoS flow identifier during GTP-U / UDP / IP protocol header encapsulation, and constructs a reliable GTP-U container extension header to carry reliable transmission information for data packets. Then, it buffers the data packets in the service flow retransmission queue corresponding to the QoS flow identifier, starts a retransmission timeout timer, and retransmits the data packet if no selected ACK confirmation is received before the timer expires. If selected ACK confirmation is received, the retransmission timer for the confirmed data packet is stopped and the data packet is deleted from the service flow retransmission queue. During data packet transmission, the gNB or UPF checks whether the reliable GTP-U container extension header has a newly defined reliable GTP-U container. If so, it replies with a GTP-U data packet carrying selected ACK information, informing the GTP-U sender which data packets have been received.

[0013] Furthermore, in step 2, determining whether to initiate reliable tunnel transmission involves the following three scenarios:

[0014] 1) When the gNB receives an uplink data packet from a user terminal over the air interface, if the gNB has enabled the reliable GTP-U extension function, the QoS of this service flow is determined by packet filtering rules. If there are reliability requirements, the gNB initiates reliable tunnel transmission.

[0015] 2) When the N6 interface of the UPF receives downlink data packets from the DN network, if the UPF has enabled the reliable GTP-U extension function, the QoS of this service flow is determined by packet filtering rules. If there are reliability requirements, the UPF initiates reliable tunnel transmission.

[0016] 3) For GTP-U packets received by UPF on the N9 / N19 interface, if UPF has enabled the reliable GTP-U extension function, it checks whether there is a newly defined reliable GTP-U container in the GTP-U extension header. If so, UPF initiates a new reliable tunnel transmission for a new satellite link after terminating the reliable transmission of the previous satellite link. Otherwise, after stripping the GTP-U / UDP / IP protocol header, UPF determines whether the QoS of this service flow requires reliability through packet filtering rules. If reliable transmission is required, UPF initiates a reliable tunnel transmission.

[0017] Furthermore, in step 3, the specific method for replying with a GTP-U data packet carrying the selected ACK information is as follows:

[0018] Set the selection ACK delay time. Use a fixed timer to check whether a selection ACK packet needs to be sent every delay time. When a selection ACK packet needs to be sent, if the receiving end has a QoS flow data packet with the same QoS flow identifier to send, then include the selection ACK information to be sent in the data packet to be sent. Otherwise, send a GTP-U data packet that only carries the selection ACK information separately.

[0019] The beneficial effects of this invention are as follows:

[0020] 1. This invention designs an extended functional module, namely a reliable GTP-U module, to be added to the GTP-U tunnel protocol module of the onboard gNB and UPF. By extending the GTP-U tunnel protocol, a caching, timeout retransmission, and acknowledgment mechanism for mobile service data packets is implemented. This allows mobile services to monitor the reception status of data packets in real time on the physical links of satellite communication (GSL and ISL), and quickly detect and retransmit lost packets at the link segment level. Onboard segment-based reliable routing and forwarding significantly improves the bandwidth utilization of satellite communication.

[0021] 2. This invention considers backward compatibility. When service data is transmitted entirely through the terrestrial network, there is no need to enable the reliable GTP-U module, thus reducing processing overhead. A switch is used to enable the reliable GTP-U function. For cases where transmission is entirely through the terrestrial network, this extended function is disabled; however, for satellite mobile communication systems using satellite segment links, the reliable GTP-U extended function can be enabled for the gNB and UPF that require reliable transmission on the physical links of satellite communication, based on network topology planning. By supporting the selective enabling and disabling of the reliable GTP-U function, the flexibility of network deployment can be greatly increased.

[0022] 3. Mobile services have diverse data flows corresponding to different QoS requirements. Routing and forwarding for QoS assurance are generally based on predefined policies from different dimensions (such as user level, service type, service content, etc.). Therefore, the on-board reliable transmission supported by satellite mobile communication systems also needs to consider service awareness, that is, the onboard gNB and UPF only perform reliable routing and forwarding for service flows with reliability requirements. On the one hand, since the gNB itself can sense service QoS, for uplink data flows sent from user terminals, the gNB can dynamically decide whether to perform on-board reliable transmission for this service flow based on the service QoS awareness result. On the other hand, since the UPF itself supports Layer 3 / 4 / 7 service identification, for downlink data flows sent from the DN side, the UPF can dynamically decide whether to perform on-board reliable transmission for this service flow based on the service QoS result obtained after service identification. In this way, satellite mobile communication systems can provide service-aware on-board reliable routing and forwarding. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of an application scenario for a satellite mobile communication system based on an authentication mechanism.

[0024] Figure 2 This is a schematic diagram of the extended protocol message definition based on the GTP-U acknowledgment mechanism. Detailed Implementation

[0025] Currently, the 3GPP standard satellite mobile communication system architecture proposes gNB and UPF uplink at the base station. The N3 interface between gNB and UPF, and the N9 / N19 interface between UPFs, all use the GTP-U tunneling protocol to encapsulate and carry the raw mobile service data packets, shielding the user terminal IP and DN (Data Network) service IP, providing a unified routing and forwarding entry point for onboard mobile service data packets. However, GTP-U and its underlying UDP and IP protocols do not provide any reliable transmission guarantees and do not retransmit lost packets. If the encapsulated raw data packet transmission uses a connection-oriented reliable transmission protocol like TCP, packet loss retransmission can only be performed at the end node. This leads to performance issues in long-distance transmission of mobile service data packets between satellite and ground. The perceived end-to-end reliable transmission is too slow, and because packet loss in satellite communication networks is much more severe than in terrestrial mobile communication networks, TCP congestion control easily deteriorates. Numerous end-to-end retransmissions cause the transmission window to essentially stagnate, resulting in very poor transmission performance.

[0026] Therefore, given the urgent need for reliable onboard transmission capabilities in satellite mobile communication systems to improve end-to-end service performance, this invention designs an extended functional module, namely the reliable GTP-U module, by adding a GTP-U tunnel protocol module to the onboard gNB and UPF. By extending the GTP-U tunnel protocol, caching, timeout retransmission, and acknowledgment mechanisms for mobile service data packets are implemented. This allows mobile services to monitor the reception status of data packets in real-time on the physical links of satellite communication (GSL and ISL), and quickly detect and retransmit lost packets at the link segment level. Onboard segment-based reliable routing and forwarding significantly improves the bandwidth utilization of satellite communication.

[0027] For backward compatibility, when service data is transmitted entirely through the terrestrial network, there is no need to enable the reliable GTP-U module to reduce processing overhead. A switch is used to enable the reliable GTP-U function. For scenarios using only the terrestrial network, this extended function is disabled; however, for satellite mobile communication systems using satellite segment links, the reliable GTP-U extended function can be enabled for the gNB and UPF that require reliable transmission on the physical links of satellite communication, based on the network topology plan. By supporting the selective enabling and disabling of the reliable GTP-U function, the flexibility of network deployment can be greatly increased.

[0028] Mobile services involve diverse data flows with varying QoS requirements. Routing and forwarding for QoS assurance are typically based on predefined policies across different dimensions (such as user level, service type, and service content). Therefore, the onboard reliable transmission supported by satellite mobile communication systems also needs to consider service awareness; that is, the onboard gNB and UPF only perform reliable routing and forwarding for service flows with reliability requirements. On one hand, because the gNB itself can sense service QoS, for uplink data flows sent from user terminals, the gNB can dynamically decide whether to perform onboard reliable transmission for this service flow based on the service QoS perception result. On the other hand, because the UPF itself supports Layer 3 / 4 / 7 service identification, for downlink data flows sent from the DN side, the UPF can dynamically decide whether to perform onboard reliable transmission for this service flow based on the service QoS result obtained after service identification. In this way, satellite mobile communication systems can provide service-aware onboard reliable routing and forwarding.

[0029] In view of this, a reliable data distribution method based on a segmented confirmation mechanism in a satellite-ground fusion network is proposed. The steps of this method are as follows:

[0030] Step 1: Based on the planned network topology of the satellite mobile communication system, enable the reliable GTP-U extension function for gNB and UPF that require reliable tunnel transmission during network deployment.

[0031] Step 2: The gNB or UPF initiates service-aware on-board reliable routing forwarding in the following three situations:

[0032] 1) When the gNB receives an uplink data packet from a user terminal over the air interface, if the gNB has enabled the reliable GTP-U extension function, it needs to determine the QoS of this service flow through packet filtering rules (such as Layer 3 / 4 / 7 service identification). If reliability is required, the gNB initiates reliable tunnel transmission.

[0033] 2) When the N6 interface of the UPF receives downlink data packets from the DN network, if the UPF has enabled the reliable GTP-U extension function, it is necessary to determine the QoS of this service flow through packet filtering rules (such as Layer 3 / 4 / 7 service identification). If there are reliability requirements, the UPF initiates reliable tunnel transmission.

[0034] 3) When the UPF receives GTP-U packets on the N9 / N19 interface, if the UPF has enabled the reliable GTP-U extension function, it needs to check whether the GTP-U extension header contains a newly defined reliable GTP-U container. If reliable information is found, the UPF initiates a new reliable tunnel transmission for the satellite link after terminating the reliable transmission of the previous satellite link. Otherwise, after stripping the GTP-U / UDP / IP protocol headers, the UPF needs to determine whether the QoS of this service flow requires reliability through packet filtering rules (such as Layer 3 / 4 / 7 service identification). If reliable transmission is required, the UPF initiates a reliable tunnel transmission.

[0035] Step 3: The gNB or UPF, acting as the reliable transmission transmitter for GTP-U, needs to implement the basic functions of buffering, timeout retransmission, and carrying reliable transmission information.

[0036] Packet data is cached in the corresponding QFI (QoS Flow ID) service flow retransmission queue.

[0037] Start a retransmission timeout timer. If no SACK (Selective ACK) acknowledgment is received by the timer expiration date, retransmit the data packet.

[0038] When encapsulating the GTP-U / UDP / IP protocol header, in addition to constructing the PDU session container type extension header to carry the QFI, a newly defined reliable GTP-U container extension header also needs to be constructed to carry reliable transmission information such as packet number and packet offset of the data packet.

[0039] As a reliable GTP-U receiver, the gNB or UPF needs to check if the GTP-U extension header contains a newly defined reliable GTP-U container. If reliable information is found, it needs to reply with a GTP-U packet carrying SACK information, informing the GTP-U sender which packets have been received. To reduce network traffic, SACK is not sent to the sender immediately after receiving a GTP-U packet. Instead, a delayed acknowledgment mechanism is used, for example, setting the SACK delay time to 100ms. However, this 100ms is not a time delay required after receiving the packet; the system has a fixed timer that checks every 100ms to determine if a SACK packet needs to be sent. This allows SACK to merge and acknowledge received packets. Additionally, if the receiver has QoS stream packets with the same QFI to send, it can include SACK information in the transmitted packets. However, it's crucial to ensure the packet length does not exceed the MTU (Mean Transmission Unit), i.e., avoid fragmentation. Otherwise, a separate GTP-U packet carrying only SACK information should be sent.

[0040] As the reliable transmission sender of GTP-U, the gNB or UPF also needs to process SACK confirmation information, stop the retransmission timer for the confirmed data packets, and delete the data packets from the buffer queue.

[0041] It's important to note that SACK acknowledgment actually includes both ACK and NACK functions. It informs the sender which consecutive and non-consecutive data packets have been received, and also indicates which packets were missed and need to be retransmitted. In high-bandwidth, low-latency scenarios, the logic for packet loss detection becomes more critical; therefore, this method employs the SACK acknowledgment mechanism.

[0042] To implement the above method, a low-Earth orbit satellite mobile communication system is provided below, including equipment such as UE (User Equipment, terminal), onboard gNB, onboard UPF, ground UPF, 5GC control plane, and ground DN network equipment.

[0043] UE terminals and DN network equipment (such as FTP servers) are the service initiation and reception points; the spaceborne gNB can realize the protocol processing function of the radio access network part of the satellite mobile communication system, and transmit services, signaling and test verification data between the 5G core network and the UE terminal; both the spaceborne UPF and the terrestrial UPF are co-located network elements of PSA (PDU Session Anchor) and I-UPF (Intermediate UPF), serving as forwarding nodes for service data. PSA is the PDU session anchor, and I-UPF is the relay point, which is often used for Xn / N2 handover and service offloading.

[0044] Figure 1 This diagram illustrates an application scenario of this method, showcasing a network architecture for real-time segmented reliable transmission on physical satellite communication links (Inter-satellite Link (ISL) and Satellite-to-Ground Link (GSL)) in a low-Earth orbit satellite mobile communication system. The N3 interface of the onboard gNB and the N3, N9, and N19 interfaces of the onboard / ground UPF all employ GTP-U / UDP / IP tunnel links. These ISLs (such as the N3 tunnel link between the onboard gNB of Satellite 1 and the onboard UPF of Satellite 5, or the N19 tunnel link between the onboard UPF of Satellite 4 and the onboard UPF of Satellite 5) and GSLs (such as the N9 tunnel link between the onboard UPF of Satellite 4 and the ground UPF) achieve reliable transmission of each segment of the N3 / N9 / N19 tunnels by enabling the added reliable GTP-U extension module. This solves the performance degradation problem caused by only being able to perform packet loss detection and retransmission end-to-end without a reliable GTP-U extension module.

[0045] A low-Earth orbit (LEO) satellite mobile communication system based on an acknowledgment mechanism includes a UE terminal, a satellite mobile platform, a 5GC control plane, a terrestrial UPF, and a service server in the DN network. The satellite mobile platform includes an onboard gNB and an onboard UPF. Both the onboard gNB and the onboard UPF have reliable GTP-U extension functionality enabled. The terrestrial UPF, through a gateway station, interconnects with the onboard UPF to provide an access point to the DN network and also has reliable GTP-U extension functionality enabled.

[0046] Considering the bandwidth consumption of ACK, the SACK acknowledgment mechanism adopts a delayed acknowledgment mode. That is, instead of replying immediately after receiving a data packet, the system starts a periodic timer (e.g., the interval is set to 100ms). After the timer expires, it checks whether a SACK packet needs to be sent. If so, a SACK packet can include multiple packet acknowledgment information. If there is a data packet to be forwarded at this time, the SACK acknowledgment information can be carried in the newly defined GTP-U extension header reliable GTP-U container of the forwarding packet without the need for fragmentation.

[0047] There are two typical application scenarios: 1) Inter-UE communication, such as Figure 1 1) Data flow between UE1 and UE3 (forwarding path indicated by the short dashed line); 2) UE access to DN network devices, such as... Figure 1 Data flow of UE2 accessing the service server in the DN network (forwarding path indicated by dotted line).

[0048] In the first scenario, communication occurs between UEs. UE1 selects the onboard gNB of satellite 1 and the onboard UPF of satellite 4 to transmit mobile services, while UE3 selects the onboard gNB of satellite 3 and the onboard UPF of satellite 5. Therefore, UE1's session anchor point is on the onboard UPF of satellite 5, and UE3's session anchor point is on the onboard UPF of satellite 4. The data streams for communication between UE1 and UE3 need to be carried through the N3 interface GTP-U tunnels between satellites 1 and 5, and between satellites 3 and 4, as well as the N19 interface GTP-U tunnel between satellites 4 and 5. By using the reliable GTP-U extension function, the data packets for communication between UE1 and UE3 can be reliably transmitted in real time on the aforementioned inter-satellite links (ISL).

[0049] In the second scenario, the UE accesses DN network equipment. UE2 selects the onboard gNB of satellite 2, the onboard UPF of satellite 4, and the terrestrial UPF to transmit mobile services. The data flow of UE2 accessing the service server in the DN network needs to be carried through the N3 interface GTP-U tunnel between satellite 2 and satellite 4, and the N9 interface GTP-U tunnel between satellite 4 and the terrestrial UPF. The forwarding of data packets for communication between UE2 and the service server can be reliably transmitted in real time on the aforementioned inter-satellite link (ISL) and the satellite-to-ground link (GSL) between the satellite and the gateway station.

[0050] Both the onboard gNB on satellites 1 / 2 / 3 and the ground-based UPF need to initiate service-aware onboard reliable routing forwarding. By detecting packet filtering (such as layer 3 / 4 / 7 service identification), it is determined that this service flow QFI has reliable transmission requirements. In the GTP-U tunnel protocol encapsulation process, in addition to adding a GTP-U extension header PDU session container to carry QFI, a newly defined GTP-U extension header also needs to be added.

[0051] The onboard UPF on satellites 4 and 5 can determine the reliable routing requirements of the service flow based on the reliable GTP-U container extension header carried in the received GTP-U messages. After terminating the reliable transmission of the previous satellite link, it initiates a new reliable tunnel transmission for the satellite link, adding a reliable GTP-U container extension header to carry reliable transmission information such as packet number and packet offset. After the GTP-U tunnel protocol packet header is encapsulated, the data packets are buffered in the retransmission queue identified by QFI, and a retransmission timer is started.

[0052] The onboard gNB or UPF on satellites 1 / 2 / 3 / 4 / 5, as well as the ground-based UPF, all need to act as receivers for reliable GTP-U transmission, processing reliable transmission information (such as packet count and packet offset) in the reliable GTP-U container extension header and marking packet reception status information. After the SACK periodic timer expires, a SACK acknowledgment message is sent to the sender.

[0053] As the reliable transmission sender of GTP-U, the gNB or UPF also needs to process SACK confirmation information, stop the retransmission timer for the confirmed data packets, and delete the data packets from the buffer queue.

[0054] The key point of this method is the extension of the GTP-U protocol. Figure 2 This is a schematic diagram of the GTP-U extended protocol message definition for this method. It shows the G-PDU protocol stack for transmitting user plane data, the GTPv1-U header definition, the extended header type values, the GTP-U extended header format, and the newly added GTP-U extended header reliable GTP-U container definition. The main ideas are as follows:

[0055] (1) The GTPv1-U header contains optional parameters for extension headers, represented by E and Next Extension Header Type. The value of E is 1, indicating that there is an extension header following. Therefore, a new extension header type is added, namely 0x10000110, which represents a reliable GTP-U container. This reliable GTP-U extension header type indicates that the extension header will carry information about reliable GTP-U transmission.

[0056] (2) Based on the standard GTP-U extension header format, a new Extension Header Content protocol format is defined for the newly added extension header type reliable GTP-U container, as described in detail below:

[0057] 1) Type (2 bits): GTP-U reliable information type. Value 0 (NONE) means no reliable information encapsulation, value 1 (PKT) means reliable information encapsulation is performed on the forwarded data packet, value 2 (SACK) means reliable information encapsulation is performed on SACK, and value 3 (PKT and SACK) means reliable information encapsulation is performed on the forwarded data packet and SACK is encapsulated at the same time.

[0058] 2) PKN Length (3 bits): Packet sequence number length. When the Type value is 1 or 3, the value is non-zero.

[0059] 3) Offset Length (3 bits): The offset length of the packet sequence number. When the Type value is 1 or 3, the value is non-zero.

[0060] 4) Packet Number: Packet sequence number, starting from 1 and incrementing. The number of bytes in this parameter is determined by the value of PKN Length.

[0061] 5) Offset Number: Packet sequence number offset, used to identify the original sequence number of the retransmitted packet. The number of bytes for this parameter is determined by the value of Offset Length.

[0062] 6) SACK Length (6 bits): Number of SACK blocks. When the Type value is 2 or 3, the value is non-zero. The maximum number of SACK blocks is 63.

[0063] 7) Left Edge of Block: The sequence number of the first data packet in a contiguous / non-contiguous block.

[0064] 8) Right Edge of Block: The sequence number of the last data packet in a contiguous / non-contiguous block.

[0065] It should be noted that, in order to save network bandwidth as much as possible, this method uses variable-length Packet Number and Offset Number when designing the reliable GTP-U container extension header format. Moreover, it allows a GTP-U packet to carry both payload information (i.e., T-PDU) and SACK acknowledgment information.

[0066] In summary, this invention presents an original low-orbit satellite mobile communication system based on an acknowledgment mechanism. By enabling the newly added reliable GTP-U extension module function on the onboard gNB, onboard UPF, and ground UPF network elements, it achieves real-time segmented reliable transmission on the satellite communication physical links (inter-satellite link ISL and satellite-to-ground link GSL).

Claims

1. A reliable data distribution method based on a segmented confirmation mechanism in a space-ground integrated network, characterized in that, Includes the following steps: Step 1: Based on the planned network topology of the satellite mobile communication system, enable the reliable GTP-U extension function for gNBs and UPFs that require reliable tunnel transmission during network deployment; Step 2: Based on the data received by gNB and UPF, determine whether to initiate reliable tunnel transmission. If initiated, proceed to step 3; otherwise, continue receiving data and repeat step 2. Step 3: The gNB or UPF, acting as the reliable GTP-U transmission sender, constructs a PDU session container type extension header to carry the QoS flow identifier during GTP-U / UDP / IP protocol header encapsulation, and constructs a reliable GTP-U container extension header to carry reliable transmission information for data packets. Then, it buffers the data packets in the service flow retransmission queue corresponding to the QoS flow identifier, starts a retransmission timeout timer, and retransmits the data packet if no selected ACK confirmation is received before the timer expires. If selected ACK confirmation is received, the retransmission timer for the confirmed data packet is stopped and the data packet is deleted from the service flow retransmission queue. During data packet transmission, the gNB or UPF checks whether the reliable GTP-U container extension header has a newly defined reliable GTP-U container. If so, it replies with a GTP-U data packet carrying selected ACK information, informing the GTP-U sender which data packets have been received.

2. The reliable data distribution method based on segmented confirmation mechanism in a satellite-ground fusion network according to claim 1, characterized in that, In step 2, the determination of whether to initiate reliable tunnel transmission is divided into the following three cases: 1) When the gNB receives an uplink data packet from a user terminal over the air interface, if the gNB has enabled the reliable GTP-U extension function, the QoS of this service flow is determined by packet filtering rules. If there are reliability requirements, the gNB initiates reliable tunnel transmission. 2) When the N6 interface of the UPF receives downlink data packets from the DN network, if the UPF has enabled the reliable GTP-U extension function, the QoS of this service flow is determined by packet filtering rules. If there are reliability requirements, the UPF initiates reliable tunnel transmission. 3) For GTP-U packets received by UPF on the N9 / N19 interface, if UPF has enabled the reliable GTP-U extension function, it checks whether there is a newly defined reliable GTP-U container in the GTP-U extension header. If so, UPF initiates a new reliable tunnel transmission for a new satellite link after terminating the reliable transmission of the previous satellite link. Otherwise, after stripping the GTP-U / UDP / IP protocol header, UPF determines whether the QoS of this service flow requires reliability through packet filtering rules. If reliable transmission is required, UPF initiates a reliable tunnel transmission.

3. The reliable data distribution method based on segmented confirmation mechanism in a satellite-ground fusion network according to claim 1, characterized in that, In step 3, the specific method for replying with a GTP-U data packet carrying the selected ACK information is as follows: Set the selection ACK delay time. Use a fixed timer to check whether a selection ACK packet needs to be sent every delay time. When a selection ACK packet needs to be sent, if the receiving end has a QoS flow data packet with the same QoS flow identifier to send, then include the selection ACK information to be sent in the data packet to be sent. Otherwise, send a GTP-U data packet that only carries the selection ACK information separately.

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