Method and device for enhancing reliability of ATG communication system

Abstract

The invention provides a method and a device for enhancing the reliability of an ATG (Automatic Train Generation) communication system, which belong to the technical field of wireless communication, and are characterized in that two physically isolated data transmission paths are formed by establishing wireless dual connections with two different base stations for an air terminal, and two independent protocol data unit sessions are established on a core network side. The system realizes differential transmission according to the service type and the network load state: for a flight control signal, the same repeated data packet is simultaneously sent on double paths, so that the reliability is improved; for application layer data, different data packets are sent in parallel through double paths in low load so as to improve the rate, and single path transmission with better signal quality is selected in medium and high load. According to the method, space diversity is effectively utilized to resist interference, transmission efficiency and resource utilization are both considered, and the method is suitable for 4G / 5G and future 6G air-space-ground integrated networks.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and in particular to a method and apparatus for enhancing the reliability of air-to-ground communication systems. Specifically, this invention is applicable to ATG communication systems based on wireless access technologies such as 4G LTE, 5G NR, and 5G Advanced, and can also be extended to other air-to-ground private wireless network systems, V2X communication, and future 6G integrated air-to-ground networks. Background Technology

[0002] ATG (Air-to-Ground), also known as A2G, is a communication system that establishes a direct wireless connection between ground base stations deployed along flight routes and aircraft. Compared to flight route coverage systems composed of satellites and ground stations, it offers advantages such as rapid deployment, low cost, large bandwidth, and low latency, and is less affected by high-altitude weather conditions. It has become a crucial communication method for the development of the low-altitude economy. With the rise of the low-altitude economy concept, ATG based on 4G / 5G wireless network technology has also developed. With 3GPP incorporating ATG into its standard in Release 18, ATG systems will operate within existing terrestrial network frequency bands; however, the problem of interference and coexistence between ATG and terrestrial networks is becoming increasingly prominent.

[0003] In ATG systems, because airborne radio signals propagate virtually unobstructed, aircraft at high altitudes often simultaneously receive line-of-sight signals from multiple ground base stations, which can easily lead to system-wide interference. Furthermore, sidelobe signals from ground base stations, external interference from other terrestrial or satellite communication systems, and even malicious interference, can further degrade communication link quality, causing data transmission delays or packet loss, severely impacting the reliable transmission of critical services such as flight control commands and air traffic management.

[0004] Currently, traditional methods for improving wireless link reliability mainly include time-domain retransmission, reducing coding rate, or employing equipment redundancy backup mechanisms. However, these methods have the following drawbacks: Repeated transmission or low bit rate transmission: Although it can improve the reliability of a single link, the overall transmission efficiency is significantly reduced, which cannot meet the high bandwidth service requirements such as high-definition video backhaul. Equipment redundancy backup: While it can improve system availability, it increases network construction costs and equipment complexity, and cannot fundamentally solve the multipath interference problem; Traditional handover mechanism: During aircraft movement, the "disconnect first, reconnect later" handover method will cause user plane data interruption, which cannot meet the strict requirements of flight control services for continuous communication.

[0005] Therefore, there is an urgent need in this field for a solution that can effectively improve the reliability of ATG communication systems while maintaining high transmission efficiency, especially a system-level optimization solution when facing multipath interference, mobility management and differentiated service type requirements.

[0006] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide a solution that can effectively improve the reliability of ATG communication systems while maintaining high transmission efficiency.

[0008] To achieve the above objectives, the present invention provides the following solution: A method for enhancing the reliability of an ATG communication system includes the following steps: To establish a wireless dual connection between an air terminal and two different base stations, wherein the air terminal establishes a first connection with a first base station as the master node and a second connection with a second base station as the auxiliary node, thereby forming two physically isolated data transmission paths. On the core network side, two independent Protocol Data Unit (PDU) sessions are established for the air terminal, wherein the first PDU session is transmitted via the first base station and the second PDU session is transmitted via the second base station. Identify the service type of the data to be transmitted by the air terminal; If the service type is flight control signal, the same duplicate data packets are sent simultaneously on the two physically isolated data transmission paths to improve transmission reliability. If the service type is application layer data, then one of the following modes will be selected for data transmission based on the network load status: Mode 1: Under low network load conditions, different data packets are sent simultaneously on the two physically isolated data transmission paths to improve the transmission rate; Mode 2: Under medium to high network load conditions, select the path with better signal quality from the two physically isolated data transmission paths to send data packets.

[0009] Optionally, the steps for establishing a wireless dual connection by the over-the-air terminal specifically include: The air terminal first successfully establishes a connection with the first base station and configures it as the master node; The air terminal continuously measures the signal quality of neighboring cells; When the air terminal detects that the signal quality of the second base station meets the threshold condition of the A4 event, it reports a measurement report to the network side. Based on the measurement report, the network side initiates a secondary node addition process to establish a second connection between the air terminal and the second base station.

[0010] Optionally, the flight control signal corresponds to a service with a QCI / 5QI value of 75, and the application layer data corresponds to services with other QCI / 5QI values; the identification of the service type is based on the QCI / 5QI identifier transmitted by the core network to the wireless base station through the NG interface or S1 interface.

[0011] Optionally, in the transmission of the flight control signal, the first connection uses a primary cell group as the bearer, the second connection uses a secondary cell group as the bearer, and the same duplicate data packets are transmitted independently through the primary cell group and the secondary cell group.

[0012] Optionally, in the transmission of application layer data, when mode one is selected, a split bearer or independent bearer method is adopted to transmit different data streams through the first connection and the second connection respectively.

[0013] Optionally, the step of selecting a path with better signal quality includes: For uplink transmission, the air terminal selects the path with less path loss for uplink data transmission based on the path loss estimation of the first base station and the second base station. For downlink transmission, the network-side scheduler selects the path with better channel quality for downlink scheduling of the air terminal based on the channel state information reported by the air terminal regarding the first connection and the second connection.

[0014] Optionally, the total uplink transmit power of the air terminal is dynamically allocated between the first connection and the second connection; The allocation strategies include: equal power distribution, allocation proportional to uplink rate demand, or allocation inversely proportional to path loss.

[0015] An apparatus for enhancing the reliability of an ATG communication system, comprising: The dual-connection establishment module is configured to establish wireless dual connections for the air terminal with the first base station as the master node and the second base station as the auxiliary node, forming two physically isolated data transmission paths. The dual-session management module is configured to establish and maintain two independent Protocol Data Unit (PDU) sessions for the air terminal on the core network side, wherein the two PDU sessions are respectively transmitted via the first base station and the second base station; The service identification module is configured to identify the service type of the data to be transmitted by the air terminal and distinguish between flight control signals and application layer data. Data transmission control module, configured for: When the service type is flight control signal, the two physically isolated data transmission paths are controlled to send the same duplicate data packets simultaneously. When the service type is application layer data, depending on the network load status, the two paths are controlled to send different data packets simultaneously, or the path with better signal quality is selected to send data packets.

[0016] Optionally, the dual-connection establishment module is further configured to: After successfully establishing a connection with the first base station, the air terminal is controlled to continuously measure the neighboring cell signal. In response to the measurement report reported by the air terminal that the signal quality of the second base station meets the threshold condition of the A4 event, the network side is triggered to execute the secondary node addition process to establish the second connection.

[0017] Optionally, the communication system in which the device is used employs a back-to-back antenna deployment method to form a network, wherein the two antennas of each station cover the flight path at a 180-degree angle and are respectively connected to different distributed units to provide the two physically isolated data transmission paths.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method and apparatus for enhancing the reliability of an ATG (Air-to-Ground) communication system. Its core innovation lies in establishing wireless dual-connectivity and dual-protocol data unit sessions, and implementing differentiated data transmission strategies based on service type and network load conditions, resulting in the following significant technical advantages: Significantly improves the reliability of critical business transmission: For critical services such as flight control signals, the method of simultaneously sending the same duplicate data packets on two physically isolated paths is adopted. Spatial diversity is used to effectively combat multipath interference and signal fading, which greatly reduces the risk of data loss and delay and ensures flight safety.

[0019] Flexible adaptation to business and network conditions, balancing efficiency and resource utilization: For application layer data, the system can intelligently select the transmission mode according to the network load: under low load, different data packets are transmitted in parallel through dual paths to improve throughput; under medium to high load, single-path transmission with better signal quality is preferred, which not only ensures user experience but also improves network resource utilization efficiency.

[0020] Optimize mobility and power management: A smooth dual-connectivity establishment is achieved through a secondary node addition mechanism based on A4 events, reducing handover interruptions; uplink power can be dynamically allocated according to path loss, rate requirements, etc., further improving link performance and energy efficiency.

[0021] The system is highly feasible for deployment: it supports the use of existing 4G / 5G network architecture and standard interfaces, and can build physically isolated paths through back-to-back antenna networking, which has good engineering feasibility and compatibility. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram illustrating the simultaneous transmission of the same data packet through two data paths, as provided in an embodiment of the present invention.

[0024] Figure 2 This is a schematic diagram illustrating the simultaneous transmission of different data packets through two data paths, as provided in an embodiment of the present invention.

[0025] Figure 3 This is a schematic diagram illustrating how each AUE selects a data path with good signal quality to send data packets, as provided in an embodiment of the present invention.

[0026] Figure 4 This is a schematic diagram of the DU-RU connection method provided in an embodiment of the present invention.

[0027] Figure 5 This is a schematic diagram illustrating another networking method from an embodiment of the present invention.

[0028] Figure 6 This is a schematic diagram of dual connections at different locations on the flight path, provided as an embodiment of the present invention.

[0029] Figure 7 This is a schematic diagram of faults and interferences comparing single-point faults with system reliability, provided for embodiments of the present invention.

[0030] Figure 8 This diagram illustrates the comparison between traditional methods with single-connection single-point failure and system reliability.

[0031] Figure 9 This is a schematic diagram illustrating the process of adding an SN as provided by the present invention.

[0032] Figure 10 This is a schematic diagram of the SN release process provided by the present invention.

[0033] Figure 11 This is a schematic diagram of the MN switching process provided by the present invention.

[0034] Figure 12This is a schematic diagram of the end-to-end QoS processing flow corresponding to the PDU Session provided in an embodiment of the present invention.

[0035] Figure 13 This is a schematic diagram of the PDU Session establishment process provided in an embodiment of the present invention.

[0036] Figure 14 This is a schematic diagram of the PDU Session release process provided in an embodiment of the present invention.

[0037] Figure 15 This is a schematic diagram of the uplink and downlink link selection process provided in an embodiment of the present invention. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] The purpose of this invention is to provide a solution that can effectively improve the reliability of ATG communication systems while maintaining high transmission efficiency.

[0040] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] Example 1: This example provides a method and apparatus for enhancing the reliability of an ATG communication system. This example fully utilizes the characteristic of multiple LOS paths in an ATG system to establish dual connections for the terminal, transforming interference paths into signal transmission paths and improving communication reliability.

[0042] This embodiment can effectively distinguish between flight control signals (QCI / 5QI=75) and other data applications (QCI / 5QI=other values). For flight control signals, dual connections are used to send duplicate data to improve reliability, while for other data applications, dual connections are used to send different data to improve transmission rate (low network load) or select a connection with good link quality to transmit data (medium and high network load). This embodiment proposes a dual PDU session method, in which the two PDU channels run on two physically isolated sets of physical devices that serve as backups for each other, thereby enhancing reliability and without sacrificing operating efficiency compared to traditional backup methods.

[0043] UAV communication can be broadly divided into: C2 communication and application layer data communication; C2 communication is used to transmit flight control commands and air traffic management information, including aircraft status information, location information, flight route planning or changes, obstacle avoidance or collision avoidance, and dynamic geofencing.

[0044] The type of application-layer data communication depends on the drone's purpose, such as a short message (package delivered) or high-definition real-time video. Generally, the uplink bandwidth requirement for application-layer data is greater than the downlink bandwidth requirement.

[0045] Table 1 Communication Data Table

[0046] C2 communication: Improves reliability through two physically isolated data paths: such as... Figure 1 As shown.

[0047] Because C2 services require reliability, two independent physical links are established between AUE and UTM / UOM. The path includes UPF, CU, DU and RU as well as interconnected N6 / N3 / F1 / FH / Uu connections. For each AUE, dual connectivity is established simultaneously with two cells on the network side, corresponding to end-to-end dual PDU sessions (including two independent DRBs and N3 tunnels) to enhance reliability; For each data packet between AUE and UTM / UOM, the sending end retransmits it on both physical links, and the receiving end can submit it upwards as soon as it receives a data packet on either link within the receiving window.

[0048] Application Layer Communication-1: Improving speed through two physically isolated data paths. For example... Figure 2 As shown.

[0049] For other application data, similar to the ground terminal GUE, the AUE can utilize the established dual connection / dual PDUssession to send different data packets on two data paths, maximizing the transmission rate to support typical applications such as high-definition video backhaul. Since the two links share the AUE uplink transmit power, the uplink power can be statically divided equally or allocated inversely according to the path loss magnitude. If the uplink transmit power of the AUR is limited, one of the radio links can be selected at a certain time to transmit uplink data. The selection can be based on the path loss estimate of the AUE, that is, the radio link with the smaller path loss is used for transmission.

[0050] Application Layer Communication - 2: Selecting a path with good signal quality to improve communication quality. For example... Figure 3 As shown.

[0051] When wireless resources in the air network are scarce, in order to support more schedulable users, regardless of uplink or downlink scheduling, wireless links with good signal quality are selected for scheduling.

[0052] Although L3 still maintains a dual-link configuration, at any given time, the AUE's uplink or downlink uses only one radio link. That is, only one cell schedules the AUE's uplink resources, and only one cell schedules the AUE's downlink resources. The two cells can be the same or different.

[0053] In general, the number of schedulable users / capacity supported by the network can be doubled.

[0054] For ATG networks, base station antennas transmit into the air at a certain upward tilt angle; Since there are no obstructions to wireless signals in the air, large wireless communication terminals on drones have multiple LOS signal paths, while for ground networks, there is usually only one LOS path (from the terminal to the current serving base station).

[0055] like Figure 4 As shown, for coverage of fixed flight routes, base stations can be networked in a "back-to-back" antenna configuration, meaning that at each site, two antennas are positioned at a 180-degree angle and parallel to the flight route for coverage.

[0056] Each site's left-side covered RU / antenna (blue) and right-side covered RU / antenna (yellow) connect to two different DUs, thereby obtaining two independent reachable links.

[0057] AUE establishes connections with two cells simultaneously via NR-DC. The cells in between can be on the same frequency or different frequencies (frequency reuse factor N=2). The network with different frequencies has lower latency and higher reliability.

[0058] The specific implementation mechanism of NR-DC: Referring to protocol 3GPP 37.340, NR-DC, or NR-NR Dual Connectivity, means that in the NR-RAN architecture, a terminal connects to one gNB as the MN and simultaneously connects to another gNB as the SN. Furthermore, a terminal can also establish dual connections with the same gNB, where that gNB simultaneously serves as both the MN and SN.

[0059] In this context, MN stands for Master Node, which provides control plane connectivity to the 5G core network in NR-DC; SN stands for Secondary Node, which does not have control plane connectivity to the 5G core network and only provides additional user plane channels for terminals.

[0060] Terminals typically establish dual connectivity (NR-DC) in two steps. The first connection established between the terminal and the network side is the MN. After the MN is successfully established, the SN can be added by reporting the A4 event (i.e., the neighboring cell signal quality is higher than a specified threshold); the SN can be released by reporting the A2 event (the serving cell signal quality is lower than a specified threshold); and the handover process can be triggered by reporting the A3 event (the neighboring cell service quality is higher than the SpCell service quality by a specified offset value) or the A5 event (the serving cell signal quality is lower than a specified threshold, while the neighboring cell signal quality is higher than a specified threshold).

[0061] The process of adding an SN is as follows: Figure 9 As shown. The release process of SN is as follows. Figure 10 As shown.

[0062] MN switching process as follows Figure 11 As shown.

[0063] Within MN and SN, multiple bearer methods are provided (as shown in the figure below): MCG bearer, SCG bearer, or split bearer.

[0064] For the C2 communication mentioned in this invention, MN uses MCG Bearer and SN uses SCG Bearer, so that they are independent of each other and increase reliability; For the application layer communication-1 mentioned in this invention, method a) MN uses MCG Bearer and SN uses SCGB Bearer; method b) uses a Split Bearer and imports a portion of the data into SN (or MN) through the Xn interface. For the application layer communication-1 mentioned in this invention, MN can use MCG Bearer or SN can use SCG Bearer; either one is acceptable.

[0065] Another perspective on networking methods is illustrated in the diagram below. Figure 5 As shown.

[0066] Minimize the number of handovers and improve link quality: After the AUE accesses the network, it can maintain dual connectivity at different locations on the flight path through SN addition, SN / MN Modification and SN deletion, and always maintain a communication link at the time of transition, without interruption of user plane data. Furthermore, during the movement, the traditional network handover was not used at all. The handover adopted the "disconnect first, then reconnect" method, which inevitably caused interruption of user plane data. like Figure 6In the diagram shown, uppercase letters represent the base station / BS side beam and lowercase letters represent the terminal / AUE side beam. There are two radio links available at any location along the flight path.

[0067] like Figure 7 As shown, fault 1 - RRU or AAU on the tower fails, and the orange radio link of AUE1 is affected, but it can still communicate using the blue radio link; fault 2 - DU1 fails, and the blue radio links of AUE1, AUE2 and AUE3 are all unavailable, but all three have orange radio links to maintain a connection with the network.

[0068] Interference 3 - Due to the presence of GUE (Ground UE) in the building, which is our ordinary mobile phone, the elevation angle of the ground cellular network signal is increased, causing interference to AUE3. The blue wireless link is suppressed and becomes unusable, but AUE3 can still use the orange wireless link to maintain a connection with the network.

[0069] like Figure 8 As shown, fault 1 - the RRU or AAU on the tower fails, at which time the communication of the affected AUE1 is interrupted; Fault 2 - DU1 fault, at which point communication between AUE1 and AUE2 is interrupted.

[0070] Fault 3 - Due to the presence of GUE (Ground UE) in the building, which is the same as our ordinary mobile phone, the elevation angle of the ground cellular network signal is increased, causing interference to AUE3. AUE3 communication may be interrupted or greatly affected (such as the occurrence of high block error rate).

[0071] Dual PDU Session Establishment and Maintenance Process: The PDU Session corresponds to the end-to-end QoS processing flow (from the core network 5GC to the 5G RAN to the UE), such as... Figure 12 As shown, one PDU Session corresponds to one UPF network element and connects the radio base station NB (NodeB) and the terminal UE. One PDU Session can contain one or more Radio Bearers, and one Radio Bearer can contain one or more QoS Flows.

[0072] The establishment and release of dual PDU sessions are no different from other management processes; they can be considered a simple superposition of two independent single PDU session establishment and release signaling processes. In the implementation of this invention, the establishment of the second PDU session can begin after the first PDU session is established. Furthermore, the UPF is a user plane network element of the core network 5GC, responsible for packet processing and forwarding, but the PDU session establishment process involves multiple core network control plane network elements; the details are irrelevant to this invention. Figure 13 and Figure 14 The diagram shows the process of establishing and releasing a PDU Session initiated by the UE.

[0073] Specific implementations of power allocation algorithms (such as dynamic power allocation strategies): Power allocation is initially equal, for example, if the total transmit power of the UE is 23dBm, each path (leg) is initially 20dBm.

[0074] During communication, the UE reports its PHR (Power Headroom), which is the UE's remaining transmit power. The network-side scheduling and power control algorithms can refer to this value to determine which path to compensate, especially when the uplink power requirements of two paths cannot be met simultaneously. The network side needs to make a decision, and specific measurements include, but are not limited to: (1) Divide the remaining power equally; (2) The power is distributed proportionally to the uplink speed on both sides, that is, the higher the uplink speed, the more power is allocated. (3) The power is distributed proportionally to the road loss on both sides, that is, the greater the road loss, the more power is allocated.

[0075] QCI / 5QI differentiates scheduling strategies (e.g., how the scheduler distinguishes and processes different services): QCI stands for QoS Class Identifier, a service quality level identifier used in 4G LTE or 5G NSA. A specific QCI value typically corresponds to metrics such as the default priority level, packet delay budget, and packet error rate. 5QI stands for 5G QoS Identifier, with essentially the same meaning as QCI. The mapping table between QCI values ​​and service types and requirements is defined in 3GPP 23.203, while the mapping table for 5QI values ​​is defined in 3GPP 23.501. Besides the QCI / 5QI mappings to service types and requirements specified in the protocols, some values ​​are reserved for operators to define their own service types and requirements.

[0076] QCI / 5QI values ​​are transmitted from the core network to the radio base station scheduler via the S1 interface (4G or 5G NSA) or the NG interface (5G SA). The scheduler will consider the service type and requirements corresponding to the value to allocate the corresponding radio resources, such as the number of RBs and the MCS level.

[0077] The uplink and downlink link selections are slightly different, as follows: Figure 15 The flowchart shown.

[0078] The present invention can detect and analyze using air interface protocols (Uu) or wired interface protocols such as N6, N3, F1 and Open FH (Front Haul) to determine the use of the methods mentioned in the present invention.

[0079] The method mentioned in this invention can also be determined by the device topology and connection method.

[0080] In addition to ATG based on 4G and 5G wireless access technologies, this invention is also applicable to other proprietary, air-to-ground wireless access technologies and networking technologies. As an integrated air-space-ground communication technology is one of the goals of 6G, this invention is also applicable to future 6G wireless communication standards.

[0081] V2X networks and ATG networks have many similarities, and this invention is also applicable to V2X communication systems.

[0082] This technical solution can also exceed the limitations of the current 3GPP protocol, allowing the AU3 terminal to establish more than two connections with the network side.

[0083] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0084] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for enhancing the reliability of an ATG communication system, characterized in that, Includes the following steps: To establish a wireless dual connection between an air terminal and two different base stations, wherein the air terminal establishes a first connection with a first base station as the master node and a second connection with a second base station as the auxiliary node, thereby forming two physically isolated data transmission paths. On the core network side, two independent Protocol Data Unit (PDU) sessions are established for the air terminal, wherein the first PDU session is transmitted via the first base station and the second PDU session is transmitted via the second base station. Identify the service type of the data to be transmitted by the air terminal; If the service type is flight control signal, the same duplicate data packets are sent simultaneously on the two physically isolated data transmission paths to improve transmission reliability. If the service type is application layer data, then one of the following modes will be selected for data transmission based on the network load status: Mode 1: Under low network load conditions, different data packets are sent simultaneously on the two physically isolated data transmission paths to improve the transmission rate; Mode 2: Under medium to high network load conditions, select the path with better signal quality from the two physically isolated data transmission paths to send data packets.

2. The method for enhancing the reliability of an ATG communication system according to claim 1, characterized in that, The specific steps for an over-the-air terminal to establish a wireless dual connection include: The air terminal first successfully establishes a connection with the first base station and configures it as the master node; The air terminal continuously measures the signal quality of neighboring cells; When the air terminal detects that the signal quality of the second base station meets the threshold condition of the A4 event, it reports a measurement report to the network side. Based on the measurement report, the network side initiates a secondary node addition process to establish a second connection between the air terminal and the second base station.

3. The method for enhancing the reliability of an ATG communication system according to any one of claims 1-2, characterized in that, The flight control signal corresponds to a service with a QCI / 5QI value of 75, and the application layer data corresponds to services with other QCI / 5QI values; the identification of the service type is based on the QCI / 5QI identifier transmitted by the core network to the wireless base station through the NG interface or S1 interface.

4. The method for enhancing the reliability of an ATG communication system according to claim 1, characterized in that, In the transmission of the flight control signal, the first connection uses a primary cell group as the bearer, the second connection uses a secondary cell group as the bearer, and the same duplicate data packets are transmitted independently through the primary cell group and the secondary cell group.

5. The method for enhancing the reliability of an ATG communication system according to claim 1, characterized in that, In the transmission of application layer data, when mode one is selected, a split bearer or independent bearer method is adopted to transmit different data streams through the first connection and the second connection respectively.

6. The method for enhancing the reliability of an ATG communication system according to claim 1, characterized in that, The step of selecting the path with better signal quality includes: For uplink transmission, the air terminal selects the path with less path loss for uplink data transmission based on the path loss estimation of the first base station and the second base station. For downlink transmission, the network-side scheduler selects the path with better channel quality for downlink scheduling of the air terminal based on the channel state information reported by the air terminal regarding the first connection and the second connection.

7. The method for enhancing the reliability of an ATG communication system according to claim 1, characterized in that, The total uplink transmit power of the air terminal is dynamically allocated between the first connection and the second connection; The allocation strategies include: equal power distribution, allocation proportional to uplink rate demand, or allocation inversely proportional to path loss.

8. A device for enhancing the reliability of an ATG communication system, characterized in that, include: The dual-connection establishment module is configured to establish wireless dual connections for the air terminal with the first base station as the master node and the second base station as the auxiliary node, forming two physically isolated data transmission paths. The dual-session management module is configured to establish and maintain two independent Protocol Data Unit (PDU) sessions for the air terminal on the core network side, wherein the two PDU sessions are respectively transmitted via the first base station and the second base station; The service identification module is configured to identify the service type of the data to be transmitted by the air terminal and distinguish between flight control signals and application layer data. Data transmission control module, configured for: When the service type is flight control signal, the two physically isolated data transmission paths are controlled to send the same duplicate data packets simultaneously. When the service type is application layer data, depending on the network load status, the two paths are controlled to send different data packets simultaneously, or the path with better signal quality is selected to send data packets.

9. The apparatus for enhancing the reliability of an ATG communication system according to claim 8, characterized in that, The dual-connection establishment module is further configured to: After successfully establishing a connection with the first base station, the air terminal is controlled to continuously measure the neighboring cell signal. In response to the measurement report reported by the air terminal that the signal quality of the second base station meets the threshold condition of the A4 event, the network side is triggered to execute the secondary node addition process to establish the second connection.

10. The apparatus for enhancing the reliability of an ATG communication system according to claim 8, characterized in that, The communication system in which the device is used employs a back-to-back antenna deployment method to form a network. Each site has two antennas that cover the flight path at a 180-degree angle and are connected to different distributed units to provide the two physically isolated data transmission paths.

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