Vehicle-mounted multimode communication system and method

Abstract

The invention belongs to the technical field of vehicle-mounted communication, and provides a vehicle-mounted multi-mode communication system and method, and the system comprises a communication function module and a multi-mode communication module. The communication function module comprises a first interface and a second interface which support different communication systems; the AT command control unit establishes communication connection with the communication unit through a first interface, and reports the connection state of the communication unit to the communication system selection unit by using a first T primitive; the train access unit automatically establishes communication connection, judges the communication availability, and reports the connection state of the train access unit to the communication system selection unit by using the first T primitive through a specified port of a second interface; and the communication system selection unit determines a communication system used for establishing communication connection with the ground equipment according to the received first T primitive and a preset priority among different communication systems. And the vehicle-mounted multi-mode communication system automatically judges the communication system and monitors the connection state in real time, so that the efficiency of establishing the communication connection between the vehicle-mounted multi-mode communication system and the ground equipment is improved.

Description

Technical Field

[0001] The present disclosure belongs to the field of vehicle-mounted communication technologies, and particularly relates to a vehicle-mounted multi-mode communication system and method. Background Art

[0002] Current vehicle-ground communication adopts a secure communication model, which can be divided into a security function module and a communication function module. The communication function module realizes reliable and transparent transmission of upper-layer security data based on a reliable transmission protocol stack. From a functional perspective, through the communication function module, isolation between security applications and network modes (network terminals) can be achieved. Multi-mode communication does not affect existing applications and security protocols, and only involves the selection and switching of the interfaces between the communication function module and communication networks.

[0003] Under current standard specifications, different data communication methods are adopted in different railway scenarios.

[0004] Urban rail transit: Signal vehicle-mounted equipment adopts WLAN (Wireless Local Area Network) and LTE-M (Cellular Internet of Things technology) networks, and data is transparently transmitted based on an Ethernet interface through an Ethernet terminal.

[0005] Suburban (regional) railway LTE (Long-Term Evolution technology) mobile communication system: Vehicle-mounted equipment communicates with the network using an Ethernet interface.

[0006] In CTCS-3 level train control system (Chinese Train Control System - level 3), high-speed rail ATO system (Automatic Train Operation system), and suburban (regional) railway train control systems, the GSM-R (Global System for Mobile Communications) circuit domain and GSM-R packet domain and the evolving 5G-R (Railway 5G Mobile Communication System) involved: The Igsm-r interface is used. GSM-R, GPRS (General Packet Radio Service technology), and 5G (Fifth Generation Mobile Communication Technology) communication modules need to support the PPP (Point-to-Point Protocol) protocol. Vehicle-mounted equipment controls the communication module with AT commands. AT commands are a set of instructions for communication interfaces and are standard instructions for analog modems. After the communication module establishes an IP (Internet Protocol) connection with the vehicle-mounted equipment, data communication is realized. At this time, the physical layer adopts an RS-422 interface.

[0007] In order to achieve multi-mode communication for vehicle-mounted equipment in the prior art, the following methods have been proposed: GSM-R circuit domain and 5G-R multi-mode communication in high-speed railways: Different network modes are indicated by adding a connection information packet SP131. There are many problems with the planned multi-mode communication integration module to be adopted, such as a single multi-mode network scenario, the newly added data packet not being applicable to multi-mode communication in the packet domain, the lack of a mature solution and commercial product for the multi-mode communication module, no standard specification support, and a long cycle for landing applications and experimental verification.

[0008] Partial customization multi-mode communication radio solution: Customize the multi-mode communication radio according to engineering requirements, but still has the following problems: It cannot meet the handover requirements of existing standard technical specifications and networks such as WLAN and LTE-M; The interface with in-vehicle equipment does not support interconnection and interoperability; The application layer of in-vehicle equipment participates in the selection of communication systems, resulting in excessive coupling between signal equipment and communication equipment, which is not conducive to product development, maintenance, and expansion. Summary of the Invention

[0009] To solve the above problems, the present disclosure provides an in-vehicle multi-mode communication system and method. The in-vehicle multi-mode communication system is provided with a first interface and a second interface, and the first interface and the second interface support different communication systems. The AT command control unit establishes a communication connection with the communication unit through the first interface, and uses the first T primitive to report the connection status of the communication unit to the communication system selection unit; The train access unit automatically establishes a communication connection, judges communication availability, and uses the first T primitive to report the connection status of the train access unit to the communication system selection unit through the specified port of the second interface; The communication system selection unit determines the communication terminal and communication system used for establishing a communication connection between the in-vehicle multi-mode communication system and the ground equipment according to the received first T primitive and the preset priority between different communication systems.

[0010] The present invention is realized through the following technical solutions: In a first aspect, an embodiment of the present disclosure provides an in-vehicle multi-mode communication system, and the system includes: a communication function module and a multi-mode communication module; The communication function module includes a communication system selection unit, an AT command control unit, a first interface, and a second interface, and the first interface and the second interface support different communication systems; The multi-mode communication module includes communication units of different communication systems and a train access unit, and the communication units of different communication systems and the train access unit are used as communication terminals of the in-vehicle multi-mode communication system to establish a communication connection with the ground equipment; The AT command control unit establishes a communication connection with the communication unit through the first interface, and uses the first T primitive to report the connection status of the communication unit to the communication system selection unit; The train access unit automatically establishes a communication connection, judges communication availability, and uses the first T primitive to report the connection status of the train access unit to the communication system selection unit through the specified port of the second interface; The communication system selection unit determines the connection status of the communication unit and the connection status of the train access unit according to the received first T primitive, and determines the communication terminal and communication system used for establishing a communication connection with the ground equipment according to the preset priority between different communication systems.

[0011] Further, The communication function module further includes a storage unit; The storage unit includes a transmission mode table for power-off storage, and the communication systems preferred by the ground device are recorded in the transmission mode table; The communication system selection unit determines the communication system preferred by the ground device through the transmission mode table, and uses the second T primitive to instruct the communication terminal corresponding to the preferred communication system to establish a communication connection with the ground device; wherein, The second T primitive includes: the type of the communication system and the communication terminal for establishing the communication connection.

[0012] Furthermore, If the communication terminal corresponding to the preferred communication system successfully establishes a communication connection with the ground device, the connection status is monitored in real time; If the communication terminal corresponding to the preferred communication system fails to successfully establish a communication connection with the ground device, the communication system selection unit sequentially sends the second T primitive to the AT command control unit and the train access unit according to the preset priority until it is determined that a communication terminal corresponding to a communication system successfully establishes a communication connection with the ground device.

[0013] Furthermore, If the communication system selection unit cannot determine the preferred communication system through the transmission mode table, the communication system selection unit sequentially sends the second T primitive to the AT command control unit and the train access unit according to the preset priority until it is determined that a communication terminal corresponding to a communication system successfully establishes a communication connection with the ground device.

[0014] Furthermore, The communication system selection unit determines the number of available communication systems according to all the received first T primitives; If the number of available communication systems is greater than one, the communication system selection unit retrieves the device number of the ground device in the transmission mode table, determines the preferred communication system through the transmission mode table, and generates a second T primitive; The communication system selection unit sends the second T primitive to the AT command control unit or the train access unit; the AT command control unit or the train access unit determines the preferred communication system and the corresponding communication terminal according to the second T primitive.

[0015] Furthermore, The first T primitive includes: the type of the communication system, the communication terminal for establishing the communication connection, and the connection status of the communication terminal; wherein, the connection status includes available, unavailable, and unknown.

[0016] Furthermore, If the communication connection between the communication terminal and the ground device is abnormal, the first T primitive is fed back to the communication mode selection unit through the AT command control unit or the train access unit, and the connection status in the first T primitive is unavailable; After receiving the first T primitive with an unavailable connection status, the communication mode selection unit sequentially sends the second T primitive to the AT command control unit and the train access unit according to the preset priority until it is determined again that a communication terminal corresponding to a communication mode has successfully established a communication connection with the ground device.

[0017] Further, The communication mode selection unit directly determines the communication mode corresponding to the first received T primitive with an available connection status, and uses it as the communication mode for the vehicle-mounted multimode communication system to establish a communication connection with the ground device; Or according to the preset priority, select a communication mode from the communication modes corresponding to the first T primitives with available connection statuses as the communication mode for the vehicle-mounted multimode communication system to establish a communication connection with the ground device.

[0018] In a second aspect, based on the same inventive concept, an embodiment of the present disclosure further provides a vehicle-mounted multimode communication method, and the method includes: The AT command control unit establishes a communication connection with the communication unit through the first interface, and reports the connection status of the communication unit to the communication mode selection unit using the first T primitive; The train access unit automatically establishes a communication connection, judges communication availability, and reports the connection status of the train access unit to the communication mode selection unit through the designated port of the second interface using the first T primitive; The communication mode selection unit determines the connection status of the communication unit and the connection status of the train access unit according to the received first T primitive, and determines the communication terminal and the communication mode for establishing a communication connection with the ground device according to the preset priority among different communication modes.

[0019] Further, The communication mode selection unit determines the communication mode preferentially used by the ground device through the transmission mode table, and uses the second T primitive to instruct the communication terminal corresponding to the preferentially used communication mode to establish a communication connection with the ground device.

[0020] Compared with the prior art, the present disclosure has the following advantages: 1. Two types of interfaces are set, which are compatible with more types of communication modes. Moreover, the vehicle-mounted multimode communication system can judge the communication mode by itself, without external instructions or manual settings; 2. In the process of selecting the communication mode, the newly added T primitive is used, which is not affected by the communication mode and is applicable to the existing communication modes and the communication modes that may be updated in the future; 3. The communication connection availability status between the vehicle-mounted multi-mode communication system and the ground equipment can be monitored in real time. When anomalies such as disconnection or network dropout occur, the communication mode can be switched in a timely manner to re-establish the communication connection. 4. Set a transmission mode table to improve the efficiency of establishing a communication connection between the vehicle-mounted multi-mode communication system and the ground equipment. Moreover, the transmission mode table can be updated according to the connection status of the ground equipment to achieve self-adaptive selection of the communication mode for engineering applications and improve the connection speed.

[0021] Other features and advantages of the present disclosure will be described in the subsequent specification. Moreover, some of them will become apparent from the specification or be understood by implementing the present disclosure. The objectives and other advantages of the present disclosure can be realized and obtained through the structures pointed out in the specification, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] To more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present disclosure. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1 It is a block diagram of a vehicle-mounted multi-mode communication system provided by an embodiment of the present disclosure; Figure 2 It is a communication schematic diagram of a vehicle-mounted multi-mode communication system provided by an embodiment of the present disclosure; Figure 3 It is another communication schematic diagram of a vehicle-mounted multi-mode communication system provided by an embodiment of the present disclosure; Figure 4 It is a communication flowchart of a vehicle-mounted multi-mode communication system provided by an embodiment of the present disclosure; Figure 5 It is a flowchart of a vehicle-mounted multi-mode communication method provided by an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present disclosure clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present disclosure with reference to the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are some, but not all, of the embodiments of the present disclosure. Based on the embodiments of the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present disclosure.

[0025] In the first aspect, Figure 1 It is a block diagram of a vehicle-mounted multi-mode communication system provided by an embodiment of the present disclosure, asFigure 1 As shown in Figure 1 , an embodiment of the present disclosure provides an in-vehicle multimode communication system, which includes a communication function module and a multimode communication module. The communication function module includes a communication mode selection unit, an AT command control unit, a first interface, and a second interface; the multimode communication module includes communication units of different communication modes and a train access unit. The communication units of different communication modes and the train access unit serve as communication terminals of the in-vehicle multimode communication system to establish a communication connection with ground equipment. The AT command control unit establishes a communication connection with the communication unit through the first interface and reports the connection status of the communication unit to the communication mode selection unit using the first T primitive. The train access unit automatically establishes a communication connection, determines communication availability, and reports the connection status of the train access unit to the communication mode selection unit using the first T primitive through a specified port of the second interface. The communication mode selection unit determines the connection status of the communication unit and the connection status of the train access unit according to the received first T primitive, and determines the communication terminal and communication mode used by the in-vehicle multimode communication system to establish a communication connection with ground equipment according to the preset priority among different communication modes.

[0026] In an embodiment of the present disclosure, the in-vehicle multimode communication system further includes a security layer, a connection management module, and an in-vehicle security application module. The security layer encrypts the data in the vehicle-ground communication, authenticates and authorizes both communication parties, and executes a series of security protocols. The connection management module can determine whether network mode switching is required according to factors such as network conditions, signal strength, and the location of in-vehicle devices, and reasonably allocate communication resources, including bandwidth, channels, etc. The in-vehicle security application module monitors the status of in-vehicle devices in real time, including communication devices, sensors, actuators, etc., and collaborates with other systems on the train.

[0027] It should be understood that the security layer, connection management module, and in-vehicle security application module of the in-vehicle multimode communication system can directly use existing setting methods, and under the existing setting methods of each module, the added first interface, second interface, and communication mode selection unit are added.

[0028] In an embodiment of the present disclosure, the communication function module includes an ALE layer (Automatic Link Establishment layer), a TCP (Transmission Control Protocol) layer, an IP layer, and a PPP protocol stack; the ALE layer is located between the communication mode selection unit and the TCP layer and is used to implement the functions of automatic link establishment and management; the TCP layer and the IP layer constitute a TCP / IP protocol stack, which is used to establish a communication connection between the communication unit and the AT command control unit.

[0029] It should be understood that the communication function module further includes a CS-TP circuit domain transport protocol stack, an X.224 protocol stack, a T.70 protocol CSPDN (circuit switched public data network), an HDLC (high-level data link control procedure), etc. The specific setting method can be adjusted and modified according to the actual situation, and multiple software protocol stacks are configured in parallel.

[0030] In the embodiments of the present disclosure, the preset priority is the priority for different communication terminals to attempt to establish a communication connection with the ground device; specifically, it includes the priority between the communication unit corresponding to the AT command control unit and the train access unit, and the priority for the communication units of different communication systems corresponding to the AT command control unit to attempt to establish a communication connection with the ground device. For example, when the communication system selection unit simultaneously receives the first T primitive sent by the AT command control unit and the train access unit, it selects the communication unit connected by the AT command control unit or the train access unit according to the preset priority to establish communication with the ground device. The multi-mode communication module includes communication units of different communication systems. The AT command control unit attempts to establish connections with the communication units of different communication systems in sequence according to the preset priority. After successfully completing the IP connection, this communication unit is considered available. The AT command control unit uses the first T primitive to report the connection status of the communication unit to the communication system selection unit. The communication system selection unit can directly determine the communication system corresponding to the first received first T primitive and use it as the communication system for the vehicle-mounted multi-mode communication system to establish a communication connection with the ground device; it can also enable all communication units to attempt to establish connections and select the communication system corresponding to one communication unit from the multiple successfully established communication units as the communication system for the vehicle-mounted multi-mode communication system to establish a communication connection with the ground device.

[0031] In the embodiments of the present disclosure, a first T primitive is added on the basis of the existing T primitive. The existing T primitive includes a connection request T-CONNECT.request, a connection response T-CONNECT.indication, a data request T-DATA.request, a data response T-DATA.indication, etc. The first T primitive is denoted as T-IPCONNECT.indication. The first T primitive includes a network identifier, a device identifier, and a connection status; the network identifier indicates the type of communication system, for example, it indicates any one of the communication systems such as GSM-R circuit domain, GPRS, 5G-R, and LTE; the device identifier indicates the communication terminal that establishes the communication connection. The communication terminal includes communication units of different communication systems and a train access unit; the connection status indicates the communication connection status of the communication terminal, and the connection status includes unknown, available, and unavailable.

[0032] It should be understood that in addition to using the first T primitive, the network registration primitive T-REGISTRATION.indication in the prior art specifications can also be used. This primitive belongs to a non-security-related primitive and is used to report the registration status of a communication terminal.

[0033] In some examples, the first interface and the second interface support different communication systems. The communication systems supported by the first interface include GSM-R, GPRS, and 5G-R, and the communication systems supported by the second interface include 5G, LTE-M, and the public network. The types of the first interface include RS-422 interface and Igsm-r interface; the RS-422 interface is a commonly used serial communication interface, and the full name of the RS-422 standard is "Electrical Characteristics of Balanced Voltage Digital Interface Circuit"; the Igsm-r interface is an interface based on the GSM-R (Global System for Mobile Communications - Railway) system. The second interface is an Ethernet interface, for example, an Ethernet 802.3 interface; the communication systems supported by the Ethernet interface include 5G, LTE-M, and the public network.

[0034] It should be understood that the first interface and the second interface can be independent different communication interface boards or integrated on one communication interface board. The specific setting method of the first interface and the second interface can be flexibly configured according to engineering applications.

[0035] In the embodiments of the present disclosure, the communication function module further includes a storage unit. A transmission mode table is stored in the storage unit, and the transmission mode table is stored in a power-off storage manner. When the vehicle-mounted device loses power, the transmission mode table will not be affected. The communication systems that the ground device preferentially uses are recorded in the transmission mode table; the communication systems that the ground device preferentially uses can be preset according to the type of the ground device or determined according to the communication history between the vehicle-mounted multi-mode communication system and the ground device. The communication system selection unit determines the communication systems that the ground device preferentially uses through the transmission mode table, and uses the second T primitive to instruct the communication terminal corresponding to the preferentially used communication system to establish a communication connection with the ground device. When the second T primitive is sent to the AT command control unit, the AT command control unit determines the communication system and the corresponding communication unit according to the second T primitive. When the second T primitive is sent to the train access unit, the train access unit configures the port of the Ethernet interface according to the second T primitive.

[0036] Further, the second T primitive is represented as T-IPCONNECT.request, and the second T primitive includes a network identifier and a device identifier; the network identifier indicates the type of communication system, for example: indicating any one of the communication systems of GSM-R circuit domain, GPRS, 5G-R, and LTE; the device identifier indicates the communication terminal corresponding to the communication system; the second T primitive may also include information such as the device code of the ground device, and the specific content can be adjusted according to the actual deployment situation.

[0037] In some examples, if the communication terminal corresponding to the preferentially used communication system successfully establishes a communication connection with the ground device, the connection status is monitored in real time; if the communication terminal corresponding to the preferentially used communication system fails to successfully establish a communication connection with the ground device, the communication system selection unit sequentially sends the second T primitive to the AT command control unit and the train access unit according to the preset priority until it is determined that a communication terminal corresponding to a communication system successfully establishes a communication connection with the ground device. If the communication system selection unit cannot determine the preferentially used communication system through the transmission mode table, the communication system selection unit sequentially sends the second T primitive to the AT command control unit and the train access unit according to the preset priority until it is determined that a communication terminal corresponding to a communication system successfully establishes a communication connection with the ground device.

[0038] Both the preset priority and the preferentially used communication system recorded in the transmission mode table can be preset and formulated by the user himself; when the communication terminal corresponding to the preferentially used communication system fails to successfully establish a communication connection with the ground device, the communication system selection unit sequentially sends the second T primitive to the AT command control unit and the train access unit according to the preset priority, and attempts to establish a communication connection with the ground device using different communication systems one by one until all communication systems are polled.

[0039] Taking the preset priority as GPRS, LTE, 5G-R, and GSM-R circuit domain in sequence as an example, the preferentially used communication system is GPRS; when the communication systems corresponding to the second T primitive are GPRS, GSM-R circuit domain, and 5G-R, the communication system selection unit sends the second T primitive to the AT command control unit; when the communication system corresponding to the second T primitive is LTE, the communication system selection unit sends the second T primitive to the train access unit.

[0040] If it is not possible to successfully establish a communication connection between the communication terminal corresponding to the GPRS communication system and the ground device, the communication system selection unit generates a second T primitive. At this time, the network identifier and device identifier of the second T primitive correspond to LTE. The second T primitive is sent to the train access unit, enabling the communication terminal (train access unit) corresponding to the LTE communication system to attempt to establish a communication connection with the ground device. If it is still not possible to successfully establish a communication connection between the communication terminal (train access unit) corresponding to the LTE communication system and the ground device, the communication system selection unit generates a second T primitive again. At this time, the network identifier and device identifier of the second T primitive correspond to 5G-R. The second T primitive is sent to the AT command control module, enabling the communication terminal corresponding to the 5G-R communication system to attempt to establish a communication connection with the ground device. If it is still not possible to successfully establish a communication connection between the communication terminal corresponding to the 5G-R communication system and the ground device, the communication system selection unit generates a second T primitive again. At this time, the network identifier and device identifier of the second T primitive correspond to the GSM-R circuit domain. The second T primitive is sent to the AT command control module, enabling the communication terminal corresponding to the GSM-R circuit domain communication system to attempt to establish a communication connection with the ground device. If, after polling all communication systems, it is still not possible to determine that a communication terminal has successfully established a communication connection with the ground device, the communication system selection unit can start again from the preferred communication system, that is, from GPRS, and send the second T primitive to the AT command control unit and the train access unit in sequence according to the preset priority, and attempt to establish a communication connection with the ground device using different communication systems one by one.

[0041] In some examples, the communication system selection unit determines the number of available communication systems based on all the received first T primitives. If the connection status in the first T primitive is available, it is determined that the communication system corresponding to this first T primitive is available. If the number of available communication systems is greater than one, the communication system selection unit retrieves the device number of the ground device in the transmission mode table, determines the preferred communication system through the transmission mode table, and generates a second T primitive. The communication system selection unit sends the second T primitive to the AT command control unit or the train access unit; the AT command control unit or the train access unit determines the preferred communication system and the corresponding communication terminal based on the second T primitive. If the communication system selection unit cannot determine the preferred communication system through the transmission mode table, the communication system selection unit sends the second T primitive to the AT command control unit and the train access unit in sequence according to the preset priority until it is determined that a communication terminal corresponding to a communication system has successfully established a communication connection with the ground device.

[0042] In some examples, if the communication connection between the communication terminal and the ground device is abnormal, the first T primitive is fed back to the communication mode selection unit through the AT command control unit or directly, and the connection status in the first T primitive is unavailable; after receiving the first T primitive with an unavailable connection status, the communication mode selection unit sequentially sends the second T primitive to the AT command control unit and the train access unit according to the preset priority until it is determined again that a communication terminal corresponding to a communication mode successfully establishes a communication connection with the ground device. The communication mode selection unit determines the target communication terminal and the target communication mode used by the vehicle-mounted multimode communication system to establish a communication connection with the ground device according to the first T primitive and the preset priority among different communication modes. When the communication connection between the target communication terminal and the ground device is abnormal, if the target communication terminal is the train access unit, the first T primitive is directly fed back to the communication mode selection unit; otherwise, the first T primitive is fed back to the communication mode selection unit through the AT command control unit, and the connection status in the first T primitive is unavailable; the communication mode selection unit sequentially sends the second T primitive to the AT command control unit and the train access unit according to the preset priority to determine a new target communication terminal and a new target communication mode for establishing a communication connection with the ground device again.

[0043] Embodiment 1: During the train operation, the vehicle-mounted multimode communication system deployed on the train needs to communicate with the ground device.

[0044] The vehicle-mounted multimode communication system provided in the embodiments of the present disclosure includes a communication function module and a multimode communication module. The communication function module includes a communication mode selection unit, an AT command control unit, a first interface, and a second interface; the multimode communication module includes communication units of different communication modes and a train access unit. The communication units of different communication modes and the train access unit are used as communication terminals of the vehicle-mounted multimode communication system to establish a communication connection with the ground device. The AT command control unit establishes a communication connection with the communication unit through the first interface and reports the connection status of the communication unit to the communication mode selection unit using the first T primitive. The train access unit automatically establishes a communication connection, judges the communication availability, and reports the connection status of the train access unit to the communication mode selection unit using the first T primitive through the designated port of the second interface. The communication mode selection unit determines the connection status of the communication unit and the connection status of the train access unit according to the received first T primitive, and determines the communication mode used by the vehicle-mounted multimode communication system to establish a communication connection with the ground device according to the preset priority among different communication modes.

[0045] In the embodiments of the present disclosure, the first interface and the second interface support different communication systems. The communication systems supported by the first interface include GSM-R, GPRS, and 5G-R, and the communication systems supported by the second interface include 5G, LTE-M, and public network. The types of the first interface include RS-422 interface and Igsm-r interface; the RS-422 interface is a commonly used serial communication interface, and the full name of the RS-422 standard is "Electrical Characteristics of Balanced Voltage Digital Interface Circuit"; the Igsm-r interface is an interface based on the GSM-R system. The second interface is an Ethernet interface, for example, Ethernet 802.3 interface; the communication systems supported by the Ethernet interface include 5G, LTE-M, and public network. Hereinafter, taking the first interface as the RS-422 interface and the second interface as the Ethernet interface as an example, the description of Embodiment 1 will be continued.

[0046] It should be understood that the first interface and the second interface can be independent as different communication interface boards, or can be integrated on one communication interface board. The specific setting method of the first interface and the second interface can be flexibly configured according to engineering applications.

[0047] In the embodiments of the present disclosure, a first T primitive is added on the basis of the existing T primitive. The first T primitive includes a network identifier, a device identifier, and a connection status; the network identifier indicates the type of the communication system, for example: indicating any one of the communication systems of GSM-R circuit domain, GPRS, 5G-R, and LTE; the device identifier indicates the communication terminal that establishes the communication connection, and the communication terminal includes communication units of different communication systems and a train access unit; the connection status indicates the communication connection status of the communication terminal. For example: after the 5G-R communication unit successfully establishes a connection with the AT command control unit, the AT command control unit uses the first T primitive to report the connection status of the 5G-R communication unit to the communication system selection unit. At this time, the network identifier of the first T primitive is 5G-R; the device identifier is the 5G-R communication unit; the connection status is that the IP connection has been successfully established and is in the available state; the connection status also includes unknown and unavailable. The unknown state is the state when the communication terminal has not attempted to establish a communication connection; after the communication terminal attempts to establish a communication connection, the available state and the unavailable state will appear. When a disconnection or reconnection occurs, the first T primitive is generated again and fed back to the communication system selection unit to update the connection status.

[0048] It should be understood that, as a communication terminal, the train access unit can automatically complete registration, network access, and communication establishment after power-on. The TCP / IP protocol stack is integrated inside the train access unit, which supports automatic dialing. The train access unit itself determines the communication availability and reports the connection status of the train access unit to the communication mode selection unit through a specified port of the Ethernet interface using the first T primitive. At this time, the network identifier of the first T primitive is determined by the train access unit. For example, LTE; the device identifier is the train access unit; the connection status is also determined by the train access unit itself. The train access unit's self-determination of communication availability includes: determining whether the train access unit can successfully complete registration, network access, network communication establishment, and automatic dialing after power-on, determining whether the TCP / IP protocol stack can work properly, determining whether it can smoothly enter the data transparent transmission mode, etc.; the specified port of the Ethernet interface can be pre-configured. For example, configure the specified port as port 25000.

[0049] Based on the received first T primitive, the communication mode selection unit determines the connection status of the communication unit and the connection status of the train access unit, and determines the communication mode used for the in-vehicle multimode communication system to establish a communication connection with the ground device according to the preset priority. The communication mode selection unit simultaneously receives the first T primitives sent by the AT command control unit and the train access unit, and selects to use the communication unit connected to the AT command control unit or the train access unit according to the preset priority to establish communication with the ground device. The multimode communication module includes communication units of different communication modes. The AT command control unit attempts to establish connections with the communication units of different communication modes in sequence according to the preset priority. After successfully completing the IP connection, it is considered that this communication unit is available. The AT command control unit uses the first T primitive to report the connection status of the communication unit to the communication mode selection unit.

[0050] In the embodiments of the present disclosure, the communication mode selection unit directly determines the communication mode corresponding to the first T primitive whose received first connection status is available as the communication mode used for the in-vehicle multimode communication system to establish a communication connection with the ground device; or selects a communication mode from the communication modes corresponding to the first T primitives with multiple available connection statuses according to the preset priority as the communication mode used for the in-vehicle multimode communication system to establish a communication connection with the ground device. For example, select a communication mode according to the network strength and signal quality of the communication terminal corresponding to the communication mode.

[0051] It should be understood that the in-vehicle multimode communication system can be an independent integrated multimode communication terminal. The in-vehicle device only performs simple communication, and the selection of the communication mode is completed by the in-vehicle multimode communication system in the integrated multimode communication terminal; the in-vehicle multimode communication system can also be integrated in the in-vehicle device to simplify the hardware.

[0052] Such as Figure 2As shown, after the in-vehicle device is started or after the multi-mode communication system is powered on, the AT command control unit controls the communication unit to automatically register through the RS-422 interface, and then, according to the registration status of the communication unit, controls it to attempt attachment and PDP (Packet Data Protocol) context activation, establish a PPP connection, and obtain an IP address. After successfully completing the IP connection, this communication unit is considered available. The AT command control unit uses the first T primitive to report the connection status of the communication unit to the communication mode selection unit, and the communication unit waits for connection; when the communication unit and the AT command control unit successfully complete the IP connection, the first T primitive is represented as T-IPCONNECT.indication / IP available.

[0053] Continue to refer to Figure 2 , after determining the communication mode between the in-vehicle multi-mode communication system and the ground device, use the corresponding communication unit to establish a TCP connection with the ground device. Establishing a TCP connection includes three steps, namely, the "three-way handshake"; the first handshake (TCP SYN): the communication unit sends a SYN packet (including the initial sequence number) to the ground device to request connection establishment. The second handshake (TCP SYN ACK): after receiving it, the ground device sends back a SYN-ACK packet (including the initial sequence number of the ground device and the confirmation of the sequence number of the communication unit). The third handshake (TCP ACK): after receiving the packet from the ground device, the communication unit sends an ACK packet (confirming the sequence number of the ground device), and the connection is established. After the communication unit and the ground device complete the TCP connection, the in-vehicle multi-mode communication system sends a secure connection request to the ground device through the communication unit. After receiving the secure connection request, the ground device sends back a secure connection confirmation to the multi-mode communication system through the communication unit. At this time, the communication connection between the multi-mode communication system and the ground device is completed, and other data interactions can be carried out.

[0054] During the communication between the in-vehicle multi-mode communication system and the ground device, if an abnormality such as radio network disconnection occurs between the communication unit and the AT command control unit, resulting in the disconnection of the PPP, communication cannot be carried out at this time. The AT command control unit uses the first T primitive to report to the communication mode selection unit that the connection status of the communication unit is unavailable. At this time, the first T primitive is represented as T-IPCONNECT.indication / IP unavailable.

[0055] In the embodiments of the present disclosure, the communication modes of the communication unit include GSM-R, GPRS, and 5G-R. Each communication mode corresponds to a communication unit. The AT command control unit attempts to establish a connection in sequence according to a preset priority, for example, the 5G-R communication unit, the GPRS communication unit, and the GSM-R communication unit. After the 5G-R communication unit successfully establishes a connection with the AT command control unit, the AT command control unit reports the connection status of the 5G-R communication unit to the communication mode selection unit using the first T primitive. The 5G-R communication unit waits for a connection. At this time, the communication mode selection unit can directly determine to use the 5G-R communication unit to establish a connection with the ground device.

[0056] As Figure 3 shown, after the train access unit is powered on, it automatically completes registration, network access, and communication establishment. The train access unit internally integrates a TCP / IP protocol stack, supports automatic dialing, and the train access unit itself determines the communication availability and reports the connection status of the train access unit to the communication mode selection unit using the first T primitive through a specified port of the Ethernet interface. When the train access unit is in the data transparent transmission mode and is in the connected state, the first T primitive sent to the communication mode selection unit is expressed as T-IPCONNECT.indication / IP available. After the train access unit reports the connection status to the communication mode selection unit, it enters the data transparent transmission mode and waits for a communication connection with the ground device. The data transparent transmission mode can transmit data from the train access unit to the ground device, keeping the original format and content of the data unchanged, without any interpretation, processing, or modification of the data, and only responsible for transmitting the data from the source to the destination.

[0057] Continuing to refer to Figure 3 , after determining that the vehicle-mounted multi-mode communication system communicates with the ground device through the train access unit, use the train access unit to establish a TCP connection with the ground device. Establishing a TCP connection includes three steps, namely, the "three-way handshake"; the first handshake (TCP SYN): The train access unit sends a SYN packet (including the initial sequence number) to the ground device to request the establishment of a connection. The second handshake (TCP SYN ACK): After receiving it, the ground device sends back a SYN-ACK packet (including the initial sequence number of the ground device and the confirmation of the sequence number of the communication unit). The third handshake (TCP ACK): After receiving the packet from the ground device, the train access unit sends an ACK packet (confirming the sequence number of the ground device), and the connection is established. After the train access unit and the ground device complete the TCP connection, the multi-mode communication system sends a secure connection request to the ground device through the train access unit. After receiving the secure connection request, the ground device feeds back a secure connection confirmation to the multi-mode communication system through the train access unit. At this time, the communication connection between the multi-mode communication system and the ground device is completed, and other data interactions can be performed.

[0058] During the communication between the in-vehicle multimode communication system and the ground equipment, if an abnormality such as network disconnection occurs in the train access unit and communication is impossible at this time, the train access unit uses the first T primitive to report to the communication mode selection unit that the connection status of the train access unit is unavailable. At this time, the first T primitive is expressed as T-IPCONNECT.indication / IPunavailable.

[0059] In the embodiment of the present disclosure, if the communication connection between the communication terminal and the ground equipment is abnormal, the first T primitive is fed back to the communication mode selection unit through the AT command control unit or directly. The connection status in the first T primitive is unavailable, which is expressed as T-IPCONNECT.indication / IP unavailable. After receiving the first T primitive with the connection status unavailable, the communication mode selection unit re-determines a communication terminal corresponding to a communication mode to successfully establish a communication connection with the ground equipment.

[0060] Embodiment 2: During the running of the train, the in-vehicle multimode communication system deployed on the train needs to communicate with the ground equipment.

[0061] In the embodiment of the present disclosure, the communication function module further includes a storage unit. A transmission mode table is stored in the storage unit. The transmission mode table is stored in the storage unit in a power-off storage manner, and the transmission mode table will not be affected when the vehicle-mounted device is powered off. The communication modes preferentially used by the ground equipment are recorded in the transmission mode table; the communication modes preferentially used by the ground equipment can be preset or determined according to the communication history between the in-vehicle multimode communication system and the ground equipment. The communication mode selection unit determines the communication mode preferentially used by the ground equipment through the transmission mode table, and uses the second T primitive to instruct the communication terminal corresponding to the preferentially used communication mode to establish a communication connection with the ground equipment.

[0062] When the in-vehicle multimode communication system communicates with the ground equipment for the first time, the communication mode of the ground equipment cannot be directly determined. The communication mode can be determined and a connection can be established in the manner of Embodiment 1, or a preferred communication mode can be determined according to the preset order between different communication modes separately set in the description corresponding to the ground equipment in the communication transmission mode table; in order to improve the efficiency of establishing a connection between the in-vehicle multimode communication system and the ground equipment, a transmission mode table is stored in the storage unit. The communication mode corresponding to the ground equipment can be quickly determined according to the transmission mode table, the connection establishment speed can be accelerated, the communication efficiency can be improved, and meaningless connection attempts can be avoided.

[0063] As shown in Table 1, Table 1 is the transmission mode table provided by the present disclosure. The transmission mode table includes the device number of the ground device, the type of communication system, and additional descriptions. The device number of the ground device is uniquely determined according to the railway industry standard specification and is a 32-bit value. The communication systems included in Table 1 are LTE and GPRS. LTE corresponds to the train access unit, and GPRS corresponds to the GPRS communication unit that establishes an IP connection with the AT command control unit. Each communication system includes three states: unknown, yes, and no. When the ground device has not established a connection with the vehicle-mounted multimode communication system, the state of the communication system is set to the initial value, which is unknown. After successfully establishing a communication connection with the ground device using this communication system, it is set to yes, and if it fails, it is set to no.

[0064] It should be understood that in the actual deployment process, the transmission mode table may include more types of communication systems and other additional descriptions. Table 1 is only an example.

[0065]

[0066] Table 1 Continuing to refer to Table 1, for the ground device with the device number NID_TSRS1, no connection has been established with the vehicle-mounted multimode communication system. Therefore, the states of both LTE and GPRS are unknown, and the preferred communication system cannot be determined. "No connection has been established" is recorded in the additional description section, and at the same time, a preferred communication system "preferred LTE connection" is preset. For the ground device with the device number NID_TSRS2, a communication connection has been successfully established using the communication system LTE. When the vehicle-mounted multimode communication system establishes a connection with the ground device with the device number NID_TSRS2 next time, LTE connection is preferred. For the ground device with the device number NID_TSRS3, a communication connection has been successfully established using the communication system GPRS. When the vehicle-mounted multimode communication system establishes a connection with the ground device with the device number NID_TSRS3 next time, GPRS connection is preferred. For the ground device with the device number NID_TSRS4, the corresponding communication scenario is a special scenario that only appears during engineering requirements or faults. LTE connection is preferred, and in other cases, LTE and GPRS can be polled and tried, and the communication system is determined according to the trial results.

[0067] Before the ground device and the vehicle-mounted multimode communication system need to establish a connection, the vehicle-mounted multimode communication system receives a wireless connection command, and the wireless connection command includes the device number of the ground device requesting to establish a connection. It can be understood that there may be other ways for the vehicle-mounted multimode communication system to determine the device number of the ground device. Only one example is given here and no further specific limitations are made.

[0068] Such asFigure 4 As shown, when the vehicle-mounted multi-mode communication system establishes a connection with a ground device, the communication mode selection unit determines the number of available communication modes according to all the received first T primitives. Each first T primitive includes the connection state corresponding to the communication mode. If the connection state of the first T primitive is the available state, the corresponding communication mode is determined to be available. If the number of available communication modes is greater than one, the communication mode selection unit retrieves the device number of the ground device in the transmission mode table, determines the communication mode to be preferentially used through the transmission mode table, generates a second T primitive, and the communication mode selection unit sends the second T primitive to the AT command control unit or the train access unit. The AT command control unit or the train access unit determines the communication mode to be preferentially used and the corresponding communication terminal according to the second T primitive. If there is only one available communication mode, the communication terminal corresponding to the unique communication mode attempts to establish a communication connection with the ground device.

[0069] If the communication terminal corresponding to the communication mode to be preferentially used determined by the transmission mode table successfully establishes a communication connection with the ground device, the connection status is monitored in real time. If the communication terminal corresponding to the communication mode to be preferentially used determined by the transmission mode table fails to successfully establish a communication connection with the ground device, the communication mode selection unit sequentially sends the second T primitive to the AT command control unit and the train access unit according to the preset priority until a communication terminal corresponding to a communication mode successfully establishes a communication connection with the ground device. After the communication terminal successfully establishes a communication connection with the ground device, the transmission mode table is updated according to the actual connection status, that is, the actually used communication mode.

[0070] If the communication mode selection unit cannot determine the communication mode to be preferentially used through the transmission mode table, the communication mode selection unit sequentially sends the second T primitive to the AT command control unit and the train access unit according to the preset priority until a communication terminal corresponding to a communication mode successfully establishes a communication connection with the ground device.

[0071] Furthermore, the second T primitive is represented as T-IPCONNECT.request. The second T primitive includes a network identifier and a device identifier. The network identifier indicates the type of the communication mode. For example, it indicates any one of the communication modes such as GSM-R circuit domain, GPRS, 5G-R, and LTE. The network identifier is confirmed through the transmission mode table. The device identifier indicates the communication terminal corresponding to the communication mode. The second T primitive may also include information such as the device code of the ground device, and the specific content can be adjusted according to the actual deployment situation.

[0072] In the embodiments of the present disclosure, a preset order is set separately according to the type of the ground device and stored in the description part corresponding to the ground device in the transmission mode table. If the communication terminal corresponding to the communication system determined by the transmission mode table as the preferred one cannot successfully establish a communication connection with the ground device, the communication mode selection unit sequentially sends the second T primitive to the AT command control unit and the train access unit according to the preset order corresponding to the ground device until it is determined that a communication terminal corresponding to a communication system successfully establishes a communication connection with the ground device. In this way, the efficiency of the in-vehicle multimode communication system connecting with the ground device is improved. When the preferred communication system cannot successfully establish a connection, targeted polling attempts are made for communication systems.

[0073] In the embodiments of the present disclosure, the transmission mode table can support at least 1024 configurable ground devices, meeting the communication requirements of various ground devices across the country. The ground devices include RBC (Radio Block Center) and TSRS (Temporary Speed Restriction Server).

[0074] Furthermore, if an abnormality occurs in the communication connection between the communication terminal and the ground device, the first T primitive is fed back to the communication mode selection unit through the AT command control unit or the train access unit, and the connection status in the first T primitive is unavailable. If the current communication terminal is the communication unit corresponding to the AT command control unit, the first T primitive is fed back to the communication mode selection unit through the AT command control unit. If the current communication terminal is the train access unit, the train access unit directly feeds back the first T primitive to the communication mode selection unit. After receiving the first T primitive with an unavailable connection status, the communication mode selection unit sequentially sends the second T primitive to the AT command control unit and the train access unit according to the preset priority until it is determined again that a communication terminal corresponding to a communication system successfully establishes a communication connection with the ground device.

[0075] It should be understood that the process of the communication mode selection unit sequentially sending the second T primitive to the AT command control unit and the train access unit according to the preset priority and determining that a communication terminal corresponding to a communication system successfully establishes a communication connection with the ground device has been described above and will not be elaborated here.

[0076] After the in-vehicle multi-mode communication system is connected to the ground device and then disconnected, after replacing the communication mode and re-establishing the communication connection, the preferred communication mode corresponding to the ground device in the transmission mode table is updated, and the status corresponding to the communication mode is changed. Continuing to refer to Table 1, for the ground device with the device number NID_TSRS1, after successfully establishing a communication connection using the communication mode LTE, the status of LTE is changed to "yes". After a period of time, a disconnection occurs, and LTE is replaced by GPRS and a communication connection is successfully established. At this time, the additional description in the transmission mode table is changed to preferentially use the GPRS network connection, the status of LTE is changed to "no", and the status of GPRS is changed to "yes"; for the ground device with the device number NID_TSRS2, after successfully establishing a communication connection using the communication mode LTE, a disconnection occurs, and LTE is replaced by GPRS and a communication connection is successfully established. At this time, the additional description in the transmission mode table is changed to preferentially use the GPRS network connection, the status of LTE is changed to "no", and the status of GPRS is changed to "yes".

[0077] In the embodiments of the present disclosure, the multi-mode in-vehicle communication system has the following advantages: 1. Two interfaces are set to be compatible with more types of communication modes. Moreover, the in-vehicle multi-mode communication system can automatically judge the communication mode without external instructions or manual settings; 2. During the process of selecting the communication mode, the newly added T primitive is used, which is not affected by the communication mode and is applicable to the existing communication modes and the communication modes that may be updated in the future; 3. The available status of the communication connection between the in-vehicle multi-mode communication system and the ground device can be monitored in real time. When abnormalities such as disconnection and network drop occur, the communication mode can be switched in time to re-establish the communication connection; 4. A transmission mode table is set to improve the efficiency of establishing a communication connection between the in-vehicle multi-mode communication system and the ground device. Moreover, the transmission mode table can be updated according to the connection situation of the ground device to realize the adaptive selection of the communication mode in engineering applications and improve the connection speed.

[0078] In the second aspect, Figure 5 is a flowchart of an in-vehicle multi-mode communication method provided by the embodiments of the present disclosure. As Figure 5 shown, based on the same inventive concept, the embodiments of the present disclosure further provide an in-vehicle multi-mode communication method, and the method includes: S1: The AT command control unit establishes a communication connection with the communication unit through the first interface and reports the connection status of the communication unit to the communication mode selection unit using the first T primitive; S2: The train access unit automatically establishes a communication connection, judges the communication availability, and reports the connection status of the train access unit to the communication mode selection unit using the first T primitive through the designated port of the second interface; S3: The communication mode selection unit determines the connection status of the communication unit and the connection status of the train access unit according to the received first T primitive, and determines the communication terminal and communication mode used to establish a communication connection with the ground device according to the preset priority between different communication modes.

[0079] In some examples, for the on-vehicle multimode communication method, the method further includes: S3': The communication mode selection unit determines the communication mode preferentially used by the ground device through the transmission mode table, and uses the second T primitive to instruct the communication terminal corresponding to the preferentially used communication mode to establish a communication connection with the ground device.

[0080] Although the present disclosure has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. A vehicle-mounted multi-mode communication system, characterized in that: The system comprises: a communication function module and a multi-mode communication module; The communication function module includes a communication standard selection unit, an AT command control unit, a first interface and a second interface, wherein the first interface and the second interface support different communication standards; the multi-mode communication module includes communication units of different communication standards and a train access unit, and the communication units of different communication standards and the train access unit are used as communication terminals of the vehicle-mounted multi-mode communication system to establish a communication connection with ground equipment; The AT command control unit establishes a communication connection with the communication unit through the first interface, and uses the first T primitive to report the connection status of the communication unit to the communication mode selection unit; The train access unit automatically establishes a communication connection, determines the communication availability, and reports the connection status of the train access unit to the communication system selection unit using the first T primitive through the designated port of the second interface; The communication standard selection unit determines the connection status of the communication unit and the connection status of the train access unit based on the received first T primitive, and determines the communication terminal and communication standard used to establish a communication connection with the ground equipment based on the preset priority between different communication standards.

2. The system according to claim 1, characterized in that The communication function module also includes a storage unit; The storage unit includes a transmission mode table stored in a power-off state, wherein the transmission mode table records the communication system preferentially used by the ground equipment; The communication mode selection unit determines the communication mode that the ground device preferentially uses through the transmission mode table, and uses the second T primitive to instruct the communication terminal corresponding to the preferential communication mode to establish a communication connection with the ground device; wherein, The second T primitive includes: the type of communication standard and the communication terminal for establishing the communication connection.

3. The system according to claim 2, characterized in that If the communication terminal corresponding to the preferred communication system successfully establishes a communication connection with the ground equipment, the connection status is monitored in real time; If the communication terminal corresponding to the preferred communication standard cannot successfully establish a communication connection with the ground equipment, the communication standard selection unit sends the second T primitive to the AT command control unit and the train access unit in sequence according to the preset priority until it is determined that a communication terminal corresponding to a communication standard has successfully established a communication connection with the ground equipment.

4. The system according to claim 2, characterized in that If the communication standard selection unit cannot determine the communication standard to be used preferentially through the transmission mode table, the communication standard selection unit sends the second T primitive to the AT command control unit and the train access unit in sequence according to the preset priority until a communication terminal corresponding to a communication standard is determined to successfully establish a communication connection with the ground equipment.

5. The system according to claim 1, characterized in that The communication standard selection unit determines the number of available communication standards according to all the first T primitives received; If the number of available communication modes is greater than one, the communication mode selection unit uses the device number of the ground device to search the transmission mode table, determines the communication mode to be used preferentially through the transmission mode table, and generates a second T primitive; The communication standard selection unit sends the second T primitive to the AT command control unit or the train access unit; the AT command control unit or the train access unit determines the communication standard and the corresponding communication terminal to be used preferentially according to the second T primitive.

6. The system according to claim 1, characterized in that The first T primitive includes: the type of communication standard, the communication terminal for establishing the communication connection and the connection status of the communication terminal; wherein the connection status includes available, unavailable and unknown.

7. The system according to any one of claims 1 to 6, characterized in that: If the communication connection between the communication terminal and the ground equipment is abnormal, the first T primitive is fed back to the communication system selection unit through the AT command control unit or the train access unit, and the connection status in the first T primitive is unavailable; After the communication standard selection unit receives the first T primitive indicating that the connection status is unavailable, it sends the second T primitive to the AT command control unit and the train access unit in sequence according to the preset priority until it is determined again that a communication terminal corresponding to a communication standard has successfully established a communication connection with the ground equipment.

8. The system according to claim 1, characterized in that The communication mode selection unit directly determines the communication mode corresponding to the first T primitive whose first connection state is available and uses it as the communication mode used by the vehicle-mounted multi-mode communication system to establish a communication connection with the ground equipment; Or according to the preset priority, a communication standard is selected from the communication standards corresponding to the first T primitives whose connection status is available, and used as the communication standard for the vehicle-mounted multi-mode communication system to establish a communication connection with the ground equipment.

9. A vehicle-mounted multi-mode communication method, characterized in that: The method comprises: The AT command control unit establishes a communication connection with the communication unit through the first interface, and uses the first T primitive to report the connection status of the communication unit to the communication mode selection unit; The train access unit automatically establishes a communication connection, determines the communication availability, and reports the connection status of the train access unit to the communication system selection unit using the first T primitive through the designated port of the second interface; The communication mode selection unit determines the connection status of the communication unit and the connection status of the train access unit according to the received first T primitive, and determines the communication terminal and communication mode used to establish a communication connection with the ground equipment according to the preset priority between different communication modes.

10. The method according to claim 9, characterized in that The method further comprises: The communication standard selection unit determines the communication standard that is preferentially used by the ground device through the transmission mode table, and uses the second T primitive to instruct the communication terminal corresponding to the preferential communication standard to establish a communication connection with the ground device.

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