Reliable train-ground data transmission method for urban rail transit

Abstract

The invention discloses a reliable train-ground data transmission method for urban rail transit, which comprises the steps of train-ground link accessibility confirmation, train-ground reliable communication link initialization, train-ground reliable communication exception handling mechanism, train-ground reliable communication data integrity verification mechanism and recording of the current data transmission progress. And the method has the capability of recovering breakpoint resume in real time. According to the method, the stability of train-ground data transmission can be ensured under the condition that a communication channel is unstable, the breakpoint resume capability is achieved, and the integrity of the data is ensured; according to the method, special hardware does not need to be installed, meanwhile, the method is not restricted by network formulating and system software, the problems of data repeated transmission and serious packet falling in the multi-vehicle-ground data transmission process can be solved, and the data quality is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle - to - ground wireless communication protocols, and specifically, to a reliable vehicle - to - ground data transmission method for urban rail transit. Background Art

[0002] In the current rapidly developing urbanization process, the urban rail transit system, as the backbone of urban public transportation, undertakes the important mission of alleviating traffic congestion and promoting the sustainable development of the city. With the continuous progress of information technology, achieving efficient and reliable vehicle - to - ground data transmission has become the key to improving the intelligent level of the urban rail transit system. Vehicle - to - ground data transmission, that is, the information exchange between trains and ground control centers or trackside equipment, covers multiple aspects such as train status monitoring, signal control, operation dispatching, and passenger information services. Its reliability directly affects the safety, efficiency, and service quality of the rail transit system.

[0003] Traditionally, vehicle - to - ground communication in urban rail transit mainly relied on wired technologies such as track circuits and loops. However, these methods have problems such as poor flexibility, limited scalability, and high maintenance costs. With the rapid development of wireless communication technology, especially the application of LTE (Long - Term Evolution) and its evolved versions LTE - M, NB - IoT, and future 5G technology, it provides a broader development space for vehicle - to - ground communication.

[0004] However, the urban rail transit environment is complex and changeable, including factors such as high - speed movement, tunnel occlusion, and electromagnetic interference, which pose severe challenges to the stability and reliability of wireless communication. Currently, some companies have adopted the method of installing communication boards to achieve reliable vehicle - to - ground communication, but it needs to be bound to hardware and does not conduct much development on the communication protocol itself.

[0005] Therefore, it is particularly important to develop a reliable vehicle - to - ground data transmission method for urban rail transit. Such a method needs to comprehensively consider the establishment of a trusted communication method, a data integrity verification mechanism, and a data breakpoint resumption mechanism. Summary of the Invention

[0006] The purpose of the present invention is to provide a reliable vehicle - to - ground data transmission method for urban rail transit.

[0007] The technical solution for achieving the purpose of the present invention is: A reliable vehicle - to - ground data transmission method for urban rail transit, including:

[0008] Before constructing the vehicle - to - ground link, a two - way link reachability detection mechanism that simultaneously uses the reachability verification from the on - vehicle device to the ground server and the reachability verification from the ground server to the on - vehicle device is adopted to realize the detection of the channel reachability between the on - vehicle and ground devices;

[0009] After confirming that the channel is reachable, a single communication handshake and waving mechanism is used to simplify the initialization process of reliable vehicle-ground communication connection, initialize the vehicle-ground communication link, and establish vehicle-ground communication;

[0010] A unique data transmission code and a transmission data packet number are created at the communication packet header, and a check code is created at the communication packet tail. With the help of the unique code and the data packet number during the transmission process, data transmission progress records and real-time breakpoint recovery and continuation are realized; at the same time, with the help of the transmission unique code, the transmission data packet number and the check code, abnormal situations in the transmission project can be judged, including whether the abnormality is caused by the vehicle-mounted equipment or the ground equipment, and the specific communication stage where the failure occurs;

[0011] When a transmission anomaly occurs, the data transmission unique code, transmission data packet number and check code are used to classify and handle the anomaly, ensure the continuity of the transmission content, and eliminate repeated transmission of the same content;

[0012] The unique code, data packet number and check code information are integrated to achieve data integrity verification for reliable vehicle-to-ground communication, improve the quality of vehicle-to-ground transmission data, and eliminate low-quality data caused by discarded packets and channel fluctuations.

[0013] The simplified initialization process of the reliable vehicle-ground communication connection simplifies the link initialization mechanism of three handshakes and four waves to a reliable communication connection that only requires one handshake and one wave between the vehicle-mounted device and the ground server.

[0014] Furthermore, after the communication initialization is completed, a unique data transmission code is generated. The code consists of a 6-bit random number and is included in the packet header of each message interaction in the vehicle-ground trusted communication. Data transmission can only be continued when the data unique code is consistent. Once the data transmission unique code changes, the on-board and ground equipment immediately terminate the current transmission progress and discard all historical data in this transmission.

[0015] Furthermore, after the communication initialization is completed, a transmission data packet number is generated, and the number increases with each transmission process until the number is consistent with the total number of data packets. After any abnormal situation occurs, the current number will be maintained until the communication is restored and the data transmission unique code remains unchanged. It will be accumulated repeatedly; if the data transmission unique code changes, the transmission data packet number will become invalid and reset to 0.

[0016] Furthermore, after the communication initialization is completed, a check code is generated and placed at the end of the packet. The CRC32 mechanism is used, and the check code is calculated for each packet of data and each packet of data is checked. When the number of the data packet to be transmitted is the same as the total number of transmitted packets, the total data is checked. If the data check passes, it means that the current transmission is successful. If the check fails, it means that the data transmission has failed, and the historical data is discarded.

[0017] Furthermore, the data transmission progress record can record the current transmission progress. Based on the unique data transmission code and the data packet number, it can respectively confirm the current transmission progress of the in-vehicle device and the ground server. When the unique data transmission code remains unchanged, it can count the current transmitted packet number and the total number of packets, and use the ratio of the two as the real-time record of the transmission progress to achieve the data transmission record function.

[0018] Furthermore, the real-time resume of interrupted transmission means that when the unique data transmission code remains unchanged, the data packet number accumulates normally, but the checksum fails, the ground server resumes the interrupted transmission based on the previous transmission progress of the terminal; during the transmission process, the unique data transmission code remains unchanged, and the data packet number increases until the total number of packets. After the CRC check passes, the interrupted transmission is completed.

[0019] Furthermore, based on the unique data transmission code, the data packet number and the checksum, the following abnormal situations are accurately located:

[0020] The data download request from the ground server fails to reach the in-vehicle device: The ground server sends a data download request to the in-vehicle device and sends the unique data transmission code in the request header; if the ground server does not receive the return status from the in-vehicle device within 1 minute, it will send a request with the same unique data transmission code to the in-vehicle device again; repeat the attempt 10 times. If the connection still cannot be established, the current download request is abandoned; the current unique data transmission code is discarded;

[0021] The return status of the in-vehicle device fails to reach the ground server: The in-vehicle device replies that the data is ready to the ground server, but the reply status fails to reach the ground server; if the in-vehicle device has not received the request for the first packet of data from the ground server within 1 minute, it will reply to the ground again that the data preparation is completed; repeat the attempt 10 times. If the connection still cannot be established, the current download request is abandoned; the current unique data transmission code is discarded;

[0022] The request for the first packet of data from the ground server fails to reach the in-vehicle device: The ground server sends a data request to the in-vehicle device. If the ground server does not receive the return status from the in-vehicle device within 1 minute, it will send a request with the same unique data transmission code to the in-vehicle device again; repeat the attempt 10 times. If the connection still cannot be established, the current download request is abandoned; the current unique data transmission code is retained, and the current transmission failure packet sequence number is recorded. When the link is reachable next time, the data is retransmitted based on the ability to resume the interrupted transmission.

[0023] The first packet of data sent back by the vehicle-mounted device fails to reach the ground server: The vehicle-mounted device sends the requested data packet to the ground server, but the request packet fails to reach the ground server. It attempts to resend 10 times. If the transmission still cannot succeed, the unique encoding of this data transmission is retained, and the serial number of the currently failed packet is recorded. When the link is reachable next time, the ground server retransmits the data based on the ability to resume from the breakpoint.

[0024] The data transmission completed by the ground server fails to reach the vehicle-mounted device: The ground server confirms the end of the data transmission and sends the data transmission end status to the vehicle-mounted device. If the vehicle-mounted device has sent all data packets and has not received the data transmission end message sent by the ground server within 20 minutes, it ends the current data transmission by itself, retains the unique encoding of this data transmission, and when the link is reachable next time, the ground server retransmits the data based on the ability to resume from the breakpoint.

[0025] The data transmission termination request from the ground server fails to reach the vehicle-mounted device: The ground server confirms the interruption of the data transmission and sends a data transmission interruption request to the vehicle-mounted device, but the interruption request is not received by the vehicle-mounted device. After not receiving the ground server message within 1 minute, it will send the same data to the ground server again. It attempts to resend 10 times. If no reply is received after 10 attempts, the transmission of this packet of data is abandoned. The unique encoding of this data transmission is retained, and the serial number of the currently failed packet is recorded. When the link is reachable next time, the ground server will attempt 10 times again until the transmission is completed.

[0026] Further, the elimination of duplicate transmissions of the same content means that, based on the ability to resume from the breakpoint, the packet numbers are accumulated normally according to the packet numbers, and the situation of duplicate transmissions of the same packet number is avoided.

[0027] Further, for the data integrity verification of reliable vehicle-ground communication, under normal data conditions, that is, when the data unique code remains unchanged, the packet numbers are accumulated to the total number, and the verification code passes, reliable vehicle-ground data transmission is achieved. If any of the three verifications fails, it is analyzed and disposed of according to the abnormal situation.

[0028] Compared with the prior art, the significant advantages of the present invention are: (1) The present invention does not require the use of special hardware and belongs to the application layer software, having a broad application prospect; (2) The present invention proposes a triple verification mechanism, which can ensure the reliable transmission of vehicle-ground data at the application layer, eliminate duplicate transmissions of data, and enhance the usage efficiency of the vehicle-ground network channel. Description of the Drawings

[0029] Figure 1 It is a schematic diagram for detecting the reachability of the vehicle-ground bidirectional link.

[0030] Figure 2 It is a schematic diagram of normal vehicle-ground communication.

[0031] Figure 3 Schematic diagram for sending data to the ground when there is no vehicle-mounted available data

[0032] Figure 4 Schematic diagram for the ground server to actively interrupt data transmission

[0033] Figure 5 Schematic diagram for the data download request from the ground server not reaching the vehicle-mounted device

[0034] Figure 6 Schematic diagram for the vehicle-mounted device's feedback status not reaching the ground server

[0035] Figure 7 Schematic diagram for the ground server's request for the first packet of data not reaching the vehicle-mounted device

[0036] Figure 8 Schematic diagram for the vehicle-mounted device's feedback of the first packet of data not reaching the ground server

[0037] Figure 9 Schematic diagram for the ground server's transmission completion not reaching the vehicle-mounted device

[0038] Figure 10 Schematic diagram for the ground server's transmission termination request not reaching the vehicle-mounted device

[0039] Figure 11 Flowchart of a reliable vehicle-ground data transmission method for urban rail transit Detailed implementation manner

[0040] The present invention does not require the use of special hardware, proposes a triple verification mechanism, can ensure the reliable transmission of vehicle-ground data at the application layer, eliminate duplicate data transmission, and enhance the usage efficiency of the vehicle-ground network channel. The method includes: detecting the reachability of the vehicle-ground bidirectional link; simplifying the handshake process between the vehicle and the ground; performing data transmission; detecting vehicle-ground transmission anomalies; recovering from vehicle-ground communication anomalies; and completing vehicle-ground data transmission

[0041] Combined with Figure 11 , a reliable vehicle-ground data transmission method for urban rail transit according to the present invention includes:

[0042] Vehicle-ground bidirectional link reachability verification mechanism

[0043] Simplifying the initialization process of the reliable vehicle-ground communication connection

[0044] Vehicle-ground reliable communication anomaly handling mechanism

[0045] Vehicle-ground reliable communication data integrity verification mechanism

[0046] At the same time, record the current data transmission progress and have the ability to resume interrupted data transmission in real time

[0047] Furthermore, this method is implemented based on the application layer, and all communication mechanisms do not need to be implemented with the aid of special hardware, without special hardware requirements.

[0048] Furthermore, the vehicle-ground bidirectional link reachability verification mechanism is specifically as follows:

[0049] The on-vehicle device will send an ICMP request to the ground server. When the request can be correctly replied, it proves that the vehicle-ground link is reachable. When the ICMP request is not correctly replied, it is considered that the vehicle-ground link is unreachable; similarly, the ground also has the ability to send ICMP requests to verify whether the vehicle-ground communication is reachable bidirectionally;

[0050] Furthermore, simplify the initialization process of the vehicle-ground reliable communication connection, specifically as follows:

[0051] After confirming that the link is reachable, the ground server will first send a handshake request to the on-vehicle device. Only by answering the current own status can the initialization of the connection be completed, without the need for multiple handshakes or waving mechanisms;

[0052] Furthermore, the data integrity verification mechanism of the vehicle-ground reliable communication relies on the exception handling mechanism of the vehicle-ground reliable communication. The vehicle-ground transmission is divided into normal situations and abnormal situations. When an abnormal situation is encountered, the abnormal handling mechanism is started for corresponding processing;

[0053] Furthermore, the new data integrity verification mechanism of the vehicle-ground reliable communication adopts a triple authentication method of unique data transmission encoding, data packet numbering, and CRC checksum to confirm the integrity of the data transmitted in the communication link and can retransmit the data packets with transmission errors:

[0054] The following will describe in detail the specific steps of the reliable vehicle-ground data transmission method of the present invention for urban rail transit in conjunction with the specification drawings and embodiments.

[0055] As Figure 1 shown, the bidirectional link reachability detection includes the following steps:

[0056] Step 1: ICMP request

[0057] The on-vehicle device sends an ICMP request to the ground server.

[0058] Step 2: ICMP reply

[0059] The ground server replies to the ICMP request to the on-vehicle device.

[0060] In actual projects, the ground server can also send an ICMP request to the on-vehicle device, and the reachability verification can be carried out bidirectionally. As long as one party is reachable, it can be confirmed that the link is available.

[0061] like Figure 2 As shown, the normal vehicle-ground data flow includes the following steps:

[0062] Step 1: Data download request

[0063] The ground server sends a data download request to the vehicle-mounted device, and sends a unique data transmission code in the request header;

[0064] Step 2: Data Preparation

[0065] Data preparation by on-board equipment

[0066] Step 3: Data preparation is complete

[0067] The vehicle-mounted device replies data to complete preparations and sends it to the ground server

[0068] Step 4: Packet Request

[0069] The ground server sends a data request to the vehicle-mounted device and records the current data packet as the first packet, and accumulates them in sequence until all data packets are transmitted.

[0070] Step 5: Data Packet Transmission

[0071] The vehicle-mounted device sends the requested data packet to the ground server

[0072] Step 6: Data transfer completed

[0073] The ground server confirms the end of data transmission and sends the data transmission end status to the vehicle-mounted device. At this point, all data transmission is completed and the link is closed.

[0074] like Figure 3 As shown, the process of normal situation 2 where there is no available vehicle data to be sent to the ground includes the following steps:

[0075] Step 1: Data download request

[0076] The ground server sends a data download request to the vehicle-mounted device, and sends a unique data transmission code in the request header;

[0077] Step 2: Data Preparation

[0078] The vehicle equipment replied to the ground that there was no data available for transmission.

[0079] Step 3: Data transfer completed

[0080] The ground server confirms the end of data transmission and sends the data transmission end status to the vehicle-mounted device. At this point, all data transmission is completed and the link is closed.

[0081] like Figure 4As shown in the figure, the schematic diagram of the ground server actively interrupting data transmission under normal circumstances includes the following steps:

[0082] Step 1: Data download request

[0083] The ground server sends a data download request to the in-vehicle device and sends a unique data transmission code in the request header;

[0084] Step 2: Data preparation

[0085] The in-vehicle device performs data preparation

[0086] Step 3: Data preparation completed

[0087] The in-vehicle device replies to the ground server that the data preparation is completed

[0088] Step 4: Data packet request

[0089] The ground server sends a data request to the in-vehicle device, records the current data packet as the first packet, and accumulates sequentially until all data packets are transmitted

[0090] Step 5: Data packet transmission

[0091] The in-vehicle device sends the requested data packet to the ground server

[0092] Step 6: Data transmission interruption request

[0093] The ground server confirms the data transmission interruption and sends a data transmission interruption request to the in-vehicle device

[0094] Step 7: Data transmission interruption reply

[0095] The in-vehicle device replies to the data interruption request to the ground server

[0096] Step 8: Data interruption sending

[0097] The ground server sends the data interruption transmission status to the in-vehicle device

[0098] As Figure 5 shown, in abnormal situation 1, the data download request from the ground server fails to reach the in-vehicle device, including the following steps:

[0099] Step 1: Data download request not delivered

[0100] The ground server sends a data download request to the in-vehicle device and sends a unique data transmission code in the request header; if the ground server does not receive the return status from the in-vehicle device within 1 minute, it will send a request with the same data transmission unique code to the in-vehicle device again; repeat the attempt 10 times. If the connection still cannot be established, the current download request will be abandoned; discard the current data transmission unique code;

[0101] As shown Figure 6 in the figure, when the status returned by the on-vehicle device in abnormal situation 2 fails to reach the ground server, the following steps are included:

[0102] Step 1: Data download request

[0103] The ground server sends a data download request to the on-vehicle device and sends a unique data transmission code in the request header;

[0104] Step 2: Data preparation

[0105] The on-vehicle device performs data preparation

[0106] Step 3: Data preparation completed but not delivered

[0107] The on-vehicle device replies to the ground server that the data preparation is completed, but the reply status fails to reach the ground server; if the on-vehicle device does not receive the ground server's request for the first packet of data within 1 minute, it will reply to the ground again with the status that the data preparation is completed; repeat the attempt 10 times. If the connection still cannot be established, the current download request will be abandoned; discard the current unique data transmission code;

[0108] As shown Figure 7 in the figure, when the ground server's request for the first packet of data fails to reach the on-vehicle device in abnormal situation 3, the following steps are included:

[0109] Step 1: Data download request

[0110] The ground server sends a data download request to the on-vehicle device and sends a unique data transmission code in the request header;

[0111] Step 2: Data preparation

[0112] The on-vehicle device performs data preparation

[0113] Step 3: Data preparation completed

[0114] The on-vehicle device replies to the ground server that the data preparation is completed

[0115] Step 4: Packet request not delivered

[0116] The ground server sends a data request to the on-vehicle device. After the ground server does not receive the return status from the on-vehicle device within 1 minute, it will send a request with the same unique data transmission code to the on-vehicle device again; repeat the attempt 10 times. If the connection still cannot be established, the current download request will be abandoned; retain the current unique data transmission code and record the current sequence number of the failed transmission packet. When the link is reachable next time, retransmit the breakpoint data with reference to Figure 2 the breakpoint data;

[0117] As shownFigure 8 As shown in the figure, for abnormal situation 4 where the first packet of data transmitted back by the on-vehicle device fails to reach the ground server, the following steps are included:

[0118] Step 1: Data download request

[0119] The ground server sends a data download request to the on-vehicle device and sends a unique data transmission code in the request header;

[0120] Step 2: Data preparation

[0121] The on-vehicle device performs data preparation

[0122] Step 3: Data preparation completed

[0123] The on-vehicle device replies to the ground server that the data preparation is completed

[0124] Step 4: Data packet request

[0125] The ground server sends a data request to the on-vehicle device, records the current data packet as the first packet, and accumulates sequentially until all data packets are transmitted;

[0126] Step 5: Data packet transmission fails to reach

[0127] The on-vehicle device sends the requested data packet to the ground server, and the request packet fails to reach the ground server; retry 10 times. If the transmission still fails, retain the current unique data transmission code and record the serial number of the current failed transmission packet. When the link is reachable next time, the ground server will retransmit the data for the breakpoint data; Figure 2 For retransmission of breakpoint data;

[0128] As Figure 9 shown, for abnormal situation 5 where the ground server fails to reach the on-vehicle device after the transmission is completed, the following steps are included:

[0129] Step 1: Data download request

[0130] The ground server sends a data download request to the on-vehicle device and sends a unique data transmission code in the request header;

[0131] Step 2: Data preparation

[0132] The on-vehicle device performs data preparation

[0133] Step 3: Data preparation completed

[0134] The on-vehicle device replies to the ground server that the data preparation is completed

[0135] Step 4: Data packet request

[0136] The ground server sends a data request to the in-vehicle device, records the current data packet as the 1st packet, and accumulates sequentially until all data packets are transmitted

[0137] Step 5: Data packet transmission

[0138] The in-vehicle device sends the requested data packet to the ground server

[0139] Step 6: Data transmission ends

[0140] The ground server confirms the end of data transmission and sends the data transmission end status to the in-vehicle device. If the in-vehicle device has sent all data packets and has not received the data transmission end message sent by the ground server within 20 minutes, it will end the current data transmission by itself, retain the unique encoding of this data transmission, and when the link is reachable next time, the ground server will refer to Figure 2 Re-transmit the breakpoint data;

[0141] As Figure 10 shown, for abnormal situation 6 where the ground server's transmission termination request fails to reach the in-vehicle device, it includes the following steps:

[0142] Step 1: Data download request

[0143] The ground server sends a data download request to the in-vehicle device and sends the unique encoding of data transmission in the request header;

[0144] Step 2: Data preparation

[0145] The in-vehicle device performs data preparation

[0146] Step 3: Data preparation completed

[0147] The in-vehicle device replies to the ground server that the data preparation is completed

[0148] Step 4: Data packet request

[0149] The ground server sends a data request to the in-vehicle device, records the current data packet as the 1st packet, and accumulates sequentially until all data packets are transmitted

[0150] Step 5: Data packet transmission

[0151] The in-vehicle device sends the requested data packet to the ground server

[0152] Step 6: The data transmission interruption request fails to reach

[0153] The ground server confirms the data transmission interruption and sends a data transmission interruption request to the in-vehicle device. If the interruption request is not received by the in-vehicle device and no message from the ground server is received within 1 minute, the same data will be sent to the ground server again; this will be repeated 10 times. If no reply is received after 10 attempts, the transmission of this packet of data will be abandoned; the unique code for this data transmission will be retained, and the serial number of the currently failed packet will be recorded. When the link is reachable again next time, the ground service will refer to it together. Figure 4 Terminate the data transmission.

Claims

1. A reliable vehicle-to-ground data transmission method for urban rail transit, characterized in that: include: Before the vehicle-to-ground link is established, a two-way link reachability detection mechanism is used to verify the communication reachability from the vehicle-mounted device to the ground server and from the ground server to the vehicle-mounted device, so as to detect the channel reachability between the vehicle-mounted device and the ground device. After confirming that the channel is reachable, a single communication handshake and waving mechanism is used to simplify the initialization process of reliable vehicle-ground communication connection, initialize the vehicle-ground communication link, and establish vehicle-ground communication; Create a unique data transmission code and a transmission data packet number at the communication packet header, and a check code at the communication packet tail. With the help of the unique code and data packet number during the transmission process, data transmission progress records and real-time breakpoint recovery and continuation can be achieved. At the same time, with the help of the transmission unique code, transmission data packet number and check code, abnormal situations in the transmission project can be judged. When a transmission anomaly occurs, the data transmission unique code, transmission data packet number and check code are used to classify and handle the anomaly, ensure the continuity of the transmission content, and eliminate repeated transmission of the same content; The unique code, data packet number and check code information are integrated to achieve data integrity verification for reliable vehicle-to-ground communication, improve the quality of vehicle-to-ground transmission data, and eliminate low-quality data caused by discarded packets and channel fluctuations.

2. The reliable vehicle-to-ground data transmission method for urban rail transit according to claim 1 is characterized in that: The bidirectional link reachability detection mechanism carries out bidirectional link reachability verification between the vehicle and the ground. A verification request can be sent from the vehicle-mounted device to the ground server, or from the ground server to the vehicle-mounted device. If either party detects that the destination is reachable, a reliable communication connection initialization process can be performed.

3. The reliable vehicle-to-ground data transmission method for urban rail transit according to claim 1 is characterized in that: The simplified initialization process of the reliable vehicle-ground communication connection simplifies the link initialization mechanism of three handshakes and four waves to a reliable communication connection that only requires one handshake and one wave between the vehicle-mounted device and the ground server.

4. The reliable vehicle-to-ground data transmission method for urban rail transit according to claim 1 is characterized in that: After the communication initialization is completed, a unique data transmission code is generated. The code consists of a 6-bit random number and is included in the packet header of each message interaction in the vehicle-ground trusted communication. Data transmission can only be continued when the data unique code is consistent. Once the data transmission unique code changes, the on-board and ground equipment immediately terminate the current transmission progress and discard all historical data in this transmission.

5. The reliable vehicle-to-ground data transmission method for urban rail transit according to claim 1 is characterized in that: After the communication initialization is completed, the transmission data packet number is generated. The number increases with each transmission process until the number is consistent with the total number of data packets. After any abnormal situation occurs, the current number will be maintained until the communication is restored and the data transmission unique code remains unchanged. It will be accumulated repeatedly; if the data transmission unique code changes, the transmission data packet number will become invalid and reset to 0.

6. The reliable vehicle-to-ground data transmission method for urban rail transit according to claim 1 is characterized in that: After the communication initialization is completed, a check code is generated and placed at the end of the packet. The CRC32 mechanism is used to calculate the check code for each packet of data and verify each packet of data. When the number of the data packet to be transmitted is the same as the total number of transmitted packets, the total data is verified. If the data verification passes, it means that the current transmission is successful. If the verification fails, it means that the data transmission has failed and the historical data is discarded.

7. The reliable vehicle-to-ground data transmission method for urban rail transit according to claim 1 is characterized in that: The data transmission progress record can record the current transmission progress, and based on the data transmission unique code and the data packet number, confirm the current transmission progress of the vehicle-mounted equipment and the ground server respectively. When the data transmission unique code remains unchanged, the current transmission packet number and the total number of packets are counted, and the ratio of the two is used as a real-time record of the transmission progress, thereby realizing the data transmission recording function.

8. The reliable vehicle-to-ground data transmission method for urban rail transit according to claim 1 is characterized in that: The real-time recovery of breakpoint-resume transmission is that when the data transmission unique code remains unchanged, the data packet numbers are accumulated normally, but the check code fails, the ground server performs breakpoint-resume transmission based on the transmission progress in front of the terminal; during the transmission process, the data transmission unique code remains unchanged, the data packet numbers increase incrementally until the total number of packets, and the breakpoint-resume transmission is completed after the CRC check passes.

9. The reliable vehicle-to-ground data transmission method for urban rail transit according to claim 1 is characterized in that: Based on the unique data transmission code, data packet number and checksum, the following abnormal situations can be accurately located: The data download request from the ground server is not delivered to the vehicle-mounted device: the ground server sends a data download request to the vehicle-mounted device, and sends the data transmission unique code in the request header; if the ground server does not receive a return status from the vehicle-mounted device within 1 minute, it will send a request with the same data transmission unique code to the vehicle-mounted device again; if the connection cannot be established after 10 repeated attempts, the download request will be abandoned; the data transmission unique code will be discarded; The status of the vehicle-mounted device is not sent to the ground server: the vehicle-mounted device replies that the data is ready to be sent to the ground server, but the reply status is not sent to the ground server; if the vehicle-mounted device has not received the ground server's request for the first data packet within 1 minute, it will reply to the ground again that the data is ready to be sent; repeat the attempt 10 times, if the connection cannot be established, the download request is abandoned; the unique code of this data transmission is discarded; The first data packet requested by the ground server is not delivered to the vehicle-mounted device: the ground server sends a data request to the vehicle-mounted device. If the ground server does not receive a return status from the vehicle-mounted device within 1 minute, it will send a request with the same data transmission unique code to the vehicle-mounted device again; repeat the attempt 10 times. If the connection cannot be established, the download request is abandoned; the unique code of this data transmission is retained, and the sequence number of the current transmission failure packet is recorded. When the link is reachable next time, the data is retransmitted based on the breakpoint recovery capability; The first data packet sent back by the vehicle-mounted device was not delivered to the ground server: the vehicle-mounted device sent the requested data packet to the ground server, but the request packet was not delivered to the ground server; repeated attempts were made 10 times. If the transmission still failed, the unique code of this data transmission was retained, and the sequence number of the current failed transmission packet was recorded. When the link is reachable next time, the ground server retransmits the data based on the breakpoint recovery capability; The ground server completes the transmission but does not deliver it to the vehicle-mounted device: The ground server confirms the completion of data transmission and sends the data transmission completion status to the vehicle-mounted device. If the vehicle-mounted device has sent all data packets and has not received the data transmission completion message sent by the ground server within 20 minutes, it will automatically terminate the current data transmission and retain the unique code for this data transmission. When the next link is reachable, the ground server will retransmit the data based on the ability to resume breakpoint transmission. The ground server's transmission termination request is not delivered to the vehicle-mounted device: the ground server confirms the data transmission interruption and sends a data transmission interruption request to the vehicle-mounted device. The interruption request is not received by the vehicle-mounted device. If no message from the ground server is received within 1 minute, the same data will be sent to the ground server again; repeat the attempt 10 times. If no reply is received, the data transmission of this package is abandoned; the unique code of this data transmission is retained, and the current transmission failure package sequence number is recorded. When the link is reachable next time, the ground service will try again 10 times until the transmission is completed; The elimination of repeated transmission of the same content is to prevent repeated transmission of the same data packet number based on the breakpoint resume capability and normal accumulation of data packet numbers.

10. The reliable vehicle-to-ground data transmission method for urban rail transit according to any one of claims 1, 7, 8, 9 or 10, characterized in that: Data integrity verification for reliable vehicle-ground communication, when the data is normal, that is, the data unique code remains unchanged, the data packet number is accumulated to the total number, and the verification code passes, reliable vehicle-ground data transmission is achieved. If any of the three fails the verification, it will be analyzed and handled as an abnormal situation.

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