A method for optimizing information transmission delay in CTCS-3 train control system

Abstract

The present invention discloses a method for optimizing information transmission delay in a CTCS-3 train control system. The method includes: at the beginning of the current communication cycle, a wireless communication transmitter connected to a radio block center selects a value for an HDLC frame retransmission timer to minimize the expected wireless message transmission delay within the current communication cycle, sends a wireless message to an onboard device based on the HDLC frame retransmission timer value for the current communication cycle, and then modifies the upper limit of the HDLC frame retransmission timer for the current communication cycle based on the wireless message transmission result; and a radio station connected to the onboard device makes a wireless parameter decision, selects a value for the HDLC frame retransmission timer to minimize the expected wireless message transmission delay within the current communication cycle, and sends the wireless message to the radio block center. This method controls wireless data transmission delay by making wireless communication parameter decisions in each communication cycle, thereby reducing information transmission delay in the CTCS-3 train control system.

Description

Technical Field

[0001] The present invention relates to the technical field of train operation control, and in particular to a method for optimizing information transmission delay of a CTCS-3 level train control system. Background Art

[0002] With the development of computer technology, communication technology and control technology, the train operation control system has become the core equipment of the railway system. The train operation control system uses two-way wireless communication to realize the message transmission between the train and the ground equipment, ensuring that the train runs safely at the prescribed speed. The CTCS-3 level train operation control system currently in use uses GSM-R to realize the periodic wireless message transmission of the train control system. Figure 1 As shown in the figure, taking a GSM-R based train control system as an example, the train control system's Radio Block Center (RBC) is connected to a GSM-R base station, while the Automatic Train Protection (ATP) onboard equipment is connected to a GSM-R mobile station. Messages exchanged between the RBC and ATP onboard equipment are achieved through a wireless communication link established between the radio and the base station.

[0003] Train control systems are safety-critical, placing high demands on the reliability and trustworthiness of message transmission within the system. As a wireless communication system, the GSM-R system inevitably introduces delays during wireless message transmission, including message transmission delays and message loss caused by random transmission errors. In severe cases, wireless timeouts can lead to degradation of the train control system, significantly reducing operational efficiency and increasing operating costs.

[0004] Therefore, it is urgent to study the wireless message transmission delay of the GSM-R-based train control system, quantitatively analyze the wireless message transmission delay and wireless message packet loss rate through the secure communication protocol, analyze the parameters affecting the wireless message transmission delay of the train control system, and propose an optimization method to control the wireless message transmission delay based on this, thereby reducing the impact of mobile authorization message delay on train operation control. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for optimizing the information transmission delay of a CTCS-3 level train control system, which can reduce the information transmission delay of the train control system.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for optimizing information transmission delay in a CTCS-3 train control system, comprising:

[0008] At the beginning of the current communication cycle, the wireless communication transmitter connected to the radio block center makes a wireless parameter decision based on the size of the mobile authorization to be sent, the wireless channel environment at the location of the vehicle-mounted device, and the upper limit of the HDLC frame retransmission timer for the current communication cycle, and selects a value for the HDLC frame retransmission timer for the current communication cycle so that the expected value of the wireless message transmission delay in the current communication cycle is minimized; the HDLC frame is a high-level data link control frame;

[0009] The wireless communication transmitter connected to the radio block center sends a wireless message to the vehicle-mounted device according to the value of the HDLC frame retransmission timer in the current communication cycle, and modifies the upper limit of the HDLC frame retransmission timer in the current communication cycle according to the wireless message transmission result;

[0010] The radio station connected to the on-board equipment makes a wireless parameter decision, selects an HDLC frame retransmission timer value within the upper limit of the HDLC frame retransmission timer in the current communication cycle, and minimizes the expected value of the wireless message transmission delay in the current communication cycle. The radio station sends a wireless message to the radio block center based on the HDLC frame retransmission timer value selected in the current communication cycle, completing the wireless communication in the current communication cycle.

[0011] It can be seen from the technical solution provided by the present invention that by making wireless communication parameter decisions in each communication cycle, the wireless data transmission delay is controlled, thereby reducing the information transmission delay of the CTCS-3 level train control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0013] Figure 1 Schematic diagram of the CTCS-3 train control wireless communication system provided as background technology of the present invention;

[0014] Figure 2 This is a flowchart of a method for optimizing information transmission delay in a CTCS-3 train control system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0015] The following is a clear and complete description of the technical solutions in the embodiments of the present invention, in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0016] First, the following terms may be used in this article:

[0017] The terms "include," "comprises," "contains," "has," or other similar expressions should be interpreted as non-exclusive. For example, "including certain technical features (such as raw materials, components, ingredients, carriers, dosage forms, materials, dimensions, parts, components, mechanisms, devices, steps, procedures, methods, reaction conditions, processing conditions, parameters, algorithms, signals, data, products, or manufactured articles, etc.) should be interpreted as including not only the technical features explicitly listed, but also other technical features known in the art that are not explicitly listed.

[0018] Next, the prior art related to the present invention is briefly described.

[0019] The CTCS-3 train control system uses GSM-R for periodic wireless message transmission. For example, the train control system's Rail-to-Board (RBC) is connected to a GSM-R base station, while the ATP onboard equipment is connected to a GSM-R mobile radio. Message exchange between the RBC and ATP onboard equipment occurs via a wireless communication link established between the radio and the base station. In the CTCS-3 train control system, GSM-R-based wireless communication latency has a direct impact on train operation. Specifications require that onboard equipment periodically send position reports to the ground-based RBC during train operation. Upon receiving the position reports, the RBC sends a Movement Authorization (MA) to the onboard equipment based on track occupancy and line data. The onboard safety computer calculates the target speed profile based on the MA and monitors train operation. If the MA is not updated in a timely manner due to wireless transmission latency, this can lead to train deceleration or downgraded operation, impacting operational efficiency.

[0020] To reduce the impact of mobile authorization delays caused by GSM-R wireless communication transmission delays, and even degradation caused by wireless transmission interruptions, the CTCS-3 train control system's train-to-ground wireless communication system has set up link failure detection mechanisms at the application layer and the EuroRadio (European wireless communication) link layer.

[0021] The CTCS-3 level train control system ATP vehicle equipment application layer detects wireless transmission failure through T NVCONTECTAfter receiving the security message sent by RBC, if NVCONTECT If no new safety message is received from the RBC within the time specified by the timer, the corresponding operation is triggered according to the application layer parameter settings, such as downgrading or parking after emergency braking.

[0022] The detection of communication failure in the EuroRadio protocol of the ATP onboard equipment of the CTCS-3 train control system is mainly determined by the values of the link layer related timers T1, N2 and T3. Among them:

[0023] The T1 timer is the link layer HDLC frame retransmission timer. It is started after each frame is sent. If no response frame is received from the other end, the HDLC (High-Level Data Link Control) frame retransmission is started after the timer times out.

[0024] The N2 timer is the number of HDLC frame retransmissions, indicating the maximum number of retransmissions allowed for an HDLC frame;

[0025] The T3 timer is calculated by the base station and the vehicle radio respectively. The timer is reset every time a frame is correctly received. After the timer expires, the connection is considered disconnected.

[0026] It can be concluded that in the CTCS-3 system, the transmission delay of a single HDLC frame consists of the delays in multiple transmission processes and the delays caused by multiple retransmission timers. The transmission delay of a single HDLC frame with retransmissions is T HDLC_frame It can be calculated using the following formula.

[0027]

[0028] Where n represents the number of times a single HDLC frame is retransmitted, T1_Timeout represents the HDLC frame retransmission response timeout specified by the T1 timer; T wireless Indicates the time required for HDLC frames to be transmitted over the air interface.

[0029] When the number of retransmissions of a single HDLC frame exceeds N2, the connection is reestablished or the connection is directly disconnected and the HDLC frame is transmitted again.

[0030] For the T3 timer timeout scenario, when the link layer detects a communication failure, the timer T NVCONTECT If the timeout does not occur, the CTCS-3 train control system will assume that the communication connection still exists and the CFM module will start to re-establish the secure connection. NVCONTECT Before the timer times out, if the on-board train control user receives a new safety message sent by RBC again, it will not affect the train operation.

[0031] In the CTCS-3 system, in actual applications, train control user data is transmitted as ordinary user data. The size of the link layer MA data packet generally exceeds a single 40-byte HDLC frame and needs to be split into different HDLC frames for transmission. Therefore, the overall transmission delay of MA is T MAdelay It can be calculated using the following formula:

[0032] T MAdelay =T HDLC_frame (m)+(m-1)*ΔT

[0033] Where m is the total number of HDLC frames that need to be transmitted, ΔT is the transmission interval between adjacent HDLC frames, and T HDLC_frame (m) is the transmission delay of a single HDLC frame. For example, when RBC sends a 500-byte MA, the total length at the link layer is 671 bytes, which is split into 16 40-byte HDLC frames and one 31-byte HDLC frame for transmission.

[0034] Based on the above-mentioned prior art, the present invention defines the value of the N2 timer as a variable and provides a method for optimizing the information transmission delay of a CTCS-3 level train control system to reduce the wireless message transmission delay.

[0035] like Figure 1 FIG. 1 is a flowchart of a method for optimizing information transmission delay of a CTCS-3 train control system according to an embodiment of the present invention, which mainly includes the following steps:

[0036] Step 1: At the beginning of the current communication cycle, the wireless communication transmitter connected to the radio block center makes a wireless parameter decision based on the size of the mobile authorization to be sent, the wireless channel environment at the location of the vehicle-mounted device, and the upper limit of the HDLC frame retransmission timer for the current communication cycle. The value of the HDLC frame retransmission timer for the current communication cycle is selected to minimize the expected value of the wireless message transmission delay in the current communication cycle.

[0037] Step 2: The wireless communication transmitter connected to the RBC sends a wireless message to the onboard device based on the value of the HDLC frame retransmission timer in the current communication cycle, and modifies the upper limit of the HDLC frame retransmission timer in the current communication cycle based on the wireless message transmission result.

[0038] Step 3: The radio station connected to the on-board device makes a wireless parameter decision, selects an HDLC frame retransmission timer value within the upper limit of the HDLC frame retransmission timer in the current communication cycle, and minimizes the expected value of the wireless message transmission delay in the current communication cycle. The radio station then sends a wireless message to the radio block center based on the selected HDLC frame retransmission timer value in the current communication cycle, completing the wireless communication in the current communication cycle.

[0039] Since ground wireless transmission and vehicle-mounted wireless transmission are two independent sets of equipment, considering the independence of the equipment, the vehicle-mounted end also needs to be recalculated once. The calculation method is the same as that of the ground end (that is, the method of step 1), so it will not be repeated.

[0040] For each communication cycle, wireless parameter decisions are made according to the above scheme, and the most appropriate HDLC frame retransmission timer upper limit N is selected for each communication cycle. 2max On this basis, the HDLC frame retransmission timer value that minimizes the expected value of the wireless message transmission delay is selected, thereby reducing the wireless message transmission delay of the train control system.

[0041] For ease of understanding, the present invention is described in detail below using a specific application scenario as an example.

[0042] Step a: When the train is put into operation, set the upper limit of the HDLC frame retransmission timer N 2max Set to 1.

[0043] Step b: At the beginning of the current communication cycle, the wireless communication transmitter connected to the radio block center sends a mobile authorization size as needed, the wireless link signal-to-noise ratio (SNR) of the location of the vehicle-mounted equipment, and the upper limit N of the HDLC frame retransmission timer in the current communication cycle. 2max Equal input, wireless parameter decision, integer set [0,N 2max ] range, select the corresponding HDLC frame retransmission timer value N2∈[0,N 2max ], so that the expected value of wireless message transmission delay in the current communication cycle is minimized;

[0044] In the embodiment of the present invention, given the signal-to-noise ratio SNR, the total number of HDLC frames m required to complete the mobile authorization transmission, and the upper limit N of the HDLC frame retransmission timer, 2max Under the premise of , the expected value of wireless message transmission delay in the current communication cycle is the sum of the expected value of single HDLC frame transmission delay and the total transmission interval.

[0045] According to the HDLC frame transmission delay T HDLC_frame and MA overall transmission delay T MAdelay Formula to calculate the expected value of wireless message transmission delay T est_MA (SNR,m,N2), expressed as:

[0046]

[0047] Where SNR is the signal-to-noise ratio, which represents the wireless channel environment at the location of the vehicle-mounted device; m is the total number of HDLC frames required to complete the mobile authorization transmission (the entire mobile authorization needs to be split into an integer m fixed-byte HDLC frame transmission, where m is the size of the mobile authorization); ΔT is the interval between adjacent HDLC frame transmissions, and N2 represents the value of the HDLC frame retransmission timer, which is an integer set [0, N 2max ],N 2max Indicates the upper limit of the HDLC frame retransmission timer in the current communication cycle; T est_HDLC_frame represents the expected value of the transmission delay of a single HDLC frame, which is the sum of the product of the probability of all retransmissions and their corresponding transmission delays, and the sum of the product of the probability of transmission failure and the transmission failure processing time; p SNR represents the probability of frame transmission error when the signal-to-noise ratio is SNR; T HDLC_fram (i e -1) represents the transmission delay of the HDLC frame retransmitted i-1 times; T Re Indicates the time it takes to resume wireless transmission after the connection is reestablished;

[0048] By traversing the integer set [0,N 2max ], obtain the minimum value of the expected value of the wireless message transmission delay within the communication cycle, and the N2 value corresponding to the minimum value is used as the value of the HDLC frame retransmission timer of the current communication cycle.

[0049] In step c, the wireless communication transmitter of the RBC connection sends a wireless message based on the HDLC frame retransmission count timer N2 selected for the current communication cycle. If wireless transmission fails due to exceeding the retransmission count limit, the process proceeds to step d. If reconnection does not occur due to exceeding the retransmission count limit, the process proceeds to step e.

[0050] Step d: If the wireless transmission fails for the first time during the current communication cycle due to the number of retransmissions exceeding the limit (i.e., the number of retransmissions exceeds the value of the HDLC frame retransmission timer of the current communication cycle), the upper limit N of the HDLC frame retransmission timer of the current communication cycle is set to 2max Plus one, that is, N 2max =N 2max +1. Make wireless parameter decisions again and reselect the value of the HDLC frame retransmission timer for the current communication cycle to minimize the expected value of wireless message transmission delay within the communication cycle. At the same time, the total delay of wireless transmission failure, link re-establishment, and wireless transmission again does not exceed the wireless transmission failure timer T NVCONTECT Afterwards, the wireless communication transmitter connected to the radio block center sends a wireless message to the on-board device again according to the reselected HDLC frame retransmission timer value of the current communication cycle.

[0051] Step e: The radio station connected to the vehicle-mounted device makes a wireless parameter decision and selects the HDLC frame retransmission timer value N2∈[0,N 2max ], so that the expected value of the wireless message transmission delay in the current communication cycle is minimized, and the wireless message is sent to the radio block center to complete the wireless communication in the current cycle.

[0052] The above steps b to e are implemented in the current communication cycle. In the next communication cycle, the process returns to step b and continues to execute steps b to e.

[0053] In the above-mentioned solution of the embodiment of the present invention, an initial HDLC frame retransmission timer value is set before the train control system wireless message transmission begins. During the train control system wireless message transmission process, the upper limit of the HDLC frame retransmission timer within the current communication cycle is determined based on the mobile authorization size and the channel environment, and the HDLC frame retransmission timer value that minimizes the estimated expected value of the wireless transmission delay is selected. Therefore, the train control system wireless message transmission delay can be reduced.

[0054] Through the description of the above embodiments, those skilled in the art will clearly understand that the above embodiments can be implemented through software or by using software plus a necessary general-purpose hardware platform. Based on this understanding, the technical solutions of the above embodiments can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (such as a CD-ROM, a USB flash drive, a mobile hard disk, etc.) and includes a number of instructions for causing a computer device (such as a personal computer, a server, or a network device) to execute the methods described in the various embodiments of the present invention.

[0055] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for optimizing information transmission delay in a CTCS-3 train control system, characterized in that: include: At the beginning of the current communication cycle, the wireless communication transmitter connected to the radio block center makes a wireless parameter decision based on the size of the mobile authorization to be sent, the wireless channel environment at the location of the vehicle-mounted device, and the upper limit of the HDLC frame retransmission timer for the current communication cycle, and selects a value for the HDLC frame retransmission timer for the current communication cycle so that the expected value of the wireless message transmission delay in the current communication cycle is minimized; the HDLC frame is a high-level data link control frame; The wireless communication transmitter connected to the radio block center sends a wireless message to the vehicle-mounted device according to the value of the HDLC frame retransmission timer in the current communication cycle, and modifies the upper limit of the HDLC frame retransmission timer in the current communication cycle according to the wireless message transmission result; The radio station connected to the on-board equipment makes a wireless parameter decision, selects an HDLC frame retransmission timer value within the upper limit of the HDLC frame retransmission timer in the current communication cycle, minimizes the expected value of the wireless message transmission delay in the current communication cycle, and sends a wireless message to the radio block center based on the HDLC frame retransmission timer value selected in the current communication cycle, completing the wireless communication in the current communication cycle. The selecting of a value for the HDLC frame retransmission count timer so that the expected value of the wireless message transmission delay in the current communication cycle is minimized includes: Given the signal-to-noise ratio (SNR), the total number of HDLC frames m required to complete mobile authorization transmission, and the upper limit N of the HDLC frame retransmission timer, 2max Under the premise of , the expected value of wireless message transmission delay in the current communication cycle is the sum of the expected value of single HDLC frame transmission delay and the total transmission interval; the calculated expected value of wireless message transmission delay T est_MA (SNR,m,N2), expressed as: Where SNR is the signal-to-noise ratio, which represents the wireless channel environment at the location of the vehicle-mounted device; m is the mobile authorization size, that is, the total number of HDLC frames required to complete the mobile authorization transmission; ΔT is the interval between adjacent HDLC frame transmissions, and N2 represents the value of the HDLC frame retransmission timer, which is an integer set [0, N 2max ],N 2max Indicates the upper limit of the HDLC frame retransmission timer in the current communication cycle; T est_HDLC_frame represents the expected value of the transmission delay of a single HDLC frame, which is the sum of the product of the probability of all retransmissions and their corresponding transmission delays, and the sum of the product of the probability of transmission failure and the transmission failure processing time; p SNR represents the probability of frame transmission error when the signal-to-noise ratio is SNR; T HDLC_frame (i-1) represents the transmission delay of the HDLC frame retransmitted i-1 times; T Re Indicates the time it takes to resume wireless transmission after the connection is reestablished; By traversing the integer set [0,N 2max ], obtain the minimum value of the expected value of the wireless message transmission delay within the communication cycle, and the N2 value corresponding to the minimum value is used as the value of the HDLC frame retransmission timer of the current communication cycle.

2. The method for optimizing information transmission delay of a CTCS-3 train control system according to claim 1, characterized in that: The modifying of the upper limit of the HDLC frame retransmission count timer of the current communication cycle according to the wireless message transmission result includes: If wireless transmission failure occurs for the first time due to exceeding the retransmission limit in the current communication cycle, the upper limit of the HDLC frame retransmission timer in the current communication cycle is increased by one.

3. The method for optimizing information transmission delay of a CTCS-3 train control system according to claim 2, characterized in that: The method further includes: After the upper limit of the HDLC frame retransmission timer in the current communication cycle is increased by one, the wireless parameter decision is made again, and the value of the HDLC frame retransmission timer in the current communication cycle is reselected to minimize the expected value of the wireless message transmission delay in the communication cycle. At the same time, the total delay of wireless transmission failure, link re-establishment and wireless transmission again does not exceed the wireless transmission failure timer T NVCONTECT ; Afterwards, the wireless communication transmitter connected to the radio block center sends the wireless message to the vehicle-mounted device again according to the reselected value of the HDLC frame retransmission count timer of the current communication cycle.

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