CN116939737A

CN116939737A - Rail transit communication system and method for establishing link

Info

Publication number: CN116939737A
Application number: CN202210353360.4A
Authority: CN
Inventors: 白小飞; 从善亚
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2022-04-01
Filing date: 2022-04-01
Publication date: 2023-10-24

Abstract

A rail transit communication system and a method of establishing a link are provided. The system comprises: the system comprises a vehicle-mounted access point, a first track side access point and a second track side access point. A link exists between the first track side access point and the vehicle-mounted access point. The vehicle-mounted access point transmits a beacon frame. The first trackside access point receives the beacon frame and measures the signal strength of the beacon frame to obtain a first signal strength value. The second trackside access point receives the beacon frame and measures a signal strength of the beacon frame to obtain a second signal strength value. The vehicle-mounted access point determines whether to change a link between the first track side access point and the vehicle-mounted access point according to the first signal intensity value and the second signal intensity value. In the scheme, the vehicle-mounted access point actively transmits the beacon frame to build the link, so that the timeliness of the link establishment between the vehicle-mounted access point and the track side access point and the communication reliability of the system can be improved.

Description

Rail transit communication system and method for establishing link

Technical Field

The present application relates to the field of wireless communications technologies, and in particular, to a rail traffic communication system and a method for establishing a link.

Background

Wireless local area networks (wireless local area network, WLAN) are widely used in home, hospital, business office, industrial production, and rail transit scenarios. The rail transit such as subways, light rails and trams plays a vital role in the construction and development of modern cities, so that the traveling, working, shopping and living of urban residents are more convenient.

In a track traffic scene, a special WLAN system is required to carry out ground communication between a station and a train so as to ensure the rapid, safe and efficient operation of the track traffic. For example, a wireless mesh (mesh) network may be employed between a station and a train to carry communication data. Wherein communication data needs to be transmitted through a link between an Access Point (AP) and an on-board (AP).

Disclosure of Invention

The application provides a track traffic communication system and a method for establishing a link in the track traffic communication system.

In a first aspect, the present application provides a rail transit communication system. The system comprises: the system comprises a vehicle-mounted access point, a first track side access point and a second track side access point, wherein a link exists between the first track side access point and the vehicle-mounted access point.

The vehicle-mounted access point is used for sending the beacon frame.

The first trackside access point is used for receiving the beacon frame, measuring the signal strength of the beacon frame to obtain a first signal strength value, and sending the first signal strength value to the vehicle-mounted access point.

The second trackside access point is configured to receive the beacon frame, measure a signal strength of the beacon frame to obtain a second signal strength value, and send the second signal strength value to the vehicle-mounted access point via the first trackside access point.

The vehicle-mounted access point is further used for determining whether to change a link between the first track side access point and the vehicle-mounted access point according to the first signal intensity value and the second signal intensity value.

The vehicle-mounted AP and the trackside AP in the rail transit communication system belong to the same-frequency AP, and the vehicle-mounted AP and the trackside AP all transmit signals through the same wireless channel. In the scheme that the trackside APs transmit the beacon frames, a situation may occur in which two trackside APs transmit the beacon frames simultaneously. The two beacon frames interfere with each other, so that the vehicle-mounted AP cannot receive the two beacon frames, and the link is affected.

In one possible implementation, the vehicle-mounted access point is mounted in a train traveling on a track along which a plurality of track-by-track access points are mounted, the plurality of track-by-track access points including a first track-by-track access point and the second track-by-track access point.

In one possible implementation, the rail transit communication system further comprises a controller. The second trackside access point is specifically configured to send the second signal strength value to the controller, and the controller is configured to send the second signal strength value to the vehicle-mounted access point via the first trackside access point.

In one possible implementation, the vehicle access point is specifically configured to: if the first signal strength value is smaller than the second signal strength value, establishing a link with the second trackside access point and disconnecting the link with the first trackside access point; if the first signal strength value is greater than or equal to the second signal strength value, maintaining a link with the first trackside access point.

In a second aspect, the present application provides a method of establishing a link. The method is applied to the vehicle-mounted access point in the rail transit communication system. A first trackside access point and a second trackside access point in the system receive the beacon frame, a link exists between the first trackside access point and the vehicle-mounted access point.

The method comprises the following steps: transmitting a beacon frame, and receiving a first signal strength value and a second signal strength value of the beacon frame, wherein the first signal strength value is obtained by measuring the signal strength of the beacon frame by the first track side access point, and the second signal strength value is obtained by measuring the post signal strength of the beacon frame by the second track side access point; and determining whether to change a link between the first track side access point and the vehicle-mounted access point according to the first signal intensity value and the second signal intensity value.

In one possible implementation, the vehicle-mounted access point is mounted in a train traveling on a track along which a plurality of track-by-side access points are mounted, the plurality of track-by-side access points including the first track-by-side access point and the second track-by-side access point.

In one possible implementation, determining whether to change the link between the first trackside access point and the vehicle-mounted access point according to the first signal strength value and the second signal strength value includes: if the first signal strength value is smaller than the second signal strength value, establishing a link with the second trackside access point and disconnecting the link with the first trackside access point; if the first signal strength value is greater than or equal to the second signal strength value, maintaining a link with the first trackside access point.

In a third aspect, the present application provides a method of establishing a link. The method is applied to the trackside access points in the rail transit communication system. The method comprises the following steps: receiving a beacon frame sent by a vehicle-mounted access point in the system, and measuring the signal intensity of the beacon frame to obtain a signal intensity value; and sending the signal strength value to the vehicle-mounted access point.

In one possible embodiment, the on-board access point is mounted in a train running on the track, and the track bypass access point is mounted along the track.

In one possible implementation manner, the sending the signal strength value to the vehicle-mounted access point includes: the signal strength value is sent to the vehicle-mounted access point via another trackside access point, wherein a link exists between the other trackside access point and the vehicle-mounted access point.

In a possible implementation manner, the system further includes a controller, and the sending the signal strength value to the vehicle-mounted access point includes: and sending the signal intensity value to the controller, wherein the controller is used for sending the signal intensity value to the vehicle-mounted access point through another trackside access point.

In a fourth aspect, the present application provides a rail transit communication system. The system comprises: the system comprises a vehicle-mounted access point, a first track side access point, a second track side access point and a controller, wherein a link exists between the first track side access point and the vehicle-mounted access point.

The vehicle-mounted access point is used for sending a beacon frame.

The first trackside access point is configured to receive the beacon frame, measure a signal strength of the beacon frame to obtain a first signal strength value, and send the first signal strength value to the controller.

The second trackside access point is configured to receive the beacon frame, measure a signal strength of the beacon frame to obtain a second signal strength value, and send the second signal strength value to the controller.

The controller is configured to determine, according to the first signal strength value and the second signal strength value, whether the vehicle-mounted access point changes a link between the first track side access point and the vehicle-mounted access point.

In one possible implementation, the vehicle-mounted access point is mounted in a train running on a track along which a plurality of track-by-track access points are mounted, the plurality of track-by-track access points including the first track-by-track access point and the second track-by-track access point.

In one possible embodiment, the controller is specifically configured to: if the first signal intensity value is smaller than the second signal intensity value, first information is sent to the vehicle-mounted access point through the first trackside access point, and the first information is used for indicating the vehicle-mounted access point to establish a link with the second trackside access point and disconnect the link with the first trackside access point; and if the first signal intensity value is greater than or equal to the second signal intensity value, sending second information to the vehicle-mounted access point through the first trackside access point, wherein the second information is used for indicating the vehicle-mounted access point to keep a link with the first trackside access point.

In a fifth aspect, an embodiment of the present application provides a method for establishing a link, which is applied to a controller in a rail transit communication system. The method comprises the following steps: receiving a first signal intensity value sent by a first track side access point and a second signal intensity value sent by a second track side access point, wherein the first signal intensity value is obtained by the first track side access point for measuring the signal intensity of a beacon frame sent by a vehicle-mounted access point, and the second signal intensity value is obtained by the second track side access point for measuring the signal intensity of the beacon frame sent by the vehicle-mounted access point; and determining whether to change a link between the first track side access point and the vehicle-mounted access point according to the first signal intensity value and the second signal intensity value.

In one possible implementation, the determining whether to change the link between the first trackside access point and the vehicle-mounted access point according to the first signal strength value and the second signal strength value includes: if the first signal intensity value is smaller than the second signal intensity value, first information is sent to the vehicle-mounted access point through the first trackside access point, and the first information is used for indicating the vehicle-mounted access point to establish a link with the second trackside access point and disconnect the link with the first trackside access point; and if the first signal intensity value is greater than or equal to the second signal intensity value, sending second information to the vehicle-mounted access point through the first trackside access point, wherein the second information is used for indicating the vehicle-mounted access point to keep a link with the first trackside access point.

In a sixth aspect, the present application provides an in-vehicle access point. The vehicle-mounted access point comprises: the system comprises a sending module, a receiving module and a chain building module.

The sending module is used for sending the beacon frame.

The receiving module is configured to receive a first signal strength value and a second signal strength value of the beacon frame via a link between a first track side access point and the vehicle-mounted access point, where the first signal strength value is obtained by measuring a signal strength of the beacon frame by the first track side access point, and the second signal strength is obtained by measuring a signal strength of the beacon frame by the second track side access point.

The link establishment module is used for determining whether to change a link between the first track side access point and the vehicle-mounted access point according to the first signal intensity value and the second signal intensity value.

In one possible embodiment, the link building module is specifically configured to: if the first signal strength value is smaller than the second signal strength value, establishing a link with the second trackside access point and disconnecting the link with the first trackside access point; if the first signal strength value is greater than or equal to the second signal strength value, maintaining a link with the first trackside access point.

In a seventh aspect, the present application provides a track side access point. The track side access point includes: a receiving module and a transmitting module.

The receiving module is used for receiving a beacon frame sent by the vehicle-mounted access point and measuring the signal intensity of the beacon frame to obtain a signal intensity value.

The sending module is used for sending the signal intensity value to the vehicle-mounted access point.

In one possible implementation manner, the sending module is specifically configured to:

the signal strength value is sent to the vehicle-mounted access point via another trackside access point, wherein a link exists between the other trackside access point and the vehicle-mounted access point.

In a possible implementation manner, the system further includes a controller, and the sending module is further configured to: and sending a signal strength value to the controller, wherein the controller is used for sending the signal strength value to the vehicle-mounted access point through another trackside access point.

In an eighth aspect, the present application further provides a controller. The controller includes: the device comprises a receiving module and a judging module.

The receiving module is configured to receive a first signal strength value sent by a first track side access point and a second signal strength value sent by a second track side access point, where the first signal strength value is obtained by the first track side access point measuring a signal strength of a beacon frame sent by a vehicle-mounted access point, and the second signal strength value is obtained by the second track side access point measuring a signal strength of the beacon frame sent by the vehicle-mounted access point.

The judging module is used for determining whether to change the link between the first track side access point and the vehicle-mounted access point according to the first signal intensity value and the second signal intensity value.

In one possible implementation manner, the judging module is specifically configured to: if the first signal intensity value is smaller than the second signal intensity value, first information is sent to the vehicle-mounted access point through the first trackside access point, and the first information is used for indicating the vehicle-mounted access point to establish a link with the second trackside access point and disconnect the link with the first trackside access point; and if the first signal intensity value is greater than or equal to the second signal intensity value, sending second information to the vehicle-mounted access point through the first trackside access point, wherein the second information is used for indicating the vehicle-mounted access point to keep a link with the first trackside access point.

In a ninth aspect, the present application provides a computing device. The computing device includes: a processor and a memory, the processor being configured to execute a computer program stored in the memory to implement any one of the foregoing second aspect and alternative embodiments thereof, or to implement any one of the foregoing third aspect and alternative embodiments thereof, or to implement any one of the foregoing fifth aspect and alternative embodiments thereof.

In a tenth aspect, the present application provides a computer readable storage medium comprising instructions which, when run on a computer, cause the computer to perform any one of the aspects of the second aspect and alternative embodiments thereof, or perform any one of the aspects of the third aspect and alternative embodiments thereof, or perform any one of the aspects of the fifth aspect and alternative embodiments thereof.

In an eleventh aspect, the present application provides a computer program product, comprising program code which, when run on a computer, causes the computer to perform any one of the solutions of the second aspect and its alternative embodiments, or perform any one of the solutions of the third aspect and its alternative embodiments, or perform any one of the solutions of the fifth aspect and its alternative embodiments.

Drawings

Fig. 1 is a schematic structural diagram of a rail transit communication system according to an embodiment of the present application;

fig. 2 is a flowchart of a method for establishing a link in a rail transit communication system according to an embodiment of the present application;

fig. 3 is a schematic link diagram in a rail transit communication system according to an embodiment of the present application;

fig. 4 is a schematic diagram of link disassembly and link establishment in a rail transit communication system according to an embodiment of the present application;

fig. 5 is a flowchart of a method for establishing a link in another rail transit communication system according to an embodiment of the present application;

fig. 6 is a flowchart of a method for establishing a link in another rail transit communication system according to an embodiment of the present application;

fig. 7 is a flowchart of a method for establishing a link applied to a vehicle-mounted AP according to an embodiment of the present application;

fig. 8 is a flowchart of a method for establishing a link applied to a trackside AP according to an embodiment of the present application;

fig. 9 is a flowchart of a method for establishing a link applied to a controller according to an embodiment of the present application;

fig. 10 is a schematic structural diagram of a vehicle-mounted AP according to the present application;

fig. 11 is a schematic structural diagram of a trackside AP according to the present application;

FIG. 12 is a schematic diagram of a controller according to the present application;

Fig. 13 is a schematic structural diagram of a computing device provided by the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the embodiments of the present application will be described below with reference to the accompanying drawings.

In describing embodiments of the present application, words such as "for example" or "for example" are used to mean serving as examples, illustrations, or descriptions. Any embodiment or design described herein as "such as" or "for example" in embodiments of the application should not be construed as preferred or advantageous over other embodiments or designs. Rather, the use of words such as "or" for example "is intended to present related concepts in a concrete fashion.

In the description of the embodiments of the present application, the term "and/or" is merely an association relationship describing an association object, and indicates that three relationships may exist, for example, a and/or B may indicate: a alone, B alone, and both A and B. In addition, unless otherwise indicated, the term "plurality" means two or more. For example, a plurality of systems means two or more systems, and a plurality of screen terminals means two or more screen terminals.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating an indicated technical feature. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless expressly specified otherwise.

Before describing embodiments of the present application, track traffic is briefly described below.

Rail traffic refers to a transportation mode of traveling along a track. Rail traffic may include transporting passengers and goods using wheeled vehicles running on rails, such as railway transportation (english), light rail (english), tram (english), and subway. Rail traffic may also include modes of transportation that do not use wheel forms, but still travel along the rail, such as magnetic levitation (english), cable car (english), and cableway (english). In rail traffic, vehicles running on a track are guided in a track-oriented manner.

In the embodiment of the application, the rail traffic communication system is illustrated by taking rail traffic as a subway system as an example. It will be appreciated that the scheme described in the embodiments of the present application may be applied to other types of rail traffic as well.

Fig. 1 is a schematic structural diagram of a rail transit communication system provided by the application.

Referring to fig. 1, the rail traffic communication system includes a vehicle-mounted AP, a plurality of trackside APs, and a controller. The vehicle-mounted AP and the multiple trackside APs establish a wireless mesh network in a same-frequency networking mode, so that data transmission is realized.

The vehicle-mounted AP adopts a fat mode and is installed in a train running on a track. The multiple trackside APs are installed along the track in fit mode. The plurality of trackside APs includes a first trackside AP and a second trackside AP. A wireless link exists between the vehicle-mounted AP and the first trackside AP, and communication is carried out through the wireless link. For example, the controller may send information data to the vehicle-mounted AP via the first trackside AP, and the vehicle-mounted AP may provide information services to passengers on the train according to the information data. Alternatively, the information service may include audio content or video content, and may be played to passengers through a vehicle-mounted terminal provided on the train.

The controller may be one of an access controller (access controller, AC), a wireless local area network controller, or other type of controller. The controller is connected with each trackside AP in a wired mode. The controller controls and manages each trackside AP. For example, the AC may send station information of the subway to the first trackside AP, such that the onboard AP may receive the station information from the first trackside AP. The site information may include names of subway stations or other information, among others.

The controller and the trackside APs may also be bridged by a switch, thereby increasing the number of trackside APs. For example, in a subway system, a train travels along a longer track, and the number of trackside APs is greater, resulting in greater connection pressure to the controller. Thus, a management trackside AP for switch batch zoning can be provided in a subway system. Specifically, the controller is connected to a plurality of switches, and each switch is further connected to a certain number of trackside APs, thereby increasing the number of trackside APs controlled and managed by the controller.

In order to ensure the safety of train running, the on-board AP needs to continuously perform data transmission with the first trackside AP. During the forward travel of the train, the distance between the first trackside AP and the vehicle-mounted AP may become far, resulting in a weakening of the signal strength of the first trackside AP. When the signal strength of the first trackside AP is weaker, communication between the first trackside AP and the vehicle-mounted AP may be affected, which may cause the vehicle-mounted AP to fail to accurately and timely receive the information sent by the first trackside AP. Therefore, in order to realize uninterrupted and stable communication between the vehicle-mounted AP and the first trackside AP, the vehicle-mounted AP needs to continuously determine the signal strength of the first trackside AP in the running process of the train. For example, when the signal strength value corresponding to the first trackside AP is smaller than the minimum threshold, the link is torn down, and another trackside AP with a large signal strength value is reselected to establish the link.

Generally, when a wireless link is established between a vehicle-mounted AP and a trackside AP, the vehicle-mounted AP needs to find the trackside AP within a certain distance as a neighbor thereof, so as to realize link establishment.

In one embodiment, the onboard AP may collect neighbor information by passively listening for beacon frames (beacon frames) sent by the trackside AP. In the scheme, the vehicle-mounted AP selects a first trackside AP with the maximum signal strength to establish a wireless link according to the signal strength of the beacon frames received from the trackside APs, and the wireless link is used for transmitting data sent by the vehicle-mounted AP or the first trackside AP. The signal strength value may include a strength indication (received signal strength indicator, RSSI) value of the signal, among other things. For example, when the vehicle-mounted AP receives the beacon frames sent by the three trackside APs, the RSSI values of the three beacon frames are RSSI1, RSSI2, and RSSI3, respectively. When the vehicle-mounted AP determines that the RSSI3 is the maximum value of three RSSI values, the vehicle-mounted AP establishes a link with the trackside AP corresponding to the RSSL3.

Besides the single-link establishment mode, the vehicle-mounted AP can also adopt a multi-link establishment mode so as to improve the communication stability of the vehicle-mounted AP and the trackside AP. Specifically, the vehicle-mounted AP may establish a plurality of wireless links with a plurality of trackside APs, and select one link with the strongest signal strength from the plurality of wireless links as an active link, and the other links as candidate links. The active links are used for transmitting data, when the trackside AP corresponding to the active links fails to operate due to sudden faults, the vehicle-mounted AP can select one link from the candidate links to transmit the data, and interruption of data transmission with the trackside AP can be avoided. Because the signal strength of the active link changes from strong to weak along with the change of the distance, and the signal strength of the candidate link changes from weak to strong, the vehicle-mounted AP can take one of the candidate links as a new active link in the train running process. The multiple redundant candidate links ensure high reliability of communication.

The scheme that the beacon frame is sent by the trackside AP to realize chain building can realize interconnection and intercommunication between the train and the ground station in the running process, but the following problems still exist.

First, broadcasting beacon frames by the trackside AP occupies larger air interface resources.

Because each AP in the track traffic system belongs to the same-frequency AP, namely the vehicle-mounted AP and the trackside AP all transmit signals through the same wireless channel. And the number of the trackside APs in the rail transit communication system is large. Multiple trackside APs send beacon frames, wasting a lot of air interface resources.

Second, when the trackside APs transmit wireless signals, such as beacon frames, two trackside APs transmit simultaneously. The signals sent by the two trackside APs interfere with each other, so that the vehicle-mounted APs cannot correctly receive the signals. If the antenna arrangement of the trackside APs is such that there are hidden nodes between the trackside APs, the likelihood of mutual interference between signals is greater. If the second trackside AP cannot hear the signal being transmitted by the first trackside AP, the first trackside AP is a hidden node.

In order to increase the signal strength of the trackside APs, the trackside APs typically employ directional antennas as shown in fig. 1, i.e., with the main lobe of the antenna pattern facing the incoming train and the back lobe facing the other trackside APs. As can be seen from fig. 1, the back lobe is smaller than the main lobe. The left trackside AP may not hear that the right trackside AP is sending a signal to the vehicle-mounted AP due to the small back lobe (small directional receive gain). The right trackside AP may not hear the signal sent by the left trackside AP due to the small back lobe of the left trackside AP (weak directional signal). So that the trackside APs may be hidden nodes from each other. If two trackside APs send signals at the same time, the signals interfere with each other, so that the vehicle-mounted APs cannot receive the signals.

Therefore, the embodiment of the application provides a method for establishing a link in a rail transit communication system, which is to actively send a beacon frame by a vehicle-mounted AP to collect neighbor information so as to establish a wireless link, thereby solving the problems.

Fig. 2 is a method for establishing a link according to an embodiment of the present application.

As shown in fig. 2, the method includes the following steps S201 to S204.

In step S201, the in-vehicle AP transmits a beacon frame.

As the train travels forward, the onboard AP on the train may send beacon frames in broadcast. For example, the vehicle-mounted AP may broadcast beacon frames periodically according to a preset measurement period.

In step S202, the first trackside AP and the second trackside AP receive the beacon frame and measure signal strengths of the beacon frame, respectively, to determine signal strength values. As shown in fig. 3, the first trackside AP is a trackside AP that has established a link with the vehicle-mounted AP, and the second trackside AP is a trackside AP that has not established a link with the vehicle-mounted AP. The link between the vehicle-mounted AP and the first trackside AP in fig. 3 represents a link. It should be noted that the number of second trackside APs may be any number. The second trackside APs may include all trackside APs within a range of distances that do not establish a link with the onboard AP. In addition, in the scheme of establishing multiple links between the vehicle-mounted AP and the multiple trackside APs, the first trackside AP may include trackside APs corresponding to active links in all links established by the vehicle-mounted AP, and the second trackside AP may include other trackside APs within a certain distance range except for the trackside AP corresponding to the active links.

Specifically, after receiving the beacon frame, the first trackside AP and the second trackside AP measure their signal strengths to obtain signal strength values, and send the signal strength values to the controller. As previously described, the signal strength values may include RSSI values. For convenience of description, the signal strength value measured by the first trackside AP is referred to as a first signal strength value, and the signal strength value measured by the second trackside AP is referred to as a second signal strength value.

In one example, the onboard AP may transmit multiple beacon frames during one measurement period. Accordingly, when one trackside AP receives a plurality of beacon frames, the RSSI value of each beacon frame may be calculated as the signal strength value of the beacon frame. For example, when the first trackside AP receives a plurality of beacon frames, calculating a first signal strength value of each beacon frame; and when the second trackside AP receives a plurality of beacon frames, calculating a second signal strength value of each beacon frame. Optionally, a trackside AP alpha filters the signal strength values of the plurality of beacon frames prior to transmitting them to reduce the effects of signal fluctuations.

In step S203, the first trackside AP sends a first signal strength value to the vehicle-mounted AP, the second trackside AP sends a second signal strength value to the controller, and the controller sends the second signal strength value to the vehicle-mounted AP via the first trackside AP.

And the controller integrates the second signal intensity values sent by the second trackside APs after receiving the second signal intensity values, and sends the integrated data to the first trackside APs. The first trackside AP forwards the data to the onboard AP. For example, the AC receives signal strength values transmitted by a plurality of trackside APs and integrates them into a measurement report, and then transmits the measurement report to a first trackside AP, where the measurement report includes signal strength values measured by the plurality of trackside APs.

In step S204, the vehicle-mounted AP determines whether to change the link between the first trackside AP and the vehicle-mounted AP according to the first signal strength value and the second signal strength value.

After receiving the first signal intensity value and the second signal intensity value, the vehicle-mounted AP compares the magnitudes of the first signal intensity value and the second signal intensity value, and determines whether to change a link between the first trackside AP and the vehicle-mounted AP according to a comparison result.

Specifically, when the first signal strength value is greater than or equal to the second signal strength value, the vehicle-mounted AP may maintain the link established with the first track side access point, i.e., without tearing down and re-establishing the link.

Specifically, when the first signal strength value is smaller than the second signal strength value, as shown in fig. 4, the vehicle-mounted AP disconnects the link with the first trackside AP and reestablishes the link with the second trackside AP.

In an embodiment where a vehicle-mounted AP transmits multiple beacon frames in one cycle, the vehicle-mounted AP may measure an average of multiple signal strength values for each trackside AP. I.e. one trackside AP corresponds to one signal strength average. And the vehicle-mounted AP performs the judgment according to the signal intensity average value corresponding to each trackside AP, so as to determine whether to tear down and reestablish the chain.

In one embodiment, when the vehicle-mounted AP adopts a multilink establishment manner, the vehicle-mounted AP may compare magnitudes of signal strength values measured by the respective trackside APs, and select N trackside APs with the largest signal strength values from the plurality of trackside APs to establish links. After the on-board AP establishes the wireless links at the N trackside APs, the active links of the on-board AP may be updated. When a plurality of second trackside APs exist, a link corresponding to the trackside AP with the largest signal strength value is selected as a new active link. It should be noted that if a wireless link has been previously established with a certain one of the plurality of second trackside APs, the step of establishing the link is not performed. That is, when the vehicle establishes a link with N trackside APs, the trackside that is not linked with the N trackside APs can be determined according to the trackside AP list of the already linked. The track side APs which are not built in the N track side APs can be determined by comparing the track side APs in the list with the N track side APs.

In one embodiment, if the signal strength corresponding to one trackside AP is less than the minimum signal strength, or the signal strength corresponding to one trackside AP is not updated for a period of time, the link established with that trackside AP may be torn down.

In one embodiment, when the vehicle-mounted AP establishes a link, a TCP handshake may be used to establish a link with the trackside AP.

Based on the rail traffic communication system shown in fig. 1, the embodiment of the application also provides another method for establishing a link.

Fig. 5 is a flowchart of another method for establishing a link according to an embodiment of the present application.

As shown in fig. 5, the method includes the following steps S501 to S503.

In step S501, the in-vehicle AP transmits a beacon frame.

In step S502, the first trackside AP and the second trackside AP receive the beacon frame and measure signal strengths of the beacon frame to obtain a first trackside signal strength value and a second trackside signal strength value, respectively. And the first trackside AP sends a first signal intensity value to the vehicle-mounted AP, and the second trackside AP sends a second signal intensity value to the vehicle-mounted AP through the first trackside AP.

For the first trackside AP, the first signal strength value may be sent directly to the onboard AP since a link has been established with the onboard AP. For the second trackside AP, since no link is established with the onboard AP, the second signal strength value may be sent to the onboard AP via the first trackside AP, i.e., forwarded by the first trackside AP.

In step S503, the vehicle-mounted AP determines whether to change the link with the first trackside AP according to the first signal strength and the second signal strength.

The specific description of the above step S501 and step S503 may be referred to the description of the step S201 and step S204 in the embodiment shown in fig. 2, which is not repeated here.

Based on the rail transit communication system shown in fig. 1, the embodiment of the application further provides a method for establishing a link.

As shown in fig. 6, the method includes the following step S601

In step S601, the in-vehicle AP transmits a beacon frame.

In step S602, the first trackside AP and the second trackside AP receive the beacon frame and measure signal strengths of the beacon frame to obtain a first trackside signal strength value and a second trackside signal strength value.

The specific description of the steps S601 and S602 may be referred to the description of the steps S201 and S202 in the embodiment shown in fig. 2, which is not repeated here.

In step S603, the first trackside AP and the second trackside AP send the controller first trackside signal strength value and the second trackside signal strength value.

In step S604, the controller determines whether to change the link between the in-vehicle AP and the first trackside according to the first signal strength value and the second signal strength value.

The controller may send, when it is determined that the first signal strength value is smaller than the second signal strength value, first information to the vehicle-mounted AP via the first trackside AP, where the first information is used to instruct the vehicle-mounted AP to establish a link with the second trackside AP and disconnect the link from the first trackside AP. When the vehicle-mounted AP receives the first information, a link between the vehicle-mounted AP and the first trackside AP is disconnected, and a link is established between the vehicle-mounted AP and the second trackside AP.

The controller may further send, when the first signal strength is determined to be greater than or equal to the second signal strength, second information to the vehicle-mounted AP via the first trackside AP, the second information indicating that the vehicle-mounted AP maintains a link with the first trackside AP. And when the vehicle-mounted AP receives the second information, the link between the vehicle-mounted AP and the first trackside AP is kept unchanged.

The method for establishing the link shown in fig. 2, fig. 5 and fig. 6, in which the beacon frame is sent by the vehicle-mounted APs, can solve the problem that the number of the vehicle-mounted APs is far smaller than the number of the trackside APs, and the occupation of the port resources is large when the trackside APs send the beacon frame. In addition, the problem that interference exists between beacon frames when the beacon frames are sent by the vehicle-mounted AP can be solved, so that the link can be timely changed by the vehicle-mounted AP, and the communication reliability of the system is improved.

Based on the embodiments described in fig. 2 and fig. 5, the embodiment of the present application further provides a method for establishing a link, where the method is applied to a vehicle-mounted AP in the rail traffic communication system shown in fig. 1.

Fig. 7 is a method for establishing a link applied to a vehicle-mounted AP according to an embodiment of the present application.

As shown in fig. 7, the method includes the following steps S701 to S703.

In step S701, a beacon frame is transmitted.

In step S702, a first signal strength value and a second signal strength value of a beacon frame are received via a link between a first trackside access point and the vehicle access point. The first signal intensity value is obtained by measuring the signal intensity of the beacon frame by a first trackside AP in the track traffic communication system, and the second signal intensity value is obtained by measuring the signal intensity of the beacon frame by a second trackside AP in the track traffic communication system. Wherein the first trackside AP and the second trackside AP are not limited to two trackside APs. In one embodiment, the number of second trackside APs may be arbitrary. For example, the second trackside AP may also include all trackside APs within a certain distance range that do not establish a link with the onboard AP. In addition, in the scheme that the vehicle-mounted AP adopts multiple links, the first trackside AP may include trackside APs corresponding to active links in multiple links established by the vehicle-mounted AP.

In step S703, it is determined whether to change the link between the first trackside AP and the in-vehicle AP according to the first signal strength value and the second signal strength value.

The specific description of the steps S701 to S703 may be referred to the description of the embodiment shown in fig. 2, and will not be repeated here.

Based on the embodiments described in fig. 2 and fig. 5, the embodiment of the present application further provides a method for establishing a link, where the method is applied to a trackside AP in the rail transit communication system shown in fig. 1.

Fig. 8 is a method for establishing a link applied to a trackside AP according to an embodiment of the present application.

As shown in fig. 8, the method includes the following steps S801 and S802.

In step S801, a beacon frame transmitted by the vehicle-mounted AP is received, and the signal strength of the beacon frame is measured to obtain a signal strength value.

In step S802, a signal strength value is transmitted to the in-vehicle AP.

In a further embodiment of the present application,

the system further comprises a controller, and the sending the signal strength value to the vehicle-mounted access point comprises:

and sending the signal intensity value to the controller, wherein the controller is used for sending the signal intensity value to the vehicle-mounted access point through another trackside access point.

The specific description of the steps S801 to S802 may be referred to the description of the embodiment shown in fig. 2, and will not be repeated here.

Based on the method embodiment shown in fig. 6, the embodiment of the application also provides a method for establishing a link, and the method is applied to a controller in a rail transit communication system.

Fig. 9 is another method for establishing a link according to an embodiment of the present application.

As shown in fig. 9, the method includes steps S901 to S902.

In step S901, a first signal strength value transmitted by a first track side access point and a second signal strength value transmitted by a second track side access point are received. The first signal intensity value is obtained by the first track side access point measuring the signal intensity of the beacon frame sent by the vehicle-mounted access point, and the second signal intensity value is obtained by the second track side access point measuring the signal intensity of the beacon frame sent by the vehicle-mounted access point.

In step S902, it is determined whether to change a link between the in-vehicle AP and the first trackside AP according to the first signal strength value and the second signal strength value.

Specifically, if the first signal strength value is smaller than the second signal strength value, first information is sent to the vehicle-mounted access point via the first trackside access point, and the first information is used for indicating the vehicle-mounted access point to establish a link with the second trackside access point and disconnect the link with the first trackside access point.

Specifically, if the first signal strength value is greater than or equal to the second signal strength value, second information is sent to the vehicle-mounted access point via the first trackside access point, where the second information is used to instruct the vehicle-mounted access point to maintain a link with the first trackside access point.

The specific description of the steps S901 to S902 may be referred to the description of the embodiment shown in fig. 2, and will not be repeated here.

Based on the method embodiment shown in fig. 7, the embodiment of the present application further provides a vehicle-mounted AP, so as to implement the method embodiment shown in fig. 7.

Fig. 10 is a schematic structural diagram of a vehicle-mounted AP according to an embodiment of the present application. As shown in fig. 10, the in-vehicle AP1000 includes: a transmitting module 1001, a receiving module 1002 and a linking module 1003.

Wherein the transmitting module 1001 is configured to transmit a beacon frame.

The receiving module 1002 is configured to receive, via a link between a first track-side access point and the vehicle-mounted access point, a first signal strength value and a second signal strength value of the beacon frame, where the first signal strength value is obtained by measuring a signal strength of the beacon frame by the first track-side access point, and the second signal strength is obtained by measuring a signal strength of the beacon frame by the second track-side access point.

The link establishment module 1003 is configured to determine whether to change a link between the first track side access point and the vehicle-mounted access point according to the first signal strength value and the second signal strength value.

It should be noted that, in the method for establishing a link according to the embodiment of fig. 10, only the above-mentioned division of each functional module is used for illustration, and in practical application, the above-mentioned functional allocation may be performed by different functional modules according to needs, that is, the internal structure of the device is divided into different functional modules, so as to perform all or part of the functions described above. In addition, the vehicle-mounted AP for establishing a link provided in the foregoing embodiment belongs to the same concept as the method embodiment for establishing a link shown in fig. 7, and detailed implementation processes of the method embodiment are detailed in the method embodiment, which is not described herein again.

Based on the method embodiment shown in fig. 8, the embodiment of the present application further provides a trackside AP to implement the method embodiment shown in fig. 8.

Fig. 11 is a schematic structural diagram of a trackside AP according to an embodiment of the present application. As shown in fig. 11, the trackside AP includes: a receiving module 1101 and a transmitting module 1102.

The receiving module 1101 is configured to receive a beacon frame sent by a vehicle access point, and measure a signal strength of the beacon frame to obtain a signal strength value.

The sending module 1102 is configured to send the signal strength value to the vehicle-mounted access point.

It should be noted that, in the method for establishing a link by using the trackside AP1100 provided in the embodiment of fig. 11, only the above-mentioned division of each functional module is used as an example, in practical application, the above-mentioned functional allocation may be performed by different functional modules according to needs, that is, the internal structure of the device is divided into different functional modules to perform all or part of the functions described above. In addition, the trackside AP for establishing a link provided in the foregoing embodiment belongs to the same concept as the method embodiment for establishing a link shown in fig. 8, and detailed implementation procedures of the method embodiment are detailed in the method embodiment, which is not described herein again.

Based on the method embodiment shown in fig. 9, the embodiment of the present application further provides a controller to implement the method embodiment shown in fig. 9.

As shown in fig. 12, the controller 1200 includes: a receiving module 1201 and a judging module 1202.

The receiving module 1201 is configured to receive a first signal strength value sent by a first track side access point and a second signal strength value sent by a second track side access point, where the first signal strength value is obtained by the first track side access point measuring a signal strength of a beacon frame sent by a vehicle-mounted access point, and the second signal strength value is obtained by the second track side access point measuring a signal strength of the beacon frame sent by the vehicle-mounted access point.

The determining module 1202 is configured to determine whether to change a link between the first track side access point and the vehicle-mounted access point according to the first signal strength value and the second signal strength value.

It should be noted that, in the method of establishing a link, the controller 1200 provided in the embodiment shown in fig. 12 is only exemplified by the above-mentioned division of each functional module, and in practical application, the above-mentioned functional allocation may be performed by different functional modules according to needs, that is, the internal structure of the device is divided into different functional modules to perform all or part of the functions described above. In addition, the controller for establishing a link provided in the above embodiment belongs to the same concept as the method embodiment for establishing a link shown in fig. 9, and detailed implementation processes of the controller are shown in the method embodiment, which is not repeated here.

Fig. 13 is a schematic diagram of a hardware architecture of a computing device 1300 according to an embodiment of the present application.

The computing device 1300 may be an onboard AP, a trackside AP, or a controller as described above. Referring to fig. 13, the computing device 1300 includes a processor 1301, a memory 1302, a communication interface 1303, and a bus 1304, the processor 1301, the memory 1302, and the communication interface 1303 being connected to each other through the bus 1304. Processor 1301, memory 1302, and communication interface 1303 may also be connected using other connections than bus 1304.

The memory 1302 may be various types of storage media, such as random access memory (random access memory, RAM), read-only memory (ROM), nonvolatile RAM (NVRAM), programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (electrically erasable PROM, EEPROM), flash memory, optical memory, hard disk, and the like.

Where processor 1301 may be a general-purpose processor, the general-purpose processor may be a processor that performs certain steps and/or operations by reading and executing content stored in a memory (e.g., memory 1302). For example, the general purpose processor may be a central processing unit (central processing unit, CPU). Processor 1301 may include at least one circuit to perform all or part of the steps of the methods provided by the embodiments shown in fig. 7 or fig. 8 or fig. 9.

Among other things, communication interface 1303 includes input/output (I/O) interfaces, physical interfaces, logical interfaces, and the like for implementing device interconnections within computing device 1100, as well as interfaces for implementing computing device 1100 to interconnect with other devices (e.g., other computing devices or user devices). The physical interface may be an ethernet interface, a fiber optic interface, an ATM interface, etc.

Wherein the bus 1304 may be any type of communication bus, such as a system bus, that is used to interconnect the processor 1301, the memory 1302, and the communication interface 1303.

The above devices may be provided on separate chips, or may be provided at least partially or entirely on the same chip. Whether the individual devices are independently disposed on different chips or integrally disposed on one or more chips is often dependent on the needs of the product design. The embodiment of the application does not limit the specific implementation form of the device.

The computing device 1300 shown in fig. 13 is merely one embodiment provided by the present application, and the computing device 1300 may also include other components during implementation, which are not listed here.

In the above embodiments, it may be implemented in whole or in part by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loaded and executed on a computer, produces a flow or function in accordance with embodiments of the present application, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a computer network, or other programmable apparatus. The computer instructions may be stored in or transmitted from one computer-readable storage medium to another, for example, by wired (e.g., coaxial cable, optical fiber, digital Subscriber Line (DSL)), or wireless (e.g., infrared, wireless, microwave, etc.). The computer readable storage medium may be any available medium that can be accessed by a computer or a data storage device such as a server, data center, etc. that contains an integration of one or more available media. The usable medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a magnetic tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a Solid State Disk (SSD)), or the like.

It will be appreciated that the various numerical numbers referred to in the embodiments of the present application are merely for ease of description and are not intended to limit the scope of the embodiments of the present application. It should be understood that, in the embodiment of the present application, the sequence number of each process does not mean the sequence of execution, and the execution sequence of each process should be determined by the function and the internal logic of each process, and should not limit the implementation process of the embodiment of the present application.

The foregoing embodiments have been provided for the purpose of illustrating the general principles of the present application in further detail, and are not to be construed as limiting the scope of the application, but are merely intended to cover any modifications, equivalents, improvements, etc. based on the teachings of the application.

Claims

1. A rail transit communication system, the system comprising: the system comprises a vehicle-mounted access point, a first track side access point and a second track side access point, wherein a link exists between the first track side access point and the vehicle-mounted access point;

the vehicle-mounted access point is used for sending a beacon frame;

The first track side access point is used for receiving the beacon frame, measuring the signal intensity of the beacon frame to obtain a first signal intensity value, and sending the first signal intensity value to the vehicle-mounted access point;

the second trackside access point is configured to receive the beacon frame, measure a signal strength of the beacon frame to obtain a second signal strength value, and send the second signal strength value to the vehicle-mounted access point via the first trackside access point;

the vehicle-mounted access point is further configured to determine whether to change a link between the first track side access point and the vehicle-mounted access point according to the first signal strength value and the second signal strength value.

2. The system of claim 1, wherein the vehicle-mounted access point is mounted in a train traveling on a track along which a plurality of track-by-track access points are mounted, the plurality of track-by-track access points including the first track-by-track access point and the second track-by-track access point.

3. The system of claim 1 or 2, further comprising a controller,

the second trackside access point is specifically configured to send the second signal strength value to the controller;

The controller is configured to send the second signal strength value to the vehicle-mounted access point via the first trackside access point.

4. A system according to any one of claims 1-3, wherein the vehicle access point is specifically configured to:

if the first signal strength value is smaller than the second signal strength value, establishing a link with the second trackside access point and disconnecting the link with the first trackside access point;

if the first signal strength value is greater than or equal to the second signal strength value, maintaining a link with the first trackside access point.

5. A method of establishing a link for use with a vehicle access point, the method comprising:

transmitting a beacon frame;

receiving a first signal strength value and a second signal strength value of the beacon frame via a link between a first track bypass access point and the vehicle-mounted access point, the first signal strength value being obtained by the first track bypass access point measuring the signal strength of the beacon frame, the second signal strength value being obtained by a second track bypass access point measuring the signal strength of the beacon frame;

and determining whether to change a link between the first track side access point and the vehicle-mounted access point according to the first signal intensity value and the second signal intensity value.

6. The method of claim 5, wherein the vehicle-mounted access point is mounted in a train traveling on a track along which a plurality of track-by-side access points are mounted, the plurality of track-by-side access points including the first track-by-side access point and the second track-by-side access point.

7. The method of claim 5 or 6, wherein the determining whether to change the link between the first trackside access point and the vehicle access point based on the first signal strength value and the second signal strength value comprises:

8. A method of establishing a link for use with a track-side access point, the method comprising:

receiving a beacon frame sent by a vehicle-mounted access point, and measuring the signal intensity of the beacon frame to obtain a signal intensity value;

and sending the signal strength value to the vehicle-mounted access point.

9. The method of claim 8, wherein the on-board access point is mounted in a train traveling on a track along which the track-side access point is mounted.

10. The method of claim 8 or 9, wherein transmitting the signal strength value to the in-vehicle access point comprises:

11. The method according to any one of claims 8-10, further comprising a controller in the system, wherein the transmitting the signal strength value to the vehicle access point comprises:

12. A rail transit communication system, the system comprising: the system comprises a vehicle-mounted access point, a first track side access point, a second track side access point and a controller, wherein a link exists between the first track side access point and the vehicle-mounted access point;

the vehicle-mounted access point is used for sending a beacon frame;

The first track side access point is used for receiving the beacon frame, measuring the signal intensity of the beacon frame to obtain a first signal intensity value, and sending the first signal intensity value to the controller;

the second trackside access point is configured to receive the beacon frame, measure a signal strength of the beacon frame to obtain a second signal strength value, and send the second signal strength value to the controller;

the controller is configured to determine whether to change a link between the first track side access point and the vehicle-mounted access point according to the first signal strength value and the second signal strength value.

13. The system of claim 12, wherein the vehicle-mounted access point is mounted in a train traveling on a track along which a plurality of track-by-track access points are mounted, the plurality of track-by-track access points including the first track-by-track access point and the second track-by-track access point.

14. The system according to claim 12 or 13, wherein the controller is specifically configured to:

if the first signal intensity value is smaller than the second signal intensity value, first information is sent to the vehicle-mounted access point through the first trackside access point, and the first information is used for indicating the vehicle-mounted access point to establish a link with the second trackside access point and disconnect the link with the first trackside access point;

And if the first signal intensity value is greater than or equal to the second signal intensity value, sending second information to the vehicle-mounted access point through the first trackside access point, wherein the second information is used for indicating the vehicle-mounted access point to keep a link with the first trackside access point.

15. A method of establishing a link for use with a controller, the method comprising:

receiving a first signal intensity value sent by a first track side access point and a second signal intensity value sent by a second track side access point, wherein the first signal intensity value is obtained by the first track side access point for measuring the signal intensity of a beacon frame sent by a vehicle-mounted access point, and the second signal intensity value is obtained by the second track side access point for measuring the signal intensity of the beacon frame sent by the vehicle-mounted access point;

16. The method of claim 15, wherein the determining whether to change the link between the first trackside access point and the vehicle access point based on the first signal strength value and the second signal strength value comprises:

17. An in-vehicle access point, the in-vehicle access point comprising:

a transmitting module, configured to transmit a beacon frame;

a receiving module, configured to receive a first signal strength value and a second signal strength value of the beacon frame via a link between a first track-side access point and the vehicle-mounted access point, where the first signal strength value is obtained by the first track-side access point measuring a signal strength of the beacon frame, and the second signal strength is obtained by the second track-side access point measuring a signal strength of the beacon frame;

And the link establishment module is used for determining whether to change the link between the first track side access point and the vehicle-mounted access point according to the first signal intensity value and the second signal intensity value.

18. The vehicle-mounted access point of claim 17, wherein the vehicle-mounted access point is mounted in a train traveling on a track along which a plurality of track-by-track access points are mounted, the plurality of track-by-track access points including the first track-by-track access point and the second track-by-track access point.

19. The vehicle access point according to claim 17 or 18, wherein the link establishment module is specifically configured to:

20. A track side access point, the track side access point comprising:

the receiving module is used for receiving a beacon frame sent by the vehicle-mounted access point and measuring the signal intensity of the beacon frame to obtain a signal intensity value;

And the sending module is used for sending the signal intensity value to the vehicle-mounted access point.

21. The track-side access point of claim 20, wherein the in-vehicle access point is mounted in a train traveling on the track, the track-side access point being mounted along the track.

22. The track side access point according to claim 20 or 21, wherein the sending module is specifically configured to:

23. The track side access point of any one of claims 20-22, wherein the system further comprises a controller, the transmitting module further configured to:

and sending a signal strength value to the controller, wherein the controller is used for sending the signal strength value to the vehicle-mounted access point through another trackside access point.

24. A controller, the controller comprising:

the receiving module is used for receiving a first signal intensity value sent by a first track side access point and a second signal intensity value sent by a second track side access point, wherein the first signal intensity value is obtained by the first track side access point for measuring the signal intensity of a beacon frame sent by a vehicle-mounted access point, and the second signal intensity value is obtained by the second track side access point for measuring the signal intensity of the beacon frame sent by the vehicle-mounted access point;

And the judging module is used for determining whether to change the link between the first track side access point and the vehicle-mounted access point according to the first signal intensity value and the second signal intensity value.

25. The controller according to claim 20, wherein the judging module is specifically configured to:

26. A computing device, the computing device comprising: a processor and a memory for executing a computer program stored in the memory for implementing the method of any one of claims 5 to 7, or for implementing the method of any one of claims 8 to 11, or for implementing the method of claim 15 or claim 16.

27. A computer readable storage medium comprising instructions which, when run on a computer, cause the computer to perform the method of any one of claims 5 to 7, or to perform the method of any one of claims 8 to 11, or to perform the method of claim 15 or claim 16.