CN115866558A - Dynamic networking method for rail transit wireless vehicle-mounted terminal based on 5G - Google Patents

Abstract

The invention provides a dynamic networking method for a rail transit wireless vehicle-mounted terminal based on 5G, and belongs to the field of rail transit communication. The method comprises the steps that a TRDP packet of a real-time data protocol of a train is obtained based on an existing vehicle-mounted terminal, TDRP < - > IP protocol conversion is carried out to access a 5G network, meanwhile, a T-GRE server is installed on the side of a 5G core network, and a T-GRE tunnel is established between each 5G vehicle-mounted terminal and the server; after the network topology structure is changed, the switch automatically negotiates with other network equipment according to a train topology discovery protocol, and allocates a 5G IP address for a new 5G vehicle-mounted terminal to realize dynamic sensing discovery of nodes; and the server analyzes the uploaded data of all the trains to carry out marshalling of the vehicle-mounted terminals, so that dynamic networking of the vehicle-mounted terminals is realized. The invention meets the requirements of high speed, high reliability and low time delay required by train communication, realizes the dynamic perception discovery of the vehicle-mounted terminal node, and simultaneously reduces the manual address configuration and marshalling.

Description

Dynamic networking method for rail transit wireless vehicle-mounted terminal based on 5G

Technical Field

The invention belongs to the field of rail transit communication, and particularly relates to a rail transit wireless vehicle-mounted terminal dynamic networking method based on 5G.

Background

The communication function and the control system of the rail transit are required to be realized through a communication network. The current train network is based on the real-time Ethernet to guarantee data interaction; with the implementation of intelligent tracks, the number of nodes of sensors and vehicle-mounted equipment is increased continuously, and a wired network cannot meet the communication and control requirements. For future intelligent tracks, communication systems employing the railway long term evolution (LTE-R) standard are being considered; however, the maximum bandwidth of the LTE-R system is only 20MHz, and only the data rate of Mbps level can be supported, and the requirements such as real-time Ultra High Definition (UHD) video transmission, a secure Closed Circuit Television (CCTV) in a train car, remote maintenance of a train, high data rate wireless unloading at a train station, and the like cannot be met; the wireless data transmission system based on General Packet Radio Service (GPRS) utilizes the advantages of wide GPRS coverage and low cost to realize wireless data transmission, but its low communication rate cannot meet the requirements of future intelligent tracks. The 5G network has the characteristics of high speed, low time delay, large connection and the like, brings a new opportunity for wireless communication, and can meet the requirements of a rail transit wireless communication system on high speed and low time delay.

In a communication network of rail transit, a vehicle-mounted terminal is always in a motion state along with the movement of a train, and the performance of the vehicle-mounted terminal determines the quality of a communication state and is a key node. The data transmission of the current 5G vehicle-mounted terminal is mainly based on a tunnel protocol, and the 5G vehicle-mounted Internet of things is composed of a 5G terminal, an access network and a core network. The access network and the core network are interconnected by adopting a TCP/IP protocol, and the IP address of the terminal is independently distributed by the core network. The IP address allocation of the 5G terminal and the IP address of the TRDP data packet of the train vehicle-mounted service terminal are independent and cannot be communicated directly, so that the TRDP data packet is encapsulated by adopting a tunnel protocol technology, and a transmission tunnel is established between the two train vehicle-mounted service terminals to realize the data interaction of the train vehicle-mounted service terminals.

Currently, common tunnel protocols include Generic Routing Encapsulation (GRE), link Layer Tunneling Protocol (L2 TP), point-to-Point Tunneling Protocol (PPTP), IPSec, multi-Protocol Label Switching (MPLS), IPinIP, GTP (GPRS Tunneling Protocol), and the like. In the IP multicast transmission model, the sender does not care about the location of the receiver, and as long as the sender sends data to the appointed destination address, the rest of the work is handed to the network to be completed, the multicast device in the network must collect the information of the receiver and implement the forwarding and copying of the multicast message according to the correct path, and in the development process of IP multicast, a set of complete protocol is formed to complete the task. Common multicast protocols are: a Multicast Group Management Protocol (IGMP), a Protocol Independent Multicast (PIM), a Multicast Source Discovery Protocol (MSDP), a Multicast Border Gateway Protocol (MBGP), and the like.

Different tunnel protocols have different characteristics in the aspects of supported data stream quantity, protocol overhead degree, service quality guarantee capability, data encryption and the like, and if the protocols are applied to the aspect of networking of future intelligent rail vehicle-mounted terminals, certain problems exist. PPTP is characterized by high speed, easy installation and use, almost all platforms support the protocol, but a firewall can intercept the PPTP protocol, which is one of the unsafe protocols, and the protocol does not support QoS. L2TP is a two-layer tunneling protocol, which is a virtual tunneling protocol, and is usually used in a virtual private network, but L2TP and IPSec use a connection-oriented overlay model, and thus have many problems in scalability; the addition, deletion, and change of new user nodes all require the reconfiguration of all existing nodes. MPLS is a new technology for guiding high-speed and efficient data transmission on open communication networks by using labels, but it will require all relevant routers inside a public 5G network to be able to support MPLS, so this technology has more special requirements on the network.

Disclosure of Invention

In view of the above-mentioned defects or shortcomings in the prior art, embodiments of the present invention provide a dynamic networking method for a 5G-based rail transit 5G vehicle-mounted terminal, which proposes and creates a T-GRE tunnel protocol, implements 5G multicast communication for the 5G vehicle-mounted terminal, meets requirements of high speed, high reliability and low delay required by train communication, completes neighbor discovery and physical topology discovery of the 5G vehicle-mounted terminal (i.e., the 5G vehicle-mounted terminal) according to a radio signal strength manner in a wireless communication network, implements dynamic discovery of vehicle-mounted terminal nodes, performs grouping of multicast group members according to a dynamic discovery result, and completes group measurement on a T-GRE server, implements multicast communication transmission from point to point, implements service terminal intercommunication in one multicast while supporting dynamic network perception, and reduces manual address configuration and grouping.

In order to achieve the above purpose, the embodiment of the invention adopts the following technical scheme:

a rail transit wireless vehicle-mounted terminal dynamic networking method based on 5G comprises the following steps:

step S1, on the basis of a standard Ethernet protocol stack, performing TDRP < - >5G IP protocol conversion on a train real-time data protocol, and providing end-to-end data transmission with safety guarantee for process data and message data communication between any two devices in a 5G rail transit network; meanwhile, a T-GRE server is installed on the 5G core network side, a T-GRE tunnel is established between each 5G vehicle-mounted terminal and the server and is connected with other 5G vehicle-mounted terminals, and a two-layer tunnel is opened among all devices in the current network environment through the T-GRE server, so that service intercommunication in a multicast group is realized;

s2, according to a train topology discovery protocol, after a network topology structure of a switch of the 5G rail transit network is changed, discovering a changed node based on network perception, automatically negotiating with other network equipment, and allocating an IP address for the changed 5G vehicle-mounted terminal according to a new instruction of a train compartment;

s3, uploading the position information, the cell ID, the uplink and downlink information and the speed information of the train terminal to a T-GRE server in real time for the found node;

s4, analyzing the uploading data of all trains on the server, and judging whether the trains are in the T-GRE coverage area or not based on the train position information and the 5G coverage area IDs of all nodes and the 5G vehicle-mounted terminals of the local nodes found in the current network topology structure; a logic bus is established on the T-GRE, a logic switch is arranged on the T-GRE tunnel and the logic bus which are used for connecting each train in a coverage area of a server, a grouping logic determines which trains can be communicated, a virtual broadcast domain is formed for the communicated 5G vehicle-mounted terminals, the communication of TTDP/TRDP messages is realized, and dynamic networking is realized.

As a preferred embodiment of the present invention, the message structure of the TRDP layer includes four layers, which are, from top to bottom, a version and total length layer, a flag and slice offset layer, a TTL and protocol UDP check layer, and a source IP address and a destination IP address layer.

As a preferred embodiment of the present invention, the network topology changes, including the initial configuration change at the start of the train and the configuration change occurring after the position change of the train car after the start of the train.

As a preferred embodiment of the present invention, the configuring a train topology discovery protocol to enable a switch of a 5G rail transit network to automatically negotiate with other network devices after a network topology structure is changed includes:

step S21, judging the state of the BN node according to a train topology discovery protocol, and if the state is UNNAMED, turning to step S22; if NAMING status, go to step S23; if the NAMED state is detected, the step S24 is executed;

step S22, entering an initial UNNAMED state after the train is powered on or reset; in the state, the topology directory is not established, and the network message is bypassed before entering the NAMING state;

step S23, in NAMING state, BN is running a starting protocol; entering a NAMED state with an effective train topology directory when the start is successfully completed; if an unrecoverable failure is detected, return to the "UNNAMED" state; when the system is started, each BN node broadcasts a HELLO message, the radio power is set to be the minimum initial value, the length of two vehicles can be covered, and each node collects an ACK message in a certain time range; if the number of the received messages is less than 4, retransmitting the HELLO messages for increasing the radio power; each node repeats this operation until it collects at least 4 ACK packets or the timeout timer Tmax expires;

step S24, the topology discovery protocol under the NAMED state is divided into two stages: the first stage, neighbor discovery, using radio signal strength to find neighboring nodes and estimating the relative position of BN; the second stage, topology discovery, wherein the topology frame comprises the MAC address information of the BN currently discovered by the BN; and each BN keeps the updated physical and logical topology directories according to the received HELLO and the topology frame, and after receiving the topology frame, the BN updates the physical and logical topology directories to realize topology discovery.

As a preferred embodiment of the present invention, the neighbor discovery process is as follows: each BN sends the HELLO frame together with the MAC address thereof to the neighbor nodes to try to discover the MAC addresses of the neighbor nodes; each BN receives HELLO frames from its left and/or right incoming links, the BN at hand learns the MAC addresses of neighbors; at which time the reception of these two frames completes the neighbor discovery phase.

As a preferred embodiment of the present invention, step S4 specifically includes:

step S41, when a new 5G vehicle-mounted terminal is added as a group member, the multicast IP is unified according to the neighbor topology directory, after the marshalling is finished, the terminal with the smallest private address in the marshalling is selected as an administrator to undertake the marshalling communication task between the multicast group and the T-GRE server, and the administrator sends a registration request to the T-GRE server; if the administrator is invalid, other terminals will reselect a new administrator after the administrator timer is overtime; when a new node is found, the logical topology directory is updated, the server sends a query request to an administrator at regular time, and if the logical topology directory changes, the network configuration of the node is updated;

step S42, when group member maintenance is carried out on the 5G vehicle-mounted terminal in the group, the group members are maintained by a logical topology directory and a node network configuration directory on a server, and the two directories keep consistency; when the logical topology directory is different from the node network configuration directory and the consistency conflicts, updating the node network configuration by taking the logical topology directory as a reference;

step S43, when the 5G vehicle-mounted terminal leaves the group, the logical topology directory is updated, and when the T-GRE sends the query request next time, the new configuration information is updated; if there is no member in the group, T-GRE sends three times of inquiry request without response, then deletes the group network configuration.

The invention has the following beneficial effects:

the 5G-based dynamic networking method for the vehicle-mounted terminal of the 5G is based on a standard Ethernet protocol stack, a TRDP layer is added between a transmission layer and an application layer of a real-time data protocol of the train for TDRP < - > IP protocol conversion, and end-to-end data transmission with safety guarantee can be provided for process data and message data communication between any two devices in a 5G rail transit network; meanwhile, a T-GRE server is installed on the 5G core network side, a T-GRE tunnel is established between each 5G vehicle-mounted terminal and the server to establish connection with other 5G vehicle-mounted terminals, and a two-layer tunnel is opened among all devices in the current network environment through the T-GRE server to realize service intercommunication in a multicast group; according to a train topology discovery protocol, after a network topology structure of a switch of the 5G rail transit network is changed, the switch discovers the changed node based on network perception, automatically negotiates with other network equipment, and allocates an IP address for the changed 5G vehicle-mounted terminal according to a new train compartment instruction, so that dynamic perception discovery of the node is realized; uploading the position information, the cell ID, the uplink and downlink information and the speed information of the train terminal to a T-GRE server in real time for the found node; analyzing the uploading data of all trains on the server, and judging whether the trains are in the T-GRE coverage area or not based on the train position information and the 5G coverage area ID for all the nodes found in the current network topology structure and the 5G vehicle-mounted terminals of the local nodes; a logic bus is established on the T-GRE, a logic switch is arranged on the T-GRE tunnel and the logic bus which are used for connecting each train in a coverage area of a server, a grouping logic determines which trains can be communicated, a virtual broadcast domain is formed for the communicated train terminals, the intercommunication of TTDP/TRDP messages is realized, and dynamic networking is realized. The invention provides a T-GRE tunnel protocol mode to realize the 5G multicast communication of the vehicle-mounted wireless terminal, and meets the requirements of high speed, high reliability and low time delay required by train communication; according to the TTDP protocol, neighbor discovery and physical topology discovery of the vehicle-mounted terminal are completed in a mode of radio signal strength in a wireless communication network, and dynamic sensing discovery of the vehicle-mounted terminal node is realized; meanwhile, grouping of multicast group members is carried out according to the dynamic discovery result of the vehicle-mounted terminal node, and group detection is completed on the T-GRE server, so that point-to-many multicast communication transmission is realized, and manual address configuration and grouping are reduced.

Of course, not all of the advantages described above need to be achieved at the same time in the practice of any one product or method of the invention.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic diagram of a dynamic networking method for a wireless vehicle-mounted terminal of rail transit based on 5G provided by an embodiment of the invention;

fig. 2 is a schematic diagram of a TRDP message structure in the embodiment of the present invention;

FIG. 3 is a diagram illustrating a tunneling protocol packet structure according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of an existing vehicle-mounted terminal accessing a 5G rail transit network in an embodiment of the present invention;

FIG. 5 is a schematic diagram of a point-to-multipoint network environment deployment in an embodiment of the present invention;

FIG. 6 is a flow chart of a train startup state transition in an embodiment of the present invention;

FIG. 7 is a flow chart of topology discovery in an embodiment of the present invention;

FIG. 8 is a flow chart of dynamic sensing and grouping in an embodiment of the invention;

fig. 9 is a flow chart of grouping process member joining in an embodiment of the present invention.

Detailed Description

After finding the above problems, the inventors of the present application have conducted intensive studies on the existing rail transit communication network, especially on the networking technology of the vehicle-mounted terminal. Research shows that in the existing network architecture, the transmission distance between a terminal and a core network is too long, which causes congestion of a backhaul network and intense resource competition, and affects the transmission quality of delay-sensitive services. The problem can be well solved by deploying Multi-access Edge Computing (MEC) as the supplement of the center cloud at the position close to the terminal side, and meanwhile, the safety isolation between services is realized by combining the 5G network slicing technology, so that special network and application resources are provided for the terminal nearby.

Meanwhile, a multi-mode (4G, 5G) wireless module, a WLAN data communication module, a wireless AP hotspot access module, a main control module, an external interface-based vehicle-mounted wireless communication terminal, and the like have been developed. The wireless module is an information inlet through which various intelligent terminals can access the Internet of things, is also a key element component through which the wireless terminal can be positioned, and is subdivided into a 2/3/4/5G module, NB-IOT (network entry point) modules of LPWAN (Long period network wide area), e-MTC modules and the like according to different technologies; generally, a 4G module is a module capable of accessing to a 4G network of an operator, a 2G module is mainly applied to the field of shared bicycles with low data demand, a 3G module is mainly applied to the field of mobile payment such as POS (point of sale) machines, a 4G module is mainly applied to the field of vehicle-mounted vehicles and video monitoring with high requirements on speed, LPWAN modules are more applied to the field of meter reading with low requirements on power consumption, and Wi-Fi, bluetooth and ZigBee have short transmission distances and are mainly applied to the consumption fields of medical treatment, smart home and the like.

When the 5G network is adopted to replace the original vehicle-mounted main network, the IP address of the 5G vehicle-mounted terminal and the TRDP data packet address IP of the train terminal are mutually independent and can not be intercommunicated, the TRDP data packet needs to be encapsulated by a tunnel, and a transmission tunnel is established between the two vehicle-mounted service terminals, so that the data interaction of the train vehicle-mounted service terminals can be realized to realize the intercommunicating between the train terminals. The precondition for establishing the tunnel protocol is as follows: an online address (i.e., an address allocated by a 5G core network) of the 5G vehicle-mounted terminal is required to be a fixed IP address, and a tunnel destination IP and a tunnel source IP of the vehicle-mounted terminal are required to be configured on a service. Because the 5G vehicle-mounted terminal can carry out dynamic grouping according to the change of the physical position, the adoption of the static configuration mode is not flexible and convenient. Therefore, the method and the device utilize the tunnel protocol to carry out 5G customized transformation on the vehicle-mounted terminal, provide a wireless topology discovery protocol to carry out dynamic network perception and node discovery when the vehicle-mounted terminal is changed so as to enable the vehicle-mounted terminal to be accessed into a 5G network, adapt to the existing data, realize point-to-point and point-to-multipoint communication of the 5G vehicle-mounted terminal, and obtain high reliability and high data rate services required by train communication.

The TRDP data is adapted in the existing tunnel scheme, a two-layer tunnel is opened among a plurality of 5G vehicle-mounted terminals, all devices in the current environment are in the same network segment, a gateway does not need to be configured for the terminals, and all devices in the network environment can communicate with each other. However, when the TRDP protocol data transmission is required between the point-to-multipoint nodes, if a tunnel is established between the point-to-point nodes, the configuration amount is large and errors are prone to occur. The method and the system provide a corresponding grouping strategy for multicast dynamic grouping, a T-GRE server is installed on a 5G core network side, a tunnel is established between each 5G vehicle-mounted terminal and the server, and the existing vehicle-mounted terminals are connected into a 5G rail transit network through the 5G vehicle-mounted terminals. The T-GRE server of L2GRE (Layer 2 GREnnels) establishes communication with the 5G vehicle-mounted terminal, creates an elastic VPN, allows the same VLAN to be connected with each other at a plurality of positions, and realizes service intercommunication in a multicast group.

In addition, in the current train network, after the existing vehicle-mounted terminal data is packaged into a TRDP data packet, the TRDP data packet is sent to other terminals through a train vehicle-mounted network switch and a backbone network router in an IP multicast mode, and a terminal IP address generally adopts a private network address. On the basis of a tunnel protocol, the TRDP protocol data transmission is needed between the point-to-multipoint of the 5G vehicle-mounted terminal, when a multi-train forms a marshalling, more than two tunnels are needed to be built for each train to form a cross network, the configuration of the vehicle-mounted network needs to be changed, and loop suppression is needed. The invention provides a dynamic grouping strategy, thereby realizing service intercommunication in multicast and reducing manual configuration.

It should be noted that the defects of the solutions in the prior art are the results of the inventor after practice and careful study, and therefore, the discovery process of the above problems and the solutions proposed by the embodiments of the present invention to the above problems should be the contribution of the inventor to the present invention in the process of the present invention.

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. The components of embodiments of the present invention generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations. It should be noted that the embodiments and features of the embodiments of the present invention may be combined with each other without conflict.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures. In the description of the present invention, the terms "first", "second", "third", "fourth", and the like are used only for distinguishing the description, and are not intended to indicate or imply relative importance.

After the deep analysis, the application provides a dynamic networking method of a rail transit wireless vehicle-mounted terminal based on 5G, firstly, multicast communication between the 5G vehicle-mounted terminals can be supported through a tunnel protocol and multicast group management, and currently, equipment for supporting the multicast communication of the 5G terminals is not in commercial use; secondly, in order to support vehicle-to-vehicle communication and infinite grouping more flexibly, the protocol function supporting wireless node discovery is provided, and dynamic network perception is supported; thirdly, for the discovered newly added vehicle-mounted terminal, the invention provides a dynamic grouping strategy through a server at the 5G core network side, realizes the intercommunication of the service terminals in a multicast and reduces the manual address configuration and grouping.

As shown in fig. 1, the dynamic networking method for the wireless vehicle-mounted terminal in the rail transit based on 5G provided by the embodiment of the present invention includes the following steps:

step S1, on the basis of a standard Ethernet protocol stack, adding a TRDP layer between a transmission layer and an application layer to a train real-time data protocol, performing TDRP < - > IP protocol conversion, and providing end-to-end data transmission with safety guarantee for process data and message data communication between any two vehicle-mounted terminals in a 5G rail transit network; meanwhile, a T-GRE server is installed on the 5G core network side, a T-GRE tunnel is established between each 5G vehicle-mounted terminal and the server and is connected with other 5G vehicle-mounted terminals, and two-layer tunnels are opened among all 5G vehicle-mounted terminals in the current network environment through the T-GRE server, so that service intercommunication in a multicast group is realized.

In this step, the message structure of the TRDP layer is shown in fig. 2, and includes four layers, which are, from top to bottom, a version and total length layer, a mark and slice offset layer, a TTL and protocol UDP check layer, and a source IP address and destination IP address layer.

The TRDP layer is defined by IEC61375-2-3 standard and is positioned above a TCP/UDP transmission layer. The Train real-time data protocol TRDP specifies the communication flow of Train Control Network (Train Control Network, TCN) process data and message data in a Train communication Network.

According to the structure of the 5G network, the 5G vehicle-mounted terminal is connected with other 5G vehicle-mounted terminals (the same vehicle/different vehicles) through the core network by the T-GRE server installed on the 5G core network side. As shown in fig. 3, the T-GRE packet structure adds a new IP field and a GRE header field to the original TRDP packet; as shown in fig. 4, the establishing of the T-GRE tunnel between the 5G vehicle-mounted terminal and the server and the establishing of the connection with other 5G vehicle-mounted terminals specifically includes: the existing vehicle-mounted terminal data are packaged through a tunnel protocol, and logical connection is established through a T-GRE server, so that 5G transmission communication between terminals is realized. As shown in fig. 5, the network environment deployment for implementing service interworking in a multicast group includes: and filling a new wireless IP above the terminal IP, and establishing connection with the server through the T-GRE tunnel.

And S2, according to a train topology discovery protocol, after a network topology structure of a switch of the 5G rail transit network is changed, the switch discovers the changed node based on network perception, automatically negotiates with other network equipment, and allocates an IP address for the changed 5G vehicle-mounted terminal according to a new train compartment instruction, and a network administrator or other operators do not need to manually configure network equipment again, so that the operation efficiency is improved, and configuration errors are reduced.

In this step, the network topology changes, including the initial configuration change during train start and the configuration change due to the change of the car position after train start. Due to the actions of marshalling, decompiling, throwing and hanging and the like of the train, the topological structure of the train is always dynamically and frequently changed. Each time a car changes, the network needs to be reconfigured, which is time consuming and error prone if done manually. The train topology discovery protocol is developed to improve the efficiency of rail transit network configuration, and can realize network awareness and node discovery.

The configuration of the train topology discovery protocol enables the switch of the 5G rail transit network to automatically negotiate with other network devices after the network topology is changed, and the negotiation comprises the following steps:

step S21, judging the state of the BN node according to a train topology discovery protocol, and if the state is UNNAMED, turning to step S22; if NAMING status, go to step S23; if the NAMED state is detected, the process proceeds to step S24.

As shown in fig. 6, when a train starts, an action of configuring a train network topology is defined as train start, the train normal start is performed when a train operation state changes or power-on (reset) time occurs, and the initialization is performed to find a physical network topology, that is, a sequence and a direction of a Backbone Node (BN) in a linear network topology. The BN here is the 5G vehicle terminal. Each BN node is in one of three states: unNamed, NAMING, NAMED. Therefore, the discovery of the network topology change corresponding to the above three states further includes:

step S22, entering an initial UNNAMED state after the train is powered on or reset; in this state, the topology directory is not established yet, and therefore communication cannot be performed through the BN in this state, and the network packet is bypassed before entering the NAMING state.

Step S23, in the NAMING state, the BN is running the start program, and when the start is successfully completed, it will enter into the NAMED state with a valid train topology directory; if an unrecoverable failure is detected, the status is returned to "UNNAMED". As shown in fig. 7, when starting up, each BN node broadcasts a HELLO message whose radio power is set to a minimum initial value, which can cover the length of two vehicles. And each node collects the ACK message in a certain time range. And if the number of the received messages is less than 4, retransmitting the HELLO message with the increased radio power. Each node repeats this operation until it collects at least 4 ACK packets or the timeout timer Tmax expires.

Step S24, the topology discovery protocol under the NAMED state is divided into two stages: the first phase, neighbor discovery, uses radio signal strength to find neighboring nodes and estimate the relative location of the BN. Since the topology discovery protocol is designed assuming that each train car (or car) in the neighborhood is connected by a direct wired cable, it cannot be directly used in a wireless communication environment. In such a wire train communication system, it is very simple to find a neighbor node. By exchanging the network addresses (usually indicated by MAC addresses) of the nodes with directly connected neighbor nodes via HELLO frames, any backbone node can find the addresses of its neighbor nodes and hence their relative positions in the overall network topology. However, in wireless communication, the HELLO frame is broadcast, and a plurality of non-geographic neighbors can receive the HELLO frame, which affects the judgment of finding geographic neighbors, so that a manner of using radio signal strength is adopted to find neighboring nodes. Specifically, each BN sends a HELLO frame to the neighbor nodes along with its MAC address, attempting to discover the neighbor nodes' MAC addresses. Due to the nature of the train, the physical network topology is a linear topology, and it is easy to find neighbor BN connected by switched ethernet. Each BN receives HELLO frames from incoming links to its left and/or right side. Since each frame carries the MAC address sent to the neighbor, the neighboring BNs learn the MAC addresses of each other. The reception of these two adjacent frames completes the neighbor discovery phase. And in the second stage, topology discovery. The physical topology is constructed by sharing neighbor node information using a topology frame containing MAC address information of a BN currently discovered by the sending BN. Each BN maintains an updated physical and logical topology catalog based on previously received HELLO and topology frames. After receiving the topology frame, the BN updates its physical and logical topology directory to implement topology discovery.

The BN in the NAMED state can join the network and the user data is transmitted through the train core network. During operation, the BN also checks for changes in the topology of the train backbone. When any change or forced initiation is detected, it will disable the user data exchange on the train core network and enter the NAMING state through the initiation process.

And S3, uploading the position information, the cell ID, the uplink and downlink information and the speed information of the train terminal to a T-GRE server for the found node in real time.

S4, analyzing the uploading data of all trains on the server, and judging whether the trains are in the T-GRE coverage area or not based on the train position information and the 5G coverage area IDs of all nodes and the 5G vehicle-mounted terminals of the local nodes found in the current network topology structure; a logic bus is established on the T-GRE, a logic switch is arranged on the T-GRE tunnel and the logic bus which are connected with each train in the coverage area of the server, the grouping logic determines which trains can be communicated, and the communicated 5G vehicle-mounted terminal forms a virtual broadcast domain to realize the communication of TTDP/TRDP messages.

In this step, as shown in fig. 8, in order to avoid the grouping redundancy, only allowing the train within the target range to automatically group the network in the scheduling policy, in this embodiment, first, whether the train is within the T-GRE coverage area is determined based on the train position information and the 5G coverage area ID; then, based on the set bus, a marshalling logic (which can be manually designated, or automatically configured according to the vehicle position, the base station information, etc.) determines which trains can be intercommunicated, and a virtual broadcast domain is formed for intercommunicated train terminals to realize the intercommunication of TTDP/TRDP messages.

The nodes with the opened logic switches are grouped according to a neighbor logic topology directory, and the management of multicast group members mainly comprises three parts of group member joining, group member maintenance and group member leaving, wherein the group members are 5G vehicle-mounted terminals. Based on this, the method specifically comprises the following steps:

step S41, when a new 5G vehicle-mounted terminal is added as a group member, as shown in FIG. 9, multicast IP is unified according to the neighbor topology directory, after grouping is completed, the terminal with the smallest private address in the grouping is selected as an administrator to undertake the grouping communication task between the multicast group and the T-GRE server, and the administrator sends a registration request to the T-GRE server. If the administrator fails, the other terminal will re-elect a new administrator after the administrator timer expires. When a new node is discovered, the logical topology directory is updated, the server sends a query request to an administrator at regular time (60 s), and if the logical topology directory changes, the network configuration of the node is updated.

And step S42, when group member maintenance is carried out on the 5G vehicle-mounted terminal in the group, maintaining the group members by using the logical topology directory and the node network configuration directory on the server, wherein the two directories need to keep consistency. And when the logical topology directory is different from the node network configuration directory and the consistency conflicts, updating the node network configuration by taking the logical topology directory as a reference.

And S43, when the 5G vehicle-mounted terminal leaves the group, updating the logic topology directory, and updating the logic topology directory to be new configuration information when the T-GRE sends the query request next time. If there is no member (including administrator) in the group, T-GRE sends three times of inquiry request without response, then deletes the network configuration of the group.

According to the technical scheme, the dynamic networking method of the rail transit wireless vehicle-mounted terminal based on the 5G provided by the embodiment of the invention provides a T-GRE tunnel protocol mode to realize 5G multicast communication of the wireless vehicle-mounted terminal, and meets the requirements of high speed, high reliability and low time delay required by train communication; according to the TTDP protocol, the neighbor discovery and the physical topology discovery of the 5G vehicle-mounted terminal are completed in a mode of radio signal strength in a wireless communication network, and the dynamic perception discovery of the vehicle-mounted terminal node is realized; meanwhile, grouping of multicast group members is carried out according to the dynamic discovery result of the vehicle-mounted terminal node, and group detection is completed on the T-GRE server, so that point-to-many multicast communication transmission is realized, and manual address configuration and grouping are reduced.

The above description is only a preferred embodiment of the invention and an illustration of the applied technical principle and is not intended to limit the scope of the claimed invention but only to represent a preferred embodiment of the invention. It will be appreciated by those skilled in the art that the scope of the invention herein disclosed is not limited to the particular combination of features described above, but also encompasses other arrangements formed by any combination of the above features or their equivalents without departing from the spirit of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.

Claims (6)

1. A rail transit wireless vehicle-mounted terminal dynamic networking method based on 5G is characterized by comprising the following steps:

step S1, on the basis of a standard Ethernet protocol stack, performing TDRP < - >5G IP protocol conversion on a train real-time data protocol, and providing end-to-end data transmission with safety guarantee for process data and message data communication between any two devices in a 5G rail transit network; meanwhile, a T-GRE server is installed on the 5G core network side, a T-GRE tunnel is established between each 5G vehicle-mounted terminal and the server and is connected with other 5G vehicle-mounted terminals, and a two-layer tunnel is opened among all devices in the current network environment through the T-GRE server, so that service intercommunication in a multicast group is realized;

s2, according to a train topology discovery protocol, after a network topology structure of a switch of the 5G rail transit network is changed, the switch discovers the changed node based on network perception, automatically negotiates with other network equipment, and allocates an IP address for the changed 5G vehicle-mounted terminal according to a new train compartment instruction;

s3, uploading the position information, the cell ID, the uplink and downlink information and the speed information of the train terminal to a T-GRE server for the found node in real time;

s4, analyzing the uploading data of all trains on the server, and judging whether the trains are in the T-GRE coverage area or not based on the train position information and the 5G coverage area IDs of all nodes and the 5G vehicle-mounted terminals of the local nodes found in the current network topology structure; a logic bus is established on the T-GRE, a logic switch is arranged on the T-GRE tunnel and the logic bus which are used for connecting each train in a coverage area of a server, a grouping logic determines which trains can be communicated, a virtual broadcast domain is formed for the communicated 5G vehicle-mounted terminals, the communication of TTDP/TRDP messages is realized, and dynamic networking is realized.

2. The dynamic networking method of 5G-based rail transit wireless vehicle-mounted terminal according to claim 1, wherein the message structure of the TRDP layer comprises four layers, namely a version and total length layer, a mark and slice offset layer, a TTL and protocol UDP check layer, and a source IP address and a destination IP address layer from top to bottom.

3. The dynamic networking method for the wireless vehicle-mounted terminal in the 5G-based rail transit system according to claim 1, wherein the network topology changes, including an initial configuration change during train starting and a configuration change caused by carriage position change after the train starting.

4. The dynamic networking method of the rail transit wireless vehicle-mounted terminal based on 5G of claim 3, wherein the switch of the 5G rail transit network automatically negotiates with other network devices after a network topology structure is changed by configuring a train topology discovery protocol, and the method comprises the following steps:

step S21, judging the state of the BN node according to a train topology discovery protocol, and if the state is UNNAMED, turning to step S22; if NAMING status, go to step S23; if the NAMED state is detected, the step S24 is executed;

step S22, entering an initial UNNAMED state after the train is powered on or reset; in this state, the topology directory is not established yet, and before entering the NAMING state, the network message is bypassed;

step S23, in NAMING state, BN is running a starting protocol; entering a NAMED state with an effective train topology directory when the start is successfully completed; if an unrecoverable failure is detected, return to the "UNNAMED" state; when the system is started, each BN node broadcasts a HELLO message, the radio power is set to be the minimum initial value, the length of two vehicles can be covered, and each node collects an ACK message in a certain time range; if the number of the received messages is less than 4, retransmitting the HELLO message for increasing the radio power; each node repeats this operation until it collects at least 4 ACK packets or the timeout timer Tmax expires;

step S24, the topology discovery protocol under the NAMED state is divided into two stages: the first stage, neighbor discovery, using radio signal strength to find neighboring nodes and estimating the relative position of BN; the second stage, topology discovery, wherein the topology frame comprises the MAC address information of the BN currently discovered by the BN; and each BN keeps the updated physical and logical topology directories according to the received HELLO and the topology frame, and after receiving the topology frame, the BN updates the physical and logical topology directories to realize topology discovery.

5. The dynamic networking method for the rail transit wireless vehicle-mounted terminal based on 5G of claim 4, wherein the neighbor discovery process is as follows: each BN sends the HELLO frame together with the MAC address thereof to the neighbor nodes to try to discover the MAC addresses of the neighbor nodes; each BN receives HELLO frames from its left and/or right incoming links, the BN at hand learns the MAC addresses of neighbors; at which time the reception of these two frames completes the neighbor discovery phase.

6. The dynamic networking method for the wireless vehicle-mounted terminal of the 5G-based rail transit system according to claim 1, wherein the step S4 specifically comprises:

step S41, when a new 5G vehicle-mounted terminal is added as a group member, the multicast IP is unified according to the neighbor topology directory, after the marshalling is finished, the terminal with the smallest private address in the marshalling is selected as an administrator to undertake the marshalling communication task between the multicast group and the T-GRE server, and the administrator sends a registration request to the T-GRE server; if the administrator is invalid, other terminals will reselect a new administrator after the administrator timer is overtime; when a new node is found, the logical topology directory is updated, the server sends a query request to an administrator at regular time, and if the logical topology directory changes, the network configuration of the node is updated;

step S42, when group member maintenance is carried out on the 5G vehicle-mounted terminal in the group, the group members are maintained by a logical topology directory and a node network configuration directory on a server, and the two directories keep consistency; when the logical topology directory is different from the node network configuration directory and the consistency conflicts, updating the node network configuration by taking the logical topology directory as a reference;

step S43, when the 5G vehicle-mounted terminal leaves the group, the logical topology directory is updated, and when the T-GRE sends the query request next time, the new configuration information is updated; if there is no member in the group, T-GRE sends three times of inquiry request without response, then deletes the group network configuration.

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