A method for seamless handover between an LTE network and a WiFi network

Abstract

The application provides a seamless switching method between LTE network and WiFi network, relates to the technical field of wireless communication, and comprises the following steps: one of network terminals is configured as a master device in two virtual router redundancy protocol groups respectively, and the rest of network terminals are configured as standby devices; in the process of train driving, each network terminal detects the link state of its uplink in real time and sends the link state to other network terminals; when the link state of the master device is abnormal, the master device is configured as a standby device; when the link state of the received master device is abnormal and the priority of the network terminal is the highest among all the network terminals with normal link states, the standby device is configured as a master device; when the master device is a WiFi terminal, the master device forwards service traffic through the WiFi network; and when the master device is an LTE terminal, the master device forwards service traffic through the LTE network. The beneficial effect is that seamless switching between LTE network and WiFi network is realized, and train-ground integrated communication service is ensured without interruption.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wireless communication technology, in particular to a method for seamless switching between LTE network and WiFi network. BACKGROUND

[0002] With the development of urban rail transit business, it plays an increasingly important role in urban operation, and users' requirements for train-ground communication business are also increasing.

[0003] In the traditional urban rail transit construction, the train-ground wireless communication system uses the fourth generation wireless cellular LTE network for communication. With the development of WiFi technology, the train-ground wireless communication system begins to explore the use of WiFi6 technology. This results in that in some rail transit lines, the first-stage line comprehensive communication train-ground wireless network adopts LTE-U wireless technology, and the second-stage line train-ground wireless network adopts WiFi6 wireless technology. Therefore, how to realize seamless switching between LTE network and WiFi network during train running to ensure uninterrupted train-ground comprehensive communication business becomes a technical problem to be solved. SUMMARY

[0004] In view of the problems in the prior art, the present application provides a method for seamless switching between LTE network and WiFi network, which is applied to a rail transit train. The rail transit train is configured with a vehicle-mounted switch and a plurality of vehicle-mounted terminals and a plurality of network terminals connected to the vehicle-mounted switch. Each network terminal includes at least one WiFi terminal and at least one LTE terminal. The method comprises the following steps:

[0005] Step S1, two virtual router redundancy protocol groups are constructed, and one of the network terminals is configured as a master device in each of the two virtual router redundancy protocol groups, and the remaining network terminals are configured as standby devices in each of the two virtual router redundancy protocol groups, and each standby device has different priority in the two virtual router redundancy protocol groups.

[0006] Step S2, during the running of the rail transit train, the uplink of each WiFi terminal accesses a wayside WiFi base station through a WiFi network, the uplink of each LTE terminal accesses a wayside LTE base station through an LTE network, each network terminal detects the link state of its uplink in real time, and sends the link state to other network terminals through the vehicle-mounted switch.

[0007] Step S3, the network terminal as the master device judges whether the link state is normal.

[0008] If not, the network terminal configures itself as the backup device in the two virtual router redundancy protocol groups, and then goes to step S4;

[0009] If yes, go to step S5;

[0010] Step S4, the network terminal as the backup device configures itself as the master device in the corresponding virtual router redundancy protocol group when the link state of the master device received is abnormal and the priority of the network terminal is the highest among all the network terminals with normal link states;

[0011] Step S5, the master device forwards the traffic of each vehicle terminal through the WiFi network when the master device is the WiFi terminal, and forwards the traffic of each vehicle terminal through the LTE network when the master device is the LTE terminal.

[0012] Preferably, in step S1, the method further comprises:

[0013] The default gateway of part of the vehicle terminals is configured as the virtual IP address of one of the virtual router redundancy protocol groups, and the default gateway of the rest of the vehicle terminals is configured as the virtual IP address of the other virtual router redundancy protocol group;

[0014] In step S5, when the master devices in the two virtual router redundancy protocol groups are the same network terminal, the master device forwards the traffic of all the vehicle terminals, and when the master devices in the two virtual router redundancy protocol groups are different network terminals, the two network terminals correspondingly forward the traffic of part of the vehicle terminals with the corresponding virtual IP address.

[0015] Preferably, in step S2, the method further comprises:

[0016] During the running of the rail transit train, the downlink of each network terminal accesses the vehicle switch through the Ethernet interface, and detects the link state of the downlink in real time, and sends the link state to other network terminals through the vehicle switch;

[0017] After performing step S2, the method further comprises:

[0018] Each network terminal judges whether the link state of the downlink is normal:

[0019] If yes, go to step S3;

[0020] If not, the network terminal configures itself as the backup device in both of the virtual router redundancy protocol groups, and then returns to step S2.

[0021] Preferably, in step S2, the network terminal further comprises:

[0022] During the running of the rail transit train, each network terminal acquires its working state in real time, and sends the working state to other network terminals through the on-board switch.

[0023] After step S2, the network terminal further comprises:

[0024] Each network terminal judges whether its working state is normal:

[0025] If yes, the network terminal turns to step S3.

[0026] If not, the network terminal configures itself as the backup device in both of the virtual router redundancy protocol groups, and then returns to step S2.

[0027] Preferably, the WiFi terminal comprises a tail WiFi terminal arranged at the tail position of the rail transit train and a head WiFi terminal arranged at the head position of the rail transit train, and the LTE terminal comprises a tail LTE terminal arranged at the tail position of the rail transit train and a head LTE terminal arranged at the head position of the rail transit train.

[0028] Preferably, the tail WiFi terminal is configured as the master device in both of the virtual router redundancy protocol groups.

[0029] The priority of each backup device in one of the virtual router redundancy protocol groups is in descending order of the head WiFi terminal, the head LTE terminal and the tail LTE terminal.

[0030] The priority of each backup device in the other of the virtual router redundancy protocol groups is in descending order of the head WiFi terminal, the tail LTE terminal and the head LTE terminal.

[0031] Preferably, the on-board terminal comprises an on-board camera, and each trackside WiFi base station and each LTE base station is connected to a station video server through a three-layer switch.

[0032] In step S5, when the primary device is the WiFi terminal, the forwarding of service traffic between each of the vehicle-mounted cameras and the station video server is achieved through the WiFi network; when the primary device is the LTE terminal, the forwarding of service traffic between each of the vehicle-mounted cameras and the station video server is achieved through the LTE network.

[0033] Preferably, the vehicle-mounted terminal includes a vehicle-mounted passenger information system, and each of the trackside WiFi base stations and each of the LTE base stations are connected to the passenger information system server through a three-layer switch;

[0034] In step S5, when the primary device is the WiFi terminal, the forwarding of service traffic between each of the vehicle passenger information systems and the passenger information system server is achieved through the WiFi network; when the primary device is the LTE terminal, the forwarding of service traffic between each of the vehicle passenger information systems and the passenger information system server is achieved through the LTE network.

[0035] The above technical solution has the following advantages or beneficial effects:

[0036] 1) By constructing two virtual router redundancy protocol groups, and triggering the switching of the primary and backup devices in the two virtual router redundancy protocol groups based on the uplink link state changes, seamless switching between LTE and WiFi networks for rail transit trains is achieved, ensuring uninterrupted integrated vehicle-to-ground communication services.

[0037] 2) The uplink and downlink of the network terminal are linked, so that any abnormality in the state of either the uplink or the downlink will trigger the switching of the primary and backup equipment, further ensuring the seamless switching of rail transit trains between LTE network and WiFi network.

[0038] 3) By constructing two virtual router redundancy protocol groups and using them as gateways for some vehicle terminals, when the primary devices of the two virtual router redundancy protocol groups are different network devices, the two primary devices can share the load of service traffic of each vehicle terminal, effectively ensuring the communication quality of vehicle-to-ground integrated communication services. Attached Figure Description

[0039] Figure 1 A flowchart illustrating a method for seamless switching between an LTE network and a WiFi network, as a preferred embodiment of the present invention.

[0040] Figure 2 This is a schematic diagram of a rail transit train network, representing a preferred embodiment of the present invention. Detailed Implementation

[0041] The application will be described in detail below with reference to the drawings and specific embodiments. The application is not limited to the embodiment, and other embodiments can also fall within the scope of the application as long as they meet the main idea of the application.

[0042] In the preferred embodiment of the application, in order to solve the above problems existing in the prior art, a method for seamless switching between LTE network and WiFi network is provided, which is applied to a rail transit train. The rail transit train is configured with a vehicle-mounted switch and a plurality of vehicle-mounted terminals and a plurality of network terminals connected to the vehicle-mounted switch. Each network terminal includes at least one WiFi terminal and at least one LTE terminal. As shown in the figure, the method includes the following steps. Figure 1

[0043] Step S1, two virtual router redundancy protocol groups are constructed, and one of the network terminals is configured as a master device in each of the two virtual router redundancy protocol groups, and the remaining network terminals are configured as standby devices in each of the two virtual router redundancy protocol groups, and each standby device has a different priority order in the two virtual router redundancy protocol groups.

[0044] Step S2, during the driving of the rail transit train, the uplink of each WiFi terminal accesses a wayside WiFi base station through a WiFi network, and the uplink of each LTE terminal accesses a wayside LTE base station through an LTE network. Each network terminal detects the link state of its own uplink in real time, and sends the link state to other network terminals through the vehicle-mounted switch.

[0045] Step S3, the network terminal as the master device judges whether its own link state is normal.

[0046] If not, the network terminal is configured as a standby device in the two virtual router redundancy protocol groups, and then proceeds to step S4.

[0047] If yes, proceed to step S5.

[0048] Step S4, the network terminal as the standby device is configured as a master device in the corresponding virtual router redundancy protocol group when it receives that the link state of the master device is abnormal and its priority order in all network terminals with normal link states is the most advanced.

[0049] Step S5, the master device forwards the service traffic of each vehicle-mounted terminal through the WiFi network when the master device is a WiFi terminal, and forwards the service traffic of each vehicle-mounted terminal through the LTE network when the master device is an LTE terminal.

[0050] Specifically, in the embodiment, as shown in the figure, Figure 2 ​As shown, the above WiFi terminals include a tail WiFi terminal 100 arranged at a tail position of the rail transit train and a head WiFi terminal 101 arranged at a head position of the rail transit train, the LTE terminals include a tail LTE terminal 200 arranged at the tail position and a head LTE terminal 201 arranged at the head position, and the two virtual router redundancy protocol groups are respectively a first virtual router redundancy protocol group VRRP1 and a second virtual router redundancy protocol group VRRP2. Preferably, the tail WiFi terminal 100 is configured as a master device MASTER in both virtual router redundancy protocol groups;

[0051] The priority of each backup device BAKEUP in the first virtual router redundancy protocol group VRRP1 is ranked from high to low as the head WiFi terminal 101, the head LTE terminal 201 and the tail LTE terminal 200;

[0052] The priority of each backup device BAKEUP in the second virtual router redundancy protocol group VRRP2 is ranked from high to low as the head WiFi terminal 101, the tail LTE terminal 200 and the head LTE terminal 201.

[0053] It can be seen that each backup device BAKEUP has different priority in the first virtual router redundancy protocol group VRRP1 and the second virtual router redundancy protocol group VRRP2.

[0054] Further specifically, when the rail transit train travels in the distribution area of each wayside WiFi base station, the area is covered by the WiFi network signal, at this time, the tail WiFi terminal 100 and the head WiFi terminal 101 both work normally, and the corresponding detected uplink link states should both be normal, but since the tail WiFi terminal 100 is the master device MASTER in both the first virtual router redundancy protocol group VRRP1 and the second virtual router redundancy protocol group VRRP2, at this time, the tail WiFi terminal 100 forwards all the traffic of the on-board terminals. The detection of the uplink link state preferably adopts the establishment of a GRE tunnel and the implementation of a bidirectional forwarding detection mechanism, and the specific process is the prior art and is not taken as the invention point of the present technical solution, and will not be described here.

[0055] The above only considers the uplink link state, and each network terminal also accesses the on-board switch 400 through an Ethernet interface, if the downlink between the network terminal and the on-board switch 400 fails, the train-ground integrated communication service will also be interrupted, based on this, in the preferred embodiment of the present application, the step S2 further includes:

[0056] In the process of the rail transit train running, the downlink of each network terminal accesses the vehicle-mounted switch through the Ethernet interface, and detects the link state of the downlink in real time, and sends the link state to other network terminals through the vehicle-mounted switch.

[0057] After step S2 is executed, the method further comprises:

[0058] Each network terminal judges whether the link state of the downlink is normal:

[0059] If yes, turn to step S3;

[0060] If no, configure itself as a backup device in the two virtual router redundancy protocol groups, and then return to step S2.

[0061] In other words, the link state of any one of the uplink and the downlink is abnormal, and the master-standby switching is needed to be performed, so as to ensure that the train-ground integrated communication link formed between the network switch-master device and the wayside base station is not interrupted.

[0062] Further, considering that if the network terminal fails due to power failure and other factors, the train-ground integrated communication service will also be interrupted, based on this, in the preferred embodiment of the application, step S2 further comprises:

[0063] In the process of the rail transit train running, each network terminal respectively acquires the working state of itself in real time, and sends the working state to other network terminals through the vehicle-mounted switch;

[0064] After step S2 is executed, the method further comprises:

[0065] Each network terminal judges whether the working state of itself is normal:

[0066] If yes, turn to step S3;

[0067] If no, configure itself as a backup device in the two virtual router redundancy protocol groups, and then return to step S2.

[0068] In summary, when the rail transit train travels in the distribution area of each trackside WiFi base station, if the tail WiFi terminal 100 and the head WiFi terminal 101 both work normally (i.e., the working states are both normal), the corresponding detected uplink link states should both be normal. However, since the tail WiFi terminal 100 is the master device MASTER in both the first virtual router redundancy protocol group VRRP1 and the second virtual router redundancy protocol group VRRP2, at this time, the tail WiFi terminal 100 forwards all the traffic of the on-board terminals. In other words, as long as the tail WiFi terminal 100 works normally, the head WiFi terminal 101 forwards all the traffic of the on-board terminals by the tail WiFi terminal 100 regardless of whether the head WiFi terminal 101 works normally or not. If the working state of the tail WiFi terminal 100 is abnormal and the head WiFi terminal 101 works normally, according to the priority ranking, the head WiFi terminal 101 is ranked first in both the first virtual router redundancy protocol group VRRP1 and the second virtual router redundancy protocol group VRRP2. At this time, the tail WiFi terminal 100 is switched to the backup device BAKEUP, the head WiFi terminal 101 is switched to the master device MASTER, and the head WiFi terminal 101 forwards all the traffic of the on-board terminals.

[0069] When the rail transit train travels in the distribution area of the trackside WiFi base station and travels towards the area adjacent to the trackside LTE base station, the area is covered by both the WiFi network signal and the LTE network signal. However, as the train travels, the closer to the distribution area of the trackside LTE base station, the more likely that the corresponding uplink of the tail WiFi terminal 100 and the head WiFi terminal 101 is abnormal, such as unstable link or non-link, etc. If the corresponding uplink of the tail WiFi terminal 100 and the head WiFi terminal 101 is abnormal, according to the priority ranking, at this time, the head LTE terminal 201 is ranked first in the first virtual router redundancy protocol group VRRP1, so the head LTE terminal 201 is switched to the master device MASTER, and the tail LTE terminal 200 is ranked first in the second virtual router redundancy protocol group VRRP2, so the tail LTE terminal 200 is switched to the master device MASTER. It can be seen that the master devices of the two virtual router redundancy protocol groups are different network terminals. At this time, the tail LTE terminal 200 and the head LTE terminal 201 can both forward the traffic of the on-board terminals. In order to realize load sharing, in the preferred embodiment of the present application, the step S1 further comprises:

[0070] configuring the default gateway of part of the on-board terminals as the virtual IP address of one of the virtual router redundancy protocol groups and configuring the default gateway of the remaining part of the on-board terminals as the virtual IP address of the other virtual router redundancy protocol group.

[0071] In step S5, when the master device in the two virtual router redundancy protocol groups is for the same network terminal, the master device forwards the traffic of all vehicle terminals, and the two virtual router redundancy protocol groups are not used.

[0072] When the master device in the two virtual router redundancy protocol groups is for different network terminals, the two network terminals correspondingly forward the traffic of part of the vehicle terminals having the corresponding virtual IP address.

[0073] Based on this, the head LTE terminal 201 is the master device MASTER of the first virtual router redundancy protocol group VRRP1, and is responsible for forwarding the traffic of each vehicle terminal configured with the virtual IP address of the first virtual router redundancy protocol group VRRP1. The tail LTE terminal 200 is the master device MASTER of the second virtual router redundancy protocol group VRRP2, and is responsible for forwarding the traffic of each vehicle terminal configured with the virtual IP address of the second virtual router redundancy protocol group VRRP2, so as to realize load sharing.

[0074] When the rail transit train travels in the distribution area of each trackside LTE base station, the area is covered by the LTE network signal, at this time, the tail LTE terminal 200 and the head LTE terminal 201 are both in the LTE network signal coverage area, and the tail LTE terminal 200 and the head LTE terminal 201 are both in the LTE network signal coverage area.

[0075] When the rail transit train travels in the distribution area of each trackside LTE base station, the area is covered by the LTE network signal, at this time, the tail LTE terminal 200 and the head LTE terminal 201 are both in the LTE network signal coverage area, and the tail LTE terminal 200 and the head LTE terminal 201 are both in the LTE network signal coverage area.

[0076] When the rail transit train travels in the distribution area of the trackside LTE base station and travels towards the area adjacent to the trackside WiFi base station, the area is covered by the WiFi network signal and the LTE network signal at the same time, but as the train travels, the closer to the distribution area of the trackside WiFi base station, the more likely the uplink corresponding to the tail LTE terminal 200 and the head LTE terminal 201 is abnormal, such as unstable link or link failure. If the uplink corresponding to the tail LTE terminal 200 and the head LTE terminal 201 is abnormal, according to the priority sorting, at this time, the tail WiFi terminal 100 in the first virtual router redundancy protocol group VRRP1 is sorted in the most front position, so that the tail WiFi terminal 100 is switched to the master device MASTER, the tail WiFi terminal 100 in the second virtual router redundancy protocol group VRRP2 is sorted in the most front position, so that the tail WiFi terminal 100 is switched to the master device MASTER, it can be seen that the master devices of the two virtual router redundancy protocol groups are the same network terminal, at this time, the tail WiFi terminal 100 is responsible for forwarding the service traffic between all the vehicle terminals.

[0077] In the preferred embodiment of the present application, as shown in Figure 2 The vehicle terminal includes a vehicle camera 301, each trackside WiFi base station and each LTE base station are connected to the station video server 600 through a three-layer switch 500.

[0078] Then in step S5, when the master device is the WiFi terminal, the service traffic between each vehicle camera 301 and the station video server 600 is forwarded through the WiFi network, and when the master device is the LTE terminal, the service traffic between each vehicle camera 301 and the station video server 600 is forwarded through the LTE network.

[0079] In the preferred embodiment of the present application, the vehicle terminal includes a vehicle passenger information system 302,

[0080] Each trackside WiFi base station and each LTE base station are connected to the passenger information system server 700 through a three-layer switch 500.

[0081] Then in step S5, when the master device is the WiFi terminal, the service traffic between each vehicle passenger information system 302 and the passenger information system server 700 is forwarded through the WiFi network, and when the master device is the LTE terminal, the service traffic between each vehicle passenger information system 302 and the passenger information system server 700 is forwarded through the LTE network.

[0082] 5The above description is merely preferred embodiments of the present application, and is not intended to limit the embodiments and protection scope of the present application. It should be noted that any modifications made by those skilled in the art based on the description and drawings of the present application should be included in the protection scope of the present application.

Claims

1. A method for seamless switching between LTE and WiFi networks, applied to rail transit trains, characterized in that, The rail transit train is equipped with an onboard switch and multiple onboard terminals and multiple network terminals connected to the onboard switch, each of the network terminals including at least one WiFi terminal and at least one LTE terminal; then the method includes: Step S1: Construct two virtual router redundancy protocol groups, and configure one of the network terminals as the primary device in each of the two virtual router redundancy protocol groups, and configure the remaining network terminals as backup devices in each of the two virtual router redundancy protocol groups, with each backup device having a different priority order in the two virtual router redundancy protocol groups. Step S2: During the operation of the rail transit train, the uplink of each WiFi terminal accesses the trackside WiFi base station through the WiFi network, and the uplink of each LTE terminal accesses the trackside LTE base station through the LTE network. Each network terminal detects the link status of its own uplink in real time and sends the link status to other network terminals through the vehicle-mounted switch. Step S3: The network terminal, acting as the primary device, determines whether its own link status is normal. If not, then configure itself as the backup device in the two virtual router redundancy protocol groups, and then proceed to step S4; If so, proceed to step S5; Step S4: When the network terminal acting as the backup device receives an abnormal link status from the primary device and its own priority ranking is the highest among all network terminals with normal link statuses, it configures itself to act as the primary device in the corresponding virtual router redundancy protocol group. Step S5: When the primary device is the WiFi terminal, the service traffic of each vehicle terminal is forwarded through the WiFi network; when the primary device is the LTE terminal, the service traffic of each vehicle terminal is forwarded through the LTE network.

2. The method according to claim 1, characterized in that, Step S1 further includes: The default gateway of some of the vehicle terminals is configured as the virtual IP address of one of the virtual router redundancy protocol groups, and the default gateway of the remaining vehicle terminals is configured as the virtual IP address of another virtual router redundancy protocol group. In step S5, when the primary device in the two virtual router redundancy protocol groups is the same network terminal, the primary device forwards the service traffic of all the vehicle terminals. When the primary devices in the two virtual router redundancy protocol groups are different network terminals, the two network terminals respectively forward the service traffic of the vehicle terminals with the corresponding virtual IP addresses.

3. The method according to claim 1, characterized in that, Step S2 further includes: During the operation of the rail transit train, the downlink of each network terminal is connected to the on-board switch via an Ethernet interface, and the downlink status of its own downlink is detected in real time, and the link status is sent to the other network terminals through the on-board switch. After performing step S2, the process further includes: Each network terminal determines whether the link status of its own downlink is normal: If so, proceed to step S3; If not, configure itself as the backup device in both virtual router redundancy protocol groups, and then return to step S2.

4. The method according to claim 1, characterized in that, Step S2 further includes: During the operation of the rail transit train, each of the network terminals obtains its own working status in real time and sends the working status to the other network terminals through the on-board switch; After performing step S2, the process further includes: Each network terminal determines whether its own working status is normal: If so, proceed to step S3; If not, configure itself as the backup device in both virtual router redundancy protocol groups, and then return to step S2.

5. The method according to claim 1, characterized in that, The WiFi terminal includes a rear WiFi terminal located at the rear of the rail transit train and a front WiFi terminal located at the front of the rail transit train. The LTE terminal includes a rear LTE terminal located at the rear of the train and a front LTE terminal located at the front of the train.

6. The method according to claim 5, characterized in that, The rear-end WiFi terminal is configured to be the primary device in both of the virtual router redundancy protocol groups; In one of the virtual router redundancy protocol groups, the priority order of each backup device from high to low is the front WiFi terminal, the front LTE terminal, and the rear LTE terminal; In another virtual router redundancy protocol group, the priority order of each backup device, from high to low, is the front WiFi terminal, the rear LTE terminal, and the front LTE terminal.

7. The method according to claim 1, characterized in that, The vehicle-mounted terminal includes a vehicle-mounted camera, and each of the trackside WiFi base stations and each of the LTE base stations are connected to the station video server through a three-layer switch. In step S5, when the primary device is the WiFi terminal, the forwarding of service traffic between each of the vehicle-mounted cameras and the station video server is achieved through the WiFi network; when the primary device is the LTE terminal, the forwarding of service traffic between each of the vehicle-mounted cameras and the station video server is achieved through the LTE network.

8. The method according to claim 1, characterized in that, The vehicle-mounted terminal includes a vehicle-mounted passenger information system, and each of the trackside WiFi base stations and each of the LTE base stations are connected to the passenger information system server through a three-layer switch; In step S5, when the primary device is the WiFi terminal, the forwarding of service traffic between each of the vehicle passenger information systems and the passenger information system server is achieved through the WiFi network; when the primary device is the LTE terminal, the forwarding of service traffic between each of the vehicle passenger information systems and the passenger information system server is achieved through the LTE network.

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