TWI454085B - Mobile router system for high-speed trains and seamless handover therefor - Google Patents

Description

Mobile router system for high-speed train and seamless handoff control method thereof

The present invention relates to a mobile router system applied to a high-speed train and a seamless handoff control method thereof, and more particularly to a mobile router system capable of seamlessly changing hands on a high-speed moving train, and a base used in the mobile router system Taiwan change hands.

In the case of high-speed trains, it is an inevitable demand for passengers to use their own mobile devices to access the Internet. Currently operating high-speed trains, such as the French TGV system, Japan's Shinkansen, and Taiwan's high-speed railway, the speed of the car is set at 250-300 kilometers per hour. Some planned high-speed train systems set the speed at more than 350 kilometers per hour. In such a train traveling at a high speed, how to maintain good communication quality between the in-vehicle device and the wireless communication system outside the vehicle has become a technical challenge.

Network mobility is a concept that addresses this technical dilemma. It is planned to provide passenger-owned or in-vehicle-attached devices with relatively low power consumption and a small network coverage, such as through WiFi or Ethernet and other methods are connected to the mobile router in the car, while the mobile router communicates with the ground base station with its high computing power and high-level hardware devices and technologies, such as multi-antenna MIMO. Thereby achieving high quality, low cost mobile wireless communication.

The biggest bottleneck faced by the above mobile network technologies is how to maintain good communication quality under frequent handoff requirements. In other words, high-speed trains travel at speeds of more than 250 kilometers per hour. The mobile router in the car must frequently replace the connected base station. Also because of the high speed of the train, the time to compress the hand change (the hand change must be completed at the overlap of the coverage of the two base stations), and the time of the change is not easy to choose. The base stations connected before and after may belong to different domains (subnet). Or domain and other factors, such that the change of hands affects the quality of communication, resulting in communication interruption or packet loss.

The prior art solves the problem of handoffs by giving a special address preamble (called a mobile network prefix) to the mobile router on the high-speed train to shorten the handoff when changing hands with the base station. Negotiation time. However, this kind of practice is not effective in improving the vehicle for long distances. Furthermore, when the mobile device transmits and receives data, the base station is handed over, and the communication is interrupted and the packet is lost.

Therefore, there must be a novel mobile router system for high-speed trains, which can seamlessly change the base station when the train is driving at a high speed.

At the same time, there must be a mobile router system that can achieve communication quality for high-speed trains with a simple structure and low cost.

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel mobile router system for a high-speed train that can seamlessly change a base station when the train is traveling at a high speed.

It is also an object of the present invention to provide a novel mobile router system that achieves communication quality sufficient for use by high speed trains with a simple structure and low cost.

It is also an object of the present invention to provide a seamless handoff control method for a high speed train mobile router system such that the mobile router system can be used on a train traveling at a high speed.

The mobile router system according to the present invention is used on a train having a considerable length and capable of traveling along a specific track at a high speed, as a base station on a train or a passenger carrying a wired or wireless communication device and a train within an effective range. Mobile communication transfer station between stations. The mobile router system includes: a first mobile router, wherein the device is in a forward direction of the traveling direction to wirelessly connect the external wireless communication base station for data exchange; and the second mobile router has a device on the train at the rear end of the traveling direction. Wirelessly connecting an off-air wireless communication base station for data exchange; a set of gateway controllers respectively connecting the first mobile router and the second mobile router to control the first mobile router and the second mobile router The data transmission and transmission direction between the connected wireless communication base stations; at least one set of third routers are installed on the train to receive the control of the gateway controller, collect data from the in-vehicle communication device, and send the data to the vehicle An internal communication device; wherein the gateway controller stops transmitting the uploaded data to the first mobile router when the first mobile router is about to start replacing the connected wireless communication base station (handover); After the router completes the change of hands, the first mobile router starts downloading and uploading data, and stops uploading the data. To the second mobile router; and after the completion of the second mobile router handoff, recovered by the second mobile router to download and upload data.

For clarity, the first and second mobile routers, gateway controllers, and third routers mentioned in this document are described separately according to their functions. In fact, they can be made in hardware or software, and installed in the same or multiple physical machines with multiple corresponding network interfaces, as long as the two antennas of the external (to the ground base station) are moved first and second. The router position setting can be. For example, the gateway controller and the third router are on the same physical machine, or the first or second mobile router is combined with the gateway controller, or even all four functional modules are implemented in one entity. On the machine.

In the above control, a "normal state" is generated for a period of time, that is, the time when the first mobile router and the second mobile router are all connected to the same ground base station. At this time, the first mobile router and the second mobile router can upload and download data to the base station. However, in the preferred embodiment of the present invention, the "normal state" may also be defined as that both the first mobile router and the second mobile router can upload data, but only the second mobile router can download data. One of the reasons for this design is that the handoff of the first mobile router does not affect the download of the data.

In the example of the present invention, the first mobile router, the second mobile router, and the third router may be any commercially available mobile routers, and the functions may be modified as appropriate. However, the first mobile router and the second mobile router are preferably mobile routers having high-order wireless transmission function devices (for example, WiMAX, LTE-Advanced, etc.) and using wireless signal enhancement technologies such as multi-antenna MIMO to ensure communication quality and Change the efficiency. Applicable devices include: WiMAX CPE (Customer Premise Equipments), femtocell base station, and the like. As for the third router, any wired or wireless router can be used. It is also possible to use the same device as the first mobile router and the second mobile router. Of course, if a wired router is used, the data exchange with the in-vehicle device needs to be through the cable.

The gateway controller can usually use Cisco's branch router or mobile internet router series and modify its functionality as appropriate.

In the embodiment of the present invention, the first and second mobile routers, the gateway controller and the third router are respectively described according to their functions. In fact, they can be installed as functional modules in the same physical machine with the corresponding network interface, as long as the external (for the ground base station) antenna is placed in the first and second mobile router positions.

The ratio of the distance between the two mobile routers (L meters) and the speed of the train (V meters / sec = 3.6V km / h) is closely related to the performance of the handoff. It is assumed that at the time of the type and setting of the terrestrial wireless access network, the long-span single antenna (group) position system not generally of the present invention requires a hand change time of T (seconds), thereby achieving seamless handoff. The spacing L is preferably greater than or equal to V times T (i.e., L ≧ VT). For example, if T is 2 seconds and the train speed is 360 kilometers, if the distance between two mobile routers is more than 200 meters, it can be seamlessly changed. Similarly, if the distance between two mobile routers is 300 meters, T is At 2 seconds, when the train speed is less than 540 km, the seamless change can be achieved by using the present invention. It is worth noting that even if the train speed is too fast, the distance between the two mobile routers is too small, or the T is increased due to other system errors, although it may affect the effect of seamless handoff, it is achieved by the distance between the two mobile routers. The time difference can also greatly reduce the delay caused by the hand-off procedure and reduce the communication interference between the vehicle and the outside world.

A seamless handoff control method for a mobile router system for a high-speed train according to the present invention includes a method of using a mobile router system having the above features to perform a handover with an off-board wireless communication base station. The method includes: when a first mobile router in front of a driving direction on a train is about to start to replace the connected wireless communication base station (handover), stopping transmitting the uploaded data to the first mobile router; After the first mobile router completes the handover, the first mobile router starts downloading and uploading data, and stops transmitting the uploaded data to a second mobile router of the device on the back end of the train along the traveling direction; and in the second After the mobile router completes the handover, the data is downloaded and uploaded by the second mobile router.

Since the present invention uses the mobile router system for high-speed trains as described above, when the first mobile router performs a handover, data uploading and downloading is still performed via the second mobile router, and after the first mobile router completes the handover procedure, the first switch is performed. The mobile router takes over the data upload and download, and performs the handover work of the second mobile router. Therefore, a seamless change of the high-speed train mobile network can be realized.

The system provided by the present invention can be implemented by any suitable commercially available means with appropriate modifications. The control method is also simple. Therefore, the mobile router system can be seamlessly changed in the high-speed train without increasing the system cost.

Several embodiments of the mobile router system for high speed train of the present invention and its seamless handoff control method will be described below with reference to the drawings. It is to be understood that the following examples are merely illustrative of several preferred embodiments of the invention, and the scope of the invention is not limited to the examples.

Although not wishing to be bound or limited by any theory, the inventors have found that the current wireless communication base station, such as a mobile phone base station, has a signal coverage of about 5 kilometers, and the overlap coverage of the two base stations is about 400 meters. If the speed of the high-speed train is set at 450km/hr, the length of the train passing through a certain point is 0.8-3.2 seconds under the condition of 100 to 400 meters. Get a lot of valuable hands-on time for mobile routers. Therefore, if a mobile router is installed at the front end and the back end of the train, it will be sufficient to achieve a seamless handover of the base station. The invention does not limit the setting mode of the base station, and even in the case of the conventional base station, that is, the base station is not disposed along the track, it can be implemented.

Fig. 1 is a system diagram showing the system of a mobile router system for a high speed train according to the present invention. As shown, the train 1 is equipped with a gateway controller 10 that connects and controls two sets of mobile routers, including a first mobile router 11 disposed at the train head and a second mobile router 12 disposed at the rear of the train. The functions of the first mobile router 11 and the second mobile router 12 are connected to the wireless communication base stations 2 and 3 installed outside the vehicle to transmit and receive data. In order to enable the wireless communication device (not shown) in the vehicle to pass through the first mobile router 11 or the second mobile router, via the connected wireless base stations 2, 3, and then via the local network to which each wireless communication device belongs (home) Network) or a virtual private network exchanges information with its target communication device.

In application, the first mobile router 11 and the second mobile router 12 may be any commercially available mobile routers that are suitably modified to ensure good communication quality with the base station while the train is moving at high speed. In general, a mobile router having wireless technologies such as LTE, LTE-Advanced, or WiMAX can achieve the needs of the present invention. Suitable commercial products include: WiMAX CPE and femtocell base station.

There are no restrictions on the specifications of the wireless communication base station, and it is usually a mobile phone or data exchange base station such as LTE, LTE-Advanced, WiMAX, or the like. Other base station devices that can interface the first mobile router 11 and the second mobile router 12 to a mobile telephone system, the Internet, or other communication network can also be applied to the present invention.

It is also shown in FIG. 1 that the gateway controller 10 is further connected to a third router 13, and the third router 13 is connected to a local fixed and mobile node (LFMN) network 14 and a Visitoring mobile node (VMN) network 15. The function of the third router 13 is only for interfacing the LFMN network 14 and the VMN network 15 to the gateway controller 10. Therefore, there is not much demand for its communication capabilities. A commercially available wired or wireless router can meet the needs of the system. The example of the first mobile router 11 and the second mobile router 12 described above can be applied to the third router 13.

The LFMN network 14 functions as a local fixed and mobile communication device integrated in the vehicle, such as a driver, a vehicle owner, and the like, and a communication device used in the in-vehicle system. In addition, service equipment such as public pay phones in the car may also be included. Therefore, it includes a communication interface connected to the third router 13, and a local fixed and mobile communication device installed in the vehicle. The communication objects of these communication devices are relatively fixed, usually the home network of the mobile router system. The routing of the communication is relatively simple and does not affect the communication quality. The communication protocol used is also fixed. As long as you use a simple network design, you can provide what you need. On the contrary, the VMN network 15 is used to provide a communication device carried by the passengers for mobile communication under high-speed train travel. The VMN network 15 includes a communication interface connected to the third router 13, and various types of mobile communication devices carried by the passengers, such as mobile phones, Internet mobile phones, personal digital assistants, portable computers, and the like. The communication object is located in the Internet, so the choice of communication path is very important to reduce end-to-end transmission delay and signal jitter. The communication protocols used by these passenger-carrying communication devices are all-encompassing and may include Mobile IP (v6), Dynamic DNS, SIP or Skype. Each VMN is owned by each passenger and the mobile router system is unlikely to support all communication protocols. Two network systems are better controlled in different ways.

Based on the above and other reasons, in the preferred embodiment of the present invention, the system supported by the third router 13 is divided into the LFMN network 14 and the VMN network 15 to process their data streams, respectively. In addition, for security reasons, it is also supported to separate the two networks. Of course, it is also a feasible method to provide only a single type of network in a train 2, not to a LFMN or a VMN, respectively, to the third router 13. In addition, in addition to the above two types of networks, it is another feasible method to separately classify other networks according to the specifications of the communication device, the communication protocol, and the type of data.

In the application of the present invention, the train 1 may be a high speed railway train, a general long-distance rail train or a regional express train. The ratio of the distance between the two mobile routers (L meters) and the speed of the train (V meters / sec = 3.6V km / h) is closely related to the performance of the handoff. It is assumed that at this time, under the type and setting of the ground wireless access network, the long-span single antenna (group)/router location system not generally of the present invention requires a handoff time of T (seconds), and seamless switching can be achieved. The spacing L of the hand is preferably greater than or equal to V times T (i.e., L ≧ VT). For example, if T is 2 seconds and the train speed is 360 kilometers, if the distance between two mobile routers is more than 200 meters, it can be seamlessly changed. Similarly, if the distance between two mobile routers is 300 meters, T is At 2 seconds, when the train speed is less than 540 km, the seamless change can be achieved by using the present invention. It is worth noting that even if the train speed is too fast, the distance between the two mobile routers is too small, or the T is increased due to other system errors, although it may affect the effect of seamless handoff, it is achieved by the distance between the two mobile routers. The time difference can also greatly reduce the delay caused by the hand-off procedure and reduce the communication interference between the vehicle and the outside world.

The gateway controller 10 is one of the focuses of the present invention. As shown in FIG. 1, the gateway controller 10 is connected to the first mobile router 11 and the second mobile router 12, respectively, to control the first mobile router 11 and the second mobile router 12 and the connected wireless. 2, 2 data transmission and transmission directions of the communication base station. On the other hand, the gateway controller 10 is also connected to the third router 13, and thus to the LFMN network 14 and the VMN network 15. The gateway controller 10 forwards the data sent by the third router 13 to the first mobile router 11 and the second mobile router 12 to be sent to the target domain or target through the connected base stations 2, 3. The communication device also transmits the data received by the first mobile router 11 and the second mobile router 12 to the third router 13 for forwarding to the LFMN network 14 and the VMN network 15. In the present invention, the gateway controller 10 is controlled to pass through the first mobile router 11 and the second mobile terminal, and the gateway controller 10 is controlled to pass through the first mobile router 11 and the second mobile router 12. Uploading and downloading data streams to achieve high-speed train travel, allowing the mobile router system to seamlessly change hands.

In short, the handover control method of the gateway controller 10 includes: when the first mobile router 11 is about to start replacing the connected wireless communication base station (handover), stopping transmitting the uploaded data to the first mobile Router 11; after the first mobile router 11 completes the handover, starts downloading and uploading data by the first mobile router 11, and stops transmitting the uploaded data to the second mobile router 12; and at the second mobile router 12 After the handover is completed, the data downloaded and uploaded by the second mobile router 12 is resumed.

In the above steps, a "normal state" is generated for a period of time, that is, the time when the first mobile router 11 and the second mobile router 12 are all connected to the same base station 2. At this time, the first mobile router 11 and the second mobile router 12 can upload and download data to the base station 2. However, in the embodiment, the "normal state" is defined as: the first mobile router 11 and the second mobile router 12 can upload data, but only the second mobile router 12 can download data. One of the reasons for this design is to prevent the first mobile router 11 from changing hands, causing the system to stop downloading data.

Fig. 2 is a flow chart showing a seamless handoff control method for the mobile router system for high speed train of the present invention. Hereinafter, a method in which the gateway controller 10 controls the hand change in the embodiment of the present invention will be described based on Fig. 2.

In step 201, the gateway controller 10 determines that the first mobile router 11 is about to change hands, and then stops transmitting the uploaded data to the first mobile router 11 in step 202. The gateway controller 10 determines the timing of starting a hand change without any technical limitation. In general, it may be that when the first mobile router 11 detects that the base station 2 coverage has been detached or is about to leave the link, for example, when the signal strength received by the base station 2 is reduced to a predetermined strength value. However, it is also possible that the gateway controller 10 predicts, in any way, the coverage of the base station 2 that is about to be disconnected, for example, when the predicted value obtained from the past hand history statistics arrives. Any other technique for judging the timing of the first mobile router 11 to change hands can also be used in the present invention.

In step 202, the first mobile router 11 initiates a base station handover procedure, including scanning and selecting a suitable base station, requesting the base station at the time to negotiate the handover, interrupting the connection with the base station connected at the time, and confirming And connect the next base station and other steps. The above steps are known in the art and have been applied to existing mobile communication systems. The detailed steps and practices will not be described here.

In step 202, the uploaded material is all transmitted via the second mobile router 12 and not sent to the first mobile router 11. Therefore, the handoff operation of the first mobile router 11 does not affect the data downloading operation of the in-vehicle system. On the other hand, since the first mobile router 11 has started the handover operation, the base station 2 does not send the downloaded data to the first mobile router 11 but to the second mobile router 12. Therefore, the handoff operation of the first mobile router 11 does not affect the operation of downloading the system data in the vehicle.

Thereafter, in step 203, the first mobile router 11 has completed the handover operation, and the gateway controller 10 starts the function of downloading and uploading data by the first mobile router 11, and stops transmitting the uploaded data to the second mobile router. 12. In this step, since the first mobile router 11 has completed the connection with the next base station 3, the data download and upload are transmitted through the first mobile router 11. At this time, stopping the uploading of data from the second mobile router 12 does not affect the operation of downloading the system data in the vehicle.

In this step 203, the gateway controller 10 controls the second mobile router 12 to perform a handover. The handover operation of the second mobile router 12 is the same as that of the first mobile router 11. At this time, since the data to be uploaded is not provided to the second mobile router 12, the handover operation of the second mobile router 12 does not affect the uploading of the system data in the vehicle. At the same time, also because the second mobile router 12 has entered the handover operation, the connected base station 2 does not send the downloaded data to the second mobile router 12. Therefore, the handover operation of the second mobile router 12 does not affect the download of the system data in the vehicle.

In practical applications, a train with a length of 100-400 meters travels at a speed of 360 kilometers per hour, and the hand-over time for the present invention is about 1 to 4 seconds, which is sufficient for the first mobile router 11 to complete the handover. And more than enough. As for the handoff time available to the second mobile router 12, it is more abundant.

In step 204, the gateway controller 10 determines that the second mobile router 12 has completed the handover operation and is connected to the next base station 3, that is, the second mobile router 12 starts downloading and uploading data. In this way, the base station change operation of the present invention is completed.

Since the invention utilizes the advantage of the length of the high-speed train, the change of the first mobile router 11 can be completed within the change time generated by the captain, thereby achieving the purpose of seamless hand change.

Thereafter, if necessary, the gateway controller 10 may stop downloading data from the first mobile router 11 in step 205, so that the "normal state" between the two handoffs is only downloaded from the second mobile router 12. data. For the purpose of this design, on the one hand, the data is downloaded only by a single mobile router, which simplifies the management of data downloading. On the other hand, when the first mobile router 11 performs a handover, no additional management data download is required.

To verify the effect of the present invention, a train of 300 meters in length is simulated, traveling at different speeds, with the system of the present invention (2MR) and a system (1MR) installed at the rear using a single mobile router and a single mobile The router is placed at the rear of the vehicle and compared with a system (1MR-f) that attaches a forwarding tunnel between the base station and the next base station. The data received is transmitted at a fixed bit rate (CBR) of 64 Kbps, and the packet interval of each node is 10 ms. The resulting handoff delay is shown in Figure 3. The so-called handoff delay time refers to the difference between the time when the last packet is received by the base station in the connection, and the time when the next packet is received from the next base station. As shown in the figure, the present invention can significantly shorten the handoff delay time regardless of the speed of the vehicle.

In addition, since the uploading and downloading of data is not interrupted when the first mobile router 11 performs the handoff, the communication can be avoided, and the data is lost. It is indeed possible to achieve a seamless hand change.

The above is a description of the preferred embodiment of the invention. It is not difficult for those skilled in the art to understand the content and spirit of the present invention, and to make various changes and modifications in accordance with the disclosed technology. It is to be understood that the system, architecture, or method of the embodiments, as well as the derivatives and variations thereof, are within the scope of the invention.

2, 3. . . Wireless communication base station

10. . . Gateway controller

11. . . First mobile router

12. . . Second mobile router

13. . . Third router

14. . . Local fixed and mobile communication node network

15. . . Guest mobile node network

Fig. 1 is a system diagram showing the system of a mobile router system for a high speed train according to the present invention.

Fig. 2 is a flow chart showing a seamless handoff control method for the mobile router system for high speed train of the present invention.

Figure 3 is a comparison of handoff delay times between the present invention and known techniques.

Claims (10)

A mobile router system for high-speed trains, comprising: a first mobile router, wherein the device is connected to the front end of the traveling direction of the train to wirelessly connect the external wireless communication base station for data exchange; and the second mobile router, the device is on the upper edge of the train At the rear end of the driving direction, the wireless communication base station is wirelessly connected to perform data exchange; a group of gateway controllers are respectively connected to the first mobile router and the second mobile router to control the first mobile router and the second Data transmission and transmission direction between the mobile router and the connected wireless communication base station; at least one set of third routers are installed on the train to receive the control of the gateway controller, receive data from the in-vehicle communication device, and The data is sent to the in-vehicle communication device; wherein the gateway controller stops transmitting the uploaded data to the first mobile router when the first mobile router is about to start replacing the connected wireless communication base station (changing hand); After the first mobile router completes the handover, the first mobile router starts to download and upload data, and When the second mobile router to begin changing hands, stop transmitting upload data to the second mobile router; and after the completion of the second mobile router handoff, recovered by the second mobile router to download and upload data. The mobile router system of claim 1, wherein the gateway controller stops downloading data by the first mobile router after the second mobile router completes the handover. The mobile router system of claim 1 or 2, wherein the first mobile router performs a handover operation after the uploading of the data stops transmitting to the first mobile router. The mobile router system of claim 1 or 2, wherein the second mobile router performs a handover operation after the uploading of the data stops transmitting to the second mobile router. For example, in the mobile router system of claim 1 or 2, wherein the first mobile router requires a handoff time of T (seconds) and a train setting maximum speed of V meters/second. The linear distance L of the mobile router satisfies the following formula: L≧VT. The mobile router system of claim 1 or 2 further includes a local fixed and mobile node (LFMN) network and a visiting mobile node (VMN) network, both of which are Connected to the third router; wherein the LFMN network is used to integrate local fixed and mobile communication devices installed in the vehicle, and the VMN network is used to provide communication devices carried by passengers for mobile communication under high-speed train travel Required. A seamless handoff control method for a mobile router system for a high-speed train, the method comprising the steps of: replacing a connected wireless communication base station with a first mobile router at a front end of a device along a direction of travel on a train (changing hands And stopping transmitting the uploaded data to the first mobile router; after the first mobile router completes the handover, starting to download and upload data by the first mobile router, and stopping transmitting the uploaded data to a device on the train a second mobile router that is on the back end of the traveling direction; and after the second mobile router completes the handover, resumes downloading and uploading data by the second mobile router. The method of claim 7, further comprising the step of stopping the downloading of data by the first mobile router after the second mobile router completes the handover. The method of claim 7 or 8, wherein the first mobile router performs a handover operation after the uploading of the data stops transmitting to the first mobile router. The method of claim 7 or 8, wherein the second mobile router performs a handover operation after the uploading of the data stops transmitting to the second mobile router.