JP2012182735A - Handover compensator and mobile radio communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mobile radio communication system, configured to perform data communication by radio using multiple radio communication circuits on land side and mobile unit side, which can perform efficient and stable data communication, with the effects of handover on data communication stability reduced as a whole of the system.SOLUTION: A ground side handover compensator 15 and a vehicle side handover compensator 25 respectively transmit packets which have been distributed from a router to each circuit to their addressed circuits directly as are, and also, if any circuit is found to be in a handover state, transmit a handover mode transition instruction to the counter handover compensator. A handover compensator, which has received the handover mode transition instruction from the counter handover compensator, transmits those packets from the router which are addressed to the circuit in a handover state to another circuit which is different from at least the circuit in a handover state.

Description

  The present invention relates to a mobile radio communication system configured such that a mobile moving on a predetermined movement route on the ground can perform data communication with the ground side by radio during the movement, and a handover used for the mobile radio communication system The present invention relates to a compensation device.

  2. Description of the Related Art Conventionally, when a moving body such as a railway vehicle or an automobile is moving, an information processing terminal such as a personal computer (hereinafter referred to as “PC”) inside the moving body is connected to a ground side network such as the Internet. Various mobile radio communication systems have been proposed that can perform data communication with each other even when the mobile is moving.

  To give a more specific example of this mobile radio communication system, in a railway vehicle (train) as a mobile object, for example, a radio (hereinafter referred to as “vehicle radio unit”) that transmits and receives data wirelessly with the ground side. Or an on-board communication system consisting of a router that relays data between the on-board radio unit and the information processing terminal in the vehicle is constructed. A terrestrial communication system including a plurality of radio devices (hereinafter also referred to as “terrestrial radio units”) arranged at intervals and a router that relays data between these terrestrial radio units and the Internet or the like is constructed. In addition, wireless data transmission and reception between the on-board radio unit and the ground radio unit enables information processing terminals in the train to connect to the Internet on the ground side and communicate with each other. It becomes. As a data communication protocol, the well-known TCP / IP is generally used.

  The communication range of each terrestrial radio unit in the terrestrial communication system is basically set individually for each terrestrial radio unit, but the end region in the train movement path direction in the communication range is the other adjacent region. It partially overlaps with the end area of the communication range of the terrestrial radio section. And the ground radio | wireless part which an on-board radio | wireless part communicates by radio | wireless switches sequentially by well-known handover with the movement of a train. Note that “handover” in this specification means physical switching of the terrestrial radio unit in which the on-board radio unit performs wireless data transmission / reception (transmission / reception of radio waves), in other words, below the data link layer in the network protocol. Means a radio switching process.

  In other words, the on-board radio unit within the communication range of a certain ground radio unit moves with the movement of the train, and the end region of the communication range (i.e., the position of the on-board radio unit of the ground radio unit currently in radio communication) The radio waves from the terrestrial radio section become weaker as they approach the boundary (near the overlapping section) between the communication range and the communication range of the next terrestrial radio section adjacent in the moving direction. Therefore, when the vicinity of the boundary (overlapping portion) is reached, the handover is performed according to the radio field intensity from the currently communicating ground radio unit (or according to the radio field intensity from the next adjacent ground radio unit). By performing the processing, the terrestrial radio unit of the radio communication partner of the on-board radio unit is switched to the next terrestrial radio unit adjacent in the moving direction.

  In the conventional mobile radio communication system configured as described above, every time the handover is performed during movement of the train, data communication between the on-board communication system and the ground communication system, that is, information processing in the train. Data communication between the terminal and the Internet on the ground side is interrupted for a certain time. Moreover, the time during which this data communication is interrupted is longer than the time required for the handover. This is because even if the wireless communication between the wireless units is completed after the handover between the wireless units is completed, the data is not processed until a predetermined control process (for example, a time-out process in TCP) in the upper protocol is completed. This is because communication is not resumed.

  Such temporary interruption of data communication caused by the handover becomes a factor of lowering the stability of data communication between the vehicle and the ground in the mobile radio communication system. In particular, in high-speed moving bodies such as Shinkansen trains, although depending on the arrangement interval and communication range of the terrestrial radio section, handover tends to occur relatively frequently due to the high moving speed. Even if the data communication interruption occurs in a short time, even if it is for a short time, the influence on the stability of the communication becomes large as a whole.

  As a method for solving this problem, a method of providing a plurality of communication systems between the train and the ground and transmitting and receiving the same data in each system is conceivable. An example of a communication system having a configuration in which a plurality of communication systems are provided in this manner is disclosed in Patent Document 1.

  In Patent Document 1, although not a wireless communication system, in a system that transmits and receives packets between the first LAN and the second LAN via the Internet, between the first LAN and the second LAN. A plurality of transmission paths with different relay destinations are provided. The transmission side transmits the same packet to each of the plurality of transmission paths, and the reception side selects the packet received first among the packets from the plurality of transmission paths. Technology is disclosed.

  Therefore, if the technical idea described in Patent Document 1 is applied to the mobile radio communication system described above to provide a plurality of radio communication systems between the ground and the vehicle, any one system is provided. Even if a handover occurs, data communication can be continued by another system during that time.

JP 2000-261478 A

  However, although the method of using a plurality of wireless communication systems as described above can suppress the influence on the stability of communication due to the handover, the data communication can be performed at the normal time when handover does not occur, that is, if there is one wireless communication system. Even when possible, the same data (packet) is transmitted and received by a plurality of systems, which is inefficient.

  On the other hand, as a wireless communication system using a plurality of communication systems, a wireless communication system that does not transmit the same packet to each of a plurality of systems but distributes data (packets) to be transmitted to each system has also been known. Yes. A distribution method of how to distribute packets can be considered as appropriate. For example, a method of sequentially distributing packets to be transmitted to a plurality of systems can be considered. Specifically, for example, when there are two communication systems, odd-numbered packets are transmitted to one system, and even-numbered packets are transmitted to the other system.

  According to the wireless communication system configured to perform distributed transmission in this way, compared to the method of transmitting the same packet to a plurality of systems as described in Patent Document 1, the communication speed can be increased by effectively using a plurality of systems. Since the speed can be increased, there is an advantage in that efficient data communication can be performed.

  However, in a wireless communication system that performs such distributed transmission, it is possible to improve the efficiency of data communication. On the other hand, if a handover occurs in one of the systems, even if no handover occurs in the other system, as a whole Data communication is interrupted. For example, in TCP, if the odd numbered packet is normally received from one system, but the even numbered packet is not normally received from the other system, the data communication will continue. Will stop. In other words, in the distributed transmission method, in order to perform data communication normally, it is assumed that all systems to which packets are distributed and transmitted are in a state where data can be normally transmitted and received. As a result, data communication is interrupted as a whole.

  As described above, in a wireless communication system having a plurality of wireless communication systems, if the method described in Patent Document 1 is adopted, the influence of handover can be suppressed, but it is inefficient. On the other hand, the above-described distributed transmission method is adopted. Then, although the wireless communication system can be used efficiently, the problem of instability of communication due to handover remains, so none of them is an effective method.

  The present invention has been made in view of the above problems, and in a mobile radio communication system configured to perform wireless data communication using a plurality of radio communication systems on the ground side and the mobile side, as the entire system, An object of the present invention is to enable efficient and stable data communication while suppressing the influence on the stability of data communication due to occurrence of handover.

  In order to solve the above-mentioned problem, the invention according to claim 1 is directed to a mobile communication system provided in a mobile that moves along a predetermined movement route, and a ground communication system provided along the movement route. In the mobile radio communication system configured to be able to perform wireless data communication in a plurality of systems, the handover compensation device is provided in the mobile radio communication system.

  Among the communication systems constituting the mobile radio communication system, the mobile communication system is provided with mobile radio transmission / reception means for each system, and the ground communication system is arranged at predetermined intervals along the movement path. A group of terrestrial networks, each of which is formed by connecting a plurality of terrestrial wireless transmission / reception means connected via a transmission path, is individually provided for each system. The wireless transmission / reception means and the ground wireless transmission / reception means of the same system perform wireless data transmission / reception, and the wireless data transmission / reception is performed in packet units of a predetermined format. Each time, the terrestrial side wireless transmission / reception means for transmitting / receiving data to / from the mobile body side wireless transmission / reception means is configured to be handed over by sequentially switching as the mobile body moves.

  The mobile communication system is a device that relays data transmission between each mobile radio transmission / reception means and communication equipment in the mobile, and transmits transmission data to the ground communication system input from the communication equipment. A mobile-side data relay device configured to transmit to each mobile-side wireless transmission / reception means of a normal transmission system, which is one of the systems selected by a predetermined distribution method, is provided for each packet; The communication system is a device that relays data transmission between the local upper network and the external network, and transmits transmission data to the mobile unit input from the external network for each packet in a predetermined distribution of each system. There is provided a terrestrial data relay device configured to transmit to the terrestrial wireless transmission / reception means of the regular transmission system which is one of the systems selected by the method. That.

  The handover compensation apparatus of the present invention (Claim 1) is provided between the data relay apparatus and the radio transmission / reception means in each of the mobile communication system and the terrestrial communication system, that is, the mobile data relay in the mobile communication system. In the terrestrial communication system, between the apparatus and each mobile radio transmission / reception means, it is provided to relay data transmission between the terrestrial data relay apparatus and each upper network.

This handover compensation apparatus includes a handover determination unit, a handover information transmission unit, and a transmission data control unit.
Among these, the handover determination means is, for each system, whether the handover has been started or the state of data transmission / reception between the mobile-side wireless transmission / reception means and the ground-side wireless transmission / reception means is a predetermined state immediately before the start of handover. It is determined whether or not a handover state has occurred.

  The handover information sending means is a system on the side where the handover compensation apparatus is provided in the mobile communication system and the terrestrial communication system when any one of the systems is judged to be in the handover state by the handover judging means. By transmitting handover information indicating that the handover determination system is in the handover state to wireless transmission / reception means in a system other than the handover determination system which is the system determined to be in the handover state in a local system, the handover information Is transmitted wirelessly to a partner system which is a communication partner system for the own system.

  Then, the transmission data control means sends the transmission data from the data relay device in its own system to the wireless transmission / reception means of the regular transmission system for each packet at the normal time when the handover information is not received from the counterpart system. When operating in normal mode and when handover information is received from the other system, at least until the handover corresponding to the handover information is completed, the packets constituting the transmission data from the data relay device in the own system Among them, for the handover system side packet that is a handover determination system in which the normal transmission system is determined to be in the handover state in the counterpart system, a packet different from the normal transmission system is used instead of or in addition to the normal transmission system. Handover mode sent to wireless transceiver Donite to work.

  In the handover compensator according to claim 1, configured as described above, if any system is determined to be in the handover state, a system other than the system determined to be in the handover state (that is, a system that is not in the handover state) ) To wirelessly transmit the handover information to the other system.

  Transmission (relay) of transmission data (packets) from the data relay device of the own system to the wireless transmission / reception means side is performed automatically during normal times (ie, in normal mode) when handover information is not received from the partner system. The packet from the data relay device of the system is relayed and transmitted as it is. That is, the data is transmitted as it is to the regular transmission system selected by the data relay apparatus of the own system. Therefore, in the normal mode, each packet can be distributed and transmitted to the regular transmission system selected by the data relay device, so that data communication using a plurality of systems efficiently is possible.

  On the other hand, when handover information is received from the partner system (that is, in the handover mode), a packet whose normal transmission system is not the handover determination system among the packets from the data relay apparatus of the own system is relayed as it is. Although the packet is transmitted, a packet whose normal transmission system is the handover determination system is transmitted to at least a system different from the handover determination system. It should be noted that whether or not to transmit to a handover determination system that is a transmission destination that should originally be transmitted may be determined as appropriate, and is not particularly limited.

  Therefore, in the handover mode, since the packet whose normal transmission system is the handover determination system is transmitted to at least another system (not in the handover state), the packet is normally transmitted to the other system via the system. Can be transmitted wirelessly, and data communication can be continued as a whole system.

  Therefore, according to the handover compensation device of claim 1, the mobile radio communication system as a whole can perform efficient and stable data communication while suppressing the influence on the stability of data communication due to the occurrence of handover. It becomes possible to do.

  Here, there are various ways in which the handover determination unit determines that the handover state is determined as the handover state. For example, when the handover is actually started, the handover state is changed to the handover state. Although it can be determined that it has become, more preferably, as described in claim 2, it may be configured to be able to determine that it is in the handover state before the handover is started.

  That is, the invention according to claim 2 is the handover compensation device according to claim 1, wherein the handover determination means is a state of wireless data transmission / reception between the mobile-side wireless transmission / reception means and the ground-side wireless transmission / reception means. Is determined to be in the state just before the start, and if it is in the state just before the start, it is determined that the state is in the handover state.

  In other words, determining whether or not a state immediately before the start has been reached means that the occurrence of a handover is predicted in advance. Rather than shifting to the handover mode after the handover is actually started, by predicting it before the handover is started and shifting to the handover mode in advance, it is possible to ensure interruption of data communication due to the handover. Can be prevented, and the stability of data communication can be further increased.

  Various specific methods for determining whether or not the handover determination means has entered the state immediately before the start of the handover can be considered. For example, the determination is based on a packet received from the partner system as described in claim 3. Alternatively, for example, as described in claim 4, the determination may be made based on the radio wave intensity in the wireless communication.

  In other words, the invention according to claim 3 is the handover compensation device according to claim 2, wherein the handover determining means indicates, for each system, the reception state of the packet from the partner system by the wireless transmission / reception means in its own system. Monitoring is performed, and when the reception state of the packet in any of the systems becomes a reception abnormality state that indicates a state that is set in advance and is not normally received, it is determined that the state immediately before the start is reached.

  For example, when the packet loss rate exceeds a certain level, for example, when the RTT (Round Trip Time) exceeds a predetermined time, the reception abnormal state is determined. Can be determined as appropriate.

  In general, in a mobile radio communication system, when a handover occurs or immediately before a handover occurs, the packet reception state deteriorates. In other words, if the reception state of a packet is deteriorated, it can be inferred that it is a state in which handover is started soon with a high probability.

  Therefore, as described in claim 3, if it is determined whether or not there is a reception abnormal state based on the reception state of the packet that is actually transmitted and received, the reception abnormal state does not interfere with actual data communication. (That is, the state immediately before the start of handover) can be accurately determined.

  The invention according to claim 4 is the handover compensation apparatus according to claim 2, wherein each wireless transmission / reception means detects the intensity of the received radio wave from the wireless transmission / reception means targeted for data transmission / reception in the counterpart system. Radio wave intensity detection means is provided. The handover determining unit determines that the state immediately before the start has been reached when the intensity of the received radio wave detected by the radio wave intensity detecting unit is equal to or less than a preset radio field intensity threshold.

  Generally, in a mobile radio communication system, the closer the handover is, the weaker the radio field intensity between the mobile radio transmission / reception means and the ground radio transmission / reception means that are currently performing radio communication. In other words, it can be inferred that the lower the radio wave intensity, the higher the probability that the handover will be started soon.

  Therefore, as described in claim 4, even in the method of determining whether or not the reception is abnormal based on the radio wave intensity, the reception abnormal state is not disturbed (that is, the start of handover). It is possible to accurately determine that the state is the immediately preceding state.

  Next, the invention according to claim 5 is the handover compensation apparatus according to any one of claims 1 to 4, wherein any one of the systems is determined to be in the handover state by the handover determining means. Thereafter, an end determination means for determining whether or not the handover in the determined handover determination system is completed, and one or a plurality of systems in the own system when the end determination means determines that the handover is completed. Ending information sending means for sending the ending information to the counterpart system wirelessly by sending ending information indicating that the handover has ended to the wireless transmitting / receiving means. Then, the transmission data control means starts the operation in the handover mode by receiving the handover information from the counterpart system, and then shifts to the operation in the normal mode when the end information is received from the counterpart system. .

  In the invention according to any one of claims 1 to 4 described above, the transition to the handover mode is basically performed passively upon receipt of the handover information from the counterpart system. In other words, if it is determined that the other party system is in the handover state, there is a possibility that the packet transmitted from the own system may not be normally received in the other party system, so the other party system sends the handover information to the own system, As a result, the own system shifts to the handover mode.

  Therefore, the timing for shifting from the handover mode to the normal mode again follows the determination result in the counterpart system. That is, when the partner system determines that it is in the handover state and sends handover information, it determines whether or not the handover has ended. If it is determined that the handover has ended, the counterpart system transmits end information to the own system. In response to this, the local system shifts to the normal mode.

  Therefore, according to the handover compensator described in claim 5, since switching between the handover mode and the normal mode is performed in accordance with an instruction from the counterpart system, an appropriate response according to the state of the radio communication viewed from the counterpart system Mode switching is possible, and the efficiency of data communication can be further increased.

  Here, various considerations can be made as to how the end determination means specifically determines the end of handover. For example, it can be determined as described in claim 6. That is, the invention described in claim 6 is the handover compensator according to claim 5, wherein the transmission data control means is operable even after the operation in the handover mode is started by receiving the handover information from the counterpart system. The handover system side packet is also transmitted to the regular transmission system. Then, after the handover information sending means of the own system sends the handover information, the end judging means indicates that the data reception state from the partner system in the handover judging system indicates that the handover corresponding to the handover information is finished. When a predetermined handover end state is reached, it is determined that the handover has ended.

  The handover compensator configured in this way continues to send the handover system side packet to the regular transmission system even after shifting to the handover mode based on the handover information from the partner system. Even if a packet is sent to the handover decision system that is determined to be in the handover state in the other party system, the packet cannot be normally received by the other party system during the handover execution. However, when the handover is completed, the packet to the handover determination system can be received again by the counterpart system. For this reason, the counterpart system can determine that the handover has been completed when the packet from the handover determination system can be received again.

  Therefore, according to the handover compensator described in claim 6, it is possible to appropriately and reliably determine that the handover has been completed based on the reception state of the packet from the counterpart system. Therefore, since the transition from the handover mode to the normal mode can be instructed at an appropriate timing, the efficiency of data communication can be further increased.

  Next, the invention according to claim 7 is the handover compensation apparatus according to any one of claims 1 to 6, wherein the transmission data control means is provided for each system by the handover judgment means of its own system. When any one is determined to be in the handover state, at least until the handover corresponding to the handover state is completed, the system itself operates in the handover mode with the system determined as the handover state as the handover determination system.

  In other words, when the handover state is determined, not only the handover information is transmitted to the partner system and the partner system is shifted to the handover mode, but in addition, itself is also switched to the handover mode. By doing in this way, the stability of data communication can be improved more.

  Next, according to an eighth aspect of the present invention, there is provided a plurality of communication systems between a mobile communication system provided in a mobile moving along a predetermined movement route and a ground communication system provided along the movement route. This is a mobile radio communication system configured to enable wireless data communication in a system.

  Among the communication systems constituting the mobile radio communication system, the mobile communication system is provided with mobile radio transmission / reception means for each system, and the terrestrial communication system has predetermined intervals along the movement path. A group of terrestrial networks each formed by connecting a plurality of arranged terrestrial wireless transmission / reception means via a transmission line is individually provided for each system. The wireless transmission / reception means and the ground wireless transmission / reception means of the same system perform wireless data transmission / reception, and the wireless data transmission / reception is performed in packet units of a predetermined format. Each time, the terrestrial side wireless transmission / reception means for transmitting / receiving data to / from the mobile body side wireless transmission / reception means is configured to be handed over by sequentially switching as the mobile body moves.

  The mobile communication system is a device that relays data transmission between each mobile radio transmission / reception means and communication equipment in the mobile, and transmits transmission data to the ground communication system input from the communication equipment. A mobile-side data relay device configured to transmit to each mobile-side wireless transmission / reception means of a normal transmission system, which is one of the systems selected by a predetermined distribution method, is provided for each packet; The communication system is a device that relays data transmission between the local upper network and the external network, and transmits transmission data to the mobile unit input from the external network for each packet in a predetermined distribution of each system. There is provided a terrestrial data relay device configured to transmit to the terrestrial wireless transmission / reception means of the regular transmission system which is one of the systems selected by the method. That.

  And between the mobile-side data relay device and each mobile-side wireless transmission / reception means in the mobile-side communication system, and between the terrestrial-side data relay device and each local-side network in the terrestrial communication system, respectively. The handover compensation device according to any one of items 7 is provided.

  Therefore, according to the mobile radio communication system according to claim 8, the handover compensation device according to any one of claims 1 to 7 is provided. The same effect as that of the invention described in any one of the items can be obtained.

It is a block diagram showing the whole structure of the mobile radio | wireless communications system of embodiment. It is a block diagram showing internal structure of the apparatus etc. which comprise a mobile radio | wireless communications system, (a) is an internal block diagram of a 1st vehicle-mounted radio | wireless part, (b) represents an internal block diagram of a vehicle upper side handover compensation apparatus. . It is explanatory drawing showing the schematic structure of a packet. It is explanatory drawing for demonstrating the packet relay method of the hand-over compensation apparatus at the time of hand-over mode, (a) is for demonstrating the relay method of the packet for 1st systems when it becomes hand-over mode by the hand-over of 1st system | strain FIG. 7B is an explanatory diagram for explaining a method of relaying a packet for the second system when the handover mode is set by the handover of the second system. In a mobile radio | wireless communications system, it is explanatory drawing for demonstrating the packet transmission / reception state in the state (state A: normal mode) in which each system is not handed over. FIG. 6 is an explanatory diagram for explaining a packet transmission / reception state in a state where a train travels from state A in FIG. 5 and a first-system handover is performed (state B: handover mode). It is explanatory drawing for demonstrating the packet transmission / reception state in the state (state C: normal mode) in which the driving | running | working of the train further advanced from the state B of FIG. It is a flowchart showing the mode transition control process performed in a handover compensation apparatus. It is a flowchart showing the packet transmission control process performed in a handover compensation apparatus. It is a flowchart showing the hand-over judgment control process performed in a hand-over compensation apparatus. It is explanatory drawing for demonstrating the effectiveness of a handover compensation apparatus. It is a flowchart showing another Example of the hand-over judgment control process performed in a hand-over compensation apparatus.

Preferred embodiments of the present invention will be described below with reference to the drawings.
As shown in FIG. 1, a mobile radio communication system 10 according to an embodiment to which the present invention is applied includes a train 20 that travels on a predetermined travel route (in this example, a railroad track (not shown) laid on the ground). Between the on-vehicle communication system provided (corresponding to the mobile communication system of the present invention) and the ground communication system provided along the movement path of the train 20 (that is, along the track), The two communication systems of the second system are configured so that wireless data communication is possible.

  The train 20 of the present embodiment is formed by connecting a plurality of vehicles, and is a high-speed train that can travel at a maximum speed of about 300 km, for example. In the following description, for the convenience of description, the traveling direction of the train 20 is referred to as one of the leading vehicle directions (the right direction in FIG. 1) as the upward direction, and the other traveling direction (the left side in FIG. 1). Direction) will be referred to as the downward direction.

  The on-board communication system in the train 20 is provided with a first on-board radio unit 21 and a second on-board radio unit 22 that are radio units that perform wireless data transmission / reception (radio wave transmission / reception) with the ground side. Among these, the first on-board radio unit 21 is responsible for data communication by the first system, and the antenna 20a wirelessly communicates data with the first system ground radio unit 11 of the same first system on the ground side. Send and receive. The second onboard radio unit 22 is responsible for data communication by the second system, and the antenna 20b wirelessly communicates data with the second system terrestrial radio unit 12 of the same second system on the ground side. Send and receive.

  Here, the configuration of each of the on-board wireless units 21 and 22 will be described with reference to FIG. The on-board radio units 21 and 22 are basically the same in configuration and function, although the systems and radio frequencies responsible for data transmission and reception are different. Therefore, FIG. 2A shows the first on-board wireless unit 21 as a representative.

  As shown in FIG. 2 (a), the first on-board wireless unit 21 mainly includes an RF unit 31 and a baseband unit 32. The RF unit 31 demodulates radio waves received by the antenna 20a, outputs the demodulated reception data to the baseband unit 32, and modulates transmission data input from the baseband unit 32 to the antenna 20a. By transmitting, it is transmitted by radio from the antenna 20a.

  The RF unit 31 detects the intensity of the radio wave received by the antenna 20 a and outputs a signal indicating the radio wave intensity to the baseband unit 32. Specifically, a known RSSI (Received Signal Strength Indication) is detected as the radio wave intensity, and the detection result is output to the baseband unit 32 as an RSSI signal.

  The baseband unit 32 performs data processing based on a predetermined protocol. In the mobile radio communication system of the present embodiment, for example, data communication based on the well-known TCP / IP (Transmission Control Protocol / Internet Protocol) is performed. Since TCP / IP is well known, its detailed description is omitted here.

  Therefore, data transmission in the on-vehicle communication system on the train 20 side, data transmission in the ground-side ground communication system, and wireless data transmission / reception between these communication systems are performed in units of packets (IP packets).

  However, in this embodiment, since data communication is performed using two systems, a packet transmitted in this embodiment has a system identifier in the header portion of a standard IP packet as shown in FIG. include. That is, FIG. 3 shows an outline of a packet (IP packet) transmitted in the present embodiment, which is roughly composed of a data part and a header part. The header includes a destination address, a destination address, and the like. Various information based on the IP protocol is included. Furthermore, in this embodiment, a system identifier is included in the header.

  This system identifier is information indicating which system the packet belongs to, and is given by a transmission source router (either an on-vehicle router 23 or a ground router 13 described later).

  The baseband unit 32 performs a predetermined process based on TCP / IP on the data received from the RF unit 31 and then sends the data to the on-vehicle router 23 side (specifically, to the on-vehicle side handover compensation device 25 described later). . The baseband unit 32 also performs a predetermined process on the RSSI signal input from the RF unit 31 and sends the RSSI signal to the in-vehicle handover compensation device 25 as RSSI data (RSSI data). Further, the baseband unit 32 performs a predetermined process based on TCP / IP on transmission data transmitted from the on-vehicle router 23 (specifically, transmitted from the vehicle upper side handover compensation device 25), and then performs RF processing. To the unit 31.

  In addition, an access point (AP) 24 that is a wireless relay device for connecting passengers and the like to the Internet using an information communication terminal such as a PC 26 is installed inside the train 20. . In the on-board communication system in the train 20, a well-known wireless LAN that can be connected to the Internet through the wireless communication of the PC 26 and the like with the AP 24 is constructed. Since the AP 24 is a well-known wireless relay device that is often used in a wireless LAN, the detailed configuration thereof is omitted here.

  In the on-board communication system, between the on-board radio units 21 and 22 and the AP 24 (specifically, between the upper-side handover compensator 25 and the AP 24), the data transmission between them is relayed. The on-vehicle router 23 is connected. Although only one AP 24 is shown in FIG. 1, actually, one (or a plurality) of APs 24 is installed for each of a plurality of vehicles constituting the train 20, and these APs 24 are installed on the vehicle. It is connected to the router 23.

The on-vehicle router 23 is a known data relay device that performs routing of data (packets) based on a network layer protocol in the OSI reference model.
The on-board router 23 of the present embodiment further selects and determines a transmission destination system (transmission system) for each packet of transmission data from the AP 24 by a predetermined distribution method, and the selected system Then, as illustrated in FIG. 3, a system identifier is added to the header of the packet. Then, the packet with the system identifier added is sent to the vehicle-side handover compensation device 25. Therefore, for example, when the selected transmission system is the first system, the system identifier indicating the first system is added to the header, and then the packet is transmitted to the vehicle-side handover compensation device 25.

  There are various possible distribution methods for the on-vehicle router 23. For example, every time a packet is input from the AP 24, a method of alternately distributing the systems in the order of input or a method of distributing the systems based on the destination address of the packet is considered. It is done. Of course, these methods are merely examples.

  In the present embodiment, as an example, it is assumed that packets are distributed by the former distribution method. That is, for example, in the packet input order, odd-numbered (2n-1th, n is a natural number) packets are addressed to the first system, and even-numbered (2nth) packets are addressed to the second system.

  As described above, the on-board router 23 uses, as a transmission system, any transmission system (packet) input to the ground side, which is input from the AP 24, for each packet, which is selected by the above distribution method. Is added to the vehicle-side handover compensation device 25.

  On the other hand, in the ground communication system on the ground side, a plurality of ground radio units are arranged at predetermined intervals along the movement route of the train 20 for each system. That is, for the first system, a plurality of first system terrestrial radio units 11 (11-1, 11-2, 11-3...) Are arranged at predetermined intervals, and for the second system, a plurality of Second system terrestrial radio units 12 (12-1, 12-2, 12-3...) Are arranged at predetermined intervals.

  In the present embodiment, the first system terrestrial radio unit 11 and the second system terrestrial radio unit 12 are arranged at the same position when viewed individually. That is, one first system terrestrial radio unit and one second system terrestrial radio unit are arranged at the same position. However, the first system terrestrial radio unit and the second system terrestrial radio unit arranged at the same position, as an example in this embodiment, perform radio transmission / reception with radio waves of different frequencies (channels) in order to prevent radio wave interference. Do.

  In addition, a group of terrestrial networks is constructed by connecting the first system terrestrial radio units 11-1, 11-2, 11-3... In the first system via the first transmission path 51. As for the two systems, a group of terrestrial networks is constructed by connecting the second system terrestrial radio units 12-1, 12-2, 12-3... Via the second transmission path 52.

  And each 1st system ground radio | wireless part 11 is comprised so that it may mutually transmit / receive data by radio | wireless, performing a handover between the 1st vehicle-mounted radio | wireless parts 21 provided in the train 20, The system ground radio unit 12 is configured to perform wireless data transmission / reception while performing handover with the second onboard radio unit 22 provided in the train 20. That is, while the train 20 is traveling, wireless communication is performed between the train 20 side and the ground side while performing handover for each system.

  In the present embodiment, an area in which the terrestrial radio units 11 and 12 of each system on the ground side can communicate (can transmit and receive radio waves) is the terrestrial radio unit for each terrestrial radio unit as illustrated in FIG. Is set to be within a predetermined range (communication area) centered at the center, and between the communication areas adjacent to each other in the movement path direction of the train 20, its end area (end part in the movement path direction) is one. It is set so as to overlap.

  That is, as shown in FIG. 5, the communication areas of the leftmost first system ground radio unit 11-1 and second system ground radio unit 12-1 in FIG. 1 is a predetermined first communication area centered on 1, and the next first system ground radio unit 11-2 and second system ground adjacent to each of the ground radio units 11-1 and 12-1 in the upward direction. The communication area of the radio unit 12-2 is a predetermined second communication area centered on each of these terrestrial radio units 11-2 and 12-2, and with respect to each of these terrestrial radio units 11-2 and 12-2. The communication areas of the next first-system terrestrial radio unit 11-3 and second-system terrestrial radio unit 12-3 adjacent in the uplink direction are predetermined firsts centered on these terrestrial radio units 11-3 and 12-3. 3 communication areas. The end areas of the first communication area and the second communication area partially overlap, and the end areas of the second communication area and the third communication area also partially overlap.

Note that the terrestrial radio units 11 and 12 of each system are configured such that the use frequency (channel) is different between adjacent communication areas in the same system.
The on-board radio units 21 and 22 of each system provided in the train 20 transmit and receive data to and from each other within the communication area of the ground radio unit with the ground radio unit of the same system on the ground side. I do. And every time the position of the onboard radio unit on the train 20 side moves from the communication area of a certain ground radio unit on the ground side to the communication area of the next ground radio unit as the train 20 travels, the ground side and the train 20 side Both communication partners are switched by performing a handover process between the wireless units.

  Each of the terrestrial radio units 11 and 12 has basically the same configuration and function as the on-vehicle radio units 21 and 22 (see FIG. 2A) provided in the train 20, so here Detailed description thereof is omitted.

  Further, on the ground side, between each transmission path 51, 52 of each system and the Internet 14 as an external network (specifically, between the ground-side handover compensation device 15 and the Internet 14), data transmission between them is performed. Is connected to the ground router 13.

  Since the ground router 13 has basically the same configuration and function as the on-vehicle router 23 provided in the train 20, detailed description thereof is omitted here. That is, the ground router 13 also performs routing of data (packets), and selects and determines a transmission destination system (transmission system) for each packet of transmission data from the Internet 14 by a predetermined distribution method. Then, according to the selected system, a system identifier is added to the header of the packet as illustrated in FIG. Then, the packet with the system identifier added is sent to the ground-side handover compensation device 15. In this embodiment, the packet distribution method in the ground router 13 is the same as the distribution method in the on-vehicle router 23 described above.

  Here, in the mobile radio communication system of the present embodiment, as described above, handover is performed for each system as the train 20 travels. Therefore, every time handover is performed, wireless communication (radio wave transmission / reception) between the wireless units is temporarily interrupted (for example, about 0.1 second). Due to the interruption of the radio wave due to this handover, the data communication between the ground and the vehicle is interrupted for a longer time (for example, about 1 second) than the interruption of the radio wave connection between the radio units. This is because even if the wireless units are connected by handover, connection control (timeout processing or the like) is performed using a higher-layer protocol such as the TCP protocol.

  Therefore, in the present embodiment, when a handover compensation device is provided on both the ground side and the train 20 side, and it is predicted immediately before a handover occurs in any system, and the occurrence of a handover is predicted, This is notified to the handover compensation device. Then, by notifying the other party that has made the notification, the packet addressed to the system for which the occurrence of the handover is predicted out of the packets sent from the router on the other party side to the other system side. Is transmitted not only to the predicted system but also to the other system.

  Here, “opposite” means the train 20 (vehicle communication system; partner system) from the ground side (ground communication system; own system), and the train 20 side (vehicle communication system side; From the perspective of the own system, it means the ground (terrestrial communication system; partner system).

  That is, in the mobile radio communication system 10 of this embodiment, the vehicle upper side for relaying data transmission between the on-vehicle router 23 and the on-vehicle radio units 21 and 22 in the on-vehicle communication system. A handover compensation device 25 is provided, both between the ground router 13 and each terrestrial radio unit 11, 12 in the terrestrial communication system (specifically, between the terrestrial router 13 and each transmission path 51, 52). A ground-side handover compensation device 15 for relaying data transmission between them is provided.

  The vehicle-side handover compensation device 25 and the ground-side handover compensation device 15 basically have the same configuration / function. Therefore, here, the vehicle-side handover compensation device 25 provided in the train 20 as a representative is described in its configuration / Explain the function.

  The vehicle upper side handover compensation device 25 basically relays the received data from the onboard radio units 21 and 22 as they are and sends them to the onboard router 23, and also transmits the transmission data from the onboard router 23 to the packet. Each has a function of transmitting to the system (regular transmission system) side indicated by the system identifier of the header of the first system and the second system.

  A schematic configuration of the vehicle upper side handover compensation device 25 is shown in FIG. As shown in FIG. 2B, the vehicle upper side handover compensation device 25 mainly includes a system side input / output unit 41, a router side input / output unit 43, and a communication control unit 42.

  Transmission data from the on-vehicle router 23 is input to the communication control unit 42 via the router side input / output unit 43. In addition, the received data from the on-vehicle radio units 21 and 22 are input to the communication control unit 42 via the system-side input / output unit 41, respectively.

The communication control unit 42 includes the above-described basic functions, and further includes a handover prediction function, a handover notification function, and a mode switching function.
Among them, the handover prediction function is a function for predicting the occurrence of handover for each system based on the received packet from the corresponding system side.

  Due to the characteristics of wireless data transmission, if the radio wave condition becomes worse in a certain system due to switching of communication areas (ie, approaching handover), packets from that system cannot be normally received before handover. That is, even if the radio units on the ground side and the train 20 side are wirelessly connected and radio waves can still be transmitted and received, if the radio wave state (radio wave intensity) deteriorates, data (packets) cannot be transmitted normally. Therefore, in this embodiment, for each system, the reception state of the packet is monitored, and when it is determined that the packet cannot be normally received (a state immediately before the start of the present invention, which corresponds to an abnormal reception state), the system is not handed over. Predict that it is the state just before it happens.

  Various specific prediction methods are conceivable. For example, in the present embodiment, since each router sequentially and alternately transmits packets, packets destined for each system arrive alternately at the other side. Although the packet arrival may be slightly coarse or dense, it does not deviate greatly from arriving at only one of the systems. On the other hand, if one of the routes (for example, the first system) is in a state immediately before the handover, at this time, the packet from the first system side does not arrive at all, and only the packet from the second system side arrives. If this state is detected, the occurrence of handover can be predicted in advance.

  Including such a method, for example, a prediction method such as a method based on a packet loss rate for each system, a method based on RTT (Round Trip Time), and a method based on radio wave intensity as described later can be appropriately employed. .

  What is common to both methods is that no special data (such as ping) is used for handover prediction, and it is actually performed between the ground and the vehicle. This is one of the characteristic configurations of the present embodiment. In this example, the prediction is performed using the data communication status (raw data (packets) transmitted and received in this example). .

  Further, when a handover is predicted for a certain system, the handover is soon performed in that system (corresponding to the handover determination system of the present invention), but the communication control unit 42 detects the end of the handover after predicting the handover. It also has a function.

  Although various handover end detection methods are conceivable, in this embodiment, as an example, the state of packet reception in a system that has predicted handover is continuously monitored, and a packet from that system is normally received again (in the present invention) It is determined that the handover has been completed.

  There are various ways to determine whether or not the packet is normally received again. For example, if one packet is received from the system after the handover is started, it is normal. For example, it may be determined whether or not a packet from the system can be normally received from various viewpoints such as a packet loss rate and an RTT. May be.

  In addition, the handover notification function is a function for notifying the opposite handover compensator to that effect when a handover is predicted, and to the opposite handover compensator when detecting the end of handover in the predicted system. It is a function to notify.

  That is, when the communication control unit 42 predicts a handover in any system by the above-described handover prediction function, the communication control unit 42 is information indicating that a handover is about to occur in the system, and the communication control unit 42 A handover mode transition command, which is a command for switching the operation mode to the handover mode (details will be described later), is transmitted to the opposite handover compensation device via a system different from the system that predicted the handover. Specifically, a packet indicating a handover mode transition command is generated and transmitted via the wireless unit of the own system.

  In addition, when the end of the handover is detected after the handover mode transition command is transmitted, this information is used to switch the operation mode of the opposite handover compensator to the normal mode (details will be described later). Is transmitted to the opposite handover compensator via at least one of the systems.

  The mode switching function is a function for switching its own operation mode to either the handover mode or the normal mode according to the mode transition command when each mode transition command is received from the opposite handover compensator.

  Here, the normal mode means that transmission data (packet) addressed to the opposite (other party) system from the router in the corresponding own system is simply sent to the corresponding system side according to the system identifier added to the packet. It is a mode that operates to send.

  On the other hand, the handover mode is an operation mode when a handover mode transition command is received from the opposing handover compensator, and is indicated by a system identifier among transmission data (packets) from the corresponding router in its own system. For the packet (handover system side packet) whose normal transmission system is the system (handover determination system) for which handover is predicted in the other system, it is copied not only to the normal transmission system but also to the other system. It is a mode that operates to send out. It should be noted that it may be transmitted only to the other system without transmitting to the regular transmission system where the handover is performed.

  The packet copy transmission in the handover mode will be specifically described with reference to FIG. FIG. 4 (a) is a diagram for the first system after transition to the handover mode when a handover mode transition command indicating that the handover of the first system has been predicted in the opposite handover compensation device. The example of a process of a packet (2n-1 packet) is shown.

  In this case, the system identifier of the packet transmitted from the router of the own system indicates the first system that is a regular transmission destination. However, the first system is a system in which handover is predicted in the opposite handover compensator. Therefore, in this case, the communication control unit 42 generates the packet separately by copying the packet as the operation in the handover mode. Then, address rewriting is performed on the copy generated packet. That is, the system identifier is rewritten from the first system, which is a normal transmission system, to the second system.

  Then, the packet (copy packet) in which the system identifier is rewritten is transmitted to the second system, which is a system corresponding to the system identifier after the rewriting (a non-regular system that was not originally a normal transmission destination). Further, the original regular packet (copy source packet) is sent as it is to the first system which is the regular transmission system.

  In the first system, which is the regular transmission system, since handover should have been performed, it does not reach the opposing handover compensator until the handover is completed. However, when the handover is completed, it reaches the opposite handover compensator again, and as a result, the normal mode shift command is transmitted from the opposite handover compensator as described above.

  FIG. 4B is a diagram for the second system after transition to the handover mode when a handover mode transition command indicating that the handover of the second system is predicted in the opposite handover compensation apparatus is transmitted. The example of a process of a packet (2nd n packet) is shown.

  In this case, the system identifier of the packet transmitted from the router of the own system indicates the second system that is a regular transmission destination. However, the second system is a system in which handover is predicted in the opposite handover compensator. Therefore, in this case, the communication control unit 42 generates the packet separately by copying the packet as the operation in the handover mode. Then, address rewriting is performed on the copy generated packet. That is, the system identifier is rewritten from the second system, which is a normal transmission system, to the first system.

  Then, the packet (copy packet) in which the system identifier is rewritten is transmitted to the first system which is a system corresponding to the system identifier after the rewrite (originally a non-regular system that was not a normal transmission destination). Also, the original regular packet (copy source packet) is sent as it is to the second system which is the regular transmission system.

  In the second system, which is the regular transmission system, since handover should have been performed, it does not reach the opposing handover compensator until the handover is completed. However, when the handover is completed, it reaches the opposite handover compensator again, and as a result, the normal mode shift command is transmitted from the opposite handover compensator as described above.

  Thus, the communication control unit 42 operates in the normal mode during normal times when handover is not performed in any system. When a handover in one of the systems is predicted by the opposite handover compensator, and a handover mode transition command is transmitted from the opposite handover compensator, the operation is performed in the handover mode. Then, when a normal mode transition command is transmitted thereafter, the normal mode is operated again.

  The switching of the operation mode of the handover compensator accompanying the traveling of the train 20 in the mobile radio communication system 10 of the present embodiment configured as described above will be described with reference to FIGS.

  First, FIG. 5 shows a state A in which no handover is performed in any of the systems in the mobile radio communication system 10, and the handover compensation devices on the ground side and the train 20 side are both operating in the normal mode. Is shown.

  In this state A, in the train 20, the first on-board wireless unit 21 is present in the first communication area on the ground side, and the first system of the same first system having the first communication area as the communication range. Wireless communication is performed with the ground radio unit 11-1. The second onboard radio unit 22 is present in the second communication area on the ground side, and the second second-system terrestrial radio unit 12-2 of the same second system having the second communication area as a communication range. Wireless communication between the two.

  In this state A, since handover has not occurred or predicted in any of the systems, each of the handover compensators 15 and 25 directly accepts the packet from the router in its own system according to the system identifier. Send to the corresponding system side (radio unit side). Therefore, for example, for a packet transmitted from the ground side to the train 20 side, as illustrated in FIG. 5, the normal transmission system selected by the ground router 13 is the first system packet (second n−1 packet; first , 3, 5... Packets are sent to the first system side (to the first transmission path 51), and the regular transmission system selected by the ground router 13 is the second system packet (second n packet; second). , 4, 6... Packets are sent to the second system side (to the second transmission path 52). In the figure, circled numbers indicate packet numbers (transmission order).

  Then, the travel (upward direction) of the train 20 proceeds from the state A, and the first on-board wireless unit 21 is in the vicinity of the boundary region between the first communication area and the second communication area as in the state B shown in FIG. In each handover compensation device, handover in the first system is predicted. For example, when the first-system handover is predicted based on the packet reception status from the ground side in the vehicle-side handover compensation device 25, the handover from the vehicle-side handover compensation device 25 to the opposite ground-side handover compensation device 15 is performed. A mode transition command is sent.

  When receiving the handover mode shift command, the opposing ground side handover compensation device 15 shifts its operation mode to the handover mode. As a result, as illustrated in FIG. 6, the normal transmission system selected by the ground router 13 is the normal one for the first system packet (second n-1 packet; first, third, fifth,... Packet). Is continued to be transmitted to the first system, and the copy packet is generated as described with reference to FIG. In the figure, the numbers with squares indicate the copy packet numbers.

Therefore, in this state B, although handover is performed in the first system, all packets can be transmitted through the second system.
And if the run (up direction) of the train 20 further proceeds from the state B, the first on-board radio unit 21 of the train 20 moves from the first communication area to the second communication area, Packets addressed to the first system from the first system terrestrial radio unit 11-2 of the same first system with the second area as the communication range can be received.

  Therefore, when the vehicle-side handover compensator 25 can normally receive the packet from the first system again via the first on-vehicle radio unit 21, the vehicle-side handover compensator 25 issues a normal mode transition command to the opposite ground-side handover compensator 15. And the ground-side handover compensator 15 is again shifted to the normal mode. Thereby, as in the state C illustrated in FIG. 7, the ground-side handover compensation device 15 again operates in the normal mode.

Next, the various processes described above executed by the communication control unit 42 in each handover compensation apparatus will be described using the flowcharts of FIGS.
The communication control unit 42 executes the control process of the mode transition control process shown in FIG. 8, the packet transmission control process shown in FIG. 9, and the handover determination control process shown in FIG.

  Among these, first, the mode transition control process of FIG. 8 will be described. When starting the mode transition control process, the communication control unit 42 first determines in S110 whether or not a handover mode transition command has been received from the opposite handover compensator.

  Note that when the communication control unit 42 starts the mode transition control process, the operation mode of the communication control unit 42 (and thus the operation mode of the handover compensation device) is set to the normal mode.

  In the determination process of S110, the process waits until a handover mode transition command is received. If the handover mode shift command is received, the process proceeds to S120, and its own operation mode is set to the handover mode.

  After setting to the handover mode, in S130, it is determined whether or not a normal mode transition command is received from the opposite handover compensation device. That is, in S130, the process waits until a normal mode transition command is received. If a normal mode transition command is received, the process proceeds to S140, where its own operation mode is set to the normal mode, and the process returns to S110 again.

  Next, the packet transmission control process of FIG. 9 will be described. When starting the packet transmission control process, the communication control unit 42 first determines in S210 whether or not a packet has been received from the router on the own system side. Then, while the packet is not received, the determination process of S210 is repeated. However, when the packet is received from the router, the process proceeds to S220, and the mode currently set in itself is determined.

  At this time, if the normal mode is set, the process proceeds to S230, and the packet is transmitted to the destination system determined (selected) by the router, that is, the system indicated by the system identifier. In other words, the packet is distributed and transmitted as it is according to the destination specified for each packet by the router. In this example, the odd-numbered packet is transmitted to the first system, and the even-numbered packet is transmitted to the second system. It will be.

  On the other hand, if the handover mode is set, the process proceeds to S240, and packet relay corresponding to the handover mode is performed. That is, the transmission is performed as it is (distributed transmission) to the regular transmission system designated by the router. Then, based on the distributed transmission, for the packet destined for the handover system, as described in FIG. 6, the packet is copied and the system identifier is rewritten and transmitted to the system after the rewriting (copy). Send.

  Next, the handover determination control process in FIG. 10 will be described. When starting the handover determination control process, the communication control unit 42 first monitors incoming packets of each system from the counterpart system in S310. Then, in S320, it is determined whether or not the reception state of the packet from either the first or second system is abnormal. If the reception state of any system is normal, the process returns to S310. However, if a reception abnormality is detected in any system, it is predicted that the system is immediately before the handover is started in that system (handover system). In S330, a handover mode transition command is transmitted to the opposite handover compensator via a system other than the handover system.

  Thereafter, the process proceeds to S350, and the incoming packets of each system from the partner system are continuously monitored. Then, in S360, it is determined whether or not the packet is normally received from the counterpart system via the handover system (system in which handover is predicted in S320 to S330). Then, while the normal reception of the packet from the handover system is not resumed, the process returns to S350. However, when the normal reception restart of the packet from the handover system is detected, the completion of the handover in the handover system is detected (S370). ) In S380, a normal mode transition command is transmitted to the opposite handover compensator.

  In addition, in this embodiment, when the passenger etc. are not communicating (the internet connection etc.) with the ground side using PC26 etc. in the train 20, in other words, substantial between the ground side and the train 20 side. While the data communication is not performed, each handover compensation device does not perform the above-described processes of FIGS.

  FIG. 11 shows a comparative example of the communication speed between the mobile radio communication system 10 of this embodiment provided with a handover compensation device and a conventional mobile radio communication system not provided with a handover compensation device. As shown in FIG. 11, in the conventional system, when the handover is started at time t1, the communication speed becomes zero. Even if the handover is completed at time t2, the communication speed does not immediately return due to the above-described connection control in the upper layer, and communication is possible again at time t3 when a predetermined time has elapsed from the end of handover. It becomes.

  On the other hand, in the system of the present embodiment, it is predicted immediately before the start of handover, and a handover mode transition command is transmitted to the opposite handover compensation device. Communication can be continued using one system. Therefore, as shown in FIG. 11, even if the handover is started at time t1, data communication is continuously performed although the communication speed is halved. Then, when the handover is completed at time t2, it is possible to immediately recover and to quickly return to the original (normal mode) data communication.

  As described above, according to the mobile radio communication system 10 of the present embodiment, the handover compensation device is provided on each of the ground side and the train 20 side, and thereby the handover mode transition command is received from the opposite handover compensation device. Then, its own operation is set to the handover mode, whereby data communication can be continued in at least one of the systems. Therefore, the mobile radio communication system 10 as a whole can perform efficient and stable data communication while suppressing the influence on the data communication stability due to the occurrence of handover.

  Further, in this embodiment, since the handover is not shifted to the handover mode after the handover is actually started, the handover is predicted in advance before the handover is started. Data communication interruption can be reliably prevented, and the stability of data communication can be further improved.

  Moreover, the prediction of the handover (determination of whether or not the reception is abnormal) is not performed using special control data or the like for the prediction, but based on the reception state of the actual packet that is actually transmitted and received. Therefore, it is possible to predict with high accuracy without hindering actual data communication.

  In this embodiment, the return from the handover mode to the normal mode is also performed in accordance with a command from the counterpart handover compensator. Therefore, appropriate mode switching according to the state of wireless communication viewed from the other party system is possible, and the efficiency of data communication can be further increased.

  In the present embodiment, the on-board radio units 21 and 22 correspond to the mobile-side radio transmission / reception means of the present invention, the terrestrial radio units 11 and 12 correspond to the terrestrial-side radio transmission / reception means of the present invention, The router 23 corresponds to the mobile data relay device of the present invention, the ground router 13 corresponds to the ground data relay device of the present invention, and the communication control unit 42 in each of the handover compensation devices 15 and 25 determines the handover determination of the present invention. Means, means for transmitting handover information, means for transmitting data control, means for determining termination, and means for transmitting termination information.

[Modification]
Although the embodiments of the present invention have been described above, the embodiments of the present invention are not limited to the above-described embodiments, and can take various forms as long as they belong to the technical scope of the present invention. Needless to say.

  For example, in the above embodiment, both the handover start prediction and the handover end detection are performed based on the reception status of the packet received from the counterpart system. However, this is merely an example, and the start prediction is performed. -As long as each end detection can be performed appropriately, the specific method is not particularly limited.

For example, as shown in FIG. 12, it is also possible to perform handover prediction / end detection based on the radio wave intensity of the received radio wave.
FIG. 12 shows another embodiment of the handover determination control process shown in FIG. When the communication control unit 42 starts the handover determination control process of FIG. 12, first, in S410, the RSSI data is acquired from the radio units of the respective systems currently in radio communication, and based on the RSSI, radio communication is performed. Monitor the radio field strength of each system during communication. In S420, it is determined whether RSSI in either the first or second system is equal to or less than a predetermined threshold. This threshold value may be determined as appropriate, for example, as an RSSI in a state where data communication can be normally performed, or a value larger (or smaller) by a predetermined amount than the RSSI.

  Then, if the RSSI of any system is larger than the threshold value, the process returns to S410. If the RSSI of any system is less than or equal to the threshold value, it is predicted that the system (handover system) is just before the handover is started ( In S430) and S440, a handover mode transition command is transmitted to the opposite handover compensator via a system other than the handover system.

  Thereafter, the process proceeds to S450, and the radio field intensity of each system is monitored based on RSSI in exactly the same manner as in S410. Then, in S470, it is determined whether or not the RSSI of the handover system (system in which handover is predicted in S420 to S430) has exceeded a threshold value. While the RSSI of the handover system does not exceed the threshold value, the process returns to S450. However, when the RSSI of the handover system exceeds the threshold value, it is detected that the handover in the handover system has ended (S470), and in S480 The normal mode transition command is transmitted to the opposite handover compensator.

  As described above, even by a method of performing handover prediction and end detection based on the radio field intensity (RSSI), it is possible to accurately perform prediction / end detection without hindering actual data communication.

  In the above-described embodiment, the mode transition in each handover compensator has been described as passively performed according to the transition command from the opposite handover compensator. However, such a passive transition is not essential. For example, when a handover is predicted and a handover mode shift command is transmitted to the opposite handover compensator, both themselves may shift to the handover mode.

  Further, the transmission of the handover mode transition command is not limited to when the handover is predicted, but may be performed when the handover is actually started. However, in order to stabilize the data communication, it is preferable to predict and transmit a handover mode transition command before the start of handover as in the above embodiment.

  In the handover mode, all packets are sent to both systems regardless of the system identifier (that is, regardless of which system the normal transmission system is) in the handover mode. Also good. That is, it transmits twice to each system.

In the above embodiment, the ground radio units of each system are arranged at the same position / interval on the ground side. However, this is merely an example.
In the above embodiment, the communication area of each wireless unit is a predetermined area centered on the wireless unit (see FIG. 5 and the like). However, this is merely an example, and the communication area of each wireless unit. It is possible to appropriately determine how to set the radio frequency and how to set the radio frequency (channel) of each radio unit.

  As an example, for the first system terrestrial radio unit 11, for example, by using an antenna having directivity in the down direction, a range from the installation position to a position away from the installation direction by a certain distance becomes a communication area. The dual-system terrestrial radio unit 12 uses an antenna having directivity in the upward direction so that a range from the installation position to a position separated by a certain distance in the upward direction becomes a communication area. In each system, the communication areas adjacent to each other in the traveling direction of the train 20 are set so that the end regions (end portions in the traveling direction) partially overlap as in the above embodiment. In this case, the radio frequencies of the ground radio units 11 and 12 of the respective systems installed at the same position can be the same frequency.

  On the other hand, in the train 20, for example, the first on-board radio unit 21 of the first system is installed in the leading vehicle on the upside of the train 20 and the antenna having directivity in the up direction is used. The range from the position to a position separated by a certain distance in the upward direction becomes a communication area, and the second onboard radio unit 22 of the second system is installed in the leading vehicle on the down direction side in the train 20 and By using an antenna having directivity in the direction, a range from the installation position to a position separated by a certain distance in the downward direction becomes a communication area.

  As described above, the present invention can be applied to a mobile radio communication system in which the communication area of each radio unit is set as described above. Of course, it is needless to say that the example of setting the communication area exemplified above is merely an example.

  Moreover, in the said embodiment, although the mobile radio | wireless communications system 10 which has two systems, a 1st system and a 2nd system, was mentioned as an example and demonstrated, the application of this invention has two systems It is not limited to.

  1a, 1b, 1c, 2a, 2b, 2c, 20a, 20b ... antenna, 10 ... mobile radio communication system, 11 (11-1, 11-2, 11-3 ...) ... first system ground radio unit , 12 (12-1, 12-2, 12-3...) ... second system terrestrial radio unit, 13 ... ground router, 14 ... internet, 15 ... ground side handover compensator, 20 ... train, 21 ... 1 on-vehicle radio unit, 22 ... second on-vehicle radio unit, 23 ... on-vehicle router, 24 ... AP, 25 ... on-vehicle side handover compensation device, 26 ... PC, 31 ... RF unit, 32 ... baseband unit, 41 ... System side input / output unit, 42 ... Communication control unit, 43 ... Router side input / output unit, 51 ... First transmission path, 52 ... Second transmission path

Claims (8)

Configuration that enables wireless data communication in a plurality of systems between a mobile communication system provided on a mobile moving along a predetermined movement route and a ground communication system provided along the movement route And
The mobile communication system includes mobile radio transmission / reception means for each of the systems, and the ground communication system includes a plurality of ground wireless transmission / reception means arranged at predetermined intervals along the movement path. A group of terrestrial networks connected to each other is provided individually for each of the systems, and data is transmitted and received wirelessly between the mobile-side wireless transmission / reception means and the terrestrial-side wireless transmission / reception means of the same system. The wireless data transmission / reception is performed in packet units of a predetermined format, and the ground side wireless transmission / reception means for transmitting / receiving data to / from the mobile body side wireless transmission / reception means is connected to the mobile body for each system. It is configured to be handed over sequentially with the movement of
The mobile-side communication system is an apparatus that relays data transmission between each mobile-side wireless transmission / reception means and communication equipment in the mobile body, and that is connected to the terrestrial communication system input from the communication equipment. A mobile-side data relay device configured to send transmission data to each mobile-side wireless transmission / reception means of a regular transmission system that is one of the systems selected by a predetermined distribution method for each packet. The terrestrial communication system is a device that relays data transmission between the local network and the external network, and transmits transmission data to the mobile unit input from the external network for each packet. To the terrestrial wireless transmission / reception means of the regular transmission system which is one of the systems selected by a predetermined distribution method. Cormorant configured ground side data relay apparatus is provided, in a mobile radio communication system,
Data transmission is performed between the mobile data relay device and the mobile radio transmission / reception means in the mobile communication system and between the ground data relay device and the local network in the ground communication system. A handover compensation device provided for relaying,
Whether the handover is started for each system, or whether the state of data transmission / reception between the mobile-side wireless transmission / reception unit and the ground-side wireless transmission / reception unit is the state immediately before the start of the handover immediately before the start of the handover. A handover determining means for determining whether or not a handover state has occurred,
When the handover determining means determines that any one of the systems is in the handover state, the own system which is a system on the side where the handover compensation device is provided in the mobile communication system and the terrestrial communication system The handover information indicating that the handover determination system is in the handover state is transmitted to the wireless transmission / reception means of a system other than the handover determination system which is the system determined to be in the handover state. Handover information sending means for wirelessly transmitting to a partner system which is a communication partner system for the own system;
In normal mode when the handover information is not received from the counterpart system, the transmission data from the data relay device in the own system is sent to the wireless transmission / reception means of the regular transmission system for each packet. When the handover information is received from the counterpart system, the transmission data from the data relay device in the local system is configured at least until the handover corresponding to the handover information is completed. Among the packets to be performed, for the handover system side packet whose normal transmission system is the handover determination system, instead of the normal transmission system or in addition to the normal transmission system, the system of a system different from the normal transmission system Operates in handover mode for sending to wireless transceiver That, and the transmission data control means,
A handover compensation apparatus comprising: The handover compensation device according to claim 1,
The handover determining means determines whether or not the state of wireless data transmission / reception between the mobile-side wireless transmission / reception means and the ground-side wireless transmission / reception means is the state immediately before the start, and has entered the state immediately before the start. In this case, it is determined that the handover state has been established. The handover compensation device according to claim 2, wherein
The handover determining unit monitors the reception state of the packet from the counterpart system by the wireless transmission / reception unit in the local system for each system, and the reception state of the packet in any of the systems is set in advance. The handover compensator characterized by determining that the state immediately before the start is reached when a reception abnormal state indicating that the reception is not normally performed. The handover compensation device according to claim 2, wherein
Each of the wireless transmission / reception means includes radio field intensity detection means for detecting the intensity of the received radio wave from the radio transmission / reception means for data transmission / reception in the counterpart system
The handover determining unit determines that the state immediately before the start has been reached when the intensity of the received radio wave detected by the radio field intensity detecting unit is equal to or less than a preset radio field intensity threshold value. . The handover compensation device according to any one of claims 1 to 4,
An end determination means for determining whether or not the handover in the determined handover determination system is completed after any one of the systems is determined as the handover state by the handover determination means;
When the end determination unit determines that the handover has ended, by sending end information indicating that the handover has ended to one or a plurality of wireless transmission / reception units of the own system, End information sending means for wirelessly transmitting the end information to the counterpart system;
With
The transmission data control means starts the operation in the handover mode by receiving the handover information from the counterpart system, and then receives the end information from the counterpart system when the end information is received from the counterpart system. A handover compensator characterized by transitioning to operation. The handover compensation device according to claim 5, wherein
The transmission data control means is configured to send the handover system side packet to the regular transmission system even after starting the operation in the handover mode by receiving the handover information from the counterpart system. ,
After the handover information sending means of the own system sends the handover information, the termination judging means indicates that the handover status corresponding to the handover information indicates that the data reception state from the counterpart system in the handover judgment system is A handover compensation device, characterized in that, when a predetermined handover completion state indicating completion has been reached, it is determined that the handover has been completed. The handover compensation device according to any one of claims 1 to 6,
When the transmission data control unit determines that any one of the systems is in the handover state by the handover determination unit of the own system, at least until the handover corresponding to the handover state ends, The handover compensator characterized by operating in the handover mode with the system determined to be in the handover state as the handover determining system. Configuration that enables wireless data communication in a plurality of systems between a mobile communication system provided on a mobile moving along a predetermined movement route and a ground communication system provided along the movement route And
The mobile communication system includes mobile radio transmission / reception means for each of the systems, and the ground communication system includes a plurality of ground wireless transmission / reception means arranged at predetermined intervals along the movement path. A group of ground-side networks connected to each other are individually provided for each system, and wireless transmission and reception of data is performed between the mobile-side wireless transmission / reception means and the ground-side wireless transmission / reception means of the same system. The wireless data transmission / reception is performed in units of packets in a predetermined format, and the ground side wireless transmission / reception means for transmitting / receiving data to / from the mobile body side wireless transmission / reception means for each system. It is configured to be handed over sequentially as it moves,
The mobile-side communication system is an apparatus that relays data transmission between each mobile-side wireless transmission / reception means and communication equipment in the mobile body, and that is connected to the terrestrial communication system input from the communication equipment. A mobile-side data relay device configured to send transmission data to each mobile-side wireless transmission / reception means of a regular transmission system that is one of the systems selected by a predetermined distribution method for each packet. The terrestrial communication system is a device that relays data transmission between the local network and the external network, and transmits transmission data to the mobile unit input from the external network for each packet. To the terrestrial wireless transmission / reception means of the regular transmission system which is one of the systems selected by a predetermined distribution method. Cormorant configured ground side data relay apparatus is provided, a mobile radio communication system,
Between the mobile data relay device and each mobile radio transmission / reception means in the mobile communication system, and between the terrestrial data relay device and the local network in the ground communication system, respectively, A mobile radio communication system comprising the handover compensation device according to any one of claims 1 to 7.