JP2016171497A - Communication redundancy terminal, communication redundancy system, communication redundancy method and communication redundancy program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent interruption of communication, while maintaining communication quality in wireless communication.SOLUTION: A communication redundancy device includes a plurality of communication means each establishing a wireless communication path with a separate base station, and performing communication with a communication destination device via the wireless communication path thus established, and control means for making n (n is an integer of 2 or more) other communication means continue communication with the communication destination device, even in a period not communicating with the communication destination device, because one communication means switches the base station for establishing the wireless communication path with the own communication means, in the handover period.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a communication redundancy terminal, a communication redundancy system, a communication redundancy method, and a communication redundancy program for performing communication on a redundant communication path.

  Wireless communication systems in which a communication terminal as a mobile station performs wireless communication with a base station as a fixed station are widely used. In such a wireless communication system, a communication terminal or the like performs wireless communication while moving. Therefore, the communication state of communication performed between the communication terminal and the base station etc. changes every moment.

  In order to perform stable wireless communication under such conditions that the communication status changes, a technique for switching a wireless channel used for wireless communication described in Patent Document 1 or a technique described in Patent Document 2 are described. Various techniques such as a technique for speeding up the handover are used.

  First, the technique described in Patent Document 1 will be described. In Patent Document 1, a plurality of wireless channels are prepared in order to realize good communication in a communication system affected by an external influence such as a wireless LAN, and the wireless channels are switched and used according to the communication status. It is described.

  This will be described more specifically. In the communication system described in Patent Document 1, an S / N ratio (signal-noise ratio) is measured as a value representing the communication quality of communication using a wireless channel in use. Then, the measured S / N ratio is compared with a preset threshold value. If the comparison shows that the S / N ratio of communication using the wireless channel in use has dropped below the threshold level, a new one is created based on the wireless conditions at the time of measurement including surrounding interference waves. The wireless channel to be used for communication is determined, and the communication is continued by switching to the determined wireless channel.

  Next, the technique described in Patent Document 2 will be described. Patent Document 2 describes a wireless communication system for performing handover between wireless base stations at high speed when a plurality of wireless devices are used simultaneously.

  More specifically, in the wireless communication system described in Patent Document 2, a plurality of wireless communication units corresponding to each of a plurality of base stations are provided. Further, in the wireless communication system described in Patent Document 2, the wireless state by the plurality of wireless communication units is constantly monitored. As described above, in the wireless communication system described in Patent Document 2, since a wireless communication unit having a good wireless state can be grasped by always monitoring, a wireless communication unit having a good quality is always selected for communication with a base station. The time required for handover can be reduced to a short time.

JP 2003-244761 A JP 2005-341453 A

  By using the techniques described in Patent Document 1 and Patent Document 2 described above, handover between base stations that accompanies radio channel switching can be performed. Then, stable communication can be continued by communicating with the handover destination base station via the switched radio channel.

  However, in these techniques, there is a problem that there is a moment when the wireless communication path is interrupted with the control process of switching between the wireless channel and the base station to perform handover.

  Considering this problem, when performing handover by switching radio channels, it is considered to perform handover on the radio channel after switching while one radio communication path in the radio channel before switching remains connected. It is done. As a result, the wireless communication path is not cut off. However, if the state of the connected wireless communication path is unstable, the communication quality cannot be maintained as a result.

  Therefore, the present invention provides a communication redundancy terminal, a communication redundancy system, a communication redundancy method, and a communication redundancy program that can maintain communication quality in wireless communication and prevent communication from being interrupted. For the purpose.

  According to the first aspect of the present invention, a plurality of communications, each of which establishes a wireless communication path with a separate base station and communicates with a communication destination device via the established wireless communication path. Even during the period of not performing communication with the communication destination device because any one of the communication means switches the base station that establishes the wireless communication path with the own communication means in the handover period, There is provided a communication redundancy device, comprising: n (where n is an integer of 2 or more) other communication means, a control means for continuing communication with the communication destination device.

  According to a second aspect of the present invention, there is provided a communication redundancy system including the communication redundancy apparatus provided by the first aspect, the base station, and the communication destination apparatus, wherein the plurality of bases The base station is installed so that the degree of station overlap is m (m is an integer of 2 or more), the communication destination device is connected to the plurality of base stations, and the communication destination device and the communication redundancy An apparatus is provided with a communication redundancy system that performs communication via the plurality of base stations and the plurality of wireless communication paths.

  According to the third aspect of the present invention, a plurality of communication means each establishing a separate wireless communication path with a separate base station can communicate with a communication destination device via the established wireless communication path. A plurality of communication steps for performing the communication, and during the handover period, any one of the communication means switches the base station that establishes a wireless communication path with the own communication means, so that the communication with the communication destination apparatus is performed. There is provided a communication redundancy method characterized by performing a control step in which n (n is an integer of 2 or more) other communication means continues communication with the communication destination device even during a period of time Is done.

  According to a fourth aspect of the present invention, there is provided a communication redundancy program, wherein a computer establishes a wireless communication path with each separate base station, and passes through the established wireless communication path. A plurality of communication means for communicating with a communication destination apparatus, and any one of the communication means switches a base station that establishes a wireless communication path with the communication means during the handover period; Even during the period of not performing the communication, the communication means is provided with control means for continuing communication with the communication destination apparatus in other communication means (n is an integer of 2 or more). A communication redundancy program is provided.

  According to the present invention, it is possible to maintain communication quality in wireless communication and prevent communication from being interrupted.

It is a figure showing an example of the environment where the radio | wireless communications system which is embodiment of this invention is installed. It is a block diagram showing the functional block contained in the radio | wireless communications system which is embodiment of this invention. It is an image figure showing assignment | providing of the sequence number in the packet in embodiment of this invention. It is a flowchart which shows an example of the operation | movement at the time of transmission of the fixed station side communication control part in embodiment of this invention. It is a flowchart which shows an example of the operation | movement of the base station selection at the time of the communication start of the mobile station side communication control part in embodiment of this invention. It is a flowchart which shows an example of the operation | movement of the base station selection of the mobile station side communication control part in embodiment of this invention. It is a timing chart showing transition of the establishment state of the radio | wireless communication path | route with each base station in embodiment of this invention. It is a flowchart which shows an example of the operation | movement at the time of reception of the mobile station side communication control part in embodiment of this invention. It is a flowchart which shows an example of the operation | movement about management of the sequence number based on the timer in embodiment of this invention. It is a flowchart which shows an example of the operation | movement at the time of transmission of the mobile station side communication control part in embodiment of this invention. It is a flowchart which shows an example of the operation | movement at the time of reception of the fixed station side communication control part in embodiment of this invention.

  First, an outline of an embodiment of the present invention will be described. The present embodiment relates to a radio communication system in which a mobile terminal performs handover between base stations in a closed environment where structures and shielding objects exist. In such a wireless communication system, in general technology, the wireless communication path is not made redundant at the time of communication or at the time of handover. For this reason, the communication performance may be temporarily lowered due to a change in the communication status accompanying the movement of the mobile terminal.

  Therefore, in this embodiment, when performing wireless communication, a redundant configuration is adopted by always establishing a plurality of wireless communication paths of two or more. Specifically, at least one packet of the same content is received on each of the plurality of wireless communication paths, and a plurality of received same packets are received so as not to cause a contradiction caused by receiving a plurality of packets of the same content. Of those packets, unnecessary packets are discarded. Thereby, it is possible to perform wireless communication made redundant by a plurality of wireless communication paths without causing any contradiction.

  Moreover, it is conceivable that the call quality in the existing wireless communication path is deteriorated due to the movement of the mobile terminal. Therefore, in the present embodiment, when three or more wireless communication paths are established, the wireless communication path with the lowest communication quality is blocked. Then, while continuing communication on at least two wireless communication paths, a new wireless communication path with higher communication quality is searched.

  In this embodiment, in this way, by maintaining a state in which a wireless communication path with high communication quality is always redundant, seamless communication is possible through wireless communication, and reliability is improved.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram illustrating an example of an environment in which a wireless communication system 1 according to an embodiment of the present invention is installed.

  Referring to FIG. 1, a radio communication system 1 includes a host apparatus 100, a fixed station side control apparatus 200, a first base station 301, a second base station 302, a third base station 303, a fourth base station 304, and a mobile terminal 400. including.

  The mobile terminal 400 includes a mobile station side first communication unit 401, a mobile station side second communication unit 402, a mobile station side third communication unit 403, a mobile station side control device 410, and a lower order device 420.

  Here, the present embodiment is a system that performs communication between the upper device 100 and the lower device 420. The upper device 100 and the lower device 420 transmit and receive data by packet communication.

  The fixed station side control device 200 and the mobile station side control device 410 control the packet communication between the higher order device 100 and the lower order device 420.

  The first base station 301, the second base station 302, the third base station 303, and the fourth base station 304 are base stations that perform radio communication with the mobile terminal 400.

  The mobile station-side first communication unit 401, the mobile station-side second communication unit 402, the mobile station-side third communication unit 403, and the mobile station-side control device 410, which are radio devices in the mobile terminal 400, communicate with these base stations. Establish a wireless communication path between them.

  In summary, in the present embodiment, these devices are connected by wire or wirelessly as described below, thereby realizing a communication path between the upper device 100 and the lower device 420.

  First, the host device 100 and the fixed station side control device 200 are connected by either wired or wireless or a combination thereof. Further, the fixed station side control apparatus 200 and the first base station 301, the second base station 302, the third base station 303, and the fourth base station 304 are connected by wire.

  Further, the first base station 301, the second base station 302, the third base station 303, and the fourth base station 304 are the mobile station side first communication unit 401 and the mobile station side second communication unit 402 in the mobile terminal 400. And the mobile station side third communication unit 403 is wirelessly connected.

  In addition, the mobile station side first communication unit 401, the mobile station side second communication unit 402, and the mobile station side third communication unit 403 are wiredly connected to the mobile station side control device 410 in the mobile terminal 400. Further, the mobile station side control device 410 is connected to the lower level device 420 by wire in the mobile terminal 400.

  Next, the communication area of each base station and the movement range of the mobile terminal 400 will be described.

  In FIG. 1, an area that can communicate with the first base station 301 is represented as a first base station communication area 310. Similarly, an area that can communicate with the second base station 302 is represented as a second base station communication area 320. Further, an area that can communicate with the third base station 303 is represented as a third base station communication area 330. Further, an area that can communicate with the fourth base station 304 is represented as a fourth base station communication area 340.

  In FIG. 1, a range in which the mobile terminal 400 may move is represented as a terminal movement range 2.

  Each base station can perform wireless communication with the mobile terminal 400 located in its own communicable area. If the communicable areas of a plurality of base stations overlap, each of the plurality of base stations can perform radio communication with the mobile terminal 400 located in the overlapping area. Thus, when the communicable areas overlap, the degree is called the “overlap degree” of the base station. For example, if the communicable areas of two base stations overlap, the degree of overlap is 2.

  And it is necessary to make the duplication degree of a base station become more than predetermined number in all the points in the terminal movement range 2. FIG. In addition, in order to realize handover, it is necessary to increase the degree of duplication more than a predetermined number at at least some points in the terminal movement range 2.

  The predetermined number of overlaps is determined by the minimum number of wireless communication paths that should always be established during normal operation or handover. In this regard, as described above, in the present embodiment, the minimum number of wireless communication paths that should always be established is two.

  Therefore, in the present embodiment, the predetermined number of overlaps is 2. That is, the overlapping degree of the base stations is set to 2 at all points in the terminal movement range 2. Furthermore, in order to execute a handover, the degree of overlap needs to be 3 or more at least at some points in the terminal movement range 2. In order to satisfy these conditions, wherever the mobile terminal 400 moves within the terminal movement range 2, the mobile terminal 400 is in the communication area of at least two base stations, and the mobile terminal 400 is at least within the terminal movement range 2. When moving to some points, the base station is intentionally installed so that the mobile terminal 400 is located in the communication area of at least three base stations.

  Thus, the mobile terminal 400 can communicate with at least two base stations at any location within the terminal movement range 2 and can perform a handover when moving to at least some points within the terminal movement range 2. It becomes possible to carry out.

  Next, with reference to FIG. 2, each functional block included in the fixed station side control device 200 and the mobile station side control device 410 will be described in detail.

  The fixed station side control device 200 includes a fixed station side packet conversion unit 210, a fixed station side transmission unit 220, a fixed station side reception unit 230, and a fixed station side sequence number storage unit 240.

  The fixed station side packet conversion unit 210 receives a packet from the host device 100 via the fixed station side reception unit 230. Then, the fixed station side packet conversion unit 210 generates the same number of packets as the number of base stations as transmission destinations by duplicating the received packet. Further, the fixed station side packet conversion unit 210 assigns the same sequence number to each of the generated packets having the same contents as identification information for determining whether or not the contents of the packets are the same. Is transmitted to each base station one by one via the fixed station side transmission unit 220.

  Further, the fixed station side packet converting unit 210 deletes the sequence number included in the packet received from the base station via the fixed station side receiving unit 230. Then, the fixed station side packet conversion unit 210 transmits the packet from which the sequence number has been deleted to the higher-level device 100 via the fixed station side transmission unit 220. Here, the detailed contents of the sequence numbers in this embodiment will be described later.

  The fixed station side transmission unit 220 is a part that transmits packets to the host device 100 and each base station.

  The fixed station side receiving unit 230 is a part that receives packets from the host device 100 and each base station. In addition, when a plurality of packets having the same contents are received from each base station, the fixed station side receiving unit 230 sets only the first received packet as a packet to be transmitted to the higher-level device 100, and discards other unnecessary packets. To do.

  The fixed station side sequence number storage unit 240 is a part that stores a sequence number included in a packet received from each base station.

  On the other hand, the mobile station side control device 410 includes a base station selection unit 411, a mobile station side transmission unit 412, a mobile station side reception unit 413, a mobile station side packet conversion unit 414, and a mobile station side sequence number storage unit 415. The mobile station side control device 410 has substantially the same configuration as the fixed station side control device 200 except that it includes a base station selection unit 411.

  The base station selection unit 411 is a part that selects a wireless communication path used for packet transmission / reception. The mobile station side first communication unit 401, the mobile station side second communication unit 402, and the mobile station side third communication unit 403 perform communication using the wireless communication path selected by the base station selection unit 411. Packets received by the mobile station side first communication unit 401, the mobile station side second communication unit 402, and the mobile station side third communication unit 403 are transmitted to the mobile station side reception unit 413. The packet transmitted by the mobile station side transmission unit 412 is transmitted to each base station via the first communication unit 401, the mobile station side second communication unit 402, and the mobile station side third communication unit 403.

  The mobile station side transmission unit 412 is a part that transmits a packet to the lower order apparatus 420. The mobile station side transmission unit 412 is a part that transmits packets to each base station via each mobile station side communication unit.

  The mobile station side receiving unit 413 is a part that receives a packet from the lower level device 420. The mobile station side receiving unit 413 is a part that receives packets from each base station via each mobile station side communication unit. In addition, when a plurality of packets having the same contents are received from each base station, the mobile station side receiving unit 413 sets only the first received packet as a packet to be transmitted to the lower level device 420 and discards other unnecessary packets. To do.

  The mobile station side packet conversion unit 414 generates the same number of packets as the number of base stations as transmission destinations by duplicating the packet received from the lower-level device 420 via the mobile station side reception unit 413. Then, the mobile station side packet conversion unit 414 assigns the same sequence number to each of the generated packets having the same contents as identification information for determining whether or not the contents of the packets are the same. Further, the mobile station side packet converting unit 414 transmits one packet to which this sequence number is assigned to each base station via the mobile station side transmitting unit 412 one by one.

  Further, the mobile station side packet conversion unit 414 deletes the sequence number included in the packet received from each mobile station side communication unit via the mobile station side reception unit 413. Then, the mobile station side packet converting unit 414 transmits the packet from which the sequence number has been deleted to the lower order apparatus 420 via the mobile station side transmitting unit 412.

  The mobile station side sequence number storage unit 415 is a part that stores a sequence number included in a packet received from each base station.

  Next, the sequence numbers in this embodiment will be described in detail.

  In the present embodiment, each base station and each mobile station side communication unit establishes a plurality of radio communication paths using different radio channels for each combination of the base station and the mobile station side communication unit.

  Then, the fixed station side control device 200 and the mobile station side control device 410 perform communication using the plurality of redundant wireless communication paths. Specifically, each of the fixed station side control apparatus 200 and the mobile station side control apparatus 410 generates a plurality of identical content packets by duplicating a packet transmitted by itself. The plurality of packets are transmitted one by one in each wireless communication path. Thus, communication using each of the plurality of wireless communication paths is performed.

  In this way, the transmitting side transmits a plurality of packets having the same content. However, on the receiving side, even if a plurality of packets having the same content are received, it is not necessary to transfer all of the packets to the upper apparatus 100 and the lower apparatus 420, and even one of the packets is not higher than the upper apparatus 100 or the lower apparatus 420. It only has to be transferred to. Therefore, the receiving side transfers only the first received packet among the plurality of packets having the same content received through the plurality of wireless communication paths to the upper device 100 or the lower device 420, and the same content received thereafter. Is discarded.

  In order to perform such processing, it is necessary to specify which packet and which packet of the received many packets have the same contents. Therefore, in this embodiment, in order to specify the same content packet, the same sequence number is included in each of the same content packets transmitted by the transmission side. Then, the receiving side checks whether this sequence number is the same as the sequence number of the packet received in the past. If the sequence number is the same, the packet may have the same contents as the packet received in the past. I understand. Since it is not necessary to receive a packet having the same content as a packet received in the past, the received packet is discarded. On the other hand, if the sequence numbers are different, the received packet is transferred to the lower level device 420 because the packet is different in content from the previously received packet.

  Next, a specific configuration of a packet including a sequence number will be described with reference to FIG. As shown in FIG. 3, the packet is roughly divided into a header portion and a payload portion.

  The header portion stores information that conforms to the protocol used for communication. For example, information such as the version of the protocol used for communication, header length, and packet length, and information such as a source address and a destination address are stored.

  On the other hand, the payload portion includes the body of data to be transmitted / received. In this embodiment, 16 bits are added to the beginning of the payload as an area for including a sequence number. In this area, the sequence number “1” is first stored and then a packet is transmitted. Thereafter, each time a packet having a new content is transmitted, the value of the stored sequence number is incremented by one. In the process, if the value of the sequence number is a small value less than 65,536 which is the maximum value that can be represented by 16 bits, the sequence number value is continuously incremented by one. If the sequence number becomes 65,536 or more as a result of continuing to increase the value of the sequence number, the value of the sequence number is reset to 1. Then, every time a packet with new contents is transmitted, the sequence number value to be stored is incremented by one until the sequence number reaches 65,536 or more again.

  By doing so, the same sequence number is assigned to packets having the same contents, and different sequence numbers are assigned to packets having different contents. Therefore, on the receiving side, as long as this sequence number stored in a predetermined position in the packet is referred to, which packet and which packet has the same content among the many received packets. You can see if there is.

  Next, the specific contents of the operation of the present invention will be described with reference to the flowcharts of FIGS.

  First, with reference to FIG. 4, the operation when the fixed station side control apparatus 200 transmits a packet received from the higher order apparatus 100 to each base station will be described. Such a packet is a packet having the higher-level device 100 as a transmission source and the lower-level device 420 as a destination.

  First, the fixed station side control apparatus 200 sets “N”, which is the value of the sequence number assigned to the packet to be transmitted, to “1” (step S11). Note that N is a positive integer.

  Next, the fixed station side control apparatus 200 stands by until a packet destined for the lower apparatus 420 is received from the upper apparatus 100 (No in step S12).

  When the fixed station side control apparatus 200 receives a packet destined for the lower apparatus 420 from the upper apparatus 100 (Yes in step S12), the fixed station side control apparatus 200 stores the sequence number in the head part of the payload of the received packet. An area for bits is assigned, and the value of N is stored in this area. Furthermore, the fixed station side control apparatus 200 duplicates the packet to which this sequence number is assigned by the number of base stations that are the transmission destinations.

  After that, the fixed station side control apparatus 200 transmits the duplicated packets to the first base station 301, the second base station 302, the third base station 303, and the fourth base station 304 one by one (step S14). .

  Next, the fixed station side control apparatus 200 increases the sequence number by 1 by adding “1” to N which is the value of the sequence number (step S15). Next, the fixed station side control apparatus 200 confirms whether or not N, which is the sequence number value after addition, is greater than or equal to 65,536, which is the maximum value that can be represented by 16 bits (step S16). ).

  If the value N of the sequence number is less than 65,536 (No in step S16), the process from step S12 is performed again while keeping the value of the sequence number increased by one in step S15. On the other hand, if the value N that is the number of sequence numbers is 65,536 or more (Yes in step S16), the process returns to step S11, the sequence number value N is reset to 1, and then step S12 is performed again. Process from.

  As a result, one packet having the same content with the same sequence number is transmitted to each base station.

  Next, the operation on the mobile terminal 400 side will be described with reference to FIG.

  The mobile terminal 400 needs to establish a wireless communication path in advance before the communication between the upper device 100 and the lower device 420 is started.

  For this purpose, first, each mobile station side communication unit (the mobile station side first communication unit 401, the mobile station side second communication unit 402, and the mobile station side third communication unit 403) establishes a base station for establishing a wireless communication path. The station is searched (No in step S21 and step S22). Here, the base station search in the present embodiment may use a general technique well known to those skilled in the art.

  Then, one of the mobile station side communication units (any one of the mobile station side first communication unit 401, the mobile station side second communication unit 402, and the mobile station side third communication unit 403) becomes a base station ( 1st base station 301, 2nd base station 302, 3rd base station 303, and 4th base station 304) are discovered, and a radio | wireless communication path is established between discovered base stations (in step S22 Yes) ). As a result, the first wireless communication path is established.

  Further, the mobile station side radio communication unit other than the mobile station side radio communication unit that established the radio communication path in step S22 continues to search for the base station (No in step S23 and step S24).

  Then, the mobile station side radio communication unit other than the mobile station side radio communication unit that established the radio communication path in step S22 discovers the base station and establishes the radio communication path with the found base station (step S22). Yes in S24). As a result, the second wireless communication path is established.

  When two wireless communication paths are established in this way, the fixed station side control device 200 and the mobile terminal 400 are transmitted and received between the upper apparatus 100 and the lower apparatus 420 via the two established wireless communication paths. Relay the packet.

  As a result, redundant communication between the higher-level device 100 and the lower-level device 420 through a plurality of wireless communication paths is possible.

  Next, base station selection control performed by the base station selection unit 411 will be described with reference to FIG. When three or more wireless communication paths are established, the base station selection unit 411 continues communication using two wireless communication paths with high communication quality, and communication with other wireless communication paths with low communication quality is performed. Cut off. In the following description, electric field strength is used as a measure representing communication quality. However, this is only an example, and other measures such as an S / N ratio may be used as a measure representing communication quality.

  As a premise, it is assumed that the processing described with reference to FIG. 5 is performed, and that two wireless communication paths are currently established between the mobile terminal 400 and two base stations.

  Here, since the mobile terminal 400 includes three mobile station side communication units, a wireless communication path other than the mobile station side wireless communication unit that has established the wireless communication path in steps S22 and S24 is still established. There is one mobile station side communication unit that is not. In the following description, a mobile station side communication unit that has not yet established a wireless communication path is referred to as an “empty mobile station side communication unit”. In addition, the mobile station side wireless communication unit that has established the wireless communication path in step S22 is referred to as a “first communicating mobile station side communication unit”. Further, the mobile station side wireless communication unit that has established the wireless communication path in step S24 is referred to as a “second communication mobile station side communication unit”.

  Referring to FIG. 6, first, the vacant mobile station side communication unit searches for a base station (No in step S31 and step S32).

  Then, when the empty mobile station side communication unit finds a new base station that has not established a wireless communication path with any of the first communicating mobile station side communication unit and the second communicating mobile station side communication unit (step S32). Yes), the vacant mobile station side communication unit measures the electric field strength of the discovered base station. The first communicating mobile station side communication unit also measures the electric field strength of the first communicating base station, which is the base station with which it is communicating. Furthermore, the mobile station side communication unit in the second communication also measures the electric field strength of the second base station in communication which is the base station with which it is communicating. Then, the base station selection unit 411 compares these measured electric field strengths.

  Specifically, the base station selection unit 411 first compares the electric field strength of the base station discovered by the empty mobile station side communication unit with the electric field strength of the first communicating base station (step S33).

  As a result of the comparison in step S33, when the electric field strength of the base station discovered by the vacant mobile station side communication unit is weaker than the electric field strength of the first communicating base station (No in step S33), the process proceeds to step S41. Then, the base station selection unit 411 compares the electric field strength of the base station discovered by the vacant mobile station side communication unit with the electric field strength of the second communicating base station (step S41).

  As a result of the comparison in step S33, when the electric field strength of the base station discovered by the free mobile station side communication unit is weaker than the electric field strength of the second communicating base station (No in step S41), the free mobile station side communication The electric field strength of the base station discovered by the unit is weaker than the electric field strength of each communicating base station. Therefore, the base station discovered by the free mobile station side communication unit is not selected as the handover destination, and the free mobile station side communication unit searches for a new base station again (step S31).

  On the other hand, as a result of the comparison in step S33, when the electric field strength of the base station discovered by the vacant mobile station side communication unit is higher than the electric field strength of the first communicating base station (Yes in step S33), the process goes to step S34. move on. Then, the base station selection unit 411 compares the electric field strength of the first communicating base station with the electric field strength of the second communicating base station (step S41).

  Here, when the electric field strength of the second communicating base station is stronger than the electric field strength of the first communicating base station (No in step S34), the base station discovered by the vacant mobile station side communication unit, the first communication The field strength of the first communicating base station is the weakest among the three base stations of the middle base station and the second communicating base station. Therefore, the wireless communication path with the first communicating base station is blocked.

  For this purpose, first, the vacant mobile station side communication unit establishes a new wireless communication path with the base station discovered by itself. Then, in addition to the existing two wireless communication paths, redundant communication is performed through a total of three wireless communication paths, thereby relaying packets transmitted and received by the upper apparatus 100 and the lower apparatus 420 (step S39). In this way, while establishing a new wireless communication path, the communication is continued while the two existing wireless communication paths remain connected, thereby blocking the wireless communication path while maintaining communication quality in wireless communication. Wireless communication can be continued.

  Thereafter, the wireless communication path with the first communicating base station having the weakest electric field strength is blocked (step S40). Then, the base station of the wireless communication path newly established in step S39 is set as the new first communicating base station, and the wireless communication path is established with the first communicating base station, but the wireless communication path is blocked in step S40. The mobile station side radio communication unit thus made is set as a new empty mobile station side communication unit, and the process of step S31 is performed again.

  That is, the new vacant mobile station side communication unit starts searching for a new base station (step S31).

  As a result of the comparison in step S34, when the electric field strength of the first communicating base station is stronger than the electric field strength of the second communicating base station (Yes in step S34), the detected base station as a result of the comparison in step S41. If the field strength of the station is stronger than the field strength of the second communicating base station (Yes in step S41), the base station discovered by the vacant mobile station side communication unit, the first communicating base station, and the second Of the three base stations in communication, the electric field strength of the second base station in communication is the weakest. Therefore, the wireless communication path with the second communicating base station is blocked.

  For this purpose, first, the vacant mobile station side communication unit establishes a new wireless communication path with the base station discovered by itself. Then, in addition to the existing two wireless communication paths, redundant communication is performed through a total of three wireless communication paths, thereby relaying packets transmitted and received by the upper apparatus 100 and the lower apparatus 420 (step S36 or step S43). ). In this way, while establishing a new wireless communication path, the communication is continued while the two existing wireless communication paths remain connected, thereby blocking the wireless communication path while maintaining communication quality in wireless communication. Wireless communication can be continued.

  Thereafter, the wireless communication path with the second communicating base station having the weakest electric field strength is blocked (step S37 or step S44). Then, the base station of the wireless communication path newly established in step S36 or step S43 is set as a new second communicating base station, and the wireless communication path is established with the second communicating base station, but step S37 or step S44 is established. In step S31, the mobile station side wireless communication unit whose wireless communication path has been blocked is changed to a new empty mobile station side communication unit.

  That is, the new vacant mobile station side communication unit starts searching for a new base station (step S31).

  As described above, in the present embodiment, a period during which handover is performed in steps S35 to 37, steps S38 to 40, and steps S42 to S44 while a free mobile station side communication unit searches for a base station. Even during the handover period, communication using at least two wireless communication paths is always continued. Therefore, in this embodiment, there is an effect that redundant wireless communication using a plurality of wireless communication paths can always be performed.

  This point will be described with reference to FIG. FIG. 7 is a timing chart showing the transition of the establishment state of the wireless communication path between the mobile terminal 400 and each base station.

  First, at time T1 in the figure, one of the mobile station side communication units establishes a wireless communication path with the first base station 301 (corresponding to the processing of Yes in step S21 and step S22 in FIG. 5).

  Subsequently, at time T2 in the figure, one of the mobile station side communication units establishes a wireless communication path with the second base station 302 (corresponding to the processing of Yes in step S23 and step S24 in FIG. 5).

  Thereby, after the time point T2, communication via the two wireless communication paths is performed between each base station and each mobile station side communication unit.

  Thereafter, it is assumed that the user of the terminal 400 moves from the left side to the right side of the mobile terminal range 2 shown in FIG. As a result, the terminal 400 is located in the third base station communication area 330.

  Accordingly, the mobile station side communication unit that has not yet established the wireless communication path finds the third base station 303 by searching (corresponding to the processing of Yes in step S31 and step S32 in FIG. 6). When the three wireless communication paths are established in this way, the base station selection unit 411 compares the electric field strengths of the base stations in these three wireless communication paths (corresponding to the processing in step S33, step S34, and step S41 in FIG. 6). ). This time, it is assumed that the electric field strength of the first base station 301 is the weakest (corresponding to Yes in step S33 and No in step S34 in FIG. 6).

  Then, at time T3, the mobile station side communication unit that has found the third base station 303 establishes a wireless communication path with the third base station 303 (corresponding to the process of step S38 in FIG. 6). As a result, three wireless communication paths are established (corresponding to the process of step S39 in FIG. 6).

  Next, at time T4, the wireless communication path with the first base station 301 is blocked (corresponding to the process of step S40 in FIG. 6).

  Next, the mobile station side communication unit that has established the wireless communication path with the first base station 301 finds the fourth base station 304 by searching (corresponding to the processing of Yes in step S31 and step S32 in FIG. 6). . When the three wireless communication paths are established in this way, the base station selection unit 411 compares the electric field strengths of the base stations in these three wireless communication paths (corresponding to the processing in step S33, step S34, and step S41 in FIG. 6). ). This time, it is assumed that the electric field strength of the second base station 302 is the weakest (corresponding to Yes in step S33 in FIG. 6 and Yes in step S34).

  Then, at time T5, the mobile station side communication unit that has found the third base station 303 establishes a wireless communication path with the fourth base station 304 (corresponding to the process of step S35 in FIG. 6). Thereby, three wireless communication paths are established (corresponding to the process of step S36 in FIG. 6).

  Next, at time T6, the wireless communication path with the first base station 301 is blocked (corresponding to the process of step S37 in FIG. 6).

  In this way, in the present embodiment, communication using at least two wireless communication paths is always continued while the vacant mobile station side communication unit searches for a base station and also includes a handover period. Therefore, in this embodiment, there is an effect that redundant wireless communication using a plurality of wireless communication paths can always be performed.

  Note that the present embodiment may be modified so that communication using at least three wireless communication paths is always continued. In this case, the handover may be performed when four wireless communication paths are established.

  Further, the number of wireless communication paths may be increased more than three, and the communication by the number of wireless communication paths larger than at least four may be continuously maintained.

  Next, with reference to FIG. 8, the operation when the mobile station side control apparatus 410 receives a packet transmitted from each base station will be described. Such a packet is a packet having the higher-level device 100 as a transmission source and the lower-level device 420 as a destination.

  The mobile station side receiving unit 413 in the mobile station side control device 410 stands by until a packet transmitted from the base station is received via any mobile station side communication unit (No in step S51).

  Then, when the mobile station side receiving unit 413 receives the packet transmitted from the base station via any mobile station side communication unit (Yes in step S51), the sequence number included in the received packet is: It is confirmed whether or not it matches the sequence number stored in the mobile station side sequence number storage unit 415 (step S52). Here, the sequence number stored in the mobile station side sequence number storage unit 415 is the sequence number of a packet received in the past. Since packets with the same sequence number have the same contents, it is not necessary to receive any more packets with the same sequence number as the sequence numbers of already received packets. Therefore, the confirmation of step S52 is performed, and if the sequence number of the received packet matches the stored sequence number (Yes in step S52), the received packet is discarded. Then, the process is performed again from step S51.

  On the other hand, if the sequence numbers do not match (No in step S52), it means that a packet having the same sequence number as the received packet has not been received, and the received packet needs to be transmitted to the lower level device 420. Further, the sequence number of the received packet needs to be stored in the mobile station side sequence number storage unit 415.

  Therefore, the mobile station side reception unit 413 first stores the sequence number of the received packet in the mobile station side sequence number storage unit 415 (step S53).

  Next, the mobile station side reception unit 413 sets a timer to the sequence number stored in the mobile station side sequence number storage unit 415 (step S54). The reason for setting the timer and the detailed contents of the timer will be described later with reference to FIG.

  The mobile station side receiving unit 413 deletes the sequence number in the received packet. In this regard, as described with reference to FIG. 3, in this embodiment, the sequence number is stored in the first 16 bits of the payload portion of the packet. Therefore, the mobile station side receiving unit 413 deletes the first 16 bits of the payload portion of this packet. The reason why the sequence number is deleted is that the sequence number is used for control in the fixed station side control device 200 and the mobile terminal 400, and is a higher-level device 100 or a lower-level device 420 that is a packet transmission source or destination. Because it is irrelevant information.

  The packet from which the sequence number has been deleted is transmitted to the lower order apparatus 420 via the mobile station side transmission unit 412 (step S56). Thereafter, the process returns to step S51, and when a new packet is received (Yes in step S51), the processes after step S52 are repeated.

  The packet transmitted from the higher-level device 100 is received by the lower-level device 420 in the operation described with reference to FIGS. That is, communication between the higher-level device 100 and the lower-level device 420 can be realized. Further, such communication can be performed by redundant communication through a plurality of wireless communication paths.

  Further, in the operation described with reference to FIG. 8, unnecessary packets among a plurality of received identical packets are discarded so as not to cause a contradiction caused by receiving a plurality of packets having the same contents. . Thereby, it is possible to perform wireless communication made redundant by a plurality of wireless communication paths without causing any contradiction.

  In the present embodiment, when three or more wireless communication paths are established by the operation described with reference to FIG. 6, the wireless communication path having the weakest electric field strength is blocked. Thus, by maintaining a state where the wireless communication path having a strong electric field strength is always redundant, it is possible to perform seamless communication by wireless communication and improve reliability.

  Next, the timer in this embodiment will be described. As described in the description of step S53 and step S54 described above, the timer is set for the sequence number stored in the mobile station side sequence number storage unit 415.

  Here, the reason for setting the timer in this embodiment will be described.

  In this embodiment, the sequence number is expressed by 16 bits. Therefore, the sequence numbers used in this embodiment are “1” to “65,535”. Considering this, as described in the description of step S16, when the sequence number is “65,535” or more, the sequence number is reset and the sequence number is counted again from “1”.

  In this way, for example, the sequence number of the first received packet is “1”, and the sequence number of the 65th, 536th received packet is also “1”. Therefore, these two packets cannot be distinguished by the sequence number.

  However, these two packets are different contents. Therefore, even if the sequence number is the same “1”, it is necessary to distinguish these two packets and perform reception without discarding not only the first received packet but also the 65th and 536th packets. is there.

  Therefore, in this embodiment, the sequence number of the received packet is stored in the mobile station side sequence number storage unit 415 as the sequence number of the received packet, but a timer is set to the stored sequence number (step S53 and step S53). S54). Then, when the timer has elapsed, the stored sequence number is deleted from the mobile station side sequence number storage unit 415. As a result, the packet with the deleted sequence number is not yet received.

  In this way, for example, the sequence number “1” of the first received packet is deleted, and the packet with the sequence number “1” is not yet received. Therefore, the 65th and 536th packets with the sequence number “1” are determined not to be received, and are received without being discarded (No in step S52).

  In the present embodiment, the 65th and 536th and subsequent packets can be received by managing the sequence numbers in this way.

  Next, with reference to FIG. 9, the management of sequence numbers based on a timer in the mobile station sequence number storage unit 415 of the present embodiment will be described.

  Referring to FIG. 9, first, the mobile station side sequence number storage unit 415 checks whether or not a new sequence number is stored in itself (step S61), and waits until a new sequence number is stored (step S61). No).

  If a new sequence number is stored (Yes in step S61, step S53), the process proceeds to step S62. In step S62, it is confirmed whether or not a timer has been set to the newly stored sequence number (step S62), and waits until the timer is set (No in step S62).

  If the timer is set at the newly stored sequence number (Yes in step S62, step S54), the process proceeds to step S63. Note that the length of the timer set in the present embodiment varies depending on the environment and system state in which the present embodiment is constructed. Therefore, it is preferable to set a timer of an arbitrary length in consideration of these. For example, if the number of bits used to store the sequence number is larger than 16 bits, the total number of available sequence numbers increases. Therefore, in this case, the timer time may be increased. For example, when the communication speed in the communication according to the present embodiment is high, many packets are transmitted and received in a short time, and the sequence number is consumed quickly. Therefore, in this case, it is preferable to shorten the timer time.

In step S63, it is confirmed whether or not the timer set in step S62 has elapsed (step S63).
As a result of the confirmation, if the timer has not elapsed (No in step S64), the confirmation of the timer is repeated again (No in step S63 and step S64).

  On the other hand, if the timer has elapsed as a result of the confirmation (Yes in step S64), the process proceeds to step S65. Then, the sequence number for which the set timer has elapsed is deleted. Then, the process returns to step S61 again and waits until the sequence number deleted in step S65 is newly saved (step S61). If a new sequence number is stored (Yes in step S61, step S53), the processes after step S62 are executed again.

  In the present embodiment, by performing such processing for all sequence numbers, it is possible to receive the 65th and 536th and subsequent packets.

  Next, with reference to FIG. 10 and FIG. 11, an operation when the upper device 100 receives a packet transmitted from the lower device 420 will be described.

  When the lower device 420 receives a packet from the higher device 100 through the above-described operation, the lower device 420 transmits a packet to the higher device 100 to the mobile station side control device 410 as a response. Further, the lower order device 420 transmits a packet to the higher order device 100 to the mobile station side control device 410 not only in response but also spontaneously.

  Such a packet is a packet having the lower device 420 as a transmission source and the higher device 100 as a destination. Note that it is assumed that the mobile terminal 400 has established a plurality of wireless communication paths with a plurality of base stations by the processing described with reference to FIG. 5 and FIG. 6 as a premise.

  Further, as described with reference to FIG. 9, the mobile terminal 400 manages the sequence numbers stored in the mobile station side sequence number storage unit 415 based on the timer. Also, it is assumed that the sequence number stored in the fixed station side sequence number storage unit 240 is managed by the same management method.

  First, with reference to FIG. 10, the operation | movement at the time of the transmission by the mobile terminal 400 is demonstrated. The mobile terminal 400 sets “M”, which is the value of the sequence number assigned to the packet to be transmitted, to “1” (step S71). Note that M is a positive integer.

  Next, the mobile terminal 400 waits until a packet destined for the higher-level device 100 is received from the lower-level device 420 (No in step S72).

  When the mobile terminal 400 receives a packet destined for the higher-level device 100 from the lower-level device 420 (Yes in step S72), the mobile terminal 400 has 16 bits for storing the sequence number at the beginning of the payload of the received packet. An area is assigned and the value of M is stored in this area. Further, the mobile terminal 400 duplicates the packet with this sequence number by the number of wireless communication paths used for transmission. It should be noted that the processing such as the assignment of the payload number is performed in the same manner as the processing such as the assignment of the payload number by the fixed station side control device 200 described with reference to FIG.

  Thereafter, the mobile terminal 400 transmits the duplicated packets one by one to the base station that has established the wireless communication path via the wireless communication unit that has established the wireless communication path (step S74). .

  Next, the mobile terminal 400 increments the sequence number by one by adding “1” to M, which is the value of the sequence number (step S75). Next, the mobile terminal 400 checks whether or not M, which is the sequence number value after addition, is equal to or greater than 65,536, which is the maximum value that can be represented by 16 bits (step S76).

  If the sequence number value M is less than 65,536 (No in step S76), the sequence number value is increased by one in step S75 and the processing from step S72 is performed again. On the other hand, if the value M that is the number of sequence numbers is 65,536 or more (Yes in step S76), the process returns to step S71, the sequence number value M is reset to 1, and then step S72 is performed again. Process from.

  As a result, one packet with the same content assigned the same sequence number is sent to each base station that has established a wireless communication path via the wireless communication unit that has established the wireless communication path. Sent.

  Next, with reference to FIG. 11, the operation at the time of reception by the fixed station side control apparatus 200 will be described.

  First, the fixed station side receiving unit 230 waits until it receives a packet from the lower apparatus 420 in the mobile terminal 400 via any base station (No in step S81). When any of the base stations receives a packet from the lower level device 420 in the mobile terminal 400, the base station transmits the received packet to the fixed station side receiving unit 230 in the fixed station side control device 200.

  Then, when the fixed station side receiving unit 230 receives the packet from the lower apparatus 420 in the mobile terminal 400 via any of the base stations (Yes in Step S81), the sequence number included in the received packet is Then, it is confirmed whether or not it matches the sequence number stored in the fixed station side sequence number storage unit 240 (step S82). Here, the sequence number stored in the fixed station side sequence number storage unit 240 is a sequence number of a packet received in the past. Since packets with the same sequence number have the same contents, it is not necessary to receive any more packets with the same sequence number as the sequence numbers of already received packets. Therefore, confirmation in step S82 is performed. If the sequence number of the received packet matches the stored sequence number (Yes in step S82), the received packet is discarded. Then, the process is performed again from step S81.

  On the other hand, if the sequence numbers do not match (No in step S82), it means that a packet having the same sequence number as the received packet has not been received, and it is necessary to transmit the received packet to the host device 100. Further, it is necessary to store the sequence number of the received packet in the fixed station side sequence number storage unit 240.

  Therefore, the fixed station side receiving unit 230 first stores the sequence number of the received packet in the fixed station side sequence number storing unit 240 (step S83).

  Next, the fixed station side receiving unit 230 sets a timer to the sequence number stored in the fixed station side sequence number storing unit 240 (step S84). The reason for setting the timer and the detailed contents of the timer are as described above with reference to FIG.

  The fixed station side receiving unit 230 deletes the sequence number in the received packet. In this regard, as described with reference to FIG. 3, in this embodiment, the sequence number is stored in the first 16 bits of the payload portion of the packet. Therefore, the fixed station side receiving unit 230 deletes the first 16 bits of the payload portion of this packet. The reason why the sequence number is deleted is that the sequence number is used for control in the fixed station side control device 200 and the mobile terminal 400, and is a higher-level device 100 or a lower-level device 420 that is a packet transmission source or destination. Because it is irrelevant information.

  The packet from which the sequence number has been deleted is transmitted to the higher-level device 100 via the fixed station side transmission unit 220 (step S86). Thereafter, the process returns to step S81, and when a new packet is received (Yes in step S81), the processes after step S82 are repeated.

  With the operation described above with reference to FIGS. 10 and 11, the packet transmitted from the lower apparatus 420 is received by the upper apparatus 100. That is, communication between the higher-level device 100 and the lower-level device 420 can be realized. Further, such communication can be performed by redundant communication through a plurality of wireless communication paths.

  Further, in the operation described with reference to FIG. 11, unnecessary packets among a plurality of received identical packets are discarded so as not to cause a contradiction caused by receiving a plurality of packets having the same contents. . Thereby, it is possible to perform wireless communication made redundant by a plurality of wireless communication paths without causing any contradiction.

  In the present embodiment, when three or more wireless communication paths are established by the operation described with reference to FIG. 6, the wireless communication path having the weakest electric field strength is blocked. Thus, by maintaining a state where the wireless communication path having a strong electric field strength is always redundant, it is possible to perform seamless communication by wireless communication and improve reliability.

  Note that each of the host device, the fixed station side control device, each base station, and the mobile terminal can be realized by hardware, software, or a combination thereof. In addition, the wireless communication method performed in cooperation by the host device, the fixed station side control device, each base station, and the mobile terminal can also be realized by hardware, software, or a combination thereof. Here, “realized by software” means realized by a computer reading and executing a program.

  The program may be stored using various types of non-transitory computer readable media and supplied to the computer. Non-transitory computer readable media include various types of tangible storage media. Examples of non-transitory computer readable media include magnetic recording media (for example, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (for example, magneto-optical disks), CD-ROMs (Read Only Memory), CD- R, CD-R / W, and semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (random access memory)).

  Moreover, although the above-described embodiment is a preferred embodiment of the present invention, the scope of the present invention is not limited only to the above-described embodiment, and various modifications are made without departing from the gist of the present invention. Implementation in the form is possible.

  For example, the number of base stations, the number of mobile station side communication units, and the number of mobile terminals 400 included in this embodiment are not limited to the numbers included in the above embodiment.

  The upper device 100 and the lower device 420 may be devices that use the communication environment provided by the present embodiment, and the upper device 100 and the lower device 420 are specifically limited to specific devices. There is no. In addition, there is no particular limitation on the specific contents of data transmitted and received between the higher-level device 100 and the lower-level device 420.

  A part or all of the above-described embodiment can be described as in the following supplementary notes, but is not limited thereto.

(Supplementary Note 1) A plurality of communication units each establishing a wireless communication path with a separate base station and performing communication with a communication destination device via the established wireless communication path;
In the handover period, any one of the communication means switches the base station that establishes the wireless communication path with the own communication means. n is an integer equal to or greater than 2) control means for causing other communication means to continue communication with the communication destination device;
A communication redundancy apparatus comprising:

(Supplementary Note 2) When n + 1 or more communication means establish a wireless communication path, the control means instructs one of the communication means to switch the base station that establishes the wireless communication path with the own communication means. ,
The communication redundancy according to appendix 1, wherein the communication unit that has received the instruction performs switching of a base station that establishes a wireless communication path with the communication unit upon receiving the instruction. Device.

  (Supplementary note 3) The control means selects a communication means based on the communication quality between each communication means and each base station, and instructs the selected communication means to perform the switching. The communication redundancy apparatus according to appendix 2.

(Additional remark 4) The said communication means transmits in each of these wireless communication path | routes in the said communication destination apparatus, Each receives the packet of the same content,
Any one of appendices 1 to 3, wherein the control means uses any one of the plurality of packets having the same contents received by the communication means, while discarding other packets. The communication redundancy apparatus according to 1.

  (Supplementary note 5) The communication redundancy apparatus according to supplementary note 4, wherein the use of any one of the received packets is to transfer any of the received packets to a transfer destination device.

(Additional remark 6) The packet received from the said communication destination apparatus contains the information used in order that the said control part discards an unnecessary packet,
The control means deletes information used for discarding the unnecessary packet included in a packet transferred to the transfer destination device, and transfers the packet after deleting the information to the transfer destination device. The communication redundancy apparatus according to appendix 5.

  (Supplementary note 7) The communication redundancy apparatus according to any one of supplementary notes 1 to 6, wherein a degree of overlap of the plurality of base stations is m (m is an integer of 2 or more).

(Supplementary note 8) A communication redundancy system including the communication redundancy device according to supplementary note 7, the base station, and the communication destination device,
The base station is installed so that the overlapping degree of the plurality of base stations is m,
The communication destination device is connected to the plurality of base stations;
The communication redundancy system, wherein the communication destination device and the communication redundancy device perform communication via the plurality of base stations and the plurality of wireless communication paths.

(Supplementary note 9) A plurality of communication units, each of which establishes a separate wireless communication path with a separate base station, communicates with a communication destination device via the established wireless communication path Steps,
In the handover period, any one of the communication means switches the base station that establishes the wireless communication path with the own communication means. a control step in which n is an integer greater than or equal to 2) other communication means continues communication with the communication destination device;
The communication redundancy method characterized by performing.

(Supplementary Note 10) A communication redundancy program,
Computer
A plurality of communication means each establishing a wireless communication path with a separate base station and performing communication with a communication destination device via the established wireless communication path;
In the handover period, any one of the communication means switches the base station that establishes the wireless communication path with the own communication means. n is an integer equal to or greater than 2) control means for causing other communication means to continue communication with the communication destination device;
A communication redundancy program that functions as a communication redundancy device.

  (Additional remark 11) It is a system which always enables communication through two or more wireless communication paths, and communicates with the mobile communication terminal with any of the first, second, third and fourth base stations. And a second wireless communication unit and a third wireless communication unit, and the first wireless communication unit, the second wireless communication unit, and the third wireless communication unit of the mobile communication terminal simultaneously receive and process the same packet. Means is provided.

  (Supplementary Note 12) At the time of handover of a base station, a wireless communication unit that has not established a wireless communication path finds a base station with strong electric field strength, establishes a third wireless communication path, and After the wireless communication unit and the third wireless communication unit simultaneously receive and process the same packet, the wireless communication path with weak electric field strength is blocked. Accordingly, the wireless communication unit that has not established a wireless communication path is characterized by communication means for searching for a new base station having a strong electric field strength.

  INDUSTRIAL APPLICABILITY The present invention can be applied when seamlessly switching connected base stations in a network configuration that requires a communication terminal including a wireless terminal, and is particularly high in which communication between base stations is frequently performed and communication disconnection is not allowed. It is suitable in situations where a quality wireless communication system is required.

DESCRIPTION OF SYMBOLS 1 Radio | wireless communications system 100 Host apparatus 200 Fixed station side control apparatus 210 Fixed station side packet conversion part 220 Fixed station side transmission part 230 Fixed station side receiving part 240 Fixed station side sequence number preservation | save part 301 1st base station 302 2nd base station 303 Third base station 304 Fourth base station 310 First base station communication area 320 Second base station communication area 330 Third base station communication area 340 Fourth base station communication area 400 Mobile terminal 401 First communication unit 402 Second communication Unit 403 third communication unit 410 mobile station side control device 411 base station selection unit 412 mobile station side transmission unit 413 mobile station side reception unit 414 mobile station side packet conversion unit 415 mobile station side sequence number storage unit 420 subordinate device

Claims (10)

A plurality of communication means each establishing a wireless communication path with a separate base station and performing communication with a communication destination device via the established wireless communication path;
In the handover period, any one of the communication means switches the base station that establishes the wireless communication path with the own communication means. n is an integer equal to or greater than 2) control means for causing other communication means to continue communication with the communication destination device;
A communication redundancy apparatus comprising: The control means, when n + 1 or more communication means establishes a wireless communication path, instructs one of the communication means to switch a base station that establishes a wireless communication path with the own communication means,
2. The communication according to claim 1, wherein the communication unit that receives the instruction performs switching of a base station that establishes a wireless communication path with the communication unit when the instruction is received. 3. Redundant device.   The control unit selects a communication unit based on communication quality between each communication unit and each base station, and instructs the selected communication unit to perform the switching. The communication redundancy device described in 1. The communication means transmits the packet of the same content, each of the communication destination devices transmitting in each of the plurality of wireless communication paths,
4. The control unit according to claim 1, wherein the control unit uses any one of the plurality of packets having the same contents received by the communication unit, while discarding another packet. The communication redundancy apparatus according to claim 1.   5. The communication redundancy apparatus according to claim 4, wherein the use of any received packet is to transfer the received packet to a transfer destination apparatus. The packet received from the communication destination device includes information used by the control unit to discard unnecessary packets,
The control means deletes information used for discarding the unnecessary packet included in a packet transferred to the transfer destination device, and transfers the packet after deleting the information to the transfer destination device. The communication redundancy apparatus according to claim 5.   The communication redundancy apparatus according to any one of claims 1 to 6, wherein the redundancy of the plurality of base stations is m (m is an integer of 2 or more). A communication redundancy system including the communication redundancy device according to claim 7, the base station, and the communication destination device,
The base station is installed so that the overlapping degree of the plurality of base stations is m,
The communication destination device is connected to the plurality of base stations;
The communication redundancy system, wherein the communication destination device and the communication redundancy device perform communication via the plurality of base stations and the plurality of wireless communication paths. A plurality of communication steps in which a plurality of communication means each establishing a separate radio communication path with a separate base station communicate with a communication destination device via the established radio communication path;
In the handover period, any one of the communication means switches the base station that establishes the wireless communication path with the own communication means. a control step in which n is an integer greater than or equal to 2) other communication means continues communication with the communication destination device;
The communication redundancy method characterized by performing. A communication redundancy program,
Computer
A plurality of communication means each establishing a wireless communication path with a separate base station and performing communication with a communication destination device via the established wireless communication path;
In the handover period, any one of the communication means switches the base station that establishes the wireless communication path with the own communication means. n is an integer equal to or greater than 2) control means for causing other communication means to continue communication with the communication destination device;
A communication redundancy program that functions as a communication redundancy device.

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