JP5361313B2 - Relay station and wireless communication relay method - Google Patents

Description

  The present invention relates to a relay station and a wireless communication relay method capable of relaying wireless communication between a wireless communication terminal and a base station.

  In recent years, wireless communication terminals typified by mobile phones and PHS (Personal Handy phone System) terminals have become widespread, making it possible to make calls and obtain information regardless of location or time. Especially in recent years, the amount of available information has been increasing, and high-speed and high-quality wireless communication systems have been introduced to download large amounts of data.

  As one of such high-speed digital wireless communication systems, there are OFDMA (Orthogonal Frequency Division Multiplex Access) systems represented by IEEE 802.11 and WiMAX (for example, Non-Patent Document 1). The OFDMA method is classified as one of data multiplexing methods, uses a large number of carriers on the unit time axis, and sets the carrier band so that the phase of the signal wave to be modulated is orthogonal between adjacent carriers. This is a method of effectively using the frequency band by overlapping a part. In addition, the OFDMA system, in which OFDM (Orthogonal Frequency Division Multiplexing) system in which subchannels are allocated in time division for each individual user, a plurality of users share all subchannels, Is characterized by allocating a subchannel with the highest transmission efficiency.

  When the next-generation high-speed wireless communication system such as WiMAX uses a high-frequency band of 2.5 GHz or higher, the communication range (coverage) for one base station in an area where the radio wave condition is bad such as many obstacles. ) Becomes smaller, and a large number of base stations must be installed to cover the whole area. In addition, since the wraparound of radio waves is suppressed, there is a high possibility of being out of service indoors. Therefore, by installing a relay station that relays between the base station device and the wireless communication terminal, it communicates with the base station regardless of the service area due to shadowing effects caused by obstruction by obstacles such as buildings. A technique capable of reducing the range incapable of being disclosed is disclosed.

  In addition, the relay station is not limited to a fixed installation in a building or a tower, but can also be mounted on a moving body on which a person can get on and off such as a bus or a train. A relay station mounted on a mobile unit is a base station installed outside the casing of the mobile unit so that a communication unit communicating with the radio communication terminal can maintain a relative positional relationship with the radio communication terminal. The communication unit that communicates with the wireless communication terminal can perform harmless communication, so that stable communication of the wireless communication terminal can be ensured.

With regard to a relay station mounted on such a mobile body, a technique has been disclosed that includes a measuring device for measuring the position of the mobile body, and stores in advance the position for executing a handover for changing a base station as a communication target ( For example, Patent Document 1).
JP 2000-229571 A "Mobile WiMAX? Part I: A Technical Overview and Performance Evaluation" Prepared on Behalf of the WiMAX Forum, February 21, 2006, http://www.intel.com/netcomms/technologies/wimax/WiMAX_Overview_v2.pdf

  By the way, when a relay station mounted on a mobile object approaches the outside of the communication range of a communicating base station and hands over to another adjacent base station, the frequency used for new wireless communication with the other base station is If the frequency is the same as the frequency used by the relay station and the wireless communication terminal in the moving body for wireless communication, the channel of that frequency causes interference. Therefore, the relay station changes the frequency used for wireless communication with the wireless communication terminal to a frequency different from the frequency used for wireless communication with the base station.

  However, the relay station selects a frequency that is different from the frequency used for communication with the base station and that does not overlap between a plurality of wireless communication terminals in the moving body in which the relay station is mounted, and Since they are used for wireless communication, depending on the communication environment, the frequencies of the two become extremely close to each other, causing interference with each other.

  In view of such problems, the present invention provides a relay station that can more reliably avoid interference between a radio communication channel between a base station and a relay station and a radio communication channel between the relay station and a radio communication terminal. It is another object of the present invention to provide a wireless communication relay method.

  In order to solve the above problems, a typical configuration of the present invention is a relay station capable of relaying wireless communication between a wireless communication terminal and a base station, and a plurality of divided frequency bands that can be used for wireless communication. Of these divided frequency bands, a terminal communication unit that performs wireless communication with the base station using a channel included in one divided frequency band determined by the base station that performs wireless communication, is used for wireless communication with the base station. A frequency selection unit that selects a division frequency band different from the division frequency band that is being used, and a base station communication unit that communicates with a wireless communication terminal using a channel included in the division frequency band selected by the frequency selection unit, It is characterized by providing.

  In the present invention, the entire frequency band is divided into a plurality of divided frequency bands, a divided frequency band including a channel used for wireless communication between the base station and the relay station, and a relay station and a mobile body in which the relay station is mounted. Different frequency bands are selected for selection of channels to be used in wireless communication with the wireless communication terminal. With this configuration, the channel used for wireless communication between the base station and the relay station and the channel used for wireless communication between the relay station and the wireless communication terminal can be separated more reliably, and mutual interference can be avoided. It becomes possible.

  The relay station further includes a history storage unit that stores a divided frequency band used in wireless communication with the base station, and the frequency selection unit prioritizes a divided frequency band different from the divided frequency band stored in the history storage unit. You may choose.

  With this configuration, when a mobile unit equipped with a relay station moves over a communicable range with the base station, the relay station is used for wireless communication with the wireless communication terminal, avoiding the divided frequency band once used. The frequency band to be divided can be selected. Thus, when re-passing the communicable range of the base station that has passed previously, the divided frequency band used for wireless communication between the base station and the relay station overlaps with the divided frequency band used for wireless communication between the relay station and the wireless communication terminal. Without changing the channel used for wireless communication between the relay station and the wireless communication terminal, processing load and power consumption can be reduced.

  The history storage unit stores the divided frequency bands used in wireless communication with the base station in time series, and the frequency selection unit has a divided frequency band that is different from the divided frequency band stored in the history storage unit, Of the stored divided frequency bands, the oldest divided frequency band may be selected.

  When a mobile unit equipped with a relay station periodically moves in a predetermined area across the base station and uses all the divided frequency bands in wireless communication between the base station and the relay station during movement, It is necessary to select from the divided frequency bands having a history of use. At this time, depending on how to select the division frequency band, it is necessary to frequently change the radio communication channel between the relay station and the radio communication terminal. In the present invention, by selecting the oldest divided frequency band from among the stored divided frequency bands, for example, when the mobile body is a round-trip route by a train, the number of channel changes can be reduced most. , Reduce processing load and power consumption.

  The history storage unit stores the divided frequency bands used in wireless communication with the base station in time series, and the frequency selection unit has a divided frequency band that is different from the divided frequency band stored in the history storage unit, The latest divided frequency band is selected from the stored divided frequency bands.

  When a mobile unit equipped with a relay station periodically moves in a predetermined area across the base station and uses all the divided frequency bands in wireless communication between the base station and the relay station during movement, It is necessary to select from the divided frequency bands having a history of use. At this time, depending on how to select the division frequency band, it is necessary to frequently change the radio communication channel between the relay station and the radio communication terminal. In the present invention, by selecting the latest divided frequency band from among the stored divided frequency bands, for example, when the mobile body is a train and a circular route, the number of channel changes can be reduced most, Processing load and power consumption can be reduced.

  Another typical configuration of the present invention is a wireless communication relay method for performing wireless communication using a relay station capable of relaying wireless communication between a wireless communication terminal and a base station, and is all available for wireless communication. Of the plurality of divided frequency bands obtained by dividing the frequency band, wireless communication is performed with the base station using a channel included in one divided frequency band determined by the base station that performs wireless communication, and wireless communication with the base station is performed. A division frequency band different from the division frequency band being used is selected, and communication is performed with a wireless communication terminal using a channel included in the selected division frequency band.

  The above-described components based on the technical idea of the relay station and the description thereof can be applied to the wireless communication relay method.

  As described above, according to the present invention, it is possible to more reliably avoid interference between the radio communication channel between the base station and the relay station and the radio communication channel between the relay station and the radio communication terminal.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In the present specification and drawings, elements having substantially the same function and configuration are denoted by the same reference numerals, and redundant description is omitted, and elements not directly related to the present invention are not illustrated. To do.

  Wireless communication terminals such as mobile phones and PHS terminals construct a wide-area wireless communication system with a plurality of distributed base stations, and communicate with other wireless communication terminals and servers on the communication network through this wireless communication system. Carry out. Furthermore, in next-generation high-speed wireless communication systems such as WiMAX, in order to avoid a reduction in the communication range (coverage), a mobile object having a poor radio wave condition, a place where buildings are densely populated, or a radio wave condition changes significantly. In addition, a relay station functioning as a base station can be provided to take part of the wireless communication system. In the present embodiment, a case where a relay station is mounted on a mobile object will be described.

  Here, in order to facilitate understanding of the present embodiment, first, a schematic configuration of the entire wireless communication system including the relay station will be described, and then a specific operation of each device configuring the wireless communication system will be described. .

(Wireless communication system 100)
FIG. 1 is a block diagram illustrating a schematic configuration of a wireless communication system 100. The radio communication system 100 includes radio communication terminals 110 (110A and 110B), base stations 120 (120A and 120B), a relay station 130, an ISDN (Integrated Services Digital Network) line, the Internet, a dedicated line, and the like. Communication network 140, relay server 150, and mobile body 160.

  Here, wireless communication such as a mobile phone, a PHS terminal notebook personal computer, a PDA (Personal Digital Assistant), a digital camera, a music player, a car navigation system, a portable TV, a game device, a DVD player, and a remote controller is possible as the wireless communication terminal 110. Various electronic devices can also be used.

  In the wireless communication system 100 described above, when a user performs communication from his / her own wireless communication terminal 110A to another wireless communication terminal 110B, the wireless communication terminal 110A makes a wireless connection request to the base station 120A within the communicable range. I do. The base station 120A that has received the wireless connection request requests the relay server 150 to establish a communication connection with the communication partner via the communication network 140, and the relay server 150 refers to the location registration information of the other wireless communication terminal 110B, The base station 120B within the radio communication range of the other radio communication terminal 110B is extracted to secure a communication path between the base station 120A and the base station 120B, and communication between the radio communication terminal 110A and the radio communication terminal 110B is executed (established). )

  Here, when the user gets on, for example, a train as the moving body 160, the wireless communication terminal 110A switches to communication via the relay station 130 instead of directly with the base station 120A. The relay station 130 is fixed to the moving body 160 and moves with the moving body 160 to play a role of extending the coverage to the moving body. In the present embodiment, the moving body 160 is a train, but various vehicles such as automobiles, buses, trains (trains), ships, airplanes, and the like on which people can get on and off may be used.

  The wireless communication terminal 110A and the relay station 130 possessed by the user who has entered the moving body move together without any change in the positional relationship unless an operation such as searching for a vacant seat occurs, and also shields between the two. Since there is no barrier to this, stable wireless communication can be ensured. Therefore, the wireless communication terminal 110A can stably maintain communication with the other wireless communication terminal 110B via the relay station 130 regardless of the movement of the moving body 160.

  Hereinafter, the wireless communication terminal 110, the base station 120, and the relay station 130 that configure the wireless communication system 100 will be described individually.

(Wireless communication terminal 110)
FIG. 2 is a functional block diagram showing a hardware configuration of the wireless communication terminal 110, and FIG. 3 is a perspective view showing an appearance of the wireless communication terminal 110. As shown in FIG. The wireless communication terminal 110 includes a terminal control unit 210, a terminal memory 212, a display unit 214, an operation unit 216, a voice input unit 218, a voice output unit 220, and a terminal wireless communication unit 222. The

  The terminal control unit 210 manages and controls the entire wireless communication terminal 110 using a semiconductor integrated circuit including a central processing unit (CPU). The terminal control unit 210 also performs a call function, a mail transmission / reception function, an imaging function, a music playback function, and a TV viewing function using the program in the terminal memory 212. The terminal memory 212 includes a ROM, a RAM, an EEPROM, a nonvolatile RAM, a flash memory, an HDD, and the like, and stores a program processed by the terminal control unit 210, audio data, and the like.

  The display unit 214 includes a liquid crystal display, an EL (Electro Luminescence) display, etc., and is stored in the terminal memory 212 or provided from an application relay server (not shown) via the communication network 140, An application GUI (Graphical User Interface) can be displayed. The operation unit 216 includes switches such as a keyboard, a cross key, and a joystick, and receives a user operation input.

  The voice input unit 218 includes voice conversion means such as a microphone, and converts a user voice input during a call or the like into an electrical signal that can be processed in the wireless communication terminal 110. The audio output unit 220 includes a speaker, and converts the audio signal of the other party received by the wireless communication terminal 110 into audio and outputs it. The voice output unit 220 can also output a ringtone, an operation sound of the operation unit 216, an alarm sound, and the like. The terminal wireless communication unit 222 performs wireless communication with the base station 120 or the relay station 130 in the communication network 140. In addition to OFDMA systems such as WiMAX, ARIB (Association of Radio Industries and Businesses) STD T95, PHS MoU (Memorandum of Understanding), the terminal wireless communication unit 222 includes OFDM systems and TDMA (Time Division Multiple Access). Various wireless communication methods such as a method can be applied.

(Base station 120)
FIG. 4 is a block diagram illustrating a schematic configuration of the base station 120. The base station 120 includes a base station control unit 250, a base station memory 252, a base station wireless communication unit 254, and a base station wired communication unit 256.

  The base station control unit 250 manages and controls the entire base station 120 using a semiconductor integrated circuit including a central processing unit (CPU). The base station memory 252 includes a ROM, a RAM, an EEPROM, a nonvolatile RAM, a flash memory, an HDD, and the like, and stores a program processed by the base station control unit 250.

  The base station wireless communication unit 254 performs wireless communication with the wireless communication terminal 110 or the relay station 130 using, for example, the OFDMA method, and performs QoS (Quality Of Service) according to the communication state with the wireless communication terminal 110 or the relay station 130. For example, the modulation scheme can be adaptively changed (adaptive modulation). The base station wired communication unit 256 can communicate with various servers including the relay server 150 via the communication network 140.

(Relay station 130)
FIG. 5 is a block diagram showing a schematic configuration of relay station 130. The relay station 130 includes a relay station wireless communication unit 310, a relay station control unit 312, and a relay station memory 314. The relay station 130 is mounted (installed) in the moving body 160.

  The relay station wireless communication unit 310 performs wireless communication with both the wireless communication terminal 110 and the base station 120 and relays between the wireless communication terminal 110 and the base station 120. The relay station wireless communication unit 310 functions as a terminal communication unit 350, a connection control unit 352, and a base station communication unit 354.

  The terminal communication unit 350 is installed outside the housing of the mobile unit 160, functions as a wireless communication terminal 110 for communication with the base station 120, and includes a physical layer (layer 1) and a data link layer (layer 2) in the OSI reference model. Bear. In the present embodiment, a configuration is described in which only one terminal communication unit 350 is provided based on the OFDMA method. However, the present invention is not limited to this, and a plurality of terminal communication units 350 are provided in the OFDMA method and in other communication methods. It is also possible to provide it. When a plurality of terminal communication units 350 are provided as described above, communication can be performed independently by different base stations 120.

  Furthermore, the terminal communication unit 350 includes a plurality of divided frequency bands included in one divided frequency band determined by the base station 120 that performs wireless communication among a plurality of divided frequency bands obtained by dividing all frequency bands available for wireless communication. Wireless communication is performed with the base station 120 using, for example, one of the channels.

  In the present embodiment, the total frequency band available for wireless communication is a band having a width of, for example, 30 MHz centered on an arbitrary frequency defined by the Radio Law, and the total frequency band is, for example, 5 MHz divided into six. Each band is referred to as a divided frequency band. In such a divided frequency band, different divided frequency bands are allocated to the adjacent base stations 120 so that the plurality of base stations 120 do not cause interference so that the channels of the base stations 120 do not overlap each other.

  When a plurality of wireless communication terminals 110 are connected to a base station communication unit 354, which will be described later, the connection control unit 352 performs channel control (MAC tracer function), and adopts the OFDMA method as in this embodiment. If so, communication data is allocated to a channel map in which subchannels, which are the minimum transmission unit of communication data, are arranged in the time and frequency directions. Further, the connection control unit 352 can adaptively change the QoS according to the communication state between the base station communication unit 354 and the wireless communication terminal 110 that is performing wireless communication.

  The base station communication unit 354 is installed inside the casing of the mobile body 160, functions as the base station 120 for communication with the wireless communication terminal 110 existing in the casing, and serves as a physical layer and a data link layer in the OSI reference model. As shown in FIG. 5, only one base station communication unit 354 is provided for each relay station in the present embodiment. Moreover, when it applies to a space large to some extent, such as a ship and an aircraft, it can also comprise in multiple. With this base station communication unit 354, even if the wireless communication terminal 110 performs wireless communication with the relay station 130 instead of with the base station 120, the wireless communication terminal 110 operates as if it is performing wireless communication with the base station 120.

  Furthermore, the base station communication unit 354 performs wireless communication with the wireless communication terminal 110 using, for example, one channel among a plurality of channels included in one divided frequency band among the plurality of divided frequency bands.

  The relay station control unit 312 manages and controls the entire relay station 130 by a semiconductor integrated circuit including a central processing unit (CPU). The relay station control unit 312 includes a frequency selection unit 370.

  The frequency selection unit 370 selects a divided frequency band that is different from the divided frequency band used in wireless communication with the base station 120, and instructs the base station communication unit 354 to use the divided frequency band.

  Since the relay station 130 is housed in an integrally formed casing, the terminal communication unit 350 and the base station communication unit 354 described above are often not separated from each other by a sufficient distance. Under such circumstances, if the channel used for communication with the base station 120 and the channel used for communication with the wireless communication terminal 110 are equal, the leakage power of the transmission data on the transmission side becomes the reception side. There is a possibility that the reception side may interfere with the reception data and the reception side cannot receive the reception data correctly. In the present embodiment, the channel used for the wireless communication between the base station 120 and the relay station 130 and the channel used for the wireless communication between the relay station and the wireless communication terminal are made more reliable by making the divided frequency bands different. They can be separated, and mutual interference can be avoided.

  The relay station memory 314 includes a ROM, a RAM, an EEPROM, a nonvolatile RAM, a flash memory, an HDD, and the like, and stores a program processed by the relay station control unit 312. The relay station memory 314 includes a history storage unit 390.

  The history storage unit 390 stores the divided frequency band used for wireless communication with the base station 120. In the present embodiment, the frequency selection unit 370 preferentially selects a divided frequency band different from the divided frequency band stored in the history storage unit 390 as a divided frequency band used for communication with the wireless communication terminal 100. .

  With this configuration, when the mobile unit 160 on which the relay station 130 is mounted moves across the communicable range with the base station 120, the relay station 130 avoids the divided frequency band that has been used once, The divided frequency band to be used for wireless communication can be selected. Thus, when passing through the communicable range of the base station that has passed before, the division frequency band used for radio communication between the base station 120 and the relay station 130 and the division used for radio communication between the relay station 130 and the radio communication terminal 110 are divided. Since the frequency bands do not overlap and there is no need to change the channel used for wireless communication between the relay station 130 and the wireless communication terminal 110, the processing load and power consumption can be reduced.

  FIG. 6 is an explanatory diagram comparing a wireless communication example between the relay station 130 and the wireless communication terminal 110 with a comparative example. FIG. 6A is a comparative example, and FIG. 6B is an example to which the present embodiment is applied. 6 is a cell indicating the communicable range of one base station 120, and four cells (cell A, cell B, cell C, cell D) arranged in a horizontal row. Performs wireless communication with the wireless communication terminal 110, the relay station 130, etc. using the divided frequency bands Fa, Fb, Fc, and Fd, respectively. Here, the divided frequency band used in a certain cell is represented by adding F to the lower case letter of the alphabet indicating that cell. In addition, a vertically long hexagon is drawn for explanation, but an actual cell is close to a regular hexagon. In addition to a regular hexagon, a shape close to a regular triangle or a regular square may be used.

  Then, the mobile unit 160 equipped with the relay station 130 moves across cells, and the terminal communication unit 350 of the relay station 130 selects a channel according to the divided frequency bands Fa, Fb, Fc, and Fd corresponding to the entered cell. To do. The characters in the mobile unit 160 indicate the divided frequency band used for the wireless communication between the relay station 130 and the wireless communication terminal 110, and indicate when the divided frequency band is changed by hatching. The history storage unit 390 shows the state at each position indicated by the dashed-dotted ellipse in the figure when the relay station 130 moves in the order of cell A, cell B, cell C, and cell D. The definition of such cells and divided frequency bands in FIG. 6 is also applied to FIGS.

  In the comparative example of FIG. 6A, the relay station 130 does not have the history storage unit 390, and the divided frequency band used for the wireless communication between the relay station 130 and the wireless communication terminal 110 is set to the wireless communication of the base station 120. Select at random within the divided frequency band not used for. First, it is assumed that relay station 130 passes through cell A, uses divided frequency band Fa for communication with base station 120, and uses divided frequency band Fc for communication with radio communication terminal 110. When the mobile unit 160 equipped with the relay station 130 moves further and enters the adjacent cell B, the divided frequency band Fb is used for radio communication with the base station 120. At this time, since the divided frequency band Fb used for the wireless communication with the base station 120 and the divided frequency band Fc used for the wireless communication of the wireless communication terminal 110 are different, the wireless communication between the relay station 130 and the wireless communication terminal 110 is divided. The frequency band is not changed.

  Thereafter, when the mobile unit 160 moves and enters the adjacent cell C, the divided frequency band Fc is used for wireless communication with the base station 120. Here, since the divided frequency band Fc for wireless communication with the base station 120 overlaps with the divided frequency band Fc for wireless communication with the wireless communication terminal 110, the relay station 130 determines the latter as a divided frequency other than the divided frequency band Fc. A band is randomly changed to, for example, a divided frequency band Fd. Then, when the mobile unit 160 moves to the cell D, further change occurs. At this time, if the relay station 130 randomly selects the divided frequency band Fc, the change is made again when entering the cell C in the forward path of the mobile unit 160. Arise. In the example of FIG. 6B, the divided frequency band of the wireless communication with the wireless communication terminal 110 is changed five times during one and a half rounds from the cell A to the cell D, and the divided frequency band Fe, The change of the divided frequency band is repeated until Ff is selected.

  On the other hand, in the embodiment of FIG. 6B, the relay station 130 has a history storage unit 390, and by referring to the history storage unit 390, the history of the division frequency selected in the past can be grasped. it can. Here, the rectangular cells described below in FIG. 6B indicate the state of the history storage unit 390 at each position in FIG. 6B, that is, the terminal communication unit 350 of the relay station 130 uses for wireless communication. The history of the divided frequency band is shown. Such history is newer in the upper part and is arranged in time series from the bottom. First, it is assumed that the relay station 130 passes through the cell A, uses the divided frequency band Fa for communication with the base station 120, and uses the divided frequency band Fc for communication with the wireless communication terminal 110, for example. The history storage unit 390 stores the divided frequency band Fa at the position A.

  When the mobile body 160 moves and enters the adjacent cell B, the divided frequency band Fb is used for wireless communication with the base station 120. At this time, since the divided frequency band Fb used for the wireless communication with the base station 120 and the divided frequency band Fc used for the wireless communication of the wireless communication terminal 110 are different, the wireless communication between the relay station 130 and the wireless communication terminal 110 is divided. The frequency band is not changed. The history storage unit 390 stores the divided frequency band Fb at the position B.

  Thereafter, when the mobile unit 160 moves and enters the adjacent cell C, the divided frequency band Fc is used for wireless communication with the base station 120. Here, since the division frequency band Fc of the wireless communication with the base station 120 overlaps with the division frequency band Fc of the wireless communication with the wireless communication terminal 110, the relay station 130 determines the latter other than the division frequency band Fc, Further, before leaving the previous area B, the frequency is changed to a divided frequency band other than the divided frequency bands Fa and Fb stored in the history storage unit 390, for example, the divided frequency band Fd. The history storage unit 390 stores the divided frequency band Fc at the position C.

  Further, when the moving body 160 moves and enters the cell D, the divided frequency band Fd is used for wireless communication with the base station 120. Here, since the division frequency band Fd of the wireless communication with the base station 120 overlaps with the division frequency band Fd of the wireless communication with the wireless communication terminal 110, the relay station 130 determines the latter other than the division frequency band Fd, Before leaving the previous cell C, the frequency is changed to the divided frequency band Fe that is not stored in the history storage unit 390. The history storage unit 390 stores the divided frequency band Fd at the position D.

  In the example of FIG. 6B, the divided frequency band Fe is not used in the base station 120 of the cell on the forward path of the mobile body 160. Therefore, thereafter, the divided frequency band for wireless communication with the base station 120 and the divided frequency band for wireless communication with the wireless communication terminal 110 do not overlap each other no matter how many times the mobile unit 160 makes a round trip on the same outbound path. This eliminates the need to change the divided frequency band for wireless communication with the wireless communication terminal 110, thereby reducing processing load and power consumption.

  Further, the history storage unit 390 stores the divided frequency bands used in the wireless communication with the base station 120 in time series, and the frequency selection unit 370 has a different division from the divided frequency bands stored in the history storage unit 390. When there is no frequency band, the oldest divided frequency band may be selected from the stored divided frequency bands.

  As described above, since the divided frequency bands are divided into, for example, all frequency bands available for wireless communication of the wireless communication terminal 110, the total number of the divided frequency bands Fa, Fb, Fc, Fd, Fe, Ff is Limited (6). Therefore, as shown in FIG. 6B, even if it is attempted to select a divided frequency band stored in the history storage unit 390, all six divided frequency bands may be stored and cannot be selected. In other words, it is necessary to select a divided frequency band stored in (1), that is, a divided frequency band that has been used in the past.

  For example, when the moving body 160 is a train and runs on a round-trip line, all the divided frequency bands are used in the cell of the round-trip line, and are different from the divided frequency bands stored in the history storage unit 390. When the division frequency band cannot be selected, the frequency selection unit 370 of the present embodiment selects the oldest division frequency band among the stored division frequency bands. With this configuration, when it is necessary to select a divided frequency band stored in the history storage unit 390, the number of channel changes can be reduced most, and processing load and power consumption can be reduced.

  FIG. 7 is an explanatory diagram illustrating an example of a round trip route for selecting a divided frequency band stored in the history storage unit 390 in the wireless communication between the relay station 130 and the wireless communication terminal 110. In addition, the area shown by hexagons in FIG. 7 is a cell indicating the communicable range of one base station 120 as in FIG. 6, and six cells A, B, C, D, E arranged in a horizontal row. , F perform wireless communication with the wireless communication terminal 110, the relay station 130, and the like using the divided frequency bands Fa, Fb, Fc, Fd, Fe, and Ff, respectively.

  In the history storage unit 390 in FIG. 7, after the relay station 130 moves the round trip route in the order of cell A, cell B, cell C, cell D, cell E, cell F, cell F, cell E, cell D, The state when moving in the order of cell C, cell B, and cell A (reverse direction) shows the state at each position indicated by the dashed-dotted ellipse.

  When the relay station 130 enters the cell F while using the division frequency Ff for radio communication with the radio communication terminal 110, the relay station 130 uses the division frequency band Ff used for radio communication with the base station 120 and the radio communication terminal 110. Therefore, a divided frequency band different from the divided frequency band Ff must be selected. However, since all the divided frequency bands are already stored in the history storage unit 390, a divided frequency band that is not stored in the history storage unit 390 cannot be selected.

  At this time, the frequency selection unit 370 selects the oldest divided frequency band Fa among the divided frequency bands stored in the history storage unit 390. Here, the oldest divided frequency band is the newest divided frequency band among the divided frequency bands stored in the history storage unit 390 when the same divided frequency band is stored. The history is selected.

  When the moving body 160 moves from the position F to the position B, and further moves from the position B to the position A (when entering the cell A), the history storage unit 390 at the previous position B stores Fb, Fc in order from the newest one. , Fd, Fe, Ff, Fe... Are stored, and the divided frequency band Fb is the newest among the two overlapping frequency bands Fb, that is, the first divided frequency band Fb from the top is selected. . Similarly, the newest ones of Fc, Fd, Fe, Ff, and Fa are shown surrounded by a dashed ellipse. Among the selection targets (the divided frequency bands surrounded by the broken-line ellipses) thus extracted, the oldest one is the divided frequency band Ff. The relay station 130 changes the divided frequency band Fa of the wireless communication with the wireless communication terminal 110 to the divided frequency band Ff at the position A.

  In the forward path as shown in FIG. 7, the change of the divided frequency band Fa and the divided frequency band Ff is repeated. Thus, the frequency change is minimized even in a round-trip train or the like when the divided frequency band stored in the history storage unit 390 must be used. Therefore, when the mobile body 160 is a mobile body that assumes a round trip such as a train, the number of channel changes can be reduced most, and the processing load and power consumption can be reduced.

  Further, the history storage unit 390 stores the divided frequency bands used in the wireless communication with the base station 120 in time series, and the frequency selection unit 370 determines that the moving locus of the moving body 160 is a specific locus (for example, an annular locus). When there is no division frequency band different from the division frequency band stored in the history storage unit 390, even when the latest division frequency band is selected from the division frequency bands stored in the history storage unit 390, Good.

  FIG. 8 is an explanatory diagram illustrating an example of an annular route for selecting a divided frequency band stored in the history storage unit 390 in wireless communication between the relay station 130 and the wireless communication terminal 110. In FIG. 8, the history storage unit 390 is a dot-and-dash line in the diagram when the relay station 130 repeatedly moves the ring route in the order of cell A, cell B, cell C, cell D, cell E, and cell F. The state of the history at each position indicated by an ellipse is shown.

  When the moving body 160 moves from the position A to the position B in FIG. 8, the divided frequency band Fb is used for wireless communication with the base station 120. Here, since the division frequency band Fb of the radio communication with the base station 120 overlaps with the division frequency band Fb of the radio communication with the radio communication terminal 110, the relay station 130 further changes the latter to other than the division frequency band Fb. An attempt is made to select a divided frequency band that is not stored in the history storage unit 390 before exiting the immediately preceding position A. However, since the history storage unit 390 has already stored all the divided frequency bands, The division frequency band that is not stored in the unit 390 cannot be selected, and must be selected from the division frequency bands that have been used. Depending on how the division frequency band is selected, the wireless communication between the relay station and the wireless communication terminal You will have to change the channel frequently.

  At this time, the frequency selection unit 370 selects the latest divided frequency band among the divided frequency bands stored in the history storage unit 390. The latest divided frequency band here is simply the latest history stored in the history storage unit 390. In this case, the divided frequency band Fa (Fa surrounded by a solid oval) used for wireless communication with the base station at the position A immediately before is the latest divided frequency band.

When the above rules are followed, when the cell A to cell F are repeatedly circulated, the divided frequency band used for wireless communication with the wireless communication terminal 110 is changed for every five cells. In this way, the frequency change is the smallest in a train on a circular route when the divided frequency band stored in the history storage unit 390 must be used. Therefore, even when the moving body 160 moves on a ring route by train, the number of channel changes can be reduced most, and the processing load and power consumption can be reduced.
(Wireless communication relay method)
Next, a wireless communication relay method for performing wireless communication using the wireless communication terminal 110, the base station 120, and the relay station 130 will be described in detail.

  FIG. 9 is a flowchart showing a flow of processing for selecting a divided frequency band when the relay station 130 is mounted on a round-trip train. When handover is started in wireless communication between the base station 120 and the relay station 130 (S400 YES), the divided frequency band of the handover destination and the divided frequency band used in the wireless communication between the relay station 130 and the wireless communication terminal 110 Are matched (S402). If they do not match (NO in S402), the wireless communication between the base station 120 and the relay station 130 waits until the next handover is started.

  If they match (YES in S402), it is determined whether or not the divided frequency bands that are not stored in the history storage unit 390 remain and can be selected (S404). When remaining (S404 YES), the frequency selection unit 370 selects one divided frequency band from the remaining divided frequency bands (S406). When there is no remaining divided frequency band that is not stored (NO in S404), the frequency selection unit 370 selects the oldest divided frequency band from the arrangement of the divided frequency bands stored in the history storage unit 390. In order to select the oldest division frequency band, the frequency selection unit 370 first determines whether the division frequency bands of all the frequency bands have already been read from the history storage unit 390 in order to refer to all the division frequency bands ( S408). When the divided frequency bands of all the frequency bands have not been read (NO in S408), the divided frequency band that has not been read yet is read from the newer one of the history storage unit 390 (S410). Then, it is determined whether or not the read divided frequency band matches the read divided frequency band (S412).

  When it matches with the divided frequency band read so far (YES in S412), the old divided frequency band is deleted (S414), and the process returns to the step of determining whether the divided frequency bands of all frequency bands have been read (S408). If they do not match (NO at S412), the read divided frequency band is held (S416). When the above processing is repeated and reading of the divided frequency bands of all the bands is completed (S408 YES), the oldest divided frequency band is selected (S418).

  Then, the divided frequency band used for wireless communication with the wireless communication terminal 110 is changed to the selected divided frequency band (S420), and waits until the next handover is started in the wireless communication between the base station 120 and the relay station 130. .

  FIG. 10 is a flowchart showing a flow of processing for selecting a divided frequency band when the relay station 130 is mounted on a ring train.

  Even in the circular route, after the handover is started by the wireless communication between the base station 120 and the relay station 130 (S400), the divided frequency bands that are not stored in the history storage unit 390 remain and the divided frequency bands that are not in the history are selected. Up to (S406), the processing is substantially the same as in the case of the round-trip route in FIG. 9, so the description thereof is omitted here. When there is no remaining divided frequency band stored in the history storage unit 390 (S404 NO), the frequency selection unit 370 selects the latest divided frequency band stored in the history storage unit 390 (S450), and thereafter As in the case of the round-trip route, the divided frequency band used for the wireless communication with the wireless communication terminal 110 is changed to the selected divided frequency band (S420), and the next handover is performed by the wireless communication between the base station 120 and the relay station 130. Wait for it to start.

  When the frequency selection unit 370 selects a divided frequency band from the history, the frequency selection unit 370 performs a process of selecting a divided frequency band in the preset round-trip route of FIG. 9 or the annular route of FIG. Further, the frequency selection unit 370 stores in the history storage unit 390 whether the moving body 160 on which the relay station 130 is mounted is moving, for example, as a round-trip route of a train or a circular route. It may be determined from the history of the divided frequency band, and it may be determined which of the processes of FIGS. 9 and 10 selects the divided frequency band.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  Note that each step in the wireless communication relay method of the present specification does not necessarily have to be processed in time series in the order described as a sequence diagram, and may include processing in parallel or by a subroutine.

  The present invention can be used for a relay station and a wireless communication relay method capable of relaying wireless communication between a wireless communication terminal and a base station.

1 is a block diagram showing a schematic configuration of a wireless communication system. It is the functional block diagram which showed the hardware constitutions of the radio | wireless communication terminal. It is the perspective view which showed the external appearance of the radio | wireless communication terminal. It is the block diagram which showed the schematic structure of the base station. It is the block diagram which showed the schematic structure of the relay station. It is explanatory drawing which compared the example of the wireless communication of a relay station and a wireless communication terminal, and a comparative example. It is explanatory drawing explaining the example of the round-trip route which selects the division | segmentation frequency band memorize | stored in the log | history memory | storage part in the radio | wireless communication of a relay station and a radio | wireless communication terminal. It is explanatory drawing explaining the example of the cyclic route which selects the division | segmentation frequency band memorize | stored in the log | history memory | storage part in the radio | wireless communication of a relay station and a radio | wireless communication terminal. It is the flowchart which showed the flow of the process of selection of a division | segmentation frequency band when a relay station is mounted in the train of a round-trip route. It is the flowchart which showed the flow of the process of selection of a division | segmentation frequency band when a relay station is mounted in the train of a ring route.

Explanation of symbols

DESCRIPTION OF SYMBOLS 110 ... Radio | wireless communication terminal 120 ... Base station 130 ... Relay station 170 ... Mobile body 350 ... Terminal communication part 354 ... Base station communication part 370 ... Frequency selection part 390 ... History storage part

Claims (6)

A relay station capable of relaying wireless communication between a wireless communication terminal and a base station,
Execute wireless communication with the base station using a channel included in one divided frequency band determined by the base station that performs wireless communication among a plurality of divided frequency bands obtained by dividing all frequency bands that can be used for the wireless communication A terminal communication unit,
A frequency selection unit that selects a division frequency band different from the division frequency band used in wireless communication with the base station;
A base station communication unit that communicates with the wireless communication terminal using a channel included in the divided frequency band selected by the frequency selection unit;
A history storage unit for storing a divided frequency band used in wireless communication with the base station;
With
The relay station, wherein the frequency selection unit preferentially selects a divided frequency band different from the divided frequency band stored in the history storage unit. The history storage unit stores the divided frequency bands used in wireless communication with the base station in time series,
The frequency selection unit, when there is no division frequency band different from the division frequency band stored in the history storage unit, to select the oldest division frequency band among the stored division frequency bands, The relay station according to claim 1. The history storage unit stores the divided frequency bands used in wireless communication with the base station in time series,
The frequency selection unit selects the latest division frequency band from among the stored division frequency bands when there is no division frequency band different from the division frequency band stored in the history storage unit. The relay station according to claim 1. A relay station capable of relaying wireless communication between a wireless communication terminal and a base station,
Stores a history of frequency bands used for wireless communication with the base station, and stores the frequency band used for wireless communication with the wireless communication terminal when newly performing wireless communication with the base station after storage. A relay station that selects a frequency band different from the band with priority. A wireless communication relay method for performing wireless communication using a relay station capable of relaying wireless communication between a wireless communication terminal and a base station,
Wireless communication is performed with the base station using a channel included in one divided frequency band determined by a base station that performs wireless communication among a plurality of divided frequency bands obtained by dividing all frequency bands that can be used for the wireless communication. And
Stores a history of divided frequency bands used in wireless communication with the base station,
Select and preferentially select a division frequency band different from the stored division frequency band,
A wireless communication relay method, wherein communication is performed with the wireless communication terminal using a channel included in the selected divided frequency band. A wireless communication relay method of a relay station that relays wireless communication between a wireless communication terminal and a base station,
Stores a history of frequency bands used for wireless communication with the base station, and stores the frequency band used for wireless communication with the wireless communication terminal when newly performing wireless communication with the base station after storage. A wireless communication relay method, wherein priority is selected from a frequency band different from the band.

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