JP2013115446A - Radio relay system and radio relay device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize acquisition of good radio quality and increase in radio capacity at the same time.SOLUTION: A radio relay system comprises a base station for providing a radio communication area and a radio relay device for relaying communication between the base station and a radio terminal. The radio relay device comprises: a radio terminal unit for connecting with the base station; a plurality of base station units for connecting with other radio relay devices and the radio terminal; and a control unit for controlling operation of the radio terminal unit and the base station units. The control unit obtains the radio environment of a radio wave transmitted by the base station, and on the basis of the obtained radio environment, determines whether the radio relay device will connect with the base station via the radio terminal unit or it will connect with another radio relay device via the base station unit, stopping operation of the radio terminal unit.

Description

  The present invention relates to a radio relay device mounted on a mobile body, and more particularly to a technique for selecting a communication path between a radio relay device mounted on each vehicle of a train and a base station.

  In a radio relay system mounted on a train, continuation of a stable radio service is required. Nowadays, with the spread of communication terminals represented by smartphones, there are increasing opportunities for data communication even within trains, and there is a need to ensure stable communication quality and provide wireless services even within moving trains. Yes. As a technique for maintaining the quality of wireless communication in a train, there are techniques described in Patent Documents 1 and 2.

  In the invention described in Patent Document 1, a diversity reception system is employed in order to maintain at least two wireless receivers on a train and maintain wireless quality. For example, by receiving diversity reception of two wireless receivers mounted on the leading vehicle and the trailing vehicle, the received signal quality can be stabilized even when one of the reception environments is bad.

  Further, in Patent Document 2, in order to ensure stable communication quality, when relaying communication of a wireless communication terminal, the communication quality with the wireless communication terminal is monitored to estimate the position of the wireless communication terminal, A relay station that switches the QoS of wireless communication with a wireless communication terminal and switches a handover criterion according to the position of the wireless communication terminal is disclosed.

Japanese Patent Laid-Open No. 2004-56697 JP 2009-267750 A

  When providing a radio relay system in a train using the above-described conventional technique, it is necessary to select one reception demodulated signal for diversity reception. In this case, although the radio quality of the selected received demodulated signal is ensured, a radio service cannot be provided using a plurality of received demodulated signals. Further, even when the quality of one received demodulated signal is high, the communication capacity limit of the selected received demodulated signal cannot be exceeded. As described above, since data traffic is currently increasing, it is required to simultaneously ensure radio quality and increase radio capacity.

  A typical example of the invention disclosed in the present application is as follows. That is, a wireless relay system comprising: a base station that provides a wireless communication area; and a wireless relay that relays communication between the base station and a wireless terminal, wherein the wireless relay is connected to the base station A wireless terminal unit to be connected, a plurality of base station units to be connected to the other wireless relay device and the wireless terminal, and a control unit to control operations of the wireless terminal unit and the base station unit, , Acquiring a radio environment of radio waves transmitted from the base station, or depending on the acquired radio environment, connect to the base station via the radio terminal unit or stop the operation of the radio terminal unit, It is determined whether to connect to another wireless relay device via the base station.

  According to the exemplary embodiment of the present invention, it is possible to provide a stable wireless service according to a wireless environment.

It is a figure which shows the structural example of the radio relay system of embodiment of this invention. It is a block diagram which shows the structural example of the radio relay machine of embodiment of this invention. It is a block diagram which shows the structural example of the relay control part of embodiment of this invention. It is a block diagram which shows the structural example of the terminal base station part of embodiment of this invention. It is a flowchart which shows the process at the time of starting of the radio relay machine of embodiment of this invention. It is a figure explaining the example of storing to the auxiliary memory memory | storage part of the electric field strength of embodiment of this invention. It is a flowchart which shows the process at the time of the weak electric field of embodiment of this invention. It is a flowchart which shows the process at the time of ad hoc communication impossible of embodiment of this invention. It is a flowchart which shows the process at the time of the ad hoc communication connection request waiting of embodiment of this invention. It is a flowchart which shows the subunit | mobile_unit connection determination process of embodiment of this invention. It is a figure explaining the example by which wireless relay machines were connected by ad hoc communication in embodiment of this invention. In the embodiment of the present invention, it is a flowchart of processing when the wireless environment between the wireless terminal unit and the base station changes. In embodiment of this invention, it is a flowchart of a process when a subunit | mobile_unit receives the electric field strength fall notification. In the embodiment of the present invention, it is a flowchart of processing executed by the parent machine when the electric field strength becomes a weak electric field.

  Hereinafter, embodiments will be described with reference to the drawings.

  FIG. 1 is a diagram illustrating a configuration example of a wireless relay system according to an embodiment of this invention.

  The wireless relay system of this embodiment includes a base station 100 and a wireless relay device 200. The wireless repeater 200 is connected to the adjacent wireless repeater 200 via the dedicated line 10. Note that the line 10 connecting the wireless repeaters 200 may be shared with other communications. The line 10 is preferably a wireless line, but may be a wired line (for example, wired LAN, power line communication using a PLC adapter, etc.).

  The base station 100 provides public wireless communication (for example, WiMAX, 3G, LTE, etc.) and is connected to the wireless repeater 200 by the public wireless communication. The wireless repeater 200 is connected to the base station 100 by the public wireless communication, and is connected to the mobile terminal 1 by wireless communication (for example, WiFi).

  FIG. 2 is a block diagram illustrating a configuration example of the wireless repeater 200 according to the embodiment of this invention.

  The wireless relay device 200 of this embodiment includes a wireless terminal unit 201, a plurality of terminal base station units 205A, 205B, and 205C, a relay control unit 204, an auxiliary storage unit 203, a main storage unit 202, an antenna 206, An antenna 207.

  The wireless terminal unit 201 has a function of performing wireless communication with the base station 100. The terminal base station units 205A, 205B, and 205C have a function of performing wireless communication with the terminal base station unit 205 of the mobile terminal 1 and other wireless relay devices 200.

  The relay control unit 204 has a function of controlling the radio repeater 200 such as control of operations of the radio terminal unit 201 and the terminal base station units 205A, 205B, and 205C. The relay control unit 204 has a function of determining the congestion state of the device and a function of routing data from the terminal base station unit 205A and the like.

  The auxiliary storage unit 203 is configured by a non-volatile storage medium such as a flash memory or a magnetic disk drive, and stores various data according to instructions from the relay control unit 204 or the like. The main storage unit 202 is configured by a volatile memory such as a DRAM, and stores data for the relay control unit 204 to execute various data processing. The relay control unit 204 performs various types of data processing by executing programs stored in the main storage unit 202 or the auxiliary storage unit 203.

  The antenna 206 is connected to the terminal base station unit 205A and the like, and transmits and receives radio waves transmitted and received by the terminal base station unit 205A and the like. The antenna 207 is connected to the wireless terminal unit 201 and transmits / receives radio waves transmitted / received by the wireless terminal unit 201.

  The wireless terminal unit 201 has a function of automatically starting after power supply, detecting a wireless signal transmitted from the base station 100, and automatically connecting to the base station 100. The terminal base station units 205A, 205B, and 205C can select either the base station mode or the terminal mode (ad hoc communication connection mode) according to an instruction from the relay control unit 204. In the base station mode, the terminal base station unit 205A, 205B, and 205C Has a function to connect.

  FIG. 3 is a block diagram illustrating a configuration example of the relay control unit 204 according to the embodiment of this invention.

  The relay control unit 204 of this embodiment is mainly configured by a network processor 1201.

  The network processor 1201 has an I / O port 1202 and a memory port 1203, is connected to the terminal base station units 205A to 205C and the wireless terminal unit 201 via the I / O port 1202, and is connected to the main memory unit via the memory port 1203. 202 and the auxiliary storage unit 203. The main storage unit 202 stores data used when data processing is performed. The auxiliary storage unit 203 stores various data necessary for the operation of the relay control unit 204.

  A crystal oscillator 1204 is connected to the network processor 1201. The crystal oscillator 1204 supplies a clock signal for the network processor 1201 to operate. The network processor 1201 is supplied with power from the power supply device 1205.

  FIG. 4 is a block diagram illustrating a configuration example of the terminal base station unit 205A according to the embodiment of this invention. 4 shows a configuration example of the terminal base station unit 205A, the terminal base station units 205B and 205C also have the same configuration and function.

  The terminal base station unit 205A includes a baseband unit 1301, a DAC / ADC 1302, a bandpass filter 1303, a front end module (FEM) 1304, and a connector 1305.

  The baseband unit 1301 processes a baseband signal. The DAC / ADC 1302 generates an analog signal by digital-to-analog conversion of the baseband signal, and generates a baseband signal by analog-to-digital conversion of the analog signal. The band pass filter 1303 passes or blocks a signal having a specific frequency. The front end module 1304 has functions such as amplifying and distributing analog signals. An antenna 206 is connected to the connector 1305.

  The baseband unit 1301 has a function of communicating with the relay control unit 204 using a digital signal, and outputs a digital signal converted from an analog signal received from the mobile terminal 1 to the relay control unit 204. Further, the baseband unit 1301 converts the data output from the relay control unit 204 into an analog signal and transmits it to the mobile terminal 1.

  4 has a MIMO configuration having a plurality of transmission / reception units, it may have one transmission / reception unit.

  Next, processing executed by the wireless relay device 200 will be described with reference to FIG.

  The wireless repeater 200 starts to supply power to the wireless terminal unit 201 and the wireless terminal unit 201 starts autonomously (step 301).

  After being activated, the wireless terminal unit 201 is connected to the base station 100 via a wireless line (step 302). After connecting to the base station 100, the wireless terminal unit 201 periodically acquires the electric field strength of the connected wireless channel, and notifies the relay control unit 204 of the acquired electric field strength value (step 303).

  The relay control unit 204 stores the acquired electric field strength in the auxiliary storage unit 203 and updates the stored content every time it is notified. The relay control unit 204 compares the electric field strength notified from the wireless terminal unit 201 with a predetermined threshold value and determines whether the electric field strength is a medium / strong electric field or a weak electric field (step 304).

  As a result of the determination, when the electric field strength notified from the wireless terminal unit 201 is a weak electric field, a process (FIG. 7) at the time of the weak electric field is executed (step 307). On the other hand, when the electric field strength is a medium / strong electric field (a state in which the charge dependency is medium or strong), the relay control unit 204 activates the terminal base station units A and B (205A and 205B) in the base station mode, The state of the base station parts A and B (205A and 205B) is changed to a state waiting for a communication connection request from the portable terminal 1 (step 305).

  After that, when there is a connection request from the mobile terminal 1 to the terminal base station parts A and B (205A and 205B), the terminal base station parts A and B (205A and 205B) give out the connection ID and wirelessly communicate with the mobile terminal 1 Connect the line.

  Also, the relay control unit 204 activates the terminal base station unit C (205C) in the terminal mode, and changes the state of the terminal base station unit C (205C) to an ad hoc communication connection request waiting state (step 306). Processing in the ad hoc communication connection request waiting state will be described later with reference to FIG.

  Here, a method of storing the electric field strength in the auxiliary storage unit storage unit 203 will be described with reference to FIG.

  The electric field strength acquired from the wireless terminal unit 205 is temporarily stored in the temporary storage area 1403 of the main storage unit 202 via the I / O port 1202 of the network processor. Thereafter, the electric field strength is stored in the auxiliary storage unit 203 via the memory port 1203. The auxiliary storage unit 203 has a storage area divided in units of data to be stored. In the present embodiment, a wireless terminal field strength storage area 1402 for storing the field strength is predetermined in a plurality of data storage areas 1401, and the field strength is stored in the determined wireless terminal field strength storage area 1402. Is stored.

  Next, an operation sequence during a weak electric field will be described with reference to FIG.

  First, the relay control unit 204 activates the terminal base station unit A (205A) in the terminal mode (step 401). The terminal base station part A (205A) searches for a radio channel capable of ad hoc communication transmitted by the adjacent radio repeater 200 (step 402), and determines whether there is a communicable channel (step 403). .

  As a result of the search, if there is no radio channel capable of ad hoc communication, processing when ad hoc communication is not possible (FIG. 8) is executed (step 412). On the other hand, if there is a radio channel capable of ad hoc communication, the ad hoc communication line is connected using the radio channel capable of ad hoc communication (step 404). The ID and password required for the ad hoc communication connection are those stored in advance in the auxiliary storage unit 203. Then, when connecting the ad hoc communication line, the terminal base station units 205 are connected to each other by checking the ID and password stored in advance in the auxiliary storage unit 203.

  After establishing an ad hoc communication line with the adjacent radio repeater 200, the relay control unit 204 transmits a connection permission request in the slave mode to the adjacent radio repeater 200 (master) (step 405). ). When a reply notification is received from the wireless relay device 200 as the parent device (step 406), the relay control unit 204 determines whether connection in the child device mode is permitted (step 407). Note that the parent device may include the number of portable terminals 1 permitted to connect to the child device in the reply notification. By notifying the number of mobile terminals that are allowed to be connected and limiting the number of mobile terminals 1 that are connected, it is possible to ensure the throughput of the master unit.

  When the slave connection permission notification is received from the wireless relay device 200 as the parent device, the wireless terminal unit 201 is stopped (step 408). The wireless terminal unit 201 stops after disconnecting the wireless line with the base station 100. By stopping the wireless terminal unit 201, the load on the backhaul side can be reduced.

  After the wireless terminal unit 201 is stopped, the relay control unit 204 activates the terminal base station unit B (205B) in the base station mode, and transitions to a state waiting for a communication connection request from the mobile terminal 1 (step 409). Thereafter, the relay control unit 204 activates the terminal base station unit C (205C) in the terminal mode, and makes a transition to an ad hoc communication connection request wait (step 410). Processing in the ad hoc communication connection request waiting state will be described later with reference to FIG. When there is a connection request from the mobile terminal 1 to the terminal base station part B, the connection ID is issued, and the mobile terminal 1 is connected to the wireless line.

  On the other hand, when a slave unit connection non-permission notification is received from the wireless relay device 200 serving as the master unit, the connection in the slave unit mode is not permitted, and therefore the relay control unit 204 determines that another wireless relay device 200 serving as the master unit is used. In order to search for an ad hoc communication connection destination wireless channel from the communicable channel (step 411). Thereafter, the terminal base station part A (205A) searches for an ad hoc communication possible channel again (steps 402 and 403).

  Next, an operation sequence when ad hoc communication is impossible will be described with reference to FIG.

  The relay control unit 204 activates the terminal base station units A and B (205A and B) in the base station mode, and transitions the state to the communication connection request waiting state from the mobile terminal 1 (step 501). In addition, when there is a connection request from the mobile terminal 1 to the terminal base stations A and B (205A, B), the connection ID is issued and the mobile terminal 1 is connected to the wireless line.

  Thereafter, the terminal base station part C (205C) is activated in the terminal mode, and the state is shifted to awaiting an ad hoc communication connection request (step 502). Processing in the ad hoc communication connection request waiting state will be described later with reference to FIG.

  In the process when ad hoc communication is disabled shown in FIG. 8, even if the electric field is weak, if there is no radio repeater 200 capable of ad hoc communication, the radio base station 100 is connected via the radio terminal unit 201. By doing in this way, even if throughput is bad, the communication opportunity of the portable terminal 1 is securable.

  Next, an operation sequence when a connection request is received while waiting for an ad hoc communication connection request will be described with reference to FIG.

  The radio repeater 200 activates the terminal base station unit C (205C) in the terminal mode so as to receive the ad hoc communication connection request from the adjacent radio repeater 200, and changes the state to the ad hoc communication connection request waiting state. ing. When an ad hoc communication connection request is received (step 601), the relay control unit 204 determines whether it is operating as a slave (step 602).

  As a result, when the device itself is not operating in the child device mode, it is determined whether or not the child device is connected according to the child device connection determination sequence (see FIG. 10) (step 608).

  On the other hand, when the mobile terminal itself is operating in the handset mode, it transmits a handset connection permission request to the wireless relay device 200 that is the base unit (step 603), and receives a reply notification from the base unit (step 604).

  As a result, when the reply notification from the parent device indicates that the child device connection is permitted (Yes in step 605), the connection permission is notified to the wireless relay device 200 that is the ad hoc communication connection request source (step 606). On the other hand, when the reply notification from the parent device is not permitted to connect to the child device (No in step 605), the rejection of the connection is notified to the wireless relay device 200 that is the ad hoc communication connection request source (step 607).

  When the number of mobile terminals 1 that are allowed to be connected to the slave unit is notified from the master unit, the permission of the already assigned mobile terminal 1 is transmitted without transmitting a slave unit connection permission request to the master unit. A part of the number may be given to the radio repeater 200 which is the ad hoc communication connection request source.

  Next, the slave unit connection determination sequence will be described with reference to FIG.

  When the adjoining wireless repeater 200 is connected by ad hoc communication, when receiving an ad hoc communication connection request from the relevant wireless repeater 200, the relay control unit 204 acquires the electric field strength from the wireless terminal unit 201 (step 701). Then, the obtained electric field strength is compared with a predetermined threshold value to determine whether the electric field is a medium / strong electric field or a weak electric field (step 702).

  If the acquired electric field strength is a weak electric field, the wireless relay device 200 that is the ad hoc communication connection request source is notified of connection rejection (step 705). On the other hand, when the acquired electric field strength is a medium / strong electric field, the relay control unit 204 determines whether or not it is in a congestion state from the current data processing amount (step 703).

  If the relay control unit 204 determines that it is not in the congestion state, the relay control unit 204 notifies the connection permission to the wireless relay device 200 that is the ad hoc communication connection request source (step 704). On the other hand, if it is determined that the state is congested, the wireless relay device 200 that is the ad hoc communication connection request source is notified of connection rejection (step 705).

  FIG. 11 is a diagram illustrating an example in which the wireless relay devices 200 are connected by ad hoc communication according to the above-described sequence.

  Since the wireless repeater 200A is under a strong electric field, it connects the base station 100 and the wireless line via the wireless terminal unit 201. On the other hand, the radio repeaters 200B and 200C do not connect the base station 100 and the radio channel via the radio terminal unit 201. This is because, when the electric field is weak, the base station 100 is not connected to the radio line, and is connected to the adjacent radio repeater 200B by ad hoc communication according to the operation sequence when the electric field is weak (FIG. 7). By such an operation, it is possible to provide a stable wireless service by actively using a wireless line that is connected in a medium / strong electric field.

  The mobile terminal 1 connected to the wireless relay device 200A performs data communication with the base station 100 through the wireless relay device 200A. On the other hand, the mobile terminal 1 connected to the wireless relay device 200B and the mobile terminal 1 connected to the wireless relay device 200B are routed by the relay control unit 204 in the wireless relay devices 200B and 200C, and the wireless relay device 200A. To perform data communication with the base station 100.

  Since the position of the train moves, the wireless environment changes with time. The operation when the wireless environment changes will be described below.

  FIG. 12 is a flowchart of processing when the wireless environment between the wireless terminal unit 201 and the base station 100 changes in the embodiment of the present invention.

  The wireless repeater 200 acquires the electric field strength from the wireless terminal unit 201 and stores the acquired electric field strength in the auxiliary storage unit 203. The relay control unit 203 periodically acquires the electric field strength stored in the auxiliary storage unit 203 (step 901). It is determined whether the acquired electric field strength is a medium / strong electric field or a weak electric field (step 902). As a result of the determination, if the acquired electric field strength is a medium / strong electric field, the process returns to step 901 to repeat periodic acquisition of the electric field strength.

  On the other hand, when the acquired electric field strength is a weak electric field, it is determined that it is difficult to continue a stable service by radio. Then, it is determined whether or not a slave unit is connected to the own radio repeater 200 (step 903). If the slave unit is connected, the electric field strength decrease notification is transmitted to the slave unit by the process shown in FIG. 13 (step 904). On the other hand, when the handset is not connected, the weak electric field transition sequence is executed. The weak electric field transition sequence will be described later with reference to FIG.

  FIG. 13 is a flowchart of the process when the slave unit receives the electric field strength decrease notification in the embodiment of the present invention.

  In step 904 of FIG. 12 described above, the wireless relay device 200 that is the slave device receives the electric field strength decrease notification from the wireless relay device 200 that is the parent device (step 1001), and the slave device is subordinate to the own wireless relay device 200. Is connected (step 1002).

  As a result, when the slave unit is connected, a field strength decrease notification is transmitted to the connected slave unit (step 1009). On the other hand, when the handset is not connected, the wireless terminal unit 201 installed in the own wireless repeater 200 is activated (step 1003). The wireless terminal unit 201 connects the base station 100 and the wireless line after activation (step 1004).

  After the wireless line is connected, the relay control unit 203 acquires the electric field strength from the wireless terminal unit 201 (step 1005), and determines whether the acquired electric field strength is a medium / strong electric field or a weak electric field (step 1006). When the acquired electric field strength is a weak electric field, in order to search for another wireless relay device 200 as a parent device, a slave unit connection operation is performed according to the operation sequence at the time of the weak electric field shown in FIG. 7 (step 1010).

  On the other hand, if the acquired electric field strength is a medium or strong electric field, the ad hoc communication connection with the base unit is disconnected (step 1007), and then the terminal base station unit A is activated in the base station mode to operate as the base unit Then, the state is changed to a communication connection request waiting state from the portable terminal 1 (step 1008). When a connection request is issued from the mobile terminal 1 to the terminal base station part A (205A), a connection ID is issued and the mobile terminal 1 is connected to the wireless line.

  FIG. 14 is a flowchart of processing executed by the parent device when the electric field strength becomes a weak electric field in the embodiment of the present invention.

  The relay control unit 203 determines whether the mobile terminal 1 is connected to the terminal base station unit A (205A) (step 1101).

  As a result, when the portable terminal 1 is not connected, an adjacent wireless relay device 200 capable of ad hoc communication connection is searched according to the operation sequence in the weak electric field shown in FIG. 7 (1002). On the other hand, when the mobile terminal 1 is connected, the electric field strength is acquired again (step 1102), and it is determined whether the acquired electric field strength is a medium / strong electric field or a weak electric field (step 1104).

  As a result, when the acquired electric field strength is a weak electric field, since the weak electric field state continues, the mobile terminal 1 connected to the terminal base station part A (205A) is disconnected (step 1105). On the other hand, when the re-acquired electric field strength is other than the weak electric field (medium / strong electric field), the wireless line to the mobile terminal 1 connected to the terminal base station part A (205A) is disconnected, as shown in FIG. The electric field strength is periodically acquired according to the sequence (step 1106).

  As described above, the wireless relay device 200 according to the embodiment of the present invention is wirelessly connected to the base station 100 via the wireless terminal unit 201 after activation. In addition, a relay service between the mobile terminal 1 and the base station is provided by activating the terminal base station unit 205 and establishing a wireless connection with the surrounding mobile terminal 1. The wireless terminal unit 201 acquires the electric field strength, and the relay control unit 204 grasps the wireless environment of the wireless relay device 200. As a result, when the wireless environment is good, the wireless terminal unit 201 connects the base station 100 and provides a wireless service. On the other hand, when the wireless environment is bad, the other adjacent wireless repeater 200 is searched, a wireless line is connected to the other searched wireless repeater 200, the operation of the wireless terminal unit 201 is stopped, and the other A wireless service is provided via the wireless relay device 200. Also, when the wireless environment is bad and the connectable wireless repeater 200 cannot be searched, the wireless terminal unit 201 is used to provide a service.

  For this reason, a stable wireless service can be provided according to the wireless environment. In particular, even if the wireless environment of the repeater installed on the train varies from vehicle to vehicle, the wireless repeater with good wireless environment becomes the master unit, and the wireless repeater with poor wireless environment becomes the slave unit. Good and high quality wireless service can be provided.

1 mobile terminal 100 base station 200 wireless relay unit 201 wireless terminal unit 202 main storage unit 203 auxiliary storage unit 204 relay control unit 205A terminal base station unit A
205B Terminal base station part B
205C Terminal base station part C
206 Terminal base station antenna 207 Radio terminal antenna

Claims (10)

A wireless relay system comprising: a base station that provides a wireless communication area; and a wireless relay that relays communication between the base station and a wireless terminal,
The wireless repeater is
A wireless terminal connected to the base station;
A plurality of base station units connected to the other wireless repeater and the wireless terminal;
A control unit for controlling operations of the wireless terminal unit and the base station unit,
The controller is
Obtain radio environment of radio waves transmitted from the base station,
Depending on the acquired wireless environment, whether to connect to the base station via the wireless terminal unit, or to stop the operation of the wireless terminal unit and connect to another wireless relay device via the base station unit, A wireless relay system characterized by determining The base station unit is connected to the other wireless repeater and the wireless terminal by a wireless LAN,
Among the plurality of base station units, at least first and second base station units operate in a base station mode connectable to the wireless terminal, and a third base station unit connects to the other radio repeater. The wireless relay system according to claim 1, wherein the wireless relay system operates. The base station unit is connected to the other wireless repeater and the wireless terminal by a wireless LAN,
Among the plurality of base station units, the first base station unit operates in a terminal mode in which the other radio relay unit can be connected as a base unit, and at least the second base station unit is a base station mode in which the radio terminal can be connected. The wireless relay system according to claim 1, wherein the third base station unit operates in an ad hoc mode connectable with the other wireless relay device.   The wireless relay device searches for another wireless relay device when the acquired wireless environment is bad and connects to the searched wireless relay device via the base station unit. The wireless relay system according to any one of the above.   The wireless relay device connects to the base station via the wireless terminal unit when the acquired wireless environment is bad and wireless connection to the other wireless relay device is not possible. 4. The wireless relay system according to any one of 4 above.   6. The wireless relay device according to claim 1, wherein when receiving a connection request from the other wireless relay device, the wireless relay device determines whether or not the connection is permitted depending on whether the wireless relay device is in a congested state. A wireless relay system according to any one of the above.   The wireless relay device, when the acquired wireless environment deteriorates, notifies the wireless relay device connected to the wireless relay device as a slave unit of the deterioration of the wireless environment. The wireless relay system according to any one of the above.   The wireless relay device connects to the base station via the wireless terminal unit when receiving a notification of deterioration of wireless environment from a wireless relay device connected as a parent device. 8. The wireless relay system according to any one of 7.   The wireless relay system according to claim 1, wherein the wireless repeater connects the other wireless repeater with a wire. A wireless repeater that relays communication between a base station that provides a wireless communication area and a wireless terminal,
A wireless terminal connected to the base station;
A plurality of base station units connected to the other wireless repeater and the wireless terminal;
A control unit for controlling operations of the wireless terminal unit and the base station unit,
The controller is
Obtain radio environment of radio waves transmitted from the base station,
Depending on the acquired wireless environment, whether to connect to the base station via the wireless terminal unit, or to stop the operation of the wireless terminal unit and connect to another wireless relay device via the base station unit, A wireless repeater characterized in that

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