JP2008172283A - Multi-hop radio communication system and configuration method thereof, and radio communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a configuration method of a multi-hop radio communication system that has a simple configuration, prevents throughput characteristics from deteriorating without increasing costs sharply, can improve communication performance, and can solve the problem of unfairness in the communication performance even if the number of access points and mobile terminals that can be stored increases in a multi-hop radio network, and to provide a multi-hop radio communication system and a radio communication device. <P>SOLUTION: In the radio communication among a plurality of radio communication base stations, radio transmission and reception for relay in one radio communication base station are performed by a different interface and a channel having a different frequency. In this case, a channel in an interface used by radio transmission for relay is dynamically adjusted to the channel of a frequency in an interface for reception used by the radio communication base station of one's reception party. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  In the present invention, a plurality of access points for accommodating wireless terminals are connected by wireless communication using technology using a wireless LAN device or the like, and wirelessly connected to an access point connected to a backbone network such as the Internet in multiple stages. The present invention relates to a configuration method of a multi-hop wireless communication system relayed by the wireless communication system, a multi-hop wireless communication system, and a wireless communication apparatus.

JP-A-2005-130193 JP 2004-364287 A JP 2003-069600 A JP 2002-325273 A JP 2002-320256 A

  With the rapid development and popularization of wireless LAN devices in recent years, it is expected to establish a communication environment that allows mobile terminals such as notebook personal computers and PDAs (Personal Digital Assistants) to be connected to backbone networks such as the Internet from anywhere. Has been. In a wireless LAN based on the IEEE 802.11 standard that is currently in widespread use (hereinafter simply referred to as “wireless LAN”), a wireless communication base station that accommodates wireless terminal stations as mobile terminals such as notebook personal computers and PDAs is used. An access point (AP) having a role is connected to a backbone network such as the Internet by a wired cable.

  Therefore, in order to expand the area of the wireless LAN that can be used by the wireless terminal station, when arranging a large number of access points in the infrastructure mode, it is necessary to lay communication cables to the installation locations of all the access points, There is a problem that the installation cost is greatly increased.

  Therefore, in order to solve such a problem, as shown in FIG. 20, the access points are also connected by a wireless LAN similar to a normal wireless LAN, and a plurality of access points are relayed in multiple stages by wireless communication. Therefore, the configuration of a multi-hop wireless network that can easily expand the wireless LAN area while suppressing the installation cost is being studied. Currently, as a wireless mesh network, standardization in IEEE 802.11s TG (Task Group) Work is underway. In such a multi-hop wireless network, it is not necessary to connect all the access points to the wired network, so that the range of use of the wireless LAN can be easily expanded.

  By the way, when configuring a multi-hop network using wireless LAN access points, throughput increases as the number of hops, which is the number of access points relayed wirelessly from an access point accommodating a wireless terminal station, increases. It is known that various problems such as a significant deterioration in characteristics, exposed terminal problems, and unfairness in communication performance occur.

  More specifically, one of the multi-hop network configurations that can be used in the wireless LAN system is a wireless distribution system (WDS). This wireless distribution system not only accommodates wireless terminals in the access point, but also functions as a bridge to other access points, and provides a function of relaying data to an access point connected to the Internet or the like by wire Is.

  According to the wireless distribution system, the access point can achieve both communication with a mobile terminal and communication between access points by using only a single wireless interface, so the configuration is very simple. It has the advantage of being.

  However, in wireless distribution systems, due to restrictions on system specifications, it is necessary for all wireless terminals and access points to use the same wireless channel, and as the number of wireless terminals and access points increases, In this case, the throughput characteristic is remarkably lowered, and the communication performance is deteriorated.

  That is, among the above access points, for example, at an access point connected to a backbone network such as the Internet, communication with a mobile terminal accommodated by the access point, relay between adjacent access points, and from the access point to the Internet, etc. Since it is necessary to communicate with the backbone network, the throughput characteristics are significantly lowered and the communication performance is deteriorated as the number of wireless terminals and access points increases.

  Among the above access points, in the access points connected to the backbone network such as the Internet and the access points adjacent to the access points, the throughput accompanying the increase in the number of wireless terminals and access points as described above. Due to the significant deterioration in characteristics, mobile terminals accommodated by access points connected to a backbone network such as the Internet or access points adjacent to the access point have a throughput characteristic compared to other remote access points. However, there is a problem that communication performance is unfairly reduced.

  Furthermore, the multi-hop wireless network employing the wireless distribution system has a problem that a hidden terminal problem is likely to occur. The wireless distribution system employs a method that enables autonomous distributed access control, and is configured such that data is transferred by an access point and a mobile terminal in the same procedure. The basic operation of this data transfer is to check the usage status of the radio channel in advance so that a mobile terminal trying to transmit a signal does not collide with a signal transmitted by another mobile terminal. If there is, the signal is transmitted immediately, and if it is “in use”, the transmission is postponed until the unused state.

  As shown in FIG. 21, the hidden terminal problem is that a mobile terminal C that does not receive radio waves transmitted from the mobile terminal A to the mobile terminal B even though the mobile terminal A is communicating with the mobile terminal B. Since the state of being “in use” cannot be known, the mobile terminal B in communication is requested to communicate, and a collision of transmission signals occurs.

  Therefore, countermeasures by exchanging RTS / CTS (Request to Send / Clear to Send) signals are indispensable for such a hidden terminal problem. However, in a network environment using a single channel, RTS / CTS exchange is required. It has become clear that a problem called an exposed terminal problem is newly generated due to the problem that the communication performance is remarkably deteriorated or the link is severely disconnected.

  Here, the exposed terminal problem will be described with reference to FIG. Now, as shown in FIG. 22, the area where each node can communicate directly is limited to adjacent nodes, and communication is performed in the order of (1) to (6) between the nodes. First, it is assumed that the node 1 performs RTS / CTS exchange with the node 2, and then performs DATA / ACK (Acknowledgment) exchange as shown in (3) and (6). Node 3 enters the NAV period in order to receive the CTS frame from node 2. Here, the NAV period refers to a period of radio channel occupation time (Network Allocation Vector) until an ACK frame that is information included in an RTS frame or a CTS frame is returned.

  Next, it is assumed that the node 3 attempts the RTS / CTS exchange with the node 3 as a transmission destination as shown in (4) of FIG. 22 during the NAV period. However, in this case, since the node 3 is in the NAV period, the CTS is not returned to this RTS. Therefore, the RTS / CTS exchange fails between node 4 and node 3. This phenomenon is called NAV Blocking. Here, since the node 3 has intercepted the data communication of the adjacent node 2, communication with the other node 4 has been suppressed, and this problem is called a terminal problem.

  Several proposals have been made for techniques for preventing deterioration in communication performance due to the exposed terminal problem. First, in order to prevent erroneous detection of link disconnection in TCP (Transmission Control Protocol), there is a method of reducing the maximum congestion window size of TCP. In this method, 1 or 4 is used as the maximum congestion window size of TCP. This increases the packet transmission interval between access points, and prevents erroneous detection due to link disconnection due to RTS / CTS exchange failure.

  However, with this method, it is necessary to be aware of the transport layer, there is a possibility that sufficient throughput may not be obtained in an environment with a large end-to-end delay, UDP (User Datagram Protocol) It has problems such as being able to cope.

  Further, in order to avoid erroneous detection of link disconnection, the value of SRL (Short Retry Limit) which is the maximum value of SSRC (Station Short Retry Count) which is a counter of the number of times of failure of RTS / CTS exchange is set large, and RTS A method for increasing the allowable range of the number of failed / CTS exchanges has been proposed.

  However, this alone does not fundamentally solve the exposed terminal problem, and not only the virtual carrier sense error function cannot be solved, but rather, the RTS / CTS exchange failure continues, which causes unnecessary surroundings. There is a problem that the influence of the carrier sense error function that suppresses the frame transmission of the mobile terminal becomes large.

  In view of this, there has been proposed a method of transmitting a CRTS (Cancel RTS) for canceling the NAV period to a node that has already received the RTS when the RTS / CTS exchange has failed.

  In this method, a better throughput than the existing method is obtained, but the exposed terminal problem is not solved, it cannot be said that a high throughput is obtained, and by increasing the value of the SRL However, there is a problem that detection of link disconnection is delayed due to continued failure of the RTS / CTS exchange.

  Furthermore, a method for preventing reception of unnecessary RTS / CTS by giving directivity to the antenna has been studied, but in this method, each node needs to point the antenna at the communication partner, In addition to a decrease in flexibility when arranging access points, there remains a problem that it is difficult to form an adjacent relationship with a plurality of access points.

  As techniques related to such problems, those disclosed in JP-A-2005-130193, JP-A-2003-69600, JP-A-2002-325273, JP-A-2002-320256, etc. It has already been proposed.

The wireless communication device according to the above-mentioned Japanese Patent Application Laid-Open No. 2005-130193 is wireless in a wireless communication system including a wireless communication device as a wireless communication base station existing on a wired LAN network and a plurality of other wireless communication devices. In communication equipment,
The wireless communication device includes two or more wireless signal transmission / reception units, a wireless communication control unit, and a storage unit,
The wireless communication control unit performs control to transfer reception data from another wireless communication device to another wireless communication device, and captures a plurality of information transmission destination candidates and compares them with preset conditions. With a protocol controller,
The storage unit stores a plurality of information transmission destination candidates, a comparison condition of information transmission destination candidates, and a multi-hop information storage unit that stores a result of comparison according to setting conditions, and the multi-hop protocol control unit includes: While communicating using one of the wireless signal transmitting / receiving units, the other wireless signal transmitting / receiving unit is used to detect other wireless communication devices existing in the vicinity and exchange information with each other, Captures a plurality of other information transmission destination candidates, stores in the storage unit a comparison result obtained by comparing the information transmission destination during communication and the plurality of captured information transmission destinations according to preset conditions, When communication with the wireless signal transmission / reception unit cannot be maintained, another information transmission destination is selected according to the comparison result, and communication with the selected wireless communication device is started.

Further, the communication method according to the above Japanese Patent Application Laid-Open No. 2004-364287 is a method in which the plurality of base elements adaptively communicate with each other in a wireless mesh network environment including a plurality of base elements,
Operation of the first base element of the plurality of base elements to communicate with a destination via a second base element of the plurality of base elements using a first directional antenna beam;
Determining that the first infrastructure element can alternatively communicate with the destination via a third infrastructure element of the plurality of infrastructure elements;
An operation of the first base element communicating with the destination via the third base element using a second directional antenna beam.

  Further, the relay method of the multi-hop network according to the above-mentioned Japanese Patent Application Laid-Open No. 2003-69600 introduces a WM (wireless middleware) layer between the IP layer and the MAC layer in the wireless node, and the destination address and relay node in the WM layer And the routing table for managing the port to transmit, the WM header of the packet received in the WM layer is analyzed, and if it is a packet addressed to its own node, the packet is taken over to the IP layer, and if it is a packet addressed to another node, A network interface is selected based on the routing table, and relaying is performed using the network interface.

  Further, the wireless communication system according to the above-mentioned JP-A-2002-325273 has a plurality of wireless stations, each wireless station has at least one wireless channel for packet wireless communication, and each wireless station has another In a wireless communication system capable of communicating directly with or via at least one wireless station, each wireless station communicates with a nearby wireless station in a centralized control access or autonomous distributed access for each wireless channel. In the case of centralized control access, each radio station adaptively controls the transmission right and transmits a signal according to the control of the own station for each radio channel, or control of the master station The centralized control access and the autonomous distributed access are configured to be performed for each wireless station and for each wireless channel by dividing in time. It is.

  Further, in the frequency allocation system for a wireless network according to the above Japanese Patent Laid-Open No. 2002-320256, a plurality of wireless stations are distributed, and each wireless station has a directional antenna with each of a plurality of nearby wireless stations. In a frequency assignment system for a radio network that establishes radio links facing each other, topology analysis means for analyzing the topology of the network, and category classification means for classifying each radio link into a plurality of categories based on the analysis result of the topology Frequency allocation means for assigning different frequency slots to each category; and frequency operation means for operating each radio link in the frequency slot assigned to the category to which the radio link belongs, wherein the category classification means includes: Multiple reference standards established by the reference radio station with other radio stations It classifies each link into different categories, in which the other radio links in a predetermined positional relationship with each reference radio link, and configured to classify the same category as the reference radio link.

  However, the conventional technique has the following problems. That is, in the case of the wireless communication device according to the above Japanese Patent Application Laid-Open No. 2005-130193, when a change occurs in an information transmission path configured by a wireless communication base station and a plurality of wireless communication devices, an immediate response is made. Although it is possible, there are problems such as an exposed terminal problem, a decrease in throughput when the number of access points and mobile terminals increases, and an unfairness in communication performance between mobile terminals cannot be resolved. Yes.

  In addition, in the case of the communication method according to Japanese Patent Application Laid-Open No. 2004-354287, as described above, each node needs to point the antenna at the communication partner, and the flexibility when arranging the access point is reduced. There is a problem that it is difficult to form an adjacent relationship with a plurality of access points.

  Furthermore, in the case of the relay method of the multi-hop network according to Japanese Patent Application Laid-Open No. 2003-69600, the exposed terminal problem, the throughput decrease when the number of access points and mobile terminals increases, and the communication performance between mobile terminals The problem is that it is impossible to eliminate the unfairness.

  Further, in the case of the wireless communication system according to Japanese Patent Laid-Open No. 2002-325273, the centralized control access and the autonomous distributed access are performed for each wireless station and for each wireless channel divided in time. However, when the number of access points and mobile terminals increases, there is a problem that the throughput must be reduced and the unfairness of communication performance between mobile terminals cannot be resolved. is doing.

  Furthermore, in the case of the frequency allocation system according to Japanese Patent Application Laid-Open No. 2002-320256, since a directional antenna is assumed, as described above, flexibility in arranging access points is reduced, and a plurality of It is difficult to form an adjacent relationship with other access points, and it is necessary to provide transmission / reception units having different frequencies for each of the plurality of radio stations, resulting in a complicated configuration and a significant increase in cost. is doing.

  Therefore, the present invention has been made to solve the above-described problems of the prior art, and the object of the present invention is to increase the number of access points and mobile terminals that can be accommodated in a multi-hop wireless network. Even so, the configuration is simple and the communication performance can be improved by preventing the deterioration of the throughput characteristics without significantly increasing the cost, and the unfairness of the communication performance can be eliminated. It is an object of the present invention to provide a multi-hop wireless communication system configuration method, a multi-hop wireless communication system, and a wireless communication apparatus.

That is, the invention described in claim 1 includes at least one wireless communication base station connected to the backbone network by wire,
In a configuration method of a multi-hop wireless communication system comprising a plurality of wireless communication base stations connected by wirelessly relaying with a plurality of wireless communication base stations including a part of the wireless communication base station,
In radio communication between the plurality of radio communication base stations, relay radio transmission and radio reception for relay in one radio communication base station are performed using channels with different interfaces and different frequencies, and the relay A channel in an interface used for wireless transmission is dynamically configured to a frequency channel in a reception interface used in a receiving radio communication base station. .

  According to the first aspect of the present invention, in radio communication between a plurality of radio communication base stations, relay radio transmission and radio reception for relay in one radio communication base station have different frequencies. By using a channel, the number of radio communication base stations increases, and even when the number of hops relayed between a plurality of radio communication base stations increases, wireless transmission for relaying and wireless reception for relaying, Since channels using different frequencies are used, it is possible to avoid radio channels from competing, and a high throughput can be maintained without a significant decrease in throughput.

  The invention described in claim 2 is the configuration method of the multi-hop wireless communication system according to claim 1, wherein the wireless reception for relay is performed using a channel of a fixed frequency. .

  According to the second aspect of the present invention, in wireless communication between a plurality of wireless communication base stations, relay wireless transmission and wireless reception for relay in one wireless communication base station have different frequencies. Wireless communication in consideration of radio wave interference by dynamically adjusting the channel used in the wireless transmission for relaying to the channel of the frequency used in the receiving wireless communication base station When designing the arrangement of base stations and the channels to be used, it is only necessary to statically set relay radio reception so as not to interfere with adjacent radio communication base stations, thereby facilitating network design.

  Furthermore, the invention described in claim 3 is such that the radio communication base station has a radio communication function for accommodating a mobile terminal that communicates with a mobile terminal, and the radio communication for accommodating the mobile terminal is transmitted to a radio for relay. The method of configuring a multi-hop wireless communication system according to claim 1 or 2, wherein radio reception for transmission and relay is performed using channels having different frequencies.

  The invention described in claim 4 is characterized in that the wireless communication for accommodating mobile terminals used in the adjacent wireless communication base stations is performed using channels having different frequencies. A multihop wireless communication system configuration method according to any one of the above.

Furthermore, the invention described in claim 5 includes at least one or more wireless communication base stations connected to the backbone network by wire,
In a multi-hop wireless communication system comprising a plurality of wireless communication base stations connected by wirelessly relaying with a plurality of wireless communication base stations including a part of the wireless communication base station,
The plurality of wireless communication base stations include a relay wireless transmission means and a relay wireless reception means,
In the multi-hop wireless communication system, the relay wireless transmission unit and the relay wireless reception unit use channels having different frequencies.

  According to a sixth aspect of the present invention, the radio communication base station includes radio communication means for accommodating a mobile terminal that communicates with a mobile terminal, and the radio communication means for accommodating the mobile terminal is configured for the relay. 6. The multi-hop wireless communication system according to claim 5, wherein communication is performed using channels having different frequencies with said wireless transmission means and relay wireless reception means.

Furthermore, the invention described in claim 7 includes at least one or more wireless communication base stations connected to the backbone network by wire,
In a wireless communication apparatus used in a multi-hop wireless communication system including a plurality of wireless communication base stations connected by wirelessly relaying with a plurality of wireless communication base stations including a part of the wireless communication base station,
The radio communication apparatus as the radio communication base station includes a relay radio transmission means, a relay radio reception means, and a mobile terminal accommodating transmission / reception means,
The relay wireless transmission unit and the relay wireless reception unit use channels having different frequencies.

  According to the invention described in claim 7, the number of radio communication base stations is increased by using channels having different frequencies in the relay radio transmission means and the relay radio reception means, Even when the number of hops relayed between a plurality of wireless communication base stations increases, wireless transmission for relaying and wireless reception for relaying are performed using channels having different frequencies, so that wireless channels compete for each other. This can be avoided, and a significant reduction in throughput does not occur, and high communication performance can be maintained.

  According to the seventh aspect of the present invention, a radio communication apparatus that takes into account radio wave interference by operating a relay radio reception means on a fixed channel and a relay radio transmission means on a variable channel. When designing the arrangement and the channel to be used, it is sufficient to design statically so that the wireless channel set in the wireless receiving means for relay does not interfere with adjacent wireless communication devices, and network design is facilitated.

  The invention described in claim 8 is characterized in that a channel having a different frequency is used in a transmitting / receiving unit for accommodating a mobile terminal between the adjacent wireless communication devices. A wireless communication device.

  In the present invention, the multi-hop wireless network may be an ad hoc network in which a node that relays data itself has mobility, but here, it is mainly installed in a fixed state as a communication base and is mobile. An access point as a wireless communication base station that provides connectivity to a terminal is assumed, and the case of relaying between the plurality of access points by a wireless LAN system is targeted. However, it goes without saying that the data relay node itself may be applied to an ad hoc network having mobility.

  According to the present invention, even if the number of access points and mobile terminals increases in a multi-hop wireless network, the configuration is simple and the degradation of throughput characteristics is prevented without significantly increasing the cost. Thus, it is possible to provide a multi-hop wireless communication system configuration method, a multi-hop wireless communication system, and a wireless communication device that can improve communication performance and eliminate unfairness in communication performance. .

  Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1
FIG. 2 is a schematic configuration diagram showing a multi-hop radio communication system to which the multi-hop radio communication system configuration method according to Embodiment 1 of the present invention is applied.

  As shown in FIG. 2, the multi-hop wireless communication system 1 includes a plurality of access points (AP) 101 to 103 serving as wireless communication base stations that are wireless communication devices, and the plurality of access points 101 to 103. Among them, some access points 101 are connected to a backbone network 150 such as the Internet via a communication cable 160 in a wired manner. The backbone network 150 is not limited to the Internet, but of course includes a wired LAN laid on the site of a predetermined company or factory, such as an intranet (registered trademark). The access point 101 is connected to a terminal 170 made up of a server, a personal computer, etc. via a backbone network 150 made up of the Internet having a communication speed of 100 Mb / s, for example. Of course, the access point 101 connected to the backbone network 150 via the communication cable 160 is not limited to one, and a plurality of access points 101 may be installed. In the illustrated example, only three access points 101 to 103 are shown for convenience, but the number of access points is not limited to this, and it is needless to say that many access points may be arranged over four or more.

  In the multi-hop wireless communication system 1, as shown in FIG. 2, a plurality of access points 101 to 103 including the access point 101 connected to the backbone network 150 via the communication cable 160 are connected to each other between adjacent access points. Are connected to each other via the same wireless communication. Of course, the number of adjacent access points is not limited to one.

By the way, in the first embodiment, at least one wireless communication base station connected to the backbone network by wire,
In a configuration method of a multi-hop wireless communication system comprising a plurality of wireless communication base stations connected by wirelessly relaying with a plurality of wireless communication base stations including a part of the wireless communication base station,
In radio communication between the plurality of radio communication base stations, relay radio transmission and relay radio reception in one radio communication base station are performed using channels having different frequencies, and the relay radio The channel used for transmission is configured to dynamically match the channel of the frequency used by the receiving radio communication base station.

  FIG. 1 is a block diagram showing an access point as a radio communication base station to which a configuration method for a multi-hop radio communication system according to Embodiment 1 of the present invention is applied. Although all access points are basically configured in the same manner, an access point connected to the backbone network 150 is connected to the backbone network 150 via a communication cable 160 by a signal processing unit / transmission unit described later. Has been.

  As shown in FIG. 1, the access point 102 is roughly divided into a transmission unit 110 for communication between access points as a transfer interface, a reception unit 120 for communication between access points as a reception interface, and a terminal accommodation interface. And a transmission / reception unit 130 for terminal-to-terminal communication.

  The transmission unit 110 for communication between access points is used for transmitting data relayed between the access points 101 to 102. The transmission unit 110 for communication between access points is, for example, IEEE 802.11a. It is configured to be able to transmit data to be relayed from the access point communication antenna 113 by selecting a channel defined by standards such as IEEE 802.11b and the transmission partner. It has a function of dynamically adjusting to a reception channel fixed in advance of an access point (for example, access point 101 in the case of FIG. 1).

  A transmission channel variable control unit 111 is connected to the inter-access point communication transmission unit 110, and the transmission channel variable control unit 111 transmits data between the access point communication units 110. The transmission channel used at the time is variably controlled so as to dynamically match the reception channel of the access point of the transmission partner.

  The transmission channel variable control unit 111 includes a reception channel table 112 for each access point. The reception channel table 111 for each access point is stored in a rewritable storage means such as a RAM. Yes.

  On the other hand, the receiving unit 120 for inter-access point communication receives data transmitted from other access points through a receiving channel fixed in advance for each access point by the receiving antenna 121, and receives the received relay data. Is sent to the signal processing unit / transmission unit 140.

  The channel used by the receiving unit 120 for inter-access point communication is determined in advance as a fixed channel. In the example shown in FIG. 2, the access point 101 is 36 ch, the access point 102 is 40 ch, and the access point 103 is set to 44 ch, respectively.

  Further, as shown in FIG. 1, the transmission / reception unit 130 for terminal-to-terminal communication transmits data transmitted from a wireless terminal (STA) in the access point area or a wireless terminal (STA in the access point area). ) Is transmitted / received by the inter-terminal transmission / reception antenna 131, and the reception data received by the inter-terminal transmission / reception antenna 131 and the transmission data to be transmitted are transmitted to the signal processing unit / transmission unit 140. It is configured. As the transmission / reception unit 130 for inter-terminal communication, for example, a module conforming to the IEEE 802.11g standard is used.

  A channel used for transmission / reception in the transmission / reception unit 130 for inter-terminal communication is determined in advance and is set to be different from that of an adjacent access point. In the example shown in FIG. 2, the access point 101 is set to 1ch, the access point 102 is set to 6ch, the access point 103 is set to 11ch, and the channel used between the adjacent access points 101 to 103 is 2 for example. In the case of IEEE 802.11b and IEEE 802.11g in the 4 GHz band, at least 5 channels are set to be different from each other, and the exposed terminal problem between adjacent access points 101 to 103 is not caused.

  In the above configuration, in the multi-hop wireless communication system according to the first embodiment, the multi-hop wireless communication system is configured as described below, and data is transmitted and received between access points.

  That is, in the multi-hop wireless communication system 1 according to the first embodiment, as shown in FIG. 2, a plurality of other access points 102 and 103 are connected to the access point 101 connected to the backbone network 150 such as the Internet. Similar to a wireless LAN, data is relayed between access points constituting a multi-hop wireless network by wireless communication.

  In this multi-hop wireless communication system 1, as shown in FIG. 2, an access point 101 connected to a backbone network 150 such as the Internet is installed, and a position sequentially separated from the access point 101 by a predetermined distance The other access points 102 and 103 are installed. As described above, these access points 102 and 103 are not connected by the wired communication cable 160, and relay data between access points by wireless communication as in the case of wireless LAN.

  Considering the case where data is transmitted from the mobile terminal (STA3) 303 used in the area 203 of the access point 103 to the server 170 connected to the backbone network 150 such as the Internet, the mobile terminal (STA3) 303 Then, predetermined data is transmitted to the access point 103 using the 11ch frequency which is a channel for accommodating the terminal of the access point 103.

  Then, as shown in FIG. 1, the access point 103 receives the data transmitted from the mobile terminal (STA3) 303 using the 11ch frequency by the inter-terminal communication antenna 131, and for the inter-terminal communication. The data from the mobile terminal (STA3) 303 received by the antenna 131 is sent to the transmission / reception unit 130 for inter-terminal communication, and the transmission / reception unit 130 for inter-terminal communication demodulates the received data, and the signal processing unit / transmission To part 140.

  The signal processing unit / transmission unit 140 transmits data to the transmission unit 110 for inter-access point communication in order to send the received data to the server 170. The transmission unit 110 for inter-access point communication transmits the data sent from the signal processing unit / transmission unit 140 to the adjacent access point 102, and transmits the data of the adjacent access point 102 via the transmission channel variable control unit 111. 40 channels that are reception channels are acquired by referring to the reception channel table 112 of each access point.

  The inter-access point communication transmitter 110 sets the transmission channel to 40 channels by the transmission channel variable control unit 111 and transmits predetermined data to the adjacent access point 102.

  The relay data transmitted from the transmission unit 110 for inter-access point communication of the access point 103 is received by the communication antenna 121 between the access points 10 of the access point 102 which is an adjacent access point. Data received by the inter-access point communication receiving antenna 121 is sent to the inter-access point communication receiving unit 120, demodulated by the inter-access point communication receiving unit 120, and sent to the server 170. The data is analyzed.

  Then, the receiving unit 120 for inter-access point communication sends data to the signal processing unit / transmission unit 140, and the signal processing unit / transmission unit 140 sends the received data to the server 170. The data is transmitted to the transmitting unit 110. The transmission unit 110 for inter-access point communication transmits the data sent from the signal processing unit / transmission unit 140 to the adjacent access point 101, via the transmission channel variable control unit 111. The 36ch that is the reception channel is obtained by referring to the reception channel table 112 of each access point.

  The inter-access point communication transmitting unit 110 sets the transmission channel to 36 channels by the transmission channel variable control unit 111 and transmits predetermined data to the adjacent access point 101.

  Thus, the relay data transmitted from the transmission unit 110 for inter-access point communication of the access point is received by the communication antenna 121 between the access points of the access point 101, and the received data is the access data. It is sent to the receiving unit 120 for inter-point communication, demodulated by the receiving unit 120 for inter-access point communication, and analyzed as data to be sent to the server 170.

  The inter-access point communication receiving unit 120 sends data to the signal processing unit / transmission unit 140, and the signal processing unit / transmission unit 140 transmits the received data to the server 170. The data from the mobile terminal 303 is transmitted to the server 170 via the backbone network 150 such as the above.

  In the multihop wireless communication system 1, communication between other access points and communication between mobile terminals in the area of the access point are also executed by the same process.

  By the way, in the multi-hop wireless communication system 1, as shown in FIG. 3, even when a new access point 104 is newly added, it is only necessary to install a new access point 104 at a predetermined installation location.

  In this new access point 104, a reception channel for communication between fixed access points and a channel for communication between terminals are allocated in advance so as not to overlap with adjacent access points. The communication channel is configured to use a reception channel for communication between these fixed access points and a channel for communication between terminals.

  At that time, since the adjacent access point 103 is known in advance in the new access point 104, each access point reception channel table 112 of the new access point 104 includes information for communication between access points of the adjacent access points 103. Are received, and communication with the adjacent access point 103 is possible.

  Further, in the existing access point 103 adjacent to the new access point 104, a reception channel (for example, 48ch) for communication between access points used by the new access point 104 is written in each access point reception channel table 112. Not. In this case, for example, at a predetermined timing such as when a new access point 104 is installed, a reception channel (for example, 48 ch) for communication between its own access points is established from the new access point 104 to the adjacent existing access point 103. ), The existing access point 103 can know the reception channel for inter-access point communication used by the new access point 104, and the existing access point 103 is used by the new access point 104. By automatically adding the reception channel for communication between access points to each access point reception channel table 112, communication from the existing access point 103 to the new access point 104 is also possible.

Experimental example 1
In order to confirm the effect of the multi-hop wireless communication system according to the first embodiment, the inventors made a prototype of the multi-hop wireless communication system 1 as shown below and conducted an experiment to actually confirm the effect. .

  As shown in FIG. 4, the experimental multi-hop wireless communication system 1 includes a personal computer 101 having a wireless LAN function as an access point as a server, and a position approximately 8 m away from the personal computer 101 by a linear distance. A personal computer 102 having a wireless LAN function as an access point installed in the personal computer 102, a personal computer having a wireless LAN function as an access point installed at a position approximately 13 m away from the personal computer 102 by a linear distance, Similarly, a personal computer equipped with a wireless LAN function as an access point installed at a position about 13 m away from the personal computer 102 at a straight line distance, and a position about 10 m away from the personal computer at a straight line distance. A system comprising: a personal computer having a wireless LAN function as an installed access point; and a personal computer having a wireless LAN function as a mobile terminal installed at a position approximately 25 m away from the personal computer by a linear distance. Using.

  The first access point 101 uses 40 ch of 5 GHz band as a channel to be used in the reception wireless interface, the second access point 102 uses 52 ch, the third access point 103 uses 48 ch, The access point 104 is set to use 36 ch, the fifth access point 105 uses 64 ch, and the sixth access point 106 uses 60 ch.

  FIG. 5 is a graph showing the results of Experimental Example 1.

  As is apparent from FIG. 5, in Experimental Example 1, even though the number of hops was 4, a very high throughput of 21.4 Mb / s could be maintained, whereas the conventional single unit In the WDS system using this interface, it was found that when the number of hops is 4, the throughput is greatly reduced to 6.1 Mb / s.

Experimental example 2
Next, in order to confirm the effect of the multi-hop wireless communication system according to the first embodiment, the present inventors assume a multi-hop wireless communication system as shown below, perform a computer simulation, and perform the present invention. An experiment was conducted to confirm the effect of.

  As an experimental multi-hop wireless communication system, a system in which six access points 101 to 106 are connected in series by a wireless LAN as shown in FIG. 6 was used. In this simulation model, as shown in FIG. 6, only the access point 101 among the six access points 101 to 106 is connected to the wired network 160 and has a role of a gateway. In addition, it is assumed that all access points 101 to 106 communicate wirelessly, and each access point 101 to 106 accommodates a mobile terminal station in the area.

  In Experimental Example 2 of the present invention, IEEE802.11a is used as a transmission interface and a reception interface for relaying between the access points 101 to 106, and the access point terminal accommodating interface and the mobile terminal are all connected. IEEE802.11a and IEEE802.11g shall be used in order to use channels that do not interfere at points 101-106. All transmission rates were fixed at 54 Mb / s. The distances between the access points 101 to 106 and between the access point and the terminal were all 50 m. Furthermore, it is assumed that each access point 101 to 106 operates as an IP router by changing a network segment between adjacent access points 101 to 106, and routing is performed statically.

  The following four types of methods were used as evaluation targets.

Sing1e: A method using a single channel for relaying
multi: A method of using different interfaces and channels for each relay section
proposed1: Proposed method 1 as a comparative example
proposed2: Proposed method 2, which is an experimental example of the present invention

  Here, as shown in FIG. 7, the proposed method 1 as a comparative example is configured to use the same channel for the interface for accommodating terminals and the interface for relaying. Also, in the proposed method 1 of this comparative example, IEEE802.11a is used as all the radio interfaces of the access point and the terminal.

  In the sing1e method, an access point has two interfaces, one for accommodating terminals and the other for inter-access point connection. This is an existing method in which all the access points use the same channel.

  In the multi method, an access point has a plurality of interfaces, one is used for accommodating terminals and the other is used for connection between access points. Each access point has a dedicated interface. The different channels are set so that interference does not occur in all radio sections. Since the number of interfaces and the number of channels corresponding to the number of adjacent access points are used, a very large number of communication means are required and the cost is increased, but it is considered that an ideal result can be obtained in terms of communication performance.

  Focusing on the throughput characteristics when TCP communication was performed as a performance index, the following items were investigated.

(1) Relationship between the number of hops and throughput characteristics (2) Characteristics when communications with different numbers of hops coexist (3) Differences in characteristics between methods in various communication patterns (4) When multiple communications occur randomly Characteristics In this experimental example, QualNet of Scalable Network Technologies was used as a simulator.

  FIG. 8 is a graph showing the experimental results of examining the relationship between the number of hops and throughput characteristics.

  Here, one hop is defined as passing through one radio link (section) without distinguishing between the mobile terminal and the access point and between the access points.

  In FIG. 6, which is a simulation model, the average throughput characteristic when one TCP flow is transmitted from the mobile terminal 301 (STA1) connected to the access point 101 to the server 170 in the wired network is 1 hop, the mobile terminal FIG. 8 shows the result of examining the same communication from the STA 2 to the server as a 2-hop characteristic and thereafter investigating up to 6 hops.

  As is clear from FIG. 8, when the number of hops is 3 hops or more, the performance of the Single method is remarkably deteriorated, whereas in other methods, even when the number of hops is increased, the performance is hardly deteriorated. I found it impossible. Also, in the proposed method 1 of the comparative example, compared to the performance of 1 hop, the throughput is reduced by about 10% at the second hop, but after the second hop, even if the number of hops increases, the performance degradation does not occur. can not see. Further, the multi method and the proposed method 2 of the present invention have almost the same performance, and it can be seen that in the present invention, an ideal characteristic is obtained in the relationship between the number of hops and the throughput characteristic.

  Next, we investigated the throughput characteristics when multiple communications are concentrated in the gateway connecting the wireless network and the wired network.

  First, in the configuration of FIG. 6, three of the five wireless terminals from the mobile terminal (STA2) to the mobile terminal (STA6) excluding the mobile terminal 301 (STA1) connected to the access point 101 serving as a gateway. The average throughput of each TCP flow when three wireless terminals continue to flow a packet of segment size 1500 bytes for 5 seconds almost simultaneously with TCP with a server connected to the wired network by randomly selecting a wireless terminal The characteristics were investigated.

  FIG. 9 shows the results of 100 simulations.

  Here, “STA → Server” is a characteristic when data is transferred from the three wireless terminals STA to the server, and “Server → STA” is conversely directed to the three wireless terminals STA from the server. Represents the characteristics when data is transferred.

  As can be seen from FIG. 9, the multi method and the proposed method 2 of the present invention achieve high throughput both in the direction from the wireless terminal (STA) to the server and from the server to the wireless terminal (STA). . In the proposed method 1, which is a comparative example, when the access point receives the relay data and transfers it to the wireless terminal connected to the access point, it receives the relay data and transmits the data to the terminal using one local interface. Therefore, it can be seen that the characteristics of communication from the server in the direction of the wireless terminal STA are deteriorated compared to the case of the reverse direction.

  Subsequently, in order to investigate the individual characteristics of each flow when a plurality of communications are concentrated, each of the five wireless terminals from the wireless terminal (STA2) to the wireless terminal (STA6) in the configuration of FIG. An experiment was conducted to generate a TCP flow of books toward the server almost simultaneously.

  In this case, five TCP flows having different hop numbers are concentrated from the access point 102 to the access point 101. The throughput characteristics of each flow are shown in FIG.

  In FIG. 10, the flow 1 is a server from the wireless terminal (STA2), the flow 2 is the server from the wireless terminal STA3, the flow 3 is the server from the wireless terminal (STA4), the flow 4 is the server from the wireless terminal STA5, and the flow 5 is the wireless terminal ( STA6) represents the flow from the server to the server, and average represents the average throughput from flow 1 to flow 5.

  From FIG. 10, it is clear that in the proposed method 1 which is a comparative example, only the flow 1 with a short hop count has a very high throughput, and there is a problem regarding the fairness of the communication performance. In addition, it can be seen that the proposed method 2 which is the present invention has an average throughput of 4.93 Mb / s, and exhibits good characteristics as compared with other methods.

  Next, assuming various communication patterns, we investigated the differences in the characteristics of each method.

  As shown in FIG. 11, the flow 1 is from the wireless terminal (STA1) to the wireless terminal (STA2), the flow 2 is from the wireless terminal (STA4) to the wireless terminal (STA3), and the flow 3 is from the wireless terminal (STA6) to the wireless terminal (STA3). It is defined as a TCP flow that goes to STA5), and the throughput characteristics of each flow when these communications are performed almost simultaneously are obtained.

  FIG. 12 shows the investigation result in the traffic pattern 1 described above.

  Here, average indicates the average throughput of flows 1 to 3. In this communication pattern, although there is no overlapping part of the wireless section, the Sing1e method has a significant performance degradation, and the problem that there is one channel used for relay between access points is remarkable. Yes. In the proposed method 1 which is a comparative example, since the relay data is received and data is transmitted to the terminal by one local interface, the throughput is lower than that of the proposed method 2 of the multi method and the present invention. In all three cases, the same throughput is obtained.

  Next, as shown in FIG. 13, flow 1 is defined as a TCP flow from the wireless terminal (STA3) to the server, and flow 2 is defined as a TCP flow from the wireless terminal (STA2a) to the wireless terminal (STA2b). The throughput characteristics of each flow when it was performed almost simultaneously were obtained.

  FIG. 14 shows the result of investigation in the traffic pattern 2 described above. Here, average represents the average throughput of flows 1 and 2.

  It can be seen that the multi scheme and the proposed scheme 2, which is the present invention, also provide good throughput characteristics in this case. On the other hand, with respect to the proposed method 1 as a comparative example, in this communication pattern, in the local interface of the access point 2, the packet is received from the wireless terminal 3 of the flow 1 to the server, and the access point 101 of the flow 1 to the access point There are four types of communication function contention: reception of packets of packet 2, transmission of packets from the wireless terminal (STA2a) in flow 2 to the access point 102, and transmission of packets from the access point 102 in flow 2 to the wireless terminal (STA2b). Has occurred. For this reason, the throughput characteristics are kept low compared to the multi method and the proposed method 2 of the present invention.

  Further, as shown in FIG. 15, the flow 1 is defined as a TCP flow from the wireless terminal (STA3) to the server, and the flow 2 is defined as a TCP flow from the wireless terminal (STA2) to the wireless terminal (STA4). The throughput characteristics of each flow when performed simultaneously were obtained.

  FIG. 16 shows the results of the above experiment. Here, average represents the average throughput of flow 1 and flow 2.

  In this communication pattern, two flows share a radio section, but the multi scheme and the proposed scheme 1 which is a comparative example show an average throughput characteristic of about 10 Mb / s in a similar manner. On the other hand, in the proposed method 2 which is the present invention, an average throughput of 15 Mb / s or more is achieved.

  In the multi scheme, the access point 102 and the access point 103 have dedicated wireless interfaces for connecting to the access point 103 and the access point 102, respectively. Since the traffic toward the point 102 shares the same radio link, contention occurs between the flow 1 and the flow 2. However, in the proposed method 2 according to the present invention, the traffic from the access point 102 to the access point 103 is transferred from the transmission interface of the access point 102 to the reception interface of the access point 103, and travels from the access point 103 to the access point 102. Since the traffic is transmitted from the transmission interface of the access point 103 to the reception interface of the access point 102, the flow 1 and the flow 2 do not compete with each other, and the performance does not deteriorate. That is, it can be seen that the proposed method 2 according to the present invention provides very good characteristics when the main direction of data flow is different.

  It is assumed that four wireless terminals (STAs) are connected to all six access points, and randomly between all 24 wireless terminals (STAs) and one server connected to the wired network. Assume that communication occurs. It is assumed that a flow is generated at intervals of 3 seconds, and communication is performed for 3 seconds per line. Under such conditions, the average throughput characteristics of each TCP flow when the number of simultaneously generated flows was changed were investigated. The simulation is executed 100 times under the same conditions, and the average is obtained.

  FIG. 17 shows the results of the above experiment.

  From this result, the proposed method 2 according to the present invention showed the best characteristics, and its effectiveness was verified. In addition, the proposed method 1 as a comparative example, although inferior in throughput characteristics compared to the multi method and the proposed method 2 as the present invention, always has better performance than the single method, and uses two interfaces. As a method for configuring an access point, the superiority of the proposed method 1, which is a comparative example, is shown.

  As described above, according to the present invention, even when the number of access points and accommodable mobile terminals is increased in a multi-hop wireless network, the configuration is simple and the cost is not significantly increased. In addition, it is possible to prevent a decrease in throughput characteristics, improve communication performance, and eliminate unfairness in communication performance.

Embodiment 2
FIG. 18 shows a second embodiment of the present invention. The same parts as those of the first embodiment are described with the same reference numerals. In the second embodiment, a plurality of access points are provided. Are connected to each other by wireless, and constitutes a multi-hop wireless mesh network.

  In the second embodiment, as shown in FIG. 18, a multi-hop wireless mesh network is formed in which one access point is connected to a plurality of access points by radio. In general, a mesh network has a plurality of transmission paths. Depending on the amount of traffic or load on the network, or on the occurrence of a fault in the network due to a disconnection of the transmission path or a device failure, the network It has a function of controlling the internal transmission path to an appropriate path. For example, a telephone network, the Internet network, or a power network is also configured by a mesh network, and the reliability of the entire system is improved by providing redundancy by the mesh network.

  In FIG. 18, when considering the data flow from the mobile terminal (STA3) 303 used in the area of the access point 103 to the server 170 on the wired network side, in addition to the route of the access point 103 → 102 → 101, In addition, there are many other routes such as 103 → 104 → 101 and 103 → 106 → 105 → 101. If a failure occurs in the access point 102, the transmission path from the mobile terminal 303 to the server 170 can be secured by switching from the path 103 → 102 → 101 to the path 103 → 104 → 101, for example. Thus, by providing redundancy by the mesh network, the reliability of the network is improved.

  The mesh network shown in FIG. 18 is an example, and even in a mesh network generally having a plurality of routes, each access point has three types of transmission, reception, and STA accommodation for communication between access points. A wireless interface may be provided, and the functional operation can be realized by providing a path control function to the configuration shown in the block diagram of FIG.

  FIG. 19 illustrates a difference in transmission channel due to a difference in transmission path, for example, when data is transmitted from the access point 103 to the access point 101. When the transmission path is the access point 103 → 102 → 101, the access point 103 first transmits data in accordance with the reception channel Bch of the access point 102 that is the transmission partner, and the access point 102 is the access point that is the transmission partner. The data is relayed and retransmitted in accordance with the receiving channel Ach of 101 and received by Ach of the access point 101.

  Next, when the transmission path is access point 103 → 104 → 101, first, the access point 103 transmits data in accordance with the reception channel Dch of the access point 104 which is the transmission partner, and the access point 104 is the transmission partner. Data is relayed and retransmitted in accordance with the reception channel Ach of a certain access point 101 and received by the Ach of the access point 101.

  That is, the access points 102 and 104 can be selected as transmission partners of the access point 103. When the transmission destination is the access point 102, data is transmitted according to the reception channel Bch of the access point 102, and the transmission destination is the access point 104. At this time, data is transmitted in accordance with the reception channel Dch of the access point 104. The change of the transmission channel is realized in the block diagrams 112, 111 and 110 of FIG.

  Further, by operating radio reception for relaying between access points with a fixed channel and radio transmission with a variable channel in this way, the operation of each access point can be simplified and the design of the radio network system itself becomes easy. Specifically, in general, in the placement of access points in the design of a wireless network system, the placement of access points and the design of channels used in consideration of radio wave interference are required, which complicates the work. Therefore, by using the access point and the configuration method according to the present invention, it is sufficient to design statically so that the radio channel set for radio reception for relaying between access points does not interfere with adjacent access points, and the radio network design is extremely It will be easier.

  Since other configurations and operations are the same as those of the first embodiment, description thereof is omitted.

FIG. 1 is a block diagram showing an access point of a multi-hop wireless communication system to which a method for configuring a multi-hop wireless communication system according to Embodiment 1 of the present invention is applied. FIG. 2 is a schematic configuration diagram showing a multi-hop radio communication system to which the multi-hop radio communication system configuration method according to Embodiment 1 of the present invention is applied. FIG. 3 is a schematic configuration diagram showing a case where an access point is added in the multi-hop radio communication system to which the multi-hop radio communication system configuration method according to Embodiment 1 of the present invention is applied. FIG. 4 is a schematic configuration diagram showing the configuration of Experimental Example 1. FIG. 5 is a graph showing the results of Experimental Example 1. FIG. 6 is a schematic configuration diagram showing the configuration of Experimental Example 2. FIG. 7 is a schematic configuration diagram showing a configuration of a comparative example. FIG. 8 is a graph showing the results of Experimental Example 2. FIG. 9 is a chart showing the results of Experimental Example 2. FIG. 10 is a graph showing the results of Experimental Example 2. FIG. 11 is a schematic configuration diagram showing the configuration of Experimental Example 2. FIG. 12 is a graph showing the results of Experimental Example 2. FIG. 13 is a schematic configuration diagram showing the configuration of Experimental Example 2. FIG. 14 is a graph showing the results of Experimental Example 2. FIG. 15 is a schematic configuration diagram showing the configuration of Experimental Example 2. FIG. 16 is a graph showing the results of Experimental Example 2. FIG. 17 is a graph showing the results of Experimental Example 2. FIG. 18 is a schematic configuration diagram showing a multi-hop radio communication system to which the multi-hop radio communication system configuration method according to Embodiment 2 of the present invention is applied. FIG. 19 is a schematic configuration diagram showing a multi-hop radio communication system to which the multi-hop radio communication system configuration method according to Embodiment 2 of the present invention is applied. FIG. 20 is a schematic configuration diagram showing a conventional multi-hop wireless communication system. FIG. 21 is an explanatory diagram showing the hidden terminal problem. FIG. 22 is an explanatory diagram showing the exposed terminal problem.

Explanation of symbols

  1: multi-hop wireless communication system, 101-103: access point (AP), 150: backbone network, 110: transmission unit for communication between access points, 120: reception unit 120 for communication between access points, 130: between terminals A transceiver for communication.

Claims (8)

At least one wireless communication base station connected by wire to the backbone network;
In a configuration method of a multi-hop wireless communication system comprising a plurality of wireless communication base stations connected by wirelessly relaying with a plurality of wireless communication base stations including a part of the wireless communication base station,
In radio communication between the plurality of radio communication base stations, relay radio transmission and radio reception for relay in one radio communication base station are performed using channels with different interfaces and different frequencies, and the relay A method for configuring a multi-hop wireless communication system, wherein a channel in an interface used for wireless transmission is dynamically matched to a frequency channel in a receiving interface used in a receiving wireless communication base station. The method of configuring a multi-hop wireless communication system according to claim 1, wherein the wireless reception for relay is performed using a channel having a fixed frequency. The radio communication base station has a radio communication function for accommodating a mobile terminal that communicates with a mobile terminal, and the radio communication for accommodating the mobile terminal is different in frequency from radio transmission for relay and radio reception for relay. The method of configuring a multi-hop wireless communication system according to claim 1 or 2, wherein the method is performed using a channel. 4. The multi-hop wireless communication system according to claim 1, wherein the wireless communication for accommodating mobile terminals used in the adjacent wireless communication base station is performed using channels having different frequencies. 5. Configuration method. At least one wireless communication base station connected by wire to the backbone network;
In a multi-hop wireless communication system comprising a plurality of wireless communication base stations connected by wirelessly relaying with a plurality of wireless communication base stations including a part of the wireless communication base station,
The plurality of wireless communication base stations include a relay wireless transmission means and a relay wireless reception means,
A multi-hop wireless communication system, wherein the relay wireless transmission means and the relay wireless reception means use channels having different frequencies. The radio communication base station includes mobile terminal accommodating radio communication means for communicating with a mobile terminal, and the mobile terminal accommodating radio communication means includes the relay radio transmitting means and the relay radio receiving means. The multi-hop wireless communication system according to claim 5, wherein communication is performed using channels having different frequencies. At least one wireless communication base station connected by wire to the backbone network;
In a wireless communication apparatus used in a multi-hop wireless communication system including a plurality of wireless communication base stations connected by wirelessly relaying with a plurality of wireless communication base stations including a part of the wireless communication base station,
The radio communication apparatus as the radio communication base station includes a relay radio transmission means, a relay radio reception means, and a mobile terminal accommodating transmission / reception means,
The wireless communication apparatus according to claim 1, wherein the relay wireless transmission means and the relay wireless reception means use channels having different frequencies. 8. The wireless communication apparatus according to claim 7, wherein a channel having a different frequency is used in a transmitting / receiving unit for accommodating a mobile terminal between the adjacent wireless communication apparatuses.

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