JP2009302694A - Radio communication network system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication network system and a radio communication device, which can perform communications by simple route control in the radio network in which radio nodes perform radio relay in a tree shape between a radio gateway with an upper network and radio terminals of the end. <P>SOLUTION: The radio node consists of a radio master station 9 and radio auxiliary stations 8, the radio master station 9 prepares a means to detect and report route information such as a number of connected radio auxiliary stations, a circuit usage ratio, a round trip time, a number of relay etc., and the radio auxiliary stations 8 of other radio nodes collect the route information reported from a plurality of radio master stations, and decides the connecting radio master station 9. Even after the connecting radio master station 9 is decided, the route information is periodically collected, and the radio master station 9 to which the radio auxiliary station 8 is to be connected is automatically changed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wireless communication network system and a wireless communication apparatus in which a plurality of wireless nodes each having a wireless master station and a slave station exist, and more particularly to a wireless communication network system that performs communication path control between wireless nodes.

  In a wireless LAN defined by the IEEE 802.11 standard, communication is performed using a single communication channel between a wireless communication master station connected to an upper network by wire and a plurality of communication slave stations. For this reason, in order to secure a wide communication area, a wired network for arranging a plurality of wireless communication master stations is necessary.

  A multi-hop or mesh network in which a plurality of wireless nodes relay information and can expand a communication area without using a wired network has attracted attention. In these networks, radio path control is important, and various systems have been proposed.

  As described in [Patent Document 1], multi-hop networks are broadly divided into autonomous distributed systems in which each wireless node autonomously controls routes and systems in which network management devices centrally control routes, and both systems are combined. Other methods are also being considered.

  In the autonomous decentralized method, the transmitting station transmits a packet for searching for a route to the receiving station in a broadcast mode that can be received by all nodes, and determines the route by returning the search packet that has reached the receiving station to the transmitting station. There is a method to make it. There is also a method of determining a route by measuring a packet response time RTT (round trip time) for all routes when there are a plurality of routes.

  On the other hand, in the method in which the network management device centrally controls the route, the network management device creates a routing table and transmits the table to each wireless node. The packet can be relayed to the next wireless node, and finally the packet can be relayed to the receiving station.

JP 2007-36361 A

  The conventional autonomous distributed method described above has a complicated communication procedure until route search, and the centralized management method needs to transmit a routing table to each wireless node as the communication state changes. Therefore, there is a problem that the amount of communication increases and throughput decreases.

  An object of the present invention is to provide a wireless communication network system and a wireless communication system capable of performing communication by simple route control in a wireless network in which wireless nodes are wirelessly relayed in a tree form between a wireless gateway with a higher-level network and a terminal wireless terminal. It is to provide a communication device.

  In order to achieve the above object, a wireless communication network system of the present invention includes a wireless gateway connected to an upper network, a wireless node that relays packets, and a wireless terminal that transmits and receives device information, and the wireless node is wired. The wireless master station and the wireless slave station are connected to each other, and the mutual information is transmitted and received by wired communication. A wireless master station in a wireless node and a wireless slave station in another wireless node communicate with each other wirelessly and relay in a wired manner within the wireless node, so that communication between wireless nodes is performed between the wireless master station and the wireless slave station. Communication in the infrastructure mode widely used in wireless LAN.

  Since the radio master station in the radio node is provided with means for detecting the number of relays from the radio gateway and notifying it, the radio slave station of the radio node receives the number of relays of the master station when searching for a route. Thus, it is possible to select a wireless node (master station) with a small number of relays to the wireless gateway.

  The wireless master station in the wireless node is provided with means for measuring and reporting the number of wireless slave stations that are communicating and the channel usage rate of the wireless communication channel. By receiving the number of wireless slave stations of the station and the line usage rate of the wireless communication channel, it is possible to select the wireless node (master station) with the shortest transmission waiting time.

  The radio master station in the radio node is provided with means for measuring and notifying the round trip time (RTT) that is the packet arrival time with the radio gateway or the upper communication management device. By receiving the RTT of the parent station when the slave station searches for a route, a wireless node (parent station) having a short packet arrival time to the wireless gateway can be selected.

  In the slave station in the radio node, after selecting the radio master station of the radio node to be connected, the number of relays of the selected radio master station, the number of radio slave station connections, the line usage rate, and the RTT are received and other radio Since the means for collecting the information is provided in the wireless master station of the node, an appropriate wireless node can be determined.

  According to the present invention, a wireless node is composed of a master station and a slave station, and the number of relays, line usage rate, and RTT, which are significant information when the master station selects a route, is measured and notified, so The slave station can easily select the wireless node master station to be connected from the information.

  An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram of a wireless communication network according to the present embodiment. FIG. 1 also shows information used for route selection notified from a wireless master station.

  As shown in FIG. 1, the control device 1 communicates with a device 5 such as a sensor connected to a wireless terminal 4 via a wireless communication network, and performs, for example, plant monitoring control. The control device 1 is connected to a wireless gateway 2 (hereinafter referred to as a wireless GW 2) via a wired network 6 and converts packet data into wireless information by the wireless GW 2 for communication.

  The wireless node 3 includes a wireless master station 9 and a wireless slave station 8, and is connected to each other via a wire 7 so that communication is possible. The wireless node 3 relays wirelessly with other wireless nodes 3 or wireless terminals 4.

  The wireless GW 2 becomes a wireless master station and communicates with the wireless slave stations 8 of the wireless nodes 3 b, 3 c, 3 d, and the wireless master station 9 sends packets from the wireless GW 2 to the same wireless master station 9 of the wireless nodes 3 b, 3 c, 3 d. The wireless master station 9 of the wireless node 3b has a network configuration on a tree that communicates with the wireless slave stations 8 of the wireless nodes 3a and 3g.

  In this way, the wireless node is composed of a master station and a slave station, and communication between the master station and the slave station is also performed between the wireless nodes. Therefore, a multi-hop network can be configured by combining the slave station and the master station. I can do it. The final stage wireless terminal 4 has a wireless slave station 8 but no wireless master station 9.

  In FIG. 1, a wireless node is composed of one master station and one slave station. However, either one of the master station or slave station is used as a plurality, or both the master station and slave stations are used as a plurality. A wireless node may be configured.

  When communication is performed between the wireless GW 2 and the wireless terminal 4c illustrated in FIG. 1, the wireless nodes 3d, 3e, and 3l wirelessly relay packets. Starting from the wired GW 2, the wireless node 3 d is at the relay number 1, the wireless node 3 e is at the relay number 2, and the wireless node 3 l is at the relay number 3 position.

  By storing and transmitting the number of relays as beacon information periodically transmitted from the wireless master station 9 shown in FIG. 1, the slave station in the wireless node that has received the beacon information can determine the number of relays from the wireless GW 2 Therefore, it becomes possible to easily select a master station to be relayed.

  The round trip time (RTT), which is a packet arrival time with the wireless GW or the higher-level communication management device, notified from the wireless master station 9, is transmitted as a packet from the wireless master station 9 to the wireless GW 2 or the higher-level control device 1. It is the response time until it is sent back to the wireless master station 9 again.

  A packet for RTT measurement transmitted from the wireless master station 9 to the wireless GW 2 is transferred to the wireless slave station 8 in the same wireless node connected by wire, and wirelessly communicated from the wireless slave station 8 to the wireless node 3 that relays it. To do. After that, it is relayed by the wireless node 3 and arrives at the wireless GW 2 as in the normal packet communication. When the wireless GW 2 receives a packet for RTT measurement, the wireless GW 2 exchanges the transmission address and the reception address of the packet and returns the packet to the wireless master station 9 of the transmission source wireless node.

  The RTT measuring packet transmission source master station can measure the RTT from the difference between the transmission time and the received RTT measuring packet reception time. As described above, the RTT is a packet response time from the wireless node to the wireless GW, and is advantageous information for grasping the communication state of the relay route.

  The number of relays does not include a time element, but the RTT is a measurement value that includes a time element, and is an amount that varies with time due to radio wave conditions and the amount of communication between other wireless nodes. It is possible to control the route according to the communication status from the information.

  The example in which the RTT measurement packet is transmitted from the master station has been described. However, the RTT measurement packet is transmitted from the wireless GW 2, and the RTT measured by the wireless GW 2 is notified to the corresponding wireless node of the RTT information. Can also be realized. If time synchronization is established throughout the wireless communication network, the RTT can be measured from the difference between the transmission time and the reception time.

  As shown in FIG. 1, the information notified from the wireless node master station includes the number of slave station connections and the line usage rate. The RTT is information for grasping the communication state from the wireless node, whereas the number of connected slave stations and the line usage rate indicate the communication state between the wireless node master station and other wireless node slave stations communicating with it. Information.

  The line usage rate is the sum of the communication time transmitted / received by the master station and the time during which communication cannot be performed from other wireless nodes using the same communication channel (hereinafter referred to as communication CH) or due to radio noise. The smaller the sum of times, the less the transmission waiting time and the more packets can be transmitted.

  Therefore, more accurate route selection can be performed by evaluating both the RTT and the line usage rate. The number of slave stations connected and the line usage rate are often proportional, but since a large number of packets may be transmitted from one slave station, there is an effect of measuring and broadcasting the line usage rate.

  The number of CHs for radio communication is limited, and there are many cases where the same radio communication CH is used by a plurality of radio master stations 9. In such a case, communication performance deteriorates due to mutual interference. Therefore, in wireless communication, there are many examples in which a CSMA access method is used in which carrier sense is performed and transmission is performed after confirming that no wireless station is transmitting. With this carrier sense function, it is easy to measure the time during which communication is not possible due to other wireless nodes or radio noise.

  A specific operation of each part for realizing the present embodiment will be described with reference to FIGS. FIG. 2 is a configuration diagram of the wireless master station 9 configuring the wireless node, and FIG. 3 is a configuration diagram of the wireless slave station 8 configuring the wireless node.

  The wireless master station 9 and the wireless slave station 8 provided in the wireless node 3 are connected to each other by a wired 7 by the external interface 19, and a packet wirelessly received by the wireless master station 9 is wirelessly transmitted via the wired 7. The packet is transferred to the slave station 8 and transmitted wirelessly from the wireless slave station 8 to be relayed.

  As shown in FIG. 2, a radio signal is transmitted / received via the antenna 14 of the radio master station 9, transmitted from the radio transmitter 17 through the switch 15 at the time of transmission, and received from the switch 15 by the radio receiver 16 at the time of reception. Is done.

  The radio signal received and processed by the radio receiving unit 16 is converted into digital data and assembled as a packet by the main control unit 18. The received power measuring unit 21 connected to the main control unit 18 measures and records the received power for each packet that is a transmission source of the received packet.

  The line usage rate measuring unit 22 connected to the main control unit 18 measures the total time of the time transmitted or received per unit time and the time that cannot be used by communication of other wireless devices using the same communication CH. To do. This line usage rate indicates the ratio of communication used in the CH communicated by the wireless master station 9, and for other wireless node slave stations newly considering connection with this master station, it is determined whether or not it is possible. Information. In other words, the lower the line usage rate, the easier it is to secure the communication time allocated to the new slave station, so the transmission waiting time of the slave station is shortened.

  Since the main control unit 18 of the wireless master station 9 decodes and generates packets transmitted and received wirelessly, it can measure and record how many slave stations are wirelessly connected. The master station can detect the number of relays by transferring information related to the number of relays of another radio node master station detected by the radio slave station 8 to the radio master station 9 via the wire 7. For example, if the number of relays transferred from the wireless slave station 8 is 1, the number of relays is 2 plus 1 because the wireless master station 9 further relays.

  The information such as the number of connected slave stations, the line usage rate, the RTT, and the number of relays described above is transmitted as beacon information periodically transmitted by the wireless master station 9, so that other wireless node slave stations that have received this information A master station suitable for connection can be selected.

  FIG. 4 is a configuration diagram of the beacon information, and shows a comparison between the beacon information of the wireless LAN standard and the beacon information of the present embodiment. In the conventional wireless LAN standard beacon information, there are communication parameters that can be used such as identification information, encryption and speed of a master station (wireless LAN access point). It does not include information such as the number of relays that can be used for route control and the line usage rate. In the beacon information of the present embodiment shown in FIG. 4B, in addition to the conventional beacon information, information on the number of connected slave stations 10, the line usage rate 11, the RTT 12, and the number 13 of relays are used as beacon information.

  As described above, the beacon information is periodically transmitted from the master station, and the cycle is about 100 ms in the wireless LAN. For this reason, it is necessary for the slave station searching for the master station to wait until the beacon information is transmitted. This waiting time does not become long when there is one communicable master station, but the waiting time becomes long when there are multiple master stations, so in response to a beacon transmission request from a slave station, By providing a mode in which information is transmitted irregularly, it is possible to shorten the information collection time for route control.

  As shown in FIG. 3, the wireless slave station 8 is connected to a switch 15 connected to the antenna 14, a wireless reception unit 16 connected to the switch 15, a wireless transmission unit 17, a wireless reception unit 16, and a wireless transmission unit 17. Main control unit 18, line usage rate measurement unit 22 connected to main control unit 18, received power measurement unit 21, radio node master station selection unit 26, beacon information collection unit 27, external connected to main control unit 18 The interface 19 is configured.

  The beacon information collection unit 27 collects beacon information periodically transmitted from the master station, and also collects beacon information of radio node master stations other than the other radio node master station that is normally communicating. Here, the beacon information is information including information on the number of connected slave stations 10, the line usage rate 11, the RTT 12, and the number of relays 13 in this embodiment. The radio node master station selection unit 26 selects a master station from the information of each master station collected by the beacon information collection unit 27.

  The route selection procedure at the slave station will be described with reference to FIGS. FIG. 5 is a route selection flowchart of the wireless slave station 8. In the example shown in FIG. 5, description will be made assuming that the CHs for wireless communication are four CH1 to CH4. In step 30, the communication CH is set to CH1, and in step 32, beacon information from other radio node master stations using CH1 is collected. In step 33, the beacon information is similarly changed from CH1 to CH2, and these collections are repeated up to CH4 to create a beacon information list shown in FIG.

  In the example shown in FIG. 6, there are master stations in CH1, CH2, and CH4, and in the conventional wireless device, the higher the reception strength, the more stable the communication is, so the priorities are given in order of reception strength. In this embodiment, information on the number of slave station connections 10, line usage rate 11, RTT 12, and number of relays 13 is acquired, and the master station is selected from these information in addition to the received intensity. The smaller the number of relays, the lower the line usage rate, and the shorter the RTT, the more suitable as a master station to relay.

  This is because it takes a long time for a packet to arrive at the wireless GW if the number of relays is large even if the reception strength is high. In this way, priority is given to the other radio node master station, a connection request is transmitted to the master station from the highest order, and if there is permission from the master station, it is determined to connect to the master station. In the case of disapproval, a connection request is made to the master station having the next priority to realize route selection.

  In the flowchart shown in FIG. 5, the initial procedure is shown. However, the beacon information collection unit 27 of the wireless slave station 8 periodically periodically changes the master station to be connected and performs packet communication. Beacon information is collected for the wireless master station 9 and the beacon information list shown in FIG. 6 is updated. In this way, appropriate route control can be performed at the slave station. In the case of wireless communication, communication performance degradation often occurs due to fluctuations in received intensity or noise. Thus, by updating the beacon information list, it is possible to cope with the above-mentioned communication failure in a short time. .

  In addition, when communication with the master station that normally communicated becomes impossible, it is possible to switch the route to the master station with the next priority in the beacon information list, There is no need to perform a master station search.

  As described above, according to the present embodiment, in a multi-hop wireless communication network system that performs communication by performing a plurality of wireless relays, a wireless node to be wirelessly relayed is composed of a master station and a slave station, and the master station is connected to the slave station. A means to detect and notify routing control information such as number, line usage rate, RTT, number of relays, etc. is provided, and the slave station selects the master station to be connected from the routing control information, so that the wireless node is autonomously accurate. Path control can be realized. In addition, since the amount of control information related to path control can be reduced compared with the method in which the communication management device collects information and determines the path of each wireless node, the time available for packet communication increases, which is effective. Communication speed can be improved.

  The present invention is applied to a multi-hop wireless communication network system that efficiently performs route control of wireless nodes.

1 is a configuration diagram of a wireless communication network according to an embodiment of the present invention. The apparatus block diagram of the radio | wireless node master station of a present Example. The apparatus block diagram of the radio | wireless node slave station of a present Example. The figure which shows beacon information. The flowchart of the path | route control of the slave station of a present Example. The figure which shows the path | route selection table of the slave station of a present Example.

Explanation of symbols

1 control device 2 wired GW (wireless master station)
3 Wireless node 4 Terminal device 5 Sensor 6 Wired network 7 Wired 8 Wireless slave station 9 Wireless master station 10 Number of slave station connections 11 Line usage rate 12 Round robin time 13 Number of relays 14 Antenna 15 Switch 16 Wireless receiver 17 Wireless transmitter 18 Main control unit 19 External interface 20 Transmission / reception packet data 21 Received power measurement unit 22 Line usage rate measurement unit 23 RTT measurement unit 24 Beacon generation unit 25 Radio channel selection unit 26 Radio node master station selection unit 27 Beacon information collection unit

Claims (4)

  A wireless gateway connected to a wired network, and a wireless communication network system that communicates with a wireless terminal by wirelessly relaying the wireless gateway and a plurality of wireless nodes, wherein the wireless node is a wireless parent connected by wire A wireless communication system comprising a station and a wireless slave station, wherein a wireless master station and a wireless slave station in the other wireless node communicate wirelessly in the wireless node between the wireless node and another wireless node Network system.   The radio master station of the radio node includes the number of radio slave stations of other radio nodes that communicate with the radio master station, the channel usage rate of the communication channel with which the radio master station communicates, and the radio master station of the radio node Detecting packet data transmission time between the wireless gateway or between the wireless gateway and the communication control device connected by the wired network, and path information of the number of wireless relays from the wireless gateway of the wireless node The wireless slave station of the wireless node receives the route information broadcast by the wireless master station of the other wireless node, and receives a plurality of other wireless nodes. 2. The wireless communication network system according to claim 1, wherein a wireless master station of a wireless node to be connected is selected from route information of the wireless master station.   The route information broadcast by the wireless master station of the wireless node is transmitted in addition to the beacon information periodically transmitted by the wireless master station, and is transmitted according to a transmission request from a wireless slave station of another wireless node. The wireless communication network system according to claim 2, wherein the route information is transmitted.   The wireless slave station of the wireless node is provided with means for ranking the wireless master stations to be connected from the route information received from the wireless master stations of a plurality of other wireless nodes, and is ranked by the ranking means. 4. The wireless communication network according to claim 2, further comprising means for updating rank information every time the route information is acquired, and means for selecting a wireless master station based on the rank information. system.

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