JP2007036361A - Method of forming radio multihop network and radio communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a radio multihop network capable of shortening a transmission time of a packet, and to provide a radio communication device. <P>SOLUTION: The method of forming the radio multihop network having a plurality of nodes connected to enable communication by radio includes a first step for detecting a close node capable of communication by one hop at each node; a second step for connecting the adjacent nodes each other for enabling communication by a polling system, and for forming a plurality of polling clusters each comprising one node operating as a master and at least one node operating as a slave; a third step for detecting adjacent polling clusters at each polling cluster; and a fourth step for setting a communication route enabling communication by a carrier sense system between the adjacent polling clusters. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for forming a wireless multi-hop network suitable for application to a hot zone system, and a wireless communication apparatus constituting the wireless multi-hop network.

  A hot zone system is a system that provides a wide wireless LAN service area by connecting wireless LAN switches to a plurality of access points (hereinafter referred to as APs) one by one and connecting the wireless LAN switches wirelessly. is there. Since the hot zone system connects APs by radio instead of by wire, there is an advantage that the cost can be reduced without the trouble of laying cables. In this hot zone system, APs are arranged finely to cover a designated service area, and APs are arranged at high density in places where the number of service users is large.

  A network constructed by interconnecting a plurality of wireless communication devices (for example, a wireless LAN switch) as in a hot zone system, a packet input from an arbitrary AP is desired via a plurality of wireless communication devices. It is called a wireless multi-hop network in order to transmit to the AP.

  As an access method for such a wireless multi-hop network, a carrier sense method using CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) has been known.

  If this carrier sense method is applied to communication between wireless communication devices in a wireless multi-hop network, the transmission interval of each wireless communication device changes at random. Therefore, a plurality of wireless communication devices transmit packets at the same time. Collisions can be avoided.

  However, in a wireless multi-hop network to which only the carrier sense method is applied, there is a problem that collision of packets cannot be avoided because the number of contentions increases when the arrangement density of wireless communication devices increases. When a packet collision occurs, the packet transmission waiting time increases approximately twice each time, leading to an increase in packet transfer delay. For this reason, when the wireless multi-hop network is used in an application that requires real-time performance such as voice communication, voice quality may be deteriorated.

  As another method applicable to communication between wireless communication devices in a wireless multihop network, there is a polling method described in Non-Patent Document 1.

  In a wireless multi-hop network to which a polling method is applied, each wireless communication device takes on the role of either Master or Slave. In this specification, an aggregate composed of one wireless communication device serving as a master and at least one wireless communication device serving as a slave is referred to as a polling cluster (hereinafter abbreviated as a PCF cluster). In a wireless multi-hop network to which a polling method is applied, a plurality of wireless communication devices (hereinafter referred to as slave nodes) in which a wireless communication device serving as a master (hereinafter referred to as a master node) is slaved according to a predetermined schedule. Packets are transmitted and received by sequentially polling.

  When a packet is transmitted from the master node to the slave node, the master node transmits the packet at a polling timing with respect to the destination slave node. Conversely, when transmitting a packet from the slave node to the master node, the slave node transmits the packet at the timing when the polling from the master node is received. In such a method, since the master node controls the transmission timing of the slave node, it is possible to avoid packet collision in communication between the slave nodes or between the master node and the slave node, and consequently reduce the packet transfer time. it can.

  However, in a wireless multi-hop network to which the polling method is applied, the waiting time due to polling increases in proportion to the number of slave nodes forming the PCF cluster, and the polling in each PCF cluster is caused by packets passing through a plurality of PCF clusters. There is a problem that waiting time is accumulated.

  FIG. 15 shows a configuration example of a wireless multi-hop network including 18 wireless LAN switches (WS: Wireless Switch) WS1 to WS18 to which only a polling method is applied. FIG. 16 shows a polling waiting time that occurs when a packet is transferred from WS2 to WS15 shown in FIG.

  In the wireless multi-hop network shown in FIG. 15, WS1, WS7, WS12, and WS16 operate as master nodes, and WS2-4, WS5, WS6, WS8-11, WS13-15, WS17, and WS18 operate as slave nodes, respectively. This is an example.

  As shown in FIG. 15, the first PCF cluster having WS1 as a master node includes WS2, WS3, WS4, WS5, and WS6 as slave nodes. The second PCF cluster having WS7 as a master node includes WS6, WS8, WS9, WS10, and WS11 as slave nodes. In addition, the third PCF cluster having WS 12 as a master node includes WS 10, WS 13, WS 14, and WS 15 as slave nodes. Further, the fourth PCF cluster having WS16 as a master node includes WS13, WS17, and WS18 as slave nodes.

  The radio frequency used in each of the first PCF cluster to the fourth PCF cluster is set so as not to interfere between the PCF clusters. In FIG. 15, the first PCF cluster uses radio frequency f1, the second PCF cluster uses radio frequency f2, the third PCF cluster uses radio frequency f3, and the fourth PCF cluster is radio. An example using the frequency f4 is shown.

  In such a configuration, for example, when packets are transferred from WS2 to WS15 shown in FIG. 15, in the first PCF cluster, packets are transferred in the order of WS2 to WS1, WS1 to WS6. At this time, in the first PCF cluster, the packet transmission timing is controlled by the master node WS1. Therefore, after the packet transfer from WS2 to WS1 is completed as shown in FIG. 16, the packet transfer from WS1 to WS6 is performed next. A polling waiting time (waiting time 1) occurs before the start of.

  In the second PCF cluster, packets are transferred in the order of WS6 to WS7, WS7 to WS10, and after the packet transfer from WS1 to WS6 is finished, the polling waiting time (waiting) is started until the next packet transfer from WS6 to WS7 is started. After the packet transfer from WS6 to WS7 is completed, a polling waiting time (waiting time 3) is generated until the next packet transfer from WS7 to WS10 starts.

  Similarly, in the third PCF cluster, packets are transferred in the order of WS10 to WS12 and WS12 to WS15, and the polling waiting time (waiting time 4) from the end of the previous packet transfer to the start of the next packet transfer. , Waiting time 5) occurs.

Therefore, in the wireless network shown in FIG. 15, when packets are transferred from WS2 to WS15, delays (latency times) in which the polling waiting time in each of the first PCF cluster, the second PCF cluster, and the third PCF cluster is accumulated. 1 to 5).
K. Mizuno, M. Katayama, H. Suda, "A New QoS-guaranteed Multichannel MAC Protocol for Multihop Wireless Networks," Vehicular Technology Conference 2002, VTC Spring 2002, IEEE 55th, Volume 2, 6-9 May 2002, pp. 967-971, vol.2

  As described above, in the configuration in which only the carrier sense method is applied in the conventional wireless multi-hop network, if the wireless communication devices are arranged at a high density, the contention number increases, resulting in packet collision. As a result, there is a problem that the transfer delay becomes large.

  Further, in the configuration in which only the polling method is applied, there is a problem that the packet transfer delay increases because the polling waiting time in each PCF cluster is accumulated when passing through a plurality of PCF clusters.

  The present invention has been made to solve the above-described problems of the prior art, and provides a wireless multi-hop network forming method and a wireless communication apparatus capable of reducing the packet transfer time. For the purpose.

To achieve the above object, a method for forming a wireless multi-hop network according to the present invention is a method for forming a wireless multi-hop network including a plurality of nodes that are communicably connected by radio,
A first step of detecting, for each node, neighboring nodes capable of communicating in one hop;
A second step of connecting the neighboring nodes so as to enable communication by a polling method, and forming a plurality of polling clusters including one node operating as a master and at least one node operating as a slave;
A third step of detecting adjacent neighboring polling clusters for each of the polling clusters;
A fourth step of setting a communication route that enables communication by a carrier sense method between the neighboring polling clusters;
It is the method which has.

On the other hand, the wireless communication device of the present invention is a wireless communication device for configuring a wireless multi-hop network that transfers packets wirelessly,
A neighboring node discovery unit that detects neighboring nodes that can communicate in one hop;
An association execution unit that selects the own wireless communication device as either a master or a slave of a polling cluster that is an aggregate of wireless communication devices, and connects to the neighboring nodes so as to enable communication by a polling method;
A neighboring cluster discovery unit that detects neighboring polling clusters adjacent to each polling cluster;
An inter-cluster connection unit that sets a communication route that enables communication by a carrier sense method between the neighboring polling clusters;
It is the structure which has.

  In the wireless multi-hop network forming method and the wireless communication apparatus as described above, neighboring nodes are connected so as to be able to communicate with each other by a polling method. From one node operating as a master and at least one node operating as a slave Packet collision between neighboring nodes compared to a configuration using only the carrier sensing method by forming a plurality of polling clusters and setting a communication route that enables communication by the carrier sensing method between neighboring polling clusters The delay time due to polling is reduced, and the delay time due to the polling waiting time between polling clusters is reduced as compared with the configuration using only the polling method.

  According to the present invention, neighboring nodes are connected so as to be able to communicate with each other in a polling manner, and a plurality of polling clusters including one node operating as a master and at least one node operating as a slave are formed. By setting a communication route that enables communication using the carrier sense method between polling clusters, the delay time caused by packet collisions between neighboring nodes is reduced compared to a configuration using only the carrier sense method. Compared to a configuration using only the delay time, the delay time caused by polling waiting time between polling clusters is reduced. Accordingly, packet transfer delay in the wireless multi-hop network is reduced.

  Next, the present invention will be described with reference to the drawings.

  FIG. 1 is a flowchart showing a procedure of a method for forming a wireless multi-hop network according to the present invention.

  As shown in FIG. 1, in the present invention, a wireless multi-hop network is formed by the following four steps S1 to S4.

  Step S1 is a step of detecting neighboring nodes for each wireless communication device (hereinafter referred to as a node) (Neighbor Discovery). In step S1, a neighboring node that can be reached by one hop is detected for each node, and the number of neighboring nodes that can be connected by the wireless interface is calculated.

  Step S2 is a process of forming a PCF cluster. In step S2, information on the number of neighboring nodes detected in step S1 is exchanged between neighboring nodes that can be reached in one hop. Then, the node having the largest number of neighboring nodes is selected as a master node in the PCF cluster, and an association is requested to each of the selected nodes. At this time, if there are a plurality of nodes having the maximum number of neighboring nodes, the node having the maximum received electric field strength of the radio signal transmitted from those nodes is selected as the master node. Further, when there are a plurality of nodes having the maximum number of neighboring nodes and the maximum received electric field strength, a node having a minimum (or maximum) value such as a MAC address assigned to each node is selected as a master node. . Each information on the number of neighboring nodes, the received electric field strength, and the MAC address is notified to each other by sending and receiving packets by the carrier sense method.

  When the number of neighboring nodes of the own node is maximum, the own node is selected as a master node and an association request from another node is awaited. However, when there is a node having the maximum number of neighboring nodes in addition to the self node, the self node is selected as the master node when the received electric field strength is the maximum as described above. Further, when there are other nodes having the maximum number of neighboring nodes and the maximum received electric field strength, the own node is selected as the master node when the MAC address is minimum (or maximum).

  The master node that has received the association request returns a response message to the transmission source node. All the nodes that have received the response message for the association request operate as a slave node. In the present invention, a polling method is used for communication within the PCF cluster constituted by the Master node and the Slave node selected in Step B.

  The master node of each PCF cluster selected in the process of step S2 determines the radio frequency to be used in its own PCF cluster so that the radio frequency does not interfere with other PCF clusters.

  Step S3 is a step of detecting neighboring PCF clusters in units of PCF clusters. In step S3, a list of neighboring PCF clusters connectable with the own PCF cluster is generated.

  Step S4 is a step of connecting PCF clusters. In step S4, a communication route for transmitting and receiving packets between adjacent PCF clusters is determined. In the present invention, a carrier sense method is used for communication between PCF clusters.

  Next, a method for forming a wireless multi-hop network of the present invention will be specifically described with reference to the drawings.

  FIG. 2 is a schematic diagram showing a configuration example of a packet used in the method for forming a wireless multi-hop network of the present invention, and FIG. 3 is a block diagram showing a configuration example of a node constituting the wireless multi-hop network of the present invention. is there.

  As shown in FIG. 2, in the present invention, a packet transmitted / received between nodes includes fields of a transmission station address, a reception station address, a transmission destination address, and a transmission source address. A packet having each field shown in FIG. 2 is defined by, for example, IEEE 802.11. The transmitting station address is a field in which the address of the packet transfer source node is stored, and the receiving station address is a field in which the address of the packet transfer destination node is stored. The destination address and the source address are fields in which end to end addresses of terminals that transmit and receive packets via the AP are stored, respectively. FIG. 2 shows only the minimum information necessary for packet transmission / reception. An actual packet includes a field in which information for identifying the type of the packet is mounted following the address field, a data field in which data to be transmitted / received is mounted, and the like. Various packets to be transmitted / received between the nodes to form a wireless multi-hop network, which will be described later, have a configuration including these fields.

  As illustrated in FIG. 3, the node 100 includes two wireless interfaces, and one wireless interface is used for polling communication, and the other wireless interface is used for carrier sense communication. The wireless interface included in each node 100 can select an arbitrary wireless channel from a finite number of wireless channels used for packet transfer. Each node 100 may include two or more wireless interfaces for communication within the PCF cluster and for communication between the PCF clusters. In that case, since the effective data rate can be prevented from lowering due to interference by using different radio channels, the radio band can be used effectively.

  As shown in FIG. 3, the node 100 includes a first wireless interface 101, a second wireless interface 102, a wired interface 103, a master / slave operation unit 104, a neighboring node discovery unit 105, an association execution unit 106, and a radio frequency survey. And a neighboring cluster discovery unit 108 and an intercluster connection unit 109.

  1st wireless interface 101, 2nd wireless interface 102, wired interface 103, Master / Slave operation part 104, neighborhood node discovery part 105, association execution part 106, radio frequency investigation part 107, neighborhood cluster discovery part 108, and between clusters The connection unit 109 may be configured by using, for example, a logic circuit or a memory, and the function may be realized by an LSI or the like in which these are integrated. In addition to the first wireless interface 101, the second wireless interface 102, and the wired interface 103, the node 100 includes a CPU (or DSP) and a memory, and the CPU (or according to a program stored in the memory). DSP) executes the processes of the master / slave operation unit 104, the neighborhood node discovery unit 105, the association execution unit 106, the radio frequency investigation unit 107, the neighborhood cluster discovery unit 108, and the intercluster connection unit 109 described below, for example, It can also be realized by a computer.

  The first wireless interface 101 is a wireless interface for transmitting and receiving packets by a polling method, which is mainly used for communication within a PCF cluster. Between the nodes of the PCF cluster, in order to form a wireless multi-hop network, a neighbor node discovery packet, a neighbor node response packet, a neighbor node number notification packet, an association request packet, an association response packet, a radio frequency investigation instruction packet, which will be described later, Radio frequency investigation result packets, intra-cluster radio frequency notification packets, neighboring cluster discovery instruction packets, neighboring cluster response notification packets, cluster connection request transmission instruction packets, cluster connection response result packets, and the like are transmitted and received.

  The second wireless interface 102 is a wireless interface for transmitting and receiving packets by a carrier sense method, which is mainly used for communication between PCF clusters. In order to form a wireless multi-hop network between nodes of different PCF clusters, a radio frequency investigation packet, a radio frequency busy packet, a neighboring cluster discovery packet, a neighboring cluster response packet, a cluster connection request packet, a cluster connection response packet, etc., which will be described later Are sent and received.

  The wired interface 103 is an interface for performing packet communication with the AP via a wired transmission path.

  The Master / Slave operation unit 104 performs processing for operating the own node as a Master node or Slave node of the PCF cluster.

  The neighboring node discovery unit 105 detects neighboring nodes that can be connected by the first wireless interface 101 or the second wireless interface 102. When detecting a neighboring node, the neighboring node discovery unit 105 first transmits / receives a neighboring node discovery packet between other nodes using the first wireless interface 101. Neighboring node discovery packets are transmitted only to neighboring nodes that can be reached in one hop. When the neighboring node discovery packet is received from another node, the neighboring node discovery unit 105 returns a response message to the transmission source node by the neighboring node response packet. The neighboring node discovery unit 105 that has transmitted the neighboring node discovery packet calculates the number of neighboring nodes by counting the number of neighboring node response packets received from other nodes. Then, the calculated number of neighboring nodes of the own node is notified to each neighboring node using the neighboring node number notification packet.

  The association execution unit 106 forms a PCF cluster using the information detected by the neighboring node discovery unit 105. Association execution unit 106 compares the number of neighboring nodes received first from each neighboring node with the number of neighboring nodes of the own node. If there is no master node in the vicinity and the number of neighboring nodes of the own node is the maximum, the own node is selected as the master node and an association request packet from another node is waited for. However, when there are a plurality of nodes having the maximum number of neighboring nodes, the local node is selected as the master node when the received electric field strength is maximum. Further, when there are a plurality of nodes having the maximum number of neighboring nodes and the maximum received electric field strength, the local node is selected as the master node when the value of the MAC address or the like is minimum (or maximum).

  When the neighboring node number notification packet is received from the master node, or when the number of neighboring nodes of the own node is smaller than the number of neighboring nodes of the other node, the node having the largest number of neighboring nodes is selected and the association request packet is transmitted. . When there are a plurality of nodes having the maximum number of neighboring nodes, the node having the maximum received electric field strength is selected. Further, when there are a plurality of nodes having the maximum number of neighboring nodes and the maximum received electric field strength, the node having the minimum (or maximum) value such as the MAC address is selected.

  The node that has received the association response packet regards the transmission source of the association response packet as a master node in its own PCF cluster, and operates as a slave node. The operation as the master node or slave node is controlled by the master / slave operation unit 104.

  When the association execution unit 106 receives an association request packet from a neighboring node when the node is the master, the association execution unit 106 returns an association response packet to the transmission source neighboring node. However, when the number of associations exceeds a predetermined threshold value, the response of the association response packet to the neighboring node that has transmitted the association request packet is stopped when the threshold value is exceeded. By performing such processing, the number of slave nodes in the PCF cluster is limited.

  The radio frequency examining unit 107 determines a radio frequency to be used in the own PCF cluster when the own node is a master. The radio frequency investigation unit 107 knows the radio frequency to be used in another PCF cluster, and uses the radio frequency investigation packet (information on the radio frequency to be used) in the own PCF cluster (or the radio frequency to be used). Are exchanged between each PCF cluster. The first wireless interface 101 is used for transmission / reception of the radio frequency survey packet.

  When exchanging radio frequency survey packets, there are a case where a radio frequency survey packet is transmitted from a master node and a case where a radio frequency survey packet is transmitted to an adjacent PCF cluster via a slave node. When transmitting a radio frequency survey packet to an adjacent PCF cluster via a slave node, the radio frequency survey unit 107 of the master node transmits a radio frequency survey instruction packet to the slave node. The master node carries information on the radio frequency used in the own PCF cluster in the radio frequency investigation instruction packet. The radio frequency investigation unit 107 of the slave node that has received the radio frequency investigation instruction packet transmits the radio frequency investigation packet to each neighboring node.

  The radio frequency survey unit 107 of the node that has received the radio frequency survey packet refers to the transmitting station address, and if it is different from the address of the node belonging to the own PCF cluster, information on the used radio frequency in the radio frequency survey packet is displayed. get. Then, information on the radio frequency used in the own PCF cluster (used radio frequency) is mounted on the radio frequency busy packet and returned to the transmission source node. If the transmission station address matches the address of a node belonging to the own PCF cluster, no response is returned to the transmission source node. When the node that has received the radio frequency busy packet is a slave node, the radio frequency survey unit 107 loads the radio frequency busy packet information into the radio frequency survey result packet and transmits it to the master node of the own PCF cluster.

  The neighboring cluster discovery unit 108 detects neighboring clusters that can be connected wirelessly. When the own node is a master, the neighboring cluster discovery unit 108 transmits a neighboring cluster discovery packet by itself. Alternatively, a neighboring cluster discovery instruction packet is transmitted to each slave node in the own PCF cluster. In that case, the neighboring cluster discovery unit 108 of the slave node transmits a neighboring cluster discovery packet to each neighboring node.

  When the neighboring cluster discovery unit 108 receives the neighboring cluster discovery packet, the neighboring cluster discovery unit 108 refers to the transmitting station address, and if it is different from the address of the node belonging to the PCF cluster of the own node, returns the neighboring cluster response packet to the transmission source node. . If the transmission station address matches the address of a node belonging to the own PCF cluster, no response is returned to the transmission source node. When the node that received the neighborhood cluster response packet is a slave node, the neighborhood cluster discovery unit 108 mounts information on the neighborhood cluster response packet and information on the received electric field strength included in the neighborhood cluster response packet in the neighborhood cluster response notification packet. It transmits to the master node of its own PCF cluster.

  The inter-cluster connection unit 109 connects the local PCF cluster and the neighboring PCF cluster based on the information in the neighboring cluster response packet and the neighboring cluster response notification packet collected by the neighboring cluster discovery unit 108 when the own node is a master. To decide. At this time, when there are a plurality of communication routes for the same neighboring PCF cluster, a connection route having a stronger received electric field strength is selected.

  The inter-cluster connection unit 109 transmits a cluster connection request packet when requesting a direct connection to a node of another PCF cluster when the own node is a master. When a connection is requested to a node of another PCF cluster via a slave node in the own PCF cluster, a cluster connection request transmission instruction packet is transmitted to the slave node. The inter-cluster connection unit 109 of the slave node that has received the cluster connection request transmission instruction packet transmits the cluster connection request packet to the neighboring nodes.

  The inter-cluster connection unit 109 of the master node that has received the cluster connection request packet transmits a cluster connection response packet to the node of the PCF cluster that has requested the cluster connection. When the cluster connection response packet is received by the slave node, the inter-cluster connection unit 109 mounts the received cluster connection response packet information in the cluster connection response notification packet and transmits it to the master node of the own PCF cluster. As a result, a connection with another PCF cluster is established.

  Next, a method for forming a wireless multi-hop network according to the present invention will be described with reference to FIGS.

  FIG. 4 is a flowchart showing a processing procedure of the neighboring node discovery unit shown in FIG. 3, and FIG. 5 is a state transition diagram showing processing of the association execution unit shown in FIG. 6 and 7 are flowcharts showing the processing procedure of the radio frequency examining unit shown in FIG. 3, and FIGS. 8 and 9 are flowcharts showing the processing procedure of the neighboring cluster finding unit 108 shown in FIG. 10 and 11 are flowcharts showing the processing procedure of the inter-cluster connection unit shown in FIG.

  As shown in FIG. 4, the neighboring node discovery unit 105 of each node first transmits a neighboring node discovery packet (step A1). The neighboring node discovery unit 105 of the node that has transmitted the neighboring node discovery packet enters a reception waiting state for the neighboring node response packet (step A2).

  Next, the neighboring node discovery unit 105 determines whether or not a neighboring node response packet has been received (step A3). If the neighboring node response packet has been received, the neighboring node finding unit 105 counts up the number of neighboring nodes of the own node (step S3). A4).

  Subsequently, the neighboring node discovery unit 105 determines whether or not a neighboring node discovery packet has been received (step A5). When the neighboring node discovery packet is received, a neighboring node response packet is returned to the transmission source node. (Step A6).

  If the neighboring node discovery packet is not received in the process of step A5, the neighboring node discovery unit 105 determines whether or not a predetermined time has passed (time over) (step A7). Returning to the process, steps A3 to A7 are repeated. Further, when a time-over is detected in the process of step A7, the number of neighboring nodes of the own node is mounted in the neighboring node number notification packet and transmitted to each neighboring node (step A8). The node that has transmitted the neighboring node number notification packet enters a reception waiting state for the neighboring node number notification packet from the neighboring node (step A9).

  Next, the neighboring node discovery unit 105 determines whether or not a neighboring node number notification packet has been received (step A10). When the neighboring node number notification packet is received, the information (number of neighboring nodes) is transmitted from the transmission source. Save each associated with a node.

  If the neighboring node count notification packet is not received, it is determined whether or not a predetermined time has passed (time over) (step A11). If the time is not over, the process returns to step A10 and the processing from step A1 to step A11 is performed. repeat. If the time is over, the process by the neighboring node discovery unit 105 is terminated.

  As shown in FIG. 5, the association execution unit 106 first compares the number of neighboring nodes detected by the neighboring node discovery unit 105 with the number of neighboring nodes notified from other nodes. When the master node is not in the vicinity and the number of neighboring nodes of the own node is the maximum, the own node is selected as the master node and the reception of the association request packet from the neighboring node is awaited. Here, when there are a plurality of nodes having the maximum number of neighboring nodes, the local node is selected as the master node when the received electric field strength is maximum. Further, when there are a plurality of nodes having the maximum number of neighboring nodes and the maximum received electric field strength, the local node is selected as the master node when the MAC address value is minimum (or maximum).

  On the other hand, if there is a node having a larger number of neighboring nodes than the own node, the node having the largest number of neighboring nodes is selected, and an association request packet is transmitted to that node. When there are a plurality of nodes having the maximum number of neighboring nodes, the node having the maximum received electric field strength is selected. When there are a plurality of nodes having the maximum number of neighboring nodes and the maximum received electric field strength, the node having the minimum (or maximum) MAC address value is selected, and the association request packet is transmitted to that node.

  When the association execution unit 106 of the node selected as the master receives the association request packet, it returns an association response packet to the transmission source node.

  The node that has transmitted the association request packet waits to receive an association response packet. When an association response packet is received, the node becomes a slave node. The node that has not received the association response packet performs the neighboring node detection process by the neighboring node discovery unit 105 shown in FIG. 4 again (cluster reset).

  In the node selected as the master, the radio frequency investigation unit 107 determines the radio frequency used in the own PCF cluster.

  As shown in FIG. 6, the radio frequency survey unit 107 first transmits a radio frequency survey packet to the nodes of the neighboring PCF cluster (step C1). The radio frequency survey unit 107 that has transmitted the radio frequency survey packet enters a reception wait state for a radio frequency busy packet that is returned from a nearby PCF cluster and that includes information on the radio frequency used in the PCF cluster (used radio frequency). (Step C2).

  Next, the radio frequency investigation unit 107 determines whether or not a radio frequency busy packet has been received (step C3), and when a radio frequency busy packet is received, extracts information on the used radio frequency included therein, The used radio frequency for each PCF cluster is stored (step C4). If the radio frequency busy packet is not received, it is determined whether a predetermined time has passed (time over) or not (step C5). If the time is not over, the process returns to step C3 to perform the processing from step C3 to step C5. repeat. When time is over, the radio frequency investigation instruction packet is transmitted to all the slave nodes, and the radio frequency used in the neighboring PCF cluster is investigated through the slave node (step C6). The radio frequency investigation unit 107 of the slave node that has received the radio frequency investigation instruction packet executes processing according to the flowchart shown in FIG.

  When transmitting the radio frequency investigation instruction packet, the radio frequency investigation unit 107 of the master node determines whether or not a radio frequency investigation result packet has been received from the slave node (step C7). When the radio frequency investigation result packet is received from the slave node, information on the radio frequency used for each PCF cluster included in the packet is stored (step C8).

  If the radio frequency survey result packet is not received, it is determined whether a predetermined time has passed (time over) or not (step C9). If the time is not over, the process returns to step C7 to perform the processing from step C7 to step C9. repeat. When the time is over, the unused radio frequency is determined as the used radio frequency of the own PCF cluster with reference to the stored used radio frequency of the neighboring PCF cluster (step C10), and information on the determined used radio frequency is the cluster. It is mounted on the internal radio frequency notification packet and notified to each slave node in its own PCF cluster (step C11).

  As shown in FIG. 7, the radio frequency investigation unit 107 of the slave node is waiting to receive a radio frequency investigation instruction packet (step D1). Radio frequency investigation unit 107 determines whether or not a radio frequency investigation instruction packet has been received from the master node (step D2). If no radio frequency investigation instruction packet has been received, it waits for a radio frequency investigation instruction packet from the master node. . When receiving the radio frequency survey instruction packet from the master node, the radio frequency survey packet is transmitted to the neighboring node (other PCF cluster) (step D3). Then, the radio frequency examining unit 107 determines whether or not a radio frequency busy packet has been received from a neighboring node (step D4). If a radio frequency busy packet is received, the radio frequency used by other PCF clusters included therein is determined. Is loaded into the radio frequency survey result packet and returned to the master node of the own PCF cluster. If a radio frequency busy packet is not received, it is determined whether a predetermined time has passed (time over) or not (step D5). If not, the process returns to step D3 and steps D3 to D5 are performed. Repeat the process. When the time is over, information indicating “no response” is mounted in the radio frequency survey result packet and returned to the master node of the own PCF cluster, and the process is terminated.

  When the master node determines the use radio frequency of the own PCF cluster, the master node detects a neighboring PCF cluster that can be connected by the neighboring cluster discovery unit 108.

  As shown in FIG. 8, the neighboring cluster discovery unit 108 of the Master node first transmits a neighboring cluster discovery packet to the neighboring node (step E1). The neighborhood cluster discovery unit 108 that has transmitted the neighborhood cluster discovery packet enters a reception waiting state for the neighborhood cluster response packet (step E2).

  Next, the neighboring cluster discovery unit 108 determines whether or not a neighboring cluster response packet has been received (step E3). If a neighboring cluster response packet has been received, the neighboring cluster information included in the packet is stored (step E3). E4). The neighboring cluster information is information for identifying other PCF clusters existing in the vicinity of the own PCF cluster. If the neighboring cluster response packet is not received, it is determined whether a predetermined time has passed (time over) or not (step E5). If not, the process returns to step E3 to perform the processing from step E3 to step E5. repeat. If the time is over, a neighbor cluster discovery instruction packet is transmitted to the slave node (step E6). The neighbor cluster discovery unit 108 of the slave node that has received the neighbor cluster discovery instruction packet executes processing according to the flowchart shown in FIG.

  The neighboring cluster discovery unit 108 of the master node that has transmitted the neighboring cluster discovery instruction packet enters a reception waiting state for the neighboring cluster response notification packet from the slave node (step E7).

  Subsequently, the neighboring cluster discovery unit 108 determines whether or not a neighboring cluster response notification packet has been received from the slave node (step E8). When the neighboring cluster response notification packet has been received, the neighboring cluster included in the packet is determined. Information is saved (step E9). If the neighboring cluster response notification packet is not received, it is determined whether a predetermined time has passed (time over) or not (step E10). If the time is not over, the process returns to step E8 and the processing from step E8 to step E10 is performed. repeat. If the time is over, the process by the neighboring cluster discovery unit 108 is terminated.

  As shown in FIG. 9, the neighbor cluster discovery unit 108 of the slave node is in a waiting state for reception of a neighbor cluster discovery instruction packet from the master node (step F1). The neighboring cluster discovery unit 108 first determines whether or not a neighboring cluster discovery instruction packet has been received from the master node (step F2). If the neighboring cluster discovery instruction packet has not been received, the neighboring cluster discovery instruction packet is received from the master node. I wait. When the neighboring cluster discovery instruction packet is received from the master node, the neighboring cluster discovery packet is transmitted to the neighboring node (other PCF cluster) (step F3). Then, it is determined whether or not a neighboring cluster response packet has been received from a neighboring node (step F4). If a neighboring cluster response packet has been received, neighboring cluster information included therein is stored (step F5). If the neighboring cluster response packet is not received, it is determined whether a predetermined time has passed (time over) or not (step F6). If the time is not over, the process returns to step F4 to return from step F4 to step F6. Repeat the process. When the time is over, the stored neighboring cluster information is mounted in the neighboring cluster response notification packet, and the reply is returned to the master node of the own PCF cluster, and the process is terminated.

  When the master node collects the neighboring cluster information by the neighboring cluster discovery unit 108, the master node determines a communication route with the neighboring PCF cluster by the inter-cluster connection unit 109.

  As shown in FIG. 10, the inter-cluster connection unit 109 of the Master node first refers to the collected neighboring cluster information (step G1), and determines whether there is one communication route with each neighboring PCF cluster. (Step G2). When there is one communication route with a neighboring PCF cluster, when the master node is directly connected to the PCF cluster, a cluster connection request packet is transmitted from the master node. When connecting to the PCF cluster via the slave node, a cluster connection request transmission instruction packet is transmitted to the slave node (step G6).

  On the other hand, when there are a plurality of communication routes with neighboring PCF clusters, the inter-cluster connection unit 109 selects a communication route that minimizes the number of hops (step G3). Then, it is determined whether or not there is one communication route that minimizes the number of hops with the neighboring PCF cluster (step G3). If there is one communication route that minimizes the number of hops, the process proceeds to step G6. The process proceeds to processing, and a cluster connection request packet or a cluster connection request transmission instruction packet is transmitted. If there are a plurality of communication routes with the smallest number of hops, the communication route with the maximum received electric field strength of the neighboring cluster response packet is selected (step G5), and the process proceeds to step G6, where the cluster connection request packet or A cluster connection request transmission instruction packet is transmitted. The inter-cluster connection unit 109 of the slave node that has received the cluster connection request transmission instruction packet executes processing according to the flowchart shown in FIG.

  The master node that has transmitted the cluster connection request packet or the cluster connection request transmission instruction packet enters a state of waiting for reception of a cluster connection response packet from another PCF cluster or a cluster connection response result packet from the slave node (step G7).

  The inter-cluster connection unit 109 determines whether or not a cluster connection response packet from all PCF clusters that transmitted the cluster connection request packet or a cluster connection response result packet from the slave node has been received (step G8). If no response packet or cluster connection response result packet has been received, reception of these packets is awaited. If a cluster connection response packet or a cluster connection response result packet is received, the process ends.

  As shown in FIG. 11, the inter-cluster connection unit 109 of the slave node is in a waiting state for receiving a cluster connection request transmission instruction packet from the master node (step H1). When the inter-cluster connection 109 receives the cluster connection request transmission instruction packet from the master node, the inter-cluster connection 109 transmits the cluster connection request packet to the designated neighboring PCF cluster (step H2). Then, it is determined whether or not a cluster connection response packet has been received from the neighboring PCF cluster (step H3). If no cluster connection response packet is received, the reception of the cluster connection response packet is awaited. When a cluster connection response packet is received, information contained in the packet is loaded into the cluster connection response result packet and transmitted to the master node of the own PCF cluster (step H4), and connection with the neighboring PCF cluster is established. Establish and end processing.

  According to the present invention, neighboring nodes are connected so as to be able to communicate with each other in a polling manner, and a plurality of polling clusters including one node operating as a master and at least one node operating as a slave are formed. By setting a communication route that enables communication using the carrier sense method between polling clusters, the delay time caused by packet collisions between neighboring nodes is reduced compared to a configuration using only the carrier sense method. Compared to a configuration using only the delay time, the delay time caused by polling waiting time between polling clusters is reduced. Accordingly, packet transfer delay in the wireless multi-hop network is reduced.

(Example)
Next, an embodiment of a method for forming a wireless multi-hop network according to the present invention will be described.

  In this embodiment, a case where a wireless multi-hop network is formed from a state where 18 wireless LAN switches WS1 to WS18 are arranged as shown in FIG. 12 will be described as an example.

  Each wireless LAN switch (node) WS1 to WS18 arranged as shown in FIG. 12 first calculates the number of neighboring nodes of the own node according to the procedure shown in FIG. The calculation results are shown in Table 1.

ＷＳ１〜ＷＳ１８は、自ノードの近傍ノード数を、近傍ノード数通知パケットを用いてそれぞれ近傍ノードへ通知する。

WS1 to WS18 notify the neighboring nodes of the number of neighboring nodes of the own node using neighboring node number notification packets.

  As shown in Table 1, WS1 to WS18 are not all Master nodes, and WS1, WS7, WS12, and WS16 have the maximum number of neighboring nodes. Therefore, these nodes wait for association request packets from other nodes. WS2, WS3, WS4, WS5, WS6, WS8, WS9, WS10, WS11, WS13, WS14, WS15, and WS17 transmit an association request packet to the node having the largest number of neighboring nodes.

  Specifically, WS2, WS3, WS4, and WS5 transmit an association request packet to WS1 having the maximum number of neighboring nodes.

  WS8, WS9, WS10, and WS11 transmit an association request packet to WS7. Here, as shown in Table 1, in WS6, the neighboring nodes WS1 and WS7 each have the maximum (five) number of neighboring nodes. Therefore, the WS 6 transmits an association request packet to a node having a larger received field strength of the neighborhood node response packet. Here, it is assumed that the neighboring node response packet is received from WS7 with a stronger received electric field strength than WS1. Therefore, WS6 transmits an association request packet to WS7.

  WS14 and WS15 transmit an association request packet to WS12. WS13, WS17, and WS18 transmit an association request packet to WS16.

  Upon receiving the association request packet, WS1, WS7, WS12, and WS16 each return an association response packet to the transmission source node. The WS1, WS7, WS12, and WS16 that have received the association request packet are master nodes of the PCF cluster. On the other hand, the other node that has received the association response packet becomes a slave node of the PCF cluster.

  Next, each of WS1, WS7, WS12, and WS16 selected as the master determines a radio frequency to be used in its own PCF cluster. The radio frequency used in each PCF cluster is determined according to the procedure shown in FIGS. Here, the first PCF cluster uses radio frequency f1, the second PCF cluster uses radio frequency f2, the third PCF cluster uses radio frequency f3, and the fourth PCF cluster uses radio frequency f2. Use f4.

  Subsequently, the WS1, WS7, WS12, and WS16 selected as the master detect neighboring PCF clusters using the neighboring cluster discovery packet and the neighboring cluster discovery instruction packet according to the procedure shown in FIGS. Table 2 shows the detection results of neighboring PCF clusters.

表２に示す例では、ＷＳ１をＭａｓｔｅｒノードとする第１のＰＣＦクラスタでは第２のＰＣＦクラスタに対する通信ルートを２つ発見する。また、ＷＳ７をＭａｓｔｅｒノードとする第２のＰＣＦクラスタでは、第１のＰＣＦクラスタに対する２つの通信ルートと、第３のＰＣＦクラスタ及び第４のＰＣＦクラスタに対する通信ルートをそれぞれ１つずつ発見する。また、ＷＳ１２をＭａｓｔｅｒノードとする第３のＰＣＦクラスタでは、第２のＰＣＦクラスタ及び第４のＰＣＦクラスタに対する通信ルートをそれぞれ１つずつ発見する。また、ＷＳ１６をＭａｓｔｅｒノードとする第４のＰＣＦクラスタでは、第２のＰＣＦクラスタ及び第３のＰＣＦクラスタに対する通信ルートをそれぞれ１つずつ発見する。

In the example shown in Table 2, two communication routes for the second PCF cluster are found in the first PCF cluster having WS1 as the master node. Further, in the second PCF cluster having WS7 as the master node, two communication routes for the first PCF cluster and one communication route for the third PCF cluster and the fourth PCF cluster are found one by one. Further, in the third PCF cluster having WS 12 as the master node, one communication route for each of the second PCF cluster and the fourth PCF cluster is found. Further, in the fourth PCF cluster having WS 16 as the master node, one communication route for each of the second PCF cluster and the third PCF cluster is found.

  Here, there are a plurality of communication routes between the first PCF cluster and the second PCF cluster. In this case, the master node of the first PCF cluster and the second PCF cluster selects a communication route with the smallest number of hops. In the example shown in Table 2, when transmitting from the first PCF cluster to the second PCF cluster, the communication route passing through WS1 to WS6 is the shortest. When transmitting from the second PCF cluster to the first PCF cluster, the communication route passing from WS6 to WS1 is the shortest.

  The master node of each PCF cluster selects the minimum communication route for the neighboring PCF cluster, transmits the cluster connection request packet or the cluster connection request transmission instruction packet, and receives the cluster connection response packet or the cluster connection response result packet. Establish a connection with a neighboring PCF cluster.

  FIG. 13 shows an example of a wireless multi-hop network formed by the above procedure. FIG. 14 shows how a packet is transferred from WS2 to WS15 of the wireless multi-hop network shown in FIG.

  As shown in FIG. 14, in the wireless multi-hop network shown in FIG. 13, when packets are transferred from WS2 to WS15, the packets are transferred in the order of WS2 to WS1, WS1 to WS6 in the first PCF cluster. As shown in FIG. 14, in the first PCF cluster, the packet transfer from WS2 to WS1 is controlled by WS1, which is the master node, but since the packet is transferred from WS1 to WS6 by the carrier sense method, waiting for polling is performed. Time does not occur.

  Further, in the second PCF cluster, packets are transferred in the order of WS6 to WS7 and WS7 to WS10. However, since the packets are transferred by the carrier sense method, no polling waiting time occurs.

  Further, in the third PCF cluster, packets are transferred in the order of WS10 to WS12 and WS12 to WS15, but no packet waiting time is generated because packets are transferred from WS10 to WS12 by the carrier sense method. However, there is a polling waiting time from the end of packet transfer from WS10 to WS12 to the start of packet transfer from WS12 to WS15. However, since the polling waiting time is significantly reduced as compared with the conventional wireless multi-hop network shown in FIG. 15, in the wireless multi-hop network configured by the forming method of the present invention, the packet transfer delay is greatly increased. Can be reduced.

  In the above description, when forming a PCF cluster, a method of limiting the number of slave nodes constituting the PCF cluster by not returning an association response packet when the master node exceeds the predetermined number of associations has been shown.

  However, when there are a plurality of nodes that can be master nodes, that is, when there are a plurality of nodes having the maximum number of neighboring nodes, the slave node sends the current association to the nodes before sending the association request packet. The association request packet may be transmitted to the node with the smallest number of associations from the inquiry result. In that case, since the number of Slave nodes belonging to each PCF cluster becomes uniform, there is an effect that the processing load of each Master node is smoothed.

It is a flowchart which shows the procedure of the formation method of the radio | wireless multihop network of this invention. It is a schematic diagram which shows one structural example of the packet used with the formation method of the radio | wireless multihop network of this invention. It is a block diagram which shows one structural example of the node which comprises the radio | wireless multihop network of this invention. It is a flowchart which shows the process sequence of the adjacent node discovery part shown in FIG. It is a state transition diagram which shows the process of the association execution part shown in FIG. It is a flowchart which shows the process sequence of the radio frequency investigation part shown in FIG. It is a flowchart which shows the process sequence of the radio frequency investigation part shown in FIG. 4 is a flowchart illustrating a processing procedure of a neighboring cluster discovery unit illustrated in FIG. 3. 4 is a flowchart illustrating a processing procedure of a neighboring cluster discovery unit illustrated in FIG. 3. It is a flowchart which shows the process sequence of the connection part between clusters shown in FIG. It is a flowchart which shows the process sequence of the connection part between clusters shown in FIG. It is a block diagram which shows the example of arrangement | positioning of the node which comprises the radio | wireless multihop network of this invention. It is a block diagram which shows one structural example of the radio | wireless multihop network of this invention formed from the example of arrangement | positioning of the node shown in FIG. It is a schematic diagram which shows the example of generation | occurrence | production of the delay time at the time of packet transmission of the radio | wireless multihop network shown in FIG. It is a block diagram which shows the example of 1 structure of the conventional radio | wireless multihop network. FIG. 16 is a schematic diagram illustrating an example of occurrence of a delay time during packet transfer in the wireless multi-hop network illustrated in FIG. 15.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Node 101 1st wireless interface 102 2nd wireless interface 103 Wired interface 104 Master / Slave operation part 105 Neighboring node discovery part 106 Association execution part 107 Radio frequency investigation part 108 Neighboring cluster discovery part 109 Intercluster connection part WS1-WS18 Wireless LAN switch

Claims (18)

A method of forming a wireless multi-hop network comprising a plurality of nodes that are communicably connected by radio,
A first step of detecting, for each node, neighboring nodes capable of communicating in one hop;
A second step of connecting the neighboring nodes so as to enable communication by a polling method, and forming a plurality of polling clusters including one node operating as a master and at least one node operating as a slave;
A third step of detecting adjacent neighboring polling clusters for each of the polling clusters;
A fourth step of setting a communication route that enables communication by a carrier sense method between the neighboring polling clusters;
A method for forming a wireless multi-hop network. The second step includes
Select the node with the largest number of nearby nodes as the master,
When there are a plurality of nodes having the maximum number of neighboring nodes, the node having the largest received electric field strength from the neighboring nodes is selected as the master,
When there are a plurality of nodes having the maximum number of neighboring nodes and the maximum received electric field strength from the neighboring nodes, the node having the smallest or largest address value assigned to each of the nodes is set as the master. The method of forming a wireless multi-hop network according to claim 1 to select. The second step includes
Select the node with the largest number of nearby nodes as the master,
2. The method of forming a wireless multi-hop network according to claim 1, wherein when there are a plurality of nodes having the maximum number of neighboring nodes, a node having the smallest number of nodes that requested association with the node is selected as the master. The fourth step includes
2. The wireless multi-hop network according to claim 1, wherein when there are a plurality of communication routes that enable communication by a carrier sense method between the neighboring polling clusters, a communication route that minimizes the number of hops with respect to the neighboring polling cluster is selected. Forming method. The fourth step includes
5. The formation of a wireless multi-hop network according to claim 4, wherein when there are a plurality of communication routes having a minimum number of hops with respect to the neighboring polling cluster, a communication route having a maximum received electric field strength from the neighboring polling cluster is selected. Method. The second step includes
6. The method according to claim 1, further comprising a process of transmitting information on a radio frequency used by each of the neighboring polling clusters and selecting an unused radio frequency in another polling cluster. A method for forming a wireless multi-hop network. A wireless communication device for configuring a wireless multi-hop network for transferring packets by wireless,
A neighboring node discovery unit that detects neighboring nodes that can communicate in one hop;
An association execution unit that selects the own wireless communication device as either a master or a slave of a polling cluster that is an aggregate of wireless communication devices, and connects to the neighboring nodes so as to enable communication by a polling method;
A neighboring cluster discovery unit that detects neighboring polling clusters adjacent to each polling cluster;
An inter-cluster connection unit that sets a communication route that enables communication by a carrier sense method between the neighboring polling clusters;
A wireless communication device. The association execution unit
Select the node with the largest number of nearby nodes as the master,
When there are a plurality of nodes having the maximum number of neighboring nodes, the node having the largest received electric field strength from the neighboring nodes is selected as the master,
When there are a plurality of nodes having the maximum number of neighboring nodes and the maximum received electric field strength from the neighboring nodes, the node having the smallest or largest address value assigned to each of the nodes is set as the master. The wireless communication device according to claim 7 to be selected. The association execution unit
Select the node with the largest number of nearby nodes as the master,
8. The wireless communication apparatus according to claim 7, wherein when there are a plurality of nodes having the maximum number of neighboring nodes, the node having the smallest number of nodes that requested association with the node is selected as the master. The inter-cluster connection unit is
The wireless communication apparatus according to claim 7, wherein when there are a plurality of communication routes that enable communication by a carrier sense method between the neighboring polling clusters, the wireless communication device selects a communication route that minimizes the number of hops with respect to the neighboring polling cluster. The inter-cluster connection unit is
The wireless communication apparatus according to claim 10, wherein when there are a plurality of communication routes having a minimum number of hops with respect to the neighboring polling cluster, the wireless communication device selects a communication route having a maximum received electric field intensity from the neighboring polling cluster.   12. The radio frequency survey unit according to claim 7, further comprising: a radio frequency examining unit that transmits information on a radio frequency used by each neighboring polling cluster and selects an unused radio frequency in another polling cluster. The wireless communication device according to item. A program for causing a computer constituting a wireless multi-hop network that transfers packets by radio to execute the program,
A first step of detecting neighboring nodes capable of communicating in one hop;
A second step of selecting the own wireless communication device as either a master or a slave of a polling cluster that is an aggregate of wireless communication devices and connecting the neighboring nodes so as to enable communication by a polling method;
A third step of performing processing for detecting neighboring polling clusters adjacent to each of the polling clusters;
A fourth step of executing a process for setting a communication route enabling communication by a carrier sense method between the neighboring polling clusters;
A program that causes a computer to execute. The second step includes
Select the node with the largest number of nearby nodes as the master,
When there are a plurality of nodes having the maximum number of neighboring nodes, the node having the largest received electric field strength from the neighboring nodes is selected as the master,
When there are a plurality of nodes having the maximum number of neighboring nodes and the maximum received electric field strength from the neighboring nodes, the node having the smallest or largest address value assigned to each of the nodes is set as the master. The program according to claim 13 to be selected. The second step includes
Select the node with the largest number of nearby nodes as the master,
14. The program according to claim 13, wherein when there are a plurality of nodes having the maximum number of neighboring nodes, the node having the smallest number of nodes that requested association with the node is selected as the master. The fourth step includes
The program according to claim 13, wherein when there are a plurality of communication routes that enable communication by a carrier sense method between the neighboring polling clusters, a communication route that minimizes the number of hops with respect to the neighboring polling cluster is selected. The fourth step includes
The program according to claim 16, wherein when there are a plurality of communication routes having a minimum number of hops with respect to the neighboring polling cluster, the communication route having the maximum received electric field intensity from the neighboring polling cluster is selected. The second step includes
18. The method according to claim 13, further comprising a process of transmitting information on a radio frequency used by each of the neighboring polling clusters and selecting an unused radio frequency in another polling cluster. program.

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