WO2013136527A1

WO2013136527A1 - Path selection method and wireless device

Info

Publication number: WO2013136527A1
Application number: PCT/JP2012/056940
Authority: WO
Inventors: 岳夫本田; 秀成三輪; 瑞直石川; 正和由良
Original assignee: 富士通株式会社
Priority date: 2012-03-16
Filing date: 2012-03-16
Publication date: 2013-09-19

Abstract

This wireless device has a power supply information acquisition unit, a rating value calculation unit, and a path selection unit. The power supply information acquisition unit acquires power supply information indicating whether the power supply of a neighboring wireless device or the device itself is an internal power supply or an external power supply. The rating value calculation unit, if the power supply information acquired by the power supply information acquisition unit indicates an internal power supply, calculates a first value as a rating value of a path between the neighboring wireless device and the device itself. The rating value calculation unit, if the power supply information indicates an external power supply, calculates a second value representing being of higher quality than the first value as the rating value. The path selection unit selects a neighboring wireless device corresponding to the rating value representing being of highest quality among a sum of a rating value for a path from each neighboring wireless device to a destination and the rating value calculated at the rating value calculation unit, as a forwarding destination when transmitting packets to the destination.

Description

Route selection method and wireless device

The present invention relates to a route selection method and a wireless device.

In recent years, research on an ad hoc network in which a plurality of wireless devices are interconnected in an autonomous and distributed manner is underway. Hereinafter, the wireless device is simply referred to as a node. In an ad hoc network, an access point is not installed, and each node transmits a packet to a destination by relaying the packet received from an adjacent node to another node based on communication path information. That is, each node calculates an evaluation value of a plurality of communication paths leading to a certain target node, selects an adjacent node included in a communication path with a better evaluation value as a relay node as a packet transfer destination, and selects a packet. Forward. The communication path evaluation value is calculated using, for example, an evaluation formula that combines a plurality of types of evaluation parameters.

Also, in a recent ad hoc network, it is assumed that a node using an external power source such as an AC power source as a driving power source and a node using an internal power source such as a battery as the driving power source coexist. Even in this case, each node selects a relay node as a packet transfer destination regardless of the type of power supply of the node. For this reason, nodes using an AC power source and nodes using a battery are equally selected as packet transfer destinations. However, a node using a battery becomes unusable when the electric power stored in the battery is exhausted. Therefore, it is desired to suppress the power consumption of the node using the battery as much as possible.

As a technology to reduce the power consumption of nodes using batteries, each node acquires information indicating the type of power supply of other nodes, and when the acquired information indicates an AC power supply, the other node is selected as a packet transfer destination, There is a technique for excluding other nodes from the packet transfer destination when a battery is indicated. Further, there is a technique in which each node measures the remaining power of the battery of another node and determines whether or not to select another node as a packet transfer destination based on the measured remaining power.

JP 2004-282268 A Japanese Patent Laid-Open No. 2005-160062

However, the above-described conventional technology has a problem in that although it is possible to suppress power consumption of a node using a battery as a power source, an appropriate communication path may not necessarily be selected.

That is, in the technique of excluding another node from the packet transfer destination when the power type of the other node indicates a battery, only the node using the AC power supply as the power supply is selected as the packet transfer destination. For this reason, when nodes using AC power supplies are installed at positions separated from each other, the communication path becomes a detour and there is a possibility that the arrival rate of the packet is lowered.

Further, in the technology for determining whether or not to select another node as a packet transfer destination based on the remaining power of the other node, the other node having the smallest remaining power is excluded from the packet transfer destination. Only the node using the AC power supply is selected as the packet transfer destination. For this reason, when nodes using AC power supplies are installed at positions separated from each other, the communication path becomes a detour and there is a possibility that the arrival rate of the packet is lowered.

The disclosed technology has been made in view of the above, and provides a route selection method and a wireless device capable of selecting an appropriate communication route while suppressing power consumption of a node using a battery as a power source. With the goal.

The route selection method disclosed in the present application is, in one aspect, a route selection method in a wireless device constituting an ad hoc network. In the route selection method, power information indicating whether an adjacent wireless device or the power supply of the wireless device is an internal power supply or an external power supply is acquired. The route selection method calculates a first value as an evaluation value of a route between the adjacent wireless device and the wireless device when the acquired power supply information indicates an internal power supply. In the route selection method, when the power supply information indicates an external power supply, a second value indicating that the evaluation value is higher in quality than the first value is calculated. In addition, the route selection method may include the neighboring corresponding to the evaluation value representing the highest quality among the addition values of the evaluation value of the route from each adjacent wireless device to the destination and the calculated evaluation value. Are selected as transfer destinations when packets are transmitted to the destination.

According to one aspect of the route selection method disclosed in the present application, it is possible to select an appropriate communication route while suppressing power consumption of a node using a battery as a power source.

FIG. 1 is a diagram illustrating the configuration of the ad hoc network according to the first embodiment. FIG. 2 is a diagram illustrating an example of a data structure of a hello packet according to the first embodiment. FIG. 3 is a functional block diagram illustrating the configuration of the node according to the first embodiment. FIG. 4 is a diagram illustrating an example of a data structure of the work table according to the first embodiment. FIG. 5 is a diagram illustrating an example of a data structure of the communication path table according to the first embodiment. FIG. 6 is a diagram illustrating an example of a data structure of a conversion table held by the evaluation value calculation unit according to the first embodiment. FIG. 7 is a diagram for explaining an example of a processing flow from when the node according to the first embodiment receives a hello packet to when a data packet transfer destination is selected. FIG. 8 is a flowchart illustrating a processing procedure of processing for calculating an evaluation value of a wireless link from a node according to the first embodiment to a destination node and storing the evaluation value in a communication path table. FIG. 9 is a flowchart showing a processing procedure of processing for transferring a data packet. FIG. 10 is a flowchart illustrating a processing procedure of processing for transmitting a hello packet. FIG. 11 is a flowchart illustrating a processing procedure for transmitting a data packet. FIG. 12 is a diagram illustrating verification conditions of the verification method according to the first embodiment. FIG. 13 is a diagram illustrating weighting factors of other evaluation parameters. FIG. 14 is a diagram illustrating a configuration of an ad hoc network applied to a simulation program. FIG. 15 is a diagram illustrating a result of comparing the average value of the number of relay packets of the battery nodes included in the ad hoc network for each verification condition. FIG. 16 is a diagram illustrating a result of comparing the average value of the number of relay packets of the AC power supply node included in the ad hoc network for each verification condition. FIG. 17 is a diagram illustrating a result of comparing the ratio between the number of relay packets of the AC power supply node and the number of relay packets of the battery node in the total number of packets for each verification condition. FIG. 18 is a diagram illustrating a result of comparing the drop rate for each verification condition. FIG. 19 is a diagram (part 1) illustrating an example of a data structure of a conversion table held by the evaluation value calculation unit according to the second embodiment. FIG. 20 is a diagram (part 2) illustrating an example of a data structure of a conversion table held by the evaluation value calculation unit according to the second embodiment. FIG. 21 is a flowchart illustrating a processing procedure of processing for calculating an evaluation value of a wireless link from a node according to the second embodiment to a destination node and storing the evaluation value in a communication path table. FIG. 22 is a diagram illustrating a result of comparing the number of out-of-battery nodes included in the ad hoc network for each verification condition. FIG. 23 is a diagram illustrating a hardware configuration of a computer that configures a node according to the first and second embodiments.

Hereinafter, embodiments of the route selection method and the wireless device disclosed in the present application will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

The configuration of the ad hoc network according to the first embodiment will be described. FIG. 1 is a diagram illustrating the configuration of the ad hoc network according to the first embodiment. As shown in FIG. 1, the ad hoc network includes a GW (Gate Way) 1 and nodes 100a to 100e. The nodes 100a to 100e are examples of wireless devices. Although not shown here, the ad hoc network may have other nodes.

GW1 and each of the nodes 100a to 100e are connected to adjacent nodes by wireless links. A wireless link is an example of a route. For example, the GW 1 is connected to the

nodes

100c, 100d, and 100e. The node 100a is connected to the

nodes

100b and 100c. The node 100b is connected to the

nodes

100a, 100d, and 100e. The node 100c is connected to the

nodes

100a, 100e, and GW1. The node 100d is connected to the nodes 100b and GW1. The node 100e is connected to the

nodes

100b, 100c, and GW1.

In the ad hoc network shown in FIG. 1, a node using an external power source as a driving power source and a node using an internal power source as a driving power source coexist. For example, the

nodes

100a, 100b, and 100e are nodes (hereinafter referred to as “AC power supply nodes”) that use AC power as an example of external power as drive power. The

nodes

100c and 100d are nodes (hereinafter referred to as “battery nodes”) that use batteries, which are examples of internal power supplies, as drive power supplies. Hereinafter, the nodes 100a to 100e are collectively referred to as the node 100 when the nodes 100a to 100e are not particularly distinguished.

The node 100 constructs a communication path by transmitting and receiving a hello packet. When constructing a communication path, the node 100 calculates a communication path evaluation value using a plurality of types of evaluation parameters including a parameter indicating the type of power supply of the node 100 or the adjacent node 100. When the node 100 receives the data packet to be transferred or transmits a new data packet, the node 100 selects a communication path corresponding to the evaluation value indicating the highest quality, and selects the selected communication path. The data packet is transferred.

For example, the node 100 calculates a different value as the evaluation value of the radio link with the adjacent node 100 depending on whether the power type of the adjacent node 100 or the own node 100 is a battery or an AC power supply. To do. Specifically, when the type of power supply of the adjacent node 100 or the own node 100 is an AC power supply, the node 100 uses a value indicating that the quality is higher than the value corresponding to the battery as the evaluation value of the radio link. calculate. Then, the node 100 transmits, to the destination, a route having the highest quality of the added value of the evaluation value of the wireless link from the adjacent node 100 to the destination node 100 and the calculated evaluation value of the wireless link. Select as the destination of the data packet. Thereby, it is possible to preferentially select the communication path including the AC power supply node while reducing the opportunity for selecting the communication path including the battery node.

In the first embodiment, as an example, the higher the quality of the radio link, the smaller the evaluation value. The evaluation value that decreases as the quality of the radio link increases is equivalent to an evaluation value in which the quality of the radio link is replaced with the concept of distance, and is also referred to as “path quality distance”.

Next, the data structure of the hello packet transmitted / received by the node 100 will be described. FIG. 2 is a diagram illustrating an example of a data structure of a hello packet according to the first embodiment. As shown in FIG. 2, this hello packet has a transmission source, power supply information, a destination, ΣD, and the number of hops. Among these, the “source” stores the address of the node that is the source of the hello packet. The “power supply information” stores power supply information indicating whether the power source of the “transmission source” node of the hello packet is a battery or an AC power supply. “Destination” stores the address of the destination node of the communication path. “ΣD” stores the total value of the evaluation values of the radio links from the “destination” node to the “transmission source” node of the hello packet. The “hop count” stores the number of hops from the “source” node to the “destination” node of the hello packet.

Next, the configuration of the node 100 shown in FIG. 1 will be described. FIG. 3 is a functional block diagram illustrating the configuration of the node according to the first embodiment. As illustrated in FIG. 3, the node 100 according to the first embodiment includes a wireless communication unit 110, an input unit 120, a display unit 130, a storage unit 140, and a control unit 150.

The wireless communication unit 110 is a device that performs wireless data communication with adjacent nodes. For example, the wireless communication unit 110 corresponds to a wireless link module or the like. The control unit 150 transmits / receives a hello packet, a data packet, and the like to / from an adjacent node via the wireless communication unit 110.

The input unit 120 is an input device for inputting various information to the node 100. For example, the input unit 120 corresponds to a keyboard, a mouse, a touch panel, and the like. The display unit 130 is a display device that displays various types of information. For example, the display unit 130 corresponds to a display, a touch panel, and the like.

The storage unit 140 stores a work table 141 and a communication path table 142, for example. The storage unit 140 corresponds to, for example, a semiconductor memory element such as a RAM (Random Access Memory), a ROM (Read Only Memory), and a flash memory (Flash Memory), or a storage device such as a hard disk or an optical disk.

The work table 141 is a table for temporarily storing hello packet information. FIG. 4 is a diagram illustrating an example of a data structure of the work table according to the first embodiment. As shown in FIG. 4, this work table 141 has a destination, a transfer destination, ΣD, D, and the number of hops. Among these, the destination and the transfer destination store the destination and source of the hello packet shown in FIG. As the hop count, a value obtained by incrementing the hop count of the hello packet is stored. D stores the evaluation value of the radio link between the transfer destination node and the own node 100. ΣD stores an addition value of the value of ΣD of the hello packet and the value of D of the work table 141.

The communication path table 142 is a table that stores information on communication paths. FIG. 5 is a diagram illustrating an example of a data structure of the communication path table according to the first embodiment. As illustrated in FIG. 5, the communication path table 142 stores a destination, a transfer destination, ΣD, the number of hops, and an update time in association with each other.

Of these, the destination indicates the destination of the packet. The transfer destination indicates a transfer destination when the packet is transferred to the destination. ΣD is a total value of the evaluation values of the radio links from the own node 100 to the destination node. The number of hops indicates the number of hops from the own node 100 to the destination node. The update time indicates the latest update time of the record in the communication path table 142.

The communication path table 142 shown in FIG. 5 indicates that there are a plurality of communication paths having the same destination. For example, in FIG. 5, there are two communication paths for the destination “GW1”. Specifically, there are a communication path having the transfer destination “node 100b” and a communication path having the transfer destination “node 100c”. In FIG. 5, for convenience of explanation, the name of the node is shown as the destination or transfer destination, but the address of the node may be registered.

The control unit 150 includes a power supply information acquisition unit 151, an evaluation value calculation unit 152, a route selection unit 153, a hello packet generation unit 154, and a data packet generation unit 155. For example, the control unit 150 corresponds to an integrated device such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA). Moreover, the control part 150 respond | corresponds to electronic circuits, such as CPU and MPU (Micro Processing Unit), for example.

The power source information acquisition unit 151 acquires and acquires power source information indicating whether the power source of the adjacent node or the own node 100 is a battery or an AC power source at the time of transmission / reception of a hello packet with the adjacent node. The power supply information is output to the evaluation value calculation unit 152.

An example of processing in which the power information acquisition unit 151 acquires power information will be described. When receiving the hello packet, the power information acquisition unit 151 extracts the power information included in the hello packet and acquires the power information of the adjacent node that is the transmission source of the hello packet. Furthermore, the power information acquisition unit 151 acquires the power information of the own node 100 held in a predetermined area of the storage unit 140. The power information acquisition unit 151 outputs the acquired power information of adjacent nodes and the power information of the own node 100 to the evaluation value calculation unit 152.

The evaluation value calculation unit 152 calculates the evaluation value D of the radio link between the adjacent node and the own node 100 at the time of transmission / reception of the hello packet with the adjacent node. The evaluation value D of the radio link calculated by the evaluation value calculation unit 152 is a different value depending on the type of power supply of the adjacent node or the own node 100. For example, the evaluation value calculation unit 152 calculates “20” as the evaluation value of the radio link when the power supply of the adjacent node or the own node 100 is a battery. On the other hand, the evaluation value calculation unit 152 sets “1” indicating that the evaluation value of the radio link is higher than “20” as the evaluation value of the radio link when the power supply of the adjacent node or the own node 100 is an AC power supply. calculate.

An example of processing in which the evaluation value calculation unit 152 calculates the evaluation value of the wireless link will be described. First, the evaluation value calculation unit 152 detects the reception quality of a hello packet when a hello packet is received from an adjacent node. In the present embodiment, the evaluation value calculation unit 152, as an example of reception quality, uses an average value of the radio wave intensity of the hello packet, a dispersion value of the radio wave intensity of the hello packet, an average value of the reception period of the hello packet, and a reception period of the hello packet The variance value of is detected. The evaluation value calculation unit 152 receives the power supply information of the adjacent node and the power supply information of the own node 100 from the power supply information acquisition unit 151. The evaluation value calculation unit 152 holds a conversion table in which each reception quality and power supply information as evaluation parameters are associated with evaluation values that are conversion values of the evaluation parameters.

FIG. 6 is a diagram illustrating an example of a data structure of a conversion table held by the evaluation value calculation unit 152 according to the first embodiment. The conversion table shown in FIG. 6 stores evaluation parameters and evaluation values in association with each other. Among these, the evaluation parameter includes items of radio wave intensity average value, radio wave intensity dispersion value, reception cycle average value, reception cycle dispersion value, and power supply information. The radio field intensity average value indicates the average radio field intensity of the hello packet. The radio field intensity dispersion value indicates the dispersion value of the radio field intensity of the hello packet. The reception period average value indicates an average value of the reception period of the hello packet. The reception cycle dispersion value indicates a dispersion value of the reception cycle of the hello packet. The evaluation parameter further includes an item of power supply information. The power source information indicates whether the power source of the node is a battery or an AC power source. Moreover, an evaluation value shows the conversion value of each evaluation parameter.

The evaluation value becomes smaller as each reception quality is higher. For example, in FIG. 6, the evaluation value becomes smaller as the radio wave intensity average value “x” is larger. For example, the evaluation value becomes smaller as the radio wave intensity dispersion value “y” is smaller. For example, the smaller the reception cycle average value “z” is, the smaller the evaluation value is. The smaller the reception cycle dispersion value “w” is, the smaller the evaluation value is. The evaluation value is smaller than the value corresponding to the battery when the power supply information indicates an AC power supply. For example, in FIG. 6, the evaluation value “1” when the power supply information “ps” is “AC power supply” is smaller than the evaluation value “20” corresponding to “battery”.

Subsequently, the evaluation value calculation unit 152 compares the conversion table with the detected reception quality and the received power supply information to determine an evaluation value. For example, in FIG. 6, the evaluation value calculation unit 152 determines the evaluation value “2” when the radio wave intensity average value “x” that is the reception quality is “45”. For example, the evaluation value calculation unit 152 determines the evaluation value “20” when the power supply information “ps” is “battery”.

Subsequently, the evaluation value calculation unit 152 applies the determined evaluation value to an evaluation formula that adds each reception quality and power supply information, which are evaluation parameters, while weighting them, so that the adjacent node and the own node 100 can be compared. The evaluation value D of the wireless link is calculated. For example, the evaluation value calculation unit 152 calculates the evaluation value D of the radio link between the adjacent node and the own node 100 by applying the determined evaluation value to the evaluation formula shown by the following formula (1). To do. In Equation (1), a, b, c, d, and d are weighting factors. Px, Py, Pz, Pw, and Pps are evaluation parameters indicating a radio wave intensity average value, a radio wave intensity variance value, a reception cycle average value, a reception cycle variance value, and radio wave information, respectively. The evaluation value calculation unit 152 stores the calculated D in the work table 141.

D = a · Px + b · Py + c · Pz + d · Pw + e · Pps (1)

When the received hello packet includes the evaluation value Da of the wireless link between the adjacent node and the node 100 as the destination, the evaluation value calculation unit 152 uses the following equation (2). May be used to calculate the evaluation value D of the radio link. In the formula (2), Db is D in the formula (1). D calculated using equation (2) is a round-trip evaluation value of the radio link.

D = √ (Da × Db) (2)

Moreover, when the evaluation value calculation unit 152 receives a hello packet, the evaluation value calculation unit 152 stores information included in the hello packet in the work table 141 and updates the communication path table 142 based on the record of the work table 141.

An example of processing in which the evaluation value calculation unit 152 updates the communication path table 142 will be described. Specifically, the evaluation value calculation unit 152 receives the hello packet and sets the destination included in the hello packet as the destination of the work table 141. The evaluation value calculation unit 152 sets the transmission source node of the hello packet as the transfer destination of the work table 141. The evaluation value calculation unit 152 stores a value obtained by adding the D value of the work table 141 to the ΣD value of the hello packet in the ΣD of the work table 141. ΣD stored in the work table 141 corresponds to the evaluation value of the radio link from the own node 100 to the destination node. The evaluation value calculation unit 152 stores a value obtained by incrementing the hop number of the hello packet in the hop number of the work table 141. Note that the evaluation value calculation unit 152 sets D in the work table 141 to have been set by the above processing.

Subsequently, the evaluation value calculation unit 152 updates the communication path table 142 based on the work table 141. Specifically, the evaluation value calculation unit 152 sets the destination, transfer destination, ΣD, and hop count included in the work table 141 in the communication path table 142, and sets the current time as the update time of each record.

The route selection unit 153 is a processing unit that selects a packet route when a packet is transmitted to a destination based on the communication route table 142.

A process in which the route selection unit 153 selects a route of a packet will be described. First, a process in which the route selection unit 153 selects a route for transmitting a data packet will be described. The route selection unit 153 receives a data packet from a data packet generation unit 155 described later. The route selection unit 153 refers to the communication route table 142 and compares ΣD for each identical destination. As a result of the comparison, the route selection unit 153 selects the transfer destination node having the smallest value of ΣD in the communication route table 142, and transmits the data packet to the selected transfer destination node. In the example shown in FIG. 5, the destinations of the first stage and the second stage are the same, and the value of the first stage ΣD is smaller than the value of the second stage ΣD. For this reason, the path selection unit 153 selects the node 100b that is the first transfer destination having the smallest value of ΣD, and transmits the data packet to the selected node 100b. In other words, the path selection unit 153 does not select the node 100c that is the second-stage transfer destination having a value of ΣD larger than that of the first stage. Node 100b is an AC power supply node, and node 100c is a battery node. Therefore, the node 100 according to the present embodiment can reduce the chance of selecting a route in which the transmission destination of the data packet is a battery node, and can preferentially select the AC power supply node as the transmission destination of the data packet.

Next, a process in which the route selection unit 153 selects a route for transferring the data packet will be described. When the route selection unit 153 receives a data packet to be transferred, the route selection unit 153 refers to the communication route table 142 and compares ΣD for each identical destination. As a result of the comparison, the route selection unit 153 selects the transfer destination node having the smallest value of ΣD in the communication route table 142, and transfers the data packet to the selected transfer destination node. In the example shown in FIG. 5, the destinations of the first stage and the second stage are the same, and the value of the first stage ΣD is smaller than the value of the second stage ΣD. For this reason, the route selection unit 153 selects the node 100b that is the first-stage transfer destination having the smallest value of ΣD, and transfers the data packet to the selected node 100b. In other words, the path selection unit 153 does not select the node 100c that is the second-stage transfer destination having a value of ΣD larger than that of the first stage. Node 100b is an AC power supply node, and node 100c is a battery node. Therefore, the node 100 according to the present embodiment can reduce the chance of selecting a route in which the transfer destination of the data packet is a battery node, and can preferentially select the AC power supply node as the transfer destination of the data packet.

The hello packet generation unit 154 is a processing unit that generates a hello packet based on the communication path table 142 and broadcasts the generated hello packet. For example, the hello packet generation unit 154 generates a hello packet every time a clock event occurs, and broadcasts the generated hello packet.

An example of a process in which the hello packet generation unit 154 generates a hello packet will be described. The hello packet generation unit 154 refers to the communication path table 142 and groups records for each destination. The hello packet generation unit 154 sets a common destination for the group as the destination of the hello packet, and sets its own node 100 as the transmission source of the hello packet. The hello packet generation unit 154 sets the hop number of the communication path table 142 to the hop number of the hello packet, and sets the power information of the own node 100 to the power information of the hello packet. Then, the hello packet generation unit 154 generates a hello packet by setting the minimum ΣD among the ΣDs included in the group to ΣD of the hello packet.

The data packet generation unit 155 is a processing unit that generates a data packet and outputs the generated data packet to the route selection unit 153. For example, the data packet generation unit 155 generates a data packet when receiving a data packet transmission instruction from the input unit 120. The data packet generation unit 155 may generate a data packet every time a clock event occurs.

Next, an example of a processing flow from when the node 100 according to the first embodiment receives a hello packet until a data packet transfer destination is selected will be described. FIG. 7 is a diagram for explaining an example of a processing flow from when the node 100 according to the first embodiment receives a hello packet to when a transfer destination of a data packet is selected.

As illustrated in FIG. 7, when the node 100 receives the hello packet 161 from the adjacent node, the node 100 extracts the power supply information included in the hello packet 161, so that the power supply information of the adjacent node that is the transmission source of the hello packet 161 is obtained. 162 is acquired. The node 100 acquires the power supply information 163 of the own node 100 held in the storage unit 140. Further, the node 100 detects the reception quality 164 of the received hello packet 161.

Subsequently, the node 100 associates the reception quality and power supply information as evaluation parameters with evaluation values that are conversion values of the evaluation parameters, power supply information 162 of adjacent nodes, and power supply information 163 of the own node 100. And the reception quality 164 is compared. The own node 100 determines the evaluation value as a result of the comparison, and applies the determined evaluation value to an evaluation expression that weights and adds each evaluation parameter, thereby allowing the radio link between the adjacent node and the own node 100 to The evaluation value 165 is calculated. When the evaluation value of the wireless link between the adjacent node and the node 100 as the destination is included in the hello packet 161, the node 100 calculates the evaluation value 165 of the wireless link round-trip. Also good.

Subsequently, the node 100 adds the calculated evaluation value 165 to the evaluation value 166 of the wireless link from the adjacent node to the destination node included in the hello packet 161, and reaches from the node 100 to the destination node. An evaluation value 167 of the wireless link is calculated. The own node 100 sets the evaluation value 167 of the radio link from the own node 100 to the destination node in the communication route table 168, and updates the communication route table 168. The communication path table 168 corresponds to the communication path table 142 illustrated in FIG.

Subsequently, when the node 100 receives the data packet 169 to be transferred, the node 100 refers to the communication path table 142 and compares ΣD for each identical destination. As a result of the comparison, the node 100 selects the transfer destination node having the smallest value of ΣD, and transfers the data packet 169 to the selected transfer destination node.

Next, the processing procedure of the node 100 according to the first embodiment will be described. FIG. 8 is a flowchart illustrating a processing procedure of processing for calculating an evaluation value of a wireless link from a node according to the first embodiment to a destination node and storing the evaluation value in a communication path table. For example, the process illustrated in FIG. 8 is executed when a hello packet is received.

As shown in FIG. 8, when the node 100 has not received the hello packet (step S101; No), the process ends. On the other hand, when the node 100 receives the hello packet (step S101; Yes), the node 100 acquires the power information of the adjacent node that is the transmission source of the hello packet and the power information of the own node 100 held in the storage unit 140. (Step S102). Further, the node 100 detects the reception quality of the received hello packet.

The node 100 calculates the evaluation value D of the radio link between the adjacent node and the own node 100 based on the acquired power supply information and the received reception quality of the hello packet (step S103). The node 100 newly creates a record in the work table 141 (step S104), and sets the “destination” included in the hello packet in the “destination” of the work table 141 (step S105). The node 100 sets the address of the “transmission source” node of the hello packet in “transfer destination” of the work table 141 (step S106).

The node 100 stores “D” calculated in step S103 in “D” of the work table 141 (step S107). The node 100 stores a value obtained by adding “ΣD” included in the hello packet and “D” of the work table 141 as “ΣD” of the work table 141 (step S108).

When the same “destination” and “transfer destination” records do not exist in the communication path table 142 (step S109; No), the node 100 stores the created record in the work table 141 in the communication path table 142. A new addition is made (step S110). Then, the node 100 moves the process to step S112.

On the other hand, when the same “destination” and “forwarding destination” records exist in the communication path table 142 (step S109; Yes), the node 100 overwrites them (step S111). When there is an unprocessed packet received (step S112; Yes), the node 100 acquires unprocessed information (step S113), and returns the process to step S104.

On the other hand, when there is no unprocessed packet received (step S112; No), the node 100 ends the process.

Next, a process in which the node 100 according to the first embodiment transfers a data packet will be described. FIG. 9 is a flowchart showing a processing procedure of processing for transferring a data packet. For example, the process shown in FIG. 9 is executed when a data packet is received.

As shown in FIG. 9, when the node 100 has not received a data packet (step S201; No), the process ends. On the other hand, when receiving the data packet (step S201; Yes), the node 100 determines whether or not the destination of the data packet is its own address (step S202). If the destination of the data packet is its own address (step S202; Yes), the node 100 executes predetermined data processing based on the data packet (step S203).

On the other hand, when the destination of the data packet is not its own address (step S202; No), the node 100 searches the communication path table 142 and groups the same “destination” (step S204). The node 100 compares “ΣD” in the group, selects the “transfer destination” with the smallest “ΣD” (step S205), and adds the selected “transfer destination” to the header of the data packet (step S206). ). Then, the node 100 transfers the data packet to the selected “transfer destination” node (step S207).

Next, a process in which the node 100 according to the first embodiment transmits a hello packet will be described. FIG. 10 illustrates a process for transmitting a hello packet. FIG. 10 is a flowchart illustrating a processing procedure of processing for transmitting a hello packet. For example, the process shown in FIG. 10 is executed when a clock event occurs.

As shown in FIG. 10, when there is no clock event, the node 100 returns the process to step S301. On the other hand, when there is a clock event (step S301; Yes), the node 100 searches the communication path table 142 and groups the same “destination” (step S302). The node 100 sets a common destination for the group in the “destination” of the hello packet (step S303).

The node 100 sets its own address as the “source” of the hello packet (step S304). The node 100 sets the “hop number” of the communication path table 142 to the “hop number” of the hello packet (step S305), and sets the power information of the node 100 to the “power information” of the hello packet (step S306). ). The node 100 sets the minimum “ΣD” in the group to “ΣD” of the hello packet (step S307). Then, the node 100 transmits a hello packet (step S308).

Next, a process in which the node 100 according to the first embodiment transmits a data packet will be described. FIG. 11 is a flowchart illustrating a processing procedure for transmitting a data packet. For example, the process illustrated in FIG. 11 is executed when a data packet transmission instruction is received.

As illustrated in FIG. 11, when the node 100 has not received a data packet transmission instruction (step S401; No), the process returns to step S401. On the other hand, when the node 100 receives a data packet transmission instruction (step S401; Yes), the node 100 generates a data packet (step S402). The node 100 searches the communication route table 142 and groups the same “destination” (step S403).

The node 100 compares “ΣD” in the group and selects the “transfer destination” with the smallest “ΣD” (step S404). The node 100 adds the selected “transfer destination” to the header of the data packet (step S405). Then, the node 100 transmits a data packet (step S406).

Next, the effect of the ad hoc network according to the first embodiment will be described. The node 100 included in the ad hoc network calculates a different value as the evaluation value of the radio link with the adjacent node according to the type of the power supply of the adjacent node or the own node 100. That is, the node 100 calculates a value indicating that the quality is higher than the value corresponding to the battery as the evaluation value of the radio link when the type of the power supply of the adjacent node or the node 100 is an AC power supply. Then, the own node 100 selects, as the transfer destination of the packet to be transmitted to the destination, the route having the highest quality value of the evaluation values of the radio links from the own node 100 to the destination node. Therefore, the node 100 can preferentially select the communication path including the AC power supply node while reducing the chance of selecting the communication path including the battery node. As a result, the node 100 can select an appropriate communication path while suppressing the power consumption of the battery node. For example, in the case where the AC power supply nodes are installed at positions separated from each other, the node 100 does not make a detour by selecting a communication path including a battery node instead of the AC power supply node, and packet It is possible to select a route that maintains the arrival rate.

Next, a method for verifying the effect of the ad hoc network according to the first embodiment and a result of the verification will be described. In this verification method, the battery life of a battery node and the arrival rate of packets in an ad hoc network were verified using an existing simulation program. In the verification of the battery life of the battery node, the average value of the number of packets relayed by each of the AC power supply node and the battery node as an intermediate node of the ad hoc network (hereinafter “relay packet number”) is compared for each verification condition described later. The average value of the number of relay packets is a value obtained by dividing the total number of packets by the number of AC power supply nodes or the number of battery nodes. Further, in the verification of the arrival rate of packets, the Drop rate, which is the ratio of unreachable packets that have not reached the destination, with respect to all packets is compared for each verification condition described later.

Next, verification conditions for the verification method according to the first embodiment will be described. FIG. 12 is a diagram illustrating verification conditions of the verification method according to the first embodiment. In the verification method according to the first embodiment, the above-described evaluation formula (1) is applied to the simulation program. As shown in FIG. 12, the verification condition “A” is a condition that the evaluation parameter “Pps” corresponding to the power supply information is deleted from the evaluation formula shown by the formula (1). That is, in the verification condition “A”, “0” is set to the weighting coefficient “e” of the evaluation parameter “Pps”. In addition, the verification condition “B” is a condition that a relatively small value is set in the weighting coefficient “e” of the evaluation parameter “Pps” in the evaluation formula shown by the formula (1). That is, in the verification condition “B”, “10” is set to the weighting coefficient “e” of the evaluation parameter “Pps”. The verification condition “C” is a condition in the evaluation formula shown by the formula (1) that a value larger than the value of the verification condition “B” is set for the weighting coefficient “e” of the evaluation parameter “Pps”. . That is, in the verification condition “C”, “100” is set to the weighting coefficient “e” of the evaluation parameter “Pps”. In addition, the verification condition “D” is a condition that the maximum value in the simulation program is set to the weighting coefficient “e” of the evaluation parameter “Pps” in the evaluation formula shown by the formula (1). That is, in the verification condition “D”, the maximum value “65535” is set to the weighting coefficient “e” of the evaluation parameter “Pps”. The verification condition “D” corresponds to the prior art that excludes the battery node from the packet transfer destination. In this verification method, the values shown in FIG. 13 are used as the weighting coefficients of evaluation parameters other than the evaluation parameter “Pps”. FIG. 13 is a diagram illustrating weighting factors of other evaluation parameters. In this verification method, the conversion table shown in FIG. 6 is used as a conversion table in which each evaluation parameter is associated with an evaluation value.

Next, the configuration of the ad hoc network applied to the simulation program for the verification method according to the first embodiment will be described. FIG. 14 is a diagram illustrating a configuration of an ad hoc network applied to a simulation program. The ad hoc network shown in FIG. 14 includes one gateway (GW), 25 AC power supply nodes, and 81 battery nodes.

Next, the verification result of the battery life of the battery node will be described. FIG. 15 is a diagram illustrating a result of comparing the average value of the number of relay packets of the battery nodes included in the ad hoc network for each verification condition. FIG. 16 is a diagram illustrating a result of comparing the average value of the number of relay packets of the AC power supply node included in the ad hoc network for each verification condition. FIG. 17 is a diagram illustrating a result of comparing the ratio between the number of relay packets of the AC power supply node and the number of relay packets of the battery node in the total number of packets for each verification condition. From the results shown in FIGS. 15 and 16, it can be seen that the average value of the number of relay packets of the battery node corresponding to the verification conditions “B” to “D” is smaller than the verification condition “A”. Further, it can be seen that the average value of the number of relay packets of the battery node corresponding to the verification conditions “B” to “D” is larger than the verification condition “A”. From the results shown in FIG. 17, it can be seen that the ratio of the number of relay packets of the AC power supply node is larger than the ratio of the number of relay packets of the battery node in the verification conditions “B” to “D”. These results show that each node of the ad hoc network according to the first embodiment preferentially selects the communication path including the AC power supply node while reducing the chance of selecting the communication path including the battery node. means. That is, in Example 1, it can be seen that the battery life of the battery node can be extended.

Next, the verification result of the packet arrival rate will be described. FIG. 18 is a diagram illustrating a result of comparing the drop rate for each verification condition. From the result shown in FIG. 18, the Drop rate corresponding to the verification condition “D” is the largest, and the Drop rate corresponding to the verification conditions “B” and “C” is maintained equal to the Drop rate corresponding to the verification condition “A”. You can see that. These results mean that each node of the ad hoc network according to the first embodiment selects an appropriate route that maintains the packet arrival rate.

Next, a node according to the second embodiment will be described. Since the node according to the second embodiment is the same as the first embodiment except that the processing content of the evaluation value calculation unit 152 is different from the node according to the first embodiment, the description overlapping with the first embodiment is omitted.

The evaluation value calculation unit 152 measures the remaining power of the battery of the own node 100 at the time of transmission / reception of the hello packet with the adjacent node, and between the adjacent node and the own node 100 according to the measured remaining power. An evaluation value D of the radio link is calculated.

An example of processing in which the evaluation value calculation unit 152 calculates the evaluation value of the wireless link will be described. First, the evaluation value calculation unit 152 detects the reception quality of a hello packet when a hello packet is received from an adjacent node. In the embodiment, the evaluation value calculation unit 152 includes, as an example of reception quality, an average value of the radio wave intensity of the hello packet, a dispersion value of the radio wave intensity of the hello packet, an average value of the reception period of the hello packet, and a reception period of the hello packet. Detect the variance value. The evaluation value calculation unit 152 receives the power supply information of the adjacent node and the power supply information of the own node 100 from the power supply information acquisition unit 151.

Subsequently, the evaluation value calculation unit 152 measures the remaining power of the battery when the power supply information of the own node 100 indicates the battery. The evaluation value calculation unit 152 holds a conversion table in which each received product as an evaluation parameter, power supply information, and remaining power of the battery are associated with an evaluation value that is a conversion value of the evaluation parameter.

19 and 20 are diagrams illustrating an example of a data structure of a conversion table held by the evaluation value calculation unit 152 according to the second embodiment. The conversion table shown in FIG. 19 stores the radio wave intensity average value, radio wave intensity dispersion value, reception period average value, reception period dispersion value, power supply information, and power supply information as evaluation parameters in association with each other. The conversion table shown in FIG. 20 stores the remaining power of the battery as the evaluation parameter and the evaluation value of the power supply information indicating the battery in association with each other. The explanation of the radio wave intensity average value, radio wave intensity dispersion value, reception period average value, reception period dispersion value, and power supply information is the same as that in FIG. The remaining power of the battery indicates the remaining power of the battery of the own node 100. Moreover, an evaluation value shows the conversion value of each evaluation parameter.

The evaluation value becomes smaller as each reception quality is higher. For example, in FIG. 19, the evaluation value becomes smaller as the radio wave intensity average value “x” is larger. For example, the evaluation value becomes smaller as the radio wave intensity dispersion value “y” is smaller. For example, the smaller the reception cycle average value “z” is, the smaller the evaluation value is. The smaller the reception cycle dispersion value “w” is, the smaller the evaluation value is.

The evaluation value is a fixed value smaller than the value corresponding to the battery when the power supply information indicates an AC power supply, and is larger than the fixed value corresponding to the AC power supply when the power supply information indicates a battery. It becomes. Furthermore, when the power supply information indicates a battery, the difference between the evaluation value and the fixed value corresponding to the AC power supply increases as the remaining power of the battery decreases. For example, in FIGS. 19 and 20, the evaluation value when the power supply information “ps” is “battery” becomes a larger value as the remaining power “b” of the battery is smaller. Further, in FIG. 19 and FIG. 20, the difference between the evaluation value when the power information “ps” is “battery” and the evaluation value “1” when the power information “ps” is “AC power” increases. .

Subsequently, the evaluation value calculation unit 152 determines the evaluation value by comparing the conversion table with the detected reception quality, the received power supply information, and the remaining power of the battery. For example, in FIG. 19, the evaluation value calculation unit 152 determines the evaluation value “1” when the power supply information “ps” is “AC power supply”. For example, in FIG. 19 and FIG. 20, the evaluation value calculation unit 152 causes the AC power supply when the power information “ps” is “battery” and the remaining power “b” of the battery of the node 100 is “5500”. An evaluation value “4” larger than the evaluation value “1” is determined. For example, the evaluation value calculation unit 152 determines the evaluation value “20” when the power supply information “ps” is “battery” and the remaining power “b” of the battery of the node 100 is “1500”. Then, the difference from the evaluation value “1” of the AC power supply is increased. That is, the evaluation value calculation unit 152 increases the difference between the evaluation value of the AC power source, which is a fixed value, and the evaluation value of the battery according to the decrease in the remaining power of the battery of the own node 100.

Subsequently, the evaluation value calculation unit 152 applies the determined evaluation value to an evaluation formula that adds each weighted reception quality and power supply information, which are evaluation parameters, while weighting, so that the node between the adjacent node and the own node 100 can be applied. An evaluation value D of the radio link is calculated. For example, the evaluation value calculation unit 152 calculates the evaluation value D of the radio link between the above equation (1). The evaluation value calculation unit 152 stores the calculated D in the work table 141.

Next, the processing procedure of the node 100 according to the second embodiment will be described. FIG. 21 is a flowchart illustrating a processing procedure of processing for calculating an evaluation value of a wireless link from a node according to the second embodiment to a destination node and storing the evaluation value in a communication path table. For example, the process illustrated in FIG. 21 is executed when a hello packet is received. Note that steps S505 to S514 in FIG. 21 are the same as steps S104 to S113 in FIG. 8, and a detailed description thereof will be omitted.

As shown in FIG. 21, when the node 100 has not received a hello packet (step S501; No), the process ends. On the other hand, when the node 100 receives the hello packet (step S501; Yes), the node 100 obtains the power information of the adjacent node that is the transmission source of the hello packet and the power information of the own node 100 held in the storage unit 140. (Step S502). Further, the node 100 detects the reception quality of the received hello packet.

When the power information of the node 100 indicates a battery, the node 100 measures the remaining power of the battery of the node 100 (Step S503). The node 100 calculates the evaluation value D of the radio link between the adjacent node and the own node 100 based on the remaining battery power, the power supply information, and the reception quality of the hello packet (step S504), and the process is performed in step S505. Move to.

Next, the effect of the ad hoc network according to the second embodiment will be described. The node 100 included in the ad hoc network measures the remaining power of the battery when the power information of the node 100 is a battery. The node 100 increases the difference between the evaluation value corresponding to the AC power source, which is a fixed value, and the evaluation value corresponding to the battery, according to the measured decrease in the remaining power of the battery. Then, the node 100 selects, as the transfer destination of the packet to be transmitted to the destination, the route having the highest quality value of the evaluation value of the radio link from the node 100 to the destination node. For this reason, as the remaining power of the battery of the battery node decreases, the node 100 can reduce the chance of selecting a communication path including the battery node, and as a result, the number of nodes that run out of batteries can be suppressed. it can.

Next, a method for verifying the effect of the ad hoc network according to the second embodiment and a result of the verification will be described. In this verification method, the number of battery nodes that run out of batteries (hereinafter referred to as “battery dead nodes”) among battery nodes in the ad hoc network was verified using an existing simulation program. In the verification of the number of battery exhausted nodes, the number of battery exhausted nodes is compared for each verification condition. In this verification method, since the remaining power of the battery of the battery node and the number of relay packets of the battery node are in an inversely proportional relationship, the battery node whose number of relay packets of the battery node exceeds a predetermined number (for example, 1000) Was counted as a battery dead node with a remaining power of “0”. The verification conditions of this verification method are the same as the verification conditions “A” to “C” of the first embodiment shown in FIG. Further, in this verification method, the values of the first embodiment shown in FIG. 13 are used as the weighting coefficients of the evaluation parameters other than the evaluation parameter “Pps”. Moreover, in this verification method, the conversion table shown in FIG.19 and FIG.20 was used as a conversion table which matched each evaluation parameter and evaluation value. In this verification method, the configuration shown in FIG. 14 is used as the configuration of the ad hoc network applied to the simulation program.

Next, the verification result of the number of nodes out of battery will be described. FIG. 22 is a diagram illustrating a result of comparing the number of out-of-battery nodes included in the ad hoc network for each verification condition. In FIG. 22, the vertical axis indicates the number of nodes that have run out of battery, and the horizontal axis indicates the time that has elapsed since the start of execution of the simulation program. From the results shown in FIG. 22, it is understood that the number of out-of-battery nodes corresponding to the verification conditions “B” and “C” is smaller than the verification condition “A” when the same time has elapsed. That is, in Example 2, it can be seen that the number of nodes that run out of batteries can be suppressed.

By the way, each component of the

nodes

100 and 200 is functionally conceptual and does not necessarily need to be physically configured as illustrated. That is, the specific forms of the

nodes

100 and 200 are not limited to those shown in the drawings, and can be configured to be functionally or physically distributed and integrated in arbitrary units according to various loads and usage conditions. For example, the functions of the processing units 151 to 155 in FIG.

The functions of the node 100 shown in the first and second embodiments are realized by installing each function corresponding to the node in an information processing apparatus such as a known PC (Personal Computer) or PDA (Personal Digital Assistant). You can also. FIG. 23 is a diagram illustrating a hardware configuration of a computer that configures a node according to the first and second embodiments.

As shown in FIG. 23, the computer 300 includes a CPU 301 that executes various arithmetic processes, an input device 302 that receives input of data from a user, and a display 303. The computer 300 also includes a reading device 304 that reads a program and the like from a storage medium, and an interface device 305 for connecting to other devices. The computer 300 also includes a wireless communication device 306 that is wirelessly connected to other devices, a RAM 307 that temporarily stores various types of information, and a hard disk device 308. Each device 301 to 308 is connected to a bus 309.

The hard disk device 308 stores various programs such as a power information acquisition program, an evaluation value calculation program, and a route selection program.

The CPU 301 reads out each program stored in the hard disk device 308, develops it in the RAM 307, and performs various processes. In addition, these programs can cause the computer to function as the power supply information acquisition unit 151, the evaluation value calculation unit 152, and the route selection unit 153 in FIG.

Note that the above program does not necessarily have to be stored in the hard disk device 308. For example, the computer 300 may read and execute a program stored in a storage medium such as a CD-ROM. Each program may be stored in a storage device connected to a public line, the Internet, a LAN (Local Area Network), a WAN (Wide Area Network), or the like. In this case, the computer 300 may read and execute each program from these.

1 GW (Gate Way)
100, 100a to 100e Node 110 Wireless communication unit 120 Input unit 130 Display unit 140 Storage unit 141 Work table 142 Communication path table 150 Control unit 151 Power supply information acquisition unit 152 Evaluation value calculation unit 153 Route selection unit 154 Hello packet generation unit 155 Data Packet generator

Claims

A route selection method in a wireless device constituting an ad hoc network,
Obtaining power information indicating whether an adjacent wireless device or a power supply of the wireless device is an internal power supply or an external power supply;
When the acquired power supply information indicates an internal power supply, a first value is calculated as an evaluation value of a path between the adjacent wireless device and the wireless device, and when the power supply information indicates an external power supply, Calculating a second value representing higher quality than the first value as the evaluation value;
When a packet is received from a plurality of adjacent wireless devices, the highest value among the addition values of the evaluation value of the route from each adjacent wireless device included in the packet to the destination and the calculated evaluation value Selecting a neighboring wireless device corresponding to an evaluation value representing quality as a transfer destination when a packet is transmitted to the destination.
The process of calculating the evaluation value of the path between the adjacent wireless device and the wireless device is performed by measuring the remaining power of the internal power supply when the power supply information of the wireless device indicates the internal power supply. As the remaining power decreases, the difference between the second value, which is a fixed value, and the first value calculated as an evaluation value of a path between the adjacent wireless device and the wireless device is increased. The route selection method according to claim 1, wherein:
A wireless device constituting an ad hoc network,
A power information acquisition unit that acquires power information indicating whether the power of an adjacent wireless device or its own device is an internal power supply or an external power supply;
When the power supply information acquired by the power supply information acquisition unit indicates an internal power supply, a first value is calculated as an evaluation value of a path between the adjacent wireless device and the own device, and the power supply information is an external power supply. An evaluation value calculation unit that calculates a second value representing the higher quality than the first value as the evaluation value,
When a packet is received from a plurality of adjacent wireless devices, an evaluation value of a route from each adjacent wireless device included in the packet to a destination and an evaluation value calculated by the evaluation value calculation unit A wireless device comprising: a route selection unit that selects the adjacent wireless device corresponding to an evaluation value representing the highest quality among the added values as a transfer destination when a packet is transmitted to the destination.
The evaluation value calculation unit measures the remaining power of the internal power supply when the power supply information of the own device indicates an internal power supply, and the second value that is a fixed value according to a decrease in the measured remaining power The wireless apparatus according to claim 3, wherein a difference between the first value calculated as an evaluation value of a route between the adjacent wireless apparatus and the own apparatus is increased.