JP2006325142A - Radio terminal and communication method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the number of hops as a whole network, thereby meeting a request for further power saving in the overall network. <P>SOLUTION: Each radio terminal (sensor node 10a-10o) constituting an ad hoc network includes a route information retention part 102 for retaining at least one route information to an information destination, an information retention part 107 for retaining first information to the above destination generated in either the self-terminal or another terminal, an information reception means (radio communication portion 105) for receiving second information having the same destination as the first information retained in the information retention part 107 and a source different from the first information, an information combiner 110 for combining the first information retained in the information retention 107 with the second information received in the radio communication unit 105 into a single information set, and a transmission means (radio communication unit 105) for transmitting the single information combined in the information combinater 110 to a next other terminal according to the route information having a minimum hops to the above destination. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a wireless terminal in a multi-hop wireless ad hoc network (hereinafter referred to as “ad hoc network”) configured by a plurality of wireless terminals, and particularly a network in which information of the same destination is generated at the same time, for example, The present invention relates to a technique applied to a wireless terminal function or operation having an information routing function in a network that requires power saving such as a sensor network.

  An ad hoc network is a network composed of a plurality of wireless terminals having wireless communication and networking capabilities. As a feature of the ad hoc network operation, there is a mode (multi-hop communication) in which, when wireless communication is not possible directly from an arbitrary information start terminal to an information end terminal, communication is performed by relaying wireless terminals existing between them (multi-hop communication) ( Non-patent document 1).

  Further, an on-demand route control method has been proposed as a method for constructing a multi-hop route when a wireless terminal performs communication (see Non-Patent Document 2).

  In the on-demand route control protocol, it is determined whether a route to a destination exists with reference to a table (hereinafter referred to as a routing table) in which route information is described when a wireless terminal performs communication. If no route exists, a routing table is created using a procedure called “route discovery”.

FIG. 20 is a diagram illustrating the route finding method described in Non-Patent Document 1.
The route discovery is realized by transmitting an RREQ (Route Request) message from the start terminal to the entire network and acquiring an RREP (Route Reply) message returned from the end terminal.

When the routing table can be referred to, the wireless terminal (starting terminal) transmits the information to the wireless terminal that is the destination of the information held (hereinafter referred to as the terminal terminal), and the wireless that is the next transmission destination from the routing table. Information is transferred to a terminal (hereinafter referred to as a relay terminal). In this way, the information arrives at the end terminal by the wireless terminal successively transferring information by multi-hop.
"Wireless LAN and Ubiquitous Network" Shozo Komaki et al., Maruzen Corporation 2004 “C. Perkins and E. Royer“ Ad-hoc On-Demand Distance Vector (AODV) Routing ”RFC 3561, Jul. 2003

  However, the wireless terminal used in the conventional ad hoc network always selects the one having the smallest number of information transfers (hops) until reaching the terminal terminal with reference to the routing table.

  FIG. 21 is a diagram illustrating an example of information transfer when the conventional route control is used. Note that FIG. 21 shows an ad hoc network including five terminals of terminal A, terminal B, terminal C, terminal D, and terminal E, and wireless communication is possible between terminals connected by dotted lines. Shall.

  In such a network, when information α, β (information: destination E) to terminal E, which is the same destination, is generated in terminal A and terminal B, when information is transferred according to the minimum number of hops in the routing table, information α of terminal A Relay terminal C to terminal E and terminal B relays terminal D to terminal E. At this time, the information α of the terminal A reaches the terminal E in two hops, and the information β of the terminal B reaches the terminal E in two hops, and a total of four hops are transferred.

  Therefore, it is impossible to further reduce the number of hops in the entire system, and it has not been possible to meet the demand for further realizing power saving in the entire network.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a wireless terminal capable of further reducing the number of hops in the entire system and responding to a desire to further realize power saving in the entire network and a method thereof. .

  By the way, as a result of detailed analysis of the prior art, the inventor of the present application performs transfer processing separately for each piece of information to improve communication efficiency even when multiple pieces of information of the same destination exist in nearby wireless terminals. I realized there was a problem with not considering combining information. In FIG. 21, the terminal A and the terminal B are connected by a dotted line, that is, the terminal A and the terminal B can directly communicate with each other. Therefore, it was discovered that there is room to reduce the number of hops in the entire network because it is not considered to combine information.

  Therefore, the present invention solves the above-described conventional problems, and efficiently fuses (combines) information existing on different paths, thereby reducing the number of hops and realizing power saving in the entire network. Provided is a wireless terminal of an ad hoc network that can be used.

  Specifically, in the wireless terminal according to the present invention, the wireless terminal constituting the ad hoc network, the route information holding means for holding at least one route information to the information destination, Information holding means for holding the first information destined for the destination generated in any of the above, and information for receiving, from another terminal, second information having the same destination and the same destination as the first information held by the information holding means A receiving means, an information combining means for combining the first information held by the information holding means and the second information received by the information receiving means as one information, and one information combined by the information combining means. And transmitting means for transmitting to the next other terminal according to the route information that is the minimum number of hops to the destination.

  Thus, by combining the first and second information with the same destination and different origins, the number of hops in the entire ad hoc network can be reduced, and efficient communication with low power consumption is possible.

  Further, in the wireless terminal according to the present invention, the wireless terminal further includes a control information transmitting means for transmitting control information for transmitting / receiving the first information to another terminal, including a destination of the first information, Whether the destination acquisition unit that acquires the destination of the information included in the control information received from the terminal, the destination of the information acquired by the destination acquisition unit, and the destination of the information held by the information holding unit are the same Using the destination determination unit to determine, the determination result of the destination determination unit, and the information of the route information holding unit, the information destination of the information holding unit follows the route information that minimizes the number of hops in the entire ad hoc network. Destination determining means for determining the next other terminal; information changing means for changing the transfer destination of the first information according to the destination of the next terminal determined by the destination determining means; and the information changing means Change the first information to the transfer destination of the terminal has, further comprising an information transfer means for transferring the second information may be characterized.

  As a result, it is determined whether the destination information included in the control information from the other terminal is the same as the destination of the information held by the terminal, and if the destination is the same, the other terminal that is the control information transmission source By transferring the information held by the terminal itself, the number of hops in the entire ad hoc network can be reliably reduced.

  In the radio terminal according to the present invention, the control information may be a transmission request message representing a transmission request for the first information held by the information holding unit.

  In this case, the destination information of the information held by the terminal is put in the information transmission request message as control information, for example, the transmission request message (RTS: Request To Send) in IEEE802.11 standard in the wireless LAN. Use. As a result, information having the same destination can be combined and transferred while avoiding information collision including collision in the hidden terminal problem, which is a basic function of RTS, around the terminal that transmits control information. Communication is possible.

  In the radio terminal according to the present invention, the control information may be a transmittable message indicating that the first information held by the information holding means can be sent.

  In this case, the destination information of the information held by the terminal is put in the information transmission possible message as control information, for example, the IEEE 802.11 transmission standard message (CTS: Clear To Send) which is standard in the wireless LAN. Use. Even in this manner, information having the same destination can be combined and transferred while avoiding information collision including collision in the hidden terminal problem, which is a basic function of CTS, around the terminal that transmits control information. Communication is possible.

  In the wireless terminal according to the present invention, the control information may include the number of hops to the destination of the first information.

  In this case, it is possible to cope with the case where the terminal that receives the control information does not hold the route information of the terminal that transmits the control information. That is, even when the destination cannot be determined by comparing the number of hops on the routing table, the number of hops for determining the destination can be compared by referring to the number of hops included in the control information. Thereby, even when there is no routing table, information having the same destination can be combined and transferred, and efficient communication is possible.

  In the wireless terminal according to the present invention, the control information may include a plurality of destinations to different terminals as destinations of the first information.

  In this case, when a plurality of pieces of information having different destinations are held in the terminal, the destination information can be transmitted as a single piece of control information. Thereby, aggregation of a plurality of information can be performed efficiently.

  Further, in the wireless terminal according to the present invention, the wireless terminal further receives the next destination determined by the destination determination unit when the destination acquisition unit acquires a destination of information included in the control information received from another terminal. An interrupt information transmitting means for transmitting interrupt information for transferring the second information to the terminal may be provided.

  In this case, the destination information included in the control information is acquired, and the terminal itself does not have the information, but if it is determined that the information can be transferred by the destination determination, the interrupt information is transmitted to the next transfer destination terminal. Keep it. In this way, information is received from the terminal that sent the control information after reserving the information transfer destination, and the information transfer range is extended by sending the information to the reserved transfer destination terminal. Enables efficient communication.

  In the wireless terminal according to the present invention, the wireless device further acquires a destination of the information included in the control information and determines a destination of the first information held by the information holding unit It is also possible to provide a time management means for setting.

  In this case, information is held in the wireless terminal for a certain period of time, and the waiting frequency until the information of the same destination reaches the nearby wireless terminal is set. As a result, even when the time at which the information of the same destination is generated at each wireless terminal is different, the information can be combined and transferred, and efficient communication is possible.

  Note that the present invention can be realized not only as such a wireless terminal, but also as a communication method using steps characteristic of the wireless terminal, or causing a computer to execute these steps. It can also be realized as a program. Needless to say, such a program can be distributed via a recording medium such as a CD-ROM or a transmission medium such as the Internet.

  As is clear from the above description, according to the wireless terminal of the present invention, it is possible to reduce the number of hops and achieve power saving for the entire transmission power network by efficiently fusing (combining) information. It becomes possible. This prolongs the lifetime of individual terminals and further extends the lifetime of the entire network.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a diagram showing a schematic configuration of a sensor network using a terminal according to Embodiment 1 of the present invention.

  The sensor network 1 is a network for collecting environmental data acquired by each sensor node (terminal) in a base station. A plurality of sensor nodes 10a to 10o, a base station 20, the Internet / LAN 30, and a user And a computer device 40 to be used. In addition, as an observation target of the sensor nodes 10a to 10o, application to fixed point observation of the environment such as temperature is being studied in various fields such as people, things, buildings, and nature.

  Each of the sensor nodes 10a to 10o is a wireless terminal having a phenomenon detection (sensor) function, an information processing function, and a wireless communication function for transmitting information.

  The base station 20 collects information obtained from sensor nodes, and may also operate as a gateway of the Internet / LAN 30.

  The computer device 40 used by the user can refer to information collected by the base station 20 via the Internet / LAN 30 and can transmit a command for controlling the entire sensor network 1.

  Next, the configuration of the sensor nodes 10a to 10o will be described. Since the sensor nodes 10a to 10o have the same configuration, the configuration of the sensor node 10a will be described as a representative example.

  As shown in FIG. 2, the sensor node 10a includes a control information transmission unit 101, a route information holding unit 102, a destination determination unit 103, a destination determination unit 104, a wireless communication unit 105, a control unit 106, an information A holding unit 107, an information changing unit 108, a time management unit 109, an information combining unit 110, a sensor information processing unit 112, a sensor unit 113, an antenna 114, and the like are provided. Note that the control information transmission unit 101 and the wireless communication unit 105 are configured by a transmission I / F. The route information holding unit 102 and the information holding unit 107 are configured by a memory. The destination determination unit 103, the destination determination unit 104, the control unit 106, the information change unit 108, and the information combination unit 110 are configured by a CPU. The sensor unit 113 includes a sensing device and a communication I / F. The sensor information processing unit 112 is configured by an A / D converter. The time management unit 109 is configured by a timer.

  The wireless communication unit 105 is used to communicate control information and sensor information with other sensor nodes. The wireless communication unit 105 is weak wireless, specific low power wireless, ZigBee (802.15.4), Bluetooth, UWB. (802.15.4a) and 802.11 systems (a, b, g, n, etc.) are supported. In the case of performing wireless communication, the antenna 114 is used.

  The sensor unit 113 measures and detects a physical phenomenon or a chemical phenomenon. Examples of measurement objects include various physical and chemical phenomena such as temperature, humidity, light, video, sound, ultrasound, infrared, magnetism, pressure, vibration, acceleration, and gas, or combinations of these. Also good. Information observed by the sensor unit 113 is converted from analog data to digital data (A / D conversion) by the sensor information processing unit 112 and held in the information holding unit 107 as sensor information of the sensor node.

  Further, functions necessary for communication processing include a control information transmission unit 101, a route information holding unit 102, a destination determination unit 103, a destination determination unit 104, and the like.

  The control information transmitting unit 101 transmits control information (RTS, CTS) used mainly for collision avoidance (anti-collision) techniques when performing ad hoc communication between terminals. The route information holding unit 102 has a function of holding route information (routing table), and holds work topology information such as a connection relationship between terminals.

  The destination determination unit 103 and the destination determination unit 104 have a function of determining whether a terminal that receives information next may be described in the control information and determining to select another relay terminal according to a condition. is there. When there is a change in the destination for the information, the destination is changed to the destination determined by the information changing unit 108. In addition, the terminal can hold information in the information holding unit 107 and can combine information having the same destination in the information combining unit 110.

  Here, each of the sensor nodes 10a to 10o constructs an ad hoc network in order to perform wireless communication. In order to collect sensor information to the base station 20 via each of the sensor nodes 10a to 10o, path construction and It is necessary to provide a mechanism for performing multi-hop communication. Hereinafter, each procedure will be described with reference to FIG. 3 which is a simpler model.

  FIG. 3 is a diagram in which the sensor node portion shown in FIG. 1 is simplified, and shows an ad hoc network (sensor network) including five sensor nodes (terminals A to E). In FIG. 3, it is assumed that the wireless transmission range of terminals is limited, and communication is possible only between terminals indicated by dotted lines. For example, the terminal A can communicate directly with the terminal B, but cannot communicate directly with the terminal D. Further, it is assumed that information is generated in the terminal A and the terminal B by the sensor function, and the generated information reaches the terminal E via the terminal C and the terminal D. Terminal E is a terminal connected to the base station, and is an end terminal from each terminal. In addition, although the terminal E is used as the information destination to the base station as the destination, the destination of the base station can also be used.

  First, the case where each terminal AE is installed in the initial stage is assumed as an initial state. That is, there is no route control information (routing table) describing how the terminals A to E are connected to each other (whether the route is configured). Therefore, the routing table is constructed according to the following procedure.

  When the information α is transmitted from the terminal A, it is necessary to grasp the route to the terminal E. First, the wireless communication unit 105 of the terminal A broadcasts a route request message (RREQ: Route Request) and tries to acquire a route to the terminal E.

FIG. 4 is a diagram in which terminal A broadcasts an RREQ throughout the network.
For example, the RREQ from the terminal A is transmitted to the terminals C and B, transferred from each terminal to the next terminal, and the transfer is repeated until the terminal E is reached.

  As a method for avoiding the case where the RREQ does not reach the terminal terminal or becomes an infinite loop, a method for limiting the number of RREQ hops or a method for specifying the message existence time may be applied. Is possible.

  The terminal E that has received the RREQ from the terminal A selects the route with the smallest number of hops before reaching the RREQ, and configures the RREP. In this case, the route from terminal A to terminal C and reaching terminal E is selected because it has the smallest number of hops, and RREP is transmitted.

FIG. 5 is a diagram illustrating transmission of RREP at this time.
Based on the RREP information, the terminal that receives the RREP constructs a destination table, a terminal to which information is transferred next for transmission to the terminal, and a routing table that represents the cost (number of hops) to the destination terminal. Is done. When RREP reaches terminal A, a routing table having path information that can reach terminal E with the minimum number of hops is constructed.

  In FIG. 5, a routing table 50a is constructed for the terminal A, a routing table 50c is constructed for the terminal C, and a routing table 50e is constructed for the terminal E.

  The routing table includes “To”, “Next”, and “Cost” as information, where “To” is a destination terminal, “Next” is a terminal that transfers information next to the destination, “ “Cost” indicates the number of hops and indicates how many hops it takes for the information to reach the destination terminal. For example, in the routing table 50a, in order to transfer information from the terminal A to the terminal E, the terminal to which information is transferred next is the terminal C, and the terminal E has two hops.

  Next, a route from terminal B to terminal E is constructed. RREQ is broadcast from terminal B as well as terminal A.

  When the RREQ arrives at the terminal E via the terminal D, it is returned as RREP at the terminal E as a route with the minimum hop number 2. Further, the RREQ from the terminal B reaches the terminal A, and the terminal A refers to its own routing table 50a and returns the route information to the terminal E that it holds.

FIG. 6 is a diagram showing RREP transmission at this time.
In this way, the terminal B holds the routing table 50b, the terminal D holds the routing table 50d, and the terminal E holds the new routing table 50b to which the record is added.

  The routing table 50b holds two types of routes: a hop number 2 route that relays terminal D to reach terminal E, and a hop number 3 route that relays terminal C from terminal A to terminal E. is doing. Each terminal can hold one or a plurality of routes in the route information holding unit 102.

  Through the above procedure, the terminal A and the terminal B can each secure a route to the terminal E.

  Thus, when the terminal A and the terminal B each secure a route to the terminal E, the number of hops is reduced by the combination of information shown in FIG.

  FIG. 7 is a diagram illustrating the hop count reduction according to the present invention. FIG. 7 shows an ad hoc network having the same configuration as that in FIG. 21, and similarly shows a case where terminal A and terminal B have information for terminal E.

  Information β from terminal B is transferred to terminal A, and information β is combined with information α at terminal A. The combined information α + β is transferred to the terminal terminal E via the relay terminal C. At this time, the number of hops in the network is 3 hops including 1 hop from terminal B to terminal A and 2 hops from terminal A to terminal E, which is reduced by 1 hop from the 4 hops shown in FIG. Yes.

  By reducing the number of hops in this way, it is possible to realize power saving for the entire transmission power network. This prolongs the lifetime of individual terminals and further extends the lifetime of the entire network.

  Next, each terminal operation when the sensor information is transferred to the destination terminal after the path construction between the terminals will be described in detail.

  As described above, when the terminal B holds the sensor information that is the destination E, there are two routes on the routing table: a route that relays the terminal D and a route that relays the terminal A. Here, in the prior art, in order to select a route having the minimum number of hops, a route that always relays the terminal D is selected without depending on other terminal operations.

  On the other hand, in the present invention, the terminal B selects the optimum route from the two routes by monitoring the control information from the terminal A.

  First, it is assumed that the information on the destination E exists in the terminal B and the information does not exist in the terminal A. Since terminal A does not hold information, control information for transmission is not transmitted to terminal B. Accordingly, terminal B selects a route that reaches terminal E by relaying terminal D, which is the route having the minimum number of hops, from the routing table, as in the prior art.

Next, a case where the information of the destination E exists at the same time for both the terminal B and the terminal A is shown.
FIG. 8 is a sequence diagram from when information is generated in terminal A and terminal B to when the information is combined and transferred in terminal A.

  In FIG. 8, information α (destination E) and information β (destination E) are first generated in terminal A and terminal B, respectively.

  When the information α (destination E) is transmitted from the terminal A to the terminal E that is the terminal terminal, the next relay terminal is set as the terminal C with reference to the routing table 50a.

  Next, an RTS (Request To Send) packet including the destination of the information α held by the terminal A is transmitted to the terminals B and C that are terminals within the wireless communication range from the terminal A (S11).

  The RTS is used for avoiding a hidden terminal problem as a control signal of a transmission request message.

FIG. 9 is a diagram showing an RTS configuration including destination information.
As shown in FIG. 9, the RTS packet 801 holds an end-point address (Recycling Station Address) 806 in addition to a source address (Source Address) 804 and a relay terminal address (Destination Address) 805 as addresses. .

  The end terminal address 806 is an address that is a destination of information held by a terminal that transmits control information (here, RTS), and is used for destination determination at the terminal that has received the control information. Note that frame control 802, duration ID 803, FCS 807, and the like constituting the RTS packet 801 are equivalent to the RTS structure used in the conventional wireless LAN, and thus the description thereof is omitted.

  When the RTS is received from the terminal A, the destination determination unit 103 of the terminal B first confirms the relay terminal address and the end terminal address included therein, and in a predetermined case, the destination determination unit 104 determines that the terminal A and the terminal A A route is selected so that the number of hops when the information of B is transmitted together is reduced, and the destination is determined to be terminal A (S12). Details of this will be described later.

  When the destination determination / determination at the terminal B is completed (S12), an RTS for transferring information from the terminal B to the terminal A is transmitted (S13). In this RTS, the address of the terminal C is included in the relay terminal address, and the address of the terminal E is included in the end terminal address. The RTS functions as interrupt information.

  On the other hand, when the terminal C is ready to receive information, the terminal C transmits a CTS to the terminal A (S14).

  The terminal A, which has received the RTS from the terminal B and the CTS from the terminal C, transmits a CTS on the assumption that information can be transmitted to the terminal B (S15). Note that a CTS is transmitted to the terminal C on the assumption that information can be transmitted (S15).

On the other hand, the terminal B transmits the information β to be transferred to the terminal A (S16).
When the information is transferred, the information combining unit 110 of the terminal A combines the information α held in advance with the transferred information β having the same destination (information combining (S17)), and the terminal C which is the relay terminal Information α + β is transmitted to (S18). Note that the transmission of the information α + β is transmitted as information to be sent back since the CTS for transmitting the first information α is received from the transmitting terminal C.

  In this way, the terminal B can reduce the number of hops transmitted as a network by confirming the destination of the information held by the terminal B based on the destination information included in the control information (RTS) from the terminal A. .

FIG. 10 is a flowchart showing the operation of the terminal A during control signal transmission.
When the information α is generated, the terminal A transmits an RTS packet including the destination of the information α held by the terminal A to the terminals B and C that are terminals within the wireless communication range from the terminal A (S21, S11). ). Terminal A waits for CTS or RTS reception from another terminal (S22). When a CTS or RTS is received from another terminal, it is determined whether or not it is an RTS interrupt from another terminal (S23).

  As a result of the determination, if it is an RTS interrupt (Yes in S23), a CTS is transmitted to other terminals (in this case, terminals B and C) (S24). And the information (beta) from the other terminal (here terminal B) which transmitted RTS is received, and information (beta) is couple | bonded with information (alpha) (S25, S17). On the other hand, as a result of the determination, if it is not an RTS interrupt (No in S23), the retained information α is left as it is (S26).

  Then, terminal A transmits information α + β obtained by combining information β with information α or information α as it is to the next terminal (in this case, terminal C) (S27, S18).

11 and 12 are flowcharts showing the operation of the terminal B when receiving the control signal.
The terminal B waits to receive an RTS from another terminal (here, the terminal A) (S31). When receiving the RTS, the terminal B first confirms the relay terminal address included in the RTS, and determines whether or not the relay terminal address is its own terminal (S32). If the terminal B is designated as a relay terminal in the RTS (Yes in S32), a transmittable message (CTS: Clear To Send) is returned to the terminal A (S33). In this example, since the relay terminal address is the terminal C, in response to the RTS from the terminal A, the terminal C returns a CTS to the terminal A that is the transmission source address (S14).

  Next, the terminal B confirms the end terminal address 806 in the RTS, and determines whether the terminal A is transmitting the same destination information (step S34). If the information β held by the terminal B and the terminal address of the information α to be transmitted by the terminal A are the same (Yes in S34), the terminal B determines whether the information should be transferred to the terminal A. Proceed to the next step. If the end terminal address is different, the terminal B waits for the time specified by the RTS (step S35).

  When the terminal terminal address of the RTS from the terminal A and the terminal terminal address of the information held by the terminal B are the same, the terminal B refers to the routing table (S36) and determines whether the information should be transferred to the terminal A. (Step S37). As information for this determination, reference is made to information on the number of hops to the end terminal held in the routing table 50b of the terminal B. As held in the routing table 50b, the number of hops that the terminal B relays to the terminal A and the information reaches the terminal terminal E is “3”. The number of hops that reach terminal E from terminal B through terminal D is “2”. By using these pieces of information, terminal B calculates the number of hops when relaying a terminal that relays information held by terminal B and combining information by relaying terminal A and when transmitting information by relaying terminal D. decide.

  In the route calculation in the routing table, when relaying terminal A, the route from terminal B to terminal A is one hop. The terminal A fuses information and reaches the terminal E via the terminal C in two hops, and uses a total of three hops.

  On the other hand, the number of hops when the terminal A is not relayed is also calculated. The number of hops from the terminal A to the terminal E can be determined to be 2 by subtracting “1” from the hop number 3 from the terminal B to the terminal E (terminal A relay). When terminal A and terminal B transmit information individually, two hops are required from terminal A to terminal E to reach terminal E by relaying terminal D from terminal B to terminal D. Therefore, the total number of hops in the network is 4 hops.

  The destination determination unit 104 in the terminal B performs the above calculation, and compares the number of hops when the terminal A is relayed and when not relayed, so that the number of hops when the information of the terminal A and the terminal B is transmitted together. Select a route that reduces. That is, if “1” subtracted from the number of hops from the control information transmission terminal to the end terminal is equal to or less than the number of hops from the own terminal to the end terminal, the route is selected and the destination is determined as A (S38). .

  Then, the terminal B transmits RTS to the terminal A (S13) and waits for CTS reception from the terminal A (S39). When receiving the CTS (Yes in S39), the terminal B transfers the information β to the terminal (control information terminal) that issued the control information (here, RTS) (S40).

  In addition, when there are a plurality of other routes on the routing table, the number of hops to the destination terminal when combining the information of the terminal of the control signal transmission source and the terminal holding the routing table is considered. A route that minimizes the total number of hops is selected.

  In addition, since it is also possible to include a plurality of end terminal addresses in the control information, it may be possible to check whether the destination of each information matches each end terminal address. Therefore, when there are a plurality of end terminal addresses in the control information, the above steps are repeated for the addresses (S41).

  By performing the operations shown in FIGS. 10 to 12, the sequence of FIG. 8 is executed. After the exchange of RTS and CTS, information β is hopped from terminal B to terminal A. The information α held in advance and the transferred information β are combined with the same destination, and the information is transmitted to the terminal C which is a relay terminal.

  In this way, the terminal B can reduce the number of hops transmitted as a network by confirming the destination of the information held by the terminal B based on the destination information included in the control information (RTS) from the terminal A. .

  In the above description, the case where terminal A, which is a terminal to which information is combined, transmits RTS first has been described. However, RTS is transmitted first from the terminal that transfers information (terminal B in the above description). May be.

  FIG. 13 is a diagram illustrating a case where a terminal that combines information receives an RTS to another terminal. In FIG. 13, it is assumed that the terminal B has information γ with the destination being the terminal C, and the terminal A similarly has information δ with the destination being the terminal C. At this time, RTS (relay terminal address: D, end terminal address: C) is transmitted to the peripheral terminals in order to relay the terminal D with reference to the routing table and transmit information to the destination terminal C. When terminal A receives RTS from terminal B, terminal A itself holds information δ with the same destination, so it is determined that combining information γ is more efficient, and CTS is returned to terminal B. To do. This CTS functions as interrupt information. Terminal B transfers information to terminal A by CTS from terminal A, combines the information at terminal A, and transfers the information to terminal C. In this way, it is possible to determine the RTS of another terminal and change its own terminal to a relay terminal. Accordingly, the terminal B can reduce the number of hops transmitted as a network by confirming the destination of the information held by the terminal B based on the destination information included in the control information (CTS) from the terminal A.

  Also, by including the end-point terminal address in the CTS, it is possible for terminals that do not hold information to combine information.

FIG. 14 is a diagram showing information combination using CTS.
Terminal C transmits a CTS to the RTS from terminal A. At this time, the terminal terminal address may be included in the CTS. The CTS functions as interrupt information for the terminal B. Thereby, the terminal B transmits the held information δ to the terminal C.

FIG. 15 is a diagram illustrating a case where the end terminal address is included in the CTS.
As shown in FIG. 15, the CTSTS packet 901 holds an end-point address (Recycling Station Address) 906 in addition to a source address (Source Address) 904 as an address.

  The end terminal address 906 is an address that is a destination of information held by a terminal that receives control information (here, CTS), and is used for destination determination at the terminal that has received the control information. Note that the frame control 902, Duration ID 903, FCS 907, and the like constituting the CTS packet 901 are the same as the RTS structure used in the conventional wireless LAN, and thus the description thereof is omitted.

  When the terminal B determines that the information of the same terminal address is held by the CTS from the terminal C, the terminal B transfers the information to the terminal C. In terminal C, the information of terminal A and the information of terminal B are combined and transferred to the next relay terminal. Thereby, the terminal B can reduce the number of hops transmitted as a network by confirming the destination of the information held by the terminal B based on the destination information included in the control information (CTS) from the terminal C.

Next, control signal waiting in each information terminal will be described.
In the present embodiment, a sensor network is assumed in which a search query is transmitted from a terminal node, and a corresponding terminal transmits information.

FIG. 16 is a diagram illustrating transmission of a search query.
In FIG. 16, a search query is transmitted from terminal E to terminal A and terminal B which are sensor nodes. When the sensor node acquires the search query, the sensor information is transmitted according to the information (sensor information type, number of hops, time, etc.) included therein.

FIG. 17 is a diagram illustrating waiting between terminals when a search query is used.
As shown in FIG. 17, the search query includes the number of hops from the terminal collecting the sensor information. Each terminal refers to the search query arrival time and the number of hops included in the search query, and determines the information transmission scheduled time of the terminal itself. At this time, the terminal having a larger hop number is set to be transmitted earlier, and the terminal having the same hop number is set to match the scheduled transmission time. Further, the scheduled transmission time is set with a certain margin from the search query arrival time.

  By setting in this way, a terminal at a similar distance from a terminal that collects information can transmit information at a similar time, and when relaying information, the time at which control information of other terminals is waited Can be set efficiently.

  The scheduled transmission time of each terminal may be set using the sequence number of the search query as information similar to the number of hops.

(Embodiment 2)
In sensor networks and ad hoc networks, applications that periodically transmit information from sensors without using search queries are also being considered.

  In the second embodiment, an application that periodically transmits information from each terminal is assumed. The procedure for monitoring the control information between the terminals and combining the information is the same as in the first embodiment, and here, the description will be given with particular attention to the waiting between the terminals.

FIG. 18 is a diagram illustrating an ad hoc network according to the second embodiment.
In FIG. 18, each terminal transmits and relays information such as sensor nodes and mobile devices, and forms an ad hoc network that is linked to neighboring terminals. In such a network, since the information generation time cannot be defined, it is necessary to consider how to set the waiting time at each terminal.

  As an example of setting the waiting time, consider the real-time property of information. Information includes information that should guarantee time (video, audio, emergency information) and information that does not require real-time characteristics. At this time, with respect to information that requires real-time properties, the waiting time is set short and the relay terminals are transferred one after another. On the other hand, for information that does not require much real-time property, a long waiting time is set to ensure a long waiting time for control information from each terminal.

FIG. 19 is an example of setting a waiting time for information.
In FIG. 19, when information X, information Y, and information Z are used, information X with a high real-time property is set with a small waiting time, and information Z with a very low real-time property is set with a long waiting time.

  In this way, by setting the waiting time in consideration of the quality of information, it becomes possible to combine information of the same destination, and power saving can be realized by reducing the number of hops of the entire network. .

  The wireless terminal according to the present invention can be applied as a sensor node on a sensor network, a mobile ad hoc terminal, or the like for the purpose of power saving by reducing the number of hops in the entire system.

It is a schematic block diagram of the sensor network in Embodiment 1 of this invention. It is a functional block diagram of the sensor terminal in Embodiment 1 of this invention. It is a figure which shows the sensor network structural example in Embodiment 1 of this invention. It is a figure which shows the broadcast of RREQ in Embodiment 1 of this invention. It is a figure which shows RREP transmission to the terminal A in Embodiment 1 of this invention. It is a figure which shows RREP transmission to the terminal B in Embodiment 1 of this invention. It is a figure which shows reduction of the hop number by this invention. FIG. 3 is a sequence diagram from information generation to combination in Embodiment 1 of the present invention. It is an RTS packet block diagram in Embodiment 1 of this invention. It is a terminal operation | movement flowchart at the time of the control signal transmission in Embodiment 1 of this invention. It is a terminal operation | movement flowchart at the time of the control signal reception in Embodiment 1 of this invention. It is a terminal operation | movement flowchart at the time of the control signal reception in Embodiment 1 of this invention. It is a figure which shows the transfer interruption by RTS monitoring in Embodiment 1 of this invention. It is a figure which shows the transfer interruption by CTS monitoring in Embodiment 1 of this invention. It is a CTS packet block diagram in Embodiment 1 of this invention. It is a figure which shows search query operation | movement in Embodiment 1 of this invention. It is a figure which shows the information transmission scheduled time setting in Embodiment 1 of this invention. It is a figure which shows the ad hoc network in Embodiment 2. FIG. It is a figure in the waiting time setting example for every information in Embodiment 2 of this invention. It is a figure which shows the route discovery method described in the nonpatent literature 1. It is a figure which shows the example of the transfer of information at the time of using the conventional route control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor network 10a-10o Sensor node 20 Base station 30 Internet / LAN
40 Computer apparatus 101 Control information transmission unit 102 Path information holding unit 103 Destination determination unit 104 Destination determination unit 105 Wireless communication unit 106 Control unit 107 Information holding unit 108 Information change unit 109 Time management unit 110 Information combination unit 112 Sensor information processing unit 113 Sensor unit 114 Antenna

Claims (10)

A wireless terminal constituting an ad hoc network,
Route information holding means for holding at least one route information to an information destination;
Information holding means for holding the first information addressed to the destination generated in either the own terminal or another terminal;
Information receiving means for receiving, from another terminal, second information having the same destination as the first information held by the information holding means but having a different source;
Information combining means for combining the first information held by the information holding means and the second information received by the information receiving means as one information;
A wireless terminal comprising: transmission means for transmitting one piece of information combined by the information combining means to the next other terminal according to route information that is the minimum number of hops to the destination. The wireless terminal further includes control information transmitting means for transmitting control information for transmitting / receiving the first information to another terminal, including the destination of the first information,
Destination acquisition means for acquiring a destination of information included in the control information received from another terminal;
A destination determination unit for determining whether or not the destination of the information acquired by the destination acquisition unit is the same as the destination of the information held by the information holding unit;
Using the determination result of the destination determination unit and the information of the route information holding unit, the destination of the information of the information holding unit is determined to be the next other terminal that follows the route information that minimizes the number of hops in the entire ad hoc network. A destination determination means;
Information changing means for changing the transfer destination of the first information according to the destination of the next terminal determined by the destination determining means;
The wireless terminal according to claim 1, further comprising: information transfer means for transferring the first information as the second information to another terminal of the transfer destination changed by the information change means. The wireless terminal according to claim 2, wherein the control information is a transmission request message indicating a transmission request for first information held by the information holding unit. The wireless terminal according to claim 2, wherein the control information is a transmittable message indicating that the first information held by the information holding means can be sent. The wireless terminal according to claim 2, wherein the control information includes the number of hops to the destination of the first information. The wireless terminal according to claim 2, wherein the control information includes a plurality of destinations to different terminals as destinations of the first information. The wireless terminal further transfers the second information to the next terminal determined by the destination determination unit when the destination acquisition unit acquires a destination of information included in the control information received from another terminal. The wireless terminal according to claim 2, further comprising: interrupt information transmitting means for transmitting interrupt information to be transmitted. The wireless device further includes:
The time management means for setting the time from the acquisition of the destination of the information included in the control information to the determination of the destination of the first information held by the information holding means is provided. Wireless terminal. A communication method used for wireless terminals constituting an ad hoc network,
A route information holding step for holding at least one route information to the destination of the information;
An information holding step of holding the first information of the destination generated in either the own terminal or another terminal;
An information receiving step for receiving from the other terminal second information having the same destination as the first information held in the information holding step and having a different source;
An information combining step of combining the first information held in the information holding step and the second information received in the information receiving step as one information;
And a transmitting step of transmitting the one information combined in the information combining step to the next other terminal according to the route information that is the minimum number of hops to the destination.   A program for causing a computer to execute the steps included in the communication method according to claim 9.

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