JP2008306293A - Ad-hoc network system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ad-hoc network system capable of prolonging an operation time by controlling an output voltage when a plurality of one-hop communicable parties exist, and having stability in a network path. <P>SOLUTION: In the ad-hoc network system composed of a plurality of communication terminals for performing mutual communication through ad-hoc wireless communication, each of the communication terminals is provided with a search packet generating section 50 for generating a search packet for collecting information about other communication terminals; a transmitting/receiving section 20, having a function of setting a transmission power value and transmitting and receiving the search packet; a network topology analyzing section 30 for collecting the information about the other communication terminals, on the basis of the searching packet transmitted from other communication terminals and received in the transmitting/receiving section 20; and a transmission power determining section 40 for generating transmission power value data, on the basis of the information about the other communication terminals and the transmission power value, set in the transmitting/receiving section 20. The transmitting/receiving section 20 updates the setting of the transmission power value, on the basis of the transmission power value data generated by the transmission power determining section 40. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an ad hoc network system including a plurality of communication terminals capable of controlling transmission power.

  An ad hoc network is a network composed of mobile terminals having an exchange function that does not depend on an exchange or a base station. In an ad hoc network, terminal devices communicate with each other on an equal basis. A route in an ad hoc network is generally determined by a routing protocol. The ad hoc routing protocol is a communication protocol that forms a network between a plurality of terminals in a wireless environment, and realizes construction of a route by transmitting and receiving search packets.

  Routing protocols are roughly classified into two types, a proactive type and a reactive type, in route discovery processing. The proactive type is a method of confirming and grasping the surrounding network state in advance prior to communication, and one example is OLSR (Optimized Link State Routing). In the OLSR protocol, among nodes that have received radio waves, a node that has a large number of peripheral nodes that directly receive radio waves becomes a relay node on behalf of the neighboring nodes, so that unnecessary relay flooding is suppressed, so flooding is performed efficiently. There is a feature that can be. The reactive type is a method in which a route discovery process is performed only when a request for a certain node to communicate with another node is triggered.

For example, Patent Document 1 describes an ad hoc network system that avoids communication interruption that occurs when switching from direct communication to two-hop communication in communication between a fixed terminal and a mobile terminal using OLSR. In this ad hoc network system, each terminal acquires position information and speed information and advertises them to peripheral terminals. Furthermore, the fixed terminal detects in advance that the mobile terminal moves out of the communication area from the position / speed information of the mobile terminal, and switches to the two-hop communication via the relay terminal. Therefore, according to this ad hoc network system, in communication between a mobile terminal and a fixed terminal, when the mobile terminal moves out of the communication area of the fixed terminal, the communication is switched from direct communication to two-hop communication without interruption. Can do.
JP 2007-74177 A

  However, each terminal constituting the ad hoc network consumes power when transmitting and receiving a search packet and data. In particular, transmission consumes a large amount of power, but each terminal is often a mobile terminal using a battery or the like, which causes a problem of affecting the operation time.

  Also, in an environment where terminals are crowded so that a plurality of terminals can simultaneously receive transmission of search packets from one terminal, the network path is difficult to stabilize, and problems such as packet collision also occur.

  The present invention solves the above-described problems of the prior art. When there are a plurality of counterparts capable of communication in one hop, the output power is controlled to extend the operation time, and the stability of the network path is high. It is an object to provide an ad hoc network system.

  In order to solve the above problems, an ad hoc network system according to the present invention is an ad hoc network system including a plurality of communication terminals that communicate with each other by ad hoc wireless communication, and each of the plurality of communication terminals includes: A generation unit that generates a search packet for collecting information about other communication terminals, a transmission power value setting function, a transmission / reception unit that transmits and receives the search packet, and a transmission packet that is transmitted from another communication terminal. Based on the search packet received by the transmission / reception unit, an analysis unit that collects information on the other communication terminal, information on the other communication terminal collected by the analysis unit, and a transmission power value set in the transmission / reception unit, And a transmission power value data generation unit for generating transmission power value data, and the transmission / reception unit transmits the transmission power value data. And updates the setting of the transmission power value based on the transmission power value data generated by the power value data generator.

  According to the present invention, since transmission power is controlled based on information of other communication terminals collected using the search packet, the operation time of the communication terminal using the battery is extended and the stability of the route is improved. be able to.

  Embodiments of an ad hoc network system according to the present invention will be described below in detail with reference to the drawings.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of a communication terminal of an ad hoc network system according to a first embodiment of this invention. This ad hoc network system includes a plurality of communication terminals that communicate with each other by ad hoc wireless communication.

  First, the configuration of the present embodiment will be described. As shown in FIG. 1, each of the plurality of communication terminals used in the ad hoc network system of the present embodiment includes an antenna 10, a transmission / reception unit 20, a network topology analysis unit 30, a transmission power determination unit 40, a search packet generation unit 50, And a time measuring unit 60.

  The antenna 10 is an antenna such as a monopole antenna that is normally used in a portable information terminal device or the like, and is connected to the transmission / reception unit 20.

  The transmission / reception unit 20 has a transmission power value setting function and transmits / receives a search packet, communication data, and the like via the antenna 10. In this embodiment, the transmission / reception unit 20 is configured by a wireless device capable of setting a transmission power value, and the transmission power value setting is updated by a transmission power determination unit 40 described later.

  The search packet generation unit 50 corresponds to the generation unit of the present invention, generates a search packet for collecting information related to other communication terminals, and outputs the search packet to the transmission / reception unit 20. At this time, the search packet generation interval is based on time information measured by the timer 60. The search packet function in the present invention is, for example, collecting information about adjacent communication terminals, but is not limited thereto, and various functions necessary for constructing an ad hoc network and performing route control are not limited thereto. Information may be included.

  The timer 60 measures time and outputs the time information to the search packet generator 50 and the network topology analyzer 30 described later.

  The network topology analysis unit 30 corresponds to the analysis unit of the present invention, and collects information on other communication terminals based on search packets transmitted from the other communication terminals via the antenna 10 and received by the transmission / reception unit 20. Specifically, the network topology analysis unit 30 calculates the number of communication terminals that can transmit and receive a search packet in one hop based on the search packet transmitted by another communication terminal.

  Here, the “communication terminal capable of transmitting and receiving in one hop” means that when the search packet of the same message is transmitted (flooded) from the own communication terminal to all the communication terminals that can transmit, An adjacent communication terminal that can directly transmit a search packet without relaying the communication terminal.

  For example, the network topology analysis unit 30 calculates the number of communication terminals that can transmit the search packet in one hop based on the time information measured by the time measurement unit 60 and the number of search packets received by the transmission / reception unit 20. That is, the network topology analysis unit 30 can calculate the number of adjacent communication terminals by receiving a search packet flooded from another adjacent communication terminal.

  In order to calculate the number of communication terminals described above, the search packet generation unit 50 can provide the search packet with the number of hops, time information, information on the transmission source communication terminal, and the like. Further, when the transmitted search packet passes through the communication terminal, the network topology analysis unit 30 of each communication terminal transmits the search packet by performing flooding or the like by adding information related to the via communication terminal to the search packet. The search packet transmitted from another communication terminal is referred to the content of the search packet transmitted immediately before, and the search packet transmitted within a predetermined time is compared by comparing the time information at the time of transmission. By extracting, information of adjacent communication terminals can be collected.

  Note that the function of the network topology analysis unit 30 is not limited only to the calculation of the number of adjacent communication terminals, but collects information related to other communication terminals so as to grasp the topology (connection form) of the entire network. It may have an algorithm for performing the communication path control.

  In the above-described method for collecting information on adjacent communication terminals, the network topology analysis unit 30 calculates the number of adjacent communication terminals based on a search packet transmitted from another communication terminal. However, for example, when using the reactive protocol, each communication terminal exchanges search packets irregularly, so that a search that is accidentally sent by another communication terminal without transmitting the search packet itself. A method of using packet information is also conceivable. In this case, the network topology analysis unit 30 classifies which communication terminal has transmitted the search packet at which hop, based on the search packet transmitted by another communication terminal, and performs its own communication terminal with one hop. The number of communication terminals that transmitted the search packet is calculated. Here, it is good to exchange information between communication terminals periodically when not communicating, such as when using a proactive protocol, but information exchange is irregular, such as when using a reactive protocol. In some cases, a method of discarding old information based on time information included in a search packet may be considered. In any case, it is only necessary that the network topology analysis unit 30 can finally calculate the number of adjacent communication terminals.

  The transmission power determination unit 40 corresponds to the transmission power value data generation unit of the present invention, and is based on information on other communication terminals collected by the network topology analysis unit 30 and the transmission power value set in the transmission / reception unit 20. The transmission power value data is generated. In the present embodiment, the transmission power determination unit 40 generates transmission power value data according to the number of communication terminals calculated by the network topology analysis unit 30.

  FIG. 2 is a block diagram illustrating a detailed configuration of the transmission power determination unit 40 of the present embodiment. As illustrated in FIG. 2, the transmission power determination unit 40 includes a terminal number information acquisition processing unit 42, a transmission power acquisition processing unit 44, a transmission power determination processing unit 46, and a transmission power setting processing unit 48.

  The terminal number information acquisition processing unit 42 acquires the number of communication terminals that can transmit and receive a search packet with one hop calculated by the network topology analysis unit 30. Further, the transmission power acquisition processing unit 44 acquires the transmission power value set in the transmission / reception unit 20. The timing at which these processes are performed may be regular or a predetermined timing (for example, when transmitting some data to a specific communication terminal).

  The transmission power determination processing unit 46 includes the information on the number of communication terminals acquired by the terminal number information acquisition processing unit 42 and the transmission power value set in the current transmission / reception unit 20 acquired by the transmission power acquisition processing unit 44. Based on this, transmission power value data is generated and output to the transmission power setting processing unit 48. A specific method for generating transmission power value data will be described later.

  The transmission power setting processing unit 48 outputs the transmission power value data generated by the transmission power determination processing unit 46 to the transmission / reception unit 20.

  The transmission / reception unit 20 updates the setting of the transmission power value based on the transmission power value data generated by the transmission power determination unit 40. Therefore, the transmission / reception unit 20 transmits a search packet and communication data with the updated transmission power value. The reach of the transmission radio wave of each communication terminal changes according to the transmission power value set in the transmission / reception unit 20.

  The transmission power determination unit 40 according to the present embodiment generates transmission power value data according to the number of communication terminals calculated by the network topology analysis unit 30, but is based on the network topology created by the network topology analysis unit 30. It is also possible to generate transmission power value data. Alternatively, it is also conceivable that the transmission power determination unit 40 generates transmission power value data based on geographical position information by equipping each terminal with a GPS.

  Next, the operation of the present embodiment configured as described above will be described. First, in this embodiment, each of a plurality of communication terminals constituting an ad hoc network system transmits a search packet generated by the search packet generation unit 50 to another communication terminal (adjacent communication) via the transmission / reception unit 20 and the antenna 10. Terminal). The communication terminal that has received the search packet adds information related to its own communication terminal (routed communication terminal information) and information such as the number of hops to the received search packet, and forwards it to the adjacent communication terminal. Here, since the communication terminal that first generated and transmitted the search packet receives the search packet transmitted from the adjacent communication terminal, information on the communication terminal that can transmit the search packet in one hop can be obtained. . At this time, the network topology analysis unit 30 may be configured to validate the search packet transmitted within a predetermined time based on the time information timed by the time measuring unit 60.

  The search packet transfer method described above is an example, and the search packet transfer method can be flexibly changed according to the protocol used and the configuration of each communication terminal. Accordingly, the transfer timing of the search packet may be every fixed time or may be when a transmission request is made. In addition, the search packet is not necessarily transmitted to all adjacent communication terminals, but another method may be used to obtain information efficiently. In any case, it is only necessary that the network topology analysis unit 30 of each communication terminal can finally calculate the number of adjacent communication terminals.

  Next, the operation when each communication terminal receives a search packet will be described. As described above, each communication terminal also performs an operation of adding and transferring necessary information when a search packet other than the search packet transmitted by itself is received. Only the operation when the obtained search packet is received will be described.

  Each communication terminal receives the search packet by the transmission / reception unit 20 via the antenna 10. The transmission / reception unit 20 outputs the received search packet to the network topology analysis unit 30.

  The network topology analysis unit 30 accumulates information included in the input search packet and collects information regarding other communication terminals. In particular, the network topology analysis unit 30 calculates the number of communication terminals (number of adjacent communication terminals) that can transmit the search packet in one hop based on the search packet. In the calculation, the network topology analysis unit 30 extracts only the information of the search packet transmitted within a predetermined time based on the time information timed by the time measuring unit 60 and calculates the number of adjacent communication terminals.

  Here, it supplements about utilization of the time information time-measured by the time measuring part 60. FIG. Using the time information timed by the time measuring unit 60, its own communication terminal transmits search packets at predetermined time intervals. The network topology analysis unit 30 can calculate the number of adjacent communication terminals by accumulating information of received search packets. Further, the network topology analysis unit 30 can accumulate only the information of the search packet received by itself within a predetermined time by using the time information timed by the time measuring unit 60 and discard old information. This is because, if each communication terminal is a mobile terminal, for example, a communication terminal that was an adjacent communication terminal one hour ago is not always adjacent, and extremely old information lacks reliability.

  Further, the network topology analysis unit 30 may calculate the number of adjacent communication terminals at regular time intervals, or may calculate the number of adjacent communication terminals when a transmission request is made by an external input or the like.

  Note that the network topology analysis unit 30 not only calculates the number of adjacent communication terminals, but also collects information on other communication terminals, grasps the topology (connection form) of the entire network, and performs communication path control of the ad hoc network. It may be configured.

  The network topology analysis unit 30 outputs information regarding the calculated number of adjacent communication terminals to the transmission power determination unit 40. In addition, the transmission / reception unit 20 outputs data of the currently set transmission power value to the transmission power determination unit 40. The timing at which these pieces of information and data are output to the transmission power determination unit 40 may be anything, may be regular, or may be when requested by the transmission power determination unit 40.

  The transmission power determination unit 40 generates transmission power value data within a predetermined range based on whether or not the number of communication terminals calculated by the network topology analysis unit 30 is a predetermined number or more. FIG. 3 is a flowchart showing the operation of the transmission power determination unit 40 in the ad hoc network system according to the present embodiment. First, as a premise, the transmission power determination unit 40 controls the transmission power value by raising and lowering the transmission power value currently set in the transmission / reception unit 20 stepwise. Furthermore, the transmission power determination unit 40 controls the reference value N for the number of adjacent communication terminals, the range of transmission power values that can be set in the transmission / reception unit 20 (maximum output value and minimum output value that can be set), and the transmission power value. The amount of change in power per step when it is performed (for example, 1 mW in this embodiment) is stored. These values may be set in advance in the transmission power determination unit 40 or may be set by an operator by means such as an external input. Further, the adjacent reference value N and the amount of power change per stage may be set to be updated by the transmission power determination unit 40 based on some algorithm. The transmission power determination unit 40 may automatically acquire the range of transmission power values that can be set in the transmission / reception unit 20 from the transmission / reception unit 20.

  This will be described with reference to the flowchart of FIG. First, the transmission power determination unit 40 determines whether or not the number of communication terminals calculated by the network topology analysis unit 30 is N or more, which is a reference value (step S101). The value of N can be arbitrarily set by the operator, but an appropriate number of communication terminals should be selected in order to stabilize the network path even in a place where communication terminals are dense.

  Next, when the number of communication terminals calculated by the network topology analysis unit 30 is not equal to or more than the reference value N (when communication terminals are not crowded), the transmission power determination unit 40 is set to the current transmission / reception unit 20. It is determined whether or not the transmitted power value is the maximum output value (step S103). Here, when the transmission power value currently set in the transmission / reception unit 20 is not the maximum output value, the transmission power determination unit 40 increases the transmission output by one level (step S105). That is, the transmission power determination unit 40 generates a value obtained by adding 1 mW to the currently set transmission power value as new transmission power value data, and outputs the new transmission power value data to the transmission / reception unit 20. The transmission / reception unit 20 sets a new transmission power value based on the transmission power value data input by the transmission power determination unit 40. In this case, since the transmission / reception unit 20 sets a value 1 mW larger than the conventional value as the transmission power value, the reach of the transmission radio wave is expanded, and the number of adjacent communication terminals is increased.

  In step S103, when the transmission power value currently set in the transmission / reception unit 20 is the maximum output value, the transmission output is maintained as it is (step S107). Therefore, the transmission power determination unit 40 does not generate new transmission power value data, and the transmission power value currently set in the transmission / reception unit 20 is maintained as it is.

  In step S101, when the number of communication terminals calculated by the network topology analysis unit 30 is N or more which is a reference value (when communication terminals are crowded), the transmission power determination unit 40 It is determined whether or not the transmission power value set to 20 is the minimum output value (step S109). Here, when the transmission power value currently set in the transmission / reception unit 20 is the minimum output value, the transmission output is maintained as it is (step S107). Therefore, the transmission power determination unit 40 does not generate new transmission power value data, and the transmission power value currently set in the transmission / reception unit 20 is maintained as it is.

  In step S109, when the transmission power value currently set in the transmission / reception unit 20 is not the minimum output value, the transmission power determination unit 40 decreases the transmission output by one level (step S111). That is, the transmission power determination unit 40 generates a value obtained by subtracting 1 mW from the currently set transmission power value as new transmission power value data, and outputs the new transmission power value data to the transmission / reception unit 20. The transmission / reception unit 20 sets a new transmission power value based on the transmission power value data input by the transmission power determination unit 40. In this case, since the transmission / reception unit 20 sets a value that is 1 mW smaller than the conventional transmission power value, the reach of the transmission radio wave is narrowed, and the number of adjacent communication terminals is reduced.

  As described above, since the transmission power determination unit 40 controls the transmission power value so that the number of adjacent communication terminals is close to N, the ad hoc network system in the present invention suppresses the power consumption of each communication terminal. In an area where communication terminals are crowded, the optimum number of adjacent communication terminals can be maintained and stable route control can be performed.

  As described above, according to the ad hoc network system according to the first embodiment of the present invention, the transmission power is controlled based on the information of other communication terminals collected using the search packet. The operation time of the communication terminal can be extended and the stability of the route can be improved.

  In particular, the network topology analysis unit 30 calculates the number of communication terminals that can transmit and receive a search packet with one hop based on the search packet received from another communication terminal. Therefore, the transmission power determination unit 40 can set an appropriate transmission power value for the transmission / reception unit 20 and can control the number of adjacent communication terminals to achieve path stability.

  Note that, when the number of adjacent communication terminals is small, the transmission power determination unit 40 increases the transmission power value set in the transmission / reception unit 20, and thus the power consumption of each communication terminal is not always reduced. . However, the ad hoc network system according to the present invention can perform stable path control, and suppresses the transmission power value in the transmission / reception unit 20 in a congested area of communication terminals, and consequently does not control the transmission power value. Compared to the case, the power consumption is reduced.

  Further, the network topology analysis unit 30 can accumulate only the information of the search packet received by itself within a predetermined time by using the time information timed by the time measuring unit 60 and discard old information. Thereby, only the latest information with high reliability can be accumulated.

  Furthermore, based on the time information by the time measuring unit 60, the network topology analyzing unit 30 can also calculate the number of adjacent communication terminals at regular time intervals.

  Moreover, since the transmission power determination part 40 produces | generates transmission power value data based on whether the number of adjacent communication terminals is more than a predetermined reference value, it can control power consumption more concretely. For example, when the reference value for the number of adjacent communication terminals is set low, the transmission power value is controlled so as to reduce the number of adjacent communication terminals, so that power consumption can be suppressed. Of course, in order to perform stable wireless communication, a minimum number of adjacent communication terminals is required. Therefore, it is also possible to set the reference value based on the circumstances such as whether or not it is used in an area where the number of communication terminals is large.

  Furthermore, since the transmission power determination unit 40 generates transmission power value data within the range of transmission power values that can be set by the transmission / reception unit 20, even if the transmission power setting of each communication terminal has a different standard, The ad hoc network system of the present invention can be configured.

  The ad hoc network system according to the present invention can be used for an ad hoc network system including mobile terminals such as a mobile phone, a PDA, and a mobile personal computer.

It is a block diagram which shows the structure of the ad hoc network of the form of Example 1 of this invention. It is a block diagram which shows the detailed structure of the transmission power determination part of the ad hoc network system of the form of Example 1 of this invention. It is a flowchart figure which shows operation | movement of the transmission power determination part of the ad hoc network system of the form of Example 1 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Antenna 20 Transmission / reception part 30 Network topology analysis part 40 Transmission power determination part 42 Number-of-terminals information acquisition process part 44 Transmission power acquisition process part 46 Transmission power determination process part 48 Transmission power setting process part 50 Search packet generation part 60 Timing part

Claims (4)

An ad hoc network system composed of a plurality of communication terminals that communicate with each other by ad hoc wireless communication,
Each of the plurality of communication terminals is
A generating unit that generates a search packet for collecting information on other communication terminals;
A transmission / reception unit that has a transmission power value setting function and that transmits and receives the search packet;
Based on a search packet transmitted from another communication terminal and received by the transmission / reception unit, an analysis unit that collects information on the other communication terminal;
A transmission power value data generation unit that generates transmission power value data based on information on other communication terminals collected by the analysis unit and a transmission power value set in the transmission / reception unit;
The said transmission / reception part updates the setting of the said transmission power value based on the transmission power value data produced | generated by the said transmission power value data production | generation part, The ad hoc network system characterized by the above-mentioned. The analysis unit calculates the number of communication terminals that can transmit and receive a search packet in one hop based on a search packet transmitted from another communication terminal and received by the transmission and reception unit,
The ad hoc network system according to claim 1, wherein the transmission power value data generation unit generates transmission power value data according to the number of communication terminals calculated by the analysis unit. Each of the plurality of communication terminals includes a time measuring unit for measuring time,
The ad hoc network system according to claim 2, wherein the analysis unit further calculates the number of communication terminals capable of transmitting a search packet in one hop based on the time information timed by the time measuring unit. The transmission power value data generation unit generates transmission power value data within a predetermined range based on whether or not the number of communication terminals calculated by the analysis unit is a predetermined number or more. The ad hoc network system according to claim 2 or claim 3.

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