JP2006246317A - Communication device constituting ad hoc network - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication device which performs control so that a name information table having small deviation from the actual state of an ad hoc network can be held. <P>SOLUTION: The communication device has a means of holding the name information table for name solution and acquiring position information on its device. When a name information signal including name information, address, position information, and speed information of a communication device constituting the ad hoc network is received, effective time is calculated based upon the position information and speed information included in the name information signal, position information of the device itself, and speed information of the device itself calculated from a history of position information of the device itself, and the name information, address, position information, and speed information are put in one record; and the calculated effective time is registered as effective time of the record in the name information table and a record whose effective time expired is deleted from the name information table. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a communication device that constitutes an ad hoc network, and more specifically, a name in an ad hoc network that acquires address information for communicating with the communication device from name information such as a host name assigned to each communication device. It is about a solution.

  A communication network that is autonomously configured by a communication device having wireless communication means is called an ad hoc network. For example, in the field of ITS (Intelligent Transport Systems), an automobile is a wireless LAN (Local Area Network) device or a mobile phone. It is assumed to be used in a form in which a communication device having a wireless communication means such as a telephone is mounted and information is exchanged between vehicles.

  Usually, there is a limit on the reach of radio waves transmitted by a communication device, and in order to communicate with a communication device that is outside the range of this limitation, that is, communication is performed via one or more other communication devices. There is a need to do. In such an ad hoc network, various methods have been proposed for name resolution for obtaining address information used for communication with a communication device from name information such as a host name assigned to each communication device. .

  One proposed name resolution method is to install a dedicated domain name system (DNS) server in an ad hoc network.

  Further, Patent Document 1 describes another name resolution method. In the name resolution method described in Patent Document 1, a communication device in an ad hoc network periodically transmits a broadcast signal including its host name and address to the ad hoc network, and the communication device that receives the broadcast signal The host name and address included in the broadcast signal are registered in the name information table, or information already registered is updated. Furthermore, when the communication device performs name resolution, if the host name that is the target of name resolution does not exist in its own name information table, a name resolution request signal including the target host name is broadcast to the ad hoc network. It is also described that the communication device that has received the name resolution request signal determines whether or not the included host name indicates its own device, and if it indicates its own device, returns an address. That is, the method described in Patent Document 1 is a method in which all communication devices independently manage name information.

JP 2002-354016 A

  In an ad hoc network, the position of each communication device constituting the ad hoc network, and the existence thereof, change from moment to moment, and thus a configuration or method is always required to guarantee access to the DNS server. The configuration and method have not been established.

  In addition, as described above, each communication device constituting the ad hoc network changes from moment to moment, and the address itself may be changed. Therefore, when the name resolution described in Patent Document 1 is used. The problem is the transmission interval of broadcast signals. That is, if the transmission interval of the broadcast signal is lengthened, the difference between the name information table held by each communication device and the state of the ad hoc network increases, and the name information table becomes useless. On the other hand, if the broadcast signal transmission interval is too short, traffic for name information increases and the processing load on the ad hoc network increases, resulting in an impact on communications such as data that should actually be transmitted and received. It becomes. Therefore, the transmission interval of the broadcast signal needs to be equal to or greater than a certain interval determined based on the link speed between the communication apparatuses and the processing speed of the communication apparatus so as not to affect the communication to be actually transmitted / received. .

  However, for example, when it is assumed to be used in ITS, it may occur that the communication devices constituting the ad hoc network and the addresses of the respective communication devices are changed with a frequency equal to or higher than the determined broadcast signal transmission interval. As described above, since the broadcast signal transmission interval needs to be a certain period or longer, in the method described in Patent Document 1, there is a difference between the name information table held by each communication device and the state of the ad hoc network. Can not be prevented from becoming large.

  Therefore, the present invention provides a communication device that performs control such that each communication device holds a name information table and performs name resolution so that the name information table can be held with little difference from the actual state of the ad hoc network. The purpose is to provide.

According to the communication device of the present invention,
A communication device that constitutes an ad hoc network, has a name information table for name resolution, and has a means for acquiring location information of the device itself, and includes name information, address, and location information of the communication device constituting the ad hoc network When the name information signal including the speed information is received, the position information and the speed information included in the name information signal, the position information of the own apparatus, and the speed of the own apparatus calculated from the history of the position information of the own apparatus. If the record for the name information included in the name information signal does not exist in the name information table after calculating the effective time based on the information, the name information, the address, the position information, and the speed information are one record. The calculated effective time is registered in the name information table as the effective time of the record, and a record about the name information included in the name information signal is stored in the name information table. If it exists, the name information, address, position information, and speed information are set as one record, the calculated effective time is set as the effective time of the record, the existing record is updated, and the effective time has passed. The record is deleted from the name information table.

According to another embodiment of the communication device of the present invention,
When there is no record of the name resolution target device in the name information table, the name resolution request signal having the name information of the target device is broadcast and the target device receives the name resolution request signal indicating its own device. In this case, the target device is the name information of the own device, a response signal including the address of the own device, position information, and speed information is transmitted to the source of the name resolution request signal, and the response signal addressed to the own device is transmitted. When received, the effective time is calculated based on the position information and speed information included in the response signal and the position information and speed information of the own device, and the name information of the target device included in the received response signal, It is also preferable to register the address, position information, and speed information as one record, and register the calculated effective time in the name information table as the effective time of the record.

According to another embodiment of the communication device of the present invention,
When the target device receives a name resolution request signal indicating another communication device, it checks whether or not the record of the target device exists in the name information table of its own device. It is also preferable to transmit the proxy response signal including the address of the record for the other communication device in the name information table, the position information, and the speed information to the transmission source of the name resolution request signal as the other communication device.

Furthermore, according to another embodiment of the communication device of the present invention,
The position information included in the proxy response signal is the position information, speed information, and acquisition of the record instead of the record value for the name resolution target device in the name information table of the communication device that performs the proxy response. It is also preferable to use estimated position information at the time of performing the proxy response calculated based on the time.

Furthermore, according to another embodiment of the communication device of the present invention,
The proxy response signal is transmitted only when the record for the target device indicated by the received name resolution request signal exists in the name information table and is within a predetermined number of hops from the name resolution request signal transmission source device. Is also preferable.

Furthermore, according to another embodiment of the communication device of the present invention,
It is also preferable that the proxy response signal is transmitted only when a record for the target device indicated by the received name resolution request signal exists in the name information table and is within a predetermined number of hops from the target device.

Furthermore, according to another embodiment of the communication device of the present invention,
It is also preferable that the proxy response signal is transmitted only when a record for the target device indicated by the received name resolution request signal exists in the name information table and the period until the valid time of the record is equal to or greater than a predetermined value. .

Furthermore, according to another embodiment of the communication device of the present invention,
The valid time is preferably determined according to a period in which the distance between the name information signal transmission source device or the target device of the response signal or proxy response signal and the own device reaches a predetermined distance or more.

Furthermore, according to another embodiment of the communication device of the present invention,
The valid time is preferably determined within a range between a predetermined minimum value and a maximum value.

  When exchanging name information with each communication device that constitutes an ad hoc network, the location information and speed information of each communication device are also exchanged, and the name information acquired from the own device from the location information and speed information of the own device By calculating the effective time according to the positional relationship with the device and deleting the information after the effective time, it is possible to maintain name information according to the change even for ad hoc networks that change every moment To do.

  In response to the name resolution request signal, which is a broadcast signal, it is possible to eliminate the need to always send a broadcast signal to the target device by enabling a proxy response. By limiting the effective time of records in the name information table, unnecessary traffic increase can be suppressed and highly reliable name information can be collected.

  The best mode for carrying out the present invention will be described in detail below with reference to the drawings.

  FIG. 1 is a block diagram of an ad hoc network according to the present invention. According to FIG. 1, the ad hoc network 11 includes a plurality of communication devices indicated by reference numeral 12. Reference numeral 13 indicates the wireless coverage of each communication apparatus, that is, the communicable range. For example, the communication device E communicates with the communication device B that is out of its wireless coverage via the communication device A in which both the communication devices E and B are within the wireless coverage. As long as the wireless coverage of each communication device overlaps, the communication devices can communicate with each other, and can communicate with the ad hoc network 11 by overlapping each wireless coverage. A communication network composed of communication devices.

  Reference numeral 14 denotes a GPS (Global Positioning System) satellite, and each communication device 12 receives a signal from the GPS satellite 14, acquires position information such as the current latitude and longitude, and stores the position information. At the same time, from the update history of the position information, the moving speed and moving direction of the communication device, hereinafter referred to as speed information, are calculated and stored.

  FIG. 2 is a sequence diagram in the first embodiment of name resolution according to the present invention in the configuration of FIG. As shown in FIG. 1, the communication device A is within the wireless coverage of the communication device E, the communication devices E and B are within the wireless coverage of the communication device A, and the communication device is within the wireless coverage of the communication device B. Assume that A and C are communication devices B and D within the radio coverage of the communication device C, and that the communication device C is within the radio coverage of the communication device D.

  The communication device A transmits the name information signal HEL including A, which is its own name information, its own address, its own position information acquired by GPS, and speed information obtained from the position information history, at predetermined intervals in the ad hoc network. Broadcast to. Each communication device that has received the name information signal HEL performs a registration process, that is, the name of the communication device included in the name information signal HEL, its address, position information, and speed information after performing an effective time calculation to be described later. And the calculated effective time and the time when the name information signal HEL is received are registered in the name information table. If a record having the name of the communication device included in the name information signal HEL already exists in the name information table, the record is updated. Each communication device that receives the name information signal HEL transfers the name information signal HEL to another communication device.

Hereinafter, the effective time calculation will be described with reference to FIG. In FIG. 5, X _{A to} X _D are position vectors of communication apparatuses A to D, that is, position information, respectively, and V _{A to} V _D are speed vectors of communication apparatuses A to D, that is, speed information, respectively. Yes, d is a radius of a predetermined circle centering on the communication device A. In addition, it is assumed that each communication device holds a predetermined minimum value n _min and maximum value n _max regarding the valid time.

In the state of FIG. 5, for example, when the communication device A receives the name information signal HEL from the communication device B, the communication device A calculates the effective time of the information notified by the name information signal HEL by the following calculation. .
(A) If | X _B -X _A |> d,
Effective time = n _min
( _A ) When | X _B −X _A | ≦ d and | X _B −X _A + n _max (V _B −V _A ) | ≦ d,
Effective time = n _max
(C) When | X _B −X _A | ≦ d and | X _B −X _A + n _max (V _B −V _A ) |> d,

  The basic idea of the effective time is that communication devices that are separated by a predetermined distance d or more first have a low correlation at this stage, and therefore use the minimum value of the effective time uniformly, and communication that is within the predetermined distance d. For an apparatus, an effective time proportional to the time until the distance to the apparatus reaches a predetermined distance d is used. However, a maximum value is set to prevent the effective time from increasing without limit.

  FIG. 4 is a diagram illustrating a name information table included in each communication device. As shown in FIG. 4, each record of the name information table includes a name field indicating the name information of each communication device, an address field indicating the address of the communication device indicated by the name field, and a latitude and longitude storing the position information. The field includes a moving speed and moving direction field for storing speed information, an acquisition time field indicating the time when the information of the record is acquired, and an effective time field indicating the effective time of the record. The communication device deletes the record whose valid time has passed from the name information table. The moving direction is expressed as an angle in the clockwise direction, for example, with north being 0 °.

  Returning to FIG. 2, for example, when the communication device A performs name resolution of the communication device D, the communication device A refers to the name information table held by the own device, but the name information table includes the name of the communication device D. If there is no record, a name resolution request signal REQ including the name of the communication device D that is the target of name resolution is broadcast to the ad hoc network.

  The communication device that has received the name resolution request signal REQ refers to the target device of the resolution included in the name resolution request signal REQ, and simply transfers it if it is not its own device. In response to the name resolution request signal REQ, the communication device D, which is a target device for name resolution, sends a response signal REP having the name information, position information, speed information, and address of the target communication device D to the communication device Send to A. The communication device A that has received the response signal REP performs the above-described effective time calculation processing and registration processing from the received response signal REP.

  FIG. 3 is a sequence diagram in the second embodiment of name resolution according to the present invention. The communication device D transmits a name information signal HEL, and the record of the communication device D is registered in the name information table of the communication device C. On the other hand, since there is no record of the communication device D in the name information table of the communication device A, the communication device A broadcasts a name resolution request signal REQ in which the name resolution target device is the communication device D. In the case of the first embodiment, the communication device C simply performs transfer because the target device of the name resolution request signal REQ is not its own device, but in this embodiment, the name information of the communication device C is used. Since the record of the communication device D that is the target device of the name resolution request signal REQ exists in the table, the communication device C does not transfer the name resolution request signal REQ, but the proxy response, that is, the communication device C is the target. The device is D, and a proxy response signal REP ′ including the position information, speed information, and address of the communication device D recorded in its own record is created and transmitted to the communication device A.

  When the name resolution request signal REQ is received, it is checked whether or not the record of the target device exists in the name information table of the own device, and if it does not exist, transfer is performed as in the first embodiment. In this case, the proxy response signal REP ′ is generated based on the information recorded in the record of the name information table and sent back to the name resolution request signal transmission source, so that an increase in traffic for name resolution can be suppressed.

  The proxy response, that is, when a device other than the target device included in the name resolution request signal REQ generates and transmits the proxy response signal REP ′, the time when the information of the name information table is acquired and the proxy response are In order to correct the positional information shift due to the time difference from the time to be performed, the device that performs the proxy response does not transmit the value recorded in the name information table as it is, but the estimated position calculated by a predetermined method. It is preferable to transmit information.

The estimated position information is the time when the proxy response is made when the latitude recorded in the name information table is Y ₁ , the longitude is X ₁ , the moving speed is V ₁ , the moving direction is d ₁ , and the acquisition time is T _1. Estimated latitude and longitude at t, for example
Estimated latitude = Y ₁ + (t−T ₁ ) × V ₁ × cos (d ₁ )
Estimated longitude = X ₁ + (t−T ₁ ) × V ₁ × sin (d ₁ )
Asking.

  It is also preferable to limit the device that performs the proxy response by the number of hops from the transmission source device of the name resolution request signal REQ. For example, in FIG. 3, when the hop number limit is set to 2 for the name resolution request signal REQ of the communication apparatus A, the communication apparatuses B, C, and E can make proxy responses, but the hop number limit is set to 1. In this case, the communication device C cannot make a proxy response. In this way, by limiting the number of hops from the source device of the name resolution request signal REQ to the device that performs the proxy response, the number of proxy response signals REP ′ that can be generated more than one can be reduced. Necessary traffic can be prevented. The number of hops may be configured to use a predetermined value in the ad hoc network, or may be configured to be notified by the name resolution request signal REQ by the device that transmits the name resolution request signal REQ.

  It is also preferable to limit the device that performs the proxy response by the number of hops from the target device of the name resolution request signal REQ. For example, in FIG. 3, when the hop number limit is set to 2 for the name resolution request signal REQ of the communication apparatus A, the communication apparatuses B and C can perform proxy responses, but the hop number limit is set to 1. Only the communication device C can make a proxy response. In this way, by limiting the devices that perform proxy responses with the number of hops from the target device of the name resolution request signal REQ, the communication devices that can perform proxy responses can be limited to communication devices near the target device. Generally, it is considered that the information of the communication device in the vicinity of the target device is closer to the current state of the target device than the information of the communication device at a remote location, so the reliability of the proxy response information is increased. be able to. The number of hops from the target device is normally stored in a routing table (not shown), and each communication device recognizes the number of hops from the routing table. Furthermore, it can be used in combination with the restriction on the number of hops from the own device. The hop count may be configured to use a predetermined value in the ad hoc network, or may be configured such that a device that transmits the name resolution request signal REQ notifies the name resolution request signal REQ.

  Furthermore, it is also preferable to limit so that only the communication device whose period until the valid time of the record of the target device is a predetermined value or more can perform a proxy response. Thereby, it is possible to prevent the transmission apparatus of the name resolution request signal REQ from acquiring old information whose valid time passes within a predetermined period, and to improve the reliability of the acquired name information. As described above, the predetermined value may be configured to use a fixed value in the ad hoc network, or the device that transmits the name resolution request signal REQ may be notified by the name resolution request signal REQ. Is

It is a block diagram of the communication system by this invention. It is a sequence diagram in 1st Embodiment of the name resolution by this invention. It is a sequence diagram in 2nd Embodiment of the name resolution by this invention. It is a figure which shows the name information table which each communication apparatus has. It is a figure explaining effective time calculation.

Explanation of symbols

11 Ad hoc network 12 Communication device 13 Wireless coverage 14 GPS satellite

Claims (9)

A communication device that constitutes an ad hoc network, has a name information table for name resolution, and has means for acquiring location information of the device itself,
When a name information signal including name information, address, position information, and speed information of a communication device constituting an ad hoc network is received,
Calculate the effective time based on the position information and speed information included in the name information signal, the position information of the own apparatus, and the speed information of the own apparatus calculated from the history of the position information of the own apparatus,
If the name information record included in the name information signal does not exist in the name information table, the name information, the address, the position information, and the speed information are set as one record, and the calculated effective time is set to the effective time of the record. Register it in the name information table as time,
If there is a record for the name information included in the name information signal in the name information table, the name information, the address, the position information, and the speed information are set as one record, and the calculated effective time is set to the effective time of the record. Update the existing record as time,
A communication apparatus, wherein a record whose valid time has passed is deleted from the name information table. When there is no record of the target device for name resolution in the name information table, a name resolution request signal having the name information of the target device is broadcast,
When the target device receives a name resolution request signal indicating the own device, the target device is the name information of the own device, and a response signal including the address of the own device, position information, and speed information is the name resolution request signal. To the sender of
When receiving a response signal addressed to its own device, calculate the effective time based on the position information and speed information included in the response signal and the position information and speed information of the own device,
The name information, address, position information, and speed information of the target device included in the received response signal are set as one record, and the calculated effective time is registered in the name information table as the effective time of the record. The communication device according to claim 1.   When the target device receives a name resolution request signal indicating another communication device, it checks whether or not the record of the target device exists in the name information table of its own device. A proxy response signal including a record address, position information, and speed information for the other communication device in the name information table is transmitted to the source of the name resolution request signal as the other communication device. The communication device according to claim 2.   The position information included in the proxy response signal is the position information, speed information, and acquisition of the record instead of the record value for the name resolution target device in the name information table of the communication device that performs the proxy response. The communication apparatus according to claim 3, wherein the position information is estimated position information at a time of performing a proxy response calculated based on the time.   The proxy response signal is transmitted only when the record for the target device indicated by the received name resolution request signal exists in the name information table and is within a predetermined number of hops from the name resolution request signal transmission source device. The communication device according to claim 3 or 4, characterized by the above.   The proxy response signal is transmitted only when a record for the target device indicated by the received name resolution request signal exists in the name information table and is within a predetermined number of hops from the target device. Item 6. The communication device according to any one of Items 3 to 5.   The proxy response signal is transmitted only when the record for the target device indicated by the received name resolution request signal exists in the name information table and the period until the valid time of the record is equal to or greater than a predetermined value. The communication device according to any one of claims 3 to 6.   The effective time is determined according to a period in which a distance between the name information signal transmission source device or a target device of a response signal or a proxy response signal and the own device reaches a predetermined distance or more. The communication device according to any one of 1 to 7.   The communication apparatus according to claim 1, wherein the valid time is determined within a range between a predetermined minimum value and a maximum value.

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