JP2000252992A - Wireless ad hoc terminals - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To limit the range in which a control packet is broadcast-transmitted to the vicinity of a terminal whose route is to be reconstructed, thereby preventing traffic reduction due to useless broadcast of control packets. When a direct communication cannot be performed between a source terminal and a destination terminal, a control packet signal for searching for a communication route is transmitted, and the result is received to specify the radio signal and to transmit a data packet. In an ad hoc network, when the currently used communication route becomes unavailable, means (S211) for holding the number of relays by the relay terminal of the unavailable communication route and control for searching for a new communication route Means for creating a packet, adding a fixed value m predetermined in the wireless ad-hoc network to the number of relays as a limit on the lifetime of the control packet, and setting the result as a limited number of relays, and adding the result to the control packet to broadcast ( S215).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless ad hoc terminal used in an ad hoc network for reconstructing a route by broadcasting a control packet when a currently used communication route becomes unavailable. In particular, the present invention relates to a wireless ad hoc terminal that limits the lifetime of a control packet according to the number of relays of the control packet.

[0002]

2. Description of the Related Art In an ad hoc network, when a currently used route cannot be used, a control packet is broadcast and transmitted to reconstruct the route. Data communication methods and devices and wireless data communication systems "are known. In such a system,
Even when the source terminal that is the source of the data packet and the destination terminal that is the destination cannot directly communicate due to the distance or the like, there is one that exists between the source terminal and the destination terminal.
Alternatively, when a plurality of wireless terminals can be used, data transfer from the source terminal to the destination terminal is performed by using those wireless terminals as relay terminals for relaying data. However, for example, when a wireless terminal on a route specified to relay a data packet moves and cannot perform relaying, it is necessary to secure a new communication route, and generally secure a communication route. As a method, a route is constructed by broadcasting a packet for constructing a communication route (hereinafter referred to as a control packet) and receiving the result. By transmitting the control packet with a limited lifetime during broadcast transmission, the control packet is prevented from being transmitted forever.

There are the following methods for limiting the lifetime of a control packet. (1) A method of discarding a received control packet if it has already been received (2) A method of limiting the number of relays of a control packet

The method (1) is disclosed in Japanese Patent Application Laid-Open No. 8-9782.
This is adopted as a method of limiting the lifetime of a control packet in Japanese Patent Application Publication No. 1 (1993) -209. FIG. 5 is a diagram illustrating a method of the related art, and is a diagram illustrating a case where a control packet is transmitted from relay terminals A and C. Upon receiving the control packets transmitted from relay terminals A and C, relay terminal B performs processing based on the flowchart shown in FIG. Upon receiving the control packet (step S61), the relay terminal B recognizes the identifier of the relay terminal that has relayed, described in the received control packet (step S62). At this time, if the identification information of the control packet itself is present as in the packet (b) in FIG. 5, the control packet is discarded (step S63 → step S64), and the packet in FIG. As in a), when the identification information of the own device does not exist in the control packet, the identification information of the own device is added to the control packet (step S63).
→ Step S65), and broadcast the control packet (step S66).

[0005] In the method (2), the control packet generating terminal has a certain number of relay times sufficient to enable the route reconstruction during the control packet (hereinafter referred to as a limited number of relay times).
And broadcast transmission. FIG. 7 illustrates this method, and FIG. 8 illustrates a flowchart. As shown in the flowchart of FIG. 8, the terminal that has received this control packet (step S
81), and recognizes the limited relay count described in the received control packet (step S82). At this time, if the limited relay count in the control packet is “0” (step S83), as in the packet (b) in FIG. 7, the control packet is discarded (step S83 → step S8).
4), if the limited relay count in the control packet is not “0” as in the packet (a) in FIG.
After describing its own identification information in the control packet (step S83 → step S85), “1”
Is described as the limited number of relays (step S8).
6) Broadcast transmission of the control packet is performed (step S87).

Further, in the prior art (2), if the route reconstruction is not completed within a certain period of time, the control packet transmitting terminal sets the same limited number of relays and then broadcasts again.

[0007]

According to the prior art (1), as a restriction for preventing repetition of broadcast transmission of a control packet, the history of a relay terminal that has relayed the control packet is viewed and discarded if it has already been received. The method has been adopted. In this method, since the number of transmissions of the control packet itself is not limited, even when the number of relay terminals becomes extremely large, the control packet is always transmitted to the relay terminal capable of relaying.
There is a problem that traffic due to control packets increases.

Further, the prior art (2) restricts the relay of the control packet to only the number of relays sufficient to enable the route reconstruction, thereby coping with a case where the number of relay terminals becomes extremely large. is there. In this method, even when a terminal for which the route is to be reconstructed is nearby, a control packet is always broadcast-transmitted within the range of the number of relays specified by the limited number of relays, and transmission of useless control packets is repeated. There is a problem.

Further, in the prior art (2), if the route reestablishment is not completed within a certain period of time, the control packet transmitting terminal sets the same limited number of relays and then broadcasts again. Can be dealt with, but there is a problem that it cannot be dealt with if the terminal to be reconstructed does not reach the limited number of relays.

As described above, in the prior art, even when the number of relay terminals becomes extremely large, a control packet is always transmitted to a relay terminal capable of relaying, and a route is reconstructed. Even when a terminal is nearby, there is a problem that control packets are always broadcasted within the range of the number of relays specified by the limited number of relays, and unnecessary control packets are repeatedly transmitted. There is a problem that the route cannot be reconstructed if the control packet does not reach the terminal within the limited number of relays. In view of these problems, the present invention makes it possible to limit the range in which a control packet is broadcast-transmitted to the vicinity of a terminal on which route reconstruction is performed, and to broadcast useless control packets. Provided is a wireless ad hoc terminal capable of preventing traffic reduction due to transmission and solving a problem that a control packet does not reach a target terminal for route reconstruction due to a limitation by a predetermined limited number of relays. The purpose is to:

[0011]

According to the present invention, at least three wireless terminals each having all functions of transmitting, receiving, and relaying data packets are used, and any wireless terminal is connected to a data packet. Source terminal, a destination terminal to which a data packet is to be transmitted, or a relay terminal that relays a data packet, and when direct communication between the source terminal and the destination terminal is not possible, Transmitting a signal for searching for the communication route, identifying a communication route using one or more of the relay terminals, receiving the result, and identifying a data packet using the identified communication route. In the wireless ad hoc network to be transferred, the wireless terminal being one of the source terminal, the relay terminal, or the destination terminal, If the over door can no longer be used,
Control packet transmitting means for generating a packet (hereinafter referred to as a control packet) for searching for a new communication route, adding a restriction on the lifetime of the control packet to the control packet, and transmitting the control packet by broadcast; Relay number holding means for holding the number of relays by the relay terminal of the communication route that has become unusable, and the number of relays has a fixed value predetermined in the wireless ad hoc network, or a variable value determined according to the number of relays The first determined by
The control packet transmitting means includes a control means for adding the limited number of relays to the control packet as a limitation on the lifetime of the control packet to the control packet, and transmitting the control packet by broadcast. It is characterized by:

A second aspect of the present invention uses at least three wireless terminals each having all of the functions of transmitting, receiving, and relaying data packets, and uses any wireless terminal as a source of a data packet. Source terminal, a destination terminal to which a data packet is to be transmitted, or a relay terminal that relays a data packet, and when direct communication cannot be performed between the source terminal and the destination terminal, one or more An ad hoc network that transmits a signal for searching for the communication route, specifies a communication route using the relay terminal, receives the result, and transfers a data packet using the specified communication route. In the wireless terminal to be one of the source terminal, the relay terminal or the destination terminal, and the communication route currently used is used. If missing packets to construct a new communication route (hereinafter referred to as control packets)
Is created, and a limit of the lifetime of the control packet is added to the control packet for broadcast transmission. When the communication route reconstruction is not completed within a certain time, control is performed again. Control packet transmitting means for transmitting a packet, limited relay number holding means for holding the number of relays defined as the limit of the lifetime of the control packet as the limited number of relays, and the limited number of relays predetermined in the wireless ad hoc network. Fixed value, or a variable value determined according to the number of relays, a result of adding a second number determined by the number of relays is defined as a limited number of relays, when transmitting the control packet, After holding the defined limit number of relays in the relay number holding unit, the control packet transmitting unit may limit the lifetime of the control packet. Te is added to the limit number of relays in the control packet, there is to broadcast the control packet, the route until the rebuild has completed, repeatedly, the second to the limited number of relays in the limited number of relays retaining means
And control means for causing the control packet transmitting means to broadcast the control packet to which the limited number of relays has been added.

According to the present invention, the control packet is broadcast-transmitted by defining the number of relays of the communication route that has become unusable as the lifetime and transmitting the control packet with the number of relays added with a margin as the limited number of relays. It is possible to limit the range to the vicinity of the terminal for which the route is to be reconstructed, which has the effect of reducing the traffic caused by the broadcast transmission of useless control packets. If it is not completed, by adding a fixed number to the limited number of relays and transmitting the control packet again, it is possible to obtain the effect of being able to cope with the case where the terminal targeted for route reconstruction does not reach the limited number of relays. The most important feature.

In the prior art, a control packet is transmitted to all terminals, or the range of transmitting a control packet is limited to a fixed number of relays. The difference is that the control packet transmission range is determined using the control packet transmission range.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4, FIG.
Is an explanatory diagram of the first embodiment, FIG. 2 is a flowchart of the first embodiment, FIG. 3 is a flowchart of the second embodiment, and FIG. 4 is an explanatory diagram of the second embodiment. FIG. 1 is a diagram showing an embodiment of the present invention. Here the first
The second embodiment corresponds to the invention described in claim 1 of the present application, and the second embodiment corresponds to the invention described in claim 2. In addition,
Although not shown, in the first embodiment, each wireless terminal has a storage device for holding the number of relays by the relay terminal of the communication route that has become unusable, and in the second embodiment, each wireless terminal The terminal has a storage device that holds, as the limited number of relays, the number of relays defined as the limit on the lifetime of the control packet.

In the first embodiment and the second embodiment, when starting route restructuring by transmitting a control packet, a source terminal serving as a source of a data packet, a source terminal of a data packet, Destination terminal to send to, ○
A control packet is transmitted from any of the relay terminal on the source terminal side that has recognized the relay terminal that can no longer be used as the root, and the relay terminal on the destination terminal side that has recognized the relay terminal that has become unusable as the root. It is possible to adapt to the case.

Further, in the first embodiment, a fixed value (first number in claim 1) (hereinafter referred to as m) is added to the number of relays up to that time in order to define the limited number of relays at the time of route reconstruction.
And the fixed value (the second number in claim 2) (hereinafter referred to as n) for repeatedly increasing the limited relay count in the second embodiment is a fixed value predetermined in the wireless ad hoc network. It is determined by a value or a variable value determined according to the number of relays. The fixed value predetermined in the wireless ad hoc network is a value determined by a value set at the time of constructing the wireless ad hoc network, the variable value determined according to the number of relays, for example, a certain ratio in the number of relays, "10" when the number of relays is "100" and the ratio is 10%
And up to "10", and "2" up to "30". In the following embodiment, the number of relays is “5” as a value corresponding to the number of relays.
Up to, assuming that m = 0 and n = 1 are set,
An embodiment will be described.

FIGS. 1 and 2 show an example of the first embodiment. The terminals in FIG. 1 are arranged so as to be able to communicate only with terminals existing in the vicinity. (1) in FIG.
The case where the data packet is transmitted from the transmitting terminal S to the destination terminal Z by relaying the relay terminals A, B, and C as shown in FIG. When the relay terminal C cannot be used as a route due to movement or power cutoff as shown in (2) in FIG. 1 during transmission of the data packet, the fact is transmitted to the source terminal S, and the source terminal S is notified. The present invention will be described in the case where S is a control packet transmitting terminal.

As shown in the flowchart of FIG. 2, the source terminal S holds the number of relays on the currently used route (step S211). If the route cannot be used (step S212), the source terminal S holds the number of relays. By adding m as a margin to the number of relays performed as described above, the number of relays is limited (step S213), and described in a control packet and transmitted (steps S214 and S215). The relay terminal that has received the transmitted control packet (step S221)
Recognizing the limited number of relays (step S222), "0"
If it is, the control packet is discarded (step S223 → step S224). If it is not “0”, its own identification information is described, and the number obtained by subtracting “1” from the limited number of relays is set as the number of limited relays. (Steps S225 and S226), and broadcasts the control packet (step S227). Here, step S2
The processing order of 25 and S226 is not limited to the illustrated order.

In FIG. 1 (2), m = 0, and the number “3” obtained by adding m = 0 to the number of relays “3” (the number of relay terminals A, B, C) of the communication route used. Is described in a control packet as a limited relay number and transmitted. In this case, as shown by (3) in FIG.
Receives the control packet describing the limited number of relays “1” transmitted from the relay terminal B after relaying the relay terminal A, so that the limited number of relays “0” transmitted by the relay terminal D
When the relay terminal E receives it,
Since the limited relay count becomes “0”, it is discarded. On the other hand, since the control packet transmitted from the relay terminal F is delivered to the destination terminal Z, a route that relays the relay terminals A, B, and F is adopted as a data packet transmission route ((4 in FIG. 1). )).

As a modification of the above-described first embodiment of the present invention, a form in which the method of discarding the once received control packet described in the prior art (1) can be used together.

FIGS. 3 and 4 show an example of the second embodiment of the present invention. The terminals in FIG. 4 are arranged so as to be able to communicate only with terminals existing in the vicinity. FIG.
As shown in (1), the transmitting terminal S sends the relay terminals A, B,
If the relay terminal C cannot be used as a route due to movement or power cut while transmitting the data packet to the destination terminal Z via the relay terminal C, the fact is notified to the source terminal S, and the transmission is performed. The present invention will be described when the former terminal S is a control packet transmitting terminal.

In the example shown in FIG. 4, as shown in FIG. 3, the source terminal S uses the same method as the prior art (2) or the first embodiment to define the limited number of relays (in this case, Limit relay times = 3) (step S)
301) and store it in the storage device (step S30).
2), when described and transmitted in the control packet (step S303), as shown in (2) in FIG. 4, the relay terminal E and the relay terminal G transmit the control packet having the limited number of relays of “0”. , The control packet is discarded. Therefore, the route restructuring is not completed, and the control packet transmitting terminal S retransmits the control packet after a certain period of time.

As shown in FIG. 3, the control packet transmitting terminal S retains the limited number of relays at the time of transmitting the control packet (step S302). If it is determined that the reconstruction has not been completed (the determination result of step S304 is “N
o "), a positive constant n is added to the held number of limited relays to obtain a limited number of relays (step S305), which is held (step S302), and then described and transmitted in a control packet (step S303). This process is repeated until the route reconstruction is completed.

In (3) of FIG. 3, since the result of the route restructuring is not notified within a certain period of time, the control packet transmitting terminal S recognizes that the route restructuring has not been completed, and retains it. "1" (positive constant n)
= 1) and the control packet is broadcasted with the number “4” as the limit relay count. The relay terminal H receives the control packet with the limited relay count “0” and discards the control packet. However, since the control packet transmitted by the relay terminal E is transmitted to the destination terminal Z, the route restructuring is completed (step S306). ).

[0026]

As described above, by using the wireless ad hoc terminal of the first aspect, it is possible to determine the lifetime of the control packet when reconstructing the route according to the route that cannot be used. Even in environments where wireless terminals move freely, it is possible to predict the range of broadcast transmission of control packets, compared to a method that always transmits control packets at the same number of relays, regardless of the number of relays of the route used. As a result, it is possible to reduce traffic caused by unnecessary transmission of control packets by broadcast.

According to the second aspect of the present invention, not only when route reconstruction cannot be completed due to packet damage due to collision of control packets, but also when control packet relay is not performed with the set limited number of relays In addition, the route can be reconstructed. The route reconstruction in a wireless terminal that moves freely can not always be dealt with with a fixed number of relays, but can be dealt with by the present invention.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a first embodiment.

FIG. 2 is a flowchart according to the first embodiment.

FIG. 3 is a flowchart of the second embodiment.

FIG. 4 is an explanatory diagram of a second embodiment.

FIG. 5 is an explanatory diagram of a conventional technique (1).

FIG. 6 is a flowchart of a conventional technique (1).

FIG. 7 is an explanatory view of a conventional technique (2).

FIG. 8 is a flowchart of a conventional technique (2).

[Explanation of symbols]

 S Source terminal A, B, C, D, E, F, G, H Relay terminal Z Destination terminal

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hitoshi Takanashi 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Japan Telegraph and Telephone Corporation (72) Inventor Masahiro Morikura 3-19, Nishishinjuku, Shinjuku-ku, Tokyo No. 2 Nippon Telegraph and Telephone Corporation F-term (reference) 5K033 CB13 CC01 DA19 DB12 DB18

Claims (2)

[Claims] 1. A wireless communication system comprising: at least three wireless terminals each having all functions of transmitting, receiving, and relaying a data packet; A communication using one or more of the relay terminals when the destination terminal or the relay terminal that relays the data packet cannot communicate directly between the source terminal and the destination terminal. In a wireless ad hoc network that transmits a signal for searching for the communication route, transmits a signal for searching the communication route, receives the result, and transfers a data packet using the specified communication route, the transmission source terminal, If the current communication route cannot be used if the wireless terminal is either the relay terminal or the destination terminal, a new Control packet transmitting means for generating a packet (hereinafter referred to as a control packet) for searching for a suitable communication route, adding a restriction on the lifetime of the control packet to the control packet, and transmitting the control packet by broadcast; Relay number holding means for holding the number of relays by the relay terminal of the communication route that is no longer possible, a fixed value predetermined in the wireless ad hoc network, or a variable value determined according to the number of relays, The result of adding the first number determined by the above is defined as a limited number of relays, and the control packet transmitting means adds the limited number of relays to the control packet as a limitation on the lifetime of the control packet, and broadcasts the control packet. A wireless ad hoc terminal comprising: 2. Using at least three wireless terminals each having all functions of transmitting, receiving and relaying data packets, an arbitrary wireless terminal is connected to a source terminal as a source of a data packet, A communication using one or more of the relay terminals when the destination terminal or the relay terminal that relays the data packet cannot communicate directly between the source terminal and the destination terminal. In an ad-hoc network that transmits a signal for searching for the communication route, transmits a signal for searching the communication route, receives the result, and transfers a data packet using the specified communication route, the source terminal, If a wireless terminal that is either a relay terminal or the destination terminal and the currently used communication route becomes unavailable, a new A packet for constructing a communication route (hereinafter referred to as a control packet) is created, and a limit on the lifetime of the control packet is added to the control packet to be transmitted by broadcasting. Within
Control packet transmitting means for transmitting a control packet again when communication route restructuring is not completed; limited relay number holding means for holding the number of relays defined as the limit of the lifetime of the control packet as the limited number of relays; The result obtained by adding the second number determined by the fixed number of relays limited in the wireless ad hoc network or a variable value determined in accordance with the number of relays to the wireless ad hoc network is defined as the limited number of relays. When transmitting the control packet, the control packet transmitting means, after causing the limited relay number holding means to hold the specified limited number of relay times, the control packet transmitting means A control packet is added, and the control packet is broadcast-transmitted. Control means for causing the limited number of relays holding means to hold a value obtained by adding a second number to the limited number of relays, and causing the control packet transmitting means to broadcast a control packet to which the limited number of relays is added. A wireless ad hoc terminal, comprising: