JP2007174389A - Packet relay method of terminal in mobile ad-hoc network, terminal, and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a packet relay method or the like of a terminal in a mobile adhoc network capable of carrying out multihop communication, whereby a necessity minimum number of relay terminals is provided and information transmitted from one terminal can be relayed with an information amount as small as possible in the network as a whole. <P>SOLUTION: When the terminal receives a data packet from a first terminal, a reception history recording section of the terminal stores the history information denoting the reception of the data packet. When the terminal receives a request packet from a second terminal to request the terminal for acting like a relay terminal for a data packet transmitted from the first terminal (S202), the terminal transmits an acknowledgement packet for denoting that the terminal acts like the relay terminal, when the reception history recording section has a reception recording of the data packet from the first terminal (S203). When the terminal receives a data packet from the first terminal, the terminal further transmits the data packet (S205). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a packet relay method for a terminal in a mobile ad hoc network, the terminal and a program thereof.

  Conventionally, a terminal for a mobile ad hoc network has a wireless communication function and a relay function that relays a data packet received from a first terminal to a second terminal. As an example using this terminal, there is an “information exchange type driving support system”. In this system, a terminal transmits a data packet including its own information to the entire network, and is based on a broadcast technique. Other terminals distribute the data packet to the entire network by relaying the data packet while giving up each other.

  When such a terminal is mounted on an automobile, the terminal transmits a data packet including information on the position, speed, direction, and the like of the automobile to the surroundings. It is left to the terminal how to handle information received from another terminal. For example, another car approaching at an intersection with poor visibility can be displayed on the car navigation system.

  However, when a terminal transmits a data packet, if all the terminals that have received the data packet relay it, the amount of communication increases enormously. Such a communication method is called “flooding”. This technique tries to suppress the entire communication amount by discarding the data packet without relaying when the data packet is received in duplicate. However, duplicate transmission of data packets eventually consumes radio resources without permission.

  Therefore, a method for minimizing the number of terminals functioning as relay terminals within the network has been proposed (see, for example, Non-Patent Documents 1 and 2).

The essence of this method assumes a case where communication is possible between terminal A-terminal C and terminal B-terminal C, and communication between terminal A-terminal C is impossible.
Terminal A-Terminal C-Terminal B

At this time, the terminal C becomes a relay terminal for the terminal A and the terminal B when the following conditions are satisfied. In this case, it is necessary to periodically exchange information “who knows the neighboring terminal” between the terminals.
・ "Self (terminal C) knows terminal A and terminal B"
"Terminal A does not know terminal B" and "Terminal B does not know terminal A"

Specifically, the terminal needs to periodically transmit the following information set to the entire adjacent terminals. The adjacent terminal that receives the packet including the set of information determines whether or not to relay the packet further.
・ Identifier of its own terminal ・ Identifier of its own terminal (terminal of 1 hop ahead) ・ Identifier of its neighboring terminal (terminal of 2 hops)

J. Wu, “Extende Dominating-Set-Based Routing in AdHoc Wireless Networks with Unidirectional Links”, IEEE Trans. Paralelel and Distributed Systems, Vol. 9, No. 3, pp.189-200, September 2002 Fei Dai and J. Wu, “An Extended Localized Algorithm for Connected Dominating Set Formation in Ad Hoc Wireless Networks”, IEEE Trans.Parallel and Distributed Systems, Vol.15, No.10, October 2004

  However, according to Non-Patent Documents 1 and 2, although the number of relay terminals can be minimized, the amount of information becomes enormous depending on the application system in order to exchange information of two hops ahead. This increases overall network traffic and communication delays. In particular, in a system that requires real-time characteristics, such as a driving support system, communication delay becomes a very important issue. Further, the quality of the radio link between terminals is not taken into consideration, and it cannot be said that the reliability of data relay is ensured.

  Therefore, the present invention relates to a mobile ad hoc network capable of multi-hop communication, and information transmitted from one terminal is relayed with as little information as possible in the entire network while minimizing the number of relay terminals. An object of the present invention is to provide a packet relay method for a terminal, the terminal, and a program.

According to the packet relay method of the present invention,
A first step of holding history information indicating that the data packet has been received in the reception history recording unit when the data packet is received from the first terminal;
When a request packet requesting to become a relay terminal for the first terminal is received from the second terminal, if the reception history recording unit has a reception record of the data packet from the first terminal, the relay terminal A second step of sending a response packet indicating that it functions as:
And a third step of further transmitting the data packet to relay the data packet when the data packet is received from the first terminal.

According to another embodiment of the packet relay method of the present invention,
Regarding the second step, when a response packet for the request packet is received from another terminal before transmitting the response packet, it is preferable not to transmit the response packet.

According to another embodiment of the packet relay method of the present invention,
Regarding the second step, when a response packet for a request packet is received from another terminal after transmitting the response packet, the magnitude relationship of the predetermined conditions of both response packets is compared, and the response packet transmitted by itself is small. In this case, it is preferable not to relay the data packet.

Furthermore, according to another embodiment of the packet relay method of the present invention,
When a data packet is received from a terminal that is not recorded in the reception history recording unit, it is also preferable to transmit a response packet on the assumption that the request packet has been received from the terminal.

Furthermore, according to another embodiment of the packet relay method of the present invention,
For the first step, the reception history recording unit records the packet reception rate,
If a data packet from the first terminal is recorded in the reception history recording unit, but the packet reception rate is lower than a predetermined threshold, a request packet requesting that the adjacent terminal becomes a relay terminal is transmitted. It is also preferable to further include a step.

Furthermore, according to another embodiment of the packet relay method of the present invention,
It is also preferable that when response packets are received from a plurality of adjacent terminals after transmitting the request packet, only one of the adjacent terminals is set as a relay terminal and a stop packet is transmitted to the other adjacent terminals. .

Furthermore, according to another embodiment of the packet relay method of the present invention,
A step of transmitting a stop packet to the adjacent terminal when a data packet smaller than the number of hops recorded in the reception history recording unit is received for the data packet in which the adjacent terminal is a relay terminal. Is also preferable.

According to the terminal of the present invention,
Reception history recording means for recording history information indicating that the data packet has been received when the data packet is received from the first terminal;
When receiving a request packet requesting to become a relay terminal for the first terminal from the second terminal, if the reception history recording means has a reception record of the data packet from the first terminal, the relay terminal Relay control means for transmitting a response packet indicating that it functions as:
When receiving a data packet from the first terminal, it further comprises relay means for further transmitting to relay the data packet.

According to another embodiment of the terminal of the present invention,
The relay control means preferably does not transmit a response packet when a response packet for the request packet is received from another terminal before transmitting the response packet.

Also, according to another embodiment of the terminal of the present invention,
When the relay control means receives the response packet for the request packet from another terminal after transmitting the response packet, the relay control means compares the magnitude relationship of the predetermined conditions of both response packets, and the response packet transmitted by itself becomes small In this case, it is preferable not to relay the data packet.

Furthermore, according to another embodiment of the terminal of the present invention,
When the relay control unit receives a data packet from a terminal not recorded in the reception history recording unit, the relay control unit preferably regards that the request packet has been received from the terminal and transmits a response packet.

Furthermore, according to another embodiment of the terminal of the present invention,
The reception history recording means further records the packet reception rate,
If a data packet from the first terminal is recorded in the reception history recording means, but the packet reception rate is lower than a predetermined threshold, a request packet requesting that the adjacent terminal becomes a relay terminal is transmitted. It is also preferable to further include a relay request unit.

Furthermore, according to another embodiment of the terminal of the present invention,
When the relay request means receives response packets from a plurality of adjacent terminals after transmitting the request packet, only one of the adjacent terminals is set as the relay terminal, and the stop packet may be transmitted to the other adjacent terminals. preferable.

Furthermore, according to another embodiment of the terminal of the present invention,
The relay request unit transmits a stop packet to the adjacent terminal when a data packet smaller than the number of hops recorded in the reception history recording unit is received for the data packet in which the adjacent terminal is the relay terminal. It is also preferable.

According to the program of the present invention for causing a computer mounted on a terminal to function,
Reception history recording means for recording history information indicating that the data packet has been received when the data packet is received from the first terminal;
When receiving a request packet requesting to become a relay terminal for the first terminal from the second terminal, if the reception history recording means has a reception record of the data packet from the first terminal, the relay terminal Relay control means for transmitting a response packet indicating that it functions as:
When the data packet is received from the first terminal, the computer is caused to function as a relay unit that further transmits the data packet to relay the data packet.

  According to the present invention, in a mobile ad hoc network capable of multi-hop communication, information transmitted from one terminal is relayed with as little information as possible in the entire network while minimizing the number of relay terminals. . Thereby, the traffic of the whole network is reduced and the communication delay is reduced. In particular, in a system that requires real-time characteristics such as a driving support system, communication delay can be shortened, and communication band can be effectively used.

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

  FIG. 1 is a configuration diagram of a MAC header in the present invention.

  The configuration of the MAC header has an existing part, an extension part, and a transmission information part. The existing part includes “packet type”, “hop count”, and “sequence number”.

The “packet type” has the following classification. This is one of the features of the present invention.
“REQ (Request) packet”: When the packet reception rate from a certain terminal is lower than a predetermined threshold, a request is made for an adjacent terminal to become a relay terminal for a data packet from that terminal.
“REP (Reply) packet”: When a REQ packet is received, if there is a reception record of a data packet from a terminal requested to be relayed, it responds that it functions as a relay terminal.
“STP (Stop) packet”: When a REP packet is received from a plurality of terminals, in order to avoid duplicating relay, the terminal that does not want to relay is requested to stop the function as a relay terminal.
“DATA packet”: a data packet including transmission information.

  The “hop count” is “0” when the data source terminal transmits a data packet, and is incremented by 1 when relaying.

  The “sequence number” is incremented by 1 when the data source terminal transmits a data packet (setting range is 0 to 255). The data packet to be relayed is used as it is.

  The extension unit includes “data source ID”, “relay request data source ID”, “transmission source ID”, “request source ID”, and “transmission source hop number”.

  The “data source ID” is the ID of the terminal that is the source that transmitted the DATA packet. When a terminal transmits a data packet as a transmission source, the terminal sets an ID (identifier) of the terminal. The data packet to be relayed is used as it is.

  “Relay request data source ID” is used only by the control packet, and sets the ID of the data source terminal desired to be relayed.

  “Sender ID” sets the ID of the sender terminal of the control packet. Therefore, when a DATA packet is received from a relay terminal, it becomes the ID of the relay terminal. In the case of an STP packet, the ID of the REP transmission source terminal or a wild card (0xFFFF) is set.

  The “request source ID” sets the ID of the transmission source terminal of the REQ packet when transmitting the REP packet and the STP packet.

  The “transmission source hop count” sets the hop count from the own terminal to the terminal of the relay request data source ID when transmitting the REQ and REP packets. The number of hops is the number of relay terminals that have passed from the terminal of the data source ID. Here, the hop number of the relay request data source ID included in the reception history recording unit described later is used.

  According to FIG. 1, information included in the “information exchange type driving support system” is specifically described as transmission information. Such information varies depending on the system to which the information is applied.

The terminal has a reception history recording unit, and records the following information when receiving a DATA packet.

  The packet reception rate is a rate at which a DATA packet received directly from the data source ID is received. When the DATA packet is periodically transmitted at a predetermined time interval, the packet reception rate is calculated based on the number of times the DATA packet is received and the elapsed time.

  FIG. 2 is a first sequence diagram which is a basic pattern of the present invention.

  According to FIG. 2, the data source terminal is terminal A, and between terminal A and terminal B and between terminal B and terminal C, the strength of the radio link is strong and the packet reception rate is also high. On the other hand, between terminal A and terminal C, the strength of the radio link is weak and the packet reception rate is low.

The packet transmitted by each terminal is described in FIG. 2 as follows.
[Packet type, number of hops, sequence number, data source ID,
Relay request data source ID, source ID, request source ID, source hop count]

(S201) Terminal A transmits a DATA packet with sequence number 1.
[DATA, 0, 1, A,-,-,-,-]
Number of hops: 0, sequence number: 1, data source ID: A
It is assumed that this DATA packet is received by terminal B but not received by terminal C.

(S202) If terminal C knows the presence of terminal A but the packet reception rate from terminal A is equal to or lower than a predetermined threshold, relay request data is sent to allow an adjacent terminal to operate as a relay terminal. A REQ packet with the source ID “terminal A” is transmitted.
[REQ, 0, 1, C, A, C,-, 1]
Number of hops: 0, sequence number: 1, data source ID: C
Relay request data source ID: A, source ID: C
Number of source hops: 1

(S203) Upon receiving the REQ packet from the terminal C, the terminal B searches the reception history recording unit. Then, the terminal B searches whether a DATA packet having the terminal A as the data source ID has been received before. When receiving the DATA packet from the terminal A, the terminal B transmits a REP packet having the relay request data source ID “terminal A” in order to function as a relay terminal between the terminal A and the terminal C.
[REP, 0, 1, B, A, B, C, 1]
Number of hops: 0, sequence number: 1, data source ID: B
Relay request data source ID: A, source ID: B
Requester ID: C, source hop count: 1

(S204) Next, terminal A transmits a DATA packet with sequence number 2.
[DATA, 0, 2, A,-,-,-,-]
Number of hops: 0, sequence number: 2, data source ID: A
This DATA packet transmitted from terminal A is received by terminal B.

(S205) Terminal B further broadcasts to relay the DATA packet received from terminal A. Thereby, this DATA packet is received by the terminal C.
[DATA, 1, 2, A,-,-,-,-]
Number of hops: 1, sequence number: 2, data source ID: A

  FIG. 3 is a second sequence diagram in the present invention.

  According to FIG. 3, the data source terminal is terminal A, and between terminal A-terminal B, terminal A-terminal C, terminal B-terminal C, terminal B-terminal D, and terminal C-terminal D The strength of the radio link is strong and the packet reception rate is also high. On the other hand, between terminal A and terminal D, the strength of the radio link is weak and the packet reception rate is low.

  According to FIG. 3, in order to relay the DATA packet transmitted from the terminal A to the terminal D, both the terminal B and the terminal C can be relay terminals. Here, it is necessary to avoid that terminal B and terminal C overlap and become relay terminals.

(S301) Terminal A transmits a DATA packet with sequence number 1.
[DATA, 0, 1, A,-,-,-,-]
Number of hops: 0, sequence number: 1, data source ID: A
It is assumed that this DATA packet is received by terminal B and terminal C but not received by terminal D.

(S302) The terminal D knows the existence of the terminal A, but when the packet reception rate from the terminal A becomes equal to or less than a predetermined threshold, the relay request data source is set so that the adjacent terminal operates as a relay terminal. A REQ packet with ID “terminal A” is transmitted.
[REQ, 0, 1, D, A, D,-, 1]
Number of hops: 0, sequence number: 1, data source ID: D
Relay request data source ID: A, source ID: D
Number of source hops: 1
The REQ packet transmitted from the terminal D is received by the terminal B and the terminal C, but is not received by the terminal A.

(S303) When the terminal B receives the REQ packet from the terminal D, the terminal B searches the reception history recording unit and searches whether or not the DATA packet having the terminal A as the data source ID has been received before. When the DATA packet is received from the terminal A, the terminal B transmits a REP packet having the relay request data source ID “terminal A” in order to function as a relay terminal between the terminal A and the terminal D.
[REP, 0, 1, B, A, B, D, 1]
Number of hops: 0, sequence number: 1, data source ID: B
Relay request data source ID: A, source ID: B
Requester ID: D, source hop count: 1

  Here, when the terminal C receives the REP packet from the terminal B before transmitting the REP packet, the terminal C stops transmitting its own REP packet. This is to prevent multiple terminals that have received the REQ packet from relaying redundantly.

  As another embodiment, when the terminal C receives the REP packet from the terminal B after transmitting the REP packet, the terminal C compares the magnitude relationship of the predetermined conditions of both response packets, and determines that the response packet transmitted by itself is small. In such a case, data packets are not relayed. Here, the predetermined condition may be the ID of the terminal that transmitted the REP packet. That is, it is absolutely necessary that one of them is determined. If the ID of the terminal C is numerically smaller than the ID of the terminal B, the terminal C is controlled not to relay the data packet although it transmits the REP packet.

(S304) Next, the terminal A transmits the following DATA packet.
[DATA, 0, 2, A,-,-,-,-]
Number of hops: 0, sequence number: 2, data source ID: A
The DATA packet transmitted from terminal A is received by terminal B and terminal C.

(S305) Terminal B relays and further broadcasts the DATA packet received from terminal A. Thereby, this DATA packet is received by the terminal D.
[DATA, 1, 2, A,-,-,-,-]
Number of hops: 1, sequence number: 2, data source ID: A

  FIG. 4 is a third sequence diagram in the present invention.

  According to FIG. 4, the data source terminal is terminal A, and the strength of the radio link is between terminal A-terminal B, terminal A-terminal C, terminal B-terminal D, and terminal C-terminal D. Strong and high packet reception rate. On the other hand, between terminal A and terminal D, the strength of the radio link is weak and the packet reception rate is low. Furthermore, it is assumed that there is an obstacle between the terminal B and the terminal C, and the hidden terminal problem has occurred.

  According to FIG. 4, in order to relay the DATA packet transmitted from terminal A to terminal D, both terminal B and terminal C can be relay terminals. Here, it is necessary to avoid that terminal B and terminal C overlap and become relay terminals.

(S401) This is exactly the same as S301.
(S402) Same as S302.
(S403) Same as S303. Note that the REP packet transmitted by the terminal B cannot be received by the terminal C.

(S404) Upon receiving the REQ packet from the terminal D, the terminal C searches the reception history recording unit, and searches for whether or not a DATA packet having the terminal A as the data source ID has been received before. When the DATA packet is received from the terminal A, the terminal C transmits a REP packet having the relay request data source ID “terminal A” in order to function as a relay terminal between the terminal A and the terminal D.
[REP, 0, 1, C, A, C, D, 1]
Number of hops: 0, sequence number: 1, data source ID: C
Relay request data source ID: A, source ID: C
Requester ID: D, source hop count: 1
Note that the REP packet transmitted by the terminal C cannot be received by the terminal B.

(S405) Terminal A receives the REP packet from terminal B and the REP packet from terminal C in duplicate. Terminal A transmits an STP packet to terminal C that has received the second REP packet in order to avoid duplicate relay.
[STP, 0, 2, A, A, C, D,-]
Number of hops: 0, sequence number: 2, data source ID: A
Relay request data source ID: A, source ID: C
Requester ID: D
The terminal C that has received the STP packet stops relaying the data packet having the data source ID “terminal A”.

(S406) Next, terminal A transmits the following DATA packet.
[DATA, 0, 3, A,-,-,-,-]
Number of hops: 0, sequence number: 3, data source ID: A
The DATA packet transmitted from terminal A is received by terminal B and terminal C.

(S407) Terminal B relays and further broadcasts the DATA packet received from terminal A. Thereby, this DATA packet is received by the terminal D.
[DATA, 1, 3, A,-,-,-,-]
Number of hops: 1, sequence number: 3, data source ID: A

  FIG. 5 is a simplified sequence diagram by assuming that a REQ packet has been received.

(S501) Terminal A transmits a DATA packet with sequence number 1.
[DATA, 0, 1, A,-,-,-,-]
Number of hops: 0, sequence number: 1, data source ID: A
It is assumed that the DATA packet transmitted from the terminal A is received by the terminal B but not received by the terminal C.

  When the terminal B receives the DATA packet from the terminal A, the terminal B searches whether the terminal A is recorded in the data source ID of the reception history recording unit. Here, it is assumed that the terminal A is not recorded as the data source ID in the reception history recording unit. Thereby, it is recognized for the terminal B that the DATA packet from the terminal A is received for the first time.

(S502) Terminal B performs the following two operations.
Operates as if a REQ packet was received from a new data source ID (terminal A).
(Relay request data source ID = received data source)
Operates as if a REQ packet was received from each received data source ID (terminal C).
(Relay request data source ID = new received data source ID)

Terminal B transmits a REP packet whose request source ID is “terminal A”.
[REP, 0, 1, B, C, B, A, 1]
Number of hops: 0, sequence number: 1, data source ID: B
Relay request data source ID: C, transmission source ID: B
Requester ID: A, number of sender hops: 1
Thereby, the terminal B relays the DATA packet transmitted from the terminal A to the terminal C.

(S503) In addition, the terminal B transmits a REP packet having the request source ID “terminal C”.
[REP, 0, 1, B, C, B, C, 1]
Number of hops: 0, sequence number: 1, data source ID: B
Relay request data source ID: C, transmission source ID: B
Requester ID: C, source hop count: 1
Thereby, the terminal B relays the DATA packet transmitted from the terminal C to the terminal A.

(S504) Terminal C transmits a DATA packet with sequence number 1.
[DATA, 0, 1, C,-,-,-,-]
Number of hops: 0, sequence number: 1, data source ID: C
This DATA packet is received by terminal B.

(S505) Terminal B further broadcasts to relay the DATA packet received from terminal C. As a result, this DATA packet is received by the terminal A.
[DATA, 1, 1, C,-,-,-,-]
Number of hops: 1, sequence number: 1, data source ID: C

(S506) Terminal A transmits a DATA packet with sequence number 2.
[DATA, 0, 2, A,-,-,-,-]
Number of hops: 0, sequence number: 2, data source ID: A
This DATA packet is received by terminal B.

(S507) Terminal B further broadcasts to relay the DATA packet received from terminal A. As a result, this DATA packet is received by the terminal A.
[DATA, 1, 2, A,-,-,-,-]
Number of hops: 1, sequence number: 2, data source ID: A

  FIG. 6 is a sequence diagram for stopping the relay when the data source terminal approaches.

(S601) Terminal A transmits a DATA packet having sequence number 2. The DATA packet is received by terminal B but not received by terminal C.
(S602) Terminal B further broadcasts to relay the DATA packet. As a result, the DATA packet is received by the terminal C.

(S603) Then, it is assumed that the terminal A and the terminal C approach and are connected by a strong link. At this time, the DATA packet of sequence number 5 transmitted from terminal A is also directly received by terminal C.

  When the terminal C receives the DATA packet, the terminal C searches the reception history recording unit. In the reception history recording unit, “transmission source ID: B, data source ID: A, hop count: 1” is recorded. Here, the DATA packet from terminal A received by terminal C is “transmission source ID: A, data source ID: A, hop count: 0”. Then, since a DATA packet with a small number of hops has been received, there is no need for terminal B to relay.

(S604) Terminal C transmits an STP packet to terminal B.
[STP, 0, 1, C, A, 0xFFFF, C,-]
Number of hops: 0, sequence number: 1, data source ID: C
Relay request data source ID: A, source ID: 0xFFFF
Requester ID: C, source hop count:-
Terminal B that has received the STP packet stops relaying the data packet from terminal A.

(S605) Although the terminal C has transmitted the STP packet, the terminal C may receive the data packet relayed from the terminal B. In this case, since the duplicate packet has been received, the data packet relayed by the terminal B is discarded.

  FIG. 7 is a functional configuration diagram of a terminal in the present invention.

  According to FIG. 7, the terminal 1 includes a data transmission / reception unit 10, a reception history recording unit 11, a relay control unit 12, a relay unit 13, and a relay request unit 14. These functions can also be realized by a program that causes a computer installed in the terminal to function.

  The data transmission / reception unit 10 transmits and receives data packets, and records the reception history of received data packets in the reception history recording unit 11.

  The reception history recording unit 11 records the received data packet as shown in Table 1 described above.

  The relay control unit 12 refers to the reception history recording unit 11 when receiving a request packet requesting to become a relay terminal from another terminal. The relay control unit 12 indicates that the request packet functions as a relay terminal when the request packet requests the relay of the data packet from the first terminal and there is a reception record of the data packet from the first terminal. Send a response packet. When a data packet is received from a terminal that is not recorded in the reception history recording unit, it is assumed that a request packet has been received from that terminal, and a response packet is transmitted.

  The relay unit 13 controls the start / stop of relay for each data packet under the control of the relay control unit 12.

  When the packet reception rate of a certain data source ID, which is recorded in the reception history recording unit, is lower than a predetermined threshold, the relay request unit 14 transmits a request packet that requests an adjacent terminal to become a relay terminal. . In addition, when the relay request unit 14 receives response packets from a plurality of adjacent terminals after transmitting the request packet, only one of the adjacent terminals is set as a relay terminal, and a stop packet is transmitted to the other adjacent terminals. To do.

  As described above in detail, according to the present invention, in a mobile ad hoc network capable of multi-hop communication, information transmitted from one terminal is transmitted in the entire network while minimizing the number of relay terminals. It is relayed with as little information as possible. Thereby, the traffic of the whole network is reduced and the communication delay is reduced. In particular, in a system that requires real-time characteristics such as a driving support system, communication delay can be shortened, and communication band can be effectively used.

  According to the various embodiments of the present invention described above, various changes, modifications, and omissions within the scope of the technical idea and the viewpoint of the present invention can be easily made by those skilled in the art. The above description is merely an example, and is not intended to be restrictive. The invention is limited only as defined in the following claims and the equivalents thereto.

It is a block diagram of the MAC header in this invention. It is a 1st sequence diagram used as the basic pattern of this invention. It is a 2nd sequence diagram in this invention. It is a 3rd sequence diagram in the present invention. FIG. 5 is a sequence diagram simplified by assuming that a REQ packet has been received. It is a sequence diagram for stopping a relay when a data source terminal approaches. It is a function block diagram of the terminal in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Terminal 10 Data transmission / reception part 11 Reception history recording part 12 Relay control part 13 Relay part 14 Relay request part

Claims (15)

In a packet relay method for a terminal in a mobile ad hoc network,
A first step of holding history information indicating that the data packet has been received in the reception history recording unit when the data packet is received from the first terminal;
When receiving a request packet requesting to become a relay terminal for the first terminal from the second terminal, the reception history recording unit has a reception record of the data packet from the first terminal, A second step of transmitting a response packet indicating functioning as a relay terminal;
And a third step of further transmitting the data packet to relay the data packet when the data packet is received from the first terminal.   2. The packet relay according to claim 1, wherein, in the second step, when the response packet for the request packet is received from another terminal before transmitting the response packet, the response packet is not transmitted. Method.   For the second step, after receiving the response packet, when a response packet for the request packet is received from another terminal, the magnitude relationship of the predetermined conditions of both response packets is compared, and the response transmitted by itself 3. The packet relay method according to claim 1, wherein when the packet becomes small, the data packet is not relayed.   4. When receiving a data packet from a terminal not recorded in the reception history recording unit, it is assumed that the request packet has been received from the terminal, and the response packet is transmitted. The packet relay method according to any one of the above. For the first step, the reception history recording unit records a packet reception rate,
When a data packet from the first terminal is recorded in the reception history recording unit, but the packet reception rate is lower than a predetermined threshold, a request packet requesting that the adjacent terminal becomes a relay terminal is transmitted. 5. The packet relay method according to claim 1, further comprising a step of:   When the response packet is received from a plurality of adjacent terminals after transmitting the request packet, only one of the adjacent terminals is set as a relay terminal, and a step of transmitting a stop packet to the other adjacent terminals is further included. The packet relay method according to claim 5.   For a data packet indicating that the adjacent terminal is a relay terminal, a stop packet is transmitted to the adjacent terminal when a data packet smaller than the number of hops recorded in the reception history recording unit is received. The packet relay method according to claim 5 or 6, further comprising a step. In terminals that relay data packets for mobile ad hoc networks,
Reception history recording means for recording history information indicating that the data packet has been received when the data packet is received from the first terminal;
When receiving a request packet requesting to become a relay terminal for the first terminal from the second terminal, when the reception history recording means has a reception record of the data packet from the first terminal, Relay control means for transmitting a response packet indicating functioning as a relay terminal;
And a relay means for further transmitting the data packet when the data packet is received from the first terminal.   9. The terminal according to claim 8, wherein the relay control means does not transmit the response packet when receiving a response packet for the request packet from another terminal before transmitting the response packet.   When the relay control unit receives a response packet for the request packet from another terminal after transmitting the response packet, the relay control unit compares the magnitude relationship of predetermined conditions of both response packets, and the response packet transmitted by itself The terminal according to claim 8 or 9, wherein when the value of becomes small, data packets are not relayed.   When the relay control unit receives a data packet from a terminal not recorded in the reception history recording unit, the relay control unit considers that the request packet has been received from the terminal and transmits the response packet. The terminal according to claim 8. The reception history recording means further records a packet reception rate,
If a data packet from the first terminal is recorded in the reception history recording means, but the packet reception rate is lower than a predetermined threshold, a request packet requesting that the adjacent terminal becomes a relay terminal is transmitted. The terminal according to any one of claims 8 to 11, further comprising a relay requesting unit for executing the relay request.   When the relay request unit receives the response packet from a plurality of adjacent terminals after transmitting the request packet, only one of the adjacent terminals is set as a relay terminal, and a stop packet is transmitted to the other adjacent terminals. The terminal according to claim 12, wherein:   For the data packet indicating that the adjacent terminal is a relay terminal, the relay requesting unit is configured to notify the adjacent terminal when a data packet smaller than the number of hops recorded in the reception history recording unit is received. The terminal according to claim 12 or 13, wherein a stop packet is transmitted. In a program for functioning a computer installed in a terminal that relays data packets for a mobile ad hoc network,
Reception history recording means for recording history information indicating that the data packet has been received when the data packet is received from the first terminal;
When receiving a request packet requesting to become a relay terminal for the first terminal from the second terminal, when the reception history recording means has a reception record of the data packet from the first terminal, Relay control means for transmitting a response packet indicating functioning as a relay terminal;
A program for causing a computer to function as a relay means for further transmitting a data packet when the data packet is received from the first terminal.

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