JP2009260594A - Data communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the raise of a transmission load and to reduce the delay of transmission time in the cases of a normality and the abnormality of a relay node concerning multicast communication by a radio ad hoc network. <P>SOLUTION: Identifiers A1, B1, R1 for specifying nodes are assigned to each node. Concerning a transmission source node A, the identifier B1 for specifying a destination node B is designated in the data header of multicast data, and also, standby time T is designated which is the time from the reception of the multicast data by each relay node to the transfer of the data by each relay node. Concerning the relay nodes R, the multicast data received only by the node possessing a route to the destination node is held for the portion of the standby time, and the data is transferred only when the data are not received from the adjacent relay node. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a data communication method using a wireless ad hoc network, and more particularly to securing a communication path and data transfer when an abnormality occurs in a relay node in multicast communication.

  An ad hoc network using radio enables communication between radio terminals that do not reach radio directly via other radio terminals. In this network, wireless terminals can autonomously build routes, avoid obstacles, and resolve addresses in response to wireless conditions, and research and development are also underway.

  For example, in research on wireless ad hoc networks, various communication path searches and maintenances that take into account changes in connection status due to the mobility of nodes, which is a problem specific to wireless, and efficient use of wireless bandwidth, are considered. A routing protocol has been proposed.

  On the other hand, the SCADA system that collects data by combining a personal computer and a remote I / O unit plays a major role in the operation of factories and plants, and is required to have higher reliability.

  As for the reliability of the ad hoc network using wireless communication, various studies are still in progress, and it is difficult to say that the reliability is high enough to be applied to the SCADA system.

  As an example of the routing of an ad hoc network using radio, multicast communication is performed between wireless terminals including a mobile unit, and a destination node is determined by setting a plurality of nodes including a destination node and its adjacent nodes as destinations in this communication. Data transmission that is uninterrupted even when moving is enabled (see, for example, Patent Document 1).

As another example of routing, the reception node returns reception completion to the transmission node, thereby realizing that only a limited number of nodes perform transfer and reducing the load on the network (for example, see Patent Document 2).
JP 2007-258982 A JP 2006-246174 A

  In a wireless ad hoc network, the route from the source to the destination via the relay node is determined by the action of the routing protocol. Once the route to the destination node is determined, the destination may be a request for a specific node. For example, transmission using unicast is basically performed for the relay node between the transmission source node and the destination node.

  FIG. 5 shows an example of data relay when transmitting by unicast, and nodes other than the corresponding relay node do not sense it, so when one specific relay node has an abnormality, the transmission data is not delivered successfully. As a result, a retransmission is performed again from the transmission source, leading to a delay in delivery time and an increase in transmission load. In this figure, a case where two retransmissions occur due to an abnormality of the relay node 10 is shown.

  On the other hand, in the method of Patent Document 1, when a broadcast (including multicast) is used for a request for a specific node, retransmission is not necessary regardless of the abnormality of any relay node, but the request is received. Since all the relay nodes perform forwarding processing to the destination node, data that has already been delivered correctly on a certain route is transferred along multiple routes at the same time, which is unnecessary. Will increase the load on the network. FIG. 6 shows an example of data relay when transmission is performed by multicast. Data transfer is performed via another relay node 5 or the like even if the relay node 6 becomes abnormal.

  Further, as described in Patent Document 2, even when a method of returning the reception completion of the reception node to the transmission node is used, extra communication for notifying success or failure of reception is necessary.

  An object of the present invention is to provide a data communication method capable of suppressing an increase in transmission load and reducing a delay in delivery time during normal times and when a relay node malfunctions in multicast communication using a wireless ad hoc network.

  In order to solve the above problems, the present invention assigns an identifier for identifying a node to each node in multicast data communication using a wireless ad hoc network, and waits for multicast data received only by a node having a route to a destination node. Data communication method for transferring data only when there is no reception of the data from the adjacent relay node, and further specifying a waiting time for transferring the multicast data for each relay node. A node having a higher priority given by the delivery time to the destination node and the number of hops is designated with a shorter time, and is characterized by the following method.

(1) A data communication method that uses a wireless ad hoc network, performs multicast communication from a transmission source node to a relay node, and transmission from a relay node to another relay node, and transmits data to a destination node.
Assign an identifier that identifies the node by node,
The transmission source node has a processing procedure for designating an identifier for identifying the destination node in the data header of the multicast data, and designating a waiting time until each relay node receives the multicast data and transfers it,
The relay node has a processing procedure for holding multicast data received only by a node having a route to a destination node for the waiting time and transferring data only when the data is not received from an adjacent relay node.
It is characterized by that.

(2) Assign a unique multicast address to each node,
The source node has a processing procedure for designating a multicast address corresponding to the destination node as a destination address at the time of data transmission,
The relay node has a processing procedure for waiting for reception of the multicast address only when the relay node holds a route to the destination node.
It is characterized by that.

(3) A multicast address is made common among nodes constituting an ad hoc network, and a unique network port number is assigned to each node.
The source node has a processing procedure for designating a network port number corresponding to the destination node as the destination port number at the time of data transmission,
The relay node has a processing procedure for waiting for reception of the network port number only when the route to the destination node is held.
It is characterized by that.

  (4) The standby time is specified for each relay node, and a shorter time is specified for a node having a higher priority given by the delivery time to the destination node and the number of hops.

  As described above, according to the present invention, in multicast data communication using a wireless ad hoc network, an identifier for identifying a node is assigned to each node, and multicast data received only by a node having a route to a destination node is held for a waiting time. And a data communication method for transferring data only when the data is not received from an adjacent relay node, and a waiting time until multicast data is transferred is designated for each relay node. The higher the priority given by the delivery time and the number of hops, the shorter the time is specified, so that the increase in transmission load can be suppressed and the delivery time delay can be reduced at the normal time and when the relay node malfunctions .

In particular,
(1) Even when an abnormality occurs in a specific relay node, an increase in transmission load and a delay in delivery time can be reduced by transferring the same data as it is from another relay node.

  (2) By setting a standby time for the transfer process in each relay node, it is possible to prevent the adjacent relay node from transferring the same data through another route, thereby reducing the transmission load of the network.

  (3) By changing the waiting time of the transfer process in each relay node for each node, the possibility of data collision associated with the transfer process is reduced, and the reliability of the unnecessary transfer process preventing measure for the same data is improved.

  (4) The waiting time for each node improves the delivery time by shortening the waiting time for the transfer process for a node having a higher priority.

(Embodiment 1)
FIG. 1 is a node configuration and data configuration diagram in the present embodiment. Each node has a computer as a central part, constitutes an electronic device having a transmission / reception function, and is a system in which a transmission source node A performs data communication to a destination node B via a plurality of relay nodes R, for route search of an ad hoc network Uses a proactive (such as OLSR) routing protocol, thereby building a wireless ad hoc network. In this network, multicast communication is performed for transmission from the transmission source node A to the relay node R and transmission from the relay node R to the relay node R.

  The multicast address is common among the nodes constituting the ad hoc network, and identifiers A1, R1, and B1 for identifying the node are given to each node. The source node A designates an identifier B1 that identifies the destination node in the data header of the multicast data. Further, the source node A designates in the data header a waiting time T until each relay node receives the multicast data and transfers it.

  FIG. 2 is a data relay processing flow of the relay node. When each relay node R receives the multicast data (S1), it is transmitted from the source node A if it does not hold the route R2 to the destination node B requested by the source node A in its own node. The multicast data is discarded (S2, S3), and if it is retained, the multicast data transmitted from the transmission source node A is retained (S2, S4). This limits the nodes that perform the transfer.

  Next, each relay node R waits for a predetermined time designated by the source node A (S4). This time is a waiting time T from the reception of the multicast data designated by the source node A to the transfer of the multicast data. Each relay node R checks whether or not the same data has been received from two or more nodes after the standby time has elapsed (S5), and if received, determines that the relay processing has been completed at another node. The multicast data that has been held is discarded (S6). If not received, the held multicast data is transferred to the relay node on the route R2 toward the destination node (S7).

  FIG. 3 shows a specific example of data relay in multicast communication according to the present embodiment. The transmission source node A transmits data toward a relay node located in the multicast communication area M1 (the reachable range of multicast transmission data). Among these, the relay nodes 1 and 4 discard the data because they do not have a route to the destination node (route configured by the routing protocol). Since the relay nodes 2 and 3 hold the route to the destination node, they hold the data and wait for a predetermined time.

  When the relay nodes 2 and 3 transfer the received data to the destination node, the relay nodes 2 and 3 confirm that the same data is not received from others after the waiting time. When this check is performed by the relay node 3, if the transfer of the relay node 2 has been performed first, data is received from the relay node 2, and no data transfer is performed.

  As a result, data transfer from the relay node 2 is performed, and the data is transferred to the relay nodes 5 and 6 that are located in the same communication area M2 and become the route to the destination node. In this data transfer, if there is no abnormality in the relay node 6, data transfer from the relay node 6 to the relay node 9 is performed, and transfer processing by the relay node 5 is not performed. However, if there is an abnormality in the relay node 6, data transfer to the relay node 9 is not performed, and therefore data transfer by the relay node 5 is performed.

  In either case, the relay node 9 performs data transfer to the destination node B and ends one data communication.

  As described above, in this embodiment, only the node having the route to the destination node holds the multicast data received for the waiting time, and transfers the data only when the data is not received from the adjacent relay node. Thus, an unnecessary increase in transmission load of the entire network can be suppressed.

  Even when an abnormality occurs in a relay node on the transfer route, another relay node transfers the same data as it is, so that a delay in delivery time can be reduced without re-transmission from the transmission source.

(Embodiment 2)
In the present embodiment, the identifier assigned to each node in the first embodiment is a multicast address.

  That is, a unique multicast address is assigned to each node. The transmission source node designates a multicast address corresponding to the destination node as a destination address at the time of data transmission. Each relay node waits to receive the multicast address only when it holds a route to the destination node.

  According to this embodiment, the data link layer determines whether data is received or discarded, and the CPU load can be reduced.

(Embodiment 3)
In this embodiment, the identifier assigned to each node in the first embodiment is a port of a multicast address.

  That is, the multicast address is common among the nodes constituting the ad hoc network, and a unique network port number is assigned to each node. Thereby, the transmission source node designates the network port number corresponding to the destination node as the destination port number at the time of data transmission. Each relay node waits for reception of the network port number only when it holds a route to the destination node.

  According to this embodiment, while reducing the CPU load, it is not necessary to prepare multicast addresses for the number of nodes, so management of multicast addresses becomes unnecessary.

(Embodiment 4)
In the data communication methods of the first to third embodiments, unnecessary transfer processing can be prevented and the load on the entire network can be reduced. On the other hand, a plurality of relay nodes that receive multicast data from one transmission source node have a certain waiting time. If the transfer processing is performed all at once after this, there is a high possibility that the transmission data will collide depending on the respective relay processing speeds.

  In order to prevent this, in this embodiment, the transmission source node sets the waiting time of each node in the multicast data to a different time. Each relay node can reduce the possibility of data collision associated with the transfer process by performing the transfer process according to the waiting time for each node specified by the transmission source node, and also ensure the reliability of measures for preventing unnecessary transfer processes. Can be improved.

(Embodiment 5)
In this embodiment, each of the adjacent relay nodes is prioritized according to the delivery time and the number of hops to the destination in advance, and the waiting time is shortened as the node having a higher priority becomes faster and more reliable. To reach.

  FIG. 4 shows an example of the header structure of multicast data. Each node number has a priority, and the standby time of a node having a high priority is also shortened.

The node structure and data block diagram in embodiment of this invention. Data relay processing flow of the relay node. Specific example of data relay in multicast communication. An example of a header structure of multicast data. Example of data relay in unicast transmission (conventional). An example of data relay in multicast transmission (conventional).

Explanation of symbols

A Source node B Destination node R Relay node

Claims (4)

A data communication method that uses a wireless ad hoc network, performs multicast communication from a transmission source node to a relay node, and transmission from a relay node to another relay node, and transmits data to a destination node.
Assign an identifier that identifies the node by node,
The transmission source node has a processing procedure for designating an identifier for identifying the destination node in the data header of the multicast data, and designating a waiting time until each relay node receives the multicast data and transfers it,
The relay node has a processing procedure for holding multicast data received only by a node having a route to a destination node for the waiting time and transferring data only when the data is not received from an adjacent relay node.
A data communication method characterized by the above. Assign a unique multicast address to each node,
The source node has a processing procedure for designating a multicast address corresponding to the destination node as a destination address at the time of data transmission,
The relay node has a processing procedure for waiting for reception of the multicast address only when the relay node holds a route to the destination node.
The data communication method according to claim 1. The multicast address is common among the nodes constituting the ad hoc network, and a unique network port number is assigned to each node.
The source node has a processing procedure for designating a network port number corresponding to the destination node as the destination port number at the time of data transmission,
The relay node has a processing procedure for waiting for reception of the network port number only when the route to the destination node is held.
The data communication method according to claim 1.   The standby time is specified for each relay node, and a shorter time is specified for a node having a higher priority given by the delivery time to the destination node and the number of hops. The data communication method according to item 1.

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