KR101039815B1 - Method for sharing a Time schedule information of Node - Google Patents

Abstract

The present invention relates to a method of sharing time schedule information of a node in a sensor network and packet data used therein. According to the present invention, packet data including a header area 10 for storing a time schedule of a neighboring node located within two hops of its own node is provided. Then, the packet data is provided, and the seed node 100 and the time schedule of the seed node 100 are first determined in a network topology in which a plurality of nodes are arranged. Subsequently, when the seed node 100 transmits its time schedule to neighboring nodes B: 102 (C: 104) (F: 106) that are one hop away, the neighbor node B: 102 (C: 104). (F: 106) determines its own time schedule so as not to overlap the time schedule of the seed node 100, and the seed node 100 and another neighbor node (D: 108) (E: 110). (G: 112). Then, the other neighbor nodes (D: 108) (E: 110) (G: 112) are connected to the time schedules of the seed node 100 and the neighbor nodes B: 102 (C: 104) (F: 106). The time schedule is determined not to be duplicated, and the time schedule is transmitted to the seed node 100 via the neighbor nodes B: 102, C: 104, and F: 106. Therefore, specific nodes can share time schedules of neighboring nodes located within 2 hops based on themselves, and perform data communication with neighboring nodes based on this. In the data communication, the node is activated only at the time of receiving data due to sharing of time schedule between nodes. According to the present invention, channel collisions can be prevented due to time schedule sharing of nodes, and power consumption of nodes can be minimized.

Sensor network, node, time schedule, 2 hops

Description

Method for sharing a time schedule information of node in sensor network

The present invention relates to a time schedule sharing of a node, and more particularly, in a sensor network in which a specific node participating in an underwater network topology shares a time schedule of a neighbor node located within 2 hops of the node. Relates to a method of sharing time schedule information.

The present specification describes an underwater sensor network among sensor networks.

Recently, research on underwater sensor network technology is active. This is due to the increasing demand for marine water resources and the environment, the development of sea resources due to land resource limitations, the increase of social demands due to the interest of alternative resources, and the interest of the marine environment as new alternatives to existing technologies in accordance with the demand for measuring the water quality environment. Because it is getting.

In the underwater sensor network technology, information about the marine environment, especially the underwater environment is essential.

For this purpose, a network topology is constructed using the MAC (Medium Access Control) protocol, which is an active and suitable communication method for the underwater environment.

The network topology includes a plurality of nodes. The node monitors various types of information, transmits and receives monitored information while communicating with other sensor nodes, and processes the transmitted and received monitored information.

However, the prior art has the following problems.

First, when each node transmits and receives data through an assigned transport channel, a collision occurs with a transport channel of another neighboring node.

In general, when a node is driven after all nodes constituting the network topology have been deployed, each node determines its own transmission start time and starts a data transmission / reception operation. At this time, since one node does not know a time schedule of another neighboring node, various types of channel collisions occur. An example of channel collision will be described with reference to FIG. 1. In this case, the time schedule refers to time information when a node transmits or receives data to a neighbor node.

1A illustrates an example in which data transmission and reception occur simultaneously in a specific node. As shown, when 'node A' 1 receives data from 'node B' 2, at the same time 'node A' 1 sends data to 'node C' 2, the channel A conflict occurs.

FIG. 1B is an example in which two data are simultaneously received by a specific node. As shown, 'node A' 1 is simultaneously receiving data from 'node B' 2 and 'node C' 3. This is because 'node B' (2) and 'node C' (3) only know the time schedule of 'node A' (1), which is one hop away, and do not know each other's time schedule.

That is, in the conventional network topology, one node knows only the time schedule of another neighboring node that is only one hop away, and the time schedule of the node that is two hops away is not considered at all.

As described above, if a channel collision occurs during data transmission and reception, a data transmission failure occurs, and thus the node requests retransmission.

The data retransmission request causes another problem that consumes the battery power of the node. It is important for the node to perform a sensing function for a long time in the network topology by minimizing the consumption of battery power installed in the node. However, if a frequent data retransmission request due to a channel collision occurs, the battery life is consumed accordingly, which shortens the life cycle of the node.

In addition, the nodes that are more than two hops apart do not share information, so they do not know when to receive data from other nodes, and therefore should always be active. This continuous activation also causes battery power to be consumed.

Accordingly, an object of the present invention is to solve the above problem, and to allow all nodes located within two hops in the network topology of an underwater environment to share a time schedule.

Another object of the present invention is to minimize the power consumption of the node.

According to a feature of the present invention for achieving the above object, a plurality of nodes transmit and receive packet data, the packet data and the header area for storing the time schedule of the neighboring node located within two hops of the node; And a data area for storing data actually transmitted during data communication with another node according to the time schedule, wherein the header area includes 'T': type of frame and 'D': destination address ( destination address), 'S': source address, 'A': address of the neighbor nodes, 'M': missing node, 'J': join node ( Joining Node), 'SYNC': configured to include Next transmission time information.

When the node is initialized, only the header area transmits and receives with its own neighbor nodes.

According to another feature of the invention, the first step of determining a seed node in a network topology consisting of a plurality of nodes; Determining a time schedule of the seed node related to data transmission / reception of the seed node; Transmitting, by the seed node, its time schedule to neighboring nodes one hop away; A fourth step of determining, by the neighbor node, a time schedule related to data transmission / reception thereof so that the neighbor node does not overlap with the time schedule of the seed node; A fifth step of, when the time schedule of the neighbor node is determined, the neighbor node forwards its own time schedule to the seed node and at the same time to another neighbor node; Determining a time schedule related to data transmission / reception so that the other neighbor node does not overlap with the seed node and the time schedule of the neighbor node; And a seventh step in which the other neighbor node transmits its own time schedule to the seed node via the neighbor node.

The first to seventh steps may be performed when the plurality of nodes is initialized with the plurality of nodes arranged in the network topology.

When a node is newly added to the network topology, the added node determines a time schedule related to data transmission / reception thereof without overlapping the time schedule of the seed node and the time schedule of the neighbor node one hop away from the seed node. And transmits the determined time schedule to the seed node.

The seed node, the neighbor node, and the other neighbor node are switched from the inactive state to the active state only when receiving data from another neighbor node neighboring itself.

In the present invention, a node participating in a network topology determines and shares a time schedule required for data transmission and reception with itself and other neighboring nodes within two hops. This prevents channel collisions that occur when a particular node sends data to a neighbor, when it receives data from another neighbor, and when a particular node simultaneously receives data from two or more neighbors. Therefore, the probability of transmission failure of data between nodes can be minimized.

Since each node shares time schedules of other neighboring nodes within two hops with each other, each node can wake up and receive data only when the neighboring node transmits data, thereby providing battery power to the node. Consumption can be minimized, resulting in a longer formation time of the network topology.

Hereinafter, a method of sharing time schedule information of a node and a packet data used therein in a sensor network according to the present invention will be described in detail with reference to a preferred embodiment shown in the accompanying drawings.

First, a structure of packet data for sharing time schedule information according to the present invention will be described. The packet data is shown in FIG.

Referring to FIG. 2, packet data includes information about all nodes within two hops and RPs in order to prevent channel collisions between message collisions between nodes, i.e., transmit-receive and receive-receive. A header area 10 including a message is provided. Hereinafter, the header area 10 is also referred to as an RP message. The RP message is 'T' (11): frame type (Type of frame), 'D' (12): destination address (destination address) used for broadcasting, 'S' (13): source address (source address), 'A' (14): address of the neighbor node, 'M' (15): Missing Node, 'J' (16): Joining Node 'SYNC' 17: Next transmission time information.

That is, the RP message 10 includes information for knowing when any node transmits data. However, the RP message 10 does not necessarily include all the messages of the above structure. In other words, when the RP message 10 performs data communication between nodes, the RP message 10 may share information of neighbor nodes so as to prevent a collision of a transmission channel between nodes. Therefore, only the transmission / reception time information may be included.

The packet data may include a data area 20 in which data actually transmitted when communication with a predetermined node is performed according to information stored in the header area 10.

Next, a process of sharing information of a neighbor node according to an exemplary embodiment of the present invention will be described with reference to FIGS. 3 and 4. 3 is a structure diagram of a sensor network proposed for explanation of the present invention, and FIG. 4 is a flowchart illustrating a method of sharing time schedule information of a node in a sensor network according to an exemplary embodiment of the present invention.

First, an initialization process is performed. The initialization process is for any node to know each other's time schedules of neighboring nodes two hops apart.

First, as shown in the figure, it is assumed that a total of seven nodes from node A (100) to node G (112) participate in the network topology, among which node A (100) is determined as the seed node (s100). . Node B 102 is also a source node of node D 108, node C 104 is a source node of node E 110, and node F 106 is a source node of node G 112. do.

In this state, the first node A 100 determined as the seed node determines its own time schedule related to data transmission and reception (s102). The time schedule refers to a data transmission time of the node A 100. Of course, if another node is determined as the seed node, it is natural that a time schedule related to transmitting and receiving data of the node determined as the seed node is preferentially determined.

Next, the node A 100 broadcasts a beacon signal including its time schedule to the node B 102, the node C 104, and the node F 106, which are neighbor nodes (s104). In this case, it is preferable that only information in the header area 10 is transmitted, and data in the data area 20 is not transmitted.

When Node B 102, Node C 104, and Node F 106 receive the beacon signal, Node B 102, Node C 104, and Node F 106 receive Node A 100. The time schedule is determined to avoid its own time schedule (s106). That is, the time schedule of the node A 100 is compared with the time schedule of the node A 100 to determine an appropriate time schedule that avoids a conflict with the time schedule of the node A 100.

Once the time schedule of Node B 102, Node C 104, and Node F 106 is determined, Node B 102, Node C 104, and Node F 106 may RP the determined time schedule. The message 10 is transmitted to the neighbor node using the message 10 (s108). Here, the neighboring nodes are node A 100, node D 108, node E 110, and node G 112. Thus, when an RP message including time schedules of node B 102, node C 104, and node F 106 is delivered to node A 100, which is the seed node, node A 100 is a node. Know the time schedules of B 102, Node C 104, and Node F 106. If an RP message is also sent to the node D 108, the node E 110, and the node G 112, the node D 108, the node E 110, and the node G 112 are not only the node A 100. It is possible to know the time schedules of the node B 102, the node C 104, and the node F 106 which are their source nodes. At this time, the RP message is regarded as a beacon signal.

Based on this, the node D 108, node E 110, and node G 112 are time nodes and seed nodes of node B 102, node C 104, and node F 106, which are source nodes. The collision with the time schedule of A (100) is avoided to determine an appropriate time schedule (S110).

When the node D 108, the node E 110, and the node G 112 determine their own time schedules, the node D 108, the node E 110, and the node G 112 receive an RP message including their own time schedules. 104) and node F 100 via node F 106 (s112).

According to the above process, the node A 100 has a time schedule of node B 102, node C 104, and node F 106 that are one hop away, and node D 108 that is two hops away from itself. Knowing the time schedules of Node E 110 and Node G 112, on the contrary, Node D 108, Node E 110, and Node G 112 are their source nodes, Node B 102 and Node C, respectively. The time schedules of the 104 and the node F 106 and the node A 100 can be known (s114).

Accordingly, when the initialization process is completed, each node shares when the nodes within two hops transmit and receive data.

When the initialization is completed, each node starts to transmit data according to the time schedule (s116). In the data transmission, only nodes corresponding to a time determined by the time schedule included in the header area 10 are activated to transmit and receive data included in the data area.

For example, between node B 102, node A 100, and node C 104, node A 100 receives data from node B 102 while transmitting data to node C 104. Explain. In this case, conventionally, the node B 102 and the node C 104 are two hops apart from the node A 100 and do not share their time schedules with each other. Thus, as described in the prior art, channel collision occurs and data transmission fails. However, in this embodiment, since node B 102 knows when node C 104 receives data from node A 100, node B 102 avoids the reception time of node C 104. To transmit data to the Node A 100. At this time, each node is activated only during data transmission and reception time, and maintains an inactive state at other times, thereby minimizing battery power consumption.

Similarly, this is the case where node A 100 receives data from node B 102 and node C 104. Even in this case, since the node B 102 and the node C 104 know each other's time schedule, the node B 102 and the node C 104 can transmit data to the node A 100 by avoiding each other's transmission time. Node A 100 also knows when data is being sent from Node B 102 and Node C 104 and is activated to receive data only at that time and remains inactive at other times.

As described above, according to the present embodiment, when data communication is performed using a Mac-based transmission protocol in a sensor network structure, each node participating in the network topology is in a time schedule of a node two hops apart from itself. Accordingly, it can be seen that communication with neighboring nodes can prevent channel collisions that frequently occur when performing data communication using a wireless medium.

Although described with reference to the illustrated embodiment of the present invention as described above, this is merely exemplary, those skilled in the art to which the present invention pertains various modifications without departing from the spirit and scope of the present invention. It will be apparent that other embodiments may be modified and equivalent. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

That is, in the present embodiment, an underwater sensor network has been described as an example. However, as described above, when a specific node transmits data to a neighbor node, a network topology such as receiving data from another neighbor node or simultaneously receiving data from the neighbor node is received. The present invention can be applied to other sensor network structures having a ridge structure.

1 is a state diagram illustrating a channel collision phenomenon when data transmission and reception simultaneously occur in a specific node or two data are simultaneously received in a specific node according to the related art.

2 is a packet data structure diagram for sharing time schedule information according to an embodiment of the present invention.

3 is a structural diagram of a sensor network proposed for explanation of the present invention.

4 is a flowchart illustrating a method for sharing time schedule information of a node in a sensor network according to an exemplary embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

10: header area 20: data area

100 to 112: node A to node G

Claims (6)

delete delete Determining a seed node in a network topology consisting of a plurality of nodes; Determining a time schedule of the seed node related to data transmission / reception of the seed node; Transmitting, by the seed node, its time schedule to neighboring nodes one hop away; A fourth step of determining, by the neighbor node, a time schedule related to data transmission / reception thereof so that the neighbor node does not overlap with the time schedule of the seed node; A fifth step of, when the time schedule of the neighbor node is determined, the neighbor node forwards its own time schedule to the seed node and at the same time to another neighbor node; Determining a time schedule related to data transmission / reception so that the other neighbor node does not overlap with the seed node and the time schedule of the neighbor node; And Transmitting, by the other neighbor node, its time schedule to the seed node via the neighbor node; Method of sharing time schedule information of a node in the sensor network comprising a. The method of claim 3, The first to seventh steps are performed when the plurality of nodes are initialized in a state where the plurality of nodes are arranged in the network topology. The method of claim 3, When a node is newly added to the network topology, the added node determines a time schedule related to data transmission / reception thereof without overlapping the time schedule of the seed node and the time schedule of the neighbor node one hop away from the seed node. And transmitting the determined time schedule to the seed node. The method according to claim 3 or 5, The seed node, the neighbor node, and the other neighbor node share the time schedule information of the node in the sensor network, wherein the state is switched from inactive state to active state only when receiving data from another neighbor node neighboring itself. Way.

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