KR20110007324A - Apparatus and method for controlling topology of wireless ad-hoc network, node device of wireless ad-hoc network and method for communication link formation of node device of wireless ad-hoc network - Google Patents

Abstract

PURPOSE: A topology control device of the wireless ad-hoc network for diminishing the transmission power by selecting cooperative nodes is provided to improve the connectivity of network by generating cooperative communication link. CONSTITUTION: A cluster generating unit(120) generates a plurality of clusters. A cooperative communication link generator(130) generates a plurality of cooperative communication links between a transmission node and a reception node. A link selection unit(140) selects the final cooperation communications link of cooperation communications links based on the average transmission. The link selection unit selects communication link based on the average transmission power for the general communication. A topology determination unit(150) determines the topology of network.

Description

Apparatus and method for controlling topology of wireless ad-hoc network, node device of wireless ad-hoc network and method for communication link formation of node device of wireless ad-hoc network}

The present invention relates to a method and apparatus for controlling a topology of a wireless ad hoc network, a node device for a wireless ad hoc network, and a method for forming a communication link for a node device for a wireless ad hoc network, and more specifically, a general communication link between wireless nodes and An apparatus and method for determining an optimal network topology using a cooperative communication link.

A wireless ad hoc network has a structure in which wireless nodes wirelessly communicate with each other by single or multi hop without an infrastructure. Therefore, it does not have a preset network structure (topology). Since wireless nodes receive power from a battery, there is a need to reduce power consumption while maintaining a connection with other wireless nodes.

The topology control technique is a technique for determining a power value of each wireless node so as to reduce the transmit power of the wireless nodes while connecting the wireless nodes constituting the entire network with each other through a wireless link. Topology control techniques reduce the number of generated radio links, which reduces transmission power and reduces interference between radio links. As a representative example of the study of topology control techniques, the local minimum spanning tree (LMST) can be used to minimize the number of wireless links while ensuring connectivity between wireless nodes by making the topology of the network into a tree.

Meanwhile, cooperative communication, which is a recently studied technology, refers to a technique for transmitting with the help of cooperating nodes around the transmitting node when the transmitting node transmits data to the receiving node. By cooperating communication, the transmitting node and the cooperating nodes simultaneously transmit independent copies of the same data to the receiving node so that the receiving node can combine and decode the signals received from the respective nodes. In this case, neighboring nodes that are one hop away from each other within the transmission range of the transmitting node may be cooperative nodes. That is, the antennas provided in each of the plurality of nodes through cooperative communication are used together to form one antenna array. Cooperative communication is applied to various fields such as topology control, broadcasting, and routing since the use of cooperative communication can achieve strong coupling, coverage expansion, and power saving.

Existing topology control techniques have been proposed to reduce power consumption by cooperative communication technology. However, this topology control technique is applicable at the initial stage given a tightly coupled network topology. A tightly coupled network is a network that has a path from which all nodes can reach other nodes. However, wireless ad hoc networks are likely to be disconnected due to wireless node mobility, low node density and power consumption constraints. In this regard, previous studies have suggested that cooperative communication technology can strengthen the connection between disconnected networks, but it is clear about the problem of topology control that reduces the transmission power while increasing the connectivity in consideration of the expansion of coverage by cooperative communication. The conclusion was not drawn.

The technical problem to be solved by the present invention is to reduce the transmission power consumed for data transmission by a plurality of wireless nodes located on a wireless ad hoc network, and to cooperate between wireless nodes that cannot transmit or receive data by general communication with each other. The present invention provides a method and method for controlling a topology of a wireless ad hoc network, a node device of a wireless ad hoc network, and a node device of a wireless ad hoc network to enable communication.

Another technical problem to be solved by the present invention is to reduce the transmission power consumed by a plurality of wireless nodes located on a wireless ad hoc network for data transmission, and to communicate between wireless nodes that cannot transmit or receive data by general communication with each other. A computer-readable record that records a program for executing a topology of a wireless ad-hoc network topology control method and a method of forming a communication link of a node device of a wireless ad-hoc network to enable a cooperative communication to increase connectivity of a separated network. To provide the medium.

In order to achieve the above technical problem, the apparatus for controlling a topology of a wireless ad hoc network according to the present invention includes a node information receiving unit for receiving location information and node ID of each wireless node from a plurality of wireless nodes located on a wireless ad hoc network. ; Create a plurality of clusters of wireless nodes connected by a general communication link among the wireless nodes capable of transmitting and receiving data to each other, and any one of the node IDs of the wireless nodes belonging to each cluster is the cluster ID of the corresponding cluster. A cluster generation unit for determining and transmitting to wireless nodes belonging to the same cluster; A cooperative communication link generation unit for generating a plurality of cooperative communication links between a transmitting node and a receiving node having different cluster IDs among the wireless nodes and capable of transmitting and receiving data to each other by cooperative communication; Selecting a final cooperative communication link based on an average transmit power for performing cooperative communication among the plurality of cooperative communication links, and selecting an average transmit power for performing general communication among general communication links among wireless nodes having the same cluster ID. A link selector for selecting a final general communication link based on the; And a topology determiner configured to determine a topology of a network including the final cooperative communication link and the final general communication link and transmit the topology to the wireless nodes.

In accordance with another aspect of the present invention, there is provided a method for controlling a topology of a wireless ad hoc network, including node information for receiving location information and node ID of each wireless node from a plurality of wireless nodes located on a wireless ad hoc network. Receiving step; Create a plurality of clusters of wireless nodes connected by a general communication link among the wireless nodes capable of transmitting and receiving data to each other, and any one of the node IDs of the wireless nodes belonging to each cluster is the cluster ID of the corresponding cluster. A cluster generation step of determining and transmitting to wireless nodes belonging to the same cluster; Generating a plurality of cooperative communication links between a transmitting node and a receiving node having different cluster IDs among the wireless nodes and capable of transmitting and receiving data to each other by cooperative communication; Selecting a final cooperative communication link based on an average transmit power for performing cooperative communication among the plurality of cooperative communication links, and selecting an average transmit power for performing general communication among general communication links among wireless nodes having the same cluster ID. A link selection step of selecting a final general communication link based on the; And a topology determination step of determining a topology of a network consisting of the final cooperative communication link and the final general communication link and transmitting the topology to the wireless nodes.

In order to achieve the above technical problem, a node apparatus of a wireless ad hoc network according to the present invention is located on a wireless ad hoc network and operates as a wireless node for transmitting and receiving data, and the other wireless nodes on the wireless ad hoc network. Communication unit for performing communication; When the location information and node ID of each general node are received from a general node capable of communicating through a general communication link among the wireless nodes, one of the node IDs is determined as a cluster ID of a cluster belonging to the general node. A cluster forming unit; The communication unit transmits a cooperative communication request message including its location information, node ID, and the cluster ID to each receiving node of the wireless nodes other than the normal node by the cooperative communication using the common node as the cooperative node. Cooperative communication request unit for transmitting through; When the cooperative communication response message including the location information and node ID of the receiving node and the cluster ID of the cluster to which the receiving node belongs is received from the receiving node receiving the cooperative communication request message, the cooperative communication link with the receiving node is established. Generating a cooperative communication link generation unit; Cooperative communication link information including its own node ID, transmission power for performing cooperative communication with the receiving node, node ID of the receiving node, and cluster ID of the cluster to which the receiving node belongs, the cluster ID as the node ID. An information transmitter for transmitting to the cluster node through the communication unit; Selecting a final cooperative communication link that matches the last cooperative communication link information received from the cluster node among the cooperative communication links, and based on an average transmit power for performing general communication through the general communication link among the general communication links. A link selector for selecting a general communication link; And a topology determination unit configured to determine a partial topology of a network including the final cooperative communication link and the final general communication link and transmit the partial topology to the wireless nodes.

According to another aspect of the present invention, there is provided a method of forming a communication link in a node device of a wireless ad hoc network, from a general node capable of communicating through a general communication link among other wireless nodes on a wireless ad hoc network. A cluster forming step of determining any one of the node IDs as a cluster ID of a cluster belonging to the general node when the location information and the node ID of the general node are received; Cooperating to transmit a cooperative communication request message including its location information and node ID and the cluster ID to each receiving node of the wireless nodes excluding the common node by cooperating communication using the common node as a cooperating node; A communication request step; When the cooperative communication response message including the location information and node ID of the receiving node and the cluster ID of the cluster to which the receiving node belongs is received from the receiving node receiving the cooperative communication request message, the cooperative communication link with the receiving node is established. Generating a cooperative communication link; Cooperative communication link information including its own node ID, transmission power for performing cooperative communication with the receiving node, node ID of the receiving node, and cluster ID of the cluster to which the receiving node belongs, and the cluster ID among the general nodes. An information transmitting step of transmitting to the cluster node with the node ID; Selecting a final cooperative communication link that matches the last cooperative communication link information received from the cluster node among the cooperative communication links, and selecting a general communication link based on an average transmission power for performing general communication among the general communication links. Link selection step; And a topology determination step of determining a partial topology of a network consisting of the final cooperative communication link and the final general communication link and transmitting to the wireless nodes.

According to the method and apparatus for controlling a topology of a wireless ad hoc network, a node device of a wireless ad hoc network, and a method for forming a communication link of a node device of a wireless ad hoc network, a separate network cannot transmit or receive data with each other by general communication. By creating a cooperative communication link between a plurality of wireless nodes forming a, it is possible to increase the connection degree of the network. In addition, by selecting an optimal number of cooperative nodes used for cooperative communication among wireless nodes capable of general communication with a transmitting node, it is possible to reduce the transmission power used for cooperative communication, thereby improving communication efficiency.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Hereinafter, a preferred embodiment of a method and apparatus for controlling a topology of a wireless ad hoc network, a node device for a wireless ad hoc network, and a method for forming a communication link for a node device for a wireless ad hoc network will be described in detail with reference to the accompanying drawings. do.

1 is a block diagram showing the configuration of a first preferred embodiment of a topology control apparatus for a wireless ad hoc network according to the present invention.

Referring to FIG. 1, a first embodiment of a topology control apparatus of a wireless ad hoc network includes a node information receiver 110, a cluster generator 120, a cooperative communication link generator 130, a link selector 140, The topology determination unit 150 is provided. In addition, the topology control apparatus of the wireless ad hoc network according to the present invention may be implemented as a separate device for communicating with wireless nodes on the wireless ad hoc network, or may be provided in any one wireless node.

The node information receiver 110 receives location information and node ID of each wireless node from a plurality of wireless nodes located on the wireless ad hoc network.

On the wireless ad-hoc network, a plurality of wireless nodes which perform wireless communication with each other in a single or multi-hop without an infrastructure are located. In order to determine the network topology such that these wireless nodes can communicate with each other, it is necessary to know information about each of the wireless nodes. Accordingly, the node information receiving unit 110 receives location information of each wireless node and node ID, which is a unique identification code of the wireless node, from all wireless nodes on the wireless ad hoc network. This information is used to determine the network topology.

The cluster generation unit 120 generates a plurality of clusters of wireless nodes connected to each other by a general communication link and transmitting and receiving data, and any one of node IDs of wireless nodes belonging to each cluster. Is determined as the cluster ID of the corresponding cluster and transmitted to wireless nodes belonging to the same cluster.

A cluster refers to a set of wireless nodes capable of transmitting and receiving data by performing general communication with each other. Therefore, even if the wireless nodes located on the same wireless ad hoc network cannot perform general communication with each other, they may not form the same cluster, and a plurality of clusters may be generated on one wireless ad hoc network. In addition, since wireless nodes included in different clusters cannot exchange data with each other through general communication, network separation occurs. At this time, the means for transmitting and receiving data between wireless nodes included in different clusters is cooperative communication.

When a transmitting node transmits data to a receiving node, the cooperating node may be used in a separate network, i.e., where the wireless nodes cannot be connected by a general communication link. 2A-2C illustrate a plurality of wireless nodes located on a wireless ad hoc network.

Referring to FIG. 2A, since nodes A to C are all within a transmission range of each other, they may be connected by a general communication link to transmit data. However, since the nodes D and E are located outside the transmission range of the nodes A to C, the nodes A to C cannot transmit data by the general communication with the nodes D and E. Therefore, the network is separated, and nodes A to C form one cluster, and nodes D and E form another cluster. As such, a cluster refers to a set of wireless nodes connected to each other by a general communication link to exchange data.

Cooperative communication is thus used to allow data to be transmitted and received between wireless nodes belonging to different clusters. For cooperative communication, in addition to a transmitting node transmitting data and a receiving node receiving data, cooperative nodes are required to assist the transmitting node in transmitting data. Referring to FIG. 2B, when node A, a transmitting node, wants to transmit data to node D, a receiving node, node A and node D belong to different clusters and thus cannot transmit data through general communication. Therefore, node A requests to participate in cooperative communication for node B and node C in the first time slot t1 to communicate with node D. When Node B and Node C participate in cooperative communication, if Node A to Node C simultaneously transmit the same data to Node D in the second time slot t2, the transmission power is increased and the transmission range is widened so that data can be transferred to Node D. Can be. Referring to FIG. 2C, as node B and node C operate as cooperating nodes, the data transmission range of node A is widened to include node D. FIG. In other words, if cooperative communication is used, data cannot be transmitted through general communication, so that separate networks can be connected.

In order to classify the wireless nodes on the wireless ad-hoc network into a plurality of clusters, the cluster generator 120 should determine whether general communication can be performed between the wireless nodes. Whether general communication is possible between two wireless nodes can be determined as follows. First assume that each wireless node has the same maximum transmit power limit, P _MAX . At this time, in order for the transmitting node i to perform general communication with the receiving node j, the following Equation 1 should be satisfied.

Where P _i is the transmit power of the transmitting node i, d _ij is the distance between the transmitting node i and the receiving node j, α is a path loss exponent, and τ is for decoding the data received at the receiving node. Signal-to-Noise Ratio (SNR).

The cluster generation unit 120 generates a plurality of clusters on a wireless ad hoc network by allowing wireless nodes connected to each other by a general communication link to transmit and receive data according to Equation 1 belonging to the same cluster.

3 illustrates a plurality of clusters created on a wireless ad hoc network. Referring to FIG. 3, each cluster includes wireless nodes connected to each other by a general communication link, and a wireless node that cannot perform general communication with any node forms a cluster alone. However, in the case of a cluster including one wireless node, since it does not have a cooperative node capable of cooperative communication, it is excluded from the process of creating a cooperative communication link described later.

Next, the cluster generation unit 120 assigns cluster IDs to wireless nodes belonging to the same cluster. The cluster ID may be determined as one of node IDs of wireless nodes belonging to the same cluster, and the node ID having the largest value may be determined as the cluster ID of the corresponding cluster. The cluster ID is transmitted along with the node ID when the wireless node transmits data. Therefore, each wireless node can know whether data received by the wireless node is transmitted by general communication from a wireless node belonging to the same cluster or by cooperative communication from a wireless node belonging to another cluster.

The cooperative communication link generation unit 130 generates a plurality of cooperative communication links between a transmitting node and a receiving node having different cluster IDs and capable of transmitting and receiving data to each other by cooperative communication.

Similarly to determining whether general communication is possible between wireless nodes, distance information between wireless nodes is used to determine whether wireless nodes having different cluster IDs can transmit and receive data by cooperative communication. Distance information may be calculated from the location information of each wireless node.

When one or more cooperating nodes within the transmission radius of the transmitting node and the transmitting node transmit data of the transmitting node to the receiving node at the same time by using cooperative communication, the receiving node may combine and decode the signals transmitted by each node into one signal. . In order to successfully decode data transmitted by a transmitting node and a cooperating node at a receiving node, the following Equation 2 must be satisfied.

Where Ω is a node set including a transmitting node and a cooperating node, P _i is a transmission power of node i among nodes belonging to the node set, d _ij is a distance between node i and a receiving node j, α is a path loss index, And τ is the minimum average noise ratio for decoding the data received at the receiving node.

If the cooperative communication link generation unit 130 determines that cooperative communication may be performed between two wireless nodes having different cluster IDs by Equation 2, the cooperative communication link generating unit 130 may use the corresponding wireless nodes as the transmitting node and the receiving node, respectively. Create a communication link. 4 illustrates a plurality of cooperative communication links created between wireless nodes belonging to different clusters.

When creating a cooperative communication link between a transmitting node and a receiving node having different cluster IDs, all the wireless nodes capable of performing general communication with the transmitting node are determined as cooperative nodes for the cooperative communication, so that the transmitting node and all cooperative nodes are determined. When a node sends data to a receiving node, the power consumption of the nodes increases. That is, as the number of cooperating nodes increases, the transmission power of each node required for the creation of the cooperating communication link decreases, but when the cooperating node is far from the transmitting node, transmission for general communication between the transmitting node and the cooperating node. The power may increase, rather than the transmit power for cooperative communications.

5A and 5B are diagrams for comparing differences in transmit power according to distances between a transmitting node, a cooperating node, and a receiving node. Referring to FIG. 5A, since the receiving node is far from the transmitting node, the transmitting node should transmit data at maximum power using all wireless nodes located as cooperative nodes. However, because the distance between the cooperating node and the transmitting node is close, the transmitting node does not need to use the maximum power when transmitting data to the cooperating node. That is, the transmit power of the transmitting node for maintaining the cooperative communication link is greater than the transmit power for maintaining the general communication link with the cooperating node. As described above, when the cooperative node is located closer to the transmitting node, the transmission power may decrease as the number of cooperative nodes increases.

On the other hand, referring to FIG. 5B, it can be seen that the distance between the receiving node and the transmitting node is shorter and the distance between the cooperating node B and the transmitting node is longer among the cooperative nodes around the transmitting node than in FIG. 5A. In this case, the transmitting node consumes more power than the transmitting power for maintaining the cooperative communication link with the receiving node because the transmitting node must use the maximum transmit power to maintain the general communication link with the cooperating node B. Therefore, rather than selecting all the wireless nodes located within the data transmission range of the transmitting node as the cooperative node, it is optimal to consider both the transmit power for general communication between the transmitting node and the cooperative node and the transmit power for cooperative communication with the receiving node. There is a need to select a cooperative node combination.

Two methods can be used to select the optimal cooperative node combination. First, referring to the first embodiment of the topology control apparatus according to the present invention illustrated in FIG. 1, the cooperative communication link generation unit 130 may include a wireless node set generation unit 132, a transmission power calculating unit 134, and a cooperative node. An aggregate determination unit 136 is provided.

The wireless node set generation unit 132 generates a plurality of wireless node sets by combining wireless nodes capable of general communication with a transmitting node connected to a receiving node through a cooperative communication link for each cooperative communication link. In this case, the wireless node capable of performing general communication with the transmitting node refers to a wireless node which is located at one hop distance from the transmitting node and can directly transmit and receive data with the transmitting node by general communication.

As described above, the cooperative communication link refers to a communication link connecting two wireless nodes belonging to different clusters to each other. Among the two wireless nodes connected by the cooperative communication link, a wireless node transmitting data is a transmitting node and a wireless node receiving data is a receiving node. The transmitting node and the receiving node may be reversed according to the transmission direction of the data. The cooperating node is selected from among wireless nodes capable of general communication with the transmitting node. In the following description, it is assumed that data is transmitted in only one direction along a cooperative communication link.

A wireless node set may include any one of the wireless nodes capable of performing general communication with a transmitting node or an empty set that does not include any wireless node, or may include any wireless node capable of performing general communication with a transmitting node. It may also include. In other words, 0 to all of the plurality of wireless nodes are selected to generate a set of all possible wireless nodes. A wireless node set that can operate as a cooperative node for cooperative communication between a transmitting node and a receiving node is selected from the plurality of wireless node sets generated in this way.

The transmit power calculating unit 134 selects, for each radio node set, radio nodes belonging to the general transmit power and the radio node set, which are the transmit powers of the transmit node for performing general communication with the radio node having the longest distance from the transmit node. The cooperative transmission power which is the transmission power of the transmitting node for performing cooperative communication with the receiving node as the cooperative node is calculated.

The transmission power calculator 134 calculates the transmission power of the transmission node as a reference for selecting a set that can be used for cooperative communication with the receiving node among the wireless node set generated by the wireless node set generation unit 132. As such, the reason for selecting the cooperative node based on only the transmission power of the transmitting node without calculating the transmission power of the wireless node included in the wireless node set is that the transmission of the wireless nodes belonging to the same wireless node set when the transmission power of the transmitting node decreases. Power can also be reduced and the calculation process can be simplified.

First, general transmit power for a set of wireless nodes refers to transmit power of a transmitting node for maintaining a general communication link between a transmitting node and a wireless node having the longest distance from the transmitting node among the wireless nodes belonging to the wireless node set. It is calculated by the following equation (3).

Where ω _d (u, H (u)) is the general transmit power of the transmitting node u for the wireless node set H (u), τ is the minimum average noise ratio for decoding the data received at the receiving node, and α is the path loss The index and d _uj are the distance between the transmitting node u and the wireless node j belonging to the wireless node set H (u).

Next, the cooperative transmit power for the wireless node set refers to transmit power for cooperative communication with the receiving node using the transmitting node as the cooperative nodes, all of the wireless nodes belonging to one wireless node set. Is calculated.

Here, ω _c (u, v, H (u)) denotes the cooperative operation of the transmitting node u for performing cooperative communication with the receiving node v using the wireless nodes belonging to the wireless node set H (u) as the cooperative node. Transmit power, τ is the minimum average noise ratio for decoding the data received at the receiving node v, α is the path loss index, Ω is the set containing both the transmitting and radio node sets H (u), and d _iv is the set Ω The distance between node i and receiving node v belonging to

Equation 3 and Equation 4 above calculate both general transmit power and cooperative transmit power for each of a plurality of radio node sets, and are used for cooperative communication between a transmitting node and a receiving node based on the two transmit power values. The wireless node set is determined.

The cooperative node set determination unit 136 is a cooperative node that is used for cooperative communication between a transmitting node and a receiving node with a radio node set that minimizes a transmission power having a larger value among general transmit power and cooperative transmit power among a plurality of radio node sets. Decide on a set.

As described above, the plurality of radio node sets generated for one transmitting node in the cluster each have two values of general transmit power and cooperative transmit power. The larger of these values is the transmit power representing the corresponding wireless node set. This is because the transmitting node is the maximum transmit power consumed when the transmitting node performs cooperative communication with the receiving node using all of the wireless nodes included in the corresponding radio node set. The cooperative node set determination unit 136 determines the cooperative node set so as to minimize the value of the transmission power representative of the wireless node set.

However, Equations 3 and 4 above consider only transmission power used when a transmitting node transmits data to a receiving node using cooperative communication among transmitting nodes and receiving nodes connected by one cooperative communication link. For more accurate calculation of the transmission power, two-way cooperative communication, that is, the transmission power used by the receiving node when the transmitting node receives data from the receiving node by the cooperative communication, may be used to use the average value with the transmitting power of the transmitting node. have.

In the above, a process of selecting an optimal cooperative node set according to the first embodiment of the topology control apparatus shown in FIG. 1 has been described. However, in this method, general transmission power and cooperative transmission power of all the wireless node sets should be calculated and compared with each other in order to determine an optimal cooperative node set among a plurality of radio node sets. As the number of wireless nodes increases, the complexity of the calculation may increase exponentially. Therefore, a method for quickly determining a cooperative node set through a simplified calculation process will be described.

6 is a block diagram showing the configuration of the second preferred embodiment of the topology control apparatus for the wireless ad hoc network according to the present invention.

Referring to FIG. 6, the second embodiment of the topology control apparatus according to the present invention has the same components as the first embodiment of the topology control apparatus illustrated in FIG. 1, but the cooperative communication link generation unit 130 is identical. It can be seen that the configuration of) is different. In the second embodiment of the topology control apparatus according to the present invention, the cooperative communication link generation unit 130 may determine a power coordination node set, a power gain calculator 232, a power cost calculator 234, and a cooperative node set. The determination unit 236 is provided.

The power gain calculation unit 232 receives the transmission power of the transmitting node for performing general communication with the receiving node for each cooperative communication link and one of the wireless nodes capable of performing general communication with the transmitting node as the cooperative node. A power gain, which is a difference in transmit power of a transmitting node for performing cooperative communication with the node, is calculated for each of a plurality of wireless nodes capable of performing general communication with the transmitting node.

In short, the power gain refers to a gain that the transmitting node can obtain compared with the general communication with the receiving node when the transmitting node performs cooperative communication with the receiving node using one neighbor node as the cooperating node. The power gain can be calculated by the following equation (5).

Where b _i is the power gain of the transmitting node for wireless node i, P _d (u, v) is the transmit power of transmitting node u for general communication with receiving node v, and P _c (u + i, v) is transmitting The transmission power of the transmitting node u for cooperating communication with the receiving node v using the wireless node i as the cooperating node, α is the path loss index, d _uv is the distance between the transmitting node u and the receiving node v, Ω is any one of the node, and d _Ωv from the sending node u, or the wireless node i is the distance between the node and the receiving node Ω v.

Next, the power cost calculator 234 calculates a power cost that is a transmission power of a transmitting node for performing general communication with the wireless node for each wireless node capable of performing general communication with the transmitting node.

Since the power cost is the transmit power of the transmitting node for general communication between the transmitting node and the wireless node, it is calculated by the following equation (6) as shown in equation (1).

Where c _i is the power cost of the transmitting node for wireless node i, P _d (u, i) is the transmit power of transmitting node u for general communication with wireless node i, α is path loss index, and d _ui is transmission Is the distance between node u and wireless node i.

The cooperative node set determination unit 236 is a cooperative node for cooperative communication between a transmitting node and a receiving node sequentially from a wireless node having a maximum power gain to power cost ratio among wireless nodes capable of general communication with a transmitting node. In addition, the set of wireless nodes for minimizing the transmit power value of the transmitting node for the cooperative communication is determined as the cooperative node set used for the cooperative communication between the transmitting node and the receiving node.

In order for a wireless node capable of general communication with a transmitting node to act as a cooperating node used for cooperative communication of the transmitting node, the power gain and the transmitting node when the transmitting node performs cooperative communication with the wireless node as a cooperating node There is a need to compare power costs with other wireless nodes when performing general communication with the wireless node. In other words, in order to use the wireless node as a cooperative node, the transmitting node should have a gain in transmission power for performing cooperative communication while maintaining a general communication link with the wireless node.

The cooperative node set determination unit 236 first generates a cooperative set of cooperative nodes to select a cooperative node to be used for cooperative communication of the transmitting node among wireless nodes capable of general communication with the transmitting node. Next, among the plurality of wireless nodes, the ratio of power gain to power cost, that is, the b _i / c _i value calculated from Equation 5 and Equation 6 is sequentially included in the cooperative node set, starting from the wireless node having the largest value.

Whenever the wireless nodes are included in the cooperative node set one by one, the cooperative node set determination unit 236 determines whether the transmitting node can transmit data to the receiving node by cooperative communication using the wireless node currently included in the cooperative node set as the cooperative node. That is, whether or not the condition for performing cooperative communication of Equation 2 is satisfied is examined. If all of the wireless nodes included in the current cooperative node set are the cooperative nodes but do not satisfy Equation 2, the wireless node having the highest b _i / c _i value among the remaining wireless nodes is added to the cooperative node set again. .

When all of the radio nodes included in the current cooperative node set are used as cooperative nodes, and the transmitting node can transmit data to the receiving node, the cooperative node set determining unit 236 examines whether the current cooperative node set satisfies the following conditions. do. If one additional wireless node is added to the current cooperative node set, if the transmit power of the transmitting node for cooperative communication with the receiving node increases, the current cooperative node set is determined as the final cooperative node set without adding the wireless node. Output However, when one more wireless node is added to the current cooperative node set, and thus the transmission power of the transmitting node for cooperative communication decreases, the corresponding wireless node is added to the cooperative node set. This is because the cooperative node set finally determined by the cooperative node set determination unit 236 should be an optimal set capable of minimizing the transmit power of a transmitting node used for cooperative communication.

As described above, the cooperative communication link generation unit 130 may determine an optimal cooperative node set from among a plurality of radio node sets according to the first embodiment of the present invention shown in FIG. According to the second embodiment of the present invention, the optimal cooperative node set may be determined by sequentially adding the cooperative nodes from the wireless node having the maximum ratio of power gain to power cost. Finally, when two nodes connected through each cooperative communication link shown in FIG. 4 operate as transmitting nodes, an optimal set of cooperative nodes for the corresponding transmitting node is obtained.

However, referring to the plurality of cooperative communication links illustrated in FIG. 4, it can be seen that a plurality of cooperative communication links connecting two clusters exist. Since the cooperative communication link performs a function of connecting clusters that form separate networks because data cannot be transmitted by general communication, there is no need for a plurality of cooperative communication links between the two clusters. In addition, it is necessary to minimize the transmission power of a transmitting node and a cooperating node for data transmission by minimizing the number of cooperative communication links. For example, if node a belonging to cluster A wants to send data to node b belonging to cluster B, node a does not communicate with itself even if node a and node b are not directly connected by a cooperative communication link. And may transmit data to node c, which is connected to node b by a cooperative communication link, through general communication, so that node c transmits data to node b by cooperative communication.

Similarly, in the case of a general communication link connecting wireless nodes in the same cluster, not all nodes need to be directly connected by a general communication link. In the above example, even though node a and node c are not directly connected by a general communication link, node d has the same cluster ID as node a and node c, and through node d connected to node a and node c through a general communication link, respectively. Node a may send data to node c. Therefore, it is necessary to eliminate unnecessary cooperative communication links or general communication links so that each wireless node can transmit data using a minimum transmission power.

The link selector 140 selects a final cooperative communication link based on an average transmission power for performing cooperative communication among a plurality of cooperative communication links, and performs general communication among general communication links between wireless nodes having the same cluster ID. The final general communication link is selected based on the average transmit power.

A communication link with a small average transmit power may reduce power consumption when the transmitting node performs cooperative and general communications. Accordingly, the link selector 140 selects a final cooperative communication link capable of connecting all clusters to each other and a final general communication link capable of connecting all wireless nodes within the cluster based on the average transmission power. As such, the most preferred method that can be used when selecting the final cooperative communication link and the final general communication link is the Minimum Spanning Tree (MST) algorithm.

The link selector 140 first selects a final cooperative communication link by applying a minimum spanning tree algorithm having a weighted average power for maintaining the cooperative communication link for the plurality of cooperative communication links.

The minimum spanning tree refers to a tree in which trunks connecting a plurality of nodes have weights, and the sum of weights of trunks is the smallest in the spanning tree without the direction of the trunks. Applying this to a plurality of cooperative communication links as shown in FIG. 4, each cluster becomes a node of the spanning tree and the cooperative communication link becomes the trunk of the spanning tree. Two nodes connected by a cooperating communication link may act as a transmitting node or a receiving node and thus have no directionality. In addition, the weight of the cooperative communication link for applying the minimum spanning tree algorithm is an average transmit power for performing cooperative communication through the cooperative communication link when two nodes connected by the cooperative communication link operate as transmitting nodes. For example, when wireless node a belonging to cluster A and wireless node b belonging to cluster B are connected by the cooperative communication link ab, the weight of the cooperative communication link ab is such that the wireless node a operates as a transmitting node to perform cooperative communication. It is the average of the transmit power of radio node a for performing and the transmit power of radio node b for operating cooperative communication by acting as a transmitting node.

There are two methods for obtaining the minimum spanning tree: the Prim algorithm and the Kruskal algorithm. The prim algorithm is an algorithm that extends edges one by one from the empty set so that all nodes are included in the set, and the Kruskal algorithm sequentially adds edges having the minimum weight among all edges within a range that does not form a loop. It repeats until all nodes are connected by edges. In the present invention, the final cooperative communication link is selected using the Kruskal algorithm.

The link selector 140 connects all clusters by applying a minimum spanning tree algorithm to the plurality of cooperative communication links generated by the cooperative communication link generation unit 130, but minimizes the sum of weights of all cooperative communication links. Select the final cooperative communication link. 7 shows the final cooperative communication links selected by the link selector 140. Referring to FIG. 7, five cooperative communication links are finally selected among the plurality of cooperative communication links shown in FIG. 4. By applying a minimum spanning tree algorithm, all clusters on a wireless ad hoc network can be connected by a cooperative communication link of minimum number and minimum weight. For example, if cluster A and cluster B are not directly connected by a cooperative communication link, but there is a cluster C that is connected by two clusters and a cooperative communication link, respectively, wireless node a belonging to cluster A is wireless node c belonging to cluster C. The data can be transmitted through cooperative communication, and finally, the data can be transmitted to the wireless node b belonging to the cluster B.

In addition, the wireless node shown in black in FIG. 7 represents a wireless node connected to a cooperative communication link and cooperative nodes used for cooperative communication of the corresponding wireless node. Wireless nodes marked in white are not used for cooperative communications. The cooperative nodes shown in FIG. 7 correspond to nodes selected by the optimal cooperative node set selection method described above.

Next, the link selector 140 applies a minimum spanning tree algorithm that weights average transmission power for performing general communication through the general communication link to the general communication links between wireless nodes having the same cluster ID. Select the general communication link.

In the plurality of clusters shown in FIG. 3, the wireless nodes within each cluster are connected to each other by a general communication link, and FIG. 3 shows all possible general communication links between the wireless nodes. However, as described above, when transmitting data between wireless nodes belonging to the same cluster, not all general communication links such as those shown in FIG. 3 are used. Therefore, there is a need to optimize the general communication links in the cluster as well as the cooperative communication links.

The process of selecting the final cooperative communication link among the cooperative communication links was performed by treating each cluster as nodes of a tree for the entire wireless ad hoc network. However, when selecting the final general communication link among general communication links, the minimum spanning tree algorithm is applied independently for each cluster. That is, wireless nodes belonging to the same cluster become nodes of the tree, and a general communication link connecting two wireless nodes is treated like the trunk of the tree. In addition, the average transmission power of each wireless node for performing general communication between two wireless nodes connected by the general communication link becomes a weight of the general communication link.

When applying the minimum spanning tree algorithm for each cluster, the Kruskal algorithm is used as in the case of selecting the final cooperative communication link. Therefore, among the general communication links connecting the wireless nodes belonging to the same cluster, the minimum number of general communication links having the minimum sum of weights is selected as the final general communication link. 8 shows the final general communication link selected in each cluster by the link selector 140. Referring to FIG. 8, it can be seen that wireless nodes having the same cluster ID are connected to each other by a minimum number of final general communication links. As an example of transmitting data between wireless nodes in a cluster, if node a wants to transmit data to node b, which has the same cluster ID as itself and is not directly connected by a general communication link, node a first needs to send data to the public. It is possible to transmit data to node c connected with itself by the communication link, and to allow node c to transmit data to node b via the general communication link. As a result, all nodes in the cluster can transmit and receive data over a minimum number of general communication links.

The topology determiner 150 determines a topology of a network including a final cooperative communication link and a final general communication link and transmits the topology to the wireless nodes.

As described above, the final cooperative communication link selected by the link selecting unit 140 is obtained from the plurality of cooperative communication links generated by the cooperative communication link generation unit 130, and the plurality of wireless nodes in each cluster are connected to each other. The final general communication link selected by the link selector 140 is obtained from the general communication link of. The topology determination unit 150 finally determines the topology of the network including all of them.

9 is a diagram illustrating a topology of a network finally determined by the topology determiner 150. Referring to FIG. 9, the determined topology includes both the final cooperative communication link shown in FIG. 7 and the final general communication link shown in FIG. 8, and the optimal cooperative node set determined by the cooperative communication link generation unit 130 is also displayed. I can confirm that there is. All wireless nodes on the wireless ad-hoc network will transmit and receive data with other wireless nodes according to the determined topology. Therefore, the topology determination unit 150 transmits the topology determined by the above process to the wireless nodes on the wireless ad-hoc network so that each wireless node can know the information about which wireless node should transmit the data. However, the network topology shown in FIG. 9 further includes one general communication link in the final general communication link shown in FIG. 8, and the added one general communication link cooperates with the transmitting node for cooperative communication of the transmitting node. A communication link representing normal communication between nodes.

10 is a flowchart illustrating a preferred embodiment of a method for controlling a topology of a wireless ad hoc network according to the present invention.

Referring to FIG. 10, the node information receiver 110 receives location information and a node ID of each wireless node from a plurality of wireless nodes located on a wireless ad hoc network (S1010). The received location information and node ID are used to determine the topology of the network, which is the communication path between the wireless nodes.

Next, the cluster generation unit 120 generates a plurality of clusters of wireless nodes that are connected by a general communication link among the wireless nodes and transmit and receive data with each other, and among the node IDs of the wireless nodes belonging to each cluster. Any one, preferably, the node ID having the largest value is determined as the cluster ID of the corresponding cluster and transmitted to the wireless nodes belonging to the same cluster (S1020). Whether general communication between the wireless nodes is possible can be determined based on Equation 1 as described above. When a plurality of clusters are generated on the wireless ad hoc network, the wireless nodes belonging to each cluster have the same cluster ID.

The cooperative communication link generation unit 130 generates a plurality of cooperative communication links between a transmitting node and a receiving node having different cluster IDs and capable of transmitting and receiving data to each other by cooperative communication (S1030). The possibility of cooperative communication can be determined based on Equation 2, and there are two methods for determining a cooperative node for a wireless node operating as a transmitting node transmitting data among two wireless nodes connected through a cooperative communication link. Can be used.

11A and 11B are flowcharts illustrating the performance of the first and second embodiments for determining a cooperative node in the topology control method of the wireless ad hoc network according to the present invention, respectively.

First, referring to FIG. 11A as the first embodiment, the wireless node set generation unit 132 generates a plurality of wireless node sets by combining wireless nodes capable of performing general communication with a transmitting node for each cooperative communication link. (S1031). Next, the transmission power calculating unit 134 includes radios belonging to the general transmission power and the radio node set which are transmission powers of the transmission node for performing general communication with the radio node having the longest distance from the transmission node for each radio node set. The cooperative transmission power which is the transmission power of the transmitting node for performing the cooperative communication with the receiving node using the nodes as the cooperative nodes is calculated (S1032). In this case, the general transmission power may be calculated by Equation 3, and the cooperative transmission power may be calculated by Equation 4. Finally, the cooperative node set determination unit 136 is used for cooperative communication between a transmitting node and a receiving node with a wireless node set that minimizes a transmission power having a larger value among general transmit power and cooperative transmit power among a plurality of wireless node sets. It is determined as a cooperative node set (S1033).

Referring to FIG. 11B, which is a second embodiment, the power gain calculator 232 may perform general communication with a transmitting node and transmission power of a transmitting node for performing general communication with a receiving node for each cooperative communication link. A power gain, which is a difference in transmission power of a transmitting node for performing cooperative communication with a receiving node using one of the wireless nodes as a cooperative node, is calculated for each of the plurality of wireless nodes capable of performing general communication with the transmitting node (S1131). ).

Next, the power cost calculation unit 234 calculates a power cost that is a transmission power of a transmitting node for the wireless node to perform general communication with the wireless node for each wireless node capable of performing general communication with the transmitting node ( S1132).

The cooperative node set determination unit 236 first adds, as a cooperative node, a wireless node having a maximum power gain to power cost ratio among wireless nodes capable of general communication with the transmitting node (S1133). In this case, it is determined whether the transmitting node can perform cooperative communication with the receiving node using the added cooperative node, that is, whether the condition of Equation 2 is satisfied (S1134), and the power for the power cost until such a condition is satisfied. The wireless nodes having the maximum ratio of gains are sequentially added to the cooperative nodes (S1133).

If the condition of Equation 2 is satisfied by sequentially adding the cooperative nodes from the wireless nodes having a large power gain to power cost ratio, the wireless node having the maximum power gain to power cost ratio among the next remaining wireless nodes is the cooperative node. To add (S1135). If the transmission power of the transmitting node for the cooperative communication is reduced by adding the cooperative node (S1136), it is determined whether all the wireless nodes have been added as the cooperative node (S1137), and the power gain of the power cost among the remaining wireless nodes is determined. The wireless node having the maximum ratio is added as a cooperative node (S1135). This process is repeated until the transmission power of the transmitting node is not reduced by the addition of the cooperating node. If the transmission power of the transmitting node does not decrease (S1136), the set of cooperative nodes before the wireless node is added is output (S1138).

In the flowchart of FIG. 10 again, the link selector 140 selects a final cooperative communication link based on an average transmit power for performing cooperative communication among a plurality of cooperative communication links, and selects a general coordination between wireless nodes having the same cluster ID. The final general communication link is selected based on the average transmission power for performing general communication among the communication links (S1040). As described above, this is to remove unnecessary links so that communication can be most efficiently performed in terms of transmit power. The final cooperative communication link and the final general communication link can also be selected by applying the minimum spanning tree algorithm.

Finally, the topology determination unit 150 determines the topology of the network consisting of the final cooperative communication link and the final general communication link and transmits the topology to the wireless nodes (S1050).

So far, the process of determining the network topology based on the location information and node ID of all wireless nodes on the wireless ad hoc network has been described. The network topology may be determined by one device that knows all the wireless nodes' information in this way, but each wireless node creates only the communication link associated with it to determine the partial topology of the network, and they are all combined into the network topology. May be determined. Hereinafter, a case in which a cooperative communication link or a general communication link that connects itself with another wireless node in each wireless node on the wireless ad hoc network is determined as a partial topology of the network will be described.

12 is a block diagram showing the configuration of the first preferred embodiment of the node device of the wireless ad hoc network according to the present invention.

12, a first embodiment of a node device according to the present invention includes a communication unit 1210, a cluster generation unit 1220, a cooperative communication request unit 1230, a cooperative communication link generation unit 1240, and an information transmission unit. 1250, a link selector 1260, and a topology determiner 1270.

The communication unit 1210 is provided in a node apparatus according to the present invention, which is located on a wireless ad hoc network and operates as a wireless node for transmitting and receiving data, and communicates with other wireless nodes on the wireless ad hoc network. Since the node device according to the present invention is one of a plurality of wireless nodes located on the wireless ad hoc network described above, the node device transmits and receives data to and from other wireless nodes through the communication unit 1210. The communication unit 1210 performs both general communication and cooperative communication.

When the cluster generation unit 1220 receives the location information and the node ID of each general node from the general node that can communicate through the general communication link among the wireless nodes, the cluster generation unit 1220 belongs to one of the node IDs together with the general node. Determined by the cluster ID of. As described above, the largest value among the plurality of node IDs may be determined as the cluster ID.

The topology control apparatus according to the present invention as described above receives the location information and node IDs of all the wireless nodes on the wireless ad-hoc network, and determines whether general communication is possible based on their location relationship to generate a plurality of clusters. However, when the cluster generation unit 1220 of the node device according to the present invention generates a cluster, the cluster generation unit 1220 generates one cluster together with general nodes, which are wireless nodes capable of performing general communication with itself, among neighboring wireless nodes. do. However, whether to perform general communication is made based on Equation 1 as in the topology control apparatus. If there is a larger value than the node ID among the node IDs of the general nodes belonging to the same cluster as the node, the node ID is determined as the cluster ID which is the identification code of the cluster. These cluster IDs are sent with the data. On the other hand, if there is no value larger than its own node ID among the node IDs received from the general nodes, its node ID is determined as the cluster ID. At this time, the node apparatus according to the present invention transmits its location information and node ID to other wireless nodes, and determines the cluster ID based on the node ID received from other wireless nodes.

The cooperative communication request unit 1230 is a cooperative communication request message including its location information, a node ID, and a cluster ID to each receiving node among the wireless nodes except for the normal node by the cooperative communication using the general node as the cooperative node. Is transmitted through the communication unit 1210.

The topology control apparatus according to the present invention described above generates a cooperative communication link between wireless nodes determined to be cooperative by Equation 2 based on the location information and node IDs of all wireless nodes on the wireless ad hoc network. However, the node device according to the present invention generates a cooperative communication link with a wireless node capable of cooperative communication with each other without being involved in creating a cooperative communication link between other wireless nodes. In this case, since the cooperative communication link may be created when both parties can transmit and receive data, the cooperative communication request unit 1230 first uses all general nodes connected through the general communication link with itself as a cooperative node, and thus, on the wireless ad hoc network. The cooperative communication request message is transmitted to receiving nodes except the general node among the wireless nodes. If a response message is received from the receiving node which received the message, it is possible to create a cooperative communication link.

When the cooperative communication link generation unit 1240 receives the cooperative communication response message including the location information of the receiving node and the node ID and the cluster ID of the cluster to which the receiving node belongs from the receiving node receiving the cooperative communication request message, Create a cooperative communication link.

At this time, if all the general nodes belonging to the same cluster as the node apparatus according to the present invention are used for cooperative communication with the receiving node, the same problem as mentioned in the above topology control apparatus may occur. Therefore, there is a need to select the optimal cooperative nodes as described above.

Referring to the first embodiment of the node apparatus shown in FIG. 12, the cooperative communication link generation unit 1240 includes a wireless node set generation unit 1242, a transmission power calculator 1244, and a cooperative node set determination unit 1246. It is provided. The function of these components is substantially the same as the components provided in the topology control device, but the node device according to the present invention is applied to all cooperative communication links on the wireless ad-hoc network in that it selects a cooperative node among general nodes connected to it. It is different from the topology control, which selects a cooperating node for

The wireless node set generator 1242 generates a plurality of wireless node sets by combining the general nodes. The wireless node set includes an empty set as described above, and as many wireless node sets as possible in all cases can be generated from the plurality of general nodes.

Next, the transmission power calculating unit 1244 cooperates with the general nodes belonging to the general transmission power and the wireless node set, which are transmission powers for performing general communication with the general node that is farthest from the radio node for each wireless node set. The cooperative transmission power which is the transmission power for performing cooperative communication with the receiving node is calculated. The general transmit power can be calculated by Equation 3 and the cooperative transmit power by Equation 4. In applying the equations 3 and 4, the node device according to the present invention operates as a transmitting node.

The cooperative node set determination unit 1246 is a cooperative node set used for cooperative communication with a receiving node, wherein the cooperative node set determination unit 1246 is a coordinating node set used for cooperative communication with a receiving node. Decide This process is also the same as the cooperative node determination process by the cooperative node set determination unit 236 in the first embodiment of the topology control apparatus. However, the topology control apparatus targets all wireless nodes connected through a cooperative communication link, and the node apparatus according to the present invention differs in selecting a cooperative node to be used for its cooperative communication among general nodes connected thereto.

Next, FIG. 13 is a block diagram showing a configuration of a second preferred embodiment of a node device of a wireless ad hoc network according to the present invention. The second embodiment of the node device shown in FIG. 13 has the same components as the first embodiment of the node device shown in FIG. 12, and differs only in the configuration of the cooperative communication link generation unit 1240.

Referring to FIG. 13, the cooperative communication link generation unit 1240 includes a power gain calculator 1342, a transmission cost calculator 1344, and a cooperative node set determination unit 1346.

The power gain calculator 1342 may generate a plurality of general power gains, which are a difference between transmission power for performing general communication with a receiving node and transmission power for performing cooperative communication with a receiving node using one of the general nodes as a cooperative node. Calculate for each node. The calculation of the power gain may be performed by Equation 5, and the power gain calculation process is the same as described above.

The power cost calculator 1344 calculates a power cost which is transmission power for performing general communication with the general node for each general node. Calculation of the power cost may also be performed by Equation 6 in the same process as described above.

Finally, the cooperative node set determiner 1346 sequentially adds a cooperative node for cooperative communication with a receiving node from a common node having a maximum power gain to power cost ratio among the common nodes, and transmits a transmission power value for cooperative communication. Determine a set of general nodes to minimize the cooperative node set used for cooperative communication with the receiving node. As described above, the process of selecting the cooperative node in the second embodiment of the node apparatus according to the present invention is the same as the process of selecting the cooperative node in the second embodiment of the topology control apparatus described above.

The information transmitter 1250 clusters the cooperative communication link information including the node ID of the node, the transmit power for performing cooperative communication with the receiving node, the node ID of the receiving node, and the cluster ID of the cluster to which the receiving node belongs. The ID is transmitted to the cluster node having the node ID through the communication unit 1210.

In the node apparatus according to the present invention, since the communication link is generated around itself, it does not have information about the communication link generated for other wireless nodes. Therefore, it is difficult to optimize the cooperative communication link, that is, the application of the minimum spanning tree, made in the topology controller described above. As a result, it is preferable that one wireless node selected in each cluster receives all information about the cooperative communication links generated for the other wireless nodes and apply a minimum spanning tree. Performing this process is a wireless node having a cluster ID as the node ID, that is, a wireless node having the largest node ID in the cluster, which is called a cluster node. The information transmitter 1250 transmits the information about the cooperative communication link generated between the receiving node to the cluster node so that the cluster node can know all about the cooperative communication link generated for the wireless nodes belonging to the cluster. do. However, when the node apparatus itself according to the present invention is a cluster node, the cooperative communication link information is received from other general nodes.

The cluster node selects final cooperative communication link information based on average transmission power for performing cooperative communication among cooperative communication link information received from a plurality of general nodes. That is, the minimum extension tree algorithm is applied to a plurality of cooperative communication links with a weight of average transmission power for performing cooperative communication through the cooperative communication link. Since the application process of the minimum spanning tree algorithm has been described above, a detailed description thereof will be omitted. The cluster node transmits information about the final cooperative communication link, that is, node ID and cluster ID of two wireless nodes connected by the final cooperative communication link, to general nodes of the cluster to which the cluster node belongs.

The link selector 1260 selects a final cooperative communication link that matches the last cooperative communication link information received from the cluster node among the cooperative communication links, and transmits an average for performing general communication through the general communication link among the general communication links. Select the final generic communication link based on power.

If the node apparatus according to the present invention is not a cluster node, the link selector 1260 may generate a plurality of cooperative communication links generated by the cooperative communication link generation unit 1240 based on the last cooperative communication link information transmitted from the cluster node. Select the final cooperative communication link. Next, for the general communication links generated between the general nodes in the same cluster, the final general communication link is selected by applying the minimum extension tree algorithm in the same manner as described above.

The topology determination unit 1270 transmits a partial topology of the network consisting of the final cooperative communication link and the final general communication link to the wireless nodes.

The final cooperative communication link and the final general communication link selected by the link selector 1260 described above are communication links connected to the node device according to the present invention. That is, the final cooperative communication link and the final general communication link together form a partial topology of the network. In order to combine all the partial topologies determined for each wireless node and finally complete the overall topology of the network, each wireless node on the wireless ad hoc network needs to transmit its partial topology to the other wireless nodes. Therefore, the topology determination unit 1270 transmits a partial topology to a general node, which is a wireless node belonging to the same cluster, through general communication, and performs cooperative communication to a receiving node belonging to another cluster and connected by a cooperative communication link. Partial topology is transmitted over. As a result, all wireless nodes on the wireless ad hoc network can have information about the completed network topology, and can transmit and receive data to and from each other according to the network topology.

14 is a flowchart illustrating a preferred embodiment of a method for forming a communication link in a node device of a wireless ad hoc network according to the present invention.

Referring to FIG. 14, the cluster generation unit 1220 receives a node ID having the largest value when location information and node ID are received from a general node that can communicate through a general communication link among other wireless nodes on a wireless ad hoc network. It is determined by the cluster ID of the cluster belonging to the general node (S1410). Next, the cooperative communication request unit 1230 is a cooperative communication including a location information, a node ID, and a cluster ID of each of the wireless nodes among the wireless nodes by the cooperative communication using the common node as the cooperative node. The request message is transmitted (S1420).

When the cooperative communication link generation unit 1240 receives the cooperative communication response message including the location information of the receiving node and the node ID and the cluster ID of the cluster to which the receiving node belongs from the receiving node receiving the cooperative communication request message, Create a cooperative communication link (S1430). At this time, the two methods of selecting a cooperative node used for cooperative communication among the general nodes are the same as described above in the first and second embodiments of the node apparatus according to the present invention.

Next, the information transmitter 1250 receives the cooperative communication link information including its node ID, transmit power for performing cooperative communication with the receiving node, node ID of the receiving node, and cluster ID of the cluster to which the receiving node belongs. The cluster ID is transmitted to the cluster node using the cluster ID as the node ID (S1440). Next, the link selecting unit 1260 selects a final cooperative communication link that matches the last cooperative communication link information received from the cluster node among the cooperative communication links, and based on an average transmit power for performing general communication among the general communication links. Selects the final general communication link (S1450). Finally, the topology determination unit 1270 transmits the partial topology of the network including the final cooperative communication link and the final general communication link to the wireless nodes by general communication or cooperative communication (S1460).

Experiments were conducted to evaluate the performance of the present invention. Since the purpose of the present invention is to reduce the consumption of transmit power through network topology control and to connect separate networks to each other, the value of the transmit power and the network connectivity are used as a criterion for evaluating the performance of the present invention.

In this experiment, 10 to 110 wireless nodes were randomly placed in a space of 500 x 500 m ² , and the path loss index α was set to 2 or 4. For each path loss index, the maximum transmit power, P _MAX, is set to 4900 and 24010000, respectively, so that the maximum transmit range for general communications is 70m. For convenience, the minimum average noise ratio τ is set to one. In order to approach more reliable results, the average value of data obtained from a plurality of network topologies was calculated and used as a criterion for evaluating the performance of the present invention.

FIG. 15 is a graph illustrating average transmit power according to the number of wireless nodes when the path loss index is 2, and FIG. 16 is a graph illustrating average transmit power according to the number of wireless nodes when the path loss index is 4.

15 and 16, the average transmission power is highest when all the cooperative communication links generated by the cooperative communication link generation units 130 and 1240 are maintained, and the cooperative communication link is in descending order of the average transmission power. And all general communication links are maintained, in the case of the second embodiment of the present invention, in the case of the first embodiment of the present invention, when no cooperative communication link is used and the minimum spanning tree is applied (prior art 1). And a conventional topology control method (prior art 2) that uses cooperative communication but does not apply to a separated network. In the case of the first embodiment and the second embodiment of the present invention, there is a slight difference and almost the same value in terms of average transmission power. It can be seen from FIG. 15 and FIG. 16 that transmission power can be reduced when cooperative communication is used. In addition, the difference in transmit power between the respective methods increases as the number of nodes increases, because when the number of nodes is small, there is not enough cooperative node and cooperative communication cannot be used. If the number of nodes is large enough, since most nodes can be connected by a general communication link, it can be seen that the average transmission power value varies greatly depending on whether or not the minimum spanning tree algorithm is applied.

FIG. 17 is a graph illustrating network connectivity according to the number of wireless nodes when the path loss index is 2, and FIG. 18 is a graph illustrating network connection diagram according to the number of wireless nodes when the path loss index is 4.

17 and 18, it can be seen that the network connection degree is higher than the case where all the cooperative communication links are maintained and the case according to the first and second embodiments of the present invention. This difference in connectivity is smaller when the path loss index is 4, which means that the number of clusters connected to each other by the cooperative communication link decreases as the path loss index increases. In the case where there is no cooperative communication link and all general communication links are maintained, and in case of the prior art 1 and the prior art 2, the same network connectivity value is irrespective of the path loss index. This is because the maximum transmission range is fixed.

From the experimental results shown in FIGS. 15 to 18, it can be seen that although the present invention uses a little more transmission power than the conventional technology, the network connection can be increased up to 3 times.

The invention can also be embodied as computer readable code on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of the computer-readable recording medium include a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, and the like, and may be implemented in the form of a carrier wave (for example, transmission via the Internet) . The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

Although the preferred embodiments of the present invention have been shown and described above, the present invention is not limited to the specific preferred embodiments described above, and the present invention belongs to the present invention without departing from the gist of the present invention as claimed in the claims. Various modifications can be made by those skilled in the art, and such changes are within the scope of the claims.

1 is a block diagram showing the configuration of a first preferred embodiment of a topology control apparatus for a wireless ad hoc network according to the present invention;

2a to 2c illustrate a plurality of wireless nodes located on a wireless ad hoc network;

3 illustrates a plurality of clusters created on a wireless ad hoc network;

4 illustrates a plurality of cooperative communication links created between wireless nodes belonging to different clusters;

5A and 5B are diagrams for comparing a difference in transmit power according to a distance between a transmitting node, a cooperating node, and a receiving node;

6 is a block diagram showing the configuration of a second preferred embodiment of a topology control apparatus for a wireless ad hoc network according to the present invention;

7 shows the final cooperative communication links selected by the link selector;

8 shows a final general communication link selected in each cluster by the link selector;

9 is a diagram illustrating a topology of a network finally determined by a topology determination unit;

10 is a flowchart illustrating a preferred embodiment of a method for controlling a topology of a wireless ad hoc network according to the present invention;

11A and 11B are flowcharts illustrating the performance of the first and second embodiments for determining a cooperating node in the topology control method of the wireless ad hoc network according to the present invention, respectively.

12 is a block diagram showing a configuration of a first preferred embodiment of a node device of a wireless ad hoc network according to the present invention;

Fig. 13 is a block diagram showing the construction of a second preferred embodiment of a node device of a wireless ad hoc network according to the present invention;

14 is a flowchart illustrating a preferred embodiment of a method for forming a communication link in a node device of a wireless ad hoc network according to the present invention;

15 is a graph showing an average transmit power according to the number of wireless nodes when the path loss index is 2.

16 is a graph showing an average transmit power according to the number of wireless nodes when the path loss index is 4;

17 is a graph showing a network connection diagram according to the number of wireless nodes when the path loss index is 2, and

18 is a graph illustrating a network connection diagram according to the number of wireless nodes when the path loss index is four.

Claims (24)

A node information receiver configured to receive location information and node ID of each wireless node from a plurality of wireless nodes located on a wireless ad hoc network; Create a plurality of clusters of wireless nodes connected by a general communication link among the wireless nodes capable of transmitting and receiving data to each other, and any one of the node IDs of the wireless nodes belonging to each cluster is the cluster ID of the corresponding cluster. A cluster generation unit for determining and transmitting to wireless nodes belonging to the same cluster; A cooperative communication link generation unit for generating a plurality of cooperative communication links between a transmitting node and a receiving node having different cluster IDs among the wireless nodes and capable of transmitting and receiving data to each other by cooperative communication; Selecting a final cooperative communication link based on an average transmit power for performing cooperative communication among the plurality of cooperative communication links, and selecting an average transmit power for performing general communication among general communication links among wireless nodes having the same cluster ID. A link selector for selecting a final general communication link based on the; And And a topology determiner for determining a topology of a network comprising the final cooperative communication link and the final general communication link and transmitting the topology to the wireless nodes. The method of claim 1, The cooperative communication link generation unit, A wireless node set generator for generating a plurality of wireless node sets by combining wireless nodes capable of general communication with the transmitting node for each of the cooperative communication links; With respect to each of the radio node sets, a cooperative node is a general transmission power, which is a transmission power of the transmission node for performing general communication with a radio node farthest from the transmitting node, and radio nodes belonging to the radio node set. A transmission power calculating unit for calculating a cooperative transmission power which is a transmission power of the transmission node for performing cooperative communication with the receiving node; And Determining a wireless node set that minimizes a transmission power having a larger value among the general transmission power and the cooperative transmission power as a cooperative node set used for cooperative communication between the transmitting node and the receiving node among the plurality of wireless node sets; Topology control apparatus for a wireless ad hoc network comprising a; cooperative node set determination unit. 3. The method of claim 2, The general transmission power is a topology control device of a wireless ad hoc network, characterized in that calculated by the following equation A: Equation A

Ω _d (u, H (u)) is the general transmit power of the transmitting node for the set of wireless nodes, τ is the minimum average noise ratio for decoding the data received at the receiving node, α is the path loss index, And d _uj is a distance between the transmitting node and a wireless node belonging to the wireless node set. The method of claim 2 or 3, Wherein the cooperative transmission power is calculated by Equation B below: Equation B

Here, ω _c (u, v, H (u)) is the cooperative transmission power of the transmitting node for performing cooperative communication with the receiving node using the wireless nodes belonging to the wireless node set as the cooperative node, τ is a minimum average noise ratio for decoding data received at the receiving node, α is a path loss index, Ω is a set including both the transmitting node and the wireless node set, and d _iv is a node i belonging to the set Ω And the distance between the receiving node. The method of claim 1, The cooperative communication link generation unit, Cooperate with the receiving node using, as a cooperating node, one of a transmission power of the transmitting node for performing general communication with the receiving node and a wireless node capable of performing general communication with the transmitting node for each cooperative communication link. A power gain calculator configured to calculate, for each of a plurality of wireless nodes capable of performing general communication with the transmitting node, a power gain that is a difference in transmit power of the transmitting node for performing communication; A power cost calculator configured to calculate, for each wireless node capable of general communication with the transmitting node, a power cost which is a transmission power of the transmitting node for performing general communication with the wireless node; And Among the wireless nodes capable of general communication with the transmitting node, the cooperative communication is sequentially added from the wireless node having the maximum ratio of the power gain to the power cost to the cooperative node for the cooperative communication between the transmitting node and the receiving node. And a cooperative node set determining unit configured to determine a set of wireless nodes for minimizing a transmit power value of the transmitting node as a cooperative node set used for cooperative communication between the transmitting node and the receiving node. Topology control device in wireless ad hoc network. The method of claim 5, Wherein the power gain is calculated by Equation C: Equation C

Where b _i is the power gain of the transmitting node for the wireless node, P _d (u, v) is the transmit power of the transmitting node for general communication with the receiving node, P _c (u + i, v) Is a transmission power of the transmitting node for cooperative communication with the receiving node using the wireless node as the cooperating node, α is a path loss index, d _uv is a distance between the transmitting node and the receiving node, Ω is either the transmitting node or the wireless node, and d _Ωv is the distance between the node Ω and the receiving node. The method according to claim 5 or 6, The power cost is calculated by the following equation D topology control apparatus of a wireless ad hoc network, characterized in that: [Equation D]

Where c _i is the power cost of the transmitting node for the wireless node, P _d (u, i) is the transmit power of the transmitting node for general communication with the wireless node, α is a path loss index, and d _ui Is the distance between the transmitting node and the wireless node. A node information receiving step of receiving location information and a node ID of each wireless node from a plurality of wireless nodes located on a wireless ad hoc network; Create a plurality of clusters of wireless nodes connected by a general communication link among the wireless nodes capable of transmitting and receiving data to each other, and any one of the node IDs of the wireless nodes belonging to each cluster is the cluster ID of the corresponding cluster. A cluster generation step of determining and transmitting to wireless nodes belonging to the same cluster; Generating a plurality of cooperative communication links between a transmitting node and a receiving node having different cluster IDs among the wireless nodes and capable of transmitting and receiving data to each other by cooperative communication; Selecting a final cooperative communication link based on an average transmit power for performing cooperative communication among the plurality of cooperative communication links, and selecting an average transmit power for performing general communication among general communication links among wireless nodes having the same cluster ID. A link selection step of selecting a final general communication link based on the; And And a topology determination step of determining a topology of a network comprising the final cooperative communication link and the final general communication link and transmitting the topology to the wireless nodes. The method of claim 8, The cooperative communication link creation step, Generating a plurality of wireless node sets by combining wireless nodes capable of general communication with the transmitting node for each of the cooperative communication links; With respect to each of the radio node sets, a cooperative node is a general transmission power, which is a transmission power of the transmission node for performing general communication with a radio node farthest from the transmitting node, and radio nodes belonging to the radio node set. A transmission power calculating step of calculating a cooperative transmission power which is a transmission power of the transmitting node for performing cooperative communication with the receiving node; And Determining a wireless node set that minimizes a transmission power having a larger value among the general transmission power and the cooperative transmission power as a cooperative node set used for cooperative communication between the transmitting node and the receiving node among the plurality of wireless node sets; Determining a cooperative node set; and a topology control method for a wireless ad hoc network. The method of claim 8, The cooperative communication link creation step, Cooperate with the receiving node using, as a cooperating node, one of a transmission power of the transmitting node for performing general communication with the receiving node and a wireless node capable of performing general communication with the transmitting node for each cooperative communication link. A power gain calculating step of calculating, for each of a plurality of wireless nodes capable of performing general communication with the transmitting node, a power gain that is a difference in transmit power of the transmitting node for performing communication; A power cost calculating step of calculating, by the transmitting node, a power cost which is a transmission power of the transmitting node for performing general communication with the wireless node, for each wireless node capable of performing general communication with the transmitting node; And Among the wireless nodes capable of general communication with the transmitting node, the cooperative communication is sequentially added from the wireless node having the maximum ratio of the power gain to the power cost to the cooperative node for the cooperative communication between the transmitting node and the receiving node. And a cooperative node set determining step of determining a set of wireless nodes for minimizing a transmit power value of the transmitting node as a cooperative node set used for cooperative communication between the transmitting node and the receiving node. Topology control method for wireless ad hoc network. In a node device of a wireless ad hoc network located on a wireless ad hoc network and operating as a wireless node for transmitting and receiving data, A communication unit for communicating with other wireless nodes on the wireless ad hoc network; When the location information and node ID of each general node are received from a general node capable of communicating through a general communication link among the wireless nodes, one of the node IDs is determined as a cluster ID of a cluster belonging to the general node. A cluster forming unit; The communication unit transmits a cooperative communication request message including its location information, node ID, and the cluster ID to each receiving node of the wireless nodes other than the normal node by the cooperative communication using the common node as the cooperative node. Cooperative communication request unit for transmitting through; When the cooperative communication response message including the location information and node ID of the receiving node and the cluster ID of the cluster to which the receiving node belongs is received from the receiving node receiving the cooperative communication request message, the cooperative communication link with the receiving node is established. Generating a cooperative communication link generation unit; Cooperative communication link information including its own node ID, transmission power for performing cooperative communication with the receiving node, node ID of the receiving node, and cluster ID of the cluster to which the receiving node belongs, wherein the cluster ID is the node ID. An information transmitter for transmitting to the cluster node through the communication unit; Selecting a final cooperative communication link that matches the last cooperative communication link information received from the cluster node among the cooperative communication links, and based on an average transmit power for performing general communication through the general communication link among the general communication links. A link selector for selecting a general communication link; And And a topology determiner configured to determine a partial topology of a network comprising the final cooperative communication link and the final general communication link and transmit the partial topology to the wireless nodes. The method of claim 11, And the final cooperative communication link information is selected based on an average transmission power for performing cooperative communication among cooperative communication link information received by the cluster node from the plurality of general nodes. The method of claim 11 or 12, The cooperative communication link generation unit, A wireless node set generation unit for generating a plurality of wireless node sets by combining the general nodes; For each wireless node set, general transmission power which is a transmission power for performing general communication with a general node farthest from a normal node belonging to the wireless node set and general nodes belonging to the wireless node set A transmission power calculating unit configured to calculate a cooperative transmission power which is transmission power for performing cooperative communication with the receiving node as a cooperative node; And A cooperative node set that determines a cooperative node set used for cooperative communication with the receiving node, wherein a coordinating node set used for cooperative communication with the receiving node is selected from among the plurality of radio node sets. Node unit of a wireless ad hoc network, characterized in that it comprises a. The method of claim 13, The general transmit power is a node device of a wireless ad hoc network, characterized in that calculated by Equation A: Equation A

Where ω _d (u, H (u)) is the general transmit power for the set of wireless nodes, τ is the minimum average noise ratio for decoding the data received at the receiving node, α is the path loss index, and d _uj is Distance from a general node belonging to the wireless node set. 15. The method of claim 14, The node transmission apparatus of the wireless ad hoc network, characterized in that the cooperative transmission power is calculated by the following equation B: Equation B

Here, ω _c (u, v, H (u)) is cooperative transmission power for cooperative communication with the receiving node using general nodes belonging to the radio node set as cooperative nodes, τ is received by the receiving node. Minimum average noise ratio for decoding data, α is a path loss index, Ω is a set including both the wireless node itself and the set of wireless nodes, and d _iv is the distance between node i and the receiving node belonging to the set Ω . The method of claim 11 or 12, The cooperative communication link generation unit, For each of the plurality of general nodes, a power gain that is a difference between transmission power for performing general communication with the receiving node and transmission power for performing cooperative communication with the receiving node using one of the general nodes as a cooperative node. A power gain calculating unit for calculating; A power cost calculator configured to calculate a power cost which is a transmission power for performing general communication with the general node for each general node; And Among the general nodes, the general nodes having the maximum ratio of the power gain to the power cost are added to the cooperative node for cooperative communication with the receiving node sequentially to minimize the transmit power value for the cooperative communication. And a cooperative node set determining unit for determining a set as a cooperative node set used for cooperative communication with the receiving node. The method of claim 16, The node gain of the wireless ad hoc network, characterized in that the power gain is calculated by the following equation C: Equation C

Where b _i is the power gain for the wireless node, P _d (u, v) is the transmit power for general communication with the receiving node, and P _c (u + i, v) is the wireless node as the cooperating node. Transmit power for cooperative communication with the receiving node, α is a path loss index, d _uv is the distance to the receiving node, Ω is either the wireless node itself or the wireless node, and d _Ωv is the Is the distance between node Ω and the receiving node. The method of claim 17, The node cost of the wireless ad hoc network, characterized in that the power cost is calculated by the following equation D: [Equation D]

Where c _i is the power cost for the wireless node, P _d (u, i) is the transmit power for general communication with the wireless node, α is a path loss index, and d _ui is the distance from the wireless node. . A method of forming a communication link in a node device of a wireless ad hoc network operating as a wireless node located on a wireless ad hoc network and transmitting and receiving data, the method comprising: When the location information and node ID of each general node are received from a general node capable of communicating through a general communication link among other wireless nodes on the wireless ad hoc network, a cluster belonging to one of the node IDs together with the general node. Forming a cluster ID of the cluster ID; Cooperating to transmit a cooperative communication request message including its location information and node ID and the cluster ID to each receiving node of the wireless nodes excluding the common node by cooperating communication using the common node as a cooperating node; A communication request step; When the cooperative communication response message including the location information and node ID of the receiving node and the cluster ID of the cluster to which the receiving node belongs is received from the receiving node receiving the cooperative communication request message, the cooperative communication link with the receiving node is established. Generating a cooperative communication link; Cooperative communication link information including its own node ID, transmission power for performing cooperative communication with the receiving node, node ID of the receiving node, and cluster ID of the cluster to which the receiving node belongs, and the cluster ID among the general nodes. An information transmitting step of transmitting to the cluster node with the node ID; Selecting a final cooperative communication link that matches the last cooperative communication link information received from the cluster node among the cooperative communication links, and selecting a general communication link based on an average transmission power for performing general communication among the general communication links. Link selection step; And And determining a partial topology of a network comprising the final cooperative communication link and the final general communication link and transmitting the partial topology to the wireless nodes. The method of claim 19, The final cooperative communication link information is selected by the cluster node based on an average transmission power for performing cooperative communication among cooperative communication link information received from the plurality of general nodes. Forming method. The method of claim 19 or 20, The cooperative communication link creation step, Generating a plurality of wireless node sets by combining the general nodes; For each wireless node set, general transmission power which is a transmission power for performing general communication with a general node farthest from a normal node belonging to the wireless node set and general nodes belonging to the wireless node set A transmission power calculating step of calculating a cooperative transmission power which is transmission power for performing cooperative communication with the receiving node as a cooperative node; And A cooperative node set that determines a cooperative node set used for cooperative communication with the receiving node, wherein a coordinating node set used for cooperative communication with the receiving node is selected from among the plurality of radio node sets. Determining step; comprising a communication link of a node device of a wireless ad hoc network. The method of claim 19 or 20, The cooperative communication link creation step, For each of the plurality of general nodes, a power gain that is a difference between transmission power for performing general communication with the receiving node and transmission power for performing cooperative communication with the receiving node using one of the general nodes as a cooperative node. Calculating a power gain calculating step; A power cost calculation step of calculating a power cost which is transmission power for performing general communication with the general node for each general node; And Among the general nodes, the general nodes having the maximum ratio of the power gain to the power cost are added to the cooperative node for cooperative communication with the receiving node sequentially to minimize the transmit power value for the cooperative communication. And a cooperative node set determining step of determining a set as a cooperative node set used for cooperative communication with the receiving node. A computer-readable recording medium having recorded thereon a program for executing the method of controlling the topology of the wireless ad hoc network according to any one of claims 8 to 10. A computer-readable recording medium having recorded thereon a program for executing a communication link formation method of a node device of a wireless ad hoc network according to claim 19 or 20.

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