KR20090070547A - Method and system for minimizing delay time between terminal - Google Patents

Abstract

A system for minimizing delay time between terminals and a method thereof are provided to transmit data through multi-hop multicasting using network coding and accumulated multicast modes, thereby shortening data transfer delay between terminals. Destination nodes(130,131) receive data. A source node(110) determines the destination nodes and transmits the data by determining routing to the destination node. A plurality of mediate nodes(120~123) codes received data and transmits the coded data to the adjacent nodes to a node having a good channel state based on data transmission speed.

Description

Data transfer system and method for minimizing end-to-end time delay {METHOD AND SYSTEM FOR MINIMIZING DELAY TIME BETWEEN TERMINAL}

The present invention relates to a data transmission system and method for minimizing end-to-end time delay, and more particularly, to a system and method for calculating power of an intermediate node and transmitting data through accumulated multicast.

In the downlink transmission scheme of the sensor network, 1-hop broadcasting transmits control signals to all sensor nodes under the jurisdiction of the sink node. In other words, the transmitting entity transmits data to a plurality of receiving entities, and the transmitting entity simultaneously transmits data to multiple receiving entities using the same frequency resource. Conventional sensor networks are often used for a single application, such as temperature measurement, humidity measurement, photometric measurement, and motion measurement, where the receiving sensor performs only a single application task. Broadcasting is used to send data to multiple receiving nodes without distinguishing between receiving nodes.

However, the recent sensor network has been developed into a Ubiquitous Sensor Network (USN) environment that interworks with all networks. Since each sensor node performs various applications in the USN environment, the sink node selects a specific sensor node, transmits a control signal, and collects necessary information. Therefore, in the USN environment, the 1-hop broadcasting method of transmitting control signals and collecting data for all sensor nodes is inadequate.

That is, multi-hop multicasting is suitable where the sink node transmits a control signal only to a specific node over several hops. Multihop multicasting is a method in which a transmitting entity transmits data to a specific receiving entity, and data is transmitted over multiple hops through an intermediate relay node. Multi-hop multicasting can reduce the interference from the neighboring network as compared with 1-hop broadcasting because the transmitting entity specifies the receiving entity and transmits data only for the corresponding receiving entity.

However, in 1-hop broadcasting, data is transmitted through intermediate relay nodes in multi-hop multicasting, in contrast to transmitting data in a transmitting entity. Therefore, there is a need for a method of controlling data transmission time, power consumption, and the like at an intermediate relay node in order to increase the efficiency of data transmission.

SUMMARY OF THE INVENTION The present invention has been proposed to meet the above demands. The present invention proposes a data transmission system that transmits data by applying accumulated multicast to multihop multicasting using network coding and calculates power of an intermediate node that minimizes end-to-end time delay. And a multi-hop multicasting method.

SUMMARY OF THE INVENTION The present invention proposed to meet the above demands comprises a data transmission system using multi-hop multicasting, comprising: an object node for transmitting data; A source node for determining the destination node, for determining routing to the destination node, and transmitting the data; And a plurality of intermediate nodes that code the received data and transmit the coded data to the plurality of adjacent nodes based on a data transmission rate to a node having a good channel state among the adjacent plurality of nodes to which the coded data is to be transmitted. Characterized in that it comprises a.

In addition, the present invention is a multi-hop multicasting method using network coding,

Determining a destination node to which data is to be transmitted, determining routing to the destination node, and transmitting the data; Receiving data processing information from an intermediate node that codes the received data and transmits the data to adjacent nodes; And calculating power of the intermediate node that minimizes time delay at the intermediate node based on the received data processing information.

The data transmission system and method for minimizing the end-to-end time delay of the present invention can reduce the number of data transmissions by transmitting data through multi-hop multicasting using network coding and accumulated multicast schemes. This can reduce the time delay of data transmission from end to end. In addition, the source node receives data processing information from the intermediate node to calculate a data transmission probability of each intermediate node. The power value of each intermediate node that minimizes the data transmission time delay between the ends is calculated through the calculated data transmission probability.

According to the present invention, by efficiently allocating limited resources, the efficiency of data transmission can be maximized.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, whereby those skilled in the art may easily implement the technical idea of the present invention. There will be. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention relates to a data transmission system and method for minimizing end-to-end time delay. Since the data transmission system of the present invention basically transmits data through multi-hop multicasting using network coding, data transmitted from the source node is transmitted to the destination node through several hops through a plurality of intermediate nodes. The source node calculates the power of each intermediate node that minimizes the end-to-end time delay through the data transmission probability of each intermediate node. The intermediate node minimizes end-to-end time delay through accumulated multicast.

1 is a diagram illustrating a network configuration of a data transmission system to which network coding is applied according to an embodiment of the present invention. As shown, the data transmission system consists of a source node 110, intermediate nodes 120-123, and destination nodes 130, 131. Multiple sensor networks coexist in the space, and the source node of each network is a USN structure that transmits collected data to the Internet through a gateway.

The source node 110 determines the destination nodes 130 and 131 to which data is to be transmitted, determines the routing to the destination nodes 130 and 131, and transmits the data. Since the source node 110 of the present invention transmits data by multi-hop multicasting, it selects and specifies the target nodes 130 and 131 to transmit data. For example, when the source node 110 wants to receive data from the target nodes T1 130 and T2 131, the source node 110 moves to the target nodes T1 130 and T2 131. Control signals can be sent. In FIG. 1, a control signal consisting of data a and b is transmitted to T1 130 and T2 131 which are target nodes by multi-hop multicasting.

In addition, the source node 110 collects information related to the size of data transmitted from the intermediate nodes 120 to 123 from the intermediate nodes 120 to 123 and the time of existence of the data transmission event to collect the information of the intermediate nodes 120 to 123. The data transmission probability is calculated, and the power of the intermediate nodes 120 to 123 is minimized through the data transmission probability of the intermediate nodes 120 to 123. The present invention applies a distributed optimization algorithm in order to minimize the delay time in the process in which predetermined data is transmitted from the source node 110 to the destination node (130, 131). The distributed optimization technique is proposed by Wu and Bertsekas, and it is used more easily than the central management technique in actual system implementation. (C.Wu and D. Bertsekas, Distributed power control algorithms for wireless networks, IEEE Transactions on Vehicular Technology, 50 (2) (2001) 504-514.)

The distributed algorithm not only makes decisions using local information, but also achieves the overall goal by making distributed decisions for each of the individual elements that make up the objective function. The present invention aims to minimize the end-to-end time delay and solves the problem by distributing it to the problem of minimizing the time delay at each intermediate node. If the time delay at each intermediate node (120 to 123) is minimized, it can be seen that the time delay between ends is minimized. Accordingly, when the time delay at each intermediate node 120 to 123 is minimized, the power value of each intermediate node 120 to 123 is calculated, thereby minimizing the end-to-end time delay. The process of calculating the power value will be described in detail with reference to Equation after explaining data transmission through multicasting accumulated in FIGS. 1 to 3.

The intermediate nodes 120 to 123 code the received data, and transmit the coded data based on a data transmission rate to a node having a good channel state among adjacent nodes to transmit the coded data, and a plurality of intermediate nodes 120 to 123 may exist. The intermediate nodes 120 to 123 simultaneously transmit data to a plurality of adjacent nodes. In this case, since the intermediate nodes 120 to 123 transmit based on the data transmission rate to the node having a good channel state, the node having a poor channel state receives only a part of data. Therefore, when the intermediate nodes 120 to 123 transmit data to nodes having poor channel conditions, the intermediate nodes 120 to 123 transmit data through accumulated multicast. In other words, data is divided and transmitted over several events. The contents related to the accumulated multicast will be described in detail with reference to FIGS. 2A to 2C.

The destination nodes 130 and 131 refer to nodes to which the source node 110 wishes to transmit data, and may be composed of one node or a plurality of nodes.

The present invention shortens the end-to-end time delay by transmitting data by multi-hop multicasting using network coding. The source node 110 selects T1 130 and T2 131 as the destination node, determines the routing for transmitting data to the destination nodes 130 to 131, and selects data a and b as the intermediate node M1 (120). ), M2 (121). M1 transmits the received data a to adjacent nodes M3 122 and T1 130. M2 transmits the received data b to the adjacent nodes M3 122 and T2 131. The intermediate node M3 122 codes the received data a by an XOR operation, and transmits the coded data a + b to the intermediate node M4 123. M3 can reduce the transmission time delay between ends by coding and transmitting simultaneously without transmitting data a and b, respectively. In addition, M4 123, which is an intermediate node, transmits the received data a + b to T1 130 and T2 131, which are adjacent nodes.

2A to 2C are diagrams illustrating a network configuration of a data transmission system to which accumulated multicast is applied according to an embodiment of the present invention. FIG. 2A to FIG. 2C specifically illustrate data transmission processes of M1 120 and M2 121, which are intermediate nodes. Explain.

Wireless transmission has the property of essentially sharing medium. Thus, intermediate nodes 120-123 of the present invention transmit data to adjacent nodes. However, since the present invention transmits data based on the transmission rate to a node having a good channel state in the process of transmitting data to a plurality of adjacent nodes, some nodes may not receive a part of data. Accordingly, the data transmission system of the present invention applies accumulated multicast, so that the intermediate nodes 120 to 123 can transmit data over a plurality of events.

Table 1 describes the multi-hop multicasting process using network coding step by step.

Figure 2a is a representation of the first to fourth steps of Table 1 on the network. The source node 110 transmits data a to M1 120 which is an intermediate node and data b to M2 121 which is an intermediate node.

In the data transmission system of the present invention, in transmitting the same data to a plurality of adjacent nodes, the same data is simultaneously transmitted based on a transmission rate to a node having a good channel state among the plurality of adjacent nodes. Therefore, there is a possibility that data transmission to a node having a poor channel state may not be completed. In the third step of Table 1, the intermediate node M1 120 simultaneously transmits data a to the intermediate node M3 122 and the destination node T1 which are data to a plurality of adjacent nodes. At this time, the channel state to the intermediate node M3 122, which is relatively close to the target node T1 130, may be good, and the intermediate node M1 120 may increase the transmission rate to the intermediate node M3 122 having a good channel state. As a reference, data a is simultaneously transmitted to the intermediate node M3 122 and the destination node T1 130. In the third step, all data transmission from M1 ends when the data transmission to M3 ends. That is, since the channel state is based on the transmission rate to a node having a good channel state, a transmission to a node having a relatively poor channel state may not be able to transmit a part of data. Similarly to the third step, the transmission process of the data b in the fourth step of Table 1 may be a part of the data that is not transmitted in the transmission to T2, which has a relatively poor channel state.

FIG. 2B illustrates the fifth step of Table 1 on a network, and illustrates an accumulated multicast process in which M1 120 and M2 121 transmit data through a plurality of events. First, the intermediate node M3 122 receiving different data a and b codes the data a and b through an XOR operation and transmits the coded data a and b to the next intermediate node M4 123. At this time, the M1 120 transmits a portion of data a that has not been transmitted to the T1 130 in the third step, and the M2 121 transmits a portion of data b that has not been transmitted to the T2 131 in the fourth step. . That is, during the main transmission of the M3 122, M1 120 and M2 121 transmit data whose transmission is not completed through the previous event through sub-transmission.

2C shows the sixth step of Table 1 on a network. The intermediate node M4 123 transmits coded data a + b to T1 130 and T2 131 which are destination nodes. Since the present invention transmits data through multi-hop multicasting using network coding, unlike other multicasts that do not use network coding, the intermediate node 123, which is one-hop before the destination nodes 130 and 131, is coded. The transferred data to the destination nodes 130 and 131 at the same time.

3 is a diagram illustrating a transmission event on a network according to an embodiment of the present invention. The intermediate nodes 120 to 123 transmit data to a plurality of adjacent nodes, and may transmit one data over a plurality of events.

Transmission events are divided into main transmissions and additional transmissions. The main transmission is indicated by a solid line and the additional transmission is indicated by a dotted line. Part of the data was not transmitted during the main transmission phase (for example, part of the data could not be transmitted due to the transmission of data to a node with poor channel conditions, based on the rate of transmission to the node with good channel conditions). In the additional transmission, the rest of the data is transmitted. (a) shows a situation in which M1 performs main transmission and M2 and M4 perform additional transmission. If a part of data cannot be transmitted to T1 in the main transmission step of M1, M1 transmits the remaining data through steps (b) and (c). That is, M1 transmits data a to T1 over three events. (b) shows a situation in which M2 performs main transmission and M1 and M4 perform additional transmission. If a part of data cannot be transmitted to T2 in the main transmission step of M2, M2 transmits the remaining data through steps (a) and (c). That is, M2 sends data b to T2 over three events.

As such, various transmission events may exist on the network, and each node may transmit data through a predetermined transmission event. In addition, the data transmission event in each node may be mathematically represented to define a data transmission probability in each node, thereby calculating the power of the node that minimizes the end-to-end time delay.

1 to 3 illustrate data transmission using accumulated multicasting in multicasting using network coding in order to minimize end-to-end time delay. However, when all intermediate nodes transmit data at the same power, the data transmission speed on a predetermined channel may be lowered due to interference due to other transmission signals. For example, in the fifth step of Table 1, the links (M1, T1), (M3, M4), and (M2, T2) are simultaneously used. Since the (M3, M4) link is located at the center of the network, it can be seen that the interference is relatively higher than that of other links. If the M1, M2, and M3 nodes use the same power, the (M3, M4) link is used. Will be relatively low. Therefore, we now look at the process of calculating the power of each intermediate node that minimizes the end-to-end time delay.

When data is to be transmitted from node i to node j, the transmission probability is Φ _ij (Φ ≧ 0). When the transmission probability Φ _ij is interpreted in terms of time, it can be regarded as a time allocated for transmission from node i to node j of the total routing time from the source node 110 to the destination nodes 130 and 131. In this regard, P. Floreen, P. Kaski, J. Kohonen, and P. Orponen, Lifetime maximization for multicasting in energy-constrained wireless networks, IEEE Journal on Selected Areas in Communications 23 (1) (2005) 117-126 It is.

Since the present invention assumes the use of a single frequency band, in order to transmit data with limited resources, appropriate resource distribution should be made according to various transmission and reception situations of a plurality of intermediate nodes 120 to 123. This may be expressed as in Equation 1.

Equation 1 expresses the situation of resource allocation in the case where the effects of interference by other transmissions are not reflected. However, when data is transmitted in a single frequency band, since it cannot be free from interference by other transmissions, Equation 2 reflects the effect of interference by other transmissions as the data transmission speed on the link (i, j).

^(m)은 이벤트 m에서의 전송 속도를 의미한다. SINR_ij ^(m)은 이벤트 m에서의 신호대간섭잡음비를 의미한다. SINR_ij ^(m)은 수학식 3을 통해 구할 수 있다. Φ _ij ^(m) means transmission probability in event m,

^(m) means the transmission rate in event m. SINR _ij ^(m) means the signal-to-interference noise ratio in the event m. SINR _ij ^(m) can be obtained through Equation 3.

In Equation 3, φ _ij ^(m) denotes a probability that data is transmitted from node i to node j in the mth event. P _ij represents the transmit power allocated to the link (i, j) and has a fixed value. g _ij denotes a gain value between node i transmitting data and node j receiving data, and V _j denotes the strength of noise at node j receiving data. When data is transmitted from node i to node j, data is also transmitted from other nodes at the same time. Therefore, when transmitting data simultaneously with node i in the remaining nodes except for node i and node j, interference by data transmission from other nodes should be considered. Also, consider the noise at node j receiving the data. The interference due to the data transmission of the peripheral node and the noise at the receiving node are represented in the denominator of Equation 3.

Equation 4 is obtained by knowing Φ _ij ^(m) , which is the probability of transmitting data from node i to node j in the mth event, and the power P _ij allocated to the link (i, j) connecting node i and node j. Can be used to find the average power at node i.

P _ij means power used in the link (i, j) and has a fixed value. Φ _ij ^(m) means a time for transmitting data from node i to node j in the mth event of the entire routing time T. Therefore, φ _ij ^(m) P _ij means the average power used in the link (i, j) at the mth event of the total routing time T. That is, φ _ij can be regarded as a data transmission probability from node i to node j and has a meaning as a power adjustment factor. And, through this, it is possible to calculate P _i , which is the size of average power used at node i. For example, in FIG. 3, M1 transmits data a over a total of three events to transmit data a to T1. Therefore, the total transmission probability from M1 to T1 can be obtained through the sum of three transmission probabilities, and the average power magnitude in M1 can be obtained from the transmission probabilities.

Since the present invention aims to minimize the end-to-end time delay, from now on, it is possible to minimize the end-to-end time delay through Equations 5 to 10 related to the size of data transmitted from each node and the existence time of the data transmission event. Look at conditions using expressions.

P ^{(s, dk )} means a set of a plurality of links constituting a path from the source node 110 to the destination node (d _k ) to which data is to be transmitted. I _ij means the size of data transmitted from the node i through the link (i, j) existing between the node i and node j. r _ij means the data transfer rate between the node i and node j can be obtained through equation (2). Therefore, I _ij / r _ij means the time for transmitting data on the link (i, j), that is, the time delay on the link (i, j). The process of repeating this process for all the links existing in the network is represented in Equation 5, where T (s, d _k ) means a time delay in the entire path of the network. Therefore, in order to minimize the time delay between the end can be expressed as Equation 6.

In addition, since the present invention transmits data using network coding, as described in FIG. 2C, an intermediate node 1-hop from the destination node simultaneously transmits coded data to a destination node. Therefore, since the time delays in the various paths on the network are all the same, Equation 6 may be modified as in Equation 7.

Equations 8 to 10 represent constraints for obtaining the power of the intermediate nodes 120 to 123 which minimize the end-to-end time delay.

Equation 8 indicates that the total data transmission probability of the link (i, j) can be obtained as the sum of the probabilities of each transmission event.

Equation 9 means that the sum of the data sizes transmitted through the individual transmission events is equal to the total data size to be transmitted by the node i.

Since the present invention assumes the use of a single frequency band, Equation 10 means that the data transmission probability at node i cannot exceed 1. Node i is connected to a plurality of adjacent nodes and can exchange data with a plurality of adjacent nodes. Thus, the sum of the data transfer probability from node i to node j and the data transfer probability from node j to node i cannot exceed one.

Equations 1 to 10 summarized the conditions for achieving the end-to-end time delay, which is an objective function, so that Φ _ij , the data transmission probability at each node, is a key variable for minimizing the end-to-end time delay. Was confirmed. Therefore, from now on, the relevant equations are summarized in terms of the main variable Φ _ij . Equations 11 to 13 illustrate a process of calculating I (Φ _ij ) at the source node 110 through data processing information transmitted from the intermediate nodes 120 to 123. Here, the data processing information means the size of data transmitted from each intermediate node and the data transmission event existence time.

Data transmission from node i to node j is performed over a number of events, and the size of data transmitted in the event is calculated through Equation 11. I (Φ _ij ^(m) ) refers to the size of data transmitted through the link (i, j) in the m-th event, I _total means the total data transmitted through the link (i, j). Therefore, I (Φ _ij) , which is the size of data transmitted in the mth event by subtracting the sum of the size of data transmitted through the event except the mth event from the size of the total data transmitted through the entire link (i, j). ^(m) ) is calculated.

^(m)를 사용하여 t(Φ_ij(m))를 산출할 수 있다. t (Φ _ij ^(m) ) means the existence time of the m th event. I (Φ _ij ^(m) ) calculated through Equation 11 and calculated through Equation 2

using ^(m) can be calculated by the t (Φ _ij (m)).

는 링크 (u,v) 간의 데이터 전송 속도를 의미한다. 네트워크상에서는 동시에 다수의 중간 노드에서 데이터를 전송한다. 따라서, 링크 (i,j)에서 m번째 이벤트로 데이터를 전송하는 경우, 이와 동시에 링크 (u,v)에서도 데이터가 전송된다. 링크 (i,j)와 링크(u,v)는 동시에 데이터를 전송하므로 데이터를 전송하는 시간은 동일하다고 볼 수 있으므로, 수학식 13을 통해 링크(u,v)에서 전송되는 데이터의 크기를 산출할 수 있다.

Is the data transfer rate between links (u, v). In a network, data is transmitted from multiple intermediate nodes at the same time. Therefore, when data is transmitted in the mth event on the link (i, j), the data is also transmitted on the link (u, v) at the same time. Since link (i, j) and link (u, v) transmit data at the same time, the data transmission time can be regarded as the same, so that the size of data transmitted on link (u, v) is calculated through Equation can do.

Equation 14 expresses Equation 7 as a Lagrange dual function. M denotes the number of intermediate nodes transmitting data, and K denotes the number of intermediate nodes receiving data. The present invention aims to solve the objective function of calculating the power of intermediate nodes 120-123 that minimizes end-to-end time delay. In addition, the constraints related thereto are expressed through Equations 11 to 13. In order to solve the objective function that includes a number of constraints, first, the process of including the constraints in the objective function, that is, Lagrange Relaxation, is applied. Including a plurality of constraints in Equation 7 produces Equation 14, a Lagrange dual function. In this case, each constraint is related to each other through λ, which is a Lagrange multiplier.

Equation 15 calculates an optimal transmission probability of each of the intermediate nodes 120 to 123, that is, a transmission probability of minimizing delay time. Here, Φ means a set of data transmission probabilities satisfying the constraints expressed in Equations 8 to 10. However, Φ _ij ^(m) value calculated through Equation 15 has a duality gap from an optimal value to be obtained in the present invention. Processes for reducing such duality gaps are represented in Equations 16 and 17.

The present invention aims to calculate the power of each of the intermediate nodes 120-123, which minimizes end-to-end time delay. However, φ _ij ^(m) calculated by applying λ given as an initial value has an optimal value and a duality gap to be obtained in the present invention, and thus λ needs to be updated. Equation 16 means a dual problem to reduce the duality gap. Equation 17 suggests a sub-gradient method as one means for solving Equation 16. In Equation 17, [] ⁺ means projecting to 0 when the number in [] is less than 0. γ is the gradient step size. Through this process, λ can be updated to minimize the duality gap. Λ updated by Equation 17 is substituted into Equation 15 to yield φ _ij ^(m) . By repeatedly performing this process, the data transmission probability of the intermediate nodes 120 to 123 which minimizes the time delay between the end points can be calculated, and the power of the intermediate nodes 120 to 123 can be calculated through the optimal data transmission probability. have.

The present invention is to calculate the power of each of the intermediate nodes (120 to 123) to minimize the end-to-end time delay through the distributed optimization theory, briefly summarized the process described above is as follows.

In a first step, the source node 110 sets the values of Φ _ij ^(m) , λ _{ij , u} , and I (Φ _ij ^(m) ), which are values for calculating the power of each of the intermediate nodes 120 to 123, to t = 0. Initialize with

In the second step, the source node receives information related to the size of data transmitted from each intermediate node 120 to 123, the time of existence of the data transmission event, and optimizes the end-to-end time delay through the received information. Estimate the data transmission probability. In this process, the λ value is updated to calculate the optimal data transmission probability. The relation is as follows.

If (t is not 0) {

}

The source node 110 attempts to obtain an optimal data transmission probability for minimizing the end-to-end time delay for each intermediate node 120 to 121 existing in the network. Therefore, when the data transmission probability of node i is calculated, the data transmission probability of node u transmitting data simultaneously with node i is calculated based on the value. The related equation is as follows.

The data transmission probability calculated for node i is substituted as a constant in the above equation (*) to calculate the data transmission probability of node u.

The size of data transmitted from the node u is calculated through the existence time of the m th event.

To calculate the data transmission probability that minimizes the time delay at the intermediate node, update λ _{ij , u} through the subgradient method. This process is repeated until the determinant data transmission probability _{φ i} ^(m) converges to an optimal value that minimizes the end-to-end time delay.

The power of node i is computed through Φ _ij ^(m) converged to an optimal value that minimizes end-to-end time delay. The source node 110 calculates the power of each of the intermediate nodes 120 through 123 through this process, thereby minimizing the time delay between the end nodes.

4 is a diagram illustrating an operation sequence of the source node 110 according to an embodiment of the present invention.

The source node 110 determines the destination nodes 130 and 131 to transmit data on the network (S410), and determines the routing for transmitting data to the corresponding destination nodes 130 and 131 (S420). If the routing is determined, the source node 110 transmits data (S430). Since the source node 110 transmits data to the destination nodes 130 and 131 by multi-hop multicasting, the source node 110 transmits data through a plurality of intermediate nodes 120 to 123. Accordingly, the source node 110 receives the data processing information from the intermediate nodes 120 to 123 (S440), calculates a data transmission probability of minimizing the end-to-end time delay through the received information, and calculates the optimal data. The power of the intermediate nodes 120 to 123 is calculated based on the transmission probability (S450). A detailed process of calculating the power of the intermediate node is based on Equations 1 to 17 described above.

5 is a diagram illustrating an operation sequence of an intermediate node according to an embodiment of the present invention.

The plurality of intermediate nodes 120 to 123 transmits the data received from the transmitting node 110 over several hops and transmits the data to the destination nodes 130 and 131. The intermediate nodes 120 to 123 receive data (S510) and code the received data (S520). By coding and transmitting the data, the number of data transmissions can be reduced, thereby reducing the time delay between the ends. The intermediate nodes 120 to 123 transmit the coded data through accumulated multicast (S530). In addition, each intermediate node 120 to 123 transmits data processing information (size of data to be transmitted, existence time of a data transmission event) to the source node 110 (S540).

FIG. 6 is a diagram illustrating an accumulated multicast sequence according to an embodiment of the present invention, and specifically illustrates the accumulated multicast step of FIG. 5.

Intermediate nodes 120-123 transmit data to a plurality of adjacent nodes due to the nature of radio transmissions sharing medium. In this case, data is simultaneously transmitted to a plurality of adjacent nodes based on a transmission rate with a node having a good channel state (for example, a channel having low interference) among the plurality of adjacent nodes. Since the intermediate nodes 120 to 123 transmit based on the transmission rate to the node having a good channel state, a part of data may not be transmitted to a predetermined node. Accordingly, the intermediate nodes 120 to 123 check whether there is a node whose data transmission is incomplete (S620), and transmit the remaining data through a plurality of events for the node whose transmission is incomplete (S630).

For example, in FIG. 2A, when the intermediate node M1 120 transmits data to the adjacent nodes M3 122 and T1 130, data is transmitted based on the transmission to the M3 122 having a good channel condition. Therefore, only a part of data a to be transmitted to T1 130 is transmitted. Thus, node M1 transmits the remaining data when M3 122 transmits data to M4 123, as shown in FIG. 2C. That is, M1 transmits data a to T1 through two events.

As described above, the method of the present invention may be implemented as a program and stored in a recording medium (CD-ROM, RAM, ROM, floppy disk, hard disk, magneto-optical disk, etc.) in a computer-readable form. Since this process can be easily implemented by those skilled in the art will not be described in more detail.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

1 is a network diagram of a data transmission system to which network coding is applied according to an embodiment of the present invention.

2A to 2C are network configuration diagrams of a data transmission system applying accumulated multicast according to an embodiment of the present invention.

3 is a network diagram illustrating a transmission event in a data transmission system according to an embodiment of the present invention.

4 is an operation flowchart of a source node according to an embodiment of the present invention.

5 is an operation flowchart of an intermediate node according to an embodiment of the present invention.

6 is a flowchart of accumulated multicast according to an embodiment of the present invention.

Claims (18)

In a data transmission system using multi-hop multicasting, A destination node to which data is to be transmitted; A source node for determining the destination node, for determining routing to the destination node, and transmitting the data; And A plurality of intermediate nodes that transmit the coded data to the plurality of neighboring nodes based on a data transmission rate to the received plurality of neighboring nodes which code the received data and to which the coded data is to be transmitted. Data transmission system comprising a. The method of claim 1, The intermediate node is When transmitting data to a node having a poor channel state among the plurality of adjacent nodes, transmitting the coded data through a plurality of transmission events. Data transmission system. The method of claim 2, The sum of data sizes transmitted through the plurality of transmission events is Equal to the size of the entire data to be transmitted in the intermediate node Data transmission system. The method of claim 1, The source node is from the intermediate node The data transmission probability of the intermediate node is calculated by collecting the existence time of the data transmission event and the size information of the data transmitted by the event, and calculating the power of the intermediate node through the data transmission probability of the intermediate node. Data transmission system. The method of claim 4, wherein The source node calculates the power of the intermediate node by the following equation Data transmission system. [Equation]

Where P _i is The magnitude of the average power used at node i, P _ij is the power used at link (i, j), and Φ _ij ^(m) is the probability of data transfer from node i to node j in the mth event. The method of claim 4, wherein The source node is To calculate the data transmission probability of the intermediate node by the following equation Data transmission system. [Equation]

Where I (Φ _ij ^(m) ) is the size of data transmitted from node i to node j in the mth event, I _total is the total data transmitted via link (i, j),

^(m) is the transmission rate in the mth event, and λ is the Lagrange multiplier. The method of claim 6, The source node is By sequentially calculating the data transmission probability of the intermediate node r that transmits data simultaneously with the intermediate node i from the data transmission probability of the intermediate node i using the following equation Data transmission system. [Equation]

Where φ _ij ^(m) is the transmission probability of node i in the mth event,

^(m) is the transmission rate in the mth event, t (Φ _ij ^(m) ) is the existence time of the mth event, and I (Φ _ij ^(m) ) is the size of data transmitted in the mth event. The method of claim 7, wherein The source node is Lagrange dual function to calculate the transmission probability of the intermediate node Data transmission system. [Equation]

Where I (Φ _ij ^(m) ) is the size of data transmitted in the mth event,

^(m) is the transmission rate in the mth event, and λ is the Lagrange multiplier. The method of claim 8, The source node is Updating the Lagrange multiplier λ by the following equation Data transmission system. [Equation]

Where λ is the Lagrange multiplier and γ is the gradient step size. In the multi-hop multicasting method using network coding, Determining a destination node to which data is to be transmitted, determining routing to the destination node, and transmitting the data; Receiving data processing information from an intermediate node that codes the received data and transmits the data to adjacent nodes; And Calculating power of the intermediate node that minimizes time delay at the intermediate node based on the received data processing information Multi-hop multicasting method comprising a. The method of claim 10, The intermediate node is Transmitting data to a plurality of adjacent nodes based on a transmission rate to a node having a good channel state among the plurality of adjacent nodes Multihop multicasting method. The method of claim 11, The intermediate node is When transmitting data to a node having a poor channel state among the plurality of adjacent nodes, transmitting the coded data through a plurality of transmission events. Multihop multicasting method. The method of claim 10, The data processing information The existence time of the data transmission event, the size information of the data transmitted by the event Multihop multicasting method. The method of claim 13, The source node calculates the power of the intermediate node by the following equation Multihop multicasting method. [Equation]

Where P _i is The magnitude of the average power used at node i, P _ij is the power used at link (i, j), and Φ _ij ^(m) is the probability of data transfer from node i to node j in the mth event. The method of claim 13, The source node is To calculate the data transmission probability of the intermediate node by the following equation Multihop multicasting method. [Equation]

Where I (Φ _ij ^(m) ) is the size of data transmitted from node i to node j in the mth event, I _total is the total data transmitted via link (i, j),

^(m) is the transmission rate in the mth event, and λ is the Lagrange multiplier. The method of claim 15, The source node is By sequentially calculating the data transmission probability of the intermediate node r that transmits data simultaneously with the intermediate node i from the data transmission probability of the intermediate node i using the following equation Multihop multicasting method. [Equation]

Where φ _ij ^(m) is the transmission probability of node i in the mth event,

^(m) is the transmission rate in the mth event, t (Φ _ij ^(m) ) is the existence time of the mth event, and I (Φ _ij ^(m) ) is the size of data transmitted in the mth event. The method of claim 16, The source node is Lagrange dual function to calculate the transmission probability of the intermediate node Multihop multicasting method. [Equation]

Where I (Φ _ij ^(m) ) is the size of data transmitted in the mth event,

^(m) is the transmission rate in the mth event, and λ is the Lagrange multiplier. The method of claim 17, The source node is Updating the Lagrange multiplier λ by the following equation Multihop multicasting method. [Equation]

Where λ is the Lagrange multiplier and γ is the gradient step size.

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