KR101375365B1 - Method for data transmission in multirate multihop wireless network - Google Patents

Abstract

The present invention relates to a data transmission method in a multi-rate multi-hop wireless network, wherein each transmission node constituting a multi-hop wireless network in a multi-rate environment in which any one of a plurality of transmission speeds can be selected is transmitted. Calculating an effective transmission rate for each rate, and selecting each transmission node having the highest effective transmission rate among the plurality of transmission rates as an optimal transmission rate based on the effective transmission rate, According to the present invention, an intrasession network coding scheme is used in a multirate multi-hop wireless network, so that each transmitting node can select an optimal transmission rate with the maximum effective transmission rate, thereby improving network throughput.

Description

METHOD FOR DATA TRANSMISSION IN MULTIRATE MULTIHOP WIRELESS NETWORK}

The present invention relates to a data transmission method in a multirate multihop wireless network, and more particularly, to calculate an effective transmission rate at each transmission node using an intrasession network coding scheme in a multirate environment and to optimally transmit the data. A data transmission method in a multirate multihop wireless network selecting a speed.

Multihop wireless networks can be installed and used at a relatively low cost, while performance may be affected by signal strength reduction, channel instability, and interference due to transmission distance.

The wireless device wants to have a high transmission rate and a long transmission radius, but when using the same power, the transmission speed and the transmission radius are in a trade off relationship. Because of this, the singlerate environment has one compromise between two conditions.

On the other hand, the multirate environment has a number of transmission speeds, and thus, compromises as many as the transmission rate, and a process of selecting a transmission rate suitable for a given situation from among various compromises of the multirate is required.

On the other hand, the conventional routing method is to set the path to transfer the information first and then transmit. If transmission fails, the transmission path is newly set again and sent. This is an inefficient method in situations where the probability of loss of information is high due to the nature of the wireless environment.

To improve this point, opportunistic routing has been proposed as a new method to reduce information loss by utilizing the channel's broadcast characteristics and spatial diversity.

This method transmits by prioritizing the transmission node closest to the destination in the transmission of each node without determining the transmission path on the network in advance. In this process, nodes other than the designated receiving node also receive information. Therefore, the transmission by using the eavesdropping nodes around them improves the transmission efficiency and improves the throughput.

However, there is a problem that multiple nodes redundantly transmit the same information unnecessarily, and the performance improvement and scalability are limited by increasing the complexity of transmission scheduling.

Related Prior Art Korean Patent Publication No. 2010-0068168 (published on Jun.22, 2010, entitled " Method and apparatus for transmitting data in a multi-hop wireless network ") is available.

In the present invention, the multirate multi-hop wireless network environment uses an intrasession network coding scheme to calculate an effective transmission rate at each transmission node and select an optimal transmission rate based on the multirate multi-hop wireless network. It is an object of the present invention to provide a data transmission method in a hop wireless network.

Data transmission method in a multi-rate multi-hop wireless network according to an aspect of the present invention is that each of the transmission nodes constituting the multi-hop wireless network in a multi-rate environment in which any one of a plurality of transmission rates can be selected Calculating an effective transmission rate for each of the two transmission rates; And selecting, by the transmission node, an optimal transmission rate from among the plurality of transmission rates, the transmission rate having the highest effective transmission rate based on the effective transmission rate.

In the present invention, each transmitting node is characterized by transmitting information in a network coding scheme.

In the present invention, each of the transmitting nodes is characterized by transmitting information in an intrasession network coding scheme using the same source node and the same destination node.

In the step of calculating the effective transmission rate of the present invention, the effective transmission rate is calculated from a transmission node close to the target node.

In the present invention, the effective transmission rate is calculated based on the transmission rate and the link transmission probability for each transmission rate.

In the present invention, the effective transmission rate is calculated by reflecting the maximum effective transmission speed of the neighboring nodes belonging to the transmission candidate node set.

The present invention includes the steps of each of the transmission node to select the simultaneous transmission set based on the optimum transmission rate; And transmitting, by each transmitting node, information at the optimum transmission rate to a transmitting node selected as the simultaneous transmission set.

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The present invention further includes the step of calculating the throughput of the multi-hop wireless network using linear programming after the step of transmitting the information.

In the present invention, the throughput is calculated by reflecting the time scheduling conditions of the simultaneous transmission set.

According to the present invention, an intrasession network coding scheme is used in a multirate multi-hop wireless network, so that each transmitting node can select an optimal transmission rate with the maximum effective transmission rate, thereby improving network throughput.

In addition, according to the present invention, it is possible to determine the simultaneous transmission set at each transmission node using the optimal transmission rate and to calculate the throughput between the source node and the destination node using the linear programming method, thereby confirming the change in throughput in a multirate environment. .

1 is a diagram schematically illustrating a configuration of a multirate multihop wireless network according to an embodiment of the present invention.
2 is a diagram illustrating a configuration of a multirate multihop wireless network based on one transmitting node according to an embodiment of the present invention.
3 is a flowchart illustrating an operation of a data transmission method in a multirate multihop wireless network according to an embodiment of the present invention.
FIG. 4 is a graph illustrating throughput when a data transmission method in a multirate multihop wireless network according to an embodiment of the present invention is applied to a grid topology.
FIG. 5 is a graph illustrating throughput when a data transmission method in a multirate multihop wireless network according to an embodiment of the present invention is applied to a random topology.

Hereinafter, a data transmission method in a multirate multihop wireless network according to the present invention will be described in detail with reference to the accompanying drawings. In this process, the thicknesses of the lines and the sizes of the components shown in the drawings may be exaggerated for clarity and convenience of explanation. In addition, the terms described below are defined in consideration of the functions of the present invention, which may vary depending on the intention or custom of the user, the operator. Therefore, definitions of these terms should be made based on the contents throughout this specification.

1 is a view schematically showing the configuration of a multi-rate multi-hop wireless network according to an embodiment of the present invention, Figure 2 is a transmission of a configuration of a multi-rate multi-hop wireless network according to an embodiment of the present invention It is a figure centering on a node.

As shown in FIG. 1, a multirate multihop wireless network according to an embodiment of the present invention may include a source node n _s , a transmitting node n _i , and a destination node n _d .

The source node n _s refers to a node that generates information and starts transmission for the first time. The destination node n _d refers to a node to which information transmitted from the source node n _s is finally transmitted. (n _i ) means a plurality of nodes that are passed through the information transmitted from the source node (n _s ) to the destination node (n _d ).

In multi-rate (Multirate) environment, each transport node (n _i) by selecting one transmission rate from among a plurality of transmission rates can transmit the information.

If, when it is assumed that the sending node (n _i) is to be sent selects one transmission rate from among the L number of transmission rate, may indicate the transmission rate to have the sending node (n _i) as R ^m _i. Here, m is an indicator variable for distinguishing the transmission speed, m = 1,…. , L.

In addition, when the transmission node n _i transmits at the transmission rate R _i ^m , the transmission range may be represented by T _i ^m , and as shown in FIG. 2, the transmission range T _i ^m. There are several peripheral nodes n _j inside. At this time, the transmitting node (n _i) a may represent the length of the link formed between the peripheral node (n _j) to d _ij, transmission probability of the link transmitting at a transmission rate R _i ^m can be expressed by p _ij ^m .

Since the transmission range depends on the transmission speed, the number of neighbor nodes n _j is affected by the transmission speed. Specifically, as the transmission speed increases, the transmission range narrows, and the number of neighboring nodes n _j decreases, and as the transmission speed decreases, the transmission range increases, and the number of neighboring nodes n _j also increases. There is a tendency.

Each sending node (n _i) is aware of the location of the neighboring nodes (n _j) within the current location and transmission range, this position information is the purpose, all the sending node (n _i) including a source node (n _s) the node ( n _d ) is used to calculate the effective baud rate needed to reach n _d ).

On the other hand, in the multi-rate multi-hop wireless network according to the present invention, each transmitting node (n _i ) is characterized in that for transmitting information in an intrasession network coding scheme.

The network coding scheme refers to a scheme in which each transmitting node n _i generates independent information by combining received different packets, and the intrasession network coding scheme refers to the same source node n _s and a destination node. This means that a network coding scheme is applied to a session using (n _d ).

In the intrasession network coding scheme, each transmitting node n _i simultaneously transmits information to transmission candidate nodes whose distance from the destination node n _d is closer to that of the neighboring nodes n _j than that of the transmitting node n _i . do.

In this case, as shown in FIG. 2, the transmission candidate node set, which is a collection of transmission candidate nodes, is represented by F _i ^m = {n _i1,. , n _iq }. Further, the links occurring between the transmitting node n _i and the transmitting candidate node set F _i ^m are l _ii1 ^m _,. l _iiq ^m , where p _ii1 ^m ,... , p _iiq ^m

In the case of using the intrasession network coding scheme, there is an advantage that the efficiency of link use is better than the conventional routing scheme of determining and transmitting a path through which information is transmitted in one session.

In addition, there is an advantage that the scheduling is simpler and the link latency is reduced compared to the opportunistic routing method of prioritizing and transmitting the receiving node receiving the information.

Therefore, when the intrasession network coding scheme is used, the overall link usage of the network can be improved, thereby increasing the network throughput between the source node n _s and the destination node n _d .

3 is a flowchart illustrating an operation of a data transmission method in a multirate multi-hop wireless network according to an embodiment of the present invention, with reference to this will be described the specific operation of the present invention.

First, the effective transmission rate of all nodes constituting the multi-rate multi-hop wireless network is initialized to '0' (S100).

Subsequently, an effective transmission rate _Di ^m for a plurality of transmission rates is calculated from the transmission node n _i close to the destination node n _d to the source node n _{s in step} S110.

In this case, the effective transmission speed (D _i ^m ) may be calculated based on the transmission rate R _i ^m and the transmission probability of the link for each transmission speed p _ij ^m , and the neighboring nodes belonging to the transmission candidate node set F _i ^m (n). It can be calculated by reflecting the maximum effective transmission rate D _j of _j ).

That is, the effective transmission rate (D _i ^m) can be calculated by Equation 1 below.

As described above, calculating the effective transmission rate _Di ^m from the transmitting node n _i close to the destination node n _d has the following meaning.

The destination node n _d is always designated as a candidate for transmission by the neighboring transmission node n _i . In addition, these transmitting nodes n _i are designated as transmission candidate nodes by neighboring nodes farther from the destination node n _d , and this process is repeated up to the source node n _s .

As a result, the effective transmission rate D _i ^m is calculated from the transmission node n _i close to the destination node n _d , and the maximum effective transmission rate D _j that the current transmission node n _i can have is next. It can be reflected in the calculation of the effective transmission rate (D _i ^m ) of the transmission node (n _i ).

Therefore, all transmission nodes n _i including the source node n _s may calculate the effective transmission speed D _i ^m in consideration of the efficiency of the entire network.

After that, each sending node (n _i) is a plurality of transmission rates ^{_{R i m (m = 1,}} ..., L) and on the basis of the effective transmission rate (D _i ^m) calculated for each of the selected optimum transmission rate (S120 ).

In this case, the optimal transmission rate may be selected as the highest transmission rate among the plurality of transmission rates R _i ^m (m = 1, ..., L ) with the effective transmission rate _Di ^m .

That is, the transmission rate with the highest effective transmission rate _Di ^m among the L transmission rates may be selected as the optimal transmission rate.

As such, when an optimal transmission rate is selected in all transmission nodes n _i including the source node n _s , each transmission node n _i determines a simultaneous transmission set CT _α (S130).

In a multi-hop wireless network, all transmitting nodes n _i transmit information in a broadcast manner. Therefore, a link is simultaneously generated and transmitted to the transmitting node n _i and the neighboring transmitting candidate node.

Each transmitting node n _i may not have a receiving link during the transmission of information, and a node having a receiving link may in no case receive information from more than one transmitting node at the same time.

The simultaneous transmission set CT _α means a set of transmission candidate nodes satisfying the conditions ① and ②, and each transmission node n _i has a different transmission candidate node.

If the set of nodes on the network is defined as V, it may be expressed as Equation 2 below. In addition, if a set of links formed between the transmission node n _i and the transmission candidate node is defined as E, it may be expressed as Equation 3 below.

The process of expressing the conditions for constructing the simultaneous transmission set (CT _α ) can be represented by the following equations (4) and (5). In this case, α is an indicator variable for distinguishing each simultaneous transmission set (CT _α ).

Here, X _ij ^{m α} corresponds to an indicator variable indicating whether the link l _ij ^m is used in the simultaneous transmission set (CT _α ), and when X _ij ^mα becomes 1, the transmission node (n) has a transmission rate R _i ^m . _i ) means that the link generated between the neighbor node (n _j ) is used in the simultaneous transmission set (CT _α ).

Here, ε _i ^{m α} corresponds to an indicator variable indicating whether the transmitting node n _i is used in the simultaneous transmission set CT _α , and when ε _i ^{m α} is 1, the transmitting node n _i transmits simultaneously. It means that it is selected as a transmitting node or a receiving node in the set (CT _α ).

With reference to Equations 4 and 5, the transmitting node and the receiving node in the simultaneous transmission set CT _α may be expressed as Equation 6 below.

Further, that the use is when the following expression (7) is that showing a condition having a respective transfer node (n _i) depending on the link, has a transmission link or a receiving link the node is included in the broadcast set (CT _α) Indicates.

Different transmission nodes n _i included in the same simultaneous transmission set CT _α should be selected to have different transmission candidate nodes. This condition is shown in Equation 8 below.

Where I represents an indicator variable for determining the interference relationship of the link. That is, it is shown that links in the same transmission set do not interfere with each other or are generated at the same transmission node n _i . In the case of interference between links, simultaneous transmission is not shown in Equation 9 below.

Referring back to FIG. 3, after determining the simultaneous transmission set CT _α , each transmission node n _i transmits information to nodes belonging to the simultaneous transmission set CT _α at an optimal transmission speed (S140).

In detail, the source node n _s simultaneously transmits information to the nodes belonging to the simultaneous transmission set CT _α at the optimum transmission rate, and the plurality of transmission nodes n _{i that} have received the same information transmit their optimal transmission rates. It transmits information to nodes belonging to its simultaneous transmission set (CT _α ). This transmission is repeated so that the information generated at the source node n _s is delivered to the destination node n _d .

As described above, when each transmitting node n _i selects an optimal transmission rate having the maximum effective transmission rate and transmits the information, the network throughput γ can be improved.

On the other hand, after the transmission of the information in this way it is possible to calculate the network throughput (γ) using the linear programming method (S150).

In the wireless network environment, there are a total of M sets of simultaneous transmission sets (CT _α ) and α = 1,. , M . In this case, each simultaneous transmission set transmits at a time ratio of λ _α .

As a result, it is possible to replace the end-to-end throughput calculation problem of the network with the time scheduling problem of the simultaneous transmission set (CT _α ). Also, in any situation, two or more simultaneous transmission sets CT _α cannot transmit at the same time, so the sum of the respective time ratios cannot exceed 1.

 Throughput calculation of a multi-hop wireless network can be accomplished through the use of linear programming to set up and solve optimization problems.

That is, a function for maximizing the throughput γ of the network is set as the objective function, and a constraint on the flow rate applied to each link is set. In this case, the maximum throughput of the network can be obtained by establishing a conditional expression based on the network coding scheme and setting a constraint of the simultaneous transmission set (CT _α ).

The equation of 것을 indicates that the sum of the flow rates of the transmission link and the reception link at one node is zero, which means that all nodes in the network except the source node n _s and the destination node n _d have a condition. . x _ij ^m1 and x _ji ^m2 are variables representing the flow rate of the link.

의 수식은 소스 노드(n_s)에서 전송된 링크의 플로우 레이트의 합은 네트워크 전체의 처리율(γ)과 같음을 나타낸다.

The equation of _s denotes that the sum of the flow rates of the links transmitted at the source node n _s is equal to the throughput γ of the entire network.

의 수식은 목적 노드(n_d)에서 수신된 링크의 플로우 레이트 합이 네트워크 전체 처리율(γ)과 동일함을 나타낸다.Conversely,

The equation of denotes that the sum of the flow rates of the links received at the destination node n _d is equal to the overall network throughput γ.

의 수식은 링크의 플로우 레이트에 대한 조건으로, 항상 0보다 크거나 같은 값을 가짐을 보여준다.

The equation for is a condition for the flow rate of the link, and shows that it always has a value greater than or equal to zero.

의 수식과

의 수식은 동시전송집합(CT_α)의 스케줄링에 대한 수식이다.

With the formula

Is a formula for scheduling of simultaneous transmission set (CT _α ).

은 모든 동시전송집합(CT_α)에 할당된 시간 비율을 더하면 1을 넘지 않는 조건을 나타내고,

은 각각의 동시전송집합(CT_α)에 할당된 시간 비율이 항상 0보다 크거나 같음을 보여준다.Specifically,

Denotes a condition not exceeding 1 by adding the time ratio allocated to all simultaneous transmission sets (CT _α ),

Shows that the ratio of time allocated to each simultaneous transmission set (CT _α ) is always greater than or equal to zero.

은 링크의 플로우 레이트를 결정하는 수식으로 각각의 링크가 가질 수 있는 최대의 플로우 레이트를 동시전송집합(CT_α)의 시간 비율과 링크의 전송 확률을 통해 나타내었다.

Is a formula for determining the flow rate of a link. The maximum flow rate that each link can have is represented by the time ratio of the simultaneous transmission set (CT _α ) and the transmission probability of the link.

FIG. 4 is a graph illustrating throughput when a data transmission method in a multirate multihop wireless network according to an embodiment of the present invention is applied to a grid topology, and FIG. 5 is a multirate multicast according to an embodiment of the present invention. It is a graph showing the throughput when the data transmission method in the hop wireless network is applied to a random topology.

FIG. 4 shows the results of calculating and comparing the throughputs of the single rate and the multirate for the transmission rates R, 1.5R, and 2R in a grid topology of 5x5 and 25 nodes in total.

FIG. 5 shows the results of calculating and comparing the throughputs of the single rate and the multirate for the transmission rates R, 1.5R, and 2R in a random topology in which 35 nodes were randomly arranged in an area composed of 50 units × 50 units. have.

4 and 5, the node at the bottom left of the topology is set as the source node n _s , the node at the top right is designated as the destination node n _d , and the transmission range is determined according to the transmission speed. It is assumed that the interference range is the same as the transmission range.

As shown in FIG. 4, in the case of the grid topology, the throughput may be improved in the case of the multirate in comparison with the case of using the single rate.

In addition, as shown in Figure 5, even in a random topology it can be seen that the case of the multirate is improved compared to the case of using a single rate.

As described above, according to the data transmission method of a multirate multihop wireless network, an optimal transmission speed of each transmitting node n _i is optimal using an intrasession network coding scheme in a multirate multihop wireless network. Since the transmission speed can be selected, the network throughput γ can be improved.

In addition, according to the present invention, the simultaneous transmission set CT _α is determined at each transmission node using an optimal transmission rate, and the throughput γ between the source node n _s and the destination node n _d is determined using a linear programming method. Since it can calculate, the change of the processing rate (gamma) in a multirate environment can be confirmed.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. I will understand. Accordingly, the technical scope of the present invention should be defined by the following claims.

n _s : source node
n _i : transport node
n _d : destination node
n _j : peripheral node

Claims (10)

Calculating, by each transmitting node constituting a multi-hop wireless network, an effective transmission rate for each of the plurality of transmission rates in a multirate environment in which any one of a plurality of transmission rates can be selected; And
Selecting, by each transmission node, an optimal transmission rate among the plurality of transmission rates based on the effective transmission rate as an optimal transmission rate. .
2. The method of claim 1, wherein each transmitting node transmits information in a network coding scheme.
3. The method of claim 2, wherein each transmitting node transmits information in an intrasession network coding scheme using the same source node and the same destination node.
2. The method of claim 1, wherein calculating the effective transmission rate
The effective transmission rate is calculated from a transmitting node close to a target node.
5. The method of claim 4, wherein the effective transmission rate is calculated based on the transmission rate and link transmission probability for each transmission rate.
5. The method of claim 4, wherein the effective transmission rate is calculated by reflecting a maximum effective transmission rate of neighboring nodes belonging to a transmission candidate node set.
delete The method of claim 1,
Selecting, by each transmitting node, a simultaneous transmission set based on the optimum transmission rate; And
And transmitting, by the transmitting node, information to the transmitting node selected as the simultaneous transmission set at the optimum transmission rate.
9. The method of claim 8, further comprising, after the step of transmitting said information:
Calculating a throughput of the multi-hop wireless network using a linear programming method.
10. The method of claim 9, wherein the throughput is calculated by reflecting a time scheduling condition of the simultaneous transmission set.

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