CN103096412A - Data fusion method with time delay restriction in delay tolerant network - Google Patents

Abstract

Provided is a data fusion method with a time delay restriction in a delay tolerant network. The data fusion method with the time delay restriction in the delay tolerant network comprises the following steps: a plurality of movable and capable of starting wireless communication nodes are initially arranged in a detecting area, and then utilizing historical information met with the nodes to acquire the encounter time distribution of the nodes, discovering the average time and the shortest path from each node from root nodes as a topological structure of data route, accordingly a data route tree; under the restriction of the total time delay, distributing the optimizing time of waiting children nodes for each node of a data fusion tree, and enabling the objective nodes to ultimately collect the maximum expected value of data quantity; in the process of collecting the data, if current time surpasses the longest waiting time of the nodes, then the nodes combine the data which are collected by the nodes and the data which are produced by the nodes, and the data is transmitted father nodes of the next time encounter, otherwise, the data of own children nodes are continuously waited by the nodes. The data fusion method with the time delay restriction in the delay tolerant network utilizes the encounter characteristic between the nodes, acquires better transmission success ratio than other route protocols, reduces the times of data transmission simultaneously and saving network transmission cost.

Description

In delay-tolerant network with the data fusion method of delay constraint

Technical field

What the present invention relates to is delay-tolerant network, be specifically related to be in a kind of delay-tolerant network with the data fusion method of delay constraint, belong to networking technology area.

Background technology

Delay-tolerant network (Delay Tolerant Networks, DTNs) refer to the network that a class is special, in such network, be difficult to set up the path of an end-to-end lasting connection, message in network is all to transmit in the mode of " carry-and-forward " usually, thereby the time-delay of propagating is larger.The application scenario of time-delay tolerant network is many at present, such as: disaster recovery, inter-vehicular communication, wildlife tracking etc.

In delay-tolerant network, due to the movement of node or the loose line of network itself, cause the internodal chance of meeting very limited, therefore how effectively to utilize these scarce resources to make data success forward rate increase and become very important.Can learn by analyzing MIT Reality data set, the number of times that on average meets in two nodes one day is 0.024 time.And Data fusion technique is having good performance aspect the minimizing communication overhead, and it is a variety of that its way of realization has, and what we comparatively were familiar with has: max, min, count, average etc.The usage data fusion method can be removed the redundant information that exists in initial data, thereby the communication information of whole network also greatly reduces thereupon.

Due to the limitation of delay-tolerant network self character, adopt the data fusion method with delay constraint to be faced with many difficulties, as: 1, network delay is large, and internodal meeting normally cannot be predicted.2, connect unstablely, because the mobility of node, dormancy dispatching or self-energy are considered, the connection between node is discontinuity normally.3, there is no stable access path end to end.4, how long the node how to confirm just goes out the data retransmission of collecting, and whom is transmitted to if should waiting.5, how to guarantee having repetition sensitiveness in fusion process, namely same piece of data can not repeatedly appear in the fused data bag.

In the static sensor network, have the method that many relevant datas merge to put forward, but they are under and connective good prerequisite constant in network topology structure.Although in vehicle network, have the method that some relevant datas merge to be suggested recently, they do not consider Data duplication sensitiveness, do not consider the problem of data fusion under limited delay constraint yet yet.

Summary of the invention

The object of the invention is to overcome the deficiency that prior art exists, data fusion method with delay constraint is provided in a kind of delay-tolerant network, it is for the extremely limited characteristic of the delay-tolerant network communication resource, data transmission performance from network, in conjunction with the network node feature of meeting, realize having and highly repeat sensitiveness, do not affect the data retransmission success rate, greatly reduce the data fusion of expense all night.

The present invention solves its technical problem by the following technical programs:

With the data fusion method of delay constraint, it is characterized in that in a kind of delay-tolerant network, comprise the following steps:

The first step, network design, in the surveyed area of delay-tolerant network, dispose some movably nodes that can carry out radio communication, it is the root node of collecting data that other nodes produce that a node is wherein arranged, and the data that other nodes produce all must be transferred to this root node;

Second step, netinit, in the time of one section of node motion after, analyze the historical data of meeting between every two nodes, obtain the distribution at the Encounter Time interval between every two nodes.

The structure of the 3rd step, Data Fusion Tree, claim a figure with network modelling, limit in figure between node is meeting between node, the weights on limit are the average time interval w=1/ λ that node meets, wherein λ is the internodal phase encountering rate that is obtained by described second step, use the Dijsktra algorithm to calculate each node to the shortest path of root node, namely obtain Data Fusion Tree;

The 4th goes on foot, determines that on described Data Fusion Tree, each node is waited for the optimum wait time that receives its child nodes data, the amount of information that described root node is finally collected is maximum, the stand-by period of this root node is the given maximum delay of system, and the stand-by period of other nodes must be less than the stand-by period of root node;

The forwarding of the 5th step, data, if a node runs into other nodes, at first check whether the node that runs into is father's node of this node, if, then check the maximum wait time of oneself, if the current time, this node was done fusion with own local data and the data of collecting, and is transmitted to father's node greater than the stand-by period of this node; Otherwise the data of other child nodes are waited in continuation; Each node repeats said process, until with data retransmission to root node.

The optimum wait time that upper each node wait of specified data fusion tree described in the 4th step receives its child nodes data refers to: under limited delay constraint, data-oriented merges tree, target is to make the problem of the amount of information maximum that root node collects have optimum minor structure, and is

$m[i,{\mathrm{\&tau;}}_i]=\left\{\begin{array}{cc}\underset{j\&Element;C\left(i\right)}{\mathrm{\&Sigma;}}\underset{0<{\mathrm{\&tau;}}_j<{\mathrm{\&tau;}}_i}{\max }\left\{m\right[j,{\mathrm{\&tau;}}_j]\&CenterDot;p_{\mathrm{ji}}\}+1,& C\left(i\right)\&NotEqual;0,\\ 1,& C\left(i\right)=0,\end{array}\right.$

Wherein, m[i, τ _i] represent that the stand-by period when node i is τ _iThe time, the maximum fault information that node i can be collected is supposed that here the amount of information that each node produces equates, and is 1,

The child nodes set of C (i) expression node i,

When node i is leaf node, its amount of information only comprise it and also be 1,

When i is intermediate node, its maximum fault information of collecting expectation summation that is all child nodes maximum fault informations,

0＜τ _i＜τ _iGuarantee that the stand-by period of child nodes is less than the stand-by period of father's node;

Then, determine that node j is at time window [τ _j, τ _i] in, data successfully are transmitted to the Probability p of i _ji:

$p_{\mathrm{ij}}=F(w_{\mathrm{ij}},{\mathrm{\&lambda;}}_{\mathrm{ij}})=1-e^{-{\mathrm{\&lambda;}}_{\mathrm{ij}}{w}_{\mathrm{ij}}},,$

Wherein, w=τ _i-τ _jLength for time window.

The invention has the advantages that:

(1) data fusion method of the present invention can in the situation that delay-tolerant Network Communication resource is very nervous, when guaranteeing network communication quality, reduce cost on network communication.

(2) the present invention has good repetition sensitiveness, can guarantee that all data are at most only merged once.

Description of drawings

Fig. 1 is network model of the present invention.

Fig. 2 is method flow diagram of the present invention.

Embodiment

The below elaborates to enforcement of the present invention, and the present embodiment has provided detailed implementation method and specific operation process take the invention technical scheme as prerequisite, but protection scope of the present invention is not limited to following embodiment.

The present invention is directed to the delay-tolerant network communication resource extremely limited, from the data transmission performance of network, in conjunction with the network node feature of meeting, realized a kind of data fusion method that does not affect the data retransmission success rate, greatly reduces communication overhead.Encounter Time in setting network between every two nodes is spaced apart exponential distribution, and this was proved in other documents.Detailed step with the data fusion method of delay constraint in described delay-tolerant network is as follows:

The first step, network design: in the surveyed area of delay-tolerant network, dispose some movably, can carry out the node (such as sensor node) of radio communication, wherein there is a node to be used for collecting the data that other nodes produce, be called root node (collector node), that is to say that the data that other nodes produce all must be transferred to this root node.

Second step, netinit: after in the time of one section of node motion, analyze the historical data of meeting between every two nodes, obtain the distribution at the Encounter Time interval between every two nodes.

The structure of the 3rd step, Data Fusion Tree: Data Fusion Tree is the topological structure of node-routing namely, and collector node is root node; Claim a figure with network modelling, the limit in figure between node is meeting between node, and the weights on limit are the average time interval w=1/ λ that node meets, and wherein λ is internodal phase encountering rate, can obtain by the second step step; Next, use the Dijsktra algorithm to calculate each node to the shortest path of root node, so just obtained a shortest path tree, i.e. described Data Fusion Tree.

The 4th step, specified data merge upper each node of tree waits for the optimum wait time that receives its child nodes data, and the amount of information that final root node is collected is maximum; The stand-by period of root node is the given maximum delay of system, and the stand-by period of other nodes must be less than root node; The below provides the process of optimum wait time how to estimate each node: by analysis, under limited delay constraint, make the problem of the amount of information maximum that root node collects have optimum minor structure, and be

$m[i,{\mathrm{\&tau;}}_i]=\left\{\begin{array}{cc}\underset{j\&Element;C\left(i\right)}{\mathrm{\&Sigma;}}\underset{0<{\mathrm{\&tau;}}_j<{\mathrm{\&tau;}}_i}{\max }\left\{m\right[j,{\mathrm{\&tau;}}_j]\&CenterDot;p_{\mathrm{ji}}\}+1,& C\left(i\right)\&NotEqual;0,\\ 1,& C\left(i\right)=0,\end{array}\right.$

Wherein, m[i, τ _i] represent that the stand-by period when node i is τ _iThe time, the maximum fault information that node i can be collected is supposed that here the amount of information that each node produces equates, and is 1,

The child nodes set of C (i) expression node i,

When node i is leaf node, its amount of information only comprise it and also be 1,

When i is intermediate node, its maximum fault information of collecting expectation summation that is all child nodes maximum fault informations,

0＜τ _i＜τ _iGuarantee that the stand-by period of child nodes is less than the stand-by period of father's node.

Next be how to ask node j at time window [τ _j, τ _i] in, data successfully are transmitted to the Probability p of i _jiIf the stand-by period of node j and its father's node i is respectively τ _j, τ _i, the time window of the transmission message of the permission of node j is [τ like this _j, τ _i], because node j only just can be gone out the data retransmission of oneself over the stand-by period of oneself in the time, and node i waits for that own child's maximum duration also is no more than τ _iBecause the Encounter Time of node is spaced apart exponential distribution, therefore node j is at time window [τ _j, τ _i] the interior Probability p that data successfully is transmitted to i _jiFor

W=τ _i-τ _jLength for time window.

The repeating process of the 5th step, data a: if node runs into other nodes, at first check whether the node that runs into is the father's node of oneself, if, then check the maximum wait time of oneself, if the current time is greater than the stand-by period of oneself, node is done fusion with own local data and the data of collecting so, is transmitted to father's node; Otherwise the data of other child nodes are waited in continuation.Each node repeats said process, until with data retransmission to root node.

Claims (2)

1. In a delay-tolerant network with the data fusion method of delay constraint, it is characterized in that, comprise the following steps:

   The first step, network design, in the surveyed area of delay-tolerant network, dispose some movably nodes that can carry out radio communication, it is the root node of collecting data that other nodes produce that a node is wherein arranged, and the data that other nodes produce all must be transferred to this root node;

   Second step, netinit, in the time of one section of node motion after, analyze the historical data of meeting between every two nodes, obtain the distribution at the Encounter Time interval between every two nodes.

   The structure of the 3rd step, Data Fusion Tree, claim a figure with network modelling, limit in figure between node is meeting between node, the weights on limit are the average time interval w=1/ λ that node meets, wherein λ is the internodal phase encountering rate that is obtained by described second step, use the Dijsktra algorithm to calculate each node to the shortest path of root node, namely obtain Data Fusion Tree;

   The 4th goes on foot, determines that on described Data Fusion Tree, each node is waited for the optimum wait time that receives its child nodes data, the amount of information that described root node is finally collected is maximum, the stand-by period of this root node is the given maximum delay of system, and the stand-by period of other nodes must be less than the stand-by period of root node;

   The forwarding of the 5th step, data, if a node runs into other nodes, at first check whether the node that runs into is father's node of this node, if, then check the maximum wait time of oneself, if the current time, this node was done fusion with own local data and the data of collecting, and is transmitted to father's node greater than the stand-by period of this node; Otherwise the data of other child nodes are waited in continuation; Each node repeats said process, until with data retransmission to root node.
2. In delay-tolerant network according to claim 1 with the data fusion method of delay constraint, it is characterized in that, the optimum wait time of determining each its child nodes data of node wait reception on described Data Fusion Tree in described the 4th step refers to: under limited delay constraint, data-oriented merges tree, target is to make the problem of the amount of information maximum that root node collects have optimum minor structure, and is

   $m[i,{\mathrm{\&tau;}}_i]=\left\{\begin{array}{cc}\underset{j\&Element;C\left(i\right)}{\mathrm{\&Sigma;}}\underset{0<{\mathrm{\&tau;}}_j<{\mathrm{\&tau;}}_i}{\max }\left\{m\right[j,{\mathrm{\&tau;}}_j]\&CenterDot;p_{\mathrm{ji}}\}+1,& C\left(i\right)\&NotEqual;0,\\ 1,& C\left(i\right)=0,\end{array}\right.$

   Wherein, m[i, τ _i] represent that the stand-by period when node i is τ _iThe time, the maximum fault information that node i can be collected is supposed that here the amount of information that each node produces equates, and is 1,

   The child nodes set of C (i) expression node i,

   When node i is leaf node, its amount of information only comprise it and also be 1,

   When i is intermediate node, its maximum fault information of collecting expectation summation that is all child nodes maximum fault informations,

   0＜τ _i＜τ _iGuarantee that the stand-by period of child nodes is less than the stand-by period of father's node;

   Then, determine that node j is at time window [τ _j, τ _i] in, data successfully are transmitted to the Probability p of i _ji:

   $p_{\mathrm{ij}}=F(w_{\mathrm{ij}},{\mathrm{\&lambda;}}_{\mathrm{ij}})=1-e^{-{\mathrm{\&lambda;}}_{\mathrm{ij}}{w}_{\mathrm{ij}}},,$

   Wherein, w=τ _i-τ _jLength for time window.

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