KR101534526B1 - Method of message delivery based on node density in delay tolerant network, recording medium and apparatus for performing the method - Google Patents

Abstract

Provided is a method for forwarding a message which adaptively determines a message forwarding scheme on each node in delay tolerant networks, and comprises the steps of: measuring the number (Ni) of periphery nodes connected into the forwarding radius of the node; comparing the number (Ni) of the periphery nodes of the node with a predetermined reference value (N) in case that the node is contacted with the other node; determining a message forwarding scheme for forwarding a message to the other node according to a comparison result of the number (Ni) of the periphery nodes and the reference value (N); and forwarding the message to the other node according to the determined message forwarding scheme. Accordingly, the entire message transfer rate can be increased by dynamically changing the message forwarding scheme according to the periphery node density and appropriately controlling diffusion of the message.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a node-density-based message delivery method in a delay-tolerant network, and a recording medium and a device for performing the same.

The present invention relates to a message delivery method based on node density in a delay-tolerant network, and a recording medium and an apparatus for performing the same. More particularly, And more particularly, to a message delivery method for efficiently delivering a message to a destination node according to a predetermined criterion, and a recording medium and an apparatus for performing the message delivery method.

Recently, a study on a Delay Tolerant Network (DTN) in which a connection between a calling node and a called node is not ensured is being actively researched. Since the end-to-end connection is not guaranteed in DTN, existing routing protocols that perform routing routines are not suitable, and new routing protocols based on Store-Carry-Forward are needed. In the DTN, each node stores a message to be transmitted in a buffer, and when it encounters another node, it forwards the message to the final destination by forwarding the stored message.

The DTN routing protocol is classified into a deterministic protocol applied in an environment that predicts changing network information and a dynamic protocol applied in an environment in which network information can not be predicted in advance. Among them, Epidemic routing protocol based on flooding scheme, PRoPHET routing protocol for performing probabilistic transmission using cumulative contact information of each node, and Spray step for carrying out retransmission with redundancy in the copy of message And a Spray and Wait protocol consisting of a Wait step that does not perform transmission until the destination node is reached using both the copy and the copy.

The epidemic routing protocol exchanges index information of messages with each other when a node is in contact with the network and delivers a message that the other party does not hold. And a packet loss may occur due to an increase in the probability of a wireless access collision.

The PRoPHET routing protocol transmits a message to a node with a high probability of delivery success probability based on the stored contact information when each node in the network contacts another node. It has a disadvantage that diffusion is slow and transmission rate is low. Also, if the density of nodes is low, the number of times the message is transmitted is smaller. Therefore, in a low-density environment of nodes, there is a possibility that a message to be transmitted can not be rapidly spread because of low opportunity for message transmission. Therefore, it is disadvantageous in that it is not suitable for a network in which the speed of the node is fast and the mobility is irregular.

The Spray and Wait protocol uses the Binary Spray and Wait protocol, which handles half of the remaining copies of the contact node. However, since the retransmission is performed only by a fixed amount, there is an advantage that the load is constant and the transmission success rate is good. However, the success rate may be lowered depending on the mobility of the node, and the extension range of the packet is limited.

KR 10-2013-0046612 A KR 10-2012-0045349 A

  X. Lu and P. Hui, "An Energy-efficient n-epidemic routing protocol for delay tolerant networks," IEEE International conference on networking, architecture, and storage, 2010.   "Modified Spray And Wait Protocol Based on Node Density in DTN Environment", Journal of Korea Information Science Society, Vol. 11, No. 1, pp. 91-99, January 2013.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide a message delivery method for adaptively determining a message delivery scheme in each node of a delay-

Another object of the present invention is to provide a recording medium for performing a message delivery method for adaptively determining a message delivery scheme at each node of the delay-admission network.

Yet another object of the present invention is to provide a message delivery device, which is provided in each node of a delay-allowed network and adaptively determines a message delivery scheme reflecting the density of peripheral nodes.

According to another aspect of the present invention, there is provided a message delivery method for adaptively determining a message delivery method in each node of a delay-allowed network, the method comprising: Ni); Comparing the number of surrounding nodes (Ni) of the node with a predetermined reference value (N) when the node contacts the other node; Determining a message delivery scheme for delivering a message to the other node according to a result of comparison between the number of surrounding nodes (Ni) and the reference value (N); And delivering a message to the other node according to the determined message delivery scheme.

According to an exemplary embodiment of the present invention, the step of determining a message delivery method for delivering a message to the other node according to a result of comparison between the number Ni of surrounding nodes and the reference value N may include: Determining whether the node transmits a message that is not present in the other node to the another node when the node Ni is smaller than or equal to the reference value N. [

According to an exemplary embodiment of the present invention, the step of determining a message delivery method for delivering a message to the other node according to a result of comparison between the number Ni of surrounding nodes and the reference value N may include: (N) is greater than the reference value (N), comparing the transfer probability value of the node with the destination of the other node; And determining that the node forwards its message to the other node when the transfer probability value for the destination of the other node is large.

In an exemplary embodiment of the present invention, the message delivery method may further include presetting the reference value N for adaptively determining the message delivery scheme.

In an embodiment of the present invention, the message delivery method further comprises the step of, when the node makes contact with another node, exchanging a message list including information on a message owned by the node with the other node .

In an embodiment of the present invention, the message delivery method may further include storing the number (Ni) of the measured peripheral nodes.

According to another aspect of the present invention, there is provided a computer-readable storage medium storing a computer program for performing a message delivery method for adaptively determining a message delivery method at each node of the delay- Is recorded.

According to another aspect of the present invention, there is provided a message delivery device provided at each node of a delay-allowed network for adaptively determining a message delivery method, the message delivery device including a message storage part; A density measuring unit for measuring the number (Ni) of surrounding nodes connected within the transmission radius of the node; A controller for comparing a number (Ni) of peripheral nodes of the node with a predetermined reference value (N) when the node makes contact with the other node, and determining a message delivery method for delivering the message to the other node; And a message delivery unit for delivering the stored message to the other node according to the determined message delivery scheme.

In an embodiment of the present invention, the control unit may further include: a comparison unit comparing the number of peripheral nodes (Ni) of the node with a preset reference value (N) when the node contacts the other node; And a determination unit for determining a message delivery scheme for delivering the message to the other node according to a result of comparison between the number of surrounding nodes (Ni) and the reference value (N).

In an embodiment of the present invention, the determination unit may determine the message delivery scheme to be an epidemic routing scheme when the number Ni of neighboring nodes is less than or equal to the reference value N, When the number of nodes (Ni) is larger than the reference value (N), the message delivery scheme can be determined as a PRoPHET routing scheme.

In an embodiment of the present invention, the control unit may further include a reference value setting unit for previously setting the reference value (N) for adaptively determining the message delivery scheme.

In the delay tolerant network, the node measures the number of neighboring nodes within the radius of the neighboring transmission, and if the number of neighboring nodes is less than the reference value, the node always delivers the message to the neighboring node in the Epidemic protocol. If the neighboring node exceeds the reference value, PRoPHET It compares the probability values in a protocol manner and delivers the message. In the present invention, since the density of neighboring nodes is low considering the density of neighboring nodes, message delivery of nodes having low message delivery opportunities can be smoothly performed, thereby increasing the overall message transmission rate. In addition, it is possible to adaptively apply the transmission method reflecting the transmission radius change with time.

1 is a block diagram of a message delivery device based on node density in a delay tolerant network according to an embodiment of the present invention.
2 and 3 are block diagrams of the control unit of FIG.
4 to 6 are flowcharts of a message delivery method based on node density in a delay-allowed network according to an embodiment of the present invention.

The following detailed description of the invention refers to the accompanying drawings, which illustrate, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It should be understood that the various embodiments of the present invention are different, but need not be mutually exclusive. For example, certain features, structures, and characteristics described herein may be implemented in other embodiments without departing from the spirit and scope of the invention in connection with an embodiment. It is also to be understood that the position or arrangement of the individual components within each disclosed embodiment may be varied without departing from the spirit and scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is to be limited only by the appended claims, along with the full scope of equivalents to which such claims are entitled, if properly explained. In the drawings, like reference numerals refer to the same or similar functions throughout the several views.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the drawings.

1 is a block diagram of a message delivery device based on node density in a delay tolerant network according to an embodiment of the present invention.

In the present invention, in the Delay Tolerant Network (DTN) including a plurality of nodes, the message delivery device 10 adaptively determines a message delivery method based on the surrounding node density. In the delay tolerant network, each node stores a message to be transmitted in a message storage unit in a way that the connection between the source node and the destination node is not guaranteed. When the node meets another node, .

Referring to FIG. 1, a message delivery apparatus 10 according to the present embodiment includes a message storage unit 110, a density measurement unit 130, a control unit 150, and a message delivery unit 170.

The message storage unit 110 includes a memory and stores programs and data required for the operation of the message delivery apparatus 10 and data generated during operation of the message delivery apparatus 10 in a memory.

For example, the message storage unit 110 stores a message to be transmitted to another node in a memory. The message storage unit 110 may store a message list (summary vector) stored by the node. The message and message list stored in the message storage unit 110 may be exchanged when they are in contact with another node. Some or all of the message copies generated from the messages stored in the message storage unit 110 may be transmitted to the other node.

The density measuring unit 130 measures the node density around the node. To this end, the density measuring unit 130 may count the number (Ni) of surrounding nodes connected within a predetermined transmission radius of the node. The predetermined transmission radius can be preset and can be changed over time. The number (Ni) of the counted surrounding nodes may be stored in a memory (not shown) inside the density measuring unit 130.

When the node contacts the other node, the controller 150 compares the number Ni of neighbor nodes of the node with a predetermined reference value N, and transmits a message delivery method .

2, the control unit 150 includes a comparison unit 153 for comparing the number Ni of neighbor nodes of the node with a preset reference value N, a number Ni of neighboring nodes, And a determination unit 155 for determining a message delivery method for delivering a message to the other node according to the comparison result of the reference value N. [

3, the control unit 150 may further include a reference value setting unit 151 for previously setting the reference value N for adaptively determining a message transmission scheme. The reference value N is the number of reference nodes existing around each node, for example, within a predetermined transmission radius.

When the number Ni of surrounding nodes is smaller than or equal to the reference value N as a result of comparing the number Ni of surrounding nodes of the node with a preset reference value N, Decides to copy and forward the message that is not present in the other node.

That is, when the ambient density of the node is low (when the number of neighboring nodes is less than the set reference value), it is determined that the chance of message delivery is low due to low density around the node. Exchange messages, and copy messages that do not belong to the other party.

If the number Ni of neighboring nodes is greater than the reference value N as a result of comparing the number Ni of neighbor nodes of the node with a preset reference value N, And the delivery predictability of the destination of the other node, and determines that the node transmits its message to the other node only when the delivery probability value for the destination of the other node is large.

That is, when the number of neighboring nodes is larger than the set reference value, that is, when the circumference density of the node is high, it is determined that the message transmission opportunity is appropriate, and the neighboring node, such as the PRoPHET (History of Encounters and Transitivity) And the probability value of the destination of the message are compared with each other and the message is transmitted.

The message delivery unit 170 copies the message stored in the message storage unit 110 according to the message delivery method determined by the controller 150 and delivers the message to the other node.

Thus, since the message delivery apparatus 10 according to the present invention reflects the situation around the node, that is, it transmits a message according to the node density, it can diffuse more messages when the density of the nearby nodes is low in the transmission radius have. In addition, when the density of neighboring nodes is high, it is possible to prevent the disconnection of the message transmission by comparing the probability values and to reliably transmit the messages, to prevent the situation where the message is not spread well due to the node density, .

4 to 6 are flowcharts of a message delivery method based on node density in a delay-allowed network according to an embodiment of the present invention.

The message delivery method according to the present embodiment can be performed in substantially the same configuration as the message delivery device 10 of FIG. Therefore, the same components as those of the message delivery device 10 of FIG. 1 are denoted by the same reference numerals, and repeated descriptions are omitted.

Referring to FIG. 4, a method for transmitting a message according to an embodiment of the present invention includes: measuring the number Ni of surrounding nodes connected within a radius of the node (step S30); when the node contacts another node (Step S50) of comparing the number Ni of surrounding nodes of the node with a preset reference value N, and determining whether the number of neighboring nodes (Step S70), and delivering the message to the other node according to the determined message delivery method (step S90).

5, in order to adaptively determine a message delivery scheme, the reference value N may be set in advance (step S11). The reference value N is the number of nodes around each node, for example, a reference within a predetermined radius of transmission.

Each node checks whether a neighboring node is detected (step S13), and if there is no neighboring node, it can check at regular intervals. Alternatively, the process may return to step S11 to set the reference value N again.

On the other hand, when neighboring nodes are detected around each node, the number of neighboring nodes (Ni) connected within the radius of the node is measured (step S31). Each node can store the number of measured neighbor nodes (Ni).

Thereafter, when the node makes contact with another node (step S41), the number Ni of surrounding nodes of the node is compared with a preset reference value N (step S51). To do this, the node can exchange its own message list with the other node (step S43).

In step S51, a message delivery method for delivering a message to the other node is determined according to a result of comparing the number of peripheral nodes (Ni) with the reference value (N), and the message is delivered to the other node (step S85 And step S80).

If the number Ni of surrounding nodes is smaller than or equal to the reference value N, the node copies and delivers a message that is not present in the other node (step S85). That is, when the number Ni of neighboring nodes is less than or equal to the reference value N, it is determined that the chance of message delivery is low due to a low density around the node, and a message is copied to the correspondent node contacted by the epidemic routing method It sends it.

On the other hand, if the number Ni of surrounding nodes is greater than the reference value N, the node compares the transmission probability value with the destination of the other node (step S81). As a result of the comparison in the step S81, only when the transfer probability value for the destination of the other node is large, the node delivers its message to the other node (S83).

That is, when the number of neighboring nodes (Ni) is larger than the reference value (N), the message is copied and transmitted only when the delivery predictability of the node contacted by the PRoPHET routing method is larger.

If the number Ni of surrounding nodes is smaller than or equal to a preset reference value N by comparing the number Ni of neighbor nodes of the node with the reference value N, If the number of neighboring nodes (Ni) is larger than the reference value (N), the probability value of the other node in contact with the other node is compared to transmit the message only when the probability of the other node is higher.

In the present invention, the Epidemic routing method and the PRoPHET routing method are dynamically selected according to the node density, and if the number of neighbor nodes of the node is less than the reference value, it operates in an Epidemic manner so that transmission can be more actively performed. .

The PRoPHET protocol is based on the fact that nodes visit more frequently based on previous movement patterns rather than random movements. In the PRoPHET protocol, the delivery predictability P _{(a, b)} having _a value between 0 and 1 for all the destination nodes b at each node a is defined as shown in Equation (1 ₎ below.

[Equation 1]

In Equation (1), P _{(a, b) old} is a previously stored transfer probability value, and P _init is an initial probability value having a value between 0 and 1. If the two nodes do not contact each other for a long time, the transfer probability values of the two nodes are reduced, so that the transfer probability value is expressed by the following equation.

&Quot; (2) "

If the node a frequently contacts the node b and the node b frequently contacts the node c, the probability that the node a and the node c frequently contact each other is large. Therefore, the transfer probability value between the node a and the node c can be expressed by the following equation .

&Quot; (3) "

In Equation (3),? Corresponds to a scaling factor having a value between 0 and 1. In the PRoPHET protocol, two nodes exchange summary vectors similar to the Epidemic protocol when they are in contact, exchanging the delivery probability values of each node. Each node uses this information to update its own delivery probability value, and the message is delivered to the node having a larger delivery probability value as the destination.

The forwarding method of the PRoPHET protocol is advantageous in that it transmits the message only when the probability of the destination node of the other node is high by comparing the probability with respect to each of the contact nodes, and carries out careful message transmission. On the other hand, since there are disadvantages that the number of message relays is small and message spread is slow, and when the density of the surrounding nodes is low, the number of times of message transmission is smaller. The message to be transmitted may not be spread quickly.

In the present invention, the Epidemic protocol and the PRoPHET protocol are dynamically selected and transmitted according to the node density according to the circumference of the node. In other words, when the density of peripheral nodes in the transmission radius is low, more messages are spread using the Epidemic protocol. In the case where the density of peripheral nodes is high, reliable transmission is performed using the PRoPHET protocol to prevent disconnection And the message is not spread well due to the node density, thereby facilitating the message transmission, thereby increasing the overall message transmission rate.

In the above-described delay tolerant network, the node density-based message delivery method may be implemented in the form of program instructions that can be executed through various computer components and recorded in a computer-readable recording medium. The computer-readable recording medium may include program commands, data files, data structures, and the like, alone or in combination.

The program instructions recorded on the computer-readable recording medium may be ones that are specially designed and configured for the present invention and are known and available to those skilled in the art of computer software.

Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks and magnetic tape, optical recording media such as CD-ROMs and DVDs, magneto-optical media such as floptical disks, media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like.

Examples of program instructions include machine language code such as those generated by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware device may be configured to operate as one or more software modules for performing the processing according to the present invention, and vice versa.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims. You will understand.

In the message delivery method according to the present invention, each node measures and stores the number of neighbor nodes currently connected to the node, and determines a message delivery method according to the number of neighboring neighbor nodes. When the number of neighboring nodes is less than the set reference value, it is determined that the chance of message delivery is low due to a low density around the node. Thus, the message list is exchanged for every contact node, such as the epidemic routing method.

On the other hand, when the number of neighboring nodes is larger than the set reference value, that is, when the density of the node is high, it is determined that the message transmission opportunity of the node is appropriate. Thus, as in the PRoPHET routing method, predictability) and transmits the message. As a result, compared with the conventional PRoPHET protocol, more messages can be transmitted, but proper transmission standards can be established to prevent excessive overhead and latency and improve the transmission rate, .

10: message delivery device 110: message storage
130: density measuring unit 150:
170: message transferring unit 151: reference value setting unit
153: comparison unit 155:

Claims (11)

A message delivery method for adaptively determining a message delivery scheme at each node of a delay-allowed network,
Measuring the number of surrounding nodes (Ni) connected within the transmission radius of the node;
Setting a reference value (N) for adaptively determining the message delivery scheme;
Comparing the number of peripheral nodes (Ni) of the node with the reference value (N) when the node contacts the other node;
Determining a message delivery scheme for delivering a message to the other node according to a result of comparison between the number of surrounding nodes (Ni) and the reference value (N); And
And delivering the message to the other node according to the determined message delivery method.
2. The method of claim 1, wherein determining a message delivery scheme for delivering a message to the other node according to a result of comparison between the number of surrounding nodes (Ni) and the reference value (N)
Determining if the number of neighboring nodes (Ni) is less than or equal to the reference value (N), to forward the message that the node does not have to the other node to the other node.
2. The method of claim 1, wherein determining a message delivery scheme for delivering a message to the other node according to a result of comparison between the number of surrounding nodes (Ni) and the reference value (N)
Comparing a transfer probability value of the node with a destination of the other node when the number Ni of neighboring nodes is greater than the reference value N; And
And determining that the node should forward its message to the other node if the delivery probability value for the destination of the other node is large.
delete The method according to claim 1,
Further comprising the step of: if the node is in contact with another node, the node exchanges a message list containing information about the message it owns with the other node.
The method according to claim 1,
Wherein the node further comprises storing a number (Ni) of the measured peripheral nodes.
A computer program for performing a message delivery method for adaptively determining a message delivery scheme at each node of a delay grant network according to any one of claims 1 to 3 and 5 to 6, Readable recording medium.
A message delivery apparatus provided in each node of a delay-allowed network for adaptively determining a message delivery scheme,
A message storage unit for storing a message to be transmitted to another node;
A density measuring unit for measuring the number (Ni) of surrounding nodes connected within the transmission radius of the node;
A comparison unit comparing a number Ni of surrounding nodes of the node with a predetermined reference value N when the node contacts the other node and comparing the number Ni of the surrounding nodes with the reference value N And a determination unit determining a message delivery scheme for delivering the message to the other node according to a result of the determination. And
And a message delivery unit for delivering the stored message to the other node according to the determined message delivery method.
delete 9. The apparatus according to claim 8,
Determining the message delivery scheme to be an epidemic routing scheme when the number Ni of neighbor nodes is less than or equal to the reference value N,
And determines the message delivery scheme to be a PRoPHET routing scheme when the number of neighbor nodes (Ni) is greater than the reference value (N).
9. The apparatus according to claim 8,
Further comprising a reference value setting unit for presetting the reference value (N) for adaptively determining the message delivery scheme.

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