KR20200093752A - Apparatus and method for controlling time-synch of node - Google Patents

Abstract

According to the present invention, a node time synchronization control apparatus may comprise: a synchronization information transmitting and receiving unit for sharing synchronization information by spreading a message including the synchronization information to neighboring nodes in a network; a network time reference (NTR) selection unit which selects one of the plurality of neighboring nodes or an own node as a reference node and selects an NTR; a first time synchronization correction unit for performing time synchronization correction of the own node based on the NTR of the selected reference node; and a second time synchronization correction unit for performing distributed time synchronization correction of the own node based on the synchronization information received from the plurality of neighboring nodes.

Description

Node time synchronization control device and its method{APPARATUS AND METHOD FOR CONTROLLING TIME-SYNCH OF NODE}

The present invention relates to a technique for controlling time synchronization of a node in a network, and more specifically, time synchronization between nodes based on hybrid time synchronization combining a reference node-based time synchronization protocol and a distributed time synchronization protocol. It relates to a node time synchronization control device and method that can control the.

As is known, in various types of networks, such as mobile ad-hoc networks, sensor networks, and military tactical networks, it is essential to keep time synchronization between communication nodes in order to obtain accurate information.

In addition, time synchronization between communication nodes is essential to support a communication protocol such as Time Division Multiple Access (TDMA).

In general, in the case of a base station-based cellular network, a base station periodically transmits a preamble for time synchronization between communication nodes and synchronizes the time of each node based on this.

On the other hand, in the case of an ad-hoc network in which a base station does not exist, a node including a preamble is transmitted from a node to be transmitted and a receiving node adjusts time synchronization based on this.

However, in the ad-hoc network, unlike the base station, since each node's own time accuracy decreases, and errors accumulate through multiple hops in multiple stages, the node to be transmitted using the preamble is one slot boundary when it is transmitted. There is a problem that it is difficult to accurately determine within the (slot boundary).

In addition, in the ad-hoc network, even when a node acquires data, it is difficult to find an accurate acquisition point.

Therefore, due to the above-mentioned reasons, in the ad-hook and sensor networks, even when a preamble is used, global time synchronization between nodes is additionally required, and such global time synchronization is mainly a timestamp between nodes. ).

Here, the method of achieving time synchronization of the network based on the time stamp can be roughly divided into two methods. For example, there are a reference node based time synchronization protocol and a consensus based distributed time synchronization protocol.

First, the reference node-based time synchronization protocol is a method of selecting a reference node (root node) in a network and synchronizing the time of the remaining nodes based on a timestamp of the reference node.

In addition, the consensus-based distributed time synchronization protocol corrects time synchronization by averaging time stamp information of neighboring nodes including itself after each node periodically exchanges a time synchronization message (Beacon) including a time stamp in a distributed manner. Is the way to do it. That is, in the distributed time synchronization based on consensus, it is possible to achieve time synchronization by spreading the average value of the time synchronization information between neighboring nodes of each node throughout the network. This consensus-based distributed time synchronization model is characterized by high utilization in a flexible network and relatively high time synchronization accuracy among neighboring nodes, as it does not require a reference node (root node) as a reference.

Here, as a reference node-based time synchronization protocol, for example, FTSP (Flooding Time Sychronization Protocol), PulseSync, Glossy, etc. are representative, and as a consensus-based distributed time synchronization protocol, for example, GTSP (Gradient Time Synchronization Protocol), MTS , ATS, etc. are typical.

First, in the consensus-based time synchronization protocol, unlike the reference node-based time synchronization protocol that matches the time synchronization of all nodes based on one node, there is no node to be used as a reference node, and furthermore, all of the nodes in the network. There is a problem in that the synchronization completion time is relatively long because the time synchronization needs to be adjusted.

In addition, the time synchronization protocol based on consensus has a problem that energy consumption is excessive due to the need to periodically transmit unnecessary time synchronization messages even in a stable situation without a time synchronization error because the time synchronization period is statically fixed. .

That is, in the consensus-based time synchronization protocol, since time synchronization messages are averaged after receiving the time synchronization messages from neighbor nodes within 1 hop, the shorter the time synchronization period, the shorter the synchronization completion time, but the larger the number of time synchronization messages must be transmitted. Energy consumption increases.

Conversely, the time synchronization protocol based on consensus has a problem in that energy consumption decreases when the time synchronization period increases, whereas the synchronization completion time required to achieve time synchronization of the entire network increases.

Korean Registered Patent No. 10-1788196 (Notice: 2017. 10. 19.)

The present invention provides a node time synchronization control apparatus and method in a network capable of controlling time synchronization between nodes based on hybrid time synchronization combining a reference node based time synchronization protocol and a distributed time synchronization protocol. Want to provide

The present invention is based on a hybrid time synchronization that combines a reference node-based time synchronization protocol and a distributed time synchronization protocol to store a computer program that allows a processor to perform a node time synchronization control method in a network capable of controlling a node's time synchronization. It is intended to provide a computer-readable recording medium.

The problem to be solved by the present invention is not limited to those mentioned above, and another problem to be solved that is not mentioned can be clearly understood by a person having ordinary knowledge to which the present invention belongs from the following descriptions. will be.

According to an aspect of the present invention, a synchronization information transmitting/receiving unit for sharing synchronization information by propagating a message including synchronization information to neighboring nodes in a network, and one or a plurality of neighboring nodes as a reference node An NTR selection unit for selecting and selecting a network time reference (NTR), a first time synchronization correction unit for performing time synchronization correction of the own node based on the selected NTR of the reference node, and the plurality of Based on the synchronization information received from the neighboring nodes, it is possible to provide a node time synchronization control device including a second time synchronization correction unit for performing distributed time synchronization correction of the own node.

The synchronization information transmitting and receiving unit of the present invention can propagate the message including its own synchronization information to neighboring nodes of one hop.

The NTR selection unit of the present invention may select a node having a minimum ID among the own node and the plurality of neighboring nodes as the reference node.

The NTR selection unit of the present invention compares the relative ID of the specific node with the own ID of the own node if there is a specific node that is already operating based on the NTR, and if the relative ID is faster than the own ID, the specific node Is selected as the reference node, and if the identity ID is faster than the relative ID, the identity node may be selected as the reference node.

The present invention, after the NTR is selected, monitors whether or not the NTR deviates, and if a deviation is detected, generates NTR deviation information, propagates it to the plurality of neighboring nodes, initializes the state of the own node, and then the A node management unit that redistributes the synchronization information may be further included.

The second time synchronization correcting unit of the present invention may correct synchronization information of the own node by using an average value of synchronization information collected from the plurality of neighboring nodes.

The network of the present invention may be a mobile ad-hoc network (MANET) or a sensor network.

According to another aspect of the present invention, a method of sharing synchronization information by propagating a message including synchronization information to neighboring nodes in a network, and selecting one or a plurality of neighboring nodes as a reference node as a reference node Selecting a network time reference (NTR), performing time synchronization correction of the own node based on the selected NTR of the reference node, and synchronizing information received from the plurality of neighboring nodes. Based on this, it is possible to provide a node time synchronization control method comprising the step of performing distributed time synchronization correction of the own node.

The sharing step of the present invention may propagate the message including its own synchronization information to one-hop neighbor nodes.

In the selecting step of the present invention, the node having the minimum ID among the own node and the plurality of neighboring nodes may be selected as the reference node.

In the selecting step of the present invention, if there is a specific node that is already operating based on the NTR, comparing the relative ID of the specific node with the identity of the identity of the identity node, and as a result of comparison, the identity of the identity is the identity of the identity. If it is faster than the ID, the step of selecting the specific node as the reference node, and as a result of the comparison, if the user ID is faster than the relative ID, may include the step of selecting the user node as the reference node.

The present invention, after the NTR is selected, monitoring whether or not the NTR deviates, and when the deviation is detected, generates NTR departure information and propagates it to the plurality of neighboring nodes, and then the status of the own node It may further include the step of initializing and re-executing the process from the sharing step.

In the step of performing the correction of the distributed time synchronization of the present invention, the synchronization information of the own node may be corrected using an average value of synchronization information collected from the plurality of neighboring nodes.

According to another aspect of the present invention, a computer readable recording medium storing a computer program for causing a processor to perform a node time synchronization control method, wherein the node time synchronization control method comprises: Sharing synchronization information by propagating to neighboring nodes; selecting a network time reference (NTR) by selecting one or a plurality of neighboring nodes as a reference node; and selecting the selected reference node. Comprising the steps of performing the time synchronization correction of the own node, and performing distributed time synchronization correction of the own node based on the synchronization information received from the plurality of neighboring nodes, according to the NTR of It is possible to provide a readable recording medium.

According to an embodiment of the present invention, by controlling (correcting) time synchronization between nodes based on hybrid time synchronization combining a reference node-based time synchronization protocol and a distributed time synchronization protocol, convergence of time synchronization of nodes It can reduce the time and improve the time accuracy of one hop.

1 is a block diagram of a node time synchronization control device in a network according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating a main process of performing time synchronization based on hybrid time synchronization in which reference node-based time synchronization and distributed time synchronization are combined according to an embodiment of the present invention.
3 is an exemplary conceptual diagram illustrating a principle of propagating a message including synchronization information to neighboring nodes based on a reference node according to an embodiment of the present invention.
FIG. 4 is an exemplary diagram for explaining the principle of performing distributed time synchronization correction using synchronization information received from a plurality of neighboring nodes.
5 is an exemplary diagram of a topology for verifying a time synchronization technique.
6 is an exemplary environment for simulating a time synchronization technique.
7 is an exemplary diagram of an application scenario according to a topology change.
8 is a timing diagram exemplarily showing that the maximum error and the average error change with propagation time.
9 is an exemplary view showing an average error and a maximum error for each section.

Advantages and features of the present invention, and methods for achieving them will be clarified with reference to embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various forms, and only these embodiments allow the disclosure of the present invention to be complete, and have ordinary knowledge in the art to which the present invention pertains. It is provided to fully inform the person of the scope of the invention, and the scope of the invention is only defined by the claims.

In describing the embodiments of the present invention, detailed descriptions of known functions or configurations will be omitted except when actually necessary in describing the embodiments of the present invention. In addition, terms to be described later are terms defined in consideration of functions in an embodiment of the present invention, which may vary according to a user's or operator's intention or practice. Therefore, the definition should be made based on the contents throughout this specification.

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

1 is a block diagram of a node time synchronization control device in a network according to an embodiment of the present invention, an information transmitting and receiving unit 102, a network time reference (NTR) selection unit 104, a first time synchronization correction unit (106), the second time synchronization correction unit 108 and the node management unit 110. Here, the node time synchronization control device may be included in each node.

Referring to FIG. 1, the information transmitting and receiving unit 102 generates a message (eg, a timestamp message for correcting a time synchronization of a node) including its own synchronization information at a predetermined period, and neighboring nodes adjacent to the network. A function (e.g., a function of sharing synchronization information) such as propagating (broadcasting) data to neighbor nodes and receiving messages of each neighboring node (not shown) is stored in memory Can provide. Here, the network may be, for example, a mobile ad-hoc network (MANET) or a sensor network.

In addition, propagation of a message including synchronization information may be performed in a manner broadcast to neighboring nodes of one hop, as shown in FIG. 3 as an example.

In addition, the NTR selection unit 104 may provide a function such as selecting one or a plurality of neighbor nodes as a reference node and selecting a network time reference (NT) of the selected reference node.

Here, the NTR selection unit 104 may select, for example, a node having a minimum ID among its own node (own node) and a plurality of neighboring nodes as a reference node.

Also, the NTR selection unit 104 compares the relative ID of the specific node with the ID of the own node if there is a specific node that is already operating based on the NTR, and selects the specific node as the reference node when the relative ID is faster than the ID. And, if the user ID is faster than the relative ID, a function such as selecting the user node as the reference node can be provided.

In addition, the NTR selection unit 104 may select the own node as an NTR if there is no specific node already in operation, and the NTR is a reference node for performing network time synchronization during network configuration, network merging, and network departure. Can be defined as

Next, the first time synchronization correcting unit 106 performs time synchronization correction (own time synchronization update) of the own node based on the NTR of the reference node selected through the NTR selection unit 104, that is, the reference node Based on this, it can provide functions such as correcting time synchronization.

Then, the second time synchronization correcting unit 108 performs distributed time synchronization correction of the own node based on synchronization information received (collected) from a plurality of neighboring nodes through the information transmitting and receiving unit 102, for example A function such as correcting synchronization information of the own node may be provided using an average value of the synchronization information (average value of a slot start point) collected from a plurality of neighboring nodes.

Here, the reference node-based time synchronization correction by the first time synchronization correction unit 106 and the distributed time synchronization correction by the second time synchronization correction unit 108 may be performed simultaneously.

FIG. 4 is an exemplary diagram for explaining the principle of performing distributed time synchronization correction using synchronization information received from a plurality of neighboring nodes.

Referring to FIG. 4, basically, in the case of nodes in one hop with the NTR, after correcting the time synchronization based on the NTR, propagating its synchronization information to neighboring nodes.

In addition, nodes with 2 hops or more in NTR may perform correction based on the average value of nodes closer to NTR than themselves.

That is, when the time synchronization is matched with the NTR, the NTR and one-hop nodes can correct the time synchronization based on the NTR and propagate their corrected synchronization information to neighboring nodes.

In addition, when the time synchronization is set to a node close to the NTR, nodes with n(n>1) hops or higher in the NTR correct the time synchronization based on the average value of the nodes closer to the NTR than their own, and NTR and n(n> 1) Hop nodes can propagate their corrected synchronization information to neighbor nodes.

Next, the node management unit 110 monitors whether or not the NTR deviates after the NTR is selected by the NTR selection unit 104, and when the monitoring detects the departure of the node NTR, the NTR departure information is displayed. Generate and propagate to a number of neighboring nodes, initialize the state of the own node, and re-run the sharing of synchronization information to control and manage the information transmitting and receiving unit 102 and the like so that time synchronization correction (hybrid time synchronization correction) is performed again. It can provide functions such as.

Here, the departure of the NTR, for example, may be determined as a network departure when more than 6 frames are lost among frames exchanged between nodes.

Next, in a series of processes for performing time synchronization based on hybrid time synchronization in which reference node-based time synchronization and distributed time synchronization are combined using the node time synchronization control device of the present embodiment having the above-described configuration. It will be described in detail.

FIG. 2 is a flowchart illustrating a main process of performing time synchronization based on hybrid time synchronization in which reference node-based time synchronization and distributed time synchronization are combined according to an embodiment of the present invention.

Referring to FIG. 2, the information transmitting and receiving unit 102 generates a message including its own synchronization information, for example, a timestamp message for time synchronization correction of a node, at a predetermined period, and propagates to neighboring neighboring nodes. A procedure of sharing synchronization information may be performed by receiving messages of each neighboring node propagated from neighboring nodes and storing them in a memory (not shown) (step 202).

Next, the NTR selection unit 104 may select one or a plurality of neighbor nodes as a reference node and select a network time reference (NTR) of the selected reference node, for example, the own node (Own node) and a node having a minimum ID among a plurality of neighboring nodes may be selected as a reference node (step 204).

In this case, the NTR selection unit 104 compares the relative ID of the specific node with the own ID of the own node if there is a specific node that is already operating based on the NTR, and selects the specific node as the reference node when the relative ID is faster than the own ID If the user ID is faster than the relative ID, the user node can be selected as the reference node.

In addition, the NTR selection unit 104 may select a node as its own NTR if there is no specific node already in operation, where NTR is a criterion for performing time synchronization of the network when configuring the network, merging the network, and leaving the network. It can be defined as a node.

Next, the node management unit 110 monitors whether or not the NTR deviates after the NTR is selected by the NTR selection unit 104 (step 206). If a deviation from the NTR is detected as a result of monitoring here, the NTR departure information Generates and propagates to a number of neighboring nodes, initializes the state of the own node, and re-runs the sharing of synchronization information to control the information transmitting and receiving unit 102 and the like so that time synchronization correction (hybrid time synchronization correction) is performed again. Management (step 208).

Here, the departure of the NTR, for example, may be determined as a network departure when more than 6 frames are lost among frames exchanged between nodes.

As a result of monitoring in step 206, if there is no deviation of the NTR, the first time synchronization correcting unit 106 corrects the time synchronization of the own node based on the NTR of the reference node selected through the NTR selecting unit 104 ( Perform own time synchronization update), that is, correct the time synchronization based on the reference node (step 210).

In addition, the second time synchronization correcting unit 108 performs distributed time synchronization correction of the own node based on synchronization information received (collected) from a plurality of neighboring nodes through the information transmitting and receiving unit 102, for example The synchronization information of the own node is corrected using the average value of the synchronization information collected from a plurality of neighboring nodes (step 212).

Here, the reference node-based time synchronization correction by the first time synchronization correction unit 106 and the distributed time synchronization correction by the second time synchronization correction unit 108 may be performed simultaneously.

The inventors of the present invention in an environment as shown in FIGS. 5 and 6 to check whether the node time synchronization control device according to the present invention, that is, the time synchronization algorithm is capable of time synchronization in a mobile ad-hoc net (MANET) environment in which the topology changes. Simulation (M&S) was performed in the scenario shown in FIG. 7.

5 is an exemplary diagram of a topology for verifying a time synchronization technique, FIG. 6 is an exemplary diagram of an environment for simulating a time synchronization technique, and FIG. 7 is an exemplary diagram of an application scenario according to a topology change.

Referring to FIGS. 5 to 7, as an example, a node 1 having the lowest node ID is selected as a reference node, and it is located in the middle of 60 nodes, and after confirming that time synchronization occurs in the entire network in section 1, the scenario Scenarios 1 to 4 were applied.

8 is a timing diagram exemplarily showing that the maximum error and the average error change with propagation time, and FIG. 9 is an exemplary diagram showing the average error and the maximum error for each section.

Referring to FIGS. 8 and 9, in scenario 1, the maximum error and the average error when the reference node 1 is turned off to escape the reference node can be confirmed.

That is, as can be seen from FIGS. 8 and 9, it was confirmed that the maximum error and the average error increase and decrease again until the synchronization information of the new reference node, node 2, propagates as the reference node is turned off in section 2.

In addition, in scenario 2, a node with a node ID of 5 multiples is reset one by one every 5 seconds, and topology changes caused by leaving neighbor nodes are given. As shown in FIG. 8, it was confirmed that the maximum error in section 3 increases but operates within a certain range.

In addition, in scenarios 3 and 4, all nodes with odd node IDs are turned off/on to confirm operation in an environment in which one network is separated and merged, which is also a predetermined range in sections 4 and 5 I could confirm that it was working normally.

That is, according to the node time synchronization control method of this embodiment, it was confirmed that the error can be maintained within a certain range in the MANET environment.

Meanwhile, combinations of each block of the block diagram and each step of the flowchart may be performed by computer program instructions. These computer program instructions may be mounted on a processor of a general purpose computer, special purpose computer, or other programmable data processing equipment, so that instructions executed through a processor of a computer or other programmable data processing equipment may be used in each block or flowchart of the block diagram. In each step, means are created to perform the functions described.

These computer program instructions can also be stored in a computer readable or computer readable memory or the like that can be directed to a computer or other programmable data processing equipment to implement a function in a particular way, so the computer readable or computer readable memory The instructions stored in it are also possible to produce an article of manufacture containing instructions means for performing the functions described in each step of each block or flowchart of the block diagram.

In addition, since computer program instructions may be mounted on a computer or other programmable data processing equipment, a series of operation steps are performed on the computer or other programmable data processing equipment to generate a process executed by the computer to generate a computer or other program. It is also possible for instructions to perform possible data processing equipment to provide steps for performing the functions described in each block of the block diagram and in each step of the flowchart.

Further, each block or each step may represent a module, segment, or portion of code that includes at least one executable instruction for executing the specified logical function(s). It should also be noted that in some alternative embodiments it is possible that the functions mentioned in blocks or steps occur out of order. For example, two blocks or steps shown in succession may in fact be executed substantially simultaneously, or it is also possible that the blocks or steps are sometimes performed in reverse order depending on the corresponding function.

The above description is merely illustrative of the technical idea of the present invention, and those of ordinary skill in the art to which the present invention pertains may have various substitutions, modifications, changes, etc. without departing from the essential characteristics of the present invention. You will easily see this possible. That is, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to describe the present invention, and the scope of the technical spirit of the present invention is not limited by these embodiments.

Therefore, the protection scope of the present invention should be interpreted by the claims that will be described later, and all technical ideas within an equivalent range should be interpreted as being included in the scope of the present invention.

102: information transmitting and receiving unit
104: NTR selection department
106: first time synchronization correction unit
108: second time synchronization correction unit
110: node management unit

Claims (14)

A synchronization information transmitting and receiving unit for sharing synchronization information by propagating a message including synchronization information to neighboring nodes in a network,
An NTR selection unit for selecting a network time reference (NTR) by selecting one or a plurality of neighbor nodes as a reference node,
A first time synchronization correcting unit for performing time synchronization correction of the own node based on the selected NTR of the reference node,
And a second time synchronization correcting unit performing distributed time synchronization correction of the own node based on synchronization information received from the plurality of neighboring nodes.
Node time synchronization control device. According to claim 1,
The synchronization information transmitting and receiving unit,
Propagating the message including its own synchronization information to one-hop neighbor nodes
Node time synchronization control device. According to claim 1,
The NTR selection unit,
The node having the minimum ID among the own node and the plurality of neighboring nodes is selected as the reference node
Node time synchronization control device. The method of claim 3,
The NTR selection unit,
If there is a specific node that is already operating based on the NTR, the relative ID of the specific node is compared with the own ID of the own node, and when the relative ID is faster than the own ID, the specific node is selected as the reference node, If the identity ID is faster than the relative ID, selecting the identity node as the reference node
Node time synchronization control device. According to claim 1,
After the NTR is selected, if the deviation is detected by monitoring the deviation of the NTR, NTR deviation information is generated, propagated to the plurality of neighbor nodes, and the status of the own node is initialized and the synchronization information is shared. Further comprising a node management unit to redo
Node time synchronization control device. According to claim 1,
The second time synchronization correction unit,
Correcting synchronization information of the own node using an average value of synchronization information collected from the plurality of neighboring nodes
Node time synchronization control device. According to claim 1,
The network,
Mobile Ad-hoc Network (MANET) or sensor network
Node time synchronization control device. Sharing the synchronization information by propagating a message containing the synchronization information to neighboring nodes in the network,
Selecting a network time reference (NTR) by selecting one or a plurality of neighbor nodes as a reference node;
Performing time synchronization correction of the own node based on the selected NTR of the reference node,
And performing distributed time synchronization correction of the own node based on synchronization information received from the plurality of neighbor nodes.
Node time synchronization control method. The method of claim 8,
The step of sharing,
Propagating the message including its own synchronization information to one-hop neighbor nodes
Node time synchronization control method. The method of claim 8,
The selecting step,
The node having the minimum ID among the own node and the plurality of neighboring nodes is selected as the reference node
Node time synchronization control method. The method of claim 10,
The selecting step,
Comparing the relative ID of the specific node with the own ID of the own node, if there is a specific node that is already operating based on the NTR;
As a result of the comparison, if the relative ID is faster than the ID, selecting the specific node as the reference node,
As a result of comparison, when the identity of the identity is faster than the identity of the opponent, the step of selecting the identity node as the reference node
Node time synchronization control method. The method of claim 8,
Monitoring whether the NTR deviates after the NTR is selected,
When the churn is detected, the method further includes generating NTR churn information, propagating it to the plurality of neighboring nodes, initializing the state of the node, and redoing the process from the sharing step.
Node time synchronization control method. The method of claim 8,
The step of performing the correction of the dispersion time synchronization,
Correcting synchronization information of the own node using an average value of synchronization information collected from the plurality of neighboring nodes
Node time synchronization control method. A computer-readable recording medium storing a computer program that enables a processor to perform a node time synchronization control method,
The node time synchronization control method,
Sharing the synchronization information by propagating a message containing the synchronization information to neighboring nodes in the network,
Selecting a network time reference (NTR) by selecting one or a plurality of neighbor nodes as a reference node;
Performing time synchronization correction of the own node based on the selected NTR of the reference node,
And performing distributed time synchronization correction of the own node based on synchronization information received from the plurality of neighbor nodes.
Computer-readable recording media.

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