CN110649985B - Method for obtaining minimum-level node in communication network - Google Patents

Method for obtaining minimum-level node in communication network Download PDF

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CN110649985B
CN110649985B CN201910997593.6A CN201910997593A CN110649985B CN 110649985 B CN110649985 B CN 110649985B CN 201910997593 A CN201910997593 A CN 201910997593A CN 110649985 B CN110649985 B CN 110649985B
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CN110649985A (en
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刘勤
胡崇浩
黄鹏宇
李红艳
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Xidian University
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    • H04—ELECTRIC COMMUNICATION TECHNIQUE
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    • H04J3/0635—Clock or time synchronisation in a network

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Abstract

The invention discloses a method for acquiring a minimum-grade node in a communication network based on a trend walking method, which mainly solves the problem of large calculation amount of the minimum-grade node when the time synchronization of the communication network is completed in the prior art. The implementation scheme is as follows: selecting any node as an initial foot falling node and calculating the stage number of the node; sending out from the initial drop-foot node, and repeatedly selecting the node with the minimum grade number and no more than the grade number of the current drop-foot node in the adjacent candidate nodes of the current drop-foot node; and taking the selected node as a new foot falling node, repeating the selection process until the new foot falling node cannot be selected, and taking the final foot falling node as a time reference node. Compared with the prior art, the method has the advantages that the minimum-level node is obtained through trend walking, the calculation complexity is reduced, unnecessary calculation resource loss is reduced, and the method can be used for selecting the reference node during the time synchronization of the communication network.

Description

Method for obtaining minimum-level node in communication network
Technical Field
The invention belongs to the technical field of communication, and further relates to a method for acquiring a node with the minimum level number, which can be used for selecting a reference node during time synchronization of a communication network.
Background
The time synchronization implementation mode of the existing communication network is based on the basis of bidirectional comparison time synchronization between two points, and according to the network topology adjacency relation, a time reference node is used as an initial node, and the synchronization is performed to peripheral nodes step by step according to a hierarchical structure by a breadth-first traversal principle until all nodes of the network reach a synchronization target.
In the time synchronization, the communication network time synchronization is performed step by step, and each step of time synchronization has errors and time delay. As the number of layers of the network step-by-step synchronization process increases, the absolute error and the time delay of the node completing synchronization and the initial time reference are amplified. It can be seen that better synchronization performance can be obtained by reducing the total number of synchronization layers as much as possible, so that a node with the minimum network synchronization level needs to be selected as a time reference node.
Tibo, published in the paper "time synchronization of satellite networks" 2019.04, the master university paper, the university of western electronic technology, discloses a method of using the maximum of the minimum number of hops for a node to reach other nodes in a synchronization network as the node progression, and performing the progression through all nodes in the network, and then using the minimum node of the progression as a time reference node.
The method for determining the time reference nodes has the disadvantages that all nodes in the network need to be traversed to calculate the series, the overall calculation amount is overlarge, more calculation resources are occupied, and the calculation process consumes longer time.
Disclosure of Invention
The invention aims to provide a method for acquiring the node with the minimum level number in the communication network based on trend walking to reduce the calculation amount, reduce the calculation time and realize the optimization of the process of acquiring the time synchronization reference node of the communication network aiming at the defects of the prior art.
The technical idea of the invention is that any node is selected as an initial foot-falling node and the stage number is calculated, the set trend walking process is sent from the foot-falling node, the node with the minimum stage number and no more than the stage number of the current foot-falling node in the adjacent candidate nodes of the current foot-falling node is repeatedly selected as the next foot-falling node until no new foot-falling node exists, and the final foot-falling node is taken as a time reference node, and the implementation steps comprise:
s1: selecting a Node from communication networkiTaking the node as an initial foot falling node, and calculating the corresponding progression L evel of the nodeiSetting up the checked set
Figure BDA0002239068170000021
Node is to beiInto the checked set C, i.e. C-C ∪ { NodeiWhere i is an ID number of a certain node in the network, i is 1, 2, 3 … N, and N is the number of nodes in the network;
s2: node of current foot-falling NodeiAs a candidate neighbor node set AiA isiMerge into the checked set C, i.e. C-C ∪ { Nodei}；
S3: computing a set of candidate neighbor nodes AiSelecting A as the grade of all the nodesiNode with minimum middle-level numberjIf the number of stagesIf the minimum node is not unique, selecting the node with the minimum node number in the nodes with the minimum level number, wherein j is the ID number of a certain node in the network, and j is 1, 2, 3 … N, and j is not equal to i;
s4, selecting the minimum node grade L evel of the grade selected in S3jProgression L evel from current drop foot nodeiMaking comparison if L evelj>LeveliThen execution proceeds to S5; otherwise, use NodejAs a drop foot node, return to S2;
s5: and outputting the current foot falling node as a node with the minimum stage number, namely the finally selected time reference center node.
The invention only calculates the grade number of the nodes on the walking path by the trend walking, thereby having the following advantages:
1. the method avoids calculating the grade of all nodes in the network, thereby reducing the calculation amount, reducing the calculation time and overcoming the defects of large calculation amount and long calculation time when calculating the grade minimum node in the prior art.
2. The process of determining a communication network time synchronization reference node is optimized.
Drawings
FIG. 1 is a flow chart of an implementation of the present invention;
FIG. 2 is an exemplary diagram of a satellite communications network used in an embodiment of the present invention;
FIG. 3 is a comparison graph of simulation for obtaining nodes with minimum level numbers by the present invention and the prior art method, respectively.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
Referring to fig. 1, the specific steps of the present invention are as follows:
step 1, obtaining initial foot-falling nodes and setting a checked set
1a) Randomly selecting a Node from a communication networkiAs an initial foot-falling node, the node,
1b) calculating corresponding series L evel of the nodei：
1b1) Setting a total set
Figure BDA0002239068170000022
Current set
Figure BDA0002239068170000023
And neighbor node set
Figure BDA0002239068170000024
The Node to be solved isiIncorporated in the Total and Now, setting a counting variable n to 1;
1b2) merging the Neighbor nodes of all the nodes in the current set Now into a Neighbor node set Neighbor;
1b3) judgment of
Figure BDA0002239068170000025
Whether or not:
if not, making n equal to n +1, then Total equal to Total ∪ Neighbor, Now equal to Neighbor-Neighbor ∩ Total, returning to 1b2), otherwise, outputting the stage number n;
1c) setting up a checked set
Figure BDA0002239068170000031
NodeiInto the checked set C, i.e. C-C ∪ { NodeiWhere i is the ID number of a certain node in the network, i ═ 1, 2, 3 … N, and N is the number of nodes in the network.
The network used in this example is a satellite communication network, and as shown in fig. 2, the network has 10 nodes in total, that is, N is 10.
And 2, acquiring a candidate neighbor node set.
Each foot NodeiThere are many neighbor nodes, some of which may be in the checked set C, and some of which are not in the checked set C, and the specific implementation of this step is:
firstly, finding out the current foot NodeiAll neighbor nodes not in the examined set C;
then the neighbor nodes are taken as a candidate neighbor node set AiAnd A isiInto a checked set C, i.e. C-C ∪ Ai。
And 3, acquiring the next step of the foot falling node.
3a) Computing the candidate neighbor node set A according to the same method as the above 1b)iSelecting A as the grade of all the nodesiNode with minimum middle-level numberjAnd the Node with the minimum level number is usedjThe number of steps is recorded as L evelj(ii) a If the node with the minimum level number is not unique, selecting the node with the minimum node number in the nodes with the minimum level number, wherein j is the ID number of a certain node in the network, and j is 1, 2, 3 … N, and j is not equal to i;
3b) node with minimum number of stagesjL evel series ofjProgression L evel from current drop foot nodeiMaking comparison if L evelj>LeveliIf yes, executing step 4; otherwise, use NodejAnd (5) as a foot falling node, returning to the step 2.
And 4, obtaining the node with the minimum level number.
And outputting the node with the current foot falling node as the node with the minimum stage number, namely the node for finally selecting the time reference center.
The effect of the present invention can be further illustrated by the following simulation experiment:
1. simulation experiment conditions are as follows:
the hardware platform of the simulation experiment of the invention: the processor is Intel (R) Xeon (R) CPU, the main frequency is 3.1GHz, and the memory is 8 GB.
The software platform of the simulation experiment of the invention is as follows: windows 7 operating system and Matlab R2017 a.
2. The prior art adopted by the simulation experiment is as follows: tibo, published in the paper "time synchronization of satellite networks" 2019.04, the university of sienna electronics, university of technology, shui shi, discloses a method for performing time synchronization by traversing the node with the smallest number of stages for all nodes in a communication network. The method obtains the node with the minimum level number by solving the level number of all nodes in the network and comparing. When the number of nodes in the network is N, the number of nodes needing to solve the series is N. The number of the nodes of which the levels need to be calculated in the method is compared with the number of the nodes of which the levels need to be calculated in the invention, so that a simulation graph is formed.
3. Simulation content and result analysis thereof:
simulation 1, adopting the present invention and the above prior art, respectively solving the node with the minimum number of stages for a plurality of input communication network topology structures, comparing the number of nodes whose number of stages needs to be calculated in the process of solving the node with the minimum number of stages, and the result is shown in fig. 3.
The abscissa in fig. 3 represents the number of nodes in the communication network, the ordinate represents the number of nodes whose number of levels is to be calculated on average, the curve marked by a diamond represents the change curve of the number of nodes whose number of levels is to be calculated in the prior art, and the curve marked by a star represents the change curve of the number of nodes whose number of levels is to be calculated in the present invention.
As can be seen from fig. 3, when the number of nodes in the communication network is 10, 20, 30, 40, 50, and 60, the number of nodes in the same communication network topology is smaller than that in the prior art, the number of nodes whose number of stages is calculated by the trend walking method for calculating the node with the minimum number of stages is 6.2, 12.3, 18.5, 25.0, 30.5, and 41.1 in sequence, which are all smaller than that in the prior art, i.e., 10, 20, 30, 40, 50, and 60. Therefore, the method and the device can solve the problems of large calculation amount and long calculation time when the minimum node of the number of stages is solved in the prior art. The calculation amount is reduced by the nodes with the minimum number of stages of the trend walking search, the calculation time is reduced, the optimization of the process of determining the time synchronization reference nodes of the communication network is realized, and the advantage becomes more obvious along with the increase of the number of the nodes of the communication network.
Simulation 2. the minimum node of the number of stages of the satellite communication network shown in fig. 2 is solved by the invention and the existing method respectively, and the number of stages of the nodes 1 to 10 in fig. 2 are respectively as follows: 6,4,5,4,3,4,6,4,5,5. When the node with the minimum level number is obtained by adopting the prior art, the level numbers of the nodes from 1 to 10 are required to be obtained, and then comparison is carried out to obtain the node 5 as the node with the minimum level number. The method adopts the trend walking method to solve the node with the minimum progression, supposes that the initial foot falling node is the node No. 6, firstly calculates the progression of the node No. 6 and the node No. 5 of the adjacent node, then the foot falling node is updated to the node No. 5, and then calculates the progression of the adjacent nodes No. 5, 2,4 and 8, finds that the termination condition of the algorithm is satisfied at the moment, outputs the node No. 5 as the node with the minimum progression, and only needs to calculate the progression of 5 nodes in the whole process.
The simulation 2 result shows that when the node with the minimum level number of the communication network is obtained, the number of the nodes needing to calculate the level number is reduced and the calculation amount is reduced by adopting the trend walking method compared with the prior art.

Claims (1)

1. A method for obtaining a node with the minimum level number in a communication network is characterized by comprising the following steps:
s1: selecting a Node from communication networkiTaking the node as an initial foot falling node, and calculating the corresponding progression L evel of the nodeiThe method comprises the following steps:
(S11) setting a total set
Figure FDA0002523511760000011
Current set
Figure FDA0002523511760000012
And neighbor node set
Figure FDA0002523511760000013
The Node to be solved isiIncorporated into Total and Now; setting a counting variable n to 1;
(S12) merging the Neighbor nodes of all the nodes in the current set Now into a Neighbor node set Neighbor;
(S13) judgment
Figure FDA0002523511760000014
If the result is not true, if n is n +1, Total is Total ∪ Neighbor, Now is Neighbor-Neighbor ∩ Total, and the process returns to (S12), otherwise, the number of stages n is output;
setting up a checked set
Figure FDA0002523511760000015
Node is to beiInto the checked set C, i.e. C-C ∪ { NodeiWhere i is an ID number of a certain node in the network, i is 1, 2, 3 … N, and N is the number of nodes in the network;
s2: node of current foot-falling NodeiAs a candidate neighbor node set AiA isiInto a checked set C, i.e. C-C ∪ Ai；
S3: computing a set of candidate neighbor nodes AiSelecting A as the grade of all the nodesiNode with minimum middle-level numberjIf the node with the minimum level number is not unique, selecting the node with the minimum node number in the nodes with the minimum level number, wherein j is the ID number of a certain node in the network, j is 1, 2, 3 … N, and j is not equal to i;
s4, selecting the minimum node grade L evel of the grade selected in S3jProgression L evel from current drop foot nodeiMaking comparison if L evelj>LeveliThen execution proceeds to S5; otherwise, use NodejAs a drop foot node, return to S2;
s5: and outputting the current foot falling node as a node with the minimum stage number, namely the finally selected time reference center node.
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Citations (1)

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Publication number Priority date Publication date Assignee Title
CN104427607A (en) * 2013-08-26 2015-03-18 北京信威通信技术股份有限公司 Method for time synchronization between nodes in self-organizing network

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CN104244400B (en) * 2014-09-22 2018-01-02 中国电子科技集团公司第二十研究所 Non-cutting time benchmark Bootload based on precise synchronization self-organizing network
CN109510681B (en) * 2018-11-29 2020-04-07 西安电子科技大学 Reference node selection method with minimum time synchronization series of communication network
CN110266423B (en) * 2019-06-21 2020-09-08 西安电子科技大学 Time synchronization method based on minimum node average synchronization stage number in communication network

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CN104427607A (en) * 2013-08-26 2015-03-18 北京信威通信技术股份有限公司 Method for time synchronization between nodes in self-organizing network

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