CN112040528B - Method for selecting control node of wireless ad hoc network center - Google Patents

Abstract

The invention discloses a method for selecting a central control node of a wireless ad hoc network, wherein each communication node in the wireless ad hoc network establishes a routing information table from one hop to m hops, wherein m is more than 1; each communication node respectively counts the number { X1, X2, …, XP } of the communication nodes corresponding to 1~P hops, and calculates the sum S of the number of 1~P hops communication nodes, wherein P is a preset transmission hop threshold and is more than or equal to m; when P > m, xm +1=0, xm +2=0, …, XP =0; and all the communication nodes meeting S & ltgtS & gt form a candidate central control node combination, weighting calculation is carried out on { X1, X2, …, XP } corresponding to each candidate central control node, the communication node with the largest weighted value is the central control node, and S & ltS & gt is a preset node number sum threshold. The invention selects the control node of the wireless ad hoc network center based on the criterion of the minimum average hop number, reduces the information interaction time delay and improves the working efficiency of the network.

Description

Method for selecting control node of wireless ad hoc network center

Technical Field

The invention relates to the technical field of wireless ad hoc networks, in particular to a method for selecting a central control node of a wireless ad hoc network.

Background

The wireless ad hoc network is a novel wireless network architecture completely different from a traditional wireless cellular network, and comprises a temporary autonomous network of a plurality of communication nodes. The nodes in the network are all peer-to-peer, each communication node is provided with a wireless transceiver and has the functions of transmitting, forwarding and receiving, so that any two nodes in the network can communicate through a direct link or a multi-hop link. Compared with the traditional cellular network, the wireless ad hoc network does not need to depend on infrastructure, has the advantages of flexible and simple networking, high network reliability, large coverage range and the like, and is widely applied to the fields of public safety, military battlefields, post-disaster reconstruction, emergency tasks and the like.

With the rapid development of multimedia service demands and the mature application of broadband communication technologies represented by OFDM-MIMO (orthogonal frequency division multiple access and multiple input multiple output) technologies, wireless ad hoc networks based on the broadband communication technologies should be developed. Due to the lack of uniform technical specifications of wireless broadband ad hoc networks, some manufacturers generally adopt the existing wireless broadband communication technology to develop customized wireless ad hoc network nodes based on a proprietary protocol, such as a WiFi protocol and a 4G LTE protocol, by modifying or referring to the communication protocol of the existing wireless broadband cellular network.

According to different network designs, the wireless ad hoc network comprises two conditions of a central control node and a non-central control node. In a wireless ad hoc network with a central control node, the central control node is responsible for topology management, frequency selection, timing synchronization and the like of the whole network, is in a decision and management position, and other communication nodes are configured by receiving some system messages broadcasted by the central control node. In a wireless ad hoc network without a central control node, all communication nodes are in equal positions and independently determine adopted configuration, resources and the like. After all communication nodes in the network go through a large amount of message interaction and games, the whole network tends to converge. In the existing wireless ad hoc network, in order to enable the network to converge quickly, at least in the network establishment phase, a central control node is reserved or a temporary central control node is selected.

In the prior art, the selection of the central control node (including the temporary central control node) is relatively arbitrary, and there is no fixed following principle, for example, the node which is first powered on is selected as the central control node, or the node with a certain ID is selected as the central control node. The selection method has randomness, and the defects of the wireless ad hoc network containing fewer nodes are not obvious. However, for a wireless ad hoc network including many nodes, the central control node is far away from some network nodes by a large number of hops, which causes a very large time delay for time synchronization or data transmission.

Disclosure of Invention

In view of the technical deficiencies, the present invention provides a method for selecting a central control node of a wireless ad hoc network, which selects the central control node of the wireless ad hoc network based on a criterion of a minimum average hop count, reduces information interaction delay, and improves the working efficiency of the network.

In order to solve the technical problems, the invention adopts the following technical scheme:

the invention provides a method for selecting a control node of a wireless ad hoc network center, which comprises the following steps: each communication node in the wireless ad hoc network establishes a routing information table from one hop to m hops, wherein m is more than 1;

each communication node respectively counts the number { X1, X2, …, XP } of the communication nodes corresponding to 1~P hops, and calculates the sum S of the number of 1~P hops communication nodes, wherein P is a preset transmission hop threshold, and P is more than or equal to m; when P > m, xm +1=0, xm +2=0, …, XP =0;

and all the communication nodes meeting S & ltgtS & gt form a candidate central control node combination, weighting calculation is carried out on { X1, X2, …, XP } corresponding to each candidate central control node, the communication node with the largest weighted value is the central control node, and S & ltS & gt is a preset node number sum threshold.

Preferably, each communication node establishes its own one-hop to m-hop node routing information table by:

the communication node i sends a discovery signal in a distributed time unit, and all other nodes capable of receiving and successfully detecting the discovery signal are adjacent points of the communication node i, wherein the communication node i =1,2,3, …, N;

after acquiring all the adjacent nodes of the communication node i, establishing a one-hop node routing information table of the communication node i, wherein the one-hop node routing information table comprises the ID information of the adjacent nodes;

the communication node i sends the one-hop node routing information table to all the adjacent nodes, each adjacent node compares the received one-hop node routing information table with the own one-hop node routing information table, and the ID information of the adjacent node and the repeated ID information of the communication node are eliminated, so that the rest communication nodes in the received routing information table are all nodes capable of carrying out two-hop communication;

after acquiring all the two-hop nodes of the communication node i, establishing a two-hop node routing information table of the communication node i, and sending the two-hop node routing information table to all the adjacent nodes, comparing the received two-hop node routing information table with a one-hop node routing information table and the two-hop node routing information table of the communication node i, and excluding repeated ID information of the communication node, wherein the rest communication nodes in the received routing information table are all nodes capable of carrying out three-hop communication;

therefore, the communication node i establishes an m-1 hop node routing information table of the communication node i and sends the m-1 hop node routing information table to all adjacent nodes, the adjacent nodes compare the received two-hop node routing information table with a one-hop-to-m-1 hop node routing information table of the communication node i, repeated communication node ID information is eliminated, and the rest communication nodes in the received routing information table are all nodes capable of performing m-hop communication; all communication nodes in the network establish own m-hop node routing information table.

Preferably, the { X1, X2, …, XP } corresponding to each of the candidate central control nodes is weighted by: the preset weighting coefficients { a1, a2, …, aP } satisfy that a1 is more than or equal to a2 and more than or equal to … and more than or equal to aP, and the weighting value is Q = a1X1+ a2X2+ … + aPXP.

Preferably, if the Q values corresponding to two or more communication nodes are the same and the maximum, the node with the maximum value corresponding to X1 is the central control node;

if the values of the X1 are the same, the node corresponding to the maximum value of the X2 is taken as a central control node;

by analogy, if the values of { X1, X2, … and XP-1} are the same, the node corresponding to the XP with the largest value is the central control node;

and if the values of XP are the same, selecting the node with the minimum or maximum node ID as the central control node.

Preferably, after all nodes in the network complete sending and detecting the discovery signal, all neighboring nodes of the node can be known;

after all nodes in the network complete the sending and receiving comparison of the m-1 hop node routing information table, all m hop nodes of the network can be obtained.

The invention has the beneficial effects that:

(1) The establishment of the central control node can simplify the design of network related protocols, reduce the network establishment time and enable the resource scheduling and data transmission to be more effective;

(2) The central control node is selected based on the principle of minimum average hop count, so that the information interaction time delay can be reduced, and the working efficiency of the network is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic diagram of a wireless ad hoc network including a central control node in the prior art;

FIG. 2 is a diagram of a time cell and discovery signal resource in the prior art;

FIG. 3 is a flow chart of a central control node selection scheme of the present invention;

fig. 4 is a diagram of a wireless ad hoc network according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention provides a method for selecting a central control node of a wireless ad hoc network. If a plurality of wireless ad hoc network subnets are fused into a large wireless ad hoc network or one large wireless ad hoc network is split into a plurality of ad hoc networks, even if the newly formed large network or subnet contains the old central control node, the central control node needs to be selected again and updated.

For a wireless ad hoc network with a large network scale, a central control node may need to perform multi-hop transmission when communicating with other communication nodes in the network. Considering that a large amount of information interaction is required between the central control node and other communication nodes, in order to reduce the information transmission delay, the number of transmission hops between the central control node and other communication nodes needs to be reduced as much as possible. Therefore, the invention performs the selection of the central control node based on the criterion of the minimum average hop count, and the scheme is as follows

1. Assuming that the wireless ad hoc network comprises N communication nodes, for a communication node i (i =1,2,3, …, N) to send a Discovery Signal (Discovery Signal) in an allocated time unit, all other nodes capable of receiving and successfully detecting the Discovery Signal are adjacent points of the communication node i, and for the sake of clearer distinction, the other nodes capable of receiving and successfully detecting the Discovery Signal are named as communication nodes j, namely if the communication nodes j (j ≠ i) receive the Discovery Signal and successfully detect the Discovery Signal, the communication nodes i and the communication nodes j are adjacent nodes;

for a wireless ad hoc network, a discovery signal sequence and mapped physical resources are usually specified by physical layer technical specifications, and after a communication node is started, the communication node sends a discovery signal in an allocated time unit to enable other nodes to discover itself and establish a transmission route; after the communication node i sends the discovery signal, other communication nodes in the network receive the discovery signal and detect the discovery signal, if the communication node j is located in the coverage range of the communication node i, the discovery signal can be successfully detected, the communication node i and the communication node j can directly communicate without being relayed by other nodes, and the communication node j marks the communication node i as an adjacent node; wherein, the detection process and algorithm of the discovery signal belong to the prior art and are not within the protection scope of the invention;

after all nodes in the network finish sending and detecting the discovery signal, all the neighbor nodes of the nodes can be obtained.

2. After learning all the neighbor nodes of the communication node i, the communication node i establishes a neighbor node routing information table (i.e., a one-hop node routing information table) of the communication node i, where the routing information table includes ID information of the node.

3. The communication node i sends the routing information table of the adjacent node to all the adjacent nodes, each adjacent node compares the received routing information table with the routing information table of the adjacent node, and the ID of the adjacent node and the ID of the repeated communication node are eliminated, so that the rest communication nodes in the received routing information table are all nodes capable of two-hop communication, namely, the communication node i is used for relaying and can carry out two-hop communication;

and for each communication node in the network, sending the own adjacent node routing information table to the own adjacent node. After receiving the routing information table, each adjacent node is compared with the own adjacent node routing information table, and if a certain node ID exists in two routing information tables at the same time except the ID of the adjacent node, the adjacent node can directly communicate with the adjacent node and does not belong to a two-hop node; and for the node only existing in the received routing information table but not existing in the routing information table of the node, the node and the adjacent node are two-hop nodes;

after all nodes in the network complete the sending and receiving comparison of the adjacent node routing information table, all the two-hop nodes of the network can be obtained.

4. The communication node i establishes a two-hop node routing information table of the communication node i and sends the two-hop node routing information table to all adjacent nodes, and the adjacent nodes acquire a three-hop node routing information table through comparison of the routing information table;

according to the description of step 3, after all nodes in the network complete the sending and receiving comparison of the two-hop node routing information table, all three-hop nodes of the network can be obtained.

5. According to the step 3 and the step 4, the communication node i establishes an m-1 hop node routing information table of the communication node i and sends the m-1 hop node routing information table to all adjacent nodes, the adjacent nodes acquire the m hop node routing information table through the comparison of the routing information table, and all the communication nodes in the network establish the m hop node routing information table of the communication node i;

6. assuming that a preset transmission hop threshold is P, each communication node in the network respectively counts the number of communication nodes { X1, X2, …, XP } corresponding to transmission hop {1,2, …, P } according to a routing information table of the communication node, and calculates the total S of 1~P hop communication node numbers;

considering the influence of transmission delay, the value of the transmission hop threshold P should not be too large, and if P =3, each communication node needs to count the number of its own neighboring nodes, the number of two-hop nodes, the number of three-hop nodes, and the sum of the number of 1~P hop nodes;

considering that the communication nodes only need to count the number of the corresponding communication nodes when the maximum hop count is P, in order to save resource overhead, when each node establishes its m-hop routing information table in step 5, the value of m is not more than P at most, that is, P is not less than m, because each node establishes the m-hop routing information table at most, and when P is greater than m, then m +1, m +2, …, xm +1, xm +2, … corresponding to P hop, XP can not obtain corresponding values, so Xm +1, xm +2, … and XP are designated as 0.

7. Forming a candidate center control node set by all communication nodes corresponding to S ≧ S according to a preset node number sum threshold S ≧ S;

consider that a node, if it were to become a central control node, would have as many nodes connected directly or through multiple hops as possible. From the perspective of resource overhead, it is not cost effective to calculate the number of nodes whose hop count exceeds P, so the candidate central control node is selected by the number of nodes whose hop count does not exceed P.

8. Calculating candidate central control nodes in the candidate central control node set according to preset weighting coefficients { a1, a2, …, aP } and corresponding { X1, X2, …, XP }, so as to obtain Q = a1X1+ a2X2+ … + aPXP, wherein the corresponding communication node with the largest Q value is the central control node;

according to the principle of minimum average hop count, carrying out weighted calculation on the number of communication nodes corresponding to different hop counts, considering that the transmission delay is reduced, the weighting coefficient should meet the condition that a1 is more than or equal to a2 is more than or equal to … is more than or equal to aP, so that the smaller the value of the hop count is, the larger the ratio of the hop count is; according to the weighting calculation result, the communication node corresponding to the maximum value is taken as a central control node;

if the Q values corresponding to two or more communication nodes are the same and the maximum, the node corresponding to the maximum X1 value is taken as a central control node;

if the values of the X1 are the same, the node with the largest value corresponding to the X2 is a central control node;

by analogy, if the values of { X1, X2, … and XP-1 are the same, the node corresponding to the XP with the largest value is taken as a central control node;

and if the values of XP are the same, selecting the node with the minimum or maximum node ID as the central control node.

Further, for the sake of clarity of the present invention, assume a wireless ad hoc network including 10 communication nodes, and the network topology is shown in fig. 4;

according to the scheme of the invention, firstly, a communication node 1 sends a discovery signal in a distributed time unit, other communication nodes in a network receive and detect the discovery signal, only a communication node 3 can successfully detect the discovery signal sent by the communication node 1 according to the network topology, and the communication node 3 marks the communication node 1 as an adjacent node; then the communication node 2 sends a discovery signal in the allocated time unit, the communication nodes 3 and 4 can successfully detect the discovery signal, and the communication node 2 is marked as a neighboring node; similarly, the communication nodes 3 to 10 sequentially send discovery signals in the allocated time units, and other communication nodes capable of detecting the discovery signals mark the discovery signals as neighboring nodes; after the communication nodes 1 to 10 respectively learn their neighboring nodes, they respectively establish their neighboring node routing information tables (which may also be referred to as one-hop routing information tables) which mainly include IDs of the neighboring nodes, as shown in table 1:

table 1 neighbor node routing information table

Node ID	Neighbor node ID
		1	3
2	3，4
		3	1，2，5，6
4	2，7
		5	3，6，7，8
6	3，5，9
		7	4，5
8	5，10
		9	6
10	8

According to the scheme of the invention, the communication nodes 1 to 10 respectively send own adjacent node routing information tables to adjacent nodes, the adjacent nodes compare the received routing information tables with the own adjacent node routing information tables, and if a certain communication node ID (not equal) only exists in the received routing information tables but does not exist in the own adjacent node routing information tables except for the ID of the adjacent nodes, the node belongs to a two-hop node of the current node, namely, the communication can be carried out through the two-hop link;

for example, the communication node 1 sends the adjacent node routing information table to the adjacent node 3, the adjacent node 3 firstly excludes the self ID in the received routing information table, then compares the self ID with the self adjacent node routing information table, and after the self ID is excluded, the received routing information table is empty, so that no two-hop node capable of being relayed by the communication node 1 exists; taking the communication node 5 as an example, the communication node 5 sends the adjacent node routing information tables to the adjacent nodes 3,6,7,8 respectively, after the communication node 3 receives the routing information tables, the communication node 3 excludes itself firstly, then compares the routing information tables with the own adjacent node routing information tables, finds that the communication nodes 7 and 8 contained in the received routing information tables are not in the own adjacent node routing tables, and then the communication nodes 7 and 8 are two-hop nodes capable of relaying through the communication node 5; similarly, for communication node 6, communication nodes 7 and 8 are two-hop nodes that can be relayed through communication node 5; for communication node 7, communication nodes 3,6 and 8 are two-hop nodes that can be relayed by communication node 5; for communication node 8, communication nodes 3,6 and 7 are two-hop nodes that can be relayed by communication node 5;

after the communication nodes 1 to 10 acquire the two-hop nodes of the communication nodes, establishing a two-hop node routing information table as shown in table 2:

table 2 two-hop node routing information table

Node ID	Two-hop node ID
		1	2，5，6
2	1，5，6，7
		3	4，7，8，9
4	3，5
		5	1，2，4，9，10
6	1，2，7，8
		7	2，3，6，8
8	3，6，7
		9	3，5
10	5

According to the method for acquiring the two-hop routing information table, the communication nodes 1 to 10 respectively transmit the m-1-hop routing information table to adjacent nodes, and each adjacent node respectively acquires nodes capable of communicating with the adjacent node through m hops; after the communication nodes 1 to 10 acquire nodes capable of communicating with the communication nodes through m hops, respectively establishing m-hop node routing information tables; according to the description of the invention scheme, the value of m is not more than P.

In this embodiment, it is assumed that P =2, that is, the central control node is selected according to the number of one-hop and two-hop nodes; according to the step 6 and the table 1~2, the number of the one-hop node and the number of the two-hop node corresponding to each communication node, and the sum of the number of the one-hop node and the two-hop node are respectively calculated and obtained, as shown in table 3:

TABLE 3 one-hop and two-hop node counts

Node ID	Number of one hop node	Number of two-hop nodes	Total number of
				1	1	3	4
2	2	4	6
				3	4	4	8
4	2	2	4
				5	4	5	9
6	3	4	7
				7	2	4	6
8	2	3	5
				9	1	2	3
10	1	1	2

According to step 7 of the invention scheme, assuming that the threshold S =6, the communication nodes {2,3,5,6,7} meet the threshold requirement, and jointly form a candidate node combination; according to the step 8 of the invention scheme, assuming that the weighting coefficients are 0.7 and 0.3 respectively, namely the weighting coefficient of the number of one-hop nodes is 0.7 and the weighting coefficient of the number of two-hop nodes is 0.3, for the candidate central control node {2,3,5,6,7}, the weighted value is {2.6,4,4.3,3.3,2.6}; according to the weighted value, it can be known that the weighted value corresponding to the communication node 5 is the largest, and then the communication node 5 is the central control node.

In some cases, two or more weighted values may be the same, and when the central control node is selected, the number of one-hop nodes, the number of two-hop nodes, or the number of up to P-hop nodes are respectively compared in sequence as described in step 8; and if the central control node can not be selected, selecting the node with the minimum or maximum ID as the central control node.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims (4)

1. A method for selecting a control node of a wireless ad hoc network center is characterized by comprising the following steps:

each communication node in the wireless ad hoc network establishes a routing information table from one hop to m hops, wherein m is more than 1;

each communication node respectively counts the number { X1, X2, …, XP } of the communication nodes corresponding to 1~P hops, and calculates the sum S of the number of 1~P hops communication nodes, wherein P is a preset transmission hop threshold and is more than or equal to m; when P > m, xm +1=0, xm +2=0, …, XP =0;

all the communication nodes meeting S & gt are combined into a candidate central control node combination, weighting calculation is carried out on { X1, X2, …, XP } corresponding to each candidate central control node, the communication node with the largest weighted value is the central control node, and S & gt is a preset node number sum threshold;

wherein { X1, X2, …, XP } corresponding to each candidate center control node is weighted as follows:

the preset weighting coefficients { a1, a2, …, aP } satisfy a1 ≧ a2 ≧ … ≧ aP, and the weighting value is Q = a1X1+ a2X2+ … + axpp.

2. The method as claimed in claim 1, wherein each communication node establishes its own one-hop to m-hop node routing information table by:

the communication node i sends a discovery signal in a distributed time unit, and all other nodes capable of receiving and successfully detecting the discovery signal are adjacent points of the communication node i, wherein the communication node i =1,2,3, …, N;

after acquiring all the adjacent nodes of the communication node i, establishing a one-hop node routing information table of the communication node i, wherein the one-hop node routing information table comprises the ID information of the adjacent nodes;

the communication node i sends the one-hop node routing information table to all the adjacent nodes, each adjacent node compares the received one-hop node routing information table with the own one-hop node routing information table, and the ID information of the adjacent node and the repeated ID information of the communication node are eliminated, so that the rest communication nodes in the received routing information table are all nodes capable of carrying out two-hop communication;

after acquiring all two-hop nodes of a communication node i, establishing a two-hop node routing information table of the communication node i, and sending the two-hop node routing information table to all adjacent nodes, comparing the received two-hop node routing information table with a one-hop node routing information table and the two-hop node routing information table of the communication node i, and excluding repeated ID information of the communication node, wherein the rest communication nodes in the received routing information table are all nodes capable of performing three-hop communication;

therefore, the communication node i establishes an m-1 hop node routing information table of the communication node i and sends the m-1 hop node routing information table to all adjacent nodes, the adjacent nodes compare the received two-hop node routing information table with a one-hop-to-m-1 hop node routing information table of the communication node i, repeated communication node ID information is eliminated, and the rest communication nodes in the received routing information table are all nodes capable of performing m-hop communication; all communication nodes in the network establish own m-hop node routing information tables.

3. The method according to claim 1, wherein if there are two or more communication nodes that have the same and the largest Q value, the node with the largest value corresponding to X1 is the central control node;

if the values of the X1 are the same, the node corresponding to the maximum value of the X2 is taken as a central control node;

by analogy, if the values of { X1, X2, … and XP-1} are the same, the node corresponding to the XP with the largest value is the central control node;

and if the XP values are the same, selecting the node with the minimum or maximum node ID as the central control node.

4. The method for selecting the central control node of the wireless ad hoc network according to claim 1 or 2, wherein when all nodes in the network finish sending and detecting discovery signals, all neighboring nodes of the node can be known;

after all nodes in the network complete the sending and receiving comparison of the m-1 hop node routing information table, all m hop nodes of the network can be obtained.

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