CN105245563B - A kind of dynamic clustering method based on vehicle node connection stability - Google Patents
A kind of dynamic clustering method based on vehicle node connection stability Download PDFInfo
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Abstract
The present invention relates to a kind of dynamic clustering method based on vehicle node connection stability, belong to field of communication technology.This method comprises the following steps：Step 1) vehicle node combination information of vehicles and it is presently in road environment, initializes vehicular ad hoc network, and dynamic clustering；Step 2) sub-clustering adaptive maintenanc, including node leaving and adding, the merging of cluster, the fractionation of cluster.A kind of dynamic clustering method based on vehicle node connection stability provided by the invention, improve vehicular ad hoc network sub-clustering stability, it can effectively adapt to In-vehicle networking environment, adaptively changing is made for different road environments, remains to keep relatively stable cluster head number and relatively low sub-clustering expense under the scene of network size and changes in vehicle speed.
Description
Technical Field
The invention belongs to the technical field of communication, and relates to a dynamic clustering method based on vehicle node communication stability.
Background
With the continuous development of wireless networks, the operating efficiency of various application systems is greatly improved through the connection of the networks. The traffic system using automobiles as basic nodes is developed into an intelligent traffic system in an automatic and intelligent way, and the network transmission technology is also necessary.
The combination of the urgent demand for traffic intelligence and the rapid development of wireless communication technology has been promoted. The intelligent traffic system is a traffic comprehensive management system integrating advanced technologies such as sensing, communication and computers. The design goal of the system is to establish a platform for communication among vehicles, so that the vehicles can share vehicle condition (such as position, direction, speed and the like) information and real-time road condition information, and the vehicles can realize intelligent safe driving through the system, thereby improving traffic efficiency and safety and reliability of vehicle driving.
As part of the initial research of the intelligent transportation system, the vehicle-mounted ad hoc network researches the communication between vehicles, and unlike the conventional wireless mobile ad hoc network, the vehicle-mounted ad hoc network is a wireless ad hoc network establishing communication between vehicles, and comprises two parts: communication between cars on a road, wireless communication between cars and infrastructure. As a special wireless mobile self-organizing network, the vehicle-mounted self-organizing network adopts a distributed structure, has the characteristics of dynamic, centerless, self-organization, multi-hop and the like, and vehicle nodes are not only terminal nodes but also routing nodes and can establish a complete dynamic network through a wireless transceiver.
The vehicle-mounted self-organizing network applies the mobile self-organizing network technology to the communication between vehicles, thereby greatly expanding the visual field of a driver, enabling the driver to obtain the running information and road condition information of the vehicles outside the visual range, and improving the road utilization rate and the driving safety. The benefits brought by the vehicle-mounted ad hoc network are far beyond this, and with the continuous intellectualization and informatization of automobiles, the vehicle-mounted network also begins to play a role in the fields of sensor information acquisition, disaster relief, military communication, emergency command, internet access and the like besides intelligent transportation. By being equipped with GPS equipment, the vehicle node can acquire and update the current position information in real time and provide the position inquiry service of the whole network; by accessing the internet, drivers and passengers can obtain real-time streaming media services and the like.
Disclosure of Invention
In view of this, the present invention provides a dynamic clustering method based on vehicle node connectivity stability, which can effectively improve the stability of vehicle-mounted ad hoc network clustering.
In order to achieve the purpose, the invention provides the following technical scheme:
a dynamic clustering method based on vehicle node communication stability comprises the following steps:
step 1) initializing a vehicle-mounted self-organizing network, and dynamically clustering;
and 2) clustering self-adaptive maintenance, including node leaving and node adding, cluster merging and cluster splitting.
Further, the step 1) specifically comprises the following steps:
step 1-1) all vehicle nodes in the vehicle-mounted self-organizing network are common nodes, and vehiclesThe node i obtains the current position p (x, y), the speed v and the moving direction d, judges the current road environment according to the current road position identification, and calculates the node degree Degi and the node average communication time of the node at the current moment
Step 1-2) filling BM beacon information by a node i, and broadcasting the BM beacon information to neighbor nodes; receiving BM beacon messages from neighbor nodes, updating a neighbor list, and starting clustering waiting time timing;
step 1-3) judging whether a cluster M and a cluster head node CH exist in a current area by a node i through neighbor BM beacon information, if the cluster exists in a road environment where the node i is located, the node i receives a CM cluster message from a node j, inserting the information of the node j into a cluster head list, filling an ID of the cluster head node j into the BM beacon message, and sending the BM beacon message to the cluster head node j; the node j receives the beacon message from the node i, compares the cluster head information, adds the node i into a cluster member list, and then jumps to the step 1-8); if not, jumping to the next step;
step 1-4) when no cluster exists in the environment of the node i, judging whether the cluster waiting time exceeds the preset cluster waiting time tw of the system, if so, electing the node as a cluster head node, and executing the step 1-6); if not, jumping to the next step;
step 1-5) the node firstly judges the position mark of the current road, calculates the communication stability Wstability (i) of the current node, and judges whether the requirement that the Wstability (i) is more than or equal to W is met th Wherein W is th A communication stability threshold value is set for the system;
if the conditions are met, the nodes directly create a cluster and enter the step 1-6); if the condition is not met, the node waits for the time t0 and returns to the step 1-2);
step 1-6), the node i becomes a cluster head node and broadcasts a CM clustering message to a neighbor node; the clustering message comprises a cluster head ID, establishment time and a message type; wherein the message type flag creates < Cluster Create > for the Cluster;
step 1-7) the neighbor node j receives the CM clustering message from the node i, inserts the information of i into the cluster head list, fills the ID of the cluster head node i into the BM beacon message, and sends the BM beacon message to the cluster head node i; the node i receives the beacon message from the j, compares the cluster head information and adds the j into a cluster member list;
step 1-8) repeating steps 1-1) to 1-8) until all nodes in the network have joined the cluster.
Further, the road position identification includes a section identification Segment (x, y) or an Intersection identification interaction (x, y).
Further, the node average connection timeAnd the average time length value of the link connection between the node i and all the adjacent nodes which can be directly connected at the time t is obtained.
Further, the road identifier is a section identifier, and when the node i and the node j are in a connected state at time t, the link connection time Tij (t) that the node i and the node j can keep is as follows:
T ij (t) satisfies the condition D ij (t+T ij (t))≤D th ，D th Is a distance threshold, D th R is less than or equal to r, r is the communication radius of the nodes, d is the distance between the nodes i and j in the direction vertical to the road, d is approximately 0 when the nodes i and j are on the same lane, and d is approximately equal to d when the nodes i and j are on the adjacent lane r Wherein d is r Is the width of the segment (x, y), theta is the included angle between the segment and the horizontal direction, theta is more than or equal to 0 degree and less than or equal to 90 degrees, and x i (t) is the abscissa of the node i, x j (t) is the ordinate of the node i,is the average relative velocity of node i and node j over Δ t.
Further, when the road mark is an Intersection mark, the node i and the node j are simultaneously positioned at an Intersection (x, y), and when the node i and the node j are positioned at the same road section before entering the Intersection, the node i and the node j leave the Intersection and drive into different road sections; if the distance D between the node i and the node j ij (t) satisfies the following formula
Then T ij (t) =0, in which l i Length of Intersection (x, y) region; w is a i Width of Intersection (x, y) region; omega is an included angle between two road sections (x, y) at the node i and the node j under the intersection model, and meets the condition that omega is more than or equal to 0 degree&180 degrees, under a vertical intersection model, theta =0 degrees, omega =90 degrees;
when the node i and the node j are positioned on different road sections before entering the intersection, and the node i and the node j leave the intersection and drive into different road sections; if the distance between the node i and the node j is less than or equal to D at the moment of t + delta t th Then, then
Wherein, Δ v x The difference value of the speed of the node i and the speed of the node j in the delta t at the coordinate horizontal component; Δ x is the difference between the coordinate horizontal components of the node i and the node j at the time t; Δ v y The difference value of the speed of the node i and the speed of the node j in the coordinate vertical component in the delta t is obtained; and deltay is the difference of the coordinate vertical components of the node i and the node j at the moment t.
Further, the node connection stability Wstability (i) is calculated by the following formula:
wherein, ω 1, ω 2, ω 3, ω 4 are weighting factors,the average connection time normalization value of the node i is obtained;characterizing connectivity of node i, deg i Is the node degree, deg, of a node th Is a system node degree threshold;the motion state of a current vehicle node i is characterized, delta (i, t) is a speed variance value v of the node i in a (t-delta t, t) time period max Is the maximum travel speed, v i Is the current driving speed of node i, N c The number of the neighbor nodes with the movement direction consistent with the node i is N, and the N is the number of the neighbor nodes of the node i.
Further, the leaving and joining of the node comprises the following steps:
step 2-1-1) the cluster member node j periodically acquires the beacon information of the neighbor node and updates a cluster head list;
step 2-1-2) in a time period of t1, when the cluster member node j does not receive beacon information from the current cluster head node i, indicating that the cluster member node j leaves the communication radius of the cluster M (i), entering step 2-1-3); when a cluster member node j simultaneously receives BM beacon information from a new cluster head node k, the current node enters the communication radius of a cluster M (k), and the step 2-1-6 is executed;
step 2-1-3) when the cluster member node j judges that the current cluster M (i) is left, searching whether other cluster head node beacon information exists or not, and if the cluster member node j leaves the current cluster M (i), performing the next step; if the node j does not receive the beacon information from other cluster head nodes, executing the step 2-1-5);
step 2-1-4) judging the road environment of the node j, and calculating the link connection time T between the node j and the cluster head node k when the node is positioned in the section Segment (x, y) kj (T) if T is satisfied kj (t)＞T th If the node is added into the cluster M (k), the ID of the cluster head node k is filled into the BM beacon message and broadcasted to the neighbor nodes, and if the ID is not met, the step is executed2-1-5); when the node j is positioned at the Intersection (x, y), if the cluster head node k is positioned at the Intersection (x, y), the node j is directly added into the cluster M (k); if the cluster head node k is in the Segment (x, y), j and the cluster head node k are judged to satisfy T kj (t)＞T th If yes, adding the cluster M (k), otherwise, entering the next step 2-1-5);
step 2-1-5) waiting for tw time, repeatedly judging whether available clusters exist, if no clusters exist, starting a cluster initialization clustering process by a node j, and executing the step 1);
step 2-1-6) if the node j receives the beacon information of the cluster head node i and the new cluster head node k at the same time, calculating the link communication maintaining time T between the node j and the current cluster head node i and the new cluster head node k respectively ij (T) and T kj (t); if T is kj ≥η·T ij If the node j selects to leave the current cluster M (i), a new cluster M (k) is added, and meanwhile, a BM beacon message is broadcasted to the neighbor nodes; otherwise, the node does not perform any processing; wherein eta cluster head switching proportionality coefficient satisfies eta is more than or equal to 1.
Further, the merging of the clusters specifically comprises the following steps:
step 2-2-1) when a cluster head node i receives a BM beacon message from a neighbor cluster head node k, the two cluster head nodes are mutually within the communication radius of each other, and a cluster M (i) and a cluster M (k) are merged;
step 2-2-2): comparing the communication stability Wstability (i) and Wstability (k) of the cluster head node i and the cluster head node k, if Wstability (i) > Wstability (k) is met, giving up the cluster head node k as a cluster head, resolving the cluster M (k), and emptying a cluster member list; a Cluster head node k creates a CM message packet and broadcasts the CM message packet to a neighbor node, wherein the CM message packet comprises a Cluster head ID and a message type, and the message type is set as a Cluster resolution;
step 2-2-3) after the member node of the cluster M (k) receives the message of the dispersed cluster CM from the cluster head node k, deleting the corresponding cluster head item in the cluster head list; and the nodes in the communication range of the cluster head node i are added into the cluster M (i), and other nodes search the BM beacon message and execute the leaving and adding processes of the nodes.
Further, the splitting of the cluster specifically comprises the following steps:
step 2-3-1), the cluster head node k updates the cluster member list at regular time, and when the number of the cluster member list members calculated by the cluster head node is greater than a threshold value Mmax, the cluster head carries out a cluster splitting process;
step 2-3-2) the Cluster head node k creates a CM clustering message packet which contains Cluster head ID and message type, wherein the message type is set as Cluster splitting < Cluster Divide >;
and 2-3-3) the cluster member node j receives the clustering splitting message from the cluster head node k, deletes the k information in the current cluster head list, traverses the cluster head list and executes the leaving and joining process of the node.
The invention has the beneficial effects that: the dynamic clustering method based on the vehicle node communication stability improves the clustering stability of the vehicle-mounted self-organizing network, can effectively adapt to the vehicle-mounted network environment, can change the self-adaption according to different road environments, and can still keep more stable cluster head number and lower clustering overhead under the scene of network scale and vehicle speed change.
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In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail with reference to the accompanying drawings, in which:
FIG. 1 is a schematic diagram of network node connection time prediction;
fig. 2 is a schematic diagram of initialized road segment clustering.
Detailed Description
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
The dynamic clustering method based on the vehicle node communication stability can effectively adapt to vehicle-mounted network environments, can be self-adaptively changed aiming at different road environments, and can still keep more stable cluster head number and lower clustering overhead under the scene of network scale and vehicle speed change. The method comprises the following steps: step 1) initializing a vehicle-mounted self-organizing network, and dynamically clustering; and 2) clustering self-adaptive maintenance, including node leaving and node adding, cluster merging and cluster splitting.
Since the vehicles in the vehicle-mounted ad hoc network continuously move, the distance between the vehicles and the link keeping time are directly influenced by the position, the moving speed and the driving direction of the vehicles. Therefore, in this embodiment, connectivity of nodes in the vehicle-mounted ad hoc network is predicted, according to characteristics of roads in an urban environment, the roads can be divided into a Segment Model (Segment Model) and an Intersection Model (Intersection Model), and link connection time of the nodes is calculated respectively, and fig. 1 is a schematic diagram illustrating prediction of network node connection time.
The road section and road environment means that the position relation between vehicles is approximately on a straight line, and the movement between the vehicles is divided into the same direction and the opposite direction. The communication time under the environment is predicted to be the communication time T which can be kept between i and j when the nodes i and j are in the communication state at the moment T ij (t) satisfies the condition D ij (t+T ij (t))≤D th ，D th As a distance threshold, D is satisfied th R is less than or equal to r. Link connection time T that i and j can keep at time T ij (t)，d is the distance between nodes i, j in the direction perpendicular to the road, d is approximately 0 when i and j are on the same lane, and d is approximately equal to d on the adjacent lane r Wherein d is r Is the width of the segment (x, y), theta is the included angle between the segment and the horizontal direction, and the included angle is more than or equal to 0 degree and less than or equal to 90 degrees, and x i (t) is the abscissa of the node i, x j (t) is the ordinate of the node i,is the average relative velocity of node i and node j over Δ t.
The intersection road environment means that the relative movement direction between the vehicle nodes is presented as the same road section direction or the cross road section direction. The connected time prediction in this environment is classified into the following two cases: 1) The node i and the node j are simultaneously positioned at an Intersection (x, y), and when the node i and the node j are positioned at the same road section before entering the Intersection, the node i and the node j leave the Intersection and drive into different road sections; 2) When the node i and the node j are in different road sections before entering the intersection, and the node i and the node j leave the intersection and drive into different road sections.
Under the condition of a road at an Intersection, the node i and the node j are simultaneously positioned at an Intersection (x, y), when the node i and the node j are positioned at the same road section before entering the Intersection and the moving directions of the node i and the node j are respectively directed to different road sections by the Intersection, namely the node i and the node j leave the Intersection and drive into different road sections; for example, the vehicle C and the vehicle D are located at the same intersection, the vehicle C and the vehicle D travel on the same road segment before entering the intersection, and after passing the intersection, the vehicle C turns left and the vehicle D turns right, and travels to different road segments; if the distance D between i and j ij (t) satisfies the following formula
Then T ij (t)＝0，l i Length of Intersection (x, y) region; w is a i Width of Intersection (x, y) region; omega is an included angle between two road sections (x, y) at the node i and the node j under the intersection model, and meets the condition that omega is more than or equal to 0 degree&And lt, 180 degrees, under a vertical intersection model, theta =0 degrees, and omega =90 degrees.
Under the condition of a road at an intersection, when a node i and a node j are in different road sections before entering the intersection and the node i and the node j leave the intersection to drive into different road sections, the above conditions are not satisfied, for example, as shown in fig. 1, a vehicle D and a vehicle E are positioned at the same intersection, before entering the intersection, the vehicle D and the vehicle E drive on different road sections, after passing through the intersection, the vehicle D and the vehicle E drive straight, and the vehicle D and the vehicle E drive on different road sections; if the distance between the vehicles i and j is less than or equal to Dth at the time t + delta t, then
Δv x The difference value of the speed of the node i and the speed of the node j in the delta t at the coordinate horizontal component; Δ x is the difference between the coordinate horizontal components of the node i and the node j at the time t; Δ v y The difference value of the speed of the node i and the speed of the node j in the coordinate vertical component in the delta t is obtained; Δ y is the difference between the coordinate vertical components of node i and node j at time t.
All vehicles of the vehicle-mounted self-organizing network are assumed to adopt omnidirectional antennas, the transmission radiuses of the nodes are the same, and all communication is bidirectional links. The nodes and the neighbor nodes in the network acquire the information of the neighbor nodes through periodic BM (Beacon Message) Beacon messages, wherein the information comprises a node ID, a position p (x, y), a speed v, a direction d and a cluster head ID. The Cluster head node and the Cluster member nodes complete the network initialization Cluster establishment and the dynamic Cluster maintenance process through CM (Cluster Message) clustering messages. The symbol definitions used in the clustering algorithm are shown in table 1.
TABLE 1 notation definition notes sheet
For a given network G (V, E), the clustering process is a process of partitioning nodes into sets M using a clustering algorithm.
The Cluster Head Node in the network is CH (Cluster Head), and the Common Node is CN (Common Node).
The ID owned by each node in the network is unique; the network road environment is divided into two models: road segments and intersections. Each road section has a unique identifier, and the identifier is marked as Segment (x, y); each Intersection has a unique identifier, denoted as interaction (x, y).
The moving direction of the cluster M (i) is the moving direction of the cluster head i, and the cluster moves along with the movement of the cluster head.
Fig. 2 is a schematic diagram of initialized road segment clustering.
The dynamic clustering initialization process is that when the clustering initialization is started, all nodes in a network are common nodes CN, the nodes update own neighbor tables by acquiring BM beacon messages of neighbor nodes, and establish or join clusters through the following process to promote cluster head nodes CH. The method specifically comprises the following steps:
step 1-1) a vehicle node i acquires a current position p (x, y), a speed v and a moving direction d, judges the current road environment according to the current road position identification, and calculates the node degree Degi and the node average connection time of the current node
The road location identification is a section identification Segment (x, y) or Intersection identification interaction (x, y).
The average connection time of the nodes is the average time length value of the connection between the node i and all the directly connected neighbor node links at the time t, and is used for measuring the connection quality of the nodes.
The node degree is the sum of the number of nodes which are arranged around the vehicle node i at the time t and can be directly connected, and is used for measuring the connection condition of the vehicle node i at the time t.
Step 1-2) node i fills BM beacon message, broadcasts BM beacon message to neighbor node; receiving BM beacon messages from neighbor nodes, updating a neighbor list, and starting clustering waiting time timing;
step 1-3) judging whether a cluster M and a cluster head node CH exist in a current area by a node i through neighbor BM beacon information, if the cluster exists in a road environment where the node i is located, the node i receives a CM cluster message from a node j, inserting the information of the node j into a cluster head list, filling an ID of the cluster head node j into the BM beacon message, and sending the BM beacon message to the cluster head node j; the node j receives the beacon message from the node i, compares the cluster head information, adds the node i into a cluster member list, and then jumps to the step 1-8); if not, jumping to the next step;
step 1-4) when no cluster exists in the environment of the node i, judging whether the cluster waiting time exceeds the system preset cluster waiting time tw, if so, the node is elected as a cluster head node, and executing step 1-6); if not, jumping to the next step;
step 1-5) the node firstly judges the position mark of the current road, calculates the communication stability Wstability (i) of the current node, and judges whether the requirement that the Wstability (i) is more than or equal to W is met th Wherein W is th A connectivity stability threshold set for the system;
if the conditions are met, the node directly creates a cluster and enters the step 1-6); if the condition is not met, the node waits for the time t0 and returns to the step 1-2);
the node communication stability is a comprehensive evaluation index of a node i at the time t, the value is calculated by the factors of the average node communication time, the node degree, the node speed, the node movement direction and the like, and the larger the value is, the more preferentially the node becomes a cluster head node.
Adopting an improved scheme based on weighting clustering WCA to perform weighting calculation on different weights, wherein the calculated comprehensive weight value is the node communication stability, the performance is optimal when the node communication stability is the maximum, the node communication stability is preferentially selected as a cluster head node, and the communication stability of the node is calculated as follows:
wherein:the average communication time normalization value of the node i represents the relative size of the average communication time of the current node and the neighbor node, and meets the requirement of
The connectivity of the node i is represented, the better the connectivity of the node is, the higher the value is, the requirement is met
The motion state of the current vehicle node i is represented, the condition that delta v (i) is less than or equal to 1 is met, and the lower the variation of the speed in unit time is, the larger the delta v (i) is. And defines the speed of the vehicle i at [0,1 ]]In the interval, =1, = v (i);
the correlation degree of the current node i and the moving direction of the neighbor node is represented, and the requirements of the correlation degree
In the formula, ω 1, ω 2, ω 3, and ω 4 are weighting factors, and the values thereof are different in the road section and the intersection environment, and the sum thereof is 1.
Averaging the connection time for the node i;the average communication time of the neighbor node j; n is the number of neighbor nodes of the node i; deg i Is the node degree, deg, of a node th A system node degree threshold value, the size of which depends on the network scale and the number of vehicles; v. of max Is the maximum travel speed; v. of i The current running speed is the node i; delta (i, t) is the speed variance value of the node i in the (t-delta t, t) time period; n is a radical of hydrogen c The number of neighbor nodes with the movement direction consistent with the node i.
Under the Segment (x, y), the vehicle node with larger average connection time and highest direction correlation degree has larger connection stability W stability Preferentially becoming a cluster head; at Intersection (x, y), the longer the average connection time of the vehicle, and the lower the running speed, the connection stability W stability The higher the node becomes the cluster head, the more stable the clustering isHigh, the longer the cluster survival time.
Step 1-6), the node i becomes a cluster head node, and a CM clustering message is broadcasted to a neighbor node; the clustering message comprises a cluster head ID, establishment time and a message type; where the message type flag creates < Cluster Create > for the Cluster.
Step 1-7) the neighbor node j receives the CM clustering message from the node i, inserts the information of the node i into a cluster head list, simultaneously fills the ID of the cluster head node i into the BM beacon message, and sends the BM beacon message to the cluster head node i; and the node i receives the beacon message from the j, compares the cluster head information and adds the j into the cluster member list.
Step 1-8) repeating steps 1-1) to 1-8) until all nodes in the network have joined the cluster.
The self-adaptive cluster maintenance process mainly aims at the joining and moving-out of vehicle nodes, the reselection of cluster head nodes and the combination and the splitting of clusters. By dividing the cluster self-adaptation according to the road environment, the stability of the cluster is ensured to be enhanced, and the network overhead is reduced.
The leaving and joining of the nodes specifically comprises the following steps:
step 2-1-1) the cluster member node j periodically acquires the beacon information of the neighbor node and updates a cluster head list;
step 2-1-2) in a time period of t1, when a cluster member node j does not receive beacon information from a current cluster head node i, namely the current cluster head i is found to be unreachable, indicating that the cluster member node j leaves the communication radius of the cluster M (i), and entering step 2-1-3); and when the cluster member node j simultaneously receives the BM beacon information from the new cluster head node k, the current node enters the communication radius of the cluster M (k), and the steps 2-1-6) are executed.
Step 2-1-3) when the cluster member node j judges that the current cluster M (i) is left, searching whether other cluster head node beacon information exists, and if so, performing the next step 2-1-4); if the node j does not receive the beacon information from other cluster head nodes, executing the step 2-1-5).
Step 2-1-4) judging the road environment of the node j, and calculating the node j and the cluster head node when the node is in the section (x, y)k link connection time T kj (T) if T is satisfied kj (t)＞T th If the node is in the cluster M (k), filling the ID of the cluster head node k into the BM beacon message and broadcasting the BM beacon message to the neighbor nodes, and if the ID is not in the cluster head node k, executing the step 2-1-5); when the node j is positioned at the Intersection (x, y), if the cluster head node k is positioned at the Intersection (x, y), the node j is directly added into the cluster M (k); if the cluster head node k is in the Segment (x, y), j and the cluster head node k are judged to meet T kj (t)＞T th If yes, adding the cluster M (k), otherwise, entering the next step 2-1-5).
Step 2-1-5) waiting for tw time, repeatedly judging whether available clusters exist, if no clusters exist, starting a cluster initialization clustering process by the node j, and executing the step 1).
Step 2-1-6) if the node j receives the beacon information of the cluster head node i and the new cluster head node k at the same time, calculating the link connection maintaining time T between the node j and the current cluster head node i and the new cluster head node k respectively ij (T) and T kj (t) of (d). If T kj ≥η·T ij If the node j selects to leave the current cluster M (i), a new cluster M (k) is added, and meanwhile, a BM beacon message is broadcasted to the neighbor nodes; otherwise, the node does not perform any processing; wherein eta cluster head switching proportionality coefficient satisfies eta is more than or equal to 1.
The cluster merging specifically comprises the following steps:
step 2-2-1) when a cluster head node i receives a BM beacon message from a neighbor cluster head node k, the two cluster head nodes are mutually within the communication radius of each other, and a cluster M (i) and a cluster M (k) are merged;
step 2-2-2): comparing the communication stability Wstability (i) and Wstability (k) of the cluster head node i and the cluster head node k, if Wstability (i) > Wstability (k) is met, giving up the cluster head node k as a cluster head, resolving the cluster M (k), and emptying a cluster member list; the Cluster head node k creates a CM message packet and broadcasts the CM message packet to the neighbor nodes, wherein the CM message packet contains Cluster head ID and message type, and the message type is set as disperse Cluster < Cluster Disolution >.
Step 2-2-3) after the member node of the cluster M (k) receives the message of the dispersed cluster CM from the cluster head node k, deleting the corresponding cluster head item in the cluster head list; and the nodes in the communication range of the cluster head node i are added into the cluster M (i), and other nodes search the BM beacon message and execute the leaving and adding processes of the nodes.
The splitting of the cluster is that when the density of vehicle nodes in the region is increased, member nodes in the cluster are increased, and in order to maintain the stability of the cluster, when the cluster size reaches a quantity threshold value, the splitting is carried out in the cluster. The method specifically comprises the following steps:
step 2-3-1), the cluster head node k updates the cluster member list at regular time, and when the number of the cluster member list members calculated by the cluster head node is greater than a threshold value Mmax, the cluster head carries out a cluster splitting process;
step 2-3-2) the Cluster head node k creates a CM Cluster message packet containing Cluster head ID and message type, wherein the message type is set as Cluster split < Cluster digital >.
And 2-3-3) the cluster member node j receives the clustering splitting message from the cluster head node k, deletes the k information in the current cluster head list, traverses the cluster head list and executes the leaving and joining process of the node.
Finally, it is noted that the above-mentioned preferred embodiments illustrate rather than limit the invention, and that, while the invention has been described in detail with reference to the above-mentioned preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims.
Claims (6)
1. A dynamic clustering method based on vehicle node communication stability is characterized in that: the method comprises the following steps:
step 1) initializing a vehicle-mounted self-organizing network, and dynamically clustering;
step 2) clustering self-adaptive maintenance, including node leaving and joining, cluster merging and cluster splitting;
the step 1) specifically comprises the following steps:
step 1-1) all vehicle nodes in the vehicle-mounted self-organizing network are common nodes, and the vehicle node i acquires the current position p (x, y), the speed v and the motionThe direction d, according to the current road position mark, judging the current road environment, and calculating the node degree Degi and the node average connection time of the node at the current moment
Step 1-2) filling BM beacon information by a node i, and broadcasting the BM beacon information to neighbor nodes; receiving BM beacon information from a neighbor node, updating a neighbor list, and starting clustering waiting time timing;
step 1-3) judging whether a cluster M and a cluster head node CH exist in a current area or not by a node i through neighbor BM beacon information, if the cluster exists in a road environment where the node i is located, the node i receives a CM cluster message from a node j, the node i inserts the information of the node j into a cluster head list, and meanwhile, an ID of the cluster head node j is filled into the BM beacon message and sends the BM beacon message to the cluster head node j; the node j receives the beacon message from the node i, compares the cluster head information, adds the node i into the cluster member list, and then jumps to the step 1-8); if not, jumping to the next step;
step 1-4) when no cluster exists in the environment of the node i, judging whether the cluster waiting time exceeds the preset cluster waiting time tw of the system, if so, electing the node as a cluster head node, and executing the step 1-6); if not, jumping to the next step;
step 1-5) the node firstly judges the position mark of the current road, calculates the communication stability Wstability (i) of the current node, and judges whether the requirement that the Wstability (i) is more than or equal to W is met th Wherein W is th A communication stability threshold value is set for the system; if the conditions are met, the nodes directly create a cluster and enter the step 1-6); if the condition is not met, the node waits for the time t0 and returns to the step 1-2);
step 1-6), the node i becomes a cluster head node, and a CM clustering message is broadcasted to a neighbor node; the clustering message comprises a cluster head ID, establishment time and a message type; wherein the message type flag creates < Cluster Create > for the Cluster;
step 1-7) the neighbor node j receives the CM clustering message from the node i, inserts the information of the node i into a cluster head list, simultaneously fills the ID of the cluster head node i into the BM beacon message, and sends the BM beacon message to the cluster head node i; the node i receives the beacon message from the node j, compares the cluster head information and adds the node j into a cluster member list;
step 1-8) repeating the steps 1-1) to 1-8) until all nodes in the network are added into the cluster;
the leaving and joining of the node comprises the following steps:
step 2-1-1) the cluster member node j periodically acquires the beacon information of the neighbor node and updates a cluster head list;
step 2-1-2) in a time period of t1, when the cluster member node j does not receive beacon information from the current cluster head node i, indicating that the cluster member node j leaves the communication radius of the cluster M (i), entering step 2-1-3); when a cluster member node j simultaneously receives BM beacon information from a new cluster head node k, the current node enters the communication radius of a cluster M (k), and the step 2-1-6 is executed;
step 2-1-3) when the cluster member node j judges that the current cluster M (i) is left, searching whether other cluster head node beacon information exists or not, and if the cluster member node j leaves the current cluster M (i), performing the next step; if the node j does not receive the beacon information from other cluster head nodes, executing the step 2-1-5);
step 2-1-4) judging the road environment of the node j, and calculating the link connection time T between the node j and the cluster head node k when the node is positioned in the section Segment (x, y) kj (T) if T is satisfied kj (t)＞T th If the node is in the cluster M (k), filling the ID of the cluster head node k into the BM beacon message and broadcasting the BM beacon message to the neighbor nodes, and if the ID is not in the cluster head node k, executing the step 2-1-5); when the node j is positioned at the Intersection (x, y), if the cluster head node k is positioned at the Intersection (x, y), the node j is directly added into the cluster M (k); if the cluster head node k is in the Segment (x, y), j and the cluster head node k are judged to meet T kj (t)＞T th If yes, adding the cluster M (k), otherwise, entering the next step 2-1-5); wherein T is th Is a connected time threshold;
step 2-1-5) waiting for tw time, repeatedly judging whether available clustering exists, if no clustering exists, starting a cluster initialization clustering process by a node j, and executing the step 1);
step 2-1-6) if the node j receives the beacon information of the cluster head node i and the new cluster head node k at the same time, calculating the link connection maintaining time T between the node j and the current cluster head node i and the new cluster head node k respectively ij (T) and T kj (t); if T kj ≥η·T ij If the node j selects to leave the current cluster M (i), a new cluster M (k) is added, and meanwhile, a BM beacon message is broadcasted to the neighbor nodes; otherwise, the node does not perform any processing; wherein eta cluster head switching proportionality coefficient satisfies eta is more than or equal to 1;
the merging of the clusters specifically comprises the following steps:
step 2-2-1) when a cluster head node i receives a BM beacon message from a neighbor cluster head node k, the two cluster head nodes are mutually within the communication radius of each other, and a cluster M (i) and a cluster M (k) are merged;
step 2-2-2): comparing the communication stability Wstability (i) and Wstability (k) of the cluster head node i and the cluster head node k, if Wstability (i) > Wstability (k) is met, giving up the cluster head node k as a cluster head, resolving the cluster M (k), and emptying a cluster member list; a Cluster head node k creates a CM message packet and broadcasts the CM message packet to a neighbor node, wherein the CM message packet comprises a Cluster head ID and a message type, and the message type is set as a Cluster resolution;
step 2-2-3) after the member node of the cluster M (k) receives the message of the dispersed cluster CM from the cluster head node k, deleting the corresponding cluster head item in the cluster head list; the node in the communication range of the cluster head node i is added into the cluster M (i), and other nodes search the BM beacon message and execute the leaving and adding processes of the node;
the splitting of the cluster specifically comprises the following steps:
step 2-3-1), the cluster head node k updates the cluster member list at regular time, and when the number of the cluster member list members calculated by the cluster head node is greater than a threshold value Mmax, the cluster head carries out a cluster splitting process;
step 2-3-2) the Cluster head node k creates a CM clustering message packet which contains a Cluster head ID and a message type, wherein the message type is set as Cluster splitting < Cluster Divide >;
and 2-3-3) the cluster member node j receives the clustering splitting message from the cluster head node k, deletes the k information in the current cluster head list, traverses the cluster head list and executes the leaving and joining process of the node.
2. The dynamic clustering method based on the vehicle node connectivity stability of claim 1, wherein: the road position identification comprises a section identification (x, y) or Intersection identification (x, y).
3. The dynamic clustering method based on the vehicle node connection stability as claimed in claim 2, characterized in that: average connection time of the nodesAnd the average time length value of the link connection of the node i and all the adjacent nodes which can be directly connected at the time t is obtained.
4. The dynamic clustering method based on the vehicle node connection stability of claim 3, characterized in that: the road mark is a road section mark, and when the node i and the node j are in a connected state at the moment T, the link connection time T which can be kept between the node i and the node j ij (t) is:
T ij (t) satisfies the condition D ij (t+T ij (t))≤D th ，D th Is a distance threshold, D th R is less than or equal to r, r is the node communication radius, d is the distance between the node i and the node j in the direction vertical to the road, d is 0 when the node i and the node j are on the same lane, and d is equal to d when the node i and the node j are on the adjacent lanes r Wherein d is r Is the width of the segment (x, y), theta is the included angle between the segment and the horizontal direction, theta is more than or equal to 0 degree and less than or equal to 90 degrees, and x i (t) is the abscissa of the node i, x j (t) is the ordinate of the node i,is the average relative velocity of node i and node j over Δ t.
5. The dynamic clustering method based on the vehicle node connection stability of claim 3, characterized in that: when the road mark is an Intersection mark, the node i and the node j are simultaneously positioned at an Intersection interaction (x, y), and when the node i and the node j are positioned at the same road section before entering the Intersection, the node i and the node j leave the Intersection and drive into different road sections; if the distance D between the node i and the node j ij (t) satisfies the following formula
Then T ij (t) =0, in which l i Length of Intersection (x, y) region; w is a i Width of Intersection (x, y) region; omega is an included angle between two road sections (x, y) at the node i and the node j under the intersection model, and meets the condition that omega is more than or equal to 0 degree&180 degrees; when the node i and the node j are positioned on different road sections before entering the intersection, and the node i and the node j leave the intersection and drive into different road sections; if the distance between the node i and the node j at the moment t + delta t is less than or equal to the distance threshold value D th Then, then
Wherein, Δ v x The difference value of the speed of the node i and the speed of the node j in the delta t at the coordinate horizontal component; Δ x is the difference between the coordinate horizontal components of the node i and the node j at the time t; Δ v y The difference value of the speed of the node i and the speed of the node j in the coordinate vertical component in the delta t is obtained; Δ y is the difference between the coordinate vertical components of node i and node j at time t.
6. The dynamic clustering method based on the vehicle node connectivity stability of claim 1, wherein: the node connection stability Wstability (i) is calculated by the following formula:
wherein, ω 1, ω 2, ω 3, ω 4 are weighting factors,the average connection time normalization value of the node i is obtained;characterizing connectivity, deg, of node i i Is the node degree, deg, of a node th A system node degree threshold;the motion state of a current vehicle node i is characterized, delta (i, t) is a speed variance value v of the node i in a (t-delta t, t) time period max At maximum driving speed, v i As node i current speed of travel, N c The number of neighbor nodes with the movement direction consistent with the node i is N, and the number of the neighbor nodes of the node i is N.
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