CN103873485A - Cluster MAC protocol implementation method based on link duration time in vehicle-mounted self-organizing network - Google Patents

Abstract

The invention discloses a cluster MAC protocol implementation method based on link duration time in a vehicle-mounted self-organizing network and belongs to the technical field of vehicle-mounted self-organizing networks. A clustering method based on the link duration time is included. Through the average link linkage time and the node communication degree of vehicle nodes, node priority is determined, a node with the highest priority becomes a cluster head node, a node with the priority second to the cluster head node becomes a standby cluster head, through the standby cluster head, during a cluster updating and maintaining process, the stability of a cluster can be well improved, and expenditure is lowered. The cluster head broadcasts sub-cluster control information to neighbor nodes, and the neighbor nodes are invited to join a sub-cluster with a current node as the cluster head. After clustering, hierarchical management is carried out, the network is divided into a plurality of clusters, nodes in each cluster are communicated with cluster head nodes through a CSMA/TDMA mixed mechanism, data collision is lowered, the cluster head nodes are communicated with neighbor cluster heads through a CSMA/CA mechanism, the reliability of data transmission is obviously improved, and data transmission delay can be effectively lowered.

Description

Bunch MAC agreement implementation method based on the link duration in vehicle-mounted self-organizing network

Technical field

The invention belongs to vehicle-mounted self-organization network technology field, relate to bunch MAC agreement implementation method based on the link duration in a kind of vehicle-mounted self-organizing network, comprise specifically the clustering method based on the link duration in a kind of vehicle-mounted self-organizing network, bunch MAC agreement based on the link duration in the update method in a kind of vehicle-mounted self-organizing network bunch and a kind of vehicle-mounted self-organizing network.

Background technology

Along with vehicle-mounted self-organizing network (VANET) is to high transfer rate, high reliability and high-efficiency future development, the communication mechanism between vehicle is subject to common concern and research.But because vehicle node translational speed is very fast, cause network topology often to change, make traditional MAC agreement face unprecedented challenge.

The network configuration of cluster has good grade difference and division of labor mechanism, utilizes Clustering Algorithm to carry out the transmission of message, can produce effective transmission of messages mechanism.The main purpose of cluster is to choose suitable bunch head, make this bunch of head can safeguard relevant routing iinformation and network topological information, stability that can largeizationr bunch, reduce the impact bringing due to change in topology, reduce offered load, be convenient to the management to whole network, be applicable to large scale network.

The main advantage of MAC agreement based on competition is that it can well adapt to the variation of network, working method very flexibly, between node, do not need to carry out accurate synchronous.And the maximum drawback that it brings be the information dropout causing due to conflict under this mechanism be this quasi-protocol cannot solve completely.And MAC agreement based on distribution mechanism, by being multiple subchannels by a channel distribution, again by the mode of subchannel distribution node, internodal transfer of data has staggered, avoid the generation of conflict, but with respect to the MAC agreement based on competition, this quasi-protocol is poor to the adaptability of network change.

Summary of the invention

In view of this, the object of the present invention is to provide bunch MAC agreement implementation method based on the link duration in a kind of vehicle-mounted self-organizing network, bunch MAC agreement based on the link duration in the update method specifically having comprised in the clustering method based on the link duration in a kind of vehicle-mounted self-organizing network, vehicle-mounted self-organizing network bunch and vehicle-mounted self-organizing network.

For achieving the above object, the invention provides following technical scheme:

The clustering method based on the link duration in vehicle-mounted self-organizing network, comprises the following steps: step 1: node obtains position, speed, acceleration, the node type information of vehicle node by GPS and periodic basic controlling message; Step 2: determine the average link duration between node and neighbor node according to the node location obtaining, velocity information; Step 3: the degree of communication of determining this node according to the historical neighborhood of node and current neighborhood; Step 4: choose the node of priority maximum according to the size of internodal average link duration and degree of communication as a bunch head; Step 5: choosing according to the priority of node the node that is only second to bunch head becomes spare cluster head; Step 6: bunch head, to its bunch of interior nodes broadcast Clustering control message, declares oneself to become a bunch head, and bunch interior nodes is according to the position of oneself and receive that it oneself is a bunch interior nodes that status message is determined, and replys to bunch head.

Further, node location, the velocity information that described basis is obtained determined the average link time between node and neighbor node, is specially:

Node i is obtained current location S by GPS _i, speed v _i, acceleration a _iinformation;

Node i is obtained the current location S of neighbor node j by periodic basic controlling message _j, speed v _j, acceleration a _jinformation;

Node i is calculated the position relationship that can communicate by letter with node j according to following formula:

$\left\{\begin{array}{cc}\frac{1}{2}{(a_j-a_i)t}^2+(v_j-v_i)t=R-(S_j-S_i)& 0\≤t\≤t_1\\ \frac{1}{2}(a_j-a_i)t^2+(v_j-v_i)t=R+(S_j-S_i)& t>t_1\end{array}\right.$

Wherein, t ₁represent that two cars start to having the needed time of identical speed from initial link,

Node i is the link time with neighbor node j according to following formula calculating:

$T_i=\left\{\begin{array}{cc}\min (t,t_{\max })& a_j-a_i\≠0,v_j-v_i=0\\ t_{\max }& a_j-a_i=0,v_j-v_i=0\end{array}\right.$

Node i calculate according to following formula and neighbors between average link time:

$E\left[\mathrm{link}\right]=\frac{\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{T}_i}{N}$

Wherein: N is the neighbor node number of not determining state, t _ifor present node and node i (i=1,2 ..., N) between the link duration, t _maxfor the internodal maximum link duration.

Further, describedly determine that according to the historical neighborhood of node and current neighborhood the degree of communication of node is specially:

Node passes through periodically interaction mode information, records t ₀moment neighbor node set N ₀, and current time t (i) ₁neighbor node set N ₁(i), prediction neighbor node changes frequent degree;

Node i calculate according to following formula and neighbors between degree of communication:

$\mathrm{MC}\left[i\right]=\frac{|N_0\left(i\right)\∪N_1\left(i\right)|-|N_0\left(i\right)\∩N_1\left(i\right)|}{|N_0\left(i\right)\∪N_1\left(i\right)|}$

Wherein: | N ₀(i) ∪ N ₁(i) | for node is at t ₀moment and t ₁all neighbor node numbers of moment, | N ₀(i) ∩ N ₁(i) | for node is at t ₀moment and t ₁the number of the neighbor node that the moment has simultaneously.

Further, described in choose the highest node of average link duration as a bunch head, comprising:

Determine the priority of node according to the average link duration of node, the link duration is larger, and node degree of communication is less, and priority is larger, using the node with the highest link duration as a bunch head, the node that priority is only second to bunch head becomes spare cluster head; Bunch head, to its bunch of interior nodes broadcast Clustering control message, declares oneself to become a bunch head, and bunch interior nodes determines it oneself is bunch interior nodes or spare cluster head according to own state, and to a bunch head reply; Node does not around have other neighbor nodes, and this node forms independent bunch, sets oneself bunch head.

The update method that the present invention also provides in a kind of vehicle-mounted self-organizing network bunch, specifically comprises:

Leader cluster node CH, bunch member node CM and a spare cluster BKCH upgrade according to the variation of the variation of self-position and priority;

Leader cluster node periodically detects, if the average link duration of bunch member CM is greater than self, this member node becomes a bunch head, and broadcasts Clustering control message, and former leader cluster node becomes member node; If the average link duration of leader cluster node CH is still maximum, leader cluster node only need maintain the state of oneself, upgrades its bunch of member's the information such as speed, position; If leader cluster node is not received the periodic broadcasting status messages of certain member node, bunch first this member node is deleted from its membership table so;

Leave the scope of bunch head if exceed 10% bunch member, but do not leave the scope of spare cluster head, just spare cluster head is converted into a bunch head; If bunch head enters into 1/3 of neighbours' bunch transmission range, just setting spare cluster head is bunch head, if spare cluster head is still in 1/3 of neighbours' bunch transmission range, just send last information, declaration merges to neighbours bunch, other bunch of member or add neighbours bunch, or get back to unsettled condition.

The present invention also provides bunch MAC agreement based on the link duration in a kind of vehicle-mounted self-organizing network, comprising: after bunch foundation completes, the stabilization sub stage entering bunch, bunch stabilization sub stage start the transmitting-receiving of business datum; In hierarchical network, leader cluster node must and oneself bunch in the ordinary node retention time on synchronous, make orderly the uploading of data; In bunch MAC agreement, bunch interior nodes adopts CSMA/TDMA mixed mechanism and leader cluster node to communicate; In bunch MAC agreement, leader cluster node adopts CSMA/CA mechanism and neighbours' bunch head to communicate; In bunch MAC agreement according to bunch between syncretizing mechanism solve two bunches of reservation time slot allocation collision problems that produce while meeting.

Further, in the synchronous period, leader cluster node is to a bunch interior nodes broadcast bunch control message, this message is that each bunch of interior nodes distributed the concrete moment of communicating by letter with bunch head, bunch interior nodes, according to the control message of bunch hair cloth, arranges the activity of oneself, when needs oneself are communicated by letter with regard to open communication module, when demand oneself is not communicated by letter, communication close module enters resting state.

Further, bunch head to bunch in member node broadcast tdma communication time slot table, a bunch member receives after broadcast, competitive channel in one's own time slot send the data that monitor to bunch hair; Bunch head is responsible for receiving the data that bunch interior nodes sends and a bunch internal information of receiving is merged, and communicates with adjacent cluster head;

The time frame of bunch first-born one-tenth, is made up of several time slots and a time slot; In each time frame, in bunch, member respectively assigns to a time slot, and member node only could be sent data to a bunch hair by preferential busy channel in the time slot of oneself; Bunch head is issued the distribution of next round time slot, new clock sync signal in time slot, and in bunch, member node, all in the state of intercepting, completes and the communicating by letter of bunch head, and upgrades time slot and clock.

Further, bunch head is received after bunch information of interior nodes transmission, adopts CSMA/CA mechanism to realize communicating by letter between neighbours' bunch head; Bunch head is sending before data, down hop neighbours' bunch head first sends request frame, and its neighbours bunch head receives that sending CTS after RTS replys, and a bunch head sends data to neighbours' bunch head, when neighbours' bunch head is received after packet, to source, a bunch hair send ACK frame acknowledgement data bag to be correctly received; After other neighbours bunch head listens to RTS or CTS, wait for, until this Packet Generation finish after at competitive channel.

Further, according to node bunch in diverse location node is divided into three kinds of different roles: a bunch front nodal point, leader cluster node and a bunch posterior nodal point; The node of diverse location adopts different rules in the time selecting the reservation time slot of oneself, if node is selected the basic time slot of reservation time slot n as oneself, a bunch front nodal point requires n%2=0, and a bunch posterior nodal point requires n%2=1; Two bunches meet after, if two nodes that first meet find two bunches in time slot allocation have the situation of conflict just in the FI of self, corresponding time slot to be made as to the free time, the new time slot of the node application of notice conflict to be to solve time slot allocation conflict, the fusion realizing bunch.

Beneficial effect of the present invention is: the invention provides bunch MAC agreement implementation method based on the link duration in a kind of vehicle-mounted self-organizing network, the stability that the method is conducive to improve in vehicle-mounted self-organizing network bunch, reduces network overhead; Obviously improve the reliability of transfer of data, can effectively reduce data transfer delay.

Accompanying drawing explanation

In order to make object of the present invention, technical scheme and beneficial effect clearer, the invention provides following accompanying drawing and describe:

Fig. 1 is the flow chart that in the embodiment of the present invention, self-organizing network is become to bunch capitiform by unsettled condition;

Fig. 2 is that in the embodiment of the present invention, node periodically sends and accept basic controlling message format;

Fig. 3 be in the embodiment of the present invention in state transition diagram in bunch renewal and maintenance process;

Fig. 4 is the synchronous schematic diagram on the ordinary node retention time in leader cluster node and oneself bunch in the embodiment of the present invention;

Fig. 5 be in the embodiment of the present invention bunch between the schematic diagram of syncretizing mechanism;

Fig. 6 be in the embodiment of the present invention bunch head to bunch in the distribution principle schematic diagram of member node broadcast tdma communication time slot table;

Fig. 7 is that in the embodiment of the present invention, the distribution of MAC protocol channels utilizes schematic diagram;

Fig. 8 is MAC protocol algorithm flow chart in the embodiment of the present invention.

Embodiment

Below in conjunction with accompanying drawing, the preferred embodiments of the present invention are described in detail.

Fig. 1 is the flow chart that in the embodiment of the present invention, self-organizing network is become to bunch capitiform by unsettled condition, and as shown in the figure, the detailed process of node selection bunch head can comprise:

Steps A 1--obtains the information such as node and neighbours' thereof position, speed, acceleration.

Specifically describe as follows, node obtains the information such as the position of self by GPS navigation system, and informs the information such as oneself position, speed and acceleration to neighbours by periodic basic controlling message.

Node calculates the average link duration of oneself by the information of the neighbor node received.

Referring to Fig. 2, Fig. 2 obtains the periodicity basic controlling message format of information of neighbor nodes for the vehicle providing in the embodiment of the present invention.Node is according to the state of type of message judgement oneself, and type of message Type comprises: 0 state information for neighbor node, and 1 is first information of bunch head, and 2 is a bunch control message, and 3 is last information of bunch head.

Steps A 2--is according to node location, the speed obtained, and acceleration information determines that average between node and neighbor node is connected the duration.

Concrete, node i is obtained current location S by GPS _i, speed v _i, acceleration a _ietc. information, node i is obtained the current location S of neighbor node j by periodic basic controlling message _j, speed v _j, acceleration a _jetc. information.Node can be communicated by letter with neighbor node, and position relationship need to meet following formula.

$\left\{\begin{array}{cc}\frac{1}{2}{(a_j-a_i)t}^2+(v_j-v_i)t=R-(S_j-S_i)& 0\≤t\≤t_1\\ \frac{1}{2}(a_j-a_i)t^2+(v_j-v_i)t=R+(S_j-S_i)& t>t_1\end{array}\right.$

Wherein, t ₁represent that two cars start to having the needed time of identical speed from initial link,

Node is according to the average link time between following formula computing node and neighbor node.

$E\left[\mathrm{link}\right]=\frac{\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{T}_i}{N}$

Wherein, $T_i=\left\{\begin{array}{cc}\min (t,t_{\max })& a_j-a_i\≠0,v_j-v_i=0\\ t_{\max }& a_j-a_i=0,v_j-v_i=0\end{array}\right.$

Steps A 3-node is determined the degree of communication of node according to the neighbor node set of interaction mode information acquisition.

Concrete, node passes through periodically interaction mode information, records t ₀moment neighbor node set N ₀, and current time t (i) ₁neighbor node set N ₁(i), prediction neighbor node changes frequent degree; Node i is according to the degree of communication between following formula calculating and neighbors.

$\mathrm{MC}\left[i\right]=\frac{|N_0\left(i\right)\∪N_1\left(i\right)|-|N_0\left(i\right)\∩N_1\left(i\right)|}{|N_0\left(i\right)\∪N_1\left(i\right)|}$

| N ₀(i) ∪ N ₁(i) | for node is at t ₀moment and t ₁all neighbor node numbers of moment, | N ₀(i) ∩ N ₁(i) | for node is at t ₀moment and t ₁the number of the neighbor node that the moment has simultaneously, t ₀and t ₁interval less, calculate more accurate, but can increase network overhead, therefore define it and be spaced apart the mutual cycle of state information;

Steps A 4-choose a bunch head according to internodal average connection duration and node degree of communication.

All node broadcasts state informations, node is received the average connection duration E[link of neighbor node], with the E[link of oneself] relatively, E[link] maximum node becomes a bunch head, if there are multiple maximum E[link], choose degree of communication MC value less for bunch head.

Bunch head, to neighbor node broadcast Clustering control message, is declared oneself to become bunch head and invites neighbor node to add this bunch.If neighbor node is not received Clustering control message within the scope of timer, oneself form independent bunch.If neighbor node is received Clustering control message and is had the E[link that is only second to bunch head], setting oneself is spare cluster head.

Referring to Fig. 3, Fig. 3 is bunch state transition diagram that upgrades and safeguard in the embodiment of the present invention.Due to the fast moving of node, often cause bunch member node to leave the communication range of bunch head, it is necessary therefore bunch upgrading timely and safeguard.

Renewal and the maintenance of steps A 5-bunch head.

Concrete, bunch head periodically detects bunch member's basic status information, if there is the E[link of node in bunch member node] value is greater than leader cluster node, be set with maximum E[link] node be bunch head, former leader cluster node becomes member node, otherwise leader cluster node only upgrades the information such as speed, acceleration and the position of bunch member node.If bunch head is not received bunch member's state information, bunch head is just deleted this member from this bunch so.

When vehicle exceedes transmission range apart from the distance of bunch head, just leave and bunch find next bunch and add, or oneself become independent bunch.Bunch within the scope of, the highest E[link except bunch head] car be made as spare cluster head, this spare cluster head does not form one new bunch, waits for that the state that merges to other bunches or change oneself becomes a master bunch.

After a period of time, bunch member is still in the scope of bunch head, and bunch head just maintains the state of oneself.Because causing a border bunch member, the acceleration and deceleration of vehicle leave bunch.Leave the scope of bunch head if exceed 10% bunch member, but do not leave the scope of spare cluster head, just spare cluster head is converted into a bunch head.

If bunch head enters into 1/3 of neighbours' bunch transmission range, just setting spare cluster head is bunch head, if spare cluster head is still in 1/3 of neighbours' bunch transmission range, just send last information, declaration merges to neighbours bunch, other bunch of member or add neighbours bunch, or get back to independent state.

In the embodiment of the present invention, a bunch MAC process for CSMA/TDMA mixed mechanism comprises:

Step B1-bunch head and synchronous on bunch interior nodes retention time.

Concrete, referring to Fig. 4, Fig. 4 is the synchronous schematic diagram on the ordinary node retention time in leader cluster node and oneself bunch in the embodiment of the present invention.In the synchronous period, leader cluster node is to a bunch interior nodes broadcast bunch control message, in this message, distribute the concrete moment of communicating by letter with bunch head for each bunch of interior nodes, bunch interior nodes is according to the control message of bunch hair cloth, arrange the activity of oneself, when needs oneself are communicated by letter with regard to open communication module, when demand oneself is not communicated by letter, communication close module enters resting state.

Between step B2-leader cluster node adopts bunch syncretizing mechanism for bunch in member distribute time slot.

Concrete, referring to Fig. 5, Fig. 5 be in the embodiment of the present invention bunch between the schematic diagram of syncretizing mechanism.Bunch syncretizing mechanism detailed process is as follows.

I: between bunch, syncretizing mechanism is divided into three kinds of different roles according to the different position of node by node: a bunch front nodal point, leader cluster node and a bunch posterior nodal point.

Ii: the node of diverse location adopts different rules in the time selecting the reservation time slot of oneself, if node is selected the basic time slot of reservation time slot n as oneself, a bunch front nodal point requires n%2=0, a bunch posterior nodal point requires n%2=1.

Iii: node receives that FI frame just upgrades the time slot allocation list of oneself, if there are two nodes to use same time slot, is made as the free time by this time slot at every turn.

Iv: the node clashing will re-start the application of time slot.

After two bunches are met, if two nodes that first meet find two bunches in time slot allocation have the situation of conflict just in the FI of self, corresponding time slot to be made as to the free time, the new time slot of the node application of notice conflict to be to solve time slot allocation conflict, the fusion realizing bunch.

Step B3-bunch head according to distributed time slot to bunch member's time slot table.

The time frame of bunch first-born one-tenth, is made up of several time slots and a time slot.Referring to Fig. 6, Fig. 6 be in the embodiment of the present invention bunch head to bunch in the distribution principle schematic diagram of member node broadcast tdma communication time slot table.In each time frame, in bunch, member respectively assigns to a time slot, and member node only could be sent data to a bunch hair by preferential busy channel in the time slot of oneself.Bunch head is issued the distribution of next round time slot, new clock sync signal in time slot, and in bunch, member node, all in the state of intercepting, completes and the communicating by letter of bunch head, and upgrades time slot and clock.

Step B4-bunch head and bunch interior nodes communicate according to a bunch MAC agreement.

Concrete, in the time slot being assigned with at oneself in CSMA/TDMA period each bunch of interior nodes, preferentially communicate by letter with leader cluster node, in overstepping one's bounds timing gap with other bunch of interior nodes contention access channel.At CSMA period leader cluster node competitive channel, after competitive channel success, communicate by letter with neighbours' bunch head, now, a bunch interior nodes enters resting state.

Referring to Fig. 7, Fig. 7 is that in the embodiment of the present invention, the distribution of MAC protocol channels utilizes schematic diagram.Channel is take 100ms as one-period, and each cycle is divided into two parts: CSMA time period and TDMA time period.Each time period is respectively 50ms.Each time period is divided into 10 time slots, each time slot 5ms.

Between CSMA time period CH, adopt CSMA contention access channel, carry out transfer of data.In the CSMA/TDMA time period, CH allocates time slot in advance to each CM, CM contention access channel, and the CM priority access channel in the assigned timeslot distributing at CH, the stand-by period is SIFS.If not in the own time slot distributing, CM equally can contention access channel, but the stand-by period is DIFS.Guarantee that like this other CM are accessible channel also in the time that CM is idle in distributed time slot, improve the utilance of channel.

Referring to Fig. 8, Fig. 8 is the flow chart based on link duration bunch MAC process that the embodiment of the present invention provides.In bunch MAC, the process of bunch head and bunch interior nodes access channel transmission data is as follows:

Formed bunch by Clustering Algorithm, choose a bunch head;

Bunch head according to synchronization mechanism and bunch between syncretizing mechanism distribute corresponding time slot for a bunch interior nodes;

Node judges according to the state of oneself period that control frame arranges;

If bunch head is communicated by letter the period with a bunch member, bunch member judges oneself to be whether the time slot that bunch head distributes, and if so, waits for competitive channel after SIFS, otherwise waits for after DIFS at competitive channel;

If the communication period between bunch head, adopt CSMA mechanism to communicate with neighbours' bunch head.

Finally explanation is, above preferred embodiment is only unrestricted in order to technical scheme of the present invention to be described, although the present invention is described in detail by above preferred embodiment, but those skilled in the art are to be understood that, can make various changes to it in the form and details, and not depart from the claims in the present invention book limited range.

Claims (10)

1. the clustering method based on the link duration in vehicle-mounted self-organizing network, is characterized in that: comprise the following steps:

Node obtains position, speed, acceleration, the node type information of vehicle node by GPS and periodic basic controlling message;

Determine the average link duration between node and neighbor node according to the node location obtaining, velocity information;

Determine the degree of communication of this node according to the historical neighborhood of node and current neighborhood;

Choose the node of priority maximum according to the size of internodal average link duration and degree of communication as a bunch head;

Choose according to the priority of node the node that is only second to bunch head and become spare cluster head;

Bunch head, to its bunch of interior nodes broadcast Clustering control message, declares oneself to become a bunch head, and bunch interior nodes is according to own position and receive that it oneself is a bunch interior nodes that status message is determined, and to a bunch head reply.

2. the clustering method based on the link duration in vehicle-mounted self-organizing network according to claim 1, is characterized in that: node location, the velocity information that described basis is obtained determined the average link time between node and neighbor node, is specially:

Node i is obtained current location S by GPS _i, speed v _i, acceleration a _iinformation;

Node i is obtained the current location S of neighbor node j by periodic basic controlling message _j, speed v _j, acceleration a _jinformation;

Node i is calculated the position relationship that can communicate by letter with node j according to following formula:

$\left\{\begin{array}{cc}\frac{1}{2}{(a_j-a_i)t}^2+(v_j-v_i)t=R-(S_j-S_i)& 0\≤t\≤t_1\\ \frac{1}{2}(a_j-a_i)t^2+(v_j-v_i)t=R+(S_j-S_i)& t>t_1\end{array}\right.$

Wherein, t ₁represent that two cars start to having the needed time of identical speed from initial link,

Node i is the link time with neighbor node j according to following formula calculating:

$T_i=\left\{\begin{array}{cc}\min (t,t_{\max })& a_j-a_i\≠0,v_j-v_i=0\\ t_{\max }& a_j-a_i=0,v_j-v_i=0\end{array}\right.$

Node i calculate according to following formula and neighbors between average link time:

$E\left[\mathrm{link}\right]=\frac{\underset{i=1}{\overset{N}{\mathrm{\Σ}}}{T}_i}{N}$

Wherein: N is the neighbor node number of not determining state, t _ifor present node and node i (i=1,2 ..., N) between the link duration, t _maxfor the internodal maximum link duration.

3. the clustering method based on the link duration in vehicle-mounted self-organizing network according to claim 2, is characterized in that: describedly determine that according to the historical neighborhood of node and current neighborhood the degree of communication of node is specially:

Node passes through periodically interaction mode information, records t ₀moment neighbor node set N ₀, and current time t (i) ₁neighbor node set N ₁(i), prediction neighbor node changes frequent degree;

Node i calculate according to following formula and neighbors between degree of communication:

$\mathrm{MC}\left[i\right]=\frac{|N_0\left(i\right)\∪N_1\left(i\right)|-|N_0\left(i\right)\∩N_1\left(i\right)|}{|N_0\left(i\right)\∪N_1\left(i\right)|}$

Wherein: | N ₀(i) ∪ N ₁(i) | for node is at t ₀moment and t ₁all neighbor node numbers of moment, | N ₀(i) ∩ N ₁(i) | for node is at t ₀moment and t ₁the number of the neighbor node that the moment has simultaneously.

4. the clustering method based on the link duration in vehicle-mounted self-organizing network according to claim 3, is characterized in that: described in choose the highest node of average link duration as a bunch head, comprising:

Determine the priority of node according to the average link duration of node, the link duration is larger, and node degree of communication is less, and priority is larger, using the node with the highest link duration as a bunch head, the node that priority is only second to bunch head becomes spare cluster head;

Bunch head, to its bunch of interior nodes broadcast Clustering control message, declares oneself to become a bunch head, and bunch interior nodes determines it oneself is bunch interior nodes or spare cluster head according to own state, and to a bunch head reply;

Node does not around have other neighbor nodes, and this node forms independent bunch, sets oneself bunch head.

5. the update method in vehicle-mounted self-organizing network bunch, is characterized in that: specifically comprise:

Leader cluster node CH, bunch member node CM and a spare cluster BKCH upgrade according to the variation of the variation of self-position and priority;

Leader cluster node periodically detects, if the average link duration of bunch member CM is greater than self, this member node becomes a bunch head, and broadcasts Clustering control message, and former leader cluster node becomes member node; If the average link duration of leader cluster node CH is still maximum, leader cluster node only need maintain the state of oneself, upgrades its bunch of member's the information such as speed, position; If leader cluster node is not received the periodic broadcasting status messages of certain member node, bunch first this member node is deleted from its membership table so;

Leave the scope of bunch head if exceed 10% bunch member, but do not leave the scope of spare cluster head, just spare cluster head is converted into a bunch head; If bunch head enters into 1/3 of neighbours' bunch transmission range, just setting spare cluster head is bunch head, if spare cluster head is still in 1/3 of neighbours' bunch transmission range, just send last information, declaration merges to neighbours bunch, other bunch of member or add neighbours bunch, or get back to unsettled condition.

6. bunch MAC agreement based on the link duration in vehicle-mounted self-organizing network, is characterized in that: comprising:

After bunch foundation completes, the stabilization sub stage entering bunch, bunch stabilization sub stage start the transmitting-receiving of business datum; In hierarchical network, leader cluster node must and oneself bunch in the ordinary node retention time on synchronous, make orderly the uploading of data;

In bunch MAC agreement, bunch interior nodes adopts CSMA/TDMA mixed mechanism and leader cluster node to communicate;

In bunch MAC agreement, leader cluster node adopts CSMA/CA mechanism and neighbours' bunch head to communicate;

In bunch MAC agreement according to bunch between syncretizing mechanism solve two bunches of reservation time slot allocation collision problems that produce while meeting.

7. bunch MAC agreement based on the link duration in vehicle-mounted self-organizing network according to claim 6, it is characterized in that: in the synchronous period, leader cluster node is to a bunch interior nodes broadcast bunch control message, this message is that each bunch of interior nodes distributed the concrete moment of communicating by letter with bunch head, bunch interior nodes, according to the control message of bunch hair cloth, arranges the activity of oneself, when needs oneself are communicated by letter with regard to open communication module, when demand oneself is not communicated by letter, communication close module enters resting state.

8. bunch MAC agreement based on the link duration in vehicle-mounted self-organizing network according to claim 7, it is characterized in that: bunch head to bunch in member node broadcast tdma communication time slot table, bunch member receives after broadcast, competitive channel in one's own time slot, send the data that monitor to bunch hair;

Bunch head is responsible for receiving the data that bunch interior nodes sends and a bunch internal information of receiving is merged, and communicates with adjacent cluster head; The time frame of bunch first-born one-tenth, is made up of several time slots and a time slot; In each time frame, in bunch, member respectively assigns to a time slot, and member node only could be sent data to a bunch hair by preferential busy channel in the time slot of oneself; Bunch head is issued the distribution of next round time slot, new clock sync signal in time slot, and in bunch, member node, all in the state of intercepting, completes and the communicating by letter of bunch head, and upgrades time slot and clock.

9. bunch MAC agreement based on the link duration in vehicle-mounted self-organizing network according to claim 8, is characterized in that: bunch head is received after bunch information of interior nodes transmission, adopts CSMA/CA mechanism to realize communicating by letter between neighbours' bunch head;

Bunch head is sending before data, down hop neighbours' bunch head first sends request frame, and its neighbours bunch head receives that sending CTS after RTS replys, and a bunch head sends data to neighbours' bunch head, when neighbours' bunch head is received after packet, to source, a bunch hair send ACK frame acknowledgement data bag to be correctly received; After other neighbours bunch head listens to RTS or CTS, wait for, until this Packet Generation finish after at competitive channel.

10. bunch MAC agreement based on the link duration in vehicle-mounted self-organizing network according to claim 9, is characterized in that: according to node bunch in diverse location node is divided into three kinds of different roles: a bunch front nodal point, leader cluster node and a bunch posterior nodal point; The node of diverse location adopts different rules in the time selecting the reservation time slot of oneself, if node is selected the basic time slot of reservation time slot n as oneself, a bunch front nodal point requires n%2=0, and a bunch posterior nodal point requires n%2=1;

Two bunches meet after, if two nodes that first meet find two bunches in time slot allocation have the situation of conflict just in the FI of self, corresponding time slot to be made as to the free time, the new time slot of the node application of notice conflict to be to solve time slot allocation conflict, the fusion realizing bunch.

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