CN108650141A - A kind of access model of large scale network being connected to base based on car networking - Google Patents
A kind of access model of large scale network being connected to base based on car networking Download PDFInfo
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- H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
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Abstract
A kind of access model of large scale network being connected to base based on car networking.Consider car networking network node redundancy properties, gives a kind of car networking network topology structure, i.e., car networking is connected to base, and gives connection base building method using heuritic approach.From connection base internal structure attribute and dynamic characteristic, in conjunction with half Markov mobility model of smooth Gaussian, demonstrate the connectivity and stability of car networking large scale network, give car networking access theoretical model, the theoretical model can be to the network connectivty and stability progress accurate evaluation under car networking high dynamic environment, simultaneously theory support is provided for network layer, real time data guarantee is provided for application layer, so that keeping stablizing lasting transmission important information under car networking high dynamic network environment, such as traffic accident information, real time media data etc., it is worth with important theory and actual application.
Description
Technical field
The present invention relates to car networking complex network fields.
Background technology
In recent years, domestic and foreign scholars are concentrated mainly on a certain special scenes to the research of car networking network performance or are based on
On network-in-dialing Journal of Sex Research under certain assumed conditions, existing car networking connection Journal of Sex Research is mainly concentrated and two aspects：(1) it holds
To end connectivity；(2) network entirety connectivity.
Connected probability under end to the section connection main research trends network environment of Journal of Sex Research between two nodes at present.It is such
Research is modeled as 1-D cyberspaces generally directed to certain a road section in highway either City scenarios, then foundation
Certain Node distribution model such as random distribution are evenly distributed or Poisson distribution carrys out connected probability and vehicle between analysis node
The relationship of density.But these researchs are under the premise of vehicle node distribution is under the jurisdiction of a certain mathematical distribution model, research is high
The pass between end to end connectivity probability and node density in fast highway scene or city in a section between two nodes
Network entirety connectivity and stability are studied not from car networking large scale network scene by system.
Network entirety connectivity is based primarily upon the relationship that theoretical research network-in-dialing and node density are oozed in Chongqing, oozes reason according to exceeding
By the required node density of network-in-dialing is solved, solution procedure does not account for the mobility and network topology of car networking node
The inherent attribute of structure does not provide the scale for weighing network performance under large-scale network environment in real time still.
In conclusion the correlative study for car networking network performance is concentrated mainly on network connectivty, including end is arrived
Hold two aspect of connectivity and network entirety connectivity.End to end connectivity Journal of Sex Research mainly considers small using Node distribution model analysis
The relationship of connected probability and traffic density and communication radius under scale network environment between two nodes, not from overall network angle
Degree, which sets out, studies network connectivity.And network is integrally connected to Journal of Sex Research and is generally basede on to exceed and oozes theory analysis network static connectivity
With the variation of traffic density, node mobility is not considered, can not provide the scale for weighing network connectivty in real time.Therefore, vehicle
The research work of intranet network performance is not furtherd investigate, and can not accurately weigh the performance of large scale network in real time.
Invention content
The present invention is based on the connection base components to interconnect (filed in 11 days October in 2017 of the inventors such as Cheng Jiujun
《The connection base component building method that car networking large scale network interconnects》(applicant：Tongji University, number of patent application
201710397807 7), give car networking large scale network access model.
Technical solution of the present invention is：
A kind of access model of car networking large scale network, specific method include the following steps：
Car networking access analysis of the step 1. based on connection base；
Access model of the step 2. based on connection base；
Step 21. joint movements model；
Step 22. network connectivty；
Step 23. network stabilization；
The access model of step 24. network
Advantageous effect
Do not consider from overall network angle and node mobility for current car networking, can not provide in real time
The scale for weighing network connectivty, the problems such as leading to not accurately weigh the performance of large scale network in real time, the present invention is based on mutual
Join the connection base component of intercommunication (filed in 11 days October in 2017 of the inventors such as Cheng Jiujun《Car networking large scale network interconnects
The connection base component building method of intercommunication》(applicant：Tongji University, number of patent application 201710397807.7) out of connection base
Portion's structure attribute and dynamic characteristic are set out, and in conjunction with-half Markov mobility model of smooth Gaussian, have studied the extensive net of car networking
The connectivity and stability of network give car networking access theoretical model, which can be to car networking high dynamic ring
Network connectivty and stability under border carry out accurate evaluation, while providing theory support for network layer, are provided for application layer
Real time data guarantee so that keep stablizing lasting transmission important information, such as traffic thing under car networking high dynamic network environment
Therefore information, real time media data etc., there is important theory and actual application to be worth.
Description of the drawings
Fig. 1 communication path schematic diagrames
Fig. 2 one hop link models
Difference Δ t lower network stability errors CDF when Fig. 3 α=0.9
Fig. 4 Δ t=0.2s difference α lower network stability errors CDF
Network is access when Fig. 5 communication radius is 300 meters and the relationship of delivery ratio and traffic density
Network is access when Fig. 6 communication radius is 500 meters and the relationship of delivery ratio and traffic density
Network is access when Fig. 7 communication radius is 300 meters and the relationship of delivery ratio and speed mean square deviation
Network is access when Fig. 8 communication radius is 500 meters and the relationship of delivery ratio and speed mean square deviation
Fig. 9 is the method for the present invention flow chart
Specific implementation mode
The access Study on Problems of car networking network is one important direction of car networking research field, is car networking internetworking
Can the important indicator that can be judged, the data that it is related to network accurately reach the destination and keep being stably connected with.At present about
The research of car networking connectivity focuses primarily upon two aspect of end to end connectivity and network entirety connectivity.End to end connectivity is ground
Study carefully the main connected probability and traffic density for considering to use under Node distribution model analysis small scale network environment between two nodes
With the relationship of communication radius, not from overall network angle research network connectivity.And network is integrally connected to Journal of Sex Research
It is generally basede on the variation for exceeding and oozing theory analysis network static connectivity with traffic density, does not consider node mobility, can not be given
The scale for going out to weigh network connectivty in real time, to can not accurately weigh the performance of large scale network in real time.The present invention be directed to
Upper problem provides the access model of large scale network that base is connected to based on car networking, and the model is based on the connection base to interconnect
Component is (filed in 11 days October in 2017 of the inventors such as Cheng Jiujun《The connection base group that car networking large scale network interconnects
Part building method》(applicant：Tongji University, number of patent application 201,710,397,807 7), the technical side which provides
Case is：Considering car networking network node redundancy properties, gives a kind of car networking network topology structure, i.e. car networking is connected to base,
And give connection base building method using heuritic approach.), from connection base internal structure attribute and dynamic characteristic, knot
Close smooth Gaussian-half Markov mobility model, it was demonstrated that the connectivity and stability of car networking large scale network give vehicle
Network access theoretical model, the theoretical model can under car networking high dynamic environment network connectivty and stability into
Row accurate evaluation, while theory support is provided for network layer, provide real time data guarantee for application layer so that car networking high dynamic
It keeps stablizing lasting transmission important information, such as traffic accident information, real time media data etc. under network environment, have important
Theory and actual application value.
The specific implementation process of the present invention is as shown in figure 9, including following 3 aspects：
1. the access analysis of car networking based on connection base
2. the access model based on connection base
3. testing
4. network stabilization is verified
5. the verification of the access model of network
①
The access analysis of car networking based on connection base
Currently invention addresses car networking large scale network is access, because car networking connection base has only screened several connected member sections
Point constitutes connection base, reduces network node redundancy, and network size is smaller compared to former network, and does not influence the normal of network
Operation, based on the research of connection base, network is access can effectively reduce access computation complexity.
Here, for any given network G, wherein vehicle node integrates as V, link set E.G can regard as by network section
Point device, the communication link of connecting node and the dynamic topological structure that is made of node and link form.Connect if network G exists
Logical baseIt is connected member node and ordinary node G points, and the communication full powers between ordinary node give and dominate its company
Logical member node processing, then any two points v in networki, vjBetween network it is access be vi, vjBetween connection base it is access again
In addition connection base and two node adjacent links it is access, that is,：
WhereinFor vi, vjBetween connection base.
When centre forwarding connected member node is more, it is connected to the access of link between base and node and can be ignored,
V at this timei, vjBetween network access be：
So the access of network G is approximately equal to its connection baseIt is access.Namely：
The access of network depends primarily on network connectivty and network stabilization, and the present invention analyzes it from these two aspects
The influence access to network：
(1) network connectivty Co
In car networking, node wireless transmission range is limited, ability phase when being in corresponding communication radius range between node
Even.Network connectivty has reacted the connected state between terminal, is the key factor for determining that network is access.
(2) network stabilization St
Due to the high-speed mobility of vehicle node, between node the transmission range moment change, old path disconnects and new route is built
Vertical frequently alternating, network topology dynamic change is quickly.Network stabilization is to ensure that data can stablize the basis of transmission.
The connection base of network G is sought respectivelyConnectivityAnd stabilityIt can be obtained the access of G
Ac (G), just like minor function relationship：
②
Access model based on connection base
(1) joint movements model
For car networking network, the movement of vehicle has certain regularity, to study the access of mobile status lower network
It needs network node motion model.Present invention assumes that the topological structure of network does not become within a shorter time
Change, continuous movement discretization is described into the change of topological structure at any time using-half Markov mobility model SGM of smooth Gaussian
Change.
For a given car networking network, be cut into equal short time interval Δ t first, in this way continuous time
Each tempon is represented by tk=Δ t+tk-1；K=1,2 ..., n.Assuming that in network all nodes according to SGM move and
The initial position of node is it is known that node viInitial position be (xi0,yi0).V can so be obtainediIn kththThe position at a moment
(xik,yik) be：
Wherein VeikIndicate viIn kththThe speed at a moment, θikIndicate viThe direction of motion.In time interval Δ t, I
Movement direction of nodes is regarded as it is constant.The position of node any moment in a network in this way can be solved by above formula, if Δ t
Value is smaller, and the node location solved is more accurate.
It can calculate node v by formula (5)iAnd vjIn kththThe Euclidean distance at a moment is：
According to the Euclidean distance D between nodeij(tk) and node communication radius can be between decision node connection status,
aijIndicate that the connection status between node, R indicate communication radius, then
According to kththThe time-varying adjacency matrix that connection status between moment arbitrary node can build network is：
A(tk) indicate kththThe whole network period is divided into n time interval by the network topology structure at moment, and network is every
The adjacency matrix at a moment can be acquired according to above formula, and then understand the network connection state at each moment, be moved for establishing
The access model of state lower network is significant.
(2) network connectivty
Connection base is to cover the topological structure of whole network, and ensure that each node only has one to the distance of connected member
It jumps, the car networking connectivity assessment based on connection base is exactly to assess the connectivity for being connected to base.
Define 1 communication path：The alternate sequence w=v of nodes and side0e0v1e1v2e2…vkekvk+1For access
Diameter.Wherein k is the hop count of communication path.If v in communication path w0=vk+1, then communication path is referred to as connected ring.
Fig. 1 is communication path schematic diagram.In network a, v1And v6Between hop count be 3 the number of communication path be 4, point
It is not：v1v2v3v6, v1v2v5v6, v1v4v3v6, v1v4v5v6.And in network b, v1And v5Hop count be 3 communication path number
For：v1v2v4v5And v1v3v4v5.Network a contains more communication paths than network b, even if partial link disconnects in network, network
A can still keep being connected to.Therefore, the connectivity ratio b of network a is strong.Therefore it may be concluded that it is alternative between nodes
The number in path determines network connectivty.It is possible thereby to infer, the connectivity of the car networking based on connection base depends on connection
The number size of communication path in base.For network G, connection base isThe number of middle communication path is arbitrary connected member
It is rightBetween hop count be k communication path numberSum.But in large scale networkDifficulty in computation it is larger,
The complexity of calculating can be very high, and the number for being connected to loop can also measure the number of communication path in network, computation complexity
It will be lower.Connection loop number be：
WhereinExpression hop count is k, and starting point isConnection loop number, NkIndicate that all hop counts are in connection base
The number of the connection loop of k.Sum is bigger, illustrates that the number of backup path is more, the connectivity for being connected to base is stronger.But it is counting
When calculating Sum, the case where side and node repeat is contained, final Sum values may be intended to infinity.For arbitrary connected member pairThe more connection loop of hop count and the repetitive rate that other loops calculate are higher, it should reduce the connection loop more than hop count
In the ratio that Sum is accounted for, therefore to NkIt is weighted, i.e.,：
Wherein λiTo be connected to the characteristic value of base adjacency matrix.
Found out by above formula, Sum ' can be calculated by the characteristic value of adjacency matrix and be obtained.But when network size is larger, Sum '
It will be a prodigious number.For the sake of convenient, by Sum ' carry out logarithm operations, connection base is obtainedConnectivity value
Formally see,It is proportional relation with Sum ',It is connection base adjacency matrixAll features
The special average value of value, has only passed through an exponent arithmetic and logarithm operation.
After the motion model of node, kth can be acquired according to formula (11)thThe network connectivty at momentEqually network cycle is discrete for after multiple time interval Δ t, the network-in-dialing degree at each moment can be asked
Solution.Δ t values are smaller, and obtained network connectivty is more accurate.
Specific network connectivty calculates step should be as follows：
1. structure connection baseThe initial position of acknowledging time interval of delta t, the communication radius of node, connected member, then root
According to connection status of the position information confirming of connected member between it, and then build the adjacency matrix of initial time
2. according to kththThe adjacency matrix at momentIt calculatesCharacteristic value, then according to formula (11) calculate
Connectivity
3. if network life cycle is also not finished, (k+1) is calculated according to SGMthThe position of each connected member in moment network
It sets, and establishes adjacency matrix at this timeConnectivity is recalculated, until whole network life cycle terminates.
(3) network stabilization
Connection base be cover whole network topological structure, by be connected to base dynamic network topology stability analysis come
The stability for analyzing whole network, the network stabilization Journal of Sex Research based on connection base are substantially the stability for studying connection base.
Car networking is that its topological dynamics, link are established and disconnect frequent, the link longevity with the maximum difference of traditional network
Life can weigh the stability of a link.In real network, directly by sent the message between node confirm node it
Between link available duration there are certain error and interference, Kalman Filter Technology can remove noise reduction truthful data.Therefore
The present invention is based on node motion models and Kalman filtering to calculate the link service life, and then derive the stability of network.
For any two node vAAnd vB, enable VeAkAnd VeBkV is indicated respectivelyAAnd vBIn kththThe speed at moment.According to
SGM models can be obtained node in kth+1thThe speed at moment.Further, node vAAnd vBAt (k+1)thThe speed relatively at moment
Degree can be calculated as follows：
Wherein, VeRk=VeAk-VeBk, yRk=yAk-yBk, it is clear that yRkIt is 0 for mean value, variance σR 2=2 σ2Gaussian random
Variable.
In order to calculate the link service life, following one hop link model, such as Fig. 2 are considered.Two vehicle node vAAnd vBExist according to figure
It is moved in network.Although vAAnd vBIt is moved all in accordance with SGM, it is assumed that vAIt is static, vBAccording to the relative velocity movement in formula (12).
Network regards a coordinate system, vehicle v asAIn origin, as long as vehicle vBBetween coordinate (- R, 0) to (R, 0), vAAnd vBIt establishes
Link.As vehicle vBInto vATransmission radius when, vABeacon message is will receive, and Kalman filtering is begun to use to calculate
vBDisplacement distance and and vBBetween relative velocity, and then calculate two nodes between the link service life.
Kalman filter is realtime recurrent algorithm, is used for carrying out optimal estimation, algorithm to the state variable of dynamical system
Including two important equations：The state equation and observational equation of system.
State equation is provided first, and in the above two node links model, state variable includes vehicle vBOperating range
And vBMovement speed, according to SGM models, the two variables are all related to previous moment, therefore (k+1)thThe state at moment
Process equation is：
Wherein xk+1And xkRespectively refer to vehicle vBAt (k+1)thAnd kthThe position at moment；yRkAnd yxkIt is independent incoherent
Gaussian random variable, mean value are 0, and variance is respectively σR 2And σx 2.The matrix form of state equation is：
Process equation can be regarded as a kind of common version X by above formulak+1=TXk+wk, Xk+1For state variable vector, T
It is kththThe state-transition matrix at moment, wkBe mean value it is 0 for observation noise, covariance matrix is the Gaussian random variable of Q.
Can obtain Q according to formula (14) is：
Observational equation is uniformly provided by Kalman filter, kththThe observational equation at moment is Zk=HXk+μk, wherein ZkIt is to see
Direction finding amount, H are observing matrix, μkIt is observation noise, it is that mean value is 0, and covariance matrix is the gaussian variable of R.
Then it enablesFor XkPrior estimate,For XkPosterior estimator,And PkRespectively priori and posteriority covariance
Matrix.Value of the initial value namely in k=0, diagonal element should be king-sized value at this time, and off-diagonal element
Should be 0.ThereforeInitial value be：
Renewal process is updated and observed according to the time of Kalman filter algorithm, we can be to the link service life of network
It is estimated.As shown in Figure 2, as vehicle vBInto vACommunication range within when, vAV can be passed throughBThe Beacon sended over
Information detection is to vB, vehicle v can be obtainedAWith vBAt (k+1)thThe link life estimation value at moment is：
Wherein
For network G, connection base isNetwork stabilization by all links of connection base weighted average Life Table
Show, the weights of each of the links are the ratio for being connected to the communication path number comprising this link in base and accounting for all communication paths.Then net
Network stabilityFor：
Wherein EiIndicate i-th side in connection base, niTo include link E in connection baseiCommunication path number,For even
The number on side, n in logical baseiFor the number of all communication paths in connection base.It is steady to give the measurement network G a certain moment
Qualitative calculation formula, according to formula (18) and Kalman filter algorithm, it can be deduced that any time network in dynamic network
Stability value.
(4) the access model of network
Car networking network is access, i.e., fast implements network interconnection intercommunication according to current task, and keeps stablizing shape in real time
State is for the purpose of completing current task.Access network refers to the network that i.e. connection is stablized again, and the access model of network is then to use
To integrate the connectivity and stability of weighing target network.Because car networking large-scale network node is in large scale, it is directly analyzed
Access difficulty is high, and founding the access model of network based on car networking connection capital construction can smaller network size.For in G arbitrary two
A node vAAnd vB, access network is vAAnd vBBetween connection base net network it is access, then network G is access, be
It is connected to the access of base, it can be deduced that the access calculation formula of network：
WhereinFor the connection base of network G, CothFor network connectivty threshold value, according to the car networking application program of source vehicle
Depending on demand.Network-in-dialing is that access network first has to the condition met, and therefore, the access model of network should first judge net
Whether network connectivity meets application demand, and when connectivity value is more than its threshold value, then network meets application program requirement, at this time network
The access product for connectivity and stability.When network connectivty is less than connectivity threshold value, access is 0.
③
Experiment
Emulation platform and experimental method that the present invention uses with (filed in 11 days October in 2017 of the inventors such as Cheng Jiujun
《The connection base component building method that car networking large scale network interconnects》(applicant：Tongji University, number of patent application
201710397807 is 7) identical, and in order to verify the correctness of proposed access model, the present invention is continuing with (Cheng Jiujun etc.
Filed in 11 days October in 2017 of inventor《The connection base component building method that car networking large scale network interconnects》(Shen
It asks someone：Tongji University, 7) City scenarios terrain vehicle networking scenario that number of patent application 201710397807 designs, in field experiment
The upper left corner and the lower right corner of scape are put respectively there are one fixed roadside infrastructure, and one is source node, is responsible for transmission data packet,
One is destination node, is the destination that data packet is sent.Table 1 is experiment parameter used, according to the regulation of DSRC,
The communication radius of IEEE802.11p be 300 meters to 1000 meters, this experiment be respectively adopted 300 meters and 500 meters it is sensible to analyze network
The variation relation of property and network performance index.
Steps are as follows for specific experiment：
(1) it is first depending on (filed in 11 days October in 2017 of the inventors such as Cheng Jiujun《Car networking large scale network interconnects
The connection base component building method of intercommunication》(applicant：Tongji University, 7) connection that number of patent application 201710397807 provides
Base building method builds car networking and is connected to base；
(2) the Associated Memory parameter alpha and time interval Δ t in smooth Gaussian-Semi-Markov Process are controlled, observation is carried
Go out the correctness of network stabilization, research is suitable for the optimal α under simulating scenes and Δ t values.
(3) the Routing Protocol DSDV geography source-routed protocols based on map are used, number is sent from source node to destination node
According to packet.Control traffic density and car speed standard deviation in network, the delivery ratio and network of research network middle-end to end data packet
Delay, and the network that calculates with access model herein gained is access compares, and verifies the correctness of access model.
④
Network stabilization is verified
To calculate network stabilization, simulation time is needed to be split by Δ t.According to SGM models to the position of node
It is updated with speed, node location and speed is once updated every Δ t.When vehicle B enters the communication range of vehicle A
When, A starts to calculate the relative velocity and relative position with B, has also just obtained the measurement data of Kalman filtering.In simulations,
Each vehicle can calculate the stability on its place side every time Δt, and network snapshots at this time are extracted every time Δt,
Every snapshot network regards static network as, and analyze this moment is really network stabilization.The η definition of network stabilization error
For the poor ratio between true stationary value of the stability value and true stationary value that are calculated according to network stabilization model：
Network stabilization error amount is acquired, and is plotted as figure, as shown in Figures 3 and 4.
Fig. 3 is the network stabilization error CDF under the different Δ t of α=0.9.The result shows that when Δ t is less than or equal to 0.5s,
70% network stabilization error can be less than 20%.This is because as Δ t becomes larger, according to the number for the value that Kalman filtering calculates
Mesh tails off, and then the network stabilization error derived will become larger.Fig. 4 is Δ t=0.2s difference α network stabilization errors
CDF.When α is 0.8 or 0.9, the network stabilization error for being more than 60% is less than 20%.This is it can be appreciated that subtracting with α
Few, velocity variations can be more random between each tempon for node, so network stabilization error can be caused to increase.According to above
Experiment can be inferred that when α=0.9, Δ t=0.2s, network stabilization model can the accurate stability for calculating network.
⑤
The verification of the access model of network
To verify the correctness of the access model of network, consider to carry out pair so that network data packet delivery fraction and network are access
Than.
Emulation experiment is carried out under different traffic densities first, the car speed mean square deviation in setting emulation is all 5m/
s.The average delivery ratio from source node to destination node data packet under different vehicle density is counted under different communication radius, together
When calculate the corresponding access value of averaging network under different vehicle density, and draw the access curve with traffic density of network
Figure.As it can be seen in figures 5 and 6, blue line represents the access theoretical value of network, orange line represents the average throwing for the DSDV agreements that statistics is got
Pass rate.
Under different communication radius, can all have when traffic density deficiency, network is access very low, starts with vehicle
Density increases, and the access speedup of network is slow, and when reaching a threshold value, access beginning sharp increase reaches most to the end
High level, and it is last also there are one threshold value, and speedup is slow after threshold value.
To be found out by Figures 5 and 6, the communication radius of vehicle affects the position of threshold value, when transmission range is 300 meters, network
The access position for starting sharp increase is 0.025/meter, is then 0.02/meter when transmission range is 500 meters.This says
Bright, under other conditions unanimous circumstances, node-node transmission range is bigger, and access network is more easy to implement.When node-node transmission model
No matter enclosing when being 300 or 500 meters, by the correspondence of blue line and orange line position, it can be seen that being calculated according to access model
The access value obtained is more conform with data packet delivery fraction with the conversion curve of traffic density.It is access according to network
Value and data packet delivery fraction can be seen that with the variation relation of traffic density when node ratio is sparse, and connectivity value is not up to
To connectivity threshold value, access network is 0, and the access value of network is not consistent with data packet delivery fraction change curve at this time, still
The access data transmission capabilities that can accurately weigh network of most of situation network.
Then carry out emulation experiment under different speed mean square deviations, set emulation in traffic density as 0.035/
Rice.The average delivery from source node to destination node data packet under friction speed mean square deviation is counted under different communication radius
Rate, while calculating the corresponding access value of averaging network under different vehicle density, and it is access with traffic density to draw network
Curve graph.As shown in FIG. 7 and 8.
Fig. 7 is node communication radius when being 300 meters, and network is access and the change of data packet delivery fraction and speed mean square deviation
Change relationship.When speed mean square deviation is 2m/s, delivery ratio reaches 80%, with the increase of speed mean square deviation, the access sum number of network
All start to reduce according to delivery ratio, and reaches minimum when speed mean square deviation is 10m/s.By to network topology property with speed
The research of the variation of mean square deviation is spent, it is found that the relative velocity between vehicle becomes larger, in network this is because speed mean square deviation increases
Link is easily broken off, and increases network topology dynamic, so data delivery rate can be reduced with the increase of speed mean square deviation.
In Fig. 8 this point is also demonstrated when ranging from 500 meters of node-node transmission.As can be seen from Figures 7 and 8, even if leading in different
Believe under radius and different speed mean square deviations, network is access and delivery ratio as the variation tendency of speed mean square deviation is also basic
Identical, this demonstrates the access models of network to meet simulation result.
In conclusion the access model of car networking large scale network based on connection base can be to the data transmissions of network
Power carries out accurate evaluation.Therefore, using the access model of this network come predict network it is access be it is accurate believable, be suitable for vehicle
Networking large scale network scene.
Innovative point:
The present invention proposes a kind of theoretical model that characterization car networking large scale network is access, to help accurately to weigh
Measure the network performance that car networking large scale network is real-time and stablizes.At present about the research of car networking connectivity not from integral net
Network angle is set out, and does not consider node mobility, the scale for weighing network connectivty in real time can not be provided, thus can not be real-time
The accurate performance for weighing large scale network.The present invention is in view of the above problems, provide the large scale network for being connected to base based on car networking
Access model, based on the connection base component to interconnect, (inventors such as Cheng Jiujun applied the model on October 11st, 2017
's《The connection base component building method that car networking large scale network interconnects》(applicant：Tongji University, number of patent application
201710397807 7), and the technical solution which provides is：Consider car networking network node redundancy properties, gives
A kind of car networking network topology structure, i.e. car networking are connected to base, and give connection base building method using heuritic approach.),
From connection base internal structure attribute and dynamic characteristic, in conjunction with-half Markov mobility model of smooth Gaussian, it was demonstrated that vehicle connection
The connectivity and stability of net large scale network give car networking access theoretical model, which can join vehicle
Network connectivty and stability under net high dynamic environment carry out accurate evaluation, while providing theory support for network layer, are
Application layer provides real time data guarantee so that it keeps stablizing lasting transmission important information under car networking high dynamic network environment,
Such as traffic accident information, real time media data etc., there is important theory and actual application to be worth.
Claims (4)
1. a kind of access model of large scale network being connected to base based on car networking, which is characterized in that car networking network is access,
Network interconnection intercommunication is fast implemented according to current task, and keeps stable state for the purpose of completing current task in real time；It is logical
Refer to the network that i.e. connection is stablized again up to property network, the access model of network is then for the comprehensive connectivity for weighing target network
And stability.For any two node v in GAAnd vB, access network is vAAnd vBBetween connection base net network it is access,
So the access of network G is then connected to the access of base for it, it can be deduced that the access calculation formula of network：
WhereinFor the connection base of network G, CothFor network connectivty threshold value, according to the car networking application requirement of source vehicle
It is fixed.
2. the access model of large scale network of base is connected to based on car networking as described in claim 1, which is characterized in that network
Connection is that access network first has to the condition met, and therefore, whether the access model of network first should judge network connectivty
Meet application demand, when connectivity value is more than its threshold value, then network meets application program requirement, and network is access for connection at this time
The product of property and stability；When network connectivty is less than connectivity threshold value, access is 0.
3. being connected to the access model of large scale network of base based on car networking as described in claim 1 or 2, feature exists
In, obtain connection baseConnectivity value
Formally see,It is proportional relation with Sum ',It is connection base adjacency matrixAll characteristic values
Special average value；
After the motion model of node, kth can be acquired according to formula (11)thThe network connectivty at moment
4. being connected to the access model of large scale network of base based on car networking as described in claim 1 or 2, feature exists
In then network stabilizationFor：
Wherein EiIndicate i-th side in connection base, niTo include link E in connection baseiCommunication path number,To be connected to base
The number on middle side, niFor the number of all communication paths in connection base.
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