CN103052093A - Link stability assessment method in VANET (Vehicular Ad-Hoc Network) - Google Patents

Abstract

The invention relates to a link stability assessment method in a VANET (Vehicular Ad-Hoc Network). The link stability assessment method in the VANET comprises the following steps of: resolving the velocity vector between two vehicles into Vx at the parallel direction of a road and Vy at the vertical direction of a road; assessing the duration time delta t of a link formed between two vehicles according to the current distance d between two vehicles, the maximal wireless transmission distance of vehicle nodes as well as the current velocity Vx; and calculating the credibility for the assessed and calculated duration time. The link stability assessment method in the VANET can be used for selecting the next hop transmission node of a data package through calculating the stability of the link, and can be used for improving the link robustness, improving the throughput rate of the whole path, and reducing the transmission time delay of the data package.

Description

A kind of VANET link stability assessment method

Technical field

The present invention relates to the wireless network communication technique field, particularly relate to the appraisal procedure of a kind of link stability under the VANET environment.

Background technology

VANET(VehicularAd-hocNETwork, vehicle self-organizing network) node motion speed is fast in, and network topology change is fast, and link ruptures easily, therefore we wish to find and a kind ofly can calculate the link Lifetime, and the method for this Lifetime confidence level.The method can be applied to Route Selection, improves the performance in whole piece path.

Route Selection is the key factor of wireless communication, and it has determined the throughput of network, and transmission delay directly affects the overall performance of network.This almost all has discussion at all in about the technical literature of Wireless Network Routing Protocol and research paper.Relevant document: LEE J W, CHUN C L, SHIH P T, " A hybrid traffic geographic routing withcooperative traffic information collection scheme in VANET ", 201113th International ConferenceonAdvanced Communication Technology (ICACT), Feb2011, pp.1496-1501.Hartenstein H andLaberteanx K P. " A tutorial survey on vehicular Ad hoc networks[J] " .IEEE CommunicationsMagazine, vol.46, no.6, pp.164-171,2008.

Along with becoming increasingly conspicuous of traffic problems, the transformation of traffic administration theory, the improvement of traffic policy and the application of using many technology such as intelligent transportation raising traffic, intelligent transport technology has become one of current Environment Science study hotspot field.An important component part as intelligent transportation system, Vehicle Ad-Hoc Network (VANET) enjoys world scholars' extensive concern always in recent years, and it is mobile ad-hoc network (MANET) and the concrete application of wireless sensor network (WSN) in intelligent transportation system.By method direct communication or multi-hop communications such as vehicle and vehicle (V2V), vehicle and wayside infrastructure (V2I), make up a self-organizing, dynamic, distributed control network.

Related documents: Chen Lijia, Jiang Hao, Wu waits quietly. and " Vehicle Ad-Hoc Network transmission control research ", Journal of Software, 2007,18 (6): 1477-1490.Wantanee Viriyasitavat, Fan Bai, Ozan K.Tonguz, " Dynamics of Network Connectivityin Urban Vehicular Networks ", IEEE Journal on Selected Areas in Communications, vol.29, no.3, Mar.2011.Yuchen Wu, Yanmin Zhu, Bo Li, " An Infrastructure-Assisted Routing in VehicularNetworks ", 2012Proceedings IEEE INFOCOM, Mar2012, pp.1485-1493.Nianbo Liu, Ming Liu, Guihai Chen, Jiannong Cao, " The Sharing at Roadside:Vehicular Content Distribution UsingParked Vehicles ", 2012Proceeding IEEE INFCOM, Mar.2012, pp.2641-2645.

At present, done large quantity research aspect the Route Selection of Chinese scholars in VANET, propose a lot of schemes and solved this problem, such as active Routing Protocol (optimized link state routing, OLSR), geographic routing agreement (geography source routing, GSR), and other Routing Protocols HTGR (hybrid traffic geographic routing), GPSR (greedy perimeter stateless routing), LAR (1ocaton-aided routing), RTRP (road andtraffic-aware routing protoco1).Yet, can provide the prerequisite of reliability services for vehicle network, namely the research of the connective aspect of VANET topology is also relatively less.

Related documents: B.Karp and H.Kung, " GPSR:Greedy perimeter stateless routing for wirelessnetworks ", Proc.6th Annu.Int.MobiCom, Aug.2000, pp.2315-2319.M.Jerbi, S.M.Senouci, T.Rasheed, Y.Ghamri-Doudane, " Towards Efficient Geographic Routing in Urban VehicularNetworks ", IEEE Transaction onvehicular Technology, vol.58, no.9, pp.5048-5059, Nov.2009.Xiaojun Feng, Jin Zhang, and Qian Zhang, " Trajectory-Assisted Delay-Bounded Routing withMoving Receivers in Vehicular Ad-hoc Networks ", Proceedingsofthe Nineteenth InternationalWorkshop on Quality of Service, ACM, Jun.2011, pp.1-3.Ruobing Jiang, Yanmin Zhu, " Coverage-aware Geocast Routing in Urban Vehicular Networks ", 2012IEEE26th InternationalParallel and Distributed Processing Symposium Workshops﹠amp; PhD Forum (IPDPSW), May2012, pp.2522-2525.

Summary of the invention

For the problems referred to above, the present invention proposes the appraisal procedure of a kind of link stability under the VANET environment.

A kind of VANET link stability assessment method provided by the invention may further comprise the steps:

One, vehicle node speed is decomposed into the road parallel direction and with the road vertical direction;

Two, the functional relation of establishing vehicle node and time t is,

$\left\{\begin{array}{c}{x}_i\left(t\right)=x_i\left(0\right)+v_{\mathrm{ix}}\·\cos {\mathrm{\θ}}_i\·t\\ y_i\left(t\right)=y_i\left(0\right)+v_{\mathrm{iy}}\·\sin {\mathrm{\θ}}_i\·t\end{array}\right.$

Wherein, v _IxBe car speed decompose with the amount of road horizontal direction, v _IyBe car speed decompose with the amount of road vertical direction, θ _iIt is the angle of car speed and road horizontal direction; x _i(0) expression vehicle t ₀The time be engraved in position on the road horizontal direction, y _i(0) expression vehicle t ₀The time be engraved in position on the road vertical direction; x _iBe engraved in the position on the road horizontal direction when (t) representing vehicle t, y _iBe engraved in the position on the road vertical direction when (t) representing vehicle t;

Three, carry out the calculating of link duration, comprise according to the relative velocity v between two vehicle node, relative displacement d, calculating link duration T=(R-d)/and v, wherein R is the wireless transmission distance of vehicle node maximum;

Four, definition s (L _i, t ₀, Δ t) and expression t ₀Moment link L _iUnder the condition that exists, L _iAt t ₀+ Δ t the moment is effective probability still, the stability S of path P (P, t ₀, Δ t) and be illustrated in t ₀The transmission path P that constantly sets up is at t ₀The probability that+Δ t still is communicated with constantly;

Five, in the vehicle-mounted self-organizing network of definition between two cars probability density function and the cumulative function at interval be respectively f _g(x)=λ e ^{-λ x}And F _g(x)=1-e ^{-λ x}, λ=σ/Ev wherein, σ is the arrival rate that vehicle crosses a certain section on the street, Ev is the average speed of all vehicles;

Six, being located at long is to have the probability P of n vehicle node to obey Poisson distribution in the highway section of L, and expression formula is as follows,

$P(X=n)=\frac{{\left(\mathrm{\λL}\right)}^n}{n!}{e}^{-\mathrm{\λL}}$

Wherein, X is the quantity of vehicle node, and P (X=n) refers to that the quantity of vehicle node is the probability of n;

Seven, be located at the probability P that there is at least a vehicle node in the vehicle node transmission range with as follows apart from the relational expression of d,

P=1-P(X=0)

=1-e ^-λd

Eight, obtain two vehicle node and form link L _iStability be s (L _i, t ₀, Δ t)=P ₀, wherein

d ₀T between two cars ₀Distance constantly.

Vehicle-mounted net is to transmit packet and select next-hop node as transmission node with the vehicle in the road, realizes self-organizing and certainly management.Because the vehicle node movement velocity is fast, and the mobile road constraint etc. of being subjected to affects, so that the link that forms ruptures easily, affects greatly the transmission of packet in vehicle-mounted net.The link stability is to weigh the key factor of route robustness and reliability.The present invention is directed to the computational methods that Based on Probability thought under the VANET environment has proposed the link stability.Can be used for selecting according to the stability of calculating the expection link down hop transmission node of packet, improve the robustness of link, reach the throughput that improves the whole piece path and the transmission delay that reduces packet.

Description of drawings

Fig. 1 is the vehicle movement schematic diagram of the embodiment of the invention;

Fig. 2 is that the data of the embodiment of the invention are transmitted schematic diagram.

Embodiment

Technical solution of the present invention can adopt the computer software flow process to realize automatically operation in the specific implementation.Describe technical solution of the present invention in detail below in conjunction with drawings and Examples.

Embodiment provides VANET link stability assessment method may further comprise the steps:

One, with vehicle node speed by shown in Figure 1 be decomposed into the road horizontal direction and with the road vertical direction.Among Fig. 1, d is the distance between two cars, v _iBe the speed of vehicle, θ represents the angle of two car relative velocities and road horizontal direction, v _IxBe car speed decompose with the amount of road horizontal direction, v _IyBe car speed decompose with the amount of road vertical direction.

Two, the functional relation of establishing vehicle node and time t is:

$\left\{\begin{array}{c}{x}_i\left(t\right)=x_i\left(0\right)+v_{\mathrm{ix}}\·\cos {\mathrm{\θ}}_i\·t\\ y_i\left(t\right)=y_i\left(0\right)+v_{\mathrm{iy}}\·\sin {\mathrm{\θ}}_i\·t\end{array}\right.$

v _IxBe car speed decompose with the amount of road horizontal direction, v _IyBe car speed decompose with the amount of road vertical direction, θ _iIt is the angle of car speed and road horizontal direction.x _i(0) expression vehicle t ₀The time be engraved in position on the road horizontal direction, y _i(0) expression vehicle t ₀The time be engraved in position on the road vertical direction.x _iBe engraved in the position on the road horizontal direction when (t) representing vehicle t, y _iBe engraved in the position on the road vertical direction when (t) representing vehicle t.

Three, carry out the calculating of link duration.Comprise according to the relative velocity v between two vehicle node, relative displacement d, calculating link duration T=(R-d)/and v, wherein R is the wireless transmission distance of vehicle node maximum.

Four, definition link L _iStability s (L _i, t ₀, Δ t) and expression t ₀Moment link L _iUnder the condition that exists, L _iAt t ₀+ Δ t the moment is effective probability still.The stability S of path P (P, t ₀, Δ t) and be illustrated in t ₀The transmission path P that constantly sets up is at t ₀The probability that+Δ t still is communicated with constantly.

Five, in the vehicle-mounted self-organizing network of definition between any two cars probability density function and the cumulative function at interval be respectively f _g(x)=λ e ^{-λ x}And F _g(x)=1-e ^{-λ x}, λ=σ/Ev wherein, σ are that vehicle crosses that the arrival rate of a certain section is that what cars per minute has through this section on the street.Ev is the over-all velocity of all vehicles.X is the distance between two cars.

Six, being located at long is to have the probability P of n vehicle node to obey Poisson distribution in the highway section of L, and expression formula is as follows:

$P(X=n)=\frac{{\left(\mathrm{\λL}\right)}^n}{n!}{e}^{-\mathrm{\λL}}$

Wherein, X is the quantity of vehicle node, and P (X=n) refers to that the quantity of vehicle node is the probability of n.

Seven, it is as follows to be located at the relational expression of the probability P that has at least a vehicle node in the vehicle node transmission range and distance:

P=1-P(X=0)

＝1-e ^-λd

D is the distance between two vehicle node, i.e. distance between two cars, relative displacement.

Eight, obtaining the stability that two vehicle node form link is s (L _i, t ₀, Δ t)=P ₀, wherein

d ₀T between two cars ₀Distance constantly.

The present invention mainly obtains following two step results:

(1) prediction of path duration.

(2) calculating of link stability.

In the step (1), embodiment resolves into the velocity vector between two cars and road parallel direction V _xWith with road vertical direction V _yLike this, according to the wireless transmission distance R of the current distance d between two cars and vehicle node maximum and current speed V _x, we can estimate to form between two cars duration Δ t of link.Step (2) is carried out the calculating of confidence level to the duration that estimates in the step (1).

The implementation procedure that below describes respectively (1) and (2) among the embodiment in detail is as follows:

(1) prediction of path duration

Suppose that the distance between two vehicle node is d, the intensity of signal is only relevant with the transmission range of signal.So at a time, link keep to be communicated with only need between two nodes apart from d less than internodal maximum wireless transmission range R.But suppose to carve at a time direct communication between node i, the j, and the position of known node i is (x _i, y _i), speed v _iBecome θ with two car line directions _iAngle,

Then the displacement computing formula of vehicle node i is:

$\left\{\begin{array}{c}{x}_i\left(t\right)=x_i\left(0\right)+v_{\mathrm{ix}}\·\cos {\mathrm{\θ}}_i\·t\\ y_i\left(t\right)=y_i\left(0\right)+v_{\mathrm{iy}}\·\sin {\mathrm{\θ}}_i\·t\end{array}\right.$

In like manner, the position (x of definable vehicle node j _j, y _j), speed v _j, then can calculate two car relative displacement d, two nodes keep the time T of link=(R-d)/v so, and wherein v is the relative velocity between two nodes.Two-site model is expanded to the Lifetime that the whole piece path just can get outbound path.

(2) calculating of link stability

Link L _iStability, definition s (L _i, t ₀, Δ t) and be illustrated in t ₀Moment link L _iUnder the condition that exists, L _iAt t ₀+ Δ t the moment is effective probability still.The stability S of path P (P, t ₀, Δ t) and expression t ₀The transmission path P that constantly sets up is at t ₀The probability that+Δ t still is communicated with constantly.

When vehicle freely when highway travels, the spacing distance between vehicle is obeys index distribution.So can followingly express apart from d between two cars:

f(d)=λe ^-λd

Wherein, λ is the density of wagon flow.

Suppose that R is the maximum wireless transmission range of vehicle node.The probability FR, the λ that are communicated with of two cars then) available following formula calculates:

$F(R,\mathrm{\&lambda;})=P(d<R)=\underset{0}{\overset{R}{\&Integral;}}f\left(d\right)\mathrm{dd}=1-e^{-\mathrm{\&lambda;R}}$

Supposing has m car in length is the one-way road of L, m-1 workshop fragment then just arranged between this m car, and the link that is comprised of this m car so is if be communicated with, and then distance is less than maximum transmitted scope R between two cars between per two cars in this link.The probability expression that this link is communicated with is as follows, and m can round approximate calculation with L/R here.

$P(\mathrm{\&lambda;},R,m)=\underset{1}{\overset{m-1}{\mathrm{\&Pi;}}}F(R,\mathrm{\&lambda;})={(1-e^{-\mathrm{\&lambda;R}})}^m$

In vehicle-mounted self-organizing network, probability density function and cumulative function that embodiment defines interval between two cars are respectively f _g(x)=λ e ^{-λ x}And F _g(x)=1-e ^{-λ x}, λ=σ/Ev wherein, σ are that vehicle crosses that the arrival rate of a certain section is that what cars per minute has through this section on the street.Ev is the average speed of vehicle.The highway section (0, L] in the probability P of n node is arranged is to obey Poisson distribution.Expression formula is as follows:

$P(X=n)=\frac{{\left(\mathrm{\&lambda;L}\right)}^n}{n!}{e}^{-\mathrm{\&lambda;L}}$

Dist (n among Fig. 2 ₁, n ₂) be two vehicle node n ₁And n ₂Between distance, R is the maximum wireless transmission range of vehicle node.Solid circles is centered by a phop among Fig. 2, and R is the circle of radius.Node n ₁Apart from the nearest node of destination node and be apart from phop node farthest in node phop transmission range.

Suppose n ₁, n ₂Between can not direct communication, make n ₁, n ₂Between can be communicated with n then ₁, n ₂Between a via node n will be arranged at least _xBy poisson distribution formula as can be known, n ₁, n ₂Between have at least the probability P of a node to be:

$P=1-P(X=0)$

$=1-e^{-\mathrm{\&lambda;}\&CenterDot;d(n_1,n_x)}$

N wherein _xN ₁, n ₂Between node, n then ₁, n _xBetween the probability P that is communicated with ₀With distance d (n ₁, n _x) following relation arranged:

$d(n_1,n_x)>\frac{\ln (1-P_0)}{-\mathrm{\&lambda;}}$

Link Lifetime then

V is the vehicle relative velocity.So link is at t ₀+ Δ t constantly still effectively probability also be P ₀, i.e. link L _iStability s (L _i, t ₀, Δ t)=P ₀

Specific embodiment described herein only is to the explanation for example of the present invention's spirit.Those skilled in the art can make various modifications or replenish or adopt similar mode to substitute described specific embodiment, but can't depart from spirit of the present invention or surmount the defined scope of appended claims.

Claims (1)

1. a VANET link stability assessment method is characterized in that, may further comprise the steps:

One, vehicle node speed is decomposed into the road parallel direction and with the road vertical direction;

Two, the functional relation of establishing vehicle node and time t is,

$\left\{\begin{array}{c}{x}_i\left(t\right)=x_i\left(0\right)+v_{\mathrm{ix}}\&CenterDot;\cos {\mathrm{\&theta;}}_i\&CenterDot;t\\ y_i\left(t\right)=y_i\left(0\right)+v_{\mathrm{iy}}\&CenterDot;\sin {\mathrm{\&theta;}}_i\&CenterDot;t\end{array}\right.$

Wherein, v _IxBe car speed decompose with the amount of road horizontal direction, v _IyBe car speed decompose with the amount of road vertical direction, θ _iIt is the angle of car speed and road horizontal direction; x _i(0) expression vehicle t ₀The time be engraved in position on the road horizontal direction, y _i(0) expression vehicle t ₀The time be engraved in position on the road vertical direction; x _iBe engraved in the position on the road horizontal direction when (t) representing vehicle t, y _iBe engraved in the position on the road vertical direction when (t) representing vehicle t;

Three, carry out the calculating of link duration, comprise according to the relative velocity v between two vehicle node, relative displacement d, calculating link duration T=(R-d)/and v, wherein R is the wireless transmission distance of vehicle node maximum;

Four, definition s (L _i, t ₀, Δ t) and expression t ₀Moment link L _iUnder the condition that exists, L _iAt t ₀+ Δ t the moment is effective probability still, the stability S of path P (P, t ₀, Δ t) and be illustrated in t ₀The transmission path P that constantly sets up is at t ₀The probability that+Δ t still is communicated with constantly;

Five, in the vehicle-mounted self-organizing network of definition between two cars probability density function and the cumulative function at interval be respectively f _g(x)=λ e ^{-λ x}And F _g(x)=1-e ^{-λ x}, λ=σ/Ev wherein, σ is the arrival rate that vehicle crosses a certain section on the street, Ev is the average speed of all vehicles;

Six, being located at long is to have the probability P of n vehicle node to obey Poisson distribution in the highway section of L, and expression formula is as follows,

$P(X=n)=\frac{{\left(\mathrm{\&lambda;L}\right)}^n}{n!}{e}^{-\mathrm{\&lambda;L}}$

Wherein, X is the quantity of vehicle node, and P (X=n) refers to that the quantity of vehicle node is the probability of n;

Seven, be located at the probability P that there is at least a vehicle node in the vehicle node transmission range with as follows apart from the relational expression of d,

P=1-P(X=0)

=1-e ^-λd

Eight, obtain two vehicle node and form link L _iStability be s (L _i, t ₀, Δ t)=P ₀, wherein

d ₀T between two cars ₀Distance constantly.

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