CN102413423A - Vehicular ad-hoc network uploading method based on dynamic selection of roadside units - Google Patents

Abstract

The invention discloses a vehicular ad-hoc network uploading method based on dynamic selection of roadside units. The method can be applied to uplink communication of vehicles to the roadside units in the vehicular ad-hoc network and especially for vehicles in an overlapped communication range of multiple roadside units. The method provided by the invention comprises the following steps: acquiring the roadside unit information of the present vehicle position covered by the communication range; acquiring the distance from the vehicle to different roadside units and the connection number of the roadside units; calculating uploading factors; and determining a destination roadside unit of vehicle uploading. The method provided by the invention mainly aims to improve the multi-roadside-unit selection which cannot be considered in the simple uploading scheduling method in the prior art, and simultaneously consider the distance from the vehicle to the roadside units and the communication quality of the roadside unit. As the policy of dynamic selection of the roadside units is introduced, the uploading efficiency and success rate of the vehicle can be improved.

Description

A kind of method for uploading of the vehicular ad hoc network based on the Dynamic Selection roadside unit

Technical field

The invention belongs to vehicular ad hoc network ruton letter technical field, specifically be based on the method for uploading of the vehicular ad hoc network of Dynamic Selection roadside unit.

Background technology

Vehicular ad hoc network network (Vehicular Ad-hoc Networks; VANET) be a kind of form of mobile self-grouping network; Be applicable between several the contiguous cars and ad hoc network system that vehicle and near fixation means carry out communication; Its objective is to the driver provides a safety, comfortable traffic environment, simultaneously road information is monitored in real time, realize traffic intelligentization.

The vehicular ad hoc network network is a kind of system that does not have Centroid.Its communication is divided into two parts, the communication of communication and vehicle and roadside unit between car and the car.On the vehicle, thereby road both sides and crossroad place mounting electronic device realizes communication.To the driver accident warning message, road markings prompting and real-time traffic situation are provided, thereby increase the coefficient of safety that the driver goes, facilitate for the driver selects best travel route.

Method for uploading in the vehicular ad hoc network network on the roadside unit is most important.Roadside unit is removed equipment such as adopting camera, magnetic induction coil and is obtained outside the traffic information, more real-time, the fresh data that more need vehicle and fed back.And vehicle needs outstanding method for uploading to support to the communication process of roadside unit.The method for uploading of vehicular ad hoc network is different with traditional service dispatch: in traditional service dispatch; Service end can have time enough service is provided and does not worry that the user can lose with server and be connected to the user; But in the vehicular ad hoc network network because vehicle is a mobile node and roadside unit is to fix; The time that vehicle is in the roadside unit communication context in the process of moving is limited, and it also is limited sending the time of serving to roadside unit like this; And when vehicle was in the communication context that a plurality of roadside units cover each other, different roadside units were different apart from the distance of vehicle, the communication qualities of different roadside units are different, made that the purpose roadside unit of vehicle is selective.Like this, the method for uploading of the location that selects your destination efficiently is particularly important.

At present the method for uploading of main flow have the beeline mode of priority (Shortest Distance First, SDF) with the minimum linking number mode of priority (Least Connection First, LCF).

The SDF method meaning be only consider when uploading with vehicle apart from this factor, the nearest roadside unit of chosen distance current vehicle location is uploaded.This is the simplest a kind of method, realizes also very conveniently, and resource consumption is minimum.But SDF does not consider the communication quality of this roadside unit, and the load of possible this roadside unit is very big, is easy to like this cause upload packet and block and lose.So in VANET, this method for uploading and imperfection.

The LCF method is different with the angle that the SDF method is considered, this method has been considered roadside unit and this key factor of surrounding vehicles linking number among the VANET.Generally, the linking number of roadside unit and surrounding vehicles is big more, and the load of this roadside unit is big more, and the data packet discarding phenomenon is blocked even occurred in service queue more easily.The roadside unit linking number that can cover the vehicle current location is few more, and the validity of the data message of uploading can guarantee more.Yet vehicle can not stop to the communication of carrying out of this roadside unit; The vehicle distances roadside unit is far away more, and signal strength signal intensity is poor more, and the possibility that this message is successfully uploaded on vehicle is low more; Thereby this method also is single considering a problem, and can not well deal with problems.

Summary of the invention

The objective of the invention is for avoiding above-mentioned existing in prior technology weak point; A kind of innovation on having on the propagation algorithm basis; Be primarily aimed at and simply upload the multichannel edge element that dispatching method fails to consider in the past how the optimized choice problem is improved; Proposed a kind of vehicular ad hoc network based on the Dynamic Selection roadside unit method for uploading (Dynamic Roadside Unit Selection Scheme, DRS).

For realizing that the technical scheme that above-mentioned purpose the present invention adopts is:

A kind of method for uploading of the vehicular ad hoc network based on the Dynamic Selection roadside unit, its step is following:

1. obtain the roadside unit information that communication context covers the vehicle current location

When vehicle sails certain roadside unit communication context into; Roadside unit sends information to this vehicle; Inform that vehicle has sailed the communication context of this roadside unit into; Can carry out communication with it, the information that roadside unit sends comprises number information, positional information and the existing vehicle linking number of the current roadside unit information of roadside unit.

2. obtain vehicle to the distance of different roadside units and the linking number of roadside unit

After vehicle gets access to the information more than a roadside unit; Write down number information, positional information and vehicle linking number information that each roadside unit sends; And obtain current vehicle location through vehicle GPS equipment, calculate the distance between vehicle and each roadside unit.

3. calculate and upload the factor

Two roadside units that chosen distance is nearest, definition is along vehicle heading, and that forward is RSU ₁, after leaning on is RSU ₂, with the vehicle RSU that calculates ₁And RSU ₂Distance store D respectively into _RSU1And D _RSU2In, the vehicle linking number that obtains from corresponding roadside unit stores K into _RSU1And K _RSU2In, with D _RSU1, D _RSU2, K _RSU1And K _RSU2Substitution formula (1) calculates and uploads factor t;

$t=\frac{\mathrm{\α}(D_{{\mathrm{RSU}}_2}-D_{{\mathrm{RSU}}_1})}{5}+b(K_{{\mathrm{RSU}}_2}-K_{{\mathrm{RSU}}_1})---\left(1\right)$

Wherein the value of a and b is confirmed according to actual needs.Further, parameter a, b are the real number greater than 0.

4. confirm the purpose roadside unit that vehicle is uploaded

Judge the size of t value and 0, if t greater than 0, then adopts RSU ₁As the purpose roadside unit of uploading, otherwise, RSU then adopted ₂As the purpose roadside unit of uploading.

The 4th step complete after, if this vehicle also need upload data to roadside unit, then coming back to for the 1st step continues to carry out.

The present invention compared with present technology, its useful technique effect is embodied in:

The present invention has considered that simultaneously vehicle is to the distance of roadside unit and the communication quality of this roadside unit; Introduce the strategy of Dynamic Selection roadside unit; Increase efficient and the success rate that vehicle is uploaded through the destination node uploaded of control vehicle, accomplished truly efficient.

Description of drawings

Fig. 1 is based on the method for uploading schematic flow sheet of the vehicular ad hoc network of Dynamic Selection roadside unit;

Fig. 2 service dispatch configuration diagram of the present invention;

Fig. 3 simulating scenes sketch map of the present invention;

Fig. 3 (a) is the emulation under the VISSIM, and Fig. 3 (b) is the emulation under the OPNET;

Roadside unit Data Receiving rate comparative graph under the different a of Fig. 4 formula (1), the b parameter;

Fig. 4 (a) is the situation of a=1, b=0.5, and Fig. 4 (b) is the situation of a=1, b=1, and Fig. 4 (c) is the situation of a=1, b=2;

Roadside unit Data Receiving rate comparative graph under the different traffic densities of Fig. 5;

Fig. 5 a) is low traffic density, and Fig. 5 (b) is high traffic density;

Vehicle data-bag lost rate comparative graph under Fig. 6 different pieces of information amount;

Fig. 6 is 1 second a situation for per 10 seconds dwell time gaps 2 seconds, packet send the gap a);

Fig. 6 b) be 0.5 second situation for per 10 seconds dwell time gaps 2 seconds, packet send the gap;

Fig. 6 c) be that no dwell time gap, packet transmission gap are 0.5 second situation;

Symbol description:

VANET: vehicular ad hoc network network

SDF: the beeline mode of priority

LCF: the minimum linking number mode of priority

DRS: based on the method for uploading of Dynamic Selection

D _RSU1: roadside unit 1 is to the distance of vehicle

D _RSU2: roadside unit 2 is to the distance of vehicle

K _RSU1: vehicle number in roadside unit 1 communication context

K _RSU2: vehicle number in roadside unit 2 communication contexts

T: upload the factor

A: upload factor calculation formula middle distance correction weights

B: upload vehicle number correction weights in the factor calculation formula

Embodiment

Describe below in conjunction with the accompanying drawing specific embodiments of the invention, so that understand the present invention better.

Shown in Figure 2 is the framework of an In-vehicle networking, and roadside unit is placed on the both sides of road.In a single day through the communication context of roadside unit, in the time of promptly can carrying out communication with roadside unit, vehicle sends request message wait service message then to roadside unit to vehicle in the road driving process.When vehicle is in the communication context of a plurality of roadside units, as among Fig. 2 the mark "? " Vehicle, the destination address of how selecting to upload becomes a problem.This vehicle adopts the strategy of uploading of the present invention according to flow process shown in Figure 1.Through adopting method proposed by the invention, can confirm the purpose unit fast, improve efficient and success rate that data are sent.

Exemplary embodiment is analyzed:

Whether efficiently roadside unit Data Receiving rate (Data Traffic Rcvd) is to weigh method for uploading important indicator.The Data Receiving rate is meant the accessed quantity of data packets of roadside unit per second.Because the disposal ability and the channel width of roadside unit are limited; The purpose unit of how uploading through rational arrangement; Thereby make roadside unit obtain request message to greatest extent, and improve the problem that channel bandwidth utilization ratio is the consideration of method for uploading emphasis as much as possible.

Vehicle data loss rate (Dropped Data Packets) is whether efficiently another one weighs method for uploading important indicator.Vehicle data packet loss more explain that the current communication quality of vehicle is worse more, to method for uploading, are exactly that the roadside unit selected is unreasonable more.The data-bag lost rate is reflected under the identical data flow; Method for uploading is selected the resonable degree of roadside unit, and it is more to be reflected in the vehicle communication simultaneously, and the network communication situation is relatively poor; Under the limited situation of roadside unit disposal ability deficiency and channel width, the survivability of method for uploading.

Based on the method for uploading of Dynamic Selection roadside unit mainly is on transmission method basis traditionally; Considered that simultaneously vehicle is to the distance of roadside unit and the communication quality of this roadside unit; Introduce the Dynamic Selection strategy; Through the parameter of roadside unit on every side of obtaining of vehicle dynamic, select according to the performance principle of priority, thereby increase efficient and the success rate that vehicle is uploaded.

In order to verify validity based on the method for uploading of Dynamic Selection roadside unit; The author carries out emulation from aspects such as roadside unit Data Receiving rate and vehicle data loss rate to the method that is proposed respectively, and with the author before the SDF method that proposes compare analysis.Microscopic traffic simulation instrument VISSIM and network and communication emulation tool OPNET that the emulation tool that uses is generally acknowledged by industry.

The simulating scenes that experiment is disposed is as follows:

Be depicted as following 3000 meters * 3000 meters street scene of VISSIM like Fig. 3 (a).Scene center is a crossroad.Different vehicles is gone with different speed according to traffic rules from the four direction of road.

Shown in Fig. 3 (b), network simulation is carried out in a highway section of cut-away view 3 (a) street scene on OPNET, disposes a roadside unit along road is every at a distance from 300 meters, vehicle employing on the road different on propagation algorithm carry out communication with roadside unit at random.In order to make the emulated data of Fig. 3 (b) convincing, in Fig. 3 (b), in the moving parameter of mobile node and the VISSIM emulation the moving parameter of corresponding vehicle in full accord.

Two kinds of Different Traffic Flows amounts of emulation on VISSIM are respectively low traffic density and high traffic density.Low traffic density standard is to cross 27 cars in per 60 seconds, and high traffic density standard is to cross 60 cars per 60 seconds.Experimentize respectively to the Different Traffic Flows amount in the present invention.

The simulation parameter that operates on the OPNET is as follows:

1) only consider and from the vehicle to the roadside unit, one jump communication, that is to say communication between vehicle and the vehicle, roadside unit to the communication between the roadside unit not within limit of consideration.

2) emulation on all OPNET, the communication time started is the time that vehicle occurs, and the communication concluding time is set to not have.

3) the last special parameter of OPNET: the dwell time gap, different under different experimental situations.

4) the packet size is set to 1024 bytes, but packet transmitting time gap is different under the different experiments environment.

5) the last vehicle parameter of OPNET is consistent with VISSIM, and the speed of vehicle does not per hour per hour wait to 80 kilometers from 50 kilometers.

6 kinds of different services are provided on roadside unit, and concrete COS is as follows:

1) non-vital data such as hotel, shop; 2) area map inquiry; 3) penalty note information; 4) route information; 5) road block acoustic information; 6) emergency safety information such as traffic accident.

Fig. 4 is a roadside unit Data Receiving rate comparative graph under the different a of formula (1), the b parameter, and wherein Fig. 4 (a) is the situation of a=1, b=0.5, and Fig. 4 (b) is the situation of a=1, b=1, and Fig. 4 (c) is the situation of a=1, b=2.For simple comparison a and two parameters of b, other parameters are set to identical in experiment: the magnitude of traffic flow is low traffic density; The dwell time gap is to stop 2 seconds in per 10 seconds; It is 1 second that packet sends the gap.The scene 1 (scenario1) of Fig. 4 is based on the experimental result of SDF, and scene 2 (scenario2) is then based on DRS.

From Fig. 4, can get, under experiment scene, when a value be 1, when the b value is 0.5, the Data Receiving rate of two scenes is basic identical, this be because b be 0.5 o'clock, the K in the DRS method computing formula (1) _RSU1And K _RSU2Difference little to the influence of the value of overall t, at this moment active still D _RSU1And D _RSU2Poor.Only consider when SDF then uploads with vehicle apart from this factor, just D _RSU1And D _RSU2Poor.So two curve basically identicals among Fig. 4 (a).

When a value be 1, when the b value is 1, the Data Receiving rate of scene 2 is higher than scene 1, this be because b be 1 o'clock, the K in the DRS method formula (1) _RSU1And K _RSU2Difference to the generation of overall t certain influence, K at this moment _RSU1And K _RSU2The difference correction because simple consider roadside unit and vehicle apart from problem that this factor caused.When then uploading, SDF only considers D _RSU1And D _RSU2This factor of difference, whether what, channel of the linking number of roadside unit busy etc., and factor is not considered.Therefore Fig. 4 (b) scene 2 effective than scene 1.

Yet when b greater than 1 the time, the performance of scene 2 begins to descend gradually, when a value be 1, when the b value is 2, the Data Receiving rate of scene 1 is just obviously than the height of scene 2, shown in Fig. 4 (c).This is because b is 2 o'clock, the K in the DRS method formula (1) _RSU1And K _RSU2Difference not only do not play the corrected range effect of factors; On the contrary this factor of roadside unit linking number is become leading factor; Distance becomes secondary cause like this, and the communication context of roadside unit is conditional, in case roll communication context away from; Packet on the vehicle just can not be sent to roadside unit, can only abandon.Therefore Fig. 4 (c) scene 1 effective than scene 2 on the contrary.

On the basis of Fig. 4 (a), Fig. 4 (b) and Fig. 4 (c), the value of further refinement a of the author and b has been done a large amount of experiments.Value through more finally drawing middle parameter a of formula (1) and b is 1,1 o'clock, and effect is best.

Fig. 5 is a roadside unit Data Receiving rate comparative graph under the different traffic densities, and wherein Fig. 5 (a) is low traffic density, and Fig. 5 (b) is high traffic density.For simple comparison traffic density parameter, other parameters are set to identical in experiment: the value of parameter a and b is 1,1 in the formula (1); The dwell time gap is to stop 2 seconds in per 10 seconds; It is 1 second that packet sends the gap.The scene 1 (scenario1) of Fig. 5 is based on the experimental result of SDF, and scene 2 (scenario2) is then based on DRS.

No matter from Fig. 5, can get, be low traffic density or high traffic density, and the scene 2 always roadside unit Data Receiving rate than scene 1 is high, and this explanation method proposed by the invention is applicable to general situation.Contrast through Fig. 5 (a) and Fig. 5 (b) can know, when the magnitude of traffic flow is bigger, traffic density is when higher, and the DRS method is compared SDF, and effect is more obvious.

Fig. 6 is a vehicle data-bag lost rate comparative graph under the different pieces of information amount; Wherein Fig. 6 (a) is 1 second for per 10 seconds dwell time gaps 2 seconds, packet send the gap; Fig. 6 (b) is 0.5 second for per 10 seconds dwell time gaps 2 seconds, packet send the gap, and Fig. 6 (c) be that no dwell time gap, packet transmission gap are 0.5 second.For simple comparison traffic density parameter, other parameters are set to identical in experiment: the magnitude of traffic flow is low traffic density in the formula (1); The value of parameter a and b is 1,1.The scene 1 (scenario1) of Fig. 6 is based on the experimental result of SDF, and scene 2 (scenario2) is then based on DRS.

From Fig. 6, can get, regardless of being that packet sends dwell time gap among gap or the OPNET, the scene 2 always vehicle data loss rate than scene 1 is low, and this explanation method proposed by the invention is applicable to general situation.Contrast through Fig. 6 (a), Fig. 6 (b) and Fig. 6 (c) can know that the data volume of sending when vehicle is big more, and the DRS method is compared SDF, and effect is also just obvious more.

In sum, compare the SDF method based on the method for uploading of the vehicular ad hoc network of Dynamic Selection roadside unit at aspects such as roadside unit Data Receiving rate and vehicle data loss rate and all shown good performance.And along with vehicle number purpose in the roadside unit communication context increases, sends the increase of the quantity of message, this method is compared still with the SDF method can show preferable performance, has shown good extensibility.

Claims (2)

1. the method for uploading based on the vehicular ad hoc network of Dynamic Selection roadside unit is characterized in that, said method for uploading comprises step:

Step 1: obtain the roadside unit information that communication context covers the vehicle current location, concrete implementation method is:

When vehicle sails certain roadside unit communication context into; Roadside unit sends information to this vehicle; Inform that vehicle has sailed the communication context of this roadside unit into; Can carry out communication with it, the information that roadside unit sends comprises number information, positional information and the existing vehicle linking number of the current roadside unit information of roadside unit;

Step 2: obtain vehicle to the distance of different roadside units and the linking number of roadside unit, concrete implementation method is:

After vehicle gets access to the information more than a roadside unit; Write down number information, positional information and vehicle linking number information that each roadside unit sends; And obtain current vehicle location through vehicle GPS equipment, calculate the distance between vehicle and each roadside unit;

Step 3: calculate and upload the factor, concrete implementation method is:

Two roadside units that chosen distance is nearest, definition is along vehicle heading, and that forward is RSU ₁, after leaning on is RSU ₂, with the vehicle RSU that calculates ₁And RSU ₂Distance store D respectively into _RSU1And D _RSU2In, the vehicle linking number that obtains from corresponding roadside unit stores K into _RSU1And K _RSU2In, with D _RSU1, D _RSU2, K _RSU1And K _RSU2Substitution formula (1) calculates and uploads factor t;

$t=\frac{\mathrm{\α}(D_{{\mathrm{RSU}}_2}-D_{{\mathrm{RSU}}_1})}{5}+b(K_{{\mathrm{RSU}}_2}-K_{{\mathrm{RSU}}_1})---\left(1\right)$

In the formula, a: distance is revised weights;

B: vehicle number correction weights;

Wherein the value of a and b is confirmed according to actual needs;

Step 4: confirm the purpose roadside unit that vehicle is uploaded, concrete implementation method is:

According to the result of calculation of formula (1), judge the size of t value and 0, if t greater than 0, then adopts RSU ₁As the purpose roadside unit of uploading, otherwise, RSU then adopted ₂As the purpose roadside unit of uploading;

Step 5: after step 4 is complete,, then comes back to step 1 and continue to carry out if vehicle also need be uploaded data to roadside unit.

2. the method for uploading of the vehicular ad hoc network based on the Dynamic Selection roadside unit according to claim 1 is characterized in that: parameter a, b are the real number greater than 0 in the said formula (1).

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