CN103475710B - Inter-vehicle cooperation downloading scheme based on feedback method - Google Patents
Inter-vehicle cooperation downloading scheme based on feedback method Download PDFInfo
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Abstract
The invention provides an inter-vehicle cooperation downloading scheme based on a feedback method to overcome the effects that in an existing vehicle data downloading method and technology, contradiction exists among the coverage area, the data downloading rate and the traffic expenses. According to the method, the data downloading time of a single vehicle can be obviously shortened. Meanwhile, due to the fact that data can be shared through V2V communication, time is shortened, no expenses are produced when V2V communication is used, and the expenses for data downloading are greatly lowered. The 3G communication method and the DSRC communication method are utilized at the same time, the 3G communication method is used as a control channel and responsible for uploading request information to a roadside access point so that data can be prepared well before the vehicle passes by the roadside access point, the DSRC communication method is used for downloading the data, and therefore the data can be downloaded at a high speed.
Description
Technical field：
The invention belongs to field of traffic, and in particular to data file downloading field in traffic.
Background technology
Now with car networking (VANET) [HARTENSTEIN H, LABERTEAUX K P.Vanet vehicular
Application and inter-network technologies [M] .] and Internet of Things development and standard it is continuous complete
Kind, people are more and more interested for the business development of vehicle-mounted data information service, such as car entertainment and vehicle-mounted office
[UZCATEGUI R,ACOSTA-MARUM,G.Wave:a tutorial[J].IEEECommunication
Magazine.2009:126-133.].It is therefore contemplated that in the near future increasing automobile will install vehicle-mounted nothing
Line communication equipment, we will be to Intelligent life further.Intelligent transportation system has boundless application scenarios：Push away to vehicle
Send local more detailed transport information（Such as traffic safety prompting, map rejuvenation, the advertisement based on current location）, from network
Specific data message is obtained on server（Such as neighbouring parking stall, local hotel is introduced and scenic spot is introduced）[ZHU
J,ROY S.Mac for dedicated short range communications in intelligent transport
system[J].IEEE Communications Magazine,2003,41:60-67.], etc..
Current intelligent transportation system is based primarily upon wide variety of 2G/3G networks and the vehicle being applied between vehicle
Dedicated Short Range Communications（DSRC）For vehicle data information service [UZCATEGUI R, ACOSTA-MARUM, G.Wave:a
tutorial[J].IEEE Communication Magazine.2009:126-133.].Current many vehicle-mounted service company
Mainly carry out the communication module of data cube computation with existing Cellular Networks coming from network-side download service information by can carry,
Because the laying of existing Cellular Networks is extensively and commercial through for a long time, the stability and coverage that its data is downloaded can be protected
What card communicated is stably connected with, the continuity that data are downloaded.On the other hand with the constantly improve of 802.11P agreements, also there is portion
Branch company and research institution attempt passing through DSRC（Vehicle Dedicated Short Range Communications）To reach car and car, car and roadside infrastructure
（Download as data and use）Direction communication, the agreement of the vehicle development due to being specific to high-speed mobile, so being in a ratio of
2G the and 3G Cellular Networks of mobile communication design, DSRC communications can reach very high data download rate, and also constantly complete
In kind.
But both communication modes have its limitation：For 2G/3G networks, its data transmission bauds it is not high and
For expensive especially relative download mass file data, therefore also greatly reduce the related vehicle-mounted scope being served by,
Such as vehicle-mounted office and car entertainment require data volume greatly or the application of real-time Communication for Power for prior art cannot realize；And
Although DSRC communications meet high data communication requirements but are limited to the coverage and access point of roadside basis access point
Distribution density it is difficult to ensure that communicating requirement [JIANG D, the DELGROSSI L.IEEE802.11p of continuous seamless:Toward
an international standard for wireless access in vehicular environments[C]//
Vehicular Technology Conference.2008:2036-2040.].Even if being to increase current roadside basis to access
The laying density of point, on the one hand needs substantial amounts of fund input, on the other hand before certain density is reached, it is also desirable to certain
Time, therefore in a short time this communication mode is also the communication support for not reaching requirement.
The mode that cooperation is downloaded between the difficult vehicle that data distribution runs in order to overcome above car networking is occurred in that：If
Downloading data content can be obtained in the part of a group vehicle, while other vehicles are wanted to download the data content, then use V2V
（Vehicle-to-Vehicle）Vehicle-to-vehicle communication reaches P2P（Peer-to-Peer）The method of content distribution can greatly contract
Short download time is simultaneously economically also very economical.
Cooperation download be it is a kind of data distribution is carried out in all nodes of network agreement [KORKMAZG, EKICI E,
OZGUNER F,et al.Urban multi-hop broadcast protocol for inter-vehicle
communication systems[C]//ACM Intl workshop on Vehicularad hoc networks.2004:
76-85.][XU B,OUKSEL A,WOLFSON O.Opportunistic resource exchange in inter-
vehicle ad-hoc networks[C]//IEEE Mobile Data Management.2004,4-12.].At present, the party
Method receive in the learned society and commercial undertaking for researching and developing and improving car networking very big concern [GHANDEHARIZADE S,
KAPADIA S,KRISHNAMACHARI.Pavan:a policy framework for content availability in
vehicular ad-hoc networks[C]//the1st ACM international workshop on Vehicular
ad hoc networks.2004:57-65.], become the study hotspot of industry.The general data distribution master in car networking
[JERBI M, MARLIER P.Experimental assessment of V2V and I2V are made up of two stages
communications[C]//IEEE International Conference on Mobile Ad hoc and Sensor
Systems.2007:1-6.][JERBI M,SENOUCI S.Characterizing multi-hop communication
in vehicular networks[C]//IEEE Wireless Communications and Networking
Conference.2008:3309-3313.]：
Vehicle-to-Infrastructure (V2I) vehicles and roadside access points connection communication stage：In the stage,
When vehicle is entered in the coverage of roadside access points, vehicle is from access point AP（Access Point）Place obtains data
Vehicle-to-Vehicle（V2V）Car and inter-vehicle communication stage：When vehicle leaves the covering model of roadside access points
After enclosing, information is exchanged with each other between vehicle.All of node all obtains identical data at the end of the stage.
The cooperation that this programme considers is downloaded the cooperation mainly in a vehicle " cluster " and is downloaded rather than no matter between vehicle
Distance several workshops how far can.Workshop V2V leads to wherein in the Forming Mechanism and maintenance mechanism and cluster of vehicle " cluster "
The mode of letter refers to [LITTLE T D C, AGARWAL A.An information propagation scheme for
vanets[C]//IEEE Conference on Intelligent Transportation Systems.2005:13-
16.].V2I processes are concern is primarily with this programme by the way of based on feedback from roadside access points AP downloading data files
I.e. accepted partial document was first uploaded AP and only broadcasts non-receiving portion corresponding to vehicle by vehicle before file is downloaded.
And compare, based on random packet selection mode be simple repetition from whole file it is random under pass
Vehicle is given in part, therefore the repetitive rate of vehicle download part is very high.It is assumed that the file grouping that vehicle is followed by being subject to through V2I（Text
The size of part is weighed with how many packet Packets）Can completely share in the V2V stages and exchange.In order to vehicle downloads content
Privacy and security consideration, roadside access points AP once only communicate with a car and downloads file, and other vehicles can not obtain this article
Part information（Different from broadcast distribution data）.
We claim a cluster through a download point, and vehicle downloads corresponding document in cluster（V2I）, leave cluster after the download point
Pass through V2V between interior vehicle（Car communicates with car）It is one " circulation " to share respective download content completely（V2I+V2V）.Therefore under
Carry a big file to be accomplished by just to be completed through multiple circulations.The theory analysis of back and emulation show that the present invention is carried
Scheme can greatly shorten data in car networking and download required time（It is presented as that cycle-index greatly reduces）.The present invention's is main
Contribution：First, theory analysis and demonstrate based on feedback system vehicle cooperation download needed for time（With cycle-index as list
Position）Repeat to select packet mode contrast with random, substantially reduce the download time of file.Second, analytic explanation is relative to increasing
Plus the vehicle number that cooperation is downloaded is participated in, preferentially increase the download capabilities of single unit vehicle（The packet number downloaded when AP）Can be with
Significantly more efficient shortening download time.3rd, increasing the vehicle number of cooperation download can shorten download time, but not more
It is better, to the effect very little of reduction download time after vehicle number increases to certain value, it might even be possible to ignore.
The defect that the present invention exists for existing vehicle data downloading mode and technology：Coverage, downloading data rate, with
And the contradiction between flow rate problem three, it is proposed that cooperation data download method between the vehicle based on feedback system, can be with
Single unit vehicle data download time is significantly shorter, while passing through V2V（Car and car）The shared mutual data of communication, not only shorten
Time V2V communications simultaneously do not produce cost, and the rate for also making downloading data substantially reduce.
Vehicle boarded 2G/3G communication modules download major way as data, are made using existing ripe mobile phone Cellular Networks
For communication network, reliable and stable and communication should not be interrupted, and charge method presses regular handset flow rate, by the charge of existing flow
Standard User is easy to receive, easily popularization.
Although existing ripe communication technology is used data in car networking and is downloaded by the program, convenient stable, 2G/3G nets
Network technology is developed mainly for mobile phone, has the upper limit to require mobile speed, frequently changes in topological structure and speed is very high
In the case of, data download rate does not reach the download rate of its publicity, and is similar to vehicle-mounted office, car entertainment etc. i.e. under data
Carry speed there are certain requirements（Meet requirement of real-time）, again the total amount of data of download is very big（Entertainment applications）So as to produce rate mistake
High problem, all forms to the diversification of forms of vehicular applications in real use and hinders.
V2I (vehicle-to-infrastructure) vehicles, by random fashion download communication, lead to roadside access points
Letter agreement is characterized in that data transmission rate is high for DSRC（After vehicle and access point connection request related content, random selection portion
Vehicle is passed under point）, leave and DSRC is passed through with car by V2V (vehicle-to-vehicle) cars after the coverage of access point
Communicate mutual sharing download content（The vehicle opportunistic of traveling mutually runs into one and its download content identical vehicle, by phase
Mutual communication is shared by data content interaction）.
Because it is random from access point downloading data there is the situation that content repeats of downloading, this is building with access point
It is very unworthy to waste communication opportunity in the case that vertical communication connection chance is very precious.Secondly, vehicle will run into has it to be intended to
The limited opportunities of another car of downloading data content, and on condition that the vehicle can inquire other side with all vehicles that it meets
Whether there is related data content, easily cause communication flooding, block communication channel, on the contrary decline data transmission rate.
The content of the invention
Goal of the invention：The defect that the present invention exists for existing vehicle data downloading mode and technology：Coverage, download
Contradiction between data transfer rate and flow rate problem three, it is proposed that cooperation data are downloaded between the vehicle based on feedback system
Method, can be significantly shorter single unit vehicle data download time, while passing through V2V（Car and car）The shared mutual number of communication
According to, not only shortening time V2V communications simultaneously and do not produce cost, the rate for also making downloading data are substantially reduced.Utilize two simultaneously
Communication mode 3G and DSRC communication is planted, 3G is responsible for as control channel so to make to roadside access points upload request information
Vehicle is by the way that, just by DSR, DSRC is downloaded as data and used, can be with high-speed downloads data before roadside access points.
Scheme of the invention
System model：
Because the distribution relative discrete of roadside download point is distributed, cause vehicle a very long time not in the covering of download point
In the range of, vehicle is always intermittent with the connection of download point, and interval is relatively long, not yet in effect to use.Consider simultaneously
Single unit vehicle is each downloaded respective file and is not cooperated each other, and this programme proposes the mode of cooperation download, makes full use of
Vehicle not in the interval time of roadside download point coverage, after the covering interval of download point is left, by DSRC (between vehicle
Short-range communication protocol) V2V that carries out between vehicle（Car communicates with car）Respective download content is mutually shared, cooperation download is reached double
The purpose of win.In order to realize that respective download content is shared completely in V2V communications, we are using a kind of adjacent vehicle in geographical position
Form the mode of vehicle " cluster ".Vehicle in one vehicle " cluster " can completely share mutual downloading data.Simultaneously for
Machine downloading mode, without linking up between vehicle and download point, the content of download is probably the data content portion that vehicle has contained,
This is undoubtedly the waste to bandwidth and downloading machine meeting.The system model of the present invention is not wasted often using the downloading mode for being based on feedback
Secondary downloading machine meeting.Specific embodiment is, as control channel, to want the access point for closing on using the wide spreadability of 3G channels
Upload the existing data division of vehicle, so when vehicle enters roadside download point, access point can targetedly only to
Vehicle passes down the data division that vehicle is not also received, it is to avoid redundancy and repetition, while make use of wide spreadability and the roadside of 3G
The advantage of the High Data Rate that access point is downloaded.To realize object above, this programme also needs to set up an AP（Download access point）
Server, preserves the positional information of all roadside access points, so when vehicle using 3G channels upload receiving portion data and
Current vehicle position（By onboard installing GPS positioning device）Afterwards, server can contrast current vehicle location and AP positions,
The position of the next AP that vehicle traveling direction will be reached is found out, can now notify that the access point is ready, it is and corresponding
Vehicle content to be downloaded content server connection, in advance obtain download content, when vehicle enter the AP（Download access point）
Coverage after, pass the data of its non-receiving portion down to vehicle.
Complete system model is as shown in figure 1, cooperation download flow process is expressed as below between a complete vehicle：
The vehicle flow travelled on road can be mutually made up of " cluster " one by one many adjacent cars of geographical position, be claimed each
Individual " cluster " accordingly " cluster head " vehicle is header, and " cluster tail " vehicle is trailer.Consider such a scene：In certain cluster
There is k car simultaneously（Red vehicle in figure）Want to download file of the same size for M packet（It is assumed that this M packet is compiled respectively
Number it is:P1,P2..., PM）.This fileinfo to be downloaded of k car is aggregated into " cluster head " vehicle, is uploaded information by the vehicle
（For example, reported by mobile network）, then be sent in the content server of storage this document [12] by the webserver.It is assumed that
Processing the webserver of this document download request can obtain the geographical location information and the direction of motion of the cluster（Vehicle is installed
GPS positioning device）, and the webserver preserves the exact position of all roadside access points, such that it is able to judge this
The access point that " cluster " will be reached, then downloads file content from content server and is stored in the middle of the server, when cluster enters
After entering the coverage of the access point, communicate download this document information with k car in cluster.
Might as well assume that any one packet number downloaded in the V2I stages in k car is homogeneously all m（m<M）, m is less than
File total packet number M.Obviously, m how is selected from M packet and is grouped the system of selection for being downloaded to vehicle to whole file
The performance of download system is most important.Consider herein using the selection mode based on feedback：In the V2I stages of each car, car
First the file grouping catalogue having been received by is uploaded to into roadside download point AP, such roadside access points AP is not just received from the vehicle
To packet in select m at random and be out downloaded to vehicle.
After cluster trailer also leaves the overlay area of roadside access points AP, all vehicles in cluster enter the V2V stages.
The stage, all vehicle sharing download contents in cluster.Therefore wait after the completion of V2V, all k cars all will be containing identical content
（All vehicles download content sum）.When vehicle enters next download point, this above-mentioned downloading process of k repetition in cluster is straight
To complete file of download.
The performance and Simulation Evaluation of the present invention：
For simplifying the analysis, it is assumed that each cluster that vehicle flow is formed is relatively stable, will not be because of the difference of speed between vehicle
Cause frequently to add and exit certain cluster.Such hypothesis is that cooperation is feasible in relatively short time interval.It is assumed that net
There is any k car size to be downloaded in network in certain cluster for the M file being grouped.As described above, in each V2I stage, k car
In any one from download point out download m be grouped（m≤M）.In the ensuing V2V stages, this k car is exchanged with each other it
Just-downloaded this m packet, therefore m packet of each car all containing other vehicles is the packet count that contains of each car by m
It is individual to increase to km（May be grouped comprising identical is repeated）.Assume the x in i-th circulationiRepresent different in this km packet
Packet number（Remove remaining packet number after repeated packets）.Obvious xiBe a stochastic variable value collection be combined into 0,1,
2,…,km}.Next we define SiFor the packet number that each car during i-th loop ends contains（Each is grouped not phase
Together, do not repeat）.Therefore there is x in each loop endsiIndividual new packet is added thereto, therefore to SiThere is following recurrence formula
Si=Si-1+xi (1)
When all vehicles are all containing this M packet, send downloading process and just stop.If variable T is to download when completing
Cycle-index.Then have
WhereinRounding operation in expression, because one cycle at most downloads km different packet therefore to complete to download
It is minimum to needIt is secondary.
Next calculate using the sending method based on feedback, complete the probability-distribution function for downloading required cycle-index T
And expected value（Download completes required cycle-index）.
Formula 1:Given Si-1During=s, different grouping number x increased newly in i-th circulationiConditional probability distribution function such as
Under：
Prove：Probability P（xi=x|Si-1=s) meaning that shows is that vehicle has received s bag in the next one（V2I+
V2V）During increase the number of bag newly, each car all can be from remaining（M-s）It is random in individual bag to download m different packet, because
This x at least equal to m, when remaining bag number（M-s）Vehicle one has surely received remaining bag during ＜ m.So have and take as x [1,
2 ..., min (m, M-s)] when, conditional probability P（xi=x|Si-1=s）=1, wherein min (m, M-s) shows if residue is not downloaded
Bag number less than vehicle download capabilities m when, vehicle can only at most take this remaining bag or packet.
Situation as x >=m is as follows：
Denominator represent from (M-s) take m packet be possible to number of combinations.Molecule is represented in this k car composition
Just increased the individual different packets of x in set newly is possible to number of combinations.
Obviously the expression formula of denominator is well understood by.Here we only explain biomolecule expressions.Represent from remaining
X is selected in M-s packet.AndRepresent front fromIn select
Certain x be grouped in this k car permutation and combination number in how many.
Formula is stressed belowIts meaning for representing is k car
M packet is selected in (M-s) individual packet that each car is all never received, it is added together rear except the packet of deduplication identical is remaining not
With packet be precisely fromIn select certain x packet.Assume fromIn the x that selects be grouped into set (P1,
P2,...,Px).Above event be equivalent to one in k car from（P1, P2..., Px) in select m out, remaining (k-1)
Car also selects m out from the set, but this (k-1) car selects respectively the individual summations of m to include in set removes that
M outer remaining (x-m) car in addition, i.e. their union of car choosing must be set itself.Such as in k car one
(P is selected1,P2,...,Px) in (P1,P2,...,Pm) this m packet, then (k-1) * m that remaining (k-1) car is selected
(P must be included in individual packetm+1,Pm+2,...,Px) this remaining (x-m) individual packet, their union constitutes set (P1,
P2,...,Px) itself.The problem can be in Combinational Mathematics inclusion-exclusion principle calculate.Assume this remaining (x-m) be individual to be grouped into
Set { p '1, p '2..., p 'x-m}.Set E represents event：(k-1) car selects m packet (x from x packet respectively>=m).
Its element number for including is designated as | E |（Hereinafter the number of all events is used |. | represent）Then haveIf event
A1,A2,...,Ax-mFor the subset of finite aggregate E, Ai=(x | xE, and make not containing packet p ' in Ei, then, so eventMean that and meet in property E simultaneously
Comprising p '1, p '2..., p 'x-mThe event of this (x-m) individual packet（As required by us）.Subset A1,A2,...,Ax-mWith right
Property is claimed therefore to make：
…
By inclusion-exclusion principle：If F1,F2,...FnFor the subset of finite aggregate F, then
Therefore, it can be derived formula as follows：
Formula 2：The derivation of the probability-distribution function for completing to download the cycle-index needed for the file of whole M sizes is as follows：
The span of TNumerical value be to complete the minimal circulation time needed for downloading
Number,Numerical value be complete to download needed for most cycle-indexes.
Wherein, P (St-1=s) can be calculated by following iterative formula
Initially formula is：
Performance evaluation result：
This part to more than based on feedback mode cooperate download theoretical analysis result carried out checking and and
The result that real process draws is contrasted, with matlab by simulation result drafting pattern.
We have write C++ programs and have calculated the vehicle of theory analysis respectively and have downloaded circulation time needed for particular size file
Several meansigma methodss and its probability distribution probability function；Simultaneously the cooperation downloading mode is abstracted with C++ programs, simulated true
The cycle-index downloaded in real field scape, the actual scene emulation in following figure is 300 the data obtaineds of operation, and gained is equal
Value compares to verify our theoretical analysis result with theory analysis value.Simultaneously and based on the random packet selecting party for repeating
Cooperation method for down loading is contrasted between vehicle under formula, and the method for as a result showing this programme substantially reduces the download time of file.
Fig. 2 shows fixed vehicle number k=6, vehicle when AP downloads packet number m=3, the change of file size M
Impact situation to completing to download required cycle-index.As seen from the figure the theory analysis of this programme and actual emulation based on feedback
Mode selects the curve that cooperation method for down loading is formed between the vehicle being grouped to coincide substantially, it was demonstrated that the correctness of theory analysis.Together
When give under equal conditions based on random selection packet mode vehicle between cooperation method for down loading with file size change
Change curve, it can be seen that the download time for substantially reducing file is downloaded in cooperation between the vehicle based on feedback system, and with text
Part increase effect is all the more obvious.
Fig. 3 is illustrated under M=40, m=3 equal conditions, as the expectation that the increase of vehicle number is completed needed for file download is followed
Ring number of times gradually decrease complete download time gradually decrease.What is be also apparent from figure sees when vehicle number reaches more than 30
When, basic stopping is declined the time required to completing download, therefore have the upper limit to shorten download time increase vehicle number, more than certain
The quantity effect that then it is produced is not just obvious.
M=40 is set in Fig. 4, with the increase of k during m*k=12, the required cycle-index for completing to download gradually changes feelings
Condition.M*k=12 shows that the total number packets shared between V2V stage vehicles are identical, from the situation in figure, now increases vehicle
Number k can shorten download time.Therefore it is, when considering to increase vehicle number and increase vehicle download capabilities, to be to our enlightenment
Shortening download time preferentially increases shared vehicle number and can reach more preferable effect.
Beneficial effect
1）The defect that the present invention exists for existing vehicle data downloading mode and technology：Coverage, downloading data rate,
And the contradiction between flow rate problem three, it is proposed that cooperation data download method between the vehicle based on feedback system, can
To be significantly shorter single unit vehicle data download time, while passing through V2V（Car and car）The shared mutual data of communication, not only contract
The V2V communications simultaneously of short time do not produce cost, and the rate for also making downloading data are substantially reduced.
2）Compared to random fashion vehicle between cooperation data download and 3G network, based on feedback vehicle between cooperation download
The advantage of both is combined, by the use of the ubiquitous of 3G network as control channel, just by car before into roadside access points
Request download information be uploaded to network, when vehicle enter access point coverage after, using roadside access points AP transmit
High Data Rate, down-transmitting data content.
3）Cooperative, compares the single vehicle of 3G network each downloading data content, and method proposed by the present invention adopts vehicle
Between cooperate with each other the shared content each downloaded, the inner capacitiess that how shared the vehicle of cooperation is more are bigger, for single unit vehicle
Income is bigger.
Description of the drawings
Fig. 1：System model.
Fig. 2：The impact of cycle-index of the change of M to completing to download.
Fig. 3：Impact of the vehicle number to cycle-index.
Fig. 4：Impacts of the vehicle number k to cycle-index when m*k is definite value.
Specific embodiment
Because the distribution relative discrete of roadside download point is distributed, cause vehicle a very long time not in the covering of download point
In the range of, vehicle is always intermittent with the connection of download point, and interval is relatively long, not yet in effect to use.Consider simultaneously
Single unit vehicle is each downloaded respective file and is not cooperated each other, and this programme proposes the mode of cooperation download, makes full use of
Vehicle not in the interval time of roadside download point coverage, after the covering interval of download point is left, by DSRC (between vehicle
Short-range communication protocol) V2V that carries out between vehicle（Car communicates with car）Respective download content is mutually shared, cooperation download is reached double
The purpose of win.In order to realize that respective download content is shared completely in V2V communications, we are using a kind of adjacent vehicle in geographical position
Form the mode of vehicle " cluster ".Vehicle in one vehicle " cluster " can completely share mutual downloading data.Simultaneously for
Machine downloading mode, without linking up between vehicle and download point, the content of download is probably the data content portion that vehicle has contained,
This is undoubtedly the waste to bandwidth and downloading machine meeting.The system model of the present invention is not wasted often using the downloading mode for being based on feedback
Secondary downloading machine meeting.Specific embodiment is as control channel, to the access point for closing on using the wide spreadability of 3G channels
Upload the existing data division of vehicle, so when vehicle enters roadside download point, access point can targetedly only to
Vehicle passes down the data division that vehicle is not also received, it is to avoid redundancy and repetition, while make use of wide spreadability and the roadside of 3G
The advantage of the High Data Rate that access point is downloaded.To realize object above, this programme also needs to set up an AP（Download access point）
Server, preserves the positional information of all roadside access points, so when vehicle using 3G channels upload receiving portion data and
Current vehicle position（By onboard installing GPS positioning device）Afterwards, server can contrast current vehicle location and AP positions,
The position of the next AP that vehicle traveling direction will be reached is found out, can now notify that the access point is ready, it is and corresponding
Vehicle content to be downloaded content server connection, in advance obtain download content, when vehicle enter the AP（Download access point）
Coverage after, pass the data of its non-receiving portion down to vehicle.
Complete system model is as shown in figure 1, cooperation download flow process is expressed as below between a complete vehicle：
The vehicle flow travelled on road can be mutually made up of " cluster " one by one many adjacent cars of geographical position, be claimed each
Individual " cluster " accordingly " cluster head " vehicle is header, and " cluster tail " vehicle is trailer.Consider such a scene：In certain cluster
There is k car simultaneously（Red vehicle in figure）Want to download file of the same size for M packet.This file to be downloaded of k car
Information is aggregated into " cluster head " vehicle, is uploaded information by the vehicle（For example, reported by mobile network）, then by the webserver
In being sent to the content server of storage this document.It is assumed that processing the webserver of this document download request can obtain the cluster
Geographical location information and the direction of motion（Vehicle installs GPS positioning device）, and the webserver preserves all roadsides
The exact position of access point, such that it is able to judge the access point that " cluster " will be reached, then downloads from content server
File content is stored in the middle of the server, and after cluster enters the coverage of the access point, communicate download with k car in cluster
This document information.
Might as well assume that any one packet number downloaded in the V2I stages in k car is homogeneously all m（m<M）, m is less than
File total packet number M.Obviously, m how is selected from M packet and is grouped the system of selection for being downloaded to vehicle to whole file
The performance of download system is most important.This programme is considered using the selection mode based on feedback：In the V2I stages of each car,
The file grouping catalogue having been received by first is uploaded to roadside download point AP by vehicle, such roadside access points AP just from the vehicle not
Select m in the packet for receiving at random and be out downloaded to vehicle.
After cluster trailer also leaves the overlay area of roadside access points AP, all vehicles in cluster enter the V2V stages.
The stage, all vehicle sharing download contents in cluster.Therefore wait after the completion of V2V, all k cars all will be containing identical content
（All vehicles download content sum）.When vehicle enters next download point, this above-mentioned downloading process of k repetition in cluster is straight
To complete file of download.
Claims (1)
1. cooperation download scenarios between a kind of vehicle based on feedback system, it is characterised in that the data in car networking download by
Two stage compositions, including：
Vehicle-to-Infrastructure (V2I) vehicles and roadside access points connection communication stage：In the stage, work as car
Enter roadside access points coverage in when, vehicle obtains data from from access point AP (Access Point)；
Vehicle-to-Vehicle (V2V) cars and inter-vehicle communication stage：After vehicle leaves the coverage of roadside access points,
Information is exchanged with each other between vehicle；All of node all obtains identical data at the end of the stage；
It is the cooperation download in a vehicle " cluster " that cooperation is downloaded, rather than regardless of several how far away workshops of spaces of vehicles all
Can with；V2I processes using based on feedback by the way of from roadside access points AP downloading data files, i.e. vehicle download file it
It is front first the partial document for having received to be uploaded into AP, only broadcast non-receiving portion corresponding to vehicle；
But be that the random from whole file of simple repetition is passed down partly to vehicle based on random packet selection mode,
Therefore the repetitive rate of vehicle download part is very high；Vehicle is needed first to upload download part catalogue, such download point before downloading
The partial data that vehicle is not received just only is passed down；It is assumed that the file grouping that vehicle is received after V2I, the size use of file
How many packet Packets are weighed to share completely in the V2V stages and exchanged；The privacy of content is downloaded for vehicle to examine with safe
Consider, roadside access points AP once only communicates with a car and downloads file, and other vehicles can not obtain this document information, different from wide
Broadcast distribution data；
Through a download point, vehicle downloads corresponding document V2I to one cluster in cluster, leaves and pass through between vehicle in cluster after the download point
V2V, i.e. car communicate with car and share completely respective content of downloading for " circulation " V2I+V2V；Therefore a big text is downloaded
Part is accomplished by just to be completed through multiple circulations；
There is x in each loop endsiIndividual new packet is added thereto, therefore to SiThere is following recurrence formula：
Si=Si-1+xi (1)
When all vehicles are all containing this M packet, send downloading process and just stop, if variable T is to download circulation when completing
Number of times, then have：
WhereinRounding operation in expression, because one cycle at most downloads km different packet, therefore will complete to download at least
NeedIt is secondary.
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| CN105704694B (en) * | 2016-01-18 | 2019-02-19 | 北京邮电大学 | The calculation method and device of expense allocation value when collaboration downloading |
| US11064065B2 (en) | 2016-04-14 | 2021-07-13 | Ford Global Technologies, Llc | Method and apparatus for cellular network backup connectivity |
| CN107426787A (en) * | 2017-05-12 | 2017-12-01 | 东华大学 | A kind of content requests retransmission method based on mixing mobile content central site network |
| CN108023946A (en) * | 2017-11-30 | 2018-05-11 | 毛国强 | Switching method and its system during a kind of vehicle mixed communication |
| CN108650657B (en) * | 2018-04-20 | 2021-02-26 | 京东方科技集团股份有限公司 | Content distribution method, content updating method and related devices in Internet of vehicles |
| KR102526968B1 (en) * | 2018-09-18 | 2023-04-28 | 현대자동차주식회사 | vehicle and method for controlling the same |
| CN109600715B (en) * | 2018-11-29 | 2020-11-20 | 哈尔滨工程大学 | Internet of vehicles V2X communication auxiliary file downloading method |
| CN110430237A (en) * | 2019-07-02 | 2019-11-08 | 北京梧桐车联科技有限责任公司 | A kind of information processing method, device, the vehicles and storage medium |
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