CN103118381B - Vehicular ad hoc network minimizing 3G is utilized to share the method and system of data download - Google Patents

Abstract

The invention discloses a kind of method and system utilizing vehicular ad hoc network minimizing 3G to share data download, the method comprises the steps: system initialization, obtain vehicle history to meet the data message that information and needing downloads, obtain the vehicle set needing these data simultaneously; Determine that multistage strategy needs the number of times performed; Based on the historical information that vehicle meets, download policy is calculated in conjunction with transmission requirement and current transmission situation, depict the optimization problem that 3G downloads, solve this optimization problem and make and download decision accordingly, the data downloaded by 3G are transferred to the vehicle node needing these data again by vehicle network, and according to the execution number of times determined, repeat this step; And all vehicle node not obtaining data download corresponding data by 3G, by the present invention, both can reduce the cost that 3G downloads, meet again the timeliness requirement of transfer of data.

Description

Vehicular ad hoc network minimizing 3G is utilized to share the method and system of data download

Technical field

The method and system that the present invention downloads about a kind of 3G data, particularly relate to a kind of method and system utilizing vehicular ad hoc network minimizing 3G to share data download.

Background technology

Vehicle network is network emerging in recent years, and various countries are used for the standard of the Dedicated Short RangeCommunications (Dedicated Short Range Communications, technology) of vehicle network also in formulation with in improving.Vehicle self-organizing network is made up of vehicle node, radio communication is carried out by the Wireless Telecom Equipment that vehicle is installed, transceiving data, to realize the multi-hop wireless communication between vehicle, between vehicle and static infrastructure, is built into the mobile radio network that can complete point to point link.In the network, each car is all the routing node of whole network, therefore realizes the interconnected of vehicle in whole city.The shortcoming of vehicle network is that coverage is little, and network connection is unstable, and propagation delay time is high.Advantage spends substantially can ignore, and transmission rate is high.

3 G mobile communication network (3rd-generation, 3G) is being widely used now.Mobile device, as notebook computer, smart mobile phone are all equipped with the radio communication that 3G module realizes high speed, wide scope.It is wide that 3G communication has communication range, the advantages such as speed is fast.But, due to the more expensive user of causing of rate can not be random download and rate problem must be considered.

Multi net voting Mixed Weibull distribution is repeatedly discussed at academic and practise area.System discussed here is 3G, vehicle hybrid network, and the vehicle node in vehicle network not only can complete transfer of data by short haul connection, can also access 3G module and carry out data download (such as downloading map rejuvenation information etc.).It solves the problem of following scene: a subclass in vehicle network needs to download identical data, and this kind of data can only be downloaded by 3G network at the beginning.Need to pay the certain expense of operator because 3G downloads, downloaded separately by 3G so the highest method of cost is each car in set, but the maximum time delay of this method cost is minimum.Another one method be individual node in set by 3G downloading data, and then passed to other vehicle node in set by vehicle network.Although this method least cost, because vehicle network transmission delay is higher, cause part of nodes can not receive the data of needs download in certain timeliness.

Summary of the invention

For overcoming above-mentioned the deficiencies in the prior art, the object of the present invention is to provide a kind of method and system utilizing vehicular ad hoc network minimizing 3G to share data download, it assists 3G to download in conjunction with vehicular ad hoc network, realize the cost both having reduced 3G download, the object that the timeliness meeting again transfer of data requires.

For reaching above-mentioned and other object, the invention provides a kind of system utilizing vehicular ad hoc network minimizing 3G to share data download, at least comprising:

Initialization module, for system initialization, obtains vehicle history and to meet the data message that information and needing downloads, obtain the vehicle set needing these data simultaneously;

Perform number of times determination module, for determining that multistage strategy needs the number of times performed;

Download policy calculates and process module, according to the execution number of times determined, be repeated below process: the historical information of meeting based on vehicle, download policy is calculated in conjunction with transmission requirement and current transmission situation, depict the optimization problem that 3G downloads, solve this optimization problem and make and download decision accordingly, the data downloaded by 3G are transferred to the vehicle node needing these data again by vehicle network; And

3G downloads module, before the last moment of timeliness restriction arriving downloading request, makes all vehicle node not obtaining data download corresponding data by 3G network.

Further, the calculating of this download policy and process module also comprise:

Transmission situation collects module, for collecting transmission situation;

Weight upgrades module, according to transmission situation and the vehicle node local cache information of the current network collected, upgrades the weight of seed node to be selected;

Optimization problem portrays module, download problem is formulated for optimization problem, and target minimizes the data volume downloaded by 3G, and constraint is that each vehicle node will obtain the data needing to download before time-constrain, and solve this optimization problem, obtain approximate optimal solution;

Transfer of data module, utilizes the transmittability of vehicular ad hoc network, uses double bounce transmission data to be transmitted in vehicle network.

Further, this transmission situation comprises in the buffer memory of each vehicle node needs the number of the packet transmitted and the packet of transmission success.

Further, this optimization problem is portrayed module and in the following way download problem is formulated for optimization problem:

Minimize: $\underset{u_i\∈U}{\mathrm{\Σ}}\underset{p_k\∈P}{\mathrm{\Σ}}{X}_i^{\left(k\right)}$

Be constrained in: $\frac{\left|\right|{W_{\mathrm{avg}}}^{\left(k\right)}\left(T\right)\left|\right|}{\left|\right|W_c\left|\right|}\·\mathrm{Cos}\_\mathrm{Sim}({W_{\mathrm{avg}}}^{\left(k\right)}\left(T\right),W_c)\≥1-\mathrm{\δ}$

W _c＝{ε,ε,ε,...}

Vehicle in vehicle network is expressed as a set V={v ₁, v ₂, v ₃..., v _n, a wherein subclass U={u of V ₁, u ₂, u ₃..., u _mfor needing the vehicle identifiers of downloading data bag, set P={p ₁, p ₂..., p _krepresent the packet needing to download, represent vehicle u _idownloading data p _k, vector $W^{\left(k\right)}\left(T\right)=u_j\∈U(\underset{u_i\∈S^{\left(k\right)}}{\mathrm{\Π}}{W}_{i1}^{\left(k\right)}T,...,\underset{u_i\∈S^{\left(k\right)}}{\mathrm{\Π}}{W}_{\mathrm{ij}}^{\left(k\right)}T),W_{\mathrm{avg}}^{\left(k\right)}\left(T\right)=\frac{1}{\left|P\right|}\underset{k\∈P}{\mathrm{\Σ}}{W}^{\left(k\right)}\left(T\right).$

Further, this optimization problem is portrayed module and is solved this optimization problem by greedy algorithm.

For reaching above-mentioned and other problem, the present invention also provides a kind of method utilizing vehicular ad hoc network minimizing 3G to share data download, comprises the steps:

Step one, system initialization, obtains vehicle history and to meet the data message that information and needing downloads, obtain the vehicle set needing these data simultaneously;

Step 2, determines that multistage strategy needs the number of times performed;

Step 3, based on the historical information that vehicle meets, download policy is calculated in conjunction with transmission requirement and current transmission situation, depict the optimization problem that 3G downloads, solve this optimization problem and make and download decision accordingly, the data downloaded by 3G are transferred to the vehicle node needing these data again by vehicle network, and according to the execution number of times that step 2 is determined, repeat this step; And

Step 4, before the last moment of timeliness restricted T arriving downloading request, all vehicle node not obtaining data download corresponding data by 3G.

Further, step 3 also comprises the steps:

Collect transmission situation;

According to transmission situation and the vehicle node local cache information of the current network collected, upgrade the weight of seed node to be selected;

Download problem is formulated for optimization problem, and target minimizes the data volume downloaded by 3G, and constraint is that each vehicle node will obtain the data needing to download before time-constrain, and solves this optimization problem, obtains approximate optimal solution; And

Utilize the transmittability of vehicle self-organizing network, use double bounce transmission data to be transmitted in vehicle network.

Further, the transmission situation that this collection transmission situation is collected comprises in the buffer memory of each vehicle node and needs the number of the packet transmitted and the packet of transmission success.

Further, download problem is formulated for optimization problem step and in the following way download problem is formulated for optimization problem by this,

Minimize: $\underset{u_i\∈U}{\mathrm{\Σ}}\underset{p_k\∈P}{\mathrm{\Σ}}{X}_i^{\left(k\right)}$

Be constrained in: $\frac{\left|\right|{W_{\mathrm{avg}}}^{\left(k\right)}\left(T\right)\left|\right|}{\left|\right|W_c\left|\right|}\·\mathrm{Cos}\_\mathrm{Sim}({W_{\mathrm{avg}}}^{\left(k\right)}\left(T\right),W_c)\≥1-\mathrm{\δ}$

W _c＝{ε,ε,ε,...}

Vehicle in vehicle network is expressed as a set V={v ₁, v ₂, v ₃..., v _n, a wherein subclass U={u of V ₁, u ₂, u ₃..., u _mfor needing the vehicle identifiers of downloading data bag, set P={p ₁, p ₂..., p _krepresent the packet needing to download, represent vehicle u _idownloading data p _k, vector $W^{\left(k\right)}\left(T\right)=u_j\∈U(\underset{u_i\∈S^{\left(k\right)}}{\mathrm{\Π}}{W}_{i1}^{\left(k\right)}T,...,\underset{u_i\∈S^{\left(k\right)}}{\mathrm{\Π}}{W}_{\mathrm{ij}}^{\left(k\right)}T),W_{\mathrm{avg}}^{\left(k\right)}\left(T\right)=\frac{1}{\left|P\right|}\underset{k\∈P}{\mathrm{\Σ}}{W}^{\left(k\right)}\left(T\right).$

Further, greedy algorithm is utilized to solve this optimization problem in step 3.

Compared with prior art, the present invention is a kind of to be utilized vehicular ad hoc network to reduce 3G to share method and system that data download and to meet information based on the history of vehicle, by choosing the seed node being conducive to vehicle network transmission most, the transmittability making full use of vehicle network by data packet delivery to the destination node needing this packet, utilize vehicular ad hoc network, reach and both met transmission requirement, reduce again the application target of 3G download.

Accompanying drawing explanation

Fig. 1 is a kind of system architecture diagram utilizing vehicular ad hoc network minimizing 3G to share the system that data are downloaded of the present invention;

Fig. 2 is a kind of flow chart of steps utilizing vehicular ad hoc network minimizing 3G to share the method that data are downloaded of the present invention;

Fig. 3 is the timeliness schematic diagram of present pre-ferred embodiments;

Fig. 4 is a kind of flow chart of steps utilizing vehicular ad hoc network minimizing 3G to share the preferred embodiment of the method that data are downloaded of the present invention.

Embodiment

Below by way of specific instantiation and accompanying drawings embodiments of the present invention, those skilled in the art can understand other advantage of the present invention and effect easily by content disclosed in the present specification.The present invention is also implemented by other different instantiation or is applied, and the every details in this specification also can based on different viewpoints and application, carries out various modification and change not deviating under spirit of the present invention.

Before describing the present invention, the proper noun used in the present invention is first introduced:

(1) 3G, vehicle network hybrid network: vehicle, as mobile node, car is equipped with the common Dedicated Short Range Communications (Dedicated Short Range Communications, technology) of vehicle network for the communication between vehicle.Vehicle also equipped with 3G access device for accessing existing 3G network simultaneously.

(2) vehicle history is met information: in statistics a period of time, adjacent required time of meeting for twice (interval Encounter Time) between vehicle and vehicle.Research before shows, the interval Encounter Time index of coincidence distribution between vehicle.

(3) multistage: before whole data download the deadline, node repeatedly makes the number of times downloaded and determine.

(4) seed node: by the vehicle node of 3G technology downloading data content.

(5) downloading request: be directed to each data, needs the vehicle node of these data to be downloaded by 3G before the time T specified or to be obtained by vehicle network.

Fig. 1 is a kind of system architecture diagram utilizing vehicular ad hoc network minimizing 3G to share the system that data are downloaded of the present invention.As shown in Figure 1, a kind of system utilizing vehicular ad hoc network minimizing 3G to share data download of the present invention, for 3G, vehicle network hybrid network, at least comprise: initialization module 10, execution number of times determination module 11, download policy calculate and process module 12 and 3G download module 13.

Wherein initialization module 10 is for system initialization, obtains vehicle history and to meet data number, the number that information and needing downloads, obtain the vehicle set needing these data simultaneously; Perform number of times determination module 11 for determining that multistage strategy needs the number of times performed; Download policy calculates and processes module 12 according to the execution number of times determined, be repeated below process: the historical information of meeting based on vehicle, download policy is calculated in conjunction with transmission requirement and current transmission situation, depict the optimization problem that 3G downloads, solve this optimization problem and make and download decision accordingly, the data downloaded by 3G are transferred to the vehicle node needing these data again by vehicle network; 3G downloads module 13 for before the last moment of timeliness restricted T arriving downloading request, makes all vehicle node not obtaining data download corresponding data by 3G network.

Specifically, download policy calculates and process module 12 comprises further: transmission situation collects module 120, weight upgrades module 121, optimization problem portrays module 122 and transfer of data module 123, transmission situation collects module 120 for collecting transmission situation, comprise in the buffer memory of each vehicle node the number of packet needing to transmit, the information such as packet of transmission success; Weight upgrades module 121, according to transmission situation and the vehicle node local cache information of the current network collected, upgrades the weight of seed node to be selected; Optimization problem is portrayed module 122 and download problem is formulated for optimization problem, target minimizes the data volume downloaded by 3G, constraint is that each vehicle node will obtain the data needing to download before time-constrain, by this optimization problem of greedy algorithm solution, obtains approximate optimal solution; Transfer of data module 123 utilizes the transmittability of vehicular ad hoc network, uses double bounce transmission data to be transmitted in vehicle network.

Optimization problem is portrayed in module 122:

Minimize: $\underset{u_i\∈U}{\mathrm{\Σ}}\underset{p_k\∈P}{\mathrm{\Σ}}{X}_i^{\left(k\right)}$

Be constrained in: $\frac{\left|\right|{W_{\mathrm{avg}}}^{\left(k\right)}\left(T\right)\left|\right|}{\left|\right|W_c\left|\right|}\·\mathrm{Cos}\_\mathrm{Sim}({W_{\mathrm{avg}}}^{\left(k\right)}\left(T\right),W_c)\≥1-\mathrm{\δ}$

W _c＝{ε,ε,ε,...}

(1) vehicle in vehicle network is expressed as a set V={v ₁, v ₂, v ₃..., v _n, a wherein subclass U={u of V ₁, u ₂, u ₃..., u _mfor needing the vehicle identifiers of downloading data bag, set P={p ₁, p ₂..., p _krepresent the packet needing to download. represent vehicle u _idownloading data p _k.Vector $W^{\left(k\right)}\left(T\right)=u_j\∈U(\underset{u_i\∈S^{\left(k\right)}}{\mathrm{\Π}}{W}_{i1}^{\left(k\right)}T,...,\underset{u_i\∈S^{\left(k\right)}}{\mathrm{\Π}}{W}_{\mathrm{ij}}^{\left(k\right)}T)$ Represent wherein set expression.For packet p _k, select by the vehicle S set through electing data feeds node as ^(k), packet p _karrive the weight of each destination node.Wherein represent for all data needing to download, the mean value of seed node weight to be selected.

(2) each w in weight vectors W _ij ^(k)(T) u is chosen in expression _ifor seed node downloading data bag pk arrived destination node u before data age T _jweight.

(3) vectorial W _cfor constant vector, the value by changing ε determines the transmission requirement that will reach, and ε is generally and is less than 1 and very little numerical value.

(4) represent the length ratio of weight vectors and constrained vector, Cos_Sim (X, Y) expression solves two vectorial cosine similarity.The product of the two is greater than 1-δ, represents that the weight vectors of the seed node selected will be tried one's best close to constraint constant vector, to reach transmission requirement.

In numbering 0, select downloading data p _kthe weighting function of seed node be be defined as follows:

this equation represents chooses u _ifor seed node downloading data bag p _kdestination node u is arrived at time T _jfailed probability.Wherein represent u _ifor seed node downloading data bag p _kby intermediate relaying node v _rdestination node u was arrived before time T _jprobability.Research before shows, adjacent between vehicle meet for twice between interval Encounter Time obeys index distribution.λ _iju _iand u _jthe rate parameter of interval Encounter Time exponential distribution.Therefore can obtain from seed u _snode, through via node v _rdouble bounce arrives destination node u _dprobability be:

$P_{\mathrm{srd}}^{\left(k\right)}\left(T\right)=\frac{h_r^{\left(k\right)}{\mathrm{\λ}}_{\mathrm{rd}}}{h_r^{\left(k\right)}{\mathrm{\λ}}_{\mathrm{rd}}-g_s^{\left(k\right)}{\mathrm{\λ}}_{\mathrm{sr}}}(1-e^{-g_s^{\left(k\right)}{\mathrm{\λ}}_{\mathrm{sr}}T})+\frac{g_s^{\left(k\right)}{\mathrm{\λ}}_{\mathrm{sr}}}{g_s^{\left(k\right)}{\mathrm{\λ}}_{\mathrm{sr}}-h_r^{\left(k\right)}{\mathrm{\λ}}_{\mathrm{rd}}}(1-e^{-h_r^{\left(k\right)}{\mathrm{\λ}}_{\mathrm{rd}}T})$

Wherein be respectively packet p _kcan by seed node u in single meets _swith via node v _rthe average probability of transmission, relevant with data volume waiting for transmission in vehicle node buffer memory, cache information can be collected module 120 by transmission situation and obtain.

Fig. 2 is a kind of flow chart of steps utilizing vehicular ad hoc network minimizing 3G to share the method that data are downloaded of the present invention.Fig. 3 is the timeliness schematic diagram of present pre-ferred embodiments.Coordinate shown in Fig. 2 and Fig. 3, a kind of method utilizing vehicular ad hoc network minimizing 3G to share data download of the present invention, for 3G, vehicle network hybrid network, comprises the steps:

Step 201, system initialization, obtains vehicle history and to meet data number, the number that information and needing downloads, obtain the vehicle set needing these data simultaneously.

Step 202, determines that multistage strategy needs the number of times performed.

Step 203, based on the historical information that vehicle meets, download policy is calculated in conjunction with transmission requirement and current transmission situation, depict the optimization problem that 3G downloads, solve this optimization problem and make and download decision accordingly, the data downloaded by 3G are transferred to the vehicle node needing these data again by vehicle network, and according to the execution number of times that step 202 is determined, repeat this step.

Step 204, before the last moment of timeliness restricted T arriving downloading request, all vehicle node not obtaining data download corresponding data by 3G.

Fig. 4 is a kind of flow chart of steps utilizing vehicular ad hoc network minimizing 3G to share the preferred embodiment of the method that data are downloaded of the present invention.Below cooperation Fig. 4 is further illustrated step 203, in step 203, the step in each stage is as follows:

3.1 collect transmission situations: comprise in the buffer memory of each vehicle node the number needing the packet transmitted, the information such as packet of transmission success.

The transmission situation of 3.2 current networks collected by step 0 and vehicle node local cache information, upgrade the weight of seed node to be selected.

Download problem is formulated for optimization problem by 3.3, and target minimizes the data volume downloaded by 3G, and constraint is that each vehicle node will obtain the data needing to download before time-constrain, solves this optimization problem, obtain approximate optimal solution by greedy algorithm.

3.4 transmittabilities utilizing vehicle self-organizing network, use double bounce transmission data to be transmitted in vehicle network.

Optimization problem in step 0 is:

Minimize: $\underset{u_i\∈U}{\mathrm{\Σ}}\underset{p_k\∈P}{\mathrm{\Σ}}{X}_i^{\left(k\right)}$

Be constrained in: $\frac{\left|\right|{W_{\mathrm{avg}}}^{\left(k\right)}\left(T\right)\left|\right|}{\left|\right|W_c\left|\right|}\·\mathrm{Cos}\_\mathrm{Sim}({W_{\mathrm{avg}}}^{\left(k\right)}\left(T\right),W_c)\≥1-\mathrm{\δ}$

W _c＝{ε,ε,ε,...}

(1) vehicle in vehicle network is expressed as a set V={v ₁, v ₂, v ₃..., v _n, a wherein subclass U={u of V ₁, u ₂, u ₃..., u _mfor needing the vehicle identifiers of downloading data bag, set P={p ₁, p ₂..., p _krepresent the packet needing to download. represent vehicle u _idownloading data p _k.Vector $W^{\left(k\right)}\left(T\right)=u_j\∈U(\underset{u_i\∈S^{\left(k\right)}}{\mathrm{\Π}}{W}_{i1}^{\left(k\right)}T,...,\underset{u_i\∈S^{\left(k\right)}}{\mathrm{\Π}}{W}_{\mathrm{ij}}^{\left(k\right)}T)$ Represent wherein set expression.For packet p _k, select by the vehicle S set through electing data feeds node as ^(k), packet p _karrive the weight of each destination node, wherein represent for all data needing to download, the mean value of seed node weight to be selected.

(2) each w in weight vectors W _ij ^(k)(T) u is chosen in expression _ifor seed node downloading data bag pk arrived destination node u before data age T _jweight.

(3) vectorial W _cfor constant vector, the value by changing ε determines the transmission requirement that will reach, and ε is generally and is less than 1 and very little numerical value.

(4) represent the length ratio of weight vectors and constrained vector, Cos_Sim (X, Y) expression solves two vectorial cosine similarity.The product of the two is greater than 1-δ, represents that the weight vectors of the seed node selected will be tried one's best close to constraint constant vector, to reach transmission requirement.

In numbering 0, select downloading data p _kthe weighting function of seed node be be defined as follows:

this equation represents chooses u _ifor seed node downloading data bag p _kdestination node u is arrived at time T _jfailed probability.Wherein represent u _ifor seed node downloading data bag p _kby intermediate relaying node v _rdestination node u was arrived before time T _jprobability.Research before shows, adjacent between vehicle meet for twice between interval Encounter Time obeys index distribution.λ _iju _iand u _jthe rate parameter of interval Encounter Time exponential distribution.Therefore can obtain from seed u _snode, through via node v _rdouble bounce arrives destination node u _dprobability be:

$P_{\mathrm{srd}}^{\left(k\right)}\left(T\right)=\frac{h_r^{\left(k\right)}{\mathrm{\λ}}_{\mathrm{rd}}}{h_r^{\left(k\right)}{\mathrm{\λ}}_{\mathrm{rd}}-g_s^{\left(k\right)}{\mathrm{\λ}}_{\mathrm{sr}}}(1-e^{-g_s^{\left(k\right)}{\mathrm{\λ}}_{\mathrm{sr}}T})+\frac{g_s^{\left(k\right)}{\mathrm{\λ}}_{\mathrm{sr}}}{g_s^{\left(k\right)}{\mathrm{\λ}}_{\mathrm{sr}}-h_r^{\left(k\right)}{\mathrm{\λ}}_{\mathrm{rd}}}(1-e^{-h_r^{\left(k\right)}{\mathrm{\λ}}_{\mathrm{rd}}T})$

Wherein be respectively packet p _kcan by seed node u in single meets _swith via node v _rthe average probability of transmission, relevant with data volume waiting for transmission in vehicle node buffer memory, cache information can be obtained by step 3.1.

Before each decision phase starts, the weight of seed node to be selected need be upgraded according to the network information of the transmission situation of previous stage and current time.Separate this optimization problem and can use greedy algorithm, obtain approximate optimal solution.

In sum, the present invention is a kind of to be utilized vehicular ad hoc network to reduce 3G to share method and system that data download and to meet information based on the history of vehicle, by choosing the seed node being conducive to vehicle network transmission most, the transmittability making full use of vehicle network by data packet delivery to the destination node needing this packet, utilize vehicular ad hoc network, reach and both met transmission requirement, reduce again the application target of 3G download.

Compared with prior art, the present invention has the following advantages:

1. assist the 3G network of high expense to download by the vehicle network transmittability of low expense, reach the object reducing user cost expense.

2. use multistage decision thought, in conjunction with current transmission situation in repeatedly decision-making, can make and download decision more accurately, reduce the expense that 3G uses.

3. utilize the information of meeting of vehicle history, effectively can formulate download policy, make full use of the transmittability of vehicle network.

Above-described embodiment is illustrative principle of the present invention and effect thereof only, but not for limiting the present invention.Any those skilled in the art all without prejudice under spirit of the present invention and category, can carry out modifying to above-described embodiment and change.Therefore, the scope of the present invention, should listed by claims.

Claims (6)

1. utilize vehicular ad hoc network minimizing 3G to share a system for data download, at least comprise:

Initialization module, for system initialization, obtains vehicle history and to meet the data message that information and needing downloads, obtain the vehicle set needing these data simultaneously;

Perform number of times determination module, for determining that multistage strategy needs the number of times performed;

Download policy calculates and process module, according to the execution number of times determined, be repeated below process: the historical information of meeting based on vehicle, download policy is calculated in conjunction with transmission requirement and current transmission situation, depict the optimization problem that 3G downloads, solve this optimization problem and make and download decision accordingly, the data downloaded by 3G are transferred to the vehicle node needing these data again by vehicle network;

And 3G downloads module, makes all vehicle node not obtaining data download corresponding data by 3G network;

This download policy calculates and process module also comprises:

Transmission situation collects module, for collecting transmission situation;

Weight upgrades module, according to transmission situation and the vehicle node local cache information of the current network collected, upgrades the weight of seed node to be selected;

Optimization problem portrays module, download problem is formulated for optimization problem, and target minimizes the data volume downloaded by 3G, and constraint is that each vehicle node will obtain the data needing to download before time-constrain, and solve this optimization problem, obtain approximate optimal solution;

Transfer of data module, utilizes the transmittability of vehicular ad hoc network, uses double bounce transmission data to be transmitted in vehicle network;

This optimization problem is portrayed module and in the following way download problem is formulated for optimization problem:

Minimize:

Be constrained in: $\frac{||{W_{avg}}^{\left(k\right)}\left(T\right)||}{||W_c||}\·Cos\_Sim\left({W_{avg}}^{\left(k\right)}\right(T),W_c)\≥1-\mathrm{\δ}$

W _c＝{ε,ε,ε,...}

Vehicle in vehicle network is expressed as a set V={v ₁, v ₂, v ₃..., v _n, a wherein subclass U={u of V ₁, u ₂, u ₃..., u _mfor needing the vehicle identifiers of downloading data bag, set P={p ₁, p ₂..., p _krepresent the packet needing to download, represent vehicle u _idownloading data p _k, represent and do not download, vector $W^{\left(k\right)}\left(T\right){=}_{u_j\∈U}(\underset{u_i\∈S^{\left(k\right)}}{\Π}{W}_{i1}^{\left(k\right)}T,...,\underset{u_i\∈S^{\left(k\right)}}{\Π}{W}_{ij}^{\left(k\right)}T)$ Represent wherein set expression, for packet p _k, select the vehicle S set being chosen as data feeds node ^(k), packet p _karrive the weight of each destination node, represent for all data needing to download, the mean value of seed node weight to be selected; Each w in weight vectors W _ij ^(k)(T) u is chosen in expression _ifor seed node downloading data bag p _kdestination node u was arrived before data age T _jweight; Vector W _cfor constant vector, the value by changing ε determines the transmission requirement that will reach, and ε is less than 1 and very little numerical value; represent the length ratio of weight vectors and constrained vector, Cos_Sim (X, Y) expression solves two vectorial cosine similarity, and the product of the two is greater than 1-δ, represent that the weight vectors of the seed node selected will be tried one's best close to constraint constant vector, to reach transmission requirement.

2. utilize vehicular ad hoc network to reduce 3G as claimed in claim 1 and share the system that data download, it is characterized in that: this transmission situation comprises in the buffer memory of each vehicle node needs the number of the packet transmitted and the packet of transmission success.

3. utilize vehicular ad hoc network minimizing 3G to share the system of data download as claimed in claim 1, it is characterized in that: this optimization problem is portrayed module and solved this optimization problem by greedy algorithm.

4. utilize vehicular ad hoc network minimizing 3G to share a method for data download, comprise the steps:

Step one, system initialization, obtains vehicle history and to meet the data message that information and needing downloads, obtain the vehicle set needing these data simultaneously;

Step 2, determines that multistage strategy needs the number of times performed;

Step 3, based on the historical information that vehicle meets, download policy is calculated in conjunction with transmission requirement and current transmission situation, depict the optimization problem that 3G downloads, solve this optimization problem and make and download decision accordingly, the data downloaded by 3G are transferred to the vehicle node needing these data again by vehicle network, and according to the execution number of times that step 2 is determined, repeat this step; And

Step 4, all vehicle node not obtaining data download corresponding data by 3G;

Step 3 also comprises the steps:

Collect transmission situation;

According to transmission situation and the vehicle node local cache information of the current network collected, upgrade the weight of seed node to be selected;

Download problem is formulated for optimization problem, and target minimizes the data volume downloaded by 3G, and constraint is that each vehicle node will obtain the data needing to download before time-constrain, and solves this optimization problem, obtains approximate optimal solution; And

Utilize the transmittability of vehicle self-organizing network, use double bounce transmission data to be transmitted in vehicle network;

Download problem is formulated for optimization problem step and in the following way download problem is formulated for optimization problem by this,

Minimize:

Be constrained in: $\frac{||{W_{avg}}^{\left(k\right)}\left(T\right)||}{||W_c||}\·Cos\_Sim\left({W_{avg}}^{\left(k\right)}\right(T),W_c)\≥1-\mathrm{\δ}$

W _c＝{ε,ε,ε,...}

Vehicle in vehicle network is expressed as a set V={v ₁, v ₂, v ₃..., v _n, a wherein subclass U={u of V ₁, u ₂, u ₃..., u _mfor needing the vehicle identifiers of downloading data bag, set P={p ₁, p ₂..., p _krepresent the packet needing to download, represent vehicle u _idownloading data p _k, represent and do not download, vector $W^{\left(k\right)}\left(T\right){=}_{u_j\∈U}(\underset{u_i\∈S^{\left(k\right)}}{\Π}{W}_{i1}^{\left(k\right)}T,...,\underset{u_i\∈S^{\left(k\right)}}{\Π}{W}_{ij}^{\left(k\right)}T),$ represent wherein set expression, for packet p _k, select the vehicle S set being chosen as data feeds node ^(k), packet p _karrive the weight of each destination node, represent for all data needing to download, the mean value of seed node weight to be selected; Each w in weight vectors W _ij ^(k)(T) u is chosen in expression _ifor seed node downloading data bag p _kdestination node u was arrived before data age T _jweight; Vector W _cfor constant vector, the value by changing ε determines the transmission requirement that will reach, and ε is less than 1 and very little numerical value; represent the length ratio of weight vectors and constrained vector, Cos_Sim (X, Y) expression solves two vectorial cosine similarity, and the product of the two is greater than 1-δ, represent that the weight vectors of the seed node selected will be tried one's best close to constraint constant vector, to reach transmission requirement.

5. a kind ofly as claimed in claim 4 utilize vehicular ad hoc network to reduce 3G to share the method that data download, it is characterized in that: the transmission situation that this collection transmission situation is collected comprises in the buffer memory of each vehicle node and needs the number of the packet transmitted and the packet of transmission success.

6. utilize vehicular ad hoc network minimizing 3G to share the method for data download as claimed in claim 5, it is characterized in that: in step 3, utilize greedy algorithm to solve this optimization problem.