CN102917054A - Vehicle-mounted network stream media prefetching method and device - Google Patents

Abstract

The invention discloses a vehicle-mounted network stream media prefetching method and relates to the field of video application of a mobile Internet. The method comprises the steps that a vehicle detects a neighboring vehicle in a wireless signal coverage range and calculates relative stability of the neighboring vehicle and the vehicle; the vehicle applies for prefetching a video content to the neighboring vehicle with relatively high stability; and the neighboring vehicle prefetches the video content and sends the video content to the vehicle. By the method, the efficiency of sharing stream media resources between the vehicles can be improved, and extremely high feasibility is realized.

Description

A kind of In-vehicle networking Streaming Media forecasting method and device

Technical field

The present invention relates to the field of video applications of mobile Internet, particularly a kind of In-vehicle networking Streaming Media forecasting method and device.

Background technology

Along with the development of wireless vehicle mounted network technology, some new application are disposed in In-vehicle networking.802.11p can provide the playing stream media video needed high bandwidth, thereby realize the Stream Media Application under the In-vehicle networking.Usually rely on the ad hoc(point-to-point between the moving vehicle) mode carries out vehicle-to-vehicle(V2V) communication, thereby realize that resource information shares and cooperate with each other, be conducive to the deployment of large-scale vehicle-mounted stream media system.Yet the fast moving of wireless channel inherent instability and vehicle all can be brought tremendous influence to level and smooth broadcast of Streaming Media.Secondly, for the download of this jumbo file of video, the mode (vehicle with AP between communicate by letter) that only depends on V2I is removed to obtain video content and can be brought long download time, thereby reduces the efficient of sharing of video resource.

At present, cooperation has become the fundamental guiding ideology of optimization system performance in the various fields, as based on the onboard system of cooperation, based on the vehicle encounters early warning system of cooperation, based on the data transfer optimization of P2P etc.Yet, in existing research, mostly adopt the mode downloading video files based on the AP cooperation, namely vehicle is at first from the AP of current access _iObtain initial stream medium data, pass through again AP _iSearch the AP that may access in a certain period in future when vehicle in front _j, and request AP _jAssist vehicle to download required video content.As vehicle process AP _jThe time, AP _jThe video content that can look ahead is transferred to vehicle, thereby realizes accelerating the purpose of download.

For example, existing being correlated with assisted being suggested of the common scheme of downloading based on AP recently.This technology allows vehicle to use the selected AP of WWAN radio (such as GPRS) notice to assist to look ahead.The stream medium data of looking ahead copies on this locality or other mobile vehicles, and when the vehicle of assisting to look ahead when request met with through this AP or with mobile vehicle, this vehicle then can obtain the stream medium data that cooperates and look ahead.Vehicle has been broken through the restriction of bandwidth by looking ahead of assisting based on AP, and can download large-scale video file within a short period of time.The MobTorrent technology has improved throughput and the resource-sharing situation of VANETs, but depends on the prerequisite an of necessity: the flowing information of vehicle must use automatic station-keeping system (AVL) and mobile historical record of past to carry out the high-precision forecast vehicle travel route in future.

Another has proposed a density-based AP deployment strategy based on the solution that AP assists, and downloads to optimize the performance that multi-hop transmits by utilizing in the cooperation between vehicle under the urban environment.Thereby this solution must be obtained the possibility of enough Vehicle Driving Cycle historical record prediction vehicle encounters, and then realizes the cooperation transmission between vehicle.Yet, the interference such as the time-delay that multi-hop transmission can be grown usually and the frequent disconnection of communication connection, thus efficiency of transmission reduced.

Another kind of solution has proposed one and has utilized the mode of associated diagram to select the carrier that cooperates.By thereby the historical driving trace between the vehicle being set up the associated diagram between the vehicle.AP can estimate by associated diagram the vehicle and the probability that cooperates and meet with between the vehicle of downloading of foradownloaded video content, thereby selects suitable cooperation vehicle to assist to download required stream medium data for it.Yet, by AP estimate to AP and AP to information exchange between the vehicle possibility that two cars meets can not well guarantee to cooperate carrier can be at short notice with the content delivery of looking ahead to the request vehicle, and larger information exchange expense and long startup time delay all do not meet the real-time requirement of streaming media service.

In realizing process of the present invention, the inventor finds that there is following problem at least in prior art:

Solution of the prior art is assisted download to need continuous interaction message between AP based on AP, and is also needed to obtain in advance for the running route of vehicle, and the efficient of sharing streaming media resource between vehicle is not high, thereby has reduced the feasibility of this solution.

Summary of the invention

In order to solve the problem of prior art, the embodiment of the invention provides a kind of In-vehicle networking Streaming Media forecasting method and device.Described technical scheme is as follows:

A kind of In-vehicle networking Streaming Media forecasting method, described method comprises:

Neighbours' vehicle in its wireless signal coverage of vehicle detection calculates the relative stability of described neighbours' vehicle and described vehicle;

Described vehicle is to the high neighbours' vehicle request of the relative stability video content of looking ahead;

Described neighbours' vehicle described video content of looking ahead, and send to described vehicle.

The relative stability of the described neighbours' vehicle of described calculating and described vehicle comprises:

Set up neighbours' vehicle tabulation neiL of described vehicle _i=(v ₁, v ₂..., v _n), and setting cycle T carries out the renewal of neighbor list;

For still being positioned at described neighbours' vehicle tabulation neiL after the process renewal _i=(v ₁, v ₂..., v _n) in neighbours' vehicle carry out relative stability assessment;

According to described neighbours' vehicle at described neighbours' vehicle tabulation neiL _i=(v ₁, v ₂..., v _n) in time of existing determine the relative stability of described neighbours' vehicle.

Described method also comprises:

Set up described vehicle V _iStable neighbor vehicle S set, described

S=(newneiL _i∩ neiL _i)=(v _a, v _b..., v _k); Wherein, described newneiL _i=(v ₁, v ₂..., v _m) be the neighbours' vehicle tabulation after upgrading;

Neighbours' vehicle intensity of variation G (V _i)=E (S ^(c))-I (S ^(p)) G (V _i) ∈ [1,1] E (S wherein ^(c)) and I (S ^(p)) be the amount of information of upgrading neighbours' vehicle intensity of variation among the S of front and back;

Described G (V _i) larger, described vehicle V then _iThe stability of neighbours' vehicle is higher.

Described cycle T is set according to following mode:

Intensity of variation G (V according to described neighbours' vehicle _i) adjustment cycle T, if G is (V _i) value lower, it is less then to adjust described T; Otherwise, if G is (V _i) value higher, it is larger then to adjust described T.

The setting of described cycle T is also set according to the intensity of variation of the high neighbours' vehicle of described relative stability.

Described method also comprises:

Assess the stability of described neighbours' vehicle with weighted factor; Described weighted factor

Wherein,

With

With respect to described vehicle V before and after described neighbours' vehicle list update _iThe normalized value of relative velocity; With

With respect to described vehicle V before and after described neighbours' vehicle list update _iThe normalized value of displacement;

Described vr _IjValue lower, described neighbours' vehicle v then _jStability larger.

Described vehicle comprises to the high neighbours' vehicle request of the relative stability video content of looking ahead:

Described vehicle V _iSend probe message to described neighbours' vehicle;

Described neighbours' vehicle adds its memory space and bandwidth information to and is back to V _iMessage in;

Described V _iFrom return messages, extract memory space and the bandwidth information of neighbours' vehicle;

As described V _iNeed its neighbours' vehicle to cooperate when looking ahead, select relative stability high and can have neighbours' vehicle of enough memory spaces and remaining bandwidth, as cooperation neighbours vehicle, ask needed video content.

A kind of In-vehicle networking Streaming Media prefetching device, described device comprises probe unit, stable computing unit, request unit and the transmitting element of looking ahead, wherein,

Described probe unit is for the neighbours' vehicle in the wireless signal coverage of surveying described vehicle;

Described stable computing unit is for the relative stability that calculates described neighbours' vehicle and described vehicle;

The described request unit is for the video content of looking ahead to the high neighbours' vehicle request of relative stability;

The described transmitting element of looking ahead is used for looking ahead described video content, and sends to described vehicle.

Described stable computing unit further comprises neighbours' vehicle tabulation subelement, intensity of variation computation subunit, cycle setting subelement and assessment subelement, wherein,

Described neighbours' vehicle tabulation subelement is used for storing the information of neighbours' vehicle and dynamically updating;

Described intensity of variation computation subunit is for the intensity of variation that calculates neighbours' vehicle tabulation neighbours vehicle;

The described cycle is set subelement, is used for calculating and adjusting the cycle that dynamically updates of described neighbours' vehicle tabulation subelement neighbours vehicle tabulation;

Described assessment subelement is for assessment of the stability of neighbours' vehicle.

The described request unit further comprises surveys subelement, storing sub-units and request subelement, wherein,

Described detection subelement is used for sending probe message to described neighbours' vehicle;

Described storing sub-units is used for described neighbours' vehicle storage space and bandwidth information storage;

The described request subelement is used for according to described neighbours' vehicle storage space and bandwidth information, and the stability of neighbours' vehicle is to described neighbours' vehicle request video content of looking ahead.

The beneficial effect that the technical scheme that the embodiment of the invention provides is brought is:

By obtaining the stability of the neighbours' vehicle in the automobile wireless signal cover, the neighbours vehicle high to stability sends request, requires look ahead video content and return to vehicle and play of neighbours' vehicle.According to the variation of travel average speed and the distance of each vehicle stable weight as each neighbours' vehicle, thereby the stability of regulating accurately the respective neighbours vehicle realizes assessing more accurately the stability of vehicle.The embodiment of the invention does not need to obtain the running route of vehicle, cooperate between the vehicle based on V2V, come common foradownloaded video content by bandwidth and the memory space that utilizes other vehicles to other vehicles, downloading process that not only can the large file of accelerating video, and can improve the efficient of sharing streaming media resource between vehicle, have very high feasibility.

Description of drawings

In order to be illustrated more clearly in the technical scheme in the embodiment of the invention, the accompanying drawing of required use was done to introduce simply during the below will describe embodiment, apparently, accompanying drawing in the following describes only is some embodiments of the present invention, for those of ordinary skills, under the prerequisite of not paying creative work, can also obtain according to these accompanying drawings other accompanying drawing.

Fig. 1 is the In-vehicle networking Streaming Media forecasting method flow chart that the embodiment of the invention provides;

Fig. 2 is the relative stability schematic diagram that the embodiment of the invention one provides;

Fig. 3 is the In-vehicle networking Streaming Media prefetching device structural representation that the embodiment of the invention two provides;

Fig. 4 is stable computing unit 200 structural representations that the embodiment of the invention two provides;

Fig. 5 is request unit 300 structural representations that the embodiment of the invention two provides.

Embodiment

For making the purpose, technical solutions and advantages of the present invention clearer, embodiment of the present invention is described further in detail below in conjunction with accompanying drawing.

All ignored between vehicle based on V2V for the solution of sharing of streaming media resource content in the In-vehicle networking in the prior art and cooperated, namely asked to set up cooperation relation between the vehicle of streaming medium content and its down hop vehicle.When asking vehicle to require its stable down hop vehicle to be its certain video content of looking ahead, then not only can guaranteeing cooperates can share streaming medium content between the both sides effectively, and has reduced the dependence of looking ahead by AP.

The embodiment of the invention has proposed under a kind of In-vehicle networking the Streaming Media prefetch policy based on stable cooperation neighbours perception, is called for short SND.Each vehicle all is considered as down hop neighbours vehicle (being called for short neighbours' vehicle) with all vehicles in its 802.11p signal cover, and the wireless signal overlay area is defined as its direct neighbor zone (INR).By the intelligently variation of sensing neighbor vehicle running state (leaving or stay INR) thus assess the stability (resting on the time of INR) of each neighbours' vehicle, the most stable neighbours' vehicle can be selected the cooperation neighbours required media content of looking ahead that goes to cooperate, the vehicle of request streaming media resource can require the highest neighbours' vehicle of stability to be its certain video content of looking ahead, and after download is finished, be transmitted to the request vehicle, thereby realize that efficient streaming media resource shares.

Embodiment one

As shown in Figure 1, the In-vehicle networking Streaming Media forecasting method flow chart that provides for the embodiment of the invention, wherein,

Neighbours' vehicle in the step 10, its wireless signal coverage of vehicle detection, the relative stability of calculating neighbours' vehicle and this vehicle.

In the urban area of a non-linear route, vehicle all is equipped with gps receiver and a radio network interface.The embodiment of the invention is by utilizing gps receiver to realize " location aware ", each car V _iCan obtain the geographical position of each neighbours' vehicle in the direct neighbor zone (INR).Onboard wireless network interface support unit V _iAnd the transmission of several data and information is mutual between its neighbours' vehicle, realizes V2V communication.Not only can realize the transmission of streaming media video data, can also make V _iObtain the state information that comprises average speed of neighbours' vehicle.

V _iStore the relevant information of it and neighbours' vehicle: neiL with a tabulation _i=(v ₁, v ₂..., v _n), this is V _iNeighbours' vehicle tabulation, wherein,

2 yuan of arrays, (X _c, Y _c) and sp _cRespectively vehicle V _cPhysical address and average speed.Along with the movement of vehicle, the position of neighbours' vehicle is also in dynamic variation, and neiL therefore tabulates _iIt also is dynamic change.

By reusing the method for " location aware ", V _iJust can obtain new neighbours' vehicle tabulation a: newneiL _i=(v ₁, v ₂..., v _m).By the comparison to new and old tabulation, V _iJust can obtain the situation of change (add, leave or stop) of each neighbours' vehicle.If neighbours' vehicle v _jLeave or join V _iINR in, v so _jInformation just from neiL _i=(v ₁, v ₂..., v _n) middle deletion or increase.If neiL is through after upgrading, v _jStill therein, V so _iJust its stability is assessed.

The stability assessment of neighbours' vehicle depends on their time of staying in INR.The time of staying is longer, and its stability is just higher so.Concrete process is as follows:

If S=is (newneiL _i∩ neiL _i)=(v _a, v _b..., v _k) be V _iStable neighbor vehicle set because among the S each node all through after once or repeatedly upgrading still at V _iNeighbours' vehicle tabulation in, wherein S length is k.

Time interval T of SND definition comes more new neighbor vehicle stock table.In order to accomplish timely assessment to neighbours' vehicle, will be set to the variable update cycle update time.

Be used for assessing the stability of neighbours' vehicle based on the stability assessment model of weight.With V _iCome computational stability with relative velocity and the relative displacement of neighbours' vehicle among the S as weight.

Specifically, along with the movement of vehicle, geographical position between neighbours' vehicle relation also can dynamic change, thereby makes neiL _iIn element also change (being leaving or entering of node).V _iCan reuse " location aware " by T, obtain new immediate neighbor collection newneiL _iCompare newneiL _iWith neiL _i, V _iNot only can be clearly stable neighbours' vehicle and the variation in their geographical position, state (average speed and distance) intensity of variation that can also the discovering neighbor vehicle.According to information theory model, we use comentropy G (V _i) represent neighbours' vehicle intensity of variation, as shown in Equation (1).

G (V _i)=E (S ^(c))-I (S ^(p)) G (V _i) ∈ [1,1] formula (1)

E (S wherein ^(c)) and I (S ^(p)) be the amount of information of upgrading neighbours' vehicle intensity of variation among the S of front and back, drawn by formula (2) and follow-up formula (12) respectively.

$E\left(S^{\left(c\right)}\right)=\left\{\begin{array}{cc}{-P}^{\left(c\right)}{\log }_2{P}^{\left(c\right)}& 0<P^{\left(c\right)}<1\\ 0& P^{\left(c\right)}=0\\ 1& P^{\left(c\right)}=1\end{array}\right.$ Formula (2)

P wherein ^(c)For upgrading rear S ^(c)The amount of information that the mobile status of middle all elements (average speed and distance) produces.By analyzing S ^(c)The state information of middle all elements distributes, and we use least square method and linear regression analysis to calculate P ^(c)Make D (S ^(c)) be S ^(c)The state information set of middle all elements, wherein each element is made of 2 tuples, is used for respectively storing S ^(c)In each element with respect to V _iRelative velocity and relative displacement, by formula (3) gained.

$D\left(S^{\left(c\right)}\right)=\{(v_a^{{\mathrm{sd}}_{\mathrm{ia}}},v_a^{\left|{\mathrm{sp}}_{\mathrm{ia}}\right|}),(v_b^{{\mathrm{sd}}_{\mathrm{ib}}},v_b^{\left|{\mathrm{sp}}_{\mathrm{ib}}\right|}),...,(v_k^{{\mathrm{sd}}_{\mathrm{ik}}},v_k^{\left|{\mathrm{sp}}_{\mathrm{ik}}\right|})\}$ Formula (3)

Wherein

With

For each element among the S to V _iDisplacement and average relative.

Initial value can be by formula (4) gained.

$v_j^{{\mathrm{sd}}_{\mathrm{ij}}}=\sqrt{{(X_i-X_j)}^2+{(Y_i-Y_j)}^2}0\&le;v_j^{{\mathrm{sd}}_{\mathrm{ij}}}\&le;v_{\mathrm{MAX}}^{\mathrm{sd}}$ Formula (4)

Wherein (Xi, Yi) and (Xj, Yj) is respectively the physical address of Vi and vj,

Be and V _iThe value that distance is maximum, can with

Value be set to the radius R of INR.

Initial value depend on the absolute value of the difference of average speed, by formula (5) gained.

$v_j^{\left|{\mathrm{sp}}_{\mathrm{ij}}\right|}=\left\{\begin{array}{cc}|V_i^{\mathrm{sp}}-v_j^{\mathrm{sp}}|& 0\&le;|V_i^{\mathrm{sp}}-v_j^{\mathrm{sp}}|<v_{\mathrm{MAX}}^{\mathrm{sp}}\\ v_{\mathrm{MAX}}^{\mathrm{sp}}& |V_i^{\mathrm{sp}}-v_j^{\mathrm{sp}}|\&GreaterEqual;v_{\mathrm{MAX}}^{\mathrm{sp}}\end{array}\right.$ Formula (5)

Wherein

With

Be respectively V _iAnd v _jAverage speed,

It is the maximum of relative velocity among the SND.For convenience's sake, with D (S ^(c)) in each element carry out normalization, shown in formula (6).

${\hat{v}}_j^{\left|{\mathrm{sp}}_{\mathrm{ij}}\right|}=\frac{v_j^{\left|{\mathrm{sp}}_{\mathrm{ij}}\right|}}{v_{\mathrm{MAX}}^{\mathrm{sp}}},$ ${\hat{v}}_j^{{\mathrm{sd}}_{\mathrm{ij}}}=\frac{v_J^{{\mathrm{sd}}_{\mathrm{ij}}}}{v_{\mathrm{MAX}}^{\mathrm{sd}}}$ ${\hat{v}}_j^{\left|{\mathrm{sp}}_{\mathrm{ij}}\right|},{\hat{v}}_j^{{\mathrm{sd}}_{\mathrm{ij}}}\&Element;\left[\mathrm{0,1}\right]$ Formula (6)

If V _iBe the initial point of this coordinate system, as shown in Figure 2, x axle and y axle represent respectively relative distance and relative velocity.D (S ^(c)) in element just can be mapped in this coordinate system.L is D (S ^(c)) linear regression straight line,

That initial point is to the distance of l.Carry out linear regression processing by least square method, we can obtain its coefficient correlation And vertical range

Assess Pi, shown in formula (7).

$P^{\left(c\right)}=r^{D\left(S^{\left(c\right)}\right)}\&times;(1-d_{V_i\&RightArrow;l}^{D\left(S^{\left(c\right)}\right)}),P^{\left(c\right)}\&Element;\left[\mathrm{0,1}\right]$ Formula (7)

Wherein Be the coefficient correlation of linear regression fit, it has shown S ^(c)The different conditions level of middle all elements is calculated gained by formula (8).

Value larger, the state difference of middle element is just less.

$r^{D\left(S^{\left(c\right)}\right)}=\frac{\underset{c=1}{\overset{k}{\mathrm{\&Sigma;}}}|{\hat{v}}_c^{\left|{\mathrm{sp}}_{\mathrm{ic}}\right|}-\stackrel{\&OverBar;}{{\hat{v}}^{\mathrm{sp}}}||{\hat{v}}_c^{{\mathrm{sd}}_{\mathrm{ic}}}-\stackrel{\&OverBar;}{{\hat{v}}^{\mathrm{sd}}}|}{\sqrt{\underset{c=1}{\overset{k}{\mathrm{\&Sigma;}}}{|{\hat{v}}_c^{\left|{\mathrm{sp}}_{\mathrm{ic}}\right|}-\stackrel{\&OverBar;}{{\hat{v}}^{\mathrm{sp}}}|}^2}\&times;\sqrt{\underset{c=1}{\overset{k}{\mathrm{\&Sigma;}}}{|{\hat{v}}_c^{{\mathrm{sd}}_{\mathrm{ic}}}-\stackrel{\&OverBar;}{{\hat{v}}^{\mathrm{sd}}}|}^2}},r^{D\left(S^{\left(c\right)}\right)}\&Element;\left[\mathrm{0,1}\right]$ Formula (8)

Wherein

With

Be respectively with respect to average speed and displacement, its value is calculated gained by formula (9).

$\stackrel{\&OverBar;}{{\hat{v}}^{\mathrm{sp}}}=\frac{\underset{c=1}{\overset{k}{\mathrm{\&Sigma;}}}{\hat{v}}_c^{\left|{\mathrm{sp}}_{\mathrm{ic}}\right|}}{k},$ $\stackrel{\&OverBar;}{{\hat{v}}^{\mathrm{sd}}}=\frac{\underset{c=1}{\overset{k}{\mathrm{\&Sigma;}}}{\hat{v}}_c^{{\mathrm{sd}}_{\mathrm{ic}}}}{k}\stackrel{\&OverBar;}{{\hat{v}}^{\mathrm{sp}}},\stackrel{\&OverBar;}{{\hat{v}}^{\mathrm{sd}}}\&Element;\left[\mathrm{0,1}\right]$ Formula (9)

Shown S ^(c)The mobile status of middle all elements and V _iThe deviation of mobile status, calculate gained by formula (10).

Value lower, S then is described ^(c)Possibility among the INR that middle all elements rests on is higher.

$d_{V_i\&RightArrow;l}^{D\left(S^{\left(c\right)}\right)}=\frac{|b_l\stackrel{\&OverBar;}{{\hat{v}}^{\mathrm{sp}}}-\stackrel{\&OverBar;}{{\hat{v}}^{\mathrm{sd}}}|}{\sqrt{1+b_l^2}},d_{V_i\&RightArrow;l}^{D\left(S^{\left(c\right)}\right)}\&Element;\left[\mathrm{0,1}\right]$ Formula (10)

B wherein _lD (S ^(c)) slope of linear fit straight line, calculate gained by formula (11).

$b_l=\frac{\underset{c=1}{\overset{k}{\mathrm{\&Sigma;}}}{\hat{v}}_c^{\left|{\mathrm{sp}}_{\mathrm{ic}}\right|}{\hat{v}}_c^{{\mathrm{sd}}_{\mathrm{ic}}}-k\stackrel{\&OverBar;}{{\hat{v}}^{\mathrm{sp}}}\stackrel{\&OverBar;}{{\hat{v}}^{\mathrm{sd}}}}{\underset{c=1}{\overset{k}{\mathrm{\&Sigma;}}}{\left({\hat{v}}_c^{{\mathrm{sd}}_{\mathrm{ic}}}\right)}^2-k{\left(\stackrel{\&OverBar;}{{\hat{v}}^{\mathrm{sd}}}\right)}^2},b_l\&Element;[-\&infin;,+\&infin;]$ Formula (11)

Formula (12) has been described V _iNeighbours' vehicle tabulation S before upgrading ^(c)The amount of information that the mobile status of middle all elements (average speed and distance) produces.

$I\left(S^{\left(p\right)}\right)=\left\{\begin{array}{cc}{-P}^{\left(p\right)}{\log }_2{P}^{\left(p\right)}& 0<P^{\left(p\right)}<1\\ 0& P^{\left(p\right)}=0\\ 1& P^{\left(p\right)}=1\end{array}\right.$ Formula (12)

$P^{\left(p\right)}=r^{D\left(S^{\left(p\right)}\right)}\&times;(1-d_{V_i\&RightArrow;l}^{D\left(S^{\left(p\right)}\right)}),P^{\left(p\right)}\&Element;\left[\mathrm{0,1}\right]$ Formula (13)

P ^(p)Computational methods and P ^(c)Identical.G (V _i) value larger, change just less, i.e. V _iNeighbours' vehicle just relatively stable.

The cycle T especially, here is according to the intensity of variation G (V of neighbours' vehicle _i) adjustment cycle, if G is (V _i) value lower, it is less then to adjust T; Otherwise, if G is (V _i) value higher, it is larger then to adjust T.The setting of cycle T is also set according to the intensity of variation of the high neighbours' vehicle of described relative stability.Specific as follows:

Update strategy main thought based on timer is to make each portable terminal upgrading its 1-hop neighbours in the unit interval every T, can be divided into two kinds according to the update cycle kind: the update cycle of Static and dynamic.For the update cycle of static state, portable terminal sends detection information to its 1-hop neighbours after each update cycle.The setting of update cycle has determined to safeguard 1-hop neighbours' cost and effect.For example, the update cycle is longer, can reduce the quantity of probe message, but can't obtain 1-hop neighbours' real-time status.On the contrary, the update cycle is shorter, can in time obtain 1-hop neighbours' real-time status, but it needs often to send detect-message, thereby increases the quantity of probe message.Present embodiment proposes the self-regulation update mechanism (SPUM) of a update cycle.V _iMake update cycle of dynamics change assess the state variation degree of the neighbours' vehicle among the INR.Thereby SPUM can adjust the update cycle according to the state variation degree self adaptation of neighbours' vehicle.SPUM not only can bring and upgrade cheaply (probe message quantity is few), but also guarantees in time to find stable neighbours' vehicle.If have a large amount of neighbours' vehicles to leave or enter V before and after upgrading _iINR, V _iThereby just reduce the state information that the update cycle in time obtains neighbours' vehicle and find stable neighbours' vehicle, the state information of the neighbours' candidate that especially cooperates.Otherwise, V _iWill increase the probe message quantity that the update cycle reduces to be sent to neighbours' vehicle.

If ut _iBe the update cycle, and its initial value is set to greater than 0s.Its update mechanism is determined by following formula (14):

Ut _i=ut ' _i(1+R _i* sin (G (V _i))) formula (14)

Ut wherein _iAnd ut _i' be respectively V _iRenewal before and after update cycle, G (V _i) be the intensity of variation of current renewal, by formula (1) gained.R _iTo affect G (V _i) weighted value, as shown in Equation (15).

$R_i=\frac{\left|S\right|}{\left|{\mathrm{newneiL}}_i\right|},R_i\&Element;\left[\mathrm{0,1}\right]$ Formula (15)

Wherein | S| and | newneiL _i| be respectively S set and newneiL _iElement number.R _iBe | S| and | newneiL _i| the quantity ratio, its value is larger, regulates ut ' _iAbility just stronger.

Further, the stability assessment for neighbours' vehicle also needs to have concrete model to set up.FOR ALL WE KNOW, neighbours' vehicle time of staying in INR is longer, and phase stability is just higher.Consider the impact that node mobility brings, we use the weighting time of staying (weighted factor) to assess its stability.The intensity of variation of weighted factor (weight factor) is by shown in the formula (16).

${\mathrm{vr}}_{\mathrm{ij}}=\sqrt{{({\hat{v}}_j^{\left|{\mathrm{sp}}_{\mathrm{ij}}\right|}-{\left({\hat{v}}_j^{\left|{\mathrm{sp}}_{\mathrm{ij}}\right|}\right)}^{\&prime;})}^2+{({\hat{v}}_j^{{\mathrm{sd}}_{\mathrm{ij}}}-{\left({\hat{v}}_j^{{\mathrm{sd}}_{\mathrm{ij}}}\right)}^{\&prime;})}^2}$ Formula (16)

Wherein

With

To upgrade the INR front and back with respect to V _iThe normalized value of relative velocity.

With

To upgrade the INR front and back with respect to V _iThe normalized value of displacement.Vr _IjValue lower, v then _jMobile status change more stable.

V _iNeighbours' vehicle v _jStability can calculate gained by formula (17).

${\mathrm{st}}_{\mathrm{ij}}=\left\{\begin{array}{cc}{\mathrm{st}}_{\mathrm{ij}}^{\&prime;}+{\mathrm{ut}}_i\&times;\cos \left({\mathrm{vr}}_{\mathrm{ij}}\right)& {\mathrm{PD}}_{\mathrm{INR}}>0\\ 0& {\mathrm{PD}}_{\mathrm{INR}}=0\end{array}\right.$ Formula (17)

St wherein _iAnd st _i' be respectively V _iThe renewal of neighbours' vehicle before and after the stability assessment value.PDINR is neighbours' vehicle experiences the update cycle in INR quantity.If v _jBe the neighbours' vehicle that newly adds INR, its value is 0 so.Otherwise, v is described _jStable neighbours' vehicle, i.e. v _jRest on and surpass a update cycle in the INR.Therefore, the neiL that will tabulate _iIn element be expanded into 3 tuples by 2 tuples and store its stability assessment value, form is as follows: v _c＜=((X _c, Y _c), sp _c, st _c), st wherein _cIt is the stability assessment value.

Step 20, vehicle is to the high neighbours' vehicle request of the relative stability video content of looking ahead.

At first need to calculate according to the stability in the above-mentioned steps, obtain the value of the stability of each neighbours' vehicle, then choose the higher neighbours' vehicle of stability in order to the request video content of looking ahead.As a rule, be to choose the highest neighbours' vehicle of stability to come request content.

As previously mentioned, V _iNeed to select the most stable neighbours' vehicle as the cooperation neighbours.Although stability is a very important factor, because the requirement of the length of the video block of looking ahead, cooperation neighbours' local memory space and bandwidth all need to consider, thereby satisfy V _iDemand.V _iSend probe message to its neighbours' vehicle, neighbours' vehicle adds its memory space and bandwidth information to and is back to V _iMessage in.V _iFrom return messages, extract memory space and the bandwidth information of neighbours' vehicle.Work as V _iNeed its neighbours' vehicle to cooperate when looking ahead V _iJust select the highest neighbours' vehicle of stability assessment value and can have enough memory spaces and remaining bandwidth removes the cooperation V that looks ahead as its cooperation neighbours _iRequired video data.The prefetch request message format is defined as follows: req=(vID, spt, len, source), and wherein vID represents that the video ID that asks, spt and len are respectively look ahead starting point and the length of video segment of request, source is the resource provisioning person of video content.When the cooperation neighbours obtained video block, the cooperation neighbours just notified V _i, and prepare to be transferred in due course V _i

Step 30, the neighbours' vehicle described video content of looking ahead, and send to this vehicle.

In fact, present embodiment is to be based upon under the prerequisite that each vehicle forms In-vehicle networking jointly, when a vehicle need to obtain video content, need to finish with other neighbours' vehicle cooperative of periphery.Namely need to choose the cooperation neighbours of oneself, and connect with the neighbours that cooperate, finish the preparation of prefetching content.And the request that is chosen as cooperation neighbours' vehicle and receives other vehicle when car is when looking ahead video content information, need to respond to this request, namely need according to this request, in conjunction with bandwidth and other situation of self, the video content information of looking ahead, and send to this request vehicle.So far, the In-vehicle networking Streaming Media process of looking ahead finishes.

In the embodiment of the invention, the vehicle of request video resource is take the parameter as assessment neighbours intact stability in its 802.11p signal cover time of staying, thereby the stability assessment model of neighborhood between the vehicle of the video resource of filing a request and its neighbours' vehicle, what make that selected cooperation neighbours can be stable provides the cooperation service of looking ahead for the request vehicle.Distance between selection Vehicle Driving Cycle average speed and vehicle changes evaluate parameter as neighbours' intact stability of assessment request vehicle, thereby obtains the variable quantity of all neighbours' car speeds and distance in each update cycle, and then regulates the update cycle.The dynamic update cycle can reduce the traffic volume of updating message effectively, and can find timely neighbours' vehicle of asking vehicle periphery stable.

Embodiment two

As shown in Figure 3, the embodiment of the invention provides a kind of In-vehicle networking Streaming Media prefetching device, and this device comprises probe unit 100, stable computing unit 200, request unit 300 and the transmitting element 400 of looking ahead, and is specific as follows:

Probe unit 100 is for the neighbours' vehicle in the wireless signal coverage of detection vehicle.

Stability computing unit 200 is for the relative stability that calculates neighbours' vehicle and this vehicle.

Request unit 300 is for the video content of looking ahead to the high neighbours' vehicle request of relative stability.

The transmitting element 400 of looking ahead is used for looking ahead video content, and sends to this vehicle.

Especially, the transmitting element 400 of looking ahead here is actually at this device during as neighbours' vehicle, and requested look ahead during video content carried out work according to request.In-vehicle networking Streaming Media prefetching device in the present embodiment is installed on the concrete vehicle usually, and vehicle all is equipped with gps receiver and radio network interface.By utilizing gps receiver to realize " location aware ", each car V _iCan obtain the geographical position of each neighbours' vehicle among the INR.Onboard wireless network interface support unit V _iAnd the transmission of several data and information is mutual between its neighbours' vehicle, realizes V2V communication, not only can realize the transmission of streaming media video data, can also make V _iObtain the state information that comprises average speed of neighbours' vehicle.

Further, as shown in Figure 4, stable computing unit 200 further comprises neighbours' vehicle tabulation subelement 201, intensity of variation computation subunit 202, cycle setting subelement 203 and assessment subelement 204, and is specific as follows:

Neighbours' vehicle tabulation subelement 201 is used for storing the information of neighbours' vehicle and dynamically updating.

Intensity of variation computation subunit 202 is for the intensity of variation that calculates neighbours' vehicle tabulation neighbours vehicle.

Cycle is set subelement 203, is used for calculating and adjusting the cycle that dynamically updates of neighbours' vehicle tabulation subelement 201 neighbours' vehicles tabulation.

Assessment subelement 204 is for assessment of the stability of neighbours' vehicle.

Further, as shown in Figure 5, request unit 300 further comprises surveys subelement 301, storing sub-units 302 and request subelement 303, specific as follows:

Survey subelement 301, be used for sending probe message to neighbours' vehicle.

Storing sub-units 302 is used for neighbours' vehicle storage space and bandwidth information storage.

Request subelement 303 is used for according to neighbours' vehicle storage space and bandwidth information, and the stability of neighbours' vehicle is to neighbours' vehicle request video content of looking ahead.

In sum, each embodiment of the present invention is by obtaining the stability of the neighbours' vehicle in the automobile wireless signal cover, and the neighbours vehicle high to stability sends request, requires look ahead video content and return to vehicle and play of neighbours' vehicle.According to the variation of travel average speed and the distance of each vehicle stable weight as each neighbours' vehicle, thereby the stability of regulating accurately the respective neighbours vehicle realizes assessing more accurately the stability of vehicle.The embodiment of the invention does not need to obtain the running route of vehicle, cooperate between the vehicle based on V2V, come common foradownloaded video content by bandwidth and the memory space that utilizes other vehicles to other vehicles, downloading process that not only can the large file of accelerating video, and can improve the efficient of sharing streaming media resource between vehicle, have very high feasibility.

Need to prove: when the In-vehicle networking Streaming Media prefetching device that above-described embodiment provides is looked ahead business at triggering In-vehicle networking Streaming Media, only the division with above-mentioned each functional module is illustrated, in the practical application, can as required the above-mentioned functions distribution be finished by different functional modules, the internal structure of the equipment of being about to is divided into different functional modules, to finish all or part of function described above.In addition, the In-vehicle networking Streaming Media prefetching device that above-described embodiment provides and In-vehicle networking Streaming Media forecasting method embodiment belong to same design, and its specific implementation process sees embodiment of the method for details, repeats no more here.

The invention described above embodiment sequence number does not represent the quality of embodiment just to description.

The all or part of step that one of ordinary skill in the art will appreciate that realization above-described embodiment can be finished by hardware, also can come the relevant hardware of instruction to finish by program, described program can be stored in a kind of computer-readable recording medium, the above-mentioned storage medium of mentioning can be read-only memory, disk or CD etc.

The above only is preferred embodiment of the present invention, and is in order to limit the present invention, within the spirit and principles in the present invention not all, any modification of doing, is equal to replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (10)

1. In-vehicle networking Streaming Media forecasting method is characterized in that described method comprises:

Neighbours' vehicle in its wireless signal coverage of vehicle detection calculates the relative stability of described neighbours' vehicle and described vehicle;

Described vehicle is to the high neighbours' vehicle request of the relative stability video content of looking ahead;

Described neighbours' vehicle described video content of looking ahead, and send to described vehicle.

2. the method for claim 1 is characterized in that, the relative stability of the described neighbours' vehicle of described calculating and described vehicle comprises:

Set up neighbours' vehicle tabulation neiL of described vehicle _i=(v ₁, v ₂..., v _n), and setting cycle T carries out the renewal of neighbor list;

For still being positioned at described neighbours' vehicle tabulation neiL after the process renewal _i=(v ₁, v ₂..., v _n) in neighbours' vehicle carry out relative stability assessment;

According to described neighbours' vehicle at described neighbours' vehicle tabulation neiL _i=(v ₁, v ₂..., v _n) in time of existing determine the relative stability of described neighbours' vehicle.

3. method as claimed in claim 2 is characterized in that, described method also comprises:

Set up described vehicle V _iStable neighbor vehicle S set, described

S=(newneiL _i∩ neiL _i)=(v _a, v _b..., v _k); Wherein, described newneiL _i=(v ₁, v ₂..., v _m) be the neighbours' vehicle tabulation after upgrading;

Neighbours' vehicle intensity of variation G (V _i)=E (S ^(c))-I (S ^(p)) G (V _i) ∈ [1,1] E (S wherein ^(c)) and I (S ^(p)) be the amount of information of upgrading neighbours' vehicle intensity of variation among the S of front and back;

Described G (V _i) larger, described vehicle V then _iThe stability of neighbours' vehicle is higher.

4. method as claimed in claim 3 is characterized in that, described cycle T is set according to following mode:

Intensity of variation G (V according to described neighbours' vehicle _i) adjustment cycle T, if G is (V _i) value lower, it is less then to adjust described T; Otherwise, if GV _i) value higher, it is larger then to adjust described T.

5. method as claimed in claim 4 is characterized in that, the setting of described cycle T is also set according to the intensity of variation of the high neighbours' vehicle of described relative stability.

6. method as claimed in claim 2 is characterized in that, described method also comprises:

Assess the stability of described neighbours' vehicle with weighted factor; Described weighted factor

Wherein, With

With respect to described vehicle V before and after described neighbours' vehicle list update _iThe normalized value of relative velocity;

With

With respect to described vehicle V before and after described neighbours' vehicle list update _iThe normalized value of displacement;

Described vr _IjValue lower, described neighbours' vehicle v then _jStability larger.

7. the method for claim 1 is characterized in that, described vehicle comprises to the high neighbours' vehicle request of the relative stability video content of looking ahead:

Described vehicle V _iSend probe message to described neighbours' vehicle;

Described neighbours' vehicle adds its memory space and bandwidth information to and is back to V _iMessage in;

Described V _iFrom return messages, extract memory space and the bandwidth information of neighbours' vehicle;

As described V _iNeed its neighbours' vehicle to cooperate when looking ahead, select relative stability high and can have neighbours' vehicle of enough memory spaces and remaining bandwidth, as cooperation neighbours vehicle, ask needed video content.

8. an In-vehicle networking Streaming Media prefetching device is characterized in that, described device comprises probe unit, stable computing unit, request unit and the transmitting element of looking ahead, wherein,

Described probe unit is for the neighbours' vehicle in the wireless signal coverage of surveying described vehicle;

Described stable computing unit is for the relative stability that calculates described neighbours' vehicle and described vehicle;

The described request unit is for the video content of looking ahead to the high neighbours' vehicle request of relative stability;

The described transmitting element of looking ahead is used for looking ahead described video content, and sends to described vehicle.

9. device as claimed in claim 8 is characterized in that, described stable computing unit further comprises neighbours' vehicle tabulation subelement, intensity of variation computation subunit, cycle setting subelement and assessment subelement, wherein,

Described neighbours' vehicle tabulation subelement is used for storing the information of neighbours' vehicle and dynamically updating;

Described intensity of variation computation subunit is for the intensity of variation that calculates neighbours' vehicle tabulation neighbours vehicle;

The described cycle is set subelement, is used for calculating and adjusting the cycle that dynamically updates of described neighbours' vehicle tabulation subelement neighbours vehicle tabulation;

Described assessment subelement is for assessment of the stability of neighbours' vehicle.

10. device as claimed in claim 8 is characterized in that, the described request unit further comprises surveys subelement, storing sub-units and request subelement, wherein,

Described detection subelement is used for sending probe message to described neighbours' vehicle;

Described storing sub-units is used for described neighbours' vehicle storage space and bandwidth information storage;

The described request subelement is used for according to described neighbours' vehicle storage space and bandwidth information, and the stability of neighbours' vehicle is to described neighbours' vehicle request video content of looking ahead.

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