CN101771964A - Information correlation based opportunistic network data distributing method - Google Patents
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- CN101771964A CN101771964A CN201010033641A CN201010033641A CN101771964A CN 101771964 A CN101771964 A CN 101771964A CN 201010033641 A CN201010033641 A CN 201010033641A CN 201010033641 A CN201010033641 A CN 201010033641A CN 101771964 A CN101771964 A CN 101771964A
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Abstract
The invention provides an information correlation based opportunistic network data distributing method. The method comprises the following steps: dividing regions of an electronic map carried on a vehicle through specifically defined information format, abstract bus routes and station information, and simultaneously carrying out binary coding on the regions based on the division; ensuring that each route station acquires a unique code; summarizing interest information to form a vehicle interest list; calculating the correlation of social information through the interest list to drive information distribution; and transmitting the information to the region which is interested in the information. The method acquires priori knowledge through an active studying mode by using the characteristics of fixed bus routes and stable people interests in the region, drives data oriented distribution by using accumulated knowledge, improves the hit rate of information querying, and simultaneously reduces network load and message distribution delay.
Description
Technical field
The present invention relates to a kind of wireless communication data distribution method, be specifically related to a kind of opportunistic network data distributing method, belong to wireless communication technology field based on information correlation.
Background technology
Opportunistic network (Opportunistic Networks, be called for short OppNet) be meant between the class communication source and target and do not have a complete path, move the wireless self-organization network (list of references [1]: opportunistic network that the junctor meeting that brings realizes communication by equipment, author Xiong Yongping etc., Journal of Software, Vol.20, No.1, January 2009, pp.124-137).In this class self-organizing network, the sparse or fast moving because mobile device distributes adds factors such as wireless channel decline interference, can't form a connected network.
The opportunistic network of forming by the moving vehicle that carries short-distance communication equipment based on the ad-hoc network of vehicle (vehicular ad-hoc networks is called for short VANETs).Can be between vehicle by the formation communication opportunity that meets, and utilize this chance to transmit current traffic information, the advertising message in a distant place and the interest information of subscription etc.Yet in the vehicle ' scene, because the circuit of vehicle ' and the randomness of scope cause message to transmit the uncertainty of effect, this efficient and time delay that can make message transmit is uncertain.But the public transit vehicle circuit is fixed, and vehicle ' fixed interval and juxtaposition circuit are many, we can utilize this specific character of bus, sum up history message, store and transmit message targetedly, with the forward efficiency that improves message and reduce message delay.
At present, the ad-hoc network data distributing method based on vehicle mainly is divided into following three kinds:
1) based on sender's data distributing method
In data distributing method based on the sender, the transmission target area and the term of validity of sender's specify message.Yet the method that this storage is transmitted also is not suitable for transmits dynamic message, traffic accident report for example, the vehicle event report etc. that blocks up.Because in the message diffusion process, can not remove out-of-date and useless information in time in this way, simultaneously, if use the method for this static broadcasting, when network node density is big, can produce bigger offered load, cause communication channel to block up, more typical algorithm is infectious disease broadcast algorithm (an Epidemic algorithm), the circulation way of information is the same just like the virus diffusion in this algorithm, a node can infected (promptly receiving and preservation information) need two prerequisites: the one, and it does not produce same information, and another is that it did not receive such information before this.The node that receives information is saved in information in the local buffer memory, and is the easiest to be infected when node was not received information, and this easy infected node touches behind the node (node that promptly has information) that has infected promptly infected.After a node was given other node with forwards, this node self just no longer had this information, and it also has immunization to this information simultaneously, promptly can not receive this information again and then also can not provide forwarding for this information.
2) based on the retransmission method of competing
Based on the position of the retransmission method of competing, select the forward node of next jumping in the mode of competition by node around the perception present node.A kind of method is a present node in transmitting data procedures, around selecting node mid-range objectives position recently or node farthest as the node of transmitting, suppress other node simultaneously.Another kind method is the judgement of assisting route by the use numerical map, and this judgement depends on stronger this fact of connectedness in the zone, intersection, therefore selects the node of crossing intersection part as next-hop node.Though considered the routing direction of internodal distance and next jumping based on the method for competition, but there are not the interior destination address of process information and the life span of information, make distribution of information to destination address be not very accurate, simultaneously also more outdated information may appear in the network.
3) content-based message forwarding method
In the content-based message forwarding method, the node that receives message utilizes its own knowledge to determine whether transmitting at once message, temporary back is transmitted still to abandon and do not transmitted.The forwards process no longer is that source node drives, but is transmitted according to content by middle forward node, yet these nodes will be made the message that the behavior judgement need gather the overall situation, and this implements very difficult concerning the vehicle network that the zone isolates relatively.
Summary of the invention
A kind of opportunistic network data distributing method that the present invention proposes based on information correlation, be with public transit vehicle as the information transmitting carrier, carry out the method for selective information distribution based on the information content.Designed a kind of geocoding mode among the present invention, can carry out matching addresses fast and obtain accurate matching result, simultaneously, the present invention utilizes matching addresses result and knowledge to sum up the degree of correlation of having calculated social information, and the degree of correlation of social information characterizes the interest level of public transit vehicle to certain social information.The relatedness computation of social information is the key that public transit vehicle carries out distribution of information, in the opportunistic network that public transit vehicle constitutes, for same social information, its relevance degree that calculates and the residing circuit of public transit vehicle, position, time are relevant with type of message.The present invention utilizes the value of utility of relatedness computation social information, can describe the matching degree of incident and vehicle carrier more accurately, provides foundation for vehicle carries and transmit social information.
A kind of opportunistic network data distributing method based on information correlation comprises the steps:
Step 1: initialization partition address coding, the vehicle electronics map is carried out area dividing, simultaneously to regional code and initialization station code, after the partition address coding was finished, all there was a unique address code each bus station, and execution in step two then;
This step is used the partition address coding, and (D presentation address sign indicating number is represented by 16 bits for Subarea Address Coding, SAC) method, D (i) (i=0,1 ... 15) the i bit address sign indicating number that begins from a high position of expression, D (0)～D (4) is an area code, the expression scope is 0～(2
5-1), D (5)～D (15) is district's ISN, and the expression scope is 0～(2
11-1); The partition address cataloged procedure adopts the method for layering, and the zone that D (i+1) divides D (i) (0≤i＜14) is carried out north and south or thing once more and divided.Stipulate that first north and south divides the order that thing is divided again, if website is positioned at the north or the east in zone, this position is encoded to 1, if website is positioned at south or western part, this position is encoded to 0.
Step 2: judge at first whether vehicle continues operation, if out of service, the expression system finishing, otherwise vehicle continues to exercise and acquisition of information; Vehicle constantly detects self-position in the process of moving, and with vehicle electronics map comparison judging vehicle present located position, if when vehicle and other vehicles meet, change the step 5 execution; If vehicle does not meet with other vehicle and during the no show website, change step 3 and carry out; When arriving website if vehicle does not meet with other vehicle, the social information of destination address and this website coupling in the enquiring vehicle database, if have, degree of correlation order from high to low according to social information is broadcasted away the social information of mating, continue to collect social information and Query Information simultaneously, change step 3,, then directly change step 3 and carry out if do not have;
Step 3: judge whether vehicle receives social information, if not changeing step 2 carries out, if receive social information, then the social information that receives is stored in the vehicle its data storehouse, if the database of vehicle has been stored full, adopt least-recently-used method to replace least active social information, execution in step four then;
Step 4: vehicle in the process of moving, if receive Query Information, upgrade interest list, the Query Information that is about to receive adds that the position when vehicle receives Query Information forms the interest tuple and add in the interest list, vehicle is inquired about the Query Information of receiving in the vehicle data storehouse simultaneously, if the social information that hits is arranged, the social information that hits is outwards transmitted according to the degree of correlation order from high to low of social information, changeing step 2 carries out, if the social information that does not hit directly changes step 2 and carries out; If do not receive Query Information, change step 2 and carry out;
Step 5: vehicle meets or when arriving website and meeting in the process of moving, exchange interest list each other, carry out the relatedness computation of social information, and obtain the social information that oneself needs from the other side, vehicle can judge when receiving social information whether self database stores full, if the data that adopt in the least recently used method replacement data storehouse have been expired in storage, change step 4 then and carry out.
Public transit vehicle BusA, BusB exchange public transit vehicle interest list E
a, E
bBusA is according to E
bCalculate that all social informations recomputate the relevance degree for oneself again for the relevance degree of BusB in the own vehicle data storehouse.Then, BusA distributes a part of social information to BusB, and this part social information is for the degree of correlation numerical value of the BusB mean value greater than social information's relevance degree in the vehicle data of the BusB storehouse own.BusB according to relevancy ranking, replaces the less social information of relevance degree in the vehicle database with this two parts social information.Otherwise BusB also carries out same work.
The advantage and the good effect of the present invention proposes a kind of opportunistic network data distributing method based on information correlation are:
(1) fix owing to the public transit vehicle circuit, the vehicle ' fixed interval, Vehicular occupant interest is relatively stable, and this method has made full use of above-mentioned characteristic and has carried out the data distribution, makes that the flow direction of social information is more pointed.
(2) this method has adopted the address partitioned method, adopts binary coded system to encode, and this makes coding rate fast, and transport overhead is little, and matching addresses is accurate.
(3) this method has made full use of the correlation of information in message stores and repeating process, comprises the correlation of rise time, place and the classification of message, makes vehicle selectively to receive and forwarding information, to improve the diffusion velocity of information.
(4) in the information exchanging process of this method between vehicle, by the exchange interest list, calculate self social information degree of correlation then for the other side's vehicle characteristics information, vehicle becomes in the process of exchange social information each other and has purpose like this, both improve the hit rate of information inquiry, reduced offered load again.
Description of drawings
Fig. 1 is an opportunistic network data distributing method flow chart of steps of the present invention;
Fig. 2 is embodiment of the invention partition address coding schematic diagram;
Fig. 3 concerns comparison diagram for vehicle hour and hit rate in the present invention and the Epidemic algorithm;
Fig. 4 concerns comparison diagram for vehicle hour and message time delay in the present invention and the Epidemic algorithm;
Fig. 5 concerns comparison diagram for vehicle hour and bandwidth consumed in the present invention and the Epidemic algorithm;
Fig. 6 is the graph of a relation of vehicle hour among the present invention and information exchange frequency.
Embodiment
The present invention is described in further detail below in conjunction with drawings and Examples.
At first carry out defined declaration:
Define 1 query messages: use Q to represent, it is the message that the user sends when carrying out information inquiry, and its form is: and Q (destination, time, type).Wherein destination is the address code on search purposes ground, and time is the time that query messages produces, and type is the event category of query messages.
Define 2 social informations: use I to represent that it is produced by information source, its form is: and I (source, destination, time, type, limite).Wherein source is that social information generation address is the address of information source, and destination is the destination address that social information will mail to, and time is social information's rise time, and type is an event category, and limite is the term of validity of social information.
Define 3 interest tuples: use H to represent, the corresponding query messages that receives of each interest tuple.Each bar query messages destination, time that public transit vehicle will receive, three components of type add that an interest tuple is formed in the position when vehicle receives Query Information, and its form is: and H (source, destination, time, type).Wherein source is the address of receiving query messages, and all the other parameters are the content in the corresponding query messages.
Define 4 interest list (Hobby List is called for short HL): use E to represent that each bus all has an interest list that is made of a plurality of interest tuples, the quantity statistics information of different society information category in preceding 4 bytes store interest list of interest list.Public transit vehicle is collected query messages in motion, is summarized as the interest tuple and is stored in the interest list.
Define 5 public transit vehicle characteristic informations: use B to represent that it has described the line information and the interest list of public transit vehicle, its form is: B (L (N, stop
1, stop
2..., stop
N), E).Wherein L is a route information, and N is the sum of the website of circuit public transit vehicle process for this reason, website stop
1, stop
2..., stop
NBe the site address of public bus network process successively, E is an interest list.
A kind of opportunistic network data distributing method based on information correlation as shown in Figure 1, specifically comprises the steps:
Step 1: initialization partition address coding, carry out area dividing to the vehicle electronics map, simultaneously to regional code and initialization station code; This step is used partition address coding (Subarea Address Coding is called for short SAC) method, and D presentation address sign indicating number is represented by 16 bits, D (i) (i=0,1 ... 15) the i bit address sign indicating number that begins from a high position of expression, D (0)～D (4) is an area code, the expression scope is 0～(2
5-1), D (5)～D (15) is district's ISN, and the expression scope is 0～(2
11-1); The partition address cataloged procedure adopts the method for layering, the zone that D (i+1) divides D (i) (0≤i≤14) is carried out north and south or thing once more and is divided, regulation adopts first north and south to divide the order that thing is divided again, if website is positioned at the north or the east in zone, this position is encoded to 1; If be positioned at south or western part, this position is encoded to 0.
As shown in Figure 2, the black round dot is a website to be encoded, and dark border is the geographic area scope.Divide and carry out from bottom to top: be two districts, north and south with this area dividing for the first time, the black round dot is positioned at the south; For the second time first level is divided into four districts, the black round dot is positioned at the east; In like manner, carry out the division of north and south and thing once more with the 4th time for the third time, at this moment whole zone has been divided into 16 zonules, and at this moment, the black round dot is encoded as 0100 among Fig. 2, continues to divide, and will obtain final address code.
The advantage of this partition address coding method is:
1) efficient height: during from high-order start address sign indicating number coupling, in case the unmatched situation of a certain position coding occurs, matching process stops immediately.According to the number of the coding of finishing coupling, can draw matching result.
2) result is accurate: the matching result of two address codes is divided into following three kinds of situations: a) do not match: from a high position begin before j position (j 〉=0 and j≤9) identical, the remainder difference illustrates that these two addresses are positioned at different regions, or be in areal but the distance far away.B) fully the coupling: from a high position begin all the position all identical, illustrate that these two addresses are identical.C) part is mated: j position (j＞9 and j＜16) is identical before beginning from a high position, and promptly area code is identical, and district's ISN same section is no less than 5, and the remainder difference illustrates that these two addresses are in the same area close together.
3) make things convenient for correlation to judge: matching result can calculate their address degree of correlation numerical value for the address code of part coupling, and two address code match bit array are many more, illustrates that two website distances are near more.
Step 2: judge at first whether vehicle continues operation, if out of service, expression data distribution procedure finishes; If vehicle continues to exercise, then acquisition of information; Vehicle constantly detects self-position in the process of moving, and with vehicle electronics map comparison obtaining vehicle present located position, if when this vehicle and other vehicles meet, change the step 5 execution; If this vehicle does not meet with other vehicle and during the no show website, change step 3 and carry out; When arriving website if vehicle does not meet with other vehicle, the social information of destination address and this website coupling in the enquiring vehicle database, if have, relevance degree order from high to low according to social information is broadcasted away the social information of mating, continue to collect social information and Query Information simultaneously, change step 3,, then directly change step 3 and carry out if do not have;
Positioning equipment and short-distance wireless communication equipment are housed on the vehicle.It is the cycle to obtain current position information with 10s that vehicle can utilize positioning equipment in the process of moving, and this information is latitude and longitude information, by latitude and longitude information and vehicle electronics cartographic information are compared, obtains the residing region code of vehicle then.The Query Information of vehicle and the listening port of social information remain open mode simultaneously, can receive near the Query Information of road and the social information of issue so constantly.When storage social information, with information source address and information destination address is that keyword carries out the duplicate key storage, when receiving inquiry, carry out the social information that binary search can obtain the relevant position like this, in the system that has the larger data amount, the bigger efficient that promoted.
When in vehicle is being exercised on the way, meeting, change in the step 5 and handle.When vehicle ' arrives website, in the meeting inquiry current database is the social information of destination with this place, broadcast away successively then, so just make that the data distribution just is not what drive with the inquiry, also outside on one's own initiative simultaneously pushed information, the data time delay that is diffused into designated area and community of interest significantly reduces like this, changes step 4 then and carries out.As, when public transit vehicle BusA arrived website P, BusA broadcasted away the social information of destination address in social information's database and current place website P coupling.
Step 3: judge whether vehicle receives social information, if not changeing step 2 carries out, if receive social information, then the social information that receives is deposited in the vehicle its data storehouse, if the database of vehicle is filled with, use least-recently-used method to replace least active social information, execution in step four then.
After social information replace to preserve, if the situation of social information's address sort mistake, then need the social information in the database is resequenced.
Step 4: vehicle is in the process of moving if receive Query Information, upgrade interest list, the Query Information that is about to receive adds that the position when vehicle receives Query Information forms the interest tuple and add in the interest list, this process shows that vehicle is interested in this information, needs other vehicles that such social information is provided when promptly vehicle meets.Vehicle is inquired about the Query Information of receiving in the vehicle data storehouse simultaneously, if the social information that hits is arranged, with the social information that hits is Query Result, outwards transmit according to relevance degree order from high to low, changeing step 2 carries out, if the social information that does not hit directly changes step 2 and carries out.If vehicle is not received Query Information in the process of moving, change step 2 and carry out.
When public transit vehicle BusA arrives website P, users broadcasting query messages Q, public transit vehicle BusA receives query messages, and it is stored in the interest list, simultaneously in its social information's database, search corresponding social information, and the social information that successfully finds is transmitted to inquiring user.
Step 5: when vehicle meets, exchange the characteristic information in the interest list each other, so that allow the other side's vehicle understand the interest of self, thereby obtain own useful social information from the other side, vehicle can judge when receiving social information whether self database stores full, if the data that adopt in the least recently used method replacement data storehouse have been expired in storage, change step 4 then and carry out.
Public transit vehicle BusA, BusB exchange public transit vehicle interest list E
a, E
bBusA is according to E
bCalculate that all social informations recomputate the relevance degree for oneself again for the relevance degree of BusB in the own vehicle data storehouse.Then, BusA distributes a part of social information to BusB, and this part social information is for the degree of correlation numerical value of the BusB mean value greater than social information's relevance degree in the vehicle data of the BusB storehouse own.BusB according to relevancy ranking, replaces the less social information of relevance degree in the vehicle database with this two parts social information.Otherwise BusB also carries out same work.
Vehicle can judge when receiving social information whether self database stores completely, if the data that adopt in the least recently used method replacement data storehouse have been expired in storage.Changeing step 4 then carries out.
Utilize information correlation to calculate, use R to represent the degree of correlation of social information, the degree of correlation numerical value of a social information is big more, illustrates that this bus is high more to its interested degree.R (I) is the relatedness computation function:
R(I)＝relevance(I.destination)+relevance(I.time)+relevance(I.type)
＝R
d(I.destination)+R
t(I.time)+R
e(I.type)
The relatedness computation function of social information is made up of three parts: address degree of correlation R
d, time correlation degree R
tWith event category degree of correlation R
e, respectively according to the destination address of social information, rise time and event category calculate, and then separately calculated value are added up.
R (I) is the relatedness computation function of social information, and relevance represents the degree of correlation, and I represents social information;
The social information of the degree of correlation to be calculated must be effectively, promptly satisfies condition: source address and destination address coding are correct, generation time belongs to the scope of previous definition early than current time, event category, and invalid social information directly abandons.The preferential receiver address of the public transit vehicle social information that the match is successful considers the long and high social information of event category degree of correlation numerical value of residue life span then.
The address degree of correlation is the variable that plays a decisive role, and it presents the trend of successively decreasing with the destination address of social information and the increase apart from this parameter of current address.In the present invention, the distribution density function λ e of selection index function
-λ xAt different destination addresses, define different lambda parameters:
When I.destination was positioned on the travel route of public transit vehicle, this class social information directly sent to the destination,
R
d(I.destination)=λ e
-λ x, λ=1.5 wherein, and x=distance (I.destination, Bus.location)/distance (Bus.B.stop
1, Bus.B.stop
N).I.destination is the destination address of social information in the formula, and Bus.location is the public transit vehicle current address.Distance (location wherein
1, location
2) be distance function, be used to calculate two address location
1With location
2Between distance, use the i position in location (i) presentation address, the weights from a high position to the low level are that 15～0 usefulness V (i) represent, from a high position to the low level two-address is compared, if highest order is inequality, then layback is 2
15At first putting distance if highest order is identical is 2
15-1, more successively to the low level comparison, if location
1(i)=location
2(i) then at every turn will be apart from deducting 2
V (i), if then layback inequality.
When I.destination was arranged in the public transit vehicle interest list, the number of times that the destination address of interest tuple and I.destination mate fully in the public transit vehicle interest list was k, R
d(I.destination)=λ e
-λ x, λ=0.5+k/Bus.B.E.sum_H wherein, and x=distance (Bus.H.source, Bus.location)/distance (Bus.B.stop
1, Bus.B.stop
N).Bus.B.E.sum_H is the sum of interest tuple in the public transit vehicle interest list, Bus.H.source is the source address of the interest tuple of being mated, if k＞0 directly uses k as parameter, if k=0 then from (0, select an integer as parameter at random in Bus.B.E.sum_H).
During other situation, Rd (I.destination)=λ e
-λ x, λ=0.5 wherein, and x=distance (I.destination, Bus.location).
Time correlation degree function is a decreasing function, and along with the residue life span reduces, time correlation number of degrees value diminishes.R
t(I.time)＝(I.time-current_time)/limit。Wherein I.time is the rise time of social information, and current_time is the current time, and limit is the life span of social information.
The computational methods of the event category degree of correlation, R
e(I.type)=and v/Bus.B.E.sum_H, wherein v is the number of the interest tuple that event category is identical with I.type in the public transit vehicle interest list, Bus.B.E.sum_H is the sum of interest tuple.
In order to assess the performance of said method, the distance of setting wireless telecommunications in the simulation process is 50 meters, use the situation of 200～1000 circuits to test respectively, 30 buses travel on every circuit, the simulating area size is 80km*80km, and Vehicle Speed is 40km/h, every long 20km of circuit, 20 of websites are arranged on every circuit, use the Manhattan mobility model.The increase and decrease of circuit is uniformly in the simulation process, increases and decreases 100 at every turn.Vehicle can stop 2s at each website, and the wait of reaching terminal continued to travel round about in 10 minutes afterwards.Under the initial situation of each emulation, vehicle does not carry any prior information.Near the fixed time broadcast query messages road, vehicle is received query messages and has information matches to be and hit that then to query node feedback Query Result, vehicle Cache size is 1G.Above-mentioned emulation uses OMNeT++ as simulated environment, and parameter is provided with as shown in table 1.
Table 1 experiment parameter specifically is provided with table
| Parameter name | Variable name | Unit | Value |
| Number of, lines | ??Ln | Bar | ?200，300，400，500，600，700，800 |
| Every circuit number of vehicles | ??LBn | {。##.##1}, | ?10，20，30，40，50 |
| Running time | ??T | Hour | ?0～100 |
| Bandwidth | ??BW | ?? |
0～just is infinite |
| Hit rate | ??R | ??％ | ?0～100 |
| Scatter time delay | ??D | ?? |
0～just is infinite |
| The information exchange frequency | ??Re | Inferior/ |
0～just is infinite |
Simulated environment shown in Figure 3, the public transit vehicle quantity that every circuit is set is 30, vehicle receives extraneous social information in the process of moving, and and other public transit vehicle exchanges the other side information of interest.As shown in Figure 3, after travelling 5 hours, vehicle is received the hit rate of query messages near 60%, and vehicle constantly accumulates the high information of the degree of correlation subsequently, and after travelling 20 hours, the hit rate of vehicle query reaches more than 90%.Along with the increase of time, vehicle is constantly learnt, and its interest list is relatively stable, and the query hit rate tends to be steady.Constantly increase the quantity of circuit subsequently, i.e. the density of circuit, at this moment the query hit rate has to a certain degree and must promote.When adopting the infectious disease broadcast algorithm, when not using HL, vehicle is in 20 hours of beginning to travel, and hit rate continues to rise, and this is because Cache also is not filled with, and owing to increasing of information, the hit rate of inquiry is improved.After Cache is filled with, the information that vehicle receives will replace the oldest information, the information that replace this moment may be that vehicle receives a period of time, but the information of the destination of also not being able to do in time to be diffused into according to the address can make the query hit rate descend like this.This shows that the method that the present invention proposes can reach than higher query hit rate after short learning process.
Simulated environment shown in Figure 4 adopts fixes 100 social information sources and 100 purpose zones, judges that stationary information source generation information arrives the average delay in purpose zone, at initial time, scatters time delay and is designated as infinity.When public bus network is 200, vehicle is through after 5 hours travel, and beginning receives and send message selectively.As time goes on, public transit vehicle constantly improves the interest list of self, receives and transmit social information more accurately.Vehicle can be delivered to the purpose zone with social information the enough shorter time like this.When vehicle ' after 20 hours, interest list is relatively stable, and the social information that information source produces also can be delivered to the purpose zone by metastable time delay, as shown in Figure 4.When adopting the infectious disease broadcast algorithm, when not using HL, vehicle receives all social informations, in this case, vehicle will slowly reduce at 20 hours propagation delays that begin to travel, after Cache is filled with, because vehicle is constantly replaced the message among the Cache, make that scattering time delay increases.Find out that thus the method that the present invention proposes can be controlled at the distribution time delay of social information in the stable time range.
Simulated environment shown in Figure 5 adopts and fixes 100 social information sources, and the bandwidth of system consumption was 0 when emulation was initial.The simulated conditions of 200 public bus networks is adopted in emulation, and vehicle is through after 5 hours travel, and the bandwidth consumption of entire system is 49Mbps.This is because vehicle by continuous learning process, perceives self needed information more, and exchange interest list each other made bandwidth consumption increase when vehicle met.After the vehicle operating 20 hours, the interest list of self is relatively stable, so the bandwidth occupancy of exchange message also tends to be steady, as shown in Figure 5.Along with the increase of public bus network, occupied bandwidth also increases naturally thereupon, but all is tending towards a definite value.When adopting the infectious disease broadcast algorithm, when not using HL, vehicle receives all social informations, information exchange between the vehicle is very fast takies massive band width, increase along with the time, taking of bandwidth can reach a metastable value, and this is because vehicle always spreads the full detail that self Cache fills when meeting.Find out that thus the method that the present invention proposes can reduce offered load to a certain extent.
Simulated environment shown in Figure 6 adopts 800 public bus networks, and the number of vehicles on every public bus network is 30.As shown in Figure 6, growth along with the time, the exchanges data frequency of each car is in continuous increase, and after 20 hours, vehicle information exchange number of times hourly reaches the top, had a interest list that relative complete sum stable on the vehicle this moment, As time goes on, the interest list relative fixed of vehicle, a lot of query messages solve, when meeting, need not to ask for too much information, but autotelic reception is to self Useful Information to the other side.Therefore as can be seen, the information exchange frequency of vehicle slowly descended after 20 hours and tends towards stability, can't the unconfined growth along with the time.
Claims (5)
1. the opportunistic network data distributing method based on information correlation is characterized in that, may further comprise the steps:
Step 1: the vehicle electronics map is carried out area dividing, with the partition address coding method encoded in the zone simultaneously, and the initialization station code, after the partition address coding was finished, all there was a unique address code each bus station, and execution in step two then;
Step 2: judge at first whether vehicle continues operation, if out of service, expression data distribution procedure finishes, if vehicle continues to exercise, then collects social information and Query Information; Vehicle constantly detects self-position in the process of moving, and with vehicle electronics map comparison obtaining vehicle present located position, if when this vehicle and other vehicles meet, change the step 5 execution; If vehicle does not meet with other vehicle and during the no show website, change step 3 and carry out; When arriving website if vehicle does not meet with other vehicle, the social information of destination address and this website coupling in the enquiring vehicle database, if have, relevance degree order from high to low according to social information is broadcasted away the social information of mating, continue to collect social information and Query Information simultaneously, change step 3,, then directly change step 3 and carry out if do not have;
Step 3: judge whether vehicle receives social information, if not changeing step 2 carries out, if receive social information, then the social information that receives is stored in the vehicle its data storehouse, if the database of vehicle has been stored full, adopt least-recently-used method to replace least active social information, execution in step four then;
Step 4: vehicle in the process of moving, if receive Query Information, upgrade interest list, the Query Information that is about to receive adds that the position when vehicle receives Query Information forms the interest tuple and add in the interest list, vehicle is inquired about the Query Information of receiving in the vehicle data storehouse simultaneously, if the social information that hits is arranged, the social information that hits is outwards transmitted according to the relevance degree order from high to low of social information, changeing step 2 carries out, if the social information that does not hit directly changes step 2 and carries out; If do not receive Query Information, change step 2 and carry out;
Step 5: when vehicle meets, exchange interest list each other, the relevance degree that carries out social information calculates, and obtain the social information that oneself needs from the other side, vehicle can judge when receiving social information whether self database stores full, if the data that adopt in the least recently used method replacement data storehouse have been expired in storage, change step 4 then and carry out.
2. according to the described a kind of opportunistic network data distributing method of claim 1 based on information correlation, it is characterized in that, partition address coding method described in the step 1, adopt first north and south to divide again the order that thing is divided, if website is positioned at the north or the east in zone, this position is encoded to 1, if website is positioned at south or western part, this position is encoded to 0; Address code D represents by 16 bits, the i bit address sign indicating number that D (i) expression begins from a high position, and i=0 wherein, 1 ..., 15; D (0)～D (4) is an area code, and the expression scope is 0～(2
5-1), D (5)～D (15) is district's ISN, and the expression scope is 0～(2
11-1); The partition address coding adopts the method for layering, and the zone that D (i+1) divides D (i) is carried out the division of north and south or thing, wherein 0≤i≤14 once more.
3. according to the described a kind of opportunistic network data distributing method of claim 1 based on information correlation, it is characterized in that, the degree of correlation of step 2, the described social information of step 5, characterize the interest level of public transit vehicle to certain social information, relevance degree is big more, illustrate that this bus is high more to the interested degree of this social information, its computational methods are:
R(I)＝relevance(I.destination)+relevance(I.time)+relevance(I.type)
＝R
d(I.destination)+R
t(I.time)+R
e(I.type)
R (I) is the relatedness computation function of social information, and relevance represents the degree of correlation, and I represents social information;
The I of social information is produced by information source, its form is: I (source, destination, time, type, limite), wherein source is that information generation address is the address of information source, and destination is the destination address that social information will mail to, and time is social information's rise time, type is an event category, and limite is the term of validity of social information;
The relatedness computation function of social information is made up of three parts: address degree of correlation R
d, time correlation degree R
tWith event category degree of correlation R
e, according to the destination address of social information, rise time and event category calculate respectively; It is effectively that the social information of the degree of correlation to be calculated requires, and promptly correct, the generation time of source address and destination address coding belongs to the scope of previous definition early than current time, event category, and invalid social information directly abandons;
Address degree of correlation R
dBe the variable that plays a decisive role, it presents the trend of successively decreasing, R with the destination address of social information and current address apart from this parameter
d(I.destination)=λ e
-λ xAt different destination addresses, define different lambda parameters:
When I.destination was positioned on the travel route of public transit vehicle, this class social information directly sent to the destination, λ=1.5, x=distance (I.destination, Bus.location)/distance (Bus.B.stop
1, Bus.B.stop
N);
When I.destination is arranged in the public transit vehicle interest list, λ=0.5+k/Bus.E.sum_H, x=distance (Bus.H.source, Bus.location)/distance (Bus.B.stop
1, Bus.B.stop
N);
Under other situation, λ=0.5, x=distance (I.destination, Bus.location);
Wherein, I.destination represents the destination address of social information; Bus.location represents the public transit vehicle current address; Bus.B.stop
1First station address of expression public transit vehicle, Bus.B.stop
NThe address, terminus of expression public transit vehicle; Distance (location
1, location
2) be distance function, be used to calculate two address location
1With location
2Between distance; Bus.B.E.sum_H represents the sum of interest tuple in the public transit vehicle interest list; Bus.H.source represents the source address of the interest tuple of being mated; K is the destination address of interest tuple in the public transit vehicle interest list and the number of times that I.destination mates fully, if k＞0, directly uses k as parameter, if k=0 then from (0, select an integer as parameter at random in Bus.B.E.sum_H);
Wherein, E represents interest list, each bus all has an interest list that is made of a plurality of interest tuples, the quantity statistics information of different society information category in preceding 4 bytes store interest list of interest list, public transit vehicle is collected query messages in motion, is summarized as the interest tuple and is stored in the interest list;
B represents the public transit vehicle characteristic information, has described the line information and the interest list of public transit vehicle, and form is: B (L (N, stop
1, stop
2..., stop
N), E), wherein L is a route information, N is the sum of the website of circuit public transit vehicle process for this reason, website stop
1, stop
2..., stop
NSite address for public bus network process successively;
Time correlation degree function is a decreasing function, and along with the residue life span reduces, time correlation number of degrees value diminishes R
t(I.time)=(I.time-current_time)/limit; Wherein I.time is the rise time of social information, and current_time is the current time, and limit is the term of validity of social information;
Event category degree of correlation R
e(I.type)=and v/Bus.B.E.sum_H, wherein v is the number of the interest tuple that event category is identical with R.type in the public transit vehicle interest list, Bus.B.E.sum_H is the sum of interest tuple.
4. according to the described a kind of opportunistic network data distributing method of claim 3, it is characterized in that described distance function distance (location based on information correlation
1, location
2), be used to calculate two address location
1With location
2Between distance, be specially: use the i position in location (i) presentation address, the weights from a high position to the low level are that 15～0 usefulness V (i) represent, from a high position to the low level two-address is compared, if highest order is inequality, then layback is 2
15At first putting distance if highest order is identical is 2
15-1, more successively to the low level comparison, if location
1(i)=location
2(i) then at every turn will be apart from deducting 2
V (i), if the numerical value that then returns current distance inequality.
5. according to the described a kind of opportunistic network data distributing method of claim 1 based on information correlation, it is characterized in that, when the described vehicle of step 5 meets, exchange interest list each other, the relevance degree that carries out social information calculates, and obtain the social information that oneself needs from the other side, and be specially: as public transit vehicle BusA, when BusB meets, BusA, BusB exchange public transit vehicle interest list E
a, E
b, BusA is according to E
bCalculate in the own vehicle data storehouse all social informations for the relevance degree of BusB, recomputate relevance degree again for oneself, then, BusA distributes a part of social information to BusB, this part social information is for the relevance degree of the BusB mean value greater than social information's relevance degree in the vehicle data of the BusB storehouse own, BusB sorts this two parts social information according to relevance degree, replace the less social information of relevance degree in the vehicle database; Equally, BusB also carries out same work.
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