CN103476006A - Enhanced neighbor information-based multi-hop broadcast protocol - Google Patents
Enhanced neighbor information-based multi-hop broadcast protocol Download PDFInfo
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Abstract
The invention provides an enhanced neighbor information-based multi-hop broadcast protocol (ENIMBP) in a highway scene. A optimal transmitting vehicle is selected by combining neighbor information of vehicles with positions, steering speeds and directions of the vehicles to determine transmitting waiting time. According to the positions of the vehicles, the ENIMBP can initially determine the transmitting waiting time of the vehicles different in distance from a broadcast vehicle. Under the condition of same distance between the vehicles and the broadcast vehicle, the ENIMBP differentiates the transmitting waiting time by means of speeds and directions of the vehicles. The ENIMBP solves the network partitioning problem and node hiding/exposing problem in the highway scene. Simulation results show that the end-to-end delay can be remarkably reduced in a sparse network, and meanwhile, a very high packet arrival rate is maintained. As the speeds and directions of the vehicles are introduced, the transmitting waiting time of the vehicles with same distance can be differentiated, and under the scene of great vehicle density, the high packet arrival rate can be further maintained.
Description
Technical field
The bright field of traffic that belongs to of person's character, be specifically related to Information Communication field in traffic.
Background technology
According to WHO (World Health Organization) the global road safety status report of 2013, the whole world has 3,400 people nearly to die from traffic accident every day, and reach nearly ten million because of the injured or disabled number of traffic accident every year.Data show that most of traffic accidents are because driver's false judgment causes, because they can not expect the unsafe condition of road ahead.In addition, weather and sight line are blocked and are all likely further reduced the understanding of driver to road ahead.
Fortunately, along with countries in the world expert and researcher constantly study and inquire into vehicle communication, this problem is expected to be resolved.The Demo2000 of Japan is the research project about inter-vehicular communication the earliest; The C2C-CC in Europe, FleetNet project, CarTalk2000 etc. are studied and develop intrinsic problem and the novel DAS (Driver Assistant System) of inter-vehicular communication, and CVIS has opened V2V (Vehicle to Vehicle), V2I (Vehicle to Infrastructure) technical research; The U.S. issues and has revised Wireless Access Standard WAVE.These projects are having important realistic meaning aspect the research of inter-vehicular communication.In addition, VANET (Vehicular Ad hoc NETwork) has become one of study hotspot nearly ten years.Because VANET has great potentiality on the convenience that solves vehicle and road safety, traffic efficiency and driver and passenger and comfortableness.To mainly concentrating on the design and implementation of framework the research of VANET, research work comprises: route, broadcast, service quality, fail safe etc. at present.
Yet, in many research fields and application, the Radio Broadcasting Agreements in VANET occupies very important status.The rarest two the very important application of Radio Broadcasting Agreements in VANET.The first, many Routing Protocols end to end need to be used broadcast, and as the route discovery of passive type Routing Protocol, the neighbor table of active Routing Protocol is upgraded, and based on the geographic routing algorithm, need to broadcast and obtain positional information etc.The purpose of broadcast will send a request message to destination node exactly quickly and efficiently.In the second, VANET, most application all needs to use the vehicle packet distribution of Radio Broadcasting Agreements to specific region, as early warning information, traffic congestion information, traffic accident, collaborative driving, entertainment news etc.
Radio Broadcasting Agreements in VANET can be divided into two kinds: one jumps broadcast and multi-hop broadcast.One jumps the i.e. interior broadcast of a jumping scope of broadcast, and typical application is the HELLO bag that obtains middle broadcast of neighbor node list.Yet in most cases, one jumps the application requirements that broadcast can not meet VANET.Vehicle detection is during to dangerous information, need to be to the more remote vehicle of notice, and be not only the vehicle in a jumping scope, in this case, just need to adopt the multi-hop Radio Broadcasting Agreements.Multi-hop broadcast can be regarded a plurality of single-hop broadcasting process as, need to find suitable via node to farther regional forwarding data bag in a jumping scope of broadcast node.
Due to the intrinsic characteristic of VANET, as factors such as vehicle fast moving, node skewness, network topology frequent variations, multi-hop broadcast exists many challenges and problem demanding prompt solution.In the situation that vehicle is intensive, there is many cars broadcast data packet simultaneously, thereby constitute competition and conflict.And, when vehicle is sparse, easily cause again the network segmentation problem, in broadcasting van one jumping scope, do not have vehicle to can be used as via node to farther regional forwarding data bag.Simultaneously, the existence of a large amount of hide/exposed nodes also can affect the reliability of broadcast message distribution.
Wireless broadcasting method at least can be divided into two kinds: the method based on topological and the method based on statistics.Method based on topological utilizes network topology (node density in the double bounce scope) to select via node to forward broadcast message.The advantage of its maximum is can be in the situation that do not know that node distributes, reduction broadcast redundancy, and the higher arrival rate of maintenance.Yet this method needs neighbor information accurately, but because the VANET network topology change is very fast, therefore need to send the message of the obtaining topological data neighbor information that just can upgrade in time with very high frequency.Method based on statistics does not need to use fast-changing neighbor information, but by calculating one or several variate-value, and decide heavily broadcast according to calculated value.Due to the intrinsic stochastic behaviour of method based on statistics, it can not always can guarantee to obtain satisfied arrival rate.
Document [WISITPONGPHAN N, TONGUZ O.K, PARIKH J.S, et al.Broadcast storm mitigation techniques in vehicular ad hoc networks[J] .IEEE Wireless Communications, 2007,14 (6): 84-94.] propose the broadcast inhibition technology of three kinds of lightweights: weighting p-continues, and time slot 1-continues and time slot p-continues.Weighting p-continues the broadcast defining node after receiving packet for the first time, with Probability p forwarding data bag; Otherwise packet discard.Time slot 1-continues broadcast and distributes the different stand-by period according to the distance of nodal distance broadcast node, and distance is far away, and the stand-by period is shorter.If node received packet and also do not receive the copy of broadcast data packet after the stand-by period of distributing, with probability 1 forwarding data bag; Otherwise packet discard.Time slot p-continues broadcast and combines the advantage that weighting p-continues broadcast and the lasting broadcast of time slot 1-.After vehicle receives packet, calculate the stand-by period of distribution according to the distance of broadcast node and self.If also do not receive the copy of packet before the stand-by period finishes, with Probability p forwarding data bag; Otherwise packet discard.
This scheme distributes and can reduce end-to-end delay under scene comparatively uniformly at vehicle, keeps higher packet delivery rate simultaneously.Yet time slot p continues broadcast and has two main problems.In sparse network, may there be any vehicle in the time slot of distribution, thereby has increased the unnecessary stand-by period.And, for dense network, there are a large amount of vehicles in same time slot, therefore also can cause and compete frequently and conflict.
Document [LI D, HUANG H, LI X, et al.A Distance-Based Directional Broadcast Protocol for Urban Vehicular Ad Hoc Network[C] .Proceedings of3
rdiEEE International Conference on Wireless Communications, Networking and Mobile Computing (WiCOM2007), 2007:1520-1523] a kind of Radio Broadcasting Agreements---efficient direction broadcast (EDB) of distance-based proposed.EDB is used directional antenna, and regulation is responsible for the forwarding data bag with the receiving node farthest of exercising opposite direction, and at the parting of the ways, the directional relay device is installed, for assisting to each highway section forwarding data bag.Node waits for a period of time after receiving packet, and the distance between this stand-by period and sender and recipient is inversely proportional to.If receiving node does not also receive the copy of broadcast data packet after the stand-by period, forward this packet; Otherwise packet discard.
This scheme need to be installed repeater at the parting of the ways, is unfavorable for universal and realizes.And, in the situation that height of car is intensive, the competition between node may cause time delay to increase.And in traffic density under sparse scene, may there be any vehicle in the wait time slot of distribution, has increased the unnecessary stand-by period.Therefore EDB be applicable to different scenes.
Summary of the invention
Goal of the invention: the present invention is directed to the problem existed under the intrinsic characteristic of VANET (vehicle fast moving, node skewness, network topology frequent variations etc.) and different vehicle density scene and (when vehicle is intensive, easily constitutes competition and conflict; When vehicle is sparse, easily produce that network is cut apart and the problem such as blank stand-by period), propose a kind of enhancement mode multi-hop Radio Broadcasting Agreements based on neighbor information and be called for short ENIMBP (Enhanced Neighbor Information-based Broadcast Protocol).ENIMBP has solved the network segmentation problem under the highway scene, in sparse network, can reduce significantly end-to-end delay, and can adapt to different traffic density scenes.
Technical scheme
System model
Suppose that each car can obtain by navigation system oneself exact position, speed and travel direction.Each car has identical processor and computing capability, and the transmission speed of wireless signal approaches the light velocity.Therefore, although the end-to-end delay of broadcast is relevant with the queue latency delays with processing delay, the transmission delay of packet, because processing delay and transmission delay can be regarded constant as, so what real, end-to-end delay is played a decisive role is the queue latency delays.
The most highway is all two-way, the vehicle of selecting backward going as forward node except can solving the network segmentation problem in sparse network, can also adapt to different scenes [NADEEM T, SHANKAR P, IFTODE L.A comparative study of data dissemination models for vanets[C] .3rd Annual International Conference on Mobile and Ubiquitous Systems (MOBIQUITOUS), 2006].
In addition, ENIMBP requires the neighbor table of vehicle maintenance oneself, therefore need to periodically send out the HELLO bag.
Define 1 relaying zone and ignore zone
ENIMBP adopts omnidirectional antenna, and the broadcasting area of vehicle i is divided into to two zones: be positioned at the zone of broadcasting van back, be defined as relaying zone R
i; Be positioned at the zone of broadcasting van front, be defined as and ignore regional I
i.As shown in Figure 1.The ENIMBP regulation, only be positioned at relaying zone R in the neighbor table of vehicle i
ivehicle just be responsible for the forwarding data bag, ignore regional I and be positioned at
ivehicle packet discard.As shown in Figure 1.Definition 2 forwards stand-by period WT
i
ENIMBP adopts the broadcast of receiver-based to suppress technology, by the recipient, according to the information of oneself, determines when broadcasted.The forwarding stand-by period of definition vehicle i is WT
i, waiting for WT
iafter time, if also do not receive any packet, broadcasted.WT
icalculating at B joint, set forth.
Relay point is selected
A. data packet format
When vehicle detection arrives emergency, can generate and broadcast data packet.Vehicle can calculate according to neighbor table the interstitial content N that is positioned at the relaying zone.Data packet format is as shown in table 1.
Table 1 data packet format
| VID | Position | Velocity | N | MID | Message |
Wherein VID means broadcasting van ID; Position means the position of broadcasting van; Velocity means the velocity of vehicle, comprises size and Orientation; N is the number of vehicles that is positioned at broadcast node relaying zone; MID means message id; Message describes detailed road event.
B. calculate WT
i
After the neighbor node of broadcasting van is received broadcast data packet, according to broadcast data packet and position separately, velocity information, calculate the corresponding stand-by period that forwards.The velocity magnitude of supposing broadcasting van i is v
i, normalized unit vector is
the velocity magnitude that receives vehicle j is v
j, normalized unit vector is
number of vehicles in the relaying zone of broadcasting van i is N
i, receive vehicle j and calculate the vehicle number n between self and broadcasting van i according to oneself neighbor table
j, i(not comprising broadcasting van).In the situation that there is no parallel vehicles, just can distinguish the forwarding stand-by period of different vehicle according to (1) formula.Formula (1) can calculate and receive vehicle j is apart from broadcasting van i N
i-n
j, ivehicle far away, wherein C
1for the unit stand-by period, receive farthest vehicle and wait for C
1, inferior reception vehicle far away is waited for 2C
1, by that analogy.
Yet, in many actual scenes, tend to occur many situations that car is parallel, that is to say that receiving farthest vehicle likely has many.Therefore, ENIMBP is improved formula (1), has considered the factors such as node speed and direction, show that the forwarding stand-by period of reception vehicle j is:
Can find out from formula (2), in the situation that distance is identical, with the reverse reception vehicle of broadcasting van, forward little that the stand-by period can be than with broadcasting van reception vehicle in the same way, therefore can preferential forwarding data bag.In the situation that the identical and broadcasting van of distance and reception vehicle are in the same way, the preferential forwarding data bag of the vehicle that speed is little, because the relative distance of the little reception vehicle of speed and broadcasting van is larger; And, in the situation that the identical and broadcasting van of distance is reverse with the reception vehicle, the preferential forwarding data bag of the vehicle that speed is large, because the relative distance of the large reception vehicle of speed and broadcasting van is larger.Suitable selectivity constant C
1with C
2, can effectively distinguish the forwarding priority that receives vehicle.
The broadcast flow process
Therefore neighbor information broadcasting scheme NIBS has only considered unidirectional highway scene, during the network segmentation problem when having sparse network in, can cause the broadcast interruption.Yet the highway great majority in reality are all two-way, therefore, here for two-way highway, a kind of practicable forwarding algorithm is proposed.
/ exposed node problems hiding in order to solve, in broadcasting van relaying zone, during without any vehicle, broadcasting van can be broadcasted a cancellation packet that only comprises event id, and the vehicle that notice is ignored in zone is abandoned broadcast.
As shown in Fig. 2 (a), at vehicle A place, something unexpected happened, by vehicle A, produces broadcast data packet, and complete the propagation of information by following flow process:
The step 1) broadcasting van calculates the number of vehicles N that is positioned at own relaying zone according to neighbor table, if N=0 enters step 2; Otherwise, enter step 3, as shown in Fig. 2 (b).
Step 2) if the number of vehicles N=0 in the relaying zone, broadcasting van can broadcast data packet.Whether meanwhile, this vehicle constantly upgrades neighbor table, upgrade neighbor table at every turn and all can detect and have vehicle to be positioned at the relaying zone of oneself.When vehicle appears in the relaying zone, enter step 3; Otherwise, continue storage and carry.
If the number of vehicles N in step 3) relaying zone > 0, broadcasting van upgrades corresponding information in broadcast data packet with oneself ID, position and relaying zone number of vehicles, and broadcast data packet, enters step 4.It should be noted that, for fear of the packet loss caused because of link down, broadcast node can periodically be broadcasted always, until receive the broadcast data packet copy or cancel packet.
Step 4) receives vehicle and at first according to the broadcast node position in packet and the position judgment of oneself, lays oneself open to which zone of broadcast node.If in ignoring zone, do not do any processing, directly packet discard; If in the relaying zone, according to the event information of packet, the driver is made to corresponding prompting, and enter step 5.
Step 5) receives vehicle and calculates the stand-by period of oneself according to the data that receive and formula (2), and judges in the relaying zone according to the neighbor table of oneself whether vehicle is arranged.If have, forward step 3 to; If no, enter step 6.
Step 6) is when receiving vehicle relaying zone and there is no vehicle, and packet is cancelled in receiving node broadcast, makes way for to ignore regional vehicle and abandon unnecessary broadcast (because now have vehicle more not farther than this reception vehicle distances broadcasting van).Receive this vehicle of cancelling packet and will abandon broadcast.
For example, for the vehicle shown in Fig. 2, distribute, vehicle A is source point, and it produces packet.Due to vehicle B, C, D being arranged in the relaying zone, so vehicle A broadcasts this packet.Vehicle E is arranged in the zone of ignoring of A, therefore direct packet discard.According to formula (2), vehicle B is first broadcast node, but, because there is not any vehicle in the relaying zone of B, therefore packet is cancelled in broadcast, vehicle A, C, D abandon follow-up broadcast after receiving and cancelling packet.After after a while, vehicle C will enter the relaying zone (vehicle A and vehicle B go in the same direction) of B, the B corresponding data in new data packets more now, and broadcast this packet.
According to above-mentioned step, the flow chart of the enhancement mode multi-hop Radio Broadcasting Agreements based on neighbor information as shown in Figure 3.
Performance Evaluation result of the present invention
Simulated environment
Simulating scenes is two-way highway scene, 3 tracks of each direction, the wide 4m in track, road overall length 5km.The movement that utilizes In-vehicle networking to move simulator VanetMobiSim simulating vehicle, suppose the vehicle random distribution, and produce the vehicle mobile trace file.Network Simulation Software is selected NS-2.34, this version is integrated IEEE802.11p/WAVE[EICHLER S.Performance evaluation of the IEEE802.11p WAVE communication standard[C] //Vehicular Technology Conference, 2007.VTC-2007Fall.2007IEEE66th.IEEE, 2007:2199-2203; GHANDOUR A J, DI FELICE M, ARTAIL H, et al.Dissemination of safety messages in IEEE802.11p/WAVE vehicular network:Analytical study and protocol enhancements[J] .Pervasive and Mobile Computing, 2013]. therefore module is well suited for the emulation for VANET.Simulation parameter is as shown in table 2.
Table 2 simulation parameter
Simulation result and analysis
A. end-to-end delay
Fig. 4 is that NIBS, time slot p-continue the end-to-end delay of (p=0.5) and tri-kinds of schemes of ENIMBP along with the traffic density situation of change.As can be seen from the figure, under any traffic density scene, the end-to-end delay of ENIMBP all is better than NIBS and time slot p-continues scheme.In the situation that traffic density is extremely low, the end-to-end delay that the existence of network segmentation problem causes NIBS and time slot p-to continue scheme increases severely; And, along with the continuous increase of traffic density, the vehicle of same distance also increases thereupon, thereby continuing scheme, NIBS and time slot p-all increase to some extent.Yet, the ENIMBP network segmentation problem of traffic density when low that utilized reverse vehicle to solve well; Forward the stand-by period has introduced the factors such as car speed and direction simultaneously, in the situation that the vehicle of same distance is on the increase, still can distinguish well the forwarding stand-by period between vehicle.
B. wrap arrival rate
Fig. 5 is that NIBS, time slot p-continue the bag arrival rate of (p=0.5) and tri-kinds of schemes of ENIMBP along with the traffic density situation of change.As can be seen from the figure, in the situation that traffic density is extremely low, due to the existence of network segmentation problem, the bag arrival rate that NIBS and time slot p-continue scheme is all very low; Along with the increase of traffic density, the bag arrival rate that NIBS and time slot p-continue scheme significantly improves, but, when traffic density increases to a certain degree, the vehicle of same distance increases, and the bag arrival rate descends again to some extent.And ENIMBP has solved the network segmentation problem, and introduce car speed and direction, under which kind of traffic density scene, can guarantee high bag arrival rate.
Beneficial effect
1) at first the present invention improves the package forward stand-by period of multi-hop Radio Broadcasting Agreements in VANET, utilizes the neighbor information of vehicle to determine and forward the stand-by period in conjunction with position, travel speed and the direction of vehicle simultaneously, to select optimum forwarding vehicle.The present invention only need to utilize neighbor information can complete the forwarding of packet, does not need the participation of via node, and this implementation is conducive to universal and disposes, and has effectively reduced the end-to-end delay in the sparse network simultaneously.In addition, neighbor information also comprises the information such as the travel speed of vehicle and direction, the vehicle identical with the broadcast node distance can utilize these information to distinguish and forward the stand-by period, therefore in traffic density under large scene, effectively reduce competition and conflict between vehicle, improved the packet arrival rate.
2) secondly, the present invention is according to 1) in the package forward stand-by period computing formula of proposition, a kind of enhancement mode multi-hop Radio Broadcasting Agreements based on neighbor information is proposed.This agreement, by sending the mode of cancelling packet, has solved the problem of hide/exposed node in good time, in traffic density, under extremely low scene, also can keep very high packet arrival rate.Therefore, the present invention can adapt to different traffic density scenes.From emulation experiment, can find out, this scheme, under different vehicle density scene, can both keep low end-to-end delay and very high packet arrival rate.
The accompanying drawing explanation
Fig. 1 broadcasting area is divided
Fig. 2 ENIMBP broadcasting process: (a) source node broadcast data packet; (b) through τ after the time, vehicle B broadcast data packet
Fig. 3 ENIMBP broadcasts flow chart
Fig. 4 end-to-end delay
Fig. 5 bag arrival rate
Embodiment:
System model
Suppose that each car can obtain by navigation system oneself exact position, speed and travel direction.Each car has identical processor and computing capability, and the transmission speed of wireless signal approaches the light velocity.Therefore, although the end-to-end delay of broadcast is relevant with the queue latency delays with processing delay, the transmission delay of packet, because processing delay and transmission delay can be regarded constant as, so what real, end-to-end delay is played a decisive role is the queue latency delays.
The most highway is all two-way, the vehicle of selecting backward going as forward node except can solving the network segmentation problem in sparse network, can also adapt to different scenes [NADEEM T, SHANKAR P, IFTODE L.A comparative study of data dissemination models for vanets[C] .3rd Annual International Conference on Mobile and Ubiquitous Systems (MOBIQUITOUS), 2006].
In addition, ENIMBP requires the neighbor table of vehicle maintenance oneself, therefore need to periodically send out the HELLO bag.
Define 1 relaying zone and ignore zone
ENIMBP adopts omnidirectional antenna, and the broadcasting area of vehicle i is divided into to two zones: be positioned at the zone of broadcasting van back, be defined as relaying zone R
i; Be positioned at the zone of broadcasting van front, be defined as and ignore regional I
i.As shown in Figure 1.The ENIMBP regulation, only be positioned at relaying zone R in the neighbor table of vehicle i
ivehicle just be responsible for the forwarding data bag, ignore regional I and be positioned at
ivehicle packet discard.As shown in Figure 1.Definition 2 forwards stand-by period WT
i
ENIMBP adopts the broadcast of receiver-based to suppress technology, by the recipient, according to the information of oneself, determines when broadcasted.The forwarding stand-by period of definition vehicle i is WT
i, waiting for WT
iafter time, if also do not receive any packet, broadcasted.WT
ithe calculating meeting 2.2, set forth.
Relay point is selected
C. data packet format
When vehicle detection arrives emergency, can generate and broadcast data packet.Vehicle can calculate according to neighbor table the interstitial content N that is positioned at the relaying zone.Data packet format is as shown in table 1.
Table 1 data packet format
| VID | Position | Velocity | N | MID | Message |
Wherein VID means broadcasting van ID; Position means the position of broadcasting van; Velocity means the velocity of vehicle, comprises size and Orientation; N is the number of vehicles that is positioned at broadcast node relaying zone; MID means message id; Message describes detailed road event.
D. calculate WT
i
After the neighbor node of broadcasting van is received broadcast data packet, according to broadcast data packet and position separately, velocity information, calculate the corresponding stand-by period that forwards.The velocity magnitude of supposing broadcasting van i is v
i, normalized unit vector is
the velocity magnitude that receives vehicle j is v
j, normalized unit vector is
number of vehicles in the relaying zone of broadcasting van i is N
i, receive vehicle j and calculate the vehicle number n between self and broadcasting van i according to oneself neighbor table
j,i(not comprising broadcasting van).In the situation that there is no parallel vehicles, just can distinguish the forwarding stand-by period of different vehicle according to (1) formula.Formula (1) can calculate and receive vehicle j is apart from broadcasting van i N
i-n
j,ivehicle far away, wherein C
1for the unit stand-by period, receive farthest vehicle and wait for C
1, inferior reception vehicle far away is waited for 2C
1, by that analogy.
Yet, in many actual scenes, tend to occur many situations that car is parallel, that is to say that receiving farthest vehicle likely has many.Therefore, ENIMBP is improved formula (1), has considered the factors such as node speed and direction, show that the forwarding stand-by period of reception vehicle j is:
Can find out from formula (2), in the situation that distance is identical, with the reverse reception vehicle of broadcasting van, forward little that the stand-by period can be than with broadcasting van reception vehicle in the same way, therefore can preferential forwarding data bag.In the situation that the identical and broadcasting van of distance and reception vehicle are in the same way, the preferential forwarding data bag of the vehicle that speed is little, because the relative distance of the little reception vehicle of speed and broadcasting van is larger; And, in the situation that the identical and broadcasting van of distance is reverse with the reception vehicle, the preferential forwarding data bag of the vehicle that speed is large, because the relative distance of the large reception vehicle of speed and broadcasting van is larger.Suitable selectivity constant C
1with C
2, can effectively distinguish the forwarding priority that receives vehicle.
The broadcast flow process
Therefore neighbor information broadcasting scheme NIBS has only considered unidirectional highway scene, during the network segmentation problem when having sparse network in, can cause the broadcast interruption.Yet the highway great majority in reality are all two-way, therefore, here for two-way highway, a kind of practicable forwarding algorithm is proposed.
/ exposed node problems hiding in order to solve, in broadcasting van relaying zone, during without any vehicle, broadcasting van can be broadcasted a cancellation packet that only comprises event id, and the vehicle that notice is ignored in zone is abandoned broadcast.
As shown in Fig. 2 (a), at vehicle A place, something unexpected happened, by vehicle A, produces broadcast data packet, and complete the propagation of information by following flow process: the step 1) broadcasting van calculates the number of vehicles N that is positioned at own relaying zone according to neighbor table, if N=0, enter step 2; Otherwise, enter step 3, as shown in Fig. 2 (b).
Step 2) if the number of vehicles N=0 in the relaying zone, broadcasting van can broadcast data packet.Whether meanwhile, this vehicle constantly upgrades neighbor table, upgrade neighbor table at every turn and all can detect and have vehicle to be positioned at the relaying zone of oneself.When vehicle appears in the relaying zone, enter step 3; Otherwise, continue storage and carry.
If the number of vehicles N in step 3) relaying zone > 0, broadcasting van upgrades corresponding information in broadcast data packet with oneself ID, position and relaying zone number of vehicles, and broadcast data packet, enters step 4.It should be noted that, for fear of the packet loss caused because of link down, broadcast node can periodically be broadcasted always, until receive the broadcast data packet copy or cancel packet.
Step 4) receives vehicle and at first according to the broadcast node position in packet and the position judgment of oneself, lays oneself open to which zone of broadcast node.If in ignoring zone, do not do any processing, directly packet discard; If in the relaying zone, according to the event information of packet, the driver is made to corresponding prompting, and enter step 5.
Step 5) receives vehicle and calculates the stand-by period of oneself according to the data that receive and formula (2), and judges in the relaying zone according to the neighbor table of oneself whether vehicle is arranged.If have, forward step 3 to; If no, enter step 6.
Step 6) is when receiving vehicle relaying zone and there is no vehicle, and packet is cancelled in receiving node broadcast, makes way for to ignore regional vehicle and abandon unnecessary broadcast (because now have vehicle more not farther than this reception vehicle distances broadcasting van).Receive this vehicle of cancelling packet and will abandon broadcast.
For example, for the vehicle shown in Fig. 2, distribute, vehicle A is source point, and it produces packet.Due to vehicle B, C, D being arranged in the relaying zone, so vehicle A broadcasts this packet.Vehicle E is arranged in the zone of ignoring of A, therefore direct packet discard.According to formula (2), vehicle B is first broadcast node, but, because there is not any vehicle in the relaying zone of B, therefore packet is cancelled in broadcast, vehicle A, C, D abandon follow-up broadcast after receiving and cancelling packet.After after a while, vehicle C will enter the relaying zone (vehicle A and vehicle B go in the same direction) of B, the B corresponding data in new data packets more now, and broadcast this packet.
According to above-mentioned step, the flow chart of the enhancement mode multi-hop Radio Broadcasting Agreements based on neighbor information as shown in Figure 3.
Claims (2)
1. the enhancement mode multi-hop Radio Broadcasting Agreements based on neighbor information, is characterized in that,
Enhancement mode multi-hop Radio Broadcasting Agreements based on neighbor information, be called for short ENIMBP, utilizes the neighbor information of vehicle to determine and forward the stand-by period in conjunction with position, travel speed and the direction of vehicle simultaneously, to select optimum forwarding vehicle; According to the position of vehicle, ENIMBP can tentatively determine the forwarding stand-by period of the vehicle different from the broadcasting van distance; And, in the situation that identical with the broadcasting van distance, ENIMBP utilizes car speed and direction to distinguish and forwards the stand-by period; ENIMBP has solved the network segmentation problem under the highway scene and hide/exposed node problems well.
2. the enhancement mode multi-hop Radio Broadcasting Agreements based on neighbor information according to claim 1, is characterized in that,
System model
Suppose that each car can obtain by navigation system oneself exact position, speed and travel direction; Each car has identical processor and computing capability, and the transmission speed of wireless signal approaches the light velocity; Therefore, although the end-to-end delay of broadcast is relevant with the queue latency delays with processing delay, the transmission delay of packet, because processing delay and transmission delay can be regarded constant as, so what real, end-to-end delay is played a decisive role is the queue latency delays;
The most highway is all two-way, and the vehicle of selection backward going except can solving the network segmentation problem in sparse network, can also adapt to different scenes as forward node;
Define 1 relaying zone and ignore zone
ENIMBP adopts omnidirectional antenna, and the broadcasting area of vehicle i is divided into to two zones: be positioned at the zone of broadcasting van back, be defined as relaying zone R
i; Be positioned at the zone of broadcasting van front, be defined as and ignore regional I
i; As shown in Figure 1; The ENIMBP regulation, only be positioned at relaying zone R in the neighbor table of vehicle i
ivehicle just be responsible for the forwarding data bag, ignore regional I and be positioned at
ivehicle packet discard; As shown in Figure 1; Definition 2 forwards stand-by period WT
i
ENIMBP adopts the broadcast of receiver-based to suppress technology, by the recipient, according to the information of oneself, determines when broadcasted; The forwarding stand-by period of definition vehicle i is WT
i, waiting for WT
iafter time, if also do not receive any packet, broadcasted; WT
icalculating at B joint, set forth;
Relay point is selected
A. data packet format
When vehicle detection arrives emergency, can generate and broadcast data packet; Vehicle can calculate according to neighbor table the interstitial content N that is positioned at the relaying zone; Data packet format is as shown in table 1;
Table 1 data packet format
Wherein VID means broadcasting van ID; Position means the position of broadcasting van; Velocity means the velocity of vehicle, comprises size and Orientation; N is the number of vehicles that is positioned at broadcast node relaying zone; MID means message id; Message describes detailed road event;
B. calculate WT
i
After the neighbor node of broadcasting van is received broadcast data packet, according to broadcast data packet and position separately, velocity information, calculate the corresponding stand-by period that forwards; The velocity magnitude of supposing broadcasting van i is v
i, normalized unit vector is
the velocity magnitude that receives vehicle j is v
j, normalized unit vector is
number of vehicles in the relaying zone of broadcasting van i is N
i, receive vehicle j and calculate the vehicle number n between self and broadcasting van i according to oneself neighbor table
j, i(not comprising broadcasting van); In the situation that there is no parallel vehicles, just can distinguish the forwarding stand-by period of different vehicle according to (1) formula; Formula (1) can calculate and receive vehicle j is apart from broadcasting van i N
i-n
j, ivehicle far away, wherein C
1for the unit stand-by period, receive farthest vehicle and wait for C
1, inferior reception vehicle far away is waited for 2C
1, by that analogy;
Yet, in many actual scenes, tend to occur many situations that car is parallel, that is to say that receiving farthest vehicle likely has many; Therefore, ENIMBP is improved formula (1), has considered the factors such as node speed and direction, show that the forwarding stand-by period of reception vehicle j is:
Can find out from formula (2), in the situation that distance is identical, with the reverse reception vehicle of broadcasting van, forward little that the stand-by period can be than with broadcasting van reception vehicle in the same way, therefore can preferential forwarding data bag; In the situation that the identical and broadcasting van of distance and reception vehicle are in the same way, the preferential forwarding data bag of the vehicle that speed is little, because the relative distance of the little reception vehicle of speed and broadcasting van is larger; And, in the situation that the identical and broadcasting van of distance is reverse with the reception vehicle, the preferential forwarding data bag of the vehicle that speed is large, because the relative distance of the large reception vehicle of speed and broadcasting van is larger; Suitable selectivity constant C
1with C
2, can effectively distinguish the forwarding priority that receives vehicle;
The broadcast flow process
/ exposed node problems hiding in order to solve, in broadcasting van relaying zone, during without any vehicle, broadcasting van can be broadcasted a cancellation packet that only comprises event id, and the vehicle that notice is ignored in zone is abandoned broadcast;
At vehicle A place, something unexpected happened, by vehicle A, produces broadcast data packet, and complete the propagation of information by following flow process:
The step 1) broadcasting van calculates the number of vehicles N that is positioned at own relaying zone according to neighbor table, if N=0 enters step 2; Otherwise, enter step 3;
Step 2) if the number of vehicles N=0 in the relaying zone, broadcasting van can broadcast data packet; Whether meanwhile, this vehicle constantly upgrades neighbor table, upgrade neighbor table at every turn and all can detect and have vehicle to be positioned at the relaying zone of oneself; When vehicle appears in the relaying zone, enter step 3; Otherwise, continue storage and carry;
If the number of vehicles N in step 3) relaying zone > 0, broadcasting van upgrades corresponding information in broadcast data packet with oneself ID, position and relaying zone number of vehicles, and broadcast data packet, enters step 4; It should be noted that, for fear of the packet loss caused because of link down, broadcast node can periodically be broadcasted always, until receive the broadcast data packet copy or cancel packet;
Step 4) receives vehicle and at first according to the broadcast node position in packet and the position judgment of oneself, lays oneself open to which zone of broadcast node; If in ignoring zone, do not do any processing, directly packet discard; If in the relaying zone, according to the event information of packet, the driver is made to corresponding prompting, and enter step 5;
Step 5) receives vehicle and calculates the stand-by period of oneself according to the data that receive and formula (2), and judges in the relaying zone according to the neighbor table of oneself whether vehicle is arranged; If have, forward step 3 to; If no, enter step 6;
Step 6) is when receiving vehicle relaying zone and there is no vehicle, and packet is cancelled in receiving node broadcast, makes way for to ignore regional vehicle and abandon unnecessary broadcast (because now have vehicle more not farther than this reception vehicle distances broadcasting van); Receive this vehicle of cancelling packet and will abandon broadcast.
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