Research Article A Lightweight Neighbor-Info-Based Routing...
Transcript of Research Article A Lightweight Neighbor-Info-Based Routing...
Research ArticleA Lightweight Neighbor-Info-Based Routing Protocol forNo-Base-Station Taxi-Call System
Xudong Zhu Jinhang Wang and Yunchao Chen
School of Computer Science amp Information Engineering Zhejiang Gongshang University Hangzhou 310018 China
Correspondence should be addressed to Xudong Zhu zhuxdzjgsueducn
Received 26 October 2013 Accepted 28 November 2013 Published 9 March 2014
Academic Editors W Sun G Zhang and J Zhou
Copyright copy 2014 Xudong Zhu et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited
Since the quick topology change and short connection duration the VANET has had unstable routing and wireless signal qualityThis paper proposes a kind of lightweight routing protocol-LNIB for call system without base station which is applicable to theurban taxis LNIB maintains and predicts neighbor information dynamically thus finding the reliable path between the source andthe target This paper describes the protocol in detail and evaluates the performance of this protocol by simulating under differentnodes density and speed The result of evaluation shows that the performance of LNIB is better than AODV which is a classicprotocol in taxi-call scene
1 Introduction
The VANET has characteristics of mobile ad hoc networksuch as self-organization flexible structure multihop rout-ing dynamic changes of network topology and need ofgood scalability Special application environment such asnarrow road high density node distribution high-speednode moving and other factors will directly influence theinformation transmission ability of VANET network whichleads to the increase of packet loss and delay Meanwhile thelimitedwireless channel and huge network scale challenge thedata transmission of VANET
The key to solve the above problems is how to designa routing protocol [1ndash7] Since the nodes in VANET are ofhigh mobility it results in connection failure while applyingrouting protocol of the traditional MANET [8ndash10] such asAODV [11ndash13] andDSR [14 15] into theVANET thus leadingto delay or even failure to transmit information to the targetnode
Due to the special environment in VANET it cannot havea widely applicable routing algorithm The typical algorithmin VANET such as GSR routing protocol involves eachnode storing the neighbor lists topology table next hoptable and distance table All of them maintain the stateinformation of adjacent nodes and choose the appropriate
router according to the location and topological informationIn small network with high mobility and limited bandwidththe performance of transmission is good However it requiresthe node to maintain the network topology And with theincrease of network size the routing information that needsto be exchanged will increase exponentially Another type ofalgorithm such as the GPSR [16 17] is based on positionIt depends on the overall geographical location informationsearch system It cannot work without GPS
When applied to the urban taxi-calling scene theVANETvehicle network has the following characteristics (1) Thedensity distribution of vehicle is uneven Places such as thebusiness center theaters and bus stations are dense The tra-ditional VANET routing protocols have serious informationchannel congestion problem (2)Thecalling passenger has nospecial requirements to the not-taken taxis so all the nearbytaxis can serve While the traditional VANET routing proto-cols always have designated transmission target or specifiesthe routing service of all nodes in the target area whichwill lead to huge routing overhead further deteriorating thechannel congestion problem (3) The data transmission istime valid Passengersrsquo calls need to be responded to in ashort time while the routing connection time is fairly long insome of the traditional VANET routing protocols Thereforeit cannot effectively find not-taken taxis with such application
Hindawi Publishing Corporatione Scientific World JournalVolume 2014 Article ID 601913 9 pageshttpdxdoiorg1011552014601913
2 The Scientific World Journal
and will have bad effects on passengersrsquo experiences Wedescribe some of the work roughly in [18]
This paper aims to solve the quick topology change shortconnection duration and unstable wireless signal quality ofthe VANET network thus proposing a kind of lightweightrouting protocol applicable to the urban taxi-call withoutbase stations The protocol maintains and predicts neighborinformation dynamically in order to find the reliable pathbetween the source and the target This paper describes theprotocol in detail and evaluates the performance of thisprotocol by simulating under different nodes density andspeedThe result of evaluation shows that the performance ofLNIB is better than that of AODV which is a classic protocolin taxi-call scene
The second chapter analyzes the application and proposesthe model the third chapter describes the routing protocoland its algorithm the fourth chapter is about the experi-ment and data analyses chapter five concerns other relatedresearch the last part will draw a conclusion
2 Transmission Mode and Analyses
In the taxi-calling scene the vehicle network has two setstaxi nodes 119876 = 119902
1 1199022 119902119899 and passenger nodes 119875 =
1199011 1199012 119901119898 From the start of the call to get on the car
or the call to cancel a connection should be set up in thenetwork Because the passenger always waits at the originalplace or moves slowly suppose 119901 is a static node And 119901 onlyacts as the initiator of data transmission or receiver not asmediator in other routings The node 119902 can send receive oract as a routing node to transmit data Assume that the speedscalar of each node in 119876 is |V|
When 119901 initiates a call the message transits through thetaxi nodes so 119901 can quickly find nearby not-taken cars node119902119904that can meet the requirementsSupposing there are two nodes 119886 and 119887 in the network the
signal coverage radii for them are respectively 119877119886and 119877
119887 If
the distance between 119886 and 119887 is 119863119886119887le min(119877
119886 119877119887) it can
be called ldquomeetrdquo To be more general assuming that signalcoverage radius of each node in the network is 119877 then ldquomeetrdquoin time 119905 means 119863
119886119887(119905) le 119877 Define 119867
119886119902119904
as the minimalnumber of hops to transmit message from 119886 to 119902
119904 Among
all 119902119904that get the call request119867
119886is the lowest of119867
119886119902119904
21 Prediction Based on Neighbor Information In order topercept the current meet nodes in real time 119902 needs tosend broadcast packets to notice their own state informationperiodically In the starting time 119905 of every broadcast cycle119902 measures their own motion state including the speed thecurrent position and other information According to theabove information 119902 predicts the coordinates at the time of119905 + 119905119891and broadcasts the position The broadcast cycle is 119905
119887
If 119905119887is small then the channel will be occupied by a large
number of broadcast packets thus influencing the normaldata transmission However large 119905
119887will lose the predic-
tion value due to the frequent changes in actual situationTherefore 119905
119887should be set properly such as 10 seconds A
broadcast cycle can be divided intomultiple correction cycles
The node in a correction period measures their movementstate While finding the coordinatesrsquo different Δ119904 between thecurrent forecast coordinate at 119905 + 119905
119891and the last broadcast
coordinates surpasses it indicates that the vehiclersquos drivingcondition changes If Δ119904 is greater than a certain value thenode broadcasts the position again to correct the predictposition of itself in neighbor nodesrsquo state table thus to ensurethe prediction accuracy Suppose the correct period is 119905
119903
Meanwhile if 119902 receives the position broadcast of thenearby nodes it maintains an adjacent link (see Table 1) torecord node information that meets with 119902 It can be seenfrom the table that 119902
2measures its position and velocity at
131112101584036 and broadcasts 1199021receives the position broadcast
If11986311990211199022
(119905) le 119877 then it can be predicted that at 119905 + 119905119891 1199021and
1199022will keepmeeting If 119902
2is not in the table 119902
1adds the infor-
mation of 1199022to the table and sets 119902
2to be active If 119902
2is already
in the table update the information of 1199022 When 119902
1receives
the correction broadcast of 1199022 the position information of 119902
2
also needs updating If it can be predicted that 1199021and 1199023will
not meet at 119905 + 119905119891 set 119902
3to be inactive As to the inactive
node in the table if no broadcasts are received in more thanone broadcast cycle then delete the entry of this inactivenode Each time the passenger calls a taxi several links will beproduced If 119902
1and 1199023are neighbors and are both in one link
then they set up link ID in the entry for each other in theirown table Link ID is a large number that is randomly gener-ated It can be assumed that it is unique in a limited region
When 1199021receives the broadcast of neighbors at time 119905 it
will predict coordinates of itself and neighbor nodes at 119905 + 119905119891
respectively If the two cars can keep communication at thattime (such as 119902
2) the communication is effective Therefore
1199021stores the information of 119902
2in the table otherwise discards
it (such as the 1199023)
In order to provide the position information and routingof not-taken taxis the hop distance should be introducedwhen 119902 node is broadcasting message (including positionand correction broadcast) Periodically 119902
119904sets 119867
119902119904
to 0 andsends broadcastThe 119902
119904discards any broadcast information it
received without processing The 119902 sets119867119902value toinfin when
no neighbor nodes can reach 119902119904node When 119902
1receives the
broadcast of 1199022with the active state if 119867
1199022
+ 1 lt 1198671199021
1199021
modifies the1198671199021
value to1198671199022
+ 1Once 119867
1199021
changes 1199021will spread to notify neighbor
nodes to be updated by periodical breakfast But each cyclecan only update 1 hop on the link If 119867
11990211199022
= 119899 it needs 119899cycle to update119867
1199022
In order to improve the broadcast speed of119867 the sending
phase of each cycle is divided into two time slices The nodeof119867 changes but no broadcast will be broadcasted at the firsttime slice If the 119867 value has no change after last broadcastthe node broadcasts in the second time slice Thus the valueof119867may spread 2 hops in a cycle For the length of link willbe limited in 3-4 hops in the actual system two cycles cancomplete the information disclosure of not-taken taxis by theimproved broadcast speed
22 Links Setting and Handshake When 119901 launches the callit needs to find suitable not-taken taxis 119902
119904as soon as possible
and make an appointment In this process the following
The Scientific World Journal 3
Table 1 State of the 1199021rsquos Neighbor Nodes
Neighbor 119867119902119899119902119904
Position Direction of speed Link ID Reliability Measuringtime State
1199022
3 120213476E30321768N 119889
1199022
182378627 094 131112101584036 Active
1199023
5 120213484E30321775N 119889
1199023
452766732 083 131037101584034 Inactive
p
qa(H = 2)
qb(H = 5)
qc(H = 3)
qd(H = 1)
(a)
qs
q998400a(Dp1q119904= 200m)
q998400b(Dp3q119904= 300m)
(b)
Figure 1 (a) If there are the 119902 nodes within the single hop range of 119901 then they shake hands and choose one as 119902119886that has minimal hop
distance to 119902119904to make an appointment (b) If there are several 119902 nodes around 119902
119904and several 119901 nodes send the appointment requests then
they shake hands and choose the nearest 119901 node to response
questions need to be solved First how to find 119902119904in the
shortest time and establish the link to 119902119904 Secondly if there
are several 119902119904nodes how to choose one of the most suitable
ones to make an appointmentThe simplest method is to use the broadcast to send out
the call until a node of 119902119904receives the request and returns a
response The response will go backtracking to the 119901 nodeIf 119901 receives several responses then choose one from themafter which appointment confirmation will be sent to thechosen node through the path just set up Meanwhile itwill send negative responses to other not-taken taxis Thismethod is easy to be implemented but in the real VANETscene there are serious problems the message must pass thewhole link three times request response and appointmentOn the one hand it will lead to serious delay and difficulties inkeeping the link on the other hand the flooding of breakfastwill deteriorate the network environment and influence thenormal communication
This paper proposes a two-end handshake agreement togreat link (show as Figures 1 and 2) According to the neighbornodesrsquo information described in Section 21 each node canknow the nearest (by hop distance) 119902
119904and the shortest route
to arrive at the node If 119901 sending the request broadcast itsneighbor 119902 node which receives 119901rsquos breakfast directly canjudge whether it can reach 119902
119904or not In fact it is supposed
that the whole data transmission is a single route (the nodeon the link will transmit a message to only one neighbor
p qc qc qs
Figure 2 The two-end handshake agreement
node) Once 119902 is identified as the first hop the routing from119901 to 119902
119904will also be established The 119902 can directly send a
request response to the 119901 If 119901 receives responses from several119902 nodes it chooses a 119902 node as 119902
119886to make appointment
confirmation and send a veto appointment to other response119902 After that 119902
119886accepts the confirmation and sends it to the 119902
119904
4 The Scientific World Journal
based on the routing information that is to transmitmessageto the neighbor 119902 node in which 119867
119902= 119867119902119886
+ 1 On therouting node 1199021015840 will record the information of last hop whilereceiving the message Meanwhile transmit to the next hopwhich119867
119902= 1198671199021015840 + 1 until sent to the node which119867
119902= 0 that
is 119902119904The 119902119904end of the link also needs handshaking If several
neighbor 119902 nodes in which 119867119902= 1 are for the same 119902
119904
node they will send appointment requests to the 119902119904 and the
119902119904sends a confirmation response to one of them and negative
responses to othersThe two-end handshaking method can reduce the three
times handshaking to two times thus reducing the risk ofdelaying and disconnectionMeanwhile the broadcast can becontrolled in 1 hop and can avoid the flooding
23 Disconnection Suppose 119867119902119904
= 0 1198671199021
= 1 1198671199022
= 2 and1198671199023
= 3 If 1199022receives the position correction information
from 1199021 the adjusted position predictions indicate that 119902
1will
lose contact with 1199022 Since 119867
1199021
is the minimum 119867 stored in1199022 after 119902
2node deletes the 119902
1 it modifies its own119867 value to
infin and triggers an extra position correction broadcast Alsowhen 119902
3receives the position correction by this broadcast it
continues the same operationIn the communication process the effectiveness of link
should be guaranteed from the sending of 119901rsquos request to119902119904rsquos response return to 119901 Once a pair of nodes on the link
are disconnected it should be processed correspondentlyThe relatively ideal way is to find the third node beforedisconnection and to maintain the link Another simplemethod is to notify 119901 and 119902
119904to abandon the appointment on
both ends Thus it can avoid feedback loss which will resultin information consistency Then the 119901 initiates the requestprocess again
As the vehiclersquos speed is fast and unstable the time oflink maintains a relatively short time The frequently brokenlinks will lead to repeated reconnection To avoid this higherreliable links are required So in the 119902rsquos neighbor nodes statetable the reliability attribute is added for each neighbor nodeThe reliability refers to the prediction accuracy at 119905 + 119905
119891and
the help to effective datagram transmission on the link Itmainly depends on the following two conditions (1) during 119905to 119905 + 119905
119891period the relative position between 1199021015840 and 119902 If the
distance is far on the one hand the weak signal can lead totransmission instability on the other hand since 1199021015840 has beenclose to the edge of the 119902 communication range the slightchange of the vehicles will make 1199021015840 out of 119902rsquos communicationrange and cause broken connection If 1199021015840 and 119902 are closethe data transmission will take place in a short distance Thedatagramwill not move a lot in geographical location thus itinfluences the efficiency of data transmissionThus supposing1198801199021199021015840(1199051015840) = 2|119863
1199021199021015840(1199051015840) minus 119877|119877 refers to the transmission
reliability of 119902 and 1199021015840
1198801199021199021015840 (119905 119905 + 119905
119891) =
integration(119905 119905 + 119905
119891) (1)
Modify the condition of correcting 119867119902in Section 21
Given the reliable threshold 119903 isin [0 1] and after 1199021node
receives the broadcast of 1199022node if state (119902
2) = active119867
1199022
+
1 lt 1198671199021
and1198801199021199021015840(119905 119905 + 119905
119891) gt 119903 then modify the119867
1199021
value tobe 1199022+ 1
3 Protocol Implementation
In order to further introduce the implementation of theprotocol the pseudocode algorithms of taxi 119902 node andpassenger 119901 node are given respectively in this section Tobe simple based on the discussion in the second section thefollowing several types of datagram in the taxi-call networkwill be referred to
Broadcast (119871 119881119867 119905119888) represents position broadcast The
taxi node sends periodically and the nearby taxi nodereceives1198721minus6
represents the six kinds of datagrams in the two-endhandshaking protocol after the passengers make a request119872119890represents the cancelation of the reserved datagram
while finding the abnormal disconnectionAlgorithm 1 is divided into two parts The timer gets
the position and speed information for a short time (eg3 seconds) If the interval exceeds 119905
119891 then send broadcast
to the nodes around According to the current measureddata the position at 119905 + 119905
119891can be predicted If there exists
significant difference between the position and the position ofthe last broadcast then send broadcast without consideringwhether the time intervals exceed 119905
119891or not The timer will
also inspect the neighbor node that is not updated over timein the adjacency list and set these nodes as inactive Sincethe time in the record is the position measuring time toconsider the communication delay the overtime windowwillbe slightly amplified to 11119905
119891 If not updated for more than
two broadcast cycles then delete the nodeAs for the inactive nodes check whether they are in the
current communication connection If it is true then send119872119890
to other connected nodes to cancel the conformationThe other part of Algorithm 1 is the listener After the
listener receives a datagram heshe judges data types If it isthe position broadcast datagram then update the list Oncethe predicted node position changes are identified in thecurrent connection and in a short time will overpass thescope of communication and then notify other nodes on theconnection to cancel the appointmentWhen accepting othertypes of datagram again transmit or respond based on theprotocol
Algorithm 2 mainly includes two timers and a listenerWhen initiating the request timer
1is set At the same time
the listener will put the received response to the responsequeue When timer
1is triggered it checks the queue If the
queue is empty it means no response and it sends the requestagain Otherwise it chooses the response that has the nearesttransmission distance from passengers to not-taken taxis inorder to make appointment And it simultaneously sendsveto to other response nodes After sending the appointmentdatagram set timer
2 Once no appointment conformation
1198724in a certain time 119872
4 then the timer
2will be launched
and send request1198721again Attention here once the listener
receives an 119872119890 the datagram cancellation is caused by
The Scientific World Journal 5
Initialization 119905 = 0Initiate the prediction position 119878 = 0Initialization 119867 = infinSet timerTimer task()
Obtain the current position L speed V time 119879119888
119867new = 119867If (no-load)119867new = 0
Calculate prediction position 1198781015840 at (119905 + 119905119891)
If (119905119888minus 119905ge119905119891)
119867 = 119867newbroadcast(L V H 119905
119888)
119905 = 119905119888
119878 = 1198781015840
else if (|119878 minus 1198781015840| larger than threshold 119867 minus 119867new⟨⟩0)119867 = 119867new
broadcast(L V H 119905119888)
119905 = 119905119888
119878 = 1198781015840
For each node q in tableget qrsquos prediction time 119905
119902
if (state(q) == active ampamp 119905119888minus 119905119902ge 11119905
119891)
state(q) = inactiveif (q have the link ID)send119872
119890to other node which have the same lnik ID as q
If (119905119888minus 119905119902ge 2119905119891)
Remove q from table
Update H
Count = 0 reset 0 after passengers getting off or appointment cancellationBlock listen(Message)
Switch typeof(Message) Case119872
119887
update tableupdate Hif q node that sends119872
119887gets out of the communication range and it has link ID in the table
send119872119890to other node
which have the same link ID as qbreak
Case1198721
If (119867 lt infin)send1198722back
breakCase119872
3
If (Message == Reserve)If (119867 == 0 ampamp count == 0)
Count = 1send119872
4(Agree or Disagree) back
else if (119867 == 1)Set link IDsend119872
3to all q in table which119867
119902= 0
else
Algorithm 1 Continued
6 The Scientific World Journal
Set link IDsend119872
3to one q which119867
119902= 119867 minus 1
Case1198724
If (Message == Agree)Send119872
4forward to q which119867
119902= 119867 + 1
and have the same link IDdelete link ID
If (119867 == 1)Send Confirm back
Default
Algorithm 1 Algorithm of taxi node
Initiation queue = emptyCall taxi
Get its position LBroadcast(119872
1)
Set Timer1()
Timer1 task()If (queue = empty)
Call taxi()elseChoose the nearer hop qProduce link IDSend119872
3(Reserve link ID) to q
Send1198723(Negative) to other
Set timer2
Timer2 task() Call taxi() Block listen(Message)Switch typeof(Message)
Case1198722
Add q to queueBreak
Case1198724
Cancel Timer2Break
Case119872119890
Set Timer2 current timeBreak
Default
Algorithm 2 Algorithm of passenger node
connection errorThen immediately start the timer2and send
request again
4 Performance Analysis
In order to evaluate the performance of the proposed routingprotocol the paper uses NS2 and VanetMobiSim to simulate
TheNS2rsquosmain parameters are shown in Table 1The sim-ulation scene size is 5times 5 square kilometers InVanetMobiSimsimulation the scene size is 5times 5 square kilometers too In thetotal area there are 20 traffic signals and the entire simulationarea is divided into several regions In every region the densityof streets and the allowed maximum speed are different Theregions which have higher street density have lower allowedmaximum speed When vehicles get into the correspondingregion they choose the speed from street allowed maximumspeed and self-allowedmaximum speed with a low one In allof our simulations the empty taxis account for 40
We set the interval of route maintain message 119879119887to be
equal to 10 s and then set the maximum speed of taxi nodesto be equal to 60 kmh When we adjusted the density of taxinodes we got the probability of passenger node 119875 to findempty taxi node 119879
119863and the probability of node 119875 to receive
the message from 119879119863as shown in Table 3
As shown in Table 3 when node density is too low thetransmission range will be so small that it is hard to maintainthe information of nodes for a long time Hence when 119875appears the number of nodes that 119875 can communicate withis small and the time of link is short so that it is hard tocommunicate with 119879
119863 As the node density becomes higher
situations are getting better but some nodes have highervelocity which leads tomore failure Because the links chosenare the links that have long duration so the probability ofnode 119875 receiving acknowledgement messages from node 119879
119863
is pretty highThen if we fix the density of taxi nodes as 5 per km2 and
fix the transmission range as 500m we will get the relation ofthe maximum speed and the successful ratio
We called it successful calling when the passenger nodefinds the empty taxi node In Figure 3 we could see that whenthemaximumspeed of taxi is equal 60 kmh it has the highest
The Scientific World Journal 7
74
76
78
80
82Su
cces
sful r
ate (
)
Maximum speed (kmh)40 50 60 70 80 90 100
04
06
08
1
12
14
Link
bro
ken
ratio
()
Successful rateLink broken ratio
Figure 3 The relation of the maximum speed of taxi nodes and theratio of passenger node contacting empty taxi nodes successfully
successful ratio which enables the passenger node to find theempty taxi nodes This is because when the nodersquos movingspeed is low the node can contact with fewer other nodesAnd when the nodersquos moving speed is high the networktopology changes fast which causes fewer available routinglink and thus causes lower successful calling
Figure 4 shows the impact of nodersquos moving speed on theamount of switching packets of entire network
As shown in Figure 4 the amount of switching packetsgrows up as the vehicle movement speed increases Thisis because when the speed of node movement increases itcauses more correcting message resulting in the increaseof network data traffic In addition in one simulation therouting overhead is higher at the beginning and graduallydeclines over time This is because when the simulationstarts all taxi nodes are active at the same time and all taxinodes broadcast at the same time which causesmore channelcollision leading to an increasing number of retransmissionsAs time progresses due to the correcting message the taxirouting maintenance cycles gradually stagger and the entirenetwork routing overhead declines
Thenwe adjust the density of taxi nodes in the regionTheaverage density of taxi nodes is set at 1ndash6 per square kilometerand the vehiclemaximumspeed is set at 60 kmh and then theresults are shown in Figure 5
As shown in Figure 5 when the taxi nodes are scarcethe rate of the success calling drastically reduces Whileincreasing the number of taxi nodes the rate of success callingimproves accordingly This is because when the number oftaxi nodes is too small there is no taxi node around passengernode so that the passenger node cannot contact with anynode resulting in more calling failure When the numberof taxi nodes increase and the passenger node sends anappointment request the number of alternative routing pathsincreases so the node can choose a more stable routing pathto delivery packet thereby the rate of success calling willincrease
2 4 6 8 10
1900
1950
2000
2050
Ove
rhea
d (p
acke
t)
Time (min)
40kmh60kmh80kmh
Figure 4 The impact of nodersquos moving speed on the amount ofswitching packets of entire network
20
40
60
80
100
Succ
essfu
l rat
e (
)
1 2 3 4 5 60
2
4
6
8
Link
bro
ken
ratio
()
Successful ratioLink broken ratio
The density of taxi nodes (km2)
Figure 5 The impact of nodes density on successful ratio
Table 2 The NS2 parameters
Parameters ValuesLoss model PropagationTwoRayGroundPhysical model PhyWirelessPhyExtAntenna AntennaOmniAntennaTransmission rate 2MbpsNetwork protocol IEEE 80211
At last we control node velocity between 0 and 20msinterval of 119879
11988710 s transmission range is 500m and the
density is 4 per square kilometers Compared to AODV(show as Table 4) the results are shown in Table 2 We cansee that the proposed routing protocol performs better than
8 The Scientific World Journal
Table 3 The impact of nodes density and transmission range on successful calling ratio
Transmission rangeDensity of taxi
4 6The probability to
find 119879119863
The probability toreceive from 119879
119863
The probability to find119879119863
The probability toreceive from 119879
119863
200m 148 785 498 955300m 443 912 784 942500m 611 941 873 946
Table 4 Compare with AODV
CBLIGR AODVDelivery rate() 611 523Control messagepacket 12068 18150
AODV More importantly our protocol communication datais scattered throughout the network while AODV is relativelyconcentrated As a result our protocol performs better in thechannel collision It is because AODV requires a great dealof broadcast to maintain the entire link routing informationand has no efficient methods to deal with the disconnectionof links
5 Conclusion
This paper proposes a routing protocol for taxi-calling appli-cation Firstly it analyzes scenes of taxi-calling applicationand studies the differences between the common vehicleapplication scene and the taxi-calling application sceneSecondly it proposes the routing information maintainingalgorithm based on position prediction which performsbetter reliability Thirdly a self-network forming method fortaxi-calling application is drawn up
Our protocol queries the destination node by nodesrsquokeeping the information of the hop count to destination anddecreases the routing cost Meanwhile the validity of routesis guaranteed by predicting the future position of themselvesand their neighbors
This protocol has also been evaluated by a traffic sim-ulator The results indicate that our protocol can efficientlyfind the target nodes in the area It has also been found thatthe number of broadcasts is affected by nodesrsquo velocity Andthe fact that our protocol generates 30 less messages thanAODV has been proven here
As to future work our protocol can probably be extendedto solve the low delivery rate problem when the density ofvehicle is low
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgment
This work is supported in part by the Natural ScienceFoundation of China ldquoResearch on the snapshot data securitystorage technology for authorization of releaserdquo no 61100057
References
[1] C Rezende R W Pazzi and A Boukerche ldquoAn efficientneighborhoood prediction protocol to estimate link availabilityin VANETsrdquo in Proceedings of the 7th ACM International Sym-posiumonMobilityManagement andWireless Access (MobiWACrsquo09) pp 83ndash90 Tenerife Spain October 2009
[2] T Zahn G OrsquoShea and A Rowstron ldquoFeasibility of contentdissemination between devices in moving vehiclesrdquo in Proceed-ings of the 5th International Conference on Emerging NetworkingExperiments and Technologies (CoNEXT rsquo09) pp 97ndash108 RomeItaly December 2009
[3] N Wisitpongphan F Bai P Mudalige and O K Tonguz ldquoOnthe routing problem in disconnected vehicular ad Hoc net-worksrdquo in Proceedings of the 26th IEEE International Conferenceon Computer Communications (IEEE INFOCOM rsquo07) pp 2291ndash2295 Anchorage Alaska USA May 2007
[4] A Boukerche H A B F Oliveira E F Nakamura and A AF Loureiro ldquoVehicular Ad Hoc networks a new challenge forlocalization-based systemsrdquoComputer Communications vol 31no 12 pp 2838ndash2849 2008
[5] C E Perkins and P Bhagwat ldquoHighly dynamic destination-sequenced distance-vector routing (DSDV) for mobile com-putersrdquo in Proceedings of the Conference on CommunicationsArchitectures Protocols and Applications (SIGCOMM rsquo94) pp234ndash244 1994
[6] T Spyropoulos T Turletti and K Obraczka ldquoRouting indelay-tolerant networks comprising heterogeneous node pop-ulationsrdquo IEEE Transactions on Mobile Computing vol 8 no 8pp 1032ndash1047 2009
[7] C Lochert M Mauve H Fuszligler and H Hartenstein ldquoGeo-graphic routing in city scenariosrdquo Mobile Computing andCommunication Review vol 9 no 1 pp 69ndash72 2005
[8] M Jerbi and S M Senouci ldquoTowards efficient routing invehicular Ad Hoc networksrdquo in Proceedings of the 3rd IEEEInternational Workshop on Mobile Computing and Networking2006
[9] H Menouar M Lenardi and F Filali ldquoAn intelligentmovement-based routing for VANETsrdquo in Proceedings ofthe ITS World Congress London UK October 2006
[10] K Shafiee and V C M Leung Connectivity-Aware Minimum-Delay Geographic Routing with Vehicle Tracking in VANETsElsevier BV 2010
The Scientific World Journal 9
[11] J Haerri F Filali and C Bonnet ldquoPerformance comparisonof AODV and OLSR in VANETs urban environments underrealistic mobility patternsrdquo in Proceedings of the Med-Hoc-Net2006 5th Annual Mediterranean Ad Hoc NetworkingWorkshopLipari Italy June 2006
[12] C E Perkins and E M Royer ldquoAd-hoc on-demand distancevector routingrdquo in Proceedings of the 2nd IEEE Workshop onMobile Computing Systems and Applications (WMCSA rsquo99) pp90ndash100 New Orleans La USA February 1999
[13] T W Chen and M Gerla ldquoGlobal state routing a new routingscheme for Ad-hoc wireless networksrdquo in Proceedings of theIEEE International Conference on Communications (ICC rsquo98)vol 1 pp 171ndash175 Atlanta Ga USA June 1998
[14] B Karp and H T Kung ldquoGPSR greedy perimeter statelessrouting for wireless networksrdquo in Proceedings of the 6th AnnualInternational Conference on Mobile Computing and Networking(MOBICOM rsquo00) pp 243ndash254 Boston Mass USA August2000
[15] D B Johnson D A Maltz and J Broch ldquoDSR the dynamicsource routing protocol for multi-hop wireless Ad hoc net-worksrdquo in Ad Hoc Networking C E Perkins Ed chapter 5 pp139ndash172 Addison-Wesley New York NY USA 2001
[16] D B Johnson D A Maltz and J Broch ldquoDSR the dynamicsource routing protocol for multi-Hop wireless ad hoc net-worksrdquo in Ad Hoc Networking C E Perkins Ed chapter 5 pp139ndash172 Addison-Wesley New York NY USA 2001
[17] Z Wei and S Weibin ldquoResearch of GPSR routing protocol forwireless sensor networksrdquo Electronic Measurement Technologyvol 33 no 9 2010
[18] GWei Y Chen andX Zhu ldquoA vanet-oriented routing protocolfor intelligent taxi-call systemsrdquo in Proceedings of the IEEE 14thInternational Conference on Communication Technology (ICCTrsquo12) pp 41ndash45 Chengdu China November 2012
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DistributedSensor Networks
International Journal of
2 The Scientific World Journal
and will have bad effects on passengersrsquo experiences Wedescribe some of the work roughly in [18]
This paper aims to solve the quick topology change shortconnection duration and unstable wireless signal quality ofthe VANET network thus proposing a kind of lightweightrouting protocol applicable to the urban taxi-call withoutbase stations The protocol maintains and predicts neighborinformation dynamically in order to find the reliable pathbetween the source and the target This paper describes theprotocol in detail and evaluates the performance of thisprotocol by simulating under different nodes density andspeedThe result of evaluation shows that the performance ofLNIB is better than that of AODV which is a classic protocolin taxi-call scene
The second chapter analyzes the application and proposesthe model the third chapter describes the routing protocoland its algorithm the fourth chapter is about the experi-ment and data analyses chapter five concerns other relatedresearch the last part will draw a conclusion
2 Transmission Mode and Analyses
In the taxi-calling scene the vehicle network has two setstaxi nodes 119876 = 119902
1 1199022 119902119899 and passenger nodes 119875 =
1199011 1199012 119901119898 From the start of the call to get on the car
or the call to cancel a connection should be set up in thenetwork Because the passenger always waits at the originalplace or moves slowly suppose 119901 is a static node And 119901 onlyacts as the initiator of data transmission or receiver not asmediator in other routings The node 119902 can send receive oract as a routing node to transmit data Assume that the speedscalar of each node in 119876 is |V|
When 119901 initiates a call the message transits through thetaxi nodes so 119901 can quickly find nearby not-taken cars node119902119904that can meet the requirementsSupposing there are two nodes 119886 and 119887 in the network the
signal coverage radii for them are respectively 119877119886and 119877
119887 If
the distance between 119886 and 119887 is 119863119886119887le min(119877
119886 119877119887) it can
be called ldquomeetrdquo To be more general assuming that signalcoverage radius of each node in the network is 119877 then ldquomeetrdquoin time 119905 means 119863
119886119887(119905) le 119877 Define 119867
119886119902119904
as the minimalnumber of hops to transmit message from 119886 to 119902
119904 Among
all 119902119904that get the call request119867
119886is the lowest of119867
119886119902119904
21 Prediction Based on Neighbor Information In order topercept the current meet nodes in real time 119902 needs tosend broadcast packets to notice their own state informationperiodically In the starting time 119905 of every broadcast cycle119902 measures their own motion state including the speed thecurrent position and other information According to theabove information 119902 predicts the coordinates at the time of119905 + 119905119891and broadcasts the position The broadcast cycle is 119905
119887
If 119905119887is small then the channel will be occupied by a large
number of broadcast packets thus influencing the normaldata transmission However large 119905
119887will lose the predic-
tion value due to the frequent changes in actual situationTherefore 119905
119887should be set properly such as 10 seconds A
broadcast cycle can be divided intomultiple correction cycles
The node in a correction period measures their movementstate While finding the coordinatesrsquo different Δ119904 between thecurrent forecast coordinate at 119905 + 119905
119891and the last broadcast
coordinates surpasses it indicates that the vehiclersquos drivingcondition changes If Δ119904 is greater than a certain value thenode broadcasts the position again to correct the predictposition of itself in neighbor nodesrsquo state table thus to ensurethe prediction accuracy Suppose the correct period is 119905
119903
Meanwhile if 119902 receives the position broadcast of thenearby nodes it maintains an adjacent link (see Table 1) torecord node information that meets with 119902 It can be seenfrom the table that 119902
2measures its position and velocity at
131112101584036 and broadcasts 1199021receives the position broadcast
If11986311990211199022
(119905) le 119877 then it can be predicted that at 119905 + 119905119891 1199021and
1199022will keepmeeting If 119902
2is not in the table 119902
1adds the infor-
mation of 1199022to the table and sets 119902
2to be active If 119902
2is already
in the table update the information of 1199022 When 119902
1receives
the correction broadcast of 1199022 the position information of 119902
2
also needs updating If it can be predicted that 1199021and 1199023will
not meet at 119905 + 119905119891 set 119902
3to be inactive As to the inactive
node in the table if no broadcasts are received in more thanone broadcast cycle then delete the entry of this inactivenode Each time the passenger calls a taxi several links will beproduced If 119902
1and 1199023are neighbors and are both in one link
then they set up link ID in the entry for each other in theirown table Link ID is a large number that is randomly gener-ated It can be assumed that it is unique in a limited region
When 1199021receives the broadcast of neighbors at time 119905 it
will predict coordinates of itself and neighbor nodes at 119905 + 119905119891
respectively If the two cars can keep communication at thattime (such as 119902
2) the communication is effective Therefore
1199021stores the information of 119902
2in the table otherwise discards
it (such as the 1199023)
In order to provide the position information and routingof not-taken taxis the hop distance should be introducedwhen 119902 node is broadcasting message (including positionand correction broadcast) Periodically 119902
119904sets 119867
119902119904
to 0 andsends broadcastThe 119902
119904discards any broadcast information it
received without processing The 119902 sets119867119902value toinfin when
no neighbor nodes can reach 119902119904node When 119902
1receives the
broadcast of 1199022with the active state if 119867
1199022
+ 1 lt 1198671199021
1199021
modifies the1198671199021
value to1198671199022
+ 1Once 119867
1199021
changes 1199021will spread to notify neighbor
nodes to be updated by periodical breakfast But each cyclecan only update 1 hop on the link If 119867
11990211199022
= 119899 it needs 119899cycle to update119867
1199022
In order to improve the broadcast speed of119867 the sending
phase of each cycle is divided into two time slices The nodeof119867 changes but no broadcast will be broadcasted at the firsttime slice If the 119867 value has no change after last broadcastthe node broadcasts in the second time slice Thus the valueof119867may spread 2 hops in a cycle For the length of link willbe limited in 3-4 hops in the actual system two cycles cancomplete the information disclosure of not-taken taxis by theimproved broadcast speed
22 Links Setting and Handshake When 119901 launches the callit needs to find suitable not-taken taxis 119902
119904as soon as possible
and make an appointment In this process the following
The Scientific World Journal 3
Table 1 State of the 1199021rsquos Neighbor Nodes
Neighbor 119867119902119899119902119904
Position Direction of speed Link ID Reliability Measuringtime State
1199022
3 120213476E30321768N 119889
1199022
182378627 094 131112101584036 Active
1199023
5 120213484E30321775N 119889
1199023
452766732 083 131037101584034 Inactive
p
qa(H = 2)
qb(H = 5)
qc(H = 3)
qd(H = 1)
(a)
qs
q998400a(Dp1q119904= 200m)
q998400b(Dp3q119904= 300m)
(b)
Figure 1 (a) If there are the 119902 nodes within the single hop range of 119901 then they shake hands and choose one as 119902119886that has minimal hop
distance to 119902119904to make an appointment (b) If there are several 119902 nodes around 119902
119904and several 119901 nodes send the appointment requests then
they shake hands and choose the nearest 119901 node to response
questions need to be solved First how to find 119902119904in the
shortest time and establish the link to 119902119904 Secondly if there
are several 119902119904nodes how to choose one of the most suitable
ones to make an appointmentThe simplest method is to use the broadcast to send out
the call until a node of 119902119904receives the request and returns a
response The response will go backtracking to the 119901 nodeIf 119901 receives several responses then choose one from themafter which appointment confirmation will be sent to thechosen node through the path just set up Meanwhile itwill send negative responses to other not-taken taxis Thismethod is easy to be implemented but in the real VANETscene there are serious problems the message must pass thewhole link three times request response and appointmentOn the one hand it will lead to serious delay and difficulties inkeeping the link on the other hand the flooding of breakfastwill deteriorate the network environment and influence thenormal communication
This paper proposes a two-end handshake agreement togreat link (show as Figures 1 and 2) According to the neighbornodesrsquo information described in Section 21 each node canknow the nearest (by hop distance) 119902
119904and the shortest route
to arrive at the node If 119901 sending the request broadcast itsneighbor 119902 node which receives 119901rsquos breakfast directly canjudge whether it can reach 119902
119904or not In fact it is supposed
that the whole data transmission is a single route (the nodeon the link will transmit a message to only one neighbor
p qc qc qs
Figure 2 The two-end handshake agreement
node) Once 119902 is identified as the first hop the routing from119901 to 119902
119904will also be established The 119902 can directly send a
request response to the 119901 If 119901 receives responses from several119902 nodes it chooses a 119902 node as 119902
119886to make appointment
confirmation and send a veto appointment to other response119902 After that 119902
119886accepts the confirmation and sends it to the 119902
119904
4 The Scientific World Journal
based on the routing information that is to transmitmessageto the neighbor 119902 node in which 119867
119902= 119867119902119886
+ 1 On therouting node 1199021015840 will record the information of last hop whilereceiving the message Meanwhile transmit to the next hopwhich119867
119902= 1198671199021015840 + 1 until sent to the node which119867
119902= 0 that
is 119902119904The 119902119904end of the link also needs handshaking If several
neighbor 119902 nodes in which 119867119902= 1 are for the same 119902
119904
node they will send appointment requests to the 119902119904 and the
119902119904sends a confirmation response to one of them and negative
responses to othersThe two-end handshaking method can reduce the three
times handshaking to two times thus reducing the risk ofdelaying and disconnectionMeanwhile the broadcast can becontrolled in 1 hop and can avoid the flooding
23 Disconnection Suppose 119867119902119904
= 0 1198671199021
= 1 1198671199022
= 2 and1198671199023
= 3 If 1199022receives the position correction information
from 1199021 the adjusted position predictions indicate that 119902
1will
lose contact with 1199022 Since 119867
1199021
is the minimum 119867 stored in1199022 after 119902
2node deletes the 119902
1 it modifies its own119867 value to
infin and triggers an extra position correction broadcast Alsowhen 119902
3receives the position correction by this broadcast it
continues the same operationIn the communication process the effectiveness of link
should be guaranteed from the sending of 119901rsquos request to119902119904rsquos response return to 119901 Once a pair of nodes on the link
are disconnected it should be processed correspondentlyThe relatively ideal way is to find the third node beforedisconnection and to maintain the link Another simplemethod is to notify 119901 and 119902
119904to abandon the appointment on
both ends Thus it can avoid feedback loss which will resultin information consistency Then the 119901 initiates the requestprocess again
As the vehiclersquos speed is fast and unstable the time oflink maintains a relatively short time The frequently brokenlinks will lead to repeated reconnection To avoid this higherreliable links are required So in the 119902rsquos neighbor nodes statetable the reliability attribute is added for each neighbor nodeThe reliability refers to the prediction accuracy at 119905 + 119905
119891and
the help to effective datagram transmission on the link Itmainly depends on the following two conditions (1) during 119905to 119905 + 119905
119891period the relative position between 1199021015840 and 119902 If the
distance is far on the one hand the weak signal can lead totransmission instability on the other hand since 1199021015840 has beenclose to the edge of the 119902 communication range the slightchange of the vehicles will make 1199021015840 out of 119902rsquos communicationrange and cause broken connection If 1199021015840 and 119902 are closethe data transmission will take place in a short distance Thedatagramwill not move a lot in geographical location thus itinfluences the efficiency of data transmissionThus supposing1198801199021199021015840(1199051015840) = 2|119863
1199021199021015840(1199051015840) minus 119877|119877 refers to the transmission
reliability of 119902 and 1199021015840
1198801199021199021015840 (119905 119905 + 119905
119891) =
integration(119905 119905 + 119905
119891) (1)
Modify the condition of correcting 119867119902in Section 21
Given the reliable threshold 119903 isin [0 1] and after 1199021node
receives the broadcast of 1199022node if state (119902
2) = active119867
1199022
+
1 lt 1198671199021
and1198801199021199021015840(119905 119905 + 119905
119891) gt 119903 then modify the119867
1199021
value tobe 1199022+ 1
3 Protocol Implementation
In order to further introduce the implementation of theprotocol the pseudocode algorithms of taxi 119902 node andpassenger 119901 node are given respectively in this section Tobe simple based on the discussion in the second section thefollowing several types of datagram in the taxi-call networkwill be referred to
Broadcast (119871 119881119867 119905119888) represents position broadcast The
taxi node sends periodically and the nearby taxi nodereceives1198721minus6
represents the six kinds of datagrams in the two-endhandshaking protocol after the passengers make a request119872119890represents the cancelation of the reserved datagram
while finding the abnormal disconnectionAlgorithm 1 is divided into two parts The timer gets
the position and speed information for a short time (eg3 seconds) If the interval exceeds 119905
119891 then send broadcast
to the nodes around According to the current measureddata the position at 119905 + 119905
119891can be predicted If there exists
significant difference between the position and the position ofthe last broadcast then send broadcast without consideringwhether the time intervals exceed 119905
119891or not The timer will
also inspect the neighbor node that is not updated over timein the adjacency list and set these nodes as inactive Sincethe time in the record is the position measuring time toconsider the communication delay the overtime windowwillbe slightly amplified to 11119905
119891 If not updated for more than
two broadcast cycles then delete the nodeAs for the inactive nodes check whether they are in the
current communication connection If it is true then send119872119890
to other connected nodes to cancel the conformationThe other part of Algorithm 1 is the listener After the
listener receives a datagram heshe judges data types If it isthe position broadcast datagram then update the list Oncethe predicted node position changes are identified in thecurrent connection and in a short time will overpass thescope of communication and then notify other nodes on theconnection to cancel the appointmentWhen accepting othertypes of datagram again transmit or respond based on theprotocol
Algorithm 2 mainly includes two timers and a listenerWhen initiating the request timer
1is set At the same time
the listener will put the received response to the responsequeue When timer
1is triggered it checks the queue If the
queue is empty it means no response and it sends the requestagain Otherwise it chooses the response that has the nearesttransmission distance from passengers to not-taken taxis inorder to make appointment And it simultaneously sendsveto to other response nodes After sending the appointmentdatagram set timer
2 Once no appointment conformation
1198724in a certain time 119872
4 then the timer
2will be launched
and send request1198721again Attention here once the listener
receives an 119872119890 the datagram cancellation is caused by
The Scientific World Journal 5
Initialization 119905 = 0Initiate the prediction position 119878 = 0Initialization 119867 = infinSet timerTimer task()
Obtain the current position L speed V time 119879119888
119867new = 119867If (no-load)119867new = 0
Calculate prediction position 1198781015840 at (119905 + 119905119891)
If (119905119888minus 119905ge119905119891)
119867 = 119867newbroadcast(L V H 119905
119888)
119905 = 119905119888
119878 = 1198781015840
else if (|119878 minus 1198781015840| larger than threshold 119867 minus 119867new⟨⟩0)119867 = 119867new
broadcast(L V H 119905119888)
119905 = 119905119888
119878 = 1198781015840
For each node q in tableget qrsquos prediction time 119905
119902
if (state(q) == active ampamp 119905119888minus 119905119902ge 11119905
119891)
state(q) = inactiveif (q have the link ID)send119872
119890to other node which have the same lnik ID as q
If (119905119888minus 119905119902ge 2119905119891)
Remove q from table
Update H
Count = 0 reset 0 after passengers getting off or appointment cancellationBlock listen(Message)
Switch typeof(Message) Case119872
119887
update tableupdate Hif q node that sends119872
119887gets out of the communication range and it has link ID in the table
send119872119890to other node
which have the same link ID as qbreak
Case1198721
If (119867 lt infin)send1198722back
breakCase119872
3
If (Message == Reserve)If (119867 == 0 ampamp count == 0)
Count = 1send119872
4(Agree or Disagree) back
else if (119867 == 1)Set link IDsend119872
3to all q in table which119867
119902= 0
else
Algorithm 1 Continued
6 The Scientific World Journal
Set link IDsend119872
3to one q which119867
119902= 119867 minus 1
Case1198724
If (Message == Agree)Send119872
4forward to q which119867
119902= 119867 + 1
and have the same link IDdelete link ID
If (119867 == 1)Send Confirm back
Default
Algorithm 1 Algorithm of taxi node
Initiation queue = emptyCall taxi
Get its position LBroadcast(119872
1)
Set Timer1()
Timer1 task()If (queue = empty)
Call taxi()elseChoose the nearer hop qProduce link IDSend119872
3(Reserve link ID) to q
Send1198723(Negative) to other
Set timer2
Timer2 task() Call taxi() Block listen(Message)Switch typeof(Message)
Case1198722
Add q to queueBreak
Case1198724
Cancel Timer2Break
Case119872119890
Set Timer2 current timeBreak
Default
Algorithm 2 Algorithm of passenger node
connection errorThen immediately start the timer2and send
request again
4 Performance Analysis
In order to evaluate the performance of the proposed routingprotocol the paper uses NS2 and VanetMobiSim to simulate
TheNS2rsquosmain parameters are shown in Table 1The sim-ulation scene size is 5times 5 square kilometers InVanetMobiSimsimulation the scene size is 5times 5 square kilometers too In thetotal area there are 20 traffic signals and the entire simulationarea is divided into several regions In every region the densityof streets and the allowed maximum speed are different Theregions which have higher street density have lower allowedmaximum speed When vehicles get into the correspondingregion they choose the speed from street allowed maximumspeed and self-allowedmaximum speed with a low one In allof our simulations the empty taxis account for 40
We set the interval of route maintain message 119879119887to be
equal to 10 s and then set the maximum speed of taxi nodesto be equal to 60 kmh When we adjusted the density of taxinodes we got the probability of passenger node 119875 to findempty taxi node 119879
119863and the probability of node 119875 to receive
the message from 119879119863as shown in Table 3
As shown in Table 3 when node density is too low thetransmission range will be so small that it is hard to maintainthe information of nodes for a long time Hence when 119875appears the number of nodes that 119875 can communicate withis small and the time of link is short so that it is hard tocommunicate with 119879
119863 As the node density becomes higher
situations are getting better but some nodes have highervelocity which leads tomore failure Because the links chosenare the links that have long duration so the probability ofnode 119875 receiving acknowledgement messages from node 119879
119863
is pretty highThen if we fix the density of taxi nodes as 5 per km2 and
fix the transmission range as 500m we will get the relation ofthe maximum speed and the successful ratio
We called it successful calling when the passenger nodefinds the empty taxi node In Figure 3 we could see that whenthemaximumspeed of taxi is equal 60 kmh it has the highest
The Scientific World Journal 7
74
76
78
80
82Su
cces
sful r
ate (
)
Maximum speed (kmh)40 50 60 70 80 90 100
04
06
08
1
12
14
Link
bro
ken
ratio
()
Successful rateLink broken ratio
Figure 3 The relation of the maximum speed of taxi nodes and theratio of passenger node contacting empty taxi nodes successfully
successful ratio which enables the passenger node to find theempty taxi nodes This is because when the nodersquos movingspeed is low the node can contact with fewer other nodesAnd when the nodersquos moving speed is high the networktopology changes fast which causes fewer available routinglink and thus causes lower successful calling
Figure 4 shows the impact of nodersquos moving speed on theamount of switching packets of entire network
As shown in Figure 4 the amount of switching packetsgrows up as the vehicle movement speed increases Thisis because when the speed of node movement increases itcauses more correcting message resulting in the increaseof network data traffic In addition in one simulation therouting overhead is higher at the beginning and graduallydeclines over time This is because when the simulationstarts all taxi nodes are active at the same time and all taxinodes broadcast at the same time which causesmore channelcollision leading to an increasing number of retransmissionsAs time progresses due to the correcting message the taxirouting maintenance cycles gradually stagger and the entirenetwork routing overhead declines
Thenwe adjust the density of taxi nodes in the regionTheaverage density of taxi nodes is set at 1ndash6 per square kilometerand the vehiclemaximumspeed is set at 60 kmh and then theresults are shown in Figure 5
As shown in Figure 5 when the taxi nodes are scarcethe rate of the success calling drastically reduces Whileincreasing the number of taxi nodes the rate of success callingimproves accordingly This is because when the number oftaxi nodes is too small there is no taxi node around passengernode so that the passenger node cannot contact with anynode resulting in more calling failure When the numberof taxi nodes increase and the passenger node sends anappointment request the number of alternative routing pathsincreases so the node can choose a more stable routing pathto delivery packet thereby the rate of success calling willincrease
2 4 6 8 10
1900
1950
2000
2050
Ove
rhea
d (p
acke
t)
Time (min)
40kmh60kmh80kmh
Figure 4 The impact of nodersquos moving speed on the amount ofswitching packets of entire network
20
40
60
80
100
Succ
essfu
l rat
e (
)
1 2 3 4 5 60
2
4
6
8
Link
bro
ken
ratio
()
Successful ratioLink broken ratio
The density of taxi nodes (km2)
Figure 5 The impact of nodes density on successful ratio
Table 2 The NS2 parameters
Parameters ValuesLoss model PropagationTwoRayGroundPhysical model PhyWirelessPhyExtAntenna AntennaOmniAntennaTransmission rate 2MbpsNetwork protocol IEEE 80211
At last we control node velocity between 0 and 20msinterval of 119879
11988710 s transmission range is 500m and the
density is 4 per square kilometers Compared to AODV(show as Table 4) the results are shown in Table 2 We cansee that the proposed routing protocol performs better than
8 The Scientific World Journal
Table 3 The impact of nodes density and transmission range on successful calling ratio
Transmission rangeDensity of taxi
4 6The probability to
find 119879119863
The probability toreceive from 119879
119863
The probability to find119879119863
The probability toreceive from 119879
119863
200m 148 785 498 955300m 443 912 784 942500m 611 941 873 946
Table 4 Compare with AODV
CBLIGR AODVDelivery rate() 611 523Control messagepacket 12068 18150
AODV More importantly our protocol communication datais scattered throughout the network while AODV is relativelyconcentrated As a result our protocol performs better in thechannel collision It is because AODV requires a great dealof broadcast to maintain the entire link routing informationand has no efficient methods to deal with the disconnectionof links
5 Conclusion
This paper proposes a routing protocol for taxi-calling appli-cation Firstly it analyzes scenes of taxi-calling applicationand studies the differences between the common vehicleapplication scene and the taxi-calling application sceneSecondly it proposes the routing information maintainingalgorithm based on position prediction which performsbetter reliability Thirdly a self-network forming method fortaxi-calling application is drawn up
Our protocol queries the destination node by nodesrsquokeeping the information of the hop count to destination anddecreases the routing cost Meanwhile the validity of routesis guaranteed by predicting the future position of themselvesand their neighbors
This protocol has also been evaluated by a traffic sim-ulator The results indicate that our protocol can efficientlyfind the target nodes in the area It has also been found thatthe number of broadcasts is affected by nodesrsquo velocity Andthe fact that our protocol generates 30 less messages thanAODV has been proven here
As to future work our protocol can probably be extendedto solve the low delivery rate problem when the density ofvehicle is low
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgment
This work is supported in part by the Natural ScienceFoundation of China ldquoResearch on the snapshot data securitystorage technology for authorization of releaserdquo no 61100057
References
[1] C Rezende R W Pazzi and A Boukerche ldquoAn efficientneighborhoood prediction protocol to estimate link availabilityin VANETsrdquo in Proceedings of the 7th ACM International Sym-posiumonMobilityManagement andWireless Access (MobiWACrsquo09) pp 83ndash90 Tenerife Spain October 2009
[2] T Zahn G OrsquoShea and A Rowstron ldquoFeasibility of contentdissemination between devices in moving vehiclesrdquo in Proceed-ings of the 5th International Conference on Emerging NetworkingExperiments and Technologies (CoNEXT rsquo09) pp 97ndash108 RomeItaly December 2009
[3] N Wisitpongphan F Bai P Mudalige and O K Tonguz ldquoOnthe routing problem in disconnected vehicular ad Hoc net-worksrdquo in Proceedings of the 26th IEEE International Conferenceon Computer Communications (IEEE INFOCOM rsquo07) pp 2291ndash2295 Anchorage Alaska USA May 2007
[4] A Boukerche H A B F Oliveira E F Nakamura and A AF Loureiro ldquoVehicular Ad Hoc networks a new challenge forlocalization-based systemsrdquoComputer Communications vol 31no 12 pp 2838ndash2849 2008
[5] C E Perkins and P Bhagwat ldquoHighly dynamic destination-sequenced distance-vector routing (DSDV) for mobile com-putersrdquo in Proceedings of the Conference on CommunicationsArchitectures Protocols and Applications (SIGCOMM rsquo94) pp234ndash244 1994
[6] T Spyropoulos T Turletti and K Obraczka ldquoRouting indelay-tolerant networks comprising heterogeneous node pop-ulationsrdquo IEEE Transactions on Mobile Computing vol 8 no 8pp 1032ndash1047 2009
[7] C Lochert M Mauve H Fuszligler and H Hartenstein ldquoGeo-graphic routing in city scenariosrdquo Mobile Computing andCommunication Review vol 9 no 1 pp 69ndash72 2005
[8] M Jerbi and S M Senouci ldquoTowards efficient routing invehicular Ad Hoc networksrdquo in Proceedings of the 3rd IEEEInternational Workshop on Mobile Computing and Networking2006
[9] H Menouar M Lenardi and F Filali ldquoAn intelligentmovement-based routing for VANETsrdquo in Proceedings ofthe ITS World Congress London UK October 2006
[10] K Shafiee and V C M Leung Connectivity-Aware Minimum-Delay Geographic Routing with Vehicle Tracking in VANETsElsevier BV 2010
The Scientific World Journal 9
[11] J Haerri F Filali and C Bonnet ldquoPerformance comparisonof AODV and OLSR in VANETs urban environments underrealistic mobility patternsrdquo in Proceedings of the Med-Hoc-Net2006 5th Annual Mediterranean Ad Hoc NetworkingWorkshopLipari Italy June 2006
[12] C E Perkins and E M Royer ldquoAd-hoc on-demand distancevector routingrdquo in Proceedings of the 2nd IEEE Workshop onMobile Computing Systems and Applications (WMCSA rsquo99) pp90ndash100 New Orleans La USA February 1999
[13] T W Chen and M Gerla ldquoGlobal state routing a new routingscheme for Ad-hoc wireless networksrdquo in Proceedings of theIEEE International Conference on Communications (ICC rsquo98)vol 1 pp 171ndash175 Atlanta Ga USA June 1998
[14] B Karp and H T Kung ldquoGPSR greedy perimeter statelessrouting for wireless networksrdquo in Proceedings of the 6th AnnualInternational Conference on Mobile Computing and Networking(MOBICOM rsquo00) pp 243ndash254 Boston Mass USA August2000
[15] D B Johnson D A Maltz and J Broch ldquoDSR the dynamicsource routing protocol for multi-hop wireless Ad hoc net-worksrdquo in Ad Hoc Networking C E Perkins Ed chapter 5 pp139ndash172 Addison-Wesley New York NY USA 2001
[16] D B Johnson D A Maltz and J Broch ldquoDSR the dynamicsource routing protocol for multi-Hop wireless ad hoc net-worksrdquo in Ad Hoc Networking C E Perkins Ed chapter 5 pp139ndash172 Addison-Wesley New York NY USA 2001
[17] Z Wei and S Weibin ldquoResearch of GPSR routing protocol forwireless sensor networksrdquo Electronic Measurement Technologyvol 33 no 9 2010
[18] GWei Y Chen andX Zhu ldquoA vanet-oriented routing protocolfor intelligent taxi-call systemsrdquo in Proceedings of the IEEE 14thInternational Conference on Communication Technology (ICCTrsquo12) pp 41ndash45 Chengdu China November 2012
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
The Scientific World Journal 3
Table 1 State of the 1199021rsquos Neighbor Nodes
Neighbor 119867119902119899119902119904
Position Direction of speed Link ID Reliability Measuringtime State
1199022
3 120213476E30321768N 119889
1199022
182378627 094 131112101584036 Active
1199023
5 120213484E30321775N 119889
1199023
452766732 083 131037101584034 Inactive
p
qa(H = 2)
qb(H = 5)
qc(H = 3)
qd(H = 1)
(a)
qs
q998400a(Dp1q119904= 200m)
q998400b(Dp3q119904= 300m)
(b)
Figure 1 (a) If there are the 119902 nodes within the single hop range of 119901 then they shake hands and choose one as 119902119886that has minimal hop
distance to 119902119904to make an appointment (b) If there are several 119902 nodes around 119902
119904and several 119901 nodes send the appointment requests then
they shake hands and choose the nearest 119901 node to response
questions need to be solved First how to find 119902119904in the
shortest time and establish the link to 119902119904 Secondly if there
are several 119902119904nodes how to choose one of the most suitable
ones to make an appointmentThe simplest method is to use the broadcast to send out
the call until a node of 119902119904receives the request and returns a
response The response will go backtracking to the 119901 nodeIf 119901 receives several responses then choose one from themafter which appointment confirmation will be sent to thechosen node through the path just set up Meanwhile itwill send negative responses to other not-taken taxis Thismethod is easy to be implemented but in the real VANETscene there are serious problems the message must pass thewhole link three times request response and appointmentOn the one hand it will lead to serious delay and difficulties inkeeping the link on the other hand the flooding of breakfastwill deteriorate the network environment and influence thenormal communication
This paper proposes a two-end handshake agreement togreat link (show as Figures 1 and 2) According to the neighbornodesrsquo information described in Section 21 each node canknow the nearest (by hop distance) 119902
119904and the shortest route
to arrive at the node If 119901 sending the request broadcast itsneighbor 119902 node which receives 119901rsquos breakfast directly canjudge whether it can reach 119902
119904or not In fact it is supposed
that the whole data transmission is a single route (the nodeon the link will transmit a message to only one neighbor
p qc qc qs
Figure 2 The two-end handshake agreement
node) Once 119902 is identified as the first hop the routing from119901 to 119902
119904will also be established The 119902 can directly send a
request response to the 119901 If 119901 receives responses from several119902 nodes it chooses a 119902 node as 119902
119886to make appointment
confirmation and send a veto appointment to other response119902 After that 119902
119886accepts the confirmation and sends it to the 119902
119904
4 The Scientific World Journal
based on the routing information that is to transmitmessageto the neighbor 119902 node in which 119867
119902= 119867119902119886
+ 1 On therouting node 1199021015840 will record the information of last hop whilereceiving the message Meanwhile transmit to the next hopwhich119867
119902= 1198671199021015840 + 1 until sent to the node which119867
119902= 0 that
is 119902119904The 119902119904end of the link also needs handshaking If several
neighbor 119902 nodes in which 119867119902= 1 are for the same 119902
119904
node they will send appointment requests to the 119902119904 and the
119902119904sends a confirmation response to one of them and negative
responses to othersThe two-end handshaking method can reduce the three
times handshaking to two times thus reducing the risk ofdelaying and disconnectionMeanwhile the broadcast can becontrolled in 1 hop and can avoid the flooding
23 Disconnection Suppose 119867119902119904
= 0 1198671199021
= 1 1198671199022
= 2 and1198671199023
= 3 If 1199022receives the position correction information
from 1199021 the adjusted position predictions indicate that 119902
1will
lose contact with 1199022 Since 119867
1199021
is the minimum 119867 stored in1199022 after 119902
2node deletes the 119902
1 it modifies its own119867 value to
infin and triggers an extra position correction broadcast Alsowhen 119902
3receives the position correction by this broadcast it
continues the same operationIn the communication process the effectiveness of link
should be guaranteed from the sending of 119901rsquos request to119902119904rsquos response return to 119901 Once a pair of nodes on the link
are disconnected it should be processed correspondentlyThe relatively ideal way is to find the third node beforedisconnection and to maintain the link Another simplemethod is to notify 119901 and 119902
119904to abandon the appointment on
both ends Thus it can avoid feedback loss which will resultin information consistency Then the 119901 initiates the requestprocess again
As the vehiclersquos speed is fast and unstable the time oflink maintains a relatively short time The frequently brokenlinks will lead to repeated reconnection To avoid this higherreliable links are required So in the 119902rsquos neighbor nodes statetable the reliability attribute is added for each neighbor nodeThe reliability refers to the prediction accuracy at 119905 + 119905
119891and
the help to effective datagram transmission on the link Itmainly depends on the following two conditions (1) during 119905to 119905 + 119905
119891period the relative position between 1199021015840 and 119902 If the
distance is far on the one hand the weak signal can lead totransmission instability on the other hand since 1199021015840 has beenclose to the edge of the 119902 communication range the slightchange of the vehicles will make 1199021015840 out of 119902rsquos communicationrange and cause broken connection If 1199021015840 and 119902 are closethe data transmission will take place in a short distance Thedatagramwill not move a lot in geographical location thus itinfluences the efficiency of data transmissionThus supposing1198801199021199021015840(1199051015840) = 2|119863
1199021199021015840(1199051015840) minus 119877|119877 refers to the transmission
reliability of 119902 and 1199021015840
1198801199021199021015840 (119905 119905 + 119905
119891) =
integration(119905 119905 + 119905
119891) (1)
Modify the condition of correcting 119867119902in Section 21
Given the reliable threshold 119903 isin [0 1] and after 1199021node
receives the broadcast of 1199022node if state (119902
2) = active119867
1199022
+
1 lt 1198671199021
and1198801199021199021015840(119905 119905 + 119905
119891) gt 119903 then modify the119867
1199021
value tobe 1199022+ 1
3 Protocol Implementation
In order to further introduce the implementation of theprotocol the pseudocode algorithms of taxi 119902 node andpassenger 119901 node are given respectively in this section Tobe simple based on the discussion in the second section thefollowing several types of datagram in the taxi-call networkwill be referred to
Broadcast (119871 119881119867 119905119888) represents position broadcast The
taxi node sends periodically and the nearby taxi nodereceives1198721minus6
represents the six kinds of datagrams in the two-endhandshaking protocol after the passengers make a request119872119890represents the cancelation of the reserved datagram
while finding the abnormal disconnectionAlgorithm 1 is divided into two parts The timer gets
the position and speed information for a short time (eg3 seconds) If the interval exceeds 119905
119891 then send broadcast
to the nodes around According to the current measureddata the position at 119905 + 119905
119891can be predicted If there exists
significant difference between the position and the position ofthe last broadcast then send broadcast without consideringwhether the time intervals exceed 119905
119891or not The timer will
also inspect the neighbor node that is not updated over timein the adjacency list and set these nodes as inactive Sincethe time in the record is the position measuring time toconsider the communication delay the overtime windowwillbe slightly amplified to 11119905
119891 If not updated for more than
two broadcast cycles then delete the nodeAs for the inactive nodes check whether they are in the
current communication connection If it is true then send119872119890
to other connected nodes to cancel the conformationThe other part of Algorithm 1 is the listener After the
listener receives a datagram heshe judges data types If it isthe position broadcast datagram then update the list Oncethe predicted node position changes are identified in thecurrent connection and in a short time will overpass thescope of communication and then notify other nodes on theconnection to cancel the appointmentWhen accepting othertypes of datagram again transmit or respond based on theprotocol
Algorithm 2 mainly includes two timers and a listenerWhen initiating the request timer
1is set At the same time
the listener will put the received response to the responsequeue When timer
1is triggered it checks the queue If the
queue is empty it means no response and it sends the requestagain Otherwise it chooses the response that has the nearesttransmission distance from passengers to not-taken taxis inorder to make appointment And it simultaneously sendsveto to other response nodes After sending the appointmentdatagram set timer
2 Once no appointment conformation
1198724in a certain time 119872
4 then the timer
2will be launched
and send request1198721again Attention here once the listener
receives an 119872119890 the datagram cancellation is caused by
The Scientific World Journal 5
Initialization 119905 = 0Initiate the prediction position 119878 = 0Initialization 119867 = infinSet timerTimer task()
Obtain the current position L speed V time 119879119888
119867new = 119867If (no-load)119867new = 0
Calculate prediction position 1198781015840 at (119905 + 119905119891)
If (119905119888minus 119905ge119905119891)
119867 = 119867newbroadcast(L V H 119905
119888)
119905 = 119905119888
119878 = 1198781015840
else if (|119878 minus 1198781015840| larger than threshold 119867 minus 119867new⟨⟩0)119867 = 119867new
broadcast(L V H 119905119888)
119905 = 119905119888
119878 = 1198781015840
For each node q in tableget qrsquos prediction time 119905
119902
if (state(q) == active ampamp 119905119888minus 119905119902ge 11119905
119891)
state(q) = inactiveif (q have the link ID)send119872
119890to other node which have the same lnik ID as q
If (119905119888minus 119905119902ge 2119905119891)
Remove q from table
Update H
Count = 0 reset 0 after passengers getting off or appointment cancellationBlock listen(Message)
Switch typeof(Message) Case119872
119887
update tableupdate Hif q node that sends119872
119887gets out of the communication range and it has link ID in the table
send119872119890to other node
which have the same link ID as qbreak
Case1198721
If (119867 lt infin)send1198722back
breakCase119872
3
If (Message == Reserve)If (119867 == 0 ampamp count == 0)
Count = 1send119872
4(Agree or Disagree) back
else if (119867 == 1)Set link IDsend119872
3to all q in table which119867
119902= 0
else
Algorithm 1 Continued
6 The Scientific World Journal
Set link IDsend119872
3to one q which119867
119902= 119867 minus 1
Case1198724
If (Message == Agree)Send119872
4forward to q which119867
119902= 119867 + 1
and have the same link IDdelete link ID
If (119867 == 1)Send Confirm back
Default
Algorithm 1 Algorithm of taxi node
Initiation queue = emptyCall taxi
Get its position LBroadcast(119872
1)
Set Timer1()
Timer1 task()If (queue = empty)
Call taxi()elseChoose the nearer hop qProduce link IDSend119872
3(Reserve link ID) to q
Send1198723(Negative) to other
Set timer2
Timer2 task() Call taxi() Block listen(Message)Switch typeof(Message)
Case1198722
Add q to queueBreak
Case1198724
Cancel Timer2Break
Case119872119890
Set Timer2 current timeBreak
Default
Algorithm 2 Algorithm of passenger node
connection errorThen immediately start the timer2and send
request again
4 Performance Analysis
In order to evaluate the performance of the proposed routingprotocol the paper uses NS2 and VanetMobiSim to simulate
TheNS2rsquosmain parameters are shown in Table 1The sim-ulation scene size is 5times 5 square kilometers InVanetMobiSimsimulation the scene size is 5times 5 square kilometers too In thetotal area there are 20 traffic signals and the entire simulationarea is divided into several regions In every region the densityof streets and the allowed maximum speed are different Theregions which have higher street density have lower allowedmaximum speed When vehicles get into the correspondingregion they choose the speed from street allowed maximumspeed and self-allowedmaximum speed with a low one In allof our simulations the empty taxis account for 40
We set the interval of route maintain message 119879119887to be
equal to 10 s and then set the maximum speed of taxi nodesto be equal to 60 kmh When we adjusted the density of taxinodes we got the probability of passenger node 119875 to findempty taxi node 119879
119863and the probability of node 119875 to receive
the message from 119879119863as shown in Table 3
As shown in Table 3 when node density is too low thetransmission range will be so small that it is hard to maintainthe information of nodes for a long time Hence when 119875appears the number of nodes that 119875 can communicate withis small and the time of link is short so that it is hard tocommunicate with 119879
119863 As the node density becomes higher
situations are getting better but some nodes have highervelocity which leads tomore failure Because the links chosenare the links that have long duration so the probability ofnode 119875 receiving acknowledgement messages from node 119879
119863
is pretty highThen if we fix the density of taxi nodes as 5 per km2 and
fix the transmission range as 500m we will get the relation ofthe maximum speed and the successful ratio
We called it successful calling when the passenger nodefinds the empty taxi node In Figure 3 we could see that whenthemaximumspeed of taxi is equal 60 kmh it has the highest
The Scientific World Journal 7
74
76
78
80
82Su
cces
sful r
ate (
)
Maximum speed (kmh)40 50 60 70 80 90 100
04
06
08
1
12
14
Link
bro
ken
ratio
()
Successful rateLink broken ratio
Figure 3 The relation of the maximum speed of taxi nodes and theratio of passenger node contacting empty taxi nodes successfully
successful ratio which enables the passenger node to find theempty taxi nodes This is because when the nodersquos movingspeed is low the node can contact with fewer other nodesAnd when the nodersquos moving speed is high the networktopology changes fast which causes fewer available routinglink and thus causes lower successful calling
Figure 4 shows the impact of nodersquos moving speed on theamount of switching packets of entire network
As shown in Figure 4 the amount of switching packetsgrows up as the vehicle movement speed increases Thisis because when the speed of node movement increases itcauses more correcting message resulting in the increaseof network data traffic In addition in one simulation therouting overhead is higher at the beginning and graduallydeclines over time This is because when the simulationstarts all taxi nodes are active at the same time and all taxinodes broadcast at the same time which causesmore channelcollision leading to an increasing number of retransmissionsAs time progresses due to the correcting message the taxirouting maintenance cycles gradually stagger and the entirenetwork routing overhead declines
Thenwe adjust the density of taxi nodes in the regionTheaverage density of taxi nodes is set at 1ndash6 per square kilometerand the vehiclemaximumspeed is set at 60 kmh and then theresults are shown in Figure 5
As shown in Figure 5 when the taxi nodes are scarcethe rate of the success calling drastically reduces Whileincreasing the number of taxi nodes the rate of success callingimproves accordingly This is because when the number oftaxi nodes is too small there is no taxi node around passengernode so that the passenger node cannot contact with anynode resulting in more calling failure When the numberof taxi nodes increase and the passenger node sends anappointment request the number of alternative routing pathsincreases so the node can choose a more stable routing pathto delivery packet thereby the rate of success calling willincrease
2 4 6 8 10
1900
1950
2000
2050
Ove
rhea
d (p
acke
t)
Time (min)
40kmh60kmh80kmh
Figure 4 The impact of nodersquos moving speed on the amount ofswitching packets of entire network
20
40
60
80
100
Succ
essfu
l rat
e (
)
1 2 3 4 5 60
2
4
6
8
Link
bro
ken
ratio
()
Successful ratioLink broken ratio
The density of taxi nodes (km2)
Figure 5 The impact of nodes density on successful ratio
Table 2 The NS2 parameters
Parameters ValuesLoss model PropagationTwoRayGroundPhysical model PhyWirelessPhyExtAntenna AntennaOmniAntennaTransmission rate 2MbpsNetwork protocol IEEE 80211
At last we control node velocity between 0 and 20msinterval of 119879
11988710 s transmission range is 500m and the
density is 4 per square kilometers Compared to AODV(show as Table 4) the results are shown in Table 2 We cansee that the proposed routing protocol performs better than
8 The Scientific World Journal
Table 3 The impact of nodes density and transmission range on successful calling ratio
Transmission rangeDensity of taxi
4 6The probability to
find 119879119863
The probability toreceive from 119879
119863
The probability to find119879119863
The probability toreceive from 119879
119863
200m 148 785 498 955300m 443 912 784 942500m 611 941 873 946
Table 4 Compare with AODV
CBLIGR AODVDelivery rate() 611 523Control messagepacket 12068 18150
AODV More importantly our protocol communication datais scattered throughout the network while AODV is relativelyconcentrated As a result our protocol performs better in thechannel collision It is because AODV requires a great dealof broadcast to maintain the entire link routing informationand has no efficient methods to deal with the disconnectionof links
5 Conclusion
This paper proposes a routing protocol for taxi-calling appli-cation Firstly it analyzes scenes of taxi-calling applicationand studies the differences between the common vehicleapplication scene and the taxi-calling application sceneSecondly it proposes the routing information maintainingalgorithm based on position prediction which performsbetter reliability Thirdly a self-network forming method fortaxi-calling application is drawn up
Our protocol queries the destination node by nodesrsquokeeping the information of the hop count to destination anddecreases the routing cost Meanwhile the validity of routesis guaranteed by predicting the future position of themselvesand their neighbors
This protocol has also been evaluated by a traffic sim-ulator The results indicate that our protocol can efficientlyfind the target nodes in the area It has also been found thatthe number of broadcasts is affected by nodesrsquo velocity Andthe fact that our protocol generates 30 less messages thanAODV has been proven here
As to future work our protocol can probably be extendedto solve the low delivery rate problem when the density ofvehicle is low
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgment
This work is supported in part by the Natural ScienceFoundation of China ldquoResearch on the snapshot data securitystorage technology for authorization of releaserdquo no 61100057
References
[1] C Rezende R W Pazzi and A Boukerche ldquoAn efficientneighborhoood prediction protocol to estimate link availabilityin VANETsrdquo in Proceedings of the 7th ACM International Sym-posiumonMobilityManagement andWireless Access (MobiWACrsquo09) pp 83ndash90 Tenerife Spain October 2009
[2] T Zahn G OrsquoShea and A Rowstron ldquoFeasibility of contentdissemination between devices in moving vehiclesrdquo in Proceed-ings of the 5th International Conference on Emerging NetworkingExperiments and Technologies (CoNEXT rsquo09) pp 97ndash108 RomeItaly December 2009
[3] N Wisitpongphan F Bai P Mudalige and O K Tonguz ldquoOnthe routing problem in disconnected vehicular ad Hoc net-worksrdquo in Proceedings of the 26th IEEE International Conferenceon Computer Communications (IEEE INFOCOM rsquo07) pp 2291ndash2295 Anchorage Alaska USA May 2007
[4] A Boukerche H A B F Oliveira E F Nakamura and A AF Loureiro ldquoVehicular Ad Hoc networks a new challenge forlocalization-based systemsrdquoComputer Communications vol 31no 12 pp 2838ndash2849 2008
[5] C E Perkins and P Bhagwat ldquoHighly dynamic destination-sequenced distance-vector routing (DSDV) for mobile com-putersrdquo in Proceedings of the Conference on CommunicationsArchitectures Protocols and Applications (SIGCOMM rsquo94) pp234ndash244 1994
[6] T Spyropoulos T Turletti and K Obraczka ldquoRouting indelay-tolerant networks comprising heterogeneous node pop-ulationsrdquo IEEE Transactions on Mobile Computing vol 8 no 8pp 1032ndash1047 2009
[7] C Lochert M Mauve H Fuszligler and H Hartenstein ldquoGeo-graphic routing in city scenariosrdquo Mobile Computing andCommunication Review vol 9 no 1 pp 69ndash72 2005
[8] M Jerbi and S M Senouci ldquoTowards efficient routing invehicular Ad Hoc networksrdquo in Proceedings of the 3rd IEEEInternational Workshop on Mobile Computing and Networking2006
[9] H Menouar M Lenardi and F Filali ldquoAn intelligentmovement-based routing for VANETsrdquo in Proceedings ofthe ITS World Congress London UK October 2006
[10] K Shafiee and V C M Leung Connectivity-Aware Minimum-Delay Geographic Routing with Vehicle Tracking in VANETsElsevier BV 2010
The Scientific World Journal 9
[11] J Haerri F Filali and C Bonnet ldquoPerformance comparisonof AODV and OLSR in VANETs urban environments underrealistic mobility patternsrdquo in Proceedings of the Med-Hoc-Net2006 5th Annual Mediterranean Ad Hoc NetworkingWorkshopLipari Italy June 2006
[12] C E Perkins and E M Royer ldquoAd-hoc on-demand distancevector routingrdquo in Proceedings of the 2nd IEEE Workshop onMobile Computing Systems and Applications (WMCSA rsquo99) pp90ndash100 New Orleans La USA February 1999
[13] T W Chen and M Gerla ldquoGlobal state routing a new routingscheme for Ad-hoc wireless networksrdquo in Proceedings of theIEEE International Conference on Communications (ICC rsquo98)vol 1 pp 171ndash175 Atlanta Ga USA June 1998
[14] B Karp and H T Kung ldquoGPSR greedy perimeter statelessrouting for wireless networksrdquo in Proceedings of the 6th AnnualInternational Conference on Mobile Computing and Networking(MOBICOM rsquo00) pp 243ndash254 Boston Mass USA August2000
[15] D B Johnson D A Maltz and J Broch ldquoDSR the dynamicsource routing protocol for multi-hop wireless Ad hoc net-worksrdquo in Ad Hoc Networking C E Perkins Ed chapter 5 pp139ndash172 Addison-Wesley New York NY USA 2001
[16] D B Johnson D A Maltz and J Broch ldquoDSR the dynamicsource routing protocol for multi-Hop wireless ad hoc net-worksrdquo in Ad Hoc Networking C E Perkins Ed chapter 5 pp139ndash172 Addison-Wesley New York NY USA 2001
[17] Z Wei and S Weibin ldquoResearch of GPSR routing protocol forwireless sensor networksrdquo Electronic Measurement Technologyvol 33 no 9 2010
[18] GWei Y Chen andX Zhu ldquoA vanet-oriented routing protocolfor intelligent taxi-call systemsrdquo in Proceedings of the IEEE 14thInternational Conference on Communication Technology (ICCTrsquo12) pp 41ndash45 Chengdu China November 2012
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
4 The Scientific World Journal
based on the routing information that is to transmitmessageto the neighbor 119902 node in which 119867
119902= 119867119902119886
+ 1 On therouting node 1199021015840 will record the information of last hop whilereceiving the message Meanwhile transmit to the next hopwhich119867
119902= 1198671199021015840 + 1 until sent to the node which119867
119902= 0 that
is 119902119904The 119902119904end of the link also needs handshaking If several
neighbor 119902 nodes in which 119867119902= 1 are for the same 119902
119904
node they will send appointment requests to the 119902119904 and the
119902119904sends a confirmation response to one of them and negative
responses to othersThe two-end handshaking method can reduce the three
times handshaking to two times thus reducing the risk ofdelaying and disconnectionMeanwhile the broadcast can becontrolled in 1 hop and can avoid the flooding
23 Disconnection Suppose 119867119902119904
= 0 1198671199021
= 1 1198671199022
= 2 and1198671199023
= 3 If 1199022receives the position correction information
from 1199021 the adjusted position predictions indicate that 119902
1will
lose contact with 1199022 Since 119867
1199021
is the minimum 119867 stored in1199022 after 119902
2node deletes the 119902
1 it modifies its own119867 value to
infin and triggers an extra position correction broadcast Alsowhen 119902
3receives the position correction by this broadcast it
continues the same operationIn the communication process the effectiveness of link
should be guaranteed from the sending of 119901rsquos request to119902119904rsquos response return to 119901 Once a pair of nodes on the link
are disconnected it should be processed correspondentlyThe relatively ideal way is to find the third node beforedisconnection and to maintain the link Another simplemethod is to notify 119901 and 119902
119904to abandon the appointment on
both ends Thus it can avoid feedback loss which will resultin information consistency Then the 119901 initiates the requestprocess again
As the vehiclersquos speed is fast and unstable the time oflink maintains a relatively short time The frequently brokenlinks will lead to repeated reconnection To avoid this higherreliable links are required So in the 119902rsquos neighbor nodes statetable the reliability attribute is added for each neighbor nodeThe reliability refers to the prediction accuracy at 119905 + 119905
119891and
the help to effective datagram transmission on the link Itmainly depends on the following two conditions (1) during 119905to 119905 + 119905
119891period the relative position between 1199021015840 and 119902 If the
distance is far on the one hand the weak signal can lead totransmission instability on the other hand since 1199021015840 has beenclose to the edge of the 119902 communication range the slightchange of the vehicles will make 1199021015840 out of 119902rsquos communicationrange and cause broken connection If 1199021015840 and 119902 are closethe data transmission will take place in a short distance Thedatagramwill not move a lot in geographical location thus itinfluences the efficiency of data transmissionThus supposing1198801199021199021015840(1199051015840) = 2|119863
1199021199021015840(1199051015840) minus 119877|119877 refers to the transmission
reliability of 119902 and 1199021015840
1198801199021199021015840 (119905 119905 + 119905
119891) =
integration(119905 119905 + 119905
119891) (1)
Modify the condition of correcting 119867119902in Section 21
Given the reliable threshold 119903 isin [0 1] and after 1199021node
receives the broadcast of 1199022node if state (119902
2) = active119867
1199022
+
1 lt 1198671199021
and1198801199021199021015840(119905 119905 + 119905
119891) gt 119903 then modify the119867
1199021
value tobe 1199022+ 1
3 Protocol Implementation
In order to further introduce the implementation of theprotocol the pseudocode algorithms of taxi 119902 node andpassenger 119901 node are given respectively in this section Tobe simple based on the discussion in the second section thefollowing several types of datagram in the taxi-call networkwill be referred to
Broadcast (119871 119881119867 119905119888) represents position broadcast The
taxi node sends periodically and the nearby taxi nodereceives1198721minus6
represents the six kinds of datagrams in the two-endhandshaking protocol after the passengers make a request119872119890represents the cancelation of the reserved datagram
while finding the abnormal disconnectionAlgorithm 1 is divided into two parts The timer gets
the position and speed information for a short time (eg3 seconds) If the interval exceeds 119905
119891 then send broadcast
to the nodes around According to the current measureddata the position at 119905 + 119905
119891can be predicted If there exists
significant difference between the position and the position ofthe last broadcast then send broadcast without consideringwhether the time intervals exceed 119905
119891or not The timer will
also inspect the neighbor node that is not updated over timein the adjacency list and set these nodes as inactive Sincethe time in the record is the position measuring time toconsider the communication delay the overtime windowwillbe slightly amplified to 11119905
119891 If not updated for more than
two broadcast cycles then delete the nodeAs for the inactive nodes check whether they are in the
current communication connection If it is true then send119872119890
to other connected nodes to cancel the conformationThe other part of Algorithm 1 is the listener After the
listener receives a datagram heshe judges data types If it isthe position broadcast datagram then update the list Oncethe predicted node position changes are identified in thecurrent connection and in a short time will overpass thescope of communication and then notify other nodes on theconnection to cancel the appointmentWhen accepting othertypes of datagram again transmit or respond based on theprotocol
Algorithm 2 mainly includes two timers and a listenerWhen initiating the request timer
1is set At the same time
the listener will put the received response to the responsequeue When timer
1is triggered it checks the queue If the
queue is empty it means no response and it sends the requestagain Otherwise it chooses the response that has the nearesttransmission distance from passengers to not-taken taxis inorder to make appointment And it simultaneously sendsveto to other response nodes After sending the appointmentdatagram set timer
2 Once no appointment conformation
1198724in a certain time 119872
4 then the timer
2will be launched
and send request1198721again Attention here once the listener
receives an 119872119890 the datagram cancellation is caused by
The Scientific World Journal 5
Initialization 119905 = 0Initiate the prediction position 119878 = 0Initialization 119867 = infinSet timerTimer task()
Obtain the current position L speed V time 119879119888
119867new = 119867If (no-load)119867new = 0
Calculate prediction position 1198781015840 at (119905 + 119905119891)
If (119905119888minus 119905ge119905119891)
119867 = 119867newbroadcast(L V H 119905
119888)
119905 = 119905119888
119878 = 1198781015840
else if (|119878 minus 1198781015840| larger than threshold 119867 minus 119867new⟨⟩0)119867 = 119867new
broadcast(L V H 119905119888)
119905 = 119905119888
119878 = 1198781015840
For each node q in tableget qrsquos prediction time 119905
119902
if (state(q) == active ampamp 119905119888minus 119905119902ge 11119905
119891)
state(q) = inactiveif (q have the link ID)send119872
119890to other node which have the same lnik ID as q
If (119905119888minus 119905119902ge 2119905119891)
Remove q from table
Update H
Count = 0 reset 0 after passengers getting off or appointment cancellationBlock listen(Message)
Switch typeof(Message) Case119872
119887
update tableupdate Hif q node that sends119872
119887gets out of the communication range and it has link ID in the table
send119872119890to other node
which have the same link ID as qbreak
Case1198721
If (119867 lt infin)send1198722back
breakCase119872
3
If (Message == Reserve)If (119867 == 0 ampamp count == 0)
Count = 1send119872
4(Agree or Disagree) back
else if (119867 == 1)Set link IDsend119872
3to all q in table which119867
119902= 0
else
Algorithm 1 Continued
6 The Scientific World Journal
Set link IDsend119872
3to one q which119867
119902= 119867 minus 1
Case1198724
If (Message == Agree)Send119872
4forward to q which119867
119902= 119867 + 1
and have the same link IDdelete link ID
If (119867 == 1)Send Confirm back
Default
Algorithm 1 Algorithm of taxi node
Initiation queue = emptyCall taxi
Get its position LBroadcast(119872
1)
Set Timer1()
Timer1 task()If (queue = empty)
Call taxi()elseChoose the nearer hop qProduce link IDSend119872
3(Reserve link ID) to q
Send1198723(Negative) to other
Set timer2
Timer2 task() Call taxi() Block listen(Message)Switch typeof(Message)
Case1198722
Add q to queueBreak
Case1198724
Cancel Timer2Break
Case119872119890
Set Timer2 current timeBreak
Default
Algorithm 2 Algorithm of passenger node
connection errorThen immediately start the timer2and send
request again
4 Performance Analysis
In order to evaluate the performance of the proposed routingprotocol the paper uses NS2 and VanetMobiSim to simulate
TheNS2rsquosmain parameters are shown in Table 1The sim-ulation scene size is 5times 5 square kilometers InVanetMobiSimsimulation the scene size is 5times 5 square kilometers too In thetotal area there are 20 traffic signals and the entire simulationarea is divided into several regions In every region the densityof streets and the allowed maximum speed are different Theregions which have higher street density have lower allowedmaximum speed When vehicles get into the correspondingregion they choose the speed from street allowed maximumspeed and self-allowedmaximum speed with a low one In allof our simulations the empty taxis account for 40
We set the interval of route maintain message 119879119887to be
equal to 10 s and then set the maximum speed of taxi nodesto be equal to 60 kmh When we adjusted the density of taxinodes we got the probability of passenger node 119875 to findempty taxi node 119879
119863and the probability of node 119875 to receive
the message from 119879119863as shown in Table 3
As shown in Table 3 when node density is too low thetransmission range will be so small that it is hard to maintainthe information of nodes for a long time Hence when 119875appears the number of nodes that 119875 can communicate withis small and the time of link is short so that it is hard tocommunicate with 119879
119863 As the node density becomes higher
situations are getting better but some nodes have highervelocity which leads tomore failure Because the links chosenare the links that have long duration so the probability ofnode 119875 receiving acknowledgement messages from node 119879
119863
is pretty highThen if we fix the density of taxi nodes as 5 per km2 and
fix the transmission range as 500m we will get the relation ofthe maximum speed and the successful ratio
We called it successful calling when the passenger nodefinds the empty taxi node In Figure 3 we could see that whenthemaximumspeed of taxi is equal 60 kmh it has the highest
The Scientific World Journal 7
74
76
78
80
82Su
cces
sful r
ate (
)
Maximum speed (kmh)40 50 60 70 80 90 100
04
06
08
1
12
14
Link
bro
ken
ratio
()
Successful rateLink broken ratio
Figure 3 The relation of the maximum speed of taxi nodes and theratio of passenger node contacting empty taxi nodes successfully
successful ratio which enables the passenger node to find theempty taxi nodes This is because when the nodersquos movingspeed is low the node can contact with fewer other nodesAnd when the nodersquos moving speed is high the networktopology changes fast which causes fewer available routinglink and thus causes lower successful calling
Figure 4 shows the impact of nodersquos moving speed on theamount of switching packets of entire network
As shown in Figure 4 the amount of switching packetsgrows up as the vehicle movement speed increases Thisis because when the speed of node movement increases itcauses more correcting message resulting in the increaseof network data traffic In addition in one simulation therouting overhead is higher at the beginning and graduallydeclines over time This is because when the simulationstarts all taxi nodes are active at the same time and all taxinodes broadcast at the same time which causesmore channelcollision leading to an increasing number of retransmissionsAs time progresses due to the correcting message the taxirouting maintenance cycles gradually stagger and the entirenetwork routing overhead declines
Thenwe adjust the density of taxi nodes in the regionTheaverage density of taxi nodes is set at 1ndash6 per square kilometerand the vehiclemaximumspeed is set at 60 kmh and then theresults are shown in Figure 5
As shown in Figure 5 when the taxi nodes are scarcethe rate of the success calling drastically reduces Whileincreasing the number of taxi nodes the rate of success callingimproves accordingly This is because when the number oftaxi nodes is too small there is no taxi node around passengernode so that the passenger node cannot contact with anynode resulting in more calling failure When the numberof taxi nodes increase and the passenger node sends anappointment request the number of alternative routing pathsincreases so the node can choose a more stable routing pathto delivery packet thereby the rate of success calling willincrease
2 4 6 8 10
1900
1950
2000
2050
Ove
rhea
d (p
acke
t)
Time (min)
40kmh60kmh80kmh
Figure 4 The impact of nodersquos moving speed on the amount ofswitching packets of entire network
20
40
60
80
100
Succ
essfu
l rat
e (
)
1 2 3 4 5 60
2
4
6
8
Link
bro
ken
ratio
()
Successful ratioLink broken ratio
The density of taxi nodes (km2)
Figure 5 The impact of nodes density on successful ratio
Table 2 The NS2 parameters
Parameters ValuesLoss model PropagationTwoRayGroundPhysical model PhyWirelessPhyExtAntenna AntennaOmniAntennaTransmission rate 2MbpsNetwork protocol IEEE 80211
At last we control node velocity between 0 and 20msinterval of 119879
11988710 s transmission range is 500m and the
density is 4 per square kilometers Compared to AODV(show as Table 4) the results are shown in Table 2 We cansee that the proposed routing protocol performs better than
8 The Scientific World Journal
Table 3 The impact of nodes density and transmission range on successful calling ratio
Transmission rangeDensity of taxi
4 6The probability to
find 119879119863
The probability toreceive from 119879
119863
The probability to find119879119863
The probability toreceive from 119879
119863
200m 148 785 498 955300m 443 912 784 942500m 611 941 873 946
Table 4 Compare with AODV
CBLIGR AODVDelivery rate() 611 523Control messagepacket 12068 18150
AODV More importantly our protocol communication datais scattered throughout the network while AODV is relativelyconcentrated As a result our protocol performs better in thechannel collision It is because AODV requires a great dealof broadcast to maintain the entire link routing informationand has no efficient methods to deal with the disconnectionof links
5 Conclusion
This paper proposes a routing protocol for taxi-calling appli-cation Firstly it analyzes scenes of taxi-calling applicationand studies the differences between the common vehicleapplication scene and the taxi-calling application sceneSecondly it proposes the routing information maintainingalgorithm based on position prediction which performsbetter reliability Thirdly a self-network forming method fortaxi-calling application is drawn up
Our protocol queries the destination node by nodesrsquokeeping the information of the hop count to destination anddecreases the routing cost Meanwhile the validity of routesis guaranteed by predicting the future position of themselvesand their neighbors
This protocol has also been evaluated by a traffic sim-ulator The results indicate that our protocol can efficientlyfind the target nodes in the area It has also been found thatthe number of broadcasts is affected by nodesrsquo velocity Andthe fact that our protocol generates 30 less messages thanAODV has been proven here
As to future work our protocol can probably be extendedto solve the low delivery rate problem when the density ofvehicle is low
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgment
This work is supported in part by the Natural ScienceFoundation of China ldquoResearch on the snapshot data securitystorage technology for authorization of releaserdquo no 61100057
References
[1] C Rezende R W Pazzi and A Boukerche ldquoAn efficientneighborhoood prediction protocol to estimate link availabilityin VANETsrdquo in Proceedings of the 7th ACM International Sym-posiumonMobilityManagement andWireless Access (MobiWACrsquo09) pp 83ndash90 Tenerife Spain October 2009
[2] T Zahn G OrsquoShea and A Rowstron ldquoFeasibility of contentdissemination between devices in moving vehiclesrdquo in Proceed-ings of the 5th International Conference on Emerging NetworkingExperiments and Technologies (CoNEXT rsquo09) pp 97ndash108 RomeItaly December 2009
[3] N Wisitpongphan F Bai P Mudalige and O K Tonguz ldquoOnthe routing problem in disconnected vehicular ad Hoc net-worksrdquo in Proceedings of the 26th IEEE International Conferenceon Computer Communications (IEEE INFOCOM rsquo07) pp 2291ndash2295 Anchorage Alaska USA May 2007
[4] A Boukerche H A B F Oliveira E F Nakamura and A AF Loureiro ldquoVehicular Ad Hoc networks a new challenge forlocalization-based systemsrdquoComputer Communications vol 31no 12 pp 2838ndash2849 2008
[5] C E Perkins and P Bhagwat ldquoHighly dynamic destination-sequenced distance-vector routing (DSDV) for mobile com-putersrdquo in Proceedings of the Conference on CommunicationsArchitectures Protocols and Applications (SIGCOMM rsquo94) pp234ndash244 1994
[6] T Spyropoulos T Turletti and K Obraczka ldquoRouting indelay-tolerant networks comprising heterogeneous node pop-ulationsrdquo IEEE Transactions on Mobile Computing vol 8 no 8pp 1032ndash1047 2009
[7] C Lochert M Mauve H Fuszligler and H Hartenstein ldquoGeo-graphic routing in city scenariosrdquo Mobile Computing andCommunication Review vol 9 no 1 pp 69ndash72 2005
[8] M Jerbi and S M Senouci ldquoTowards efficient routing invehicular Ad Hoc networksrdquo in Proceedings of the 3rd IEEEInternational Workshop on Mobile Computing and Networking2006
[9] H Menouar M Lenardi and F Filali ldquoAn intelligentmovement-based routing for VANETsrdquo in Proceedings ofthe ITS World Congress London UK October 2006
[10] K Shafiee and V C M Leung Connectivity-Aware Minimum-Delay Geographic Routing with Vehicle Tracking in VANETsElsevier BV 2010
The Scientific World Journal 9
[11] J Haerri F Filali and C Bonnet ldquoPerformance comparisonof AODV and OLSR in VANETs urban environments underrealistic mobility patternsrdquo in Proceedings of the Med-Hoc-Net2006 5th Annual Mediterranean Ad Hoc NetworkingWorkshopLipari Italy June 2006
[12] C E Perkins and E M Royer ldquoAd-hoc on-demand distancevector routingrdquo in Proceedings of the 2nd IEEE Workshop onMobile Computing Systems and Applications (WMCSA rsquo99) pp90ndash100 New Orleans La USA February 1999
[13] T W Chen and M Gerla ldquoGlobal state routing a new routingscheme for Ad-hoc wireless networksrdquo in Proceedings of theIEEE International Conference on Communications (ICC rsquo98)vol 1 pp 171ndash175 Atlanta Ga USA June 1998
[14] B Karp and H T Kung ldquoGPSR greedy perimeter statelessrouting for wireless networksrdquo in Proceedings of the 6th AnnualInternational Conference on Mobile Computing and Networking(MOBICOM rsquo00) pp 243ndash254 Boston Mass USA August2000
[15] D B Johnson D A Maltz and J Broch ldquoDSR the dynamicsource routing protocol for multi-hop wireless Ad hoc net-worksrdquo in Ad Hoc Networking C E Perkins Ed chapter 5 pp139ndash172 Addison-Wesley New York NY USA 2001
[16] D B Johnson D A Maltz and J Broch ldquoDSR the dynamicsource routing protocol for multi-Hop wireless ad hoc net-worksrdquo in Ad Hoc Networking C E Perkins Ed chapter 5 pp139ndash172 Addison-Wesley New York NY USA 2001
[17] Z Wei and S Weibin ldquoResearch of GPSR routing protocol forwireless sensor networksrdquo Electronic Measurement Technologyvol 33 no 9 2010
[18] GWei Y Chen andX Zhu ldquoA vanet-oriented routing protocolfor intelligent taxi-call systemsrdquo in Proceedings of the IEEE 14thInternational Conference on Communication Technology (ICCTrsquo12) pp 41ndash45 Chengdu China November 2012
International Journal of
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Active and Passive Electronic Components
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RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
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Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
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Electrical and Computer Engineering
Journal of
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Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
The Scientific World Journal 5
Initialization 119905 = 0Initiate the prediction position 119878 = 0Initialization 119867 = infinSet timerTimer task()
Obtain the current position L speed V time 119879119888
119867new = 119867If (no-load)119867new = 0
Calculate prediction position 1198781015840 at (119905 + 119905119891)
If (119905119888minus 119905ge119905119891)
119867 = 119867newbroadcast(L V H 119905
119888)
119905 = 119905119888
119878 = 1198781015840
else if (|119878 minus 1198781015840| larger than threshold 119867 minus 119867new⟨⟩0)119867 = 119867new
broadcast(L V H 119905119888)
119905 = 119905119888
119878 = 1198781015840
For each node q in tableget qrsquos prediction time 119905
119902
if (state(q) == active ampamp 119905119888minus 119905119902ge 11119905
119891)
state(q) = inactiveif (q have the link ID)send119872
119890to other node which have the same lnik ID as q
If (119905119888minus 119905119902ge 2119905119891)
Remove q from table
Update H
Count = 0 reset 0 after passengers getting off or appointment cancellationBlock listen(Message)
Switch typeof(Message) Case119872
119887
update tableupdate Hif q node that sends119872
119887gets out of the communication range and it has link ID in the table
send119872119890to other node
which have the same link ID as qbreak
Case1198721
If (119867 lt infin)send1198722back
breakCase119872
3
If (Message == Reserve)If (119867 == 0 ampamp count == 0)
Count = 1send119872
4(Agree or Disagree) back
else if (119867 == 1)Set link IDsend119872
3to all q in table which119867
119902= 0
else
Algorithm 1 Continued
6 The Scientific World Journal
Set link IDsend119872
3to one q which119867
119902= 119867 minus 1
Case1198724
If (Message == Agree)Send119872
4forward to q which119867
119902= 119867 + 1
and have the same link IDdelete link ID
If (119867 == 1)Send Confirm back
Default
Algorithm 1 Algorithm of taxi node
Initiation queue = emptyCall taxi
Get its position LBroadcast(119872
1)
Set Timer1()
Timer1 task()If (queue = empty)
Call taxi()elseChoose the nearer hop qProduce link IDSend119872
3(Reserve link ID) to q
Send1198723(Negative) to other
Set timer2
Timer2 task() Call taxi() Block listen(Message)Switch typeof(Message)
Case1198722
Add q to queueBreak
Case1198724
Cancel Timer2Break
Case119872119890
Set Timer2 current timeBreak
Default
Algorithm 2 Algorithm of passenger node
connection errorThen immediately start the timer2and send
request again
4 Performance Analysis
In order to evaluate the performance of the proposed routingprotocol the paper uses NS2 and VanetMobiSim to simulate
TheNS2rsquosmain parameters are shown in Table 1The sim-ulation scene size is 5times 5 square kilometers InVanetMobiSimsimulation the scene size is 5times 5 square kilometers too In thetotal area there are 20 traffic signals and the entire simulationarea is divided into several regions In every region the densityof streets and the allowed maximum speed are different Theregions which have higher street density have lower allowedmaximum speed When vehicles get into the correspondingregion they choose the speed from street allowed maximumspeed and self-allowedmaximum speed with a low one In allof our simulations the empty taxis account for 40
We set the interval of route maintain message 119879119887to be
equal to 10 s and then set the maximum speed of taxi nodesto be equal to 60 kmh When we adjusted the density of taxinodes we got the probability of passenger node 119875 to findempty taxi node 119879
119863and the probability of node 119875 to receive
the message from 119879119863as shown in Table 3
As shown in Table 3 when node density is too low thetransmission range will be so small that it is hard to maintainthe information of nodes for a long time Hence when 119875appears the number of nodes that 119875 can communicate withis small and the time of link is short so that it is hard tocommunicate with 119879
119863 As the node density becomes higher
situations are getting better but some nodes have highervelocity which leads tomore failure Because the links chosenare the links that have long duration so the probability ofnode 119875 receiving acknowledgement messages from node 119879
119863
is pretty highThen if we fix the density of taxi nodes as 5 per km2 and
fix the transmission range as 500m we will get the relation ofthe maximum speed and the successful ratio
We called it successful calling when the passenger nodefinds the empty taxi node In Figure 3 we could see that whenthemaximumspeed of taxi is equal 60 kmh it has the highest
The Scientific World Journal 7
74
76
78
80
82Su
cces
sful r
ate (
)
Maximum speed (kmh)40 50 60 70 80 90 100
04
06
08
1
12
14
Link
bro
ken
ratio
()
Successful rateLink broken ratio
Figure 3 The relation of the maximum speed of taxi nodes and theratio of passenger node contacting empty taxi nodes successfully
successful ratio which enables the passenger node to find theempty taxi nodes This is because when the nodersquos movingspeed is low the node can contact with fewer other nodesAnd when the nodersquos moving speed is high the networktopology changes fast which causes fewer available routinglink and thus causes lower successful calling
Figure 4 shows the impact of nodersquos moving speed on theamount of switching packets of entire network
As shown in Figure 4 the amount of switching packetsgrows up as the vehicle movement speed increases Thisis because when the speed of node movement increases itcauses more correcting message resulting in the increaseof network data traffic In addition in one simulation therouting overhead is higher at the beginning and graduallydeclines over time This is because when the simulationstarts all taxi nodes are active at the same time and all taxinodes broadcast at the same time which causesmore channelcollision leading to an increasing number of retransmissionsAs time progresses due to the correcting message the taxirouting maintenance cycles gradually stagger and the entirenetwork routing overhead declines
Thenwe adjust the density of taxi nodes in the regionTheaverage density of taxi nodes is set at 1ndash6 per square kilometerand the vehiclemaximumspeed is set at 60 kmh and then theresults are shown in Figure 5
As shown in Figure 5 when the taxi nodes are scarcethe rate of the success calling drastically reduces Whileincreasing the number of taxi nodes the rate of success callingimproves accordingly This is because when the number oftaxi nodes is too small there is no taxi node around passengernode so that the passenger node cannot contact with anynode resulting in more calling failure When the numberof taxi nodes increase and the passenger node sends anappointment request the number of alternative routing pathsincreases so the node can choose a more stable routing pathto delivery packet thereby the rate of success calling willincrease
2 4 6 8 10
1900
1950
2000
2050
Ove
rhea
d (p
acke
t)
Time (min)
40kmh60kmh80kmh
Figure 4 The impact of nodersquos moving speed on the amount ofswitching packets of entire network
20
40
60
80
100
Succ
essfu
l rat
e (
)
1 2 3 4 5 60
2
4
6
8
Link
bro
ken
ratio
()
Successful ratioLink broken ratio
The density of taxi nodes (km2)
Figure 5 The impact of nodes density on successful ratio
Table 2 The NS2 parameters
Parameters ValuesLoss model PropagationTwoRayGroundPhysical model PhyWirelessPhyExtAntenna AntennaOmniAntennaTransmission rate 2MbpsNetwork protocol IEEE 80211
At last we control node velocity between 0 and 20msinterval of 119879
11988710 s transmission range is 500m and the
density is 4 per square kilometers Compared to AODV(show as Table 4) the results are shown in Table 2 We cansee that the proposed routing protocol performs better than
8 The Scientific World Journal
Table 3 The impact of nodes density and transmission range on successful calling ratio
Transmission rangeDensity of taxi
4 6The probability to
find 119879119863
The probability toreceive from 119879
119863
The probability to find119879119863
The probability toreceive from 119879
119863
200m 148 785 498 955300m 443 912 784 942500m 611 941 873 946
Table 4 Compare with AODV
CBLIGR AODVDelivery rate() 611 523Control messagepacket 12068 18150
AODV More importantly our protocol communication datais scattered throughout the network while AODV is relativelyconcentrated As a result our protocol performs better in thechannel collision It is because AODV requires a great dealof broadcast to maintain the entire link routing informationand has no efficient methods to deal with the disconnectionof links
5 Conclusion
This paper proposes a routing protocol for taxi-calling appli-cation Firstly it analyzes scenes of taxi-calling applicationand studies the differences between the common vehicleapplication scene and the taxi-calling application sceneSecondly it proposes the routing information maintainingalgorithm based on position prediction which performsbetter reliability Thirdly a self-network forming method fortaxi-calling application is drawn up
Our protocol queries the destination node by nodesrsquokeeping the information of the hop count to destination anddecreases the routing cost Meanwhile the validity of routesis guaranteed by predicting the future position of themselvesand their neighbors
This protocol has also been evaluated by a traffic sim-ulator The results indicate that our protocol can efficientlyfind the target nodes in the area It has also been found thatthe number of broadcasts is affected by nodesrsquo velocity Andthe fact that our protocol generates 30 less messages thanAODV has been proven here
As to future work our protocol can probably be extendedto solve the low delivery rate problem when the density ofvehicle is low
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgment
This work is supported in part by the Natural ScienceFoundation of China ldquoResearch on the snapshot data securitystorage technology for authorization of releaserdquo no 61100057
References
[1] C Rezende R W Pazzi and A Boukerche ldquoAn efficientneighborhoood prediction protocol to estimate link availabilityin VANETsrdquo in Proceedings of the 7th ACM International Sym-posiumonMobilityManagement andWireless Access (MobiWACrsquo09) pp 83ndash90 Tenerife Spain October 2009
[2] T Zahn G OrsquoShea and A Rowstron ldquoFeasibility of contentdissemination between devices in moving vehiclesrdquo in Proceed-ings of the 5th International Conference on Emerging NetworkingExperiments and Technologies (CoNEXT rsquo09) pp 97ndash108 RomeItaly December 2009
[3] N Wisitpongphan F Bai P Mudalige and O K Tonguz ldquoOnthe routing problem in disconnected vehicular ad Hoc net-worksrdquo in Proceedings of the 26th IEEE International Conferenceon Computer Communications (IEEE INFOCOM rsquo07) pp 2291ndash2295 Anchorage Alaska USA May 2007
[4] A Boukerche H A B F Oliveira E F Nakamura and A AF Loureiro ldquoVehicular Ad Hoc networks a new challenge forlocalization-based systemsrdquoComputer Communications vol 31no 12 pp 2838ndash2849 2008
[5] C E Perkins and P Bhagwat ldquoHighly dynamic destination-sequenced distance-vector routing (DSDV) for mobile com-putersrdquo in Proceedings of the Conference on CommunicationsArchitectures Protocols and Applications (SIGCOMM rsquo94) pp234ndash244 1994
[6] T Spyropoulos T Turletti and K Obraczka ldquoRouting indelay-tolerant networks comprising heterogeneous node pop-ulationsrdquo IEEE Transactions on Mobile Computing vol 8 no 8pp 1032ndash1047 2009
[7] C Lochert M Mauve H Fuszligler and H Hartenstein ldquoGeo-graphic routing in city scenariosrdquo Mobile Computing andCommunication Review vol 9 no 1 pp 69ndash72 2005
[8] M Jerbi and S M Senouci ldquoTowards efficient routing invehicular Ad Hoc networksrdquo in Proceedings of the 3rd IEEEInternational Workshop on Mobile Computing and Networking2006
[9] H Menouar M Lenardi and F Filali ldquoAn intelligentmovement-based routing for VANETsrdquo in Proceedings ofthe ITS World Congress London UK October 2006
[10] K Shafiee and V C M Leung Connectivity-Aware Minimum-Delay Geographic Routing with Vehicle Tracking in VANETsElsevier BV 2010
The Scientific World Journal 9
[11] J Haerri F Filali and C Bonnet ldquoPerformance comparisonof AODV and OLSR in VANETs urban environments underrealistic mobility patternsrdquo in Proceedings of the Med-Hoc-Net2006 5th Annual Mediterranean Ad Hoc NetworkingWorkshopLipari Italy June 2006
[12] C E Perkins and E M Royer ldquoAd-hoc on-demand distancevector routingrdquo in Proceedings of the 2nd IEEE Workshop onMobile Computing Systems and Applications (WMCSA rsquo99) pp90ndash100 New Orleans La USA February 1999
[13] T W Chen and M Gerla ldquoGlobal state routing a new routingscheme for Ad-hoc wireless networksrdquo in Proceedings of theIEEE International Conference on Communications (ICC rsquo98)vol 1 pp 171ndash175 Atlanta Ga USA June 1998
[14] B Karp and H T Kung ldquoGPSR greedy perimeter statelessrouting for wireless networksrdquo in Proceedings of the 6th AnnualInternational Conference on Mobile Computing and Networking(MOBICOM rsquo00) pp 243ndash254 Boston Mass USA August2000
[15] D B Johnson D A Maltz and J Broch ldquoDSR the dynamicsource routing protocol for multi-hop wireless Ad hoc net-worksrdquo in Ad Hoc Networking C E Perkins Ed chapter 5 pp139ndash172 Addison-Wesley New York NY USA 2001
[16] D B Johnson D A Maltz and J Broch ldquoDSR the dynamicsource routing protocol for multi-Hop wireless ad hoc net-worksrdquo in Ad Hoc Networking C E Perkins Ed chapter 5 pp139ndash172 Addison-Wesley New York NY USA 2001
[17] Z Wei and S Weibin ldquoResearch of GPSR routing protocol forwireless sensor networksrdquo Electronic Measurement Technologyvol 33 no 9 2010
[18] GWei Y Chen andX Zhu ldquoA vanet-oriented routing protocolfor intelligent taxi-call systemsrdquo in Proceedings of the IEEE 14thInternational Conference on Communication Technology (ICCTrsquo12) pp 41ndash45 Chengdu China November 2012
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
6 The Scientific World Journal
Set link IDsend119872
3to one q which119867
119902= 119867 minus 1
Case1198724
If (Message == Agree)Send119872
4forward to q which119867
119902= 119867 + 1
and have the same link IDdelete link ID
If (119867 == 1)Send Confirm back
Default
Algorithm 1 Algorithm of taxi node
Initiation queue = emptyCall taxi
Get its position LBroadcast(119872
1)
Set Timer1()
Timer1 task()If (queue = empty)
Call taxi()elseChoose the nearer hop qProduce link IDSend119872
3(Reserve link ID) to q
Send1198723(Negative) to other
Set timer2
Timer2 task() Call taxi() Block listen(Message)Switch typeof(Message)
Case1198722
Add q to queueBreak
Case1198724
Cancel Timer2Break
Case119872119890
Set Timer2 current timeBreak
Default
Algorithm 2 Algorithm of passenger node
connection errorThen immediately start the timer2and send
request again
4 Performance Analysis
In order to evaluate the performance of the proposed routingprotocol the paper uses NS2 and VanetMobiSim to simulate
TheNS2rsquosmain parameters are shown in Table 1The sim-ulation scene size is 5times 5 square kilometers InVanetMobiSimsimulation the scene size is 5times 5 square kilometers too In thetotal area there are 20 traffic signals and the entire simulationarea is divided into several regions In every region the densityof streets and the allowed maximum speed are different Theregions which have higher street density have lower allowedmaximum speed When vehicles get into the correspondingregion they choose the speed from street allowed maximumspeed and self-allowedmaximum speed with a low one In allof our simulations the empty taxis account for 40
We set the interval of route maintain message 119879119887to be
equal to 10 s and then set the maximum speed of taxi nodesto be equal to 60 kmh When we adjusted the density of taxinodes we got the probability of passenger node 119875 to findempty taxi node 119879
119863and the probability of node 119875 to receive
the message from 119879119863as shown in Table 3
As shown in Table 3 when node density is too low thetransmission range will be so small that it is hard to maintainthe information of nodes for a long time Hence when 119875appears the number of nodes that 119875 can communicate withis small and the time of link is short so that it is hard tocommunicate with 119879
119863 As the node density becomes higher
situations are getting better but some nodes have highervelocity which leads tomore failure Because the links chosenare the links that have long duration so the probability ofnode 119875 receiving acknowledgement messages from node 119879
119863
is pretty highThen if we fix the density of taxi nodes as 5 per km2 and
fix the transmission range as 500m we will get the relation ofthe maximum speed and the successful ratio
We called it successful calling when the passenger nodefinds the empty taxi node In Figure 3 we could see that whenthemaximumspeed of taxi is equal 60 kmh it has the highest
The Scientific World Journal 7
74
76
78
80
82Su
cces
sful r
ate (
)
Maximum speed (kmh)40 50 60 70 80 90 100
04
06
08
1
12
14
Link
bro
ken
ratio
()
Successful rateLink broken ratio
Figure 3 The relation of the maximum speed of taxi nodes and theratio of passenger node contacting empty taxi nodes successfully
successful ratio which enables the passenger node to find theempty taxi nodes This is because when the nodersquos movingspeed is low the node can contact with fewer other nodesAnd when the nodersquos moving speed is high the networktopology changes fast which causes fewer available routinglink and thus causes lower successful calling
Figure 4 shows the impact of nodersquos moving speed on theamount of switching packets of entire network
As shown in Figure 4 the amount of switching packetsgrows up as the vehicle movement speed increases Thisis because when the speed of node movement increases itcauses more correcting message resulting in the increaseof network data traffic In addition in one simulation therouting overhead is higher at the beginning and graduallydeclines over time This is because when the simulationstarts all taxi nodes are active at the same time and all taxinodes broadcast at the same time which causesmore channelcollision leading to an increasing number of retransmissionsAs time progresses due to the correcting message the taxirouting maintenance cycles gradually stagger and the entirenetwork routing overhead declines
Thenwe adjust the density of taxi nodes in the regionTheaverage density of taxi nodes is set at 1ndash6 per square kilometerand the vehiclemaximumspeed is set at 60 kmh and then theresults are shown in Figure 5
As shown in Figure 5 when the taxi nodes are scarcethe rate of the success calling drastically reduces Whileincreasing the number of taxi nodes the rate of success callingimproves accordingly This is because when the number oftaxi nodes is too small there is no taxi node around passengernode so that the passenger node cannot contact with anynode resulting in more calling failure When the numberof taxi nodes increase and the passenger node sends anappointment request the number of alternative routing pathsincreases so the node can choose a more stable routing pathto delivery packet thereby the rate of success calling willincrease
2 4 6 8 10
1900
1950
2000
2050
Ove
rhea
d (p
acke
t)
Time (min)
40kmh60kmh80kmh
Figure 4 The impact of nodersquos moving speed on the amount ofswitching packets of entire network
20
40
60
80
100
Succ
essfu
l rat
e (
)
1 2 3 4 5 60
2
4
6
8
Link
bro
ken
ratio
()
Successful ratioLink broken ratio
The density of taxi nodes (km2)
Figure 5 The impact of nodes density on successful ratio
Table 2 The NS2 parameters
Parameters ValuesLoss model PropagationTwoRayGroundPhysical model PhyWirelessPhyExtAntenna AntennaOmniAntennaTransmission rate 2MbpsNetwork protocol IEEE 80211
At last we control node velocity between 0 and 20msinterval of 119879
11988710 s transmission range is 500m and the
density is 4 per square kilometers Compared to AODV(show as Table 4) the results are shown in Table 2 We cansee that the proposed routing protocol performs better than
8 The Scientific World Journal
Table 3 The impact of nodes density and transmission range on successful calling ratio
Transmission rangeDensity of taxi
4 6The probability to
find 119879119863
The probability toreceive from 119879
119863
The probability to find119879119863
The probability toreceive from 119879
119863
200m 148 785 498 955300m 443 912 784 942500m 611 941 873 946
Table 4 Compare with AODV
CBLIGR AODVDelivery rate() 611 523Control messagepacket 12068 18150
AODV More importantly our protocol communication datais scattered throughout the network while AODV is relativelyconcentrated As a result our protocol performs better in thechannel collision It is because AODV requires a great dealof broadcast to maintain the entire link routing informationand has no efficient methods to deal with the disconnectionof links
5 Conclusion
This paper proposes a routing protocol for taxi-calling appli-cation Firstly it analyzes scenes of taxi-calling applicationand studies the differences between the common vehicleapplication scene and the taxi-calling application sceneSecondly it proposes the routing information maintainingalgorithm based on position prediction which performsbetter reliability Thirdly a self-network forming method fortaxi-calling application is drawn up
Our protocol queries the destination node by nodesrsquokeeping the information of the hop count to destination anddecreases the routing cost Meanwhile the validity of routesis guaranteed by predicting the future position of themselvesand their neighbors
This protocol has also been evaluated by a traffic sim-ulator The results indicate that our protocol can efficientlyfind the target nodes in the area It has also been found thatthe number of broadcasts is affected by nodesrsquo velocity Andthe fact that our protocol generates 30 less messages thanAODV has been proven here
As to future work our protocol can probably be extendedto solve the low delivery rate problem when the density ofvehicle is low
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgment
This work is supported in part by the Natural ScienceFoundation of China ldquoResearch on the snapshot data securitystorage technology for authorization of releaserdquo no 61100057
References
[1] C Rezende R W Pazzi and A Boukerche ldquoAn efficientneighborhoood prediction protocol to estimate link availabilityin VANETsrdquo in Proceedings of the 7th ACM International Sym-posiumonMobilityManagement andWireless Access (MobiWACrsquo09) pp 83ndash90 Tenerife Spain October 2009
[2] T Zahn G OrsquoShea and A Rowstron ldquoFeasibility of contentdissemination between devices in moving vehiclesrdquo in Proceed-ings of the 5th International Conference on Emerging NetworkingExperiments and Technologies (CoNEXT rsquo09) pp 97ndash108 RomeItaly December 2009
[3] N Wisitpongphan F Bai P Mudalige and O K Tonguz ldquoOnthe routing problem in disconnected vehicular ad Hoc net-worksrdquo in Proceedings of the 26th IEEE International Conferenceon Computer Communications (IEEE INFOCOM rsquo07) pp 2291ndash2295 Anchorage Alaska USA May 2007
[4] A Boukerche H A B F Oliveira E F Nakamura and A AF Loureiro ldquoVehicular Ad Hoc networks a new challenge forlocalization-based systemsrdquoComputer Communications vol 31no 12 pp 2838ndash2849 2008
[5] C E Perkins and P Bhagwat ldquoHighly dynamic destination-sequenced distance-vector routing (DSDV) for mobile com-putersrdquo in Proceedings of the Conference on CommunicationsArchitectures Protocols and Applications (SIGCOMM rsquo94) pp234ndash244 1994
[6] T Spyropoulos T Turletti and K Obraczka ldquoRouting indelay-tolerant networks comprising heterogeneous node pop-ulationsrdquo IEEE Transactions on Mobile Computing vol 8 no 8pp 1032ndash1047 2009
[7] C Lochert M Mauve H Fuszligler and H Hartenstein ldquoGeo-graphic routing in city scenariosrdquo Mobile Computing andCommunication Review vol 9 no 1 pp 69ndash72 2005
[8] M Jerbi and S M Senouci ldquoTowards efficient routing invehicular Ad Hoc networksrdquo in Proceedings of the 3rd IEEEInternational Workshop on Mobile Computing and Networking2006
[9] H Menouar M Lenardi and F Filali ldquoAn intelligentmovement-based routing for VANETsrdquo in Proceedings ofthe ITS World Congress London UK October 2006
[10] K Shafiee and V C M Leung Connectivity-Aware Minimum-Delay Geographic Routing with Vehicle Tracking in VANETsElsevier BV 2010
The Scientific World Journal 9
[11] J Haerri F Filali and C Bonnet ldquoPerformance comparisonof AODV and OLSR in VANETs urban environments underrealistic mobility patternsrdquo in Proceedings of the Med-Hoc-Net2006 5th Annual Mediterranean Ad Hoc NetworkingWorkshopLipari Italy June 2006
[12] C E Perkins and E M Royer ldquoAd-hoc on-demand distancevector routingrdquo in Proceedings of the 2nd IEEE Workshop onMobile Computing Systems and Applications (WMCSA rsquo99) pp90ndash100 New Orleans La USA February 1999
[13] T W Chen and M Gerla ldquoGlobal state routing a new routingscheme for Ad-hoc wireless networksrdquo in Proceedings of theIEEE International Conference on Communications (ICC rsquo98)vol 1 pp 171ndash175 Atlanta Ga USA June 1998
[14] B Karp and H T Kung ldquoGPSR greedy perimeter statelessrouting for wireless networksrdquo in Proceedings of the 6th AnnualInternational Conference on Mobile Computing and Networking(MOBICOM rsquo00) pp 243ndash254 Boston Mass USA August2000
[15] D B Johnson D A Maltz and J Broch ldquoDSR the dynamicsource routing protocol for multi-hop wireless Ad hoc net-worksrdquo in Ad Hoc Networking C E Perkins Ed chapter 5 pp139ndash172 Addison-Wesley New York NY USA 2001
[16] D B Johnson D A Maltz and J Broch ldquoDSR the dynamicsource routing protocol for multi-Hop wireless ad hoc net-worksrdquo in Ad Hoc Networking C E Perkins Ed chapter 5 pp139ndash172 Addison-Wesley New York NY USA 2001
[17] Z Wei and S Weibin ldquoResearch of GPSR routing protocol forwireless sensor networksrdquo Electronic Measurement Technologyvol 33 no 9 2010
[18] GWei Y Chen andX Zhu ldquoA vanet-oriented routing protocolfor intelligent taxi-call systemsrdquo in Proceedings of the IEEE 14thInternational Conference on Communication Technology (ICCTrsquo12) pp 41ndash45 Chengdu China November 2012
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
The Scientific World Journal 7
74
76
78
80
82Su
cces
sful r
ate (
)
Maximum speed (kmh)40 50 60 70 80 90 100
04
06
08
1
12
14
Link
bro
ken
ratio
()
Successful rateLink broken ratio
Figure 3 The relation of the maximum speed of taxi nodes and theratio of passenger node contacting empty taxi nodes successfully
successful ratio which enables the passenger node to find theempty taxi nodes This is because when the nodersquos movingspeed is low the node can contact with fewer other nodesAnd when the nodersquos moving speed is high the networktopology changes fast which causes fewer available routinglink and thus causes lower successful calling
Figure 4 shows the impact of nodersquos moving speed on theamount of switching packets of entire network
As shown in Figure 4 the amount of switching packetsgrows up as the vehicle movement speed increases Thisis because when the speed of node movement increases itcauses more correcting message resulting in the increaseof network data traffic In addition in one simulation therouting overhead is higher at the beginning and graduallydeclines over time This is because when the simulationstarts all taxi nodes are active at the same time and all taxinodes broadcast at the same time which causesmore channelcollision leading to an increasing number of retransmissionsAs time progresses due to the correcting message the taxirouting maintenance cycles gradually stagger and the entirenetwork routing overhead declines
Thenwe adjust the density of taxi nodes in the regionTheaverage density of taxi nodes is set at 1ndash6 per square kilometerand the vehiclemaximumspeed is set at 60 kmh and then theresults are shown in Figure 5
As shown in Figure 5 when the taxi nodes are scarcethe rate of the success calling drastically reduces Whileincreasing the number of taxi nodes the rate of success callingimproves accordingly This is because when the number oftaxi nodes is too small there is no taxi node around passengernode so that the passenger node cannot contact with anynode resulting in more calling failure When the numberof taxi nodes increase and the passenger node sends anappointment request the number of alternative routing pathsincreases so the node can choose a more stable routing pathto delivery packet thereby the rate of success calling willincrease
2 4 6 8 10
1900
1950
2000
2050
Ove
rhea
d (p
acke
t)
Time (min)
40kmh60kmh80kmh
Figure 4 The impact of nodersquos moving speed on the amount ofswitching packets of entire network
20
40
60
80
100
Succ
essfu
l rat
e (
)
1 2 3 4 5 60
2
4
6
8
Link
bro
ken
ratio
()
Successful ratioLink broken ratio
The density of taxi nodes (km2)
Figure 5 The impact of nodes density on successful ratio
Table 2 The NS2 parameters
Parameters ValuesLoss model PropagationTwoRayGroundPhysical model PhyWirelessPhyExtAntenna AntennaOmniAntennaTransmission rate 2MbpsNetwork protocol IEEE 80211
At last we control node velocity between 0 and 20msinterval of 119879
11988710 s transmission range is 500m and the
density is 4 per square kilometers Compared to AODV(show as Table 4) the results are shown in Table 2 We cansee that the proposed routing protocol performs better than
8 The Scientific World Journal
Table 3 The impact of nodes density and transmission range on successful calling ratio
Transmission rangeDensity of taxi
4 6The probability to
find 119879119863
The probability toreceive from 119879
119863
The probability to find119879119863
The probability toreceive from 119879
119863
200m 148 785 498 955300m 443 912 784 942500m 611 941 873 946
Table 4 Compare with AODV
CBLIGR AODVDelivery rate() 611 523Control messagepacket 12068 18150
AODV More importantly our protocol communication datais scattered throughout the network while AODV is relativelyconcentrated As a result our protocol performs better in thechannel collision It is because AODV requires a great dealof broadcast to maintain the entire link routing informationand has no efficient methods to deal with the disconnectionof links
5 Conclusion
This paper proposes a routing protocol for taxi-calling appli-cation Firstly it analyzes scenes of taxi-calling applicationand studies the differences between the common vehicleapplication scene and the taxi-calling application sceneSecondly it proposes the routing information maintainingalgorithm based on position prediction which performsbetter reliability Thirdly a self-network forming method fortaxi-calling application is drawn up
Our protocol queries the destination node by nodesrsquokeeping the information of the hop count to destination anddecreases the routing cost Meanwhile the validity of routesis guaranteed by predicting the future position of themselvesand their neighbors
This protocol has also been evaluated by a traffic sim-ulator The results indicate that our protocol can efficientlyfind the target nodes in the area It has also been found thatthe number of broadcasts is affected by nodesrsquo velocity Andthe fact that our protocol generates 30 less messages thanAODV has been proven here
As to future work our protocol can probably be extendedto solve the low delivery rate problem when the density ofvehicle is low
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgment
This work is supported in part by the Natural ScienceFoundation of China ldquoResearch on the snapshot data securitystorage technology for authorization of releaserdquo no 61100057
References
[1] C Rezende R W Pazzi and A Boukerche ldquoAn efficientneighborhoood prediction protocol to estimate link availabilityin VANETsrdquo in Proceedings of the 7th ACM International Sym-posiumonMobilityManagement andWireless Access (MobiWACrsquo09) pp 83ndash90 Tenerife Spain October 2009
[2] T Zahn G OrsquoShea and A Rowstron ldquoFeasibility of contentdissemination between devices in moving vehiclesrdquo in Proceed-ings of the 5th International Conference on Emerging NetworkingExperiments and Technologies (CoNEXT rsquo09) pp 97ndash108 RomeItaly December 2009
[3] N Wisitpongphan F Bai P Mudalige and O K Tonguz ldquoOnthe routing problem in disconnected vehicular ad Hoc net-worksrdquo in Proceedings of the 26th IEEE International Conferenceon Computer Communications (IEEE INFOCOM rsquo07) pp 2291ndash2295 Anchorage Alaska USA May 2007
[4] A Boukerche H A B F Oliveira E F Nakamura and A AF Loureiro ldquoVehicular Ad Hoc networks a new challenge forlocalization-based systemsrdquoComputer Communications vol 31no 12 pp 2838ndash2849 2008
[5] C E Perkins and P Bhagwat ldquoHighly dynamic destination-sequenced distance-vector routing (DSDV) for mobile com-putersrdquo in Proceedings of the Conference on CommunicationsArchitectures Protocols and Applications (SIGCOMM rsquo94) pp234ndash244 1994
[6] T Spyropoulos T Turletti and K Obraczka ldquoRouting indelay-tolerant networks comprising heterogeneous node pop-ulationsrdquo IEEE Transactions on Mobile Computing vol 8 no 8pp 1032ndash1047 2009
[7] C Lochert M Mauve H Fuszligler and H Hartenstein ldquoGeo-graphic routing in city scenariosrdquo Mobile Computing andCommunication Review vol 9 no 1 pp 69ndash72 2005
[8] M Jerbi and S M Senouci ldquoTowards efficient routing invehicular Ad Hoc networksrdquo in Proceedings of the 3rd IEEEInternational Workshop on Mobile Computing and Networking2006
[9] H Menouar M Lenardi and F Filali ldquoAn intelligentmovement-based routing for VANETsrdquo in Proceedings ofthe ITS World Congress London UK October 2006
[10] K Shafiee and V C M Leung Connectivity-Aware Minimum-Delay Geographic Routing with Vehicle Tracking in VANETsElsevier BV 2010
The Scientific World Journal 9
[11] J Haerri F Filali and C Bonnet ldquoPerformance comparisonof AODV and OLSR in VANETs urban environments underrealistic mobility patternsrdquo in Proceedings of the Med-Hoc-Net2006 5th Annual Mediterranean Ad Hoc NetworkingWorkshopLipari Italy June 2006
[12] C E Perkins and E M Royer ldquoAd-hoc on-demand distancevector routingrdquo in Proceedings of the 2nd IEEE Workshop onMobile Computing Systems and Applications (WMCSA rsquo99) pp90ndash100 New Orleans La USA February 1999
[13] T W Chen and M Gerla ldquoGlobal state routing a new routingscheme for Ad-hoc wireless networksrdquo in Proceedings of theIEEE International Conference on Communications (ICC rsquo98)vol 1 pp 171ndash175 Atlanta Ga USA June 1998
[14] B Karp and H T Kung ldquoGPSR greedy perimeter statelessrouting for wireless networksrdquo in Proceedings of the 6th AnnualInternational Conference on Mobile Computing and Networking(MOBICOM rsquo00) pp 243ndash254 Boston Mass USA August2000
[15] D B Johnson D A Maltz and J Broch ldquoDSR the dynamicsource routing protocol for multi-hop wireless Ad hoc net-worksrdquo in Ad Hoc Networking C E Perkins Ed chapter 5 pp139ndash172 Addison-Wesley New York NY USA 2001
[16] D B Johnson D A Maltz and J Broch ldquoDSR the dynamicsource routing protocol for multi-Hop wireless ad hoc net-worksrdquo in Ad Hoc Networking C E Perkins Ed chapter 5 pp139ndash172 Addison-Wesley New York NY USA 2001
[17] Z Wei and S Weibin ldquoResearch of GPSR routing protocol forwireless sensor networksrdquo Electronic Measurement Technologyvol 33 no 9 2010
[18] GWei Y Chen andX Zhu ldquoA vanet-oriented routing protocolfor intelligent taxi-call systemsrdquo in Proceedings of the IEEE 14thInternational Conference on Communication Technology (ICCTrsquo12) pp 41ndash45 Chengdu China November 2012
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
8 The Scientific World Journal
Table 3 The impact of nodes density and transmission range on successful calling ratio
Transmission rangeDensity of taxi
4 6The probability to
find 119879119863
The probability toreceive from 119879
119863
The probability to find119879119863
The probability toreceive from 119879
119863
200m 148 785 498 955300m 443 912 784 942500m 611 941 873 946
Table 4 Compare with AODV
CBLIGR AODVDelivery rate() 611 523Control messagepacket 12068 18150
AODV More importantly our protocol communication datais scattered throughout the network while AODV is relativelyconcentrated As a result our protocol performs better in thechannel collision It is because AODV requires a great dealof broadcast to maintain the entire link routing informationand has no efficient methods to deal with the disconnectionof links
5 Conclusion
This paper proposes a routing protocol for taxi-calling appli-cation Firstly it analyzes scenes of taxi-calling applicationand studies the differences between the common vehicleapplication scene and the taxi-calling application sceneSecondly it proposes the routing information maintainingalgorithm based on position prediction which performsbetter reliability Thirdly a self-network forming method fortaxi-calling application is drawn up
Our protocol queries the destination node by nodesrsquokeeping the information of the hop count to destination anddecreases the routing cost Meanwhile the validity of routesis guaranteed by predicting the future position of themselvesand their neighbors
This protocol has also been evaluated by a traffic sim-ulator The results indicate that our protocol can efficientlyfind the target nodes in the area It has also been found thatthe number of broadcasts is affected by nodesrsquo velocity Andthe fact that our protocol generates 30 less messages thanAODV has been proven here
As to future work our protocol can probably be extendedto solve the low delivery rate problem when the density ofvehicle is low
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
Acknowledgment
This work is supported in part by the Natural ScienceFoundation of China ldquoResearch on the snapshot data securitystorage technology for authorization of releaserdquo no 61100057
References
[1] C Rezende R W Pazzi and A Boukerche ldquoAn efficientneighborhoood prediction protocol to estimate link availabilityin VANETsrdquo in Proceedings of the 7th ACM International Sym-posiumonMobilityManagement andWireless Access (MobiWACrsquo09) pp 83ndash90 Tenerife Spain October 2009
[2] T Zahn G OrsquoShea and A Rowstron ldquoFeasibility of contentdissemination between devices in moving vehiclesrdquo in Proceed-ings of the 5th International Conference on Emerging NetworkingExperiments and Technologies (CoNEXT rsquo09) pp 97ndash108 RomeItaly December 2009
[3] N Wisitpongphan F Bai P Mudalige and O K Tonguz ldquoOnthe routing problem in disconnected vehicular ad Hoc net-worksrdquo in Proceedings of the 26th IEEE International Conferenceon Computer Communications (IEEE INFOCOM rsquo07) pp 2291ndash2295 Anchorage Alaska USA May 2007
[4] A Boukerche H A B F Oliveira E F Nakamura and A AF Loureiro ldquoVehicular Ad Hoc networks a new challenge forlocalization-based systemsrdquoComputer Communications vol 31no 12 pp 2838ndash2849 2008
[5] C E Perkins and P Bhagwat ldquoHighly dynamic destination-sequenced distance-vector routing (DSDV) for mobile com-putersrdquo in Proceedings of the Conference on CommunicationsArchitectures Protocols and Applications (SIGCOMM rsquo94) pp234ndash244 1994
[6] T Spyropoulos T Turletti and K Obraczka ldquoRouting indelay-tolerant networks comprising heterogeneous node pop-ulationsrdquo IEEE Transactions on Mobile Computing vol 8 no 8pp 1032ndash1047 2009
[7] C Lochert M Mauve H Fuszligler and H Hartenstein ldquoGeo-graphic routing in city scenariosrdquo Mobile Computing andCommunication Review vol 9 no 1 pp 69ndash72 2005
[8] M Jerbi and S M Senouci ldquoTowards efficient routing invehicular Ad Hoc networksrdquo in Proceedings of the 3rd IEEEInternational Workshop on Mobile Computing and Networking2006
[9] H Menouar M Lenardi and F Filali ldquoAn intelligentmovement-based routing for VANETsrdquo in Proceedings ofthe ITS World Congress London UK October 2006
[10] K Shafiee and V C M Leung Connectivity-Aware Minimum-Delay Geographic Routing with Vehicle Tracking in VANETsElsevier BV 2010
The Scientific World Journal 9
[11] J Haerri F Filali and C Bonnet ldquoPerformance comparisonof AODV and OLSR in VANETs urban environments underrealistic mobility patternsrdquo in Proceedings of the Med-Hoc-Net2006 5th Annual Mediterranean Ad Hoc NetworkingWorkshopLipari Italy June 2006
[12] C E Perkins and E M Royer ldquoAd-hoc on-demand distancevector routingrdquo in Proceedings of the 2nd IEEE Workshop onMobile Computing Systems and Applications (WMCSA rsquo99) pp90ndash100 New Orleans La USA February 1999
[13] T W Chen and M Gerla ldquoGlobal state routing a new routingscheme for Ad-hoc wireless networksrdquo in Proceedings of theIEEE International Conference on Communications (ICC rsquo98)vol 1 pp 171ndash175 Atlanta Ga USA June 1998
[14] B Karp and H T Kung ldquoGPSR greedy perimeter statelessrouting for wireless networksrdquo in Proceedings of the 6th AnnualInternational Conference on Mobile Computing and Networking(MOBICOM rsquo00) pp 243ndash254 Boston Mass USA August2000
[15] D B Johnson D A Maltz and J Broch ldquoDSR the dynamicsource routing protocol for multi-hop wireless Ad hoc net-worksrdquo in Ad Hoc Networking C E Perkins Ed chapter 5 pp139ndash172 Addison-Wesley New York NY USA 2001
[16] D B Johnson D A Maltz and J Broch ldquoDSR the dynamicsource routing protocol for multi-Hop wireless ad hoc net-worksrdquo in Ad Hoc Networking C E Perkins Ed chapter 5 pp139ndash172 Addison-Wesley New York NY USA 2001
[17] Z Wei and S Weibin ldquoResearch of GPSR routing protocol forwireless sensor networksrdquo Electronic Measurement Technologyvol 33 no 9 2010
[18] GWei Y Chen andX Zhu ldquoA vanet-oriented routing protocolfor intelligent taxi-call systemsrdquo in Proceedings of the IEEE 14thInternational Conference on Communication Technology (ICCTrsquo12) pp 41ndash45 Chengdu China November 2012
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
The Scientific World Journal 9
[11] J Haerri F Filali and C Bonnet ldquoPerformance comparisonof AODV and OLSR in VANETs urban environments underrealistic mobility patternsrdquo in Proceedings of the Med-Hoc-Net2006 5th Annual Mediterranean Ad Hoc NetworkingWorkshopLipari Italy June 2006
[12] C E Perkins and E M Royer ldquoAd-hoc on-demand distancevector routingrdquo in Proceedings of the 2nd IEEE Workshop onMobile Computing Systems and Applications (WMCSA rsquo99) pp90ndash100 New Orleans La USA February 1999
[13] T W Chen and M Gerla ldquoGlobal state routing a new routingscheme for Ad-hoc wireless networksrdquo in Proceedings of theIEEE International Conference on Communications (ICC rsquo98)vol 1 pp 171ndash175 Atlanta Ga USA June 1998
[14] B Karp and H T Kung ldquoGPSR greedy perimeter statelessrouting for wireless networksrdquo in Proceedings of the 6th AnnualInternational Conference on Mobile Computing and Networking(MOBICOM rsquo00) pp 243ndash254 Boston Mass USA August2000
[15] D B Johnson D A Maltz and J Broch ldquoDSR the dynamicsource routing protocol for multi-hop wireless Ad hoc net-worksrdquo in Ad Hoc Networking C E Perkins Ed chapter 5 pp139ndash172 Addison-Wesley New York NY USA 2001
[16] D B Johnson D A Maltz and J Broch ldquoDSR the dynamicsource routing protocol for multi-Hop wireless ad hoc net-worksrdquo in Ad Hoc Networking C E Perkins Ed chapter 5 pp139ndash172 Addison-Wesley New York NY USA 2001
[17] Z Wei and S Weibin ldquoResearch of GPSR routing protocol forwireless sensor networksrdquo Electronic Measurement Technologyvol 33 no 9 2010
[18] GWei Y Chen andX Zhu ldquoA vanet-oriented routing protocolfor intelligent taxi-call systemsrdquo in Proceedings of the IEEE 14thInternational Conference on Communication Technology (ICCTrsquo12) pp 41ndash45 Chengdu China November 2012
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of
International Journal of
AerospaceEngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014
RoboticsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Active and Passive Electronic Components
Control Scienceand Engineering
Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
International Journal of
RotatingMachinery
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporation httpwwwhindawicom
Journal ofEngineeringVolume 2014
Submit your manuscripts athttpwwwhindawicom
VLSI Design
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Shock and Vibration
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Civil EngineeringAdvances in
Acoustics and VibrationAdvances in
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Electrical and Computer Engineering
Journal of
Advances inOptoElectronics
Hindawi Publishing Corporation httpwwwhindawicom
Volume 2014
The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014
SensorsJournal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Modelling amp Simulation in EngineeringHindawi Publishing Corporation httpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Chemical EngineeringInternational Journal of Antennas and
Propagation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
Navigation and Observation
International Journal of
Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014
DistributedSensor Networks
International Journal of