a traffic light based reliable routing protocol for urban vanets...

Copyright © 2012, [email protected]

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A Traffic Light Based Reliable Routing Protocol for Urban VANETs

都會區車載隨意網路下基於紅綠燈之可靠繞徑技術指導教授：王國禎博士學生：張景喬

國立交通大學網路工程研究所行動計算與寬頻網路實驗室


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Outlines

• Introduction• Background• Related work• Proposed traffic light based routing protocol• Simulation and discussion• Conclusion• Future work• References


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Introduction

• In urban vehicular ad hoc networks (VANETs), each vehicle (node) is independent and moves along the roads

• VANETs are highly mobile wireless ad hoc networks

• Due to high mobility in VANETs, wireless links would be disconnected frequently


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Introduction (cont.)

• Thus, routing paths may be very unstable due to network topology changes in VANETs

• Broken routing paths cause the decrease of packet delivery ratio and the increase of end-to-end delay


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Background

• DSR (Dynamic Source Routing) [3]− Node-centric routing protocol− Main characteristics:

− Route discovery− Route maintenance

− Once a node receives a ROUTE REQUEST (RREQ) packet, if the node has not seen it before, it adds its node ID to the route and forwards the RREQ to its neighbors

− If there is any broken link due to the network topology changes, source node can issue another RREQ to find a new route


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Background

• AODV (Ad-hoc On-demand Distance Vector) [2]− Source node broadcasts RREQ until the packets reach to

destination node or intermediate nodes containing the routes to destination node

− Once a node receives a RREQ packet, the node replies back to source node along the route

− When a broken link is detected, ROUTE ERROR will be sent to source node by a node recently using this broken link, then the source node issues new route discovery


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Background

• The disadvantages of DSR [3] and AODV [2] [15]:− High velocity nodes result in very short window of

communication between nodes on different streets− The built route expires quickly and the source node needs

to re-issue new route discovery after sending only few data

− When applied to urban environments, these protocols cause a high control overhead in terms of RREQ and RREP packets


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Related work

• CLA (ConnectionLess Approach) Routing [15]− No need to build routing tables to maintain the position

of neighbor nodes − No need to maintain a hop-by-hop route between the

source and destination nodes− The nodes belong to the selected cells can receive or

forward data− When a relay node leaves the selected cell, it is no need

to relay data


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Related work• CLA

− Streets are divided into cells

Building

Building

Cell A Cell CCell B


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Related work

• An example of CLA− RP: reference point

Source node

Destination node

Cell size

Increment_Y

S(XS,YS)

D(XD,YD)

RP1(X1,Y1)

RP2(X2,Y2)

RP3(X3,Y3)


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Related work

• Disadvantages of CLA:− Cell A and cell C are located in road intersections where

nodes would pass as fast as possible− A relay node would not relay data long enough, so a

different node needs to be found frequently to relay data− In the selected cells, high speed nodes may be chosen if

we do not set different backoff delays to nodes with different speeds


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Related work

• Road-based using vehicular traffic (RBVT) [12]− RBVT protocol utilizes real-time vehicular traffic

information to create paths consisting of road intersections which may have network connectivity among them with higher probability

− To reduce a path’s sensitivity to individual node movements, geographical forwarding is chosen to transfer packets between intersections on the path

− RBVT does not consider the speed of nodes to forward data, so data loss may occur frequently


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Related workRouting protocol

CLA [15] RBVT [12] TLR (proposed)

Class of routing protocol

Road-based Road-based Road-based

Street partition method

Virtual cell Virtual intersection Virtual cell and traffic light cell

Choice of nodes to relay

data

A node is farther away from

previous node

A node is farther away from

previous node

Node waiting at red traffic light or a node is

farther away from previous node

Usage of traffic light information

No No Yes


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Proposed TLR

• TLR (Traffic Light based Routing)− When vehicles stop at red traffic lights, nodes with no

mobility can forward data to next nodes− Divide an area into numbers of virtual cells and traffic

light cells− Select a list of virtual cells to be a packet forwarding path

between source and destination nodes, and a traffic light cell is included in a virtual cell

− Equipment required:− GPS (Global Positioning System)− Digital map


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Proposed TLR

• Virtual Cell ID:− Virtual cell IDs are specified on road intersections− Road intersections in urban areas usually have traffic

lights − The red lights on means nodes must stop at the

intersection− Using reliable and stable node to relay data packets may

increase the packet delivery ratio


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Proposed TLR

• Example of specifying virtual cell IDs on road intersections:

S

D

A101A201

A301

A102

A103

A104

A105

A202

A203

A204

A302

A303

A304

A205A2b05

A305


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Proposed TLR• A road intersection is divided into two cells: virtual cell and

traffic light cell

Virtual cell A

Traffic light cell A

Virtual cell B

Traffic light cell B

Stationary node has high priority to relay data packet in traffic light

cell

If there is no nodes in traffic light cell, choose a relay node in virtual cell


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Proposed TLR

• Route discovery:− Source node broadcasts RREQ packets− RREQ packets contain <source node ID, destination node

ID, sequence number, virtual cell record>− Virtual cell record contains a list of virtual cell IDs− When an intermediate node receives an RREQ packet, it

attaches its current virtual cell ID into the virtual cell record and forward the updated RREQ


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Proposed TLR

• Route discovery:− If the destination node receives an RREQ packet then it

records the following information to an RREP packet:• Current virtual cell ID of virtual cell ID record• Its direction• Sends the RREP packet back along the route• RREP packet contains <source node ID, destination

node ID, sequence number, virtual cell ID record, destination direction>


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Proposed TLR

• Flowchart of a node forwarding a data packet from source to destination nodes

Start

Receive data packet

Destination node?

The node’ s virtual cell ID is in the virtual cell ID record?

no

yes

yes

no

Stop transmitting

Discard Data packet

A


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Proposed TLR

• Flowchart of a node forwarding a data packet from source to destination nodes

located on traffic light cell?

no

yesBackoff

delay = α +ϒ*Spd

Backoff delay =

β +λ (MAX_DIST-Dist)

Sensing other nodes are transmitting?

Discard Data

packet

Forward data

packet

yes

no

A


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Proposed TLR

• Data forwarding procedure:− An algorithm for nodei receives a data packet from nodej:

1. If nodei is a destination node, stop forwarding the data packet

2. If nodei is not in the selected virtual cells, stop transmitting the data packet

3. Otherwise, nodei’s virtual cell ID is in the virtual cell ID record, and then computes backoff delay; if sensing no other nodes transmitting, then nodei transmits the data packet


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Proposed TLR

• Backoff delay computation of nodei receiving a data packet:− For nodei in a traffic light cell:

where α is a random number in μ seconds (0 ≦ α < 51.2)

ɣ is a delay thresholdSpdi is the speed of nodei

ii SpdDELAYBACKOFF * _


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Proposed TLR

• Backoff delay computation of nodei receiving data packet :− For noden in a virtual cell:

where β is a random number in μ seconds (51.2 ≦ β < 102.4)

λ is a delay thresholdDistnm is a current distance between node n and

previous node mMAX_DIST is a maximum radio range

)_(* _ nmn DistDISTMAXDELAYBACKOFF


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Proposed TLR

)_(* _

* _

nmn

nn

DistDISTMAXDELAYBACKOFFelse

SpdDELAYBACKOFFtrue)==LightCellif(Traffic

• Backoff delay calculation:


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Proposed TLR

• An example of data forwarding: Virtual

cell A

4km/hr

15km/hr

9km/hr

Traffic light cell A

0km/hrSender

Virtual cell B

Traffic light cell B


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Simulation and discussion

• Packet delivery ratio [13]: Total number of packets successfully received from the destination node divided by total number of packets sent by the source node which generated by the CBR source

• End-to-end delay [13]: This number indicates the average

time measured in millisecond from the beginning of a packet transmission (including route acquisition delay) at a source node until packet delivery to a destination

generated packets data ofnumber Totalpackets data receivedly SuccessfulveryRatioPacketDeli


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• Simulation setting for GlomoSim [16]

Simulation time 900sMobility model VanetMobiSimTerrain dimensions 1000 m * 1000 mMAC protocol 802.11Data traffic generation CBRPacket size 512 bytesRadio range 376 m [15]



• VanetMobiSim [14] parameters for road layouts[15]

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Simulation time 900 sMax traffic lights 80Terrain size 1000 m*1000 mMin. speed 1 m/s (3.6km/hr)Max. speed 15 m/s (54km/hr)Nodes (vehicles) 50, 100, 150, 200Max. acceleration 0.6 m/s2

Normal deceleration 0.5 m/s2


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50 100 150 2000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Effect of number of nodes on packet delivery ratio

TLR (proposed) CLA

Number of nodes

Pack

et d

eliv

ery

ratio


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50 100 150 2000

10

20

30

40

50

60

70

80

90

100Effect of number of nodes on end-to-end delay

TLR (proposed) CLA

Number of nodes

End

-to-

end

dela

y (m

s)


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• Simulation setting for GlomoSim [16]

Simulation time 300 s [12]Mobility model VanetMobiSimTerrain dimensions 1500 m*1500 m [12]MAC protocol 802.11Data traffic generation CBRPacket size 512 bytesRadio range 376 m Packet rate (packet/s) 0.5 to 5 [12]



• VanetMobiSim [14] parameters for road layouts [12]

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Simulation time 300 s [12]Max traffic lights 80Terrain size 1500 m*1500 m [12]Min. speed 11.1 m/s (40 km/hr) [12]Max. speed 24.4 m/s (88 km/hr) [12]Nodes (vehicles) 250 [12]Max. acceleration 0.6 m/s2

Normal deceleration 0.5 m/s2


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0.5 1 2 3 4 50

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Effect of Packet rate on packet delivery ratio

TLR (proposed) CLA

RBVT-P

Packet rate (packet/s)

Pack

et d

eliv

ery

ratio


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0.5 1 2 3 4 50

20

40

60

80

100

120

140

160

Effect of Packet rate on end-to-end delay

TLR (proposed)CLARBVT-P

Packet rate (packet/s)

End-

to-E

nd D

elay

(ms)


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Conclusion

• We propose a traffic light based routing protocol for urban VANETs

• Proposed TLR improves 10 % and 20 % of the packet delivery ratio compared to CLA and RBVT-P, respectively

• Proposed TLR reduces 20 ms and 80 ms of the end-to-end delay compared to CLA and RBVT-P

• Delivering packets to a relay node which is waiting for the red traffic light effectively improves the packet delivery ratio

• The end-to-end delay can be reduced by the selecting stationary nodes as relay nodes and running backoff delay


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Future work

• Make the proposed TLR be able to establish multiple paths to provide a more reliable routing protocol for urban VANETs

• Combine multimedia streaming with TLR to provide reliable multimedia for urban VANETs


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References[1] Y. Toor, P. Muhlethaler, and A. Laouiti, “Vehicle ad hoc networks: Applications and

related technical issues,” IEEE Communications Surveys & Tutorials, pp. 74–88, 2008.

[2] C. E. Perkins and E. M. Royer. “Ad Hoc On-Demand Distance Vector Routing,” in Proc. 2nd IEEE Workshop on mobile comput. Syst. Appl., pp. 90-100, February 1999.

[3] D. B. Johnson, D. A. Maltz, Y. C. Hu, J. G. Jetcheva, "The Dynamic Source Routing Protocol for Mobile Ad Hoc Networks," in IETF MANET Working Group, INTERNET-DRAFT, 2 March 2001.

[4] B. Parkinson and S. Gilber, “NAVSTAR: global positioning system – 10 years later,” in Proc. of IEEE, vol.71, no.10, pp. 1177- 1186, Oct. 1983.

[5] M. Gerla, X. Hong, and G. Pei, “Fisheye state routing protocol (FSR) for ad hoc networks,” IETF Draft, 2002.

[6] C. E. Perkins and P. Bhagwat., “Highly Dynamic Destination-Sequenced Distance-Vector Routing (DSDV) for Mobile Computers,” in Proc. of the SIGCOMM ’94 Conference on Communications Architectures, Protocols and Applications, pp. 234–244, August 1994.


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References[7] P. Jaqcuet, P. Muhlethaler, T. Clausen, A. Laouiti, A. Qayyum, and L. Viennot,

“Optimized link state routing protocol for ad hoc networks,” in Proc. of IEEE INMIC Multi Topic Conference, 2001. Technology for the 21st Century., pp. 62- 68, 2001.

[8] S. Grafling, P. Mahonen, and J. Riihijarvi , "Performance evaluation of IEEE 1609 WAVE and IEEE 802.11p for vehicular communications," in Second International Conference on Ubiquitous and Future Networks (ICUFN), pp.344-348, 16-18 June 2010.

[9] H. Hartenstein and K. P. Laberteaux, “A Tutorial Survey on Vehicular Ad Hoc Networks,” IEEE Communications Magazine, vol. 46, no. 6, pp. 164–171, June 2008.

[10] A.H. Ho, Y.H. Ho, and K. A. Hua, “A Connectionless Approach to Mobile Ad Hoc Networks in Street Environments,” in Proc. of IEEE Intelligent Vehicles Symposium, 575 – 582, 2005.

[11] P. Bose, P. Morin, I. Stojmenovic, and J. Urrutia, “Routing with guaranteed delivery in ad hoc wireless networks,” ACM Wirel. Netw., vol. 7, no. 6, pp. 609–616, Nov. 2001.


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References[12] J. Nzouonta, N. Rajgure, A. Guiling Wang, and C. Borcea, “VANET routing on city

roads using real-time vehicular traffic information,” IEEE Trans. Veh. Commun. pp. 3609 - 3626, 2009.

[13] A. K. Pandey, H. Fujinoki, “Study of MANET routing protocols by GloMoSim simulator,” International Journal of Network Management, v.15 n.6, p.393-410, November 2005.

[14] M. Fiore, J. Härri, F. Filali, and C. Bonnet, “Vehicular mobility simulation for VANETs,” in Proc. 40th Annual Simulation Symp., Mar. 2007, pp. 301-307.

[15] Y. H. Ho, A. H. Ho, and K. A. Hua, “Routing Protocols for Inter-Vehicular Networks: A Comparative Study in High-Mobility and Large Obstacles Environments, ” Computer Communications Journal - Special Issue on Mobility Protocols for ITS/VANET 2008.

[16] X. Zeng, R. Bagrodia, and M. Gerla, “GloMoSim: A library for parallel simulation of large-scale wireless networks,” in Proc. of 12th Workshop on Parallel and Distributed Simulations, pp. 154-161, 1998.

a traffic light based reliable routing protocol for urban vanets...

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