Th e International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
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100 200 300 400 £ 
Number of Nodes in the network 
3(a) 10% communication pairs 
Routing Protocol: 
♦ AODV 
■ DSDV 
♦ DSR 
° 1 1 1 1 
100 200 300 400 
Number of Nodes in the network 
r 
500 
3(b) 20% communication pairs 
Figure 3. Routing load vs. number of nodes 
Routing ProtocoF 
♦ AODV 
■ DSDV 
♦ DSR 
i 
100 
200 300 400 500 
Number of Nodes in the network 
3(c) 30% communication pairs 
Figure 3 illustrates the routing load of different ad hoc routing 
protocols vs. number of nodes in the network; thereinto, Figure 
3(a) is for 10 percent of the communication pairs, 3(b) is for 20 
percent of the communication pairs, and 3(c) is for 30 percent 
of the communication pairs. We understand that the AODV in 
general has higher routing request, especially for larger network 
size and higher percentage of communication pairs. The DSDV 
and DSR have a comparatively stable routing load overhead in 
different mobility scenarios. 
5. CONCLUSIONS 
Recent advances in automobile electronics, wireless communi 
cation, and pervasive computing have enabled the development 
of the vehicular ad hoc network (VANET), which is a brand 
new term for an old technology - a network that does not rely 
on pre-established infrastructure or centralized administration. 
When integrated into the intelligent transportation system (ITS), 
it can provide direct vehicle-to-vehicle (V2V) and vehicle-to- 
infrastructure (V2I) communications, thereby can greatly im 
prove the safety and efficiency of road traffic. However, many 
problems remain to be solved before this emerging & promising 
technology becomes a commonplace. 
In this paper, we focus on the routing performance in vehicular 
ad hoc networks. We present an extensive simulation studies to 
compare the following routing protocols: AODV, DSDV, and 
DSR, using a variety of highway scenarios, characterized by the 
mobility, load, and size of the networks. Our simulation results 
indicate that those routing protocols dedicated for MANET is 
totally unsuitable for VANET scenarios in terms of packet 
delivery ratio, routing load, and end-to-end delay. 
ACKNOWLEDGEMENTS 
This paper is partly supported by the National Natural Science 
Foundation of China under Grant No.40571134; the National 
Research Foundation for the Doctoral Program of Higher 
Education of China under Grant No.20070486001; the Program 
for Changjiang Scholars and Innovative Research Team in 
University under Grant No.40721001. 
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