In this paper, used existing AODV, DSR and GPSR routing
protocols. AODV [10] and DSR [11] are MANET reactive
routing protocols. GPSR [12] is a MANET geographical
routing protocol.
In AODV (Ad hoc On Demand), when any source vehicle
wants to communicate with any destination vehicle, a route is
created on demand. The route request (RREQ) packet is
flooded to reach the destination vehicle and reply (RREP)
packet is unicast along the path given by the backward
pointers.
In DSR (Dynamic Source Routing) intermediate nodes
forward the RREP by changing their name as sender. If the
reply is not received by given time, the source vehicle restarts
again discovery of route.
In GPSR (Greedy Perimeter Stateless Routing), data
forwarding from the source vehicle to the destination vehicle
is based on geographic positions of vehicles and uses greedy
method to choose intermediate vehicle.
4. PERFORMANCE EVALUATION
This section presents the evaluation of the routing protocols
using the network simulator NS-2.33 [8]. To evaluate the
performance use the city map scenario generated and
described in above section. In this paper, existing AODV,
DSR and GPSR are used. Considered simulation parameters
for NS2 are given in Table 1. One assumption is that each
vehicle has embedded GPS. The performance of the routing
protocols is evaluated by varying the network density.
4.1 Performance Metrics
The following are metrics used to measure the performance
Average Throughput: This metric is defined as the number of
data packets that were received at destination over simulation
time.
Packet Delivery Ratio: This metric is defined as the number
of data packets that were successfully delivered at destinations
by the number data packets that were sent by sources.
Packet Loss: Number of packets that do not reach the
destination.