Gugrajah_Yuvaan_ Ramesh_2003.pdf
Gugrajah_Yuvaan_ Ramesh_2003.pdf
Gugrajah_Yuvaan_ Ramesh_2003.pdf
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Simulation ofa Load Balancing Routing Protocol<br />
3.9. Summary<br />
Chapter 3<br />
The routing protocols that have been proposed for ad hoc networks generally<br />
consider the shortest path as the main routing criteria. However, simple examples can<br />
be used to show that congestion may be caused when the shortest path is always<br />
used. In this chapter the Dynamic Load Aware Routing protocol [GedaOO] is<br />
described, with 3 schemes that each employ load balancing by determining the usage<br />
of the buffers at each node. A new fourth DLAR scheme is proposed in this chapter<br />
that takes into account signal quality and network load in order to alleviate<br />
congestion in the network and reduce delay.<br />
Simulations were performed to compare the new DLAR protocol to the other DLAR<br />
protocols and to AODV, which is a prominent routing protocol for ad hoc networks.<br />
The two quantities of interest that were measured was average packet delivery ratio<br />
and average end-to-end delay. The simulator implements physical layer modelling, .<br />
medium access control and a mobility model, all of which have been described. The<br />
mobility of the network was characterized by using a pause time for which the nodes<br />
do not move. A high pause time implies a slow changing topology, while a low pause<br />
time implies a rapidly changing topology. The load offered to the nodes was<br />
determined by a packet generation time assigned repeatedly to each node. When the<br />
packet generation time expires, the node begins transmitting packets to a randomly<br />
selected destination. The node is then reassigned a random packet generation time<br />
which is no greater than the maximum allowed for the simulation run.<br />
The results obtained using the simulator are discussed. It was found that the DLAR 4<br />
routing scheme has the best performance in comparison to the other protocols in<br />
terms of aver-age packet delivery ratio for all mobility scenarios and offered traffic,<br />
while AODV has the worst performance due to the selection of routes based purely<br />
on their length. It was also found that as the offered load was reduced, the difference<br />
between AODV and the DLAR 4 protocols reduced. This demonstrates that the<br />
implementation of load balancing does increase packet delivery ratio for high offered<br />
load.<br />
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