It is observed that packet forwarding can be encouraged by incorporating any method or mechanism in AODV routing protocol of mobile ad hoc networks while simulating in NS2. The path chosen is only one between source and destination with fixed number of intermediate nodes. How is that there is an improvement in throughput and packet delivery ratio when more number of nodes are added to the network when the path and intermediate nodes remain same. In short, how does the results get varied with the network size?
As long as there is no movement in the intermediate nodes, then the network traffic could be same. If the intermediate nodes are mobile, then the packets sent by the source should be forwarded by different set of nodes and hence the results vary. The number of nodes increase will only affect the total network power, total throughput, delay, etc. If you are planning to cmpute the end to end delay, the number of intermediate nodes may not have any effect if they are not mobile.
NS-2 simulator shows poor performance for large ad-hoc wireless networks .
The following link might be helpful for you.
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.58.2079&rep=rep1&type=pdf
The problems in a ad-hoc network is a function of the density of the network, the number of hops, and the traffic.
If the density is very high, the interferences in the network will be high, and the performance low.
If the number of hops in the path is high, the probability of lost a frame in the path increase.
If the traffic in the network is high, the probability of collisions increase.
If you increase the number of hops, you usually increase the 3 paramters. Bigger density, usually longer paths, and if there are more nodes generating traffic, the traffic in the network increase. In this case, the performance decrease.
There are particular cases that increase the size don't increase the problems. For example, the density is constant (more nodes but the density is more or less constant) and the nodes tries to communicate close nodes, not nodes that are in the other extreme of the network
Try to change the seed of your simulations. This will effect the exact node that would initiate the network discovery. Having multiple seeds for the same scenario will highlight if your observation is correct.
Try to collect at least 31 runs results for each scenario and do a 5% confidence on your results.
If the network performance is still improving after deploying more nodes to the network, then there might be something wrong with your scenario settings if you are absolutely sure that the path from source to destination did not change at all.
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