A simulation study on the impact of mobility models on routing protocol performance with unidirectional link presence

This paper considers the impact of unidirectional link on Ad-hoc on-demand distance vector routing protocol from a mobility perspective. Most routing protocols assume that all wireless connectivity is symmetrical and bidirectional. Such assumptions are not generally true. Wireless nodes exhibit non-uniform transmission power, non-uniform reception quality and signal to noise ratio which may result in unidirectional links, leading to sub-optimal performance. We present a scheme based on previous work, DR-AODV, which further improves network performance. The proposed scheme is efficient as it computes alternative path during route discovery. Additional broadcast incurred packets are not significant unlike the DR-AODV scheme. Each node maintains an alternative path towards the source in its backup routing table. As such, each node may quickly switch to them when the primary reverse route is blocked as a consequence of unidirectional link operation. It is shown, by simulation, that this technique is reliable and resilient to networks with high unidirectional links presence. Also, we further investigate routing protocol performance under different mobility models. Results obtained from these models are compared, and significant differences are immediately noticeable under several performances metric.