Variable Route Expiration Time based on a Fixed Probability of Failure for Ad-Hoc Networks Routing Applications

In reactive routing algorithms on Ad-Hoc networks, one of the most important challenges is to minimize the number of route discovery processes, due to their high cost in bandwidth. This is achieved through a careful selection of the expiration time, i.e. the time each node keeps active the current route. Most implementations use system-wide random or arbitrary values for this parameter, even though the failure probability of a route depends of its size. Thus the use of a fixed expiration time is not necessarily efficient, and a variable allocation of expiration times for routes, according to their size, is proposed by introducing the VTOA (Variable Time Out Allocation) method. VTOA can be applied to any Ad-Hoc routing algorithm. In particular, an implementation of this method on the AODV algorithm is presented. The results obtained by simulation show VTOA improves the network's performance, both in terms of the routing overhead (8.5% lower) and average end-to-end delay (21.3% lower), when compared to the original AODV, while other indicators, as the packet delivery fraction, remain the same or are slightly better.