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.