A mobility-based upper bound on route length in MANETs

In mobile ad-hoc networks (MANETs) routes are usually found by means of discovery packets that are injected to the network by sender nodes. Once the intended destination is reached by a discovery packet, it replies back to the sender using the same route. Upon reception of the reply message, data transfer from sender to destination can initiate. Node mobility, however, negatively affects route duration time since position changes may lead to connectivity disruptions. Furthermore, the whole process of route discovery breaks down when, due to position changes, the route followed by a discovery packet is useless by the time it reaches the destination. In this paper the conditions leading to this effect are studied and it is shown that they impose a practical limit on how long a route can be. The paper introduces a model to compute an upper bound on route length in MANETs, which is derived from the combination of a route duration model and an access delay model for multi-hop routes. The model was validated by simulations with different network settings. From this model, it was found that the node transmission range, node mobility and total per-hop delays actually define the maximum feasible number of hops in a route. To the best of the authors’ knowledge, this is a fundamental scaling problem of mobile ad-hoc networks that has not been analyzed before from a mobility-delay perspective.