The hop count shift problem and its impacts on protocol design in wireless ad hoc networks

Abstract

The hop count information has been exploited in the design of networking protocols in wireless ad hoc multi-hop networks. The hop count setup process normally assumes a perfect disk communication model and uses a simple controlled flooding approach. However, the practical communication model may not be such a disk communication model but time-varying and lossy. Sometimes transmissions can be successful beyond the nominal transmission range, i.e., the radius of such a disk model. The defacto hop count which are setup via time-varying and lossy radio channels may be different from the one based on the disk communication model. This paper introduces the hop count shift problem in realistic radio channels and investigates its impacts, via extensive simulations, on some representative hop count based protocols. Our simulation results suggest that these protocols' performance generally suffers from the hop count shift problem, and the degradation is dependent on how the practical communication model deviates from the disk communication model. We also propose a strategy to combat the hop count shift problem and conduct simulations to show its effectiveness. The study of this paper necessitates reexaminations for the design of new hop count setup mechanism and the hop count based networking protocols.