Turning heterogeneity into an advantage in wireless ad-hoc network routing

With increasing diversity of wireless devices, heterogeneity in transmission power is expected to commonly appear in ad-hoc networks. We observe that the existence of high-power nodes may adversely affect the performance of traditional ad-hoc routing protocols such as AODV and DSR. A simple fallback strategy (i.e. high-power nodes transmitting at low-power levels) may solve the problem, but may not be efficient since it ignores the extra capability of high-power nodes. In this work, we view different levels of power heterogeneity as different tiers in the network. We propose a Tier-based Routing Framework (TRIF) which tackles the asymmetric link problem while taking advantage of long-range transmissions by high-power nodes. In contrast to other approaches that require periodic beaconing, TRIF allows the source to discover paths with symmetric links on the fly. By avoiding dependence on periodic beaconing, TRIF requires low overhead and is robust to network dynamics. TRIF does not require changes to the MAC layer, and can be utilized by any wireless devices that support dynamic transmission power control. TRIF can be leveraged to compute the optimal transmission power level over each link in order to reduce interference. Our simulation results show that TRIF can significantly outperform traditional ad-hoc routing protocols in heterogeneous environments. (C) 2009 Elsevier B.V. All rights reserved.