Abstract
In this paper, we investigate the deficiency of uncontrolled asymmetrical transmission power over multiple channels in ad hoc environments. We further propose a novel distributed transmission power control protocol called the distributed power level (DPL) protocol for multi-channel ad hoc networks without requiring clock synchronization. Specifically, different transmission power levels are assigned to different channels, and nodes search for an idle channel on the basis of the received power so that the maximum allowable power of the preferred data channel is larger than or equal to the received power. If the most preferred channel of the least maximum power is busy, the nodes are able to select the next channel and so forth. As a result, interference is reduced over channels because the nodes that require higher transmission power are separated from interfering with the nodes that require lower transmission power. Two transmission power control modes are introduced for DPL: symmetrical and asymmetrical. For the symmetrical DPL protocol (mode), nodes transmit at the same power level assigned to the selected channel. On the other hand, for the asymmetrical DPL protocol, nodes are allowed to transmit at a lower or equal power level that is assigned to the selected channel. Extensive ns-2-based simulation results are presented to demonstrate that the proposed protocols can enhance the network throughput compared with the existing uncontrolled asymmetrical transmission power protocol. Copyright (C) 2012 John Wiley & Sons, Ltd.