Gradational power control in multi-channel multi-radio wireless ad hoc networks

Various power control techniques have been proposed to boost aggregate network throughput by reducing the interference impact and encouraging more concurrent transmissions in medium-shared wireless systems. In this paper, we do not intend to devise new power control mechanisms. Rather, we investigate an interesting problem of how to apply power control techniques in a multichannel networking environment, where every wireless node is equipped with multiple radio transceivers, each statically binding to a dedicated channel. For a single radio transceiver, more reduction on transmit power generally results in lower network connectivity, leading to a longer route (if path exists) for multi-hop communication (bad for end-to-end throughput). On the other hand, small transmit power helps accommodate more concurrent transmitters (good for aggregate throughput). For wireless ad hoc networks with multi-hop communication as the major behavior, how to take both route length and medium utilization into consideration to improve system capacity is thus important. Motivated by this, we propose to apply power control with different connectivity degrees on radio interfaces. Imagine several superposed network topologies having gradational connectivity levels over multiple non-interfering channels, hence the name, gradational power control (abbreviated as GradPC), is given. In our proposed GradPC protocol, a base channel is designated to use default transmit power (no power control on this radio). For other non-base radios, we adopt neighbor-based power control mechanisms to tailor the connectivity degree for each radio channel. After GradPC has successfully configured transmit power for all radios, our other corresponding protocols run in the following two phases: (i) a variant DSR is performed over the base channel to discover a multi-hop route, and (ii) once the route is ready, a radio selection procedure is activated to judiciously schedule the next link-layer packet sent over an appropriate channel. Simulation results demonstrate that the proposed GradPC along with its corresponding protocols outperform strategies with no power control and the same connected topology, by imposing gradational power levels on radios to balance the requirements for short route and high medium utilization.