Single-beam flow routing for wireless sensor networks

Directional antenna has great potential to reduce power consumption in energy constrained wireless sensor networks. We consider a two-tier wireless sensor network where directional antenna is employed for upper-tier aggregation and forwarding nodes (AFNs). Existing flow routing solutions for maximizing network lifetime require each AFN to transmit multiple flows to different nodes at the same time, which we call multi-beam flow routing solution. In this paper, we show that it is possible to develop single-beam flow routing solution for nodes with directional antenna. More important, we show that the single-beam flow routing solution developed here is provably optimal in terms of network lifetime performance. This result is based on a novel technique to transform the optimal multi-beam flow routing into an equivalent single-beam flow routing solution. Numerical example illustrating how to obtain an optimal single-beam flow routing solution is also given