Efficient routing protocols for a free space optical sensor network

For very low power, high bandwidth applications, free space optical sensor networks (FSOSN) have shown potential. They promise increasing node functionality, lower energy consumption, lower cost and smaller sizes. However, the new optical communication architecture yields new routing challenges. The objective of our paper is to introduce novel routing protocols for FSOSN that take into account the line-of-sight requirement for optical communications. Our network is modeled as a directed hierarchical random sector geometric graph, in which sensors route their data via multi-hop paths, to a powerful base station, through a cluster head. Following the dominant communication pattern in sensor networks, we propose a new efficient routing algorithm for local neighborhood discovery and a base station (up-link and down-link) discovery algorithm. We show that our routing protocols require Olog(n) storage at each node, versus O(n) seen in the literature, and present analytical and simulation results to evaluate the proposed protocols