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In designing wireless multihop sensor networks, determining system parameters that guarantee a reasonably connected network is crucial. In this paper, we investigate node isolation in wireless optical sensor networks (WOSNs) as a topology attribute for network connectivity. Our results pertain to WOSNs modeled as random-scaled sector graphs that employ directional broad-beamed free space optics for point-to-point communication. We derive a generalized analytical expression relating the probability that no node is isolated to the physical layer parameters of node density, transmitter radius, and angular beam width. Through simulations, we demonstrate that for probability values close to 1, dense networks, and increasing beam width, the probability that the WOSN is connected is tightly upper bounded by the probability that no isolated node exists. In addition, our study demonstrates conditions for probabilistic K-connectivity guarantees and provides empirical insights on the impact of clustering on connectivity by employing simulations to validate analytical derivations. Our analysis provides a methodology of practical importance to choosing physical layer parameter values for effective network level design.

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There has been recent interest in the development of untethered sensor nodes that communicate directionally via free space optical communications for mission critical settings in which high-speed link guarantees in hostile environments are needed. Directional wireless optical sensor networks have the potential to provide gigabits per second speeds for relatively low power consumption enabling bursty traffic and longer network lifetimes. In randomly deployed sensor settings, the crucial steps of ad hoc route setup and node localization are not only nontrivial, but also vulnerable to security attacks. In response to these challenges, this paper proposes a lightweight securityaware integrated routing and localization approach that exploits the benefits of link directionality inherent to wireless optical sensor networks. The circuit-based algorithm that makes use of directional routing loops, called SIRLoS, leverages the resources of the base station and a hierarchical network structure to identify topological information and detect security violations in neighborhood discovery and routing mechanisms. We study the performance of the SIRLoS algorithm demonstrating that reduced localization error, routing overhead, and likelihood of attack in various contexts are possible within lightweight computational constraints. Index Terms-Directional optical mission critical network, secure routing and localization, free space optical sensor network, circuit-based routing. I. INTRODUCTIONT HE LAST few decades has seen a substantial transformation of wireless networking technologies leading to the recent interest in the integration of computation, communications and sensing mechanisms for low cost untethered device development. There is currently also an active interest in enabling a tighter coupling of this sensor networking technology to the physical world through actuation. This would lead to numerous new applications including smart vehicles, autonomous disaster exploration, and the surveillance and control of critical infrastructure. In such life-critical contexts designing for safety often translates to ensuring communication system security and device "awareness". For example, in disaster exploration, autonomous agents must have the ability to acquire and transmit sensed multimedia data such as temperature and video signals as well as identify their location in order to provide essential information to first responders.Research in mission critical networks (MCNs) addresses such challenges through the development of mechanisms Manuscript received