Optical Wireless Sensor Networks For Critical Infrastructure Surveillance

1. Introduction
There is a growing need in society, especially in light of Homeland Security, for surveillance of our critical civil infrastructure. There is an equally compelling concern for the effectiveness of first responders to major incidents that may be terrorist related, but could also be the result of major weather events or hazardous spills. In both cases, there is an urgent need for high quality video-based surveillance, advanced specialized sensors and high bandwidth communications that is portable, secure, and reconfigurable and offers high availability. Such sensor communication (SC) networks will be extensive, must be compatible with our legacy communication infrastructure, and must be able to transport very large quantities of data, which could involve Gb/s data flows from systems of high-resolution cameras. Extensive video-based monitoring, with rapid image update rates, and high resolution is data flow intensive, and would overwhelm the capacity of any proposed RF solution to this problem.

RF communications have limited bandwidth, are not secure from intercept or detection, and are intrinsically non-scalable [1]. Fiber communications infrastructure has the data capacity, but cannot be installed easily everywhere. There is a communications gap between most of the places where want to communicate from, and existing fiber networks. This has been referred to as the last (or first) mile problem and continues to be the greatest obstacle we face in implementing broadband networks from everywhere to everywhere. The portability, security, reconfigurability and availability features of our proposed system overcome these shortcomings.

The use of free space laser communication links, often called “optical wireless” is emerging as an important solution to this problem. It is our belief that autonomous optical wireless communication nodes have the ability to meet the data egress requirements of advanced SC networks. They provide the data rates required, do not interfere with our existing RF mobile communications infrastructure, and provide a “bridge” from where data are generated to the nearest fiber. It has been estimated that 80% of small and medium buildings in the USA do not have a high data rate fiber connection, yet are within 1 mile of the nearest fiber. In this proposal we describe a program of research to study in a comprehensive way the use of optical wireless in conjunction with other technologies to provide a robust, advanced SC network for critical infrastructure and transportation system monitoring. A key focus of this work is the development of autonomous, possibly solar-powered, optical wireless transceivers, which have the ability to point and track, can handle continuous or “bursty” data, and which can function in a dynamic network environment.