| Recently, the wireless networks research community has taken considerable interest in concurrently utilizing the ultra-wideband (UWB) spectrum with narrow-band systems to implement coexisting and cognitive spectrum solutions. In parallel, multi-channel multi-radio wireless systems are being developed to achieve improved network capacity by exploiting non-overlapping channel transmissions. Our motivation is to exploit the synergy between the above two approaches, in developing a multi-functional wireless system with significant support to applications of practical relevance. The goal, therefore, is to provide a exible framework for situational awareness in infrastructure-less covert surveillance circumstances, such as hostage rescue, first-emergency response, natural disaster recovery, or military surveillance. The primary requirements for such applications include the capability for detection of long range targets, distributed computing, and securely communicating the information across a multi-sensor network. These situations are further characterized by the absence of any central infrastructure, limited spectrum availability, varying topological environments, and growing wireless security concerns.;It is well known that UWB noise radar achieves covert high-resolution imaging of targets and terrain. The wide bandwidth yields fine range resolution, while the noise waveform provides immunity from detection, interference, and interception. Having multiple noise radars networked with each other can provide significant benefits in target detection and recognition. An ad hoc network harnessing the combined advantages of UWB radar sensing and wireless communications is a viable solution to the above requirement. This dissertation, therefore, proposes a unique scheme to modify the UWB noise radar to supplement it with orthogonal frequency division multiplexing (OFDM) based secure multi-user network communication capabilities, thus architecting the multi-functional UWB noise-OFDM netted radar. The salient features of this multi-functional radar system include surveillance with embedded OFDM-based communications, coexistence, multi-user capability, and physical layer security. Furthermore, with this availability of OFDM's multiple frequencies and a number of radars to share it between, this dissertation solves the problem of multi-user multi-carrier resource allocation by proposing a simple yet fully-distributed and cross-layered channel-diversity-aided algorithm. It constructs a contention-free medium access solution which scales logarithmically with the number of radar nodes, and dynamically adapts to network topology changes and wireless channel variations. Building on this contention-free local connectivity, this dissertation also qualitatively proposes a multi-carrier enhancement to the ad hoc on-demand distance vector (AODV) routing protocol for mobile ad hoc networks. Incorporating this enhancement will not only allow the ad hoc radar network to be resilient to mobility, but also provide routing protocol security, hence bridging one of the drawbacks of AODV. |
