Adaptive Radiolocation for Mobile Sensor Networks

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Advances in radios, sensors, actuators and embedded computing technology have enabled a proliferation of wireless sensing networks. These networks offer an affordable way of performing distributed sensing for a seemingly unbounded set of applications. Accurate positioning is a key enabler for many sensor applications including surveillance networks, robotic sensors, location-based routing in wireless ad-hoc sensor networks, smart spaces and environmental monitoring by mobile sensors. Although GPS can potentially provide accurate positioning, the complexity of the required receivers may be too costly for inexpensive sensor nodes. Furthermore, the GPS signal is extremely weak and positioning can be unreliable inside buildings or under dense foliage. These drawbacks to GPS positioning have led to increasing interest in GPS-less distributed radiolocation methods for wireless sensor systems. This project focuses on techniques GPS-less cooperative radiolocation using time-of-arrival over ISM-band radios (e.g. 802.11b)There are numerous problems that must be solved for adaptive radiolocation in sensor networks. Multiaccess interference occurs if multiple sensors transmit acknowledgements at the same time. The presence of multipath can obscure and interfere with correct estimation of the time-of-arrival causing range errors. The RF power amplifier is a major energy consumer; therefore positioning estimates must be made with minimal communication. The project addresses these problems through: 1) Analysis and development of multiuser estimation algorithms that can jointly estimate times of arrival (TOAs) from multiple sensors. 2) Creation of a reconfigurable computational core, which enables an adaptive radiolocation platform for embedded systems. The core will be designed to enable tradeoffs between different system parameters, including power/energy, latency and accuracy of the positioning algorithms. 3) Development of new distributed estimation algorithms for sensor networks. 4) Implementation of cooperative radiolocation algorithms in a testbed operating in the 2.4 GHz ISM band. 5) Design of antenna arrays and sensing algorithms for the radiolocation network