AbstractsComputer Science

Pulsed ultra-wideband (UWB) radio uses extremely short pulses to transmit information. Such pulses provide very fine timing information, which has led to technological advances in high-precision localization. This thesis investigates UWB localization strategies with a focus on receiver synchronization algorithms for time-difference-of-arrival localization to achieve centimeter accuracies in a 3-dimensional space. The system that consists of a reference transmitter, several receivers each with a sampling module and a wireless local area network interface, and a computer to process the data and to run the localization algorithm is targeted for deployment in a dense-multipath environment  – a metal-enclosed space with substantial amount of metallic objects inside it. An algorithm based on the existing reference broadcast synchronization with a coarse synchronization stage and a fine synchronization stage is developed for this application. Coarse synchronization synchronizes the clocks of the independently running receivers to within nanoseconds or tens of nanoseconds, and is implemented in an FPGA. The sampled data by all receivers are transmitted to a computer and then processed by a fine synchronization algorithm. This proposed algorithm is simulated in Matlab and Simulink. Major factors that may cause a synchronization error such as propagation delay and path overlap are modeled and included in this simulation model. In addition, challenges due to non-idealities of a practice environment are examined by implementing this algorithm in a properly working hardware. In particular, different sampling rates of all receivers are found to be a major issue that must be resolved. Different clock speeds affect both the coarse and the fine synchronization accuracies. Therefore, this thesis proposes a method that uses a reference signal with a stable pulse repetition frequency to overcome this issue.