Design and analysis of impulse radio ultra wideband receivers for communications and geolocation
This dissertation considers performance analysis and receiver design issues of impulse radio (IR) ultra wideband (UWB) systems, and investigates algorithms for accurate positioning of mobile users in UWB and other wireless networks.
First, trade-offs among processing gain parameters are investigated in the presence of timing jitter for IR-UWB systems with and without pulse-based polarity randomization. For a large and fixed total processing gain, effects of changing the number of pulses per symbol (pulse combining gain ) and the number of chips per frame (pulse spreading gain ) are analyzed for additive white Gaussian noise (AWGN) and multipath channels1. Then, a detailed performance analysis of IR-UWB systems with pulse-based polarity randomization is performed in asynchronous environments, considering the effects of both multiple-access interference (MAI) and inter-frame interference (IFI), and approximate expressions for the bit error probability (BEP) of Rake receivers with various combining schemes are derived.
After the performance analysis study, design of optimal and suboptimal IR-UWB receivers is investigated. In order to optimize the system performance, both the selection of multipath components to be employed at the receiver and the combination of those selected components for symbol detection are studied.
In addition to receiver design considerations for UWB communications purposes, time of arrival (TOA) estimation for positioning applications is studied, and a two-step TOA estimation algorithm, which can provide an accurate estimate in a reason able time interval from low-rate signal samples, is proposed. Moreover, two algorithms to mitigate errors due to non-line-of-sight (NLOS) propagation are investigated.
Finally, extensions and applications of our performance analysis study of IR-UWB systems are considered. First, the analysis is extended to IR-UWB systems that use multiple types of UWB pulses, or various processing gain parameters for different users. Then, performance of a transmitted-reference (TR) based scheme is analyzed based on the previously developed performance analysis techniques.
1By an AWGN channel, a free-space propagation scenario is meant; hence, the received signal consists of a sum of the attenuated signal and AWGN noise.