Demodulation and tracking with dirty templates for UWB impulse radio: algorithms and performance

Major challenges in ultrawideband (UWB) communications include timing acquisition, tracking, and low complexity demodulation. Timing with dirty templates (TDT) is a recently proposed acquisition algorithm with attractive features. Starting with a performance analysis of TDT, this paper goes on to considerably broaden its scope by developing novel tracking loops and detectors by naturally following the TDT operation. Specifically, upper bounds on the mean square error of the blind and data-aided TDT estimators are derived, along with TDT-based demodulators, obviating the need to know the underlying channel and time hopping code. Analytical comparisons reveal that TDT demodulators outperform RAKE with limited number of fingers in the medium-high SNR range. TDT demodulation performance in the presence of timing errors is evaluated and shown to be robust to mistiming. In order to follow timing offset variations, an adaptive loop is also introduced to track the first multipath arrival of each symbol. For a given input disturbance, parameters of the loop are selected to optimize jointly transient and steady state performance. Analytical results are corroborated by simulations.