Periodical-pilot-assisted tracking loop with RAKE combining for high rate DS-UWB receivers

Tracking constitutes a major challenge in Ultra-Wideband (UWB) communications due to dense multipath environment and low power consumption. Most of the existing studies on tracking fall within low rate Impulse Radio UWB (IR-UWB) scope, with the assumption that Inter-Frame Interference (IFI) or Inter-Symbol Interference (ISI) is absent. In this paper, we settle on high rate Direct-Sequence UWB (DS-UWB) systems, in which ISI is inevitable. A Periodical-Pilot-Assisted Tracking Loop with RAKE combining, which we termed PPATL, is proposed for high rate DS-UWB scenario. The proposed tracking loop can effectively combat ISI and capture multipath energy. Analytical expressions of Probability Density Function (PDF) of timing error in locked state, Mean Square Error (MSE, or termed timing jitter) and Mean Time to Lose Lock (MTLL) are derived. Numerical results are presented and then confirmed by means of extensive computer simulation results. These results corroborate our theoretical analysis. Additionally, this proposed PPATL has been used and justified in our realistic DS-UWB system.