Effects of Channel Models and Rake Receiving Process on UWB-IR System Performance

In ultra-wideband impulse radio (UWB-IR) systems, multipath-delayed received pulses may overlap if two consecutive multipaths arrive within less than the pulse duration. This condition makes it nontrivial for the Rake receiver to capture enough multipath energies for reliable communications. In this paper, we study in detail the effects of channel models and Rake receiving process on the performance of UWB-IR systems. Specifically, we consider T_c- and T-spaced channel models and different Rake receiver implementations to maximize the captured signal energy, where we discuss their validity for real system considerations. Also, we show that code shift keying (CSK) impulse modulation can achieve about 1 dB performance gain over conventional pulse position modulation (PPM) when there is pulse overlapping, as it randomizes pulse transmit locations as opposed to fixed pulse transmit locations used by PPM.