Multiuser transmitted reference ultra-wideband communication systems

A conventional transmitted reference (TR) modulation scheme is an effective means to combat severe multipath distortion in an ultra-wideband (UWB) system, significantly relaxing the equalization requirements. However, it suffers from multiple-access interference and a data rate loss. In this paper, we propose a multiuser TR scheme to extend TR modulation to the multiuser case, while almost doubling the data rate by allowing arbitrarily small spacing of pulse pairs. The proposed scheme assigns a pair of pseudorandom sequences to each user to enable multiple access, modulating the amplitude of data and reference pulses, respectively. A waveform template is first estimated, followed by data demodulation. A time-hopping code can be employed to further minimize the effect of signal collisions. The method is appropriate for both pulse amplitude modulation and pulse position modulation. Waveform estimation and bit-error rate analysis are provided, and confirmed with simulations. Substantial detection improvements over conventional TR detectors are observed.