A 4 × 4 unipolar Space-Time PPM-code with simplified decoding for IR-UWB transmissions

Abstract

In this paper, we propose a novel 4×4 Space-Time (ST) code that can be associated with Impulse-Radio Ultra-Wideband (IR-UWB) systems using Pulse Position Modulation (PPM). The proposed rate-1 and fully diverse code can be applied with unipolar M-PPM constellations for all even values of M without introducing any constellation expansion. In other words, as in single-antenna IR-UWB systems, information is conveyed only by the time delays of the modulated sub-nanosecond pulses without introducing any amplitude amplification or phase rotation. An adapted simple Maximum-Likelihood (ML) decoder and diversity-preserving suboptimal decoders that take the structure of the proposed code into consideration are also presented.