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

In this paper, we propose a novel 4times4 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.