Novel high-rate transmit diversity schemes for MIMO IR-UWB and delay-tolerant Decode-and-Forward IR-UWB transmissions

In this paper, we consider the problem of Space-Time (ST) coding for multiple-input-multiple-output (MIMO) and Decode-and-Forward (DF) impulse-radio ultra-wideband (IR-UWB) systems. In particular, we propose three novel transmission schemes that are suitable for such systems. The first scheme is a multiplexing scheme that transmits at a rate higher than that of spatial multiplexing with the same complexity. The second scheme is a unipolar fully diverse and totally-real scheme that is suitable for pulse position modulation (PPM). The rate of this scheme exceeds that of full-rate ST codes with a lower decoding complexity. The third scheme corresponds to a 2 times 2 full-rate and fully diverse ST code that has a non-vanishing coding gain when associated with pulse amplitude modulation (PAM). These diversity schemes are appealing since they are tolerant to the asynchronization between the relays in DF networks.