Transmit diversity for multiband OFDM UWB systems

Multiband orthogonal frequency division multiplexing (MB-OFDM) has been proposed as an effective solution for providing high speed data transmission over the ultra-wideband spectrum in short range wireless links. The employment of transmit diversity techniques based on block codes can achieve enhancement in such a wireless system's performance since it greatly reduces the detrimental effects of multipath fading. In a MB-OFDM UWB system the space coded symbols can be distributed as space-time block codes over successive OFDM symbols or as spacefrequency block codes over neighbouring subcarriers. The authors investigate the performance of a MB-OFDM UWB system when it operates in conjunction with transmit diversity. More specifically, they analyse the suitability and performance of both space-time and space-frequency block coded MB-OFDM UWB system under various UWB channel models. The study shows that for the channel models considered, space-time block coding provides the best performance.