Adaptive vector OFDM system for transmission over doubly selective fading channels

Multipath delay, Doppler shift and spread lead to overlapping and distortion in both the time and frequency domain of a wireless wideband signal. Although the resulting time-and-frequency-selective (or namely, doubly selective) fading may degrade the system performance, it also enables possible multipath and Doppler diversity when the system is properly designed. In this paper, based on the basis expansion model (BEM) and the time-frequency domain transformation, an Adaptive Vector OFDM (AVOFDM) transmission scheme is proposed. It is demonstrated that AVOFDM can achieve considerable joint Multipath-Doppler diversity gain over doubly selective channels, which is even more closer to the upper bound of the maximum achievable multipath-Doppler diversity in comparison with that can be achieved by the traditional non-adaptive Vector OFDM. Furthermore, the number of bits carried by each modulated symbol increases and the overhead cost by the 2-dimension cyclic prefix is reduced. Both factors contribute to an increased data throughput.