Double time domain spread unitary space-time modulated OFDM for multiuser downlink broadband mobile communication

In many wireless broadband physical channels, such as mobile urban radio channels, Doppler-spread is decidedly occurring and the channel characteristics are of both time-selectivity and frequency-selectivity (double-selectivity), which produces performance degradation for those systems only utilizing the frequency-selectivity channel characteristics. A double time domain spread unitary space-time modulated orthogonal frequency division multiplexing (OFDM) scheme is proposed for high data rate multiuser downlink broadband mobile communication. The proposed scheme makes the system not only capable of efficiently exploiting the double-selective characteristics of the wireless mobile fading channels to attain large diversity gain but also with both high data rate and high system capacity.