A Layered Space-Time-Frequency Coded Transmission for MIMO-OFDM Systems

In this paper, we propose a layered space-time-frequency (STF) coded Orthogonal Frequency Division Multiplexing (OFDM) for next generation mobile multimedia systems. In [9], the architecture of a layered space-time-frequency coded transmission scheme is devised as a combination of orthogonal precoding and hybrid space-time block code (STBC). By doing so, it is possible to obtain higher spectral and power efficiencies than other conventional schemes [3][5]. However, this approach has performance degradation due to the loss of the orthogonality of STBC codes in high mobility environments. Therefore, we applied a time domain spreading method to [9], which individually distributes the data symbols over several OFDM symbols in a time domain. The proposed scheme provides both maximum transmit diversity and spatial multiplexing gains with a moderate complexity over multipath fading channels. Simulation results show that it is possible to obtain an additional transmit diversity gain by means of spreading in a time domain.