Rate-Embedded Doubly Directional Differential Space-Time-Frequency Coding Schemes

Due to a great many redundancy symbols, most of the existing differential space-time-frequency (DSTF) coding schemes suffer very low transmission rates. To overcome the disadvantage and obviously enhance the total transmission rate in a differential multiple-input-multiple-output (MIMO) orthogonal-frequency-division-multiplexing (OFDM) system, a rate embedded doubly directional DSTF coding scheme is proposed for doubly selective fading channels in this paper. High rate differentially coded matrices are embedded into proper time blocks and sub-carriers. In the frequency domain, both high rate non-unitary message matrices and low rate unitary message matrices are differentially transmitted alternately. In the time domain, all message matrices have full rates. Simulation results verify that, compared with those conventional DSTF coding schemes, the proposed scheme can achieve better error performances with higher transmission rates.