Diversity and Coding Gains of Space-Time-Frequency Coded MIMO-OFDM

Space-time-frequency (STF) coding for multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) over frequency-selective Rayleigh fading channels is considered. The maximum diversity order and coding gain of the system are derived when linear constellation preceding (LCP) is applied to OFDM symbols. It is also shown that with a proper subcarrier grouping of the OFDM symbols, the system implementation can be greatly simplified while maintaining the diversity order and coding gain. In particular, as long as the group size F is not less the number of effective resolvable channel taps L, the maximum diversity order can always be achieved. Moreover, if F ges L, and F is an Euler number or an integer power of 2, the maximum coding gain can be achieved. Otherwise, the achievable coding gain approximates 70% of the maximum one.