A space-time block code using orthogonal frequency-shift-keying

We investigate in this paper an Alamouti-type space-time block code (STBC) using orthogonal M-ary frequency-shift-keying (MFSK). The signal is coherently detected using the channel estimates derived from the unmodulated (or implicit pilot) component of the orthogonal signal. An exact bit error probability expression for BFSK and tight union bound for MFSK are derived for the proposed coherent ST-FSK receiver. It is observed that the receiver can maintain close to ideal coherent performance even at very fast fading rates. In comparison with differential STBC, the two approaches yield similar error performance in a static fading environment. However, the error performance of differential STBC deteriorates rapidly as the fade rate increases. In terms of implementation complexity and delay, the proposed coherent ST-FSK receiver is similar to differential STBC, as both approaches employ digital filters of similar lengths. The findings in this paper suggest that despite its larger bandwidth requirement, ST-FSK is a very attractive alternative space-time signaling format.