We introduce a space-time block-coded orthogonal frequency-division multipl
exing (STBC-OFDM) scheme for frequency-selective fading channels which does
not require channel knowledge either at the transmitter or at the receiver
. The decoding algorithm is based on generalized maximum-likelihood sequenc
e estimation. We investigate the performance of the proposed scheme over tw
o-tap Rayleigh fading channels. Simulation results show the performance to
be near optimum.