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Summary: Abstract-- We introduce a space-time block-coded orthogonal
frequency-division multiplexing (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
sequence estimation. Due to the assumed orthogonality structure of
STBC, the decoding rule reduces to a single step. Its form also
allows the derivation of a recursive expression, which can be easily
implemented by a Viterbi-type algorithm. We investigate the
performance of the proposed scheme over two-tap Rayleigh fading
channels. Simulation results show the performance of the proposed
recursive-type receiver to be near optimum.
Index terms-- Space-time coding, OFDM, frequency-selective
fading channels, maximum-likelihood sequence estimation.
I. INTRODUCTION
Space-time trellis coding (STTC) was introduced in [1] as an
effective transmit diversity technique to combat fading. For a
fixed number of transmit antennas, its decoding complexity
increases exponentially with the transmission rate. Space-time
block coding (STBC) [2,3] was proposed as an attractive
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