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The authors consider a space-time coded (STC) orthogonal frequency-division multiplexing (OFDM) system with multiple transmitter and receiver antennas over correlated frequency- and time-selective fading channels. They propose first a maximum-likelihood (ML) receiver for space-time block code OFDM systems based on the expectation-maximisation (EM) algorithm. They then propose a low-density parity-check (LDPC)-code-based STC-OFDM system to interface with the EM algorithm. When comparing the proposed scheme with the conventional space-time trellis code, the LDPC-based STC significantly improves the system performance by exploiting both spatial and selective-fading diversity in wireless channels. Compared with the recently proposed turbo-code-based STC scheme, LDPC-based STC exhibits a lower complexity and more flexible scalability.