Low Complexity Implementation for the Quasi-Orthogonal Space-Time Block Coded OFDM System

Employing space-time block codes in Orthogonal Frequency Division Multiplexing (OFDM) can effectively improve the system performance. The straightforward implementations, including space-time coded OFDM and space-frequency coded OFDM, require the separate inverse discrete Fourier transform (IDFT) operation for each transmitter. In this paper, we propose a low complexity implementation of four-antenna quasi-orthogonal space-time block coded OFDM system. The block coding is done in both time and frequency dimensions simultaneously. Based on the symmetric characteristics of the DFT/IDFT operations, the proposed design can significantly reduce the computational load comparing with the straightforward implementations. Computer simulations on the Bit-Error-Rate performance show that this scheme adopts well in both time and frequency selective channels.

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