Full Rate Orthogonal Space-Time Block Coding in OFDM Transmission Using Time Reversal

A novel method of utilizing the channel state information at the transmitter (CSIT) for orthogonal frequency division multiplexing (OFDM) systems with multiple transmit antennas is presented in this paper. Using the conventional time reversal (TR) technique along with a specific OFDM symbol structure, the method facilitates the application of full-rate orthogonal space-time block coding (OSTBC) to systems with more than two transmit antennas for complex signalling. Compared to the conventional eigen- beamforming method, which maximizes the received signal- to-noise ratio (SNR) when CSIT is available, it is shown that the proposed system has a much reduced computational complexity. However, this complexity reduction comes at the expense of a loss of diversity in an uncoded system, which we show through an analysis of bit error rate (BER). Despite this drawback, we show through simulations that the proposed method achieves BER performance almost as well as the eigenbeamforming method when channel coding is employed, which is the case in most practical systems.