Transmitter diversity for OFDM systems with mobile wireless channels

Transmitter diversity is an effective technique used to improve wireless communication performance. We investigate transmitter diversity using space-time coding for OFDM systems in high-speed wireless data applications. We develop channel parameter estimation approaches, which are crucial for the decoding of the space-time codes, and derive the MSE bounds of the estimators. The overall receiver performance using such a transmitter diversity scheme is demonstrated by extensive computer simulations. For an OFDM system with two transmitter antennas and two receiver antennas with transmission efficiency as large as 1.475 bits/sec/Hz, the required signal-to-noise ratio is only about 7 dB for a 146 bit error rate and 9 dB for a 10% word error rate assuming channels with two-ray, typical urban, and hilly terrain delay profiles, and a 40 Hz Doppler frequency. In summary, combining OFDM with transmitter diversity using space-time coding is a promising technique for highly efficient data transmission over mobile wireless channels