Pilot sequence aided channel estimation for space time coded OFDM systems

Space time coded OFDM systems have been recently proposed as a promising approach with transmit diversity and higher coding gain for transmission over frequency selective fading channels. This paper considers the channel estimation techniques for space time coded OFDM systems using space time block coded (STBC) pilot sequences. The performance of least square (LS) and minimum mean square error (MMSE) channel estimation techniques and their complexity are examined. A low rank channel estimation technique based on the eigen vector decomposition (EVD) is investigated and the system performance is examined under reduced rank conditions as well. Further the performance of different space time codes with different modulation schemes are examined under MMSE and EVD based channel estimation schemes. Numerical results are provided to demonstrate the performance of these techniques in a more general scenario