Bias removal of the reduced complexity channel estimator for OFDM systems with transmit diversity in mobile wireless channels

Transmit diversity is an effective technique for combating fading in mobile wireless channels and improving the capacity of wireless networks. On the other hand, to cope with frequency selective fading channels, OFDM systems can be applied to transform the channels into multiple flat fading channels and solve the multipath induced ISI problem. Therefore, combining OFDM with transmit diversity can provide reliable and high-rate transmission in wide-area cellular networks. For the decoding of space-time or space-frequency coded OFDM transmit diversity systems, efficient channel estimation methods have to be developed at the receiver to obtain the up-to-date channel state information. However, channel estimation and tracking in OFDM transmit diversity systems suffers from high computation complexity due to the simultaneous estimation of channel parameters of all transmit antennas. In this paper, we first investigate the issue of estimation bias in the reduced complexity algorithm. Two bias removal schemes will then be proposed by exploiting the temporal correlation of channel responses. Simulation results show that the proposed methods can greatly reduce the estimation MSE of the reduced complexity algorithm for high frequency selective and fast fading channels.