Channel estimation for TDS-OFDM transmit diversity systems over doubly selective channels

This paper presents a channel estimation (CE) method for transmit diversity systems based on time-domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) scheme. Compared with conventional methods, the proposed CE method doesn´t need the hypothesis that the channel responses over two consecutive signal frames or over two adjacent subcarriers are equal. Thus, it can greatly improve the system performance, especially over doubly selective fading channels. We theoretically calculate the minimum square error (MSE) lower bound and derive the design criterion for optimal training sequences. Based on these results, an optimal training sequence for multiple antenna applications is proposed. Simulation results confirm that an obvious gain in the signal-to-noise-ratio (SNR) can be obtained using the proposed method.