A Novel LMMSE-EM Channel Estimator for High Mobility STBC-OFDM System

Abstract

In time-selective fading channel, the Alamouti orthogonality principle is lost due to the variation of channel from symbol-to-symbol in space–time block-coded orthogonal frequency division multiplexing (STBC-OFDM) system and causes co-channel interference (CCI) effects. To combat the CCI effects, various signal detection schemes have been proposed earlier by assuming that a priori channel state information (CSI) is known to the receiver. However, in practice, the CSI is unknown and therefore accurate estimation of channel is required for efficient signal detection. In this paper, by exploiting circulant properties of the channel frequency response (CFR) autocorrelation matrix [Formula: see text], we propose an efficient low complexity linear-minimum-mean-square-error (LMMSE) estimator. This estimator applies an expectation–maximization (EM) iterative process to reduce the computational complexity significantly. Finally, we compare the proposed LMMSE-EM estimator with conventional least square (LS) and LMMSE estimator in terms of performance and computational complexity. The simulation results show that the proposed LMMSE-EM estimator achieves exactly the same performance as the optimal LMMSE estimator with much lower computational complexity.

Performance enhancement of audio transmission based on LMMSE method

“…The spatial multiplexing could transmit several independent data streams through multipath channels without required increasing bandwidth in terms of achieving a high data rate. LMMSE method could estimate the transmitted signal via combining the linear weight of received version of the signals [8,9]. However, LMMSE method is complex [10].…”

A Low Complexity Optimal LMMSE Channel Estimator for OFDM System

“…However these SVD based estimation methods require still high computational complexity as decomposing the R HH matrix using SVD method itself requires cubic complexity [8]. A low complexity linear minimum mean square error estimation-expectation maximization (LMMSE-EM) based channel estimation was proposed in [9] for OFDM system with transmit diversity by exploiting the circulant property of the channel matrix. In [10], the authors approximate the LMMSE estimator using the law of large numbers to reduce the computational complexity of the channel to O(N log N ).…”