Carrier-Frequency Offset Estimation via the EM Algorithm for MIMO-OFDM Iterative Receivers

In this paper, we consider carrier-frequency offset (CFO) estimation issue in a multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) system using low-density parity-check (LDPC) codes at transmitter and iterative detection based on the maximum a posteriori expectation-maximization (MAP-EM) demodulator and a soft LDPC decoder at receiver. Based on the EM algorithm, we first present a novel pilot-aided CFO estimator that allows fast Fourier-transform (FFT)-based fast implementation. Then this CFO estimator is incorporated into the initialization step of the iterative receiver. Experimental results show the effectiveness of our receiver design in combating CFO.