An iterative Estimation and Detection Technique for OFDM Systems with Multiple Frequency Offsets (Doppler Shifts)

An iterative frequency offsets (FOs) estimation and correction technique for OFDM is proposed to track multiple frequency offsets due to distinct Doppler shifts associated with multi- paths. The pilot symbols available in an OFDM symbol for channel estimation can be combined with the soft estimates of the data symbols in an iterative manner to track carrier frequency offsets. The main merit of this iterative method is its capability of tracking frequency offsets. The proposed iterative technique has the ability to resolve multipaths, bringing the multiple frequency offset problem into the estimation of distinct frequency offsets. We verify the detection performance using BER curves and the estimation performance through comparison of the variance of estimates with the Cramer-Rao lower bounds (CRLB).