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This paper considers pilot symbol assisted LDPC coded 16 QAM over flat fading channels. Iterative channel estimation and decoding method with hard, soft and threshold-controlled hard decision feedback is suggested to improve performance. We find that the hard decision feedback performs best with the 16 QAM modulation and Wiener smoothing. For faster fading case with normalized Doppler spread fdTs=0.02, 1.8 dB performance improvement is achieved over PSAM system, with only 1.5 dB gap to the perfect CSI performance. For slower fading case fdTs=0.005, 1.0 dB performance improvement is achieved with only 0.3 dB gap to the perfect CSI performance.