An iterative phase synchronization scheme for general QAM constellations

This paper concerns a new synchronizing scheme designed for block turbo coded system. The phase estimation relies on the feedback of the extrinsic information. A near optimum version of the algorithm based on the block turbo decoder devised by Pyndiah allows easy implementation. We display various results showfing that the proposed algorithm is able to track frequency shifts and that it works very well in the case of general Quadrature Amplitude Modulation (QAM) constellations. We also show that this turbo synchronizer works at low Signal to Noise Ratios (SNR) taking completely advantage of the turbo coding possibilities.