Iterative Information-Reduced Carrier Synchronization Using Decision Feedback for Low SNR Applications

Abstract — This paper addresses the carrier-phase estimation problem under low SNR conditions as are typical of turboand LDPC-coded applications. In [1], [2] closed-loop carrier synchronization schemes for error-correction coded BPSK and QPSK modulation were proposed that were based on feeding back hard data decisions at the input of the loop, the purpose being to remove the modulation prior to attempting to track the carrier phase as opposed to the more conventional decisionfeedback schemes that incorporate such feedback inside the loop. In this paper, we consider an alternative approach wherein the soft information from the iterative decoder of turbo or LDPC codes is instead used as the feedback. I.