Low-Complexity Iterative Synchronization for A Robust Receiver at Low Signal-to-Noise Ratios

The problem of carrier and clock synchronization without a training sequence for a robust receiver working at low signal-to-noise (SNR) ratios is considered. Both short packet and long burst transmission scenarios are taken into account. A low-complexity iterative symbol timing and carrier synchronization algorithm making use of the extrinsic information from the soft- input soft-output (SISO) decoder is proposed. The non-data-aided (NDA) algorithms are used for initial synchronization. In order to solve the phase ambiguity problem inherent in the NDA phase synchronization algorithm, two SISO decoders denoted by I and Q decoders, respectively, along with a differential decoder are proposed. The simulation results show that the proposed iterative synchronizer and decoder can reach the ideal performance at very low SNR with an increased allowed residual frequency offset and [-pi,pi] phase uncertainty region.