Effective techniques for blind phase offset estimation in LDPC coded systems

We consider the problem of carrier phase offset estimation and propose two blind estimation techniques for low-density parity-check (LDPC) coded systems. The first technique is applied to a binary phase shift keying (BPSK) modulation while the second is applied to higher order modulations. These techniques are based on the calculation and minimization of functions of the log-likelihood ratios (LLR) of the syndrome elements obtained according to the parity check matrix of the error correcting code. In the case of a BPSK modulation, the global minimum of the cost function is obtained using the gradient descent method while for higher order modulations, we use the simulated annealing algorithm. Simulation results show that the proposed techniques significantly outperform many phase estimation methods and are very powerful even at low signal-to-noise ratios.