Non-Pilot-Aided Phase Estimator for 2-Source BPSK NOMA Channel with Closed-Form Solver

In this paper, we focus on developing the non-pilot-aided phase CSE (Channel State Estimator) for 2-source BPSK generic NOMA (Non-Orthogonal Multiple Access) scenario. Apart of the exact CSE form, we develop also the low-SNR approximation which allows us to find a closed-form ML (Maximum Likelihood) solver. Both, exact and low-SNR (Signal to Noise Ratio) forms will be analyzed in terms of their fundamental mean-square error performance limits. We will use classical and mismatched model Cramer-Rao Lower Bound (CRLB) analysis. The numerical analysis shows that the mismatched low-SNR model CRLB nicely pairs the true estimator performance for low and medium SNRs.