Iterative LDPC-Hadamard Code-Aided Carrier Frequency Synchronization at Extremely Low SNR

In this paper, we consider a method of code-aided carrier frequency synchronization at extremely low signal-to noise values based on LDPC-Hadamard code. This system comprises a low-rate LDPC-Hadamard code that is close to Shannon limit at extremely low SNR values and an EM-based carrier frequency synchronizer that makes use of the posterior probabilities of the data symbols, provided by the iterative decoder. Simulations show that the proposed synchronizer can achieve a bit-error-rate (BER) performance of 10^-5 at Es/No=-10 dB, and has negligible BER performance degradation as compared to the ideally synchronized system. Through analysis and simulation, we show that our synchronization strategies are very effective at extremely low SNR values.