A Joint Assisted Carrier Synchronization Algorithm with Code and Pilot Based on Low Rate LDPC Code
一种基于低码率LDPC码的编码与导频联合辅助载波同步算法

Considering that the code-aided and data-aided carrier recovery algorithms perform small synchronization range and big inaccuracy in low Signal to Noise Ratio (SNR) deep space communication systems, a joint assisted carrier synchronization algorithm with code and pilot is proposed. First a coarse synchronization algorithm with optimal pilot placement is constructed based on the sum of autocorrelation function of the pilots, whose frequency estimator can approximate Cramer-Rao Bound. The impact mechanism of pilot type on the trade-off between range and accuracy of estimation is analyzed. And then, a modified expectation maximization fine carrier synchronization is got with means of inserting pilot symbols and adding an integrator. Finally the simulations with the LDPC-Hadamard code with rate 1/12 verify that the new algorithm can increase synchronization range and improve accuracy, and achieve perfect synchronization with a certain amount of pilots at very low Signal to Noise Ratio.