一种低复杂度编码辅助载波同步算法

该文针对低信噪比下编码辅助同步算法存在复杂度高的问题，在分析了后验信息概率分布特性的基础上，通过设定表征可靠性大小的门限值得到了只有3种状态的简化后验均值和新的后验似然比。将新的后验均值和似然比分别运用到基于软扫频的粗同步和基于期望最大的细同步算法中，得到一种新的同步算法。新算法使用了一种新的评价函数和简化的期望最大算法。通过码率为1/6的Turbo码验证了新算法可以大幅降低加法及乘法的运算次数，在信噪比大于-7.9 dB时能达到理想同步，最大性能损失仅为0.05 dB。

A Low Complexity Code-aided Carrier Synchronization Algorithm

Considering the condition of low Signal to Noise Ratio (SNR), the Code-aided carrier recovery algorithm performs high computational complexity. Based on the analysis of the probability density function of posterior information, modified posterior information mean with three states and new Log-Likelihood Ratio (LLR) are proposed according a probability threshold that represents the information reliability. Then a new carrier synchronization algorithm is obtained when the new posterior information mean and log-likelihood ratio are separately applied into the expectation maximization and soft frequency sweep algorithm. There is a simplified expectation maximization algorithm and evaluation function. In last, the simulations by the Turbo code with 1/6 code rate verify that the new algorithm improves the performance of computational complexity, increases the synchronization range and achieves perfect synchronization with only 0.05dB loss when SNR exceeds -7.9 dB.