宽范围的码辅助载波恢复算法

码辅助同步算法将译码软信息引入到同步参数的估计过程，能够在更低的信噪比区间有效实现载波同步，但是这类算法存在同步范围小、复杂度高的问题。首先针对判决可靠性较高的符号，定义一种新的评价函数，用其最大值对应的参数粗估计值补偿信号；然后利用后验均值对补偿后的信号去调制，再分别采用改进的自相关函数方法和最大似然方法来纠正剩余的频偏和相偏，进而有效实现载波恢复。仿真结果表明，该算法能够以较少的计算复杂度为代价，大幅提高同步范围，可获得近似理想同步条件下的译码性能。 

Extended Range Code-Aided Carrier Recovery Algorithm

The code-aided (CA) synchronization algorithm exploits soft decoding information to estimate synchronization parameters, and it can achieve the reliable carrier synchronization at lower signal to noise ratio (SNR) values. But the algorithm performs small synchronization range and high complexity. Firstly, a new evaluation function is defined in view of the symbols with high decision reliability, and the signal is compensated using coarse parameters estimation corresponding to the maximum of the function. And then the modulated information of compensated signal is eliminated by posterior average value. Finally, the residual frequency and phase offset is rectified by the improved algorithm based on autocorrelation function and maximum likelihood (ML) criterion respectively, so the accurate carrier recovery is achieved. The simulation results verify that this algorithm can increase synchronization range greatly at the cost of some less computation complexity, and almost perfect synchronization decoding performance is achieved.