中文摘要：

研究了基于编码辅助的信噪比期望最大（EM）估计算法。在分析编码辅助算法模型的基础上，建立了无编码辅助算法与编码辅助算法的联系，将无编码辅助算法看作是编码辅助算法的一种特殊情况。此外，将同步估计中的嵌入估计算法运用到信噪比迭代估计中，得到了一种简化的编码辅助算法，克服了原算法计算量过大的缺点。仿真结果表明，简化后的算法在降低算法复杂度的同时，仍能保持原算法的估计性能。

英文摘要：

The expectation-maximization （EM） estimation of signal-to-noise ratio （SNR） for coded transmission systems is researched. By studying the model of code-aided （CA） estimation, a connection of the CA algorithm with the conventional non-code-aided （NCA） estimators is made. There- fore, the CA estimator can be used to implement the NCA estimation. Further, a simplified version of the code-aided （CA） estimation algorithm is pro- posed by introducing the embedded estimation technique to reduce the computational complexity related to the iterative process of the estimator. The per- formance of the improved CA approach is shown to be close to the original CA at considerably reduced complexity.