等价于MAP的SOVA译码方法
MAP Decoding Methods Derived from SOVA
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摘要: 不同于MAP(Maximum A Posteriori)算法，SOVA(Soft-Output Viterbi Algorithm)算法的软输出不是真正意义上的后验概率，很少有文献给出SOVA算法的完整数学解释。该文给出了一种完整的SOVA的数学表达形式，并从SOVA的数学表达出发推导出了两种等价于MAP，具有SOVA形式的译码方法，一种是Li等人(1995)给出的适用于连续传输的最佳软输出算法(Optimal Soft output Algorithm, OSA)；后一种是对OSA算法的改进，后者可以得到与前者等价的软输出，但是降低了运算复杂度。Abstract: Different from MAP, the soft output of SOVA is not the exact a posteriori probability, and few literatures describe SOVA in mathematical form. This paper gives a new comprehensive mathematical expression of SOVA, and deduces two MAP-equivalent SISO decoding methods in the form of SOVA. The first method is just OSA algorithm given by Li et al, (1995)which is suitable for continuous decoding. The other one is the improved version of OSA，whose output is equivalent to that of OSA with the decrease of complexity.
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