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文章针对OQPSK信号最大似然估计计算复杂度较高的问题,提出了一种基于软解映射的算法对信息比特进行最大似然估计,相比基于网格的算法,计算复杂度大大降低,而性能与Max-Log-Map完全等价并给出了等价证明。以Max-Log-Map为代表的VA类算法,其本质是利用前后星座点的约束关系,而在OQPSK信号中,这种约束关系仅仅与两个相邻星座中相同的1个比特有关,约束长度仅仅为1,该比特的软信息仅与两个相邻星座的实部(或虚部)有关。
In order to solve the problem of high computational complexity of maximum likelihood estimation of OQPSK signals, a new algorithm based on soft demapping is proposed to estimate the maximum likelihood of information bits. Compared with grid-based algorithm, the computational complexity is greatly reduced. Performance is completely equivalent to Max-Log-Map and gives proof of equivalence. The VA algorithm represented by Max-Log-Map is essentially based on the constraint of constellation points before and after, whereas in OQPSK signals, this constraint is only related to the same 1 bit in two adjacent constellations. Constraints The length is only 1, and the soft information for this bit is only related to the real part (or imaginary part) of two adjacent constellations.