[Objective]The commonly used max-log-map algorithm reduces the complexity of soft information computation com-pared to the log-map algorithm.However,it still consumes a large number of resources for high-order Orthogonal Amplitude Modulation(QAM),such as 8QAM,16QAM Probability Shaping(PS),and 64QAM PS.[Methods]8QAM adopts the meth-od of constellation region division,and the soft information is represented by the distance information from the received symbol to the perpendicular of the nearest bit 0 and bit 1.The distance information is simplified and calculated using angle rotation and regional symmetry.For 16QAM PS and 64QAM PS distributed by non Maxwell Boltzmann(MB)distribution,the central boundary between the edges of the region where bit 1 is located and the central boundary between bit 0 on both sides of the re-gion bit 1 no longer coincide.The region merging approximation is used to handle the region ownership between the two bound-aries,and the max-log-map expression is factorized to simplify the distance difference to calculate the soft information.The soft information of 16QAM PS and 64QAM PS based on MB distribution can be obtained by simplifying the soft information expression of non MB distribution.[Results]After the above simplification,the multiplication and addition/subtraction times of 8QAM soft information calculation were reduced from 48 and 75 times to 12 and 16 times respectively with a degradation of on-ly about 0.05 dB;The 16QAM PS with MB distribution has 192 multiplication times and 260 addition/subtraction times re-duced to 2 and 4 times,respectively,resulting in a degradation of only about 0.05 dB.Higher order 64QAM PS has a greater reduction in resource consumption reduced the multiplication and addition/subtraction times from 1 152 and 1 542 times to 3 and 6 times,respectively.[Conclusion]This article proposes a soft information calculation method suitable for 8QAM and MB distribution of 16QAM PS,MB distribution of 64QAM PS,non MB distribution of 16QAM PS,and non MB distribution of 64QAM PS.When the probability satisfies the MB distribution,the soft information calculation method suitable for non MB distribution can be converted into the MB distribution calculation method.When the shaping factor is 0,the expression based on the MB distribution can be converted into a uniformly distributed soft information calculation formula.The soft information calculation for non MB distribution,MB distribution,and uniformly distributed probability can be designed uniformly on the same circuit,improving circuit reuse rate and reducing the hardware resource consumption.
关键词
光通信/数字信号处理/正交幅度调制/对数似然比/概率整形
Key words
optical communication/digital signal processing/QAM/log likelihood ratio/PS
维普
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