简化的和积算法.doc

简化的和积算法#
侯军奎,邢莉娟,李卓**
(西安电子科技大学通信工程学院,西安 710071)

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摘要:介绍了经典和积算法,提出了双曲正切函数和反双曲正切函数的一种改变形式,用分
段线性函数和量化表近似改变后的双曲正切函数和反双曲正切函数得到两种简化的算法,分
析比较了经典算法与简化算法的复杂度,仿真结果及分析表明,与经典算法相比,两种简化
算法计算复杂度得到大幅度降低,硬件实现更加简单,且性能损失较小,分段线性函数近似
的算法在低信噪比时性能好于经典算法。
关键词:和积算法;分段线性函数;量化表
中图分类号:
Simplified Sum-Product Algorithm
HOU Junkui, XING Lijuan, LI Zhuo
(Communications Engineering School, Xidian University, Xi'an 710071)
Abstract: The classical sum-product algorithm is introduced. A modified form of hyperbolic
tangent function and inverse hyperbolic tangent function is proposed. Approximating the modified
hyperbolic tangent function and inverse hyperbolic tangent function using a piecewise linear
function and a quantization table produces two simplified algorithms plexities are
compared with the classical algorithm. Simulations and analysis indicate that putational
complexity of the two simplified algorithms is greatly reduced, the hardware implementation is
simpler and the loss of performance is smaller. The performance of the algorithm with
approximation by piecewise linear function is slightly better than the classical algorithm when
signal-to-noise ratio is small.
Keywords: sum-product algorithm; piecewise linear function; quantization table
0 引言
低密度奇偶校验码(LDPC)是一类由稀疏校验矩阵定义的分组纠错码,首先由 Gallager[1]
在十九世纪六十年代提出,但却被忽略了许多年,直到九十年代被 MacKay[2]重新发现