简化的和积算法

he 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 whose complexities are compared with the classical algorithm. Simulations and analysis indicate that the computational 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.