Polar code visibly approaches channel capacity in practice and is thereby a constituent code of the 5G standard. Compared to low-density parity-check code, however, the performance of short-length polar code has rooms for improvement that could hinder its adoption by a wider class of applications. As part of the program that addresses the performance issue at short length, it is crucial to understand how fast binary memoryless symmetric channels polarize. A number, called scaling exponent, was defined to measure the speed of polarization and several estimates of the scaling exponent were given in literature. As of 2022, the tightest overestimate is 4.714 made by Mondelli, Hassani, and Urbanke in 2015. We lower the overestimate to 4.63.

翻译：极地代码在实际操作中明显接近了频道能力,因此是5G标准的组成代码。但是,与低密度对等检查代码相比,短极代码的性能有改进的余地,这可能会妨碍其被更广泛的应用类别采纳。作为短期处理性能问题的方案的一部分,了解无内存性对称通道两极分化的速度至关重要。一些被称为缩放速率的系统被确定为衡量两极分化速度,文献中也给出了对缩放速率的若干估计数。截至2022年,最接近的估计数是Montalli、Hassani和Urbanke在2015年作出的4.714,我们把高估率降低到4.63。