what’s the pass band ripple and stop band attenuation of a digital filter? – Signal Processing Stack Exchange https://dsp.stackexchange.com/questions/38564/whats-the-pass-band-ripple-and-stop-band-attenuation-of-a-digital-filter
1.什么是互信息：https://www.zhihu.com/question/304499706/answer/544609335
2.为什么把最大互信息定义为信道容量https://www.zhihu.com/question/67066372
1. 概率整形
a. the low-amplitude constellation points are sent with a high probability than the high-amplitude ones. Besides, the constellation points under the same amplitude layer are sent equally likely. Therefore, the average symbol power will be decreased, but at a cost of lower source entropy.
b. The first PS scheme was proposed by Gallager, which is based on many-to-one mapping.
c. There are some methods proposed to further reduce the complexity of CCDM, like multiset-partition distribution matching and sreaming distribution matching.
2. CCDM
a. K-L散度（相对熵）
jianshu.com/p/43318a3dc715
b. All approaches are variable length, which can lead to varying transmission rate, large buffer sizes, error propagation and synchronization problem.
fixed-to-fixed length codes do not have these issues.
统计学中的“矩” – 日记 – 豆瓣 https://m.douban.com/note/686004725/
统计学中「矩」这个概念是怎么引入的？它为什么被称为矩？它与物理意义上的矩有什么相同与不同？
https://www.zhihu.com/question/19915565
moment:矩
1. 群速度失配在涉及交叉相位调制的非线性效应中起着很重要的作用；
ISI：channel equalization and inter symbol interference ISI model
BCJR: Bahl, Cocke, Jelinek, Raviv
Viterbi Algorithm:维特比算法
数字通信中最广泛的两个算法: BCJR算法和维特比算法
温故知新：眼图形成及其原理总结 – 知乎 https://zhuanlan.zhihu.com/p/45394136
