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
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.
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.
ISI：channel equalization and inter symbol interference ISI model
BCJR: Bahl, Cocke, Jelinek, Raviv
温故知新：眼图形成及其原理总结 – 知乎 https://zhuanlan.zhihu.com/p/45394136