alt Hacker News> Calculating the limit is easy with Shannon's theorem. Approaching it in practice is hard.
Many modern modulations already operate basically on Shannon's limit for a given band/SNR. Well, on raw data, the encoding almost always use some kind of error correction so the decoded bitrate is few % lower than the wire one
That’s understating the importance of the error coding. The modulation scheme is almost a side show, it’s the modern error coding algorithms (LDPC or Turbo coding) that allows you to get arbitrary close to the Shannon limit.