Hmm, well I went over it in some detail in response to "Are there any particular interesting events connected to the transmission of the signal with 4G (or in general)? I remember seeing something about radio echo while skimming over the Wikipedia article, and it sounded fascinating," so to add to this answer, have a look at that again.

To elaborate, and perhaps clarify a bit, I'd say the most important difference between analogue and digital processing is that you can do with a small digital chip what it would take a room full of analogue electronics to do.

The reason is that digital processors are general purpose programmable, you can make them do almost any calculation that you can fathom (given enough time, of course). However, with analogue, you basically need a special purpose circuit for any operation. If you want to estimate frequency errors, you need a circuit for that, if you want to estimate how fast you are moving, to correct for frequency shift, you need a circuit for that, etc. With a programmable processor, all of these things can be done with a single circuit (i.e. the processor). That's what I'm talking about when I say modern digital processing.

The rest is complicated. I've typed out most of it now, so I might as well finish it, but frankly this is getting pretty technical, to the point where I simply cannot make it very easy to understand. And even now, I'm simplifying a lot. The book which introduces these concepts is several hundred pages long.

From memory, here's what you do with the data in 4G (from a base station to a phone, for example):

- You start with a set of bits that you want to send. These are a bunch of 1s and 0s, as that's all computers understand. 4G knows nothing about what these bits are for, they are just some information some application (for example WhatsApp) will be sending.

- From this point on, everything we do to the data is to protect it from the channel. The reason is that the channel (i.e. the air around us) is noisy, full of surfaces which will reflect it all over the place, and can even absorb some of the signal. By the time it reaches your device, it's total shit. You need ways to recover the original signal in a reliable manner.

- You send these bits through a turbo coder. This essentially adds a bunch of extra bits at the end, based on what bits you're sending. Typically you'd add something like twice as many bits at the end as what you're actually sending. The reason is that by representing each bit with three bits, we can make a safer guess about what it's supposed to be. To illustrate; imagine that 101 represents 0, and 010 represents 1. These are the only combinations which will be sent out. What if you receive 110? Obviously an error has been introduced by the channel, but what's more likely, that we sent out 101 and both the second and third bit are wrong, or that we sent 010 and only the first bit is wrong? Clearly it's more likely that only one bit is wrong, and so we "guess" that we should've received 010.

- We then slap on a few more bits at the end, a "CRC". This is a value, like a hash, which is calculated based on the preceding bits. You will, when receiving, calculate your own CRC. If it matches with the received CRC, it means that every bit you've guessed is correct. Otherwise, you accept defeat, and ask for the data to be retransmitted; the signal was too poor.

- We then scramble the bits, i.e. "randomly" mix them up. This is so that if one part of the bandwidth you're transceiving on has a weak signal, it'll affect random single bits instead of a chunk of related bits. Combined with the turbo coder, this increases robustness.

- Once all of this has been done, the bits are converted to complex numbers, using quadrature amplitude modulation. Each one of these complex numbers will be sent on an individual frequency. Now you see that by scrambling them, the bits are distributed across frequencies. You do an inverse Fourier Transform, to turn it into a waveform. At this point you leave the digital domain. The waveform is sent to a digital to analogue converter, and transmitted over an antenna.

When receiving, you basically do the same thing, but in the opposite order.

I don't know how interesting this is for you, as I simply can't give a full explanation of each concept. It would be too difficult to understand, and too time consuming to write out (especially as there are numerous books out there on the subject). However, this gives a reasonably full overview of the signal chain.