[sdiy] Information Content of Signals

[Magnus Danielson]

From: "Paul Schreiber" <synth1 at airmail.net>
Subject: Re: [sdiy] Information Content of Signals
Date: Sat, 17 May 2003 09:32:08 -0500

> In a previoius life, I was a modem designer :)

Good that you have reincarnated since... ;O)

> If you REALLY want to read about how modems use all sorts of bizarre modulation schemes
> (including ISDN, DSL, microwaves, etc) the holy grail is:
> 
> "Advanced Digital Communications" by Kamilo Feher, Prentice-Hall.
> 
> This is an easy-to-read book (well, relatively speaking) that has 100's of USEFUL graphs
> explaining the pros and cons of like 20 different modulation schemes. He has a very easy to read
> style, like Bob Pease. Feher has other books on cell phone schemes (CDMA versus TDMA).
> 
> It also answers the question "What good is all this calculus for anyway? I'll NEVER use it!" It's
> nice to see how elegant these modulations schemes are, and how you can calculate the performance.
> Well, *I* thought it was elegant :)

Well, might be worth a look.

> Also, many telcom digital base-band encoding schemes are *specifically* engineered for reducing
> crosstalk in copper wiring. I spent many an hour in MathCAD calculating 50-pair crosstalk for
> different schemes. Gack!

Doesn't sound like much fun.

Most of the modulations that I am involved in these days doesn't really care
anything about crosstalk, they are about DC-balance, clock recovery issues and
things like that. It is easier.

I do like the aspects of *real* CDMA modulation (not the kind of CDMA/CD which
people call Ethernet, even if it *IS* CDMA when you really think about it).

Cheers,
Magnus