Vladimir Vassilevsky <[email protected]> writes:

> Randy Yates wrote:
>> Does a modulation with q different symbol states absolutely require a
>> code over X^n, where X = {a_1, a_2, ..., a_q}? Or can you use a
>> symbol set (X) with a different order (count)?
>> A slightly different question: is this *typically* done (q symbol states
>> ==> order q symbol set)? I.e., although it's not required, is it
>> typically done this way?
>
> Ideally you want coding to be matched to the modulation, so the
> Hamming distance corresponds to the Euclidean distance.

Euclidean distance as in the correlation metrics when you're doing
soft-decision decoding?

>> As a simple example, could a binary (7,4) Hamming code be applied to 16
>> QAM, such that 4/7 codewords fit into one symbol?
>
> The result is likely to be worse then the uncoded QAM. Proakis Chapter
> 8 is exactly about your questions.

That narrows it down to 120 pages or so. Thanks...
--
Randy Yates % "And all you had to say
Digital Signal Labs % was that you were
mailto://[email protected] % gonna stay."
http://www.digitalsignallabs.com % Getting To The Point', *Balance of Power*, ELO