Re: Are Multidimensional Digital Comm Signals Also Pulse-Shaped?

Randy Yates wrote:
When discussing pulse-shaping, Proakis uses the M-level PAM model

v(t) = \sum_{n=0}^{\infty} I_n g(t - nT),

where g(t) is the pulse shape and I_n is from an alphabet of M levels
(usually +/-1, +/-3, etc.), and v(t) is the ideal baseband signal.

He then goes on to discuss designing g(t) for bandlimited channels and
other similar topics for this model.

Well, what if, instead of simple M-level PAM we have an L-dimensional
time-domain signal.
[...]
My question is, do we also pulse-shape these multidimensional basis
functions?

Sure, you also have to pulse shape them. If you read the formulas for
any modulation, you'll see that all of them have a pulse term like
g(t).

What would be interesting, and I've never done myself, is to generalize
the conditions for zero ISI derived for PAM to any other
multidimensional constellation.

HTH,

--
Miguel Bazdresch

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