> Please tell me which is a reliable modulation to use in CATV system, QPSK
> or QAM? What are the advantages and disadvantages. Please discuss it in a
> "lay man's term" and set some examples. Thank you and more power.
Well, more power is exactly what you have in a CATV system, and that is
why higher-order modulations like QAM make more sense.
In a nutshell, the closer the constellation points are, the more
susceptible the modulation is to noise. That's why, for noisy systems
like mobile radios, "low-order" modulations (M-ary PSK, FSK) are better.
OTOH, CATV systems have a lot of power, or high SNR, so one can take
advantage of that power to send more information (per bandwidth) down
the "pipe."
--
% Randy Yates % "So now it's getting late,
%% Fuquay-Varina, NC % and those who hesitate
%%% 919-577-9882 % got no one..."
%%%% <yates@ieee.org> % 'Waterfall', *Face The Music*, ELO
http://www.digitalsignallabs.com
Reply by nonahvy●February 6, 20082008-02-06
Please tell me which is a reliable modulation to use in CATV system, QPSK
or QAM? What are the advantages and disadvantages. Please discuss it in a
"lay man's term" and set some examples. Thank you and more power.