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Date:   Tue, 16 Nov 1999 11:37:10 -0500
To:     "Andres Benitez" <dorego@conexion.com.py>
From:   Stu Card <stu@critical.com>
Subject: Re: dqpsk
Cc:     netdev@nuclecu.unam.mx
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At 08:00 PM 1999-11-15 -0400, you
("Andres Benitez" <dorego@conexion.com.py>) wrote:

>    We are students of electronic Engeniering, and  we need information and
>aplications of dqpsk modulation, could you send us  something at this
>mail-adress pleace!

I'm afraid you will find that most of the members of this list know nothing
of DQPSK, as it has nothing to do with the subject of the list, which is
Linux network software development.  DQPSK is Differential Quadrature Phase
Shift Keying.  It is a variant of QPSK which does not require fully coherent
demodulation.  QPSK is a phase-only modulation, commonly used in satellite
communications and other situations where either the signal to noise ratio
is very low, or it is necessary to use very power-efficient amplifiers
(which operate Class C, are therefore nonlinear and thus cannot amplify
signals with any amplitude component to their modulation).  QPSK provides
2 bits per symbol.  A more sophisticated variation on this theme is
trellis-coded 8-PSK, which provides the same information rate in the
same bandwidth, with a slightly better error rate, at the expense of
substantially more complexity in the demodulator/decoder.

------------------------------------------------------------------------
Stuart W. Card, Chief Scientist & Vice-Pres., Critical Technologies Inc.
Suite 400 Technology Center, 4th Floor 1001 Broad Street, Utica NY 13501
315-793-0248   FAX -9710    <stu@critical.com>   http://www.critical.com