Re: [Discuss-gnuradio] How to implement 64QAM?

[idg101]

Hi,
  I haven't looked at any of the QAM-related code in the GNU Radio baseline,
but it should be possible to design a generic MQAM demodulator.  

In fact, you should be able to build a generic MQAM demodulator for a given
constellation set.  This, I've done before in Matlab.  You start with an
AGC, feed through an equalizer which is optimized for minimizing the phase
error between recovered and truth symbols.  Another way to look at it that
for each symbol, find the symbol that matches closest to the constellation
vector (thats your decode symbol) and then feed the error into the
equalizer.  

I believe there is a way to form a generic carrier recovery and symbol
recovery loops that can deal with generic MPSK style constellation of which
MQAM is a part of.  In fact, you could write a routine that can do anything
from BPSK to 64QAM.

my 2 cents,
Isaac


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