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

[Tom Rondeau]

On Wed, Feb 3, 2010 at 6:43 PM, alanluo <address@hidden> wrote:
>
> Thanks Isaac for your kindly suggestion. I think i have to dive into python
> now...
>
>
>
> idg101 wrote:
>>
>> 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


You can look at gnuradio-core/src/python/gnuradio/blks2impl/qam*.py
for a place to start. It doesn't really do proper synchronization,
just the symbol mapping, but it should give you a way forward.

Tom