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Re: [Discuss-gnuradio] Differential QPSK modulation resampling


From: George Nychis
Subject: Re: [Discuss-gnuradio] Differential QPSK modulation resampling
Date: Mon, 19 May 2008 09:44:46 -0400





On May 19, 2008, at 5:42 AM, irene159 <address@hidden> wrote:


Hello,

Just another question concerning the file "gr_mpsk_receiver_cc.cc".

In the extract of code below, why are phase_error_detector_generic and
decision_generic  used for all BPSK, QPSK and other modulations?
Have optimized algorithms for BPSK and QPSK already been implemented?

// Select a phase detector and a decision maker for the modulation order
 switch(d_M) {
 case 2:  // optimized algorithms for BPSK
   d_phase_error_detector =
&gr_mpsk_receiver_cc::phase_error_detector_generic; //bpsk;
   d_decision = &gr_mpsk_receiver_cc::decision_generic; //bpsk;
   break;

 case 4: // optimized algorithms for QPSK
   d_phase_error_detector =
&gr_mpsk_receiver_cc::phase_error_detector_generic; //qpsk;
   d_decision = &gr_mpsk_receiver_cc::decision_generic; //qpsk;
   break;

 default: // generic algorithms for any M (power of 2?) but not pretty
   d_phase_error_detector =
&gr_mpsk_receiver_cc::phase_error_detector_generic;
   d_decision = &gr_mpsk_receiver_cc::decision_generic;
   break;


This is just a guess based on the block names... But given that the block names have "generic" in them, I'd guess they are generic enough to work with psk modulations given some configuration.

- George




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