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soft demodulation using itpp library

P: 1
Hi everyone,
I have a problem with the output of the soft demapper function (demodulate_soft_bits) of itpp library when using 16-QAM and 64-QAM modulation.
here is a portion of the code (64-QAM):

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  1. cvec comple; 
  2. Modulator_2D qam; 
  3. ivec cont_d = "0:1:63";
  4. vec qam_r = "-7 -7 -7 -7 -7 -7 -7 -7 -5 -5 -5 -5  -5 -5 -5 -5 -3 -3 -3 -3 -3 -3 -3 -3 -1 -1 -1 -1 -1 -1 -1 -1  1  1  1  1  1  1  1 1  3  3  3  3  3  3  3  3  5  5  5  5  5  5  5 5  7  7  7  7  7  7  7  7";
  5. vec qam_i = "-7 -5 -3 -1  1  3  5  7 -7 -5 -3 -1   1  3  5  7 -7 -5 -3 -1  1  3  5  7 -7 -5 -3 -1  1  3  5  7 -7 -5 -3 -1  1  3  5 7 -7 -5 -3 -1  1  3  5  7 -7 -5 -3 -1  1  3  5 7 -7 -5 -3 -1  1  3  5  7";
  6. comple.set_length(qam_i.length(),false); 
  7. for(int i=0; i<qam_i.length(); i++)
  8. comple(i) = std::complex<double>(qam_r(i)/sqrt((double)42),qam_i(i)/sqrt((double)42));
  9. qam.set(comple, cont_d);  
  10. temp = qam.demodulate_soft_bits( symb_recus,channel,1);
symb_recus is the output of a realistic 4x4 MIMO channel
channel is the channel gain
At the output I got a random values which doesn't correspond to the hard output and I got also a succession of 0
exp :
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  1. temp : [6.80 3.33 1.64 -14.27 -7.06 -3.51 0 0 0 0 0 0 -3.47 .....]
  2. Hard output : [0 1 0 1 1 1 1 1 0 0 1 1 0 ... ]
Can you please help me.
Apr 25 '16 #1
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