DPSK Modulation-Demodulation Compatibility Considerations

Replace all instances of modem.dpskmod and modem.dpskdemod with comm.DPSKModulator and comm.DPSKDemodulator.

• User-defined symbol mapping is not supported.

• The comm.DPSKModulator System object™ does not support initial phase specification. However, this code sample shows you how to specify initial phase for DPSK-modulated signals:

  %% Initial Phase
  x = randi([0,7],10,1); 
  phRot = pi/8;
  initPh = pi/4;
  
  %% Using modem.dpskmod modulate the signal
  m = modem.dpskmod('M',8,'PhaseRotation',phRot,'InitialPhase',initPh);
  ym = modulate(m, x);
  
  %% Using comm.DPSKModulator modulate the signal
  s = comm.DPSKModulator('PhaseRotation',phRot,'SymbolMapping','Binary');
  ys = s(x);
  ys1 = ys .* exp(1i * initPh);
  
  %% Compare results
  err = max(abs(ys1 - ym))
  

  err =
  
     2.6390e-15
  

• This code sample shows you how to simulate multichannel input/output for DPSK-modulated signals:

  %% Multichannel input/output
  x = randi([0,7],10,3);
  phRot = pi/8;
  
  %% Using modem.dpskmod modulate the signal
  m = modem.dpskmod('M',8,'PhaseRotation',phRot);
  ym1 = m.modulate(x);
  % Process one more frame to verify interframe state handling
  ym2 = m.modulate(x);
  
  %% Using comm.DPSKModulator modulate the signal
  % Create as many System objects as number of channels
  s1 = comm.DPSKModulator('PhaseRotation',phRot,'SymbolMapping','Binary');
  s2 = comm.DPSKModulator('PhaseRotation',phRot,'SymbolMapping','Binary');
  s3 = comm.DPSKModulator('PhaseRotation',phRot,'SymbolMapping','Binary');
  
  ys1 = complex(zeros(size(x),'like',x));
  ys2 = ys1;
  
  % Process first frame
  % Process each channel by its specific System object
  ys1(:,1) = s1(x(:,1)); 
  ys1(:,2) = s2(x(:,2)); 
  ys1(:,3) = s3(x(:,3)); 
  
  % Process second frame
  ys2(:,1) = s1(x(:,1)); 
  ys2(:,2) = s2(x(:,2)); 
  ys2(:,3) = s3(x(:,3)); 
  
  %% Compare results
  err1 = (max(abs(ys1(:) - ym1(:))))
  err2 = (max(abs(ys2(:) - ym2(:))))
  
  

  err1 =
  
     2.0411e-15
  
  err2 =
  
     2.4431e-15