qpsk.m

qpsk调制的MATLAB实现

% QPSK Modualtion

% Intialization
Ld=4096;
OSF=4;
SNR_dB=10;
load('RRC_4.mat');
PSF_Len=length(RRC_4);
% RRC_4=[];
% QPSK_Constellation=1/sqrt(2)*[1+j, -1+j,  1-j,-1-j];

% Source data
d=randint(1,Ld,2);                                                      
% QPSK Modulation
Mod=(1-2*d(1:2:end)+j*(1-2*d(2:2:end)))/sqrt(2);
% Upsample
Mod_Upsample=reshape([Mod;zeros(OSF-1,Ld/2)],1,OSF*Ld/2);
% TX pulse shaping filter  (Power normalization)
s=conv(OSF*Mod_Upsample,RRC_4);
% Select
tx=s((PSF_Len-1)/2+1:end-(PSF_Len-1)/2);
% AWGN Channel
rx=awgn(tx,SNR_dB-10*log10(OSF),'measured');
% RX matched filter (pulse shaping filter)
rx_filter=conv(rx,RRC_4);
% Select (sychronization)
rx_decision=rx_filter((PSF_Len-1)/2+1:end-(PSF_Len-1)/2);
% downsample
Mod_downsample=rx_decision(1:OSF:end);
% Hard decision
re=real(Mod_downsample);
im=imag(Mod_downsample);
for wy=1:Ld/2
  if re(wy)>0 dr(wy)=0;
   else dr(wy)=1;
  end      
  if im(wy)>0 di(wy)=0;
   else di(wy)=1;
  end
end
%output data
dd=reshape([dr;di],1,Ld);