to get the proper scatter plot
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Hi...
How do i map the random symbols after binary to symbol mapping to get the constellation diagram of M-ary QAM correctly . i am getting the incorrect constellation diagram.
clc;
closeall;
clearall;
M=64;% QAM Signal Constellation
fft_size=64;
fspacing=15000;
fs=15000*64;
Ts = 1/fs;% Sampling period of channel
Fd = 0;% Max Doppler frequency shift
k = log2(M);% Number of bits per symbol
nbits=k*fft_size;
nsym = fft_size*2;%1000
cp_length=round(0.06*fft_size);% length of cyclic prefix
xbits = randi([0 1],1,nbits);% Random binary data stream
% mappedData = wlanConstellationMap(xbits,k);
xsym = bi2de(reshape(xbits,k,(length(xbits)/k)).','left-msb');
tx=[];
% QAM Modulation
QAM_Modulation=qammod(xsym,M,'PlotConstellation',true);
% scatterplot(QAM_Modulation);
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Accepted Answer
斯利Tadavarty
on 1 Apr 2021
Hi Abdul,
散点图的使用是正确的。我可以先w why do you feel the constellation is incorrect?
Since, xbits are random, possibly, same number of bits might make a symbol, leading to partial constellation while looking from scatterplot.
Try this:
M=64;% QAM Signal Constellation
fft_size=64;
fspacing=15000;
fs=15000*64;
Ts = 1/fs;% Sampling period of channel
Fd = 0;% Max Doppler frequency shift
k = log2(M);% Number of bits per symbol
nbits=k*fft_size;
nsym = fft_size*2;%1000
cp_length=round(0.06*fft_size);% length of cyclic prefix
xbits = randi([0 1],1,nbits*10);% Random binary data stream (Updated with 10 times the previous length)
% mappedData = wlanConstellationMap(xbits,k);
xsym = bi2de(reshape(xbits,k,(length(xbits)/k)).','left-msb');
tx=[];
% QAM Modulation
QAM_Modulation=qammod(xsym,M,'PlotConstellation',true);
scatterplot(QAM_Modulation)
Hope this helps.
Regards,
斯利
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