to get the proper scatter plot

6 views (last 30 days)
ABDUL
ABDUL on 25 Mar 2021
Commented: ABDULon 4 Apr 2021
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);

Accepted Answer

斯利Tadavarty
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
1 Comment
ABDUL
ABDUL on 4 Apr 2021
thank you sriram

Sign in to comment.

More Answers (0)

美军陆军nity Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!