Compare PSK and PAM modulation schemes to demonstrate that PSK is more sensitive to phase noise. This is the expected result because the PSK constellation is circular while the PAM constellation is linear.
Specify the number of symbols and the modulation order parameters. Generate random data symbols.
len = 10000;
M = 16;
msg = randi([0 M-1],len,1);
Modulate msg using both PSK and PAM to compare the two methods.
txpsk = pskmod(msg,M);
txpam = pammod(msg,M);
Perturb the phase of the modulated signals by applying a random phase rotation.
Plot the constellation points using one of the symbol sets. For each constellation point, assign a label indicating the Gray and natural binary values for each symbol.
For Gray binary symbol mapping, adjacent constellation points differ by a single binary bit and are not numerically sequential.
For natural binary symbol mapping, adjacent constellation points follow the natural binary encoding and are sequential.
scatterplot(symgray,1,0,'b*');
for k = 1:M
text(real(symgray(k))-0.2,imag(symgray(k))+.15,...
dec2base(mapgray(k),2,4));
text(real(symgray(k))-0.2,imag(symgray(k))+.3,...
num2str(mapgray(k)));
text(real(symbin(k))-0.2,imag(symbin(k))-.15,...
dec2base(mapbin(k),2,4),'Color',[1 0 0]);
text(real(symbin(k))-0.2,imag(symbin(k))-.3,...
num2str(mapbin(k)),'Color',[1 0 0]);
end
axis([-2 2 -2 2])
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