str = 'qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM';
data = repmat(str, 1, 100);
vol = 20;

input = int8(data);
mod = qammod(input, 256);
signal = awgn(mod, vol, 'measured');
% res = char(qamdemod(signal, 256))

sPlot = scatterplot(mod, 1, 0, 'k*');
hold on
scatterplot(signal, 1, 0, 'r.', sPlot);
hold off