What is wrong with this code, please help!

this is the code to qam modulate a quantized sine wave, for some reason i get only 15 constellation points instead of 16.

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t = 0:.001:2*pi; % Times at which to sample the sine function

sig = sin(2*t); % Original signal, a sine wave

partition = [-1:2/15:1]; % Length 16, to represent 17 intervals

codebook = [0:1:16]; % Length 17, one entry for each interval

quants= quantiz(sig,partition,codebook); % Quantize.

x=quants;

M = 16;

yy = qammod(x,M);

y = awgn(yy,10)

% demodulate

z = qamdemod(y,M);

plot(t,sig, 'cd', t,quants,'bo', t,z,'rx'),grid

legend('Original signal','Quantized signal','recovered signal');

scatterplot(y)

title('scatterplot QAM')

Answer 1

[Walter Roberson]

Your line

codebook = [0:1:16]; % Length 22, one entry for each interval

will only assign 17 values, not 22. This is right after your line

partition = [-1:2/15:1]; % Length 21, to represent 22 intervals

which only assigns 16 values...

[jessica david]

Oops! that was a mistake in the comment only. I forgot to change it, what I actually meant was

partition = [-1:2/15:1]; % Length 16, to represent 17 intervals

codebook = [0:1:16]; % Length 16, one entry for each interval

[Paulo Silva]

codebook length is still 17 not 16

[jessica david]

i tried codebook = [0:1:15] but it still only gives 15 points only :(

[Andrew Newell]

>> length([0:16])

ans =

17

[jessica david]

i tried changing the codebook to [0:1:15], [0:16] etc, but nothing seems to work, i still have only 15 points :(

[Paulo Silva]

Are you referring to the groups of points in the scatterplot?

[jessica david]

yes, there has to b 16 points, but i am getting only 15 points