channel coding using convolutional code

clc;
clear;
N=20;
BITS=randint(1,N);
constlength=9;
traceback=5*constlength;
polynomial=[657 435];
trellis = poly2trellis(constlength,polynomial);
x=convenc(BITS,trellis);

SNR=0:2:30;
r1=(pskmod(x,2));

   %for  k=1:16

Rx_sequence= awgn(r1,0,'measured'); %signal with noise
SNR_of_level=0
r2=pskdemod(Rx_sequence,2);
error=xor(x,r2); %getting number of errors 
number_errors=sum(error)

   %end

l=vitdec(r2,trellis,traceback,'trunc','hard')

what's wrong

Answer 1

[Image Analyst]

Well, the failure to tell us what those functions (vitdec, etc.) are or what toolbox they can be found in is one thing that's wrong. Lack of sufficient comments is another. Not telling us what causes you to think there's something wrong is a third. There could be more....

http://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer