Scrambling Function, what I am doing wrong

Hi,

I am trying write a scrambling program,Summary is as follow -Random data -Scrambling function with x^32 polynomial and e being initial states of 32 bit length. -Modulation -Demodulation -DeScrambling,

Now if I compare the output after the deScrambling it matches for first run but failed for rest. I have tried to clear/release the deScrambling handler and all possible solutions which I can think of.

I need to put Scrambling block into my already build physical layer simulation with other coding and modulation schemes. Code below is just test code which fails to return which is expected from deScrambling object

clc
clear all

N = 2;
px=[1,1,1,0,1,1,0,1,1,0,1,1,1,0,0,0,1,0,0,0,0,0,1,1,0,0,1,0,0,0,0,0,1;];
e= [1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;];
hSCR = comm.Scrambler(N,px,e);

p=4;
data = randint(p, 5);

for ii=1:p
    scrData(ii,:) = step(hSCR, data(ii,:)');
end

hModulator = comm.BPSKModulator;
for ii=1:p
    modData(ii,:) = step(hModulator, scrData(ii,:)');
end
hDemod = comm.BPSKDemodulator;
hDSCR = comm.Descrambler(N,px,e);

for ii=1:p
    DemodData(ii,:) = step(hDemod, modData(ii,:)');
end
release(hDemod);
hDSCR = comm.Descrambler(N,px,e);
for ii=1:p
    deScrData(ii,:) = step(hDSCR, DemodData(ii,:)');
    release(hDSCR);
   a(ii,:)=isequal(data(ii,:),deScrData(ii,:));
    [data(ii,:)' deScrData(ii,:)']
%    clear hDSCR;
end
a

[Walter Roberson]

http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup

Answer 1

[Shan]

here is simplified version of this code,

uncomment the nested LOOP , which results in Scrambling function to fail, Why?????

clc
clear all

N = 2;
px=[1,1,1,0,1,1,0,1,1,0,1,1,1,0,0,0,1,0,0,0,0,0,1,1,0,0,1,0,0,0,0,0,1;];
e= [1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;];
hSCR = comm.Scrambler(N,px,e);
hDSCR = comm.Descrambler(N,px,e);
for  jj=1:5
   data(jj,:) = randint(1, 4);  
   scrData(jj,:) = step(hSCR, data(jj,:)');
end

for  jj=1:5
%       for counter = 1:3 %uncomment this loop and Scrambler fails, WHY?
    deScrData = step(hDSCR, scrData(jj,:)');
    a(jj)=isequal(data(jj,:)', deScrData);
%       end
end

disp(a);

[Kaustubha Govind]

What version are you using? I uncommented the inner loop and was able to run your code successfully on R2011b.

[Shan]

Im using R2011b, But still have this error,

Why on 2nd loop it fails

:-(

[Shan]

I am testing that code on 2011b, When I enable nested loop scrambler fails.

Seems like bug in scrambling block?