Scrambler/Descrambler in MATLAB

[esto1990]

Hello,

Im trying to implement 802.11 scrambler/descrambler in matlab. Based on the standard, it should look sth like this:



My code looks like this

data=zeros(1,7); %data
register=[1 0 1 1 1 0 1]; %initial state

for i=1:7
   temp=xor(register(1),register(4)); % x7 and x4 xor 
   out(8-i,1)=xor(data(8-i,1),temp); %output bit
   register=circshift(register',-1,1)'; %shift left
   register(7)=data(8-i,1); %insert data to register
end

When im trying to descramble data, with same code and same initial state it gives wrong results.

What am i doing wrong??

Is there any way to guess or estimate initial state at the receiver side??


Best,
Ernest