Re: [Discuss-gnuradio] GRC 3.6 / 802.11 a/g test signal

[Bastian Bloessl]

On 08 Oct 2014, at 14:23, Ernest Szczepaniak <address@hidden> wrote:

> So... After going deep into Annex L i found that my scrambler fails. Also
> MATLAB built-in scrambler gives wrong results. Could you pls check this code
> fragment?
> 
> Asumme that we have 20 data bits to scramble. Initial scrambler state is [1
> 0 1 1 1 0 1] (bit nr 7 left side).
> 
> scrambler_register=[1 0 1 1 1 0 1];                                   %
> scrambler seed
> data_bits=randi([0 1],1,20);                                             %
> data to be scrambled
> 
> for i=1:20
>   temp=xor(scrambler_register(1),scrambler_register(4));  % x7 and x4 xor
> operation
>   data_scrambled(i)=xor(data_bits(i),temp);                      % output
> bit
>   register=circshift(scrambler_register',-1,1)';                    % shift
> left register
>   register(7)=data_scrambled(i); 

the scrambler is independent from the data. you want to feedback temp and not 
data_scrambled.

Maybe you want to have a look at Figure 1 in

http://www.ccs-labs.org/bib/bloessl2015scrambler/

Bastian



> end
> 
> To clarify, left side of register has index (1), right side has index (7).
> 
> Best, 
> Ernest
> 
> 
> 
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--
Dipl.-Inform. Bastian Bloessl
Distributed Embedded Systems Group
University of Paderborn, Germany
http://www.ccs-labs.org/~bloessl/