How can implement descrambler operation ?

Question

murat alboga 2018-9-9

0
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https://ww2.mathworks.cn/matlabcentral/answers/418253-how-can-implement-descrambler-operation

编辑： Phung Dao 2020-9-18

Hello,

I am trying to channel modelling in Matlab. I should complete descrambler processing in Receiver in order to recover original signal. I completed Scrambler part with XOR operation but I stuck about descrabler process. I shared below my scrambler process codes.

    length = 1200;       
    binaryalph = [0,1];
    randomData = randsrc(1,length,binaryalph);
    seed = [[0,0,1,1, 1,1,1,1, 1,1,1,1, 1,1,1]
        [0,1,1,1, 1,1,1,1, 1,1,1,1, 1,1,1]
        [1,0,1,1, 1,1,1,1, 1,1,1,1, 1,1,1]
        [1,1,1,1, 1,1,1,1, 1,1,1,1, 1,1,1]];
    initialState = seed(1);
    % Generator polynomial for LFSR ( 1 + x^(-14) + x^(-15) )
    generatorPolynomial = [1,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,1,1];
    % Mask represents the value to tap from LFSR as output
    mask = [1,0,0,0, 0,0,0,0, 0,0,0,0, 0,0,0];
    % Create PN Sequence object having the recommended generator polynomial and
    % given initialState
    % scr = comm.Scrambler(length(generatorPolynomial),'1 + x^(-14) + x^(-15)',         
    h =  commsrc.pn('GenPoly',generatorPolynomial,    ...
              'InitialStates',initialState,     ...
              'CurrentStates',initialState,     ...
              'Mask',mask,                      ...
              'NumBitsOut',1);
    % Number of bits to generate for scrambling must be equal to the number of
    % bits in the input
    set(h,'NumBitsOut',numel(randomData));
    % Do bitwise xor between input bits and generated pseudo-random bits to get
    % the scrambled output bits
    scrambledBitVector = bitxor(randomData,reshape(generate(h),1,[]));