<matlab> 實現線性反饋移位寄存器單元<LFSR>
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%  該函數實現產生偽隨機序列的部件 —— 線性反饋移位寄存器單元                        %
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%  SFlog2為擴頻因子的底數為2的對數值，cycle為PN序列的周期，其值為2^SFlog2    %
%  initial_state為移位寄存器的初始狀態，generator_polynomial_coefficient為           %
%  生成PN序列所需的本原多項式，對應于移位寄存器的連接向量。                         %
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function [m_sequences] = linear_feedback_shift_register(SFlog2,cycle,...
    initial_state,generator_polynomial_coefficient)
if max(generator_polynomial_coefficient) > SFlog2
    error('本原多項式系數對應的最高階不能大于移位寄存器的階數');
end
if length(initial_state) > SFlog2
    error('移位寄存器的初始狀態序列長度不能大于寄存器的階數');
end
if SFlog2 > 32
    error('擴頻因子超出仿真器處理范圍！');
end
len = length(generator_polynomial_coefficient);    
m_sequences = zeros(1,cycle);                   % 初始化反饋序列
register_index = generator_polynomial_coefficient;
%%
% 開始線性反饋移位寄存器的迭代計算過程
h = waitbar(0,'m 序列生成中...................');
for m = 1:cycle 
    temp = initial_state(register_index(2));
    for n = 3:len
        temp = bitxor(initial_state(register_index(n)),temp);
    end
    m_sequences(m) = initial_state(1);                      % 線性反饋移位寄存器的輸出
    initial_state = [temp,initial_state];       % 更新線性反饋移位寄存器的狀態
    initial_state(SFlog2+1) = [];
    waitbar(m/cycle);
end
close(h);
%%
m_sequences = 2*m_sequences - 1;                % 生成雙極性的隨機序列