cyclic3.m

Cylic 编码的matlab仿真程序

clear;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Encoding
n = 15; k = 7; m = 8;                       % Where n is codeword length, k
                                            % is message length and m is
                                            % the number of the messages.
g = [1 0 0 0 1 0 1 1 1];                    % Set generator polynomial.
msg = [];
code = [];
for a = 1:m
    msg(a,:)= bitget(a-1,k:-1:1);           % Message is a binary matrix.
    stage = [0 0 0 0 0 0 0 0];              % Set original registers.
    for i = 1:k                             % Input messages bit by bit.
        temp = xor(msg(a,i),stage(1));
        s_temp = stage;
        stage(n-k) = temp;
        for j = 1:(n-k-1)
            if g(n-k-j+1)
                stage(n-k-j) = xor(temp,s_temp(n-k-j+1));
            else
                stage(n-k-j) = s_temp(n-k-j+1);
            end
        end
    end
    code = [code;msg(a,:) stage];
end
msg                                         % Display original message.
code                                        % Display codeword.

% Add random error
error = randerr(m,n,[2 1])                  % We got 1 or 2 errors here.
code_r = xor(code, error)                   % Put error into codeword.


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
ep = [1 0 0 1 0 1 1 1               % position 0,14
    1 0 1 0 1 1 1 0                 %          1,14
    1 1 0 1 1 1 0 0                 %          2,14
    0 0 1 1 1 0 0 0                 %          3,14
    1 1 1 0 0 1 1 1                 %          4,14
    0 1 0 0 1 1 1 0                 %          5,14
    0 0 0 0 1 0 1 1                 %          6,14
    1 0 0 0 0 0 0 1                 %          7,14
    1 0 0 0 0 0 1 0                 %          8,14
    1 0 0 0 0 1 0 0                 %          9,14
    1 0 0 0 1 0 0 0                 %          10,14
    1 0 0 1 0 0 0 0                 %          11,14
    1 0 1 0 0 0 0 0                 %          12,14
    1 1 0 0 0 0 0 0                 %          13,14
    1 0 0 0 0 0 0 0];               %          14

% Decoding
code_de = code_r;
for b = 1:m
    for c = 1:n
        code_in = circshift(code_r(b,:), [1,1-c]);      % Shift the sequence
        stage_r = [0 0 0 0 0 0 0 0];
        for i = 1:n                                     % Calculate syndromes
            temp_r = xor(code_in(i),stage_r(1));
            s_temp_r = stage_r;
            stage_r(n-k) = temp_r;
            for j = 1:(n-k-1)
                if g(n-k-j+1)
                    stage_r(n-k-j) = xor(temp_r,s_temp_r(n-k-j+1));
                else
                    stage_r(n-k-j) = s_temp_r(n-k-j+1);
                end
            end
        end
        syndrome = stage_r;
        for d = 1:n
            judge = 0;
            [num,ratio] = biterr(syndrome,ep(d,:));
            if num == 0
                if syndrome == [1 0 0 0 0 0 0 0]        % I only one error happend.
                    temp_p = c;
                    code_de(b,temp_p) = ~code_r(b,temp_p);
                    judge = 1;
                    break;
                else                                    % If two errors happend.
                    temp_p1 = c;
                    temp_p2 = n-d+c;
                    code_de(b,temp_p1) = ~code_de(b,temp_p1);
                    code_de(b,temp_p2) = ~code_de(b,temp_p2);
                    judge = 1;
                    break;                              % Jump out from d loop.
                end
            else
            end
        end
        if judge
            break;                                      % Jump out from c loop.
        else
        end
    end
end
code_de                                                 % Display decoded codeword.
msg_de = code_de(:, 1:k)                                % Display decoded message.