preliminary_channel_coding.asv

小区初搜为GSM系统中的一个关键过程

function tx_block260 = Preliminary_channel_coding(tx244)
tx244 = round(rand(1,244));
%有用bit的抽取
g_function = [39 40	41	42	43	44	48	87	45	2,...
               3 8	10	18	19	24	46	47	142	143,...
             144	145	146	147	92	93	195	196	98	137,...
             148	94	197	149	150	95	198	4	5	11,...
              12	16	9	6	7	13	17	20	96	199,...
               1	14	15	21	25	26	28	151	201	190,...
             240	88	138	191	241];
l_gf = length(g_function);
for i = 1:l_gf
    tx_impt(i) = tx244(g_function(i)); 
end
%CRC
g = [1 0 0 0 1 1 1 0 1];  
out = addcrc(tx_imp,g);
p = out(66,73);
%
w(1:71) = tx244(1:71);
w(74:123) = tx244(74-2:123-2);
w(126:178) = tx244(126-4:178-4);
w(181:230) = tx244(181-6:230-6);
w(233:252) = tx244(233-8:252-8)
w(72) = w(73) = tx244(70);
w(124) = w(125) = tx244(120);
w(179) = w(180) = tx244(173);
w(232) = w(73) = tx244(70);


function output=addcrc(infor,g)
% infor is the input data.
% g is the coefficient array of ploy genarator
% output is the infor added crc codes
% infor = [ 0     0     1     0     1     1     0     0     0     1     1     0  ...
%     0       1    1     0     0     0     1     0     0     0     1     1     1 ];          % for 20070817_13  
%  infor = [  1     0     1     0     1     1     0     0     0     1     0     1 ...
%      1     0     1     0     1     0     0     0     0     0     1     0   0  ];          % for 22  
%   infor = [   1     0     1     0     1     1     0     0     1     0     0     1     0 ...
%      0     1     1     1     0     1     0     1     0     1     0     0    ];          %for  \20070824_35.
% %  infor = [ 1 0 1 1 0 0 1 0 1];
% 
%   infor = [   1     0     1     0     1     1     0     0     1     0     1     1     1 ...
%      0     1     1     0     1     0     0     0     0     1     1     0  ];          %for  \20070824_31.
%  
% g = [1 0 1 0 1 1 1 0 1 0 1];
% g = [1 0 0 1];

a=length(infor);
b=length(g);
x=[infor zeros(1,b-1)]; % add g '0s'to the infor
len=length(x);
for i=1:a
    if x(i)~=0
        x(i:(i+b-1))=xor(x(i:(i+b-1)),g);
    end
end
% output=[infor x((len):(-1):(len-b+2))];
output=[infor x((len-b+2):(len))];
% CRC = [x((len-b+2):(len))]
%  crcr =      [  0    1     0     1     1     1     0     1     1     0 ];    % for 20070817_13  
%  crcr =      [ 1   1     0     0     1     0     0     1     1     0 ];    %for  \20070824_35.
 
%  crcr =      [ 1    0     1     0     1     0     0     0     1     0 ];    %for  \20070824_31.
% 
% % crcr =      [  0     1     1     1     0     0     1     0     1     1 ];    % for 22
% %  crcr =      [    1     1     0     1     0     0     1     1     1     0 ];    % for 22
% xor( CRC,crcr)