<matlab> CDMA業務信道接收機仿真實現
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%  該函數仿真CDMA接收機的功能，包括解擴，解交織，信道編碼(卷積碼)        %
%  解碼，信源編碼(CRC)解碼5個功能模塊，生成用于數字基帶傳輸的信號序列    %  
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function [original_sequence] = cdma_reciever(mul_fad_sequence,frame_length,...
    crc_select,cov_select,in_info_len,in_supv_len,sf,add_bits,i_add_bits,max_delay,fade_sign)
% sequence           輸入的待解擴序列
% frame_length      CRC編碼的碼字長度
% crc_select          CRC編碼生成多項式的選項 1 - CRC_CCITT,2 - CRC_CIT,3 - CRC32
% cov_select         卷積碼的編碼其選擇 1 - 約束長度為9，效率1/2，2 - 約束長度9，效率1/3
% in_info_len         交織器的信息位長度
% in_supv_len        交織器的監督位長度
% sf                     擴頻因子
% add_bits            CRC編碼時添加的尾比特
% i_add_bits          分組交織器添加的尾比特
% max_delay         信道延遲
% fade_sign          瑞利信道衰落符號
sequence = mul_fad_sequence;
len = length(sequence);
sequence = fade_sign.*sequence(1:(len-max_delay));
despread_seq = DS_modulation_demodulation(sequence,sf,2);     % 解擴部分
despread_seq = sign(despread_seq);
inter_seq = (despread_seq + 1)/2;                                           % 轉單極性碼
de_inter_seq = block_cancellation_interlace(...
    inter_seq,in_info_len,in_supv_len,i_add_bits);                         % 解交織
rev_seq = convolutional_decode_Viterbi(de_inter_seq,45,cov_select);         % 卷積解碼
%%
if crc_select == 1 
    code_generator = 1;                                                          % CRC解碼部分
    code_len = 16;
elseif crc_select == 2
    code_generator = 2;
    code_len = 16;
else
    code_generator = 3;
    code_len = 32;
end
iterate_num = length(rev_seq)/(frame_length+code_len); 
rev_seq = reshape(rev_seq,(frame_length+code_len),iterate_num);
rev_seq = rev_seq';
decode_seq = zeros(iterate_num,frame_length);
frame_error = 0;
for k = 1:iterate_num
    [output_seq,err] = cyclic_redundancy_decode(rev_seq(k,:),(frame_length+code_len),code_generator);
    if err == 1
        frame_error = frame_error + 1;
%         decode_seq(k,:) = 0.5 * ones(1,frame_length);
        decode_seq(k,:) = output_seq;
    else
        decode_seq(k,:) = output_seq;
    end
end
decode_seq = reshape(decode_seq',1,iterate_num*frame_length);       % 解碼
if ~isempty(add_bits)                                               % 在接受端增加的一個參數add_bits
    len = iterate_num*frame_length;
    decode_seq((len-add_bits+1):len) = [];
end
original_sequence = 2*decode_seq - 1;                               % 得到原序列