<matlab> CDMA業(yè)務(wù)信道卷積解碼實(shí)現(xiàn)
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%                                                                                    %
%  該函數(shù)根據(jù)上下行信道區(qū)分生成不同碼率的卷積碼序列          %
%  original_sequence是原始輸入序列，channel_select              %
%  是信道選擇參數(shù)，其中下行碼率為1/2，上行信道為1/3          %
%                                                                                    %
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function [decode_sequence] = convolutional_decode(...
    convolutional_sequence,tail_bits_length,channel_select)
seq_len = length(convolutional_sequence);                       % 得到輸入數(shù)據(jù)序列的長度
if length(seq_len) < 1                                                    % 輸入數(shù)據(jù)序列必須不為空
    error('輸入序列錯誤！');
end
if nargin < 3
    channel_select = 1;                                                   % 選擇正向業(yè)務(wù)信道
end
if nargin < 2
    error('輸入?yún)?shù)不足！');
end
if tail_bits_length < 1 | rem(tail_bits_length,1) ~= 0 
    error('參數(shù)tail_length必須是大于0的正整數(shù)！');
end
register_order = 8;                                                      % 初始化移位寄存器的階數(shù)
if channel_select == 1  
    restricted_length = 9;                                              % 卷積碼的約束長度為9
%     code_rate = [1 2];                                              % 正向業(yè)務(wù)信道的編碼效率為1/2
%     xor_generator_0 = [1 0 1 1 1 0 0 0 1];                 % 初始化編碼效率為1/2的連接向量器0
%     xor_generator_1 = [1 1 1 1 0 1 0 1 1];      
    xor_cal_generator = [561,753];                                % 初始化連接器
    trellis = poly2trellis(restricted_length,...
        xor_cal_generator);
    decode_sequence = vitdec(convolutional_sequence,trellis,tail_bits_length,'cont','hard');
    decode_sequence(1:tail_bits_length) = [];
elseif channel_select == 2    
    restricted_length = 9;                                    % 卷積碼的約束長度為9
%     code_rate = [1 3];                                    % 默認(rèn)正向業(yè)務(wù)信道的編碼效率為1/2
%     xor_generator_0 = [1 0 1 1 0 1 1 1 1];        % 初始化編碼效率為1/3的連接向量器0
%     xor_generator_1 = [1 1 0 1 1 0 0 1 1];      
%     xor_generator_2 = [1 1 1 0 0 1 0 0 1];      
    xor_cal_generator = [557,663,711];                % 初始化連接器
    trellis = poly2trellis(restricted_length,...
        xor_cal_generator);
    decode_sequence = vitdec(convolutional_sequence,trellis,tail_bits_length,'cont','hard');
    decode_sequence(1:tail_bits_length) = [];
else
    error('信道選擇參數(shù)channel_select錯誤! 1 - 正向業(yè)務(wù)信道，2 - 反向業(yè)務(wù)信道');
end