pcm_decode.m

Matlab 模拟 CDMA 直接扩频。m序列生成矩阵为p(x) = 1 + x^5 + x^7 + x^8 + x^9 + x^13 + x^15。能画出每阶段的时域、频域图。

function [ output ] = pcm_decode( bitsIn )
%UNTITLED1 Summary of this function goes here
%  Detailed explanation goes here
SLENGTH = length(bitsIn)/8;

bytesIn = zeros(3,SLENGTH);
for i = 1:SLENGTH,
    bytesIn(1,i) = bitsIn(8*(i-1)+1);
    for j = 2:4,
        bytesIn(2,i) = bytesIn(2,i) + bitsIn(8*(i-1)+j)*2^(4-j);
    end
    for j = 5:8
        bytesIn(3,i) = bytesIn(3,i) + bitsIn(8*(i-1)+j)*2^(8-j);
    end
end

%==>== DECODE ====%

output = zeros(1,SLENGTH);
for i = 1:SLENGTH
    % in case!
    if bytesIn(2,i) == 0,
        preByte = (1/2)^7;
        preByte1 = 0;
    else
        preByte = (1/2)^(8-bytesIn(2,i));
        preByte1 = preByte;
    end
    output(i) = (-1)^(bytesIn(1,i))*...
                (preByte1+...
                preByte*(bytesIn(3,i))/16);
end
clear preByte;
clear preByte;