modulator2.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。

%% Made by Zheng Xiao (052815 05b04)
%% Group Member: Ji Yue, Sun Xin, Zheng Xiao

%clear
% Generate Signal
%M = 16; %-the number of Sample per Period in input signal
N = 32; %-the number of Sample per Period in BPSK Modulated signal
M = 64; %-the number of Sample per Period in input signal
P1 = [0 5 7 8 9 13 15];
P2 = [1 2 3 4 10 12 14];
%tk = 0:1/M:(1024/M);
%input = sin(2*pi*tk) + cos(pi*tk);
%ratio = max(input);
%input = input/ratio;
% A-law PCM encode

% Lengthen PCM code
%%pcmCode = [1];
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 1
original=[0 1 0]; % User Code
nOriginal = length(original);
pcmCode=expand_bit(original);%must be 64xN length
key1 = genM(M,P1);
pcmCode=xor(pcmCode,periodExpand(key1,nOriginal));
pcmCode = genBipolar(pcmCode); % 转换为双极性码

stem(pcmCode);
pause

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 2

original2=[1 1 1]; % User Code
nOriginal2 = length(original2);
pcmCode2=expand_bit(original2);%must be 64xN length
key2 = genM(M,P2);
pcmCode2=xor(pcmCode2,periodExpand(key2,nOriginal2));
pcmCode2 = genBipolar(pcmCode2); % 转换为双极性码

stem(pcmCode2);
pause

%%%%%%%%%%%%%%%%%%%%%%%% FUSION %%%%%%%%%%%%%

pcmCode = (pcmCode + pcmCode2);
stem(pcmCode);
pause

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

npcmCode = length(pcmCode); %-number of total symbol
pcmCode = [pcmCode;zeros((N-1),npcmCode)];
pcmCode = reshape(pcmCode,1,N*npcmCode);
pcmCode = conv(pcmCode,ones(1,N));
pcmCode = pcmCode(1:N*npcmCode);


% BPSK Modulation
tk = 0:1/N:(1-1/N);
carrier = sin(4*pi*tk);
carrier = padarray(carrier,npcmCode-1,'circular','post');
carrier = reshapeSeq(carrier);
signal = carrier .* pcmCode; %<= THIS IS THE MODULATED SIGNAL
%plot(signal);

%%%%% Here comes through the channel %%%%%
%=================[Media]================%

%NOISE
stem(signal);
pause
signalIn = addNoise(signal, sqrt(5)/5);
stem(signalIn);
pause


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 1
% BPSK Demodulation
signalIn = signal .*carrier; %<= INPUT SIGNAL OF DEMODULATOR
 %plot(signalIn)
judger = reshapeColumn(signalIn,N);
judger = sum(judger,2);
judger(find(judger>=0)) = 0; % 转化为单极性
judger(find(judger<0)) = 1;
judger = judger';

nFinal = length(judger)/M;
final = xor(judger, periodExpand(key1,nFinal));
finalFinal = finalJudge(final,M); % the final output
subplot(2,1,1)
stem(finalFinal);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 2
% BPSK Demodulation
signalIn = signal .*carrier; %<= INPUT SIGNAL OF DEMODULATOR
 %plot(signalIn)
judger = reshapeColumn(signalIn,N);
judger = sum(judger,2);
judger(find(judger>=0)) = 0; % 转化为单极性
judger(find(judger<0)) = 1;
judger = judger';

nFinal = length(judger)/M;
final = xor(judger, periodExpand(key2,nFinal));
finalFinal = finalJudge(final,M); % the final output
subplot(2,1,2)
stem(finalFinal);