%在DS-spread spectrum系統中,噪聲為加性高斯白噪聲,傳統單用戶檢測,線性解相關多用戶檢測和最小均方誤差多用戶檢測的性能比較clear allclose allclc;prompt={'Enter the numbers of user:','Enter the length of user code:','Enter the power of the user code','Enter the power of Noise','Enter the kth user which you want to test?'};name=['CDMA MUD TEST'];line=1;defaultanswer={'10','5000','1 2 3 4 5 6 7 8 9 10', '10','1'};glabel=inputdlg(prompt,name,line,defaultanswer);num1=str2num(char(glabel(1,1)));num2=str2num(char(glabel(2,1)));num3=str2num(char(glabel(3,1)));num4=str2num(char(glabel(4,1)));k=str2num(char(glabel(5,1)));UserNumber=num1;%用戶數inflength=num2;%用戶信息序列長度a=num3;  %用戶信息功率Pn=num4; %噪聲功率sigma=1;%噪聲標準差N=31;R=(ones(UserNumber)+(N-1)*eye(UserNumber))/N; %相關系數矩陣b=2*randint(UserNumber,inflength)-1;   %用戶信息矩陣(隨機+1，-1矩陣)%******Generate M sequence******************coefficients=[1 0 1 0 0]; %5級左移m序列碼發生器的反饋系數mseq=mseries(coefficients); %生成31×31的m序列碼矩陣mseq=mseq(1:UserNumber,1:N);%*******************************************%**********Generate noise*******************n1=Pn*normrnd(0,1,1,inflength*N);n=zeros(UserNumber,inflength);for j=1:inflength   ntemp=n1(1,((j-1)*N+1):j*N);   n(:,j)=(mseq*ntemp')/N;end%*******************************************    A=diag(a);    y=R*A*b+n;  %傳統單用戶檢測    ydec=inv(R)*y;   %線性解相關多用戶檢測    ymmse=inv(R+sigma^2*inv(A))*y;  %最小均方誤差多用戶檢測   for i=1:UserNumber    ylen(i)=length(find(sign(real(y(i,:)))-b(i,:)));      ydeclen(i)=length(find(sign(real(ydec(i,:)))-b(i,:)));    ymmselen(i)=length(find(sign(real(ymmse(i,:)))-b(i,:)));    BER_y(i)=ylen(i)/inflength;    BER_ydec(i)=ydeclen(i)/inflength;    BER_ymmse(i)=ymmselen(i)/inflength;   end      snr=20*log10(a(1)/Pn);    disp('信噪比為');    disp(snr);    disp('誤碼個數為');    disp(ylen(k));    disp(ydeclen(k));    disp(ymmselen(k));    disp('誤碼率為');    disp( BER_y(k));    disp(BER_ydec(k));    disp(BER_ymmse(k));