matlab_二用户CDMA系统_加性高斯信道_BPSK调制_15位M序列扩频_PSK调制信号_时域和频域特性

%本程序模拟2用户CDMA系统，信道为加性高斯信道，可以正确解扩解调， %信噪比(dB)约为5的时候，误码率基本在0.1以内 %信噪比(dB)大于9的时候，基本不会出现误码了 %本程序中时间单位是微秒 %频率单位为MHz %码元速率单位是Mb/s global dt df t f N close all N=2^14; %采样点数 L=64; %每码元的采样点数 M=N/L; %码元数 Rb=2; Ts=0.5; %码元宽度是0.5us dt=Ts/L; df=1/(N*dt); %MHz T=N*dt; %截短时间 Bs=N*df/2; %系统带宽 w0=28*pi; Eb_N0=input('请输入信噪比dB（5以上基本无误码）'); t=[-T/2+dt/2:dt:T/2]; %时域横坐标 f=[-Bs+df/2:df:Bs]; %频域横坐标 figure(1) set(1,'Position',[10,600,400,150]) %设定图1的窗口位置及大小 figure(2) set(2,'Position',[10,400,400,150]) %设定图2的窗口位置及大小 figure(3) set(3,'Position',[10,200,400,150]) %设定图3的窗口位置及大小 figure(4) set(4,'Position',[10,0,400,150]) %设定图4的窗口位置及大小 figure(5) set(5,'Position',[430,600,400,150]) %设定图1的窗口位置及大小 figure(6) set(6,'Position',[430,400,400,150]) %设定图2的窗口位置及大小 figure(7) set(7,'Position',[430,200,400,150]) %设定图3的窗口位置及大小 figure(8) set(8,'Position',[430,0,400,150]) %设定图4的窗口位置及大小 figure(9) set(9,'Position',[850,600,400,150]) %设定图3的窗口位置及大小 figure(10) set(10,'Position',[850,400,400,150]) %设定图4的窗口位置及大小 figure(11) set(11,'Position',[850,200,400,150]) %设定图3的窗口位置及大小 figure(12) set(12,'Position',[850,0,400,150]) %设定图4的窗口位置及大小 m1=[1 1 1 -1 -1 1 -1 1 1 -1 1 -1 1 -1 -1]; %用户一的m序列 m2=[1 1 -1 -1 1 -1 1 1 1 -1 -1 1 -1 -1 1]; %用户二的m序列 %%%%%%%%%%%%%%%%%%%%%%%%%% 生成噪声，信噪比为11 %Eb_N0=11 %Eb/N0 in dB eb_n0=10^(Eb_N0/10); Eb=1; n0=Eb/eb_n0; %信道的噪声谱密度 sita=n0*Bs; %信道中噪声功率 n_ch=sqrt(sita)*randn(size(t)); %信道噪声 NOISE=abs(t2f(n_ch)); %%%%%%%%%%%%%%%%%%%%%%%%%%%产生用户1的数字基带信号供传输 n=1; %每次有偶数个1 while rem(n,2)~=0 a=round(rand(1,M)); n=length(find(a==1)); end aaa=a; %保存原序列（0、1），供最后比较误码率使用 aa=find(a==0); %将（0、1）序列变换为（+1、-1）序列，以方便扩频使用 a(aa)=-ones(size(aa)); nrz1=zeros(L,M); %将序列扩展成为时域，方便做F变换和时域显示 for loop=1:L,nrz1(loop,:)=a; end nrz1=reshape(nrz1,1,N); %%%%%%%%%%%%%%%%%%%%%%%%%%%产生用户2的数字基带信号供传输 n=1; %每次有偶数个1 while rem(n,2)~=0 b=round(rand(1,M)); n=length(find(b==1)); end bbb=b; bb=find(b==0); %bb是a中奇序数1的位置 b(bb)=-ones(size(bb)); %所有位于cc的0变成-1 nrz2=zeros(L,M); for loop=1:L nrz2(loop,:)=b; end nrz2=reshape(nrz2,1,N); %%%%%%%%%%%%%%%%%%%%%%生成扩频要用的M序列 mx1=zeros(1,16384); for i=1:64:16384 mx1(i:i+4)=m1(1); mx1(i+5:i+8)=m1(2); mx1(i+9:i+12)=m1(3); mx1(i+13:i+16)=m1(4); mx1(i+17:i+20)=m1(5); mx1(i+21:i+24)=m1(6); mx1(i+25:i+28)=m1(7); mx1(i+29:i+32)=m1(8); mx1(i+33:i+36)=m1(9); mx1(i+37:i+40)=m1(10); mx1(i+41:i+44)=m1(11); mx1(i+45:i+48)=m1(12); mx1(i+49:i+52)=m1(13); mx1(i+53:i+56)=m1(14); mx1(i+57:i+63)=m1(15); end mx2=zeros(1,16384); for i=1:64:16384 mx2(i:i+4)=m2(1); mx2(i+5:i+8)=m2(2); mx2(i+9:i+12)=m2(3); mx2(i+13:i+16)=m2(4); mx2(i+17:i+20)=m2(5); mx2(i+21:i+24)=m2(6); mx2(i+25:i+28)=m2(7); mx2(i+29:i+32)=m2(8); mx2(i+33:i+36)=m2(9); mx2(i+37:i+40)=m2(10); mx2(i+41:i+44)=m2(11); mx2(i+45:i+48)=m2(12); mx2(i+49:i+52)=m2(13); mx2(i+53:i+56)=m2(14); mx2(i+57:i+63)=m2(15); end %%%%%%%%%%%%%%%%%%%%%%%得到扩频码 user11=nrz1.*mx1; user22=nrz2.*mx2; user1=(user11+1)/2; user2=(user22+1)/2; %%%%%%%%%%%%%%%%%%%%%% 直接PSK调制产生的信号频谱 psk1=sin(w0*t+nrz1.*pi); PSK1=t2f(psk1); aPSK1=abs(PSK1); %PSK调制频谱的幅值 psk2=sin(w0*t+nrz2.*pi); PSK2=t2f(psk2); aPSK2=abs(PSK2); %PSK调制频谱的幅值 %%%%%%%%%%%%%%%%%%%%% 基带信号的频谱 NRZ1=t2f(nrz1); %nrz1信号的傅氏变换 aNRZ1=abs(NRZ1); NRZ2=t2f(nrz2); %nrz2信号的傅氏变换 aNRZ2=abs(NRZ2); %%%%%%%%%%%%%%%%%%%% 对扩频码进行PSK调制 USER1=t2f(sin(w0*t+user1.*pi)); %nrz信号的傅氏变换 aUSER1=abs(USER1); USER2=t2f(sin(w0*t+user2.*pi)); %nrz信号的傅氏变换 aUSER2=abs(USER2); %%%%%%%%%%%%%%%%%%% 每个用户接受到的信号 recieve=f2t(USER1+USER2+NOISE); %%%%%%%%%%%%%%%%%%% 用户1解调 y1=recieve.*mx1; y11=y1.*sin(w0*t)*2; x1=zeros(1,256); for i=1:256 x1(i)=sum(y11(64*i-63:64*i)); %解扩序列（+1、-1） end k1=sign(x1); %解扩序列重生（0，1） for i=1:256 if k1(i)==1 x1(i)=0; else x1(i)=1; end end x11=zeros(L,M); for loop=1:L,x11(loop,:)=x1; end x11=reshape(x11,1,N); %解扩信号时域 p1=abs(x1-aaa); wrong1=sum(p1)/256 %误码率 X1=t2f(x11); %解扩信号的频谱 X1=abs(X1); %%%%%%%%%%%%%%%%%%% 用户2解调 y2=recieve.*mx2; y22=y2.*sin(w0*t)*2; x2=zeros(1,256); for i=1:256 x2(i)=sum(y22(64*i-63:64*i)); end k2=sign(x2); for i=1:256 if k2(i)==1 x2(i)=0; else x2(i)=1; end end x22=zeros(L,M); for loop=1:L,x22(loop,:)=x2; end x22=reshape(x22,1,N); p2=abs(x2-bbb); wrong2=sum(p2)/256 X2=t2f(x22); %解扩信号的频谱 X2=abs(X2); %%%%%%%%%%%%%%%%%%%%%%%% figure(1) plot(t,n_ch,'g') hold on plot(t,nrz1,'r') grid axis([-2,+2,-1.5,1.5]) title('用户1的基带信号') xlabel('t (us)') ylabel('s(t) (V)') figure(2) plot(t,n_ch,'g') hold on plot(t,user1,'r') grid axis([-2,+2,-1.5,1.5]) title('用户1的扩频时域信号') xlabel('t (us)') ylabel('psk (V)') figure(3) plot(t,n_ch,'g') hold on plot(t,nrz2,'r') grid axis([-2,+2,-1.5,1.5]) title('用户2的基带信号') xlabel('t (us)') ylabel('s(t) (V)') figure(4) plot(t,n_ch,'g') hold on plot(t,user2,'r') grid axis([-2,+2,-1.5,1.5]) title('用户2的扩频时域信号') xlabel('t (us)') ylabel('s(t) (V)') figure(5) plot(f,NOISE,'g') hold on plot(f,aNRZ1,'r') grid axis([-10,+10,-1,15]) title('用户1的基带信号的频谱') xlabel('f (Hz)') ylabel('NRZ') figure(6) plot(f,NOISE,'g') hold on plot(f,aUSER1,'r') grid axis([-30,+30,-1,15]) title('用户1的扩频信号的频谱') xlabel('f (Hz)') ylabel('psk') figure(7) plot(f,NOISE,'g') hold on plot(f,aNRZ2,'r') grid axis([-10,+10,-1,15]) title('用户2的基带信号的频谱') xlabel('f (Hz)') ylabel('psk') figure(8) plot(f,NOISE,'g') hold on plot(f,aUSER2,'r') grid axis([-30,+30,-1,15]) title('用户2的扩频信号的频谱') xlabel('f (Hz)') ylabel('psk') figure(9) plot(t,x11,'r') grid axis([-2,+2,-0.25,1.25]) title('解调的用户1的信号') xlabel('t (us)') ylabel('s(t) (V)') figure(10) plot(f,X1,'r') grid axis([-10,+10,-1,15]) title('用户1的解扩以后的信号的频谱') xlabel('f (Hz)') figure(11) plot(t,x22,'r') grid axis([-2,+2,-0.25,1.25]) title('解调的用户2的信号') xlabel('t (us)') ylabel('s(t) (V)') figure(12) plot(f,X2,'r') grid axis([-10,+10,-1,15]) title('用户2的解扩以后的信号的频谱') xlabel('f (Hz)')