final4.m

升余弦信号传输的 曲线

clc;
clear;

global dt t f df N T
close all
clear Eb_N0 Pe

N=2^15; %采样点数
L=4;    %每码元的采样点数
M=N/L   %码元数
Rb=2;		%码速率是2Mb/s
Ts=1/Rb;        %码元间隔
dt=Ts/L;        %时域采样间隔
df=1/(N*dt)     %频域采样间隔
T=N*dt          %截短时间
Bs=N*df/2       %系统带宽
alpha=0.5 
tao=Ts/2;
%滚降系数

t=linspace(-T/2,T/2,N); %时域横坐标
f=linspace(-Bs,Bs,N)+eps;   %频域横坐标

figure(1)
 set(1,'Position',[10,30,900,700])
                %设定窗口位置及大小 
  
%升余弦
hr1=sin(pi*t/Ts)./(pi*t/Ts);
hr2=cos(alpha*pi*t/Ts)./(1-(2*alpha*t/Ts).^2);
hr=hr1.*hr2;
HR=abs(t2f(hr));%取模是为了忽略时延
GT=sqrt(HR);
GR=GT;
C=abs(1-0.5*exp(-j*2*pi*f*tao));

for loop1=1:10
 Eb_N0(loop1)=(loop1-1)  %Eb/N0 in dB
 eb_n0(loop1)=10^(Eb_N0(loop1)/10);
 Eb=1;	
 n0=Eb/eb_n0(loop1); %信道的噪声谱密度   
 sita=n0*Bs; %信道中噪声功率

 n_err=0;     %误码计数

 for loop2=1:20  
  a=sign(randn(1,M));
  imp=zeros(1,N);    %产生冲激序列
  imp(L/2:L:N)=a/dt;
  IMP=t2f(imp);
  
  n_ch=sqrt(sita)*randn(size(t)); %信道噪声
  nr=real(f2t(t2f(n_ch).*GR.*C));     %输出噪声

  sr=real(f2t(IMP.*HR.*C))+nr;       %接收信号
  y=sr(L/2:L:N);		  %取样
  aa=sign(y);       %判决                 
  n_err=n_err+length(find(aa~=a))  
 end
 Pe(loop1)=n_err/(M*loop2)
 figure(1) 
  semilogy(Eb_N0,Pe,'g');
  eb_n0=10.^(Eb_N0/10);
  hold on
  semilogy(Eb_N0,0.5*erfc(sqrt(eb_n0)));
  axis([0,9,1e-4,1])
  xlabel('Eb/N0')
  ylabel('Pe')
 end