gusucode.com > 基于4PAM调制性能误码率仿真源码程序 > 基于4PAM调制性能误码率仿真源码程序/designFilter.m

    clear all; clc;

Nb = 40000;
T = 1; % T: symbol period
a = 0.25; % a: roll-off factor
N = 4; % N: filter delay in symbol period T
Fs = 4; % Fs: samples/symbol
%EbN0dB = 30;
%EbN0 = 10^(EbN0dB/10);

EbN0dB=1:30; %Eb/N0 in dB
EbN0 = 10.^(EbN0dB/10);
Nerr=zeros(1,length(EbN0)); % initialize Nerr vector
for k=1:length(EbN0)

% 0 or 1 random input data
b=rand(1,Nb)>0.5; 
b2 = reshape(b,2,[])';

%4PAM mapping
    for i = 1:length(b2)    
        x(1,i) = (2*b2(i,1) -1) * (2*(b2(i,2)==0)+1); 
    end

    %trasmit filter
%xs = upsample(x,Fs);
h = srrc_fir(a,N,Fs,T);

s = rcosflt(x,1,Fs,'filter',h);
%s = filter(h,1,xs);
%r = awgn(s,EbN0dB(1,k),'measured');
    Eb=1; % bit energy
    N0=Eb/EbN0(k); % noise PSD (W/Hz)
    varn=N0/2; % noise variance
    noise=sqrt(varn)*randn(length(s),1); % AWGN ~ N(0,varn)
    r=s+noise; % received signal
%y = filter(h,1,r);
y = rcosflt(r,1,Fs,'Fs/filter',h);
z2 = downsample(y,Fs); % Downsample.
z = [z2(2*N+1:end-2*N)]'; % Account for delay.


%eyediagram(y(1:2000),Fs*2)
%grid on;

%plot(z,'.')
%grid on;

%4PAM demapping 
for i = 1:length(z)
    d2(1,i) = z(1,i)>0;
    d2(2,i) = abs(z(1,i)) < 2;
end
d = reshape(d2,1,[]);
 
 Nerr(k)=sum(b~=d); % the number of error bits
end
ber=Nerr/Nb; % bit error rate by simulation
EbN0dB2=0:0.01:10;
EbN02=10.^(EbN0dB2/10);
ber2=Q(sqrt(2*EbN02)); % bit error rate by theory
figure;
semilogy(EbN0dB,ber,'s'); hold on;
semilogy(EbN0dB2,ber2);
xlabel('E_b/N_0'); ylabel('BER'); grid on;
legend('Simulation', 'Theory');