alamuti1.m

waterfilling principle

% alamuti kod
SNR_db=5:2:15;
SNR=10.^(SNR_db/10);
for brojac=1:length(SNR)
    tocni=0;pogresni=0;pogresni1=0;tocni1=0;
for i=1:1000
    c=randint(2,1,[0,63]);
    s=qammod(c,64)/sqrt(42);
    k=random('norm',0,0.5,1,2)+j*random('norm',0,0.5,1,2);
    k1=[conj(k(2)) -conj(k(1))];
    soednaantena=k(1);
    h=[k ; k1];
    r1=h*s;
    nizkanalsoedna=k(1)*s;
    r=awgn(r1,SNR(brojac))*sqrt(42);
    osumen=awgn(nizkanalsoedna,SNR(brojac))*sqrt(42);
    r2=h'*r;
    r3=r2/(abs(k(1))^2+abs(k(2))^2);
    predodlucuvanje=osumen*conj(k(1))/(abs(k(1))^2);
    d=qamdemod(r3,64);
    odluka=qamdemod(predodlucuvanje,64);
    if c(1)==d(1)
        tocni=tocni+1;
    else
        pogresni=pogresni+1;
    end
    if c(2)==d(2)
        tocni=tocni+1;
    else
        pogresni=pogresni+1;
    end
        
    if c(1)==odluka(1)
        tocni1=tocni1+1;
    else
        pogresni1=pogresni1+1;
    end
    if c(2)==odluka(2)
        tocni1=tocni1+1;
    else
        pogresni1=pogresni1+1;
    end
end
ber(brojac)=pogresni/(tocni+pogresni);
ber1=log10(ber);
ber2(brojac)=pogresni1/(pogresni1+tocni1);
ber3=log10(ber2);
end
hold on;
plot(SNR_db,ber3,'->','color','r')
plot(SNR_db,ber1,'-o','color','b')
xlabel('SNR in dB, sinata linija e za alamuti kodot, a crvenata e za prakanje na signal niz edna antena')
ylabel('logaritam od BER')
grid on