clear all; close all; clc;

%% Параметры модели
B = 16;
Nfft = 1024; Ng = Nfft/4; Nofdm = Ng+Nfft; % Параметры OFDM сигнала
nCar = 312;
Nbps = 4; M = 2^Nbps;
Nsym = 30;                % Колличество генерируемых OFDM символов
H_QAM4=modem.qammod('M',M,'PhaseOffset', 0, 'SymbolOrder',...
    'binary', 'InputType', 'bit');
Es = 1; A = (3/2/(M-1)*Es);

%% Формируем N символов OFDM сигнала
tx = [];

fft_in = complex(zeros(Nfft,Nsym),zeros(Nfft,Nsym));
QAM = zeros(Nsym,nCar);
In_Data = randi([0 1],Nsym,nCar*log2(M));
QAM = A*modulate(H_QAM4, In_Data');
fft_in(1:nCar/2,:) = QAM(1:nCar/2,:);
fft_in(end-nCar/2+1:end,:) = QAM(nCar/2+1:end,:);
fft_out = ifft(fft_in);
tx = [fft_out(end-Ng+1:end,:); fft_out]';
tx = reshape(tx', 1, Nsym*Nofdm);


sig=awgn(tx, 20, 'measured', 'dB');
BuffObserv = zeros(1, 2*Nfft+Ng);

buff1 = zeros(1,length(sig)-Nofdm);
P = [];
for num = 1:floor(length(sig)/(2*Nfft+Ng))
    BuffObserv = sig(1, (num-1)*(2*Nfft+Ng)+1:num*(2*Nfft+Ng));
    
    for d = 0:(Nfft+Ng)/B-1
        corr(d+1) = sum(BuffObserv(d*B+(1:B)).*conj(BuffObserv(d*B+(1:B)+Nfft)));
        energ(d+1) = sqrt(sum(abs(BuffObserv(d*B+(1:B)).^2))).*sqrt(sum(abs(BuffObserv(d*B+(1:B)+Nfft).^2)));
    end
    P = [P abs(corr./energ)];
    
end

plot(abs(P));