clc; clear all; close all;

Fs = 48000; % Частота дискретизации сигнала
SNR = 20; % ОСШ
Nfft = 1024; Ng = Nfft/4; Nofdm = Ng+Nfft; % Параметры OFDM сигнала
Tofdm = Nfft/Fs; % Длительность OFDM сигнала в сек
nCar = 312; % Кол-во поднесущих
Nbps = 6; M = 2^Nbps;
Nsym = 10000; % Колличество генерируемых OFDM символов
H_QAM4=modem.qammod('M',M,'PhaseOffset', 0, 'SymbolOrder',...
'binary', 'InputType', 'bit');
Es = 1; A = (3/2/(M-1)*Es);


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 = awgn(tx, 10*log10(nCar/Nfft) + SNR, 'measured', 'dB');
out_sig = add_phase_noise(sig_awgn, 300e3, [10 100 1e3 10e3 100e3], [-80 -125 -145 -148 -150], 0);
rx = add_phase_noise(out_sig, 300e3, [10 100 1e3 10e3 100e3], [-80 -125 -145 -148 -150], 0);


for k = 1:Nsym
% Демодуляция OFDM с фазовым шумом
OFDM_rx = rx(1,Ng+(k-1)*Nofdm+1:k*Nofdm);
carier = fft(OFDM_rx);
QAM_rx = [carier(1,1:nCar/2) carier(1,end-nCar/2+1:end)];

OFDM_sig_awgn = sig_awgn(1,Ng+(k-1)*Nofdm+1:k*Nofdm);
carier = fft(OFDM_sig_awgn);
QAM_awgn = [carier(1,1:nCar/2) carier(1,end-nCar/2+1:end)];

OFDM_tx = tx(1,Ng+(k-1)*Nofdm+1:k*Nofdm);
carier = fft(OFDM_tx);
QAM_tx = [carier(1,1:nCar/2) carier(1,end-nCar/2+1:end)];

noise(1,k) = sum(abs(QAM_awgn - QAM_tx).^2);
SNR_awgn(1,k) = 10*log10(sum(abs(QAM_tx).^2)/noise(1,k));

noise(1,k) = sum(abs(QAM_rx - QAM_tx).^2);
SNR_ph(1,k) = 10*log10(sum(abs(QAM_tx).^2)/noise(1,k));
end

SNR = mean(SNR_ph) - mean(SNR_awgn)

function Sout = add_phase_noise( Sin, Fs, phase_noise_freq, phase_noise_power, VALIDATION_ON )
%
% function Sout = add_phase_noise( Sin, Fs, phase_noise_freq, phase_noise_power, VALIDATION_ON )
%
% Oscillator Phase Noise Model
%
% INPUT:
% Sin - input COMPLEX signal
% Fs - sampling frequency ( in Hz ) of Sin
% phase_noise_freq - frequencies at which SSB Phase Noise is defined (offset from carrier in Hz)
% phase_noise_power - SSB Phase Noise power ( in dBc/Hz )
% VALIDATION_ON - 1 - perform validation, 0 - don't perfrom validation
%
% OUTPUT:
% Sout - output COMPLEX phase noised signal
%
% NOTE:
% Input signal should be complex
%
% EXAMPLE ( How to use add_phase_noise ):
% Assume SSB Phase Noise is specified as follows:
% -------------------------------------------------------
% | Offset From Carrier | Phase Noise |
% -------------------------------------------------------
% | 1 kHz | -84 dBc/Hz |
% | 10 kHz | -100 dBc/Hz |
% | 100 kHz | -96 dBc/Hz |
% | 1 MHz | -109 dBc/Hz |
% | 10 MHz | -122 dBc/Hz |
% -------------------------------------------------------
%
% Assume that we have 10000 samples of complex sinusoid of frequency 3 KHz
% sampled at frequency 40MHz:
%
% Fc = 3e3; % carrier frequency
% Fs = 40e6; % sampling frequency
% t = 0:9999;
% S = exp(j*2*pi*Fc/Fs*t); % complex sinusoid
%
% Then, to produce phase noised signal S1 from the original signal S run follows:
%
% Fs = 40e6;
% phase_noise_freq = [ 1e3, 10e3, 100e3, 1e6, 10e6 ]; % Offset From Carrier
% phase_noise_power = [ -84, -100, -96, -109, -122 ]; % Phase Noise power
% S1 = add_phase_noise( S, Fs, phase_noise_freq, phase_noise_power );

% Version 1.0
% Alex Bur-Guy, October 2005
% alex@wavion.co.il
%
% Revisions:
% Version 1.5 - Comments. Validation.
% Version 1.0 - initial version

% NOTES:
% 1) The presented model is a simple VCO phase noise model based on the following consideration:
% If the output of an oscillator is given as V(t) = V0 * cos( w0*t + phi(t) ),
% then phi(t) is defined as the phase noise. In cases of small noise
% sources (a valid assumption in any usable system), a narrowband modulation approximation can
% be used to express the oscillator output as:
%
% V(t) = V0 * cos( w0*t + phi(t) )
%
% = V0 * [cos(w0*t)*cos(phi(t)) - sin(w0*t)*sin(phi(t)) ]
%
% ~ V0 * [cos(w0*t) - sin(w0*t)*phi(t)]
%
% This shows that phase noise will be mixed with the carrier to produce sidebands around the carrier.
%
%
% 2) In other words, exp(j*x) ~ (1+j*x) for small x
%
% 3) Phase noise = 0 dBc/Hz at freq. offset of 0 Hz
%
% 4) The lowest phase noise level is defined by the input SSB phase noise power at the maximal
% freq. offset from DC. (IT DOES NOT BECOME EQUAL TO ZERO )
%
% The generation process is as follows:
% First of all we interpolate (in log-scale) SSB phase noise power spectrum in M
% equally spaced points (on the interval [0 Fs/2] including bounds ).
%
% After that we calculate required frequency shape of the phase noise by X(m) = sqrt(P(m)*dF(m))
% and after that complement it by the symmetrical negative part of the spectrum.
%
% After that we generate AWGN of power 1 in the freq domain and multiply it sample-by-sample to
% the calculated shape
%
% Finally we perform 2*M-2 points IFFT to such generated noise
% ( See comments inside the code )
%
% 0 dBc/Hz
% \ /
% \ /
% \ /
% \P dBc/Hz /
% .\ /
% . \ /
% . \ /
% . \____________________________________________/ /_ This level is defined by the phase_noise_power at the maximal freq. offset from DC defined in phase_noise_freq
% . \
% |__| _|__|__|__|__|__|__|__|__|__|__|__|__|__|__|__|__|__|__|__ (N points)
% 0 dF Fs/2 Fs
% DC
%
%
% For some basics about Oscillator phase noise see:
% http://www.circuitsage.com/pll/plldynamics.pdf
%
% http://www.wj.com/pdf/technotes/LO_phase_noise.pdf

if nargin < 5
VALIDATION_ON = 0;
end

% Check Input
error( nargchk(4,5,nargin) );

if ~any( imag(Sin(:)) )
error( 'Input signal should be complex signal' );
end
if max(phase_noise_freq) >= Fs/2
error( 'Maximal frequency offset should be less than Fs/2');
end

% Make sure phase_noise_freq and phase_noise_power are the row vectors
phase_noise_freq = phase_noise_freq(:).';
phase_noise_power = phase_noise_power(:).';
if length( phase_noise_freq ) ~= length( phase_noise_power )
error('phase_noise_freq and phase_noise_power should be of the same length');
end

% Sort phase_noise_freq and phase_noise_power
[phase_noise_freq, indx] = sort( phase_noise_freq );
phase_noise_power = phase_noise_power( indx );

% Add 0 dBc/Hz @ DC
if ~any(phase_noise_freq == 0)
phase_noise_power = [ 0, phase_noise_power ];
phase_noise_freq = [0, phase_noise_freq];
end

% Calculate input length
N = prod( size( Sin ) );

% Define M number of points (frequency resolution) in the positive spectrum
% (M equally spaced points on the interval [0 Fs/2] including bounds),
% then the number of points in the negative spectrum will be M-2
% ( interval (Fs/2, Fs) not including bounds )
%
% The total number of points in the frequency domain will be 2*M-2, and if we want
% to get the same length as the input signal, then
% 2*M-2 = N
% M-1 = N/2
% M = N/2 + 1
%
% So, if N is even then M = N/2 + 1, and if N is odd we will take M = (N+1)/2 + 1
%
if rem(N,2), % N odd
M = (N+1)/2 + 1;
else
M = N/2 + 1;
end


% Equally spaced partitioning of the half spectrum
F = linspace( 0, Fs/2, M ); % Freq. Grid
dF = [diff(F) F(end)-F(end-1)]; % Delta F


% Perform interpolation of phase_noise_power in log-scale
intrvlNum = length( phase_noise_freq );
logP = zeros( 1, M );
for intrvlIndex = 1 : intrvlNum,
leftBound = phase_noise_freq(intrvlIndex);
t1 = phase_noise_power(intrvlIndex);
if intrvlIndex == intrvlNum
rightBound = Fs/2;
t2 = phase_noise_power(end);
inside = find( F>=leftBound & F<=rightBound );
else
rightBound = phase_noise_freq(intrvlIndex+1);
t2 = phase_noise_power(intrvlIndex+1);
inside = find( F>=leftBound & F<rightBound );
end
logP( inside ) = ...
t1 + ( log10( F(inside) + realmin) - log10(leftBound+ realmin) ) / ( log10( rightBound + realmin) - log10( leftBound + realmin) ) * (t2-t1);
end
P = 10.^(real(logP)/10); % Interpolated P ( half spectrum [0 Fs/2] ) [ dBc/Hz ]

% Now we will generate AWGN of power 1 in frequency domain and shape it by the desired shape
% as follows:
%
% At the frequency offset F(m) from DC we want to get power Ptag(m) such that P(m) = Ptag/dF(m),
% that is we have to choose X(m) = sqrt( P(m)*dF(m) );
%
% Due to the normalization factors of FFT and IFFT defined as follows:
% For length K input vector x, the DFT is a length K vector X,
% with elements
% K
% X(k) = sum x(n)*exp(-j*2*pi*(k-1)*(n-1)/K), 1 <= k <= K.
% n=1
% The inverse DFT (computed by IFFT) is given by
% K
% x(n) = (1/K) sum X(k)*exp( j*2*pi*(k-1)*(n-1)/K), 1 <= n <= K.
% k=1
%
% we have to compensate normalization factor (1/K) multiplying X(k) by K.
% In our case K = 2*M-2.

% Generate AWGN of power 1

if ~VALIDATION_ON
awgn_P1 = ( sqrt(0.5)*(randn(1, M) +1j*randn(1, M)) );
else
awgn_P1 = ( sqrt(0.5)*(ones(1, M) +1j*ones(1, M)) );
end

% Shape the noise on the positive spectrum [0, Fs/2] including bounds ( M points )
X = M * sqrt( dF .* P ) .* awgn_P1; %(2*M-2)

% Complete symmetrical negative spectrum (Fs/2, Fs) not including bounds (M-2 points)
X( M + (1:M-2) ) = fliplr( conj(X(2:end-1)) );

% Remove DC
X(1) = 0;

% Perform IFFT
x = ifft( X );

% Calculate phase noise
phase_noise = exp( j * real(x(1:N)) );

% Add phase noise
if ~VALIDATION_ON
Sout = Sin .* reshape( phase_noise, size(Sin) );
else
Sout = 'VALIDATION IS ON';
end

if VALIDATION_ON
figure;
plot( phase_noise_freq, phase_noise_power, 'o-' ); % Input SSB phase noise power
hold on;
grid on;
plot( F, 10*log10(P),'r*-'); % Input SSB phase noise power
X1 = fft( phase_noise );
plot( F, 10*log10( ( (abs(X1(1:M))/max(abs(X1(1:M)))).^2 ) ./ dF(1) ), 'ks-' );% generated phase noise exp(j*x)
X2 = fft( 1 + j*real(x(1:N)) );
plot( F, 10*log10( ( (abs(X2(1:M))/max(abs(X2(1:M)))).^2 ) ./ dF(1) ), 'm>-' ); % approximation ( 1+j*x )
xlabel('Frequency [Hz]');
ylabel('dBc/Hz');
legend( ...
'Input SSB phase noise power', ...
'Interpolated SSB phase noise power', ...
'Positive spectrum of the generated phase noise exp(j*x)', ...
'Positive spectrum of the approximation ( 1+j*x )' ...
);
end