M = 4;
apply_precode_at_tx = 1;

bitpattern = [];
s = RandStream('twister','Seed',1);
for i = 1:log2(M)
    N = 2^(17-1); %length of prbs
    bitpattern(:,i) = randi(s,[0 1], N, 1);
end

if M == 6
    bitpattern = reshape(bitpattern',[],1);
    bitpattern = bitpattern(1:end-mod(length(bitpattern),5));
end

bits = Informationsignal(bitpattern);

symbols = PAMmapper(M,0).map(bits);

if apply_precode_at_tx
    symbols_tx = Duobinary().precode(symbols);
else
    symbols_tx = symbols;
end
disp(['Tx Sequenz: -- RMS:',sprintf('%.1f',rms(symbols_tx.signal)),' - - Levels -',num2str(numel(unique(symbols_tx.signal)))]);
unique(symbols_tx.signal)
disp('- - - - - - - - - -');

symbols_tx.signal = awgn(symbols_tx.signal,20,"measured",1);
% show2Dconstellation(symbols_tx,symbols_tx,"displayname",'VNLE Out','fignum',2241);
    

if apply_precode_at_tx
    % Entschiedene Symbole codieren: d_DB(n) = d(n) + d(n-1)    (im Fall von PAM4 7 level [0 1 2 3 4 5 6])
    symbols_db = Duobinary().encode(symbols_tx);

    disp(['DB encoded -- RMS:',sprintf('%.1f',rms(symbols_db.signal)),' - - Levels -',num2str(numel(unique(symbols_db.signal)))]);
    unique(symbols_db.signal)
    disp('- - - - - - - - - -');
    
    % Entschiedene codierte Symbole decodieren: d_dec(n) = d_DB(n) mod4
    symbols_rx = Duobinary().decode(symbols_db);
else
    symbols_db = Duobinary().encode(symbols_tx);
    symbols_rx = Duobinary().decode(symbols_db);
end

% Vergleichen von b(n) und d_dec(n)
bits_rx = PAMmapper(M,0).demap(symbols_rx);
disp(['Wieder normal -- RMS:',sprintf('%.1f',rms(symbols_rx.signal)),' - - Levels -',num2str(numel(unique(symbols_rx.signal)))]);
unique(symbols_rx.signal)
disp('- - - - - - - - - -');


[~,~,ber,~] = calc_ber(bits.signal,bits_rx.signal,"skip_front",10,"skip_end",10,"returnErrorLocation",1);

disp(['BER: ',sprintf('%.1E',ber),' - - PAM-',num2str(M)]);

figure()
subplot(1,2,1)
histogram(symbols_tx.signal,100,'Normalization','count')

subplot(1,2,2)
histogram(symbols_db.signal,100,'Normalization','count')