% einstellungen
M = 2;
apply_precode_at_tx = 0;

% daten erzeugen
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

tx_bits = Informationsignal(bitpattern);
tx_symbols = PAMmapper(M,0).map(tx_bits);

if apply_precode_at_tx

    % Precode
    tx_symbols_precoded = Duobinary().precode(tx_symbols);
    % 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(tx_symbols_precoded);
    % Entschiedene codierte Symbole decodieren: d_dec(n) = d_DB(n) mod4
    rx_symbols = Duobinary().decode(symbols_db);
    bits_rx = PAMmapper(M,0).demap(rx_symbols);

    figure(1)
    clf
    hold on
    stairs(tx_symbols.signal(1:100),'DisplayName','Tx Symbols','LineStyle','-','LineWidth',2);
    stairs(rx_symbols.signal(1:100),'DisplayName','Rx Symbols','LineStyle',':','LineWidth',1);
    legend
    ylim([-2 2])


    [~,~,ber,~] = calc_ber(tx_bits.signal,bits_rx.signal,"skip_front",0,"skip_end",0,"returnErrorLocation",1);
    disp(['BER: ',sprintf('%.1E',ber)]);
    assert(ber == 0)
else


    % 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(tx_symbols);

    % Entschiedene codierte Symbole decodieren: d_dec(n) = d_DB(n) mod4
    rx_symbols = Duobinary().decode(symbols_db);
    bits_rx = PAMmapper(M,0).demap(rx_symbols);

    % ref symbole precoden:
    tx_symbols_ref = Duobinary().encode(tx_symbols);
    tx_symbols_ref = Duobinary().decode(tx_symbols_ref);
    tx_bits_ref = PAMmapper(M,0).demap(tx_symbols_ref);

    % step plot to check visually if symbols overlap
    figure(1)
    clf
    hold on
    stairs(tx_symbols_ref.signal(1:100),'DisplayName','Tx Symbols','LineStyle','-','LineWidth',2);
    stairs(rx_symbols.signal(1:100),'DisplayName','Rx Symbols','LineStyle',':','LineWidth',1);
    legend
    ylim([-2 2])


    [~,~,ber,~] = calc_ber(tx_bits_ref.signal,bits_rx.signal,"skip_front",1,"skip_end",1,"returnErrorLocation",1);
    disp(['BER: ',sprintf('%.1E',ber)]);
    assert(ber == 0)
end