function  [output] = imdd_model(varargin)

simulation_mode = 1;

%%% Change folder
% curFolder = pwd;
% funcFolder=fileparts(mfilename('fullpath'));
% if ~isempty(funcFolder)
%     cd(funcFolder);
% end

%%% Run parameters
% TX
M               = 4;
fsym            = 150e9;
bitrate         = [];

apply_pulsef    = 0;
fdac            = 256e9;
fadc            = 256e9;
random_key      = 1;

rcalpha         = 0.05;
kover           = 16;

vbias_rel       = 0.5;
u_pi            = 3;
vbias           = -vbias_rel*u_pi;

laser_wavelength    = 1293;
laser_linewidth     = 0;
tx_bw_nyquist       = 0.65;

% Channel
link_length     = 1;
channel_mode = "physical";
channel_snr_dB = 20;
channel_alpha = 0;
channel_delay_symbols = 1;

% RX
rop = 2;
rx_bw_nyquist = 0.8;

vnle_order1 = 50;
vnle_order2 = 7;
vnle_order3 = 7;

vnle_order=[vnle_order1,vnle_order2,vnle_order3];
dfe_order = [0 0 0];

pf_ncoeffs = 1;

eml_alpha = 0;

len_tr  = 4096*2;

mu_ffe1 = 0.0001;
mu_ffe2 = 0.0008;
mu_ffe3 = 0.001;
mu_dc = 0.005;
% mu_dc = 0;

mu_ffe = [mu_ffe1 mu_ffe3 mu_ffe3];
mu_dfe = 0.0004;


dfe_ = sum(dfe_order)>0;

duob_mode = db_mode.no_db;
decoding_mode = [];
providedFields = string.empty;

%%% change specific parameter if given in varargin
% Parse optional input arguments
if ~isempty(varargin)
    var_s = varargin{1};
    if isstruct(var_s)
        fields = fieldnames(var_s);
        providedFields = string(fields);
        for i = 1:numel(fields)
            fieldName = fields{i};
            if ~isvarname(fieldName)
                error('Invalid parameter name "%s".', fieldName);
            end
            eval([fieldName, ' = var_s.(fieldName);']);
        end
    else
        error('Optional variables should be passed as a struct.');
    end
end

hasFsym = any(providedFields == "fsym");
hasBitrate = any(providedFields == "bitrate");

if M == 6
    bitsPerSymbol = 2.5;
else
    bitsPerSymbol = log2(M);
    if abs(bitsPerSymbol - round(bitsPerSymbol)) > 1e-12
        error('Unsupported PAM order M=%d. Only powers of two and PAM-6 are supported.', M);
    end
end

if hasFsym && hasBitrate
    error('either bitrate or symbolrate!')
elseif hasBitrate
    fsym = bitrate / bitsPerSymbol;
else
    bitrate = fsym * bitsPerSymbol;
end

f_nyquist       = fsym/2;


%%%%% START SIMULATION

measure_tf = 0;
if measure_tf
    freqresp = ChannelFreqResp("Nacq",1024,"Navg",64,"Ncp",70,"f_ref",fadc);
    Digi_sig = freqresp.buildOFDM();
else
    Pform       = Pulseformer("fsym",fsym,"fdac",4*fsym,"pulse","rc","pulselength",16,"alpha",rcalpha);
    [Digi_sig,Symbols,Tx_bits] = PAMsource(...
        "fsym",fsym,"M",M,"order",18,"useprbs",0,...
        "fs_out",fdac,...
        "applyclipping",0,"clipfactor",1.5,...
        "applypulseform",apply_pulsef,"pulseformer",Pform,...
        "randkey",random_key,...
        'duobinary_mode',duob_mode,...
        "mrds_code",0,"mrds_blocklength",512).process();
end

% Digi_sig.spectrum("displayname",'Digi Spectrum','fignum',10,'normalizeTo0dB',1);

channel_mode = lower(string(channel_mode));

switch channel_mode
    case "physical"

        %%%%% AWG
        El_sig = M8199B("kover",kover).process(Digi_sig);
        % El_sig = AWG("fdac",fdac,"f_cutoff",fsym,"lpf_active",1,"kover",kover,"bit_resolution",12,"upsampling_method","samplehold","precomp_sinc_rolloff",0,"H_lpf",H_awg).process(Digi_sig);
        % El_sig.spectrum("displayname",'Digi Spectrum','fignum',100,'normalizeTo0dB',0);
        % El_sig = El_sig.setPower(0,"dBm");

        %%%%% Low-pass el. components %%%%%%
        % tx_bwl = tx_bw_nyquist.*f_nyquist;
        tx_bwl = 85e9;
        El_sig = Filter('filtdegree',4,"f_cutoff",tx_bwl,"fs",fdac*kover,"filterType",filtertypes.bessel_inp,"active",true).process(El_sig);
        % El_sig.spectrum("displayname",'Digi Spectrum','fignum',100,'normalizeTo0dB',1);

        %%%%% Electrical Driver Amplifier %%%%%%
        % El_sig = Amplifier("amp_mode","ideal_no_noise","gain_mode","gain","amplification_db",3).process(El_sig);
        El_sig = El_sig.normalize("mode","oneone");
        scaling = 0.7*(u_pi/2-abs(vbias-u_pi/2));
        El_sig = El_sig .* scaling;

        %%%%% MODULATE E/O CONVERSION %%%%%%
        [Opt_sig] = EML("mode",eml_mode.im_cosinus,"power",3,"fsimu",El_sig.fs,"lambda",laser_wavelength,"bias",vbias,"u_pi",u_pi,"linewidth",laser_linewidth,"randomkey",random_key+1,"alpha",eml_alpha).process(El_sig);

        % figure(10)
        % hold on
        % scatter(El_sig.signal(1:100000)+vbias,(abs(Opt_sig.signal(1:100000)).^2)*1e3,0.1,'.','DisplayName','Modulator TF')
        % ylim([0 u_pi]);
        % xlim([-u_pi/2, u_pi/2]+vbias);
        % xlabel('Input in V')
        % ylabel('abs(Output) in mW')


        % Opt_sig.spectrum("displayname",'Opt Spectrum','fignum',10,'normalizeTo0dB',1);
        Opt_sig    = Fiber("fsimu",Opt_sig.fs,"fiber_length",link_length,"alpha",0.3,"D",0,"lambda0",1310,"gamma",0,"Dslope",0.07).process(Opt_sig);

        %%%%%% ROP %%%%%%
        Rx_sig = Amplifier("amp_mode","ideal_no_noise","gain_mode","output_power","amplification_db",rop).process(Opt_sig);

        %%%%%% PD Square Law %%%%%%
        Rx_sig = Photodiode("fsimu",fdac*kover,"dark_current",2e-08,"responsivity",1,"temperature",20,"nep",1.8e-11).process(Rx_sig);

        %%%%%% Low-pass RX (PD, El. Connectors and Scope %%%%%%
        % rx_bwl = rx_bw_nyquist.*f_nyquist;
        rx_bwl = 90e9;
        Rx_sig = Filter('filtdegree',4,"f_cutoff",rx_bwl,"fs",fdac*kover,"filterType",filtertypes.butterworth,"active",true).process(Rx_sig);

        % %%%%%% Low-pass Scope %%%%%%
        Lp_scpe = Filter('filtdegree',4,"f_cutoff",110e9,"fs",fadc,"filterType",filtertypes.butterworth,"active",true);

        % Rx_sig.spectrum("displayname",'Analog Rx Spectrum','fignum',10,'normalizeTo0dB',1);

        %%%%%% Scope %%%%%%
        Rx_sig = Scope("fsimu",fdac*kover,"fadc",fadc,...
            "delay",0,"fixed_delay",0,"filtertype",filtertypes.butterworth,...
            "samplingdelay",0,"rand_samplingdelay",0,"freq_offset",0,"samp_jitter",0,...
            "adcresolution",8,"quantbuffer",0.1,'block_dc',1,'lpf_active',1,'H_lpf',Lp_scpe).process(Rx_sig);

    case "awgn"
        Rx_sig = awgn_channel(Digi_sig, ...
            "snr_dB", channel_snr_dB, ...
            "randkey", random_key + 2);

    case {"awgn_alphad", "awgn_1alphad", "awgn_1_plus_alpha_d"}
        delaySamples = max(1, round(channel_delay_symbols * Digi_sig.fs / fsym));
        Rx_sig = awgn_alpha_d_channel(Digi_sig, ...
            "alpha", channel_alpha, ...
            "delay_samples", delaySamples, ...
            "snr_dB", channel_snr_dB, ...
            "randkey", random_key + 2);

    otherwise
        error('Unknown channel_mode "%s". Supported: physical, awgn, awgn_alphaD.', channel_mode);
end

if measure_tf
    Rx_sig = Rx_sig.resample("fs_out",freqresp.f_ref);
    freqresp.estimate(Rx_sig,"fileName",'','save',false);
    freqresp.plot()
    return;
end

Rx_sig.spectrum("displayname",'Sampled Rx Spectrum','fignum',1996,'normalizeTo0dB',1);

txPulseformer = [];
if apply_pulsef
    txPulseformer = Pform;
end

dspParameters = struct();
dspParameters.len_tr = len_tr;
dspParameters.mu_ffe = mu_ffe;
dspParameters.mu_dfe = mu_dfe;
dspParameters.mu_dc = mu_dc;
dspParameters.use_ffe = 1;
dspParameters.use_dfe = 0;
dspParameters.use_vnle_mlse = 0;
dspParameters.use_dbtgt = 0;
dspParameters.use_dbenc = 0;
dspParameters.use_ml_mlse = 0;
dspParameters.pf_ncoeffs = pf_ncoeffs;
dspParameters.ffe_order_ffe = [50, 0, 0];
dspParameters.ffe_order_dfe = [50, 0, 0];
dspParameters.dfe_feedback_order = [2, 0, 0];
dspParameters.ffe_order_vnle = [50, 4, 4];
dspParameters.dfe_order_vnle = dfe_order;
dspParameters.ffe_order_dbtgt = [50, 4, 4];
dspParameters.dfe_order_dbtgt = dfe_order;
dspParameters.decoding_mode = decoding_mode;

scopeOutput = dsp_scope_signal(Rx_sig, Symbols, Tx_bits, ...
    "fsym", fsym, ...
    "M", M, ...
    "duob_mode", duob_mode, ...
    "parameters", dspParameters, ...
    "preprocess_mode", "auto", ...
    "tx_pulseformer", txPulseformer, ...
    "debug_plots", true);

output = struct();
output.ffe_results = scopeOutput.ffe_package;
output.dfe_results = scopeOutput.dfe_package;
output.vnle_results = scopeOutput.vnle_package;
output.mlse_results = scopeOutput.mlse_package;
output.dbt_results = scopeOutput.dbtgt_package;
output.dbenc_results = scopeOutput.dbenc_package;
output.mlmlse_results = scopeOutput.mlmlse_package;

disp('- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ')
fprintf('\n')
end