% Minimal IMDD model for investigating FFE noise enhancement.
% Parameters mirror the current IMDD_base_system/imdd_it.m,
% IMDD_base_system/imdd_model.m, and the FFE branch in dsp_scope_signal.m.

clearvars;
close all;

%% Sweep parameters from imdd_it.m
fsym_values = 172e9;%(152:16:200).*1e9;

precomp = 0;
laser_wavelength = 1310;
M = 4;
link_length = 2;
channel_alpha = 0.5;
duob_mode = db_mode.db_precoded;
decoding_mode = db_decoder.sequencedetection;
channel_mode = channel_model.physical;
channel_snr_dB = 20;
rop = 0;

%% Inner model parameters from imdd_model.m
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_linewidth = 0;
eml_alpha = 0;

len_tr = 4096*2;
pf_ncoeffs = 1;
mu_dc = 0.005;

nRates = numel(fsym_values);

eq_names = ["FFE","VNLE"];
nEqs = numel(eq_names);
emptyResult = struct("fsym",[],"ROP",[],"equalizer",[],"BER",[],"SNR",[],"numBitErr",[], ...
    "eq_noise",[],"eq_signal_sd",[],"eq",[],"Rx_sig",[],"Tx_sig",[],"Tx_symbols",[]);
results = repmat(emptyResult,nRates,nEqs);
cols = flip(cbrewer2('RdYlBu',nRates+4));
midIdx = floor(size(cols,1)/2) + (-1:2);
cols(midIdx,:) = [];

for i = 1:numel(fsym_values)
    fsym = fsym_values(i);
    fprintf("Running %.0f GBd (%d/%d)\n", fsym*1e-9, i, numel(fsym_values));

    if isempty(bitrate)
        bitrateCurrent = fsym * log2(M);
    end

    Pform = Pulseformer("fsym",fsym,"fdac",4*fsym,"pulse","rc","pulselength",18,"alpha",rcalpha);
    [Digi_sig, Symbols, 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();

    rateResults = repmat(emptyResult,nEqs);


    Tx_sig = Digi_sig;

    El_sig = M8199B("kover",kover).process(Digi_sig);

    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 = El_sig.normalize("mode","oneone");
    scaling = 0.7*(u_pi/2-abs(vbias-u_pi/2));
    El_sig = El_sig .* scaling;

    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);

    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);



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

    Rx_sig = Photodiode("fsimu",fdac*kover,"dark_current",2e-08, ...
        "responsivity",0.6,"temperature",20,"nep",1.8e-11).process(Rx_sig);

    rx_bwl = 90e9;
    Rx_sig = Filter("filtdegree",4,"f_cutoff",rx_bwl,"fs",fdac*kover, ...
        "filterType",filtertypes.butterworth,"active",true).process(Rx_sig);

    Lp_scpe = Filter("filtdegree",4,"f_cutoff",110e9,"fs",fadc, ...
        "filterType",filtertypes.butterworth,"active",true);

    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);

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

    Scpe_sig = preprocessSignal(Rx_sig, Symbols, fsym, ...
        "mode","auto", ...
        "tx_pulseformer",txPulseformer, ...
        "debug_plots",0);
    Scpe_sig.signal = Scpe_sig.signal(1:2*Symbols.length);
    Scpe_sig.signal = real(Scpe_sig.signal);

    %%
    % -------------------- VNLE + MLSE --------------------
    pf_ncoeffs  = 1;
    ffe_order3  = [50, 0, 0];
    eq_ = FFE("epochs_tr",5,"epochs_dd",5,"len_tr",len_tr, ...
        "mu_dd",1e-3,"mu_tr",0.4,"order",50, ...
        "sps",2,"decide",0,"optmize_mus",0,"dd_mode",1, ...
        "adaption_technique","nlms","mu_dc",1e-3);
    pf_         = Postfilter("ncoeff",pf_ncoeffs,"useBurg",1);

    mlse_ = MLSE("duobinary_output",0,'M',M,'trellis_states',PAMmapper(M,0).levels);

    [vnle_results, mlse_results] = vnle_postfilter_mlse(eq_, pf_, mlse_, M, Scpe_sig, Symbols, Bits, ...
        "precode_mode", duob_mode, 'showAnalysis', 1, "postFFE", [], "eth_style_symbol_mapping", 0);

end