Hi Jimmy,
Please see responses to 2 and 3 inline below.
For 1, I leave it to others. As far as I know, interference noise has not been used so far.
Regards,
Hossein
From: Zhimin Liang [mailto:jimmy.liang@xxxxxxxxxxx]
Sent: October 23, 2026 8:29 PM
To: STDS-802-3-COM@xxxxxxxxxxxxxxxxx
Subject: [802.3_COM] COM 4.17.0 interference and quantization noise discrepancies with 178A
Hi,
I noticed some seeming discrepancies between the 4.17.0 COM code and the 802.3dj Draft 3.3 178A. So I wanted to get confirmation, and put attention on them so they can get fixed.
1.
Transmitter rise time filter is not applied to interference noise (shown in Figure 178A-8).
But it appears to be applied in the code.
The interference noise uses sdd21p
%% compute S_in ( eq 178A-24 d0.2 )
% S_in = 0 when Rx Calibration is not performed
if OP.PSDRXCAL
% interpolate to fvec
result.H_noise=H_interp(chdata(end).sdd21p,chdata(1).faxis,fvec,f_b);
Which has H_t, the transmitter rise time filter, included
if include_die
s21p= H_t.*s21.*(1-gamma_tx).*(1+gamma_rx)./(1.- s11.*gamma_tx - s22.*gamma_rx -s21.*s12.*gamma_tx.*gamma_rx +s11.*s22.*gamma_tx.*gamma_rx);
2.
When quantization noise is added the cursor is skipped in the code
[HS] no, it has not been skipped. The output noise is first set to input and then all the pre and post cursors are applied. Setting it to input is the same as
applying the main cursor (which is always equal to 1).
if irxffe ~= cursor_tap
quantization_noise_in_pdf_scale = scalePDF(quantization_noise_in_pdf, abs(h_rxffe(irxffe)));
quantization_noise_pdf = conv_fct(quantization_noise_pdf, quantization_noise_in_pdf_scale);
end
But the draft says to use all the taps
"The probability distribution function for the quantization noise at the detector input pqn(y) is initialized to a
Dirac delta function and the assignment defined by Equation (178A–46) is repeated for each value n in the
feed-forward filter tap index vector i (i.e., over all of the feed-forward filter coefficients)."
3.
Vqc is defined as
"the quantization clipping amplitude Vqc is a positive value that satisfies the relationship Psn(–Vqc) = Pqc / 2"
But the code does not divide by 2
[HS] The code is correct. CDF inverse is also one sided, so it is already the amplitude and divided by 2.
adc_clip = -CDF_inv_ev(param.P_qc, sig_after_ctle_pdf, sig_after_ctle_cdf);
Jimmy
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