Re: [10GBT] Proposed PAM8 vs. PAM12 resolution process
Henri
The original requirements for external noise immunity were just of this
sort. There is an AM radio transmitter near a shopping center in the
Boston area whose field strength was used as the value. Rich Graham would
probably know more.
Geoff
At 11:11 AM 7/19/2004 -0700, Koeman, Henriecus wrote:
"urn:schemas-microsoft-com:vml"
xmlns:o = "urn:schemas-microsoft-com:office:office" xmlns:w =
"urn:schemas-microsoft-com:office:word">
If you really want to test
noise impact, travel to Tokyo, Japan and take residence under the Tokyo
Tower. Given 10GBASE-T is a wideband system, it will give you a great
experience on noise rejection ability.
Henri.
- -----Original Message-----
- From: stds-802-3-10gbt@IEEE.ORG
[mailto:stds-802-3-10gbt@IEEE.ORG]
On Behalf Of Dove, Dan
- Sent: Monday, July 19, 2004 9:35 AM
- To: STDS-802-3-10GBT@listserv.ieee.org
- Subject: Re: [10GBT] Proposed PAM8 vs. PAM12 resolution
process
Vivek,
Why not have a "Dove test" which is just like the Crane
test except it uses randomly spaced transient impulses of a finite
amplitude? :)
Back in 1000BASE-T days, I provided a presentation where I measured
noise on CAT-5 installations and one site in particular was located next
to an 89.9MHz radio transmission tower. I really expected to see a lot of
89.9MHz carrier on the wire, but much to my surprise, found transient
pulses due to what was likely an air-conditioner that were much worse in
amplitude. The amplitude of these pulses varied from a few mV (which is
approximately the Vpp of the 89.9MHz carrier on the wire) to as much as
19mVpk.
The model for such a noise source could be readily defined as
randomly distributed between 50 and 70Hz and from 1mV to 20mV. One
could shape the distribution if they wanted to. Also, the pulse spectra
could be defined. I don't have the data, but I believe I can dig up that
presentation and perform some FFT to get it if it would be
useful.
Dan
-----Original Message-----
From: stds-802-3-10gbt@IEEE.ORG
[mailto:stds-802-3-10gbt@IEEE.ORG]On
Behalf Of Vivek Telang
Sent: Sunday, July 18, 2004 4:25 AM
To: STDS-802-3-10GBT@listserv.ieee.org
Subject: Re: [10GBT] Proposed PAM8 vs. PAM12 resolution
process
Hi Scott,
On the subject of the Crane test, it is just a simple way of
evaluating system robustness against noise. There is no reason why it
cannot be evaluated with worst case impairments ON, as well as OFF. But I
believe the cancellers/equalizers do need to be frozen, because the
intent is to capture the effect on the system of a transient noise event,
that is not long enough to allow the system to adapt to it. I agree with
you that the coding gain validity is in question, but since we are
(fortunately) comparing very similar systems (both PAM, and both using
LDPC), I'm assuming that this will affect both systems equally.
Regards,
Vivek
-----Original Message-----
From: stds-802-3-10gbt@ieee.org
[mailto:stds-802-3-10gbt@ieee.org]On
Behalf Of Scott Powell
Sent: Sunday, July 18, 2004 2:37 AM
To: STDS-802-3-10GBT@listserv.ieee.org
Subject: Re: [10GBT] Proposed PAM8 vs. PAM12 resolution
process
Hi Sailesh,
As was discussed last week, the bottom line performance goal
is 1e-12 BER which is determined most directly by the SNR at the decision
device ("slicer SNR") by the familiar BER vs SNR curves the
task force has been using so far. I'd much rather see results
presented in terms of slicer SNR than the more obscure
"input-referred RMS noise power". The margin is then
simply the dB difference between the "required SNR" and the
slicer SNR. Perhaps others could voice their preference.
As was also discussed, the "required SNR" for LDPC
codes must be determined by simulation. Error floor and BER
slope change issues inherent to many LDPC codes cannot be predicted and
simulations must be performed to demonstrate that 1e-12 BER performance
is possible from any given code. Extrapolations from 1e-9 or 1e-10
(or even 1e-11) are not always a reliable predictor of required SNR for
1e-12 BER. We have not yet seen results presented that establish
the required SNR for the PAM8 case with the proposed LDPC (2048,1723)
code as we have for the PAM12 case.
Lastly, we didn't have time to discuss this in detail last
week but there is some concern about the applicability of the so called
"Crane" noise immunity test for these PHYs.
Another bottom line performance goal is for the *PHY + connecting
hardware* to pass legally required noise immunity tests. The noise
immunity test consists of modulated sinusoidal fields applied to an
actual operating PHY in a system. This PHY will still have all
other noise sources and will have it's cancellers and equalizers in
normal operating mode. As I understand it, the "Crane
test" puts the PHY in the unrealistic condition of 1) no other
external noise sources and 2) equalizers frozen, not adapting. The
Crane test makes the further assumption that the same coding gain
predicted for white Gaussian noise will be valid for sinusoidal noise - I
don't believe I've seen presentations or literature which backs this
assumption up. I don't think we have had enough discussion on the
Crane test's advantages/disadvantages, options, and relationship to
reality to simply adopt it and use the results to base our PHY
architecture decision on.
Regards,
- Scott
Dr. Scott Powell
Senior Manager, Ethernet PHYs
Broadcom Corp.
(949)926-5105
spowell@broadcom.com
-----Original Message-----
From: stds-802-3-10gbt@ieee.org
[mailto:stds-802-3-10gbt@ieee.org]
On Behalf Of hiroshi takatori
Sent: Friday, July 16, 2004 11:09 PM
To: STDS-802-3-10GBT@listserv.ieee.org
Subject: Re: [10GBT] Proposed PAM8 vs. PAM12 resolution
process
Sailesh,
Please, define default cancellation parameters and necessary
parameters to create transmit PSDs for both PAM8 and 12.
Hiroshi
KeyEye
From: stds-802-3-10gbt@IEEE.ORG
[mailto:stds-802-3-10gbt@IEEE.ORG]
On Behalf Of Sailesh Rao
Sent: Friday, July 16, 2004 9:01 PM
To: STDS-802-3-10GBT@listserv.ieee.org
Subject: [10GBT] Proposed PAM8 vs. PAM12 resolution
process
All,
I would like to propose the following process for resolving the
robustness of PAM8 vs. PAM12 towards external noise.
1. Compute the Optimum DFE SNR Margin for PAM8 and PAM12 using
solarsep_varlen7a.m for Models 1 and 3 using default cancellation
parameters and -150dBm/Hz background noise.
2. Compute the input-referred RMS noise power at the slicer by
integrating the residual noise in the Optimum DFE solution. I volunteer
to add this code to solarsep_varlen7a.m unless someone else wants to do
so.
3. Compute the input-referred external noise power that can be
tolerated for a BER of 1E-12 for both systems using the results from (1)
and (2) above. I volunteer to add this code to solarsep_varlen7a.m unless
someone else wants to do so.
Regards,
Sailesh Rao.