| Thread Links | Date Links | ||||
|---|---|---|---|---|---|
| Thread Prev | Thread Next | Thread Index | Date Prev | Date Next | Date Index |
|
All – I spoke with Steffen Graber this morning, and we concur – mixed crosstalk is not only likely, but probably unavoidable in installations. We need to consider systems which autonegotiate between 10BASE-T1L and 100BASE-T1L, and that
means that the exact mix of disturbers will not necessarily be determined on installation.
Additionally, we discussed the mitigation of the near-far problem, and a number of reasons why we may not wish to mitigate this with power back off – mainly because we are dominated by impulse noise in the 100BASE-T1L ecosystem. I will
note that we need to be very mindful of the existing ecosystem of installers & operators of the target networks. If we make the planning complicated to fit an improved noise model, 802.3dg could be too cumbersome to use correctly. Personally, I think we
should keep it as simple as possible and try to live in a mixed crosstalk environment, without power back off, or with minimal power back off. I will leave the specific choices (particularly dealing with near-far) to PHY proposers, as there may be tradeoffs to be made – perhaps less aggressive power backoff to reduce the AWGN levels in exchange for better impulse immunity. These
are considerations for proposers. Reflecting these, I have updated my analysis and put forward the multiple models. The most robust one (no mitigation of the near-far problem, mixed crosstalk) would suggest using an AWGN source of -113-10log10(fbaud/75) dBm/Hz, although
the other cases are shown as well. See attached. -george From: stds-802-3-spep2p@xxxxxxxxxxxxxxxxx <stds-802-3-spep2p@xxxxxxxxxxxxxxxxx>
On Behalf Of George Zimmerman All – attached is my homework item, with a few things for us to discuss. I have included both a proposed evaluation noise model for equal-length long-line 100BASE-T1L. I have also included a proposed evaluation model for mixed crosstalk
with 10BASE-T1L. The first uses a single AWGN source, the second, a sum of 2 sources. The presentation also highlights the importance of dealing with the near-far problem in 100BASE-T1L. For those unfamiliar, disturbing signals coupling in as FEXT sources on short links can create substantially greater crosstalk. This
is especially important when PSAACR-F coupling is strong, as it is here. I recall from the excellent contributions we have seen that PSAACR-F couples at the marshalled connectors in process automation plants. While I generally agree with Peter, and want
to handle all conditions without management, this is a particular situation where it may be that a little configuration management (or use of modular connectors rather than screw terminals) could save some significant trouble in the PHY and also improve the
impulse resistance of all links. I’m counting on the experience of our participants familiar with the operating environment. Note – we all know we can solve this with cabling, but here it is especailly important to hear from those who are familiar with the
operators and installers of systems. Feel free to email me if you have questions. -george From: Peter Jones (petejone) <petejone@xxxxxxxxx>
George, I strongly agree with you. We should be striving to recreate the success of the BASE-T ecosystem, and that means accepting a mix of multiple speeds in the environment. Regards Peter _______________________________________________________________ Peter Jones Distinguished Engineer,
Cisco Networking Hardware Chair, Ethernet Alliance
Mobile: +1 408 315 8024 Email:
petejone@xxxxxxxxx Web:
https://about.me/petergjones
Webex:
https://cisco.webex.com/meet/petejone Book a call:
Peter's booking page _______________________________________________________________ From: George Zimmerman <george@xxxxxxxxxxxxxxxxxxxx>
All – in generating a noise environment, it occurs to me that the low frequency noise might be substantially different if we consider an environment with some 10BASE-T1L and some 100BASE-T1L disturbers. (I have substantial experience in
mixed crosstalk environments from prior work, both in Ethernet and DSL systems). This tends to increase the noise at low frequencies and could be important. My own experience tells me such installations would likely be commonplace; however, I would like to ask other practitioners their experience, particularly whether they would likely see the inline connector distributions of the two technologies
mixed in an operational process automation scenario. It isn’t a huge effect, but if this happens, including it can be a useful way to avoid putting too little low frequency noise. George Zimmerman, Ph.D. President & Principal CME Consulting, Inc. Experts in Advanced PHYsical Communications 310-920-3860 To unsubscribe from the STDS-802-3-SPEP2P list, click the following link:
https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-SPEP2P&A=1 To unsubscribe from the STDS-802-3-SPEP2P list, click the following link:
https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-SPEP2P&A=1 To unsubscribe from the STDS-802-3-SPEP2P list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-SPEP2P&A=1 |
Attachment:
zimmerman_3dgah_01a_01292024.pdf
Description: zimmerman_3dgah_01a_01292024.pdf