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Ruben – thank you for your answers, and, in particular for the pointer to the presentations. Bob – thank you for the discussion. I spent some time looking through the presentations, but, more particularly I then went to the CSD responses.
I must apologize, because we have been discussing the issue of ‘being future proof’ when I don’t see it in the CSD responses.
I also don’t see that the broad market potential response lives or dies on a residential market. (we could argue all day about home networking requirements – other than the wireless guys, I don’t think anyone has really figured out that market).
The CSD response for BMP identifies those markets as: “This includes application in home and small office networking, automotive, industrial, medical and other market segments
where harsh environmental requirements exist and/or use of long link lengths is not required.”.
Perhaps we are all wound up on the fact that home networking is listed first (something that could be easily fixed)? I could offer other edits, but I don’t think that’s a good use of reflector chatter. (Bob – you can contact me offline
if you’re interested, some things could be done to improve clarity and avoid questions, but I don’t think they’re essential). I do have a question of clarification, that I think is important to defining the markets in the Broad Market Potential
CSD response: I understand the clause “where harsh environmental…and/or long link… is not required” to apply as a description of the
set of markets (home & small office, automotive, industrial, …) , for example, clearly it doesn’t address the longer-reach parts of the industrial or medical markets.
Do I understand this correctly? If so, this might be worded more clearly, simply by putting the “where … required” clause first, and listing the others as “for example” or “including”. On technical feasibility, I’m still a little off on the multi-vendor aspect of the presentations, and the references
don’t entirely close the simulation questions or necessarily tie to the objectives, but I think the tutorial should help close those gaps.
Because of the large amount of PHY work going on in dot 3, it hasn’t been possible to sit in on this study group’s work, particularly for copper PHY experts
like myself, who are quite familiar with the signal processing required, and the likely pitfalls in simulation or demonstration test conditions
- hence, I suspect the tutorial will be important for many dot-3 voters. On technical feasibility, it is important to tie that question to the specific link characteristics in the objectives,
and this brings me to a question. When I look at the objectives,
I see that the key objectives relevant to technical feasibility (at 1Gbps rate) are: “For the automotive environment: • Specify operation over at least 15m of POF with 4 POF connections • Specify operation over at least 40m of POF with no POF connections • For the home and industrial environment specify operation over at least 50m of POF with 1 POF connection • Maintain a bit error ratio (BER) better than or equal to 10-12 at the MAC/PLS service interface “ My question (probably for Bob & the Study Group) is whether it is an objective (or should be an objective) of this project
to define the performance characteristics of the referenced 15m, 40m and 50m link segments (and environments), as 802.3bp did (see page 3 of
http://www.ieee802.org/3/bp/Updated_Objectives_0514.pdf), or, if the objectives should reference the appropriate external standards groups, as, for example, the 4-pair BASE-T PHYs do – see,
for example, http://www.ieee802.org/3/bq/Objectives.pdf ).
George Zimmerman Principal, CME Consulting Experts in Advanced
PHYsical Communications Technology george@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx 310-920-3860 (PLEASE NOTE NEW EMAIL ADDRESS.
THE OTHER WILL STILL WORK, BUT PLEASE USE THIS FOR CME BUSINESS) From:
Rubén Pérez-Aranda [mailto:rubenpda@xxxxxxxxx] Peter and George: Thank you for your feedback. I'd like to clarify some points concerning to worst case POF channel issue:
Other comments that I would like to point out regarding to channel model and knowledge about non-linearity:
Finally, some comments about using other wavelengths:
_____________________________________ El 08/10/2014, a las 19:41, Carlos Pardo <carlospardo@xxxxxxxxx> escribió:
FYI
Peter – I thank you for your diligence. I have been considering these issues, and find as some
of these arguments overreaching. Particularly the ‘future proof’ discussion for the home network market. I would note first that the most prevalent home networking technologies
are not even considered in the presentations from September (a hybrid of wired BASE-T Ethernet and advanced 802.11 wireless – and yes, I know that in some markets these have been argued as unavailable by construction and regulation, but the presentation environment
was not limited by those considerations). What I see are market justifications that don’t necessarily get linked to objectives. For
example, if future proofing were to be considered as important to enabling this market, the objectives should make some provision for an autonegotiation protocol
(at least an optional one) – to build a base for that future. I will have to leave the optical testing issues to your analysis. Coming from the copper
world, when we have simulation models they are fairly detailed, and call out each of the residual impairments, using widely known and demonstrated techniques for cancellation. I don’t get that same feeling from the analysis I have seen in the record of presentations.
I have been reviewing the detail of the presentations but get the impression that they are predominantly using a linearized model on a channel known for nonlinearities. While some reference in the documents is made
to signal processing for removing nonlinearities, the required accuracy and the performance limitations of those in the target environments is neither well known nor tracked in multi-vendor presentations. I am not
saying it cannot be done – just that technical feasibility and noise components for this channel need to be better shown before they live up to the ‘effects are well known and understood’ criteria for technical feasibility. Hopefully
these will be addressed in the tutorial in November. George Zimmerman Principal, CME Consulting Experts in Advanced PHYsical Communications Technology 310-920-3860 (PLEASE NOTE NEW EMAIL ADDRESS. THE OTHER WILL STILL WORK, BUT PLEASE USE THIS FOR CME
BUSINESS) From: Peter
Stassar [mailto:Peter.Stassar@xxxxxxxxxx] Hi Bob, Thanks for your email response sent about 3 weeks ago. I would like to start to re-emphasize that my main concern was in the end of the email which I sent on 22 July: “In conclusion I have not been convinced that 1Gb/s Ethernet over 50m of worst case POF is technically feasible
and even more that an installed POF link can be upgraded to higher speeds, which I believe is necessary to justify long lifetimes of home-installed POF networks.” As you suggested I took a close look to the presentations to the meeting in Ottawa, 4 weeks ago. Before commenting to those I will first address the 5 points from your email. I inserted comments in “red” in
the thread below. So back to the September presentations. In Eugene_GEPOF_01_0914 I see a strong claim that POF is future proof and that it is superior to existing technologies
like twisted pair, coax and power line. This presentation also says “Tomorrow SMART HOME needs future proof networking medium”, which is a statement which I fully support and, I believe, have always clearly stated. This is however also the weak point of all
presentations which I have seen so far. I continuously fail to find any evidence that POF and the 1GbE technology to work with it, is sufficiently future proof. In Tsukamoto_GEPOF_02_0914 the following is said “Customers may use the network over 30 to 50
years. Is GbE enough in such a far future?”. This is exactly the point I tried to make during the CFI consensus building meeting in Beijing and during the San Diego meeting. It’s my strong belief that 1 Gb/s is NOT sufficiently high speed to justify deployment
of POF in the home. Some references have been made to shorter wavelength windows of POF which could provide lower attenuation than at 650nm. Having looked at the Ottawa presentations I see some inconsistencies. While in Eugene_GEPOF_01_0914 I see a claim that
in the range 450 to 580 nm the attenuation will be lower than at 650 nm, I conclude from Tsukamoto_GEPOF_01b_0914 that the POF standard is only specified for the 650nm window and that therefore operation is other wavelength windows is not specified and thus
not guaranteed. A lower attenuation in the range 450 – 580nm would indeed be great, but what will be the bandwidth of POF in that wavelength range? It is not trivial that it will be the same or better or worse. I am under the impression that POF is a kind
of multimode fiber and bandwidth is strongly dependent on the wavelength. In conclusion, having looked in detail at the presentations to the Ottawa meeting and the clarifications in your email,
I am still of the opinion that insufficient evidence has been provided that the proposed solutions are capable of multi-vendor interoperability (capability of developing a multi-vendor interoperable transceiver design from the specification under worst case
conditions) and that the POF medium is sufficiently future-proof (or in other words upgradeable to speeds well in excess of 1Gb/s) to justify installations in the home for many decades to come. Kind regards, Peter Stassar, 施笪安 Technical Director, 技术总监 Huawei Technologies Ltd, 华为技术有限公司 European Research Center, 欧洲研究所 Karspeldreef 4, 1101CJ Amsterdam The Netherlands Tel: +31 20 4300 832 Mob: +31 6 21146286 From: ROBERT
GROW [mailto:bobgrow@xxxxxxx] Peter: Thank you for documenting your concerns following the July plenary meeting. We reviewed your concerns during our interim Study Group meeting, and I offer some general response. I
believe these thoughts are consistent with the consensus of the GEPOF SG. Detailed responses to your specific points will likely follow from me and others. A few general points: 1. We have certainly noted your acknowledgement that you are satisfied with POF applicability for two of the three markets our participants want to address (i.e., automotive and
industrial). Study Group members though did express some confusion because many of the presentations you choose to comment about were clearly only addressing requirements for the automotive market. Please see September presentations for additional support
for the application to home networking. Peter: I just looked at the available documentation. I understood that many were addressing the 15m automotive market. 2. In response to your repeated comment “15m (typical?)”, yes 15 meters is the requirement for automobiles. That is reflected in one of our link length objectives for 15 meters
with four in-line connections. If you look, you will see similar 15 meter objectives for p802.3bp and p802.3bw. Peter: I do understand the 15m objective. I only put some questions marks on the testing done on 15m links. In the optics world a laboratory test on a TYPICAL fiber is completely
different from a test on a worst case fiber under worst case operating conditions. Worst case conditions have a big impact on maximum loss and (I assume for POF) also on bandwidth. Therefore optics people are generally not convinced by a laboratory test on
just 15 km of typical fiber. What kind of margins are available, etc. 3. You also frequently commented on the lack of detail on modulation techniques. We apologize for that, your question would have been answered if you had been able to attend SG
meetings. In defense of SG presenters, please understand that most of our participants helped develop a VDE specification for operation at up to and including 1 Gb/s with link lengths consistent with our automotive and home reach objectives. Consequently,
much is assumed to be a given with those folk, and it is perhaps excusable that presenters did not have an outside reader trying to understand everything from only the presentation in mind when preparing the presentation. Peter: I am of the opinion that details on how to actually “do it” needs to be provided by presentations and not via verbal clarifications. I understand that often things are a
given for a limited group of people, but I also think you are very much aware that in 802.3 one needs to convince 75% of the plenary and not only the “insiders”. There are implementations of the VDE specification from multiple vendors. All tests that used a PHY used one of these implementations. If you look at September presentations, you
will see that additional presentations on testing include detailed one slide summaries of the characteristics of the VDE PHY. Peter: Thanks for pointing this out. It would be great to see some evidence of those different implementations and interworking testing. I am under the impression that all test
results shown at the September meeting (Lichtenegger_GEPOF_0914 and perezaranda_GEPOF_01_0914) were from the same PHY vendor and not between PHYs from different vendors. So it would have been very interesting to see results from interoperability testing between
devices from different vendors. 4. You also repeatedly commented that simulation was not sufficient for justification of technical feasibility. While you are entitled to that opinion, but give no rationale why
simulation is not valid for demonstration of technical feasibility, I would point out that we have approved projects in the past based on simulation (in my personal experience as far back as 1000BASE-T). Please also note that simulation is listed in IEEE
802 rules as an acceptable evidence of technical feasibility. As is true for most engineers, the participants in our SG find it useful to look to both simulation and lab testing and when possible implementation tests expecting consistency.
As noted in my point 3, many of the test presentations you critiqued used an existence proof of technical feasibility – an implementation of the VDE specifications tested at 1000 Mb/s. We do not only relay on simulation as some previous 802.3 projects have. Peter: regarding to your statement “While you are entitled to that opinion, but give no rationale why simulation is not valid for demonstration of technical feasibility, I would
point out that we have approved projects in the past based on simulation (in my personal experience as far back as 1000BASE-T)”, I would like to point out that for optical PHYs many years of (bad) experience have taught most optical engineers that simulations
in the optical field in most cases need to be confirmed by experiments in order to judge the accuracy of the simulations. That’s why I (and probably not only myself) keep repeating that to demonstrate technical feasibility of Optical PHYs results from simulations
are generally not sufficient. 5. You also repeated in your comments a question about worst case channel. Please note that the environmental requirements for automotive applications have higher temperature, greater
EMC, and specific connector requirements. Industrial applications similarly will also have higher temperature than home, and greater EMC challenges. While vibration effects on optical power is important for the automotive channel, it is not considered relevant
to the channel for nome networking, so our participants have looked at the effects of vibration on optical power, and consequently the automotive channel will include losses for vibration. With our three major markets asking for a standard POF solution, and
different objectives that address those markets, it is appropriate for a presentation to focus only on one particular market application, and unfailr for you to criticize those presentations for not also covering the home network application. Peter: on the topic of worst case channel I am NOT referring the range of environmental characteristics, despite the fact that they do play a significant role. I am referring to
an optical link model with worst case characteristics appropriate for a distance of at least 50m. A test with a spool of 50m of typical POF is generally not regarded as testing a link under worst case conditions. I am under the impression that in many in-force
optical specification in 802.3 a lot of work has been done on defining a worst case channel. This generally is defined such that it will support manufacturers in designing, manufacturing and testing transceivers. Performing a test on a spool of 50m POF is
indeed proof of concept, but by far not enough to claim complete technical feasibility, or in other words sufficient maturity of the technology that it actually can be manufactured in high volume and with a high yield, work on worst case links of 50m POF in
the home in a multi-vendor environment. I am afraid that this has not yet been demonstrated. The fiber shown on page 16 of perezaranda_GEPOF_01_0914 had an attenuation of 0.19 dB/m, but according to page 5 of Tsukamoto_GEPOF_01b_0914.pdf, IEC 60793-2-40 category
A4a.2 has a maximum loss of 0.4 dB/m. What was the bandwidth of the test fiber and how does that relate to the worst case specification? Furthermore it was not my intent to criticize those presentations not covering the home market. If I came across to criticize them then I apologize for that. I was just putting
remarks to those presentations what they were aimed at and what they were not aimed at. Please see September and upcoming November presentations for additional support of feasibility for home networking. —Bob |