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Albert,
I have
to disagree. I think the 45x complexity (again, I said this is a first-order
approximation) *does* apply to the cancellers. You are assuming that
the "system resource sharing and advanced DSP techniques" are not already being
used in the 1000BASE-T PHYs that are being shipped today. Unless I missed
something, the techniques that I saw in the presentations are not unique to the
10GBASE-T system. Considering that today's 1000BASE-T PHYs have power numbers
that are an order of magnitude lower than those in '99, you should assume that
many of these techniques are already being employed today.
If
there was something in the techniques that was specific to the 10GBASE-T
proposal, please point me to the particular presentation.
Regards,
Vivek
Vivek,
DSP feasibility is an important point that would need to be properly
addressed. However, the DSP filter orders do not necessarily follow
the x6.7 rule.
There have been at least two presentations, which showed that with a
relatively simple processing in the analog front end, the DSP burden
could be substantially reduced. Further, there would be savings from
the system resource sharing and the use of advance DSP techniques.
Regards,
Albert
Vivek Telang wrote:
To
re-iterate the point that Dan made yesterday, I would add to the feasibility
list:
DSP feasibility for the above
configurations.
Note that going from 100BASE-TX to 1000BASE-T, the symbol rate
(125MBaud) didn't change, and the DSP processing period was a relatively
healthy 8ns. In the proposed transition from 1000BASE-T to 10GBASE-T, the
symbol rate goes up from 125MBaud to 833MBaud, which means the DSP
processing period is reduced from 8ns to 1.2ns (a factor of 6.7). Also, note
the double whammy in that the number of cancellation filter taps (Echo
and NEXT) for the same coverage goes *up* by the same factor (x6.7). So
one could argue that to the first order the canceller complexity is ~45x the
canceller complexity of 1000BASE-T. Of course, the processes that will be
used for 10GBASE-T will be faster than those used for 1000BASE-T,
but it's an issue that requires some thought and discussion before
we're all comfortable.
Vivek Telang
Cicada Semiconductor
While I understand the motive behind
stressing the benefits of DSP based ANEXT compensation, and installation
based ANEXT mitigation, I have to emphasize that these methods and their
practical value are subject to ongoing debate. For example, one of the
ANEXT mitigation methods is to insert patch cords of longer length/geater
insertion loss into the channel. This is not only counter-intuitive it has
other problems as well, such as the possibility of re-qualifying the
channel for length and insertion loss, as well as possibly violating TIA
requirements for patch cord wire gauge and insertion loss assumptions. For
the formulation of the 5 critters, I contend these arguments are
non-starters. All of these things, however can be cosidered and debated on
their merits in the task group. Please try to focus on establishing a
baseline position that everyone can support by indicating your support for
the following options:
Class F at 100 meters
Class E STP at 100
meters
Class E UTP at 50 meters
ADC feasibility for above
configurations
Commitment to develop:
Cabling performance standards for:
Class D
STP
Class D UTP
Retrofit
based mitigation techniques for:
Class E UTP > 50
meters
Class D STP ?
Class D
UTP (dependent upon result of cabling standards developed
above)
DSP based ANEXT
cancellation
ADC feasibility for the above
configurations
Based upon level of support for these objectives, we
can add new objectives or delete/augment. Remember, the objectives must
have broad support within the group to survive at higher levels of
approval.
Sterling
George Zimmerman wrote:
Presentations are given by individuals, not companies, but you can find
them on the 10GBASE-T study group site. Among those of note are a
January presentation from Stephen Bates, up to one just in July by Shadi
AbuGhazaleh & Rehan Mahmood (there are more on mitigation and on
feasibility studies, Ron Nordin & Vanderlaan, Albert Vareljian, Bijit
Halder all come to mind).
There really isn't any mystery here - going to shorter distances
increases the received signal proportionally, and mitigating alien NEXT
decreases the noise, hence, more capacity. What is more, because the
crossover point (signal/noise=1) occurs at a higher frequency, only
increasing the capacity further.
George Zimmerman
gzimmerman@solarflare.com
tel: (949) 581-6830 ext. 2500
cell: (310) 920-3860
-----Original Message-----
From: Sreen Raghavan [mailto:sreen-raghavan@vativ.com]
Sent: Tuesday, July 29, 2003 4:24 PM
To: George Zimmerman; sreen@vativ.com; 'DOVE,DANIEL J
(HP-Roseville,ex1)';
'Alan Flatman'; 'Kardontchik, Jaime'
Cc: '[unknown]'; 'Sterling Vaden'
Subject: RE: [10GBASE-T] PAR and 5 critters
George,
Please indicate which company's presentation has independently
confirmed
your claims, and where I can find such a presentation.
-----Original Message-----
From: George Zimmerman [mailto:gzimmerman@solarflare.com]
Sent: Tuesday, July 29, 2003 3:16 PM
To: sreen@vativ.com; DOVE,DANIEL J (HP-Roseville,ex1); Alan Flatman;
Kardontchik, Jaime
Cc: [unknown]; Sterling Vaden
Subject: RE: [10GBASE-T] PAR and 5 critters
Sreen & all -
I believe some clarification is in order.
What the presentation you reference from Portsmouth, New Hampshire
showed was that with an assumption of a high-degree of alien NEXT and
a
further assumption that it could not be mitigated in any way,
cat5e/cat6
could not support 100meter operation at 10G. This is a different
statement altogether as to whether cat5e/6 can support 10G either with
alien NEXT mitigation, or at shorter reaches, both of which have been
shown to yield sufficient capacity to allow 10G in numerous
presentations by multiple vendors.
The consensus proposal presented at San Francisco argued that even
without alien NEXT mitigation, there was a sufficient portion of the
installed base of 5e & 6 coverable to merit broad market potential
(>60%
installed base at 50m or less), and that in addition to SolarFlare
showing both receiver-based (DSP) and installation-practices based
alien
NEXT mitigation examples, other companies have now shown significant
alien NEXT mitigation through installation practices.
These developments significantly change the capacity relations you
refer
to, making 10GBASE-T practical on the economically feasible installed
base of cat5e & 6.
On your technical points for implementation, I respectfully disagree,
and we have put forward our requirements, and these have been
confirmed
by at least one independent presentation.
George Zimmerman
gzimmerman@solarflare.com
tel: (949) 581-6830 ext. 2500
cell: (310) 920-3860
-----Original Message-----
From: Sreen Raghavan [mailto:sreen-raghavan@vativ.com]
Sent: Tuesday, July 29, 2003 1:58 PM
To: 'DOVE,DANIEL J (HP-Roseville,ex1)'; sreen@vativ.com; 'Alan
Flatman';
'Kardontchik, Jaime'
Cc: '[unknown]'; 'Sterling Vaden'
Subject: RE: [10GBASE-T] PAR and 5 critters
Dan:
We are really referring to the theory (Shannon Capacity) when we say
10Gbps
cannot be achieved over CAT-5e or CAT-6 cabling. Theory shows that
10Gbps
can be achieved over CAT-7 cabling. Practical issues to accomplish
10Gbps
over CAT-7 cabling include (assuming PAM-10 modulation):
1. Building an 11-bit effective ADC at 833 MBaud,
2. Performing large number (x8 relative to 1000BaseT) of DSP
calculations
at
833MHz,
3. DDFSE critical path to be implemented in 1.2 ns
4. Building a linear transmit driver with an 833MGz bandwidth & 40
dB
SNR
The above list by no means is exhaustive, but shows the
implementation
issues that need to be considered.
Sreen
-----Original Message-----
From: DOVE,DANIEL J (HP-Roseville,ex1) [mailto:dan.dove@hp.com]
Sent: Tuesday, July 29, 2003 1:09 PM
To: 'sreen@vativ.com'; 'Alan Flatman'; 'Kardontchik, Jaime'
Cc: '[unknown]'; 'Sterling Vaden'
Subject: RE: [10GBASE-T] PAR and 5 critters
Hi Sreen,
One thing that occurs to me on this point is the difference between
theory and application. Specifically, how many process actions have
to
take place within a baud time to close the loops on the DSP and what
process geometry would be required to make that timing closure?
I know that with 1000BASE-T, the theory was rock solid long before
the
processes to implement it were reliable.
Dan
HP ProCurve
-----Original Message-----
From: Sreen Raghavan [mailto:sreen-raghavan@vativ.com]
Sent: Tuesday, July 29, 2003 11:52 AM
To: 'Alan Flatman'; 'Kardontchik, Jaime'
Cc: '[unknown]'; 'Sterling Vaden'
Subject: RE: [10GBASE-T] PAR and 5 critters
Just to clarify, Vativ, Broadcom & Marvell presented capacity
calculations
at the Portsmouth meeting and showed that worst-case CAT-7
(Class F) cabling
had sufficient channel capacity to achieve 10Gbps throughput
at 100 meter
distance. The reason for "may be possible" statement in the
conclusions was
that the 3 PHY vendors felt that more work needed to be done
on practical
implementation issues before the conclusion could be altered to a
more
definitive statement.
In addition, we proved conclusively that there was NOT
sufficient channel
capacity on existing CAT-5e (Class D), or CAT-6 (Class E)
cables to achieve
10 Gbps throughput.
Sreen Raghavan
Vativ Technologies
-----Original Message-----
From: owner-stds-802-3-10gbt@majordomo.ieee.org
[mailto:owner-stds-802-3-10gbt@majordomo.ieee.org] On Behalf
Of Alan Flatman
Sent: Tuesday, July 29, 2003 9:51 AM
To: Kardontchik, Jaime
Cc: [unknown]; Sterling Vaden
Subject: RE: [10GBASE-T] PAR and 5 critters
Message text written by "Kardontchik, Jaime"
Was any reason given why it would not run on Class F ? Was it for
technical reasons or for marketing reasons ?<
The 3-PHY vendor presentation made in Portsmouth (sallaway_1_0503)
calculated 49.36 Gbit/s capacity using unscaled Cat 7/Class F
cabling. This
figure was reduced to 37.71 Gbit/s with worst case limits.
Overall,
I
thought that this was a refreshingly realistic presentation and I
interpreted the summary statement "Capacity calculations with
measured data
indicate 10 Gigabit data transmission over 100m Cat 7 may be
possible"
(slide 16, bullet 3) as overly cautious engineering judgement.
So, what has changed since the May interim? Not the laws of
physics!
Best regards,
Alan Flatman
Principal Consultant
LAN Technologies
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