RE: [10GBASE-T] PAR and 5 critters
Hi,
I think George's work is valuable. Here is my opinion regarding the DSP
Alien mitigation:
1. It does not matter whether the Alien NEXT disturbers are synchronous
with the victim or not. The ANEXT mitigation is based on the noise
auto-correlation between different pair lines of a victim. There is no
need to recover the ANEXT data. It is not like the 1000BaseT on which we
need to cancel the self-NEXT, therefore, the synchronization and
aggressor's data pattern have to be identified in order to achieve high
amount of cancellation.
2. It doe not matter whether the number of disturber is one, six, or
more. What it cares is the difference (or uniformity) of aggregated
noise applied on the 4 pairs of signal of victim.
3. It does not matter whether there is a long latency introduced by DSP
processing or not. The Alien mitigation, on my opinion, requires a time
domain window of data to process. It is not like DFE or FFE which we
cancel the pre- or post-cursor interference on the spot of sampling
time. I anticipate that the Alien mitigation DSP look more like a
post-processing job and therefore will cause long latency. It may affect
the link latency budget but not the accuracy.
However, I do think the complexity of the DSP is a big challenge. That's
why everybody is working so hard.
Regards,
-Joseph
-----Original Message-----
From: owner-stds-802-3-10gbt@majordomo.ieee.org
[mailto:owner-stds-802-3-10gbt@majordomo.ieee.org] On Behalf Of Sreen
Raghavan
Sent: Tuesday, July 29, 2003 3:40 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:
We pointed out at the July plenary the flaws in Solarflare's approach to
receiver ANEXT mitigation, namely,
1. You did not assume 6-neighboring cables in your ANEXT model, 2. You
have mistakenly assumed that the data on the interfering cable, and the
cable under test to be synchronous (not true!).
Sreen
-----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
> >
> >
> >
> >
> >
>
>