RE: [10GBASE-T] PAR and 5 critters
Sreen,
Over the course of last four IEEE 10GBASE-T SG meetings plus
the CFI (Nov. 2002) and through several presentations I have
highlighted the difficulty of realizing a stand alone CMOS ADC
with ~1GS/s and ENOB=11 bits. I have also pointed out the
problem of jitter-limited ENOB that is a result of integrating
four such ADCs along with large number of digital gates on the
same chip.
I have also offered some alternative solutions that involve
implementing part of the signal processing in analog. The
following three bullets are borrowed from Prof. Richard Spencer's
July presentation:
*A mostly digital (DSP) solution will severely tax the sate-of-
the-art ADC capabilities
*The AFE could include significant equalization to reduce burden
on the ADC and back end DSP
*The AFE might also include some echo cancellation and/or NEXT
cancellation
http://www.ieee802.org/3/10GBT/public/jul03/spencer_1_0703.pdf
I agree with you that traditional AFE + DSP approach, in this case,
runs into trouble however, alternative approaches do exist. Some
of these approaches have been successfully applied to high data-rate
read channels.
Regards,
Joseph N. Babanezhad
Plato Labs.
-----Original Message-----
From: "Sreen Raghavan" <sreen-raghavan@vativ.com>
To: "'Kardontchik, Jaime'" <jaime@integration.com>, <stds-802-3-
10gbt@ieee.org>
Date: Tue, 29 Jul 2003 15:35:04 -0700
Subject: RE: [10GBASE-T] PAR and 5 critters
>
>
> I understand there is a huge difference between implementing a 7-bit
> precision ADC and an 11-bit precision ADC.
>
> Sreen Raghavan
>
> -----Original Message-----
> From: owner-stds-802-3-10gbt@majordomo.ieee.org
> [mailto:owner-stds-802-3-10gbt@majordomo.ieee.org] On Behalf Of
> Kardontchik,
> Jaime
> Sent: Tuesday, July 29, 2003 2:53 PM
> To: stds-802-3-10gbt@ieee.org
> Subject: RE: [10GBASE-T] PAR and 5 critters
>
>
> Yeah, the analog target specs look reasonable ...
>
> For comparison, in my previous life (company) I did some
> system simulations (and actual design) and came to the
> conclusion that one could run 10 Gbps over cat-7 STP to
> a distance of about 25 meters with a 7-bit effective ADC
> at 625 Mbaud (PAM-5 modulation). At least, the 7-bit
> effective ADC was achievable ...
>
> Jaime E. Kardontchik, PhD
> Integration
> Mountain View, CA 94041
>
> -----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
> >
> >
> >
> >
> >