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RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel ca pacity estim...

Lets be real (no pun intend) here that we are dealing with a baseband system.  So it is well understood that the -140 is single sided.  So for future reference and so as not to confuse things when considering transmit PSDs, lets agree to use single sided definitions. 


-----Original Message-----
From: []
Sent: Tuesday, February 25, 2003 2:25 PM
To: Ze'ev Roth
Subject: RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel
ca pacity estim...


Thank you for your message.  Your observation is right.  I thought that the
-140dBm/Hz background noise level is a double-sided PSD when I got it from
the document.  Either reducing the background noise by 3dB or increasing
the input signal PSD by 3dB should fix the problem.   You have also
provided the capacity results after the modification.  They basically tell
us the same story we have been facing.

Of course the smooth limit line model used in the program will be replaced
by the scaled, selected, measured channel data when they are offically
available.  Only couples of dB SNR improvement to performance based on the
channel limit model should be expected.   Once we obtain more accurate
results on the channel capacity, we will be able to to assess our
achievable targets for the 10GBT standard.



"Ze'ev Roth" <> on 02/25/2003 05:50:48 AM

To:    "''" <>,

Subject:    RE: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel
       ca   pacity  estim...

Xiaopeng hi,
Very good work.

In order to probe into this deeper,  I  initially simplified your
to having only a single simple impairment - background noise (i.e., I
removed from your simulation all other impairment: NEXT, FEXT, ANEXT,
The resulting capacity was 15.29Gbit/sec.
This simplification allows me to  compare your results with my program's
results. Running my routine on same parameters I got capacity of
So clearly there was a discrepancy in the results.
Previously I've cross checked my routine on simple problems and compared to
textbook results, as well as put it to scrutiny with a several colleagues,
so I am quite confident it yields correct results.

Therefore, I dug a bit into your equations (in the Matlab file), I think
there is a slight problem with the definition of spectral density (it
doesn't account for double sided) - there is a subtlety in capacity
equations (the usual 3dB problem) and I think you may have fallen into this
pit. And indeed when I add 3 dB to the noise floor in my simulation I get
capacity of 15.327. The difference from 15.29 can probably be attributed to
a different frequency grid and that I used an older version of the
loss limit equation which is marginally different than the one you've used.

I've taken the liberty to modify your code (I started out with the latest
version you've sent) to account for the double sided density (one can
switch between the original code and my correction) and attached it herein.
I've added comments showing were the single sided - double sided spectral
density switch occurred in my opinion. I've also  added a sanity check
option for simple AWGN channel case.

Running the modified program I got the following results:
Cable=CAT-5E   Cancellation=Marvell             Capacity= 8.89 Gb/sec
Cable=CAT-6     Cancellation=Marvell            Capacity=11.36 Gb/sec

I've also added the option to use Solarflare's figures for impairements'
DSP-improvement as presented in Kauai.
Running the modified program under these assumptions yields:
Cable=CAT-5E      Cancellation=SOLARFLARE        Capacity=5.57 Gb/sec
Cable=CAT-6       Cancellation=SOLARFLARE        Capacity=7.26 Gb/sec

Summarizing, although there was a small flaw in the original M file, your
basic conclusions seem to hold water and moreover using Solarflare's
assumptions regarding DSP cancellation performance yield that neither CAT5E
nor CAT6 can support 10Gb/sec for 100m cable length.


-----Original Message-----
From: []
Sent: Monday, February 24, 2003 8:24 PM
Subject: Re: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel
capacity estim...

Chris,  and everyone,

I have attached the latest copy of my channel capacity estimation program
to this email.  Please check it out.  If you have any program to get it,
please let me.  I can send you a copy directly.

Best Regards,

Marvell Semiconductor

(See attached file: i3e.m) on 02/24/2003 05:14:48 AM


Subject:    Re: [10GBT-Modeling] RE: [10GBT-Cabling] [10GBASE-T] a channel
       capacity estim...


Can you please reply with a copy of  the models you
had distributed in earlier e-mail?

Want to make sure a have the latest copy under discussion.



<< Albert,

 Thank you for your input.  With the consideration of ANEXT, the Shannon
 capacity of CAT-6 is 10Gbps by using the models presented in my program.
 Accordingly, your calculation shows the Shannon capacity is 12Gbps.  I
 admit this is a significant difference.  However, even with the 12Gbps
 Shannon capacity, there is no way we can achieve 10Gbps effective
 throughput over 100m CAT-6 cable if the ANEXT cannot be suppressed by any




(See attached file: i3e_v2.m)