Re: [10GBT] THP Fixed Set TF
Hi Pedro,
It would be good if vendors could independently evaluate
the proposed so far pre-coder TF sets in their specific
Tx and Rx configurations.
As far as the mentioned high-pass filter (HPF) is concerned
(not sure why you are referring to it as "boosting"). This
HPF is merely introducing a DC null in the channel, which it
does in a bit more "aggressive" way than the line transformer
(helps reduce channel variations sensitivity w.r.t transformer).
In "ungerboeck_1_1104" p. 15 one could notice that a first
order "DC null" filter with cut-off at 4 MHz is built into
the Tx chain -- this is the same HPF.
The way the channel is configured from the pre-coder TF point
of view in both "ungerboeck_1_1104" and "vareljian_1_1104",
this HPF could be moved from Tx to Rx side with no effect on
the final results. (By the same considerations we could move
the DFE from receiver to transmitter in the first place.)
So, there are no fundamental differences in the analyses, as
far as the HPF is concerned. [This is not to say that the
filter in question (as specified) does not have a significant
impact on the system performance.]
Hope, this clarifies.
Regards,
Albert
Reviriego, Pedro (Pedro) wrote:
>Hi Albert,
>
>
>So far several precoder proposals have been presented: one is your
>proposal and another one is Ungerboeck's.
>
>They assume different Rx Architectures, namely analog high pass boosting
>is used in yours but not in Ungerboeck's. I think we need to assess the
>performance loss of your precoders with a receiver that does no boosting
>and the performance of Ungerboeck precoders with a receiver that
>includes boosting.
>
>This will show if setting the precoder coefficients limits the options
>for Rx implementation in which case we should consider making the
>precoder programmable.
>
>Regards,
>
>Pedro
>
>
>
>
>
>-----Original Message-----
>From: Albert Vareljian [mailto:albertv@ieee.org]
>Sent: Wednesday, December 15, 2004 7:36 PM
>To: Reviriego, Pedro (Pedro); STDS-802-3-10GBT@listserv.ieee.org
>Subject: Re: [10GBT] THP Fixed Set TF
>
>Pedro,
>
>I did not use the Rx filter you mentioned below primarily
>due to aliasing associated with its not very steep roll-off.
>(Also pointed by Gottfried during Nov meeting.)
>
>Regards,
>
>Albert
>
>
>
>
>Reviriego, Pedro (Pedro) wrote:
>
>
>
>>Albert,
>>
>>Have you tried using the receive filter presented in
>>
>>
>"ungerboeck_1_1104"
>
>
>>with your precoder? If so what kind of performance do you get?
>>
>>Regards,
>>
>>Pedro
>>
>>-----Original Message-----
>>From: IEEE P802.3an Reflector [mailto:stds-802-3-10gbt@IEEE.ORG] On
>>Behalf Of Albert Vareljian
>>Sent: Saturday, December 11, 2004 2:14 AM
>>To: STDS-802-3-10GBT@listserv.ieee.org
>>Subject: [10GBT] THP Fixed Set TF
>>
>>Dear All,
>>
>>Further to our Nov meeting discussions on fixed THP TF set,
>>pls find for evaluation attached material outlining 3 TF sets.
>>This is aimed in combination with THP bypass option -- i.e.
>>four THP modes in total.
>>
>>All simulations were performed in time domain as per
>>"vareljian_1_1104" and showed reasonably good performance
>>with relatively short (24-Tap and shorter) FFE. Performance
>>impact due to 7-bit coefficient quantization effects was
>>found to be very small.
>>
>>Similar results were observed in simulations for a 2nd order
>>Tx LPF @ 200 MHz as per "ungerboeck_1_1104" in place of the
>>3rd order Tx LPF @ 400 MHz.
>>
>>Hope, the posting will stimulate discussion on our, otherwise
>>relatively quiet, reflector.
>>
>>Happy Holidays to everyone.
>>
>>Regards,
>>
>>Albert
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>
>
>
>
>