Hal,
Very much appreciated.
I’m not advocating multiple PHYs, just stating one rationale behind it.
If I’m not mistaken, so far we haven’t referenced 1 GHz and I wonder if we should do it at the SG level.
Regards,
Charaf
From: Hal Roberts [mailto:Hal.Roberts@xxxxxxxxx]
Sent: Tuesday, May 08, 2012 3:21 PM
To: Charaf HANNA; STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
Subject: RE: [802.3_EPOC] Latest objectives proposal
Charaf,
Yes, I have heard the same and would submit the same reasoning I sent out before, “If a single PHY can operate over the wildly varying conditions found in wireless transmission (i.e. LTE or Wi-Fi with huge swings in signal strength, interference, multipath etc) surely a single PHY should suffice within the more controlled cable environment”.
Obviously the PHY parameters would have to be adjustable, i.e. QAM constellation density, FEC, guard interval and others. This is what is done in LTE and Wi-Fi.
What shouldn’t need to change is subcarrier spacing, symbol duration and other more difficult to change parameters.
As I sent out before, “The burden of proof should be on demonstrating the need for two PHYs.”
Having said all of that, it is much more likely that two PHYs might be considered to work well with TDD vs FDD.
With FDD the downstream would be a continuous signal (with idle patterns when no data is sent) just like DOCSIS which allows easy synchronization to the downlink and eliminates the need for preambles at the beginning of a burst (i.e. there are no bursts in the downstream). Whereas with TDD we have to define downstream frames and upstream frames along with guard times.
LTE solves this with two types of frame structures, Type 1 for FDD and Type 2 for TDD (see below).
As long as we consider two frame structures as defined under one single PHY then we still need only one PHY.
“The burden of proof should be on demonstrating the need for two PHYs.”
Therefore I would suggest a variation on Gomez’ suggestion:
"Specify one PHY to support subscriber access networks using the EPON protocol and operating on point-‐to-‐multipoint RF distribution plants comprised of all-‐coaxial cable or hybrid fiber/coaxial media, with enough flexibility to operate both below and above 1GHz and in TDD or FDD duplexing modes."
Thanks,
Hal
From: Charaf HANNA [mailto:charaf.hanna@xxxxxx]
Sent: Tuesday, May 08, 2012 2:37 PM
To: Hal Roberts; STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
Subject: RE: [802.3_EPOC] Latest objectives proposal
Gentlemen,
From the 5 Criteria discussion, it seems to me the reference to more than 1 PHY has to do with passive versus active coax plants rather than below versus above 1 GHz.
Charaf
From: Hal Roberts [mailto:Hal.Roberts@xxxxxxxxx]
Sent: Tuesday, May 08, 2012 2:03 PM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_EPOC] Latest objectives proposal
Kevin,
If a single PHY can operate over the wildly varying conditions found in wireless transmission (i.e. LTE or Wi-Fi with huge swings in signal strength, interference, multipath etc) surely a single PHY should suffice within the more controlled cable environment.
Hal
From: Noll, Kevin [mailto:kevin.noll@xxxxxxxxxxx]
Sent: Tuesday, May 08, 2012 1:53 PM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_EPOC] Latest objectives proposal
There is some concern that operating in the lower bands is significantly different than operating above 1GHz, thus the PHY might need to be different. The reason for "at least one" is not to have equal and competing specifications, but to allow for two implementations that address multiple sets of coaxial conditions.
If the same goal can be attained by a single configurable PHY, then we would probably be okay with that.
--kan--
From: "Gomez Chano (LQNA MED)" <Chano.Gomez@xxxxxxxxxx>
To: Kevin Noll <kevin.noll@xxxxxxxxxxx>
Cc: "<STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>" <STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>
Subject: Re: [802.3_EPOC] Latest objectives proposal
Hi,
I did not attend the last conference calls, but I have been following progress through the reflector. I have a question about the wording in Objective 1, which is now
"Specify at least one PHY to support subscriber access […]"
while previous proposal was:
"Specify a PHY to support subscriber access networks […] "
Can somebody clarify the rationale for the new wording, which seems to "almost" encourage the group to develop more than one PHY? We have all seen other IEEE groups that quickly yielded to the temptation of adopting multiple PHYs as soon as they realized that having the group agree on a single PHY was hard work. I would hate to see the same thing happening in EPoC, as this would cause market fragmentation and slow down adoption.
The objective should be "one PHY". Only if the group finds at a later stage a very good reason to develop more than one PHY then that option should be considered.
Just to be clear, for me it would be OK if the PHY for downstream and upstream channels have different parameters. As long as vendors do not have to face the decision of choosing between multiple and equally valid PHY options when implementing their products, that would still qualify as "one PHY" for me.
Best Regards
Chano Gómez
Lantiq North America
On May 8, 2012, at 9:38 AM, Noll, Kevin wrote:
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