Re: [802.3_EPOC] EPoC Bandwidth Discussion
It’s easy to see how bandwidth married bit rate and lived happily ever after. When discussing simple on-off keying or NRTZ for digital signaling, the first approximation for the required spectral bandwidth (i.e., the maximum frequency of the digital signal) for a specific bit rate was (bit rate)/2.
Now, back to solving the terminology issue…
Curtis
From: Hal Roberts [mailto:Hal.Roberts@xxxxxxxxx]
Sent: Monday, August 20, 2012 7:17 PM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_EPOC] EPoC Bandwidth Discussion
Ha! Great point Jorge.
I guess we are just ‘polluted’ with the bandwidth terminology for data rate.
I come from a physics background so my bias is obvious.
I think we all agree that a common understanding of terminology is most important.
I see Rajeev basically said the same in a concurrent post.
-H
From: Salinger, Jorge [mailto:Jorge_Salinger@xxxxxxxxxxxxxxxxx]<mailto:[mailto:Jorge_Salinger@xxxxxxxxxxxxxxxxx]>
Sent: Monday, August 20, 2012 8:10 PM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>
Subject: Re: [802.3_EPOC] EPoC Bandwidth Discussion
If we don't leave bandwidth alone, do we need to change DBA?
From: Salinger, Jorge [mailto:Jorge_Salinger@xxxxxxxxxxxxxxxxx]<mailto:[mailto:Jorge_Salinger@xxxxxxxxxxxxxxxxx]>
Sent: Monday, August 20, 2012 09:07 PM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx> <STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>>
Subject: Re: [802.3_EPOC] EPoC Bandwidth Discussion
Hal,
How about we leave bandwidth alone as it is used in EPON, and use the term spectrum to refer to RF capacity? I think that should work just fine with EPON folks and cable heads.
Jorge
From: Hal Roberts [mailto:Hal.Roberts@xxxxxxxxx]<mailto:[mailto:Hal.Roberts@xxxxxxxxx]>
Sent: Monday, August 20, 2012 08:50 PM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx> <STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>>
Subject: Re: [802.3_EPOC] EPoC Bandwidth Discussion
All,
EPoC has introduced the RF concepts of spectrum, spectral width, channel width to EPON and it is not surprising that there is “bandwidth confusion”.
Geoff is correct with his analogy to the highway, road width vs. cars per minute, but that doesn’t change the EPON usage of the term “bandwidth” for “data rate” in the past.
We can be purists and say that bandwidth should always refer to the width of the RF spectrum for a channel. Or we can recognize that this will result in confusion and adopt terms in EPoC that are not subject to confusion.
So the term “bandwidth” as a stand in for “channel bit rate” or “data rate” should be banished. But we should not assume that “bandwidth” will now always be recognized to refer to the RF attribute.
“RF Bandwidth” or Spectral Bandwidth” would seem to do the job for the RF side. For the digital side it seems like it will be hard to settle on a single term but the ones that Geoff suggested work for me.
Hal
From: Marek Hajduczenia [mailto:marek.hajduczenia@xxxxxxxxx]<mailto:[mailto:marek.hajduczenia@xxxxxxxxx]>
Sent: Monday, August 20, 2012 7:28 PM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>
Subject: Re: [802.3_EPOC] EPoC Bandwidth Discussion
Jorge,
In EPON, we used term “bandwidth” in the meaning of “data rate” / “channel capacity”, which in the retrospect perhaps was not the best idea. For example, we had statements like “Flexible architecture allowing dynamic allocation of bandwidth”, which does not speak of spectrum allocation, but rather channel capacity allocation. I could produce more examples where it is used in this context, but I think you get the idea where it is going.
In general, EPON we only spoke of wavelength / wavelength band allocation in Clause 75/60, which is effectively spectrum allocation. However, the term used was “wavelength” and ”wavelength band/range”.
Does this help ?
Marek
From: Salinger, Jorge [mailto:Jorge_Salinger@xxxxxxxxxxxxxxxxx]<mailto:[mailto:Jorge_Salinger@xxxxxxxxxxxxxxxxx]>
Sent: Tuesday, August 21, 2012 01:15
To: Marek Hajduczenia; stds-802-3-epoc@xxxxxxxxxxxxxxxxx<mailto:stds-802-3-epoc@xxxxxxxxxxxxxxxxx>
Subject: Re: [802.3_EPOC] EPoC Bandwidth Discussion
Marek,
I understand.
So, how is the term bandwidth used in EPON parlance? I looked down in the thread and can't see an example, but maybe I missed it.
Thanks!
Jorge
From: Marek Hajduczenia <marek.hajduczenia@xxxxxxxxx<mailto:marek.hajduczenia@xxxxxxxxx>>
Date: Monday, August 20, 2012 8:08 PM
To: "Salinger, Jorge" <Jorge_Salinger@xxxxxxxxxxxxxxxxx<mailto:Jorge_Salinger@xxxxxxxxxxxxxxxxx>>, EPoC Study Group <STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>>
Subject: RE: [802.3_EPOC] EPoC Bandwidth Discussion
Jorge,
The only concern that I have with this is that multiple times we speak of “bandwidth” without other denominators, leaving it open to interpretation.
While I can certainly understand where Geoff would like us to go, if we set different terminology from what was used in EPON before, we will create a rift and people who understand EPON, will have to get used to a different terminology for EPoC, something that I’d rather (personally) avoid.
Marek
From: Salinger, Jorge [mailto:Jorge_Salinger@xxxxxxxxxxxxxxxxx]
Sent: Tuesday, August 21, 2012 01:04
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>
Subject: Re: [802.3_EPOC] EPoC Bandwidth Discussion
All,
No quite being an RF guy, but having worked in the cable industry for over 20 years… (for those thinking that I am old… I started when I was 19 years old ;-)
My 2 cents…
I would propose that when speaking of RF capacity we refer to it as spectrum. So, in the case of the discussion referenced by this Email thread, we say "spectrum for EPoC" or "EPoC spectrum".
I think that the term bandwidth can be ambiguous unless it is used in a specific context, such as "the bandwidth of an analog cable channel is 6 MHz" and I also hear "the bandwidth of the highest HSD tier is 300 Mbps".
Jorge
From: Duane Remein <Duane.Remein@xxxxxxxxxx<mailto:Duane.Remein@xxxxxxxxxx>>
Reply-To: Duane Remein <Duane.Remein@xxxxxxxxxx<mailto:Duane.Remein@xxxxxxxxxx>>
Date: Monday, August 20, 2012 1:15 PM
To: EPoC Study Group <STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>>
Subject: Re: [802.3_EPOC] EPoC Bandwidth Discussion
Geoff,
I see your point, could we at least agree to preface there term with “Spectra” when referring to RF (old habits, the only kind I have at this point, die hard)?
Best Regards,
Duane
FutureWei Technologies Inc.
duane.remein@xxxxxxxxxx<mailto:duane.remein@xxxxxxxxxx>
Director, Access R&D
919 418 4741
Raleigh, NC
From: Geoff Thompson [mailto:thompson@xxxxxxxx]
Sent: Monday, August 20, 2012 1:04 PM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>
Subject: Re: [802.3_EPOC] EPoC Bandwidth Discussion
Colleagues-
Just goes to show the extent to which Wikipedia is not an authoritative source.
The answer to this question is obvious within the word itself. Bandwidth is the width of the spectral band, i.e. it is an analog measurement.
The so called "digital bandwidth" is not a bandwidth it is "channel capacity" or "data rate" or "bit rate".
To illustrate how silly it is to use the spectral term for the digital term just think of it in concrete terms.
You would never use the term "pavement width" when you mean "cars per hour".
I took a brief tour of older clauses of 802.3 and the term is mostly used correctly. There are several instances (which are unfortunately duplicated in several places) where "bit rate" would have been more accurate.
I would strongly prefer that we preserve its analog meaning and use other appropriate terminology for digital rate measurement (even if it means bucking current common terminology).
Geoff Thompson
On 208//12 9:22 AM, Hesham ElBakoury wrote:
Jim,
Wikipedia defines bandwidth as follows:
Bandwidth has several related meanings:
* Bandwidth (signal processing)<http://en.wikipedia.org/wiki/Bandwidth_%28signal_processing%29> or analog bandwidth, frequency bandwidth or radio bandwidth: a measure of the width of a range of frequencies, measured in hertz
* Bandwidth (computing)<http://en.wikipedia.org/wiki/Bandwidth_%28computing%29> or digital bandwidth: a rate of data transfer, bit rate or throughput, measured in bits per second (bps
Hesham
From: Jim Farmer [mailto:jfarmer@xxxxxxxxxx]
Sent: Monday, August 20, 2012 8:50 AM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>
Subject: Re: [802.3_EPOC] EPoC Bandwidth Discussion
Unfortunately, as if often the case, we have multiple different definitions for the same term – as an RF nerd myself, I had difficulty getting used to “bandwidth” referring to data. But the data usage certainly is a common use of the term. If we need to differentiate the two, I’d suggest the shorter term “RF bandwidth” when we need to differentiate the two.
Thanks,
jim
Jim Farmer, K4BSE
Chief System Architect,
FTTP Solutions
Aurora Networks
1220 Old Alpharetta Rd.
Ste. 370
Alpharetta, GA 30005 USA
678-339-1045 (office)
678-640-0860 (mobile)
jfarmer@xxxxxxxxxx<mailto:jfarmer@xxxxxxxxxx>
From: Duane Remein [mailto:Duane.Remein@xxxxxxxxxx]
Sent: Monday, August 20, 2012 11:32 AM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>
Subject: Re: [802.3_EPOC] EPoC Bandwidth Discussion
Steve,
Your use ot the term “bandwidth” completely threw me, I’ve always associated this term with data bandwidth.
Can I suggest we use something like Spectrum Channel Width – defined as a portion of RF spectrum dedicated to a transmission channel or sub-channel.
Once we agree on such a term Marek can then add this to the definitions list.
Best Regards,
Duane
FutureWei Technologies Inc.
duane.remein@xxxxxxxxxx<mailto:duane.remein@xxxxxxxxxx>
Director, Access R&D
919 418 4741
Raleigh, NC
From: Shellhammer, Steve [mailto:sshellha@xxxxxxxxxxxx]
Sent: Friday, August 17, 2012 6:42 PM
To: STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx<mailto:STDS-802-3-EPOC@xxxxxxxxxxxxxxxxx>
Subject: [802.3_EPOC] EPoC Bandwidth Discussion
EPoC Group,
Several of us had a good discussion on EPoC bandwidth this morning. I would like to see if there are other who would like to join us for future calls on Friday mornings (10 AM Pacific Time).
If anyone else would like to join us, please send me an email and I will add you to the meeting invite.
Once we have some slides put together we will review them on the Monday AM calls, hosted by Comcast.
Steve
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