[EFM] meaning of DBA in context of TDMA
Hi All,
The TDMA access scheme in the uplink means static-multiplexing between ONUs.
This is a zero statistical-multiplexing scenario. DBA introduces dynamic
changes to the TDMA structure, allowing for statistical-multiplexing.
If we wish to gain statistical gain of any kind, DBA mechanisms must exist.
So in fact, DBA as presented does not convey a 20% gain over Statistical
Muxing. It's an enabler for any type of statistical gain at all.
In EPON this means the difference between a static 31Mb link, and the
ability to burst to 1Gb on demand.
Ariel Maislos
Passave
-----Original Message-----
From: owner-stds-802-3-efm@majordomo.ieee.org
[mailto:owner-stds-802-3-efm@majordomo.ieee.org]On Behalf Of Dolors Sala
Sent: Tuesday, July 17, 2001 2:23 PM
To: Menard, Francois
Cc: Roberts, Hal; stds-802-3-efm@ieee.org
Subject: [EFM] EPON requirements and evaluation scenarios
"Menard, Francois" wrote:
> > I confess I am a little lost by the 20% bandwidth loss number.
>
> You seem to have missed the beginning of the thread ;)
> I'm not stating this number, Ajay at Broadcom is. He is saying that DBA
> confers a 20 to 30% bandwidh advantage over Stat Mux. DBA is equivalent
to
> request/grant mechanisms of DOCSIS.
This number comes from simulation results of two specific scenarios given in
our
presentation.
It is difficult to evaluate the advantage of statistical multiplexing
because it
is different for every scenario. It depends on the number of users sharing
the
bandwidth, the traffic generated and other factors. Those particular
examples
were for 32 ONUs. So this 20-30 only applies in that context.
We can only agree on the need of DBA or not once we have the evaluation of
the
target scenarios for the design. We can then discuss if this x% improvement
for
each scenario is cost effective for the added complexity.
Hence it is important to agree on the EPON specific requirements and
evaluation
scenarios. And this is one of the topics/presentations scheduled for the
next
meeting. I, Glen Kramer, and JC Kuo have volunteered to prepare it. I am
currently drafting a first version of it based on what it has been presented
so
far. Any additional comments or specific suggestions for the list are
welcome.
We can discuss and approve the individual requirements and scenarios during
the
EPON sessions in the meeting.
Dolors