RE: [EFM] Split ratios
Carlos, yes, I understand all these considerations. That was not my
question. The apparent consensus with splits of 16 and 32 seems to have been
arrived at devoid of any engineering considerations. Those engineering
considerations are exactly what I was suggesting are needed. The final
comment you made of "just don't ask me why" is what I WAS asking.
Use of 16 or 32 for interim discussion purposes is fine; I am just
suggesting we not get too attached to those numbers since other ratios may
prove to be more beneficial for Ethernet PON based on more detailed
considerations. 16 and 32 have not been cast in concrete, correct?
-----Original Message-----
From: Carlos Ribeiro [mailto:cribeiro@xxxxxxxxxxxxxxxx]
Sent: Thursday, July 19, 2001 4:39 AM
To: Horne, David M; 'Roy Bynum'; glen.kramer@xxxxxxxxxxxx
Cc: stds-802-3-efm@ieee.org
Subject: [EFM] Split ratios
At 21:02 18/07/01 -0700, Horne, David M wrote:
>Where did the often-cited split ratios of 16 and 32 come from, anyway?
There are two considerations here. First, there is a maximum limit on the
split ratio, that depends on the power budget and attenuation. I believe
that distance is not going to be the major attenuation factor in the access
network situation; the number of points where you have signal degradation
(connectors, splits, etc) is going to be the major factor. The actual
physical construction of the access network is going to be completely
different, specially if we have any hope of providing FTTH service; there
are a lot of practical and operational issues still unsolved.
The other consideration is economical. A true point-to-point network can be
equated to a 1:1 split ratio. OTOH the split ratio in a PON network can
range from 1:8, 1:16, or even 1:64. Bigger split ratios mean less bandwidth
available for each customer, but it also costs less to deploy. Se rhere is
a cost equation, depending on a lot of factors - technical and marketing
included - that will tell what is the best ratio in economical terms. I
don't expect this answer to be known at this point; we will only be able to
find this number with practical knowledge, ooking at the real situations.
As for myself, I feel comfortable with a 1:16 split ration Just don't ask
me why <wink>.
Carlos Ribeiro
CTBC Telecom