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RE: [EFM] EFM Requirements

Than you for the input.  Do not get too focused on the absolute number since
it will vary a lot. 

The key idea is that the need for fiber overbuild and the number of street
corner DSLAM pedestals is inversely proportional to the square of the reach.
The shorter the reach, the higher the cost per revenue producing subscriber
in the earlier years and the longer it will take to build out the network.

As an optimum, the reach should be equal to the distances that the voice
digital loop carrier (DLC)systems are designed for.  This would allow the
placement of the EFM equipment at existing DLC locations.

-----Original Message-----
From: Hugh Barrass [mailto:hbarrass@xxxxxxxxx]
Sent: Monday, August 13, 2001 4:53 PM
To: Sherman Ackley
Cc: Stds-802-3-Efm (E-mail)
Subject: Re: [EFM] EFM Requirements


Thank you for your input. I recognize that your viewpoint is based on the
provision of service to rural areas and I have some difficulty with the
applicability of your numbers.

Firstly the coverage:

3km, 100 homes. If we assume 3km radius, that is an area of ~28million
metres. this is equivalent to 282,000 square metres per home - this is
for farmland. I suggest that sfh density in suburban areas will be close to
times denser than your example.

Secondly HPNA coexistance:

It is not certain (or even likely) that HPNA will solve the home networking
needs now and into the future. Even HPNA-2 has barely enough bandwidth to
for current applications and it is difficult to guarantee QOS. HPNA requires
bridging between multiple phone line and it does not solve the problems of
reaching places where there is no current phone socket (i.e. TV locations or
other connected appliances). Outside the US, the prevalence of multiple
sockets is much lower. As soon as rewiring is required then FireWire or
(cheers!) is a better alternative. The best candidates for existing media
802.11a and HomePlug (if it can reach the bandwidth required).

Even if HPNA is used, it may be possible the 802.3ah CPE device will act as
filter to separate the HPNA signals from the local loop. It is also possible
that the FCC may require that HPNA signals are prevented from leaking onto
local loop by insertion of a filter in any case.

Thirdly rate and reach expectations

As an engineer, I feel that I should warn anyone who is asking or expecting
service well beyond the Shannon capacity of the media that their
will probably never be met. A data rate of 10Mbps at a distance of 12km on
telephone wiring is not just beyond current technology, it is beyond the
laws of

I suggest that in rural areas you should be considering fiber-based


Sherman Ackley wrote:

> Service Provider Requirements for Ethernet in the First (two) Mile(s):
> Sherman L. Ackley, CTO
> The National Rural Telecommunications Cooperative provides services to
> 350 member independent telephone companies who serve over 6 million access
> lines.  Ethernet in the first mile is the most promising technology for
> delivery of integrated voice, video and data services in the suburban and
> rural areas served by our Members.  As the Chief Technology Officer for
> NRTC, I would like to submit some practical requirements as seen by the
> service providers most likely to implement this technology in the USA.
> intent of this contribution is to help the study group prepare the
> requirements document based on actual needs.
> The user locations will be 90 percent residential and 10 percent business.
> Of those businesses, 90 percent will have 10 or fewer PCs.
> The system must work over standard high capacitance telephone outside
> cable.  Binder group integrity is not assured.  The technology should not
> force removal of bridge taps and end sections.  It needs to operate
> degradation at binder group fills over 70%.
> System reach is the most important aspect of the design.  Ethernet in the
> first mile must operate over the longest reach possible.  The number of
> households and small businesses served by a node is proportional to the
> square of the reach.  For example, a reach of 3 km can serve about 100
> single-family homes per node. Doubling the reach to 6 km increases the
> served per node to 400.  And with a 12 km reach, 1600 homes per node can
> served.  This assumes 100 percent subscribe.  At 25 percent subscription,
> short reach technology gets down to some dismal financial outlooks in
> of cost per revenue producing subscriber as well forcing the construction
> too many street corner server nodes.
> Coexistence with HomePNA on the same cable pair is essential.  This
> will be necessary in over 75% of households served with Integrated
> services.  For example, a data stream of 10 Mbps will support two MPEG-2
> high-resolution standard TV signals.  The DSL will carry this to the
> service set-top box/home gateway that can be located anywhere in the
> The Gateway device will terminate the video and data for use at the
> TV, it will then forward the second video and data over the same cable
> to other set-top boxes and PCs within the house using HomePNA.
> Peer-to Peer (or server to server) communications requires that the
> be adaptable so that full rate is available upstream or downstream as
> required by the user generated traffic.  For example, it is now possible
> record MPEG-1 video on a camcorder and e-mail it over the Internet.
> Unfortunately, sending the e-mail over a conventional fixed data rate
> ADSL/VDSL system takes forever for the 20 Mbps file.
> There is little demand for sending three simultaneous MPEG-2 video streams
> to the home.  This is based on the analysis of over 20 million DBS and
> digital cable subscribers.  In fact, two streams are required in only 30
> percent of households.  It is far more economical to install a second
> Ethernet Subscriber Loop (ESL) for the one in 100 who want three HDTV
> than to burden all with the high costs required to support a higher bit
> short reach technology such as VDSL.
> In conclusion, long reach is of paramount importance.  For delivery of two
> Standard TV signals, 10 Mbps at 12 km is required.  For one HDTV plus one
> Standard TV, 20 Mbps at 12 km is desired.  Also, the selected technology
> should allow data to flow in either direction at the full data rate.
> Finally, the technology should be spectrally compatible with HomePNA
> requiring the use of a splitter at the residence.
> Finally, feedback on these ideas from other service providers and vendors
> invited.