Re: considering covad

[<dsavage@peaknet.net>]

On Tuesday January 27, 2004 "L. V. Lammert" <lvl@omnitec.net> wrote:
> At 10:03 AM 1/27/2004, you wrote:
>
>>On Tue, 27 Jan 2004, L. V. Lammert wrote:
>>
>> > Huh?? DSL max is 18,000 ft, .. we have IDSL customers over 25,000
>> feet right now. 12,000 is not the right number for ISDN.
>>
>>Excuse my error.  It's 18,000'.
>
> 18,000 is a hard limitation for DSL, .. I do know that ISDN can run much
>  further, .. but I cannot find an actual number. Could be related to the
>  pair gain/cable plant condition:
>
>>Loops greater than 18,000 feet must meet ISDN extension technology
>> design requirements and will be considered available if ISDN compatible
>> pair gain systems are in place or planned to serve the area based on
>> scheduled placement of compatible pair gain systems.
>
>
>>My two ISDN circuits are 11,700 and 17,950 respectively.   We do have
>> issues with longer runs on the metro east side.

The key technical point here is that T-carrier signalling can be
regenerated while DSL signalling cannot. Trivia: the original T-carrier
distance spec (which ISDN shares) was the farthest distance in cable feet
between two Ma Bell manholes in downtown Manhatten. It represents the
minimum distance that T-carrier signalling must travel over 24-gauge
copper cable with sufficient signal/noise ratio for a repeater to
understand and regenerate it. The exact number in the spec escapes me, but
it's around 18,000 cable feet. (Depending upon whose database you consult,
my home is between 21,500 and 23,500 cable feet from the Edgemont Central
Office.)

I've never quite understood why T-carrier signaling, especially from
mass-produced hardware, should be any more or less expensive than DSL
signaling (also from mass-produced hardware). True, T-carrier signaling
does support synchronization from reference time standards (i.e. atomic
clocks), but how expensive can such circuitry be when it comes from Taiwan
by the container load? I guess we have the vestiges of a regulated
monopoly to blame for this disparity. A tariff doesn't have to make sense
-- it only has to exist.

The ideal solution to the landline DSL problem would be the so-called
connected blossom architecture in which central office services are
extended to remote nodes (on a pole or in a hole) via high bandwidth fiber
(is there any other kind?). Those nodes, in turn, would serve residential
and business customers in their surrounding areas out to a certain radius
either by DSL or T-carrier signaling. This architecture would eliminate
the costs and limitations of long copper cable runs back to central
offices. Unfortunately SBC/Ameritech and the rest of the Local Exchange
Carrier mafia seem determined to invest in lawyers and behind-the-scenes
lobbying to preserve the regulated status quo, rather than the needs of
their subscribers.

In the mean time, I'll see what WisperISP can offer me in the way of
broadband (802.11?) radio connectivity.

--Doc



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