Robert Bonomi wrote:
> In article <telecom24.291.5@telecom-digest.org>,
> Choreboy <choreboyREMOVE@localnet.com> wrote:
>>>> I wonder how a DSL signal can carry 1.5M through those mile of wire.
>>> DSL uses a different 'signalling technology' for sending the data down
>>> the wire.
>>> The DSL signal does _not_ go through those 'voice-grade'
>>> analog-to-digital converters that PSTN calls do. the signal is
>>> isolated before that point, and dumped into a totally _different_ kind
>>> of receiver.
>> Is DSL modulated into some sort of analog signal? It's hard to imagine
>> carrying hig-frequency digital pulses on copper telephone lines.
> Get thee to a _library_. they have entire books on the subject.
There's no library around here. I have searched the internet without
success. I hope you'll share your knowledge.
>>> DSL _does_ suffer 'performance losses', as the wire length gets
>>> greater. The degree of degradation is considerably worse than with
>>> POTS modems. E.g., at 1,000' from the C.O. you may be able to get
>>> several megabits/sec. at 15000 ft, you'll be lucky to get 256k. At
>>> 18,000 ft, even 144kbit/sec is iffy. Beyond 25,000 ft, "forget it"
>>> applies -- an analog POTS modem is higher performance.
>> The farm appears to be 35,000 feet from the central office. My browser
>> often shows downloads faster than 1.5 Mb/s (150kB/s).
> That which "appears" to be the situation is often not the reality.
> There may be a 'remote node' outlying from where you "think" the central
> office is. The DSLAM equipment can be located there.
You said DSL speed depends on the distance from the CO. I told you
how far it is to the CO. I don't understand how the presence of a
node would mean the CO was somewhere else.
I have read that with a new cluster of houses, the teclo may use a
high-speed cable to bring service to a terminal near the houses. I
understand the terminal will make it impossible for residents to dial
up at V.90 speeds. That doesn't sound like the case at the farm,
where we had V.90.
>> Some modern phones sound very good. It depends on who's calling.
> Some phones are made cheaper than others. <grin>
Features other than sound make phones expensive. How many people
listen before buying? If you get it home and the sound isn't clear,
it may not be clear that the problem is with the phone. If frequency
response and distortion were published, they could be strong selling
points, as with hi-fi gear.
>>>> As far as capacity goes, I don't know how fast is the digital stream
>>>> for a voice call,
>>> After digitalization, a standard POTS voice-grade call uses 64000
>> bits/sec.
>> Is that between telco facilities?
> Or even between the telco and _customer_ facilities that use 'digital
> entrance' to the telco.
>>>> but I'm sure DSL at 2.5Mb/s requires much more of the telco's
>>>> capacity.
>>> "Not Exactly" applies here. The DSL signal rides the wires from the
>>> customer premises _to_ the telco switching facility. *BUT* before it
>>> would get to the telco switching gear, it is separated out,
>>> segeregated, and sent to some *entirely*different* equipment -- called
>>> a DSLAM, if you care. Frequently that DSLAM equipment does *NOT*
>>> belong to the telephone company, but to the company providing DSL
>>> services. the 'upstream' connection out of the DSLAM is a dedicated
>>> data circuit -- possibly rented from the telco, but often _also_
>>> supplied by the company that runs the DSLAM. Regardless, it is not
>>> using up any capacity on the Telco's VOICE network.
>> If the telco owns the DSLAM, won't their investment cost depend on
>> capacity? If they contract for the DSLAM service, won't they be
>> charged according to traffic?
> If the telco itself is offering/providing DSL service, then it is
> virtually certain that they own the DSLAM equipment. If a third-party
> provider is doing the DSL provisioning, then the incumbent telco may,
> or _may_not_ have any involvement with the DSL equipment.
> As to 'how things are priced/charged-for', that's a whole 'nuther
> kettle of fish. Some arrangements are 'flat rate', where you pay a
> fixed price for the capacity that is available to you. Pthers are
> so-called 'burstable' rates, where you pay based on how much traffic
> you send.
I understood another poster to say the telco's big cost for DSL is in
the DSLAM equipment they must purchase for a peak capacity. If 1,000
customers had DSL at 1.5Mb/s, I wonder how much peak capacity they
would need compared to 1,000 DSL customers limited to 150kb/s.
Choreboy (choreboyREMOVE@localnet.com)