From: Bill Stewart <stewarts@ix.netcom.com>
Date: Wed, 11 Jun 1997 15:09:57 +0800
To: Lucky Green <shamrock@netcom.com>
Subject: Re: [Noise, California only] Good deal on ISDN access
In-Reply-To: <199706110355.FAA10800@basement.replay.com>
Message-ID: <3.0.1.32.19970610232831.006c26e4@popd.ix.netcom.com>
MIME-Version: 1.0
Content-Type: text/plain



At 10:28 PM 6/10/97 -0700, Lucky wrote:
>Assuming you can get 56k over your POTS line. Less than 20% of US
>households can even link up at 28.8k. 

Connecting at 28.8 is a totally different game - it's using
pure analog modems taking advantage of the relatively low noise
of most phone lines, which tend to be either short distances or
carried over T1 local loops.  It's close to the theoretical limit
of what you can get, assuming Gaussian noise distributions,
and of course 33.6 is a lot closer  :-)

The 56kbps cheats, taking advantage of the fact that the
noise on a digital line isn't Gaussian, and is mostly predictable.
It only works from the digital end (an ISP's T1) to the analog end,
and not the other way around, but for most people, that's fine -
anybody who's moving a lot more than 28.8kbps outbound probably
wants more than 56kbps anyway, and meanwhile it's a potentially big win
for the average data consumer.

>ISDN is a clean solution that will work over just about any old wire.
Actually, it's a lot pickier; the line needs to be able to carry
192kbps of digital signal to haul the 2*64+16+overhead kbps of bits.
And if you're too far away, you lose, unless the phone company
throws in a lot of expensive repeater equipment.  On analog, if you're
too far away, your signal just degrades and you get lower bit rates.
But ISDN does work for a lot of people.

>And now it has become rather inexpensive.
Cost and price are totally different questions; your phone company
may vary along with your mileage.  Some places think it's a 
high-value business service and charge big bucks for it;
other phone companies think you're getting 2.25 phone lines
and charge you for 2.  Some, like PacBell, charged a reasonable
monthly rate, assumed most of the use was business and wanted
to stimulate market growth, so they made it free at night,
not realizing what "free at night" means to computer users :-)
We'll see how long their cheap tariff lasts.

>I see little reason to stick with analog. YMMV.



#			Thanks;  Bill
# Bill Stewart, +1-415-442-2215 stewarts@ix.netcom.com
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