TELECOM Digest OnLine - Sorted: Re: Satellite GPS Can Locate Wireless Phones Within 15 Feet

Re: Satellite GPS Can Locate Wireless Phones Within 15 Feet

DevilsPGD (
Tue, 06 Dec 2005 02:37:47 -0700

In message <> TELECOM Digest Editor
noted in response to :

> [TELECOM Digest Editor's Note: I have been told GPS does not work that
> well _inside a house or an office_; that its optimal use is when
> attached to an outside thing. Most VOIP set ups are indoors, are they
> not?

Given enough time, a highend GPS receiver can typically get a lock
almost anywhere that gets sunlight. Since I suspect most VoIP gear is
installed and left in place most of it's life, so it would probably
work most of the time.

I've never had a problem getting a GPS lock on a $90 bluetooth GPS
receiver in a hotel, or even in most offices, so I suspect it's

It might take a few minutes to get a lock, but not being able to make
a 911 call for several minutes after an ATA is powered up shouldn't be
a big deal.

Who wants another $90-$200 added to their VoIP gear's price simply for
the convenience of not having to type your address into a website?

> Or, another approach might be for the TA unit to 'listen'
> for '911' being dialed, and then instantly breaking the connection and
> redialing 911 via a landline phone nearby?

If you're wanting to roll this out, and assuming that your ISP
actually knows where you are. Many people VoIP over dialup on a very
regular basis (PPPoE), which doesn't give the ISP any clue about where
you're actually located, but they can still get you to the right call
center which is all the current proposals really attempt to do anyway.

This could be implemented relatively easily with existing
infrastructure if everybody cared enough to make it work.

Establish a domain, lets call it since this is an example.

You could perform a DNS lookup of a magic keyword ""
which participating ISPs would CNAME to the correct city/state/country's
location. The default record (in's zone, for
non-participating ISPs) would route you to a call center equipped to
put you in touch with correct emergency services providers.

Anycast could be used to assist routing for non-participating ISPs.

When you dial 911 (or 112), your ATA would lookup and
connect the call to the appropriate location.

The DNS records returned could be in the form of "TXT PSTN
+1.4035551234" (meaning that the call needs to be terminated like any
other VoIP to PSTN call) or "TXT <protocol>" forms, where
protocols are assigned and managed by the central authority controlling
this system.

The VoIP adapter would also have the ability to perform lookups for records, to provide the
information for a specific locality rather then an unknown/generic
record. An ATA might not be able to use this, but a PC-driven
emergency system could. It would also allow a user to specify the
appropriate call center by city name (for travelers who don't want to
rely on local ISPs).

Since DNS is hierarchical, the number of segments could vary, it could
get as detailed as if needed, the word
"rural" could be used instead of a city if applicable, or a ZIP code
lookup could be done by looking up"

If the VoIP adapter isn't capable of performing the lookup it would
get passed up to the VoIP provider (when applicable) and the VoIP
provider could route it based on account information if applicable.

The advantage of this system is that it takes very little additional
infrastructure, DNS access is basically a given already, plus it
allows an ISP to mirror the zone so things still work when the base
provider is down (so a DDoS won't take out 911 for the entire VoIP

[TELECOM Digest Editor's Note: One question ... you stated above that
'many people use VOIP over dialup frequently', and that confuses me.
I _thought_ the idea of VOIP was to be able to avoid (for whatever
reason) telco landlines. And frankly, although VOIP works over a
dialup line just as it does with broadband, I really did not think
that dialup was 'wide enough' of fast enough to do a very good job. I
know that even with a bigger pipe (let's say, for example, DSL or
cable internet) if you get too much traffic on the line at one time
(for example two or three computers all going at once), as they all
contend for space in the pipe, times get tough. And this is what I
thought was a chronic condition when using something like dialup to
feed your VOIP. Assuming that is not correct, then why wouldn't one
simply use the telephone (on the dialup line) to call 911 and eliminate
all the subsequent steps in the interim you propose?

Now assuming dialup is _not_ a feasable way to run VOIP and that you
are using broadband as I (most people?) do; you _still_ have some
ISP don't you? In my instance, it is, (a national ISP
just like or others.) Can't they be used -- assuming they
would cooperate, etc -- to intercept any '911 dialing' on the VOIP
line and route it back to local authorities, etc? The local ISP would
be in the best position to know where to route the call, etc. PAT]

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