[Asterisk-biz] Re: 911 legislation

[David Josephson]

>
>Well, I keep asking myself the big question...
>
>Why not GPS?
>
>People can now be located for 911 purposes using GPS devices imbedded in 
>their phones right?
>  
>
Only in limited instances; it has not been universally successful, see 
the article in Consumer Reports 
http://www.consumerreports.org/main/content/display_report.jsp?WebLogicSession=Qmk7mkfww5yghQmT721tknDInJ0FgEeEkMk1YrC29BppoSr5XE21|-5812390185450324277/169937913/6/7005/7005/7002/7002/7005/-1|-6185286871948317168/169937904/6/7005/7005/7002/7002/7005/-1&FOLDER%3C%3Efolder_id=378647&ASSORTMENT%3C%3East_id=333133&bmUID=1114192794902

 "GPS technology" does not necessarily mean there's a GPS receiver in 
the phone. Some carriers use this system, in others GPS is used as a 
timing reference among cell sites (each of which has one or more GPS 
receivers) to allow triangulation to find out where the phone is, but 
each system depends on two-way communication between the phone and the 
cell sites to determine distances. You need either clear view of three 
satellites or contact with several base stations.

>So, why hasn't any of the manufacturers tried to imbed GPS in an ATA?
>  
>
Because GPS requires a fairly unobstructed view of a chunk of the sky to 
function.

If VoIP were to function on a wireless basis, with radio communications 
to sites having known locations, this would be possible because you can 
measure the time it takes for the signal to go and come back to the 
mobile. For wired VoIP, no. Now of course you could require the ATA to 
have a GPS dongle in a window that could see the sky well enough to 
update once in a while. Maybe J. Q. Public would accept that, maybe not.

There are other ways to locate portable devices that are used in a fixed 
location precisely enough for E911 (FCC hopes for 50 meter accuracy 66% 
of the time, which seems silly, particularly in cities) that don't 
require GPS. This is more of a business model problem (which is why I'm 
posting here) than a technical one. That's possible for me to say only 
because I'm an RF engineer and have designed a couple of approaches 
based on existing technology that would work for this. It's definitely 
on a far back burner for me, however. If someone would like to take this 
concept to market, email me at vbiz at altaphon.com. It would be fairly 
simple to prototype such a system, and there is no significant 
regulatory barrier to setting it up nationwide.