Vonage Selects TCS For VoIP E911 Service

Wed Jul 20 09:57:49 UTC 2005

At 10:32 AM +0100 2005-07-20, Michael.Dillon at btradianz.com wrote:

>>  While I agree that GPS is the likely answer, I wasn't expecting the
>>  ability to work inside computer rooms and basements.
>
>  It doesn't need to work in basements, etc. It only needs to keep
>  a record of the last location it was at when the signal faded
>  away. The emergency service vehicles probably can't get any closer
>  than that anyway.

	I've been doing some reading on this subject.  It seems that both 
GPS and tower triangulation methods suck.  For GPS, the problems are 
signal acquisition and penetration in urban environments, especially 
with non-dedicated handheld devices.  For tower triangulation, the 
problem appears to be areas with poor signal coverage where you might 
only be able to barely see one tower, and where TDoA, AoA, and EOTD 
aren't going to do you any good.

	In either case, simply keeping the last known signal lock may 
very well be one of the worst things you could do.

	It seems to me that we need to use both technologies in order to 
get any real hope of reasonably sustainable accuracy, either for E911 
or any other location-aware technology.  And I'm not convinced even 
that's enough.

	So, anyone want to place any bets on what's really going to happen?

-- 
Brad Knowles, <brad at stop.mail-abuse.org>

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."

     -- Benjamin Franklin (1706-1790), reply of the Pennsylvania
     Assembly to the Governor, November 11, 1755

   SAGE member since 1995.  See <http://www.sage.org/> for more info.