[e2e] 911 and cell phones

David P. Reed dpreed at reed.com
Fri Apr 1 06:53:27 PST 2005

David - exact position may not matter in most cases, but that's what 
Vonage is being beaten up about (I have 911 on the Vonage line 
activated, and it gets through to my local emergency services just fine 
because I told the system when I set it up where that was.)

I note that getting the Massachusetts "state police" is rarely useful 
unless you are driving on the Massachusetts Turnpike (they might as well 
be a call center in Bangalore).   They cannot by law assist you, and do 
not have the best means to pass on calls to localities, who might help 
you if you observe someone being mugged or raped on the street in (say) 
downtown Brockton.

As far as I know, every CDMA cell phone being sold today (the vast 
majority in the market) have GPS in them (in the form of A-GPS, a 
proprietary technology that comes from qualcomm, which used GPS receiver 
in the phone, plus an assist from towers that gets the autonomous GPS 
re-locked fast when it goes out of satellite coverage).   I think that 
GSM phones also all have GPS onboard as well.

You are right that tower triangulation has failed, but the E911 mandate 
for cell phones still holds, and GPS is the technology that has been 
universally adopted, and works pretty well, as far as getting location.

But as I said, knowing approximate or exact location isn't very good if 
the system design actually routes calls away from local responders to a 
single point of failure in some remote, windowless building that has no 
direct local presence.

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