GPS for 911 calls

Martin Lefkowitz lefko at
Tue Mar 6 02:53:42 CET 2007

Yes, but for VoIP I believe it is still in flux.  There is an especially 
nasty issue with encryption and 802.11 with the way the standard is 
described because it assumes you are already on the network.  However 
with 802.1x based systems you need to be authenticated.  As far as I 
know this has not completely been worked out. 

It would be great to take advantage of GPS to do this from the 
Application layer without having to modify the 802.11 driver and to send 
802.11 MAC frames.  You also need to make sure you do not send GPS 
coordinates unencrypted because that can be a life and death issue (for 
example a bad guy trying to figure out exactly where the victim is, by 
sniffing the air).  In fact OpenMoko may enable the described scenario 
to happen. 

I can't remember how emergency calls work in regards to TMSI in GSM.


> Date: Mon, 05 Mar 2007 18:56:08 -0500 From: "Perry E. Metzger" 
> <perry at> Ian Stirling <openmoko at> writes:
>> > Michael Welter wrote:
>>> >> What is the protocol for sending the GPS coordinates to the 911 dispatcher?
>> >
>> > I don't think there is one protocol.
>> > Unfortunately, I suspect a 'say GPS coordinates' button on the 911
>> > screen may be the most compatible way.
> Wireless Enhanced 911 for mobiles, including GPS or other
> radiolocation data, is a US standard. I don't know how the signaling
> works, but if you are selling a new phone in the US, it is mandatory
> that you comply.
> Perry

More information about the community mailing list