Re: [OT] Finding people with GSM phones (was Re: GPS heads up )

[Andre Oppermann]

Warner Losh wrote:
> 
> With CDMA, you can get a distance very easily.  The phones know what
> time it is, or CDMA doesn't work at all.  That helps a lot.  Much of
> GPS's work is knowing what time it is.  Since the phone knows what
> time it is, they can do all kinds of calculations and round trip
> things to get the distance.  From there, you have a 120degreep arch to
> worry about.  Since CDMA towers have 3 antennas, you likely get use
> slight phase differences between them to narrow it down further.  The
> CDMA folks at qualcomm tend to be smart (although as they have gotten
> larger, this tendacy is weaker than it was), so I wouldn't be
> surprised if they thought real hard and were able to do something
> simple in the end because it happened to fall out of the equasions.

Have a look at page five of this document:

 http://www.3GPP.org/News/Mobile_news_2000/Mobile_News.pdf

It describes the various ways on how to locate a mobile and which
are likely to become a standard.

-- 
Andre


To Unsubscribe: send mail to [EMAIL PROTECTED]
with "unsubscribe freebsd-hackers" in the body of the message