Date: Sun, 07 May 2000 18:40:21 +0200 From: Andre Oppermann <oppermann@pipeline.ch> To: Warner Losh <imp@village.org> Cc: Nate Williams <nate@yogotech.com>, Mike Smith <msmith@FreeBSD.ORG>, hackers@FreeBSD.ORG Subject: Re: [OT] Finding people with GSM phones (was Re: GPS heads up ) Message-ID: <39159C75.899C464@pipeline.ch> References: <200005061850.MAA18384@nomad.yogotech.com> <200005061840.MAA18274@nomad.yogotech.com> <200005061855.LAA07340@mass.cdrom.com> <200005070549.XAA68658@harmony.village.org>
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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 majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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