From owner-freebsd-hackers Sun May 7 9:39:32 2000 Delivered-To: freebsd-hackers@freebsd.org Received: from mailtoaster2.pipeline.ch (mailtoaster2.pipeline.ch [62.48.0.71]) by hub.freebsd.org (Postfix) with ESMTP id 2F5C037B99C for ; Sun, 7 May 2000 09:39:28 -0700 (PDT) (envelope-from oppermann@pipeline.ch) Received: (qmail 92038 invoked from network); 7 May 2000 16:40:38 -0000 Received: from unknown (HELO pipeline.ch) ([62.48.0.53]) (envelope-sender ) by mailtoaster2.pipeline.ch (qmail-ldap-1.03) with RC4-MD5 encrypted SMTP for ; 7 May 2000 16:40:38 -0000 Message-ID: <39159C75.899C464@pipeline.ch> Date: Sun, 07 May 2000 18:40:21 +0200 From: Andre Oppermann X-Mailer: Mozilla 4.72 [en] (Win98; U) X-Accept-Language: en MIME-Version: 1.0 To: Warner Losh Cc: Nate Williams , Mike Smith , hackers@FreeBSD.ORG Subject: Re: [OT] Finding people with GSM phones (was Re: GPS heads up ) References: <200005061850.MAA18384@nomad.yogotech.com> <200005061840.MAA18274@nomad.yogotech.com> <200005061855.LAA07340@mass.cdrom.com> <200005070549.XAA68658@harmony.village.org> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG 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