From owner-freebsd-hackers Sun May 7 11: 0:34 2000 Delivered-To: freebsd-hackers@freebsd.org Received: from picnic.mat.net (picnic.mat.net [206.246.122.133]) by hub.freebsd.org (Postfix) with ESMTP id 147F437B955; Sun, 7 May 2000 11:00:16 -0700 (PDT) (envelope-from chuckr@picnic.mat.net) Received: from localhost (chuckr@localhost [127.0.0.1]) by picnic.mat.net (8.9.3/8.9.3) with ESMTP id NAA03214; Sun, 7 May 2000 13:59:24 -0400 (EDT) (envelope-from chuckr@picnic.mat.net) Date: Sun, 7 May 2000 13:59:24 -0400 (EDT) From: Chuck Robey To: Warner Losh Cc: Nate Williams , Mike Smith , hackers@FreeBSD.ORG Subject: Re: [OT] Finding people with GSM phones (was Re: GPS heads up ) In-Reply-To: <200005070549.XAA68658@harmony.village.org> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On Sat, 6 May 2000, 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. Curious about that, I haven't been following it too closely, but I know cdma works on codes, not timing ... how do they get timing (other than bit clock recovery)? > > Warner > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-hackers" in the body of the message > ---------------------------------------------------------------------------- Chuck Robey | Interests include C & Java programming, FreeBSD, chuckr@picnic.mat.net | electronics, communications, and signal processing. New Year's Resolution: I will not sphroxify gullible people into looking up fictitious words in the dictionary. ---------------------------------------------------------------------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message