Return-Path: Received: from rly-df12.mx.aol.com (rly-df12.mail.aol.com [172.19.156.25]) by air-df03.mail.aol.com (v121.5) with ESMTP id MAILINDF034-595485b8d8d3bb; Fri, 20 Jun 2008 06:59:40 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by rly-df12.mx.aol.com (v121.5) with ESMTP id MAILRELAYINDF124-595485b8d8d3bb; Fri, 20 Jun 2008 06:59:28 -0400 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1K9eK5-0000gI-OQ for rs_out_1@blacksheep.org; Fri, 20 Jun 2008 11:58:29 +0100 Received: from [193.82.116.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1K9eK5-0000g9-Cm for rsgb_lf_group@blacksheep.org; Fri, 20 Jun 2008 11:58:29 +0100 Received: from ams-iport-1.cisco.com ([144.254.224.140]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1K9eK1-00074k-JB for rsgb_lf_group@blacksheep.org; Fri, 20 Jun 2008 11:58:29 +0100 X-IronPort-AV: E=Sophos;i="4.27,678,1204498800"; d="scan'208";a="12226399" Received: from ams-dkim-2.cisco.com ([144.254.224.139]) by ams-iport-1.cisco.com with ESMTP; 20 Jun 2008 12:58:19 +0200 Received: from ams-core-1.cisco.com (ams-core-1.cisco.com [144.254.224.150]) by ams-dkim-2.cisco.com (8.12.11/8.12.11) with ESMTP id m5KAwJVx017196; Fri, 20 Jun 2008 12:58:19 +0200 Received: from dhcp-64-103-102-184.cisco.com (dhcp-64-103-102-184.cisco.com [64.103.102.184]) by ams-core-1.cisco.com (8.13.8/8.13.8) with ESMTP id m5KAwIZP018303; Fri, 20 Jun 2008 10:58:19 GMT Message-ID: <485B8D4B.5050505@g3ysx.org.uk> Date: Fri, 20 Jun 2008 11:58:19 +0100 From: Stewart Bryant User-Agent: Thunderbird 2.0.0.12 (Macintosh/20080213) MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <005301c8d182$93d802a0$0200a8c0@LapTop1> <008f01c8d189$47145a20$0900a8c0@AM> <485A7BC5.1080206@g3ysx.org.uk> <731EB49F88B309428FFDDD2423F810E441C00F@HERMES4.ds.leeds.ac.uk> In-Reply-To: Authentication-Results: ams-dkim-2; header.From=stewart@g3ysx.org.uk; dkim=neutral X-Karma: 0: X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,none Subject: Re: LF: Re: Loran C Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=none autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-AOL-IP: 193.82.116.20 X-AOL-SCOLL-AUTHENTICATION: domain : post.thorcom.co ; SPF_helo = X-AOL-SCOLL-AUTHENTICATION: domain : g3ysx.org.u ; SPF_822_from = X-Mailer: Unknown (No Version) US base stations do need time ... and yes they do have have GPS receivers (which BTW are not cheap) at the towers. However I assumed that we were talking about the UK when I answered. When the IETF TICTOC WG files its reports on the Paris Interim that happened earlier this week I will point you to a chart that shows current and NG services and what the timing requirements are. As for GSM referenced below, there is definitely no external time reference used - just 50ppb or better frequency reference. Stewart G3YSX Andy Talbot wrote: > The whole over-air interface for the mobile phone system has to be > locked - the frame structure in GSM is critical to microseconds, and > has to be synchronised between all base stations. I believe 3G is > even more time-critical, with the PN codes carefully adjusted for > multiple users, with fine tuning for base-mobile delay. So they must > have accurate timing somewhere, but is it derived locally or is there > a central distribution. >