> If I understand it right, CDMA requires extremely precise timing > to work, but the other protocols do not...
Correct. Basically, when a CDMA phone starts looking for service, the first thing it has to do is to synchronize its clock to the sync channel on the base station. That sync channel tells it when + how to look for the rest of the information it needs to actually get on the network, and when it is allowed to speak, based on its serial number. So, a CDMA time receiver would only have to perform the first part of process that a phone performs. And you don't really need to go past the sync channel. So, you can be receive only, and still get time from a CDMA basestation. OTOH, both GSM + WCDMA networks are set up so that absolute time isn't important. They do broadcast time, but it's part of the message that is received when you have actually registered with the basestation. so, it isn't continually rebroadcast, and isn't all that accurate in the first place. (If you get 1s accuracy, you're doing pretty well. For a long time, it seemed like the US carriers were broadcasting time from a PC whose clock was set by hand every year or 2 from someone's watch. It was usually wrong by minutes.) The big problem with this is that it would be more difficult to get time on a GSM/WCDMA network as you need to be able to speak enough of the protocol to talk to a basestation. You've basically just created a phone without a mic or speaker. And, even then, time isn't required to be broadcast on the network, although it usually is these days. --Carl Ask Bjørn Hansen wrote: > On Sep 22, 2007, at 6:37, Jan Hoevers wrote: > > >> For some weeks I've been looking for equipment to get time from >> european GSM or UMTS networks, so far to no avail. Is anyone using >> such >> equipment? >> > > If I understand it right, CDMA requires extremely precise timing to > work, but the other protocols do not... > > Keep in mind though that CDMA time is based on "GPS time", so it's > just a different delivery path for GPS time, rather than a true > alternative. > > In Europe I believe the DCF77 system is a real alternative to GPS. > > > - ask > > _______________________________________________ timekeepers mailing list [email protected] https://fortytwo.ch/mailman/cgi-bin/listinfo/timekeepers
