On 9/22/07, Björn Gabrielsson <[EMAIL PROTECTED]> 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? > > I have not seen any. I guess the market is rather limited.
The reason CDMA reference clocks are so popular is that CDMA systems require a tremendous degree of accuracy and precision in the synchronization of time between base transmitter sites and mobile units, and that the CDMA (IS-95) spec calls for the entire network to be synchronized to UTC as opposed to any other time base. If I remember correctly, GSM "only" requires synchronization between its network elements to a precision of something like 1 or 2 ms. However, I don't think that's the main reason for the lack of GSM timing equipment. I suspect that there is no requirement in the GSM spec that a GSM network as a whole be synchronized to UTC as opposed to some other time standard (which could be completely made up by the operator as long as it is internally consistent). Of course, most GSM operators do maintain some sort of time-of-day standard, otherwise they wouldn't be able to set the clocks on subscribers' handsets to meaningful values. I don't know how this system works, but I suspect it may use a completely separate reference clock than what is used for network timing. I have not researched it at all, but I would assume the time sync requirements for UMTS are at least as stringent as those for IS-95 CDMA. Nevertheless, I cannot find any UMTS time receivers on the market. Perhaps the UMTS specification, while calling for close synchronization, does not mandate that the network be synced to UTC either? Even if the above is true, I would think you could at least derive an accurate pulse-per-second signal from UMTS and a slightly less accurate one from GSM. The pulses wouldn't necessarily correspond to the beginning of a UTC second, and there wouldn't necessarily be any other usable time code beyond the PPS pulses but it still seems like such a device could be useful in conjunction with outside NTP servers. Well, that's my speculation on the topic. I'd be interested to hear an explanation of this from someone who knows more about it than I. Rusty _______________________________________________ timekeepers mailing list [email protected] https://fortytwo.ch/mailman/cgi-bin/listinfo/timekeepers
