For informational purposes I will show what I use to compare with my stock Iphone. It is an app called emerald time. Screenshot at: https://www.dropbox.com/s/zt6tjrsylrrtrc3/2014-08-04%2008.06.02.png
You can set it up to sync with you own ntp server. I think. You can just spot check it. I have never done a rigorous analysis but it appears to be within 1.5s or better most of the time. Doc Sent from mobile > On Aug 4, 2014, at 7:38 AM, BIll Ezell <[email protected]> wrote: > > LTE does support the long-standard NITZ (network information and time zone) > service. It's an easy way to find out just where you are without having to > change your TZ settings constantly. In fact, if you go to time settings on > HTC Android phones, the 'automatic time update(NITZ)' setting turns on NITZ > syncing. iPhones also use NITZ, as do most 3G or LTE phones. But, not > necessarily for time. > > NITZ implementation is carrier-optional, although almost all do support it. I > know that Vodafone-Austrailia and a handful of other carriers at least at one > point didn't support it. Additionally, the standard doesn't specify how > accurate the time has to be, and it varies widely across providers. It's > usually within a few seconds, but this isn't a high-precision time reference > and can be off by minutes. But, a phone can use the timezone information to > then localize time from some other time service. > > An alternative to determine what your physical location location is uses > lower-level information such as the ECGI (extended cell group identity) or > location information from the MME (Mobile Management Entity). Don't you just > love telecom? Everything's an acronym and frequently an acronym^2 or ^3. > Anyway, the phone then looks up the physical location from whatever id it > uses, then uses a time service to get the actual time, then localizes it > based on the physical location. > > Clearly, just using something like NTP directly isn't all that useful because > you have to know your physical location to know what timezone correction to > apply. > > I work on cell infrastructure, mostly 3G and LTE (Ericsson), and it just > amazes me that phones work at all. It is incredibly complicated and > convoluted. > >> Unlike CDMA (where time distribution was an automatic part of the >> low-level protocol) I suspect the time displayed on many modern phones is >> not set by the telephony synchronous protocol but rather by IP-over-Wifi >> packets. >> >> And the packets don't seem to do a very effective job keeping the clock >> ont he phone correct. My employer gave me a Nokia Lumia 630 "Windows Phone" >> and its clock has always been off by at least a minute. >> >> There was a few years ago, a very nice article about the effort to repair >> the clocks in clock towers in many cities. What rang most true to me was >> "if you visit a town they can't even keep the clock correct, who else knows >> what else is wrong there?". >> >> Tim N3QE > > -- > Bill Ezell > ---------- > The day Microsoft makes something that doesn't suck > will be the day they make vacuum cleaners. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
