Cell Network time no longer provided [telecom]

My mother complained that her phone time did not update to daylight savings time and she was told by AT&T that they no longer provide time on their network. This morning I got a notification on my Galaxy S5 that network time is not provided, switching to manual. Cell providers have been providing time forever. I think this is a quiet change at least by AT&T, but I'm sure it is with other networks also.

Reply to
Jerry Feldman
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CDMA networks (Verizon, Sprint, and their MVNOs) are unlikely to make that change because they MUST have accurate time sources available at every cell site. Correct operation of the network requires that the sites be synchronized within milliseconds, because CDMA does soft handoffs as you travel. The network can reassemble partial reception from more than one site to piece together your conversation, and that requires that the timing be accurate. It's done by having a GPS time reference at each site. Since accurate time must be available in any case, they might as well continue to provide it to customers.

T-Mobile, the other major GSM network in the US, still provides network time.

Reply to
Shirley Márquez Dúlcey

They have to have precise timing to make CDMA soft-hand-off work, but does that necessarily translate into providing the civilian time information that the phone OS is looking for?

"Time", in a physics sense, is pretty simple. Some cool relatively stuff, and questions about why it is unidirectional notwithstanding.

But "time", in a civilian sense is complicated as hell: We want it to line up with contradictory celestial stuff and the changing whims of law makers on various levels of government and in various geographies.

Providing precise phase information to CDMA isn't the same as knowing when daylight saving time begins. Might they have just dumped the civilian part? Remember, GPS time is now many seconds off of the seconds-portion of civilian time.

Also, aren't the old GSM carriers now using updated protocols that are getting all spread spectrum on us? Do they need some of that precise timing coordination now, too?


Reply to
Kent Borg

So far, US carriers are still using legacy protocols (GSM and CDMA) for voice calls and text messages. Higher speed protocols (HSDPA, HSPA+) are used for the data side by GSM carriers; CDMA carriers use EVDO. Both use LTE for their latest data offerings. They are starting to implement VoLTE (voice over LTE) as a replacement for legacy protocols but it will be years until the switch is complete.

I don't know whether LTE includes any notion of time services; if not, the current notion of carrier-provided time will go out the window when LTE-only devices start to appear. But any LTE-capable device could easily synchronize to an NTP server on the internet if the OS includes that capability. So far as I know neither iOS nor Android currently does, though you can get third party apps to add automatic NTP synchronization to a rooted Android device.

Reply to
Shirley M?rquez D?lcey

I haven't checked it recently, but it used to be that when driving across Vermont on I-89 my Android GSM-style phone's time would jump several seconds as we entered the territory of some podunk wireless carrier, and jump back when returning the territory of a first world wireless carrier.


Reply to
Kent Borg

In article ,

Microseconds, actually. The spec says 15 microseconds, if I recall correctly.

They can't turn it off -- distribution of UT_{gps} is a mandatory part of the IS-95/IS-2000 protocol, and is available to anyone with a CDMA radio. There are timebases that are directly synchronized to CDMA (I have one) as an alternative to GPS that works in buildings where a GPS antenna is impractical. These will all break when the IS-2000 network is eventually shut down.


Reply to
Garrett Wollman

My wifi-only Nexus 5 Android tablet syncs its time automatically, so it's pretty clear that it's doing NTP.

R's, John

Reply to
John Levine

Around 2000, our entire company's Nextel phones had time that was off by quite a bit. One of the employees travelled to LA and back, and her time was correct, different from ours, until the next Daylight Savings transition, when it seems someone was more careful about setting the local time, and we all had a good time ;-)

- - Clarence A Dold - Santa Rosa, CA, USA GPS: 38.47,-122.65

***** Moderator's Note *****

When I was a Systems Analyst at NYNEX, we would occasionally have to write special one-time programs to correct AMA (Automatic Message Accounting) tapes when the clock was misset in the central office where the tapes had been recorded. The central offices did not have synchronization for their clocks, so each CO's time was set locally.

I assume that this has changed: the AMA tapes were replaced by data lines, in order to be able to bill calls more quickly, but that also meant that there is no grace period between calls and billing, and thus no chance to do a "reality check" on incoming tapes.

Bill Horne Moderator

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