Cell Phone Clock Inaccuracy [Telecom]

And all this time I thought cell phones were networked-synched for their time-of-day displays.

For the 10 years I've carried a cell phone (two qualcomms and now a Samsung), the time-of-day has been reliable and accurate.

That ended on Christmas eve day, when I temporarily lost my phone, decided to get a replacement (another Samsung) and discovered that its clock was 4-6 minutes slow. The T-mobile store people assured me this "happened all the time" -- some clocks were on, others were off. "That doesn't make any sense," I said.

They shrugged. My old phone was found and returned a few days later. I disliked the new phone for many reasons besides the slow clock, so I took it back, reactivated my old phone. And now it too was 4-6 minutes slow. I can travel to different areas and compare my phone to others' with the same carrier. They're on, I'm off.

I can manually set the clock in the phone, but within a few moments it is updated back to the wrong time. I went back to the store, checked maybe 18 display phones. Three were running 4-6 minutes slow, two were more than five hours off, the others were accurate, far as I could tell.

So now I'm trying to understand just how this is happening, assuming a network time sync signal, and moreover, how it can be fixed. (T-Mobile Tech Support said they wouldn't even consider generating a trouble ticket until "enough" people complained.)

Any ideas?

Thanks, Frank

Reply to
Frank Stearns
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I know you said that you can set your clock manually in the phone but make sure your phone is set to "Network" as opposed to "Phone" for time source. This seems to be only an option on GSM/GPRS phone carriers such as T-Mobile and AT&T. The phones you saw on display in the store may have been set to "Phone" or "Manual", which is why they may have been off. The phone's time from the Network comes from the cell tower which is either all in sync via the MSC (switch) or via the GPS antennas that all cell sites have. (As an aside, some people thing the GPS on the site is so they know where the site is....well, the site doesn't move so they know where it is - the GPS is used for time sync across the network).


Reply to

That means it is not the phone itself. The cell system is sending wrong time settings to your phone.

See if there is an option in the phone's setup menus that will turn off the network's ability to change the time on your phone. This should cure the problem (up to the accuracy limit of the clock in the phone itself, and you can set that manually every month or so if the need arises).

This will also eliminate the annoying behavior where your phone will silently reset its clock when you cross a time zone boundary (and sometimes get the boundary wrong, thus leaving you wondering which time zone it is really giving you) -- a problem I've found especially vexing in the Rocky Mountain states where coverage is sparse anyway.

Reply to
John David Galt

That really sounds strange, the phone is always in contact with the switch which has a network clock, and that must be right or other problems will be caused. The switch clock is also updated with other clocks. Also each time a call comes in the clock will update as all phone do with CID. I checked all 3 of my cell phones 1 each of a Palm, Samsung and Sanyo, all 3 have the same time, my CID box seems to be also the same. I checked my computer which is on a network clock and updates every 5 minutes and also is the same, or at least the same miute, the seconds could be off.

I know that when I had worked on CO Switches we had a cross between the network clock and a backup and the switch would not work correctly until we found and reversed the cables.

Reply to
Steven Lichter

Only CDMA (used by Verizon Wireless and Sprint PCS, for now, but not Sprint iDEN) requires accurate time synchronization. GSM systems, like your T-Mobile service, work just fine with time synchronization at the level of "whatever the MTSO technician's watch says".

A number of companies make precision timing receivers based on CDMA technology; at the office I have an NTP stratum-1 using an EndRun Technologies Praecis Ct (no longer sold) with good results. (The server currently reports an offset for that source of 50 microseconds with jitter of 15 microseconds, which is not bad considering that the server and the timecode generator both have uncompensated quartz crystal oscillators.)


Reply to
Garrett Wollman

[Moerator snip]

All I can tell you, Frank, is that my T-Mobile-supplied Nokia 6610 has a setting "Auto-update of date & time" with options "On", "Confirm first", and "Off".

You reach it by selecting, in turn, "Menu", "Settings", "Time and date settings", and "Auto-update of date & time".

I run with the "On" option. Whenever the local time changes (EST/DST changeover, or I'm in a new timezone), it's not long before that Nokia reflects the new time, which seems to be about as accurate as the carrier handling me cares to make it.

Same thing, more or less, for my wife's T-Mobile Moto RAZR V3.

Hope this has helped at least a little. Cheers,

-- tlvp

Reply to

My T-Mobile Moto RAZR V3 has settings under "Settings | Initial Settings | Time and Date" of "Autoupdate", which can be set On or Off. (I don't see a "Confirm first" setting.) If you set it to "Off" options to manually set the time and date appear.

I tried setting the time off by 5 minutes, then switching it back to autoupdate. The time got switched back immediately.

I've checked the time occasionally and it seems to be pretty close to my NTP-synchronized computer, but since the phone doesn't display seconds it's hard to be sure. I haven't crossed time zones with the phone yet so I don't know what happens then. Something a little funny happened at one of the DST transitions. I think the transition happened half an hour off or so (I don't remember whether it was early or late) but it transitioned in one jump.

If I was having trouble with the time jumping around between time zones, say, travelling at an airport on a time zone boundary (does that happen at any actual airport? I do seem to remember being at one airport which was divided down the middle by an area code boundary, and your cost for calls varied a lot based on the area code of the pay phone. That was a couple decades ago.), it looks like I could set it to manual fairly easily and stop that from happening, provided I realized it was an issue.

Reply to
Gordon Burditt

This is one of the first things I tried to check: went to a friend who is 14 miles away and also on T-mobile. Surely I was sync'd to his local tower. Powered my phone on/off - my time was still wrong, his was right.

Leads me to believe the phone is wrong, but the mechanism is unclear. Does the phone have to do some sort of time calculation based on a raw time signal? Perhaps something akin to a UNIX computer's clock based on a 32-bit number counting microseconds from 1970 or some such -- the display time of day is derived from that value. (As an aside there'll be a Y2K-like rollover issue with UNIX boxes in

2038, or something like that, IIRC.)

If so, seems odd unless there was a "failure in the silicon" inside my phone such that some intermediate place value in a CPU register (or perhaps the firmware holding some time calculation constant) is now stuck on or off, or has the wrong value, and this means there's always this 4-6 minute error.

I did find the manual setting with no updating; thanks to the poster who gave the details on this. That helps; I'll find out how much the phone time drifts.

This actually worked for me reasonably well this past September during a time-zone crossing road trip. But I can see how this could get iffy if crossing times zones a lot.

Thanks to all who had suggestions on this issue.


Reply to
Frank Stearns

Anyone has the same problem with iPhone? It seems other cellphones have a lot of QA issues.

Reply to

Like what the other poster suggested, try to check if you can turn time sync off on your Iphone or any other mobile phone.

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My Palm on the Sprint Network has an option to set the date and time network to nothing.

Reply to
Steven Lichter

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