[time-nuts] How are iPhones' clocks set under LTE?

Tim Shoppa tshoppa at gmail.com
Sun Aug 3 21:47:42 UTC 2014


Here's the article and the quote. Very appropriate for time-nuts:

http://www.washingtonpost.com/lifestyle/style/for-public-clocks-a-time-warp/2011/10/25/gIQAXOZ5jM_story.html

"If the clocks are right — on churches and in classrooms, on stores and in
bars — they tell us that things are in order, say clock advocates such as
Bernardin. They tell us that people are paying attention. If a clock is
wrong, maybe everything else is, too."


On Sun, Aug 3, 2014 at 5:41 PM, Tim Shoppa <tshoppa at gmail.com> wrote:

> 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
>
>
> On Sun, Aug 3, 2014 at 4:37 PM, Brian Garrett <garrettbrian1960 at gmail.com>
> wrote:
>
>> Hi all,
>>
>> First “time”r here.  This may not rank up there with your degree of
>> time-nuttery, but I haven’t been able to get an answer elsewhere.  Recently
>> I was discussing the issue of how the different cellular providers set
>> their time, and I told him that I’d read that CDMA phones and towers have
>> to have their clocks synced to GPS as part of the protocol, whereas GSM
>> phones do not, and can theoretically be set to wall time, and thus phones
>> on networks using CDMA would have atomic accuracy all the time since what
>> they were getting was as good as GPS.
>>
>> Well, obviously I was pathetically behind the times.  Most everybody
>> these days including Verizon, which both I and my friend have now, uses LTE
>> , as you know.  I have looked all over for info as to what LTE’s
>> time-setting requirements are, as implemented by Verizon, but I’ve not seen
>> discussions of it anywhere.  I’ve seen amusing anecdotes over what can
>> happen if your Android isn’t set to receive the network’s time, or what can
>> happen to your phone’s clock if you live near a time zone boundary, but no
>> discussion of how time dissemination is handled in-network.  I know my
>> iPhone can be, and usually is, 2 or 3 seconds fast or slow when checked
>> against an accurate reference clock, so I’m thinking they can just use wall
>> time like GSM did.
>>
>> Has this been discussed on the list before?  I haven’t seen anything in
>> the archives, and no-one at Verizon that we of the unwashed masses have
>> access to will know the answer  Pointers, anyone?
>>
>>
>> Thanks in advance,
>> Brian
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>
>



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