[ntp:questions] .1 Microsecond Synchronization

Richard B. Gilbert rgilbert88 at comcast.net
Sat Jun 6 01:32:52 UTC 2009

Rob wrote:
> Unruh <unruh-spam at physics.ubc.ca> wrote:
>> Rob <nomail at example.com> writes:
>>> Unruh <unruh-spam at physics.ubc.ca> wrote:
>>>> "Richard B. Gilbert" <rgilbert88 at comcast.net> writes:
>>>>> Harlan Stenn wrote:
>>>>>> The time on my cellphone is routinely more than 3 seconds off of GPS time.
>>>>> Is your cell phone "CDMA"?   Other technologies, there are several, may 
>>>>> not require the precise timing that CDMA does!
>>>> It will be hard for them to get CDMA in London, or Paris, or in fact anywhere in the world except
>>>> N America.
>>> It has always amazed me that in an all-digital system like GSM there is
>>> no standard way to communicate wallclock time from the network to the
>>> handhelds.  Even a once-per-hour time transmission that would sync the
>>> freerunning clock in the phone would be fine for most users.
>>> It seems there is some nonstandard stuff going around, e.g. my Nokia phone
>>> can be configured to receive time from the network but it does not work.
>>> Probably requires Nokia base stations.
>> No it requires the network to send the time when requested. Eg, Rogers
>> in Canada (GSM) does deliver the time but I have no idea what its
>> accuracy is. 
> How dumb...  something like time-of-day should be broadcast just like
> cell broadcast and everyone would be able to receive it without any
> requesting.

Time is broadcast!  WWV, WWVB, CHU, JJY, etc.  Most radio and TV 
stations broadcast the time; "At the tone the correct time will be. . . 
."  Many radio and TV stations get the time directly from WWV and 
rebroadcast the tone from WWV.

CMDA base stations also broadcast the time.  I'm not sufficiently 
familiar with the other technologies to be able to state that they do, 
or do not, supply correct time to the phones they serve.

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