[ntp:questions] Indirect GPS time source options
kostecke at ntp.org
Thu Mar 13 17:36:42 UTC 2014
On 2014-03-13, William Unruh <unruh at invalid.ca> wrote:
> On 2014-03-13, Olivier Drouin <ol.drouin at gmail.com> wrote:
>> Also, from what I understand and please correct me if I'm wrong but
>> cellular networks are indeed designed to be accurately timed because
>> it's needed for the normal operations of the cell network.
> Yes, but they are not designed to deliver accurate time to the rest of
> the world AFAIK.
CDMA requires accurate time synchronization among all base stations and
mobile stations. The accuracy must be within a few microseconds among
base stations because the pilot code phase is used to distinguish them.
When a mobile station is communicating with a base station they must be
synchronized to within a fraction of a chip (814 ns). And the "clocks"
(the PN generators) that must be synchronized have a period of 37
GPS Absolute timing accuracy of unit is under 30 nanoseconds.
CDMA Absolute timing accuracy of unit is typically under 10
Network timing accuracy 1/2 - 2 milliseconds, typical for both GPS and
CDMA NTP products.
Also see: http://www.endruntechnologies.com/cdma.htm
Steve Kostecke <kostecke at ntp.org>
NTP Public Services Project - http://support.ntp.org/
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