Hi Hesham,
On 2. Apr 2024, at 00:04, Hesham ElBakoury <[email protected]> wrote:
Hi Christian,
The problems is that Satellites move, therefore, the delay between the
different directions is different which violates the condition to run NTP
and PTP.
But GPS Satellites themselves are not in geostationary oprbit, and still
we can get precision time from them... so I would argue that must be a
solved problem, no?
Regards
Sebastian
Hesham
On Sat, Mar 2, 2024, 8:19 AM Christian von der Ropp <[email protected]>
wrote:
Hi Hesham,
You do not acquire the time from a LEO satellite but directly from the
GPS satellites which carry an atomic clock on board.
I'd not be aware of any LEO providing a GNSS signal but Xona plan such
system (although not carrying proper atomic clocks but probably chip-sized
atomic clocks that require frequent syncing with proper atomic clocks):
https://twitter.com/Megaconstellati/status/1708091536439673323
There are efforts to build trapped-ion quantum clocks that are expected
to become significantly smaller and cheaper than traditional atomic clocks
while as accurate which would make it viable to put an atomic
clock-equivalent on small LEO satellites. Once that happens you would have
an independent alternative to the big GNSS birds in MEO but with stronger
signals. I'm told that we are 5-10 years away from such trapped-ion quantum
clocks.
But for NTP clients, the described method (running a local NTP server in
the satellite terminal synced to GPS) should be good enough.
Christian
Am 2. März 2024 18:02:47 OEZ schrieb Hesham ElBakoury <
[email protected]>:
Hi Christian,
How you synchronize the time of the satellites in the network? Are you
saying each satellite has a master clock?
Hesham
On Sat, Mar 2, 2024, 7:38 AM Christian von der Ropp <[email protected]>
wrote:
Why not acquire the time directly from by the satellite terminal and run
local NTP servers instead of syncing via the Internet? LEO satellite
terminals always have onboard GNSS antennas for geolocation which is
necessary to find the satellites, so integrating a local GNSS-disciplined
Stratum-1 NTP server seems trivial to me.
Am 2. März 2024 17:25:59 OEZ schrieb Hesham ElBakoury via Starlink <
[email protected]>:
Hi Sebastian,
Can we still use PTP and NTP for time synchronization in Satellite
networks or we need new protocols? If we need new protocols, do such
protocols exist?
Thanks
Hesham
On Sat, Mar 2, 2024, 7:18 AM Sebastian Moeller <[email protected]> wrote:
Hi Hesham
On 2. Mar 2024, at 16:03, Hesham ElBakoury via Starlink <
[email protected]> wrote:
Time synchronization, for satellite networks, faces several challenges:
1. Signal Propagation Delays: Unlike terrestrial networks where
signals travel through cables at the speed of light,
[SM] The speed of light in your typical glas fibers (and accidentally
the information propagation speed in metallic conductors) comes in roughly
at 2/3 of the speed of light in vacuum, while the speed of light in air at
see level is a mere 90 KM/s slower than in vacuum.
satellite communication involves signals traveling vast distances
through space. This creates significant delays.
[SM] Sure distances might be larger, but propagation speed is around
100000Km/s faster... my main point is speed of light is a) dependent on the
medium b) not the things that differentiates space from the earth's surface
here, but mere geometry and larger distances on larger spheres...
2. Clock Drift: Even highly precise atomic clocks, used in satellites,
are susceptible to "drift" - gradually losing or gaining time. This drift,
caused by factors like temperature variations, radiation exposure, and
power fluctuations, can lead to inconsistencies in timekeeping across the
network.
3. Signal Degradation: As signals travel through space, they can
degrade due to factors like atmospheric interference, ionospheric
disturbances, and solar activity. This degradation can introduce noise and
errors, impacting the accuracy of time synchronization messages.
4. Limited Resources: Satellites have limited power and processing
capabilities. Implementing complex synchronization protocols can be
resource-intensive, requiring careful optimization to minimize their impact
on other functionalities.
5. Evolving Technologies: As satellite technologies and applications
continue to evolve, new challenges related to synchronization might emerge.
For example, the integration of constellations with thousands of satellites
poses unique synchronization challenges due to the sheer scale and
complexity of the network.
These challenges necessitate the development of robust and efficient
time synchronization protocols for satellite networks and an integrated
satellite and terrestrial networks
Are you aware of such time synchronization protocols?
I would think that using Satellite simulators is the most viable way
to develop and test these protocols given that using satellites is not that
easy.
Thanks
Hesham
_______________________________________________
Starlink mailing list
[email protected]
https://lists.bufferbloat.net/listinfo/starlink
--
Diese Nachricht wurde von meinem Android-Mobiltelefon mit K-9 Mail
gesendet.
--
Diese Nachricht wurde von meinem Android-Mobiltelefon mit K-9 Mail
gesendet.
