[Starlink] Time Synchronization in Satellite Networks

[Christian von der Ropp]

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 <starlink at lists.bufferbloat.net>:
>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 <moeller0 at gmx.de> wrote:
>
>> Hi Hesham
>>
>> > On 2. Mar 2024, at 16:03, Hesham ElBakoury via Starlink <
>> starlink at lists.bufferbloat.net> 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
>> >
>> >
>> >
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>>
>>

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