[Starlink] Time Synchronization in Satellite Networks

[Sebastian Moeller]

Hi Hesham,

caveat, this is far from my area of expertise, but I would simply try to get GPS/Glonass/Galileo antennas into the birds and have each sync their clock individually from such a source, which would remove the necessity for time synchronisation protocols. That said, I see neither PTP not NTP as suited, as both presumably assume that server and clients do not move to fast in relation to each other, while arbitrary members of a LEO constellation might have quite large relative speds, no?

Regards
	Sebastian

> On 2. Mar 2024, at 16:25, Hesham ElBakoury <helbakoury at gmail.com> wrote:
> 
> 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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