Re: [Starlink] Time Synchronization in Satellite Networks

[Hesham ElBakoury <helbakoury@gmail.com>]

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Hi Sebastian,
I agree with you that NTP and PTP are not suitable. We need new protocols.

Thanks
Hesham

On Sat, Mar 2, 2024, 7:45 AM Sebastian Moeller <moeller0@gmx.de> wrote:

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