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.
Hesham On Sat, Mar 2, 2024, 8:19 AM Christian von der Ropp <c...@vdr.net> 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 < > helbako...@gmail.com>: > >> 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 <c...@vdr.net> 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 < >>> starlink@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 <moell...@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 >>>>> > >>>>> > >>>>> > >>>>> > _______________________________________________ >>>>> > Starlink mailing list >>>>> > Starlink@lists.bufferbloat.net >>>>> > 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. >
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