5 ms·

Perhaps they should also ask: if GPS is down in an area, do the cell towers continue to operate?

by amluto 2y ago

thanksgiving 2y ago
You make me wonder, are these systems programmed to fall back to Galileo EU, Russian Or Chinese (mainland) GNSS at all? Should we fall back to systems controlled by other countries?
- throw0101a 2y ago
  > You make me wonder, are these systems programmed to fall back to Galileo EU, Russian Or Chinese (mainland) GNSS at all? In the US, per FCC rules, it is not officially allowed to listen to other GNSS frequencies as they are not licensed: > The Federal Communications Commission (FCC) rules require licensing of non-federal receive-only equipment operating with foreign satellite systems, including receive-only earth stations operating with non-U.S. licensed radionavigation-satellite service (RNSS) satellites. * https://www.gps.gov/spectrum/foreign/ https://www.gps.gov/spectrum/foreign/ The FCC allowed Galileo use in 2018: * https://www.fcc.gov/document/fcc-approves-galileo-global-navigation-system-0 https://www.fcc.gov/document/fcc-approves-galileo-global-nav... I think the reasoning is that if it is not "officially sanctioned" then if there's interference with those signals it's not the FCC's problem. By allowing it they'll take noise on those frequencies more seriously in rules and enforcement.
  - thanksgiving 2y ago
    I don't think I understand what allowed means in this context because on my OnePlus Nord phone, I have an app called GPS Test which shows me that I have so many GPS, so many GLONASS, and so many Galileo in view. Strange thing is there is no Chinese GNSS in view. (I was on a short trip to Bali recently and iirc I did see Chinese GNSS on the app while there so I think the app and phone hardware is capable of picking up Chinese GNSS?).
    - throw0101d 2y ago
      > I don't think I understand what allowed means in this context because on my OnePlus Nord phone, I have an app called GPS Test which shows me that I have so many GPS, so many GLONASS, and so many Galileo in view. That app may simply be reporting the presence of signals, but the geolocation functions and APIs may not actually use those signals in their calculations. And if they are actually processing the signals, then they are breaking FCC regulations: * https://selectcommitteeontheccp.house.gov/media/press-releases/gallagher-presses-fcc-us-cell-phones-and-devices-using-chinese-russian-gps https://selectcommitteeontheccp.house.gov/media/press-releas... Legally they could get their FCC certification pulled and not be allowed to be sold in the US if they are doing that.
- nradov 2y ago
  FAA certified avionics won't fall back from GPS to foreign GNSS constellations for authorized flight operations. If GPS is degraded then pilots have to fall back to older navigation methods. Those foreign constellations mostly all operate on similar frequency bands so if GPS is being jammed in a certain area then the other systems will likely also be impacted.
- minetest2048 2y ago
  In the context of time synchronization, my gut feeling is no, as you can't guarantee that the atomic clocks on other GNSS tick at the same time as GPS. Even if they have the same frequency. I can't find any benchmarks though that measures this
red0point 2y ago
Often they rely heavily on GPS for time and frequency synchronization (think 5G TDD, where all operators need to be aligned in time or they jam eatch other‘s uplink). The GPS antenna is also often quite visible from the outside of a base station. Still, what‘s also possible is to use PTP as backup (e.g., over eCPRI) and use the fiber / microwave backhaul to some master clock with, say, a ribidium time source as a backup, so I think it‘s not entirely unreasonable to assume that cell phone signals will remain available in the presence of a GPS outage.
throw0101a 2y ago
> Perhaps they should also ask: if GPS is down in an area, do the cell towers continue to operate? If the towers are uniquely identified, and are geo-located accurately, it could be possible to triangulate your position even if they are not operational from a make-a-phonecal perspective. They just have to perhaps keeps shouting "I'm here!". Perhaps they'd at least need a semi-accurate time source? (Like a local rubidium clock, or at least NTP/PTP over a fibre backhaul.) On the other hand smartphones can geolocate themselves decently from Wifi AP signals, and those tend to not have timestamps with-in the broadcasts.
nradov 2y ago
What do you mean by GPS being "down" in an area? The constellation is in medium orbit so no satellite is area specific. WAAS is area specific so if one of those transmitters fails then that can prevent certain aviation uses of GPS. Jamming can also impact a limited area.
- throw0101a 2y ago
  > What do you mean by GPS being "down" in an area? […] Jamming can also impact a limited area. Jamming can impact much more than just a limited area. Just ask anyone near a border with Russian: * https://gpsjam.org https://gpsjam.org Like Estonia: * https://www.wingsmagazine.com/estonia-gps-interference-2/ https://www.wingsmagazine.com/estonia-gps-interference-2/
  - nradov 2y ago
    Each Russian jammer is only effective within a limited area. Russia. Russia has deployed multiple jammers.
    - throw0101a 2y ago
      Each jammer can cost as little US$ 10: * https://hackaday.com/2020/09/08/teardown-mini-gps-jammer/ https://hackaday.com/2020/09/08/teardown-mini-gps-jammer/ And a single one can mess up an entire airport until its found: * https://trans.info/en/gps-jammer-that-brought-disruption-to-lyon-airport-353510 https://trans.info/en/gps-jammer-that-brought-disruption-to-... * https://insidegnss.com/fcc-fines-operator-of-gps-jammer-that-affected-newark-airport-gbas/ https://insidegnss.com/fcc-fines-operator-of-gps-jammer-that... Very cheap/easy to flood an area with noise.
    - p_l 2y ago
      Russian jammers regularly impact other countries
rasz 2y ago
Tons of russian gps jamming around Krolewiec, cellphones still work. Afaik every cell tower runs a rubidium clock source just for this occasion.

Perhaps they should also ask: if GPS is down in an area, do the cell towers continue to operate?

by amluto 2y ago

Perhaps they should also ask: if GPS is down in an area, do the cell towers continue to operate?

You make me wonder, are these systems programmed to fall back to Galileo EU, Russian Or Chinese (mainland) GNSS at all? Should we fall back to systems controlled by other countries?

throw0101a 2y ago
> You make me wonder, are these systems programmed to fall back to Galileo EU, Russian Or Chinese (mainland) GNSS at all? In the US, per FCC rules, it is not officially allowed to listen to other GNSS frequencies as they are not licensed: > The Federal Communications Commission (FCC) rules require licensing of non-federal receive-only equipment operating with foreign satellite systems, including receive-only earth stations operating with non-U.S. licensed radionavigation-satellite service (RNSS) satellites. * https://www.gps.gov/spectrum/foreign/ https://www.gps.gov/spectrum/foreign/ The FCC allowed Galileo use in 2018: * https://www.fcc.gov/document/fcc-approves-galileo-global-navigation-system-0 https://www.fcc.gov/document/fcc-approves-galileo-global-nav... I think the reasoning is that if it is not "officially sanctioned" then if there's interference with those signals it's not the FCC's problem. By allowing it they'll take noise on those frequencies more seriously in rules and enforcement.
- thanksgiving 2y ago
  I don't think I understand what allowed means in this context because on my OnePlus Nord phone, I have an app called GPS Test which shows me that I have so many GPS, so many GLONASS, and so many Galileo in view. Strange thing is there is no Chinese GNSS in view. (I was on a short trip to Bali recently and iirc I did see Chinese GNSS on the app while there so I think the app and phone hardware is capable of picking up Chinese GNSS?).
  - throw0101d 2y ago
    > I don't think I understand what allowed means in this context because on my OnePlus Nord phone, I have an app called GPS Test which shows me that I have so many GPS, so many GLONASS, and so many Galileo in view. That app may simply be reporting the presence of signals, but the geolocation functions and APIs may not actually use those signals in their calculations. And if they are actually processing the signals, then they are breaking FCC regulations: * https://selectcommitteeontheccp.house.gov/media/press-releases/gallagher-presses-fcc-us-cell-phones-and-devices-using-chinese-russian-gps https://selectcommitteeontheccp.house.gov/media/press-releas... Legally they could get their FCC certification pulled and not be allowed to be sold in the US if they are doing that.
nradov 2y ago
FAA certified avionics won't fall back from GPS to foreign GNSS constellations for authorized flight operations. If GPS is degraded then pilots have to fall back to older navigation methods. Those foreign constellations mostly all operate on similar frequency bands so if GPS is being jammed in a certain area then the other systems will likely also be impacted.
minetest2048 2y ago
In the context of time synchronization, my gut feeling is no, as you can't guarantee that the atomic clocks on other GNSS tick at the same time as GPS. Even if they have the same frequency. I can't find any benchmarks though that measures this

red0point 2y ago

Often they rely heavily on GPS for time and frequency synchronization (think 5G TDD, where all operators need to be aligned in time or they jam eatch other‘s uplink). The GPS antenna is also often quite visible from the outside of a base station. Still, what‘s also possible is to use PTP as backup (e.g., over eCPRI) and use the fiber / microwave backhaul to some master clock with, say, a ribidium time source as a backup, so I think it‘s not entirely unreasonable to assume that cell phone signals will remain available in the presence of a GPS outage.

throw0101a 2y ago

> Perhaps they should also ask: if GPS is down in an area, do the cell towers continue to operate? If the towers are uniquely identified, and are geo-located accurately, it could be possible to triangulate your position even if they are not operational from a make-a-phonecal perspective. They just have to perhaps keeps shouting "I'm here!". Perhaps they'd at least need a semi-accurate time source? (Like a local rubidium clock, or at least NTP/PTP over a fibre backhaul.) On the other hand smartphones can geolocate themselves decently from Wifi AP signals, and those tend to not have timestamps with-in the broadcasts.

nradov 2y ago

What do you mean by GPS being "down" in an area? The constellation is in medium orbit so no satellite is area specific. WAAS is area specific so if one of those transmitters fails then that can prevent certain aviation uses of GPS. Jamming can also impact a limited area.

throw0101a 2y ago
> What do you mean by GPS being "down" in an area? […] Jamming can also impact a limited area. Jamming can impact much more than just a limited area. Just ask anyone near a border with Russian: * https://gpsjam.org https://gpsjam.org Like Estonia: * https://www.wingsmagazine.com/estonia-gps-interference-2/ https://www.wingsmagazine.com/estonia-gps-interference-2/
- nradov 2y ago
  Each Russian jammer is only effective within a limited area. Russia. Russia has deployed multiple jammers.
  - throw0101a 2y ago
    Each jammer can cost as little US$ 10: * https://hackaday.com/2020/09/08/teardown-mini-gps-jammer/ https://hackaday.com/2020/09/08/teardown-mini-gps-jammer/ And a single one can mess up an entire airport until its found: * https://trans.info/en/gps-jammer-that-brought-disruption-to-lyon-airport-353510 https://trans.info/en/gps-jammer-that-brought-disruption-to-... * https://insidegnss.com/fcc-fines-operator-of-gps-jammer-that-affected-newark-airport-gbas/ https://insidegnss.com/fcc-fines-operator-of-gps-jammer-that... Very cheap/easy to flood an area with noise.
  - p_l 2y ago
    Russian jammers regularly impact other countries

rasz 2y ago

Tons of russian gps jamming around Krolewiec, cellphones still work. Afaik every cell tower runs a rubidium clock source just for this occasion.