Study asks: Can cell phone signals help land a plane?(newsreleases.sandia.gov)
newsreleases.sandia.gov
Study asks: Can cell phone signals help land a plane?
https://newsreleases.sandia.gov/phone_signals/
30 comments
It's easy to add an authentication packet to weed out pirate signals, but all wireless systems are still susceptible to jamming.
You cannot jam signals the aircraft has already received from an earlier point on the flight. Inertial navigation + cell towers hundreds of miles away could be useful, essentially requiring a state actor to really render such a system useless.
I'm not sure where I implied this to be the case?
I was just envisioning a local jammer being problematic for ILS systems.
I was just envisioning a local jammer being problematic for ILS systems.
> pioneering a backup system to keep an airplane on course when it cannot rely on global positioning system satellites.
So like the already existing VOR/DME network?
> The idea is to use these alternative signals to calculate a vehicle’s position and velocity.
All commercial planes have an IMU/ADIRU in them. Most are doubly if not triply redundant.
> There is no question GPS is still the gold standard for navigation
Not for flight. There are plenty of areas in Europe where it is compromised to the point of being useless.
> Scientists refer to it as “signals of opportunity”
Way back in the day pilots would use FM radio stations in the same way. If you were really lost out somewhere over a dark patch.
> If these signals are clean enough for navigation,
The bigger problem you have is while these are "fixed location" services our database of the locations isn't exactly awesome or well maintained in the face of maintenance or physical changes.
"Signals of opportunity" for flight is a bizarre regime to even consider.
So like the already existing VOR/DME network?
> The idea is to use these alternative signals to calculate a vehicle’s position and velocity.
All commercial planes have an IMU/ADIRU in them. Most are doubly if not triply redundant.
> There is no question GPS is still the gold standard for navigation
Not for flight. There are plenty of areas in Europe where it is compromised to the point of being useless.
> Scientists refer to it as “signals of opportunity”
Way back in the day pilots would use FM radio stations in the same way. If you were really lost out somewhere over a dark patch.
> If these signals are clean enough for navigation,
The bigger problem you have is while these are "fixed location" services our database of the locations isn't exactly awesome or well maintained in the face of maintenance or physical changes.
"Signals of opportunity" for flight is a bizarre regime to even consider.
> Way back in the day pilots would use FM radio stations in the same way.
Assuming you’re taking about ADF, that would use AM radio stations as a pseudo-NDB (or to listen to a ballgame).
Assuming you’re taking about ADF, that would use AM radio stations as a pseudo-NDB (or to listen to a ballgame).
That and radar... mode S can transmit data packets, uplink and downlink. Never seen it in use but it's in the European Mode S standard so any compliant radar has tested and qualified its use... data rate is very low but enough for some chat.
Before commenting on this, please read "Final Report of the GPS Spoofing Group", from Ops Group.[1] This is a group for international pilots and flight planners who have to deal with GPS spoofing routinely. They are not happy about it, for multiple reasons. Newer avionics trusts GPS too much. Bad GPS data can affect other flight systems, mis-calibrate the inertial reference systems, and even change the aircraft clock.
GPS spoofing confuses the Ground Collision Avoidance System, which uses GPS position and elevation maps to report nearness to the ground. The false alarm rate is now so high that such systems are useless in parts of the world.
There's a lot of this spoofing going on. Look at the maps in the report.
[1] https://ops.group/blog/gps-spoofing-final-report/
GPS spoofing confuses the Ground Collision Avoidance System, which uses GPS position and elevation maps to report nearness to the ground. The false alarm rate is now so high that such systems are useless in parts of the world.
There's a lot of this spoofing going on. Look at the maps in the report.
[1] https://ops.group/blog/gps-spoofing-final-report/
The link to the report doesn't work for me, and everything else seems to be behind a login wall. :\
Strange. Nothing special about it. Here's the raw PDF file.
[1] https://ops.group/dashboard/wp-content/uploads/2024/09/GPS-S...
[1] https://ops.group/dashboard/wp-content/uploads/2024/09/GPS-S...
Loran-C used to be available until it got shutdown in the 2010s because GPS was thought to be ubiquitous enough that other systems weren't needed:
* https://en.wikipedia.org/wiki/Loran-C
Turns out having a more resilient backup is useful.
China has built out an eLoran system (as well as a fibre-based precise-timing infrastructure):
* https://www.gpsworld.com/china-completes-national-eloran-net...
* https://www.mdpi.com/2076-3417/13/23/12703
* https://www.gpsworld.com/china-finishing-high-precision-grou...
I don't think Loran-c gives enough accuracy to land a plane all by itself, but it should get you to the airport, after which local beacons (VOR) will align you with the runway, and ILS will get you safely on the ground in IFR conditions.
* https://en.wikipedia.org/wiki/Loran-C
Turns out having a more resilient backup is useful.
China has built out an eLoran system (as well as a fibre-based precise-timing infrastructure):
* https://www.gpsworld.com/china-completes-national-eloran-net...
* https://www.mdpi.com/2076-3417/13/23/12703
* https://www.gpsworld.com/china-finishing-high-precision-grou...
I don't think Loran-c gives enough accuracy to land a plane all by itself, but it should get you to the airport, after which local beacons (VOR) will align you with the runway, and ILS will get you safely on the ground in IFR conditions.
For a start, "landing a plane" is a solved problem since long before GPS came along. They don't need "help".
As others have said, this seems to be a contrived "problem" to be solving. VOR, ADF, DME/DME and ILS already exist and work without GNSS. There's also LORAN if we were to need a ground based equivalent to GNSS.
As others have said, this seems to be a contrived "problem" to be solving. VOR, ADF, DME/DME and ILS already exist and work without GNSS. There's also LORAN if we were to need a ground based equivalent to GNSS.
There were far fewer planes in the air before GPS. In order to squeeze more planes into the same volume of air (aka "airspace density" or "airspace efficiency") you require high performance navigation systems. GPS isn't just used for navigation (getting from point A to point B), it's also for helping maintain separation between planes.
The US's navaid infrastructure is old. Not all airports have the "luxury" of ILS.
The US's navaid infrastructure is old. Not all airports have the "luxury" of ILS.
Perhaps they should also ask: if GPS is down in an area, do the cell towers continue to operate?
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.
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.
> 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.
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.
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.
> 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
Like Estonia:
* https://www.wingsmagazine.com/estonia-gps-interference-2/
Jamming can impact much more than just a limited area. Just ask anyone near a border with Russian:
* https://gpsjam.org
Like Estonia:
* https://www.wingsmagazine.com/estonia-gps-interference-2/
Each Russian jammer is only effective within a limited area. Russia. Russia has deployed multiple jammers.
Each jammer can cost as little US$ 10:
* 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-...
* https://insidegnss.com/fcc-fines-operator-of-gps-jammer-that...
Very cheap/easy to flood an area with noise.
* 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-...
* https://insidegnss.com/fcc-fines-operator-of-gps-jammer-that...
Very cheap/easy to flood an area with noise.
Russian jammers regularly impact other countries
Tons of russian gps jamming around Krolewiec, cellphones still work. Afaik every cell tower runs a rubidium clock source just for this occasion.
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?
> 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/
The FCC allowed Galileo use in 2018:
* 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.
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/
The FCC allowed Galileo use in 2018:
* 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.
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?).
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?).
> 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-releas...
Legally they could get their FCC certification pulled and not be allowed to be sold in the US if they are doing that.
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-releas...
Legally they could get their FCC certification pulled and not be allowed to be sold in the US if they are doing that.
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.
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
I can't find any benchmarks though that measures this
This seems hand wavy. Nothing that demonstrates that they have any understanding of how aircraft currently navigate with GPS, WAAS, levels of accuracy that enable or rule out certain procedures. It’s like they decided to just co-opt aviation because it’s mission critical and has money. “Like one day maybe we’ll be able to do the fancy airplane stuff with the radio stuff and math stuff.”
I agree. This has "secondary military goal" written all over it. For commercial flight these are just weird ideas.
> “There are actual apps you can download that allow you to spoof your location, and entire subreddits dedicated to showing you how to use it for various games,” Sanderson said.
Not judging the research itself, but this is kind of a dumb statement. The type of "spoofing" that you can do by just installing an app, which merely causes the OS to return fake coordinates, has virtually nothing in common with the type of "spoofing" that would threaten an aircraft by actually transmitting fake radio signals.