Re: [Drip] Fwd: ADSB

[Stu Card <[e-mail]>]

A few clarifications from a US perspective, but EU rules are similar…

“low-flying small UAS” in the US typically means aircraft flying under FAA regulations part 107 (https://www.ecfr.gov/current/title-14/chapter-I/subchapter-F/part-107) which limits them to a total loaded (with payload and fuel) takeoff weight under 55 pounds (25 kg) flying at less than 100 statute (not nautical) miles per hour (161 kph) at altitudes under 400 ft (122 m) Above Ground Level (AGL).

The FAA final rule for UAS RID (https://www.faa.gov/sites/faa.gov/files/2021-08/RemoteID_Final_Rule.pdf), p. 12, states in part:
4. Prohibition against the Use of ADS-B Out and Transponders This rule prohibits use of ADS-B Out and transponders for UAS operations under 14 CFR part 107 unless otherwise authorized by the FAA, and defines when ADS-B Out is appropriate for UAS operating under part 91. The FAA is concerned the potential proliferation of ADS-B Out transmitters on unmanned aircraft may negatively affect the safe operation of manned aircraft in the airspace of the United States. The projected numbers of unmanned aircraft operations have the potential to saturate available ADS-B frequencies, affecting ADS-B capabilities for manned aircraft and potentially blinding ADS-B ground receivers. Therefore, unmanned aircraft operators, with limited exceptions, are prohibited from using ADS-B Out or transponders. The prohibition against the use of ADS-B Out and transponders is discussed in section XVII of this preamble.

ADS-B is received by “ADS-B In” equipped aircraft, ground stations (that often relay it into terrestrial networks) and satellites (that downlink it into terrestrial networks). Detect And Avoid (DAA) for “self-separation” (maintenance of “well clear” so there is essentially no chance of collision even without needing to maneuver dramatically to avoid it), as well as “collision avoidance” (where self-separation has failed, well clear has been violated, and dramatic maneuver may be required), may use it. ADS-B In equipped aircraft could do AirBorne Detect And Avoid (ABDAA), and aircraft not so equipped could take advantage of ground and/or satellite based ADS-B receivers to do Ground Based Detect And Avoid (GBDAA). Thus ADS-B is very safety critical. Inter alia, this means we must not overwhelm it with transmissions. The numbers of uncrewed aircraft (in the millions) greatly exceed those of manned aircraft.

The bandwidth dedicated to ADS-B is very limited (under 4 MHz total between the 2 different frequencies used by various systems). There is discussion of this in various places (a quick Google yielded https://aviation.stackexchange.com/questions/84876/question-about-congestion-of-the-1090mhz-frequency as one decent hit) but I have not seen a proper mathematical analysis.

I have spoken directly with developers of a major satellite based ADS-B receiver network: they were _terrified_ at the prospect of large numbers of small UAS transmitting ADS-B, as each satellite sees ~1/3 of the earth’s surface at any given time, so unlike a ground based receiver with a horizon-limited range (thus area and thus total number of transmitters at any given density), the numbers of transmitters in view at once could number in the hundreds of thousands or more, _swamping_ the receiver with collisions such that essentially none of those transmissions could be demodulated and decoded.

ADS-B is an option for what are expected to be the much smaller numbers of UAS that are larger and flying higher (at least at some point in any typical flight, also typically faster), e.g. in the US under FAA part 91 as noted above.

However, ADS-B is inherently untrustworthy and it is not obvious that it can be made trustworthy while remaining backwards compatible with large numbers of installed systems, as unlike ASTM F3411 it has no provisions in its framing for authentication.

Please trust me, using ADS-B for UAS RID is a _dead issue_ for large numbers of “low-flying small UAS”.

But please continue to review our drafts and generally be involved in DRIP! 😊

From: Tm-rid <[e-mail]> On Behalf Of Alexandre PETRESCU
Sent: Tuesday, July 11, 2023 8:15 AM
To: [e-mail]
Subject: [Drip] Fwd: ADSB


(sorry, Cc'ing the list as in my first email I just wrote to Med)


-------- Message transféré --------
Sujet :
Re: [Drip] ADSB
Date :
Tue, 11 Jul 2023 14:12:55 +0200
De :
Alexandre Petrescu <[e-mail]><mailto:[e-mail]>
Pour :
[e-mail]<mailto:[e-mail]>


Hi,

ADSB for drones is this on flightradar?

https://www.flightradar24.com/EOSCUAV/3116cefd

The arch draft says "For numerous technical reasons, ADS-B itself is not suitable for low-flying small UAS." ?  The drone(?) in the figure is at approx. 500meter altitude, that I think it is very low.

Also, the arch draft says "The ADS-B is the de jure technology used in manned aviation for sharing location information, from the aircraft to ground " - but I think it is also used for other equipment at airport that is not aircraft.  It might be used for cars (kind of, but surely not flying) or trucks at airport for collision avoidance, I think.



[cid:image001.png@01D9B3D0.D92D89B0]
Alex
Le 15/09/2020 à 07:48, [e-mail]<mailto:[e-mail]> a écrit :
Hi Stu, all,

I was referring to your second point. We need to have a record on these matters in the arch draft.

The text shared by Stephan (thanks) is a good start.

Cheers,
Med

De : Tm-rid [mailto:[e-mail]] De la part de Card, Stu
Envoyé : lundi 14 septembre 2020 16:27
À : BOUCADAIR Mohamed TGI/OLN <[e-mail]><mailto:[e-mail]>
Cc : [e-mail]<mailto:[e-mail]>
Objet : Re: [Drip] ADSB

A pointer to the freely available earlier draft of what became ASTM F3411-19 was added to -reqs; is that the outcome to which you refer?
Or do we want something more about how the regulators et al have ruled out ADSB as a RID mechanism for low altitude small UAS?


On Mon, Sep 14, 2020 at 7:07 AM <[e-mail]<mailto:[e-mail]>> wrote:
Hi Stu,

I wonder whether the outcome of this thread was recorded in the arch draft.

Please share with the WG the current status of this action point.

Thank you.

Cheers,
Med

De : Tm-rid [mailto:[e-mail]<mailto:[e-mail]>] De la part de Card, Stu
Envoyé : mercredi 5 août 2020 15:20
À : BOUCADAIR Mohamed TGI/OLN <[e-mail]<mailto:[e-mail]>>
Cc : [e-mail]<mailto:[e-mail]>
Objet : Re: [Drip] ADSB

Will do.

On Wed, Aug 5, 2020, 5:13 AM <[e-mail]<mailto:[e-mail]>> wrote:
Hi Stu,

I remember that Andrei raised in the past a question about the use of ADB-S.. I suspect that others may make a similar comment in the future.
Having some text in draft-ietf-drip-arch reflecting the main arguments shared in this thread (by Shuai, Bob, Stephan, you) will be useful.

Can you please consider adding such text to the draft?

Thank you.

Cheers,
Med

> -----Message d'origine-----
> De : Tm-rid [mailto:[e-mail]<mailto:[e-mail]>] De la part de Stuart W.
> Card
> Envoyé : mardi 4 août 2020 19:12
> À : [e-mail]<mailto:[e-mail]>
> Objet : Re: [Drip] ADSB
>
> The proposed manifest and other DRIP authentication related structures
> are all independent of transport, but designed to work with the most
> constraining transport thus specified by regulators and/or other SDOs,
> that being ASTM F3411 Broadcast RID over Bluetooth 4.
>
> So, for Broadcast RID, they would be encapsulated in ASTM F3411
> messages over Bluetooth 4, Bluetooth 5 or WiFi Neighbor Awareness
> Networking (without IP).
>
> For Network RID, they could be carried in any IP based transport,
> HTTPS/TCP/IP initially (although, for Network RID, some of them are
> superfluous).
>
> On 8/4/2020 11:27 AM, Alexandre Petrescu wrote:
> > Thanks for the clarification.
> >
> > Le 04/08/2020 à 17:17, Stuart W. Card a écrit :
> >> I just want to respond to one line that I think comes from
> confusion:
> >>
> >>> But if we have reluctance about the use of ADS-B, and thus of IP,
> >>> and we recommend Bluetooth-without-IP to identify drones
> >>
> >> We aren't recommending Bluetooth-without-IP, we are _supporting_
> it,
> >
> > But, the security manifest that I have seen on slides during the
> > presentation of the DRIP WG meeting - is something below IP, right?
>
>
> --
> -----------------------------------------
> Stuart W. Card, PhD, Principal Engineer
> AX Enterprize, LLC  www.axenterprize.com<http://www.axenterprize.com>
> 4947 Commercial Drive, Yorkville NY 13495


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