Re: [Drip] ADSB

[Stephan Wenger <[e-mail]>]

Alexandre,

ADS-B is a 20+ year old technology and offers properties (bandwidth, security, cost) of a 20 year old technology.  That it just recently sees widespread adoption is a result of incredibly slow (even by IETF standards) deployment process, and that in turn is the result of the very conservative and safety conscious aviation community and regulators, as well as the high cost related to anything manmade that flies.  By speculating to use ADS-B as an underlying technology for IP, I fear you demonstrate a certain lack of background.  The Wikipedia article on ADS-B (https://en.wikipedia.org/wiki/Automatic_dependent_surveillance_–_broadcast) is mostly correct, and I recommend in particular the sections on "Theory of operation" and "System Design Considerations".

A few (of many) reasons why ADS-B is unsuitable for light drones (anything significantly smaller than a man-carrying aircraft):
-24 bit ICAO transponder code, limiting the number of (active or inactive) ADS-B equipment.  Each modern aircraft over a certain size (except the smallest two-seaters, powered parachutes, and aircraft without electrical systems such as antiques) has a unique code assigned for its lifetime.
-line-of-sight wireless connection for the "uplink" with only a few hundred ground stations for the whole US (or 70 for the whole Australia).  That means ADS-B coverage is almost everywhere only available at altitudes in which small drones are neither legal nor, in most cases, physically capable to fly (a few thousand feet in the US except near major airports where you don't want drones, 30000 ft in Australia).  Aircraft send over the uplink information such as aircraft ICAO code, aircraft type, speed, direction of flight, altitude, etc.).  Information is sent in the clear, by design.  You can buy a box receiving this info, hook it up to an Raspberry PI or something, and look at the traffic near your house and send it on to your friends--in fact, this type of crowdsourced ATC info is what makes flightradar24 and similar sites work.
-the downlink (system to aircraft) is bandwidth-limited to a few hundred kbit/s for all aircraft combined in the coverage of the satellite transponder.  (This is somewhat over-simplified, as the uplink is intentionally sent in the clear, and many ADS-B receivers monitor the uplink of other aircraft for redundancy and more up-to-date information about traffic; see abive.)  AFAIK, the whole continental US is covered by less than 20 transponders. N The downlink carries not only traffic information but also cruise and airport weather, certain airspace restrictions, and so forth.  All this is broadcasted and the ADS-B receivers in the aircraft need to filter out the information relevant for its position, course, and intentions.  Already, the bandwidth available is almost fully utilized to the point that the broadcast occasionally needs to omit certain less-critical information to make space for more critical one.  The system scales only by adding satellite transponders, which is expensive and not a fine granularity.

As for Mars, ADS-B is unsuitable until someone builds a ground-station network and has suitable satellites in orbit.  A bit closer to earth, for over-water and trans-pole operations there is ADS-C, which is completely satellite based and, AFAIK, even more bandwidth limited than ADS-B.  Yet another example for a network unsuitable to carry IP traffic, but I digress.

In short, forget ADS-B for the DRIP work..

Stephan


On 8/4/20, 6:53 AM, "Tm-rid on behalf of Alexandre Petrescu" <[e-mail] on behalf of [e-mail]> wrote:

    architectural layers discussion...

    Le 30/07/2020 à 11:49, shuaiizhao(Shuai Zhao) a écrit :
    > Just to echo Stu on the ADSB, AFAIK, ADSB will  not be feasible for
    > most of the drones mostly due to SwaP, commercial drones might be
    > exception.

    It might be that ADS-B might be forbidden in drones on Earth, but how
    about the drones on Mars? ('NASA Mars helicopters', or ESA too).  On
    Mars there would be much less such drones, so less risk of interference.

    With such a system (ADS-B under IP) one could re-use DTN (Delay Tolerant
    Networking) between planets, and so identify drones even on Mars.

    But if we have reluctance about the use of ADS-B, and thus of IP, and we
    recommend Bluetooth-without-IP to identify drones, then we might become
    too dependent on it?

    (do not get me wrong, I do like Bluetooth, but I like many other things
    together with Bluetooth).

    Alex

    > 
    > Best,
    > 
    > Shuai Zhao
    > 
    > *From: *Tm-rid <[e-mail]> on behalf of "Stuart W.
    > Card" <[e-mail]> *Date: *Wednesday, July 29, 2020 at
    > 19:46 *To: *"[e-mail]" <[e-mail]> *Subject: *[Drip]
    > ADSB (was: Review of draft-drip-arch-02 w.r.t. RFC6973, RFC8280 and
    > other)(Internet mail)
    > 
    > Sorry for the slow reply.
    > 
    > ADS-B is gradually being mandated for essentially all manned
    > aircraft.
    > 
    > ADSB-In and ADSB-Out are mandated for airliners: -In gives their
    > pilots
    > 
    > some Situational Awareness (SA) of other aircraft; -Out gives other
    > 
    > pilots SA of the airliners.
    > 
    > "ADSB-Out" is mandated even for small general aviation aircraft: it
    > does
    > 
    > not directly benefit the pilots of those aircraft; but by providing
    > SA
    > 
    > to others, it indirectly benefits all.
    > 
    > ADSB is _not_ going to be deployed on large numbers of small UAS as
    > it
    > 
    > would overwhelm the limited bandwidth available at those lower radio
    > 
    > frequencies (which propagate long ranges). In fact, it is expected to
    > be
    > 
    > explicitly prohibited in the US per the FAA NPRM; I suspect most of
    > the
    > 
    > rest of the world will do likewise.
    > 
    > ADSB is also altogether insecure.
    > 
    > On 7/9/2020 3:02 AM, Alexandre Petrescu wrote:
    > 
    > ...
    > 
    > They call it "ADS-B Receivers" (Automatic Dependent Surveillance -
    > 
    > Broadcast).
    > 
    > I wouuld like to ask if there is a packet dump available showing
    > such
    > 
    > presence data form planes?  Maybe wireshark already supports it,
    > maybe
    > 
    > it even dissects it...
    > 
    > --
    > 
    > -----------------------------------------
    > 
    > Stuart W. Card, PhD, Principal Engineer
    > 
    > AX Enterprize, LLC  www.axenterprize.com
    > 
    > 4947 Commercial Drive, Yorkville NY 13495
    > 
    > 

    -- 
    Tm-rid mailing list
    [e-mail]
    https://www.ietf.org/mailman/listinfo/tm-rid