‘License Plates’ for Drones?

March 8, 2013
Filed under Security & Surveillance, More Issues in Security & Surveillance
Tags: drones
If we’re going to put cameras on drones and let just about anyone with a few hundred bucks fly them around our neighborhoods, recording video of anyone in our backyards and doing who-knows-what with them, shouldn’t there at least be a way to identify who the drone belongs to? Shouldn’t there be something akin to a “license plate” for drones? We think so.

Drones — also known as “unmanned aerial vehicles” or “unmanned aircraft systems” — have captured the media spotlight, thanks in no small part to Kentucky Senator Rand Paul’s withering 13-hour filibuster of President Obama’s nomination of John Brennan to head the CIA. Paul’s marathon rant was in opposition to the Administration’s legal position on potential uses of militarized drones within U.S. borders.

Weaponized drones in US airspace pose several concerns; however, at CDT we’ve focused lately on the more mundane, civilian uses of drones. The Federal Aviation Administration (FAA) recently issued a Request for Comment on safety and privacy issues of civilian uses of drones. As part of a longer FAA imperative to carefully integrate drone operations into civilian airspace, the FAA will establish six drone test sites to conduct research and collect data to assess safety, privacy and operational issues with drones. Surveillance and remote imaging will be a major use of civilian drones, useful for applications including traffic monitoring, weather forecasting, and mapping. Such uses naturally raise questions that implicate the privacy interests of individuals on the ground. There are many basic questions that should be answered before drones are allowed in America’s skies:

How can the public know what drones are operating in the skies above them?
How can the public learn more about a drone’s ownership and data collection capabilities?
Should there be a “license plate” for drones, like tail numbers on larger aircraft?
International treaties and FAA regulations require all US aircraft to display an “N-Number” (sometimes referred to as a “tail number”), similar to a license plate for automobiles. Anyone can query the FAA Registry to look up a tail number such as “N155AN” to find important details about the aircraft, including, for example, the name and address of the owner.

But tail numbers on drones? That doesn’t seem like a useful type of identifier. With no pilot on board, drones can be quite small and operate at high altitudes. Even with binoculars or more expensive spotting scopes, it’s unlikely that a drone’s N-number would be readable from the ground. So a traditional license plate-like insignia doesn’t seem to meet the transparency needs of our drone-filled future. In CDT’s comments to the FAA, we plan to propose a straightforward answer to this problem: the FAA should require each civilian drone to use an on-board radio frequency transmitter to broadcast an identifier, like an aircraft tail number. This would act like a “beacon” that would communicate a drone’s unique identification number to observers on the ground.

This radio-frequency drone identifier (RFDID) would allow members of the public to itemize the drones in a given airspace with relatively simple radio receivers. Ideally, the FAA would maintain a drone registry that would both detail metadata about a given drone by RFDID — like the FAA Aircraft Registry does now — and also provide a link to other information specifically needed for drones, such as the drone operator’s Data Collection Statement (that is, a privacy policy for a given drone and its operations).

Crowd-Sourcing Comments

While comments on the FAA Request for Comment are not due until next month (23 April), CDT wants to refine this idea between now and the comment deadline. We could use your help; we are not RF engineers and have a number of questions that should be addressed to make this proposal more viable. This is a nascent idea; as far as we can tell no one has proposed such an idea before, and there might be standards from other applications that could be applied to drone identification.

Here is some of the feedback we would appreciate in order to better understand the feasibility of our RFDID proposal:

What type of radio-frequency band should be used so as to not interfere with other radio-frequency operations? Should this be a dedicated area of existing aviation spectrum or unlicensed spectrum? What modulation or signaling techniques — such as frequency-division multiplexing — would allow the optimal allocation of broadcast identifiers?
Are there widely accepted standards for radio-frequency identification transmitters and associated protocols that we should recommend for this purpose to the FAA?
What signal protocol design would accommodate areas, such as large cities, where there maybe hundreds or thousands of drones aloft at one time?
What kinds of sanctions should exist for operating a drone without such a signal or with an impaired signal?
What kinds of technical characteristics should such a signal have? For example, should the signal be verified through a cryptographic signature to avoid drones spoofing each other’s identification numbers? Or are legal and policy sanctions against such measures enough? Should the strength of an RFDID signal depend on the spatial extent of its imaging capabilities?
Are there drone platforms where broadcasting an RFDID would be inappropriate for the class of drone (e.g., small toys) or due to weight and power limitations of the platform?