Solutions - Group 4 - 2018/2019, Semester B, Quartile 3
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In this section, we consider the requirements of solutions for the problem proposed in the specific problem description, all possible solutions, and both the advantages and disadvantages of each solution.
When considering the state of the art research presented in the relevant Section, we can distinguish multiple categories in which the presented solutions might fall. In this Section, we further elaborate on these different categories, and as such provide a better overview and allow for more a more specific formulation of requirements. Firstly, different anti-UAV systems serve different purposes. For our study, we differentiate between the following purposes:
- UAV Detection
- These systems serve to detect the presence of UAVs in unwanted airspaces. They often also locate the UAV in question and sometimes include the possibility of continuous location tracking to assist systems categorised under the other purposes.
- UAV Identification
- Systems from this category serve to identify UAVs, obtaining more information about the UAV than simply its location. This information might include simple statistics, such as the average size of the drone which can often be observed by a human, given that the UAV is present in their field of view. More complicated statistics might also be obtained, such as a serial tracking number to identify commercial UAVs.
- UAV Neutralisation
- Drone neutralisation systems serve to neutralise a drone. This is the main topic of our study since UAV presence in the airspace above an airport introduces various risks, discussed in other Sections, that have to be neutralised in order to maintain public and societal security.
Now that the scope of the purpose of the anti UAV systems for airport security that we consider has become clear, we might further distinguish the main purpose considered in this study. As such, we differentiate between 3 different subcategories, all part of the drone neutralisation purpose. These categories are as follows:
- Preventative solutions
- This category encompasses all solutions that serve to prevent the problem from occurring. More specifically, entries of this category focus on keeping UAVs away from airspace belonging to airports. An example might include the geofencing system that was described previously and will be elaborated on further in the following sections.
- Corrective solutions
- Solutions from this category focus on solving the problem of UAV presence in the airspace over airports, specifically when said UAV is already present in that airspace. These solutions attempt to do so with minimal damage to the parties involved, an example might consist of a procedure where the control of the drone is overridden, either automatically or by a human, before the drone is removed from the airspace by landing or flight and after which control could be passed back to the pilot.
- Destructive solutions
- These solutions have the same area of focus as the previous category of corrective solutions, namely the minimising of further risk to air traffic above airports after a UAV has entered the airspace. The main difference is that, while corrective solutions attempt to do so in a non-destructive way, this limitation does not apply to destructive solutions. Sub-systems of a UAV or the UAV as a whole may be destroyed or permanently disabled. A coarse example consists of taking down unwanted UAVs with firearms, causing damage to the UAV and rendering it unable to continue operations.
This division into categories is not entirely black on white, however. Consider an abstract example system that temporarily incapacitates a UAV in flight, causing it to cease operation and enter a free fall towards the ground. This might result in the destruction of the drone, given the collision with the ground. We have found a grey area in our division into subcategories, and as such, we further define destructive solutions as those solutions, where the incapacitation of the drone follows from the destruction, and not the other way around. We also require the destruction to be an integral part of the solution, if we want it to count as a destructive solution. In this example, the destruction is not guaranteed nor does the incapacitation follow from the destruction. Instead, the destruction might follow from the incapacitation, dependent on other circumstances. Therefore, this specific example counts as a preventative or corrective solution, based on where the UAV in question is located. Note, however, that this is based on the keywords `temporarily incapacitates'. If the incapacitation of the UAV or one of its subsystems were permanent, the destruction would be guaranteed since it does not depend on how hard the UAV hits the ground anymore. In this case, it would count as a destructive solution.
A solution to the specific problem described will have to adhere to requirements. These requirements are not simply capabilities the solution has to provide in the form of functional requirements, but they should also cover constraints posed on the solution. The constraints can be on the design of the solution in order to meet specified levels of quality, on the environment and technology of the system, and on the project plan and development methods.
While providing these requirements, we need to make sure they are atomic. Furthermore, they need to be clearly identified, sufficiently precise and unambiguous, sufficiently verifiable, and prioritised. We use the MoSCoW model for the prioritisation of the requirements. This model considers must have, should have, could have, and won't have, which indicate the priority of a requirement.
Furthermore, these requirements might serve as a basic framework for further development of solutions to similar problems, thereby widening the scope to other problem spaces involving UAVs as well.
The functional requirements (capabilities) of the solution are as follows:
- The solution should be able to take down any type of drone effectively.
- The solution should not endanger any humans with any of its actions.
The non-functional requirements of the solution are as follows:
- The solution should adhere to the new rules proposed in the `New Rules' subsection in the `Present situation' section.
- The solution should adhere to the new rules proposed in the `Limitations' subsection in the `Present situation' section.
As we have already elaborated on, a possible solution can be categorized into the purpose it fulfils with respect to anti-UAV systems at and around airports. Since a full anti-UAV system should be able to do three things: detect aerial objects, identify that this object is an (unwanted) UAV, and lastly neutralization of the UAV. However, the identification of the object might be something that is up for discussion, since it might be safer to neutralize every aerial object, we will discuss this later on. As most possible (partial) solutions only cover one or two of the three things it should be able to do, before it can be considered at a full anti-UAV system, for each of the (partial) solutions listed below, they are divided up into categories of its purposes it fulfils. Such that, later on, we can compare and afterwards combine multiple of these partial solutions into one system that meets the needs of the users.
- Radar system for detecting the location and height of an object in the air. The radar makes use of a transmitter which produces an electromagnetic signal which is radiated into airspace with an antenna. If this signal hits an areal object, it will get reflected in many directions. This reflected signal is received by the radar antenna then it is processed to determine the geographical data of the object.
- A Wi-Fi receiver can be used to detect a UAV based on the signature of the signal reflected from the propellers of a UAV. Similar to a radar, a transmitter broadcasts signals and a receiver captures reflected signals that bounce of a UAV. 
- Detect a UAV by listening to the communication channel between the UAV and its controller using a wireless receiver. Usually, UAVs communicate with their controllers a few times per second to update their status and to receive commands from the controller. A system could collect wireless samples and observes the signal, analyse them and can then detect a UAV's presence. 
- Detection of UAVs with the use of other UAVs that fly around the airports, carrying lightweight radar systems or cameras to scan their environment.
- Identification of any specific aircraft can be done by broadcasting a coded signal, which is decoded by air traffic control towers. Such that allies and enemies can be identified and to avoid targeting a friendly aircraft. As a result, all aircraft where radar service is provided should require systems that are able to broadcast coded signals for identification, for this solution to work. 
- For identification of UAVs, employing a 2D antenna and appropriate signal processing to create a multibeam, 3D, wide area overcomes the weakness of scanning radars and achieves high detection sensitivity. A decision tree based classifier can be used to identify the difference between UAVs and other moving objects. Where it rejects non-UAV targets, decreasing the number of false positives and increases true positives. Such that when neutralizing such a moving object in the air, with high probability, it will be a drone instead of for example a flying bird. 
- A lightweight, X-Band (10.5GHz) radar system for use on a small-scale (less than 25 kg) rotorcraft. The prototype implementation of the radar is small enough to be carried by a drone and is able to differentiate other 'miniature rotorcrafts' (drones) by their doppler signature. The prototype uses a radar system which utilizes electromagnetic energy to gain information on objects by analyzing the reflected energy. 
- Taking out UAVs by using air to air missiles, where these air missiles could be launched from other UAVs used by the airport or possibly any other aerial vehicle.
- Taking out UAVs or disabling specific subsystems might be achievable by using lasers. Different kinds of lasers can be used for different purposes, either permanently or temporarily disabling a UAV. 
- Electromagnetic attacks to interfere with the GPS signals of the UAV, that the UAV uses to position itself. Jamming the GPS signals causes the UAV to not be able to follow the pilot's navigation commands accurately.
- Taking control of a UAV by spoofing the GPS signals of the UAV, such that the UAV thinks that it is still talking to the original pilot when it is actually being taken over. This way the drone can easily and safely be landed somewhere out of danger.
- Capturing a UAV using another UAV carrying a net, which drops the net over the unwanted UAV. Thereby taking control of the UAV as the net makes sure the UAVs rotors get tangled in the net making sure it is unusable for the pilot. Then with a parachute on the net, it can be made sure that the UAV lands safely on the ground
- A bazooka with an intelligent locking system to aid the controller to hit the UAV successfully, that shoots a net to capture a UAV. The rotors of the UAV will then get tangled in the net, making sure it cannot cause any harm anymore. Then a parachute that is attached to the net will make sure that the UAV will land safely on the ground. 
- Transmitting geo-fence coordinates, avoidance commands or disruption of radio communication in order to avoid UAV's entering no-fly zone. 
- Using trained eagles to neutralize UAVs. These eagles would be trained into considering UAVs as preys so that they could catch these drones and place them in a safe area. 
- Geo-fencing software built into the UAVs restricts consumer UAVs to even be able to fly within a certain range of unwanted areas such as airports. 
- Using high powered radio waves to disable drones, it blocks their communication with the controller and switches them off mid-air. 
Advantages and disadvantages
- Advantages and disadvantages based on the requirements of a solution (feasibility of actually making it and jurisdiction).
- Radar system
- A lot of the technology already exists, making the solution cheaper.
- Radar systems are very accurate.
- Most airports already have radar systems, and they don't seem to suffice. Adding custom gear could cause interference.
- WiFi receiver
- Can accurately determine the position of drones.
- Wifi is very susceptible to interference.
- WiFi signals are blocked by obstacles.
- Listening on communication between drone and ground
- Intercepting communication is an easy way to detect the presence of drones.
- Often communications are not encrypted, allowing the interception of precise location
- Prosumer or custom built drones might use very different communication standards or fly a pre-programmed path.
- Detecting drones with other drones
- as the radar system is moving, there are no objects that can block the list of sight
- Flying around with a drone at a busy airport can be quite dangerous.
- Drones can only stay in the air for a limited time due to battery constraints.
Back to the root page.
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Yin, Tung. "Game of drones: defending against drone terrorism", Tex. A&M L, 2015. Retrieved on 2019-02-06.
- ↑ 2.0 2.1 Nguyen, P., Ravindranatha, M., Nguyen, A., Han, R., & Vu, T. "Investigating Cost-effective RF-based Detection of Drones", ACM, June 2016. Retrieved on 2019-02-06.
- ↑ Jahangir, M., & Baker, C. "Persistence Surveillance of Difficult to Detect microdrones with L-band 3-D Holographic RadarTM", Sensor Signal Processing for Defence (SSPD), September 2016. Retrieved on 2019-02-07.
- ↑ Moses, A., Rutherford, M. J., & Valavanis, K. P "Radar-Based Detection and Identification for Miniature Air Vehicles", Control Applications (CCA), September 2011. Retrieved on 2019-02-07.
- ↑ Liberatore, S., "How do you catch a drone? With an even BIGGER drone and a giant net: Tokyo police reveal bizarre 'UAV catcher'", DailyMail, December 2015, Retrieved on 2019-02-07.
- ↑ Burns, M., https://techcrunch.com/2016/03/04/the-skywall-100-bazooka-captures-drones-with-a-giant-net/?guccounter=1 "The SkyWall 100 bazooka captures drones with a giant net"], TechCrunch, 2016, Retrieved on 2019-02-07.
- ↑ Etak Systems LLC."Anti-drone flight protection systems and methods", Google patents, 2016. Retrieved on 2019-02-07.
- ↑ Thuy Ong. "Dutch police will stop using drone-hunting eagles since they weren't doing what they're told", 12 December 2017, Retrieved on 14-02-2019
- ↑ Gettinger, D., & Michel, A. H. " "Drone sightings and close encounters: An analysis", Center for the Study of the Drone, Bard College, 2015. Retrieved on 2019-02-14.
- ↑ Adam Bannister. "With anti-drone tech on the market, why was Gatwick Airport so unprepared?", December 21 2018, Retrieved on 14-02-2019
- ↑ The U.S. government showed just how easy it is to hack drones made by Parrot, DBPower and Cheerson. (2017). Recode. Retrieved 15 February 2019, from