BACKGROUND

Unmanned Aerial Vehicles (UAVs) have been gaining popularity and as a result of their growing use have raised public safety concerns over their intentional and unintentional use near people and critical infrastructure such as airports, nuclear power facilities, transmission lines, bridges, sports stadiums, and the like. Recently, airports around the world have incurred direct and indirect costs from unplanned airport closures as a response to observed UAV incursions. Airplanes have been damaged in flight by UAV incursions, posing a serious safety risk to passengers, crew and the general public. Similarly, privacy and security concerns exist for high profile individuals, gatherings of people, and property owners where UAVs can easily circumvent current security and privacy measures.

The idea of using small, even toy drones is quite concerning to the security and defense community based on their experience with these drones in the field. This makes them particularly dangerous as a drone that is commercially available for $200 or less can inflict serious harm to a target person, crowd, or infrastructure. By way of example, opposing forces in the current conflict in the middle east used a DJI drone to determine where the soldiers where located; the Prime Minister of Japan had a sampling of nuclear waste from Fukushima dropped on his front lawn; and many other similar incidents have occurred. So while the disclosure includes them by way of example, these small toys can inflict asymmetric damage. Small UAVs can be used for spying, carrying biologically catastrophic payloads, weapons, and the like. A DJI Phantom 3, for example, can carry 500g of C4 explosive which bears approximately 3.25 ^χ 10 ⁶ joules of energy. Placed at a targeted location, a task ideally suited for small UAVs, can cause serious damage to any critical infrastructure.

While a new field of UAV detection is emerging, there is no effective solution for mitigating unwanted UAV incursions due to the complex legal framework in many jurisdictions around the world. For example, in the United States, airborne UAVs fall within the jurisdiction of the Federal Aviation Administration (FAA), whereas many of the agencies dealing with the aforementioned safety and security concerns are separately regulated. In these jurisdictions, it is illegal to interfere with an aircraft while in flight. Only duly authorized persons can affect interference with an aircraft, and even then, only when rigorous conditions have been satisfied.

Small UAVs pose a challenge to the conventional airspace system given their size, manoeuvrability, typical flight altitudes, and wide-spread use by practically anyone was not contemplated in the original airspace control framework. In a normally functioning airspace control system, interception responses to situations involving conventionally-operated aircraft are readily handled. For example, aircraft can be radar identified and confirmed easily as to deviations from their expected course, or potential violations to restricted airspace. Small UAVs, however, cannot be readily handled by the current airspace control system. For example, UAVs cannot easily be radar identified; those who do detect a UAV incursion often have nothing to do with the national or local airspace management system. By the time an interception order is given, it is often too late. Furthermore, current interception orders result in scrambling fighter jets, which are ineffective in dealing with small, low-flying UAVs. Given the complexity of expertise required and disjointed jurisdictions of authority, no single department is equipped to or authorized to deal with the problem. Needless to say, this complex legal loophole has enabled incursions to continue, creating a growing risk to the public. To deal with a rapidly evolving UAV incursion requires a coordinated system of separately regulated entities.

The present invention addresses these issues and enables User Agencies, including law enforcement, businesses, homeowners, and other individuals with a vested interest to enable rapid interception of offending UAVs by ensuring that communications to and from a command center with drones of many different types using different communications protocols is established and is reliable.

Present command and control (C2) capabilities have been designed to remotely pilot an aircraft unmanned aerial vehicle, or UAV. These C2 capabilities traditionally utilize an unlicensed segment of the radio-frequency spectrum, typically an Industrial, Scientific, and Medical band (902-928MHz, 2.4 - 2.4835GHz, 5.725-5.828GHz) or an U-NII band (5.15- 5.25GHz, 5.25-5.35GHZ, 5.47-5.725GHz, 5.725-5.825GHz, 57-64GHz). These RF bands are attractive and utilized since there is no license fee to use them, and they have sufficient bandwidth to handle UAV C2 applications. However, these bands are shared by others, making them unreliable, shortening the effective range, lowering the effective bandwidth, introducing communications errors, increasing latency, or various combinations of these effects. The overall range of these RF bands is low, often under 1km, and requires a radio line of sight to achieve even this range. Furthermore, the users of these RF bands are responsible for the entire infrastructure needed.

The present invention provides an elegant, relatively inexpensive solution to overcome these challenges. SUMMARY OF THE INVENTION

In accordance with an aspect of the invention, a method is provided for communicating with a UAV having a native communications protocol, wherein the UAV includes a cellular receiver or is in proximity of a cellular receiver for receiving signals over a cellular network. The method comprises: a) receiving with the cellular receiver, a signal including command or control information over the cellular network; b) decoding the signal; c) selecting from a library of protocols, a protocol the UAV is responsive to; and, d) sending sending by retransmitting the message to the UAV using the selected protocol over a frequency band which is distinct from the received signal frequency band In accordance with the invention there is further provided, in a system wherein a UAV has a built-in receiver for receiving command signals from a remote controller and wherein, in operation, the command signals are transmitted using a communications protocol and a messaging format at a frequency Fl, a method of communication over a cellular network at a frequency F2 comprising:

i. at the UAV:

a) receiving from the cellular network, an encoded message;

b) decoding the encoded message; and,

c) retransmitting the decoded message to the built-in receiver using the communications protocol, the messaging format and frequency F 1.

In accordance with another aspect of the invention a system is provided adapted to be coupled to a UAV having a native communications protocol or embedded within a UAV, for communicating between the UAV and a controller at a disparate location over a cellular network comprising:

a) a receiver for receiving cellular data transmitted over the cellular network; b) a decoder for decoding command and control information within received cellular data; and,

c) a transmitter for transmitting decoded command and control information to the UAV using the native communications layer of the UAV.

In a system wherein a UAV has a built-in receiver for receiving command signals from a remote controller and wherein, in operation, the command signals are transmitted using a communications protocol and messaging format at a frequency Fl, a method of communication over a cellular network at a frequency F2 comprising:

ii. at the UAV:

iii. receiving from the cellular network, an encoded message;

iv. decoding the encoded message;

and retransmitting the decoded message to the built-in receiver using the communications protocol and messaging format at frequency F 1. BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will now be described in which: FIGURE 1 is a diagram showing a system wherein two RF communications control devices, a cellular communications device, and an end computing device are provided in accordance with an embodiment of this invention.

FIGURE 2 is a diagram a system in accordance with this invention, wherein the communications system is comprised of only a cellular command and control network.

FIGURE 3 is a diagram of a system wherein the UAV or the C2 device function as communications repeaters for the cellular network. FIGURE 4 illustrates a device for communicating UAV C2 information over a plurality of networks.

FIGURE 5 illustrates the functioning of the controlling firmware program. Detailed Description

A communication protocol is a system of rules that allows for communication between a controller and a UAV or between two UAVs so that information may be transmitted. The protocol defines the rules, syntax, semantics, synchronization of communication and possible recovery methods, and protocols may be implemented in software, hardware, or both.

Communicating systems use well-defined formats for exchanging various messages. Each message has an exact meaning intended to elicit a response from a range of possible responses pre-determined for that particular situation. Multiple protocols often describe different aspects of a single communication. A group of protocols designed to work together are known as a protocol suite; when implemented in software they are called a protocol stack. UAVs made by different manufacturers do not all use the same protocols. More specifically to UAVs, the lowest protocol layer is a physical layer, relating to hardware such as antennas, frequency bands, etc. The highest layer is the application itself which affects what a UAVs action as a result of the communication. The layers between the lowest and highest layers are tasks required to do to establish, maintain, verify, route, start/stop, etc., These functions are typically provided by 7 protocol layer; the Open Systems Interconnection 7-layer model, which stack one on the next, often referred to as a protocol stack. A particular UAVs protocol layers are its native protocol communication layers, together forming the native protocol stack. A native UAV protocol is comprised of these same 7 layers, some of which are well-known and common in UAVs such as antennas, and some which are not common, for example, the specific pattern of frequency hopping that might be used. A preferred embodiment of this invention uses a software-defined radio (SDR) and a multi-band antenna to dynamically "re- program" it's 7 layer protocol to correspond to the manufacturer-specific protocol and its UAV-specific configuration instance.

By way of example, for the system of this invention to communicate with a target UAV made by DJI wherein the communications system comprises their Lightbridge and A3 controller products, the system would take over control by:

a) configuring its antenna to the 2.4GHz band at a gain » current remote controller received gain, nominally 3dB, or values above and below this range; b) matching the pre-existing frequency hopping pattern, i.e. bandwidth(s), centre frequency(ies) and duration for each hop;

c) inserting flow control, error checking, and sequence messages; and, d) inserting A3 control messages to effect the desired UAV response. Thus when communication is made with an intercepting UAV to a target UAV it is done using the native communication of the target UAV, however, without the joysticks, screens, and other human-interface elements that accompany the target UAV remote control device. The present invention provides a method and system for communicating with a UAV over a cellular network. In a preferred embodiment a module that can be attached to a UAV or embedded within during manufacture of the UAV has plurality of manufacturer protocols stored within which enable a software-defined radio to dynamically pair with an arbitrary UAV. The pairing can be done cooperatively, for example, through a user-initiated communications hand-over, or forcibly by assuming the physical, data link, network, session, and upper protocol layers of the C2 link for a given UAV at power levels exceeding the existing link.

Several methods exist for cooperative hand-over, including accessing an on-board UAV flight controller and issuing override commands. For example, drone manufacturer DJI of Shenzhen China offers an "On-board software development kit (SDK)" application- programming interface, which enables commands to be sent directly from a user-device to the system controller via a serial interface. A forcible take-over process combines the techniques of jamming, by way of example, inserting high power in-band "noise" and spoofing, by way of masquerading as the UAV C2 device, wherein the "noise" is the spoofed C2 messages that replicate the communications protocol layers associated with the target UAV. For example, the a device on or near a target UAV would begin transmitting lower-layer such as the physical, data link, network, session layer, information to the UAV in its native protocol format but with a stronger radio- frequency signal than the existing remote control device. This causes the UAV to effectively switch communications to the spoofing device rather than the existing, but distant remote controller. As one skilled in the art will appreciate, this method avoids the dangers associated with broad-based jamming, wherein other, friendly or otherwise important communications would be impacted, and furthermore, enables active control versus a default or unpredictable behaviour of the UAV should it's primary radio-frequency communications become unreliable.

Referring now to FIGURE 1, a system 100 is shown wherein a command and control of a UAV 102 is taken over by a communications device 108 over a cellular network. The communications system 111 is conventional and found in many prior art UAV systems. The system 110 however allows communications device 108 to take over control of the UAV 102 effectively rendering the control device 101 as useless. A radio-frequency control device 101, a UAV 102, a second radio-frequency communications control device 103, a radio-frequency network 104, a cellular communications device 105, a cellular communications tower 106, a cellular communications network 107, and an end computing device equipped with a cellular communications device 108 having interconnectivity are shown. In conventional UAV operations, command and control (C2) information is sent between a controller 101 and the UAV communications device 103 via a radio-frequency channel 104. Under a plurality of circumstances, including but not limited to a failure in the radio-frequency network 101, 103, or 104, a boundary condition of the UAV 102 being exceeded, such as flying into a restricted area, an air traffic control override, or simply by the user of the UAV desiring to switch control methods, the cellular communications system 110 takes over primary control from the RF communications system 111.

In FIGURE 2 200 depicts the system of 100 wherein the communications system consists of a cellular command and control network. In this case, the UAV 202 C2 information is sent between the controller 201 and the UAV communications device 203 via a cellular network 204 consisting of at least one cellular base station 205.

In FIGURE 3 a system 300 is shown, wherein the UAV 301 or the C2 device 302 function as communications repeaters for the cellular network 303. FIGURE 4 is a block diagram of a device 400 preferably housed within a module that can be built into a UAV or attached to a UAV for communicating UAV C2 information over a plurality of networks, comprising a cellular network physical interface 401, a cellular network encoder 402, a controlling firmware program 403, a library of UAV C2 protocols 404, a software-defined radio applicable to the unlicensed radio-frequency bands 405, and a radio- frequency network physical interface 406. In a particular embodiment a STM32F205RGT6 120MHz ARM ® Cortex M3 microcontroller is used for the cellular and protocol selection components, and a software-defined radio for the RF link, such as a RF24L01 chipset for Wi-Fi-compatible UAVs, or a LimeSDR capable of handing a plurality protocols.

FIGURE 5 is a flow chart illustrating the functioning of the controlling firmware program 403, wherein a series of steps are performed to communicate UAV C2 messages in their native format over a cellular network. The firmware executed by a processor comprises the steps of decoding a message 501 from a known messaging protocol, determining the instruction set to be carried out 502, selecting a target UAV protocol from a plurality of manufacturer protocols 503, establishing a radio-frequency link with a target UAV using the selected protocol 504, ensuring safety conditions are met 505, formulating an outgoing message conforming to the selected UAV protocol 506, sending and receiving C2 information of said radio-frequency link 507, and confirming the desired behaviour of the target UAV 508. If the link-establishment process is successful, the C2 instructions continue until such time as a pre-determined condition has been met, such as the UAV being landed, or when the C2 link has been handed back to the primary controller.

FIGURE 6 is a flowchart of the selection algorithm identified in 503. The algorithm comprises a series of steps to progressively decode the communications layers of a target UAV based on a library of known manufacturer communications protocols. The algorithm starts with monitoring a given radio-frequency band physical layer 601 and applying an RF filter function 602 to identify the signals which are likely to be emanating from the UAV. Alternatively a filter can be applied to identify signals likely to be emanating from a controller. The filter isolates single-channel communications, such as Wi-Fi as well as spread-spectrum and frequency-hopping protocols. A hierarchical pattern-matching algorithm is used to encode features of the physical layer such as base frequency spectrum, hop pattern, amplitude 603 and identify potential matches from a library of manufacturer physical layer protocols 604. If a match is found 605, the algorithm proceeds progressively through the next layers of protocol decoding 608 through 612, until the key parameters of each protocol layer has been captured. These parameters are stored in memory 614 to be used by the main C2 program 500.