Method of detecting a drone with an on-board user equipment, corresponding device and computer program

Abstract

The present invention relates to the detection of drones. The use of drones to cellular communication networks can cause problems due to the interference generated by the on-board user equipment of the drones flying above the antennas of the base stations. It is important that the telecommunication operators can control the use of drones to cellular communication networks. There are methods that allow detecting drones. Although these methods allow determining the position of the drones, they do not provide a satisfactory detection accuracy. Also, they do not allow distinguishing between two drones in similar positions. The present invention is based on the use of reference signals whose characteristics are known, and on the use of known properties of the transmission channels established between the base stations and the user equipment, to determine accurate and reliable altitude values.

Description

TECHNICAL FIELD

[0001] The field of the invention is that of drones embedding user equipment able to communicate with base stations. More particularly, the invention relates to detecting such drones by means of equipment of the communication network to which the user equipment is attached. BACKGROUND

[0002] The use of drones or UAVs ("Unmanned Aerial Vehicles") for military purposes is tending to develop in the civil field, in particular for professional and recreational purposes.

[0003] These drones are generally controlled by means of direct radio signals exchanged between the drone and the controller equipment. In order to increase the distance between the controller equipment and the drone, in particular for professional use, the direct communication established between the drone and its controller equipment is replaced by a communication established through a cellular communication network. In this case, the drone, possibly also its controller equipment, is equipped with a user equipment connected to the cellular communication network. This configuration of use based on the use of a cellular communication network is likely to develop.

[0004] However, the use of the user equipment embedded in the drone can cause problems for the cellular communication network, which has been configured to communicate with user equipment located lower than the antennas of the base stations constituting the cellular communication network, due to the interference generated by this user equipment embedded in the drone flying higher than the antennas of the base stations constituting the cellular communication network.

[0005] It is therefore important for the telecommunication operators to be able to control access to the cellular communication network and to the use of the cellular communication network by the user equipment embedded in the drone, that is to say, to allow this use when the operator decides to offer it to the users and to control access to the users authorized for this use, for example people who have subscribed to a particular offer. This need is also expressed in the TS 22.125 specification: "3GPP systems shall enable UTM to associate drones and UAV controllers, identifying them as UAS", published by the 3GPP (3rd Generation Partnership Project) standardization body.

[0006] The user equipment embedded in the drone has the possibility to identify itself to the equipment of the cellular communication network as being located on a drone by means of a specific indicator contained in a field of a signaling message exchanged with the equipment of the cellular communication network during the attachment of the user equipment to the cellular communication network. The definition of such an indicator can be found in the 3GPP_TSG_SA_WG2 related documents.

[0007] In the rest of the document, for simplicity, the expression "identified as a drone" is used to mean that a user equipment embedded in a drone identifies itself as being on a drone. However, some user equipments embedded in drones do not identify themselves as such to the cellular communication network.

[0008] There exist methods allowing to detect a drone without the drone being aware, such as the method described in Phuc Nguyen, Taeho Kim, Jinpeng Miao, Daniel Hesselius, Erin E Kenneally, Dan Frank Massey, Eric W Frew, Richard Han, Tam Vu, "Towards RF-based Localization of a Drone and Its Controller", In Proceedings of the 5th Workshop on Micro Aerial Vehicles, Systems and Applications - DroNet '19 - June 2019 - Pages 21-26.

[0009] This method is based on the analysis of radio signals coming from user equipments embedded in drones, without a priori knowledge of the messages sent by the user equipments, only a priori knowledge of the carrier frequencies and frequency bands of these radio signals. The system comprises two detection modules, able to identify the direction of reception of radio signals sent by user equipments embedded in drones and by controller devices of drones. Each detection module comprises an omnidirectional antenna for detecting radio signals coming from user equipments embedded in drones, and a directional antenna for identifying the direction of radio signals sent from user equipments embedded in drones and by controller devices.

[0010] Each detection module extracts information from radio signals sent by user equipments embedded in drones, and identifies the angle of incidence of the radio signals using the directional antenna. By combining the information obtained by each of the two detection modules, it is possible to obtain the position of the user equipment embedded in the drone, and therefore the position of the drone itself and of its controller device.

[0011] This method, although allowing to determine the position of a drone and of its controller device, does not provide satisfactory detection accuracy, especially in the case of multipath propagation of radio signals sent by user equipments embedded in drones. Similarly, this method does not allow to distinguish two drones if their positions are close.

[0012] There is therefore a need for a drone detection solution that does not have some or all of the above-mentioned drawbacks. SUMMARY

[0013] The invention meets this need by providing a method for determining a reception beam from a plurality of reception beams of the base station, through which at least one reference signal transmitted by a user equipment is received,

[0014] - determining a reception beam from a plurality of reception beams of the base station, through which at least one reference signal transmitted by a user equipment is received,

[0015] - detecting the drone as a function of at least one parameter determined from the at least one reference signal received through the determined reception beam.

[0016] This detection method is based on the use of reference signals transmitted by a user equipment embedded in a drone, and the detection of these reference signals by a base station equipped with a plurality of reception antennas. These reference signals are transmitted by the user equipment for data communication through a cellular communication network. Some reference signals are necessary for the base station to be able to correctly demodulate the data transmitted by the user equipment, while other reference signals (or sometimes the same reference signals) are used by the base station to adapt its transmission parameters to the user equipment. Examples of reference signals or reference symbols (RS) for 5G are given in the document TS 38.211 published by 3GPP.

[0017] This plurality of reception antennas of the base station can apply a processing to the reference signals received on each antenna. Such a processing is defined so that the result of its application to a received reference signal gives an indication of the power received in a given direction. This reception processing is generally predefined at the time of installation of the base station. Each processing corresponds to a reception beam, the direction of which in space is notably indicated by an elevation angle.

[0018] This detection method therefore comprises identifying the reception beam through which the reference signals transmitted by the user equipment are received, on the basis of the reception power values of the reference signals calculated for all the reception beams.

[0019] Since the reference signals used are specific to a given user equipment, the base station has the information necessary to identify this user equipment with certainty.

[0020] Since the reference signals are signals transmitted by all the user equipments connected to the base station, whether or not they are located on a drone, it is possible to use them to determine that a user equipment is embedded in a drone without the owner of the user equipment, and therefore of the drone, being aware of it.

[0021] According to one characteristic of this detection method, said at least one parameter is a high altitude degree of the user equipment determined as a function of the value of the elevation angle associated with the reception beam through which the at least one reference signal is received, and wherein the drone is detected when the altitude of the user equipment is greater than or equal to a detection threshold.

[0022] Once the reception beam is identified, the altitude of the user equipment embedded in the drone is calculated as a function of the distance separating the base station from the user equipment, and of the elevation angle of the reception beam, and thus of the altitude of the extended drone.

[0023] According to one feature of the detection method, the at least one parameter comprises a plurality of power spectral density values representative of the vibrations generated by the drone.

[0024] By studying the frequency response of the received reference signal, it is possible to detect, in a specific frequency band of the frequency response, power spectral density values representative of the vibrations generated by the drone.

[0025] Indeed, the vibrations generated by the drone in flight conditions have an impact on the reference signal transmitted by the user equipment and received by the base station. This vibration appears in the frequency response of the reference signal(s) received by the base station.

[0026] In one embodiment of the detection method, when the altitude of the user equipment is below a detection threshold, the at least one parameter comprises a plurality of power spectral density values representative of the vibrations generated by the drone.

[0027] In this other embodiment, the detection method allows to detect a drone despite the altitude of the drone being below a detection threshold. Indeed, when the presence of vibrations generated by the drone UAV is detected in the frequency response of the received reference signal, the user equipment is considered as being embedded in the drone despite the altitude of the user equipment being below a detection threshold.

[0028] It is then possible to detect the drone early, shortly after take-off, or for a drone flying deliberately at low altitude.

[0029] According to one feature of the detection method, the altitude of the user equipment is determined as a function of at least one of the following parameters:

[0030] - the distance between the base station and the user equipment,

[0031] - the received power of the at least one reference signal,

[0032] - the signal propagation loss law.

[0033] Since the detection method is based on the use of a reference signal, the characteristics of which are known (for example the transmitted power), and on the use of known properties of the propagation channel established between the base station and the user equipment (for example the signal propagation loss law through the propagation channel), the value of the altitude determined when the detection method is performed is accurate and reliable.

[0034] According to another feature, the detection method further comprises a step of sending a message to a management entity of the network, the message comprising the altitude of the drone and / or an indication of the detection in the frequency response of the at least one received control of a plurality of power spectral density values representative of the vibrations generated by the drone.

[0035] The base station sends to a management entity of the network the detection method, the altitude and / or the result of the detection in the frequency response of the received reference signal of the presence of the vibrations of the drone representative. This network management entity decides whether to maintain or not the communication session established by the base station between the user equipment and the devices of the cellular communication network depending on whether the user equipment is embedded in the drone or not.

[0036] According to a feature of said detection method, the step of determining from the plurality of reception beams of the base station the reception beam through which at least one reference signal is received comprises:

[0037] - determining for at least one reception beam a received power value of the reference signal received through said beam:

[0038]

[0039] where s pilot is the reference signal, w (r) represents the received power value of the reference signal, is a row vector of complex coefficients of dimension N x 1 representative of the reception beam; is a column vector of complex coefficients of dimension 1 x N representative of the propagation channel estimate of the predefined subcarriers between the base station and the user equipment, N being the number of reception antennas of the base station, and r e {1,..., R}, where R is the number of reception beams of the base station,

[0040] - determining the reception beam for which the received power value of the at least one reference signal is greater than the received power values of the at least one reference signal determined for the other reception beams.

[0041] The selected reception beam is the reception beam having a greater received power value than the other reception beams. In other words, the selected reception beam is the reception beam whose spatial direction is the closest to the spatial direction from which the reference signal transmitted by the user equipment comes.

[0042] In one embodiment of the detection method, the altitude of the user equipment is determined as follows:

[0043]

[0044] where h is the altitude of the user equipment and H is the altitude of the base station, is the elevation angle of the receiving beam, the value of the received power of at least one reference signal is greater than the value of the received power of the at least one reference signal determined for other receiving beams, d is the distance between the base station and the user equipment, if x>0, then sign(x)=1, otherwise sign(x)=-1.

[0045] The elevation angle is positive when the received beam is above the horizontal plane passing over the top of the base station, and negative when the received beam is below the same horizontal plane. Therefore, a negative elevation angle means that the user equipment is at an altitude lower than the base station.

[0046] The present invention also relates to a method for communication between a network management entity and a user device embedded in a drone, the method being implemented by the network management entity and comprising the following steps:

[0047] - Receive messages transmitted from a base station to which the user equipment is connected, the messages including the altitude of the drone and / or an indication of vibrations generated by the drone detected in the frequency response of at least one reference signal transmitted by the user equipment and received by the base station.

[0048] - When it is determined that the detected altitude and / or vibration correspond to a drone, a message is sent to the user equipment requesting that it recognize itself as a drone.

[0049] The network's management entity sends information to the cellular network entity about whether the user equipment is embedded or not in the drone, and the entity can decide whether to maintain the communication session established between the user equipment and the cellular network via the base station.

[0050] In an alternative embodiment of the communication method, the method includes the step of interrupting a communication session established between the user equipment and a device in the communication network via a base station when the user equipment does not identify itself as a drone.

[0051] The present invention also relates to a base station capable of detecting a drone, the drone having onboard user equipment connected to the base station, the base station including components for:

[0052] - Determine a receiving beam from among the multiple receiving beams of the base station, and receive at least one reference signal transmitted by the user equipment through that receiving beam.

[0053] - Determine the altitude of the user equipment based on the received power of the at least one reference signal and the elevation angle associated with the received beam through which the at least one reference signal is received.

[0054] - Detect drones when the user device's altitude is greater than or equal to a threshold.

[0055] Such a base station is for example a "next generation Node B" (gNB) type device.

[0056] According to one feature of the base station, the latter further comprises means for sending to a management entity of the network a message comprising an altitude of the drone and / or an indication of a plurality of power spectral density values representative of vibrations generated by the drone detected in the frequency response of said at least one received reference signal.

[0057] The application also relates to a management entity of a network able to communicate with a user equipment embedded in a drone, the management entity of the network comprising means for:

[0058] - receiving a message sent from a base station to which the user equipment is connected, the message comprising an altitude of the drone and / or an indication of vibrations generated by the drone detected in the frequency response of at least one reference signal transmitted by the user equipment and received by the base station,

[0059] - when determining that the detected altitude and / or vibrations correspond to the drone, sending to the user equipment a message requesting it to identify itself as a drone.

[0060] In one embodiment of the management entity of the network, the latter comprises, when the user equipment does not identify itself as a drone, means for implementing interrupting a communication session established by the base station between the user equipment and a device of the communication network.

[0061] The application finally relates to a computer program product comprising program code instructions for implementing a method as described above when executed by a processor.

[0062] The application also relates to a computer-readable storage medium on which a computer program is stored, the computer program comprising program code instructions for executing the steps of the method according to the application described above.

[0063] Such a recording medium can be any entity or device capable of storing the program. For example, the medium can include a storage medium, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or a magnetic recording medium, such as a USB stick or a hard disk.

[0064] On the other hand, such a recording medium can be a transmissible medium such as an electrical or optical signal, which can be transmitted by cable or by optical cable, by radio or by other means, making it possible for a remote device to execute the computer program contained in the medium. The program according to the application can in particular be downloaded from a network, for example the Internet.

[0065] Alternatively, the recording medium can be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to implement the above-mentioned method as an object of the application. BRIEF DESCRIPTION OF DRAWINGS

[0066] Other objects, characteristics and advantages of the application will become more clearly understood in the course of the following description, given by way of simple illustrative and non-limiting example, with reference to the enclosed drawings wherein:

[0067] [ Figure 1 ] is a diagram representing a system in which the method for detecting drones is implemented,

[0068] [ Figure 2 ] is a diagram representing the different steps implemented when carrying out the detection method and the communication method which are the objects of the application,

[0069] [ Figure 3 ] is a diagram representing an example of frequency response which can detect such vibrations,

[0070] [ Figure 4 ] is a diagram representing a base station according to an embodiment of the application,

[0071] [ Figure 5 ] is a diagram representing a management entity of a network according to an embodiment of the application. DETAILED DESCRIPTION

[0072] The general principle of the application is based on the use of reference signals transmitted by a user equipment located on board or embedded in a drone, and the detection of these reference signals by a base station equipped with a plurality of receiving antennas. This plurality of antennas can apply a predefined processing to the reference signals received on each receiving antenna of the base station. This processing is defined so that the result of its application to the received reference signals gives an indication of the power received in a given direction. Each receiving processing corresponds to a receiving beam whose direction in space is notably indicated by an elevation angle. Once the receiving beam has been identified, through which the reference signal is received with the highest reception power value among all the receiving beams, the altitude of the drone is calculated as a function of the distance separating the base station from the user equipment and as a function of the elevation angle of the identified receiving beam, thus enabling the drone to be detected.

[0073] With regard to Figure 1 ] a system in which the method for detecting drones is implemented is now set out.

[0074] This system comprises at least one drone UAV, which has an on-board user equipment UE. The drone UAV is located at an altitude h.

[0075] This system also comprises a base station gNB, for example a device gNB, located on a building. The base station gNB is located at an altitude H. Such a base station gNB comprises N receiving antennas, not shown in the diagram. R receiving beams p (r)r e {1,...,R} is associated with the N receive antennas of the base station gNB. Each of the R receive beams p (r) corresponds to a direction in space. Such a direction is represented by the value of the elevation angle e r When the associated receive beam is above the horizontal plane PH passing through the top of the base station gNB, the elevation angle e r has a positive value, while when the associated receive beam is below this same horizontal plane PH, the elevation angle e r has a negative value.

[0076] Finally, d denotes the distance between the base station gNB and the drone UAV or the user equipment UE.

[0077] [ Figure 2 ] denotes the different steps implemented when carrying out the detection method and the communication method which are the object of the application.

[0078] In step E1, the user equipment UE sends a first message MSG1 to the base station gNB to request registration to the devices of the cellular communication network.

[0079] In step E2, the message MSG1 is sent by the base station to the management entity AMF of the network. The details of the exchanges between the user equipment UE, the base station gNB and the management entity AMF of the network are specified in the document TS 38.331 version 15.8.0 published by 3GPP.

[0080] During step E3, the management entity AMF of the network sends to the user equipment an identification request MSG2 so that the user equipment authenticates itself to the cellular communication network as a drone.

[0081] The user equipment UE responds to the message MSG2 during step E4 by sending a message MSG3 to the management entity AMF of the network. The message MSG3 can include the identity of the drone with the user equipment UE on board, or it can indicate that the user equipment UE is not located on a drone. This exchange of messages between the user equipment UE and the management entity AMF of the network can take place between steps 19 and 21 of the procedure specified in article 4.2.2.2.2 of the document TS 23.501 version 15.8.0 published by 3GPP, or at another point in this procedure. In a particular embodiment, this step is not implemented. In this case, the non-sending of the message MSG3 by the user equipment is considered as an indication that the user equipment UE is not located on a drone UAV.

[0082] In step E5, the management entity AMF of the network sends a message MSG4 to confirm the registration of the user equipment UE to the cellular communication network.

[0083] During step E6, the user equipment UE sends a message MSG5 to the management entity AMF of the network, to request the establishment of a data session with the device of the cellular communication network, which the AMF in turn relays to the device of the cellular communication network in charge of establishing and managing this session. The document TS 23.502 version 15.8.0 clause 4.3.2.2.1 or 4.3.2.2.2 published by 3GPP specifies such a procedure.

[0084] In step E7, the drone UAV takes off. The device of the cellular communication network is not informed of this event.

[0085] These steps E1 to E6 do not directly trigger steps E7 and the following steps, but are for example prerequisite conditions to ensure that the detection method and the communication processing which are the object of the application are correctly performed.

[0086] In step E8, the management entity AMF of the network sends a message MSG6 to the station gNB, requesting the station gNB to perform measurements in order to detect the presence of a possible drone. This step E8 can be triggered at the expiry of a timeout time, the start of which is set by the management entity AMF of the network, and can be repeated over time. According to another embodiment, it is the base station gNB itself which triggers the measurements.

[0087] During step E9, the base station gNB performs the measurements. The base station gNB receives on its N receive antennas SRS reference signals, for example sounding reference signals, sent by the user equipment UE. Such SRS reference signals are sent periodically by the user equipment UE.

[0088] The base station gNB estimates from known methods for each of its N receive antennas a complex coefficient representative of the propagation channel established between the user equipment UE and the considered receive antenna. The result of this estimation is a vector h. The vector h is a 1 x N complex column vector in which are arranged all the coefficients h i , the coefficient h i corresponding to the antenna i of the base station gNB.

[0089] R receive beams p (r) where r e {1,..., R} are associated with the N receive antennas of the base station gNB. A receive beam is denoted by p (r) . The vector p (r) is a complex line vector of dimension N x 1. Each p (r)Vectors are pre-computed according to known methods in the field of beamforming to point in a given direction in space relative to the receiving antennas of the base station gNB at reception. For example, if the base station gNB is equipped with a regular array of antennas in a rectangle (so-called "upright", i.e. perpendicular to the ground), the array comprising M horizontal rows numbered m = 0...M-1 from high to low in altitude and Q vertical columns numbered q = 0...Q-1 from left to right, the reception beam can be composed of the coefficients of a two-dimensional Discrete Fourier Transform of size MxQ = N, as follows:

[0090] where:

[0091] • m = 0...M-1

[0092] • q = 0...Q-1

[0093] • n = Mxq + m

[0094] • μ(r) ∈ [0; M-1]

[0095] • μ(r') ∈ [0; M-1]

[0096] • if r ≠ r', μ(r') ≠ μ(r) • μ(r') ≠ μ(r) if r = r' (without necessarily at the same time μ(r') ≠ μ(r) and ), where r is the reception beam, μ(r) denotes the vertical direction or elevation angle, taking values between 0 and M, denotes the horizontal direction, taking values between 0 and Q.

[0097] The elevation angle corresponding to this reception beam r is given by

[0098] • θ(r) is 0 ≤ θ(r) ≤ π / 2 or 3π / 2 ≤ θ(r) ≤ 2 (positive elevation angle, taking values between 0 and π / 2)

[0099] • is π / 2 ≤ θ(r) ≤ 3π / 2 (negative elevation angle, taking values between 0 and -π / 2)

[0100] There is at least one pair (r, r') such that r ≠ r' with μ(r') ≠ μ(r) to obtain at least two reception beams (r, r') corresponding to different elevation angles that the base station gNB can choose.

[0101] Let E = {e (1) ,…,e (R) ​} is a set of elevation angles corresponding to each receive beam. The following convention is assumed: when e > 0, the direction is pointing above the horizontal plane PH, when e < 0, the direction is pointing below the horizontal plane PH.

[0102] For example, in the case of a multi-carrier waveform communication system of the orthogonal frequency division multiplexing type as described in [Y. Liu, Z. Tan, H. Hu, L. J. Cimini and G. Y. Li, "Channel Estimation for OFDM," in IEEE Communications Surveys & Tutorials, vol. 16, no. 4, pp. 1891-1908, Fourthquarter 2014], the base station gNB determines the received power values of the SRS reference signals received through each receive beam as follows:

[0103]

[0104] where s pilot is the reference signal, w (r) denotes the received power value of the reference signal, is a row vector of complex coefficients of dimension N x 1 representing the receive beam; is a column vector of complex coefficients of dimension 1 x N representing an estimate of the propagation channel of the predefined subcarriers between the base station and the user equipment, N being the number of receive antennas of the base station, and r e {1,..., R}, where R is the number of receive beams of the base station.

[0105] w (r) corresponds to the result of the predefined processing applied to the received reference signal.

[0106] The base station gNB then determines the receive beam having the highest received power value among all the calculated received power values. In a particular embodiment, the base station determines the receive beam for which the received power value is the highest:

[0107]

[0108] The base station gNB derives the corresponding elevation angle

[0109] The base station gNB then determines the distance d at which the user equipment UE is located. For example, knowing the value of the transmission power of the SRS reference signal, and knowing the signal propagation loss law It defines the power loss f(d) of the signal due to its propagation between the user equipment located at a distance d and the receiving antennas of the base station gNB, whose coefficients a and b have been measured, for example at the time of installation, and pre-recorded in the base station gNB, which measures the received power values of the SRS reference signal received at its at least one receiving antenna and from which it derives the distance d.

[0110] For example, if the base station gNB is based on the measurement of the received power values of the SRS reference signal received by a single receiving antenna, the distance d is estimated as follows:

[0111] Knowing the value of the distance d, the base station gNB then determines the altitude h of the user equipment UE. For example, the altitude h of the UE is calculated as follows:

[0112]

[0113] In a particular embodiment, in the case of an OFDM (Orthogonal Frequency Division Multiplexing) type communication system, the base station gNB also estimates the propagation channel h (k) for each subcarrier number k = 1... K of the OFDM waveform and from which it derives the frequency response for a predefined receiving antenna number n as a set of Each subcarrier corresponds to a predefined frequency. The base station gNB analyzes the frequency response thus obtained in order to detect, for a particular set of subcarriers {ki, k2,...} corresponding to a particular frequency band value, a plurality of values of corresponding to a plurality of power spectral density values representative of the vibrations produced by a drone UAV in flight with a user equipment located on board an aircraft transmitting OFDM waves. An example of a frequency response in which such vibrations can be detected is shown in [Fig. 1]. Figure 3

[0114] In fact, the vibrations produced by a drone in flight conditions have an impact on the reference signal transmitted by the UE and received by the base station. Such vibrations appear in the frequency response of the reference signal.

[0115] In a first embodiment, the base station gNB performs a series of two tests in order to determine whether the UE is on board a drone UAV. In a first test, the base station gNB determines whether the altitude h of the UE is higher than a detection threshold.

[0116] When this is the case, the base station gNB optionally performs a second test to determine the presence of vibrations produced by a drone UAV in the frequency response of the received reference signal and thereby confirms that the user equipment UE is on board a drone.

[0117] ​When the altitude h of the UE is below the detection threshold, the base station gNB optionally performs a second test to determine the presence of vibrations produced by the drone UAV in the frequency response of the received reference signal, thereby determining that the user equipment UE is embedded in the drone.

[0118] In a second embodiment, the base station gNB is able to detect the drone UAV although the altitude h of the drone is below the detection threshold. To this end, the base station gNB also performs a series of two tests to determine whether the user equipment UE is embedded in the drone UAV. In a first test, the base station gNB determines whether the vibrations produced by the drone UAV are present in the frequency response of the received reference signal.

[0119] When this is the case, the base station gNB optionally performs a second test to determine whether the altitude h of the UE is above or below the detection threshold. Indeed, when the presence of vibrations produced by the drone UAV is detected in the frequency response of the received reference signal, the user equipment UE is considered to be embedded in the drone UAV regardless of the altitude h of the UE, however, the information on the altitude of the drone can help confirm the detection result.

[0120] It is then possible to detect the drone early, i.e. shortly after its takeoff, or it is possible to detect a drone flying deliberately at low altitude.

[0121] During a step E9, the base station gNB sends a message MSG8 to the management entity AMF of the network. The message MSG8 comprises an estimate of the altitude h of the user equipment UE. This altitude is expressed with respect to the ground level, but another reference level can be used, for example the sea level, the level of the base station gNB or the level of the top of the highest building in the vicinity of the base station gNB. For example, the last example distinguishes between a device located on a drone and a "normal" user equipment UE located on the top floor of a tower.

[0122] According to an implemented embodiment, the message MGS8 also comprises a "drone vibration similarity in ex" index, the presence of which indicates that a plurality of power spectral density values representative of vibrations produced by a drone UAV have been detected in the frequency response of the received reference signal.

[0123] In a step E10, the management entity AMF of the network sends the information contained in the message MSG8 to the drone detection facility DDF in order to confirm that the user equipment UE is indeed embedded in the drone UAV. Alternatively, the management entity AMF of the network itself performs this verification and does not send information to the drone detection facility DDF.

[0124] Upon reception of the information sent by the management entity AMF of the network, the drone detection facility DDF performs the location tracking of the user equipment UE during a step E11 using known methods and analyzes the trajectory of the user equipment UE by cross-referencing it for example with mapping data. This tracking can last for an extended period of time.

[0125] The drone detection facility DDF can obtain statistical information on the mobility of the user equipment UE from a facility that specifically analyzes data from the network. This statistical information can relate to a longer or shorter period of time in the past. Such a procedure is specified in the document TS 23.288 published by 3GPP in article 6.7.2.

[0126] In step E12, the drone detection facility DDF sends a message MSG9 to the management entity AMF of the network. Depending on the level of certainty resulting from the analysis of the information collected during step E11 about the user equipment UE being embedded in a drone UAV, the message MSG9 comprises a "positive", "negative" and "unknown" indicator.

[0127] If the indicator contained in the message MSG9 is "negative", the management entity AMF of the network requests the base station to implement again step E9 after a timeout of a duration T1. If the indicator in the message MSG9 is "unknown", the management entity AMF of the network should request the base station to implement again step E9 after a timeout of a duration T2 < T1.

[0128] If the indicator contained in the message MSG9 is "positive", in step E13, the management entity AMF of the network sends a message MSG10 to the user equipment UE requesting it to identify itself to the cellular network facility as a drone UAV. In another embodiment, the management entity AMF of the network does not send a message to the UE but sends a Nsmf_PDUSession_Release message (as defined in the document TS 23.502 published by 3GPP in article 5.2.8.2.4) directly to the cellular communication network facility to trigger the interruption of the communication session established in step E6. As a result, the user equipment UE no longer has any connectivity but is still registered in the cellular communication network, allowing to continue to track it by implementing again some steps E8 to E12.

[0129] In step E14, the user equipment UE responds by sending a message MSG11 identifying it as a drone UAV on board. According to another embodiment, the user equipment UE does not respond but implements again step E1 indicating that it is on a drone UAV.

[0130] If the user equipment UE maintains its connectivity without identifying itself as a user equipment UE embedded in a drone (i.e. without performing step E14 within a certain time period after receiving the message MSG10 sent by its management entity AMF), the network’s management entity AMF sends to the devices of the cellular communication network, during step E13, a Nsmf_PDUSession_Release message to trigger the interruption of the communication session established in step E6.

[0131] In another embodiment, the network’s management entity AMF sends to the devices of the cellular communication network a Nsmf_PDUSession_UpdateSMContext message as defined in the document TS 23.502 clause 5.2.8.2.6 published by 3GPP. Such a Nsmf_PDUSession_UpdateSMContext message is modified to include an indication that the UE has been detected as being on board a drone UAV aircraft, while not having identified itself as a drone UAV. This information is stored for transmission to the billing system. Thus, the connectivity of the user equipment UE is maintained, but the “wrong” behavior of the user of the user equipment UE, who has not configured the latter so that he declares himself to the cellular communication network as if he were embedded in a drone, can be taken into account at a commercial level.

[0132] In another embodiment, it is possible to limit the communication rate of the user equipment UE to a very low value, for example 100 kb / s, which has the effect of limiting the rate of the data session established in step E6 to this value. Thus, the user equipment UE is penalized without its connectivity being completely interrupted.

[0133] In addition, the network’s management entity AMF can reject any subsequent request for the establishment of a data session that the user equipment UE can send, for a period of time, or until the user equipment UE identifies itself as a user equipment UE on board a drone UAV aircraft.

[0134] [ Figure 4 ] represents a base station gNB according to an embodiment of the application. Such a base station gNB is able to implement the various embodiments of the method described with reference to Figure 2 the various embodiments of the method described with reference to

[0135] The base station gNB can comprise at least one hardware processor 401, a storage unit 402, an interface 403 and at least one network interface 404 connected to each other by a bus 405. Of course, the constituent elements of the base station gNB can be connected by means other than a bus.

[0136] The processor 401 controls the operation of the base station gNB. The storage unit 402 stores at least one program for implementing the method according to the embodiments of the present application executed by the processor 401, and various data, for example, parameters for the calculation performed by the processor 401, intermediate data of the calculation performed by the processor 401, and the like. The processor 401 can be formed by any known and suitable hardware or software, or by a combination of hardware and software. For example, the processor 401 can be formed by a dedicated hardware such as a processing circuit, or can be formed by a programmable processing unit such as a central processing unit that executes a program stored in its memory.

[0137] The storage unit 402 can be formed by any suitable means capable of storing one or more programs and data in a computer-readable manner. Examples of the storage unit 402 include a non-transitory computer-readable storage medium such as a solid-state storage device, and a magnetic, optical, or magneto-optical recording medium loaded into a read / write unit.

[0138] The interface 403 provides an interface between the base station gNB and the user equipment UE.

[0139] The at least one network interface 404 provides a connection between the base station gNB and the management entity AMF of the network.

[0140] [ Figure 5 ] represents the management entity AMF of the network according to the embodiments of the present application. Such a management entity AMF of the network is capable of implementing various embodiments of the method described with reference to Figure 2

[0141] The management entity AMF of the network can include at least one hardware processor 501, a storage unit 502, an interface 503, and at least one network interface 504 connected to each other through a bus 505. Of course, the management entity AMF of the network can be connected by means other than the bus.

[0142] The processor 501 controls the operation of the management entity AMF of the network. The storage unit 502 stores at least one program for implementing the method according to the embodiments of the present application executed by the processor 501, and various data, for example, parameters for the calculation performed by the processor 501, intermediate data of the calculation performed by the processor 501, and the like. The processor 501 can be formed by any known and suitable hardware or software, or by a combination of hardware and software. For example, the processor 501 can be formed by a dedicated hardware such as a processing circuit, or can be formed by a programmable processing unit such as a central processing unit that executes a program stored in its memory.

[0143] ​The storage unit 502 can be formed by any suitable means capable of storing one or more programs and data in a computer-readable manner. Examples of the storage unit 502 include a non-transitory computer-readable storage medium such as a solid-state storage device, and a magnetic, optical, or magneto-optical recording medium loaded into a read / write unit.

[0144] The interface 503 provides an interface between the management entity AMF of the network and the base station gNB.

[0145] The at least one network interface 504 provides a connection between the management entity AMF of the network and other devices present in the cellular communication network.

Claims

1. A method for detecting a drone (UAV) with an airborne user equipment (UE), the method being implemented by a base station (gNB) to which the UE is connected, the method comprising the following steps: - Determine a receive beam r from among the multiple receive beams R of the base station gNB, and receive at least one reference signal s transmitted by the user equipment UE through the receive beam r. pilot , -Based on the at least one reference signal s received through the determined receiving beam r pilot At least one parameter is determined to detect the unmanned aerial vehicle (UAV), said at least one parameter being selected from the group consisting of: - Represents multiple power spectral density values ​​of the vibrations generated by the UAV; - The altitude of the user equipment is determined based on the value of the elevation angle associated with the received beam through which the at least one reference signal is received, and wherein the drone is detected when the altitude of the user equipment is greater than or equal to a detection threshold.

2. The method for detecting a drone with onboard user equipment according to claim 1, wherein, The drone is detected when the altitude of the user equipment is below a detection threshold and the at least one parameter is a plurality of power spectral density values ​​representing vibrations generated by the drone.

3. The method for detecting a drone with onboard user equipment according to claim 1, wherein, The altitude of the user equipment is determined based on at least one of the following parameters: - The distance between the base station and the user equipment. - The received power of the at least one reference signal, - Law of signal propagation loss.

4. The method for detecting a drone with onboard user equipment according to any one of the preceding claims further includes the step of sending a message to a network management entity, the message including the altitude of the drone and / or an indication of a plurality of power spectral density values ​​representing vibrations generated by the drone detected in the frequency response of the received at least one reference signal.

5. The method for detecting a drone with onboard user equipment according to claim 1, wherein, The step of determining, from the plurality of receiving beams of the base station, the receiving beam through which at least one reference signal is received includes: - Determine the received power value of the reference signal received through at least one receiving beam: Where w (r) p represents the received power value of the reference signal. (r) h is a complex row vector of dimension N×1. (r) It is a complex column vector with dimension 1×N. It is a row vector of dimension N×1 representing the received beam; Let r be a 1×N column vector representing the estimated transmission channel established between the base station and the user equipment, where N is the number of receiving antennas of the base station, and r∈{1,……,R}, where R is the number of receiving beams of the base station. - A receiving beam that determines that the received power value of the at least one reference signal is greater than the received power value of the at least one reference signal determined for other receiving beams.

6. The method for detecting a drone with onboard user equipment according to claim 4, wherein, The altitude of the user equipment is determined as follows: Where h is the altitude of the user equipment, and H is the altitude of the base station. is the elevation angle of the receiving beam, the received power value of at least one reference signal of the receiving beam is greater than the received power value of the at least one reference signal determined for other receiving beams, and d is the distance between the base station and the user equipment.

7. A method for communicating between a network management entity and a user device embedded in a drone, the method being implemented by the network management entity, comprising the following steps: - Receive a message from a base station to which the user equipment is attached, the message including the altitude of the UAV and / or an indication of vibrations detected by the UAV in the frequency response of at least one reference signal transmitted by the user equipment and received by the base station. - When it is determined that the detected altitude and / or vibration correspond to a drone, a message is sent to the user equipment requesting that it recognize itself as a drone.

8. The method for communication between a network management entity and a user device embedded in a drone, as described in claim 7, comprising: The step of interrupting the communication session established between the user equipment and the device in the communication network via the base station when the user equipment does not recognize itself as a drone.

9. A base station gNB capable of detecting a drone (UAV) with an onboard user equipment (UE) attached to the base station gNB, the base station gNB including components for: - Determine a receive beam r from a plurality of receive beams R of the base station gNB, and receive at least one reference signal s transmitted by the user equipment UE through the receive beam r. pilot , -Based on the at least one reference signal s received through the determined receiving beam r pilot At least one parameter is determined to detect the unmanned aerial vehicle (UAV), said parameter being selected from the group consisting of: - Represents multiple power spectral density values ​​of the vibrations generated by the UAV; - The altitude of the user equipment is determined based on the value of the elevation angle associated with the received beam through which the at least one reference signal is received, and wherein the drone is detected when the altitude of the user equipment is greater than or equal to a detection threshold.

10. The base station of claim 9, further comprising a component for sending a message to a network management entity, the message including the altitude of the UAV and / or an indication of a plurality of power spectral density values ​​representing vibrations generated by the UAV detected in the frequency response of the received at least one reference signal.

11. A management entity (AMF) of a network capable of communicating with a user equipment (UE) embedded in a drone (UAV), the AMF comprising components for: - Receive a message from the base station gNB to which the user equipment UE is connected, the message including the altitude h of the UAV and / or an indication of vibrations generated by the UAV detected in the frequency response of at least one reference signal transmitted by the user equipment UE and received by the base station gNB. - When it is determined that the detected altitude h and / or vibration corresponds to a UAV, a message is sent to the User Equipment (UE) requesting that it identify itself as a UAV.

12. The management entity of the network capable of communicating with user equipment embedded in a drone according to claim 11, comprising a component for interrupting a communication session established between the user equipment and a device in the communication network via the base station when the user equipment does not identify itself as a drone.

13. A computer program product comprising program code instructions for implementing, when executed by a processor, the method for detecting a drone having onboard user equipment as described in claim 1.

14. A computer program product comprising program code instructions for implementing, when executed by a processor, the method for communicating between a network management entity and a user device embedded in a drone, as described in claim 7.

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