Controlling a beam of an antenna on an aircraft

Abstract

This application is concerned with selecting a base station (35a, 35b, 35c) to serve a UE 2 located on an aircraft 1 or unmanned aerial vehicle (UAV) and directing a beam 7 from the aircraft to the ba

Description

Technical Field of the Disclosure The disclosure concerns controlling a beam of an antenna on an aircraft, in which the antenna is part of a communication system onboard the aircraft configured for communication with a cellular network. Implementations may include a computer program and / or a system for controlling a beam of an antenna on an aircraft. Background to the Disclosure There are many known techniques for wireless communication with aircraft, especially with an Unmanned Aerial Vehicle (UAV), for example an autonomous aerial system flying beyond visual line of sight (BVLOS). It is desirable for the aircraft to communicate with existing cellular networks. The aircraft carries a User Equipment (UE) for the cellular network that includes an antenna, for example as described in US2022 / 069876 and US9848391B2. Advantageously, the antenna has a steerable beam, allowing the UE to communicate with a selected cell (base station) of the cellular network based on its location and mobility. For example, beamforming is well established in Long Term Evolution (LTE) and 5G standards, as set by the Third Generation Partnership Project (3GPP). It has already been foreseen that an extension of beamforming and / or beam steering into three dimensions (including azimuth and elevation) would be beneficial (see “LTE and Drones” White Paper, Sequans Communications, https: / / lteanddrones.com / ). Bespoke implementations are known for UAVs that reactively adjust antenna direction on an aircraft based on current radio conditions, including those described in GB2554975A, US2019 / 0363769A1 and US10321517B2 that are not specifically designed for cellular network operation. US2022 / 069876 describes configuring transmission beamforming or handover of a UE onboard a UAV, based on the flight path of the UAV. Whilst using the flight path of the UAV in this way has advantages, it does not make best use of the air interface between the UE and cellular network. It would be desirable to improve such communication. Summary of the Disclosure Against this background, the present disclosure provides a method for controlling a beam of an antenna on an aircraft according to claim 1, a computer program in line with claim 14 and a system for controlling a beam of an antenna on an aircraft, the antenna being part of a communication system onboard the aircraft configured for communication with a cellular network as defined by claim 15. Other preferred features are disclosed with reference to the claims and in the description below. A database is provided at a location outside the aircraft (for example, a server, normally located on the ground). The database is in communication with the cellular network, particularly a core network of the cellular network. This database is queried (by the UE of the cellular network onboard the aircraft or a device or server in communication with the UE) using positional information of the aircraft, to obtain three-dimensional location information for one or more base stations of the cellular network in the vicinity of the aircraft. A base station is selected from the query results using the location information. Optionally, the database may be queried repeatedly before the selection takes place (and the selection might use or might only use results from the last query). The beam of the UE antenna is then controlled for communication with the selected base station according to the location information (and optionally also according to other information, for instance environmental condition information, which may include weather). The aircraft may be a UAV. This approach offers the ability to improve data-link quality to and from a UE onboard an aircraft significantly, allowing such a UE to upload or download high-bandwidth data streams such as High Definition (HD) video with minimised interruption (inter-cell coverage). These features are especially advantageously for autonomous aerial systems, including UAVs, flying beyond visual line of sight (BVLOS). The selected base station may be that which optimises one or more of: received signal quality; predicted throughput; predicted error rate; and predicted reliability. The positional information of the aircraft used for the query may be measured (as discussed below) or estimated, for example based on a flight plan for the aircraft. The selection of a base station and / or control of the antenna beam may use the same positional information as for the query or different information, for example a determined position of the aircraft (by measurement or estimation). The database can provide other details (in particular, about each of the one or more base stations) as well as the location information. The additional details about each of the one or more base stations may include one or more of: base station frequency; base station throughput and / or capacity; base station utilisation; base station geographical coverage; and base station predicted coverage quality; and / or wherein the additional details comprise environmental condition information. Advantageously, the other details can also be used to select the base station with which the UE will communicate. Each of the obtained location information and / or additional details may be obtained together with a respective associated confidence level (for example, indicating how valid or trustworthy the information can be considered). The associated confidence level for each item of information can also be used in selecting the base station with which the UE will communicate. In embodiments, the database querying and / or base station selection is performed at a server that is located outside the aircraft (and is in communication with the database). Then, one or both of the obtained three-dimensional location information and the selected base station are communicated from the server to the aircraft (more specifically, the UE aboard the aircraft). Where the database is queried to obtain additional details, these may also be communicated from the server to the aircraft. If the database query is performed at the server, there may be situations when communication between the server and aircraft is disrupted or other unavailable. In that case, the base station may still be selected at the aircraft. For example, the aircraft may use older information received from the server to perform the selection. The aircraft may provide information to the server. For example, information about the aircraft and / or measurements taken by the aircraft may be communicated from the aircraft to the server. Such measurements may comprise one or more of: environmental condition information; a determined location or position for the aircraft; information about other aircraft nearby; one or more received performance measurements in respect of at least one of the one or more base stations. For example, the one or more received performance measurements may comprise one or more of: signal quality; latency; and throughput. In embodiments, at least one parameter of the one or more base stations may be set based on the measurements communicated to the server (for example, to improve resource allocation and / or air interface performance). Beneficially, the selection of the base station may also be based on the measurements communicated to the server. Controlling the beam of the antenna may include one or more of: mechanically steering the (directional) antenna; controlling one or more switch-controlled multiplexed directional sub-antennas; and beamforming an antenna array. All aspects may be implemented as a computer program and / or as a system (which may comprise a controller for the aircraft, a server, a database or a combination of the two). A network entity or UE within such a system may also be considered. Brief Description of the Drawings The approach of the disclosure may be put into practice in various ways, one of which will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 schematically shows a system and method for controlling a beam of an antenna on an aircraft in accordance with the disclosure; and Figure 2 depicts directional vectors for communication between an aircraft and ground-located base station. Detailed Description of Preferred Embodiments Referring first to Figure 1, there is schematically shown a system and method for controlling a beam of an antenna on an aircraft in accordance with the disclosure. The system has four main components: an aircraft (shown in this drawing as a UAV) 1; a database 10; a server 20; and a cellular network 30. The cellular network is managed by a Mobile Network Operator (MNO) and comprises: a core network 32; and a plurality of base stations (which are equivalently termed cells in the context of the present disclosure) 35. The server 20 operates a primary control software (that may be a bespoke application) and may be coupled to (or part of) the core network 32. The server 20 may be hosted in a data centre. It may be proximate to the aircraft 1 for lower latency, for example in a similar configuration to that of a Multi-Access Edge Computing (MEC) system, as may be used with 5G architectures. Aircraft 1 is specifically depicted as a BVLOS UAV, but this is only an example. Aircraft 1 could be any type of airborne vehicle (fixed-wing or rotary and manned or unmanned), including other types of UAV, aeroplane, glider or airship, for instance. A UE 2 of the cellular network is provided on the aircraft 1, comprising: a modem 3; processor 4; antenna steering mechanism 5; and an antenna array 6. The processor controls operation of the antenna steering mechanism 5, thereby causing the antenna array 6 to communicate (transmit and / or receive) in a set direction, illustrated by antenna main beam 7. In this case, the antenna array 6 is controlled to communicate with a first base station 35a. Two other base stations are shown: second base station 35b has poor environmental conditions 40 nearby; and third base station 35c is located in a dense, urban (congested) area 50. The poor environmental conditions 40 and congested area 50 are relevant factors in the choice of base station with which the UE 2 onboard aircraft 1 should communicate. The method of controlling the antenna main beam 7 is now discussed. In this example, the server 20 is used as an interface between the UE 2 and the database 10, but it will be appreciated that the functionality of the server 20 can be divided in different ways, for example, without the need for any server 20 (such that its functionality is entirely divided between the UE 2 and the database 10), by using multiple servers or some combination of these approaches. In a first step 100, the server 20 obtains positional information for the aircraft 1. This may be based on communication from the UE 2 to the server 20 via the cellular network 30 (for example, from a Global Navigation Satellite System, GNSS, measurement at the aircraft 1, which may then be reported as discussed below or based on cell site information for the UE 2) and / or information about a location of the aircraft 1 (for instance, a flight path), which may be stored at the UE 2 or server 20. As part of the first step, the UE 2 may provide a report 110 to the server 20. The report 110 may include one or more of: positional information for the aircraft 1 (as mentioned above); information about the aircraft 1 and / or UE 2; and information about environmental and / or air interface conditions. Beneficially, the report 110 may also provide frequency and / or cell capacity measurements. As an example, the report 110 may have the following format. Not all data may be provided in practice and any combination of the data could be required and / or sent. Position 3D coordinates of aircraft Aircraft type Maximum speed, minimum speed, wing type, weight Equipment Modem type, capabilities Actual coverage quality Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), Signal to Noise Ratio (SNR), Experienced throughput in Mbps, Round trip latency Environment Sensor data from aircraft: wind speed, humidity, visibility; detection of other aircraft in vicinity The server 20 sends a query 120 the database 10 using the obtained positional information for the aircraft 1 (that is, the query term may be based on or may be the obtained positional information). The database 10 is in communication with the cellular network 30 and stores information about the cell sites of the cellular network 30 (including the first base station 35a, second base station 35b and third base station 35c). The information stored about the cell sites includes a three-dimensional location for each cell site (base station). It may also include one or more of: cell frequency; current cell throughput and / or capacity; cell utilisation; cell geographical coverage; and cell predicted coverage quality. This information may be updated at the database 10 (regularly and / or based on demand) from the cellular network 30 and optionally from the report 110 provided by the UE 2. The information at the database 10 is beneficially updated in effectively or close to real-time. The MNO may provide an Application Programming Interface (API) for this updating. The query 120 (which may be termed coverage enhancement data) is typically pulled by the server 120 or pushed by the UE 2 on the aircraft 1 at regular intervals and as and when decided by either system component. Based on the positional information provided in the query, the database 10 provides a list of possible cells 130 with which the UE 2 may communicate and for each possible cell, the respective three-dimensional location. Together with that list, the database 10 may additionally provide any other information about each possible cell that it stores. Advantageously, the server 20 also obtains environmental condition information for the current position of the aircraft 1, for instance from the report 110 (as discussed above). This may include weather conditions, for instance the existence and / or one or more parameters of environmental conditions 40, examples of which may include rainfall estimation, cloud cover or other factors (one example may be the poor environmental conditions 40 near to the second base station 35b). The server 20 then selects 140 a cell with which the UE 2 should communicate from the list provided by the database. The selection is based on the data obtained from the database and optionally, data provided by the UE 2 with the report 110. The criterion or criteria for selection may be to provide the best quality connection for the UE 2 according to the position given for it. Multiple reports 110 and / or queries 120 may take place before a cell is selected 140. It should be noted that selection of a cell does not mean that the UE 2 immediately communicates with the selected cell or indeed, that the UE 2 is forced to communicate with the selected cell. As will be explained below, the UE 2 still operates according to the cellular network protocols, including those governed by 3GPP standards. The server 20 then communicates 150 information about the selected cell, including the three-dimensional location information about the cell, to the UE 2. The communication may further indicate information about the coverage quality for the selected cell and / or environmental (which may include weather and / or radio) conditions. For each data item provided in the communication 150, an associated confidence level may be provided (as a percentage or equivalent). The MNO may provide an API for this communication 150. Control of directional antenna orientation via MNO API Cell-site sector direction and azimuth and three-dimensional location may then be stored in the flight-plan of the aircraft 1. Multiple data sources, for instance one or more of weather, mobile network data and data received from other aircraft, may optionally be used to augment the data sent by the server 20 to the UE 2. The processor 4 of the UE 2 can then use a current position for the aircraft 1 and the received three-dimensional location information about the cell to steer the beam 7 of the antenna array 6 accordingly. Such control is thereby effected dynamically. Multiple reports 110, queries 120 and / or selections 140 may take place before the server 20 communicates 150 information about the selected cell to the UE 2. Steering of the antenna array 6, together with the information about the selected cell provided to the processor 4 of the UE 2, should cause the UE 2 to attach or hand over to the selected cell. As an example, the communication 150 may have the following format. Not all data may be provided in practice and any combination of the data could be required and / or sent. Target position 3D coordinates of cell tower and cell beam coverage (or convergence point) to which the antenna should be pointed Confidence % Predicted coverage quality RSRP, RSRQ, SNR, Predicted throughput in Mbps, Round trip latency Confidence % Environment Weather conditions local to the aircraft (for instance, wind speed and / or rain density) Confidence % Optionally, the server 20 may communicate 150 information about multiple cells. Either one of the multiple cells can be indicated as selected or the selection step can take place at the processor 4 of the UE 2. Received data may be cached at the UE 2 for use at later times. In this way, the UE 2 can continue to try communicating with an appropriate cell even if cellular network coverage becomes poor. In the absence of fresh or cached data, the modem 3 of the UE 2 may fall back to cell-selection behaviour as defined by the governing standards, until it can resume communication with the server 20. The antenna steering mechanism 5 may be based on one or more of the following techniques: mechanically steerable directional antenna; multiplexed directional antennas using RF switches, where the antenna with best link budget is used; and beamforming antenna array. This effectively allows the aircraft to benefit from close to real time knowledge of geographical coverage, taking into account environmental and / or network conditions. The antenna array 6 may be pre-emptively and / or dynamically steered to a cell that will keep communications throughput at a high quality (in terms of any one or more of data throughput, error, latency or other performance or quality indication). This approach may further allow the MNO to manage cell capacity by directing the UE 2 onboard the aircraft 1 to attach to less congested cell sites and / or by adjusting network parameters to allocate resources in an improved way (based on feedback from the aircraft). In addition, aerial radio and environmental conditions may be passively surveyed by the server 20 based on data received from multiple aircraft 1. Aggregated such data may then fed back to the cellular network 30 for further analysis and reuse, enabling the MNO to qualify and supplement their coverage models for instance. All of the communication between the UE 2, server 20, database 10 and cellular network 30 is beneficially encrypted in transport. Only reports 110 from trusted aircraft are accepted at the server 20. In the above description, control of cell-site selection and antenna direction is split between the server 20 and the UE 2 onboard the aircraft 2 (such that, if the UE 2 is not currently connected to the cellular network 30, it will be able to use cached data previously sent from the server 20), but other options are possible, including the UE 2 taking additional functionality described in respect of the server 20 above (or indeed, incorporating all functionality described in respect of the server 20). In general terms, there may be considered a method or system for controlling a beam of an antenna on an aircraft. The antenna is part of a communication system onboard the aircraft configured for communication with a cellular network. The method may comprise steps based on the approach described herein and any such method may be implemented as a computer program, whereas the system may comprise one or more processors configured to control or instruct one or more of a server, database, cellular network and User Equipment (UE) according to the approach. Three-dimensional location information for one or more base stations of the cellular network in the vicinity of the aircraft is obtained from a database based on a position of the aircraft (which may be a measured position or estimated based on a flight plan for the aircraft). The database is located outside the aircraft and is in communication with the cellular network. A base station is selected from the one or more base stations, based at least on the obtained three-dimensional location information (and beneficially a location of the aircraft, which may be the same as the obtained position, but need not necessarily be so). Then, the beam of the antenna is controlled for communication with the selected base station, based on the obtained three-dimensional location information for the selected base station (and advantageously a current location of the aircraft, which may be the same as the obtained position and / or the location used for selection, but need not necessarily be so). The aircraft may be a UAV and / or partially or fully autonomous, for instance an autonomous aerial system flying BVLOS. This approach may allow improved performance of the communication system onboard an aircraft with a cellular network and / or operation of the cellular network with such communication systems. For example, the base station may be selected from the one or more base stations to optimise one or more of: received signal quality; predicted throughput; predicted error rate; and predicted reliability. It should be noted that the selection need not be performed each time three-dimensional location information is obtained, but rather three-dimensional location information may be obtaining multiple times before a selection takes place. Optionally, additional details may be obtained from the database. Then, the selection may further be based on the additional details. The additional details may comprise additional details for each of the one or more base stations. For example, the additional details for each of the one or more base stations may comprise one or more of: base station frequency; base station throughput and / or capacity; base station utilisation; base station geographical coverage; and base station predicted coverage quality; and / or wherein the additional details comprise environmental condition information. In embodiments, each of the obtained three-dimensional location information and / or the additional details is obtained together with a respective associated confidence level. The selection of a base station is optionally further based on each obtained confidence level. Beneficially, the three-dimensional location information is obtained and / or the base station is selected at a server that is located outside the aircraft and is in communication with the database. The beam of the antenna may be controlled by communicating the obtained three-dimensional location information and / or the selected base station from the server to the aircraft (and optionally, if appropriate, communicating the additional details obtained from the database from the server to the aircraft). In embodiments, the three-dimensional location information is obtained at the server and communicated to the aircraft. Then, the base station may be selected at the aircraft. In particular, this selection may take place irrespective of whether communication between the server and the aircraft is possible when the selecting is performed. In embodiments, information about the aircraft and / or measurements taken by the aircraft is communicated from the aircraft to the server. Optionally, the measurements comprise one or more of: environmental condition information; a determined location or position for the aircraft; information about other aircraft nearby; one or more received performance measurements in respect of at least one of the one or more base stations. The one or more received performance measurements may comprise one or more of: signal quality; latency; and throughput. This form of feedback from the aircraft to the server may be useful for improving the base station selection and / or operation of the cellular network (particularly in combination with the aircraft or other aircraft). A number of further advantageous implementations may be considered. In embodiments, at least one parameter of the one or more base stations may be set within the cellular network, based on the measurements communicated to the server. Beneficially, the base station may be selected based on the measurements communicated to the server. The beam of the antenna may be controlled by one or more of: where the antenna is directional, mechanically steering the antenna; controlling operation of the antenna using switches (where the antenna comprises one or more multiplexed directional sub-antennas, each controlled by a respective one of the switches); and where the antenna comprises an antenna array, beamforming of the antenna. A brief description of an example method for calculating the antenna steering position based on the received three-dimensional location information about the selected cell (or the cell tower). The aim is to point the antenna towards the given coordinate of the cell or cell tower. Referring to Figure 2, there are depicted directional vectors for communication between an aircraft and ground-located base station. An arbitrary common origin point, O, is shown, but it will be recognised that the exact location of this point is not significant and can be configured as appropriate. If the aircraft three-dimensional position is denoted by (x1, y1, z1) and the target three-dimensional coordinate is denoted by (x2, y2, z2), the direction vector pointing from the position of the aircraft to the target coordinate can be calculated as a vector (dx, dy, dz): dx = x2-x1 dy = y2-y1 dz = z2-z1 This vector (dx, dy, dz) represents the direction the directional antenna needs to be pointed in order to face the cell coverage area (target). As the aircraft moves, the antenna position is advantageously continually adjusted to point towards this target cell coverage area. 5 Example Code for implementing such calculations is provided below, import math import numpy as np import pandas as pd import pydeck as pdk # Function to calculte direction def calculate_direction_vector(lon 1, Iat1, heightl, Ion2, Iat2, height2, rpm, time seconds, directional_component): # Convert degrees to radians lonl rad, latlrad = math.radians(lonl), math.radians(latl) Ion2_rad, Iat2_rad = math.radians(lon2), math.radians(lat2) # Earth radius in meters (approx) R = 6371000.0 # Calculate Cartesian coordinates (x, y, z) for points A and B x1 = (R + heightl) * math.cos(lat1_rad) * math.cos(lon 1rad) y1 =(R + heightl) * math.cos(lat1_rad) * math.sin(lonl rad) z1 = (R + heightl) * math.sin(lat1_rad) x2 = (R + height2) * math.cos(lat2 rad) * math.cos(lon2_rad) y2 = (R + height2) * math.cos(lat2_rad) * math.sin(lon2 rad) z2 = (R + height2) * math.sin(lat2_rad) # Calculate direction vector from B to A dx = x1 - x2 dy = y1 - y2 dz = z1 - z2 # Normalize direction vector length = math.sqrt(dx**2 + dy**2 + dz**2) unit_vector = np.array([dx / length, dy / length, dz / length]) # Apply directional component to the initial direction vector initial_rotation_matrix = np.array([ [math.cos(directionaLcomponent), -math.sin(directionaLcomponent), 0], [math.sin(directional_component), math.cos(directional_component), 0], [0, 0,1] ]) initial direction vector = np.dot(initial rotation matrix, uniLvector) # Calculate angular velocity (convert rpm to rad / s) angular_velocity = (2 * math.pi * rpm) / 60 # Calculate rotation matrix for the given time rotationmatrix = np.array([ [math.cos(angulacvelocity * timeseconds), -math.sin(angular_velocity * time_seconds), 0], [math.sin(angular_velocity * time_seconds), math.cos(angular_velocity * timeseconds), 0], [0, 0,1] ]) # Apply rotation matrix to the initial direction vector rotated vector = np.dot(rotation matrix! initial direction vector) return rotated_vector # Coordinates of point A and B in Ireland Ion1, Iat1, heightl = -6.0872, 53.1424, 500 # Coordinates for point A Ion2, Iat2, height2 = -6.0789, 53.1453, 50 # Coordinates for point B rpm = 1000 # Rotation speed in rpm timeseconds = 60 # Time in seconds directional_component = 1 / 2 # Directional component in radians directionvector = calculate_direction_vector(lon1, Iat1, heightl, Ion2, Iat2, height2, rpm, time_seconds, directional_component) print("Updated Direction Vector:", direction vector) df = pd.DataFrame(data=[[lon1, Iat1, heightl], [Ion2, Iat2, height2]], columns=['lon', 'lat', 'height']) # Set view state viewstate = pdk.ViewState( Iatitude=(lat1 + Iat2) / 2, Iongitude=(lon1 + Ion2) / 2, zoom=10, pitch=50, bearing=20 ) # Define column layer to display on map layer = pdk.Layer( "ColumnLayer", data=df, get_position=["lon", "lat"], get_elevation="height", elevationscale=100, radius=50, get_fill_color=[255, 0, 0], pickable=True, auto_highlight=True, ) # Render r = pdk.Deck(layers=[layer], initial_view_state=view_state) r.to_html('demo.htmr) Any of the methods described herein may be implemented as a computer program. The computer program may be configured to control a MS, UE and / or a network node or entity to perform any method according to the disclosure. A server or network node of a cellular network may also be provided, configured to operate in accordance with certain methods disclosed herein. For example, the server or network node may include a processor and at least one communication interface, particularly comprising one or both of a transmitter and receiver. A UE for an aircraft may also be provided, configured to operate in accordance with certain methods disclosed herein. The UE may likewise include a processor and at least one communication interface, particularly comprising one or both of a transmitter and receiver. Although specific embodiments have now been described, the skilled person will understand that various modifications and variations are possible. For example, whilst the disclosure is described in relation to existing network architecture, it will be understood that changes to the architecture (and / or nomenclature) are possible, but the present disclosure may still be applicable in this case. Also, combinations of any specific features shown with reference to one embodiment (or aspect) or with reference to multiple embodiments (or aspects) are also provided, even if that combination has not been explicitly detailed herein.

Claims

1. A method for controlling a beam of an antenna on an aircraft, the antenna being part of a communication system onboard the aircraft configured for communication with a cellular network, the method comprising:obtaining, from a database that is located outside the aircraft and is in communication with the cellular network, three-dimensional location information for one or more base stations of the cellular network in the vicinity of the aircraft based on a position of the aircraft;selecting a base station from the one or more base stations based on the obtained three-dimensional location information; andcontrolling the beam of the antenna for communication with the selected base station based on the obtained three-dimensional location information for the selected base station.

2. The method of claim 1, further comprising: obtaining additional details from the database; and wherein the step of selecting is further based on the additional details.

3. The method of claim 2, wherein the additional details comprise additional details for each of the one or more base stations, comprising one or more of: base station frequency; base station throughput and / or capacity; base station utilisation; base station geographical coverage; and base station predicted coverage quality; and / or wherein the additional details comprise environmental condition information.

4. The method of claim 2 or claim 3, wherein each of the obtained three-dimensional location information and / or the additional details is obtained together with a respective associated confidence level and wherein the step of selecting is further based on each obtained confidence level.

5. The method of any preceding claim, wherein the step of obtaining the three-dimensional location information and / or the step of selecting the base station is performed at a server that is located outside the aircraft and is in communication with the database.

6. The method of claim 5, wherein controlling the beam of the antenna comprises:communicating the obtained three-dimensional location information and / or the selected base station from the server to the aircraft.

7. The method of claim 6, wherein the step of obtaining the three-dimensional location information is performed at the server and communicated to the aircraft and wherein the step of selecting the base station is performed at the aircraft irrespective of whether communication between the server and the aircraft is possible when the selecting is performed.

8. The method of claim 6 or claim 7, when dependent on any of claims 2 to 4, wherein controlling the beam of the antenna comprises:communicating the obtained additional details from the server to the aircraft.

9. The method of any one of claims 5 to 8, further comprising: communicating information about the aircraft and / or measurements taken by the aircraft from the aircraft to the server.

10. The method of claim 9, wherein one or more of:(a) the measurements comprise one or more of: environmental condition information; a determined location or position for the aircraft; information about other aircraft nearby; one or more received performance measurements in respect of at least one of the one or more base stations, optionally wherein the one or more received performance measurements comprise one or more of: signal quality; latency; and throughput;(b) the method further comprises setting, within the cellular network, at least one parameter of the one or more base stations based on the measurements communicated to the server; and(c) the step of selecting the base station is based on the measurements communicated to the server.

11. The method of any preceding claim wherein one or more of:(i) the step of selecting is performed to select the base station from the one or more base stations that optimises one or more of: received signal quality; predicted throughput; predicted error rate; and predicted reliability;(ii) the step of obtaining is performed multiple times before the step of selecting;(iii) the position of the aircraft is estimated based on a flight plan for the aircraft;(iv) the step of selecting and / or controlling is based on a determined position of the aircraft that differs from the position of the aircraft used in the step of obtaining;(v) the step of selecting is further based on environmental condition information.

12. The method of any preceding claim, wherein the aircraft comprises an autonomous aerial system flying beyond visual line of sight (BVLOS).

13. The method of any preceding claim, wherein the step of controlling the beam of the antenna comprises one or more of:mechanically steering the antenna, the antenna being directional;controlling operation of the antenna using switches, the antenna comprising one or more multiplexed directional sub-antennas, each controlled by a respective one of the switches;beamforming of the antenna, the antenna comprising an antenna array.

14. A computer program, comprising instructions configured when executed by a processor to cause the processor to perform the method of any preceding claim.

15. A system for controlling a beam of an antenna on an aircraft, the antenna being part of a communication system onboard the aircraft configured for communication with a cellular network, the system being configured to perform the method of any preceding claim.

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