Patent Description:
The main goal of air traffic surveillance is to provide safe and efficient movement of passengers from a departure point A to a destination point B across the globe. Historically, Air Traffic Surveillance (ATS) has been achieved through the use of radars in conjunction with the radio communication between pilots and air traffic controllers. A surveillance system is typically required to provide periodically an accurate estimate of the position of all targets within the area of responsibility and possibly identification and altitude of each detected entity, a.

Traditional ATC (Air Traffic Control) radars, called primary radars, are provided with a rotating antenna which transmits continuously radar pulses and receives back the return energy (radar echo) reflected by any entity (target) within their coverage volume. The range of the target is then calculated by the two-way time of flight while the bearing of the target is based on the current antenna position. Such radars allow detection and ranging of any target with a certain level of reflectivity (radar cross section) based on their distance. These radars do not provide either altitude or identification of targets.

Because of the above limits of standard primary radars, cooperative sensors were introduced in the ATC scenario in the early <NUM>'s. Cooperative sensors, also called secondary surveillance radars (SSR), were developed to improve the ATC surveillance proving, in addition to an extended coverage, additional surveillance data, mainly target identification and altitude. The main difference between primary radars and cooperative sensors was the need of an onboard "cooperative" equipment, the aircraft transponder, able to respond to the secondary radar interrogations and transmit back the additional information. Limit of this technology was the fact that the non-cooperative targets (either no transponder or transponder off) cannot be detected.

Several forms of cooperative technologies were developed since then which could work either stand alone or integrated with primary surveillance, although the combination of primary and secondary surveillance guarantees the optimal solution because it takes advantage of both the higher safety of primary surveillance and higher performance of secondary surveillance.

With the introduction of the A-SMGCS System (Advanced surface movement guidance and control system), ground surveillance systems started to play a major role and two main technologies were introduced: Surface Movement Radars (SMRs), also called Ground Movement Radars (GMR) or Airport Surface Detection Equipment (ASDE), as primary surveillance source, and the Multilateration system (MLAT) as main secondary surveillance source. In addition, the MLAT systems are typically provided with an ADS-B (Automatic Dependent Surveillance-Broadcast) channel which receives the aircraft GPS position from the aircraft transponders and handles it as an additional, independent secondary surveillance source, which in this case is cooperative and "dependent", as the quality of the surveillance data relies on the accuracy of the aircraft navigation system, causing some major safety concerns.

A Multi Sensor Fusion system can be installed in the ATC to integrate and fuse then the surveillance data coming from the different systems (MLAT and one or more SMRs).

Definition - Visual Aids (a. airport signalling device) are any device used providing visual guidance to pilots for landing, take off and ground movement until the park position of the aircraft. Visual Aids comprise Aeronautical Ground lighting (AGL) lights and Visual Docking Guidance Systems (VDGS).

<CIT> discloses an airport luggage transport vehicle remote positioning using ultra-wide band signals. <CIT> discloses an airport surface target tracking system using a network of distributed multilateration sensors and distributed W-band radar sensors.

Standard ground surveillance systems have several drawbacks. First of all, both SMR and MLAT/ADS-B technologies are quite expensive and as mentioned before the combination of both is required in order to take advantage of the higher performance of the secondary surveillance (MLAT) and the higher safety of the primary surveillance. In addition, the cost for civil and electrical works required to install the systems and to provide them with network connection to the Air Traffic Control Tower typically is almost comparable to the cost of the procurement of the systems. Indeed, for coverage and redundancy reasons, medium/large size airports require typically a large set of MLAT sensors (above <NUM>) and more than <NUM> SMRs per runway. Each SMR typically also requires the construction of a radar tower <NUM>/<NUM> high and related equipment shelter. Such high cost for procurement installation and deployment of these surveillance systems represent a high limit in the development or upgrade of the ground surveillance systems in several airports.

From a technical point of view, it is important to notice that SMR coverage is typically limited to the manoeuvring areas, so all the apron and parking areas are excluded as too "cluttered" and also MLAT performance are typically affected in apron areas where the number of obstacles and reflecting elements increase dramatically. The international standards (ED-87C) require an overall positional accuracy of <NUM> in <NUM>% of the cases in the manoeuvring areas, <NUM> in <NUM>% of the cases in the apron taxiways and aircraft stand taxi lanes and <NUM> in <NUM>% of the cases at the stands.

By manoeuvring area is meant the part of an aerodrome to be used by aircraft for take-off, landing, and taxiing, excluding aprons and areas designed for maintenance of an aircraft.

Due to the difficulty in covering aprons and parking areas many airports have often to implement video coverage of specific areas of the airport to remedy the low accuracy or eventual coverage gaps of the surveillance systems. This solution has also its weak points though, especially during bad weather conditions, and increases the already high costs of the surveillance systems as well as their maintenance costs.

There is therefore a need in the art of providing an aerodrome accurate positioning system coverage. Equally, a need exists for an improved identification of the objects/persons, especially in apron area. There is also a need in the art of providing aerodrome positioning systems allowing easier maintenance and monitoring.

According to a first aspect of the invention, there is therefore provided an ultra-wideband positioning system for determining a position of at least one entity on an airport field.

According to a second aspect of the invention, there is provided a surveillance system for an airport field according to claim <NUM> of the amended claims.

Advantageously, the above mentioned positioning system utilizing Ultrawideband technology integrated into airfield lighting devices installed in high numbers across the manoeuvring area of an airport provides both primary and secondary ground surveillance with a higher coverage, better positional accuracy of objects (Aircraft, Vehicle) or foreign object debris detection compared to classical surface movement technologies (MLAT , SMR).

This disclosure concerns the use of ultra-wideband devices <NUM>, like a chip within airfield fixtures <NUM>,<NUM> such as airport signalling device <NUM> and/or airport surveillance stationary device <NUM> to transmit radar pulse signals <NUM>, <NUM> and locate moving and fixed targets <NUM>, also called entity with a high degree of accuracy. By ultra-wideband (UWB) is meant a pulse radio whose frequency lies in the range of <NUM> to <NUM> range. By an airport signalling device (also known as signalling unit) <NUM> is meant a visual aid. We understand by an airport surveillance stationary device a fixture/device/apparatus dedicated to an airfield surveillance (e.g. camera, a multilateration antenna mast).

An ultra-wideband (UWB) transmitter/receiver module <NUM> such as transceiver is installed within the airfield visual aids <NUM> (e.g. runway lights, taxiway lights, elevated lights, approach lights, visual docking guidance system (VDGS), signs, etc.), hereby called UWB sensing visual aids <NUM>.

In one embodiment, the sensing visual aid <NUM> transmits a radar pulse <NUM> signal which hits a target <NUM> in coverage and bounces back. The two-way time of flight of the radar signal <NUM>, <NUM> is used to determine the ranging of the target <NUM>.

Other techniques like angle of arrival estimation or use of multiple directional antennas are used to determine the bearing of the targets <NUM>. The short pulses of UWB technology (order of nanoseconds) allow higher accuracy and resolution than standard ATC systems with no difference in performance between apron <NUM> and manoeuvring areas <NUM>, <NUM>.

<FIG> shows a traditional ATC (Air Traffic Control) radars, called primary radars, provided with a rotating antenna which transmits continuously radar pulses and receives back the return energy (radar echo) reflected by any entity (target) within their coverage volume. The range of the target is then calculated by the two-way time of flight while the bearing of the target is based on the current antenna position. Such radars allow detection and ranging of any target with a certain level of reflectivity (radar cross section) based on their distance. These radars do not provide either altitude or identification of targets.

<FIG> shows a cooperative sensor, also called secondary surveillance radars (SSR). The main difference between primary radars and cooperative sensors is the need of an onboard "cooperative" equipment, the aircraft transponder, able to respond to the secondary radar interrogations and transmit back the additional information. Limit of this technology is the fact the non-cooperative targets (either no transponder or transponder off) cannot be detected.

<FIG> shows a multi sensor fusion system installed in the ATC to integrate and fuse then the surveillance data coming from the different systems (MLAT and one or more SMRs). Surface Movement Radars (SMRs), also called Ground Movement Radars (GMRs) are used as primary surveillance source, and the Multilateration system (MLAT) as main secondary surveillance source. In addition, the MLAT systems are typically provided with an ADS-B (Automatic Dependent Surveillance-Broadcast) channel which receives the aircraft GPS position from the aircraft transponders and handle it as an additional, independent secondary surveillance source, which in this case is cooperative and "dependent", as the quality of the surveillance data rely on the accuracy of the aircraft navigation system, causing some major safety concerns.

<FIG> represents an ultra-wideband positioning system according to the invention adapted to a runway <NUM>. The moving entity is an airplane <NUM> and the runway <NUM> comprises grounded central lights <NUM> provided with UWB pulse radars <NUM> for detecting the passage of the airplane <NUM> using an outbound <NUM> and echoed return signal <NUM> (complementary or alternatively the grounded central lights <NUM> can be configured to send outbound poll <NUM> signal or receive return reply <NUM>). The lights <NUM> disposed on both long sides in <FIG> are adapted to allow a positioning of the airplane, vehicle (not shown) or foreign object debris FOD <NUM>. The positioning can performed through the calculation of the time of flight of either:.

Furthermore, the lights <NUM> comprise UWB transceivers <NUM> adapted to receive an UWB signal <NUM>' periodically sent from an onboard UWB transceiver of the airplane <NUM>. The times of flights of the UWB signal <NUM> detected by the runway UWB transceivers <NUM> fixed to the lights <NUM> disposed on both long sides of the runway <NUM> are sent to a positioning determining unit <NUM> (not shown) where the exact coordinates of the airplane <NUM> are determined. These coordinates of the airplane <NUM> can be compared with those determined by the grounded central lights <NUM>, enhancing the reliability of the positioning. The embodiment in <FIG> illustrates that lights <NUM> can perform both primary (via <NUM>, <NUM> signals) and secondary surveillance (<NUM>, <NUM>, <NUM>') independently or complementary to surface movement radars (SMRs not shown in <FIG>) and the multilateration system (MLAT not shown in <FIG>), which are the traditional sensors for primary and secondary surveillance, respectively. <FIG> illustrates one way to carry out the invention. The scope of the invention should not be restricted to this advantageous embodiment since several modifications starting from <FIG> within the scope of the claims can be foreseen. For example the lights <NUM> can be used to monitor the positioning not only of airplanes <NUM> but also service vehicles, staff circulating on critical airfield areas (e.g. apron, taxiway).

<FIG> represents another embodiment of the invention where the positioning units <NUM> are fixed to aeronautical ground lights <NUM> and spread over a runway <NUM>, taxiways <NUM> and an apron <NUM>. The positioning units <NUM> can perform both primary surveillance through detection of echoed signals <NUM> and secondary surveillance via reception of return signals <NUM> containing position and identification data. Furthermore, the positioning units <NUM> can be further configured to positioning an entity <NUM> using time of arrivals of returns signals <NUM>.

The use of UWB signals guarantees also high resilience to multipath especially in busy airfield areas like aprons and parking stands. In addition, the system, thanks to the UWB technology, results also immune to interferences of other radio transmissions within the airport and secure against potential spoofing.

The installation of the surveillance within the AGL fixture <NUM> avoid the installation costs and guarantee a distribution of sensors across all manoeuvring areas and parking stands.

Furthermore, the power consumption of standard surveillance radars <NUM>, <NUM> can be completely eliminated by the disclosed surveillance solutions guaranteeing also a huge step in the direction of green airfields.

This disclosure includes the possibility to connect all the sensing UWB visual aids <NUM> with a surveillance processing <NUM> able to combine data from all sensors <NUM> in a unique surveillance data output. The surveillance processing <NUM> may be able to combine the detections from all sensors <NUM> and accurately calculate also the size, the speed of the targets <NUM> and their direction. The data output may follow standard Eurocontrol format (Asterix) in order to be immediately compatible with the other ATC systems.

The size of the aircraft <NUM> may be calculated based on the amount and identity of the sensors <NUM> detecting the aircraft simultaneously.

The combination of such a large set of distributed UWB sensors <NUM> increases not only the overall accuracy but also the system probability of detection.

Furthermore, the high accuracy and resolution of UWB measures allow the use of this radar technology also for detection of Foreign Objects Debris <NUM> (FOD) which cause sever safety issues in airport operations and cause annually damages and delays.

The FOD detections and alerts may be presented to a dedicated HMI <NUM> (Human Machine Interface) for the airfield maintenance and safety teams.

The communication between sensing visual aids <NUM> and central surveillance processing <NUM> may be implemented via different communication links.

As a first option, the powerline communication channel used by the AGL equipment <NUM> may be used to connect the field sensors <NUM> via a communication interface <NUM> to a surveillance data receiving unit <NUM> in the AGL substations. This receiving unit <NUM> is then connected via physical network connection to the surveillance central processing <NUM>, as shown in <FIG>.

Alternatively or in addition to the previous paragraph, the UWB data communication capability <NUM> could be used to set up a dedicated network and transmit data from the UWB devices <NUM> to a receiving unit <NUM> in the substation, as shown in <FIG>.

Alternatively or in addition to the previous paragraph, in case the visual aids <NUM> are equipped with LTE/<NUM> modem <NUM>, and there is an LTE/<NUM> private network in place in the airport, the surveillance data can be transmitted wireless to the central processing <NUM> via the position determining unit (<NUM>), as shown in <FIG>.

The present invention includes also the possibility to use the same UWB device <NUM> to locate and also identify other UWB peer devices <NUM> within its coverage range and use the UWB technology as an alternative to the standard <NUM> communication channel for ground cooperative surveillance.

The UWB visual aids <NUM> and the other UWB radios <NUM>, for instance mounted airport surveillance stationary device <NUM> can initialize a communication exchange that is used for accurate ranging but also data exchange (e.g. target identification, target speed, target mission, target planned trajectory, etc.).

UWB devices <NUM> may be installed within any vehicle <NUM> accessing the airfield as a cheaper solution in alternative to expensive standard <NUM>-<NUM> ADS-B transponders, as shown in <FIG>.

In addition to lower costs, these new vehicle cooperative UWB will also avoid reduction of the utilization of the <NUM> band that is already quite congested by all the existing ground-air communications initiated by the secondary surveillance radars and MLAT systems as well as by the air-air communication between aircraft transponders (TCAS).

In addition, each physical person accessing the airfield may be provided with his own UWB device <NUM> in order to be detected and identified by the installed sensing UWB visual aids <NUM>. Personal UWB devices <NUM> may be provided in either personal tags <NUM> or mobile phones <NUM> provided with UWB capability and dedicated mobile application, as shown in <FIG>.

Similarly, the disclosed sensing devices are provided with the capability to detect and communicate with any aircraft <NUM> embarking a UWB device <NUM>, as shown in <FIG>.

This technique allows to combine the ranging of the same target <NUM> by several receivers <NUM> and calculate the target position accurately via triangulation or Time Difference of Arrival algorithms allowing to reach accuracy of the order of cm.

As an alternative, the angle of arrival can be measured by a single UWB sensor <NUM> with multiple antennas so that the bearing information together with the range information provide the exact location of the device <NUM>.

The combined use of this network of UWB sensing devices <NUM> for both primary surveillance (radar pulses <NUM>, <NUM>) and secondary surveillance (UWB ranging and communication between peer devices) forms a unique ground surveillance system capable to deliver with one single system both primary and secondary (cooperative) surveillance to ATC system, shown in <FIG>.

The surveillance system <NUM> may produce a single output for both primary surveillance and secondary surveillance as well as a fused surveillance output that combine the surveillance data from both traditional surveillance chains <NUM> , <NUM>, namely SMR and MLAT systems. All output may follow Eurocontrol Standard formats (Asterix).

Such combined surveillance system <NUM> will have a coverage of all ground maneuvering areas and all aprons and parking stands, as long as the UWB sensing visual aids <NUM> are installed instead of standard AGL fixtures.

The surveillance system <NUM> may further comprise a processing unit <NUM> dedicated to the monitoring of Foreign Object Debris FOD <NUM>. A dedicated human machine interface HMI <NUM> for monitoring the foreign object debris FOD is connected to the surveillance system <NUM> so as to receive the data to be displayed, as shown in <FIG>.

Detection and identification of UWB devices <NUM> may be used to create restricted areas of different topology (e.g. areas restricted only for aircraft of a certain wing-span, area restricted for aircraft and vehicles, area restricted for non-authorized ground personnel) in the airport and generate alarms and warning based on the role/identity of the device that may be displayed on the ATC controllers Human Machine Interfaces, shown in <FIG>.

Similarly, detection and identification of UWB devices <NUM> may be used to generate runway incursion alarms and other airport safety nets.

Once an alarm is generated it may be displayed in the HMI <NUM> and associated to an audible signal until an ATC controller acknowledges it.

In addition, the UWB communication channel may be used to transmit the warning directly to the taxing crew of the aircraft or vehicle, if it embarks the UWB device <NUM>.

The use of the UWB technology as a secondary surveillance source could also allow either the surveillance system <NUM> or the ATC sensor data fusion to use the UWB surveillance to validate the aircraft GPS position broadcast via ADS-B messages, guaranteeing a safe use of the ADS-B data for ground surveillance.

In order to validate the quality of the ADS-B data of each aircraft, the UWB detection has to be compared with the received ADS-B position and mark as valid the ADS-B positions which are within a certain range threshold from the correspondent UWB detection, as shown in <FIG>.

Once an ADS-B transponder is marked as "valid", the system may keep its validity for a certain duration of time from the last validation, achieved via comparison with the UWB surveillance data.

The use of this disclosed validation technique may allow airport to overcome the safety issues related to the ADS-B technology and install standalone ADS-B system without the need for a full MLAT deployment for standard <NUM> cooperative surveillance, guaranteeing same or better performance with a much cheaper solution.

<FIG> shows an airport light-signalling device <NUM>, in which a positioning unit, namely a ranging device <NUM> is integrated. The ranging device <NUM> comprises an ultra-wideband module <NUM> that is adapted to receive one or more ultra-wideband pulse radio signals emitted or echoed by a moving entity <NUM> such as an aircraft taxing along. The one or more ultra-wideband pulse radio signals are received via one or more antennas of the ultra-wideband module <NUM> and transform said signal into raw positioning data. The ultra-wideband module <NUM> comprises besides the one or more antennas and UWB unit a communication unit. The communication unit is adapted to communicate with a computing unit. The computing unit is configured to receive (via the communication unit) and accumulate (in a Data storage) said raw positioning detection data received. The computing unit is also adapted to process the raw positioning data from the communication unit and to deliver positioning data to the communication unit. In the embodiment of <FIG>, the communication unit is adapted to generate LTE (e.g. LTE <NUM>, LTE <NUM>) positioning data signals that are beamed/emitted to a position determining unit <NUM> not shown (not shown) via the one or more antennas. Other means of communication can be foreseen between the ultra-wideband module <NUM> and position determining unit <NUM>, such as through the power line or using the UWB network formed by a network of ultra-wideband ranging device <NUM> spread over an airfield. The ranging devices <NUM> is powered by the airport light-signalling device <NUM>. Besides the ranging device <NUM> comprises an autonomous power supply <NUM>.

In <FIG>, one communication unit with an hardware adapted to preform both UWV and LTE communication is presented. Alternatively, a first communication unit with its antenna for the UWB signals and a second communication unit with its antenna for the LTE signals can be foreseen.

In <FIG>, the ranging device <NUM> forms an unit that is integrated in a "traditional" airport light-signalling device <NUM>. Control interfaces between the ranging device <NUM> and the lighting module <NUM> ensure that the computing unit of ranging device <NUM> can control the controlling unit of the airport light-signalling device <NUM>. This situation occurs when the light LTE control signals are received remotely via the one or antennas mounted on the ranging device <NUM> or via the UWB network formed by a network of ultra-wideband ranging devices <NUM>.

A position determining unit <NUM> adapted to cooperate with the ranging device <NUM> of the airport light-signalling device <NUM> of <FIG> can comprise communication unit configured to exchange data wirelessly with the airfield device <NUM>, in particular WiFi, LTE <NUM>, LTE <NUM>.

The position determining unit <NUM> comprises a centralized processor being configured to receive said positioning data send by the ranging devices <NUM> of the airport light-signalling device <NUM> and to determine therefrom a positioning of the above mentioned moving entity <NUM>, namely an aircraft, based on said positioning data. The centralized processor can be configured to compare the positioning data sent by the ranging devices <NUM> of the airfield devices with data containing the predefined location of the airport light-signalling devices <NUM> spread over an airfield.

The centralized processor can be configured to identify the entity of the above mentioned moving entity <NUM> using the positioning data sent by the ranging devices <NUM> of the airport light-signalling device <NUM>.

The centralized processor can be configured to merge the positioning data sent by the ranging devices <NUM> of the airfield devices to achieve high accuracy in the position calculation.

The centralized processor can be provided with a memory to store the calculated positions and the time of calculation of the above mentioned moving entity <NUM>.

The centralized processor can be configured to process some or all calculated positions of the above mentioned moving entity <NUM>, to calculate in a configurable time window with positions previously calculated and stored in the memory and to associate the ones related to the above mentioned moving entity <NUM>.

The centralized processor can be configured to fuse and smooth the positions associated to the same target and generate a single final position update via a tracking filter, in particular Kalman filtering.

The centralized processor can be configured to transmit all smoothed or new calculated positions of the above mentioned moving entity <NUM> to an external user or higher level system such as the central monitoring unit <NUM>.

Claim 1:
Ultra-wideband positioning system (<NUM>) for determining a position of at least one entity (<NUM>) on an airport field comprising at least one of a manoeuvring area (<NUM>, <NUM>) and an apron (<NUM>), said system comprising:
- at least one airport light-signalling device (<NUM>), in particular an approach light, a runway light, a taxiway light, an elevated light, an inset light, a light box, or a visual docking guidance system, said device (<NUM>) being located on or around the least one of the manoeuvring area (<NUM>, <NUM>) and the apron (<NUM>);
- wherein the at least one airport light-signalling device (<NUM>) comprises a positioning unit (<NUM>) being arranged in or on the at least one airport light-signalling device (<NUM>), said unit (<NUM>) comprising an ultra-wideband module (<NUM>) configured to at least:
- transmit at least one ultra-wideband pulse radio outbound signal (<NUM>, <NUM>), in particular in direction of the at least one entity (<NUM>) and to receive at least one ultra-wideband pulse radio signal (<NUM>, <NUM>, <NUM>', <NUM>) sent spontaneously, returned or echoed by the at least one entity (<NUM>),
or
- receive at least one ultra-wideband pulse radio signal (<NUM>, <NUM>, <NUM>', <NUM>) sent spontaneously, returned, or echoed by the at least one entity (<NUM>);
- a position determining unit (<NUM>) in data communication with the positioning unit (<NUM>) of the at least one airport light-signalling device (<NUM>), said position determining unit (<NUM>) being configured to calculate the position of the at least one entity (<NUM>) using positioning data extracted at least from the at least one ultra-wideband pulse radio signal (<NUM>, <NUM>, <NUM>', <NUM>) sent spontaneously, returned or echoed by the at least one entity (<NUM>),
wherein the positioning unit (<NUM>) of the at least one airport light-signalling device (<NUM>) comprises a first communication unit (<NUM>) that is configured for ultra-wideband data communication with the at least one entity (<NUM>).