EP4281802A1

EP4281802A1 - Cooperative vehicular wavefield imaging

Info

Publication number: EP4281802A1
Application number: EP21732009.2A
Authority: EP
Inventors: Ivan RUSSO; Dario TAGLIAFERRI; Stefano Tebaldini; Monica Nicoli; Umberto Spagnolini; Christian Mazzucco
Original assignee: Huawei Technologies Co Ltd; Politecnico di Milano
Current assignee: Huawei Technologies Co Ltd; Politecnico di Milano
Priority date: 2021-06-10
Filing date: 2021-06-10
Publication date: 2023-11-29
Also published as: CN117413204A; WO2022258182A1

Abstract

Disclosed are an orchestrator device (1) and a wavefield imaging client (2) for wavefield imaging of a target area (6). The orchestrator device (1) is configured to: receive (11) respective wavefield imaging capability information from each of a plurality of wavefield imaging clients (2); select (12) one or more wavefield imaging clients (2) from the plurality of wavefield imaging clients (2) in accordance with the received wavefield capability information; receive (15) a number of wavefield images (4) of the target area (6) from the one or more wavefield imaging clients (2); and combine (16) the received number of wavefield images (4) of the target area (6) in a wavenumber domain representation to obtain a combined wavefield image (5). The wavefield imaging client (2) is configured to: send (21) wavefield imaging capability information to one or more orchestrator devices (1) for the wavefield imaging of the target area (6); generate (24) a number of wavefield images (4) of the target area (6); and send (25) the number of wavefield images (4) of the target area (6) to the one or more orchestrator devices (1). The quality of wavefield imaging of the target area (6) by hardware/resource-limited wavefield imaging sensors is thus improved.

Description

COOPERATIVE VEHICULAR WAVEFIELD IMAGING

Technical Field

The present disclosure relates to wavefield imaging and, for example, to an orchestrator device, a wavefield imaging device, a wavefield imaging peer comprising aforesaid devices, and to methods of operating the same.

Background Art

The quality of wavefield imaging might be bounded for example by hardware limitations or resource limitations of individual wavefield imaging sensors.

For imaging sensors installed onboard a single entity/platform capable of wavefield imaging, performance may depend on available resources in terms of bandwidth in transmission, number of on-board sensors (such as antenna or microphone arrays), transmitted power, integration time at the receiver, or on motion relatively to the target area while an acquisition is made.

Summary

Devices and methods according to this disclosure allow to improve the quality of wavefield imaging of a target area even when hardware/resource-limited wavefield imaging sensors are used.

The foregoing and other objects are achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

The term “imaging” as used herein may refer to a generation of a two- or three-dimensional spatial map of a target area, where different objects (such as cars, motorcycles, buildings, sidewalks, pedestrians, dogs, etc..) appear at pixel locations that correspond to their physical positions in space. The concept of imaging differs from that of localization, which only provides position, and possibly velocity, of detected specific objects in terms of that they are seen as point targets. Accordingly, a localization system can „tell“ that a certain object was detected at a certain position, whereas an imaging system „shows“ an image of the environment. An imaging system provides, therefore, detailed information about a shape of illuminated objects within the target area, which can be seen as groups of distributed scatterers. The term “wavefield” imaging as used herein may refer to the case of sensors being able to illuminate the target area by transmitting a primary wavefield, and to receive a secondary wavefield backscattered by all objects within the target area in response to the primary wavefield. In practical applications, this is for example the case of radar imaging for electromagnetic sensors or acoustic imaging for acoustic sensors. The imaging process may refer to a homogeneous (same) type/set of sensors, which are involved.

A performance of wavefield imaging can be primarily assessed by spatial resolution and signal- to-noise ratio (SNR). Spatial resolution as used herein may refer to a maximum spatial separation of the imaging between two close-by physical objects so that they do not appear as a single object. SNR as used herein may, as in any other sensing system, refer to a ratio of power of the desired signal to any disturbance source. Specifically, the SNR can refer to the ratio of power between the true imaging of pixels representing the objects, and the noise or any other disturbance in the imaging not related to the objects.

This disclosure addresses the case where resources available to single entities may be significantly limited, for example.

According to a first aspect, an orchestrator device is provided for wavefield imaging of a target area. The orchestrator device is configured to: receive respective wavefield imaging capability information from each of a plurality of wavefield imaging clients; select one or more wavefield imaging clients from the plurality of wavefield imaging clients in accordance with the received wavefield capability information; receive a number of wavefield images of the target area from the one or more wavefield imaging clients; and combine the received number of wavefield images of the target area in a wave-number domain representation to obtain a combined wavefield image.

In a possible implementation form the orchestrator device may further be configured to: send the combined wavefield image of the target area to each of the plurality of wavefield imaging clients; or send a portion of the combined wavefield image to each of the plurality of wavefield imaging clients. The portion has a spatial resolution higher than a respective spatial resolution of the received number of wavefield images of the target area. In a possible implementation form the orchestrator device may further be configured to: select the one or more wavefield imaging clients based further on an optimization policy.

In a possible implementation form the optimization policy may comprise one or more of: the number of wavefield images of the target area increases a coverage of the combined wavefield image of the target area in the wavenumber domain representation; a number of wavefield images of more than one target area increases an effective field of view, FoV, of the one or more wavefield imaging clients; the number of wavefield images of the target area increases a signal-to-noise ratio, SNR, of portions of intersecting coverage of the combined wavefield image of the target area in the wavenumber domain representation; and the number of wavefield images of the target area is associated with a radio frequency interference, RFI, level lower than an RFI threshold.

In a possible implementation form the orchestrator device may further be configured to: send own wavefield imaging configuration information to the selected one or more wave-field imaging clients.

According to a second aspect, a wavefield imaging client is provided for wavefield imaging of a target area. The wavefield imaging client is configured to: send wavefield imaging capability information to one or more orchestrator devices for the wavefield imaging of the target area; generate a number of wavefield images of the target area; and send the number of wavefield images of the target area to the one or more orchestrator devices.

In a possible implementation form the generation of the number of wavefield images of the target area may comprise one or more of: a transmission of a primary wavefield to the target area, and a reception of a secondary wavefield from the target area.

In a possible implementation form the primary and/or secondary wavefield may comprise one of: a radar wavefield, a light detection and ranging, LIDAR, wavefield, and an acoustic detection and ranging wavefield.

In a possible implementation form the number of sent wavefield images of the target area may comprise one of: raw wavefield acquisition data, range-compressed wavefield acquisition data, interpolated wavefield acquisition data, ground-projected wavefield acquisition data, and a wavenumber domain representation of the generated wavefield image of the target area.

In a possible implementation form the wavefield imaging capability information may comprise one or more of: an identifier of the wavefield imaging client, a timing information of the wavefield imaging client, a position information of the wavefield imaging client, a frontal direction of the wavefield imaging client, a yaw, roll and/or pitch of the wavefield imaging client, a velocity of the wavefield imaging client, an accuracy information of the wavefield imaging client position, a quantity of wavefield transceiver units of the wavefield imaging client, a state of charge of a battery of the wavefield imaging client, an identifier of a wavefield transceiver unit of the wavefield imaging client, a boresight direction of the wavefield transceiver unit relative to the frontal direction of the wavefield imaging client, an available FoV of the wavefield transceiver unit, a carrier frequency of the wavefield transceiver unit, an available bandwidth of the wavefield transceiver unit, an available energy of the wavefield transceiver unit, and an SNR of the wavefield transceiver unit.

In a possible implementation form the wavefield imaging client may comprise a wavefield transceiver unit being configured to transmit and/or receive in one of: the available bandwidth of the wavefield transceiver unit, and a bandwidth of a reliable radio access control link.

In a possible implementation form the wavefield imaging client may further be configured to: determine the timing information and/or the position information using one or more of: a global navigation satellite system, GNSS, sensor, an inertial measurement unit, IMU, an odometer, a wheel-based velocity sensor, a steering angle sensor, a camera sensor, a magnetometer sensor, an ultrasound sensor, and a light detection and ranging, LIDAR, sensor.

In a possible implementation form the wavefield imaging client may comprise a vehicle, for example, a ground vehicle or an air vehicle.

In a possible implementation form the wavefield imaging client may further be configured to: receive a combined wavefield image of the target area from the one or more orchestrator devices; or receive a portion of the combined wavefield image from the one or more orchestrator devices. The portion has a spatial resolution higher than a respective spatial resolution of the sent number of wavefield images of the target area. In a possible implementation form the wavefield imaging client may further be configured to: receive wavefield imaging configuration information from the one or more orchestrator devices.

According to a third aspect, a wavefield imaging peer is provided, comprising: an orchestrator device according to the first aspect or any of its implementations; and a wavefield imaging client according to the second aspect or any of its implementations.

According to a fourth aspect, a method of operating an orchestrator device is provided. The method comprises: receiving respective wavefield imaging capability information from each of a plurality of wavefield imaging clients; selecting one or more wavefield imaging clients from the plurality of wavefield imaging clients in accordance with the received wavefield capability information; receiving a number of wavefield images of the target area from the one or more wavefield imaging clients; and combining the received number of wavefield images of the target area in a wave-number domain representation to obtain a combined wavefield image.

According to a fifth aspect, a method of operating a wavefield imaging client is provided. The method comprises: sending wavefield imaging capability information to one or more orchestrator devices for the wavefield imaging of the target area; generating a number of wavefield images of the target area; and sending the number of wavefield images of the target area to the one or more orchestrator devices.

According to a sixth aspect, a computer program is provided comprising executable instructions, which when executed by a processor, cause the processor to perform the method according to the fourth or fifth aspect.

It should be noted that all devices, elements, units and means described in the present application could be implemented in the software or hardware elements or any kind of combination thereof. All steps which are performed by the various entities described in the present application as well as the functionalities described to be performed by the various entities are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities. Even if, in the following description of specific embodiments, a specific functionality or step to be performed by external entities is not reflected in the description of a specific detailed element of that entity which performs that specific step or functionality, it should be clear for a skilled person that these methods and functionalities can be implemented in respective software or hardware elements, or any kind of combination thereof.

Advantageous Effects

The present disclosure addresses the case where resources available to individual wavefield imaging entities may be significantly limited, for example, and identifies an orchestration strategy to allow a group of imaging entities to operate as a single distributed wavefield imaging sensor. The single distributed wavefield imaging sensor is capable of greatly improving image quality with respect to individual imaging entities despite each might have limited resources.

The present disclosure is distinguished from prior art in an arbitrary and dynamic formation of imaging entities, where the number of imaging entities and the trajectories are changing. The degrees of freedom can be on the choice of at least two imaging entities used for data acquisition, the carrier frequency and the bandwidth of operation, for example.

The orchestration may enhance a resolution of a spatial domain representation of the wavefield image by covering a larger, for example contiguous, region in a wavenumber domain representation of the wavefield image. Yet, the role of the orchestration is not limited to that, and can be extended to include:

- RFI protection: dynamically selecting in which frequency band each transmission occurs may optimize imaging performance while ensuring protection against Radio Frequency Interference (RFI).

- SNR improvement: acquiring a same wavenumber region multiple times may abate random noise by coherent averaging.

- FoV extension: images of different FoVs (i.e., target areas) may enable generating a high- resolution image with extended Field of View (FoV).

Brief Description of Drawings

The above-described aspects and implementations will now be explained with reference to the accompanying drawings, in which the same or similar reference numerals designate the same or similar elements. The features of these aspects and implementations may be combined with each other unless specifically stated otherwise.

The drawings are to be regarded as being schematic representations, and elements illustrated in the drawings are not necessarily shown to scale. Rather, the various elements are represented such that their function and general purpose become apparent to those skilled in the art.

FIG. 1 illustrates an exemplary wavefield imaging scenario;

FIGs. 2-3 illustrate a spatial domain representation (FIG. 2) and a corresponding wavenumber domain representation (FIG. 3) of an exemplary high-resolution wavefield/radar image;

FIGs. 4-5 illustrate a spatial domain representation (FIG. 4) and a corresponding wavenumber domain representation (FIG. 5) of an exemplary low-resolution wavefield/radar image;

FIGs. 6-7 illustrate a spatial domain representation (FIG. 6) and a corresponding wavenumber domain representation (FIG. 7) of an exemplary low-resolution wavefield/radar image;

FIGs. 8-9 illustrate a spatial domain representation (FIG. 8) and a corresponding wavenumber domain representation (FIG. 9) of an exemplary combined wavefield/radar image resulting from an uncoordinated combination of low-resolution wavefield/radar images;

FIGs. 10-11 illustrate a spatial domain representation (FIG. 10) and a corresponding wavenumber domain representation (FIG. 11) of an exemplary combined wavefield/radar image resulting from a coordinated combination of low-resolution wavefield/radar images;

FIG. 12 illustrates an interacting orchestrator device and a wavefield imaging client;

FIG. 13 illustrates two interacting wavefield imaging peers interacting; FIGs. 14-15 illustrate a relation of spatial domain representation and wavenumber domain representation for individual pulse frequencies /in monostatic (FIG. 14) and bistatic (FIG. 15) sensing/acquisition;

FIGs. 16-17 illustrate a relation of spatial domain representation and wavenumber domain representation for a range/bandwidth B=f_mDrf of pulse frequencies in monostatic (FIG. 16) and bistatic (FIG. 17) sensing/acquisition; and

FIGs. 18-19 illustrate a relation of spatial domain representation and wavenumber domain representation for a range/bandwidth B f_max-f of pulse frequencies and an aperture Dy in monostatic (FIG. 18) and bistatic (FIG. 19) sensing/acquisition.

Detailed Descriptions of Drawings

In the following description, reference is made to the accompanying drawings, which form part of the disclosure, and which show, by way of illustration, specific aspects of embodiments of the invention or specific aspects in which embodiments of the present invention may be used. It is understood that embodiments of the invention may be used in other aspects and comprise structural or logical changes not depicted in the figures. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

For instance, it is understood that a disclosure in connection with a described method may also hold true for a corresponding apparatus or system configured to perform the method and vice versa. For example, if one or a plurality of specific method steps are described, a corresponding device may include one or a plurality of units, e.g. functional units, to perform the described one or plurality of method steps (e.g. one unit performing the one or plurality of steps, or a plurality of units each performing one or more of the plurality of steps), even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, for example, if a specific apparatus is described based on one or a plurality of units, e.g. functional units, a corresponding method may include one step to perform the functionality of the one or plurality of units (e.g. one step performing the functionality of the one or plurality of units, or a plurality of steps each performing the functionality of one or more of the plurality of units), even if such one or plurality of steps are not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary embodiments and/or aspects described herein may be combined with each other, unless specifically noted otherwise.

From a perspective of signal analysis, wavenumbers can be thought of as the coordinates in which a Fourier Transform (FT) of an image is expressed.

The FT is an invertible operator, so that it is always possible to re-obtain the original image expressed in spatial coordinates by an Inverse Fourier Transform (IFT). For this reason, many engineers like to think of an image in terms of the information it carries, which can be either represented in the spatial or in the wavenumber domain to highlight specific properties.

A link between wavenumbers and acquisition geometry is formalized by the Fundamental Equation of Diffraction Tomography (FEDT). Diffraction tomography as used herein may refer to a reconstruction technique used to find a shape of a scattering object by illuminating it with probing waves and recording the reflections. The FEDT allows to calculate a region in a wavenumber domain representation that will be covered by a wavefield acquisition given the transmitted frequency band B and the trajectories of the transmitting and the receiving wavefield imaging sensors relative to the target area.

Explicative illustrations of the relation between spatial and wavenumber domain representations are explained in more detail in connection with FIGs. 14 - 19 below.

Spatial resolution is among those properties that show up particularly well in the wavenumber domain. Those skilled in the art will appreciate the general principle that the finer is the resolution of a spatial domain representation of a given image, the larger is the region in the wavenumber domain representation of the same image.

Finer, higher or enhanced spatial resolution as used herein may refer to smaller pixel dimensions in a spatial domain representation of an image.

FIG. 1 illustrates an exemplary wavefield imaging scenario.

In a street view perspective, an entity/vehicle equipped with a wavefield imaging sensor (see top of FIGs 12, 13 depicting entities/vehicles including wavefield imaging devices 2), such as a radar sensor, is configured to move in a driving direction represented by the x axis and to acquire a wavefield image of a lateral target area 6, i.e., in a lateral direction represented by the y axis. The scenario includes parked cars (see items A, B), parking poles, a sidewalk (see item C), and a building faqade (see item D).

FIGs. 2-3 illustrate a spatial domain representation (FIG. 2) and a corresponding wavenumber domain representation (FIG. 3) of an exemplary high-resolution wavefield/radar image 4.

FIG. 2 shows a spatial domain representation of an exemplary radar image 4 of the scenario of FIG. 1 obtained by a reference high-resolution radar sensor onboard the moving vehicle. The spatial domain representation features centimetric spatial resolution, and allows clear imaging of the parked cars (see A, B), parking poles, sidewalk (see C), and building faqade (see D). This is reflected by the large region occupied by the image 4 in a wavenumber domain representation depicted in FIG. 3.

FIGs. 4-5 illustrate a spatial domain representation (FIG. 4) and a corresponding wavenumber domain representation (FIG. 5) of an exemplary low-resolution wavefield/radar image 4.

FIG. 4 shows a spatial domain representation of an exemplary radar image 4 of the scenario of FIG. 1 obtained by a low-cost radar sensor onboard the moving vehicle, with severe limitations on transmitted bandwidth and acquisition time. The spatial domain representation is characterized by a much coarser spatial resolution as compared to FIG. 2, and this is very clearly reflected by the fact that the coverage of the image 4 in the wavenumber domain representation is much smaller (see FIG. 5).

FIGs. 6-7 illustrate a spatial domain representation (FIG. 6) and a corresponding wavenumber domain representation (FIG. 7) of an exemplary low-resolution wavefield/radar image 4.

FIG. 6 shows a spatial domain representation of an exemplary radar image 4 of the scenario of FIG. 1 obtained by a similar resource-limited radar sensor onboard another moving vehicle. The one element of difference with respect to FIGs. 4 - 5 relates to a different position of the moving vehicle with respect to the target area 6, which results in a different coverage of the image 4 in the wavenumber domain representation (see FIG. 7). The key to improve imaging performance when sensor resources are limited is to consider a group of vehicles, or more generally entities, capable of operating as a single distributed wavefield imaging sensor, using the FEDT to cover a much larger region in the wavenumber domain representation than allowed to individual entities.

A naive implementation of this idea could simply let each entity acquire a low-resolution image independently. This implementation may be referred to as unorchestrated or uncoordinated, and is exemplified in FIGs. 8 - 9 for the case of seven independent entities contributing a total of seven images 4.

FIGs. 8-9 illustrate a spatial domain representation (FIG. 8) and a corresponding wavenumber domain representation (FIG. 9) of an exemplary combined wavefield/radar image 5 resulting from an uncoordinated combination of low-resolution wavefield/radar images 4.

It is immediate to see that the resulting coverage of the combined image 5 in the wavenumber domain representation is limited to a sort of a “punctured arc”, and many regions in the wavenumber domain representation remain white (see FIG. 9). When expressed in the spatial domain, the resulting radar image 4 (see FIG. 8) shows limited improvement - if any - over images 4 acquired by individual imaging entities (see FIGS. 4, 6) and it is contaminated by the presence of side lobes.

As opposed to this situation, the present disclosure proposes an orchestration strategy that orchestrates or coordinates all entities in the acquisition phase, so as to cover a large and, for example, contiguous region of the wavenumber domain representation and thus approach the imaging quality of high-performance sensors. The orchestration proceeds from a description of the position of individual entities at a given time instant and of the resources available to each entity (like available frequency bands, acquisition time, etc.), and uses the FEDT to optimize the wavenumber coverage.

Contrary to the naive implementation, the orchestration also includes the possibility of bistatic acquisitions, gathered by letting one entity act as transmitter and another as receiver, or multistatic acquisitions. By the FEDT, such acquisitions allow to explore regions of the wavenumber domain that are forbidden to acquisitions by individual entities. FIGs. 10-11 illustrate a spatial domain representation (FIG. 10) and a corresponding wavenumber domain representation (FIG. 11) of an exemplary combined wavefield/radar image 5 resulting from a coordinated combination of low-resolution wavefield/radar images 4 in accordance with the present disclosure.

The example assumes the same group of seven entities considered in FIGs. 8 - 9, but it allows for bistatic acquisitions using selected entities for pairing (in general groups of N receivers and groups of M transmitters in the multistatic case).

An entity pair may be selected for bistatic acquisition if that particular pair covers a region in the wavenumber domain representation that is needed to improve a spatial resolution, i.e., to get closer to the result of FIG. 3. More than two entities may be paired for multistatic acquisitions, where multiple receivers may simultaneously acquire a signal of a single transmitter.

The resulting coverage in the wavenumber domain representation of FIG. 11 is free of gaps, and much larger than in the un-orchestrated case (see FIG. 9). Evidently, bistatic as well as multistatic imaging may extend a coverage in a wavenumber domain representation to previously spared wavenumber regions that have been plotted as white areas in FIG. 9.

The resulting combined image 4 of FIG. 10 shows a clear improvement with respect to FIG. 9, approaching the same spatial resolution as the one by the high-performance radar sensor (see FIG. 3).

As will be explained in more detail in connection with FIGs. 12 and 13 below, the orchestration may involve distributed or centralized approaches.

FIG. 12 illustrates an orchestrator device 1 and a wavefield imaging client 2 interacting in accordance with the present disclosure. For a better understanding, the orchestrator device 1 and the wavefield imaging client 2 are respectively depicted on top of corresponding flow diagrams and highlighted by respective vehicle shapes.

In other words, FIG. 12 relates to the centralized orchestration which is characterized by a functional split between a central “orchestrator device” (e.g., a road side unit) and distributed “wavefield imaging entities” (i.e., moving vehicles), wherein the “orchestrator device” may involve the “wavefield imaging entities” as needed.

The goal of orchestration is to obtain a maximum, potentially contiguous, coverage in a wavenumber domain representation of a wavefield acquisition of a target area 6 by:

- optimal selection of at least one (or more than one) cooperating entity (or entities) to perform the wavefield acquisition; and

- optimal allocation of sensing and communication resources (bandwidth/time) to the selected entities for wavefield acquisition.

“Optimal” as used herein may refer to selecting/allocating those that among all possible combinations/options that maximize a resulting image quality.

Image quality as used herein may refer to one or more of: a spatial resolution, an SNR, and a Signal-to-Interference-plus-Noise Ratio (SINR).

Other entities which are not involved in the wavefield acquisition may simply receive the resulting combined image 5 of the target area 6.

It is assumed that each entity has an a-priori coarse knowledge on where the target area 6 to be imaged is located in space, either in global or local coordinates. This assumption is needed for the proper selection of the cooperating entities and related on-board wavefield sensors.

The wavefield imaging client 2 may comprise a vehicle, for example, a ground vehicle such as a car, truck, etc. or an air vehicle, i.e., an air-borne platform such as an UAV, airplane, helicopter, etc. In particular, the vehicle may be a moving vehicle, which enables image acquisitions of the target area 6 from a range of lateral angles relative to the target area 6.

The wavefield imaging client 2 may comprise a wavefield transceiver unit, such as an active wavefield sensor, being configured to transmit and/or receive in one of: an available bandwidth of the wavefield transceiver unit, and a bandwidth of a reliable radio access control link. Of note, the wavefield transceiver unit may operate on a frequency bandwidth that may possibly be shared with other entities. The wavefield sensor may be identified by a local “sensorlD” field (whose format is standard for all the considered entities) and the on-board placement and capabilities of each wavefield sensor are assumed to be known at the entity, comprising a relative pointing angle of the boresight with respect to a frontal direction (direction of motion of the entity), the FoV, the available bandwidth, and all the parameters characterizing the operation of the wavefield sensor.

The wavefield imaging client 2 may further comprise a navigation unit configured to provide at least a position of the entity over time. In particular, it is assumed that the navigation unit is able to provide at least the position over time of each wavefield sensor on-board the entity, as well as a global timestamp of each data. Each signal emitted and received from each wavefield sensor is labelled with the global timestamp. Possible extensions to the previous case include the orientation/direction of motion of each wavefield sensor on-board the entity (if the entity is moving).

The wavefield imaging client 2 may further comprise a transceiver unit configured for inter entity communication, allowing an exchange of control information and data between entities. The inter-entity communication may possibly share the same bandwidth with the on-board wavefield sensor(s). Of course, if the considered wavefield sensors are of acoustic type, there is no mutual interference. Similarly, if wavefield sensors and inter-entity communication operate on different spectrum portions (e.g., sub-6 GHz as 5GNew Radio Frequency Range 1 communication system and 76-81 GHz for a typical automotive radar), there is no mutual interference. Differently, if wavefield sensors and inter-entity communication systems operate on the same spectrum portion, the available bandwidth refers to the effective bandwidth that can be allocated for wavefield acquisitions and, similarly, the allocated bandwidth is related to a portion of the former one. The dynamic bandwidth allocation for both wavefield acquisition and communication is not detailed herein any further.

The wavefield imaging client 2 may further comprise an on-board processing unit for processing of navigation data as well as received wavenumber acquisitions. It is assumed that each entity is uniquely identified by a univocal “entitylD” field.

A first orchestration phase involves an exchange of information.

The information to be exchanged is the wavefield imaging capabilities of each entity. Centralized orchestration involves exchanging wavefield imaging capabilities with a centralized orchestrator device, and developing a centralized knowledge of the imaging capabilities of the entities.

Accordingly, the wavefield imaging client 2 is configured to send 21 wavefield imaging capability information to one or more orchestrator devices 1 for wavefield imaging of the target area 6.

The wavefield imaging capability information may comprise one or more of: an identifier of the wavefield imaging client 2, a timing information of the wavefield imaging client 2, a position information of the wavefield imaging client 2, a frontal direction of the wavefield imaging client 2, a yaw, roll and/or pitch of the wavefield imaging client 2, a velocity of the wavefield imaging client 2, an accuracy information of the wavefield imaging client position, a quantity of wavefield transceiver units of the wavefield imaging client 2, a state of charge of a battery of the wavefield imaging client 2 (to accommodate the possibility of dealing with non ground-based entities or fully electric entities), an identifier of a wavefield transceiver unit of the wavefield imaging client 2, a boresight direction of the wavefield transceiver unit relative to the frontal direction of the wavefield imaging client 2, an available FoV of the wavefield transceiver unit, a carrier frequency of the wavefield transceiver unit, an available bandwidth B of the wavefield transceiver unit, an available energy (i.e., maximum emitted power) of the wavefield transceiver unit, and an SNR of the wavefield transceiver unit. The wavefield imaging capability information may further comprise an interference level sensed by a respective wavefield sensor of each entity on the available bandwidth.

In particular, the wavefield imaging client 2 may further be configured to: determine the timing information and/or the position information using one or more of: a global navigation satellite system, GNSS, sensor, an inertial measurement unit, IMU, an odometer, a wheel-based velocity sensor, a steering angle sensor, a camera sensor, a magnetometer sensor, an ultrasound sensor, and a light detection and ranging, LIDAR, sensor.

The wavefield imaging capability information may thus comprise all the information and circumstances of the wavefield imaging client 2 that may be of relevance for orchestrated wavefield imaging. Correspondingly, the orchestrator device 1 is configured to receive 11 the respective wavefield imaging capability information from each of a plurality of wavefield imaging clients 2.

A second orchestration phase involves selecting the cooperating entities and selecting the wavefield sensors on-board each cooperating entity.

The orchestrator device 1 is further configured to select 12 one or more wavefield imaging clients 2 from the plurality of wavefield imaging clients 2 in accordance with the received wavefield capability information; and may further be configured to select 12’ the one or more wavefield imaging clients 2 based further on an optimization policy.

The goal of this phase is to select a meaningful subset of the available entities (and candidate wavefield sensors) to perform the wavefield acquisition. The cooperating entities are selected as the minimum set that maximizes a, for example, contiguous coverage in the wavenumber domain representation.

The optimization policy may comprise one or more of: the number of wavefield images 4 of the target area 6 increases a coverage of the combined wavefield image 5 of the target area 6 in the wavenumber domain representation; a number of wavefield images 4 of more than one target area 6 increases an effective field of view, FoV of the one or more wavefield imaging clients 2; the number of wavefield images 4 of the target area 6 increases a signal-to-noise ratio, SNR, of portions of intersecting coverage of the combined wavefield image 5 of the target area 6 in the wavenumber domain representation; and the number of wavefield images 4 of the target area 6 is associated with a radio frequency interference, RFI, level lower than an RFI threshold.

Those skilled in the art will appreciate that this describes candidate objectives and candidate constraints of an optimization problem that may be solved by way of various mathematical methods, such as mathematical programming/optimization, for example.

The orchestrator device 1 may further be configured to send 13 own wavefield imaging configuration information to the selected one or more wave-field imaging clients 2. Correspondingly, the wavefield imaging client 2 may further be configured to receive 23 wavefield imaging configuration information from the one or more orchestrator devices 1. The information to be communicated from the centralized orchestrator entity/device to the selected cooperating entities is:

- the selected cooperating entities by means of the “entitylD” quantity,

- the selected wavefield sensors for each cooperating entity for the acquisition, by means of the “sensorlD” quantity,

- the role of each wavefield sensor, namely transmitter and receiver (monostatic acquisition) or receiver only (for bi static acquisitions only),

- the allocated bandwidth used by each transmitting wavefield sensor, and

- the allocated power used by each transmitting wavefield sensor.

This notifies the selected one or more wave-field imaging clients 2 that they are being considered for coordinated wavefield imaging, so that those of the one or more wave-field imaging clients 2 that have not been selected may save processing, communication and energy resources. In addition, this would allocate the resources to each cooperating entity for wavefield acquisition, in accordance with the preceding selection.

Of note, this explicit signaling may be performed if and only if the orchestration is centralized. For fully distributed orchestration (see below), this signaling phase is not necessary, as each entity is able to autonomously determine whether to perform the wavefield acquisition and the related parameters.

However, it is possible to proceed without this feedback also in centralized orchestration, resulting in potentially less optimum quality of the resulting image.

A third orchestration phase involves generating, exchanging and processing the wavefield acquisitions.

Centralized orchestration involves exchanging wavefield acquisitions with the centralized orchestrator device 1.

Thus, no matter if the particular wavefield imaging client 2 actually received wavefield imaging configuration information from the one or more orchestrator devices 1, it is nevertheless configured to generate 24 a wavefield image 4 of the target area 6. The generation of the number of wavefield images 4 of the target area 6 may comprise one or more of: a transmission of a primary wavefield to the target area 6, and a reception of a secondary wavefield from the target area 6.

The primary and/or secondary wavefield may comprise one of: a radar wavefield, a light detection and ranging, LIDAR, wavefield, and an acoustic detection and ranging wavefield.

The wavefield imaging client 2 is further configured to send 25 the wavefield image 4 of the target area 6 to the one or more orchestrator devices 1.

The sent wavefield image of the target area 6 may comprise one of: raw wavefield acquisition data (with associated global timestamps), partially (i.e., range-) compressed wavefield acquisition data (with associated global timestamps), locally processed wavefield acquisition data (i.e., low-quality images), interpolated wavefield acquisition data, ground-projected wavefield acquisition data, and a wavenumber domain representation of the generated wavefield image of the target area 6.

Interpolated wavefield acquisition data as used herein may refer to an output of a regridding done by the respective wavefield imaging client. Regridding is the process of interpolating from one grid resolution to a different grid resolution. This could relate to different domains but, most commonly, regridding refers to spatial interpolation, such as conversion from a polar coordinate description into a Cartesian coordinate description, for example. The regridding process from polar to Cartesian will implicitly contain a spatial interpolation to the destination coordinate grid.

Ground-projected wavefield acquisition data as used herein may refer to a typical corrected output of SAR (Synthetic Aperture Radar) imaging after compensation of the trajectory of the sensor by proper focusing and/or autofocusing algorithms (i.e. Time Domain Back Projection). Indeed, in SAR applications, the image formation process exploits the movement of the sensor along a trajectory forming a synthetic aperture. The trajectory shall be ideally straight but, in real cases, follows a non-straight path. In this case, the sent information is already an image (not an acquisition data anymore) because it has already undergone the focusing processes to compensate the non-straight trajectory. Correspondingly, the orchestrator device 1 is configured to receive 15 the number of wavefield images 4 of the target area 6 from the one or more wavefield imaging clients 2; and combine 16 the received number of wavefield images 4 of the target area 6 in a wave-number domain representation to obtain a combined wavefield image 5. In other words, the wave-number domain representation is augmented by the received number of wavefield images 4.

As such, the orchestrator device 1 receives all the wavefield acquisitions from cooperating entities and maps them into a same wavefield domain representation using the FEDT as exemplified in FIGs. 14 - 19.

The orchestrator device 1 may further be configured to: send 17 the combined wavefield image 5 of the target area 6 to each of the plurality of wavefield imaging clients 2, or send 17’ a portion of the combined wavefield image 5 to each of the plurality of wavefield imaging clients 2, wherein the portion has a spatial resolution higher than a respective spatial resolution of the received number of wavefield images 4 of the target area 6. Likewise, the wavefield imaging client 2 may further be configured to receive 27 the combined wavefield image 5 of the target area 6 from the one or more orchestrator devices 1, or receive 27’ the portion of the combined wavefield image 5 from the one or more orchestrator devices 1.

The centralized orchestrator device 1 thus exchanges the final image with all the entities, not only the cooperating ones. In this way, also the non-cooperating entities obtain the resulting image of the target area 6.

The above-described interaction is in accordance with a method of operating an orchestrator device 1, which comprises steps of: receiving 11 respective wavefield imaging capability information from each of a plurality of wavefield imaging clients 2; selecting 12 one or more wavefield imaging clients 2 from the plurality of wavefield imaging clients 2 in accordance with the received wavefield capability information; receiving 15 a number of wavefield images 4 of the target area 6 from the one or more wavefield imaging clients 2; and combining 16 the received number of wavefield images 4 of the target area 6 in a wave-number domain representation to obtain a combined wavefield image 5. The above-described interaction is further in accordance with a method of operating a wavefield imaging client 2, which comprises steps of: sending 21 wavefield imaging capability information to one or more orchestrator devices 1 for the wavefield imaging of the target area 6; generating 24 a number of wavefield images 4 of the target area 6; and sending 25 the number of wavefield images 4 of the target area 6 to the one or more orchestrator devices 1.

FIG. 13 illustrates two wavefield imaging peers 3 interacting in accordance with the present disclosure. For a better understanding, the wavefield imaging peers 3 are respectively depicted on top of corresponding flow diagrams and highlighted by respective vehicle shapes. Each of the wavefield imaging peers 3 is depicted as comprising an orchestrator device 1 of the first aspect or any of its implementations, and a wavefield imaging client 2 of the second aspect or any of its implementations.

That is to say, FIG. 13 relates to distributed orchestration, which features a coordination among equal-ranking “wavefield imaging peers” (i.e., moving vehicles) comprising both functionalities of the “orchestrator device” and the “wavefield imaging entities”.

As such, a wavefield imaging peer 3 comprises an orchestrator device 1 of the first aspect or any of its implementations, and a wavefield imaging client 2 of the second aspect or any of its implementations.

In particular, distributed orchestration differs from centralized orchestration by

- mutually exchanging wavefield imaging capabilities among cooperating entities instead of with a centralized orchestrator device,

- developing a distributed knowledge of the imaging capabilities of the cooperating entities instead of a centralized knowledge,

- each entity being able to autonomously determine whether to perform a wavefield acquisition and to devise the related parameters, and

- mutually exchanging wavefield acquisitions among cooperating entities instead of with the centralized orchestrator device. Advantageously, the technical effects and advantages described above in relation with the orchestrator device and the wavefield imaging entity equally apply to the wavefield imaging peer having corresponding features.

FIGs. 14-15 illustrate a relation of spatial domain representation and wavenumber domain representation for individual pulse frequencies /in monostatic (FIG. 14) and bistatic (FIG. 15) sensing/ acqui sition.

As customary in the literature of radar, acoustic, and geophysical imaging, the present disclosure is here presented with reference to the duality between spatial coordinates (x, y) and wavenumbers (k_x,k_y), which plays the same role in wavefield imaging as played by the well- known duality between time and frequency in conventional signal analysis. Such a correspondence is fundamental to the understanding of the present disclosure, and it is therefore briefly exemplified in the following.

FIG. 14 relates to monostatic acquisition wherein a same entity, i.e., vehicle, acts as a wavefield transmitter and receiver on an individual pulse frequency f.

A left-hand side of FIG. 14 shows a rectangular coordinate system spanned by a driving direction represented by the x axis and a lateral direction represented by the y axis. In this reference system, a transmitting and receiving vehicle at position (x; y=0) and a lateral target area 6 at position (x=0; y) are arranged relative to one another.

In accordance with monostatic acquisition, a lateral transmission angle y_Tc and a lateral reception angle p_Rx of the vehicle with respect to the target area 6 are the same:

Ytc = Yϋc = Y

A right-hand side of FIG. 14 depicts a rectangular coordinate system spanned by corresponding wavenumbers k_x, k_y. The corresponding wavenumber vectors for transmission and reception and their sum vector thus have a same angle/direction p_m : FIG. 15 depicts the rectangular coordinate systems of FIG. 14 but relates to bistatic acquisition wherein one entity, i.e., vehicle, acts as a wavefield transmitter and another entity acts as a wavefield receiver on the individual pulse frequency f.

To the left of FIG. 15, a transmitting vehicle at position (x; y=0), a lateral target area 6 at position (x=0; y) and a receiving vehicle at position (x; y=0) are arranged relative to one another.

In bistatic acquisition, a lateral transmission angle y_Tc and a lateral reception angle ip_Rx of the respective vehicle with respect to the target area 6 are not necessarily the same:

Ytc ¹ 4>RX

In the wavenumber domain representation, the corresponding wavenumber vectors for transmission and reception thus have different angles/directions, and their sum vector is given as:

FIGs. 16-17 illustrate a relation of spatial domain representation and wavenumber domain representation for a range/bandwidth B=f_max-f of pulse frequencies in monostatic (FIG. 14) and bistatic (FIG. 15) sensing/acquisition.

The difference with respect to FIGs. 14 - 15 is that the range/bandwidth B of pulse frequencies is mapped to a line-shaped rather than point-shaped wavenumber region.

For monostatic acquisition:

For bistatic acquisition: FIGs. 18-19 illustrate a relation of spatial domain representation and wavenumber domain representation for a range/bandwidth B=f_max-f of pulse frequencies and an aperture Dy in monostatic (FIG. 14) and bistatic (FIG. 15) sensing/acquisition.

The difference with respect to FIGs. 16 - 17 is that the involved vehicles may move and thus sweep a range of angles Dy, called aperture. For simplicity, it is assumed that the range of angles Dy is the same for transmission and reception, although generally these ranges may differ. The range/bandwidth B of pulse frequencies and the range of angles Dy are mapped to an arc-shaped rather than line-shaped wavenumber region.

For both monostatic (FIG. 18) and bistatic cases (FIG. 19), the coverage in the wavenumber domain representation is thus basically dependent on the bandwidth B and carrier frequency / of the transmitted and received pulses (radial dependence), and on the aperture/FoV Dy of the exploited sensor (angular dependence).

The present disclosure has been described in conjunction with various embodiments as examples as well as implementations. However, other variations can be understood and effected by those persons skilled in the art and practicing the claimed matter, from the studies of the drawings, this disclosure and the independent claims. In the claims as well as in the description the word “comprising” does not exclude other elements or steps and the indefinite article “a” or “an” does not exclude a plurality. A single element or other unit may fulfill the functions of several entities or items recited in the claims. The mere fact that certain measures are recited in the mutual different dependent claims does not indicate that a combination of these measures cannot be used in an advantageous implementation. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

Claims

1. An orchestrator device (1) for wavefield imaging of a target area (6), the orchestrator device (1) being configured to: receive (11) respective wavefield imaging capability information from each of a plurality of wavefield imaging clients (2); select (12) one or more wavefield imaging clients (2) from the plurality of wavefield imaging clients (2) in accordance with the received wavefield capability information; receive (15) a number of wavefield images (4) of the target area (6) from the one or more wavefield imaging clients (2); and combine (16) the received number of wavefield images (4) of the target area (6) in a wavenumber domain representation to obtain a combined wavefield image (5).

2. The orchestrator device (1) of claim 1, further being configured to: send (17) the combined wavefield image (5) of the target area (6) to each of the plurality of wavefield imaging clients (2); or send (17’) a portion of the combined wavefield image (5) to each of the plurality of wavefield imaging clients (2), the portion having a spatial resolution higher than a respective spatial resolution of the received number of wavefield images (4) of the target area (6).

3. The orchestrator device (1) of any one of the preceding claims, further being configured to: select (12’) the one or more wavefield imaging clients (2) based further on an optimization policy.

4. The orchestrator device (1) of claim 3, wherein the optimization policy comprises one or more of: the number of wavefield images (4) of the target area (6) increases a coverage of the combined wavefield image (5) of the target area (6) in the wavenumber domain representation; a number of wavefield images (4) of more than one target area (6) increases an effective field of view, FoV of the one or more wavefield imaging clients (2); the number of wavefield images (4) of the target area (6) increases a signal-to-noise ratio, SNR, of portions of intersecting coverage of the combined wavefield image (5) of the target area (6) in the wavenumber domain representation; and the number of wavefield images (4) of the target area (6) is associated with a radio frequency interference, RFI, level lower than an RFI threshold.

5. The orchestrator device (1) of any one of the preceding claims, further being configured to: send (13) own wavefield imaging configuration information to the selected one or more wavefield imaging clients (2).

6. A wavefield imaging client (2) for wavefield imaging of a target area (6), the wavefield imaging client (2) being configured to: send (21) wavefield imaging capability information to one or more orchestrator devices (1) for the wavefield imaging of the target area (6); generate (24) a number of wavefield images (4) of the target area (6); and send (25) the number of wavefield images (4) of the target area (6) to the one or more orchestrator devices (1).

7. The wavefield imaging client (2) of claim 6, the generation of the number of wavefield images (4) of the target area (6) comprising one or more of: a transmission of a primary wavefield to the target area (6), and a reception of a secondary wavefield from the target area (6).

8. The wavefield imaging client (2) of claim 7, the primary and/or secondary wavefield comprising one of: a radar wavefield, a light detection and ranging, LIDAR, wavefield, and an acoustic detection and ranging wavefield.

9. The wavefield imaging client (2) of any one of the claims 6 to 8, the number of sent wavefield images of the target area (6) comprising one of: raw wavefield acquisition data, range-compressed wavefield acquisition data, interpolated wavefield acquisition data, ground-projected wavefield acquisition data, and a wavenumber domain representation of the generated wavefield image of the target area (6)

10. The wavefield imaging client (2) of any one of the claims 6 to 9, the wavefield imaging capability information comprising one or more of: an identifier of the wavefield imaging client (2), a timing information of the wavefield imaging client (2), a position information of the wavefield imaging client (2), a frontal direction of the wavefield imaging client (2), a yaw, roll and/or pitch of the wavefield imaging client (2), a velocity of the wavefield imaging client (2), a quantity of wavefield transceiver units of the wavefield imaging client (2), a state of charge of a battery of the wavefield imaging client (2), an identifier of a wavefield transceiver unit of the wavefield imaging client (2), a boresight direction of the wavefield transceiver unit relative to the frontal direction of the wavefield imaging client (2), an available FoV of the wavefield transceiver unit, a carrier frequency of the wavefield transceiver unit, an available bandwidth of the wavefield transceiver unit, an available energy of the wavefield transceiver unit, and an SNR of the wavefield transceiver unit.

11. The wavefield imaging client (2) of any one of the claims 6 to 10, comprising a wavefield transceiver unit being configured to transmit and/or receive in one of: the available bandwidth of the wavefield transceiver unit, and a bandwidth of a reliable radio access control link.

12. The wavefield imaging client (2) of claim 10 or claim 11, further being configured to: determine the timing information and/or the position information using one or more of: a global navigation satellite system, GNSS, sensor, an inertial measurement unit, IMU, an odometer, a wheel-based velocity sensor, a steering angle sensor, a camera sensor, a magnetometer sensor, an ultrasound sensor, and a light detection and ranging, LIDAR, sensor.

13. The wavefield imaging client (2) of any one of the claims 6 to 12, comprising a vehicle, for example, a ground vehicle or an air vehicle.

14. The wavefield imaging client (2) of any one of the claims 6 to 13, further being configured to: receive (27) a combined wavefield image (5) of the target area (6) from the one or more orchestrator devices (1); or receive (27’) a portion of the combined wavefield image (5) from the one or more orchestrator devices (1), the portion having a spatial resolution higher than a respective spatial resolution of the sent number of wavefield images (4) of the target area (6).

15. The wavefield imaging client (2) of any one of the claims 6 to 14, further being configured to: receive (23) wavefield imaging configuration information from the one or more orchestrator devices (1).

16. A wavefield imaging peer (3), comprising: an orchestrator device (1) of any one of the claims 1 to 5; and a wavefield imaging client (2) of any one of the claims 6 to 15.

17. A method of operating an orchestrator device (1), comprising: receiving (11) respective wavefield imaging capability information from each of a plurality of wavefield imaging clients (2); selecting (12) one or more wavefield imaging clients (2) from the plurality of wavefield imaging clients (2) in accordance with the received wavefield capability information; receiving (15) a number of wavefield images (4) of the target area (6) from the one or more wavefield imaging clients (2); and combining (16) the received number of wavefield images (4) of the target area (6) in a wavenumber domain representation to obtain a combined wavefield image (5).

18. A method of operating a wavefield imaging client (2), comprising: sending (21) wavefield imaging capability information to one or more orchestrator devices (1) for the wavefield imaging of the target area (6); generating (24) a number of wavefield images (4) of the target area (6); and sending (25) the number of wavefield images (4) of the target area (6) to the one or more orchestrator devices (1).

19. A computer program comprising executable instructions, which when executed by a processor, cause the processor to perform the method of claim 17 or claim 18.