Determining handover behavior based on estimated sensing performance

Abstract

A system (1) is configured to collect measurements on candidate cells (41,42) and estimate a communication performance for each of the candidate cells based on the measurements. The candidate cells include a current cell (41) serving a mobile device (31). The system is further configured to estimate a sensing performance for each of the candidate cells, identify, from the candidate cells, the best cell for serving the mobile device based on the estimated communication performances and the estimated sensing performances, and cause the mobile device to be handed over from the current cell to the best cell if the current cell is determined not to be the best cell and / or cause the mobile device not to be handed over from the current cell to another cell if the current cell is determined to be the best cell.

Description

[0001] DETERMINING HANDOVER BEHAVIOR BASED ON ESTIMATED SENSING

[0002] PERFORMANCE

[0003] FIELD OF THE INVENTION

[0004] The invention relates to a system for determining, from a plurality of candidate cells, a best cell for serving a mobile device, the plurality of candidate cells including a current cell serving the mobile device, to a base station for receiving a handover instruction, and to a mobile device for reporting an event to a base station currently serving the mobile device.

[0005] The invention further relates to a method of determining, from a plurality of candidate cells, a best cell for serving a mobile device, the plurality of candidate cells including a current cell serving the mobile device, to a method of receiving a handover instruction, and to a method of reporting an event to a base station currently serving a mobile device.

[0006] The invention also relates to computer program products enabling a computer system to perform such a method.

[0007] BACKGROUND OF THE INVENTION

[0008] 6G network technology is envisioned to natively facilitate both communication and sensing services under the denominator of JCAS (‘Joint Communications and Sensing’) or ISAC (‘Integrated Sensing and Communications’), incorporating solutions which enable the resource-efficient support of requirements imposed by either service type. The paper "Enabling Joint Communication and Radar Sensing in Mobile Networks — A Survey” by J. A. Zhang et al., in IEEE Communications Surveys & Tutorials, vol. 24, no. 1, pp. 306-345, First quarter 2022, provides a survey of different technologies for realizing JCAS / ISAC.

[0009] In this context, the term sensing typically refers to detection and / or tracking of a target object, which may or may not be connected (or able to connect) to the mobile network in a communications sense. Use cases include real-time object detection for autonomous driving, home intruder detection, UAV detection, UAV flight control / coordination, and real-time monitoring including high-precision localization of objects for industrial applications. A target object may have different attributes, e.g. shape, size, velocity, distance, location, orientation, type of material, color, temperature, heartbeat, pitch, yaw, and / or roll.

[0010] In sensing, a distinction is made between surveillance mode and tracking mode. In surveillance mode, the sensing objective is to detect the presence of a target object, typically including detection of one or more of the aforementioned object’s attributes, e.g. its location. In tracking mode, the sensing objective is to follow the trajectory of a sensed target object, typically requiring the estimation of the object’s speed, changes therein and its direction of movement.

[0011] Base stations (abbreviated as BS) and / or regular mobile devices, i.e. UEs (User Equipment), may be used as JCAS nodes, for example. For instance, a base station may communicate with regular mobile devices, while being meanwhile used to sense / detect one or more objects. In sensing, at least one JCAS node emits a radio signal, which may be impacted by one or more objects in the neighborhood. The signals may be received by at least one JCAS node. If so, the received signals reflect an impact of the one or more objects on the transmitted wireless communication signals being impacted by the one or more objects and can be processed to detect the attributes of the objects, e.g. the above-mentioned attributes.

[0012] JCAS / ISAC may entail straightforward sharing of e.g. antenna, spectrum and time resources in an ‘orthogonal’ sense, i.e. using such resources exclusively for one service type or the other. Alternatively, a given signal may be utilized to support services of both types concurrently, e.g. when the reflections of a communication signal are also utilized for the purpose of sensing the e.g. presence or movement of an object. In this latter scenario, each mobile device connects to the cell that is expected to provide the best communication performance (i.e. mobile device and cell pairing). Sensing may then be realized with the existing mobile device and cell pairings. However, these pairings may make it more difficult to achieve the desired sensing performance since the latter is not taken into account in the device-cell pairing decision. Note that in general, a UE can be paired (associated) with multiple cells concurrently.

[0013] SUMMARY OF THE INVENTION

[0014] It is a first objective of the invention to provide a system which makes it possible to achieve a better tradeoff between communication performance and sensing performance when communication signals are used for the purpose of sensing.

[0015] It is a second objective of the invention to provide a method which makes it possible to achieve a better tradeoff between communication performance and sensing performance when communication signals are used for the purpose of sensing. In a first aspect of the invention, a system for determining, from a plurality of candidate cells, a best cell for serving a mobile device, the plurality of candidate cells including a current cell serving the mobile device, includes at least one processor configured to collect measurements on the plurality of candidate cells, estimate a communication performance for each of the plurality of candidate cells based on the measurements, estimate a sensing performance for each of the plurality of candidate cells, identify, from the plurality of candidate cells, the best cell for serving the mobile device based on the communication performances estimated for the plurality of candidate cells and the sensing performances estimated for the plurality of candidate cells, and cause the mobile device to be handed over from the current cell to the best cell if the current cell is determined not to be the best cell and / or cause the mobile device not to be handed over from the current cell to another cell if the current cell is determined to be the best cell. Said measurements may include received signal strength indicators and / or cell loads, for example.

[0016] Compared to traditional inter-cell handovers of communication tasks, the aforementioned system may effectuate a ‘JCAS-proactive handover’ or a ‘JCAS-prevented handover’ in enhanced support of sensing services. By enhancing traditional inter-cell handovers of communication tasks with a ‘JCAS-proactive handover’ and a ‘JCAS-prevented handover’, communication signals may be re-used for sensing purposes with a better tradeoff between communication performance and sensing performance. The system may be used to achieve an improved sensing performance at no or a bearable sacrifice in communication performance. Based on operator policy, the performance or efficiency of the communication link may be sacrificed to a certain degree if that enhances the sensing performance.

[0017] The traditional handover of communication tasks, e.g. that of 4G / 5G networks, does not consider the performances of the sensing tasks. The usefulness of a transmission associated with a given communication task to aid in a sensing task depends on e.g. the directivity of this transmission, which is determined by the serving cell and the applied traffic beam, both traditionally optimized purely from the communication session’s perspective. Then it is a mere consequence of this communication session-oriented optimization whether the resulting traffic beam is useful for a sensing task at hand.

[0018] The ‘JCAS-proactive handover’ deliberately changes the connections between mobile devices and cells and thereby the sensing topology (the set of nodes participating in a sensing task). The ‘JCAS-prevented handover’ prevents a change in the connections between mobile devices and cells, and thereby a change in the sensing topology, that would occur in the case of a traditional handover procedure.

[0019] The above-described system makes it possible to make the selection of the serving cell, the applied traffic beam and the utilized resources not purely communication session-oriented but, more generally, JCAS-oriented. This in the sense that e.g. the serving cell and the applied traffic beam of a given communication call may be optimized such that they provide the best option in the joint light of both the communication and sensing tasks. The characteristics of the communication signal, e.g. the directionality, width and transmit power of the transmitted beam, may even be optimized from a combined communication and sensing perspective.

[0020] When estimating the communication performance, only the communication performance experienced by the mobile device in question may be estimated or also the communication performance experiences by other devices. This allows the performance impact of a potential handover on other UE sessions to be taken into account. When estimating the sensing performance, this may address one or multiple sensing tasks who may utilize (or experience interference from) the current and / or candidate new beam sent to the mobile device in question.

[0021] The at least one processor may be configured to collect the measurements on the plurality of candidate cells by collecting measurements on a plurality of candidate reference beams, each of the plurality of candidate reference beams being associated with one of the plurality of candidate cells, estimate the communication performance for each of the plurality of candidate cells by estimating a communication performance for each of the plurality of candidate reference beams based on the measurements, estimate the sensing performance for each of the plurality of candidate cells by estimating a sensing performance for each of the plurality of candidate reference beams, identify a best reference beam from the plurality of candidate reference beams based on the communication performances estimated for the plurality of candidate reference beams and the sensing performances estimated for the plurality of candidate reference beams, and identify the best cell for serving the mobile device by determining the cell associated with the best reference beam.

[0022] The plurality of candidate reference beams may consist of the strongest one or more reference beams per candidate cell, for example. The candidate reference beams may include Synchronization Signal Block beams, for example, in case of 5G. For the currently serving cell (which is among the candidate cells) communication performance may also be estimated based on actual traffic beams and / or the experienced performance rather than only on reference beams. In addition to the measurements on the candidate reference beams, the estimation of sensing performance may also use the contribution of other signals such as traffic beams.

[0023] By estimating the communication performance and sensing performance for multiple beams of a candidate cell, a better tradeoff between communication performance and sensing performance may be achieved. For example, the use of a certain traffic beam might not yield the best communication performance and might not yield the best sensing performance when these services are considered separately, but can still provide the best tradeoff between communication performance and sensing performance. Identification, by the system, of a best reference beam from the plurality of candidate reference beams is especially beneficial if the at least one processor is configured to instruct the mobile device to identify the best reference beam or to cause a cell / base station to instruct the mobile device to identify the best reference beam. If the reference beam identified as best reference beam by the system will not or might not be automatically selected when this reference beam’s cell is selected (and a traffic beam corresponding to the best reference beam is therefore not automatically assigned to the mobile device), the mobile device may be instructed to identify the best reference beam (to its base station) or a cell / base station may be caused to instruct the mobile device to identify the best reference beam (to its base station) to ensure that the best reference beam is actually selected.

[0024] The at least one processor may be configured to adjust the communication performances estimated for the plurality of candidate reference beams based on beam differences between the plurality of candidate reference beams and corresponding traffic beams, and identify the best reference beam from the plurality of candidate reference beams based on the sensing performances estimated for the plurality of candidate reference beams and the adjusted communication performances. By taking into account the beam differences between the candidate reference beams on which the measurements are obtained and traffic beams to be used for the communication task, on which no measurements are obtained, the communication performances may be estimated more accurately. For example, the extra beamforming gain of narrower traffic beams in comparison to the wider SSB (reference) beams may be taken into account in this way.

[0025] The at least one processor may be configured to collect the measurements on the plurality of candidate cells by collecting measurements on a plurality of reference beams and derive one or more recommended traffic beams based on the measurements on the reference beams, each of the plurality of recommended traffic beams being associated with one of the plurality of candidate cells, estimate the communication performance for each of the plurality of candidate cells by estimating a communication performance for each of the plurality of recommended traffic beams based on the measurements, estimate the sensing performance for each of the plurality of candidate cells by estimating a sensing performance for each of the plurality of recommended traffic beams, identify a best traffic beam from the plurality of recommended traffic beams based on the communication performances estimated for the plurality of recommended traffic beams and the sensing performances estimated for the plurality of recommended traffic beams, and identify the best cell for serving the mobile device by determining the cell associated with the best traffic beam. The reference beams may include Channel Status Information Reference Signal (CSI-RS) beams, for example, in case of 5G.

[0026] The at least one processor may be configured to determine a contribution of the use of a traffic beam to a sensing performance, the traffic beam being used by a base station in the current cell to serve the mobile device, determine whether the contribution exceeds a threshold, and upon determining that the contribution does not exceed the threshold, identify the best cell for serving the mobile device based on the communication performances and the sensing performances and cause the mobile device to be handed over from the current cell to the best cell if the current cell is determined not to be the best cell. The ‘JCAS-proactive handover’ is not performed in response to a conventional trigger, hence the term “proactive”. The contribution of the use of the traffic beam to the (overall) sensing performance (e.g. achieved by all pairs of nodes for a certain sensing task) may be estimated based on reference beam measurements, for example.

[0027] As determining the contribution of the use of an active / current traffic beam to a sensing performance may be performed relatively quickly and purely on the network side, it does not need to consume any potentially scarce transmission resources or processing / energy resources of the mobile device. As identifying the best cell does need to consume potentially scarce processing / energy resources of the mobile device and involves a measurement / reporting procedure that also requires more time and the use of transmission resources, it is beneficial to do this only upon determining that the contribution does not exceed the threshold.

[0028] The at least one processor may be configured to identify the best cell for serving the mobile device upon determining that the mobile device has reported an event which indicates that a further cell has become better than the current cell in terms of communication performance, the event being reported to a base station currently serving the mobile device, and cause the mobile device not to be handed over from the current cell to another cell if the current cell is determined to be the best cell, i.e. in terms of joint communication and sensing performance.

[0029] The ‘JCAS-prevented handover’ is for example performed in response to a conventional trigger: a reported event which indicates that a further cell has become better than the current cell in terms of communication performance. If such an event would normally trigger a handover, this handover may be prevented if the current cell is determined to be the best cell, i.e. is determined to be the cell that is estimated to provide the best combined sensing and communication performance. The plurality of candidate cells may include only the current cell and the further cell, for example. The at least one processor may be configured to cause the mobile device not to be handed over from the current cell to another cell by instructing the base station not to perform a handover in response to the event being reported to the base station. This is beneficial if it is not the base station which identifies the best cell, e.g. if the system is separate from any base station.

[0030] The at least one processor may be configured to obtain an operator policy, the operator policy specifying weights, assign the weights to the communication performances and / or to the sensing performances, and identify the best cell for serving the mobile device based on the weighted communication performances and / or the weighted sensing performances. This makes a non-trivial weighting of possibly conflicting aspects related to communication quality, sensing quality and resource efficiency possible, for example.

[0031] In a second aspect of the invention, a base station for receiving a handover instruction, the base station serving a mobile device, includes at least one processor configured to receive a handover instruction, the handover instruction identifying the mobile device, and perform a handover of the mobile device to a best cell specified in the handover instruction and / or not perform a handover of the mobile device in response to an event being reported to the base station if the handover instruction indicates that mobile device should not be handed over to another cell, the event indicating that a further cell has become better than the current cell of the mobile device in terms of communication performance.

[0032] In a third aspect of the invention, a mobile device for reporting an event to a base station currently serving the mobile device, includes at least one processor configured to report, to the base station currently serving the mobile device, an event which indicates that a further cell has become better than a current cell of the mobile device in terms of communication performance, and receive a response to the reported event from the base station, and for a predetermined amount of time, either postpone reporting any new event which indicates that the further cell has become better than the current cell of the mobile device in terms of communication performance or adjust one or more thresholds for determining whether the further cell has become better than the current cell of the mobile device in terms of communication performance.

[0033] Upon rejection of a handover request from a current serving cell A to a target cell B, the mobile device refrains from considering cell B as a handover target for the next five seconds, for example. The network may however decide that the downlink beam is only needed for another two seconds, for example, after which it will happily support the mobile device’s handover from cell A to cell B. The claimed solution enables the network to instruct the mobile device to refrain sending new handover requests for the next two seconds (possibly unless it is at the risk of losing connectivity altogether). The benefit is that the mobile device does not need to consume any energy / processing / transmission resources of measuring candidate cells and generating / submitting handover requests. Additionally, presuming that the desired target cell is unchanged, the UE may be connected to its desired target cell sooner (after two rather than five seconds) and consequently experience an improved connectivity / QoS. Note that several scenario variations exist, e.g. with respect to the default / instructed UE behavior and what may be the best candidate cell after a given time period.

[0034] In a fourth aspect of the invention, a method of determining, from a plurality of candidate cells, a best cell for serving a mobile device, the plurality of candidate cells including a current cell serving the mobile device, includes collecting measurements on the plurality of candidate cells, estimating a communication performance for each of the plurality of candidate cells based on the measurements, estimate a sensing performance for each of the plurality of candidate cells, identifying, from the plurality of candidate cells, the best cell for serving the mobile device based on the communication performances estimated for the plurality of candidate cells and the sensing performances estimated for the plurality of candidate cells, and causing the mobile device to be handed over from the current cell to the best cell if the current cell is determined not to be the best cell and / or cause the mobile device not to be handed over from the current cell to another cell if the current cell is determined to be the best cell. The method may be performed by software running on a programmable device. This software may be provided as a computer program product.

[0035] In a fifth aspect of the invention, a method of receiving a handover instruction includes receiving a handover instruction, the handover instruction identifying a mobile device, and performing a handover of the mobile device to a best cell specified in the handover instruction and / or not perform a handover of the mobile device in response to an event being reported to the base station if the handover instruction indicates that mobile device should not be handed over to another cell, the event indicating that a further cell has become better than the current cell of the mobile device. The method may be performed by software running on a programmable device. This software may be provided as a computer program product.

[0036] In a sixth aspect of the invention, a method of reporting an event to a base station currently serving a mobile device includes reporting, to the base station currently serving the mobile device, an event which indicates that a further cell has become better than a current cell of the mobile device in terms of communication performance, and receiving a response to the reported event from the base station, and for a predetermined amount of time, either postponing reporting any new event which indicates that the further cell has become better than the current cell of the mobile device in terms of communication performance or adjusting one or more thresholds for determining whether the further cell has become better than the current cell of the mobile device in terms of communication performance. The method may be performed by software running on a programmable device. This software may be provided as a computer program product.

[0037] Moreover, a computer program for carrying out the methods described herein, as well as a non-transitory computer readable storage-medium storing the computer program are provided. A computer program may, for example, be downloaded by or uploaded to an existing device or be stored upon manufacturing of these systems.

[0038] A non-transitory computer-readable storage medium stores at least a first software code portion, the first software code portion, when executed or processed by a computer, being configured to perform executable operations for determining, from a plurality of candidate cells, a best cell for serving a mobile device, the plurality of candidate cells including a current cell serving the mobile device.

[0039] The executable operations include collecting measurements on the plurality of candidate cells, estimating a communication performance for each of the plurality of candidate cells based on the measurements, estimate a sensing performance for each of the plurality of candidate cells, identifying, from the plurality of candidate cells, the best cell for serving the mobile device based on the communication performances estimated for the plurality of candidate cells and the sensing performances estimated for the plurality of candidate cells, and causing the mobile device to be handed over from the current cell to the best cell if the current cell is determined not to be the best cell and / or cause the mobile device not to be handed over from the current cell to another cell if the current cell is determined to be the best cell.

[0040] A non-transitory computer-readable storage medium stores at least a second software code portion, the second software code portion, when executed or processed by a computer, being configured to perform executable operations for receiving a handover instruction.

[0041] The executable operations include receiving a handover instruction, the handover instruction identifying a mobile device, and performing a handover of the mobile device to a best cell specified in the handover instruction and / or not perform a handover of the mobile device in response to an event being reported to the base station if the handover instruction indicates that mobile device should not be handed over to another cell, the event indicating that a further cell has become better than the current cell of the mobile device.

[0042] A non-transitory computer-readable storage medium stores at least a third software code portion, the third software code portion, when executed or processed by a computer, being configured to perform executable operations for reporting an event to a base station currently serving a mobile device.

[0043] The executable operations include reporting, to the base station currently serving the mobile device, an event which indicates that a further cell has become better than a current cell of the mobile device in terms of communication performance, and receiving a response to the reported event from the base station, and for a predetermined amount of time, either postponing reporting any new event which indicates that the further cell has become better than the current cell of the mobile device in terms of communication performance or adjusting one or more thresholds for determining whether the further cell has become better than the current cell of the mobile device in terms of communication performance.

[0044] As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a device, a method or a computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a "circuit", "module" or "system." Functions described in this disclosure may be implemented as an algorithm executed by a processor / microprocessor of a computer. Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied, e.g., stored, thereon.

[0045] Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of a computer readable storage medium may include, but are not limited to, the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of the present invention, a computer readable storage medium may be any tangible medium that can contain, or store, a program for use by or in connection with an instruction execution system, apparatus, or device.

[0046] A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

[0047] Program code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber, cable, RF, etc., or any suitable combination of the foregoing. Computer program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java(TM), Smalltalk, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer, or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0048] Aspects of the present invention are described below with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor, in particular a microprocessor or a central processing unit (CPU), of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer, other programmable data processing apparatus, or other devices create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0049] These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function / act specified in the flowchart and / or block diagram block or blocks.

[0050] The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0051] The flowchart and block diagrams in the figures illustrate the architecture, functionality, and operation of possible implementations of devices, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s).

[0052] It should also be noted that, in some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and / or flowchart illustrations, and combinations of blocks in the block diagrams and / or flowchart illustrations, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

[0053] BRIEF DESCRIPTION OF THE DRAWINGS

[0054] These and other aspects of the invention are apparent from and will be further elucidated, by way of example, with reference to the drawings, in which:

[0055] Fig. 1 is a flow chart of a first embodiment of the method of determining a best cell;

[0056] Fig. 2 is a flow chart of a second embodiment of the method of determining a best cell;

[0057] Fig. 3 is a flow chart of a third embodiment of the method of determining a best cell;

[0058] Fig. 4 illustrates the methods of Figs. 2 and 3;

[0059] Fig. 5 is a flow chart of a fourth embodiment of the method of determining a best cell;

[0060] Fig. 6 illustrates the method of Fig. 5; Fig. 7 is a flow chart of a fifth embodiment of the method of determining a best cell and of an embodiment of the method of receiving a handover instruction;

[0061] Fig. 8 is a flow chart of a sixth embodiment of the method of determining a best cell;

[0062] Fig. 9 is a flow chart of a seventh embodiment of the method of determining a best cell;

[0063] Fig. 10 is a block diagram of an embodiment of the system; and

[0064] Fig. 11 is a block diagram of an exemplary data processing system for performing the method of the invention.

[0065] Corresponding elements in the drawings are denoted by the same reference numeral.

[0066] DETAILED DESCRIPTION OF THE DRAWINGS

[0067] In a JCAS scenario, deployed cellular base stations, present UEs, possible further nodes and (radio / processing) resources can be utilized to handle both communication and sensing tasks. In the simplest scenario, distinct sets of nodes and resources would be involved in handling distinct tasks, e.g. a given communication task would be handled by a connection between base station BSA and UEA using time-frequency resources TFA, while e.g. a given sensing task would be carried out by transmitting base stations BSB.C, ...,F, receiving base stations BSG.H, ...,L and receiving UEs UEB.C, ...,H, using time-frequency resources TFB .

[0068] However, in a more complex and potentially more efficient scenario, a given node and / or resource may be shared by one or more communication and sensing tasks, e.g. in a scenario where the transmissions generated by B SA on time-frequency resource TFA to serve a given communication call towards UEA, are also used, potentially along with other (either communication or dedicated sensing) signals, to conduct a sensing task, utilizing received reflections of said transmissions.

[0069] In such a scenario, the usefulness of a transmission associated with a given communication task to aid in a sensing task, depends on e.g. the directivity of said transmission, which is determined by the serving cell and the applied transmission beam, both traditionally optimized purely from the communication call’s perspective. Then it is a mere consequence of this communication session-oriented optimization whether the resulting transmission beam is useful for a sensing task at hand.

[0070] It is considered an opportunity to make the selection of the serving cell, the applied transmission beam and the utilized resources not purely communication session- oriented but, more generally, JCAS-oriented. A first embodiment of the method of determining, from a plurality of candidate cells, a best cell for serving a mobile device is shown in Fig. 1. The plurality of candidate cells includes a current cell serving the mobile device. A step 101 comprises collecting measurements on the plurality of candidate cells. The measurements may include received signal strength indicators and / or cell loads, for example. An optional step 102 comprises obtaining communication requirements.

[0071] A step 103 comprises estimating a communication performance for each of the plurality of candidate cells based on the measurements collected in step 101 and optionally based on communication requirements obtained in step 102. When estimating the communication performance, only the communication performance experienced by the mobile device in question may be estimated or also the communication performance experiences by other devices. This allows the performance impact of a potential handover on other UE sessions to be taken into account.

[0072] An optional step 105 comprises obtaining sensing requirements. The sensing requirements may, for example, specify one or more of: one or more targeted areas, one or more targeted directions, one or more targeted object types, one or more targeted objects (e.g. one or more object identifiers), targeted object velocities, targeted object sizes, and sensing performance requirements. The sensing performance requirements may specify requirements on sensing accuracy, sensing urgency, and / or sensing reliability, for example. The sensing accuracy requirement may comprise a targeted range resolution, for example. The sensing reliability requirement may comprise a minimum likelihood of detection and a limit on the false alarm rate, for example.

[0073] The sensing requirements may, for example, relate to surveillance mode or a tracking mode:

[0074] • In surveillance mode, the sensing objective is to detect the presence of a target object, typically including one or more of the aforementioned object’s attributes, e.g. its location. Possible sensing requirements include the detection range, detection accuracy and detection speed (time needed), with individual such requirements potentially imposed for any targeted attribute of the object.

[0075] • In tracking mode, the sensing objective is to follow the trajectile of a sensed target object, typically requiring the estimation of the object’s speed, changes therein and its direction of movement. Possible sensing requirements include the maximum detectable speed, granularity of speed detection and movement direction, with individual such requirements potentially imposed for any targeted attribute of the object or the object’s trajectory. Both the surveillance mode and the tracking mode may be enhanced by further determining the e.g. shape and orientation of the detected / tracked target object. Possible sensing requirements here are the orientation accuracy and shape accuracy.

[0076] A step 107 comprises estimating a sensing performance for each of the plurality of candidate cells, e.g. based on the sensing requirements obtained in step 105. When estimating the sensing performance, this may address one or multiple sensing tasks who may utilize (or experience interference from) the current and / or candidate new beam sent to the mobile device in question. The sensing performance may be estimated for a certain candidate cell, for example, by estimating the total sensing performance for the one or more sensing tasks assuming that the mobile device is served by this certain candidate cell. Optionally, the sensing performances may be estimated based on the measurements collected in step 101.

[0077] Steps 101 and 103 and step 107 may be performed (fully or partly) in parallel or in sequence (e.g. the sequence 101,103,107 or the sequence 107,101,103).

[0078] A step 109 comprises identifying, from the plurality of candidate cells, the best cell for serving the mobile device based on the communication performances estimated for the plurality of candidate cells in step 103 and the sensing performances estimated for the plurality of candidate cells in step 107. In step 109, all involved advantages and disadvantages related to the QoS (Quality of Service) of both the communication and the sensing tasks, the control signaling overhead and / or the efficiency of resource use may be taken into account.

[0079] A step 111 comprises causing the mobile device to be handed over from the current cell to the best cell if the current cell is determined in step 109 not to be the best cell and / or causing the mobile device not to be handed over from the current cell to another cell if the current cell is determined to be the best cell in step 109. Additionally, one or more steps of one or more of the embodiments of Figs. 2-3, 5, and 7-9 may be added to the embodiment of Fig. 1.

[0080] In addition to the method of Fig, 1, another method may be performed in parallel which continuously or periodically checks whether the performance requirements of communication and sensing tasks are satisfied, triggering actions when this is not the case. Such actions may e.g. include a renewed selection of what nodes (BSs, UEs) should be involved in carrying out a given sensing task and which payload or dedicated sensing signals are utilized.

[0081] A second embodiment of the method of determining, from a plurality of candidate cells, a best cell for serving a mobile device is shown in Fig. 2. The plurality of candidate cells includes a current cell serving the mobile device. The method of Fig. 2 may be performed for each of a plurality of mobile devices.

[0082] A step 121 comprises determining whether the traffic beam that is used by a base station to serve the mobile device has been adapted at a certain time instance. This beam adaptation may be based on e.g. CSI (Channel State Information) feedback periodically provided by the mobile device or on base station measurements of an SRS (Sounding Reference Signal) periodically transmitted by the mobile device. The beam adaptation may be conducted in a classical, purely communications task-oriented fashion, e.g. when the mobile device moves, but may also be conducted in ‘JCAS fashion’, in which case the beam adaptation (directionality, beamwidth, transmit power) may be done with the performance requirements of both the communication and sensing tasks in mind. The step in which the traffic beam is adapted is not shown in Fig. 2.

[0083] Step 107 is performed if it is determined in step 121 that the traffic beam that is used by a base station to serve the mobile device has been adapted. Step 107 comprises estimating a sensing performance for each of the plurality of candidate cells, e.g. based on obtained sensing requirements.

[0084] Next, step 101 comprises collecting measurements on the plurality of candidate cells. The measurements may include received signal strength indicators and / or cell loads. Step 103 comprises estimating a communication performance for each of the plurality of candidate cells based on the measurements collected in step 101.

[0085] Step 109 comprises identifying, from the plurality of candidate cells, the best cell for serving the mobile device based on the communication performances estimated for the plurality of candidate cells in step 103 and the sensing performances estimated for the plurality of candidate cells in step 107.

[0086] Optionally, step 109 comprises two sub steps a and b. In sub step a, the preliminary best cell for serving the mobile device is identified from all the candidate cells except the current cell based on the combined communication and sensing performances estimated for these cells. Sub step b comprises determining whether the combined communication and sensing performance estimated for the preliminary best cell identified in step a exceeds the combined communication and sensing performance estimated for the current cell, thereby identifying the best cell from all of the candidate cells.

[0087] A step 127 comprises determining whether the best cell identified in step 109 is the current cell. If so, then step 121 is repeated, and the method proceeds as shown in Fig. 2. If it is determined in step 127 that the current cell is not the best cell, then step 111 is performed. If step 109 comprises the above-described sub steps a and b, step 127 may comprise determining that the best cell is the current cell if it is determined in step b that the combined communication and sensing performance estimated for the preliminary best cell identified in step a does not exceed the combined communication and sensing performance estimated for the current cell. In an alternative embodiment, steps 109 and 127 are combined in one step.

[0088] In the embodiment of Fig. 2, step 111 is implemented by a step 129. Step 129 comprises causing the mobile device to be handed over from the current cell to the best cell. This is also referred to in this specification as a ‘JCAS-proactive handover’. The ‘JCAS- proactive handover’ deliberately changes the connections between mobile devices and cells and thereby the sensing topology (the set of nodes participating in a sensing task). Step 121 is repeated after step 129, and the method then proceeds as shown in Fig. 2. Additionally, one or more steps of one or more of the embodiments of Figs. 3 and 7-9 may be added to the embodiment of Fig. 2.

[0089] A third embodiment of the method of determining, from a plurality of candidate cells, a best cell for serving a mobile device is shown in Fig. 3. The embodiment of Fig. 3 is an extension of the embodiment of Fig. 2. In the embodiment of Fig. 3, steps 123 and 125 are performed between steps 107 and 101 of Fig. 2.

[0090] Step 123 comprises determining a contribution C of the use of the adapted traffic beam to an (overall) sensing performance (e.g. achieved by all pairs of nodes for a certain sensing task). Contribution C may be determined based on obtained sensing requirements, e.g. with respect to the sensing task. Step 125 comprises determining whether the contribution C determined in step 123 exceeds a threshold T. The contribution may be a percentage, for example. Optionally, sensing performance requirements are taken into account in step 123 and / or step 125. Step 101 is performed if it is determined in step 125 that the contribution C does not exceed the threshold T, and the method then proceeds as shown in Fig. 3 and described in relation to Fig. 2. It may for example be that the mobile device has moved in a direction requiring a beam that is no longer directed towards the target sensing area.

[0091] Step 121 is repeated if it is determined in step 125 that the contribution C exceeds the threshold T, and the method then proceeds as shown in Fig. 3. Additionally, one or more steps of one or more of the embodiments of Figs. 7-9 may be added to the embodiment of Fig. 3.

[0092] The benefit of additional steps 123 and 125 is that steps 101, 103, and 109 are not performed if not needed. Steps 123 and 125 may be performed relatively quickly and purely on the network side and do not need to consume any potentially scarce transmission resources or processing / energy resources of the mobile device. As identifying the best cell does need to consume potentially scarce processing / energy resources of the mobile device and involves a measurement / reporting procedure that also requires more time and the use of transmission resources, it is beneficial to do this only upon determining that the contribution does not exceed the threshold.

[0093] The ‘JCAS-proactive handover’ of Figs. 2 and 3 is explained with the help of Fig. 4. In the example of Fig. 4, a UE 31 is served by base station 11 with a traffic beam 51 at a first moment. This traffic beam 51 can also be used to sense one or more objects in the target sensing area 9. The sensing range of traffic beam 51 is indicated with a dotted ellipse. As an addition or alternative to using traffic beams, one or more of the supporting CSI-RS control beams may be used to aid in the sensing task. The UE 31 moves in the direction of the arrow and stays within cell 41, i.e. UE 31 has not yet entered the best service area of the base station 12 to the degree indicated by the handover hysteresis and / or the time to trigger parameter, so UE 31 would traditionally not (yet) be handed over to the base station 12. As UE 31 moves in the indicated direction, its traffic beam follows this movement and becomes ever less beneficial to be used for the sensing task, as its transmission direction less and less matches the location of the target sensing area 9, causing an ever weaker signal reflection from a possible object in the target sensing area 9.

[0094] In a traditional scenario, UE 31 would continue to be served by base station 11 until it would cross the boundary of cell 41 and then be handed over for service to base station 12. However, with the method of Fig. 2 or 3, the ‘JCAS-proactive handover’ is already performed when the UE 31 reaches the indicated new position in the cell 41 at a second moment. When the adapted traffic beam 52 is used, generated by the original serving base station 11, cell 42 served by base station 12 is identified in step 109 as the best cell for serving the UE 31 from a joint communication and sensing perspective. The sensing range of adapted traffic beam 52 is indicated with a dotted ellipse. The system 1 determines that it is best to proactively / prematurely hand over UE 31 to base station 12, considering that this causes a traffic beam 53 to be established to serve the UE which is nicely directed towards the target sensing area 9. The sensing range of traffic beam 53 is indicated with a dotted ellipse.

[0095] A fourth embodiment of the method of determining, from a plurality of candidate cells, a best cell for serving a mobile device is shown in Fig. 5. The plurality of candidate cells include a current cell serving the mobile device. The plurality of candidate cells might include only the current cell and the further cell. The method of Fig. 5 may be performed for each of a plurality of mobile devices.

[0096] A step 141 comprises determining whether the mobile device has reported an event (to a base station currently serving the mobile device) which indicates that a further cell has become better than the current cell in terms of communication performance. For example, the mobile device may report that its measurements indicate that an SSB RSRP in a neighbor cell (sufficiently) exceeds the RSRP of the strongest SSB in the mobile device’s currently serving cell.

[0097] If the method of Fig. 5 is not performed by the base station that receives the event report, this base station may report receipt of the event to the system that performs the method of Fig. 5. It may depend on technology and operator-configured handover parameters which information mobile devices report at which moment and / or how a base station determines whether to convey a handover request to another base station.

[0098] Step 107 is performed if it is determined in step 141 that the mobile device has reported an event which indicates that a further cell has become better than the current cell in terms of communication performance. Step 107 comprises estimating a sensing performance for each of the plurality of candidate cells, e.g. based on obtained sensing requirements.

[0099] Next, step 101 comprises collecting measurements on the plurality of candidate cells. Step 103 comprises estimating a communication performance for each of the plurality of candidate cells based on the measurements collected in step 101.

[0100] Step 109 comprises identifying, from the plurality of candidate cells, the best cell for serving the mobile device based on the communication performances estimated for the plurality of candidate cells in step 103 and the sensing performances estimated for the plurality of candidate cells in step 107. If the plurality of candidate cells includes only the current cell and the further cell, step 109 may simply comprise comparing the combined communication and sensing performances of the two cells.

[0101] A step 143 comprises determining whether the best cell identified in step 109 is the current cell. If not, then step 141 is repeated, and the method proceeds as shown in Fig. 5. Repeating step 141 will allow (i.e. not prevent) the mobile device to be handed over to another cell. If it is determined in step 143 that the current cell is the best cell, then step 111 is performed. In an alternative embodiment, steps 109 and 143 are combined in one step.

[0102] In the embodiment of Fig. 5, step 111 is implemented by a step 145. Step 145 comprises causing the mobile device not to be handed over from the current cell to another cell. This is also referred to in this specification as a ‘JCAS-prevented handover’. The ‘JCAS-prevented handover’ prevents a change in the connections between mobile devices and cells, and thereby a potential change in the sensing topology, that would occur in the case of a traditional handover procedure.

[0103] Step 145 may comprise instructing the base station not to perform a handover in response to the event being reported to the base station, e.g. if the method of Fig. 5 is not performed by this base station. Additionally, one or more steps of one or more of the embodiments of Figs. 7-9 may be added to the embodiment of Fig. 5.

[0104] In the embodiment of Fig. 5, the ‘JCAS-prevented handover’ is performed in response to a conventional trigger, i.e. a reported event which indicates that a further cell has become better than the current cell in terms of communication performance. If such an event would normally trigger a handover, this handover may be prevented if the current cell is determined to be the best cell, i.e. is determined to be the cell that is estimated to provide the best combined sensing and communication performance.

[0105] The ‘JCAS-prevented handover’ of Fig. 5 is explained with the help of Fig. 6. In the example of Fig. 6, like in the example of Fig. 4, a UE 31 is served by base station 11 with a traffic beam 51 at a first moment and this traffic beam 51 can also be used to sense one or more objects in the target sensing area 9. The UE 31 moves in the direction of the arrow. As UE 31 moves away from its serving base station, i.e. base station 11, the strength of its connection becomes weaker and at some point UE 31 starts scanning for candidate surrounding cells to handover to.

[0106] In a traditional scenario, UE 31 would continue to be served by base station 11 until it would cross the boundary of cell 41 (reflecting where e.g. the measured SSB RSRP falls below some threshold) and then be handed over for service to base station 12. However, with the method of Fig. 5, the traditionally natural handover is prevented in step 145 and is therefore a ‘JCAS-prevented handover’. In step 109 of Fig. 5, cell 41 is identified as best cell at the new position of UE 31, because despite its weakening link, base station 11 continues to serve the UE with a traffic beam 52 which is nicely directed towards the target sensing area 9, and is hence more beneficially used for the sensing task at hand than the traffic beam 53, alternatively provided by base station 12 / cell 42, would.

[0107] Therefore, the system 1 causes the mobile device not to be handed over from cell 41 to cell 42. In the example of Fig. 6, some level of quality of the communication task is likely sacrificed in favor of the achieved quality (e.g. accuracy, reliability, latency) of the sensing task. The sensing range of traffic beams 51-53 is indicated with dotted ellipses.

[0108] A fifth embodiment of the method of determining, from a plurality of candidate cells, a best cell for serving a mobile device is shown in Fig. 7. The fifth embodiment of Fig. 7 is an extension of the first embodiment of Fig. 1. Fig. 7 also shows an embodiment of the method of receiving a handover instruction.

[0109] In the embodiment of Fig. 7, step 111 of Fig. 1 has been implemented by a step 161. Step 111 comprises causing the mobile device to be handed over from the current cell to the best cell if the current cell is determined in step 109 not to be the best cell and / or cause the mobile device not to be handed over from the current cell to another cell if the current cell is determined to be the best cell in step 109.

[0110] Step 161 comprises transmitting a handover instruction to a base station. The handover instruction identifies the mobile device. The handover instruction may request the base station to handover the mobile device to the cell specified in the handover instruction, i.e. the best cell identified in step 109, or may simply identify the best cell. Alternatively, the handover instruction may indicate that the mobile device should not be handed over to another cell. A step 163 comprises the base station receiving the handover instruction.

[0111] A step 165 comprises performing a handover of the mobile device to a best cell specified in the handover instruction and / or not perform a handover of the mobile device in response to an event being reported to the base station if the handover instruction indicates that mobile device should not be handed over to another cell. The event indicates that a further cell has become better than the current cell of the mobile device in terms of communication performance. The mobile device reporting this event to the base station currently serving the mobile device may receive a response to the reported event from the base station and for a predetermined amount of time, either postpone reporting any new event which indicates that the further cell has become better than the current cell of the mobile device in terms of communication performance or adjust one or more thresholds for determining whether the further cell has become better than the current cell of the mobile device in terms of communication performance. Receipt of this event is not shown in Fig. 7. Additionally, one or more steps of one or more of the embodiments of Figs. 2-3, 5, and 8-9 may be added to the embodiment of Fig. 7.

[0112] A sixth embodiment of the method of determining, from a plurality of candidate cells, a best cell for serving a mobile device is shown in Fig. 8. The embodiment of Fig. 8 is an extension of the embodiment of Fig. 1. In the embodiment of Fig. 8, step 109 is implemented by a step 175 and steps 171 and 173 are performed before step 175.

[0113] Step 171 comprises obtaining an operator policy which specifies weights. Steps 101 and 103, step 107, and step 171 may be performed (fully or partly) in parallel or in sequence (e.g. the sequence 171,101,103,107 or the sequence 107,101,103,171). Step 173 comprises assigning the weights obtained in step 171 to the communication performances estimated in step 103 and / or to the sensing performances estimated in step 105.

[0114] Step 175 comprises identifying, from the plurality of candidate cells, the best cell for serving the mobile device based on the communication performances estimated for the plurality of candidate cells in step 103, weighted with weights assigned in step 173 if applicable, and the sensing performances estimated for the plurality of candidate cells in step 107, weighted with weights assigned in step 173 if applicable. Additionally, one or more steps of one or more of the embodiments of Figs. 2-3, 5, 7, and 9 may be added to the embodiment of Fig. 8.

[0115] A seventh embodiment of the method of determining, from a plurality of candidate cells, a best cell for serving a mobile device is shown in Fig. 9. A step 181 comprises collecting measurements on a plurality of candidate reference beams. Each of the plurality of candidate reference beams is associated with one of the plurality of candidate cells.

[0116] The candidate reference beams may include Synchronization Signal Block beams, for example, in case of 5G. The measurements collected in step 181 may be SSB RSRP measurements which are collected, for example, (a) by asking the mobile device to conduct a regular scan of (cell, SSB) pairs in surrounding cells and reporting on those whose RSRPs exceed a given threshold; or (b) by instructing the mobile device to measure a specific set of (cell, SSB) pairs which have been pre-selected as potentially useful from both a communications and sensing perspective using e.g. a radio network planning tool and an estimation of the mobile device location.

[0117] A step 183 comprises estimating a communication performance for each of the plurality of candidate reference beams based on the measurements collected in step 181. For the currently serving cell (which is among the candidate cells) communication performance may also be estimated based on actual traffic beams, e.g. the experienced performance with the actual traffic beams, rather than only on reference beams.

[0118] Optionally, step 183 may comprise adjusting the estimated communication performances based on beam differences between the plurality of candidate reference beams and corresponding traffic beams. Since reporting on non-serving cells will typically be done based on SSB measurements, while actual payload transmissions typically use narrower traffic beams, the extra beamforming gain of the narrower traffic beams in comparison to the wider SSB (reference) beams may be taken into account in this way. Moreover, the estimation may take into account beam adjustments relative to the reported SSB beam in line with beam adaptation done in ‘JCAS fashion’.

[0119] Step 185 comprises estimating a sensing performance for each of the plurality of candidate reference beams, e.g. based on obtained sensing requirements. The sensing performance may be determined for a certain candidate reference beam, for example, by determining the total sensing performance for the one or more sensing tasks assuming that the mobile device is served by this certain candidate reference beam, preferably with a suitably adjusted radiation pattern and a higher main lobe gain because a traffic beam is generally narrower and has a higher beamforming gain than a reference beam. The sensing performances may be determined in step 185 by determining a value that represents an estimate of the sensing performance per sensing task and in the case of multiple sensing tasks, determining a further value that represents an estimate of the sensing performance of all sensing tasks based on the multiple values. The values may be SNR values, probability of detection values (e.g. converted from SNR values), or values of a metric integrating the probability of detection under some conditions related to false alarm rate, sensing accuracy and / or sensing time, for example.

[0120] Each sensing task involves one or more pairs of nodes. If a single transmitter transmits to multiple receivers, then the sensing task may comprise a pair of nodes per respective receiver of the multiple receivers, each pair comprise the transmitter and the respective receiver. If multiple transmitters transmits to multiple receivers, then the sensing task may comprise a pair of nodes for each combination of a single transmitter of the multiple transmitters and a single receiver of the multiple receivers.

[0121] In the embodiment of Fig. 9, at least one of these pairs of nodes is the pair of nodes which comprises the mobile device as receiver. This pair of nodes comprises the base station which provides coverage to the candidate reference cell as transmitter. If there are two candidate cells (e.g. BSA and BSB) and five candidate reference beams (e.g. BSA- SSBI,BSA-SSB2,BSA-SSB3,BSB-SSBI,BSB-SSB2), then five values (if there is one sensing task) or five further values (if there are multiple sensing tasks) are determined and the references beam with the best (further) value is selected.

[0122] To determine a probability of detection, the BS / cell and UE locations may be taken into account, as the BS / cell and UE locations relative to a potential location of the sensing object will affect the propagation loss, the SNR estimate and consequently the probability of detection. To determine the probability of detection, the cell-specific azimuth / tilt / antenna aspects / maximum transmit power and the carrier frequencies assigned to a cell may be taken into account, as these parameters affect the propagation loss, the SNR estimate and consequently the probability of detection. To determine the probability of detection, the sensitivity / noise figure / other characteristics of cell / UE receivers may be taken into account, as these parameters affect the SNR estimate and consequently the probability of detection.

[0123] The probability of detection may be calculated by applying radar equations first at pixel (part of the target sensing area) level and then integrating these over the target sensing area. An example of how the probability of detection may be calculated is given below. To estimate the probability of detection, the target sensing area is divided into a set of non-overlapping pixels, either in the two- or three-dimensional space, depending on the dimensionality of the target sensing area. The probability of detection for each node combination may first be estimated for each pixel of the target sensing area as follows: i. Calculate / estimate the distances between all the receivers from Nsand the target 3D-pixel (RR ) ii. Calculate / estimate the distances between all the transmitters from Msand the 3D-pixel (Rr,i), iii. Calculate / estimate the received signal power for all the pairs: where, i G {1, ca rd (s)} and j G {1, card(lVs)} and iv. The combined SNR for considering the total number of receivers and transmitters in a given set further depends on whether the signals are combined (a) coherently or (b) incoherently.

[0124] ■ Assuming in a fully synchronized system operating in a coherent way, the combined SNR (for a particular pixel and a given set of transmitters and receivers) is given by

[0125] ■ Alternatively, combining the signals in an incoherent way would yield a somewhat lower total SNR (for a particular pixel and a given set of transmitters and receivers), which is given by where, v. Convert the total SNR into probability of detection (using a probability -of- detection vs SNR chart)

[0126] In the calculation (of the probability of detection) above, it was assumed that signals (e.g. IQ-samples, plot-level information) from all receivers are available at the system. There are different ways to calculate the probability of detection which might be appropriate in some scenarios such as the absence of signals (IQ-samples) from all receivers at the system. For instance, by assuming the receivers independently determine the receiverspecific probability of detection, could be calculated using the above mentioned steps. However, in this case, the proper adjustments in the equations in step (iii) and (iv-a) needs to be made, i.e. 2; ,Ej 1 could be calculated for example. This strategy assumes that one detection is enough. Other strategies are also possible.

[0127] Information indicating the central wavelength, the transmission power of the i-th transmitter, the antenna gains, the form factors, the losses, the distances, the equivalent system temperature, and the (noise) bandwidth at the j -th receiver that are used in the calculation above may be obtained from the nodes. Normally, the manufacturer of the receiver specifies the system noise temperature (or the equivalent noise figure / factor, which could be converted to the noise temperature as Fs = 1+ Ts / 290).

[0128] The (bistatic) RCS of a given pair (i, j) may be determined from the sensing requirements. For example, the sensing requirements may indicate an average / a minimum / a range of value(s) of the RCS for a given sensing task. Tables exist in the literature with average RCS values of certain objects, e.g. humans and airplanes.

[0129] The received signal power is calculated / estimated in step iii) per transmitter and receiver pair under the assumption that at least a certain reference beam is used. The received signal power may further based calculated / estimated in step iii) per transmitter and receiver pair under the assumption that one or more other beams can also be used, e.g. traffic beams. The antenna gains and / or losses may be determined based on the beam characteristics of this beam / these beams. Even if a transmitter transmits a dedicated sensing signal, antenna gains and losses will normally vary between pixels of the target sensing area.

[0130] Once the pixel-specific probabilities of detection have been estimated, the overall probability detection for the entire target sensing area may be determined by e.g. straightforward averaging of the pixel-specific probabilities of detection, for equally likely occupancy of pixels. Alternatively, weighted averaging may be used in case e.g. the targeted object is more likely present near the center of the target sensing area and it is therefore more important for the probability of detection in the more centrally located pixels to be high.

[0131] The overall probability of detection for the entire target sensing area is preferably estimated for a window of observation in which detection of the object(s) may be attempted multiple times. The probability of detection then increases with the number of attempts, as every additional attempt gives an additional opportunity for successful sensing. With pnthe estimated probability at attempt n, 1 - ( 1 -pi) * (1- P2) * ... * (1-PN) may be used as estimated probability after N attempts. If a receiver receives a first beam with first beam characteristics from a transmitter at a first moment and a second beam with second beam characteristics from this transmitter at a second moment, the probability of detection will likely be different.

[0132] Instead of determining the overall probability detection for the entire target sensing area, an overall SNR for the entire target sensing area may be determined by e.g. straightforward averaging of the pixel-specific SNR values. This overall SNR value may be used as an estimate of the sensing performance instead of the overall probability of detection.

[0133] In the above description of the calculations, it was assumed that sensing was performed in surveillance mode. When sensing is performed in tracking mode, additional data is available and may be used. For example, instead of estimating the RCS from the sensing requirements, the RCS may be estimated based on sensing data. It may also be possible to determinate location estimates and / or SNR estimates from the sensing data and the target sensing area may be estimated based on the location estimates determined earlier and the confidence interval around those. So if detection has happened and tracking mode is active, then sensing information such as location estimates, estimates of SNR, and estimates of RCS may be used. If surveillance mode is active, the calculations typically rely on specification and tables.

[0134] When the contribution C of the use of the adapted traffic beam to an (overall) sensing performance (e.g. achieved by all pairs of nodes for a certain sensing task) is determined in step 123 of Fig. 3, the above calculations may be used to determine this contribution. For example, for a certain sensing task (e.g., surveillance), the contribution of this pair of nodes to the overall performance metric (e.g., probability of detection when in the surveillance mode; accuracy of the velocity of the target in tracking mode) is determined in step 123. Because the relation between SNR and, for example, the probability of detection is not linear, one way to calculate the contribution is to compare the probability of detection with and without this pair. The gain in probability of detection due to this pair can then be used as its contribution. If this sensing task only involves one pair of nodes, the contribution of this pair would be 100%. The individual contributions and the overall SNR value may have been previously calculated in the manner described above when step 109 was performed and then stored. Alternatively, the contribution C may have already been calculated and stored in step 109 and may then simply be retrieved in step 123.

[0135] Optionally, step 185 may comprise adjusting the estimated sensing performances based on beam differences between the plurality of candidate reference beams and correspondingly estimated traffic beams. Moreover, the estimation may take into account beam adjustments relative to the reported SSB beam in line with beam adaptation done in ‘JCAS fashion’.

[0136] Step 187 comprises identifying a best reference beam from the plurality of candidate reference beams based on the (optionally adjusted) communication performances estimated for the plurality of candidate reference beams in step 183 and the sensing performances estimated for the plurality of candidate reference beams in step 185. For example, step 187 may comprise selecting the candidate (cell, SSB) pair with the highest combined communication and sensing performance. If the method of Fig. 9 is combined with the method of Fig. 8, the best reference beam may be identified in step 187 based on the weighted combined communication and sensing performance for each of the measured / reported (cell, SSB) pairs, with the weights or degree of prioritization prescribed by an operator policy.

[0137] A step 189 comprises identifying, from the plurality of candidate cells, the best cell for serving the mobile device by determining the cell associated with the best reference beam identified in step 187. A step 111 comprises causing the mobile device to be handed over from the current cell to the best cell if the current cell is determined in step 189 not to be the best cell and / or cause the mobile device not to be handed over from the current cell to another cell if the current cell is determined to be the best cell in step 189.

[0138] Optionally, a step 191 is performed after step 111. Step 191 comprises instructing the mobile device to identify the best reference beam or causing a base station to instruct the mobile device to identify the best reference beam. For example, a traffic beam corresponding to a selected SSB beam may be assigned to the UE by specifying only the selected SSB beam and its associated RACH resources in the RRCReconfiguration message. If a traffic beam corresponding to the reference beam identified as best reference beam will not or might not be automatically assigned to the UE when this beam’s cell is identified as best cell, this may be used to ensure that a traffic beam corresponding to the best reference beam is actually assigned to the UE. Additionally, one or more steps of one or more of the embodiments of Figs. 2-3, 5, and 7-8 may be added to the embodiment of Fig. 9.

[0139] Fig. 10 is a block diagram of an embodiment of a system for determining a best cell for serving a mobile device, system 1, and embodiments of a base station for receiving a handover instruction, base stations 11 and 12. Fig. 10 further shows a single UE 31. In this embodiment, the system 1 is separate from base stations and UEs and may be located in the radio access network, for example. The base stations 11 and 12 may comprise a plurality of distributed units that share a common centralized unit in a Centralized RAN (C-RAN) architecture, for example.

[0140] The system 1 comprises a receiver 3, a transmitter 4, a processor 5, and a memory 7. The processor 5 is configured to collect measurements on a plurality of candidate cells, estimate a communication performance for each of the plurality of candidate cells based on the measurements, and estimate a sensing performance for each of the plurality of candidate cells, e.g. for sensing a target object 9. The plurality of candidate cells includes a current cell serving the mobile device.

[0141] The processor 5 is further configured to identify, from the plurality of candidate cells, the best cell for serving the mobile device based on the communication performances estimated for the plurality of candidate cells and the sensing performances estimated for the plurality of candidate cells, and cause the mobile device to be handed over from the current cell to the best cell if the current cell is determined not to be the best cell and / or cause the mobile device not to be handed over from the current cell to another cell if the current cell is determined to be the best cell.

[0142] In the embodiment of Fig. 10, the processor 5 is further configured to transmit a handover instruction to base station 11 or 12. The handover instruction identifies the mobile device. The handover instruction may request the base station to handover the mobile device to the cell specified in the handover instruction, i.e. the best cell identified in step 109, or may simply identify the best cell. Alternatively, the handover instruction may indicate that mobile device should not be handed over to another cell.

[0143] The base stations 11 and 12 each comprise a receiver 23, a transmitter 24, a processor 25, and a memory 27. In the embodiment of Fig. 10, the processor 25 is configured to receive a handover instruction, the handover instruction identifying the mobile device, and perform a handover of the mobile device to a best cell specified in the handover instruction and / or not perform a handover of the mobile device in response to an event being reported to the base station if the handover instruction indicates that mobile device should not be handed over to another cell, the event indicating that a further cell has become better than the current cell of the mobile device in terms of communication performance.

[0144] When base station 11 serves UE 31, the system 1 transmits the handover instruction to base station 11. When base station 12 serves UE 31, the system 1 transmits the handover instruction to base station 12. In the embodiment shown in Fig. 10, the mobile device 31 comprises a receiver 43, a transmitter 44, a processor 45, and a memory 47. The processor 45 is configured to report (via the transmitter 44), to the base station currently serving the mobile device 31, an event which indicates that a further cell has become better than a current cell of the mobile device 31 in terms of communication performance, and receive (via the receiver 43) a response to the reported event from the base station, and for a predetermined amount of time, either postpone reporting any new event which indicates that the further cell has become better than the current cell of the mobile device 31 in terms of communication performance or adjust one or more thresholds for determining whether the further cell has become better than the current cell of the mobile device 31 in terms of communication performance.

[0145] When base station 11 serves UE 31, the UE 31 reports the event to base station 11. When base station 12 serves UE 31, the UE 31 reports the event to base station 12.

[0146] In the embodiment shown in Fig. 10, the system 1 comprises one processor. In an alternative embodiment, the system 1 comprises multiple processors. The processor 5 may be a general-purpose processor, e.g., an Intel or an AMD processor, or an applicationspecific processor, for example. The processor 5 may comprise multiple cores, for example. The processor 5 may run a Unix-based or Windows operating system, for example. The memory 7 may comprise solid state memory, e.g., one or more Solid State Disks (SSDs) made out of Flash memory, or one or more hard disks, for example.

[0147] The receiver 3 and the transmitter 4 may use one or more wired or wireless communication technologies to communicate with base stations 11 and 12. The receiver 3 and the transmitter 4 may use one or more communication technologies (wired or wireless) to communicate with other systems in the radio access network or in the core network, for example. The receiver 3 and the transmitter 4 may be combined in a transceiver. The system 1 may comprise other components typical for a component in a mobile communication network, e.g., a power supply.

[0148] In the embodiment shown in Fig. 10, the base stations 11 and 12 comprise one processor. In an alternative embodiment, one or more of the base stations 11 and 12 comprise multiple processors. The processor of the base stations 11 and 12 may be a general- purpose processor, e.g., an Intel or an AMD processor, or an application-specific processor, for example. The processor may comprise multiple cores, for example. The processor may run a Unix-based or Windows operating system, for example. The memory 27 may comprise solid state memory, e.g., one or more Solid State Disks (SSDs) made out of Flash memory, or one or more hard disks, for example. The receiver 23 and the transmitter 24 may use one or more wireless communication technologies such as Wi-Fi, LTE, and / or 5G New Radio to communicate with UEs, e.g. UE 31. The receiver 23 and the transmitter 24 may use one or more communication technologies (wired or wireless) to communicate with other systems in the radio access network or in the core network, for example. The receiver 23 and the transmitter 24 may be combined in a transceiver. The base stations may comprise other components typical for a component in a mobile communication network, e.g., a power supply. In the embodiment shown in Fig. 10, each of the base stations may comprise a single unit or a central unit and one or multiple distributed units, for example.

[0149] In the embodiment shown in Fig. 10, the mobile device 31 comprises one processor 45. In an alternative embodiment, the mobile device 31 comprises multiple processors. The processor 45 may be a general-purpose processor, e.g., an ARM or Qualcomm processor, or an application-specific processor. The processor 45 may run Google Android or Apple iOS as operating system, for example.

[0150] The receiver 43 and the transmitter 44 of the mobile device 31 may use one or more wireless communication technologies such as Wi-Fi, LTE, and / or 5G New Radio to communicate with base stations, for example. The receiver 43 and the transmitter 44 may be combined in a transceiver. The UE 31 may comprise other components typical for user equipment, e.g., a battery and / or a power connector.

[0151] A UE may also be referred to by those skilled in the art as a mobile station (MS), a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a wireless terminal, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal (AT), a mobile terminal, a remote terminal, a handset, a terminal, a user agent, a mobile client, a client, or some other suitable terminology.

[0152] Fig. 11 depicts a block diagram illustrating an exemplary data processing system that may perform the method as described with reference to Figs. 1-3, 5, and 7-9.

[0153] As shown in Fig. 11, the data processing system 300 may include at least one processor 302 coupled to memory elements 304 through a system bus 306. As such, the data processing system may store program code within memory elements 304. Further, the processor 302 may execute the program code accessed from the memory elements 304 via a system bus 306. In one aspect, the data processing system may be implemented as a computer that is suitable for storing and / or executing program code. It should be appreciated, however, that the data processing system 300 may be implemented in the form of any system including a processor and a memory that is capable of performing the functions described within this specification. The memory elements 304 may include one or more physical memory devices such as, for example, local memory 308 and one or more bulk storage devices 310. The local memory may refer to random access memory or other non-persistent memory device(s) generally used during actual execution of the program code. A bulk storage device may be implemented as a hard drive or other persistent data storage device. The processing system 300 may also include one or more cache memories (not shown) that provide temporary storage of at least some program code in order to reduce the number of times program code must be retrieved from the bulk storage device 310 during execution.

[0154] Input / output (I / O) devices depicted as an input device 312 and an output device 314 optionally can be coupled to the data processing system. Examples of input devices may include, but are not limited to, a keyboard, a pointing device such as a mouse, or the like. Examples of output devices may include, but are not limited to, a monitor or a display, speakers, or the like. Input and / or output devices may be coupled to the data processing system either directly or through intervening I / O controllers.

[0155] In an embodiment, the input and the output devices may be implemented as a combined input / output device (illustrated in Fig. 11 with a dashed line surrounding the input device 312 and the output device 314). An example of such a combined device is a touch sensitive display, also sometimes referred to as a “touch screen display” or simply “touch screen”. In such an embodiment, input to the device may be provided by a movement of a physical object, such as e.g. a stylus or a finger of a user, on or near the touch screen display.

[0156] A network adapter 316 may also be coupled to the data processing system to enable it to become coupled to other systems, computer systems, remote network devices, and / or remote storage devices through intervening private or public networks. The network adapter may comprise a data receiver for receiving data that is transmitted by said systems, devices and / or networks to the data processing system 300, and a data transmitter for transmitting data from the data processing system 300 to said systems, devices and / or networks. Modems, cable modems, and Ethernet cards are examples of different types of network adapter that may be used with the data processing system 300.

[0157] As pictured in Fig. 11, the memory elements 304 may store an application 318. In various embodiments, the application 318 may be stored in the local memory 308, the one or more bulk storage devices 310, or separate from the local memory and the bulk storage devices. It should be appreciated that the data processing system 300 may further execute an operating system (not shown in Fig. 11) that can facilitate execution of the application 318. The application 318, being implemented in the form of executable program code, can be executed by the data processing system 300, e.g., by the processor 302. Responsive to executing the application, the data processing system 300 may be configured to perform one or more operations or method steps described herein.

[0158] Various embodiments of the invention may be implemented as a program product for use with a computer system, where the program(s) of the program product define functions of the embodiments (including the methods described herein). In one embodiment, the program(s) can be contained on a variety of non-transitory computer-readable storage media, where, as used herein, the expression “non-transitory computer readable storage media” comprises all computer-readable media, with the sole exception being a transitory, propagating signal. In another embodiment, the program(s) can be contained on a variety of transitory computer-readable storage media. Illustrative computer-readable storage media include, but are not limited to: (i) non-writable storage media (e.g., read-only memory devices within a computer such as CD-ROM disks readable by a CD-ROM drive, ROM chips or any type of solid-state non-volatile semiconductor memory) on which information is permanently stored; and (ii) writable storage media (e.g., flash memory, floppy disks within a diskette drive or hard-disk drive or any type of solid-state random-access semiconductor memory) on which alterable information is stored. The computer program may be run on the processor 302 described herein.

[0159] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0160] The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of embodiments of the present invention has been presented for purposes of illustration, but is not intended to be exhaustive or limited to the implementations in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope of the present invention. The embodiments were chosen and described in order to best explain the principles and some practical applications of the present invention, and to enable others of ordinary skill in the art to understand the present invention for various embodiments with various modifications as are suited to the particular use contemplated.

Claims

CLAIMS:

1. A system (1) for determining, from a plurality of candidate cells (41,42), a best cell for serving a mobile device (31), the plurality of candidate cells (41,42) including a current cell (41) serving the mobile device (31), the system (1) including at least one processor (5) configured to:- collect measurements on the plurality of candidate cells (41 ,42),- estimate a communication performance for each of the plurality of candidate cells (41,42) based on the measurements,- estimate a sensing performance for each of the plurality of candidate cells(41,42),- identify, from the plurality of candidate cells (41,42), the best cell for serving the mobile device (31) based on the communication performances estimated for the plurality of candidate cells (41,42) and the sensing performances estimated for the plurality of candidate cells (41,42), and- cause the mobile device (31) to be handed over from the current cell (41) to the best cell if the current cell (41) is determined not to be the best cell and / or cause the mobile device (31) not to be handed over from the current cell (41) to another cell if the current cell (41) is determined to be the best cell.

2. A system (1) as claimed in claim 1, wherein the at least one processor (5) is configured to:- collect the measurements on the plurality of candidate cells (41,42) by collecting measurements on a plurality of candidate reference beams, each of the plurality of candidate reference beams being associated with one of the plurality of candidate cells(41.42),- estimate the communication performance for each of the plurality of candidate cells (41,42) by estimating a communication performance for each of the plurality of candidate reference beams based on the measurements,- estimate the sensing performance for each of the plurality of candidate cells(41.42) by estimating a sensing performance for each of the plurality of candidate reference beams,- identify a best reference beam from the plurality of candidate reference beams based on the communication performances estimated for the plurality of candidate reference beams and the sensing performances estimated for the plurality of candidate reference beams, and- identify the best cell for serving the mobile device (31) by determining the cell associated with the best reference beam.

3. A system (1) as claimed in claim 2, wherein the at least one processor (5) is configured to:- adjust the communication performances estimated for the plurality of candidate reference beams based on beam differences between the plurality of candidate reference beams and corresponding traffic beams, and- identify the best reference beam from the plurality of candidate reference beams based on the sensing performances estimated for the plurality of candidate reference beams and the adjusted communication performances.

4. A system (1) as claimed in claim 2 or 3, wherein the at least one processor (5) is configured to instruct the mobile device (31) to identify the best reference beam or to cause a base station (11,12) to instruct the mobile device (31) to identify the best reference beam.

5. A system (1) as claimed in claim 2, 3, or 4, wherein the candidate reference beams include Synchronization Signal Block beams.

6. A system (1) as claimed in any one of the preceding claims, wherein the at least one processor (5) is configured to:- determine a contribution of the use of a traffic beam to a sensing performance, the traffic beam being used by a base station (11,12) in the current cell (41) to serve the mobile device (31),- determine whether the contribution exceeds a threshold, and- upon determining that the contribution does not exceed the threshold, identify the best cell for serving the mobile device (31) based on the communication performances and the sensing performances and cause the mobile device (31) to be handed over from the current cell (41) to the best cell if the current cell (41) is determined not to be the best cell.

7. A system (1) as claimed in any one of the preceding claims, wherein the at least one processor (5) is configured to:- identify the best cell for serving the mobile device (31) upon determining that the mobile device (31) has reported an event which indicates that a further cell has become better than the current cell (41) in terms of communication performance, the event being reported to a base station (11,12) currently serving the mobile device (31), and- cause the mobile device (31) not to be handed over from the current cell (41) to another cell if the current cell (41) is determined to be the best cell.

8. A system (1) as claimed in claim 7, wherein the at least one processor (5) is configured to cause the mobile device (31) not to be handed over from the current cell (41) to another cell by instructing the base station (11,12) not to perform a handover in response to the event being reported to the base station (11,12).

9. A system (1) as claimed in claim 7 or 8, wherein the plurality of candidate cells (41,42) include only the current cell (41) and the further cell.

10. A system (1) as claimed in any one of the preceding claims, wherein the at least one processor (5) is configured to:- obtain an operator policy, the operator policy specifying weights,- assign the weights to the communication performances and / or to the sensing performances, and- identify the best cell for serving the mobile device (31) based on the weighted communication performances and / or the weighted sensing performances.

11. A system (1) as claimed in any one of the preceding claims, wherein the measurements include received signal strength indicators and / or cell loads.

12. A base station (11,12) for receiving a handover instruction, the base station(11,12) serving a mobile device (31), the base station (11,12) including at least one processor (25) configured to:- receive a handover instruction, the handover instruction identifying the mobile device (31), and- perform a handover of the mobile device (31) to a best cell specified in the handover instruction and / or not perform a handover of the mobile device (31) in response to an event being reported to the base station (11,12) if the handover instruction indicates thatmobile device (31) should not be handed over to another cell, the event indicating that a further cell has become better than the current cell (41) of the mobile device (31) in terms of communication performance.

13. A mobile device (31) for reporting an event to a base station (11,12) currently serving the mobile device (31), the mobile device (31) including at least one processor configured to:- report, to the base station (11,12) currently serving the mobile device (31), an event which indicates that a further cell has become better than a current cell (41) of the mobile device (31) in terms of communication performance, and- receive a response to the reported event from the base station (11,12), and- for a predetermined amount of time, either postpone reporting any new event which indicates that the further cell has become better than the current cell (41) of the mobile device (31) in terms of communication performance or adjust one or more thresholds for determining whether the further cell has become better than the current cell (41) of the mobile device (31) in terms of communication performance.

14. A method of determining, from a plurality of candidate cells, a best cell for serving a mobile device, the plurality of candidate cells including a current cell serving the mobile device, the method including:- collecting (101) measurements on the plurality of candidate cells;- estimating (103) a communication performance for each of the plurality of candidate cells based on the measurements;- estimating (107) a sensing performance for each of the plurality of candidate cells;- identifying (109), from the plurality of candidate cells, the best cell for serving the mobile device based on the communication performances estimated for the plurality of candidate cells and the sensing performances estimated for the plurality of candidate cells; and- causing (111) the mobile device to be handed over from the current cell to the best cell if the current cell is determined not to be the best cell and / or cause the mobile device not to be handed over from the current cell to another cell if the current cell is determined to be the best cell.

15. A method of receiving a handover instruction, the method including:- receiving (163) a handover instruction, the handover instruction identifying a mobile device; and- performing (165) a handover of the mobile device to a best cell specified in the handover instruction and / or not perform a handover of the mobile device in response to an event being reported to the base station if the handover instruction indicates that mobile device should not be handed over to another cell, the event indicating that a further cell has become better than the current cell of the mobile device.

16. A method of reporting an event to a base station currently serving a mobile device, the method including:- reporting, to the base station currently serving the mobile device, an event which indicates that a further cell has become better than a current cell of the mobile device in terms of communication performance, and- receiving a response to the reported event from the base station, and- for a predetermined amount of time, either postponing reporting any new event which indicates that the further cell has become better than the current cell of the mobile device in terms of communication performance or adjusting one or more thresholds for determining whether the further cell has become better than the current cell of the mobile device in terms of communication performance.

17. A computer program or suite of computer programs including at least one software code portion or a computer program product storing at least one software code portion, the software code portion, when run on a computer system, being configured for performing the method of claim 14, 15 or 16.

Images