Technique for determining paths of a wireless communication

Abstract

A technique for determining paths (302-1, 302-2) of a wireless communication between a first station (304) and a second station (306) in an environment (300) is described. As to a device aspect of the technique, the device (100) is operable to obtain (S202) one or more first paths (302-1) between the first station (304) and the second station (306), wherein each of the one or more first paths (302-1) comprises zero or more electromagnetic interactions (320-1) within the environment (300). The device (100) is further operable to determine (S206) one or more second paths (302-2) between the first station (304) and the second station (306) based on the one or more first paths (302-1) by changing the zero or more interactions (320-1) and minimizing a path length of the one or more second paths (302-2) in accordance with the zero or more changed interactions (320-2).

Description

[0001] TECHNIQUE FOR DETERMINING PATHS OF A WIRELESS COMMUNICATION

[0002] Technical Field

[0003] The present disclosure relates to the field of wireless communication. More specifically, and without being limited thereto, a device and a method are disclosed for determining paths of a wireless communication in an environment.

[0004] Background

[0005] The electromagnetic propagation of a wireless communication can be efficiently predicted by a ray approximation in certain environments. This approximation relies on the assumption that electromagnetic propagation can be treated as a collection of rays, which travel in segments of straight lines and undergo interactions at interaction points joining the segments according to specular reflection, diffraction and diffusive scattering at point-like, linear or two-dimensional interfaces in the environment.

[0006] Ray optical approximation can predict both optical wireless communication (OWC) and radio wave propagation, e.g. if the dimensions of interaction objects and the distances between such objects in the environment are significantly larger than a carrier wavelength of the wireless communication. Electromagnetic propagation can also be predicted in an environment, which comprises objects that block a direct line-of-sight, based on paths circumventing the blocking object by reflections from neighboring objects or diffraction at edges of any object.

[0007] Predicting wireless channels is highly useful for planning and operating a wireless communication network and for a wireless communication when the influence of deterministic features of the wireless channels needs to be captured, such as reflective or diffractive objects moving in the environment on predictable trajectories. A city bus running on schedule is an example for such a predictable object in the cellular environment of a radio access network (RAN). The RAN may provide radio access according a radio access technology (RAT) specified by the Third Generation Partnership Project (3GPP), such as Fourth Generation (4G) Long Term Evolution (LTE) and Fifth Generation (5G) New Radio (NR). The ray optical approximation becomes more relevant and more accurate with higher frequencies, larger bandwidths, and more antennas used to develop and deploy RATs for mobile and wireless communication of the Fifth Generation (5G), the Sixth Generation (6G) and beyond as this technique enables "an analysis of what the behaviors of linear wave equation solutions may be in a short wavelength or asymptotic limit" (Introduction to quantum chaos, D. Ullmo and S. Tomsovic, 2014). In addition to optical access networks and radio access networks, predicting wireless channels is also important for a wireless communication directly between wireless devices and in a mesh network, which are also supported by 3GPP sidelinks. Therefore, ray tracing is commonly used to generate site-specific models of radio frequency (RF) propagation in terms of “propagation paths”, the paths representing the propagation of waves in deterministic geometrical scenarios. These models are used when predicting the performance of wireless communications systems, such as cellular systems for mobile communications, in cell planning tools as well as in product development tools that simulation and emulation the link-level or the system -level.

[0008] An inherent disadvantage of ray tracing with finite shooting resolution, i.e., launching a finite number of rays in different direction, is that in some directions many paths with equivalent interactions are generated due to finite-sized capture objects while the launching misses other directions that would have revealed further interactions.

[0009] Ray tracing is a computationally expensive technique, especially considering its applications in real-time simulations such as RF propagation modeling. Since a lot of information remains valid during consecutive ray tracing runs (for example, the set of rays launched if transmitters do not move, or ray interaction points on static objects), there exist many methods that reuse previous ray tracing results to accelerate or completely bypass further ray tracing runs. Examples include moving Tx and / or Rx nodes and moving objects in the environment, typically but not necessarily organized in the time domain.

[0010] In the remote technical domain of graphics, various recently developed techniques are used to enhance the resolution of images generated with ray tracing. One method by Advanced Micro Devices, Inc. (AMD) uses super-sampling and exploits temporal information to achieve higher frame rates and / or enhanced resolution (community.amd.com / t5 / gaming / first-look-at-amd-fidelityfx-super-resolution-3 / ba- p / 626581, accessed 2024-01-01). Another method by Nvidia Corporation referred to as Deep Learning Super Sampling (DLSS) is a neural graphics technology that multiplies performance using artificial intelligence to create entirely new frames, display higher resolution through image reconstruction, and improve the image quality of intensive ray-traced content using deep learning to create approximate “upscaled” images (https: / / developer.nvidia.com / rtx / dlss, Accessed 2024-01-01), effectively enhancing the resolution of the ray bundles and corresponding samples of space. However, graphics applications do not model properties essential for representing RF propagation such as polarization and wedge diffraction, rendering those techniques of limited usage in an RF modeling tool.

[0011] As a consequence, ray tracing becomes increasingly computationally demanding, when the propagation scenario gets large and when the number of nodes (i.e., transmitters and receivers of the wireless communication) grows.

[0012] For example, F. Quatresooz, S. Demey and C. Oestges, "Tracking of Interaction Points for Improved Dynamic Ray Tracing," in IEEE Transactions on Vehicular Technology, vol. 70, no. 7, pp. 6291-6301, July 2021 (doi: 10.1109 / TVT.2021.3081766) teach that performing ray tracing at each discrete time instant is computationally expensive. Instead, their approach is to extrapolate results obtained from a single ray tracing run. It relies on the geometric tracking of interaction points (i.e., reflection or diffraction points), enabling analytical or numerical predictions of the evolution of any ray identified during an initial ray tracing run.

[0013] However, all these conventional methods, can only modify existing paths by replacing either or both nodes (i.e., the endpoints) of a given path with new node positions, while retaining all the interaction types (specular reflection, diffraction, etc.) of the interior points of a path (i.e., the interaction points). The propagation channel properties are determined, and limited, by the low-density set of base nodes or corresponding base paths, which puts high requirements on the minimum density of base points needed to get a representative behavior for arbitrary node positions between the base points.

[0014] Summary

[0015] Accordingly there is a need for a technique that improves path space coverage by determining relevant paths without the exponentially increasing computation complexity caused by dense base points. In other words, there is a need for a technique that efficiently generates additional relevant propagation paths that were not determined in initial lower-resolution ray tracing, without the need for further resource-intensive ray tracing runs.

[0016] As to a device aspect, a device for determining paths of a wireless communication between a first station and a second station in an environment is provided. The device comprises memory operable to store instructions and processing circuitry operable to execute the instructions, such that the device is operable to obtain one or more first paths between the first station and the second station. Each of the one or more first paths comprises zero or more electromagnetic interactions within the environment. The device is further operable to determine one or more second paths between the first station and the second station based on the one or more first paths by changing the zero or more interactions and minimizing a path length of the one or more second paths in accordance with the zero or more changed interactions.

[0017] Embodiments of the device can meet the abovementioned need, i.e. increase the spatial detailedness and accuracy of radio propagation predictions based on the one or more second paths, while maintaining computational efficiency. Same or further embodiments can address the computational challenges and limitations inherent to ray tracing in wireless communication, notably for predicting deterministic wireless channel properties in large environments. By determining the one or more second paths, embodiments can ensure that radio propagation predictions cover all relevant portions of the path space, which implies capturing a comprehensive range of potential propagation paths without high -resolution ray tracing. Embodiments of the device may be based on a set of base points with base ray-tracing for obtaining one or more first paths, which are post-processed, because the changing of interactions determines one or more second paths more efficiently than the base ray-tracing. A density of base points can be reduced in the base ray-tracing, and / or interactions are added in post-processing.

[0018] By changing the zero or more interactions, embodiments can capture strong interactions in the one or more second paths, which are conventionally lost due to finite number of rays and / or base points in ray tracing. Same or further embodiments can add one or more interactions, which is important when an interaction object appears in the environment and / or intersects any one of the one or more first paths and / or enters a Fresnel zone around any one of the one or more first paths.

[0019] The zero or more electromagnetic interactions may be briefly referred to as the zero or more interactions. Furthermore, when referring to (e.g., specifying or discussing or describing) features introduced as being “at least one” or “one or more” or “zero or more”, such quantity declaration may be dropped for ease of reading. That is, the interaction may refer to the zero or more interactions, the first path may refer to one or each of the one or more first paths, and the second path may refer one or each of the one or more second paths. Moreover, referring to "any path" or "the respective path" may refer to the first path, the second path or both. The preamble of the "device for determining paths" may refer to determining at least the one or more second paths. Furthermore, either one, or collectively both, of the first and second stations may be referred to as endpoints of the respective path, e.g. as a result of shifting the endpoints from base points to the first and second stations. Still further, “the at least one” interaction may refer to the second alternative of “the zero or more interactions”. That is, the case of more than zero interactions is equivalent to, and antecedent basis for, the at least one interaction.

[0020] The zero or more interactions of the respective path may be a sequence of interactions along the respective path. In case of zero interactions, the sequence of the first path may be an empty set. In the case of at least one interaction in the first path, the sequence may be an ordered set (e.g., a list) of interactions. The sequence of interactions along the respective path may also be referred to as path properties or a path signature. For example, the path signature may be implemented by a hash value of the sequence of interactions. The path signature may be uniquely indicative of the sequence of interactions.

[0021] Embodiments can overcome the inherent disadvantages of obtaining the first paths by ray tracing resulting in duplicate paths in terms of the interaction signature, particularly in the case of ray tracing for radio frequency (RF), after paths are required to fulfill Fermat’s principle of least time (e.g., shortest distance, in homogeneous media) by the minimizing of the path length. Multiple ray-traced paths may end up with identical path signatures, namely identical sequence of interactions with interaction elements in the environment, resulting in duplicate paths once the path length is minimized to fulfill Fermat’s principle. These duplicate paths need to be removed (which is also referred to as “pruned”) to avoid double-counting of power (i.e., to avoid double-counting their contribution to the resulting radio propagation) and for reasons of computational efficiency when using the ray-traced paths to determine the radio propagation or any basis for a physical action. To allow duplicate detection, each path may be associated with a unique identifier, for example a hash value, based on the likewise unique path signature of the path, namely the sequence of interactions with elements in the environment. Same or further embodiments can supplement the one or more second paths with different path signatures that were missed when launching rays with finite angular density.

[0022] The path signature may depend on properties of the path, for example at least one of the number and order of interaction points (also referred to as path points of vertices), an index of each object with which the path interacts, a type of the interactions at each of the path points (optionally exempting endpoints of the path, which may represent a wireless transmitter node, Tx node, and a receiver node, Rx node), and discrete path point index (e.g. for fixed grid points).

[0023] The above-mentioned conventional methods keep the path signature unmodified. That is, the conventional techniques do not create further paths with modified, reordered, or new interaction types, whereas the device may change the path signature by changing the zero or more interactions.

[0024] Embodiments of the device may base the determining of the one or more second paths on up-sampling previous ray tracing results. Firstly, one or a series of base ray tracing runs may be performed (for example for several time points with changing environment and / or node positions) and or for a grid of base points. The environment and nodes used in these runs may be referred to as base environment objects and base nodes at the base points. Secondly, propagation paths across different ray tracing runs (or within one run, across different transmitter and / or receiver node positions) are grouped via some type of hashing (e.g., of the path signature) to yield base paths. Information about base paths is collected across base ray tracing runs to assess conditions under which the base paths can be reused, and the rules and / or equations of how they change with changing conditions. Thirdly, for an approximated simulation (for example a next time point and / or after a movement in the environment and / or when the endpoints of the base path have been shifted) the validity of the base paths is analyzed, e.g. given information collected in the base ray tracing runs and / or information about (e.g., moved) objects in the environment. For those base paths deemed valid, their geometric may be recalculated, e.g. by minimizing the path length without changing the path signature, resulting in the one or more first paths. Optionally, electromagnetic properties of the first paths are recalculated, e.g. with the help of information obtained in the previous step, thus providing the one or mor first (propagation) paths without additional ray tracing as an example of the obtaining step.

[0025] The first station may correspond to (e.g., an antenna of) a receiver (Rx). The second station may correspond to (e.g., an antenna of) a transmitter (Tx), or vice versa. In an embodiment, the changing of the zero or more interactions for the second path may comprise adding, along at least one of the one or more second paths, one or more interactions absent along the first path. Alternatively or in addition, the changing of the zero or more interactions for the second path may comprise removing, for at least one of the one or more second paths, one or more interactions present in the first path.

[0026] Changing the zero or more interactions (e.g., changing the path properties) may comprise adding an interaction (e.g., an interaction point) along the second path compared to the first path; changing a type of at least one interaction (e.g., an interaction point) in the sequence of interactions; and / or removing at least one interaction (e.g., an interaction point) from the sequence of interactions.

[0027] For example, the obtaining may comprise modifying the (e.g., ray-traced) base path (e.g., in the case of zero interactions, a base path that directly connects a first base point and a second base point, such as base points for which a ray-traced base path is available from a data base). The changing may comprise adding one or more interactions as a result of shifting (e.g., attaching) either endpoint of the first path to the first and second stations (e.g., to a transmitter “Tx” or receiver “Rx” other than the ray-traced base points available from the database), e.g. because the shifting causes an intersection with an object in the environment.

[0028] Alternatively or in addition, the first path may pass through an object of the environment, which may cause an attenuation of an electromagnetic amplitude contributed by the first path. The changing may comprise adding one or more interactions (e.g. in the case of zero interactions in the first path) by adding an interaction with the object as interaction object of the second path.

[0029] The obtaining of the one or more first paths between the first station and the second station may comprise determining the one or more first paths by ray tracing a plurality of rays launched in different directions from the first station until hitting the second station, or retrieving the one or more first path from a database of base paths covering the environment.

[0030] Alternatively or in addition, in an embodiment, the obtaining of the one or more first paths between the first station and the second station may comprise determining the one or more first paths by ray tracing a plurality of rays launched in different directions from the first station until hitting a capture surface enclosing the second station. Alternatively or in addition, the obtaining of the one or more first paths between the first station and the second station may comprise spatially modifying each of the determined one or more first paths by shifting an endpoint from the capture surface to the second station without changing the zero or more interactions of the respective one of the one or more first paths. Alternatively or in addition, the obtaining of the one or more first paths between the first station and the second station may comprise minimizing a path length of the spatially modified one or more first paths in accordance with the zero or more interactions. In an embodiment, the obtaining of the one or more first paths between the first station and the second station may comprise determining one or more base paths by ray tracing a plurality of rays launched in different directions from one or more first base points in the vicinity of the first station, or by ray tracing a plurality of rays passing through the vicinity of the first station, to one or more second base points in the vicinity of the second station or passing through the vicinity of the second station; or retrieving the one or more base paths from a database of base paths covering the environment. Alternatively or in addition, the obtaining of the one or more first paths between the first station and the second station may comprise spatially modifying the one or more base paths to connect the first station and the second station without changing the zero or more interactions of the respective one of the one or more base paths). Alternatively or in addition, the obtaining of the one or more first paths between the first station and the second station may comprise minimizing a path length of the spatially modified one or more base paths in accordance with the zero or more interactions resulting in the one or more first paths.

[0031] The base paths in the database may fulfil Fermat's principle already. For example, the base paths may result from preemptively ray tracing, e.g. to connect base points (e.g., grid points of a grid or a point set with a dynamically adjusted density of base points) in the environment. The base paths may also be referred to as initial paths or pre-traced paths.

[0032] The one or more base paths or first paths may not fulfil Fermat's principle, e.g. as a result of shifting the endpoints to the first and / or second stations. For example, the base paths connecting base points may fulfil Fermat's principle and the one or more first paths may result from one or more of the base paths having end points closest to the first and second stations by shifting the endpoints to the first and second stations (e.g. according to the spatial modification as a sub-operation of the obtaining operation).

[0033] Minimizing the path length of the one or more first paths may result in one or more physical first paths, e.g. each fulfilling Fermat's principle. In other words, the one or more first paths may result from minimizing a path length of the respective one or more base paths consistently with the unchanged zero or more interactions.

[0034] Any two or more of the alternative sub-operations of the obtaining operation may be combined. For example, the one or more base paths or first paths determined by ray tracing may be stored in the database, e.g., indexed or labeled using a hash value of the segments and / or interactions of the respective one or more base paths or first paths. The one or more base paths or first paths may be retrieved from the database.

[0035] Endpoints of the one or more base paths determined by ray tracing and / or retrieved from the database may be grid points of a grid covering the environment. Spatially modifying the one or more first paths may comprise shifting the endpoints from the grid points to the first and second stations, respectively. After the spatially modifying, the minimizing of the path length may yield one or more physical first paths.

[0036] While embodiments are primarily described by shifting one endpoint of the ray-traced path to connect to the second station (e.g., a receiver node), a variant of any embodiment may shift the other endpoint of the ray-traced path to connect to the first station (e.g., a transmitter node) or both.

[0037] Alternatively or in addition, the obtaining of the one or more first paths may comprise a visibility-based method for generating the one or more first paths or for generating the base paths stored in the database.

[0038] Any one or each of the one or more base paths may be spatially modified to connect the first station and the second station without changing the zero or more interactions of the respective one of the one or more base paths by shifting the endpoints of the one or more base paths to connect to the first station and the second station, respectively. Alternatively or in addition, the one or more base paths may be spatially modified by removing an interaction point (e.g., in each of the vicinities of the first and second stations) and shifting the resulting endpoint of the modified base path directly to the first and second stations, respectively, or by adding a line segment from the removed interaction point directly to the first and second stations, respectively. The interaction point may be removed and / or the endpoint may be connected to another one of the first and second stations at each end of the modified base path.

[0039] Herein, "minimizing a path length" of any path (e.g., the first and / or the second paths) may mean that the respective path is a physical path that fulfils Fermat's principle (e.g., between the first station and the second station). The minimizing of a path length of a path may result in a local minimum (e.g., local in a path space comprising the path) of the path length or a path which path length is stationary with respect to variations of the path.

[0040] Herein, "a path length" of any path may be a spatial path length or an optical path length. For example, in vacuum or air, the minimization may use "a path length" that is unweighted or corresponds to the spatial length. If the path passes through a medium with a relevant optical density (e.g. a medium that has a dielectric response at a radio frequency of the wireless communication) or any spatially varying index of refraction, n(r), the minimizing may use "a path length" that is weighted by the index of refraction. In other words, the path length of the path may be the optical path length, e.g. path length =

[0041] ,-Second Station

[0042] JJcFi1rs ,t-c S,t.ation n(r) ds (vr) ' .

[0043] Minimizing the path length in accordance with the zero or more (e.g., changed or unchanged) interactions may encompass minimizing the path length consistently with the zero or more (e.g., respectively changed and unchanged) interactions. In an embodiment, the at least one interaction may define a constraint of an interaction point of the first path when minimizing the path length of the first path and / or the at least one changed interaction defines a constraint of an interaction point of the second path when minimizing the path length of the second path, and. The changing of the least one interaction of the first path compared to the least one interaction of the second path may involve a change of the constraint.

[0044] The constraint of the interaction point may be a boundary condition of the respective path.

[0045] In an embodiment, the at least one interaction of the at least one first path may constrain an interaction point of the at least one interaction to an edge. The at least one changed interaction of the at least one second path may constrain the interaction point of the at least one changed interaction to a surface. The edge may be on a border of the surface). Alternatively or in addition, the at least one interaction of the at least one first path may constrain an interaction point of the at least one interaction to a surface. The at least one changed interaction of the at least one second path may constrain the interaction point of the at least one changed interaction to an edge. The edge may be on a border of the surface.

[0046] In an embodiment, the device may be further operable to determine an electromagnetic propagation of the wireless communication in the environment from the first station to the second station based on a superposition of contributions of the one or more first paths and the one or more second paths.

[0047] In an embodiment, one or each of the at least one interaction may comprise an interaction point on the respective path at which the respective interaction occurs.

[0048] Alternatively or in addition, one or each of the at least one interaction may comprise an interaction element of an interaction object in the environment with which the respective interaction occurs. Optionally, the interaction element of the interaction object may define a constraint of the minimization of the path length.

[0049] Alternatively or in addition, one or each of the at least one interaction may comprise an interaction type of the respective interaction. Optionally, the interaction type may be one of reflection, specular reflection, diffusive reflection, diffraction, transmission, and refraction.

[0050] The type of at least one (e.g., changed) interaction may specify a constraint for the minimizing of the path length, for example a dimensionality of the constraint. Changing the type of the interaction may change the dimensionality of the constraint posed by the (e.g., changed) interaction. For example, the interaction reflection (e.g., a specular reflection or a diffusive reflection) may comprise a (reflection) surface as the constraint. The interaction diffraction may comprise a (diffraction) edge as the constraint. The interaction transmission or refraction may comprise a (transmission or refraction) volume. The interaction point may be a point on the interaction element (e.g., a surface) of the respective interaction object or slightly offset from the interaction element for numerical robustness when launching one or more further rays from the interaction point (e.g., for diffusive reflection). Alternatively or in addition, the interaction point may be on an edge (e.g., a wedge) between two adjacent surfaces of the interaction object.

[0051] In an embodiment, the changing of the zero or more interactions may comprise changing a type of at least one interaction in the first path for the at least one changed interaction in the second path. Optionally, an interaction object of the at least one changed interaction may be unchanged compared to the at least one interaction in the first path.

[0052] Changing the at least one interaction may change the interaction type and / or may maintain the interaction object and / or may change the interaction element of the unchanged interaction object. Maintaining the interaction object may mean that the first path’s at least one interaction, the type of which is changed in the second path’s at least one changed interaction, refers to the same interaction object to which the second path’s at least one changed interaction refers.

[0053] In an embodiment, each of the one or more first paths and / or the one or more second paths may comprise one or more path segments of the respective path. Optionally, each interaction point of the at least one interaction may join a pair of subsequent path segments of the respective path.

[0054] Each path segment may be a straight line.

[0055] Each path segment associated with diffraction as the interaction may intersect (or may terminate at) a corresponding edge as the interaction element of an interaction object in the environment. The edge may be the boundary of a surface (e.g., in a plane) or two adjacent surfaces (e.g., in two planes). The surface or the two adjacent surfaces may function as the interaction element (and thus as the constraint) of the changed interaction, e.g. according to a surface-related interaction type (e.g., reflection).

[0056] Alternatively or in addition, each path segment of associated with specular reflection or diffuse reflection (i.e., diffuse scattering) may intersect (or may terminate at) a surface as the interaction element of an interaction object in the environment.

[0057] In an embodiment, the device may be further operable to obtain (e.g. measure or receive measurement results of) one or more interaction objects along the one or more first paths. The determining of the one or more second paths may comprise adding one more interaction points and / or path segments to at least one of the one or more second paths based on at least one of the one or more first paths for one or more added interactions where the at least one first path intersects with at least one of the obtained one or more interaction objects. The first path may intersect with one of the obtained interaction objects if one of the segments the interaction object, i.e. if a ray defining the first path interacts with the interaction object.

[0058] The segment and the corresponding interaction (e.g., interaction point) may be added to the second path based on the first path when or in response to the minimizing of the path length of the first path (e.g., which causes an additional intersection with an interaction object in the environment) and / or the changing of the zero or more interactions (e.g., adding of at least one interaction) and / or the spatially modifying of the first path (e.g., which causes an additional intersection with an interaction object in the environment).

[0059] In an embodiment, the device may be further operable to perform or initiate a physical action that is dependent on the determined one or more second paths in the environment. Optionally, the physical action may comprise modelling a channel of the wireless communication along the determined one or more second paths in the environment. Alternatively or in addition, the device may be further operable to model a channel of the wireless communication along the determined one or more second paths in the environment. Optionally, the modeling of the channel further may comprise performing or initiating a physical action that is dependent on the modeled channel.

[0060] In an embodiment, the physical action may comprise transmitting the wireless communication at the first station towards the second station along the determined one or more second paths in the environment and / or based on the modeled channel. Alternatively or in addition, the physical action may comprise receiving the wireless communication from the first station at the second station along the determined one or more second paths in the environment and / or based on the modeled channel. Alternatively or in addition, the physical action may comprise transmitting the wireless communication at the second station towards the first station along the determined one or more second paths in the environment and / or based on the modeled channel. Alternatively or in addition, the physical action may comprise receiving the wireless communication from the second station at the first station along the determined one or more second paths in the environment and / or based on the modeled channel.

[0061] Embodiments of the device may be further configured to determine or emulate a wireless electromagnetic propagation, e.g., a radio frequency (RF) propagation, in the environment based on the determined (first and / or second) paths, e.g. to assist in developing wireless communication equipment such as user equipment and base stations, or to optimize and predict the performance of a wireless communication system comprising such wireless communication equipment.

[0062] Furthermore, since embodiments of the device can determine the true shortest path for each of the one or more second paths, duplicate paths can be excluded (also referred to as "pruned") based on path vertex data and / or the other means of detection of overlap based on interaction data. Path vertex data may comprise coordinates of points (i.e., vertices) which are connected by line segments to build a complete path. Path vertices may also be referred to as "coordinates" or "points", namely interaction points within the path and endpoints at the ends of the path. Duplicates may be identified based on polygons.

[0063] The computational efficiency of the technique can enable wireless devices (e.g. mobile devices, user equipments, UEs, including wearable devices) to determine a wireless propagation path based on structural information about their environment, such as location information and camera images. Due to the reduced computational complexity, embodiments of the device can enable wireless devices to perform autonomous scheduling and / or wireless communication over sidelinks without coverage or without support of a radio access network (RAN). Alternatively or in addition, the reduced computational complexity can enable a RAN to perform radio resource management (RRM), to control a handover of a wireless device (e.g., a UE), or to control dual connectivity (DC) in real-time. For example, the RAN can react to a change in channel conditions based on current or predicted positions of the first station and the second station without delay caused by a radio resource measurements or channel measurements or channel estimates.

[0064] In an embodiment, the physical action may comprise or the device may be further operable to model a channel of the wireless communication along the determined one or more second paths.

[0065] The modeling of the channel may take the propagation of a radio wave along the determined one or more second paths into account. The propagation of the radio wave may include the zero or more changed interactions, e.g. reflection at zero or more reflective surfaces and / or diffraction at zero or more diffractive edges. The radio wave may be represented by an electric field vector, and / or a magnetic field vector, and / or an electromagnetic vector potential.

[0066] Based on the modeled channel, a network node of a radio access network (e.g., a gNB) and / or a radio device (e.g., a UE) may perform beamforming (e.g., configure a precoder) for transmission and / or reception of the wireless communication, e.g. without (or before) receiving a reference signal (e.g. a demodulation reference signal, DM-RS, or a sounding reference signal, SRS). Thus, signaling overhead and latency may be reduced.

[0067] The minimizing of the path length may be holistic, i.e., the technique may determine the entire path of the wireless communication from the first station (e.g., the transmitter) to the second station (e.g., the receiver), and e.g., not a section of the path.

[0068] In an embodiment, the device may be further operative to model a channel of the wireless communication and / or the device may be further operable to perform or initiate a physical action that is dependent on the modeled channel. The modeled channel may be used for the physical action (e.g., performed or initiated by the device). Alternatively or in addition, the physical action may be dependent on the modeled channel along the determined one or more second paths in the environment.

[0069] In any aspect, the first station may be a transmitter node (briefly: transmitter) and the second station may be a receiver node (briefly: receiver) of the wireless communication in the environment. Alternatively or in addition (e.g., in a duplex or bidirectional wireless communication), the second station may be the transmitter and the first station may be the receiver of the wireless communication in the environment.

[0070] In any aspect, the device for determining a path may refer to the one or more second paths. In a first aspect, the device may be a device for determining paths, e.g. a device for performing a physical action based on the one or more second paths of a wireless communication. In a second aspect, the device may be implemented as a device for modeling a channel of a wireless communication.

[0071] While the technique is described for the device, a method aspect of the technique provides a method of determining paths of a wireless communication in an environment, the method comprises steps performing the corresponding functionality of the device. In any aspect, the technique may be implemented as a method of determining further paths between the first and second stations (e.g., transmitter and the receiver), e.g. for improved fidelity of a channel estimation or channel emulation of radio frequency propagation in the environment.

[0072] In an embodiment, performing the physical action may comprise transmitting the wireless communication at the first station towards the second station along the determined one or more second paths in the environment and / or based on the modeled channel. Alternatively or in addition, performing the physical action may comprise receiving the wireless communication from the first station at the second station along the determined one or more second paths in the environment and / or based on the modeled channel. Alternatively or in addition, performing the physical action may comprise transmitting the wireless communication at the second station towards the first station along the determined one or more second paths in the environment and / or based on the modeled channel. Alternatively or in addition, performing the physical action may comprise receiving the wireless communication from the second station at the first station along the determined one or more second paths in the environment and / or based on the modeled channel.

[0073] The transmitting of the wireless communication and / or the receiving of the wireless communication may comprise transmitting a radio signal of the wireless communication and / or receiving a radio signal of the wireless communication, respectively. The radio signal may be transmited or received, or the transmission or reception of the radio signal may be controlled, using the modeled channel. For example, a radio signal may be transmited or received using the modeled channel.

[0074] Embodiments enable quickly modeling the (e.g., radio) channel between transmiter and receiver (e.g., a 5G Radio Access Network, 5G RAN, such as a Next-Generation NodeB, gNB, and a User Equipment, UE). Some embodiments can improve beamforming and MIMO techniques. For example, by accurately modeling the radio channel, the transmiter (e.g., a RAN node) can employ advanced beamforming and Multiple-Input Multiple-Output (MIMO) techniques. Beamforming focuses the transmited signal towards the intended UE, improving signal strength and reducing interference. For example, MIMO enables multiple spatial streams to be transmited simultaneously, increasing data rates and overall network capacity. Accurate channel modeling helps optimize these techniques for beter performance.

[0075] Same or further embodiments can improve interference mitigation. For example, based on radio channel characteristics such as the determined one or more second paths and / or the modeled channel, the device (e.g., the transmiter and / or a RAN node) can identify and mitigate interference sources. By quickly determining the one or more second paths for modeling the channel, the device can adapt (e.g., for tracking a moving radio device) transmission parameters, such as power allocation, frequency allocation, and scheduling, to minimize the impact of interference, resulting in improved signal quality and increased throughput. The conventional approach of launching significantly denser rays (such that a resulting path may be considered a sufficiently close approximation of the shortest path) would require more (e.g., parallelized) computational resources, and thus, energy consumption, or would require more computation time, which contradicts the aim of a tracking moving radio devices in real-time.

[0076] Same or further embodiments can improve adaptive modulation and coding. For example, channel modeling enables the RAN to estimate the quality of a radio link, e.g. between the network node and the UE. With this information, the RAN can adapt the modulation and coding scheme (MCS) according to the channel conditions. This can ensure that the UE receives data at the highest achievable data rate while maintaining an acceptable error rate. Adaptive MCS based on the determined one or more second paths and / or the modeled channel can optimize the overall system throughput and efficiency.

[0077] Same or further embodiments can dynamically allocate radio resource. For example, by quickly modeling the channel, the RAN can dynamically allocate radio resources based on the channel conditions. The RAN may allocate more radio resources (e.g. time slots, frequency bands, or spatial layers) to UEs with favorable channel conditions, while allocating fewer resources to UEs experiencing poor channel conditions for improving system capacity and ensuring efficient utilization of available resources. Alternatively, the RAN may allocate less radio resources (e.g. time slots, frequency bands, or spatial layers) to UEs with favorable channel conditions, while allocating more resources to UEs experiencing poor channel conditions to counter channel conditions and fulling a required quality of service (QoS). Same or further embodiments can efficiently control transmit power. For example, based on the accurate channel modeling and / or the determined one or more second paths, the device may control a transmit power (e.g., of the network node or the UE). By understanding the channel characteristics based on the modeled channel and / or the determined one or more second paths, the RAN can adjust the transmit power levels to meet the required signal quality at the UE. Efficient power control can minimize interference, reduce energy consumption, and enhance overall network performance.

[0078] Moreover, the modeling of the channel may be performed along the direction of transmission or the modeling of the channel may be performed opposite to the direction of transmission (e.g., by virtue of channel reciprocity). Alternatively or in addition, e.g. once the one or more second paths are determined, the modeling of the channel along the one or more second paths may be performed from the first station to the second station (which may also be referred to as “downstream” or in the opposite direction (which may be referred to as “upstream”).

[0079] The capture surface may surround or enclose the second station (e.g., a receiver), e.g. an antenna of the second station. The location of the second station (e.g., a center of the capture surface) may correspond to the antenna of the second station. The capture surface may be a closed surface, or a non-closed surface or capturing object such as a circle or square.

[0080] By changing the zero or more interactions, the one or more second paths (e.g. in combination with the one or more first paths) in the environment can be accurately represent the electromagnetic propagation in the environment.

[0081] In an embodiment, the one or more first paths may have minimized path length and / or may correspond to the one or more first paths resulting from ray tracing a finite set of rays launched at the first station and intersecting the capture surface of the second station.

[0082] As to a method aspect, a method of determining paths of a wireless communication between a first station and a second station in an environment is provided. The method comprises or initiates a step of obtaining one or more first paths between the first station and the second station. Each of the one or more first paths comprises zero or more electromagnetic interactions within the environment. The method further comprises or initiates a step of determining one or more second paths between the first station and the second station based on the one or more first paths by changing the zero or more interactions and minimizing a path length of the one or more second paths in accordance with the zero or more changed interactions.

[0083] The method may be a computer-implemented method, e.g. at the first station and / or the second station. The method may further comprise any feature or step (e.g., functionality) disclosed in the context of the device aspect. For example, the method may further comprise performing or initiating a physical action that is dependent on the determined one or more second paths in the environment. Alternatively or in addition, the method may further comprise modeling a channel of the wireless communication along the determined one or more second paths (and optionally the structural information of the environment).

[0084] The technique may be implemented as a device for, and a method of, post-processing a first path resulting from a ray tracing, the first path comprising at least one of a segment and an interaction between two segments.

[0085] The method may comprise adding a second path, wherein the second path is based on the first path by adding an interaction on the segment or changing a type of the interaction between the two segments or removing the interaction by replacing the two segments by a single straight segment. Alternatively or in addition, the changed interaction of the second path is on the same surface as the interaction of the first path. Alternatively or in addition, an interaction point may be changed from edge to surface, or vice versa. Alternatively or in addition, the interaction may be changed from diffusive surface reflection to specular surface reflection, or vice versa.

[0086] The device may be part of a system or tool implemented in a virtualized and / or distributed and / or scalable computing network (also referred to as cloud).

[0087] As to another aspect, a computer program product is provided. The computer program product comprises program code portions for performing any one of the steps of the method aspect and / or any of the functionality of the one device aspect or the other device aspect disclosed herein, when the computer program product is executed by one or more computing devices. The computer program product may be stored on a computer-readable recording medium. The computer program product may also be provided for download, e.g., via the radio network, the RAN, the Internet and / or the host computer. Alternatively, or in addition, the method may be encoded in a Field-Programmable Gate Array (FPGA) and / or an Application-Specific Integrated Circuit (ASIC), or the functionality of the device aspect may be provided for download by means of a hardware description language.

[0088] The device may be embodied by a user equipment (UE). The UE may be configured to communicate with a base station (e.g., directly on an uplink or downlink, or through another UE functioning as a gateway or relay) or with a peer UE (e.g., on a sidelink). The UE may comprise a radio interface and processing circuitry configured to execute any of the steps and functionality disclosed for the device.

[0089] Alternatively or in addition, the device may be embodied by a base station, e.g. acting as the first station or the second station and / or configured to communicate with a UE. The base station may comprise a radio interface and processing circuitry configured to execute any of the steps and functionality disclosed for the device.

[0090] Alternatively or in addition, the device may be embodied by a core network node configured to communicate with a base station. The core network node may comprise memory operable to store instructions and processing circuitry operable to execute the instructions, such that the core network node is operable to perform any one of the steps and functionality disclosed for the device.

[0091] The physical action may be dependent on the determined one or more second paths.

[0092] In a first variant of any embodiment, the same device that is determining the one or more path may also perform the physical action. In a second variant of any embodiment or in combination with the first variant, the device may initiate (e.g., trigger) the physical action, which is accordingly performed by another device other than the device that is determining the one or more second paths. For example, the device and the other device may be distributed nodes or networked (e.g., cloud-based) implementations. The device and the other device may be spaced apart from each other. Moreover, initiating the physical action may comprise outputting instruction (which may be machine readable and / or which may be human readable) for the performing of the physical action.

[0093] The rays may model a channel of the wireless communication. Performing the physical action may comprise testing a transmitter node or a receiver node, particularly determining whether or not a base station or an antenna node is capable of providing radio coverage at a position of the first or second station in the environment. Based on the channel modeling, the radio base station or the antenna system for the radio base station can be tested, different designs can be compared, and / or further developed.

[0094] The physical action may comprise modeling (e.g., the device may be further operable to model) a channel of the wireless communication based on the determined one or more second paths between a transmitter node at the launch point and at least one receiver node at the position of the receiver in the environment and / or between a receiver node at the launch point and the position of the transmitter node in the environment.

[0095] Modeling the channel (or modeling a channel state, briefly: channel modeling) may comprise modeling amplitudes and phase shifts of actual or hypothetical signals between actual or hypothetical transmitters and receivers, e.g. based on the determined one or more second paths, rather than a measured channel state. The result of the channel modeling may be a vector or matrix comprising complex-valued gains of the channel between the launch point and the at least one position, e.g. each pair of transmit antenna and receive antenna and / or in a similar format as a channel estimate for a measured channel state.

[0096] Alternatively or in addition, the result of the channel modeling may be polarimetric, i.e., having (potentially) independent complex-valued gains per polarization state, e.g. for orthogonal transmit antennas or orthogonal receive antennas. Any two mutually orthogonal polarization states also orthogonal to the ray (or path direction) may be used to represent the polarimetric properties of the signal associated with the ray.

[0097] The subject technique can deal with channel modeling and its applications for a range of use cases. For a given computational complexity, the changing of the zero or more interactions can increase a fidelity between the modeled channel and the real channel, which increases the value of using said channel models in the use cases, e.g. even though the finite size of set of launched rays and / or of base paths and / or of base points reduces the computational complexity.

[0098] A result of the modeling of the channel may be a channel estimate (e.g., a matrix comprising matrix elements, each representing amplitude and phase between any pair of transmit antenna at the transmit node and receive antenna at the receive node, optionally including antennas with orthogonal polarizations). Therefore, the step of modeling may also be referred to as determining a channel estimation (e.g., as opposed to performing a channel estimation that is solely based on measuring reference signals).

[0099] The modeling of the channel may comprise determining an electromagnetic propagation of an electromagnetic field (e.g., based on the Lienard-Wiechert potential) along the determined one or more second paths. For example, the electromagnetic propagation may be configured to associate to the one or more second paths at least one of a phase shift of the electromagnetic field, a change in an electrical field component of the electromagnetic field, and a change in magnetic field component of the electromagnetic field. The channel may be modeled by superimposing the electromagnetic field propagated along each of the one or more second paths.

[0100] In any aspect, the one or more second paths may be the basis of an electromagnetic propagation (e.g., a radio propagation or an infrared or visual light propagation) used by the wireless communication. Alternatively or in addition, the wireless communication may be a radio frequency communication or a visible light communication (VLC).

[0101] An antenna of the transmitter node may be at the first station and / or at least one antenna of a receiver node may at the second station, or vice versa. The transmitter node may be a network node of a radio access node (RAN). Alternatively or in addition, the receiver node may be a radio device (e.g., a user equipment, UE), or vice versa.

[0102] The first station may be a transmitter node in the environment or a diffusive point source functioning as a launch point within the environment. The second station in the environment may be a receiver node in the environment. Alternatively (e.g. according to channel reciprocity) or in addition (e.g., for bidirectional or full-duplex wireless communication), the first station may be a receiver node of the wireless communication in the environment. The second station in the environment may be a transmitter node in the environment.

[0103] The environment may be susceptible to the multipath propagation of the wireless communication, for example, due to (e.g., specular and / or diffusive) reflections and / or (e.g., edge) diffractions of the rays within the environment.

[0104] The transmitting node for transmitting the wireless communication may be a radio device (such as a user equipment, UE), e.g. in an uplink (UL) or in a sidelink (SL). Alternatively or in combination (e.g., for a duplex wireless communication), the transmitting node for transmitting the wireless communication may be a base station (such as a next generation Node B, gNB) of a radio access network (RAN) in a downlink (DL). Furthermore, the receiving node for receiving the wireless communication may be a radio device, e.g. in a DL or in a SL. Alternatively or in combination (e.g., for a duplex wireless communication), the receiving node for receiving the wireless communication may be a base station of a RAN in an UL.

[0105] The wireless communication in the environment may be performed (e.g., transmitted or received) or controlled (e.g., initiated) based on the determined one or more second paths.

[0106] The transmitting or receiving may comprise transmitting or receiving data or transmitting or receiving control signaling, e.g. a random access preamble, a random access response, a reference signal (RS, e.g., a sounding RS in the uplink from a radio device to a network node or a channel state information, CSI, RS in the downlink) or a paging signal or radio resource control (RRC) message.

[0107] The determining of the one or more second paths may support a channel estimation (at a receiver node or at a transmitter node) of the wireless communication. The channel estimation may encompass receiving (e.g., measuring) radio signals and processing the measured radio signals (e.g., comparing to known reference signals, RSs) to estimate an amplitude and phase shifts of signals wirelessly propagated between the transmitter node and the receiver node.

[0108] Alternatively or in addition, controlling the wireless communication may comprise beam management, e.g., steering, tracking or predicting a radio beam based on the determined one or more second paths. Alternatively or in addition, controlling the wireless communication may comprise configuring the transmitter node and / or the receiver node of the wireless communication based on the determined one or more second paths.

[0109] Initiating the physical action may comprise initiating the transmitting or the receiving of the wireless communication. For example, the transmission or the reception may be initiated by controlling or triggering a lower layer (e.g., the physical layer) to perform the transmitting or the receiving of the wireless communication. Herein, initiating the transmitting or the receiving of the wireless communication may or may not refer to an action that starts the wireless communication (such as transmitting a random access preamble or a paging signal). For example, initiating the physical action may comprise modeling a channel (e.g., computing a channel state) based on the determined multipath propagation, wherein the multipath propagation is determined based on a previous wireless communication (e.g., a reception of RSs) at a receiver.

[0110] The physical action may (e.g., further) comprise positioning a radio device at the at least one position in the environment based on the determined one or more second paths, optionally by comparing radio signals received at the radio device in the environment with radio signals expected or modeled at the second station in the environment according to the determined one or more second paths and / or by comparing radio signals received from the radio device in the environment with radio signals expected or modeled at the second station in the environment according to the determined one or more second paths. Alternatively or in addition, the physical action may (e.g., further) comprise adjusting the transmission of the wireless communication or controlling the wireless communication to ensure compliance with regulations based on the determined one or more second paths, optionally by determining an energy flux in the environment based on the determined one or more second paths.

[0111] The radio device may be positioned by transmitting reference signals (e.g. positioning reference signals, PRSs) from a base station at the launch point to the radio device at the at least one position. The positioning may be performed at the radio device or the reference signals received (e.g., measured) at the radio device may be reported to the base station for the positioning. Alternatively or in addition, the radio device may be positioned by transmitting reference signals (e.g. channel state information reference signals, CSI RSs) from the radio device at the launch point to one or more base stations at the at least one position. The positioning may be performed at the base station or the reference signals received (e.g., measured) at the base station may be reported to the radio device for the positioning.

[0112] Positioning the radio device may encompass locating the radio device, e.g., determining a current position or location of the radio device. Alternatively or in addition, positioning the radio device may encompass navigating the radio device, e.g., controlling the radio device (e.g. controlling a drive train of an autonomously driven vehicle embodying the radio device) to reach a target position and / or to move along a predefined route. Navigating the radio device may comprise a closed loop of determining the current position and providing corrective instructions (which may or may not be machine-readable) to counter a deviation of the current position from the predefined route.

[0113] The regulations may refer to radio regulations and / or health regulations. For example, the transmission may be adjusted or the wireless communication may be controlled to fulfill a limit for the energy flux, e.g. in terms of equivalent isotropic radiated power (EIRP). The physical action may (e.g. further) comprise emulating the channel of the wireless communication based on the determined one or more second paths, and / or emulating the channel of the wireless communication based on the modeled channel.

[0114] The transmitter node for the emulating of the channel may correspond to, or refer to, the first station. Alternatively or in addition, the receiver node for the emulating of the channel may correspond to or refer to the second station.

[0115] Emulating the channel (or emulating a channel state, briefly: channel emulation) may comprise physically transmitted signals that are artificially shifted in amplitude and phase based on the modeled channel, rather than naturally shifted based on radio wave propagation and interactions in the real world. Here, artificially shifted may mean that the transmitter node is wired (e.g., in the analog domain) to an emulating device embodying the device aspect, which applies the shift in amplitude and phase based on the determined multipath propagation, and which output is wired (e.g., in the analog domain) to the receiver node. A wireless communication equipment (i.e., transmitter or receiver) may operate (i.e., perform its functions including at least one of channel estimation, decoding, beamforming, possibly channel prediction, etc.) on the emulated channel rather than actual channels. Typical use cases of the emulated channel are in equipment testing or in digital twins (DTs). The computational efficiency increase, which can be brought about by the finite size of the traced rays and / or the reducing the number of first paths or base paths or base points can still enable using more accurate channel models (e.g., detailed or more complex surfaces in the environment), e.g. in equipment testing or DTs, based on the determined one or more second paths.

[0116] Alternatively or in addition, modeling or emulating the channel of the wireless communication may comprise predicting the channel, e.g. based on controlled or scheduled motion of objects (e.g., the reflective surfaces or the diffractive edges) in the environment. For example, the environment may be a manufacturing environment, comprising robots that perform a scheduled or controlled motion influencing the multipath propagation.

[0117] The physical action may (e.g., further) comprise deploying at least one transmitter node and / or at least one receiver node in the environment based on the determined multipath propagation, optionally based on the modeled and / or emulated channel.

[0118] The deployed transmitter node may correspond to, or may refer to, the (at least one) transmitter node of the modeling of the channel or the emulating of the channel. Alternatively or in addition, the deployed receiver node may correspond to, or may refer to, the (at least one) receiver node of the modeling of the channel or the emulating of the channel. Deploying the transmitter node and / or the receiver node based on the determined multipath propagation may comprise a raytracing -based radio network dimensioning.

[0119] The one or more second paths may be determined in real-time or the channel may be modeled in real-time or the channel may be emulated in real-time, e.g. for the transmitting of the wireless communication or the receiving of the wireless communication or the controlling of the wireless communication or the initiating of the of transmitting of the wireless communication or the initiating of the receiving of the wireless communication.

[0120] By using the less rays to determine the one or more first path and / or by reducing a number of base paths or base points, the channel can be modeled in real-time, e.g. for beamforming and / or for controlling the radio network. Alternatively or in addition, the one or more second paths may be determined taking reflective and / or diffractive interactions in the radio frequency (RF) propagation with real-time movement in the environment into account.

[0121] Herein, real-time (e.g., determining the multipath propagation in real-time) may mean that if an object of linear size L is moving at a velocity V, the one or more second paths of the propagation can be determined (e.g., periodically updated) within less than L / V time.

[0122] The determining of the one or more second paths may comprise determining multiple paths of a multipath propagation along the plurality of launched rays and / or continued at each of hit point in the environment.

[0123] In any aspect, the different directions of the finite set of rays launched from the first station may be uniformly or quasi-uniformly (i.e., near-uniformly) distributed in angle, optionally in each of the groups. For example, the rays in the first group may be uniformly distributed. Uniformly may mean that the directions of the plurality of the launched rays may be equally distributed as intersections on a sphere around the first station or on a portion of a sphere (e.g., a hemisphere). The diameter of the sphere may be sufficiently small so that all rays have a point of intersection with said sphere prior to intersecting a (e.g., real) surface in the environment. Moreover, the sphere radius does not matter in this context as the launched rays may be defined in angular space independent of the space of the environment. In more mathematical terms, the launched rays may be elements of a tangent space of the manifold representing the environment, wherein the tangent space is an element of a tangent bundle at the location of the first station.

[0124] Exactly uniformly distributed directions are (in three dimensions) only possible for the five Platonic solids. The uniformly distributed directions may correspond to vertices of a convex regular polyhedron enclosing the launch point, optionally wherein the launch point is at the center of convex regular polyhedron. Quasi-uniformly distributed directions may be defined by the vertices of a uniform convex polyhedron. Alternatively or in addition, further groups of quasi-uniformly distributed directions may be defined by further subdividing each edge (i.e., line between next neighbors) of the previous group. For example, the group So may correspond to an icosahedron. To achieve quasi-uniformity for the group Si, the directions of the rays in the group Si may correspond to the midpoints of each edge in the group so. The ratio between the longest and shortest distance between neighboring intersections on the sphere can be ensured to be less than some threshold of about 1.2. The rays or directions in any one of the sets may correspond to midpoints of neighboring vertices for the rays in the previous group. The midpoints may be on straight lines or on a great circle on the surface comprising the neighboring vertices.

[0125] Embodiments of the technique (i.e., any aspect of the technique) may be applied for paths including a sequence of one or more specular interactions (e.g., from surfaces of buildings, ground, etc.) and / or one or more diffractive interactions (e.g. from edges). Furthermore, a first point and / or a last point of a subpath, to which the technique is applied independently, may be subject to diffuse interactions modeled as point interactions. For example, a physical path from a transmitter to a receiver may include a point of diffuse scattering, which acts as the point for launching the finite set of rays according to an embodiment of the technique. Same or further embodiments may be used in a ray tracing -based radio frequency (RF) propagation model for deterministic and site-specific radio network modeling and simulation.

[0126] In any radio access technology (RAT), the technique may be implemented for a downlink (DL, transmission from a radio device to a network node), an uplink (UL, transmission from a network node to a radio device) and / or a sidelink (SL, transmission from one radio device to another radio device) The SL may be implemented using proximity services (ProSe), e.g. according to a 3GPP specification.

[0127] Any radio device may be a user equipment (UE), e.g., according to a 3GPP specification.

[0128] The radio device and the RAN may be wirelessly connected in an uplink (UL) and / or a downlink (DL) through a Uu interface. Alternatively or in addition, the SL may enable a direct radio communication between proximal radio devices, e.g., the remote radio device and the relay radio device, optionally using a PC5 interface. Services provided using the SL or the PC5 interface may be referred to as proximity services (ProSe). Any radio device (e.g., a remote radio device and / or a relay radio device) supporting the SL may be a ProSe-enabled radio device.

[0129] The radio device and / or the network node and / or the RAN may form, or may be part of, a radio network, e.g., according to the Third Generation Partnership Project (3GPP) or according to the standard family IEEE 802.11 (Wi-Fi). The method aspect may be performed by one or more embodiments of the radio device, the network node and the RAN (e.g., a base station). The RAN may comprise one or more base stations, e.g., performing the method aspect. Alternatively or in addition, the radio network may be a vehicular, ad hoc and / or mesh network comprising two or more radio devices, e.g., acting as a remote radio device and / or the relay radio device.

[0130] Any of the radio devices may be a 3GPP user equipment (UE) or a Wi-Fi station (STA). The radio device may be a mobile or portable station, a device for machine-type communication (MTC), a device for narrowband Internet of Things (NB-IoT) or a combination thereof. Examples for the UE and the mobile station include a mobile phone, a tablet computer and a self-driving vehicle. Examples for the portable station include a laptop computer and a television set. Examples for the MTC device or the NB-IoT device include robots, sensors and / or actuators, e.g., in manufacturing, automotive communication and home automation. The MTC device or the NB-IoT device may be implemented in a manufacturing plant, household appliances and consumer electronics.

[0131] Whenever referring to the RAN, the RAN may be implemented by one or more network node (e.g., base stations).

[0132] The transmitting or receiving node (e.g., a radio device) may be wirelessly connected or connectable (e.g., according to a radio resource control, RRC, state or active mode) with the receiving node and transmitting node, respectively (e.g., a relay radio device or a network node of the RAN).

[0133] The network node (e.g., a base station) may encompass any station that is configured to provide radio access to any of the radio devices. The base station may be a cell, a transmission and reception point (TRP), a central unit (CU), a distributed unit (DU), a radio access node or an access point (AP). The base station and / or the relay radio device may provide a data link to a host computer providing user data to the (e.g., remote) radio device or gathering user data from the (e.g., remote) radio device. Examples for the base stations may include a 3G base station or Node B (NB), 4G base station or eNodeB (eNB), a 5G base station or gNodeB (gNB), a Wi-Fi AP and a network controller (e.g., according to Bluetooth, ZigBee or Z-Wave).

[0134] The RAN may be implemented according to the Global System for Mobile Communications (GSM), the Universal Mobile Telecommunications System (UMTS), 3GPP Long Term Evolution (LTE) and / or 3GPP New Radio (NR).

[0135] Any aspect of the technique may be implemented on a Physical Layer (PHY), a Medium Access Control (MAC) layer, a Radio Link Control (RLC) layer, a packet data convergence protocol (PDCP) layer, and / or a Radio Resource Control (RRC) layer of a protocol stack for the radio communication. Herein, referring to a protocol of a layer may also refer to the corresponding layer in the protocol stack. Vice versa, referring to a layer of the protocol stack may also refer to the corresponding protocol of the layer. Any protocol may be implemented by a corresponding method.

[0136] As to a still further aspect a communication system including a host computer is provided. The host computer comprises a processing circuitry configured to provide user data, e.g., included in the transmission and / or reception of the physical action. The host computer further comprises a communication interface configured to forward the user data to a cellular network (e.g., the RAN and / or the base station) for transmission to a UE.

[0137] A processing circuitry of the cellular network may be configured to execute any one of the steps of the method aspect. Alternatively or in addition, the UE comprises a radio interface and processing circuitry, which is configured to execute any one of the steps of the method aspect.

[0138] The communication system may further include the UE. Alternatively, or in addition, the cellular network may further include one or more base stations configured for radio communication with the UE and / or to provide a data link between the UE and the host computer using the method aspect.

[0139] The processing circuitry of the host computer may be configured to execute a host application, thereby providing the user data and / or any host computer functionality described herein. Alternatively, or in addition, the processing circuitry of the UE may be configured to execute a client application associated with the host application.

[0140] Any one of the devices, the first station, the second station, the transmitting node, the receiving node, the UE, the network node, the base station, the communication system or any node or station for embodying the technique may further include any feature disclosed in the context of the method aspect, and vice versa the method aspect may comprise any step or feature disclosed in the context of the device aspects. Particularly, any one of the units and modules disclosed herein may be configured to perform or initiate one or more of the steps of the method aspect, and the devices may comprise a unit or a module performing any of the steps of the method aspect. Brief Description of the Drawings

[0141] Further details of embodiments of the technique are described with reference to the enclosed drawings, wherein:

[0142] Fig. 1 shows a schematic block diagram of an embodiment of a device for determining paths of a wireless communication between a first station and a second station in an environment;

[0143] Fig. 2 shows a flowchart of an embodiment of a method of determining paths of a wireless communication between a first station and a second station in an environment, which method may be implementable by the device of Fig. 1;

[0144] Fig. 3 schematically illustrates a top-view of an exemplary environment for performing the method of Fig. 2 of determining paths in the environment;

[0145] Fig. 4 schematically illustrates, based on the top-view of Fig. 3, base paths associated with a first base point in an implementation of the step of obtaining the first paths;

[0146] Fig. 4A shows schematically a perspective view of an interaction present in the base path of

[0147] Fig. 4;

[0148] Fig. 5 schematically illustrates, based on the top-view of Fig. 3, base paths associated with a second base point in an implementation of the step of obtaining the first paths;

[0149] Fig. 6 schematically illustrates, based on the top-view of Fig. 3, spatially modified base paths in an implementation of the step of obtaining the first paths;

[0150] Fig. 7 schematically illustrates, based on the top-view of Fig. 3, a second path resulting from an implementation of the step of determining one or more second paths;

[0151] Fig. 7A shows schematically a perspective view of a changed interaction in a second path of

[0152] Fig. 7;

[0153] Fig. 8 schematically illustrates, based on the exemplary top-view of Fig. 3, changing the interaction of a diffractive first path of Fig. 6 to determine a reflective second path according to a first embodiment; Fig. 9 schematically illustrates, based on the exemplary top-view of Fig. 3, changing the interaction of a diffusive first path to determine a reflective second path according to a second embodiment of the device of Fig. 1 or the method of Fig. 2;

[0154] Fig. 10 schematically illustrates obtaining a base path that contains an interaction according to a third embodiment of the device of Fig. 1 or the method of Fig. 2;

[0155] Fig. 11 schematically illustrates spatially modifying a first path that contains the same interaction of Fig. 10 according to the third embodiment of the device of Fig. 1 or the method of Fig. 2;

[0156] Fig. 12 schematically illustrates determining a second path with the interaction of Fig. 10 removed according to the third embodiment of the device of Fig. 1 or the method of Fig. 2;

[0157] Fig. 13 schematically illustrates obtaining a base or first path that contains an interaction according to a fourth embodiment of the device of Fig. 1 or the method of Fig. 2;

[0158] Fig. 14 schematically illustrates determining a second path with an interaction added to the first path of Fig. 13 according to the fourth embodiment of the device of Fig. 1 or the method of Fig. 2;

[0159] Fig. 15 show a schematic flowchart of a fifth embodiment of the method of Fig. 1;

[0160] Fig. 16 schematically illustrates obtaining a base path that contains an interaction according to a sixth embodiment of the device of Fig. 1 or the method of Fig. 2;

[0161] Fig. 17 schematically illustrates spatially modifying a first path that contains the same interaction of Fig. 16 according to the sixth embodiment of the device of Fig. 1 or the method of Fig. 2;

[0162] Fig. 18 schematically illustrates a first sub-step for determining a second path with the interaction of Figs. 16 and 17 changed according to the sixth embodiment of the device of Fig. 1 or the method of Fig. 2;

[0163] Fig. 19 schematically illustrates a second sub-step for determining a second path with the changed interaction of Fig. 18 according to the sixth embodiment of the device of Fig. 1 or the method of Fig. 2; Fig. 20 shows a block diagram of a radio device embodiment of the device of Fig. 1;

[0164] Fig. 21 shows a block diagram of a base station embodiment of the device of Fig. 1; and

[0165] Fig. 22 shows a block diagram of a core network embodiment of the device of Fig. 1.

[0166] Detailed Description

[0167] In the following description, for purposes of explanation and not limitation, specific details are set forth, such as a specific network environment in order to provide a thorough understanding of the technique disclosed herein. It will be apparent to one skilled in the art that the technique may be practiced in other embodiments that depart from these specific details. Moreover, while the following embodiments are primarily described for a New Radio (NR) or 5G implementation, it is readily apparent that the technique described herein may also be implemented for any other radio communication technique, including a Wireless Local Area Network (WLAN) implementation according to the standard family IEEE 802. 11, 3GPP LTE (e.g., LTE-Advanced or a related radio access technique such as MulteFire), for Bluetooth according to the Bluetooth Special Interest Group (SIG), particularly Bluetooth Low Energy, Bluetooth Mesh Networking and Bluetooth broadcasting, for Z-Wave according to the Z-Wave Alliance or for ZigBee based on IEEE 802.15.4.

[0168] Moreover, those skilled in the art will appreciate that the functions, steps, units and modules explained herein may be implemented using software functioning in conjunction with a programmed microprocessor, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a Digital Signal Processor (DSP) or a general purpose computer, e.g., including an Advanced RISC Machine (ARM). It will also be appreciated that, while the following embodiments are primarily described in context with methods and devices, the invention may also be embodied in a computer program product as well as in a system comprising at least one computer processor and memory coupled to the at least one processor, wherein the memory is encoded with one or more programs that may perform the functions and steps or implement the units and modules disclosed herein.

[0169] Fig. 1 schematically illustrates a block diagram of an embodiment of a device for wireless communication in an environment, e.g. for determining paths of a wireless communication in an environment. The device is generically referred to by reference sign 100.

[0170] The device 100 comprises a First Path Obtainment Module 102 configured to acquire one or more initial paths, known as first paths, that connect the first and second stations. These paths may comprise various electromagnetic interactions within the environment, such as reflections or diffractions caused by interaction objects such as obstacles or surfaces. The role of this module 102 is to capture baseline data concerning potential signal trajectories between the communication endpoints. The device 100 optionally comprises an Interaction Obtainment Module 104, which operates in conjunction with the module 102. Its primary responsibility is to provide technical data on presence or absence of interaction objects and / or electromagnetic interactions along the one or more first paths. This may involve identifying specific points of interaction or the nature and characteristics of those interactions, which are usable for determining how the wireless signal might be influenced as it propagates through the environment in the vicinity of each of the one or more first paths.

[0171] The device 100 further comprises a Second Path Determination Module 106, which builds on the first paths obtained by the module 102, and optionally the results of the module 104, by changing the zero or more interactions of at least one or each of the one or more first paths to determine one or more second paths, which ameliorate the set of paths available for analyzing or predicting the electromagnetic propagation in the environment. The module 106 accounts for changed constraints as a consequence of the zero or more changed interactions, and / or changes of the relevant interaction objects of the environment by re-evaluating the one or more first paths, when minimizing the overall path length of what results in the one or more second paths.

[0172] The change in at least one interaction may change a constraint for an interaction point of the second path in the minimization, which ensures alignment with the principles guiding the propagation of electromagnetic waves, such as Fermat's principle. Alternatively or in addition, one or more interaction points may be added or removed in the one or more second paths compared to the one or more first paths as a consequence of a spatial modification (e.g., of the endpoints) when obtaining the one or more first paths. Alternatively or in addition, interactions may be added or removed compared to the one or more first paths as a consequence of shifting an interaction point along a (e.g., changed) interaction constraint. In accordance with the latter interdependence, the changing of the zero or more interactions and the minimizing of the path length may be performed simultaneously or iteratively.

[0173] Jointly, these modules 102 and 106, and optionally the module 104, within the device 100 can determine one or more physically accurate second paths that significantly contribute to the electromagnetic propagation.

[0174] Alternatively or in addition, the technical aspect may be defined as a device 100 configured to determine (e.g., generate) in a Second Path Determination Module 106 one or more second paths (i.e., further paths) from one or more first paths (i.e., initial paths, e.g. base paths or a purely spatial modifications of base paths). The one or more first paths are obtained by a First Path Obtainment Module 102, e.g. as a result from ray tracing and / or an existing (e.g., stored) set of ray-traced base paths). The one or more further paths have different path signatures due to the zero or more changed interactions compared to the one or more first paths (e.g., compared to corresponding base paths in the existing set of ray-traced base paths). The zero or more interactions may be changed in terms of a number of interactions along the respective second path, the type of the interaction, and / or the interaction object. For the latter, the Interaction Obtainment Module 104 may receive or measure along the one or more first paths candidates of interaction objects for interactions to be added or sizes of interaction objects for interactions to be removed since there is no intersection anymore in the respective second path.

[0175] At least one of the zero or more interactions of each of the one or more second paths is different from the zero or more interactions of each of the one or more first paths.

[0176] The one or more first paths of the technique may directly or indirectly result from ray tracing in the environment. The one or more second paths resulting from the technique may contribute to an electromagnetic propagation in radio frequency (briefly: radio propagation) or higher frequencies (e.g. optical communication not limited to visible light). While the ray tracing may be part of a (e.g., deterministic) simulation (i.e., a part of an embodiment of the device may be a simulator), the resulting radio propagation (e.g., a propagation analysis) in the environment is the basis of a physical action such as emulating a signal exchange between physical transmitter and receiver devices or deploying physical antenna systems based on the resulting radio propagation.

[0177] Embodiments of the technique can improve the computational efficiency of determining the radio propagation by determining (e.g., creating) the one or more second paths that contribute significantly to the resulting radio propagation without further ray tracing. The physical interactions included in the created paths may comprise at least one of diffraction at a linear edge (also referred to as wedge diffraction), diffuse scattering at a surface, and specular reflection.

[0178] Any of the modules of the device 100 may be implemented by units configured to provide the corresponding functionality.

[0179] The device 100 may be embodied by an emulator or a network node (e.g., a transmitting and / or receiving node) of a RAN.

[0180] Fig. 2 presents a flowchart outlining steps involved in an embodiment of a method 200 for determining (e.g., ascertaining) paths for a wireless communication between a first station and a second station situated within an environment. The method 200 commences with the step S202 of obtaining one or more first paths that link the first station to the second station, with the characteristic that each first path encompasses a zero or more electromagnetic interactions occurring within the environment.

[0181] Delving into specifics, the method 200 optionally comprises sub-steps within the step S202 that refine the obtaining of the first paths. Sub-step S202-1 involves the task of identifying one or multiple base paths through a technique of ray tracing conducted within the environment. As an alternative (or in addition by storing the ray-traced base paths), sub-step S202-2 retrieves one or more of these base paths from a specialized database that encompasses a collection of paths encapsulating the environment. The following sub-step S202-3 advocates for a spatial alteration of these preliminary base paths to link the first station and the second station without altering the previously identified zero or more electromagnetic interactions. Lastly, sub-step S202-4 reduces the path length of (e.g., each of) these spatially adjusted base paths in direct relation to their respective sequence of interactions, thus arriving at one or more first paths.

[0182] The method 200 optionally progresses further with step S204, which entails the acquisition of one or more interaction objects that might be situated along (e.g., in the vicinity of) the one or more first paths. This step S204 can underpin the determining step that follows.

[0183] The method 200 culminates with the step S206, which is bedrocked on the one or more first paths previously obtained in the step S202. Here, one or more second paths are determined by changing the zero or more interactions encountered and concurrently striving to minimize the path lengths of these second paths. This minimization is distinctly performed in concordance with the zero or more interactions that have been changed.

[0184] Embodiments of the technique can generate (in the step S206) one or more further paths (i.e., second paths) with path signatures different from one or more initial paths (i.e., the first paths, which may be the base paths of spatial modifications thereof), without the need for ray tracing, e.g. from the one or more existing initial paths generated using ray tracing. The one or more second paths are generated based on the one or more first paths with specific (i.e., changed) path interactions.

[0185] Embodiments of the technique can exploit (e.g., when changing the zero or more interactions) the fact that specific interaction types in a base path (or equivalently in a first path) infer the possible existence of one or more further paths with other interaction types and / or with removed or added path points (i.e., interaction points).

[0186] Embodiments of the technique can increase the richness of the determined radio propagation (e.g., the propagation analysis or predicted propagation channel) in an environment. Same or further embodiments provide an electromagnetic field continuity and / or allow sparser (e.g., lower-resolution) sets of base node positions, hence decreasing execution time, reducing memory requirements (i.e., in terms of CPUs and / or GPUs), and improving computational efficiency during path finding, compared to conventional ray tracing -only techniques.

[0187] Specifically, channel richness can be increased since one or more further paths with different path signatures (e.g., different interaction types) are determined, thus capturing scattering phenomena that the existing ray tracing for a low-resolution grid of base nodes may have missed. Conversely, a conventional higher-resolution ray tracing may find the paths with such path signatures as well, but that would be achieved at the cost of increased execution time and memory consumption.

[0188] Similarly, electromagnetic field continuity (which is also referred to as spatial consistency) is improved, since the generated one or more further paths involve interactions that are (potentially) missing in the ray- traced initial paths. Hence, coherently combining of the one or more further paths and the one or more existing initial path can result in a field distribution with better continuity (e.g., less discrete domains or even unphysical discontinuities in terms of field strength), which can be essential for the resulting physical action based on the determined radio propagation, e.g. in channel modeling and radio access network (RAN) simulations in the environment using the determined radio propagation in the environment.

[0189] Based on one or more existing first or base paths, embodiments of the technique generate one or more further paths, i.e. second paths, with path signatures different from those of the existing first or base paths, thus filling a gap of lacking path signatures, for example by adding one or more further paths on surfaces associated with specific interactions in the set of existing initial paths.

[0190] This may allow the existing first or base paths to be generated with a sparse set of base points, e.g. since every diffraction interaction will offer potential surface interactions. Without the subject technique, identifying these potential surface interactions would require much higher-resolution ray tracing at the cost of computational efficiency.

[0191] The method 200 may be performed by the device 100. For example, the modules 102, 104, and 106 may perform the steps S202 (and optionally S202-1, S202-2, S202-3, and / or S202-4), S204, S206, respectively.

[0192] The technique may be applied to an uplink (UL), a downlink (DL) as the wireless communication and / or a direct communication between radio devices, e.g., device-to-device (D2D) communications or sidelink (SL) communications.

[0193] The device 100 may be embodied by, or may control, a radio device or a network node of a RAN (e.g., a base station). Herein, any radio device may be a mobile or portable station and / or any radio device wirelessly connectable to a base station or RAN, or to another radio device. For example, the radio device may be a user equipment (UE), a device for machine-type communication (MTC) or a device for (e.g., narrowband) Internet of Things (loT). Two or more radio devices may be configured to wirelessly connect to each other, e.g., in an ad hoc radio network or via a 3GPP SL connection. Furthermore, any base station may be a station providing radio access, may be part of a radio access network (RAN) and / or may be a node connected to the RAN for controlling the radio access. For example, the base station may be an access point, for example a Wi-Fi access point. Herein, a list of the form A, B, and / or C (also written as A, B and / or C) may correspond to at least one or each of A, B, and C, i.e., A and / or B and / or C.

[0194] To provide a general overview of the following description, embodiments of the device 100 can be beneficially applied in a situation schematically illustrated in the figures following the Fig. 3. For example the step of obtaining S202 the first path may comprise at least one of the sub-steps illustrated in, or described with reference to, Figs. 3 to 6. More specifically, Fig. 3 illustrates a schematic environment 300. Figs. 4, 4A, and 5 schematically illustrate the sub-steps of determining S202-1 or retrieving S202-2 one or more base paths 302-0 in the environment 300. Fig. 6 schematically illustrates the sub-step of spatially modifying S202-3 the one or more base paths 302-0, which results in the one or more first paths 302-1, preferably after minimizing S202-4 the path length of the one or more spatially modified base paths.

[0195] Fig. 3 schematically illustrates a two-dimensional top-view of a scenario comprising a wireless transmitter 304 (abbreviated: Tx) emitting signals into a propagation channel with a scattering interaction object 308 (briefly: scatterer) and two base points 305. The base points 305 may be positions that represent wireless receivers (abbreviated: Rx), e.g. later during real-time control of the wireless communication.

[0196] In the context of a geometrical optics (i.e., ray tracing) representation of wave propagation, the signal propagation is represented by paths comprising line segments (briefly: segments) connecting consecutive interaction points at which the electromagnetic wave represented by the geometrical optics ray interacts with an interaction element (e.g., an edge or surface) of an interaction object 308 in the environment 300.

[0197] Fig. 4 schematically shows two such base paths 302-0 (also referred to as initial paths) in the environment 300 of Fig. 3. Each of the one or more base paths 302-0 comprises at least one interaction 320-1. The base paths 302-0 are initially identified (i.e., determined S202-1) using ray tracing. The base paths 302-0 shown in Fig. 4 represent signal propagation from a transmitter 304 to the right base point 305 (e.g. a candidate position of a receiver) via a left comer or left edge (of the interaction object 308 extending perpendicular to the plane of view) and via a right comer or right edge, respectively, on the interaction object 308 as a scatterer.

[0198] The perspective view of Fig. 4A, which includes the third dimension perpendicular to the plane of view of Fig. 4, schematically illustrates the edge 324-1 as the interaction element of the interaction 320-1. Note that the interaction element 324-1 defines a boundary condition, which is a constraint 324-1 for the interaction point 322. Fig. 5 shows corresponding initial rays for base paths to another base point 305 on the left (e.g., a candidate position of a moving receiver at a later point in time). Both sets of base paths 302 shown in the Figs. 4 and 5, respectively, are associated with comer interactions as a type of the interaction 320-1, which - in geometrical optics models - are typically modeled using edge diffraction. For edge diffraction (also referred to as wedge diffraction) existing wedge diffraction models, such as Uniform Geometrical Theory of Diffraction (UTD), may be applied. While the base paths 302-0 are indicated in the Figs. 4 and 5 by line segments with arrows to indicate consecutive line segments in the respective paths, no one-way direction of propagation is implied, e.g. due to channel reciprocity.

[0199] Any path 302 (e.g., including cases referred to by reference sign 302-x with x = 0, 1, 2) discussed herein can be used for (e.g. may contribute to) determining the electromagnetic propagation of the wireless communication in the environment 300.

[0200] In other words, Figs. 3 to 5 schematically illustrate a top-view of a scenario shown in Fig. 3 including a wireless transmitter Tx 304 emitting signals into a propagation channel with one scatterer 308 and traced base points 305 (e.g., two receivers). The one or more base paths 302-0 have zero or more interactions 322-1, e.g. a diffraction interaction 322-1 at edges (e.g., wedges) at the upper surface (shown as an edge in the top-view of Fig. 4) of the scatterer 308 associated with the base points 305 to the right in Fig. 4 and to the left in Fig. 5.

[0201] In a first variant of any embodiment, the base points 305 may already correspond to receivers (generically referred to by reference sign 306 herein).

[0202] In a second variant of any embodiment, the base points 305 may be within a vicinity of a receiver 306. For example, the base path may be stored in a database and the position of the receiver 306 may be the result of a positioning measurement.

[0203] In a third variant of any embodiment, the receiver 306 (which may have a small interaction cross-section or, if represented by a point, zero interaction cross-section) may be enclosed by a capture surface and the ray tracing terminates upon the ray intersecting with the capture surface. In this variant, the point of intersection plays the role of any one of the aforementioned base points.

[0204] While the technique has been described with reference to a transmitter node 304, the technique is applicable to any first station 304.

[0205] At least for the second and third variant, the base path 302-0 has to be spatially modified S202-3 by shifting at least one of the endpoints of the base path 302-0 to the position of the receiver 306, e.g. as schematically illustrated in Fig. 6. A partial method, which may be combined with any embodiment of the subject technique, performs up- sampling (e.g., interpolating) to reach one or more positions of one or more further nodes 306 that were not present during ray tracing to the base points 305, as is schematically illustrated in Fig. 6. That partial method uses ray-traced base paths 302-0 (also referred to as initial paths) and modifies S202-3 them by replacing one or more base points 305 used during ray tracing (i.e., any endpoint of the respective base path 302-0) with positions of further nodes 306, e.g., by reattaching the respective last line segments in the ray-traced initial paths 302-0 to the one or more further nodes 306, which is an example of the second station.

[0206] Preferably, after the spatial modification S202-3, and the path length of the modified base path 302-1 is minimized (e.g., using a shortest path algorithm) to determine from each modified base path 302-1 the shortest path by shifting the interaction points 322 along the respective object border (i.e., the interaction element defining the constraint 324-1) of the interaction 320-1, i.e. to fulfil Fermat’s principle.

[0207] Herein, the interaction element defined by the respective object border of the interaction object 308, i.e., the constraint 324-1, of the interaction 320-1 may be a surface (e.g., planar, optionally at least piecewise planar surface) in case the interaction 320-1 comprises a (e.g., diffusive or specular) reflection or a transmittance (e.g., including refraction); a line (e.g., a straight line, optionally parallel to an edge or wedge or post in the environment 300) in case the interaction 320-1 comprises an edge diffraction (e.g., with the segment laying on a Keller's cone and emerging from the interaction point laying at the tip of the Keller's cone); or a point (e.g., a tip or comer) in case the interaction comprises scattering.

[0208] The case of a line 324-1, i.e. a linear constraint 324-1, is shown in Fig. 4 and 4A. Thus, minimizing the path length of the modified base path 302-1, which results in the first path 302-1 shown in Fig. 6, may comprise shifting the interaction point 322 along the linear constraint 324-1.

[0209] In other words, Fig. 6. schematically illustrates a partial method for up-sampling (e.g., interpolation) of modifying the one or more initial paths 302-0 to reach to respective shifted node positions 306 not present during ray tracing. This partial method results in modified base paths as the first paths 302-1 with the same path signature as the base paths 302-0, i.e., the same sequence of interactions 320-1 (optionally up to shifting the interaction point 322 on the constraint 324-1 of the interaction 320-1, which is wedge diffraction in the illustrated example case of Figs. 4 to 6), since the ray-traced base paths 302-0 to the base points 305 present during ray tracing are the basis for the spatial modification S202-3 (e.g., for the spatial up-sampling).

[0210] However, using this partial method alone (i.e., spatial modification S202-3 and / or path length minimization S202-4) is limited in that it cannot produce further paths (i.e., the second paths 302-2) with the zero or more changed interactions 320-2, e.g. further interactions, which may be represented by path signatures different from those of the given set of base paths or the one or more first path 302-1. This is also a common limitation of other prior art solutions in the up-sampling (e.g., interpolation) of ray tracing.

[0211] For example, for the base points 305 (e.g., base node positions) in Figs. 3 to 6, ray tracing cannot find any path comprising a specular reflection as the zero or more interactions 320-1 of the first paths 302-1 associated with the top surface 324-2 schematically illustrated in Fig. 7A, since the base points 305 reached by the base paths 302-0 are outside a region 310 of specular reflection 310, which is schematically illustrated in Fig. 7. Hence, critically important second paths 302-2, e.g. with dominating contribution to the electromagnetic propagation (e.g. represented by a path gain), if present, i.e. further paths 302-2 with a significant contribution to the (e.g., radio) propagation of the wireless communication, are missing when applying up-sampling solely based on modifying S202-3 endpoints of the base paths 302-0. Depending on both the properties of a propagation channel for a given base point 305 and the types of interactions 320-1 allowed during ray tracing, existing techniques may miss critically important second paths 302-2.

[0212] Alternatively or in addition, such critically important second paths 302-2 can be missed due to a limited shooting resolution (e.g., the finite angular density of rays launched at one endpoint of the base path) during ray tracing, e.g. when two casted (i.e., launched) neighboring rays hit edges of an interaction object 308, while none of the launched rays hits a surface of same object 308 between said edges.

[0213] In other words, Fig. 7 schematically illustrates an example of the second path 302-2, which is a limitation of an existing up-sampling method. A low (e.g., insufficient) resolution of ray tracing nodes means that the second paths 302-2 with important interactions 320-2 (e.g., specular reflection in the case of Figs. 7 and 7A) are missed. These second paths 302-2 are further paths with important interactions 320-2 and cannot be generated by the spatial up-sampling alone based on base points 305 for a second station 306 that otherwise would be reached by ray-traced paths when using a higher ray tracing resolution, which is of course computationally expensive and could be too slow for real-time control of the wireless communication.

[0214] If, however, specular reflection on the surface 324-2 of the object 308 is included as an interaction of a second path 302-2 and the determining S206 includes the minimization of the path length (i.e., the Fermat’s principle is fulfilled, e.g., by applying a shortest path algorithm) is applied to such a path, the resulting interaction point 322 (i.e., the specular reflection point) is on the surface 324-2, if the second station 306 (e.g., as a further target point) is in the specular region 310. In other words, the determining S206 of the one or more second paths 302-2 comprises shifting (see curved arrow in Fig. 7A) the interaction point 322 consistently with the constraint 324-2 of the changed interaction 320-2 (that is different from the constraint 324-1 of the interaction 320-1 of the first path 302-1). Embodiments of the technique address the objective of covering relevant portions of the path space (i.e., the space of all paths in the environment 300) in a computationally efficient manner, e.g. without the need for high-resolution ray tracing or without any further ray tracing after ray-tracing the one or more base paths 302-0 and before generating the relevant one or more second paths 302-2. The path space may be a function space, e.g. the space of all continuous paths from one endpoint 304 to another endpoint 306 in the environment 300. Smooth paths (such as differentiable paths) may be neglectable or excluded from the path space, as their contribution to the radio propagation may be irrelevant or zero.

[0215] Embodiments address the objective by generating the one or more second paths 302-2, which includes changing not only or not necessarily the interaction points 322 (e.g., path points (or vertices) between segments (or edges) or, more generally speaking, the continuous and non-differentiable points of a path), but by changing the zero or more interactions associated with a first path 302-1 for determining the second path 302-2. Such changes may encompass at least one of removing an interaction point 322, adding an interaction point 322, and changing the type of the interaction 320 (optionally in association with shifting the interaction point).

[0216] In one embodiment, the device 100 generates in the step S206 one or more second paths 302-2 based on an existing set of ray-traced base paths 302-0 by exploiting properties of existing interactions 320-1 (e.g., associated with each base path 302-0). A second path 302-2 is generated by changing a base path 302-0 in the set of ray-traced base paths 302-0 (and / or a first path 302-1 resulting from modifying the base path) with respect to its path signature. The changes in the step S206 can include a change of interaction type for a given interaction point 322, the removal of an interaction point 322, the insertion of an interaction point 322, and combinations thereof.

[0217] Examples of such changes may include at least one of the following:

[0218] - Any path interaction 320-1 involving diffraction is associated with a corresponding wedge 324-1, the two planes 324-2 of which can support various surface-related interaction types as the changed interaction 320-2.

[0219] This allows generating second paths 302-2 with specular and diffuse interactions 320-2 without ray tracing by exploiting the plane equation for each plane 324-2 as a basis for placement of further or changed interaction points 322.

[0220] - Any path interaction 320-1 involving diffuse scattering is associated with a surface as the interaction element 324-1 of the first interaction 320-1.

[0221] This allows generating specular paths 302-2 without ray tracing by exploiting the plane equation for the (or each) plane 324-1 also as the interaction element 324-2 of the changed interaction 320-2, i.e. as a basis for placement of further or changed interaction points 322 of the changed interaction 320-2.

[0222] - A path interaction 320-1 involving diffraction into the “lit region”, i.e., not into the region 310 shadowed by the diffraction wedge 324-1, implies that other interaction points 322 of the first path 302-1 before and after the diffraction 320-1 may have line-of-sight visibility.

[0223] This allows generating a second path 302-2 (e.g., a new candidate path) with the diffraction point 322 removed from the base path 302-0.

[0224] - A further path interaction 320-2 may be inserted into the first path 302-1 (e.g., the base path 302-0) to represent an interaction with an interaction object 308 that was not present or not explicitly modeled in the environment 300 during the ray tracing S202-1 or that were not intersecting with the base path 302-0 prior to the modification S202-3.

[0225] Such objects 308 may be relatively small objects such as cars, people, furniture, etc. and / or objects that are often not provided in spatial information (e.g. 3D geometrical data). Alternatively, such objects 308 are included in the environment 300 but excluded during ray tracing S202-1 (e.g. “hidden” from a ray-tracer) to limit the complexity of the ray tracing. The spatial information as to the object 308 may be obtained in the step S204.

[0226] Finally, by applying a shortest-path algorithm S202-4, the determined S206 second path 302-2 is constrained to fulfill Fermat’s principle.

[0227] Embodiments of the technique create in the step S206 one or more further paths 302-2 with interaction types (e.g., path signatures) different from the initial paths 302-0 or 302-1 as opposed to an existing up- sampling technique, which only spatially modifies (e.g., in the step S202-3) one or both endpoints from base points 305 to stations 304 and / or 306 or which modifies (e.g., in the step S202-4) intermediate interactions points 322 and updates by enforcing Fermat's principle of the shortest path for the given and unchanged sequence of interactions 320-1, i.e. restricted to only spatially modifying initial paths 302-0 with given interaction types, e.g., maintaining the path signatures.

[0228] A conventional channel estimation is based on measuring reference signals, which is time consuming and occupies transmission resources. Due to the delay caused by measuring the channel and processing, at the time of transmission the channel estimate may be already outdated. If the channel is more rapidly modeled using only on a finite set of rays, e.g. a random set for a Monte-Carlo simulation, the fidelity of the modeled channel is low, which can cause inaccurate beamforming and interference at neighboring UEs 310, as indicated by the dashed beams. Embodiments of the device 100 and the method 200 can improve the fidelity of the modeled channel and / or the accuracy of the determined S206 one or more second paths 302-2 (e.g., represent the dominant contribution to the signal propagation of the wireless communication). For example, based on the modeled channel and / or the determined one or more second paths 302-2, transmission parameters and / or precoders at the first station (for transmitting and / or receiving) the wireless communication can be improved, e.g. a signal -to-noise ratio (SNR) or a signal-to-interference and noise ratio (SINR) at user equipments (UEs).

[0229] The ray optical technique can strike a balance between the fast, non-deterministic stochastic channel models, on the one hand, and the more accurate, but computationally challenging, full-wave electromagnetic modeling on the other hand. The latter cannot be used for any meaningful real-world propagation scenarios due to their size in terms of wavelengths, while the former depends on statistics from measurement campaigns which means that in principle all deterministic information is lost, even on a macro scale.

[0230] Herein, a shortest path, i.e. the result of minimizing the path length of a first or second path between two endpoints 304 and 306 (e.g. represented by points in the environment 300) is a path that either connects the points directly (by a straight line), or connects them via one or more interactions 320 with interaction objects 308, such as transmission (e.g., pass through), reflection (e.g., specular reflection), and / or diffraction (e.g., edge diffraction shown at reference sign 322 in Fig. 4A, also referred to as wedge diffraction), or arbitrary combinations thereof, in such a way as to minimize the travel time (or geometric path length in a homogeneous medium) of the path, in accordance with Fermat’s principle.

[0231] Since ray-tracing samples space discretely, the first paths 302-1 are modified base paths 302-0 (as represented by the combination of line segments between objects 308 identified during the ray tracing) and do not in general fulfill Fermat’s principle. As a consequence, conventionally predicted fields of the electromagnetic propagation are inaccurate. An inaccuracy caused by the finite angular resolution of the ray tracing may scale with distance and radio frequency, as the deviation in length causes a phase shift. In contrast, embodiments of the technique can not only correct for the spatial modification S202-3 of the endpoints by minimizing the path length S202-4, but determine S206 one or more further second paths 302-2 comprising sequences of interactions 320 not obtained by since ray-tracing samples space discretely.

[0232] The technique may be combined with any suitable method for ray tracing, e.g. in the step S202-1 and S202-3, to find the first path 302-1. The first path 302-1 may be found by finite resolution ray tracing, that does not in general fulfill the Fermat’s principle. It’s the path 302-1 used as a starting point for finding the second path 302-2. The first path 302-1 starts in a first station 304 (e.g., the transmitter) and ends in a second station 306 (e.g., at the capture surface 404 of the receiver or after shifting the end point to the receiver in the step S202-3). The finite set of rays originating from the first station 304 (e.g., a transmitter), i.e. the finite angular density at launch, and the non-zero size of the capture surface (e.g., a capture sphere) efficiently yield the at least one first path 302-1 in the step S202. As schematically illustrated in Fig. 6, the modification S202-3 of a base path 302-0 directly from ray tracing shift an endpoint of the first path 302-1 from the intersection on the capture surface to a location of the second station 306.

[0233] Any minimization of the path length (for the first path 302-1 in the sub-step S202-4 or for the second path 302-2 in the step S206) may comprise that the respective path is unwrapped for all interactions involving specular reflection (i.e., mirroring the path and the downstream interaction objects of the environment 300) to remove the specular interaction points 322.

[0234] Herein, to "unwrap" may be defined as the replacement of the remainder of a path after (i.e., "downstream") a specular reflection 602 by its mirror image (i.e., the mirrored path), when mirrored in a plane coplanar with the surface (at the point of reflection) in which the specular reflection 320 takes place. This may be implemented using for example imaging methods and involves imaging of both the interaction points 322 and the interaction objects 308 (e.g., a line along a diffraction edge 324 and a specular reflective surfaces 324) with which the path (and thus the mirrored path) interacts.

[0235] The path length of the mirrored (i.e. unwrapped) path is reduced, e.g., by apply a "taut string" process to get the shortest unwrapped path, optionally via the zero or more mirrored diffractive edges downstream of the mirrored path. Herein "zero or more" refers to all those diffraction edges (if any) with which the path interacts, so that the mirrored path also interacts (i.e. remains attached as a boundary condition) with the correspondingly mirrored diffractive edges 324 downstream of the (temporarily) eliminated specular reflection 320.

[0236] The minimization of the path length may be performed in one way or another.

[0237] In a sub-step of the minimization of the path length, the path is de-imaged, i.e. the imaging performed in the sub-step prior to the minimization of the mirrored path length is reversed, of course including the effect of reducing of the path length so that the resulting path is different. That comprises reintroducing the one or more reflective surfaces 324 and the zero or more diffractive edges 324. At each reintroduction of one of the one or more reflective surfaces 324, the remaining path (and, in a first variant, the zero or more diffractive edges 324) downstream of the corresponding point of the reintroduced reflection are mirrored (i.e., de-imaged) with respect to a plane coplanar with the reintroduced reflective surface 324. In a second variant, the zero or more diffractive edges 324 are determined directly from the structural information of the environment 300, e.g. obtained in the step S202 for the first path or in the step S204 for the second path. The sub-step of de-imaging includes determining updated reflection interaction points 322 (which are different from the reflection interaction points prior to the path length minimization) on the original respective surfaces 324 (e.g., according to the obtained structural information). Furthermore the zero or more diffraction interaction points 322 are updated, e.g. by mirroring the diffraction points of the shorted path back along the original diffractive edges 324 (e.g., according to the obtained structural information).

[0238] The path resulting from this minimization of the path length is the shortest path in the original environment 300 with the same sequence of interactions according as prior to the minimization of the path length.

[0239] All practically useful tools for predicting deterministic wireless channel properties are based on ray tracing. Such tools are essential for providing propagation analysis (such as channel models) for wireless systems (such as radio access networks, RAN) based on site-specific information, for example for real- word testing of radio equipment within the laboratory based on emulated signal propagation, system analysis of radio access networks, development (such as modification and expansion of antenna systems), and performance optimization. The ray tracing method provides a path (one or more continuous line segments) representation of the propagating waves between a transmitter and a receiver in the presence of geometric models of the propagation environment. Ray tracing is inherently computationally challenging due to the size (in wavelengths) of the propagation environment.

[0240] The subject technique is applicable to ray tracing tools for path finding that support several types of path interactions, e.g. wherein at least one of the zero or more interactions 320-1 in the first path 302-1 are used to infer the existence of other potential interactions 320-2, e.g. included in the zero or more changed interactions 320-2. Hence, the method 200 is particularly suited for ray tracing tools dedicated to wireless propagation channel predictions, since geometrical optics-based wireless propagation modeling involves a variety of interaction types, these types being related to point-, line-, and surface-interactions. The method is computationally efficient as it generates new paths based on paths that have already been ray-traced.

[0241] Embodiments of the technique address the problem of conventional up-sampling being limited to the generation of paths having the same path signatures as the ray-traced initial paths on which the up- sampled paths are based. Embodiments of the technique solve the problem by generating (i.e., creating) further path candidates having modified path signatures based on the properties of the path signatures of the ray-traced paths in a base set of initial paths.

[0242] When the method 200 is applied to a new node not present in the base set of nodes 305, for a given ray- traced path 302-0, path interactions 320-2 that can be derived from existing path interactions 320-1 are identified. New paths 302-2, with new path signatures, are introduced where the existing interaction type for a given base path 302-0 or first path point 302-1 is changed to an interaction type that can be supported by a point 324-2, line 324-2, or surface 324-2 associated with said interaction point 322 of the base interaction 320-1.

[0243] For example, a wedge 324-1 has two half-planes 324-2 associated with it, and these half-planes 324-2 can support surface-related interactions 320-2 such as specular reflection and diffuse scattering offer. Similarly, a diffuse interaction 320-1 is associated with a plane 324, which can support a specular reflection 320-2, or a diffuse interaction 320-2 at another point, if the corresponding interaction point 322 falls within the boundaries of the corresponding surface of the interaction object 308.

[0244] Two separate ray-traced path scenarios, which are embodiments of the method 200, exemplify how specific interaction types of the first interaction 320-1 can be used for determining S206 one or more second paths 302-2 (i.e., new paths), the first scenario involving ray-traced paths 302-0 with wedge diffraction interactions 320-1 and the second involving paths 302-0 with diffuse interactions 320-1, as schematically illustrated in Figs. 8 and 9, respectively.

[0245] In the scenario involving a base path 302-0 (similar to Figs. 4 and 5) with a comer diffraction from ray tracing S202-1, one or two spatially modified S202-3 first paths 302-1 are generated by shifting the endpoints to the second station 306, as a non-limiting example of the step S202.

[0246] In the step S206, by replacing the interaction point 322 associated with the diffraction interaction 320-1 by an interaction point 322 for specular reflection 320-2 on one (as illustrated in Fig. 8) or both surfaces 324-2 attached at the wedge (reference sign 324-1 analogous Fig. 4A, not shown in Figs. 4 and 8 as it is covered by the interaction point 322 in the top view).

[0247] In the scenario shown in Fig. 8, the specular reflection point 322 of the changed interaction 320-2 may be placed anywhere in the plane 324-2 of the corresponding surface. Typically, visibility requirements will be applied for the surface 324-2 of the new interaction point 322 and path points both before and after the new point 322 in the sequence of interactions of the second path 302-2. A scalar product between a normal vector of the respective surface 324-2 and a vector connecting endpoint 306 and interaction point 322 may indicate (e.g., by the sign of the scalar product), which one of the surfaces 324-2 is visible for a convex wedge 324-1.

[0248] In other words, Fig. 8 illustrates a method 200 of generating path candidates 302-2 having interactions 322 with new interaction types on one or both surfaces 324-2 associated with a wedge 324-1 for which ray-traced paths 302-0 exist for the lower-resolution set of base nodes 305. Visibility requirement can be applied to disallow path candidates 302-2 (e.g., as indicated by the crossed-out interaction point) passing through a surface associated with the new interaction 320-2. In the scenario of Fig. 9, a first path 302-1 resulting from ray tracing S202-1 (optionally with spatial modification S202-3 for shifting endpoints from a base point 305 to a second station 306) comprises a diffuse interaction 320-1. A second path 302-2 (as a new path) is generated S206 by replacing the interaction point 322 of the first path 302-1 associated with the diffuse interaction 320-1 by a specular reflection point 322 on the surface 324-2, where the diffuse interaction point 322 of the changed interaction 320-2 is located.

[0249] In any case, the second path 302-2 may be generated by a shortest path algorithm, which effectively “slides” the interaction point 322 on the surface constraint 324-2 of the changed interaction 320-2 to the point 322 of specular reflection 320-2. The shortest path algorithm will also adjust all other points related to line- and surface-interactions in the second path 302-2 as needed to fulfill Fermat’s principle for the full path 302-2.

[0250] Figs. 10, 11, and 12 schematically illustrate an embodiment of the method 200, wherein the changing of the at least one (as the second alternative of the "zero or more") interactions 320-1 of the first path 302-1 comprises removing at least one interaction resulting in the zero or more changed interactions 320-2.

[0251] As schematically illustrated in Fig. 10, a base path 302-0 to a base point 305 (e.g., a grid point) comprises a (e.g., diffraction) interaction 320-1. The base path 302-0 may be obtained by ray tracing S202-1 or retrieved from a database S202-1.

[0252] The base path 302-0 is spatially modified S202-3 for the second station 306 (e.g., a new Rx point), which is schematically illustrated in Fig. 11. The result is the first path 302-1.

[0253] In the step S206 a second path 302-2 is determined from the base path 302-0 of Fig. 10 or the first path 302-1 of Fig. 11 with one interaction 320-1 (e.g., the diffraction illustrated in Figs. 10 and 11) removed. The result is the second path 302-2, which may be a direct path (i.e., with a single segment as illustrated in Fig. 12). Thus, the second path 302- includes a segment that is absent in the base path 302-0 (or the first path 302-1) due to blockage by another object 308 (e.g., a building).

[0254] While Figs. 10 to 12 schematically illustrate removing an interaction from the at least one interaction of the first path 302-1 for the example of removing a single point, variants of any embodiment can remove any subset or permutation of N > 1 interaction points.

[0255] Figs. 13 and 14 schematically illustrate an embodiment of the method 200, wherein the changing of the zero or more interactions 320-1 of the first path 302-1 comprises adding at least one interaction 320-2 resulting in the zero or more changed interactions 320-2. Noteworthy, adding an interaction 320-2 is not a mutually exclusive alternative to removing an interaction 320-1, since interaction can be added and removed at different locations along the same path. As schematically illustrated in Fig. 13, the base path 302-0 or the first path 302-1 (with or without spatial modification S202-3, the latter being illustrated in Fig. 13) leads to a base point 305 (e.g., a grid point), which may be identical to the second station 306. In the step S206 illustrated in Fig. 14, an interaction point 322 for the interaction 320-2 is added to the path 302-2. This interaction 320-2 may comprise scattering from an object 308 that is too small to be reliably captured by ray tracing S202-1 with a finite shooting resolution (i.e., a finite angular resolution of rays launched at the first station 304).

[0256] In a variant of any embodiment of the device 100 or the method 200, the one or more second paths 302-2 are checked for feasibility with respect to blockage (e.g., by the interaction objects 308 of the environment 300). This may exclude the crossed-out interaction point on the surface shown to the left of Fig. 8.

[0257] In general, a second path 302-2 resulting from (or within) the step S206 is retained if its path signature is unique. The path signature may be calculated for the second path 302-2 after one or more interaction points 322 of a corresponding base path 302-0 or first path 302-1 have been changed to generate the second path 302-2. A path signature value for the path signature of the second path 302-2 is compared with existing path signatures of base paths 302-0 or first paths 302-1, and the second path 302-2 is discarded if non-unique (e.g., if already stored in the database of the sub-step S202-2).

[0258] Fig. 15 show a flowchart of an implementation of the method 200 of determining wireless communication paths within an environment. The method 200 begins with an input operation, wherein a base path 302-0 is obtained. The base path 302-0 may be a predefined path obtained from a database according to S202-2 or newly determined through ray tracing or other means according to S202-1.

[0259] The method 200 further involves a decision-making process, wherein it is determined which points (e.g., one or more endpoints and / or interaction points) of the base path 302-0 are spatially modified to obtain a first path 302-1.

[0260] A new second path 302-2 with a revised path signature compared to the first path 302-1 is created according to the step S206. The revised path signature may involve altering the path's interactions with the environment, which may include changing, adding, and / or removing interaction points that affect the wireless propagation.

[0261] As a further sub-step of the second path determination S206, the newly created second path 302-2 is assessed to ensure it is a valid path for the propagation of wireless communication signals.

[0262] If the newly created path is determined to be valid, it is stored for further use (e.g., determining the electromagnetic propagation, the channel emulation, or any other physical action). For example, the determined one or more second paths are added to the database of viable paths or utilizing it in the wireless communication system to predict signal propagation more accurately. On the other hand, if the path fails to meet the validity criteria — perhaps due to not adhering to physical constraints or leading to inefficient (e.g., blocked) signal propagation — it is discarded.

[0263] A further embodiment of the method 200 described with reference to Fig. 16 comprises identifying S202- 1 by ray tracing for a given pair of base points 305 a base path 302-0. E.g., the base points 305 are members of a low-resolution set of grid points 305. The base path 302-0 includes zero or more interactions 320-1, e.g. via a comer 324-1 of a scatterer 308.

[0264] A new node position 306 is introduced in the step S202-3 and the last path segment of the ray-traced base path 302-0 is changed to attach to the new node 306, creating a first path 302-1 with the same path signature as the ray-traced base path 302-0, e.g. as illustrated in Fig. 17.

[0265] The step S206 detects that the first path 302-1 contains an interaction point 322 for wedge diffraction 320-1, and copies the first path 302-1 to yet another second path 302-2, changes the type of interaction from diffraction 320-1 to specular reflection 320-2, and position the changed interaction point 322 (at an arbitrary position) in the plane 324-2 of the surface attached to the comer where the interaction point 322 of the edge diffraction 320-1 was located. Fig. 18 illustrates an example of the second path 302-2.

[0266] Optionally, e.g. as illustrated in Fig. 19, the step S206 further checks for at least one of path uniqueness, visibility, apply shortest path (restricting the movement of the changed point 322 to the plane 324-2 of the interaction surface attached to the interaction comer) to make the interaction 320-2 of the interaction point 322 of the changed interaction a specular interaction, and check for blockage.

[0267] Since the technique does not require ray tracing for finding the one or more second paths (i.e., determining further paths), the technique can be applied based on a set of pre-computed base ray-traced paths (i.e., initial paths) for a low-density grid of base nodes 305, either standalone on a central processing unit (CPU) or on a combined CPU and GPU system. For efficiency, blockage detection may use GPU-based solutions if a graphics processing unit (GPU) is available.

[0268] Similar examples can be drawn for one or more second paths 302-2 that are discarded due to at least one of: (1) the check for uniqueness based on path signature, (2) the check for visibility between the surface of the new point and point before and after in the new path, and (3) the check for blockage of the final shortest path, and similarly for one or more second paths 302-2 where an interaction point 322 for specular reflection 320-2 replaces an interaction point 322 for diffuse scattering 320-1.

[0269] Each embodiment may be implemented with at least one of the following variant. Pruning variations

[0270] The step S202 (e.g., S202-1) contains a pruning sub-step, wherein very weak paths are discarded. Such pruning is done to limit the memory consumption for storing the identified paths, and the complexity involved in processing the paths in e.g. a wireless system simulator or channel emulator. In a further variant, since the subject technique is able to find paths that are potentially stronger e.g. the path with a specular reflection in step S206, it can be premature to prune paths before applying the method 200 (e.g., the step S206). In one embodiment of the device 100 or the method 200, the path pruning done during ray tracing S202-1 is adjusted in one or more of the following ways:

[0271] The threshold for retaining identified paths is lowered.

[0272] Paths are not pruned until after interaction changing step S206 has been performed.

[0273] The path pruning is done in two steps, during step S202 (e.g., S202-1) with a lower first threshold and the interaction changing step S206 with a higher second threshold.

[0274] Path point properties

[0275] The method 200 described has focused on replacing interaction types. A variation could also replace an interaction with another of the same type, such as a diffuse interaction at a nearby grid position, or a specular reflection on an adjacent surface 324-2 with a different angle.

[0276] A variation to replacing a wedge diffraction 320-1 by a specular interaction 320-2 is to instead replace it by a diffuse interaction 320-2. One way to determine deterministic diffuse scattering points on an object is to use a virtual grid as described (e.g., a gird of points 305 projected onto the surface 324-2). A new second path 302-2 may be constructed by replacing an interaction point 322 of a wedge diffraction 320-1 by a nearby interaction point 322 of a diffuse reflection 320-2 from a virtual grid in the plane 324-1 (being equal to the plane 324-2) of the, e.g., the diffraction wedge visible from the incoming ray direction.

[0277] Scattering objects

[0278] Adding and / or replacing interaction points 322 in the step S206 may be done with respect to small scattering objects 308 absent in the base ray tracing S202-1. Small scatterers 308 are impractical to include in base ray tracing S202-1, as they require very dense ray shooting (angular density at launching a bundle of rays). Furthermore, small scatterers 308 often represent moving objects in the environment 300 (vehicles, pedestrians), and therefore are more efficiently handled with up-sampling based on a ray tracing of a static scene. Replacing diffraction and reflection points in the neighborhood of an added small scatterer 308 with a scattering point 322 will provide a set of new second paths 302-2 scattering around this object 308, otherwise infeasible to resolve (i.e., to hit) with ray tracing S202-1. These one or more second paths 302-2 are also potentially stronger than corresponding diffracted paths, as scatterers can have favorable conductivity and directional scattering properties. The small objects 308 may be of decimeter (dm) size. Instead of dense ray-tracing S202-1, it is added in post-processing S206. A trigger for including the object 308 in the step S204 may be its motion (e.g., an intersection or vicinity to the first path). A criterion for the inclusion may be that segments of the first path 302-1 are close enough to the object or strong enough segments.

[0279] Data compression

[0280] The method 200 described may be utilized to compress the data created during ray tracing S202-1 by removing second paths 302-2 from a database that can be easily recreated based on first paths 302-1 according to the method 200. For instance, diffuse interactions can lead to a great number of paths. Compressing (e.g., collapsing) them to diffractions for storage (e.g., in memory) and upon request, recreating them using an embodiment of the method 200. A parameter for the point density of diffusive interactions on a surface could be used to re-generate the diffusive points, or the diffusive points are stored.

[0281] General interactions

[0282] Embodiments of the method 200 uses edge diffractions 320-1 to create new interactions 320-2 on planes 324-2 connected to the edge 324-1. A variant may be to use comers 324-1 of the wedges (intersection points of multiple edges), i.e., comer diffractions to create new second paths 302-2 on edge diffractions 320-2 and / or connected planes 324-2 for surface scattering 320-2 or specular reflection 320-2.

[0283] Fig. 20 shows a schematic block diagram for a radio device embodiment of the device 100. The device 100 comprises processing circuitry, e.g., one or more processors 2004 for performing the method 200 and memory 2006 coupled to the processors 2004. For example, the memory 2006 may be encoded with instmctions that implement at least one of the modules 102, 104, and 106.

[0284] The one or more processors 2004 may be a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, microcode and / or encoded logic operable to provide, either alone or in conjunction with other components of the device 100, such as the memory 2006, wireless access device (e.g., radio device) functionality. For example, the one or more processors 2004 may execute instructions stored in the memory 2006. Such functionality may include providing various features and steps discussed herein, including any of the benefits disclosed herein. The expression "the device being operative to perform an action" may denote the device 100 being configured to perform the action.

[0285] As schematically illustrated in Fig. 20, the device 100 may be embodied by a radio device 2000, e.g., functioning as a UE. The radio device 2000 comprises a radio interface 2002 coupled to the device 100 for radio communication with one or more other nodes, e.g., including base stations or other UEs. Fig. 21 shows a schematic block diagram for an access network node embodiment of the device 100. The device 100 comprises processing circuitry, e.g., one or more processors 2104 for performing the method 200 and memory 2106 coupled to the processors 2104. For example, the memory 2106 may be encoded with instructions that implement at least one of the modules 102, 104, and 106.

[0286] The one or more processors 2104 may be a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, microcode and / or encoded logic operable to provide, either alone or in conjunction with other components of the device 100, such as the memory 2106, access network node (e.g., base station) functionality. For example, the one or more processors 2104 may execute instructions stored in the memory 2106. Such functionality may include providing various features and steps discussed herein, including any of the benefits disclosed herein. The expression "the device being operative to perform an action" may denote the device 100 being configured to perform the action.

[0287] As schematically illustrated in Fig. 21, the device 100 may be embodied by a base station 2100, e.g., functioning as a gNB. The base station 2100 comprises a wired and / or radio interface 2102 coupled to the device 100 for communication with one or more other access nodes, e.g., including base stations, and / or for radio communication with one or more UEs.

[0288] Fig. 22 shows a schematic block diagram for a further embodiment of the device 100. The device 100 comprises processing circuitry, e.g., one or more processors 2204 for performing the method 200 and memory 2206 coupled to the processors 2204. For example, the memory 2206 may be encoded with instructions that implement at least one of the modules 102, 104, and 106.

[0289] The one or more processors 2204 may be a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, microcode and / or encoded logic operable to provide, either alone or in conjunction with other components of the device 100, such as the memory 2206, core node functionality or edge computing functionality. For example, the one or more processors 2204 may execute instructions stored in the memory 2206. Such functionality may include providing any of the steps and functions discussed herein. For example, steps and functions disclosed in the context of the radio device 2000 and / or the network node 2100 may alternatively be performed by the core node 2200 or edge computing node 2200.

[0290] As schematically illustrated in Fig. 22, the device 100 may be embodied by a core network node 2200, e.g., a function fortesting and validation of 5G systems and / or protocols under realistic channel conditions. The core network node 2200 comprises a wired and / or radio interface 2202 coupled to the device 100 for communication with access nodes, e.g., including base stations 2100, and / or for radio communication with one or more UEs 2000.

[0291] The embodiments of the Figs. 20 to 22 may be located in the environment 300. The one or more interaction objects 308 may be located within a cell served by a network node 2100 (also referred to as base station, e.g., a gNB) of an access network (AN), e.g. a radio access network (RAN). The access network is served by a core network (CN) comprise at least one CN node 2200. The AN node 2100 or the CN node 2200 may embody the device 100.

[0292] The access network node 2100 provides wireless access (e.g., in the optical spectrum or radio access) to wireless devices (e.g., radio devices 2000) such as a mobile station or user equipment (UE). The UE may be referred to by the reference sign 2000, if the UE acts as the device 100, e.g. as the first station 304 or the second station 306.

[0293] Any one of the wireless access device 2000 and the access network node 2100 may act as the first station 304 or the second station 306.

[0294] In a variant of any embodiment, the one or more second paths 302-2 determined in the step S206 are recorded. Based on the determined one or multiple paths 302-2, a physical action is performed and / or the channel of the wireless communication is modeled in a subsequent step.

[0295] In one example of the physical action, the device 100 comprises an emulating unit. In developing and testing radio communication equipment, it is desirable to replicate the conditions that are expected when the equipment is deployed and used in the environment 300. To this end, the physical channel of the wireless communication is emulated based on the determined one or more second paths 302-2 (and optional the first paths 302-1) between at least one transmitter node 304 and at least one receiver node 306. The emulation may be based on the channel modeled based on the one or more second path 302-2. It is noted that "shortest" may refer to a local minimum of the length in the environment 300 or a minimum of the length given the sequence of zero or more changed interactions.

[0296] The embodiment of the device 100 for emulation comprises an RF input and an RF output coupled to the transmitter node 304 and the receiver node 306, respectively, to let the equipment experience radio channels of different kinds. The technique can be applied in this context by letting the device 100 generate the radio channels to be emulated. Real-time or near real-time determining of the one or more second path 302-2 of the propagation enables real-time or near real-time emulation of the radio channel, which is important for this use case.

[0297] Performing the physical action based on the determined one or more second paths may comprise transmitting or receiving the wireless communication based on the one or more propagation path 302-2 determined in the step S206. Alternatively or in addition, the interface 2102 may be a control interface (e.g., a network interface or an Fl interface). For example, the node 2100 may be a central unit (CU) of a network node (e.g., a gNB). Performing the physical action may comprise controlling the wireless communication in the environment 300 based on the determined S206 propagation path 302-2.

[0298] Alternatively or in addition, the physical action may comprise locating or handing-over a radio device in the environment 300. The transmission of the wireless communication, or the controlling of the wireless communication, may be adjusted (e.g. beamformed) to ensure compliance with regulations based on the determined one or more second paths, for example the determined electromagnetic (e.g., multipath) propagation. For example, an energy flux in the environment 300 may be determined based on the determined one or more second paths 302-2 and / or the modeled channel.

[0299] Alternatively or in addition, the physical action may comprise controlling directional gain and / or transmit power of the wireless communication in the environment 300. For example, a radio device 2000 (e.g., a UE) may determine its position or a network node 2100 (e.g., a gNB) may determine the position of a radio device 2000 in the environment 300 based on the one or more second paths 302-2 determined in the step S206.

[0300] In one embodiment, radio signals received at the radio device 2000 in the environment 300 are compared with radio signals expected (e.g., modeled in the step S206) at the at least one position in the environment 300 according to the determined propagation path 302-2. In another embodiment, the radio signals received from a radio device 2000 in the environment 300 at a network node 2100 are compared with radio signals expected (e.g., modeled) at the at least one position in the environment 300 according to the propagation path 302-2 determined in the step S206.

[0301] Alternatively or in addition, a construction or an upgrade of a radio access network (RAN), e.g., when a radio frequency of the RAN is increased, may depend on the one or more second paths 302-2 determined in the step S206. For example, the position for deploying at least one a base station 2100 (e.g. acting as transmitter 304 / 306 and receiver node 306 / 304) in the environment 300 may be determined based on the one or more second paths 302-2 (e.g., based on the modeled channel and / or the emulated channel as a function of the position).

[0302] In any embodiment, the propagation path 302-2, e.g. the modeled or emulated channel, may be determined in real-time, optionally for the transmitting of the wireless communication and / or the receiving of the wireless communication or the controlling of the wireless communication (or for initiating of the transmitting or the receiving of the wireless communication).

[0303] Throughout the method 200, a processing circuitry and memory within a computing device (e.g. referred to by reference signs 2004 and 2006, respectively, in Fig. 20, or the further to Figs. 21 and 22) may perform the execution of the steps S202 and S206 (and optionally S204), conditionally storing the one or more second paths, and ensuring that the newly determined S206 second paths enhance the design and analysis of wireless communication pathways.

[0304] As has become apparent from above description, at least some embodiments of the technique can more quickly and / or more accurately model a channel and / or a spatial path of a wireless communication (e.g., in a 5G RAN). This can improve beamforming, MIMO, interference mitigation, adaptive modulation and coding, dynamic resource allocation, and power control. These advantages, individually or collectively, can enhance network performance, increase network capacity, improve data rates, and optimize the overall user experience.

[0305] Unless specified otherwise, reference signs may have the following meaning:

[0306] 100 Device for determining paths

[0307] 102 First path obtainment module

[0308] 104 Interaction obtainment module

[0309] 106 Second path obtainment module

[0310] S202 Obtaining first path

[0311] S202-1 Determining base path

[0312] S202-2 Retrieving base path

[0313] S202-3 Spatially modifying base path

[0314] S202-4 Minimizing path length for first path

[0315] S204 Obtaining interaction object

[0316] S206 Determining second path

[0317] 300 Environment

[0318] 302-0 Base path

[0319] 302-1 First path, e.g. spatially modified base path

[0320] 302-2 Second path

[0321] 304 First station

[0322] 305 Base point

[0323] 306 Second station

[0324] 308 Interaction object, e.g. scatterer

[0325] 310 Region accessible by specular reflection

[0326] 320 Electromagnetic interaction

[0327] 320-1 Electromagnetic interaction of base path or first path

[0328] 320-2 Changed electromagnetic interaction of second path

[0329] 322 Interaction point of base path or first path or second path

[0330] 324 Interaction element of an interaction object

[0331] 324-1 Constraint for first path along first interaction element of interaction object 324-2 Constraint for second path along second interaction element of interaction object 2000 Radio device embodiment

[0332] 2004 Processing circuitry of radio device

[0333] 2006 Memory of radio device

[0334] 2100 Network node embodiment 2104 Processing circuitry of network node

[0335] 2106 Memory of network node

[0336] 2200 Core node embodiment

[0337] 2204 Processing circuitry of core node

[0338] 2206 Memory of core node

[0339] Many advantages of the present invention will be fully understood from the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the units and devices without departing from the scope of the invention and / or without sacrificing all of its advantages. Since the invention can be varied in many ways, it will be recognized that the invention should be limited only by the scope of the following claims.

Claims

Claims1. A device (100) for determining paths (302-1, 302-2) of a wireless communication between a first station (304) and a second station (306) in an environment (300), the device (100) comprising memory (2006; 2106; 2206) operable to store instructions and processing circuitry (2004; 2104; 2204) operable to execute the instructions, such that the device (100) is operable to: obtain (S202) one or more first paths (302-1) between the first station (304) and the second station (306), wherein each of the one or more first paths (302-1) comprises zero or more electromagnetic interactions (320-1) within the environment (300); and determine (S206) one or more second paths (302-2) between the first station (304) and the second station (306) based on the one or more first paths (302-1) by changing the zero or more interactions (320-1) and minimizing a path length of the one or more second paths (302-2) in accordance with the zero or more changed interactions (320-2).

2. The device (100) of claim 1, wherein the changing of the zero or more interactions (320-1) for the second path (302-2) comprises at least one of: adding, along at least one of the one or more second paths (302-2), one or more interactions (320-2) absent along the first path (302-1); and removing, for at least one of the one or more second paths (302-1), one or more interactions (320- 1) present in the first path (302-1).

3. The device (100) of claim 1 or 2, wherein the obtaining (S202) of the one or more first paths (302-1) between the first station (304) and the second station (306) comprises: determining (S202-1) the one or more first paths (302-1) by ray tracing a plurality of rays launched in different directions from the first station (304) until hitting a capture surface enclosing the second station (306); spatially modifying (S202-3) each of the determined (S202-1) one or more first paths (302-1) by shifting an endpoint from the capture surface to the second station (306) without changing the zero or more interactions (320-1) of the respective one of the one or more first paths (302-1); and minimizing (S202-4) a path length of the spatially modified (S202-3) one or more first paths (302-1) in accordance with the zero or more interactions (320-1).

4. The device (100) of claim 1 or 2, wherein the obtaining (S202) of the one or more first paths (302-1) between the first station (304) and the second station (306) comprises: determining (S202-1) one or more base paths (302-0) by ray tracing a plurality of rays launched in different directions from one or more first base points (305) in the vicinity of the first station (304), or by ray tracing a plurality of rays passing through the vicinity of the first station (304), to one or more second base points (305) in the vicinity of the second station (306) or passing through the vicinity of the second station (306); or retrieving (S202-2) the one or more base paths (302-0) from a database of base paths (302-0) covering the environment (300); spatially modifying (S202-3) the one or more base paths (302-0) to connect the first station (304) and the second station (306) without changing the zero or more interactions (320-1) of the respective one of the one or more base paths (302-0); and minimizing (S202-4) a path length of the spatially modified (S202-3) one or more base paths (302-1) in accordance with the zero or more interactions (320-1) resulting in the one or more first paths (302-1).

5. The device (100) of any one of claims 1 to 4, wherein the at least one interaction (320-1) defines a constraint (324-1) of an interaction point (322) of the first path (302-1) when minimizing the path length of the first path (302-1) and / or the at least one changed interaction (320-2) defines a constraint (324-2) of an interaction point (322) of the second path (302-2) when minimizing the path length of the second path (302-2), and wherein the changing of the least one interaction (320-1) of the first path (302-1) compared to the least one interaction (320-2) of the second path (302-2) involves a change of the constraint (324-1; 324-2).

6. The device (100) of any one of claims 1 to 5, wherein the at least one interaction (320-1) of the at least one first path (302-1) constrains an interaction point (322) of the at least one interaction (320-1) to an edge (324-1) and wherein the at least one changed interaction (320-2) of the at least one second path (302-2) constrains the interaction point (322) of the at least one changed interaction (320-2) to a surface (324-2), wherein the edge (324-1) is on a border of the surface (324-2), or wherein the at least one interaction (320-1) of the at least one first path (302-1) constrains an interaction point (322) of the at least one interaction (320-1) to a surface and wherein the at least one changed interaction (320-2) of the at least one second path (302-2) constrains the interaction point (322) of the at least one changed interaction (320-2) to an edge, wherein the edge is on a border of the surface.

7. The device (100) of any one of claims 1 to 6, wherein the device (100) is further operable to: determine an electromagnetic propagation of the wireless communication in the environment(300) from the first station (304) to the second station (306) based on a superposition of contributions of the one or more first paths (302-1) and the one or more second paths (302-2).

8. The device (100) of any one of claims 1 to 7, wherein each of the at least one interaction (320-1; 320-2) comprises at least one of:- an interaction point (322) on the respective path (302-1; 302-2) at which the respective interaction (320-1; 320-2) occurs;- an interaction element (324-1; 324-2) of an interaction object (308) in the environment (300) with which the respective interaction (320-1; 320-2) occurs, optionally wherein the interaction element (324-1; 324-2) of the interaction object (308) defines a constraint (324-1; 324-2) of the minimization of the path length; and- an interaction type of the respective interaction (320-1; 320-2), optionally wherein the interaction type is one of reflection, specular reflection, diffusive reflection, diffraction, transmission, and refraction.

9. The device (100) of any one of claims 1 to 8, wherein the changing of the zero or more interactions (320-1) comprises changing a type of at least one interaction (320-1) in the first path (302-1) for the at least one changed interaction (320-2) in the second path (302-2), optionally wherein an interaction object (308) of the at least one changed interaction (320-2) is unchanged compared to the at least one interaction (320-1) in the first path (302-1).

10. The device (100) of any one of claims 1 to 9, wherein each of the one or more first paths (302-1) and / or the one or more second paths (302-2) comprises one or more path segments of the respective path (302-1; 302-2), optionally wherein each interaction point (322) of the at least one interaction (320-1; 320-2) joins a pair of subsequent path segments of the respective path (302-1; 302-2).

11. The device (100) of any one of claims 1 to 10, wherein the device (100) is further operable to: obtain (S204) one or more interaction objects (308) along the one or more first paths (302-1), wherein the determining (S206) of the one or more second paths (302-2) comprises adding one more path segments to at least one of the one or more second paths (302-2) based on at least one of the one or more first paths (302-1) for one or more added interactions (322) where the at least one first path (302-1) intersects with at least one of the obtained (S204) one or more interaction objects (308).

12. The device (100) of any one of claims 1 to 11, wherein the device (100) is further operable to at least one of: perform or initiate a physical action that is dependent on the determined (S206) one or more second paths (302-2) in the environment (300), optionally wherein the physical action comprises modelling a channel of the wireless communication along the determined (S206) one or more second paths (302-2) in the environment (300); andmodel a channel of the wireless communication along the determined one or more second paths (302-2) in the environment (300), optionally wherein the modeling of the channel further comprises performing or initiating a physical action that is dependent on the modeled channel.

13. The device (100) of claim 12, wherein the physical action comprises: transmitting the wireless communication at the first station (304; 2000; 2100) towards the second station (306; 2100; 2000) along the determined (S206) one or more second paths (302-2) in the environment (300) and / or based on the modeled channel; receiving the wireless communication from the first station (304; 2000; 2100) at the second station (306; 2100; 2000) along the determined (S206) one or more second paths (302-2) in the environment (300) and / or based on the modeled channel; transmitting the wireless communication at the second station (306; 2000; 2100) towards the first station (304; 2100; 2000) along the determined (S206) one or more second paths (302-2) in the environment (300) and / or based on the modeled channel; and / or receiving the wireless communication from the second station (306; 2000; 2100) at the first station (304; 2100; 2000) along the determined (S206) one or more second paths (302-2) in the environment (300) and / or based on the modeled channel.

14. A method (200) of determining paths (302-1, 302-2) of a wireless communication between a first station (304) and a second station (306) in an environment (300), the method (200) comprising or initiating: obtaining (S202) one or more first paths (302-1) between the first station (304) and the second station (306), wherein each of the one or more first paths (302-1) comprises zero or more electromagnetic interactions (320-1) within the environment (300); and determining (S206) one or more second paths (302-2) between the first station (304) and the second station (306) based on the one or more first paths (302-1) by changing the zero or more interactions (320-1) and minimizing a path length of the one or more second paths (302-2) in accordance with the zero or more changed interactions (320-2).

15. A computer program product comprising program code portions for performing the functionality of any one of the claims 1 to 13 or the steps of claim 14 when the computer program product is executed on one or more computing devices (2004; 2104; 2204), optionally stored on a computer-readable recording medium (2006; 2106; 2206).

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