Technique for determining a wireless propagation path

Abstract

A technique for determining a path (304) of a wireless communication in an environment (300) is provided. As to one aspect of the technique, a device (100) for determining a path (304) of a wireless communication in an environment (300) is provided. The device (100) comprises memory (1506; 1606; 1706) operable to store instructions and processing circuitry (1504; 1604; 1704) operable to execute the instructions, such that the device (100) is operable to obtain (S202) structural information indicative of one or more reflective surfaces (306) in the environment (300). The device (100) is further operable to determine (S204) a first path (302) in the environment (300) from a finite set of traced rays originating from a first station (400; 402; 1500; 1600) in the environment (300) and intersecting a capture surface (404) of a second station (402; 400; 1600; 1500) in the environment (300). The device (100) is further operable to modify (S206) the structural information by eliminating (S206A) the one or more reflective surfaces (306) along the first path (302) resulting in a mirrored (S206B) first path (302'). The device (100) is further operable to determine (S208) a second path (304') by reducing a length of the mirrored (S206B) first path (302') according to the modified (S206) structural information. The device (100) is further operable to determine (S210) a third path (304) by reintroducing (S210A) the one or more reflective surfaces (306) along the second path (304') resulting (S210B) in a third path (304). The device (100) is further operable to perform or initiate a physical action (S212) that is dependent on the determined (S210) third path (304) in the environment (300).

Description

[0001] TECHNIQUE FOR DETERMINING A WIRELESS PROPAGATION PATH

[0002] Technical Field

[0003] The present disclosure relates to a wireless communication technique based on rapidly determining a wireless communication path in a given environment. More specifically, and without being limited thereto, a device and a method are disclosed for determining a path of a wireless communication in an environment.

[0004] Background

[0005] A ray optical approximation predicts electromagnetic propagation efficiently in certain environments. It relies on the assumption that electromagnetic propagation can be treated as a collection of rays, which travel in straight lines and undergo reflection and refraction at interfaces in the environment. Ray optical approximation can predict optical wireless communications (OWC) as well as radio wave propagation, e.g. if the dimensions of objects and the distances between objects in the environment are significantly larger than a carrier wavelength. 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.

[0006] 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.

[0007] Conventional ray optical techniques to predict propagation are based on ray tracing, also referred to as ray launching and "shooting and bouncing rays" (SBR), which requires launching a plurality of rays from an origin such as a transmitter node. The rays are allowed to interact with objects representing the geometry of the propagation environment, until captured at a receiver node. Ray tracing is by necessity performed with finite resolution, which means that rays, and by extension the paths built from segments of rays, sample space discretely. Therefore, the computational cost for determining the dominant paths grows rapidly with the size and complexity of the environment.

[0008] Summary

[0009] Accordingly, there is a need for a technique that efficiently determines a wireless propagation path in complex and realistic environments. An alternative or more specific object is to close the loop between structural information obtained for a propagation environment and controlling a wireless network in the environment in real-time.

[0010] As to a device aspect, a device for determining a path of a wireless communication 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 structural information indicative of one or more reflective surfaces in the environment. The device is further operable to determine a first path in the environment from a finite set of traced rays originating from a first station in the environment and intersecting a capture surface of a second station in the environment. The device is further operable to modify the structural information by eliminating the one or more reflective surfaces along the first path resulting in a mirrored first path. The device is further operable to determine a second path by reducing a length of the mirrored first path according to the modified structural information. The device is further operable to determine a third path by reintroducing the one or more reflective surfaces along the second path resulting in a third path. The device is further operable to perform or initiate a physical action that is dependent on the determined third path in the environment.

[0011] For example, the device may perform a combination of imaging (i.e., mirroring) and shortest path computation (i.e., reducing the length) for propagation paths that involve one or more reflections at reflective surfaces (e.g., specular reflections) and optionally diffractions at diffractive edges (e.g., wedge diffractions).

[0012] The device can perform ray-tracing with sparse launching of rays according to the finite set, which saves both execution time and computer memory, for a given level of propagation channel fidelity. Still, the third path resulting from the technique can fulfill Fermat’s principle, which means that modules for the electromagnetic propagation under (e.g., specular) reflection and (e.g., wedge) diffraction can be applied without approximations.

[0013] Furthermore, since embodiments of the device can determine the true shortest path as the third path, 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". Duplicates may be identified based on polygons or indices of planar objects (e.g., triangles or rectangles, or other planar objects, e.g. an indexed polygon) or edges (e.g. wedges or other linear objects) with which a path interacts, or based on coefficients uniquely representing the objects (for example coefficients in the representation of a plane), or based on hashes calculated from one of the above.

[0014] Eliminating the reflective surfaces can enable embodiments of the technique to reduce the length of the second path independently of the reflective surfaces, e.g. analogously to tautening a line in the modified environment. While conventional techniques for approximating a shortest path rely on a high angular density of rays originating from the transmitter to accidentally find a good approximation for the shortest path, embodiments of the technique require limited computation resources according to the finite set of rays and can determine the shortest path (e.g. an exact local minimum) by eliminating the reflections in a modified environment and returning to the original environment after the minimization.

[0015] Same or further embodiments can determine the third path as the actual shortest path, e g. by performing the determining of the second path in a closed form and / or without an approximate or iterative approach, which is less accurate or can be time-consuming to converge with comparable accuracy.

[0016] Same or further embodiments can perform less complex closed-form algorithms to determine the second path and / or the third path. In contrast, a reference example using a more complex closed-form algorithms (without the eliminating and reintroduction of the reflective surfaces) would involve significantly more boundary conditions, e.g. with points of the path being constrained to the plane of the reflective surfaces, in addition to being constrained to the lines of the diffractive edges (e.g., wedges). In case diffractive edges are present in the environment, embodiments may determine the second path, after the eliminating of all reflective surfaces, by directly finding the shortest path (i.e., an example of the second path) for the mirrored first path (also referred to as unwrapped path) with all points of interaction with the diffractive edges being constrained to be on their respective diffractive edge.

[0017] 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.

[0018] The technique may be implemented as a device or a method of computing a shortest path, e g. for paths comprising at least one of reflections and diffractions in a given environment.

[0019] 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 third path and the structural information of the environment.

[0020] The modeling of the channel may take the propagation of a radio wave along the determined third path into account. The propagation of the radio wave may include interactions of reflection at one 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.

[0021] 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.

[0022] As to another device aspect, a device for determining a path of a wireless communication 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 structural information indicative of one or more reflective surfaces in the environment. The device is further operable to determine a first path in the environment from a finite set of traced rays originating from a first station in the environment and intersecting a capture surface of a second station in the environment. The device is further operable to modify the structural information by eliminating the one or more reflective surfaces along the first path resulting in a mirrored first path. The device is further operable to determine a second path by reducing a length of the mirrored first path according to the modified structural information. The device is further operable to determine a third path by reintroducing the one or more reflective surfaces along the second path resulting in a third path. The device is further operable to model a channel of the wireless communication along the determined third path and the structural information of the environment.

[0023] Any feature or step disclosed in the context of the one device aspect may also be applicable to the other device aspect. For example, any feature or step of the modeling disclosed for the one device aspect may also be applicable to the other device aspect. The one and / or the other device aspect may comprise any feature and / or any step disclosed hereinbelow.

[0024] The reducing of the 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.

[0025] In an embodiment, the modeling of the channel may comprise or the device may be further operable to perform or initiate a physical action that is dependent on the modeled channel.

[0026] 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 third path in the environment.

[0027] 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.

[0028] In any aspect, the device for determining a path may refer to the third path. In the first aspect, the device for determining a path may be implemented as a device for performing a physical action based on a path of a wireless communication. In the second aspect, the device for determining a path may be implemented as a device for modeling a channel of a wireless communication.

[0029] While the technique is described for the device, a method aspect of the technique provides a method of determining a path 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 a shortest path between the transmitter and the receiver, e g. for improved fidelity of a channel estimation of radio frequency propagation in the environment.

[0030] In an embodiment, the modifying of the structural information may comprise, for each of the one or more reflective surfaces along the first path, eliminating the one or more reflective surfaces. Alternatively or in addition, the modifying of the structural information may comprise, for each of the one or more reflective surfaces along the first path, mirroring with respect to the eliminated reflective surface the first path, the zero or more remaining reflective surfaces, and / or the second station downstream of a point of reflection on the eliminated reflective surface. By eliminating the one or more reflective surfaces, the second path may be determined as a straight line from the first station to the (mirrored) second station or as a sequence of straight lines from the first station via one or more diffractive edges to the second station.

[0031] In an embodiment, the determining of the second path may comprise minimizing a length of the mirrored first path according to the modified structural information.

[0032] "According to the modified structural information" may mean that the modified structural information defines one or more boundary conditions for the minimizing.

[0033] "Minimizing the length of the mirrored first path" may mean determining the second path as the shortest path or a path shorter than the mirrored first path. This step may be performed in closed form (e.g., directly resulting in the second path having the reduced or minimized length) or may be performed iteratively or approximately (e.g., with an on-going minimization). In other words, minimizing may encompass any method that is based on a minimization of the length or that tends towards reducing the length.

[0034] In an embodiment, the determining of the third path may comprise, for each of the reflective surfaces along the second path, reintroducing each of the one or more reflective surfaces along the second path. Alternatively or in addition, the determining of the third path may comprise, for each of the reflective surfaces along the second path, mirroring the second path with respect to the reintroduced reflective surface downstream of a point of reflection on the respectively reintroduced reflective surface.

[0035] Herein, "mirroring with respect to the (reintroduced) reflective surface" may mean mirroring with respect to the plane of the (reintroduced) reflective surface, e.g., regardless of a size of the (reintroduced) reflective surface.

[0036] "Mirroring the second path downstream of the point of reflection on the reintroduced reflective surface" may mean that the third path results from mirroring the second path on the plane of the respectively reintroduced reflective surface.

[0037] The determining of the third path may further comprise (e.g., for each of the reintroduced one or more reflective surfaces along the second path) mirroring each object of the environment that is influencing (e.g., interacting with) the (e.g., second or third) path downstream of the respectively reintroduced reflective surface of the one or more reflective surfaces.

[0038] Herein, "downstream" may refer to a direction within the environment from any point of reflection on the eliminated or reintroduced reflective surface towards the first station or towards the second station. The opposite direction may be referred to as "upstream". The direction "downstream" may be chosen independently for each step in the modifying of the structural information (i.e., for mirroring all objects downstream of the respectively eliminated one of the one or more reflective surfaces along the first path) and / or for each step in the determining of the third path (i.e., for mirroring all objects downstream of the respectively reintroduced one of the one or more reflective surfaces along the second path).

[0039] It is noted that one should not confuse (a) the direction "downstream" for consistently mirroring all objects downstream of the eliminated or reintroduced reflective surface), and (b) an order (or sequence) of elimination or reintroducing the individual reflective surfaces along the first path or the second path, respectively.

[0040] The order of performing the eliminating of the one or more reflective surfaces (for the modifying of the structural information) and / or the order of performing the reintroducing of the one or more reflective surfaces (for the determining of the third path) may be implemented independently of the direction "downstream". That is, the order of eliminating the one or more reflective surfaces along the first path and the order of reintroducing the one or more reflective surfaces along the second path may be the same direction "downstream" or the same direction "upstream". Alternatively, the order of eliminating the one or more reflective surfaces along the first path and the order of reintroducing the one or more reflective surfaces along the second path may be the opposite directions "downstream" and "upstream", respectively, or vice versa. Furthermore, the eliminating or reintroducing may start with any reflective surface (even an interior reflective surface along the first or second path between other reflective surfaces with which the first or second path interacts), as long as all reflective surfaces hit by the first path are eliminated and reintroduced.

[0041] In an embodiment, performing the physical action may comprise transmitting the wireless communication at the first station towards the second station along the determined third path 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 third path 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 third path 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 third path in the environment and / or based on the modeled channel.

[0042] 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.

[0043] 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.

[0044] Same or further embodiments can improve interference mitigation. For example, based on radio channel characteristics such as the determined third path 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 third path 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 atacking moving radio devices in real-time.

[0045] 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 third path and / or the modeled channel can optimize the overall system throughput and efficiency.

[0046] 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 third path, 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 third path, 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.

[0047] The direction "downstream" may or may not coincide with a direction of transmission of the wireless communication. For example, the first station may be a transmitter and the second station may be a receiver of the wireless communication, so that the direction "downstream" may correspond to a direction of signal propagation (e.g., along the third path). Alternatively (or in addition, e.g., in a bidirectional wireless communication), the transmitter may be the second station and the receiver may be the first station, so that the direction "upstream" may correspond to the direction of signal propagation.

[0048] 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 third path is determined, the modeling of the channel along the third path may be performed downstream (i.e., in the direction used for consistently mirroring all objects downstream of any one of the eliminated or reintroduced reflective surfaces) or "upstream".

[0049] Herein, mirroring an object (or a portion of a path) on the plane of the respectively eliminated reflective surface may mean that the mirroring is not limited by a size of the respectively eliminated reflective surface. The respectively eliminated reflective surface defines the plane of the mirroring. The mirroring may also be referred to as imaging.

[0050] Preferably, the mirrored objects of the environment (i.e., the modified environment) are not a mirrored image of the environment, because the mirroring is not applied equally to all objects in the environment. Rather, it is the temporal order of interaction with the first path (i.e., the location downstream of the respective point of reflection) that determines if the object is mirrored when eliminating the respective reflective surface.

[0051] In an embodiment, the determined first path may result from tracing the finite set of rays launched from the first station. Alternatively or in addition, at least one or each point, S2, of reflection of the third path may be offset on the respective reflective surface relative to the point, Si, of reflection of the first path. Alternatively or in addition, the device may be further operable to repeat the determining of the first path using the direction of the third path originating from the first station, if a point S2 of reflection of the third path is outside of an extent of at least one of the one or more reflective surfaces. Alternatively or in addition, the device may be further operable to change an endpoint of the first path from the intersection on the capture surface to a location of the second station.

[0052] Embodiments can achieve real-time control of the physical action by virtue of the finite set of rays to be traced and can eliminate a discretization error caused by the finite set by accurately determining the second path, and thus the third path as the shorted in the environment.

[0053] The finite set of rays originating from the first station (e.g., launched from the first station) may correspond to all or a subset of the vertices of a Platonic solid centered at the first station or subdivisions of edges between such vertices. Alternatively or in addition, the finite set of rays may correspond to randomly (e.g., pseudo-randomly) determined directions originating from the first station.

[0054] The point S2 of the third path may be offset on the respective reflective surface relative to the point Si of the first path due to the reducing (e.g., minimizing) of the length.

[0055] If a point of reflection of the third path falls outside of an extent (e.g. a size) of the corresponding reflective surface (or a point of reflection of the second path falls outside of a size of the corresponding mirrored reflective surface), e.g. according to the obtained structural information, the method may return to the determining of the first path using the initial ray of the third path originating from the first station. The obtained structural information may be indicative of the size.

[0056] 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.

[0057] By changing the endpoint after determining the first path based on the finite set and before determining the second path, the third path (as the shortest path) in the environment can be accurately determined even when starting with the finite set of traced rays.

[0058] In an embodiment, the obtained structural information may be further indicative of one or more diffractive edges in the environment. Alternatively or in addition, the step of modifying the structural information by eliminating each of the reflective surfaces along the first path may further comprise mirroring any of the one or more diffractive edges downstream of the point of reflection on the respectively eliminated reflective surface. Alternatively or in addition, each of the one or more mirrored diffractive edges may be a linear constraint for the second path (in the step of determining the second path) when reducing the length of the mirrored first path according to the modified structural information. Alternatively or in addition, the reducing of the length may comprise shifting the one or more points of the second path at the zero or more diffractive edges in the environment along the zero or more diffractive edges.

[0059] The diffractive edges may comprise linear boundaries of one or more objects in the environment (e.g., any object that is not transparent or opaque for the wireless communication, optionally in the optical or radio spectrum of electromagnetic radiation carrying the signals of the wireless communication). For example, any diffractive edge may be a linear boundary with an acute angle, such as a wedge. The one or more diffractive edges may or may not include wedges, e.g. since a tapering shape of edges may or may not contribute to a diffraction of the wireless communication (e.g., as long as the object is sufficiently opaque).

[0060] Eliminating the reflective surfaces enables embodiments of the technique to reduce (e.g., minimize) the length of the second path independent of the reflective surfaces, e.g. analogously to tautening a line that runs abutting the mirrored one or more diffractive edges in the modified environment.

[0061] Determining the second path by reducing the length of the mirrored first path according to the modified structural information may mean that (a) the length of the second path assumes a (e.g., local) minimum in the modified environment and / or (b) the length of the second path is reduced compared to the length of the mirrored first path and / or (c) the second path and the mirrored first path are topologically equivalent in the modified environment, i.e., the minimizing of the length does not cross the one or more diffractive edges and maintains the order in which the first and second paths pass the one or more diffractive edges.

[0062] Mirroring the zero or more diffractive edges downstream of the point of reflection on the respectively eliminated reflective surface may mean that all the zero or more diffractive edges of the one or more diffractive edges that are downstream of the point of reflection (i.e., the zero or more diffractive edges that interact with the first path between the point of reflection and the receiver) are mirrored. For example, the mirroring may be applied to all reflective surfaces and diffractive edges interacting with the first path downstream of the respective reflection point.

[0063] The tracing of any one of the rays in the finite set may comprise reflecting the ray at the respective reflection point Si intersecting any one of the reflective surfaces. Alternatively or in addition, the tracing of any one of the rays (e.g., originating from the first station and / or after one or multiple reflections from the one or more reflective surfaces in the environment) may comprise determining an interaction with a diffractive edge, if the ray intersects a capture surface around any one of the zero or more diffractive edges in the environment. The capture surface for (e g., partially) enclosing any one of the zero or more diffractive edges may be cylinders (or portions thereof) that surround the respective diffractive edges (e.g., coaxial with the diffractive edge). For example, determining the first path may comprise tracing a ray. If the ray intersects (i.e., hits) a capture surface (e.g., cylinder) that surrounds any one of the diffractive edges, the intersections (i.e., the hit point, e.g. the end point of an incoming line segment of the traced ray) may be indicative of (e.g., replaced by or moved to) the point on the diffractive edge (i.e., the linear boundary) closest to the line defined by the incoming line segment (i.e., the traced ray). This point (i.e., the point on the diffractive edge) may thus be a result of an adjustment of the last line segment. This point may be shifted (e.g., moved linearly) along the diffractive edge for determining the second path.

[0064] Preferably, the determining of the second path may comprise shifting each point of intersection along the respective diffractive edge to reduce the length (e.g., to find the shortest path) resulting in the second path. For example, while the initial point on the diffractive edge may be only an approximation based on the capture surface of the diffractive edge, embodiments can determine the corrected location of the point of intersection as the intersection between the second (or third) path and the diffractive edge.

[0065] The zero or more diffractive edges downstream of the respective point of reflection may be the zero or more remaining diffractive edges downstream (i.e., in the direction from the transmitter to the receiver) after the respective point of reflection. The remaining diffractive edges may be zero if the one or more diffractive edges of the environment are upstream of the point of reflection on the respectively (or currently) eliminated reflective surface. On the other hand, eliminating at least one of the reflective surfaces along the first path may further comprise mirroring at least one diffractive edge of the environment if there is a diffractive edge along the first path from the respective reflective surface in the downstream direction (e.g., towards the second station such as a receiver).

[0066] In an embodiment, the first path may be the shortest path among the finite set of traced rays that intersects the capture surface of the second station.

[0067] Tracing the finite set of rays may yield a multiplicity of paths having interaction points on the capture surface, e.g. in the same group of rays, i.e., the same order of the angular density of rays launched at the first station. Only one path of the multiplicity of paths may be needed or may be used as the first path. This reduction of computational complexity and increased control responsiveness can be achieved without loss of accuracy, e.g. since the same third path would be the result even if all paths intersecting the capture surface were subjected to the functionality of the device as the first path. The device may further prune duplicates, e.g. due to representing the same propagation path.

[0068] According to a first variant of any embodiment, multiple first paths are down-selected to only one baseline path before the mirroring and the reducing of the length.

[0069] In an embodiment, multiple first paths intersecting the capture surface of the second station may result from tracing the finite set of traced rays. For each of the multiple first paths, the structural information may be modified, the second path may be determined, and / or the third path may be determined. Alternatively or in addition, the device may be further operative to eliminate duplications among the multiple third paths resulting from the multiple first paths, respectively, e.g., by comparing path vertices of the multiple third paths. The channel may be modeled based on a sum of transfer coefficients computed for each of the multiple third paths.

[0070] According to a second variant of any embodiment, duplicates in multiple third paths may be eliminated. Optionally, transfer functions determined for each of the multiple (e g., different) third paths may be superimposed (e.g., added up) for modeling the channel of multi-path propagation.

[0071] In an embodiment, the determining of the second path, for each of the multiple first paths, may further comprise detecting and / or eliminating one or more second paths whose intersection point fall outside of the corresponding reflective surface (or, if any, the corresponding mirrored diffractive edge) of the modified structural information. Alternatively or in addition, the determining of the third path for each of the multiple first paths may further comprise detecting and / or eliminating one or more third paths whose interaction points fall outside of the respective reflective surface (or, if any, the respective diffractive edge) of the environment.

[0072] The method may comprise detecting and pruning (i.e., eliminating) one or more paths whose interaction points fall outside the surface for specular reflection or outside the segment for edge diffraction (i.e., the diffractive edge) as a result of the reducing (e.g., minimizing) of the length.

[0073] By detecting and eliminating such paths, embodiments of the device can achieve rapid real-time control based on the determined third path and / or the modeled channel, without contributions from unphysical paths.

[0074] In an embodiment, the device may further be operative to detect and / or eliminate one or more second paths (or third paths) whose interaction points are swapped compared to the first path or swapped between different reflective surfaces.

[0075] The method may comprise detecting and pruning (i.e., eliminating) one or more paths for which the interaction points become swapped as a result of reducing (e.g., minimizing) of the length. The determining of the second path (for each of the multiple first paths) and / or the determining of the third path (for each of the multiple first paths) may further comprises detecting and eliminating one or more third paths whose interaction points are swapped compared to the first path or swapped between different reflective surfaces.

[0076] By detecting and eliminating such paths, embodiments of the device can achieve rapid real-time control based on the determined third path and / or the modeled channel, without contributions from unphysical paths. For example, when the environment comprises different reflective surfaces abutting each other.

[0077] The swapping may be detected when reducing the length (e.g. when determining the shortest path) as the second path or after the mirroring for determining the third path.

[0078] As to a method aspect, a method of determining a path of a wireless communication in an environment is provided. The method comprises or initiates a step of obtaining structural information indicative of one or more reflective surfaces in the environment. Alternatively or in addition, the method comprises determining a first path in the environment from a finite set of traced rays originating from a first station in the environment and intersecting a capture surface of a second station in the environment. Alternatively or in addition, the method comprises modifying the structural information by eliminating the one or more reflective surfaces along the first path resulting in a mirrored first path. Alternatively or in addition, the method comprises determining a second path by reducing a length of the mirrored first path according to the modified structural information. Alternatively or in addition, the method comprises determining a third path by reintroducing the one or more reflective surfaces along the second path resulting in a third path.

[0079] The method may be a computer-implemented method.

[0080] 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 third path in the environment. Alternatively or in addition, the method may further comprise modeling a channel of the wireless communication along the determined third path and the structural information of the environment.

[0081] 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.

[0082] 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. Alternatively or in addition, the device may be embodied by a base station 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.

[0083] 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 (1700) is operable to perform any one of the steps and functionality disclosed for the device.

[0084] The physical action may be dependent on the determined third path.

[0085] In a first variant of any embodiment, the same device that is determining the third 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 third path. 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.

[0086] 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.

[0087] 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 third path 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.

[0088] 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 at least one third path, 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.

[0089] 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.

[0090] The subject technique can deal with channel modeling and its applications for a range of use cases. For a given computational complexity, the reducing of the length can increase a fidelity between the modeled channel and a (possibly hypothetical) 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 the mirrorings reduce computational complexity.

[0091] 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).

[0092] 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 third paths. For example, the electromagnetic propagation may be configured to associate to the third path 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 multiple third paths.

[0093] In any aspect, the one or more third 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).

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] The wireless communication in the environment may be performed (e.g., transmitted or received) or controlled (e.g., initiated) based on the one or more determined third paths.

[0099] 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.

[0100] The determining of the at least one third path 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.

[0101] 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 at least one third path.

[0102] 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 at least one third path.

[0103] 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.

[0104] 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 at least one third path, 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 at least one third path 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 at least one third path. 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 at least one third path, optionally by determining an energy flux in the environment based on the determined at least one third path.

[0105] 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.

[0106] 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.

[0107] 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 third path, and / or emulating the channel of the wireless communication based on the modeled channel.

[0108] 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.

[0109] 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 of the length and / or the mirroring can enable using more accurate channel models (e.g., detailed or more complex surfaces in the environment), e.g. in equipment testing or DTs.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] Deploying the transmitter node and / or the receiver node based on the determined multipath propagation may comprise a raytracing -based radio network dimensioning. The at least one third path 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.

[0114] By using the less rays to determine the first path and / or by reducing the length before and after the respective mirroring (i.e., in an efficient imaged space), the channel can be modeled in real-time, e.g. for beamforming and / or for controlling the radio network. Alternatively or in addition, the at least one third path may be determined taking reflective and / or diffractive interactions in the radio frequency (RF) propagation with real-time movement in the environment into account.

[0115] 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 third path of the propagation can be determined (e.g., periodically updated) within less than L / V time.

[0116] The determining of the at least one third path 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.

[0117] 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.

[0118] 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.

[0119] The other method aspect may further comprise any feature and / or any step disclosed in the context of the one device aspect or the other device aspect.

[0120] 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.

[0121] 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.

[0122] Any radio device may be a user equipment (UE), e.g., according to a 3GPP specification.

[0123] 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.

[0124] 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 one method aspect or the other 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) or the further remote radio device, respectively. The RAN may comprise one or more base stations, e.g., performing the third 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 the remote radio device and / or the relay radio device and / or the further remote radio device.

[0125] 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.

[0126] Whenever referring to the RAN, the RAN may be implemented by one or more network node (e.g., base stations).

[0127] 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).

[0128] 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).

[0129] The RAN may be implemented according to the Global System for Mobile Communications (GSM), the Universal Mobile Telecommunications System (UMTS), 3GPP Eong Term Evolution (LTE) and / or 3GPP New Radio (NR).

[0130] 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.

[0131] 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.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] Brief Description of the Drawings

[0137] Further details of embodiments of the technique are described with reference to the enclosed drawings, wherein:

[0138] Fig. 1 shows a schematic block diagram of an embodiment of a device for determining a path of a wireless communication in an environment;

[0139] Fig. 2 shows a flowchart of an embodiment of a method for determining a path of a wireless communication in an environment, which method may be implementable by the device of Fig. 1;

[0140] Fig. 3 schematically illustrates a portion of a first exemplary environment comprising embodiments of the device of Fig. 1 performing the method of Fig. 2 for determining paths in the environment;

[0141] Fig. 4 schematically illustrates a portion of a second exemplary environment comprising a transmitter node and receiver node, at least one of which may embody the device of Fig. 1 for performing the method of Fig. 2;

[0142] Fig. 5A is a schematic perspective rendering of structural information obtained for a third exemplary environment comprising transmitting and receiving stations;

[0143] Fig. 5B is a schematic vertical projection of the structural information of Fig. 5A in an x-z- plane;

[0144] Fig. 5C is a schematic horizontal projection of the structural information of Fig. 5A in an x-y- plane;

[0145] Fig. 6 is a schematic perspective rendering of an example of the first path in the third exemplary environment of Figs. 5 A to 5C;

[0146] Fig. 7 is a schematic perspective view of shifting an end point of the first path from a capture surface to the receiving station;

[0147] Fig. 8 is a schematic perspective view of modifying the structural information of Fig. 6 by eliminating a reflective surface, resulting in a mirrored first path; Fig. 9 is a schematic perspective view of determining a second path by reducing the length of the mirrored first path of Fig. 8;

[0148] Fig. 10 is a schematic perspective view of reintroducing the reflective surface along the second path of Fig. 9;

[0149] Fig. 11A is a schematic perspective view of mirroring the second path of Fig. 9 and objects downstream of a point of reflection of the reintroduced reflective surface of Fig. 10, resulting in a third path;

[0150] Fig. 1 IB is a schematic vertical projection of the third path of Fig. 11A in an x-z-plane;

[0151] Fig. 11C is a schematic horizontal projection of the third path of Fig. 11A in an x-y-plane;

[0152] Fig. 12 is a schematic perspective view of a more complex fourth exemplary environment and a third path determined according to an embodiment of the method of Fig. 2;

[0153] Fig. 12A is a schematic horizontal projection of a portion of the fourth exemplary environment of Fig. 12 including two reflective surfaces and a first path therein;

[0154] Fig. 12B is a schematic horizontal projection of a first substep of modifying the structural information by eliminating one of the two reflective surfaces of Fig. 12A;

[0155] Fig. 12C is a schematic horizontal projection of a second substep of modifying the structural information by eliminating the other one of the two reflective surfaces of Fig. 12B, resulting in a mirrored first path;

[0156] Fig. 12D is a schematic horizontal projection of determining a second path by reducing the length of the mirrored first path of Fig. 12C, which can lead to the swapping of a point of reflection;

[0157] Fig. 13 shows a flowchart of a first implementation of the method of Fig. 2;

[0158] Fig. 14 shows a flowchart of a second implementation of the method of Fig. 2;

[0159] Fig. 15 shows a block diagram of a radio device embodiment of the device of Fig. 1 ;

[0160] Fig. 16 shows a block diagram of a base station embodiment of the device of Fig. 1; and Fig. 17 shows a block diagram of a core network embodiment of the device of Fig. 1.

[0161] Detailed Description

[0162] 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.

[0163] 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.

[0164] Fig. 1 schematically illustrates a block diagram of an embodiment of a device for wireless communication in an environment, e.g. for determining a path of a wireless communication in an environment. The device is generically referred to by reference sign 100.

[0165] The device 100 comprises a structural information module 102 that obtains structural information indicative of one or more reflective surfaces in the environment. The device 100 further comprises a first path determination module 104 that determines a first path in the environment from a finite set of traced rays originating from a first station in the environment and intersecting a capture surface of a second station in the environment. The device further comprises a modification module 106 that modifies the structural information by eliminating the one or more reflective surfaces along the first path resulting in a mirrored first path. The device further comprises a second path determination module 108 that determines a second path by reducing a length of the mirrored first path according to the modified structural information. The device further comprises a third path determination module 110 that determines a third path by reintroducing the one or more reflective surfaces along the second path resulting in a third path.

[0166] The device 100 further comprises a physical action module 112 that performs or initiates a physical action that is dependent on the determined third path in the environment.

[0167] Any of the modules of the device 100 may be implemented by units configured to provide the corresponding functionality.

[0168] The device 100 may be embodied by an emulator or a network node (e.g., a transmitting and / or receiving node) of a RAN.

[0169] Fig- 2 shows an example flowchart for a method 200 for determining a path of a wireless communication in an environment. The method 200 comprises a step S202 of obtaining structural information indicative of one or more reflective surfaces in the environment. The method 200 further comprises a step S204 of determining a first path in the environment from a finite set of traced rays originating from a first station in the environment and intersecting a capture surface of a second station in the environment. The method 200 further comprises a step S206 of modifying the structural information by eliminating the one or more reflective surfaces along the first path resulting in a mirrored first path. The method 200 further comprises a step S208 of determining a second path by reducing a length of the mirrored first path according to the modified structural information. The method 200 further comprises a step S210 of determining a third path by reintroducing the one or more reflective surfaces along the second path resulting in a third path. The method 200 further comprises a step S212 of performing or initiating a physical action that is dependent on the determined third path in the environment.

[0170] The method 200 may be performed by the device 100. For example, the modules 102, 104, 106, 108, 110, and 112 may perform the steps S202, S204, S206, S208, S210, and S212, respectively.

[0171] The technique may be applied to uplink (UL), downlink (DL) or direct communications between radio devices, e.g., device-to-device (D2D) communications or sidelink (SL) communications.

[0172] 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.

[0173] Fig. 3 schematically illustrates a first example of an environment 300 for which the device can determine the dominant path 304 of wireless (e.g., radio) propagation. The environment 300 comprises at least one object with a reflective surface 306, i.e. a (e.g., flat or curved) surface that is reflective for wireless signals of the wireless communication. The object may be located within a cell served by a network node 1600 (also referred to as base station, e.g., a gNB) of an access network, e.g. a radio access network (RAN). The access network is served by a core network (CN) comprise at least one CN server 1700. The network node 1600 or the CN server 1700 may embody the device 100.

[0174] The network node 1600 provides wireless access (e.g., in the optical spectrum or radio access) to wireless device (e.g., radio devices) such as a mobile station or user equipment (UE). The UE is referred to by the reference sign 1500, if the UE act as the first station 400 or the second station 402 and / or if the UE embodies the device 100. A generic UE is referred to by reference sign 310.

[0175] Any one of the wireless device 1500 and the network node 1600 may act as the first station 400 or the second station 402.

[0176] 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.

[0177] Embodiments of the device 100 and the method 200 can improve the fidelity of the modeled channel and / or the accuracy of the determined third path (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 third path, 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 UEs 310 or 1500 can be increased.

[0178] Embodiments of the device 100 and the method 200 allow ray-tracing with a finite number of launched rays (i.e., the finite set of rays originating from the first station 400), while still fulfilling Fermat’s principle, both for specular reflection and edge diffraction. At least one first propagation path 302 from the first station 400 (e.g., an origin or transmitter) to the second station 402 (e.g., a target or receiver) is determined in the step S204 (e.g., detected and stored) even though they do not fulfill Fermat’s principle. To correct the first path 302, the method 200 performs imaging in the step S206 and reimaging in the step S210 to efficiently determine the shortest path in the step S208, which makes the resulting at least one propagation path 304 fulfill Fermat’s principle.

[0179] Fig. 4 schematically illustrates an example of ray launching with finite resolution, i.e. a finite set of traced rays originating from the first station 400 towards the second station 402, e.g. a receiver location.

[0180] Since ray-tracing samples space discretely, it is unlikely that a given point in continuous space representing a (e.g., receiver) location is reached by a finite resolution of rays. Therefore, the second station 402 is represented by a capture surface 404 as a finite-size object, e.g. surrounding the receiver location, to capture rays. Typically, a sphere (also referred to as capture sphere) is used as the capture surface 404, although other shapes are also possible. Paths that intersect the capture surface 404 are recorded connecting the first station 400 and the second station 402 (e.g. as "hitting" the receiver location) and therefore contribute to the wireless channel between the first station 400 (e.g. a source position) and the second station 404 (e.g., the receiver location).

[0181] The thick black paths 302 A and 302B are examples of the first path 302, since its ray is recorded as hitting the capture sphere 404 surrounding the receiver location 402, whereas the dashed paths 304 represent the physically correct paths determined according to the method 200 by the device 100, e.g. obeying Fermat’s principle. Conventional ray-tracing cannot determine these physically correct third paths, since the rays are launched with a finite resolution (e.g., a finite angular resolution) at the first station 400. Consequently, none of the paths found by ray-tracing only fulfills Fermat’s principle.

[0182] The ray optical models 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.

[0183] For the purposes of the present discussion, a shortest path 304 between two nodes 400 and 402 (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 object interactions, such as transmission (e.g., pass through), reflection (e.g., specular reflection at reference sign 306), and / or diffraction (e.g., edge diffraction shown at reference sign 308 in Fig. 5A, 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. Since ray-tracing does sample space discretely, the predicted paths 302 (as represented by the combination of line segments between object identified during the tracing) do not in general fulfill Fermat’s principle. Consequently, conventional ray-tracing techniques predict propagation paths 302, which are to be used for modeling the electromagnetic fields, but do not represent the shortest path between the first station 400 (e.g., a source or transmitter) and the second station 402 (e.g. a target or receiver). The fundamental interaction models in radio wave propagation, e.g. specular reflection and edge diffraction, require that the shortest propagation path is determined according to the steps S208 and S210 ofthe method 200. Otherwise, as in conventional ray-tracing, the predicted fields are inaccurate. An inaccuracy caused by the finite angular resolution may scale with distance and radio frequency, as the deviation in length causes a phase shift.

[0184] Conventional techniques to compute channel state information based on ray-tracing of radio waves ignore the effect of the first paths 302 not being the shortest paths 304, and simply assume that the error due to the finite resolution can be made small enough to be acceptable. However, launching rays with high angular density and not finite (i.e., small) set of traced rays, can alleviate the inaccuracy only to a certain extent and at the cost of exponentially increasing computational resources. The denser the rays are launched, the smaller the error in the prediction. However, the problem with launching rays with sufficient resolution, particularly for large environments (such as cities) is that the number of rays must be very large to achieve small prediction errors. In the limit, the required number of rays can be too large to make the ray-tracing feasible, or can be extremely costly, due to the execution time and / or computer memory constraints. Also, launching rays densely results in multiple, similar but not identical, paths representing the same interactions in the propagation channel, which makes pruning (i.e., the removal of duplicate paths) challenging and time-consuming.

[0185] It is noted that in the most common ray-tracing applications for graphical applications, i.e., computer graphics-related applications, Fermat’s principle is not a major issue. In computer graphics, results on pixel-level tend to be composed of multiple overlapping ray or path contributions based on a multiplicity of rays launched in random directions, aggregated to create a final color and intensity, and this computation is almost exclusively based on reflection and refraction. In graphics, diffraction is not generally modeled using the asymptotic models used for wave propagation, since diffraction effects can be safely ignored at optical frequencies. Furthermore, graphics applications rarely, if ever, apply coherent combining of complex-valued vectors. In radio propagation, coherent addition can be essential, for example when summing the contribution from a direct path with the contribution from a diffracted path, since the (coherent) sum of the contributions is what ensures that the total contribution (i.e. the electromagnetic field) is spatially continuous. Fermat’s principle can be stated as: the path taken by a ray between two given points is the path that has a stationary, typically minimum, time with respect to variations of the path. Embodiments of the device 100 determine the third path 304 as the shortest path between two node points 400 and 402, via at least one specular reflection 306 and zero or more edge diffractions (e.g. at reference sign 308 in Fig. 5A). The first path 302 may define a given set of interactions (e.g., a sequence of objects and types for the interactions). The shortest path 304 can be used for modeling a radio channel according to radio frequency (RF) propagation, e.g. compliant with Fermat’s principle. The channel may be modeled in real-time based on determined third path 304. The modeled channel can replace a conventional channel estimation, which is time-delayed and radio-resource consuming due to reference signal measurements.

[0186] In a variant of any embodiment, any number of shortest paths 304 (such as the paths 304A and 304B in Figs. 3 and 4) may be determined (e.g., based on a corresponding or greater number of first path 302) between the two stations (e.g., nodes) 400 and 402. Each path 304 may involve a unique combination (or sequence) of interactions, so that each path 304 can be determined according to the method 200.

[0187] Furthermore, while the technique is described for a transmitter and a receiver as the two nodes 400 and 402, the roles of transmitter and receiver may be interchanged. For example, the shortest path 304 may be determined starting from the location of the receiver 400, wherein the capture surface 404 is located at the transmitter 402.

[0188] The finite directional resolution of the rays conventionally causes the low fidelity of the conventional channel estimation, because the resulting first paths 302A and 302B underlying the conventional channel estimation are suboptimal. Embodiments of the device 100 and the method 200 can determine the optimal paths 304A and 304B, respectively, without increasing the directional resolution of rays.

[0189] Figs. 5A to 5C schematically illustrate an environment 300. Fig. 5A is a perspective view, Fig. 5B is a horizontal view, and Fig. 5C is a top view of the environment 300. Each object of the environment 300 (e.g. at least each object of the environment 300 with which the first path 302 interacts), such as one or more reflective surfaces 306 and zero or more diffractive edges 308, are encoded in the structural information.

[0190] Fig. 6 schematically illustrates an example of the first path 302. The first path 302 resulting from the step S204 does not in general fulfill Fermat’s principle.

[0191] The technique may be combined with any suitable method for ray-tracing, e.g. in the step S202 or S204, to find the first path 302 as a baseline path. The baseline path 302 may be a first path found by any means, for example by finite resolution ray-tracing, that does not in general fulfill the Fermat’s principle. It’s the path 302 used as a starting point for finding the proper path 304. The baseline path 302 starts in an initial point 400 (e.g., the transmitter) and ends in a final point 402 (e g., at the capture surface 404 of the receiver). The path 304 is made up of line segments between points of interaction (e.g., points 604 of reflection) which maintain the radius of curvature in at least one dimension, i.e., specular reflection (e.g., wherein the angle of incidence equals the angle of reflection) and edge diffraction (e.g., wherein the diffracted rays are on Keller's cone), not point diffraction. "Maintaining the radius of curvature in at least one dimension" may mean that the tangent vector of the path (e.g., of the first path and / or the second path and / or the third path) is continuous in at least one dimension (i.e., in a linear subspace), preferably in the two-dimensional plane of the reflective surface 306.

[0192] The finite set of rays originating from the first station (e g., a transmitter), i.e. the finite angular density at launch, and the non-zero size of the capture surface 404 (e.g., a capture sphere) efficiently yield the at least one first path 302 as a baseline path in the step S204. As schematically illustrated in Fig. 7, the modification S205 of the first path 302, which may be a substep of the step S204, changes an endpoint of the first path 302 from the intersection on the capture surface 404 to a location of the second station 402.

[0193] The tracing of the rays for the determining S204 of the first path 302 may be terminated when (e.g., as soon as) one of the traced rays intersects the capture surface 404 of the second station 402. Alternatively or in addition, each of a plurality of rays originating from the first station 400 (e.g., the transmitter or receiver of the wireless communication) in different directions is assigned an index. The plurality of rays may be grouped in disjoint sets, wherein the sets are ordered such that each of the indices in any one of the ordered sets is less than each of the indices in a subsequent set of the ordered sets. The determining S204 of the first path 302 may comprise increasing the number of ordered sets in the finite set of traced rays until at least one of the traced rays intersects the capture surface 404.

[0194] An angular density of the finite set of rays may be equal to or greater than a minimum angular density that is necessary to ensure that at least one of the rays in the finite set of rays intersects (i.e., reaches) the capture surface 404. For example, further rays with different directions originating from the transmitter may be included to an initial finite set of rays (e g., by including the next group of rays), if none of the rays in the initial finite set intersects (i.e., reaches) the capture surface 404. In other words, the finite set may result from gradually increasing the angular density of the rays originating from the first station 400 (e.g., transmitter or receiver).

[0195] By terminating the increasing of the angular density when (e.g., as soon as) at least one of the traced rays intersects the capture surface 404, the computational complexity is reduced compared to a conventional computation in which an accuracy of the determined shorted path increases only by increasing the angular density.

[0196] Different rays in the finite set of rays may have different directions. For example, the directions of the rays in the finite set of rays (e.g., for each group of rays) may be uniformly distributed (e.g., according to vertices of a Platonic solid centered at the first station 400) and / or regularly distributed (e.g., by iteratively subdividing straight lines between the vertices of a Platonic solid). Each subdivision may correspond to a next group of rays.

[0197] Then, the first path 302 is modified resulting in the third path 304 as the shortest path by the device 100 performing the method 200 according to the steps S206 to S210, e.g. as explained below.

[0198] In a step S206 schematically illustrated in Fig. 8, given the baseline path 302 as the first path with properties as described, the first path 302 is unwrapped for all interactions involving specular reflection (i.e., mirroring S206B the path and the downstream objects of the environment 300) to remove S206A the specular points Si at reference sign 602.

[0199] Herein, "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 302'), when mirrored S206B in a plane coplanar with the surface 306 (at the point of reflection 602) in which the specular reflection takes place. This may be implemented using for example imaging methods and involves imaging of both the path points and the objects (e.g., lines along the diffraction edges 308 and the specular reflective surfaces 306) with which the first path 302 (and thus the mirrored path 302') interacts.

[0200] That is, the "unwrapping" does not only relate to the first path 302 but also relates to the zero or more objects of the environment 300 in any further interaction after a first reflection of same path. Moreover, any mirroring that is performed may be unique per path.

[0201] The modifying S206 of the structural information may comprise (e.g., for each of the eliminated one or more reflective surfaces 306 along the first path 302) mirroring each object of the environment 300 that is interacting (e.g., touching or intersecting) with the first path 302 (e.g., a further reflective surface 306 or a diffractive edge 308) downstream of the respectively eliminated reflective surface of the one or more reflective surfaces 306. For example, the modifying S206 of the structural information may further comprise (e g., for each of the eliminated one or more reflective surfaces 306 along the first path 302) mirroring zero or more diffractive edges 308 downstream of the respectively eliminated reflective surface of the one or more reflective surfaces 306.

[0202] More specifically, an object (e.g., 306 and 308) that is located downstream of N reflective surfaces (1 < N) may be mirrored N times (or up to N times) during the eliminating S206A of the one or more reflective surfaces. (The object may be mirrored exactly N times, if the same direction "downstream" is used for the mirroring at each eliminated reflective surface.)

[0203] In a step S208 schematically illustrated in Fig. 9, the length of the mirrored (i.e. unwrapped) first path 302' is reduced, e.g., by apply a "taut string" process to get the shortest unwrapped path as the second path 304', optionally via the zero or more mirrored diffractive edges 308' downstream of the mirrored path 302'. Herein "zero or more" refers to all those diffraction edges 308 (if any) with which the first path 302 interacts, so that the mirrored path 302' also interacts (i.e. remains attached as a boundary condition) with the correspondingly mirrored diffractive edges 308' downstream of the eliminated (S206A) specular reflection.

[0204] The "taut string" process is one example of performing the step S208. The "taut string" process may be implemented according at least one of the following variants. In a first variant, a "taut string" is the string that connects the points of the mirrored first path 302', which string is pulled tight. In the present technique, the string (i.e., the paths 302' and 304') are constrained to attach to lines representing the mirrored diffraction edges 308'. Along the mirrored diffraction edges 308', the string can move freely when pulled tight. In a second variant, which may be combined with the first variant, the pulled-tight taut string (i.e., the second path 304') is determined in closed form, particularly when the path contains only a few interactions with diffractive edges 308'. In a third variant, which may be combined with the first and / or second variant, the pulled-tight taut string (i.e., the second path 304') is determined using an iterative method. This step may be implemented using at least some features of Hong Trang, Le & Truong, Quynh & Dang, Tran. (2017), "An Iterative Algorithm for Computing Shortest Paths Through Line Segments in 3D", pages 73-84.

[0205] The determining S208 of the shortest path 304' may be performed in one way or another.

[0206] The mirrored points 602 of reflection may be determined along the second path 304' by computing intersections of the second path 304' with the mirrored reflective surfaces 306, e.g. during the determining S208 of the second path 304' and / or before the determining S210 of the third path 304. Herein, for brevity, the reference sign 306 is used for both the reflective surfaces according to the obtained structural information and the mirrored reflective surfaces (e.g., according to the modified structural information).

[0207] It is noted that the "second" path 304' or "third" path 304 interacting (or hitting or intersecting) any of the (reintroduced) one or more reflective surfaces 306 may be used interchangeably in the technical sense that the one or more reflections 306 caused by the reintroducing S210A of the one or more reflective surface transform the second path 304' to the third path 304.

[0208] In a step S210 schematically illustrated in Fig. 10, the second path 304' is de-imaged, i.e. the imaging performed in the step S206 is reversed, of course including the effect of reducing S208 of the path length so that the resulting third path 304 is different from the first path 302. That comprises reintroducing S210A the one or more reflective surfaces 306 and the zero or more diffractive edges 308. At each reintroduction of one of the one or more reflective surfaces 306, the remaining path (and, in a first variant, the zero or more diffractive edges 308') 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 306. In a second variant, the zero or more diffractive edges 308 are determined directly from the obtained structural information.

[0209] The step S210 includes determining updated reflection points S2 at reference sign 604 (which are different from the reflection points Si at reference sign 602 of the first path 302) on the original one or more reflective surfaces 306 (e.g., according to the obtained structural information). Furthermore the zero or more diffraction points are updated, e g. by mirroring the diffraction points of the second path 304' back along the original diffractive edges 308 (e.g., according to the obtained structural information). In other words, the zero or more diffraction points of the third path 304 are located along the diffractive edges 308 and determined based on the second path 304'.

[0210] The resulting third path 304 is the shortest path in the original environment 300 with the same sequence of interactions according to the first path 302.

[0211] The step S210 may comprise at least one of the following substeps. In a first substep S210A, the mirroring (i.e., de-imaging) is performed for each specular reflection separately in order (i.e., the reflective surface 306 is reintroduced S210A). In a second substep, for each specular reflection, the intersection 604 between the segment of the shortest path and the plane of the reflection surface is determined. In a third substep, the intersection point 604 is added as an updated specular reflection point S2 of the shortest path 304. In a fourth substep S210B, e.g. as schematically illustrated in Figs. 11A to 11C, the path downstream of the updated reflection point 604 is mirrored (i.e., reflected or de-imaged). In other words, the parts of the shortest path 304 beyond the reintroduced surface of the reflection is mirrored. Fig. 11 A shows a schematic perspective of the third path 304, while Figs. 11B and 11C show corresponding vertical and horizontal views, respectively.

[0212] These substeps are repeated for each specular reflection, i.e., for each reflective surface 306 or each original point 602 of reflection, along the second path 304'.

[0213] Embodiments of the method 200 can yield paths 304 which fulfill Fermat’s principle, e.g. for any first path 302 with one or more interactions that maintain the radius of curvature in at least one dimension (e.g., there is a plane of projection, so that the path projected in that plane is straight at the point of reflection 604 or the point of diffraction). Hence, the method 200 leads to a substantial improvement for determining the electromagnetically proper propagation, i.e. the third path 304, and optionally a channel model based thereon.

[0214] For example, the determining S210 of the third path 304 may further comprise (e.g., for each of the reintroduced one or more reflective surfaces 306 along the second path 304') mirroring (with respect to the reintroduced reflective surface 306) zero or more diffractive edges 308 downstream of the respectively reintroduced reflective surface of the one or more reflective surfaces 306. Alternatively or in addition, the determining S210 of the third path 304 may further comprise (e.g., for each of the reintroduced one or more reflective surfaces along the second path 304') mirroring - with respect to the reintroduced reflective surface 306 - the zero or more reflective surfaces 306 downstream of the respectively reintroduced reflective surface 306. Alternatively or in addition, the determining of the third path 304 may further comprise (e.g., for each of the reintroduced one or more reflective surfaces 306 along the second path 3041) mirroring the second station 402 with respect to the reintroduced reflective surface 306.

[0215] More specifically, an object 306 or 308 that is located downstream of N reflective surfaces, N> 1, may be mirrored N times (or up to N times) during the reintroducing S210A of the one or more reflective surfaces. Moreover, as a result of mirroring S210B the object ' times (or instead of mirroring the object the last time), the object may be located and orientated as indicated by the obtained structural information.

[0216] After the reintroducing S210A of all reflective surfaces 306, the objects of the environment 300 may be at the very same position and orientation as indicated by the obtained structural information, e.g. if the same direction "downstream" is used throughout the eliminating and the reintroducing. Otherwise, a spatial representation of the entire system may be rotated, e g. without significance for the physical properties of the determined third path 304.

[0217] In other words, the reintroduced reflective surfaces may be defined by (or taken from) the original (i.e., not modified) environment 300 (i.e., according to the obtained structural information) and / or may result from mirroring (i.e., mirroring for a second time) on each of the one or more reflective surfaces. The environment 300 for the third path 304 may correspond to the original (i.e., not modified) environment according to the obtained structural information and / or may result from de-imaging (i.e., mirroring S210B for the second time after the mirroring S206B) with respect to a plane coplanar to the one or more reflective surfaces 306 any further object of the modified structural information (such mirrored reflective surfaces, mirrored diffractive edges, and the mirrored second station).

[0218] Herein, the reflective surfaces 306 may be configured for specular reflection, and optionally in addition, for diffusive reflection. The points of reflection on the reflective surfaces may be referred to as specular reflection points. Alternatively or in addition, the specular reflection points of the shortest path may be determined by determining the intersection of shortest path 304' with (possibly mirrored) reflective surfaces (i.e., planes of surfaces with specular reflections) before the de-imaging (i.e., before the reintroducing S210A of the reflective surfaces for the determining S210 of the third path 304).

[0219] In any embodiment, the modifying S206 of the structural information by eliminating S206A the one or more reflective surfaces 306 along the first path 302 may use the obtained structural information as a starting point. Alternatively or in addition, the determining S210 of the third path 304 by reintroducing S210A the one or more reflective surfaces along the second path may use the modified structural information.

[0220] The modifying S206 of the structural information along the first path 302 (e.g., including the piecewise mirroring of the first path 302') may be performed along the first path 302 in the order from the transmitter to the receiver or along the first path in the order from the receiver to the transmitter, e g. because the steps of mirroring S206B are commutative. Furthermore, the modifying S206 (i.e., the eliminating S206A) may start at a reflective surface 306 within the first path 302 and / or the determining S210 of the third path 304 (i.e., the reintroducing S210A along the second path 304') may start at a reflective surface 306 within the second path 304'.

[0221] Independent of the order of the eliminating S206A of the reflective surfaces, the mirroring S206B may be performed downstream of the respective point of reflection for all objects along the first path 302 or the (e.g., partially) mirrored paths 302'. For example, the modifying S206 of the structural information (e g., including the mirroring S206A of the first path 302) may be implemented by a main loop over the points 602 of reflection along the first path 302, and a second loop operating downstream of the respective one of the points 602 of reflection.

[0222] Eliminating S206A each of the reflective surfaces 302 may comprise eliminating the respective point 602 of reflection on the respectively eliminated reflective surface of the one or more reflective surfaces. For example, the eliminated points 602 of reflection may be irrelevant and / or define no constraint for the determining S208 of the second path 304'. In other words, for the reducing (e.g., minimizing) of the length of the mirrored first path 3041, i.e., for the determining of the second path 304' based on the modified structural information, the points 602 of reflection in the original environment may be absent or pose no constraints.

[0223] Downstream of a point 602 of reflection on the respectively eliminated reflective surface 306, the first path 302 being mirrored may mean that the piece of the first path 302 between the point of reflection 602 and the receiver 400 or 402 is mirrored. Alternatively or in addition, downstream of a point of reflection 602 on the respectively eliminated reflective surface 306, the zero or more reflective surfaces 306 being mirrored may mean that all the zero or more reflective surfaces of the one or more reflective surfaces that are downstream of the point 602 of reflection (i.e., the zero or more reflective surfaces that interact with the first path 302 between the point 602 of reflection and the receiver 400 or 402) are mirrored S206B.

[0224] While above first, second, and third exemplary environments 300 included only one reflective surface 306 for clarity, the technique can be applied for any number of interactions, e.g., any number of reflective surfaces interacting with the first path 302. Fig. 12 schematically illustrates a fourth exemplary environment 300 with multiple reflective surfaces 306-1 and 306-2 and multiple diffractive edges 308-1 to 308-5.

[0225] In a variant of any embodiment, the determining S204 of the first path 302, the modifying S206 of the structural information, the determining S208 of the second path 304', and the determining S210 of the third path 304 may be repeated. These steps may be repeated using the previously in the step S210 determined third path 304, or the multiple third paths 304 (e.g., after eliminating duplications), in the finite set of traced rays to include one or more further interactions with the environment 300 not included in the previously determined first path 302.

[0226] In other words, the ray-tracing (or briefly: tracing) may be re-run along the previously determined third path 304 as the shortest path to capture potential other interactions occurring due to a changed point S2 of the previously determined third path compared to the previously determined first path, e.g. compared to a point Si of the previously determined first path 302. The device 100 may re-run the tracing to check that the second path 304' of reduced length (e.g., the shortest path) is not blocked by an object in the environment 300. Alternatively or in addition, the device 100 may check that the third path 304 (e g., the shortest path) falls within the extent (e.g., the size) of the one or more surfaces 306 and / or edges 308 (e.g. in a longitudinal direction of the respective diffractive edge 308) with which the third path 304 interacts. The device 100 may eliminate the third path if the reducing of the length (e.g., a shortest path calculation) shifts (vividly spoken: "pulls off') the second path 304' (and thus the resulting third path 304) outside of the extent of any of the reflective surfaces 306 or outside of a finite length of any of the diffractive edges. Alternatively or in addition, the reducing of the length of the mirrored first path for determining S210 the third path may be constrained by the extent of the edges 308 (e.g., the wedges). That is, a point on an edge 308 may only be allowed to be shifted within an extent (e.g., a length) of the edge 308, and optionally may be fixed at either end point of the edge 308 if the reducing of the path length (according to a method ignoring the finite size of the edge 308) results in a point outside the extent of the edge 308. In short, reducing the path length by shifting may be stopped at the end of an edge 308. Alternatively or in addition, reducing the path length by alternating a point of reflection on a surface 306 may be restricted to shifting along an edge of the surface 306, and / or may stop at a comer of the surface 306, if the shortest path would fall outside of the extent of the surface 306.

[0227] Eliminating duplications in the determined third paths 304 is one example of eliminating (e.g., not using for modeling the channel) one or more of multiple determined third paths 304.

[0228] Alternatively or in addition, a criterion for eliminating one or more paths 304' or 304 is a change in the order of interactions caused by the step S208. For example, the first path 302 may comprise a first reflection from a first reflective surface 306-1 followed by a second reflection from a second reflective surface 306-2, which is schematically illustrated in Fig. 12A. The imaging S206, i.e., the sequential mirroring S206 is shown in Figs. 12B and 12C as substeps 206-1 and 206-2, respectively, for the two reflective surfaces 306-1 and 306-2, respectively.

[0229] When the length of the mirrored (or unwrapped) path 302' is reduced in an exemplary environment 300, e.g. as schematically illustrated in Fig. 12D, it can occur that the second path 304' (and thus the de- imaged third path 304) hits the second reflective surface 306-2 first, which is also referred to as "swapping" the points of interaction.

[0230] As explained with reference to exemplary embodiments above, the functionality of the device 100 and the method 200 may optionally comprise at least one of the following steps. One step comprises rerunning the ray-tracing along the determined shortest path 304 to capture potential other (e.g. additional) interactions occurring due to the changed path points in the environment 300. Another step comprises determining the specular reflection points 604 of the shortest path 304 by determining one or more intersections of the shortest path with (optionally imaged) planes of surfaces 306 with specular reflections, e.g. before the de-imaging S210. Another step comprises detecting and eliminating (i.e., pruning) paths 304' or 304 whose interaction points fall outside the surface 306 (for specular reflection) or line segment 308 (for edge diffraction) after the determining S208 the shortest path. Another step comprises detecting and eliminating paths 304' or 304 for which the interaction points become swapped after determining S208 the shortest path.

[0231] The determining S206B of the mirrored first path 302' may be reminiscent to unfolding a meterstick or yardstick (representing the first path, cf. Fig. 8 or the sequence of Figs. 12A to 12C), wherein each bend of the stick corresponds to a point of reflection, but the first path is straightened-out at each point of reflection by mirroring (not by rotation) and all objects of the environment interacting downstream of the point of reflection are also subjected to the mirroring. The key point is the eliminating S206A (i.e., removal) of the reflective surfaces 306, wherein the mirroring S206B may be applied to all objects in any direction "downstream", i.e. mirroring all objects (and path segments of the first path) downstream either towards the first station 400 or towards the second station 402. The result is the mirrored first path 302', i.e., an unwrapped path without reflections (to which an algorithm may be applied for determining a shortest path as the second path).

[0232] Preferably, the direction "downstream" is applied consistently for the eliminating S206A of the one or more reflective surfaces and for the reintroducing S210A of the one or more reflective surfaces 306. As an advantage, a spatial representation of the entire system may be unchanged.

[0233] In one example, the second path 304' may be a straightened-out version of the first path in an initial direction of the direction "downstream". For example, if one chooses the direction "downstream" towards the second station and if one chooses to start the eliminating S206A from the first station 400 towards the second station 402, the second path 304' may be a straightened-out version of the first path 302 in the direction of the ray of the first path 302 closest to the first station 400. If one chooses the direction "downstream" towards the first station 400 and if one chooses to start the eliminating from the second station 402 towards the first station 400, the second path 304' may be a straightened-out version of the first path 302 in the direction of the ray of the first path closest to the second station 402.

[0234] Figs. 13 and 14 show flowcharts of two implementations of the method 200. The one or more third paths 304 determined in the step S210 are recorded. Based on the determined one or multiple paths 304, a physical action is performed and / or the channel of the wireless communication is modeled in a step S212.

[0235] 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 propagation paths 304 between at least one transmitter node 400 and at least one receiver node 402. The emulation may be based on the channel modeled in the step S212 based on the one or more shortest path 304. 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 interactions (e.g. according to the corresponding first path 302).

[0236] The embodiment of the device 100 for emulation comprises an RF input and an RF output coupled to the transmitter node 400 and the receiver node 402, respectively, to let the equipment 400 and / or 402 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 propagation path 304 enables real-time or near real-time emulation of the radio channel, which is very important for this use case.

[0237] Fig. 15 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 1504 for performing the method 200 and memory 1506 coupled to the processors 1504. For example, the memory 1506 may be encoded with instructions that implement at least one of the modules 102 to 112.

[0238] The one or more processors 1504 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 1506, radio device functionality. For example, the one or more processors 1504 may execute instructions stored in the memory 1506. 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. As schematically illustrated in Fig. 15, the device 100 may be embodied by a radio device 1500, e.g., functioning as a UE. The node 1500 comprises a radio interface 1502 coupled to the device 100 for radio communication with one or more other nodes, e.g., including base stations or UEs.

[0239] Fig. 16 shows a schematic block diagram for a network node embodiment of the device 100. The device 100 comprises processing circuitry, e.g., one or more processors 1604 for performing the method 200 and memory 1606 coupled to the processors 1604. For example, the memory 1606 may be encoded with instructions that implement at least one of the modules 102 to 112.

[0240] The one or more processors 1604 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 1606, network node functionality. For example, the one or more processors 1604 may execute instructions stored in the memory 1606. 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.

[0241] As schematically illustrated in Fig. 16, the device 100 may be embodied by a radio device 1600, e.g., functioning as a gNB. The node 1600 comprises a wired or radio interface 1602 coupled to the device 100 for radio communication with one or more other nodes, e.g., including base stations and UEs, respectively.

[0242] Performing the physical action S212 may comprise transmitting or receiving the wireless communication based on the propagation path 304 determined in the step S210. Alternatively or in addition, the interface 1502 may be a control interface (e.g., a network interface or an Fl interface). For example, the node 1500 may be a central unit (CU) of network node (e.g., a gNB). Performing the physical action S212 may comprise controlling the wireless communication in the environment 300 based on the determined propagation path 304.

[0243] Alternatively or in addition, the physical action S212 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 to ensure compliance with regulations based on the determined multipath propagation. For example, an energy flux in the environment 300 may be determined based on the determined propagation path 304 and / or the modeled channel of the step S210. Alternatively or in addition, the physical action S212 may comprise controlling directional gain and / or transmit power of the wireless communication in the environment 300. For example, a radio device 1500 (e.g., a UE) may determine its position or a network node 1600 (e.g., a gNB) may determine the position of a radio device 310 in the environment 300 based on the propagation path 304 determined in the step S210.

[0244] In one embodiment, radio signals received at the radio device 1500 in the environment 300 are compared with radio signals expected (e.g., modeled in the step S212) at the at least one position in the environment 300 according to the determined propagation path 304. In another embodiment, the radio signals received from a radio device 310 in the environment 300 at a network node 1600 are compared with radio signals expected (e.g., modeled in the step S212) at the at least one position in the environment 300 according to the propagation path 304 determined in the step S210.

[0245] 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 propagation paths 304 determined in the step S210. For example, the position for deploying at least one a base station 1600 (e.g. acting as transmitter and receiver node) in the environment 300 may be determined based on the propagation path 304 (e.g., based on the modeled channel and / or the emulated channel as a function of the position).

[0246] In any embodiment, the propagation path 304, 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).

[0247] Fig. 17 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 1704 for performing the method 200 and memory 1706 coupled to the processors 1704. For example, the memory 1706 may be encoded with instructions that implement at least one of the modules 102 to 112.

[0248] The one or more processors 1704 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 1706, core node functionality or edge computing functionality. For example, the one or more processors 1704 may execute instructions stored in the memory 1706. 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 1500 and / or the network node 1600 may alternatively be performed by the core node 1700 or edge computing node 1700.

[0249] 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

[0250] (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.

[0251] 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 a path (304) of a wireless communication in an environment (300), the device (100) comprising memory (1506; 1606; 1706) operable to store instructions and processing circuitry (1504; 1604; 1704) operable to execute the instructions, such that the device (100) is operable to: obtain (S202) structural information indicative of one or more reflective surfaces (306) in the environment (300); determine (S204) a first path (302) in the environment (300) from a finite set of traced rays originating from a first station (400; 402; 1500; 1600) in the environment (300) and intersecting a capture surface (404) of a second station (402; 400; 1600; 1500) in the environment (300); modify (S206) the structural information by eliminating (S206A) the one or more reflective surfaces (306) along the first path (302) resulting in a mirrored (S206B) first path (302'); determine (S208) a second path (304') by reducing a length of the mirrored (S206B) first path (302') according to the modified (S206) structural information; determine (S210) a third path (304) by reintroducing (S210A) the one or more reflective surfaces (306) along the second path (304') resulting (S210B) in a third path (304); and perform or initiate a physical action (S212) that is dependent on the determined (S210) third path (304) in the environment (300).

2. The device (100) of claim 1, wherein the physical action (S212) comprises or the device (100) is further operable to: model a channel of the wireless communication along the determined (S210) third path (304) and the structural information of the environment (300).

3. A device (100) for determining a path (304) of a wireless communication in an environment (300), the device (100) comprising memory (1506; 1606; 1706) operable to store instructions and processing circuitry (1504; 1604; 1704) operable to execute the instructions, such that the device (100) is operable to: obtain (S202) structural information indicative of one or more reflective surfaces (306) in the environment (300); determine (S204) a first path (302) in the environment (300) from a finite set of traced rays originating from a first station (400; 402; 1500; 1600) in the environment (300) and intersecting a capture surface (404) of a second station (402; 400; 1600; 1500) in the environment (300); modify (S206) the structural information by eliminating (S206A) the one or more reflective surfaces (306) along the first path (302) resulting in a mirrored (S206B) first path (302'); determine (S208) a second path (304') by reducing a length of the mirrored (S206B) first path (302') according to the modified (S206) structural information;determine (S210) a third path (304) by reintroducing (S210A) the one or more reflective surfaces (306) along the second path (304') resulting (S210B) in a third path (304); and model (S212) a channel of the wireless communication along the determined (S210) third path (304) and the structural information of the environment (300).

4. The device (100) of claim 3, wherein the modeling (S212) of the channel comprises orthe device (100) is further operable to: perform or initiate a physical action that is dependent on the modeled channel.

5. The device (100) of any one of claims 1 to 4, wherein the modifying (S206) of the structural information comprises for each of the one or more reflective surfaces (306) along the first path (302): eliminating (S206A) the one or more reflective surfaces (306), and mirroring (S206B) with respect to the eliminated (S206A) reflective surface (306) the first path (302), the zero or more remaining reflective surfaces (306), and the second station (402; 400; 1600; 1500) downstream of a point (602) of reflection on the eliminated (S206A) reflective surface (306).

6. The device (100) of any one of claims 1 to 5, wherein the determining (S208) of the second path (304') comprises minimizing a length of the mirrored first path (302') according to the modified structural information.

7. The device (100) of any one of claims 1 to 6, wherein the determining (S210) of the third path (304) comprises for each of the reflective surfaces (306) along the second path (304'): reintroducing (S210A) each of the one or more reflective surfaces (306) along the second path (304'), and mirroring (S210B) the second path (304') with respect to the reintroduced (S210A) reflective surface (306) downstream of a point (604) of reflection on the respectively reintroduced (S210A) reflective surface (306).

8. The device (100) of any one of claims 1 to 7, wherein performing the physical action (S212) comprises: transmitting the wireless communication at the first station (400; 1500; 1600) towards the second station (402; 1600; 1500) along the determined (S210) third path (304) in the environment (300) and / or based on the modeled channel; receiving the wireless communication from the first station (400; 1500; 1600) at the second station (402; 1600; 1500) along the determined (S210) third path (304) in the environment (300) and / or based on the modeled channel;transmitting the wireless communication at the second station (402; 1500; 1600) towards the first station (400; 1600; 1500) along the determined (S210) third path (304) in the environment (300) and / or based on the modeled channel; and / or receiving the wireless communication from the second station (402; 1500; 1600) at the first station (400; 1600; 1500) along the determined (S210) third path (304) in the environment (300) and / or based on the modeled channel.

9. The device (100) of any one of claims 1 to 8, wherein the determined first path (302) results from tracing the finite set of rays launched from the first station (400; 1600; 1500); and / or wherein at least one or each point, S2 (604), of reflection of the third path (304) is offset on the respective reflective surface (306) relative to the point, Si (602), of reflection of the first path (302); and / or the device (100) being further operable to repeat the determining (S204) of the first path (302) using the direction of the third path (304) originating from the first station (400; 402; 1500; 1600), if a point S2 (604) of reflection of the third path (304) is outside of an extent of at least one of the one or more reflective surfaces (306); and / or the device (100) being further operable to change (S205) an endpoint of the first path from the intersection on the capture surface (404) to a location of the second station (402; 400; 1600; 1500).

10. The device (100) of any one of claims 1 to 9, wherein the obtained (S202) structural information is further indicative of one or more diffractive edges (308) in the environment (300), wherein the step of modifying (S206) the structural information by eliminating (S206A) each of the reflective surfaces (306) along the first path (302) further comprises mirroring (S206B) any of the one or more diffractive edges (308) downstream of the point (602) of reflection on the respectively eliminated (S206A) reflective surface (306), and / or wherein each of the one or more mirrored (S206B) diffractive edges (308') is a linear constraint for the second path (304') in the determining (S208) of the second path (304') by reducing the length of the mirrored first path (302') according to the modified structural information and / or wherein the reducing of the length comprises shifting the one or more points of the second path (304') at the zero or more diffractive edges (308) in the environment along the zero or more diffractive edges (308).

11. The device (100) of any one of claims 1 to 10, wherein the first path (302) is the shortest path among the finite set of traced rays that intersects the capture surface (404) of the second station (402; 400; 1600; 1500).

12. The device (100) of any one of claims 1 to 11, wherein multiple first paths (302) intersecting the capture surface (404) of the second station (402; 400; 1600; 1500) result from tracing the finite set of traced rays, and wherein the structural information is modified (S206), the second path (304') isdetermined (S208), and / or the third path (304) is determined (S210) for each of the multiple first paths (302), optionally the device (100) being further operative to eliminate duplications among the multiple third paths (304) resulting from the multiple first paths (302), respectively, by comparing path vertices of the multiple third paths (304), and / or wherein the channel is modeled (S212) based on a sum of transfer coefficients computed for each of the multiple third paths (304).

13. The device (100) of claim 12, wherein the determining (S208) of the second path (304') for each of the multiple first paths (302) further comprises detecting and eliminating one or more second paths (304') whose intersection point fall outside of the corresponding reflective surface (306) or, if any, the corresponding mirrored diffractive edge (308) of the modified structural information, or wherein the determining (S210) of the third path (304) for each of the multiple first paths (302) further comprises detecting and eliminating one or more third paths (304) whose interaction points fall outside of the respective reflective surface (306) or, if any, the respective diffractive edge (308) of the environment (300).

14. The device (100) of claim 12 or 13, further operative to detect and eliminate one or more second paths (304') whose interaction points (602, 604) are swapped compared to the first path (302) or swapped between different reflective surfaces (306-1, 306-2).

15. A method (200) of determining a path (304) of a wireless communication in an environment (300), the method (200) comprising or initiating: obtaining (S202) structural information indicative of one or more reflective surfaces (306) in the environment (300); determining (S204) a first path (302) in the environment (300) from a finite set of traced rays originating from a first station (400; 402; 1500; 1600) in the environment (300) and intersecting a capture surface (404) of a second station (402; 400; 1600; 1500) in the environment (300); modifying (S206) the structural information by eliminating (S206A) the one or more reflective surfaces (306) along the first path (302) resulting in a mirrored (S206B) first path (302'); determining (S208) a second path (304') by reducing a length of the mirrored (S206B) first path (302') according to the modified (S206) structural information; and determining (S210) a third path (304) by reintroducing (S210A) the one or more reflective surfaces (306) along the second path (304') resulting (S210B) in a third path (304).

16. A computer program product comprising program code portions for performing the functionality of any one of the claims 1 to 14 or the steps of claim 15 when the computer program product is executed on one or more computing devices (1504; 1604; 1704), optionally stored on a computer-readable recording medium (1506; 1606; 1706).

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