EP4695772A1

EP4695772A1 - Wireless communication technique for diffusive propagation

Info

Publication number: EP4695772A1
Application number: EP23717986.6A
Authority: EP
Inventors: Sinh Nguyen; Martin Johansson; Henrik Asplund; Magnus Lundevall
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2023-04-13
Filing date: 2023-04-13
Publication date: 2026-02-18
Also published as: WO2024213245A1

Abstract

A technique for wireless communication in an environment (300) is provided. As to one device aspect of the technique, a device (100) comprises memory (1006) operable to store instructions and processing circuitry (1004) operable to execute the instructions, such that the device (100) is operable to determine (S202) a multipath propagation of a plurality of rays (306) launched in different directions from a launch point (302) in the environment (300). The launched rays (306) are arranged in a sequence, k = 0, 1, …, of disjoint sets, s _k, wherein each ray in the subsequent set, s _k ₊₁, is a next neighbor of at least two rays in the set s _k, and wherein each of the launched rays (306) that intersects with a diffusive surface (308) in the environment (300) at a hit point (304) is a diffusive point source (406A; 406B) of the multipath propagation if the launched ray (306) is in one of the sets s _k with k ≤ K _min. The device (100) is further operable to perform or initiate a physical action (S208) that is dependent on the determined (S202) multipath propagation towards at least one position in the environment (300).

Description

WIRELESS COMMUNICATION TECHNIQUE FOR DIFFUSIVE PROPAGATION

Technical Field

The present disclosure relates to a wireless communication technique based on multipath propagation including diffuse scattering interaction, i.e. diffusive reflection, e.g. as opposed to specular reflection. More specifically, devices and methods are provided for wireless communication that take diffusive surfaces into account.

Background

Ray tracing is used for determining radio frequency (RF) wave propagation as a technique for planning and operating a wireless communication network such as a cellular radio access network (RAN). This technique becomes more relevant and more accurate with higher frequencies, larger bandwidths, and more antennas used to develop and deploy radio access technologies (RATs) for mobile and wireless communication of the Fifth Generation (5G), the Sixth Generation (6G) and beyond. Indeed, 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).

The ray tracing technique, which is also referred to as ray launching technique or "shooting and bouncing rays", allows predicting the propagation of radio waves in a specific environment, typically using a ray optical approximation. Here, rays are launched from one or many origin points (i.e., launch points, e.g., transmitter nodes), allowed to interact with the world objects representing the geometry of the environment, until captured at one or many receiver nodes.

In real-world systems the radio wave propagation includes diffusive reflections. The numerical representation of the world objects used in the radio wave propagation modeling tools are by computational necessity often of reduced complexity, which means that real-world geometric objects will be represented by simplified models. For example, a wall of a building may be modeled as flat, smooth, and with homogeneous material properties, even though the real wall is very complex, with doors and windows, window sills and drain pipes, etc., all with different material properties. Even more detailed models capturing large-scale variations in geometry and material properties tend to produce less scattering than observed during measurements.

The diffuse interaction causes scattering from surfaces, thus representing real-world walls more accurately, at least in an average sense. Hence, while referred to as "diffuse", the diffuse interaction is a model intended to capture both the proper diffuse scattering from rough surfaces and the backscattering due to small-scale geometric variations over surfaces. While the former is captured in a diffuse model, such as a Lambertian diffuse pattern with roughness as a surface parameter and causing scattering proportional to cos²(cp), the later typically is implemented by placing diffuse scattering points separated by a parameter ("diffuse delta a") apart in a grid on object surfaces (e.g. buildings’ facade). Since diffuse scattering is the most computationally demanding model, the value of this parameter can have major impact on the overall execution time.

Existing methods for diffuse interaction modeling use environment surface discretization into fixed- size "tiles", whose center are separated by the parameter " diffuse delta a" . Then they perform a computationally expensive pre-calculation step to form a "visibility relation" between every surface tile to the transmitter nodes and the receiver nodes for first-order diffuse propagation paths, and additionally between every surface tile pairs for second-order diffuse propagation paths as published by Z. Lai et al., “An intelligent ray launching for urban prediction,” in Proc. 3rd Eur. Conf. Antennas Propag. ”, Berlin, Germany, Mar. 2009, pp. 2867-2871.

The publication J. S. Lu et al., "A Discrete Environment-Driven GPU-Based Ray Launching Algorithm," in IEEE Transactions on Antennas and Propagation, vol. 67, no. 2, pp. 1180-1192, Leb. 2019, discloses fully discrete Ray Launching field prediction algorithm that takes advantage of environment preprocessing to efficiently trace rays undergoing both specular and diffuse interactions. The algorithm is "environment-driven", because rays are traced from the ray source according to the presence and distribution of obstacles in the surrounding space, therefore adapting ray density to the environment’s characteristics. The environment is discretized into simple regular shapes to facilitate faster geometric computations, to allow for visibility preprocessing and for the algorithm to be parallelized in a straightforward way.

An example of the visibility concept is illustrated in Pig. 11. Due to the presence of a building 404 "B", not all tiles in a surface of a building 404 "A" are visible to both the transmitter node 402 and the receiver node 410. First-order diffuse propagation paths in this case are the ones originating from the transmitter node 402 via the visible tiles and reaching the receiver node 410.

These conventional methods suit only a static environment as the visibility relation changes when there are moving objects 404 in the environment. Furthermore, the conventional methods do not scale well with (or even computationally impede) higher orders of interactions. For example, for second-order diffuse paths the visibility needs to be calculated between every tile of the first interaction to every other tile of the second interactions, on top of the visibility calculation from the transmitter nodes to the first interaction tiles, and from the receiver nodes to the second interaction tiles. Thus, the computational complexity grows exponentially with the order.

Summary

Accordingly, there is a need for accurately determining multipath propagation including diffusive scattering in a manner that is fast enough for real-time control. As to one device aspect, a device for wireless communication in an environment is provided. The device comprising memory operable to store instructions and processing circuitry operable to execute the instructions, such that the device is operable to determine a multipath propagation of a plurality of rays launched in different directions from a launch point in the environment. The launched rays are arranged in a sequence, k = 0, 1, . . . , of disjoint sets, Sk, wherein each ray in the subsequent set, S +i, is a next neighbor of at least two rays in the set S . Each of the launched rays that intersects with a diffusive surface in the environment at a hit point is a diffusive point source of the multipath propagation if the launched ray is in one of the sets Sk with k < K_mm. The device is further operable to perform or initiate a physical action that is dependent on the determined multipath propagation towards at least one position in the environment.

The physical action may be dependent on the multipath propagation (e.g., towards the at least one position in the environment) resulting from the launched rays and the determined zero or more diffusive point sources.

In a first variant of any embodiment, the same device that is determining the multipath propagation 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 multipath propagation. 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.

The rays may model a channel of the wireless communication. Performing the 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 the at least one position 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.

The physical action may comprise modeling (or the device may be further operable to model) a channel of the wireless communication based on the determined multipath propagation between a transmitter node at the launch point and at least one receiver node at the at least one position in the environment and/or between a receiver node at the launch point and at least one transmitter node at the at least one position in the environment.

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 multipath propagation, rather than a measured channel state. The result of the 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. in a similar format as a channel estimate. The subject technique can deal with channel modeling and its applications for a range of use cases. For a given computational complexity, the selection criterion k < K_mm 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.

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). 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).

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 multiple paths, i.e., based on the determined multipath propagation. For example, the electromagnetic propagation may be configured to associate 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 along the path. The multipath propagation channel may be determined by superimposing the electromagnetic field propagated along each of the multiple paths.

As to another device aspect, a device for wireless communication in an environment is provided. The device comprising memory operable to store instructions and processing circuitry operable to execute the instructions, such that the device is operable to determine a multipath propagation of a plurality of rays launched in different directions from a launch point in the environment. The launched rays are arranged in a sequence, k = 0, 1, . . . , of disjoint sets, Sk, wherein each ray in the subsequent set, S +i, is a next neighbor of at least two rays in the set S . Each of the launched rays that intersects with a diffusive surface in the environment at a hit point is a diffusive point source of the multipath propagation if the launched ray is in one of the sets Sk with k < K_mm. The device is further operable to model a channel of the wireless communication based on the determined multipath propagation between a transmitter node at the launch point and at least one receiver node at the at least one position in the environment and/or between a receiver node at the launch point and at least one transmitter node at the at least one position in the environment.

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.

In any aspect, the determining of the multipath propagation may comprise determining multiple paths for the multipath propagation channel. Each of the multiple paths may correspond to one of the rays launched at the at least one antenna location of the transmitter node, subject to the requirement that the path intersects with (e.g., terminates at) the receiver node, e.g., a predefined capture zone of the receiver node. The capture zone may be, or comprise, at least one antenna location of the receiver node or a sphere or a polyhedron enclosing the receiver node.

In any aspect, the multipath propagation of the rays 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).

The diffusive point source may be a further launch point. In other words, a plurality of further rays may be launched in different directions from each diffusive point source. The diffusive point sources may also be referred to as diffusive reflection points.

An antenna of the transmitter node may be at the launch point and at least one antenna of a receiver node may be at the at least one position in the environment.

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.

The launch point may be a transmitter node in the environment or a diffusive point source functioning as a further launch point. The at least one position 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 launch point may be a receiver node of the wireless communication in the environment. The at least one position in the environment may be a transmitter node in the environment. In either case, the at least one position may be different from the launch point, and/or the at least one position may be different from the zero or more diffusive point source, and/or the at least one position may be different from the one or more hit points.

The environment may be susceptible to the multipath propagation of the wireless communication, for example, due to (e.g., specular and/or diffusive) reflections of the rays within the environment and/or because the diffusive point source is a further launch point for a further plurality of rays.

The hit point may be a diffusive source point if (e.g., only if) the launched ray (that intersects with the diffusive surface at said hit point) is in one of the sets Sk with k < K_mm. In other words, the hit point may be a diffusive point source if (e.g., only if) the respective one of the rays is within the union Sk of the sets Sk for k = 0, ..., K.

The criterion, k < K_mm, may be referred to as a selection criterion, e.g. for determining (i.e., selecting) the diffusive point sources out of the hit points. In other words, the hit point may be selectively a diffusive point source according to the criterion. It goes without saying that the criterion specified as k < K_mm is equivalent to k < A_mm+1 or k < X'min, etc. Furthermore, referring to the minimum number, K_mm, of the sets st, k < K_mm may or may not mean that the number of sets used is equal to K_min. For example, the number of used sets may be Tmm+1 is the first set is labelled k = 0.

A plurality of further rays (i.e., sub-rays) may be launched from each diffusive point source. The multipath propagation may be determined by means of recursion, i.e., the step of determining the multipath propagation may be performed recursively at each diffusive source point. Alternatively or in addition, determining the multipath propagation may comprise subsequently applying a launching unit (e.g., configured to launch a plurality of rays) to each of the diffusive point sources selected by the criterion.

Conventionally, the number of rays launched for determining the multipath propagation in an environment grows exponentially (e.g., in time or in the number of diffusive reflections, i.e. intersections with a diffusive surface). For example, when a plurality of As rays is launched in different directions from a launch point S being a source point (e.g. a transmitter node or receiver node of the wireless communication), a fraction a of the As rays intersects with a diffusive surface at a hit point. At each hit point (being conventionally a diffusive source point) AD further rays (i.e., sub-rays of the incident ray) are launched leading to the propagation of As a- AD rays. That is, taking R diffusive reflections into account conventionally requires determining the propagation of S^O D^ rays. While the number of reflections may be cut-off due to attenuation at some value R. the number of rays As^a-Ao^ grows exponentially in R since a- AD > 1.

By virtue of the criterion, k < K_mm, only a fraction P of the hit points on a diffusive surface may on average fulfill the criterion to be a diffusive point source, so that the number of rays in the step of determining the multipath propagation may grow as As (a-p-Ao^. For example, in some scenarios of the environment a- P AD < 1, SO that the number of rays in the multipath propagation may be finite without a cut-off, R. for the number of reflections.

The hit points may include absorption points, specular reflection points, and diffusive point sources. For example, the hit points on the diffusive surface may comprise components of each of absorption and reflection. Furthermore, reflection may comprise components of each of specular reflection and diffusive reflection. That is, the energy of the ray intersecting (impinging) at the hit point may be partially absorbed (so that a part of the incident power is dissipated), reflected (so that a part of the incident energy is carried by a ray launched from the hit point at an angle of reflection equal to the angle of incidence), and scattered (so that the further rays spawn in different directions from the hit point carry a part of the incident energy).

The diffusive surface in the environment may be a surface causing diffuse reflection (also referred to as scattering) of the multipath propagation. The determining of the multipath propagation may take the scatering into account by means of the diffusive point sources, i.e., by those rays fulfilling the selection criterion. Electromagnetic power that is carried by diffusive (i.e. scatered) rays can correspond to a coefficient of diffusive reflection of the diffusive surface. A power per scatered ray (i.e. the sum of power of all the further rays launched at the diffusive point source or the power of each of the further rays launched at the diffusive point source) may be increased inversely proportional to the down-selection of the selection rule. For example, the power per scatered ray may be proportional to the ratio of the number of all the hit points to the number of the diffusive point sources.

The device for wireless communication in an environment may be implemented as a ray-tracer performing the step of determining the multipath propagation.

The diffusive surface may be a surface of an object in the environment.

In any aspect, K_mm may be the minimum number of sets Sk, k < K_min, of the launched rays that fulfils a density criterion of the diffusive point sources on the diffusive surface.

The sets S according to the selection criterion k < K_mm may be the minimum integer number of K_mm sets that fulfils the density criterion.

Determining the diffusive point sources out of the hit points on the diffusive surface may limit the surface density of the diffusive point sources to fulfil the (minimum) density criterion (e.g. the density of the diffusive point sources is equal to or greater than a minimum surface density) using the minimum number, K_mm, of the sets Sk of the launched rays. The diffusive point sources may fulfill a local density criterion on the surface with a minimum number, K_mm > 0, of the sets Sk for k = 0, ..., K_mm. For example, is the smallest integer so that the surface (i.e., areal) density of hit points of the rays in the sets Sk, k < Amm, at the diffusive surface is equal to or greater than the minimum surface density (e.g., locally, i.e. in the vicinity of the respective hit point that is assessed as to whether the hit point functions as a diffusive point source).

By using the minimum number, A_mm, of the sets Sk, k < K_mm that fulfills the predefined density criterion, the number of diffusive point sources can be limited by means of the density criterion (e.g., the minimum surface density) and reduced compared to a conventional technique for determining a multipath propagation based on rays. The limited or reduced number of diffusive point sources significantly (e.g., exponentially) reduces the computational complexity without decreasing the fidelity of the determined multipath propagation, since the surface density of the diffusive point sources does not fall below the minimum surface density.

For example, the determining of the diffusive point sources may be performed per ray (e.g., consecutively for each of the launched rays or for each of the hit points on the surface) and/or on the fly (e.g., subsequently along the rays from surface to surface). For example, dependent on the distance travelled by each of the launched rays, a divergence of the launched rays can be determined (e.g., regardless if neighboring rays actually intersect with the diffusive surface). If this divergence is greater than the minimum surface density, the hit point may be a diffusive point source, i.e. this specific ray triggers a subsequent launch of further (i.e. diffuse) rays. Determining whether the density criterion is fulfilled may or may not comprise a comparison with any neighboring ray or neighboring hit point, e.g. since the information needed to take the decision (i.e., determining K_mm and assessing whether or not the hit point is a diffusive point source) may be fully captured in the index k of the set Sk to which the ray belongs.

The density criterion may be a minimum surface density (e.g., a maximum surface distance) of the diffusive point sources on the diffusive surface. The density criterion may require that a (e.g., local) surface distance of the diffusive point sources is equal to or less than the maximum surface distance or a (e.g., local) surface density of the diffusive point sources is equal to or greater than the minimum surface density.

The density criterion may comprise a parameter (e.g., labelled "a" or "delta_a" or "diffuse_delta_a") of the diffusive surface. The parameter may be, or may correspond to, the minimum surface density. For example, the parameter A may be the maximum surface distance. The minimum surface density may be inversely proportional to the square of the maximum surface distance (e.g., the parameter).

The parameter may be a parameter of the diffusive surface and/or the object in the environment.

Herein, the hit points (in plural form) considered for the density criterion of the diffusive point sources (e.g., for defining the surface density of the diffusive point sources) may refer to the intersections of the plurality of launched rays of all sets si_:. k < K for a non-negative integer K. That is, the surface density, o, ("sigma") of the diffusive point sources may be function of K: o = o(A). The non-negative integer K may be denoted the hierarchy or hierarchy level of the launched rays. Denoting the minimum surface density by Omm, the minimum number Amm may be the smallest integer fulfilling o_min < o(A_mm). Alternatively or in addition, the hit point (in singular form) may refer to the hit point for which it is to be determined whether or not the hit point is a diffusive point source.

The surface density of the diffusive point sources may be inversely proportional to an area on the diffusive surface, e.g. centered at the hit point. The area on the diffusive surface may be a circle, a square, closed convex polygon, or a regular polygon. In a first option, the area may be the largest area not comprising a further one of the hit points or the largest area comprising only the nearest neighbor of the hit points. In a second option, the area may be the closed convex polygon defined by the next-neighboring hit points relative to the hit point. Herein, the next-neighboring hit points may encompass those of the hit points on the diffusive surface that are directly connected (i.e., connected by a single edge) with the hit point according to a Delaunay triangulation of the hit points on the diffusive surface. In a third option, the area may be a Voronoi cell of the hit points on the surface. This option has the advantage that the Voronoi cell avoids predefining a shape of the area for determining the surface density. In any aspect, K_mm may be determined independently for each of the hit points.

The criterion, k < K_mm, for whether or not the respective one of the hit points is a diffusive point source may be evaluated (i.e., assessed) per ray (e.g., for each of the hit points) and/or sequentially downstream along the propagation of each of the launched rays (also referred to as on-the-fly). For example, both determining the value of K_mm and assessing the criterion may be performed independently for each of the hit points (or for each ray).

In any aspect, K_mm may be dependent on a distance travelled by the respective one of the launched rays between the launch point and the hit point (304). Alternatively or in addition, K_mm may be dependent on an incidence angle of the respective one of the launched rays with the surface at the hit point.

The value of K_mm may be determined as a function of the distance (e.g., travelled by the respective one of the launched rays between the launch point and the hit point) and the incidence angle (e.g., of the respective one of the launched rays with the surface at the hit point). In case the ray is reflected (e.g., by specular reflection or a previous diffusive reflection) before intersecting with the diffusive surface, the distance may correspond to the sum of the lengths of the line segments between the launch point and the hit point on the diffusive surface.

Each of the rays may be associated with its set by, e.g., implementing the ray as an object of the set and/or using indices. For example, each ray may be as an object of a ray-class, which may include an indicator of the set (e.g., the hierarchy level) of the respective ray. Alternatively or in addition, each of the rays to may be associated with an index and the set may be derived from the index.

Each of the launched rays may be associated with an index that is indicative of its set st. Alternatively or in addition, the determination of the multipath propagation may comprise determining for each hit point whether or not the hit point is a diffusive point source based on whether or not k < K_mm.

The determining for each hit point whether or not the hit point is a diffusive point source based on whether or not k < K_mm (i.e., the selection criterion) may be referred to as selecting each hit point as a diffusive point source if k < K_mm (i.e., if the selection criterion is fulfilled).

Each of the rays launched from the launch point may be assigned an index. The sets may be arranged and/or the indices may be sorted, such that each of the indices in any one set Sk of the sets is less than each of the indices in the subsequent set s,t+i of the sets. Furthermore, the criterion, k < K_mm, may be equally implemented by a criterion i < I_mm, wherein i is the index of the ray (e.g., for which the criterion determines whether or not the ray is a diffusive point source) and 7mm is the greatest index in the set svmin. Herein, using the minimum number, K_mm, of the sets may mean combining the minimum number of the sets in the order of the sequence. Alternatively or in addition, using the minimum number, K_mm, of the sets may mean combining the first K_mm sets in the order of increasing indices.

Since the directions of the rays are different, the direction of each of the rays in any one of the sets are pairwisely distinct from the direction of each of the rays in the another one of the sets. Since the directions of the rays are different and/or since the subsequent set includes further next neighbors, an angular density of the rays at the launch point is increased by using (e.g., combining) more of the sets, e.g. by combining a first set with a second set of the arranged sets.

Herein, referring to one index being less than another index may mean that the index is a numerical value (e.g., an integer) and the numerical value of the one index is less than the numerical value of the other index.

The indices assigned to the plurality of the launched rays may be unique, e.g. unique per launch point (i.e., unique for each launch point). The indices of the launched rays may be consecutive (i.e., numbered consecutively), e.g. at each launch point. Assigning the indices to the rays may also be referred to as ray indexing. The ray indexing may be applied per launch point (i.e., for each launch point).

Performing the physical action may comprise transmitting or receiving the wireless communication based on the determined multipath propagation or controlling the wireless communication in the environment based on the determined multipath propagation.

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.

The wireless communication in the environment may be performed (e.g., transmitted or received) or controlled (e.g., initiated) based on the launched rays and/or the determined zero or more diffusive point sources.

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. The determining of the multipath propagation 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.

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 multipath propagation. Alternatively or in addition, controlling the wireless communication may comprise configuring the transmitter node and/or the receiver node of the wireless communication.

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.

Transmitting, receiving and/or controlling based on the determined multipath propagation may be implemented by raytracing -informed transmitting, receiving and/or controlling.

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 multipath propagation, optionally by comparing radio signals received at the radio device in the environment with radio signals expected or modeled at the at least one position in the environment according to the determined multipath propagation and/or by comparing radio signals received from the radio device in the environment with radio signals expected or modeled at the at least one position in the environment according to the determined multipath propagation. 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 multipath propagation, optionally by determining an energy flux in the environment based on the determined multipath propagation or the modeled channel.

Positioning and/or adjusting based on the determined multipath propagation may be implemented by raytracing-informed positioning and/or adjusting.

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.

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.

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 multipath propagation between at least one transmitter node and at least one receiver node, and/or emulating the channel of the wireless communication based on the modeled channel.

The transmitter node for the emulating of the channel may correspond to or refer to the transmitter node of the modeling of the channel. Alternatively or in addition, the receiver node for the emulating of the channel may correspond to or refer to the receiver node of the modeling of the channel.

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 is wired (e.g., in the analog domain) to an emulating device, 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 at least one receiver. 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 selection criterion of the subject technique, enables using more accurate channel models (e.g., detailed or more complex surfaces in the environment), e.g. in equipment testing or DTs. 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 diffusive surface) 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.

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.

The deployed transmitter node may correspond to, or may refer to, the (at least one) transmitter node of the modeling of the channel or the emulating of the channel. Alternatively or in addition, the deployed receiver node may correspond to, or may refer to, the (at least one) receiver node of the modeling of the channel or the emulating of the channel.

Deploying the transmitter node and/or the receiver node based on the determined multipath propagation may comprise a raytracing -based radio network dimensioning.

The multipath propagation may be determined in real-time or the diffusive point sources 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.

By using the minimum number of the sets in the order of the sequence that fulfills the predefined density threshold on the surface in the vicinity of the hit point, the number of diffusive point sources is limited by means of the predefined density threshold such that the multipath propagation channel can be determined in real-time and/or for beamforming and/or for controlling the radio network. Alternatively or in addition, the multipath propagation channel may be determined taking diffusion interaction in the radio frequency (RF) propagation with real-time movement in the environment into account. For example, the minimum surface density may be controlled depending on an availability of computational resources for the determining of the multipath propagation and/or depending on a required update rate or a maximum latency for the determining of the multipath propagation or the modeling channel.

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 multipath propagation is determined (e.g., periodically updated) within less than L/V time. The determining of the multipath propagation may comprise determining multiple paths of the multipath propagation along the plurality of launched rays and/or continued at each of the hit points by a further ray per hit point according to specular reflection and/or, if the hit point is a diffusive point source, by a plurality of further rays according to diffusive reflection.

The diffusive surface may also be a reflection surface. Determining the multipath propagation may comprise reflecting the launched rays at each of the hit points. The further ray per launched from the hit point (i.e., the reflected ray) according to specular reflection may obey the laws of reflection, e.g. including at least one of: (i) The incident ray (i.e., the launched ray leading to the hit point), the reflected ray, and the normal to the reflection surface at the point of the incidence may lie in the same plane, (ii) The incident angle (i.e., the angle between the incident ray and the normal) is equal to the emergent angle (i.e., the angle between reflected ray and the same normal), (iii) The reflected ray and the incident ray are on the opposite sides of the normal.

In any aspect, the determining of the multipath propagation may comprise determining multiple paths, e.g. based on the launched rays and continued at the hit points of the launched rays by the further rays launched at the hit points. The further rays may include one further ray per hit point for specular reflection and the plurality of further rays for diffusive reflection.

For example, the reflection (i.e., the launching of the reflected ray) is not subject to the determination of whether or not the hit point is a diffusive point source (i.e., the selection) and/or is not limited to the minimum number of the sets. The reflecting may be included in the multipath propagation at the hits points resulting from all launched rays (e.g., from all sets or a maximum number of sets).

In any aspect, the different directions of the plurality of rays launched from the launch point may be uniformly or quasi-uniformly distributed in angle, optionally in each of the sets. For example, the rays in the first set (e.g., so = So, i.e., for k=0) 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 launch point 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. 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, quasi-uniformly distributed directions may be defined by further subdividing each edge (i.e., line between next neighbors) of the previous set in the sequence of set. For example, the set so may correspond to an icosahedron. To achieve quasi-uniformity for the set Si, the directions of the rays in the set Si may correspond to the midpoints of each edge in the set 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 set. The midpoints may be on straight lines or on a great circle on the surface comprising the neighboring vertices.

A number of the rays in each set, Sk, and/or an angular density of the directions of the rays in each set, Sk, may be progressively increasing in the sequence, k = 0, 1, . . . , of sets.

A number of the rays in each set, Sk, and/or an angular density of the directions of the rays in each set, Sk, may be progressively increasing from each set, Sk, to the subsequent set, Sk+\, in the sequence, k = 0, 1, . . . , of sets. Progressively may mean faster than linear (also denoted as super-linear) in the index k. For example, progressively increasing may mean polynomially increasing or exponentially increasing.

The angular density in each set may be defined as the average of angles between neighboring rays in the respective set. Herein, neighboring rays of the launched rays (or neighboring directions) may be defined by neighboring intersections with a (e.g., sufficiently small) sphere around the launch point. Alternatively or in addition, the angular density may be defined by the density of the intersections with a (e.g., sufficiently small) sphere around the launch point.

In one option, the number of rays in a set Sk+\ may be greater than the number of rays in the previous set Sk, so that the number of rays in the combined sets Sk is increasing faster than linear in the index k. In another option, the number of rays in a set Sk+\ may be greater than the number of rays in the previous combined set Sk, so that the number of rays in the combined sets Sk is increasing faster than quadratic in the index k.

For example, a first set .v of rays may comprise the rays with indices 0 to index_thri-l, which may also be referred to as hierarchy level k=0. A second set si of rays may comprise the rays with indices index_thri to index_thr2-l, which may also be referred to as hierarchy level k= . A third set s-> of rays may comprise the rays with indices index_thr2 to index_thr3-l, which may also be referred to as hierarchy level k=2. By way of example, index_thri=12, index_thr2=30+12=42, and index_thr3=42+120=162.

The plurality of rays may be launched in two dimensions. The different directions of the plurality of launched rays may correspond to equally spaced points on a circle, optionally wherein the launch point is at the center of the circle or on a line perpendicular to the plane of the circle, and/or wherein the sets comprise the rays resulting from bisecting the equally spaced points of a previous set.

The plurality of launched rays may be in the plane of the circle (i.e., if the launch point is the center of the circle), which may also be referred to as a two-dimensional bundle of rays. Alternatively or in addition, the plurality of launched rays may be in a cone (i.e., if the launch point is on the line perpendicular to the plane of the circle). In any aspect, determining the multipath propagation may comprise launching a plurality of rays (e.g., as described for the launch point) from each of the diffusive point sources determined (i.e., selected) according to the selection criterion. In other words, the device may be configured to iteratively perform determining whether a hit point (e.g., wherever a ray intersects with a further diffusive surface in the environment) is a diffusive point source according to the selection criterion and, if so, launch from each diffusive point source a further plurality of rays.

The plurality of rays launched at each of the diffusive point sources may also be referred to as diffusive rays or spawned rays. The directions of the diffusive rays may be uniform or quasi-uniformly distributed using any one of the methods disclosed herein for the launching of the plurality of rays, optionally restricted to a half space (e.g., uniform or quasi-uniformly distributed on a hemisphere) on one side of the diffusive surface.

As to one method aspect, a method for wireless communication (e.g., a method of supporting and/or performing a wireless communication) in an environment is provided. The method comprises or triggers a step of determining a multipath propagation of a plurality of rays launched in different directions from a launch point in the environment, wherein the launched rays are arranged in a sequence, k = 0, 1, . . . , of disjoint sets, st. Each ray in the subsequent set, Sk+i, is a next neighbor of at least two rays in the set Sk, and wherein each of the launched rays that intersects with a diffusive surface in the environment at a hit point is a diffusive point source of the multipath propagation if the launched ray is in one of the sets Sk with k < K_mm. The method further comprises or triggers a step of performing or initiating a physical action that is dependent on the determined multipath propagation towards at least one position in the environment.

The one 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.

As to another method aspect, a method for wireless communication (e.g., a method of supporting and/or performing a wireless communication) in an environment is provided. The method comprises or triggers a step of determining a multipath propagation of a plurality of rays launched in different directions from a launch point in the environment, wherein the launched rays are arranged in a sequence, k = 0, 1, . . . , of disjoint sets, Sk. Each ray in the subsequent set, Sk+i, is a next neighbor of at least two rays in the set Sk, and wherein each of the launched rays that intersects with a diffusive surface in the environment at a hit point is a diffusive point source of the multipath propagation if the launched ray is in one of the sets Sk with k < K_mm. The method further comprises or triggers a step of modeling a channel of the wireless communication based on the determined multipath propagation between a transmitter node at the launch point and at least one receiver node at the at least one position in the environment and/or between a receiver node at the launch point and at least one transmitter node at the at least one position in the environment. 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.

Embodiments of the technique (i.e., any aspect of the technique) may be applied for diffuse scattering interaction, e.g., from surfaces of buildings, ground, etc. 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.

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.

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

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.

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.

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.

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

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).

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).

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).

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.

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 one method aspect and/or the other method 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 may be provided for download by means of a hardware description language. 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.

A processing circuitry of the cellular network may be configured to execute any one of the steps of the one method aspect and/or the other 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 one method aspect and/or the other method aspects.

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 one method aspect and/or the other method aspect.

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.

Any one of the devices, the transmitting node, the receiving node, the UE, 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 aspects, and vice versa the method aspects 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 aspects, and the devices may comprise a unit or a module performing any of the steps of the method aspects.

Brief Description of the Drawings

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

Fig. 1 shows a schematic block diagram of an embodiment of a device for wireless communication using a multipath propagation;

Fig. 2 shows a flowchart of an embodiment of a method for wireless communication using a multipath propagation, which method may be implementable by the device of Fig. 1; Fig. 3A schematically illustrates a portion of an example environment for determining whether or not a hit point is a diffusive point source, which may be implementable by any embodiment of the device of Fig. 1 or the method of Fig. 2;

Figs. 3B and 3C schematically illustrate how a selection criterion for determining whether or not a hit point is a diffusive point source depends on an angle of incidence;

Fig. 4 schematically illustrates an example of an environment for embodiments of the device of Fig. 1 or the method of Fig. 2;

Fig. 5 schematically illustrates examples for different values of a parameter specifying a surface density for the selection criterion;

Fig. 6 shows a three-dimensional (3D) example of a plurality of rays launched in different sets;

Fig. 7 shows a two-dimensional (2D) example of a plurality of rays launched in different sets;

Fig. 8 shows a flowchart of an implementation of the method of Fig. 2;

Fig. 9 shows a block diagram of an emulating embodiment of the device of Fig. 1;

Fig. 10 shows a block diagram of a network node embodying the device of Fig. 1; and

Fig. 11 illustrates a reference example for diffuse propagation paths using a conventional visibility concept.

Detailed Description

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.

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.

Fig. 1 schematically illustrates a block diagram of an embodiment of a device for wireless communication in an environment. The device is generically referred to by reference sign 100.

The device 100 comprises memory operable to store instructions and processing circuitry operable to execute the instructions, such that the device 100 is operable to perform the one method aspect and/or the other method aspect.

Alternatively or in addition, the device comprises a propagation determination module 102 that determines a multipath propagation of a plurality of rays launched in different directions from a launch point in the environment. The launched rays are arranged in a sequence, k = 0, 1, . . . , of disjoint sets, Sk, wherein each ray in the subsequent set, S +i, is a next neighbor of at least two rays in the set S .

By way of example, "next neighbors" may be defined by a Delaunay triangulation of intersection of the rays with a (sufficiently small) sphere around the launch point. Two rays are next neighbors if the corresponding intersections are connected by an edge of the Delaunay triangulation. As another example, two rays which directions make an angle that is less than an angle threshold value may be "next neighbors". The angle threshold value may be a decreasing function of the number of rays.

Each of the launched rays that intersects with a diffusive surface in the environment at a hit point is a diffusive point source of the multipath propagation, if the launched ray is in one of the sets Sk with k Amin.

According to one device aspect, the device 100 further comprises an action module 108 that performs or initiates a physical action that is dependent on the determined multipath propagation towards at least one position in the environment. According to another device aspect, the device 100 further comprises a modeling module 106 that models a channel of the wireless communication based on the determined multipath propagation between a transmitter node at the launch point and at least one receiver node at the at least one position in the environment and/or between a receiver node at the launch point and at least one transmitter node at the at least one position in the environment.

Optionally, the device 100 according to the one method aspect also comprises the modeling module 106 according to the other method aspect. The physical action may depend (alternatively or additionally to the determined multipath propagation towards at least one position in the environment) on the modeled channel.

Alternatively or in addition, in any aspect, the device 100 further comprises a selection module 104 that determines for each of the hit points whether or not the hit point is a diffusive point source according to the selection criterion k < K_mm, i.e. based on whether or not k < K_mm, wherein each of the launched rays is associated with an index k that is indicative of its set st.

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

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

Fig. 2 shows an example flowchart for a method 200 for wireless communication in an environment. In a step S202 of the method 200, a multipath propagation is determined based on a plurality of rays launched in different directions from a launch point in the environment. The launched rays are arranged in a sequence, k = 0, 1, . . . , of disjoint sets, Sk, wherein each ray in the subsequent set, S +i, is a next neighbor of at least two rays in the set S . Each of the launched rays that intersects with a diffusive surface in the environment at a hit point is a diffusive point source of the multipath propagation if the launched ray is in one of the sets Sk with k < K_mm.

According to one method aspect, in a step S208 of the method 200, a physical action that is dependent on the determined multipath propagation towards at least one position in the environment is performed or initiated.

According to another method aspect, in a step S206 of the method 200, a channel of the wireless communication is modeled based on the determined multipath propagation between a transmitter node at the launch point and at least one receiver node at the at least one position in the environment.

Alternatively or in addition, a channel of the wireless communication is modeled based on the determined multipath propagation between a receiver node at the launch point and at least one transmitter node at the at least one position in the environment. Optionally, the method 200 comprises the step S206 and the step 208. Alternatively or in addition, the method 200 comprises a step S204, e.g. as a sub-step of the step S202, of determining for each hit point whether or not the hit point is a diffusive point source based on whether or not k < K_min.

The method 200 may be performed by the device 100. For example, the modules 102, 104, 106, and 108 may perform the steps S202, S204, S206, and S208, respectively.

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.

Each of 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.

In any aspect, since a subset of the hit points is determined to be a diffusive point source according to the selection criterion, the technique may be described as a ray selection method for diffusive reflection (i.e., diffusive interaction), e.g. in radio frequency ray tracing.

The method can be efficient, since not all hit points are selected to be diffusive point sources. Furthermore, the method can accurately determine the multipath propagation, because Am may be the minimum number of sets Sk, k < Am, of the launched rays that fulfils a density criterion of the diffusive point sources on the diffusive surface.

The technique may be embodied by a method including a diffuse scattering interaction (e.g., from surfaces of buildings, ground, etc.) into a radio frequency (RF) propagation model for deterministic and site-specific radio network modelling and simulation based on ray tracing based.

The number K_mm of sets S , which are used (e.g., combined to Sk) for the diffusive reflection (i.e., the diffuse interaction), is also referred to as the hierarchy level. Arranging the rays in such sets, optionally with consecutive indices for the rays, is also referred to as hierarchical ray indexing. In other words, each of the launched rays may be associated with an index that is indicative of its set Sk. The hierarchy level K_mm may be determined independently for each of the hit points. In other words, the technique can involve determining (according to the step S204) on-the-fly the diffuse interaction at each diffusive surface based on the hierarchical ray indexing. The diffusive point sources on the environment’s diffusive surfaces may be determined based on a model-based diffuse source distribution (that can be changed during runtime).

The diffusive point sources may be determined (according to the step S204) by the hit point when rays hit surfaces. In one embodiment, a parameter "diffuse_delta_a" is a length parameter for small-scale geometric variations over surfaces. I.e., on the average there is a diffusive point source for every diffuse delta a [e.g. in meters]. In other words, the parameter "diffuse_delta_a" is an example for the density criterion of the diffusive point sources on the diffusive surface. The hierarchy level K_mm is determined so that diffusive point sources on the diffusive surface fulfil the density criterion.

For example, the hierarchy level K_mm is dependent on at least one of: a distance travelled by the respective one of the launched rays between the launch point and the hit point; and an incidence angle of the respective one of the launched rays with the surface at the hit point.

This allows to fulfil the density criterion and to determine whether or not a hit point is a diffusive point source independently for each ray, i.e. on the fly.

Fig. 3A schematically illustrates a portion of an example environment 300 for determining whether or not a hit point 304 is a diffusive point source.

A plurality of rays 306 is launched from a launch point 302. The greater the hierarchy level K of the combined sets so U ... U SK = SK, the denser (in terms of angle) is the bundle of launched rays.

The parameter 314 labelled a or "diffuse_delta_a" can be different for different surfaces, for example depending on the surface type. A more flat and homogeneous building surface 308 can have a larger parameter "diffuse_delta_a".

By ray launching with hierarchical ray indexing, the launched rays are indexed in a structured group (i.e., the set Sk) so that each ray "level" can be determined from its index (i.e., the "level" k of the set Sk can be determined from the index i of the ray). One example for such hierarchical ray indexing for ray launching in three dimensions is via a triangular grid enclosing the launch point, e.g. as further detailed below.

The hierarchy level K_mm is determined dependent on the distance 310 (labelled "/") travelled by the respective one of the launched rays 306 between the launch point 302 and the hit point 304 and the incidence angle 312 (labelled "/?") of the respective one of the launched rays 306, so that the density of the diffusive point sources fulfils the density criterion 314.

The hierarchy level K (also referred to as resolution level) corresponds to an angular separation a_K of the rays 306 [e.g., in radians]. The length parameter 314 represents a required maximum separation a of diffusive point sources. The incidence angle ft is the angle between a normal of the diffusive surface 308 and the direction of the respective one of the rays 306.

Accordingly, the spatial separation of the launched rays 306 at the distance I for a hierarchy (resolution) level T in a plane perpendicular to the launch direction is w_K « I • a_N.

Fig. 3B schematically illustrates the density of rays in a plane 308' that is perpendicular to the direction of the ray 306 for which it is to be determined whether or not it causes a diffusive point source at the hit point 304.

If the diffusive surface 308 is tilted by the incidence angle 314 ("/?"), the distance between the hit points 304 (and accordingly the distance between the diffusive point sources) is stretched in one dimension according to

For ray selection to trigger diffuse scattering, i.e., for the selection criterion k < K_mm, one has to find the minimum value A for the hierarchy level K for which d_r < a (or d_r < a). The rays 306 corresponding to a larger hierarchy level K, i.e. rays from a set SK for K > K_mm are not allowed.

While the way to determine K_mm as a function of the incidence angle and the distance has been explained in two dimensions with reference to Fig. 3A, the same holds true for the three-dimensional environment 300, as is illustrated in Fig. 3C. Both dimension of the grid of hit points 304 is stretched by the distance 310, and one dimension of the grid of hit points 304 is stretched by the angle 312 of incidence.

The hit points 304 will appear on a grid on the diffusive surface 308, with the grid configuration being dependent on the grid of launched rays 306 (e.g., a triangular grid) and the orientation of the diffusive surface 308 (which distorts the triangles along one dimension).

One implementation to determine K_mm in 3D for ray selection is to find the minimum value for the hierarchy level K for which and don’t allow rays 306 corresponding to a larger K values to trigger diffuse scattering. This implementation matches the density criterion 314 (e.g., a length parameter a) in one dimension and causes oversampling in the perpendicular dimension.

Another implementation for determining K_min in 3D for ray selection is to find the minimum value K_mm of the hierarchy level K for which ri, and don’t allow rays 306 corresponding to larger K values to trigger diffuse scattering. This implementation matches the density criterion 314 (namely the length parameter a) in one dimension, and causes undersampling in the perpendicular dimension.

Yet another possible implementation may use more elaborate hierarchical indexing that could support different resolutions in different dimensions. For example, the density criterion may be represented by an area 316 of a Delaunay triangulation of the grid of hit points 304.

At least some embodiments of the technique use a hierarchical ray indexing for the launched rays 306 from the launch point 302 (e.g., a transmitter node, or from a previous diffusive point source, or from diffraction interaction points), combined with a parameter 314 for the diffusive point source distribution (i.e., for the surface density of diffusive point sources on the diffusive surface 308) to model radio wave diffuse interaction and tracing. Specifically, embodiments involve a method of determining according to the step S204 whether a ray 306, when hitting a surface 308, results in diffuse interactions which in turn results in launching new hierarchical rays 306 for subsequent ray tracing and radio wave modelling.

The rays 306 launched from a launch point 302 are hierarchically indexed, i.e. they are assigned an index i that is indicative of the set Sk (i.e., the hierarchy level k). The launch point 302 may be a transmitter node, a diffusive point source, or a diffraction interaction points.

If a ray 306 hits a surface 308, whose diffuse model is characterized by a parameter 314 for the surface density (e.g., a length parameter "diffuse_delta_a") of the diffusive point sources, based on the distance 310 the ray 306 has traveled and the incidence angle 312 to the surface 308, a specific ray level is determined and compared with the hierarchy level k of the rays 306 (from the hierarchical index i of the ray) to determine in the step S204 if new diffuse rays are spawned after the hit and continued to be traced. Specifically, the following steps need to be performed.

The step S204 may comprise at least one of the following sub-steps:

- Determine the travel distance 310, 1, of the ray 306 from the last point source (i.e. the launch point 302, which may be a transmitter node or a previous diffusive point source). - Calculate the required minimum ray index level K_mm at distance I so that rays 306 hit the surface according to the surface density criterion 314, e.g. separated by at most the length parameter diffuse delta a.

- If the ray index (assigned at the launching phase or at the last diffusive point source) is larger than the required minimum ray index level, i.e. if the selection criterion is not fulfilled, there is no diffuse ray spawned at this hit point. Otherwise, spawn new diffuse rays 306.

An example of the environment 300 is illustrated in Fig. 4. The environment comprises a transmitter node 402 causing a launch point 302 (e.g., at each antenna of the transmitter node 402), objects 404 that are obstacles (i.e., impermeable) for the propagation of RF rays 306, and a receiver node 408.

Fig. 4 illustrates an example of specular-diffuse interaction combination (i.e., specular and diffusive reflection). The building A is specified having smooth surface without diffusive point source, while building B has a diffusive surface 308, e.g. according to the parameter 314 for a length diffuse delta a separating the diffusive point sources 406 distributed over its surface 308. When hitting building B’s wall surface, rays 1 and 3 produces diffuse scattering at the diffusive point sources 406A and 406B (on top of specular reflection), while ray 2 produces specular reflection only at the hit point 304 between the diffusive point sources 406A and 406B.

Examples of first order diffuse propagation paths when the parameter 314 for the length "diffuse_delta_a" varies are illustrated in Fig. 5.

The surface density of the diffusive point sources according to the parameter 314 may vary from surface to surface and/or within the surface 308. For example, each triangle information holder ("struct") representing a part of the surface 308 may be indicative of a triangle-specific parameter 314 (e.g., the length "diffuse_delta_a"), for example in the form of an explicit numeric value or as an index to a global vector of "diffuse_delta_a" values accessible from all triangles.

The rays are launched at the transmitter node 402 and indexed (e.g., over a three-dimensional triangular grid or a cone) according to the hierarchical sets Sk. Diffuse ray selection, i.e., the selection criterion, is based on the per-surface parameter 314 for the surface density of diffusive point sources (i.e., diffuse source distribution, e.g., "diffuse_delta_a"), is on-the-fly and independent from one surface to another.

As illustrates in Fig. 4, the determining S202 of the multipath propagation comprises determining multiple paths of the multipath propagation along the plurality of launched rays 306 and continued at each of the hit points 304 by a further ray per hit point according to specular reflection and/or, if the hit point 304 is a diffusive point source (e.g. 406A or 406B), by a plurality of further rays according to diffusive reflection. The hierarchical indexing may be based on a three-dimension (e.g., triangular) grid as illustrated in Fig. 6, or a two-dimension circle as illustrated in Fig. 7, with bisection indexing. That is, for the next set st+i (i.e., for the next higher hierarchical level), the directions of the rays are centered between the directions of neighboring rays of the set Sk.

By ray launching with hierarchical ray indexing, the launched rays are indexed in a structured group, i.e. the sets Sk, so that each ray "level" k can be determined from the index i of the respective ray 306. One such hierarchical ray indexing for ray launching in the three-dimensional environment 300 is using a (e.g., triangular) grid enclosing the launch point 302, or a two-dimensional cone or circle enclosing the launch point 302.

Starting from a base set so (e.g., the vertices of a Platonic solid), the subsequent sets Sk, k= , . . . can be iteratively determined using angular bisection.

Fig. 6 schematically illustrates hierarchical ray indexing over a three-dimensional triangular grid.

At subdivision level 0, i.e. for the set so, there are 12 launched rays each indexed from 0, 1, . . . , 11, having directions to the icosahedron vertices. At subdivision level 1, i.e. for the set Si = so U st, the launched rays 306 are indexed from 0 to 41, including the 12 rays 306 in the first subdivision level 0 (i.e., in the set So), and 30 new rays (i.e., in the set st) from subdividing the 20 triangle faces of the icosahedron, and so on...

For illustration, an example of a ray that is in the base (or initial) set so is illustrated at reference sign 602. An example of a ray that is in the first level set si is illustrated at reference sign 604. It is at the midpoint of the edge connecting two vertices corresponding to two rays in the base set so. By iteration, an example of a ray in the second level set S2 is illustrated at reference sign 606, which is at the midpoint between the ray 604 and the ray with index z=l.

The smallest triangle edge (i.e., the resolution width) at the hierarchy level X+l is approximately half of one at level K.

Inspection of this examples shows that the number of the rays 306 in each set, Sk, and accordingly the angular density of the directions of the rays in each set, Sk, is progressively increasing in the sequence, k = 0, 1, . . . , of sets, that is faster than linear.

Fig. 7 schematically illustrates hierarchical ray indexing over a circle (or cone). The rays in the base set sO may correspond to a predefined number of rays, which directions are equally distributed over the circumference of the circle with the launch point 302 at its center. At the next level +I, rays are spawned by bisecting the angle between rays at level K, and hence their resolution width reduced by half (i.e., their angular density doubles). Fig. 8 shows a flowchart of an implementation of the method 200.

As indicated on the left-hand side of Fig. 8, the preparatory steps S201A to S201C do not include a computationally expensive "visibility relation" pre-calculation step.

An example implementation of the step S202 is shown in more detail on the right-hand side of Fig. 8. The selection criterion is evaluated at the substep step S204 of the step S202 per surface and per ray, i.e. on- the-fly.

The multiple paths determined in the step S202 are recorded. Based the determined multiple paths, the physical action is performed S208 and/or the channel of the wireless communication is modeling S206.

An example of the physical action is shown in Fig. 9. Fig. 9 shows a block diagram of an emulating embodiment of the device of Fig. 1. 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 multipath propagation between at least one transmitter node 402 and at least one receiver node 408 (which in turn may be based on the channel modeled in the step S206).

The device 100 comprises an RF input 902 and an RF output 904 coupled to the transmitter node 402 and the receiver node 408, respectively, to let the equipment 402 and/or 408 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 multipath propagation enables real-time or near real-time emulation of the radio channel, which is very important for this use case.

Fig. 10 shows a schematic block diagram for an embodiment of the device 100. The device 100 comprises processing circuitry, e.g., one or more processors 1004 for performing the method 200 and memory 1006 coupled to the processors 1004. For example, the memory 1006 may be encoded with instructions that implement at least one of the modules 102, 104, 106, and 108.

The one or more processors 1004 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 1006, transmitter or receiver functionality. For example, the one or more processors 1004 may execute instructions stored in the memory 1006. 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. 10, the device 100 may be embodied by a transmitter and/or receiver node 1000, e.g., functioning as a base station (e.g., a network node of a RAN) or a radio device (e.g., a UE). The node 1000 comprises a radio interface 1002 coupled to the device 100 for radio communication with one or more other nodes, e.g., including base stations or UEs.

Performing the physical action S208 may comprise transmitting S208-1 or receiving S208-2 the wireless communication based on the determined multipath propagation determined in the step S202. Alternatively or in addition, the interface 1002 may be a control interface (e.g., a network interface or an Fl interface). For example, the node 1000 may be a central unit of network node. Performing the physical action S208 may comprise controlling S208-0 the wireless communication in the environment 300 based on the determined multipath propagation.

Alternatively or in addition, the physical action S208 may comprise positioning one or more radio devices in the environment 300. The transmission S208-1 of the wireless communication, or the controlling S208-0 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 multipath propagation of the step S202 or the modeled channel of the step S206.

Alternatively or in addition, the physical action S208 may comprise controlling directional gain and/or transmit power of the wireless communication in the environment 300. For example, a radio device 1000 (e.g., a UE) may determine its position or a network node 1000 (e.g., a gNB) may determine the position of a radio device in the environment 300 based on the multipath propagation determined in the step S202.

In one embodiment, radio signals received S208-2 at the radio device 1000 in the environment 300 are compared with radio signals expected (e.g., modeled S206) at the at least one position in the environment 300 according to the determined S202 multipath propagation. In another embodiment, the radio signals received S208-2 from a radio device in the environment 300 at a network node 1000 are compared with radio signals expected (e.g., modeled S206) at the at least one position in the environment 300 according to the determined S202 multipath propagation.

Alternatively or in addition, the construction or upgrade of a RAN (e.g., when the radio frequency the RAN is increased) may depend on the determined S202 multipath propagation. For example, the position for deploying at least one a base station 1000 (i.e., a transmitter and receiver node 402, 408) in the environment 300 may be determined based on the determined S202 multipath propagation (e.g., based on the modeled S206 and/or emulated S208 channel). In any embodiment, the multipath propagation, and thus the modeled or emulated channel, may be determined in real-time, optionally for the transmitting S208-1 of the wireless communication or the receiving S208-2 of the wireless communication or the controlling S208-0 of the wireless communication (or for initiating S208-0 of the of transmitting S208-1 or receiving S208-2 of the wireless communication).

As has become apparent from above description, at least some embodiments of the technique can eliminate the need for a computationally expensive "visibility relation" pre-calculation step, as the determining of the multipath propagation can include determining on the fly whether launched rays hit or miss the diffuse tiles. The diffuse interactions (i.e., the diffusive reflection) can be calculated on-the-fly, and hence, is suitable also for a dynamic environment or real-time network simulation applications.

Same or further embodiments can adapt the distribution (e.g., density) of the diffusive point sources on diffusive surfaces for different surface types. E.g., different building types can be assigned different parameters "diffuse_delta_a".

Same or further embodiments can model any combinations of diffuse scattering (i.e., diffusive reflection) with other interactions (transmission, specular reflections, diffraction). I.e., the diffusive point sources can have a direct line-of-sight to the transmitter and receiver nodes, or line-of-sight to them via intermediate points (specular reflection, diffraction, or another diffusive point sources). This can be done within the ray-tracing shoot-and-bounce framework, while this combination is conventionally very computationally costly if done via a pre-calculated "visibility relation" matrix.

Embodiments of the technique can be very efficient for parallel-processing and/or on GPU-hardware accelerated ray-tracing.

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

1. A device (100) for wireless communication in an environment (300), the device (100) comprising memory (1006) operable to store instructions and processing circuitry (1004) operable to execute the instructions, such that the device (100) is operable to: determine (S202) a multipath propagation of a plurality of rays (306) launched in different directions from a launch point (302) in the environment (300), wherein the launched rays (306) are arranged in a sequence, k = 0, 1, . . . , of disjoint sets, Sk, wherein each ray in the subsequent set, S +i, is a next neighbor of at least two rays in the set S , and wherein each of the launched rays (306) that intersects with a diffusive surface (308) in the environment (300) at a hit point (304) is a diffusive point source (406A; 406B) of the multipath propagation if the launched ray (306) is in one of the sets Sk with k < K_mm,' and perform or initiate a physical action (S208) that is dependent on the determined (S202) multipath propagation towards at least one position in the environment (300).

2. The device (100) of claim 1, wherein the physical action (S208) comprises or the device (100) is further operable to: model (S206) a channel of the wireless communication based on the determined (S202) multipath propagation between a transmitter node (402; 1000) at the launch point (302) and at least one receiver node (408; 1000) at the at least one position in the environment (300) and/or between a receiver node (408; 1000) at the launch point (302) and at least one transmitter node (402; 1000) at the at least one position in the environment (300).

3. A device (100) for wireless communication in an environment (300), the device (100) comprising memory (1006) operable to store instructions and processing circuitry (1004) operable to execute the instructions, such that the device (100) is operable to: determine (S202) a multipath propagation of a plurality of rays (306) launched in different directions from a launch point (302) in the environment (300), wherein the launched rays (306) are arranged in a sequence, k = 0, 1, . . . , of disjoint sets, Sk, wherein each ray in the subsequent set, Sk+i, is a next neighbor of at least two rays in the set Sk, and wherein each of the launched rays (306) that intersects with a diffusive surface (308) in the environment (300) at a hit point (304) is a diffusive point source (406A; 406B) of the multipath propagation if the launched ray (306) is in one of the sets Sk with k < K_mm,' and model (S206) a channel of the wireless communication based on the determined (S202) multipath propagation between a transmitter node (402; 1000) at the launch point (302) and at least one receiver node (408; 1000) at the at least one position in the environment (300) and/or between a receiver node (408; 1000) at the launch point (302) and at least one transmitter node (402; 1000) at the at least one position in the environment (300).

4. The device (100) of any one of claims 1 to 3, wherein K_mm is the minimum number of sets Sk, k < K_min, of the launched rays (306) that fulfils a density criterion (314) of the diffusive point sources (406A; 406B) on the diffusive surface (308).

5. The device (100) of any one of claims 1 to 4, wherein K_mm is determined independently for each of the hit points (304).

6. The device (100) of any one of claims 1 to 5, wherein K_mm is dependent on at least one of: a distance (310) travelled by the respective one of the launched rays (306) between the launch point (302) and the hit point (304); and an incidence angle (312) of the respective one of the launched rays (306) with the surface at the hit point (304).

7. The device (100) of any one of claims 1 to 6, wherein each of the launched rays (306) is associated with an index that is indicative of its set Sk, and/or wherein the determination (S202) of the multipath propagation comprises determining (S204) for each hit point (304) whether or not the hit point (304) is a diffusive point source (406A; 406B) based on whether or not k < K_mm.

8. The device (100) of any one of claims 1 to 7, wherein performing the physical action (S208) comprises transmitting (S208-1) or receiving (S208-2) the wireless communication based on the determined (S202) multipath propagation or controlling (S208-0) the wireless communication in the environment (300) based on the determined (S202) multipath propagation.

9. The device (100) of claim 8, wherein the physical action (S208) further comprises at least one of: positioning a radio device (1000) at the at least one position in the environment (300) based on the determined (S202) multipath propagation, optionally by comparing radio signals received (S208-2) at the radio device (1000) in the environment (300) with radio signals expected or modeled (S206) at the at least one position in the environment (300) according to the determined (S202) multipath propagation and/or by comparing radio signals received (S208-2) from the radio device (1000) in the environment (300) with radio signals expected or modeled (S206) at the at least one position in the environment (300) according to the determined (S202) multipath propagation; and adjusting the transmission (S208-1) of the wireless communication or controlling (S208-0) the wireless communication to ensure compliance with regulations based on the determined (S202) multipath propagation, optionally by determining an energy flux in the environment based on the determined (S202) multipath propagation or the modeled (S206) channel.

10. The device (100) of any one of claims 1 to 9, wherein the physical action (S208) comprises: emulating the channel of the wireless communication based on the determined (S202) multipath propagation between at least one transmitter node (402; 1000) and at least one receiver node (408; 1000), and/or emulating the channel of the wireless communication based on the modeled (S206) channel.

11. The device (100) of any one of claims 1 to 10, wherein the physical action comprises: deploying at least one transmitter node (402; 1000) and/or at least one receiver node (408; 1000) in the environment (300) based on the determined (S202) multipath propagation, optionally based on the modeled (S206) and/or emulated (S208) channel.

12. The device (100) of any one of claims 1 to 11, the multipath propagation is determined (S202) in real-time or the diffusive point sources (406A; 406B) are determined (S204) in real-time or the channel is modeled (S206) in real-time or the channel is emulated in real-time, optionally for the transmitting (S208- 1) of the wireless communication or the receiving (S208-2) of the wireless communication or the controlling (S208-0) of the wireless communication or the initiating (S208-0) of the of transmitting (S208-1) of the wireless communication or the initiating (S208-0) of the receiving (S208-2) of the wireless communication.

13. The device (100) of any one of claims 1 to 12, wherein the determining (S202) of the multipath propagation comprises determining multiple paths of the multipath propagation along the plurality of launched rays and continued at each of the hit points (304) by a further ray per hit point according to specular reflection and/or, if the hit point (304) is a diffusive point source (406A; 406B), by a plurality of further rays according to diffusive reflection.

14. The device (100) of any one of claims 1 to 13, wherein a number of the rays in each set, Sk, and/or an angular density of the directions of the rays in each set, S , is progressively increasing in the sequence, k = 0, 1, ... , of sets.

15. A method (200) for wireless communication in an environment (300), the method (200) comprising or triggering: determining (S202) a multipath propagation of a plurality of rays (306) launched in different directions from a launch point (302) in the environment (300), wherein the launched rays (306) are arranged in a sequence, k = 0, 1, . . . , of disjoint sets, Sk, wherein each ray in the subsequent set, Sk+i, is a next neighbor of at least two rays in the set Sk, and wherein each of the launched rays (306) that intersects with a diffusive surface (308) in the environment (300) at a hit point (304) is a diffusive point source (406A; 406B) of the multipath propagation if the launched ray (306) is in one of the sets Sk with k < K_mm,' and performing or initiating a physical action (S208) that is dependent on the determined (S202) multipath propagation towards at least one position in the environment (300).

16. A method (200) for wireless communication in an environment (300), the method (200) comprising or triggering: determining (S202) a multipath propagation of a plurality of rays (306) launched in different directions from a launch point (302) in the environment (300), wherein the launched rays (306) are arranged in a sequence, k = 0, 1, . . . , of disjoint sets, Sk, wherein each ray in the subsequent set, S +i, is a next neighbor of at least two rays in the set S , and wherein each of the launched rays (306) that intersects with a diffusive surface (308) in the environment (300) at a hit point (304) is a diffusive point source (406A; 406B) of the multipath propagation if the launched ray (306) is in one of the sets Sk with k < K_mm,' and modeling (S206) a channel of the wireless communication based on the determined (S202) multipath propagation between a transmitter node (402; 1000) at the launch point (302) and at least one receiver node (408; 1000) at the at least one position in the environment (300) and/or between a receiver node (408; 1000) at the launch point (302) and at least one transmitter node (402; 1000) at the at least one position in the environment (300).

17. The method (200) of claim 15 or 16, further comprising any feature or step of any one of the claims 2 or 4 to 14.

18. A computer program product comprising program code portions for performing the steps of any one of the claims 14 to 17 when the computer program product is executed on one or more computing devices (1004), optionally stored on a computer-readable recording medium (1006).