Devices and methods for selecting an optimal beamwidth for beam-formed communication

Abstract

A wireless receiver apparatus (120) is disclosed for beam-formed communication with a wireless transmitter apparatus (110). The wireless receiver apparatus is configured to obtain a statistical measure of a performance metric, such as a signal-to-noise ratio, of a beam-formed transmission from the wireless transmitter apparatus to the wireless receiver apparatus. Moreover, the wireless receiver apparatus is configured to determine one or more parameters of a statistical distribution of the beam misalignment between the wireless transmitter apparatus and the wireless receiver apparatus based on the statistical measure of the performance metric and an expected performance metric of the beam-formed transmission from the wireless transmitter apparatus to the wireless receiver apparatus depending on the statistical distribution. The wireless receiver apparatus is further configured to provide the one or more parameters of the statistical distribution of the beam misalignment to the wireless transmitter apparatus.

Description

[0001] DEVICES AND METHODS FOR SELECTING AN OPTIMAL BEAMWIDTH FOR BEAM-FORMED

[0002] COMMUNICATION

[0003] TECHNICAL FIELD

[0004] The present invention relates to wireless communications. More specifically, the present invention relates to a wireless transmitter apparatus and a wireless receiver apparatus for selecting an optimal beamwidth for beam-formed transmission.

[0005] BACKGROUND

[0006] For wireless communications the use of higher operating frequencies is foreseen as a solution to the spectrum contingency problem at lower frequency bands. Additionally, the availability of large, almost contiguous bandwidths at the terahertz / subterahertz bands renders these frequency ranges attractive to communicate with very large data rates suitable for certain data- demanding applications, such as holographic communications and ultra-high capacity wireless x-hauling. However, higher propagation losses at higher frequencies introduces challenges to reliably detect data from a transmitter to a receiver. For instance, at the sub-THz band, propagation loss introduced by free-space propagation and molecular absorption losses is more pronounced when compared to the sub-6 GHz frequency range. Such propagation conditions can be compensated for by introducing high gain antennas at both communicating nodes. As an example, highly directive transmitter antennas point the energy at the direction of the receiver, at the cost of being susceptible to severe gain losses whenever one of the antennas is slightly displaced. This is due to the fact that the beam- width of the adopted beam is narrower than usual, and hence, any slight displacement in the transmit and / or receive antennas introduces a loss in the expected antenna gain.

[0007] SUMMARY OF THE IN VFNTION

[0008] It is an objective of the present disclosure to provide a wireless transmitter apparatus and a wireless receiver apparatus for beam-formed transmission allowing for the selection of an optimized beamwidth for beamed transmission.

[0009] The foregoing and other objectives are achieved by the subject matter of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures. In the following some or more of the following abbreviations and acronyms will be used:

[0010] BW beam-width

[0011] HPBW half-power beam- width

[0012] LOS line-of-sight

[0013] PDF probability density function

[0014] RPL received power level

[0015] THz Terahertz

[0016] ULA uniform linear array

[0017] According to a first aspect a wireless receiver apparatus for beam-formed communication with a wireless transmitter apparatus is provided. The wireless receiver apparatus according to the first aspect is configured to obtain a statistical measure of a performance metric of the beam-formed transmission from the wireless transmitter apparatus to the wireless receiver apparatus. The performance metric of the beam-formed transmission may be, for instance, a signal-to-noise ratio, a received power level, an error vector magnitude, an observed throughput, and the like. The wireless receiver apparatus according to the first aspect is further configured to determine one or more parameters of a statistical distribution of the beam misalignment of the beam-formed transmission between the wireless transmitter apparatus and the wireless receiver apparatus based on the statistical measure of the performance metric and based on an expected performance metric value of the beam-formed transmission from the wireless transmitter apparatus to the wireless receiver apparatus depending on the statistical distribution. Moreover, the wireless receiver apparatus according to the first aspect is configured to provide the one or more parameters of the statistical distribution of the beam misalignment to the wireless transmitter apparatus. This allows the wireless transmitter apparatus to determine an optimally adjusted beam width for the beam-formed transmission from the wireless transmitter apparatus to the wireless receiver apparatus based on the one or more parameters of the statistical distribution of the beam misalignment and the expected performance metric value of the beam-formed transmission from the wireless transmitter apparatus to the wireless receiver apparatus depending on the statistical distribution.

[0018] In a further possible implementation form, the wireless receiver apparatus is configured to obtain the statistical measure of the performance metric of the beam-formed transmission from the wireless transmitter apparatus to the wireless receiver apparatus based on a plurality of measurements of the performance metric, i.e. a plurality of measured performance metric values of the beam-formed transmission from the wireless transmitter apparatus to the wireless receiver apparatus for a plurality of points in time.

[0019] In a further possible implementation form, for determining the one or more parameters of the statistical distribution of the beam misalignment between the wireless transmitter apparatus and the wireless receiver apparatus based on the statistical measure of the performance metric and based on the expected performance metric value of the beam-formed transmission from the wireless transmitter apparatus to the wireless receiver apparatus depending on the statistical distribution, the wireless receiver apparatus is configured to determine the expected performance metric value of the beam-formed transmission based on a radiation pattern G(x) of the wireless transmitter apparatus, wherein x denotes the angular deviation from a main beam direction.

[0020] In a further possible implementation form, the wireless receiver apparatus is configured to determine the expected performance metric value of the beam-formed transmission based on the radiation pattern G(x) of the wireless transmitter apparatus using the following equation:

[0021] Rana = Y fxGWf(x)d.X, wherein Ranadenotes the expected performance metric value of the beam-formed transmission, denotes the statistical distribution of the beam misalignment between the wireless transmitter apparatus and the wireless receiver apparatus, and y denotes a scaling factor. The scaling factor y may depend on the receiver gain, a channel path loss coefficient, the transmit power as well as an additive white Gaussian noise power.

[0022] In a further possible implementation form, the statistical distribution of the beam misalignment is the PDF of a distribution function and the distribution function is defined by one or more distribution function parameters.

[0023] In a further possible implementation form, the one or more distribution function parameters comprise a variance a2.

[0024] In a further possible implementation form, the wireless receiver apparatus according to the first aspect is configured to determine the variance a2based on the following equation: wherein R denotes the statistical measure of the performance metric and Ranadenotes the expected performance metric value of the beam-formed transmission.

[0025] According to a second aspect a method is provided for operating a wireless receiver apparatus for beam-formed communication with a wireless transmitter apparatus. The method according to the second aspect comprises: obtaining a statistical measure of a performance metric of a beam-formed transmission from the wireless transmitter apparatus to the wireless receiver apparatus; determining one or more parameters of a statistical distribution of the beam misalignment between the wireless transmitter apparatus and the wireless receiver apparatus based on the statistical measure of the performance metric and based on an expected performance metric value of the beam-formed transmission from the wireless transmitter apparatus to the wireless receiver apparatus depending on the statistical distribution; and providing the one or more parameters of the statistical distribution of the beam misalignment to the wireless transmitter apparatus.

[0026] The method according to the second aspect can be performed by the wireless receiver apparatus according to the first aspect. Thus, further features of the method according to the second aspect result directly from the functionality of the wireless receiver apparatus according to the first aspect as well as its different implementation forms described above and below.

[0027] According to a third aspect a wireless transmitter apparatus for beam-formed communication with a wireless receiver apparatus is provided. The wireless transmitter apparatus according to the third aspect is configured to perform a beam- formed transmission to the wireless receiver apparatus. Moreover, the wireless transmitter apparatus is configured to receive one or more parameters of a statistical distribution of the beam misalignment between the wireless transmitter apparatus and the wireless receiver apparatus based on a statistical measure of a performance metric and based on an expected performance metric value of the beam-formed transmission from the wireless transmitter apparatus to the wireless receiver apparatus depending on the statistical distribution. The wireless transmitter apparatus according to the third aspect is further configured to determine an adjusted beam width for the beam-formed transmission to the wireless receiver apparatus based on the one or more parameters of the statistical distribution of the beam misalignment and the expected performance metric value of the beam-formed transmission to the wireless receiver apparatus depending on the statistical distribution.

[0028] In a further possible implementation form, the wireless transmitter apparatus is configured to determine the adjusted beam width for the beam-formed transmission to the wireless receiver apparatus based on the one or more parameters of the statistical distribution of the beam misalignment and the expected performance metric value of the beam-formed transmission to the wireless receiver apparatus depending on the statistical distribution as the beam width resulting in the optimal performance metric value of the beam-formed transmission to the wireless receiver apparatus for the one or more parameters of the statistical distribution.

[0029] In a further possible implementation form, the one or more parameters of the statistical distribution of the beam misalignment between the wireless transmitter apparatus and the wireless receiver apparatus are based on the expected performance metric value of the beam- formed transmission and the expected performance metric value is based on a radiation pattern G(x) of the wireless transmitter apparatus, wherein x denotes the angular deviation from a main beam direction.

[0030] In a further possible implementation form, the expected performance metric value Ranais based on the radiation pattern G(x) of the wireless transmitter apparatus in the following form: Rana = Y fxGWf(x)d.X, wherein denotes the statistical distribution of the beam misalignment between the wireless transmitter apparatus and the wireless receiver apparatus, and y denotes a scaling factor. The scaling factor y may depend on the receiver gain, a channel path loss coefficient, the transmit power as well as an additive white Gaussian noise power.

[0031] In a further possible implementation form, the statistical distribution of the beam misalignment is a probability density function, PDF, of a distribution function and wherein the distribution function is defined by one or more distribution function parameters.

[0032] In a further possible implementation form, the one or more distribution function parameters comprise a variance ai, .

[0033] In a further possible implementation form, the variance ai, of the PDF of the distribution function is based on the following equation:

[0034] &p = argmin^lR - Rana(Op)| wherein R denotes the statistical measure of the performance metric and Ranadenotes the expected performance metric value of the beam-formed transmission.

[0035] According to a fourth aspect a method is provided for operating a wireless transmitter apparatus for beam-formed communication with a wireless receiver apparatus. The method according to the fourth aspect comprises: performing a beam-formed transmission to the wireless receiver apparatus; receiving one or more parameters of a statistical distribution of the beam misalignment between the wireless transmitter apparatus and the wireless receiver apparatus based on a statistical measure of a performance metric and based on an expected performance metric of the beam-formed transmission from the wireless transmitter apparatus to the wireless receiver apparatus depending on the statistical distribution; and determining an adjusted beam width for the beam-formed transmission to the wireless receiver apparatus based on the one or more parameters of the statistical distribution of the beam misalignment and the expected performance metric value of the beam-formed transmission to the wireless receiver apparatus depending on the statistical distribution.

[0036] The method according to the fourth aspect can be performed by the wireless transmitter apparatus according to the third aspect. Thus, further features of the method according to the fourth aspect result directly from the functionality of the wireless transmitter apparatus according to the third aspect as well as its different implementation forms described above and below.

[0037] According to a fifth aspect a computer program product is provided, comprising program code which causes a computer or a processor to perform the method according to the second aspect or the method according to the fourth aspect, when the program code is executed by the computer or the processor.

[0038] Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In the following, embodiments of the present disclosure are described in more detail with reference to the attached figures and drawings, in which:

[0040] Fig. la shows a schematic diagram illustrating a wireless transmitter apparatus according to an embodiment performing a beam-formed transmission to a wireless receiver apparatus according to an embodiment;

[0041] Fig. lb shows a variant of figure la for a beam-formed transmission from the wireless transmitter apparatus according to an embodiment to the wireless receiver apparatus according to an embodiment with a larger beam size;

[0042] Fig. 2 shows a flow diagram illustrating steps for adjusting a transmission beam size by a wireless transmitter apparatus according to an embodiment and a wireless receiver apparatus according to an embodiment;

[0043] Fig. 3 shows a signalling diagram illustrating the interaction between a wireless transmitter apparatus according to an embodiment and a wireless receiver apparatus according to an embodiment for adjusting a transmission beam size of the wireless transmitter apparatus;

[0044] Fig. 4 shows graphs illustrating an expected received power level and a simulated measured received power level as a function of an antenna misalignment error variance for the beamed transmission from a wireless transmitter apparatus according to an embodiment to a wireless receiver apparatus according to an embodiment;

[0045] Fig. 5 shows a flow diagram illustrating steps of a method for operating a wireless receiver apparatus according to an embodiment; and

[0046] Fig. 6 shows a flow diagram illustrating steps of a method for operating a wireless receiver apparatus according to an embodiment.

[0047] In the following, identical reference signs refer to identical or at least functionally equivalent features.

[0048] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0049] In the following description, reference is made to the accompanying figures, which form part of the disclosure, which illustrate specific aspects of embodiments of the present disclosure or specific aspects in which embodiments of the present disclosure may be used. It is understood that embodiments of the present disclosure may be used in other aspects and comprise structural or logical changes not depicted in the figures. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims.

[0050] For instance, it is to be understood that a disclosure in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if one or a plurality of specific method steps are described, a corresponding device may include one or a plurality of units, e.g. functional units, to perform the described one or plurality of method steps (e.g. one unit performing the one or plurality of steps, or a plurality of units each performing one or more of the plurality of steps), even if such one or more units are not explicitly described or illustrated in the figures. On the other hand, for example, if a specific apparatus is described based on one or a plurality of units, e.g. functional units, a corresponding method may include one step to perform the functionality of the one or plurality of units (e.g. one step performing the functionality of the one or plurality of units, or a plurality of steps each performing the functionality of one or more of the plurality of units), even if such one or plurality of steps are not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary embodiments and / or aspects described herein may be combined with each other, unless specifically noted otherwise.

[0051] Figure la shows a schematic diagram illustrating a wireless transmitter apparatus 110 according to an embodiment performing a beam-formed transmission with a first beam size 110a, 120a to a wireless receiver apparatus 120 according to an embodiment. Figure lb shows a beam-formed transmission from the wireless transmitter apparatus 110 according to an embodiment to the wireless receiver apparatus 120 according to an embodiment with an adjusted beam size 110b, 120b, which by way of example is larger than the beam size used for the transmission illustrated in figure la. In an embodiment, the wireless transmitter apparatus 110 and the wireless receiver apparatus 120 may be, for instance, base stations 110, 120 of a radio access network of a mobile network, such as a 3GPP network. In an embodiment, the wireless transmitter apparatus 110 and / or the wireless receiver apparatus 120 implement wireless x-hauling, for instance, wireless backhauling, wireless fronthauling, and the like. As illustrated in figures la and lb, the wireless transmitter apparatus 110 and / or the wireless receiver apparatus 120 may be arranged on the top of a pole, mast or tower for a beamed point-to-point communication and may be exposed to twists and sways caused by an external phenomenon, such as wind gusts or mechanical vibration. The beam size of a beamed transmission may be expressed, for instance, in terms of a beamwidth, BW, or the half power beam width, HPBW, wherein the beamwidth of a radiation, i.e. beamforming pattern is defined as the angular separation between two identical points on opposite sides of the pattern maximum and wherein in a plane containing the direction of the maximum of a beam, the HPBW is the angle between the two directions in which the radiation intensity is one-half value of the beam. As will be appreciated, the more narrow BW illustrated in figure la may achieve a larger antenna gain, but is more susceptible to beam misalignments, while the more wide BW illustrated in figure lb achieves a smaller antenna gain, but is less susceptible to beam misalignments.

[0052] As illustrated in figure la, the wireless transmitter apparatus 110, e.g. base station 110, may comprise a processing circuitry 111 and a communication interface 113, in particular a communication interface 113 including one or more antennas enabling a beam-formed communication with an adjustable beam size with the wireless receiver apparatus 120. The processing circuitry 111 may be implemented in hardware and / or software and may comprise digital circuitry, or both analog and digital circuitry. Digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), digital signal processors (DSPs), or general-purpose processors. The wireless transmitter apparatus 110 may further comprise a memory 115 configured to store executable program code which, when executed by the processing circuitry 111, causes the wireless transmitter apparatus 110 to perform the functions and methods described herein.

[0053] Likewise, as indicated in figure la, the wireless receiver apparatus 120, e.g. base station 120, may comprise a processing circuitry 121 and a communication interface 123, in particular a communication interface 123 including one or more antennas enabling a beam- formed communication with an adjustable beam size with the wireless transmitter apparatus 110. The processing circuitry 121 may be implemented in hardware and / or software and may comprise digital circuitry, or both analog and digital circuitry. Digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), digital signal processors (DSPs), or general-purpose processors. The wireless receiver apparatus 120 may further comprise a memory 125 configured to store executable program code which, when executed by the processing circuitry 121, causes the wireless receiver apparatus 120 to perform the functions and methods described herein.

[0054] Aspects of one or more of the embodiments disclosed herein are based on one or more of the following observations. A highly directive beam may be generated by a Uniform Linear Array, ULA, of antennas, which in an embodiment may be implemented as part of the communication interfaces 113, 123 of the wireless transmitter apparatus 110 and / or the wireless receiver apparatus 120. For instance, a 1024 antenna element may generate a radiation beam of 30 dBi gain and a HPBW than can be calculated according to the following formula:

[0055] > 0.8862 ftdfl -dN. wherein 2 is the wavelength, d is the antenna element separation distance, and N is the number of antenna elements of the ULA. For the exemplary values d = and N = 1024, this becomes p-,ii, = 0.1°. This means that for an inclination of 0.1 degrees, the antenna gain is dropped by half.

[0056] In order to produce a high antenna gain, the HPBW is inversely proportional to the number of antenna elements, potentially resulting in a very narrow BW with small HPBW that can reach fractions of a degree.

[0057] For instance, in Asia Pacific Telecommunity, ‘ ‘Draft APT Recommendation on Model(s) for FWS Link Performance Degradation due to Wind,” The 29th Meeting of the APT Wireless Group, March 2022 the effect of wind on the inclination of the pole holding an antenna was modeled based on measurements. A monotonic increase of the inclination degrees as a function of the wind speed was shown, where it was shown that for 20m / s wind speeds, more than 0.5 degrees of pole inclination was measured, which exceeds the HPBW calculated for a 1024 ULA antenna.

[0058] For an ULA, the antenna gain 6(0) may be expressed in the following form: wherein 0Ois the desired beam steering direction (or differently put the direction of maximum beam power). For, 0O= 0°, and given an inclination of 0.5 degrees, the corresponding antenna gain is around 7.1dB, which is approximately 40 times less that the expected maximum gain of 30dB. For the exemplary case of N = 128 the corresponding antenna gain is around 16dB, which is around 10 times higher than that for the case of N = 1024.

[0059] For a fraction of a degree of an antenna pole inclination, a severe loss in the antenna gain is observed for narrow BW patterns. Thus, as will be appreciated, the pole inclination, i.e. antenna misalignment may have a large impact on the possible antenna gain reductions, and the impact of BW adaptation on the achievable antenna gain given and antenna misalignment.

[0060] Embodiments of the wireless transmitter apparatus 110 and the wireless receiver apparatus 120 disclosed herein allow adopting an optimized antenna BW in the sense that it provides, for instance, an optimized, i.e. highest received power level, RPL, given an wireless transmitter apparatus 110 and / or wireless receiver apparatus 120 connected to a pole that is continuously being affected by swaying caused by an external phenomenon such as wind or mechanical vibrations.

[0061] According to embodiments disclosed herein this may be achieved by adapting the BW based on the long-term behavior of the pole swaying that causes random antenna misalignments and / or adapting the BW based on the random fluctuations of, for instance, the RPL, without having to rely on external hardware to collect specific angular measurements. In other words, according to embodiments disclosed herein the wireless transmitter apparatus 110 and the wireless receiver apparatus 120 are used for selecting a more optimal BW.

[0062] As will be described in more detail in the following, the wireless receiver apparatus 120 is configured to obtain a statistical measure of a performance metric of the beam- formed transmission from the wireless transmitter apparatus 110. The performance metric of the beam-formed transmission may be, for instance, a signal-to-noise ratio, a received power level, an error vector magnitude, an observed throughput, and the like. The wireless receiver apparatus 120 is further configured to determine one or more parameters of a statistical distribution of the beam misalignment of the beam-formed transmission from the wireless transmitter apparatus based on the statistical measure of the performance metric and based on an expected performance metric value of the beam-formed transmission from the wireless transmitter apparatus that depends on the statistical distribution. Moreover, the wireless receiver apparatus 120 is configured to provide the one or more parameters of the statistical distribution of the beam misalignment to the wireless transmitter apparatus 110. This allows the wireless transmitter apparatus 110 to determine an adjusted beam width for the beam- formed transmission based on the one or more parameters of the statistical distribution of the beam misalignment and the expected performance metric value of the beam- formed transmission from the wireless transmitter apparatus to the wireless receiver apparatus depending on the statistical distribution.

[0063] Thus, the wireless transmitter apparatus 110 and the wireless receiver apparatus 120 allow implementing a low overhead beam adjustment scheme to combat random misalignments based on random antenna movement. As described above, this scheme includes an estimation of statistical parameters relevant to antenna misalignment (e.g., misalignment variance) based on measurements of a performance metric, e.g. RPL and the selection of a BW which maximizes the expected RPL based on the average monitored RPL readings.

[0064] In an embodiment, the wireless transmitter apparatus 110, i.e. node A 110 and the wireless receiver apparatus 120, i.e. node B 120 are configured to communicate in the sub- THz frequency range, therefore experiencing excessive propagation loss. As already described above, beamforming may be adopted by both nodes to increase the antenna gains and thus combat the propagation loss. It may be assumed that a LoS channel condition is present and dominates over the rest of the multipath traces, therefore emulating a fronthaul / backhaul use case. The path loss channel coefficient L may be calculated in the following way: where K( / ) is the molecular absorption coefficient, c is the speed of light in m / s, dTRis the distance between the wireless transmitter apparatus 110 and the wireless receiver apparatus 120 in meters, and f is the operating frequency in Hertz.

[0065] As already described above, the wireless transmitter apparatus 110, i.e. node A 110 may experience random misalignments with vertical and horizontal shaking, while the wireless receiver apparatus 120, i.e. node B 120 may be idle, i.e. does not move. For an exemplary scenario, the movements of the wireless transmitter apparatus 110, i.e. node A in the vertical and horizontal directions (perpendicular to the main beam direction) are assumed to be independent, and identically distributed Gaussian random variables with ai, representing the variance of the random antenna misalignment error. Given these assumptions, the probability density function, PDF, describing the misalignment may be written as: i.e., as a Rayleigh distribution, wherein is the variance defining the width of the Rayleigh distribution. While the wireless transmitter apparatus 110, i.e. node A performs beamed transmissions, the wireless receiver apparatus 120, on the other hand, collects instantaneous RPL readings, and computes the average thereof in the following way: where Q is the length of the RPL sequence, and RPL(i) is the RPL measured at time instant i. The wireless receiver apparatus 120, i.e. node B has the capability to determine the expected RPL, denoted by Rana, using the following equation: wherein y =l'T'L^< 1'. pTxi, GRxare the transmit power, the additive white Gaussian noise variance and the receiver antenna gain, respectively. The dummy variable 6 represents the angle of departure.

[0066] It can be shown that an approximate closed-form expression of I can be written as: where F(a, x) = e-£t“-1dt is the upper incomplete Gamma function, and T(. ) is the Gamma function.

[0067] Thus, according to this embodiment, the wireless receiver apparatus 120 is configured to determine R, compare it with Rana, and then estimate the antenna misalignment variance error (JRby solving the equation: p = argmin^R - Rana(o*)|

[0068] Then, Node A selects the optimal BW configuration by solving ^3dB ar9maxP'ios^ana('dp) transmitter apparatus 110, i.e. Node A may change its BW accordingly.

[0069] Figure 2 shows a flow diagram illustrating steps for adjusting the transmission beam size by the wireless transmitter apparatus 110 and the wireless receiver apparatus 120 according to an embodiment.

[0070] In step 201 of figure 2, the wireless receiver apparatus 120 according to an embodiment monitors the RPL for the beamed transmission from the wireless transmitter apparatus 110, i.e. it records the RPL at different times and computes an average RPL R in step 203 of figure 2.

[0071] In step 204 of figure 2, the wireless receiver apparatus 120 according to an embodiment computes the expected RPL Rana, for instance, in the way described in detail above.

[0072] In step 205 of figure 2, the wireless receiver apparatus 120 according to an embodiment estimates the antenna misalignment variance error by comparing R and Ranawhile varying (JR.

[0073] In step 207 of figure 2, the wireless receiver apparatus 120 according to an embodiment (and / or the wireless transmitter apparatus 110) according to an embodiment selects the BW configuration which yields the maximum expected RPL.

[0074] In step 209 of figure 2, the wireless transmitter apparatus 110 according to an embodiment changes the beamwidth of the beamed transmission in accordance with the BW configuration determined in step 207. Figure 3 shows a signalling diagram illustrating the interaction between the wireless transmitter apparatus 110, i.e. node A 110 according to an embodiment and the wireless receiver apparatus 120, i.e. node B 120 according to an embodiment for adjusting the transmission beam size used by the wireless transmitter apparatus 110.

[0075] In stage 301 of figure 3, the wireless transmitter apparatus 110, i.e. the node A 110 and the wireless receiver apparatus 120, e.g. the node B 120 exchange the available BWs on both sides respectively, transmit power PTxand the separation distance dTR.

[0076] In stages 303, 305 and 307 of figure 3, the wireless receiver apparatus 120, i.e. the node B 120 measures R, determines Ranaand estimates the misalignment variance ffpTx, as described in detail above. Moreover, the wireless receiver apparatus 120, i.e. the node B 120 provides the variance &ppxto the wireless transmitter apparatus 110, i.e. node A 110.

[0077] In stage 309 of figure 3, the wireless transmitter apparatus 110, i.e. node A 110 selects the optimized BW in the way described above based on the variance &pTxprovided by the wireless receiver apparatus 120, i.e. node B 120. Thus, in stage 307 of figure 3, the antenna misalignment variance error &pTxis estimated by the wireless receiver apparatus 120, i.e. node B 120 and signaled to the wireless transmitter apparatus 110, i.e. node A to adopt the best BW configuration maximizing the average RPL.

[0078] Figure 4 shows graphs illustrating the expected received power level and a simulated measured received power level as a function of the antenna misalignment error variance for different BW configurations. In this example, the following parameters have been used: GRx= 15dB, dTR= 25m, f = 250GHz and PTx= OdBm. As will be appreciated, for the example shown in figure 4 (a) R and Ranaclosely match and (b) three gain domination regions may be identified, namely a lowest BW configuration, wherein the gains dominate over low antenna misalignment error variances; a medium BW configuration, wherein gains dominate over the medium antenna misalignment error variance ranges; and a largest BW configuration, where gains dominate over the high misalignment error variance ranges. For each dominating gain region, the corresponding BW is selected to maximize the RPL.

[0079] Figure 5 shows a flow diagram illustrating steps of a method 500 according to an embodiment for operating the wireless receiver apparatus 120 for beam- formed communication with the wireless transmitter apparatus 110. The method 400 comprises a step 501 of obtaining a statistical measure of a performance metric of the beam-formed transmission from the wireless transmitter apparatus 110 to the wireless receiver apparatus 120. Moreover, the method 500 comprises a step 503 of determining one or more parameters of a statistical distribution of the beam misalignment between the wireless transmitter apparatus 110 and the wireless receiver apparatus 120 based on the statistical measure of the performance metric and an expected performance metric of the beam-formed transmission from the wireless transmitter apparatus 110 to the wireless receiver apparatus 120 depending on the statistical distribution. The method 500 further comprises a step 505 of providing the one or more parameters of the statistical distribution of the beam misalignment to the wireless transmitter apparatus 110 for allowing the wireless transmitter apparatus 110 to select an optimized beamwidth based on the one or more parameters.

[0080] Figure 6 shows a flow diagram illustrating steps of a method 600 according to an embodiment for operating the wireless transmitter apparatus 110 for beam-formed communication with the wireless receiver apparatus 120. The method 600 comprises a step 601 of performing a beam- formed transmission to the wireless receiver apparatus 120. Moreover, the method 600 comprises the step 603 of receiving one or more parameters of a statistical distribution of the beam misalignment between the wireless transmitter apparatus 110 and the wireless receiver apparatus 120 based on a statistical measure of a performance metric and an expected performance metric of the beam-formed transmission from the wireless transmitter apparatus 110 to the wireless receiver apparatus 120 depending on the statistical distribution. The method 600 further comprises a step 605 of determining an adjusted beam width for the beam-formed transmission to the wireless receiver apparatus 120 based on the one or more parameters of the statistical distribution of the beam misalignment and the expected performance metric of the beam-formed transmission to the wireless receiver apparatus 120 depending on the statistical distribution.

[0081] The person skilled in the art will understand that the "blocks" ("units") of the various figures (method and apparatus) represent or describe functionalities of embodiments of the present disclosure (rather than necessarily individual "units" in hardware or software) and thus describe equally functions or features of apparatus embodiments as well as method embodiments (unit = step).

[0082] In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus, and method may be implemented in other manners. For example, the described embodiment of an apparatus is merely exemplary. For example, the unit division is merely logical function division and may be another division in an actual implementation. For example, a plurality of units or components may be combined or integrated into another system, or some features may be ignored or not performed. In addition, the displayed or discussed mutual couplings or direct couplings or communication connections may be implemented by using some interfaces. The indirect couplings or communication connections between the apparatuses or units may be implemented in electronic, mechanical, or other forms. The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one position, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the objectives of the solutions of the embodiments.

[0083] In addition, functional units in the embodiments of the invention may be integrated into one processing unit, or each of the units may exist alone physically, or two or more units are integrated into one unit.

Claims

CLAIMS1. A wireless receiver apparatus (120) for beam- formed communication with a wireless transmitter apparatus (110), wherein the wireless receiver apparatus (120) is configured to: obtain a statistical measure of a performance metric of a beam- formed transmission from the wireless transmitter apparatus (120) to the wireless receiver apparatus (110); determine one or more parameters of a statistical distribution of the beam misalignment between the wireless transmitter apparatus (110) and the wireless receiver apparatus (120) based on the statistical measure of the performance metric and an expected performance metric of the beam-formed transmission from the wireless transmitter apparatus (110) to the wireless receiver apparatus (120) depending on the statistical distribution; and provide the one or more parameters of the statistical distribution of the beam misalignment to the wireless transmitter apparatus (110).

2. The wireless receiver apparatus (120) of claim 1, wherein the wireless receiver apparatus (120) is configured to obtain the statistical measure of the performance metric of the beam-formed transmission from the wireless transmitter apparatus (110) to the wireless receiver apparatus (120) based on a plurality of measurements of the performance metric of the beam-formed transmission from the wireless transmitter apparatus (110) to the wireless receiver apparatus (120) for a plurality of points in time.

3. The wireless receiver apparatus (120) of claim 1 or 2, wherein, for determining the one or more parameters of the statistical distribution of the beam misalignment between the wireless transmitter apparatus (110) and the wireless receiver apparatus (120) based on the statistical measure of the performance metric and the expected performance metric of the beam- formed transmission from the wireless transmitter apparatus (110) to the wireless receiver apparatus (120) depending on the statistical distribution, the wireless receiver apparatus (120) is configured to determine the expected performance metric of the beam-formed transmission based on a radiation pattern G(x) of the wireless transmitter apparatus (110).

4. The wireless receiver apparatus (120) of claim 3, wherein the wireless receiver apparatus (120) is configured to determine the expected performance metric of the beam- formed transmission based on the radiation pattern G(x) of the wireless transmitter apparatus (120) using the following equation:Rana = Y fxGWf(x)d.X, wherein Ranadenotes the expected performance metric of the beam-formed transmission, (x) denotes the statistical distribution of the beam misalignment between the wireless transmitter apparatus (110) and the wireless receiver apparatus (120), and y denotes a scaling factor.

5. The wireless receiver apparatus (120) of claim 4, wherein the statistical distribution of the beam misalignment is a probability density function, PDF.

6. The wireless receiver apparatus (120) of any one of the preceding claims, wherein the one or more parameters compnse a variance cr^ .

7. The wireless receiver apparatus (120) of claim 6, wherein the wireless receiver apparatus (120) is configured to determine the variancebased on the following equation: ap2= argmin^fR - Rana(o2)l wherein R denotes the statistical measure of the performance metric and Ranadenotes the expected performance metric of the beam-formed transmission.

8. A method (500) of operating a wireless receiver apparatus (120) for beam-formed communication with a wireless transmitter apparatus (110), wherein the method (400) comprises: obtaining (501 ) a statistical measure of a performance metric of a beam-formed transmission from the wireless transmitter apparatus (110) to the wireless receiver apparatus (120); determining (503) one or more parameters of a statistical distribution of the beam misalignment between the wireless transmitter apparatus (110) and the wireless receiver apparatus (120) based on the statistical measure of the performance metric and an expected performance metric of the beam- formed transmission from the wireless transmitter apparatus (110) to the wireless receiver apparatus (120) depending on the statistical distribution; and providing (505) the one or more parameters of the statistical distribution of the beam misalignment to the wireless transmitter apparatus (110).

9. A wireless transmitter apparatus (110) for beam-formed communication with a wireless receiver apparatus (120), wherein the wireless transmitter apparatus (110) is configured to: perform a beam-formed transmission to the wireless receiver apparatus (120); receive one or more parameters of a statistical distribution of the beam misalignment between the wireless transmitter apparatus (110) and the wireless receiver apparatus (120) based on a statistical measure of a performance metric and an expected performance metric of the beam-formed transmission from the wireless transmitter apparatus (110) to the wireless receiver apparatus (120) depending on the statistical distribution; and determine an adjusted beam width for the beam-formed transmission to the wireless receiver apparatus (120) based on the one or more parameters of the statistical distribution of the beam misalignment and the expected performance metric of the beam-formed transmission to the wireless receiver apparatus (120) depending on the statistical distribution.

10. The wireless transmitter apparatus (110) of claim 9, wherein the wireless transmitter apparatus (110) is configured to determine the adjusted beam width for the beam-formed transmission to the wireless receiver apparatus (120) based on the one or more parameters of the statistical distribution of the beam misalignment and the expected performance metric of the beam-formed transmission to the wireless receiver apparatus (120) depending on the statistical distribution as the beam width resulting in the optimal performance metric of the beam-formed transmission to the wireless receiver apparatus (120) for the one or more parameters of the statistical distribution.

11. The wireless transmiter apparatus (110) of claim 9 or 10, wherein the one or more parameters of the statistical distribution of the beam misalignment between the wireless transmitter apparatus (110) and the wireless receiver apparatus (120) are based on the expected performance metric of the beam-formed transmission and wherein the expected performance metric is based on a radiation pattern G(x) of the wireless transmiter apparatus (110).

12. The wireless transmitter apparatus (110) of claim 11, wherein the expected performance metric Ranais based on the radiation pattern G(x) of the wireless transmiter apparatus (110) in the following form:Rana = Y fxGWf(x)d.X, wherein (x) denotes the statistical distribution of the beam misalignment between the wireless transmitter apparatus (110) and the wireless receiver apparatus (120), and y denotes a scaling factor.

13. The wireless transmiter apparatus (110) of any one of claims 9 to 12, wherein the statistical distribution of the beam misalignment is a probability density function, PDF.

14. The wireless transmiter apparatus (110) of any one of claims 9 to 13, wherein the one or more parameters compnse a variance cr^ .

15. The wireless transmiter apparatus (110) of claim 14, wherein the variance a2ofthe PDF of the distribution function is based on the following equation: ap2= argmin„2 R - Rana((j2) | wherein R denotes the statistical measure of the performance metric and Ranadenotes the expected performance metric of the beam-formed transmission.

16. A method (600) of operating a wireless transmitter apparatus (110) for beam-formed communication with a wireless receiver apparatus (120), wherein the method (600) comprises: performing (601) a beam- formed transmission to the wireless receiver apparatus (120); receiving (603) one or more parameters of a statistical distribution of the beam misalignment between the wireless transmiter apparatus (110) and the wireless receiver apparatus (120) based on a statistical measure of a performance metric and an expected performance metric of the beam-formed transmission from the wireless transmitter apparatus (110) to the wireless receiver apparatus (120) depending on the statistical distribution; and determining (605) an adjusted beam width for the beam-formed transmission to the wireless receiver apparatus (120) based on the one or more parameters of the statistical distribution of the beam misalignment and the expected performance metric of the beam-formed transmission to the wireless receiver apparatus (120) depending on the statistical distribution.

17. A computer program product comprising a computer-readable storage medium for storing program code which causes a computer or a processor to perform the method (500) of claim 8 or the method (600) of claim 16 when the program code is executed by the computer or the processor.14

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