WO2019101291A1

WO2019101291A1 - Estimation device, communication device and methods thereof

Info

Publication number: WO2019101291A1
Application number: PCT/EP2017/079894
Authority: WO
Inventors: Chaitanya TUMULA; Neng Wang
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2017-11-21
Filing date: 2017-11-21
Publication date: 2019-05-31

Abstract

The invention relates to an estimation device (200) for estimating parameters associated with a Direction of Arrival, DoA, of an incoming signal (502) at an antenna array (112), the estimation device (200) is configured to apply a first receive beam on the incoming signal (502) so as to obtain a first received symbol, wherein the first receive beam corresponds to a phase shift γ ₁ between any two adjacent antenna elements of the antenna array (112) along a first dimension (X); and apply a second receive beam on the incoming signal (502) so as to obtain a second received symbol, wherein the second receive beam corresponds to one of phase shifts π + γ ₁or −π + γ ₁between the two adjacent antenna elements along the first dimension (X). The estimation device (200) is configured to estimate a first set of parameters associated with the DoA of the incoming signal (502) based on the first received symbol and the second received symbol. Furthermore, the invention also relates to a communication device comprising the estimation device (200), corresponding methods, and a computer program.

Description

ESTIMATION DEVICE, COMMUNICATION DEVICE AND METHODS THEREOF

Technical Field

The invention relates to an estimation device and a communication device. Furthermore, the invention also relates to corresponding methods and a computer program.

Background

Direction of arrival (DoA) or direction finding of incoming signals is a well-researched problem for different applications, such as radar, sonar, acoustic signal separation, electronic surveillance, etc. Recently, with the use of large antenna arrays for multiple-input multiple-out (MIMO) communications and the associated beamforming techniques, DoA estimation algorithms found their way into the wireless communications field.

In fifth generation (5G) systems also known as new radio (NR), base station (BS) and/or user equipment (UE) may be equipped with antenna arrays having a large number of antenna elements. The transmission and reception of signals in the downlink (DL) and uplink (UL) are based on beam based transmissions, i.e. the data is transmitted using narrow beams with most of the signal energy transmitted in the direction of the receiver, and a beam can be viewed as a MIMO precoding vector or matrix.

In case of millimeter wave (mmWave) frequency systems, such as used in NR, the transmitter and receiver may use an antenna structure with analog-digital precoding at the transmitter and analog-digital combining at the receiver. The receiver for mmWave systems may be equipped with multiple antenna arrays each comprising multiple antenna elements. Each antenna array can be a two dimensional array or a one dimensional array. Typically, all antenna elements corresponding to a given polarization in an antenna array are connected to an analog-to-digital converter (ADC) through a set of phase shifters. By adjusting the phase values of different phase shifters, the receive beam can be steered in a given direction, that can be referred to as the look angle. In the art, the processing of combining the signal received at different antenna elements using phase shifters is also known as analog combining.

In conventional beam sweeping approach, the receiver selects the best receive beam by sweeping through different receive beams one after the other, and measuring the received signal power at the output of an ADC or measuring a reference signal received power (RSRP). Typically, the receive beam that maximizes the RSRP can be selected as the best receive beam for a given transmit beam. The conventional beam sweeping approach has drawbacks in terms of: i) delay for selecting the best receive beam by trying one receive beam after another is not efficient; and ii) the receive beamforming gain obtained by the receive antenna array is limited by the size of receive beam codebook, i.e. the number of beams that are used in the sweeping procedure. In order to achieve the largest receive beamforming gain, the receive beam codebook size should be very large, which may further lead to delay in beam acquisition process.

In correlation based DoA estimation method, the phase information of the correlation coefficient is computed using the signal outputs from the ADCs connected to antenna elements from two separate antenna arrays and is used for DoA estimation. The correlation method is not applicable in practical systems as antenna arrays may be placed with a larger separation in a receiving device and hence the channels observed by different antenna arrays are uncorrelated in a mmWave communication system.

Summary

An objective of embodiments of the invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions.

The above and further objectives are solved by the subject matter of the independent claims. Further advantageous embodiments of the present invention can be found in the dependent claims.

According to a first aspect of the invention, the above mentioned and other objectives are achieved with an estimation device for estimating parameters associated with a Direction of Arrival, DoA, of an incoming signal at an antenna array, the estimation device being configured to

apply a first receive beam on the incoming signal so as to obtain a first received symbol, wherein the first receive beam corresponds to a phase shift g_c between any two adjacent antenna elements of the antenna array along a first dimension;

apply a second receive beam on the incoming signal so as to obtain a second received symbol, wherein the second receive beam corresponds to one of phase shifts p + g₁ or -p + g₁ between the two adjacent antenna elements along the first dimension;

estimate a first set of parameters associated with the DoA of the incoming signal based on the first received symbol and the second received symbol.

The parameters associated with the DoA of the incoming signal may correspond to the angles of arrival values in azimuth and elevation (zenith) planes. Alternatively, the parameters associated with the DoA of the incoming signal may be functions of the angles of arrival in the azimuth and elevation planes. In an implementation, the functions of the angles of arrival may correspond to the values of the phase shifts between the received signals of any two adjacent antenna elements of the antenna array.

A receive beam can correspond to a (unit) vector of phase shift values applied at the phase shifters connected to antenna elements of an antenna array. Different receive beams can be formed by applying different phase shift values to phase-shifters connected to the antenna elements of the antenna array.

That the first receive beam corresponds to a phase shift g_c could in this disclosure be understood to mean that the receive beam at the estimation device is formed such that any two phase-shifters connected to any two adjacent antenna elements of the antenna array along the first dimension have their phase shift values differ by a value g_c. For example, for a one dimensional antenna array comprising four antenna elements, a receive beam corresponding to g could refer to a vector

By using the first and second receive beams, the estimation device could estimate a phase shift value (corresponding to the DoA of the incoming signal) between the received signals of any two adjacent antenna elements along the first dimension of the antenna array.

An advantage of the present estimation device is that the beam acquisition processing delay can be reduced as well as the receive beamforming gain can be improved as the receive beam vector can be chosen based on the estimated DoA, which is more accurate compared to conventional solutions.

In an implementation form of an estimation device according to the first aspect,

the first receive beam further corresponds to a phase shift b₁ between any two adjacent antenna elements of the antenna array along a second dimension;

the second receive beam further corresponds to the phase shift b₁ between the two adjacent antenna elements of the antenna array along the second dimension.

The second dimension is in one implementation form orthogonal to the first dimension. Moreover, in the case of a two-dimensional antenna array, the first dimension can relate to the length of the antenna array and the second dimension to the width of the antenna array or vice versa. An advantage with this implementation form is that even with a two-dimensional antenna array, only two receive beams need to be used to estimate the parameters associated with the DoA of the incoming signal. This implementation form is especially useful if the two-dimensional antenna array has more antenna elements along the first dimension compared to the second dimension.

In an implementation form of an estimation device according to the first aspect, the estimation device is further configured to

apply a third receive beam on the incoming signal so as to obtain a third received symbol, wherein the third receive beam corresponds to the phase shift g_c between the two adjacent antenna elements along the first dimension and one of phase shifts p + b₁ or -p + b₁ between the two adjacent antenna elements along the second dimension;

estimate a second set of parameters associated with the DoA of the incoming signal based on the first received symbol, the second received symbol and the third received symbol.

An advantage with this implementation form is that by using a third receive beam in addition to the first and second receive beams, the estimation device could estimate a phase shift value (corresponding to the DoA of the incoming signal) between the received signals of any two adjacent antenna elements along the second dimension of the antenna array further improving the DoA estimation.

apply a fourth receive beam on the incoming signal so as to obtain a fourth received symbol, wherein the fourth receive beam corresponds to one of the phase shifts p + g_c or -p + g₁ between the two adjacent antenna elements along the first dimension and to one of the phase shifts p + b₁ or -p + b₁ between the two adjacent antenna elements along the second dimension;

estimate a third set of parameters associated with the DoA of the incoming signal based on the first received symbol, the second received symbol, the third received symbol and the fourth received symbol.

An advantage with this implementation form is that by using a fourth receive beam, the estimation device could obtain multiple estimates of the phase shift values (corresponding to the DoA of the incoming signal) between the received signals of any two adjacent antenna elements along the first and second dimensions of the antenna array. Thereby, improved estimated DoA can be provided. In an implementation form of an estimation device according to the first aspect, the estimation device is further configured to

estimate at least one of the first set of parameters, the second set of parameters and the third set of parameters based on a sum of one or more cross-correlations between two distinct linear combinations of reference signals associated with the same resource element in at least two of the first received symbol, the second received symbol, the third received symbol and the fourth received symbol.

An advantage with this implementation form is that it provides an explicit method for obtaining at least one of the first set of parameters, the second set of parameters and the third set of parameters associated with the DoA of the incoming signal.

In an implementation form of an estimation device according to the first aspect, each one of the first set of parameters, the second set of parameters, and the third set of parameters comprises at least one of

at least one first phase shift value between the two adjacent antenna elements along the first dimension; and

at least one second phase shift value between the two adjacent antenna elements along the second dimension;

wherein the first phase shift value and the second phase shift value are associated with the DoA of the incoming signal.

This implementation form provides details about the first, second and the third set of parameters. By associating the first, second and the third set of parameters with the phase shift values between the two adjacent antenna elements along the first and second dimensions, the DoA of the incoming signal is easily modelled. In addition the next receive beam to receive further incoming signal(s) can be selected in a simple manner based on these phase shift values.

In an implementation form of an estimation device according to the first aspect, the estimation device is further configured to determine at least one of

a first phase shift estimate y between the two adjacent antenna elements along the first dimension based on a first weighted combination of the first phase shift values of the first set of parameters, the second set of parameters and the third set of parameters; and a second phase shift estimate b between the two adjacent antenna elements along the second dimension based on a second weighted combination of the second phase shift values of the first set of parameters, the second set of parameters and the third set of parameters.

An advantage with this implementation form is that it provides a method to obtain the phase shift estimates (corresponding to the DoA of the incoming signal) g and b between the two adjacent antenna elements along the first and the second dimension, respectively.

determine weights for the first phase shift values and the second phase shift values of the first set of parameters, the second set of parameters, and the third sets of parameters, respectively, based on a respective associated effective received signal strength, ERSS, wherein each respective associated ERSS is a function of an absolute value of a sum of one or more cross-correlations between two distinct linear combinations of reference signals associated with the same resource element in at least two of the first received symbol, the second received symbol, the third received symbol and the fourth received symbol.

An advantage with this implementation form is that it provides an explicit method in which the first, second and the third set of parameters are combined based on associated effective received signal strength to obtain the phase shift estimates (corresponding to the DoA of the incoming signal) g and b between the two adjacent antenna elements along the first and the second dimension, respectively.

a first phase shift estimate y between the two adjacent antenna elements along the first dimension based on selecting the first phase shift value of the first set of parameters, the second set of parameters, and the third set of parameters having the highest respective associated ERSS; and

a second phase shift estimate b between the two adjacent antenna elements along the second dimension based on selecting the second phase shift value of the first set of parameters, the second set of parameters, and the third set of parameters having the highest respective associated ERSS;

wherein each respective associated ERSS is a function of an absolute value of a sum of one or more cross-correlations between two distinct linear combinations of reference signals associated with the same resource element in at least two of the first received symbol, the second received symbol, the third received symbol and the fourth received symbol.

An advantage with this implementation form is that it provides a simplified method in which the first, second and the third set of parameters can be combined based on associated effective received signal strength to obtain the phase shift estimates y and b between the two adjacent antenna elements along the first and the second dimension, respectively.

In an implementation form of an estimation device according to the first aspect, at least one of the phase shift y_x e [- p, p ] and the phase shift b₁ e [- p, p ] .

An advantage with this implementation form is that suitable values for phase shifts y₁ and b₁ to be used in selecting the first, second, third and the fourth receive beams can be selected.

In an implementation form of an estimation device according to the first aspect, the estimation device is configured to

select a receive beam for reception of a subsequent incoming signal at the antenna array based on at least one of the first set of parameters, the second set of parameters, the third set of parameters, the first phase shift estimate y and the second phase shift estimate b, wherein the subsequent incoming signal is subsequent to the incoming signal.

An advantage with this implementation form is that the estimation device can select the next receive beam based on the estimated phase shift values y and b. By selecting the receive beam based on the estimated phase shift values, a better receive beamforming gain may be obtained in comparison with conventional solutions since the estimated phase shift values y and b are more accurate.

select a transmit beam for transmission of an outgoing signal at the antenna array based on at least one of the first set of parameters, the second set of parameters, the third set of parameters, the first phase shift estimate y and the second phase shift estimate b.

In case of transmit/receive beam correspondence at the estimation device, the estimated DoA information of the incoming signal could be used to select the transmit beam for transmitting outgoing signal. An advantage with this implementation form is by selecting the transmit beam based on the estimated phase shift values, a better transmit beamforming gain may be obtained in comparison with conventional solutions.

According to a second aspect of the invention, the above mentioned and other objectives are achieved with a communication device for a wireless communication system, the communication device comprising the estimation device according to any implementation form of the first aspect or to the first aspect as such.

Advantages of the communication device according to the second aspect of the invention are the same as for the estimation device according to the first aspect of the invention.

In an implementation form of a communication device according to the second aspect, the communication device further comprises

the antenna array comprising a plurality of antenna elements in the first dimension and a plurality of antenna elements in the second dimension,

at least one additional antenna array comprising a plurality of antenna elements in the first dimension and a plurality of antenna elements in the second dimension; and wherein the communication device is further configured to at least one of

determine at least one of the first set of parameters, the second set of parameters and the third set of parameters independently for the antenna array and the additional antenna array; and

determine at least one of the first set of parameters, the second set of parameters and the third set of parameters jointly for the antenna array and the additional antenna array.

An advantage with this implementation form is that, in case a communication device has two antenna arrays, the first, second and the third set of parameters could be estimated independently for each antenna array. This implementation form is useful if the antenna arrays are placed with a larger separation on the communication device. Alternatively, if the two antenna arrays are placed closely, the communication device could estimate the first, second and the third set of parameters jointly for the two antenna arrays. This implementation form is advantageous if the two antenna arrays are co-located.

According to a third aspect of the invention, the above mentioned and other objectives are achieved with a method for an estimation device, the method comprises

applying a first receive beam on the incoming signal so as to obtain a first received symbol, wherein the first receive beam corresponds to a phase shift g₁ between any two adjacent antenna elements of the antenna array along a first dimension; applying a second receive beam on the incoming signal so as to obtain a second received symbol, wherein the second receive beam corresponds to one of phase shifts p + g_c or—p + g_c between the two adjacent antenna elements along the first dimension;

estimating a first set of parameters associated with the DoA of the incoming signal based on the first received symbol and the second received symbol.

The method according to the third aspect can be extended into implementation forms corresponding to the implementation forms of the estimation device according to the first aspect. Hence, an implementation form of the method comprises the feature(s) of the corresponding implementation form of the estimation device.

The advantages of the methods according to the third aspect are the same as those for the corresponding implementation forms of the estimation device according to the first aspect.

The invention also relates to a computer program, characterized in code means, which when run by processing means causes said processing means to execute any method according to the present invention. Further, the invention also relates to a computer program product comprising a computer readable medium and said mentioned computer program, wherein said computer program is included in the computer readable medium, and comprises of one or more from the group: ROM (Read-Only Memory), PROM (Programmable ROM), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically EPROM) and hard disk drive.

Further applications and advantages of the present invention will be apparent from the following detailed description.

Brief Description of the Drawings

The appended drawings are intended to clarify and explain different embodiments of the present invention, in which:

- Fig. 1 shows an estimation device according to an embodiment of the invention;

- Fig. 2 shows a communication device according to an embodiment of the invention;

- Fig. 3 shows a method according to an embodiment of the invention;

- Fig. 4 shows a section of a communication device according to an embodiment of the invention;

- Fig. 5 illustrates a wireless communication system according to an embodiment of the invention;

- Fig. 6 illustrates an incoming signal at a two-dimensional antenna array in the X-Y plane. Detailed Description

If a transmitter is using a certain transmit beam, the incoming signal may arrive at a receiver from a certain direction, i.e. the direction of arrival (DoA) of the incoming signal. An example illustration of the DoA is shown in Fig. 6. In mentioned Fig. 6, it is assumed that a two- dimensional antenna array is placed in the X-Y plane, and the incoming signal 502 is arriving at an azimuth angle of f and a zenith angle 0, respectively. The DoA (0, ø) of the incoming signal 502 introduces phase shifts between received signals at the antenna elements of the antenna array. Assuming half-wavelength spacing between antenna elements in the X-Y plane, the phase shift corresponding to the DoA of the incoming signal 502 ( q , f) between any two adjacent antenna elements along the X-dimension is given by y = p sin Q cos f. Similarly, the phase shift corresponding to the DoA of the incoming signal 502 (0, ø) between any two adjacent antenna elements along the Y-dimension is given by b = p sin 0 sin f. For a two- dimensional antenna array with eight antenna elements shown in Fig. 6 (each antenna element being indexed from 1 to 8 in Fig. 6), the phase shifts at different antenna elements corresponding to the DoA of the incoming signal 502 is given by

It can be noted that for the general case with inter-antenna element spacing of d_x along the X- dimension, and inter-antenna element spacing d_y along the Y-dimension, the phase shift corresponding to the DoA (q, ) of the incoming signal 502 between any two adjacent antenna elements along the X- and Y-dimensions are given by y = ^- d_x sin 0 cos f and b =

0 sin 0, respectively, where l denotes the wavelength of the incoming signal 502.

When receiving an incoming signal 502, if the receiver uses a phase shift g' = d_x sin 0' cos f' along the X-dimension and a phase shift b' = d_v sin 0' cos f' along the Y-

dimension, the analog combining vector (also known as receive beam) corresponding to phase shifts (g', b') is given by the expression:

However, the receiver has no prior knowledge of the DoA of the incoming signal 502. Hence, the receiver has to use different receive beams by choosing different analog combining vectors (or phase values for the phase shifters) and choose the best receive beam for the given transmit beam. This process of choosing the best receive beam is known as beam acquisition or beam selection. If the receiver can estimate the DoA of the incoming signal 502, or equivalently the phase shifts (between adjacent antenna elements) corresponding to the DoA of the incoming signal 502, the receiver can choose the best receive beam, i.e. the receive beam that maximizes the beamforming gain in the DoA, based on an estimated DoA of the incoming signal 502.

Hence, in the present application, an estimation device and a corresponding method which estimate parameters associated with the DoA of the incoming signal 502 is disclosed. The estimation device may be part of, or comprised in a communication device 100, such as the one shown in Fig. 2.

Fig. 1 shows an estimation device 200 according to an embodiment of the invention. In this embodiment a two-dimensional antenna array 1 12 (first dimension X and second dimension Y) is coupled to the estimation device 200 by means of coupling/communication means 102 illustrated with arrows. It is also illustrated in Fig. 1 how an incoming wireless communication signal 502 is received at the antenna array 1 12.

The estimation device 200 is configured to apply a first receive beam on the incoming signal 502 so as to obtain a first received symbol. The first receive beam corresponds to a phase shift g₁ between any two adjacent antenna elements of the antenna array 1 12 along the first dimension X. The estimation device 200 is further configured to apply a second receive beam on the incoming signal 502 so as to obtain a second received symbol. The second receive beam corresponds to one of the phase shifts p + ^ oG -p + g-_ί between the two adjacent antenna elements along the first dimension X. The estimation device 200 is further configured to estimate a first set of parameters associated with the DoA of the incoming signal 502 based on the first received symbol and the second received symbol. Acording to an embodiment, the phase shift value g e [—p, p\ .

The estimation device 200 can in one example be implemented as software instructions or functions executed in a processing device 202 as shown in Fig. 2. In this respect the software instructions or functions may be stored in an internal or an external memory (not shown) of the processing device. However, the estimation device 200 can in another example be implemented using dedicated circuits, e.g. as functional hardware blocks configured to perform the method according to the invention. A combination of software and hardware implementation is also possible.

The estimation device 200 in Fig. 1 is in the general case configured to estimate a first set of parameters associated with the DoA of the incoming signal 502 in one dimension. However, embodiments of the invention are not limited thereto and can also estimate further sets of parameters associated with the DoA of the incoming signal 502 in two dimensions which will be described in the following disclosure. In this respect a third receive beam and a fourth receive beam may be applied on the incoming signal so as to obtain a third received symbol and a fourth received symbol, respectively. Therefore, the estimation device 200 can be configured to estimate at least one of a first set of parameters, a second set of parameters, and a third set of parameters associated with the DoA of the incoming signal 502 based on obtained received symbols. Mentioned sets of parameters may comprise a phase shift value (associated with the DoA of the incoming signal) between two adjacent antenna elements along a first dimension X or a second dimension Y of the antenna array 1 12.

Fig. 2 shows a communication device 100 according to an embodiment of the invention. The communication device 100 may e.g. be a client device or a network access node in a long term evolution (LTE) system or in a new radio (NR) system. As shown in Fig. 2, the communication device 100 comprises an estimation device 200 as previously described. The estimation device 200 in Fig. 2 includes a receive beam selection block 204 and a transmit beam selection block 206, each coupled to a processing device 202 of the estimation device 200. The processing device 202 can comprise at least one processor core which can be coupled to an internal or external memory with coupling/communication means known in the art. The processing device 202 may further comprise a plurality of processor cores (not shown). The memory may store program code for performing the actions or functions as described herein by the processor core(s) of the processing device 202. The processing device 202 can further comprise input means and output means (not shown) which are both coupled to the processor core with coupling/communication means known in the art. That the processing device 202 is configured to perform certain actions or functions should in this disclosure be understood to mean that the processing device 202 comprises suitable means, such as e.g. the processor core(s), configured to perform said actions. The processing device 202 may for example be a baseband processor for use in a client device for a mobile communication network.

The receive beam selection block 204 is in an embodiment configured to provide the receive beams used by the processing device 202 to obtain the received symbols. The receive beams may be predefined and stored in the receive beam selection block 204 in this respect.

Moreover, the receive beam selection block 204 is in an embodiment configured to select a receive beam for reception of a subsequent incoming signal 504 at the antenna array 1 12 based on at least one of the first set of parameters, the second set of parameters, the third set of parameters, a first phase shift estimate y and a second phase shift estimate b. The first phase shift estimate f and the second phase shift estimate b can e.g. be obtained by performing a weighted combining of the first set of parameters, the second set of parameters, and the third set of parameters. The subsequent incoming signal 504 is subsequent to the incoming signal 502, i.e. received after the incoming signal 502. Therefore, parameters and/or estimated phase shift values may be sent from the processing device 202 to the receive beam selection block 204 so that the receive beam selection block 204 after DoA estimation based on the incoming signal 502 can select the next receive beam for receiving the subsequent incoming signal 504.

The transmit beam selection block 206 is in an embodiment configured to select a transmit beam for transmission of an outgoing signal 512 at the antenna array 1 12 based on at least one of the first set of parameters, the second set of parameters, the third set of parameters, the first phase shift estimate y and the second phase shift estimate b. Therefore, parameters and/or estimated phase shift values may be sent from the processing device 202 to the transmit beam selection block 206 so that the transmit beam selection block 206 can select the transmit beam.

Fig. 3 shows a flow chart of a method 300 which may be executed in an estimation device 200, such as the one shown in Fig. 1 . The method 300 comprises applying 302 a first receive beam on the incoming signal so as to obtain a first received symbol. The first receive beam corresponds to a phase shift y_x between any two adjacent antenna elements of the antenna array along a first dimension. The method 300 further comprises applying 304 a second receive beam on the incoming signal so as to obtain a second received symbol. The second receive beam corresponds to one of phase shifts p + y₁ or -p + y₁ between the two adjacent antenna elements along the first dimension. The method 300 further comprises estimating 306 a first set of parameters associated with the DoA of the incoming signal based on the first received symbol and the second received symbol.

Moreover, the communication device 100 can comprise two or more separate antenna arrays as illustrated in Fig. 4, which shows a section of a communication device 100. That is, the communication device 100 comprises at least one antenna array 1 12 having a plurality of antenna elements in the first dimension X and a plurality of antenna elements in the second dimension Y, and at least one additional antenna array 1 12^' having a plurality of antenna elements in the first dimension X and a plurality of antenna elements in the second dimension Y. Each antenna element of the antenna arrays 1 12, 1 12^' may belong to one of two orthogonal polarizations, e.g. a +45 degree polarization and a -45 degree polarization (not illustrated in Fig. 4). Moreover, the communication device 100 further comprises a first baseband circuit 132 which is coupled to the antenna array 1 12 via a first analog-to-digital convertor (ADC) 122 and a second baseband circuit 134 which is coupled to the antenna array 1 12 via a second ADC 124. In embodiments, the first baseband circuit 132 may be coupled to only a part of the elements of the antenna array 1 12 via a first ADC 122 and the second baseband circuit 134 may be coupled to remaining elements of the antenna array 1 12 via a second ADC 124. Correspondingly, the communication device 100 further comprises a third baseband circuit 132^' which is coupled to the additional antenna array 1 12^' via a third ADC 122^' and a fourth baseband circuit 134^' which is coupled to the antenna array 1 12^' via a fourth ADC 124^'. The coupling of the baseband circuits 132, 134, 132^', 134^' to other parts of the communication device 100, such as the estimation device 200, is not shown in Fig. 4.

According to this embodiment, the communication device 100 is configured to determine at least one of the first set of parameters, the second set of parameters and the third set of parameters independently for the antenna array 1 12 and the additional antenna array 1 12^'. However, the communication device 100 may also be configured to determine at least one of the first set of parameters, the second set of parameters and the third set of parameters jointly for the antenna array 1 12 and the additional antenna array 1 12^' according to an embodiment.

Fig. 5 illustrates an exemplary wireless communication system 500 according to an embodiment of the invention. The wireless communication system 500 comprises a client device 400 configured for downlink and/or uplink communications with a network access node 600. In this respect the client device 400 is wirelessly connected with the network access node 600 which act as a serving network access node. The client device 400 herein comprises a communication device 100 according to embodiments of the invention. The incoming signal 502 at the downlink and the outgoing signal 512 in the uplink are illustrated as dashed arrows between the communication device 100 and the network access node 600 in Fig. 5. Also, the previously mentioned subsequent incoming signal 504 is shown in Fig. 5. For simplicity, the wireless communication system 500 shown in Fig. 5 only comprises one client device 400 and one network access node 600. However, the wireless communication system 500 may comprise any number of client devices 400 and any number of network access nodes 600 without deviating from the scope of the invention.

In the following description, further embodiments of the estimation device 200 and corresponding method are presented so as to provide a deeper understanding of the invention. Especially, it is herein described how to obtain estimates for a two-dimensional antenna array 1 12 and further how to obtain more than one set of parameters associated with the DoA of the incoming signal 502 for improved accuracy. In this respect a two-dimensional antenna array 1 12 in the X-Y plane is assumed. The antenna array 1 12 comprises a plurality of antenna elements in the first X-dimension and a plurality of antenna elements in the second Y- dimension. Each antenna element may be connected to a phase-shift element. The phase- shifted signals of the antenna elements are then combined and connected to a single ADC. The estimated set of parameters associated with the DoA of the incoming signal 502 can e.g. be used for a beam acquisition process as previously described. However, embodiments of the invention can also be used in a communication device 100 comprising multiple antenna arrays, by estimating the parameters associated with the DoA of the incoming signal 502, either jointly or independently for each of the antenna arrays.

Moreover, the following embodiments are described in a downlink (DL) scenario in which a network access node 600 is transmitting orthogonal frequency division multiplexing (OFDM) signals to a client device 400. However, the principles are equally applicable in the uplink (UL) in which a client device 400 is transmitting signals to the network access node 600. Therefore, in the uplink scenario the network access node 600 comprises a communication device 100 according to embodiments of the invention. Further, it is assumed that the transmitter (e.g. a network access node 600) choose a transmit beam and sends the data signal to the receiver (e.g. a client device). The incoming signal 502 is arriving at the receiver at DoA (0, ø) as previously described with reference to Fig. 6. Furthermore, the embodiments are described with reference to a 4x2 antenna array placed in the X-Y plane as shown in Fig. 6. However, the embodiments of the present invention can be applicable for any arbitrary two-dimensional antenna array 1 12.

With reference to Fig. 6, if the incoming signal 502 corresponding to a line of sight (LOS) path is arriving at an angle q, f in the zenith and azimuth planes, with Q e [0, p ] and f e [-p, p] , the baseband channel corresponding to the LOS path is given by

with a denoting the fading coefficient between a transmitter antenna array and a receiving antenna array,

0 cos f denoting the phase difference between the received signals at any two adjacent antenna elements along the X-dimension and b = ^ d_v sin Q sin f denoting the phase difference between the received signals any two adjacent antenna elements along the Y-dimension. The objective is to estimate (g, b), which is equivalent to estimating (0, ø). Embodiments of the invention are in the following explained by considering four OFDM symbols (of the first incoming signal 502) but is not limited thereto. For obtaining the first received OFDM symbol, the estimation device 200 applies a first receive beam on the incoming signal 502, i.e. n e-M ⁺²n e- ⁽J^{} +3}n^'>) (2)

The first receive beam corresponds to a phase shift g_c between any two adjacent antenna elements of the antenna array 1 12 along the first dimension X. Acording to an embodiment, the phase shift value g e [—p, p\ .

The received signal model of the first received OFDM symbol can be written as:

where k corresponds to the resource element (RE) index in the frequency domain. The RE indices may correspond to the subcarrier indices carrying reference signals. For example, if we consider the OFDM symbol corresponding to the secondary synchronization sequence (SSS) symbol in the NR, the pilot sequence length is M = 127. The vector w_k(i) = [w _i ... w_Ni]^T _{> j} = 1, 2 , 3, 4 is the noise vector corresponding to the /cth RE of the ith OFDM symbol, and we assume that the entries of w_k /) are i.i.d. entries with complex circularly symmetric Gaussian distribution (CCSGD) with zero mean and variance s². The quantity s_k denotes the known or unknown reference symbol transmitted on the /cth RE. The term n_fc(i) denotes the effective noise on the /cth RE. Note that n_fc(i) is also CCSGD random variable with zero mean and variance s².

Next, the estimation device 200 applies a second receive beam on the incoming signal 502 so as to obtain a second received OFDM symbol carrying the same data as the first OFDM symbol, i.e.

The same data may e.g. refer to the same reference signals. It can further be noted that the second receive beam is orthogonal to the first receive beam, i.e. a^H (g₂, b₂)a(g i, bi) = 0. In the general case the second receive beam corresponds to one of phase shifts p + g_c or -p + g_c between the two adjacent antenna elements along the first dimension X.

The received signal model of the second received OFDM symbol can be written as:

y_k(_.2) = a^H(y₂, /?₂)h(y, /?) s_fe + a^H(y₂, /¾)w_fe(2), k = 1 , .. , M,

= a^H(y₂, /?₂)h(y, /?)s_fe + n_k(2), k = 1, . . , M (5)

We therefore have a^H(Ui,bi )Kg, b)

and

+ _ej((/?-ft)+2(y-ri)) _ _ej((/3-/3i)+3(y-n))j (7)

From equations (6) and (7), we have

Based on the observation from equation (8) and (9), the estimation device 200 can estimate the y value by performing the following steps:

1. Computing the principal value:

2. Resolving the possible wrapping of phase in A_x. In the first step, the value of A_x need not be equal to -(y - gb) due to wrapping of phase to (~p,p\. For example, in case we have g_c = -p, and if the phase shift corresponding to incoming signal direction along the X-dimension y e [-p, 0], A₁ = -(g - g^ e (-p, 0) and the value of A will not be wrapped around. However, if y e [O,p], A₁ = 2p - (g - gb) with -(y - y e [~2p, - p ] and A_x e [O, p] Hence, we have unwrapped phases as: > o

3. Finally, the estimation device 200 can obtain a first set of parameters associated with the DoA of the incoming signal 502 (such as the estimate of phase shift corresponding to the DoA of the incoming signal along the X-dimension) as:

7^{1 =} - [^bi - 7i] (11) Generally, equation (10) can be understood as to mean that the first set of parameters associated with the DoA of the incoming signal 502 are estimated based on a sum of one or more cross-correlations between two distinct linear combinations of reference signals associated with the same resource element in the first received symbol and the second received symbol. It can further be noted that in equation (10), knowledge of fading coefficient or the data on each subcarrier becomes irrelevant as long as the data is composed of unit- modulus symbols, e.g. BPSK or QPSK. Typically, the reference signals in wireless communication systems use unit-modulus symbols.

As described, by choosing the second receive beam a^H(g₂,b₂ ) orthogonal to the first receive beam ^(g^bb), we can estimate the phase shift corresponding to the incoming signal 502 along the X-dimension. Furthermore, the first receive beam and the second receive beam correspond to a phase shift b₁ between the two adjacent antenna elements along the second dimension Y. Acording to an embodiment, the phase shift value b₁ e [—p, p\.

Furthermore, the relation a^H (g₂, b₂)a(g i,bi) = 0 only holds for an even number of antenna elements along the X-dimension. If in case an antenna array 1 12 has an odd number of antenna elements along the X-dimension, one may connect only an even number of antenna elements to a combiner using antenna switches, and apply two orthogonal receive beams to estimate the phase shift corresponding to the DoA of the incoming signal 502 along the X- dimension.

In the above description, we described the system model assuming a two dimensional antenna array 1 12. However, those skilled in the art could apply the principles described above if the antenna array 1 12 comprises only one dimension. That is, if a communication device 100 is equipped with only one-dimensional antenna array 1 12, and by using only two receive beams, we can estimate the phase shift corresponding to the DoA of the incoming signal 502.

If the communication device 100 is equipped with a two-dimensional antenna array 1 12, the estimation device 200 can apply a third receive beam a^H(g₃, b₃ ) = a^H(g₁, p + bb) to obtain a third received OFDM symbol containing the same data. For the 4x2 antenna array placed in the X-Y plane as shown in Fig. 6, we can observe that the third receive beam is orthogonal to both the first receive beam and the second receive beam, i.e., aⁱⁱ(y₃,/?₃)a(y₁, /?₁) = a^H(g₃,b₃)a(g₂, b₂) = 0. However, for other antenna array geometries, the third receive beam may be orthogonal to only to one of the first receive beam or the second receive beam. We can write the received signal model for the third received OFDM symbol as:

We therefore have

=— h -_|- gj(y-r ) -i- _ej2 (g-Yi) _{+ ej3(}y-Y_!) _ _e Kb-bU) _ gj((/?-ft)+(y-y ))

V8 ^L

_ gj((/3-ft)+2(y-r )) _ gj((/3-/3 ) + 3(y-n)) ] (13)

Hence, from equation (6) and (13), we have

and

Based on the observations from equation (14) and (15), respectively, the estimation device 200 can use the similar steps outlined in the estimation process of y¹ to obtain b¹, i.e. by:

1 . Computing the principal value

2. Resolving the possible wrapping of phase in A₂. For example, in case we have b₁ = —p, and if the phase shift corresponding to incoming signal direction along the Y- dimension /? e [-p, 0], A₂ = -(/? - bb) e (-p, 0) and the value of A₂ will not be wrapped around. However, if b E [0, p\, A₂ = 2p - (b - b₁) with -(b - bb) e [~2p, -p\ and A₂ e [0, p] . Hence, we have unwrapped phases as:

3. Finally, the estimation device 200 can obtain the second set of parameters associated with the DoA of the incoming signal 502 (such as estimate of phase shift corresponding to the DoA of the incoming signal 502 along the Y-dimension) as

b^ί = -[B₂ - b \ (17)

Hence, by using three receive beams, the estimation device 200 can obtain the estimates y¹,/?¹ of the phase shifts corresponding to the DoA of the incoming signal 502 in the first dimension X and the second dimension Y. In case latency is not a strict requirement, the estimation device 200 can further apply a fourth receive beam a^H(g₄, b₄) = a^H(p + g₁, p + b_±) to obtain a fourth received OFDM symbol containing the same data. For the 4x2 antenna array placed in the X-Y plane as shown in Fig. 6, we can observe that the fourth receive beam is orthogonal to both the first receive beam, second receive beam and third receive beam, i.e., aⁱⁱ(y₄, /?₄)a(y₁, /?₁) = a^H g₄, b₄)a g₂, b ₂) = a^H(g₄, b₄)a(g₃,b₃) = 0. For other antenna array geometries, the fourth receive beam may only be orthogonal to a subset of the first receive beam, the second receive beam and the third receive beam.

We can write the received signal model for the third OFDM symbol as:

We have

Hence, from equation (13) and (19), we have

Based on observations from equation (20) and (21 ), respectively, and by using a similar set of steps used for obtaining the estimate y¹, the estimation device 200 can obtain another estimate y², the phase shift corresponding to the DoA of the incoming signal 502 along the X- dimension.

Furthermore, from equation (7) and (19), we have

and

Based on equation (22) and (23), respectively, and by using a similar set of steps used for obtaining the estimate b¹, the estimation device 200 can obtain another estimate b², the phase shift corresponding to the DoA of the incoming signal 502 along the Y-dimension.

Furthermore, consider

and

_

0

Based on the observations in equation (24) and (25), respectively, and by using a similar set of steps used for obtaining the estimate /?\ the estimation device 200 can obtain yet another estimate b³, the phase shift corresponding to the DoA of the incoming signal 502 along the Y- dimension. Note that here the estimation device 200 uses four observations to obtain the estimate b³.

Similarly,

„

0

and

0

Based on the observation in equation (26) and (27), respectively, and by using a similar set of steps used for obtaining the estimate y\ the estimation device 200 can obtain yet another estimate y³, the phase shift corresponding to the DoA of the incoming signal 502 along the X- dimension.

Similarly,

and

0

Based on the observations in equation (28) and (29), respectively, and by using a similar set of steps used for obtaining the estimate b¹, the estimation device 200 can obtain yet another estimate b ⁴, the phase shift corresponding to the DoA of the incoming signal 502 along the Y- dimension.

Similarly,

and

0

Based on the observations in equation (30) and (31 ), respectively, and by using a similar set of steps used for obtaining the estimate y¹, the estimation device 200 can obtain yet another estimate y⁴, the phase shift corresponding to the DoA of the incoming signal 502 along the X- dimension. Hence, by using one more additional receive beam, the estimation device 200 can obtain the third set of parameters associated with the DoA of the incoming signal 502 (three more estimates of the phase shifts corresponding to the DoA of the incoming signal 502 in the X-Y plane). As described above, by using 4 receive beams corresponding to (g-i, bb), (p + Ui,bb), (Ui, p + bi), (p + Ui, p + bi), the estimation device 200 can obtain four estimates y\ y², y³, y⁴ corresponding to y, i.e. the phase shift corresponding to the DoA of the incoming signal 502 between any two adjacent antennas along the X-dimension. The estimation device 200 also obtains four estimates /?\/?², /?³ ,b , corresponding to b, i.e. the phase shift corresponding to the DoA of the incoming signal 502 between any two adjacent antennas along the Y- dimension.

In the next step, the estimation device 200 can refine the estimates of the phase shifts corresponding to the DoA of the incoming signal 502 by weighing the different estimates based on the effective received signal strength (ERSS) associated with the receive beams used in the estimation process. Generally, a first phase shift estimate y between any two adjacent antenna elements (corresponding to the DoA of the incoming signal 502) along the first dimension X can be determined based on a first weighted combination of the first phase shift values of the first set of parameters, the second set of parameters and the third set of parameters. Correspondingly, a second phase shift estimate b between the two adjacent antenna elements (corresponding to the DoA of the incoming signal 502) along the second dimension Y can be determined based on a second weighted combination of the second phase shift values of the first set of parameters, the second set of parameters and the third set of parameters.

The weights for the first phase shift values and the second phase shift values of the first set of parameters, the second set of parameters, and the third sets of parameters, respectively, can be determined based on a respective associated ERSS. In an embodiment each respective associated ERSS is a function of an absolute value of a sum of one or more cross-correlations between two distinct linear combinations of reference signals associated with the same resource element in at least two of the first received symbol, the second received symbol, the third received symbol and the fourth received symbol.

According to another embodiment the estimation device 200 may simply select an estimate among all estimates associated with the strongest ERSS. As previously described, it can be understood that the first set of parameters, the second set of parameters and the third set of parameters each comprises one or more estimates, and the estimation device 200 selects one estimate among the one or more estimates corresponding to the highest ERSS. For example, the first set of parameters comprises y¹ and the second set of parameters comprises b¹ . Further, the third set of parameters comprises y², y³, y⁴, b², b³, b⁴. The estimation device 200 selects an estimate y from one of y¹,†²,†³, y⁴ and similarly, it selects an estimate b from one of b¹, b², b³, b⁴ based on the highest respective associated ERSS.

Generally, the estimation device 200 is in this case configured to determine a first phase shift estimate y between the two adjacent antenna elements along the first dimension X (corresponding to the DoA of the incoming signal 502) based on selecting the first phase shift value of the first set of parameters, the second set of parameters, and the third set of parameters having the highest respective associated ERSS. Correspondingly, the estimation device 200 is configured to determine a second phase shift estimate b between the two adjacent antenna elements along the second dimension Y (corresponding to the DoA of the incoming signal 502) based on selecting the second phase shift value of the first set of parameters, the second set of parameters, and the third set of parameters having the highest respective associated ERSS.

In case only two received OFDM symbols are used in the estimation, the ERSS can be derived from the expression:

In case four received OFDM symbols are used in the estimation, the ERSS can be derived

In the above description of embodiments of the invention, we have not specified any values for the phase shift estimates (gi, bb). If we chose the values of y_x and b₁ too far away from the values corresponding to the DoA of the incoming signal 502, the ERSS associated with the receive beams used in the estimation process will be low. In such a case, the estimation device 200 may select a different set of 4 receive beams corresponding to new values of y₁ and /¾. In this respect a ERSS threshold value can be used. By comparing an ERSS value against the ERSS threshold value an observation can be determined to be valid or not.

In an embodiment the estimation device 200 may advantageously choose y e {-p, -p/2,0, p/ 2} and b₁ e {- p , -p/2,0, p/2), then we have 16 receive beams to scan all of the received signal space. We can organize the 16 receive beams corresponding to

e {(-p, -p), (-p, -p/

2), (— p, 0), (— p, p/2), (-p/2, -p), (-p/2, -p/2), (-p/2,0), (-p/2, p/2), (0, -p), (0, -p/

2), (0,0), (0, p/2), (p/2, -p), (p/2, -p/2), (p/2,0), (p/2, p/2)} into four sets of four receive beams as: • S₁ = {(— 7G,— if), (— 7G, 0), (0,— if), (0,0))

• s₂ = {(-p/2, -p/2), (— 7G/2, p/2), (p/2, -p/2), (p/2, p/2)}

• S-3 = {(-p/2,— p), (-p/2,0), (p/2, -p), (p/2,0))

• S₄ {(— p,— 7G/2), (— p, p/2), (0, -p/2), (0, p/2))

The estimation device 200 can for example start with the 4 receive beams in S-_L and if none of the observations are valid, i.e. the associated ERSS value is too low, the estimation device 200 can continue scanning with receive beams from the set S₂ followed by the set S₃ and S₄. The estimation device 200 can continue this process until it finds a set with valid observations to obtain estimates corresponding to g,b.

In the above description, we have used 4 receive beams corresponding to (g₁,bi), (gi + p,bb), (g₁,b₁ + p), (g_± + p,b₁ + p), in the same order. However, the estimation device 200 may use the 4 receive beams corresponding to (gi,bb), (y₄ + p,bb), (/_!,/¾ + p), (/₄ + p,b₁ + p) in any order to estimate the phase shift values corresponding to the DoA of the incoming signal 502.

Considering set 5_{1 ;} the 4 phase shift combinations corresponding to the 4 receive beams can be generated in multiple ways. For example, one can start with the first receive beam corresponding to (/i, /?i) = (-p, -p), the second beam, the third beam and the fourth receive beam corresponding to (-p, 0), (0, -p), (0,0) can be generated using (g₁ + p,b₁), (g₁,b₁ + p), (/i + p,b₁ + p), respectively.

Alternatively, one may choose

= (0,0) and generate the remaining three phase shift combinations using (/₄ - p,bb), (/_!,/¾ - p), (/₄ - p,b₁ - p).

Using another alternative one may start with (gi,bb) = (0, -p) and generate the three remaining beams in the set by using the three phase shift combinations (g - p,bb), (g₁,b₁ + p), (/i - p,b_ί + p). Hence, it can be easily understood that one may generate the phase shift combinations corresponding to the 4 receive beams in many different ways.

Once the phase shift values corresponding to the DoA of the incoming signal 502 have been obtained, the estimation device 200 can select the next receive beam for receiving the further incoming signal 504 based on the estimated (g,b), i.e. the next receive beam vector is selected as

In a practical implementation the entries of the receive beamformer in equation (32) can be quantized depending on the possible resolution of the phase shifters used in the communication device 100.

The OFDM symbols considered herein can e.g. be transmitted with cyclic prefix (CP)-OFDM or Discrete Fourier Transform-Spread-OFDM (DFTS-OFDM). In the downlink, the OFDM symbols may correspond to sub-time unit based channel state information-reference signal (CSI-RS) resources transmitted using one of Interleaved Frequency Division Multiplexing (IFDMA) or a larger subcarrier spacing or discrete Fourier transform (DFT). Alternatively, the four OFDM symbols in the downlink may also correspond to one or more symbols of a synchronization signal (SS) block (SSB) corresponding to one or more SS burst sets. The OFDM symbols can also correspond to any other reference signals sent in the downlink. In the uplink, the OFDM symbols can e.g. correspond to sounding reference signal (SRS) symbols.

The client device 400 herein, may be denoted as a user device, a User Equipment (UE), a mobile station, an internet of things (loT) device, a sensor device, a wireless terminal and/or a mobile terminal, is enabled to communicate wirelessly in a wireless communication system, sometimes also referred to as a cellular radio system. The UEs may further be referred to as mobile telephones, cellular telephones, computer tablets or laptops with wireless capability. The UEs in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another receiver or a server. The UE can be a Station (STA), which is any device that contains an IEEE 802.1 1 - conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM). The UE may also be configured for communication in 3GPP related LTE and LTE-Advanced, in WiMAX and its evolution, and in fifth generation wireless technologies, such as New Radio.

The network access node 600 herein may also be denoted as a radio network access node, an access network access node, an access point, or a base station, e.g. a Radio Base Station (RBS), which in some networks may be referred to as transmitter,“eNB”,“eNodeB”,“NodeB” or“B node”, depending on the technology and terminology used. The radio network access nodes may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. The radio network access node can be a Station (STA), which is any device that contains an IEEE 802.1 1 -conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM). The radio network access node may also be a base station corresponding to the fifth generation (5G) wireless systems.

Furthermore, any method according to embodiments of the invention may be implemented in a computer program, having code means, which when run by processing means causes the processing means to execute the steps of the method. The computer program is included in a computer readable medium of a computer program product. The computer readable medium may comprise essentially any memory, such as a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), or a hard disk drive.

Moreover, it is realized by the skilled person that embodiments of the client device 400 and the network access node 600 comprises the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing the present solution. Examples of other such means, units, elements and functions are: processors, memory, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selecting units, switches, interleavers, de-interleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiver units, transmitter units, DSPs, MSDs, TCM encoder, TCM decoder, power supply units, power feeders, communication interfaces, communication protocols, etc. which are suitably arranged together for performing the present solution.

Especially, the processor(s) of the client device 400 and the network access node 600 may comprise, e.g., one or more instances of a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The expression“processor” may thus represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above. The processing circuitry may further perform data processing functions for inputting, outputting, and processing of data comprising data buffering and device control functions, such as call processing control, user interface control, or the like.

Finally, it should be understood that the invention is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.

Claims

1. An estimation device (200) for estimating parameters associated with a Direction of Arrival, DoA, of an incoming signal (502) at an antenna array (1 12), the estimation device (200) being configured to

apply a first receive beam on the incoming signal (502) so as to obtain a first received symbol, wherein the first receive beam corresponds to a phase shift g_c between any two adjacent antenna elements of the antenna array (1 12) along a first dimension (X);

apply a second receive beam on the incoming signal (502) so as to obtain a second received symbol, wherein the second receive beam corresponds to one of phase shifts p + g_c or—p + g_c between the two adjacent antenna elements along the first dimension (X); estimate a first set of parameters associated with the DoA of the incoming signal (502) based on the first received symbol and the second received symbol.

2. The estimation device (200) according to claim 1 , wherein

the first receive beam further corresponds to a phase shift b₁ between any two adjacent antenna elements of the antenna array (1 12) along a second dimension (Y);

the second receive beam further corresponds to the phase shift b₁ between the two adjacent antenna elements of the antenna array (1 12) along the second dimension (Y).

3. The estimation device (200) according to claim 2, configured to

apply a third receive beam on the incoming signal (502) so as to obtain a third received symbol, wherein the third receive beam corresponds to the phase shift g₁ between the two adjacent antenna elements along the first dimension (X) and one of phase shifts p + b₁ or —p + b₁ between the two adjacent antenna elements along the second dimension (Y);

estimate a second set of parameters associated with the DoA of the incoming signal (502) based on the first received symbol, the second received symbol and the third received symbol.

4. The estimation device (200) according to claim 3, configured to

apply a fourth receive beam on the incoming signal (502) so as to obtain a fourth received symbol, wherein the fourth receive beam corresponds to one of the phase shifts p + g₁ or -p + g_c between the two adjacent antenna elements along the first dimension (X) and to one of the phase shifts p + b₁ or -p + b₁ between the two adjacent antenna elements along the second dimension (Y); estimate a third set of parameters associated with the DoA of the incoming signal (502) based on the first received symbol, the second received symbol, the third received symbol and the fourth received symbol.

5. The estimation device (200) according to any of the preceding claims, configured to

6. The estimation device (200) according to claim 4 or 5, wherein each one of the first set of parameters, the second set of parameters, and the third set of parameters comprises at least one of

at least one first phase shift value between the two adjacent antenna elements along the first dimension (X); and

at least one second phase shift value between the two adjacent antenna elements along the second dimension (Y);

wherein the first phase shift value and the second phase shift value are associated with the DoA of the incoming signal (502).

7. The estimation device (200) according to claim 6, configured to determine at least one of a first phase shift estimate y between the two adjacent antenna elements along the first dimension (X) based on a first weighted combination of the first phase shift values of the first set of parameters, the second set of parameters and the third set of parameters; and

a second phase shift estimate b between the two adjacent antenna elements along the second dimension (Y) based on a second weighted combination of the second phase shift values of the first set of parameters, the second set of parameters and the third set of parameters.

8. The estimation device (200) according to claim 7, configured to

9. The estimation device (200) according to claim 6, configured to determine at least one of a first phase shift estimate y between the two adjacent antenna elements along the first dimension (X) based on selecting the first phase shift value of the first set of parameters, the second set of parameters, and the third set of parameters having the highest respective associated ERSS; and

a second phase shift estimate b between the two adjacent antenna elements along the second dimension (Y) based on selecting the second phase shift value of the first set of parameters, the second set of parameters, and the third set of parameters having the highest respective associated ERSS;

10. The estimation device (200) according to any of the preceding claims, wherein at least one of the phase shift y_x e [- p, p ] and the phase shift b₁ e [- p, p ].

1 1 . A communication device (100) for a wireless communication system (500), the communication device (100) comprising the estimation device (200) according to any of the preceding claims, the communication device (100) being configured to

select a receive beam for reception of a subsequent incoming signal (504) at the antenna array (1 12) based on at least one of the first set of parameters, the second set of parameters, the third set of parameters, the first phase shift estimate y and the second phase shift estimate b, wherein the subsequent incoming signal (504) is subsequent to the incoming signal (502).

12. The communication device (100) according to claim 1 1 , configured to

select a transmit beam for transmission of an outgoing signal (512) at the antenna array (1 12) based on at least one of the first set of parameters, the second set of parameters, the third set of parameters, the first phase shift estimate y and the second phase shift estimate b.

13. The communication device (100) according to claim 1 1 or 12, further comprising

the antenna array (1 12) comprising a plurality of antenna elements in the first dimension (X) and a plurality of antenna elements in the second dimension (Y), at least one additional antenna array (122) comprising a plurality of antenna elements in the first dimension (X) and a plurality of antenna elements in the second dimension (Y); and wherein the communication device (100) is configured to at least one of

determine at least one of the first set of parameters, the second set of parameters and the third set of parameters independently for the antenna array (1 12) and the additional antenna array (122); and

determine at least one of the first set of parameters, the second set of parameters and the third set of parameters jointly for the antenna array (1 12) and the additional antenna array (122).

14. A method (300) for an estimation device (200), the method (300) comprising

applying (302) a first receive beam on the incoming signal so as to obtain a first received symbol, wherein the first receive beam corresponds to a phase shift g_c between any two adjacent antenna elements of the antenna array along a first dimension;

applying (304) a second receive beam on the incoming signal so as to obtain a second received symbol, wherein the second receive beam corresponds to one of phase shifts p + g₁ or—p + g₁ between the two adjacent antenna elements along the first dimension;

estimating (306) a first set of parameters associated with the DoA of the incoming signal based on the first received symbol and the second received symbol.

15. Computer program with a program code for performing a method according to claim 14 when the computer program runs on a computer.