CN105519009B

CN105519009B - Antenna device and method for controlling the focusing of an antenna beam of an antenna array

Info

Publication number: CN105519009B
Application number: CN201380079378.9A
Authority: CN
Inventors: 卡瑞尔·索泰克; 王松海
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2013-09-11
Filing date: 2013-09-11
Publication date: 2019-12-24
Anticipated expiration: 2033-09-11
Also published as: WO2015036020A1; CN105519009A

Abstract

The invention relates to an antenna arrangement (600) comprising a controller (602), the controller (602) being configured to control a focusing (605) of an antenna beam of an antenna array towards a user equipment, the focusing (605) being based on a feedback loop (601) related to a pilot beam, the pilot beam comprising a set of predetermined antenna beams of the antenna array, and the focusing (605) being based on a distance (603) between the antenna array and the user equipment.

Description

Antenna device and method for controlling the focusing of an antenna beam of an antenna array

Technical Field

The present disclosure relates to an antenna arrangement and a method for controlling the focusing of antenna beams of an antenna array, and to a radio base transceiver station BTS. The present disclosure also relates to BTS antenna beamforming in cellular networks. In particular, the present disclosure relates to improved antenna beamforming accuracy.

Background

The widespread acceptance and widespread use of mobile broadband services place tremendous pressure on the available cellular network radio resources. The expensive spectrum obtained by the auction must be efficiently utilized. BTS antenna beamforming is an advanced radio interface technology that enables efficient use of the radio spectrum. By accurately controlling the direction of the antenna beam towards the mobile user equipment UE, dense multiplexing of radio frequencies in a cellular network is enabled, thereby increasing capacity and reducing the cost of mobile broadband services. In a conventional cellular network, the allocated spectrum is used equally within one cell of the network. In contrast, antenna beamforming focuses the portion of the spectrum used by a user toward that particular user. This reduces interference to other cell users and allows for a more dense reuse of the spectrum. Conventional beam control parameters include angle of incidence estimation and precoding matrix indicator PMI reporting in long term evolution LTE closed loop multiple input multiple output, MIMO, operation. One common problem in cellular networks is multipath propagation between the BTS and the UE. Radio waves from the UE are reflected on buildings and arrive at the BTS from different directions in the uplink case. In the downlink case, the same problem exists for radio waves from the BTS to the UE, i.e., in the opposite direction. Each reflection is highly frequency selective, so that in a frequency division duplex FDD system where different frequencies are used in the uplink and downlink, the reflection conditions in the uplink and downlink are different. This is why controlling the downlink beam by estimating the uplink angle of incidence estimate results in sub-optimal performance.

Fig. 1 illustrates the principle of different antenna beams determined by different PMI values. The figure illustrates closed loop PMI reporting. The BTS 101 generates a first beam 102, a second beam 104 and a third beam 106 directed to a UE 103 within a radio cell 108. The PMI may be implemented according to the 3GPP TS standard. In this particular example, the PMI is implemented in accordance with the 3GPP TS36.331 standard. The different antenna downtilt angles α of the three beams 102, 104 and 106_iCorresponding to different PMIs_iThe value is obtained. By receiving a maximum PMI_iPeriodic UE reporting of values, in this example PMI2, from which second beam 104 the BTS knows the best a_iThe downtilt value, in this example α 2, is used for payload data transmission. The UE 103 is reporting the strongest antenna main lobe direction 104 via so-called PMI reporting. The beam selection is based on the UE feedback loop.

Thus, the basic algorithm for estimating antenna downtilt values operates as follows: the BTS periodically transmits a combination of all available antenna downtilt values, with each beam being encoded by its dedicated PMI code (value). These PMI codes are decoded within the UE and the strongest PMI is reported to the BTS. When PMI2 is reported, the BTS uses a downtilt value, e.g., α 2, corresponding to the reported PMI.

This may cause non-idealities in the antenna beam, since beam sidelobes occasionally lead to erroneous PMI reports. The UE is erroneously served by the side lobe while the main lobe causes strong interference to other UEs in the cellular network. More particularly, the antenna side lobes do radiate undesired signals that can be erroneously detected by the UE, resulting in erroneous PMI reporting and alpha selection.

Fig. 2 shows an example of erroneous PMI4 reporting. BTS 201 generates a main lobe 204 directed to UE 203 within radio cell 208 and two side lobes 202 and 206. Although the side lobe beam 206 is more accurately directed to the UE 203, the PMI value associated with the main lobe 204 is reported. I.e. the antenna beam angle better covered by the side lobes of the different antenna main lobes is reported in error. As shown in fig. 1, the antenna main lobe 204 with PMI4 and downtilt angle α 4 has two side lobes 202, 206. The weaker side lobe 206 radiating direction does not have a stronger antenna main lobe with a different PMI value. The correct beam downtilt angle should be α 2 encoded with PMI 2. Detecting PMI4 would result in BTS 201 transmitting with α 4 instead of α 2. Thus, BTS 201 transmits in a different direction than towards UE 203.

The conventional implementation of antenna beam steering is based on a one-to-one mapping between UE PMI reports received by the BTS and the antenna beam angle α. The disadvantages of this approach are the inaccuracy of the selected beam angle, the channel noise and the measurement inaccuracy caused by the antenna side lobes.

Disclosure of Invention

The present invention aims to provide a technique for improving the control accuracy of antenna beams of an antenna array.

This object is achieved by the features of the independent claims. Further forms of implementation will be apparent from the dependent claims, the description and the accompanying drawings.

The present invention is based on the following findings: the distance between the BTS and the UE can be determined by measuring the propagation delay and its statistics to implement a technique for improving the control accuracy of the antenna beams of the antenna array.

In a cellular base station comprising an antenna array allowing beam direction control, the beam direction is determined by UE PMI reporting. Each reported PMI value corresponds to a beam angle to be used for the next transmission. To improve the accuracy of the beam angle, the BTS may additionally measure the propagation time between the BTS and the UE. This time can be converted into the distance between the BTS and the UE. A simple trigonometric function can be used to compare the value of alpha, i.e. the downtilt angle, with the propagation time t. The BTS may track the estimated t and a values to stay consistent with a stationary or continuously moving UE state. The failing values may be discarded, while the other values become input values for the algorithm processing and beam steering.

The invention includes the handling of other parameters available in the mobile network as timing differences between the UE and the BTS. This timing difference is also referred to as the round trip time and is estimated as the time required for the radio signal to travel from the BTS to the UE and back to the BTS. The round trip time corresponds to the distance between the BTS and the UE. This distance is effective for steering and plausibility checking of the beam selection, since it can only be varied smoothly (e.g. without discontinuous jumps). The BTS parameter equivalent to the round trip time is called the timing advance.

To select and track the BTS beam angle direction towards the UE, a timing advance parameter estimated by the BTS in conjunction with PMI reporting may be used. Thereby, the accuracy of BTS antenna beamforming in a cellular network can be improved.

For a detailed description of the invention, the following terms, abbreviations and symbols will be used:

BTS: base transceiver station

UE: user equipment

LTE: long term evolution

PMI: precoding matrix indication

Tx: sending

Rx: receiving

According to a first aspect, the invention relates to an antenna arrangement comprising a controller configured to control a focusing of an antenna beam of an antenna array towards a user equipment, said focusing being based on a feedback loop related to a pilot beam, the pilot beam comprising a set of predetermined antenna beams of said antenna array, and said focusing being based on a distance between the antenna array and the user equipment.

The accuracy of the control of the antenna beam can be improved when the focusing of the antenna beam is additionally based on a second parameter, such as the distance between the antenna array and the user equipment.

In a first implementation form of the antenna device according to the first aspect, the controller is configured to determine the distance based on a propagation time measurement.

The propagation time measurement can be easily implemented by a time stamp measurement.

In a second implementation form of the antenna arrangement according to the first implementation form of the first aspect, the propagation time measurement is based on a round trip delay measurement between the antenna array and the user equipment.

The round trip delay can be easily measured, for example, by adding a time stamp to the signal sent from the BTS to the UE and from the UE back to the BTS.

In a third implementation form of the apparatus according to the first or second implementation form of the first aspect, the propagation time measurement is based on a known processing time within the user equipment.

The travel time measurement based on the known processing time within the user equipment is accurate.

In a fourth implementation form of the antenna device according to any of the first to third implementation forms of the first aspect, the propagation time measurement is based on one of a timing advance measurement and a timestamp measurement in the signaling or payload traffic.

From the aspect of computational complexity, the timing advance and the time stamp measurement can be effectively realized. Signaling or payload traffic may be used to add timing.

In a fifth implementation form of the antenna device according to any of the second to fourth implementation forms of the first aspect, the controller is configured to determine the beam angle of the antenna beam based on a report of the user equipment.

The beam angle can be efficiently and accurately determined by using the report of the user equipment. Accuracy can be further improved by additionally using travel time measurements. Reporting by the user equipment can be efficiently achieved by reporting both the beam angle and the propagation time.

In a sixth implementation form of the antenna device according to the fifth implementation form of the first aspect, the controller is configured to: controlling the focusing of the antenna beam by using a trigonometric function related to the reported beam angle in combination with the reported beam angle and the measured propagation time.

By combining the reported beam angle and the measured propagation time, the accuracy of beam control can be improved. The trigonometric function related to the reported beam angle enables to derive a relation between the beam angle and the propagation time, e.g. the tangent of the beam angle corresponds to the relation between the BTS height and the distance between the BTS and the UE.

In a seventh implementation form of the antenna device according to the fifth or sixth implementation form of the first aspect, the controller is configured to: controlling the focusing based on statistics and/or variations of the reported beam angles and the measured propagation times.

When using statistics and/or variations of reported beam angles and measured propagation times, the accuracy of beam steering can be improved, especially in cases where the BTS is highly unknown.

In an eighth implementation form of the antenna device according to the sixth implementation form or the seventh implementation form of the first aspect, the controller is configured to: detecting a fault of the feedback loop by tracking the reported beam angle and the measured propagation time.

Tracking the reported beam angle and the measured propagation time can reveal the unstable nature of the beam angle as a fault indication. Tracking can be easily performed by using a memory, for example.

In a ninth implementation form of the antenna device according to the first aspect as such or any of the preceding implementation forms of the first aspect, the controller is configured to: encoding the set of predetermined antenna beams by using a precoding matrix.

Encoding the set of predetermined antenna beams by using a precoding matrix enables easy control of the antenna beams and application of PMI reporting at the UE side.

In a tenth implementation form of the antenna device according to the first aspect as such or any of the preceding implementation forms of the first aspect, the feedback loop is based on precoding matrix indication, PMI, reporting as defined according to a 3GPP TS standard, in particular according to a 3GPP TS36.331 standard.

When using a feedback loop based on PMI reporting, the device can be implemented in a BTS according to any standard, for example in a BTS according to the 3GPP TS36.331 standard.

According to a second aspect, the invention relates to a radio base transceiver station comprising: an antenna array capable of forming a vertical beam; a set of radio transceivers configured to drive an antenna array using transceiver signals; and a baseband module configured to process radio baseband signals based on the transceiver signals, wherein the baseband module comprises an antenna apparatus according to the first aspect or according to any one of the first to tenth implementations of the first aspect and configured to control focusing of an antenna beam of the antenna array towards the user equipment.

Furthermore, the radio base transceiver station additionally controls the focusing of the antenna beam of the antenna array based on a second parameter, e.g. the distance between the antenna array of the radio base station and the user equipment, so that the control accuracy of the antenna beam of the antenna array can be improved.

In a third aspect, the invention relates to a method for controlling the focusing of an antenna beam of an antenna array towards a user equipment, the method comprising: controlling a focusing of the antenna beam, the focusing being based on a feedback loop related to a pilot beam, the pilot beam comprising a set of predetermined antenna beams of the antenna array, and the focusing being based on a distance between the antenna array and the user equipment.

The accuracy of the control of the antenna beam may be improved when the focusing of the antenna beam is additionally based on a second parameter, such as the distance between the antenna array and the user equipment.

In a first implementation form of the method according to the third aspect, the method comprises: determining a beam angle of an antenna beam based on PMI reporting; determining the distance based on a propagation time measurement between the antenna array and the user equipment; and adjusting the focus of the antenna beam based on a difference between the reported beam angle and the beam angle corresponding to the measured propagation time.

By adjusting the focusing of the antenna beam based on the difference between the reported beam angle and the beam angle corresponding to the measured propagation time, the accuracy of the focusing can be improved.

In a second implementation form of the method according to the first implementation form of the third aspect, the method comprises: statistics and/or variations of the reported beam angles and the measured propagation times are evaluated to obtain the difference.

By evaluating statistics and/or variations of reported beam angles and measured propagation times, focusing can be performed without knowing the exact dimensions of the BTS.

Drawings

Further embodiments of the present invention will be described with reference to the following drawings, in which:

fig. 1 shows a schematic beam pattern 100 of a conventional base station 101 for illustrating the principle of different antenna beams determined by different PMI values;

fig. 2 shows a schematic beam diagram 200 of a conventional base station 201 for illustrating a wrong PMI reporting scenario caused by a UE erroneously detecting antenna side lobes;

fig. 3 shows a schematic beam pattern 300 of a BTS301 controlling the focusing of the antenna beams of an antenna array according to an embodiment of the invention;

fig. 4 shows a block diagram of a radio base station 400 according to an embodiment of the invention;

fig. 5 shows a diagram 500 illustrating an estimation of propagation time between a BTS 501 and a UE 503 according to an embodiment of the invention;

fig. 6 shows a block diagram of an apparatus 600 for controlling the focusing of antenna beams of an antenna array according to an embodiment of the invention; and

fig. 7 shows a block diagram of a method 700 for controlling the focusing of antenna beams of an antenna array according to an embodiment of the invention.

Detailed Description

PMI reporting will be described below. PMI reporting is an LTE closed-loop control mechanism, in which the UE reports the best downlink propagation path to the BTS. For vertical beamforming applications, the BTS repeatedly transmits a pilot beam comprising a mixed beam of all available downtilt beams, each encoded by a different PMI. The BTS selects the most appropriate downtilt beam for payload data transmission by UE reporting using the best PMI. PMI reporting is described, for example, in the standard 3GPP TS 36.211. Table 6.3.4.2.3-1 specifies different exemplary precoding parameter sets for spatial multiplexing depending on the codebook index and the number of spatial layers. By using these sets of precoding parameters, the antenna array can produce beam steering. PMI reporting may be used to report the effect of the used parameter set at the UE, and the UE may report quality indicators on the PMI parameter set to the BTS.

Fig. 3 shows a schematic beam pattern 300 of a BTS301 controlling the focusing of antenna beams 305 of an antenna array according to an embodiment. The cellular BTS301 includes an antenna array that allows beam steering. The beam direction is determined by ue pmi reporting. Each reported PMI value corresponds to a beam angle to be used for next transmission. To improve the accuracy of the beam angle 302, the BTS301 additionally measures the propagation time 310 between the BTS301 and the UE 303. This time is converted into the distance between the BTS and the UE. A simple trigonometric function may be used to compare the alpha value 302 to the travel time t 310. The BTS301 tracks the estimated t value 310 and alpha value 302 to coincide with a stationary or continuously moving UE state. The failing values are discarded. Other values will become input values for the algorithm processing and beam steering.

The beam control failure example described above as depicted in fig. 2 may be avoided by processing other known parameters specific to a particular UE. Such parameters are, for example, propagation time measurements between the UE 303 and the BTS301, and propagation losses between the BTS301 and the UE 303. Since propagation losses do vary rapidly due to obstructions such as walls and buildings, the propagation time 310 measurement is the most suitable method to measure and continuously observe the distance between the BTS301 and the UE 303. Because the UE 303 is either stationary or moving continuously within the cell 308, the angle α 302 and the propagation time t 310 also change constantly. In the above example described in connection with fig. 1 and 2, although the erroneous sequence is PMI 1-4-3, the UE 303 moving towards the BTS301 would follow the sequence PMI 1-2-3. The error sequence can be found by tracking t, which decreases constantly as the UE 303 moves towards the BTS 301. Thus, the accuracy of the alpha value 302 used is increased by tracking and post-processing, e.g., averaging, the estimated t.

BTS antenna beamforming is an advanced radio interface technology that enables efficient use of the radio spectrum. By precisely controlling the antenna beam direction towards the mobile UE 303, radio frequencies in a cellular network can be densely multiplexed, thereby increasing capacity and reducing the cost of mobile broadband services. The accuracy of the control of the downtilt angle α 302 is improved by measuring the propagation delay t 310 and its statistics to determine the distance between the BTS301 and the UE 303.

Fig. 3 also shows the basic principle of vertical antenna beam forming. The figure shows the relationship between the antenna beam angle alpha 302 and the distance between the BTS and the UE as determined by the estimate of the propagation time t 310. The BTS301 may focus its antenna beam towards the served UE 303. This is represented by a vertical downtilt angle α 302. By employing this downtilt angle, the BTS antenna beam is accurately directed towards the UE 303. A second parameter may be used to monitor the antenna downtilt angle to improve its accuracy. The parameter may be the distance between the UE 303 and the BTS301, which corresponds to the propagation time t 310 estimated by the BTS 301.

Fig. 4 shows a block diagram of a radio base station 400 according to an embodiment. The radio base transceiver station 400 includes: an antenna array 401 capable of forming a vertical beam; a set of radio transceivers 403 configured to drive the antenna array 401 using the transceiver signals 402; and a baseband module 407 configured to process the radio baseband signal 406 based on the transceiver signal 402. The baseband module 407 comprises the antenna device 600 described in relation to fig. 6, the antenna device 600 being configured to control the focusing of the antenna beam of the antenna array 401 towards the user equipment. The baseband module 407 provides the radio transceiver 403 with a baseband signal IQ 406, which baseband signal IQ 406 can be weighted or multiplied by a respective coefficient K in a weighting unit 405_i408. Fig. 4 shows the principle of PMI coding in the BTS. The digital baseband module 407 encodes the user data 410 into the IQ signal 406 for transmission. The IQ signal 406 is passed through a multiplication matrix X that multiplies the signalsNumber 406 multiplied by a set of coefficients K_i408 (including respective amplitudes, phases and time delays), a weighted IQ signal 404 is generated. Each PMI corresponds to a group K_iAnd (4) the coefficient. After multiplication, the resulting weighted IQ signals 404 are modulated for air interface transmission via the antenna group 401 towards the UE.

Fig. 5 shows a diagram 500 illustrating an estimation of propagation time between a BTS 501 and a UE 503 according to an embodiment. BTS 501 transmits a reference time stamp BTS Tx, which is received as UE Rx after propagation time t 510. The UE processes the timestamp internally and retransmits it as UE Tx. After the propagation delay t514, the signal returns as BTS Rx. The BTS 501 may calculate the propagation times t 510, 514 with knowledge of the UE processing delay 512. BTS 501 may convert propagation times t 510, 514 into inter-site distances between the BTS and the UE. A trigonometric function may be used to compare both alpha and the distance between the BTS and the UE. Since the BTS antenna height and the terrain between BTS 501 and UE 503 are unknown, it is in fact sufficient to track and compare the statistics and variations of both the alpha and t values.

Fig. 6 shows a block diagram of an antenna arrangement 600 for controlling the focusing of antenna beams of an antenna array according to an embodiment. The antenna apparatus 600 may be implemented in the baseband module 407 of the BTS 400 as described above with respect to fig. 4. The antenna apparatus 600 may be implemented in the BTS301 as described above with respect to fig. 3.

The antenna arrangement 600 comprises a controller 602, the controller 602 being configured to control a focusing 605 of an antenna beam of the antenna array towards the user equipment, the focusing 605 being based on a feedback loop 601 related to a pilot beam comprising a set of predetermined antenna beams of said antenna array, and the focusing 605 being based on a distance 603 between the antenna array and the user equipment.

According to an embodiment, controller 602 may be configured to determine distance 603 based on the travel time measurement. According to an embodiment, the propagation time measurement may be based on a round trip delay measurement between the antenna array and the user equipment. According to an embodiment, the propagation time measurement may be based on a known processing time within the user equipment. According to an embodiment, the propagation time measurement may be based on one of a timing advance measurement and a time stamp measurement in the signaling or payload traffic. According to an embodiment, the controller 602 may be configured to determine the beam angle of the antenna beam based on the report of the user equipment. According to an embodiment, the controller 602 may be configured to: the focusing of the antenna beam is controlled by using a trigonometric function related to the reported beam angle in combination with the reported beam angle and the measured propagation time 605. According to an embodiment, the controller 602 may be configured to control the focus 605 based on statistics and/or variations of reported beam angles and measured propagation times. According to an embodiment, the controller 602 may be configured to detect a failure of the feedback loop 601 by tracking the reported beam angle and the measured propagation time. According to an embodiment, the controller 602 may be configured to encode the set of predetermined antenna beams by using a precoding matrix. According to an embodiment, the feedback loop 601 may be reported based on a precoding matrix indication as defined according to the 3GPP TS standard, in particular according to the 3GPP TS36.331 standard.

Fig. 7 shows a block diagram of a method 700 for controlling the focusing of antenna beams of an antenna array according to an embodiment. The method 700 comprises: the focusing 705 of the antenna beam is controlled 702, the focusing 705 is based on a feedback loop 701 relating to a pilot beam comprising a set of predetermined antenna beams of said antenna array, and the focusing 705 is based on a distance 703 between the antenna array and the user equipment.

According to an embodiment, the method 700 comprises: determining a beam angle of an antenna beam based on PMI reporting; determining a distance based on a propagation time measurement between the antenna array and the user equipment 703; and adjusting the focus of the antenna beam based on a difference between the reported beam angle and the beam angle corresponding to the measured propagation time 705. According to an embodiment, the method 700 comprises: statistics and/or variations of the reported beam angles and the measured propagation times are estimated to obtain the difference.

The method 700 may be performed in the antenna apparatus 600 described above with respect to fig. 6. The method 700 may be performed in the radio base transceiver station 400 described above with respect to fig. 4. The method 700 may be performed in the BTS301 described above with respect to fig. 3.

The present invention includes a radio base transceiver station as shown in fig. 4 above, comprising: an antenna array capable of forming a vertical beam; a set of radio transceivers driving an antenna array; and a baseband module processing the radio baseband signal. The baseband module may implement the PMI algorithm in the downlink and uplink according to the 3GPP TS36.331 standard. This is explained in the example above with respect to fig. 4. A set of PMI values may be sent periodically in so-called pilot beams. The UE may determine the best PMI value and report the best PMI value back to the BTS. As shown in fig. 5 above, the BTS may perform a propagation time t measurement between the BTS and the UE. The measured time may optionally be post-processed to improve the accuracy of the measured time value. The process may use, for example, averaging, weighting, or other functions that suppress errors due to noise or numerical sampling inaccuracies. The BTS can combine the reported PMI value with its own calculated propagation time t. A simple trigonometric function or value statistic may be used to compare the downtilt value α reported by the PMI with the distance between the BTS and the UE represented by the propagation time t. Alternatively, the BTS may track the calculated t and α values. Since the UE is either stationary or moving continuously within the BTS area, the historical values of t and α that are tracked, as well as each new value, should correspond to either a stationary UE or a constantly moving UE. Each new sample that does not meet the criteria is discarded or its weighting factor is reduced. The propagation time measurement of the BTS may be implemented as a timing advance measurement implemented in an LTE system. There may also be other implementations such as dedicated timestamps in signaling or payload traffic.

From the foregoing, it will be apparent to those skilled in the art that: various methods, systems, computer programs on recording media, and the like are provided.

The present disclosure may also support a computer program product comprising computer-executable code or computer-executable instructions that, when executed, cause at least one computer to perform the performing steps and the calculating steps described herein.

The methods and apparatus described in this application may be implemented in a digital signal processor DSP, microcontroller or any other end processor as software, or within an application specific integrated circuit ASIC as hardware circuitry.

The invention can be implemented in digital electronic circuitry, or in computer hardware, firmware, and software, or in combinations of them, for example, in available hardware of conventional mobile devices, or in new hardware dedicated to processing the methods described herein.

Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the above teachings. Of course, those skilled in the art will readily appreciate that the invention has many other applications beyond those described herein. While the invention has been described with reference to one or more specific embodiments, those skilled in the art will recognize that many changes may be made thereto without departing from the scope of the invention. It is therefore to be understood that within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described herein.

Claims

1. An antenna device (600) comprising:

a controller (602), the controller (602) being configured to control a focusing (605) of an antenna beam of an antenna array towards a user equipment, the focusing (605) being based on a feedback loop (601) related to a pilot beam, the pilot beam comprising a set of predetermined antenna beams of the antenna array, and the focusing (605) being based on a distance (603) between the antenna array and the user equipment, to control the focusing (605) of the antenna beam of the antenna array towards the user equipment to control a beam angle of the antenna beam.

2. The antenna device (600) according to claim 1, wherein the controller (602) is configured to determine the distance (603) based on a propagation time measurement.

3. The antenna device (600) according to claim 2, wherein the propagation time measurement is based on a round trip delay measurement between the antenna array and the user equipment.

4. The antenna device (600) according to claim 2, wherein the propagation time measurement is based on a known processing time within the user equipment.

5. The antenna device (600) according to claim 3, wherein the propagation time measurement is based on a known processing time within the user equipment.

6. The antenna device (600) according to claim 2, wherein the propagation time measurement is based on one of a timing advance measurement and a time stamp measurement in signalling or payload traffic.

7. The antenna device (600) according to claim 3, wherein the propagation time measurement is based on one of a timing advance measurement and a time stamp measurement in signalling or payload traffic.

8. The antenna device (600) according to claim 4, wherein the propagation time measurement is based on one of a timing advance measurement and a time stamp measurement in signalling or payload traffic.

9. The antenna device (600) according to claim 5, wherein the propagation time measurement is based on one of a timing advance measurement and a time stamp measurement in signalling or payload traffic.

10. The antenna device (600) according to one of claims 3 to 9, wherein the controller (602) is configured to determine the beam angle of the antenna beam based on a report of the user equipment.

11. The antenna device (600) according to claim 10, wherein the controller (602) is configured to: controlling the focusing of the antenna beam by using a trigonometric function related to the reported beam angle in combination with the reported beam angle and the measured propagation time (605).

12. The antenna device (600) according to claim 10, wherein the controller (602) is configured to control the focusing (605) based on statistics and/or variations of reported beam angles and measured propagation times.

13. The antenna device (600) according to claim 11, wherein the controller (602) is configured to control the focusing (605) based on statistics and/or variations of reported beam angles and measured propagation times.

14. The antenna device (600) according to claim 11, wherein the controller (602) is configured to detect a failure of the feedback loop (601) by tracking the reported beam angle and the measured propagation time.

15. The antenna device (600) according to claim 12, wherein the controller (602) is configured to detect a failure of the feedback loop (601) by tracking the reported beam angle and the measured propagation time.

16. The antenna device (600) according to claim 13, wherein the controller (602) is configured to detect a failure of the feedback loop (601) by tracking the reported beam angle and the measured propagation time.

17. The antenna device (600) according to one of claims 1-9, 11-16, wherein the controller (602) is configured to encode the set of predetermined antenna beams by using a precoding matrix.

18. The antenna device (600) according to claim 10, wherein the controller (602) is configured to encode the set of predetermined antenna beams by using a precoding matrix.

19. The antenna device (600) according to one of claims 1-9, 11-16, 18, wherein the feedback loop (601) indicates PMI reporting based on a precoding matrix defined according to a 3GPP TS standard.

20. The antenna device (600) according to claim 10, wherein the feedback loop (601) is based on precoding matrix indication, PMI, reporting defined according to 3GPP TS standards.

21. The antenna device (600) according to claim 17, wherein the feedback loop (601) is based on precoding matrix indication, PMI, reporting defined according to 3GPP TS standards.

22. The antenna device (600) according to one of claims 1-9, 11-16, 18, wherein the feedback loop (601) indicates PMI reporting based on a precoding matrix defined according to the 3GPP TS36.331 standard.

23. The antenna device (600) according to claim 10, wherein the feedback loop (601) is based on precoding matrix indication, PMI, reporting defined according to 3GPP TS36.331 standard.

24. The antenna device (600) according to claim 17, wherein the feedback loop (601) is based on precoding matrix indication, PMI, reporting defined according to 3GPP TS36.331 standard.

25. A radio base transceiver station (400; 301) comprising:

an antenna array (401) capable of forming a vertical beam;

a set of radio transceivers (403) configured to: driving the antenna array (401) with a transceiver signal (402);

a baseband module (407) configured to process a radio baseband signal (406) based on the transceiver signal (402), wherein the baseband module (407) comprises an antenna device (600) according to one of claims 1 to 11 and configured to control focusing of an antenna beam of an antenna array (401) towards a user equipment.

26. A method (700) for controlling a focusing (705) of an antenna beam of an antenna array towards a user equipment, the method (700) comprising:

controlling (702) a focusing (705) of the antenna beam, the focusing (705) being based on a feedback loop (701) related to a pilot beam, the pilot beam comprising a set of predetermined antenna beams of the antenna array, and the focusing (705) controlling (702) the focusing (705) of the antenna beam to control (702) a beam angle of the antenna beam based on a distance (703) between the antenna array and the user equipment.

27. The method (700) of claim 26, comprising:

determining a beam angle of the antenna beam based on a precoding matrix indication report;

determining the distance based on a propagation time measurement between the antenna array and the user equipment (703);

adjusting the focusing of the antenna beam based on a difference between the reported beam angle and a beam angle corresponding to the measured propagation time (705).

28. The method of claim 27, comprising:

statistics and/or variations of the reported beam angles and the measured propagation times are evaluated to obtain the difference.