EP4677781A1

EP4677781A1 - Calibration of antenna arrays used for joint communications and sensing (jcas)

Info

Publication number: EP4677781A1
Application number: EP23711819.5A
Authority: EP
Inventors: Christopher MOLLÉN; Julia EQUI; Mirza Uzair BAIG; Gabor Fodor
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2023-03-03
Filing date: 2023-03-03
Publication date: 2026-01-14
Also published as: WO2024186235A1

Abstract

Embodiments include methods performed by a radio access network (RAN) node for calibration of an antenna array comprising a plurality of antenna elements. Such methods include, using a first portion of the antenna array, receiving calibration signals from one or more reference points at known locations relative to the antenna array. Such methods include, for each of the reference points, determining an angle of arrival (AoA) of the received calibration signals relative to an expected orientation of the antenna elements comprising the first portion and, based on the one or more determined AoAs and the known locations of the one or more reference points, determining an actual orientation of the antenna elements comprising the first portion. Other embodiments include RAN nodes configured to perform such methods.

Description

CALIBRATION OF ANTENNA ARRAYS USED FOR JOINT COMMUNICATIONS AND SENSING (JCAS)

TECHNICAL FIELD

The present disclosure relates generally to wireless networks, and more specifically to techniques for calibrating antenna arrays containing large numbers of antenna or elements, particularly antenna arrays used for joint communication and sensing in a wireless network.

BACKGROUND

Currently the fifth generation (“5G”) of cellular systems, also referred to as New Radio (NR), is being standardized within the Third-Generation Partnership Project (3GPP). NR is developed for maximum flexibility to support multiple and substantially different use cases. These include enhanced mobile broadband (eMBB), machine type communications (MTC), ultra-reliable low latency communications (URLLC), side-link device-to-device (D2D), and several other use cases. NR was initially specified in Rel-15 and continues to evolve through subsequent releases, such as Rel-16 and Rel-17.

In addition to providing coverage via cells as in earlier generations, NR networks also provide coverage via “beams.” In general, a downlink (DL, i.e., network to UE) “beam” is a coverage area of a network-transmitted reference signal (RS) that may be measured or monitored by a UE. In NR, for example, RS can include any of the following: synchronization signal/PBCH block (SSB), channel state information RS (CSI-RS), tracking reference signals (or any other sync signal), positioning RS (PRS), demodulation RS (DMRS), phase-tracking reference signals (PTRS), etc. In general, SSB is available to all UEs regardless of the state of their connection with the network, while other RS (e.g., CSI-RS, DM-RS, PTRS) are associated with specific UEs that have a network connection.

5G/NR networks are expected to operate at higher frequencies such as 25-60 GHz, which are typically referred to as “millimeter wave” or “mmW” for short. Such systems are also expected to utilize multi-antenna technology at the transmitter, the receiver, or both. In general, multi-antenna technology can include a plurality of antenna elements (“antenna array”) combined with advanced signal processing techniques. Multi-antenna technology can be used to improve various aspects of a communication system, including system capacity (e.g., more users per unit bandwidth per unit area), coverage (e.g., larger area for given bandwidth and number of users), and increased per-user data rate (e.g., in a given bandwidth and area).

Availability of multiple antennas at the transmitter and/or the receiver can be utilized in different ways to achieve different goals. For example, multiple antennas at the transmitter and/or the receiver can be used to shape or “form” the overall antenna beam (e.g., transmit and/or receive beam, respectively) in a certain way, with the general goal being to improve the received signal-to-interference-plus-noise ratio (SINK) and, ultimately, system capacity and/or coverage. This can be done, for example, by maximizing the overall antenna gain in the direction of the target receiver or transmitter or by suppressing specific dominant interfering signals. More specifically, the transmitter and/or receiver can determine an appropriate weight for each antenna element in an antenna array so as to produce one or more beams, with each beam covering a particular range of azimuth and elevation relative to the antenna array.

In relatively good channel conditions, the capacity of the channel becomes saturated such that further improving the SINR provides limited capacity improvements. In such cases, using multiple antennas at both the transmitter and the receiver can be used to create multiple parallel communication "channels" over the radio interface. This can facilitate a highly efficient utilization of both the available transmit power and the available bandwidth resulting in, e.g., very high data rates within a limited bandwidth without a disproportionate degradation in coverage. For example, under certain conditions, the channel capacity can increase linearly with the number of antennas and avoid saturation in the data capacity and/or rates. These techniques are commonly referred to as “spatial multiplexing” or multiple-input, multiple-output (MIMO) antenna processing.

Accordingly, spatial multiplexing is a key feature to increase the spectral efficiency and/or capacity of wireless systems, including 5G/NR. Transmitting multiple layers on the same time-frequency resource can increase the data-rate for a single user (referred to as “SU- MIMO”). Alternatively, transmitting multiple layers on the same time-frequency resource to multiple users (referred to as “MU-MIMO”) can increase the system capacity in number of users. In general, the number of antennas required for a MIMO system can be readily determined based on a desired throughput, spectral efficiency, and/or traffic load.

Channel estimation for MIMO systems benefits from reciprocity between UL and DL channels, particularly for time division duplexing (TDD) systems. Even so, impairments in the base station transmitter and/or receiver hardware - such as phase noise, active and passive intermodulation distortion, in-phase and quadrature imbalance, manufacturing imperfections, etc. - may make a channel reciprocity assumption invalid. These impairments also degrade the performance of frequency division duplexing (FDD) systems (where reciprocity is less likely) and beamforming systems used for MIMO.

However, such hardware impairments can be compensated to some degree by performing reciprocity calibration using the antenna array coupled to the base station hardware. For example, reciprocity calibration may involve a UE transmitting RS that are received and measured by the base station and/or the base station transmitting RS that are received and measured by the UE, which then reports the measurements to the base station. Based on this information, the base station can determine and compensate for some hardware impairments that would otherwise invalidate a channel reciprocity assumption. For example, the base station can adjust gains and/or phase shifts used in beamforming. This approach is also known as over-the- air (OTA) calibration and is typically employed when line-of-sight (LOS) exists between a UE and the base station antenna array.

SUMMARY

Although reciprocity calibration may be adequate for maintaining communication performance, it is inadequate to address other hardware impairments that may degrade performance when the base station uses the same antenna array for sensing objects in its proximate physical environment. These other hardware impairments may include changes to location and/or orientation of an antenna array (or portions thereof) over time, e.g., due to weather, aging, etc.

Existing techniques for “geometric calibration” of the antenna array are very coarse, typically aligning the antenna array roughly in the direction of its intended coverage (e.g., a cell sector). Remaining impairments may be insignificant for communication performance but very significant for sensing performance. Since joint communication and sensing (JCAS) is expected to become an important application in 5G networks, new geometric calibration techniques are needed.

An object of embodiments of the present disclosure is to improve JCAS operation in radio access networks (RANs), such as by providing, enabling, and/or facilitating solutions to overcome exemplary problems summarized above and described in more detail below.

Embodiments include methods e.g., procedures) performed by a RAN node (e.g., base station, eNB, gNB, ng-eNB, etc.) for calibration of an antenna array comprising a plurality of antenna elements.

These exemplary methods can include, using a first portion of the antenna array, receiving calibration signals from one or more reference points at known locations relative to the antenna array. These exemplary methods can also include, for each of the one or more reference points, determining an angle of arrival (AoA) of the received calibration signals relative to an expected orientation of the antenna elements comprising the first portion. These exemplary methods can also include, based on the one or more determined AoAs and the known locations of the one or more reference points, determining an actual orientation of the antenna elements comprising the first portion.

In some embodiments, the one or more reference points consist of a single reference point and the difference between the actual orientation and the expected orientation is a misalignment of a boresight for the antenna elements comprising the first portion. In other embodiments, the one or more reference points comprise multiple reference points and the difference between the actual orientation and the expected orientation includes one or more of the following for the antenna elements comprising the first portion: a misalignment of a boresight, a rotation around the boresight.

In some embodiments, these exemplary methods can also include, based on a difference between the actual orientation and the expected orientation, adjusting gains and/or phase shifts applied to signals transmitted and/or received via the antenna elements comprising the first portion. In some of these embodiments, the antenna array is used for JCAS and the transmitted and/or received signals, for which gains and/or phase shifts are adjusted, include signals used for sensing of objects in a physical environment proximate to the antenna array.

In other embodiments, these exemplary methods can also include, based on a difference between the actual orientation and the expected orientation, adjusting sensing results obtained from signals transmitted and/or received via the antenna elements comprising the first portion.

In some embodiments, each of the known locations has a line-of-sight (LOS) to the antenna array. In some embodiments, determining the actual orientation of the first portion is further based on known orientations of the one or more reference points. In some embodiments, the calibration signals are received via one or more of the following that is also used for communication with UEs operating in the RAN: radio spectrum, and a RAN node receiver. In some embodiments, each of the one or more reference points is one of the following: a passive signal reflector, a UE, and a further antenna array coupled to another RAN node.

In some embodiments, these exemplary methods can also include transmitting the calibration signals, which are received as reflections from the one or more reference points. In other embodiments, the one or more reference points are UEs and these exemplary methods can also include obtaining a location of each of the UEs from one of the following: the UE, a positioning node coupled to the RAN, and another RAN node. In some of these embodiments, the obtained location of each UE is used as the known location for determining the actual orientation.

In other embodiments, the one or more reference points are further antenna arrays coupled to other RAN nodes and these exemplary methods can also include obtaining, from each of the other RAN nodes, location and orientation of any of the further antenna arrays coupled to the other RAN node. In such case, the obtained location of each further antenna array is used as the known location for determining the actual orientation. In some of these embodiments, the calibration signals are transmitted by the other RAN nodes via the one or more further antenna arrays. In some of these embodiments, the RAN node and the other RAN nodes are synchronized to a common time source.

In some embodiments, the first portion of the antenna array includes all antenna elements of the antenna array. In other embodiments, the first portion of the antenna array is a single antenna element of the antenna array. In other embodiments, the first portion of the antenna array includes a subset of the antenna elements that meets one or more of the following conditions: proximate to each other in the antenna array, and coupled to different RAN node radio circuitry than the remainder of the antenna elements (i.e., other than the subset).

Other embodiments include RAN nodes configured to perform operations corresponding to any of the exemplary methods described herein. Other embodiments include non-transitory, computer-readable media storing program instructions that, when executed by processing circuitry, configure such RAN nodes to perform operations corresponding to any of the exemplary methods described herein.

These and other embodiments described herein can provide various benefits and/or advantages. For example, embodiments can facilitate JCAS using existing infrastructure in a RAN. More specifically, embodiments provide new techniques for geometric calibration of antenna arrays used in a RAN, which makes such arrays suitable not only for communication but also for accurate sensing of objects in the proximate physical environment. Such techniques are flexible in that they utilize as many reference points as are available and/or necessary to achieve a desired calibration accuracy. Such techniques are also flexible in that they can use various types of reference points having a LOS to the antenna array needing geometric calibration.

These and other objects, features, and advantages of embodiments of the present disclosure will become apparent upon reading the following Detailed Description in view of the Drawings briefly described below.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a high-level views of an exemplary 5G/NR network architecture.

Figures 2A-C show various arrangements for transmit beamforming.

Figure 3 illustrates geometric calibration of an antenna array using a reflector having a fixed, known position and orientation, according to some embodiments of the present disclosure.

Figure 4 illustrates geometric calibration of an antenna array using reflective features of various buildings in a city skyline, according to some embodiments of the present disclosure.

Figure 5 is a block diagram of an architecture for UE positioning in 5G/NR networks. Figure 6 illustrates geometric calibration of an antenna array using a UE that is initially located between two buildings, according to some embodiments of the present disclosure.

Figure 7 illustrates geometric calibration of an antenna array using an aerial-capable UE that is initially located at ground level, according to some embodiments of the present disclosure.

Figure 8 illustrates geometric calibration of an antenna array using an antenna array coupled to another RAN node, according to some embodiments of the present disclosure.

Figure 9 shows a flow diagram of an exemplary method (e.g., procedure) for a RAN node, according to various embodiments of the present disclosure.

Figure 10 shows a communication system according to some embodiments of the present disclosure.

Figure 11 shows a network node according to some embodiments of the present disclosure.

Figure 12 shows a virtualization environment in which functions implemented by some embodiments of the present disclosure may be virtualized.

DETAILED DESCRIPTION

Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided as examples to convey the scope of the subject matter to those skilled in the art.

Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. All references to a/an/the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods and/or procedures disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where it is implicit that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein can be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments can apply to any other embodiments, and vice versa. Other objects, features, and advantages of the enclosed embodiments will be apparent from the following description.

Furthermore, the following terms are used throughout the description given below: • Radio Access Node: As used herein, a “radio access node” (or equivalently “radio network node,” “radio access network node,” or “RAN node”) can be any node in a radio access network (RAN) that operates to wirelessly transmit and/or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g., gNB in a 5G/NR network or eNB in a LTE network), base station distributed components (e.g., CU and DU), a high-power or macro base station, a low-power base station (e.g, micro, pico, femto, or home base station, or the like), an integrated access backhaul (IAB) node, a transmission point (TP), a transmission reception point (TRP), a remote radio unit (RRU or RRH), and a relay node.

• Core Network Node: As used herein, a “core network node” is any type of node in a core network. Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a serving gateway (SGW), a PDN Gateway (P-GW), a Policy and Charging Rules Function (PCRF), an access and mobility management function (AMF), a session management function (SMF), a user plane function (UPF), a Charging Function (CHF), a Policy Control Function (PCF), an Authentication Server Function (AUSF), a location management function (LMF), or the like.

• Wireless Device: As used herein, a “wireless device” (or “WD” for short) is any type of device that is capable, configured, arranged and/or operable to communicate wirelessly with network nodes and/or other wireless devices. Communicating wirelessly can involve transmitting and/or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and/or other types of signals suitable for conveying information through air. Unless otherwise noted, the term “wireless device” is used interchangeably herein with the term “user equipment” (or “UE” for short), with both of these terms having a different meaning than the term “network node”.

• Network Node: As used herein, a “network node” is any node that is either part of a radio access network (e.g., a radio access node or equivalent term) or of a core network (e.g., a core network node) of a cellular communications network. Functionally, a network node is equipment capable, configured, arranged, and/or operable to communicate directly or indirectly with a wireless device and/or with other network nodes or equipment in the cellular communications network, to enable and/or provide wireless access to the wireless device, and/or to perform other functions (e.g., administration) in the cellular communications network.

• Base station: As used herein, a “base station” may comprise a physical or a logical node transmitting or controlling the transmission of radio signals, e.g., eNB, gNB, ng-eNB, en-gNB, centralized unit (CU)/distributed unit (DU), transmitting radio network node, transmission point (TP), transmission reception point (TRP), remote radio head (RRH), remote radio unit (RRU), Distributed Antenna System (DAS), relay, etc.

• Node: As used herein, the term “node” (without prefix) can be any type of node that can operate in or with a wireless network (including RAN and/or core network), including a radio access node (or equivalent term), core network node, or wireless device. However, the term “node” may be limited to a particular type (e.g., radio access node) based on its specific characteristics in any given context.

The above definitions are not meant to be exclusive. In other words, various ones of the above terms may be explained and/or described elsewhere in the present disclosure using the same or similar terminology. Nevertheless, to the extent that such other explanations and/or descriptions conflict with the above definitions, the above definitions should control.

Note that the description given herein focuses on a 3 GPP cellular communications system and, as such, 3 GPP terminology or terminology similar to 3 GPP terminology is oftentimes used. However, the concepts disclosed herein are not limited to a 3GPP system. Furthermore, although the term “cell” is used herein, it should be understood that (particularly with respect to 5G NR) beams may be used instead of cells and, as such, concepts described herein apply equally to both cells and beams.

Figure 1 shows a high-level view of an exemplary 5G network architecture, including a next-generation RAN (NG-RAN, 199) and a 5G core network (5GC, 198). As shown in the figure, the NG-RAN can include gNBs (e.g., 110a,b) and ng-eNBs (e.g., 110a,b) that are interconnected with each other via respective Xn interfaces. The gNBs and ng-eNBs are also connected via the NG interfaces to 5GC 198, more specifically to access and mobility management functions (AMFs, e.g., 130a, b) via respective NG-C interfaces and to user plane functions (UPFs, e.g., 140a, b) via respective NG-U interfaces. Moreover, AMFs can communicate with one or more policy control functions (PCFs, e.g., 150a,b) and network exposure functions (NEFs, e.g., 160a,b).

Each of the gNBs can support the NR radio interface including frequency division duplexing (FDD), time division duplexing (TDD), or a combination thereof. Each of ng-eNBs can support the fourth generation (4G) Long-Term Evolution (LTE) radio interface but unlike conventional LTE eNBs, ng-eNBs connect to the 5GC via the NG interface. Each of the gNBs and ng-eNBs can serve a geographic coverage area including one more cells (e.g., l l la-b and 121a-b shown in Figure 1). Depending on the cell in which it is located, a UE (e.g., 105 in Figure 1) can communicate with the gNB or ng-eNB serving that cell via the NR or LTE radio interface, respectively. Although Figure 2 shows gNBs and ng-eNBs separately, it is also possible that a single NG-RAN node provides both types of functionality. As mentioned above, spatial multiplexing is a key feature to increase the spectral efficiency and/or capacity of wireless systems, including 5G/NR. Transmitting multiple layers on the same time-frequency resource can increase the data-rate for a single user (referred to as “SU-MIMO”). Alternatively, transmitting multiple layers on the same time-frequency resource to multiple users (referred to as “MU-MIMO”) can increase the system capacity in number of users. In general, the number of antennas required for a MIMO system can be readily determined based on a desired throughput, spectral efficiency, and/or traffic load.

Even so, transmitting multiple layers on the same resource requires sufficient spatial isolation to keep inter-layer interference at an acceptable level. This can be done by transmitting on different orthogonal polarizations, e.g., vertical and horizontal. Since there are only two orthogonal polarizations, however, this limits spatial multiplexing order to two. This is common in current wireless networks, particularly for SU-MIMO. The main constraint is in the UE, where it is difficult to fit an antenna array of many elements having sufficient spatial separation.

There are three main beamforming techniques: analog, digital, and hybrid (a combination of analog and digital). Analog beamforming can compensate for high mmW pathloss, while digital precoding can provide additional performance gains necessary to achieve a reasonable coverage. The implementation complexity of analog beamforming is significantly less than digital since it can utilize simple phase shifters, but it is limited in terms of multi-direction flexibility (i.e., a single beam can be formed at a time and the beams are then switched in time domain), transmission bandwidth (i.e., not possible to transmit over a sub-band), inaccuracies in the analog domain, etc.

Digital beamforming requires more complex converters between the digital domain (i.e., OFDM FFT/IFFT) and the intermediate frequency (IF) radio domain. However, digital beamforming, which is often used today in LTE networks, provides the best performance in terms of data rate and multiplexing capabilities. For example, multiple beams over multiple subbands can be formed simultaneously. Even so, digital beamforming presents challenges in terms of power consumption, integration, and cost. Furthermore, while cost generally scales linearly with the number of transmit/receive units, the gains of digital beamforming increase more slowly.

Figure 2A shows an exemplary hybrid transmit beamforming arrangement, which includes baseband processing circuitry (220) coupled to an analog beamformer (BF, 240) via intermediate conversion circuitry (230). For example, the arrangement shown in Figure 2A can be part of or operably coupled to a RAN node, such any of the gNBs and ng-eNBs shown in Figure 1. The baseband processing circuitry includes a MIMO-related functionality such as layer mapping and precoding. The conversion circuitry can include one or more conversion chains, with multiple conversion chains shown in the figure. Each conversion chain can include an inverse FFT, a parallel-to-serial (P/S) converter, and a digital-to-analog converter (DAC). The analog beamformer includes a transmitter (242, also referred to as transmit circuitry) and an antenna array (244). Additionally, the arrangement shown in Figure 2A includes processing/control circuitry (210) that manages and/or controls the baseband processing circuitry, the conversion circuitry, and the transmitter.

Figure 2B shows an exemplary arrangement of analog beamformer 240. In this arrangement, antenna panel 244 includes two panels (or sub-panels), with each panel including eight (8) two-element sub-arrays. Each antenna element provides vertical and horizontal polarization, as indicated by crosses in the respective circles. Transmitter 242 includes an independent beamforming circuit for each panel, with each beamforming circuit include an upconverter (e.g., mixer) from intermediate frequency (IF) to radio frequency (RF), as well as independent phase shifters and power amplifiers (PAs, also referred to as VGAs) for each two- element sub-array.

Figure 2C shows another exemplary arrangement of analog beamformer 140. In this arrangement, antenna panel 244 includes one antenna panel with 16 two-element sub-arrays. Each antenna element provides vertical and horizontal polarization, as indicated by crosses in the respective circles. Transmitter 242 includes one beamforming circuit arranged in a similar manner as shown in Figure 2B. In this exemplary arrangement, only a single conversion chain is needed in conversion circuitry 230 shown in Figure 2A.

Note that the exemplary transmitters 242 shown in Figures 2B-C feed a single polarization on the antenna panel 244. Duplicate transmitters 242 can be used to feed the respective horizontal and vertical polarizations on the antenna panel 244.

Although the antenna arrays shown in Figures 1B-1C are two-dimensional grids of elements, this is only exemplary. Other exemplary antenna arrays can have linear and/or onedimensional arrangements of elements.

A beamformer steers the analog beam of each antenna panel toward a single orientation or direction for each polarization on each OFDM symbol. For example, the processing/control circuitry can configure the phase shifters and the PAs associated with each subarray to generate a beam having a desired orientation. The number of subarrays in a panel determines the array gain for the panel. The arrangement shown in Figure IB supports one beam per panel per polarization (four total for two panels and two polarizations), while the arrangement shown in Figure 1C supports only one beam per polarization (two total). For systems deployed at mmW frequencies, it is common to perform beamforming on the time-domain (TD) signal after OFDM transformation. The beamforming operation can either be performed by analog circuitry or by a digital implementation before digital-to-analog conversion (e.g., in the digital precoding section of Figure 1A). Since it is difficult to implement several analog beamforming networks (e.g., phase shifters and PAs) behind one antenna element, multi-layer transmission is often implemented with several panels, with each panel transmitting a single layer per polarization.

For TD beamforming, inter-layer isolation is typically provided by spatial nulling of inter-beam/inter-layer interference. In other words, when transmitting one layer, the applied BF weights should create maximal gain towards this layer while the gain should be very low in the directions where the other layers should go.

To achieve highest SU-MIMO or MU-MIMO throughput, it is necessary to transmit using beams that are optimal for the propagation channel(s) between a RAN node antenna array and the receiving UE(s). MIMO beamforming relies heavily on correct estimation of the propagation channel, which is generally unknown.

Channel estimation for MIMO may benefit from reciprocity between UL and DL channels, particularly for time division duplexing (TDD) systems. Even so, impairments in the RAN node transmitter and/or receiver hardware - such as phase noise, active and passive intermodulation distortion, in-phase and quadrature imbalance, manufacturing imperfections, etc. - may make a channel reciprocity assumption invalid. These impairments also degrade the performance of frequency division duplexing (FDD) systems (where reciprocity is less likely) and beamforming systems used for MIMO.

However, such hardware impairments can be compensated to some degree by performing reciprocity calibration using the antenna array coupled to the RAN node radio circuitry. For example, reciprocity calibration may involve a UE transmitting RS that are received and measured by the RAN node and/or the RAN node transmitting RS that are received and measured by the UE, which then reports the measurements to the RAN node n. Based on this information, the RAN node can determine and compensate for some hardware impairments that would otherwise invalidate a channel reciprocity assumption. For example, the RAN node can adjust gains and/or phase shifts used in beamforming. This approach is also known as over-the- air (OTA) calibration and is typically employed when line-of-sight (LOS) exists between a UE and the RAN node antenna array.

Although reciprocity calibration may be adequate for maintaining communication performance, such as for MIMO, it is inadequate to address other hardware impairments that may degrade performance when the RAN node uses the same antenna array for sensing objects in its proximate physical environment. In this context, the term “sensing” may include ranging, detection, identification, localization, and/or positioning of such objects.

Inclusion of sensing capabilities in a communication network is often referred to as joint communications and sensing (JCAS). One advantage of JCAS is that most of the necessary infrastructure is already in place in the RAN nodes that make up a cellular network, including the antenna arrays and radio circuitry (e.g., as in Figures 1 A-D). This infrastructure provides full area coverage and interconnection between RAN nodes, which facilitates a multi-static sensory- mesh . Hence, the sensing can be provided almost for free.

Spectrum allocations have expanded towards higher frequencies in the evolution to 5G. This trend will continue and communication spectrum in the sub -Ter hertz region will likely be available for 6G networks. The introduction of these higher frequencies increases the potential accuracy of sensing based on radar-like technology. For example, reflections of transmitted signals can be received and processed in the RAN (or other nodes/functions coupled to the RAN) to yield spatial awareness of the proximate physical environment. Beamforming using antenna arrays with many elements is a critical component of JCAS.

To meet performance requirements of current and future sensing applications, the location and orientation of each antenna element in the antenna array needs to be known when applying array processing to the received signals to detect, identify, localize, and/or position objects. Hardware impairments that affect this performance include changes to location and/or orientation (collectively referred to as “geometry”) of an antenna array (or portions thereof) over time, e.g., due to incorrect installation, weather, aging, etc. As such, the actual geometry can deviate from the nominal or expected geometry, thereby negatively impacting sensing performance.

Thus, some “geometric calibration” of an antenna array for sensing applications is needed. However, existing techniques for geometric calibration of antenna arrays are very coarse, typically aligning the antenna array generally in the direction of its intended coverage (e.g., a 120-degree sector of a cell). Remaining impairments may be insignificant for communication performance but very significant for sensing performance. Moreover, reciprocity calibration does not address these remaining impairments that affect sensing performance. Since joint communication and sensing (JCAS) is expected to become an important application in 5G and future networks, new geometric calibration techniques are needed.

Embodiments of the present disclosure address these and other problems, issues, and/or difficulties by techniques in which a RAN node calibrates its coupled antenna array based on calibration signals received, via the antenna array, from one or more reference points with known location and unobstructed line-of-sight (LOS) to the antenna array. The received calibration signals may be transmitted by the reference points themselves, or may be transmitted by the RAN node via the antenna array and received as reflections.

Based on the known information about the reference point(s), the RAN node can determine an expected (or reference) angle of arrival (AoA) of the received calibration signals relative to the reference (or expected) location and orientation of the antenna array. Based on processing the received calibration signals, the RAN node can determine an actual AoA. Any difference between the expected and actual AoAs indicates an amount of geometric calibration to be performed.

Such calibration can include, for example, adjusting gains and/or phase shifts applied to signals transmitted and/or received via the antenna array, which effectively adjusts the actual orientation of the antenna array to align with its reference (or expected) orientation. Alternately, any difference between the expected and actual AoAs can be removed or compensated for in angular calculations that are part of various sensing algorithms employed.

In various embodiments, the calibration signals can be the same, or similar, signals as used for communication with UEs. For example, various existing RS such as DM-RS, PRS, SRS, etc. can be utilized as calibration signals for the purpose of geometric calibration of antenna arrays. Alternately, new RS can be defined for the purpose of geometric calibration of antenna arrays (e.g., sensing RS). For the purposes of JCAS, however, it is desirable that the calibration signals be carried on the same radio spectrum and/or received using the same RAN node radio circuitry as used for communicating with UEs.

Various types of reference points can be used, including dedicated signal reflectors, reflective features of the environment (e.g., on buildings), UEs, and other RAN nodes (e.g., with antenna arrays). Any of these types of reference points may be used in combination for calibration of an antenna array according to disclosed embodiments.

Embodiments can provide various benefits and/or advantages. At a high level, embodiments can facilitate JCAS using existing infrastructure in a RAN. More specifically, embodiments provide new techniques for geometric calibration of antenna arrays used in a RAN, which makes such arrays suitable not only for communicating with UEs but also for accurate sensing of objects in the proximate physical environment. Such techniques are flexible in that they utilize as many reference points as are available and/or necessary to achieve a desired calibration accuracy. Moreover, such techniques are also flexible in that they can use various types of reference points having a LOS to the antenna array needing geometric calibration. Some embodiments can utilize one or more reflectors located at a known position some distance away from the antenna array, preferably in a LOS. Figure 3 illustrates geometric calibration of an antenna array using a reflector having a fixed, known position and orientation, such that it can be used as a reference point. In such embodiments, a RAN node transmits calibration signals via its coupled antenna array, which are received as reflections from the reference point.

The antenna array is also at a known position with its antenna elements arranged nominally in a plane. The normal vector to the plane (also referred to as “boresight”) has a nominal orientation based on the antenna array’s installation; this will be referred to as the expected or reference orientation of the antenna array. Given the position and orientation of the reflector and the antenna array position and reference orientation, the RAN node can determine an expected (or reference) AoA for calibration signals received from the reflector via the antenna array.

However, the actual orientation of the antenna array is different from the reference orientation by a misalignment angle. This may be due to factors such as incorrect installation, equipment aging, weather (e.g., high winds), etc. In any case, based on the known parameters and measurements of the calibration signals received via the antenna array, the RAN node determines an actual AoA that is different from the expected AoA. Ideally, this determined difference is equal to the misalignment angle shown in Figure 3, but it may differ slightly due to measurement noise and/or inaccuracies in “known” parameters (e.g., reference point location).

The determined misalignment angle can then be used for geometric calibration. As mentioned above, this can include adjusting gains and/or phase shifts applied to signals transmitted and/or received via the antenna array, which effectively adjusts the actual orientation of the antenna array to align with its reference (or expected) orientation. Alternately, the determined difference can be removed or compensated for in angular calculations that are part of various sensing algorithms employed.

Note that Figure 3 illustrates two-dimensional (2D) geometric calibration of the boresight angle of the antenna array. Three-dimensional (3D) geometric calibration of both the boresight angle and a rotation angle of the array around the boresight requires receiving and measuring calibration signals from multiple reference points (e.g., reflectors) arranged in a geometry that is conducive for this operation.

The reflector shown in Figure 3 can be a dedicated signal reflector, i.e., installed for the purpose of calibrating antenna arrays used in JCAS. Alternately, the reflector can be a reflective feature of the surrounding environment but utilized for the purpose of calibrating antenna arrays used in JCAS. Figure 4 illustrates geometric calibration of an antenna array (420) using reflective features of various buildings in a city skyline, according to some embodiments of the present disclosure. As such, the RAN node (410) can transmit calibration signals towards these reflective features, with the reflections being received via the antenna array and measured by the RAN node for geometric calibration.

In some embodiments, UEs or other nodes with UE-like functionality can be used as reference points. For example, UEs at fixed, known locations with LOS to an antenna array can be used as reference points for geometric calibration of the antenna array. As another example, positioning reference units (PRUs) can be used as reference points. A PRU is a network node or device, at a known location, which can transmit UL RS and perform positioning measurements on DL RS. Conventionally, PRUs can identify positioning errors and facilitate compensation for these errors in positions determined for UEs that are proximate in the network. Moreover, the UL RS transmitted by PRUs can also be used as calibration signals according to some embodiments.

In other embodiments, UEs in initially unknown locations can be located or positioned. If the UE’s location is preferred (e.g., from LOS perspective), then the RAN node can instruct the UE to transmit calibration signals from that preferred position. The RAN node receives the calibration signals via the antenna array and uses the determined UE position as the known location of the reference point during the geometric calibration of the antenna array.

3 GPP standards provide various ways locating or positioning UEs operating in 3 GPP networks. The following positioning methods are supported in NR:

• Enhanced Cell ID (E-CID). Utilizes information to associate the UE with the geographical area of a serving cell, and then additional information to determine a finer granularity position. The following measurements are supported for E-CID: AoA (RAN node only), UE Rx-Tx time difference, timing advance (TA) types 1 and 2, reference signal received power (RSRP), and reference signal received quality (RSRQ).

• Assisted GNSS. UE receives and measures signals transmitted by GNSS satellites (e.g., GPS), supported by assistance information provided to the UE by a positioning node.

• OTDOA (Observed Time Difference of Arrival). UE receives and measures DL RS (e.g., PRS) transmitted by the RAN, supported by assistance information provided to the UE by a positioning node.

• UTDOA (Uplink TDOA). UE transmits UL RS (e.g., SRS) that are detected and measured by RAN nodes at known positions. These measurements are forwarded to a positioning node for multilateration. • Multi -RTT : Both UE and RAN nodes compute Rx-Tx time differences, with the results being combined by a positioning node to find the UE position based upon round trip time (RTT) calculation.

• DL angle of departure (DL-AoD): RAN node or positioning node calculates the UE angular position based upon UE DL RSRP measurement results (e.g., of PRS transmitted by RAN nodes).

• UL angle of arrival (UL-AoA): RAN node calculates the UL AoA based upon measurements of a UE’s UL SRS transmissions.

In addition to these methods, a UE can also perform positioning measurements (and optionally calculate position) based on WLAN signals, Bluetooth signals, terrestrial beacon system (TBS) signals, and UE sensors (e.g., barometric pressure, accelerometer, etc.).

Furthermore, one or more of the following positioning modes can be utilized in each of the positioning methods listed above:

• UE-Assisted: UE performs measurements with or without assistance from the network and sends these measurements to a node (e.g., LMF) that calculates the UE’s position.

• UE-Based: UE performs measurements and calculates its own position with assistance from the network.

• Standalone: UE performs measurements and calculates its own position without network assistance.

The detailed assistance data may include information about network node locations, beam directions, etc. The assistance data can be provided to the UE via unicast or via broadcast.

Figure 5 is a block diagram of an architecture for UE positioning in 5G/NR networks. The NG-RAN (520) can include nodes such as gNBs (522) and ng-eNBs (521), such as discussed above. Each ng-eNB may control several transmission points (TPs), such as remote radio heads. Similarly, each gNB may control several transmission/reception points (TRPs).

In addition, NG-RAN nodes communicate with an AMF (530) in the 5GC via respective NG-C interfaces (both of which may or may not be present), while AMFs communicate with a location management function (LMF, 540) via an NLs interface. LMF supports various functions related to UE positioning, including location determination for a UE (510), obtaining DL location measurements or a location estimate from the UE, obtaining UL location measurements from the NG-RAN, and obtaining non-UE associated assistance data from the NG RAN.

In addition, positioning-related communication between UE and NG-RAN nodes occurs via the RRC protocol, while positioning-related communication between NG-RAN nodes and LMF occurs via an NRPPa protocol. Optionally, the LMF can also communicate with an evolved serving mobile location center (E-SMLC, 550) and a secure user plane location (SUPL) server (560) in an LTE network via communication interfaces that can be implemented according to standardized protocols, proprietary protocols, or a combination thereof.

In typical operation, the AMF receives a request for a location service associated with a target UE from another entity (e.g., a gateway mobile location center, GMLC), or the AMF can initiate a location service on behalf of a target UE (e.g., for an emergency call by the UE). The AMF sends a location services (LS) request to the LMF, which may send assistance data to the target UE to support UE-based or UE-assisted positioning. The LMF may obtain the UE’s position from the UE (UE-based) or based on measurements provided by the UE (UE-assisted). The LMF then returns the result of the LS request (e.g., a position estimate for the UE and/or an indication of any assistance data transferred to the UE) to the AMF or to another entity (e.g., GMLC) that requested the LS.

Various interfaces and protocols are used for positioning of UEs, not all of which are shown in Figure 5 for the sake of clarity. RRC protocol is used between UE and gNB or ng- eNB. NRPPa carries information between ng-eNB/gNB and LMF and is transparent to the AMF. LPP/NRPP are used to deliver messages such as positioning capability request, OTDOA positioning measurements request, and OTDOA assistance data to the UE from LMF. LPP/NRPP are also used to carry messages from UE to LMF including, e.g., UE capability, measurements for UE-assisted OTDOA positioning, request for additional assistance data, etc.

NRPPa is used to deliver information between ng-eNB/gNB and LMF via AMF. This can include information about PRS transmitted by ng-eNB/gNB that can be used for OTDOA positioning measurements by the UE and position determination by LMF. NGAP between AMF and NG-RAN node (e.g., gNB or ng-eNB) is used as transport for LPP and NRPPa messages over the NG-C interface, as well as to instigate/terminate NG-RAN positioning procedures.

According to various embodiments, UEs to be used as reference points for geometric calibration of an antenna array can be located or positioned using any of the 3GPP-specified techniques described above. If the UE’s location is preferred (e.g., due to LOS), then the RAN node can instruct the UE to transmit calibration signals from that preferred location.

On the other hand, if the RAN node determines that a UE is currently in a non-preferred location, such as without LOS to the antenna array, the RAN node can instruct the UE to move to a preferred location having LOS to the antenna array. Figure 6 illustrates geometric calibration of an antenna array (620) using a UE that is initially located between two buildings, such that the UE can only communicate with the RAN node (610) via transmissions that reflect off one of the buildings. Upon determining the UE’s non-preferred location (or alternately that the UE has no LOS to the antenna array), the RAN node can send additional control signaling to direct the UE to move to a preferred location with LOS to the antenna array. For example, the preferred location may be a location nearest to the UE’s initial non-preferred location but with LOS to the antenna array.

Upon reaching the preferred location, the UE may transmit the calibration signals. Alternately, the RAN node may determine that the UE has reached the preferred location and then instruct the UE to transmit the calibration signals. The RAN uses this preferred location with LOS as the known location of the reference point during the geometric calibration of the antenna array.

Figure 7 illustrates geometric calibration of an antenna array (720) using an aerial- capable UE that is initially located at ground level, according to some embodiments of the present disclosure. The aerial-capable UE may also be referred to as an unmanned aerial vehicle (UAV) or drone. Initially, the RAN node (710) determines that the UE is at ground level in a non-preferred location where a building blocks LOS to the RAN node’s antenna array. Upon determining the UE’s non-preferred location at ground level (or alternately that the UE has no LOS to the antenna array), the RAN node can send additional control signaling to direct the UE to a preferred location above ground level with LOS to the antenna array. For example, the preferred location may be a location nearest to the UE’s initial non-preferred location but with LOS to the antenna array, such as directly above the non-preferred location.

Upon reaching the preferred location above ground level, the aerial UE may transmit the calibration signals. Alternately, the RAN node may determine that the aerial UE has reached the preferred location above ground level and then instruct the aerial UE to transmit the calibration signals. The RAN uses this preferred location above ground level as the known location of the reference point during the geometric calibration of the antenna array.

In other embodiments, other RAN nodes can be used as reference points for calibration of a RAN node’s antenna array. For example, other RAN node antenna arrays - which generally are at fixed, known locations - that have LOS to the RAN node’s antenna array can be used as reference points for geometric calibration. Figure 8 illustrates geometric calibration of an antenna array using an antenna array coupled to another RAN node, according to some embodiments of the present disclosure. In particular, an antenna array (811) coupled to a first RAN node (810) is used as a reference point for geometric calibration of an antenna array (821) coupled to a second RAN node (820)

In these embodiments, an inter-node interface is used for signaling between the RAN nodes in relation to the geometric calibration. For example, an Xn interface such as shown in Figure 1 can be used for geometric calibration signaling between gNBs and/or ng-eNBs. This signaling can include the calibration source (e.g., first RAN node in Figure 8) informing the calibration target (e.g., second RAN node in Figure 8) about the location and orientation of the antenna array that will transmit the calibration signals.

In some embodiments, the control signaling can also include information about the timing of the calibration signals with respect to an absolute time base (e.g., UTC) or a relative time base (e.g., RAN node or network timing). In case the two RAN nodes are on different relative time bases, control signaling between the two RAN nodes can be used to determine an offset between the respective time bases.

In some embodiments, the control signaling can also include geometric calibration information for the antenna array being used as the calibration source. For example, the first RAN node in Figure 8 may have previously performed geometric calibration by which it determined that its antenna array is misaligned by some offset. The first RAN node can include the determined offset in the control signaling to the second RAN node, either as an explicit offset term or by adjusting the antenna array orientation provided to the second RAN node according to the offset.

Although embodiments have been described above as performing geometric calibration of an entire antenna array, it is also possible to perform geometric calibration of some portion or subset of the antenna elements comprising the antenna array. For example, different spatially contiguous subsets of the antenna elements comprising an array may calibrated at different times. As a more specific example, each of the two panels that make up the antenna array shown in Figure 2B may be geometrically calibrated independent of the other panel. More generally, geometric calibration can be performed on a portion of an antenna array that is large enough to measure calibration signal AoA with sufficient accuracy.

Various features of the embodiments described above correspond to various operations illustrated in Figure 9, which shows an exemplary method (e.g., procedure) for calibration of an antenna array comprising a plurality of antenna elements. The method can be performed by an RAN node (e.g., eNB, gNB, etc.), such as described elsewhere herein. Although Figure 9 shows specific blocks in a particular order, the operations of the exemplary method can be performed in different orders than shown and can be combined and/or divided into blocks having different functionality than shown. Optional blocks or operations are indicated by dashed lines.

The exemplary method can include the operations of block 910, where using a first portion of the antenna array, the RAN node can receive calibration signals from one or more reference points at known locations relative to the antenna array. The exemplary method can also include the operations of block 970, where for each of the one or more reference points, the RAN node can determine an angle of arrival (AoA) of the received calibration signals relative to an expected orientation of the antenna elements comprising the first portion. The exemplary method can also include the operations of block 980, where based on the one or more determined AoAs and the known locations of the one or more reference points, the RAN node can determine an actual orientation of the antenna elements comprising the first portion.

In some embodiments, the one or more reference points consist of a single reference point and the difference between the actual orientation and the expected orientation is a misalignment of a boresight for the antenna elements comprising the first portion. Figure 3 shows an example of these embodiments. In other embodiments, the one or more reference points comprise multiple reference points and the difference between the actual orientation and the expected orientation includes one or more of the following for the antenna elements comprising the first portion: a misalignment of a boresight, a rotation around the boresight.

In some embodiments, the exemplary method can also include the operations of block 990, where based on a difference between the actual orientation and the expected orientation, the RAN node can adjust gains and/or phase shifts applied to signals transmitted and/or received via the antenna elements comprising the first portion. In some of these embodiments, the antenna array is used for JCAS and the transmitted and/or received signals, for which gains and/or phase shifts are adjusted, include signals used for sensing of objects in a physical environment proximate to the antenna array.

In other embodiments, the exemplary method can also include the operations of block 995, where based on a difference between the actual orientation and the expected orientation, the RAN node can adjust sensing results obtained from signals transmitted and/or received via the antenna elements comprising the first portion. For example, the RAN node may estimate an angle towards a target using raw, uncalibrated measurements of the signals received via the sensing array The RAN node can then adjust the angle estimate based on array calibration results, including the difference between the actual orientation and the expected orientation of the first portion of the array.

In some embodiments, each of the known locations has a line-of-sight (LOS) to the antenna array. In some embodiments, determining the actual orientation of the first portion in block 980 is further based on known orientations of the one or more reference points. In some embodiments, the calibration signals are received via one or more of the following that is also used for communication with user equipment, UEs, operating in the RAN: radio spectrum, and a RAN node receiver. In some embodiments, each of the one or more reference points is one of the following: a passive signal reflector, a UE, and a further antenna array coupled to another RAN node.

In some embodiments, the exemplary method can also include the operations of block 905, where the RAN node can transmit the calibration signals, which are received in block 910 as reflections from the one or more reference points. In other embodiments, the one or more reference points are UEs and the exemplary method can also include the operations of block 915, where the RAN node can obtain a location of each of the UEs from one of the following: the UE, a positioning node coupled to the RAN, and another RAN node. In some of these embodiments, the obtained location of each UE is used as the known location for determining the actual orientation.

In other of these embodiments, the locations obtained for the respective one or more UEs are non-preferred locations and the exemplary method can also include the operations of blocks 930-940, where RAN node can send the one more UEs respective instructions to move from the non-preferred locations to respective preferred locations, and obtain respective indications that the one or more UEs are located in the respective preferred locations. Based on such indications, the one or more preferred locations are used as the known locations for determining the actual orientation. Figure 6 shows an example of these embodiments.

In some variants of these embodiments, at least one preferred location for a UE has a line-of-sight (LOS) from the UE to the antenna array and at least one non-preferred location for a UE has no LOS from the UE to the antenna array. In some variants of these embodiments, at least one preferred location for a UE is an aerial position above ground level and/or at least one non-preferred location for a UE is a terrestrial position at ground level. Figure 7 shows an example of these variants.

In other embodiments, the one or more reference points are further antenna arrays coupled to other RAN nodes and the exemplary method can also include the operations of block 950, where the RAN node can obtain, from each of the other RAN nodes, location and orientation of any of the further antenna arrays coupled to the other RAN node. In such case, the obtained location of each further antenna array is used as the known location for determining the actual orientation on block 980. Figure 8 shows an example of these embodiments.

In some of these embodiments, the calibration signals are transmitted by the other RAN nodes via the one or more further antenna arrays. In some of these embodiments, the RAN node and the other RAN nodes are synchronized to a common time source. In other of these embodiments, the exemplary method can also include the operations of block 960, where the RAN node can determine respective timing offsets between the RAN node and the respective other RAN nodes. In such case, the respective AoAs for the calibration signals are determined (e.g., in block 970) further based on the respective timing offsets.

As mentioned above, the exemplary method shown in Figure 9 can be implemented by a RAN node. For example, the RAN node can include radio circuitry arranged to transmit and/or receive signals via the antenna array, as well as processing circuitry that is operably coupled to the radio circuitry. The processing circuitry and the radio circuitry can be configured to perform operations corresponding to any of the embodiments of the exemplary method shown in Figure 9. For example, the processing circuitry can be configured to execute computer program code that facilitates such operations.

Additionally, the exemplary method shown in Figure 9 can be realized as a non- transitory, computer-readable medium storing computer-executable instructions. When executed by processing circuitry of a RAN node, the instructions configure the RAN node to perform operations corresponding to any of those described above with reference to Figure 9.

Additionally, the exemplary method shown in Figure 9 can be realized as a computer program (or computer program product) comprising computer-executable instructions. When executed by processing circuitry of a RAN node, the instructions configure the RAN node to perform operations corresponding to any of those described above with reference to Figure 9.

Figure 10 shows an example of a communication system 1000 in accordance with some embodiments. In this example, communication system 1000 includes a telecommunication network 1002 that includes an access network 1004 (e.g., RAN) and a core network 1006, which includes one or more core network nodes 1008. Access network 1004 includes one or more access network nodes, such as network nodes lOlOa-b (one or more of which may be generally referred to as network nodes 1010), or any other similar 3 GPP access node or non-3GPP access point. Network nodes 1010 facilitate direct or indirect connection of UEs, such as by connecting UEs 1012a-d (one or more of which may be generally referred to as UEs 1012) to core network 1006 over one or more wireless connections.

Example wireless communications over a wireless connection include transmitting and/or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and/or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, communication system 1000 may include any number of wired or wireless networks, network nodes, UEs, and/or any other components or systems that may facilitate or participate in the communication of data and/or signals whether via wired or wireless connections. Communication system 1000 may include and/or interface with any type of communication, telecommunication, data, cellular, radio network, and/or other similar type of system.

In the context of communication system 1000 shown in Figure 10, various embodiments of the RU discussed above or below can be part of, or coupled to, any of network nodes 1010. For example, each network node 1010 can include one or more BPUs that are coupled to the RUs (e.g., as shown in Figures 1 and 5) as well as the RU itself.

UEs 1012 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and/or operable to communicate wirelessly with network nodes 1010 and other communication devices. Similarly, network nodes 1010 are arranged, capable, configured, and/or operable to communicate directly or indirectly with UEs 1012 and/or with other network nodes or equipment in telecommunication network 1002 to enable and/or provide network access, such as wireless network access, and/or to perform other functions, such as administration in telecommunication network 1002.

In the depicted example, core network 1006 connects network nodes 1010 to one or more hosts, such as host 1016. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. Core network 1006 includes one more core network nodes (e.g., core network node 1008) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and/or hosts, such that the descriptions thereof are generally applicable to the corresponding components of core network node 1008. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and/or a User Plane Function (UPF).

Host 1016 may be under the ownership or control of a service provider other than an operator or provider of access network 1004 and/or telecommunication network 1002, and may be operated by the service provider or on behalf of the service provider. Host 1016 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio/video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server. As a whole, communication system 1000 of Figure 10 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: GSM, UMTS, LTE, NR, other suitable 2G-5G standards, and any applicable future generation 3 GPP standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and/or any other appropriate wireless communication standard, such as WiMax, Bluetooth, Z- Wave, Near Field Communication (NFC), ZigBee, LiFi, and/or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox.

In some examples, telecommunication network 1002 is a cellular network that implements 3GPP standardized features. Accordingly, telecommunication network 1002 may support network slicing to provide different logical networks to different devices that are connected to telecommunication network 1002. For example, telecommunication network 1002 may provide URLLC services to some UEs, while providing eMBB services to other UEs, and/or Massive Machine Type Communication (mMTC)/Massive loT services to other UEs.

In some examples, UEs 1012 are configured to transmit and/or receive information without direct human interaction. For instance, a UE may be designed to transmit information to access network 1004 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from access network 1004. Additionally, a UE may be configured for operating in single- or multi -RAT or multi-standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR, and LTE, such as being configured for multi-radio dual connectivity (MR-DC).

In the example, hub 1014 communicates with access network 1004 to facilitate indirect communication between one or more UEs (e.g., UE 1012c and/or lOlOd) and network nodes (e.g., network node 1010b). In some examples, hub 1014 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, hub 1014 may be a broadband router enabling access to core network 1006 for the UEs. As another example, hub 1014 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes 1010, or by executable code, script, process, or other instructions in hub 1014. As another example, hub 1014 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, hub 1014 may be a content source. For example, hub 1014 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which hub 1014 then provides to the UE either directly, after performing local processing, and/or after adding additional local content. In another example, hub 1014 acts as a proxy server or orchestrator for UEs 1012, in particular in if one or more of the UEs are low energy loT devices.

Figure 11 shows a network node 1100 in accordance with some embodiments. Examples of network nodes include, but are not limited to, access points (e.g., radio access points) and base stations (e.g., radio base stations, Node Bs, eNBs, and gNBs).

Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units and/or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).

Other examples of network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell/multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and/or Minimization of Drive Tests (MDTs).

Network node 1100 includes a processing circuitry 1102, a memory 1104, a communication interface 1106, and a power source 1108. Network node 1100 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which network node 1100 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, network node 1100 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory 1104 for different RATs) and some components may be reused (e.g., a same antenna 1110 may be shared by different RATs). Processing circuitry 1102 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and/or encoded logic operable to provide, either alone or in conjunction with other network node 1100 components, such as memory 1104, to provide network node 1100 functionality.

In some embodiments, processing circuitry 1102 includes a system on a chip (SOC). In some embodiments, processing circuitry 1102 includes one or more of radio frequency (RF) transceiver circuitry 1112 and baseband processing circuitry 1114. In some embodiments, the radio frequency (RF) transceiver circuitry 1112 and the baseband processing circuitry 1114 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry 1112 and baseband processing circuitry 1114 may be on the same chip or set of chips, boards, or units.

Memory 1104 may comprise any form of volatile or non-volatile computer-readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and/or any other volatile or non-volatile, non-transitory device-readable and/or computer-executable memory devices that store information, data, and/or instructions (collectively denoted computer program product 1104a) that may be used by processing circuitry 1102. Memory 1104 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and/or other instructions capable of being executed by processing circuitry 1102 and utilized by network node 1100. Memory 1104 may be used to store any calculations made by processing circuitry 1102 and/or any data received via communication interface 1106. In some embodiments, processing circuitry 1102 and memory 1104 is integrated.

Communication interface 1106 is used in wired or wireless communication of signaling and/or data between a network node, access network, and/or UE. As illustrated, communication interface 1106 comprises port(s)/terminal(s) 1116 to send and receive data, for example to and from a network over a wired connection. Communication interface 1106 also includes radio front-end circuitry 1118 that may be coupled to, or in certain embodiments a part of, antenna 1110. Radio front-end circuitry 1118 comprises filters 1120 and amplifiers 1122. Radio frontend circuitry 1118 may be connected to an antenna 1110 and processing circuitry 1102. The radio front-end circuitry may be configured to condition signals communicated between antenna 1110 and processing circuitry 1102.

Radio front-end circuitry 1118 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. Radio front-end circuitry 1118 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 1120 and/or amplifiers 1122. The radio signal may then be transmitted via antenna 1110. Similarly, when receiving data, antenna 1110 may collect radio signals which are then converted into digital data by radio front-end circuitry 1118. The digital data may be passed to processing circuitry 1102. In other embodiments, the communication interface may comprise different components and/or different combinations of components.

In certain alternative embodiments, network node 1100 does not include separate radio front-end circuitry 1118, instead, processing circuitry 1102 includes radio front-end circuitry and is connected to antenna 1110. Similarly, in some embodiments, all or some of RF transceiver circuitry 1112 is part of communication interface 1106. In still other embodiments, communication interface 1106 includes one or more ports or terminals 1116, radio front-end circuitry 1118, and RF transceiver circuitry 1112, as part of a radio unit (not shown), and communication interface 1106 communicates with the baseband processing circuitry 1114, which is part of a digital unit (not shown).

Antenna 1110 may include one or more antennas, or antenna arrays, configured to send and/or receive wireless signals. Antenna 1110 may be coupled to radio front-end circuitry 1118 and may be any type of antenna capable of transmitting and receiving data and/or signals wirelessly. In certain embodiments, antenna 1110 is separate from network node 1100 and connectable to network node 1100 through an interface or port.

Antenna 1110, communication interface 1106, and/or processing circuitry 1102 may be configured to perform any receiving operations and/or certain obtaining operations described herein as being performed by the network node. Any information, data and/or signals may be received from a UE, another network node and/or any other network equipment. Similarly, antenna 1110, communication interface 1106, and/or processing circuitry 1102 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and/or signals may be transmitted to a UE, another network node and/or any other network equipment.

Power source 1108 provides power to the various components of network node 1100 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). Power source 1108 may further comprise, or be coupled to, power management circuitry to supply the components of network node 1100 with power for performing the functionality described herein. For example, network node 1100 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of power source 1108. As a further example, power source 1108 may comprise a battery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail.

Embodiments of network node 1100 may include additional components beyond those shown in Figure 11 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and/or any functionality necessary to support the subject matter described herein. For example, network node 1100 may include user interface equipment to allow input of information into network node 1100 and to allow output of information from network node 1100. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for network node 1100.

Figure 12 is a block diagram illustrating a virtualization environment 1200 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to any device described herein, or components thereof, and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components. Some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines (VMs) implemented in one or more virtual environments 1200 hosted by one or more of hardware nodes, such as a hardware computing device that operates as a network node, UE, core network node, or host. Further, in embodiments in which the virtual node does not require radio connectivity (e.g., a core network node or host), then the node may be entirely virtualized.

Applications 1202 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment 1200 to implement some of the features, functions, and/or benefits of some of the embodiments disclosed herein.

Hardware 1204 includes processing circuitry, memory that stores software and/or instructions (collectively denoted computer program product 1204a) executable by hardware processing circuitry, and/or other hardware devices as described herein, such as a network interface, input/output interface, and so forth. Software may be executed by the processing circuitry to instantiate one or more virtualization layers 1206 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VMs 1208a and 1208b (one or more of which may be generally referred to as VMs 1208), and/or perform any of the functions, features and/or benefits described in relation with some embodiments described herein. The virtualization layer 1206 may present a virtual operating platform that appears like networking hardware to the VMs 1208.

VMs 1208 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer 1206. Different embodiments of the instance of a virtual appliance 1202 may be implemented on one or more of VMs 1208, and the implementations may be made in different ways. Virtualization of the hardware is in some contexts referred to as network function virtualization (NFV). NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers, and customer premise equipment.

In the context of NFV, each VM 1208 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each VM 1208, and that part of hardware 1204 that executes that VM, be it hardware dedicated to that VM and/or hardware shared by that VM with others of the VMs, forms separate virtual network elements. Still in the context of NFV, a virtual network function is responsible for handling specific network functions that run in one or more VMs 1208 on top of the hardware 1204 and corresponds to the application 1202.

Hardware 1204 may be implemented in a standalone network node with generic or specific components. Hardware 1204 may implement some functions via virtualization. Alternatively, hardware 1204 may be part of a larger cluster of hardware (e.g. such as in a data center or CPE) where many hardware nodes work together and are managed via management and orchestration 1210, which, among others, oversees lifecycle management of applications 1202. In some embodiments, hardware 1204 is coupled to one or more radio units that each include one or more transmitters and one or more receivers that may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station. In some embodiments, some signaling can be provided with the use of a control system 1212 which may alternatively be used for communication between hardware nodes and radio units.

The foregoing merely illustrates the principles of the disclosure. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. It will thus be appreciated that those skilled in the art will be able to devise numerous systems, arrangements, and procedures that, although not explicitly shown or described herein, embody the principles of the disclosure and can be thus within the spirit and scope of the disclosure. Various exemplary embodiments can be used together with one another, as well as interchangeably therewith, as should be understood by those having ordinary skill in the art.

The term unit, as used herein, can have conventional meaning in the field of electronics, electrical devices and/or electronic devices and can include, for example, electrical and/or electronic circuitry, devices, modules, processors, memories, logic solid state and/or discrete devices, computer programs or instructions for carrying out respective tasks, procedures, computations, outputs, and/or displaying functions, and so on, as such as those that are described herein.

Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processor (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and/or data communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according one or more embodiments of the present disclosure.

As described herein, device and/or apparatus can be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of a device or apparatus, instead of being hardware implemented, be implemented as a software module such as a computer program or a computer program product comprising executable software code portions for execution or being run on a processor. Furthermore, functionality of a device or apparatus can be implemented by any combination of hardware and software. A device or apparatus can also be regarded as an assembly of multiple devices and/or apparatuses, whether functionally in cooperation with or independently of each other. Moreover, devices and apparatuses can be implemented in a distributed fashion throughout a system, so long as the functionality of the device or apparatus is preserved. Such and similar principles are considered as known to a skilled person. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

In addition, certain terms used in the present disclosure, including the specification and drawings, can be used synonymously in certain instances (e.g., “data” and “information”). It should be understood, that although these terms (and/or other terms that can be synonymous to one another) can be used synonymously herein, there can be instances when such words can be intended to not be used synonymously.

Claims

1. A method performed by a radio access network, RAN, node for calibration of an antenna array comprising a plurality of antenna elements, the method comprising: using a first portion of the antenna array, receiving (910) calibration signals from one or more reference points at known locations relative to the antenna array; for each of the one or more reference points, determining (970) an angle of arrival, AoA, of the received calibration signals relative to an expected orientation of the antenna elements comprising the first portion; and based on the one or more determined AoAs and the known locations of the one or more reference points, determining (980) an actual orientation of the antenna elements comprising the first portion.

2. The method of claim 1, wherein: the one or more reference points consist of a single reference point, and the difference between the actual orientation and the expected orientation is a misalignment of a boresight for the antenna elements comprising the first portion.

3. The method of claim 1, wherein: the one or more reference points comprise multiple reference points, and the difference between the actual orientation and the expected orientation includes one or more of the following for the antenna elements comprising the first portion: a misalignment of a boresight, a rotation around the boresight.

4. The method of any of claims 1-3, further comprising, based on a difference between the actual orientation and the expected orientation, adjusting (990) gains and/or phase shifts applied to signals transmitted and/or received via the antenna elements comprising the first portion.

5. The method of claim 4, wherein one or more of the following applies: the antenna array is used for joint communications and sensing, JCAS; and the transmitted and/or received signals, for which gains and/or phase shifts are adjusted, include signals used for sensing of objects in a physical environment proximate to the antenna array.

6. The method of any of claims 1-3, further comprising, based on a difference between the actual orientation and the expected orientation, adjusting (995) sensing results obtained from signals transmitted and/or received via the antenna elements comprising the first portion.

7. The method of any of claims 1-6, wherein each of the known locations has a line-of-sight (LOS) to the antenna array.

8. The method of any of claims 1-7, wherein determining (980) the actual orientation of the first portion is further based on known orientations of the one or more reference points.

9. The method of any of claims 1-8, wherein the calibration signals are received via one or more of the following that is also used for communication with user equipment, UEs, operating in the RAN: radio spectrum, and a RAN node receiver.

10. The method of any of claims 1-9, wherein each of the one or more reference points is one of the following: a passive signal reflector; a user equipment, UE; and a further antenna array coupled to another RAN node.

11. The method of any of claims 1-10, further comprising transmitting (905) the calibration signals, which are received as reflections from the one or more reference points.

12. The method of any of claims 1-10, wherein: the one or more reference points are user equipment, UEs; and the method further comprises obtaining (920) a location of each of the UEs from one of the following: the UE, a positioning node coupled to the RAN, and another RAN node.

13. The method of claim 12, wherein the obtained location of each UE is used as the known location for determining the actual orientation.

14. The method of claim 12, wherein: the locations obtained for the respective one or more UEs are non-preferred locations; and the method further comprises: sending (930) the one more UEs respective instructions to move from the nonpreferred locations to respective preferred locations; and obtaining (940) respective indications that the one or more UEs are located in the respective preferred locations, based on which the one or more preferred locations are used as the known locations for determining the actual orientation.

15. The method of claim 14, wherein one or more of the following applies: at least one preferred location for a UE has a line-of-sight, LOS, from the UE to the antenna array, and at least one non-pref erred location for a UE has no LOS from the UE to the antenna array.

16. The method of any of claims 14-15, wherein one or more of the following applies: at least one preferred location for a UE is an aerial position above ground level, and at least one non-preferred location for a UE is a terrestrial position at ground level.

17. The method of any of claims 1-10, wherein: the one or more reference points are further antenna arrays coupled to other RAN nodes; the method further comprises obtaining (950), from each of the other RAN nodes, location and orientation of any of the further antenna arrays coupled to the other RAN node; and the obtained location of each further antenna array is used as the known location for determining the actual orientation.

18. The method of claim 17, wherein the calibration signals are transmitted by the other RAN nodes via the one or more further antenna arrays.

19. The method of any of claims 17-18, wherein one of the following applies: the RAN node and the other RAN nodes are synchronized to a common time source; or the method further comprises determining (960) respective timing offsets between the RAN node and the respective other RAN nodes, wherein the respective AoAs for the calibration signals are determined further based on the respective timing offsets.

20. The method of any of claims 1-19, wherein the first portion of the antenna array is one of the following: all antenna elements of the antenna array, a single antenna element, or a subset of the antenna elements that meets one or more of the following conditions: proximate to each other in the antenna array, and coupled to different RAN node radio circuitry than the remainder of the antenna elements.

21. A radio access network, RAN, node (110, 120, 410, 521, 522, 610, 710, 810, 1010, 1100, 1202) configured to support calibration of an antenna array (244, 420, 620, 720, 811, 821) comprising a plurality of antenna elements, the RAN node comprising: radio circuitry (1106, 1204) arranged to transmit and/or receive signals via the antenna array; and processing circuitry (1102, 1204) operably coupled to the radio circuitry, wherein the processing circuitry and the radio circuitry are configured to: using a first portion of the antenna array, receive calibration signals from one or more reference points at known locations relative to the antenna array; for each of the one or more reference points, determine an angle of arrival, AoA, of the received calibration signals relative to an expected orientation of the antenna elements comprising the first portion; and based on the one or more determined AoAs and the known locations of the one or more reference points, determine an actual orientation of the antenna elements comprising the first portion.

22. The RAN node of claim 21, wherein the processing circuitry and the radio circuitry are further configured to perform operations corresponding to any of the methods of claims 2-20.

23. A radio access network, RAN, node (110, 120, 410, 521, 522, 610, 710, 810, 1010, 1100, 1202) configured to support calibration of an antenna array (244, 420, 620, 720, 811, 821) comprising a plurality of antenna elements, the RAN node being further configured to: using a first portion of the antenna array, receive calibration signals from one or more reference points at known locations relative to the antenna array; for each of the one or more reference points, determine an angle of arrival, AoA, of the received calibration signals relative to an expected orientation of the antenna elements comprising the first portion; and based on the one or more determined AoAs and the known locations of the one or more reference points, determine an actual orientation of the antenna elements comprising the first portion.

24. The RAN node of claim B3, being further configured to perform operations corresponding to any of the methods of claims 2-20.

25. A non-transitory, computer-readable medium (1104, 1204) storing computer-executable instructions that, when executed by processing circuitry (1102, 1204) of a radio access network, RAN, node (110, 120, 410, 521, 522, 610, 710, 810, 1010, 1100, 1202) configured to support calibration of an antenna array (244, 420, 620, 720, 811, 821) comprising a plurality of antenna elements, configure the RAN node to perform operations corresponding to any of the methods of claims 1-20.

26. A computer program product (1104a, 12041) comprising computer-executable instructions that, when executed by processing circuitry (1102, 1204) of a radio access network, RAN, node (110, 120, 410, 521, 522, 610, 710, 810, 1010, 1100, 1202) configured to support calibration of an antenna array (244, 420, 620, 720, 811, 821) comprising a plurality of antenna elements, configure the RAN node to perform operations corresponding to any of the methods of claims 1-20.