Antenna array for enhancing MIMO throughput

Abstract

An apparatus comprising: an antenna array comprising a plurality of antenna elements configured to receive a multiple-input multiple-output (MIMO) signal, wherein the antenna array comprises at least a first sub-portion of the antenna array, the first sub-portion comprising a first sub-section of the plurality of antenna elements; and a second sub-portion of the antenna array comprising a second sub-section of the plurality of antenna elements, wherein an alignment of the antenna elements in the second sub-portion is substantially offset from an alignment of the antenna elements in the first sub-portion by 30° to 60°.

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of wireless communication, and in particular to Multiple Input Multiple Output (MIMO) technology. BACKGROUND

[0002] Today's and future wireless communication systems, such as Long Term Evolution (LTE) or the fifth generation (5G), also referred to as New Radio (NR), have been conceived to use MIMO multi-antenna transmission technology. The ever increasing demand for high throughput has motivated wireless communication systems such as 5G to use mmWave (millimeter wave) frequencies due to the high bandwidth available.

[0003] However, the use of mmWave frequencies poses new challenges to MIMO performance. Thus, factors such as the surrounding environment or changes in the physical orientation of the antennas will have an increased performance impact that needs to be considered for achieving the desired performance. SUMMARY

[0004] Now, an improved method and a technical device implementing the method have been invented by which the above problems can be mitigated. Various aspects include methods, apparatuses and non-transitory computer readable media comprising a computer program, or a signal stored therein. It is characterized by what is stated in the independent claims. Various details of embodiments are disclosed in the dependent claims as well as in the corresponding images and description.

[0005] The scope of protection sought for various embodiments of the invention is set forth by the independent claims. Embodiments and features that are not within the scope of the independent claims, if any, are to be interpreted as examples useful for understanding the various embodiments of the invention.

[0006] According to a first aspect, there is provided an apparatus comprising an antenna array comprising a plurality of antenna elements configured for receiving a Multiple Input Multiple Output (MIMO) signal, wherein the antenna array comprises at least a first sub-portion of the antenna array, the first sub-portion comprising a first sub-section of the plurality of antenna elements; and a second sub-portion of the antenna array comprising a second sub-section of the plurality of antenna elements, wherein an alignment of the antenna elements in the second sub-portion is substantially offset by 30° to 60° from an alignment of the antenna elements in the first sub-portion.

[0007] According to an embodiment, the apparatus comprises means for determining a value of at least one quality metric of a received Multiple Input Multiple Output (MIMO) signal; means for comparing the determined value of the at least one quality metric with a value of a corresponding threshold; and means for determining whether to use the full antenna array or the first sub-portion or the second sub-portion of the antenna array for receiving the signal based on a result of the comparison of the value of the at least one quality metric.

[0008] According to embodiments, the at least one quality metric comprises a first quality metric of Reference Signal Received Power (RSRP) and a second quality metric of Signal to Interference and Noise Ratio (SINR), wherein the means for determining is configured to control the device to receive the signal using the full antenna array in response to a value of the first quality metric or the second quality metric being below a value of a corresponding threshold.

[0009] According to embodiments, the at least one quality metric comprises a third quality metric for determining a MIMO performance of a channel matrix for the downlink transmission.

[0010] According to embodiments, the third quality metric is at least one of: MIMO rank, matrix determinant, condition number, singular value, eigenvalue.

[0011] According to embodiments, the device comprises means for measuring at least a MIMO performance of a first sub-portion of the antenna array and a MIMO performance of a second sub-portion of the antenna array.

[0012] According to embodiments, the MIMO performance of the sub-portion is configured to be measured in response to a value of the first quality metric and the second quality metric being at least equal to a value of a corresponding threshold.

[0013] According to embodiments, the device comprises means for determining a best value among the MIMO performance values of at least a first sub-portion and a second sub-portion of the antenna array; means for comparing the best MIMO value with a value of a corresponding threshold; and means for controlling the sub-portion of the antenna array having the best MIMO value to be used for receiving the signal according to a MIMO full-rank operation in response to the best MIMO value being at least equal to a value of the corresponding threshold.

[0014] According to embodiments, the means for determining is configured to control the device to receive the signal using the full antenna array in response to the best MIMO value being below a value of the corresponding threshold.

[0015] According to embodiments, the MIMO performance of the sub-portion is configured to be measured based on a received reference signal.

[0016] According to embodiments, an alignment of the antenna elements in the second sub-portion is substantially deviated by 45° from an alignment of the antenna elements in the first sub-portion.

[0017] According to embodiments, the antenna elements of the first sub-portion are adjacent to each other and the antenna elements of the second sub-portion are adjacent to each other.

[0018] According to embodiments, the antenna elements of the first sub-portion are at least partially interleaved with the antenna elements of the second sub-portion.

[0019] The method according to the second aspect comprises determining a value of at least one quality measure for a received multiple-input multiple-output (MIMO) signal; comparing the determined value of the at least one quality measure with a value of a corresponding threshold; and based on a result of the comparison of the value of the at least one quality measure, determining whether to use a full antenna array comprising a plurality of antenna elements, or a first sub-section of an antenna array comprising a first sub-portion of the plurality of antenna elements, or a second sub-portion of the antenna array comprising a second sub-section of the plurality of antenna elements, wherein an alignment of the antenna elements in the second sub-portion is substantially offset from an alignment of the antenna elements in the first sub-portion by 30° to 60° for receiving the signal.

[0020] The apparatus according to the third aspect comprises at least one processor and at least one memory, the at least one memory having computer program code stored thereon, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform determining a value of at least one quality measure for a received multiple-input multiple-output (MIMO) signal; comparing the determined value of the at least one quality measure with a value of a corresponding threshold; and based on a result of the comparison of the value of the at least one quality measure, determining whether to use a full antenna array comprising a plurality of antenna elements, or a first sub-section of an antenna array comprising a first sub-portion of the plurality of antenna elements, or a second sub-portion of the antenna array comprising a second sub-section of the plurality of antenna elements, wherein an alignment of the antenna elements in the second sub-portion is substantially offset from an alignment of the antenna elements in the first sub-portion by 30° to 60° for receiving the signal.

[0021] The computer-readable storage medium according to the further aspect comprises code for use by an apparatus, which code, when executed by a processor, causes the apparatus to perform the above method. BRIEF DESCRIPTION OF DRAWINGS

[0022] For a more complete understanding of the example embodiments, reference is now made to the following description taken in conjunction with the accompanying drawings in which:

[0023] Figure 1 A schematic block diagram of an apparatus for incorporating an antenna array arrangement according to an embodiment is shown;

[0024] Figure 2 A layout of an apparatus according to an example embodiment is shown schematically;

[0025] Figure 3 A part of an example radio access network is shown;

[0026] Fig. 4 illustrates an example of an alignment of an antenna array with a polarization of an input signal;

[0027] Fig. 5 illustrates an example of a variation of XPD depending on a polarization alignment;

[0028] Figure 6 a schematic block diagram of an antenna array arrangement according to an embodiment is shown;

[0029] Figure 7 a flow diagram of a method according to an embodiment is shown;

[0030] Figure 8 an example of XPD variation in use of an antenna array arrangement according to an embodiment is shown; and

[0031] Figure 9 An exemplary flow diagram is illustrated in accordance with at least some embodiments. DETAILED DESCRIPTION

[0032] Suitable apparatus and possible mechanisms for implementing a MIMO antenna array arrangement are described in more detail below. While the following focuses on 5G networks, the embodiments further described below are in no way limited to implementation in said networks only, but they are applicable in any network incorporating MIMO antenna arrays.

[0033] In this regard, reference is first made to Figure 1 and Figure 2 wherein Figure 1 a schematic block diagram of an exemplary apparatus or electronic device 50 that can incorporate an arrangement according to an embodiment is shown. Figure 2 A layout of an apparatus according to an example embodiment is shown. The elements of Figure 1 and Figure 2 will be explained below.

[0034] The electronic device 50 can for example be a mobile terminal or user equipment of a wireless communication system. The apparatus 50 can comprise a housing 30 for incorporating and protecting the device. The apparatus 50 can further comprise a display 32 and a keypad 34. The user interface can be implemented as a virtual keyboard or data entry system as part of a touch sensitive display instead of the keypad.

[0035] The apparatus can comprise a microphone 36 or any suitable audio input that can be a digital or analogue signal input. The apparatus 50 can further comprise an audio output device such as any one of: an earpiece 38, a speaker, or an analogue audio or digital audio output connection. The apparatus 50 can further comprise a battery 40 (or the device can be powered by any suitable mobile energy device such as a solar cell, a fuel cell or a clockwork generator). The apparatus can further comprise a camera 42 capable of recording or capturing images and / or video. The apparatus 50 can further comprise an infrared port (IR) 41 for short range wireless line of sight communication with other devices. In other embodiments, the apparatus 50 can further comprise any suitable short range communication solution, such as Bluetooth wireless connectivity or USB / firewire wired connectivity.

[0036] The apparatus 50 can comprise a controller 56 or processor for controlling the apparatus 50. The controller 56 can be connected to a memory 58 which can store both user data and instructions for implementation on the controller 56. The memory can be a random access memory (RAM) and / or a read-only memory (ROM). The memory can store computer-readable, computer-executable software including instructions that, when executed, cause the controller / processor to perform various functions described herein. In some cases, the software can not be directly executable by the processor but can cause a computer (for example, when compiled and executed) to perform functions described herein. The controller 56 can also be connected to a CODEC 54 suitable for performing encoding and decoding of audio and / or video data, or assisting in the encoding and decoding performed by the controller.

[0037] The apparatus 50 can comprise radio interface circuitry 52 connected to the controller and suitable for generating wireless communication signals for example for communication with a cellular communications network, wireless communications system or wireless local area network. The apparatus 50 can further comprise an antenna 44 connected to the radio interface circuitry 52 for sending and receiving radio frequency signals generated at the radio interface circuitry 52 to and from other apparatus(es).

[0038] In the following, different exemplary embodiments will be described using a Long Term Evolution Advanced (LTE-Advanced, LTE-A) or New Radio (NR, 5G) based radio access architecture as an example of an access architecture to which the embodiments can be applied, however, the embodiments are not limited to such an architecture. It will be appreciated by those skilled in the art that the embodiments can also be applied to other types of communications networks with suitable components by adjusting the parameters and procedures accordingly. Some examples of other options for suitable systems are Universal Mobile Telecommunication System (UMTS) Radio Access Network (UTRAN or E-UTRAN), Long Term Evolution (LTE, same as E-UTRA), Wireless Local Area Network (WLAN or WiFi), Worldwide Personal Communications Services (PCS), Wideband Code Division Multiple Access (WCDMA), systems using Ultra- Wideband (UWB) technology, sensor networks, Mobile Ad hoc Networks (MANETs) and Internet Protocol Multimedia Subsystem (IMS) or any combination thereof.

[0039] Figure 3 Examples of simplified system architecture are described, only some elements and functional entities are shown, which are all logical units whose implementation can differ from what is shown. Figure 3The shown connections are logical connections; the actual physical connections can differ. It is obvious to a person skilled in the art that the system typically also comprises other functions and structures than those shown. Figure 3 The embodiments are not, however, restricted to the systems presented as examples but a person skilled in the art can apply the solution presented in this document to other communication systems provided with necessary properties.

[0040] Figure 3 An example shows a part of an exemplary radio access network.

[0041] Figure 3 User equipments 300 and 302 are shown configured to be in wireless connection with an access node providing a cell, such as an (e / g)NodeB 304, on one or more communication channels in the cell. The physical link from the user equipment to the (e / g)NodeB is called uplink or reverse link, while the physical link from the (e / g)NodeB to the user equipment is called downlink or forward link. It should be appreciated that (e / g)NodeBs or their functionalities can be implemented by using any entities, host computers, servers or access points, etc., suited for such a use.

[0042] The communication system typically comprises more than one (e / g)NodeB, in which case the (e / g)NodeBs can also be configured to communicate with one another over links designed for the purpose, either wired or wireless. These links can be used for signalling purposes. The (e / g)NodeB is a computational device configured to control the radio resources of the communication system it is coupled to. The NodeB can also be called a base station, an access point or any other type of interfacing device including a relay station capable for operating in wireless environment. The (e / g)NodeB comprises or is coupled to a transceiver. From the transceiver of the (e / g)NodeB, a connection is provided to an antenna unit that establishes bi-directional radio links to user equipments. The antenna unit can comprise a plurality of antennas or antenna elements. The (e / g)NodeB is also connected to a core network 310 (CN or Next Generation Core NGC). Depending on the system, the counterpart on the CN side can be a serving gateway (S-GW, routing and forwarding user data packets), a packet data network gateway (P-GW) for providing the user equipment (UE) with connectivity to an external packet data network, or a mobile management entity (MME), etc. The CN can comprise network entities or nodes that can be called management entities. Examples of network entities include at least an access and mobility management function (AMF).

[0043] A user device (also known as user equipment (UE), user terminal, terminal device, wireless device, mobile station (MS), etc.) illustrates one type of apparatus to which resources on the air interface are allocated and assigned, and thus any features described herein with a user device can be implemented with a corresponding network apparatus such as a relay node, eNB and gNB. An example of such a relay node is a layer 3 relay towards a base station (self-backhauled relay).

[0044] User equipment generally refers to a portable computing device that includes wireless mobile communication devices operating with or without a subscriber identification module (SIM), including but not limited to the following types of devices: mobile stations (mobile phones), smart phones, personal digital assistants (PDAs), handheld devices, devices used in association with wireless modems (alarm or measurement devices, etc.), laptop and / or touch screen computers, tablets, game consoles, notebooks, and multimedia devices. It should be appreciated that a user equipment can also be a nearly exclusive uplink only device, an example of which is a camera or video camera that loads images or video clips to a network. A user equipment can also be a device having capability to operate in an Internet of Things (IoT) network, which is a scenario where objects are provided with the ability to transfer data over a network without requiring human interaction. Thus, a user equipment can be an IoT device. A user equipment can also utilize cloud. In some applications, a user equipment can include a small portable device having radio parts (such as a watch, earphone or glasses) and computation is performed in the cloud. A user equipment (or in some embodiments, a layer 3 relay node) is configured to perform one or more user equipment functions. A user equipment can also be referred to as a subscriber unit, mobile station, remote terminal, access terminal, user terminal or user equipment (UE), to mention just a few names or apparatuses.

[0045] The various techniques described herein can also be applied to cyber-physical systems (CPS) (systems of collaborating computational elements controlling physical entities). CPS can enable the implementation and exploitation of massive amounts of interconnected ICT devices (sensors, actuators, processors microcontrollers, etc.) embedded in physical objects at different locations. Mobile network physical systems are a subcategory of cyber-physical systems where the physical systems in question have inherent mobility. Examples of mobile physical systems include mobile robots and electronic devices transported by humans or animals.

[0046] Additionally, although the apparatus has been depicted as a single entity, different units, processors and / or memory units (not all shown in Figure 1

[0047] ​​5G implementations use multiple-input-multiple-output (MIMO) antennas, many more base stations or nodes than LTE (the so-called small cell concept), including macro sites operating in co-operation with smaller stations and using a variety of radio technologies depending on service needs, usage and / or available spectrum. The access nodes of the radio network form transmission / reception points (TRPs) and UEs are expected to access a network of multiple TRPs at least partially overlapping, such as macro cells, small cells, pico cells, femto cells, remote radio heads, relay nodes, etc. Access nodes can be provided with massive MIMO antennas, i.e. very large antenna arrays comprising e.g. tens or hundreds of antenna elements implemented in a single antenna panel or multiple antenna panels. Multiple simultaneous radio beams can be used to communicate with a UE. A UE can be provided with a MIMO antenna having an antenna array comprising multiple antenna elements, a.k.a. patches, implemented in a single antenna panel or multiple antenna panels. Thus, a UE can access one TRP using one beam, access one TRP using multiple beams, access multiple TRPs using one (common) beam, or access multiple TRPs using multiple beams.

[0048] 5G mobile communications support a wide range of use cases and related applications, including video streaming, augmented reality, different ways of data sharing, and various forms of machine type applications, such as (massive) machine type communications (mMTC), including vehicle safety, different sensors, and real-time control. 5G is expected to have multiple radio interfaces, i.e. below 6 GHz, cmWave and mmWave, and also be able to integrate with existing legacy radio access technologies, such as LTE. At least in the early stage, integration with LTE can be implemented as a system where macro coverage is provided by LTE and 5G radio interface access comes from small cells by aggregation to LTE. In other words, 5G is planned to support both inter-RAT operability, such as LTE-5G, and inter-RI operability, i.e. inter-radio interface operability, such as below 6 GHz-cmWave, below 6 GHz-cmWave-mmWave. One of the concepts believed to be used in 5G networks is network slicing, where multiple independent and dedicated virtual sub-networks (network instances) can be created within the same infrastructure to run services with different requirements on latency, reliability, throughput and mobility.

[0049] The current architecture in LTE networks is fully distributed in the radio and fully centralized in the core network. Low latency applications and services in 5G require bringing the content close to the radio which leads to local breakouts and multi-access edge computing (MEC). 5G enables analytics and knowledge generation to occur at the source of the data. This approach requires leveraging resources that can not be continuously connected to the network such as laptops, smartphones, tablets and sensors. MEC provides a distributed computing environment for application and service hosting. It also has the ability to store and process content in close proximity to the cell subscribers for faster response times. Edge computing covers a wide range of technologies such as wireless sensor networks, mobile data acquisition, mobile signature analysis, cooperative distributed peer-to-peer ad hoc networking and processing, also classifiable under local cloud / fog computing and grid / mesh computing, dew computing, mobile edge computing, small cloud, distributed data storage and retrieval, self-organizing, self-healing networks, remote cloud services, augmented and virtual reality, data caching, Internet of Things (massive connectivity and / or latency critical), critical communications (autonomous vehicles, traffic safety, real-time analytics, time-critical control, healthcare applications).

[0050] The communication system is also able to communicate with other networks, such as a public switched telephone network or the Internet 312, or utilize services provided by them. The communication system can also be able to support the usage of cloud services, for example at least part of the core network operations can be carried out as a cloud service (this is depicted in Figure 3 by "cloud" 314). The communication system can further include a central control entity, etc., providing facilities for networks of different operators to cooperate, e.g., in spectrum sharing.

[0051] Edge cloud can be brought into the Radio Access Network (RAN) by utilizing Network Function Virtualization (NFV) and Software-Defined Networking (SDN). Using edge cloud can mean that node operations are carried out, at least partly, in servers, hosts, or nodes that are operably coupled to remote radio heads or base stations that include radio parts. It is possible that node operations will be distributed among a number of servers, nodes, or hosts. The application of cloud RAN architecture enables RAN real-time functions to be carried out in the RAN side (in a Distributed Unit, DU) and non-real-time functions to be carried out in a centralized manner (in a Centralized Unit, CU 308).

[0052] It should also be understood that the distribution of labor between core network operations and base station operations can differ from the distribution of labor in LTE or can even be nonexistent. Some other technological advancements that can be used are big data and all-IP, which can change the way networks are constructed and managed. A 5G (or New Radio, NR) network is designed to support multiple hierarchies, where MEC servers can be placed between the core and the base station or nodeB (gNB). It should be understood that MEC can also be applied to 4G networks. The gNB is the next generation nodeB (or new nodeB) that supports 5G networks (i.e., NR).

[0053] 5G can also utilize non-terrestrial nodes 306 (e.g., access nodes) to enhance or complement the coverage of 5G services, for example, by providing backhauling, wireless access to wireless devices, service continuity for machine-to-machine (M2M) communication, service continuity for Internet of Things (IoT) devices, service continuity for passengers on vehicles, service availability to ensure critical communications, and / or service availability to ensure future railway / maritime / aeronautical communications. The non-terrestrial nodes can have a fixed position relative to the Earth's surface, or the non-terrestrial nodes can be mobile non-terrestrial nodes that can move relative to the Earth's surface. The non-terrestrial nodes can include satellites and / or HAPS. Satellite communications can utilize a geosynchronous Earth orbit (GEO) satellite system, but can also utilize a low Earth orbit (LEO) satellite system, in particular a mega-constellation (a system in which hundreds of (nano)satellites are deployed). Each satellite in a mega-constellation can cover several satellite-enabled network entities that create ground cells. The ground cells can be created through a ground relay node 304 or through a gNB located on the ground or in a satellite.

[0054] It will be appreciated by those skilled in the art that the described system is merely an example of a part of a radio access system, and in practice the system can comprise a plurality of (e / g)NodeBs, the user equipment can have access to a plurality of radio cells, and the system can further comprise other apparatus such as physical layer relay nodes or other network elements. At least one of the (e / g)NodeBs or possibly a Home (e / g)nodeB. In addition, in the geographical area of the radio communications system, a plurality of different kinds of radio cells as well as a plurality of radio cells can be provided. The radio cells can be macro cells (or umbrella cells), which are large cells typically having a diameter of several tens of kilometers, or smaller cells such as micro cells, femto cells or pico cells. Figure 1An (e / g)NodeB can provide any type of these cells. The cellular radio system can be implemented as a multi-tier network comprising several types of cells. Typically, in a multi-tier network one access node provides one or more types of cells and thus multiple (e / g)NodeBs are needed to provide such network structure.

[0055] Frequency bands for 5G NR are separated into two frequency ranges: Frequency Range 1 (FR1) includes frequency bands below 6 GHz, i.e. frequency bands conventionally used by previous standards, but also includes new frequency bands extending to cover potential new spectrum supplies from 410 MHz to 7125 MHz, and Frequency Range 2 (FR2) includes frequency bands from 24.25 GHz to 52.6 GHz. Thus, FR2 includes frequency bands in the mmWave range, which due to its shorter range and higher available bandwidth requires slightly different ways in radio resource management compared to frequency bands in FR1.

[0056] MIMO is one of the key enabling technologies for 5G wireless technology. The fundamental principle of MIMO is to use multiple transmit and receive antennas to increase the throughput and / or reliability of data transmission. Increased throughput can be achieved by sending / receiving different data streams on multiple antennas, while increased reliability can be achieved by using multiple antennas to send / receive multiple versions of the same data.

[0057] Beamforming antenna arrays play an important role in 5G implementations. While providing high bandwidth, mmWave frequencies have higher propagation losses, which vary greatly depending on the environment. The smaller wavelength at higher carrier frequencies allows for smaller antenna element sizes, which gives the opportunity to place one or more (e.g. two, three or more) relatively large antenna arrays at the UE. This in turn leads to various challenges to maintain the expected performance.

[0058] Considering 2x2 MIMO as a non-limiting example, downlink (DL) MIMO performance (e.g. in mmWave frequency ranges, such as FR2) can be achieved by using polarization splitting (co-polarization and cross-polarization) of dual-fed antenna arrays at the base station (hereinafter also referred to as gNB) and / or at the UE, where each polarization corresponds to one MIMO branch. The reason behind this approach is to achieve high and similar antenna gain performance in both MIMO channels, while maintaining a compact spatial antenna design.

[0059] When designing dual-polarized antenna arrays, it is important to achieve high cross-polar discrimination (XPD). XPD can be defined as the ratio of the co-polar component to the orthogonal cross-polar component of a specified polarization over a sector or beamwidth angle.

[0060] The decorrelation at the antenna array can be obtained by ensuring that each antenna feed corresponds to a single polarization and the resulting dual feed polarizations are designed to be orthogonal. This way, an antenna array with high XPD at the feed point can be designed. Assuming that the orientation of the maximum gain direction and the orthogonal polarizations are aligned between the antenna arrays at the UE and gNB, this approach will ensure full utilization of the two MIMO channels for Line of Sight (LoS) and / or Non-Line of Sight (NLoS) operation.

[0061] Furthermore, the high antenna gain of mmWave (e.g. FR2) frequencies will require to reduce its radiated beamwidth, thereby requiring beam steering at the antenna array (or arrays) to cover the required angular space. The beam steering capability can be implemented at each element in the antenna array using a tunable phase shifter, whereby the direction of the beam can be controlled electrically (phased array) instead of mechanically.

[0062] The XPD of any antenna (or antenna array) depends on its radiation pattern and can dynamically change as a function of the angle of departure (AoD) and / or angle of arrival (AoA). This dependency increases with the variation of the radiation pattern and the electrical change of the radiation lobe. Higher antenna gain patterns result in larger XPD variations over the angular space. Phase-controlled arrays also have increased XPD variations over the angular space.

[0063] This way, the physical orientation of the antennas at mmWave frequencies will have more impact on the MIMO than seen at sub-6GHz frequencies, where the decorrelation at the UE is achieved by the physical separation between the two receive antennas (each with random and different radiation patterns). In contrast, the mmWave architecture can exploit dual orthogonal polarized antennas (or antenna arrays) designed for equally high gain radiation patterns.

[0064] MIMO rank is a measure that can be used to indicate how many multipaths the channel provides. It indicates how many streams can be transmitted via the channel. For example, in a 2x2 MIMO system, the rank can be 1 or 2, and in a 4x4 MIMO system, the rank can be 1, 2, 3, or 4.

[0065] Figure 4 illustrates polarization alignment and / or misalignment. The arrows with solid lines in the figure show the orthogonal polarizations of the antenna array at the UE, while the dashed lines show the polarizations of the input MIMO signal. The aligned case on the left ( Figure 4a ) will result in high XPD, while the misaligned case on the right ( Figure 4b) will result in low XPD. The former case (4a) can result in MIMO rank 2, while the latter case (4b) can result in MIMO rank 1 measured and / or reported by the UE (e.g. by means of Rank Indication, RI), although it is configured to communicate with the access point (e.g. gNB) using 2x2 MIMO. Thus, when high XPD is lost at the UE, MIMO throughput can be reduced up to two times, since it will be more difficult or even impossible to distinguish the two MIMO channels from each other, since they are mixed on two receive chains instead of being received on two receive chains separately. Thus, in many of these cases, it is not possible to achieve MIMO with the desired quality, and the communication can be performed as if MIMO is not used.

[0066] Thus, the XPD of an antenna array can depend on the angle of arrival (AoA) and orientation (i.e. alignment) of the incoming orthogonal MIMO signals. For the considered dual-polarized antenna, the highest XPD can be achieved for a perfectly aligned input orthogonal 2x2 MIMO signal, while a 45° offset in alignment will result in the lowest XPD.

[0067] Various experiments have shown the dependency between AoA, polarization alignment and XPD. Furthermore, the XPD of the two feed points (co-polarized and cross-polarized) of a UE antenna array can also vary independently, even for the same AoA, and both antenna array feed points must have sufficiently high XPD to obtain an overall high MIMO rank. The two feed points of an antenna array can be differently affected by the non-optimal surrounding environment in which the antenna array is mounted, especially from the UE’s chassis and glass. This will result in different radiation patterns, even with the same antenna array weights (power and phase), and thereby directly affect the XPD.

[0068] Figure 5 illustrates the XPD variation depending on the alignment of the antenna array with the input MIMO signals. The maximum XPD is simulated for a perfectly aligned input orthogonal 2x2 MIMO signal, while the minimum XPD is simulated with a 45° offset in alignment. The results are shown for different AoAs, where XPD values greater than 20 dB have been truncated to 20 dB, and values less than -20 dB have been truncated to -20 dB. Furthermore, the XPD values for angular directions where the gain is less than 10 dB from the maximum antenna gain have also been truncated to -20 dB. Figure 5a The maximum and minimum XPD for the first polarization (co-polarized) of the UE antenna array is shown, while Figure 5b The XPD values for the second polarization (cross-polarized) are shown.

[0069] When the array is perfectly aligned with the incoming orthogonal MIMO signal, a XPD value of more than 5 dB (which in this example is considered the minimum XPD value for reasonable MIMO performance, but other values can also be considered depending on the MIMO capabilities of the device) is achieved by a single antenna array for 50% of the angular space. For misalignment cases with the minimum XPD value, this number drops to approximately 10%.

[0070] Furthermore, for the two feed points (co-polarized and cross-polarized) on the UE antenna array in a certain angular direction, the XPD needs to be sufficiently high (such as better than 5 dB) to ensure sufficient MIMO (in this case 2 rank) performance, and this is only achieved for approximately 46% of the angular space for perfect alignment and less than 1% for the worst case misalignment. Increasing the number of antenna arrays can also increase the XPD coverage value approximately by a multiplication factor equal to the number of antenna arrays. This way, when the incoming orthogonal MIMO signal is perfectly aligned with the antenna array at the UE, a UE with three antenna arrays (current 3GPP working assumption) can in theory (assuming limited overlap between different radiation patterns) achieve full XPD coverage, but for misalignment cases it can still be very low (sometimes even below 1%). Obviously, a typical phased antenna array that will be implemented on a smartphone will have a limited angular space in which it can actually receive a 2x2 DL orthogonal MIMO signal with the required decorrelation (e.g. resulting in at least 5 dB XPD) between the two feed points, even if the UE is in the LoS of the gNB and has potentially optimal reception conditions.

[0071] This way, by using one dual feed antenna array at the UE with similar aligned antenna elements, MIMO performance can not always be possible.

[0072] As a first aspect to at least alleviate the above-mentioned problems, an apparatus is introduced, the apparatus comprising: an antenna array comprising a plurality of antenna elements configured for receiving a multiple-input multiple-output (MIMO) signal, wherein the antenna array comprises at least a first sub-portion of the antenna array, the first sub-portion comprising a first sub-section of the plurality of antenna elements; and a second sub-portion of the antenna array comprising a second sub-section of the plurality of antenna elements, wherein an alignment of the antenna elements in the second sub-portion is substantially offset by 30° to 60° from an alignment of the antenna elements in the first sub-portion.

[0073] Thus, the antenna array comprising at least two sub-portions enables controlling which of the first and second sub-portions to be used when a sufficiently high MIMO performance, such as MIMO rank 2, is supported by the downlink channel, wherein the selection between the first and second sub-portions to be used can be performed based on which alignment better suits the incoming orthogonal MIMO signal. On the other hand, when a lower MIMO performance, such as MIMO rank 1, is supported by the downlink channel, the requirements on the alignment of the antenna elements are less strict, and thus the whole or both (first and second) sub-portions of the antenna array, i.e. the full array, can be used for downlink channel reception, enabling maximum gain in reception.

[0074] In the following, the "alignment" of the antenna elements can refer to the alignment of the antenna elements on the antenna array surface or the rotation of the antenna elements around an axis perpendicular to the antenna element surface, or both.

[0075] Figure 6 A simplified example of such an antenna array according to an embodiment is shown. Figure 6 A 1x8 antenna array 600, i.e. an antenna array having 8 antenna elements in a row, configured for receiving a MIMO signal is shown. The antenna array 600 comprises a first sub-portion 602 of the antenna array, the first sub-portion 602 comprising a first sub-section of the plurality of antenna elements, i.e. the four leftmost antenna elements in the row. The antenna array 600 further comprises a second sub-portion 604 of the antenna array, the second sub-portion 604 comprising a second sub-section of the plurality of antenna elements, i.e. the four rightmost antenna elements in the row. The alignment of the antenna elements in the second sub-portion is shown to be substantially deviated from the alignment of the antenna elements in the first sub-portion.

[0076] According to an embodiment, the alignment of the antenna elements in the second sub-portion is substantially deviated 45° from the alignment of the antenna elements in the first sub-portion.

[0077] As Figure 4b shown, the lowest XPD is at least theoretically produced when the polarization of the antenna array and the incoming MIMO signal is substantially deviated 45°. Thus, theoretically, the optimal deviation of the alignment of the antenna elements in the sub-portions is likewise substantially 45°. It is however noted that the antenna array is typically fixed to a device, such as a UE, and that the alignment of the UE, and thus of the antenna array, inevitably changes at least slightly when the UE is used, e.g. when the UE is rotated when held in hand or when carried while moving. Thus, while a substantially 45° deviation of the alignment of the antenna elements between the sub-portions as Figure 6 shown can provide the best results, a wider range of angles, such as 30° to 60°, in the deviation of the alignment of the antenna elements can provide at least almost equally good results in practical use, if the surrounding conditions remain the same.

[0078] According to an embodiment, the antenna elements of the first sub-portion are adjacent to each other, and the antenna elements of the second sub-portion are adjacent to each other.

[0079] Hence, the antenna elements of the antenna array can be clearly divided into at least two sub-portions, each sub-portion comprising antenna elements adjacent to each other. In Figure 6 Such an arrangement is disclosed in the antenna array of Fig. 6, wherein the first sub-portion 602 of the antenna array comprises the four leftmost antenna elements adjacent to each other, and the second sub-portion 604 of the antenna array correspondingly comprises the four rightmost antenna elements adjacent to each other. Such an arrangement can reduce the maximum gain by approximately 3 dB for each of the sub-portions, but can suppress the side lobes, such as 10 to 15 dB for the first side lobe.

[0080] According to an embodiment, the antenna elements of the first sub-portion are at least partially interleaved with the antenna elements of the second sub-portion.

[0081] Hence, the antenna elements can be arranged, for example, such that every second antenna element is aligned in a first direction, forming a first sub-portion of the antenna array, and the alternating antenna elements among the antenna elements are aligned in a second direction, forming a second sub-portion of the antenna array, and substantially deviating 30° to 60° from the alignment of the antenna elements in the first sub-portion. For example, in the antenna array of Fig. 5, the first, third, fifth and seventh antenna elements can be aligned in a first direction (not shown), and form a first sub-portion of the antenna array, while the second, fourth, sixth and eighth antenna elements can be aligned in a second direction substantially deviating 30° to 60° from the alignment of the antenna elements in the first sub-portion (not shown), and form a second sub-portion of the antenna array. Figure 6

[0082] It is also possible that the antenna elements of the sub-portions of the antenna array are only partially interleaved with each other. For example, in the antenna array of Fig. 6, the first, second, fourth, sixth antenna elements can be aligned in a first direction (not shown), and form a first sub-portion of the antenna array, while the third, fifth, seventh and eighth antenna elements can be aligned in a second direction substantially deviating 30° to 60° from the alignment of the antenna elements in the first sub-portion (not shown), and form a second sub-portion of the antenna array. Figure 6

[0083] ​​The obtained MIMO performance, which can be defined for example by the MIMO rank, a parameter identifying the MIMO rank or any other suitable quality metric or metrics, will depend on the channel conditions, but it can also depend on the XPD of the receive antennas at the UE. The UE cannot directly influence the channel conditions, but it can influence the way it experiences the current channel conditions by how it selects to configure its antenna array and subparts, and thus directly influence the MIMO rank of the obtained input signal.

[0084] In the following, an enhanced method for controlling the operation of a device provided with the above described antenna array will be described in more detail according to various embodiments. The embodiments described herein thus solve the above challenges by providing improvements that enable a more efficient operation of a wireless communication network. For example, the embodiments can optimize the MIMO performance according to the environment. Thus, for example, when the environment changes or the UE rotates, the embodiments can enable a dynamic optimization of the MIMO performance by changing the orientation of the orthogonality of the receive antenna elements.

[0085] The method is disclosed in the flowchart of Figure 7 reflects the operation of a terminal device, such as a user equipment (UE), comprising an antenna array according to the above described first aspect, wherein the method comprises determining (700) a value of at least one quality metric of a received multiple-input multiple-output (MIMO) signal; comparing (702) the determined value of the at least one quality metric with a value of a corresponding threshold; and determining, based on a comparison result of the value of the at least one quality metric, whether to use (704) a full antenna array comprising a plurality of antenna elements for receiving the signal or to use (706) a first subpart of the antenna array or a second subpart of the antenna array, wherein an alignment of the antenna elements deviates substantially by 30° to 60° from an alignment of the antenna elements in the first subpart for receiving the signal.

[0086] Figure 7 The method disclosed in the above described method describes the basic idea for controlling the operation of the above described antenna array. When operating in lower MIMO performance, such as MIMO rank 1, the full array and thus the maximum gain can be used, since the orientation of the device and thus of the antenna array is not important for the obtained performance. However, when the channel supports a higher MIMO performance, such as MIMO rank 2, and the MIMO is configured by the gNB, according to which alignment provides a better performance for the input orthogonal MIMO signal, only one subpart of the antenna array can be used.

[0087] The device can continuously monitor the value of the at least one quality metric and adjust the use between the full antenna array, the first subpart and the second subpart of the antenna array according to changes in the comparison of the value of the at least one quality metric with their corresponding threshold.

[0088] Figure 8 The improvements provided by the now introduced antenna array implementation are illustrated, showing the XPD performance improvement as a function of the angle of the incoming orthogonal MIMO signal. The solid line represents the XPD coverage of the conventional array 1x8 with similarly aligned antenna elements, and shows that the minimum XPD coverage (>5dB) decreases gradually as a function of the increasing alignment angle of the incoming orthogonal MIMO signal. The long dashed curve represents the XPD coverage of the novel first sub-part array 1x4, where the antenna elements are aligned similarly to the conventional array 1x8, and shows that the minimum XPD coverage of the first sub-part array 1x4 decreases approximately similarly to the conventional array 1x8. The short dashed curve represents the XPD coverage of the novel second sub-part array 1x4, where the antenna elements are aligned with a 45° rotation relative to the conventional array 1x8, and shows that the minimum XPD coverage of the second sub-part array 1x4 starts substantially from zero and increases as a function of the increasing alignment angle of the incoming orthogonal MIMO signal.

[0089] Considering the case where the downlink channel supports higher MIMO performance, such as MIMO rank 2, and the alignment angle of the incoming orthogonal MIMO signal relative to the antenna array is rather small, such as in the example of <15°, the apparatus configures the first sub-part array 1x4 with antenna elements that are aligned similarly to the conventional array 1x8 to be used. However, as the alignment angle of the incoming orthogonal MIMO signal relative to the antenna array increases, the minimum XPD coverage (>5dB) of the first sub-part array also decreases gradually, until the intersection of the decreasing XPD coverage of the first sub-part array and the increasing XPD coverage of the second sub-part array occurs. In the example of Figure 8 Figure 8 the intersection occurs approximately at 17° to 19° of the alignment angle of the incoming orthogonal MIMO signal relative to the antenna array. The apparatus then configures the second sub-part array 1x4 with antenna elements that are aligned with a 45° rotation to the conventional array 1x8 to be used.

[0090] As can be seen in the example of Figure 8 Figure 8 the combined XPD coverage performance (best values of the long dashed and short dashed curves) of the first and second sub-parts of the antenna array is significantly better, and never below 18% coverage. Compared to the conventional array 1x8 with similarly aligned antenna elements (solid line), the example of Figure 8 shows that the minimum XPD (>5dB) coverage value increases from below 1% to approximately 18%, and the total coverage above XPD of more than 5dB is improved by approximately 50%, as indicated by the area under the combined two sub-part array curves, which is approximately twice as large as the area covered by the solid line alone.

[0091] ​​​​​Thus, the introduced antenna array implementation will have a significant improvement on the MIMO performance of a handheld device operating in a dynamic environment where the alignment between the incoming orthogonal MIMO signals and the polarization of the antenna array will be random.

[0092] Reference is now made to Figure 9 the flowchart of FIG. 1, which describes in more detail the antenna array configuration process performed by an apparatus such as a UE, and various embodiments related thereto. Note that Figure 9 the steps of FIG. 1 can be performed in multiple subsets, at least partially in parallel and / or at least partially in modified order.

[0093] According to embodiments, the at least one quality metric comprises a first quality metric of Reference Signal Received Power (RSRP) and a second quality metric of Signal to Interference and Noise Ratio (SINR), wherein the means for determining is configured to control the apparatus to use the full antenna array for receiving signals in response to a value of the first quality metric or the second quality metric being lower than a value of the corresponding threshold.

[0094] Thus, the antenna array configuration process can start by determining one or more quality metrics from reference signals received from a gNB, and if the one or more quality metrics, such as RSRP or SINR, are lower than their corresponding threshold values, it can immediately indicate that the apparatus should use the full antenna array for receiving signals, since the UE is under poor radio conditions and will need to utilize the full array and thereby the maximum achievable antenna gain.

[0095] In Figure 9 , a possible implementation is described as the UE receiving (900) a scheduled SSB (Synchronization Signal Block) or CSI (Channel State Information) reference signal transmitted from a gNB, whereupon the UE determines (902) the RSRP of the best SSB or CSI beam. The UE determines (904) whether the RSRP of the best SSB / CSI beam is higher than a predetermined threshold, and if not, the UE configures (906) the full antenna array for MIMO rank 1 operation. The UE enters (908) rank 1 operation, and remains waiting for the next scheduled and available reference signal (SSB, CSI or any other suitable reference signal).

[0096] If in step 904 the RSRP of the best SSB / CSI beam is higher than the predetermined threshold, the UE determines (910) whether the SINR of the best SSB / CSI beam is higher than a predetermined threshold. Again, if not, the UE configures (906) the full antenna array for MIMO rank 1 operation. If yes, the UE waits (912) for the next scheduled reference signal, such as SSB, CSI-RS, Demodulation Reference Signal (DMRS) or any other suitable reference signal.

[0097] According to embodiments, the at least one quality metric comprises a third quality metric for determining a MIMO performance of a channel matrix of the downlink transmission. Thus, the UE determines the invertibility of the channel matrix in order to determine the type of MIMO downlink transmission to be used.

[0098] According to one embodiment, the third quality metric is at least one of: MIMO rank, matrix determinant, condition number, singular value, eigenvalue.

[0099] Thus, various metrics can be used for determining the invertibility of the channel matrix. Instead of or in addition to the MIMO rank, the matrix determinant of the MIMO channel matrix can be used to measure the orthogonality and channel quality. Similarly, the singular values or (inverse) eigenvalues can be computed based on the MIMO channel matrix. These can also be used to compute the condition number. Naturally, any metric qualifying the invertibility of the MIMO channel matrix can be used.

[0100] It is also possible to use an average of this value or any filtered version of the value, such as a sliding window, finite impulse response filter, infinite impulse response filter or any order (1, 2,..., n order). Note that the frequency averaging of the channel estimation of the MIMO channel, such as narrowband on a single subcarrier DMRS or full bandwidth allocated to the UE, should preferably be considered together with the different averaging techniques.

[0101] In the following, the "MIMO rank" can be used interchangeably with the term "third quality metric for determining a MIMO performance" and / or "MIMO performance". It should be noted that any of the above alternatives of the third quality metric can alternatively be used in such context.

[0102] According to embodiments, the apparatus comprises means for measuring at least a MIMO performance of a first sub-portion of the antenna array and a MIMO performance of a second sub-portion of the antenna array.

[0103] Thus, the apparatus is configured to measure the MIMO performance of the sub- portions of the antenna array separately. For this purpose, typically at least two reference signals are needed: one for the MIMO performance measurement of the first sub-portion and another one for the MIMO performance measurement of the second sub-portion.

[0104] According to embodiments, the MIMO performance of the sub-portion is measured in response to the values of the first quality metric and the second quality metric being at least equal to values of corresponding threshold values.

[0105] Thus, if the measurements of the first and second quality metrics, such as RSRP or SINR, indicate that the quality of the received reference signals is insufficient, the apparatus is typically configured to use the full antenna array in MIMO rank 1 operation. In this case, the MIMO performance measurements of the first and second sub-portions do not need to be performed until new reference signals with sufficient quality according to the first and second quality metrics are received.

[0106] According to an embodiment, the apparatus comprises means for determining a best value among MIMO performance values of at least a first sub-portion and a second sub-portion of the antenna array; means for comparing the best MIMO value with a value of a corresponding threshold value; and means for controlling, in response to the best MIMO value being at least equal to the value of the corresponding threshold value, the sub-portion of the antenna array having the best MIMO value to be used for receiving signals according to MIMO full rank operation.

[0107] Thus, among the MIMO performance values of the sub-portions of the antenna array, the best MIMO performance value is determined and compared with the value of the threshold value, and if the best MIMO performance value is good enough compared to the value of the threshold value, the sub-portion of the antenna array having the best MIMO value is controlled to be used for receiving signals. Herein, the sub-portion of the antenna array can be controlled to operate according to MIMO full rank operation, e.g. rank 2 in a 2x2 MIMO configuration or rank 4 in a 4x4 MIMO configuration.

[0108] According to an embodiment, the means for controlling is configured to control the apparatus to use the full antenna array for receiving signals in response to the best MIMO value being below the value of the corresponding threshold value.

[0109] Thus, if the best MIMO performance value among the MIMO performance values of the sub-portions of the antenna array is not good enough compared to the value of the threshold value, the whole antenna array is controlled to be used for receiving signals. Herein, the full antenna array can be controlled to operate according to MIMO rank 1 operation.

[0110] In Figure 9In the above embodiments, a possible implementation of the above embodiments is described as the UE measures (914) the MIMO performance (such as MIMO rank) of a first sub-portion of the antenna array based on the received reference signal (912). The UE receives (916) the next scheduled reference signal, and based on the received reference signal, the UE measures (918) the MIMO performance of a second sub-portion of the antenna array, such as MIMO rank. Among the MIMO performance values of the sub-portions of the antenna array, the UE determines the best MIMO performance value, and compares (920) this best value with the value of the threshold to determine whether the best MIMO performance value (such as MIMO rank) is suitable for higher rank MIMO operation, i.e. whether the best MIMO performance value is higher than the predetermined threshold, and if not, the UE configures (906) the full antenna array for MIMO rank 1 operation.

[0111] If the best MIMO performance value is higher than the predetermined threshold, the UE determines (922) which sub-portion of the antenna array has the best MIMO performance value, and configures the first sub-portion (924) or the second sub-portion (926) for receiving signals according to MIMO full rank operation accordingly. The selected sub-portion enters (928) MIMO full rank operation and remains waiting for the next reference signal.

[0112] Embodiments allow optimizing the UE antenna array configuration (i.e. any sub-portion of the antenna array) to improve MIMO throughput when the combined XPD of the dual-polarized antenna array is not sufficient for MIMO reception in the angular direction of the incoming orthogonal MIMO signal. Moreover, adapting the MIMO configuration of the sub-portion of the antenna array will result in increased throughput and thereby better power utilization in the UE.

[0113] A typical UE with three antenna arrays will be able to align the beams (with gain reduced from the maximum gain value by less than 5 dB) towards the angular direction of the LoS incoming orthogonal MIMO signal for more than 90% of the full angular space. However, if the incoming orthogonal MIMO signal is perfectly aligned with the polarization of the user antenna array, the XPD required for MIMO reception (> 5 dB) is only achieved for that angular space. In fact, if the incoming orthogonal MIMO signal is misaligned by 45° with respect to the polarization of the user antenna array, MIMO reception can not be possible for any angular direction. As such, the UE will experience up to 2x (e.g. from rank 2 to rank 1) throughput drop, which can be avoided by the embodiments disclosed herein, enabling maintaining full MIMO rank.

[0114] The method and its related embodiments can be implemented in an apparatus implementing a user equipment (UE). The apparatus can comprise at least one processor and at least one memory storing computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform: determining a value of at least one quality metric of a received multiple-input multiple-output (MIMO) signal; comparing the determined value of the at least one quality metric with a value of a corresponding threshold; and determining, based on a result of the comparison of the value of the at least one quality metric, whether to use a full antenna array comprising a plurality of antenna elements, or a first sub-portion of an antenna array comprising a first sub-section of the plurality of antenna elements, or a second sub-portion of the antenna array comprising a second sub-section of the plurality of antenna elements, wherein an alignment of the antenna elements in the second sub-portion substantially deviates from an alignment of the antenna elements in the first sub-portion by 30° to 60° for receiving the signal.

[0115] Such an apparatus can likewise comprise an antenna array comprising a plurality of antenna elements configured for receiving a multiple-input multiple-output (MIMO) signal, wherein the antenna array comprises at least a first sub-portion of the antenna array comprising a first sub-section of the plurality of antenna elements; and a second sub-portion of the antenna array comprising a second sub-section of the plurality of antenna elements, wherein an alignment of the antenna elements in the second sub-portion substantially deviates from an alignment of the antenna elements in the first sub-portion by 30° to 60°.

[0116] Such an apparatus can comprise the functional units disclosed in any of the figures of Figure 1 , Figure 2 and Figure 3 for implementing embodiments.

[0117] In example embodiments, a computer program can be configured to cause a method according to the above embodiments and any combination thereof. In example embodiments, a computer program product embodied on a non-transitory computer readable medium can be configured to control a processor to perform a process including the above embodiments and any combination thereof.

[0118] In example embodiments, an apparatus, such as a UE or a gNB, can comprise at least one processor and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform the above embodiments and any combination thereof.

[0119] In general, the various embodiments of the application can be implemented in hardware or special-purpose circuits, or any combination thereof. While various aspects of the application can be illustrated and described as block diagrams or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein can be implemented in hardware, software, firmware, special-purpose circuits or logic, general purpose hardware or controler or other computing devices, or some combination thereof.

[0120] As used in this application, the term "circuitry" can refer to one or more or all of the following: (a) hardware-only circuitry such as amongst others an implementation in only analog and / or digital circuitry and (b) combinations of hardware circuits and software, such as: (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and (ii) portions of hardware processor(s) with software (including digital signal processors), software, and memory that work together to cause an apparatus, such as a UE or gNB, to perform various functions and (c) hardware circuitry alone or in combination with other hardware and / or software that need not be software to operate but can temporarily be absent software when not needed against a backdrop of required software.

[0121] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application the term circuitry also covers an implementation that is at least one integrated circuit (or other hardware) and / or at least one processor (or other hardware) that executes software that can include firmware.

[0122] Embodiments can be practiced in various components such as integrated circuit modules. The design of integrated circuits is by nature a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on semiconductor chips.

[0123] Programs, such as those provided by Synopsys, Inc. of Mountain View, California and Cadence Design, of San Jose, California automatically route conductors and locate components on a semiconductor chip using well-established rules of design as well as libraries of pre-stored design modules. Once the design for a semiconductor circuit has been completed, the resultant design, in a standardized electronic format (e.g., Opus, GDSII, or the like) can be transmitted to a semiconductor fabrication facility or "fab" for fabrication.

[0124] It is to be understood that the embodiments disclosed are not limited to the particular structures, process steps, or materials disclosed herein but are extended to equivalents thereof The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0125] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase in one embodiment or in an embodiment in various places in the specification are not necessarily all referring to the same embodiment. When using the term approximating or about, it is intended that the term provide support for an exact number but also for a close approximation of the number.

[0126] As used herein, a plurality of items, structural elements, compositional elements, and / or materials can be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on its presence therein. Further, the various embodiments and examples set forth herein should not be construed as mutually exclusive alternative embodiments but rather as separate and independent embodiments that can be combined with each other.

[0127] The foregoing description has provided by way of exemplary and non-limiting examples a full and informative description of exemplary embodiments of the application. However, where made to read in connection with the accompanying drawings and the examples set forth herein, various modifications and adaptations to those embodiments of the present teachings will become apparent to those skilled in the relevant art, in view of the foregoing description. However, all such and similar modifications will still fall within the scope of the teachings of the present application.

[0128] List of Abbreviations

[0129] 3GPP Third Generation Partnership Project

[0130] AOA Angle of Arrival

[0131] AoD Angle of Departure

[0132] ASIC Application Specific Integrated Circuit

[0133] BS Base Station

[0134] CSI Channel State Information

[0135] CSI-RS Channel State Information Reference Signal

[0136] DMRS Demodulation Reference Signal

[0137] FPGA field programmable gate array

[0138] GSM global system for mobile communications

[0139] HW hardware

[0140] IoT internet of things

[0141] LoS line of sight curve

[0142] LTE long term evolution

[0143] MIMO multiple input multiple output

[0144] M2M machine to machine

[0145] NLoS non-line of sight

[0146] NR new radio

[0147] RAT radio access technology

[0148] RAN radio access node

[0149] UE user equipment

[0150] XPD cross-polarization discrimination

Claims

1. An apparatus for communication, the apparatus comprising: The apparatus comprises: a full antenna array (600) comprising a plurality of antenna elements configured for receiving a multiple-input multiple-output (MIMO) signal, wherein the full antenna array comprises at least: - a first sub-portion (602) of the full antenna array comprising a first sub-section of the plurality of antenna elements; and - a second sub-portion (604) of the full antenna array comprising a second sub-section of the plurality of antenna elements, wherein an alignment of the antenna elements in the second sub-portion is substantially offset by 30° to 60° from an alignment of the antenna elements in the first sub-portion; - means for determining (700) a value of at least one quality metric for a received multiple-input multiple-output (MIMO) signal; - means for comparing (702) the determined value of the at least one quality metric with a value of a corresponding threshold; - means for determining (704, 706) whether to use the full antenna array or the first or second sub-portion of the full antenna array for receiving the signal based on a result of the comparison of the value of the at least one quality metric.

2. The apparatus according to claim 1, wherein the at least one quality metric comprises a first quality metric of reference signal received power (RSRP) and a second quality metric of signal-to-interference-and-noise ratio (SINR), wherein, the means for determining is configured to control the apparatus to use (906) the full antenna array for receiving the signal in response to the value of the first (904) or second (910) quality metric being lower than the value of the corresponding threshold.

3. The apparatus according to claim 1 or 2, wherein the at least one quality metric comprises a third quality metric for determining a MIMO performance of a channel matrix for a downlink transmission.

4. The apparatus according to claim 3, wherein the third quality metric is at least one of: MIMO rank, matrix determinant, condition number, singular value, eigenvalue.

5. The apparatus according to claim 3, the apparatus comprising: - means for measuring at least a MIMO performance of the first sub-portion (914) of the full antenna array and a MIMO performance of the second sub-portion (918) of the full antenna array.

6. The apparatus according to claim 5, wherein the MIMO performance of the sub-portion is configured to be measured in response to the values of the first and second quality metrics being at least equal to the value of the corresponding threshold.

7. The apparatus according to claim 5 or 6, comprising: - means for determining a best value of the MIMO performance values of at least the first and second sub-portion of the full antenna array; - means for comparing (920) the best MIMO value with a value of a corresponding threshold; and - means for determining (922) whether to use the full antenna array or the first or second sub-portion of the full antenna array for receiving the signal based on a result of the comparison of the best MIMO value. - means for controlling (922, 924, 926) the sub-section of the full antenna array having the best MIMO value to receive the signal according to MIMO full-rank operation in response to the best MIMO value being at least equal to a value of the corresponding threshold value.

8. The apparatus of claim 7, wherein the means for controlling is configured to control (906) the apparatus to receive the signal using the full antenna array in response to the best MIMO value being lower than a value of the corresponding threshold value.

9. The apparatus of any of claims 5, 6, and 8, wherein the MIMO performance of the sub-section is configured to be measured based on a received reference signal.

10. The apparatus of any of claims 1-2, 4-6, and 8, wherein the alignment of the antenna elements in the second sub-section (604) is substantially offset by 45° from the alignment of the antenna elements in the first sub-section (602).

11. The apparatus of any of claims 1-2, 4-6, and 8, wherein the antenna elements of the first sub-section (602) are adjacent to each other and the antenna elements of the second sub-section (604) are adjacent to each other.

12. The apparatus of any of claims 1-2, 4-6, and 8, wherein the antenna elements of the first sub-section (602) are at least partially interleaved with the antenna elements of the second sub-section (604).

13. A method for communication, comprising: The method comprises: - determining (700) a value of at least one quality metric for a received multiple input multiple output (MIMO) signal; - comparing (702) the determined value of the at least one quality metric to a corresponding threshold value; - determining, based on a result of the comparison of the value of the at least one quality metric, whether to use (704) a full antenna array comprising a plurality of antenna elements or (706) a first sub-section of the full antenna array comprising a first sub-section of the plurality of antenna elements or a second sub-section of the full antenna array comprising a second sub-section of the plurality of antenna elements, wherein an alignment of the antenna elements in the second sub-section is substantially offset by 30° to 60° from an alignment of the antenna elements in the first sub-section, for receiving the signal.

14. An apparatus for communication, the apparatus comprising: The apparatus comprises at least one processor and at least one memory, the at least one memory stored with computer program code thereon, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform: - determining (700) a value of at least one quality metric for a received multiple input multiple output (MIMO) signal; - comparing (702) the determined value of the at least one quality metric to a value of a corresponding threshold value; - determining, based on a result of the comparison of the value of the at least one quality metric, whether to use (704) a full antenna array comprising a plurality of antenna elements or (706) a first sub-section of the full antenna array comprising a first sub-section of the plurality of antenna elements or a second sub-section of the full antenna array comprising a second sub-section of the plurality of antenna elements, wherein an alignment of the antenna elements in the second sub-section is substantially offset by 30° to 60° from an alignment of the antenna elements in the first sub-section, for receiving the signal. - based on a result of the comparison of the values of the at least one quality measure, determining whether to use (704) a full antenna array comprising a plurality of antenna elements or (706) a first sub-portion of the full antenna array comprising a first sub-section of the plurality of antenna elements or a second sub-portion of the full antenna array comprising a second sub-section of the plurality of antenna elements, wherein an alignment of the antenna elements in the second sub-portion substantially deviates from an alignment of the antenna elements in the first sub-portion by 30° to 60° for receiving the signal.

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