Uplink passive intermodulation (PIM) intrinsic canceller

Abstract

A method and network node for uplink passive intermodulation (PIM) intrinsic cancellation are disclosed. According to one aspect, a method in a network node includes determining an uplink PIM covariance matrix. The method further includes determining an uplink PIM signal subspace matrix based at least in part on the eigen decomposition of the uplink PIM covariance matrix, the uplink PIM signal subspace matrix spanned into an uplink PIM signal subspace. The method further includes determining a residual uplink signal vector that at least partially compensates for the PIM based at least in part on a spatial projection of the total received uplink signal vector onto the uplink PIM signal subspace.

Description

Technical Field

[0001] The present disclosure relates to wireless communications and, more particularly, to an uplink passive intermodulation (PIM) intrinsic canceller. Background Art

[0002] The 3rd Generation Partnership Project (3GPP) has developed and is developing standards for fourth generation (4G) (also known as Long Term Evolution (LTE)) and fifth generation (5G) (also known as New Radio (NR)) wireless communication systems. These systems provide, among other things, broadband communications between network nodes such as base stations and mobile wireless devices (WDs), as well as communications between network nodes and between WDs. Sixth generation (6G) wireless communication systems are also under development.

[0003] As cellular radio sites transmit an increasing number of downlink channels, Passive Inter-Modulation (PIM) becomes a significant concern for cellular operators. A further challenge is that the newly introduced radio channels belong to an increasing number of radio frequency bands, which increases the chances of PIM desensitizing the uplink receiver.

[0004] Traditional techniques include sending technicians to cell sites to try to reduce PIM signal sources, and PIM-Cancellation technology, which uses active noise reduction principles to adjust nonlinear models in real time to subtract a time-domain copy of the PIM signal from the received waveform of each antenna.

[0005] The problem with time-domain PIM cancellation techniques is that the number of nonlinear terms that must be generated depends on the following parameters:

[0006] Downlink (DL) signal combination (DL antenna, polarization, frequency, delay signal cross terms);

[0007] ● Number of uplink (UL) antennas;

[0008] ●UL channel number

[0009] ● The order of nonlinearity; and

[0010] • The number of intermodulation (IM) bands involved.

[0011] For certain parameter combinations, the number of nonlinear terms that must be generated grows exponentially. Furthermore, these nonlinear terms must be generated at a much larger sampling rate to avoid spectral aliasing, which results in very large implementation costs that may prohibit the use of this technique in antenna arrays.

[0012] The problem with sending a technician to a cell site is that it is expensive, and PIM issues with active antenna systems (AAS) are not always resolved. In fact, in some cases dictated by the beamforming weights, the larger antenna gain may excite PIM sources that cannot be removed from the environment, such as lamp posts or metal handrails. In this case, some active PIM mitigation techniques must be used. Summary of the invention

[0013] Some embodiments advantageously provide a method and network node for an uplink passive intermodulation (PIM) eigencanceller.

[0014] Some embodiments described herein mitigate PIM by steering an uplink null in the antenna domain of an AAS radio. This PIM null steering can be done independently in the radio without interacting with the baseband receiver algorithm.

[0015] Some embodiments include an uplink PIM spatial avoidance method in which nulls are steered in an antenna field of a large antenna array.

[0016] Some advantages of some embodiments of the PIM intrinsic canceller disclosed herein may include one or more of the following:

[0017] Some PIM intrinsic canceller methods disclosed in this paper are insensitive to the following parameters:

[0018] ■The order of the nonlinear terms involved;

[0019] ■The number of DL signal combinations (polarization, frequency, delayed signal cross terms); and

[0020] ■The number of intermodulation bands involved.

[0021] ● Some of the PIM intrinsic canceller methods disclosed in this article are implemented at baseband rates, which helps keep the implementation cost low. The complexity of the nulling actuator scales linearly with the bandwidth and the number of antenna ports:

[0022] ■The complexity of the eigendecomposition of the covariance matrix and However, the refresh rate of the PIM eigenvectors may be much lower than the NR / LTE orthogonal frequency division multiplexing (OFDM) symbol rate. Therefore, in some embodiments, the PIM eigenvector acquisition has a lower relative computational cost than the null steering actuator; and / or

[0023] • Scalability: Some algorithms disclosed herein can be configured to support a variety of deployment scenarios (ie, different numbers of antenna ports and UL channels).

[0024] According to one aspect, a method in a network node is provided. The method includes determining an uplink passive intermodulation (PIM) covariance matrix. The method also includes determining an uplink PIM signal subspace matrix based at least in part on an eigendecomposition of the uplink PIM covariance matrix, wherein the uplink PIM signal subspace matrix spans an uplink PIM signal subspace. The method also includes determining a residual uplink signal vector that at least partially compensates for PIM based at least in part on a spatial projection of a total received uplink signal vector onto the uplink PIM signal subspace.

[0025] According to this aspect, in some embodiments, the residual uplink signal vector is based at least in part on the product of a PIM eigencancellation matrix and a total received uplink signal vector, wherein the PIM eigencancellation matrix is ​​determined at least in part based on the difference between an identity matrix and a first matrix product obtained by multiplying an uplink PIM signal subspace matrix by a Hermitian transpose of the uplink PIM signal subspace matrix. In some embodiments, determining the uplink PIM signal subspace matrix is ​​performed less frequently than determining the residual uplink signal vector. In some embodiments, determining the residual uplink signal vector is performed before a transformation from antenna space to beam space. In some embodiments, determining the residual uplink signal vector is performed after a transformation from antenna space to beam space. In some embodiments, each column of the uplink PIM signal subspace matrix is ​​a PIM eigenvector determined according to one of a singular value decomposition and a heuristic decomposition of an uplink PIM covariance matrix. In some embodiments, the residual uplink signal vector is determined in the time domain using a channel bandwidth allocated for communication with at least one wireless device. In some embodiments, the residual uplink signal vector is determined in the frequency domain using a bandwidth equal to or less than a channel bandwidth allocated for communication with the at least one wireless device. In some embodiments, determining the uplink PIM signal subspace matrix is ​​performed separately for each of a plurality of polarizations of an antenna of the network node. In some embodiments, determining the uplink PIM signal subspace matrix is ​​performed in a radio unit of the network node.

[0026] According to another aspect, a network node includes a processing circuit configured to: determine an uplink passive intermodulation (PIM) covariance matrix; determine an uplink PIM signal subspace matrix based at least in part on an eigendecomposition of the uplink PIM covariance matrix, wherein the uplink PIM signal subspace matrix spans an uplink PIM signal subspace; and determine a residual uplink signal vector that at least partially compensates for PIM based at least in part on a spatial projection of a total received uplink signal vector onto the uplink PIM signal subspace.

[0027] According to this aspect, in some embodiments, the residual uplink signal vector is based at least in part on the product of a PIM eigencancellation matrix and a total received uplink signal vector, wherein the PIM eigencancellation matrix is ​​determined at least in part based on the difference between an identity matrix and a first matrix product obtained by multiplying an uplink PIM signal subspace matrix by a Hermitian transpose of the uplink PIM signal subspace matrix. In some embodiments, determining the uplink PIM signal subspace matrix is ​​performed less frequently than determining the residual uplink signal vector. In some embodiments, determining the residual uplink signal vector is performed before a transformation from antenna space to beam space. In some embodiments, determining the residual uplink signal vector is performed after a transformation from antenna space to beam space. In some embodiments, each column of the uplink PIM signal subspace matrix is ​​a PIM eigenvector determined according to one of a singular value decomposition and a heuristic decomposition of an uplink PIM covariance matrix. In some embodiments, the residual uplink signal vector is determined in the time domain using a channel bandwidth allocated for communication with at least one wireless device. In some embodiments, the residual uplink signal vector is determined in the frequency domain using a bandwidth equal to or less than a channel bandwidth allocated for communication with the at least one wireless device. In some embodiments, determining the uplink PIM signal subspace matrix is ​​performed separately for each of a plurality of polarizations of an antenna of the network node. In some embodiments, determining the uplink PIM signal subspace matrix is ​​performed in a radio unit of the network node.

[0028] According to another aspect, a method in a network node includes determining an uplink passive intermodulation (PIM) covariance matrix. The method also includes determining an uplink PIM signal subspace matrix based at least in part on identifying diagonal elements in the uplink PIM covariance matrix whose power exceeds a first threshold. When the number of identified diagonal elements is below a second threshold, the method includes determining a residual uplink signal vector by attenuating elements of a total received uplink signal vector corresponding to the identified diagonal elements.

[0029] According to this aspect, in some embodiments, determining the uplink PIM signal subspace matrix is ​​performed less frequently than determining the residual uplink signal vector. In some embodiments, determining the residual uplink signal vector is performed before the transformation from antenna space to beam space. In some embodiments, determining the residual uplink signal vector is performed after the transformation from antenna space to beam space. In some embodiments, the residual uplink signal vector is determined in the time domain using a channel bandwidth allocated for communication with at least one wireless device. In some embodiments, the residual uplink signal vector is determined in the frequency domain using a bandwidth equal to or less than the channel bandwidth allocated for communication with at least one wireless device. In some embodiments, determining the uplink PIM signal subspace matrix is ​​performed separately for each of a plurality of polarizations of an antenna of a network node. In some embodiments, determining the uplink PIM signal subspace matrix is ​​performed in a radio unit of the network node.

[0030] According to yet another aspect, a network node includes processing circuitry configured to: determine an uplink passive intermodulation (PIM) covariance matrix; determine an uplink PIM signal subspace matrix based at least in part on identifying diagonal elements in the uplink PIM covariance matrix having power exceeding a first threshold; and determine a residual uplink signal vector by attenuating elements of a total received uplink signal vector corresponding to the identified diagonal elements when the number of identified diagonal elements is below a second threshold.

[0031] According to this aspect, in some embodiments, determining the uplink PIM signal subspace matrix is ​​performed less frequently than determining the residual uplink signal vector. In some embodiments, determining the residual uplink signal vector is performed before the transformation from antenna space to beam space. In some embodiments, determining the residual uplink signal vector is performed after the transformation from antenna space to beam space. In some embodiments, the residual uplink signal vector is determined in the time domain using a channel bandwidth allocated for communication with at least one wireless device. In some embodiments, the residual uplink signal vector is determined in the frequency domain using a bandwidth equal to or less than the channel bandwidth allocated for communication with at least one wireless device. In some embodiments, determining the uplink PIM signal subspace matrix is ​​performed separately for each of a plurality of polarizations of an antenna of a network node. In some embodiments, determining the uplink PIM signal subspace matrix is ​​performed in a radio unit of the network node. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Embodiments of the present invention and their attendant advantages and features will be more readily understood with reference to the following detailed description in conjunction with the accompanying drawings:

[0033] Figure 1 is a schematic diagram of an example network architecture illustrating a communication system connected to a host through an intermediate network according to the principles of the present disclosure;

[0034] Figure 2 is a block diagram of a host communicating with a wireless device via a network node through an at least partially wireless connection according to some embodiments of the present disclosure;

[0035] Figure 3 is a flow chart illustrating an example method for executing a client application at a wireless device implemented in a communication system including a host, a network node, and a wireless device according to some embodiments of the present disclosure;

[0036] Figure 4 is a flow chart illustrating an example method for receiving user data at a wireless device implemented in a communication system including a host, a network node, and a wireless device according to some embodiments of the present disclosure;

[0037] Figure 5 is a flow chart illustrating an example method for receiving user data from a wireless device at a host, implemented in a communication system including a host, a network node, and a wireless device, according to some embodiments of the present disclosure;

[0038] Figure 6 is a flow chart illustrating an example method for receiving user data at a host implemented in a communication system including a host, a network node, and a wireless device according to some embodiments of the present disclosure;

[0039] Figure 7 is a flow chart of an example process for performing uplink passive intermodulation (PIM) intrinsic cancellation in a network node according to the principles described herein;

[0040] Figure 8 is a flow chart of another example process for performing uplink PIM intrinsic cancellation in a network node according to the principles described herein; and

[0041] Fig. 9 is a schematic diagram showing the projection of an uplink reception vector onto an uplink PIM signal subspace. DETAILED DESCRIPTION

[0042] Before describing the exemplary embodiment in detail, it should be noted that the present embodiment mainly relates to a combination of device components and processing steps related to an uplink passive intermodulation (PIM) intrinsic canceller. Therefore, in the accompanying drawings, the components have been appropriately represented by conventional symbols, and only specific details relevant to understanding the present embodiment are shown to avoid obscuring the content of the present disclosure with details that are obvious to those of ordinary skill in the art who benefit from the description herein. Throughout the description, the same numbers refer to the same elements.

[0043] As used herein, relational terms, such as "first" and "second", "top" and "bottom", etc., are used only to distinguish one entity or element from another entity or element, without necessarily requiring or implying any physical or logical relationship or order between such entities or elements. The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the concepts described herein. As used herein, the singular forms "one", "an", and "the" are also intended to include the plural forms unless the context clearly indicates otherwise. It will be further understood that the terms "comprising", "comprising", "including", and / or "comprising" when used herein specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0044] In the embodiments described herein, connection terms "in communication with" and the like may be used to indicate electrical or data communication, which may be achieved, for example, by physical contact, induction, electromagnetic radiation, radio signals, infrared signals, or optical signals. Those of ordinary skill in the art will appreciate that multiple components may interoperate, and modifications and variations in achieving electrical and data communications are possible.

[0045] In some embodiments described herein, the terms "coupled," "connected," and the like may be used herein to indicate a connection, although not necessarily a direct connection, and may include wired and / or wireless connections.

[0046] The term "network node" used in this document may be any kind of network node included in a radio network, which may further include any of the following: a base station (BS), a radio base station, a base transceiver station (BTS), a base station controller (BSC), a radio network controller (RNC), a gNode B (gNB), an evolved Node B (eNB or eNodeB), a Node B, a multi-standard radio (MSR) radio node such as an MSR BS, a multi-cell / multicast coordination entity (MCE), an integrated access and backhaul (IAB) node, a relay node, a donor node that controls a relay, a radio access point (AP), a transmission point, a transmission node, a remote radio unit (RRU) remote radio head (RRH), a core network node (e.g., a mobility management entity (MME), a self-organizing network (SON) node, a coordination node, a positioning node, an MDT node, etc.), an external node (e.g., a third-party node, a node outside the current network), a node in a distributed antenna system (DAS), a spectrum access system (SAS) node, an element management system (EMS), etc. The term "radio node" as used herein may also be used to denote a wireless device (WD) or a radio network node such as a wireless device (WD).

[0047] In some embodiments, non-limiting terms wireless device (WD) or user equipment (UE) are used interchangeably. WD herein can be any type of wireless device capable of communicating with a network node or another WD via a radio signal, such as a wireless device (WD). WD can also be a radio communication device, a target device, a device-to-device (D2D) WD, a machine type WD, or a WD capable of machine-to-machine communication (M2M), a low-cost and / or low-complexity WD, a sensor equipped with a WD, a tablet computer, a mobile terminal, a smart phone, a laptop embedded equipment (LEE), a laptop mounted device (LME), a USB dongle, a customer premises equipment (CPE), an Internet of Things (IoT) device, or a narrowband IoT (NB-IOT) device, etc.

[0048] In addition, in some embodiments, the general term "radio network node" is used. It can be any type of radio network node, which may include any of a base station, a radio base station, a base transceiver station, a base station controller, a network controller, an RNC, an evolved Node B (eNB), a Node B, a gNB, a multi-cell / multicast coordination entity (MCE), an IAB node, a relay node, an access point, a radio access point, a remote radio unit (RRU), and a remote radio head (RRH).

[0049] Note that although terminology from one particular wireless system may be used in the present disclosure, such as, for example, 3GPP LTE and / or New Radio (NR), this should not be considered to limit the scope of the present disclosure to only the aforementioned systems. Other wireless systems, including but not limited to Wideband Code Division Multiple Access (WCDMA), Worldwide Interoperability for Microwave Access (WiMax), Ultra Mobile Broadband (UMB), and Global System for Mobile Communications (GSM), may also benefit from utilizing the ideas covered by the present disclosure.

[0050] Further note that the functions described herein as being performed by a wireless device or network node may be distributed across multiple wireless devices and / or network nodes. In other words, it is contemplated that the functions of the network nodes and wireless devices described herein are not limited to being performed by a single physical device, and in fact, may be distributed across several physical devices.

[0051] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those commonly understood by those of ordinary skill in the art to which the present disclosure belongs. It will be further understood that the terms used herein should be interpreted as having a meaning consistent with their meaning in the context of this specification and the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined as such herein.

[0052] Some embodiments provide an uplink passive intermodulation (PIM) intrinsic canceller.

[0053] Referring now to the drawings, wherein like elements are represented by like reference numerals, Figure 1 , a schematic diagram of a communication system 10 according to an embodiment is shown, for example, a 3GPP-type cellular network that can support standards such as LTE and / or NR (5G), which includes an access network 12 such as a radio access network and a core network 14. The access network 12 includes a plurality of network nodes 16a, 16b, 16c (collectively referred to as network nodes 16), such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 18a, 18b, 18c (collectively referred to as coverage area 18). Each network node 16a, 16b, 16c can be connected to the core network 14 via a wired or wireless connection 20. A first wireless device (WD) 22a located in the coverage area 18a is configured to be wirelessly connected to the corresponding network node 16a, or to be paged by the corresponding network node 16a. A second WD 22b in the coverage area 18b can be wirelessly connected to the corresponding network node 16b. Although multiple WDs 22a, 22b (collectively referred to as wireless devices 22) are illustrated in this example, the disclosed embodiments are equally applicable to situations where there is only one WD in the coverage area or only one WD is connected to the corresponding network node 16. Note that although only two WDs 22 and three network nodes 16 are shown for convenience, the communication system may include more WDs 22 and network nodes 16.

[0054] Moreover, it is contemplated that the WD 22 may simultaneously and / or be configured to communicate with more than one network node 16 and more than one type of network node 16, respectively. For example, the WD 22 may have dual connectivity with a network node 16 supporting LTE and the same or different network nodes 16 supporting NR. As an example, the WD 22 may communicate with an eNB for LTE / E-UTRAN and a gNB for NR / NG-RAN.

[0055] The communication system 10 itself can be connected to a host computer 24, which can be implemented in hardware and / or software of a stand-alone server, a cloud-implemented server, a distributed server, or as a processing resource in a server farm. The host computer 24 can be under the ownership or control of a service provider, or can be operated by or on behalf of a service provider. The connections 26, 28 between the communication system 10 and the host computer 24 can extend directly from the core network 14 directly to the host computer 24, or can extend via an optional intermediate network 30. The intermediate network 30 can be one or more combinations of public, private, or managed networks. If present, the intermediate network 30 can be a backbone network or the Internet. In some embodiments, the intermediate network 30 can include two or more subnetworks (not shown).

[0056] Figure 1 The communication system as a whole realizes the connectivity between one of the connected WD 22a, 22b and the host computer 24. The connectivity can be described as being connected over the top (over-the-top, OTT). The host computer 24 and the connected WD 22a, 22b are configured to use the access network 12, the core network 14, any intermediate network 30 and possible other infrastructure (not shown) as intermediaries to communicate data and / or signaling via the OTT connection. The OTT connection can be transparent in the sense that at least some of the devices participating in the communication through which the OTT connection passes do not know the routes of the uplink and downlink communications. For example, the network node 16 may not be or need not be informed about the route passed by the incoming downlink communication, which has data from the host computer 24 to be forwarded (e.g., handed over) to the connected WD 22a. Similarly, the network node 16 does not need to know the future route of the outgoing uplink communication from the WD 22a to the host computer 24.

[0057] The network node 16 is configured to include a PIM eigencanceller 32 configured to determine a residual uplink signal vector that at least partially compensates for PIM based at least in part on a spatial projection of the total received uplink signal vector onto an uplink PIM signal subspace.

[0058] Now refer to Figure 2An example implementation of the WD 22, network node 16, and host computer 24 discussed in the previous paragraphs according to an embodiment is described. In the communication system 10, the host computer 24 includes hardware (HW) 38, which includes a communication interface 40, which is configured to establish and maintain a wired or wireless connection with the interface of different communication devices of the communication system 10. The host computer 24 also includes a processing circuit 42, which may have storage and / or processing capabilities. The processing circuit 42 may include a processor 44 and a memory 46. In particular, in addition to or instead of a processor and a memory such as a central processing unit, the processing circuit 42 may include an integrated circuit for processing and / or control, for example, one or more processors and / or processor cores and / or FPGAs (field programmable gate arrays) and / or ASICs (application-specific integrated circuits) suitable for executing instructions. The processor 44 may be configured to access (e.g., write to and / or read from) a memory 46, which may include any type of volatile and / or non-volatile memory, such as cache memory and / or buffer memory and / or RAM (random access memory) and / or ROM (read only memory) and / or optical memory and / or EPROM (erasable programmable read-only memory).

[0059] Processing circuitry 42 may be configured to control any of the methods and / or processes described herein and / or cause such methods and / or processes to be performed, for example, by host computer 24. Processor 44 corresponds to one or more processors 44 for performing the functions of host computer 24 described herein. Host computer 24 includes memory 46 configured to store data, programming software code, and / or other information described herein. In some embodiments, software 48 and / or host application 50 may include instructions that, when executed by processor 44 and / or processing circuitry 42, cause processor 44 and / or processing circuitry 42 to perform the processes described herein with respect to host computer 24. The instructions may be software associated with host computer 24.

[0060] The software 48 may be executed by the processing circuit 42. The software 48 includes a host application 50. The host application 50 is operable to provide services to a remote user, such as a WD 22 connected via an OTT connection 52 terminated at the WD 22 and the host computer 24. When providing services to a remote user, the host application 50 may provide user data sent using the OTT connection 52. "User data" may be data and information described herein as implementing the described functions. In one embodiment, the host computer 24 may be configured to provide control and functionality to a service provider, and may be operated by or on behalf of the service provider. The processing circuit 42 of the host computer 24 may enable the host computer 24 to observe, monitor, control, send and / or receive from the network node 16 and / or the wireless device 22 to the network node 16 and / or the wireless device 22.

[0061] The communication system 10 also includes a network node 16 provided in the communication system 10, and includes hardware 58 that enables it to communicate with the host computer 24 and the WD 22. The hardware 58 may include a communication interface 60 for establishing and maintaining a wired or wireless connection to the interface of different communication devices of the communication system 10, and a radio interface 62 for establishing and maintaining at least a wireless connection 64 with the WD 22 located in the coverage area 18 served by the network node 16. The radio interface 62 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and / or one or more RF transceivers. The communication interface 60 may be configured to facilitate a connection 66 to the host computer 24. The connection 66 may be direct, or it may be through the core network 14 of the communication system 10 and / or through one or more intermediate networks 30 external to the communication system 10.

[0062] In the illustrated embodiment, the hardware 58 of the network node 16 also includes a processing circuit 68. The processing circuit 68 may include a processor 70 and a memory 72. In particular, in addition to or in place of a processor such as a central processing unit and a memory, the processing circuit 68 may include an integrated circuit for processing and / or control, for example, one or more processors and / or processor cores and / or an FPGA (field programmable gate array) and / or an ASIC (application-specific integrated circuit) adapted to execute instructions. The processor 70 may be configured to access (e.g., write and / or read) the memory 72, which may include any kind of volatile and / or non-volatile memory, for example, a cache and / or buffer memory and / or a RAM (random access memory) and / or a ROM (read-only memory) and / or an optical memory and / or an EPROM (erasable programmable read-only memory).

[0063] Therefore, the network node 16 also has software 74 stored internally, for example, in the memory 72 or stored in an external memory (e.g., a database, a storage array, a network storage device, etc.) accessible by the network node 16 via an external connection. The software 74 can be executed by the processing circuit 68. The processing circuit 68 can be configured to control any of the methods and / or processes described herein and / or cause such methods and / or processes to be performed, for example, by the network node 16. The processor 70 corresponds to one or more processors 70 for performing the network node 16 functions described herein. The memory 72 is configured to store data, programming software code, and / or other information described herein. In some embodiments, the software 74 may include instructions that, when executed by the processor 70 and / or the processing circuit 68, cause the processor 70 and / or the processing circuit 68 to perform the processes described herein with respect to the network node 16. For example, the processing circuit 68 of the network node 16 may include a PIM intrinsic canceller 32 that is configured to determine a residual uplink signal vector that at least partially compensates for PIM based at least in part on a spatial projection of a total received uplink signal vector onto an uplink PIM signal subspace.

[0064] The communication system 10 also includes the already mentioned WD 22. The WD 22 may have hardware 80, which may include a radio interface 82 configured to establish and maintain a wireless connection 64 with a network node 16 serving the coverage area 18 in which the WD 22 is currently located. The radio interface 82 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and / or one or more RF transceivers.

[0065] The hardware 80 of the WD 22 also includes a processing circuit 84. The processing circuit 84 may include a processor 86 and a memory 88. In particular, in addition to or in place of a processor and a memory such as a central processing unit, the processing circuit 84 may include an integrated circuit for processing and / or control, for example, one or more processors and / or processor cores and / or an FPGA (field programmable gate array) and / or an ASIC (application-specific integrated circuit) adapted to execute instructions. The processor 86 may be configured to access (e.g., write and / or read) a memory 88, which may include any kind of volatile and / or non-volatile memory, for example, a cache and / or buffer memory and / or a RAM (random access memory) and / or a ROM (read-only memory) and / or an optical memory and / or an EPROM (erasable programmable read-only memory).

[0066] Therefore, WD 22 may also include software 90, which is stored in, for example, a memory 88 at WD 22, or in an external memory (e.g., a database, a storage array, a network storage device, etc.) accessible by WD 22. Software 90 may be executed by processing circuit 84. Software 90 may include client application 92. With the support of host computer 24, client application 92 is operable to provide services to human or non-human users through WD 22. In host computer 24, the executing host application 50 may communicate with the executing client application 92 via an OTT connection 52 terminated at WD 22 and host computer 24. When providing services to users, client application 92 may receive request data from host application 50 and provide user data in response to the request data. OTT connection 52 may transmit both request data and user data. Client application 92 may interact with users to generate user data provided by them.

[0067] The processing circuit 84 can be configured to control any method and / or process described herein and / or cause such method and / or process to be performed, for example, by the WD 22. The processor 86 corresponds to one or more processors 86 for performing the WD 22 functions described herein. The WD 22 includes a memory 88, which is configured to store data, programming software code, and / or other information described herein. In some embodiments, the software 90 and / or the client application 92 may include instructions that, when executed by the processor 86 and / or the processing circuit 84, cause the processor 86 and / or the processing circuit 84 to perform the process described herein with respect to the WD 22.

[0068] In some embodiments, the internal workings of network node 16, WD 22, and host computer 24 may be as follows: Figure 2 shown, and independently, the surrounding network topology can be Figure 1 network topology.

[0069] exist Figure 2 , the OTT connection 52 has been abstractly drawn to illustrate the communication between the host computer 24 and the wireless device 22 via the network node 16, without explicitly involving any intermediate devices and the precise routing of the messages via these devices. The network infrastructure can determine the routing, which can be configured to be hidden from the WD 22 or from the service provider operating the host computer 24, or from both. When the OTT connection 52 is active, the network infrastructure can further make decisions by which it dynamically changes the routing (e.g., based on load balancing considerations or reconfiguration of the network).

[0070] The wireless connection 64 between the WD 22 and the network node 16 is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improves the performance of the OTT service provided to the WD 22 using the OTT connection 52, where the wireless connection 64 can form the last leg. More specifically, the teachings of some of these embodiments can improve data rates, latency, and / or power consumption, and thereby provide benefits such as reduced user latency, relaxed file size restrictions, better responsiveness, extended battery life, etc.

[0071] In some embodiments, a measurement process may be provided for the purpose of monitoring data rates, latency, and other factors improved by one or more embodiments. There may also be an optional network function for reconfiguring the OTT connection 52 between the host computer 24 and the WD 22 in response to changes in the measurement results. The measurement process and / or network function for reconfiguring the OTT connection 52 may be implemented in the software 48 of the host computer 24 or in the software 90 of the WD 22 or in both. In an embodiment, a sensor (not shown) may be deployed in or associated with a communication device through which the OTT connection 52 passes; the sensor may participate in the measurement process by providing the value of the monitoring quantity exemplified above or providing the value of other physical quantities from which the software 48, 90 can calculate or estimate the monitoring quantity. The reconfiguration of the OTT connection 52 may include message formats, retransmission settings, preferred routes, etc.; the reconfiguration does not need to affect the network node 16, and it may be unknown or imperceptible to the network node 16. Some such programs and functions may be known and implemented in the art. In some embodiments, the measurement may involve proprietary WD signaling that facilitates the host computer 24 to measure throughput, propagation time, latency, etc. In some embodiments, measurements may be made as the software 48 , 90 uses the OTT connection 52 to cause messages to be transmitted, particularly empty or “dummy” messages, while monitoring propagation times, errors, etc.

[0072] Thus, in some embodiments, the host computer 24 includes processing circuitry 42 configured to provide user data and a communication interface 40 configured to forward the user data to a cellular network for transmission to the WD 22. In some embodiments, the cellular network also includes a network node 16 having a radio interface 62. In some embodiments, the network node 16 is configured to and / or the processing circuitry 68 of the network node 16 is configured to perform the functions and / or methods described herein for preparing / initiating / maintaining / supporting / ending transmissions to the WD 22, and / or preparing / terminating / maintaining / supporting / ending reception of transmissions from the WD 22.

[0073] In some embodiments, host computer 24 includes processing circuitry 42 and communication interface 40 configured to receive user data originating from a transmission from WD 22 to network node 16. In some embodiments, WD 22 is configured as and / or includes a radio interface 82 and / or processing circuitry 84 configured to perform the functions and / or methods described herein for preparing / initiating / maintaining / supporting / terminating a transmission to network node 16, and / or preparing / terminating / maintaining / supporting / terminating the reception of a transmission from network node 16.

[0074] although Figure 1 and 2 Various "units" such as PIM intrinsic canceller 32 are shown within respective processors, but it is contemplated that these units may be implemented such that a portion of the unit is stored in a corresponding memory within the processing circuit. In other words, the units may be implemented within the processing circuit in the form of hardware or a combination of hardware and software.

[0075] Figure 3 is a diagram illustrating a communication system (such as, for example, Figure 1 and Figure 2 The communication system may include a host computer 24, a network node 16, and a WD 22, which may be a reference Figure 2 Those described in the present disclosure. In a first step of the method, the host computer 24 provides user data (box S100). In an optional sub-step of the first step, the host computer 24 provides the user data by executing a host application such as the host application 50 (box S102). In a second step, the host computer 24 initiates a transmission to the WD 22 carrying the user data (box S104). In an optional third step, in accordance with the teachings of the embodiments described throughout the present disclosure, the network node 16 transmits the user data carried in the transmission initiated by the host computer 24 to the WD 22 (box S106). In an optional fourth step, the WD 22 executes a client application associated with the host application 50 executed by the host computer 24, such as the client application 92 (box S108).

[0076] Figure 4 is a diagram illustrating a communication system (such as, for example, Figure 1 The communication system may include a host computer 24, a network node 16, and a WD 22, which may be a reference Figure 1 and 2Those described. In a first step of the method, the host computer 24 provides user data (box S110). In an optional sub-step (not shown), the host computer 24 provides the user data by executing a host application such as the host application 50. In a second step, the host computer 24 initiates a transmission carrying the user data to the WD 22 (box S112). According to the teachings of the embodiments described throughout the present disclosure, the transmission can be transmitted via the network node 16. In an optional third step, the WD 22 receives the user data carried in the transmission (box S114).

[0077] Figure 5 is a diagram illustrating a communication system (such as, for example, Figure 1 The communication system may include a host computer 24, a network node 16, and a WD 22, which may be a reference Figure 1 and 2 Those described. In the optional first step of the method, WD 22 receives input data provided by host computer 24 (box S116). In the optional sub-step of the first step, WD 22 executes client application 92, which provides user data in response to the received input data provided by host computer 24 (box S118). Additionally or alternatively, in the optional second step, WD 22 provides user data (box S120). In the optional sub-step of the second step, WD provides user data by executing a client application such as client application 92 (box S122). When providing user data, the executed client application 92 can further consider the user input received from the user. Regardless of the specific manner of providing user data, WD 22 can initiate the transmission of user data to host computer 24 in an optional third sub-step (box S124). In the fourth step of the method, according to the teachings of the embodiments described throughout the present disclosure, host computer 24 receives user data transmitted from WD 22 (box S126).

[0078] Figure 6 is a diagram illustrating a communication system (such as, for example, Figure 1 The communication system may include a host computer 24, a network node 16, and a WD 22, which may be referenced Figure 1 and 2In an optional first step of the method, in accordance with the teachings of the embodiments described throughout the present disclosure, the network node 16 receives user data from the WD 22 (block S128). In an optional second step, the network node 16 initiates transmission of the received user data to the host computer 24 (block S130). In a third step, the host computer 24 receives the user data carried in the transmission initiated by the network node 16 (block S132).

[0079] Figure 7 1 is a flowchart of an example process in a network node 16 for uplink passive intermodulation (PIM) eigencancellation. One or more blocks described herein may be performed by one or more elements of the network node 16, such as by one or more of the processing circuit 68 (including the PIM eigencanceller 32), the processor 70, the radio interface 62, and / or the communication interface 60. The network node 16 is configured to determine an uplink passive intermodulation PIM covariance matrix (block S134), such as via the processing circuit 68 and / or the processor 70 and / or the radio interface 62 and / or the communication interface 60. The process also includes determining an uplink PIM signal subspace matrix based at least in part on an eigendecomposition of the uplink PIM covariance matrix, the uplink PIM signal subspace matrix spanning an uplink PIM signal subspace (block S136). The process also includes determining a residual uplink signal vector that at least partially compensates for PIM based at least in part on a spatial projection of the total received uplink signal vector onto the uplink PIM signal subspace (block S138).

[0080] In some embodiments, the residual uplink signal vector is based at least in part on a product of a PIM eigencancellation matrix and a total received uplink signal vector, the PIM eigencancellation matrix being determined at least in part based on a difference between an identity matrix and a first matrix product obtained by multiplying an uplink PIM signal subspace matrix by a Hermitian transpose of the uplink PIM signal subspace matrix. In some embodiments, determining the uplink PIM signal subspace matrix is ​​performed less frequently than determining the residual uplink signal vector. In some embodiments, determining the residual uplink signal vector is performed before a transformation from antenna space to beam space. In some embodiments, determining the residual uplink signal vector is performed after a transformation from antenna space to beam space. In some embodiments, each column of the uplink PIM signal subspace matrix is ​​a PIM eigenvector determined according to one of the singular value decompositions of the uplink PIM covariance matrix. In some embodiments, the residual uplink signal vector is determined in the time domain using a channel bandwidth allocated for communication with at least one wireless device. In some embodiments, the residual uplink signal vector is determined in the frequency domain using a bandwidth equal to or less than a channel bandwidth allocated for communication with the at least one wireless device. In some embodiments, determining the uplink PIM signal subspace matrix is ​​performed separately for each of a plurality of polarizations of an antenna of the network node. In some embodiments, determining the uplink PIM signal subspace matrix is ​​performed in a radio unit of the network node.

[0081] Figure 8 1 is a flowchart of another example process for uplink passive intermodulation (PIM) intrinsic cancellation in the network node 16. One or more blocks described herein may be performed by one or more elements of the network node 16, such as by one or more of the processing circuit 68 (including the PIM intrinsic canceller 32), the processor 70, the radio interface 62 and / or the communication interface 60. The network node 16 is configured to determine an uplink passive intermodulation PIM covariance matrix (block S140), for example, via the processing circuit 68 and / or the processor 70 and / or the radio interface 62 and / or the communication interface 60. The method also includes determining an uplink PIM signal subspace matrix (block S142) based at least in part on identifying diagonal elements in the uplink PIM covariance matrix whose power exceeds a first threshold. When the number of identified diagonal elements is below a second threshold, the method includes determining a residual uplink signal vector (block S144) by attenuating an element of the total received uplink signal vector corresponding to the identified diagonal element.

[0082] In some embodiments, determining the uplink PIM signal subspace matrix is ​​performed less frequently than determining the residual uplink signal vector. In some embodiments, determining the residual uplink signal vector is performed before the transformation from antenna space to beam space. In some embodiments, determining the residual uplink signal vector is performed after the transformation from antenna space to beam space. In some embodiments, the residual uplink signal vector is determined in the time domain using a channel bandwidth allocated for communication with at least one wireless device. In some embodiments, the residual uplink signal vector is determined in the frequency domain using a bandwidth equal to or less than the channel bandwidth allocated for communication with at least one wireless device. In some embodiments, determining the uplink PIM signal subspace matrix is ​​performed separately for each of the multiple polarizations of the antenna of the network node. In some embodiments, determining the uplink PIM signal subspace matrix is ​​performed in a radio unit of the network node. Having described the general processing flow of the arrangement of the present disclosure and provided examples of hardware and software arrangements for implementing the processes and functions of the present disclosure, the following section provides details and examples of arrangements for uplink passive intermodulation (PIM) eigencancellation.

[0083] Some embodiments provide a base station with N antennas. The total received uplink signal vector Up to four contributions can be included, as shown in equation (1):

[0084] r UL =r UE +r intercell +r PIM +r noise (1)

[0085] in:

[0086] ● is the contribution vector of the scheduled WD;

[0087] ● is the total interference vector from WDs belonging to neighboring cells;

[0088] ● is the PIM vector; and

[0089] ● is the noise vector.

[0090] Total received uplink signal covariance matrix can be expressed as:

[0091]

[0092] in:

[0093] ● E[·] is the mathematical expectation operator; and

[0094] ●(·) H is the Hermitian transpose operator.

[0095] R UL The eigendecomposition of the covariance matrix can be similar to the following form:

[0096]

[0097] in:

[0098] ● Eigenvectors corresponding to the K scheduled WDs;

[0099] ● is a matrix containing the M inter-cell interference eigenvectors;

[0100] ● Corresponding to P PIM eigenvectors;

[0101] ● is the noise subspace;

[0102] Σ UE is a K×K diagonal matrix whose diagonal elements are the eigenvalues ​​λ of the K scheduled uplink WDs 0 ,…,λ K-1 ;

[0103] ●∑ intercell It is an M×M diagonal matrix, and the diagonal elements are the M inter-cell interference eigenvalues ​​λ K ,…,λ K+M-1 ;

[0104] Σ PIM It is a P×P diagonal matrix, and the diagonal elements are the P small-interval interference eigenvalues ​​λ K+M ,…,λ K+M+P-1 ;as well as

[0105] ●∑ NOise is a (NKMP)×(NKMP) diagonal matrix, with the diagonal elements being the (NKMP) noise eigenvalues ​​λ K+M+P ,…,λ N-1 .

[0106] Uplink PIM covariance matrix R PIM This may be obtained using known methods via the radio interface 62 and processing circuitry 68 (including the PIM intrinsic canceller 32), as summarized below:

[0107] ● Method 1: A method that can be used when transmitting downlink signals but no user is scheduled in the uplink:

[0108] ■ The uplink received signal covariance matrix is ​​formed according to formula (2). It should be noted that OFDM resource elements used for initial access (such as the physical random access channel (PRACH)) may not be included in this averaging process;

[0109] ■R UL The covariance matrix contains the following: noise, all interference sources including PIM, inter-cell interference, and any other interference;

[0110] ■ Assuming that a PIM problem exists at the cell site and the averaging process (continuous or intermittent) covers a sufficiently long period of time, the dominant intrinsic components should represent the PIM contribution; and

[0111] ■R generated by this process UL The covariance matrix can then be used as an estimate of the PIM covariance matrix

[0112] ● Method 2: A method that uses the change in the DL covariance matrix (caused by power or precoder changes) to capture the ULPIM covariance matrix. For example, such a change occurs when a high-power DL symbol is followed by a low-power DL symbol in the same transmission time interval (TTI). In the uplink of two consecutive symbols, the contributions from scheduled users, inter-cell interference, and noise may be similar. Therefore, the PIM covariance matrix can be estimated by calculating the difference between the two covariance matrices on these two symbols, as shown in equation (4):

[0113]

[0114] ● Approach 3: A method that implements a “per-antenna” PIM covariance matrix capture approach (on frequency domain subcarriers) using partially occupied uplink physical resource blocks (PRBs). At different and staggered time instances, the base station receives the UL signal over the entire frequency band. At each moment, i.e., OFDM symbol, only part of the frequency band can be filled with user traffic. This can be used to formulate a cost function that, when solved, reveals some frequency domain PIM cancellation weights that can be applied to each antenna branch separately.

[0115] The above-described PIM covariance matrix acquisition method can use part of the allocated bandwidth in any given uplink TTI, reserving only the PRBs for which no users are scheduled to perform their processing.

[0116] Estimated uplink PIM covariance matrix The eigendecomposition may be performed by the PIM eigencanceller 32 to produce an estimated uplink PIM signal subspace formed by horizontally stacking P PIM eigenvectors

[0117] The contribution of the PIM sources, i.e. their received signals in the antenna domain, corresponds to the total received signal r UL To the estimated PIM signal subspace The projection on Fig. 9 As shown:

[0118]

[0119] The residual produced by subtracting the estimated PIM contribution from the total received signal corresponds to the estimated vector of WD, inter-cell interference and noise from the schedule:

[0120]

[0121] Where I is the N×N identity matrix. The spatial projection of formula (6) is called the PIM eigeneliminator.

[0122] In some embodiments, the PIM eigencanceller 32 may be implemented before any antenna space to beam space transform, such as a spatial discrete Fourier transform (DFT).

[0123] In some embodiments, when r UL When a few elements of have much higher PIM power than the majority of elements, the PIM covariance estimation and the corresponding eigenanalysis can be omitted. These elements can be obtained from the received vector r UL In this scenario, covariance estimation and the corresponding eigenanalysis can produce similar results, but with higher complexity.

[0124] In some embodiments, the PIM intrinsic canceller 32 may be implemented in a radio unit (RU).

[0125] The PIM eigencanceller 32 may be implemented in the time domain using the entire channel bandwidth or in the frequency domain using a smaller bandwidth resolution. Additionally, the PIM eigencanceller processing may combine antennas from all polarizations, or alternatively, it may be performed separately for each antenna polarization.

[0126] In some embodiments, the PIM eigenvector refresh rate can be much slower than the NR / LTE OFDM symbol rate. Therefore, the PIM eigenvector acquisition method disclosed herein has a lower relative computational cost compared to the null steering actuator.

[0127] In some embodiments, one or more of the methods described herein may be implemented in an Open Radio Access Network (ORAN) Radio Unit (O-RU).

[0128] As will be appreciated by those skilled in the art, the concepts described herein may be embodied as methods, data processing systems, computer program products, and / or computer storage media storing executable computer programs. Therefore, the concepts described herein may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects, all of which are generally referred to herein as "circuits" or "modules". Any process, step, action, and / or functionality described herein may be performed and / or associated with a corresponding module that may be implemented in software and / or firmware and / or hardware. In addition, the present disclosure may take the form of a computer program product on a tangible computer-usable storage medium having a computer program code embodied in the medium that may be executed by a computer. Any suitable tangible computer-readable medium may be used, including a hard disk, a CD-ROM, an electronic storage device, an optical storage device, or a magnetic storage device.

[0129] Some embodiments described herein refer to flowcharts and / or block diagrams of methods, systems, and computer program products. It should be understood that each block of the flowcharts and / or block diagrams and combinations of blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer (thereby creating a special-purpose computer), a special-purpose computer, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device create instructions for implementing the flowcharts and / or block diagrams. Figure 1 A device that specifies a function / action in one or more boxes.

[0130] These computer program instructions may also be stored in a computer-readable memory or storage medium, which may guide a computer or other programmable data processing device to function in a specific manner, so that the instructions stored in the computer-readable memory generate instructions including implementing the flowchart and / or block diagram. Figure 1 An article of manufacture that instructs means for performing functions / actions specified in one or more blocks.

[0131] The computer program instructions may also be loaded onto a computer or other programmable data processing device to cause a series of operation steps to be executed on the computer or other programmable device, thereby producing a computer-implemented process, so that the instructions executed on the computer or other programmable device provide for implementing the flowchart and / or block diagram. Figure 1 One or more boxes specifying the steps of a function / action.

[0132] It should be understood that the functions / actions shown in the blocks may not occur in the order shown in the operational diagram. For example, two blocks shown in succession may actually be executed substantially simultaneously, or the blocks may sometimes be executed in reverse order depending on the functions / actions involved. Although some figures include arrows on communication paths to illustrate the primary direction of communication, it should be understood that communication may occur in the opposite direction of the arrows depicted.

[0133] Computer program code for carrying out operations of the concepts described herein can be written in Python, for example The computer program code for performing the operations of the present disclosure may be written in an object-oriented programming language such as C++ or C++. However, the computer program code for performing the operations of the present disclosure may also be written in a traditional procedural programming language such as the "C" programming language. The program code may be executed entirely on the user's computer, partially on the user's computer, partially on the user's computer as an independent software package, partially on a remote computer, or entirely on a remote computer. In the latter scenario, the remote computer may be connected to the user's computer via a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0134] Many different embodiments have been disclosed herein in conjunction with the above description and accompanying drawings. It should be understood that literally describing and illustrating every combination and subcombination of these embodiments would be overly repetitive and confusing. Therefore, all embodiments may be combined in any manner and / or combination, and this specification including the accompanying drawings should be interpreted as constituting a complete written description of all combinations and subcombinations of the embodiments described herein and the manner and process of making and using them, and should support claims to any such combination or subcombination.

[0135] Abbreviations that may be used in the preceding description include:

[0136] AAS Advanced Antenna System

[0137] DFT Discrete Fourier Transform

[0138] DL Downlink

[0139] LTE Long Term Evolution

[0140] OFDM Orthogonal Frequency Division Multiplexing

[0141] O-RU ORAN Radio Unit

[0142] NR New Radio

[0143] PIM Passive Intermodulation

[0144] PRACH Physical Random Access Channel

[0145] PRB Physical Resource Block

[0146] RU Radio Unit

[0147] TTI Transmission Time Interval

[0148] UE User Equipment

[0149] UL Uplink

[0150] WD Wireless Devices

[0151] Those skilled in the art will appreciate that the embodiments described herein are not limited to what has been specifically shown and described herein above. In addition, unless otherwise mentioned above, it should be noted that all drawings are not drawn to scale. Various modifications and variations are possible according to the above teachings without departing from the scope of the appended claims.

Claims

1. A method in a network node (16), the method comprising: Determine (S134) an uplink passive intermodulation PIM covariance matrix; Determining (S136) an uplink PIM signal subspace matrix based at least in part on an eigendecomposition of the uplink PIM covariance matrix, the uplink PIM signal subspace matrix spanning an uplink PIM signal subspace; as well as A residual uplink signal vector at least partially compensated for PIM is determined (S138) based at least in part on a spatial projection of the total received uplink signal vector onto the uplink PIM signal subspace.

2. The method of claim 1 , wherein the residual uplink signal vector is based at least in part on a product of a PIM eigencancellation matrix and the total received uplink signal vector, wherein the PIM eigencancellation matrix is ​​determined based on a difference between an identity matrix and a first matrix product obtained by multiplying the uplink PIM signal subspace matrix by the Hermitian transpose of the uplink PIM signal subspace matrix.

3. The method according to any one of claims 1 and 2, wherein determining the uplink PIM signal subspace matrix is ​​performed less frequently than determining the residual uplink signal vector.

4. The method according to any of claims 1-3, wherein determining the residual uplink signal vector is performed before the transformation from antenna space to beam space.

5. The method according to any one of claims 1-3, wherein determining the residual uplink signal vector is performed after transforming from antenna space to beam space.

6. The method according to any one of claims 1-5, wherein each column of the uplink PIM signal subspace matrix is ​​a PIM eigenvector determined according to one of a singular value decomposition and a heuristic decomposition of the uplink PIM covariance matrix.

7. The method according to any one of claims 1-6, wherein the residual uplink signal vector is determined in the time domain using a channel bandwidth allocated for communication with at least one wireless device.

8. The method of any one of claims 1-6, wherein the residual uplink signal vector is determined in the frequency domain using a bandwidth equal to or less than a channel bandwidth allocated for communication with at least one wireless device.

9. The method according to any of claims 1-8, wherein determining the uplink PIM signal subspace matrix is ​​performed separately for each of a plurality of polarizations of an antenna of the network node (16).

10. The method according to any of claims 1-9, wherein determining the uplink PIM signal subspace matrix is ​​performed in a radio unit (62) of the network node (16).

11. A network node (16), comprising a processing circuit (68) configured to: Determine the uplink passive intermodulation PIM covariance matrix; determining an uplink PIM signal subspace matrix based at least in part on an eigendecomposition of the uplink PIM covariance matrix, the uplink PIM signal subspace matrix spanning an uplink PIM signal subspace; as well as A residual uplink signal vector that at least partially compensates for PIM is determined based at least in part on a spatial projection of a total received uplink signal vector onto the uplink PIM signal subspace.

12. The network node (16) of claim 11, wherein the residual uplink signal vector is based at least in part on a product of a PIM eigencancellation matrix and the total received uplink signal vector, the PIM eigencancellation matrix being determined based on a difference between an identity matrix and a first matrix product of the uplink PIM signal subspace matrix multiplied by a Hermitian transpose of the uplink PIM signal subspace matrix.

13. The network node (16) according to any of claims 11-13, wherein determining the uplink PIM signal subspace matrix is ​​performed less frequently than determining the residual uplink signal vector.

14. The network node (16) according to any of claims 11-14, wherein determining the residual uplink signal vector is performed before the transformation from antenna space to beam space.

15. The network node (16) according to any of claims 11-14, wherein determining the residual uplink signal vector is performed after a transformation from antenna space to beam space.

16. The network node (16) according to any one of claims 11-15, wherein each column of the uplink PIM signal subspace matrix is ​​a PIM eigenvector determined according to one of a singular value decomposition and a heuristic decomposition of the uplink PIM covariance matrix.

17. The network node (16) according to any of claims 11-16, wherein the residual uplink signal vector is determined in the time domain using a channel bandwidth allocated for communication with the at least one wireless device.

18. The network node (16) according to any one of claims 11-17, wherein the residual uplink signal vector is determined in the frequency domain using a bandwidth equal to or less than a channel bandwidth allocated for communication with at least one wireless device.

19. The network node (16) according to any of claims 11-18, wherein determining the uplink PIM signal subspace matrix is ​​performed separately for each of a plurality of polarizations of an antenna of the network node (16).

20. The network node (16) according to any of claims 11-19, wherein determining the uplink PIM signal subspace matrix is ​​performed in a radio unit (62) of the network node (16).

21. A method in a network node (16), the method comprising: Determining (S140) an uplink passive intermodulation PIM covariance matrix; determining (S142) an uplink PIM signal subspace matrix based at least in part on identifying diagonal elements in the uplink PIM covariance matrix having power exceeding a first threshold; as well as When the number of identified diagonal elements is below a second threshold, a residual uplink signal vector is determined (S144) by attenuating elements of the total received uplink signal vector corresponding to the identified diagonal elements.

22. The method of claim 21, wherein determining the uplink PIM signal subspace matrix is ​​performed less frequently than determining the residual uplink signal vector.

23. The method according to any one of claims 21 and 22, wherein determining the residual uplink signal vector is performed before transforming from antenna space to beam space.

24. The method according to any of claims 21-22, wherein determining the residual uplink signal vector is performed after transforming from antenna space to beam space.

25. The method of any one of claims 21-24, wherein the residual uplink signal vector is determined in the time domain using a channel bandwidth allocated for communication with at least one wireless device.

26. The method of any one of claims 21-24, wherein the residual uplink signal vector is determined in the frequency domain using a bandwidth equal to or less than a channel bandwidth allocated for communication with at least one wireless device.

27. The method according to any of claims 21-26, wherein determining the uplink PIM signal subspace matrix is ​​performed separately for each of a plurality of polarizations of an antenna of the network node (16).

28. The method according to any of claims 21-27, wherein determining the uplink PIM signal subspace matrix is ​​performed in a radio unit (62) of the network node (16).

29. A network node (16) comprising a processing circuit (68) configured to: Determine the uplink passive intermodulation PIM covariance matrix; determining an uplink PIM signal subspace matrix based at least in part on identifying diagonal elements of the uplink PIM covariance matrix having power exceeding a first threshold; as well as When the number of identified diagonal elements is below a second threshold, a residual uplink signal vector is determined by attenuating elements of the total received uplink signal vector corresponding to the identified diagonal elements.

30. The network node (16) of claim 29, wherein determining the uplink PIM signal subspace matrix is ​​performed less frequently than determining the residual uplink signal vector.

31. The network node (16) according to any of claims 29 and 30, wherein determining the residual uplink signal vector is performed before the transformation from antenna space to beam space.

32. The network node (16) according to any of claims 29-31, wherein determining the residual uplink signal vector is performed after a transformation from antenna space to beam space.

33. The network node (16) according to any of claims 29-32, wherein the residual uplink signal vector is determined in the time domain using a channel bandwidth allocated for communication with at least one wireless device.

34. The network node (16) according to any one of claims 29-32, wherein the residual uplink signal vector is determined in the frequency domain using a bandwidth equal to or less than a channel bandwidth allocated for communication with at least one wireless device.

35. The network node (16) according to any of claims 29-34, wherein determining the uplink PIM signal subspace matrix is ​​performed separately for each of a plurality of polarizations of an antenna of the network node (16).

36. The network node (16) according to any of claims 29-35, wherein determining the uplink PIM signal subspace matrix is ​​performed in a radio unit (62) of the network node (16).

Images