EP4677752A1 - Intermodulation interference mitigation without all aggressors - Google Patents

Intermodulation interference mitigation without all aggressors

Info

Publication number
EP4677752A1
EP4677752A1 EP23712347.6A EP23712347A EP4677752A1 EP 4677752 A1 EP4677752 A1 EP 4677752A1 EP 23712347 A EP23712347 A EP 23712347A EP 4677752 A1 EP4677752 A1 EP 4677752A1
Authority
EP
European Patent Office
Prior art keywords
function
unknown
aggressors
estimate
aggressor
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP23712347.6A
Other languages
German (de)
French (fr)
Inventor
Sumedh DHABU
Mark Wyville
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Telefonaktiebolaget LM Ericsson AB
Original Assignee
Telefonaktiebolaget LM Ericsson AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telefonaktiebolaget LM Ericsson AB filed Critical Telefonaktiebolaget LM Ericsson AB
Publication of EP4677752A1 publication Critical patent/EP4677752A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06—Receivers
    • H04B1/10—Means associated with receiver for limiting or suppressing noise or interference
    • H04B1/12—Neutralising, balancing, or compensation arrangements
    • H04B1/123—Neutralising, balancing, or compensation arrangements using adaptive balancing or compensation means
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/06—Receivers
    • H04B1/16—Circuits

Definitions

  • Embodiments of the present disclosure are directed to wireless communications and, more particularly, to intermodulation interference mitigation without all aggressors.
  • BACKGROUND [0002] Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. All references to a/an/the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise.
  • Intermodulation interference is a distortion signal that is generated by passing aggressor signals through some non-linear system.
  • the distortion signal can have signal power at frequencies that fall into the frequency range where a receiver is operating. In this case the distortion signal is interference with the receiver.
  • Passive intermodulation is the intermodulation product that can occur when at least one signal passes through passive components, introducing non-linear distortion to the signals.
  • passive components may be internal components such as cables, or external components such as rusty bolts, etc.
  • the PIM power level is much lower in magnitude than the signal it originates from. Nevertheless, this becomes problematic in a cellular network when the strong transmitted signals (Tx) used for sending information to user equipment (UE) interact with PIM sources, which can introduce noise in the frequency band used to detect the weaker received signals (Rx) from UEs. This interference decreases the reliability, capacity, P106021WO01 PCT APPLICATION 2 of 32 and data rate of wireless systems.
  • the Tx signals causing PIM interference are referred to as aggressors.
  • PIM mitigation There are different approaches to PIM mitigation.
  • One mitigation method is to reduce the transmitter power to effectively lower the PIM level.
  • a drawback is the impact of reduced transmitter power on coverage and/or downlink throughput.
  • Another mitigation approach includes using expensive high-quality components to reduce the PIM generated by components of the radio unit but the PIM from surrounding environmental sources remains a problem.
  • a third mitigation option is to use the Tx and/or Rx bands from a frequency spectrum with less PIM distortions, but this is not always possible because the bands are typically licensed through auction and limited spectrum is available.
  • PIM cancellation PIMC
  • Kiayani, L. Anttila, and M. Valkama “Digital cancellation of passive intermodulation in FDD transceivers,” in 201852nd Asilomar Conference on Signals, Systems, and Computers, 2018. doi: 10.1109/ACSSC.2018.8645262 pp.1375–1381), which uses the Tx and Rx signals to create a model for the PIM source(s) that are affecting the Rx signal.
  • This model is used to create an estimated replica of the received PIM signal and subtract it from the received Rx signal to obtain a ‘cleaner’ version of the Rx signal.
  • an estimated PIM model is created using the Tx signals which cause PIM.
  • an intermodulation interference component of a received signal is represented as the product between a function of known aggressors and a function of unknown aggressors.
  • Particular embodiments described herein extract the function of unknown aggressors and uses the estimate for interference mitigation.
  • the first step is to create a de-spreading signal.
  • the de-spreading signal is representative of the inverse of the function of the known aggressors (i.e., 1/(function of known aggressors)). This mathematical operation is not numerically robust because it can result in very large numbers, which requires special handling for small values of the function of known aggressors.
  • the de-spreading signal is multiplied with the received signal.
  • This operation i) reduces the bandwidth of the intermodulation interference term to be close to the bandwidth of the function of unknown aggressors, and ii) spreads out the other components of the received signal in the frequency domain.
  • the next step is to filter this signal with a filter bandwidth that is designed to pass the function of the unknown aggressor. This will remove some of the energy that is not part of the function of unknown aggressors (function of unknown aggressors is a part of the intermodulation interference). The result is an estimate of the function of unknown aggressors.
  • This result may be further used to: i) cancel/detect the intermodulation interference component by combining this result with the function of known aggressors, and/or ii) detect level of function of unknown aggressors outside the operating frequency range of the receiver.
  • the function of the unknown aggressors is estimated from the intermodulation interference in a received signal. The estimation is done by de-spreading the intermodulation interference (in the context of bandwidth in the frequency domain), which also has the effect of spreading the other components of the received signal. A filter is then used which has a frequency range to pass the function of the unknown aggressor and remove some of the energy in the other components that have been spread beyond the filters passband.
  • a method is performed by a network node for estimating intermodulation interference.
  • the method comprises receiving a radio signal that contains intermodulation interference.
  • the intermodulation interference is a function of a known aggressor and a function of an unknown aggressor.
  • the method further comprises P106021WO01 PCT APPLICATION 4 of 32 creating a de-spreading signal using the function of the known aggressor.
  • the de-spreading signal is representative of the reciprocal of the function of the known aggressor.
  • the method further comprises: multiplying the received radio signal with the de-spreading signal; filtering the multiplied signal with a filter that is limited to an expected frequency bandwidth of the function of the unknown aggressor to determine an estimate of the function of the unknown aggressor; and mitigating interference in the received radio signal based on the estimate of the function of the unknown aggressor.
  • mitigating interference in the received radio signal comprises multiplying the estimate of the function of the unknown aggressors with the function of the known aggressors to generate an estimate of the intermodulation interference.
  • the method may further comprise cancelling intermodulation interference from the received radio signal based on the estimate of the intermodulation interference.
  • the method further comprises determining a level of distortion in the received radio signal based on the estimate of the intermodulation interference.
  • the method further comprises determining a correlation coefficient between the received radio signal based on the estimate of the intermodulation interference.
  • mitigating interference in the received radio signal comprises using the estimate of the function of the unknown aggressors for spectrum sensing outside a passband of a receiver filter used for receiving the radio signal.
  • the function of the unknown aggressor comprises a first function of unknown aggressors and a second function of unknown aggressors.
  • the first function of unknown aggressors may be associated with a first radio antenna, and the second function of unknown aggressors may be associated with a second radio antenna.
  • Another computer program product comprises a non-transitory computer readable medium storing computer readable program code, the computer readable program code operable, when executed by processing circuitry to perform any of the methods performed by the network node described above.
  • Certain embodiments may provide one or more of the following technical advantages. For example, particular embodiments estimate unknown aggressor signal(s) which would otherwise be unavailable. The unknown aggressor may be used for several purposes to reduce or eliminate interference.
  • FIGURE 1 is a flow diagram illustrating an example of estimating an unknown aggressor signal
  • FIGURE 2 is a flow diagram illustrating an example of estimating intermodulation interference based on a known and unknown aggressor signal
  • FIGURE 3 is a flow diagram illustrating an example of cancelling intermodulation interference from a received signal based on a known and unknown aggressor signal
  • FIGURE 4 is a flow diagram illustrating finding a correlation coefficient between an estimate of intermodulation interference and a received signal
  • FIGURE 5 is a flow diagram illustrating finding correlation coefficients for multiple estimates of a function of the unknown aggressor
  • FIGURE 6 is a flow diagram illustrating combining multiple estimates of the function of unknown aggressors with the correlation coefficients from FIGURE 5
  • FIGURE 7 is a block diagram illustrating an open radio access network (ORAN) application with interference mitigation
  • OFRAN open radio access network
  • FIGURE 1 is a flow diagram illustrating an example of estimating an unknown aggressor signal.
  • the starting condition is a signal in a receiver that contains intermodulation interference.
  • an intermodulation distortion (IM3) term may be made up of two aggressors ( ⁇ 1 & ⁇ 2 ) with the following formula: ⁇ 1 2 ⁇ 2 ⁇ centered at a known frequency (typically denoted by 2 ⁇ 2 ⁇ ⁇ 1 ).
  • ⁇ 1 is the known aggressor
  • ⁇ 2 is the unknown aggressor.
  • the function of the known aggressors is ⁇ 1 2
  • the function of the unknown aggressors is ⁇ 2 ⁇ .
  • ⁇ 1 & ⁇ 2 represent the complex baseband representation of two radio frequency signals (aggressors) centered at frequencies ⁇ 1 & ⁇ 2 .
  • the signal processing is typically done in the digital domain, thus the signals may also be denoted as ⁇ 1 [ ⁇ ] & ⁇ 2 [ ⁇ ] to clearly show that they are represented in the discrete-time domain.
  • the de- spreading signal design is representative of the reciprocal of the function of the known aggressors, but with some rules applied to avoid very large values in the de-spreading signal for values where the known aggressor magnitude is relatively small.
  • One set of rules includes the following: 1 ⁇ ⁇ ⁇
  • the intermodulation interference component of the received signal is representative of ⁇ 2 ⁇ after multiplication with the de-spreading signal.
  • the filter removes the energy of the product that is outside the frequency range of ⁇ 2 ⁇ .
  • the other components of the residual signal are independent of the de-spreading signal, so their bandwidth will spread further in the frequency domain. Any of the signal that is spread beyond the frequency range of the filter will be removed by the filter.
  • the multiplication of the intermodulation component (which has a bandwidth that is roughly 2 ⁇ ⁇ ⁇ 1 + 1 ⁇ ⁇ ⁇ 2 ) with the de-spreading signal will result in a signal with a bandwidth that is 1 ⁇ ⁇ ⁇ 2 .
  • FIGURES 2-6 illustrate applications that use the estimate of the function of the unknown aggressor.
  • One application of the function of the unknown aggressor is cancellation of intermodulation interference, such as passive intermodulation (PIM).
  • PIM passive intermodulation
  • cancellation of intermodulation interference requires all functions of the aggressors to be known.
  • FIGURE 2 is a flow diagram illustrating an example of estimating intermodulation interference based on a known and unknown aggressor signal. To synthesize the intermodulation interference the estimate of the function of the unknown aggressors is multiplied by the function of the known aggressors. This product can then use conventional adaptive filter techniques to cancel the intermodulation interference from the received signal.
  • FIGURE 3 is a flow diagram illustrating an example of cancelling intermodulation interference from a received signal based on a known and unknown aggressor signal.
  • the synthesized signal may be used as a metric for detecting intermodulation distortion without requiring subsequent adaptive filter blocks.
  • the signal power of the product of the function of the unknown aggressors and the function of the known aggressors is representative of the level of intermodulation distortion in the received signal.
  • the estimated function of the unknown aggressor may be used for spectrum sensing outside the passband of the receiver filter. Typically, a receiver can only be used for sensing signal within the passband of the receive filter.
  • This type of application is to help in identifying an external system that is radiating radio frequency energy and is causing degradation to the receiver.
  • the phase need not be included and particular 1 ⁇ 1 embodiments may use ⁇ 2 instead of ⁇ 2 ⁇ ⁇ 2 1 [ ⁇ ] . Some embodiments may use a value of 0 1 ⁇ 1 instead of ⁇ 2 ⁇ ⁇ 2 1 [ ⁇ ] . Some embodiments interpolate the value from the preceding and/or proceeding values of the de-spreading signal (e.g., moving average filter, but without using the center value). P106021WO01 PCT APPLICATION 9 of 32 [0041] The de-spreading signal may be filtered to suppress potential high frequency effects due to numerical precision issues related to the divide operation.
  • the de-spreading signal may be the reciprocal of the known aggressor function without any special treatment for low magnitude values of the known aggressor function, which may be feasible with very high precision computations.
  • Some samples in the estimate of the function of the unknown aggressor may be modified in a similar way as in the case of small values for de- spreading signal.
  • Some embodiments include multiple intermodulation interference terms on the same antenna branch, where each term refers to a product of a function of a known aggressor with a function of an unknown aggressor, and the same functions could exist in different terms.
  • the intermodulation interference term was ⁇ 1 2 ⁇ 2 ⁇ , where ⁇ 1 2 was the function of the known aggressor and ⁇ 2 ⁇ was the function of the unknown
  • ⁇ 1 2 was the function of the known aggressor
  • ⁇ 2 ⁇ was the function of the unknown
  • the intermodulation interference is caused by inline PIM in a radio frequency (RF) cable between a radio port and an antenna port, where the signals ⁇ 1 & ⁇ 2 are the complex baseband representation of the downlink signals present in the RF cable.
  • RF radio frequency
  • Another case may have multiple intermodulation interference terms present in the received signal.
  • An example is the case with a PIM source that is near two different radios, where each radio has two antenna branches.
  • the downlink signals from the first radio are denoted by ⁇ 1 ⁇ & ⁇ 1 ⁇ for antenna ports A & B, respectively. These aggressor signals are known.
  • the downlink signals from the second radio are denoted by ⁇ 2 ⁇ & ⁇ 2 ⁇ , which correspond to unknown aggressors, because the first radio does not have access to these.
  • the alpha values are coefficients that incorporate some of the behaviors of the PIM source, the channel conditions experienced by the downlink signals up to the PIM source, and the channel conditions experienced by the intermodulation interference terms back to the location where the received signal is processed.
  • Option A groups all terms with the function of the unknown aggressors together. To find a specific function of an unknown aggressor, group all terms that contain the function of the unknown aggressor, then apply the unknown aggressor estimation method described above on just that term (i.e., ignoring the presence of the other terms). The terms that are ignored contribute to a noisier estimate of the function of the unknown aggressor. If the ⁇ coefficients are unknown, then they need to exist only in the function of the unknown aggressor.
  • particular embodiments may apply the unknown aggressor estimation method described above to this received signal using ⁇ 1 2 ⁇ ⁇ as the function of the known aggressors and then solve for ⁇ 1 ⁇ 2 ⁇ ⁇ ⁇ + ⁇ 3 ⁇ 2 ⁇ ⁇ ⁇ .
  • Example 2 the ⁇ coefficients are known. In this a grouping that will result in the ⁇ coefficients being present in the function of the known aggressor.
  • Option B estimates the function of the unknown aggressor multiple times using different terms, then combines for a single estimate.
  • the function of the unknown aggressor is ⁇ 2 ⁇ ⁇ .
  • particular embodiments may use the unknown aggressor estimation method described above on the first term by using ⁇ 1 2 ⁇ as the function of the known aggressors to get an estimate of ⁇ 1 ⁇ 2 ⁇ ⁇ .
  • particular embodiments run the unknown aggressor estimation method again but on 1 2 the fourth term by using ⁇ ⁇ as the function of the known aggressors to get an of ⁇ 4 ⁇ 2 ⁇ ⁇ .
  • the unknown aggressor estimation method may also be run with focus on the fifth term by using ⁇ 1 ⁇ ⁇ 1 ⁇ as the function of the known aggressors to get an estimate of ⁇ 5 ⁇ 2 ⁇ ⁇ .
  • the ⁇ coefficients are not needed.
  • One example method to combine the noisy estimates is to determine the correlation coefficient between the estimates and then combine them so that they add constructively.
  • the received signal used in the preceding paragraphs there are multiple functions of unknown aggressors ( ⁇ 2 ⁇ ⁇ & ⁇ 2 ⁇ ⁇ ). Each of these signals may be estimated from ⁇ ⁇ , ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ (i.e., run in parallel).
  • Some embodiments include intermodulation interference impacting multiple antenna branches. For example, consider a case with two antenna branches each with received signals that contain some common intermodulation interference terms.
  • Method 0 Run the unknown aggressor estimation method on each antenna branch in isolation (does not take advantage of correlation between branches), the result is an estimate of the functions of the unknown aggressors for each antenna branch with a received signal.
  • Method 1 Run method 0, then combine the estimates for each function of the unknown aggressors to come up with an estimate of ⁇ 2 ⁇ ⁇ & ⁇ 2 ⁇ ⁇ , which are not branch dependent. The estimates may be combined by using the correlation coefficients between the independent estimates.
  • Method 2 Run method 0 on only one branch, then use the result on other branches when applying the desired use-case (e.g., intermodulation interference cancellation).
  • FIGURE 4 is a flow diagram illustrating finding a correlation coefficient between an estimate of intermodulation interference and a received signal.
  • FIGURE 5 is a flow diagram illustrating finding correlation coefficients for multiple estimates of a function of the unknown aggressor.
  • FIGURE 6 is a flow diagram illustrating combining multiple estimates of the function of unknown aggressors with the correlation coefficients from FIGURE 5.
  • O-RAN Open Radio Area Network
  • different hardware and software functions e.g., radio unit, distributed unit, central unit, platform, application
  • ORAN inherently increases the chances of having multiple vendors equipment on a site, which means there is less opportunity to flexibly add new interfaces between equipment to share data. This means that ORAN deployments with intermodulation interference will likely have a higher probability of having the situation of a function of unknown aggressors, which will prevent cancellation of intermodulation interference.
  • the embodiments described herein may be relevant to ORAN because functions of unknown aggressors will likely be a reality.
  • FIGURE 7 is a block diagram illustrating an open radio access network (ORAN) application with interference mitigation at the open radio unit (ORU).
  • the illustrated example includes equipment from two vendors, vendor #1 and vendor #2. Unknown aggressors originating from vendor #2 equipment interfere with the signal received by vendor #1 P106021WO01 PCT APPLICATION 13 of 32 equipment.
  • the ORU of vendor #1 may perform the unknown aggressor estimation method according to particular embodiments described herein.
  • FIGURE 8 is a block diagram illustrating an ORAN application with interference mitigation at the open distributed unit (ODU).
  • the illustrated example includes equipment from two vendors, vendor #1 and vendor #2. Unknown aggressors originating from vendor #2 equipment interfere with the signal received by vendor #1 equipment.
  • FIGURE 9 illustrates an example of a communication system 100 in accordance with some embodiments.
  • the communication system 100 includes a telecommunication network 102 that includes an access network 104, such as a radio access network (RAN), and a core network 106, which includes one or more core network nodes 108.
  • the access network 104 includes one or more access network nodes, such as network nodes 110a and 110b (one or more of which may be generally referred to as network nodes 110), or any other similar 3rd Generation Partnership Project (3GPP) access node or non-3GPP access point.
  • 3GPP 3rd Generation Partnership Project
  • the network nodes 110 facilitate direct or indirect connection of user equipment (UE), such as by connecting UEs 112a, 112b, 112c, and 112d (one or more of which may be generally referred to as UEs 112) to the core network 106 over one or more wireless connections.
  • UE user equipment
  • Example wireless communications over a wireless connection include transmitting and/or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and/or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors.
  • the communication system 100 may include any number of wired or wireless networks, network nodes, UEs, and/or any other components or systems that may facilitate or participate in the communication of data and/or signals whether via wired or wireless connections.
  • the communication system 100 may include and/or interface with any type of communication, telecommunication, data, cellular, radio network, and/or other similar type of system.
  • the UEs 112 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and/or operable to communicate wirelessly with the network nodes 110 and other communication devices.
  • the network nodes 110 are arranged, capable, configured, and/or operable to communicate directly or indirectly with the UEs 112 and/or with other network nodes or equipment in the telecommunication network 102 P106021WO01 PCT APPLICATION 14 of 32 to enable and/or provide network access, such as wireless network access, and/or to perform other functions, such as administration in the telecommunication network 102.
  • the core network 106 connects the network nodes 110 to one or more hosts, such as host 116. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts.
  • the core network 106 includes one more core network nodes (e.g., core network node 108) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and/or hosts, such that the descriptions thereof are generally applicable to the corresponding components of the core network node 108.
  • Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and/or a User Plane Function (UPF).
  • MSC Mobile Switching Center
  • MME Mobility Management Entity
  • HSS Home Subscriber Server
  • AMF Session Management Function
  • AUSF Authentication Server Function
  • SIDF Subscription Identifier De-concealing function
  • UDM Unified Data Management
  • SEPP Security Edge Protection Proxy
  • NEF Network Exposure Function
  • UPF User Plane Function
  • UPF User Plane Function
  • the host 116 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio/video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server.
  • data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs
  • analytics functionality such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs
  • social media such as a plurality of UEs
  • functions for controlling or otherwise interacting with remote devices functions for an alarm and surveillance center, or any other such function performed by a server.
  • the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), and/or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and/or any other appropriate wireless P106021WO01 PCT APPLICATION 15 of 32 communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and/or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox.
  • GSM Global System for Mobile Communications
  • UMTS Universal Mobile Telecommunications System
  • LTE Long Term Evolution
  • 6G wireless local area network
  • WiFi
  • the telecommunication network 102 is a cellular network that implements 3GPP standardized features. Accordingly, the telecommunications network 102 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network 102. For example, the telecommunications network 102 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and/or Massive Machine Type Communication (mMTC)/Massive IoT services to yet further UEs.
  • URLLC Ultra Reliable Low Latency Communication
  • eMBB Enhanced Mobile Broadband
  • mMTC Massive Machine Type Communication
  • the UEs 112 are configured to transmit and/or receive information without direct human interaction.
  • a UE may be designed to transmit information to the access network 104 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network 104.
  • a UE may be configured for operating in single- or multi-RAT or multi-standard mode.
  • a UE may operate with any one or combination of Wi-Fi, NR (New Radio) and LTE, i.e. being configured for multi-radio dual connectivity (MR-DC), such as E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) New Radio – Dual Connectivity (EN-DC).
  • MR-DC multi-radio dual connectivity
  • the hub 114 communicates with the access network 104 to facilitate indirect communication between one or more UEs (e.g., UE 112c and/or 112d) and network nodes (e.g., network node 110b).
  • the hub 114 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs.
  • the hub 114 may be a broadband router enabling access to the core network 106 for the UEs.
  • the hub 114 may be a controller that sends commands or instructions to one or more actuators in the UEs.
  • Commands or instructions may be received from the UEs, network nodes 110, or by executable code, script, process, or other instructions in the hub 114.
  • the hub 114 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data.
  • the hub 114 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, the hub 114 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub 114 then provides to the UE either directly, after performing P106021WO01 PCT APPLICATION 16 of 32 local processing, and/or after adding additional local content.
  • the hub 114 acts as a proxy server or orchestrator for the UEs, in particular in if one or more of the UEs are low energy IoT devices.
  • the hub 114 may have a constant/persistent or intermittent connection to the network node 110b.
  • the hub 114 may also allow for a different communication scheme and/or schedule between the hub 114 and UEs (e.g., UE 112c and/or 112d), and between the hub 114 and the core network 106.
  • the hub 114 is connected to the core network 106 and/or one or more UEs via a wired connection.
  • the hub 114 may be configured to connect to an M2M service provider over the access network 104 and/or to another UE over a direct connection.
  • UEs may establish a wireless connection with the network nodes 110 while still connected via the hub 114 via a wired or wireless connection.
  • the hub 114 may be a dedicated hub – that is, a hub whose primary function is to route communications to/from the UEs from/to the network node 110b.
  • the hub 114 may be a non-dedicated hub – that is, a device which is capable of operating to route communications between the UEs and network node 110b, but which is additionally capable of operating as a communication start and/or end point for certain data channels.
  • FIGURE 10 shows a UE 200 in accordance with some embodiments.
  • a UE refers to a device capable, configured, arranged and/or operable to communicate wirelessly with network nodes and/or other UEs.
  • Examples of a UE include, but are not limited to, a smart phone, mobile phone, cell phone, voice over IP (VoIP) phone, wireless local loop phone, desktop computer, personal digital assistant (PDA), wireless cameras, gaming console or device, music storage device, playback appliance, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), smart device, wireless customer-premise equipment (CPE), vehicle-mounted or vehicle embedded/integrated wireless device, etc.
  • VoIP voice over IP
  • LME laptop-embedded equipment
  • LME laptop-mounted equipment
  • CPE wireless customer-premise equipment
  • a UE may support device-to-device (D2D) communication, for example by implementing a 3GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), or vehicle- P106021WO01 PCT APPLICATION 17 of 32 to-everything (V2X).
  • 3GPP 3rd Generation Partnership Project
  • NB-IoT narrow band internet of things
  • MTC machine type communication
  • eMTC enhanced MTC
  • a UE may support device-to-device (D2D) communication, for example by implementing a 3GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), or vehicle- P106021WO01 PCT APPLICATION 17 of 32 to-everything (V2X).
  • DSRC Dedicated Short-Range Communication
  • a UE may not necessarily have a user in the sense of a human user who owns and/or operates the relevant device.
  • a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller).
  • a UE may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter).
  • the UE 200 includes processing circuitry 202 that is operatively coupled via a bus 204 to an input/output interface 206, a power source 208, a memory 210, a communication interface 212, and/or any other component, or any combination thereof.
  • Certain UEs may utilize all or a subset of the components shown in FIGURE 10. The level of integration between the components may vary from one UE to another UE. Further, certain UEs may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc.
  • the processing circuitry 202 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in the memory 210.
  • the processing circuitry 202 may be implemented as one or more hardware-implemented state machines (e.g., in discrete logic, field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), etc.); programmable logic together with appropriate firmware; one or more stored computer programs, general-purpose processors, such as a microprocessor or digital signal processor (DSP), together with appropriate software; or any combination of the above.
  • the processing circuitry 202 may include multiple central processing units (CPUs).
  • the input/output interface 206 may be configured to provide an interface or interfaces to an input device, output device, or one or more input and/or output devices.
  • Examples of an output device include a speaker, a sound card, a video card, a display, a monitor, a printer, an actuator, an emitter, a smartcard, another output device, or any combination thereof.
  • An input device may allow a user to capture information into the UE 200. Examples of an input device include a touch-sensitive or presence-sensitive display, a camera (e.g., a digital camera, a digital video camera, a web camera, etc.), a microphone, a sensor, a mouse, a trackball, a directional pad, a trackpad, a scroll wheel, a smartcard, and the like.
  • the presence-sensitive display may include a capacitive or resistive touch sensor to sense input P106021WO01 PCT APPLICATION 18 of 32 from a user.
  • a sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, a biometric sensor, etc., or any combination thereof.
  • An output device may use the same type of interface port as an input device. For example, a Universal Serial Bus (USB) port may be used to provide an input device and an output device.
  • USB Universal Serial Bus
  • the power source 208 is structured as a battery or battery pack.
  • the power source 208 may further include power circuitry for delivering power from the power source 208 itself, and/or an external power source, to the various parts of the UE 200 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging of the power source 208.
  • Power circuitry may perform any formatting, converting, or other modification to the power from the power source 208 to make the power suitable for the respective components of the UE 200 to which power is supplied.
  • the memory 210 may be or be configured to include memory such as random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth.
  • the memory 210 includes one or more application programs 214, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data 216.
  • the memory 210 may store, for use by the UE 200, any of a variety of various operating systems or combinations of operating systems.
  • the memory 210 may be configured to include a number of physical drive units, such as redundant array of independent disks (RAID), flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital data storage (HDDS) optical disc drive, external mini-dual in-line memory module (DIMM), synchronous dynamic random access memory (SDRAM), external micro-DIMM SDRAM, smartcard memory such as tamper resistant module in the form of a universal integrated circuit card (UICC) including one or more subscriber identity modules (SIMs), such as a USIM and/or ISIM, other memory, or any combination thereof.
  • RAID redundant array of independent disks
  • HD-DVD high-density digital versatile disc
  • HDDS holographic digital data storage
  • DIMM external mini-dual in-line memory module
  • SDRAM synchronous dynamic random access memory
  • SDRAM synchronous dynamic random access memory
  • the UICC may for example be an embedded UICC (eUICC), integrated UICC (iUICC) or a removable UICC commonly known as ‘SIM P106021WO01 PCT APPLICATION 19 of 32 card.’
  • the memory 210 may allow the UE 200 to access instructions, application programs and the like, stored on transitory or non-transitory memory media, to off-load data, or to upload data.
  • An article of manufacture, such as one utilizing a communication system may be tangibly embodied as or in the memory 210, which may be or comprise a device-readable storage medium.
  • the processing circuitry 202 may be configured to communicate with an access network or other network using the communication interface 212.
  • the communication interface 212 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna 222.
  • the communication interface 212 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another device capable of wireless communication (e.g., another UE or a network node in an access network).
  • Each transceiver may include a transmitter 218 and/or a receiver 220 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth).
  • the transmitter 218 and receiver 220 may be coupled to one or more antennas (e.g., antenna 222) and may share circuit components, software or firmware, or alternatively be implemented separately.
  • communication functions of the communication interface 212 may include cellular communication, Wi-Fi communication, LPWAN communication, data communication, voice communication, multimedia communication, short-range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof.
  • GPS global positioning system
  • Communications may be implemented in according to one or more communication protocols and/or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband Code Division Multiple Access (WCDMA), GSM, LTE, New Radio (NR), UMTS, WiMax, Ethernet, transmission control protocol/internet protocol (TCP/IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth.
  • a UE may provide an output of data captured by its sensors, through its communication interface 212, via a wireless connection to a network node. Data captured by sensors of a UE can be communicated through a wireless connection to a network node via another UE.
  • a UE comprises an actuator, a motor, or a switch, related to a communication interface configured to receive wireless input from a network node via a wireless connection. In response to the received wireless input the states of the actuator, the motor, or the switch may change.
  • the UE may comprise a motor that adjusts the control surfaces or rotors of a drone in flight according to the received input or to a robotic arm performing a medical procedure according to the received input.
  • a UE when in the form of an Internet of Things (IoT) device, may be a device for use in one or more application domains, these domains comprising, but not limited to, city wearable technology, extended industrial application and healthcare.
  • IoT Internet of Things
  • Non-limiting examples of such an IoT device are a device which is or which is embedded in: a connected refrigerator or freezer, a TV, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door/window sensor, a flood/moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicle charging station, a smart watch, a fitness tracker, a head-mounted display for Augmented Reality (AR) or Virtual Reality (VR), a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal- or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, an Unmanned Aerial Vehicle (UAV), and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot.
  • UAV Un
  • a UE in the form of an IoT device comprises circuitry and/or software in dependence of the intended application of the IoT device in addition to other components as described in relation to the UE 200 shown in FIGURE 10.
  • a UE may represent a machine or other device that performs monitoring and/or measurements, and transmits the results of such monitoring and/or measurements to another UE and/or a network node.
  • the UE may in this case be an M2M device, which may in a 3GPP context be referred to as an MTC device.
  • the UE may implement the 3GPP NB-IoT standard.
  • P106021WO01 PCT APPLICATION 21 of 32 a UE may represent a vehicle, such as a car, a bus, a truck, a ship and an airplane, or other equipment that is capable of monitoring and/or reporting on its operational status or other functions associated with its operation.
  • a first UE might be or be integrated in a drone and provide the drone’s speed information (obtained through a speed sensor) to a second UE that is a remote controller operating the drone.
  • the first UE may adjust the throttle on the drone (e.g. by controlling an actuator) to increase or decrease the drone’s speed.
  • FIGURE 11 shows a network node 300 in accordance with some embodiments.
  • network node refers to equipment capable, configured, arranged and/or operable to communicate directly or indirectly with a UE and/or with other network nodes or equipment, in a telecommunication network.
  • network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (BSs) (e.g., radio base stations, Node Bs, evolved Node Bs (eNBs) and NR NodeBs (gNBs)).
  • APs access points
  • BSs base stations
  • Node Bs evolved Node Bs
  • gNBs NR NodeBs
  • Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations.
  • a base station may be a relay node or a relay donor node controlling a relay.
  • a network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units and/or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).
  • DAS distributed antenna system
  • network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell/multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) P106021WO01 PCT APPLICATION 22 of 32 nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and/or Minimization of Drive Tests (MDTs).
  • MSR multi-standard radio
  • RNCs radio network controllers
  • BSCs base station controllers
  • BTSs base transceiver stations
  • OFDM Operation and Maintenance
  • OSS Operations Support System
  • SON Self-Organizing Network
  • positioning nodes e.g., Evolve
  • the network node 300 includes a processing circuitry 302, a memory 304, a communication interface 306, and a power source 308.
  • the network node 300 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components.
  • the network node 300 comprises multiple separate components (e.g., BTS and BSC components)
  • one or more of the separate components may be shared among several network nodes.
  • a single RNC may control multiple NodeBs.
  • each unique NodeB and RNC pair may in some instances be considered a single separate network node.
  • the network node 300 may be configured to support multiple radio access technologies (RATs).
  • RATs radio access technologies
  • some components may be duplicated (e.g., separate memory 304 for different RATs) and some components may be reused (e.g., a same antenna 310 may be shared by different RATs).
  • the network node 300 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 300, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node 300.
  • RFID Radio Frequency Identification
  • the processing circuitry 302 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and/or encoded logic operable to provide, either alone or in conjunction with other network node 300 components, such as the memory 304, to provide network node 300 functionality.
  • the processing circuitry 302 includes a system on a chip (SOC).
  • the processing circuitry 302 includes one or more of radio frequency (RF) transceiver circuitry 312 and baseband processing circuitry 314.
  • RF radio frequency
  • the radio frequency (RF) transceiver circuitry 312 and the baseband processing circuitry 314 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital P106021WO01 PCT APPLICATION 23 of 32 units. In alternative embodiments, part or all of RF transceiver circuitry 312 and baseband processing circuitry 314 may be on the same chip or set of chips, boards, or units.
  • the memory 304 may comprise any form of volatile or non-volatile computer-readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and/or any other volatile or non-volatile, non-transitory device-readable and/or computer-executable memory devices that store information, data, and/or instructions that may be used by the processing circuitry 302.
  • volatile or non-volatile computer-readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and/or any other volatile or non-
  • the memory 304 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and/or other instructions capable of being executed by the processing circuitry 302 and utilized by the network node 300.
  • the memory 304 may be used to store any calculations made by the processing circuitry 302 and/or any data received via the communication interface 306.
  • the processing circuitry 302 and memory 304 is integrated.
  • the communication interface 306 is used in wired or wireless communication of signaling and/or data between a network node, access network, and/or UE.
  • the communication interface 306 comprises port(s)/terminal(s) 316 to send and receive data, for example to and from a network over a wired connection.
  • the communication interface 306 also includes radio front-end circuitry 318 that may be coupled to, or in certain embodiments a part of, the antenna 310.
  • Radio front-end circuitry 318 comprises filters 320 and amplifiers 322.
  • the radio front-end circuitry 318 may be connected to an antenna 310 and processing circuitry 302.
  • the radio front-end circuitry may be configured to condition signals communicated between antenna 310 and processing circuitry 302.
  • the radio front-end circuitry 318 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection.
  • the radio front-end circuitry 318 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 320 and/or amplifiers 322. The radio signal may then be transmitted via the antenna 310. Similarly, when receiving data, the antenna 310 may collect radio signals which are then converted into digital data by the radio front-end circuitry 318. The digital data may be passed to the P106021WO01 PCT APPLICATION 24 of 32 processing circuitry 302. In other embodiments, the communication interface may comprise different components and/or different combinations of components. [0104] In certain alternative embodiments, the network node 300 does not include separate radio front-end circuitry 318, instead, the processing circuitry 302 includes radio front-end circuitry and is connected to the antenna 310.
  • the RF transceiver circuitry 312 is part of the communication interface 306.
  • the communication interface 306 includes one or more ports or terminals 316, the radio front-end circuitry 318, and the RF transceiver circuitry 312, as part of a radio unit (not shown), and the communication interface 306 communicates with the baseband processing circuitry 314, which is part of a digital unit (not shown).
  • the antenna 310 may include one or more antennas, or antenna arrays, configured to send and/or receive wireless signals.
  • the antenna 310 may be coupled to the radio front-end circuitry 318 and may be any type of antenna capable of transmitting and receiving data and/or signals wirelessly.
  • the antenna 310 is separate from the network node 300 and connectable to the network node 300 through an interface or port.
  • the antenna 310, communication interface 306, and/or the processing circuitry 302 may be configured to perform any receiving operations and/or certain obtaining operations described herein as being performed by the network node. Any information, data and/or signals may be received from a UE, another network node and/or any other network equipment. Similarly, the antenna 310, the communication interface 306, and/or the processing circuitry 302 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and/or signals may be transmitted to a UE, another network node and/or any other network equipment.
  • the power source 308 provides power to the various components of network node 300 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component).
  • the power source 308 may further comprise, or be coupled to, power management circuitry to supply the components of the network node 300 with power for performing the functionality described herein.
  • the network node 300 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of the power source 308.
  • the power source 308 may comprise a source of power in the form of a battery or battery pack which is connected to, P106021WO01 PCT APPLICATION 25 of 32 or integrated in, power circuitry.
  • the battery may provide backup power should the external power source fail.
  • Embodiments of the network node 300 may include additional components beyond those shown in FIGURE 11 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and/or any functionality necessary to support the subject matter described herein.
  • the network node 300 may include user interface equipment to allow input of information into the network node 300 and to allow output of information from the network node 300. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for the network node 300.
  • FIGURE 12 is a flowchart illustrating an example method in a network node, according to certain embodiments. In particular embodiments, one or more steps of FIGURE 12 may be performed by network node 300 described with respect to FIGURE 11.
  • the network node is operable to estimate intermodulation interference.
  • the method begins at step 1212, where the network node (e.g., network node 300) receives a radio signal that contains intermodulation interference.
  • the intermodulation interference is a function of a known aggressor and a function of an unknown aggressor. .As described above, multiple aggressors may have caused the intermodulation distortion in the received radio signal.
  • the network node may have access to some form of raw data of at least one of the aggressors (known aggressors), but the network node does not have access to raw data of the other aggressors (unknown aggressors).
  • the network node creates a de-spreading signal using the function of the known aggressor.
  • the de-spreading signal is representative of the reciprocal of the function of the known aggressor.
  • rules are applied to the de-spreading signal to avoid very large values in the de-spreading signal for values where the known aggressor magnitude is relatively small.
  • the de-spreading signal is described in more detail above with respect to FIGURE 1.
  • the network node multiplies the received radio signal with the de- spreading signal. That is, the network node applies the de-spreading signal to the received radio signal to reduce the bandwidth of the intermodulation component. multiplication is described in more detail above with respect to FIGURE 1.
  • the network node filters the multiplied signal with a filter that is limited to an expected frequency bandwidth of the function of the unknown aggressor to determine an P106021WO01 PCT APPLICATION 26 of 32 estimate of the function of the unknown aggressor. The filtering is described in more detail above with respect to FIGURE 1.
  • the network node mitigates interference in the received radio signal based on the estimate of the function of the unknown aggressor.
  • Mitigating interference may refer to any operation performed by the network node based on the estimate of the function of the unknown aggressor and is not limited to removing interference.
  • mitigating interference in the received radio signal comprises multiplying the estimate of the function of the unknown aggressors with the function of the known aggressors to generate an estimate of the intermodulation interference.
  • the method may further comprise cancelling intermodulation interference from the received radio signal based on the estimate of the intermodulation interference.
  • the method further comprises determining a level of distortion in the received radio signal based on the estimate of the intermodulation interference.
  • the method further comprises determining a correlation coefficient between the received radio signal based on the estimate of the intermodulation interference.
  • mitigating interference in the received radio signal comprises using the estimate of the function of the unknown aggressors for spectrum sensing outside a passband of a receiver filter used for receiving the radio signal.
  • Examples of operations performed by the network node based on the estimate of the function of the unknown aggressor are described in more detail above with respect to FIGURES 1-6.
  • the received radio signal may comprise functions of multiple unknown aggressors. In these embodiments, the above steps may be repeated or combined to estimate functions for all the unknown aggressors.
  • the function of the unknown aggressor comprises a first function of unknown aggressors and a second function of unknown aggressors.
  • Determining an estimate of the function of the unknown aggressor may comprise determining an estimate of the first function of unknown aggressors and an estimate of the second function of unknown aggressors and combining the estimate of the first function of unknown aggressors and the estimate of the second function of unknown aggressors.
  • Determining an estimate of the function of the unknown aggressor may comprise determining a combined estimate of the first P106021WO01 PCT APPLICATION 27 of 32 function of unknown aggressors and the second function of unknown aggressors.
  • the first function of unknown aggressors may be associated with a first radio antenna, and the second function of unknown aggressors may be associated with a second radio antenna.
  • references in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to implement such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described.

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Abstract

According to some embodiments, a method is performed by a network node for estimating intermodulation interference. The method comprises receiving a radio signal that contains intermodulation interference. The intermodulation interference is a function of a known aggressor and a function of an unknown aggressor. The method further comprises creating a de-spreading signal using the function of the known aggressor. The de-spreading signal is representative of the reciprocal of the function of the known aggressor. The method further comprises: multiplying the received radio signal with the de-spreading signal; filtering the multiplied signal with a filter that is limited to an expected frequency bandwidth of the function of the unknown aggressor to determine an estimate of the function of the unknown aggressor; and mitigating interference in the received radio signal based on the estimate of the function of the unknown aggressor.

Description

INTERMODULATION INTERFERENCE MITIGATION WITHOUT ALL AGGRESSORS TECHNICAL FIELD [0001] Embodiments of the present disclosure are directed to wireless communications and, more particularly, to intermodulation interference mitigation without all aggressors. BACKGROUND [0002] Generally, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and/or is implied from the context in which it is used. All references to a/an/the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The steps of any methods disclosed herein do not have to be performed in the exact order disclosed, unless a step is explicitly described as following or preceding another step and/or where it is implicit that a step must follow or precede another step. Any feature of any of the embodiments disclosed herein may be applied to any other embodiment, wherever appropriate. Likewise, any advantage of any of the embodiments may apply to any other embodiments, and vice versa. Other objectives, features, and advantages of the enclosed embodiments will be apparent from the following description. [0003] Intermodulation interference is a distortion signal that is generated by passing aggressor signals through some non-linear system. The distortion signal can have signal power at frequencies that fall into the frequency range where a receiver is operating. In this case the distortion signal is interference with the receiver. [0004] Passive intermodulation (PIM) is the intermodulation product that can occur when at least one signal passes through passive components, introducing non-linear distortion to the signals. These passive components may be internal components such as cables, or external components such as rusty bolts, etc. Typically, the PIM power level is much lower in magnitude than the signal it originates from. Nevertheless, this becomes problematic in a cellular network when the strong transmitted signals (Tx) used for sending information to user equipment (UE) interact with PIM sources, which can introduce noise in the frequency band used to detect the weaker received signals (Rx) from UEs. This interference decreases the reliability, capacity, P106021WO01 PCT APPLICATION 2 of 32 and data rate of wireless systems. The Tx signals causing PIM interference are referred to as aggressors. [0005] There are different approaches to PIM mitigation. One mitigation method is to reduce the transmitter power to effectively lower the PIM level. A drawback is the impact of reduced transmitter power on coverage and/or downlink throughput. Another mitigation approach includes using expensive high-quality components to reduce the PIM generated by components of the radio unit but the PIM from surrounding environmental sources remains a problem. A third mitigation option is to use the Tx and/or Rx bands from a frequency spectrum with less PIM distortions, but this is not always possible because the bands are typically licensed through auction and limited spectrum is available. [0006] Another approach is PIM cancellation (PIMC) (see M. Z. Waheed, P. P. Campo, D. Korpi, A. Kiayani, L. Anttila, and M. Valkama, “Digital cancellation of passive intermodulation in FDD transceivers,” in 201852nd Asilomar Conference on Signals, Systems, and Computers, 2018. doi: 10.1109/ACSSC.2018.8645262 pp.1375–1381), which uses the Tx and Rx signals to create a model for the PIM source(s) that are affecting the Rx signal. This model is used to create an estimated replica of the received PIM signal and subtract it from the received Rx signal to obtain a ‘cleaner’ version of the Rx signal. [0007] There currently exist certain challenges. For example, in the conventional PIMC approach, an estimated PIM model is created using the Tx signals which cause PIM. To create this PIM model, all the aggressors need to be used. Therefore, such a PIMC solution cannot be used when one or more aggressors are not known. [0008] One example of such situation is illustrated as follows. Two cellular network operators are sharing a tower, but not sharing the radio or network equipment. A downlink carrier from the first operator and a downlink carrier from the second operator could hit the same PIM source and create PIM interference impacting the first operator. The first operator cannot use PIMC because the first operator does not have access to all the downlink aggressors involved in the PIM scenario. SUMMARY [0009] As described above, certain challenges currently exist with intermodulation interference mitigation without all aggressors. Certain aspects of the present disclosure and their embodiments may provide solutions to these or other challenges. For example, in P106021WO01 PCT APPLICATION 3 of 32 particular embodiments an intermodulation interference component of a received signal is represented as the product between a function of known aggressors and a function of unknown aggressors. Particular embodiments described herein extract the function of unknown aggressors and uses the estimate for interference mitigation. [0010] The first step is to create a de-spreading signal. The de-spreading signal is representative of the inverse of the function of the known aggressors (i.e., 1/(function of known aggressors)). This mathematical operation is not numerically robust because it can result in very large numbers, which requires special handling for small values of the function of known aggressors. [0011] The de-spreading signal is multiplied with the received signal. This operation i) reduces the bandwidth of the intermodulation interference term to be close to the bandwidth of the function of unknown aggressors, and ii) spreads out the other components of the received signal in the frequency domain. [0012] The next step is to filter this signal with a filter bandwidth that is designed to pass the function of the unknown aggressor. This will remove some of the energy that is not part of the function of unknown aggressors (function of unknown aggressors is a part of the intermodulation interference). The result is an estimate of the function of unknown aggressors. [0013] This result may be further used to: i) cancel/detect the intermodulation interference component by combining this result with the function of known aggressors, and/or ii) detect level of function of unknown aggressors outside the operating frequency range of the receiver. [0014] In general, the function of the unknown aggressors is estimated from the intermodulation interference in a received signal. The estimation is done by de-spreading the intermodulation interference (in the context of bandwidth in the frequency domain), which also has the effect of spreading the other components of the received signal. A filter is then used which has a frequency range to pass the function of the unknown aggressor and remove some of the energy in the other components that have been spread beyond the filters passband. The function of the unknown aggressor may then be used for cancellation of the intermodulation interference (or some other use-cases). [0015] According to some embodiments, a method is performed by a network node for estimating intermodulation interference. The method comprises receiving a radio signal that contains intermodulation interference. The intermodulation interference is a function of a known aggressor and a function of an unknown aggressor. The method further comprises P106021WO01 PCT APPLICATION 4 of 32 creating a de-spreading signal using the function of the known aggressor. The de-spreading signal is representative of the reciprocal of the function of the known aggressor. The method further comprises: multiplying the received radio signal with the de-spreading signal; filtering the multiplied signal with a filter that is limited to an expected frequency bandwidth of the function of the unknown aggressor to determine an estimate of the function of the unknown aggressor; and mitigating interference in the received radio signal based on the estimate of the function of the unknown aggressor. [0016] In particular embodiments, mitigating interference in the received radio signal comprises multiplying the estimate of the function of the unknown aggressors with the function of the known aggressors to generate an estimate of the intermodulation interference. The method may further comprise cancelling intermodulation interference from the received radio signal based on the estimate of the intermodulation interference. [0017] In particular embodiments, the method further comprises determining a level of distortion in the received radio signal based on the estimate of the intermodulation interference. [0018] In particular embodiments, the method further comprises determining a correlation coefficient between the received radio signal based on the estimate of the intermodulation interference. [0019] In particular embodiments, mitigating interference in the received radio signal comprises using the estimate of the function of the unknown aggressors for spectrum sensing outside a passband of a receiver filter used for receiving the radio signal. [0020] In particular embodiments, the function of the unknown aggressor comprises a first function of unknown aggressors and a second function of unknown aggressors. Determining an estimate of the function of the unknown aggressor may comprise determining an estimate of the first function of unknown aggressors and an estimate of the second function of unknown aggressors and combining the estimate of the first function of unknown aggressors and the estimate of the second function of unknown aggressors. Determining an estimate of the function of the unknown aggressor may comprise determining a combined estimate of the first function of unknown aggressors and the second function of unknown aggressors. The first function of unknown aggressors may be associated with a first radio antenna, and the second function of unknown aggressors may be associated with a second radio antenna. [0021] According to some embodiments, a network node network node comprises processing circuitry operable to perform any of the network node methods described above. P106021WO01 PCT APPLICATION 5 of 32 [0022] Another computer program product comprises a non-transitory computer readable medium storing computer readable program code, the computer readable program code operable, when executed by processing circuitry to perform any of the methods performed by the network node described above. [0023] Certain embodiments may provide one or more of the following technical advantages. For example, particular embodiments estimate unknown aggressor signal(s) which would otherwise be unavailable. The unknown aggressor may be used for several purposes to reduce or eliminate interference. BRIEF DESCRIPTION OF THE DRAWINGS [0024] For a more complete understanding of the disclosed embodiments and their features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which: FIGURE 1 is a flow diagram illustrating an example of estimating an unknown aggressor signal; FIGURE 2 is a flow diagram illustrating an example of estimating intermodulation interference based on a known and unknown aggressor signal; FIGURE 3 is a flow diagram illustrating an example of cancelling intermodulation interference from a received signal based on a known and unknown aggressor signal; FIGURE 4 is a flow diagram illustrating finding a correlation coefficient between an estimate of intermodulation interference and a received signal; FIGURE 5 is a flow diagram illustrating finding correlation coefficients for multiple estimates of a function of the unknown aggressor; FIGURE 6 is a flow diagram illustrating combining multiple estimates of the function of unknown aggressors with the correlation coefficients from FIGURE 5; FIGURE 7 is a block diagram illustrating an open radio access network (ORAN) application with interference mitigation at the open radio unit (ORU); FIGURE 8 is a block diagram illustrating an ORAN application with interference mitigation at the open distributed unit (ODU); FIGURE 9 illustrates an example communication system, according to certain embodiments; P106021WO01 PCT APPLICATION 6 of 32 FIGURE 10 illustrates an example user equipment (UE), according to certain embodiments; FIGURE 11 illustrates an example network node, according to certain embodiments; and FIGURE 12 illustrates a method performed by a network node, according to certain embodiments. DETAILED DESCRIPTION [0025] As described above, certain challenges currently exist with intermodulation interference mitigation without all aggressors. Certain aspects of the present disclosure and their embodiments may provide solutions to these or other challenges. For example, particular embodiments estimate the function of unknown aggressors from the intermodulation interference in a received signal. The estimation is done by de-spreading the intermodulation interference (in the context of bandwidth in the frequency domain), which also has the effect of spreading the other components of the received signal. A filter is then used which has a frequency range to pass the function of the unknown aggressor and remove some of the energy in the other components that have been spread beyond the filters passband. The function of the unknown aggressor may then be used for cancellation of the intermodulation interference. [0026] Particular embodiments are described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art. [0027] FIGURE 1 is a flow diagram illustrating an example of estimating an unknown aggressor signal. The starting condition is a signal in a receiver that contains intermodulation interference. There are multiple aggressors that caused the intermodulation distortion, and there is access a form of the raw data of at least one of the aggressors (known aggressors), and there is not access to the raw data of at least one of the aggressors (unknown aggressors). Instead of referring to the known aggressors and unknown aggressors, it is more general to refer to a function of the known aggressors and a function of the unknown aggressors. [0028] Start with the received signal that includes intermodulation interference. The mathematical structure of the intermodulation interference is assumed to be known. As an P106021WO01 PCT APPLICATION 7 of 32 example, an intermodulation distortion (IM3) term may be made up of two aggressors ( ^^1 & ^^2) with the following formula: ^^1 2 ^^2 ∗ centered at a known frequency (typically denoted by 2 ^^2 − ^^1). In this example, ^^1 is the known aggressor, and ^^2 is the unknown aggressor. The function of the known aggressors is ^^1 2, and the function of the unknown aggressors is ^^2 ∗. In these ^^1 & ^^2 represent the complex baseband representation of two radio frequency signals (aggressors) centered at frequencies ^^1 & ^^2. The signal processing is typically done in the digital domain, thus the signals may also be denoted as ^^1 [ ^^] & ^^2 [ ^^] to clearly show that they are represented in the discrete-time domain. [0029] Create a de-spreading signal using the function of the known aggressors. The de- spreading signal design is representative of the reciprocal of the function of the known aggressors, but with some rules applied to avoid very large values in the de-spreading signal for values where the known aggressor magnitude is relatively small. One set of rules includes the following: 1 ^^ ^^ ^^ | ^^2 1[ ^^]| < ^^1 [0030] Multiply the a filter that is limited to the expected bandwidth of the unknown aggressor term. [0031] In the example above, the intermodulation interference component of the received signal is representative of ^^2 ∗ after multiplication with the de-spreading signal. The filter removes the energy of the product that is outside the frequency range of ^^2 ∗. [0032] The other components of the residual signal are independent of the de-spreading signal, so their bandwidth will spread further in the frequency domain. Any of the signal that is spread beyond the frequency range of the filter will be removed by the filter. [0033] In other words, the multiplication of the intermodulation component (which has a bandwidth that is roughly 2 × ^^ ^^1 + 1 × ^^ ^^2) with the de-spreading signal will result in a signal with a bandwidth that is 1 × ^^ ^^2. This bandwidth reduction is the reason the term ‘de- spreading’ is used. It has the opposite effect on the other components in the received signal, which makes it possible to remove some of that signal energy with a filter. [0034] The filtering results in a signal estimate that is representative of the function of the unknown aggressor, which has been decoupled from the known aggressor. P106021WO01 PCT APPLICATION 8 of 32 [0035] FIGURES 2-6 illustrate applications that use the estimate of the function of the unknown aggressor. One application of the function of the unknown aggressor is cancellation of intermodulation interference, such as passive intermodulation (PIM). Typically, cancellation of intermodulation interference requires all functions of the aggressors to be known. If there are unknown aggressors causing the intermodulation distortion, then the intermodulation interference cannot be synthesized with sufficient fidelity. [0036] FIGURE 2 is a flow diagram illustrating an example of estimating intermodulation interference based on a known and unknown aggressor signal. To synthesize the intermodulation interference the estimate of the function of the unknown aggressors is multiplied by the function of the known aggressors. This product can then use conventional adaptive filter techniques to cancel the intermodulation interference from the received signal. [0037] FIGURE 3 is a flow diagram illustrating an example of cancelling intermodulation interference from a received signal based on a known and unknown aggressor signal. A key to this technique is that some of the component of the received signal that is not intermodulation interference was removed by the filter after the de-spreading operation. [0038] The synthesized signal may be used as a metric for detecting intermodulation distortion without requiring subsequent adaptive filter blocks. The signal power of the product of the function of the unknown aggressors and the function of the known aggressors is representative of the level of intermodulation distortion in the received signal. [0039] The estimated function of the unknown aggressor may be used for spectrum sensing outside the passband of the receiver filter. Typically, a receiver can only be used for sensing signal within the passband of the receive filter. One example of this type of application is to help in identifying an external system that is radiating radio frequency energy and is causing degradation to the receiver. [0040] The following are additional considerations for the de-spreading signal. For small values of the known aggressor function, the phase need not be included and particular 1 ^^∠ 1 embodiments may use ^^2 instead of ^^2 ^^ ^^2 1 [ ^^]. Some embodiments may use a value of 0 1 ^^∠ 1 instead of ^^2 ^^ ^^2 1 [ ^^]. Some embodiments interpolate the value from the preceding and/or proceeding values of the de-spreading signal (e.g., moving average filter, but without using the center value). P106021WO01 PCT APPLICATION 9 of 32 [0041] The de-spreading signal may be filtered to suppress potential high frequency effects due to numerical precision issues related to the divide operation. [0042] The de-spreading signal may be the reciprocal of the known aggressor function without any special treatment for low magnitude values of the known aggressor function, which may be feasible with very high precision computations. [0043] If some samples in the estimate of the function of the unknown aggressor have too large magnitudes, they may be modified in a similar way as in the case of small values for de- spreading signal. [0044] Some embodiments include multiple intermodulation interference terms on the same antenna branch, where each term refers to a product of a function of a known aggressor with a function of an unknown aggressor, and the same functions could exist in different terms. [0045] In the previous examples, the intermodulation interference term was ^^1 2 ^^2 ∗, where ^^1 2 was the function of the known aggressor and ^^2 ∗ was the function of the unknown This scenario could happen if the intermodulation interference is caused by inline PIM in a radio frequency (RF) cable between a radio port and an antenna port, where the signals ^^1 & ^^2 are the complex baseband representation of the downlink signals present in the RF cable. [0046] Another case may have multiple intermodulation interference terms present in the received signal. An example is the case with a PIM source that is near two different radios, where each radio has two antenna branches. With respect to PIMC for the first radio, the downlink signals from the first radio are denoted by ^^1 ^^ & ^^1 ^^ for antenna ports A & B, respectively. These aggressor signals are known. The downlink signals from the second radio are denoted by ^^2 ^^ & ^^2 ^^, which correspond to unknown aggressors, because the first radio does not have access to these. [0047] If the intermodulation interference is modelled with memoryless polynomials, then the intermodulation interference terms that are present in the received antenna port A of the first radio can be modelled as: ^^ ^^, ^^ ^^ ^^ = ^^1 ^^1 2 ^^ ^^2 ∗ ^^ + ^^2 ^^1 2 ^^ ^^2 ∗ ^^ + ^^3 ^^1 2 ^^ ^^2 ∗ ^^ + ^^4 ^^1 2 ^^ ^^2 ∗ ^^ + ^^5 ^^1 ^^ ^^1 ^^ ^^2 ∗ ^^ + ^^6 ^^1 ^^ ^^1 ^^ ^^2 ∗ ^^ [0048] The alpha values are coefficients that incorporate some of the behaviors of the PIM source, the channel conditions experienced by the downlink signals up to the PIM source, and the channel conditions experienced by the intermodulation interference terms back to the location where the received signal is processed. P106021WO01 PCT APPLICATION 10 of 32 [0049] The received signal in antenna port A also contains a component that is not intermodulation interference. It is denoted by ^^ ^^, ^^ ^^ℎ ^^ ^^. ^^ ^^, ^^ ^^ ^^ ^^ ^^ = ^^ 1 ^^ 1 2 ^^ ^^ 2 ∗ ^^ + ^^ 2 ^^ 1 2 ^^ ^^ 2 ∗ ^^ + ^^ 3 ^^ 1 2 ^^ ^^ 2 ∗ ^^ + ^^ 4 ^^ 1 2 ^^ ^^ 2 ∗ ^^ + ^^ 5 ^^ 1 ^^ ^^ 1 ^^ ^^ 2 ∗ ^^ + ^^ 6 ^^ 1 ^^ ^^ 1 ^^ ^^ 2 ∗ ^^ + ^^ ^^, ^^ ^^ℎ ^^ ^^ [0050] There are two options to estimate a function of unknown aggressors from the equation above. Option A groups all terms with the function of the unknown aggressors together. To find a specific function of an unknown aggressor, group all terms that contain the function of the unknown aggressor, then apply the unknown aggressor estimation method described above on just that term (i.e., ignoring the presence of the other terms). The terms that are ignored contribute to a noisier estimate of the function of the unknown aggressor. If the ^^ coefficients are unknown, then they need to exist only in the function of the unknown aggressor. [0051] Example 1: the ^^ coefficients are unknown, so the equation is grouped in a manner such that these coefficients only appear with the unknown aggressors: ^^ ^^, ^^ ^^ ^^ ^^ ^^ = ^^1 2 ^^ ( ^^1 ^^2 ∗ ^^ + ^^3 ^^2 ∗ ^^ ) + ^^1 2 ^^ ( ^^4 ^^2 ∗ ^^ + ^^2 ^^2 ∗ ^^ ) + ^^1 ^^ ^^1 ^^( ^^5 ^^2 ∗ ^^ + ^^6 ^^2 ∗ ^^ ) + ^^ ^^, ^^ ^^ℎ ^^ ^^ function of known aggressors ( ^^1 2 ^^ , ^^1 2 ^^ and ^^1 ^^ ^^1 ^^) and a different function of unknown aggressors ( ^^1 ^^2 ∗ ^^ + ^^3 ^^2 ∗ ^^ , ^^4 ^^2 ∗ ^^ + ^^2 ^^2 ∗ ^^ and ^^4 ^^2 ∗ ^^ + ^^2 ^^2 ∗ ^^ ). [0053] particular embodiments may apply the unknown aggressor estimation method described above to this received signal using ^^1 2 ^^ as the function of the known aggressors and then solve for ^^1 ^^2 ∗ ^^ + ^^3 ^^2 ∗ ^^ . Example 2: the ^^ coefficients are known. In this a grouping that will result in the ^^ coefficients being present in the function of the known aggressor. If the function of the unknown aggressor to estimate is ^^2 ∗ ^^ , then particular embodiments group the equation above into a format where only one term contains the desired function of the unknown aggressor to estimate: ^^ ^^, ^^ ^^ ^^ ^^ ^^ = ( ^^1 ^^1 2 ^^ + ^^4 ^^1 2 ^^ + ^^5 ^^1 ^^ ^^1 ^^) ^^2 ∗ ^^ + ^^2 ^^1 2 ^^ ^^2 ∗ ^^ + ^^3 ^^1 2 ^^ ^^2 ∗ ^^ + ^^6 ^^1 ^^ ^^1 ^^ ^^2 ∗ ^^ + ^^ ^^, ^^ ^^ℎ ^^ ^^ the function of the known aggressor is ( ^^1 ^^1 2 ^^ + ^^4 ^^1 2 ^^ + ^^5 ^^1 ^^ ^^1 ^^ ). [0056] Option B estimates the function of the unknown aggressor multiple times using different terms, then combines for a single estimate. As an example, start with the same formula for the intermodulation interference as above. P106021WO01 PCT APPLICATION 11 of 32 ^^ ^^, ^^ ^^ ^^ ^^ ^^ = ^^1 ^^ 1 2 ^^ ^^ 2 ∗ ^^ + ^^2 ^^ 1 2 ^^ ^^ 2 ∗ ^^ + ^^3 ^^ 1 2 ^^ ^^ 2 ∗ ^^ + ^^4 ^^ 1 2 ^^ ^^ 2 ∗ ^^ + ^^5 ^^1 ^^ ^^1 ^^ ^^ 2 ∗ ^^ + ^^6 ^^1 ^^ ^^1 ^^ ^^ 2 ∗ ^^ + ^^ ^^, ^^ ^^ℎ ^^ ^^ [0057] In this case the function of the unknown aggressor is ^^2 ∗ ^^ . In this option, particular embodiments may use the unknown aggressor estimation method described above on the first term by using ^^1 2 ^^ as the function of the known aggressors to get an estimate of ^^1 ^^2 ∗ ^^ . Next, particular embodiments run the unknown aggressor estimation method again but on 12 the fourth term by using ^^ ^^ as the function of the known aggressors to get an of ^^4 ^^2 ∗ ^^ . The unknown aggressor estimation method may also be run with focus on the fifth term by using ^^1 ^^ ^^1 ^^ as the function of the known aggressors to get an estimate of ^^5 ^^2 ∗ ^^ . These three noisy estimates may be combined to get a single estimate of ^^2 ∗ ^^ . In some use-cases, the ^^ coefficients are not needed. [0058] One example method to combine the noisy estimates is to determine the correlation coefficient between the estimates and then combine them so that they add constructively. [0059] In the received signal used in the preceding paragraphs there are multiple functions of unknown aggressors ( ^^2 ∗ ^^ & ^^2 ∗ ^^ ). Each of these signals may be estimated from ^^ ^^, ^^ ^^ ^^ ^^ ^^ (i.e., run in parallel). Another to estimate one of the functions of unknown then remove its contribution from ^^ ^^, ^^ ^^ ^^ ^^ ^^ by multiplying it by the appropriate function of known aggressors and subtracting it from ^^ ^^, ^^ ^^ ^^ ^^ ^^ to yield a residual of ^^ ^^, ^^ ^^ ^^ ^^ ^^. The second function of unknown aggressors may then be estimated using the residual of ^^ ^^, ^^ ^^ ^^ ^^ ^^, instead of directly using ^^ ^^, ^^ ^^ ^^ ^^ ^^. [0060] Some embodiments include intermodulation interference impacting multiple antenna branches. For example, consider a case with two antenna branches each with received signals that contain some common intermodulation interference terms. This is shown for antenna ports A&B: ^^ ^^, ^^ ^^ ^^ ^^ ^^ = ^^ 1 ^^ 1 2 ^^ ^^ 2 ∗ ^^ + ^^ 2 ^^ 1 2 ^^ ^^ 2 ∗ ^^ + ^^ 3 ^^ 1 2 ^^ ^^ 2 ∗ ^^ + ^^ 4 ^^ 1 2 ^^ ^^ 2 ∗ ^^ + ^^ 5 ^^ 1 ^^ ^^ 1 ^^ ^^ 2 ∗ ^^ + ^^ 6 ^^ 1 ^^ ^^ 1 ^^ ^^ 2 ∗ ^^ + ^^ ^^, ^^ ^^ℎ ^^ ^^ ^^ ^^, ^^ ^^ ^^ ^^ ^^ = ^^ 7 ^^ 1 2 ^^ ^^ 2 ∗ ^^ + ^^ 8 ^^ 1 2 ^^ ^^ 2 ∗ ^^ + ^^ 9 ^^ 1 2 ^^ ^^ 2 ∗ ^^ + ^^ 10 ^^ 1 2 ^^ ^^ 2 ∗ ^^ + ^^ 11 ^^ 1 ^^ ^^ 1 ^^ ^^ 2 ∗ ^^ + ^^ 12 ^^ 1 ^^ ^^ 1 ^^ ^^ 2 ∗ ^^ + ^^ ^^, ^^ ^^ℎ ^^ ^^ [0061] Some embodiments use the correlation between the two branches to estimate the functions of the unknown aggressors. P106021WO01 PCT APPLICATION 12 of 32 [0062] Method 0: Run the unknown aggressor estimation method on each antenna branch in isolation (does not take advantage of correlation between branches), the result is an estimate of the functions of the unknown aggressors for each antenna branch with a received signal. [0063] Method 1: Run method 0, then combine the estimates for each function of the unknown aggressors to come up with an estimate of ^^2 ∗ ^^ & ^^2 ∗ ^^ , which are not branch dependent. The estimates may be combined by using the correlation coefficients between the independent estimates. [0064] Method 2: Run method 0 on only one branch, then use the result on other branches when applying the desired use-case (e.g., intermodulation interference cancellation). [0065] The example above was for a third order intermodulation interference scenario, however the product of the function of the known aggressor with the function of the unknown aggressor may be used for other intermodulation orders. [0066] FIGURE 4 is a flow diagram illustrating finding a correlation coefficient between an estimate of intermodulation interference and a received signal. FIGURE 5 is a flow diagram illustrating finding correlation coefficients for multiple estimates of a function of the unknown aggressor. FIGURE 6 is a flow diagram illustrating combining multiple estimates of the function of unknown aggressors with the correlation coefficients from FIGURE 5. [0067] Virtualization and disaggregation of the network enables an Open Radio Area Network (O-RAN) architecture in which different hardware and software functions (e.g., radio unit, distributed unit, central unit, platform, application) of a node are supplied by different vendors and integrated. [0068] ORAN inherently increases the chances of having multiple vendors equipment on a site, which means there is less opportunity to flexibly add new interfaces between equipment to share data. This means that ORAN deployments with intermodulation interference will likely have a higher probability of having the situation of a function of unknown aggressors, which will prevent cancellation of intermodulation interference. Thus, the embodiments described herein may be relevant to ORAN because functions of unknown aggressors will likely be a reality. [0069] FIGURE 7 is a block diagram illustrating an open radio access network (ORAN) application with interference mitigation at the open radio unit (ORU). The illustrated example includes equipment from two vendors, vendor #1 and vendor #2. Unknown aggressors originating from vendor #2 equipment interfere with the signal received by vendor #1 P106021WO01 PCT APPLICATION 13 of 32 equipment. In the illustrated example, the ORU of vendor #1 may perform the unknown aggressor estimation method according to particular embodiments described herein. [0070] FIGURE 8 is a block diagram illustrating an ORAN application with interference mitigation at the open distributed unit (ODU). The illustrated example includes equipment from two vendors, vendor #1 and vendor #2. Unknown aggressors originating from vendor #2 equipment interfere with the signal received by vendor #1 equipment. In the illustrated example, the ODU of vendor #1 may perform the unknown aggressor estimation method according to particular embodiments described herein. [0071] FIGURE 9 illustrates an example of a communication system 100 in accordance with some embodiments. In the example, the communication system 100 includes a telecommunication network 102 that includes an access network 104, such as a radio access network (RAN), and a core network 106, which includes one or more core network nodes 108. The access network 104 includes one or more access network nodes, such as network nodes 110a and 110b (one or more of which may be generally referred to as network nodes 110), or any other similar 3rd Generation Partnership Project (3GPP) access node or non-3GPP access point. The network nodes 110 facilitate direct or indirect connection of user equipment (UE), such as by connecting UEs 112a, 112b, 112c, and 112d (one or more of which may be generally referred to as UEs 112) to the core network 106 over one or more wireless connections. [0072] Example wireless communications over a wireless connection include transmitting and/or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and/or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, the communication system 100 may include any number of wired or wireless networks, network nodes, UEs, and/or any other components or systems that may facilitate or participate in the communication of data and/or signals whether via wired or wireless connections. The communication system 100 may include and/or interface with any type of communication, telecommunication, data, cellular, radio network, and/or other similar type of system. [0073] The UEs 112 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and/or operable to communicate wirelessly with the network nodes 110 and other communication devices. Similarly, the network nodes 110 are arranged, capable, configured, and/or operable to communicate directly or indirectly with the UEs 112 and/or with other network nodes or equipment in the telecommunication network 102 P106021WO01 PCT APPLICATION 14 of 32 to enable and/or provide network access, such as wireless network access, and/or to perform other functions, such as administration in the telecommunication network 102. [0074] In the depicted example, the core network 106 connects the network nodes 110 to one or more hosts, such as host 116. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. The core network 106 includes one more core network nodes (e.g., core network node 108) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and/or hosts, such that the descriptions thereof are generally applicable to the corresponding components of the core network node 108. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Exposure Function (NEF), and/or a User Plane Function (UPF). [0075] The host 116 may be under the ownership or control of a service provider other than an operator or provider of the access network 104 and/or the telecommunication network 102, and may be operated by the service provider or on behalf of the service provider. The host 116 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio/video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server. [0076] As a whole, the communication system 100 of 1FIGURE 9 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), and/or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and/or any other appropriate wireless P106021WO01 PCT APPLICATION 15 of 32 communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and/or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox. [0077] In some examples, the telecommunication network 102 is a cellular network that implements 3GPP standardized features. Accordingly, the telecommunications network 102 may support network slicing to provide different logical networks to different devices that are connected to the telecommunication network 102. For example, the telecommunications network 102 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and/or Massive Machine Type Communication (mMTC)/Massive IoT services to yet further UEs. [0078] In some examples, the UEs 112 are configured to transmit and/or receive information without direct human interaction. For instance, a UE may be designed to transmit information to the access network 104 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from the access network 104. Additionally, a UE may be configured for operating in single- or multi-RAT or multi-standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR (New Radio) and LTE, i.e. being configured for multi-radio dual connectivity (MR-DC), such as E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) New Radio – Dual Connectivity (EN-DC). [0079] In the example, the hub 114 communicates with the access network 104 to facilitate indirect communication between one or more UEs (e.g., UE 112c and/or 112d) and network nodes (e.g., network node 110b). In some examples, the hub 114 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, the hub 114 may be a broadband router enabling access to the core network 106 for the UEs. As another example, the hub 114 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes 110, or by executable code, script, process, or other instructions in the hub 114. As another example, the hub 114 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, the hub 114 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, the hub 114 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which the hub 114 then provides to the UE either directly, after performing P106021WO01 PCT APPLICATION 16 of 32 local processing, and/or after adding additional local content. In still another example, the hub 114 acts as a proxy server or orchestrator for the UEs, in particular in if one or more of the UEs are low energy IoT devices. [0080] The hub 114 may have a constant/persistent or intermittent connection to the network node 110b. The hub 114 may also allow for a different communication scheme and/or schedule between the hub 114 and UEs (e.g., UE 112c and/or 112d), and between the hub 114 and the core network 106. In other examples, the hub 114 is connected to the core network 106 and/or one or more UEs via a wired connection. Moreover, the hub 114 may be configured to connect to an M2M service provider over the access network 104 and/or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with the network nodes 110 while still connected via the hub 114 via a wired or wireless connection. In some embodiments, the hub 114 may be a dedicated hub – that is, a hub whose primary function is to route communications to/from the UEs from/to the network node 110b. In other embodiments, the hub 114 may be a non-dedicated hub – that is, a device which is capable of operating to route communications between the UEs and network node 110b, but which is additionally capable of operating as a communication start and/or end point for certain data channels. [0081] FIGURE 10 shows a UE 200 in accordance with some embodiments. As used herein, a UE refers to a device capable, configured, arranged and/or operable to communicate wirelessly with network nodes and/or other UEs. Examples of a UE include, but are not limited to, a smart phone, mobile phone, cell phone, voice over IP (VoIP) phone, wireless local loop phone, desktop computer, personal digital assistant (PDA), wireless cameras, gaming console or device, music storage device, playback appliance, wearable terminal device, wireless endpoint, mobile station, tablet, laptop, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), smart device, wireless customer-premise equipment (CPE), vehicle-mounted or vehicle embedded/integrated wireless device, etc. Other examples include any UE identified by the 3rd Generation Partnership Project (3GPP), including a narrow band internet of things (NB-IoT) UE, a machine type communication (MTC) UE, and/or an enhanced MTC (eMTC) UE. [0082] A UE may support device-to-device (D2D) communication, for example by implementing a 3GPP standard for sidelink communication, Dedicated Short-Range Communication (DSRC), vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), or vehicle- P106021WO01 PCT APPLICATION 17 of 32 to-everything (V2X). In other examples, a UE may not necessarily have a user in the sense of a human user who owns and/or operates the relevant device. Instead, a UE may represent a device that is intended for sale to, or operation by, a human user but which may not, or which may not initially, be associated with a specific human user (e.g., a smart sprinkler controller). Alternatively, a UE may represent a device that is not intended for sale to, or operation by, an end user but which may be associated with or operated for the benefit of a user (e.g., a smart power meter). [0083] The UE 200 includes processing circuitry 202 that is operatively coupled via a bus 204 to an input/output interface 206, a power source 208, a memory 210, a communication interface 212, and/or any other component, or any combination thereof. Certain UEs may utilize all or a subset of the components shown in FIGURE 10. The level of integration between the components may vary from one UE to another UE. Further, certain UEs may contain multiple instances of a component, such as multiple processors, memories, transceivers, transmitters, receivers, etc. [0084] The processing circuitry 202 is configured to process instructions and data and may be configured to implement any sequential state machine operative to execute instructions stored as machine-readable computer programs in the memory 210. The processing circuitry 202 may be implemented as one or more hardware-implemented state machines (e.g., in discrete logic, field-programmable gate arrays (FPGAs), application specific integrated circuits (ASICs), etc.); programmable logic together with appropriate firmware; one or more stored computer programs, general-purpose processors, such as a microprocessor or digital signal processor (DSP), together with appropriate software; or any combination of the above. For example, the processing circuitry 202 may include multiple central processing units (CPUs). [0085] In the example, the input/output interface 206 may be configured to provide an interface or interfaces to an input device, output device, or one or more input and/or output devices. Examples of an output device include a speaker, a sound card, a video card, a display, a monitor, a printer, an actuator, an emitter, a smartcard, another output device, or any combination thereof. An input device may allow a user to capture information into the UE 200. Examples of an input device include a touch-sensitive or presence-sensitive display, a camera (e.g., a digital camera, a digital video camera, a web camera, etc.), a microphone, a sensor, a mouse, a trackball, a directional pad, a trackpad, a scroll wheel, a smartcard, and the like. The presence-sensitive display may include a capacitive or resistive touch sensor to sense input P106021WO01 PCT APPLICATION 18 of 32 from a user. A sensor may be, for instance, an accelerometer, a gyroscope, a tilt sensor, a force sensor, a magnetometer, an optical sensor, a proximity sensor, a biometric sensor, etc., or any combination thereof. An output device may use the same type of interface port as an input device. For example, a Universal Serial Bus (USB) port may be used to provide an input device and an output device. [0086] In some embodiments, the power source 208 is structured as a battery or battery pack. Other types of power sources, such as an external power source (e.g., an electricity outlet), photovoltaic device, or power cell, may be used. The power source 208 may further include power circuitry for delivering power from the power source 208 itself, and/or an external power source, to the various parts of the UE 200 via input circuitry or an interface such as an electrical power cable. Delivering power may be, for example, for charging of the power source 208. Power circuitry may perform any formatting, converting, or other modification to the power from the power source 208 to make the power suitable for the respective components of the UE 200 to which power is supplied. [0087] The memory 210 may be or be configured to include memory such as random access memory (RAM), read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), magnetic disks, optical disks, hard disks, removable cartridges, flash drives, and so forth. In one example, the memory 210 includes one or more application programs 214, such as an operating system, web browser application, a widget, gadget engine, or other application, and corresponding data 216. The memory 210 may store, for use by the UE 200, any of a variety of various operating systems or combinations of operating systems. [0088] The memory 210 may be configured to include a number of physical drive units, such as redundant array of independent disks (RAID), flash memory, USB flash drive, external hard disk drive, thumb drive, pen drive, key drive, high-density digital versatile disc (HD-DVD) optical disc drive, internal hard disk drive, Blu-Ray optical disc drive, holographic digital data storage (HDDS) optical disc drive, external mini-dual in-line memory module (DIMM), synchronous dynamic random access memory (SDRAM), external micro-DIMM SDRAM, smartcard memory such as tamper resistant module in the form of a universal integrated circuit card (UICC) including one or more subscriber identity modules (SIMs), such as a USIM and/or ISIM, other memory, or any combination thereof. The UICC may for example be an embedded UICC (eUICC), integrated UICC (iUICC) or a removable UICC commonly known as ‘SIM P106021WO01 PCT APPLICATION 19 of 32 card.’ The memory 210 may allow the UE 200 to access instructions, application programs and the like, stored on transitory or non-transitory memory media, to off-load data, or to upload data. An article of manufacture, such as one utilizing a communication system may be tangibly embodied as or in the memory 210, which may be or comprise a device-readable storage medium. [0089] The processing circuitry 202 may be configured to communicate with an access network or other network using the communication interface 212. The communication interface 212 may comprise one or more communication subsystems and may include or be communicatively coupled to an antenna 222. The communication interface 212 may include one or more transceivers used to communicate, such as by communicating with one or more remote transceivers of another device capable of wireless communication (e.g., another UE or a network node in an access network). Each transceiver may include a transmitter 218 and/or a receiver 220 appropriate to provide network communications (e.g., optical, electrical, frequency allocations, and so forth). Moreover, the transmitter 218 and receiver 220 may be coupled to one or more antennas (e.g., antenna 222) and may share circuit components, software or firmware, or alternatively be implemented separately. [0090] In the illustrated embodiment, communication functions of the communication interface 212 may include cellular communication, Wi-Fi communication, LPWAN communication, data communication, voice communication, multimedia communication, short-range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented in according to one or more communication protocols and/or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband Code Division Multiple Access (WCDMA), GSM, LTE, New Radio (NR), UMTS, WiMax, Ethernet, transmission control protocol/internet protocol (TCP/IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth. [0091] Regardless of the type of sensor, a UE may provide an output of data captured by its sensors, through its communication interface 212, via a wireless connection to a network node. Data captured by sensors of a UE can be communicated through a wireless connection to a network node via another UE. The output may be periodic (e.g., once every 15 minutes if it P106021WO01 PCT APPLICATION 20 of 32 reports the sensed temperature), random (e.g., to even out the load from reporting from several sensors), in response to a triggering event (e.g., when moisture is detected an alert is sent), in response to a request (e.g., a user initiated request), or a continuous stream (e.g., a live video feed of a patient). [0092] As another example, a UE comprises an actuator, a motor, or a switch, related to a communication interface configured to receive wireless input from a network node via a wireless connection. In response to the received wireless input the states of the actuator, the motor, or the switch may change. For example, the UE may comprise a motor that adjusts the control surfaces or rotors of a drone in flight according to the received input or to a robotic arm performing a medical procedure according to the received input. [0093] A UE, when in the form of an Internet of Things (IoT) device, may be a device for use in one or more application domains, these domains comprising, but not limited to, city wearable technology, extended industrial application and healthcare. Non-limiting examples of such an IoT device are a device which is or which is embedded in: a connected refrigerator or freezer, a TV, a connected lighting device, an electricity meter, a robot vacuum cleaner, a voice controlled smart speaker, a home security camera, a motion detector, a thermostat, a smoke detector, a door/window sensor, a flood/moisture sensor, an electrical door lock, a connected doorbell, an air conditioning system like a heat pump, an autonomous vehicle, a surveillance system, a weather monitoring device, a vehicle parking monitoring device, an electric vehicle charging station, a smart watch, a fitness tracker, a head-mounted display for Augmented Reality (AR) or Virtual Reality (VR), a wearable for tactile augmentation or sensory enhancement, a water sprinkler, an animal- or item-tracking device, a sensor for monitoring a plant or animal, an industrial robot, an Unmanned Aerial Vehicle (UAV), and any kind of medical device, like a heart rate monitor or a remote controlled surgical robot. A UE in the form of an IoT device comprises circuitry and/or software in dependence of the intended application of the IoT device in addition to other components as described in relation to the UE 200 shown in FIGURE 10. [0094] As yet another specific example, in an IoT scenario, a UE may represent a machine or other device that performs monitoring and/or measurements, and transmits the results of such monitoring and/or measurements to another UE and/or a network node. The UE may in this case be an M2M device, which may in a 3GPP context be referred to as an MTC device. As one particular example, the UE may implement the 3GPP NB-IoT standard. In other scenarios, P106021WO01 PCT APPLICATION 21 of 32 a UE may represent a vehicle, such as a car, a bus, a truck, a ship and an airplane, or other equipment that is capable of monitoring and/or reporting on its operational status or other functions associated with its operation. [0095] In practice, any number of UEs may be used together with respect to a single use case. For example, a first UE might be or be integrated in a drone and provide the drone’s speed information (obtained through a speed sensor) to a second UE that is a remote controller operating the drone. When the user makes changes from the remote controller, the first UE may adjust the throttle on the drone (e.g. by controlling an actuator) to increase or decrease the drone’s speed. The first and/or the second UE can also include more than one of the functionalities described above. For example, a UE might comprise the sensor and the actuator, and handle communication of data for both the speed sensor and the actuators. [0096] FIGURE 11 shows a network node 300 in accordance with some embodiments. As used herein, network node refers to equipment capable, configured, arranged and/or operable to communicate directly or indirectly with a UE and/or with other network nodes or equipment, in a telecommunication network. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (BSs) (e.g., radio base stations, Node Bs, evolved Node Bs (eNBs) and NR NodeBs (gNBs)). [0097] Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units and/or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS). [0098] Other examples of network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell/multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) P106021WO01 PCT APPLICATION 22 of 32 nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and/or Minimization of Drive Tests (MDTs). [0099] The network node 300 includes a processing circuitry 302, a memory 304, a communication interface 306, and a power source 308. The network node 300 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which the network node 300 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, the network node 300 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory 304 for different RATs) and some components may be reused (e.g., a same antenna 310 may be shared by different RATs). The network node 300 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 300, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node 300. [0100] The processing circuitry 302 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and/or encoded logic operable to provide, either alone or in conjunction with other network node 300 components, such as the memory 304, to provide network node 300 functionality. [0101] In some embodiments, the processing circuitry 302 includes a system on a chip (SOC). In some embodiments, the processing circuitry 302 includes one or more of radio frequency (RF) transceiver circuitry 312 and baseband processing circuitry 314. In some embodiments, the radio frequency (RF) transceiver circuitry 312 and the baseband processing circuitry 314 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital P106021WO01 PCT APPLICATION 23 of 32 units. In alternative embodiments, part or all of RF transceiver circuitry 312 and baseband processing circuitry 314 may be on the same chip or set of chips, boards, or units. [0102] The memory 304 may comprise any form of volatile or non-volatile computer-readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and/or any other volatile or non-volatile, non-transitory device-readable and/or computer-executable memory devices that store information, data, and/or instructions that may be used by the processing circuitry 302. The memory 304 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and/or other instructions capable of being executed by the processing circuitry 302 and utilized by the network node 300. The memory 304 may be used to store any calculations made by the processing circuitry 302 and/or any data received via the communication interface 306. In some embodiments, the processing circuitry 302 and memory 304 is integrated. [0103] The communication interface 306 is used in wired or wireless communication of signaling and/or data between a network node, access network, and/or UE. As illustrated, the communication interface 306 comprises port(s)/terminal(s) 316 to send and receive data, for example to and from a network over a wired connection. The communication interface 306 also includes radio front-end circuitry 318 that may be coupled to, or in certain embodiments a part of, the antenna 310. Radio front-end circuitry 318 comprises filters 320 and amplifiers 322. The radio front-end circuitry 318 may be connected to an antenna 310 and processing circuitry 302. The radio front-end circuitry may be configured to condition signals communicated between antenna 310 and processing circuitry 302. The radio front-end circuitry 318 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. The radio front-end circuitry 318 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 320 and/or amplifiers 322. The radio signal may then be transmitted via the antenna 310. Similarly, when receiving data, the antenna 310 may collect radio signals which are then converted into digital data by the radio front-end circuitry 318. The digital data may be passed to the P106021WO01 PCT APPLICATION 24 of 32 processing circuitry 302. In other embodiments, the communication interface may comprise different components and/or different combinations of components. [0104] In certain alternative embodiments, the network node 300 does not include separate radio front-end circuitry 318, instead, the processing circuitry 302 includes radio front-end circuitry and is connected to the antenna 310. Similarly, in some embodiments, all or some of the RF transceiver circuitry 312 is part of the communication interface 306. In still other embodiments, the communication interface 306 includes one or more ports or terminals 316, the radio front-end circuitry 318, and the RF transceiver circuitry 312, as part of a radio unit (not shown), and the communication interface 306 communicates with the baseband processing circuitry 314, which is part of a digital unit (not shown). [0105] The antenna 310 may include one or more antennas, or antenna arrays, configured to send and/or receive wireless signals. The antenna 310 may be coupled to the radio front-end circuitry 318 and may be any type of antenna capable of transmitting and receiving data and/or signals wirelessly. In certain embodiments, the antenna 310 is separate from the network node 300 and connectable to the network node 300 through an interface or port. [0106] The antenna 310, communication interface 306, and/or the processing circuitry 302 may be configured to perform any receiving operations and/or certain obtaining operations described herein as being performed by the network node. Any information, data and/or signals may be received from a UE, another network node and/or any other network equipment. Similarly, the antenna 310, the communication interface 306, and/or the processing circuitry 302 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and/or signals may be transmitted to a UE, another network node and/or any other network equipment. [0107] The power source 308 provides power to the various components of network node 300 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). The power source 308 may further comprise, or be coupled to, power management circuitry to supply the components of the network node 300 with power for performing the functionality described herein. For example, the network node 300 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of the power source 308. As a further example, the power source 308 may comprise a source of power in the form of a battery or battery pack which is connected to, P106021WO01 PCT APPLICATION 25 of 32 or integrated in, power circuitry. The battery may provide backup power should the external power source fail. [0108] Embodiments of the network node 300 may include additional components beyond those shown in FIGURE 11 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and/or any functionality necessary to support the subject matter described herein. For example, the network node 300 may include user interface equipment to allow input of information into the network node 300 and to allow output of information from the network node 300. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for the network node 300. [0109] FIGURE 12 is a flowchart illustrating an example method in a network node, according to certain embodiments. In particular embodiments, one or more steps of FIGURE 12 may be performed by network node 300 described with respect to FIGURE 11. The network node is operable to estimate intermodulation interference. [0110] The method begins at step 1212, where the network node (e.g., network node 300) receives a radio signal that contains intermodulation interference. The intermodulation interference is a function of a known aggressor and a function of an unknown aggressor. .As described above, multiple aggressors may have caused the intermodulation distortion in the received radio signal. The network node may have access to some form of raw data of at least one of the aggressors (known aggressors), but the network node does not have access to raw data of the other aggressors (unknown aggressors). [0111] At step 1214, the network node creates a de-spreading signal using the function of the known aggressor. The de-spreading signal is representative of the reciprocal of the function of the known aggressor. In some embodiments, rules are applied to the de-spreading signal to avoid very large values in the de-spreading signal for values where the known aggressor magnitude is relatively small. The de-spreading signal is described in more detail above with respect to FIGURE 1. [0112] At step 1216, the network node multiplies the received radio signal with the de- spreading signal. That is, the network node applies the de-spreading signal to the received radio signal to reduce the bandwidth of the intermodulation component. multiplication is described in more detail above with respect to FIGURE 1. [0113] At step 1218, the network node filters the multiplied signal with a filter that is limited to an expected frequency bandwidth of the function of the unknown aggressor to determine an P106021WO01 PCT APPLICATION 26 of 32 estimate of the function of the unknown aggressor. The filtering is described in more detail above with respect to FIGURE 1. [0114] At step 1220, the network node mitigates interference in the received radio signal based on the estimate of the function of the unknown aggressor. Mitigating interference may refer to any operation performed by the network node based on the estimate of the function of the unknown aggressor and is not limited to removing interference. [0115] In particular embodiments, mitigating interference in the received radio signal comprises multiplying the estimate of the function of the unknown aggressors with the function of the known aggressors to generate an estimate of the intermodulation interference. The method may further comprise cancelling intermodulation interference from the received radio signal based on the estimate of the intermodulation interference. [0116] In particular embodiments, the method further comprises determining a level of distortion in the received radio signal based on the estimate of the intermodulation interference. [0117] In particular embodiments, the method further comprises determining a correlation coefficient between the received radio signal based on the estimate of the intermodulation interference. [0118] In particular embodiments, mitigating interference in the received radio signal comprises using the estimate of the function of the unknown aggressors for spectrum sensing outside a passband of a receiver filter used for receiving the radio signal. [0119] Examples of operations performed by the network node based on the estimate of the function of the unknown aggressor are described in more detail above with respect to FIGURES 1-6. [0120] In some embodiments, the received radio signal may comprise functions of multiple unknown aggressors. In these embodiments, the above steps may be repeated or combined to estimate functions for all the unknown aggressors. [0121] In particular embodiments, the function of the unknown aggressor comprises a first function of unknown aggressors and a second function of unknown aggressors. Determining an estimate of the function of the unknown aggressor may comprise determining an estimate of the first function of unknown aggressors and an estimate of the second function of unknown aggressors and combining the estimate of the first function of unknown aggressors and the estimate of the second function of unknown aggressors. Determining an estimate of the function of the unknown aggressor may comprise determining a combined estimate of the first P106021WO01 PCT APPLICATION 27 of 32 function of unknown aggressors and the second function of unknown aggressors. The first function of unknown aggressors may be associated with a first radio antenna, and the second function of unknown aggressors may be associated with a second radio antenna. The equations for combining and estimating are described in more detail above. [0122] Modifications, additions, or omissions may be made to method 1200 of FIGURE 12. Additionally, one or more steps in the method of FIGURE 12 may be performed in parallel or in any suitable order. [0123] Modifications, additions, or omissions may be made to the methods disclosed herein without departing from the scope of the invention. The methods may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order. [0124] The foregoing description sets forth numerous specific details. It is understood, however, that embodiments may be practiced without these specific details. In other instances, well-known circuits, structures and techniques have not been shown in detail in order not to obscure the understanding of this description. Those of ordinary skill in the art, with the included descriptions, will be able to implement appropriate functionality without undue experimentation. [0125] References in the specification to “one embodiment,” “an embodiment,” “an example embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to implement such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described. [0126] Although this disclosure has been described in terms of certain embodiments, alterations and permutations of the embodiments will be apparent to those skilled in the art. Accordingly, the above description of the embodiments does not constrain this disclosure. Other changes, substitutions, and alterations are possible without departing from the scope of this disclosure, as defined by the claims below.

Claims

P106021WO01 PCT APPLICATION 28 of 32 CLAIMS: 1. A method performed by a network node for estimating intermodulation interference, the method comprising: receiving (1212) a radio signal that contains intermodulation interference, wherein the intermodulation interference is a function of a known aggressor and a function of an unknown aggressor; creating (1214) a de-spreading signal using the function of the known aggressor, wherein the de-spreading signal is representative of the reciprocal of the function of the known aggressor; multiplying (1216) the received radio signal with the de-spreading signal; filtering (1218) the multiplied signal with a filter that is limited to an expected frequency bandwidth of the function of the unknown aggressor to determine an estimate of the function of the unknown aggressor; and mitigating (1220) interference in the received radio signal based on the estimate of the function of the unknown aggressor. 2. The method of claim 1, wherein mitigating interference in the received radio signal comprises multiplying the estimate of the function of the unknown aggressors with the function of the known aggressors to generate an estimate of the intermodulation interference. 3. The method of claim 2, further comprising cancelling intermodulation interference from the received radio signal based on the estimate of the intermodulation interference. 4. The method of claim 2, further comprising determining a level of distortion in the received radio signal based on the estimate of the intermodulation interference. 5. The method of any one of claims 2-4, further comprising determining a correlation coefficient between the received radio signal based on the estimate of the intermodulation interference. P106021WO01 PCT APPLICATION 29 of 32 6. The method of claim 1, wherein mitigating interference in the received radio signal comprises using the estimate of the function of the unknown aggressors for spectrum sensing outside a passband of a receiver filter used for receiving the radio signal. 7. The method of any one of claims 1-6, wherein the function of the unknown aggressor comprises a first function of unknown aggressors and a second function of unknown aggressors and wherein determining an estimate of the function of the unknown aggressor comprises determining an estimate of the first function of unknown aggressors and an estimate of the second function of unknown aggressors and combining the estimate of the first function of unknown aggressors and the estimate of the second function of unknown aggressors. 8. The method of any one of claims 1-6, wherein the function of the unknown aggressor comprises a first function of unknown aggressors and a second function of unknown aggressors and wherein determining an estimate of the function of the unknown aggressor comprises determining a combined estimate of the first function of unknown aggressors and the second function of unknown aggressors. 9. The method of any one of claims 7-8, wherein the first function of unknown aggressors is associated with a first radio antenna, and the second function of unknown aggressors is associated with a second radio antenna. 10. A network node (300) capable of estimating intermodulation interference, the network node comprising processing circuitry (302) operable to: receive a radio signal that contains intermodulation interference, wherein the intermodulation interference is a function of a known aggressor and a function of an unknown aggressor; create a de-spreading signal using the function of the known aggressor, wherein the de- spreading signal is representative of the reciprocal of the function of the known aggressor; multiply the received radio signal with the de-spreading signal; filter the multiplied signal with a filter that is limited to an expected frequency bandwidth of the function of the unknown aggressor to determine an estimate of the function of the unknown aggressor; and P106021WO01 PCT APPLICATION 30 of 32 mitigate interference in the received radio signal based on the estimate of the function of the unknown aggressor. 11. The network node of claim 10, wherein the processing circuitry is operable to mitigate interference in the received radio signal by multiplying the estimate of the function of the unknown aggressors with the function of the known aggressors to generate an estimate of the intermodulation interference. 12. The network node of claim 11, the processing circuitry further operable to cancel intermodulation interference from the received radio signal based on the estimate of the intermodulation interference. 13. The network node of claim 11, the processing circuitry further operable to determine a level of distortion in the received radio signal based on the estimate of the intermodulation interference. 14. The network node of any one of claims 11-13, the processing circuitry further operable to determine a correlation coefficient between the received radio signal based on the estimate of the intermodulation interference. 15. The network node of claim 10, wherein the processing circuitry is operable to mitigate interference in the received radio signal by using the estimate of the function of the unknown aggressors for spectrum sensing outside a passband of a receiver filter used for receiving the radio signal. 16. The network node of any one of claims 10-15, wherein the function of the unknown aggressor comprises a first function of unknown aggressors and a second function of unknown aggressors and the processing circuitry is operable to determine an estimate of the function of the unknown aggressor by determining an estimate of the first function of unknown aggressors and an estimate of the second function of unknown aggressors and combining the estimate of the first function of unknown aggressors and the estimate of the second function of unknown aggressors. P106021WO01 PCT APPLICATION 31 of 32 17. The network node of any one of claims 10-15, wherein the function of the unknown aggressor comprises a first function of unknown aggressors and a second function of unknown aggressors and the processing circuitry is operable to determine an estimate of the function of the unknown aggressor by determining a combined estimate of the first function of unknown aggressors and the second function of unknown aggressors. 18. The network node of any one of claims 16-17, wherein the first function of unknown aggressors is associated with a first radio antenna, and the second function of unknown aggressors is associated with a second radio antenna.
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