Abstract: Methods and systems are described for reducing interference on radio units from passive intermodulation (PIM) distortion. Base station radio units can have multiple antennas, each receiving and sending communications over various frequencies. Embodiments under the present disclosure can identify the source of PIM and then reduce power of the aggressor downlink carriers on the impacted antennas. This can reduce the PIM that desensitizes the uplink receivers.

Abstract: A method in a network node and an apparatus for determining passive intermodulation (PIM) characteristics at the network node are provided. According to one aspect, a method includes capturing signals from each of at least one antenna port at a first time and a second time. The method includes determining a first covariance matrix based on signals captured at the first time. The method also includes determining a second covariance matrix based on signals captured at the second time. The method further includes determining a difference matrix, the difference matrix being based on a difference between the first and second covariance matrices, the difference matrix corresponding to changes in PIM between the first time and the second time.

Abstract: A method and radio in a network node for passive intermodulation (PIM) downlink subspace acquisition. According to one aspect, a method includes determining a downlink projection matrix that is formed using the downlink beamforming weights and determining a first downlink interference covariance matrix estimate for a current downlink orthogonal frequency division multiplexed, OFDM, symbol based at least in part on multiplying the downlink projection matrix by a scaling factor that is dependent on the passive intermodulation, PIM, power generated in one or more uplink channels.

Abstract: A network node is provided. The network node includes processing circuitry configured to determine at least one Convex Reduction of Amplitude, CRAM, projection matrix based at least in part on a signal subspace of scheduled wireless devices, and optionally cause transmission based at least in part on the at least one CRAM projection matrix.

Abstract: A method of a wireless communication transmitter is disclosed for peak-to-average power ratio (PAPR) control of communication symbols with N time-domain signal samples for transmission via each of M antenna elements. The method comprises: applying a PAPR cost function f(x) which has a proximal operator with closed form and is differentiable in an interval, and the proximal operator comprises a parameter lambda for tuning; selecting a value for lambda to perform a trade-off between PAPR and at least one other characteristic of the wireless communication transmitter; selecting a precoding for the collection of samples as a solution to an optimization problem for the selected value for lambda, wherein the optimization problem comprises minimization of an overall cost function comprising at least the PAPR cost function, and wherein solving the optimization problem comprises using the proximal operator of the PAPR cost function.

Abstract: Systems and methods are disclosed herein for a Convex Reduction of Amplitude (CRAM) based processing scheme for a Multiple Input Multiple Output (MIMO) Orthogonal Division Multiplexing (OFDM) transmitter system. In one embodiment, a method performed by a processing system for a MIMO OFDM transmitter system comprises precoding frequency-domain input signals to provide frequency-domain precoded signals for multiple subcarriers. The method further comprises processing the frequency-domain precoded signals in accordance with a CRAM-based processing scheme to provide time-domain precoded signals for respective transmit branches of the MIMO OFDM transmitter system. The CRAM-based processing scheme uses projection matrices for the subcarriers, respectively, to project clipping energy into a null space of the MIMO OFDM transmitter system. Further, the projection matrices are a function of static or semi-static information that defines the null space of the MIMO OFDM transmitter system.

Abstract: Systems and methods are disclosed herein that relate to Peak-to-Average Power Ratio (PAPR) reduction in a MIMO OFDM transmitter system. In some embodiments, a method of operation of a transmitter system includes, for each carrier of two or more carriers, performing precoding of frequency-domain input signals for the carrier to provide frequency-domain precoded signals for the carrier, the frequency-domain input signals for the carrier being for a plurality of transmit layers for the carrier, respectively. The method further includes processing the two or more pluralities of frequency-domain precoded signals for the two or more carriers, respectively, in accordance with a multi-carrier processing scheme to provide a plurality of multi-carrier time-domain transmit signals for a plurality of antenna branches, respectively, of the MIMO OFDM transmitter system.

Abstract: Systems and methods are disclosed herein that relate to Peak-to-Average Power Ratio (PAPR) reduction in a MIMO OFDM transmitter system. In some embodiments, a method of operation of a transmitter system includes, for each carrier of two or more carriers, performing precoding of frequency-domain input signals for the carrier to provide frequency-domain precoded signals for the carrier, the frequency-domain input signals for the carrier being for a plurality of transmit layers for the carrier, respectively. The method further includes processing the two or more pluralities of frequency-domain precoded signals for the two or more carriers, respectively, in accordance with a multi-carrier processing scheme to provide a plurality of multi-carrier time-domain transmit signals for a plurality of antenna branches, respectively, of the MIMO OFDM transmitter system.

Abstract: A method and network node for detection of passive intermodulation (PIM) are disclosed. According to one aspect, a method includes determining values of a covariance matrix based at least in part on uplink signals received by the network node radio. The method also includes determining a plurality of uplink (UL) channel 5 eigenvalues based at least in part on an eigen-component acquisition technique. The method further includes determining a presence or absence of PIM based at least in part on a plurality of the UL channel eigenvalues.

Abstract: A first radio node for uplink and downlink co-scheduling is provided. The first radio node includes processing circuitry containing instructions executable to configure the first radio node to: determine a scheduling restriction for joint uplink and downlink scheduling based on passive intermodulation (PIM) generated during simultaneous uplink and downlink communications where the uplink communications corresponds to communications from a second radio node to the first radio node, and perform communications according to the scheduling restriction.

Abstract: Systems and methods are disclosed herein that relate to Peak-to-Average Power Ratio (PAPR) reduction in a MIMO OFDM transmitter system. In some embodiments, a method of operation of a transmitter system includes, for each carrier of two or more carriers, performing precoding of frequency-domain input signals for the carrier to provide frequency-domain precoded signals for the carrier, the frequency-domain input signals for the carrier being for a plurality of transmit layers for the carrier, respectively. The method further includes processing the two or more pluralities of frequency-domain precoded signals for the two or more carriers, respectively, in accordance with a multi-carrier processing scheme to provide a plurality of multi-carrier time-domain transmit signals for a plurality of antenna branches, respectively, of the MIMO OFDM transmitter system.

Abstract: Systems and methods are disclosed herein that relate to Peak-to-Average Power Ratio (PAPR) reduction in a MIMO OFDM transmitter system. In some embodiments, a method of operation of a transmitter system includes, for each carrier of two or more carriers, performing precoding of frequency-domain input signals for the carrier to provide frequency-domain precoded signals for the carrier, the frequency-domain input signals for the carrier being for a plurality of transmit layers for the carrier, respectively. The method further includes processing the two or more pluralities of frequency-domain precoded signals for the two or more carriers, respectively, in accordance with a multi-carrier processing scheme to provide a plurality of multi-carrier time-domain transmit signals for a plurality of antenna branches, respectively, of the MIMO OFDM transmitter system.

Abstract: A method and apparatus for artificial neural network precoding for massive MIMO systems are disclosed. In one embodiment, a method includes processing, by an artificial neural network, ANN, precoding engine, at least one input signal by 5 performing a low peak-to-average-power ratio, PAPR, precoding on the at least one input signal; and transmitting, via at least one antenna array having at least one antenna, at least one precoded output signal processed by the ANN precoding engine.

Abstract: A first radio node including processing circuitry configured to configure the first radio node to: obtain a first interference subspace, obtain beamforming weights based on the first interference subspace where the beamforming weights configured to modify a radiation pattern in at least one communication direction of at least one interference source, and perform wireless communications based on the beamforming weights.

Abstract: Systems and methods are disclosed herein that related to Peak-to-Average Power Ratio (PAPR) reduction in a (e.g., massive) Multiple-Input Multiple-Output (MIMO) Orthogonal Division Multiplexing (OFDM) transmitter system. In some embodiments, a method of operation of a MIMO OFDM transmitter system comprises, for each carrier of two or more carriers, performing precoding of a plurality of frequency-domain input signals for the carrier to provide a plurality of frequency-domain precoded signals for the carrier, the plurality of frequency-domain input signals for the carrier being for a plurality of transmit layers for the carrier, respectively. The method further comprises processing the frequency-domain precoded signals for the two or more carriers in accordance with a multi-carrier Convex Reduction of Amplitudes (CRAM) processing scheme to provide a plurality of multi-carrier time-domain transmit signals for a plurality of antenna branches, respectively, of the MIMO OFDM transmitter system.

Abstract: Systems and methods are disclosed herein that relate to Peak-to-Average Power Ratio (PAPR) reduction in a MIMO OFDM transmitter system. In some embodiments, a method of operation of a transmitter system comprises, for each carrier of two or more carriers, performing precoding of frequency-domain input signals for the carrier to provide frequency-domain precoded signals for the carrier, the frequency-domain input signals for the carrier being for a plurality of transmit layers for the carrier, respectively. The method further comprises processing the two or more pluralities of frequency-domain precoded signals for the two or more carriers, respectively, in accordance with a multi-carrier processing scheme to provide a plurality of multi-carrier time-domain transmit signals for a plurality of antenna branches, respectively, of the MIMO OFDM transmitter system.

Abstract: A method and system for error scaling for crest factor reduction (CFR) are disclosed. According to one aspect, a method for regulating peak to average power ratio (PAR) of an output signal of the CFR circuit is disclosed. In one embodiment, the method includes receiving an input signal at an input of the CFR circuit. The magnitude of the input signal is determined and clipped to a target level to produce an error signal by comparing the input signal magnitude to a threshold in a comparator. The error signal is filtered to produce a processed error signal. The filter provides a bandpass filter frequency response. The PAR of the output signal is regulated by scaling the processed error signal by an error scaling factor to achieve a target signal to noise ratio (SNR) for the output signal corresponding to a target error vector magnitude (EVM).

Abstract: A method and system for detecting PIM signals in a wireless communication base station are disclosed. According to one aspect, a method includes receiving radio frequency, RF, signals over a frequency band spanning a plurality of frequencies of signals transmitted by at least a first transmitter external to the base station and at least a second transmitter. The method includes determining frequencies at which signals are present among the received radio frequency signals. PIM signal frequencies are calculated based on the determined frequencies at which signals are present. The method includes determining whether the calculated PIM signal frequencies interfere with selected uplink channels.

Abstract: Systems and methods are disclosed herein that related to Peak-to-Average Power Ratio (PAPR) reduction in a (e.g., massive) Multiple-Input Multiple-Output (MIMO) Orthogonal Division Multiplexing (OFDM) transmitter system. In some embodiments, a method of operation of a MIMO OFDM transmitter system comprises, for each carrier of two or more carriers, performing precoding of a plurality of frequency-domain input signals for the carrier to provide a plurality of frequency-domain precoded signals for the carrier, the plurality of frequency-domain input signals for the carrier being for a plurality of transmit layers for the carrier, respectively. The method further comprises processing the frequency-domain precoded signals for the two or more carriers in accordance with a multi-carrier Convex Reduction of Amplitudes (CRAM) processing scheme to provide a plurality of multi-carrier time-domain transmit signals for a plurality of antenna branches, respectively, of the MIMO OFDM transmitter system.

Abstract: A method, detector and radio unit for non-linear interference detection in a communication system having a victim signal and an offending signal are disclosed. According to one aspect, a method includes determining a magnitude of the victim signal raised to a first power to produce a first signal. The method also includes determining a magnitude of the offending signal raised to a second power to produce a second signal. The first signal and the second signal are correlated to produce an output signal indicative of an extent to which the offending signal interferes with the victim signal.