Methods, systems, and devices for wireless communications are described. In some systems, a transmitting device may perform a pre-distortion of a signal on a resource allocation for the signal and using discrete Fourier transform (DFT)-domain processing. For example, the transmitting device may perform a first frequency-domain (FD) to time-domain (TD) transform, which may be an example of an inverse DFT (IDFT), on a first set of FD symbols to obtain a first set of TD samples. A size of the first FD to TD transform may be based on the resource allocation for the signal. The transmitting device may perform a crest factor reduction (CFR) function on the first set of TD samples to pre-distort the signal in the TD (e.g., in the IDFT domain), which may enable the transmitting device to avoid out-of-band (OOB) emission or otherwise have greater control over where the pre-distortion contributes energy.

An apparatus comprises a digital processing device configured to generate a digital transmission signal, a digital-to-analog converter connected to the digital processing device and configured to convert the digital transmission signal into an analog transmission signal, and a power amplifier connected to the digital-to-analog converter and configured to amplify the analog transmission signal. An antenna filter is connected to the power amplifier and configured to filter the amplified analog transmission signal; the antenna filter is configured to pass frequencies in at least one passband and to attenuate frequencies in at least one stopband. The digital processing device is configured to perform a process of reducing peak power in the digital transmission signal; in this process error components having different frequencies are produced. A frequency spectrum of the error components is manipulated such that a part of the error components is deposited in the stopband of the antenna filter.

Techniques for peak-to-average power ratio (PAPR) reduction are described. Wireless devices may use one or more PAPR shaping resources, such as expanded bandwidth and/or pulse-shaping filtering, for shaping a signal to reduce PAPR. For example, expanded bandwidth may be utilized for adding a cyclic affix (CA), such as may comprise a cyclic prefix (CP), cyclic suffix (CS), etc., and combinations thereof, to a frequency domain data signal to provide a CP augmented frequency domain data signal used to generate a reduced PAPR time domain data signal. Additionally or alternatively, pulse-shaping filtering may be applied to a frequency domain signal to provide a pulse-shaped frequency domain data signal used to generate a reduced PAPR time domain data signal. Other aspects and features are also claimed and described.

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.

Aspects relate to signaling relating to a non-linearity model for power amplifier circuitry of a transmitting device. The power amplifier circuitry may apply digital pre-distortion (DPD) to a signal prior to amplification and transmission of the signal. A receiving device may apply digital post-distortion (DPoD) to a signal received from the transmitting device where the DPoD is based on the non-linearity model. The transmitting device may send to the receiving device non-linearity parameters for the non-linearity model.

This disclosure provides methods, devices and systems for reducing PAPR in wireless communications. Some implementations more specifically relate to suppressing the amplitudes of a data signal that exceed a threshold amplitude level. The data signal may represent transmit (TX) data associated with a hybrid automatic repeat request (HARQ) process. In some implementations, a transmitting device may detect one or more peaks associated with the data signal. The transmitting device may reduce the amplitudes of the samples associated with the detected peaks to produce the amplitude-suppressed data signal. The transmitting device may further generate peak suppression information indicating the amplitudes of one or more of the samples associated with the peaks. In response to receiving a NACK message, the transmitting device may transmit, to the receiving device, the peak suppression information, one or more coded bits representing the TX data (associated with the HARQ process), or any combination thereof.

Aspects relate to reconstructing a received non-linearly distorted (e.g., clipped) signal. A transmitting device may non-linearly distort a signal to be transmitted (e.g., by clipping peaks of the signal). This non-linear distortion may adversely affect decoding of the signal at a receiving device. To improve decoding performance at the receiving device, the transmitting device provides information regarding some of the non-linear distortion (e.g., information regarding a subset of the peaks that have been clipped) to the receiving device. The receiving device may reconstruct the signal based on this information (e.g., by reconstructing the subset of the peaks and adding the reconstructed peaks to the received clipped signal). In addition, the receiving device estimates the remaining non-linear distortion in the reconstructed signal (e.g., due to clipped peaks that were not indicated in the clipping information) by slicing the reconstructed signal and clipping the sliced signal, and provides a final reconstructed signal.

A method for crest factor reduction (CFR). The method includes: generating a signal, x.sub.s(t); generating a vector, x(t), of size N×1 based on x.sub.s(t), wherein N>1; generating a clipping signal vector, z(t), based on x(t), wherein z(t) is a vector of size N×1; producing a transformed signal vector, y(t), based on z(t), wherein y(t) is a vector of size N×1; and generating an output signal vector, x.sub.p(t), based on y(t) and x(t), wherein generating x.sub.o(t) comprises subtracting y(t) from x(t) and x.sub.o(t) is a vector of size N×1.

A dynamic configuration of crest factor reduction in a licensed assisted access radio system. A processing device comprises a detecting block, a clipping pulse generator, a first storage block, a selecting block, a full clipping block and a simplified clipping block. The detecting block performs a listen-before-talk (LBT) procedure on a plurality of carriers in parallel and generates a trigger signal in response to LBT success on one or more carriers. The clipping pulse generator generates, for the carrier(s) with LBT success, a clipping pulse within a time period from the receipt of the trigger signal to the start of user traffic transmission. The first storage block stores the clipping pulse for use by the full clipping block. The selecting block selects the full clipping block when there is user traffic on the carrier(s) and selects the simplified clipping block when there is no user traffic on the carrier(s).

The present application relates to a system and a method for reducing a signal peak-to-average ratio, and a computer-readable storage medium. Before the peaks in the IQ signal are scaled, a scaling effect of peak points scaling on subsequent peak points is estimated and windowing intensities of subsequent peak points are modified. It solves a problem that generated correction coefficients superimpose on top of each other leading to excessive peak shaving. In addition, the above method does not need a lot of multipliers and is easy to be implemented.