5 results about "Clipping noise" patented technology

This invention discloses an HPAM-DMT-NOMA method based on time-domain preprocessing, comprising: At the transmitting end, PAM modulation is performed on the input user transmission bits to generate PAM symbols; after power superposition, serial-to-parallel conversion, and Hermitian symmetry, the symbols are allocated to two signal components for HPAM-DMT transmission; the frequency domain signals of PAM-DMT and RPAM-DMT are calculated; an IFFT operation is performed to obtain the time domain signal; the time-domain preprocessed signal is calculated; the RPAM-DMT time domain signal is calculated and superimposed on the clipped PAM-DMT signal for synchronous transmission to obtain a mixed signal; a reconstructed signal is introduced, processed, and input to drive an LED for illumination; at the receiving end, the received signal is processed to generate a frequency domain signal, and finally, the multi-user signal is recovered. This scheme eliminates clipping noise interference between the mixed signal components, avoids error propagation problems, and achieves high spectral efficiency and power efficiency.

The invention discloses an underwater CSK-OFDM modulation and detection method based on LED linear constraint, and the method comprises the steps: enabling a transmitter to map a data bit stream of a constellation diagram into a complex symbol stream, converting the complex symbol stream into a real number time domain sequence through an ACO-OFDM module, carrying out the LED amplitude limiting of the time domain sequence, and obtaining a time domain clipping sequence; transmitting the time domain clipping sequence in a UOWC channel through a corresponding LED, introducing symbol timing deviation and amplitude limiting noise into a frequency domain by a receiver, and processing the time domain clipping sequence by using an ACO-OFDM module again to obtain a received signal; under the maximum expectation framework, the probability from each alternative constellation diagram is calculated, symbol timing deviation and additive white Gaussian noise variance are estimated, a globally optimal solution is obtained, and a constellation diagram recognition result is output through maximum likelihood demodulation. According to the method, the linear range constraint of the LED and the complex environment under the UOWC scene are comprehensively considered.

A method for suppressing peak-to-average power ratio (PAPR) of reserved subcarriers in OFDM communication systems includes the following steps: Step 1: digital clipping using a shearing method; Step 2: acquiring clipping noise; Step 3: suppressing out-of-band noise to obtain new clipping noise; Step 4: filtering out in-band noise to obtain canceled noise; Step 5: inversely superimposing the noise into the original signal; Step 6: repeating steps 1-5 to reach the maximum number of iterations; Step 7: outputting the signal after PAPR suppression. This invention expands the range of reserved subcarriers, combining the resources of out-of-band and in-band empty subcarriers, and uses them to generate a signal that suppresses high peak values ​​and cancels noise, thereby improving PAPR suppression gain and retaining the distortion-free characteristics of the reserved subcarrier method.

A digital pre-distortion circuit and a method for reducing clipping noise in a digital pre-distortion circuit are provided. The digital pre-distortion circuit includes a pre-distorter, a clipping logic, an error extraction circuit, a filter and a compensation circuit. The pre-distorter performs a pre-distortion operation according to an input signal to generate an initial pre-distortion signal, and the clipping logic clips the initial pre-distortion signal to generate a clipped pre-distortion signal. In addition, the error extraction circuit calculates a difference between the initial pre-distortion signal and the clipped pre-distortion signal to generate a clipped error signal, and the filter performs filtering on the clipped error signal to generate a filtered error signal, wherein the compensation circuit compensates the clipped pre-distortion signal according to the filtered error signal to generate an output signal.

The application discloses a neuromorphic camera denoising method for general lighting conditions, and belongs to the field of video denoising. According to the relationship between the intensity of the pulse stream noise and the scene lighting, the continuous space-time pulse stream is converted into the picture feature representation under a specific window, and the input of the traditional neural network is adapted; the dark current noise and the response inconsistency noise are removed through the calibrated dark current matrix and the response inconsistency matrix; the image features are converted into the frequency domain features through the two-dimensional discrete wavelet transform, the low-cost noise removal is realized by using the frequency domain noise separation characteristics; the shot noise and the clipping noise are removed by fusing the frequency domain features of adjacent windows; the residual noise on the frequency domain is thoroughly removed through the deep self-attention network; finally, in order to inhibit the excessive smoothing caused by the denoising, the fusion features on the frequency domain are used to refine the denoising result. The application is suitable for the field of video denoising, is used for reconstructing a clean image, reducing the noise in the image and reducing the influence of the noise on the downstream task.