76 results about "Nonlinear equalization" patented technology

A method for canceling interference at a wireless code division multiple access (CDMA) communication receiver is provided. The wireless CDMA communication system receiver receives a stream of chips generated by spreading data symbols formed by grouping bits of information at a wireless CDMA communication transmitter which are broadcast at a certain chip-rate. The received chips are de-spread and symbols pertaining to respective users are reconstructed. The method includes formatting the stream of chips into blocks of chips, and performing an iterative block decision feedback equalization in a frequency domain at the chip-rate of the broadcast stream of chips to remove inter-symbol interference by defining a transfer function. The transfer function is defined based upon iteration cycles as a function of data detected in a preceding iteration cycle. The chips generated are interleaved by spreading each data symbol being transmitted before broadcasting the stream of interleaved chips in distinct blocks of chips.

The invention discloses an optical fiber nonlinear equalization method for a 64-QAM (Quadrature Amplitude Modulation) coherent optical communication system used for processing received 64-QAM data. The method comprises the following steps: setting a received data set as a first-level data set, calculating the density parameter of each data point, setting a threshold, and selecting the data with the density parameter exceeding the specified threshold as a second-level data set; demodulating second-level data set points, dividing the second-level data set points into 64 clusters, and obtaining 64 centroids; according to the obtained centroids, classifying data in the second-level data set into a corresponding cluster according to the nearest Euclidean distance, and using 64 centroids of a newly obtained cluster to update; and allocating the first-level data set to the corresponding cluster according to the nearest Euclidean distance, obtaining the classified 64 clusters, and calculatingto obtain an optimal centroid of each cluster. The optical fiber nonlinear equalization method for the 64-QAM coherent optical communication system provided by the invention can quickly and accuratelyselect a global optimal centroid of a K-means cluster without the need of iteration, well reduce the influence of Kerr nonlinearity in an optical fiber, and the obtained bit error rate performance isone half an order of magnitude higher than the performance that is not processed before.

According to the nonlinear equalization method for the high-order QAM coherent light system, after receiving end data is subjected to phase noise compensation, an FCM algorithm is firstly used for achieving effective clipping of training data, meanwhile, test data is subjected to classification judgment, and therefore a test set and a training set of a follow-up KNN algorithm are greatly reduced.The method is based on a coherent light 16QAM system with the transmission rate of 112 Gb/s and the transmission distance of 160 km, and non-linear equalization simulation verification is carried out.Simulation results show that the same system nonlinear damage compensation effect as a traditional KNN algorithm can be obtained, but the algorithm complexity of the method is far lower than that ofthe traditional KNN algorithm, and the algorithm running time is far shorter than that of the KNN algorithm. According to the invention, the application of the coherent light QAM system in medium andlong distance optical fiber transmission can be greatly promoted.

The invention provides an optical nonlinear equalization method based on transfer learning. Trained initialized neural network parameters are migrated to a neural network of each channel through transfer learning, and each channel is assisted to quickly establish the neural network equalizer, so that quick modeling is realized, and the resource overhead, such as less new training data and less iterative compensation, is reduced. Meanwhile, once the channel state is changed, such as the optical power and the transmission distance, the nonlinear phase noise is correspondingly changed, and at themoment, if each channel is retrained respectively, huge expenditure is also corresponding. At the moment, by initializing migration of neural network parameters and supplementing a small amount of new data, rapid neural network remodeling is realized, and then updated parameters are migrated to each channel for updating, so that the response capability to channel change is improved. According tothe invention, nonlinear equalization efficiency under different channels is improved, and high tolerance to optical fiber nonlinearity is maintained.

Complex polyphase nonlinear equalizer (cpNLEQs) mitigate nonlinear distortions generated by complex in-phase/quadrature (I/Q) time-interleaved analog-to-digital converters (TIADCs). Example cpNLEQs upsample the digital waveform emitted by the TIADC, e.g., by a factor of two, then separate the upsampled digital waveform into upsampled in-phase and quadrature components. Processors in the cpNLEQs create real and imaginary nonlinear compensation terms from the upsampled in-phase and quadrature components. The nonlinear compensation terms are downsampled, and the downsampled imaginary nonlinear compensation term is phase-shifted, then combined with the downsampled real component to produce an estimated residual distortion. Subtracting the estimated residual distortion from the digital waveform emitted by the TIADC yields an equalized digital waveform suitable for further processing.

Embodiments are provided to improve direct detection for optical transmissions. In an embodiment, a method by a transmitter includes adjusting, using a nonlinear equalizer (NLE), a drive voltage for an optical modulator in accordance with a mapping between the drive voltage and an output of the optical modulator. The mapping is an inverse function of a nonlinear transfer function at the optical modulator between the output and to the drive voltage. The method further includes driving, using the adjusted drive voltage, the output of the optical modulator. The output is a single-side band (SSB) signal and is sufficiently linear with respect to the drive voltage for allowing direct detection at a receiver.

The disclosure relates to a method performed by an optical receiver, the method comprising receiving an optical communication signal comprised in a signal space, the signal comprising a set of received training symbols and a set of received payload symbols, determining a kernel operating in a feature space by using the set of training symbols and a reference set of training symbols indicative of an undistorted version of the training symbols, wherein determining a kernel further comprises determining at least an equalization mapping function ƒ configured to map received symbols to channel equalized symbols, and determining an error function (e) configured to generate a measure indicative of an error between symbols mapped by the equalization mapping function ƒ and an ideal equalization mapping function, performing nonlinear equalization of the payload symbols (C′₁ to C′_M) by performing linear equalization of the payload symbols (C′₁ to C′_M) in the feature space using the received training symbols (C₁ to C_N) and the error function (e). The disclosure further relates to an optical receiver

The invention discloses a nonlinear equalization method based on weighted principal component analysis, which belongs to the field of optical fiber communication, and comprises the following steps of: extracting complete frame data at a receiving end, performing downsampling and amplitude normalization on the complete frame data, and nonlinearly mapping the complete frame data into a Walterra series matrix by adopting a sliding window mode; calculating a weighted covariance matrix of the Woltzia series matrix by using the first weight vector, carrying out eigenvalue decomposition on the weighted covariance matrix, forming a principal component projection matrix by using a part of eigenvectors with the maximum eigenvalue, and multiplying the Woltzia series matrix by the principal component projection matrix to obtain a principal component matrix; performing weighted summation on each principal component in the principal component matrix by using the second weight vector to obtain an output signal subjected to nonlinear equalization; wherein the first weight vector is used for representing the weight of each Walterra kernel corresponding to the same sliding window, and the second weight vector is used for representing the weight of each principal component. According to the invention, the complexity can be reduced and the equalization performance deterioration can be avoided.

The present development includes a first element of an optical fibre entrance by which an information carrying signal is transmitted, an optical detector block, a non-linear equalizer block and a final processor block. The development includes an electrical non-linear equalizer block, connecting the output of the optical detector block and the input of the final processor block that compensates the quadratic non-linear characteristic of the optical detector block. Both blocks thus may present a more linear joint characteristic between the electrical field envelope of the information carrying signal in the optical fibre and the electrical signal. Consequently, the final processor block can compensate, in a more effective form, for the linear distortions that the information carrying signal suffers in the transmission through the fibre. The result may be an optical receiver with non-linear compensation of the photo-detection process and with approximate linear compensation of the linear distortions of the optical fibre transmission.

A receiver (500) and a method are described herein that address inter-symbol interference in a received signal (508) by using a two-stage equalizer (502) which includes a first demodulation stage (504) that processes the received signal and produces initial symbol decisions (510), and a non-linear equalization second stage (506) that uses the received signal to perform a sequential search in an attempt to improve upon the initial symbol decisions; wherein, if able to improve upon the initial symbol decisions then an output sequence (512) is obtained from the sequential search and if not able to improve upon the sequence metric threshold then the output sequence is the initial symbol decisions.

The invention discloses an adaptive equalization method suitable for scatter communication in the field of communication. On the premise that the complexity of the system is not increased, a linear equalizer and a nonlinear equalizer are realized by utilizing the structure of a decision feedback equalizer in combination with a channel estimation result, and compared with a scattering system adopting linear equalization, the communication capability of the system under a deep fading channel is improved; compared with a scattering system adopting decision feedback nonlinear equalization, error code diffusion under a low signal-to-noise ratio is avoided, and the communication capability under a non-deep fading channel is improved.