156 results about "Blind equalization" patented technology

In a QAM demodulator including an adaptive equalizer, a method of carrier tracking comprising the following steps is disclosed: (A) sampling a QAM signal received from a transmission channel; (B) recovering a symbol clock function from the sampled QAM signal; (C) applying the sampled QAM signal to the adaptive equalizer in order to obtain a QAM equalized signal in a Blind Equalization (BE) mode; (D) using a slicer to locate a nearest plant point for the QAM Blind equalized signal for each recovered symbol clock; (E) using a complex conjugate multiplier to obtain an instantaneous inphase component and an instantaneous quadrature component of a phase angle error signal; (F) using a linear phase detector to obtain an instantaneous phase angle error for each symbol clock; (G) averaging the instantaneous phase angle error signal by using a carrier loop filter; (H) using a complex multiplier to insert an inverse of the averaged phase angle error signal into the QAM Blind equalized signal to compensate for the carrier phase angle error; and (I) repeating the steps (D-H) to close a carrier frequency loop.

The invention relates to a method with strong anti-multi-path capability for processing moveable underwater sound communication signals, including two parts, namely a transmitter processing method and a receiver processing method, wherein the transmitter processing method includes the operations of error correction of coding, data packing, digital interpolation, base band shaping wave filtering, upper modified frequency modulation, and the like; and the receiver processing method includes the operations of digital wave filtering, frame synchronous judgment, preliminary compensation of Dopplerfrequency shift, lower modified frequency modulation, bit synchronous judgment, fine compensation of Doppler frequency shift, digital equalization, error correction of decoding, etc. The invention carries out the intercrossing treatment on technologies of synchronous judgment, compensation of Doppler frequency shift, compensation of multi-path effect, and the like, and guarantees that under the environment of strong Doppler frequency shift, the system can realize the accurate synchronism of signals and carries out real-time estimation and compensation on the effect of strong Doppler frequencyshift; and the adopted blind equalization method can carry out effective tracking compensation on the time varying multi-path effect of an underwater sound signal channel, thereby greatly increasing the integral stability and the bit error rate performance of an underwater sound communication system and enduing the system with the capability of reliable communication during movement.

According to one embodiment, an optical receiver adapted to recover OOK or PAM data carried by a modulated optical carrier has an optical detector adapted to produce a sequence of vector pairs having first and second digital vectors indicative of complex values of first and second polarization components, respectively, of the modulated optical carrier at a corresponding sampling time. The optical receiver also has a digital processor that is connected to receive the sequence and is adapted to perform a rotation on each pair in a manner that tends to compensate for polarization rotation produced by transmitting the modulated optical carrier from an optical transmitter thereof to the optical receiver. The digital processor is further adapted to estimate values of the OOK or PAM data encoded onto each of the first and second polarization components based on the vectors produced by the rotation in a manner responsive to values of energy errors in the estimated values.

The invention discloses a safe transmission method of a physical layer in wireless communication, which is characterized by comprising the following steps of: a single-antenna desired user firstly transmits unencrypted request information to a multi-antenna base station; the base station receives the request information and estimates a signal path between the base station and the desired user with a frequency piloting sequence; the base station modulates bit to be transmitted into a constellation point symbol b (n) with a known phase position modulating mode, designs a fast-variable weighting coefficient, weights the constellation point symbol b (n) to be transmitted, and transmits the weighted symbol on selected Jrand antennas according appointed gross power; the desired user receives the weighted symbol, i.e. a weighting symbol, and decodes with a maximum likelihood method; and a wiretap user fast changes the weighting coefficient due to the process of the base station, can not decode with a blind equalization method, and can not decode with the maximum likelihood method, so that the method finally realizes the safe transmission.

An apparatus, e.g. an optical receiver, includes an optical front end and an equalizer. The front end is configured for receiving an optical signal bearing first and second symbols on respective first and second polarization channels. The equalizer is configured to 1) select a first cost function if the first symbol has greater energy than the second symbol, 2) select a second different cost function if the second symbol has a greater energy than the first symbol, and 3) based on the selected cost function, update coefficients of an adaptive filter configured to demultiplex and equalize the first and second polarization channels.

An apparatus for correcting clipping distortion of a receiver system includes: an equalizer which generates a first equalization signal by equalizing a frequency domain clipping signal via a first equalization coefficient correcting a channel distortion, and generates a second equalization signal by equalizing the frequency domain clipping signal via a second equalization coefficient correcting the clipping distortion and the channel distortion; and a signal reconstruction unit which receives the first equalization signal and the second equalization signal from the equalizer, determines a transmission symbol by performing a hard decision with respect to the second equalization, and reconstructs a signal by using an amplitude of the transmission symbol and a phase of the first equalization signal when a level of the amplitude of the transmission symbol is greater than or equal to a reference value.

The invention discloses a particle swarm optimization based orthogonal wavelet blind equalization method. The method comprises the following steps of: allowing a transmitted signal a(k) to pass through a pulse response channel h(k) to acquire a channel output signal x(k); acquiring an orthogonal wavelet transformation (WT) input signal y(k) through channel noise n(k) and x(k); performing WT on the input signal y(k) to acquire an output signal R(k); taking the input signal y(k) as input of a particle swarm optimization (PSO) algorithm and randomly initializing a group of weight vectors, wherein each particle corresponds to each group of weight vectors one to one; determining a fitness function of PSO through a cost function of an orthogonal wavelet transformation-constant module algorithm (WT-CMA) blind equalization method; when a fitness value is the maximum, finding out an optimal position vector in the group and taking the optimal position vector as an initialization weight vector W(k) of the WT-CMA; and acquiring an equalizer output signal z(k) from the output signal R(k) and initialization weight vector W(k). In the method, the optimal equalizer initialization weight vector is sought through PSO, and the autocorrelation of the signal is reduced by WT. Compared with WT-CMA, the method has higher convergence rate and lower steady-state error.

An adaptive equalizer comprises an adjustable equalizer circuit that allows to enhance the frequency dependence of contents of the transmitted signals which suffer from losses in the connected transmission channel. A blind equalization tuning procedure is proposed that operates without knowledge about the characteristic of transmission channel. Phase positions of transitions in the equalized signal are detected. A digital post-processing circuit evaluates a measure for spread of the detected phase positions of transitions, accumulated over a plurality of the symbol periods. The digital post-processing circuit controls the adjustable equalizer, setting the adjustable equalizer to a setting wherein the detected spread is minimized.

A dual-polarization, 2-subcarriers code orthogonal, orthogonal frequency division multiplexed signal carrying information bits is transmitted in an optical communication network without transmitting a corresponding pilot tone or training sequence. A receiver receives the transmitted signal and recovers information bits using a blind equalization technique and by equalizing the 2-subcarriers OFDM signal as a 9-QAM signal in time domain with a CMMA (constant multi modulus algorithm) equalization method.

A method of adaptive multi-modulus equalization for an equalizer. A cost from a cost function is calculated according to a constant modulus algorithm (CMA). Equalizer coefficients are updated according to the cost, and modulus of each region is determined for a multi-modulus algorithm (MMA). The equalizer is switched to use the MMA when the cost reaches a first threshold. The MMA comprises several stages determined by thresholds, and the number of regions increases in every stage. The cost is calculated according to the MMA and modulus of each region. The equalizer coefficients are updated according to the cost, and modulus of each region is determined for the subsequent stage of the MMA. The equalizer is switched to the subsequent stage of the MMA when the MMA cost function output reaches the threshold corresponding to the current stage. The steps are repeated until the cost reaches a preset value. Then, the number of regions and equalizer coefficients are fixed to equalize the input signal.

An adaptive equalizer comprises an adjustable equalizer circuit that allows to enhance the frequency dependence of contents of the transmitted signals which suffer from losses in the connected transmission channel. A blind equalization tuning procedure is proposed that operates without knowledge about the characteristic of transmission channel. Phase positions of transitions in the equalized signal are detected. A digital post-processing circuit evaluates a measure for spread of the detected phase positions of transitions, accumulated over a plurality of the symbol periods. The digital post-processing circuit controls the adjustable equalizer, setting the adjustable equalizer to a setting wherein the detected spread is minimized.

The invention discloses a self-adaption blind equalization method in a high-speed data transmission system. A satellite communication channel is modeled and group time delay and a non-linear characteristic of the channel are simulated. In an initial working phase of an equalizer, a CMA algorithm irrelevant to decision correctness is employed. The algorithm is applicable to various constant modulus modulation signals and is applicable to various satellite communication environments. Most of ISI is eliminated by self-adaptively equalizing received signals in a very large application range. When a system is basically stable, namely when the CMA algorithm is converged stably and most of the ISI is eliminated, an error probability of passing through a decider by carrier synchronized signals is controlled within a certain range. A decision feedback loop is started at this moment. The intersymbol interference is furthered reduced by the equalizer through adoption of a DD-LMS algorithm with relatively few residual errors. The residual errors are greatly reduced, and the system performance is improved.

The invention discloses a feedback blind equalization method of a dynamic wavelet neural network based on fuzzy control, which comprises the following steps: a) passing a transmitted signal sequence x(n) through an unknown channel h(n), and then superimposing on a Gaussian white noise N(n) to obtain an observation sequence y(n); b) processing an error signal e(n) by a constant modular algorithm (CMA) to obtain a tap coefficient c(n) of a linear segment formed by transversal filters in a wavelet neural network; c) passing an input value deviation E(n) and a deviation change deltaE(n) of a fuzzy neural network controller through a fuzzy neural network controller to obtain an iteration step change value delta mu of an extension factor and a shift factor of a wavelet function in a nonlinear segment formed by wavelet neural networks in a dynamic wavelet neural network; and d) sequentially passing the observation sequence y(n) through the dynamic wavelet neural network and a judger to obtain an output signal. The method has faster convergence speed and smaller steady-state error, thereby being completely applicable to underwater acoustic channels.

The present application discloses a method for adaptive blind equalization of a PSK signal, an equalizer and a receiver. According to embodiments as provided, a conjugate product of a current output and a precedent output of an FIR filter is calculated, an equalization coefficient is updated using the conjugate product, and then an input signal is filtered using the FIR filter with the updated equalization coefficient. The embodiments as provided is applicable to adaptive blind equalization of any phase shift keying signal including a BPSK signal.

The invention relates to a wireless optical communication system blind equalization method based on an output feedback bias type complex continuous RNN structure. The method includes firstly providing a feedback power supply bias continuous time discrete state (DTCS) complex RNN structure; then achieving dynamic equation configuration of a DTCS feedback voltage bias complex RNN neutral network of multi-valued quadrature amplitude modulation (QAM) blind equalization; configuring a weight matrix of the feedback network; and finally obtaining a bias factor rho. Through introduction of the feedback voltage bias, not only the existing RNN neural network model is not broken away, but also physical realization of the network is simple, and the special requirement for enlarged searching space needed by multi-valued signal detection can be satisfied effectively.

The invention discloses a non-Gauss noise-against blind equalization method, aiming at providing the non-Gauss noise-against blind equalization method for wireless communication network, in particular between wireless sensor network nodes, in order to guarantee corrective data transmission between wireless sensor nodes. The maximal signal-to-noise energy ratio of an output signal of an equalizer is utilized as a starting point to construct a new cost function. Based on a method for converting the form of constraint condition, an alternative constraint condition is found, the constraint optimization problem is converted into a non-constraint optimization problem, secondary [epsilon]-insensitive loss functions are adopted to construct a solving method conforming to iterative reweighted least squares method, resulting in a global optimal solution for the cost function. The method can lower cell consumption of the wireless sensor network nodes and takes the requirement on small number of data as well as rapid convergence into consideration in the aspect of algorithm design. The algorithm is suitable for the problem of blind equalization for low-order and high-order quadrature amplitude modulation QAM and PSK signals. Drawings attached represent a model for signal transmission between the wireless sensor network nodes according to the invention.

The invention discloses a passive bistatic radar signal processing method based on dimension reduction constant modulus blind equalization. The passive bistatic radar signal processing method comprises the following steps: S101: restoring direct wave signals in signals received from a reference passage of a passive bistatic radar by using a constant modulus blind equalization method after dimension reduction; S102: according to the signals received from a monitoring passage of the passive bistatic radar, performing multidiameter self-adapting wave filtering processing on the direct wave signals by using a smallest mean square error algorithm; S103: estimating a doppler time delay cross-correlation detection objective of a distance between the signals obtained through the multidiameter self-adapting wave filtering processing and the direct wave signals. The passive bistatic radar signal processing method disclosed by the invention uses the energy sum of weight vectors and percentage as a threshold, omits an undersize weight vector coefficient, and can effectively decrease the number of the weight vectors participating in iteration, so that the calculated amount of the algorithm is reduced.

The invention relates to a method for a multiple input multiple output (MIMO) functional network to achieve blind equalization of wireless laser communication electric domain signals, in particular to an electric domain signal blind equalization method under the circumstance that a communication channel between a transmitter and a receiver of wireless laser communications has fading characteristics. The method for the MIMO functional network to achieve the blind equalization of the wireless laser communication electric domain signals is applicable to laser communication networks, popularizes an artificial neural network to a functional network by using generalization of the artificial neural network, designs a blind equalization processing method based on an MIMO functional frame, designs an MIMO functional network structure and a network state update principle thereof, uses functional network output drive and a principle of neural network nonlinear dynamics fully, decomposes singular value of a receipt signal matrix to obtain approximate subspace value of a signal to be detected, and performs mapping by using the approximate subspace value as an input vector, so that rapid convergence is achieved by depending on small data volume only, and the receipt signal can reappear in a true signal subspace.

The invention discloses a corrected mold decision multi-mode blind equalization method MMDMMA. The method comprises the following steps: re-defining a cost function, and acquiring a weight vector update formula of a forward equalizer and a feedback filter through the defined cost function according to a stochastic gradient descent method; replacing a fixed decision factor of the conventional mold decision multi-mold blind equalization method MMDMMA by using a leakage factor with time-variant characteristics, so that a time-varying signal can be accurately tracked. The replacement has the effects that a decision error is large, a time-varying leakage factor is large, and a convergence rate is high before convergence; the decision error is small, the time-varying leakage factor is small, and the convergence rate is low after the convergence; due to the adoption of the time-varying leakage factor, divergence of the blind equalization process in the MDMMA method is avoided, and misadjustment is avoided. The method is low in mean square error, high in convergence speed, and high in capacities of inhibiting intersymbol interference and correcting phase rotation. Compared with a mold decision multi-mode blind equalization method MDMMA and a norm blind equalization method CMA, the method MMDMMA is obviously improved.

A system and method for iteration scheduling in joint equalization and turbo decoding are provided. A method for processing received information includes cancelling interference in a received signal bearing received information, decoding the interference cancelled received signal to produce information, and processing the received information. The cancelling comprises an iterative processing of the received signal based on soft information produced by a decoding the received signal.

Some demonstrative embodiments include devices, systems and / or methods of equalizing received wireless communication signals. For example, a device may include a pre-decoding equalizer to determine a plurality of filter weights by applying both a blind-equalization and a least-mean-squares (LMS) equalization to a wireless communication signal received over a wireless communication channel; a channel estimator to estimate a channel frequency response of the channel based on the filtering weights; and a turbo-equalization scheme including a decoder to decode the wireless communication signal and a turbo equalizer to equalize the decoded wireless communication signal using the estimated channel frequency response.

The invention discloses an orthogonal wavelet constant modulus blind equalization method based on an IWPA (Improved Wolf Pack optimization Algorithm). According to the invention, A CM (Complex Method) with high local searching capacity is embedded into a WPA with high global optimizing capacity; an update mechanism of a wolf pack is improved to obtain an excellent IWPA; the new method promotes optimizing capacity of the WPA; a reciprocal of a cost function in the constant modulus blind equalization method CMA is used as a fitness function of the IWPA; an input signal of the CMA is used as an input of the IWPA; a leader wolf position captured by utilizing the IWPA is used as an initial weight vector of the CMA; then signal correlation is reduced by a wavelet; signals are output in an equalizing mode by the CMA; and an excellent equalizing effect can be obtained. Compared with the prior art, the orthogonal wavelet constant modulus blind equalization method has the advantages that correlations between the signals and between the signals and noise can be reduced; an algorithm convergence speed is improved; a steady state error is reduced; balancing quality is improved; and the orthogonal wavelet constant modulus blind equalization method has a certain practical value.

The invention provides a self-adaptive equalization method, a device and an equalizer, which relate to the field of communication. The self-adaptive equalization method comprises steps: frame positioning information about polarization state data outputted by the equalizer and a tap coefficient updated after blind equalization processing are acquired; according to the frame positioning information and performance information of the equalizer, a current operating state of the equalizer is determined; according to the current operating state of the equalizer and the tap coefficient updated after blind equalization processing, the tap coefficient or a leakage factor in blind equalization processing are correspondingly adjusted; and according to the adjusted tap coefficient or the leakage factor, self-adaptive convergence is carried out until the equalizer operates stably in a stable state. The solution of the disclosure solves the problem in an existing technical solution that the efficient and stable operation of a self-adaptive equalizer cannot be realized during a convergence process.

The invention discloses an orthogonal wavelet blind equalization method based on immune clone particle swarm optimization. The method comprises the steps of: by regarding a particle swarm as an immune system, randomly initializing particles in a search space, namely, initializing the speed and the positions of antibodies, wherein the position vectors of the particles are taken as the weight vectors of an equalizer and the number of the weight vectors is taken as the scale of the particles; randomly generating an initial population, wherein the position vector with a maximal fitness value (that is optimal solution) is used as an antigen, the particles are used as the antibodies, the affinity degree is used for presenting the approaching degree of the antibodies and the antigen, and a fitness degree function of the particle swarm optimization is selected as the affinity degree of the antibodies; carrying out immune clone operation on the antibodies with higher fitness degree through iteration to continuously generate a new-generation antibody population; carrying out the immune clone operation on the selected optimal solution in each iteration; selecting the optimal position vector (that is the generated maximal value of the corresponding fitness degree function) of the particles after the iteration ends; and iterating by taking the position vector as an initialization weight vector of the equalizer.

The invention discloses a multi-wavelet feedback blind equalization method for a nonlinear satellite channel. According to the characteristic of the satellite channel nonlinearity, the nonlinear satellite channel receives signals outputted by a filter, multi-wavelet transform is conducted on the signals, and then obtained signals are inputted in a Wiener balancer; in this way, the linear module structure and the nonlinear module structure of the Wiener balancer are established, and the satellite channel nonlinearity is compensated for through the nonlinear module structure of the Wiener balancer. Compared with a method adopting a Volterra model balancer, the method has the advantages that influences of the nonlinear satellite channel on communication quality are effectively eliminated, the convergence rate is high, the mean square error is small, and satellite communication quality is effectively improved.

The invention relates to a multistage time domain blind equalization method of OFDM signals. The method comprises the following steps that the frame format of received signals of a receiving sequence is determined through the correlated peak searching method; frame synchronization symbol information of the OFDM signals is used for completing the first stage of time domain equalization on the received signals, a cyclic prefix sequence of the OFDM signals is used for completing the second stage of time domain equalization on the received signals, and signals after the second stage of time domain equalization are output signals which can be used for subsequent processing of signals. According to the method, in the process of determining equalizer coefficients, inherent repeatability of the frame format of the OFDM signals is fully utilized, and under the condition without prior information of the received signals, signal blind equalization is achieved, and the equalization effect is good; the method has the advantages of being simple in calculation and quick in processing to the OFDM signals with multiple sub carriers.

The invention discloses a channel blind equalization method in a multi-input multi-output system, the method comprises that: the transmitting ends respectively add prefixes in the data signals on all the transmitting antennas, so as to obtain the transmitting signals of a self-related function which meet the self-related independent conditions and transmit; the receiving ends of all the receiving antennas receive the transmitting signals and carry out the channel blind equalization which is based on the self-related matching principles. The invention further discloses a system for realizing the channel blind equalization. The system complexity for realizing the channel blind equalization can be reduced and the error bit rate performances of the system can be improved according to the method.