59 results about "Carrier phase recovery" patented technology

A television receiver system capable of receiving and demodulating television signal information content that has been modulated and transmitted in accordance with a variety of modulation formats is disclosed. In particular, the system is able to accommodate receipt and demodulation of at least 8 and 16-VSB modulated signals in order to support US HDTV applications, as well as 64 and 256-QAM modulated signals, for European and potential US CATV implementations. The system includes carrier and timing recovery loops adapted to operate on an enhanced pilot signal as well as decision directed carrier phase recovery loops. Phase detectors operate on I and Q rail signals, or generate a Q rail from a Hilbert transform of the I rail. Decision directed loops incorporate a trellis decoder in order to operate on sequence estimated decisions for improved reliability in poor SNR environments.

Carrier phase recovery employs a single-axis blind cost criterion from the Bussgang class of functions, and its stochastic gradient, to generate a carrier phase error used to adjust a received and demodulated signal to near baseband. For one implementation, the estimate is derived in accordance with a Single-Axis Constant Modulus (SA-CM) criterion and its stochastic gradient via a SA-CM algorithm (SA-CMA). The carrier phase error is then used to adjust the carrier frequency and phase of the received and demodulated signal toward the frequency and phase of the carrier used to modulate the transmitted symbols, driving the carrier phase error to zero. The values used for the phase recovery may be either i) an IIR filtered signal, ii) a processed signal (e.g., decisions for the signal symbols), or iii) an equalized and processed signal.

A television receiver system capable of receiving and demodulating television signal information content that has been modulated and transmitted in accordance with a variety of modulation formats is disclosed. In particular, the system is able to accommodate receipt and demodulation of at least 8 and 16-VSB modulated signals in order to support US HDTV applications, as well as 64 and 256-QAM modulated signals, for European and potential US CATV implementations. The system includes carrier and timing recovery loops adapted to operate on an enhanced pilot signal as well as decision directed carrier phase recovery loops. Phase detectors operate on I and Q rail signals, or generate a Q rail from a Hilbert transform of the I rail. Decision directed loops incorporate a trellis decoder in order to operate on sequence estimated decisions for improved reliability in poor SNR environments.

A method for a carrier phase recovery apparatus in a multiple-link hopping radio system includes hopping among a plurality of radio links to receive bursts of radio signals on the plurality of radio links and determining channel information for each radio link from a received burst on the radio link. Further, the method includes storing the determined channel information and using the determined channel information for the radio link to reliably recover the carrier phase of a next received burst on the radio link.

A time-stretched enhanced recording scope (TiSER) is described using time stretch analog-to-digital conversion in a real-time burst mode. A chirped optical signal is modulated in response to receiving segments of an input signal. The optical signal with its modulated input signal, is stretched through an optical medium and digitized to represent the waveform segment. TiSER provides ultra-fast real-time sampling within short segment bursts of the original input signal while providing an ability to detect non-repetitive events. Methods and apparatus are also described for providing real-time information about inter-symbol information (ISI), rapidly determining bit-error rates (BER), performing time-domain reflectometry (TDR), generating eye diagrams for serial data, facilitating digital correction of data, clock recovery, optical carrier phase recovery, and otherwise increasing the speed and / or accuracy of a diverse range of high-speed signal measurement and processing activities.

The embodiments of the invention provide methods to deal with problems of cycle slips, angular skew, and residual phase noise for high-speed optical communications employing any arbitrary high-order multi-dimensional modulation formats. The embodiments use a slip process analyzer, a skew angle estimator, and a phase noise variance estimator to provide feedforward soft-decision information of a carrier phase recovery (CPE) for more accurate likelihood calculation based on a high-order hidden Markov model (HMM). The log-likelihood calculation can be done jointly in dual polarization with joint Markov state transition. Some embodiments use a kernel filter or a particle filter for log-likelihood calculation.

A method for a carrier phase recovery apparatus in a multiple-link hopping radio system includes hopping among a plurality of radio links to receive bursts of radio signals on the plurality of radio links and determining channel information for each radio link from a received burst on the radio link. Further, the method includes storing the determined channel information and using the determined channel information for the radio link to reliably recover the carrier phase of a next received burst on the radio link.

The carrier phase of a carrier wave modulated with information symbols is recovered with a multi-stage, feed-forward carrier phase recovery method. A series of digital signals corresponding to the information signals is received. For each digital signal, a coarse phase recovery is performed to determine a first phase angle which provides a first best estimate of the information symbol corresponding to the digital signal. Using the first best estimate as input, a second stage of estimation is then performed to determine a second phase angle which provides an improved (second) best estimate of the information symbol. Additional stages of estimation can be performed. The multi-stage, feed-forward carrier phase recovery method retains the same linewidth tolerance as a single-stage full blind phase search method; however, the required computational power is substantially reduced. The multi-stage, feed-forward carrier phase recovery method is highly efficient for M-QAM optical signals.

A television receiver system capable of receiving and demodulating television signal information content that has been modulated and transmitted in accordance with a variety of modulation formats is disclosed. In particular, the system is able to accommodate receipt and demodulation of at least 8 and 16-VSB modulated signals in order to support US HDTV applications, as well as 64 and 256-QAM modulated signals, for European and potential US CATV implementations. The system includes carrier and timing recovery loops adapted to operate on an enhanced pilot signal as well as decision directed carrier phase recovery loops. Phase detectors operate on I and Q rail signals, or generate a Q rail from a Hilbert transform of the I rail. Decision directed loops incorporate a trellis decoder in order to operate on sequence estimated decisions for improved reliability in poor SNR environments.

The embodiment of the invention provides a carrier phase recovery method and device based on a Kalman filtering algorithm. The method comprises the following steps: performing carrier phase estimation on a 16QAM (Quadrature Amplitude Modulation) signal through a carrier phase estimation algorithm, and obtaining a first phase estimation value; performing phase recovery on the 16QAM signal according to the first phase estimation value, and obtaining the 16QAM signal after the first recovery; performing phase estimation on the recovered 16QAM signal through the Kalman filtering algorithm, and obtaining a second phase estimation value; and performing phase recovery on the recovered 16QAM signal according to the second estimation value, and obtaining the 16QAM signal after the second recovery. By using the carrier phase recovery method and the device based on the Kalman filtering algorithm provided by the embodiment of the invention, the error of phase estimation in the Kalman filtering algorithm is effectively reduced, and the influence of phase noise and amplitude noise is removed more accurately.

In Software defined elastic optical networks, modulation format and constellation size may be flexibly modified. As a result, digital signal processing (DSP) algorithm should be compatible with different modulation schemes or readily reconfigurable at the optical coherent receiver. Therefore we propose a novel cascaded adaptive blind equalizers based on decision-directed modified least mean square (DD-MLMS) algorithm for polarization separation and carrier phase recovery. The algorithm is square quadrature amplitude modulation (QAM) independent so that it could be applied in the elastic optical systems. The 28 Gbaud polarization multiplexing quadrature phase shift keying (PM-QPSK) and PM-16QAM back-to-back transmission is demonstrated. The results show that the performance is very close to the general algorithm but with a benefit of the reduced operation complexity. We transmit the 8×240 Gb / s PM-16QAM wavelength division multiplexing (WDM) signal over 1200 km standard single mode fiber (SSMF) based on the proposed blind equalization with a bit error ratio (BER) less than 2×10−2.

The invention provides a polarization demultiplexing and carrier phase restoration method based on adaptive Kalman. The method comprises the following steps: firstly, performing polarization demultiplexing and carrier phase restoration by using an extended Calman filter; and secondly, updating an adjustment and optimization parameter Q value by using a covariance matching method, deciding a convergence condition of the algorithm according to the mean dz of the measurement margin to guide the update of the adjustment and optimization parameter Q value. The polarization demultiplexing and carrier phase restoration method has the beneficial effects that the polarization superimposition and carrier phase noise of the coherent light communication system can be processed at the same time, the adjustment and optimization parameter can be adapted to different values in different scenes, and the tolerance of the algorithm to the polarization rotation and the phase nose can be maximally improved; and meanwhile, the performance of the polarization is irrelevant to the initial adjustment and optimization parameter Q , and excellent performance of rapid convergence and high-precision estimation can be achieved.

Disclosed is a method for decoding an optical data signal. Said optical data signal is phase and amplitude modulated according to a constellation diagram with at least eight constellation points representing non-binary symbols. Said decoding method comprises the following steps: —carrying out a carrier phase recovery of a received signal ignoring the possible occurrence of phase slips, —decoding said signal after phase recovery, wherein in said decoding, possible cycle slips occurring during phase recovery are modelled as virtual input to an equivalent encoder assumed by the decoding scheme. Further disclosed are a related encoding method as well as a receiver and a transmitter.

The invention provides a carrier phase recovery method and device. The method comprises the steps of grouping data needing to carry out phase recovery; for each group, obtaining the Euclidean distance F(A<0 >) corresponding to an angle A<0 > and the Euclidean distance F(B<0 >) corresponding to the angle B<0 >, wherein the angle A<0 > and the angle B<0 > are set maximum deviation angle value and minimum deviation angle value of the group; obtaining a relatively small value in the F(A<0 >) and the F(B<0 >), taking the angle corresponding to the relatively small value and a mid-value of an original deviation angle as new boundary values, and repeating the operation to calculate a final deflection angle, wherein the repetition times is search depth; and obtaining the deflection angle and the maximum likelihood phase rotation angle of the data in the group and carrying out phase recovery on the data in the group through utilization of the maximum likelihood phase rotation angle. The problem that in related technologies, the phase recovery method is high in complexity is solved and the phase recovery complexity is reduced.

Embodiments of the present disclosure provide a signal processing apparatus, a signal transmitting apparatus and a receiver, which are adapted for a frequency division multiplexing system having a high-order modulation format. A receiver having a high-magnification sampling rate by inserting a pilot signal between neighboring subcarriers at a transmitter side, calculating a laser phase noise according to a phase of the pilot signal at a receiver side, and performing down-sampling and equalization processing after performing carrier phase recovery according to the laser phase noise, so that a laser phase noise having a wide frequency may be accurately compensated, thereby having a relatively powerful carrier phase recovery ability.

The invention relates to a method for identifying a modulation format of an optical communication signal with a differential phase amplitude ratio, and belongs to the technical field of modulation recognition. The method comprises the following steps: step A, performing coherent detection, front end equalization, dispersion compensation, clock recovery, and carrier frequency offset compensation onan input optical communication signal to be detected; step B, calculating AAR and DPDR in an MFI module; step C, calculating a modulation format identification factor R; step D, performing optical signal modulation format identification on the output of the step A; step E, performing adaptive equalization according to optical signal modulation format; step F, performing carrier phase recovery; and step G, performing decision and decoding. The method can identify the optical signal modulation format when the OSNR is not less than 12dB with no need of carrier recovery and no need of a large amount of training data sets and complex calculations, and can identify three modulation modes including QPSK, 16QAM and 64QAM when the input signal OSNR is not less than 12dB.

The invention discloses a probability distribution identification method and device under a probability shaping constellation, equipment and a medium. The method comprises the following steps: selecting each candidate probability distribution in all candidate probability distributions of a constellation shaping system and a power normalization factor thereof as a first initial condition; calculating the relative entropy between each probability distribution after L iterations and all candidate probability distributions, selecting the candidate probability distribution corresponding to the minimum relative entropy as the initial estimation of the unknown probability distribution, and taking the initial estimation of the probability distribution and the power normalization factor corresponding to the initial estimation as the second initial condition; and calculating the relative entropy between the probability distribution after T iterations and all candidate probability distributions,wherein the candidate probability distribution corresponding to the minimum relative entropy is used as the final estimation of the unknown probability distribution. According to the method, the constellation probability distribution information can be extracted from the received signal on the premise of not carrying out carrier phase recovery, and the method has important application value for constellation shaping probability distribution identification in the elastic optical network.

A digital receiver is configured to process a polarization multiplexed carrier from a communication network. The polarization multiplexed carrier includes a first polarization and a second polarization. The receiver includes a first lane for transporting a first input signal of the first polarization, a second lane for transporting a second input signal of the second polarization, a dynamic phase noise estimation unit disposed within the first lane and configured to determine a phase noise estimate of the first input signal, a first carrier phase recovery portion configured to remove carrier phase noise from the first polarization based on a combination of the first input signal and a function of the determined phase noise estimate, and a second carrier phase recovery portion configured to remove carrier phase noise from the second polarization based on a combination of the second input signal and the function of the determined phase noise estimate.

A digital receiver is configured to process a polarization multiplexed carrier from a communication network. The polarization multiplexed carrier includes a first polarization and a second polarization. The receiver includes a first lane for transporting a first input signal of the first polarization, a second lane for transporting a second input signal of the second polarization, a dynamic phase noise estimation unit disposed within the first lane and configured to determine a phase noise estimate of the first input signal, a first carrier phase recovery portion configured to remove carrier phase noise from the first polarization based on a combination of the first input signal and a function of the determined phase noise estimate, and a second carrier phase recovery portion configured to remove carrier phase noise from the second polarization based on a combination of the second input signal and the function of the determined phase noise estimate.

In Software defined elastic optical networks, modulation format and constellation size may be flexibly modified. As a result, digital signal processing (DSP) algorithm should be compatible with different modulation schemes or readily reconfigurable at the optical coherent receiver. Therefore we propose a novel cascaded adaptive blind equalizers based on decision-directed modified least mean square (DD-MLMS) algorithm for polarization separation and carrier phase recovery. The algorithm is square quadrature amplitude modulation (QAM) independent so that it could be applied in the elastic optical systems. The 28 Gbaud polarization multiplexing quadrature phase shift keying (PM-QPSK) and PM-16QAM back-to-back transmission is demonstrated. The results show that the performance is very close to the general algorithm but with a benefit of the reduced operation complexity. We transmit the 8×240 Gb / s PM-16QAM wavelength division multiplexing (WDM) signal over 1200 km standard single mode fiber (SSMF) based on the proposed blind equalization with a bit error ratio (BER) less than 2×10−2.

The invention relates to a signal compensation method for an optical fiber communication system and a system thereof. The method comprises the following steps: performing analog-to-digital conversionon a received signal of an optical fiber communication system to obtain a digital signal; obtaining parameters in the nonlinear compensation process of the current iteration based on a self-adaptive gradient descent method of the driving quantity; performing nonlinear compensation on the digital signal by adopting a digital back propagation algorithm to obtain a nonlinear compensation signal; carrying out carrier phase recovery processing by adopting a blind phase search algorithm to obtain a phase recovery signal; calculating a mean square error value of the blind estimation of the current iteration according to the phase recovery signal; judging whether a difference value between the mean square error value of the blind estimation and the mean square error value of the blind estimation of the previous iteration is greater than a set threshold value or not; if so, adding one to the number of iterations, and entering the next iteration; and if not, determining the nonlinear compensation signal as the compensated signal of the received signal. According to the invention, the operand of the signal compensation process can be reduced, and the signal compensation efficiency is improved.

The embodiments of the invention provide methods to deal with problems of cycle slips, angular skew, and residual phase noise for high-speed optical communications employing any arbitrary high-order multi-dimensional modulation formats. The embodiments use a slip process analyzer, a skew angle estimator, and a phase noise variance estimator to provide feedforward soft-decision information of a carrier phase recovery (CPE) for more accurate likelihood calculation based on a high-order hidden Markov model (HMM). The log-likelihood calculation can be done jointly in dual polarization with joint Markov state transition. Some embodiments use a kernel filter or a particle filter for log-likelihood calculation.

The invention discloses a carrier phase recovery method and system based on Q-power polarity judgment, and the method comprises the steps: carrying out the Q-power operation and phase rotation of a received signal after phase compensation, and then carrying out the power detection; selecting a signal with relatively high power after rotation to carry out polarity judgment, thereby calculating a phase offset signal; calculating a phase compensation signal of the received signal at the next moment according to the phase offset signal, and performing phase compensation on the received signal at the next moment by using the phase compensation signal. Compared with a Q-power-based polar ring, the method has the advantages that the frequency offset capture range is widened, and the noise immunity is improved; compared with a PD algorithm, the method is suitable for QPSK, 8PSK, 16APSK and other amplitude modulation modes; and compared with a DD algorithm, the frequency offset capture range isimproved.

The invention provides a channel blind equalization method based on fractional order multimode, which constructs a multimode cost function based on fractional low moment by utilizing statistical information of an equalizer output signal and a transmitting end signal, so that phase errors in channel equalization do not need to be compensated by an additional carrier recovery loop; and the weighted vector of the equalizer is updated by using the fractional derivative of the multi-mode cost function, so that the abnormal value in the strong pulse noise is inhibited. Compared with the prior art, the method not only can complete channel equalization and carrier phase recovery at the same time, but also has lower residual intersymbol interference and bit error rate in a strong pulse noise environment.

A system for carrier phase recovery, including a receiver for receiving one or more frames of L symbols. A phase estimator performs carrier phase estimation for the received frames of L symbols, and the resulting carrier phase estimates are stored in a non-transitory computer-readable storage medium. One or more rotators de-rotates the received frames of L symbols by one or more of the carrier phase estimates, and a data processor calculates a sum of the outputs of the L de-rotated signals raised to an nth power, and determines a real part of the sum. A minimum determination device determines a minimum of the real part of the sum with respect to the carrier phase estimates, and phase unwrapping and multiplier removal is performed if a minimum has been determined.

An improved Eighth-Order Statistics (EOS) blind phase recovery method is proposed for high-order coherent modulation formats. The method combining EOS blind phase estimate with maximum-likelihood (ML) carrier phase estimate uses multi-stage feed-forward carrier phase recovery algorithm. Experimental results show that the proposed new algorithm can reduce the required computational effort by more than a factor of 3 for 16-QAM system.

The embodiments of the invention provide a signal sending device, a carrier phase recovery device and method. Amplitude variable phase modulation signals are interpolated into data modulation signals, and carrier phase recovery on received signals is performed at a receiving end according to the phase modulation signals, so that the carrier phase recovery device and method can be applied to communication systems of various modulation formats, are compatible with the existing communication systems and have relatively low computing complexity. In addition, the interpolated phase modulation signals are variable in amplitude and can be flexibly configured in the data modulation signals, so that redundancy is reduced and the capacity of a system is influenced little.

The invention relates to an MSK demodulation circuit having zero-phase start-up. The MSK demodulation circuit comprises a zero-phase start-up module; and an output end of the zero-phase start-up module is connected with a third register as well as is respectively connected with a first register and a second register. The zero-phase start-up module carries out maximum correlation on a phase of a receiving signal and outputs a corresponded maximum correlation adjusting signal; the first register, the second register and the third register receive the maximum correlation adjusting signal input by the zero-phase start-up module and respectively adjust phases of output clocks of a first carrier digital oscillator, a second carrier digital oscillator and a data bit digital oscillator, so that sampling clock phases corresponded to a first carrier phase retrieval phaselocked loop, a second carrier phase retrieval phaselocked loop and a data bit phase retrieval phaselocked loop can be rapidly synchronized to the phase of the receiving signal. According to the invention, demodulation capability reliability is improved, a circuit design is simplified and the system stability and the integration level are improved; and thus, the MSK demodulation circuit is safe and reliable.