Systems and methods for performing wavelength conflict detection are provided. These are to detect situations in optical networks where two instances of the same wavelength channel have been added. Wavelength conflict detection is performed for each of a plurality of possible wavelength channels that could be present in an optical signal, each wavelength channel that is present modulated by a pilot tone signal with a respective pilot tone frequency, the pilot tone signal carrying M-ary pilot tone data, M=2.sup.n, n≧1, with a respective one of M different sequences being used to represent each of M possible data values over a data value period. Conflict detection for each wavelength channel involves performing correlation peak detection using each of the M different sequences to determine correlation peaks for each of the M different sequences, and, based on the determined correlation peaks, determining whether multiple instances of the wavelength channel are present in the optical signal.

In a phase calibration device, a first integrated circuit outputs a transmission signal for generating a transmission wave of a first transmission antenna, a second integrated circuit outputs a transmission signal for generating a transmission wave of a second transmission antenna, a calibration reception antenna is disposed in a state to be theoretically identical in electric coupling amount when receiving the transmission waves of the first transmission antenna and the second transmission antenna, a reception circuit acquires a received signal from the calibration reception antenna, and a control circuit calibrates phases of the transmission signals based on an amplitude of the received signal of the reception circuit when the first integrated circuit and the second integrated circuit output the transmission signals to the first transmission antenna and the second transmission antenna.

Disclosed are a circuit and method for compensating frequency offset in wireless frequency shift keying communication, and belongs to the field of wireless communication technologies. The circuit includes an analog-to-digital converter, a first decimating module, a digital down-converter, a second decimating module, a frequency offset estimator, a frequency shift keying demodulator, a timing recovery module, a synchronization header detector, a frequency recovery module, a numerical-control oscillator, and a differential decoding and symbol decision module. A rough frequency offset estimation value is combined with a slicer error to generate a control signal related to frequency offset in a received signal, and the control signal is transmitted to the numerical-control oscillator to adaptively adjust a center frequency of an oscillated signal.

A method for determining an angle of arrival (AOA) of a received signal is disclosed, comprising: generating a baseband information signal by mixing a received signal with a local oscillator (LO) signal, the received signal being an in-phase signal and quadrature signal uncorrelated with each other and derived from different input data sets; obtaining baseband signal samples of the baseband information signal having an in-phase signal sample and a quadrature signal sample; determining a transmitter phase offset based on an estimated correlation between the in-phase signal samples and the quadrature signal samples; performing a plurality of phase measurements using a plurality of antennas to obtain a plurality of phase measurements; correcting the plurality of phase measurements based on the transmitter phase offset to produce a plurality of corrected phase measurement; and calculating an AOA of the received signal based on the difference between the plurality of corrected phase measurements.

Systems and methods for autonomous signal modulation format identification are disclosed. In an example embodiment of the disclosed technology, a method includes applying higher-order statistics to an input signal to identify the input signal's modulation format. The method may include applying higher-order statistics to the input signal to calculate higher-order cumulant values for the input signal as higher-order cumulants are indicative of a particular modulation format signature. The method may further include employing a decision tree to determine the modulation format of the input signal.

A carrier-phase recovery method includes: (i) applying a first carrier-phase recovery algorithm to complex-valued symbols of a signal received by a product detector, yielding coarse phase-estimates, the signal being modulated per an M-QAM scheme; (ii) modelling the coarse phase-estimates as a weighted sum of M probability-density functions of an M-component mixture model; (iii) optimizing the M probability-density functions with an expectation-maximization algorithm to yield M optimized probability-density functions; (iv) mapping, based on the M optimized probability-density functions, the coarse phase-estimates to one of M symbols corresponding to the QAM scheme, each coarse phase-estimate mapped to a same symbol belonging to a same one of M clusters; (v) applying a second carrier-phase recovery algorithm to each of the M clusters to generate refined phase-estimates each corresponding to a respective coarse phase-estimate; and (vi) mapping, based on the M optimized probability-density functions, each refined phase-estimate to one of the M symbols.

A RXLOS deglitch apparatus for a receiver is provided. The RXLOS deglitch apparatus includes a sampler, an edge detecting unit and a finite state machine. The sampler receives a recovered clock, and samples a RXLOS signal according to the recovered clock. Consequently, a sampled RXLOS signal is generated. The edge detecting unit receives the RXLOS signal. When a logic level of the RXLOS signal is changed, an edge detection signal is activated by the edge detecting unit. The finite state machine receives the edge detection signal and the sampled RXLOS signal, generates an edge rest signal to control the edge detecting unit, and outputs a filtered RXLOS signal.

Embodiments of the present invention provide a carrier synchronization method, circuit, and system. The method includes performing n times frequency multiplication on a received signal; performing narrowband filtering at least twice and rectangular wave shaping at least twice on the signal obtained after the n times frequency multiplication; and performing n times frequency division on the signal obtained after the filtering and shaping, to restore a carrier signal. The variable n is a positive integer greater than or equal to 4.

Embodiments of the present invention provide a transmission status determining method, where the method includes: receiving, by a receive end device in a first time period, a first symbol sequence sent by a transmit end device; determining a first modulation parameter set according to the first symbol sequence; and determining, according to preset first mapping relationship information, a first transmission status corresponding to the first modulation parameter set as a transmission status of the transmit end device in a second time period, where the first mapping relationship information is used to indicate a one-to-one mapping relationship between N transmission statuses and N modulation parameter sets, the first modulation parameter set belongs to the N modulation parameter sets, and the second time period is later than the first time period.

A method to compensate a carrier frequency offset (CFO) in a receiver is disclosed. The method includes receiving discrete time samples, obtaining a sample vector from the received discrete time samples, obtaining tentative CFO estimates based on the sample vector, selecting a CFO having a greatest compensation coefficient from the tentative CFO estimates, and compensating the CFO in the received discrete time samples.