An optical transmitter includes a signal-process circuit to process a transmission signal; an optical modulator to modulate light input by the transmission signal output from the signal-process circuit, and output an optical signal; and a control circuit to output a control signal for controlling a carrier frequency of the optical signal, to the signal-process circuit, wherein the signal-process circuit comprises a phase-rotation circuit to apply phase rotation of the carrier frequency on a complex plane according to the control signal, to the transmission signal, a map-adjustment circuit to determine scale factor for a map according to an angle of the phase rotation, and a modulation-format-map circuit to map the transmission signal on the complex plane based on a modulation format and the scale factor, wherein the phase-rotation circuit is configured to rotate, on the complex plane, the phase of the carrier frequency mapped based on the scale factor.

A communication system comprising: input buffers adapted for buffering incoming data streams of samples from one or more channels; a receiver adapted for sequentially processing data from the input buffers; a processing rate of the receiver is higher than or equal to an incoming data rate of the incoming data; context memory adapted for saving an internal status of the receiver after processing the data corresponding with an input buffer before switching to a next input buffer and for restoring the internal status, wherein the receiver is adapted for processing the incoming data in a frame detection phase, and in a frame demodulation phase in which frames and/or subframes are demodulated into bits and wherein the internal status of the receiver related to an input buffer is only saved and restored in the frame detection phase or before and after demodulating subframes.

A method for calibrating mismatches of an in-phase signal path and a quadrature signal path of a receiver is proposed in the present invention, including: utilizing the receiver to receive at least one test signal with a specific frequency via the first signal path and the second signal path, to generate a first signal path received signal and a second signal path received signal; performing frequency analysis upon the first signal path received signal and the second signal path received signal respectively, to generate a first frequency analysis result and a second frequency analysis result; and calculating at least one calibration coefficient according to the first frequency analysis result and the second frequency analysis result. A method for calibrating mismatches of an in-phase signal path and a quadrature signal path of a transmitter is also proposed in the present invention.

A transmitter includes: a modulation circuit that modulates a data sequence using QAM by mapping the data sequence to only four symbols each of which differs in phase by 90 degrees from an adjacent one of the four symbols and at least two of which have different amplitudes; and a transmission circuit that wirelessly transmits the data sequence mapped to the four symbols through the modulation by the modulation circuit, by assigning the data sequence mapped to the four symbols through the modulation by the modulation circuit to different subcarriers for Orthogonal Frequency Division Multiplexing (OFDM).

A method, network node and system for providing joint phase and delay compensation for a plurality of antenna branches in a network node having a plurality of antennas by processing injected signals and feedback signals in a frequency domain are provided. According to one aspect, a method includes performing at least squares algorithm applied to the injected signals and the feedback signals to generate corrective signals applied to input signals of each antenna branch.

Systems and methods for reducing total skew in optical signals transmitted by optical coherent transponders without measuring the total skew are disclosed. The method may compensate for the in-phase/quadrature (I/Q) skew of optical signals in complex modulation formats. It may include providing input to a transponder to produce a periodic (and generally sinusoidal) output signal, providing the signal to an optical power meter, measuring the optical power of positive and negative harmonics of the signal while varying the amount of skew introduced by a de-skewing filter in the transponder, identifying the amount of skew introduced by the de-skewing filter when the minimum optical power measurement is taken, and causing the amount of skew introduced by the de-skewing filter to equal the identified skew offset by a one-half symbol delay. The system may provide better skew compensation using less expensive equipment than de-skewing methods based on existing skew measurement methods.

A method and a device for transmitting and receiving a signal on the basis of multiple antennas are provided. A transmitting device may include a radio frequency (RF) module transmitting a quadrature amplitude modulation (QAM) signal of a first symbol corresponding to a hybrid frequency shift keying and quadrature amplitude modulation (FQAM) mode and transmitting a QAM signal of a second symbol corresponding to a QAM mode through a second antenna; and a modulation module mapping the QAM signal of the first symbol to one frequency tone among the preset number of frequency tones according to a frequency shift keying (FSK) signal of the first symbol and mapping the second symbol to the frequency tone to which the first symbol is mapped.

The present disclosure relates to a pre-5.sup.th-Generation (5G) or 5G communication system to be provided for supporting higher data rates Beyond 4.sup.th-Generation (4G) communication system such as Long Term Evolution (LTE). The present invention relates to method and apparatus for performing a decoding with low complexity in a wireless communication system. A decoding method of a terminal in a wireless communication system comprises determining a first characteristic value indicating a statistical characteristic of an interference signal based on a received signal of a base station, determining a second characteristic value indicating a statistical characteristic of an interference signal based on data received from the base station, and decoding the data according to a decoding scheme corresponding to a difference of the first characteristic value and the second characteristic value.

A method and apparatus for orthogonal frequency division multiplexing (OFDM) modulation includes separating a frequency-domain sequence of complex numbers into a first portion and a second portion that is disjoint with the first portion, each of the first portion and the second portion including a respective half of the complex numbers of the frequency-domain sequence, and generating a time-domain sequence having a real in-phase component that is a function of the first portion only, and an imaginary quadrature-phase component that is a function of the second portion only.

A quadrature modulator and the transmission unit output a modulated wave obtained by performing quadrature modulation on a carrier wave using a first I signal and a first Q signal and wirelessly transmit the modulated wave. A reception unit and the quadrature detector detect a received signal corresponding to a wireless signal transmitted from the wireless tag using the carrier wave and to output a second I signal and a second Q signal. A filter and the amplification unit amplify a frequency component higher than a cutoff frequency in the second I signal and the second Q signal. A detector and the decoding unit decode data based on a detection signal obtained by detecting the amplified second I signal and the amplified second Q signal. A generation unit generates the first I signal and the first Q signal such that the modulated wave is a signal obtained by shifting a frequency of the carrier wave by a frequency shift amount more than the cutoff frequency and to input the first I signal and the first Q signal to the quadrature modulator.