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.

The present disclosure is directed to a system and method for measuring small frequency differences between two signals quickly and with high precision. In particular examples, an offset between two clock signals on a satellite can be accurately determined in a time period enabling rapid clock synchronization useful in position, navigation, and tracking (PNT) and satellite communications applications. The system and method may also be implemented in constellation of cooperative satellites or other space-borne and high-altitude assets, wherein a plurality of such assets are accurately time-synchronized and more accurate ensemble average calculations are enabled using two-way time transfer (TWTT) protocols. A particular application presently disclosed measurement and correction of very small frequency differences between an atomic clock signal and a tunable clock signal.

In accordance with a first aspect of the present disclosure, a communication device is provided, comprising: a receiver configured to receive one or more signals from an external communication device; a classifier configured to classify the external communication device using the signals received by the receiver and to output a corresponding classification result; and a processing unit configured to change one or more configuration settings of the communication device in dependence on the classification result. In accordance with a second aspect of the present disclosure, a corresponding method of operating a communication device is conceived. In accordance with a third aspect of the present disclosure, a corresponding computer program is provided.

Methods, systems, and devices for wireless communications are described. A user equipment (UE), that is configured for demodulation reference signal (DMRS) bundling, may receive a control message that schedules first and second sets of repetitions of an uplink transmission. The UE may determine a phase coherency configuration to be applied for DMRS transmissions corresponding to each set of repetitions. The phase coherency configuration may be determined based on a phase coherency capability of the UE, and the phase coherency configuration may specify that phase coherency is to be maintained for one or more of the first set of repetitions separate from one or more of the second set of repetitions. The UE may transmit the first set of repetitions with a first set of demodulation reference signals and the second set of repetitions with a second set of demodulation reference signals in accordance with the phase coherency configuration.

An ultra-low power data transmission method and apparatus are disclosed. An ultra-low power data transmission method to be performed by a user terminal of an ultra-low power data transmission system includes performing channel coding on a payload included in a transmission packet; interleaving a payload obtained through the channel coding, spreading the interleaved payload using a gold code and an orthogonal variable spreading factor (OVSF), combining a synchronization header spread using the gold code and the OVSF with the spread payload, and modulating a transmission packet in which the payload and the synchronization header are combined.

A method, an apparatus and a computer program product for enhancing reception of signals in a wireless communication system. A signal containing a frame including a plurality of symbols is received on an uplink communication channel. An angular position of at least one symbol in the plurality of symbols in a constellation of symbols is detected. The plurality of symbols include equalized symbols. An angular difference corresponding a phase error between the detected angular position of the symbol and an expected reference angular position in the constellation of symbols corresponding to an expected reference symbol corresponding to the received frame is determined. Using the determined phase error, a phase of the symbol is compensated.

Introduced are a data transmission method, apparatus and device based on a modulation signal and a storage medium. The method includes steps as follows: calculating a first amplitude-modulated sine wave signal and a second amplitude-modulated sine wave signal with each preset frequency individually; based on the first amplitude-modulated sine wave signal and the second amplitude-modulated sine wave signal with the each preset frequency and according to a preset mapping rule, mapping a sequence of data bits to be sent into a signal sequence; and processing the signal sequence to generate a transmittable radio-frequency signal, and sending the transmittable radio-frequency signal to a receiving end.

A reception apparatus includes a detection unit that detects occurrence of a phase slip in phase estimation values of time-series received symbol data, and determines an inclination of the phase slip, a delay processing unit that generates first received signal data obtained by delaying received signal data obtained from the time-series received symbol data by one symbol time interval, a phase shift unit that generates second received signal data by performing phase shift according to the inclination, only in a period in which one symbol time interval elapses, on only the received signal data of a symbol time at which the occurrence of the phase slip is detected among pieces of the received signal data, and a remainder processing unit that derives a remainder of a difference between the second received signal data and the first received signal data.

Joint estimation of the framer index and the frequency offset in an optical communication system are described among various other features. A transmitter can transmit data frames using pilot and framer symbols. A receiver can estimate the framer index and frequency offset using the pilot and framer symbols, and identify the beginning of a header portion of a data frame. By identifying the beginning of the header portion of a data frame, the receiver can synchronize, with less error, the data transmitted by the transmitter and the data it received. To further improve the framer index estimation, a lock indicator signal can be generated to signal to other receiver components that the estimated framer indices are reliable. The receiver can determine frequency offset and additional framer index estimations with increased reliability when performed after the lock indicator signal is generated.

Embodiments of communications devices and methods for operating a communications device are described. In an embodiment, a communications device includes a complex multiplier configured to multiply a first input complex signal with a second input complex signal to generate an output complex signal, an amplifier configured to amplify an imaginary part of the output complex signal to generate an amplification result, a delay element configured to delay a rotation angle signal that is related to the second input complex signal, and a subtractor configured to subtract the amplification result from the delayed rotation angle signal to generate the rotation angle signal. Other embodiments are also described.