A wireless communications system is configured to perform wireless communication by using a first band dedicated to the system and a second band shared by the system and another wireless communications system. The system includes a base station configured to transmit in the first band to a terminal when detecting an available carrier wave of the second band, a control signal permitting data transmission in the second band from the terminal to the base station, the base station continuously sending out a radio wave of the second band during a period until the data transmission; and the terminal configured to perform the data transmission after a predetermined time from transmission of the control signal by the base station.

A method and an apparatus for transmitting a wakeup packet in a wireless LAN system are proposed. Particularly, a transmission device configures a wakeup packet and transmits the wakeup packet to a receiving device. The wakeup packet includes a sequence configured with first information and second information by applying an OOK method. The first information and the second information are configured with an on-signal or an off-signal. The on-signal is transmitted through a first symbol, which is generated by applying a first sequence to K consecutive subcarriers in the 20 MHz band and performing 64-point IFFT. The off-signal is transmitted through a second symbol, which is generated by applying a second sequence to K consecutive subcarriers in the 20 MHz band and performing 64-point IFNT. The first information and the second information are transmitted through a third symbol in which the first symbol or the second symbol is repeated.

A communication device of the disclosure includes a phase synchronizer, a first modulator, and a detector. The phase synchronizer generates a second signal on a basis of a first signal received from a communication partner. The first modulator is able to modulate the first signal on a basis of the second signal. The detector detects that synchronization between the first signal and the second signal is lost.

Methods and system for On/Off Key (OOK) communication are described. In one embodiment, a method for OOK communication involves detecting an average symbol energy of an OOK modulated sequence and performing bit synchronization for the OOK modulated sequence in response to the detected average symbol energy. Other embodiments are also described.

A circuit for demodulating an input signal is described. The circuit may be configured to demodulate signals modulated with amplitude-based modulation schemes, such as amplitude shift keying (ASK). The demodulator may comprise a clock extractor configured to generate a clock signal in response to receiving an amplitude-modulated input signal, a phase shifter configured to generate a sampling signal by phase-shifting the clock signal by approximately /2, and a sampler configured to sample the input signal in correspondence to one or more edges (such as one or more falling edges) of the sampling signal. In this way, the amplitude-modulated input signal may be sampled at its peak, or at least near its peak, thus ensuring high signal fidelity.

System and method of adapting thresholds for constellation selection based on statistic distributions of received data symbols. To determine an adapted threshold, an expected ratio of received symbols with values in a certain range is preset based on an expected statistic distribution of data symbols across the multiple constellations. A first and a second ratios are defined based on the expected ratio, the first ratio being the expected ratio minus an error ratio and the second ratio being the expected ratio plus the error ratio. A first value is determined which makes the received symbols in a firs range to constitute the first ratio of a set of slicer inputs. A second value is determined which makes the received symbols in the second range to constitute the second ratio of a set of slicer outputs. The adapted threshold is then obtained based on the first and the second value.

Methods and system for On/Off Key (OOK) communication are described. In one embodiment, a method for OOK communication involves detecting an average symbol energy of an OOK modulated sequence and performing bit synchronization for the OOK modulated sequence in response to the detected average symbol energy. Other embodiments are also described.

Precompensator-based quantization techniques offer a way to reduce the complexity and power requirements of clock recovery modules while offering improved timing recovery performance relative to a bang-bang scheme operating in a lossy channel. One illustrative method embodiment includes: (a) obtaining a receive signal having a sequence of symbols from a symbol set, the receive signal exhibiting trailing intersymbol interference; (b) operating on the receive signal with a precompensation unit having a set of comparators to produce, for each sampling instant, a set of comparator results representing a quantized receive signal value, the set of comparators applying a set of threshold values that at least partly compensate for the trailing intersymbol interference; (c) deriving a symbol decision from each set of comparator results; (d) combining the symbol decisions with said quantized receive signal values to determine an estimated timing error for each sampling instant; and (e) filtering the estimated timing errors to generate a sampling clock.

This disclosure relates to data converters for electronic systems. An example system includes a primary analog to digital converter (ADC) circuit, a slope calculation circuit, a digital phase lock loop (DPLL) circuit, a sampling error circuit, and a summing circuit. The primary ADC circuit samples an input signal and produces a digital output signal representative of the input signal. The slope calculation circuit generates a digital slope signal representative of slope of the input signal, and the DPLL circuit provides a sampling clock signal to the primary ADC circuit. The sampling error circuit generates a sampling error signal representative of sampling error by the primary ADC circuit using the digital slope signal and the sampling clock signal. The summing circuit receives the sampling error signal and the digital output signal of the primary ADC circuit and generates an adjusted digital output signal representative of the input signal.

A backscatter tag communicate device includes, in part, a receiver configured to receive a WiFi packet conforming to a communication protocol defining a multitude of codewords, a mapper configured to map at least a first subset of the multitude of codewords disposed in the packet to a second multitude of codewords defined by the protocol, and a frequency shifter configured to shift a frequency of the second multitude of codewords such that the frequency shifted codewords are characterized by a single sideband spectrum. The communication protocol may be the 802.11b communication protocol. The mapper may optionally map the first subset of the multitude of codewords by changing phases of the first subset of the multitude of codewords.