When the ultra-low power mm-scale sensor node does not have a crystal oscillator and phase-lock loop, it inevitably exhibits significant carrier frequency offset (CFO) and sampling frequency offset (SFO) with respect to the reference frequencies in the gateway. This disclosure enables efficient real-time calculation of accurate SFO and CFO at the gateway, thus the ultra-low power mm-scale sensor node can be realized without a costly and bulky clock reference crystal and also power-hungry phase lock loop. In the proposed system, the crystal-less sensor starts transmission with repetitive RF pulses with a constant interval, followed by the data payload using pulse-position modulation (PPM). A proposed algorithm uses a two-dimensional (2D) fast Fourier transform (FFT) based process that identifies the SFO and CFO at the same time to establish successful wireless communication between the gateway and crystal-less sensor nodes.

A phase locked loop circuit that is capable of stabilizing a frequency of an input signal even in the case where the frequency is unstable is provided. The phase locked loop circuit 12 that corrects a frequency error of an output signal from an oscillator to a predetermined target frequency; an ADC 121 that converts the output signal to a digital signal; reference frequency output means 123 that outputs a reference frequency signal; frequency error detection means 122a that detects the frequency error based on the digital signal and the reference frequency signal; correction signal generation means 122b that generates an error correction signal based on the frequency error; a DAC 124 that converts the error correction signal to an analog signal; and a multiplier 125 that multiplies the output signal by the analog signal to correct the frequency error of the output signal.

A quadrature detection unit subjects an FM signal to quadrature detection using a local oscillation signal and outputs a base band signal. A first correction unit and a second correction unit correct the base band signal using a DC offset correction value. A DC offset detection unit subjects the corrected base band signal to rectangular to polar conversion and derives the DC offset correction value such that amplitudes in a plurality of phase domains defined in an IQ plane approximate each other. An FM detection unit subjects the corrected base band signal to FM detection and generates a detection signal. An addition unit adds an offset to the detection signal. An AFC unit generates a control signal for controlling a frequency of a local oscillation signal based on the detection signal to which the offset is added.

To actualize frequency synchronization with each of radio communication systems while suppressing increase in circuit scale of a user terminal in an environment in which the user terminal concurrently communicates with a plurality of radio communication systems with different frequencies, a radio base station of the present invention is a radio base station for forming a narrow-area cell to communicate with a user terminal in a radio communication system where the narrow-area cell is provided inside a wide-area cell, and has a carrier frequency synthesizer that generates a carrier frequency of the narrow-area cell based on a wide-area radio signal transmitted from a radio base station for forming the wide-area cell, and a sampling frequency synthesizer that generates a sampling frequency of a baseband signal of the narrow-area cell based on the wide-area radio signal.

In a method and system for decoding a differential M-ary phase or quadrature amplitude modulated signal, the incoming signal is decoded according to a plurality of different decoding rules, wherein said plurality of decoding rules correspond to different values of a resulting frequency difference or mismatch between a signal frequency and a local oscillator reference frequency. The invention allows to increase a tolerance window for the maximal allowable frequency offset, and thus helps to speed up an initial locking process or to allow for equipment which has a lower tuning granularity.

A method and apparatus for generating a sampling frequency are provided. A signal is generated, of which frequency is a predetermined multiple of a reference clock, and a frequency offset in a channel is extracted from the entire frequency offset. The amount of shift is calculated by dividing the extracted frequency offset by a predetermined value, and a final sampling frequency is obtained by shifting the frequency of the generated signal by the amount of shift.

A digital radio receiver adapted to receive radio signals modulated using continuous phase frequency shift keying, CPFSK. The receiver comprises means for receiving a radio signal (2), a correlator (8) arranged to estimate a frequency offset between the carrier frequency of the received radio signal and a nominal carrier frequency, means for correcting said frequency offset (4) and outputting a frequency-corrected radio signal (6), and a matched filter bank, MFB, which comprises a plurality of filters (20,22), each of which corresponds to a different bit pattern, for determining a bit sequence (36) from the frequency-corrected radio signal (6).

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 Bluetooth receiver is provided. The Bluetooth receiver comprises processing circuitry configured to receive a receive signal and to determine receive symbols based on the receive signal. The Bluetooth receiver further comprises control circuitry configured to determine a frequency offset and/or a modulation index of the receive signal based on the receive signal. The control circuitry is additionally configured to control an operation mode of the processing circuitry based on the determined frequency offset and/or the modulation index of the receive signal.

There is provided an apparatus, said apparatus comprising means for receiving from a network, at a user equipment, Doppler shift information associated with at least one cell of the network as a function of time for at least one area and using the Doppler shift information at the user equipment to compensate for the Doppler shift in communication with the network when the user equipment is in the at least one area.