46 results about "Sampling clock offset" patented technology

A SCO estimator comprises the following units. A module obtains a first data output by a first unit and copies the first data to obtain copied data. A QAM unit quadrature modulates the copied data into each sub-carrier of each OFDM symbol to regenerate transmitted modulated data. A first phase unit obtains a first phase of each sub-carrier of each OFDM symbol of the modulated data. A second phase unit obtains a second data from a second unit, and obtains a second phase of each sub-carrier of each OFDM symbol of the second data. A comparator generates a comparing result according to the first phase and the second phase of each sub-carrier of each OFDM symbol. A divider divides the comparing result of each sub-carrier by the subcarrier index within each OFDM symbol and the OFDM symbol index of each OFDM symbol. An averaging unit averages the divided comparing result over number of sub-carriers and number of OFDM symbols.

A method for time synchronization tracking in an orthogonal frequency division multiplexing (OFDM) receiver is described, the method comprising the steps: obtaining a DFT output vector; determining a sample timing offset indication using reference symbols that are extracted from the DFT output vector; and adapting the OFDM symbol timing using said determined indication. In order to provide an improved post-DFT algorithm for estimating a time tracking error in OFDM receivers such as to allow an effective time tracking even in single frequency networks, and more particular to devise a time tracking algorithm for OFDM receivers that supports longer channel impulse responses without causing inter-symbol interference, said determining step comprises the steps of : (a) estimating (162) the channel transfer function at equidistant frequency positions using said reference symbols, for a first OFDM symbol; (b) determining (163) a plurality of autocorrelations of said channel transfer function at a specific set of small frequency offsets for said OFDM symbol; (c) repeating steps (a) and (b) for a plurality of subsequent OFDM symbols; (d) linearly combining (164,165) said plurality of autocorrelations for said plurality of OFDM symbols obtained in steps (a) through (c), for obtaining said sampling clock offset indication wherein the linear combining uses nonzero weights only. Further described is an orthogonal frequency division multiplexing (OFDM) receiver circuit arrangement performing this method.

An apparatus and method for tracking a sampling clock are disclosed. The apparatus includes a compensating circuit compensating phases of a first and a second received symbols according to a compensating signal and thereby generating a first and a second compensated symbols; a data removal circuit removing a first predetermined transmitted data from the first compensated symbol, and a second predetermined transmitted data from the second compensated symbol and thereby generating a first and a second data removal symbols; and a computing circuit generating a sampling clock offset according to the first and the second data removal symbols, and adjusting the sampling clock signal according to the sampling clock offset.

An apparatus includes a receiver buffer, a phase compensation circuit, a data sampler circuit, and an error sampler circuit. The receiver buffer may generate an equalized signal on a signal node using an input signal received via a channel. The phase compensation circuit may, in response to an initiation of a training mode, replace the equalized signal on the signal node with a reference signal. The data sampler circuit may sample, using a data clock signal, the reference signal to generate a plurality of data samples. The error sampler circuit may sample, using an error clock signal, the reference signal to generate a plurality of errors samples. The phase compensation circuit may also adjust a phase difference between the data clock signal and the error clock signal using at least some of the plurality of data samples and at least some of the plurality of error samples.

The present invention discloses a method for symbol synchronisation in high speed optical orthogonal frequency division multiplexing (OOFDM) transmission systems via coding the electrical OFDM symbols by adding an independent low power-level alignment signal, converting the encoded signal into the optical domain for transmission, and in the receiver converting the received optical signal to the electrical domain and digitally processing to detect the symbol alignment offset by utilising the independent low-power level alignment signal. The present invention is suitable for point-to-point and point-to-multipoint OOFDM networks and has the additional features of timeslot and frame alignment, compensation for receiver sampling clock offset and providing physical layer network security.

An apparatus for sampling clock recovery (SCO) and methods for estimating and compensating SCO are provided. The apparatus comprises a symbol timing adjustment module for shifting forward or backward symbol timing of the transmitted OFDM symbols; a discrete Fourier transform (DFT) processor for performing DFT to an output from the symbol timing adjustment module; a channel estimator for undertaking a channel frequency response estimation based on a channel estimation sequence; a SCO phase rotator for receiving and performing phase shift on the transmitted OFDM symbols of a frame header and a frame payload; an SCO estimation stage for undertaking an SCO estimation based on a pilot-subcarrier-related output of the SCO phase rotator and the CFR estimation; and an SCO compensation distributor for dividing the SCO estimation into integer and fractional portions and then distributing them into the symbol timing adjustment module and the SCO phase rotator, respectively.

A compensating device for detecting and compensating for a sampling clock offset in a receiver. An SCO detector includes multiple calculation paths and a controller. Each calculation path receives a time domain signal and a hypothetic offset, calculates correlation coefficients between the time domain signal and a delayed version of the time domain signal according to a predetermined delay and the hypothetic offset, calculates correlation coefficient sums according to the correlation coefficients, and extracts a maximum correlation coefficient sum for the hypothetic offset from the correlation coefficient sums. The controller is coupled to the calculation paths for providing different hypothetic offsets to each calculation path and detects the SCO according to the maximum correlation coefficient sums obtained from the calculation paths. An SCO compensator receives the SCO and compensating for the SCO on a signal generated in a signal processing path of a receiver.