4978 results about "Fast Fourier transform" patented technology

The present invention is directed toward a pulse oximetry system for the determination of a physiological parameter capable of removing motion artifacts from physiological signals comprises a hardware subsystem and a software subsystem. The software subsystem is used in conjunction with the hardware subsystem to perform a method for removing a plurality of motion artifacts from the photo-plethysmographic data and for obtaining a measure of at least one physiological parameter from the data. The method comprises acquiring the raw photo-plethysmographic data, transforming the data into the frequency domain, analyzing the transformed data to locate a series of candidate cardiac spectral peaks (primary plus harmonics), reconstructing a photo-plethysmographic signal in the time domain with only the candidate cardiac spectral peaks (primary plus harmonics), computing the second order derivative of the reconstructed photo-plethysmographic signal, analyzing the candidate second order derivative photo-plethysmographic signal to determine the absence or presence of cardiac physiologic signal characteristics, and finally selecting the best physiologic candidate from the series of potential cardiac spectral peaks (primary plus harmonics) based upon a second derivative scoring system. This scoring system is preferentially based upon second derivative processing analysis, but can be equally applied using the first, third, fourth or other similar derivative processing analysis.

A noise suppression device receives data representative of a noise-corrupted signal which contains a speech signal and a noise signal, divides the received data into data frames, and then passes the data frames through a pre-filter to remove a dc-component and the minimum phase aspect of the noise-corrupted signal. The noise suppression device appends adjacent data frames to eliminate boundary discontinuities, and applies fast Fourier transform to the appended data frames. A voice activity detector of the noise suppression device determines if the noise-corrupted signal contains the speech signal based on components in the time domain and the frequency domain. A smoothed Wiener filter of the noise suppression device filters the data frames in the frequency domain using different sizes of a window based on the existence of the speech signal. Filter coefficients used for Wiener filter are smoothed before filtering. The noise suppression device modifies magnitude of the time domain data based on the voicing information outputted from the voice activity detector.

Disclosed is a method, a computer program product and a device that includes a receiver for receiving a downlink signal transmitted into a cell. The receiver is operable to obtain time, carrier frequency and cell-specific preamble synchronization to the received signal and includes a plurality of synchronization units that include a first detector to detect a frame boundary using preamble delay correlation; a second detector to detect the frame boundary with greater precision using a conjugate symmetry property over a region identified by the first detector; a cyclic prefix correlator to resolve symbol boundary repetition; an estimator, using the cyclic prefix, to estimate and correct a fractional carrier frequency offset; an operator to perform a Fast Fourier Transform of an identified preamble symbol and a frequency domain cross-correlator to identify cell-specific preamble sequences and an integer frequency offset in sub-carrier spacing. The transmitted signal may be a downlink signal transmitted into the cell from a base station that is compatible with IEEE 802.16e (WiMAX).

An apparatus and method for transmitting/receiving an random access channel (RACH) signal in a broadband wireless communication system where a total uplink frequency band is divided into M sub-bands are provided. In the RACH transmitting apparatus, a generator generates an access code. A sub-carrier allocator divides the access code into M sub-blocks and allocates each of the M sub-blocks to successive sub-carriers in a sub-band. An inverse fast Fourier transform (IFFT) processor generates an orthogonal frequency division multiplexing (OFDM) symbol by performing an IFFT on the allocated sub-blocks.

A single frequency relay station receives a signal from a master station, and retransmits it. Before retransmitting the signal, the relay station uses a digital filter to subtract from the signal components which arise from multipath interference and coupling interference. The coefficients used by the digital filter are derived from characteristics of the multipath interference and the overall transfer function of the relay station. These are derived by turning off the retransmission, so that the multipath interference can be estimated from the received signal, and commencing the retransmission again, to determine the transfer function. A simplified inverse fast Fourier transform is used to simplify the calculations.

Disclosed is a method for transmitting a reference signal for identification of each cell in a communication system including a plurality of cells each of which is identified by a cell identifier. The method includes receiving a cell identifier, and generating a block code corresponding to the cell identifier using a predetermined block code generator matrix, and generating a first part sequence using the block code; selecting a second part sequence in accordance with the cell identifier; generating a reference signal of a frequency domain using the first part sequence and the second part sequence; converting the reference signal of the frequency domain to a reference signal of a time domain through an Inverse Fast Fourier Transform operation and transmitting the reference signal of the time domain in a predetermined reference signal transmission interval.

A discrete multitone stacked-carrier spread spectrum communication method is based on frequency domain spreading including multiplication of a baseband signal by a set of superimposed, or stacked, complex sinusoid carrier waves. In a preferred embodiment, the spreading involves energizing the bins of a large Fast Fourier transform (FFT). This provides a considerable savings in computational complexity for moderate output FFT sizes. Point-to-multipoint and multipoint-to-multipoint (nodeless) network topologies are possible. A code-nulling method is included for interference cancellation and enhanced signal separation by exploiting the spectral diversity of the various sources. The basic method may be extended to include multielement antenna array nulling methods for interference cancellation and enhanced signal separation using spatial separation. Such methods permit directive and retrodirective transmission systems that adapt or can be adapted to the radio environment. Such systems are compatible with bandwidth-on-demand and higher-order modulation formats and use advanced adaptation algorithms. In a specific embodiment the spectral and spatial components of the adaptive weights are calculated in a unified operation based on the mathematical analogy between the spectral and spatial descriptions of the airlink.

A system and method for determining and monitoring various characteristics of a patient positioned on a patient support apparatus, such as a bed, stretcher, or cot, is disclosed. The system and method involve monitoring the forces exerted by the patient on one or more force sensors, which may be load cells on the support apparatus. These force sensors will detect vibrations that correspond to various conditions of the patient, including the patient's heart rate, breathing rate, and/or the seizure status of a patient. These vibrations may be analyzed, such as by Fast Fourier Transforms, in order to determine the various conditions of the patient.

A method for coexistence of an orthogonal frequency division multiple access (OFDMA) receiver (117) such as a WiMAX receiver with a synchronous frame-based transmitter (115) such as a Bluetooth transmitter within a mobile station (110) receives an estimated media access protocol (MAP′) signal indicating when a MAP message is expected to be received by the OFDMA receiver (117) and uses it at a Bluetooth shutdown signal (190) at least when a MAP message is expected to be received. The MAP′ signal can be taken directly from the ODFMA transceiver (117) or it may be produced through analysis of a receiver-enable (RXE) signal that includes not only MAP symbols but also downlink data symbols. The RXE signal can be analyzed using interrupt-and-timer, Fast Fourier Transform, covariance, and/or delay-locked loop techniques to extract historical MAP symbol information and generate expected MAP symbol information. Shutting down a Bluetooth transmitter during expected MAP message receipt permits the OFDMA receiver to maintain synchronicity with an access point while not requiring the Bluetooth transmitter to shut down every time the OFDMA receiver expects to receive an OFDMA symbol.

A method and apparatus for transmitting uplink acknowledge information (ACK) in a communication system using an orthogonal frequency division multiple access (OFDMA) scheme. The method includes receiving a data bit for the uplink ACK; outputting codewords corresponding to the data bit; performing quadrature phase shift keying (QPSK) modulation on symbols for ACK vector indexes corresponding to the codewords for the received data bit; performing inverse fast Fourier transform (IFFT) on a transmission signal having subcarrier clusters to which the modulated transmission symbols are allocated; and transmitting the IFFT-processed transmission signal.

A wireless spread spectrum communication system for transmitting data includes a plurality of end point transmitters and at least one receiver. The end point transmitters transmit data via a frequency hopped spread spectrum signal where the transmitting signal is sent without the benefit of frequency stabilization. The receiver is responsive to the frequency hopping spread spectrum signals and includes a correlator and a signal processor. The correlator samples at least a first portion of a preamble of the signal and correlates the portion of the preamble with a known preamble pattern to determine a probability of correlation. The signal processor applies a Fast Fourier Transform algorithm to the signal in response to the probability of correlation to track a narrowband frequency of the signal based on at least a second portion of the preamble and to decode data encoded within the signal subsequent to the preamble.

A method of achieving transmit diversity in a wireless communication system is disclosed. The method comprises encoding and modulating data stream based on feedback information, demultiplexing symbols to at least one encoder block, encoding the demultiplexed symbols by the at least one encoder block, transforming the encoded symbols by at least one inverse fast Fourier transform (IFFT) block, and selecting antennas for transmitting the symbols based on the feedback information.

The invention provides a synchronous processing method based on new CMMB (China Mobile Multimedia Broadcasting) synchronous signals. The CMMB synchronous signals comprise first training sequences and second training sequences; the first training sequences comprise CAZAC (Constant Amplitude Zero Auto Correlation) sequences, and the second training sequences comprise PN (Pseudo-Noise) sequences; in the synchronous processing method, the CAZAC sequences are utilized to achieve coarse symbol timing offset estimation and decimal frequency offset coarse estimation; the PN sequences are utilized to achieve the estimation of strongest path time delay in multipath, and the multipath is taken as coarse symbol timing positioning; the CAZAC sequences and the PN sequences are utilized to achieve the integer frequency offset estimation; the fast Fourier transform (FFT) is performed on the PN sequences to achieve the channel response estimation so as to estimate a first path time delay and achieve the fine symbol timing position estimation; and a maximum likelihood (ML) criterion is utilized to process the PN sequences in the second training sequences to obtain the decimal frequency offset fine estimation. The synchronous processing method can effectively improve the synchronous accuracy and can achieve better synchronization performance in the mobile communication environment with low signal-to-noise ratio.

A radio communication system divides an entire frequency band into a plurality of subcarrier bands, forms a symbol from signals on the subcarrier bands, forms a frame from a plurality of symbols, transmits a pilot signal within symbols in a predetermined position of the frame, and transmits a data signal within symbols other than the symbols for transmitting the pilot signal. A transmitter generates the pilot signal, performs an inverse fast Fourier transform (IFFT) on the pilot signal by applying an IFFT size which is less than an IFFT size applied to the data signal, and transmits the IFFT-processed reference signal to a receiver.

An apparatus and a method for reducing an error vector magnitude in an orthogonal frequency division multiplexing (OFDM) receiver. The method includes the steps of inputting a receiving symbol including a guard interval and an effective symbol interval following the guard interval, in which a front portion of the guard interval and a rear portion of the effective symbol interval have windowing intervals corresponding to windowing of a transmitter, and replacing a signal of the rear windowing interval with a signal of an interval between the front windowing interval and the effective symbol interval, thereby outputting a signal of the effective symbol interval, which substitutes for a signal of the rear windowing interval, to a fast Fourier transform (FFT) section.

An apparatus and a method for peak-to-average power ratio reduction of an OFDM signal are disclosed. The method uses the interleaved characteristics of partial transmit sequences to partition input data x[n] of length N into several disjoint subblocks in time domain, and a complete N-point signal {tilde over (x)}[n] is composed after phase optimization, where N is the length of an OFDM signal and n=0, 1, . . . , N−1. Accordingly, the apparatus comprises an N-point inverse fast Fourier transform (N-IFFT), a de-multiplexer, a combiner, a set of memory and an adder. This invention uses only one N-IFFT, whereby it can achieve significant computation reduction. This invention requires (N/2)log₂ N complex multiplications and N memory units. It also preserves the inherent property as well as advantages of an OFDM system.

Embodiments are directed to binary phase shift key modulating a first pilot symbol according to a reference sequence, and differentially binary phase shift key modulating a second pilot symbols. The original reference sequence and the delayed differentially modulated sequence are then combined before performing an Inverse Fast Fourier Transform and inserting a guard interval. Receiver operations are an inverse of the transmitter operations, which were just discussed. The receiver does not have to know the reference sequence. Embodiments are directed to specifying a plurality of seeds that are bit patterns each having r bits not all of which have a value of zero, extending the seeds into respective sequences by applying to each seed a recurrence formula; and using one of the sequences as a comb sequence and using the sequences other than the comb sequence as binary phase shift keying patterns.

In a cellular network, symbols are encoded and modulated to produce a modulated signal The modulated signal is mapped to a subcarrier using a spatial mapping matrix. An inverse fast Fourier transform is applied to the mapped signal to produce groups of tones. The groups of tones are transmitting concurrently to multiple receivers using the same channel as orthogonal frequency-division multiplexing access (OFDMA) signals. There is one group of tones for each receiver.

A method of radar-imaging a scene in the far-field of a one-dimensional radar array, comprises providing an array of backscatter data D(f_m, x′n) of the scene, these backscatter data being associated to a plurality of positions x′_n, n=0 . . . N−1, N>1, that are regularly spaced along an axis of the radar array. The backscatter data for each radar array position x′n are sampled in frequency domain, at different frequencies f_m, m=0 . . . M−1, M>1, defined by f_m=f_c−B/2+m−Δf, where f_c represents the center frequency, B the bandwidth and Δf the frequency step of the sampling. A radar reflectivity image 1(α_m′, β_n′) is computed in a pseudo-polar coordinate system based upon the formula (2) with formula (3) where j represents the imaginary unit, formula (A) is the baseband frequency, FFT2D denotes the 2D Fast Fourier Transform operator, α_m′, m′=0 . . . M−1, and β_n′, n′=0 . . . N−1 represent a regular grid in the pseudo-polar coordinate system, and P_max is chosen >0 depending on a predefined accuracy to be achieved. A corresponding method of radar-imaging a scene in the far-field of a two-dimensional radar array is also proposed.

A method for automatic left ventricle segmentation of cine short-axis magnetic resonance (MR) images that does not require manually drawn initial contours, trained statistical shape models, or gray-level appearance models is provided. More specifically, the method employs a roundness metric to automatically locate the left ventricle. Epicardial contour segmentation is simplified by mapping the pixels from Cartesian to approximately polar coordinates. Furthermore, region growing is utilized by distributing seed points around the endocardial contour to find the LV myocardium and, thus, the epicardial contour. This is a robust technique for images where the epicardial edge has poor contrast. A fast Fourier transform (FFT) is utilized to smooth both the determined endocardial and epicardial contours. In addition to determining endocardial and epicardial contours, the method also determines the contours of papillary muscles and trabeculations.