74 results about "Common phase error" patented technology

An Orthogonal Frequency Division Multiplexing (OFDM) signal receiving apparatus and method of estimating a common phase error (CPE) using data subcarriers (and pilot subcarriers) instead of only pilot subcarriers. In the OFDM signal receiver, a channel measurement unit estimates a channel from a fast-Fourier-transformed signal to generate information about good subcarrier indexes as channel state information (CSI). A Common Phase Error (CPE) estimation unit estimates good pilot subcarriers and good data subcarriers from an equalized signal output from an equalizer (EQ) based on the channel state information (CSI), calculates the first and second common phase errors from the estimated pilot and data subcarriers respectively, and combines the first and second common phase errors to generate a final common phase error.

Disclosed is a phase noise compensation apparatus to be applied to the OFDM system, comprising an ICI estimating unit for estimating inter carrier interference (ICI) using a pilot sub-carrier included in a reception signal, a estimating unit for estimating a common phase error (CPE), which is a phase noise from the reception signal as sampled, using the pilot sub-carrier, and estimating a transmission signal by removing the estimated CPE from the reception signal, a calculating unit for calculating phase change by the ICI in the reception signal by convoluting the ICI and the transmission signal, and an equalizer for compensating the calculated phase change by the ICI in the reception signal. Accordingly, phase noise can be exactly compensated by estimating as phase noise the result of convoluting a received signal where the CPE is removed in a frequency domain and the estimated ICI according to the present invention.

Signal processing methods and apparatus which incorporate I / Q imbalance compensation based on most likely estimates of the I / Q imbalance between the I and Q components of a baseband signal are disclosed. In accordance with at least one disclosed embodiment of the invention, most likely estimates of the common phase error may also be used to compensate the initial channel estimates to further improve receiver performance. Though applicable to any multicarrier OFDM communications system, the disclosed methods and apparatus may be conveniently implemented in IEEE 802.11a, IEEE 802.11g, or 802.16a compliant wireless communications systems to reduce the effects of imbalanced I / Q components of baseband signals recovered from inbound RF signals, as well as counter residual frequency offset and phase noise potentially present in such baseband signals.

A base station (BS) having a plurality of antennas transmits a plurality of spatial streams. Each user equipment (UE) of a plurality of UE estimates common phase error (CPE) of each of two or more of the plurality of spatial streams, measures correlations of the estimated CPE among the two or more of the plurality of spatial streams, and provides feedback about the CPE correlations to the BS. The BS uses the CPE correlation feedback to allocate phase tracking reference signal (PTRS) ports and to map the allocated PTRS ports to demodulation reference signal (DMRS) ports corresponding to the plurality of spatial streams.

A system and method for efficient phase error correction in range migration algorithm (RMA) for synthetic aperture radar (SAR) systems implemented by making proper shifts for each position dependent phase history so that phase correction can readily be performed using the aligned phase history data during batch processing. In its simplest form, the invention (44) is comprised of two main parts. First (60), alignment of the phase error profile is achieved by proper phase adjustment in the spatial (or image) domain using a quadratic phase function. Second (62), the common phase error can be corrected using autofocus algorithms. Two alternative embodiments of the invention are described. The first embodiment (44a) adds padded zeros to the range compressed data in order to avoid the wrap around effect introduced by the FFT (Fast Fourier Transform). This embodiment requires a third step (64): the target dependent signal support needs to be shifted back to the initial position after phase correction. The second embodiment (44b) uses the range compressed data without padded zeros. Instead, an aperture of greater length needs to be generated by the Stolt interpolation. In this embodiment, the third step (64) of shifting the signal support back can be eliminated.

An apparatus, method and computer program for correcting a common phase error (CPE) of symbols of a received OFDM signal is described, in which FFT processing may be performed on a time domain OFDM to transform the received signal to a signal in the frequency-domain. Reordered output values resulting from the FFT processing and locations of the reordered output values may be stored. One or more of the stored reordered output values for a current symbol of the OFDM signal may be transferred based on receipt of an address, and each of the transferred reordered output values may be multiplied by a corresponding reordered output value of a previous OFDM signal symbol, so as to determine phase differences between the reordered output values of the current and previous OFDM signal symbols. The CPE of the transformed OFDM signal may be corrected based on the detected phase differences.

A system and method for efficient phase error correction in range migration algorithm (RMA) for synthetic aperture radar (SAR) systems implemented by making proper shifts for each position dependent phase history so that phase correction can readily be performed using the aligned phase history data during batch processing. In its simplest form, the invention (44) is comprised of two main parts. First (60), alignment of the phase error profile is achieved by proper phase adjustment in the spatial (or image) domain using a quadratic phase function. Second (62), the common phase error can be corrected using autofocus algorithms. Two alternative embodiments of the invention are described. The first embodiment (44a) adds padded zeros to the range compressed data in order to avoid the wrap around effect introduced by the FFT (Fast Fourier Transform). This embodiment requires a third step (64): the target dependent signal support needs to be shifted back to the initial position after phase correction. The second embodiment (44b) uses the range compressed data without padded zeros. Instead, an aperture of greater length needs to be generated by the Stolt interpolation. In this embodiment, the third step (64) of shifting the signal support back can be eliminated.

A system and method (44) for focusing an image oriented in an arbitrary direction when the collected synthetic aperture radar (SAR) data is processed using range migration algorithm (RMA). In accordance with the teachings of the present invention, first (60) the data is skewed so that the direction of smearing in the image is aligned with one of the spatial frequency axes of the image. In the illustrative embodiment, the smearing is aligned in the vertical direction. This is done through a phase adjustment that was derived from the requirements for proper shift in the spatial frequency domain. Next (62), the signal support areas from all targets are aligned by proper phase adjustment in the spatial (or image) domain. Finally (64), the common phase error can be corrected using autofocus algorithms.

An apparatus and method for correcting a CPE in a signal reception apparatus of a multi-carrier communication system are provided, in which an auto-correlation of a reference signal estimated from a reference symbol among a plurality of symbols is detected, a cross-correlation between a channel estimate of the reference signal and an actual received reference signal is detected, and the CPE of the remaining symbols except the reference symbol is corrected using the auto-correlation and the cross-correlation.

A wireless device receives a frequency division multiplexed (FDM) symbol of constituent equalized FDM data subcarriers. A modulation scheme constellation diagram is subdivided into two or more regions. For each of the regions, a subset of the subcarriers that fall within the region are extracted and a respective region-specific CPE estimate is computed thereon. The respective region-specific CPE estimates are averaged to produce an overall CPE estimate used to compensate the subcarriers. Furthermore, a first CPE estimate is computed using pilot symbols embedded in a first received FDM symbol and is used to compensate the subcarriers. A following second FDM symbol that has no embedded pilot symbols is compensated using the first CPE estimate, and a second CPE estimate is computed using a blind estimation method on the second FDM symbol compensated subcarriers, which are compensated using the second CPE estimate.

The invention discloses a phase noise suppression method under the low-complexity channel estimation of an SC-FDE (single carrier-frequency domain equalization) system. The phase noise suppression method comprises the following steps of: forming a training sequence by virtue of special characters, obtaining the responses of a small amount of frequency points of CFR (crest factor reduction) and a CIR (channel impulse response) by virtue of a LS (least square) algorithm according to the received signal, obtaining the initial CFR influenced by a phase noise CPE (common phase error) via a discrete Fourier transform interpolation filter, and performing time-domain noise power estimation and frequency-domain noise power estimation according to the training sequence; after an established channel is obtained, extracting the effective order of the CIR in a time domain, and calculating the copy of the special character received signal; using special characters as cyclic prefixes of transmission data blocks, estimating the ratio of the CPE on one cyclic prefix to the CPE in the initial established channel by virtue of an MMSE (minimum mean square error) algorithm, and then obtaining the ratio of the CPE of the whole data block to the CPE in the initial established channel via linear interpolation; and finally multiplying the CPE ratio with the initial CIR influenced by the phase noise CPE to track the whole channel of the present data block, and suppressing phase noise interference via the frequency-domain MMSE equalization. The channel estimation algorithm disclosed by the invention is low in complexity, thus reducing the complexity of a phase noise suppression algorithm.

Systems and methods are presented for transmitting additional data over preexisting differential COFDM signals by modulating existing data carriers with a phase and an amplitude offset. In exemplary embodiments of the present invention, additional data capacity can be achieved for an COFDM signal which is completely backwards compatible with existing satellite broadcast communications systems. In exemplary embodiments of the present invention additional information can be overlayed on an existing signal as a combination of amplitude and phase offset from the original QPSK symbols, applied for each information bit of the overlay data. With two additional levels of modulation, a receiver can demodulate the information from each of the previous stages and combine the information into a suitable format for soft decoding. The first stage of demodulation will be recovery of overlay data from the amplitude modulated D8PSK. Because other amplitude variations due to multi-path are also expected, the data gathered from the FFT in the receiver must be equalized to the channel conditions. After channel equalization has been performed, soft overlay data can then be derived from the distance off the unit circle. In order to recover the phase modulated overlay data, the equalized symbols must first be differentially demodulated and corrected for any common phase error offset. After common phase removal, overlay phase information can be obtained.

The invention belongs to the technical field of wireless communication, and particularly relates to method for achieving compensation restraint of phase noise in a wireless communication system through an iteration method. The method comprises the steps that firstly, an equivalent dispersion time domain channel impulse response is estimated through a channel estimation sequence; then, a CPE of the phase noise is estimated through interpolation; finally, noise phase compensation is achieved through the iteration method. According to the method for achieving the compensation restraint of the phase noise, the reliability of the system is improved and the error rate is reduced.

An apparatus, method and computer program for correcting a common phase error (CPE) of symbols of a received OFDM signal is described, in which FFT processing may be performed on a time domain OFDM to transform the received signal to a signal in the frequency-domain. Reordered output values resulting from the FFT processing and locations of the reordered output values may be stored. One or more of the stored reordered output values for a current symbol of the OFDM signal may be transferred based on receipt of an address, and each of the transferred reordered output values may be multiplied by a corresponding reordered output value of a previous OFDM signal symbol, so as to determine phase differences between the reordered output values of the current and previous OFDM signal symbols. The CPE of the transformed OFDM signal may be corrected based on the detected phase differences.

The invention belongs to the technical field of wireless communication, and particularly relates to a method for realizing the phase noise estimation by an iteration method in a wireless communication system. According to the method, firstly, the equivalent discrete time domain channel impulse response is estimated through channel estimation sequences, then, a CPE (common phase error) of the phase noise is estimated through interpolation, and finally, the phase noise estimation is realized by the iteration method, so the phase noise is compensated, the reliability of the system is improved, and the bit error rate is reduced.

An apparatus and method for compensating for a phase error in a wireless communication system are provided. The apparatus includes a reception modem, a transmission modem, a Common Phase Error (CPE) compensator, a first channel estimator, a phase compensator, and a second channel estimator. The reception modem demodulates and decodes a signal received. The transmission modem encodes and modulates a signal for transmission. The CPE compensator compensates for phase errors of at least two symbols constituting a signal. The first channel estimator estimates channels for respective bursts. The phase compensator compares phases for the channels for the respective bursts with each other and compensates for a phase difference between at least two bursts. The second channel estimator estimates an interference channel.

A method and apparatus for processing a radio frequency signal. The method includes compensating a digital in-phase signal and a digital quadrature signal for any imbalance; converting the compensated digital in-phase signal and the compensated digital quadrature signal into a frequency domain digital OFDM symbol; generating a plurality of channel estimates, wherein each channel estimate corresponds to an estimate of the channel for a corresponding sub-carrier of the frequency domain digital OFDM symbol; and generating (i) a most likely estimate of the imbalance between the digital in-phase signal and the digital quadrature signal and (ii) a most likely estimate of a common phase error in the plurality of channel estimates. The most likely estimate of the imbalance is used to compensate the digital in-phase signal and the digital quadrature signal, and the most likely estimate of the common phase error is used to compensate the plurality of channel estimates.

The invention, which belongs to the technical field of wireless communication, especially relates to the field of phase noise estimation realization by using an iterative method in a wireless communication system. According to the invention, on the basis of a channel estimation sequence, an equivalent discrete time-domain channel impulse response is estimated; a common phase error (CPE) of the phase noises is estimated by interpolation; and then phase noise compensation is realized by using an iterative method. Therefore, the system reliability is improved and the error rate is reduced.

A system and method (44) for focusing an image oriented in an arbitrary direction when the collected synthetic aperture radar (SAR) data is processed using range migration algorithm (RMA). In accordance with the teachings of the present invention, first (60) the data is skewed so that the direction of smearing in the image is aligned with one of the spatial frequency axes of the image. In the illustrative embodiment, the smearing is aligned in the vertical direction. This is done through a phase adjustment that was derived from the requirements for proper shift in the spatial frequency domain. Next (62), the signal support areas from all targets are aligned by proper phase adjustment in the spatial (or image) domain. Finally (64), the common phase error can be corrected using autofocus algorithms.

The present invention relates to a digital signal reception method and apparatus. Said digital signal receiver comprises a Common Phase Error (CPE) removal unit (240) for eliminating CPE contained in the received signal by using CSI corrected pilot sub-carriers; a channel estimation (CE) unit (250) for estimating channel state information (CSI) of the received signal after removing the CPE and feed the CSI to the CPE removal unit (240), and a means (241) for generating the CSI corrected pilot sub-carriers by multiplying the CSI with 1 or -1 according to positive or negative sign of the local pilot sub-carriers only in response to continual pilots of the received signal. Said method comprises estimating the CSI of the received digital signal after removing CPE; and eliminating the CPE of the received signal by using the CSI corrected pilot sub-carriers, whereby a low complexity and high accuracy are achieved.

The invention relates to an orthogonal frequency division multiplexing (OFDM) system common phase error compensation method and a device. The method comprises steps of extracting a carrier position serial number set gamma of continuous pilot frequency of fast Fourier transform (FFT) output data; conducting conjugating multiplication for a carrier of a position serial number of a current OFDM symbol and a carrier of the same position serial number of a last OFDM symbol in accordance with position serial numbers of the carrier position serial number set gamma and obtaining a pilot frequency differential value; calculating and obtaining a common phase error increment by the aid of the pilot frequency differential value; enabling the sum of all common phase error increments prior to the current OFDM symbol to serve as the common phase error between the current OFDM symbol and a standard OFDM symbol; and conducting common phase error compensation for the current OFDM symbol by the aid of the common phase error. Accordingly, the common phase error of all OFDM symbols is compensated to a standard value, the effect of the common phase error on a system is reduced, and the OFDM system receiving performance is improved.

The invention belongs to the technical field of wireless communication, particularly relates to estimation of phase noise in a wireless communication system using a relevant algorithm, and provides a phase noise estimation method in the wireless communication system using the algorithm. According to the method, equivalent discrete time-domain channel impulse response is utilized to estimate CPE (common phase error) of the phase noise via an interpolation mode, and the phase noise is finally estimated by an iterative approach, thus system reliability is improved and error rate is reduced.

A receiver is a Digital Video Broadcasting-Terrestrial / Handheld (DVB-T / H) receiver. The DVB-T / H receiver comprises a phase error corrector and a channel estimation and equalization element. The phase error corrector rotates a signal in accordance with an estimate of a phase error, e.g., CPE, which is determined as a function of channel state information (CSI) provided by the channel estimation and equalization element.

A receiver is a Digital Video Broadcasting-Terrestrial / Handheld (DVB-T / H) receiver. The DVB-T / H receiver comprises a fast fourier transform (FFT) operative on a signal for providing an FFT output signal comprising a number of samples; a spectrum shifter for reordering the samples in the FFT output signal to provide a spectrum shifted signal; and a phase corrector for estimating a phase error from the FFT output signal and for correcting a phase of the spectrum shifted signal in accordance with the estimated phase error.

The invention provides an information transmission method and device. The method is characterized in that the method includes the steps: determining time domain density of a PTRS (phase tracking reference signal); determining frequency domain density of the PTRS according to an available bandwidth, or determining the frequency domain density of the PTRS according to scheduling or an available RB (resource block); mapping the PTRS to one or more OFDM (orthogonal frequency division multiplexing) symbols according to the time domain density and the frequency domain density; and transmitting a signal that includes the OFDM symbols where the PTRS is mapped. The invention also discloses a corresponding device. By adopting the technical solution of the present invention, the method can avoid thejump of the number of PTRSs near the threshold of the scheduling bandwidth, takes into account the accuracy and spectral efficiency of the common phase error estimation, and can achieve the uniform mapping of the PTRS within the scheduling or available bandwidth, thereby achieving the reasonable configuration of the PTRS.

A power saving receiver has a controller which is operative to remove power from the receiver when a threshold is exceeded during reception of a packet. The threshold level is formed by comparison of any of: signal energy of unoccupied subcarriers less the signal energy in occupied subcarriers; signal energy in a first range of occupied subcarriers compared to signal energy in a different range of occupied subcarriers; error vector magnitude from a first set of subcarriers to a second set of subcarriers in a different spectral region of the channel; cyclic prefix cross-correlation, or common phase error increase.