Abstract: Apparatus and methods are described to perform inter carrier interference (ICI) reduction or cancellation in an orthogonal frequency domain multiplexing (OFDM) receiver. A first and a second stage of ICI cancellation may be performed before inputting an estimated transmitted data carrier for forward error correction. Forward error correction may include a signal re-correction and reconstruction of the estimated transmitted data carrier prior to a further stage of ICI cancellation.

Abstract: According to various embodiments, a method is disclosed that includes a method is disclosed that includes determining, by a receiver, a frequency offset in a signal comprising a set of orthogonal frequency division multiplexed (OFDM) symbols by determining a first difference in phase angles between a nth OFDM symbol and a nth+1 OFDM symbol on a common OFDM carrier and a first difference in phase angles between the nth+1 OFDM symbol and a nth+2 OFDM symbol on the common OFDM carrier and determining a second difference in phase angles between the first difference in phase angles between the nth OFDM symbol and the nth+1 OFDM system and the first difference in phase angles between the nth+1 OFDM symbol and the nth+2 OFDM symbol to identify the frequency offset, wherein n?{1, . . . , N}; and correcting, by the receiver, the signal using the determined frequency offset.

Abstract: Methods and systems to compute likelihood measures of demodulated, complex-coordinate data points, to and dynamically scale the likelihood measures as a function of a channel statistic, and to decode the data points from the scaled likelihood measures. Likelihood measures may be computed relative to all points, or a subset of points of a reference constellation, such as a subset of one or more nearest constellation points. Likelihood measures may be scaled as a function of a channel frequency response variance amongst a plurality of carriers, such as carriers of an OFDM signal, and/or as a function of a channel impulse response variance.

Abstract: According to various embodiments, apparatus and methods disclosed herein include computing phase error of a received signal based on an estimate of a first component (e.g., in-phase component) of a transmitted signal and an analytic representation of the estimate of the first component of the transmitted signal. The analytic representation of the estimate of the first component of the transmitted signal may represent an estimate of a second component (e.g., quadrature phase component) of the transmitted signal. The analytic representation of the estimated first component may be computed using at least one of a Hilbert transform or Fourier transform on the estimated first component of the transmitted signal.

Abstract: According to various embodiments, apparatus and methods disclosed herein may be implemented in a digital communication (wired or wireless) receiver, and relate to minimizing noise in an estimated channel frequency response at the receiver for the purposes of channel equalization. The disclosed apparatus and methods may include determining a channel impulse response based on an estimated channel frequency response. The estimated channel frequency response, the channel impulse response, or both may include noise. An impulse response mask may be determined based on the channel impulse response, and further applied to the channel impulse response to obtain a noise-reduced channel impulse response, which may be Fourier transformed to obtain a noise-reduced channel frequency response.

Abstract: Methods and systems to resolve cyclic ambiguity of a scattered-pilot based channel impulse response as a function of transmission parameter signalling (TPS), such as in a single frequency network, including to zero-pad a first orientation of the channel impulse response to an interval of an effective symbol duration of the multi-carrier signal, compute a channel frequency response from the zero-padded first orientation of the channel impulse response, and correlate components of the channel frequency response corresponding to frequencies of TPS carriers with raw channel frequency response data of obtained from the TPS carriers. Frequency response components of multiple zero-padded orientations of the channel impulse response may be correlated with the raw TPS carrier data to identify an optimum orientation of the channel impulse response. Frequency response components of subsequent zero-padded orientations may be iteratively computed from components of preceding orientations.

Abstract: A method and system for OFDM symbol timing recovery is described. A symbol timing recovery module of an OFDM receiver is configured to determine an optimum trigger point for performing a discrete Fourier transform in a manner that minimizes inter-symbol interference.

Abstract: Methods and systems to identify a codeword associated with samples of a signal from spectral content of the samples, and to estimate a frequency offset from the spectral contents. The samples may correspond to a physical layer header of a data frame. Modulation may be removed from the samples in accordance with each of a plurality of modulation sequences, each sequence associated with a corresponding codeword. Power levels in spectral contents of the modulation-removed samples are examined to identify a peak power level indicative of a match between a modulation sequence and the samples. The corresponding codeword is identified as being associated with the header, and transmission parameters associated with the identified codeword are used to decode a corresponding frame. An estimated frequency offset may be determined from a frequency associated with the peak power level.

Abstract: According to various embodiments, devices and methods disclosed herein include performing, using a processor, a linear operation on a first plurality of channel frequency responses and a plurality of corresponding predictor coefficients to estimate a new channel frequency response. Each of the plurality of corresponding predictor coefficients may be updated based on an error value and a second plurality of channel frequency responses to obtain an updated predictor coefficient. The error value may be computed based on an estimated current channel frequency response and a predicted current channel frequency response. The new channel frequency response may be used to equalize a received modulated signal including a single-carrier modulated signal, e.g., a signal modulated using a vestigial sideband modulation scheme, or a quadrature amplitude modulation scheme.

Abstract: An embodiment of the present invention provides an apparatus, comprising a digital demodulator including an automatic gain control (AGC) circuit with a self-adapting target to provide optimum performance under all signal conditions.

Abstract: Methods and systems to determine channel frequency responses corresponding to multi-carrier signals, such as OFDM signals, including to filter or mask noise from channel frequency response estimates in a time domain.

Abstract: An embodiment of the present invention provides a method for digital television demodulation, comprising using adjacent-channel power dependent automatic gain control (AGC) for the digital television demodulation, wherein an AGC technique takes into account a total power as well as power of adjacent channels to control gain of a gain control amplifier.

Abstract: Disclosed is a receiver system, capable of receiving RF signals on television channels of multiple bandwidths. The receiver system includes a tuner, an analog IF filter, an ADC, a mixer module, one or more digital filters, an AGC module and a controller. The tuner converts an RF signal into an IF signal using a mixer frequency. The analog IF filter filters out a fixed band signal from the IF signal. The ADC module converts the fixed band signal into a digital signal, which is filtered by digital filters. The output of the digital filters is converted to a base band signal and the power level of the base band signal is controlled by the AGC module. The controller selects a mixer frequency from a group of mixer frequencies based on a function of power of the output of the AGC module by applying each mixer frequency to the tuner.

Abstract: Embodiments of a broadcast receiver and method for optimizing a scale factor in a log-likelihood ratio (LLR) mapper are generally described herein. In some embodiments, the broadcast receiver includes an LLR mapper to generate LLRs from demodulated data samples, a low-density parity-check (LDPC) decoder to generate decoded data from the LLRs, and an LLR optimizer to dynamically select a scale factor for the LLR mapper based on a number of iterations for convergence of the LDPC decoder. In some embodiments, the LLR optimizer iteratively revises the scale factor during receipt of broadcast signals until the number of iterations of the iterative decoder is either minimized for convergence or minimized for convergence failures.

Abstract: According to various embodiments, a method is disclosed that includes receiving an orthogonal frequency-division multiplexing (OFDM) modulated signal at a modulator; filtering the received modulated signal using a plurality of sets of filter coefficients with a linear predictor algorithm; and estimating a channel frequency response based on the filtering.

Abstract: Apparatuses, systems, and methods that employ conditional probabilities to calculate phase errors are disclosed. For a received signal, the embodiments may develop several phase error estimates relative to each point of a constellation, the number and location of points of the constellation depending on the modulation technique of the received signal. In addition to calculating the phase error estimates, the embodiments may also calculate weights, or probabilities, associated with each of the estimates. The embodiments may use the estimates and the weights to calculate a composite phase error estimate. The composite phase error estimate may be used to correct the received signal and eliminate or reduce the impact of the phase error.

Abstract: According to various embodiments, a method is disclosed that includes a method is disclosed that includes determining, by a receiver, a frequency offset in a signal comprising a set of orthogonal frequency division multiplexed (OFDM) symbols by determining a first difference in phase angles between a nth OFDM symbol and a nth+1 OFDM symbol on a common OFDM carrier and a first difference in phase angles between the nth+1 OFDM symbol and a nth+2 OFDM symbol on the common OFDM carrier and determining a second difference in phase angles between the first difference in phase angles between the nth OFDM symbol and the nth+1 OFDM system and the first difference in phase angles between the nth+1 OFDM symbol and the nth+2 OFDM symbol to identify the frequency offset, wherein n?{1, . . . , N}; and correcting, by the receiver, the signal using the determined frequency offset.

Abstract: Methods and systems to resolve cyclic ambiguity of a scattered-pilot based channel impulse response as a function of transmission parameter signalling (TPS), such as in a single frequency network, including to zero-pad a first orientation of the channel impulse response to an interval of an effective symbol duration of the multi-carrier signal, compute a channel frequency response from the zero-padded first orientation of the channel impulse response, and correlate components of the channel frequency response corresponding to frequencies of TPS carriers with raw channel frequency response data of obtained from the TPS carriers. Frequency response components of multiple zero-padded orientations of the channel impulse response may be correlated with the raw TPS carrier data to identify an optimum orientation of the channel impulse response. Frequency response components of subsequent zero-padded orientations may be iteratively computed from components of preceding orientations.

Abstract: Methods and systems to compute likelihood measures of demodulated, complex-coordinate data points, to and dynamically scale the likelihood measures as a function of a channel statistic, and to decode the data points from the scaled likelihood measures. Likelihood measures may be computed relative to all points, or a subset of points of a reference constellation, such as a subset of one or more nearest constellation points. Likelihood measures may be scaled as a function of a channel frequency response variance amongst a plurality of carriers, such as carriers of an OFDM signal, and/or as a function of a channel impulse response variance.

Abstract: A channel estimator for use in a DVB-T system is capable of high Doppler performance without incurring restrictive delay spread limitations, in a hardware efficient manner. A first channel impulse response is generated that has ambiguity due to under-sampling in the frequency domain. A filter is then used to filter scattered pilots to generate a mask that is capable of resolving the ambiguities. In at least one approach, a finite impulse response filter is used during the mask generation process to generate a snapshot of the channel frequency response in non-real time. In another approach, an infinite impulse response filter is used during the mask generation process to generate a channel frequency response in real time.