Abstract: A method for slicing a received signal includes the steps of receiving a signal representing one of a constellation of ideal data points in a planar signal space, the received signal being at a point in the signal space, and assigning to the received signal a decision point having a predetermined magnitude and an angle representing a corresponding ideal signal point A slicer includes a source for receiving a signal representing one of a constellation of ideal data points in a planar signal space, the received signal being at a point in the signal space, and circuitry, coupled to the signal source, for generating a signal representing a decision point having a predetermined magnitude and an angle representing an ideal signal point corresponding to the signal point .

Abstract: A receiver includes a digital phase locked loop (PLL) for performing carrier recovery. The digital PLL further includes a phase error estimator driven by hard decisions and an integrator, which accumulates a phase error signal provided by the phase error estimator. To reduce the acquisition time, the digital PLL is run in an open-loop mode during which an estimate of the carrier frequency offset is determined as a function of the phase error signal. After the estimate of the carrier frequency offset is determined, the integrator is pre-loaded with the determined estimate and the digital PLL is run in a closed-loop mode.

Abstract: A Discrete Multitone (DMT) modulator modulates symbols with subcarriers for providing DMT symbols, wherein the subcarriers are divided into a number of subcarrier subsets such that adjacent DMT symbols formed from different subcarrier subsets

Abstract: The disclosed embodiments relate to reducing adjacent channel interference in an OFDM receiver. An error metric is monitored and the carrier frequency of the desired channel is slowly adjusted in response to the error metric. In this manner, the received OFDM signal, including the desired signal corrupted by the adjacent interfering channel, may be shifted until the zero crossings of the adjacent channel line up with the FFT bins. A multi-tap equalizer may then be used to remove the inter-bin interference that results from the frequency offset in the desired channel.

Abstract: A communication system comprising a transmitter that is adapted to transmit a data signal that is broken into a plurality of time slots. The transmitter inserts communication data into a subset of the plurality of time slots and to create null data representative of information about the communication system. The null data is inserted into a subset of the plurality of time slots not occupied by communication data. A communication system comprising a receiver that receives a data signal that is broken into a plurality of time slots. The receiver identifies correlation peaks in the data signal that correspond to a subset of the plurality of time slots, the subset of the plurality of time slots including null data representative of information about the communication system. The receiver may associate logical values with the correlation peaks and decode the logical values to obtain the information about the communication system.

Abstract: The disclosed embodiments relate to a system for generating forward error correction (FEC) packets. The system includes a first FEC encoder that receives data and encodes first FEC data with the data to form FEC encoded data. Also included in the system is a second FEC encoder that encodes the FEC encoded data to produce second FEC data. An FEC packet formatter formats the second FEC data into an FEC packet.

Abstract: A method for initializing an equalizer in an Orthogonal Frequency Division Multiplexing (“OFDM”) receiver includes generating a desired equalizer tap setting based on an adaptive algorithm. An initial setting for the adaptive algorithm corresponds to an approximate inverse of a channel estimate, and the desired tap setting corresponds to an ideal inverse of the channel estimate. In an alternative embodiment, a method includes generating a channel estimate, generating an equalizer tap setting based on a complex conjugate of the estimate and a quantized magnitude squared of the estimate, and repeatedly generating subsequent tap settings until an error falls within limits.

Abstract: A receiver (10) achieves more reliable detection of signals transmitted by Direct Sequence Spread Spectrum Transmission by correlating received signals with a separate of N symbol patterns via N detector stages (181-18N). A maximum peak power detecting mechanism (241-24N, 261-26N and 28) detects which of the N correlated symbol patterns has a maximum peak power, as well as the identity of each of the N patterns actually received and an index of the peak power in each symbol. A computing mechanism (30, 32 and 34) computes a running power average of the received signals, while a ratio computing stage (36) computes the ratio of the largest peak power of the N correlated symbol patterns to the running power average. A comparator stage (38 and 40) compares the ratio to a threshold value to determine a first symbol in the received signals.

Abstract: An Orthogonal Frequency Division Multiplexing (OFDM) receiver that compensates for FFT window drift by extracting a training symbol from a fast Fourier transformed OFDM signal, and processing the extracted training symbol to derive an FFT window adjustment factor and an associated equalizer tap initialization value. The OFDM receiver controls the position of an FFT window and the initialization of equalizer taps using the FFT adjustment factor and equalizer tap initialization value. The OFDM receiver preferably filters the fast Fourier transformed OFDM signal to remove additive channel noise and increase the likelihood of reliable equalizer tap initialization in a low SNR environment.

Abstract: An Orthogonal Frequency Division Multiplexing (OFDM) receiver detects and corrects sampling offsets in the time domain. The OFDM receiver oversamples a training sequence or symbol in a received OFDM signal, correlates the oversampled training sequence with a stored copy of a truncated version of the training sequence, locates a correlation peak, and derives a sampling offset by calculating a difference in magnitude of correlation samples in the vicinity of the correlation peak.

Abstract: An Orthogonal Frequency Division Multiplexing (OFDM) receiver that detects and corrects a carrier frequency offset of a received signal is provided. The OFDM receiver samples an incoming signal in the time domain and correlates the samples with a stored version of a training or reference symbol to generate a correlation sequence. A correlation peak is detected in the correlation sequence and the index of the correlation peak is set as a reference point. The OFDM receiver acquires a sample of the incoming signal that is a predetermined distance from the reference point. Next, the phase difference between the acquired sample and the local oscillator is computed. Afterwards, the frequency of the local oscillator is adjusted to reduce the computed phase difference. The acquired sample has a known phase that is equal to the phase of the local oscillator in the absence of a carrier frequency offset.

Abstract: The disclosed embodiments relate to reducing adjacent channel interference in an OFDM receiver. An error metric is monitored and the carrier frequency of the desired channel is slowly adjusted in response to the error metric. In this manner, the received OFDM signal, including the desired signal corrupted by the adjacent interfering channel, may be shifted until the zero crossings of the adjacent channel line up with the FFT bins. A multi-tap equalizer may then be used to remove the inter-bin interference that results from the frequency offset in the desired channel.

Abstract: An Orthogonal Frequency Division Multiplexing (OFDM) receiver that compensates for FFT window drift by extracting pilots from a fast Fourier transformed and equalized OFDM signal, and processing the extracted pilots to derive an FFT window adjustment factor and an associated equalizer tap adjustment value. The OFDM receiver simultaneously controls the position of an FFT window and the phase of equalizer taps using the derived FFT adjustment factor and equalizer tap adjustment value.

Abstract: A telephone system connects to a plain old telephone service (POTS) line and includes a modem connected to the POTS line. A telephone transceiver and a data device are coupled to the modem to provide a simultaneous two-way data and voice exchange over the POTS line by detecting data for transfer and allocating bandwidth between voice and data signals to accommodate the exchange.

Abstract: A receiver (10) achieves more reliable detection of signals transmitted by Direct Sequence Spread Spectrum Transmission by correlating received signals with a separate of N symbol patterns via N detector stages (181-18N). A maximum peak power detecting mechanism (241-24N, 261-26N and 28) detects which of the N correlated symbol patterns has a maximum peak power, as well as the identity of each of the N patterns actually received and an index of the peak power in each symbol. A computing mechanism (30, 32 and 34) computes a running power average of the received signals, while a ratio computing stage (26) computes the ratio of the largest peak power of the N correlated symbol patterns to the running power average. A comparator stage (38 and 40) compares the ratio to a threshold value to determine a first symbol in the received pattern.

Abstract: An OFDM (orthogonal frequency division multiplexing) receiver that detects and corrects a sampling frequency offset of a sampled signal. The OFDM receiver samples an incoming signal in the time domain, multiplies the sampled data by a window function to widen the main lobe of each of the predetermined subcarriers' frequency domain spectrum, takes an FFT (fast Fourier transform) of the sampled signal to analyze the frequency domain samples of each predetermined subcarrier, detects a difference in magnitude of the frequency domain samples for each predetermined subcarrier, and generates a sampling frequency error based on the detected changes in magnitude.

Abstract: A wireless telephone system comprises a base transceiver having a base receiver and a plurality of wireless handsets. Each handset comprises a handset transceiver for establishing a DSSS link over a shared channel with the base unit via the base transceiver. Each receiver the base transceiver and the handset transceivers receives a spread-spectrum signal representing symbol data from a transmitter of the system, where each such receiver comprises a derotator that derotates the spread-spectrum signal in accordance with a counter-rotating signal to provide a derotated signal; a correlator for receiving the derotated signal and for providing output symbol data based on the derotated signal; a carrier tracking loop (CTL) phase error estimator for receiving the output symbol data and for generating a CTL phase error signal based upon the rotation of the spread-spectrum signal; and a CTL for generating the counter-rotating signal based on the CTL phase error signal.

Abstract: A method for initializing an equalizer in an Orthogonal Frequency Division Multiplexing (“OFDM”) receiver includes generating a desired equalizer tap setting based on an adaptive algorithm. An initial setting for the adaptive algorithm corresponds to an approximate inverse of a channel estimate, and the desired tap setting corresponds to an ideal inverse of the channel estimate. In an alternative embodiment, a method includes generating a channel estimate, generating an equalizer tap setting based on a complex conjugate of the estimate and a quantized magnitude squared of the estimate, and repeatedly generating subsequent tap settings until an error falls within limits.

Abstract: Method and Apparatus for Selective Equalizer Tap Initialization in an OFDM System A method for initializing an equalizer in an Orthogonal Frequency Division Multiplexing (“OFDM”) receiver includes inhibiting, based at least in part on (a) an equalizer tap being less than a first limit and (b) a time between OFDM signals being less than a second limit, an initialization of the tap. In an alternative embodiment, a method includes initializing equalizer taps upon startup, re-initializing the taps upon a passage of a predetermined time between OFDM signals, and selectively re-initializing at least one tap upon divergence of the tap. In another alternative embodiment, an apparatus includes an equalizer and a tap initialization controller coupled thereto. The tap initialization controller is configured to inhibit, based at least in part on (a) a tap being less than a first limit and (b) a time between OFDM signals being less than a second limit, an initialization of the tap.