Abstract: A system and method for carrier recovery independent of a pilot signal uses the frequency and phase information in the upper and lower band edges of a signal to generate a signal for correcting the frequency and phase of the local oscillator. A particular combination of raised-root cosine filters, low-pass filters, multipliers, and adders effectively uses the tails of a received signal in the frequency domain to correct phase errors.

Abstract: A receiver includes an equalizer and a decoder which decodes data from a signal. The signal is based upon an output of the equalizer. The receiver also includes an encoder, which re-encodes the decoded data, and an error generator, which generates an error vector based upon the signal and the encoded data and which weights the error vector according to a reliability that the decoder accurately decoded the data from the signal. A controller controls the equalizer in response to the weighted error vector.

Abstract: A code vector comprising 2N data elements is generated in response to N input data elements. The first N data elements of the code vector represent a replica of the N input data elements, and the second N data elements of the code vector comprise N parity data elements. The combination of the first N data elements and the second N data elements forms a Kerdock code vector. The Kerdock code vector is decoded to recover the N input data elements by selecting one of a possible 2N Kerdock code vectors as a best estimate of the Kerdock code vector. The selected Kerdock vector comprises 2N data elements, and only the first N data elements of the selected Kerdock code vector are used as the N input data elements.

Abstract: An encoder-modulator for coupling a digital baseband television signal to a VSB digital television receiver that includes filters, equalization circuitry, and forward error correction circuitry for correcting signal impairments that are below a given threshold. The encoder-modulator processes the baseband signal for low power transmission on an RF channel with less-than-nominal bandpass characteristics. A coaxial cable or other low noise communication link directly connects the RF signal to the RF input of the television receiver. Any errors or signal impairments in the transmitted signal that are below the predetermined threshold are corrected by the filters and equalization circuitry built into the VSB digital television receiver.

Abstract: A code vector comprising 2N data elements is generated in response to N input data elements. The first N data elements of the code vector represent a replica of the N input data elements, and the second N data elements of the code vector comprise N parity data elements. The combination of the first N data elements and the second N data elements forms a Kerdock code vector. The Kerdock code vector is decoded to recover the N input data elements by selecting one of a possible 2N Kerdock code vectors as a best estimate of the Kerdock code vector. The selected Kerdock vector comprises 2N data elements, and only the first N data elements of the selected Kerdock code vector are used as the N input data elements.

Abstract: An equalizer comprises: an FIR; a trellis decoder coupled to the FIR; a mapper coupled to the trellis decoder; and a decision feedback equalizer coupled to the mapper. The decision feedback equalizer receives the mapped and scaled output of the trellis decoder as input and an error signal is generated by subtracting an output of the decision feedback equalizer from the input to the trellis decoder.

Abstract: An adaptive equalizer comprises a trellis decoder; a mapper coupled to the output of the trellis decoder; and a decision feedback equalizer coupled to the output of the mapper. Each of the taps receives as input via the mapper output from a different one of the stages of the trellis decoder.

Abstract: An adaptive equalizer comprises a decision device; a decision feedback equalizer coupled to the decision device; an FIR filter coupled to the decision device; and a trellis decoder coupled to the decision device, adapted to provide a reliability output and a decoded output. An error signal is generated by subtracting an output of the decision feedback equalizer from an output of the decision device, the error signal being used to update coefficients of the taps of the FIR filter and the decision feedback equalizer. A magnitude of the change to the coefficients is selected based at least in part the reliability output of the trellis decoder.

Abstract: An iterative decoding system has a first decoder that decodes coded data and a first weighting circuit that reduces channel effects in the coded data based upon a reliability that the first decoder accurately decoded the encoded data. The first weighting circuit produces improved coded data. A second decoder of the iterative decoding system decodes the improved coded data, and a second weighting circuit additionally reduces channel effects in the improved coded data based upon a reliability that the second decoder accurately decoded the improved encoded data.

Abstract: A receiver receives a signal containing data distributed in both time and frequency. The receiver includes a vector transform arranged to perform a transform on the received signal using a plurality of receiver transform vectors. The receiver transform vectors are based upon a corresponding plurality of transmitter vectors modified in accordance with channel effects so that the data can be recovered by the vector transform even in the presence of strong ghosts.

Abstract: A receiver receives a signal containing data distributed in both time and frequency. The receiver includes a vector transform arranged to perform a transform on the received signal using a plurality of receiver transform vectors. The receiver transform vectors are based upon a corresponding plurality of transmitter vectors modified in accordance with channel effects so that the data can be recovered by the vector transform even in the presence of strong ghosts.

Abstract: A digital equalizer comprises a matched filter that, in conjunction with an FIR filter, assures a single peak with substantially greater energy than other peaks caused by ghosts, thereby permitting synchronization even with multiple, arbitrarily strong ghosts caused by strong multipathing, multiple transmitters, or both.

Abstract: Circuits for removing clock related artifacts in an offset QAM generated VSB signal includes a transmitter arrangement and a receiver arrangement. In the transmitter, a detector detects the artifacts and a correlator determines whether the artifacts repeat over two symbols or over four symbols. A signal indicative of the artifacts is used to control processing circuits for adjusting the ratios and levels of the I and Q signal components of the QAM signal for substantially eliminating the artifacts. In the receiver, the received VSB signal is divided into four parallel signals. Each parallel signal is processed to develop an average symbol level that is subtracted before the parallel signals are recombined. The four symbol repeat rate artifacts reflect a DC offset of the VSB signal symbols, which are both positive-going and negative-going and which therefore average to zero for random signals. Averaging is done over N symbols where N is a power of 2.

Abstract: Normally ordered robust VSB data are reordered in accordance with a first interleave to produce reordered robust VSB data, The reordered robust VSB data and ATSC data are reordered in accordance with a second interleave to produce normally ordered robust VSB data and reordered ATSC data. The normally ordered robust VSB data and reordered ATSC data are time multiplexed for transmission to a receiver. The receiver discards the reordered ATSC data or the normally ordered robust VSB data depending upon receiver type or user selection. A robust VSB receiver is able to process the normally ordered robust VSB data upstream of an outer decoder without an interleave thereby avoiding the delay associated with an interleave.

Abstract: Enhanced slice prediction is based upon ATSC VSB data when robust 8 VSB data are not available and is based upon robust 8 JSB data when robust 8 VSB data are available.

Abstract: A receiver receives a received signal containing a pilot up chirp and a pilot down chirp. The pilot up chirp has a frequency which increases from a time reference zero to a time reference tN, and the pilot down chirp has a frequency which decreases from the time reference tN to a time reference 2ttN. A sampler of the receiver is arranged to sample the received signal. A detector is arranged to correlate the received signal samples with a reference up chirp and a reference down chirp. The reference up chirp has a varying frequency substantially matching the pilot up chirp, and the reference down chirp has a varying frequency substantially matching the pilot down chirp. A sample adjuster is arranged to synchronize the received signal samples in response to the detector.

Abstract: A receiver receives a signal which contains a code vector. The code vector is a member of a predetermined set of code vectors. The code vectors may be Kerdock code vectors. The receiver produces a transform, such as a Walsh transform, of the received signal. The transform contains a coefficient corresponding to each of at least some of the code vectors of the predetermined set of code vectors. The receiver determines data elements transmitted as the received code vector based upon the magnitudes of the coefficients of the transform. When plural code vectors are transmitted, the receiver determines data elements transmitted as a first code vector based upon the magnitudes of the coefficients of the transform, subtracts the first code vector from the received signal, produces a new transform of the subtraction results, and determines data elements transmitted as another code vector based upon the magnitudes of the coefficients of the new transform, and so on.

Abstract: In a synchronous code division multiple access (SCDMA) system, a set of substantially orthogonal code words is selected such that each code word in the set of substantially orthogonal code words is minimally correlated with a channel characteristic such as noise. When a station transmits a data signal, it multiplies the data signal by its assigned code word in order to produce a spread data signal. The spread data signal is transmitted over the channel of the SCDMA system.

Abstract: A communication system has a plurality of stations which communicate data in a data frame having a plurality of slots, wherein the plurality of slots are new message minislots NMS, expansion minislots EMS, and data slots DS. A master station determines a range parameter R which is based upon a number of slave stations transmitting reservation requests in a data frame. The master station also determines a parameter MAP according to a number of reservation requests in a queue waiting to be processed by the master station. The parameter MAP defines the new message minislots, the expansion minislots, and the data slots in an upstream data frame. The master station transmits the range parameter R and the parameter MAP to a plurality of slave stations. Each slave station independently determines a random transmission parameter RN.

Abstract: A television signal transmission signal comprises a suppressed carrier, VSB signal having respective Nyquist slopes at the lower and upper edges of a 6 MHz television channel, the center frequency of the Nyquist slope at the lower edge of the channel being substantially coincident with the frequency of the suppressed carrier, and a pilot signal in quadrature relation with the suppressed carrier. The suppressed carrier is modulated by an N-level digitally encoded signal having a sample rate fs substantially equal to three times the NTSC color subcarrier frequency, with the frequency of the color subcarrier being less than the co-channel NTSC picture carrier by an amount equal to about fs/12. The received signal is demodulated by a synchronous detector in response to the received pilot signal and interfering NTSC beat components are attenuated by a linear filter having notches at fs/12, 5fs/12 and fs/2.