Abstract: The present disclosure provides timing recovery in optical systems in the presence of chromatic dispersion (CD), polarization mode dispersion (PMD), and polarization dependent loss (PDL) and to optimization of equalization settings based upon timing recovery moment strengths. A stable timing point may be determined in the presence of PMD and PDL impairments, even when the direct estimate of timing becomes unreliable. This determination may be performed entirely in the digital domain providing precise, predictable performance. Also, the present invention utilizes a monotonic relationship between the timing metric and CD setting error to provide directed search in setting the CD equalizer thereby reducing significantly the overall search effort in optimizing CD equalizer settings. This utilizes computations already performed by the transceiver for timing recovery function yielding a computational advantage over competing methods.

Abstract: The present disclosure relates to coherent optical receiver systems and methods for determining and correcting for optical angle and magnitude imbalance and for delay imbalance between quadrature paths. The present invention iteratively determines and corrects imbalance error and differential delay entirely in the digital domain (after an analog to digital conversion) in the presence of all the other impairments (polarization mode dispersion, chromatic dispersion, polarization gain imbalance, and polarization delay imbalance) using only the corrupted received signal during normal operation, i.e. without the use of training data. The present invention provides an effective adaptive scheme to drive impairments to zero, without using of any calibration of training, and may be applied during normal operation of the receiver via electrical circuitry or the like.

Abstract: The present disclosure provides timing recovery in optical systems in the presence of chromatic dispersion (CD), polarization mode dispersion (PMD), and polarization dependent loss (PDL) and to optimization of equalization settings based upon timing recovery moment strengths. A stable timing point may be determined in the presence of PMD and PDL impairments, even when the direct estimate of timing becomes unreliable. This determination may be performed entirely in the digital domain providing precise, predictable performance. Also, the present invention utilizes a monotonic relationship between the timing metric and CD setting error to provide directed search in setting the CD equalizer thereby reducing significantly the overall search effort in optimizing CD equalizer settings. This utilizes computations already performed by the transceiver for timing recovery function yielding a computational advantage over competing methods.

Abstract: The present disclosure relates to coherent optical receiver systems and methods for determining and correcting for optical angle and magnitude imbalance and for delay imbalance between quadrature paths. The present invention iteratively determines and corrects imbalance error and differential delay entirely in the digital domain (after an analog to digital conversion) in the presence of all the other impairments (polarization mode dispersion, chromatic dispersion, polarization gain imbalance, and polarization delay imbalance) using only the corrupted received signal during normal operation, i.e. without the use of training data. The present invention provides an effective adaptive scheme to drive impairments to zero, without using of any calibration of training, and may be applied during normal operation of the receiver via electrical circuitry or the like.

Abstract: A circuit and method is provided for reducing the effect of having potentially different sizes for an Inverse Discrete Fourier Transform (IDFT) at a transmitter and a Discrete Fourier Transform (DFT) at a receiver in a telecommunications system without requiring a change in the DFT's size. The method includes following steps. The first step includes determining whether the IDFT size is greater than, equal to, or less than the DFT size. The second step includes selecting a target impulse response length from a predefined set of impulse response lengths in accordance with a result the previous step. The third step includes training an equalizer at the receiver to the target impulse response length. The circuit comprises hardware and software for implementing the method.

Abstract: Method and system for reducing power dissipation for data transmission from a transmitter to a receiver in a digital subscriber line (DSL) system when a rate of available data is below a first predetermined data rate for a predetermined length of time. The method includes the following steps. Normal parameters for a normal rate of said data transmission are stored. New parameters for a reduced rate of the data transmission are calculated. Data is transmitted at the reduced rate of the data transmission, wherein the reduced rate requires less power for data transmission. The normal rate of the data transmission is resumed using the normal parameters when the rate of available data rises above a second predetermined data rate.

Abstract: Signal magnitude comparison apparatus and methods are disclosed. A first input circuit receives a differential input signal and provides a first output signal based on a magnitude of the differential input signal. A second input circuit is operatively coupled to the first input circuit and is operable to receive a second input signal, which may also be a differential signal, and to provide a second output signal based on a magnitude of the second input signal. The operative coupling between the first and second input circuits results in the first output signal and the second output signal forming a differential output signal that is indicative of a difference between the magnitude of the first differential input signal and the magnitude of the second input signal.

Abstract: Transporting an asynchronous transfer mode (ATM) stream through a bonding group involves properly splitting the stream into sub-streams to fit into individual member bearer's bandwidth at the transmit end, and properly merging the sub-streams to reconstruct the stream at the receive end. At the receive end, the cells can be put together in the proper sequence in a process of cell aggregation based on attached sequence numbers. Once the stream is re-constructed, the attached sequence numbers are replaced by the original field contents of the ATM headers. Methods of cell aggregation are described that assist the bonding scheme in working efficiently.

Abstract: In a coding system for asymmetric digital subscriber line (ADSL) communications, a method of encoding a sequence of information bits is provided comprising the steps of dividing the information bits into encoding bits and parallel bits; encoding the encoding bits to produce encoded bits; mapping the encoded bits and the parallel bits into first and second pulse amplitude modulation (PAM) signals; and generating a quadrature amplitude modulation (QAM) signal from these first and second PAM signals. This method overcomes the decoder complexity that would otherwise be required due to the large QAM constellations involved for ADSL communications.

Abstract: The present invention provides a method and apparatus for the efficient implementation of a totally general convolutional interleaver in a discrete multi-tone (DMT)-based digital subscriber line (xDSL) system, such as a modem or the like, that uses forward error correction (FEC) and convolutional interleaving to combat the effects of impulse noise and the like. More specifically, the present invention provides a method and apparatus for implementing a general convolutional interleaver, with no constraints, in an efficient manner, using (D?1)*(I?1)/2 memory locations for the interleaved data in all cases.

Abstract: Method and apparatus for improving data transmission in a digital subscriber line (DSL) system. The transmitter determines whether a spectrum of an inverse Fourier transform (IFT) is periodic with respect to a clock of a predetermined standard-size IFT and communicates this information to the receiver. Based on this information, the receiver adapts the FT if desired. In effect, the receiver adapts its signal processing algorithms to process the received signal in accordance with the transmitter's IFT size. In this manner, transmission performance is improved.

Abstract: The present invention provides procedures for computing Forward Error Correction (FEC) parameters given a set of constraints on maximum interleaver memory, maximum interleaver depth, maximum codeword size, maximum number of check bytes, maximum number of FEC codewords per Discrete Multi-Tone (DMT) symbol, and minimum number of DMT symbols that the FEC must correct, as well as any constraints imposed by the interleaver. These procedures are implemented on a computational engine in a modem, enabling it to achieve optimal performance in all cases. In addition these procedures can be applied as part of any bit loading algorithm to determine the optimal FEC parameters, taking into account the Signal-to-Noise Ratio (SNR) profile, the FEC coding gain, the constraints of the framer, and any application specific constraints.

Abstract: A voice and data communication system whereby a line card digitizes and packetizes voice communications signals upon the failure of Customer Premises Equipment (CPE). The system comprises a line card for coupling the CPE with a network. Furthermore, the invention provides a system that can direct the voice signals to either or both of a voice network and a data network.

Abstract: Transporting an asynchronous transfer mode (ATM) stream through a bonding group involves properly splitting the stream into sub-streams to fit into individual member bearer's bandwidth at the transmit end, and properly merging the sub-streams to reconstruct the stream at the receive end. At the receive end, the cells can be put together in the proper sequence in a process of cell aggregation based on attached sequence numbers. Once the stream is re-constructed, the attached sequence numbers are replaced by the original field contents of the ATM headers. Methods of cell aggregation are described that assist the bonding scheme in working efficiently.

Abstract: A circuit and method is provided for reducing the effect of having potentially different sizes for an Inverse Discrete Fourier Transform (IDFT) at a transmitter and a Discrete Fourier Transform (DFT) at a receiver in a telecommunications system without requiring a change in the DFT's size. The method includes following steps. The first step includes determining whether the IDFT size is greater than, equal to, or less than the DFT size. The second step includes selecting a target impulse response length from a predefined set of impulse response lengths in accordance with a result the previous step. The third step includes training an equalizer at the receiver to the target impulse response length. The circuit comprises hardware and software for implementing the method.

Abstract: Method and system for reducing power dissipation for data transmission from a transmitter to a receiver in a digital subscriber line (DSL) system when a rate of available data is below a first predetermined data rate for a predetermined length of time. The method includes the following steps. Normal parameters for a normal rate of said data transmission are stored. New parameters for a reduced rate of the data transmission are calculated. Data is transmitted at the reduced rate of the data transmission, wherein the reduced rate requires less power for data transmission. The normal rate of the data transmission is resumed using the normal parameters when the rate of available data rises above a second predetermined data rate.

Abstract: Method and apparatus for improving data transmission in a digital subscriber line (DSL) system. The transmitter determines whether a spectrum of an inverse Fourier transform (IFT) is periodic with respect to a clock of a predetermined standard-size IFT and communicates this information to the receiver. Based on this information, the receiver adapts the FT if desired. In effect, the receiver adapts its signal processing algorithms to process the received signal in accordance with the transmitter's IFT size. In this manner, transmission performance is improved.

Abstract: In a coding system for asymmetric digital subscriber line (ADSL) communications, a method of encoding a sequence of information bits is provided comprising the steps of dividing the information bits into encoding bits and parallel bits; encoding the encoding bits to produce encoded bits; mapping the encoded bits and the parallel bits into first and second pulse amplitude modulation (PAM) signals; and generating a quadrature amplitude modulation (QAM) signal from these first and second PAM signals. This method overcomes the decoder complexity that would otherwise be required due to the large QAM constellations involved for ADSL communications.

Abstract: Line interface for coupling a twisted pair telephone line with a communications network. The line interface includes a broadband analog front end for coupling the twisted pair telephone line with the line interface, and a programmable filter for filtering frequency bands to separate transmission channels, the transmission channels located in the communications network, wherein the frequency bands are determined by the programmable filter. In this manner, various services can be provided over the twisted pair telephone line.

Abstract: An integrated line card for providing an analog termination for both POTS and xDSL signals that present the appropriate impedances at xDSL frequencies for the xDSL signals and appropriate impedances at POTS frequencies for POTS signals. The line card comprises a front end for coupling combined POTS and xDSL transceiver circuits to a telephone line at a single termination and an impedance generator responsive to the frequency range of the POTS and the xDSL circuits for generating the appropriate impedances on the line at xDSL frequencies for xDSL signals and the appropriate impedances at POTS frequencies for POTS signals, such that the signals are coupled to the card without the use of a splitter. Preferably, the xDSL circuits and the POTS circuits share a common driver for driving signals onto the loop. An advantage of this arrangement is that the two circuits may be designed together thus ensuring out-of-band noise generated by either source does not interfere with the other.