Abstract: A method of communicating across a channel includes receiving information having a known bandwidth and a known spectrum. The information is preferably in the form of a multicarrier modulated signal, e.g., a DMT signal. In one aspect, this information is received at a receiver having a reduced channel bandwidth. An aliasing spectrum can be calculated based on the known spectrum and the frequency difference between the known bandwidth and the reduced-channel bandwidth. The received information can then be modified based upon the aliasing function to compensate for alias distortion. For example, the received information can be modified by modifying the noise component or signal-to-noise ratio of the received information.

Abstract: The methodology accomplishes adaptive hybrid selection during ADSL modem training. The adaptive hybrid selection method maximizes performance for ADSL modems in the presence of various impairments on the line by optimally selecting the appropriate hybrid based on line conditions. Specifically, the adaptive hybrid selection method is based on a measure directly coupled to the channel capacity.

Abstract: Time domain equalizer determination for discrete multitone systems by tone error minimization from a starting point of a single-tone equalizer.

Abstract: Disclosed are methods of selecting a multi-dimensional signal constellation in relation to impairments in a communication system having a data frame consisting of a fixed number of symbols. The methods make use of impairments detected from a Digital Impairment Learning sequence (DIL) and channel impairments, such as POE and SNR. Signal points are individually assigned to each symbol in a data frame in relation to that symbol's particular digital impairments and a pre-selected minimum performance level and maximum power constraints.

Abstract: A method for deriving coefficients for a time domain equalizer function (24) as implemented by a digital signal processor (35) in a DSL modem (20) is disclosed. A transmitting modem (10), such as at a central office, issues a pseudo-random training sequence that is received by the receiving modem (20). Correlation matrices are derived by the digital signal processor (35), from which sets of eigenvalues and eigenvectors are derived. A flatness constraint on the frequency response of the time domain equalizer is established, and included with a flatness scaling factor (?) into a minimization cost function. One or more values of the flatness scaling factor (?), preferably between minimum and maximum eigenvalues, are evaluated in the cost function, to derive the optimum filter for the time-domain equalizer. The flatness constraint ensures that the time-domain equalizer is not subject to near null conditions and large variations in its frequency response.

Abstract: Time domain equalizer determination for discrete multitone systems by tone error minimization from a starting point of a single-tone equalizer.

Abstract: The methodology accomplishes adaptive hybrid selection during ADSL modem training. The adaptive hybrid selection method maximizes performance for ADSL modems in the presence of various impairments on the line by optimally selecting the appropriate hybrid based on line conditions. Specifically, the adaptive hybrid selection method is based on a measure directly coupled to the channel capacity.

Abstract: A method for dynamically switching hybrids during modem initialization to maximize channel capacity and performance includes the steps of evaluating each hybrid in the modem according to a cost function dependent on the quiet receive noise floor and the transmit signal echo, and then selecting the hybrid that results in the minimum value for the cost function. By performing these steps, the best available hybrid is selected in order to maximize channel capacity and hence maximize modem performance.

Abstract: A dual path equalization structure is used to equalize DMT systems operating over channels in which different impairments dominate the performance of different parts of the channel. Two TEQ/DFT structures are used to process the received signal, each optimized for a different part of the channel. The outputs of the two paths are combined with appropriate frequency-domain equalization to achieve an overall equalization architecture which is better optimized for the whole channel.

Abstract: A method for deriving coefficients for a time domain equalizer function (24) as implemented by a digital signal processor (35) in a DSL modem (20) is disclosed. A transmitting modem (10), such as at a central office, issues a pseudo-random training sequence that is received by the receiving modem (20). Correlation matrices are derived by the digital signal processor (35), from which sets of eigenvalues and eigenvectors are derived. A flatness constraint on the frequency response of the time domain equalizer is established, and included with a flatness scaling factor (&lgr;) into a minimization cost function. One or more values of the flatness scaling factor (&lgr;), preferably between minimum and maximum eigenvalues, are evaluated in the cost function, to derive the optimum filter for the time-domain equalizer. The flatness constraint ensures that the time-domain equalizer is not subject to near null conditions and large variations in its frequency response.

Abstract: A method of a communicating across a channel includes receiving information having a known bandwidth and a known spectrum. The information is preferably in the form of a multicarrier modulated signal, e.g., a DMT signal. In one aspect, this information is received at a receiver having a reduced channel bandwidth. An aliasing spectrum can be calculated based on the known spectrum and the frequency difference between the known bandwidth and the reduced-channel bandwidth. The received information can then be modified based upon the aliasing function to compensate for alias distortion. For example, the received information can be modified by modifying the noise component or signal-to-noise ratio of the received information.

Abstract: A client-side modem (20) having capability of improved data rate upstream communications via a codec (2) in a central office (CO) to an Internet service provider (ISP) (10) is disclosed. The disclosed modem (20) includes a digital signal processor (DSP) (14) that, for upstream communications, performs a bit mapping function (22) upon the digital data so that the digital words are mapped to slicing levels of analog-to-digital conversion circuitry (A/D) (6) in the central office codec (2); in addition, bit mapping function (22) preferably maps the digital signal into symbols having fewer bits each than the maximum defined by the number of slicing levels of the A/D (6). A pre-equalize filter function (26) applies an approximate inverse channel response filter (as measured during the training process) to the bit mapped digital data, to maximize the transmitted data rage over the dispersive analog subscriber loop (ASL), with consideration for an average transmit power maximum specification.

Abstract: Disclosed are methods of selecting a multi-dimensional signal constellation in relation to impairments in a communication system having a data frame consisting of a fixed number of symbols. The methods make use of impairments detected from a Digital Impairment Learning sequence (DIL) and channel impairments, such as POE and SNR. Signal points are individually assigned to each symbol in a data frame in relation to that symbol's particular digital impairments and a pre-selected minimum performance level and maximum power constraints.