At+t Corp.

AT&T Intellectual Property I, LP

Lalitha Sankaranarayanan

Richard Henry Erving

Ranjan V Sonalkar

A communication device has an inner coder and an outer coder and transmits digital data over frequency channels. A method involves obtaining a characteristic of the frequency channels, and selecting performance parameters of the inner and outer coders for each channel based in part on the obtained characteristic of the channel. The performance parameter selecting step includes storing, for each of a plurality of combinations of inner and outer coder performance parameters, a corresponding transmission power requirement, and selecting a combination of inner and outer coder performance parameters by selecting a transmission power requirement, based on a multi-channel efficiency over respective data rates. Data is allocated to be transmitted to each channel.

Multi-frequency data transmission channel power allocation

In a digital data communication device, power is allocated among frequency channels by selecting an initial transmission power allocation and a corresponding data rate allocation for each channel. A first channel is identified in which a given transmission power decrement results in a data rate decrement that is proportionately smaller than corresponding data rate decrements of channels other than the first channel. The transmission power allocation of the first channel is reduced by the given transmission power decrement, and the transmission power allocation in at least one channel other than the first channel is increased by the given transmission power decrement amount.

A method of controlling a communication device that is operable to transmit digital data over a plurality of frequency channels. The method includes selecting an initial transmission power and a corresponding data rate for each channel. The method also includes identifying in a first channel a first ratio of a first decrement in transmission power to a first data rate decrement that is greater than a second ratio of a second decrement in transmission power to a second data rate decrement. Then, the initial transmission power allocation of the first channel is reduced by the first decrement. The method also includes reallocating the decremented initial transmission power of the first channel to one or more other channels.

An algorithm for computing an efficient, reduced complexity, windowed optimal linear time domain equalizer for a dispersive channel comprises the steps of determining a window of maximum energy in the impulse response of length equal to or less than a number of cyclic prefix samples associated with a received digital data signal, computing the corresponding inside and outside matrices, performing an inverse Cholesky decomposition of the inside matrix, creating a resultant matrix as the product of the outer and the upper and lower square root inner matrix, followed by Householder reduction and QL transformation to thereby compute the time domain equalizer as the linear transformation of the eigenvector corresponding to the smallest eigenvalue at the receiver. The smallest eigenvalue is determined using the aforementioned orthogonal transformations without determining all the eigenvalues efficiently but without the loss accuracy associated with iterative methods like the conventional power method. The algorithm may be most conveniently implemented, for example, in the form of a thirty-two bit digital signal processor at a data receiver.

Efficient reduced complexity windowed optimal time domain equalizer for discrete multitone-based DSL modems

A method of allocating bits to discrete frequencies in a discrete multitone modulator comprises the steps of allocating bits to frequencies on a per frequency basis such that the bits are successively allocated until a maximum power level for that frequency is exceeded. Then, a total power level for bits allocated to a plurality of transmit frequencies is calculated to see if a maximum permissible total power level is exceeded. If the maximum permissible total power level is not exceeded, then the process is complete. If the maximum total power level is exceeded, successive bits are removed until the total power level is no longer exceeded. In one bit removal method, bits are removed in order of the amount of power the bit would consume of the transmit power spectrum. The algorithm may be implemented in the combination of transmitter elements including tone ordering circuitry, gain scaling circuitry and the inverse discrete Fourier transform modulator of the discrete multitone data transmitter.

Growing community of inventors

Morris Plains, NJ, United States of America

Lalitha Sankaranarayanan