US 6,072,779 A · Adaptive allocation for variable bandwidth multicarrier communication

Abstract

Data is distributed among the channels of an asymmetric data subscriber loop (ADSL) communications system in accordance with an adaptive algorithm which from time to time measures the signal to noise ratio of the various channels and finds a margin for each channel dependent on achievement (where possible) of a given bit error rate and a desired data transmission rate. The margin distribution is achieved by augmenting the constellation signal to noise ratio to enhance computational efficiency and allow redetermination of bit allocation tables during transmission as necessary. Pairs of bit allocation tables are maintained at the transmitter and receiver and one table of each pair at the transmitter and receiver is updated while the other pair is in use for controlling communication.

Claims24

Dependent claims

In a multicarrier modulation system having a plurality of channels for transmitting data at varying rates from a transmitter to a receiver dependent on the signal to noise ratio of the respective channels, the improvement comprising:

A. means for allocating data to respective ones of said channels in accordance with an initial signal to noise ratio for the corresponding channel,
B. means for repetitively calculating trial noise margins across a set of constellation signal to noise ratios used in assigning data to said channels, and
C. means for repetitively combining said trial noise margins with the said constellation signal to noise ratios to form modified constellation signal to noise ratios for use in reallocating said data to said channels.

A. means for allocating data to respective ones of said channels in accordance with initial signal to noise ratios measured for the corresponding channels,
B. means for calculating a trial noise margin across across a set of constellation signal to noise ratios used in assigning data to said channels, said margin being calculated as a function of said initial signal to noise ratio and the difference between the amount of data transmissible over said channels with said signal to noise ratios and the amount of data desired to be transmitted,
C. means for augmenting the constellation signal to noise ratios by the trial noise margin to thereby define augmented signal to noise ratios for use in defining a revised estimate of the amount of data transmissible over said channels, and
D. means for repetitively defining successive trial noise margins as a function of the augmented signal to noise ratios and the difference between the amount of data transmissible over said channels with said augmented signal to noise ratios and the amount of data desired to be transmitted until an exit condition is reached.

1 more element

A method of allocating data to respective ones of channels in a multicarrier modulation system having a plurality of channels for transmitting data at varying rates from a transmitter to a receiver, comprising the steps of:

A. allocating data to respective ones of said channels in accordance with measured signal to noise ratio for the corresponding channel,
B. repetitively calculating trial noise margins across a set of constellation signal to noise ratios used in assigning data to said channels, and
C. repetitively combining said trial noise margins with the said constellation signal to noise ratios of said channels to form modified constellation signal to noise ratios for use in reallocating said data to said channels.

Dependencies are inferred from the claim text.

Adaptive allocation for variable bandwidth multicarrier communication

Life of this patent

Adaptive allocation for variable bandwidth multicarrier communication

Life of this patent

Abstract

Claims24