Nonlinear echo canceller for data signals using a non-redundant distributed lookup-table architecture
AssigneeAT&T Bell Laboratories
InventorOscar E. Agazzi
Life of this patent
Estimating the term…
Abstract
An echo canceler and associated method for canceling errors encountered in data communications which features reduced complexity and enhanced convergence properties arising from simplification of a table-lookup architecture corresponding to elimination of terms in a Volterra expansion. By adaptively adjusting the values stored in the reduced complexity lookup-tables, the system converges rapidly to the desired values.
Claims16
An echo canceler for generating an echo replica in response to a sequence of transmitted symbols, each symbol represented as an M-bit word, M<1, the echo canceler comprising:
- a series of echo canceler stages, each stage including at least one look-up table;
- means for applying each bit of each word to a successive pair of the echo canceler stages and means for addressing locations in each look-up table in each stage using a first subset of bits applied to that stage;
- means for multiplying the output of each look-up table by a respective subset of a second subset of the bits applied to that stage;
- and
- means for generating the echo replica as a function of the resulting products in each stage.
An echo canceler for generating an echo replica in response to a sequence of transmitted symbols, each symbol represented as an M-bit word, M.gtoreq.1, the echo canceler comprising:
- a series of echo canceler stages, each stage including at least one look-up table;
- means for applying each bit of each word to a successive pair of the echo canceler stages;
- means for addressing locations in each look-up table in each stage using the bits applied to that stage which are also applied to an adjacent stage to obtain an output from each look-up table;
- means for multiplying the output of each look-up table by a respective different subset of the bits applied to that stage which are not applied to the adjacent stage wherein each respective subset comprises at least one bit;
- and
- means for generating the echo replica as a function of the resulting products in each stage.
An echo canceler for generating an echo replica in response to a sequence of transmitted symbols, each symbol represented as an M-bit word, M.gtoreq.1, the echo canceler comprising:
- a series of echo canceler stages, each stage including at least one look-up table;
- means for applying each bit of each word to a plurality of echo canceler stages;
- means for addressing locations in each look-up table in each stage using the bits applied to that stage which are also applied to other stages to obtain an output from each look-up table;
- means for multiplying the output of each look-up table by a respective different subset of the bits applied to that stage which are not applied to the other stages wherein each subset comprises at least one bit;
- and
- means for generating the echo replica as a function of the resulting products in each stage.
A method for generating an echo replica in response to a sequence of transmitted symbols, each symbol represented as an M-bit word, M.gtoreq.1, the method comprising the steps of:
- applying each bit of each word to a successive pair of echo canceler stages in a plurality or echo canceler stages, wherein each stage includes at least one look-up table, and addressing locations in each look-up table in each stage using a first subset of bits applied to that stage;
- multiplying the output of each look-up table by a respective subset of a second subset of the bits applied to that stage;
- and
- generating the echo replica as a function of the resulting products in each stage.
A method for generating an echo replica in response to a sequence of transmitted symbols, each symbol represented as an M-bit word, M.gtoreq.1, the method comprising the steps of:
- means for applying each bit of each word to a successive pair of the echo canceler stages in a plurality of echo canceler stages, wherein each stage includes at least one look-up table;
- addressing locations in each look-up table in each stage using the bits applied to that stage which are also applied to an adjacent stage to obtain an output from each look-up table;
- multiplying the output of each look-up table by a respective different subset of the bits applied to that stage which are not applied to the adjacent stage wherein each respective subset comprises at least one bit;
- and
- generating the echo replica as a function of the resulting products in each stage.
A method for generating an echo replica in response to a sequence of transmitted symbols, each symbol represented as an M-bit word, M.gtoreq.1, the method comprising the steps of:
- applying each bit of each word to a first plurality of echo canceler stages in a second plurality of echo canceler stages, wherein each stage includes at least one look-up table;
- addressing locations in each look-up table in each stage using the bits applied to that stage which are also applied to other stages to obtain an output from each look-up table;
- multiplying the output of each look-up table by a respective different subset of the bits applied to that stage which are not applied to the other stages wherein each subset comprises at least one bit;
- and
- generating the echo replica as a function of the resulting products in each stage.
Dependencies are inferred from the claim text.