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US5317596A
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Method and apparatus for echo cancellation with discrete multitone modulation
Assignee: Silicon Valley Bank Inc
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Filing: 1992-12-01
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Granted: 1994-05-31
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Expires: 2012-12-01
Abstract
Abstract A method of echo cancellation in a full-duplex data communication system with discrete multitone modulation, comprised of an initial step of initializing a set of frequency-domain echo parameters and a set of corresponding time-domain echo parameters, and further including the repeating steps of block multiplying a frequency-domain transmit block of a transmitted signal by the set of frequency-domain echo parameters to produce a frequency-domain echo, converting the frequency-domain transmit block to a time-domain transmit block, subtracting the end of the previous time-domain transmit block from the end of the current time-domain transmit block, performing a convolution of the adjusted time-domain transmit block and the time-domain echo parameters to produce a time-domain echo, subtracting the time-domain echo from a time-domain receive block of a received signal, converting the resulting signal to the frequency-domain to produce a frequency-domain receive block, subtracting the frequency-domain echo from the frequency-domain receive block to produce an echo-free receive block, updating the frequency-domain echo parameters by comparing the echo-free receive block to the frequency-domain transmit block, infrequently updating the time-domain echo parameters by converting the frequency-domain echo parameters to the time-domain, and repeating the repeating steps for each block of the received signal.
Inventors
- 👤 Minnie Ho
- 👤 John M. Cioffi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 21:48
CPC Classifications
H; H04; H04B; H04B3/00; H04B3/02; H04B3/20; H04B3/23; H04B3/21; H04L; H04L27/00; H04L27/26; H04L27/2601
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
147 words
A multicarrier transceiver system, comprising; a multicarrier transmitter, responsive to input data, and operative to generate a frequency-domain transmit signal X(f), a time-domain transmit signal x(n) and an output transmit signal for communication to a remote receiver through a data link; a multicarrier receiver, responsive to an input receive signal received from a remote transmitter through said data link, a time-domain echo signal e(n), and a frequency-domain echo signal E(f), and operative to generate an error-free receive signal R ef (f) and output data; and an echo canceller, responsive to said frequency-domain transmit signal X(f) and said time-domain transmit signal x(n), and adaptively responsive to said error-free received signal R ef (f) and operative to generate an echo component of said output transmit signal appearing in said input receive signal including said time-domain echo signal e(n) and said frequency-domain echo signal E(f) for input to said receiver.
Claim 2
Dependent Claim
147 words
A multicarrier transceiver system, comprising; a multicarrier transmitter, responsive to input data, and operative to generate a frequency-domain transmit signal X(f), a time-domain transmit signal x(n) and an output transmit signal for communication to a remote receiver through a data link; a multicarrier receiver, responsive to an input receive signal received from a remote transmitter through said data link, a time-domain echo signal e(n), and a frequency-domain echo signal E(f), and operative to generate an error-free receive signal R ef (f) and output data; and an echo canceller, responsive to said frequency-domain transmit signal X(f) and said time-domain transmit signal x(n), and adaptively responsive to said error-free received signal R ef (f) and operative to generate an echo component of said output transmit signal appearing in said input receive signal including said time-domain echo signal e(n) and said frequency-domain echo signal E(f) for input to said receiver.
Claim 3
Dependent Claim
190 words
A multicarrier transceiver system as recited in claim 1, wherein said echo canceller includes; a frequency-domain echo canceller subsystem responsive to said frequency-domain transmit signal X(f) and said echo-free receive signal R ef (f), and operative to generate a set of frequency-domain echo parameters P(f) and said frequency-domain echo signal E(f); an IFFT subsystem responsive to said frequency-domain echo parameters p(f) and operative to generate a set of time-domain echo parameters p(n); a block delay subsystem responsive to said time-domain transmit signal x(n) and operative to store said time-domain transmit signal for one cycle and generate a previous time-domain transmit signal x i-1 ; an adder subsystem responsive to said time-domain transmit signal x(n) and said previous time-domain transmit signal x i-1 operative to subtract said previous time-domain transmit signal x i-1 from said time-domain transmit signal x(n), and to generate the result X'(n) of the subtraction; a tail cancellation and cyclic reconstruction subsystem responsive to the result x'(n) of the subtraction and the time-domain echo parameters p(n) and operative to perform a linear convolution of the result x'(n) and the parameters p(n) to produce said time-domain echo signal e(n).
Claim 4
Independent Claim
234 words
A method of cancelling echo in a multicarrier transceiver system including a multicarrier transmitter that transmits data in transmit blocks and a multicarrier receiver that receives data in receive blocks, wherein said transmitter is transmitting at the same rate that said receiver is receiving, comprising the steps of; (a) generating initial values for a set of frequency-domain echo parameters and a set of corresponding time-domain echo parameters, (b) block multiplying a frequency-domain transmit block by the set of frequency-domain echo parameters to produce a frequency-domain echo component, (c) converting the frequency-domain transmit block to a time-domain transmit block, (d) subtracting the end of the previous time-domain transmit block from the end of the current time-domain transmit block to produce a tail-adjusted transmit block, (e) performing a convolution of the tail-adjusted transmit block and the time-domain echo parameters to produce a time-domain echo component, (f) subtracting the time-domain echo component from a time-domain receive block, (g) converting the resulting signal to the frequency-domain to produce a frequency-domain receive block, (h) subtracting the frequency-domain echo component from the frequency-domain receive block to produce an echo-free receive block, (i) updating the frequency-domain echo parameters by comparing the echo-free receive block to the frequency-domain transmit block, (j) updating the time-domain echo parameters, if a predetermined condition is met, by converting the frequency-domain echo parameters to the time-domain, and (k) repeating steps (b) through (j) for each received block.
Claim 5
Independent Claim
234 words
A method of cancelling echo in a multicarrier transceiver system including a multicarrier transmitter that transmits data in transmit blocks and a multicarrier receiver that receives data in receive blocks, wherein said transmitter is transmitting at the same rate that said receiver is receiving, comprising the steps of; (a) generating initial values for a set of frequency-domain echo parameters and a set of corresponding time-domain echo parameters, (b) block multiplying a frequency-domain transmit block by the set of frequency-domain echo parameters to produce a frequency-domain echo component, (c) converting the frequency-domain transmit block to a time-domain transmit block, (d) subtracting the end of the previous time-domain transmit block from the end of the current time-domain transmit block to produce a tail-adjusted transmit block, (e) performing a convolution of the tail-adjusted transmit block and the time-domain echo parameters to produce a time-domain echo component, (f) subtracting the time-domain echo component from a time-domain receive block, (g) converting the resulting signal to the frequency-domain to produce a frequency-domain receive block, (h) subtracting the frequency-domain echo component from the frequency-domain receive block to produce an echo-free receive block, (i) updating the frequency-domain echo parameters by comparing the echo-free receive block to the frequency-domain transmit block, (j) updating the time-domain echo parameters, if a predetermined condition is met, by converting the frequency-domain echo parameters to the time-domain, and (k) repeating steps (b) through (j) for each received block.
References Cited (Backward Citations)
US5166924A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1997-05-30 | 1997-11-29 | 1998-05-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2001-05-30 | 2001-11-29 | 2002-05-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2005-05-30 | 2005-11-29 | 2006-05-31 | $7700.00 | Window Closed / Lapsed |