EP0708537A1
Expired / Lapsed
EP
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Echo canceler and echo path estimating method
Assignee: NTT Docomo Inc
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Filing: 1995-05-02
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Granted: —
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Expires: 2015-05-02
Abstract
Abstract An echo canceler which can perform the training of echo path estimation without causing any hindrance to calls. The echo canceler is equipped with a pseudo-noise generating section which generates specific training signals (pseudo-noise) which is forcedly supplied to a transmission line for transmitting the voice of a far-end talker. When the transmission level of the far-end talker is very low or when no voice is transmitted, a certain correlation is established between the pseudo-noise and the signal of the transmission line. Based on such a correlation, coefficients for generating a pseudo-echo are calculated. Therefore, the training of echo path estimation is performed based on the pseudo-noise without using the voice of the far-end talker, and an adequate pseudo-echo is produced.
Inventors
- 👤 Toshiro Kawahara
- 👤 Toshio H-1005 Fureaino-machi MIKI
- 👤 Hirohito Suda
- 👤 Tomoyuki Ohya
- 👤 Hirofumi Takagi
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 23:38
CPC Classifications
H; H04; H04B; H04B1/00; H04B1/06; H04B1/10; H04B3/00; H04B3/02; H04B3/20; H04B3/23; H04B3/238
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
94 words
An echo canceler employed in a communication line network including a first transmission line for transmitting a voice of a four-wire side and a second transmission line for transmitting a voice of a second-wire side, said echo canceler comprising: training signal generator means for generating a training signal and supplying the same to said first transmission line; and coefficient calculator means for calculating a coefficient necessary for generating an echo replica based on a correlation established between the training signal supplied to said first transmission line and a signal of said second transmission line.
Claim 2
Dependent Claim
105 words
An echo pass estimating method applicable to an echo canceler employed in a communication line network including a first transmission line for transmitting a voice of a four-wire side and a second transmission line for transmitting a voice of a second-wire side, said echo pass estimating method comprising: a training signal output step for generating a training signal and supplying the same to said first transmission line; and a coefficient calculation step for calculating a coefficient necessary for generating an echo replica based on a correlation established between the training signal supplied to said first transmission line and a signal of said second transmission line.
Claim 3
Dependent Claim
117 words
An echo canceler according to claim 1, further comprising: storage means for storing response characteristics of a plurality of hybrids; selector means for selecting one of said response characteristics based on a relation between a transmission signal propagated from said four-wire side to said two-wire side and an echo signal propagated from said two-wire side to said four-wire side; echo replica generator means for estimating an echo path by a predetermined learning algorithm and generating an echo replica by appropriately delaying the transmission signal and delaying the signal in accordance with a predetermined parameter; and initial parameter setting means for setting an initial value of said parameter based on the response characteristic selected by said selector means.
Claim 4
Dependent Claim
141 words
An echo canceler employed in a communication line network for performing a transmission between a voice transmitted through a four-wire side and a voice transmitted through a two-wire side, said echo canceler comprising: storage means for storing response characteristics of a plurality of hybrids; selector means for selecting one of said response characteristics based on a relation between a transmission signal propagated from said four-wire side to said two-wire side and an echo signal propagated from said two-wire side to said four-wire side; echo replica generator means for estimating an echo path by a predetermined learning algorithm and generating an echo replica by appropriately delaying the transmission signal and transfiguring the signal in accordance with a predetermined parameter; and initial parameter setting means for setting an initial value of said parameter based on the response characteristic selected by said selector means.
Claim 5
Dependent Claim
106 words
An echo path estimating method according to claim 2, further comprising the steps of: storing response characteristics of a plurality of hybrids; selecting one of said response characteristics based on a relation between a transmission signal propagated from said four-wire side to said two-wire side and an echo signal propagated from said two-wire side to said four-wire side; estimating an echo path by a predetermined learning algorithm and generating an echo replica by appropriately delaying the transmission signal and transfiguring the signal in accordance with a predetermined parameter; and setting an initial value of said parameter based on the response characteristic selected by said selector means.
Claim 6
Dependent Claim
135 words
An echo path estimating method for estimating an echo path with respect to a communication line network for performing a transmission between a voice transmitted through a four-wire side and a voice transmitted through a two-wire side, said method comprising the steps of: storing response characteristics of a plurality of hybrids; selecting one of said response characteristics based on a relation between a transmission signal propagated from said four-wire side to said two-wire side and an echo signal propagated from said two-wire side to said four-wire side; estimating an echo path by a predetermined learning algorithm and generating an echo replica by appropriately delaying the transmission signal and transfiguring the signal in accordance with a predetermined parameter; and setting an initial value of said parameter based on the response characteristic selected by said selector means.
Claim 7
Dependent Claim
81 words
An echo canceler according to claim 3, further comprising: delay time measuring means for measuring a delay time of the echo signal with respect to the transmission signal based on the transmission signal transmitted from said four-wire side to said two-wire side and the echo signal transmitted from said four-wire side to said two-wire side; and delay setting means for setting the delay time in said echo replica generator means to a delay time measured by said delay time measuring means.
Claim 8
Dependent Claim
119 words
An echo canceler according to claim 1, further comprising: storage means for storing frequency characteristics of a plurality of hybrids; selector means for selecting one of said frequency response characteristics based on a relation between a transmission signal propagated from said four-wire side to said two-wire side and an echo signal propagated from said two-wire side to said four-wire side; echo replica generator means for estimating an echo path by a predetermined learning algorithm and generating an echo replica by appropriately delaying the transmission signal and transfiguring the signal in accordance with a predetermined parameter; and initial parameter set means for setting an initial value of said parameter based on the frequency response characteristic selected by said selector means.
Claim 9
Dependent Claim
143 words
An echo canceler employed in a communication line network for performing a transmission between a voice transmitted through a four-wire side and a voice transmitted through a two-wire side, said echo canceler comprising: storage means for storing frequency characteristics of a plurality of hybrids; selector means for selecting one of said frequency response characteristics based on a relation between a transmission signal propagated from said four-wire side to said two-wire side and an echo signal propagated from said two-wire side to said four-wire side; echo replica generator means for estimating an echo path by a predetermined learning algorithm and generating an echo replica by appropriately delaying the transmission signal and transfiguring the signal in accordance with a predetermined parameter; and initial parameter set means for setting an initial value of said parameter based on the frequency response characteristic selected by said selector means.
Claim 10
Dependent Claim
108 words
An echo path estimating method according to claim 2, further comprising the steps of: storing frequency characteristics of a plurality of hybrids; selecting one of said frequency response characteristics based on a relation between a transmission signal propagated from said four-wire side to said two-wire side and an echo signal propagated from said two-wire side to said four-wire side; estimating an echo path by a predetermined learning algorithm and generating an echo replica by appropriately delaying the transmission signal and transfiguring the signal in accordance with a predetermined parameter; and setting an initial value of said parameter based on the frequency response characteristic selected by said selector means.
Claim 11
Dependent Claim
138 words
An echo path estimating method for estimating an echo path with respect to a communication line network for performing a transmission between a voice transmitted through a four-wire side and a voice transmitted through a two-wire side, said method comprising the steps of: storing frequency response characteristics of a plurality of hybrids; selecting one of said frequency response characteristics based on a relation between a transmission signal propagated from said four-wire side to said two-wire side and an echo signal propagated from said two-wire side to said four-wire side; estimating an echo path by a predetermined learning algorithm and generating an echo replica by appropriately delaying the transmission signal and transfiguring the signal in accordance with a predetermined parameter; and setting an initial value of said parameter based on the frequency response characteristic selected by said selector means.
Claim 12
Dependent Claim
81 words
An echo canceler according to claim 8, further comprising: delay time measuring means for measuring a delay time of the echo signal with respect to the transmission signal based on the transmission signal transmitted from said four-wire side to said two-wire side and the echo signal transmitted from said two-wire side to said four-wire side; and delay setting means for setting a delay time in said echo replica generator means to a delay time measured by said delay time measuring means.
Claim 13
Dependent Claim
119 words
An echo canceler according to claim 1, further comprising: estimation means for estimating, on the basis of a first voice signal corresponding to the voice on the four-wire side and on a second signal corresponding to the voice on the two-wire side, a response characteristic of a hybrid circuit for converting the four-wire side and the two-wire side; echo replica generator means for artificially generating an echo caused by said hybrid circuit by means of calculation using the estimated result and said second voice signal; subtraction means for subtracting an output signal of said echo replica generator means from said second voice signal; and delay means for supplying said first voice signal with a delay of a predetermined time.
Claim 14
Dependent Claim
149 words
An echo canceler employed in a communication line network for performing a transmission between a voice transmitted through a four-wire side and a voice transmitted through a two-wire side, said echo canceler comprising: estimation means for estimating, on the basis of a first voice signal corresponding to the voice on the four-wire side and on a second signal corresponding to the voice on the two-wire side, a response characteristic of a hybrid circuit for converting the four-wire side and the two-wire side; echo replica generator means for artificially generating an echo caused by said hybrid circuit by means of calculation using the estimated result and said second voice signal; and subtraction means for subtracting an output signal of said echo replica generator means from said second voice signal; wherein said echo canceler further comprises delay means for supplying said first voice signal with a delay of a predetermined time.
Claim 15
Dependent Claim
151 words
An echo canceler according to claim 1, further comprising: first sampling means for up-sampling a first digital voice signal corresponding to the voice on said four-wire side; second sampling means for up-sampling a second digital voice signal corresponding to the voice on said two-wire side at a same sampling rate as said first sampling means; estimation means for estimating, on the basis of sampling results of the first and second up-sampler means, a response characteristic of a hybrid circuit for converting the four-wire side and the two-wire side; echo replica generator means for artificially generating an echo caused by said hybrid circuit by means of calculation using the estimated result and the sampled result by said sampling means; third sampling means for down-sampling an output signal of said echo replica generator means; and substraction means for subtracting an output signal of said third sampling means from said second digital voice signal.
Claim 16
Dependent Claim
175 words
An echo canceler employed in a communication line network for performing a transmission between a voice transmitted through a four-wire side and a voice transmitted through a two-wire side, said echo canceler comprising: first sampling means for up-sampling a first digital voice signal corresponding to the voice on said four-wire side; second sampling means for up-sampling a second digital voice signal corresponding to the voice on said two-wire side at a same sampling rate as said first sampling means; estimation means for estimating, on the basis of sampling results of the first and second up-sampler means, a response characteristic of a hybrid circuit for converting the four-wire side and the two-wire side; echo replica generator means for artificially generating an echo caused by said hybrid circuit by means of calculation using the estimated result and the sampled result by said sampling means; third sampling means for down-sampling an output signal of said echo replica generator means; and substraction means for subtracting an output signal of said third sampling means from said second digital voice signal.
Claim 17
Dependent Claim
27 words
An echo canceler according to claim 15, further comprising delay means located at a front stage of said estimation means and adapted to delay a predetermined time.
Claim 18
Dependent Claim
51 words
An echo canceler according to claim 15 or 17, wherein the up-sampling or down-sampling by said first to third sampling means is performed by a single signal convertor means, said signal convertor means converting a sampling rate of the input/output signal to said estimation means and said echo replica generator means.
References Cited (Backward Citations)
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