JP2001102972A - System and method for training echo canceler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease an operation quantity by shortening the training time of an echo canceler of a transmission system like ADSL. SOLUTION: The training system for an echo canceler for multicarrier transmission whose down transmission band is wider than the up reception band is equipped with the echo canceler 200 which generates a cancel signal for line echo according to a signal having data arranged in a transmission carrier and subtracts it from received data and a training data generation part 110 which divides the transmission band by the width of the reception band, outputs a signal having training data arranged in a transmission carrier for each divided transmission band to the echo canceler, and trains the echo canceler.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an echo canceller. In particular, the present invention relates to ADSL (Asymmetric
Digital Subscriber Line)
The present invention relates to a training system and method for an echo canceller (EC) using a transmission system such as the one described above, which shortens the training time and reduces the amount of calculation.

[0002]

2. Description of the Related Art A conventional echo canceller and its problems will be described with reference to a multicarrier transmission system in which a downstream band such as the ADSL system is wider than an upstream band. The ADSL system is a type of multi-carrier transmission system, which is a DMT (Discrete Mull).
tiTone) system.

[0003] The detailed description of the DMT method is described in "Starting Countdown, ADSL in the Country of Light (Nikkei Communication, N.K.
o. 283 pp. 92-111, 1998.1.
4) ". ADSL transmission data is:
The information is grouped every several bits and is arranged as amplitude and phase information on each carrier.

[0004] Data arranged in the frequency domain is IFFT.
(Inverse fast Fourier transform) is demodulated as time domain data. ADSL received data is modulated into data in a frequency range by FFT (Fast Fourier Transform). In the ADSL system, as a means for canceling the line echo, conventionally, "METHOD AND APP"
ARATUS FOR ECHO CANCELLAT
ION WITH DISCRETE MULTITO
NE Modulation, United Stat
e-Patent (5317596) ".

FIG. 5 is a schematic diagram showing a band used in the ADSL system. As shown in this figure, the carrier is 4.312.
It is arranged every 5 kHz. In the station side device of the ADSL system, the reception band is narrower than the transmission band.
Up to 255 carriers are used, and reception uses 0 to 31 carriers.

FIG. 6 is a block diagram showing the configuration of an ADSL transmission / reception unit using a training system for an echo canceller, which is a premise of the present invention. As shown in FIG.
The transmission unit 100 of the SL transmission / reception unit includes a training data generator 110 that generates training data, and an IFF that demodulates the generated training data into time-domain data.
T (Inverse Fast Fourier Transform) 120, a parallel-to-serial converter 130 for serializing demodulated data, a digital-to-analog converter 140 for converting serialized data from digital to analog, and a signal converted to analog And a low-pass filter 150 for removing unnecessary high-frequency components from the signal.

The training data generator 110 converts the known training data X _{k, n} into IF
Output to the FT 120, the training data X _{k, n}
Is created as follows. First, 512-bit known random binary data is created, and the following conversion is performed every two bits from the beginning to create 256 complex data S _{k, n} .

1st bit 2nd bit real part imaginary part 00 → 1101 → -11 11 → -1 11 1 → 1 -1

Next, training data X _{k, n} is generated using the following equation (8). X _{k, n} = 0 (n = 0, N / 2) X _{k, n} = S _{k, n} (0 <n <N / 2) X _{k, n} = S _{k, N−n} (n> N / 2) ) (8) where k is the training number, n is the carrier number, and N
/ 2 is the number of transmission carriers (256 in the ADSL system).

Since the training data has Hamiltonian symmetry, only a real number of N samples remains in the IFFT result. The training data X _{k, n} generated by the training data generator 110 is
Is converted into data in the time domain by the parallel-serial conversion unit 130, the digital-analog conversion unit 140, the low-pass filter 150, and further passes through the hybrid transformer 300 that performs 2-wire to 4-wire conversion.
Is output to

Next, the receiving section 1000 of the ADSL transmitting / receiving section
Is a low-pass filter 1100 connected to the hybrid transformer 300 for removing unnecessary high-frequency components, an analog-to-digital converter 1200 for converting an analog signal from which high-frequency components have been removed to a digital signal, and a subtractor connected to the analog-to-digital converter 1200 Vessel 1300;
It is composed of a serial-parallel conversion unit 1400 that converts the output data of the subtractor 1300 in parallel, an FFT 1500 that demodulates the parallel-converted data into frequency-domain data, and a complex subtractor 1600 that performs a subtraction process on the demodulated data. .

The received data is transmitted to the hybrid transformer 30
0, and is demodulated to frequency band data via low-pass filters 1100 and 1200, serial-parallel converter 1400, and FFT 1500. Next, the frequency domain-time domain echo canceller 200 of the ADSL transmission / reception section includes the reception section 1
In order to perform the subtraction process by 000, cancellation data for canceling the line echo generated in the hybrid transformer 300 is formed based on the transmission data from the transmission unit 100.

Therefore, the frequency range of the ADSL transmitting / receiving section
The time domain echo canceller 200 includes the training data from the training data generator 110 and the complex subtractor 1.
Receiving the received data from the complex subtractor 1600
Frequency echo canceller 210 for outputting the data to the frequency domain echo canceller (EC) 210, IFFT 220 for demodulating the output data of the frequency domain echo canceller 210 to time domain data,
A time domain echo canceller (EC) 230 that inputs data demodulated by 220 and data demodulated by IFFT 120 and outputs the data to a subtractor 1300.

As described above, the frequency-domain / time-domain echo canceller 200 uses the frequency-domain echo canceller 21.
0, the time domain echo canceller 230 is used in combination, the training data from the training generator 110 is used, and the training for setting the optimal condition for canceling the line echo is performed. The frequency band echo canceller 210 is configured by a one-tap filter having a complex coefficient prepared for each carrier.

The time-domain echo canceller 230 has an FIR
(Finite ImpulseResponse) filter. Frequency range echo canceller 2
10 is the training data X by the following equation (9).
Tap coefficient C of carrier corresponding to each carrier of _{k and n}
Data Y _multiplied by _{k and n} ec _{k, n} is calculated.

[0016] Y ec _{k, n} = C _{k, n} × X _{k, n} ... (9) Y ec _{k, n} : internal data of carrier n frequency band echo canceller 210 in symbol k X _{k, n} : training data of carrier n in symbol k C _{k, n} : tap of carrier n frequency band echo canceller 210 in symbol k coefficient

The frequency band echo canceller 210 transmits
Data Y corresponding to carrier ec _{k, n}To the following equation (1
0) to compress the signal to the reception use band, and
Output to 0. Y ec '_{k, n}= Y ec_{k, n}+ Y ec_{k, 64 + n}+ Y ec_{k, 128 + n}+ Y ec_{k, 192 + n}+ Y ec_{k, 256 + n}+ Y ec_{k, 320 + n}+ Y ec_{k, 384 + n}+ Y ec_{k, 448 + n} (0 ≦ n <M) (10)

M: the number of receiving carriers (= 64) Y ec ' _{k, n} : output data of the frequency band echo canceller 210 The tap coefficient of the frequency band echo canceller 210 is represented by LMS (Least Mean Sq) shown in the following equation (11).
ua) algorithm.

C_{k + 1, n}= C_{k, n}+ ΜE_{k, n}X^* _{k, n} (0 ≦ n <512) (11) E_{k, n}= E '_{k, mod (n, 64)} ... (12) μ: Step size of coefficient update X^* _{k, n}: Training data X_{k, n}Complex conjugate of E '_{k, n}: Identification error

At the time of half-duplex communication, the output of the complex subtracter 1600 is only the identification error _{E'k, n} since the opposite device has stopped transmitting. Time-domain echo canceller 230
Are calculated by performing an inverse fast Fourier transform on the tap coefficients obtained by the frequency domain echo canceller 210 by the IFFT 220.

The time domain echo canceller 230 performs two preprocessings. First, the frequency domain echo canceller 210
Cancels the inter-symbol interference caused by past symbols that cannot be eliminated by the above. Second, the inter-symbol interference caused by the current transmission symbol in the next symbol section is copied to the head of the current symbol.

By these two processes, in the FFT section,
Only echoes caused by the current symbol remain with periodicity. This echo is canceled by the frequency band echo canceller 210. Output Y of time domain echo canceller 230 Since ec _n has a different sampling rate between transmission and reception, as shown in the following equation (13), ec _n is extracted one by one every eight samples and converted into data of 64 samples.

Y ec '_n' = Y ec _8n (13) where Y ec ′ _{n ′} is output data of the time-domain echo canceller 230 after being decimated. FIG. 7 is a schematic diagram showing a state of data thinning-out according to equation (13). As shown in the drawing, the data of the transmission symbol 512 becomes 64 data after the data is decimated.

In the case of full-duplex communication, the update of tap coefficients and the elimination of echo are performed in the same manner as in the case of half-duplex communication. Thus, the training system of the echo canceller is
Set the optimal echo canceller data.

[0025]

By the way, in the training system of the echo canceller, since the training data is transmitted by arranging the data on all the carriers, the echoes of a plurality of transmitting carriers are superimposed on one receiving carrier. I was Therefore, in order to obtain sufficient echo suppression characteristics, it is necessary to reduce the step size of the frequency band echo canceller 210.

However, when the step size is reduced, the convergence time of the frequency band echo canceller 210 becomes longer, and as a result, there is a problem that the training time of the entire echo canceller becomes longer. Further, since the training including the inverse fast Fourier transform is repeated to calculate the tap coefficients of the time-domain echo canceller 230, there is a problem that the amount of calculation during training increases.

Accordingly, it is an object of the present invention to provide a training system and method for an echo canceller, which can reduce the training time and the amount of calculation in view of the above problems.

[0028]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a training system for a multicarrier transmission echo canceller in which a downstream transmission band is wider than an upstream reception band, wherein data is allocated to transmission carriers. An echo canceller for forming a line echo cancel signal based on the signal thus obtained and subtracting the same from the received data, and dividing the transmission band into the width of the reception band,
A training data generating unit for outputting a signal in which training data is arranged on a transmission carrier for each transmission band to the echo canceller and performing training of the echo canceller. provide.

By this means, the transmission band is divided by the reception bandwidth, and data is transmitted for each divided transmission band, so that echoes of a plurality of transmission carriers are no longer superimposed as in the prior art. Thus, the tap coefficient of the echo canceller can be calculated by dividing the received data by the training data in the frequency domain, instead of the method of asymptotically obtaining the tap coefficient as in the LMS method, and the training time can be reduced. it can.

Preferably, the multi-carrier transmission system is an ADSL system. By this means, the present invention can be applied to a multi-carrier transmission system such as the ADSL system. Preferably, the echo canceller receives the signal in the frequency domain from the training generator, and includes a one-tap filter having a complex coefficient prepared for each carrier. Input the signal in the time domain from the
A time-domain echo canceller composed of an IR filter, and the tap coefficient of the time-domain echo canceller is calculated by performing an inverse fast Fourier transform on the tap coefficient obtained by the frequency-domain echo canceller.

By this means, inter-symbol interference caused by past symbols that cannot be canceled by the frequency band echo canceller is canceled. The inter-symbol interference generated in the next symbol section by the current transmission symbol is copied to the head of the current symbol. In the FFT section, only the echo generated by the current symbol remains with periodicity. This echo is canceled by the frequency band echo canceller.

Preferably, the echo canceller is provided with an initial value calculating circuit, and the initial value calculating circuit calculates an initial value of a tap coefficient of the frequency band echo canceller. By this means, after calculating all the tap coefficients of the frequency domain echo canceller by the initial value calculation circuit, the tap coefficient of the time domain echo canceller can be obtained only by performing the inverse fast Fourier transform once, and the amount of computation during training Can be reduced.

Preferably, a time-domain correction unit is provided between the frequency-domain echo canceller and the time-domain echo canceller, and the time-domain correction unit corresponds to a Nyquist reception carrier whose transmission carrier in the divided transmission band corresponds to Nyquist. Therefore, the tap coefficient is corrected. By this means, it is possible to improve the deterioration of the line echo suppression characteristic.

Further, the present invention provides a training method of an echo canceller for multicarrier transmission in which a downstream transmission band is wider than an upstream reception band, wherein a line echo cancel signal is provided based on a signal in which data is arranged on a transmission carrier. And forming a subtraction process on the received data;
Dividing the transmission band into the width of the reception band, outputting a signal in which training data is allocated to the divided transmission carriers for each transmission band to the echo canceller, and training the echo canceller. And a training method for an echo canceller characterized by the following.

By this means, the transmission band is divided by the reception bandwidth, and data is placed for each of the divided transmission bands and transmitted in the same manner as in the above-mentioned invention. Is no longer superimposed. Thus, the tap coefficient of the echo canceller can be calculated by dividing the received data by the training data in the frequency domain, instead of the method of asymptotically obtaining the tap coefficient as in the LMS method, and the training time can be reduced. it can.

[0036]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an ADSL transmission / reception unit using a training system for an echo canceller according to the present invention. As shown in the figure, what differs from the configuration of FIG. 6 is an initial value calculation circuit 240 of the frequency-time-domain echo canceller 200.

The initial value calculation circuit 240 receives the output of the FFT 1500 and outputs the output to the frequency domain echo canceller 210. FIG. 2 is a block diagram illustrating details of the initial value calculation circuit 240. As shown in the figure, the initial value calculation circuit 240 includes a training data generator 243, a band extension unit 241 that receives an output of the FFT 1500 of the reception unit 1000 as an input, and an averaging unit that receives an output of the band extension unit 241 as an input. It has a circuit 242 and a complex divider 244 that receives the outputs of the training data generator 243 and the averaging circuit 242 as input and outputs to the frequency domain echo canceller 210.

Frequency domain-time domain echo canceller 200
Training is performed by the following procedures. The training data generator 243 of the initial value calculation circuit 240 is the same as the training data generator 1 of the transmitting unit 100.
The same training data X ′ _{k, n} as the training data X _{k, n} output at 10 is output. N represents twice the number of transmission carriers and M represents twice the number of reception carriers (N and M are powers of 2 and N> M).

The training data generator 110
carrier from kM / 2 to ((k + 1) M / 2) and from (N- (k + 1) M / 2 + 1) to (N-kM / 2) (however, when k = 0, (NM-2 + 1) ) To (N
The training data X _{k, n} having power only in the carriers up to -1) is generated, and L symbols are repeatedly transmitted.

Here, k indicates a training number for calculating an initial value, and the initial value is 0 and takes a value up to N / M-1.
FIG. 3 is a diagram illustrating a model (here, k = 0 to 7) for explaining the training data X _{k, n} to be transmitted. As shown in the figure, the training data X _{k, n} generated by the training data generating unit 110 is arranged in the 0th to 31st and 481th to 511th carriers when k = 0, When k = 1, data is allocated to the 32nd to 63rd, 449th to 480th carriers,..., when k = 7, data is allocated to the 224th to 288th carriers.

In the conventional echo canceller, as described above, the training data is transmitted by arranging the data on all the carriers. Therefore, echoes of a plurality of transmission carriers are superimposed on one reception carrier. Therefore, in order to obtain sufficient echo suppression characteristics, it is necessary to reduce the step size of the frequency band echo canceller 210.

When the step size is reduced, the convergence time of the frequency band echo canceller 210 becomes longer, and as a result, the training time of the entire echo canceller becomes longer. On the other hand, in the echo canceller of the present invention, the transmission band is divided by the reception bandwidth, and data is transmitted for each divided band so that echoes of a plurality of transmission carriers are not superimposed.

Thus, the tap coefficient of the echo canceller can be calculated by dividing the received data by the training data in the frequency domain, instead of the method of asymptotically obtaining the tap coefficient as in the LMS method, thereby shortening the training time. can do. The band extending unit 241 provides the training data X _{k, n}
The band of the output Y _{k, n} of the FFT 1500 at the time of transmission is extended by the following equation (1).

Y ′ _{k, n} = Y _{k, mod (n, M)} (1) Y _{k, mod (n, M)} : output of FFT 1500 Y ′ _{k, n} : output of band extender 241 (carrier number) n
= 0 to N) Here, mod (n, M) represents a remainder obtained by dividing n by M. The averaging circuit 242 averages the output data of the band extending section 241 between L symbols, and outputs the data Y ″ _{k, n} to the complex divider 244.

The complex divider 244 uses the frequency domain echo canceller 210 for the carrier in which the power of the training data _{X'k, n} exists, using the following equation (2).
Is output as the tap coefficient initial value C _{k, n} . C _{k, n} = Y ″ _{k, n} / X ′ _{k, n} (2) are repeated from k = 1 to N / M−1. When all tap coefficient initial values are obtained, the complex divider 244 outputs a value to the frequency-domain echo canceller 210, and sets tap coefficient initial values.

Frequency-Time Echo Canceller 200
When the tap coefficient of the frequency-domain echo canceller 210 is set, the same operation is performed as in the conventional method. The operation of the echo canceller training system according to the present invention will be described below. Taking an ADSL station apparatus as an example, transmission is performed with 512 carriers and reception is performed with 64 carriers.

The training data generator 110 generates known training data X _{k, n} . Where k
Is the training number (k = 0 to N / M-1), N is twice the number of transmission carriers (here, 512), M is twice the number of reception carriers (here, 64), and n is the carrier number (N = 0 to N-1). Training data X
_{k and n} are generated, for example, as follows.

Firstly, the known pseudo-random binary data 64-bit product, two bits from the head performs the following transformation to generate 32 complex data S _n. 1st bit 2nd bit real part imaginary part 0 0 → 1 1 0 1 → -1 1 1 1 0 → -1 1 1 1 → 1 -1

Next, the training data X _{k, n} is generated by using the following equation (3). Training data X _{k, n} generated by the following equation (3) is called a Hamiltonian symmetry, training data X _k is the Hamiltonian _symmetry, the _n, IFFT result, has a property as a real-only data . X _{k, n} = 0 (n = 0, N / 2)

X _{k, n} = S _{n−kM / 2} (kM / 2 ≦ n ≦ (k + 1) M / 2-1) X _{k, n} = S ^* _{N−kM / 2−n} (N− (k + 1) M / 2 + 1 ≦ n ≦ N−kM / 2) However, when k = 0, (N− (k + 1) M / 2 + 1 ≦ n ≦ N−kM / 2-1. X _{k, n} = 0 (Other) ... (3)

The training data generator 110 calculates k =
The training data is output from 0 to k = 7 for each L symbol. Next, the operation of the initial value calculation circuit 240 will be described. At the time of the half-duplex communication, the device on the opposite side has stopped transmitting, so that the YFT demodulated by the FFT 1500 is used.
_{k and n} are only the echo components of the transmission data.

The initial value calculation circuit 240 derives the frequency characteristics of the echo path by dividing the echo component in the frequency range by the training data. First, the band extending unit 241 outputs the output data Y _{k, n of the} FFT 1500.
, Band expansion is performed according to the following equation (4). Y ′ _{k, n} = Y _{k, mod (n, 64)} (4)

The averaging circuit 242 calculates the band-extended Y ′
_{k, n} are averaged between L symbols, and data Y ″ _{k, n} is output. The training data generator 243 outputs the same training data X ′ _{k, n} as the data X _{k, n} output by the training data generator 110. The complex divider 244 calculates the frequency domain echo canceller 210 for the carrier on which the data is allocated, using the following equation (5).
Is calculated as an initial value C _{k, n} of the tap coefficient.

C _{k, n} = Y ″ _{k, n} / X ′ _{k, n} (5) For example, when k = 0, data is allocated to the 0th to 31st and 481st to 511st carriers. Therefore, the complex divider 244 uses the output Y ″ _{0, n} of the averaging circuit 242 and the training data X ′ _{0, n} to calculate the initial value C _{0, n} of the tap coefficient according to the following equation (6). calculate.

C _{0, n} = Y ″ _{0, n} / X ′ _{0, n} (n = 0 to 31) (6) The complex divider 244 calculates the value of the tap coefficient of the frequency-domain echo canceller 210. Save it. When the initial values of the tap coefficients for all the carriers are obtained, the complex divider 244 outputs the initial values of the tap coefficients to the frequency-domain echo canceller 210.

When the initial value of the tap coefficient is set by the initial value calculation circuit 240, the frequency band echo canceller 210 updates the echo replica characteristics and the tap coefficient as in the conventional echo canceller. In the conventional echo canceller, as described above, the training including the inverse fast Fourier transform is repeated to obtain the tap coefficient of the time-domain echo canceller 230.

On the other hand, in the echo canceller of the present invention, the initial value calculation circuit 240 is provided, and after calculating all the tap coefficients of the frequency domain echo canceller 210, the inverse fast Fourier transform is performed and the tap of the time domain echo canceller 230 is performed. Find the coefficient. Therefore, the tap coefficient of the time-domain echo canceller 230 can be obtained only by performing the inverse fast Fourier transform once, and the amount of calculation at the time of training can be reduced.

Next, the 32 × i (i = 1, 2,..., 15) -th transmission carrier corresponds to the Nyquist reception carrier. Since the imaginary number of the echo of the 32 × i-th carrier is 0 and the data is only the real number, the tap coefficient of the correct frequency band echo canceller 210 cannot be obtained.

For this reason, the correct tap coefficient of the time-domain echo canceller 230 cannot be obtained, and the echo suppression characteristic deteriorates. Therefore, the tap coefficient of the time-domain echo canceller 230 is corrected as follows. FIG. 4 is a block diagram showing another configuration of the ADSL transmitting / receiving unit using the training system of the echo canceller according to the present invention.

As shown in the figure, in the frequency domain-time domain echo canceller 200, a time domain correction section 250 is provided between the IFFT 220 and the time domain echo canceller 230. The time domain correction unit 250 corrects the tap coefficient of the time domain echo canceller 230 according to the following equation (7).

C ′_n= C_n-A_{mod (n, 64)} … (7) A_m= C_{m + 448}  C '_n: Touch of time-domain echo canceller 230 after correction
Coefficient C_n: Tap of time domain echo canceller 230 before correction
Coefficient A_m: Tap of time domain echo canceller 230 before correction
Coefficient of the latter 64 taps regarding the coefficient

N: tap number of tap coefficient of time domain echo canceller 230 (n = 0 to 511) m: tap number of stored component (m = 0 to 63) mod (n, 64): n is divided by 64 Remainder By the correction of the above equation (7), the tap coefficient of the time-domain echo canceller 230 closer to the actual echo path can be calculated, and the echo suppression amount can be improved.

[0063]

As described above, according to the present invention,
The transmission band is divided by the reception bandwidth, and data is transmitted for each divided band so that echoes of a plurality of transmission carriers are not superimposed as in the related art. Thus, the tap coefficient of the echo canceller can be calculated by dividing the received data by the training data in the frequency domain, instead of the method of asymptotically obtaining the tap coefficient as in the LMS method, and the training time can be reduced. it can.

An initial value calculation circuit 240 is provided, and after calculating all tap coefficients of the frequency band echo canceller 210,
The tap coefficient of the time-domain echo canceller 230 can be obtained by performing the inverse fast Fourier transform only once, and the amount of calculation during training can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an ADSL transmission / reception unit using a training system for an echo canceller according to the present invention.

FIG. 2 is a block diagram illustrating details of an initial value calculation circuit 240.

FIG. 3 is a diagram illustrating a model (here, k = 0 to 7) for explaining training data X _{k, n} to be transmitted.

FIG. 4 is a block diagram showing another configuration of the ADSL transmission / reception unit using the training system for the echo canceller according to the present invention.

FIG. 5 is a schematic diagram showing a use band of the ADSL system.

FIG. 6 is a block diagram showing a configuration of an ADSL transmission / reception unit using a training system for an echo canceller, which is a premise of the present invention.

FIG. 7 is a schematic diagram illustrating a state of data thinning-out according to Expression (13).

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 transmission unit 110 training data generator 120 IFFT 130 parallel-to-serial conversion unit 140 digital-to-analog conversion unit 150 low-pass filter 200 frequency-time echo canceller 210 frequency echo canceller 220 IFFT 230 time domain Echo canceller 240 ... Initial value calculation circuit 241 ... Band expansion unit 242 ... Averaging circuit 243 ... Training data generator 250 ... Time domain correction unit 300 ... Hybrid transformer 400 ... Path 1000 ... Receiving unit 1100 ... Low pass filter 1200 ... Analog-to-digital conversion Unit 1300 subtractor 1400 serial-parallel converter 1500 FFT 1600 complex subtractor

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5K022 AA07 AA11 AA28 AA42 5K046 AA00 AA01 BA06 BB05 EE06 EF00 EF01 EF07 EF11 EF15 HH01 HH11

Claims (6)

[Claims] In a training system for an echo canceller for multicarrier transmission in which a downstream transmission band is wider than an upstream reception band, data is used to form a line echo cancel signal based on a signal arranged on a transmission carrier. An echo canceller for performing subtraction processing on the reception data; and a transmission band divided into reception band widths, and a signal in which training data is arranged on a transmission carrier for each divided transmission band is output to the echo canceller. A training system for an echo canceller, comprising: a training data generator for training the echo canceller. 2. The method of multi-carrier transmission is ADS.
The echo canceller training system according to claim 1, wherein the training system is an L system. 3. The echo canceller according to claim 1, wherein the echo canceller receives the signal in the frequency domain from the training generator, and includes a 1-tap filter having a complex coefficient prepared for each carrier. A time-domain echo canceller configured to receive the time-domain signal from the training generator and configured by an FIR filter,
The tap coefficient of the time-domain echo canceller is calculated by performing an inverse fast Fourier transform on the tap coefficient obtained by the frequency-domain echo canceller.
The training system for an echo canceller described in 1. 4. The echo canceller according to claim 3, wherein an initial value calculating circuit is provided in the echo canceller, and the initial value calculating circuit calculates an initial value of a tap coefficient of the frequency domain echo canceller. Echo canceller training system. 5. A time domain correction unit is provided between the frequency domain echo canceller and the time domain echo canceller, wherein the time domain correction unit corresponds to a Nyquist reception carrier in a transmission carrier of a divided transmission band. 4. The echo canceller training system according to claim 3, wherein the tap coefficient is corrected due to the following. 6. A training method of an echo canceller for multicarrier transmission in which a downstream transmission band is wider than an upstream reception band, wherein a data echo cancellation signal is formed based on a signal arranged on a transmission carrier. Subtracting the reception data from the received data; dividing the transmission band into the width of the reception band; outputting a signal in which training data is allocated to transmission carriers for each of the divided transmission bands to the echo canceller; Training the echo canceller.