JP2006014006A - Adsl modem apparatus and synchronization establishing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of an abnormal end caused by the impossibility of establishing symbol synchronization because of the influence of a radio wave of medium frequency broadcasting. <P>SOLUTION: In this ADSL modem apparatus provided with a processor 20 for calculating an impulse response (impulse (t)) of a communication line on the basis of Y (ω) calculated from a particular signal (REVERB signal) exchanged before data communication and detecting a peak position of the impulse response (impulse (t)) and an FFT (fast Fourier transform) part 27 for applying fast Fourier transform processing to the prescribed number of sampling data from the peak position of the impulse response (impulse (t)) of the communication line, the processor 20 uses gain in a frequency band that is not used in the medium frequency broadcasting in the particular signal (REVERB signal) to calculate the impulse response (impulse (t)) of the communication line. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ADSL modem apparatus and a synchronization establishment method for establishing symbol synchronization without being affected by a medium wave.

  In recent years, an ADSL service that enables simultaneous use of a high-speed Internet connection service and a conventional telephone service using an existing telephone line has been rapidly spreading. In such an ADSL service, it is necessary to establish symbol synchronization in an initialization sequence according to the G.lite or G.dmt recommendation before starting actual data communication. The establishment of this symbol synchronization is performed by a terminal device (ATU-R) installed in a home or the like, and is usually performed using a REVERB signal received from a switching center side device (ATU-C). This is clearly described in the recommendation that the REVERB signal includes carriers from # 32 to # 127, or # 32 to # 255, and what signals are sent from ATU-C. This is because it is convenient for use in establishing symbol synchronization.

In the above G.lite or G.dmt recommendation, ANNEX. Is determined according to the communication environment of each country (or region) regarding the initialization establishment method. A, ANNEX. B, ANNEXC, etc. are recommended. Of these, ANNEX. Intended mainly for use in Japan. In the case of the C specification, synchronization called hyperframe is established in order to reduce the influence of ISDN noise, but a synchronization adjustment method that prevents the occurrence of abnormal termination due to losing sight of the hyperframe break has been proposed. (For example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 2004-007270

  However, in the conventional ADSL service, depending on the area where the terminal device is installed, the radio wave of the medium wave broadcast represented by the so-called AM broadcast may become an obstacle in the existing telephone line. In such a region, there is a problem that symbol synchronization cannot be established between ATU-R and ATU-C, and abnormal termination occurs without normal communication.

  The present invention has been made in view of the above circumstances, and an ADSL modem apparatus and synchronization that can prevent the occurrence of abnormal termination due to the inability to establish symbol synchronization due to the influence of radio waves of medium wave broadcasting It aims to provide an establishment method.

  The present invention provides control means for calculating an impulse response of a communication line based on a specific signal exchanged before data communication and detecting a peak position of the impulse response, and sampling a predetermined number of times from the peak position of the impulse response of the communication line. In an ADSL modem apparatus, comprising an arithmetic means for performing a fast Fourier transform process on data, the control means calculates an impulse response of the communication line using a gain in a frequency band that is not used in medium wave broadcasting among specific signals. It is what I did.

  According to the present invention, it is possible to prevent occurrence of abnormal termination due to failure to establish symbol synchronization due to the influence of radio waves of medium wave broadcasting.

  An ADSL modem apparatus according to a first aspect of the present invention includes a control unit that calculates an impulse response of a communication line based on a specific signal exchanged before data communication and detects a peak position of the impulse response; and the communication line And an arithmetic means for performing fast Fourier transform processing on a predetermined number of sampling data from the peak position of the impulse response of the ADSL modem device, wherein the control means is used in medium wave broadcasting among the specific signals The impulse response of the communication line is calculated using a gain in a frequency band that is not used.

  According to this configuration, the control means calculates the impulse response of the communication line using the gain in the frequency band that is not used in the medium wave broadcast among the specific signal, and detects the peak position of the impulse response. Then, symbol synchronization is established by the calculation means performing fast Fourier transform processing on a predetermined number of sampling data from the peak position of the impulse response. For this reason, it is possible to avoid a situation where symbol synchronization cannot be established due to the influence of radio waves of medium wave broadcasting. As a result, it is possible to prevent abnormal termination due to the inability to establish symbol synchronization due to the influence of radio waves of medium wave broadcasting.

  According to a second aspect of the present invention, in the ADSL modem apparatus according to the first aspect, the control means deletes a gain in a frequency band used for the medium wave broadcast from the specific signal, while the medium signal is used for the medium wave broadcast. A configuration is adopted in which an impulse response of the communication line is calculated while maintaining a gain in a frequency band that is not used.

  According to this configuration, the gain in the frequency band used in the medium wave broadcast is deleted from the specific signal, while the gain in the frequency band not used in the medium wave broadcast is maintained. For this reason, it is possible to reliably calculate the impulse response of the communication line by using the gain in the frequency band not used in the medium wave broadcasting.

  According to a third aspect of the present invention, in the ADSL modem apparatus according to the second aspect, the control unit deletes a gain in a frequency band greater than 500 kHz from the specific signal, while obtaining a gain in a frequency band equal to or lower than 500 kHz. A configuration is adopted in which the impulse response of the communication line is calculated while maintaining.

  According to this configuration, the gain in the frequency band higher than 500 kHz is deleted from the specific signal, while the gain in the frequency band lower than 500 kHz is maintained. For this reason, it is possible to reliably calculate the impulse response of the communication line while avoiding the frequency band of 526.5 kHz to 1606.5 kHz that is generally used in medium wave broadcasting.

  According to a fourth aspect of the present invention, in the ADSL modem apparatus according to the first aspect, the control means calculates the impulse response of the communication line using the gain in all frequency bands of the specific signal, When the gain in the frequency band used in the wave broadcasting is larger than the gain in the other frequency band, the impulse response of the communication line is obtained using the gain in the frequency band not used in the medium wave broadcasting among the specific signals. Use a configuration to calculate.

  According to this configuration, the gain in the frequency band used in medium-wave broadcasting is prominent compared to the gain in the other frequency bands, despite the attempt to establish symbol synchronization using a specific signal in the normal procedure. In this case, the impulse response of the communication line is calculated using the gain in the frequency band not used in the medium wave broadcast, and the peak position of the impulse response is detected. Then, symbol synchronization is established by the calculation means performing fast Fourier transform processing on a predetermined number of sampling data from the peak position of the impulse response. For this reason, symbol synchronization can be established according to a normal procedure when it is not affected by the radio waves of the medium wave broadcast, while avoiding the situation where the symbol synchronization cannot be established due to the influence of the radio waves of the medium wave broadcast. I can.

  According to a fifth aspect of the present invention, in the ADSL modem apparatus according to the first aspect, the control means calculates the impulse response of the communication line using the entire frequency band of the specific signal, and then the counterpart apparatus When the symbol synchronization cannot be established between the communication line and the signal, the impulse response of the communication line is calculated using a gain in a frequency band that is not used in medium wave broadcasting among the specific signal.

  According to this configuration, when symbol synchronization cannot be established despite the attempt to establish symbol synchronization using a specific signal in a normal procedure, the communication line is used with a gain in a frequency band that is not used in medium wave broadcasting. And the peak position of the impulse response is detected. Then, symbol synchronization is established by the calculation means performing fast Fourier transform processing on a predetermined number of sampling data from the peak position of the impulse response. For this reason, symbol synchronization can be established according to a normal procedure when it is not affected by the radio waves of the medium wave broadcast, while avoiding the situation where the symbol synchronization cannot be established due to the influence of the radio waves of the medium wave broadcast. I can.

  According to a sixth aspect of the present invention, in the ADSL modem apparatus according to the first aspect, the specific signal is a REVERB signal.

  According to this configuration, it is possible to prevent abnormal termination due to failure to establish symbol synchronization due to the influence of the radio wave of the medium wave broadcast using the REVERB signal used in the initialization procedure.

  The synchronization establishment method according to the seventh aspect of the present invention calculates an impulse response of a communication line based on a specific signal exchanged before data communication, detects a peak position of the impulse response, and detects the impulse of the communication line. A synchronization establishment method for establishing symbol synchronization by performing a fast Fourier transform process on a predetermined number of sampling data from a peak position of a response, using a gain in a frequency band that is not used in medium wave broadcasting among the specific signal Thus, the impulse response of the communication line is calculated.

  An eighth aspect of the present invention is the synchronization establishment method according to the seventh aspect, wherein the gain in the frequency band used in the medium wave broadcasting is deleted from the specific signal, while the frequency signal not used in the medium wave broadcasting is deleted. The impulse response of the communication line is calculated while maintaining the gain.

  According to a ninth aspect of the present invention, in the synchronization establishment method according to the eighth aspect, the gain in the frequency band higher than 500 kHz is deleted from the specific signal, while the gain in the frequency band lower than 500 kHz is maintained. The impulse response of the line is calculated.

  According to a tenth aspect of the present invention, in the synchronization establishment method according to the seventh aspect, the impulse response of the communication line is calculated using gains in all frequency bands of the specific signal, and then used in medium-wave broadcasting. The impulse response of the communication line is calculated using the gain in the frequency band that is not used in medium wave broadcasting among the specific signal when the gain in the frequency band is higher than the gain in the other frequency band. .

  According to an eleventh aspect of the present invention, in the synchronization establishment method according to the seventh aspect, after calculating the impulse response of the communication line using the entire frequency band of the specific signal, the symbol is exchanged with the counterpart device. When synchronization cannot be established, an impulse response of the communication line is calculated using a gain in a frequency band that is not used in medium wave broadcasting among the specific signal.

  According to a twelfth aspect of the present invention, in the synchronization establishment method according to the seventh aspect, the specific signal is a REVERB signal.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of a communication system on a terminal device (hereinafter referred to as “ATU-R”) side installed in a home or the like to which the present invention is applied.

  In the communication system shown in FIG. 1, a public line network or an equivalent line network (hereinafter referred to as “line”) is connected to an ADSL modem apparatus 2 via a splitter 1, and a user terminal 3 is connected to the ADSL modem apparatus 2. It is connected. In addition, when the user terminal 3 and the telephone 4 are used on one line, the splitter 1 is necessary. However, if the telephone 4 is not used, the splitter 1 is not necessary. It is also possible to configure the user terminal 3 to incorporate the ADSL modem apparatus 2.

  The ADSL modem apparatus 2 includes a transceiver 11 that executes ADSL communication and a host 12 that controls the overall operation including the transceiver 11. The line side end of the transceiver 11 is constituted by an analog circuit via an analog front end (hereinafter referred to as “AFE”). A driver 15 is connected to the DA converter of the AFE 13 via an analog filter 14, and an analog signal amplified by the driver 15 is sent to a line via a hybrid 16. An analog signal coming from the line is received by the receiver 17 via the hybrid 16 and input to the AD conversion unit of the AFE 13 via the analog filter 18. The AFE 13 outputs the sampling data output from the AD conversion unit to the transceiver 11.

  FIG. 2 is a functional block diagram of the transceiver 11 included in the ADSL modem apparatus 2. The processor 20 has a function of executing a handshake procedure and an initialization procedure and executing communication control during data communication (show time).

  The transmission side of the transceiver 11 includes a Reed-Solomon encoding unit 21 for adding redundant bits for error checking, an interleaving unit 22 for rearranging data to enable correction for burst errors during Reed-Solomon decoding, and a trellis code A trellis encoding unit 23 that performs convolution of data by conversion, a tone ordering unit 24 that allocates the number of bits for each carrier, a constellation encoding unit 25 that allocates the phase of transmission data on constellation coordinates, and constellation encoded. The IFFT unit 26 performs inverse fast Fourier transform (hereinafter referred to as “IFFT”) on the received data.

  The receiving side of the transceiver 11 performs fast Fourier transform (hereinafter referred to as FFT) on the sampling data of the received signal, decodes the data from the constellation of the FFT output signal, and corrects the phase on the constellation coordinates. Constellation decoding / FEQ unit 28, tone deordering unit 29 for restoring data allocated to each carrier subjected to tone ordering on the transmission side, Viterbi decoding unit 30 for Viterbi decoding received data, rearrangement on the transmission side The deinterleaving unit 31 restores the received data and the Reed-Solomon decoding unit 32 that deletes redundant bits added on the transmission side. The RAM 33 is a work area of the processor 20 and is used when a handshake procedure and an initialization procedure are executed. The transceiver 11 is connected to the host 12 via a host interface (I / F) 34.

  Here, a symbol synchronization method at the time of execution of the initialization procedure by the processor 20 will be described with reference to FIG. FIG. 3 is a functional block diagram for explaining a symbol synchronization method when the initialization procedure by the processor 20 is executed.

  Symbol synchronization at the time of execution of the initialization procedure by the processor 20 is performed using the REVERB signal received by the FFT unit 27. At that time, the processor 20 obtains X (ω), which is a signal obtained by inverse fast Fourier transform of a known REVERB signal, and Y (ω), which is a signal obtained by fast Fourier transform of the REVERB signal actually received via the line. To establish symbol synchronization.

More specifically, the processor 20 acquires X (ω) obtained by extracting the REVERB signal stored in the RAM 33 and performing inverse fast Fourier transform processing, and receives Y (ω) from the FFT unit 27. . Since the REVERB signal is a known signal described in the recommendation, in the ADSL modem apparatus 2 according to the present embodiment, X (ω) calculated from the REVERB signal is stored in the RAM 33 in advance. . The processor 20 then
Z (ω) = Y (ω) / X (ω)
And the impulse response is Impulse (t),
Impulse (t) = inversesFFT (Z (ω))
Calculate In this way, a so-called impulse response on the line (Impulse (t)) is calculated.

  FIG. 4 is a waveform diagram of the impulse response (Impulse (t)) calculated by the processor 20. The processor 20 detects the peak position of the impulse response (Impulse (t)) shown in FIG. And the signal (henceforth a "peak notification signal") which notifies the peak position of the impulse response (Impulse (t)) to the buffer 40 which the FFT part 27 has is sent out.

  The buffer 40 normally stores 512 pieces of sampling data input from the AFE 13. When 512 pieces of sampling data are stored, the FFT unit 27 performs fast Fourier transform processing. However, when receiving the peak notification signal, the buffer 40 stores 512 sampling data again from the peak position of the impulse response (Impulse (t)) included in the buffer 40. Then, fast synchronization transform processing is performed by the FFT unit 27 on 512 pieces of sampling data with reference to the peak position of the impulse response (Impulse (t)), thereby establishing symbol synchronization. Become.

  Normally, symbol synchronization is established by the method described above, but if symbol synchronization is not established by this method, there is a possibility that the radio wave of the medium wave broadcasting is an obstacle. For this reason, the processor 20 attempts to establish symbol synchronization using a portion of Y (ω) received from the FFT unit 27 that corresponds to a frequency band that is not affected by radio waves of medium wave broadcasting.

Specifically, the processor 20 forcibly inserts “0” into the gain of the frequency band that can be affected by the radio wave of the medium wave broadcast among Y (ω) received from the FFT unit 27. Using,
Z0 (ω) = Y0 (ω) / X (ω)
Calculate Then, the impulse response is set as Impulse (t),
Impulse (t) = inversesFFT (Z0 (ω))
Calculate In this way, a so-called impulse response on the line (Impulse (t)) is calculated.

  After calculating the impulse response (Impulse (t)), the peak position of the impulse response (Impulse (t)) is detected and the symbol synchronization is established in the same manner as described above.

  Generally, a frequency band of 526.5 kHz to 1606.5 kHz is used for medium wave broadcasting. Therefore, for example, the processor 20 forcibly inserts “0” into the gain of Y (ω) received from the FFT unit 27 in the frequency band higher than 500 kHz, while the FFT unit 27 in the frequency band of 500 kHz or less. Y0 (ω) can be obtained by maintaining the gain of Y (ω) received from the above. Then, an impulse response (Impulse (t)) is calculated using Y0 (ω).

  Thus, the gain in the frequency band higher than 500 kHz is deleted, while the gain in the frequency band lower than 500 kHz is maintained. Therefore, it is possible to reliably calculate the impulse response (Impulse (t)) of the line while avoiding the frequency band of 526.5 kHz to 1606.5 kHz that is generally used in medium wave broadcasting.

  In this embodiment, 500 kHz is used as an example of the boundary frequency at which “0” is forcibly inserted into the gain of Y (ω), but the present invention is not limited to this. That is, any frequency may be selected as long as “0” can be inserted into the gain of the frequency band that can be affected by radio waves of medium wave broadcasting.

  Hereinafter, an operation when establishing symbol synchronization in ADSL modem apparatus 2 according to the present embodiment will be described with reference to FIG.

  When establishing symbol synchronization, the processor 20 first obtains X (ω) obtained by extracting a known REVERB signal from the RAM 33 and performing inverse fast Fourier transform processing (ST501). Thereafter, Y (ω) obtained by performing fast Fourier transform processing on the received REVERB signal is acquired from the FFT unit 27 (ST502).

Next, the impulse response (Impulse (t)) of the line is calculated using X (ω) and Y (ω) (ST503). In particular,
Z (ω) = Y (ω) / X (ω)
After calculating
Impulse (t) = inversesFFT (Z (ω))
To calculate the impulse response (Impulse (t)).

  After calculating the impulse response (Implus (t)), the processor 20 receives a received signal in a frequency band other than that in a frequency band used in medium wave broadcasting (hereinafter referred to as “medium frequency band”). It is determined whether or not the projection is larger than the gain (ST504). That is, it is determined whether noise (hereinafter referred to as “medium wave noise”) due to radio waves of medium wave broadcasting appears in the gain of the received signal.

  If the gain of the received signal in the medium wave frequency band does not protrude, the processor 20 detects the peak position of the impulse response (Impulse (t)) and determines whether symbol synchronization has been established (ST505). ).

  If symbol synchronization can be established, the mobile terminal shifts to data communication (show time) (ST506). Thereafter, when the data communication instructed by the PC 3 is finished, the processor 20 finishes the process.

  On the other hand, if it is determined in ST504 that the gain of the received signal in the medium frequency band is prominent, or if it is determined in ST505 that symbol synchronization cannot be established, the processor 20 performs the FFT unit 27. Y0 (ω) is calculated based on Y (ω) acquired from (ST507).

  Specifically, “0” is forcibly inserted into the gain of Y (ω) received from the FFT unit 27 in the frequency band greater than 500 kHz, while Y received from the FFT unit 27 in the frequency band of 500 kHz or less. Y0 (ω) is obtained by maintaining (ω) as it is.

If Y0 (ω) is calculated, the processor 20 returns the process to ST503, and again calculates the impulse response (Impulse (t)) of the line. However, when calculating the impulse response (Impulse (t)) of the line through the processing of ST507, the processor 20
Z0 (ω) = Y0 (ω) / X (ω)
After calculating
Impulse (t) = inversesFFT (Z0 (ω))
To calculate the impulse response (Impulse (t)).

  Then, in the same manner as described above, the shift to data communication is determined through determining whether the gain of the received signal in the medium frequency band is protruding or whether symbol synchronization has been established (ST504 to ST506).

  If symbol synchronization is established after calculating the impulse response (Impulse (t)) of the line using Y0 (ω), the subsequent data communication is also affected by the radio wave of the medium wave broadcast. Conceivable. However, even in this case, when symbol synchronization is established, the tone ordering unit (24) of the ADSL modem apparatus (2) on the exchange station (ATU-C) side is affected by the radio wave of the medium wave broadcast. The number of bits allocated to the carrier is adjusted. For this reason, the situation that data communication cannot be performed under the influence of the radio wave of the medium wave broadcasting does not occur.

  As described above, according to the ADSL modem apparatus 2 according to the present embodiment, the impulse of the line using the gain in the frequency band that is not used in the medium wave broadcasting among Y (ω) calculated from the REVERB signal received by the processor 20. The response (Impulse (t)) is calculated, and the peak position of the impulse response (Impulse (t)) is detected. Then, the FFT unit 27 performs fast Fourier transform processing on 512 pieces of sampling data from the peak position of the impulse response (Impulse (t)), thereby establishing symbol synchronization. For this reason, it is possible to avoid a situation in which symbol synchronization cannot be established due to the influence of radio waves of medium wave broadcasting. As a result, it is possible to prevent abnormal termination due to the inability to establish symbol synchronization due to the influence of radio waves of medium wave broadcasting.

  In particular, according to the ADSL modem apparatus 2 according to the present embodiment, the gain in the frequency band used in medium wave broadcasting is deleted from Y (ω) calculated from the REVERB signal received by the processor 20, Gain in a frequency band not used in medium wave broadcasting is maintained. For this reason, the impulse response (Impulse (t)) of the communication line can be reliably calculated using the gain in the frequency band that is not used in the medium wave broadcasting.

  In addition, according to the ADSL modem apparatus 2 according to the present embodiment, although Y (ω) calculated from the REVERB signal received by the processor 20 is used to establish symbol synchronization in a normal procedure, If the gain in the frequency band used in medium-wave broadcasting is prominent compared to the gain in other frequency bands, or if symbol synchronization cannot be established, the line impulse is used with the gain in the frequency band not used in medium-wave broadcasting. A response (Impulse (t)) is calculated, and the peak position of the impulse response is detected. Then, symbol synchronization is established by the calculation means performing fast Fourier transform processing on a predetermined number of sampling data from the peak position of the impulse response. For this reason, symbol synchronization can be established according to a normal procedure when it is not affected by the radio waves of the medium wave broadcast, while avoiding the situation where the symbol synchronization cannot be established due to the influence of the radio waves of the medium wave broadcast. I can.

  In the above description, when calculating the impulse response (Impulse (t)), X (ω) calculated from the known REVERB signal and Y calculated from the REVERB signal actually received via the line. (Ω) is used. However, the calculation of the impulse response (Impulse (t)) is not limited to this REVERB signal. That is, any signal may be used as long as it is a signal recognized together between the switching center apparatus (ATU-C) and the terminal apparatus (ATU-R) installed in the home.

  In the above description, the ADSL modem apparatus is described as an example. However, the present invention can be similarly applied to an xDSL modem applied to other types of DSL.

  According to the ADSL modem apparatus and the synchronization establishment method according to the present invention, it is possible to prevent the abnormal termination due to the inability to establish the symbol synchronization due to the influence of the radio wave of the medium wave broadcast, and it is more highly usable. This is useful in that it can provide an ADSL service.

The figure which shows schematic structure of the communication system by the side of the terminal device installed in the house etc. where the ADSL modem apparatus which concerns on one embodiment of this invention is applied Functional block diagram of transceiver of the communication system Functional block diagram for explaining a method of symbol synchronization during execution of an initialization procedure by the processor of the transceiver Waveform diagram of impulse response calculated by the transceiver processor Flow chart for explaining the operation when establishing symbol synchronization in the ADSL modem apparatus according to the present embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Splitter 2 ADSL modem apparatus 3 User terminal 4 Telephone 11 Transceiver 12 Host 13 AFE
DESCRIPTION OF SYMBOLS 14 Analog filter 15 Driver 16 Hybrid 17 Receiver 18 Analog filter 20 Processor 21 Reed-Solomon encoding part 22 Interleaving part 23 Trellis encoding part 24 Tone ordering part 25 Constellation encoding part 26 IFFT part 27 FFT part 28 Constellation decoding / FEQ unit 29 Tone deordering unit 30 Viterbi decoding unit 31 Deinterleaving unit 32 Reed-Solomon decoding unit 33 RAM
40 buffers

Claims (12)

  Control means for calculating an impulse response of a communication line based on a specific signal exchanged before data communication and detecting a peak position of the impulse response, and a predetermined number of sampling data from the peak position of the impulse response of the communication line And an arithmetic means for performing a fast Fourier transform process, wherein the control means uses the gain in a frequency band that is not used in medium-wave broadcasting among the specific signal, and the impulse response of the communication line ADSL modem apparatus characterized by calculating   The control means deletes the gain in the frequency band used in the medium wave broadcast from the specific signal, and calculates the impulse response of the communication line while maintaining the gain in the frequency band not used in the medium wave broadcast. The ADSL modem apparatus according to claim 1.   3. The control unit is configured to calculate an impulse response of the communication line while deleting a gain in a frequency band greater than 500 kHz from the specific signal while maintaining a gain in a frequency band of 500 kHz or less. ADSL modem apparatus as described.   The control means calculates the impulse response of the communication line using the gain in the entire frequency band of the specific signal, and then compares the gain in the frequency band used in medium wave broadcasting with the gain in the other frequency bands. 2. The ADSL modem apparatus according to claim 1, wherein an impulse response of the communication line is calculated using a gain in a frequency band that is not used in medium-wave broadcasting among the specific signal when protruding.   The control means calculates the impulse response of the communication line using the entire frequency band of the specific signal, and then, when symbol synchronization cannot be established with the counterpart device, the control means uses medium-wave broadcasting of the specific signal. The ADSL modem apparatus according to claim 1, wherein an impulse response of the communication line is calculated using a gain in a frequency band that is not used.   2. The ADSL modem apparatus according to claim 1, wherein the specific signal is a REVERB signal.   The impulse response of the communication line is calculated based on a specific signal exchanged before data communication, the peak position of the impulse response is detected, and a high speed is obtained for a predetermined number of sampling data from the peak position of the impulse response of the communication line. A synchronization establishment method for establishing symbol synchronization by performing Fourier transform processing, characterized in that an impulse response of the communication line is calculated using a gain in a frequency band that is not used in medium wave broadcasting among the specific signal. How to establish synchronization.   The impulse response of the communication line is calculated while removing the gain in the frequency band used in the medium wave broadcast from the specific signal, while maintaining the gain in the frequency band not used in the medium wave broadcast. Item 8. The synchronization establishment method according to item 7.   9. The synchronization establishment method according to claim 8, wherein an impulse response of the communication line is calculated while deleting a gain in a frequency band greater than 500 kHz from the specific signal while maintaining a gain in a frequency band of 500 kHz or less. .   When the impulse response of the communication line is calculated using the gain in the entire frequency band of the specific signal, and then the gain in the frequency band used in the medium-wave broadcasting protrudes compared with the gain in the other frequency bands 8. The synchronization establishment method according to claim 7, wherein an impulse response of the communication line is calculated using a gain in a frequency band that is not used in medium wave broadcasting among the specific signal.   After calculating the impulse response of the communication line using the entire frequency band of the specific signal, in a frequency band that is not used in medium wave broadcasting among the specific signal when symbol synchronization cannot be established with the counterpart device 8. The synchronization establishment method according to claim 7, wherein an impulse response of the communication line is calculated using a gain.   8. The synchronization establishment method according to claim 7, wherein the specific signal is a REVERB signal.

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