JP2005072781A - Adsl modem and its communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the interference of an upstream signal with a downstream signal due to the skirt phenomenon of the upstream signal, thereby enabling the long distant ADSL communication. <P>SOLUTION: The ADSL modem receives a designated carrier predetermined by communication standards according to a hand-shake procedure, and revises a phase inversion system and employs the phase inversion system after the revision to transmit particular signals such as a GALF signals (C-GALF1) and a FLAG signal (R-FLAG1, C-FLAG2), the revised phase inversion system being configured such that signals ordinarily subjected to phase inversion outputted in the particular signals subjected to phase inversion by using the designated carrier are not phase-inverted, while the signals ordinarily outputted without phase inversion are phase-inverted. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ADSL modem apparatus and a communication method therefor.

  In ADSL communication, ADSL modem devices are attached to both ends of a subscriber line connecting a telephone office (center side) and a subscriber's home (remote side), and high-speed data communication is realized between the ADSL modem devices. However, in ADSL communication, a band of about several tens of KHz to 1 MKHz is used as a use band, and therefore, a high range attenuation factor is large, so that a signal communication distance is greatly limited.

In order to cope with such a limitation, the gain characteristics of the signals received in the initialization procedure are detected by the ADSL modem apparatuses on both the center side and the remote side, the gain characteristics are notified to each other, and the gain notified from the partner side A technique has been disclosed in which the signal transmission distance can be extended by correcting the gain characteristics of the subsequent transmission signal based on the characteristics, even if the attenuation in the high band is large (see, for example, Patent Document 1).
JP 2003-87352 A (FIGS. 4 and 5)

  However, even if the conventional technique is used, if the handshake procedure performed before the initialization procedure cannot be appropriately performed, a communication method used after the initialization procedure (for example, G. dmt or G.lite) cannot be selected between the center side and the remote side, and there is a problem that communication cannot be executed.

  For example, G. In Annex A of hs, the handshake procedure is executed using the carriers of index # 9, 17, 25 in the upstream and the carriers of index # 40, 56, 64 in the downstream. G. In hs Annex A, a signal such as FLAG whose phase is inverted is exchanged between the center side and the remote side. This FLAG signal is composed of a bit string “01111110”, and phase inversion occurs at the position “1”. Therefore, the phase inversion is repeatedly performed. At this time, the downstream carrier (index # 40, 56, 64) is buried by the skirt phenomenon of the upstream carrier (index # 9, 17, 25). Things can happen. As the communication distance increases, the amount of attenuation of the downstream carrier (index # 32, 64, 128) set to a high frequency increases, and the situation in which reception is difficult becomes significant.

  The present invention has been made in view of such problems, and an ADSL modem apparatus capable of reducing long-distance communication by reducing interference with downstream carriers due to upstream carrier skirt phenomenon, and the same An object is to provide a communication method.

  The present invention receives a designated carrier defined in a communication standard in advance by a handshake procedure, changes a phase inversion method normally used in a specific signal transmitted by phase inversion using the designated carrier, and The specific signal is transmitted using the phase inversion method.

  According to the ADSL modem apparatus and the communication method thereof according to the present invention, it is possible to reduce the interference with the downstream carrier due to the skirt phenomenon of the upstream carrier and to enable long-distance communication.

  An ADSL modem apparatus according to a first aspect of the present invention includes a transmission / reception unit that transmits / receives a designated carrier defined in a communication standard in advance by a handshake procedure, and a specific signal that is transmitted with phase inversion using the designated carrier. And a changing unit that changes the phase inversion method that is normally used.

  According to this configuration, the specific signal transmitted with phase inversion using the designated carrier is transmitted by changing the normally used phase inversion method. Therefore, when a FLAG signal is transmitted as a specific signal by a normal phase inversion method, a situation in which a skirt phenomenon occurs due to repeated phase inversion can be avoided. For this reason, it is possible to reduce interference with the downstream carrier due to the skirt phenomenon of the upstream carrier. As a result, even if the communication distance with the counterpart ADSL modem apparatus 2 is large, the handshake procedure can be executed reliably, so that long-distance communication can be performed.

  According to a second aspect of the present invention, in the ADSL modem apparatus according to the first aspect, the changing means does not invert the signal output by normal phase inversion in the specific signal, but does not invert the normal phase. A configuration in which the phase of the output signal is inverted is adopted.

  According to this configuration, the signal output by normal phase inversion in the specific signal is not phase-inverted, and the signal output without normal phase inversion is phase-inverted. For example, the bit string “01111110 constituting the FLAG signal” In “,” the phase inversion is normally repeated 6 times at the position “1”, but only the phase inversion is performed at the position “0”. Therefore, it is possible to avoid a situation in which a skirt phenomenon occurs due to repeated phase inversion. For this reason, it is possible to reduce interference with the downstream carrier due to the skirt phenomenon of the upstream carrier. As a result, even if the communication distance with the counterpart ADSL modem apparatus 2 is large, the handshake procedure can be executed reliably, so that long-distance communication can be performed.

  According to a third aspect of the present invention, in the ADSL modem apparatus according to the first or second aspect, the specific signal includes a GALF signal and a FLAG signal transmitted using the designated carrier.

  According to this configuration, the FLAG signal and the GALF signal transmitted using the designated carrier are transmitted by changing the normal phase inversion method. For this reason, in the bit string “01111110” constituting the FLAG signal, the phase inversion is normally repeated 6 times at the position “1”, but only the phase inversion is required at the position “0”. It becomes. Therefore, it is possible to avoid a situation in which a skirt phenomenon occurs due to repeated phase inversion. For this reason, it is possible to reduce interference with the downstream carrier due to the skirt phenomenon of the upstream carrier. As a result, even if the communication distance with the counterpart ADSL modem apparatus 2 is large, the handshake procedure can be executed reliably, so that long-distance communication can be performed.

  According to a fourth aspect of the present invention, in the ADSL modem apparatus according to the third aspect, the ADSL modem apparatus is disposed on the remote side, and the changing means is configured to change the phase of the FLAG signal according to the phase inversion method of the GALF signal transmitted from the center side. A configuration for determining whether to change the inversion method is adopted.

  According to this configuration, it is determined whether to change the phase inversion method of the FLAG signal according to the phase inversion method of the GALF signal transmitted from the center side. Therefore, the handshake procedure can be executed according to the phase inversion method selected by the center side.

  According to a fifth aspect of the present invention, in the ADSL modem apparatus according to the fourth aspect, when the phase inversion method of the GALF signal transmitted from the center side is a normal phase inversion method, the changing means When the phase inversion method of the GALF signal is changed from the normal phase inversion method without changing the phase inversion method, the configuration of changing the phase inversion method of the FLAG signal is adopted.

  According to this configuration, when the phase inversion method of the GALF signal transmitted from the center side is the normal phase inversion method, the phase inversion method of the FLAG signal is not changed, and the phase inversion method of the GALF signal is the normal phase inversion method. When the method is changed from the method, the phase inversion method of the FLAG signal is changed. For this reason, the handshake procedure can be executed in accordance with the phase inversion method of the GALF signal transmitted from the center side.

  According to a sixth aspect of the present invention, in the ADSL modem apparatus according to the third aspect, the ADSL modem apparatus is arranged on the center side, and the changing means is responsive to the reception level of the TONE signal transmitted from the remote side using the designated carrier. Thus, a configuration for determining whether to change the phase inversion method of the GALF signal is adopted.

  According to this configuration, it is determined whether to change the phase inversion method of the GALF signal according to the reception level of the TONE signal transmitted from the remote side using the designated carrier. On the other hand, the reception level of the TONE signal decreases when the communication distance with the remote ADSL modem apparatus is large. Therefore, the phase inversion method can be selected according to the communication distance with the remote ADSL modem apparatus.

  According to a seventh aspect of the present invention, in the ADSL modem apparatus according to the sixth aspect, the changing means includes a phase inversion method for the GALF signal when the attenuation value of the signal energy of the TONE signal is lower than a preset attenuation value. If the attenuation value of the signal energy of the TONE signal exceeds the preset attenuation value, the configuration of changing the phase inversion method of the GALF signal is adopted.

  According to this configuration, when the attenuation value of the signal energy of the TONE signal is lower than the preset attenuation value, the phase inversion method of the GALF signal is not changed, and the attenuation value of the signal energy of the TONE signal is set to the preset attenuation value. Is exceeded, the phase inversion method of the GALF signal is changed. For this reason, when the communication distance is larger than the communication distance corresponding to the preset attenuation value, the handshake procedure can be executed by changing the phase inversion method.

  According to an eighth aspect of the present invention, in the ADSL modem apparatus according to any one of the first to seventh aspects, the changing means changes the phase inversion method normally used in the specific signal and The transmission system is changed to start-stop synchronization.

  According to this configuration, the phase inversion method that is normally used in the specific signal is changed, and the transmission method after the specific signal is changed to the asynchronous mode. When a specific signal is transmitted in the asynchronous manner, “0” indicating the start of data is output before the specific signal. For this reason, compared with the case where only the phase inversion method is changed, it is possible to easily determine the specific signal output with the phase inversion, and to execute the handshake procedure more reliably.

  In the communication method of the ADSL modem apparatus according to the ninth aspect of the present invention, in the specific signal transmitted by receiving the designated carrier determined in advance by the communication standard in the handshake procedure and inverting the phase using the designated carrier. A normally used phase inversion method is changed, and the specific signal is transmitted using the phase inversion method after the change.

  According to this method, the specific signal transmitted with phase inversion using the designated carrier is transmitted by changing the normally used phase inversion method. Therefore, when a FLAG signal is transmitted as a specific signal by a normal phase inversion method, a situation in which a skirt phenomenon occurs due to repeated phase inversion can be avoided. For this reason, it is possible to reduce interference with the downstream carrier due to the skirt phenomenon of the upstream carrier. As a result, even if the communication distance with the counterpart ADSL modem apparatus 2 is large, the handshake procedure can be executed reliably, so that long-distance communication can be performed.

  According to a tenth aspect of the present invention, in the communication method of the ADSL modem apparatus according to the ninth aspect, when changing the phase inversion method of the specific signal, the phase of the signal output by normal phase inversion in the designated carrier is changed. While not inverted, the phase of a signal output without normal phase inversion is inverted.

  According to this method, a signal output after normal phase inversion in a specific signal is not phase-inverted, and a signal output without normal phase inversion is phase-inverted. For example, the bit string “01111110 constituting the FLAG signal” In “,” the phase inversion is normally repeated 6 times at the position “1”, but only the phase inversion is performed at the position “0”. Therefore, it is possible to avoid a situation in which a skirt phenomenon occurs due to repeated phase inversion. For this reason, it is possible to reduce interference with the downstream carrier due to the skirt phenomenon of the upstream carrier. As a result, even if the communication distance with the counterpart ADSL modem apparatus 2 is large, the handshake procedure can be executed reliably, so that long-distance communication can be performed.

  In the communication method of the ADSL modem apparatus according to the eleventh aspect of the present invention, in a specific signal transmitted by receiving a designated carrier determined in advance by a communication standard in a handshake procedure and performing phase inversion using the designated carrier. In addition to changing the normally used phase inversion method, the transmission method after the specific signal is changed to start-stop synchronization, and the specific signal is transmitted by start-stop synchronization using the phase inversion method after the change.

  According to this method, the specific signal transmitted with phase inversion using the designated carrier is transmitted by changing the normally used phase inversion method. Therefore, when a FLAG signal is transmitted as a specific signal by a normal phase inversion method, a situation in which a skirt phenomenon occurs due to repeated phase inversion can be avoided. For this reason, it is possible to reduce interference with the downstream carrier due to the skirt phenomenon of the upstream carrier. As a result, even if the communication distance with the counterpart ADSL modem apparatus 2 is large, the handshake procedure can be executed reliably, so that long-distance communication can be performed.

  Further, according to this method, the phase inversion method normally used in the specific signal is changed, and the transmission method after the specific signal is changed to the start-stop synchronization method. When a specific signal is transmitted in the asynchronous manner, “0” indicating the start of data is output before the specific signal. For this reason, compared with the case where only the phase inversion method is changed, it is possible to easily determine the specific signal output with the phase inversion, and to execute the handshake procedure more reliably.

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

(Embodiment 1)
FIG. 1 is a diagram showing a schematic configuration of a remote (ATU-R) communication system to which an ADSL modem apparatus according to Embodiment 1 of the present invention is applied. In the communication system shown in the figure, a public line network or an equivalent line network (hereinafter referred to as a 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. ing. 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. Further, the user terminal 3 can be configured to incorporate the ADSL modem apparatus 2.

  The ADSL modem apparatus 2 includes a transceiver 11 that executes a handshake procedure, which will be described later, 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) 13. 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. The processor 20 is a part having a function of executing a handshake procedure before the start of 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 RAM 33 stores a carrier table to be described later. The transceiver 11 is connected to the host 12 via a host interface (I / F) 34.

  The ADSL modem apparatus 2 on the center (HSTU-C) side is connected to the ADSL modem apparatus 2 via a metallic cable. The ADSL modem apparatus on the center side has the same configuration as the ADSL modem apparatus 2 described above. Hereinafter, the ADSL modem apparatus on the center side will be described using the same reference numeral (2). Note that the telephone 4 is not present on the center side when the exchange is installed by a communication carrier.

  The ADSL modem apparatus 2 on the center side and the remote side according to the first embodiment includes G. A handshake procedure in which the phase inversion method of a specific signal exchanged in the handshake procedure by hs Annex A is changed as necessary is executed.

  Further, in the handshake procedure, only the phase inversion method of a specific signal is changed, and a signal exchanged between the ADSL modem apparatus 2 on the center side and the remote side is a normal G.P. This is the same as in the handshake procedure by hs AnnexA. Here, the normal G.P. The handshake procedure by hs Annex A will be described. FIG. It is a sequence diagram for demonstrating the handshake procedure by AnnexA of hs.

  G. In hs Annex A, carriers with index # 9, 17, 25 are used upstream from the remote side to the center side, and carriers with index # 40, 56, 64 are used downstream from the center side to the remote side. The handshake procedure is then executed.

  As shown in the figure, first, a tone signal is requested from the remote side through a no-signal state (R-SILENT0, C-SILENT1) between the remote side (HSTU-R) and the center side (HSTU-C). R-TONES-REQ to be output. In response to this, a C-TONES signal is output from the center side. When this C-TONES signal is confirmed, R-TONE1 is output from the remote side. In these R-TONES-REQ, C-TONES, and R-TONE1, signals that are not inverted in phase are output.

  When R-TONE1 is confirmed, C-GALF1 is output from the center side. When C-GALF1 is confirmed, R-FLAG1 is output from the remote side. Further, when R-FLAG1 is confirmed, C-FLAG1 is output from the center side. When R-FLAG1 and C-FLAG1 are confirmed on the center side and the remote side, respectively, After exchanging the hs message, the handshake procedure is completed and the procedure proceeds to the initialization procedure.

  Here, C-GALF1 is composed of a bit string “10000001”, and R-FLAG1 and C-FLAG1 are composed of a bit string “01111110”. In these C-GALF1, R-FLAG1, and C-FLAG1, when "1" is transmitted, a signal whose phase is inverted is output.

  FIG. It is a figure which shows the signal waveform in the specific carrier (Upstream: # 9, 17, 25, downstream: # 40, 56, 64) of AnnexA of hs. As shown in FIG. 5A, when “0” is transmitted, a signal whose phase is not inverted is output. On the other hand, as shown in FIG. 5B, when “1” is transmitted, a signal having an inverted phase is output.

  FIG. 5 and FIG. 6 show the spectrum when “0” is transmitted and when “1” is transmitted continuously, respectively. 5 and FIG. 6 show the spectrum of the specific carrier in the upstream in particular, the same spectrum also applies to the specific carrier in the downstream. As shown in FIGS. 5 and 6, when “0” is transmitted, no skirt phenomenon occurs because phase inversion is not performed, but when “1” is transmitted continuously, the phase is not reversed. It can be seen that the skirt phenomenon occurs because of the inversion.

  FIG. It is a figure for demonstrating the output in the signal (C-GALF1, R-FLAG1, and C-FLAG1) which carries out phase inversion in the specific carrier of AnnexA of hs. As shown in the figure, in C-GALF1, “1” is continuously output twice at the maximum, but “1” is not output continuously three times or more. For this reason, the skirt phenomenon by phase inversion does not become a serious problem. However, in R-FLAG1 and C-FLAG1, "1" is always output continuously six times. For this reason, the skirt phenomenon due to phase inversion becomes a serious problem.

  For this reason, in the ADSL modem apparatus 2 according to the first embodiment, the phase inversion method for the signal to be phase inverted is changed as necessary. In other words, the ADSL modem apparatus 2 does not invert the phase for “0” and does not invert the phase for “1” in the phase inversion method in which the phase is inverted for “1” and the phase is not inverted for “0” in the normal case. Change to phase inversion method.

  When the phase inversion method is changed in this way, in C-GALF1, “0” in which phase inversion occurs is always output continuously six times. For this reason, a skirt phenomenon due to phase inversion occurs. However, C-GALF1 has a shorter output time than R-FLAG1 and C-FLAG1. And if R-FLAG1 and C-FLAG1 can be recognized reliably, there exists a situation that a handshake procedure can be performed appropriately. Therefore, the influence on the handshake procedure is small compared to the case where the skirt phenomenon occurs in R-FLAG1 and C-FLAG1. On the other hand, in R-FLAG1 and C-FLAG1, “0” in which phase inversion occurs is continuous twice at the maximum, but “0” is not output continuously three times or more. For this reason, the skirt phenomenon by phase inversion does not become a serious problem.

  As described above, the ADSL modem apparatus 2 according to the first embodiment changes the phase inversion method as necessary and executes the handshake procedure. Hereinafter, the operation in the case of executing the handshake procedure by changing the phase inversion method in the remote side and center side ADSL modem apparatuses 2 will be described. FIG. 8 and FIG. 9 are flowcharts for explaining the operation when the ADSL modem apparatus 2 on the remote side and the center side respectively execute the handshake procedure by changing the phase inversion method. First, the remote ADSL modem apparatus 2 will be described.

  The remote ADSL modem apparatus 2 is a G. When hs is started, first, R-TONES-REQ is transmitted (ST801). When the R-TONES-REQ is confirmed, the ADSL modem apparatus 2 on the center side transmits the C-TONES accordingly, and receives this (ST802). When this C-TONES is confirmed, the remote ADSL modem apparatus 2 transmits R-TONE 1 (ST803). When R-TONE1 is confirmed, the ADSL modem apparatus 2 on the center side transmits C-GALF1 in response to this, and receives this (ST804).

  If C-GALF1 is received, ADSL modem apparatus 2 on the remote side determines whether the phase inversion method in “0” and “1” constituting C-GALF1 has been changed (ST805). That is, it is determined whether a signal whose phase is inverted at “0” is output and a signal whose phase is not inverted is output at “1”.

  If the phase inversion method has been changed, ADSL modem apparatus 2 on the remote side changes the phase inversion method in “0” and “1” constituting R-FLAG 1 and transmits (ST806). That is, a signal whose phase is inverted at “0” is output, and a signal whose phase is not inverted is output at “1”. After receiving C-FLAG1 whose phase inversion method has been changed from the ADSL modem apparatus 2 on the center side according to R-FLAG1, G. The hs message exchange is performed by changing the phase inversion method (ST807). When the message exchange is completed, the G. End hs.

  On the other hand, if the phase inversion method has not been changed, remote ADSL modem apparatus 2 transmits R-FLAG1 in accordance with the normal phase inversion method (conventional type) (ST808). That is, a signal whose phase is inverted at “1” is output, and a signal whose phase is not inverted is output at “0”. After receiving C-FLAG1 from the ADSL modem apparatus 2 on the center side according to R-FLAG1, G. The hs message exchange is performed in accordance with a normal phase inversion method (conventional type) (ST809). When the message exchange is completed, the G. End hs.

  As described above, the remote ADSL modem apparatus 2 determines whether to change the phase inversion method of the FLAG signal according to the phase inversion system of the GALF signal transmitted from the center ADSL modem apparatus 2. Therefore, the handshake procedure can be executed in accordance with the phase inversion method selected by the ADSL modem apparatus 2 on the center side.

  In particular, in the remote side ADSL modem apparatus 2, when the phase inversion system of the GALF signal transmitted from the center side ADSL modem apparatus 2 is the normal phase inversion system, the phase inversion system of the FLAG signal is not changed. When the signal phase inversion method is changed from the normal phase inversion method, the FLAG signal phase inversion method is changed. For this reason, the handshake procedure can be executed in accordance with the phase inversion method of the GALF signal transmitted from the ADSL modem apparatus 2 on the center side.

  The ADSL modem apparatus 2 on the center side When hs is started, first, R-TONES-REQ is transmitted from the remote ADSL modem apparatus 2 and is received (ST901). When this R-TONES-REQ is confirmed, the ADSL modem apparatus 2 on the center side transmits C-TONES (ST902). When this C-TONES is confirmed, the remote ADSL modem apparatus 2 transmits R-TONE 1 in response to this, and receives this (ST903).

  If R-TONE1 is received, ADSL modem apparatus 2 on the center side determines whether the reception level of R-TONE1 is low (ST904). Here, the reason why the reception level of the R-TONE 1 is low is to determine the communication distance with the remote ADSL modem apparatus 2. That is, when the communication distance is large, the signal energy of R-TONE 1 is attenuated according to the communication distance, and the reception level is considered to be low.

  In the present embodiment, the low reception level of R-TONE 1 means that, for example, any of the carriers of indexes # 9, 17, and 25 is attenuated by −44 dB, −51 dB, and −56 dB, respectively. It shall be said. Such attenuation is obtained when the communication distance to the partner ADSL modem apparatus 2 is 5 km. In the first embodiment, if the attenuation value is equal to or greater than this attenuation value, it is determined that interference with the downstream carrier due to the upstream carrier skirt phenomenon is increased, and the phase inversion method is changed. The handshake procedure is executed using a normal phase inversion method.

  If the reception level of R-TONE 1 is low, it is determined that the communication distance to the remote ADSL modem apparatus 2 is large (5 km or more), and the ADSL modem apparatus 2 on the center side configures C-GALF 1 "0" The phase inversion method in “1” and “1” is changed and transmitted (ST905). That is, a signal whose phase is inverted at “0” is output, and a signal whose phase is not inverted is output at “1”. Further, a FLAG exchange with the remote ADSL modem apparatus 2 and a G.G. hs message exchange is performed by changing the phase inversion method (ST906). When the message exchange is completed, the G. End hs.

  On the other hand, if the reception level of R-TONE 1 is not low, it is determined that the communication distance to the remote ADSL modem apparatus 2 is short (5 Km or less), and the center ADSL modem apparatus 2 uses the normal phase inversion method. C-GALF1 is transmitted according to (conventional type) (ST907). That is, a signal whose phase is inverted at “1” is output, and a signal whose phase is not inverted is output at “0”. Further, a FLAG exchange with the remote ADSL modem apparatus 2 and a G.G. The hs message exchange is performed in accordance with a normal phase inversion method (conventional type) (ST908). When the message exchange is completed, the G. End hs.

  As described above, the ADSL modem apparatus 2 on the center side determines whether to change the phase inversion method of the C-GALF 1 according to the reception level of the R-TONE 1 transmitted from the remote ADSL modem apparatus 2. The reception level of this R-TONE 1 becomes small when the communication distance with the remote ADSL modem apparatus 2 is large. Therefore, the phase inversion method can be selected according to the communication distance with the remote ADSL modem apparatus 2.

  In particular, in the ADSL modem apparatus 2 on the center side, when the attenuation value of the signal energy of the R-TONE 1 falls below a preset attenuation value, the phase inversion method of the C-GALF 1 is not changed, and the signal energy of the R-TONE 1 is changed. When the attenuation value exceeds a preset attenuation value, the phase inversion method of C-GALF1 is changed. For this reason, when the communication distance is larger than the communication distance corresponding to the preset attenuation value, the handshake procedure can be executed by changing the phase inversion method.

  As described above, according to the ADSL modem apparatus 2 according to the first embodiment, the G. In the Annex A of hs, the handshake procedure is executed by changing the phase inversion method in the specific signals (C-GALF1, R-FLAG1, and C-FLAG1) output after phase inversion as necessary. As a result, it is possible to avoid a situation in which a skirt phenomenon occurs due to repeated phase inversion in R-FLAG1 and C-FLAG1. For this reason, it is possible to reduce interference with the downstream carrier due to the skirt phenomenon of the upstream carrier. As a result, even if the communication distance with the counterpart ADSL modem apparatus 2 is large, the handshake procedure can be executed reliably, so that long-distance communication can be performed.

(Embodiment 2)
The ADSL modem apparatus 2 according to the first embodiment is a G. In the Annex A of hs, the ADSL modem apparatus 2 according to the second embodiment executes the handshake procedure by changing the phase inversion method in the specific signal output by phase inversion as necessary. The phase inversion method for the specific signal output in this way is changed as necessary, and the transmission method after the specific signal is changed to the start-stop synchronization method to execute the handshake procedure.

  10 and 11 show a case where the remote side and center side ADSL modem apparatuses 2 according to the second embodiment respectively execute the handshake procedure by changing the phase inversion method and changing the transmission method to start-stop synchronization. It is a flowchart for demonstrating operation | movement. First, the remote ADSL modem apparatus 2 will be described. 10 and 11, the same reference numerals as those in FIGS. 8 and 9 are used, and the description thereof will be omitted.

  In the remote ADSL modem apparatus 2 according to the second embodiment, as in the first embodiment, processing from transmission of R-TONE-REQ to reception of C-GALF 1 is performed (ST801 to ST804). However, different processing is performed in the determination in C-GALF1. That is, in the first embodiment, it is determined whether the phase inversion method in “0” and “1” constituting the C-GALF 1 is changed. In the second embodiment, in addition to this, the transmission method is a start-stop. It is determined whether it is a synchronous system (ST1001).

  FIG. 12 shows a case where the transmission method is changed to the start-stop synchronization method. It is a figure for demonstrating the output in the signal (C-GALF1, R-FLAG1, and C-FLAG1) which carries out phase inversion in the specific carrier of AnnexA of hs. As shown in the figure, in the asynchronous mode, C-GALF1 output from the ADSL modem apparatus 2 on the center side includes “11111111” as a stop bit, “0” indicating the start of data, and C-GALF1. After the bit string is repeated, it ends with the stop bit “11111111”.

  Therefore, in ST1001, the remote ADSL modem apparatus 2 according to the second embodiment determines whether a signal whose phase is inverted at “0” is output and a signal whose phase is not inverted is output at “1”. At the same time, it is determined whether the C-GALF 1 is composed of the bit strings as described above.

  If the phase inversion method is changed and the transmission method is asynchronous, the remote ADSL modem apparatus 2 changes the phase inversion method in “0” and “1” constituting the R-FLAG1, Transmission is performed using the start-stop synchronization method (ST1002). That is, a signal whose phase is inverted at “0” is output, a signal whose phase is not inverted at “1” is output, and an R-FLAG 1 including a bit string shown in FIG. 12 is output. Specifically, it is composed of “11111111” as a stop bit, “0” indicating the start of data, and “01111110” indicating R-FLAG1, and after these bit strings are repeated, it ends with the stop bit “11111111” R-FLAG1 composed of a bit string to be output.

  After receiving the C-FLAG1 whose phase inversion method is changed from the ADSL modem apparatus 2 on the center side according to R-FLAG1 and using the asynchronous method as the transmission method, The hs message exchange is performed by changing the phase inversion method and using the asynchronous method as the transmission method (ST1003). When the message exchange is completed, the G. End hs.

  On the other hand, if the phase inversion method is changed and the transmission method is not asynchronous, the remote ADSL modem apparatus 2 transmits R-FLAG1 according to the normal phase inversion method (conventional type) (ST808). That is, a signal whose phase is inverted at “1” is output, and a signal whose phase is not inverted is output at “0”. After receiving C-FLAG1 from the ADSL modem apparatus 2 on the center side according to R-FLAG1, G. The hs message exchange is performed in accordance with a normal phase inversion method (conventional type) (ST809). When the message exchange is completed, the G. End hs.

  The center-side ADSL modem apparatus 2 according to the second embodiment performs processing from reception of the R-TONES-REQ to determination of the reception level of the R-TONE 1 as in the first embodiment (ST901 to ST904). The reason for judging whether the reception level is low and the judgment criteria are the same as in the first embodiment.

  If the reception level of R-TONE 1 is low, it is determined that the communication distance to the remote ADSL modem apparatus 2 is large (5 km or more), and the ADSL modem apparatus 2 on the center side configures C-GALF 1 "0" The phase inversion method for “1” and “1” is changed, and transmission is performed using the start-stop synchronization method (ST1101). That is, a signal whose phase is inverted at “0” is output, a signal whose phase is not inverted at “1” is output, and C-GALF 1 including a bit string shown in FIG. 12 is output.

  Further, a FLAG exchange with the remote ADSL modem apparatus 2 and a G.G. The hs message exchange is performed by changing the phase inversion method and using the asynchronous method as the transmission method (ST1102). When the message exchange is completed, the G. End hs.

  On the other hand, if the reception level of R-TONE 1 is not low, it is determined that the communication distance to the remote ADSL modem apparatus 2 is short (5 Km or less), and the center ADSL modem apparatus 2 uses the normal phase inversion method. C-GALF1 is transmitted according to (conventional type) (ST907). That is, a signal whose phase is inverted at “1” is output, and a signal whose phase is not inverted is output at “0”. Further, a FLAG exchange with the remote ADSL modem apparatus 2 and a G.G. The hs message exchange is performed in accordance with a normal phase inversion method (conventional type) (ST908). When the message exchange is completed, the G. End hs.

  As described above, according to the ADSL modem apparatus 2 according to the second embodiment, G. In the Annex A of hs, the phase inversion method for specific signals (C-GALF1, R-FLAG1, and C-FLAG1) output by phase inversion is changed as necessary, and the transmission method after the specific signal is asynchronous. Change to to execute the handshake procedure. As a result, it is possible to avoid a situation in which a skirt phenomenon occurs due to repeated phase inversion in R-FLAG1 and C-FLAG1. For this reason, it is possible to reduce interference with the downstream carrier due to the skirt phenomenon of the upstream carrier. As a result, even if the communication distance with the counterpart ADSL modem apparatus 2 is large, the handshake procedure can be executed reliably, so that long-distance communication can be performed.

  Also, according to the ADSL modem apparatus 2 according to the second embodiment, the handshaking procedure after the specific signal is executed using the start-stop synchronization method as the transmission method. When a specific signal transmitted with phase inversion is output, “0” indicating the start of data is output before the specific signal. For this reason, compared with the case where only the phase inversion method is changed, it is possible to easily determine the specific signal output with phase inversion, and it is possible to execute the handshake procedure more reliably.

  In the present embodiment, G.I. A signal output by phase inversion in a specific carrier in hs Annex A is described. However, the present invention is not limited to this. The present invention can also be applied to a signal output by phase inversion in a specific carrier in hs Annex B or Annex C. G. Also in hs Annex B and Annex C, the same effect as this embodiment can be obtained.

  The ADSL modem apparatus according to the present invention executes the handshake procedure by changing the phase inversion method in the signals (C-GALF1, R-FLAG1, and C-FLAG1) output with phase inversion as necessary. Therefore, it is useful in terms of reducing the interference with the downstream carrier due to the upstream carrier skirt phenomenon, and enabling long-distance communication.

The figure which shows schematic structure of the communication system of the remote side to which the ADSL modem apparatus which concerns on Embodiment 1 of this invention is applied. Functional block diagram of the transceiver shown in FIG. Normal G. Sequence diagram for explaining the handshake procedure by hs AnnexA G. The figure which shows the signal waveform in the specific carrier of hs AnnexA G. The figure which shows the spectrum at the time of transmitting "0" in the specific carrier of hs AnnexA G. The figure which shows the spectrum at the time of transmitting "1" continuously in the specific carrier of hs AnnexA G. The figure for demonstrating the output in the signal which carries out phase inversion in the specific carrier of hs AnnexA The flowchart for demonstrating operation | movement in the case of changing a phase inversion system and performing a handshake procedure in the remote ADSL modem apparatus which concerns on Embodiment 1. FIG. The flowchart for demonstrating the operation | movement in the case of performing a handshake procedure by changing a phase inversion system in the center side ADSL modem apparatus which concerns on Embodiment 1. FIG. The flowchart for demonstrating operation | movement in the remote ADSL modem apparatus which concerns on Embodiment 2 of this invention when changing a phase inversion system and changing a transmission system to an asynchronous system and performing a handshake procedure The flowchart for demonstrating operation | movement in the center side ADSL modem apparatus which concerns on Embodiment 2 of this invention when changing a phase inversion system and changing a transmission system to an asynchronous system and performing a handshake procedure When the transmission method is changed to start-stop synchronization, G. The figure for demonstrating the output in the signal which carries out phase inversion in the specific carrier of hs AnnexA

Explanation of symbols

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

Claims (11)

  Transmission / reception means for transmitting / receiving a designated carrier defined in a communication standard in advance by a handshake procedure; and a changing means for changing a phase inversion method normally used in a specific signal transmitted by phase inversion using the designated carrier. An ADSL modem apparatus comprising:   2. The ADSL modem according to claim 1, wherein said changing means does not invert a signal output by normal phase inversion in said specific signal, but inverts a signal output without normal phase inversion. apparatus.   3. The ADSL modem apparatus according to claim 1, wherein the specific signal includes a GALF signal and a FLAG signal transmitted using the designated carrier.   4. The ADSL modem according to claim 3, wherein the ADSL modem is arranged on a remote side, and the changing means determines whether to change the phase inversion method of the FLAG signal according to the phase inversion method of the GALF signal transmitted from the center side. apparatus.   The changing means does not change the phase inversion method of the FLAG signal when the phase inversion method of the GALF signal transmitted from the center side is the normal phase inversion method, and the phase inversion method of the GALF signal is the normal phase inversion method. 5. The ADSL modem apparatus according to claim 4, wherein the phase inversion method of the FLAG signal is changed when the signal is changed from.   2. The center side, wherein the changing means determines whether to change the phase inversion method of the GALF signal according to the reception level of the TONE signal transmitted from the remote side using the designated carrier. 3. The ADSL modem apparatus according to 3.   The changing means does not change the phase inversion method of the GALF signal when the attenuation value of the signal energy of the TONE signal falls below the preset attenuation value, and the attenuation value of the signal energy of the TONE signal is set to the preset attenuation value. 7. The ADSL modem apparatus according to claim 6, wherein the phase inversion method of the GALF signal is changed when exceeding.   The said change means changes the phase inversion system normally used in the said specific signal, and changes the transmission system after the said specific signal to a start-stop synchronous system. ADSL modem device.   Receiving a designated carrier determined in advance by a communication standard in a handshake procedure, changing the phase inversion method normally used in a specific signal transmitted by phase inversion using the designated carrier, and changing the phase inversion method after the change A method for communicating with an ADSL modem apparatus, wherein the specific signal is transmitted using an ADSL.   When changing the phase inversion method of the specific signal, the signal output by normal phase inversion in the designated carrier is not phase inverted, while the signal output without normal phase inversion is phase inverted. The communication method of the ADSL modem apparatus according to claim 9.   Receiving a designated carrier defined in a communication standard in advance by a handshake procedure, changing the phase inversion method normally used in a specific signal transmitted by phase inversion using the designated carrier, and changing the transmission method after the specific signal A communication method for an ADSL modem apparatus, wherein the specific signal is transmitted in an asynchronous manner using a phase inversion method after the change.

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