JP2001333127A - Subscriber line transmission system for avoiding crosstalk interference with ping-pong transmission, and station side and subscriber side transmission / reception devices - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a subscriber line transmission system and a station side and subscriber side transmission / reception device thereof, to improve the reliability of communication by avoiding crosstalk interference with ping-pong transmission, and to increase the transmission capacity. To secure. SOLUTION: In a digital subscriber line transmission system such as VDSL, between a station side and a subscriber side transmitting / receiving apparatus,
Synchronization signal TTR indicating burst transmission cycle of ping-pong transmission
Station-side ISDN line termination unit (OCU)
Far end crosstalk noise section (FEXT-R)
, The overlapping symbol overlapping the frequency band of the ping-pong transmission is transmitted, and the near-end crosstalk noise section (N) of the transmission timing of the subscriber side ISDN line termination unit (DSU) is transmitted.
EXT-R), non-overlapping symbols that do not overlap with the frequency band of ping-pong transmission are alternately switched and transmitted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses an existing telephone line based on a metallic line called a subscriber line, coexists with a call using an analog signal, and uses xDSL (x Digital S).
The present invention relates to a subscriber line transmission system that enables high-speed data communication by using ubscriber line technology, and a station side and subscriber side transmission / reception device, particularly, a ping-pong transmission system (TCM-I).
SDN), that is, a subscriber line transmission system for avoiding crosstalk noise interference with ping-pong transmission in an environment coexisting with a basic rate ISDN subscriber line transmission system adopted in Japan, and a station side and subscriber side transmitting / receiving apparatus thereof About.

ADSL (Asymmetric Digital Subscriber Line: Asymmetr) has different transmission speeds and the like for xDSL technology which enables high-speed data communication using existing telephone lines.
ic DSL), VDSL (Very High Speed Digital Subscriber Line: Very
There are various technologies such as high-speed DSL, which are collectively referred to as “xDSL”.

[0003] Among them, VDSL technology is applied in which the upstream transmission speed from the subscriber's home to the subscriber line accommodation station is 12.96 Mbps and the downstream transmission speed from the subscriber line accommodation station to the subscriber's house is 12.96 Mbps. An outline of the subscriber line transmission system described above will be described below.

FIG. 6 shows a model of a VDSL transmission system for connecting a subscriber line accommodation station and a subscriber home. Containment Bureau 6
1 and the subscriber's home 6-2 are connected to the existing metallic line 6-3.
In the accommodation station 6-1, a narrowband network 6-12 such as a telephone exchange and a station side VDSL modem (VTU-C: VDSL Transceiver Unit-) are connected via a splitter 6-11 for separating a signal according to a frequency. Central Offic
e) 6-13 is connected.

[0005] The splitter 6-11 provides a low frequency band of about 4 KHz used for telephone voice and a VDSL.
The high frequency band used for digital signal transmission by the modem (VTU-C) 6-13 is separated. VDSL
Modem (VTU-C) 6-13 is a broadband network 6
High-speed data communication is performed via -14.

On the other hand, the splitter 6-
21 is connected to a metallic line 6-3, and a general analog telephone 6-22 and a VDSL modem (VTU-VTS) for performing VDSL transmission via the splitter 6-21.
R: VDSL Transceiver Unit-Remote Terminal) 6-2
3 is connected to the VDSL modem (VTU-R) 6-23.
And an information communication device such as a personal computer 6-24.

With the above-described VDSL transmission system, it is possible to transmit a high-speed digital signal of up to about 50 Mbit / sec without newly laying out a line for a high-speed digital signal. It can be suitably used for multimedia communication services such as demand.

As described above, the VDSL transmission system transmits a conventional telephone voice signal and a high-speed data signal by coexisting on the same line. It provides digital transmission services.

[0009]

2. Description of the Related Art As a modulation method used for VDSL transmission, Q is used.
An AM modulation method is known. FIG. 7 shows functional blocks of a transmitting / receiving device of a VDSL transmission system using the QAM modulation coding method. FIG. 7 shows only the transmission unit and the reception unit of the transmission / reception device (transceiver) facing each other via the metallic line 7-10.

[0010] In the transmission section, the transmission data is decomposed into I / Q components, band-limited by transmission filters 7-1 and 7-3, and the sin / cos component of the carrier output from carrier generation section 7-5. Are multiplied by multipliers 7-2 and 7-4, added by an adder 7-6, and output as a QAM signal. A D / A converter 7-7, a post filter 7-8, and a line driver 7-9 It is sent to the metallic line 7-10 via the communication terminal.

The signal passing through the metallic line 7-10 passes through a pre-filter 7-11 and an A / D converter 7-12 in a receiving section, and then receives the signal sin / of the carrier output from the carrier generating section 7-13. Cos component and multiplier 7-1
4, 7-15 to decompose into I / Q components, and receive filters 7-16, 7-17, forward equalizers 7-18, 7-19, feedback equalizers 7-20, 7-21, etc. And the received data is reproduced.

In the QAM modulation in VDSL transmission, for example, as shown in FIG. 8, for the transmission in the uplink (Up) direction from the subscriber side to the accommodation station side, a carrier wave of 6084 kHz, a used frequency band of 3600 kHz to 8568 kHz, and a symbol rate of 4320 kHz The carrier code 17 is used for transmitting the baud modulation code in the down direction from the accommodation station side to the subscriber side.
30kHz, frequency band 240kHz-3220kHz
z, a modulation code having a symbol rate of 2592 kBaud is used.

In VDSL transmission, signals of different frequency bands are used for uplink / downlink transmission, and bidirectional transmission is performed by frequency division (FDM). In this example, the frequency band used is 15% wider than the baud rate frequency due to the influence of the roll-off filter.

FIG. 8 shows a ping-pong transmission (TCM-I
SDN). As shown in the figure, since the ping-pong transmission uses a frequency band of 0 kHz to 960 kHz, the band overlaps with the downstream signal of the VDSL transmission. Here, ping-pong transmission (TCM-ISD
N) is a time-division directional control transmission method in which the transmission direction (up / down) of a signal is switched over a single transmission line at predetermined timing intervals.

Next, the mutual interference of crosstalk noise will be described with reference to FIGS. In FIG. 9 and FIG. 10, the office side ISDN line termination unit (OCU: Office Chann)
el Unit) 9-1 and a subscriber side ISDN line termination unit (DSU: Digital Service Unit) 9-2 are connected by a metallic telephone line 9-3, and an ISD is connected between them.
N ping-pong transmission is performed.

On the other hand, the office side VDSL modem (VT) is located adjacent to the ISDN line termination unit (OCU) 9-1.
UC) 9-4 are accommodated, and the station side VDSL modem (V
TU-C) 9-4 is a subscriber side VDSL of another subscriber's house.
Modem (VTU-R) 9-5, metallic telephone line 9-
6 and perform VDSL transmission between them. here,
The metallic telephone line 9-3 for performing ISDN ping-pong transmission is referred to as a "ping-pong transmission line", and the metallic telephone line 9-6 for performing VDSL transmission is referred to as a "VDSL transmission line".

On the ping-pong transmission line 9-3, the station-side IS
DN line termination unit (OCU) 9-1 and subscriber side IS
The so-called ping-pong transmission is performed between the DN line terminating unit (DSU) 9-2 and time-divisionally multiplexing uplink and downlink data transmission timings for transmission. That is, 2.5
The frame period of ms is divided into two time zones, one of which is the data transmission timing of the upstream (from the subscriber side to the station side) and the other is of the downstream (from the office side to the subscriber side). Used as data transmission timing.

As described above with reference to FIG. 8, the frequency band of the downlink signal of the VDSL transmission and the frequency band used in the ISDN ping-pong transmission overlap. Therefore, the VDSL transmission line 9-6 laid adjacent to the ping-pong transmission line 9-3 is affected by the crosstalk noise from the ping-pong transmission line 9-3.

FIG. 11 shows a quad cable susceptible to crosstalk noise. As the telephone line, a cable 11-1 in which a plurality of pairs of lines called a quad cable shown in FIG. 11 are bundled is often used. When the line pair in the quad cable 11-1 includes the line pair 11-2 of the VDSL transmission line and the line pair 11-3 of the ping-pong transmission line, the two lines are physically adjacently juxtaposed. Therefore, mutual crosstalk interference is likely to occur.

Next, near-end crosstalk / far-end crosstalk will be described. In FIG. 9, the crosstalk noise from the ping-pong transmission line 9-3 viewed from the VDSL transmission line 9-6 is caused by an ISDN transmission device (for example, an ISDN transmission device installed on the side closer to the VDSL transmission device when viewed from the VDSL transmission device). When viewed from the subscriber side VDSL modem (VTU-R) 9-5, it is strongly affected by crosstalk noise generated at the transmission timing of the subscriber side ISDN line termination unit (DSU) 9-2). This crosstalk noise is “Near End Cross Talk (NEXT)”
It is called. Of course, when the band of the received signal and the near-end crosstalk noise overlap, the received signal is strongly affected by the near-end crosstalk noise.

On the other hand, an ISDN transmission device (for example, a subscriber side VDSL modem (VTU-
R) 9-5, the influence of crosstalk noise on the transmission timing of the central office ISDN line termination unit (OCU) 9-1) is relatively weak. This crosstalk noise is called “far end crosstalk noise (FEXT: FAR END Cross Talk)”.

The frequency band used for the downstream signal of the VDSL transmission and the frequency band used for the ping-pong transmission overlap. Therefore, when the ping-pong transmission line 9-3 and the VDSL line 9-6 are adjacent, the subscriber side VDSL modem (VT
UR) 9-5 is the near-end subscriber side ISDN
The upstream signal transmission timing of the line termination unit (DSU) 9-2 is strongly affected by near-end crosstalk noise (NEXT).

Further, as shown in FIG.
The reception signal of the line termination unit (OCU) 9-1 is strongly affected by the near-end crosstalk noise (NEXT) from the downstream transmission signal of the adjacent station-side VDSL modem (VTU-C) 9-4. However, the subscriber side VDSL modem (VTU-R) 9
The effect of the transmission signal (uplink signal) from -5 is far-end crosstalk noise (FEXT), and the influence is weak because the frequency band is different.

The station side VDSL modem (VTU-C)
For the received signal (uplink signal) of 9-4, the station-side ISD
Since the frequency band is different from the transmission signal of the N-line termination unit (OCU) 9-1, the influence of near-end crosstalk noise from the station-side ISDN line termination unit (OCU) 9-1 is small.

[0025]

As described above, the signal received by the subscriber-side VDSL modem (VTU-R) is transmitted to the adjacent subscriber-side ISDN line termination unit (DST).
U) Near-end crosstalk noise (NEXT) in the transmission timing section
, The signal-to-noise ratio (S / N) tends to deteriorate, and the S / N is relatively good in other timing sections.

The station-side ISDN line termination unit (O
The received signal at the CU) is always converted from the downstream signal of the station side VDSL modem (VTU-C) to the near-end crosstalk noise (NEX).
T), the signal-to-noise ratio (S / N) tends to deteriorate.

According to the present invention, when a ping-pong transmission line and a VDSL transmission line are laid adjacent to each other, mutual cross-talk noise between the ping-pong transmission and the VDSL transmission due to a partially overlapped frequency band of the ping-pong transmission and the VDSL transmission. It avoids the influence of interference to improve communication reliability, and secures as much transmission capacity as possible to achieve VDSL.
It is an object of the present invention to provide a subscriber line transmission system capable of performing transmission and a station side and subscriber side transmission / reception device thereof.

[0028]

In order to solve the above-mentioned problems, a subscriber line transmission system according to the present invention comprises a non-overlapping band overlapping with a ping-pong transmission frequency band and a non-overlapping band not overlapping with a ping-pong transmission frequency band. A frequency band switching transmission means for switching and transmitting modulation codes of two kinds of frequency bands of the overlap band in synchronization with a burst period of ping-pong transmission, and switching between the overlap band and the non-overlap band; Using a non-overlapping band in the timing section affected by edge crosstalk noise,
A modulation code is transmitted using an overlap band in a timing section affected by far-end crosstalk noise.

FIG. 1 is a diagram illustrating the principle of VDSL transmission according to the present invention. In the figure, (a) shows a synchronization signal TTR indicating a burst cycle (2.5 ms) of ping-pong transmission.
In synchronization with the ping-pong transmission synchronization signal TTR, the SDN line termination unit (OCU) transmits 377 symbols (UI) of data in a half timing section as shown in FIG. In the timing section, data of 377 symbols (UI) from the subscriber side ISDN line termination unit (DSU) is received.

The subscriber side ISDN line termination unit (DS
U) receives the signal transmitted from the station-side ISDN line termination unit (OCU) in a timing section that is half the burst period of the ping-pong transmission, as shown in FIG.
6 to 7.5 symbols from last received symbol (UI)
Thereafter, data of 377 symbols (UI) is transmitted. Note that the UI is one of the AMI encoded signals in the ping-pong transmission.
This is data for the pulse width.

Here, as shown in (d) of the figure, the near-end crosstalk noise (NE) from the subscriber line termination unit (DSU) in which the subscriber VDSL modem (VTU-R) side is close.
XT) is affected by the station side VDSL modem (V
TU-C), the section is defined as a subscriber-side near-end noise section (NEXT-R), and the other sections are defined as a subscriber-side far-end noise section (FEXT-R).

Then, as shown in FIG. 3E, the station side VDSL belonging to the subscriber side near-end noise section (NEXT-R).
The transmission symbol of the modem (VTU-C) is transmitted using a modulation code in a frequency band that does not overlap with the frequency band of ping-pong transmission, and the subscriber-side far-end noise section (F).
Station-side VDSL modem (VTU-R) belonging to EXT-R).
The transmission symbol C) is transmitted by a modulation code in a wide frequency band overlapping with the frequency band of ping-pong transmission.

That is, the station side VDSL modem (VTU-C)
The symbol transmitted in the downward direction transmitted from ping-pong transmission (T
The frequency band of the CM-ISDN) is switched to a symbol that does not overlap and a symbol that does not overlap is transmitted, and is synchronized with the ping-pong transmission synchronization signal TTR to overlap the subscriber-side far-end noise section (FEXT-R). By transmitting non-overlapping symbols in the subscriber's near-end noise section (NEXT-R),
The influence of near-end crosstalk noise (NEXT) from the office side VDSL modem (VTU-C) to the office side line termination unit (OCU), and the effect of the subscriber side line termination unit (DSU) to the subscriber side VDSL modem (VTU-R). ) Near-end crosstalk noise (NE
XT) can be avoided, and a large transmission capacity can be secured.

[0034]

FIG. 2 shows functional blocks of a transmitting / receiving apparatus in a subscriber line transmission system according to the present invention. The figure shows only the transmitting unit and the receiving unit of the transmitting / receiving device (transceiver) which are opposed via the metallic line 2-10. The transmitting side is the transmitting unit of the VDSL modem (VTU-C) on the office side, and the receiving side is the subscriber side. 2 shows a receiving unit of a VDSL modem (VTU-R).

In FIG. 2, transmission filters 2-1 and 2-
3, carrier generation units 2-5, 2-13, reception filter 2
-16,2-17, forward equalizer 2-18,2
-19, feedback equalizer 2-20, 2-21
Has a function of operating in accordance with a plurality of types of carrier frequencies and / or baud rates, or a combination of both, and has a buffer memory 2 for speed conversion in each of a transmitting unit and a receiving unit.
Except for insertion of -31 and -32, it is basically the same as the functional block of the transmission / reception device of the conventional VDSL transmission system shown in FIG. The modulation speed (baud rate) can be changed by changing the transmission data speed using the buffer memories 2-31, 2-32.

In the transmitting section, the subscriber-side far-end noise section (FEXT-R) and the subscription are synchronized with a synchronization signal (TTR) indicating a burst cycle of ping-pong transmission input from an external ping-pong transmission apparatus. Near-end noise section (N
EXT-R), the carrier frequency or the baud rate to be transmitted or a combination of both is switched.

In the receiving section, a burst period signal TTR for ping-pong transmission is reproduced from the received signal, and based on the reproduced ping-pong transmission synchronization signal (TTR), a subscriber-side far-end noise section (FEXT-R) is generated. According to the switching of the subscriber-side near-end noise section (NEXT-R), the receiving carrier frequency or the baud rate or the combination of both is switched.

In the subscriber-side near-end noise section (NEXT-R), a frequency band (non-overlap band) different from the frequency band of ping-pong transmission is assigned to the downstream signal of VDSL transmission, and the subscriber-side far-end noise section (FEXT). In -R), a frequency band (overlap band) overlapping with the frequency band of ping-pong transmission is allocated to the downstream signal of VDSL transmission, and the frequency band used in VDSL transmission is switched in a time-division manner similarly to ping-pong transmission and transmitted. By
Even if the band overlaps with the ping-pong transmission, it is possible to avoid the interference of the near-end crosstalk noise, and by using a wide band in the subscriber-side far-end noise section (FEXT-R),
Many transmission capacities can be secured.

Next, QA is used as a modulation code for VDSL transmission.
Several embodiments using the M code will be described. FIG. 3 shows an embodiment in which two types of frequency bands having the same carrier frequency but different baud rates are switched and used in the downstream direction of VDSL transmission.

The carrier wave 1730 kHz shown in FIG.
z, an overlapping symbol having a frequency band of 240 kHz to 3220 kHz and a symbol rate of 2592 kBaud,
17B, a carrier frequency band of 1171 kHz to 2289 kHz, and a symbol rate of 97 shown in FIG.
Two kinds of 2k baud non-overlapping symbols are switched and used, and a ping-pong transmission synchronization signal (TT
R) in synchronization with the subscriber far-end noise section (FEXT-R)
, And the non-overlap symbol is transmitted in the subscriber side near-end noise section (NEXT-R). By doing so, mutual influence with the ping-pong transmission line can be avoided.

FIG. 4 shows an embodiment in which two types of frequency bands having different carrier frequencies and baud rates are switched and used in the downstream direction of VDSL transmission. The carrier wave 1730 kHz and the frequency band 240 shown in FIG.
kHz to 3220 kHz, a symbol rate of 2592 kBaud, an overlap symbol of 2288 kHz and a frequency band of 1356 kHz to 32 kHz shown in FIG.
Two kinds of non-overlapping symbols of 20 kHz and a symbol rate of 1620 kbaud are used by switching, and are overlapped in the subscriber-side far-end noise section (FEXT-R) in synchronization with the ping-pong transmission synchronization signal (TTR). Can be configured to transmit non-overlapping symbols in the subscriber-side near-end noise section (NEXT-R).

FIG. 5 shows an embodiment in which transmission of each carrier is switched on / off by using a plurality of carrier frequencies in the downstream direction of VDSL transmission. As shown in FIG. 2A, the first carrier frequency is 706 kHz, the frequency band is 240 kHz to 1172 kHz, and the symbol rate is 8
10 kbaud symbol and a second carrier frequency 228
8kHz, frequency band 1356kHz-3220kHz
z, an overlapping symbol composed of two carrier frequencies of a symbol having a symbol rate of 1620 kBaud, and a second carrier 2288 kHz as shown in FIG.
z, two kinds of non-overlapping symbols having a frequency band of 1356 kHz to 3220 kHz and a symbol rate of 1620 kBaud are used.

Then, a ping-pong transmission synchronization signal (TTR)
The transmission of the first and second carrier frequencies is turned on in the subscriber-side far-end noise section (FEXT-R) in synchronism with the transmission of the overlapping symbols, and the subscriber-side near-end noise section (NEXT-R) By turning off the transmission of the first carrier frequency and turning on the transmission of the second carrier frequency to transmit non-overlapping symbols, mutual influence with the ping-pong transmission line can be avoided.

Also, instead of the QAM code, CAP (carr
ier-less amplitude / phase) modulation code can be used, in which case there is no carrier, but two frequency bands with the same center frequency and different baud rates are used, and the frequency band is the same as that of the QAM code. By doing
Similar effects can be obtained.

For the multi-valued number transmitted in each symbol,
In an initialization procedure performed before communication, an optimal value that can be assigned is calculated according to the state of the signal-to-noise ratio of the line, and the station side VDSL modem (VTU-C) and the subscriber side VDSL modem (VTU-R) By performing a handshake between them, the multivalued number transmitted by each symbol is held by both, and data transmission is performed using the multivalued number.

(Supplementary Note 1) A transmission system in which a line affected by near-end crosstalk noise and far-end crosstalk noise from a ping-pong transmission line is used for signal transmission and reception, and a part of a frequency band used for the ping-pong transmission overlaps. Transmitting means for switching a modulation rate of a transmission signal in a timing section affected by near-end crosstalk noise to a modulation rate slower than a timing section affected by far-end crosstalk noise, based on a burst period of ping-pong transmission, And a subscriber line transmission system. (Supplementary Note 2) In a subscriber line transmission system connected by a ping-pong transmission line and a line that mutually influences near-end crosstalk noise and far-end crosstalk noise, an overlap band overlapping with a ping-pong transmission frequency band and a ping-pong transmission band 2 of non-overlap band that does not overlap with transmission frequency band
A frequency band switching transmission means for switching and transmitting modulation codes of various frequency bands in synchronization with a burst cycle of ping-pong transmission, the frequency band switching transmission means switching a baud rate while keeping a carrier frequency constant, Switching between the overlap band and the non-overlap band,
A subscriber having a configuration for transmitting a modulation code using a non-overlap band in a timing section affected by near-end crosstalk noise and using an overlap band in a timing section affected by far-end crosstalk noise. Line transmission system. (Supplementary Note 3) In a subscriber line transmission system connected by a ping-pong transmission line and a line that mutually affects the near-end crosstalk noise and the far-end crosstalk noise, an overlap band overlapping with a ping-pong transmission frequency band, and a ping-pong transmission band. 2 of non-overlap band that does not overlap with transmission frequency band
Frequency band switching transmission means for transmitting a modulation code by switching frequency bands of different types in synchronization with a burst period of ping-pong transmission, wherein the frequency band switching transmission means switches a set of a carrier frequency and a baud rate to perform the overlap. A modulation code is transmitted by switching between a band and a non-overlap band, using a non-overlap band in a timing section affected by near-end crosstalk noise, and using an overlap band in a timing section affected by far-end crosstalk noise. A subscriber line transmission system having a configuration. (Supplementary Note 4) In a subscriber line transmission system connected by a ping-pong transmission line and a line that mutually influences near-end crosstalk noise and far-end crosstalk noise, an overlap band overlapping with a ping-pong transmission frequency band, and a ping-pong transmission band. 2 of non-overlap band that does not overlap with transmission frequency band
Frequency band switching transmission means for transmitting a modulation code by switching frequency bands of different types in synchronization with a burst period of ping-pong transmission, wherein the frequency band switching transmission means are respectively modulated at a predetermined baud rate and have different frequencies. Means for transmitting a modulation code by the carrier of the plurality of carriers, switching on / off of carrier transmission which is the overlap band among the plurality of carriers, and setting a non-overlap band to a timing section affected by near-end crosstalk noise. And transmitting a modulation code using an overlap band in a timing section affected by far-end crosstalk noise. (Supplementary note 5) The subscriber line transmission system according to any one of Supplementary notes 1 to 4, wherein a QAM code is used as a modulation code. (Supplementary Note 6) In a subscriber line transmission system connected by a ping-pong transmission line and a line that mutually influences near-end crosstalk noise and far-end crosstalk noise, an overlap band overlapping with a ping-pong transmission frequency band, and a ping-pong transmission band. 2 of non-overlap band that does not overlap with transmission frequency band
Frequency band switching transmission means for switching the frequency band of each type in synchronization with the burst period of ping-pong transmission and transmitting a modulation code, wherein the frequency band switching transmission means uses a CAP modulation code as a modulation code, and performs CAP modulation. The baud rate is switched while keeping the center frequency of the code constant, the overlap band and the non-overlap band are switched, and the non-overlap band is used in the timing section affected by the near-end cross-talk noise. A subscriber line transmission system having a configuration for transmitting a modulation code using an overlap band in an affected timing section. (Supplementary Note 7) In a subscriber line transmission system connected by a ping-pong transmission line and a line that mutually influences near-end crosstalk noise and far-end crosstalk noise, an overlap band overlapping with a ping-pong transmission frequency band and a ping-pong transmission band 2 of non-overlap band that does not overlap with transmission frequency band
Frequency band switching transmission means for switching the frequency band of each type in synchronization with the burst period of ping-pong transmission and transmitting a modulation code, wherein the frequency band switching transmission means uses a CAP modulation code as a modulation code, and performs CAP modulation. A set of a center frequency and a baud rate of a code is switched, and a modulation code is transmitted using a non-overlap band in a timing section affected by near-end crosstalk noise and using an overlap band in a timing section affected by far-end crosstalk noise. A subscriber line transmission system characterized by having a configuration as follows. (Supplementary Note 8) In a subscriber line transmission system connected by a ping-pong transmission line and a line that mutually affects the near-end crosstalk noise and the far-end crosstalk noise, an overlap band overlapping with a ping-pong transmission frequency band, and a ping-pong transmission band. 2 of non-overlap band that does not overlap with transmission frequency band
Frequency band switching transmission means for transmitting a modulation code by switching frequency bands of different types in synchronization with a burst period of ping-pong transmission, wherein the frequency band switching transmission means is modulated at a predetermined baud rate, and each of the center frequency Means for transmitting a plurality of different CAP modulation codes, switching on / off of CAP modulation code transmission which is the overlap band among the plurality of CAP modulation codes, and a timing section affected by near-end crosstalk noise A transmission line using a non-overlap band and transmitting a modulation code using an overlap band in a timing section affected by far-end crosstalk noise. (Supplementary Note 9) The subscriber line transmission system optimizes a multi-level number transmitted by the modulation code according to a signal-to-noise ratio by an initialization procedure before transmission, and converts multi-level number information transmitted by the modulation code. The transmitting side and the receiving side are provided with means for holding, and in synchronization with the burst period of the ping-pong transmission, the multi-valued number transmitted by the modulation code, together with the switching between the overlap band and the non-overlap band, the transmission side and the non-overlap band. 9. The subscriber line transmission system according to any one of appendices 1 to 8, wherein the subscriber line transmission system has a configuration in which switching is performed on both of the receiving side. (Supplementary Note 10) In an office-side transmitting / receiving apparatus connected by a ping-pong transmission line and a line that mutually affects near-end crosstalk noise and far-end crosstalk noise, an overlap band overlapping with a ping-pong transmission frequency band and ping-pong transmission. Frequency band switching transmission means for switching and transmitting modulation codes in two types of non-overlapping bands that do not overlap with the frequency band of the ping-pong transmission in synchronization with the burst cycle of ping-pong transmission. Switching the carrier frequency and / or baud rate to be used, or switching the transmission of the carrier frequency to be used on / off, and using the non-overlap band in the timing section affected by the near-end crosstalk noise, the far-end crosstalk noise To transmit the modulation code using the overlap band in the timing section affected by A station-side transmitting / receiving device comprising: (Supplementary note 11) The station-side transmitting / receiving apparatus according to supplementary note 10, wherein a QAM code is used as the modulation code. (Supplementary Note 12) In a station-side transmitting / receiving apparatus connected by a ping-pong transmission line and a line that mutually affects near-end crosstalk noise and far-end crosstalk noise, an overlap band overlapping with a ping-pong transmission frequency band and ping-pong transmission. Frequency band switching transmission means for switching and transmitting CAP modulation codes of two types of frequency bands of a non-overlapping band which do not overlap with the frequency band of the ping-pong transmission in synchronization with the burst period of ping-pong transmission. , The center frequency of the CAP modulation code, the baud rate or both are switched, or the CAP serving as the overlap band is changed.
The modulation code transmission is switched on / off, and a CAP modulation code is transmitted using a non-overlap band in a timing section affected by near-end crosstalk noise and using an overlap band in a timing section affected by far-end crosstalk noise. A station-side transmitting / receiving device characterized by having the following configuration. (Supplementary Note 13) The station-side transmitting / receiving apparatus optimizes a multi-level number transmitted by the modulation code according to a signal-to-noise ratio by an initialization procedure before transmission, and holds multi-level number information transmitted by the modulation code. A means for transmitting, by synchronizing with the burst period of the ping-pong transmission,
13. The station-side transmitting / receiving apparatus according to any one of supplementary notes 10 to 12, further comprising a configuration for switching the overlap band and the non-overlap band together with the switching. (Supplementary Note 14) In a subscriber-side transmitting / receiving apparatus connected by a ping-pong transmission line and a line that mutually influences near-end crosstalk noise and far-end crosstalk noise, an overlap band overlapping with a ping-pong transmission frequency band, and a ping-pong transmission band. 2 of non-overlap band that does not overlap with transmission frequency band
Frequency band switching receiving means for switching and receiving the modulation codes of the different frequency bands in synchronization with the burst period of the ping-pong transmission notified from the station side, the frequency band switching receiving means comprising a carrier frequency to be received, a baud rate Alternatively, by switching between the two, or by switching on / off the carrier frequency to be received, the modulation code of the non-overlap band is applied to the timing section affected by the near-end crosstalk noise, and the timing section affected by the far-end crosstalk noise. Characterized in that the transmission / reception apparatus receives a modulation code in an overlap band. (Supplementary note 15) The subscriber-side transmitting / receiving apparatus according to supplementary note 14, characterized by having a configuration for receiving a modulation code of a QAM code as the modulation code. (Supplementary Note 16) In a subscriber transmitting / receiving apparatus connected by a ping-pong transmission line and a line that mutually influences near-end crosstalk noise and far-end crosstalk noise, an overlap band overlapping with a ping-pong transmission frequency band, and a ping-pong transmission band. 2 of non-overlap band that does not overlap with transmission frequency band
Frequency band switching receiving means for switching and receiving CAP modulation codes of different frequency bands in synchronization with a burst period of ping-pong transmission notified from the station side, wherein the frequency band switching receiving means includes a center of the CAP modulation code. Switching the frequency, the baud rate, or both, or switching on / off the reception of the CAP modulation code as the overlap band, and transmitting the non-overlap band modulation code in the timing section affected by near-end crosstalk noise. A subscriber side transmitting / receiving apparatus having a configuration for receiving a modulation code of an overlap band in a timing section affected by crosstalk noise. (Supplementary Note 17) The subscriber-side transmitting / receiving apparatus optimizes a multi-level number received by the modulation code according to a signal-to-noise ratio by an initialization procedure before transmission, and converts multi-level number information received by the modulation code. Holding means for holding, and in synchronization with the burst period of the ping-pong transmission, switching the multi-valued number received by the modulation code together with the switching between the overlap band and the non-overlap band. 17. The subscriber transmitting / receiving apparatus according to any one of claims 16 to 16.

[0047]

As described above, according to the present invention,
Transmission is performed by switching between a band overlapping the ping-pong transmission band and a band not overlapping the ping-pong transmission band according to the subscriber-side far-end noise section and the subscriber-side near-end noise section synchronized with the burst transmission cycle of ping-pong transmission. By doing so, the effect of near-end crosstalk noise from the station side VDSL modem (VTU-C) to the subscriber line termination unit (OCU) and the subscriber side line termination unit (DSU) from the subscriber side VDSL modem (VTU-C) −R), avoiding the influence of near-end crosstalk noise, improving communication reliability, and securing a large transmission capacity in the far-end crosstalk noise section.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the principle of VDSL transmission according to the present invention.

FIG. 2 is a functional block diagram of a transmission / reception device in the subscriber line transmission system of the present invention.

FIG. 3 shows the same carrier frequency and different baud rates 2
FIG. 3 is a diagram illustrating an embodiment using different types of frequency bands.

FIG. 4 is a diagram showing an embodiment using two types of frequency bands having different carrier frequencies and baud rates.

FIG. 5 is a diagram illustrating an embodiment in which transmission / reception of each carrier is switched on / off using a plurality of carrier frequencies.

FIG. 6 is a diagram illustrating a model of an accommodation station and a subscriber house connected by a VDSL transmission system.

FIG. 7 is a functional block diagram of a transmission / reception device of a VDSL transmission system using a QAM modulation code system.

FIG. 8 is a diagram illustrating frequency bands of conventional VDSL transmission and ping-pong transmission.

FIG. 9 is an explanatory diagram of mutual interference of crosstalk noise in a subscriber side transmitting / receiving apparatus.

FIG. 10 is an explanatory diagram of mutual interference of crosstalk noise in the station side transmitting / receiving apparatus.

FIG. 11 is a diagram showing a quad cable in which a plurality of telephone lines are bundled.

[Explanation of symbols]

(A) Synchronization signal of burst cycle of ping-pong transmission (TCM-ISDN) (b) Transmission / reception timing of station-side ISDN line termination unit (OCU) (c) Subscriber-side ISDN line termination unit (DSU)
(D) Section in which the subscriber side VDSL modem (VTU-R) is affected by near-end crosstalk noise (NEXT) and distance exclusion crosstalk noise (FEXT) (e) From the station side VDSL modem (VTU-C) Overlap symbols and non-overlap symbols to be transmitted

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // H04L 27/00 H04L 27/00 B (72) Inventor Yutaka Awata 2-chome Shin-Yokohama, Kohoku-ku, Yokohama, Kanagawa Prefecture No. 3-9 Fujitsu Digital Technology Stock Company In-house (72) Inventor Nobukazu Koizumi 4-1-1 Kamikadanaka, Nakahara-ku, Kawasaki-shi, Kanagawa F-term in Fujitsu Limited (reference) 5K004 AA01 BB06 5K018 AA02 BA03 CA02 CA06 5K027 BB01 CC02 KK02 5K034 AA05 EE10 EE13 HH63 KK04 MM08 5K051 CC04 DD13 EE04 EE05 JJ01 JJ10

Claims (5)

[Claims] 1. A transmission system in which a line affected by near-end crosstalk noise and far-end crosstalk noise from a ping-pong transmission line is used for transmitting and receiving signals, and a part of a frequency band used for the ping-pong transmission overlaps. Based on the burst period of the ping-pong transmission, a transmission unit that switches the modulation rate of the transmission signal in the timing section affected by the near-end crosstalk noise to a modulation rate lower than the timing section affected by the far-end crosstalk noise and transmits the transmission signal. A subscriber line transmission system, comprising: 2. A subscriber line transmission system connected by a ping-pong transmission line and a line that mutually influences near-end crosstalk noise and far-end crosstalk noise, an overlap band overlapping a frequency band of ping-pong transmission, and Frequency band switching transmission means for transmitting a modulation code by switching between two types of frequency bands, a non-overlapping band which does not overlap with the frequency band of ping-pong transmission, in synchronization with a burst cycle of ping-pong transmission; Switching the set of carrier frequency and baud rate to switch between the overlap band and the non-overlap band, using the non-overlap band in the timing section affected by near-end crosstalk noise,
A subscriber line transmission system having a configuration for transmitting a modulation code using an overlap band in a timing section affected by far-end crosstalk noise. 3. A subscriber line transmission system connected by a ping-pong transmission line and a line that mutually influences near-end crosstalk noise and far-end crosstalk noise, an overlap band overlapping a frequency band of ping-pong transmission, and Frequency band switching transmission means for transmitting a modulation code by switching between two types of frequency bands, a non-overlapping band which does not overlap with the frequency band of ping-pong transmission, in synchronization with a burst cycle of ping-pong transmission; Has means for transmitting a modulation code using a plurality of carriers, each of which is modulated at a predetermined baud rate and has a different frequency, and switches on / off transmission of a carrier serving as the overlap band among the plurality of carriers, Non-overlap band is used in the timing section affected by end crosstalk noise, Subscriber line transmission system characterized by having a configuration for transmitting the modulated symbols by using overlap band timing interval undergoing. 4. A station side transmitting / receiving apparatus connected by a ping-pong transmission line and a line that mutually affects the near-end crosstalk noise and the far-end crosstalk noise, comprising: an overlap band overlapping with a ping-pong transmission frequency band; A frequency band switching transmission means for switching and transmitting modulation codes of two types of frequency bands of a non-overlapping band which do not overlap with a transmission frequency band in synchronization with a burst cycle of ping-pong transmission; , Switching the carrier frequency and / or baud rate to be used, or switching on / off the transmission of the carrier frequency to be used and using the non-overlap band in the timing section affected by the near-end crosstalk noise, Configuration for transmitting modulation code using overlap band in timing section affected by noise Station side transmitting and receiving device characterized in that it comprises. 5. A subscriber side transmitting / receiving apparatus connected by a ping-pong transmission line and a line that mutually affects near-end crosstalk noise and far-end crosstalk noise, comprising: an overlap band overlapping a frequency band of ping-pong transmission; Frequency band switching receiving means for switching and receiving modulation codes of two types of frequency bands of a non-overlapping band not overlapping with the frequency band of ping-pong transmission in synchronization with a burst period of ping-pong transmission notified from the station side, The frequency band switching receiving means switches the receiving carrier frequency and / or the baud rate or both, or switches the receiving carrier frequency on / off, to set the non-overlapping band in the timing section affected by the near-end crosstalk noise. The modulation code is used in the timing section affected by the far-end crosstalk noise. Subscriber transceiver apparatus characterized by having a configuration to receive.