Digital subscriber line transmission method, apparatus and system

• US 7,336,627 B1
• Filed: 09/27/2000
• Issued: 02/26/2008
• Est. Priority Date: 05/21/1999
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Hasegawa, Kazutomo, Asahina, Hidetake, Miyoshi, Seiji, Awata, Yutaka, Koizumi, Nobukazu
• Primary Examiner(s): Ryman; Daniel J.
• Application Number:
  US09/671,468
• Time in Patent Office: 2,708 Days
• Field of Search: 370/201, 370/524, 379/90.61, 379/100.15, 379/88.17, 379/242, 379/399, 379/417, 455/293
• US Class Current: 370/282
• CPC Class Codes: H04B 3/02 Details
• CPC Class Codes: H04B 3/10 by pilot signal
• CPC Class Codes: H04B 3/32 Reducing cross-talk, e.g. by compensating
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601
• CPC Class Codes: H04L 5/1438 Negotiation of transmission parameters prior to communication modified according to link quality H04L1/0001
• CPC Class Codes: H04L 5/1469 using time-sharing
• CPC Class Codes: H04L 5/1492 with time compression, e.g. operating according to the ping-pong technique
• CPC Class Codes: H04M 11/062 using different frequency bands for speech and other data
• CPC Class Codes: H04M 11/068 using time division multiplex techniques; integrated services digital networks H04Q11/0428
• CPC Class Codes: H04Q 11/0457 Connection protocols
• CPC Class Codes: H04Q 2213/13039 Asymmetrical two-way transmission, e.g. ADSL, HDSL
• CPC Class Codes: H04Q 2213/13176 Common channel signaling, CCS7
• CPC Class Codes: H04Q 2213/13209 ISDN

Abstract

A digital subscriber line transmission (xDSL) system includes a transmitting side which transmits training symbols by adding some data that is contained in a training symbol sequence onto at least one of the beginning and the end of this symbol sequence and then transmits the training symbol sequence. A receiving side removes the data that has been added onto the training symbol sequence and executes training processing. The length of the training symbol sequence and of a transmit symbol sequence at time of normal communication is set in such a manner that the symbol sequence will not fall within an interval in which effects of near-end crosstalk from a neighboring line are received. The data added to the training symbol sequence specifies an interval in which effects of the crosstalk are received.

Claims

1. A digital subscriber line transmission method for transmitting downstream data from a device on an office side to a device on a subscriber side and upstream data from the device on the subscriber side to the device on the office side over a single line by switching between these data transmissions in time-division fashion, dividing data of one symbol, modulating carrier waves having different frequencies by each item of divided data and frequency-multiplexing the modulated signals, and transmitting the frequency-multiplexed signals in bursts a few symbols at a time, said method comprising the steps of:

incorporating timing information, which specifies an interval in which effects of crosstalk from a neighboring line are received, in a training symbol sequence at a time of training carried out prior to data communication; and

transmitting the training symbol sequence in which the timing information is incorporated from the device on the office side to the device on the subscriber side wherein the subscriber side determines a transmit interval for the upstream data and a receive interval for the downstream data based on the timing information,

wherein the timing information is incorporated in the training symbol sequence by changing the phase between adjacent training symbols by the device on the office side to create a phase-change point and wherein the phase-change point in the training symbol sequence is detected by the device on the subscriber side and a timing which is a set time before or a set time after the phase-change detection time is adopted as the start timing of said interval in which effects of crosstalk from a neighboring line are received.

2. The method according to claim 1, wherein the phase of adjacent symbols constructing a training symbol sequence is varied by 90°

or 180°

.

3. The method according to claim 1, wherein a carrier wave of a predetermined frequency is quadrature modulated and the phase between adjacent symbols obtained by quadrature modulation is varied.

4. A digital subscriber line transmission apparatus in a digital subscriber line transmission system for transmitting downstream data from a device on an office side to a device on a subscriber side and upstream data from the device on the subscriber side to the device on the office side over a single line by switching between these data transmissions in time-division fashion, dividing data of one symbol, modulating carrier waves having different frequencies by each item of divided data and frequency-multiplexing the modulated signals, and transmitting the frequency-multiplexed signals in bursts a few symbols at a time, said apparatus comprising:

a timing-information insertion unit to insert timing information, which specifies an interval in which effects of crosstalk from a neighboring line are received, into a training symbol sequence at time of training carried out prior to data communication; and

a transmitting unit to transmit the training symbol sequence, into which the timing information has been inserted, from the device on the office side to the device on the subscriber side wherein the subscriber side determines a transmit interval for the upstream data and a receive interval for the downstream data based on the timing information,

wherein said timing-information insertion unit inserts the timing information into the training symbol sequence by changing the phase between adjacent training symbols to create a phase-change point and wherein the device on the subscriber side detects the phase-change point in the training symbol sequence and adopts a timing which is a set time before or a set time after the phase-change detection time, as the start timing of said interval in which effects of crosstalk from a neighboring line are received.

5. The apparatus according to claim 4, wherein said timing-information insertion unit varies by 90°

or 180°

the phase of adjacent symbols constructing a training symbol sequence.

6. A digital subscriber line transmission system for transmitting downstream data from a device on an office side to a device on a subscriber side and upstream data from the device on the subscriber side to the device on the office side over a single line by switching between these data transmissions in time-division fashion, dividing data of one symbol, modulating carrier waves having different frequencies by each item of divided data and frequency-multiplexing the modulated signals, and transmitting the frequency-multiplexed signals in bursts a few symbols at a time, said system comprising:

a cable to accommodate said line as a first line and another line as a second line on which transmission of downstream data and transmission of upstream data are performed in time-division fashion;

a training-symbol transmitting unit to transmit a training symbol via said first line at a time of training carried out prior to data communication; and

a training-symbol receiving unit to receive a training symbol via said first line;

said training-symbol transmitting unit including;

a timing-information insertion unit to insert timing information, which specifies an interval in which effects of crosstalk from said second line are received, into a training symbol sequence at time of training carried out prior to data communication; and

a transmitting unit to transmit the training symbol sequence into which the timing information is inserted from the device on the office side to the device on the subscriber side wherein the subscriber side determines a transmit interval for the upstream data and a receive interval for the downstream data based on the timing information; and

said training-symbol receiving unit includes;

a timing information extraction unit to extract the timing information from the training symbol sequence; and

a processor to execute training processing based upon this timing information,

wherein said timing-information insertion unit inserts the timing information into the training symbol sequence by changing the phase between adjacent training symbols to create a phase-change point and said timing information extraction unit detects the phase-change point in the training symbol sequence and adopts a timing which is a set time before or a set time after the phase-change detection time, as the start timing of said interval in which effects of crosstalk from said second line are received.

7. A digital subscriber line transmission apparatus in a digital subscriber line transmission system for transmitting downstream data from a device on an office side to a device on a subscriber side and upstream data from the device on the subscriber side to the device on the office side over a single line by switching between these data transmissions in time-division fashion, dividing data of one symbol, modulating carrier waves having different frequencies by each item of divided data and frequency-multiplexing the modulated signals, and transmitting the frequency-multiplexed signals in bursts a few symbols at a time, said apparatus comprising:

a timing-information insertion unit to insert timing information, which specifies an interval in which effects of crosstalk from a neighboring line are received, in a training symbol sequence at a time of training carried out prior to data communication; and

a transmitting unit to transmit the training symbol sequence in which the timing information is incorporated from the device on the office side to the device on the subscriber side,

wherein the timing-information insertion unit inserts the timing information into the training symbol sequence to create a phase-change point by varying the phase of training symbols, and a time which is a set time before or a set time after the phase-change point is regarded as the start of said interval.

8. A digital subscriber line transmission system for transmitting downstream data from a device on an office side to a device on a subscriber side and upstream data from the device on the subscriber side to the device on the office side over a single line by switching between these data transmissions in time-division fashion, dividing data of one symbol, modulating carrier waves having different frequencies by each item of divided data and frequency-multiplexing the modulated signals, and transmitting the frequency-multiplexed signals in bursts a few symbols at a time, said system comprising:

a cable to accommodate said line as a first line and another line as a second line on which transmission of downstream data and transmission of upstream data are performed in time-division fashion;

a training-symbol transmitting unit to transmit a training symbol via said first line at a time of training carried out prior to data communication; and

a training-symbol receiving unit to receive a training symbol via said first line;

said training-symbol transmitting unit including;

a timing-information insertion unit to insert timing information, which specifies an interval in which effects of crosstalk from said second line are received, into a training symbol sequence at a time of training carried out prior to data communication; and

a transmitting unit to transmit the training symbol sequence into which the timing information is inserted from the device on the office side to the device on the subscriber side; and

said training-symbol receiving unit including;

a timing-information extraction unit to extract the timing information from the training symbol sequence; and

a processor to execute training processing based upon the timing information,

wherein said timing-information insertion unit inserts the timing information into the training symbol sequence to create a phase-change point by varying the phase between adjacent training symbols, and said timing-information extraction unit detects said phase-change point and adopts a time which is a set time before or a set time after the phase-change point as the start of said interval in which effects of crosstalk from the second line are received.

9. A TDD-digital subscriber line transmission method for transmitting downstream data from a device on an office side to a device on a subscriber side and upstream data from the device on the subscriber side to the device on the office side over a single line by switching between these data transmissions in time-division fashion, dividing data of one symbol, modulating carrier waves having different frequencies by each item of divided data and frequency-multiplexing the modulated signals, and transmitting the frequency-multiplexed signals in bursts a few symbols at a time, said method comprising the steps of:

incorporating timing information, which specifies an interval in which effects of crosstalk from a neighboring ISDN ping-pong transmission line are received, in a training symbol sequence at a time of training carried out prior to data communication; and

transmitting the training symbol sequence in which the timing information is incorporated from the device on the office side to the device on the subscriber side wherein the subscriber side determines a transmit interval for the upstream data and a receive interval for the downstream data based on the timing information,

wherein the timing information is incorporated in the training symbol sequence to create a phase-change point by changing the phase between adjacent training symbols during a transmit interval of the ISDN ping-pong transmission as a FEXT interval by the device on the office side and the phase-change point in the training symbol sequence is detected by the device on the subscriber side and a timing which is a set time before or a set time after the phase-change detection time is adopted as the start timing of said interval in which effects of crosstalk from a neighboring ISDN ping-pong transmission line are received, and

wherein a carrier wave of a predetermined frequency is quadrature modulated and the phase between adjacent symbols obtained by quadrature modulation is varied by 90°

or 180°

.

10. A TDD-digital subscriber line transmission apparatus in a TDD-digital subscriber line transmission system for transmitting downstream data from a device on an office side to a device on a subscriber side and upstream data from the device on the subscriber side to the device on the office side over a single line by switching between these data transmissions in time-division fashion, dividing data of one symbol, modulating carrier waves having different frequencies by each item of divided data and frequency-multiplexing the modulated signals, and transmitting the frequency-multiplexed signals in bursts a few symbols at a time, said apparatus comprising:

timing-information insertion means for inserting timing information, which specifies an interval in which effects of crosstalk from a neighboring ISDN ping-pong transmission line are received, into a training symbol sequence at time of training carried out prior to data communication; and

transmitting means for transmitting the training symbol sequence, into which the timing information has been inserted, from the device on the office side to the device on the subscriber side wherein the subscriber side determines a transmit interval for the upstream data and a receive interval for the downstream data based on the timing information,

wherein said timing-information insertion means inserts the timing information into the training symbol sequence by changing the phase between adjacent training symbols to create a phase-change point during a transmit interval of the ISDN ping-pong transmission as a FEXT interval and the device on the subscriber side detects the phase-change point in the training symbol sequence and adopts a timing which is a set time before or a set time after the phase-change detection time, as the start timing of said interval in which effects of crosstalk from a neighboring ISDN ping-pong transmission line are received, and

wherein said timing-information insertion means quadrature-modulates a carrier wave of a predetermined frequency and varies by 90°

or 180°

the phase of adjacent symbols constructing a training symbol sequence.

11. A TDD-digital subscriber line transmission system for transmitting downstream data from a device on an office side to a device on a subscriber side and upstream data from the device on the subscriber side to the device on the office side over a single line by switching between these data transmissions in time-division fashion, dividing data of one symbol, modulating carrier waves having different frequencies by each item of divided data and frequency-multiplexing the modulated signals, and transmitting the frequency-multiplexed signals in bursts a few symbols at a time, said system comprising:

a cable to accommodate said line as a first line and a second line as an ISDN ping-pong transmission line on which transmission of downstream data and transmission of upstream data are performed in time-division fashion;

a training-symbol transmitting unit to transmit a training symbol via said first line at a time of training carried out prior to data communication; and

a training-symbol receiving unit to receive a training symbol via said first line;

said training-symbol transmitting unit including;

a timing-information insertion unit to insert timing information, which specifies an interval in which effects of crosstalk from said second line are received, into a training symbol sequence at time of training carried out prior to data communication; and

a transmitting unit to transmit the training symbol sequence into which the timing information is inserted from the device on the office side to the device on the subscriber side wherein the subscriber side determines a transmit interval for the upstream data and a receive interval for the downstream data based on the timing information; and

said training-symbol receiving unit includes;

a timing information extraction unit to extract the timing information from the training symbol sequence; and

a processor to execute training processing based upon this timing information,

wherein said timing-information insertion unit inserts the timing information into the training symbol sequence by changing the phase between adjacent training symbols to create a phase-change point during a transmit interval of the ISDN ping-pong transmission as a FEXT interval and said timing information extraction unit detects the phase-change point in the training symbol sequence and adopts a timing which is a set time before or a set time after the phase-change detection time, as the start timing of said interval in which effects of crosstalk from said second line are received, and

wherein said timing-information insertion unit quadrature-modulates a carrier wave of a predetermined frequency and varies by 90°

or 180°

the phase of adjacent symbols constructing a training symbol sequence.