Source: http://www.google.com/patents/US7555055?dq=5,742,768
Timestamp: 2016-06-29 13:42:16
Document Index: 291815888

Matched Legal Cases: ['Application No. 04027867', 'Application No. 04027868', 'Application No. 04027869', 'Application No. 04027870', 'Application No. 04027871', 'Application No. 04027872', 'Application No. 04027873']

Patent US7555055 - Digital subscriber line communicating system - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inPatentsA digital subscriber line communicating system having a central office and a remote terminal connected through a telephone line, the transmitting side comprising a sliding window transmitting unit for transmitting DMT symbols according to the sliding window through the telephone line to the receiving...http://www.google.com/patents/US7555055?utm_source=gb-gplus-sharePatent US7555055 - Digital subscriber line communicating systemAdvanced Patent SearchPublication numberUS7555055 B2Publication typeGrantApplication numberUS 10/918,071Publication dateJun 30, 2009Priority dateMay 26, 1998Fee statusPaidAlso published asEP0961449A2, EP0961449A3, EP1511256A2, EP1511256A3, EP1511257A2, EP1511257A3, EP1511258A2, EP1511258A3, EP1511259A2, EP1511259A3, EP1511260A2, EP1511260A3, EP1511261A2, EP1511261A3, EP1511262A2, EP1511262A3, EP1605656A2, US6944216, US6965649, US7088783, US7126995, US7173984, US7295620, US7386037, US20050008082, US20050008083, US20050013382, US20050013431, US20050018781, US20050025309, US20050105601Publication number10918071, 918071, US 7555055 B2, US 7555055B2, US-B2-7555055, US7555055 B2, US7555055B2InventorsSeiji Miyoshi, Yutaka Awata, Hiroyasu Murata, Nobukazu Koizumi, Takashi SasakiOriginal AssigneeFujitsu LimitedExport CitationBiBTeX, EndNote, RefManPatent Citations (31), Non-Patent Citations (17), Classifications (27), Legal Events (1) External Links: USPTO, USPTO Assignment, EspacenetDigital subscriber line communicating system
US 7555055 B2Abstract
A digital subscriber line communicating system having a central office and a remote terminal connected through a telephone line, the transmitting side comprising a sliding window transmitting unit for transmitting DMT symbols according to the sliding window through the telephone line to the receiving side, and the receiving side comprising a sliding window receiving unit for receiving DMT symbols according to the sliding window from the transmitting side, the sliding window indicating the phase of cross-talk condition due to a TCM-ISDN transmission at the receiving side, whereby TCM cross-talk can be reduced without largely departing from the standard system.
1. A digital subscriber line communicating method which performs data communication by utilizing a telephone line as a high speed data communication line, comprising:
determining whether or not a receiving side can receive a switching signal during a far end cross talk (FEXT) duration defined according to a sliding window bitmap method; and
transmitting, during training for starting data communication, a signal for representing a switching of the training sequence from a transmitting side to the receiving side in accordance with a timing when the receiving side can receive the switching signal during the far end cross talk (FEXT) duration.
2. A digital subscriber line communicating method which performs data communication by utilizing a telephone line as a high speed data communication line, comprising:
determining whether or not a receiving side can receive a head of a switching signal during a far end cross talk (FEXT) duration defined according to a sliding window bitmap method; and
transmitting, during training for starting data communication, a signal for representing a switching of the training sequence from a transmitting side to the receiving side in accordance with a timing when the receiving side can receive the head of the switching signal during the far end cross talk (FEXT) duration.
3. A digital subscriber line communicating method which performs data communication by utilizing a telephone line as a high speed data communication line, comprising:
determining whether or not a receiving side can receive a head of a switching symbol during a far end cross talk (FEXT) duration defined according to a sliding window bitmap method; and
transmitting, during training for starting data communication, a symbol for representing a switching of the training sequence from a transmitting side to the receiving side in accordance with a timing when the receiving side can receive the head of the switching symbol during the far end cross talk (FEXT) duration.
4. An xDSL apparatus which performs data communication by utilizing a telephone line as a high speed data communication line, comprising:
determining means determining whether or not a side can receive a switching signal during a far end cross talk (FEXT) duration defined according to a sliding window bitmap method; and
transmitting means transmitting, during training for starting data communication, a signal for representing a switching of the training sequence from a transmitting side to the receiving side in accordance with a timing when the receiving side can receive the switching signal during the far end cross talk (FEXT) duration.
5. An xDSL apparatus which performs data communication by utilizing a telephone line as a high speed data communication line, comprising:
determining means determining whether or not a receiving side can receive a head of a switching signal during a far end cross talk (FEXT) duration defined according to a sliding window bitmap method; and
transmitting means transmitting, during training for starting data communication, a signal for representing a switching of the training sequence from a transmitting side to the receiving side in accordance with a timing when the receiving side can receive the head of the switching signal during the far end cross talk (FEXT) duration.
6. An xDSL apparatus which performs data communication by utilizing a telephone line, which can be affected by a cross talk of ISDN ping pong transmission, as a high speed data communication line, comprising:
determining means determining whether or not a receiving side can receive a head of a switching symbol during a far end cross talk (FEXT) duration defined according to a sliding window bitmap method; and
transmitting means transmitting, during training for starting data communication, a symbol for representing a switching of the training sequence from a transmitting side to the receiving side in accordance with a timing when the receiving side can receive the head of the switching symbol during the far end cross talk (FEXT) duration. Description
The present application is a divisional of U.S. patent application Ser. No. 09/318,445 filed on May 25, 1999 now U.S. Pat. No. 6,965,649 which claims priority from Japanese Patent Application number 10-144913 filed May 26, 1998.
Firstly, transmitting data is input into an ADSL transceiver unit (ATU) in the central office and a non-symbol time (� kHz) of the data is stored in a serial to parallel buffer. The stored data are divided into a plurality of groups. A predetermined number of transmission bits per carrier signal is previously allocated to each group in accordance with a transmitting bitmap which will be described later in detail. Each group is output to an encoder. In the encoder, each group of the input bit series is converted into a signal point expressed by a complex number for an orthogonal amplitude modulation and is output to IFFT. The IFFT performs the conversion from each of the signal points to transmit the signal sequences by an inverse fast Fourier transform. The signals from the IFFT are output to a parallel to serial buffer. Here the sixteen points of the outputs of the IFFT are added as a Cyclic Prefix to the head of each DMT symbol. The output of the parallel to serial buffer is supplied to a D/A converter in which the digital signal with a sampling frequency of 1.104 MHz is converted into an analog signal. The analog signal is transmitted through a metalic line to a remote terminal.
According to another aspect of the present invention, the transmission side is a remote terminal and the receiving side is a central office. In this aspect, the remote terminal comprises: a timing signal receiving unit for receiving a timing phase via received modulated symbol according to a downstream sliding window from the central office, the timing signal being synchronized with a transmission system which interferes the central office and the remote terminal. In this aspect also, the sliding window generating unit is operatively connected to the timing signal receiving unit, and the sliding window is an upstream sliding window indicating the phase of noise condition of the central office; and a sliding window transmitting unit for transmits modulated symbols according to the upstream sliding window through the communication line to the central office. The upstream sliding window indicates a cross-talk duration due to the TCM ISDN transmission at the central office. The upstream sliding window is generated in such a way that an inside symbol of the upstream sliding window is received by the central office in a third cross-talk duration determined with a far end cross-talk duration at the central office. In an embodiment, a fourth cross-talk duration determined with a near end cross-talk duration at the central office is within a prior half of each cycle of the timing signal, and the third cross-talk duration is within a latter half of each of the timing signal, and inside of the upstream sliding window is formed within the third cross-talk duration. When the first modulated symbol is synchronized with the head of one cycle of the timing signal, the remote terminal comprises a duration discriminating unit for discriminating whether N-th modulated symbol belongs to inside or outside of the upstream sliding window.
Firstly, transmitting data is input into an ADSL transceiver unit (ATU) in the central office and a non-symbol time (�0 kHz) of the data is stored in a serial to parallel buffer 10. The stored data are divided into a plurality of groups. A predetermined number of transmission bits b0, . . . , or bi per a carrier signal is previously allocated to each group in accordance with a transmitting bitmap 60 which will be described later in detail. Each group is output to an encoder 20. In the encoder 20, each group of the input bit series is converted into a signal point expressed by a complex number for an orthogonal amplitude modulation and is output to IFFT 30. The IFFT 30 performs the conversion from each of the signal points to transmit signal sequence by an inverse fast Fourier transform. The signals from the IFFT 30 are output to a parallel to serial buffer 40. Here the sixteen tail points 240-255 of the outputs of the IFFT 30 are added as a Cyclic Prefix to the head of each DMT symbol. The output of the parallel to serial buffer 40 is supplied to a D/A converter 50 in which the digital signal with a sampling frequency of 1.104 MHz is converted into an analog signal. The analog signal is transmitted through a metalic line 100 to a remote terminal.
At the remote terminal side, the analog signal is converted into a digital signal with the sampling frequency of 1.104 MHz by an A/D converter 110. Each DMT symbol of the digital signal is stored in a serial to parallel buffer 120. In the buffer 120, the Cyclic Prefix is removed from the digital signal, and the remaining signal is output to an FFT 130. In the FFT 130, a fast Fourier transform is effected to generate or demodulate the signal points. The demodulated signal points are decoded by a decoder 140 in accordance with a receiving bitmap 160 having the same values as those in the transmitting bitmap 60. The decoded data are stored in a parallel to serial buffer 150 as receiving data of bit-sequences b0, and bi.
FIG. 2 is a diagram showing a method for transmitting synchronization signals according to an embodiment of the present invention. In FIG. 2, (1) represents a reference clock signal for transmitting a Time Compression Modulation (TCM) signal having a frequency of 400 Hz between the central office to the remote terminal; (2) represents NEXT durations, i.e., C-NEXT durations and FEXT durations, i.e., C-FEXT durations at the central office which are synchronized with the reference clock signal (1) of 400 Hz; (3) represents FEXT durations, i.e., R-NEXT durations and NEXT durations, i.e., R-NEXT durations at the remote terminal which are synchronized with the reference clock signal (1) of 400 Hz; (4) represents symbols A and B transmitted from the central office to the remote terminal during an initial training; and (5) represents symbols A and B received by the remote terminal. The time difference between (4) and (5) is the propagation delay. Each of the symbols A and B has a duration of 256 samples. The symbols A and B are used to inform the NEXT duration and the FEXT duration from the central office to the remote terminal.
FIG. 5 shows how to define the NEXT duration and the FEXT duration for measuring the S/N. In FIG. 5, (1) shows the reference clock signal of 400 Hz; (2) shows the original R-FEXT duration and the original R-NEXT duration at the remote terminal when S/N is not measured; (3) shows the definition of an R-FEXT duration “a” for measuring S/N and of an R-NEXT duration “e” for measuring S/N; (4) shows DMT symbols in the FEXT duration “a”; and (5) shows DMT symbols in the R-NEXT duration “e”. As shown in FIG. 5, the R-NEXT duration “a” for measuring S/N and the R-FEXT duration “e” for measuring S/N are defined within the original R-FEXT duration and the original R-NEXT duration, respectively. The number of bit calculated from S/N measured in the NEXT duration must be a value which can ensure a predetermined bit error rate (hereinafter referred to as BER). To this end, as shown in (4) of FIG. 5, only the DMT symbols within the R-FEXT duration “a” are used to measure the S/N in the R-FEXT duration; and as shown in (5) of FIG. 5, only-the DMT symbols within the R-NEXT duration “e” are used to measure the S/N in the R-NEXT duration. The DMT symbols which are not included in either the R-FEXT duration “a” or R-NEXT duration “e” are not used to measure the S/N because they have no meaning as information to determine the number of bits to be transmitted.
If should be noted that (d+e+f) is equal to “b” in FIG. 3 or in FIG. 11.
a transmitting capacity 1=(b−total bit number in FEXT)�α�modulation rate; and
a transmitting capacity 2=(b−total bit number in NEXT)�1.0�modulation rate.
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Signals, Systems, & Computers, Nov. 2, 1997. pp. 573-577, XP010280818.Classifications U.S. Classification375/285, 375/219, 379/399.01International ClassificationH04B3/32, H04J11/00, H04M11/06, H04L5/14, H04L7/00, H04L5/16, H04M3/00, H04B15/00, H04L27/26, H04B1/38Cooperative ClassificationH04L27/2613, H04L27/2655, H04B3/32, H04Q2213/13039, H04M11/062, H04L5/0046, H04Q2213/13209, H04L5/0007, H04Q2213/1319European ClassificationH04L5/00C4A, H04L27/26M3A, H04M11/06B, H04B3/32, H04L27/26M3Legal EventsDateCodeEventDescriptionNov 28, 2012FPAYFee paymentYear of fee payment: 4RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services