JP3766523B2 - Communication device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a communication apparatus, and more particularly to a communication apparatus that transmits a digital signal using a twisted pair wire that is likely to be mixed with noise.
[0002]
[Prior art]
In a conventional communication device, communication is always performed at a determined data transmission rate, or an available transmission rate is set by checking the state of the transmission path before communication is started, and thereafter at a determined data transmission rate. Communicating.
[0003]
[Problems to be solved by the invention]
In general, the upper limit of the data transmission rate of the communication device is determined by the SN ratio in the receiving circuit. When the noise level mixed in the transmission path fluctuates, the SN ratio changes accordingly. In a conventional communication apparatus, communication is performed at the same transmission speed for both a high SN ratio time and a low SN ratio time. For this reason, in a communication apparatus that communicates at a predetermined transmission rate, when the SN ratio fluctuates with time, transmission errors may rapidly increase at times when the SN ratio is low, and communication may become impossible. In addition, the communication device that sets the transmission speed before the start of communication has a drawback that the transmission speed is determined in accordance with the time when the SN ratio is low.
[0004]
In particular, in Japanese telephone subscriber lines, when performing high-speed data communication, there has been a problem that the data transmission speed is greatly reduced due to crosstalk noise from the existing ping-pong ISDN.
[0005]
FIG. 8 is a diagram showing a state in which far-end crosstalk noise and near-end crosstalk noise are mixed from the induced line to the induced line on the subscriber side. In general, in a digital transmission system using a telephone line, near-end crosstalk is larger than far-end crosstalk, so how to avoid near-end crosstalk is an important point for improving transmission performance. In the ping-pong system ISDN, the downstream signal from the central office to the subscriber and the upstream signal from the subscriber to the central office are temporally multiplexed, and the signals of all lines are synchronized as shown in FIG. Mutual near-end crosstalk is avoided. Here, one period of the ping-pong is 2.5 milliseconds.
[0006]
However, since transmission systems other than the ping-pong system ISDN perform data transmission regardless of the ping-pong period, near-end crosstalk from the ping-pong system ISDN cannot be avoided. In recent years, with the widespread use of the Internet, a transmission system that is faster than ISDN is desired. In particular, an asymmetric digital subscriber line (ADSL) system that places importance on the transmission speed in the downstream direction has attracted attention. However, if ADSL and ping-pong ISDN are close together in the telephone cable, the ADSL downlink transmission speed is significantly reduced or the transmission distance is remarkably shortened due to near-end crosstalk from ping-pong ISDN on the subscriber side. It will be. For this reason, the conventional ADSL communication apparatus has a problem that the applicable range is limited to a narrow range in Japan.
[0007]
SUMMARY OF THE INVENTION Therefore, a main object of the present invention is to provide a communication device that efficiently transmits data by stopping data transmission / reception during a time when the crosstalk noise level is high and performing data transmission / reception only during a time when the crosstalk noise level is low. It is.
[0008]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a communication apparatus that performs high-speed data communication with a transmitter that outputs a digitally modulated signal to a transmission line and a receiver that demodulates the received signal into data. A data transmission / reception state in which data is transmitted to the receiver and data is received by the receiver, and a data transmission / reception stop state in which data is not transmitted from the transmitter to the transmission path, and the transmitter indicates that when the data transmission / reception stop state is present Means for modulating and transmitting the signal, and the receiver includes means for demodulating the modulated signal and recognizing that the data transmission / reception is stopped. Data transmission / reception is performed by a periodic control signal synchronized with the ping-pong ISDN. Transition between the state and the data transmission / reception stop state.
[0009]
According to a second aspect of the present invention, there is provided a communication apparatus that performs high-speed data communication with a transmitter that outputs a digitally modulated signal to a transmission line and a receiver that demodulates the received signal into data. A control signal synchronized with the periodically changing crosstalk noise level, with a data transmission / reception state in which data is transmitted to the receiver and data is received by the receiver, and a data transmission / reception stop state in which data is not transmitted from the transmitter to the transmission line Accordingly, when the crosstalk noise level is high, the data transmission / reception stop state is set, and when the crosstalk noise level is low, the data transmission / reception state is set.
[0010]
In the invention according to claim 3, the transmitter according to claim 1 or 2 includes an input buffer, the receiver includes an output buffer, and the speed of data transmitted from the transmitter to the receiver varies with time. It is intended to be kept constant without any problems.
[0011]
In the invention which concerns on Claim 4, the twisted pair wire is used for the transmission path of the signal of Claim 1 or Claim 2 .
In the invention according to claim 5, the transmission of data is performed in claim 1 or claim 2 of the transmitter and receiver bidirectional respectively provided two sets.
[0012]
In the invention according to claim 6, of the two sets of transmitter and receiver of claim 5, the data transmission rate transmitted from one to the other is faster than the data transmission rate transmitted from the other to one. It is characterized by that.
[0013]
In the invention according to claim 7, the transmitter of claim 1 or claim 2 uses quadrature amplitude modulation to transmit and receive data.
[0014]
In the invention according to claim 8, the transmitter of claim 1 or claim 2 uses a plurality of carriers orthogonal to the transmission of data.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic block diagram of an embodiment of the present invention. In one embodiment of the present invention, the interval between a data transmission / reception state in which data is transmitted from the transmission circuit 1 to the transmission path and received by the reception circuit 2 and a data transmission / reception stop state in which the data is not transmitted from the transmission circuit 1 to the transmission path. It has a transition function. For this purpose, the transmission circuit 1 includes a modulator 11 and a transmission control circuit 12, and the reception circuit 2 includes a demodulator 21 and a reception control circuit 22. The modulator 11 performs communication by digitally modulating input data, and the transmission control circuit 12 causes the modulator 11 to transmit or stop data according to the control signal. The demodulator 21 of the receiving circuit 2 demodulates the data transmitted from the transmitting circuit 1 via the transmission path and outputs output data. The reception control circuit 22 demodulates or stops the demodulation by the demodulator 21 according to the control signal.
[0016]
FIG. 2 is a block diagram showing another embodiment of the present invention. In FIG. 2, the transmission circuit 1a includes an elastic buffer 13 that temporarily stores input data and supplies it to the modulator 11, and the reception circuit 2a includes an elastic buffer 23 that temporarily stores and outputs the output of the demodulator 21. The rest of the configuration is the same as in FIG.
[0017]
Thus, by providing the elastic buffers 13 and 23 in the transmission circuit 1a and the reception circuit 2a, respectively, it is possible to prevent the speed of transmitted data from fluctuating with time.
[0018]
FIG. 3 is a block diagram showing still another embodiment of the present invention. In FIG. 3, the transmission circuit 1 b includes a multiplexer 14 and a memory 15 in addition to the modulator 11 and the transmission control circuit 12. The memory 15 stores information indicating the data transmission / reception stop state in advance. In response to the selection signal from the transmission control circuit 12, the multiplexer 14 selects input data when transmission is possible, reads information from the memory 15 when transmission is impossible, and supplies the information to the modulator 11. The modulator 11 Information is transmitted to the receiving circuit 2b. Thereby, the modulator 11 continues in synchronization with the clock from the transmission control circuit 12 without stopping the modulation operation.
[0019]
The reception circuit 2 b includes a demultiplexer 24 in addition to the demodulator 21 and the reception control circuit 22. The demodulator 21 always continues to demodulate the received signal in synchronization with the clock from the reception control circuit 22. The reception control circuit 22 supplies a distribution signal to the demultiplexer 24. The demultiplexer 24 outputs the signal from the demodulator 21 as output data from the reception circuit 2b when in the data transmission / reception state, and receives control when the data transmission / reception is stopped. Output to the circuit 22. The reception control circuit 22 generates the distribution signal and the clock signal from the time when the specific information stored in the memory 15 in the transmission circuit 1b is received. Thereby, the reception circuit 2b can prevent the synchronization with the transmission circuit 1b from being lost.
[0020]
FIG. 4 is a block diagram showing still another embodiment of the present invention. This embodiment is a communication apparatus using a twisted pair wire as a transmission line, and includes a station side modem 3 and a subscriber side modem 4. The station side modem 3 and the subscriber side modem 4 are a combination of the transmission circuit and the reception circuit shown in FIG. That is, the station-side modem 3 includes a modulator 11a as a transmission circuit, a transmission control circuit 12a, a multiplexer 14a, and a memory 15a, and includes a demodulator 21a, a reception control circuit 22a, and a demultiplexer 24a as reception circuits. Furthermore, a hybrid circuit 6 for connecting the modulator 11a and the demodulator 21a to a twisted pair wire 5 as a transmission line is included.
[0021]
The subscriber-side modem 4 also includes a modulator 11b as a transmission circuit, a transmission control circuit 12b, a multiplexer 14b, and a memory 15b, and a demodulator 21b, a reception control circuit 22b, and a demultiplexer 24b as reception circuits. 11b and the demodulator 21b are included in the hybrid circuit 7 for connecting the twisted pair wire 5.
[0022]
The operations of the transmission / reception circuits of the station-side modem 3 and the subscriber-side modem 4 shown in FIG. 4 are the same as those in FIG. 3, and data can be transmitted and received in both directions. If one of them is in a transmission stop state, the other is also in a transmission stop state. Note that either a symmetric type in which both transmission speeds are equal or an asymmetric type in which one is fast may be used.
[0023]
FIG. 5 is a diagram showing a specific example of the modulation circuit used in the embodiment of the present invention. The modulator shown in FIG. 5 modulates transmission data by quadrature amplitude modulation. That is, transmission data is supplied to the encoder 111 and converted into an I phase and a Q phase. The I phase is multiplied by sin ωt by the multiplier 112, and the Q phase is multiplied by cos ωt by the multiplier 113. The respective multiplication outputs are added by the addition circuit 114, and the addition output is given to the DA converter 115 to be converted into an analog signal and outputted to the transmission line via the low-pass filter 116.
[0024]
FIG. 6 is a block diagram of a modulator using a plurality of carriers, and FIG. 7 is a diagram showing an arrangement example of the plurality of carriers shown in FIG.
[0025]
In FIG. 6, transmission data is supplied to an SP conversion circuit 51, serial data is converted into parallel data, and symbols are arranged by an encoder 52 for orthogonal modulation with a plurality of carriers. In quadrature modulation, data is two-dimensionally arranged by sine waves and cos waves, and data bits are assigned to each carrier wave according to the SN ratio. As shown in FIG. 7, the plurality of carrier waves are arranged at a carrier interval of 4.3125 kHz, for example. A plurality of bits are allocated two-dimensionally to a carrier wave having a good signal-to-noise ratio at least, and the symbol-arranged data is subjected to inverse Fourier transform by an inverse Fourier transform circuit 53, and parallel data is transformed by a PS transform circuit 54. After being converted into a serial signal and converted into an analog signal by the DA converter 55, it is output through a low-pass filter 56.
[0026]
【The invention's effect】
As described above, according to the present invention, the data transmission / reception state in which data is transmitted from the transmitter to the transmission line and the data is received by the receiver, and the data transmission / reception stop state in which data is not transmitted from the transmitter to the transmission line are provided. Data transmission / reception is stopped at a time when the crosstalk noise level is high, and data transmission / reception is performed only during a time when the crosstalk noise level is low, so that data can be transmitted efficiently.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram of an embodiment of the present invention.
FIG. 2 is a block diagram showing another embodiment of the present invention.
FIG. 3 is a block diagram showing still another embodiment of the present invention.
FIG. 4 is a block diagram showing still another embodiment of the present invention.
FIG. 5 is a diagram showing a specific example of a modulation circuit used in an embodiment of the present invention.
FIG. 6 is a block diagram of a modulator with multiple carriers.
7 is a diagram showing an example of arrangement of a plurality of carrier waves shown in FIG. 6;
FIG. 8 is a diagram illustrating an example in which far-end crosstalk noise and near-end crosstalk noise are mixed from a guide line to a guided line.
FIG. 9 is a diagram illustrating a time-multiplexed signal of a ping-pong system ISDN.
[Explanation of symbols]
1, 1a, 1b Transmission circuit 2, 2a, 2b Reception circuit 3 Station side modem 4 Subscriber side modem 5 Twisted pair wires 6, 7 Hybrid circuits 11, 11a, 11b Modulators 12, 12a, 12b Transmission control circuits 13, 23 Elastic buffer 14, 14a, 14b Multiplexer 15, 15a, 15b Memory 21, 21a, 21b Demodulator 22, 22a, 22b Reception control circuit 24, 24a, 24b Demultiplexer 51 SP conversion circuit 52 Encoder 53 Inverse Fourier transform circuit 54 PS Conversion circuit 55, 115 DA converter 56, 116 Low pass filter 111 Encoder 112, 113 Multiplier 114 Adder

Claims (8)

In a communication apparatus that performs high-speed data communication with a transmitter that outputs a digitally modulated signal to a transmission line and a receiver that demodulates the received signal into data,
A data transmission / reception state in which data is transmitted from the transmitter to the transmission path and data is received by the receiver; and a data transmission / reception stop state in which data is not transmitted from the transmitter to the transmission path;
The transmitter includes means for modulating and transmitting a signal indicating the data transmission / reception stop state;
The receiver includes means for demodulating the modulated signal and recognizing that data transmission / reception is stopped;
A communication apparatus, wherein a transition is made between the data transmission / reception state and the data transmission / reception stop state by a periodic control signal synchronized with a ping-pong system ISDN . In a communication apparatus that performs high-speed data communication with a transmitter that outputs a digitally modulated signal to a transmission line and a receiver that demodulates the received signal into data,
A data transmission / reception state in which data is transmitted from the transmitter to the transmission path and data is received by the receiver; and a data transmission / reception stop state in which data is not transmitted from the transmitter to the transmission path;
According to a control signal synchronized with a periodically varying crosstalk noise level, the data transmission / reception stop state is entered when the crosstalk noise level is high, and the data transmission / reception state is entered when the crosstalk noise level is low. ,Communication device. The transmitter includes an input buffer;
The receiver includes an output buffer;
The communication apparatus according to claim 1 or 2 , wherein a speed of data transmitted from the transmitter to the receiver is kept constant without temporal variation. The communication apparatus according to claim 1, wherein the signal transmission path is a twisted pair wire. 3. The communication apparatus according to claim 1 , wherein two sets of the transmitter and the receiver are provided to transmit data in both directions. 4.   6. The data transmission rate transmitted from one of the two sets of transmitters and receivers to the other is faster than the data transmission rate transmitted from the other to the one of claim 5. Communication device. The communication apparatus according to claim 1, wherein the transmitter uses quadrature amplitude modulation to transmit and receive data. The communication apparatus according to claim 1 , wherein the transmitter uses a plurality of carrier waves orthogonal to data transmission.

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