JP3078262B2 - Communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication device,
In particular, the present invention relates to a communication device that transmits a digital signal using a twisted pair wire into which noise is likely to be mixed.

[0002]

2. Description of the Related Art A conventional communication apparatus always communicates at a predetermined data transmission rate, or sets an available transmission rate by checking the state of a transmission line before starting communication, and thereafter sets a usable transmission rate. Communication at the specified data transmission speed.

[0003]

In the conventional communication device, the upper limit of the data transmission rate is determined by the SN ratio in the receiving circuit. When the noise level mixed into the transmission line changes, the SN ratio changes accordingly. In a conventional communication device, communication is performed at the same transmission rate both in the time when the SN ratio is high and when the SN ratio is low. For this reason, in a communication device that communicates at a predetermined transmission rate, if the SN ratio fluctuates with time, transmission errors increase sharply at a time when the SN ratio is low,
In some cases, communication became impossible. Further, in a communication device capable of setting the transmission rate before the start of communication, there is a disadvantage that the transmission rate is determined according to the time when the SN ratio is low.

[0004] In particular, in Japanese telephone subscriber lines, when high-speed data communication is performed, there is a problem that the data transmission speed is greatly reduced due to crosstalk noise from the existing ping-pong ISDN.

Therefore, a main object of the present invention is to provide a communication device capable of controlling a data transmission rate in synchronization with a cycle of a change in noise intensity.

[0006]

The invention according to claim 1 is
In a communication device that performs high-speed data communication with a transmitter that outputs a digitally modulated signal to a transmission path and a receiver that demodulates a received signal into data, a signal transmission is performed.
The transmission line is wired and at least part of it is composed of twisted pair wires,
Transmission rate control means for controlling the data transmission rate of the transmitter and the receiver by an external control signal synchronized with the cycle of the change of the noise intensity is provided.

According to a second aspect of the present invention, there is provided a communication apparatus for performing high-speed data communication with a transmitter for outputting a digitally modulated signal to a transmission path and a receiver for demodulating a received signal into data . There are few transmission lines with wires
A part thereof is formed of a twisted pair wire, the receiver includes a noise observation unit that observes a temporal change in noise intensity, and a noise analysis unit that analyzes a temporal periodicity of the observed noise intensity, Further, in synchronization with the analyzed cycle of the noise intensity change,
A transmission rate control means for controlling a data transmission rate of the transmitter and the receiver is provided. .

According to a third aspect of the present invention, one cycle of the noise intensity change of the first or second aspect is divided into at least two or more times, and a signal-to-noise ratio at the receiver side observed at each of the divided times is observed. , The processing speed of the modem included in the transceiver is switched every time.

In the invention according to claim 4, one cycle of the noise intensity change is divided into at least two or more times, and the coding rate of the error correction code is switched for each of the divided times.

In the invention according to claim 5, the signal transmission path is a twisted pair wire. In the invention according to claim 6, the transmitter uses a plurality of carriers for transmitting data.

[0011]

FIG. 1 is a block diagram of one embodiment of the present invention. In FIG. 1, a modem 1 and a modem 2 are connected by a twisted pair line, and transmission and reception of digitally modulated signals are performed between them. The modem 1 includes a transmitting circuit 11 and a receiving circuit 12, and the modem 2 includes a receiving circuit 21.
And a transmission circuit 22, a noise intensity monitor circuit 23 and a speed control signal generation circuit 24 which are features of the present invention.
And are built-in. The noise intensity monitor circuit 23 observes a temporal change in the noise intensity from the reception output of the reception circuit 21 and analyzes the temporal periodicity of the noise intensity. The output of the noise intensity monitor circuit 23 is supplied to a speed control signal generation circuit 24, which generates a speed control signal for controlling the data transmission speed in synchronization with the cycle of the noise intensity change. The generated speed control signal is supplied to the transmission circuit 22 and the transmission circuit 11 and the reception circuit 12 in the modem 1.

Next, the operation will be described. The noise intensity monitor circuit 23 monitors the noise level based on the output of the receiving circuit 21 and analyzes that the fluctuation of the noise level has a temporal periodicity. It outputs a speed control signal for switching the transmission speed between the time when the ratio is high and the time when the SN ratio is low. As a result, a large amount of data can be transmitted between the modems 1 and 2 at a time when the SN ratio is high.

FIG. 2 is a timing chart for explaining the operation of the communication apparatus shown in FIG. As shown in FIG. 2, in the case of the ping-pong ISDN, downlink data from the telephone station to the subscriber is transmitted for 1.178 msec, and uplink data from the subscriber to the telephone station is transmitted for 1.178 msec at the next instant. You. As described above, a method of transmitting one cycle by dividing it into at least two or more times is referred to as burst transmission. The time between an upstream burst and a downstream burst is 0.072 ms.
ec interval time, 2.5 ms in total
In this system, uplink bursts and downlink bursts are transmitted alternately in the ec cycle. Also, from the point of view, all IS
DN subscriber signals are transmitted and received synchronously.

Uplink burst signals from ISDN subscribers are mixed into subscriber receivers other than ISDN as near-end crosstalk noise, causing a reduction in the SN ratio. On the other hand, ISDN
The downstream burst signal to the subscriber mixes into the subscriber line other than ISDN as far-end crosstalk, which is smaller than the near-end crosstalk noise from the upstream burst. That is, the SN ratio at the time of the ISDN uplink burst and the SNR at the time of the ISDN downlink burst are
Find the optimal transmission rate for each of the N ratios,
It is preferable to switch the transmission speed in synchronization with the switching of the N burst signal.

There are two types of methods for switching the transmission speed. One is a method for switching the processing speed of the modem, and the other is a method for switching the coding rate of the error correction code.

FIG. 3 is a block diagram showing an embodiment for switching the processing speed of the modem. In FIG. 3, the transmission circuit 11 shown in FIG.
And the control circuit 113, and the receiving circuit 21
1, an output buffer 212 and a control circuit 213. The input buffer 111 is provided with input data, and the control circuit 113 is provided with a transmission speed control signal from the speed control signal generation circuit 24 shown in FIG. The control circuit 113 supplies a transmission rate control signal to the input buffer 111 and a modulation rate control signal to the modulator 112 based on the transmission rate control signal. On the other hand, the control circuit 213 of the receiving circuit 21 receives the transmission rate control signal, supplies a demodulation rate control signal to the demodulator 211, and supplies the reception rate control signal to the output buffer 212.

In this embodiment, the transmission speed of the input buffer 111 of the transmission circuit 11 and the modulation speed of the modulator 112 are controlled in accordance with the transmission speed control signal, and the demodulation speed and the output buffer of the demodulator 211 of the reception circuit 21 are controlled. By controlling the reception speed in 212, the data transfer speed can be controlled in synchronization with the cycle of the noise intensity change, and an optimum transmission speed can be set.

FIG. 4 is a block diagram showing another example of switching the processing speed of the modem. In FIG. 4, the transmission circuit 1
1 is constructed in the same way as the embodiment shown in FIG.
The receiving circuit 21 is provided with a synchronization extraction circuit 218. In the embodiment shown in FIG. 3, a demodulation rate control signal and a reception rate control signal are output in response to an external transmission rate control signal. On the other hand, in the embodiment shown in FIG. 4, the synchronization extraction circuit 2 is based on the demodulated output of the demodulator 211.
18 outputs a demodulation speed control signal and a reception speed control signal in synchronization with the cycle of the noise intensity change.

FIG. 5 is a block diagram of an embodiment for switching the coding rate of the error correction code. In FIG. 5, a transmission circuit 11 is provided with a convolutional coding circuit 114 between an input buffer 111 and a modulator 112, and a control circuit 115
Supplies a read rate control signal to the input buffer 111 and a coding rate control signal to the convolutional coding circuit 114 in response to the transmission rate control signal. On the other hand, in the receiving circuit 21, the demodulator 2
Between the output buffer 212 and the output buffer 212
4 is inserted, and the control circuit 215 outputs the decoding mode control signal to the Viterbi decoding circuit 214 according to the transmission rate control signal.
Give to.

In this embodiment, a punctured coding technique is used in which the convolutional coding circuit 114 in the transmitting circuit 11 deletes the symbols from the convolutional code by the coding rate control signal and increases the coding rate. Similarly, the receiving circuit 21
The Viterbi decoding circuit 214 performs a decoding operation corresponding to the coding rate of the received data according to the decoding mode control signal.

FIG. 6 is a block diagram of still another embodiment of the present invention. This embodiment uses a twisted pair wire as a transmission path, and is composed of an office-side modem 10 and a subscriber-side modem 20. The office-side modem 10 and the subscriber-side modem 20 are a combination of the transmission circuit and the reception circuit shown in FIG. That is, the station side modem 10 includes an input buffer 111, a modulator 112, and a communication control circuit 113 as a transmission circuit, a demodulator 215, an output buffer 216, and a reception control circuit 217 as a reception circuit. Circuit 6 for connecting demodulator 112 and demodulator 215 to twisted pair wire 5 as a transmission line
including.

The subscriber modem 20 also has an input buffer 114 as a transmission circuit, a modulator 115, and a transmission control circuit 116.
And a reception circuit including a demodulator 211, an output buffer 212, a synchronization extraction circuit 218, and a reception control circuit 213. Further, the modulator 115 and the demodulator 211 are connected by a twisted pair 5
And a hybrid circuit 7 for connecting to

The operation of each transmitting / receiving circuit of the station-side modem 10 and the subscriber-side modem 20 shown in FIG. 6 is the same as that of FIG. 4, and data can be transmitted and received in both directions. Note that both transmission speeds may be the same symmetric type or one may be the asymmetric type in which one is faster.

FIG. 7 is a block diagram showing a modulator and a demodulator using a plurality of carriers to which the present invention is applied.
(A) shows a modulator, and (b) shows a demodulator.

In FIG. 7, input data is input to a constellation encoder 31 and arranged in a symbol for quadrature modulation with a plurality of carriers. For quadrature modulation, si
Data is two-dimensionally arranged by n waves and cos waves,
Data bits are assigned to each carrier according to the SN ratio. At least, a number of bits are two-dimensionally allocated to a carrier having a good SN ratio. The symbol-arranged data is supplied to the IDFT 32 and subjected to inverse Fourier transform. The parallel data is converted to serial data by the P / S converter 33 and converted to an analog signal by the DAC 34. Then, the modulation signal is output from the driver 35. You.

On the other hand, in the demodulator shown in FIG. 7B, an input signal is supplied to a receiver 41 and converted into a digital signal by an ADC 42, and a serial signal is converted into a parallel signal by an S / P converter 43. , DFT44
, And the constellation decoder 45 performs an operation reverse to that of the constellation encoder 31 to output data.

FIG. 8 is a diagram showing an example of the arrangement of a plurality of carriers by the modem shown in FIG. In this example, 30 kHz
4.3125 kHz in the frequency range of z to 1104 kHz
A plurality of carrier waves are arranged at a frequency interval of. Such a modem using a plurality of carriers can be used in place of the modem shown in FIGS.

[0028]

As described above, according to the present invention, noise
Transmitter and receiver data synchronized with the cycle of intensity change
Since the transmission speed is controlled, the data transmission capacity
Large amount of data can be sent at high SN ratio time
And transmission efficiency can be increased. Also on the receiving side
Observe the temporal change of the noise intensity and observe the time period of the noise intensity
By analyzing the reliability, the data can be stored regardless of the control signal from the station.
Data transmission speed and simplify wiring.
Can be

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation of the embodiment shown in FIG. 1;

FIG. 3 is a block diagram showing an embodiment for switching the processing speed of the modem.

FIG. 4 is a block diagram showing an embodiment for switching the processing speed of the modem.

FIG. 5 is a block diagram showing an embodiment for switching a coding rate of an error correction code.

FIG. 6 is a block diagram of still another embodiment of the present invention.

FIG. 7 is a block diagram showing a modulator using a plurality of carriers and a demodulator to which the present invention is applied.

FIG. 8 is a layout diagram of a plurality of carriers by the modem shown in FIG. 4;

[Explanation of symbols]

 1, Modem 5 Twisted pair 6, 7 Hybrid circuit 11, 22 Transmission circuit 12, 21 Receiving circuit 23 Noise intensity monitoring circuit 24 Speed control signal generating circuit 31 Constellation encoder 32 IDFT 33 P / S 34 DAC 35 Driver 41 Receiver 42 ADC 43 S / P 44 DFT 45 Constellation decoder 111, 114 Input buffer 112, 115 Modulator 113, 115, 213, 215 Control circuit 114 Convolutional code circuit 211, 215 Demodulator 212, 216 Output buffer 214 Viterbi decoding circuit 218 Synchronous extraction circuit

Continuation of front page (56) References JP-A-10-30872 (JP, A) JP-A-9-51328 (JP, A) JP-A-8-307385 (JP, A) JP-A-8-84162 (JP) JP-A-7-154472 (JP, A) JP-A-10-303872 (JP, A) JP-A-11-313043 (JP, A) JP-A-11-331106 (JP, A) JP-A-2000 -78105 (JP, A) US Patent 5479447 (US, A) Proceedings of the 1998 IEICE General Conference, Communication 2, p403, B-8-56, "ADSL suitable for crosstalk from TCM-ISDN. Discussion "1998 IEICE Society Conference, Proceedings of the Society Conference, 2, p294, B-8-26," Study of Equalizer Switching Method in ADSL "Proceedings of the 1997 IEICE General Conference, Communication 2, p. 794-795, SB-8-4 "Study of ASDL and VDSL transmission characteristics" IEICE Technical Report, CS 98-37, "ADSL transmission performance analysis results in the presence of ISDN crosstalk noise and study of performance improvement methods" (58) Field surveyed (Int.Cl. ⁷ , DB name) H04J 11/00 H04J 1/00-1/20 H04L 27/00-27/38

Claims (5)

(57) [Claims] 1. A communication device for performing high-speed data communication with a transmitter that outputs a digitally modulated signal to a transmission line and a receiver that demodulates a received signal into data, wherein the signal transmission line is wired. At least part of it is twisted pair
And a transmission rate control means for controlling a data transmission rate of the transmitter and the receiver by an external control signal synchronized with a cycle of a change in the noise intensity. 2. A communication device for performing high-speed data communication with a transmitter that outputs a digitally modulated signal to a transmission line and a receiver that demodulates a received signal into data, wherein the transmission line of the signal is wired. At least part of it is twisted pair
In the configuration, the receiver comprises a noise observation means for observing a temporal change of the noise intensity and a noise analyzing means for analyzing the temporal periodicity of the noise intensity observed by the noise observation means, said noise A communication apparatus, comprising: a transmission rate control unit that controls a data transmission rate of the transmitter and the receiver in synchronization with a cycle of a change in noise intensity analyzed by the analysis unit. 3. The method according to claim 1, wherein one cycle of the noise intensity change is divided into at least two or more times, and the transmission / reception is performed at each time in accordance with a signal-to-noise ratio at the receiver side observed at each of the divided times. 3. The communication device according to claim 1, wherein a processing speed of a modem included in the communication device is switched. 4. The method according to claim 1, wherein one cycle of the noise intensity change is divided into at least two or more times, and a coding rate of an error correction code is switched for each of the divided times. The communication device as described. 5. The communication device according to claim 1, wherein a plurality of carriers are used for transmitting data on the transmitter side.