JPS63107248A - Signal transmission system for local area network - Google Patents

Abstract

PURPOSE:To easily separate noise and an input/output signal from each other and to surely transmit the data signal by processing the input/output signal to a power line in accordance with the spectrum spread modulating/ demodulating system. CONSTITUTION:An exchange cutting capacitor 52 is connected in series to a loop in the succeeding stage of a plug PL, and a voltage dividing resistance 53 and a line interface circuit consisting of phototransistors or light emitting diodes of photocouplers are connected in parallel to the loop. A modulator 56 and a demodulator 57 in the spectrum spread system are connected between amplifiers 54 and 55 and an interface 60 of a terminal equipment, and the noise used for modulation and demodulation is generated by a noise generator 59. It is unnecessary to lay another line because the already provided power line is used, and various noises and signals on the power line are easily separated from each other to improve the tolerance to noise because modulation and demodulation are performed in accordance with the spectrum spread system.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a local area network signal transmission system,
In particular, the present invention relates to a signal transmission method for a local area network that transmits signals using power lines.

[Prior Art] In recent years, local area networks (hereinafter referred to as LANs), which connect various different data terminal devices such as large computers, office computers, and personal computers via communication lines and perform information processing, have attracted attention. It's starting to happen. LAN is used for data communication within a company or within a relatively small area.

Twisted pair wires, coaxial cables, optical fibers, and the like have been used as transmission media to connect data terminals or host devices in a LAN. However, these conventional transmission media require new installation, which increases the cost of constructing a network and makes it difficult to change the network configuration or add or move terminal equipment. .

[Problems to be solved by the invention] On the other hand, it is not unthinkable to connect terminals and hosts using existing lines such as telephone lines and power lines to configure a network.However, telephone lines There are problems with communication speed and line quality, making it difficult to perform high-speed data transfer.

Furthermore, the technical idea of transmitting data using power lines has existed for a relatively long time, and power companies are currently implementing power line carrier telephones and remote control of power equipment (e.g. electric water heaters) via power lines. ing. Also reprinted are transport-type interfaces that use commercial power lines as communication channels, and adapter-type remote control switches. Furthermore, in home automation, ie, a centralized control system for home appliances, which has been attracting attention in recent years, technology for controlling via power lines has also been proposed.

However, when transmitting relatively large amounts of data at high speeds, such as over a LAN, power lines are not used very often.The reason is that various devices are connected to the power lines, and
This is because various noise components are mixed in, and unlike telephone lines, line standards are not defined, so there is a problem that a satisfactory S/N ratio cannot be obtained as a data communication channel. Furthermore, the impedance of the power line as a signal line is not constant, and therefore a special device is required as a driver for driving the signal line.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a signal transmission system for a local area network in which a data terminal and a host are connected via a predetermined line to perform data communication. In addition to using a power line as the line, the line is connected to the data terminal or the host through an interface means that modulates and demodulates the input/output data signals of the data terminal and host device connected to the line using a spread spectrum method. did.

[Operation] According to the above configuration, since the input/output signals to the power line are processed using the spread spectrum modulation/demodulation method, noise and input/output signals can be easily separated, and data signals can be reliably transmitted.

[Example] Hereinafter, the present invention will be described in detail based on the example shown in the drawings.

Figure 1 shows a LAN using the power yj transport system according to the present invention.
The schematic configuration of the system is shown. As shown in the figure, a workstation 3 consisting of a host computer 1, a file server 2, a personal computer and other terminals
, or a host and a terminal device such as the office computer 4 are respectively connected to the AClooV power 1lJP. An interface device 5 is inserted between the host device and the terminal. The interface device 5 and the power line P are connected by a plug PL and a connector C.

FIG. 2 shows the structure of the interface device 5 of FIG. In the interface device shown in FIG. 2, a transmitting/receiving circuit end is connected to a power line P via a connector C and a plug PL. That is, in the loop after the plug PL, m capacitors 52 for cutting off AC are connected in series, and line interface circuits each consisting of a voltage dividing resistor 53 and a phototransistor or a light emitting diode of a photocoupler are connected in parallel. be done.

An amplifier 54 for amplifying the transmitted signal to a predetermined level is connected to the light emitting diode of the photocoupler 51 on the transmitting side, and an amplifier 55 for amplifying the received signal is connected to the phototransistor of the photocoupler 51 on the receiving side. . With this configuration, the power line and the interface circuits below the amplifiers 54 and 55 are completely electrically isolated.

A spread spectrum modulator 56 and demodulator 57 are connected between the amplifiers 54, 55 and the interfaces 6o of the terminal devices 1 to 4 shown in FIG. The noise used for modulation and demodulation is generated by the noise generator 5.
Generated by 9. Modulation and demodulation are executed under the control of a computing unit 58 composed of a microprocessor or the like.

The terminal device interface 60 is, for example, R5232.
For example, serial transmission using a baseband recurrent method is performed via C or other serial ports. That is, the interface 60 inputs and outputs a serial digital pulse train.

The interface circuit 60, the spread spectrum modulator 56, and the demodulator 57 are connected by a two-wire line such as a twisted pair wire.

An outline of the modulation operation in the spread spectrum method is shown in FIGS. 3 and 4.

FIGS. 3 and 4 show power spectra before and after modulation in the spread spectrum modulation method.

As mentioned above, the digital data input from the interface circuit 60 is a pulse train transmitted in series.
The power spectrum of the input baseband signal exhibits a relatively narrow frequency band. In the spread spectrum modulation method, such an input signal is converted into a regular pseudo-random noise signal. At this time, the baseband signal is pseudo-randomized into pseudo-white noise using an arithmetic unit 58 and a noise generator 59. The power spectrum is spread from a relatively narrow band and high power spectrum shown in FIG. 3 to a relatively low level signal having a wide band as shown in FIG.

On the other hand, the noise on the power line P has a relatively narrow band and high level, such as surges, as shown by the symbol N in Figure 4.
Since the noise is hum or the like, the noise and signal can be easily separated by using a power distribution as shown in FIG.

The signal modulated as described above by the modulator 56 is input to the amplifier 54, applied to the photocoupler 51, and transmitted to the line.

On the other hand, the signal on the line is input to an amplifier 55 via a photocoupler 51 and then input to a spread spectrum demodulator 57.

In the demodulation operation, the arithmetic unit 58 performs demodulation by calculating the autocorrelation of the input signal under conditions corresponding to the regularity of pseudo-randomization during modulation.

The demodulated baseband signal is sent to the interface circuit 6
It is input to 0.

Data is input and output to and from the power line P in the manner described above. In the above configuration, the modulator 56 and the demodulator 57 only faithfully modulate or demodulate the input baseband signal into a spread spectrum signal, and the data transmission rate or communication protocol is controlled by the interface circuit of each terminal. 60.

Therefore, in principle, a network can be constructed without being influenced by conditions such as terminal transmission speed and communication protocol.

Furthermore, in the above configuration, as shown in FIG. 4, the signal transmitted to the power line P is at a low level over the entire frequency band, so the unnecessary radiant energy level of the power line is regulated by law (65 dB over the entire frequency band; Since φdB is set to 1.V, it is easy to satisfy the condition of approximately 1.8 V).

[Effects of the Invention] As is clear from the above description, according to the present invention, a data terminal and a host device are connected via a predetermined line,
In a local area network signal transmission method for data communication, a power line is used as the line, and the line is connected via an interface means that modulates and demodulates input/output data signals of data terminals and host devices connected to the line using a spread spectrum method. Since we have adopted a configuration in which the data terminal or host device is connected,
Since existing power lines are used, there is no need to install new lines, and the network can be constructed at low cost. In addition, when adding, removing, moving, or moving various types of terminal equipment, the terminal equipment can be connected to and removed from the line by simply plugging it into and unplugging it from the outlet, making it much easier to change the configuration compared to conventional networks. It also has the advantage of being easy.

Further, according to the above configuration, since modulation and demodulation is performed using the spread spectrum method, it is easy to separate signals from various noises in the power line, and there is an excellent effect that noise resistance is increased and signal input/output can be performed reliably.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a schematic configuration of a LAN adopting the present invention, Fig. 2 is a block diagram showing the configuration of the interface device in Fig. 1, and Figs. 3 and 4 are modulation in the spread spectrum method. It is an explanatory diagram showing the power spectrum before and after. l...Host computer 2...File server 3...Work station 4...Office computer 5...Interface device P...Power line 51...Photo coupler 56
...Modulator 57...Demodulator 1, ↑l 1 pin]-7 27th Illust-I and 3 work nuts Figure 1 Figure 2 Eaves mantissa n ji Go back and forth Omu Koyoi [to the faith of sorrowful change] f
Sun/Moon (Figure 4)

Claims (1)

[Claims] In a local area network signal transmission system in which a data terminal and a host device are connected via a predetermined line to perform data communication, a power line is used as the line, and input/output data of the data terminal and host device connected to the line is used. A signal transmission method for a local area network characterized by connecting a line and a data terminal or host device through an interface means that modulates and demodulates a signal using a spread spectrum method.