JP3481484B2 - Simple two-way communication system and its terminal 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 data communication system between a central control device and a terminal device using a broadband transmission line. In particular, it relates to a reception confirmation method for confirming whether or not the data transmitted from the central control device is received by the terminal device. The present invention can be applied to the reception confirmation of the control information of each terminal device in the CATV system.

[0002]

2. Description of the Related Art Conventionally, there is a system in which a central control unit and a terminal unit including a plurality of relay amplifiers are connected to a broadband transmission line to transmit and receive data. It is a system in which a central control device allocates an address to each terminal device, and by specifying the address, monitoring data, control data, measurement data and the like are transmitted and received, and a loader connected to the terminal device is controlled. For example, CAT deployed in the city
A security system using a V network is one example. This security system receives an instruction from the central control unit and sends notification information, for example, or informs the central control unit of the detection result of a fire or the like in accordance with the instruction.

Briefly, as shown in FIG. 6, the CAT
The V bidirectional data communication system includes a central control unit 10 installed in a CATV center, a coaxial cable 15 as a trunk transmission line, a branching device 35 for branching a signal, and a terminal device 25 connected to the trunk transmission line by a branching device 35. And a loader 30 connected to the terminal device 25.
The terminal device 25 is connected to the central controller 10 as shown in FIG.
It is composed of a modulator 25b that modulates and demodulates a signal from the device, a demodulator 25c, and a CPU 25a that inputs and outputs data.

The central control unit 10 sends address data to each terminal unit 25 prior to the control data. The CPU 25a of each terminal device 25 reads the address through the demodulator 25c. The terminal device 25 having the matched address receives the control data from the central controller 10 and controls the loader 30 in accordance with the command. Specifically, the loader 30 is, for example, a status monitor device of a relay amplifier provided in a transmission path, a state detector of a gate switch of an extension amplifier, and the security system of each consumer.

When the central controller 10 requests the monitoring data of the loader 30 and the like, the terminal device 25 sets the loader 30
The data is read from and the monitoring data is transmitted to the central controller 10 via the modulator 25b. This is a system to which a so-called polling method is applied. For transmission in this case, an upstream signal frequency band of 10 to 50 MHZ is used, and the modulation method is FSK modulation or PSK modulation. Each terminal device 25 transmits data to the central control device 10 by performing such modulation.

[0006]

However, in the conventional polling method, as described above, the central control unit of the CATV center sends a command, and each terminal device responds to the command. However, in some cases, even if the response is a simple response such as a reception response, the reception response is transmitted using an expensive modulator such as FSK or PSK. Some conventional CATV systems are installed on the premise of one-way communication, and in this case, there is a drawback that it is not confirmed whether or not the data from the central control device is surely received.

The present invention has been made in order to solve the above-mentioned problems, and in the conventional one-way system, by adding a new transmission method, it is possible to easily confirm the reception of the terminal device. The purpose is to provide a two-way communication system. Moreover, it aims at providing the terminal device which implements the system. Another object of the conventional bidirectional system is to provide an inexpensive reception confirmation method that does not require an expensive modulator and its terminal device.

[0008]

In order to solve the above-mentioned problems, according to the simple two-way communication system according to claim 1 , a broadband transmission line is used, and at least the central control device to each terminal device. Is a communication system for transmitting data to each of the terminal devices including a relay amplifier, after receiving data from the central control device, outputs a predetermined frequency signal as a response signal to the central control device for a predetermined time as an upstream signal , The central control unit will
Detect the signal level of the predetermined frequency signal and send the data.
The reference level when the specified frequency signal immediately after the reception is not received.
If the difference is equal to or more than the specified value,
Wavenumber signal is characterized and this <br/> be determined that the response signal from the terminal device. Each terminal device means all devices inserted in the transmission line that respond to an inquiry from the central control device. It is meant to include all terminal devices such as a relay amplifier inserted in the transmission path, an extension amplifier installed near each customer, and a home terminal installed in each customer.

Since each terminal device only outputs a predetermined frequency signal to the central controller as an upstream signal, it does not require a complicated modulation circuit, for example. Further, if the predetermined frequency signal is a single frequency signal, the reception bandwidth on the side of the central controller can be significantly reduced, so that the predetermined frequency signal becomes a reception response signal with high frequency utilization efficiency. Therefore, a simple two-way communication system that enables an inexpensive reception / response system is provided.

The predetermined frequency signal is output to the central controller for a predetermined time. For example, the predetermined time can be set to the shortest time for the central controller to reliably detect the response signal. Therefore, it is a simple two-way communication method in which the response signal is output most efficiently.

[0011]

After transmitting the data as described above, the central control unit takes the difference between the signal level of the predetermined frequency signal output from each terminal device and the reference level, and receives it only when the difference is equal to or more than the predetermined value. Since it is judged as a response, a complicated demodulation circuit is not required. Therefore, a simple two-way communication system is provided, which does not cost the determination of the response signal.

Further, the detection of the signal level is performed only for a predetermined frequency signal. For example, if the predetermined frequency signal is a single frequency signal, there is room to effectively use other frequency bands. Therefore, a simple two-way communication system with high frequency utilization efficiency is provided. Moreover, the signal level detection is performed at a predetermined time. The predetermined time is set to, for example, a time at which the central control device surely detects in the shortest time. Therefore, a simple two-way communication system is provided in which the response signal can be surely confirmed in the shortest time.

A simple two-way communication system according to claim 2 is
The simplified two-way communication system according to claim 1 , wherein the signal level of the predetermined frequency signal and the reference signal level are average values of a plurality of detections. The signal includes
Generally, noise is included. When the detected signal level and the reference signal level are averaged a plurality of times, the noise contained therein is also averaged and reduced. Therefore,
The detection accuracy is improved. Therefore, a simple two-way communication system that accurately determines the response signal is provided.

According to the simple two-way communication system of claim 3 , a broadband transmission line is used, and at least the center is used.
A communication method in which data is sent from the control device to each terminal device.
Is each terminal device including a repeater amplifier a central controller?
After receiving the data from the
Output as an upstream signal to the central controller for a fixed time
However , the central control unit counts the frequency of the predetermined frequency signal at a predetermined time after data transmission, compares the count value with the predetermined frequency value, and when the difference is within a predetermined value, a response signal from the terminal device is sent. It is characterized by determining that there is.

The response signal is judged not by the signal level of the predetermined frequency signal but by the frequency value. That is, the frequency of the predetermined frequency signal is counted and compared with a predetermined predetermined frequency value. If the difference is within a predetermined value, it is determined as a response signal. Therefore, a simple two-way communication system is provided in which an accurate determination of the response signal can be made without being influenced by the fluctuation of the signal level.

According to the simple two-way communication system of claim 4 , the simple two-way communication system of claim 3 ,
The counting is performed a plurality of times, and the average value is used as the count value. Even when the predetermined frequency signal is a single frequency signal, sporadic noise may be mixed in. In such a case, if the single frequency is counted a plurality of times and the average thereof is calculated, sporadic noise is also averaged and reduced. Thereby, the detection accuracy is further enhanced. Therefore, a simple two-way communication system in which the response signal is confirmed with higher accuracy is provided.

A simplified two-way communication system according to claim 5 is a terminal device used in the simplified two-way communication system according to any one of claims 1 to 4 , wherein It is characterized by having an oscillating means for outputting a predetermined frequency signal as a response signal for a predetermined time after receiving the data. As a result, the terminal device can notify the central controller of the reception response without using complicated modulation means. Therefore, the terminal device of the simple two-way communication system has the most reliable and low-cost response function.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the examples below. (Embodiment) FIG. 1 shows a system configuration using the simple two-way communication system of the present invention. The configuration is the same as the conventional example. The different point is that a simple single frequency response signal is output from the terminal device 100 and the central control device 200 reliably detects it. The same symbols are given to the parts having the same functions as those of the conventional example.

FIG. 2 shows a block diagram of the configuration of the terminal device 100. The terminal device 100 includes a CPU 110 that decodes / inputs / outputs data, a demodulator 120 that demodulates data sent from the central control device 200, an oscillator 130 that notifies reception of the data, and a demultiplexer 140. The demultiplexer 140 is a directional filter including a coil and a capacitor, and demultiplexes or combines the high frequency band and the low frequency band. For example, a frequency band of 70 to 770 MHZ is used for the downlink signal transmitted from the central control device 200, and conversely, a frequency band of 10 to 50 MHZ is used for the response signal which is an upstream signal to the central control device 200. The frequency band of 50 MHZ to 70 MHZ is a guard band for separating the upstream signal and the downstream signal, and the upstream signal and the downstream signal are transmitted by frequency multiplexing.

The downlink signal transmitted from the central controller 200 is branched by the demultiplexer 140 and input to the demodulator 120. The demodulator 120 demodulates a predetermined frequency in the frequency band of 70 to 770 MHZ, for example, 70 MHZ, and the demodulated address data is serialized to the CPU 11
Is transferred to 0. When the CPU 110 receives the data after matching the address data, it triggers the oscillator 130,
A response signal is output at a predetermined frequency. The predetermined frequency is a single frequency, for example, 10 MHZ. The response signal is output to the coaxial cable 15 by the demultiplexer 140 and is transmitted to the central control device 200 by following the reverse path. For example, the central control device 200 is the terminal device 100.
When the control data for turning on / off the gate switch to each consumer is transmitted to the extension amplifier which is the extension amplifier, the extension amplifier receives the command and the reception response is received by the central control device 200.
Send to. This informs the central controller 200 that the data has been reliably received.

FIG. 3 shows a block diagram of the configuration of the central control unit 200. The central controller 200 has a CPU 210 for decoding / inputting / outputting data, a modulator 230 for modulating and outputting control data and the like, a level detector 240 for detecting a response signal sent from the terminal device 100, and a level detector 240. A to convert the analog value detected by
It is composed of a / D converter 220.

The response signal transmitted from the terminal device 100 is input to the level detector 240 having a band pass filter (not shown) via the coaxial cable 15 and the demultiplexer 250. The level detector 240 is, for example, a peak hold circuit that holds the maximum peak of the signal, and outputs the signal level of the response signal as an analog value. The output analog value is input to the A / D converter 220, converted into a digital value, and sent to the CPU 210.

The operation of the CPU 210 will be described with reference to the time chart shown in FIG. The CPU 210 first outputs the control data S to the modulator 230 according to a program (not shown).
Send to. The modulator 230 modulates the frequency of, for example, 70 MHZ in the frequency band of 70 to 770 MHZ according to the address data and the control data S following it, and transmits the downlink signal (a) to the terminal device 100. Furthermore, CP
U210 reads the signal level of the response signal (b) immediately after this from the A / D converter 220 at the read timing t1,
The value is stored as A. The time of the read timing t1 is arbitrarily set when the transmission path is open. Considering the fluctuation of the signal level, it is desirable to be just before the arrival of the response signal.

The CPU 210 also sets the signal level of the response signal (b) to A / at the read timing t2.
The value is read from the D converter 220 and the value is stored as B.
Next, the CPU 210 reads the read timing t1,
The value A and the value B of the response signal level at t2 are compared.
If the difference, B−A, is 10 dB or more in consideration of a predetermined value, for example, the noise level, it is determined that the response signal has arrived,
If it is below, it is determined that the response signal has not arrived, that is, the control data S has not been received. The read timing t2 is the same as that of the central controller 200 and the terminal device 1.
In consideration of transmission delay between 00 and response delay, the CPU
210 is set to a time at which the response signal is reliably detected in the shortest time. Further, the output time of the response signal output from the terminal device 100 is set to be longer than the time for the CPU 210 to reliably detect and process the response signal.

As described above, according to the present system, when each terminal device outputs a predetermined single frequency signal as a reception response for a predetermined time, the central control unit easily confirms it as the reception response at the read timing. it can. Further, since only a predetermined single frequency is used, frequency utilization efficiency is good. Therefore, it becomes a simple two-way communication system that enables reception response / confirmation at low cost and has high frequency utilization efficiency.

(Modification) Although one embodiment representing the present invention has been described above, various modifications are conceivable. For example, in the above embodiment, the determination of the response signal was made based on the difference in the signal levels, but this determination may be replaced by the frequency. FIG. 5 shows a modification of the central controller 200. The figure is a block diagram of the configuration. In this modification, the response signal from the terminal device 100 is recognized by the central control device 200 not by the signal level but by the frequency of the response signal. Therefore, in this modification, a waveform shaper 270 that shapes the response signal input to the duplexer 250 into a rectangular wave and a frequency counter 260 that counts the frequency thereof are provided.

The response signal input from the demultiplexer 250 is
The waveform shaper 270 shapes a rectangular wave of a logic level, for example. Then, it is sent to the frequency counter 260, and the frequency is counted. For example, if the response signal (10 MHZ) from the terminal device 100 is transmitted based on the crystal oscillator, the error is extremely small.
For example, if the count is performed for 100 μsec, the count value becomes approximately 1000 ± 1 count including the phase error. Therefore, considering the error due to external noise, 1000
If the signal within ± 10 counts is determined as the response signal, the response signal can be specified with extremely high accuracy. Therefore, the central controller 200 includes a waveform shaper 270 and a frequency counter 260.
Only with the above, it is possible to confirm reception with extremely high accuracy.
Even with such a configuration, low cost and excellent responsiveness,
In addition, a simple two-way communication method is realized in which accurate reception confirmation is performed.

Further, in the above embodiment, the CPU 210 of the central control unit 200 detects the signal levels A and B of the response signal once each at the time of reception confirmation. May be obtained and used as the response signal levels A and B, respectively. By averaging, the noise included in the response signal is also averaged, and more accurate signal levels A and B are obtained. This allows
Further accurate determination of the response signal is made.

Also, when the arrival of the response signal is determined by frequency, the frequency may be detected a plurality of times and the average value thereof may be used as the count value. For the same reason, the determination accuracy can be further improved.

Further, in the CATV system, although not shown, a relay amplifier for relay-amplifying a high frequency signal is usually provided in the transmission line. At this time, the central controller may request the relay amplifier for status information such as the power supply voltage level. The above method may be used for the response to this inquiry.

Further, in the case of a bidirectional system in which the above-mentioned terminal device has a modulator in advance as in the conventional example, a response signal of a single frequency may be output for a predetermined time from this modulator. Even in such a case, a simple two-way communication system with good frequency efficiency that does not burden the central controller is obtained.

Although various other modified examples are possible, CA
In a two-way data communication system using a TV system, a terminal device is provided with an oscillator that oscillates a predetermined frequency,
A simple two-way communication system in which the predetermined frequency signal is transmitted from the oscillator after receiving the data from the central control device, and the arrival of the predetermined frequency signal at a predetermined time is confirmed to receive the data, and any type of terminal device may be used. .

[Brief description of drawings]

FIG. 1 is a system configuration diagram using a simple bidirectional communication system according to an embodiment of the present invention.

FIG. 2 is a block configuration diagram of a terminal device according to an embodiment of the present invention.

FIG. 3 is a block configuration diagram of a central control device according to an embodiment of the present invention.

FIG. 4 is a time chart of the central control unit according to the embodiment of the present invention.

FIG. 5 is a block diagram showing a modification of the central control unit according to the embodiment of the present invention.

FIG. 6 is a block diagram of a conventional CATV system that performs bidirectional data communication.

FIG. 7 is a block configuration diagram of a conventional terminal device that performs bidirectional data communication.

[Explanation of symbols]

100 terminal device 110 CPU 120 demodulator 130 oscillator 140 duplexer 200 Central control unit 210 CPU 220 A / D converter 230 modulator 240 level detector 250 duplexer

Claims (5)

(57) [Claims] 1. In a communication system in which data is transmitted from at least a central control device to each terminal device including a relay amplifier using a broadband transmission line, each terminal device has a predetermined response signal after receiving the data from the central control device. The frequency signal is output as an upstream signal to the central control unit for a predetermined time, and the central control unit outputs the frequency signal at a predetermined time after data transmission.
To detect the signal level of the predetermined frequency signal,
When the predetermined frequency signal immediately after transmission is not received
Compare with the reference signal level, and when the difference is more than the specified value,
Note that the predetermined frequency signal is a response signal from the terminal device.
A simple two-way communication method characterized by making a judgment . 2. The simplified two-way communication system according to claim 1 , wherein each of the signal level and the reference signal level is an average value of a plurality of detections. 3. A broadband transmission line is used, and at least
Data from the central control unit to each terminal unit including the relay amplifier
In the communication method for transmitting the data, each terminal device receives a response from the central control device and then responds.
Central control unit with predetermined frequency signal for predetermined time
, The central control unit counts the frequency of the predetermined frequency signal at the predetermined time after data transmission, compares the count value with a predetermined frequency value, and determines a difference between them. easy easy bidirectional communication method you and determines that a response signal from the terminal device when within values. Wherein said counting is performed a plurality of times, according to claim 3, characterized in that the average value thereof is set to the count value
Simple two-way communication method described in. 5. The method according to any one of claims 1 to 4.
Of the simple two-way communication system, characterized in that it has an oscillating means for outputting a predetermined frequency signal as a response signal for a predetermined time after receiving data from the central control unit. Terminal device.