JPH10276179A - Two-way data communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the 2-way data communication system in which a transmission fault of an incoming signal due to confluent noise is reduced so as to transmit a stable incoming signal. SOLUTION: In the case of setting a pass band of a variable filter 42 to a band width of 1 MHz around 10 MHz that is a center frequency, components around 10 MHz in confluent noise are detected by a detector 44 via a branching device 40 and fed to a CPU 32, by which the CPU 32 recognizes a level of the confluent noise around 10 MHz. Similarly, in the case of setting a pass band of a variable filter 42 to a band width of 1 MHz around 11 MHz that is a center frequency, the CPU 32 recognizes the level of the confluent noise around 11 MHz. The operation above is repeated to discriminate an optimum frequency used for transmission of an incoming signal. The CPU 32 sets the center frequency of a tuner 36 to an optimum frequency and sends information of the optimum frequency to a subscriber terminal via an outgoing digital transmission channel simultaneously. The subscriber terminal sets the center frequency of an up-converter to the optimum frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a system capable of bidirectional data communication between a host device and a plurality of terminal devices, such as a TV system, and particularly to a system having a feature in a method of transmitting an uplink signal from a terminal device to a host device.

[0002]

2. Description of the Related Art Conventionally, like a bidirectional CATV system, a television signal or the like as a service to be provided is transmitted as a downlink signal from a head end device as a host device to a subscriber terminal as a terminal device. ,
A system for transmitting a request command from the subscriber terminal as an uplink signal from the subscriber terminal to the head-end device has been considered and realized.

[0003] The upstream signal transmitted from the subscriber terminal to the head-end device has been performed using a predetermined channel in the upstream frequency band.

[0004]

However, noise generated in the vicinity of each subscriber terminal, for example, noise such as home electric equipment, electric equipment or neon sign, is present on the upstream transmission line in the bidirectional CATV system at the head end. It was transmitted toward the device and appeared as ingress noise that gathered at the upstream signal input section of the head-end device. Further, since the noise generated near the subscriber terminal is not constant in time, but also changes every moment, the upstream signal from the subscriber terminal is affected by the ingress noise and has a C / N (carrier power / noise power)
However, there has been a problem that the transmission is deteriorated and a transmission failure occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and reduces transmission disturbance of an upstream signal due to ingress noise generated by various noises from a terminal device being concentrated on an input of a host device. Accordingly, it is an object of the present invention to provide a bidirectional data communication system capable of transmitting a stable uplink signal.

[0006]

Means for Solving the Problems and Effects of the Invention In order to achieve this object, the invention according to claim 1 is a bidirectional communication system between a host device and a plurality of terminal devices connected by a wired transmission line. Data communication is possible, two or more upstream signals from the terminal device are aggregated and configured to be input to the host device, a bidirectional data communication system, wherein the host device is the terminal A tuner for receiving an uplink signal from the device, capable of changing and setting a reception channel, an uplink noise measuring unit for measuring an ingress noise in an uplink frequency band, and a measurement result obtained by the uplink noise measuring unit. An optimal uplink channel determining means for determining an optimal uplink channel relatively less affected by ingress noise, and a receiving channel of the uplink signal receiving tuner to the optimal uplink channel. Uplink reception channel switching setting means for setting the optimal uplink channel determined by the channel determination means, and optimal channel notification means for notifying the terminal device of the optimal uplink channel determined by the optimal uplink channel determination means. On the other hand, the terminal device is for transmitting an uplink signal to the host device, and an uplink signal transmitter capable of changing and setting a transmission channel, and a transmission channel of the uplink signal transmitter, which is notified from the host device. And an upstream transmission channel switching setting unit for setting an optimal upstream channel.

[0007] According to the bidirectional data communication system, the tuner for receiving the upstream signal provided in the host device can change and set the receiving channel. And the host device:
Based on the measurement result by the uplink noise measuring means, determine the optimal uplink channel relatively less affected by the ingress noise,
The receiving channel of the tuner for uplink signal reception is set to the determined optimal uplink channel, and the optimal uplink channel is notified to the terminal device side. On the other hand, the uplink signal transmitter included in the terminal device can change the transmission channel, and the terminal device sets the transmission channel of the uplink signal transmitter to the optimal uplink channel notified from the host device.

Therefore, the transmission of the upstream signal from the terminal device to the host device can be performed using the optimum channel having relatively small ingress noise, and the transmission failure of the inbound signal due to the ingress noise can be reduced. It is possible to transmit a stable uplink signal. The host device determines the optimal uplink channel based on the measurement result by the uplink noise measuring means, sets the reception channel of the tuner for uplink signal reception to the optimal uplink channel, and sets the optimal uplink channel to the terminal. It is preferable to execute a series of processes for notifying the device side when no uplink signal is received from the terminal device.

[0009] It is further preferable that the series of processes is executed at predetermined intervals while no uplink signal is received from the terminal device. The two-way data communication system as described above is applied to, for example, a CATV system. In that case, the host device is a CATV
A bidirectional CATV system in which the head-end device and the terminal device of the system are subscriber terminals of the CATV system, and a video signal corresponding to a request from the subscriber terminal is transmitted from the head-end device can be considered. Particularly, in recent years, request-based data services such as video-on-demand (VOD) are being realized, and thus application to such a bidirectional CATV system is effective. Of course, the present invention can also be applied to a system capable of bidirectional data communication other than the CATV system.

When considering a two-way data communication system in which terminal devices are arranged over a certain wide area,
It is also conceivable to provide the following bidirectional relay device between the host device and the terminal device. In other words, both having a downlink signal relay transmission unit for transmitting a downlink signal from the host device toward the terminal device and an uplink signal relay transmission unit for transmitting uplink signals from a plurality of terminal devices toward the host device. A forward relay device, and the upstream signal relay transmission means comprises:
The relay transmission channel for transmitting the uplink signal from the terminal device toward the host device is configured to be changeable, and further, the transmission channel of the uplink signal relay transmission means is notified from the host device. This is a bidirectional relay device including an upstream transmission channel switching setting unit that sets an optimal upstream channel.

In the bidirectional relay device in this case, the downstream signal relay transmission means transmits the downstream signal from the host device toward the terminal device, and the upstream signal relay transmission means transmits the upstream signal from the terminal device to the host device. In performing the basic bidirectional relay function of transmitting data toward the device, the relay transmission channel for transmitting the upstream signal toward the host device is controlled to an optimum channel.

As such a bidirectional repeater, for example, a trunk branch amplifier in a CATV system can be considered. Of course, it is not limited to the main branch amplifier,
In addition, the present invention may be applied to a distribution amplifier, an extension amplifier, a branching device, and the like.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the bidirectional data communication system of the present invention is realized as a bidirectional CATV system will be described below with reference to the drawings. First, referring to FIG. 3, the bidirectional CATV system 1 of the embodiment
Will be briefly described. The headend device 10 of the bidirectional CATV system 1 includes coaxial cables 64a to 64a.
4n, bidirectional trunk branch amplifiers 60a to 60n, and tapoffs 62a to 62n are connected to a large number of subscriber terminals 100. The outputs of the subscriber terminals 100 are connected to the TV receiver 66, respectively. In this case, the head end device 10 corresponds to a “host device”,
The subscriber terminal 100 corresponds to a “terminal device”.

Next, the internal configuration of the head-end device 10 will be described with reference to FIG. The data provided by the head-end device 10 to the subscriber terminal 100 includes television data received from outside and video data provided therein, and a TV for receiving a television signal.
The receiving antenna 12 is connected to a mixer 16 via a preamplifier 14. A multiple video disk device 22 for providing video data is connected to the mixer 16 via an analog modulator 24 and an up-converter 26. The multiple video disk unit 22 is controlled by a CPU 32 as control means.

The downstream digital signal from the CPU 32 is connected to the mixer 16 via a digital modulator 28 and an up converter 30. The output of the mixer 16 is passed through an output amplifier 18 and a duplexer 20 to the headend device 1.
The output of the subscriber terminal 10 on the coaxial cable 64a as the output of
It is transmitted to the 0 side.

The other terminal of the duplexer 20 is connected to the CPU 32 via a splitter 40, a tuner 36 as an "up signal receiving tuner", and a digital demodulator 34. On the other hand, the branch output terminal of the branching device 40 is a variable passband type bandpass filter (variable filter).
It is connected to the CPU 32 via 42 and a detector 44. The pass band of the variable pass band filter 42 is controlled by the CPU 32.

Next, the configuration of the subscriber terminal 100 will be described with reference to FIG. The coaxial cables 64a to 64n serving as drop-in lines from the tap-offs 62a to 62n are connected to the duplexer 102, and the high-frequency side terminal of the duplexer 102 is connected to the analog demodulator 1 via the splitter 104 and the tuner 106.
08. The output of the analog demodulator 108 is connected to the TV receiver 66.

The other output of the distributor 104 is connected via a tuner 118 and a digital demodulator 110 to a CPU 112 as control means. Furthermore, CPU1
A digital modulator 116 and an upconverter 114 corresponding to an “uplink signal transmitter” for transmitting the digital data from 12 are connected to the low-frequency side terminal of the duplexer 102. Also, a numeric keypad 120 for a user to input various instructions is connected to the CPU 112. Note that the tuner 106 and the up-converter 114 are
Controlled by U112, the set frequencies of the reception channel and the transmission channel can be adjusted.

Next, the normal operation will be described with reference to FIGS. The subscriber inputs the number of the program desired to be viewed from the numeric keypad 120. This input is analyzed by the CPU 112, and the CPU 112 sets the tuner 106 to a predetermined channel for a normal TV broadcast. A normal TV broadcast is received by an antenna 12 connected to a head-end device 10, and a preamplifier 14, a mixer 1
6, transmitted from the head-end device 10 through the output amplifier 18 and the duplexer 20, and sent to the main branch amplifiers 60a to 60a.
n, tap-offs 62a to 62n and coaxial cable 64a
To the subscriber terminal 100 via .about.64n. Then, the demultiplexer 102 and the distributor 10 in the subscriber terminal 100 are
4, the signal is demodulated by the analog demodulator 108 and output by the TV receiver 66, so that the subscriber can watch the desired program.

On the other hand, if the program number analyzed by the CPU 112 is assigned to the multiple video disk device 22 in the head end device 10, the CPU 112 of the subscriber terminal 100 sends the program number to the head end device 10 as a program request signal. Send to. This request signal is transmitted from the subscriber terminal 100 via the digital modulator 116, the up-converter 114, and the duplexer 102, and is transmitted to the head via the coaxial cables 64a to 64n, tap-offs 62a to 62n, and the main branch amplifier 60a to 60n. After reaching the end device 100, the duplexer 20, the splitter 38, the tuner 36, the digital demodulator 34 in the head end device 100
To reach the CPU 32 via.

The CPU 32 analyzes the request signal and instructs the multiple video disk device 22 to reproduce the video disk corresponding to the program number requested by the subscriber. The signal from the multiple video disk unit 22 is modulated by the analog modulator 24 and
6 is converted into a predetermined channel (for example, channel A). At this time, the CPU 32
6 is set to channel A, and at the same time, a confirmation signal combining the subscriber identification number and channel A is issued.

This confirmation signal is sent to the subscriber terminal 100 via the digital modulator 28, the up-converter 30, the mixer 16, the output amplifier 18 and the duplexer 20, and is sent to the main branch amplifiers 60a to 60n. Tap-off 62a
To the subscriber terminal 100 via the coaxial cables 64a to 64n. Then, the signal is sent to the CPU 112 inside the subscriber terminal 100 via the duplexer 102, the distributor 104, the tuner 118 and the digital demodulator 110 inside the subscriber terminal 100. CPU that received the confirmation signal
112 sets the tuner 106 to channel A.
Since the signal from the multiple video disk 22, that is, the program desired by the subscriber, arrives at the tuner 106 along the same route as that of a normal TV broadcast, the analog demodulator 108
Is demodulated and output by the TV receiver 66, so that the subscriber can view the desired program.

Next, referring to FIG.
A path through which a program request signal transmitted from the control unit to the headend device 10 passes, that is, an upstream transmission path will be described.
Many subscriber terminals 100, not shown in FIG. 3 but not shown, are connected to the bidirectional CATV system 1. Noise from electric equipment, electric equipment and the like used at home slightly enters each subscriber terminal 100. Also, the subscriber terminal 100 itself generates noise. The noise is transmitted to the coaxial cable 64 via the subscriber terminal 100.
a to 64n.

These noises generated in each of the many subscriber terminals 100 are transmitted to the head end device 10 via each upstream transmission path (coaxial cables 64a to 64n, tap-offs 62a to 62n, and main branch amplifiers 60a to 60n). It is concentrated on the duplexer 20. This is generally called "ingress noise". This ingress noise also appears on the low frequency side of the duplexer 20. The ingress noise is not constant in frequency and not constant in time. FIG. 4 shows the spectrum of the ingress noise at a certain moment. This figure 4 is 10M
It shows a noise level in a frequency band of Hz to 50 MHz. These ingress noises are transmitted to each subscriber terminal 1
This causes a transmission error with respect to the upstream program request signal transmitted from 00.

Therefore, in order to prevent the transmission error related to the upstream signal, it is a main object of the present invention to reduce the influence of the ingress noise. The operation performed by the bidirectional CATV system 1 to reduce the influence will be described with reference to the flowcharts of FIGS. FIG. 5 shows a process executed by the CPU 32 of the head-end device 10, and FIG. 6 shows a process executed by the CPU 112 of the subscriber terminal 100. Note that the following description proceeds assuming that the uplink signal from the subscriber terminal 100 occupies a bandwidth of 1 MHz.

The processing shown in FIG.
Is executed when there is no transmission signal from each subscriber terminal 100. First, the first step S
In 10, the pass band of the variable pass band filter (variable filter) 42 is set to a 1 MHz width centered on 10 MHz. Then, of the ingress noise, 10
The component centered on MHz is detected by the detector 40 via the branch output terminal of the branching device 40 and sent to the CPU 32.

For this reason, the CPU 32 now has 10 MHz
The level of the ingress noise near z can be measured (S
20). Note that, in this sense, the variable passband filter 42 and the split detector 40 correspond to “up-noise measuring means”. In subsequent S30, it is determined whether the measured noise level is the minimum level among the measured noise levels. If it is the minimum level (S30: YES), S4
The processing shifts to 0, and the set value of the variable passband filter 42 is stored in a predetermined internal memory.

Thereafter, the flow shifts to S50, where it is determined whether the set filter value has reached 50 MHz or more.
If a negative determination is made in S30, that is, if the noise level measured in S20 is not the minimum level, the process proceeds to S50 without executing the process in S40.

If the filter value is not equal to or higher than 50 MHz (S50: NO), the flow shifts to S60 to increase the filter value by 1 MHz, and shifts to S20 to similarly execute the noise level measurement. That is, the pass band of the variable pass band type band pass filter 42 is set to a 1 MHz width centered on 11 MHz, and the level of the ingress noise near 11 MHZ is measured. Then, the process from S30 onward is executed in the same manner.

That is, the passband of the variable passband filter 42 is initially set to 1 MHz centered on 10 MHz.
The CPU 32 measures the noise level while setting the width and then increasing the frequency by 1 MHz.
Since the ingress noise from 50 MHz to 50 MHz can be recognized, and in S30 and S40, the set value of the filter having the lowest noise level measured so far is updated and stored, the CPU 32 Can determine the optimal frequency used for uplink signal transmission. For example, in the example of the spectrum of the ingress noise shown in FIG. 4, the noise level around 27 MHz is the minimum noise level.
Is finally stored in S40.

Therefore, the CPU 32 determines in S70
The center frequency of the tuner 36 is set to the filter value (27 MHz) stored in S40, and in S80, the filter value is set as the “optimal upstream transmission center frequency” via the above-described downstream digital transmission path and subscribes. To the user terminal 100 side.

After that, it waits for a predetermined time in S90,
Return to 10. In this way, the CPU 32 can always notify the subscriber terminal 100 of the optimal uplink channel by appropriately executing the processing shown in FIG. Note that the CPU 32 determines “optimal uplink channel determining means”,
S10 of the above-described processing of FIG. 5 which corresponds to “uplink reception channel switching setting means” and “optimal channel notification means”.
Steps S60 to S60 correspond to the processing as the optimal uplink channel determination means, S70 corresponds to the processing as the uplink reception channel switching setting means, and S80 corresponds to the processing as the optimal channel notification means.

Next, processing executed by the CPU 112 of the subscriber terminal 100 will be described with reference to FIG. In the first step S110, it is determined whether there is a signal from the head end device 10. If there is a signal (S11
0: YES), and proceeds to S120 to set the specified value in upconverter 114. Specifically, the optimum filter value (27 MHz) in S80 of FIG.
Is transmitted from the head-end device 10, the CPU 112 of the subscriber terminal 100 that has received the signal sets the center frequency of the up-converter 114 to its optimum filter value (27 MHz). As a result, the subsequent uplink transmission is performed using the channel having the center frequency of 27 MHz.

The CPU 112 corresponds to "uplink transmission channel switching setting means", and the above-described processing in FIG. 6 corresponds to the processing as the uplink transmission channel switching setting means. As described above, the headend device 10 uses the variable passband type bandpass filter 42 and the split detector 40 to select the optimal upstream channel that is relatively less affected by the ingress noise in the band from 10 MHz to 50 MHz. decide. In the above description, 27 MHz is the optimum value,
The receiving channel of the tuner 36 is set to its optimum value of 27 MHz.
And notifies the subscriber terminal 100 of the optimum value. The subscriber terminal 100 sets the notified optimum value in the up-converter 114. Therefore, transmission of the upstream signal from the subscriber terminal 100 to the head end device 10 can be performed using the optimal channel having relatively small ingress noise, and transmission signal transmission failure due to ingress noise can be reduced. As a result, stable transmission of the uplink signal becomes possible.

In the present embodiment, a bidirectional CATV system is applied.
0 indicates that an operation of transmitting a video signal in response to a request from the subscriber terminal 100 frequently occurs. Particularly, in recent years, a data service corresponding to a request such as video-on-demand (VOD) is being realized, and it is highly possible that such an uplink signal from the subscriber terminal 100 frequently occurs. Therefore, adopting such a device to reduce the ingress noise is very effective also in system operation.

As described above, the present invention is not limited to such embodiments at all, and can be implemented in various forms without departing from the gist of the present invention. For example, in the above embodiment, one upstream channel is described, but a different channel may be allocated to each subscriber terminal 100. At that time, the headend device 10 may be provided with a plurality of uplink signal receiving mechanisms. In this case, the optimal upstream channel is the channel with the least noise among the unused channels.

In the above embodiment, the case where the present invention is applied as a CATV system has been described.
The present invention can be applied to a system capable of bidirectional data communication other than the system. And, for example, in the case of a bidirectional data communication system in which terminal devices are arranged to some extent over a wide area, a downlink signal from the host device side is directed between the host device and the terminal device toward the terminal device. It is also conceivable to provide a bidirectional relay device having a function of transmitting and a function of relaying an upstream signal for transmitting upstream signals from a plurality of terminal devices toward the host device. In that case, the bidirectional relay device only needs to have a function of recognizing the optimal uplink channel notified from the host device and setting the transmission channel of the uplink signal relay transmission means to the optimal uplink channel.

As such a bidirectional repeater, for example, a trunk branch amplifier in a CATV system can be considered. Of course, it is not limited to the main branch amplifier,
In addition, the present invention may be applied to a distribution amplifier, an extension amplifier, a branching device, and the like.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a headend device used in a bidirectional CATV system according to an embodiment.

FIG. 2 is a block diagram illustrating a configuration of a subscriber terminal used in the interactive CATV system according to the embodiment;

FIG. 3 is a schematic block diagram illustrating an overall configuration of a bidirectional CATV system according to the embodiment.

FIG. 4 is a spectrum diagram showing an example of ingress noise observed in a head-end device of a general bidirectional CATV system.

FIG. 5 is a flowchart illustrating a process executed by a CPU of the head-end device of the embodiment.

FIG. 6 is a flowchart illustrating a process executed by a CPU of the subscriber terminal according to the embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Head end device 12 ... Receiving antenna 14 ... Preamplifier 16 ... Mixer 18 ... Output amplifier 20, 102 ... Demultiplexer 22 ... Multiple video disk unit 24 ... Analog modulator 26, 30, 114 ... Up converter 28 116, digital modulators 32, 112, CPUs 34, 110, digital demodulators 36, 106, 118, tuners 38, upstream noise measuring means 40, splitters 42, variable pass band type band-pass filters 44, detectors 60a to 60n .. Trunk branch amplifiers 62a to 62n tap off 64a to 64n coaxial cable 66 TV receiver 100 subscriber terminal 104 distributor 108 demodulator 120 numeric keypad

Claims (6)

[Claims] 1. A two-way data communication is possible between a host device and a plurality of terminal devices connected by a wired transmission line, and two or more upstream signals from the terminal devices are aggregated to form the host device. An interactive data communication system configured to be input to a device, wherein the host device is for receiving an uplink signal from the terminal device, and a tuner for receiving a change setting of a reception channel, Uplink noise measuring means for measuring the ingress noise in the uplink frequency band, and optimal uplink channel determining means for determining an optimal uplink channel relatively less affected by the ingress noise based on the measurement result by the uplink noise measuring means. An uplink reception channel for setting a reception channel of the uplink signal reception tuner to an optimal uplink channel determined by the optimal uplink channel determination means; Switching setting means, and an optimal channel notifying means for notifying the terminal device side of the optimal uplink channel determined by the optimal uplink channel determining means, while the terminal device transmits an uplink signal to the host device. An uplink signal transmitter that is reliable and capable of changing and setting a transmission channel, and an uplink transmission channel switching setting unit that sets a transmission channel of the uplink signal transmitter to an optimal uplink channel notified from the host device. A two-way data communication system. 2. The host device determines an optimal uplink channel based on a measurement result by the uplink noise measuring means, sets a reception channel of the uplink signal receiving tuner to the optimal uplink channel, and 2. The apparatus according to claim 1, wherein a series of processes for notifying the terminal apparatus of an optimal uplink channel is performed when an uplink signal from the terminal apparatus is not received. 3. Data communication system. 3. The host device executes the series of processing,
3. The bidirectional data communication system according to claim 1, wherein the bidirectional data communication system is configured to be executed every predetermined period while no uplink signal is received from the terminal device. 4. The host device is a head-end device of a CATV system, and the terminal device is a subscriber terminal of a CATV system, and a video signal corresponding to a request from the subscriber terminal can be transmitted from the head-end device. The two-way data communication system according to any one of claims 1 to 3, wherein the two-way data communication system is configured. 5. A downlink signal relay transmission means for transmitting a downlink signal from the host device toward the terminal device, and an uplink signal for transmitting uplink signals from the plurality of terminal devices toward the host device. A bidirectional relay device having a relay transmission unit, wherein the uplink signal relay transmission unit is configured to be capable of changing and setting a relay transmission channel for transmitting an uplink signal from the terminal device toward the host device. The bidirectional relay device further comprises: an uplink transmission channel switching setting unit configured to set a transmission channel of the uplink signal relay transmission unit to an optimal uplink channel notified from the host device. Claims 1 to 4
The two-way data communication system according to any one of the above. 6. The bidirectional data communication system according to claim 5, wherein said bidirectional repeater is a trunk branch amplifier in a CATV system.