JP2000059749A - Communication level control system for two-way catv, and communication level controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the time required untill an incoming communication control signal reaches a communication setup state level at application of power of a communication terminal, without the need for special management of a signal transmission level of a CATV trunk line. SOLUTION: This system is provided with an arithmetic means 16, that receives an outgoing signal communication control signal from a CATV center means that transmits the outgoing signal communication control signal, including incoming signal level data and communication terminal identification data and calculates and generates the incoming signal level data from the input level of the outgoing signal communication control signal of the terminal identification data, a decode means 15 that generates the incoming signal level data, based on designation data of the incoming signal level included in the outgoing signal communication control signal and with a communication outgoing means that transmits an incoming signal communication control signal to the CATV center means, based on the incoming signal level data generated either of the means above. The communication output means sets an initial incoming signal communication control signal level with priority based on the incoming signal level data by the arithmetic means, and the CATV center means generates succeeding incoming signal level data and transmits the data with this as a reference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to control of a communication signal level between a CATV center device and a CATV terminal when performing telephone or computer communication using a cable television (hereinafter referred to as "CATV") trunk. About.

[0002]

2. Description of the Related Art In recent years, with the diversification of information media,
Along with the transmission of multi-channel television programs by the ATV trunk, a bidirectional CATV system capable of performing telephone and computer communication using the CATV trunk has been widely spread.

In this two-way CATV system, telephone communication and computer communication between CATV terminals installed in respective homes and the like are time-division multiplexed access (hereinafter, referred to as TDM) for performing time-division communication via a CATV center device.
A) is used.

A configuration of a TDMA communication system using a CATV trunk will be described with reference to FIG.

The center device 31 of the CATV center station
Transmits a television signal including a video and an audio signal of a television program and a downlink signal of TDMA communication related to telephone and computer communication services. The television signal transmitted from the center device 31 and the TDM
The A-communication downstream signal is transmitted to the trunk cable 32 and a plurality of trunk amplifiers 33 installed in the middle of the cable 32.
Is amplified and transmitted. This trunk amplifier 33 has C
A branching device for branching to the ATV subscriber is built in, and the television signal and the TDMA communication downstream signal branched by this branching device are transmitted to each CA via a branch trunk cable 32 '.
Delivered to TV subscribers. This branch trunk cable 32 '
, A tap-off 34 according to the number of subscribers for branching the transmitted television signal and the TDMA communication downlink signal and distributing them to the subscribers is arranged. A distributor 36 is connected to the tap-off 34 via a protector 35,
The distributor 36 distributes the television signal and the TDMA communication downstream signal, and the television signal is transmitted to the video receiving terminal 3.
The TDMA communication downstream signal is supplied to the television receiver 38 via the TDMA communication terminal 7 and to the service interface 40 via the TDMA communication terminal 39. The service interface 40 includes a communication modem for connecting to a telephone or a computer. Communication transmitted from the telephone or the computer via the service interface 40 is performed by the TDMA communication terminal 39 using a TDM communication terminal.
The signal is converted into an A-communication upstream signal and transmitted to the center device 31 via the distributor 36, the protector 35, the tap-off 34, and the trunk amplifier 33.

In the TDMA communication, thousands of TDMA communication terminals 3 are provided to a single center device 31.
9 are connected to the TDMA communication terminal 39 from the center device 31 at predetermined time intervals.
Transmit the communication down signal. The TDMA communication downlink signal includes a downlink communication control signal for each TDMA communication terminal 39. The TDMA terminal 39 receives the TDM
In accordance with the instruction content of the downlink communication control signal corresponding to each TDMA terminal 39 from the A communication downlink signal, the TDMA communication uplink signal is transmitted to the center device 31 at a designated time and at a designated signal level.

[0007] That is, the trunk cable 32 of thousands of TDMA terminals 39 connected to a single center device 31.
The signal transmission level of the TDMA terminal 39 is controlled by the signal transmission loss due to the difference in the installation distance of the distribution trunk cable 32 ', and the center device 31 is maintained so that the TDMA communication upstream signal can be normally received by the center device 31 without error. Controlled.

[0008] From the TDMA terminal 39 to the center device 3
A specific method of controlling the transmission level of the TDMA communication upstream signal transmitted to the communication device 1 will be described with reference to FIG.

In FIG. 4, the horizontal axis indicates the passage of time, and the vertical axis indicates the level of the upstream signal.

A downlink communication control signal for controlling a signal transmission level is transmitted from the center device 31 to the TDMA communication terminal 39 at intervals of 20 (H) between 00 (H) and FF (H). , An instruction to increase the level of the uplink communication signal from the TDMA communication terminal 39, but when the power of the TDMA communication terminal 39 is not turned on, the downlink communication control signal of the center device 31 TDMA communication terminal 39 does not respond.

The unit (H) indicating the upstream communication signal level indicates a hexadecimal unit hexer.

Next, the TDMA communication terminal 39 operates at time a
It is assumed that, when the power is turned on and the operating state is reached before the time, the transmission level from the TDMA communication terminal 39 is instructed to 20 (H) by the center device 31 at time a. The uplink communication control signal having the transmission level of the designated value is set to TD.
When transmitted from the MA communication terminal 39 to the center device 31,
The center apparatus 31 cannot recognize the TDMA communication terminal 39 because the level of the uplink communication control signal of the transmission level 20 (H) is low. Next, at time b, the center device 3
1 requests a signal level of 40 (H), and the TDMA communication terminal 39 transmits an uplink communication control signal of a level corresponding to 40 (H) in accordance with the request, but the center device 31 has a low level. TDMA communication terminal 39
Not recognize. In this manner, the predetermined time intervals a to
Assuming that the center device 31 can recognize the TDMA communication terminal 39 at the request instruction level A0 (H) at time e at b, b to c,... With reference to (H), control is performed to increase or decrease the request instruction level between the next times f and i to search for the best transmission level C2 (H).
The TDMA communication upstream signal level transmitted from the MA communication terminal 39 is set to the established state.

In other words, all TDMA communication terminals 39 connected to the center device 31 are sequentially instructed to request the level of the uplink communication control signal to be 20 (H) at the time point a, and at this time point a, The TDMA communication terminals 39 that cannot recognize or establish the uplink communication control signal level at the request instruction level, sequentially request and instruct the uplink communication control signal level 40 (H) at the time point b,
Until the recognition of the level of the uplink communication control signal from the DMA communication terminal 39 by the center device 31 is established, a level increase request instruction is issued every 20 (H). To this end, the TDMA
It takes a long time a to j to reach the uplink communication control signal level in the TDMA communication established state with the center device 31 after the power supply of the communication terminal 39 is turned on, and from the time the power supply is turned on until the TDMA communication becomes possible. Waiting time has made subscribers uncomfortable.

In the TDMA communication system using the CATV trunk line, the TDMA communication terminal 39 can recognize each TDMA communication terminal 39 as an adjustment control method of the uplink communication control signal level between the center device 31 and the TDMA communication terminal 39, in addition to the method described above. A method of storing the uplink communication control signal level in the center device 31 and searching for the communication establishment state from the uplink communication control signal level stored in the center device 31, or the method of searching for the center device 31 for each TDMA communication terminal 31.
There is a method of presetting a fixed uplink communication control signal level that can be recognized and searching for a communication establishment level from the preset fixed uplink communication control signal level. However, these level establishment methods strictly manage the level of the CATV trunk line. Must be performed, which leads to an increase in management cost.

[0015]

In performing TDMA communication using a CATV trunk line, it is necessary to establish an uplink communication control signal level between a TDMA communication terminal and a center device from a power-on of a TDMA communication terminal to a predetermined value. However, there is a problem that it takes a lot of time and makes a TDMA communication subscriber uncomfortable. To speed up the establishment of the uplink communication control signal level between the center device and the TDMA communication terminal,
It is necessary to constantly monitor and manage the signal level management of the ATV trunk, and there has been a problem that the management cost is increased.

The present invention reduces the time required for the TDMA communication terminal to reach the communication establishment state level of the uplink communication control signal when the power supply of the TDMA communication terminal is turned on, without the need to particularly strictly monitor and manage the signal level management of the CATV trunk line. It is an object.

[0017]

SUMMARY OF THE INVENTION The present invention provides a bidirectional CAT.
In a time division multiple access communication system using a V trunk, a CATV for transmitting a downlink signal communication control signal including data designating an uplink signal level and communication terminal identification data at predetermined time intervals via the bidirectional CATV trunk. A center means, a communication receiving means for receiving the downlink signal communication control signal sent from the CATV center means, and an input signal level from an input level of the downlink signal communication control signal of the terminal identification data received by the communication receiving means. Calculating means for calculating and generating data; decoding means for generating uplink signal level data based on designated data of the uplink signal level included in the downlink signal communication control signal received by the communication receiving means; and the arithmetic means or the decoding means The upstream signal communication control signal based on the upstream signal level data generated by any of the means. ; And a communication output means for sending to the CATV center unit, the signal level of the initial uplink signal communication control signal sent from the communication output means, the CA
The CATV center means sets the initial uplink signal communication transmitted from the communication output means, based on the uplink signal level data generated by the arithmetic means, prior to the uplink signal level data transmitted from the TV center means. This is a bidirectional CATV communication level control system that generates and transmits the next uplink signal level data based on the control signal level.

In a time division multiple access communication system between a CATV center means and a communication terminal means via a bidirectional CATV trunk, at least an upstream signal level transmitted at predetermined time intervals from the CATV center means is controlled. Receiving means for receiving a downlink signal communication control signal including data to specify and communication terminal identification data; and, according to a signal level of the downlink communication control signal, automatic gain control means for controlling a reception gain of the receiving means; An upstream signal level data generating means for generating upstream signal level data based on the gain control voltage generated by the automatic gain control means; and an upstream signal level included in the corresponding downstream communication control signal received by the receiving means. Upstream signal level data extracting means for extracting data to be specified, and the upstream signal level data generating means, or Using data of any uplink signal level of the uplink signal level data extracting means, wherein to generate a signal level controlled uplink communication control signal CAT
Output means for outputting to the V center means, the level of the initial uplink communication control signal output from the output means to the CATV center means, in preference to the uplink signal level specified by the CATV center means, A bidirectional CATV communication level control device which is generated by the upstream signal level data generating means and set using the upstream signal level data.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a communication level control device for bidirectional CATV according to the present invention. The same parts as those in FIG. 3 are denoted by the same reference numerals.

Reference numeral 11 in the figure denotes a TDMA communication terminal, and terminal 12 is connected to distributor 36 in FIG. The TDM from the center device 31 input to this terminal 12
The downlink communication signal A is frequency-converted by the downlink signal tuner 13 and supplied to the demodulator 14. The demodulator 14 demodulates and converts the frequency-converted TDMA downlink communication signal into digital data, generates an AGC voltage, and supplies it to the downlink signal tuning tuner 13. This AGC
The voltage controls an amplification degree of an amplifier circuit (not shown) constituting the down signal tuning tuner 13, and the TDM supplied to the demodulator 14 from the down signal tuning tuner 13.
A The level of the downlink communication signal is made constant. The demodulator 14
The digital data of the TDMA downlink communication signal modulated and converted by the above is supplied to the decoder / encoder 15 and performs a predetermined decoding process. This decoder / encoder 1
5 decodes and separates the data of the upstream signal level, the allocated time of the upstream signal supply, the allocated frequency of the upstream signal and the telephone call data or the computer communication data included in the TDMA downstream communication signal, and Computer data is a service interface 4
Supply 0. This service interface 40
Consists of a modem for telephone or computer communication,
The decoder / encoder 15 supplies the telephone call or the computer data that has been separated by decoding. When uplink data is supplied from a telephone or a computer connected to the service interface 40, the decoding / encoding unit 15 performs a predetermined encoding process. The decoder / encoder 15 encodes data such as the uplink signal level, uplink signal supply allocation time, and uplink signal allocation frequency, which are decoded and separated from the downlink communication signal, and supplies the data to the modulator 17. The modulator 17 modulates the signal into a TDMA uplink communication signal and supplies it to the terminal 12 as a TDMA uplink communication signal at a predetermined signal level and at a predetermined frequency at a predetermined frequency via a channel selection tuner 18 for the upstream signal.

On the other hand, the AGC voltage generated by the demodulator 14 is supplied to a control microcomputer (hereinafter referred to as a control microcomputer) 16. This control microcomputer 16
It exchanges data with the decode / encoder 15 and generates and supplies an AGC voltage for controlling the amplification of an amplifier circuit (not shown) constituting the tuner 18 for the up signal. That is, the control microcomputer 16 generates the AGC voltage corresponding to the level of the TDMA downlink communication signal supplied from the downlink signal tuner 13 by the demodulator 14, and generates the AGC voltage generated at the downlink signal level.
The control microcomputer 16 calculates an up signal level value based on the C voltage. The control microcomputer 16 calculates the upstream signal level with the AGC voltage according to the downstream signal level generated by the demodulator 14.

Thus, the level of the TDMA uplink communication signal supplied from the uplink signal tuning tuner 18 to the terminal 12 is supplied to the center device 31 as a level value signal generated by the control microcomputer 16. That is, the TDMA communication downlink signal received and demodulated by the downlink signal tuner 13 and the demodulator 14 is included in the TDMA communication downlink signal.
Regardless of the data indicating the uplink signal level for the communication terminal, the uplink communication control signal level based on the AGC voltage generated by the demodulator 14 is set based on the level of the received downlink communication control signal. That is, since the control microcomputer 16 generates the transmission level of the uplink communication control signal at the reception level necessary for receiving the downlink communication control signal, the communication establishment state with the center device 31 can be established in a short time.

This operation state will be described in detail with reference to FIG. In FIG. 2, the horizontal axis indicates time, and the vertical axis indicates the signal level in hex (H). At a time point a after power-on of the TDMA communication terminal 11, a TDMA communication downlink signal is transmitted from the center device 31, and
It is assumed that the requested instruction level of 20 (H) is the uplink communication control signal level data included in the DMA communication downlink signal. The state of signal level control during normal state communication, in which the transmission loss characteristics of the downstream signal and the upstream signal of the CATV main line in this state are almost equal, is indicated by a gram 21. The state of the signal level control at the time of the abnormal state communication, which is different from the state shown in FIG.

First, when the downlink and uplink transmission loss characteristics are normal, the level requested and indicated by the downlink communication control signal received at time a is 20 (H) indicated by a dotted line. The signal is sent to the downlink tuner 1
3, it is necessary to increase the receiving sensitivity for converting the receiving frequency with a predetermined value.
The C voltage generates a value that increases the reception sensitivity of the downlink tuner 13. Assuming that the upstream communication control signal level calculated by the control microcomputer 16 based on the AGC voltage is 90 (H) higher than the required instruction level, the upstream communication control signal level of 90 (H) is obtained. And outputs a 90 (H) level uplink communication control signal to the center device 31 to output the TDMA communication terminal 1.
Recognize 1 That is, the level A at which the TDMA communication terminal 11 can be recognized at the first time point a after the operation power is turned on.
0 (H) uplink communication control signal can be transmitted. This A0
Based on (H), a search is made for the establishment level C2 (H) of the uplink communication control signal level between the next times b and e, and the establishment of uplink communication control establishment is performed. As a result, since the initial uplink communication control signal level value can be set high after the power of the TDMA communication terminal 11 is turned on, the search for the communication establishment level can be determined in a short time.

Next, the process of recognizing the TDMA communication terminal 11 in the center unit 31 in the abnormal state where the transmission loss of the downlink differs from that of the uplink will be described with reference to the gram 22. Assuming that the operation power of the TDMA communication terminal 11 is turned on before time a, and the level requested and indicated by the downlink communication control signal at time a is 20 (H) indicated by a dotted line, this 20 The level of the upstream communication control signal calculated by the control microcomputer 16 from the AGC voltage generated by the demodulator 14 from the downstream communication control signal including the required instruction level of (H) is 60.
(H), and as a result of transmitting the uplink communication control signal to the center device 31 at the level of 60 (H), the center device 31 cannot recognize the TDMA communication terminal 11 and the next time b to d During this time, the upstream communication control signal levels are sequentially obtained from levels 40 to 80. However, the TDMA communication terminal 11 determines that the center apparatus 31 has erroneously recognized the uplink communication control signal level 60 (H) at the first time point a, and at time point b, it is +20 from the time point a.
(H), an uplink communication control signal of level 80 (H) is transmitted, and at time c, -20 from the time point a is used.
An (H) 40 (H) level uplink communication control signal is transmitted. If the center device 31 cannot recognize even if the transmission level of the uplink communication control signal of ± 20 (H) is changed between the time b and the time c at the time b and c with reference to the time 60 (H) at the time a, the time is changed again at the time d Level 80 (H) is set. This time d is the same level as the request instruction level from the center device 31, and after this time d, the recognition level value A0 (H) of the TDMA communication terminal 11 and the uplink communication control signal establishment level C2 (H) are reached as in the conventional case. Until the center device 3
The level control of the uplink communication control signal is performed at the request instruction level from 1.

As described above, the uplink communication control signal level value is set based on the AGC voltage transmitted from the center device, received by the downlink signal tuner and demodulated by the demodulator. This makes it possible to select the level value of the predetermined uplink communication control signal in a short time, and to set the predetermined level of the upstream communication control signal level without taking much time even when a transmission loss occurs in the CATV trunk line. Becomes possible.

As the upstream communication control signal level value calculated by the control microcomputer 16, a conversion comparison table between the AGC voltage value corresponding to the previously set AGC voltage and the signal level value can be used. Further, when the transmission loss of the CATV trunk line is abnormal, the initial uplink communication control signal level value may be set to a level higher than 60 (H).
It is also possible to set a value other than ± 20 (H) for the level shift value between times b and d.

[0028]

According to the present invention, the uplink communication control signal after the power of the communication terminal is turned on can be controlled to a signal level that can be recognized and established by the center device in a short time, and the discomfort of the subscriber can be eliminated. Also, even if an abnormal state occurs in the transmission loss of the CATV trunk line, the required signal level can be controlled to the required signal level in the same time as in the past, and a special monitoring system for the CATV trunk line needs to be provided. Nor.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a communication level control device for bidirectional CATV according to the present invention.

FIG. 2 is a plan view for explaining a communication level control operation of the bidirectional CATV according to the present invention.

FIG. 3 is a block diagram showing a configuration of a TDMA communication system using a conventional bidirectional CATV trunk line.

FIG. 4 is a plan view for explaining an uplink signal level control operation of a conventional TDMA communication system.

[Explanation of symbols]

11: TDMA communication terminal, 12: terminal, 13: tuner for downlink signal, 14: demodulator, 15: decode / encoder, 16: control microcomputer, 17: modulator, 18 ...
Tuning tuner for upstream signal, 40 ... Service interface.

Claims (5)

[Claims] 1. A time division multiple access communication system using a bidirectional CATV trunk, wherein a communication downlink including data specifying an uplink signal level and communication terminal identification data at predetermined time intervals via the bidirectional CATV trunk. CATV center means for transmitting a signal, communication receiving means for receiving the communication downlink signal transmitted from the CATV center means, and rising from the input level of the communication downlink signal including the corresponding terminal identification data received by the communication receiving means Calculating means for calculating and generating signal level data; decoding means for generating uplink signal level data based on designated data of the uplink signal level included in the communication downlink signal received by the communication receiving means; and the arithmetic means or the decode The upstream signal communication control signal based on the upstream signal level data generated by any of the means. Communication output means for sending to the CATV center means, wherein the signal level of the initial uplink signal communication control signal sent from the communication output means is higher than the uplink signal level data sent from the CATV center means, Based on the uplink signal level data generated by the arithmetic means, the CATV center means generates and transmits the next uplink signal level data based on the initial uplink signal communication control signal level sent from the communication output means. A communication level control system for bidirectional CATV. 2. In a time division multiple access communication system between a CATV center means and a communication terminal means via a bidirectional CATV trunk, at least an upstream signal level transmitted at predetermined time intervals from said CATV center means is controlled. Receiving means for receiving a communication downlink signal including designated data and communication terminal identification data; automatic gain control means for controlling a reception gain of the receiving means in accordance with a signal level of the communication downlink signal; An upstream signal level data generating unit for generating upstream signal level data based on the gain control voltage generated by the unit; and extracting data specifying an upstream signal level included in the communication downstream signal received by the receiving unit. Upstream signal level data extracting means, the upstream signal level data generating means, or the upstream signal level Output means for generating a signal level-controlled upstream communication control signal using the data of any one of the upstream signal levels of the data extracting means and outputting the signal to the CATV center means. The level of the initial uplink communication control signal output to the CATV center means is
A communication level control device for bidirectional CATV, wherein the upstream signal level is generated by the upstream signal level data generating means and set using the upstream signal level data, prior to the upstream signal level designated by the ATV center means. 3. When turning on the operating power of the communication terminal means,
An uplink communication control signal is generated by using the uplink signal level data generated by the uplink signal level data generating means, prior to the uplink signal level data from the CATV center means, and the CATV center means is output from the output means. 3. The bidirectional C according to claim 2, wherein
ATV communication level control device. 4. An upstream signal level data generating means for generating upstream signal level data based on a gain control voltage value generated by said automatic gain control means calculates an upstream signal level data value from said gain control voltage value. 3. The bidirectional CAT according to claim 2, wherein the calculating means is obtained by processing.
V communication level control device. 5. An up-signal level data generating means for generating up-signal level data based on the gain control voltage value generated by said automatic gain control means, comprising: a conversion signal preset from said gain control voltage value; A memory means for storing level data; and using the converted signal level data corresponding to the gain control voltage value from the memory means, sets a level of an initial uplink communication control signal output from the output means to the CATV center means. 3. The communication level control device for bidirectional CATV according to claim 2, wherein: