JP3863300B2 - Bidirectional CATV communication level control system and communication level control apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to control of a communication signal level between a CATV center apparatus and a CATV terminal when performing telephone or computer communication using a cable television system (hereinafter referred to as CATV) trunk line.
[0002]
[Prior art]
In recent years, due to the diversification of information media, interactive CATV systems that can perform telephone and computer communication using the CATV trunk line as well as the transmission of multi-channel TV programs via the CATV trunk line have become widespread.
[0003]
In this bidirectional CATV system, telephone communication and computer communication between CATV terminals installed in each home etc. are time division multiple access (hereinafter referred to as TDMA) communication in which communication is performed in a time division manner via a CATV center device. The system is used.
[0004]
A configuration of a TDMA communication system using a CATV trunk line will be described with reference to FIG.
[0005]
The center device 31 of the CATV center station transmits a television signal including video and audio signals of a television program and a downlink signal of TDMA communication related to a telephone or computer communication service. The television signal and the TDMA communication downlink signal transmitted from the center device 31 are transmitted to the trunk cable 32, and are amplified and transmitted by a plurality of trunk amplifiers 33 installed in the middle of the cable 32. The main line amplifier 33 incorporates a branching unit for branching to the CATV subscriber. The television signal and the TDMA communication downlink signal branched by the branching unit are connected to each CATV through the branching main line cable 32 '. It is delivered to the person. A tap-off 34 corresponding to the number of subscribers for branching the transmitted television signal and the TDMA communication downlink signal and distributing it to the subscribers is arranged on the branch trunk cable 32 ′. A distributor 36 is connected to the tap-off 34 via a protector 35. The distributor 36 distributes a television signal and a TDMA communication downlink signal, and the television signal is transmitted to a television via a video receiving terminal 37. The TDMA communication downlink signal is supplied to the receiver 38 and supplied to the service interface 40 via the TDMA communication terminal 39. The service interface 40 is composed of a communication modem for connecting to a telephone or computer equipment. Communication transmitted from the telephone or computer equipment via the service interface 40 is TDMA communication at the TDMA communication terminal 39. It is converted into an upstream signal and transmitted to the center device 31 via the distributor 36, the protector 35, the tap-off 34, and the main line amplifier 33.
[0006]
In the TDMA communication, thousands of TDMA communication terminals 39 are connected to a single center device 31, and the TDMA communication is performed from the center device 31 to the TDMA communication terminals 39 at predetermined time intervals. Transmit downstream signal. This TDMA communication downlink signal includes a downlink communication control signal for each TDMA communication terminal 39. The TDMA terminal 39 sends a TDMA communication uplink signal to the center device 31 at a specified time and at a specified signal level according to the instruction content of the downlink communication control signal corresponding to each TDMA terminal 39 from the received TDMA communication downlink signal. To do.
[0007]
That is, the individual signal transmission of the TDMA terminal 39 is caused by a signal transmission loss due to a difference in installation distance between the trunk cable 32 and the distribution trunk cable 32 ′ of thousands of TDMA terminals 39 connected to the single center device 31. The level is controlled so that the center device 31 can normally receive the TDMA communication uplink signal without error.
[0008]
A specific method for controlling the transmission level of the TDMA communication uplink signal transmitted from the TDMA terminal 39 to the center apparatus 31 will be described with reference to FIG.
[0009]
In FIG. 4, the horizontal axis indicates the passage of time, and the vertical axis indicates the level of the upstream signal.
[0010]
A downlink communication control signal for controlling a signal transmission level is transmitted from the center apparatus 31 to the TDMA communication terminal 39 at intervals of 20 (H) between 00 (H) and FF (H), and the TDMA Instructs to increase the uplink communication signal level from the communication terminal 39, but when the TDMA communication terminal 39 is not powered on, the TDMA communication terminal with respect to the downlink communication control signal of the center device 31 39 does not respond.
[0011]
The unit (H) indicating the uplink communication signal level indicates a hexadecimal unit hexer.
[0012]
Next, when the TDMA communication terminal 39 is turned on before the time a and is in an operating state, the transmission level from the TDMA communication terminal 39 is instructed to 20 (H) from the center device 31 at the time a. Assume. When the uplink communication control signal having the specified transmission level is transmitted from the TDMA communication terminal 39 to the center apparatus 31, the center apparatus 31 has a low level in the uplink communication control signal having the transmission level 20 (H), and therefore the TDMA communication terminal 39. Cannot be recognized. Next, at time b, the center apparatus 31 issues a request instruction for a signal level of 40 (H), and the TDMA communication terminal 39 transmits an uplink communication control signal having a level corresponding to 40 (H) in accordance with this request instruction. The center device 31 does not recognize the TDMA communication terminal 39 because the level is low. In this way, the request for raising the uplink communication control signal level is repeated successively at predetermined time intervals ab, bc,..., And the center apparatus 31 receives the TDMA communication terminal at the request instruction level A0 (H) at time e. 39, the level A0 (H) is used as a reference, the request instruction level is increased / decreased between the following times f to i, and the best transmission level C2 (H) is searched. It is assumed that the TDMA communication uplink signal level transmitted from the TDMA communication terminal 39 is established.
[0013]
In other words, all the TDMA communication terminals 39 connected to the center apparatus 31 are instructed to request the upstream communication control signal level 20 (H) sequentially at the time a, and the request instruction level at the time a. The uplink communication control signal level 40 (H) at the time point b is sequentially requested to a large number of TDMA communication terminals 39 for which the uplink communication control signal level cannot be recognized or established, and the TDMA communication terminal 39 Until the upstream communication control signal level is recognized and established by the center device 31, a level increase request instruction is issued every 20 (H). For this reason, it takes a long time a to j to reach the upstream communication control signal level in the TDMA communication established state with the center device 31 after the TDMA communication terminal 39 is turned on. The waiting time until communication is possible makes the subscriber uncomfortable.
[0014]
In the TDMA communication system using the CATV trunk line, as an adjustment control method for the uplink communication control signal level between the center apparatus 31 and the TDMA communication terminal 39, in addition to the method described above, the uplink communication control that can be recognized for each TDMA communication terminal 39 is possible. The signal level is stored in the center device 31 and the center device 31 can recognize each TDMA communication terminal 39 by a method of searching for a communication establishment state from the uplink communication control signal level stored in the center device 31. There is a method of presetting a fixed uplink communication control signal level and searching for a communication establishment level from the preset fixed uplink communication control signal level. These level establishment methods require strict management of the level of the CATV trunk line. There will be an increase in management costs.
[0015]
[Problems to be solved by the invention]
When TDMA communication is performed using the CATV trunk line, it takes a lot of time to establish the uplink communication control signal level to a predetermined value with the center device after turning on the operation power of the TDMA communication terminal, There has been a problem of giving discomfort to TDMA communication subscribers. Further, in order to speed up the establishment state of the uplink communication control signal level between the center apparatus and the TDMA communication terminal, it is necessary to constantly monitor and manage the signal level management of the CATV main line, which causes an increase in management cost. there were.
[0016]
It is an object of the present invention to shorten the time required to reach the communication established state level of the uplink communication control signal when the operation power of the TDMA communication terminal is turned on, without particularly strict monitoring and management of the signal level management of the CATV trunk line. Yes.
[0017]
[Means for Solving the Problems]
The present invention relates to a time division multiple access communication system that performs communication using a bidirectional CATV trunk line.
CATV center means for transmitting a communication downlink signal including designation data for designating an uplink signal level at predetermined time intervals and communication terminal identification data via the bidirectional CATV trunk line;
Communication receiving means for receiving the communication downlink signal transmitted from the CATV center means, and calculation means for calculating and generating uplink signal level data from the input level of the communication downlink signal including the corresponding terminal identification data received by the communication receiving means A decoding means for generating upstream signal level data based on the designated data of the upstream signal level included in the communication downstream signal received by the communication receiving means, and an upstream signal generated by either the arithmetic means or the decoding means on Ri communication control signal level data based anda communication terminal device and a communication output means for sending to said CATV center means,
The initially after power-on of the communication terminal unit, the signal level of the initial on Ri communication control signal sent from the communication output means is set on the basis of the uplink signal level data generated in the previous SL calculating means, the CATV Center unit is a communication level control system of two-way CATV said generating transmit the specified data of the next uplink signal level relative to the initial on Ri communication control signal level sent from the communication output means.
[0018]
Also, in a bidirectional CATV communication level control apparatus for performing communication control between a CATV center means and a communication terminal means via a bidirectional CATV trunk line,
The communication terminal means
Receiving means for receiving a communication downlink signal including at least specified data specifying an uplink signal level and communication terminal identification data, which are transmitted from the CATV center means at a predetermined time interval, and according to the signal level of the communication downlink signal Automatic gain control means for controlling the reception gain of the reception means, upstream signal level data generation means for generating upstream signal level data based on the gain control voltage generated by the automatic gain control means, and the reception means Any one of an uplink signal level data extracting means for extracting designated data for designating an uplink signal level included in a communication downlink signal received at the above, the uplink signal level data generating means, or the uplink signal level data extracting means Using the upstream signal level data of the upstream side, a signal level-controlled upstream communication control signal is generated to generate the CATV Comprising output means for outputting the coater unit, the,
The initial after power of the communication terminal unit, the level of initial upper Ri communication control signal output from said output means to said CATV center section, before Symbol of the uplink signal level generated by the uplink signal level data generating means data is a communication level control device for two-way CATV that will be set with.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a communication level control apparatus for bidirectional CATV according to the present invention. The same parts as those in FIG. 3 are denoted by the same reference numerals.
[0020]
Reference numeral 11 in the figure denotes a TDMA communication terminal, and the terminal 12 is connected to the distributor 36 in FIG. The TDMA downlink communication signal from the center device 31 input to the terminal 12 is frequency-converted by the downlink signal tuning 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 the AGC voltage to the downlink signal tuning tuner 13. This AGC voltage controls the amplification degree of an amplification circuit (not shown) that constitutes the downlink signal tuning tuner 13, so that the TDMA downlink communication signal supplied from the downlink signal tuning tuner 13 to the demodulator 14 is controlled. Keep the level constant. Digital data demodulation converted TDMA downlink communication signal by the demodulator 14 is supplied to the decoding / encoding unit 15, performs predetermined decoding processing. The decoder / encoder 15 decodes and separates the data of the uplink signal level, the uplink signal supply allocation time, the uplink signal allocation frequency, etc. included in the TDMA downlink communication signal and the telephone call data or the computer communication data. Then, telephone calls and computer data are supplied to the service interface 40. The service interface for 40 is composed of a modem for telephone or computer communication, telephone call or computer data decoded separated by the decoding / encoding unit 15 Ru is supplied. When upstream data is supplied from a telephone or a computer connected to the service interface 40, the decoder / encoder 15 performs a predetermined encoding process. The decoding / encoding unit 15, an uplink signal level decoded separated from the downlink communication signal, the uplink signal supplied allotted time, you supplied to the modulator 17 performs encoding on the data, such as uplink signals allocated frequency. The modulator 17 modulates the signal into a TDMA upstream communication signal, and supplies it to the terminal 12 as a TDMA upstream communication signal at a predetermined signal level and at a predetermined frequency via a channel tuning tuner 18.
[0021]
On the other hand, the AGC voltage generated by the demodulator 14 is supplied to a control microcomputer 16 (hereinafter referred to as a control microcomputer). The control microcomputer 16 exchanges data with the decoder / encoder 15 and generates and supplies an AGC voltage for controlling the amplification degree of an amplification circuit (not shown) constituting the upstream signal tuning tuner 18. That is, the control microcomputer 16 generates an AGC voltage according to the level of the TDMA downlink communication signal supplied from the downlink signal tuning tuner 13 by the demodulator 14, and after the TDMA communication terminal 11 is turned on. In the initial state , the control microcomputer 16 calculates the upstream signal level value based on the AGC voltage generated at the downstream signal level. That is, in the initial state after power-on of the TDMA communication terminal 11 , the control microcomputer 16 calculates the upstream signal level with the AGC voltage corresponding to the downstream signal level generated by the demodulator 14.
[0022]
As a result, when the TDMA communication terminal 11 is powered on and communication with the center apparatus 31 is ensured, the level of the TDMA uplink communication signal first supplied from the uplink signal tuning tuner 18 to the terminal 12 is the control microcomputer 16. Is supplied to the center device 31 as a signal of the level value generated in the above. That is, the level of the received downlink communication control signal is determined irrespective of the data indicating the uplink signal level for the TDMA communication terminal included in the TDMA communication downlink signal received and demodulated by the downlink signal tuner 13 and the demodulator 14. Based on the AGC voltage generated by the demodulator 14, the upstream communication control signal level is set. That is, since the control microcomputer 16 generates the transmission level of the uplink communication control signal at the reception level required when receiving the downlink communication control signal, the communication established state with the center device 31 can be established in a short time.
[0023]
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 by a hexer (H). At time point a after the TDMA communication terminal 11 is turned on, a TDMA communication downlink signal is transmitted from the center device 31, and 20 (H) is used as uplink communication control signal level data included in the TDMA communication downlink signal. Is the requested instruction level. Is approximately equal transmission loss characteristic of the downlink signal and uplink signal of the CATV trunk line at this state, shows the state of the signal level control in the normal state communication graph 21, the transmission loss in the CATV trunk line between the downstream signal and the upstream signal A graph 22 shows the signal level control state during abnormal state communication with different characteristics.
[0024]
First, when the downlink and uplink transmission loss characteristics are normal, the requested level in the downlink communication control signal received at time a is 20 (H) indicated by a dotted line, the downlink communication control signal is It is necessary to increase the reception sensitivity for converting the reception frequency by a predetermined value in the downlink tuning tuner 13, and the AGC voltage generated by the demodulator 14 increases the reception sensitivity of the downlink tuning tuner 13. Generate a value that If the uplink communication control signal level calculated by the control microcomputer 16 based on the AGC voltage is 90 (H) higher than the requested instruction level, the uplink communication control signal level of 90 (H) is obtained. The signal output level of the uplink signal tuning tuner 18 is controlled so as to be output at 90, and a 90 (H) level uplink communication control signal is sent to the center apparatus 31 to recognize the TDMA communication terminal 11. That is, an upstream communication control signal of level A0 (H) that can recognize the TDMA communication terminal 11 can be transmitted at the first time a after the operation power is turned on. Based on this A0 (H), the establishment level C2 (H) of the uplink communication control signal level is searched between the next times b to e, and the establishment setting of the uplink communication control is performed. As a result, since the initial uplink communication control signal level value can be set high after the TDMA communication terminal 11 is turned on, the communication establishment level search can be determined in a short time.
[0025]
Will now be described with reference to graph 22 recognition process of the center apparatus 31 of TDMA communication terminal 11 of the transmission loss is different abnormal state of the downlink and uplink. If the operating power of the TDMA communication terminal 11 is turned on before time a, and the level requested by the downlink communication control signal at time a is 20 (H) indicated by a dotted line, this 20 The uplink communication control signal level calculated by the control microcomputer 16 from the AGC voltage generated by the demodulator 14 from the downlink communication control signal including the request instruction level of (H) is 60 (H). ) Level, the TDMA communication terminal 11 cannot be recognized by the center apparatus 31, and the control microcomputer 16 causes the control microcomputer 16 to execute the next time b to d. During this period, the uplink communication control signal level is obtained sequentially from level 40 to 80. That is, the TDMA communication terminal 11 determines that the center device 31 has erroneously recognized the upstream communication control signal level 60 (H) at the first time “a”, and +20 (from the time “a” at the time “b”. H) 80 (H) level uplink communication control signal is transmitted, and at time c, -20 (H) 40 (H) level uplink communication control signal is transmitted from the time point a. If the center device 31 cannot recognize the transmission level of the upstream communication control signal of ± 20 (H) at the time points b and c with reference to the time point 60 (H) at the time point a, it will be re-appeared at the time point d. Level 80 (H) is set. This time d becomes the same level as the request instruction level from the center apparatus 31, the recognition level value A0 of the time d later as in the related art TDMA communication terminal 11 (H), and an uplink communication control signal established level C2 (H) Until it reaches, the level control of the uplink communication control signal is performed at the request instruction level from the center apparatus 31.
[0026]
As described above, after the TDMA communication terminal is powered on, it is initially transmitted from the center apparatus, received by the downlink signal tuning tuner, and based on the AGC voltage generated when the demodulator demodulates the data. By setting the upstream communication control signal level value, it becomes possible to select the level value of a predetermined upstream communication control signal in a short time, and even when a transmission loss occurs in the CATV main line, it takes less time than before. A predetermined level of uplink communication control signal level can be set.
[0027]
The upstream communication control signal level value calculated by the control microcomputer 16 can use a conversion comparison table between an AGC voltage value corresponding to a preset AGC voltage and a signal level value. Furthermore, when the transmission loss of the CATV trunk line is abnormal, the initial uplink communication control signal level value is selected to be a level higher than 60 (H), and the level shift value between times b to d is ± It is also possible to set a value other than 20 (H).
[0028]
【The invention's effect】
According to the present invention, the upstream communication control signal after the communication terminal is turned on can be controlled to a signal level that can be recognized and established in the center apparatus in a short time, and the unpleasant feeling of the subscriber can be eliminated. In addition, even if an abnormal state occurs in the transmission loss of the CATV trunk line, it is possible to control the upstream signal level of the center apparatus request instruction to the required signal level in the same time as before, and it is necessary to provide a special monitoring system for the CATV trunk line Nor.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of a bidirectional CATV communication level control apparatus according to the present invention.
FIG. 2 is a plan view for explaining a communication level control operation of 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]
DESCRIPTION OF SYMBOLS 11 ... TDMA communication terminal, 12 ... Terminal, 13 ... Down channel tuning tuner, 14 ... Demodulator, 15 ... Decode / encoder, 16 ... Control microcomputer, 17 ... Modulator, 18 ... Up channel tuning tuner 40: Service interface.

Claims (4)

In a time division multiple access communication system that performs communication using a bidirectional CATV trunk line,
CATV center means for transmitting a communication downlink signal including designation data for designating an uplink signal level at predetermined time intervals and communication terminal identification data via the bidirectional CATV trunk line;
Communication receiving means for receiving the communication downlink signal transmitted from the CATV center means, and calculation means for calculating and generating uplink signal level data from the input level of the communication downlink signal including the corresponding terminal identification data received by the communication receiving means A decoding means for generating upstream signal level data based on the designated data of the upstream signal level included in the communication downstream signal received by the communication receiving means, and an upstream signal generated by either the arithmetic means or the decoding means on Ri communication control signal level data based anda communication terminal device and a communication output means for sending to said CATV center means,
The initially after power-on of the communication terminal unit, the signal level of the initial on Ri communication control signal sent from the communication output means is set on the basis of the uplink signal level data generated in the previous SL calculating means, the CATV Center means, communication level control system of a bidirectional CATV, characterized by generating and transmitting a designation data of the next uplink signal level relative to the initial on Ri communication control signal level sent from the communication output unit. In a bidirectional CATV communication level control apparatus for performing communication control between a CATV center means and a communication terminal means via a bidirectional CATV trunk line,
The communication terminal means
Receiving means for receiving a communication downlink signal including at least designation data for designating an uplink signal level and communication terminal identification data transmitted from the CATV center means at a predetermined time interval;
Automatic gain control means for controlling the reception gain of the receiving means according to the signal level of the communication downlink signal;
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;
Uplink signal level data extracting means for extracting designated data for designating an uplink signal level included in the communication downlink signal received by the receiving means;
Using the uplink signal level data of either the uplink signal level data generating means or the uplink signal level data extracting means, an uplink communication control signal whose signal level is controlled is generated and output to the CATV center means Output means,
The initial after power of the communication terminal unit, the level of initial upper Ri communication control signal output from said output means to said CATV center section, before Symbol of the uplink signal level generated by the uplink signal level data generating means bidirectional CATV communication level control device according to claim Rukoto set with data. The upstream signal level data generating means for generating upstream signal level data based on the gain control voltage value generated by the automatic gain control means is an operation for obtaining an upstream signal level data value from the gain control voltage value bidirectional CATV communication level control device according to claim 2, characterized in that the means. The uplink signal level data generating means for generating the uplink signal level data based on the gain control voltage value generated by the automatic gain control means includes a gain control voltage value corresponding to the gain control voltage value set in advance and an uplink signal level data 3. A bidirectional CATV communication level control according to claim 2 , wherein a level of an initial uplink communication control signal output from said output means to said CATV center means is set using a conversion comparison table with signal level values. apparatus.

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