JPH06311167A - Two-way communication system - Google Patents

Abstract

PURPOSE:To reduce a polling cycle plurally providing up links and reception means to each terminal and adding identification codes to attain parallel reception of each terminal group. CONSTITUTION:The head end 1 of a center equipment is connected to conversion parts 5 through optical cables 3 and furthermore connected with many terminals 9 by way of branch parts 7. Its optical receivers 25 and demodulators 27 are in one-to-one correspondence by the same number as the conversion parts 5. Each of conversion parts 5 is provided with an optical reception circuit 51 and an optical transmission circuit 53, the optical reception circuits 51a to 51n respectively provided for individual conversion parts 5a to 5n are connected with the optical transmitter 23 of a head end 1 and the optical transmission circuits 53a to 53n are respectively connected to the optical receivers 23a to 23n of the head end 1. If communication is executed by a system like this, all the terminals of the system do not need polling in serial so as to reduce the polling cycle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a cable television (hereinafter simply referred to as CATV) based on a polling system.
Abbreviated).

[0002]

2. Description of the Related Art First, a conventional CATV two-way communication system will be described with reference to FIG. In the conventional CATV bidirectional communication system shown in FIG. 5, the headend 101 of the center device is connected to the conversion unit 5 via an optical cable, and is further connected via a branching unit 7 connected to the bidirectional coaxial cable. A hybrid system using an optical cable and a coaxial cable, which is connected to the terminal 9 of FIG. The area covered by this headend is divided into a plurality of groups (this group of terminals is hereinafter referred to as a node), the headend 101 to each node are connected by an optical trunk line, and the inside of the node is connected by a coaxial cable. .
The form of the network is a star type in which the optical trunk line extends radially to each node around the head end.

Further, in this system, the head end 1
Only in the optical trunk line section between 01 and the conversion section 5, the up line and the down line are separated and a dedicated cable is provided. Also,
The optical receiving device 125 and the demodulating device 127 are
For each 01, only one set is provided.

On the other hand, in bidirectional communication in a CATV device, the transmission band is divided into "high band" and "low band" as shown in FIG.
Communication is performed by setting lines in both bands.

Further, communication is performed by a polling method. The polling method is a method in which the headend 101 sequentially performs “request listening” to each terminal 9, and FIG.
As shown in FIG. 5, only the terminal 9 that has made a response request from the headend 101 transmits data. In this way, by sequentially controlling the transmission from each terminal 9, it is possible to perform orderly data collection work using one line.

FIG. 8 shows an example of a transmission sentence. An address is defined for each terminal 9 of the system. When exchanging data in order to determine which terminal the downlink data is for, or which terminal the uplink data is from. An address is added to the data for transmission.

In the head end 101, after demodulating the upstream signal, the communication control device 19 collects data, and the communication control device 19 controls the communication while monitoring the upstream signal, and the received data is received by the control computer 21. Is being transmitted to. The control computer 21 performs processing according to the contents based on the received data, and as a result, if necessary, also performs control for providing information to the requested terminal 9.

As described above, with the polling method adopted in the current CATV system, it is easy to imagine that if the number of terminals increases, the time required to finish polling all terminals, that is, the polling cycle, increases accordingly. To be done. As a concrete example, assuming that the number of subscriber terminals per headend is 100,000 and the polling time (see FIG. 7) is 10 msec, the polling cycle is 1000 seconds by simple calculation, that is, about 16- 17
It will take a minute.

As an application of such an interactive CATV system, provision of interactive services can be considered. What is this interactive service?
For example, it is an interactive service in which the subscriber answers the information sent from the headend to the subscriber. Since a short response time is desirable for such a service, the performance of the conventional method described above is insufficient.

[0010]

DISCLOSURE OF THE INVENTION As described above,
When communication is performed by the polling method in the conventional two-way communication system, the polling cycle is long, so when considering the application for the application requiring a short response time,
Performance was inadequate.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a bidirectional communication system capable of shortening a polling cycle.

[0012]

In order to achieve the above object, the first invention of the present application is to provide a downlink line from the center side to the terminal side provided between the center and a plurality of terminals and a downlink line from the terminal side to the center side. A two-way communication system that performs two-way communication based on a polling method via an uplink, and includes a plurality of terminal groups that are configured by the plurality of terminals and are provided with identification codes, and a plurality of terminal groups. Correspondingly, transmitting means is provided on the center side for transmitting to the terminal via the identification code given to the terminal group, and a plurality of terminal units are provided on the center side for each terminal group connected via the uplink. The gist is that the center is provided with receiving means and can receive information from each terminal in parallel for each terminal group.

The second invention of the present application is summarized in that the uplink of the bidirectional communication system according to claim 1 is provided independently for each of the plurality of terminal groups.

Further, a third invention of the present application is a two-way communication system for performing two-way communication based on a polling method via a line provided between a center and a plurality of terminals, which is constituted by the plurality of terminals. A group of terminals to which different frequencies are respectively set, transmitting means provided on the center side corresponding to the plurality of terminal groups and transmitting at a frequency set arbitrarily or for each terminal group, and via the line A plurality of receiving means provided on the center side for each frequency set in the connected terminal group, and the center can receive information from each terminal in parallel for each terminal group. And

[0015]

In the two-way communication system of the first invention of the present application, the uplink is divided into a plurality of terminal groups to which identification codes are respectively assigned, and a plurality of receiving means are provided on the center side for each terminal group. Since each terminal group can be polled simultaneously and the polling cycle depends only on the number of terminals in the terminal group, the polling cycle can be effectively shortened. Further, in the two-way communication system of the second invention of the present application, the uplink is independently provided for each of the plurality of terminal groups, thereby making the reception for each terminal group more reliable.

A bidirectional communication system according to the third invention of the present application,
Since different frequencies are set for each terminal group and multiple receiving means are provided on the center side, it is possible to poll each terminal group simultaneously, and the polling cycle depends only on the number of terminals in the terminal group. Therefore, the polling cycle can be effectively shortened. Furthermore, since the transmitting means transmits at the frequency set arbitrarily or for each terminal group, it can simultaneously transmit to all terminal groups and selectively only to any specified terminal group. You can also send.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a bidirectional communication system according to the present invention will be described in detail below with reference to the drawings.

First, referring to FIG. 1, the CATV of the present embodiment.
A schematic configuration of the bidirectional communication system will be described. The head end 1 of the center device in this embodiment is the optical cable 3
Is connected to the conversion unit 5 via the branching unit 7 connected via the bidirectional coaxial cable 35.

The headend 1 is an antenna 11 for receiving terrestrial and television broadcasts from broadcasting satellites, and a television retransmitting device 13 for retransmitting the received television broadcasts to the terminal 9 via an arbitrary transmission path. While monitoring the still image transmission device 15 for transmitting an arbitrary still image, the independent broadcast transmission device 17 for broadcasting a program etc. independently produced by the center side, and mainly the upstream optical trunk line 33. A communication control device 19 that performs communication control, a control computer 21 that controls the still image transmitting device 15, the independent broadcast transmitting device 17, and the communication control device 19, and the like, a television retransmitting device 13, a still image transmitting device 15, and an independent device. An optical transmitter 23 for transmitting a program or the like from the broadcast transmitter 17 to the terminal 9 via the downstream optical trunk line 31, and a terminal 9 and a conversion unit input via the upstream optical trunk line 33. A plurality of optical receiver 25 for receiving information from such, constituted by demodulator 27 for demodulating the information received by the optical receiver 25.

The optical receiving device 25 and the demodulating device 2 are also provided.
7 are provided by the same number as the number of nodes, which will be described later, that is, the number of conversion units 5, for example, n each, and each has a one-to-one correspondence. For example, the conversion unit 5k includes the optical receiving device 2
5k and demodulator 27k are provided correspondingly.

The node is composed of a conversion unit 5, a large number of branching units 7 connected to the conversion unit 5 in a tree shape or a ring shape, and terminals 9 connected to the branching unit 7. Further, each node is set with a node address for identifying each node, and the terminal 9 is set with an in-node address for identifying each node.
At this time, the in-node address may be the same as the conventional terminal address, and at this time, it is preferable that the terminal address is set in association with the node address of the node of the terminal.

The converter 5 comprises an optical receiver circuit 51 and an optical transmitter circuit 53, and each converter 5a, 5b,
.., 5n provided in the optical receiving circuits 51a, 51, respectively
, 51n are connected to the optical transmitter 23 of the headend 1, and the optical transmitters 53a, 53b, ..., 53n are connected to the optical receivers 23a, 23n of the headend 1 as described above.
b, ..., 23n, respectively.

That is, in contrast to the conventional example shown in FIG. 5, in the present embodiment, the optical receiving devices 25 and demodulating devices 27 for receiving upstream signals of the headend 1 are provided by the number of nodes, and the upstream lines are made independent for each node. This allows for simultaneous polling of each node.

As described above, when communication is performed in the CATV interactive communication system of this embodiment, node addresses for distinguishing nodes are set. An example of the transmission statement format in this case is shown in FIG. The node address shown in FIG. 2 is an address for distinguishing the node, and the in-node address is an address for distinguishing each terminal in the node. In this example, the terminal address of the center command is only the in-node address, and it is considered to simultaneously poll the terminals of the same address of each node. In the terminal response from each terminal, the node address is defined in addition to the in-node address so that when the data is processed at the headend, it is possible to clearly know from which terminal the data is.

When communication is performed by the system as described above, it is not necessary to serially poll all terminals of the system as in the conventional case, so that the polling cycle can be shortened in relation to the number of nodes that can be polled at the same time, and data transmission can be performed. Not only is it possible to quickly find the terminal that has the request, communication with a shorter response time can be performed, and the polling cycle depends on the number of terminals in the node, so even if the number of nodes increases, the polling is relatively constant. A cycle is obtained.

In the above description, the node address is not defined in the center command, but it may be defined if it is necessary to poll each node at different timings.

The above-mentioned uplink and downlink provided between the center of the two-way communication system and a plurality of terminals are not only physically separated but also as shown in FIG. It is also possible to divide the band by a plurality of frequencies.

An embodiment of a system according to this method is shown in FIG.
Shown in. In the system shown in FIG. 4 in which lines are separated at a plurality of frequencies, all transmission lines are configured by using bidirectional coaxial cables. Further, the demultiplexer 24 provided in the headend 1 performs line identification, that is, identification of the uplink and downlink, each node 9A and the terminal.

The upstream signals demultiplexed by the demultiplexer 24 are demodulated by the demodulators 27a, 27a for each channel (each node signal).
It is demodulating at 7b, ..., 27m.

As a result, the same operation and effect as those of the first embodiment shown in FIG. 1 can be obtained. Further, in this embodiment, the optical transmitter 23 has a function of transmitting at an arbitrary frequency or a frequency set for each node 9 (or converter 5), so that all the nodes 9 (or converters) can be transmitted. 5) can be simultaneously transmitted, and it is also possible to selectively transmit only to any specified node 9 (or the conversion unit 5), which enables efficient use of the line. It will be possible.

As described above, according to this embodiment, the polling cycle can be shortened, so that the speed of collecting information from each terminal can be increased and the response time at the time of providing an interactive service can be shortened. The effect of can be expected.

In the above embodiment, the terminal group having the conversion unit as the highest level is used as a node and an uplink is provided in units of this node, but the present invention is not limited to this, and any branching unit (or lower conversion unit) is provided. It is also possible to use a group of terminals having a higher level as a node.

In the above embodiment, the case of applying to CATV has been described as an example, but the present invention is not limited to this and can be applied to an appropriate image response system such as ITV and VRS. .

[0034]

As described above, according to the present invention, a plurality of uplinks and receiving means are provided for each terminal group, and identification codes are attached to enable parallel reception for each terminal group.
This has an effect such that the polling cycle can be shortened.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of an embodiment (an example in which an uplink is divided by a cable) of a CATV interactive communication system according to the present invention.

FIG. 2 is a diagram showing a transmission statement format in the CATV two-way communication system shown in FIG.

FIG. 3 is a diagram showing an example of frequency allocation when an uplink is divided by a transmission band.

FIG. 4 is a block diagram showing a schematic configuration of an example of a CATV interactive communication system according to the present invention (an example in which an uplink is divided into transmission bands).

FIG. 5 is a block diagram showing a configuration of a conventional CATV interactive communication system.

6 is a diagram showing frequency allocation in the bidirectional CATV device shown in FIG.

FIG. 7 is a diagram illustrating a polling method communication procedure.

8 is a diagram showing an example of a transmission statement format in the bidirectional CATV device shown in FIG.

[Explanation of symbols]

1 ... Headend, 3 ... Optical cable, 5 ... Converter, 7 ...
Branching unit, 9 ... Terminal, 11 ... Antenna, 13 ... Television retransmitting device, 15 ... Still image transmitting device, 17 ... Independent broadcast transmitting device, 19 ... Communication control device, 21 ... Control computer, 2
3 ... Optical transmitter, 25 ... Optical receiver, 27 ... Demodulator,
31 ... Downstream optical trunk line, 33 ... Upstream optical trunk line, 35 ... Bidirectional coaxial cable.

Claims (3)

[Claims] 1. Two-way communication based on a polling method through a downlink from the center side to the terminal side and an uplink from the terminal side to the center side provided between the center and a plurality of terminals. And a plurality of terminal groups each of which is configured by the plurality of terminals and is provided with an identification code, and identification codes provided to the center side corresponding to the plurality of terminal groups and provided to the terminal group. The center has a plurality of receiving means provided on the center side for each terminal group connected via the uplink, and the center receives information from each terminal or the like. A two-way communication system characterized by being able to receive in parallel for each terminal group. 2. The bidirectional communication system according to claim 1, wherein the uplink is provided independently for each of the plurality of terminal groups. 3. A two-way communication system for performing two-way communication based on a polling method via a line provided between a center and a plurality of terminals, wherein the plurality of terminals set different frequencies. A group of terminals to be connected, a transmitting unit provided on the center side corresponding to the plurality of terminal groups and transmitting at a frequency set arbitrarily or for each terminal group, and each terminal group connected via the line. A plurality of receiving means provided on the side of the center corresponding to the frequency set in, and the center can receive information from each terminal in parallel for each terminal group. Communication system.