JPH0795733B2 - Multi-channel access communication system - Google Patents

Description

[Detailed Description of the Invention] Overview In a multi-channel access (hereinafter abbreviated as MCA) communication method for performing mutual data communication between a center and terminals and between terminals via a center in a two-way CATV, a terminal is polled by polling. When collecting data, the downlink of the control channel is shared with the downlink of polling, and the polling response uses a separate polling uplink dedicated channel so that polling can be performed even when the communication channel is congested. To do.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-channel access communication system for performing data communication in bidirectional CATV.

CATV has been used as a new communication network using coaxial cables, mainly for information transmission centering on television images. In the early days, it was a facility exclusively for television blindness measures, but in recent years, with the progress of the local information society, consideration has been advanced as a social system that can transmit a large amount of information by utilizing the characteristics of coaxial cables. ing.

In recent years, as one of the new media utilizing such a CATV system, a bidirectional CATV having a function of an interactive communication network that enables bidirectional transmission as well as unidirectional transmission has been developed. This is a cable communication facility for CATV with a function to send a signal from a subscriber's terminal to the center, enabling bidirectional communication.
Various services that meet the demands of subscribers, such as home security services for disaster prevention, pay-per-view services that supply individual programs for a fee depending on the subscriber's choice, are possible. The two-way CATV transmission system uses a single coaxial cable and usually arranges the downlink signal from the center equipment for subscribers in the upper band and the reverse signal in the opposite direction in the lower band for transmission, which is called grouping. The scheme is used.

The MCA communication method for performing data communication in such a two-way CATV is one in which a large number of subscriber terminals jointly use a plurality of communication channels for mutual data communication. At the time of communication between all the subscriber terminals, when a connection request to that effect is generated, data communication is performed by allocating a vacant communication channel to both parties. However, even in the case of collecting the data of each terminal in a polling manner as in the automatic meter reading service, the data cannot be collected unless the terminals are individually called and the communication channels are allocated. Therefore MCA
In a communication system, it is desired that polling communication can be efficiently and constantly executed.

Prior art FIG. 6 shows an MCA for data communication in a bidirectional CATV.
The block diagram of a communication system is shown. In the figure, 1
Is a CATV center, which is a central processing unit (hereinafter referred to as CPU) 1a for data communication, an MCA communication device 1b, and a headend 1c.
It has and. 2 is a transmission path of a coaxial cable connected to the head end 1c, 3 ₁ , 3 ₂ , ... Is a bidirectional branch amplifier provided in the transmission path 2, 4 ₁ , 4 ₂ , ... Is a connection connected to each bidirectional branch amplifier These subscribers are equipped with an MCA terminal device 4a and a terminal 4b such as a personal computer, a television, a sensor for security services, etc. connected to the MCA terminal device 4a, and the terminal 4b and the CPU 1 of the center 1
Data communication between a is realized by the MCA communication device 1b and the MCA terminal device 4a.

Further, in such a communication system, since the uplink and the downlink are configured on the same transmission route, the frequency for performing data communication is, for example, the lower band of the transmission route to the upstream line and the upper band to the downlink. It is assigned.

Figure 7 is shows a channel structure of the MCA system in a logical image, chromatic like the mobile communication system, one of the control channel ch _0, a plurality of communication channels ch _1, ch _2, a ... ch _m The MCA communication device 1b and MCA
It is connected to each of the terminal devices 4a.

FIG. 8 is for explaining the outline of the communication procedure of the communication system configured as described above. CPU1 of center 1
When performing data communication between a and the terminal 4b, first, a channel allocation request is made to the center 1 side through the control channel ch ₀ . At this time, if the data communication with the center 1,
It becomes a connection request with the center 1. Along with this, MC of Center 1
The A communication device 1b checks the usage state of the communication channel, and instructs the MCA terminal device 4a on the subscriber side to use an empty communication channel.
Upon receiving this, the MCA terminal device 4a switches to the designated communication channel and enables communication between the CPU 1a of the center 1 and the terminal 4b. Further, when the data communication ends and the disconnection request is transmitted from the terminal 4b via the MCA terminal device 4a, the disconnection request is transmitted to the center side through the control channel. Center 1
Side gives a disconnection instruction to the terminal side through the control channel,
This disconnects both communication channels.

Next, a conventional operation procedure when polling data collection of terminals using the MCA communication system will be described with reference to FIG. First, the center CPU 1a outputs the MCA terminal number for which data is to be collected to the center MCA communication device 1b to make a connection request. Upon receiving this connection request, the MCA communication device 1b searches for an empty communication channel, selects one of them, and specifies the communication channel to the MCA terminal device 4a.
At this time, the downlink data format transmitted from the MCA communication device 1b on the center side to the MCA terminal device 4a on the subscriber side through the control channel has a channel designation and a channel number code in the MCA terminal number as shown in FIG. It will be added.

The MCA terminal device 4a that has received the channel designation switches the communication channel to the designated channel, and sends a switching response signal to that effect through the communication channel to the center MCA communication device 1b.
Return to. After that, the MCA communication device 1b notifies the CPU 1a of the channel connection, and at the same time the subscriber MCA terminal device 4a notifies the polling response terminal 4b of the channel connection, where the center CPU 1a polls for the first time through the communication channel. Polling is performed on the response terminal 4b. Then, in response to this polling, the data is returned from the terminal 4b.

When the data collection in the center CPU1a is completed, the CPU1a
A channel disconnection request is sent to the communication device 1b. Receiving this, the MCA communication device 1b instructs the MCA terminal device 4a on the polling response terminal side to disconnect the channel through the control channel, disconnects the specified channel to the terminal, and terminates.

Similarly, each free communication channel is sequentially connected to the MCA terminal and polled.

Problems to be Solved by the Invention When data is collected by polling using the conventional MCA communication system as described above, each terminal is sequentially called, and a communication channel is allocated to this,
Since the terminal data is collected by data communication, there is a problem that the data collection speed is slow, and if all communication channels are used, polling cannot be performed at all.

Further, when the automatic meter reading service and the personal computer communication service are provided by the bidirectional CATV, the polling device and the MCA communication device are required respectively, which causes a problem that the communication equipment becomes complicated.

The present invention has been made in view of the above points, and an object thereof is to enable polling at all times even when all communication channels are used, and to perform communication in a line switching system (such as personal computer communication). It is to provide an MCA communication method that enables polling type communication (such as automatic meter reading) in the same system.

Means for Solving the Problems FIG. 1 shows a block diagram of the principle of the present invention. In the figure, reference numeral 10 denotes a center, a central processing unit (hereinafter referred to as CPU) 11 for data communication, an MCA communication device 12 having polling upstream dedicated channel receiving means 13, and a head end 20.
It has and. The center 10 is a bidirectional branch amplifier 15 ₁ , 15 ₂ ,
Are connected to subscribers 14 ₁ , 14 ₂ , ... Through the ... And these subscribers are composed of an MCA terminal device 17 having a polling / MCA identification means 19 and a terminal 18. A channel for performing data communication between the center 10 and the subscribers 14 ₁ , 14 ₂ , ... Is composed of a control channel, a polling upstream dedicated channel, and a plurality of communication channels.

Operation When data is collected by polling by the multi-channel access communication system of the present invention configured as described above, the CPU 11 of the center 10 first requests the MCA communication device 12 for polling. The MCA communication device 12 polls a specific MCA terminal device 17 through the control channel. In the polled MCA terminal device 17, while switching the channel to the polling upstream dedicated channel,
Connection is notified to the polling response terminal 18. This means that the polling connection has been completed, and the polling response terminal
18 sends a polling response to the CPU 11 of the center 10 through a polling upstream dedicated channel. That is, the center
In response to the polling from 10, the terminal 18 returns the data via the polling upstream dedicated channel.

As described above, according to the present invention, by providing the dedicated polling upstream channel, it is possible to always perform polling even if all communication channels are used.

Example Hereinafter, a multi-channel access communication system of the present invention will be described in detail based on an example shown in the drawings.

FIG. 2 is a block diagram showing an embodiment of the MCA communication system of the present invention. The center 10 has a CPU 11 for data communication and an MCA communication device 12. The MCA communication device 12 has a line controller 122 connected to the CPU 11 via an interface 121.
A control channel transceiver 123 connected to the line control device 122, a plurality of communication channel transceivers 125 ₁ ... 125 _n connected to the CPU 11 via an interface 124, and a CPU 1
1 polling upstream dedicated channel receiver 128 connected via interface 129 to each of the transceivers 123 and
125 ₁ ... 125 _n and polling upstream dedicated channel receiver 12
8 and a mixer 126, which is connected to the transmission line 16 via a head end 127.

The two-way branch amplifier 15 ₁ to the transmission path 16, 15 _2, subscriber 14 _1, 14 ₂ connected ... through ... of MCA terminal device 17, two-way branch amplifier 15 _1, 15 _2, ... in A transceiver 172 connected via a tap-off 171, a control response device 173 connected to this transceiver 172, and a communication channel of the transceiver 172 and polling upstream dedicated for operation in response to a channel designation signal from the control response device 173. A channel switching device 174 that switches a channel to a designated channel, a terminal interface 175 that interfaces with the control response device 173 and a communication terminal 18a of a circuit switching system such as a personal computer, and whether there is polling connected to the transceiver 172 An interface between the polling / MCA identification device 176 that identifies whether it is MCA communication and notifies the control response device 173 of this identification result, and the control response device 173 and a polling communication terminal 18b such as a meter or a center. And a polling terminal interface 177. taking.

Next, referring to FIG. 3, this figure shows an operation procedure when collecting data of terminals by polling,
The operation of this system will be described based on this figure.

First, the center CPU 11 outputs a polling request to the MCA communication device 12. Receiving this, the MCA communication device 12 polls the designated terminal through the control channel. The data format at this time is configured as shown in FIG. 5, and a code indicating polling is added to the conventional connection channel designation portion. A signal of this data format is sent from the transceiver 123 to the subscriber side through the downlink control channel on the control channel, and bowls the specified terminal.

When the MCA terminal device 17 on the subscriber side corresponds to the polling request, the MCA terminal device 17 receives the signal transmitted through the downlink control channel by the transceiver 172 and performs polling / MC.
When the A identification device 176 identifies the polling signal, it notifies the control response device 173, and the control response device 173 instructs the channel switching device 174 to switch the channel of the transceiver 172 to the polling upstream dedicated channel. , The connection notification is sent to the terminal 18b through the polling terminal interface 177. Along with this, the data output from the polling response terminal 18b is taken in by the control response device 173 via the polling terminal interface 177,
The data is sent from the transceiver 172 to the center 10 side through the polling upstream dedicated channel.

When the data collection of the MCA terminal that has made the polling request is completed in this way, the control response device 173 of the MCA terminal device 17
Instructs the channel switching device 174 to disconnect the polling upstream dedicated channel of the transceiver 172, and starts the next operation.

As shown in FIG. 4, the above-mentioned channel configuration of this embodiment has a control channel, a plurality of communication channels, and a polling upstream dedicated channel.

Further, circuit switching communication such as personal computer communication is carried out through the route of the control response device 173 and the terminal interface 175 shown in FIG. 2. However, according to the present embodiment, a polling upstream dedicated channel is provided, Even if all the communication channels are used for the circuit switching communication such as communication, the polling communication such as the automatic meter reading can always be performed through the polling upstream dedicated channel.

As described in detail above, the MCA communication system of the present invention is configured by sharing the downlink of the control channel with the downlink of polling and providing the dedicated polling uplink channel, so that all communication channels are used. Also has the effect that polling can always be performed.

Also, circuit switching communication such as personal computer communication and polling communication such as automatic meter reading can be performed in the same system.

[Brief description of drawings]

1 is a block diagram showing the principle of the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention, FIG. 3 is a diagram showing a polling procedure in the embodiment of the present invention, and FIG. 4 is a diagram showing an embodiment of the present invention. FIG. 5 is an explanatory diagram showing a channel configuration, FIG. 5 is a diagram showing a control channel downlink data format in the embodiment of the present invention, FIG. 6 is a configuration diagram of a conventional MCA communication system, and FIG. 7 is a logical configuration of the MCA system channel. Fig. 8 is a schematic image, Fig. 8 is a diagram showing a communication procedure of the communication system, Fig. 9 is a diagram showing a polling procedure when polling is performed by the conventional MCA communication method, and Fig. 10 is a conventional control channel downlink data. It is a figure which shows a format. 10 …… Center, 11 …… CPU, 12 …… MCA communication device, 13 …… Polling upstream dedicated channel receiving means, 14 ₁ , 14 ₂ …… Subscriber, 15 ₁ , 15 ₂ …… Bidirectional branch amplifier, 16 ...... Transmission line, 17 …… MCA terminal device, 18 …… Terminal, 19 …… Polling / MCA identification means.

Claims (1)

[Claims] 1. A center (10) having a central processing unit (11) for data communication and an MCA communication device (12), and the center (1).
0) connected to the MCA terminal device (1) via the transmission line (16)
7) and a terminal (18) connected to the MCA communication device (12), in which a channel of the multi-channel access method is composed of a control channel, a polling upstream dedicated channel, and a plurality of communication channels. ) Is provided with polling upstream dedicated channel reception means (13), and the MCA terminal device (17) is provided with polling / MCA identification means (19) for identifying polling or MCA communication. Is used for polling downlink and a polling response is sent through the polling uplink dedicated channel.