JPH0779346B2 - Selective broadcast communication system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention enables two-way communication between a center device and a plurality of terminals like an urban tree-like CATV network, and signals from the center device can be transmitted simultaneously. The present invention relates to a broadcast communication system among terminals using a bidirectional time division multiple access communication path in a communication system received by all terminals.

(Prior Art) A time division multiple access communication method is an uplink (terminal → center) downlink (center → center) on a time division multiplex transmission line shared between terminals.
(Terminal) A method of setting a communication path by fixedly controlling a pair of communication time slots by the center device control or by allocating a request to a terminal to the terminal. Normally, the communication time slots are as many as the number of terminals performing simultaneous communication. is necessary. The principle of time division multiple access communication is shown in FIG. FIG. 6 shows three cases of communication time slots # 1 to # 3. Each time slot of the transmission / reception frame between the center and the terminal is allocated corresponding to each terminal, and the time slot # 1 is allocated to the terminal A. , Terminal B timeslot #
2 are used as communication time slots.

On the other hand, since the information from the center can be simultaneously received between the terminals, if any communication time slot is used as the communication time slot for the broadcast, it is not necessary to allocate as many time slots as the number of terminals. Although it is possible to use the time slots efficiently, when the terminals transmit to the center using the upstream time slots, competition occurs between the transmission time slots between the terminals, which requires exclusive control. FIG. 7 is a diagram showing contention on an upstream time slot during broadcast communication. In FIG. 7, both terminals A and B use time slot # 1 as a broadcast time slot, and since there is no competition between terminals on the downlink signal, the broadcast information from the center to terminals A and B is shown. Can be transferred, but when sending from the terminal to the center, time slot #
This shows a situation in which contention for 1 occurs and normal information transfer cannot be performed. If the information sent from the terminal to the center is data, if a small-capacity buffer is provided on the terminal side and exclusive control is performed between the terminals, it is possible to eliminate contention, although some transmission delay time will occur. Although it is applied in communications, exclusive control is required for the transmission of information with high real-time and redundancy such as voice communication because immediacy of time slot allocation is required and the time slot occupation time is long. If multiple terminals perform simultaneous transmission, the transmission information from terminals other than the terminal that acquired the transmission right will become invalid, making it difficult to apply to systems with many terminals and high transmission frequency. Different communication time slots must be assigned to each terminal.

(Means for Solving the Problem) In the present invention, when performing broadcast communication using communication time slots in a time division multiple access transmission line, the downlink slot of the broadcast time slot is used for transmission from the center device to the terminal. Although it is used conventionally, regarding the transmission from the terminal to the center device, the transmission request information is unnecessarily received by the center device from the terminal prior to the transmission, and the center device receives the transmission request information according to the allocation instruction of the command device. By granting the uplink time slot transmission permission exclusively to the, it is possible to use the uplink slot of the broadcast time slot even for information communication with high real time and redundancy such as voice communication.

That is, according to the present invention, one of a plurality of terminals is used as a command device, control information including an identifier of one terminal is transmitted from the command device to the center device, and the center device receives the control information and only the terminal having the identifier is transmitted. Allocating a communication time slot that enables transmission, controlling the discharge on the transmission path, the terminal transmits the input information (broadcast information) to the center device in the communication time slot, and the center device transmits the received input information. It relays and transmits to multiple terminals in the broadcast time slot.
The terminal sends the transmission request information to the center device before transmitting the broadcast information to the center device, the center device exclusively receives the transmission request information and transmits it to the command device, and the command device controls the reception request information in the communication time slot. Exclusive control between terminals is performed by allowing access to the communication time slot from the terminal permitted to transmit under the above condition and transmitting the control information to prohibit access to the communication time slot of other terminals. .

(Operation) According to the present invention, the downlink time slot is used for the broadcast communication between terminals using the bidirectional time division multiple access transmission line, especially for the transfer of information having high real-time property and redundancy such as voice. By using the simultaneous broadcast communication from the used center device to the terminals and the information transfer from the terminal that exclusively uses the upstream time slot to the center device, the terminal that is the sender of the broadcast information can be set arbitrarily and the minimum This can be achieved by using time slots.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of the configuration of a broadcast communication system based on the invention. The center device 11 is a time division multiple access transmission line 12
A command device 13 and a plurality of terminals 14 (terminals 1 to n) are connected via a command line, and a man-machine interface 15 is connected to each of the command device 13 and each terminal 14. The command device 13 has the same configuration as the terminal 14, that is, one of the terminals in the conventional system is the command device 13.

FIG. 2 shows a configuration example of a transmission frame transmitted and received on the time division multiple access transmission line of FIG. The transmission frame is a downlink frame 21 transmitted from the center device 11 to the command device 13 and the terminal 14, and the center device 11 from the command device 13 and the terminal 14 side.
And an upstream frame 22 transmitted to the mobile station, forming a bidirectional communication path. Both the downlink frame 21 and the uplink frame 22 consist of a control time slot 23 and a communication time slot 24, and the control time slot 23 is an individual communication time slot.
24 (TS1 to TSm) allocation release, transmission permission during broadcast communication
Control information such as stoppage is sent to the center device 11, command device 13 and terminal.
The control time slot 23 of the upstream frame 22 is exclusively used by the command device 13 or the terminal 14 designated by the center device 11 in the downlink control time slot. At the time of broadcast communication, an arbitrary pair of upstream and downstream communication time slots is allocated by the center device 11 as a broadcast time slot.

FIG. 3 shows a configuration example of the center device 11. The switching device 31 performs a switching operation of connecting / disconnecting the communication channels 32 corresponding to the individual communication time slots in FIG. The signal transmitted from the switching device 31 to the time slot multiplexing device 33 via the communication channel 32 is multiplexed as the downlink frame 21 by the time slot multiplexing device 33, and the transmitter 35
Is transmitted on the downlink multiplex transmission line 37 at. Uplink transmission line
The time slot separation device 34 extracts individual time slots from the upstream frame signal 22 received by the receiver 36 from the receiver 38, and is transmitted to the exchange device 31 via each communication channel 32. The control device 41 is connected to the time slot multiplexing device 33 / separation device 34 by the control channel 39, transmits / receives information in the control time slot 23 which is inserted in the transmission frame or extracted from the transmission frame, and via the control line 40. And controls the exchange device 31.

FIG. 4 shows a configuration example of the command device 13 and the terminal 14 together with a man-machine interface. The control time slot and the assigned communication time slot are extracted from the downlink frame signal 21 received by the receiver 53 via the downlink multiplex transmission path 51 by the time slot extraction device 55, and the information in the communication time slot is the communication channel 57. To the output device 59 of the man-machine interface 58. A speaker having a D / A conversion and amplification function can be considered as an example of the output device 59 of the terminal 14. In the case of the command device 13, a display device for displaying the information of the terminal requesting the transmission is further added.
As the input device 60, a microphone having an A / D conversion function and a keypad for inputting information to the control device 63 can be considered. It is also possible to add an acoustic echo canceller to the microphone in order to avoid an echo due to the surrounding of the sound from the speaker. In this case, the output device 59
From the input device 60 to the input device 60. The signal from the input device 60 is inserted into the designated time slot by the time slot inserting device 56 via the communication channel, and transmitted by the transmitter 54 onto the upstream multiplex transmission path 52. Corresponding to the control device 41 of the center device 11, there is a control device 63 in the command device 13 and the terminal 14, and control information is mutually transmitted and received via a control time slot. The control channel 62 sends and receives control information. The control line 61 is connected to the control device 63 and the input / output device 5
Used to transfer information to and from 9,60.

FIG. 5 shows a center unit 11, a command unit 13, and a center unit according to the present invention.
An example of a signal sequence from the start to the end of the broadcast communication between the terminals 14 (terminals 1 to n) is shown. The following is a description in order. In the following description, broadcast information is transmitted and received in a communication time slot, and other information is transmitted and received in a control time slot.

In response to the control signal from the input device, the command device 13 transmits the communication time slot allocation request 74 to the center device 11,
Upon receiving this, the center device 11 allocates a communication time slot between the command device and the center device, and notifies the command device 13 of the allocated communication time slot number. The command device 13 that has received the notification starts inserting / extracting the communication time slot. At this point, bidirectional transmission between the center and command device becomes possible.

In response to the control signal from the input device, the command device 13 transmits a broadcast start request 76 to the center device 11, and the center device 11 receiving this allocates a broadcast time slot and notifies each terminal 14 of the broadcast time slot 77. At the same time, the switching device 31 is controlled to establish a channel connection between the broadcast time slot 23 and the communication time slot assigned to the command device 13. Further, each terminal 14 and the command device 13 start extraction of the notified broadcast time slot. At this point, broadcast communication from the command device 13 to each terminal 14 becomes possible.

The broadcast information 78 input from the input device is sent from the command device 13 to the center device 11 through the communication time slot, and the center device 11 makes an exchange connection to the broadcast time slot and sends it to each terminal 14. . Each terminal 14 extracts the information of the broadcast time slot and outputs it to the output device.

In response to the control signal from the input device, the terminal 1 sends a transmission request 79 to the center device 11, and after receiving this, the center device 11 adds a transmission request terminal identifier and sends a transmission request 80 to the command device 13. As a result, the transmission request terminal identification is displayed on the output device of the command device 13.

In response to a control signal from the input device, the command device 13 causes the center device 11 to transmit a transmission permission instruction (control information) 81 including a terminal identifier and a communication time slot number (usually the same as the one assigned to the command device 13) number. The center device 11 having received this sends a transmission permission instruction 82 including the terminal identifier to the terminal. The terminal receiving the permission instruction starts inserting the communication time slot and displays it on the output device when the terminal identification corresponds to the terminal itself.

Broadcast information entered using the input device of the transmission-permitted terminal 83
Is transmitted to the center device 11 and is transmitted to the command device 13 and the terminal 14 via the broadcast time slot via the exchange device 31 in the center device.

In response to the control signal from the input device, the command device 13 sends a transmission stop instruction 84 to the center device 11, and the center device 11 receives this and then transmits a transmission stop instruction 85 to the terminal. The transmission-permitted terminal that has received the stop instruction stops the insertion of the communication time slot and displays it on the output device.

To continue the broadcast communication from the command device 13 to the terminal, the command device 13 sends the broadcast information 86 input from the input device to the center device 11, and the center device 11 makes an exchange connection to the broadcast time slot. It is performed by transmitting to the terminal and outputting to the output device at each terminal.

In response to the control signal from the input device, the command device 13 transmits a broadcast end request 87 to the center device 11, and after receiving the request, the center device 11 issues a broadcast time slot release instruction 88 to the terminal.
14 and command device 13, and in response to this, terminal 14 and command device 13 stop extracting the broadcast time slot.

In response to the control signal from the input device, the command device 13 transmits a communication time slot release request 89 to the center device 11, and the center device 11 releases the communication time slot after receiving this request and commands the communication time slot release confirmation 90. When the command is sent to the device 13, the command device 13 stops the insertion / extraction of the communication time slot.

In this embodiment, the communication time slot goes up (terminal →
The center) slot is used for transmitting broadcast information from terminals, and the downlink (center → terminal) slot of broadcast time slots is used for transmitting broadcast information from the center to each terminal. The uplink slot is used for transmitting broadcast information from the terminal, and the switching device connects the broadcast time slot from the uplink to the downlink slot so that the communication slot is not used and only the broadcast time slot is used. Embodiments are also conceivable.

(Effects of the Invention) As described above, according to the present invention, the center device designates the terminal according to the instruction given from the command device, which is a specific terminal, to the center device, and the communication time slot is assigned only to the terminal. By transmitting the information received via the communication path to each terminal in the broadcast time slot, it is possible to effectively use the communication path utilizing the network topology (uplink 1 slot, downlink 1 slot). Since one upstream and one downstream time slot are allocated during broadcast communication, the time slot is used in comparison with a 1: 1 communication channel allocation that requires allocation of n time slots. Is efficient. And according to this invention, between the command device and the plurality of terminals connected to the center device and the bidirectional time division multiple access transmission line,
Broadcast communication from the command device and broadcast communication from a terminal under the control of the command device to another terminal including the command device are possible in at most two communication time slots. Since the required number of time slots is the same as or less than that of the destination communication, it can be said that the broadcast communication method is extremely efficient in the use of time slots. Further, only the terminal permitted by the command device can transmit the broadcast information, the contention of the broadcast information can be avoided, and only the terminal which has the exclusive use can transmit the simultaneous information in real time. The control information conflict may be processed in the same manner as the conventional processing method.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a broadcast communication system based on the present invention, FIG. 2 is a diagram showing a configuration example of a transmission frame, FIG. 3 is a block diagram showing a configuration example of a center device 11,
Fig. 4 shows command device including man-machine interface,
FIG. 5 is a block diagram showing a configuration example of a terminal, FIG.
FIG. 6 is a time chart showing the principle of time division multiple access communication, and FIG. 7 is a time chart showing contention on an upstream time slot during broadcast communication. .

Claims (2)

[Claims] 1. In a multiple access communication system in which a center device and a plurality of terminals are connected by a bidirectional time division multiplex transmission line, one of the plurality of terminals is used as a command device, and the command device The control information including the identifier is transmitted to the center device, the center device receives the control information, assigns a communication time slot that allows only the terminal of the identifier to transmit, and performs exclusive control on the transmission line, and the terminal Is a communication system that transmits input information to the center device in the communication time slot, and the center device relays the received input information and transmits it to a plurality of terminals in the broadcast time slot. Broadcast communication method. 2. The terminal sends transmission request information to the center device, the center device transmits the received transmission request information to the command device, and the command device is based on the received transmission request information. 2. The selective broadcast communication according to claim 1, wherein the control information including the identifier of the terminal is transmitted to the center device when the transmission is permitted. method.