JPH0657012B2 - Multiple simultaneous broadcast system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a communication system for performing communication between a center and each terminal by performing time division multiplex transmission in a CATV network, and particularly broadcast communication. The present invention relates to a multiple broadcast communication system that simultaneously provides a plurality of systems.

[Conventional technology]

Conventionally, CATV networks provide television broadcasting, but it is considered to provide communication services such as telephones by using a transmission line routed to each subscriber's house. Frequency division multiplex communication with frequency division was considered as a telephone service using this CATV network, but this method is analog communication and it is difficult to provide an ISDN service, so digital signals are time-divided. It is proposed to communicate.

In general, CATV networks have tree-like transmission lines, and ordinary communication networks are star networks. For this reason, in the CATV network, there is a tree structure between the center and a plurality of terminal control devices, and by the TDMA (Time Division Multiplex Demand Assign) method, different frequencies are assigned to the downlink and the uplink, and a pair of transmission lines is provided to connect with the center. It has been considered to allocate a communication channel (time slot) every time a digital communication with each terminal control device is required by time division multiplex transmission. In addition, a coaxial cable is generally used as a cable forming a transmission line in the CATV network, and the signal transmission time (propagation time) of the cable changes depending on the distance between the terminal control device and the center equipment and temperature conditions. In order to adopt the TDMA method, it is necessary to measure the delay time to the center for each terminal control device and automatically control the timing of sending an upstream signal from the terminal control device.

Therefore, the downlink signal is transmitted by digital modulation from the center in the format shown in FIG. 6A. This downlink signal is provided with a sync signal at the beginning of a frame, a delay control signal next thereto, a communication control signal after a vacant time, and then n speech time slots are sequentially provided. The downlink signal of this format is transmitted at a constant period T as shown in FIG. 7, but in the measurement of the delay time,
A delay time measurement instruction and a device-specific terminal ID (identification) indicating a specific terminal control device are transmitted in the delay control signal. In the terminal control device, as shown in FIG.
The digital signal received by the frame synchronization detection circuit 12 is converted into a digital signal, the frame synchronization detection circuit 12 detects the synchronization signal from the digital signal to establish synchronization, and the delay control circuit 13 receives the digital signal according to the instruction from the frame synchronization detection circuit 12. The delay control signal is extracted from among these, and the terminal ID included in the extracted delay control signal is compared with the ID given to the terminal control device set in the ID setting circuit 14. When the delay control signal is a delay time measurement instruction, a response signal including the delay measurement time and its terminal ID is prepared, and the response signal is modulated / demodulated via the switching unit 15 in synchronization with the detection of the synchronization signal in the next cycle. It is modulated by the device 11 and sent to the center.

The center receives the response signal from the terminal control device, and measures the time t ', which is the difference between the transmission time of the frame synchronization signal transmitted from the center and the reception time of the response signal. From this time t ', the delay time between the terminal control device and the center is detected. One half of the measurement time t'is the delay time t between the terminal control device and the center. Strictly speaking, it is necessary to consider the signal processing time. At the center, the delay time designation information and the I of the terminal control device are used as the delay control signal.
D and delay time t are set, and the signal is transmitted as a downlink signal in the next cycle. The terminal control device detects frame synchronization in the same manner as described above, and when the ID included in the delay control signal and the ID held by the terminal control device match, the received delay time t is the delay control unit 13
The delay control circuit 13 is controlled so that the communication signal stored in the terminal control unit and transmitted from the terminal control device to the center is delayed by (T-t) time from the received frame synchronization signal and relayed.
In this way, a delay time corresponding to the delay with the center is set for each terminal control device. Therefore, the communication time slot assigned at the time of communication is also transmitted with a delay of the delay time (T−t) set in the terminal control device, that is, the delay time adjusted to the specific time slot position designated prior to the call. By performing control for each individual terminal, upstream signals from each terminal control device at the center are arranged in an orderly manner, and a time-division digital transmission line without overlapping between a plurality of communication time slots is configured. As for the communication time slot, every time there is a communication request from the terminal controller, the center allocates an empty communication time slot, and each terminal controller further delays the allocated communication time slot with respect to the delay time set above. Send a signal. Further, as described above, setting the delay time for each terminal so that the signals reaching the center are temporally matched is referred to as delay time control.

The center may send (T-t) as a delay time instruction. Generally, the internal processing delay time of the center and the terminal control device and the difference in the delay time due to the upstream and downstream frequency bands are small, so they are ignored, but if it is measurable in advance, it may be easy to add to the delay time designation. .

As a method of using the communication time slot, for example, a call control signal may be used to allocate a vacant communication time slot based on a channel request from a terminal control device that has a call origination request by the demand assign method.
The transmission timing of the upstream call signal from 6 to the center is controlled by delaying the call signal by instructing the call control unit 17 with a signal indicating the difference in the transmission time of the transmission communication control signal from the reception frame synchronization from the delay control unit 13. Will reach the center. In the center, in order to perform delay control according to the installation distance for each terminal control unit device that makes a call,
It is possible to prevent the received call time slot signals from overlapping. Although not shown in the figure in order to cover the control accuracy, it is necessary to consider providing a guard time between call time slots, but this is omitted because it is not directly involved in the present invention.

[Problems to be Solved by the Invention]

In such a delay control method, the center arrival time of the response signal based on the delay time measurement instruction signal differs depending on the distance from the center of the terminal control device, and the response signal from the terminal control device installed at the farthest end in the system is At the center, as shown as the delay control signal A in FIG. 6B, the response signal from the terminal control device at an intermediate distance from the center is delayed like the delay control signal A, although it is considerably delayed. Less delay than. Since the reception time of the response signal with respect to the frame synchronization signal varies depending on the distance of the terminal control device, the reception time range of the response signal is set so that the response signal from the farthest position can be received without overlapping with other signals. There is a need to. On the other hand, since the delay control signal of the downlink signal has a fixed time width and is inserted at a fixed time with respect to the frame synchronization signal, the delay control signal time width of the downlink signal and the waiting time of the response signal of the uplink signal The time difference from the range is a free time that is not used for downlink signals at all. Although the idle time is provided between the delay control signal and the communication control signal in FIG. 6A, it may be provided at any position in the frame.

In the method of performing the delay control as described above, there is a drawback that the idle time is generated in the downlink signal, and the use efficiency of the frequency is correspondingly low.

For example, QPSK modulation method speed 8.192Mbps, frame period 2m
s, assuming that the cable length to the farthest terminal control device is 15 km, the transmission delay time (center-terminal-center) is
It is about 55 μs (corresponding to about 1000 bits of transmission bits). For example, if the delay control information signal is expected to be 200 bits upstream and 200 bits downstream, it is about 800 within one frame.
A free time zone equivalent to a bit occurs.

Such a long free time was wasted.

[Means for Solving the Problems]

The present invention eliminates such drawbacks and provides a communication system for easily performing broadcast communication in a CATV network. That is, the center is provided with a plurality of means for inserting the simultaneous broadcast information to which a plurality of identification information is added in the free time zone of the downlink, and the contents of the information of the time zone in which the broadcast information is accommodated are collated by each terminal control device. However, multiple broadcasts are performed by sending the broadcast message to the output device provided separately from the communication function such as telephone only when the terminal control device matches the identification information to be received. It is a squeal.

Further, by providing a plurality of broadcast control units in the terminal control device and setting different identification information in the identification setting units, it becomes possible for one terminal control device to receive a plurality of broadcasts simultaneously. .

[Action]

According to the present invention, the utilization efficiency of frequency is enhanced by effectively using the idle time of the downlink signal, and simultaneous broadcast of a plurality of different contents is simultaneously provided to a plurality of terminal control devices or all terminal control devices. You can

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings. First
The figure shows a center in the case of simultaneously serving three types of broadcasts according to the present invention.

Although not shown in the center, timing control signals G1 to G8 are repeatedly generated for each frame period T as shown in FIG. In the figure, each timing control signal is shown with the same time width, but the signal width is different corresponding to each signal length. In FIG. 1, the multiplexing unit 2
1 is configured to output the signal of the corresponding generation unit when each timing control signal is generated. For example, when the timing control signal G1 is generated, the frame synchronization signal 1 generated by the synchronization signal generation unit 22 is output. When the timing control signal G2 is generated, a delay control signal (delay time measurement instruction + terminal ID, delay time designation information + terminal ID in FIG. 3) created by the delay control signal creating unit 23 is output. In order to multiplex the signal into the modulator 24, the input signal to the modulator 24 (the output of the multiplexer 21) can be arranged as shown in FIG. The circled numbers shown as an output signal in FIG. 4 correspond to the circled numbers given to each signal in the signal format of FIG. In the conventional method, the timing control signals G3 to G5 are not generated.

The broadcast creating units 25, 26, and 27 have the same configuration. For example, a case where the broadcast creating unit 25 is used to set a broadcast service will be described. The information type of the simultaneous broadcast may be, for example, weather forecast, residents' association information, information from the public office, stock price information, market price of agricultural products, etc., and group identification information in the simultaneous broadcast signal according to this information type. Assign Therefore, the group identification information is composed of a bit length or a combination of the number of bits that can distinguish the maximum number of information types that the system can provide. This group identification information is set by selecting and operating the identification information key 28. When the key 29 is operated after the setting, a signal (ON) indicating this is sent from the output control unit 31, and subsequently, the group identification information set by the key 28 is sent.

The key 29 is the on / off signal of the broadcast signal section shown in FIG.
Create (1). That is, for example, when the key 29 is pressed, it indicates on (off when not pressed). The sound source 32 may be the output of the microphone when the operator speaks directly into the microphone, or a tape recorder. When the signal of the sound source 31 is converted into a digital signal by the A / D conversion unit 33, it is converted into a burst signal corresponding to the transmission speed by the speed conversion unit 34, and is sent to the multiplexing unit 21 by the sending control unit 31. It The sending control unit 31 has a configuration shown in FIG. 3 by sequentially sending these information serially to the multiplexing unit 21 in synchronization with the timing signal G3.

The other broadcast creating units 26 and 27 are operated and controlled so as to be inserted into the broadcast signal similarly when there is a broadcast having different contents. However, the content of the sound source is different.

Call control signal generator 35, call time slot controller 3
6 to 37 are controlled in the same manner as described above, but it is also conceivable that they are multiplexed beforehand by the switching equipment and input to the multiplexing unit 21.

There is a vacant time between the timing control signals G5 and G6, which occurs when the vacant time in the conventional method cannot be completely used even if a plurality of broadcast signals are inserted. The use efficiency can be significantly improved as compared with the case where the broadcast service is not provided. The multiplexing unit 21 controls so that 0/1 is fixedly transmitted during this idle time.
In this way, the downlink signal shown in FIG. 3 is sent to the tree type transmission line via the modulator 24.

On the other hand, the terminal control device shown in FIG. 2 demodulates the signal shown in FIG.
Extracts a synchronizing signal and a control clock signal (not shown). For example, the control circuit unit 39 of the broadcast control unit 38 extracts a signal (broadcast signal) in a time zone in which the broadcast signal is accommodated by these synchronization signals and clock signals, and determines whether or not there is broadcast information. Check the information (on / off) shown,
For example, in the case of indicating that this information is on, the content of the identification information of the identification information setting unit 41 set by the subscriber is subsequently compared with the received group identification information,
When both match, the broadcast information of the received broadcast signal is sent to the speed conversion unit 42, the speed of the burst signal is converted at an even timing within 2 ms, and then the codec unit 43 performs D / A conversion. The broadcast information is converted and output to the external output unit (for example, a speaker) 44. When the information (on / off) indicating the presence / absence of the simultaneous broadcast information indicates off and the setting content of the identification information setting unit 41 and the content of the received group identification information do not match, the speed conversion unit 42, The codec unit 43 is not activated. Although not shown, in this case, it is necessary for the codec unit 43 to send the no-call pattern data or to control the external output unit 44 so as not to operate.

It can be easily understood that the speed conversion unit 42 and the codec unit 43 have functions opposite to those of the center speed conversion unit 34 and the A / D unit 33, respectively.

At this time, the other broadcast control units 45 and 46 of this control device also have the same configuration and operation, but different broadcast information is output by making the setting contents of the identification information setting unit different.

Further, the delay control circuit 13, the ID setting circuit 14, the call control unit 17, the telephone set 16, the switching unit 15 and the like are controlled in the same manner as in the conventional system, and will not be particularly described.

In this way, the same control is performed in all the terminal control devices, so that the same content is transmitted to the plurality of terminal control devices having the same identification information, and the terminal control in which different identification information is set is transmitted. Not transmitted to the device.

In the above description, the case where one broadcast identification information is set in the terminal control device has been described. However, a plurality of broadcast information are set in the center at the same time, and the terminal control device also sets different broadcast control units in different groups. By setting the identification information,
It may be easily possible that one terminal control device can simultaneously receive a plurality of broadcast information.

In the above example, as the structure of the broadcast signal, for example, as shown in FIG. 3, on / off is 1 bit, group identification information is 4 bits, and broadcast information is 128 bits (64 kbp for voice).
Since a maximum of 6 types of broadcasts can be provided at the same time, the available time is only 2 bits, which is highly effective in use. In the above description, the case of voice information has been described, but in the case of simultaneous broadcasting of digital data, A / D (D / D /
A) It is easy to understand what can be done by removing the codec part.

Note that the idle time of the downlink signal may be provided at any other position in the frame without being provided between the delay control signal and the communication control signal. In any case, a plurality of broadcast signals may be provided in the idle time. Insert.

〔The invention's effect〕

As described above, in a digital multiplex communication facility that performs delay control in a CATV network, the center is provided with a plurality of means for inserting a broadcast signal in an idle time of the downlink delay time, and the terminal control device performs the broadcast simultaneously. When a signal for broadcast is judged and there is a signal that the terminal control device wants to receive, that is, a signal in which the identification information matches, the broadcast information is output to an external output unit to utilize a plurality of simultaneous broadcasts by utilizing the idle time. Communication can be provided at the same time, and it is expected that CATV broadcasting services, communication services, and simultaneous broadcasting services can be achieved with a system that is unified with effective use of frequencies. In addition, although higher quality is desired for broadcast communication than for ordinary telephones, the ISDN basic service uses two call channels and one control channel, so the codec units 33, 4
By setting 3 to 7 kHz audio ADPCM, the broadcast information can be made high quality.

[Brief description of drawings]

1 is a block diagram showing an embodiment of a center according to the present invention, FIG. 2 is a block diagram showing an embodiment of a terminal control device according to the present invention, and FIG. 3 is a terminal control from a center according to the present invention. FIG. 4 is a diagram showing an embodiment of a downstream signal format transmitted to the device, FIG. 4 is a diagram showing an embodiment of the time relationship of timing control signals in the center according to the present invention, and FIG.
FIG. 6 is a block diagram showing a conventional terminal control device, FIG. 6 is a diagram showing an example of signals between a conventional center and a terminal control device, and FIG. 7 is a signal timing of signal transmission / reception between the center and the terminal control device. It is a figure.

Claims (2)

[Claims] 1. In a tree-like CATV network, upstream and downstream frequency bands are paired and used as a transmission path, and a delay control time slot for performing delay time control and a plurality of communication channel time slots are provided within the frequency band. , The delay control time slot designates the terminal control device from the center to give a delay time measurement instruction, and the terminal control device which has received the delay time measurement instruction responds the reception delay time to the center by the delay control time slot. However, in a communication network that performs time division digital multiplex communication with a plurality of terminal control devices that have more communication slots than the communication time slot and the center, the center includes identification information indicating the type of simultaneous broadcast in the idle time of the downlink signal. A plurality of means for inserting a broadcast message is provided to extract the broadcast message received by the terminal control device. A multiple broadcast communication system characterized by comprising broadcast control means for transmitting the contents of the broadcast message to the output device when the contents of the identification information set in advance and the contents of the received identification information match. 2. The multiple broadcast communication system according to claim 1, wherein the terminal control device receives a plurality of simultaneous broadcast communications by providing a plurality of the broadcast control means.