JPH02239741A - Communication system - Google Patents

Abstract

PURPOSE:To send a data to a center CPU for a short time even when lots of terminal equipments exist by replying a 2nd inquiry for a reply window time corresponding to the address of a determined high-order bit by its own station from a center CPU in the case of the reply from a terminal equipment to an inquiry data from the center CPU. CONSTITUTION:An inquiry data 'S' is sent from a center CPU 14 to terminal equipments 31-33. When a request sending a data from the terminal equipments 31-33 to the center CPU 14, a reply data 'R' is sent in response to the inquiry data 'S'. When the terminal equipments 31-33 send simultaneously the reply data 'R', the data collide with each other on the transmission line 11 and the data are destroyed. The center CPU 14 sends a 2nd inquiry data 'W' thereto. The terminal equipments 31-33 receive the 2nd inquiry data 'W', look into a high-order 2-bit of an address of its own station and send the 2nd reply data 'R' for a 1/4 designation time corresponding to the above-mentioned 2-bit in the time of the determined reply window time RA1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a communication system using a tree-shaped coaxial transmission line such as a bidirectional CATV transmission line.

[Conventional technology] Conventionally, in a communication system using a tree-shaped coaxial transmission line such as a bidirectional CATV transmission line, there is a method for transmitting alarm signals, signals, and terminal status from equipment on the terminal side to the CPU on the center side. The operation was as follows. That is, the CPU on the center side sends polling signals to the devices of each terminal in the order of their addresses. The terminal device responds to this polling signal and sends uplink data such as an alarm signal and the status of the terminal to the CPU on the center side.

In this type of communication method, it takes time to poll all the terminals when there are many terminals, so the terminals are divided into several groups and a repeater called a hub is installed in the middle of the transmission path for each group. By doing so, the center's CP
A double polling method is implemented in which polling is performed separately between the U and the hub, and between the hub and the terminal.

However, this double polling method increases the cost of the system due to the provision of a hub in the middle of the transmission path, and has problems such as maintenance and installation limitations.

Therefore, in recent years, contention methods and CSMA/CD (carrier sense・Multi-access/collision direction) method is Ethernet L
It has come to be used in accordance with the IEE 802J standard such as AN.

[Problem to be solved by the invention] However, these contention methods and CSMA
The /CD system has the disadvantage that when the number of terminals increases, the frequency of collisions increases, resulting in a significant drop in communication efficiency.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a communication system that can transmit information from a large number of terminals to a center in a short time.

[Means and effects for solving the problem] The present invention provides that when a terminal device responds to inquiry data from a center CPU, a terminal desiring to send data has a response window time of a predetermined bit of its own address. When there is a collision with another station, the station obtains the right to transmit by responding to another inquiry from the center CPU with a response window time corresponding to the address for the next bit determined by the own station. By sending uplink data to the center CPU only from terminals that have been connected, even if there are many terminals, the center CPU
It becomes possible to send data to U.

[Example] Hereinafter, an example in which the present invention is applied to a bidirectional CATV transmission line will be described with reference to the drawings.

Figure 1 shows its circuit configuration, where 11 is a transmission line using a coaxial cable that transmits TV signals such as TV broadcast waves and independent broadcast wave signals from a VTR, etc. to the terminal side, and 12 is a transmission line 1l. A frequency converter that converts the frequency of the upstream signal from the terminal side via the terminal and sends it as a downstream signal to each terminal,
13 is a distribution/synthesizer that connects the transmission line l1 and the frequency converter 12 and separates and combines the TV signal and data signal; 14;
1 is a center CPU, 15 is a display device connected to the center CPU 14, 16 is an RF modem that performs modulation and demodulation at a high frequency, 17 is a brancher that connects the transmission line 1l and the RF modem 16, and 18 is a bidirectional amplifier. Also, ■9 is a branching device, 21 is a distributor/combiner, 22 is an RF modem, 23
is a terminal device.

The center CPU 14 inquires about the presence or absence of uplink data from each terminal at regular time intervals. FIG. 2 shows the data frame structure of data sent to the terminal side in this case. That is, the data frame has a preamble, a start delimiter,
control, partner address, own address, data,
Each frame consists of an error check and a stop delimiter. The Brian frame is a pattern for synchronizing the bit synchronization frame of the communication partner, in this case each terminal device, and usually consists of a simple repeating pattern such as rl 0 1 0...j. The start delimiter frame and end delimiter frame are the start and end of data, respectively.
A frame that has a special pattern assigned to indicate the end. The control frame is a frame for controlling signal processing at the receiving station by performing data inquiries, re-inquiries, responses, confirmations, and distinguishing data contents. Further, the other party address frame and the own station address frame are addresses indicating the communication partner and the own station, and when the terminal communicates with the center CPU 14, the terminal side may simplify the address of the center CPU 14 and send it. It becomes possible. The data frame is a frame that indicates the collection of alarm information of the terminal, status information from the terminal, etc.
The error check frame is a frame that calculates and reports the error state of transmission data using a generating polynomial or the like.

Next, the operation of the above embodiment will be explained using FIGS. 3 and 4.

Figure 3 shows three terminal devices 33 to 3 on a bidirectional CATV line.
3 is connected, and here the address of the terminal device 31 is "39H(00111001)J".
, the address of the terminal device 32 is r46H (010C)0
110) J, the address of the terminal device 33 is r49H (0
1001001)J, and its operating algorithm will be shown below with reference to FIG.

Inquiry data "S" is sent from the center CPU 14 to each terminal device 31-33. Terminal devices 31 to 33
If there is a request to send data to the center CPU 14, it responds to this inquiry data rSJ and sends the response data r
Send RJ. When the terminal devices 31 to 33 transmit response data rRJ at the same time, they collide on the transmission path 1l and are destroyed. In response, the center CPU 4 transmits re-inquiry data rWJ. Terminal device 31~
After receiving this re-inquiry data rWJ, 33 looks at the upper two bits of its own address and selects 1/4 corresponding to the two bits within the predetermined response window time RA1.
The response data rRJ is transmitted again at the specified time. In this case, the terminal devices 32 and 33 each recognize the upper two bits "01" of their own address, and the response window time R
At the timing of "01" of A, the response data rRJ is simultaneously transmitted again. But again, the response data rR
J will collide on the transmission line 11 and will be destroyed. This collision is confirmed by the terminal device 31, and the terminal device 3l requests the transmission of the response data “R” at the timing of the next “00” within the response window time RA, and the next inquiry data “S” is sent. Wait until it comes. Also center CP
Ul4 detects this collision again and transmits the re-inquiry data rWJ again.

Terminal device 32. 33 receives this re-inquiry data rWJ, they each change the 3rd and 4th bits of their own address to ``00''.
” and simultaneously transmits the response data rRJ again at the timing “00” within the response window time RA2.

Here again, the response data rRJ collides on the transmission line ll and is destroyed. Center CPU14
detects this collision and sends re-inquiry data rWJ again.

After receiving this re-inquiry data rWJ, the terminal device 33
It recognizes the fifth and sixth bits "1o" of its own address and transmits the response data rRJ again at the timing of "1o" within the response window time RA3.

At this point, the response data rRJ is finally delivered to the center CPU 14 via the transmission path 1l. The center CPU 14 recognizes this and sends/receives confirmation data rAJ. on the other hand,
The terminal device 32 receives “10” within the response window time RA3.
Response data rRJ from the terminal device 33 at the timing of
It recognizes the transmission of “0” in the same response window time RA3.
The sending of the response data "R" at the timing of "1" is withheld until the next rSJ is sent from the center CPU 14.

After receiving the confirmation data rAJ from the center CPU 14, the terminal device 33 receives data rAJ including, for example, alarm information.
DJ is transmitted to the center CPU 14 via the transmission path 11. The center CPU 14 receives data r from the terminal device 33.
After receiving the DJ, processing such as displaying alarm information according to the data contents is executed. After the processing, the center CPU 14 sends the terminal device 31. The inquiry data "S" is sent to 32, and the upstream data is sequentially picked up and processed in the same manner as above.

In the above embodiment, an example has been described in which the addresses of the terminal devices 31 to 33 have an 8-bit configuration, but the address is not limited to this, and it is also possible to implement the address with an even larger number of bits. In that case, the number of re-queries will increase.

In addition, in FIG. 1, since the frequency converter l2 is provided on the center side, the RF modem 18. 22 can be transmitted at the same upstream signal frequency.

Therefore, the center CPU14 can be moved not only to the center side but also to the terminal side.

[Effects of the Invention] As described in detail above, according to the present invention, when a terminal device responds to inquiry data from the center CPU, the terminal desiring to send a response has a response window for the predetermined bits of its own address. When there is a collision with another station, the station responds to another inquiry from the center CPU with a response window time corresponding to the address for the next bit determined by the own station, thereby gaining the right to transmit. Only the terminals that have obtained the data send uplink data to the center CPU, thereby providing a communication system that allows data to be sent to the center CPU in a short time even when there are a large number of terminals.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention; Fig. 1 is a block diagram showing the circuit configuration of the center side and the terminal side, Fig. 2 is a diagram showing the structure of the data frame, and Fig. 3 shows the specific connections. FIG. 4, which is a diagram illustrating the configuration, is a diagram showing the content and timing of data transmitted and received in FIG. 3. 1l...Transmission line, 12...Frequency converter, 13.
21...Distributor/combiner, 14...Center CPU, 1
5... Display device, 1B, 22... RF modem, 17
．． 19... Branch, 1B... Bidirectional amplifier, 23
．． 31-33...Terminal devices. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] It is equipped with a center CPU that controls communication operations on a tree-shaped coaxial transmission path, and a plurality of terminal devices connected to the coaxial transmission path, and the terminal devices respond to inquiry data from the center CPU and transmit the data. A communication method in which if there is data, the data is sent to the center CPV, and the terminal device desiring to send has a response window time corresponding to the specified address bit from the upper part of the multiple divisions of its own address. When the response signal collides with the response signal of another station's terminal device on the transmission path, the center CPU that detects this collides with the response signal, and in response to another inquiry from the center CPU that detects this, the address of the own station is divided into multiple parts and the next location is sent. A communication system characterized in that only terminal devices that have obtained transmission rights by responding with a response window time corresponding to designated address bits send uplink data to a center CPU.