JPS60191537A - Digital signal transmission control system - Google Patents

Abstract

PURPOSE:To improve the transmission efficiency of a transmission line by allowing a block using station memory to store an address of a packet sender station and a destination station using exclusively a block and a kind of a terminal device and comparing/discriminating the request from a terminal device with the stored content. CONSTITUTION:An overhead signal 25 is extracted from each station receiving by a reception logical circuit 14 of a station device 9, which transmits the signal 25 to a block using station memory 24. The memory 24 stores a destination address, a sender address and the kind of the terminal device in use being the final address. When a connection request enters from a terminal device 5 and the address of communication party and a final connection terminal are clarified, an other station check request signal 26 is outputted from a transmission control circuit 22 to the memory 24. The memory 24 compares the address of communication party and the final connection terminal device with the content of the memory 24, and whether or not the final terminal device having the connection request is in use is discriminated, resulting that the signal 27 is returned to the circuit 22. When it is clear that the final connection terminal device is not in use, a packet requesting a call is transmitted to the opposite station.

Description

[Detailed Description of the Invention] (Field of Application) The present invention relates to a digital signal transmission control method, and in particular,
This invention relates to a digital signal transmission control method designed to improve the transmission efficiency of a transmission line.

(Prior art) In recent years, in small-scale communication systems such as in-house communication carried out within the premises of companies, backup using communication cables such as coaxial cables has become popular due to its economic efficiency, reliability, and high transmission efficiency. The communication system based on the j~ format is attracting particular attention.

In this packet-based communication system, a communication cable for bidirectional transmission is laid within a premises, and a large number of stations (personal computers) are connected to it. Then, from each station, the data is divided into, for example, 1,000 to 2,000 bits of data, and a 1ζ message is transmitted. A message has a destination, a serial number, and other headers added to it.

In this communication system, the network 1 is a passive transmission medium that does not have any control function, and control is completely distributed to each station. If a collision occurs with another station during transmission, both stations stop sending the message.The station that stopped sending attempts to retransmit the message after a long waiting period.3 By the way, in this communication system, each station starts transmitting data at its own discretion, so there is a possibility that packets will collide on the same transmission path. . Therefore, there is a problem that the transmission delay time is not constant, making it unsuitable for real-time transmission where the correspondence between transmission and reception in real time is important, such as conversational voice communication. ``In order to solve the above-mentioned problems, a digital signal transmission control method has been proposed that can perform real-time transmission without losing the equality of each part pull station (
For example, Japanese Patent Application No. 56-38714, etc.).

In the proposed signal transmission control method, a large frame (frame) that is periodically repeated on the time axis is further divided into a plurality of small frames (blocks) on the time axis. Then, each station (personal station) is given an opportunity for packet communication in units of these blocks.

This allows each station to have equality in using empty blocks. Not only that, but if each station occupies a given block for the time required for signal transmission, it will be given a regular opportunity to transmit signals in each repeated frame, allowing real-time transmission. It is also possible to do so.

FIG. 1 shows an example of the frame structure of a signal employed in this method.

A room that is periodically repeated on the time axis consists of N blocks (#1 to #N). , and each block has the following bit strings b1 to b9:
It is made up of.

bl・・・・・・・・・Rear guard time b2・
・・・・・・・・・Preamble b3・・・・・・
・・・・・・Address bit l) 4・・・・・・・・・
・・・Distance code P1-B5・・・・・・・・・・・・
Control bit b6・・・・・・・・・Information bit b
7...Old...Deck pit b8...
・・Old・・End flag b9・・・・・・・・・・・・
Forward guard time Here, each bit string b2 to b5. b7
, b8 are necessary for configuring a packet, and are collectively called overhead (additional) bits. Further, the two types of bit strings b1 and b9 are collectively called guard time. The address bit of b3 includes a destination address and a source address. Furthermore, the control bit b5 includes a flag indicating that the packet is a mask packet that controls system timing, a flag indicating the usage status of a plurality of terminal devices connected to the station device, and the like.

C1 In this proposed digital signal transmission control system, if no station is transmitting a signal, each station can equally transmit a signal with the frame structure described above at a completely arbitrary time. You can start.

Therefore, the station that first sends out a signal to the communication cable takes the initiative in frame synchronization. The station that has taken the initiative in this frame synchronization (mask station) sends out a packet with a d sign () that allows it to be identified as a packet sent by a mask member. Each station can establish frame synchronization for the entire system by receiving this packet and resetting the room counter 17 in FIG. 2, which will be described later, at a certain timing.

In this way, once frame synchronization is established, all stations can monitor the status of the signals transmitted over the communication cable.

FIG. 2 schematically shows an example of a communication system suitable for transmitting digital signals having the frame structure described above.

In this communication system, a coaxial cable 3 installed as a transmission path is connected at both ends to terminators 1 and 2 for characteristic impedance matching.

Each of them is connected to the coaxial cable 3 through connectors (taps) 41 to 41. All these stations have basically the same configuration. Therefore,
In the figure, only the essential parts of the A station connected to the connector 4I are shown.

Each station is equipped with a terminal device (user device) 5 including a computer, telephone, facsimile device, or the like.

The terminal device 5 includes a transmitter (encoder) 6 for transmitting digital signals in packet units to other stations, and a receiver (decoder) for receiving digital signals in packet units sent from other stations. A terminal controller 8 is provided for controlling the terminal.

Of these, the signal output from the transmitter 6 is temporarily stored in the transmission buffer memory 10. Then, they are read out all at once at a predetermined time using a clock signal equal to the transmission speed of the coaxial cable 3'' which is the transmission medium.

The read signal is sent to the transmission logic circuit 11 and converted into a predetermined packet. After passing through the transmission buffer amplifier 12, the signal is sent out onto the coaxial cable 3 through the T connector/1.1.

On the other hand, all packet signals transmitted on the coaxial cable 3 are received by the receiving buffer 7 amplifier 13 through the T connector 41 and input to the receiving logic circuit 14.

The reception logic circuit 14 selects only the packet addressed to its own station from the received packets 1-, and stores it in the reception buffer 1 memory 1.
Temporarily store in 5. The stored signal is sent to the receiver 7
The data are read out continuously using a predetermined clock. From this, a received output signal J is obtained.

The transmission and reception of the °C signal is performed as described above, and the transmission lock used in this case is generated from the transmission lock oscillator 16. Frame Tsuno Kunta 17 divides the frequency of this transmission lock to 1[1tsuk timing 18
and generate frame timing 19.

The transmission control circuit 22 controls the terminal controller 8 based on the reception signal addressed to the own station obtained from the reception logic circuit 14, and also controls the transmission logic circuit 11 according to instructions from the terminal controller 8.
control.

The transmission control circuit 22 is also equipped with a memory for storing the exclusive use status of each block within the frame, and registers whether each block is in use based on the received packet signal from each station. will be carried out.

Further, the collision detection circuit 23 checks whether or not a collision has occurred with a packet signal transmitted from another station when the first bucket 1 signal is transmitted in the block selected by the local station.

Now, in this digital signal transmission control method, after frame synchronization has been established, when another station sends out a packet signal, the empty block 11 is selected based on the contents of the memory in the transmission control circuit 22. is selected, and this block is exclusively used to send out Paku-1-Shintan.

Now, when a request for information transmission from a station A to a station B occurs, a memory for registering the usage status of the blocks described above in the transmission control circuit 22 shown in FIG. 2 in the A station equipment is generated. Select an available free space and set the destination to B.
Start transmitting packets as a station. Here, when sending a packet for the first time to the selected empty block 1], another station generates a transmission request, selects the same empty block 1, 1 as station A, and simultaneously sends a packet to the same block for the first time. There is a possibility of overturning the start of sending out the bang i~. In this way, if two or more stations simultaneously send out the BUTTON 1- to the same block, a collision will occur. If there is a collision, the station that made the transmission request will eventually secure the necessary block according to a certain retransmission procedure.

Once a station successfully sends a packet to a certain block, it has obtained the right to use the same block in subsequent consecutive frames 41 and can continue to transmit information.

By the way, this network requires call setup/release procedures before and after transmitting the '1t7i information. An example of the procedure for setting up and releasing this call is shown in FIG.

The destination address of button 1- of the call request from device A8 in Fig. 3 is station B, and the control bit b5 shown earlier sets a flag indicating that terminal B is the final destination. It is assumed that

When the 88M station receives this packet, the reception logic circuit 14 of the B station detects that the final destination is terminal B, and checks whether terminal B is in use. If it is not in use, it sends a call receipt back to station A, notifies terminal B of the incoming call, and activates it. Thereafter, information data is transmitted, and when this is completed, call release procedures such as disconnection instructions and disconnection confirmation are performed, and the communication is terminated.

On the other hand, if the b terminal is in use, the procedure is as shown in FIG. That is, when station B receives the originating ll'7' request, it detects that the final destination is terminal b, and
Perform Mf W4 to determine whether the terminal is in use 1゜l) If the terminal is in use, it will send a business response back to station A3. Receive the business response Ridden A
The station equipment notifies terminal A that the other party is busy with S=LU. Terminal A now issues a recovery request and enters a call release procedure.

In this way, in the conventional digital signal transmission control system, if the communication partner's terminal device is in use, the above-mentioned call request, business response, disconnection instruction, and disconnection confirmation are unnecessary. The signal flows through the transmission path to the port 1, which has the disadvantage that the transmission efficiency of the transmission path deteriorates.

(Objective) The present invention has been made to eliminate the above-mentioned drawbacks, and its object is to provide a digital signal transmission control system that improves the transmission efficiency of a transmission line.

(Overview) In order to achieve the above object, the present invention stores at least the addresses and types of terminals of the source station and destination station that occupy each small frame (block) in one large frame (frame). When a connection request, partner station address, and terminal type are input from the block usage notification memory and the terminal device connected to the same device, these are compared with the contents of the block usage notification memory. The present invention is equipped with a means for detecting whether or not the other party's terminal device with which communication is desired is in use, so that it is possible to detect whether or not the other party's terminal device with which communication is desired is in use without sending a packet to the transmission path. It is distinctive in that it did so.

(Example) Hereinafter, a detailed description of the present invention will be given with reference to the drawings.

FIG. 5 is a block diagram of one embodiment of the present invention.

In the figure, 24 is a block usage layer, 25 is an overhead signal, 26 is a partner station request signal, and 2 is an overhead signal.
7 indicates the partner station check result signal, and the sign of the square is:
FIG. 2 shows the same or equivalent structure.Next, the operation of this embodiment will be explained. In addition, the block usage layer is 24
Since the operations of the other parts are the same as those of the conventional device explained in FIG.

The receiving lambda logic circuit 14 extracts the A-ha head signal from the received bata 1 to signals of each station, and sends the overhead signal 25 to the block using station mech 24. As a result, the block using station menu 24 stores the destination address, source address, and type of the terminal in use that is the @Hiiragi destination of the packet that has already used each block.

Now, suppose that a connection request is received from the terminal device 5 connected to the station device 9, and the address of the communication partner and the final connected terminal are known. At that point, the transmission control circuit 22 sends the block usage layer memory 24 to the A local check request signal 26 is output. The block usage layer memory 24 compares the address of the communication partner and the last connected terminal with the contents of the block usage layer memory 24 to determine whether or not the last connected terminal that made the connection request is in use. Then, a partner station check result signal 27 representing the result is returned to the transmission control circuit 22.

If the above determination reveals that the last connected terminal to which the connection request was made is not in use, the Δ station sends a call request packet to the B station.

Next, the connection procedure according to this embodiment will be explained with reference to FIG. First, when terminal A makes a connection request to station A, station A selects an empty block. When an empty block is found,
Station A sends a signal indicating that dialing is possible to terminal A, and upon receiving the dialed contents, checks the contents of the block usage station message 24 as described above. When it is determined that the terminal B to which the connection request was made is unused (1), a call request is sent from the A station device to the B station device.

The B8 device receives the call request and 1) confirms that the terminal is unused. Furthermore, this (A) recognition is necessary for the following reasons.

Since there is a delay due to circuit operation between checking the block usage layer memory of the A station and sending the outgoing call request, immediately before the call request from the A station is received, This is because there is a possibility that a call request from the (I!! station) has arrived at 1), and 1) there is also a possibility that the terminal is being used in local mode.

When the B-station device confirms that the b-terminal device is not in use, the B-station device returns an incoming call acceptance to the A8 device, and 11 C! Notify the Af wooden device that there is an incoming call and activate it.

A connection completion signal is sent from the A station device to the A terminal device.

After that, data transmission is performed, and when it is completed, a
A recovery request is issued from the terminal. Subsequently, when the A-station device issues a disconnection instruction to the B-station device and the connection is disconnected,
A disconnection confirmation signal is sent from the B station device to the A station device. Finally, terminal a confirms the recovery.

Next, the connection procedure when the block usage layer memory of the A station device is checked and the terminal B, which is the last connected terminal device, is in use will be explained with reference to FIG.

If the block usage layer memory is checked and the last connected terminal is in use, the station equipment notifies the terminal that made the connection request that the other party is busy. As a result, a recovery request is issued from the terminal A side, and the terminal returns to the standby state.

In this way, according to this embodiment, the usage status of the other party's terminal device can be confirmed without sending any packets over the transmission path. Therefore, unnecessary packets are less likely to be sent to the transmission path, and the transmission path can be used efficiently.

(Effects) As described above, according to the present invention, the destination address of Bakut using each block and the type of terminal in use as the final destination are stored in the block usage layer memory, and a call request is made. If so, it is determined within the local station whether or not the last connected terminal of the communication partner is in use. If the transmission path is unused, a call request packet is sent to the transmission path, and if it is in use, the transmission procedure is stopped without sending a call request packet to the transmission path.

Therefore, there is a great effect that the transmission of unnecessary butterflies to the transmission path is reduced, and the transmission path can be used efficiently.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of a transmission signal, Fig. 2 is a block diagram (not showing an outline) of a conventional communication system, and Figs. 3 and 4 show the steps from connection to call release in the conventional system. Figure 5 is a block diagram showing an outline of a communication system suitable for carrying out the present invention, and Figures 6 and 7 are diagrams showing the procedure from connection to release of a call according to the method of the present invention. FIG. 5... Terminal device, 9... Station device, 11... Transmission logic circuit, 14... Reception logic circuit, 24... Block usage layer memory, 25... Overhead signal, 26...
Partner station check request signal, 27... Partner station check result signal Representative patent attorney Michito Hiraki and 1 other person

Claims (1)

[Claims] (1) Digital signals transmitted on communication cables,
A time axis that repeats periodically "A time axis that is fixedly positioned within a large frame (frame), and a time axis that is further divided within a large frame (frame) on this time axis" This small frame (block) is a unit. It provides each station with the opportunity to transmit digital signals, and allows time division multiplexing and line switching using packet format.
! In a multi-station digital signal transmission control system that transmits and receives signals automatically, the addresses of the source station and destination station in buckets 1 to 1, which occupy each small frame (block) in a single-person frame (frame). and a block usage notification memory that stores at least the type of terminal device, and when a connection request, partner station address, and terminal device type are input from a terminal device connected to the station equipment, these and the block usage notification memory are stored. 1. A digital signal transmission control system characterized by comprising means for detecting whether or not a terminal device with which communication is desired is in use by comparing the contents of the terminal device with the contents of the terminal device.