JPS6269749A - Data transmission method - Google Patents

Abstract

PURPOSE:To limit a delay time until transmission becomes successful after data to be transmitted is available by subtracting the prescribed time from the retransmission standby time of all nodes whenever nodes with different initial values become successful in data transmission. CONSTITUTION:A transmitter 1 detects whether other node signals are present or not on a communication line 10. When the transmitter 1 detects the idleness of the communication line, it activates a timer 4 and becomes transmittable after a transmission standby time Hsec. Then it checks the presence or absence or the data to be transmitted, and transmits the data when the data is present. At this time, if other nodes are transmitted in the same way, data collides. When the transmitter 1 detects the collision, it activates the timer 4, and retransmits the data after retransmission standby time i.h. If retransmission proves failure, the transmitter 1 again recognizes the idleness of the communica tion line, and becomes transmittable after the transmission stanby time H. When the transmitter 1 succeeds in its own transmission or in other nodes, it subtracts one from the value of a register 3. If the value returns to '1', the transmitter 1 sets the value to (n).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a data transmission method in a network in which a plurality of nodes are connected to a communication line.

[Prior art]

In a local area network, when each node connected to a communication line transmits data arbitrarily, the data collides with each other, causing a state in which communication is impossible. Therefore, it is necessary to organize the nodes that access the network between each node. One method is the C3M^/CD power method (for example, "Local Neno (-Fundamentals and Practice of Work Technology"r'103-I'109, published by CO Publishing). This method uses the communication line to transmit signals from other nodes. The method is to transmit the data after detecting that the data is not present, and to retransmit it if the data collides with each other. , if data collides with each other, it is retransmitted with probability p'.

(Problem to be solved by the invention) However, in such a conventional method, there is a drawback that the maximum value of the delay time from when a node has data to be communicated until successful transmission is not determined. 3) [Means for Solving the Problems] The present invention was made to solve these problems, and the present invention has been made to solve these problems. In this case, the initial setting value of the retransmission waiting time is set differently for each node, and each time any node succeeds in data transmission, the retransmission waiting time of all nodes is decreased by a predetermined amount. An object of the present invention is to provide a data transmission method that can limit the delay time from obtaining data to be transmitted to successfully transmitting the data.

The data transmission method according to the present invention is a data transmission method in a network in which a plurality of nodes are connected to a communication line and detection of data collision is impossible, and retransmission when a data collision is detected. The waiting time is initially set to a different value of 1h (i is an integer) for each node,
Thereafter, each time any node successfully transmits data, the retransmission waiting time of all nodes is reduced (h1'-).

〔Example〕

The present invention will be specifically described below based on drawings showing embodiments thereof.

As shown in FIG. 1, the communication line 10 includes n nodes Al,
A2. ^3...-An-II An is connected,
Local area r for mutual data transmission
A network has been constructed, and each notebook has a function to detect whether the communication line 10 is being used or not and a function to detect whether a collision of transmitted data has occurred when performing this data transmission. .

When starting the network, the node Al
, A2. A3...All-1+ All retransmission waiting time (seconds) is 1 ・h, 2 ・h, 3 ・h
-(n-1) ・h.

n-h, i.e. i-h (i=1,2.3 ・=n)
are initialized respectively.

(Left below) Retransmission waiting time refers to the time from when a data collision occurs to the next transmission. Note that the value of h is nh<) (However, ■! is a constant transmission waiting time from detecting that there is no signal from another node on the communication line 10 until actually starting data transmission. , and a delay in the communication line 10 is set for each layer. This is to give priority to transmission to nodes that have collided.

After the initial setting of the retransmission waiting time as described above, each time a note succeeds in transmission, the retransmission waiting time is decreased by h for all nodes. Table 1 shows the change in retransmission time for each node. After being reduced to lh, it returns to nh.

According to this method, the retransmission waiting time of each node is quite different for each node, so that when retransmitting data after a data collision occurs, these data do not collide.

In addition, since nh < H, retransmitted data is transmitted with priority over newly generated data, so in the end, with the method of the present invention, it is possible to transmit with extremely high probability when retransmitting. The retransmission waiting time of a node changes each time a node succeeds in transmission, and the priority order is updated, so that the delay time from generation to transmission of data to be transmitted can be limited.

Figure 2 shows node Ai (i=1.2.3-n-1, n
) is a block diagram schematically illustrating the configuration of a transmission device 1 that controls transmission as shown below, retransmission waiting time data i
, immediately store 1, 2, 3...n and place "ζ" in register 3.
, a dip switch 2 for initializing this, and a timer 4 for measuring the unit of retransmission waiting time or the transmission waiting time H. Ditub switch 2 connects each node to l, to2. Δ3... to n-1. Eight. According to 1.2.
3...n-1,n is set.

FIG. 3 is a flowchart 1 showing the processing procedure of transmission control by the transmission device I.

The transmission device 1 detects whether there is a signal from another node on the communication line 11j110, and when it detects that the communication line is vacant, it starts the timer 4 and enables transmission after a transmission waiting time of 11 seconds. Then, check the self-identification of C transmission-4 power data, and if it exists, transmit 3.

At this time, if other notes also transmit 1 in the same way, a data collision will occur. When the transmission device 1 detects the disturbance, it starts the timer 4 and starts the retransmission field after the C retransmission waiting time ih.

If retransmission fails for some reason, the availability of the communication line is checked again, and the transmission becomes possible after waiting time ++i for transmission 121. When the transmission device 1 succeeds in transmitting either itself or another node, it decrements 4 (fI) in the register 3 by 1. After returning to l, it is set to n.

Now assume that the waiting time for 6 transmissions of note Δ1 is 1·l+'cib, and there is data to be transmitted. If there are 1ffl successful transmissions for the entire note °(il) times, the retransmission waiting time of node A- will be the minimum l h.If note △j does not successfully transmit data by this time, checks the availability of the communication line and sends a message after the transmission waiting time H from C. Then, if a data collision occurs at this time, the retransmission waiting time is the minimum and C is the earliest to retransmit. It will be successful.

〔effect〕

As described above, the present invention makes it possible to limit the maximum delay time from when data to be transmitted is generated to when the data is actually transmitted. It can be applied to the system and enables efficient data transmission.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a network according to the present invention, FIG. 2 is a block diagram showing the configuration of one node, and FIG. 3 is a flowchart showing a transmission control processing procedure. ■...Transmission device 2...Ditub switch 3...
Register 4...-Timer IO...Communication line patent
Applicant Sanyo Electric Co., Ltd. Agent Patent Attorney Noboru Kono

Claims (1)

[Claims] 1. In a data transmission method in a network where multiple nodes are connected to a communication line and data collisions are detected, the retransmission waiting time when a data collision is detected is determined for each node. It is initially set to different values ih (i is an integer), and then every time any node succeeds in data transmission, the retransmission waiting time of all nodes is set to h.
A data transmission method characterized by decreasing data in increments.