JPS62137946A - Data transmission system - Google Patents

Abstract

PURPOSE:To collate flag information and timer information with each other to discriminate whether a reception signal should be outputted or not by adding a flag indicating a retransmission frame to an information field in the transmission side and providing a buffer and a timer for every transmission element in the reception side. CONSTITUTION:A transmission format signal where the flag is provided in one bit of the header of the information field is transmitted. A time division multiplex communication equipment in the reception side receives this signal and has an error signal eliminated in a high level data line control procedure (HDLC) corresponding part 10 and is inputted to a distributing part 11. It is distributed to a corresponding channel part 14. The corresponding part 10 detects the first transmission frame of the text to start a timer 12 in the corresponding channel part 14. The transmission signal is first stored in a buffer 13, and the timer 12 checks the flag of this stored flag; and if the flag is '0', data is outputted as it is. If the flag is '1', the value of the timer is checked, and data in the buffer 13 is outputted if it is within a prescribed time, but data in the buffer 13 is abandoned if it is not within the prescribed time.

Description

[Detailed Description of the Invention] [Summary] In a time division multiplex communication device using an HDLC procedure,
On the transmitting side, a flag indicating whether or not to retransmit is added to the beginning of the information field of the transmission formant, and on the receiving side, a buffer and a timer are provided for each channel, and the flag information is used to handle data that has been delayed for more than a specified time. I will leave the I building.

[Industrial application field]

The present invention relates to a retransmission control method for a time division multiplex communication device using an HDLC procedure.

As is well known, the data transmission method using the HDLC procedure defines a data transmission procedure between terminals or between a terminal and a host processor.

Recently, a time division multiplex communication device (hereinafter referred to as a TDM device) having an HDLC procedure has been developed, and the present invention relates to an improvement of such a TDM device.

[Conventional technology]

HDLC procedure High-level health data link control procedure-hi
gh 1level data 1ink control
This is an abbreviation for l procedures, which is a transmission method suitable for high-speed data transmission, and is a procedure for efficiently performing synchronous data transmission without being subject to any coding restrictions by transmitting frames (transmission units).

FIG. 2 is a diagram showing an example of a transmission format based on a conventional HDLC procedure.

In the figure, F is a flag sequence, A is an address, C is a control field, ■ is an information field, and Fe2 is a frame check sequence.

The transmission format of the HDLC procedure starts with flag sequence F (01111110), address A (8 bits), control field C (8 bits), information field I (arbitrary length), and frame check sequence FC3 (
16 bits), and flag sequence F (011111
10), and the station connected to the data link detects this flag sequence F and starts communication.

According to HDLC procedure, frame check sequence FC
A transmission error is detected in step 3 and step 1. When retransmission is performed using control field C and data is transmitted between a normal host processor and a terminal, data (telegram) is stored in information field I.

FIG. 3 is a diagram showing an example of data transmission via a 70M device.

In the figure, 1 is a host processor, 2 is a terminal, and 3a and 3b are 70M devices.

In the example shown in FIG.
A case is shown in which TDM devices 3a and 3b are used as transmission paths when data is transmitted according to the DLC procedure.

Of course, multiplex communication equipment is sometimes used as a transmission line like this, but multiplex communication equipment is originally used as a line.
It fulfills F, and any form of communication power multiplied by one should not impose any restrictions on it.

However, recently, in order to improve transmission efficiency, the content of the signals to be transmitted has been investigated and the transmission procedures have been changed, and HDL has been added to the TDM equipment itself.
A device with a function of detecting errors and retransmitting using C-f-order has been developed and is in practical use.

A 70M device like this one typically communicates using frames as described below.

FIG. 4(a) and FIG. 4(b) are both diagrams showing an example of a transmission frame of a conventional 70M device.

Figure 4(a) is an example used when multiplexing multiple channel data into one frame, and the information field ■ is divided into a data byte count term, a data term, and a control signal information term. , consideration has been made so that the contents of the data term and the control signal information term can be understood from the term of the number of data bytes.

Figure 4(b) is an example in which only one channel's worth of data is accommodated in one frame. When X is 1, it indicates that the content of the information field (2) is data, and when X is 0, it indicates that the content of the information field (2) is control signal information.

[Problem that the invention seeks to solve]

In general, the HDLC procedure detects line errors and performs retransmission, so it has the advantage of not receiving erroneous data, but when retransmission is performed, the transmission delay increases accordingly.

A TDM device 3a that uses frames as shown in FIG.
When data is transmitted between host processor 1 and terminal 2 via 3b, the TDM device itself may detect a transmission error and perform a retransmission operation, and when this retransmission operation is performed, the terminal 2 side In the 70M device, it may not be possible to determine whether the retransmission is by the host processor 1 or the 70M device.

FIG. 5 is a diagram explaining the problems of the conventional transmission system.

From terminal 2 to host processor 1 as shown in Figure 5
When data is transmitted as shown in , host processor 1
Assume that a retransmission request is issued as shown in . For this purpose, terminal 2
is retransmitted as shown in ■.

At this time, if the TDM device 3b requests retransmission as shown in (2) for some reason, the TDM device 3a retransmits as shown in (2). However, since the host processor 1 cannot receive the retransmitted data within the predetermined time, it prompts for a response as shown in ■.
Eventually, the retransmission data (2) is received from the TDM device 3a, and is mistaken as a response from the terminal 2.

However, as shown in (3), since the response reminder has already been sent, the retransmission data (2) arrives from terminal 2 with a delay. As a result, the host processor 1 side wonders why the data ■ has arrived.

The conventional method had the drawback of causing confusion like this.

Means for Solving Problem C] The above problem is that in a time division multiplex communication device that uses the IDLC procedure, as shown in Figure 1 (a), on the transmitting side, the beginning of the information field of the transmission formant is On the receiving side, a timer 12 and a buffer 13 are provided for each channel as shown in FIG.
If the flag f of data stored in the buffer 13 after a delay of more than the time stipulated by No. 2 indicates retransmission, the problem is solved by discarding the data.

[Effect]

According to the present invention, on the sending side, a flag is attached to the information field f to indicate that it is a retransmitted frame, and on the receiving side, a buffer and a timer are provided for each transmission element, and the flag information and timer information are compared. This produces the effect that it is possible to determine whether or not the signal should be output.

〔Example〕

FIG. 1(a) is a diagram showing an embodiment of a transmission formant of a DTM device according to the present invention.

FIG. 1(b) is a diagram showing an embodiment of a receiving side circuit of a DTM device according to the present invention.

In the figure, f is a flag according to the present invention, 1o is an HDLC compatible section, 11 is a distribution section, 12 is a timer, 13 is a buffer, 1
4 is a channel part.

The present invention will be described in detail below with reference to the drawings.

On the transmitting side, a transmission format as shown in FIG. 1(a) is used. That is, a 1-bit flag f is provided at the head of the information field I. This flag f is normally "0", but is set to "1" when retransmission is performed using the HDLC procedure.

A signal in such a transmission format is sent out to a transmission path.

Therefore, in the TDM device on the receiver 18' side, this flag f
If this flag r is "0", it is determined that the data was sent by normal transmission procedure of HDLC procedure, and if this flag r is "1", it is determined that the data was sent by retransmission of HDLC procedure. I can do it.

On the other hand, the receiving circuit of the TDM device on the receiving side is shown in Figure 1 (bl
The circuit configuration shown in FIG.
The error signal is removed and enters the distribution section 11. Here, No. 15 is distributed to the corresponding channel part 14. In the figure, only one channel part 14 is shown, but the other channel parts are omitted because they are exactly the same.

The HD LC corresponding section 10 removes the error signal as described above, but at the same time detects the first transmission frame of a series of telegrams and starts the timer 12 built in the corresponding channel part 14.

Upon entering the corresponding channel part 14, the signal is first stored in the buffer 13.

At this time, the timer 12 checks the flag f of the stored data, and if the flag f is "0", outputs that value.

If this flag r is "1", check the value of the built-in timer, and if it is within the specified time, output the data stored in the buffer 13, but if it is outside the specified time. In this case, the data stored in the buffer 13 is discarded.

C Effects of the Invention] As explained in detail above, according to the present invention, it is possible to determine whether or not the data is retransmitted on the receiver 8' side, so there is a great effect that there is no possibility of outputting the same data twice. be.

[Brief explanation of drawings]

FIG. 1 (al is a diagram showing an embodiment of the transmission format of the DTM device according to the present invention. FIG. 1 fbl is a diagram showing an embodiment of the receiving side circuit of the DTM device according to the present invention. Fig. 2 is a diagram showing an example of a transmission format based on the conventional HD LC procedure. Fig. 3 is a diagram showing an example of data transmission via a 70M device. Fig. 4(b) is a diagram showing an example of a transmission frame of a conventional 70M device. Fig. 5 shows the problems of the conventional transmission method. In the figure, F is a flag sequence, A is an address, C is a control field, ■ is an information field, Fe2 is a frame check sequence, 1 is a host processor, 2 is a terminal,
3a, 3b are 70M devices, f is a flag according to the present invention, 1
0 is the HDLC compatible part, 11 is the distribution part, 12 is the timer,
13 is a buffer, and 14 is a channel bar.迦) EGG ツ (aji (7(b) TD and reluctant song I"tbi name data I beggar 3-Remine 5 Figure

Claims (1)

[Claims] In a time division multiplex communication device for transmitting signals between a plurality of sets of data terminals via a plurality of channels using a synchronous data transmission procedure, a transmitting side transmits information fields of a transmission format. A flag (f) indicating whether or not to retransmit is attached to the beginning, and a timer (12) and a buffer (13) are provided for each channel on the receiving side, and the timer (12) is started when a message is received, and the timer The buffer (13) is delayed by more than the time specified by (12).
), the data is discarded if the flag (f) of the data stored in the data indicates retransmission.