JPS62200939A - Lookover error rate improving system - Google Patents

Abstract

PURPOSE:To confirm it as an error without overlooking in case the elimination of '0' in error and the un-elimination of '0' in error take place in the same number of times by inserting a check bit of '0' or '1' selected in advance to a predetermined position in an information field and checking the check bit at the reception side. CONSTITUTION:The information field I consists of 8-bit X n=bit, (n) is a positive integer. The 1st bit of the n-byte is used as a check bit 50 and '0' is inserted at all times. Since an address field A and a control field C are specified by the transmission control procedure, no check bit 50 is inserted. That is, the check bit 50 comprising '0' is inserted to the predetermined position of the information field I at the sending side and the result is sent to the transmission line. In receiving the said frame through the transmission line at the reception side, it is confirmed that all the check bits on the reception memory are '0' and if in error, the data is thrown away.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a no-level data link control procedure (hereinafter referred to as
Regarding data transmission methods using HDLC (referred to as HDLC),
In particular, it relates to a method for detecting code errors occurring on a transmission path.

[Conventional technology]

Generally, the format of a frame, which is a unit of transmission in HDLC, is as shown in Figure 2.

01111110, 7 lags or turns (i.e., frame synchronization patterns) F, and an 8-bit address field A.
, an 8-bit control field C, and an 8-bit information field I that is a positive integer multiple.

It consists of a 16-pit frame verification sequence FC8 (!:).

Conventionally, in HDLC, error verification is performed using an error detection code of frame verification sequence FC8.

With this error detection code, burst errors of less than 16 pits can be reliably detected, but bursts of 16 pits or more may be missed.

[Problem that the invention seeks to solve]

In HDLC, in order to make the pit pattern o1111110 of the frame synchronization pattern F unique, "fio" is inserted after a predetermined bit string (a bit string of 5 consecutive "1" bits) in the information field ■ during transmission, and the receiving side , O# after the predetermined bit string of the information field ■
We are trying to remove the . In other words, consecutive “1”
If you want to send 5 .

Then forcefully insert °゛0# on the receiving side.

Conversely, °'0# is removed. Therefore, when a bit error (one bit error) that affects one line control occurs, the following received data becomes one bit longer or shorter. From the viewpoint of error detection operation, this becomes a burst error, and a missed error may occur. For this reason, a received data size test is generally performed.

This prevents the above-mentioned oversight error.

However, as shown in Figure 3, there are cases in which 0'' is mistakenly removed due to an error in the transmission path, and cases in which 0'' is not removed by mistake due to an error in the transmission path, as shown in Figure 4. However, if they overlap the same number of times, the above-mentioned received data size verification cannot detect it, and an error may occur.

The purpose of the present invention is to confirm the above-mentioned cases where "0" is removed by mistake and O# is not removed by mistake the same number of times, without missing them. The object of the present invention is to provide a method for improving the missed error rate.

[Means for solving problems]

According to the present invention, in order to make the frame synchronization nocturne unique, the transmitting side inserts "0" after the predetermined bit string of the information field, and the receiving side inserts "0" after the predetermined focus string of the information field. In a data transmission system that removes "0"', the sending side inserts a "0" and "1" at a predetermined position in the information field.
Insert a test bit consisting of a preselected one of ``.

A method for improving the missed error rate is obtained, which is characterized in that the test bits are checked on the receiving side.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a frame format used in one embodiment of the present invention. In Figure 1, the Flakhattern F
, address field A, control field C,
The frame verification sequence FC8 shows the same as in FIG. The information field I consists of 8 bits)Xn=N bits. However, n is a positive integer. The first bit of this n byte is the test bit 50, and it is always 6
0" is inserted. Here, since the address field A and the control field C are defined by the transmission control procedure, the verification pins 1-50 are not inserted.

That is, on the transmitting side, a test bit 50 consisting of "0" is inserted into a predetermined position of the information field and sent to the transmission path. On the receiving side, when two frames are received via the transmission path, all verification bits in the receiving memory are
Confirm that it is O#, and if it is incorrect, discard the data.

In the embodiment described above, by inserting a test bit at a predetermined position in the information field to be tested for errors, it is possible to prevent burst errors that occur even when random errors of several bits occur in the HDLC format. The number of test bits present in this burst error is m
If it is a bit, it has the effect of improving the missed error rate to 2.

In the above-described embodiment, the test bit 50 is set to '0#', but it goes without saying that it may be set to 'l'.

〔Effect of the invention〕

As explained above, in the present invention, in order to make frame synchronization points and turns unique, the transmitting side inserts 0'' after a predetermined bit string of the information field, and the receiving side inserts 0'' after the predetermined bit string of the information field. In a data transmission method that removes '0#' after a bit string, it is important to avoid overlooking cases where 0# is removed by mistake and 0# is not removed the same number of times. This has the effect of improving the missed error rate.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the format of a frame according to I (DLC) used in the present invention, Fig. 2 is a diagram showing the format of a frame according to general HDLC, and Fig. 3 is a diagram showing the format of a frame according to general HDLC. FIG. 4 is a diagram for explaining the case where O is not removed by mistake due to a code error in the transmission path.F...Frack iJ? turn (frame synchronization turn).A ... Address field, C... Control field, ■... Information field, Fe2... Frame test sequence, 50... Test bit. Fig. 1 Fig. 2 Transmitted bit string transmission path error position reception Received bit string transmitted after O removal control Bit string transmission path error position Received bit string Received after 0 removal control Bit string of data to be transmitted Figure 3 = Figure 4 1-X

Claims (1)

[Claims] 1. In order to make the frame synchronization pattern unique, the transmitting side inserts "0" after the predetermined bit string of the information field, and the receiving side removes the "0" after the predetermined bit string of the information field. In the data transmission method,
On the transmitting side, a test bit consisting of a preselected one of "0" and "1" is inserted at a predetermined position in the information field, and on the receiving side, the test bit is checked. A method for improving the missed error rate.