JPH0646037A - Mode switching arq system - Google Patents

Abstract

PURPOSE:To improve the throughput by performing correction up to a predetermined bit in a continuing part of error frames. CONSTITUTION:The mode switching processing is first operated in a pure ARQ system (ARQ system without error correction capability) mode 9 on the assumption that an error does not occur on a transmission line. An error occurs N1 times, for example, if N1=3, only when errors occur three times continuously, the mode is switched to a type I hybrid ARQ system mode 10. That is, it is judged that the condition of the transmission line is not good if error frames are detected N1 times continuously. In the other cases, the normal pure ARQ system mode 9 is used to perform error correction. After the mode 10 is changed to the type I hybrid ARQ system, an error 12 in the range of the error correction capability is corrected, but retransmission is performed till arrival of an error correctale frame if the error is beyond the error correction capability.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to error control in digital communications.

[0002]

2. Description of the Related Art Conventionally, as an error control technique in digital communication, there is an ARQ (automatic repeat request) system which uses an error detection code to automatically detect an error in data and request retransmission thereof. Of this ARQ method, Ty
In the peII hybrid ARQ system, information and bits for error checking are first sent, and then, when a retransmission request is made from the receiving side, this time only bits for error correction are sent.

[0003]

However, the above-mentioned Ty
The peII hybrid ARQ system has a poor throughput depending on the state of the transmission path, as compared with the Type I hybrid ARQ system in which data is added with correction bits in advance. That is, in the Type II hybrid ARQ system, only the information bit and the check bit are first sent as in the pureARQ system, and the error correction bit is sent only when a retransmission request is made.
Therefore, when an error occurs and a retransmission request is made on a transmission line in which an error occurs, the error correction bit is sent again, and the procedure is repeated twice or more. On the other hand, T
In the ypeI hybrid ARQ system, a correction bit is added in anticipation that an error will occur in advance, so the procedure may be performed once or more. Therefore, the Type II hybrid ARQ method is advantageous when the state of the transmission path is unknown in advance, but when the state of the transmission path can be predicted to some extent, the Type II hybrid A
Ty that can reduce the transmission procedure compared to the RQ method
When the peI hybrid ARQ method is adopted, the throughput as a whole is improved.

[0004]

The present invention has been proposed in view of the above, and in error control in digital communication, when the condition of the transmission line is good, the error control is performed by using the pure ARQ system. When the state becomes worse, the Type I hybrid ARQ method is used to perform error control.

[0005]

By using the pure ARQ system and the Type I hybrid ARQ system, the state of the transmission line for error correction is narrowed down by the number of errors in the frame, and when the state of the transmission line becomes poor, the Type I hybrid ARQ system is used. Perform error correction. In cases other than this state, the error is corrected depending on the ARQ without trying to relieve the error by force, and the throughput of the intended transmission line is improved.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The mode switching ARQ method according to the present invention is pur
e ARQ system and Type I hybrid ARQ system. FIG. 1 shows a flowchart of processing of the mode switching ARQ method, and FIG. 2 shows an application example of the mode switching ARQ method.

Here, one frame has 300 bits (the number of errors is ≤300). In addition, in FIG.
(1) is a continuous data transmission frame, (2) is one frame of continuous data transmission frames, and (3) is FIG.
In FIG. 1, (4) is a number indicating the number of error bits in one frame, and (5) is a number in FIG. 1 for the frame timing for changing the mode from the pure ARQ system to the Type I hybrid ARQ system when N1 = 3. Type I hybrid AR when N2 = 3
An error-free frame section for setting a mode change timing from the Q method to the pure ARQ method, (6) an error-free section in consecutive frames, (7) an error-containing section in consecutive frames, and (8) an error. None, (9) is a frame section operating in pure ARQ mode when N1 = 3 in FIG. 1, and (10) is a frame section operating in Type I hybrid ARQ mode when N2 = 3 in FIG. 1, ( 11 is a frame section operating in pure ARQ mode when N1 = 3 in FIG.
2) is a frame that can be corrected when error correction that can perform error correction up to 10 bits is used, and the numbers are surrounded by "circles".

When the flow chart shown in FIG. 1 is applied to the error occurrence shown in FIG. 2, when a frame without error continues (2), error control is performed using the pure ARQ system (9), Throughput can be prevented from lowering due to encoding. If error frames continue (7), error correction is performed using the Type I hybrid ARQ method (10), so errors within the error correction capability are corrected and even error frames are retransmitted. Do not do. For example, in FIG. 2, if error correction up to 10 bits is used in the Type I hybrid ARQ system, the number of the error occurrence frame shown in FIG.
The part (12) surrounded by is not retransmitted.

1 and 2 will be described in more detail. In the mode switching process, it is assumed that there is no error in the transmission path at first, and the operation is performed in the pureARQ system (ARQ system having no error correction capability) mode (9). Then, when an error frame is detected, the number of consecutive frames is counted. This is because even if an error is detected, it can be a random error, in which case
It is often not necessary to enter the error correction mode because the error is often recovered in the next frame.

Therefore, assuming that N1 times, for example, N1 = 3 in FIG. 2, when three consecutive errors occur (3), the mode is changed to the Type I hybrid ARQ mode mode (10). That is, when N1 consecutive error frames are detected, it is determined that the state of the transmission path is not good. In cases other than the above, normal p
Error correction is performed using the ure ARQ method (9). Then, after changing the mode to the Type I hybrid ARQ method (10), an error (1
In 2), correction is performed, and if the frame exceeds the error correction capability, the frame is retransmitted until an error-correctable frame arrives.

When the condition of the transmission path is improved and an error-free frame can be transmitted, the pure frame is generated when the error-free frame is N2 consecutive times.
The mode is changed to the ARQ method. That is, N2
If, for example, N2 = 3 in FIG. 2, the frame is error-free for three consecutive times (5), and it is determined that the state of the transmission path is good.

[0012]

According to the present invention, when an error as shown in FIG.
The state of the transmission path is narrowed down by correcting up to a predetermined bit. Therefore, the throughput can be improved as compared with the case where error correction is performed using only the Type II hybrid ARQ method as in the related art.

In particular, when the data transmission rate is high and there is no great change in the state of the transmission line during the transmission of several frames, the state of the transmission line between these frames should be checked for the current transmission line. Can be expected. Therefore, for a predictable transmission path, Type II hybrid ARQ
The throughput can be improved by using the Type I hybrid ARQ method as compared with the case of using the method.

[Brief description of drawings]

FIG. 1 is a flowchart showing a mode switching process.

FIG. 2 is an explanatory diagram showing an example of error occurrence when data transmission is performed.

[Explanation of symbols]

1 Continuous data transmission frame 2 One frame of continuous data transmission frame 3 pureARQ when N1 = 3 in FIG.
Error frame section for taking timing to change the mode from the method to the Type I hybrid ARQ method 4 A number indicating the number of error bits in one frame 5 A mode change from the Type I hybrid ARQ method to the pure ARQ method when N2 = 3 in FIG. Error-free frame interval for timing 6 Error-free interval in consecutive frames 7 Error-free interval in consecutive frames 8 Error-free interval 9 Frame interval operating in pure ARQ mode mode when N1 = 3 in FIG. 10 Frame section operating in Type I hybrid ARQ mode when N2 = 3 in FIG. 11 Frame section operating in pure ARQ mode when N1 = 3 in FIG. 1 12 Error correction capable of error correction up to 10 bits was used Sometimes you can correct Those enclosed expressed in numbers "round" in the absence of

Claims (3)

[Claims] 1. A mode switching ARQ system characterized in that a mode switching is performed in an error control method in digital data transmission. 2. The ARQ mode is pure AR
The mode switching ARQ method according to claim 1, wherein the mode switching ARQ method is a Q method and a hybrid ARQ method. 3. The mode switching ARQ according to claim 1, having a function of judging a state of a transmission line.
method.