JP2845720B2 - Error detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for transmitting digital information, and more particularly to an apparatus for encoding and decoding an error detection code.

[0002]

2. Description of the Related Art When transmitting digital information, an "error detection code" is used to prevent the information to be transmitted from being appropriately transmitted due to noise contamination. For error detection codes, see (Imai, "Code Theory,
It is described in detail in the Institute of Electronics, Information and Communication Engineers (Document 1). The basic idea of an error detection code is to add information to the original information to be conveyed with redundancy according to a certain rule, transmit it, and then check whether the information received on the receiving side complies with this rule. Is to determine whether an error has occurred.

A digital communication system using an error detection code can be modeled as shown in FIG. In the figure, an information sequence 41 is input to an error detection encoder 42,
A coded sequence obtained by adding a redundant bit sequence to the information sequence is output, and is transmitted as a transmission sequence 43 to a transmission path 44. The process up to this point is the process on the transmitting side 48. Transmission line 44
A transmission path error is mixed in the coded sequence passed through the
In step 9, the reception sequence 45 containing the error is received. The received sequence is input to an error detection decoder 46, and a decoding result 47 is output. If the decoding result indicates that an error has occurred, either the request or the error correction processing is performed again by the system.

In some cases, not all bits of an information sequence are subjected to error detection. That is, a part of the information sequence is input to the error detection encoder, and the output of the error detection encoder and the rest of the information sequence are combined to form a transmission sequence. For example, when the importance of each bit in the information sequence is different depending on the nature of the information source, only the bits with higher importance can be input to the error detection encoder. At this time, the remaining information sequence and the output of the error detection encoder are combined into a transmission sequence.

[0005] When a received sequence contains many errors, the error detection decoder may not detect an error even though there are errors. This is called an error detection error. Here, assuming that the number of bits of the redundant bit sequence added by the error detection encoder is constant, the greater the number of information bits input to the error detection encoder, the higher the probability of an error detection error occurring. There is a property that.

[0006]

In the conventional error detection apparatus, in order to reduce error detection errors, the number of redundant bits added by the error detection encoder is increased or the number of bits of the information sequence to be detected is determined. We need to reduce the number. At this time, since the number of bits that can be transmitted in a given time is generally limited, the number of bits of the information sequence must be reduced in order to increase the number of redundant bits. Also, if the number of bits for error detection in the information sequence is reduced,
Information may not be properly transmitted due to an error mixed in a bit for which error detection is necessary due to its high importance and which is not detected.

[0007] The feature of the present invention is to solve such a problem by eliminating error detection errors without increasing the number of redundant bits and without reducing the number of bits to be subjected to error detection in the information sequence. The purpose is to reduce.

[0008]

In order to achieve the above object, an error detecting apparatus according to the present invention comprises a specific bit in an information sequence.
Switches the importance of each bit in the information sequence
The error detecting device information sequence having a property, the transmitting side, a plurality of types of error detection encoder that performs error detection coding as input some or all of the information sequence, certain of the information sequence Means for switching the error detection encoder according to bits , a reception side corresponding to a plurality of types of error detection encoders on the transmission side, and a part of a reception sequence.
Alternatively, it is characterized by comprising a plurality of types of error detection decoders that decode error detection codes by inputting all of them as inputs, and means for switching the error detection decoders according to specific bits of a received sequence.

[0009]

In the error detection apparatus according to the present invention, the transmission side switches the error detection encoder according to some of the bits to be subjected to error detection, and the other bits are input to the error detection encoder. Therefore, error detection mistakes can be reduced. Also, if the switching bit contains an error,
Since the error detection decoder is erroneously selected on the receiving side, an error is detected with a high probability. Therefore, error detection errors can be reduced without increasing the number of redundant bits and without reducing the number of bits to be subjected to error detection in the information sequence.

Further, when the error detecting device of the present invention is used,
When the information sequence has such a property that the importance of each bit in the information sequence is switched by one or more specific bits in the information sequence, the error detection encoder is switched by the bit. It becomes possible.
For example, in the field of audio coding,
Select one of the four encoding modes according to the properties,
The 2-bit mode information and the encoded audio information are
In addition, there is a method of simultaneously transmitting the information sequence. this
In such a case, if the mode information is different, the encoded audio information
The meaning of each bit of the report is different. This means that the mode information
Switches the importance of each bit in the information sequence
Means that.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an error detection device showing one embodiment of the present invention. In FIG. 1, the information sequence 1 is divided into two, a switching bit and a detection bit. Here, the switching bits are two bits. In order to switch by the two switching bits, the error detection encoder must
8 are prepared, and four types of error detection decoders 14 to 17 are prepared correspondingly. The switching bit is added to the transmission sequence 9 through 2 and the detection bit is 3
To the changeover switch 4, the changeover switch 4 is controlled by the changeover bit, and the detection bit is input to any of the four error detection encoders 5 to 8. The error detection encoder to which the detection bits have been input performs error detection encoding, and outputs the detection bits and the redundant bits. The output becomes a transmission sequence 9 together with two switching bits. On the receiving side, the detection bit and the redundant bit of the received sequence are sent to the changeover switch 13, and the changeover switch is controlled to 12 changeover bits,
The detection bits and the redundant bits are output to the error detection decoders 14 to 17.
Is input to any of The error detection decoder i performs decoding on the assumption that it has been encoded by the error detection encoder i, and detects an error.

FIG. 2 is a block diagram of an error detecting apparatus showing another embodiment of the present invention. Here, it is assumed that mode information represented by 3 bits is included in the information sequence, and the information sequence has eight types of modes. Further, since the meaning of each bit of the information sequence differs depending on the mode, it is assumed that the importance of the same bit changes depending on the mode. For this reason, the error detection device of FIG. 2 switches the bits to be subjected to error detection for each mode. In FIG. 2, three bits of mode information in the information sequence are added to a transmission sequence 26 through 22, and the other bits are input to a detection bit selector 24. The detection bit selector is controlled by the mode information of 22
Bits to be subjected to error detection and bits not to be selected are selected for each type of mode. One is an error detection encoder 25
, And the other joins the transmission sequence 26. On the receiving side, bits other than the mode information in the reception sequence 28 are 3 bits.
0 is input to the decoding bit selector 31, which is controlled by the mode information 29 to select a detection bit and a redundant bit. The selected detection bits and redundant bits are input to the error detection decoder 32, where an error is detected.

[0013]

As described above, the error detection apparatus according to the present invention divides a bit to be subjected to error detection into two bits, switches one of the error detection coding systems, and switches the other into an error detection encoder. , The number of error detection errors can be reduced. In addition, since the error detection coding method is switched according to a specific bit in the information sequence, the information sequence has a property that the importance of each bit in the information sequence changes according to the specific bit in the information sequence. When it has, it is possible to perform an operation of switching the bit to be subjected to error detection according to the content of the specific bit.

[Brief description of the drawings]

FIG. 1 is a block diagram of an example of a communication system using an error detection device according to the present invention.

FIG. 2 is a block diagram of another example of a communication system using the error detection device according to the present invention.

FIG. 3 is a block diagram of a communication system using an error detection device of the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Information sequence 2 Switching bit 3 Detection bit 4 Switching switch 5-8 Error detection encoder 9 Transmission sequence 10 Transmission line 11 Receiving sequence 12 Switching bit 13 Switching switch 14-17 Error detection decoder 18 Decoding result 21 Information sequence 22 Switching Bit 23 information sequence other than switching bits 24 detection bit selector 25 error detection encoder 26 transmission sequence 27 transmission path 28 reception sequence 29 switching bit 30 reception sequence other than switching bit 31 decoding bit selector 32 error detection decoder 33 decoding Result 41 information sequence 42 error detection encoder 43 transmission sequence 44 transmission line 45 reception sequence 46 error detection decoder 47 decoding result 48 transmission side 49 reception side

Claims (1)

(57) [Claims] The information is specified by a specific bit in an information sequence.
Has the property that the importance of each bit in the sequence switches
In the error detection device information sequence, the transmitting side, a plurality of types of error detection encoder that performs error detection coding as input some or all of the information sequence, especially among the information sequence
Means for switching the error detection encoder according to a fixed bit , corresponding to a plurality of types of error detection encoders on the transmission side on the receiving side, and receiving a part or all of the received sequence as an error. An error detection apparatus comprising: a plurality of types of error detection decoders for decoding a detection code; and means for switching the error detection decoders according to specific bits of a received sequence.