JPH08298466A - Method for generating error correction code - Google Patents

Abstract

PURPOSE: To suppress extreme reduction in an inter-bit distance when puncturing and interleaving are applied to a convolution code. CONSTITUTION: A convolution coder 1 converts information bits into a convolution code, An interleaving circuit 3 applies interleaving processing to the convolution code and a puncturing circuit 2 applies puncturing to the result.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of generating an error correction code suitable for use in a transmission line in which a burst error occurs.

[0002]

2. Description of the Related Art When information is transmitted via a transmission line, this information is often converted into an error correction code and transmitted.
One example is shown in FIG. In the figure, 1 is a convolutional encoder, which converts information bits into a convolutional code. Here, the convolutional code has higher redundancy than the information bits. That is, to transmit the convolutional code, a higher transmission rate is required than to transmit the information bit as it is.

However, there are cases where the transmission path cannot cope with the increased transmission rate. In such a case, the puncturing circuit 2 reduces the transmission rate of the convolutional code by puncturing (decimating) some bits of the convolutional code. Next, 3 is an interliving circuit,
The convolutional code after puncturing is interleaved and output.

Here, the contents of the interliving will be described with reference to FIG. FIG. 6A is a memory map of the buffer memory provided in the interliving circuit 3, and shows a state where puncturing is not performed at all. This buffer memory is configured in a matrix of “8 × d (d is an integer)” bit. The interliving circuit 3 writes the supplied convolutional code along the horizontal direction of the matrix. In the figure, the number described in each cell shows the order of the written bits.

Then, when all the bits of the buffer memory are filled, the interliving circuit 3 reads the contents in the vertical direction of the matrix. In the illustrated example, the contents of the buffer memory are read in the order of the 1st bit, the 9th bit, the 17th bit, ... The read bits are transmitted via a transmission line (not shown). Then, on the receiving side, an operation (writing in the vertical direction and reading in the horizontal direction) opposite to that of the interliving circuit 3 is performed, and the convolutional code before interliving is reproduced.

By performing such processing, the inter-bit distance increases as compared with the convolutional code before interleaving. For example, the distance between the first and second bits before inter-living is "0", while it spreads to "d" after inter-living. This improves the error correction capability especially for burst errors.

By the way, the above-mentioned example is the case where the puncturing is not performed at all, but since the puncturing is actually performed in the puncturing circuit 2, the memory map of the matrix is shown in FIG. As shown. In the figure, the convolutional code is punctured every "6" bits (6th bit, 12th bit, 18th bit, ...), and subsequent bits are sequentially shifted and written in the matrix. become.

[0008]

However, the above-mentioned technique has a problem that the distance between the bits before and after the punctured bit becomes extremely small.
For example, in FIG. 3A, the distance between the 5th and 7th bits is “2d”, whereas in FIG. 3B where the 6th bit is punctured. The distance is “d”.

If the bit-to-bit distance becomes extremely small as described above, the depth of interliving, that is, the error randomizing effect is greatly reduced, resulting in a problem that the burst error correction capability is significantly reduced. The present invention has been made in view of the above circumstances, and an object thereof is to provide a method of generating an error correction code having a high error correction capability.

[0010]

In order to solve the above problems, the present invention is characterized by performing interliving processing on a convolutional code and performing puncturing on the result.

[0011]

When the interleaving process is first performed on the convolutional code, the bit distance increases. Next, when puncturing the result of interliving,
The inter-bit distance before and after is reduced by "1" bit for each "1" bit puncturing. Then, the amount of decrease in the distance between any two bits after the puncturing is completed is the number of bits punctured between these bits.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIG. In the figure, each component is the same as that of FIG. 1, but the interliving circuit 3 is provided in the preceding stage of the puncturing circuit 2. In such a configuration, interleaving is performed on the convolutional code output from the convolutional encoder 1. That is, the convolutional code is written in the matrix of the interliving circuit 3 as shown in FIG.

Next, the contents of this matrix are read out in the vertical direction, and the puncturing circuit 2 performs puncturing. An example of the case where puncturing is performed for each "6" bit as in the conventional example is shown in FIG. 3C (this figure is not a memory map of the buffer memory, but is the same format as the buffer memory for comparison. It is what was displayed in). In the figure, "x" indicates a punctured bit.

In the figure, the distance between the fifth and seventh bits is "2d-k". Here, k is the number of bits punctured in the illustrated area P. In the above example, the value k is about "2d / 6" and the bit distance is about "5d / 3". That is, according to this embodiment, it is understood that a relatively long inter-bit distance can be maintained even when puncturing is performed.

[0015]

As described above, according to the present invention,
The amount of decrease in the distance between bits after puncturing is completed can be suppressed to the number of bits punctured between two bits. This makes it possible to maintain high error correction capability for burst errors and the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an example.

FIG. 2 is a block diagram showing a configuration of a conventional example.

FIG. 3 is an operation explanatory diagram of an example and a conventional example.

[Explanation of symbols]

 1 Convolutional encoder 2 Puncturing circuit 3 Interliving circuit

Claims (1)

[Claims] 1. A method of generating an error correction code, characterized by performing interliving processing on a convolutional code and performing puncturing on the result.