Error detection/correction and fault detection/recovery – Pulse or data error handling – Digital data error correction
Reexamination Certificate
1998-10-22
2001-09-11
Decady, Albert (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Digital data error correction
Reexamination Certificate
active
06289485
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for encoding error correcting codes and its device and method for transmitting data having error correcting codes added, and is applicable to a digital satellite broadcasting system, for example.
DESCRIPTION OF THE RELATED ART
Heretofore, this type of digital satellite broadcasting system compressively encodes image data of plural programs using an MPEG (Moving Picture Experts Group)2 system as a compression-encoding system for image data, and then multiplexes them into one bit stream for transmission. At this time, this digital satellite broadcasting system adds error correcting codes to compressively-coded image data and then transmits it on a transmitting side, and decodes the error correcting codes on a receiving side to correct errors generated in the process of transmission. Thereby, the digital satellite broadcasting system can properly restore a transmission signal on the receiving side even if the carrier-to-noise ratio (C/N ratio) of the transmission signal deteriorates owing-to rainfall or the like, when in transmission.
As shown in
FIG. 1
, a conventional image data encoding device
1
used in such digital satellite broadcasting system is composed of a source encoding circuit
2
, an outer code encoding circuit
3
, an interleave circuit
4
and an inner code encoding circuit
5
. The image data encoding device
1
inputs input image data S
1
supplied from a hard disk or the like to the source encoding circuit
2
.
The source encoding circuit
2
performs high efficiency compression coding to the input image data S
1
using the MPEG2 system, and feeds thus obtained source coded data S
2
to the outer code encoding circuit
3
. The outer code encoding circuit
3
, as shown in
FIG. 2
, performs encoding of error correction codes such as reed-solomon (RS) encoding with respect to each of successive payloads having fixed length (k-bytes) forming the source coded data S
2
to add a parity bit of fixed length to each payload. Then, the outer code encoding circuit
3
feeds outer code coded data S
3
in which the parity bit is added to this payload, formed by successive parity added data of fixed length (n-bytes), to the interleave circuit
4
.
Hereinafter, the outer code encoding circuit
3
represents the relationship between the number of bytes of payloads to be inputted and the number of bytes of the parity added data as (n, k). In this case, it is assumed that RS encoding of (n, k) form is executed. In case of the MPEG2 system, the outer code encoding circuit
3
performs RS encoding to each payload of 188 bytes and adding 16 bytes of parity bit thereto respectively. Thus obtained parity added data is outputted in data unit of 204 bytes. In this case, the outer code encoding circuit
3
can be represented that has executed RS encoding in (
204
,
188
) form.
The interleave circuit
4
changes write sequence when the outer code coded data S
3
is written into a built-in memory from read sequence when that is read from the above memory and rearranging the data of the outer code coded data S
3
, and supplies this as interleave data S
4
to the inner code encoding circuit
5
. Accordingly, in the digital satellite broadcasting system using such image data encoding device
1
, even if errors concentrated in during transmission generate, so-called burst errors generate, the burst errors can be distributed by performing deinterleave on the receiving side, thus error correction ability can be reinforced.
The inner code encoding circuit
5
performs convolution encoding to the interleave data S
4
and further reinforcing the error correction ability, and feeds this as inner code coded data S
5
to the outside. This inner code coded data S
5
is converted into a transmission signal by subjected to digital modulation by a modulator which is not shown, provided after the image data encoding device
1
, or the like, before transmitted to the receiving side. According to the above, in the digital satellite broadcasting system, since encoding of error correcting codes such as the RS encoding or the convolution encoding or the like is performed to the source coded data S
2
before transmission, even if the C/N ratio of the transmission signal deteriorates, error correcting can be performed on decoding side, provided that the errors generated in the above transmission signal is less than a prescribed threshold value. Thereby, the original input image data S
1
can be restored.
By the way, in the digital satellite broadcasting system using the image data encoding device
1
having the above configuration, since payload length and parity length are fixed, it has fixed error correction ability. Thus, in such digital satellite broadcasting system, if many errors generate during transmission and the C/N ratio lowers below the prescribed threshold value, a problem such that received transmission signals cannot be properly decoded has been occurred by unfortunately exceeding the error correction ability.
SUMMARY OF THE INVENTION
In view of the foregoing, an object of this invention is to provide a method for adding and encoding error correcting codes and its device and a method for transmitting data having error correcting codes added, capable of improving the reliability of transmitting and receiving with a simple configuration.
The foregoing object and other objects of the invention have been achieved by the provision of a method for adding and encoding error correcting codes and its device and a method for transmitting data having error correcting codes added, in which, in a method for adding and encoding prescribed error correcting codes to input data, an error correcting code of different code length is added to each fixed length of the input data according to the significance of the input data. And the error correcting codes having different error correction ability corresponding to the code length of error correcting code are encoded. Thus, coded data having different packet length according to the code length of error correcting code is generated.
As described above, an error correcting code having different code length is added to a fixed length of input data according to the significance of the input data. The error correcting codes added which have different error correction ability corresponding to its code length are encoded to generate coded data having different packet length according to the code length of the error correcting code. Thus, plural coded data having different error correction ability according to significance can be generated.
The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by like reference numerals or characters.
REFERENCES:
patent: 5748787 (1998-05-01), Sugiyama
patent: 5781561 (1998-07-01), Machida et al.
patent: 5881070 (1999-03-01), Hoshi
Wehnes et al., Fast Lossless Image Compression, IEEE, pp. 145-148, Aug. 1996.*
Whoi-Yul et al. Hierarchy Embedded Differential Image for Progressive Transmission Using Lossless Compression, IEEE, p. 1 to 13, Feb. 1995.*
Luttrell, S. P., Hierarchical Vector Quantisation, IEEE, pp. 405-413, Dec. 1989.*
Cuenca et al., An error concealment scheme for MPEG-2 video transmission over ATM-based networks, IEEE 1997.*
Cuenca et al., dynamic error concealment technique for the transmission of hierarchical encoded MPEG-2 video over ATM networks, IEEE, 1997.*
Cuenca et al., Packing scheme for layered coding MPEG-2 Video transmission over ATM based networks, IEEE, 1997.*
Pancha et al., Mpeg coding for variable bit rate Video transmission, IEEE 1994.
Chase Shelly A.
De'cady Albert
Lerner David Littenberg Krumholz & Mentlik LLP
Sony Corporation
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