An FEC multiplexing circuit (2) has a configuration in which a first memory circuit (15) is arranged on the input stage of a first RS encoding circuit (16), a second memory circuit (17) is arranged on the input stage of a second RS encoding circuit (18), error correction encoding is performed by a combination of different data having two directions, and thereafter, error correction codes are multiplexed to generate an FEC frame. On the other hand, an FEC demultiplexing circuit (6) has a configuration in which a third memory circuit (42) is arranged on the output stage of a first RS decoding circuit (41), a fourth memory circuit (44) is arranged on the output stage of a second RS decoding circuit (43), error correction is performed by a combination of different data having two directions, and, thereafter, parallel data read from the fourth memory circuit (44) are multiplexed to reproduce original information data.

An information recording method, in which when new digital information is employed to update a part of old digital information that has been divided into ECC blocks and stored on an information recording medium, the latest update position for the old digital information that is to be updated is detected based on the volume of the data of the new digital information. A predetermined volume for the old digital information that has been stored sequentially following the latest update position detected is read, and then, at least a part of the old digital information that has been read is recorded after the new digital information is recorded, so that the destruction of data that should not be rewritten can be prevented at the portion whereat the old digital information is coupled with the new digital information. As a result, the deterioration of the error correction capability for the coupled portion can be reduced.

An information recording apparatus comprises a data converting means 10 for performing data conversion on record information consisting of a digital signal in accordance with a predetermined data conversion table, a data modulating means 6 for inverting an initial output signal when bit information of data after the data conversion is "1" given that the initial output signal is "0"; and a recording means 3 for recording the output signal on an optical recording medium.

An information reproducing apparatus comprises a reading means 7 for reading information from the optical recording medium to yield a reproduced signal; a level detecting means 11 for detecting a level of the reproduced signal and outputting digital data; an error connecting correcting means 12 for, upon detection of a sequence of "01110" in a bit pattern of the digital data, correcting the sequence to a sequence of "01010" and outputting corrected data, and, upon detection of no error, outputting the digital data; and a data reverse converting means 13 for performing reverse conversion on the output data of the error correcting means in accordance with the data conversion table, yielding reproduced information.

A decoding circuit in the invention receives signals encoded in differential logical conversion, and decodes it into an original signals. During the decoding, a bit position of known data included in the original signals in the received signal is detected, and also the known data is forcedly set to the bit position of the decoded signal, thereby spread of bit error is suppressed up to the position of the known data.

A method is described for decoding messages coded as blocks consisting of a fixed number of symbols and affected by symbol substi­tutions, deletions and insertions, wherein, for each received message having a length comprised within predetermined limits, a sequence of words (error frames) is generated which comprise all possible error combinations which can be corrected in the message. By using such error frames, a decoded word is generated for each frame, the probabi­lity that a decoded word actually is the transmitted word is calcu­lated and the decoded word, whose probability value satisfies prede­termined criteria, is emitted as decoded message. A device for carrying out the method is also provided.

An error correcting encoding method and a vehicle data communication apparatus based on the same for use in data communication via fading communication channels dominated by burst errors in the data communication among vehicles such as automobiles are disclosed. The error correction encoding method detects, as data sent from a transmitting side is received by a receiving side, any error contained in the received data as a frame error rate of error frames involved in block data or a bit error rate of error bits involved in the block data and selects an error correcting code in response to the frame error rate for encoding. The vehicle data communication apparatus according to the present invention profitably employs the method, and changes an error correcting code to be used on the transmitting side in response to the extent of errors involved in the received data detected by the receiving side of a remote apparatus.

A method is described for decoding messages coded as blocks consisting of a fixed number of symbols and affected by symbol substi­tutions, deletions and insertions, wherein, for each received message having a length comprised within predetermined limits, a sequence of words (error frames) is generated which comprise all possible error combinations which can be corrected in the message. By using such error frames, a decoded word is generated for each frame, the probabi­lity that a decoded word actually is the transmitted word is calcu­lated and the decoded word, whose probability value satisfies prede­termined criteria, is emitted as decoded message. A device for carrying out the method is also provided.

In a data processing system in which two-level error correction is performed on variable length data being transferred between the host processor and the data storage device, the logical length of the data being transferred is computed during a fixed time gap with computation continuing after termination of the fixed time gap and commencement of the data transfer. The computation required for the logical length of the data field to accommodate two-level ECC is accomplished by first comparing the actual field length with a value predetermined by the subblock length of the two-level ECC. If the actual length is greater than the predetermined value, then a value equal to the subblock length plus first level ECC bytes is loaded into a counter which begins decrementing at the termination of the fixed time gap so as to synchronise the byte-by-byte transfer of the data. As the data is being transferred the computation continues. When the computation has been completed, a value equal to the difference between the computed logical length and the subblock length plus first level ECC bytes is loaded into other counters which begin decrementing when the first counter reaches zero. In this manner transfer of the data is not interrupted. This permits two-level ECC to be incorporated into prior data processing systems which utilise a conventional track format with predetermined fixed time gaps, even though such fixed time gaps would otherwise be of insufficient duration to permit computation of the logical length required for two-level ECC.

57 An error control encoding method and a mobile data communication device with use of said method in mobile communication such as that in a mobile phone for effecting data communication through a fading channel dominated by a burst error are disclosed. The error control encoding method, upon receiving data transmitted from the transmitting side on the receiving side, detects any error involved in 'said received data as a frame error rate involved in block data or a bit error rate in the block data and thereby changes the frame length in response to the detected error rates. The mobile data communication device profitably employs the error control encoding method wherein a frame length employed in the transmitting part is changed in response to the extent of any involved error in the received data detected by the remote receiving part.