Centre National Detudes Spatiales

Julia Le Maitre

Jean-Pierre Millerioux

Jean-Yves Tourneret

Raoul Prevost

Martial Coulon

David Bonacci

The invention relates to a method for correcting a message the generation of which involves transforming an initial message and inserting bit stuffing into the transformed message, which method comprises providing an observation sequence containing the message to be corrected. A number of path hypotheses are generated via a trellis diagram associated with the transformation. The nodes of the trellis diagram each represent a state of a finite-state machine capable of transforming the initial message and the branches represent the possible transitions between nodes. Among the branches of the trellis diagram, certain represent conditional transitions that may be made only when bit stuffing is present. During the generation of a path hypothesis, bit stuffing is detected and the branches taken are those associated with the detected bit stuffing. The most likely path hypothesis relative to the observation sequence is finally retained.

Method for correcting messages containing bit stuffing

The method according to the invention relates to the decoding of a sequence of symbols, the sequence of symbols having been generated by: calculating a CRC value for an initial message; combining the initial message and the CRC value so as to produce a transformed message; and, encoding the transformed message. The decoding comprises: generating a number of path hypotheses via a trellis diagram corresponding to the trellis diagram of a finite-state machine comprising the encoder and the CRC generator, in which the encoder and the CRC generator are supplied with the same input. According to a preferred embodiment of the method, the trellis diagram is adapted to take into account bit stuffing possibly inserted in the transformed message before encoding.

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Grepiac, France

Julia Le Maitre