METHOD TO DECODE NOISELESS CASCADE CODES BY MOST VALID SYMBOLS OF EXTERNAL CODE Russian patent published in 2011 - IPC H03M13/05 

FIELD: information technologies.

SUBSTANCE: first the internal code of a cascade code is decoded with detection and elimination of errors. When decoding an internal code, symbols of an external code are received, and simultaneously a "soft" decision is taken for each of the external code symbols on their validity. Then K+K₁≤N most valid symbols of the external code are selected, where N - block length of the external code, K - information length of the external code, and K₁ - length of verifying part of the external code. Then the external code is decoded with elimination of errors and erasures, and the initial information is restored. After decoding of the external code, the restored initial information is again coded by the external code, and the external code symbols are produced, which are compared with according accepted N-K-K₁ least valid symbols, and at the same time the combination of matching newly coded and received symbols of the external code is produced. Then, depending on value of match combination probability, validity of the restored initial information is assessed, and whenever the restored initial information validity exceeds the specified threshold value, the information is sent to its receiver.

EFFECT: improved validity of information restored after decoding.

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