Apparatus for error-correct decoding in a digital data communications system

An apparatus for error-control coding, which includes a data transmitter and a data receiver interconnected via a transmission channel, said data receiver including:

• first means (50, 60) for successively error-correct decoding a plurality of data frames which have been error-correct encoded at said transmitter, said first means changing decoding parameters in response to control data applied thereto, said control data being generated based on one or more than one data frames preceding a data frame currently decoded at said-first means;
• second means (52) coupled to said first means for decoding output of said first means;
• third means (54a-54b), coupled to receive outputs of said first and second means, for extracting frame characteristic data therefrom;
• fourth means (58a-58c, 56a-56b) coupled to said third means, said fourth means being responsive to said frame characteristic data and detecting a plurality of probability variable sets stored in said fourth means;
• fifth means (72) coupled to said first means for checking a data transmission error in the output of said first means, said fifth means generating a check result therefrom;
• and
• sixth means (74) coupled to said first, fourth and fifth means, said sixth means being responsive to said check result and selecting one of said plurality probability variable sets outputted from said fourth means and applying said one of said plurality probability variable sets to said first means as said control data.