Information processing and combining in channel coding

Abstract: It is proposed to characterize the performance of coding schemes by the mutual infor-mation between encoder–input- and decoder–output– sequence vs. the capacity of a channel in between, in-stead of the conventional diagrams of bit error proba-bility vs. signal–to–noise ratio or raw bit error ratio. That way a description is obtained, which proves to be nearly independent from the channel model used. Furthermore, it universally accounts for the qual-ity of reliability estimation provided by the decoder. Hence, information processing of coding schemes is characterized in an unified framework. Different codes as well as different decoding techniques can be compared and evaluated. By deriving tight bounds for the bit error probability, both a direct connection to conventional performance evaluation techniques is established and a very general method for the analy-sis of concatenated coding schemes is developed. For this purpose information combining is introduced, which links the proposed characterization to trans-fer characteristics used within EXIT charts of S. ten Brink. Due to the generalized description of infor-mation processing of component codes and decoders together with information combining the analysis of iterative decoding of arbitrarily multiply concatenated coding schemes incorporating serial and parallel con-catenated structures becomes feasible. For this analy-sis the transfer characteristics of the constituent cod-ing schemes are sufficient as long as they are linked by large interleavers. Based on the analysis, which is of extremely low computational complexity, design of novel multiply concatenated structures is demon-strated