NON-LINEAR SYSTEMATIC TURBO CODES OVER GF(4)

PETRUZZI, D. M.; LIBERATORI, M. C.; BONADERO, J. C.; CASTIÑEIRA MOREIRA, J.

Rio Gallegos, Argentina

Congreso; XII RPIC; 2007

Universidad Austral

In this paper we use non-linear Finite State Sequential Machines (FSSMs) designed overthe Finite Field GF(4) as constituent encoders of non-linear systematic turbo codes. These FSSMs have the property of showing a non-zero output for the all-zero input case. The state transitions structure and the randomness of the corresponding output of the responses to the all-zero input are studied for different initial state conditions. A relationship is found between these two characteristics and the BER performance or, equivalently, the form of the corresponding EXIT chart. It is found that FSSMs with responses of the form of long closed cycles, and good randomness properties of the corresponding output, are the best options as constituent encoders of non-linear systematic turbo codes designed over GF(4). A coefficient called the random behaviour coefficient is defined, to provide a quantitative measure of the behaviour of these FSSMs as constituent encoders of a systematic turbo code.