Multibit decoding of turbo codes

Abstract

Multibit turbo decoding is the name given to a modification of the turbo decoding algorithm (iterative bit-by-bit sum-product decoding), where the sum-product decoding is done on groups of g bits instead of single bits. By decoding over groups, the decoder may use any dependence between bits of a group to aid in error correction. This thesis presents multibit decoding, and explores the issues affecting the performance of this decoding method when using binary antipodal modulation over an additive, white Gaussian noise channel. The main results are that properly designed non-punctured multibit systems for g = 2 equal or better the performance conventional turbo codes, for both relatively short and long block lengths. The number of operations required by multibit decoding for performance equivalent to conventional decoding is lower, sometimes reaching 1/2. Other advantages of multibit decoding include reduced memory requirements, and the possibility of doing more operations in parallel.