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Early stopping turbo decoders: a high-throughput, low-energy bit-level approach and implementation

Shao, W.; Brackenbury, L.


This study presents the design for a new bit-level early stopping algorithm that can be considered as an improvement of the block-level sign-change-ratio-based early stopping approach for high-speed turbo decoding applications. Conventional early stopping methods provide limited improvements in throughput/energy efficiency but result in decoding accuracy degradations. By identifying agreement of the extrinsic log-likelihood-ratio as continuous sign matches on consecutive iterations, the trace-forward and trace-backward operations can be avoided for individual bits. This reduction in computation results in increased decoding throughput at reduced processing energy cost without affecting decoding accuracy. This is confirmed by mapping the new design onto a field programmable gate array where at Eb/No of 2 dB, the throughput is a factor of 2.3 higher with processing energy saving of 60 compared with that of a conventional turbo decoder.