Construction and Performance of New Tail-Biting Turbo Codes

A problem that was recognized early in the design of turbo-codes is the termination of the trellises. Tail-biting turbo encoders and decoders have been mentioned previously in the literature but none are as general and/or flexible as the approaches presented here. Included is a review of the dual termination method described in [7], which is extended to the dual tail-biting case here, and a review of the frame-oriented turbo-code described in [8], which is extended to full tail-biting here. Other tail-biting approaches are also presented. It is shown that the increase in complexity with tail-biting is typically only about 5%. Simulation results show that the improvement in performance with full tail-biting is typically between 0.1 and 0.2 dB for small blocks (on the order of 100 bits). The improvement at high SNRs is even greater.