TURBO DECODING CIRCUIT, CDMA BASE STATION WITH THE SAME, AND TURBO DECODING METHOD

摘要

A soft output decoder includes an addition comparator for carrying out a forward processing and a backward processing according to the reception data and the reliability information from an external reliability information storage unit and outputting state metric data for the number of treillis states and a calculating unit for calculating the reliability information on the basis of the state metric data and outputting it to the external reliability information storage unit. Memories where the state metric data from the addition comparator, the reliability information from the calculating unit and the reception data are stored have respective ring-buffer structures. With the ring-buffer structures, control of serial write of data and control of serial read of data necessary for the next calculation are performed. Further with the ring-buffer structures, a forward processing ( alpha calculation) and a backward processing ( beta calculation) are performed, and the soft output decoding result is serially extracted.