State metrics memory reduction in a turbo decoder implementation

摘要

Methods and apparatus are described for reducing memory storage cells in a turbo decoder by storing only half the state metrics generated during a scan process. States associated with each bit transmission may be divided into couples and only one state from every state couple may be stored. In one example embodiment, only the state metric for a losing state of every state couple is saved, along with a single bit, e.g., 1 or 0, indicating whether the upper state or lower state of the state couple was the winner. The winning state may be reconstituted at a later stage. In this manner, for a code rate 1/3 and constraint length 3 turbo code, instead of storing 8*10=80 bits of state metrics for each systematic bit, only (4*10)+(4*1)=44 bits of scan state metrics data need be stored, a savings of nearly 50% regardless of the transistor technology used.

主权项

1. A receiver device containing a decoder, the decoder comprising:
a processor configured to generate state metrics during a scan cycle of a decoding scan operation of the decoder based on pairs of previous state metrics, soft bits, and a state transition, wherein the pairs of previous state metrics are previously generated by the processor during a previous scan cycle of the decoding scan operation, and to output a decoded bit; a determination module configured to determine one of the pairs of previous state metrics as a first state metric and another as a second state metric; and a data store configured to store only one of the first and second state metrics and to store an indicator that indicates which of the pairs is not stored.