Low-complexity finite alphabet iterative decoders for LDPC codes

Low-density parity-check (LDPC) codes are adopted in many applications due to their Shannon-limit approaching error-correcting performance. Nevertheless, belief-propagation (BP) based decoding of these codes suffers from the error-floor problem. Recently, a new type of decoders termed finite alphabet iterative decoders (FAIDs) were introduced. The FAIDs use simple Boolean maps for variable node processing. With very short word length, they can surpass the BP-based decoders in the error floor region. This paper develops a low-complexity implementation architecture for FAIDs by making use of their properties. Particularly, an innovative bit-serial check node unit is designed for FAIDs, and the symmetric Boolean maps for variable node processing lead to small silicon area. An optimized data scheduling scheme is also proposed to increase the hardware utilization efficiency. From synthesis results, the proposed FAID implementation needs only 52% area to reach the same throughput as one of the most efficient Min-sum decoders for an example (7807, 7177) LDPC code, while achieving better error-correcting performance in the error-floor region.