Optimization Techniques for the Efficient Implementation of High-Rate Layered QC-LDPC Decoders

For high-rate low-density parity-check (LDPC) codes, layered decoding processing can be reordered such that the first-in-first-out (FIFO) buffer that stores variable-to-check (V2C) messages is not needed and, hence, the memory area can be minimized, but at the cost of increased data dependency. This paper presents three techniques that can be used to implement an efficient reordered layered decoder. First, with the assistance of a graph coloring method, the required minimum number of V2C sign memory banks can be theoretically determined, with the corresponding pipeline architecture also designed. After that, the integer linear programming technique is adopted so as to arrange the V2C sign memory banks in a manner that minimizes the number of pipeline stalls, thereby increasing throughput. In order to further simplify the decoder, the first minimum values are not stored if the proposed modified min-sum algorithm is used. The proposed techniques are demonstrated by implementing a rate-0.905 (18396,16644) QC-LDPC decoder using 90-nm CMOS technology. When using the proposed techniques, implementation results show that the throughput-to-area ratio (TAR) increases by 58.9% without sacrificing error-rate performance.