Efficient implementation of structured long block-length LDPC codes

High-speed and low-area decoders for low-density parity-check (LDPC) codes with very long block lengths are challenging to implement due to the large amount of nodes and edges required. In this paper we implement a decoder for a (32643, 30592) LDPC code that has variable nodes of degree 7, check nodes degrees of 111 and 112, and 228501 edges, making fully-parallel hardware implementation unfeasible. We analyze the structure of this code and describe a method of replacing the complex interconnect with a local, area-efficient version. We develop an modular architecture resulting in a low-complexity partially-parallel decoder architecture based on the offset min-sum algorithm. The proposed decoder is shown to achieve a minimum gain of 92% in area utilization, compared to an extremely optimistic area estimation of the fully-parallel decoder that neglects the interconnection overhead. Synthesis in 65 nm CMOS is performed resulting in a clock frequency of 370 MHz and a throughput of 24 Gbps with an area of 7.99 mm2.