A Low-Complexity Message-Passing Algorithm for Reduced Routing Congestion in LDPC Decoders
A low-complexity message-passing algorithm, called Split-Row Threshold, is used to implement low-density parity-check (LDPC) decoders with reduced layout routing congestion. Five LDPC decoders that are compatible with the 10GBASE-T standard are implemented using MinSum Normalized and MinSum Split-Row Threshold algorithms. All decoders are built using a standard cell design flow and include all steps through the generation of GDS II layout. An Spn = 16 decoder achieves improvements in area, throughput, and energy efficiency of 4.1 times, 3.3 times, and 4.8 times, respectively, compared to a MinSum Normalized implementation. Postlayout results show that a fully parallel Spn = 16 decoder in 65-nm CMOS operates at 195 MHz at 1.3 V with an average throughput of 92.8 Gbits/s with early termination enabled. Low-power operation at 0.7 V gives a worst case throughput of 6.5 Gbits/s-just above the 10GBASE-T requirement-and an estimated average power of 62 mW, resulting in 9.5 pj/bit. At 0.7 V with early termination enabled, the throughput is 16.6 Gbits/s, and the energy is 3.7 pJ/bit, which is 5.8× lower than the previously reported lowest energy per bit. The decoder area is 4.84 mm2 with a final postlayout area utilization of 97%.