Pushing the Limits of Energy Efficiency for Non-Binary LDPC Decoders on GPUs and FPGAs

Signal processing hardware designers of Low-Density Parity-Check (LDPC) decoders used in modern optical communications are confronted with the need to perform multi-parametric design space exploration, targeting very high throughput (hundreds of Mbit/s) and low-power systems. This work addresses the needs of current designers of dedicated GF(2
^m
) NB-LDPC decoders that necessitate robust approaches for dealing with the ever-increasing demand for higher BER performance. The constraints pose tremendous pressure on the on-chip design of irregular data structures and micro-circuit implementation for supporting the complex Galois field mathematics and communications of hundreds of check nodes with hundreds of variable node processors. We have developed kernels targeting GPU and FPGA (HLS and its equivalent RTL) descriptions of this class of complex circuits for comparing area, frequency of operation, latency, parallelism and throughput. Exploiting techniques such as using custom bit-widths, pipelining, loop-unrolling, array-partitioning and the replication of compute units, results in considerably faster design cycles and demands less non-recurring engineering effort. We report a throughput performance of 800 Mbps for the FPGA case.