Limited-Feedback Parity-Based Hybrid ARQ Using Spatially-Coupled LDPC Codes
Janik Frenzel, S.H. Müller-Weinfurtner, Johannes B. Huber, Ralf R. Müller · 2019
Reliability-Based Hybrid Automated Repeat reQuest (RB-HARQ) strongly improves the throughput of a communications system by identifying and retransmitting the symbols deemed most unreliable after decoding the initial transmission. Additional soft-value processing, large feedback messages and many retransmissions are required to achieve a high throughput. We compare a variant of RB-HARQ designed for limited feedback with a new low-overhead, clustered Parity-Based Partial-Retransmission (PBPR) HARQ scheme. The new scheme selects symbols connected to unsatisfied parity checks and intersects this set with a subset of all symbols consisting of uniformly distributed information or parity symbols to improve the throughput. Since clustered HARQ schemes work best with codes exhibiting high intra-codeword correlations, we use Spatially-Coupled Low-Density Parity-Check (SC-LDPC) codes for evaluation.