Optimized IR-HARQ Schemes Based on Punctured LDPC Codes Over the BEC

We study incremental redundancy hybrid automatic repeat request (IR-HARQ) schemes based on punctured, finite-length, low-density, parity-check (LDPC) codes. The transmission is assumed to take place over time-varying binary erasure channels, such as mobile wireless channels at the application layer. We analyze and optimize the throughput and delay performance of these IR-HARQ protocols under iterative, message-passing decoding. We derive bounds on the performance that are achievable by such schemes, and show that, with a simple extension, the iteratively decoded, punctured LDPC code-based IR-HARQ protocol can be made rateless and operating close to the general theoretical optimum for a wide range of channel erasure rates.