  We study incremental redundancy hybrid ARQ (IR-HARQ) schemes based on
punctured, finite-length, LDPC codes. The transmission is assumed to take place
over time varying binary erasure channels, such as mobile wireless channels at
the applications 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.
