  Automatic repeat request (ARQ) is widely used in modern communication systems
to improve transmission reliability. In conventional ARQ protocols developed
for systems with energy-unconstrained receivers, an
acknowledgement/negative-acknowledgement (ACK/NACK) message is fed back when
decoding succeeds/fails. Such kind of non-adaptive feedback consumes
significant amount of energy, and thus will limit the performance of systems
with energy harvesting (EH) receivers. In order to overcome this limitation and
to utilize the harvested energy more efficiently, we propose a novel ARQ
protocol for EH receivers, where the ACK feedback can be adapted based upon the
receiver's EH state. Two conventional ARQ protocols are also considered. By
adopting the packet drop probability (PDP) as the performance metric, we
formulate the throughput constrained PDP minimization problem for a
communication link with a non-EH transmitter and an EH receiver. Optimal
reception policies including the sampling, decoding and feedback strategies,
are developed for different ARQ protocols. Simulation results will show that
the proposed ARQ protocol not only outperforms the conventional ARQs in terms
of PDP, but can also achieve a higher throughput.
