A New Outage Probability Bound for IR-HARQ and Its Application to Power Adaptation

Abstract

This work proposes a novel upper bound on outage probability for the incremental redundancy hybrid automatic repeat request (IR-HARQ) protocol over block fading channels. The new bound is much tighter than the classical bound due to Laneman, especially when the transmit power is limited as is often the case in the Internet of Things (IoT). We demonstrate the practical use of this new bound by showing that it enables a geometric programming approach to power adaptation for IR-HARQ. Because the new bound approximates the outage probability much more exactly, the resulting new power adaptation scheme significantly outperforms those existing methods based on the classical bound.