Rethink Hybrid Automatic Repeat reQuest Design for 5G: Five Configurable Enhancements

Current mobile communications systems have a rather simple and single-mode HARQ functionality that is applied for all services. In this article we argue for having a set of user-centric HARQ enhancements that are configurable in coherence with its service requirements, as a means to more efficiently optimize the end-to-end performance. A set of HARQ enhancements are therefore proposed that can be enabled and configured per user as needed. The presented enhancements include more flexible HARQ timing configurations, early feedback estimation for latency-critical communication, options for adaptive redundancy matching with enriched feedback, more efficient handling of large transport block sizes, and optimizations particularly suited for communication with low cost and low energy-consuming devices.