Enhanced Hybrid Automatic Repeat Request Scheduling for Non-Terrestrial IoT Networks

Non-terrestrial networks (NTNs) complement their terrestrial counterparts in enabling ubiquitous connectivity globally by serving unserved and/or underserved areas of the world. Supporting enhanced mobile broadband (eMBB) data over NTNs has been extensively studied in the past. However, focus on massive machine type communication (mMTC) over NTNs is currently growing. Evidence for this are the work items included into the 3rd generation partnership project (3GPP) agenda for commissioning standards for Internet-of-Things (IoT) communications over NTNs. Supporting mMTC in non-terrestrial cellular IoT (C-IoT) networks requires jointly addressing the unique challenges introduced in NTNs and C-IoT communications. In this paper, we tackle one such issue caused due to the extended round-trip time and increased path loss in NTNs resulting in a degraded network throughput. We propose smarter transport blocks scheduling methods that can increase the efficiency of resource utilization. We conduct end-to-end link-level simulations of C-IoT traffic over NTNs. Our numerical results of throughput show the improvement in performance achieved using our proposed solutions against legacy scheduling methods.