Dynamic Frame Length Adaptation for Grant-Free IoT Access in Non-Terrestrial Networks

Kurzfassung

Supporting Internet of Things (IoT) applications over non-terrestrial networks (NTN) requires access protocols that can accommodate massive, sporadic, and uncoordinated transmissions from a large number of low-power devices. Grant-free protocols, such as irregular repetition slotted ALOHA (IRSA), are well-suited for these environments due to their simplicity and efficiency. However, these protocols are typically designed under the assumption of a fixed number of active users. They do not account for potential large variations in traffic load, which are common when considering low Earth orbit (LEO) satellites as receivers. In this work, we propose a dynamic frame length adaptation scheme for IRSA that leverages an estimate of the number of active users, obtained by observing an initial portion of the frame. The frame is then either truncated to reduce energy consumption or extended to improve decoding performance. Simulation results demonstrate that this adaptive strategy increases the user success probability by up to 40\% while achieving significant energy savings, highlighting its potential for future IoT-NTN deployments.