Low Earth Orbit (LEO) satellite based Internet of Things (IoT) is envisioned as one of the most promising IoT technology to support the massive machine-type communication (mMTC) scenarios to provide global coverage to the low-cost IoT devices for the sixth generation mobile communication (6G). Although grant-based mechanisms have been a predominant approach for wireless access and have worked well for conventional data traffic in terrestrial networks, the additional latency required for initial handshake message exchange and the extra control overhead for the hefty uplink resource allocation procedures requiring a scheduling request followed by buffer status report (BSR) transmission before the actual data transmission are not suited for satellite-based IoT networks with one-side propagation delays itself of the order of 2 − 6 ms. Grant-Free (GF) access provides a promising mechanism for carrying low and moderate traffic where data can be directly transmitted over GF access resources and therefore, fits especially well for IoT devices with sporadic traffic. In this paper, we propose a GF access scheme which performs dynamic slot allocation among the unscheduled resource blocks periodically wherein the users can transmit the data along with a BSR for any remaining data. Finally, the performance of the scheme is evaluated both analytically and with the help of extensive system-level simulations comparing the proposed scheme with conventional 5G-NR network.

https://ieeexplore.ieee.org/document/10008534