Grant-Free Massive Access for LEO-satellite based 6G IoT networks.

Low Earth Orbit (LEO) satellite based Internet of Things (IoT) is envisaged as one of the most promising IoT technology to support the massive machine-type communication (mMTC) scenarios. It facilitates global coverage to the low-cost IoT devices for the beyond 5G (B5G) and sixth generation (6G) mobile communication. Grant-based resource allocation mechanisms have been a primary approach for wireless access and have worked well for conventional data traffic in terrestrial networks. For 5G-NR uplink grant-based access, a user first transmits a scheduling request (SR) followed by a buffer status report (BSR) before the actual data transmission. Such a long-drawn uplink resource allocation procedures makes it unsuitable for satellite-based IoT networks whereby one-side propagation delays itself are of the order of 2 – 6 ms. Under such a scenario providing dedicated grants would entail massive overheads. Grant-free (GF) access and resource allocation strategy provides a promising solution to support infrequent low and moderate traffic where data can be directly transmitted over GF access resources. Therefore, it fits well in case of IoT devices with sporadic traffic. In this paper, we propose a GF access scheme which performs dynamic resource allocation among the unscheduled resource blocks periodically wherein the users can transmit their buffer-status along with their 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.