Robust Design for NOMA-Based Multibeam LEO Satellite Internet of Things

In this article, we investigate the issue of massive access in a beyond fifth-generation (B5G) multibeam low-Earth orbit (LEO) satellite Internet-of-Things (IoT) network in the presence of channel phase uncertainty due to channel-state information (CSI) conveyance from the devices to the satellite via the gateway. Rather than time-division multiple access (TDMA) or frequency-division multiple access (FDMA) with multicolor pattern, a new nonorthogonal multiple access (NOMA) scheme is adopted to support massive IoT distributed over a very wide range. Considering the limited energy on the LEO satellite, two robust beamforming algorithms against channel phase uncertainty are proposed for minimizing the total power consumption in the scenarios of noncritical IoT applications and critical IoT applications, respectively. Both theoretical analysis and simulation results validate the effectiveness and robustness of the proposed algorithms for supporting massive access in satellite IoT.