Robust precoding design for inter-satellite cooperation-based low-earth orbit satellite Internet of Things

Abstract

With the widespread application of the Internet of Things (IoT), a large demand for supporting massive access of IoT devices distributed over a large area urges researchers to focus on the low-earth orbit (LEO) satellite IoT (SIoT) network. Due to the high-speed movement of LEO satellites, SIoT is composed of dozens of satellites to thousands of LEO satellites covering the whole world, which inevitably causes inter-satellite interference. Hence, in this paper, we propose an inter-satellite cooperation framework for a SIoT network based on non-orthogonal multiple access(NOMA) and multiple-beam techniques, which can support massive access and reduce interference. However, the satellite cannot catch accurate channel state information(CSI), resulting in residual interference. In this context, we formulate a robust precoding optimization problem based on inter-satellite cooperation to minimize the total power consumption of the LEO SIoT network with outage probability constraints on the rates for the IoT devices. Because the original problem is intractable, we utilize some mathematical tools, e.g., second-order Taylor expression, Bernstein-type inequality, and penalty function, to obtain an approximate equivalent second-order cone program (SOCP) problem. Then, we propose a robust precoding algorithm to solve the SOCP problem. Finally, numerical results show the impacts of key system parameters and confirm the effectiveness and robustness of the proposed algorithm.