Performance Analysis of Selective DF Relaying for Satellite-IoT

Abstract

As the number of applications of Internet-of-things (IoT) is increasing daily, there is a growing challenge of providing real-time tracking data to users with a larger coverage area. The satellite-based network can provide global coverage to IoT devices. Due to the low power and low complexity of IoT devices using slotted-ALOHA protocol, it is desired to have visible satellites at a lower altitude than that altitude of commonly used GEO satellite constellations. Recently, sizeable Low-earth-orbit (LEO) satellite constellations such as Starlink-SpaceX and OneWeb launched in orbit can address the coverage issues at much lower power and lower latency. In addition to this, there is minimal coordination among IoT devices. Thus, the packets from multiple devices reaching the gateway may cause collisions and thus reduce the throughput at the gateway. This thesis considers a LEO satellite-based topology for an IoT network, where multiple IoT devices broadcast the information to all the visible satellites over a shared channel using slotted ALOHA. The satellites selectively Decode-and-forward (DF) the data from the IoT devices over orthogonal channels to the Ground station (GS), which does Maximal Ratio Combining (MRC). Capture and Successive interference cancellation (SIC) schemes are considered for decoding at the satellites to mitigate the interference at the satellites in the uplink. For the considered topology, the closed-form expressions are derived for the end-to-end Outage probability (OP) for an arbitrary number of IoT devices and satellites in the capture model and the two-device, two-satellite case in the case of the SIC model. The expressions are derived for both independent and non-identically distributed (inid) and independent and identically distributed (iid) uplink channels. The OP is analyzed as a function of the parameters like the number of satellites, devices, and the desired data rate. The results demonstrate that the proposed approach leverages the benefits of mega-LEO satellites to make the topology feasible and attractive for low-powered and low-complexity IoT networks.