# Performance Evaluation of Random Access Methods for IoT-over-Satellite
###### Abstract  
Low Earth orbit (LEO) satellite constellations are currently being explored to provide global and seamless coverage for IoT-over-Satellite applications. Random access techniques require low transmission overhead providing a compatible route for IoT-over-Satellite applications, however, coming at the expense of the offered quality-of-service. In this paper, we develop a realistic uplink performance framework that incorporates many practical parameters such as the satellite availability, packet collision and interference, Doppler shift, and impairments experienced in a typical Satellite-to-Ground channel. The framework is capable of assessing multiple key performance indicators of the overall IoT-over-Satellite random access system. The performance is presented in terms of the bit error rate, packet error rate, and the energy wasted per IoT device. To emulate a realistic IoT-over-Satellite network, LoRa modulated traffic is first generated and injected into the Satellite-to-Ground channel. The results indicate high resistance to Doppler shifts even without any Doppler correction and provide some resistance to highly congested environments. Satellite-to-Ground; LoRa; IoT-over-Satellite; uplink; IoT; interference; massive satellite constellation 20221423202214232022142320221423202214232022142320221423202214232022142320221423202214223202214223202214223202214223202214222214222222  
communication systems, therefore IoT-over-Satellite is not as effective for regions that have high densities of terrestrial base stations or aerial receivers, making IoT-over-Satellite only convenient in regions that lack this infrastructure. Moreover, the coverage spot provided by a single LEO satellite is smaller relative to its GEO counterparts making it difficult to achieve connectivity for extended periods of time due to the dynamic nature of the orbit. For smaller constellations the LEO backhaul connectivity of satellites might be limited, hence on-board demodulation and storage of radio packets is needed. Nevertheless, IoT communications are dominated by uplink traffic and while a large satellite footprint provides extended coverage, it also results in high aggregate interference [19]. Although interference mitigation methods such as frequency reuse and beam multiplexing can be used, the interference levels seen by a satellite are still relatively large. Therefore, the utilization mechanisms of the radio spectrum are critical to ensure that the network is providing the prescribed quality-of-service. Unlike other technologies that use the licensed spectrum, LoRa is designed to operate in the congested shared spectrum. This strategy facilitates the rapid deployment of IoT networks due to reduced administrative and licensing hurdles of securing the license spectrum. LoRa is a physical layer wireless communication technology designed for long-range communication at a low bit rate and low power to enable wireless communication of battery-powered devices. LoRa communication scheme mainly utilizes Chirp Spread Spectrum (CSS) to spread the symbols across a wider spectrum in order to mitigate the effect of narrowband interference [20]. Using CSS in LoRa also aims at reducing co-channel interference from other LoRa devices and from other narrowband transmissions. Despite all the promises of LoRa, uplink interference is still a critical issue in IoT-over-Satellite systems as LoRa typically uses a long time to transmit its frame, exposing it to other transmission overlaps. Therefore, investigating the performance of IoT-over-Satellite systems using LoRa can provide an insight of the feasibility of deploying LPWAN on IoT-over-Satellite network. In this paper, we present a LEO mega satellite constellation framework that depicts the performance of different constellation patterns for IoT-over-Satellite communications, and different random access techniques.