# Performance Evaluation of Random Access Methods for IoT-over-Satellite
## 2 Background and Related Work
However, random access methods could lead to significant uplink interference and degraded capacity levels if not carefully designed. As a result, IoT technologies for satellite applications need to implement intelligent interference mitigation techniques to enhance the performance. To enhance the interference mitigation, some complex access methods are introduced in the literature for IoT-over-Satellite. In [28], the performance of a satellite link using other access schemes, including time division multiple access (TDMA), FDMA, power division multiple access (PDMA), and turbo code division multiple access (TCDMA), have been assessed. On the other hand, in [29], the authors present a data exchange rate comparison for IoT-over-Satellite using Constrained Application Protocol/UDP (CoAP/UDP) and MQ Telemetry Transport/TCP (MQTT/TCP) via a contention resolution diversity slotted ALOHA (CRDSA) medium access control (MAC) layer. Recently, many LPWAN technologies incorporate the use packet repetition to enhance remote connectivity [30; 31]. Moreover, random access with packet repetition, such as contention resolution ALOHA (CRA), CRDSA, and irregular repetition slotted ALOHA (IRSA) have been proposed for IoT-over-Satellite in the literature [32; 33; 34]. In IRSA and CRDSA, IoT devices are required to transmit two or multiple copies of the same packet in different time slots to increase the transmission performance. An advanced access method called the Enhanced Spread Spectrum ALOHA (ESS ALOHA) can also be found in [36]. The ESS ALOHA can achieve higher throughput compared to ALOHA without the need for scheduling. Although the advanced random access and multiple access techniques can provide better interference mitigation, these techniques require the implementation of the successive interference cancellation (SIC), which in turn increases the system complexity of the ground devices. On the other hand, a packet demodulator can be incorporated on the satellite end of the network. In addition, the need for network synchronization and the increased power consumption requirements dims the CRDSA viability for IoT-over-Satellite communications. In order to understand the performance of an access method for IoT-over-Satellite for a given scenario, the convention is to perform extensive network simulations. In [37], the authors detail a simulation framework for an IoT-over-Satellite link performance. Although the simulator can provide practical performance modeling by relying on the user population and be extended by the anticipated distribution of IoT devices, it only takes into account a single LEO satellite link. On the other hand, in order to have tractable performance analysis of IoT-over-Satellite for a dense LEO constellation, analytic modeling using tools from stochastic geometry has recently emerged in [38; 39; 40]. To facilitate the investigation of random uplink access performance in IoT-over-Satellite network, this paper presents a systematic end-to-end emulation framework aiming to provide realistic performance analysis for practical dense LEO constellations such as Walker-Delta and Walker-Star. The framework can incorporate different access methods as well as different LPWAN technologies to assess their performance over a realistic Satellite-to-Ground channel and the source code for the emulation can be accessed on Github [41]. In this paper, we evaluated the performance based on LoRa IoT-over-Satellite network for different random access methods via the shared radio spectrum. The devices are assumed to operate on an identical spreading factor while jointly utilizing radio resources. The performance of the network is measured via two key indicators; (i) the BER and (ii) the energy consumption/wasted.