Next generation IoT-over-satellite performance improvement using shared radio spectrum
Creators: name: Chan, Chiu Chun
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 400606
subject: Satellite communications

description: The development of massive wireless sensors and Internet-of-Thing (IoT) networks has recently seen a rapid acceleration. Special attention is given to such applications under 5G and next generation networks due to their wide range of use-cases; such as utility metering, smart agriculture, and asset tracking. To cater for these demands, vast numbers of IoT networks are currently being deployed, connecting billions of sensors to the Internet. Some of these use-cases require IoT connectivity in remote and offshore locations to collect measurements and provide intelligent control. In such cases, the terrestrial networks are insufficient to provide the required coverage for remote locations. Accordingly, satellite constellations have emerged as a suitable alternative for terrestrial networks. IoT networks relying on satellite connectivity are referred to as IoT-over-Satellite. Many satellite networks are currently undergoing rapid deployment, with an increasing number of satellites planned in the near future. There is an ongoing standardization aiming at forming a unified global network combining both the terrestrial networks and satellite constellations. The possibility of such a hybrid satellite-terrestrial system is widely suggested in the literature, where using shared radio spectrum between the terrestrial and satellite networks will facilitate the deployment of IoT-over-Satellite. The shared use of the radio spectrum reduces the administrative and financial hurdles of leasing a segment of the spectrum. Despite all the promises of hybrid IoT-over-Satellite, deploying such networks presents new challenges. Since the satellite coverage area is extended to large swath of Earth surface, the number of interfering IoT devices within this region is extremely large, leading to elevated interference levels. Maintaining the quality-of-service becomes a significant challenge, especially for hybrid IoT-over-Satellite with shared radio spectrum. The IoT-over-Satellite system performance depends on the propagation channel conditions, which vastly differs from typical terrestrial networks. Also, satellite availability is highly dependent on the constellation altitude and antenna beamwidth. A thorough study on the uplink performance of IoT-over-Satellite is of utmost importance because the majority of sensing traffic is in the uplink direction.

This research aims to investigate the uplink performance of IoT-over-Satellite in the shared radio spectrum. The interference analysis and investigation of the uplink performance are explored in high capacity transmission scenarios. The uplink IoT-over-Satellite system performance is evaluated in terms of the signal-to-interference-plus-noise ratio; this analysis is achieved using both simulation and analytic approaches that characterize the statistical properties of the uplink interference. Moreover, we analytically formulate the uplink performance, in terms of the link success probability, using the distribution of the uplink interference and the uplink signal power. For achieving this formulation, we utilize tools from stochastic geometry and satellite channel propagation models. This work is formulated as a mathematical framework that characterizes the uplink performance based on various orbital parameters. Thereby, the optimal parameters for IoT-over-Satellite uplink performance can be obtained from the developed analytic formulas including antenna beamwidth, satellite constellation's altitude and satellite constellation size. To investigate the feasibility of IoT-over-Satellite using terrestrial low power wide area network technology and the impact of real traffic on the IoT-over-Satellite system, an emulator framework is developed to replicate practical IoT-over-Satellite systems using a self-developed MAC layer control and an in-house developed Long Range (LoRa) emulator.

Another major challenge that arises for IoT-over-Satellite links is indoor connectivity due to the large penetration loss and the absence of line of sight communications. As a result, an aggregator is required to extend the coverage to indoor IoT networks. With the emergence of 5G and beyond 5G communication systems and the explosive increase in IoT devices, millimeter-wave (mmWave) emerged as a potential candidate to enable high throughput and low latency communications. However, investigation of indoor mmWave channel characteristics requires an expensive channel sounder that hinders many researchers or field engineers in exploring the potentials in the mmWave band. This work investigates the potential of using an indoor mmWave IoT network. We develop a new approach for designing and implementing mmWave propagation measurement tools by leveraging widely available mmWave Doppler radars. By placing low-cost Doppler radars opposite to each other, the beat signals can be detected from both radars and thus can be used to infer the received signal strength. To verify the viability of the measurement testbed, several measurement scenarios have been investigated in indoor environments. The obtained results indicated a good consistency with the expected mmWave propagation characteristics.

The analytic models presented in this thesis are verified against simulations that rely on Monte-Carlo analysis. The analytic models are also compared to the emulated results to investigate the impact of measured traffic. The analytic output and experimental results presented in this thesis are either published in peer-reviewed journals, conference proceedings or are currently under review.