Researchers from the Universitat Oberta de Catalunya (UOC) in Barcelona are tackling the issue of how to connect devices to the internet where there is no mobile network infrastructure in place, by investigating how to synchronise IoT devices with satellites.
A total of 4.6 billion individuals access the internet via their mobile phones. For each user, there are more than three devices connected to the internet. The Internet of Things (IoT) encompasses all connected objects, which are increasing in number: from 15 billion today to a projected 30 billion by the end of the decade. The IoT, which includes items ranging from vehicles to irrigation sensors, remote weather stations, and autonomous drones, is creating numerous new opportunities for communication and data collection. However, it also faces significant obstacles.
The major challenge is connecting objects to the internet in areas lacking mobile network infrastructure. The solution appears to be low Earth orbit (LEO) satellites, though this approach has its own difficulties. A recent study led by Guillem Boquet and Borja Martínez, researchers from the UOC working within the Wireless Networks (WINE) group of the university’s Internet Interdisciplinary Institute (IN3), explored potential ways to enhance coordination between the billions of connected objects on Earth and the satellites orbiting in the atmosphere.
The rapid expansion of IoT over the past decade has driven innovation across various fields, including logistics, smart cities, agriculture, and shipping. This IoT revolution has largely been facilitated by the effectiveness of low-power, wide-area networks (LPWANs) and the terrestrial infrastructure established for mobile telecommunications. Despite its effectiveness, this solution struggles with connecting IoT devices in remote and rural areas where such infrastructure is unavailable.
LEO satellite constellations have recently emerged as a viable alternative to overcome the limitations of terrestrial networks. “LEO satellites are particularly relevant when it comes to the IoT because, being closer to the Earth, they need less transmit power to achieve reliable communication. This means that devices can save energy, extending battery life and saving on maintenance costs,” said Guillem Boquet. “Among other advantages, deploying a low Earth orbit satellite is considerably cheaper, which means that connectivity services can be provided at prices that are more reasonable for the IoT.”
Moreover, LEO satellites—such as SpaceX Starlink, Eutelsat OneWeb, and Amazon’s Kuiper project—offer much lower latency than geostationary satellites, have many more satellites in operation and provide greater coverage, can be deployed more quickly, and are suitable for use in various sectors. However, integrating this option with the IoT introduces its own challenges.
Incorporating satellites into the IoT network presents several issues. Some relate to industry development (deploying mega satellite constellations for uninterrupted coverage is not cost-effective for the IoT in the short term), while others are linked to the technology’s design, such as increased likelihood of communication interference, power limitations of IoT devices, and difficulties in synchronising these devices’ duty cycles with satellite communication intervals.
“IoT devices tend to be battery-powered and have regular sleep and wake-up duty-cycling intervals to save energy. These regular duty cycles are commonly used in terrestrial communications, where they are even standardised. However, as LEO constellations don’t provide uninterrupted coverage, what you end up with is short, irregular communication windows,” explained Guillem Boquet. “We therefore need to develop more advanced synchronisation strategies to ensure reliable communication and access to the connection opportunities provided by the satellite network.”
IoT devices’ power-saving modes rely on regular intervals to extend battery life by entering sleep mode. However, satellite constellations do not operate on regular schedules. To synchronise connected objects’ needs with LEO satellite access times, it is necessary to predict each satellite’s position and communication window.
“Our proposed solution is to synchronise the IoT application’s transmission needs and the network’s communication needs on the one hand with the satellite’s availability times on the other. This synchroniastion is based on the ability to predict these times by using a model of the satellite’s orbital path, starting from a known initial point,” said Guillem Boquet. “However, making predictions has a cost in terms of energy, as it requires regular calculation operations to be made and the predictive model to be updated when it deviates from the actual situation.”
The solution developed by UOC researchers was tested in a real communication scenario with the Enxaneta nanosatellite, the first satellite deployed by the Government of Catalonia under its NewSpace project. The results were promising: the satellite access ratio improved by up to 99%, ensuring long-term network access while minimising the device’s energy consumption.
“The next steps are to complete the cost-benefit analysis of implementing the solution, taking into account various applications, service networks, types of satellite constellation, IoT devices and communication technologies; and then to propose and put in place energy-saving modes that automatically adapt to communication needs and the changing conditions of non-terrestrial networks,” concluded Guillem Boquet.
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