# Trends in LPWAN Technologies for LEO Satellite Constellations in the NewSpace Context
## 4 Challenges and Limitations  
Understanding the challenges and limitations of satellite IoT communications is crucial for developing effective strategies that maximize their potential and opportunities. The significant hurdles involved in this area are as follows:  
* Real-time and critical communications: IoT communications using LPWAN technology are unsuitable for applications requiring critical or real-time communications. Thislimitation also applies to IoT satellite communications. In LEOs, constellation satellites intended for this purpose are only sometimes available in all Earth regions. This results in significant delays due to the datum's travel distance from the IoT device to the satellite and its final destination [66]. These delays can be critical for applications, such as health monitoring or public safety [5]. * Limited bandwidth: Despite the technological advancements, the bandwidth available in satellite IoT communications remains limited compared to terrestrial communications. This can hinder the efficient transmission of large volumes of data generated by IoT devices. Furthermore, bandwidth sharing among multiple users and applications can lead to congestion, affecting the quality of the service. * Limited coverage: Although LEO satellites can offer global coverage, their presence in specific areas can be limited compared to terrestrial networks. This can result in areas with no or intermittent coverage, affecting the connectivity and availability of IoT devices [67]. * Interference: Satellite communications can be impacted by natural and artificial electromagnetic interferences. Solar storms can influence the quality of satellite communications [68]. Meanwhile, signals from other satellites [69] or terrestrial sources [13] can generate interferences that affect the reception and transmission of data, leading to a degraded signal quality and increased error rates. * Security and privacy: Satellite signals can be captured by any receiver on Earth, raising concerns about the confidentiality and integrity of the transmitted information. Implementing robust security measures in satellite IoT communications in LEOs is essential, especially with the increasing risk of cyber-attacks due to the broader adoption of satellite technology [9]. * Space debris management: The growing accumulation of space debris in orbit represents a significant challenge for satellite communications. Space debris increases the risk of collisions with satellites in orbit, which can damage or destroy equipment and endanger its helpful life [70]. Mitigation measures, such as designing satellites with collision avoidance capabilities and space debris removal programs, are necessary. * Regulations on the use of frequencies: The ITU regulates access to and use of the radio frequency spectrum in satellite orbits. Compliance with these regulations is crucial to ensure the interoperability and operability of satellite IoT-based solutions. * Scalability of connected IoT devices: As the number of IoT devices increases, the satellite communications infrastructure must efficiently manage the large data volume they generate [71]. This requires efficient media access control protocols and algorithms to manage the connectivity and communications of IoT devices on the satellite network. * Core network function distribution: Deploying network functions in emerging satellite networks, especially those with sparse satellite constellations, presents unique challenges compared to traditional LPWAN architectures, like LoRaWAN and NB-IoT. In satellite networks, the assumption of constant space-ground connectivity, common in conventional setups, needs a re-evaluation. Adapting to this scenario requires a shift in network design, with crucial network functions reconfigured for distributed operations. This includes enabling autonomous operations on satellites when isolated from ground stations.