## 1 Introduction
### State-of-the-Art  
In the design of a satellite IoT network, several factors are of paramount importance, directly influencing the system performance, such as constellation design, number of satellites, number of orbital planes, elevation angle, orbital plane spacing, and the orbital eccentricity [16]. Added to these factors is the wireless access technique used by the IoT devices. Different methods have been proposed to establish a connection between a device and a satellite, with their own advantages and disadvantages. We start with indirect communication, in which data are transmitted to the satellite via a terrestrial gateway. Therefore, the biggest advantage is the possibility to use current terrestrial LPWAN technologies at the end nodes. The IoT devices actually connect to the terrestrial gateway, in which protocols, such as LoRaWAN and SigFox, can be used to connect to end nodes [1]. A disadvantage of this architecture is the limited terrestrial coverage [17]. Another negative factor is the difficulty of installing a gateway in remote regions or in cases where monitoring is carried out for a short period of time, which makes the cost of the service higher. Arguably, the most attractive method in terms of ease of deployment is direct satellite communication, better known as direct-to-satellite (Dt5-IoT) [5]. In this case, users communicate directly to the satellite, most probably a LEO satellite, without the need for a terrestrial gateway. However, some of the challenges of this approach are the long link distance and the short communication windows. LEO satellites are concentrated at altitudes between 340 and 650 km [6] and provide time windows for communication according to their passing orbits. Some manufacturers in the field of wireless communications [3; 4] have been working on cutting-edge technologies that are getting closer and closer to meeting the challenge of Dt5-IoT. In [17], interesting advances in the interconnection of technologies were already presented to allow adequate Dt5-IoT communication design using a satellite constellation and LPWAN technology such as LoRaWAN. In addition to direct and indirect communication, other alternatives are also presented, such as the hybrid land-satellite network (HSTN) proposed in [18]. Due to characteristics such as communication delay, latency, mobility, and coverage performance, the authors proposed three basic cooperative models for the HSTN. In the so-called \(L\) model, the satellite communicates with the device via a terrestrial gateway (i.e., indirect communication). An example of a network operating in the \(L\) model with LoRaWAN terrestrial devices can be found in [19]. In the \(X\) model, devices communicate using direct and indirect techniques. Communication between users-satellite and users-terrestrial base station is executed separately, sharing wireless resources. Interference patterns found in this model are diverse and complicated, such as mutual interference between users. Furthermore, they are dependent on channel fading influences and cell coverage effects. In urban areas, the satellite user and the terrestrial user coexist, yielding unwanted co-channel signals. The \(V\) model considers the cooperation of a satellite with a terrestrial base station to serve the same user, being therefore a combination of the indirect and direct approaches. Signal diversity reception is used to compensate for large channel fading. Furthermore, the terrestrial and satellite network protocols may be different, requiring translation. Independent on the architecture, whether direct, indirect, or a combination of both, medium access control (MAC) techniques implemented in commercial satellite networks were not designed to provide scalable solutions for the growing number of devices envisioned for IoT. Traditional solutions such as Code Division Multiple Access (CDMA) and Time Division Multiple Access (TDMA), when placed in the context of LEO satellites and large device density, may lose performance due to the need for strict synchronization.