Satellites are going to revolutionize the Internet of Things (IoT) connectivity enabling the ubiquitous coverage targeted by 5G and upcoming 6G networks. While the potentials of satellite IoT are unquestionable, many challenges still remain unsolved. In the present work, we design a Long Range Wide Area Network (LoRaWAN) with mobile gateways (GWs) installed on Low Earth Orbit (LEO) satellites. We address synchronization issues due to intermittent link availability between the End Devices (EDs) and the GW, and we propose a Scheduling Algorithm for LoRa to LEO Satellites (SALSA). SALSA ensures reliable communication, avoiding packets drops and packet collisions, by using a Time Division Multiple Access (TDMA) approach, rather than classic ALOHA-based LoRa. The uplink transmissions of the EDs are scheduled considering the satellite availability period, the satellite footprint, and the specific visit time for each ED. Two different policies are proposed: a First Come First Served (FCFS), and a FAIR policy. Simulation results, obtained in real conditions, with real satellites visibility, demonstrate the better performance achievable with SALSA (regardless of the policy) compared to standard LoRa. The FAIR policy outperforms the FCFS policy by giving all the EDs an equal chance to transmit, even to those that are visited last by the satellite. The performance of SALSA can be further improved considering larger constellations of LEO satellites.

The demand for safe and secure journeys over roads and highways has been growing at a tremendous pace over recent decades. At the same time, the smart city paradigm has emerged to improve citizens’ quality of life by developing the smart mobility concept. Vehicular Ad hoc NETworks (VANETs) are widely recognized to be instrumental in realizing such concept, by enabling appealing safety and infotainment services. Such networks come with their own set of challenges, which range from managing high node mobility to securing data and user privacy. The Software Defined Networking (SDN) paradigm has been identified as a suitable solution for dealing with the dynamic network environment, the increased number of connected devices, and the heterogeneity of applications. While some preliminary investigations have been already conducted to check the applicability of the SDN paradigm to VANETs, and its presumed benefits for managing resources and mobility, it is still unclear what impact SDN will have on security and privacy. Security is a relevant issue in VANETs, because of the impact that threats can have on drivers’ behavior and quality of life. This paper opens a discussion on the security threats that future SDN-enabled VANETs will have to face, and investigates how SDN could be beneficial in building new countermeasures. The analysis is conducted in real use cases (smart parking, smart grid of electric vehicles, platooning, and emergency services), which are expected to be among the vehicular applications that will most benefit from introducing an SDN architecture.

The exponential growth of Internet of Things (IoT) applications led to the deployment of IoT devices in remote areas beyond the reach of terrestrial networks, calling for satellite network solutions. Indeed, Low-Earth Orbit (LEO) satellites can provide global connectivity to direct-to-satellite (DtS)-IoT applications, with remarkable impact in several areas, as environmental monitoring, precision agriculture, and disaster prevention. One of the key challenges in DtS-IoT is supporting energy and spectral efficient multiple access, which has attracted a lot of attention recently. This work presents two novel multiple-access scheduling strategies for DtS-IoT networks, both inspired by the scheduling algorithm for LoRa to LEO satellites (SALSA). The latter prevents collisions by applying a first-come-first-served (FCFS) policy to allocate dedicated time slots according to the devices’ rise times. However, the effectiveness of SALSA decreases in high-density scenarios, for which the visibility time of many devices is insufficient to successfully schedule their transmission. In the proposed scheduling methods, we take advantage of the availability of multiple frequency channels and the ability to change the transmission scheduling order of some devices within a visibility time window to improve uplink efficiency. The numerical results show that the average number of uplinks per lap and per visible device increases with the number of available channels, providing an improvement of almost 80% in terms of system uplink efficiency, and the proposed scheduling methods are more effective with smaller packet sizes. Additionally, we explore that the fusion of both scheduling strategies can further boost the system performance while guaranteeing an uplink efficiency greater than 50%, as elucidated across the implementation algorithms with four, six, and eight multiple channels.

Through the transition from 5G to 6G, a significant rise in the number of Internet of Things (IoT) devices is anticipated, enabling pervasive and uninterrupted connectivity for several applications, in different verticals. Coping with the substantial influx of IoT devices and fulfilling the high capacity demands of different IoT technologies, such as NB-IoT, will necessitate the involvement of Non-Terrestrial Networks (NTNs), which will serve as crucial complements to terrestrial systems, enhancing the availability, resilience, and coverage of the network and will guarantee cost/benefit for some services and will fully satisfy some key requirements. Nevertheless, a primary obstacle to be faced when integrating IoT terrestrial communication systems in NTN, in particular with Non-Geostationary (NGSO) satellites, lies in the short visibility time of the flying platform due to its high speed. The latter introduces criticalities in various communication phases, including the Random Access (RA) procedure. In a highly congested scenario, the large Round Trip Delay and a limited visibility window, which varies for each user within the satellite’s coverage area, contribute to reducing the number of users successfully concluding the RA procedure. In this paper, to enhance the percentage of users who successfully conclude the RA, we introduce the concept of Coverage Enhancement Levels in time and a novel backoff mechanism, namely Smart Backoff, that leverages the beam coverage visibility period of individual users to adjust the random backoff interval. The numerical results obtained from our proposed scheme substantiate significant improvements compared to the standard backoff scheme. Specifically, our approach yields an increase of up to 16% per channel in the percentage of users who successfully complete the RA process.

One of the main application scenario that the upcoming 5G systems are expected to support is Internet of Things (IoT) traffic backhauling. With the exponential increase of devices, it follows the critical challenge of handling the huge data volume that they produce. Terrestrial networks may not be sufficient for that, or not always available. Satellites then come into play, and they can provide the ubiquitous coverage targeted by 5G. On the other side, aggregation can be an efficient strategy to reduce the amount of traffic, and use network resources in an efficient manner. Building on that, in this work, we consider a hybrid IoT-satellite network architecture for collecting message queuing telemetry transport (MQTT) traffic. We design an advanced filter, namely, MQTT message filter aggregator (MQTT-MFA), that performs MQTT topics aggregation in close proximity of MQTT Publishers before data are sent over the satellite link. The developed MQTT-MFA implementation leverages on MQTT bridge, and it is compliant with Mosquitto, an open-source MQTT broker. Extensive simulation results have demonstrated that MQTT-MFA requires only 10% of the TCP/IP overhead generated in a baseline architecture (where the bridge is not set up) and 1/4 number of bytes to transmit the same amount of information, when compression of the data payload is also enabled.