As the telecommunications industry embarks on the transition to Sixth-Generation (6G) networks, this paper examines the integration of Non-Terrestrial Networks (NTN), and in particular satellite backhauling, in the context of Fifth-Generation (5G) systems. The Integrated Access and Backhaul (IAB) technology, conceived as a wireless terrestrial backhauling system in the Next Generation Radio Access Network (NG-RAN), has been identified as a possible enabler for the integration of satellite nodes. Despite the work already done in this direction, the combination of IAB architectures with satellite nodes operating in both the access and backhaul side requires further evaluations on feasibility and limitations for networks integrating Low Earth Orbit (LEO) and Geostationary Earth Orbit (GEO) satellites. To this end, this work contributes providing insights on background technologies, as well as a detailed analysis of the issues and challenges arising from such integration and a definition of use cases to support narrow-band and broadband services. Furthermore, the design and implementation of a simulation tool is proposed for a performance evaluation in terms of registration time, link capacity, single-hop and end-to-end delay. Results show that the integration turns out to be feasible, even if with strong constraints coming from the satellite system rather than the IAB usage itself. Indeed, the earth-satellite link in LEO systems has a significant impact on the packet delivery time due to the discontinuous coverage. In case of GEO satellite instead, a non-terrestrial backhaul link could limit the performance of the whole system, especially at lower elevation angles.

Digital services and digital service chains are the heart beating of the modern economy. Their composition involves several players, i.e., processes, software, devices, and many kinds of data exchanged among them. In such a scenario, it is important to guarantee data confidentiality, integrity, as well as authentication and authorization procedures between the communicating parties of a service chain. Cyber-security frameworks are explicitly designed for this purpose. They rely on the integration of different software modules, mutually interfaced to accomplish complex security tasks. Nevertheless, it is important to guarantee a high level of protection during data exchange among the modules. Currently, standardized authentication and authorization mechanisms are implemented through proprietary “As-a-Service” products, but the deployment of a mature on-premise solution is still missing. To bridge this gap, this contribution proposes an authentication and authorization module that automatically protects the information flowing among the modules of cyber-security frameworks. It guarantees resource availability only to authenticated subjects. Thus, their operations are confined in what actions they are authorized for. The proposed module has been implemented and tested in a real cyber-security framework under development into the H2020 GUARD project. Experimental tests show that the proposed module enables authentication and authorization procedure delegation among GUARD modules, which eases their implementation, while maximizing the flexibility of the set of access control policies and an efficient protection of the services.

The Social Internet of Things is gaining momentum thanks to its unique capability of i) autonomously building social relationships among smart objects and ii) supporting the novel services within the Social Network. During the service provisioning, the Trust Management System is in charge of selecting suitable objects able to accomplish the requested services. In this context, available solutions present two relevant issues to be solved. First, they generally assume to select social objects that only achieve higher trustworthiness without considering their actual computing capabilities. Indeed, it would significantly compromise the Quality of Experience in the Social Network of objects. Second, they assume to implement this task directly within constrained devices, becoming unpractical considering their limited computational and storage capabilities. To improve and speed up service provisioning, this paper proposes a novel Trust Management System scheme that fairly distributes service requests by jointly considering the trustworthiness and resource capabilities of available objects. This Trust Management System has been designed to exploit fog computing to efficiently handle the whole process of service provisioning in real-world deployments while relieving constrained devices from all processing and storage efforts. Its behavior is investigated through computer simulations. Obtained results demonstrated that the conceived approach outperforms baseline solutions in terms of latency, fairness in services distribution, and responsiveness in malicious nodes' detection.

The adoption of the Narrowband-Internet of Things technology in satellite communications intends to boost Internet of Things services beyond the boundaries imposed by the current terrestrial infrastructures. Apart from link-level studies in the scientific literature and preliminary 3GPP technical reports, the overall debate is still open. To provide a further step forward in this direction, the work presented herein pursues a novel service-oriented methodology to design an effective solution, meticulously stitched around application requirements and technological constraints. To this end, it conducts link-level and system-level investigations to tune physical transmissions, satellite constellation, and protocol architecture, while ensuring the expected system behavior. To offer a real smart agriculture service operating in Europe, the resulting solution exploits 24 low-Earth orbit satellites, grouped into eight different orbits, moving at an altitude of 500 km. The configured protocol stack supports the transmission of tens of bytes generated at the application layer, by also counteracting the issues introduced by the satellite link. Since each satellite has the whole protocol stack onboard, terminals can transmit data without the need for the feeder link. This ensures communication latencies ranging from 16 to 75 min, depending on the served number of terminals and the physical transmission settings. Moreover, the usage of the early data transmission scheme reduces communication latencies up to 40%. These results pave the way toward the deployment of an effective proof of concept, which drastically reduces the time to market imposed by the current state of the art.

In the Social Internet of Things paradigm, the Trust Management System computes trust values of involved social objects, identifies trusted relationships, and selects the most suitable object able to provide a target service. State-of-the-art mechanisms conceived to address these tasks generally avoid considering the actual availability of social objects and demand the implementation of complex algorithms to constrained nodes. This work presents a novel multi-tiered and fog-based Social Internet of Things architecture to solve these open issues, ensuring fast service provisioning, high scalability, fault tolerance, and security. On the one hand, the Trust Management System hosted at the first fog layer of the architecture jointly addresses the trustworthiness of service providers and monitors the re-source availability exposed by social objects, thus simplifying the forwarding of service requests to trusted and unloaded nodes. From another hand, to securely implement advanced services at a large scale, a second fog layer exploits a Blockchain-based storage for sharing services, relationships, and trust values across organizations and service domains. Computer simulations demonstrate the effectiveness of the proposed architecture in a realistic Social Internet of Things while showing the performance gain obtained against a baseline approach.

Satellite Communication is expected to play a leading role in 5G & Beyond networks. Current studies, however, focus the attention on physical and link-level aspects, while ignoring to evaluate system-level performance. This paper presents a novel simulation tool, conceived as a new module for the open-source 5G-air-simulator, modeling NB-IoT satellite-based communication systems. Specifically, it implements several link-to-system abstraction models, the cell selection procedure, and a configurable satellite constellation. Furthermore, these essential features are successfully integrated within the rest of the 5G-air-simulator, thus offering the opportunity to test flexible network deployments (e.g., by varying the number and the distribution of users) under different application statistics. To demonstrate the actual effectiveness of the developed tool, this work also presents a preliminary performance assessment of an NB-IoT satellite-based communication system enabling reference monitoring scenarios.

The new generation of digital services are natively conceived as an ordered set of Virtual Network Functions, deployed across boundaries and organizations. In this context, security threats, variable network conditions, computational and memory capabilities and software vulnerabilities may significantly weaken the whole service chain, thus making very difficult to combat the newest kinds of attacks. It is thus extremely important to conceive a flexible (and standard-compliant) framework able to attest the trustworthiness and the reliability of each single function of a Service Function Chain. At the time of this writing, and to the best of authors knowledge, the scientific literature addressed all of these problems almost separately. To bridge this gap, this paper proposes a novel methodology, properly tailored within the ETSI-NFV framework. From one side, Software-Defined Controllers continuously monitor the properties and the performance indicators taken from networking domains of each single Virtual Network Function available in the architecture. From another side, a high-level orchestrator combines, on demand, the suitable Virtual Network Functions into a Service Function Chain, based on the user requests, targeted security requirements, and measured reliability levels. The paper concludes by further explaining the functionalities of the proposed architecture through a use case.

Time Slotted Channel Hopping (TSCH) is a recent enhancement of the IEEE 802.15.4 standard aimed at the industrial sector. To complement its unique features, the IPv6 over the TSCH mode of IEEE 802.15.4e (6tisch) Working Group released a set of specifications that define the way Time Slotted Channel Hopping could be integrated in embedded IPv6 networks based on the IPv6 over Low Power WPAN. TheI 6tisch standard is now available under several hardware/software platforms so that a cross-comparison of the different implementations deserves particular attention in order to properly identify performance bottlenecks and scavenge pros and cons of the 6tisch technology. The present contribution provides an experimental cross-comparison of protocol stack implementations running on top of different devices. In particular, experimental tests were conducted to characterize the behavior of OpenWSN and Contiki in Time Slotted Channel Hopping- based scenarios made up by TelosB, Zolertia Z1, and OpenMote motes. By considering star and chain topologies and different traffic load conditions, many performance indices were measured, including memory footprint, energy consumption, synchronization time, duty- cycle, end-to-end packet delays, and Packet Loss Ratio. Obtained results highlight strengths and weaknesses of each hardware/software platform, while providing trade-off considerations about flexibility, accuracy, energy-efficiency, and Quality of Service.

In the recent past, we witnessed to a dramatic growth of networks with a huge number of interconnected wireless nodes exchanging large amounts of information. This has brought to the need of ad-hoc, energy-aware protocols suitable for low-power and lossy networks. Among these, Routing Protocol for Low Power and Lossy Networks (RPL) is surely one of the most interesting ones. It chooses the optimal routes from a source to a destination node, based on specific metrics. In this work we present a RPL compliant composite metric that considers both reliability and energy. Its aim is twofold. First, it realizes energy consumption balancing, so that each node tends to consume the same amount of energy of all the others, thus prolonging the overall network lifetime. Second, it takes into account data reliability along the paths, expressed by the well known Expected Transmission Count (ETX). The effectiveness of the proposed metric is confirmed by some interesting simulation results, that strongly encourage a deeper investigation on this issue.

The importance of a Variable Bit Rate (VBR) video transmission on UMTS networks is increasing in time. The bursty nature of VBR traffic complicates the design of efficient mechanisms for video retrieval, transport, and provisioning to achieve a high bandwidth utilization and reduce the negative effects of bandwidth fluctuations in wireless channels. To this aim, several scheduling algorithms can be successfully implemented. They regulate data transmission to reduce the rate variability peculiar of VBR streams. At client side, scheduled data are temporarily stored in the client buffer before being decoded on the terminal. In this work, a novel scheduling algorithm, the Scheduling Algorithm for Interactive Video (SAIV) is presented and analyzed. It is an algorithm thought for VBR stream transmission in UMTS networks that takes into account the user interactivity. Scheduling is performed “online”, over relatively small video segments to reduce delays. SAIV dynamically varies the sampling frequency of the Real Time Control Protocol (RTCP) feedbacks that carry information on the client buffer status. The sampling frequency is modulated according to the difference between the calculated buffer fill level at server side and the real buffer fill level at client side. The latter is exploited to reschedule data with the updated information. Numerical results testify the SAIV effectiveness compared to the classical SLWIN online algorithm already known by literature, in some simulation scenarios of real interest.

A novel strategy of measurement based admission control (MBAC) for video distribution systems has been developed, aimed at obtaining the needed quality of service (QoS), expressed in terms of loss probability. The developed algorithm is based on an autoregressive (AR) adaptive filter taking into account slow and quick time bit rate variations of video stream aggregation. A simple admission control strategy is presented, able to shift from the server to the client the decision about the admission of a new video stream. Simulation results, based on real MPEG encoded videos justify the application

The main aspect of several multimedia applications is the transmission of variable bit rate (VBR) video streams requiring high bandwidth with stringent quality of service (QoS) guarantee. In such systems, a statistical bandwidth estimation is relevant for network infrastructure planning and admission control. In this paper, an original algorithm for aggregate bandwidth estimation, needed by a given number of correlated video streams, is proposed and analyzed. The obtained analytical results are validated by simulation and compared with other numerical results already present in the literature, discussing the effectiveness of the proposed solution.