Hybrid Satellite-Terrestrial Communication Networks for the Maritime Internet of Things: Key Technologies, Opportunities, and Challenges

With the rapid development of marine activities, there has been an increasing number of maritime mobile terminals, as well as a growing demand for high-speed and ultra-reliable maritime communications to keep them connected. Traditionally, the maritime Internet of Things (IoT) is enabled by maritime satellites. However, satellites are seriously restricted by their high latency and relatively low data rate. As an alternative, shore & island-based base stations (BSs) can be built to extend the coverage of terrestrial networks using fourth-generation (4G), fifth-generation (5G), and beyond 5G services. Unmanned aerial vehicles can also be exploited to serve as aerial maritime BSs. Despite of all these approaches, there are still open issues for an efficient maritime communication network (MCN). For example, due to the complicated electromagnetic propagation environment, the limited geometrically available BS sites, and rigorous service demands from mission-critical applications, conventional communication and networking theories and methods should be tailored for maritime scenarios. Towards this end, we provide a survey on the demand for maritime communications, the state-of-the-art MCNs, and key technologies for enhancing transmission efficiency, extending network coverage, and provisioning maritime-specific services. Future challenges in developing an environment-aware, service-driven, and integrated satellite-air-ground MCN to be smart enough to utilize external auxiliary information, e.g., sea state and atmosphere conditions, are also discussed

Internet of Things-aided Smart Grid: Technologies, Architectures, Applications, Prototypes, and Future Research Directions

Traditional power grids are being transformed into Smart Grids (SGs) to address the issues in existing power system due to uni-directional information flow, energy wastage, growing energy demand, reliability and security. SGs offer bi-directional energy flow between service providers and consumers, involving power generation, transmission, distribution and utilization systems. SGs employ various devices for the monitoring, analysis and control of the grid, deployed at power plants, distribution centers and in consumers' premises in a very large number. Hence, an SG requires connectivity, automation and the tracking of such devices. This is achieved with the help of Internet of Things (IoT). IoT helps SG systems to support various network functions throughout the generation, transmission, distribution and consumption of energy by incorporating IoT devices (such as sensors, actuators and smart meters), as well as by providing the connectivity, automation and tracking for such devices. In this paper, we provide a comprehensive survey on IoT-aided SG systems, which includes the existing architectures, applications and prototypes of IoT-aided SG systems. This survey also highlights the open issues, challenges and future research directions for IoT-aided SG systems

A novel network architecture for train-to-wayside communication with quality of service over heterogeneous wireless networks

In the railway industry, there are nowadays different actors who would like to send or receive data from the wayside to an onboard device or vice versa. These actors are e.g., the Train Operation Company, the Train Constructing Company, a Content Provider, etc. This requires a communication module on each train and at the wayside. These modules interact with each other over heterogeneous wireless links. This system is referred to as the Train-to-Wayside Communication System (TWCS). While there are already a lot of deployments using a TWCS, the implementation of quality of service, performance enhancing proxies (PEP) and the network mobility functions have not yet been fully integrated in TWCS systems. Therefore, we propose a novel and modular IPv6-enabled TWCS architecture in this article. It jointly tackles these functions and considers their mutual dependencies and relationships. DiffServ is used to differentiate between service classes and priorities. Virtual local area networks are used to differentiate between different service level agreements. In the PEP, we propose to use a distributed TCP accelerator to optimize bandwidth usage. Concerning network mobility, we propose to use the SCTP protocol (with Dynamic Address Reconfiguration and PR-SCTP extensions) to create a tunnel per wireless link, in order to support the reliable transmission of data between the accelerators. We have analyzed different design choices, pinpointed the main implementation challenges and identified candidate solutions for the different modules in the TWCS system. As such, we present an elaborated framework that can be used for prototyping a fully featured TWCS

Διασύνδεση ασύρματων ευρυζωνικών δικτύων με δορυφορικά δίκτυα

Η παρούσα Διδακτορική Διατριβή πραγματεύεται το πρόβλημα της διασύνδεσης μεταξύ ενός Δορυφορικού Διαδραστικού Δικτύου και ασύρματων ευρυζωνικών δικτύων. Η εκχώρηση της χωρητικότητας στις τελικές συνδέσεις του ευρυζωνικού δικτύου γίνεται μετά από χρονικό διάστημα 500 msec από τη στιγμή που στάλθηκε το αντίστοιχο αίτημα από το αντίστοιχο δορυφορικό τερματικό. Οι περισσότερες υπηρεσίες πραγματικού χρόνου δεν μπορούν να ανεχθούν τόσο μεγάλες καθυστερήσεις. Για το λόγο αυτό εισάγουμε την λογική της πρόβλεψης των αναγκών των συνδέσεων κατά την αίτηση της χωρητικότητας. Ο προτεινόμενος μηχανισμός διασύνδεσης αποτελείται από τρία τμήματα: το πρώτο είναι υπεύθυνο για τη διευθέτηση των αιτήσεων χωρητικότητας, το δεύτερο είναι υπεύθυνο για την εκχώρηση χωρητικότητας ανά δορυφορικό τερματικό, και το τρίτο είναι υπεύθυνο για τον διαμοιρασμό της δοσμένης χωρητικότητας στους συνδρομητές του ευρυζωνικού δικτύου. Στην συνέχεια της διατριβής μας, βελτιώνουμε και τα τρία τμήματα του προτεινόμενου μηχανισμού, ειδικά όσο αφορά κίνηση πραγματικού χρόνου που έχει μικρότερες ανοχές σε καθυστερήσεις. Χρησιμοποιούμε τον NLMS αλγόριθμο πρόβλεψης στο πρώτο τμήμα του μηχανισμού, επεκτείνουμε το δεύτερο τμήμα ώστε η κατανομή των χρονοθυρίδων να γίνεται σε MFTDMA, και, βελτιώνουμε τον χρονοπρογραμματιστή που λειτουργεί στο τρίτο τμήμα, ώστε ο διαμοιρασμός της χωρητικότητας στις συνδέσεις πραγματικού χρόνου του ευρυζωνικού δικτύου να γίνεται βάσει μετρικών αντίληψης ποιότητας.This doctoral thesis deals with the problem of interconnection between a satellite interactive network and broadband networks. The time difference between the capacity request of a satellite terminal and the capacity grant from the satellite network is at least equal to the round trip delay. To address this issue, schemes for predicting the needs of connections are used for capacity allocation purposes. An interconnection mechanism is proposed, which consists of three parts: 1) an entity at the satellite terminal responsible for capacity requests, 2) resource allocation to the satellite terminals and 3) sharing the capacity of a satellite terminal among the subscribers of the broadband network. We improve all three parts of the interconnection mechanism aiming to improve the overall performance of the system, especially for real time traffic that can tolerate less delay. Τhe NLMS (Normalized Least Mean Square) algorithm is chosen to be used in the first part of the proposed mechanism. We extend the second part of the mechanism for performing the slot allocation in MF-TDMA. Finally, we improve the scheduler of the third part in order to schedule traffic of real time connections of the broadband network based on Quality of Experience (QoE) metrics

Hybrid wireless broadband networks

A hybrid system is an integration of two or more different systems, particularly in this thesis referring to wireless broadband networks. However, to provide end-to-end quality of service (QoS) in a hybrid system is a challenging task due to different protocol in each system. In this thesis, we aim to improve the overall performance of hybrid networks in a disaster management by addressing the challenges as well as the problems in a homogeneous network. Such an approach allows more efficient multi-parameter optimization and significant improvements in the overall system performance. More specifically, we introduce two novel algorithms. The first is the novel end-to-end QoS algorithm for hybrid wireless broadband networks. We proposed the end-to-end QoS maps based on particular chosen parameters and analyse the simulation results. The QoS maps are applied to a few scenarios, and the performance evaluation of the constructed network is presented. Based on the results obtained by software simulation tools, the performance validation shows that the hybrid network has specific advantages and constraints in terms of number of users, preference, coverage and applications. The second algorithm presented is the novel in users’ application algorithm, the purpose of which is to optimize bandwidth for first responders applied in the PPDR project under grant agreement EU FP7 SEC PPDR-TC. This algorithm is responsible for incorporating more users and different levels of background load to a hybrid network. The proposed method analyses both positive and negative outcomes based on the results obtained. This algorithm has been presented in the PPDR project

A Survey on Wireless Security: Technical Challenges, Recent Advances and Future Trends

This paper examines the security vulnerabilities and threats imposed by the inherent open nature of wireless communications and to devise efficient defense mechanisms for improving the wireless network security. We first summarize the security requirements of wireless networks, including their authenticity, confidentiality, integrity and availability issues. Next, a comprehensive overview of security attacks encountered in wireless networks is presented in view of the network protocol architecture, where the potential security threats are discussed at each protocol layer. We also provide a survey of the existing security protocols and algorithms that are adopted in the existing wireless network standards, such as the Bluetooth, Wi-Fi, WiMAX, and the long-term evolution (LTE) systems. Then, we discuss the state-of-the-art in physical-layer security, which is an emerging technique of securing the open communications environment against eavesdropping attacks at the physical layer. We also introduce the family of various jamming attacks and their counter-measures, including the constant jammer, intermittent jammer, reactive jammer, adaptive jammer and intelligent jammer. Additionally, we discuss the integration of physical-layer security into existing authentication and cryptography mechanisms for further securing wireless networks. Finally, some technical challenges which remain unresolved at the time of writing are summarized and the future trends in wireless security are discussed.Comment: 36 pages. Accepted to Appear in Proceedings of the IEEE, 201