Characterizing the Energy Trade-Offs of End-to-End Vehicular Communications using an Hyperfractal Urban Modelling

We characterize trade-offs between the end-to-end communication delay and the energy in urban vehicular communications with infrastructure assistance. Our study exploits the self-similarity of the location of communication entities in cities by modeling them with an innovative model called "hyperfractal". We show that the hyperfractal model can be extended to incorporate road-side infrastructure and provide stochastic geometry tools to allow a rigorous analysis. We compute theoretical bounds for the end-to-end communication hop count considering two different energy-minimizing goals: either total accumulated energy or maximum energy per node. We prove that the hop count for an end-to-end transmission is bounded by $O(n^{1-\alpha/(d_F-1)})$ where $\alpha2$ is the fractal dimension of the mobile nodes process. This proves that for both constraints the energy decreases as we allow choosing routing paths of higher length. The asymptotic limit of the energy becomes significantly small when the number of nodes becomes asymptotically large. A lower bound on the network throughput capacity with constraints on path energy is also given. We show that our model fits real deployments where open data sets are available. The results are confirmed through simulations using different fractal dimensions in a Matlab simulator

AN EFFICIENT INTERFERENCE AVOIDANCE SCHEME FOR DEVICE-TODEVICE ENABLED FIFTH GENERATION NARROWBAND INTERNET OF THINGS NETWOKS’

Narrowband Internet of Things (NB-IoT) is a low-power wide-area (LPWA) technology built on long-term evolution (LTE) functionalities and standardized by the 3rd-Generation Partnership Project (3GPP). Due to its support for massive machine-type communication (mMTC) and different IoT use cases with rigorous standards in terms of connection, energy efficiency, reachability, reliability, and latency, NB-IoT has attracted the research community. However, as the capacity needs for various IoT use cases expand, the LTE evolved packet core (EPC) system's numerous functionalities may become overburdened and suboptimal. Several research efforts are currently in progress to address these challenges. As a result, an overview of these efforts with a specific focus on the optimized architecture of the LTE EPC functionalities, the 5G architectural design for NB-IoT integration, the enabling technologies necessary for 5G NB-IoT, 5G new radio (NR) coexistence with NB-IoT, and feasible architectural deployment schemes of NB-IoT with cellular networks is discussed. This thesis also presents cloud-assisted relay with backscatter communication as part of a detailed study of the technical performance attributes and channel communication characteristics from the physical (PHY) and medium access control (MAC) layers of the NB-IoT, with a focus on 5G. The numerous drawbacks that come with simulating these systems are explored. The enabling market for NB-IoT, the benefits for a few use cases, and the potential critical challenges associated with their deployment are all highlighted. Fortunately, the cyclic prefix orthogonal frequency division multiplexing (CPOFDM) based waveform by 3GPP NR for improved mobile broadband (eMBB) services does not prohibit the use of other waveforms in other services, such as the NB-IoT service for mMTC. As a result, the coexistence of 5G NR and NB-IoT must be manageably orthogonal (or quasi-orthogonal) to minimize mutual interference that limits the form of freedom in the waveform's overall design. As a result, 5G coexistence with NB-IoT will introduce a new interference challenge, distinct from that of the legacy network, even though the NR's coexistence with NB-IoT is believed to improve network capacity and expand the coverage of the user data rate, as well as improves robust communication through frequency reuse. Interference challenges may make channel estimation difficult for NB-IoT devices, limiting the user performance and spectral efficiency. Various existing interference mitigation solutions either add to the network's overhead, computational complexity and delay or are hampered by low data rate and coverage. These algorithms are unsuitable for an NB-IoT network owing to the low-complexity nature. As a result, a D2D communication based interference-control technique becomes an effective strategy for addressing this problem. This thesis used D2D communication to decrease the network bottleneck in dense 5G NBIoT networks prone to interference. For D2D-enabled 5G NB-IoT systems, the thesis presents an interference-avoidance resource allocation that considers the less favourable cell edge NUEs. To simplify the algorithm's computing complexity and reduce interference power, the system divides the optimization problem into three sub-problems. First, in an orthogonal deployment technique using channel state information (CSI), the channel gain factor is leveraged by selecting a probable reuse channel with higher QoS control. Second, a bisection search approach is used to find the best power control that maximizes the network sum rate, and third, the Hungarian algorithm is used to build a maximum bipartite matching strategy to choose the optimal pairing pattern between the sets of NUEs and the D2D pairs. The proposed approach improves the D2D sum rate and overall network SINR of the 5G NB-IoT system, according to the numerical data. The maximum power constraint of the D2D pair, D2D's location, Pico-base station (PBS) cell radius, number of potential reuse channels, and cluster distance impact the D2D pair's performance. The simulation results achieve 28.35%, 31.33%, and 39% SINR performance higher than the ARSAD, DCORA, and RRA algorithms when the number of NUEs is twice the number of D2D pairs, and 2.52%, 14.80%, and 39.89% SINR performance higher than the ARSAD, RRA, and DCORA when the number of NUEs and D2D pairs are equal. As a result, a D2D sum rate increase of 9.23%, 11.26%, and 13.92% higher than the ARSAD, DCORA, and RRA when the NUE’s number is twice the number of D2D pairs, and a D2D’s sum rate increase of 1.18%, 4.64% and 15.93% higher than the ARSAD, RRA and DCORA respectively, with an equal number of NUEs and D2D pairs is achieved. The results demonstrate the efficacy of the proposed scheme. The thesis also addressed the problem where the cell-edge NUE's QoS is critical to challenges such as long-distance transmission, delays, low bandwidth utilization, and high system overhead that affect 5G NB-IoT network performance. In this case, most cell-edge NUEs boost their transmit power to maximize network throughput. Integrating cooperating D2D relaying technique into 5G NB-IoT heterogeneous network (HetNet) uplink spectrum sharing increases the system's spectral efficiency and interference power, further degrading the network. Using a max-max SINR (Max-SINR) approach, this thesis proposed an interference-aware D2D relaying strategy for 5G NB-IoT QoS improvement for a cell-edge NUE to achieve optimum system performance. The Lagrangian-dual technique is used to optimize the transmit power of the cell-edge NUE to the relay based on the average interference power constraint, while the relay to the NB-IoT base station (NBS) employs a fixed transmit power. To choose an optimal D2D relay node, the channel-to-interference plus noise ratio (CINR) of all available D2D relays is used to maximize the minimum cell-edge NUE's data rate while ensuring the cellular NUEs' QoS requirements are satisfied. Best harmonic mean, best-worst, half-duplex relay selection, and a D2D communication scheme were among the other relaying selection strategies studied. The simulation results reveal that the Max-SINR selection scheme outperforms all other selection schemes due to the high channel gain between the two communication devices except for the D2D communication scheme. The proposed algorithm achieves 21.27% SINR performance, which is nearly identical to the half-duplex scheme, but outperforms the best-worst and harmonic selection techniques by 81.27% and 40.29%, respectively. As a result, as the number of D2D relays increases, the capacity increases by 14.10% and 47.19%, respectively, over harmonic and half-duplex techniques. Finally, the thesis presents future research works on interference control in addition with the open research directions on PHY and MAC properties and a SWOT (Strengths, Weaknesses, Opportunities, and Threats) analysis presented in Chapter 2 to encourage further study on 5G NB-IoT

Machine Learning for Unmanned Aerial System (UAS) Networking

Fueled by the advancement of 5G new radio (5G NR), rapid development has occurred in many fields. Compared with the conventional approaches, beamforming and network slicing enable 5G NR to have ten times decrease in latency, connection density, and experienced throughput than 4G long term evolution (4G LTE). These advantages pave the way for the evolution of Cyber-physical Systems (CPS) on a large scale. The reduction of consumption, the advancement of control engineering, and the simplification of Unmanned Aircraft System (UAS) enable the UAS networking deployment on a large scale to become feasible. The UAS networking can finish multiple complex missions simultaneously. However, the limitations of the conventional approaches are still a big challenge to make a trade-off between the massive management and efficient networking on a large scale. With 5G NR and machine learning, in this dissertation, my contributions can be summarized as the following: I proposed a novel Optimized Ad-hoc On-demand Distance Vector (OAODV) routing protocol to improve the throughput of Intra UAS networking. The novel routing protocol can reduce the system overhead and be efficient. To improve the security, I proposed a blockchain scheme to mitigate the malicious basestations for cellular connected UAS networking and a proof-of-traffic (PoT) to improve the efficiency of blockchain for UAS networking on a large scale. Inspired by the biological cell paradigm, I proposed the cell wall routing protocols for heterogeneous UAS networking. With 5G NR, the inter connections between UAS networking can strengthen the throughput and elasticity of UAS networking. With machine learning, the routing schedulings for intra- and inter- UAS networking can enhance the throughput of UAS networking on a large scale. The inter UAS networking can achieve the max-min throughput globally edge coloring. I leveraged the upper and lower bound to accelerate the optimization of edge coloring. This dissertation paves a way regarding UAS networking in the integration of CPS and machine learning. The UAS networking can achieve outstanding performance in a decentralized architecture. Concurrently, this dissertation gives insights into UAS networking on a large scale. These are fundamental to integrating UAS and National Aerial System (NAS), critical to aviation in the operated and unmanned fields. The dissertation provides novel approaches for the promotion of UAS networking on a large scale. The proposed approaches extend the state-of-the-art of UAS networking in a decentralized architecture. All the alterations can contribute to the establishment of UAS networking with CPS

The 5G era of mobile networks: a comprehensive study of the related technologies accompanied by an experimentation framework

Οι συνεχώς αυξανόμενες απαιτήσεις από τα δίκτυα κινητών επικοινωνιών για τη παροχή καλύτερων υπηρεσιών και τη διασύνδεση όλων και περισσότερων συσκευών, ωθούν τη κοινότητα του κλάδου στην ανάπτυξη νέων μεθόδων και τεχνολογιών οργάνωσης των δικτύων προκειμένου να αντιμετωπιστεί αποτελεσματικά αυτή η πρόκληση. Δεδομένου ότι η παρούσα τεχνολογία έχει φτάσει στα όρια της από άποψη ικανότητας διαχείρισης της κίνησης, απαιτείται η ανάπτυξη ενός νέου πλαισίου λειτουργίας το οποίο θα μπορεί να ανταποκριθεί αποτελεσματικά στις νέες συνθήκες που διαμορφώνονται από τη τηλεπικοινωνιακή αγορά. Η 5 η γενιά των δικτύων κινητών επικοινωνιών (5G) αποσκοπεί στην επίλυση ακριβώς αυτού του ζητήματος, μέσα από την ανάπτυξη ενός νέου μοντέλου λειτουργίας. Το μοντέλο αυτό αναδιαρθρώνοντας εκ βάθρων τον τρόπο λειτουργίας του δικτύου σε όλα τα επίπεδα, σχηματίζει ένα νέο οικοσύστημα δικτυακών υποδομών και λειτουργιών το οποίο επιτρέπει τη παροχή στους χρήστες υπηρεσιών υψηλού επιπέδου, προσαρμοσμένες στις εκάστοτε ανάγκες τους. Στα πλαίσια της παρούσας εργασίας μελετήθηκαν εκτενώς οι θεμελιώδεις αρχές και οι κυριότερες τεχνολογίες που διέπουν τη λειτουργία ενός δικτύου νέας γενιάς καθ’ όλο το μήκος του. Ξεκινώντας από τις καινοτομίες που αφορούν τη δομή των 5G δικτύων σε επίπεδο αρχιτεκτονικής, η ανάλυση επεκτείνεται με μία προσέγγιση από κάτω προς τα πάνω· στα επίπεδα εκπομπής και πρόσβασης στο δίκτυο (C-RAN & MAC), στους μηχανισμούς που είναι υπεύθυνοι για παροχή των λειτουργιών και υπηρεσιών του δικτύου (NFV), ενώ εν συνεχεία γίνεται αναφορά στο νέο μοντέλο δρομολόγησης και διαχείρισης της κίνησης συνολικά στο δίκτυο (SDN) και σε επόμενο στάδιο παρουσιάζεται η τεχνολογία που αφορά την ικανότητα παροχής διακριτών υπηρεσιών στους χρήστες (E2E Slicing). Ακόμα, παρουσιάζονται ορισμένοι χαρακτηριστικοί δείκτες και μετρικές που σχετίζονται με τη προτυποποίηση των τεχνολογιών του δικτύου καθώς και όλες οι τρέχουσες εξελίξεις που αφορούν την ανάπτυξη του 5G στην Ευρώπη. Στη συνέχεια παρουσιάζονται τα δεδομένα του πειράματος που διεξήχθη για τους σκοπούς της εργασίας και αφορά αφενός τη μοντελοποίηση ενός υφιστάμενου δικτύου με βάση τα νέα πρότυπα του 5G και αφετέρου την αξιολόγηση της απόδοσης του με βάση ορισμένα σενάρια σχετικά με τη τοπολογία και το πλήθος των δεδομένων που ανταλλάσσονται κάθε στιγμή στο δίκτυο. Η εξέταση των παραμέτρων αποδοτικότητας εστιάζει στην ικανότητα του ONOS SDN Controller να διαχειρίζεται τη κίνηση των δεδομένων όταν προκύπτουν ορισμένα συμβάντα που επηρεάζουν την αρχική δομή του δικτύου. Ως προς τα αποτελέσματα των μετρήσεων που διεξάγονται, παρόλο που φαίνεται το θετικό αντίκτυπο που θα έχει η ενσωμάτωση των νέων τεχνολογιών στην απόδοση των δικτύων κινητών επικοινωνιών, υπάρχουν ακόμα ορισμένα επιμέρους ανοικτά ζητήματα τα οποία χρήζουν περαιτέρω έρευνας από τη πλευρά των μελών της τηλεπικοινωνιακής κοινότητας ώστε να μην υποσκαφθεί τελικά το αρχικό όραμα της καθολικής λειτουργίας όλων των κινητών συσκευών υπό μία ενιαία ομπρέλα.The ever-increasing demand from mobile communications networks for the provision of better services and interconnection of more devices is pushing the industry's community to develop new network organization methods and technologies in order to effectively address this challenge. As the current technology has reached its limits in terms of traffic management capability, it is necessary to develop a new operating framework that can effectively respond to the new conditions created by the telecommunications market. The 5th generation of mobile communication networks (5G) aims to solve this exact issue by developing a new operating model. This model, by thoroughly restructuring the way the network operates at all levels, forms a new ecosystem of network infrastructures and functions that enables the provision of high-level services to users, tailored to their particular needs. The fundamental principles and key technologies that govern the operation of a new generation network throughout its entire length were extensively studied in the context of this paper. Starting with the innovations regarding the structure of 5G networks at the architectural level, the analysis extends to a bottom-up approach: from the broadcast and access levels to the network (C-RAN & MAC) to the mechanisms responsible for delivering the network's functions and services (NFV). Then, the new network-based routing and traffic management (SDN) model is introduced, and the technology for providing distinctive services to users (E2E Slicing) is presented. Furthermore, some characteristic indicators and metrics related to the standardization of the network's technologies are presented, as well as all the current developments related to the development of 5G in Europe. Then, the data of the experiment carried out for the purposes of the paper is presented. On the one hand, this data concerns the modeling of an existing network based on the new 5G standards and, on the other hand, the evaluation of its performance based on some scenarios regarding the topology and the amount of data exchanged at any time on the network. The examination of the efficiency parameters focuses on the ability of the ONOS SDN controller to manage the traffic of the data when certain events affecting the original network structure occur. In terms of the results of the measurements being carried out, although the positive impact of the incorporation of new technologies on the performance of mobile communications networks appears to be positive, there are still some individual open issues that need further research by members of the telecommunications community in order for the original vision of the universal operation of all mobile devices under one single umbrella not to be ultimately undermined

Resource Allocation and Service Management in Next Generation 5G Wireless Networks

The accelerated evolution towards next generation networks is expected to dramatically increase mobile data traffic, posing challenging requirements for future radio cellular communications. User connections are multiplying, whilst data hungry content is dominating wireless services putting significant pressure on network's available spectrum. Ensuring energy-efficient and low latency transmissions, while maintaining advanced Quality of Service (QoS) and high standards of user experience are of profound importance in order to address diversifying user prerequisites and ensure superior and sustainable network performance. At the same time, the rise of 5G networks and the Internet of Things (IoT) evolution is transforming wireless infrastructure towards enhanced heterogeneity, multi-tier architectures and standards, as well as new disruptive telecommunication technologies. The above developments require a rethinking of how wireless networks are designed and operate, in conjunction with the need to understand more holistically how users interact with the network and with each other. In this dissertation, we tackle the problem of efficient resource allocation and service management in various network topologies under a user-centric approach. In the direction of ad-hoc and self-organizing networks where the decision making process lies at the user level, we develop a novel and generic enough framework capable of solving a wide array of problems with regards to resource distribution in an adaptable and multi-disciplinary manner. Aiming at maximizing user satisfaction and also achieve high performance - low power resource utilization, the theory of network utility maximization is adopted, with the examined problems being formulated as non-cooperative games. The considered games are solved via the principles of Game Theory and Optimization, while iterative and low complexity algorithms establish their convergence to steady operational outcomes, i.e., Nash Equilibrium points. This thesis consists a meaningful contribution to the current state of the art research in the field of wireless network optimization, by allowing users to control multiple degrees of freedom with regards to their transmission, considering mobile customers and their strategies as the key elements for the amelioration of network's performance, while also adopting novel technologies in the resource management problems. First, multi-variable resource allocation problems are studied for multi-tier architectures with the use of femtocells, addressing the topic of efficient power and/or rate control, while also the topic is examined in Visible Light Communication (VLC) networks under various access technologies. Next, the problem of customized resource pricing is considered as a separate and bounded resource to be optimized under distinct scenarios, which expresses users' willingness to pay instead of being commonly implemented by a central administrator in the form of penalties. The investigation is further expanded by examining the case of service provider selection in competitive telecommunication markets which aim to increase their market share by applying different pricing policies, while the users model the selection process by behaving as learning automata under a Machine Learning framework. Additionally, the problem of resource allocation is examined for heterogeneous services where users are enabled to dynamically pick the modules needed for their transmission based on their preferences, via the concept of Service Bundling. Moreover, in this thesis we examine the correlation of users' energy requirements with their transmission needs, by allowing the adaptive energy harvesting to reflect the consumed power in the subsequent information transmission in Wireless Powered Communication Networks (WPCNs). Furthermore, in this thesis a fresh perspective with respect to resource allocation is provided assuming real life conditions, by modeling user behavior under Prospect Theory. Subjectivity in decisions of users is introduced in situations of high uncertainty in a more pragmatic manner compared to the literature, where they behave as blind utility maximizers. In addition, network spectrum is considered as a fragile resource which might collapse if over-exploited under the principles of the Tragedy of the Commons, allowing hence users to sense risk and redefine their strategies accordingly. The above framework is applied in different cases where users have to select between a safe and a common pool of resources (CPR) i.e., licensed and unlicensed bands, different access technologies, etc., while also the impact of pricing in protecting resource fragility is studied. Additionally, the above resource allocation problems are expanded in Public Safety Networks (PSNs) assisted by Unmanned Aerial Vehicles (UAVs), while also aspects related to network security against malign user behaviors are examined. Finally, all the above problems are thoroughly evaluated and tested via a series of arithmetic simulations with regards to the main characteristics of their operation, as well as against other approaches from the literature. In each case, important performance gains are identified with respect to the overall energy savings and increased spectrum utilization, while also the advantages of the proposed framework are mirrored in the improvement of the satisfaction and the superior Quality of Service of each user within the network. Lastly, the flexibility and scalability of this work allow for interesting applications in other domains related to resource allocation in wireless networks and beyond