Toward End-to-End, Full-Stack 6G Terahertz Networks

Recent evolutions in semiconductors have brought the terahertz band in the spotlight as an enabler for terabit-per-second communications in 6G networks. Most of the research so far, however, has focused on understanding the physics of terahertz devices, circuitry and propagation, and on studying physical layer solutions. However, integrating this technology in complex mobile networks requires a proper design of the full communication stack, to address link- and system-level challenges related to network setup, management, coordination, energy efficiency, and end-to-end connectivity. This paper provides an overview of the issues that need to be overcome to introduce the terahertz spectrum in mobile networks, from a MAC, network and transport layer perspective, with considerations on the performance of end-to-end data flows on terahertz connections.Comment: Published on IEEE Communications Magazine, THz Communications: A Catalyst for the Wireless Future, 7 pages, 6 figure

Implementation of Reference Public Safety Scenarios in ns-3

During incidents and disasters it is fundamental to provide to first responders high performance and reliable communications, in order to improve their coordination capabilities and their awareness of the surrounding environment, and to allow them to promptly transmit and receive alerts on possible dangerous situations or emergencies. The accurate evaluation of the performance of different Public Safety Communication (PSC) networking and communications technologies is therefore of paramount importance, and the characterization of the scenario in which these technologies need to operate is fundamental to obtain meaningful results. In this paper, we present the implementation of three reference PSC scenarios, which are open source and made publicly available to the research community, describing the incidents, the mobility and applications of first responders, and providing examples on how a mmWave-based Radio Access Network (RAN) can support high-traffic use cases. Moreover, we present the implementation of two novel mobility models for ns-3, which can be used to enable the simulation of realistic PSC scenarios in ns-3.Comment: 8 pages, 9 figures, submitted to WNS3 201

Convergence of millimeter-wave and photonic interconnect systems for very-high-throughput digital communication applications

In the past, radio-frequency signals were commonly used for low-speed wireless electronic systems, and optical signals were used for multi-gigabit wired communication systems. However, as the emergence of new millimeter-wave technology introduces multi-gigabit transmission over a wireless radio-frequency channel, the borderline between radio-frequency and optical systems becomes blurred. As a result, there come ample opportunities to design and develop next-generation broadband systems to combine the advantages of these two technologies to overcome inherent limitations of various broadband end-to-end interconnect systems in signal generation, recovery, synchronization, and so on. For the transmission distances of a few centimeters to thousands of kilometers, the convergence of radio-frequency electronics and optics to build radio-over-fiber systems ushers in a new era of research for the upcoming very-high-throughput broadband services. Radio-over-fiber systems are believed to be the most promising solution to the backhaul transmission of the millimeter-wave wireless access networks, especially for the license-free, very-high-throughput 60-GHz band. Adopting radio-over-fiber systems in access or in-building networks can greatly extend the 60-GHz signal reach by using ultra-low loss optical fibers. However, such high frequency is difficult to generate in a straightforward way. In this dissertation, the novel techniques of homodyne and heterodyne optical-carrier suppressions for radio-over-fiber systems are investigated and various system architectures are designed to overcome these limitations of 60-GHz wireless access networks, bringing the popularization of multi-gigabit wireless networks to become closer to the reality. In addition to the advantages for the access networks, extremely high spectral efficiency, which is the most important parameter for long-haul networks, can be achieved by radio-over-fiber signal generation. As a result, the transmission performance of spectrally efficient radio-over-fiber signaling, including orthogonal frequency division multiplexing and orthogonal wavelength division multiplexing, is broadly and deeply investigated. On the other hand, radio-over-fiber is also used for the frequency synchronization that can resolve the performance limitation of wireless interconnect systems. A novel wireless interconnects assisted by radio-over-fiber subsystems is proposed in this dissertation. In conclusion, multiple advantageous facets of radio-over-fiber systems can be found in various levels of end-to-end interconnect systems. The rapid development of radio-over-fiber systems will quickly change the conventional appearance of modern communications.PhDCommittee Chair: Gee-Kung Chang; Committee Member: Bernard Kippelen; Committee Member: Shyh-Chiang Shen; Committee Member: Thomas K. Gaylord; Committee Member: Umakishore Ramachandra

Non-Terrestrial Networks in the 6G Era: Challenges and Opportunities

Many organizations recognize non-terrestrial networks (NTNs) as a key component to provide cost-effective and high-capacity connectivity in future 6th generation (6G) wireless networks. Despite this premise, there are still many questions to be answered for proper network design, including those associated to latency and coverage constraints. In this paper, after reviewing research activities on NTNs, we present the characteristics and enabling technologies of NTNs in the 6G landscape and shed light on the challenges in the field that are still open for future research. As a case study, we evaluate the performance of an NTN scenario in which satellites use millimeter wave (mmWave) frequencies to provide access connectivity to on-the-ground mobile terminals as a function of different networking configurations.Comment: 8 pages, 4 figures, 2 tables, submitted for publication to the IEE

Interface Selection in 5G vehicular networks

ITA Negli ultimi anni, la quantità di dati condivisa nel mondo è aumentata esponenzialmente grazie alle applicazioni innovative che riguardano la sicurezza (e.g. domotica, smart cities, controllo del traffico stradale, veicoli autonomi) e i servizi di intrattenimento (e.g. audio e video streaming, ricerche web, videogiochi online di massa). Per supportare questo trend, le principali compagnie nell’industria delle telecomunicazioni stanno sviluppando nuovi standard che saranno disponibili agli utenti finali nei prossimi anni e che saranno presentati come la Quinta Generazione di Reti Cellulari (5G). Questi standard prevedono miglioramenti ai precedenti standard 4G (e.g. LTE, WiMax, DSRC) e tecnologie completamente nuove (e.g. onde millimetriche, comunicazione con luce visibile) per permettere la diffusione di nuovi servizi che richiedono un throughput estremamente alto e una latency bassa. Nella maggior parte dei casi, queste tecnologie dovranno cooperare per assicurare una rete affidabile e accessibile in ogni situazione. Una delle applicazioni più promettenti di questa nuova generazione di tecnologie sono le reti veicolari, un insieme di servizi che includono la comunicazione con le infrastrutture, come il download di un film da Internet o la ricezione di informazioni riguardanti l’ambiente circostante (e.g. un semaforo manda un messaggio a un veicolo in avvicinamento per farlo fermare), o la comunicazione direttamente tra veicoli, in questo caso il datarate è tipicamente più basso dato che l’uso più tipico sarà, per esempio, mandare informazioni riguardanti le macchine più vicine per fare in modo di diminuore il numero di incidenti stradali o gestire il traffico. Questa tesi è focalizzata sulle applicazioni per reti veicolari, l’obiettivo è di analizzare le prestazioni del protocollo IEEE 802.11p a diversi datarate in un tipico scenario V2V, e di confrontare LTE e mmWaves usando una comunicazione V2I in diverse circostanze, per mostrare come ogni tecnologia offra vantaggi per determinate applicazioni mentre non è adatta per altre. ENG In the last years, the amount of data shared among the world is increased exponentially thanks to the novel applications for security (e.g. home automation, smart cities, traffic control, autonomous vehicles) and infotainment (e.g. audio and video streaming, web browsing, massive online videogames). To support this trend, the major companies in the telecommunication industry are developing new standards that will be available to the final users in the next years and that will be presented as the Fifth Generation of Cellular Networks (5G). These standards provide improvements to the 4G standards (e.g. LTE, WiMax, DSRC) and brand new technologies (e.g. mmWaves, Visible Light Communication) to enable new services that demand extremely high throughput and low latency. In most cases these technologies will cooperate to ensure a reliable and accessible network in every situation. One of the most promising applications of these new generation technologies is vehicular networks, a set of services that includes the communication with infrastructures, such as the download of a film from the Internet or the reception of information about the surrounding environment (e.g. a traffic light sends a message to an incoming vehicle to make it stop), or the communication between vehicles, in this case the datarate is tipically lower since the typical use will be, for example, to send information about the closest cars in order to decrease the number of accidents or to manage the traffic. This thesis is focalized on the vehicular networks applications, it aims to analyze the performance of IEEE 802.11p protocol at different datarates in a typical V2V scenario, and to compare LTE and mmWaves using a V2I communication in different circumstances to show how each technology offers advantages for some applications while is not suitable for others

Integrated Access and Backhaul for 5G and Beyond (6G)

Enabling network densification to support coverage-limited millimeter wave (mmWave) frequencies is one of the main requirements for 5G and beyond. It is challenging to connect a high number of base stations (BSs) to the core network via a transport network. Although fiber provides high-rate reliable backhaul links, it requires a noteworthy investment for trenching and installation, and could also take a considerable deployment time. Wireless backhaul, on the other hand, enables fast installation and flexibility, at the cost of data rate and sensitivity to environmental effects. For these reasons, fiber and wireless backhaul have been the dominant backhaul technologies for decades. Integrated access and backhaul (IAB), where along with celluar access services a part of the spectrum available is used to backhaul, is a promising wireless solution for backhauling in 5G and beyond. To this end, in this thesis we evaluate, analyze and optimize IAB networks from various perspectives. Specifically, we analyze IAB networks and develop effective algorithms to improve service coverage probability. In contrast to fiber-connected setups, an IAB network may be affected by, e.g., blockage, tree foliage, and rain loss. Thus, a variety of aspects such as the effects of tree foliage, rain loss, and blocking are evaluated and the network performance when part of the network being non-IAB backhauled is analysed. Furthermore, we evaluate the effect of deployment optimization on the performance of IAB networks.First, in Paper A, we introduce and analyze IAB as an enabler for network densification. Then, we study the IAB network from different aspects of mmWave-based communications: We study the network performance for both urban and rural areas considering the impacts of blockage, tree foliage, and rain. Furthermore, performance comparisons are made between IAB and networks of which all or part of small BSs are fiber-connected. Following the analysis, it is observed that IAB may be a good backhauling solution with high flexibility and low time-to-market. The second part of the thesis focuses on improving the service coverage probability by carrying out topology optimization in IAB networks focusing on mmWave communication for different parameters, such as blockage, tree foliage, and antenna gain. In Paper B, we study topology optimization and routing in IAB networks in different perspectives. Thereby, we design efficient Genetic algorithm (GA)-based methods for IAB node distribution and non-IAB backhaul link placement. Furthermore, we study the effect of routing in the cases with temporal blockages. Finally, we briefly study the recent standardization developments, i.e., 3GPP Rel-16 as well as the\ua0Rel-17 discussions on routing. As the results show, with a proper planning on network deployment, IAB is an attractive solution to densify the networks for 5G and beyond. Finally, we focus on improving the performance of IAB networks with constrained deployment optimization. In Paper C, we consider various IAB network models while presenting different algorithms for constrained deployment optimization. Here, the constraints are coming from either inter-IAB distance limitations or geographical restrictions. As we show, proper network planning can considerably improve service coverage probability of IAB networks with deployment constraints

On Integrated Access and Backhaul Networks: Current Status and Potentials

In this paper, we introduce and study the potentials and challenges of integrated access and backhaul (IAB) as one of the promising techniques for evolving 5G networks. We study IAB networks from different perspectives. We summarize the recent Rel-16 as well as the upcoming Rel-17 3GPP discussions on IAB, and highlight the main IAB-specific agreements on different protocol layers. Also, concentrating on millimeter wave-based communications, we evaluate the performance of IAB networks in both dense and suburban areas. Using a finite stochastic geometry model, with random distributions of IAB nodes as well as user equipments (UEs) in a finite region, we study the service coverage rate defined as the probability of the event that the UEs' minimum rate requirements are satisfied. We present comparisons between IAB and hybrid IAB/fiber-backhauled networks where a part or all of the small base stations are fiber-connected. Finally, we study the robustness of IAB networks to weather and various deployment conditions and verify their effects, such as blockage, tree foliage, rain as well as antenna height/gain on the coverage rate of IAB setups, as the key differences between the fiber-connected and IAB networks. As we show, IAB is an attractive approach to enable the network densification required by 5G and beyond.Comment: Revised manuscript in IEEE Open Journal of the Communications Societ