Ricerc@Sapienza

The continuous growth of worldwide mobile subscriptions and the progress of mobile devices and telecommunications in the last few years has led to a tremendous increase of demand for high data rates. The scarcity of licensed spectrum and the high costs of this resource have encouraged mobile operators to move towards the unlicensed spectrum. LTE Licensed-Assisted Access is the proposed technology, that allows to work on the 5 GHz unlicensed band. To operate on these frequencies already occupied by Wi-Fi and radar systems, LTE must fairly coexist with the above.

Wireless engineers and business planners commonly raise the question on where, when, and how millimeter-wave (mmWave) will be used in 5G and beyond. Since the next generation network is not just a new radio access standard, but also an integration of networks for vertical markets with diverse applications, answers to the question depend on scenarios and use cases to be deployed. This paper gives four 5G mmWave deployment examples and describes in chronological order the scenarios and use cases of their probable deployment, including expected system architectures and hardware prototypes.

In this paper we propose and investigate an OTN/WDM network architecture for the transport of Ethernet/CPRI flows in 5G scenario. The proposed solution allows for a dynamic bandwidth resource allocation dependent on the current traffic. The network is composed by OTN/WDM rings interconnecting Access Switches and interconnected to an OTN/WDM Hub. We introduce an analytical model for the dimensioning of wavelengths of the optical rings.

The Centralized Radio Access Network (C-RAN) provides a valid solution to overcome the problem of traditional RAN in scaling up to the needed processing resource and quality expected in 5G. The Common Public Rate Interface has been defined to transport traffic flows in C-RAN and recently some market solutions are available. Its disadvantage is to increase by at least 10 times the needed bandwidth and for this reason its introduction will be gradual and will coexist with traditional RAN solutions in which Ethernet traffic is carried towards the radio base stations.

Motivated by recent theoretical challenges for 5G, this study aims to position relevant results in the literature on codedomain non-orthogonal multiple access (NOMA) from an information-theoretic perspective, given that most of the recent intuition of NOMA relies on another domain, that is, the power domain. Theoretical derivations for several code-domain NOMA schemes are reported and interpreted, adopting a unified framework that focuses on the analysis of the NOMA spreading matrix, in terms of load, sparsity, and regularity features.

In the context of massive Machine Type Communication (mMTC), 3GPP has introduced in Release 13 the Narrowband-IoT (NB-IoT) standard, that appears particularly suitable for uplink, delay-Tolerant low-rate communications. On the one hand, being compatible with the existing 4G cellular systems, and also envisioned as a primary player in next 5G, NB-IoT is developed upon the existing heterogeneous architecture, formed by several overlapping tiers (HetNets), e.g. macro and small cells.

5G is the expected next step of the evolution of the mobile cellular net- work, and it is considered as the answer to the ongoing huge increase of cellular users and services. The architecture envisioned for 5G includes a large number of different network entities and systems that share a common spectrum resource via a Dynamic Spectrum Access (DSA) approach.

This paper investigates the advantages and design challenges of leveraging Unmanned Aerial Vehicles (UAVs) to deploy 4G/5G femto- and pico-cells to provide quality-aware user service and improve network performance. In order to do so, we combine UAVs dashing flight capabilities with Software-defined Radios (SDRs) flexibility and devise the concept of self-optimizing UAV Base Stations (UABSs). The proposed framework allows for on-the-fly drone repositioning based on rigorous optimization techniques using real-time network metrics to enhance users' service.