The sixth generation of mobile communication (6G) systems is recently rising a lot of interest, introducing new futuristic and challenging use cases that will demand much more than just communications to become a reality. Higher throughput, lower latencies, higher number of connections will push the requirement of the future mobile networks to a new level, but also sensing, positioning and imaging will play an important role in the new foreseen use cases. The integration of techniques developed for wireless communications with those conceived for optical links will be essential to provide the infrastructure for the 6G networks. In this context, this paper presents a review on wireless and optical convergent access solutions towards the 6G systems. The manuscript brings the use cases, requirements and enablers for 6G networks including a discussion about the state-of-the-art on THz and sub-THz communications, wireless and optical convergence, visible light communication, integrated and free-space optics, new antenna designs, power-over-fiber deployments and the use of machine learning in the physical layer of future networks. By reviewing the most relevant contributions available in the literature for wireless and optical communications and presenting their main contributions, this paper clearly shows that, more than a technological trend, the convergence of wireless and optical technologies is a fundamental step towards the development of the 6G network infrastructure.

This letter reports the concept and development of the first optically controlled reconfigurable antenna for millimeter-wave (mm-wave) applications. It is based on a slotted-waveguide antenna array and two photoconductive switches, which are used to control the slot electrical length. This novel photonics-based reconfigurable strategy enables frequency tunability and radiation pattern reconfiguration through the 28- and 38-GHz frequency bands. Numerical simulations and experimental results illustrate its applicability for mm-wave indoor applications. The measured gain is approximately 8.0 and 9.0 dBi at 28 and 38 GHz, respectively.

The fifth-generation of mobile networks (5G) claims for a radio access network (RAN) update in order to support the enormous incoming wireless data traffic. In this context, we experimentally evaluate two distinct hybrid architectures applied to 5G New Radio (NR) FiWi systems based on different optical fronthaul approaches. The first architecture operates in non- standalone (NSA) mode, defined by the 3rd Generation Partnership Project (3GPP), for simultaneously transmitting 4G and 5G technologies through a unique FiWi system. The three considered waveforms are as follows: a filtered orthogonal frequency division multiplexing (F-OFDM) signal at 778 MHz with 10 MHz bandwidth from our 5G flexible-waveform transceiver; a Long- Term Evolution-Advanced (LTE-A) signal with five 20 MHz sub-bands centralized at 2.24 GHz; a 5G NR signal at 2.35 GHz with 100 MHz bandwidth. On the other side, the second architecture employs radio over fiber (RoF), free space optics (FSO) and wireless technologies converged into a heterogeneous network (HetNet). The additional multi-standard and multiband optical- wireless network is based on a 10-MHz bandwidth F-OFDM signal at 788 MHz, a 100-MHz bandwidth 5G NR signal at 3.5 GHz and a 400-MHz bandwidth M-QAM signal at 26 GHz. Throughput up to 3 and 1.4 Gbps are demonstrated for RoF/FSO and RoF/FSO/Wireless transmission, respectively.

This paper reports the integration and experimental performance analysis of a GFDM-based 5G transceiver in a gigabit passive optical network (GPON), using radio over fiber technology. The proposed architecture enables to simultaneously transport two 5G candidates RF signals through an active GPON under real channel conditions. One signal is generated by a GFDMbased 5G prototype transceiver at 735 MHz, whereas the second one is synthetized by a vector signal generator at 26 GHz. A dualdrive Mach-Zehnder modulator has been utilized in the optical line terminal to modulate both signals, with the purpose of mitigating the interference between them. Particularly for the GFDM-based 735 MHz signal, a modulation error ratio (MER) of 40 dB has been obtained at RF-driven signal up to -9 dBm. Furthermore, the use of a digital predistortion scheme has been efficiently employed to reduce the impact of the nonlinear distortions and enhance MER. The 26-GHz RF signal, aimed for the 5G millimeter wave band, has been investigated as a function of error vector magnitude (EVM) for bitrates up to 1 Gbit/s. EVMRMS of 2.18% and 5.70% have been obtained for 100 Mbit/s and 1 Gbit/s, respectively. Finally, the latency and throughput measurements of the baseband signal originally running over GPON have shown no significant penalties.

The appeal for more reliable, efficient and resilient power grids has become indispensable with the recent technological development and ever-increasing demand for electrical energy. These goals might be achieved by introducing sensors and actuators in the power grid, with the purpose of enabling a smart control of the power network. All power devices must be connected using a reliable communication network, which should be able to operate even when the power grid fails. Currently, several communication technologies have been applied for supporting this new application scenario. This paper aims for reviewing both academic and market use cases for technologies applied to the mission-critical, control networks and Smart Grid applications, such as teleprotection, self-healing, communication with control centers and field devices, among others. More specifically, the key aspects, potential technologies, main protocols and use cases of operating data networks in energy transmission, power distribution and smart grid environments, including circuit and packet switching technologies, are discussed into details. Furthermore, resilience and the main telecommunications technologies used in power grids, as well, the correlation among them, are exploited in practical point of view. The article provides a broad discussion on the best telecommunication options to build the emerging intelligent energy distribution systems, covering control networks, teleprotection, and smart grid applications.

The Internet of Things (IoT) and its current Internet engineering task force and IEEE dual stack model have been facing limitations, requiring applications to overcome tough constraints by their own, narrowing the full potential of this concept. For instance, the IoT dual stack model does not entirely address or support perennial naming, immutable data provenance, data accountability, mobility support, and services’ self-organization. On the other hand, future Internet architecture (FIA) research emerges as a viable candidate to compensate these gaps through evolutionary and revolutionary efforts. Regardless of the FIA proposal model, this field lacks a suitable environment that enables the performance experimentation and evaluation of distinct protocols and architectures fairly and transparently. This article proposes a novel IoT experimentation and evaluation environment based on a low-cost and open-source solution. The proposed environment integrates technologies of containers, IoT nodes emulation, and network simulation to evaluate the current IoT dual stack and a promising FIA approach called eXpressive Internet architecture. Moreover, this work combines the mentioned disjointed technologies, exploiting Docker containers, Contiki open-source operational system for IoT, and Cooja the IoT network simulator. In this way, it addresses the objective of fostering an honest experimentation and evaluation environment for FIAs. Experimental results demonstrate the feasibility and effectiveness of this approach, broadening this field and sowing a path to work with other FIAs.