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The next generation of mobile networks, namely 5G, promises significant qualitative and quantitative advances for multiple vertical domains. However, most studies and investigations assess these advances under the implicit assumption of a single network service provider, with typical national coverage. In this article, we take a close look at the automotive sector and highlight a series of challenges emerging in the context of its inherent (inter)national mobility and the corresponding importance of cross-border and/or multioperator environments. Our target is to pinpoint the key influential factors affecting the transition toward seamless (cooperative) connected and automated mobility services within and across national borders. To this end, we identify and analyze a series of challenges in the areas of, networking, application, security, and regulation. We further present and discuss a series of corresponding solutions investigated in the pragmatic context of our experimental activities.

This research argues that using an electron beam with high kinetic energy to pump perovskite quantum dots can significantly boost the efficiency of the low-frequency photon radiation conversion. Firstly, we measure the random lasing threshold and luminescence threshold of CsPbX 3 films pumped by an electron beam. Then, we simulate the spatial distribution of the electron beams in CsPbX 3 films. Combined with the above data, a low-frequency photon radiation conversion model based on the electron pumped perovskite quantum dots is presented. This could be a way to create a terahertz source with a high-power output or to multiply the terahertz power.

Antenna-coupled photomixers, serving as emitters and receivers of terahertz (THz) radiation, are the central active components of coherent optoelectronic THz systems. Here, we focus on the continuous-wave modality, which finds ample use for spectroscopy, sensing, and ranging and plays a major role in upcoming ultrahigh-frequency telecommunication applications. We demonstrate with planar receivers based on low-temperature-grown GaAs that the use of interdigital graphene electrodes instead of metal fingers enhances the responsivity by more than one order of magnitude. The increase in responsivity leads to a strongly enlarged dynamic range and doubles the frequency range covered in the detection process. We show by simulations that these improvements are a consequence of the transparency of the finger electrodes for visible/near-infrared laser radiation, which also activates the area under the fingers for the mixing process, not only their edges as in conventional devices with metal electrodes.

The use of millimeter-wave (mm-wave) frequencies is required in order to support the increasing number of connected devices expected from the fifth generation (5G) of mobile communications. Subsequently, the generation of radio-frequency (RF) carriers ranging from 10 GHz to 300 GHz and their transport through optical distribution network (ODN) is a key element of the future 5G fronthaul. Optically assisted RF carrier generation is one of the most promising solutions to tackle this issue, allowing a wide use of analog radio-over-fiber (ARoF) architectures. However the main limitation of these optical methods is related to the finite coherence of lasers sources, which can dramatically degrade data transmission in analog formats. To mitigate its impact, the use of orthogonal frequency-division multiplexing (OFDM) as the 5G standard allows employing efficient phase noise compensation algorithms. Therefore, in this study, we present an experimental demonstration of a mm-wave generation technique based on an optical phase-locked loop (OPLL) that fulfills the frequency specifications for 5G. Then, an algorithm is introduced that improves data recovery at reception and reduces the impact of a possible high phase noise carrier. Finally, a back-to-back data transmission experiment is performed, demonstrating the efficiency of the algorithm to reach the 5G requirements. These results emphasize the use of OPLLs as a viable solution to generate mm-wave carriers for 5G and beyond.

Three convergent processes are likely to shape the future of the internet beyond-5G: the convergence of optical and millimeter wave (mmWave) radio networks to boost mobile internet capacity, the convergence of machine learning solutions and communication technologies, and the convergence of virtualized and programmable network management mechanisms towards fully integrated autonomic network resource management. Aiming to enhance the joint optical and radio transport, this thesis provides game theory-based distributed network control capability to optimize resource allocation in the C-RAN and fronthaul segments of converged wireless and optical networks. In addition, an external stakeholders vs. network game is designed to extend distributed decision-making to service providers and network users. Autonomic network resource management concept brings dynamic network reconfiguration with learning and predicting the behavior of network entities. On the other hand, game theory-based resource management is studied for rational, autonomous and distributed decision-making among entities, as centralized optimization is challenging in a multi-stakeholder network environment. The focus is placed on these two approaches to design resource allocation solutions inside a distributed and autonomous management framework perspective. Autonomic networking requires control loops to monitor the network status and adapt network management by making use of observations from the monitoring stage. After presenting the challenges of autonomic networking, a management framework with monitoring and measurement, analysis and decision-making, and learning stages is introduced. In such a framework, game theoretic models are promising solutions to define the interactions between network stakeholders and to handle network management operations. This framework sets the foundation for the resource management contributions. In light of the presented autonomic network management perspective, a systematic literature review is carried out as an initial step to the resource management contributions. The review is done to analyze how resource management solutions have dealt with optimizing millimeter wave radio and optical resources, understand the dimensions of the relationship between resource allocation methods and mmWave 5G and FiWi fronthaul, and identify the current trends in resource allocation. The results of this review is used to decide on the performance metrics and the evaluation criteria in the games designed in this dissertation for distributed decision-making. Based on the outcomes of the review, two experiments are designed to enhance control capabilities of the network. The first experiment creates the control interaction between fronthaul and access, whereas the second experiment regulates the interaction between service providers and the transport network represented by the infrastructure provider. For joint access and fronthaul optimization, access — fronthaul interaction is defined as a coalition game for aggregate demand on the access side. By observing this demand, the transport network is able to distribute the available resources or reject the offer if it exceeds the total available bandwidth. When the offer is rejected, a bankruptcy game is used to distribute fronthaul resources to RRHs. On the access side, RRH utilization is improved by cooperative resource sharing. Different user distributions and service requirements bring dynamicity to the network demands. The target is to provide a game model that achieves dynamic bandwidth allocation with no fixed commitment of fronthaul resources and adapting to dynamic user load. Infrastructure sharing is made possible with the help of virtualization technologies, and this fact transformed the network architecture into a novel stakeholder called the infrastructure provider. Even though profit generation was always a factor in performance optimization for network operators, the shift in the architecture with network virtualization makes dynamic revenue gains an apparent performance criteria for resource allocation. The second experiment considers virtualized optical network resources from this profit generation perspective with a game, in which providers bid to share the optical transport network and the infrastructure provider applies a Vickery – Clarke – Groves (VCG) auctioning mechanism to provide a social-welfare maximizing outcome, while users have the switching option between service providers for user utility maximization. The outcomes of user decision-making with blind search and guided search algorithms are also presented for this switching option. The ultimate objective of this thesis is to provide a realistic guideline to optimize mmWave transport and radio resource use so that mmWave network implementations can be deployed in a cost-efficient manner. The presented experiments and results contribute to understanding how autonomous and distributed decision-making can improve network resource management and how network solutions for capacity enhancement can be exploited in an optimal way with game-theoretical algorithms., Drei zusammenlaufende Prozesse werden die Zukunft des Internets jenseits von 5G gestalten: Die Annäherung von optischen und millimeterwellen Funknetzen, um die Kapazität des mobilen Internets zu erhöhen, die Annäherung von maschinellem Lernen und Kommunikationstechnologien sowie die Annäherung der virtualisierten und programmierbaren Netzverwaltung für eine vollständig integrierte autonome Verwaltung der Netzressourcen. Mit dem Ziel, den integrierten optischen und funktechnischen Transport zu verbessern, bietet diese Arbeit eine auf der Spieltheorie basierende verteilte Netzwerksteuerung zur Optimierung der Ressourcenzuweisung in den C-RAN- und Fronthaul-Segmenten drahtloser und optischer Netzwerke. Darüber hinaus wird ein Spiel zwischen externen Akteuren und dem Netzwerk entwickelt, um die verteilte Entscheidungsverfahren auf Dienstanbieter und Netzwerknutzer auszuweiten. Das Konzept der autonomen Verwaltung der Netzwerkressourcen ermöglicht eine dynamische Umgestaltung des Netzwerks durch Lernen und Vorhersage des Netzwerkzustands. Außerdem bietet das auf der Spieltheorie basierende Ressourcenmanagement die Möglichkeit eines rationalen, autonomen und verteilten Entscheidungsverfahrens zwischen den Akteuren, um die Herausforderung der zentralisierten Optimierung mit mehreren Akteuren zu überwinden. Der Schwerpunkt der Dissertation liegt auf diesen beiden Konzepten, um Lösungen für die Zuweisung der Ressourcen innerhalb eines verteilten und autonomen Managementrahmens zu entwickeln. Autonome Netzwerke erfordern Regelkreise zur Überwachung des Netzwerkstatus und zur Anpassung des Netzwerkmanagements unter Verwendung der Überwachungsdaten. Nach der Darstellung der Herausforderungen der autonomen Vernetzung wird ein Verwaltungsrahmen mit Überwachung und Messung, Analyse, und Lernphasen vorgestellt. Die spieltheoretischen Modelle sind vielversprechende Lösungen in diesem Rahmen, um die Interaktionen zwischen den Akteuren des Netzes zu definieren und die Operationen der Netzverwaltung zu steuern. Angesichts der vorgestellten Perspektive des autonomen Netzwerkmanagements wird eine systematische Literaturanalyse durchgeführt. Dabei wird analysiert, wie Ressourcenmanagementlösungen mit der Optimierung von mmWave funk- und optischen Ressourcen umgegangen sind, werden die Ressourcenzuweisungsmethoden von den mmWave C-RAN- und Fronthaul verstanden und die aktuellen Trends in der Ressourcenzuweisung identifiziert. Die Ergebnisse dieser Analyse werden genutzt, um die Leistungs- und Bewertungskriterien für die Spiele zu verteilten Entscheidungsverfahren in dieser Dissertation zu definieren. Basierend auf den Ergebnissen der Analyse werden zwei Experimente entwickelt, um die Steuerungsmöglichkeiten des Netzes zu verbessern. Das erste Experiment schafft die Steuerungsinteraktion zwischen Fronthaul- und Funknetz, während das zweite Experiment die Interaktion zwischen Dienstanbietern und den Infrastrukturanbieter regelt. Für die gemeinsame Optimierung von Funknetz und Fronthaul wird die Interaktion zwischen den beiden als ein Koalitionsspiel definiert. Durch Beobachtung der Funknetzanforderung kann das Transportnetz die verfügbaren Ressourcen verteilen oder Anfragen ablehnen, wenn die gesamte verfügbare Bandbreite überstiegen wird. Wird die Anfrage abgelehnt, werden die Fronthaul-Ressourcen mit Hilfe eines Bankruptcy Game an die RRHs verteilt. Unterschiedliche Nutzerverteilungen und Dienstanforderungen bringen eine dynamische Entwicklung der Netzanforderungen. Ziel ist es, ein Spielmodell bereitzustellen, das eine dynamische Bandbreitenzuweisung ohne feste Bindung von Fronthaul-Ressourcen erreicht und sich an die dynamische Nutzerlast anpasst. Die gemeinsame Nutzung von Infrastrukturen wird mit Hilfe von Virtualisierungstechnologien ermöglicht, und diese Tatsache hat der Netzarchitektur einen neuen Akteur, den Infrastrukturanbieter, hinzugefügt. Obwohl die Gewinnerzielung schon immer ein Faktor bei der Leistungsoptimierung von Netzbetreibern war, macht die Architekturveränderung mit der Virtualisierung dynamische Umsätze zu einem Leistungskriterium für die Ressourcenzuweisung. Das zweite Experiment betrachtet die Ressourcen des virtualisierten Netzwerks aus der Perspektive der Gewinnerzielung mit einem Spiel, bei dem die Diensteanbieter ihre Gebote für die gemeinsame Nutzung des optischen Transportnetzwerks abgeben. Der Infrastrukturanbieter wendet einen Vickery-Clarke-Groves (VCG)-Auktionsmechanismus an, um ein die soziale Wohlfahrt maximierendes Ergebnis zu erzielen. Außerdem haben die Nutzer die Möglichkeit, zwischen den Diensteanbietern zu wechseln, um ihren Nutzen zu maximieren. Die Ergebnisse der Entscheidungsverfahren der Nutzer mit blinder Suche und geführten Suchalgorithmen werden ebenfalls für diese Wechseloption vorgestellt. Das Hauptziel dieser Dissertation ist es, ein realistisches Framework zur Optimierung der Vergabe von mmWave-Funkressourcen zu erstellen, damit mmWave-Netzwerke kostengünstig implementiert werden können. Die vorgestellten Experimente und Ergebnisse tragen dazu bei, zu verstehen, wie autonome und verteilte Entscheidungsverfahren die Verwaltung von Netzressourcen verbessern können und wie Netzlösungen zur Kapazitätserweiterung mit spieltheoretischen Algorithmen optimal genutzt werden können.

Although we don’t know exactly how 6G networks will look like beyond 2030, we may assume that we will most likely communicate using holograms, digital twins, and that the merge of real and virtual reality had happen in an hyper-reality internet. Such new ways of communications will demand large capacity and ultra-low latency with increased demands for quantum safe data transmission and storage. Developing such technologies such as Terahertz frequency, terabit data wireless links, seems a futuristic endeavor. This paper considers the role of photonics in tackling the challenge to realize systems to generate, detect, multiplex and process terabit volumes of data in 6G systems and networks.

With a fully functional point-to-point quantum key distribution link, we demonstrate secret key retrieval by a pair of encryptors and investigate how their addition impacts key network performance indicators on a 10 Gbit/s data channel.

Fifth-generation mobile networks (5G) is the established solution to satisfy the highly demanding key performance indicators such as traffic volumes, bit-rate, latency, and power consumption, among others of the future telecommunication infrastructure. The already saturated sub-6 GHz spectral band does not accommodate such requirements and forces the move towards higher frequencies, with the millimeter-wave (mm-wave) domain being an adequate band to operate. However, the exploitation of mm-wave signals in the mobile cells implies the deployment of an enormous quantity of small cells with associated equipment, footprint, and control. Thus, analog radio-over-fiber (ARoF) emerges as a suitable technology because of their attractive benefits such as low latency, low hardware complexity, and reduced power consumption. However, through investigation of experimental ARoF systems adhering to the 5G standard is scarce. Therefore, in this work, a novel and efficient bidirectional ARoF scheme based on multicore fiber (MCF) and oriented to 5G mm-wave communications is proposed and experimentally validated. The setup configurations are according to the 5G standard, enabling a wireless link at 26 GHz (n258, K-band) and time division duplex (TDD) communication. The proposed scheme is thoroughly evaluated under all the 5G numerologies and with different bandwidth settings. Moreover, key design considerations of the experimental testbed are explained and discussed to optimize the final yields of the system. The experimental results of both transmission directions are compared and analyzed, and prove the viability of the proposed bidirectional ARoF system as an excellent solution to be part of the future 5G mm-wave network.

The network slicing concept divides physical networks into logical networks and abstracts the network resources. With the help of virtualization technologies, these abstracted network resources can be allocated to service providers and resources can dynamically be added to these slices based on users' demands. The infrastructure sharing model with slicing makes it possible for services to lease the resources of the infrastructure provider. This study considers optical network resource allocation from a profit generation perspective with a game, in which service providers bid to lease C-RAN fronthaul paths via auctioning with Vickrey-Clarke-Groves outcomes. The game aims to distribute fronthaul resources with a social-welfare maximizing outcome. Service providers maximize their revenue by predicting user demand and requesting bandwidth resources from the infrastructure provider by bidding in the auction. Users have the option to change their association and switch between the service providers to maximize their utility. The results display that a balanced profit and social welfare trade-off can be achieved in converged optical and mmWave radio networks infrastructure sharing scenario with Vickrey-Dutch auctioning and distributed decision-making.

The generation and transmission of millimeter-wave signals for 5G applications require the use of broadband and high output power photodetectors to bridge from the optical and electronic domains. Therefore, the deep knowledge on the equivalent circuit characteristics of these devices is vital. This study reviews and analyzes de-embedding techniques contributing to the characterization of the physical aspects within the active region of uni-traveling carrier photodiodes. De-embedding methods analytically remove the parasitic effects of the electrical transmission lines connected to their active area allowing the extraction of their series resistance and junction capacitance toward the synthesis of an equivalent circuit with lumped elements. The open-short technique is examined and a systematic error introduced by this process underlines the vulnerability of the method on removing parasitics with higher complexity. This error is quantified leading to the implementation of a corrected equation converging with the characteristic features of an $S$-parameter-based de-embedding. These characteristics are also analyzed through simulation approaches showing minimal equivalent inaccuracies on eliminating more complex symmetrical parasitics. A thorough comparison between these three methods is conducted through the calculation of lumped components corresponding to the active region of diodes with different sizes.

A combined non-orthogonal multiple access (NOMA) and multiband carrierless amplitude and phase modulation (multiCAP) scheme is proposed for flexible resource provisioning in coherent passive optical networks (PONs). While the proposed combination increases the data-rate and the number of users through the inclusion of NOMA and multiCAP, the coherent reception increases the range and splitting factor of the network through optical power budget enhancement. The proposed system is experimentally evaluated providing a 20 Gb/s aggregated data-rate per wavelength with 10G optoelectronics and applied in two main PON scenarios with four spectral configurations from full-band CAP to four-band multiCAP. The first PON scenario consists of an existing PON that the network operator requires to increase the number of users; NOMA with full-band CAP or multiCAP can be introduced replacing one or more users of the existing PON by one or several new sub-networks and multiplexing the sub-networks by NOMA. In the other PON scenario, several PONs can be nested sharing an initial splitter and achieving a larger number of users by the combination of NOMA and multiCAP. The proposed techniques are fully compatible with other multiplexing techniques such as dense wavelength division multiplexing, which should be considered to achieve higher numbers of users. Gobierno de Aragón (T20_20R); Ministerio de Economía y Competitividad (TEC2017-85752-R, TEC2017-90034-C2-2-R); Electronic Components and Systems for European Leadership (H2020/ECSEL BRAINE - 876967).

This article presents the experimental demonstration of a fully photonics-based heterodyne subterahertz (sub-THz) system for wireless communications. A p-i-n photodiode is used as a broadband transmitter to upconvert the signal to the sub-THz domain and a photoconductive antenna downconverts the received wave to an intermediate frequency around 3.7 GHz. The optical signals used for photomixing are extracted from two independent optical frequency combs with different repetition rates. The optical phase locking reduces the phase noise of the sub-THz signal, greatly improving the performance of the system when phase modulation formats are transmitted. The sub-THz carrier is tuned between 80 and 320 GHz in 40-GHz steps, showing a power variation of 21.8 dB. The phase noise at both ends of the communication link is analyzed and compared with the phase noise of the received signal with different wireless carriers. As a proof-of-concept, a 100-Mbit/s binary-phase-shift-keying signal is successfully transmitted over 80-, 120-, and 160-GHz carriers, achieving a bit error rate below 10 −5 in the first two cases. These results show the great potential of THz communications driven by photonics to cover an extensive portion of the THz range without relying on electronic components that limit the operating range of the system to a concrete frequency band.

[EN] The sixth generation (6G) mobile systems will create new markets, services, and industries making possible a plethora of new opportunities and solutions. Commercially successful rollouts will involve scaling enabling technologies, such as cloud radio access networks, virtualization, and artificial intelligence. This paper addresses the principal technologies in the transition towards next generation mobile networks. The convergence of 6G key-performance indicators along with evaluation methodologies and use cases are also addressed. Free-space optics, Terahertz systems, photonic integrated circuits, softwarization, massive multiple-input multiple-output signaling, and multi-core fibers, are among the technologies identified and discussed. Finally, some of these technologies are showcased in an experimental demonstration of a mobile fronthaul system based on millimeter 5G NR OFDM signaling compliant with 3GPP Rel. 15. The signals are generated by a bespoke 5G baseband unit and transmitted through both a 10 km prototype multi-core fiber and 4 m wireless V-band link using a pair of directional 60 GHz antennas with 10 degrees beamwidth. Results shown that the 5G and beyond fronthaul system can successfully transmit signals with both wide bandwidth (up to 800 MHz) and fully centralized signal processing. As a result, this system can support large capacity and accommodate several simultaneous users as a key candidate for next generation mobile networks. Thus, these technologies will be needed for fully integrated, heterogeneous solutions to benefit from hardware commoditization and softwarization. They will ensure the ultimate user experience, while also anticipating the quality-of-service demands that future applications and services will put on 6G networks., This work was partially funded by the blueSPACE and 5G-PHOS 5G-PPP phase 2 projects, which have received funding from the European Union's Horizon 2020 programme under Grant Agreements Number 762055 and 761989. D. PerezGalacho acknowledges the funding of the Spanish Science Ministry through the Juan de la Cierva programme.

Despite the large range of promising applications for Terahertz technology, its real deployment has been limited by bulky equipment, mechanical disturbance, high power consumption, and low flexibility systems. Here, we present the design of a THz platform based on photonic integrated devices and photoconductive antennas that can reduce the footprint of all discrete optics in THz spectroscopy systems by two orders of magnitude. The integrated platform aims to contribute to the technological bridge that will take the THz spectrum from bulky systems to on-chip platforms.

Terahertz (THz) photomixer devices are becoming attractive components for coherent optoelectronic THz systems due to their ability to operate as THz emitters and receivers. Enhanced THz photomixer emitters based on graphene flakes and silver nanowires nanoelectrodes overcome the performance of classical interdigitated photomixers with metal electrodes. Here, we performed a simulation of the hybrid nanoelectrodes structure based on an array of graphene flakes and silver nanowires (AgNWs) to comprehend the plasmonic motion of the generated carriers in the active area of the device. The simulation results show that the conductivity of Ag-NWs was improved by the conductivity of graphene flakes. Where the graphene flakes create a spatial electric field close to their edges. Due to the confined electric field, the carriers will be transported between graphene flakes and Ag-NWs by a spatial plasmonic field, and subsequently making the graphene flakes act as connected rather than isolated. Therefore, graphene and Ag-NWs allow simultaneous carrier transport in the hybrid nanostructure.

Analog radio-over-fiber (ARoF) technology has proven to be a promising solution to be part of the future millimeter-wave (mm-wave) 5G/6G architecture due to its attractive benefits such as simplified remote antenna units (RAUs), low-power consumption, and low cost. However, ARoF channels present hefty drawbacks, such as phase noise and nonlinear effects, that need to be addressed. The probabilistic amplitude shaping (PAS) technique is able to reduce the impact of such drawbacks, allowing a fine optimization of channel capacity usage. In particular, enumerative sphere shaping (ESS) implementation stands out as an excellent PAS approach because of its energy-efficiency and low complexity for short blocklengths. In this work, for the first time to the best of our knowledge, an ESS scheme is evaluated in an experimental bidirectional mm-wave ARoF setup oriented towards 5G communications. Furthermore, a novel soft ESS demapping algorithm is proposed and explained. The experimental results confirm the ESS technique, together with the proposed algorithm, as a convenient solution to enhance the channel capacity use of mm-wave ARoF systems for the 5G/6G fronthaul.

Fifth-generation mobile networks (5G) are the solution for the demanding mobile traffic requirements, providing technologies that fulfill the requisites of different type of services. The utilization of the millimeter-wave (mm-wave) band is the straightforward technique to achieve high bit rates. Moreover, analog radio-over-fiber (ARoF) brings outstanding benefits such as low cost, low power consumption, and high spectral efficiency, among others. Thereby, mm-wave ARoF is a strong candidate to pave the way for common public radio interface (CPRI) in the fronthaul for the future 5G architecture. As orthogonal frequency-division multiplexing (OFDM) is the adopted waveform in the 5G standard, it should be also utilized in mm-wave ARoF systems for 5G. However, phase noise is one of the most degrading factors in mm-wave OFDM ARoF systems. Therefore, in this work, an analysis of the phase noise is carried out through an experimental setup up. The configuration of this setup enables to gradually modify the final phase noise level of the system. Furthermore, an original and novel algorithm to compensate the phase noise in OFDM receivers is proposed. The performance of this algorithm is experimentally evaluated through the setup for different phase noise levels and different subcarrier spacings. The obtained results show the effectiveness of the proposed algorithm under those conditions, highlighting the viability of mm-wave OFDM ARoF for 5G and beyond.

This article presents an experimental demonstration of a high-capacity millimeter-wave 5G NR signal transmission with analog radio-over-fiber (ARoF) fronthaul over multi-core fiber and full real-time processing. The demonstration validates the core of the blueSPACE fronthaul architecture which combines ARoF fronthaul with space division multiplexing in the optical distribution network to alleviate the fronthaul capacity bottleneck and maintain a centralized radio access network with fully centralized signal processing. The introduction of optical beamforming in the blueSPACE architecture brings true multi-beam transmission and enables full spatial control over the RF signal. The proposed ARoF architecture features a transmitter that generates the ARoF signal and an optical signal carrying a reference local oscillator employed for downconversion at the remote unit from a single RF reference at the central office. A space division multiplexing based radio access network with multi-core fibre allows parallel transport of the uplink ARoF signal and reference local oscillator at the same wavelength over separate cores. A complete description of the real-time signal processing and experimental setup is provided and system performance is evaluated. Transmission of an 800 MHz wide extended 5G NR fronthaul signal over a 7-core fibre is shown with full real-time signal processing, achieving 1.4 Gbit/s with a bit error rate $$ < 3.8 × 10 - 3 and thus below the limit for hard-decision forward error correction with 7% overhead.

Perfect encryption of a qubit state using the Quantum One-Time Pad (QOTP) requires 2 classical key bits. More generally, perfect encryption of a 2n-dimensional state requires 2n classical bits. However, almost-perfect encryption, with information-theoretic security, can be achieved with only little more than 1 key bit per qubit. It has been shown that key length n+2log1/ε suffices to encrypt n qubits in such a way that the cipherstate has trace distance ≤ε from the fully mixed state. In this paper, we present a fast key expansion method to create a 2n-bit pseudorandom string which is then used as a QOTP key. In this expansion we make use of 2n bits of public randomness which are included as a classical part of the cipherstate. Our key expansion is a factor 2 faster than the previous fastest scheme, while achieving the shortest known key length n+2log1/ε.

A V-band Vivaldi antenna design for beyond-5G base station applications operating within V-band is demonstrated. The device can be used for interfacing with radio-over-fibre links and optoelectronic components through a coplanar waveguide to slotline transition. Simulations show an end-fire radiation with a 3 dB gain bandwidth ranging between 46.9-77.4 GHz combined with the reflection coefficients remaining below-10dB for the same frequency range. A comb structure inspired by optical grating couplers is added providing an increased maximum gain of 12.6 dBi at 68.5 GHz. Measurement results validate the promising characteristics of the planar antenna.

This paper studied the constraint mechanism for power device design based on perovskite quantum dots pumped by an electron beam. Combined with device designing, an experimental system of self-saturation luminescence and aging failure was designed for CsPbBr3 films. On this basis, we further completed the self-saturation luminescence and aging failure experiment and constructed a model of self-saturation luminescence and aging failure for CsPbBr3 device designing. Three constraints were proposed after analyzing and discussing the experimental data. Firstly, too high of a pumping current density makes it difficult to effectively promote the enhancement of luminescence efficiency. Secondly, radiation decomposition and aging failure of CsPbBr3 films are mainly related to the polarized degree of CsPbBr3 nanocrystals. Thirdly, by increasing the pumping electric field, the pumping energy can be effectively and widely delivered to the three-dimensional quantum dots film layer space, and there is a nonlinear relationship between the attenuation of the pumping energy density and the increment of the pumping electric field, which will effectively avoid the local high-energy density of instantaneous optical pumping.

In this paper we report the implementation and experimental evaluation of a proposed hybrid communication ecosystem for CCAM applications such as cooperative adaptive cruise control (CACC) and smart intersections. Three wireless technologies have been suggested for communications between vehicles and intelligent traffic lights and are evaluated in this work: ITS-G5 based on IEEE 802.11p and LTE sidelink with PC5 air interface for direct short range links, and regular mobile LTE with LTE Uu air interface for long range or indirect links. The applications used are independent of the communication channel, to enable a comparison on the application level of the different communication technologies. Field experiments were carried out with two CACC-equipped vehicles and three intelligent traffic lights in two field test locations under ideal, i.e., no-traffic, conditions and with real traffic. Experimental results related to CACC show that the best performance in terms of latency is achieved by the ITS-G5 system, while LTE PC5 and LTE Uu links show a penalty of 20 and 50 ms respectively. However, experimental results show that all three communication technologies were still able to guarantee string stable performance of the vehicle platoon. Regarding the smart intersections, an analysis based on field measurements and comparison between long- and short-range solutions is proposed; the analysis includes the impact of each channel on the applications such as speed advisory and green light prediction. The reported experimental evaluation shows the potential of current mobile technologies for CCAM use cases and highlights the way for further CCAM applications based on 5G and beyond mobile networks.

In this work we have demonstrated a waveguide integrated uni-traveling carrier photodiode on an InP-membrane-on-silicon platform with 3 dB bandwidth beyond 110 GHz. With design optimization and an improved process, devices as small as $ \text{3}\times \text{2}\;\mu \text{m}^2$ are successfully realized. An electrical equivalent circuit model based on measured S-parameters revealed ultra-small series resistance and junction capacitance as low as 6.5 $\Omega$ and 4.4 fF, respectively, in the diodes. The model also provided insight in the photocurrent dependent characteristics in the bandwidth and resonsivity of the devices. Finally, data transmission measurements are demonstrated, showcasing the high speed telecommunication abilities of the UTC-PD.

Over the past decades, Terahertz (THz) systems development has taken a major step forward together with laser-based technologies for the generation and detection of THz signals. Optoelectronic generation of continuous-wave THz signals relies on mixing two optical signals oscillating in a high-speed photoconductive antenna, for which the photocurrent depends on the incident optical power. The capability to operate THz fields in passive devices can be combined smoothly with photonic integrated circuit (PIC) technologies to enable photonic chips with enhanced THz efficiency. There are still many open questions about implementation and improvement to reduce equipment size, noise, alignment efforts, electrical and optical power consumption, and to increase the system flexibility. In this manuscript, we introduce a new THz system platform based on photonic integrated circuits and micro-structured photoconductive antennas that will increase the integration by reducing the footprint of THz spectrometers by more than 3 orders of magnitude. Additionally, a new integrated lens-antenna consisting of a Fresnel zone plate is designed and implemented for a nanocontact based THz photomixer. The new design replaces the standard conventional bulky silicon lens, which normally no THz photomixer can avoid. THz measurements showed a comparable behavior with the Fresnel zone plate to that of the conventional bulky silicon lens, demonstrating its readiness for photonic integrated circuits-based THz systems. This integration platform will represent a technological jump from currently bulky equipment and devices to extremely flexible, portable, and energy efficient THz systems-on-chip, at much lower costs.

Three convergent processes are likely to shape the future of the internet beyond-5G: The convergence of optical and millimeter wave radio networks to boost mobile internet capacity, the convergence of machine learning solutions and communication technologies, and the convergence of virtualized and programmable network management mechanisms towards fully integrated autonomic network resource management. The integration of network virtualization technologies creates the incentive to customize and dynamically manage the resources of a network, making network functions, and storage capabilities at the edge key resources similar to the available bandwidth in network communication channels. Aiming to understand the relationship between resource management, virtualization, and the dense 5G access and fronthaul with an emphasis on converged radio and optical communications, this article presents a review of how resource management solutions have dealt with optimizing millimeter wave radio and optical resources from an autonomic network management perspective. A research agenda is also proposed by identifying current state-of-the-art solutions and the need to shift all the convergent issues towards building an advanced resource management mechanism for beyond-5G.

A new integrated lens-antenna is designed and implemented for a nanocontact based terahertz (THz) photomixer. The new design replaces the standard conventional bulky silicon lens, which normally no THz photomixer can avoid. The Fresnel Zone Plate is used to design the new lens-antenna and is simulated by the MIT open-source tool called Meep. The final design showed, with only two simple fabrication technology processing steps (standard optical lithography) that the lens-antenna can be monolithically integrated with the THz nanophotomixer. With its compact design, the THz measurements showed a comparable behavior to the conventional bulky silicon lens, therefore it would be ready for photonic integrated circuits based THz systems.

Continuous-wave terahertz emitters based on photomixers with hybrid nanoelectrodes are investigated. The nanoelectrodes consist of a nitrogen-doped single layer of graphene and silver nanowires, placed on low-temperature-grown (LTG) GaAs as photoconductive material. Due to the high transparency of graphene and the low fill factor of nanowire nanoelectrodes, high photocurrents in the range from 260 μA to 1.8 mA can be reached. Despite their very small size nanoelectrodes provide the capability of handling rather high currents, leading to THz output signals reasonably three times higher than for conventional interdigitated finger electrodes for the whole measurement range. Measurement results of generated photocurrents and THz output signals are presented, showing the increased performance of our approach while maintaining highly reliable operation of the devices.

An encryption scheme is called perfect if the cipher reveals no information whatsoever about the message that was encrypted. The quantum Vernam cipher, also known as Quantum One-Time Pad (QOTP) or private quantum channel, is a perfect quantum encryption scheme. In order to perfectly encrypt any $n$-qubit state, the necessary and sufficient key length is $2n$ bits. For someone who does not know this key, the state after encryption equals the fully mixed state regardless of the original state. It has been shown that entropic security setting allows us to have information-theoretically secure QOTP with much shorter keys than $2n$, if the adversary has high uncertainty about the message states. Adversary's uncertainty is quantified using conditional quantum min-entropy. Informally, an encryption scheme is entropically-secure if having the ciphertext does not provide a non-negligible advantage to an attacker in learning any information about the message given that he has high uncertainty about the message. Desrosiers and Dupuis constructed an entropically secure quantum encryption scheme with a key length of $n-t+2\log\fr1\qe$ where $n$ is the number of the message states, $t$ is the conditional quantum min entropy of the message state $\sH_{\infty}(X|E)$ and $\qe$ is the leakage of the cipher. They expand the short key to $2n$ using a public string with a length of $2n$ then apply QOTP. Their key expansion method utilizes universal XOR hash function which consists of Galois Field multiplication in GF$(2^{2n})$. We have also introduced an entropically secure quantum scheme with a new key expansion method and proved the same shortest key length $n-t+2\log\fr1\qe$. Our key expansion method is faster than the previous ones. This speedup depends on the entropy of the message and can be multi folds in case of high min-entropy of the message. We encrypt a bipartite state $\qf^{AE}\in\cD(\cH_A\otimes\cH_E)$ using a key $k\in\bits^\ell$ where $\ell > n$, and $\ell$ is an even integer. In short, we expand a key $k$ using two random public strings $u\in\bits^\ell$, $v\in\bits^{2n-\ell}$ by applying GF operations, and then appending the outcome to the key itself: $k \| (uk+v)_{\rm lsb}$. GF operations are in GF($2^\ell$) and lsb means taking the last $2n-\ell$ bits. Then the expanded key is used in QOTP encryption. The cipherstate consists of $n$ qubits and $2n$ classical bits.

QKD networks are costly infrastructures. This paper introduces the concept of time-sharing of QKD resources, namely receivers, transmitters and quantum links. A number of strategies for resource sharing in QKD are described. The approach is valid for any point-to-point QKD system that implements end-to-end key exchange via one-time-pad-based trusted relay. A quick modelling and analysis of one of these strategies on a sample network proves the potential for QKD CAPEX saving. Coordinated smart scheduling of slices via SDN controllers is required.

5G and beyond-5G networks need to support all the traffic pressure by extensive Internet of Things networks. In this document, we review how to improve the flexibility of 5G networks by conducting slicing. We describe the four main pillars for this transition: mass adoption of Software Defined Networking, collocation of aggregators at Multi-access Edge Computing platforms, virtualization of infrastructure and removal of Application Functions through distributed responsibilities over the network. We will present an overview of the efforts being conducted for each of these points and the vision for beyond-5G networks.

Networking is enabling a continuum comprising cloud, edge and last-mile systems. This continuum allows services and applications to join the fabric at any point and have access to processing power independently of the location of entrance. To enable this paradigm, we need to make sure we have a networking fabric capable of transporting and access network resources seamlessly and communication channels that are securitized, ensuring confidentiality and integrity of data. A challenge in securitization is that it takes computing resources away, and hence it may reduce the overall network performance. Hardware accelerations or offloads enable to reduce the burden on processing resources of securitization processes; in this contribution, we present how IPsec and TLS protocols provide a tool for a high level of securitization of the communication channels and approaches to accelerate/offload those protocols.

In this work we present, analyze, and demonstrate an efficient bidirectional ARoF system for K-band 5G fronthaul based on multicore fiber. As the 5G standard establishes, the experimental testbed is configured regarding the time division duplex scheduling and tested by transmitting OFDM signals. Furthermore, the configuration of the setup enables the reusability of several components for both directions, allowing the reduction of the power consumption, complexity, and cost of the system. The bidirectional testbed is experimentally evaluated under different bandwidth configurations and power levels, achieving a maximum throughput of 4Gbit/s over 9m of wireless link. The experimental results prove and validate the proposed bidirectional ARoF scheme as a promising solution for the future mm-Wave 5G fronthaul.

This chapter elaborates on the beneficial aspects and hardware implementations of incorporating ultradense WDM-PONs (UDWDM-PONs) with hybrid optical-wireless fronthaul links and fiber to the home applications. Simulation results on the synthesis of a low-cost and low-energy consumption optoelectronic unit within the future 5G base stations (BS) are presented. In addition, an advanced neural network is investigated capable of compensating for the linear and nonlinear effects induced by semiconductor optical amplifiers (SOA).

Fifth generation (5G) is the emerging mobile communications platform that aims to meet the market requirements in terms of enhanced broadband connectivity based on harnessing small cell and mmWave technology. These two in synergy will provide high capacity gain not only through the hyperdense deployment of small cell but also through accessing large swathes of untapped spectrum at mmWave frequencies. The envisaged architecture entails an integrated optical wireless network architecture, where optical technology will complement radio in order to handle the new demands on capacity over the backhaul and fronthaul network, leading to the notion of analog radio over fiber (ARoF). The goal of this chapter is to provide novel approaches to optimize the performances of mmWave ARoF systems that includes developing enabling technology from a digital to signal processing (DSP) and device perspective.

This paper presents a beyond 5G fronthaul network with dynamic beamforming and -steering. The proposed fronthaul solution deploys optical beamforming (OBF) by combining space division multiplexing (SDM), analogue radio-over-fiber (ARoF), and the novel optical beam forming network (OBFN) technologies. From the service management and orchestration (MANO) point of view, the proposed fronthaul solution also deploys an advanced software defined networking (SDN) and Network Function Virtualization (NFV) control and orchestration architecture developed with the goal to optimally manage and reconfigure the physical layer resources (i.e., optical and radio) at the central office and cell sites (i.e., pool of baseband units (BBUs), remote radio heads (RRHs), ARoF transceivers and OBFNs). The proposed beyond 5G fronthaul architecture is primarily oriented to deploy massive machine-type communication (mMTC) services with high-bandwidth requirements, such as for industry 4.0. In this paper we experimentally validate the novel OBFN system, and the dynamic SDN/NFV MANO of the transport connectivity and network services for optical beamforming. The obtained experimental results show that the overall delay for the provisioning and removal of an OBF service, considering the contribution of the involved optical and radio systems and the SDN/NFV MANO layer, is 134s and 18s respectively. The reconfiguration of the OBF service to add or remove a beam can be performed in the range of 65–87s.

We evaluate the impact of Power-over-Fiber (PoF) technology on the fronthaul of a 5G-NR network with an Analog-Radio-over-Fiber at 25.5 GHz on a 10 km long multicore fiber. The study in this Letter analyzes the bit error rate (BER) performance for different levels of energy transmitted by the PoF system. 133 mW of maximum optical power at reception is demonstrated showing negligible BER impact or data transmission BER improvement in a dedicated and shared scenario. Comunidad de Madrid (Y2018/EMT-4892); Ministerio de Ciencia, Innovación y Universidades (RTI2018-094669-B-C32); Horizon 2020 Framework Programme (762055).

This article presents the experimental demonstration of synchronization of two integrated semiconductor distributed Bragg reflector lasers, fabricated with a generic multiproject wafer platform, by means of injection locking. Substantial linewidth reduction and frequency stabilization of the lasers were shown during locking of the lasers to an optical frequency comb. Phase noise was measured for different injected powers and different laser cavities. For a generation of millimeter-wave signals up to 80 GHz, two lasers were simultaneously locked to the comb. Fine-tuning was performed by tuning the repetition rate of the comb and coarse-tuning was carried out by switching to another comb line. A suppression ratio of 37 dB was achieved for unwanted comb lines. The achieved signal purity, phase noise, and suppression of unwanted components demonstrate the viability of injection locking for the generation of high-quality signals at sub-THz and THz frequencies and with substantial tunability.

Component characterization is fundamental for understanding the limits of optical devices, sub-systems, and transmission systems. With the introduction of space division multiplexing in optical fiber transmission systems, new impairments, such as mode dependent loss and differential mode dispersion arise. Spatially-diverse optical vector network analyzers are capable of measuring these characteristics in a fast single sweep over a very large bandwidth. As a result of this large bandwidth, these analyzers are sensitive to differential chromatic dispersion within the interferometric measurement setup. This study discusses the influence and compensation of differential chromatic dispersion in such systems. Partial chromatic dispersion compensation is demonstrated to improve the representation and accuracy of impulse response measurements obtained from optical vector network analyzers for fibers and components with large differential chromatic dispersion. Analysis of a 39-core few-mode multi-core fiber is discussed, reporting variances of -2.9-0.1 ps/nm, and 0.6-6.9 ps/nm for the two mode groups, respectively, between the few-mode cores. A correlation with the total impulse response is observed. Furthermore, a maximum propagation skew of 20 ns between cores is observed after 13.6 km.

The introduction of 5G mobile networks, bringing multi-Gbit/s user data rates and reduced latency, opens new opportunities for media generation, transport and distribution, as well as for new immersive media applications. The expected use of millimeter-wave carriers and the strong network densification resulting from a much reduced cell size--which enable the expected performance of 5G--pose major challenges to the fronthaul network. Space division multiplexing (SDM) in the optical domain has been suggested for ultra-high capacity fronthaul networks that naturally support different classes of fronthaul traffic and further enable the use of analog radio-over-fiber and advanced technologies, such as optical beamforming. This paper discusses the introduction of SDM with multi-core fibers in the fronthaul network as suggested by the blueSPACE project, regarding both digitized and analog radio-over-fiber fronthaul transport as well as the introduction of optical beamforming for high-capacity millimeter-wave radio access. Analog and digitized radio-over-fiber are discussed in a scenario featuring parallel fronthaul for different radio access technologies, showcasing their differences and potential when combined with SDM.

This work studies and experimentally evaluates the performance enhancement by using PS-OFDM in a 5G mm-Wave ARoF system at 25 GHz for all 5G numerologies and with different phase noise levels.

A real-time millimeter wave radio-over-fiber link is experimentally demonstrated transmitting up to 1.4 Gbit/s 5G OFDM signals through a multi-core fiber to an 8 × 4 antenna array employing analog beamforming to radially track a moving receiver.

The focus of this study is the performance evaluation of Cooperative adaptive cruise control (CACC) achieved with three different wireless technologies for vehicle-to-vehicle (V2V) communications, i.e., intelligent transport system (ITS) G5 based on 802.11p and mobile long term evolution (LTE). For communications with LTE we will consider both the regular air interface LTE Uu and the device-to-device PC5, which is based on LTE sidelink. CACC employs inter-vehicle wireless communications to safely drive at short inter-vehicle distances, which improves road throughput. The underlying technical requirement to achieve this benefit is formulated by the notion of string stability, requiring the attenuation of the effects of disturbances in upstream direction. This work analyzes the relation between the communication performance and the string stable performance of a CACC string. Field experiments were carried out in Lelystad, The Netherlands, with two CACC-equipped vehicles. Results show that the latency of ITS G5 network is smaller than LTE Uu and PC5. However, since the majority latency of LTE Uu and PC5 is limited by the string stability requirement in the current test setting, string stability can still be guaranteed. The packet error with LTE PC5 and ITS G5 is observed. However, the packet error rate is small that does not significantly affect the CACC application performance.

A metal-dielectric interface is usually modeled by a zero-width layer, where dielectric permittivity suffers a discontinuity jump. In reality, there is a narrow transition region, which includes an epsilon-near-zero (ENZ) layer. We show that due to a continuous dielectric function the dispersion of the surface plasmon is modified. The energy of the surface plasmon radiates through the ENZ layer, giving rise to additional radiative losses. Direct evidence of the effects related to the transition layer is given by the observation of plasmonic resonance in the presence of a strong electric field normal to the metal film. The electric field affects the electron density within the transition layer that leads to a measurable shift of the plasmonic resonance.

Technological innovation with millimeter waves (mm waves), signals having carrier frequencies between 30 and 300 GHz, has become an increasingly important research field. While it is challenging to generate and distribute these high frequency signals using all-electronic means, photonic techniques that transfer the signals to the optical domain for processing can alleviate several of the issues that plague electronic components. By realizing optical signal processing in a photonic integrated circuit (PIC), one can considerably improve the performance, footprint, cost, weight, and energy efficiency of photonics-based mm-wave technologies. In this article, we detail the applications that rely on mm-wave generation and review the requirements for photonics-based technologies to achieve this functionality. We give an overview of the different PIC platforms, with a particular focus on hybrid silicon photonics, and detail how the performance of two key components in the generation of mm waves, photodetectors and modulators, can be optimized in these platforms. Finally, we discuss the potential of hybrid silicon photonics for extending mm-wave generation towards the THz domain and provide an outlook on whether these mm-wave applications will be a new milestone in the evolution of hybrid silicon photonics.

The sixth generation (6G) mobile systems will be the ultimate technology to support any networking requirement. 6G along with fog computing mobile nodes can support any application and use case within the supply chain delivery, regardless of the systems of systems complexity. In this paper, a holistic end-to-end framework platform based on the integration and leverage of 6G and fog mobile systems for physically-entangled systems is proposed. The framework platform, which relies on 6G fog enabled-delivery drones, terahertz communication, and artificial intelligence technologies, is described. The framework can be applied for highly cooperative, autonomous, and dynamic applications and systems such as supply chain’s last mile delivery of goods, harbour cranes, and maritime ports to help increasing access to goods in general, reduce traffic congestion and energy comsumption, and ease CO2 emissions from transportation. The proposed framework paves the way towards next generation supply chain management including last mile delivery.

New CW THz detectors based on graphene nanoelectrodes photomixer are completely investigated. The graphene nanoelectrodes are placed on low-temperature-grown (LTG) GaAs as photoconductive material. Due to the high transparency and high conductivity of graphene, increasing carrier densities were obtained which leads to the high performance detection of THz induced photocurrent being one order of magnitude higher than for conventional metallic interdigitated photomixer. The THz measurement was performed in the range of 50 GHz to 1.1 THz.

We experimentally demonstrate a heterodyne communication link using a p-i-n photodiode and a photoconductor coupled to THz antennas without bandwidth-limiting electronic components. As a proof-of-concept, a 100 Mbit/s BPSK stream is successfully transmitted at three different channels, spaced by 40 GHz, down-converting the wireless carrier to an intermediate frequency of 3.7 GHz. Optical frequency combs are employed for sub-THz generation and down-mixing to reduce the phase noise of the system.

In this paper we propose to combine the concepts of outphasing and analog-radio over fiber. The analog outphasing signals are generated centrally and transported to the remote antenna system over fiber. There, high-performance and highly non-linear power amplifiers can be used. This approach creates an energy efficient communications infrastructure based on a centralized radio network. A first demonstrator is built at Ka-band using discrete components, experimentally showing the feasibly of this concept at millimeter-wave. Preliminary results show a measured error-vector magnitude of 4.18% over a wireless channel.