George Kalfas

Aristotle University of Thessaloniki | AUTH · Department of Informatics

A fully-automated SDN-controlled real-time operation of a hybrid Fiber-Wireless 10Gb/s FSO and 5Gb/s mmWave link across 7km-fiber and 0.5m-radio distance resilient at all weather conditions is experimentally presented, supporting 25μs beam-switching and zero-touch hard handover via tunable SFP+ transceivers and simple all-passive 1x2 C-/O-band dipl...

In this paper, we jointly study the real-time user association, traffic routing and x-Network Function (xNF) placement problem in an integrated Terrestrial and Satellite 6G Network (TN-SN), with the aim of maximizing the network energy efficiency and user acceptance ratio. We formulate the aforementioned problem as a Mixed Integer Linear Program (M...

A flexibly reconfigurable optical circuit switched edge network architecture relying on wavelength-tunable SFP+ transceivers is presented for the first time for reconfigurable, low-latency 5G/6G networks. The proposed solution employs traditional cost-effective, fixed-wavelength 10G SFP+ transceivers as grey optics towards the access side of the ne...

Services from industries outside of telecoms such as factories, transportation, automotive, often referred to as verticals, have become an essential driver for the application of 5G and its further development. In this article, we introduce the concept of network application (nApp) to enable easy access of 5G services for individual verticals, alon...

We present an optimized Medium-Transparent MAC (oMT-MAC) protocol for Analog-RoF Fiber-Wireless 5G and beyond X-haul networks, capable of generating an optimal transmission schedule, which boosts the protocol's efficiency by utilizing the full delay budget of higher priority flows. Results show that oMT-MAC's optimization model can reduce delays by...

The growing demand for ubiquitous broadband connectivity in 5G/6G Radio Access Networks (RANs) has turned Centralized RAN (C-RAN) and reconfigurable Point-to-MultiPoint (PtMP) network topologies into the mainstream approach for keeping pace with the vastly increasing traffic capacities and connection densities. Relying on an all-passive Arrayed Wav...

The current work presents the first experimental demonstration of real-time Ethernet (ETH) trial services and 4K-Ultra High Definition (UHD) video application transmission over a 2λ Wavelength Division Multiplexing (WDM) analog Fiber-Wireless (FiWi) mmWave X-haul network, supporting dynamic flexible capacity allocation through an integrated silicon...

In this paper, we study the joint problem of real-time user association, traffic routing and Virtual Network Function (VNF) placement towards maximizing the mobile network's energy efficiency and user acceptance ratio. The studied problem is formulated as a Mixed Integer Linear Program (MILP), under various computational, capacity, and flow conserv...

In order to meet the ever-increasing 5G and beyond Radio Access Network (RAN) densification demands, Fiber-Wireless transport networks are expected to play a key role in accelerating 5G deployment by providing the essential RAN flexibility, while at the same time avoiding costly fiber-trenching. Due to the inefficiency of the Radio-and-Fiber (R&F)...

Towards enabling bandwidth-hungry 5G applications, a Fiber-Wireless (FiWi) mobile fronthaul architecture is experimentally presented supporting the co-existence of spectrally efficient analog transport formats with Digital Radio over Fiber transport schemes, combined with millimeter wave (mmWave) high-capacity wireless channels. Flexible transport...

The first successful demonstration of real-time Ethernet trial services over an analog 2λ-WDM Fiber-Wireless mmWave X-haul is experimentally reported, controlled through Open Daylight SDN controller for flexibly allocating capacity via a low-loss Si 3 N 4 ROADM.

We study the problem of downlink Coordinated Beamforming for dense fixed-wireless millimeter wave (mmWave) networks under a Centralized/Cloud Radio Access Network (C-RAN) setting. To compensate for the increased mmWave path loss, we consider directional transmissions via antenna array analog beamforming, which leads to a discrete set of available b...

In order to cope with the ever-increasing traffic demands and stringent latency constraints, next generation, i.e., sixth generation (6G) networks, are expected to leverage Network Function Virtualization (NFV) as an enabler for enhanced network flexibility. In such a setup, in addition to the traditional problems of user association and traffic ro...

Network Function Virtualization (NFV) is expected to be a crucial enabler of Beyond 5G (B5G) networks, supporting new services with stringent requirements, while offering high flexibility and configurability. In this paper, we consider the joint problem of Virtual Network Function (VNF) placement alongside computational and communication resource a...

The current report attempts to explore the top challenges that the MNOs need to overcome during 5G deployment in highly dense populated areas. Indicatively, the MNOs are warned about site acquisition challenges and electrification/energy related needs for a huge number of sites that shall be installed discretely at street level, the demand for rigo...

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 te...

We demonstrate experimentally a bandwidth-reconfigurable mmWave Fiber Wireless (FiWi) fronthaul bus topology for spectrally efficient and flexibly reconfigurable 5G Centralized-Radio Access Networks (C-RAN). The proposed fronthaul architecture includes four 1 Gb/s Intermediate Frequency over Fiber (IFoF) channels that can be flexibly allocated amon...

A bandwidth-reconfigurable mmWave Fiber Wireless fronthaul bus topology of four 1 Gb/s 16-QAM streams transmitted through two cascaded low-loss Si3N4-ROADM stages and a 60 GHz Phased Array Antenna with 90° steering is experimentally demonstrated the first time for 5G C-RANs.

A bandwidth-reconfigurable mmWave Fiber Wireless fronthaul bus topology of four 1 Gb/s 16-QAM streams transmitted through two cascaded low-loss Si3N4-ROADM stages and a 60 GHz Phased Array Antenna with 90° steering is experimentally demonstrated the first time for 5G C-RANs.

A bandwidth-reconfigurable mmWave Fiber Wireless fronthaul bus topology of four 1 Gb/s 16-QAM streams transmitted through two cascaded low-loss Si3N4-ROADM stages and a 60 GHz Phased Array Antenna with 90° steering is experimentally demonstrated the first time for 5G C-RANs.

Four 10 Gb/s multi-IFoF 16-QAM WDM Fiber-Wireless links are transmitted through 10km fiber and 50cm directional V-band antennas and flexibly reconfigured by a Si 3 N 4 ROADM, towards record 40 Gb/s wavelength-routed fronthaul capacity for mmWave 5G.

In order to meet the ever-increasing traffic demands, the combination of fiber and Millimeter Wave (mmWave) is expected to play a key role for 5G Centralized-Radio Access Networks (C-RANs). Due to the inefficiency of the Common Public Radio Interface for the Baseband Unit (BBU)-Remote Radio Head (RRH) communication, analog-Radio-over-Fiber (a-RoF)...

Towards relieving the bandwidth limitations in 5G mobile fronthaul networks, a Fiber Wireless(FiWi) small cell architecture is presented, relying on spectrally efficient analog transport on Intermediate Frequency over Fiber(IFoF) and a millimeter wave(mmWave) Phased Array Antenna(PAA) interfaced with a low-loss Optical Add/Drop Multiplexer(OADM) on...

We experimentally demonstrate an uplink transmission of a Fiber Wireless A-RoF/IFoF fronthaul link for 5G networks using a 32-element 60 GHz phased array antenna in the 1-m long wireless channel and 10 km of SMF spool for the optical link. At first, we characterize the link frequency response using a single tone measurement and perform a dynamic ch...

Towards the 5G millimeter Wave (mmWave) era, analog transport offers a spectrally efficient scheme for converged Fiber Wireless (FiWi) networks. Signal integrity is traditionally considered as a limiting factor due to various non-linearities attributed to the microwave photonic link, expected to be further exacerbated by the RF-chain of beamforming...

We present a fixed mobile convergence topology for analog intermediate frequency over fiber (A-IFoF)/millimeter-wave (mmWave) transmission, benefiting from the reuse of the deployed passive optical network (PON) infrastructure, towards future mobile fronthaul architectures. Powerful fully programmable gate array boards located inside the access nod...

5G networks are shaping a new ecosystem necessitating various transformations of the existing network infrastructures combined with the use of network softwarization and programmability, so as to satisfy the needs of all the involved stakeholders (telecom/service providers, infrastructure owners, tenants, vertical industries, end-users, etc.), whil...

We experimentally demonstrate a multi-user Fiber Wireless IFoF/mmWave uplink comprising a 32-element 60GHz Phased Array Antenna (PAA) and 10 km of fiber for 5G fronthaul networks, supporting beamsteering within a 120° sector and 0.6 Gb/s uplink capacity within a 5dB bandwidth of 2 GHz. The flexibility of the link is highlighted in two 3-user scenar...

An analog Intermediate-Frequency-over-Fiber (IFoF) – based fronthaul 5G architecture for high traffic hot-spot environments is presented. The proposed optical fronthaul link utilizes Photonic Integrated Circuit (PIC) Wavelength Division Multiplexing (WDM) Externally Modulated Laser (EML) - based optical transmitters at a centralized Base Band Unit...

Four Wavelength Division Multiplexed 1Gb/s QAM16 streams are transmitted through 10km fiber, an Optical Add/Drop Multiplexer and a V-band beamsteering antenna with 90° steering, demonstrating the first 5G Fiber-Wireless A-RoF architecture with 360o coverage.

5G New Radio's (NR) spectrum expansion towards higher bands, although critical towards achieving the envisioned 5G capacity requirements, creates the need for installing a very large number of Access Points (APs), which asserts tremendous capital burden on the Mobile Network Operators. Current centralization solutions such as the Cloud Radio Access...

We experimentally demonstrate an uplink transmission of a Fiber Wireless A-RoF/IFoF fronthaul link for 5G networks using a 32-element 60GHz phased array antenna in the 1-meter long wireless channel and 10km of SMF spool for the optical link. At first, we characterize the link frequency response using a single tone measurement and perform a dynamic...

We experimentally present the A-RoF/IFoF uplink transmission of three 60GHz terminals with 200Mb/s QPSK through a 32-element antenna with beamsteering up to a 60°-angle and 10km fiber, comparing for the first time the frequency and spatial division multiplexing for multiuser uplink for 5G mmWave networks.

Analog fronthauling is currently promoted as a bandwidth and energy-efficient solution that can meet the requirements of the Fifth Generation (5G) vision for low latency, high data rates and energy efficiency. In this paper, we propose an analog optical fronthaul 5G architecture, fully aligned with the emerging Centralized-Radio Access Network (C-R...

We experimentally demonstrate an optical Burst-Mode Wavelength Converter (BMWC) that simultaneously provides power equalization and wavelength conversion of Non-Return to Zero-On/Off Keying (NRZ-OOK) data and operates up to 20 Gb/s. It employs a balanced, differentially-biased, Semiconductor Optical Amplifier-Mach Zehnder Interferometer (SOA-MZI) o...

The fifth generation (5G) mobile systems can be considered the way to ubiquitous Internet, pervasive computing paradigm, and a revolution in industries like automotive, media and entertainment, and eHealth. New 5G fronthaul systems based on centralized radio access networks will eventually use technology enablers such as reconfigurable optical add-...

Centralized Radio Access Network (C-RAN) comprises one of the main technologies for high capacity and low latency fronthauling in 5G networks. In this paper, we propose and evaluate an optical fronthaul 5G C-RAN architecture that targets to meet the bandwidth, latency and energy requirements of high traffic hot-spot areas. The proposed architecture...

mmWave radio, although instrumental for achieving the required 5G capacity KPIs, necessitates the need for a very large number of access points, which places an immense strain on the current network infrastructure. In this article, we try to identify the major challenges that inhibit the design of the Next Generation Fronthaul Interface in two upco...

A 24 Gb/s analog Intermediate Frequency over Fiber Wireless V-band link is experimentally demonstrated over a 7km fiber length and 5m wireless distance, employing a digital 6-IF-carrier stream, each with a variable advanced modulation format, achieving record capacity for multi-band 5G Fronthaul networks.

Fifth generation (5G) networks are expected to combine several technologies to meet the ever-increasing capacity demands. Among them, centralized-radio access network (CRAN) architecture, enables the separation of the baseband unit (BBU) from the remote radio head (RRH) so as to achieve higher performance in terms of cost-efficiency and flexibility...

An Analog RoF-based Mobile Fronthaul architecture compatible to 5G requirements is presented. Experimental demonstration of 24 Gb/s IFoF transmission based on Digital Subcarrier Multiplexing technique is reported using a centralized DSP unit. Combined with 60 GHz radio equipment, successful indoor uplink/downlink experiments are demonstrated using...

In order to meet the traffic density requirement and cope with the technical challenges of hot-spot scenarios exhibiting extreme user density in very confined geographical areas, the fifth generation (5G) networks must undergo radical technological and architectural innovations that support a broad solution portfolio. This solution mix includes spe...

Analog optical fronthaul for 5G network architectures is currently being promoted as a bandwidth- and energy-efficient technology that can sustain the data-rate, latency and energy requirements of the emerging 5G era. This paper deals with a new optical fronthaul architecture that can effectively synergize optical transceiver, optical add/drop mult...

Passive Optical Networks (PONs) are an efficient high-performance optical access solution that is able to provide huge bandwidth in a resourceful way through the incorporation of inexpensive passive elements. PONs have been widely used for the provision of high-demand services to a number of wired end-users. However, the PON configuration may be al...

Passive Optical Networks (PONs) are an efficient high-performance optical access solution that is able to provide huge bandwidth in a resourceful way through the incorporation of inexpensive passive elements. PONs have been widely used for the provision of high-demand services to a number of wired end-users. However, the PON configuration may be al...

In this paper we demonstrate an analytical model for computing the end to end packet delay of a converged Optical/Wireless 60GHz Radio-over-Fiber (RoF) network operating under the Medium-Transparent MAC (MT-MAC) protocol. For the calculation of the cycle times this model takes into account contention both at the optical and the wireless layer, that...