George Kalfas

Aristotle University of Thessaloniki

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Nikos Pleros

Aristotle University of Thessaloniki

Christos Vagionas

Aristotle University of Thessaloniki

Amalia Miliou

Aristotle University of Thessaloniki

Agapi Mesοdiakaki

Aristotle University of Thessaloniki

Marios Gatzianas

Aristotle University of Thessaloniki

John S. Vardakas

Iquadrat (Spain)

Pavlos Maniotis

IBM Research - Thomas J. Watson Research Center

Ronis Maximidis

Aristotle University of Thessaloniki

Eugenio Ruggeri

Aristotle University of Thessaloniki

Yigal Leiba

Institute of Electrical and Electronics Engineers

Cooperative Institutions

National and Kapodistrian University of Athens

Aristotle University of Thessaloniki

National Technical University of Athens

Centre Tecnologic de Telecomunicacions de Catalunya

Institute of Communication and Computer Systems

Iquadrat (Spain)

University of Patras

Eindhoven University of Technology

Universitat Politècnica de Catalunya

Instituto de Telecomunicações

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End-to-End Real-Time Service Provisioning Over a SDN-Controllable Analog mmWave Fiber -Wireless 5G X-Haul Network

Journal of Lightwave Technology (2023)

Christos Vagionas Ronis Maximidis Ioannis Stratakos A. Margaris Agapi Mesοdiakaki

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 photonic Si ₃ N ₄ Reconfigurable Optical Add Drop Multiplexer (ROADM) and 60 GHz wireless transmission across a 7 m V-band link distance, while controlled by a Software Defined Network (SDN) controller based on Open Daylight. Analog X-haul transport of the radio signals is based on an Intermediate Frequency over Fiber (IFoF) scheme centered at 1.5 GHz using an Orthogonal Frequency Division Multiplexing (OFDM) radio-waveform with a bandwidth of 204 MHz, generated by a Field Programmable Gated Array (FPGA)-based RF System-on-Chip (SoC) processor that converts on-the-fly the real-time ETH downlink traffic to analog radio and vice-versa for the uplink. Dynamic allocation of the X-haul traffic capacity is handled through the use of the 802.1Q Virtual Local Area Network (VLAN) tag-mechanism, which controls the forwarding operation to the proper DAC and InP EML for optical modulation using Intensity Modulation/Direct Detection (IM/DD) schemes, while the wavelength routing operation is handled by the low-loss four-port Si ₃ N ₄ ROADM featuring only 2.5 dB fiber-to-fiber losses based on a cascaded MZI-interleaver design on the TriPleX platform, routing the real-time traffic to a second mmWave antenna site. Detailed measurements and traffic statistics indicate end-to-end latency of less than 260 μs and a packet loss less than 0.0054% across a dynamic range of at least 6.5 dB in the optical domain, while the high user bandwidth and signal quality are validated by an uninterrupted 4K-UHD video transmission across the FiWi X-haul mmWave transport network. The current work aims to shape a complete technology roadmap for Point-to-Multipoint FiWi transport network architectures with high spectral efficiency X-haul transport for dense areas and 5G/6G hotspots of future mmWave Centralized Radio Access Networks (C-RANs).

Optical networking

10.1109/jlt.2023.3234365

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Citations (26)

Flexible 360o 5G mmWave small cell coverage through WDM 4x1 Gb/s Fiber Wireless fronthaul and a Si3N4 OADM-assisted massive MIMO Phased Array Antenna

Optical Fiber Communication Conference (OFC) 2022 (2020)

Eugenio Ruggeri Apostolos Tsakyridis Christos Vagionas George Kalfas Ruud M. Oldenbeuving

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.

Optical add-drop multiplexer

10.1364/ofc.2020.t4a.5

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Citations (3)

Multi-RAT Fiber-Wireless Technologies towards 6G Networks

Christos Vagionas Ronis Maximidis Κωνσταντίνα Καντά Panagiotis Toumasis Giannis Giannoulis

At the dawning of the beyond 5G era, broadband last mile connectivity is stimulating rapid developments in optical and wireless technologies that will efficiently handle the traffic generated by mobile users and demanding network applications. To this end, multiple Radio Access (multi-RAT) technologies operating at various millimeter wave (mmWave) frequency bands, e.g., V-/E-/D-band are being actively pursued, in parallel with the investigation of efficient fiber wireless fronthaul schemes, e.g. Analog Radio over Fiber (aRoF) or Intermediate Frequency over Fiber (IFoF), to deliver low-complexity, broadband, last-mile connectivity. However, integration of such novel technologies in an actual mobile network infrastructure remains a challenge, as it needs to support compatibility with the network operators' equipment. The current talk aims to present a holistic Fiber Wireless (FiWi) connectivity, demonstrating the co-existence of Analog and Digital RoF traffic along with flexible, reconfigurable point-to-multipoint connectivity to multi-RAT antenna units. Experimental results on high capacity FiWi fronthaul links operating in the V- (60 GHz) and D- (145 GHz) will be presented. Moreover, end-to-end, integrated real-time traffic and network operation will also be discussed and experimentally presented, indicating a possible technology roadmap towards multi-RAT 6G networks.

Access network

Extremely high frequency

Mobile broadband

10.1109/icton59386.2023.10207366

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Citations (2)

Linearity Measurements on a 5G mmWave Fiber Wireless IFoF Fronthaul Link With Analog RF Beamforming and 120° Degrees Steering

IEEE Communications Letters (2020)

Christos Vagionas Eugenio Ruggeri Apostolos Tsakyridis George Kalfas Yigal Leiba

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 Phased Array Antennas (PAAs). The letter proposes the end-to-end evaluation of FiWi analog links as unified communication channels rather than separately for the radio or optical part, presenting a link with a 32-element 60 GHz PAA, 1 m V-band distance, 10 km fiber and 10 dB dynamic range. The measurements reveal a third order Intercept Point (IIP3) of 4.8 dBm, compared to 22.8 dBm exclusively for the optics, pinpointing the V-band radio as the main source of degradation rather than the microwave photonic link. Single user uplink is also benchmarked using 300 Mbd QPSK, 250 16-QAM and 100 Mbd 32-QAM, achieving data-rate up to 1 Gb/s and beamsteering of 120° degrees.

Optical link

True time delay

10.1109/lcomm.2020.3019733

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Citations (16)

Saturation Throughput Performance Analysis of a Medium Transparent MAC Protocol for 60 GHz Radio-Over-Fiber Networks

Journal of Lightwave Technology (2011)

George Kalfas Nikos Pleros Kostas Tsagkaris Luis Alonso Christos Verikoukis

We demonstrate an analytical model for calculating the saturation throughput performance of a medium transparent medium access control (MAC) protocol in 60 GHz radio-over-fiber (RoF) networks. The proposed model incorporates effectively the medium transparent MAC mechanism, assuming a finite number of terminals and ideal channel conditions. It takes into account contention both at the optical and wireless layer, ensuring seamless and dynamic capacity allocation over both transmission media. This model enables extensive saturation throughput performance analysis for the medium transparent MAC and has been applied to 60 GHz RoF network scenarios considering variable numbers of available optical wavelengths, wireless nodes and serving antenna elements and for two different data rate values, namely 155 Mbps and 1 Gbps. Comparison between the model-based throughput results and respective simulation-based outcomes reveals that our model is extremely accurate in predicting the system throughput. Moreover, it confirms that the proposed medium transparent MAC protocol can effectively operate in high-speed 60 GHz RoF LAN environments.

Media access control

10.1109/jlt.2011.2172392

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Citations (23)

Medium Transparent MAC access schemes for seamless packetized fronthaul in mm-wave 5G picocellular networks

George Kalfas John S. Vardakas Luis Alonso C. Verikoukis Nikos Pleros

Telecom operators are racing towards upgrading their facilities and broadband services in order to meet the highly challenging 5G operational framework in dense urban landscapes. The oversubscribed sub-6 GHz wireless band is lacking the necessary bandwidth to support the envisioned 5G data rates, suggesting the transition to mm-wave bands as the only viable scenario. In conjunction with the cell densification that is required to achieve the desired frequency reuse factor, it becomes obvious that the current CPRI-based fronthaul cannot cope with massive multi-Gbps traffic streams and a paradigm shift in resource allocation and network intelligence is necessary. To this end we propose the Medium Transparent MAC protocols as the solution towards forming and managing a converged mm-wave FiWi fronthaul infrastructure. Our approach allows for directly negotiating wavelength, frequency and time resources between the centralized unit and the wireless terminals, while offering fast on-demand link formation following closely the demand fluctuation at the picocell level. In this paper we investigate the functional and physical consolidation as well as the respective performance of MT-MAC-enabled fronthaul and report on its application and suitability for mm-wave 5G access networks.

Access network

Bandwidth allocation

10.1109/icton.2017.8025064

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Citations (1)

A QoS-Enabled Medium-Transparent MAC Protocol for Fiber-Wireless 5G RAN Transport Networks

Applied Sciences (2022)

George Kalfas D. Palianopoulos Agapi Mesοdiakaki Marios Gatzianas Christos Vagionas

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) networks for application in dense RAN topologies, Analog-Radio-over-Fiber (A-RoF) technology is regarded as a key enabling solution, since it greatly simplifies the remote antenna while offering very high spectral efficiency. For this type of dense A-RoF network, new and efficient Medium-Transparent-Medium Access Control (MT-MAC) protocols are required that can concurrently arbitrate optical and wireless resources, while at the same time offering the necessary Quality-of-Service (QoS) for correct operation of the combined Fronthaul/Midhaul/Backhaul segments present in 5G disaggregated RANs. In this paper, we propose a QoS-enabled MT-MAC (qMT-MAC) protocol that can combine Fronthaul/Midhaul/Backhaul flows under the same framework, while satisfying the strict delay and jitter requirements set by the relevant standards. Results show that qMT-MAC concurrently achieves the delay and jitter requirements for combined Fronthaul/Midhaul/Backhaul traffic even when loads approach the network’s capacity, while attested enhanced prioritization policies can offer up to a 64% delay reduction over State-of-the-Art MT-MAC protocols.

Backhaul (telecommunications)

PHY

Access network

Spectral Efficiency

10.3390/app12178708

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Citations (3)

Medium-transparent Dynamic Bandwidth Allocation for 5G Fiber Wireless Dense Fronthaul Networks

Agapi Mesοdiakaki Pavlos Maniotis Ch. Vagionas Marios Gatzianas Eftychia Datsika

Fifth generation (5G) networks are expected to combine several technologies to meet the ever-increasing capacity demands. Among them, centralized-radio access network (C- RAN) 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. Another key 5G technology is the deployment of a massive number of multiple-input multiple-output (MIMO) antennas operating at higher frequencies, i.e., at the millimeter wave (mmWave) band. However, this move towards high mmWave traffic streams make the use of the traditional interface between BBU and RRH, its main specification being the common public radio interface (CPRI), prohibitive. To that end, a novel 5G fronthaul architecture is needed, able to cope with scenarios where high fronthaul traffic is expected, e.g., in dense area networks. To ensure high performance, an efficient medium access control (MAC) protocol should be also designed for these demanding use cases. To this end, a medium transparent MAC (MT-MAC) protocol was recently proposed for fiber wireless (FiWi) fronthaul networks. Although MT-MAC was shown to achieve high performance in terms of throughput and delay for indoor scenarios, its performance under challenging outdoor scenarios is unknown. Hence, in this paper, we study the MT- MAC performance under realistic outdoor dense area network conditions and we comment on its suitability as a 5G protocol solution for FiWi fronthaul networks. Finally, further insights are given for the key parameters that should be taken into account in the design of efficient 5G protocol solutions.

Access network

10.1109/camad.2018.8514953

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Citations (3)

5G Small-Cell Networks Exploiting Optical Technologies with mmWave Massive MIMO and MT-MAC Protocols

Advances in intelligent systems and computing (2018)

S. Papaioannou George Kalfas Christos Vagionas Charoula Mitsolidou Pavlos Maniotis

10.1007/978-3-319-75175-7_79

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Citations (1)

Very High Throughput 60GHz wireless enterprise networks over GPON infrastructure

George Kalfas S. Markou D. Tsiokos Christos Verikoukis Nikos Pleros

We present our findings regarding the deployment of 60GHz Gigabit WLAN RoF enterprise networks operating under Medium Transparent-MAC protocols over existing GPON infrastructures. Two possible network scenarios are investigated: i) the GPON-plus-RoF approach considering the 60GHz RoF bus WLAN connected to a conventional GPON ONU, and ii)the RoF-over-PON, which fuses the GPON OLT with the MT-MAC Access Gate at the same Central Office (CO). Simulation-based throughput and delay results are obtained for both network scenarios, revealing the dependence of the 60GHz enterprise network performance on several network planning parameters such as the number of optical wavelengths being available to the enterprise network, the GPON dedicated bandwidth, the load of the enterprise network as well as the percentage of inter- and intra-LAN traffic, highlighting in each case the prevailing architecture.

Gigabit

Access network

10.1109/iccw.2013.6649357

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Citations (8)