The rapid advances in quantum computing pressure the existing essential cryptographic algorithms. In this context, Quantum Key Distribution (QKD) has been proposed as a quantum safe solution for key distribution. However, current QKD systems require an authenticated classical channel which relies on pre-shared symmetric keys that are manually distributed and do not guarantee the identity of the hardware that hosts them. This paper proposes a novel scheme, the Physically Unclonable Quantum Key Distribution (PU-QKD) system, to intrinsically authenticate the communicating endpoints in QKD. The PU-QKD scheme leverages classical Physical Unclonable Functions (PUFs) to encode the data transmission in discrete variable QKD protocols (e.g., BB84). Our scheme maintains the information-theoretic security of QKD protocols by integrating the PUF as an additional layer. Authentication is bound to hardware, providing a robust fingerprint, while lower post-processing overhead increases key rates. Additionally, the proposed scheme is resilient against state-of-the-art PUF vulnerabilities, such as modeling attacks.

A multi-objective optimization problem involves optimizing two or more conflicting objectives simultaneously. This type of problem arises in many scientific and industrial areas and it is classified as NP-Hard. Network routing optimization with multiple objectives falls into this category. In the context of 6G networks, solving this problem will become even more challenging due to the exponential growth of Internet of Things devices and the high quality of service requirements. Finding good quality solutions for large-scale networks will be increasingly difficult. In this paper, we introduce a quantum-inspired routing optimization scheme in which noisy-intermediate scale quantum computers (NISQ) can be used to solve the Multi-Objective Routing Problem (MORP). We evaluate the application of the proposed scheme in detail by first developing the mathematical formulas for both single-objective and multi-objective routing and mapping the problem onto gate-based models by using the quadratic unconstrained binary optimization (QUBO) approach. To validate the proposed scheme, we use the quantum approximate optimization algorithm (QAOA), the go-to approach for solving combinatorial optimization problems that are classically intractable. For the simulation, we use the IBM-Qasm simulator and Qiskit framework. Additionally, we use the Chernoff Bound as a standard technique to estimate the sample complexity of QAOA. Finally, we provide a detailed numerical and theoretical analysis of the proposed scheme, including its time complexity, resource requirements, and the challenges associated with it. Our results demonstrate that the proposed approach operates with a time complexity of O ( E 2 ) per iteration in both single and multi-objective scenarios, with an overall runtime of ( n iteration + n CB ) ⋅ O ( E 2 ) influenced by the sampling overhead, significantly outperforming Dijkstra’s algorithm in the multi-objective case, where the complexity increases to O ( 2 k ( N ( k + log N ) + 2 k E ) ) .

Time-sharing of Quantum Key Distribution (QKD) transceivers with the help of optical switches and a central Software-Defined Networking (SDN) controller is a promising technique to better amortize the large investments required to build a Quantum Key Distribution Network (QKDN). In this work, we investigate the implications of introducing Time-Division Multiplexing (TDM) in trusted-relay QKDNs at the wide-area network scale in terms of performance and cost-saving. To this end, we developed both a Mixed Integer Linear Programming (qTDM-MILP) model and a Heuristic Algorithm (qTDM-HA) to solve the allocation of QKD transceivers and network resources for a novel switched QKDN operating scheme: qTDM-QKDN. Our heuristic method provides a close-to-optimal resource planning for the offline problem that computes the minimum number of QKD transceivers and optical switch ports at each node, as well as the number of quantum channels on each link required to satisfy a target set of end-to-end secret-keyrate demands. Moreover, both the model and the heuristic provide the time fractions that each QKD transceiver needs to peer with each neighbor QKD transceiver. We compared our proposed model and heuristic algorithm for cost minimization with non-time sharing QKD transceivers (nTDM) as baseline. The results show that qTDM can achieve substantial cost-savings in the range of 10%–40% compared to nTDM. Furthermore, this work sheds light on the selection of the value for the working cycle T and its influence on network performance. • TDM optimizes QKD networks, enhancing efficiency and cost-effectiveness. • A MILP model and the qTDM-HA ease resource allocation in large-scale QKD networks. • The tools provide outstanding solutions from 10% to 40% in terms of cost-savings. • TDM minimizes the number of dedicated QKD transceivers by using shared ones wisely.

The emergence of quantum computing poses a threat to classical cryptography algorithms, necessitating a shift to quantum secure cryptography. Hybrid protocols combining at least one classical and one quantum-resistant cryptographic algorithm are becoming the standard for securing communications. In this work, we present our novel solution for integrating three different cryptographic assumptions (two of them quantumresistant) into hybrid network security protocols, ensuring that three different cryptographic assumptions must be broken before the protocol becomes vulnerable. Our solution allows for a seamless integration of classical and post-quantum (PQ) cryptography, and quantum key distribution (QKD) into existing network security protocols (e.g., TLS, IPsec) without any major modifications to the protocols themselves. This crypto-agility ensures the mitigation of some of the most well known challenges of both PQ cryptography and QKD. Our findings demonstrate the feasibility of such triple-hybrid network security protocols, showing non-substantial decrease in performance and almost no added packet overhead compared to state of the art protocols. In exchange, we pave the way towards next generation networks where the potential of new quantum-resistant cryptographic schemes can be leveraged in a dynamic and agile fashion, thus fostering a new era of unbreakable communication systems.

This paper presents the implementation of a fully functional 5G network on a compact, energy-efficient edge micro datacenter, showcasing features such as workload prediction and preemptive scaling. The network extends across multiple edge micro datacenters and incorporates quantum-secure connectivity. Our demonstration provides a blueprint for forward-looking 5G deployments aiming to meet challenging latency and throughput requirements while complying with stringent security requirements. Measurements are performed for network throughput and latency as well as for CPU load of the different components of the 5G deployment, including distributed unit, centralised unit control and user planes, 5G core and the RAN intelligent controller. Additionally, an intelligent workload prediction mechanism, based on an LSTM model, enables preemptive scaling of the centralised unit’s user plane. This proactive approach helps to mitigate bottlenecks as the number of users connecting to the network increases.

Quantum key distribution (QKD) is a symmetric key exchange mechanism designed to enhance the security of current communication systems. Although QKD provides unconditional security, it also comes with deployment challenges. One challenge is the distance limitation between the transmitter and receiver, which restricts the large-scale adoption of QKD. To overcome this, trusted relays are used as intermediate nodes, allowing QKD to evolve from distance-limited point-to-point connections to unlimited QKD networks (QKDN). With an increasing deployment of QKD and a growing number of applications requesting keys, quality of service (QoS) constraints must be set for efficient key resource management to alleviate the risk of rejecting application requests. In this work, we integrate key delivery delay and maximum requested key size as QoS constraints in a novel key allocation algorithm built on three QKDN layers – quantum, key management and service. Moreover, we design key relaying using quantum key pools and virtual quantum key pools as storage mechanisms. We use static and dynamic weights for relay path computation and evaluate their impact on the proposed key allocation strategies with QoS constraints and find that static weights show a good overall performance for QKDN, while performance with dynamic weights varies based on historical key consumption data.

The imminent advent of Quantum Computers poses a significant threat to the cryptographic algorithms supporting the public key infrastructure (PKI) of widely used communication protocols. High Performance Computing (HPC) data centers among other interested parties are well aware of the catastrophic consequences quantum attacks could have on their PKI and are consequently transitioning to Post-Quantum Cryptographic (PQC) methods, despite the substantial overhead this introduces for handling incoming network packets. This work addresses the transition to PQC within the context of the Cloud-Edge Continuum by integrating the Open Quantum Safe (OQS) library into the accelerated strongSwan developed by Mellanox for Data Processing Units (DPUs). This integration offloads cryptographic operations from central servers to data DPUs distributed across the cloud-edge continuum. Our solution ensures quantum security by providing PQ authentication through CRYSTALS-Dilithium or CRYSTALS-FALCON, PQ key exchanges via CRYSTALS-Kyber, and confidential data transmission using AES-256. Additionally, the deployment of this implementation on DPUs helps reduce the computational load on both HPC data centers and edge devices, promoting more efficient and secure operations across the entire cloud-edge continuum.

The reliance on asymmetric public key cryptography (PKC) and symmetric encryption for cyber-security in current telecommunication networks is threatened by the emergence of powerful quantum computing technology. This is due to the ability of quantum computers to efficiently solve problems such as factorization or discrete logarithms, which are the basis for classical PKC schemes. Thus, the assumption that communications networks are secure no longer holds true. Quantum Key Distribution (QKD) and post-quantum cryptography (PQC) are the first cyber-security technologies that allow communications to resist the attacks of a quantum computer. To achieve quantum-resistant communications, the aforementioned technologies need to be incorporated into a network security protocol such as Transport Layer Security (TLS). In this paper, we describe and implement two novel, hybrid solutions in which QKD and PQC are combined inside TLS for achieving quantum-resistant authenticated key exchange: Concatenation and Exclusively-OR (XOR). We present the results, in terms of complexity and security enhancement, of integrating state-of-the-art QKD and PQC technologies into a practical, industry-ready TLS implementation. Our findings demonstrate that the adoption of a PQC-only approach enhances the TLS handshake performance by approximately 9 % compared to classical methods. Furthermore, our hybrid PQC-QKD quantum-resistant TLS comes at a performance cost of approximately 117 % during the key establishment process. In return, we substantially augment the security of the handshake, paving the road for the development of future-proof quantum-resistant communication systems based on QKD and PQC.

Future mobile networks will offer high data rates based on high-capacity fronthaul. Current fronthaul design has two main components that communicate via the common public radio interface and fiber links, i.e., remote units (RUs) that implement simple signal processing and centralized baseband units (CBBUs) in high power-consuming data centers that perform complex network functions. Various functional splits between CBBUs and RUs are feasible, inducing trade-offs between centralization gains and bandwidth demands. This design lacks in capacity and flexibility, motivating the use of converged fiber-wireless (Fi-Wi) fronthaul with high-bandwidth fiber and millimeter-wave links, and splits that move functionalities to RUs reducing the delay demands. Further flexibility is offered by analog radio-over-fiber fronthaul that supports dynamic functional splitting via software-defined networking (SDN). Ensuring acceptable delay for all RUs, i.e., minimizing fronthaul grade-of-service (GoS), requires selection of CBBUs, channel bandwidth and functional splits of RUs. The split type affects fronthaul power consumption determining which fronthaul components are active and their processing power. Using a simulated annealing-based dynamic fronthaul resource allocation (DFRA) scheme, we jointly optimize GoS and power consumption in a novel SDN Fi-Wi fronthaul. Our results show that DFRA minimizes GoS and power consumption for all load levels outperforming baseline approaches.

We experimentally demonstrate a 5G digital fronthaul network that relies on multi-adaptive bandwidth/bitrate variable transceivers (BVTs) and an autonomic software-defined networking (SDN) control system for partially-disaggregated wavelength division multiplexing (WDM)/space division multiplexing (SDM). Transmission of 256-QAM 760.32 MHz orthogonal frequency-division multiplexing (OFDM) radio signal is performed, with a total radio transmission capacity of 5.667 Gb/s. Digitized signal samples are carried as a 22.25 Gb/s digitized radio-over-fiber (DRoF) data stream and transmitted over a WDM/SDM infrastructure including 40-wavelength 100-GHz arrayed waveguide gratings (AWGs) and 19-core fiber. The autonomic SDN controller deploys a control loop for the multi-adaptive OFDM-based BVTs that monitors the per-subcarrier signal to noise ratio (SNR) and assigns the optimal constellation based on the actual signal degradation. An error vector magnitude (EVM) below the targeted 2.1% is achieved while setting up connections in less than 5 s.

Flexible spectrum assignment in Elastic Optical Networks (EON) has emerged as a potential solution for allowing dynamic and elastic management of available bandwidth resources. In this paper, we demonstrate and evaluate our developed flexi-grid optical domain controller based on NETCONF/YANG. Our proposed modular architecture, based on Finite State Machines (FSMs), allows the flexibility to deploy the controller either in a centralized or in a distributed state for on the fly encrypted device management connections. A testbed composed of two physical Sliceable Bandwidth Variable Transponders (SBVTs) and an emulated flexi-grid optical network was used for our software evaluation. Controller startup and synchronization time, as well as media channel setup time are evaluated to compare the two deployment options and assess network scaling effects. Results demonstrate that our software is scalable by maintaining a relatively constant startup time on the networks tested (i.e., 1 to 64 nodes) in both deployment options. Software scalability is also supported by the media channel setup time, which presents a modest log scale growth when increasing the number of nodes from one to 64.

In this paper, we propose a new IP transmission architecture over optical fast frequency hopping code-division multiple-access (OFFH-CDMA) network capable of supporting multirate transmissions for applications in flexible optical access networks. The proposed network architecture is independent of the spreading code employed and does not require any new optical processing technology. The performance of the proposed network is analyzed under different channel utilization conditions, where the utilization is equally varied for all classes at the same instance to fairly maintain the original designed transmission rate. Furthermore, to evaluate the network performance, we derive new expressions for the decoder bit error rate (BER), total BER, packet error rate (PER), and packet throughput. We analyze the performance of a two-class OFFH-CDMA packet network, where multirate transmissions are achieved via manipulation of the user's code parameters. The analytical results show that high code weight user' classes possess better overall performance. In addition, it is shown that the packet throughput performance of low code weight user' classes is more susceptible to channel utilization variations than a user class with high code weight.

In this paper, the packet throughput performance of multiservice, multirate optical code-division multiple-access (OCDMA) networks is addressed based on two distinct multirate techniques, namely multilength code and multicode. A new analytical formalism to evaluate the packet throughput performance of both multirate techniques is proposed. The proposed formalism can be successfully applied for performance evaluation of any arbitrary number of user classes in the system as well as for both 1-D and 2-D codes. The bit error rate (BER) and packet correct probability expressions are derived considering the multiple-access interference (MAI) as binomially distributed. The packet throughput expression, by its turn, is derived considering a Poisson distribution for the composite packet arrivals. Numerical results show that the multicode technique is a good candidate for future multiservice, multirate OCDMA implementations, where higher rates and diversified patterns of data traffic will be major network requirements.

Two pulse shapes for IR-UWB transmission under the Russian spectral emission mask are proposed and their potential experimentally demonstrated. Pulses based on the hyperbolic secant square function and the frequency B-spline wavelet are shown to enable transmission of 1.25Gbit/s signals, reaching a maximum transmission distance of 6.5 m.

For the first time Ultra-Wideband record data transmission rates up to 35.1 Gbps and 21.6 Gbps are achieved, compliant with the restrictions on the effective radiated power established by both the United States Federal Communications Commission and the European Electronic Communications Committee, respectively. To achieve these record bit rates, the multi-band approach of Carrierless Amplitude Phase modulation scheme was employed. Wireless transmissions were achieved with a BER below the 7% overhead FEC threshold of 3.810-3.

In this work, we evaluate the performance of Wavelet-Coding into offering robustness for OFDM signals against the combined effects of varying fading and noise bursts. Wavelet-Code enables high diversity gains with a low complex receiver, and, most notably, without compromising the system's spectral efficiency. The results show that the Wavelet-Coded OFDM system achieves a BER of 1E-3 with nearly 6 dB less SNR than the convolutional coded OFDM system in frequency selective channels with a normalized channel response variation rate of ζ=1E-4.The proposed system fits as a key enabler for the use of mm-wave frequencies in future generation mobile communication due to its robustness against multipath fading.

Methods to upgrade the network infrastructure to cope with current traffic demands has attracted increasing research efforts. A promising alternative is signal slicing. Signal slicing aims at re-using low bandwidth equipment to satisfy high bandwidth traffic demands. This technique has been used also for implementing full signal path symmetry in real-time oscilloscopes to provide performance and signal fidelity (i.e. lower noise and jitter). In this paper the key digital signal processing (DSP) subsystems required to achieve signal slicing are surveyed. It also presents, for the first time, a comprehensive DSP power consumption analysis for both WDM and TDM systems at 1 Gbps and 10 Gbps, discussing latency penalties for each approach. For 1 Gbps WDM system 278 pJ per information bit for 4 slices is reported at 105 ns latency penalties, whereas 3898.4 pJ per information bit at 183.5 μs latency penalty is reported for 10 Gbps. Power savings of the order of hundreds of Watts can be obtained when using signal slicing as an alternative to 10 Gbps implemented access networks.

The energy efficiency in telecommunication networks is gaining more relevance as the Internet traffic is growing. The introduction of OFDM and dynamic operation opens new horizons in the operation of optical networks, improving the network flexibility and its efficiency. In this paper, we compare the performance in terms of energy efficiency of a flexible-grid OFDM-based solution with a fixed-grid WDM network in a dynamic scenario with time-varying connections. We highlight the benefits that the bandwidth elasticity and the flexibility of selecting different modulation formats can offer compared to the rigidity of the conventional networks.

The performance of radio-over-fiber optical transmission employing vertical-cavity surface-emitting lasers (VCSELs), and further wireless transmission, of the two major ultra-wideband (UWB) implementations is reported when operating in the 60-GHz radio band. Performance is evaluated at 1.44 Gbit/s bitrate. The two UWB implementations considered employ dual-carrier modulation orthogonal frequency-division multiplexing (DCM-OFDM) and binary phase-shift keying impulse radio (BPSK-IR) modulation respectively. Optical transmission distances up to 40 km in standard single-mode fiber and up to 500 m in bend-insensitive single-mode fiber with wireless transmission up to 5 m in both cases is demonstrated with no penalty. A simulation analysis has also been performed in order to investigate the operational limits. The analysis results are in excellent agreement with the experimental work and indicate good tolerance to chromatic dispersion due to the chirp characteristics of electro-optical conversion when a directly-modulated VCSEL is employed. The performance comparison indicates that BPSK-IR UWB exhibits better tolerance to optical transmission impairments requiring lower received optical power than its DCM-OFDM UWB counterpart when operating in the 60-GHz band.

Closed-form expressions for the moment generating function (MGF) of the filtered output of square envelope receivers with signal and colored Gaussian noise input are derived. The informative signal is a binary sequence of rectangular pulses. The considered Gaussian processes are the Wiener process, a Gaussian process with linear covariance (moving average), and the Ornstein-Uhlenbeck process. The derived MGFs are then applied to the problem of finding the quantum limit for optically preamplified, direct detection receivers.

We present a recursive formula for the moments of phase noise in communication systems. The phase noise is modeled using continuous Brownian motion. The recursion is simple and valid for an arbitrary initial phase value. The moments obtained bp the recursion are used to calculate approximations to the probability density function of the phase noise, using orthogonal polynomial series expansions and a maximum entropy criterion.