Quantum Key Distribution (QKD) can distribute keys with guaranteed security but remains susceptible to key exchange interruption due to physical-layer threats, such as high-power jamming attacks. To address this challenge, we first introduce a novel metric, namely Maximum Number of Affected Requests (maxNAR), to quantify the worst-case impact of a single physical-layer attack, and then we investigate a new problem of Routing and Wavelength Assignment with Minimal Attack Radius (RWA-MAR). We formulate the problem using an Integer Linear Programming (ILP) model and propose a scalable heuristic to efficiently minimize maxNAR. Our approach incorporates key caching through Quantum Key Pools (QKPs) to enhance resilience and optimize resource utilization. Moreover, we model the impact of different QKD network architectures, employing Optical Bypass (OB) for optical switching of quantum channels and Trusted Relay (TR) for secure key forwarding. Moreover, a tunable parameter is designed in the heuristic to guide the preference for OB or TR, offering enhanced adaptability and dynamic control in diverse network scenarios. Simulation results show our method significantly outperforms the baseline in terms of security and scalability.

Progressive network recovery is the problem arising when a network is subject to massive failures and the network operator has to identify the optimal sequence of repair actions to maximize carried traffic. As initial deployments of quantum-key-distribution (QKD) over optical networks start appearing in several locations worldwide, in this paper, for the first time, we model and solve the Progressive QKD Network recovery (PQNR) problem in QKD networks to accelerate the QKD network recovery after massive failures. Specifically, we formulate an Integer Linear Programming (ILP) model to model the achievable key rate for different QKD network architectures (w/o trusted relay and optical bypass). Due to the scalability issue of ILP, we also propose a scalable heuristic to solve the PQNR problem for large topologies. Our numerical results show that joint utilization of optical bypass and trusted node technologies leads to significant improvement in performance and that our heuristic solution has an acceptable optimality gap compared with ILP while reducing time.

On behalf of the Organizing Committee, we have been delighted to welcome you to the IEEE Global Telecommunications Conference (GLOBECOM 2022). The conference was held in Rio de Janeiro, Brazil from 4 to 8 December 2022. IEEE GLOBECOM is one of the two flagship conferences of the IEEE Communications Society (IEEE ComSoc). It is a premium event that brings together the best researchers and professionals from academic, industry and government to exchange novel ideas that will shape future generations of communication technologies. IEEE Globecom 2022 featured striking advances in communications research and industry development, which will certainly lead to new systems and networks and bring humanity to a new World, still unimaginable. The theme of Globecom 2022 “Accelerating the Digital Transformation through Smart Communications” reflects the fundamental role of intelligent communications in enabling dynamically adaptive societal systems.

Recently, communication in cellular networks assisted by Unmanned Aerial Vehicles (UAVs) has attracted considerable attention, as it provides wireless connectivity to devices in areas with poor coverage. With a single UAV deployed, it is difficult to achieve Line-of-Sight (LoS) probability and network availability targets for critical Ultra-Reliable Low-Latency Communication (URLLC) applications while meeting cost and system complexity requirements. To harness the advantages of UAVs in these situations, an alternative solution is to deploy a multi-UAV system, exploiting inter-connectivity to maintain uninterrupted communication with a ground transmitter. The idea is to deploy a fixed UAV on the side of a building rooftop, which acts as a relay between the ground transmitter and the flying UAV base station, thus increasing the LoS probability. Notably, a two-hop amplify-and-forward relay can provide significant improvements in the channel capacity, channel gain, and thus overall quality of service. In our study, simulations were carried out in four general environments as specified by ITU-R, namely Suburban, Urban, Dense Urban, and High Rise Urban, based on data collected in Los Angeles, USA. Numerical results demonstrate that two-hop communication via a relay UAV increases LoS probability in all environments, thus improving system reliability and feasibility.

Low altitude aerial base stations onboard unmanned aerial vehicles (UAVs) have recently gained a lot of attention to provide cellular coverage to mobile ground users. In this paper we evaluate the effect of carrier frequency offset (CFO) on the symbol error rate in the downlink of such systems, where a long-term evolution (LTE) compatible time-frequency grid based on generalized frequency division multiplexing (GFDM) is considered. The choice of GFDM as multi-carrier modulation scheme is motivated by its widely proposed application in fifth generation cellular systems and its backward compatibility with LTE. Simulation results are shown for "Better than the Nyquist (BTN)" pulse shaping filters in three different environments: Suburban, Urban and Urban High Rise. The use of BTN pulse shaping filters allows for higher robustness to CFO as compared to base line pulse shaping filer know as root-raised cosine filters for different environments conditions. Simulation results are presented considering realistic air-to-ground propagation conditions generated from the commercial Wireless InSite ray-tracing radio propagation software.

In order to estimate the Hurst parameter of Internet traffic data, it has been recently proposed a log-regression estimator based on the so-called modified Allan variance (MAVAR). Simulations have shown that this estimator achieves higher accuracy and better confidence when compared with an other method of common use based on wavelet analysis. Here we link it to the wavelets setting and stress why a different analysis for the two approaches is required. We then focus on the asymptotic analysis of the MAVAR log-regression estimator and provide new formulas for the related confidence intervals. By numerical evaluation, we analyze these formulas and make a comparison between three suitable choices on the regression weights, also optimizing over different choices on the data progression.

Long-range dependence (LRD) is a widely verified property of Internet traffic, which severeiy affects network performance yielding longer queuing delays. Token-bucket policers are commonly proposed to enforce the statistical profile of input traffic, but they can hardly reduce LRD and thus can be ineffective to protect service level agreements against LRD increase in input traffic. In this paper, we investigate by simulation the queuing performance in a downstream scheduler of LRD traffic regulated by token-bucket policers. We compare the delay distributions of regulated and unregulated LRD flows. We demonstrate that policers reduce significantly the downstream queuing delay, although they do not alter much the 1/falphaspectrum of regulated traffic. We observe also that the policed traffic does not obey a plain fractional Gaussian traffic model: first, it is not Gaussian anymore; moreover, also its third-order two-lags covariance is altered by the policer. Finally, we point out that policers can reduce noticeably the negative impact of traffic LRD increase on queuing delay, although they can diminish actual LRD only slightly.

Long-range dependence (LRD) is a widely verified property of traffic crossing the wireless LAN radio interface. LRD severely affects network performance yielding longer queuing delays. In this paper, we study how LRD and non-LRD traffic flows influence each other in the IEEE 802.11e wireless access network and their queuing behaviour in downstream schedulers. We consider scenarios with one and two wireless hops. We investigate interaction of traffic flows with the service class separation enabled by the IEEE 802.11e EDCA function, comparing results with those of the basic scenario with a single service class shared by all traffic flows. We find that a partial isolation of service classes is enabled by the IEEE 802.11e access function. However, competing flows exhibit a queuing behavior, in downstream schedulers, which cannot be accounted for by standard LRD traffic descriptors.

Long-range dependence (LRD) is a widely verified property of Internet traffic, which severely impacts network performance yielding longer queuing delays. Moreover, LRD is almost ubiquitous and very hard to remove or control. In this work, we investigated by thorough simulation the effect of schedulers on traffic LRD. We analyzed the output traffic of schedulers merging LRD flows according to various service policies, viz. plain FIFO, static-priority, earliest-deadline-first and general processor sharing. First, we noticed that traffic LRD is not affected much by crossing the scheduler, for any type of service policy. Second, we showed that LRD also propagates across different service classes with any policy except balanced GPS, which ensures complete separation between classes. This phenomenon may explain in part why LRD is so widespread in Internet traffic.

Internet traffic exhibits self-similarity and longrange dependence (LRD) on various time scales. In this paper, we propose to use the Modified Allan Variance (MAVAR) and a Modified Hadamard Variance (MHVAR) to estimate the Hurst parameter H of the LRD traffic series or, more generally, the exponent α of data with 1/fα(α ≥ 0) power-law spectrum. MHVAR generalizes the principle of MAVAR, a time-domain quantity widely used for frequency stability characterization, to higher-order differences of input data. In our knowledge, this MHVAR has been mentioned in literature only few times and with little detail so far. The behaviour of MAVAR and MHVAR with power-law random processes and some common deter-ministic signals (viz. drifts, sine waves, steps) is studied by analysis and simulation. The MAVAR and MHVAR accuracy in estimating H is evaluated and compared to that of wavelet Logscale Diagram (LD). Extensive simulations show that MAVAR and MHVAR achieve significantly better confidence and no bias in H estimation. Moreover, MAVAR and MHVAR feature a number of other advantages, which make them valuable to complement other established techniques such as LD. Finally, MHVAR and LD are also applied to a real IP traffic trace.

In this paper, we investigate possible time correlation of answered call arrivals in sets of real GSM telephone traffic data. Instead of attempting to model the empirical distribution of the call interarrival time, as done in several previous works in literature, we emphasize results obtained by the modified Allan variance (MAVAR), a widely used time-domain quantity with excellent capability of discriminating power-law noise types. The call arrival rate exhibits a diurnal trend, with peak hours in the morning and late afternoon. Besides this diurnal rate change, the number of call arrivals in a second is found perfectly uncorrelated to the number of arrivals in other seconds and Poisson distributed, with good consistency by X/sup 2/- test evaluation. Uniform and accurate whiteness of call arrivals per second is verified in all hours, regardless the time of the day. In all series analyzed, the empirical statistics of both originated and terminated call arrivals proves excellent consistency with the ideal Poisson model with diurnal variable rate lambda(t). This study may be valuable to researchers concerned about realistic traffic modelling in planning and performance evaluation of cellular networks.

Long-range dependence (LRD) is a largely verified property of Internet traffic, which severely affects network queuing An approach for guaranteeing performance requirements is controlling the statistical profile of input traffic by policing or shaping regulators. In this paper, it is investigated by simulation how the 1/falphaspectrum of LRD traffic is altered when this is regulated by either policers or shapers. Traffic spectral analysis is carried out mainly by the Modified Allan Variance, a time-domain quantity with demonstrated superior accuracy in fractional-noise parameter estimation. The queuing behaviour of LRD regulated traffic in FIFO schedulers is also investigated. Conditions under which service level agreements based on delay bounds can be violated, by varying alpha in input LRD traffic, are examined.

Long-range dependence (LRD) is a largely verified property of Internet traffic, which severely affects queuing performance in network buffers. A common approach for guaranteeing performance requirements is to control the statistical profile of the input traffic by regulators based on the leaky bucket scheme. In this paper, we investigate by simulation how the l/falphapower-law spectrum of LRD traffic is altered when traffic is regulated by a leaky bucket policer. Analysis of the traffic spectral characteristics is carried out mainly by means of the modified Allan variance, a time-domain quantity with demonstrated superior accuracy in fractional-noise parameter estimation, recently introduced also for traffic analysis. This approach allows to get a finer insight into power-law spectral characteristics of policed traffic. We also investigate some other properties of the leaky bucket fed with LRD traffic, such as its dropping probability and its effect on queuing delay in a following FIFO scheduler.

Single-frequency simulcast networks use two or more radio base stations (RBS) to transmit simultaneously the same signal on the same radio channel over the service area. To ensure correct operation and good performance, simulcast networks need accurate time and frequency synchronization. In this work, we designed a system for synchronizing RBS clocks by way of network time protocol (NTP) packets. The goal is to allow simulcast operation when external sources of synchronization, such as GPS, are not available or when the operator prefers to distribute timing alternatively, in particular by IP network facilities used for data transport. Time stamps are disseminated by a master RBS and used in slave stations to steer local clocks. The mechanism proposed was modelled, simulated and implemented in an experimental prototype. Simulation and experimental measurement results meet requirements and demonstrate the practical feasibility of this approach for commercial application.

Internet traffic exhibits self-similarity and long-range dependence (LRD) on various time scales. In this paper, we propose the use of modified allan variance (MAVAR) and modified Hadamard variance (MHVAR) for the estimation of the Hurst parameterHof LRD traffic series, or more generally, the exponent$\alpha$of data with$1/f^\alpha$$(\alpha \ge 0)$power-law spectrum. MHVAR generalizes the principle of MAVAR, a time-domain quantity widely used for frequency stability characterization, to higher-order differences of input data. In our knowledge, this MHVAR has been mentioned in literature only a few times and with little detail so far.

This paper outlines trends reshaping the business of International Long Distance (ILD) voice minutes trading. Our analysis is centered on Arbinet's business model: an electronic market-place for trading ILD voice minutes. Arbinet, who adopted a minute-based termination model, claims to have switched about 12 x 109minutes in 2005 with 13% growth. Since 2003, other competitors, like Stealth's VPF (Voice Peering Fabric), entered the long distance voice market by introducing different flavors of VoIP (Voice over IP) peering. VPF, who adopted a flat pricing scheme, claims to have routed traffic for an equivalent 18 x 109minutes in 2005 with 750% annual growth. VPF installed its first switch in London late 2005, thus stepping into the ILD arena. The huge growth of flat peering exchanges does not necessarily imply that Arbinet has to give up its minute-based termination model in favor of flat or free peering arrangements. As a matter of fact, the way termination model will change in the future is far to be clear. Drivers that determine who will be fit to survive in this thinly profitable business are thus emphasized.

We investigate the statistical properties of both originated and terminated call arrivals in sets of real GSM telephone traffic data (TIM, Italy), emphasizing results obtained by the modified Allan variance (MAVAR), a widely used time-domain quantity with excellent capability of discriminating power-law noise. The call arrival rate exhibits a diurnal trend, with peak hours in the morning and late afternoon. Besides this diurnal change, the number of call arrivals in a second is found perfectly uncorrelated to the number of arrivals in other seconds and Poisson distributed, with good consistency by chi2-test evaluation. Uniform and accurate whiteness of call arrivals per second is verified in all hours, regardless the time of the day. In all series analyzed, the empirical statistics of both originated and terminated call arrivals proved excellent consistency with the ideal Poisson model with variable rate lambda(t)- This study may be valuable to researchers concerned about realistic modelling of traffic in planning and performance evaluation of cellular networks.

The WONDER project aims at designing and building a WDM packet-switched slotted ring network, with tunable transmitters and fixed receivers. An experimental prototype is under development at the laboratories of Politecnico di Torino. In this paper, we study two different strategies of slot synchronization for such networks: in the former, a slot synchronization signal is transmitted by the master station on a dedicated control wavelength; in the latter, slave nodes achieve slot synchronization aligning on data packets received from the master. Emphasis has been given to the architecture of the WONDER network. The performance of the two synchronization strategies, in terms of packet collision probability, has been evaluated by simulation. The technique based on transmitting a timing signal on a dedicated control wavelength resulted in achieving a better performance, although being more expensive due to need of an additional wavelength. However, the technique based on aligning on data packets received from the master should be not discarded, although attaining lower timing stability, especially if limiting the number of wavelengths and receivers is a strong requirement.

Internet traffic exhibits self-similarity and long-range dependence (LRD) on various time scales. In this paper, we propose to use the Modified Hadamard Variance (MHVAR), a time-domain measure for high-resolution spectral analysis, to estimate the Hurst parameter H of LRD traffic data series or, more generally, the exponent α of traffic series with 1/fα power-law spectrum. MHVAR generalizes the principle of the Modified Allan Variance (MAVAR), a well-known tool widely used since 1981 for frequency stability characterization, to higher-order differences of input data; in our knowledge, it has been mentioned in literature only few times and with little detail so far. The behaviour of MHVAR with power-law random processes and some common deterministic signals (viz. drifts, sine waves, steps) is studied. The MHVAR performance in estimating H is evaluated by analysis and simulation, comparing it to the wavelet Logscale Diagram (LD) and to MAVAR. Extensive simulations show that MHVAR has highest accuracy and confidence in fractional-noise parameter estimation, even slightly better than MAVAR. Moreover, MHVAR features a number of other advantages, which make it useful to complement other established techniques such as MAVAR and LD. Finally, MHVAR and LD are also applied to a real IP traffic trace.

Internet traffic exhibits self-similarity and long-range dependence (LRD) on various time scales. In this work, we analyze IP traffic traces measured on a MAN link of the telecommunications operator FASTWEB. We emphasize results obtained using the modified Allan variance (MAVAR), a well-known time-domain tool originally conceived to discriminate noise types with power-law spectrum (i.e., fractional noise) in frequency stability measurement, which has been introduced in network traffic analysis only recently. MAVAR has been demonstrated to feature superior spectral sensitivity and accuracy in fractional-noise parameter estimation, coupled with outstanding robustness against nonstationarity in data analyzed. Logscale diagrams are also evaluated, to confirm MAVAR experimental findings. All traffic traces analyzed exhibit prominent evidence of fractional noise. Model parameters are estimated. Results obtained are valuable to establish IP traffic models, e.g. necessary for realistic input traffic synthesis in network simulation

Experimental measurements show that Internet traffic exhibits self-similarity and long-range dependence (LRD). A delicate issue is the estimation of traffic statistical quantities that characterize self-similarity and LRD, such as the Hurst parameter H. In this paper, we propose to use the modified Allan variance (MAVAR), a well-known time-domain tool originally studied for frequency stability characterization, for estimating the power-law spectrum and thus the H parameter of LRD traffic time series. This novel method is validated by comparison with one of the most widely adopted algorithms for analyzing LRD traffic: the log-scale diagram technique, based on wavelet analysis. Both methods are applied to a pseudo-random data series, generated with known values of H. MAVAR exhibits outstanding accuracy in estimating H, better than the classical log-scale method. Finally, both techniques are applied to a real IP traffic trace, providing a further example of the capabilities of MAVAR.

In synchronization networks, chains of slave clocks (viz. SASE, SEC) transfer timing along synchronization trails. Hence, the need to assess precisely the performance of timing transfer along such chains, not only in stationary conditions, but also under transient rearrangements occurring after phase and frequency hits on the tuning reference. In this work, the non-linear transient behavior of SEC and SASE clock chains has been simulated in the time domain, in order to evaluate their timing rearrangements after non-small phase and frequency hits on the reference. Both homogeneous and non-homogeneous chains of SEC and SASE clocks have been studied in various configurations, in order to provide synchronization engineers with a comprehensive survey, both in qualitative and quantitative terms, on the timing performance achievable when planning synchronization trails of various type and length.

Poor accuracy of frequency references used in GSM base transceiver stations (BTS) can lead to dropped calls, slow handover between cells and even co-channel interference. In this paper, we report some results of an experimental trial carried out in the Omnitel-Vodafone test plant in Milano (Italy). In authors' knowledge, this is the first paper confirming with experimental data that lack of BTS synchronization affects GSM handover performance, leading to some degradation of quality of service. The speech quality of calls between two GSM handsets, undergoing handover between two BTSs synchronized with variable frequency offset, was measured in terms of mean opinion score (MOS) and speech clipping. For values of fractional frequency offset /spl Delta/f/f/sub n/=0 and 10/sup -7/, all completed calls featured optimal quality in spite of handover. On the contrary, for /spl Delta/f/f/sub n/=10/sup -6/ and 10/sup -5/, performance degradation was experienced: about 40% of completed calls exhibited unpleasant MOS values and high speech-clipping percentages. Such experimental results confirm the importance of GSM network synchronization and warn GSM operators about leaving BTS clocks to operate in free-run: frequency accuracy in the order of 10/sup -6/ to 10/sup -5/ is typical for quartz oscillators commonly used in this equipment.

Loss differentiation algorithms (LDA) are used to provide TCP with an estimate of the cause of packet losses, to improve performance over heterogeneous networks including wired and wireless links. In this work, we compared by simulation the accuracy of several LDA schemes in various realistic scenarios. We experienced that LDA schemes originally proposed in literature exhibit poor performance in estimating the cause of packet losses. Thus, we propose enhancements to the noncongestion packet loss detection (NCPLD) and Vegas schemes, achieving higher accuracy in all network scenarios. We shown that our proposed enhanced schemes approach reasonably ideal accuracy of LDA having perfect knowledge of the cause of packet losses. These results entail the possibility to adopt such algorithms within TCP congestion control, to achieve higher performance over heterogeneous wireless networks.

The deep changes undergone by network traffic have strongly impacted its statistical characterization. The traditional assumptions on traffic characteristics have been proven to be obsolete and a new formalism has been brought about to properly take into account traffic new properties. Accordingly, newly designed analysis tools have been proposed. Our work is focused on the presentation and the test of these tools of analysis, believing that we have first of all to be confident on the methods used to properly characterize network traffic.

This work is based on the optical switch architecture proposed in [M.M Renaud, et al., April 1997] [SBregni, G Guerra, and A Pattavina, Nov. 2002] to handle variable-length packets such as IP datagrams. This optical switch is based on an AWG device to route packets and is equipped with a fiber delay-line stage as optical input buffer. Unfortunately, this switch would require considerable buffering capability to achieve acceptable performance. A possible solution, studied in this paper, is to implement efficient packet deflection inside the optical network as a mean for solving packet contentions on outputs of optical switches. Thus, optical transport networks have been simulated to assess deflection effectiveness, based on a traffic model adherent to real IP traffic measurement. Full-mesh and wheel network topologies have been considered, comparing results to assess deflection effectiveness.

In order to support the continuous growth of transmission capacity demand, optical packet switching technology is emerging as a strong candidate, promising to allow fast dynamic allocation of wavelength-division multiplexing (channels, combined with a high degree of statistical resource sharing). This work addresses the design of optical switch architectures, based on previous proposals available in the technical literature that use an arrayed waveguide grating (AWG) device to route packets. Since the port number of currently available AWGs is a limiting factor, we propose two new modified structures which better exploit the switching capability of this component in the wavelength domain. Since a limited hardware complexity is a key requirement for all-optical switches, due to the high cost of optical components, these different node configurations are compared in terms of complexity. Traffic performance of these new structures in a full optical packet switching scenario is also examined.

In order to support efficiently the fast-growing demand for transmission capacity, optical packet-switched systems seem to be strong candidates as they allow fast dynamic allocation of WDM channels combined with a high degree of statistical resource sharing. We propose the architecture of an input/shared-buffered optical packet switching node, for all-optical switching of IP traffic flows. Since a limited hardware complexity is a key requirement for all-optical switches, due to the high cost of optical components, different node configurations are compared in order to evaluate the effect of a hardware-complexity variation on the performance of the proposed architecture.

In this paper, four heuristic algorithms for the optimal allocation of limited optical-layer, resources in WDM networks (virtual-topology optimization by routing and wavelength assignment) under static traffic demand are compared. While some previous papers assumed that all connection requests must be necessarily satisfied, in this work algorithms are studied aiming at comparing their ability in minimizing both the usage of optical-layer resources and the number of connection requests that cannot be allocated. Thus, this paper reports the results obtained on a 13-nodes simplified topology of the pan-European optical transport network designed in the COST 239 Project. The results of a few hundreds simulations with different traffic matrices have been gathered, by considering separately the cost of resources allocated and the percentage of rejected connections. One algorithm resulted best performing, because in most tests it allocated the lowest cost of optical-layer resources. On the other hand, the four algorithms exhibited comparable performance with respect to the percentage of rejected connections.

The maximum time interval error (MTIE) is historically one of the main time-domain quantities for the specification of clock stability requirements in telecommunications standards. Nevertheless, plain computation of the MTIE standard estimator proves cumbersome in most cases of practical interest, due to its heavy computational weight. In this paper, MTIE is first introduced according to its standard definition. Then, a fast algorithm based on binary decomposition to compute the MTIE standard estimator is described. The computational weight of the binary decomposition algorithm is compared to that of the estimator plain calculation, showing that the number of operations needed is reduced to a term proportional to Nlog/sub 2/N instead of N/sup 2/. A heavy computational saving is therefore achieved, thus making feasible MTIE evaluation based on even long sequences of time error (TE) samples. The algorithm proposed is finally applied to TE sequences generated by simulation of all the types of power-law noise, in order to check its effectiveness and correctness.

The MTIE is historically one of the main time-domain quantities considered for the specification of clock stability requirements in telecommunications standards. In this paper, MTIE is first introduced according to its classical definition and as a percentile quantity. Then, the percentile MTIE is estimated under the assumption of time error (TE) affected by Gaussian white phase modulation noise, by deriving the probability distribution, of the TE spanned range as a function of the noise standard deviation /spl sigma/. The formulas herein derived may allow to interpret common Allan-variance factory specifications in terms of percentile MTIE as well. In order to support the theory with sound experimental evidence, some results measured on state-of-the-art telecommunications clocks are eventually provided.