A Delayed-ACK Scheme for Performance Enhancement of Wireless LANs

The IEEE 802.11 MAC protocol provides a reliable link layer using Stop & Wait ARQ. The cost for high reliability is the overhead due to acknowledgement packets in the direction opposite to the actual data flow. In this paper, the design of a new protocol as an enhancement of IEEE 802.11 is proposed, with the aim of reducing supplementary traffic overhead in order to increase the bandwidth available for actual data transmission. The performance of the proposed protocol is evaluated through comparison with IEEE 802.11 as well as with a SSCOP-based protocol. Results underline significant advantages of the proposed protocol against existing ones, thus confirming the value and potentiality of the approach

A Survey of Network Optimization Techniques for Traffic Engineering

TCP/IP represents the reference standard for the implementation of interoperable communication networks. Nevertheless, the layering principle at the basis of interoperability severely limits the performance of data communication networks, thus requiring proper configuration and management in order to provide effective management of traffic flows. This paper presents a brief survey related to network optimization using Traffic Engineering algorithms, aiming at providing additional insight to the different alternatives available in the scientific literature

Electric Power Allocation in a Network of Fast Charging Stations

In order to increase the penetration of electric vehicles, a network of fast charging stations that can provide drivers with a certain level of quality of service (QoS) is needed. However, given the strain that such a network can exert on the power grid, and the mobility of loads represented by electric vehicles, operating it efficiently is a challenging problem. In this paper, we examine a network of charging stations equipped with an energy storage device and propose a scheme that allocates power to them from the grid, as well as routes customers. We examine three scenarios, gradually increasing their complexity. In the first one, all stations have identical charging capabilities and energy storage devices, draw constant power from the grid and no routing decisions of customers are considered. It represents the current state of affairs and serves as a baseline for evaluating the performance of the proposed scheme. In the second scenario, power to the stations is allocated in an optimal manner from the grid and in addition a certain percentage of customers can be routed to nearby stations. In the final scenario, optimal allocation of both power from the grid and customers to stations is considered. The three scenarios are evaluated using real traffic traces corresponding to weekday rush hour from a large metropolitan area in the US. The results indicate that the proposed scheme offers substantial improvements of performance compared to the current mode of operation; namely, more customers can be served with the same amount of power, thus enabling the station operators to increase their profitability. Further, the scheme provides guarantees to customers in terms of the probability of being blocked by the closest charging station. Overall, the paper addresses key issues related to the efficient operation of a network of charging stations.Comment: Published in IEEE Journal on Selected Areas in Communications July 201

“This Is Totally Inappropriate”: Louis C.K.’s Use of Narrative to Build Dialogic Connections

The performance of stand-up comedy is variously isolating, inviting, linear, and transactional. The stand-up comedian occupies the stage alone, appearing distinctly independent from the audience. Simultaneously, the audience offers their feedback consistently through the presence or absence of laughter. Audience responses to, and judgment of, the stand-up comedian’s performance forms the inexorable bond between these two parties. As such, this (inter)relationship between the comedian and audience is co-created, interdependent, and dynamic. Through the lens of Mikhail Bakhtin, and a review of relevant narrative scholarship, this paper explores the use of narrative by comedian Louis C.K. as being a mode of self-disclosure that connects him with his audience. In particular, I examine how C.K.’s comedic narrative functions to build stronger dialogic connections with his audiences

A Framework for Analysis of Connectivity and Performance Bounds in Ad Hoc Networks and Its Application to a Slotted-ALOHA Scenario

In this paper, a framework is proposed to analyse the problems of connectivity and performance in ad-hoc networks through an analytical approach. To this aim, available results regarding the application of percolation theory to the study of connectivity in ad-hoc networks are exploited jointly with communication theory models in order to derive the configuration of network parameters that ensures long range connectivity among nodes and the corresponding available capacity on the wireless medium. The framework is then applied to a slotted ALOHA ad-hoc network. Theoretical and numerical results validate the approach and allow the derivation of interesting design principles for ad-hoc networks that consider the impact of physical and MAC-level parameters on network connectivity and end-to-end performance

Aspects of Leptogenesis Scenarios at Grand Unification and Sub-TeV Scales and Their Possible Low-Energy Tests

In the present Thesis, we investigate various aspects of leptogenesis scenarios based on the type-I seesaw extension of the Standard Model (SM) with 2, 3 heavy Majorana neutrinos $N_j$ with masses $M_j$, $j = 1,\,...,\,3$, as well as the possibilities to test the scenarios considered by us in currently running and/or future planned low-energy experiments. We focus first on the high-scale leptogenesis framework with strongly hierarchical mass spectrum of the heavy Majorana neutrinos, namely $M_1$ << $M_2$ << $M_3$, with $M_1$ in the range $(10^{8}-10^{14})$ GeV, concentrating on the possibility that the requisite CP-violation for the generation of the baryon asymmetry of the Universe $\eta_B$ is provided solely by the low-energy Dirac and/or Majorana phases of the light neutrino mixing (PMNS) matrix. A detailed numerical analysis of the solution to the quantum density matrix equations in this scenario, performed with the powerful ULYSSES code we have developed, reveals a number of novel features: i) $\eta_B$ going through zero and changing sign at the transitions between different flavour regimes (1-to-2 and 2-to-3) in the case of vanishing initial abundance of $N_1$ and strong wash-out effects; ii) inadequate description of the transitions between different flavour regimes by the corresponding Boltzmann equations; iii) flavour effects persisting beyond $10^{12}$ GeV and making it possible to reproduce the observed value of $\eta_B$ at these high-scales even though the CP-violation is provided only by the Dirac and/or Majorana phases of the PMNS matrix. Considering the somewhat simpler case of just two heavy Majorana neutrinos $N_{1,\,2}$ (with the heaviest $N_3$ decoupled) we show that relatively large part of the viable leptogenesis parameter space can be probed in low-energy neutrino experiments. We find, in particular, that, when the CP-violation is provided exclusively by the Dirac phase $\delta$ of the PMNS matrix, there is a correlation between the sign of $\sin\delta$ and the sign of $\eta_B$. This opens up the possibility to test part of the parameter space of this scenario in low-energy experiments on CP-violation in neutrino oscillations. A measurement of the Dirac and/or Majorana phases would also constrain the range of scales for which one can have viable leptogenesis in the considered scenario. Next, we show that in the low-scale resonant leptogenesis scenario with two heavy Majorana neutrinos $N_{1,\,2}$ forming a pseudo-Dirac pair, with $M\simeq M_{1,\,2}$ and a small mass splitting $| M_2-M_1 |$ << $M$, the observed $\eta_B$ can be reproduced for $M$ in the range $(0.1\sim 100)$ GeV by relying only on the decay mechanism, either during the production ("freeze-in") or departure from equilibrium ("freeze-out") of $N_{1,\,2}$. In this context, the inclusion of flavour and thermal effects in the formalism of Boltzmann equations is crucial for predicting the observed value of $\eta_B$. Also, we find that the viable parameter space of this resonant scenario is compatible with values of the heavy Majorana neutrino couplings to the SM that could be probed at future colliders, like at the discussed FCC-ee facility. When low-scale leptogenesis with three quasi-degenerate in mass heavy Majorana neutrinos $N_{1,\,2,\,3}$ with $M\simeq M_{1,\,2,\,3}$ is considered in the formalism of density matrix equations and, in particular, with both the heavy Majorana neutrino oscillation and decay mechanisms taken into account, the viable parameter space for $M$ in the range $(0.05-7\times 10^4)$ GeV enlarges considerably and becomes accessible to direct searches at the LHC, as well as in fixed target experiments and future colliders. We demonstrate that planned and upcoming experiments on charged lepton flavour violating processes with muons $\mu^\pm$, specifically MEG II on $\mu\to e\gamma$ decay, Mu3e on $\mu \to eee$ decay, Mu2e and COMET on $\mu - e$ conversion in aluminium and PRISM/PRIME on $\mu - e$ conversion in titanium, can test significant region of the viable leptogenesis parameter space and may potentially establish the first hint of such low-scale leptogenesis scenario

Riduzione del mutuo accoppiamento tra antenne a microstriscia mediante l'utilizzo di superfici a banda proibita

Questo lavoro di tesi tratta lo studio del mutuo accoppiamento tra due antenne a microstriscia e l’uso di superfici a banda proibita per cercare di ridurlo. Il mutuo accoppiamento è un disturbo che nasce quando due antenne sono poste nelle vicinanze. Questo rappresenta un problema, soprattutto nelle attuali apparecchiature elettroniche, dove gli elementi circuitali sono in stretto contatto. Le superfici a banda proibita sono strutture che presentano un bandgap, ossia un intervallo frequenziale in cui le onde superficiali non si propagano. Sono composte da una matrice di patch metallici stampati su un substrato dielettrico e collegati al piano di massa attraverso dei pin metallici, detti vias, posti al centro del patch, che garantiscono la presenza del bandgap. Grazie a questa loro caratteristica, stampate sullo stesso substrato delle antenne a microstriscia, garantiscono un certo disaccoppiamento. Oltre ad indagare l’efficacia di tali superfici, è stata rivolta l’attenzione all’importanza della forma dei patch per ottenere risultati migliori in termini di riduzione dell’accoppiamento e di occupazione spaziale