Aurelio La Corte

A generalized tool for accurate time-domain separation of excited modes in spin-torque oscillators

We propose and develop an advanced signal processing technique that, combined with micromagnetic simulations, is able to deeply describe the non-stationary behavior of spin-torque oscillators, both in terms of time domain and spatial distribution of the magnetization dynamics. The Hilbert-Huang Transform is used for the identification of the time traces of each oscillation in a multimode excitation and enhanced with masking signals and the Ensemble Empirical Mode Decomposition. We emphasize that the technique developed here is general and can be used for any physical non-linear system in the presence of multimode dynamical excitation or intermittence.

Quantifying the Role of Homophily in Human Cooperation Using Multiplex Evolutionary Game Theory

Nature shows as human beings live and grow inside social structures. This assumption allows us to explain and explore how it may shape most of our behaviours and choices, and why we are not just blindly driven by instincts: our decisions are based on more complex cognitive reasons, based on our connectedness on different spaces. Thus, human cooperation emerges from this complex nature of social network. Our paper, focusing on the evolutionary dynamics, is intended to explore how and why it happens, and what kind of impact is caused by homophily among people. We investigate the evolution of human cooperation using evolutionary game theory on multiplex. Multiplexity, as an extra dimension of analysis, allows us to unveil the hidden dynamics and observe non-trivial patterns within a population across network layers. More importantly, we find a striking role of homophily, as the higher the homophily between individuals, the quicker is the convergence towards cooperation in the social dilemma. The simulation results, conducted both macroscopically and microscopically across the network layers in the multiplex, show quantitatively the role of homophily in human cooperation.

Control of perceived quality of service in multimedia retrieval services: prediction-based mechanism vs. compensation buffers

Abstract. In multimedia systems end-to-end delay jitter has a great impact on the continuity of information playback. Therefore, it is necessary to introduce appropriate mechanisms to compensate for delay variations, so that the intramedia and intermedia temporal relationships can be preserved. In this paper, two methods for compensation of the network delay jitter in a distributed multimedia retrieval service are compared: the first is based on prediction of the network delay jitter suffered by each information unit and retrieval time modification at the source site; the second is based on a compensation buffer at the destination site. Comparison is made by assuming a master/slave relationship between the monomedia streams composing the multimedia data flow.

Mobility and quality of service across heterogeneous wireless networks

The ability to guarantee Quality of Service (QoS) is one of the key issues in the creation of a telecommunication system. In this paper, we deal with some aspects of providing QoS in wired cum wireless communication environment, focusing on the specific feature of guaranteeing session continuity when the wireless networks, to which a mobile terminal connects to, are also heterogeneous. The terms that define what QoS is should, in this case, be reviewed in order to account also for all aspects related to user mobility inside such an environment. In this paper, such a new framework for the representation of QoS is proposed. Moreover, a wireless mobility test case is also presented. This is based on appropriate middleware we implemented, which allows a mobile terminal to experience real wireless IP mobility while moving on a large spatial scale between different sites, scattered over a metropolitan area.

The Impact of Heterogeneity and Awareness in Modeling Epidemic Spreading on Multiplex Networks

In the real world, dynamic processes involving human beings are not disjoint. To capture the real complexity of such dynamics, we propose a novel model of the coevolution of epidemic and awareness spreading processes on a multiplex network, also introducing a preventive isolation strategy. Our aim is to evaluate and quantify the joint impact of heterogeneity and awareness, under different socioeconomic conditions. Considering, as case study, an emerging public health threat, Zika virus, we introduce a data-driven analysis by exploiting multiple sources and different types of data, ranging from Big Five personality traits to Google Trends, related to different world countries where there is an ongoing epidemic outbreak. Our findings demonstrate how the proposed model allows delaying the epidemic outbreak and increasing the resilience of nodes, especially under critical economic conditions. Simulation results, using data-driven approach on Zika virus, which has a growing scientific research interest, are coherent with the proposed analytic model.

Research: Service integration issues on an ATM DQDB MAN

Metropolitan Area Network (MAN) technology has now reached a degree of maturity as far as the transport of connectionless services is concerned. In the near future, attention will therefore focus on the transport of connection-oriented services using the asynchronous technique, with a view towards the total integration of such networks with Broadband Integrated Services Digital Networks (B-ISDN). In such a context, this paper investigates the main problems associated with the use of a Distributed Queue Dual Bus (DQDB) MAN for the integrated transport of voice, video and data services, using only the asynchronous access mode. A network architecture containing functional blocks which perform adaptation functions for connection-oriented services is proposed, and results obtained by simulation of the Queued Arbitrated access protocol when the offered load derives from both constant and variable bit-rate sources are presented

Research: Service management on an ATM DQDB MAN

In this paper a management architecture for connection-oriented services in a Distributed Queue Dual Bus (DQDB) MAN, in which channel access is exclusively queued-arbitrated, is proposed. Use of only the asynchronous information transfer mode for the integrated transport of voice/video/data services is assumed to facilitate future integration between MANs and B-ISDNs. Using a network architecture in which there are functional blocks performing adaptation functions for connection-oriented services, the authors describe a set of management processes needed to manage the node adaption blocks, services and resources assigned to them. In the description of these processes, the ways in which network resources are requested and assigned is formalized, and a certain quality is guaranteed in the connections.

A Process Approach to Manage the Security of the Communication Systems with Risk Analysis Based on Epidemiological Model

Information security means protecting information and information systems from unauthorized access, use, disclosure, disruption, modification or destruction, to assure confidentiality, availability and integrity. The new trends of telecommunications of the last year is the move towards the trasmission of voice over traditional packet switched IP network, voice over IP, that has become a valid alternative to traditional public circuit-switched telephone network and then the convergence of the communication systems, through the next generation networks definition. This environment presents many security problems and significant security challenges. The voice over IP system increase these with those normally tie to IP network. Along with a several benefits of voice over IP, there are new security threats for exchanged informations. This paper analyzes the security issues of the communication systems, starting from the traditional public switched telephone network toward the new next generation network. Then, with this paper, we want to introduce a process approach to manage the security, based on epidemiological model. This model is characterized by three steps, Analysis, Assessment and Management, and it can be applied to a general information security system, to identify, assess and classify the information assets, the processes concerning it, vulnerabilities of each level and common threats. Finally we evaluate the risk and the probability of damage that can crash the system or part of this and propose a model of failure time analysis. The target of this analysis is to calculate the extent of the risk function in order to understand the state and the degree of security of our system, by studying the statistics of failure and to ensure highest degree of security optimizing the business strategic decisions and information and communication technology security economic investments. The methodology is designed to be applied in the future to communication systems, more specifically. This does not exclude the application of this methodology in other areas of interest (biomedical or economical areas) to understand, formalize and solve problems of similar nature.

QoS management in programmable networks through mobile agents

Abstract In delivering multimedia services, quality of service represents a crucial commitment to be satisfied. Very often it has been considered only from a theoretical point of view, leaving any implementation details out of the discussion, mainly for the lack of concrete possibilities to execute its control and management effectively. Recent technological developments in the networking and distributed programming fields are now opening new challenging scenarios towards the negotiation and guarantee of QoS in the delivery of multimedia services through the network. Active or programmable networks are becoming a reality, and the migration of software components among network nodes seems to be the direction pursued by most of network manufactures. Mobile software agents represent a very attractive approach to the distributed control of computer networks and a valid alternative to the implementation of strategies for the management of QoS. In this paper, we present our approach to QoS management through mobile agents. The potentiality of this approach is shown through two application examples. The first one focuses on resource reservation through RSVP in an int-serv scenario, while the second one shows how to provide QoS to aggregated traffic flowing through a virtual network.

Generation of random variables for modelling VBR multimedia sources

The design and performance evaluation of multimedia systems require the availability of adequate models to mimic the statistical properties of the traffic generated by a multimedia source. In this paper the authors propose a very simple method for the generation of discrete‐time and discrete‐state autocorrelated random variables which can be used to model a traffic source by simulation. The probability distribution and autocorrelation sequence of the variables generated exactly match the corresponding experimental histograms of the source to be modelled when the experimental autocorrelation sequence is decreasing with downward convexity. In this paper an analytical demonstration of the method proposed is given and its use is illustrated by three telecommunications examples.