Andrea Fiaschetti

A robust adaptive congestion control for communication networks with time-varying delays

This work presents a congestion control for high-speed networks in the single bottle-neck case with time-varying multiple delays, aimed at avoiding congestion by setting the rates of the traffic flows. The novelty of this paper is that the controller explicitly deals with saturated (i.e., non persistent) sources. The controller consists in a main controller based on classical control theory coupled with a controller based on fuzzy logic: the former works properly when the sources are not saturated; the latter provides a saturation compensation by setting an adaptive multiplicative gain which acts on the rate command. The scheme provides also robust stability to time-delay uncertainties. Simulations prove its effectiveness.

On the use of semantic technologies to model and control security, privacy and dependability in complex systems

In this paper a semantic approach is presented to model and control Security, Privacy and Dependability (SPD) in complex interconnected environment composed by heterogeneous Embedded Systems. Usually, only the individual properties are locally considered to obtain desired functionalities and this could result in sub-optimal solutions. With the use of modern semantic technologies (like OWL or reasoning engines) it is possible to model not only the individual parameters but also the relations between the different (and dynamically changing) parts of the systems, thus providing enriched knowledge and more useful information that could feed control algorithms. The model presented in this paper is based on the results obtained during the first phase of the pSHIELD1 project (conceived and lead by Finmeccanica) and it is focused on a concrete application coming from a critical scenario in railway environment: the monitoring of freight trains transporting hazardous material.

The SHIELD framework: How to control Security, Privacy and Dependability in complex systems

The purpose of this paper is to present the SHIELD holistic approach: an innovative methodology to address Security, Privacy and Dependability (SPD) in the context of Embedded Systems (ES) by means of control science theory. The SHIELD methodology consider the SPD functionalities offered by the generic atomic component of a complex system at 3 different levels: node, network and middleware. Then these technologies are enhanced with a fourth vertical layer named overlay that provides composability functionality, thus creating a framework able to dynamically reconfigure to satisfy the user needs in terms of SPD, in different scenarios. In order to achieve this objective, the use of specific SPD metrics (derived from recognized standards for security, like the ISO/IEC 15408), is proposed. The results presented in this work have been developed in the scope of the pSHIELD ARTEMIS-JU project and are currently under investigation in the nSHIELD project.

Congestion pricing for dynamic bandwidth allocation in satellite networks: A game-theoretic approach

The purpose of this work is to provide an enhanced adaptive approach to classic queue-based Bandwidth-on-Demand (BoD) procedures in broadband satellite networks. In queue-based schemes, the controllers objective is to drive the buffer queue length to an appropriate reference queue length, and the efficiency of the control strictly depends on the choice of its reference value. In latest approaches, solutions to adaptively modify the target reference queue length based on a set of network information have been proposed; nevertheless, in such approaches, the satellite terminals should base their control strategies on information which are not available to them, according to the communication standards of state-of-the-art technologies, such as DVB-RCS. The novelty of the presented algorithm is that it overcomes this limit by dynamically changing the reference queue length, based on information actually broadcast to the network terminals; the algorithm is at same time simple and effective, and is based on a game-theoretic approach which benefits of recent advances in congestion pricing theory. The effectiveness of the proposed approach is supported by Opnet® simulations as well as by considerations about the real implementability of the solution.

An innovative optimal approach to Slotted-ALOHA random access protocol

This work presents an innovative, adaptive and optimal approach for Slotted-ALOHA protocols in Satellite Networks. Most ALOHA random access protocols are based on the assumptions that: i) all the involved stations receive packets with the same rate and ii) the transmission probabilities, computed analytically, are the same for each station. These assumptions are too optimistic, since, in real scenarios, different sources receive traffic with different arrival rates: a classical approach leads therefore to a sub-optimal exploitation of the available resources. The proposed algorithm takes into account the arrival rate of the traffic, considered as generated by different services. The traffic model is then used to compute the (stationary) probabilities of the traffic arrival rate of the stations: each station is characterized by a finite set of arrival rates and each arrival rate is associated to a stationary probability. Then, an optimization problem is defined, aimed at obtaining the transmission probabilities which minimize the channel collisions; the innovation is that the transmission probabilities are associated to the traffic arrival rate and are different depending on the arrival rates themselves. The increased efficiency of the proposed solution with respect to the standard ALOHA approach is proved by means event-based simulations (performed with Matlab simulation tools). The work is partially based on research activities carried out in the framework of the EmerSat project funded by ASI (Italian Space Agency).

Dynamic uplink frame optimization with ACM in DVB-RCS2 satellite networks

In current generation of satellite networks, modulation and coding schemes can be dynamically changed in real-time to face different link conditions. Therefore, the link budget is no more required to be computed under the worst-case, with relevant advantages in terms of efficiency. The new DVB-RCS2 standard extends the dynamic modulation and coding to the return link: by using different modulation and coding schemes within the uplink frame, the terminals experiencing good link conditions transmit at very high bitrates, while the terminals experiencing fade events transmit at lower bitrates. This paper addresses the problem of optimizing the uplink frame modulation and coding schemes based on the current link conditions experienced by the terminals and on their transmission capacity requirements. The problem is formulated as an Integer Program and an efficient Linear Program approximation is proposed. Simulation results validate the proposed approach.

Towards manufacturing 2.0: An innovative architecture for the Factory of the Future

Industrial manufacturing processes today show an exponential complexity growth rate and the human operator are flooded by an overwhelming complexity and information. In addition, the higher and higher production rates enforced in modern production plants do not allow any human operator to control the process efficiently with traditional tools. Therefore, innovative paradigms and technologies to cope with manufacturing processes must be explored, mainly based on massive adoption of ICT solutions. Inspired by the most recent advances in information and communication technologies developed in the Future Internet framework and, in particular, in the PLATINO project, this paper presents an innovative architectural solution to improve the capabilities and performance of modern production plants: the so-called “cognitive middleware for manufacturing”. This architectural paradigm aims at stressing the use and integration of ICT technologies (e.g. semantic, middleware, optimization algorithms, ...) into an holistic framework to be transparently adopted into existing factories as well as embedded in the design of future ones. This solution has been formalized following the guidelines and expectations depicted in the MANUFUTURE Technology Platform SRA, the most valuable EU Organization performing research in this field and represents an innovative cross-fertilization between Future Internet and Future Manufacturing.

A Cross-Layer Approach to Dynamic Bandwidth Allocation in Satellite Networks

This work presents an innovative cross-layer approach to dynamic bandwidth allocation (BoD) in Satellite DVB-RCS networks. The algorithm is based on the assumption that, by managing the traffic at IP level through interaction with MAC level, a meaningful reduction in packet loss can be achieved, thus resulting in better resource exploitation. The proposed mechanism has been embedded in a consolidated control scheme for dynamic bandwidth allocation ([23], [1]). The interaction consists in the computation of the exact amount of MAC cells to send to the air interface during the next frame; based on this computation, the proper number of IP packets are segmented, transmitted to the MAC layer and queued in the MAC buffers. In this way, a twofold result is obtained: 1) no duplication of the scheduling function, scheduling can be performed at IP layer only, and 2) avoidance of overflows of MAC buffers. Simulations results, obtained by Opnet®, confirm the effectiveness of the proposed approach.