Nicola Baldo

Energy-Efficient Routing Schemes for Underwater Acoustic Networks

Interest in underwater acoustic networks has grown rapidly with the desire to monitor the large portion of the world covered by oceans. Fundamental differences between underwater acoustic propagation and terrestrial radio propagation may call for new criteria for the design of networking protocols. In this paper, we focus on some of these fundamental differences, including attenuation and noise, propagation delays, and the dependence of usable bandwidth and transmit power on distance (which has not been extensively considered before in protocol design studies). Furthermore, the relationship between the energy consumptions of acoustic modems in various modes (i.e., transmit, receive, and idle) is different than that of their terrestrial radio counterparts, which also impacts the design of energy-efficient protocols. The main contribution of this work is an in-depth analysis of the impacts of these unique relationships. We present insights that are useful in guiding both protocol design and network deployment. We design a class of energy-efficient routing protocols for underwater sensor networks based on the insights gained in our analysis. These protocols are tested in a number of relevant network scenarios, and shown to significantly outperform other commonly used routing strategies and to provide near optimal total path energy consumption. Finally, we implement in ns2 a detailed model of the underwater acoustic channel, and study the performance of routing choices when used with a simple MAC protocol and a realistic PHY model, with special regard to such issues as interference and medium access.

An open source product-oriented LTE network simulator based on ns-3

In this paper we present a new simulation module for ns-3 aimed at the simulation of LTE networks. This module has been designed with a product-oriented perspective in order to allow LTE equipment manufacturers to test RRM/SON algorithms in a simulation environment before they are deployed in the field. First, we describe the design of our simulation module, highlighting its novel aspects. Subsequently, we discuss the testing methodology that we adopted to validate its output. Finally, we present some experimental result to assess its performance in terms of execution time and memory usage.

Fuzzy logic for cross-layer optimization in cognitive radio networks

The search for the ultimate architecture for cross-layer optimization in cognitive radio networks is characterized by challenges such as modularity, interpretability, imprecision, scalability, and complexity constraints. In this article we propose fuzzy logic as an effective means of meeting these challenges, as far as both knowledge representation and control implementation are concerned.

Experimental evaluation of high performance base course and road base asphalt concrete with electric arc furnace steel slags.

The paper presents the results of a laboratory study aimed at verifying the use of two types of electric arc furnace (EAF) steel slags as substitutes for natural aggregates, in the composition of base course and road base asphalt concrete (BBAC) for flexible pavements. The trial was composed of a preliminary study of the chemical, physical, mechanical and leaching properties of the EAF steel slags, followed by the mix design and performance characterization of the bituminous mixes, through gyratory compaction tests, permanent deformation tests, stiffness modulus tests at various temperatures, fatigue tests and indirect tensile strength tests. All the mixtures with EAF slags presented better mechanical characteristics than those of the corresponding asphalts with natural aggregate and satisfied the requisites for acceptance in the Italian road sector technical standards, thus resulting as suitable for use in road construction.

Cognitive Network Access using Fuzzy Decision Making

We consider a scenario in which wireless users want to connect to the Internet using one of several available network access opportunities, possibly using different radio technologies. We propose a distributed cognitive network access scheme with the aim of providing the best quality of service with respect to both radio link and core network performance and user application requirements. Knowledge of the service quality experienced by active connections is shared, and prospective users use Fuzzy Logic techniques to process cross-layer communication quality metrics and to estimate the expected transport-layer performance. These estimates are compared to the Quality of Service requirements of the application using Fuzzy Decision Making techniques to choose the most suitable access opportunity. This scheme naturally fits into the recently proposed Cognitive Network paradigm in that it defines a cognition process leveraging on end-to-end and cross-layer performance evaluation techniques as well as information sharing among users; moreover, it offers a significant amount of flexibility and extensibility, thanks to its modularity and its independence from the particular technology and application being used. The proposed scheme is shown to outperform state-of-the-art solutions in several multi-technology and multi-application scenarios, while at the same time achieving similar performance to application-specific omniscient schemes that we introduce in this paper as a benchmark.

A Markov framework for error control techniques based on selective retransmission in video transmission over wireless channels

We present a framework, based on Markov models, for the analysis of error control techniques in video transmission over wireless channels. We focus on retransmission-based techniques, which require a feedback channel but also enable to perform adaptive error control. Traditional studies of these methodologies usually consider a uniform stream of data packets. Instead, video transmission poses the non-trivial challenge that the packets have different sizes, and, even more importantly, are incrementally encoded; thus, a carefully tailored model is required. We therefore proceed on two different sides. First, we consider a low-level description of the system, where two main inputs are combined, namely, a video packet generation process and a wireless channel model, both described by Markov Chains with a tunable number of states. Secondly, from a highlevel perspective, we represent the whole system evolution with another Markov Chain describing the error control process, which can feed the packet generation process back with retransmissions. The framework is able to evaluate hybrid automatic repeat request with selective retransmission, but can also be adapted to study pure automatic repeat request or forward error correction schemes. In this way, we are able to comparatively evaluate different solutions for video transmission, as well as to quantitatively assess their performance trends in a variety of scenarios. Thus, our framework can be used as an effective tool to understand the behavior of error control techniques applied to video transmission over wireless, and eventually identify design guidelines for such systems.

Fuzzy Logic for Cross-layer Optimization in Cognitive Radio Networks

The search for the ultimate architecture for cross-layer optimization in cognitive radio networks is characterized by challenges such as modularity, interpretability, imprecision, scalability, and complexity constraints. In this article we propose fuzzy logic as an effective means of meeting these challenges, as far as both knowledge representation and control implementation are concerned.

Dynamic Spectrum Access Using a Network Coded Cognitive Control Channel

In this paper we propose a Dynamic Spectrum Access scheme which allows the users to opportunistically and efficiently access the channels available for communications. It addresses the following important aspects of opportunistic spectrum access: 1) implementation of the control channel, 2) multi-channel medium access control, 3) primary user detection, and 4) secondary reuse of spectrum unused by primary users. The main features of the scheme are that it is completely distributed, it does not need dedicated spectrum resources for control purposes, but rather leverages on a virtual control channel which is implemented using Network Coding techniques, and it exploits a cooperative detection strategy to identify unused spectrum. Due to these aspects, our proposal represents a significant improvement with respect to existing Dynamic Spectrum Access solutions. We carry out an evaluation study of the proposed solution to assess its performance with respect to different system and scenario parameters; the obtained results show that the proposed solution is feasible, capable of providing satisfactory performance, and suitable for implementation in real systems.

A Neural Network Based Cognitive Controller for Dynamic Channel Selection

In this paper, we present an application of the Cognitive Networking paradigm to the problem of dynamic channel selection in infrastructured wireless networks. We first discuss some of the key challenges associated with the cognitive control of wireless networks. Then we introduce our solution, in which a Neural Network-based cognitive engine learns how environmental measurements and the status of the network affect the performance experienced on different channels, and can therefore dynamically select the channel which is expected to yield the best performance for the mobile users. We carry out performance evaluation of the proposed system by experimental measurements on a testbed implementation; the obtained results show that the proposed cognitive engine is effective in achieving performance enhancements with respect to state-of-the-art channel selection strategies.

A distributed network coded control channel for multihop cognitive radio networks

Designing a solution for multihop cognitive radio networks poses several challenges such as the realization of the control channel, the detection of primary users, and the coordination of secondary users for dynamic spectrum access purposes. In this article we discuss these challenges and propose a solution that aims to meet most of them. The proposed solution is completely distributed, and does not need dedicated spectrum resources for control purposes, but rather leverages on a virtual control channel that is implemented by having users exchange control information whenever they meet in a particular channel, using network coding techniques for better dissemination performance. Due to these aspects, our proposal represents a significant improvement over existing dynamic spectrum access and multichannel MAC solutions. We discuss the effectiveness of our scheme in multihop cognitive ad hoc networks, where secondary users need to opportunistically access the spectrum at those locations and times at which it is not used by primary users. Finally, we report the results of an evaluation study assessing the performance of the proposed scheme with respect to different system and scenario parameters.