Fiore Veltri

Two-level Trajectory-Based Routing Protocol for Vehicular Ad Hoc Networks in Freeway and Manhattan Environments

This paper focuses on the routing protocol issue in two important environments for Vehicular Ad Hoc Networks (VANET): Manhattan and the Freeway. A novel protocol called Two-level Trajectory Based Routing (TTBR) protocol is proposed. Deterministic vehicles movement permits advantage to be taken of the map info to build a specific local trajectory to reach the destination node. However, in order to offer network scalability also a high level cell-based trajectory is applied to have a coarse knowledge of the cell where the destination node is moving. Our proposal needs Peer Servers and Grid subdivision of the space. Simulation results were assessed to show the improvements and scalability offered by TTBR in comparison with other Ad Hoc networks protocols such as AODV and GPSR. Performance Evaluation was evaluated in terms of Normalized Control Overhead and Data Packet Delivery Ratio. TTBR is more performing than AODV for a high speed and high density scenario for both the Manhattan and Freeway scenarios.

A New Routing Protocol for Interference and Path-Length Minimization in Vehicular Networks

Vehicular communication systems represent one of the most desirable technologies when the safety, efficiency and comfort of everyday road travel need to be improved. The main advantage is the absence of an infrastructure, typical of centralized networks, that makes them very scalable and adequate for highly-variable network topologies. Vehicular Ad-hoc NETworks (VANETs) are able to provide wireless networking capability in situations where no fixed infrastructure exists and the communication among nodes can be either direct or made via relaying nodes, as in the classical ad-hoc networks. In this paper, the attention is focused mainly on the network layer of VANETs, proposing a novel approach to reduce the interference level during mobile transmission, also considering the minimization of path lengths. We propose an interference aware routing scheme for multi-radio vehicular networks and a new metric is also proposed, based both on the maximization of the average Signal to Interference level and on the minimization of the path length of the connection between source and destination. Our solution has been integrated with the AODV routing protocol to design a new MIMO Distance Vector Protocol. NS-2 has been used for implementing and testing the proposed idea, and significant performance improvements have been obtained.

Markovian approach to model Underwater Acoustic channel: Techniques comparison

In the last years, Underwater Acoustic (UWA) sensor networks have exponentially grown in many scientific, industrial and research areas. Wireless underwater communications are required in many application fields, such as real time remote control of seabed and oil rigs, monitoring of underwater environments, collecting of scientific data recorded by stations on the seabed, conversation between divers, mapping of the seabed (in order either to detect objects or to discover new resources), prevention of disasters, and many others. In order to allow these applications, the aspect of physical phenomena affecting acoustic communications cannot be neglected. The shallow-water acoustic channel is different from the radio channels in many aspects. The available bandwidth of the UWA channel is limited and it depends on both range and frequency. Within this limited bandwidth, the acoustic signals are affected by time-varying multipath, which may create severe inter symbol interference (ISI) and large Doppler shifts and spreads. These characteristics restrict the range and bandwidth for the reliable communications. Many works have already treated underwater acoustic channel modeling problem, however, at the best of our knowledge, they work only at the bit level and they are not suitable for those contexts in which a high level model is required. For this purpose, our paper discusses about a high level channel model based on Markov Chain approach for the underwater environment. Finite State Markov Model is developed for Packet Error Rate (PER) evaluation in an underwater channel, using the concept of error trace analysis. Some high level models well known in literature are compared to obtain statistical evaluations in order to find the model best fitting the underwater channel dynamics. Simulation and analysis are made in Matlab.

Channel Modeling Approach Based on the Concept of Degradation Level Discrete-Time Markov Chain: UWB System Case Study

In this work an approach to obtain an accurate high level channel model based on Discrete-Time Markov Chain, useful in some simulation context, is provided. In particular, this model is based on the concept of error trace analysis and on the degradation level of given observation windows: an observation window is fixed and the degradation level of the link, the Packet Error Rate (PER) relative to the specific window, is evaluated. This approach is useful for any wireless transmission scheme, but in our work, we apply it to the Ultra Wideband (UWB) system. Many researchers have already treated UWB channel modeling. However, to the best of our knowledge, all the proposed channel models work at the physical level investigating only some aspects of channel interaction. It has been shown through a comparative analysis, based on the occurrence of correctly and wrongly received packets, that the degradation level approach is more accurate than the classic Gilbert-Elliot model, the 3rd order Markov model and the Markov-based Trace Analysis (MTA) model.

Interference Aware-based Ad-Hoc On Demand Distance Vector (IA-AODV) ultra wideband system routing protocol

Ultra wideband (UWB) systems are communication systems based on a baseband impulsive transmission that has recently excited interest both in the commercial and academic fields. Physical layer aspects and MAC protocols have been intensively investigated in the recent years leading, in some cases, to important and definitive results. However, many questions relating to the UWB network layer are still open. The aim of this paper is to investigate the network layer of the UWB system: for this purpose a new routing protocol called Interference Aware-based Ad-Hoc On Demand Distance Vector (IA-AODV) and based on the interference concept has been proposed. In particular, two distinct metrics are explained in detail: the first one is based on the concept of global interference perceived by each node; the second one is based on the concept of link interference perceived by a node on a wireless path to a generic neighbor. Finally, a comparative analysis between our protocol and Ad-Hoc On Demand Distance Vector (AODV) protocol are carried out in order to show the soundness of our proposal.

A multipath fading channel model for underwater shallow acoustic communications

In these last years, many studies have focalized on the design of reliable under water acoustic communication systems. However, the ocean acoustic communication channel exhibits strong amplitude and phase fluctuations and the phenomena of diffraction, refraction and reflection. Due to the complexity of environment, the motions of transducers, sea surface, etc., the underwater acoustic signals exhibit random temporal and spatial frequency fluctuations in both amplitude and phase. These highly space, time and frequency dependent features introduce numerous obstacles for any attempts to establish reliable and long-range underwater acoustic communications. Therefore, it is very important to model a so complex channel. In this paper, we propose a new multipath channel model for shallow underwater acoustic communications. In particular, our model takes into account the effects due to spreading loss, scattering and reflections.

A Novel Rate Adaptation Scheme for Dynamic Bandwidth Management in Wireless Networks

In the last years, there has been a lot of research and development in wireless networking and mobility management. We focus our attention on the management of real-time flows, in particular on the management of hand-over events, in terms of bandwidth guarantee and service continuity when the system is dealing with Mobility Independent Predictive (MIP) services, defined in Integrated Services (IS) for mobile wireless environment. The main idea of this proposal is the utilization of a pre-reservation phase in the admission control through a Markovian approach, in order to predict the amount of bandwidth needed by a mobile host during its movements among the probably visited cells. The performance evaluation of the proposed idea has been made in terms of total assigned bandwidth, system utilization and admitted/dropped MIP flows.

Two Step Based QoS Scheduler for DVB-S2 Satellite System

The new DVB-S2 standard, introduced by ETSI, is mainly based on three key concepts: best transmission performance, total flexibility and reasonable receiver complexity. The Adaptive Coding and Modulation (ACM) scheme is the tecnique allowing to achieve these main goals. In particular, this tecnique allows to adapt the modulation and code levels, performed at the physical layer, at channel variations in a dynamic way. However, often the others modules, composing a satellite terrestrial terminal, does not take advantage of the ACM potentiality. For this purpose, in this paper we propose an efficient packet scheduling strategy able to operate with the different MODCOD schemes of ACM. In particular, considering ACM policy, Frame efficiency and QoS requirements the scheduling strategy has the main goal of maximizing the overall performances of the system.

Multi-Mode DVB-RCS Satellite Terminal with Software Defined Radio

A multi-mode radio communication terminal is a tunable terminal for passing and/or receiving bands in at least two radio communication systems. In the last few years many research resources have been invested in the study of this new type of terminal. This study is intended for a multi-mode terminal is a terminal capable of communicating both with a bent-pipe satellite and with an on-board processor satellite. In the literature different technologies are presented and they can be used to realize the multi-mode capability of a terminal, but, the most suitable technology is the software defined radio (SDR). The SDR is a set of hardware and software technologies that allow one to obtain reconfigurable architectures for network and wireless terminals. The goal of this work is to plan a satellite system based on digital video broadcast with the return channel satellite (DVB-RCS) standard in which the return channel satellite terminals (RCSTs) are able to adapt to the channel state, configuring the transmission chain via software, respecting a certain quality of service (QoS) constraint on the packet error rate (PER).

Interdisciplinary issues for the management of next generation autonomic wireless systems: nature-inspired techniques and organic computing

Next generation communication systems have become a hot research issue in these last few years. For an efficient management of these networks, multidisciplinary knowledge and cooperation between different research fields is important. In particular, the next generation of wireless systems needs to satisfy some self-properties such as self-describing, self-organising, self-managing, self-configuring, self-optimising, self-monitoring, self-adapting and self-healing. In order to provide these features traditional approaches cannot be employed, owing to the computing complexity involved, so new solutions must be considered. The most suitable techniques to solve the above-mentioned issues is certainly organic computing and nature inspired techniques. Therefore, the main goal of our work is to provide a description of the principal characteristics of these new kinds of network and an overview in the various nature-inspired and organic computing techniques such as the neural network, molecular computing, Cellular Automata (CA), Genetic Algorithms (GAs), epidemic propagation strategies and finally, Swarm Intelligence (SI).