Design of a Cognitive VLC Network with Illumination and Handover Requirements

In this paper, we consider a cognitive indoor visible light communications (VLC) system, comprised of multiple access points serving primary and secondary users through the orthogonal frequency division multiple access method. A cognitive lighting cell is divided into two non-overlapping regions that distinguish the primary and secondary users based on the region they are located in. Under the assumption of equal-power allocation among subcarriers, each region is defined in terms of its physical area and the number of allocated subcarriers within that region. In this paper, we provide the lighting cell design with cognitive constraints that guarantee fulfilling certain illumination, user mobility, and handover requirements in each cell. We further argue that, under some conditions, a careful assignment of the subcarriers in each region can mitigate the co-channel interference in the overlapping areas of adjacent cells. Numerical results depict the influence of different system parameters, such as user density, on defining both regions. Finally, a realistic example is implemented to assess the performance of the proposed scheme via Monte Carlo simulations

Smart Vehicles, Technologies and Main Applications in Vehicular Ad hoc Networks

Vehicular Ad hoc NETworks (VANETs) belong to a subcategory of traditional Mobile Ad hoc NETworks (MANETs). The main feature of VANETs is that mobile nodes are vehicles endowed with sophisticated “on-board” equipments, traveling on constrained paths (i.e., roads and lanes), and communicating each other for message exchange via Vehicle-to-Vehicle (V2V) communication protocols, as well as between vehicles and fixed road-side Access Points (i.e., wireless and cellular network infrastructure), in case of Vehicle-to-Infrastructure (V2I) communications. In this chapter we will introduce the state-of-the-art of recent technologies used in vehicular networks, specifically for smart vehicles, which require novel functionalities such as data communications, accurate positioning, control and decision monitoring

Seamless Connectivity Techniques in Vehicular Ad-hoc Networks

In this chapter we describe the traditional techniques used for seamless connectivity in heterogeneous wireless network environments, and in particular adopt them in VANETs, where V2V and V2I represent the main communication protocols. Section 2 deals with the basic features of Vertical Handover (VHO) in the general context of a hybrid wireless network environment, and it discusses how decision metrics can affect handover performance (i.e. number of handover occurrences, and throughput). Instead, Section 3 briefly introduces two proposed techniques achieving seamless connectivity in VANETs. The first technique is a vertical handover mechanism applied to V2I-only communication environments; it is presented in Section 4 via an analytical model, and main simulated results are shown. The second approach is described in Section 5. It addresses a hybrid vehicular communication protocol (i.e. called as Vehicle-to-X) performing handover between V2V and V2I communications, and vice versa.

A Cross-Layer Location-Based Approach for Mobile-Controlled Connectivity

We investigate into the potentiality of an enhanced Power and Location-based Vertical Handover (PLB-VHO) approach, based on a combination of physical parameters (i.e., location and power attenuation information), for mobile-controlled connectivity across UMTS and WLAN networks. We show that the location information in a multiparameter vertical handover can significantly enhance communication performance. In the presented approach a power attenuation map for the visited area is built and kept updated by exploiting the information sharing of power measurements with other cooperating mobile devices inside the visited networks. Such information is then used for connectivity switching in handover decisions. The analytical model for the proposed technique is first presented and then compared with a traditional Power-Based approach and a simplified Location-Based technique. Simulation results show the effectiveness of PLB-VHO approach, in terms of (i) network performance optimization and (ii) limitation of unnecessary handovers (i.e., mitigation ofping-pong effect)

Analysis of the Chirality Effects on the Capacity of Wireless Communication Systems in the THz band

International audienceThe potentialities of Terahertz frequency band in the context of nano-scale communications are largely increasing, thanks to specific features that allow to overcome the issues related to the spectrum scarcity and capacity limitation. Apart from high molecular absorption and very high reflection loss that represent the main phenomena in Terahertz (THz) band, in this paper we investigate the chirality effects that affect the propagation medium, in the frequency range (4 − 10) THz. It is observed that in this interval the chiral parameter shows resonance peaks in specific frequencies. In this paper we investigate the channel capacity in a special medium affected by chirality effects, such as biomolecules, DNA chains, etc. Specifically, we analyze the signal propagation in a chiral medium where a Giant Optical Activity (GOA) is present. This effect is typical of the so-called chiral-metamaterials. Through simulation results we distinguish the behavior of a chirality-affected channel with GOA in Line-of-Sight and Non-Line-of-Sight propagations, assuming different power allocation techniques and also comparing the performance to the case of No GOA

On the Optimal Design of a Broadcast Data Dissemination System over VANET Providing V2V and V2I Communications “The Vision of Rome as a Smart City”, Journal of Telecommunications and Information Technology, 2013, nr 1

In different this paper we present the performance evaluation study of a simple broadcast data dissemination technique in new emerging Vehicular Ad hoc Networks (VANETs). Differently from the traditional Mobile Ad hoc NETworks (MANETs), VANETs require particular routing protocols, due to the high dynamism of the network topology, and to different traffic and mobility patterns. For safety and emergency message applications, broadcast data dissemination is an important key factor in VANETs. However, the design of optimal deployment of relay nodes in different network scenarios allows to enhance system performance. At this aim, this work analyzes vehicular network performances in terms of throughput and delays, for different traffic scenarios, exploiting both inter-vehicular communications, as well as the availability of fixed network infrastructure

Data Transmissions using Hub Nodes in Vehicular Social Networks

© 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.[EN] Vehicular Social Networks (VSNs) consist of groups of individuals (i.e., people) who may share common interests, preferences and needs in the context of temporal spatial proximity on roads. In this environment, the impact of human social factors, such as mobility, willingness to cooperate and personal preferences, on vehicular connectivity is taken under consideration, thus extending the concept of Vehicular Ad-hoc Networks. In VSNs, vehicles are classified based on their social degree, a vehicle considered to be a ¿social¿ one if it accesses the vehicular social network and posts messages with a frequency higher than a given threshold. Therefore, to speed up the data dissemination process within a vehicular social network, a packet should be forwarded to those vehicles showing high social activity. In a previous paper, we introduced a new probabilistic-based broadcasting scheme called SCARF (SoCial-Aware Reliable Forwarding Technique for Vehicular Communications), and we analytically demonstrated its effectiveness in packet transmission reduction while guaranteeing network dissemination. In this paper, we assess SCARF in more realistic scenarios with real traffic traces, and we compare it with other similar techniques. We show that SCARF outperforms other approaches in terms of delivery ratio, while guaranteeing acceptable time delay values and average number of forwardings.Vegni, AM.; Souza, C.; Loscrí, V.; Hernández-Orallo, E.; Manzoni, P. (2020). Data Transmissions using Hub Nodes in Vehicular Social Networks. IEEE Transactions on Mobile Computing. 19(7):1570-1585. https://doi.org/10.1109/TMC.2019.2928803S1570158519

SRB: A Selective Reliable Broadcast Protocol for Safety Applications in VANETs

In this paper we present a novel vehicular communication protocol, which aims to reduce the effect of broadcast storm problem in VANETs. When the traffic density is above a certain value (e.g., when vehicles are in congested traffic scenarios), one of the most serious problems is the increase of packet collisions and medium contentions among vehicles which attempt to communicate. Our proposed technique, namely Selective Reliable Broadcast protocol (SRB), is intended to limit the number of packet transmissions, by means of opportunistically selecting neighboring nodes, acting as relay nodes. As a result, the number of forwarder vehicles is strongly reduced, while network performance is preserved. SRB belongs to the class of broadcast protocols, and exploits the traditional vehicular partitioning behavior to select forwarders. Each cluster is automatically detected as a zone of interest, whenever a vehicle is approaching, and packets will be forwarded only to selected vehicles, opportunistically elected as cluster-heads. In respect of traditional broadcast approaches, the main strengths of SRB are the efficiency of detecting clusters and selecting forwarders in a fast way, in order to limit the broadcast storm problem. Simulation results have been carried out both in urban and highway scenarios, in order to validate the effectiveness of SRB, in terms of cluster detection and reduction of number of selected forwarders