42 research outputs found
Markov chain-based analysis of multihop IEEE 802.15.4 wireless networks with finite node buffers
No full textIn this paper, we propose a Markov chain-based analytical framework for modeling the behavior of the medium access control (MAC) protocol in IEEE 802.15.4 wireless networks. Two scenarios are of interest. First, we consider networks where the (sensor) nodes communicate directly to the network coordinator. Then, we consider scenarios where (sensor) nodes communicate to the coordinator through an intermediate relay node, which forwards the packets received from the sources (i.e., the sensors). In both scenarios, no acknowledgment messages are used to confirm successful data packet deliveries, and communications are beaconed (i.e., they rely on synchronization packets denoted as “beacons”). In all cases, our focus is on networks where the relay and the source nodes have finite queues (denoted as buffers) to store data packets. Network performance is characterized in terms of aggregate network throughput and packet delivery delay. Our results show a very good agreement between the proposed analytical model and realistic ns-2 simulation results. In particular, the impact of the buffer size is accurately taken into account in our model
Multihop IEEE 802.15.4 wireless networks with finite node buffers: Markov chain-based analysis
No full textIn this paper, we propose a Markov chain-based analytical framework for modeling the behavior of the medium access control (MAC) protocol in IEEE 802.15.4 wireless sensor networks. Two scenarios are of interest. First, we consider networks where the sensor nodes communicate directly to the network coordinator. Then, we consider scenarios where sensor nodes communicate to the coordinator through an intermediate relay node, which forwards the packets received from the sources (i.e., the sensors). In both scenarios, no acknowledgment messages are used to confirm successful data packet deliveries, and communications are beaconed (i.e., they rely on synchronization packets denoted as “beacons”). In all considered scenarios, our focus is on networks where the relay and the source nodes have finite queues (denoted as buffers) to store data packets. Network performace is characterized in terms of aggregate network throughput and packet delivery delay. Our results show a very good agreement between the proposed analytical model and realistic ns-2 simulation results. In particular, the impact of the buffer size is accurately taken into account in our model
Performance analysis of broadcast protocols in VANETs with Poisson vehicle distribution
No full textIn this paper, we propose a general framework for performance analysis of broadcast protocols in vehicular ad-hoc networks (VANETs) with vehicles' positions modeled as Poisson points. In fact, in this specific configuration, it can be shown that the positions of a finite number of nodes falling in a finite segment have equally spaced average values. On the basis of this result, it is possible to derive a tractable analytical framework suitable for average (from a topology viewpoint) performance evaluation of a large number of broadcasting algorithms in VANETs. In this work, the proposed analytical framework is applied to the class of probabilistic broadcast multihop protocols with silencing, with focus on a novel polynomial broadcasting algorithm. The validity of the proposed analytical approach is assessed by means of realistic (ns-2) numerical simulations
I2V Highway and Urban Vehicular Networks: A Comparative Analysis of the Impact of Mobility on Broadcast Data Dissemination
No full textIn this paper, we consider the problem of disseminating data in Infrastructure-to-Vehicular (I2V) IEEE 802.11 networks. We analyze, with a comparative approach, the performance in highway and urban scenarios. In particular, after characterizing the mobility in these scenarios we analyze the performance in terms of data dissemination from a fixed Road Side Unit (RSU) to the vehicles passing in its proximity through a recently proposed multihop probabilistic broadcasting protocol, namely Irresponsible Forwarding (IF). In the case of highway-like Vehicular Ad-Hoc NETworks (VANETs), we first characterize a mobile scenario in such a way to make a direct comparison with a static scenario meaningful, taking into account a physical characterization of the network (e.g., in terms of vehicle spatial density). Then, we consider a few mobile urban scenarios, characterized by the presence of junctions regulated by Traffic Lights (TLs) and Roundabouts (Rs). Our results show that, from a single packet perspective, the vehicles’ mobility does not affect the behavior of the IF protocol, at least in the considered mobile scenarios (both highway and urban). However, different conclusions are reached when an information flow (i.e., a series of consecutive packets) is considered. In this context, we determine the maximum amount of data which can be transferred from the RSU to the mobile vehicles passing through a certain Region Of Interest (ROI) around the RSU
UWB-based Tracking of Autonomous Vehicles with Multiple Receivers
No full textIn this paper, we consider real-time tracking of an Autonomous Guided Vehicle (AGV) in an indoor industrial scenario. An on-board odometer provides information about the dynamic state of the AGV, allowing to predict its pose (position and orientation). At the same time, an external Ultra Wide Band (UWB) wireless network provides the information necessary to compensate the error drift accumulated by the odometer. Two novel alternative solutions for real-time tracking are proposed: (i) a classical Time Differences of Arrivals (TDOA) approach with a single receiver; (ii) a “Twin-receiver” TDOA (TTDOA) approach, that requires the presence of two independent receivers on the AGV. The performance of the two proposed algorithms is evaluated in realistic conditions. The obtained results clearly show the tradeoff existing between the frequency of UWB measurements and their quality
Cross-network information dissemination in VANETs
No full textIn this work, we provide an overview of an innovative approach for effective cross-network information dissemination, with applications to Vehicular Ad-hoc Networks (VANETs). In particular, we describe the main approach followed in an on-going bilateral Italy-Israel project (“Cross-Network Effective Traffic Alert Dissemination,” X-NETAD). The X-NETAD project leverages on the spontaneous formation of WiFi local VANETs, with direct connections between neighboring vehicles, in order to disseminate, very quickly and inexpensively, traffic alerts received from the UMTS network
Experimental analysis of VHO-enabled mobile application for data offloading in heterogeneous wireless networks
No full textRecent years have seen the relentless market explosion of mobile devices, whose ever increasing capabilities (in terms of computational power, networking, and sensing) make them attractive to an endless number of connected applications and services (especially in business and infotainment domains) which can be fully experienced in mobility. This huge market growth naturally involves a constant increase of mobile internet accesses with a consequent overload for mobile operators and potentially a reduced performance for mobile users. In this scenario and during last years, the research field of data offloading and Vertical HandOver (VHO) has gained a significant attention by service providers to start offloading mobile data traffic from 3G/4G networks to WiFi networks. The reduction of the load on cellular network is instrumental to allow the user to be Always Best Connected (ABC) with limited costs. In this paper, we present and analyze the performance of a real VHO-enabled ABC mobile application for Android Platform. The application has been tested in a national trial involving several users all over Italy, commercial (Guglielmo Srl) and private WiFi networks and cellular networks of the main Italian mobile operators for more than a month and 150.000 distinct logs collected during the evaluation
Comparative investigation of single-hop and multi-hop broadcast strategies for information dissemination in VANETs
No full textIn recent years, Vehicular Ad-hoc NETworks (VANETs) have experienced an intense development, driven by academia, industry, and public authorities. On the basis of this, it is reasonable to expect that VANETs will finally hit the market in the near future. In order to reach commercial success, VANETs must effectively operate also during the first years of deployment, when the market penetration rate will be unavoidably low and, consequently, only a small number of suitably equipped vehicles (VANET-enabled) will be present in the roads. Among the possible strategies to face the initial sparse VANET scenarios, the deployment of an auxiliary network constituted by fixed Road Side Units (RSUs), either Dissemination Points (DPs) or relays, is certainly a promising one. In order to maximize the benefits offered by this support infrastructure, the placement of RSUs needs to be carefully studied. In this work, we analyze, by means of numerical simulations, the performance of an application that leverages on a finite number of DPs for disseminating information to the transiting vehicles. The positions of the DPs are determined through a recently proposed family of optimal placement algorithms, on the basis of properly generated (through simulations) vehicular mobility traces. The analysis is carried out considering two realistic urban scenarios. In both cases, the performance improvement brought by the use of multi-hop broadcast protocols, with respect to classical single-hop communications with DPs, is investigated
Surface Modes in Antiresonant Reflecting Optical Waveguides with Rectangular Hollow Core
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