57 International Journal on Advances in Telecommunications, vol 6 no 1 & 2, year 2013, http://www.iariajournals.org/telecommunications/ 2013, © Copyright by authors, Published under agreement with IARIA - www.iaria.org Smart Navigation in Intelligent Transportation Systems: Service Performance and Impact on Wireless Networks Alessandro Bazzi, Barbara Mav` ı Masini, Gianni Pasolini, and Oreste Andrisano CNR-IEIIT and DEI, University of Bologna at Wilab, Bologna, Italy Email: alessandro.bazzi@cnr.it, barbara.masini@ieiit.cnr.it, gianni.pasolini@unibo.it, oreste.andrisano@unibo.it Abstract—Wireless communications are nowadays considered as enablers of innovation in the field of smart mobility in smart cities. In this work, we focus on the smart navigation service, which is aimed at providing drivers with the best route to destination taking into account real time traffic conditions. Smart navigation is increasingly used today and expected to reduce traffic congestions, but the real impact on travel time and the cost in terms of wireless network resources are still open issues. These aspects are here discussed starting from the objectives and the outputs of the Italian project PEGASUS. More specifically, to what extent this application can reduce the travel duration and how frequently traffic information must be updated will be firstly discussed; then, the impact on wireless networks of both the uplink collection of traffic information and the downlink transmission to vehicles is shown, focusing on the UMTS cellular technology; finally, the use of short range IEEE 802.11p wireless communications technology is investigated to offload cellular networks. Through simulations performed in a dense urban scenario, it is shown that 30% to 50% travel time can be saved, that the needed information exchange might reduce the cellular network capacity available for other services of 20% or more, and that the deployment of few road side units and multi-hop transmissions can be effectively used to offload cellular networks. Keywords—Smart navigation, Intelligent transportation systems (ITS), Vehicular networks (VANETs), Simulations, UMTS, IEEE 802.11p. I. I NTRODUCTION Keeping traffic moving is a challenge that governments, industries and researchers are facing worldwide. Effective so- lutions can only be obtained with a capillary and continuously updated knowledge of traffic conditions: the creation of an infrastructure for communication between vehicles, service centers and sensors, is thus one of the main needs identified by international institutions, service providers and car manufactur- ers to address with satisfactory results the problems generated by traffic, justifying the big efforts that are being pushed both in Europe and in the rest of the world. Many projects have been carried out in the last decade on these topics. Among the others, an interesting example is the Italian project PEGASUS [1], [2], which relies on over one million vehicles already equipped with devices periodically transmitting their position and speed to a control center. Safety, enhanced mobility, and smart navigation systems were the services targeted by the project. With the expression smart navigation we refer to the best route discovery service, which is based on the collection of measurements from vehicles equipped with sensor devices, hereafter on board units (OBUs), and the provision of updated traffic information to those vehicles equipped with on board navigators, hereafter smart navigators (SNAVs). Each OBU periodically collects and sends data to a remote control center and each SNAV receives from the control center information related to the actual traveling speed on the interested road seg- ments, exploiting this information to update the path toward its final destination. Indifferently, SNAVs can be either on-board navigation systems or personal smartphones with specific apps. Starting from the outputs of PEGASUS, here we focus on the benefits provided by the smart navigation and its impact on the communications network. The various topics addressed by PEGASUS, discussed in [3]–[8] and summarized for the first time in [1], are here extended and discussed with an integrated approach to provide an overview of smart navigation even from the point of view of wireless communications. More specifically, in this paper we will discuss: i) the impact of updated traffic information on travel time and the amount of data that must be transferred through the wireless networks to make the smart navigation effective, ii) the feasibility and the impact of uplink transmissions of data from a large number of OBUs through cellular networks, iii) the feasibility and the impact of downlink transmissions of updated traffic information to a large number of SNAVs through cellular networks, and iv) the feasibility and the performance of short range vehicle-to-vehicle (V2V) and vehicle-to-roadside (V2R) communications used to offload the cellular networks. These issues are hereafter addressed through simulations carried out adopting a simulation platform that integrates a vehicular traffic simulator, which reproduces the urban mobil- ity, and a wireless network simulator, which models the details of the communication protocols and the signal propagation. The paper is organized as follows: In Section II, the en- visioned application is detailed and the addressed issues are introduced. In Section III, the simulation platform is described. In Section IV, we focus on the smart navigation service and we evaluate the saved travel time. In Section V, the cellular system and the related performance in the considered scenario are investigated. In Section VI, short range communications