Integration of RFID and WSN Technologies in a Smart Parking System L. Mainetti, L. Palano, L. Patrono, M. L. Stefanizzi, R. Vergallo Dept. of Innovation Engineering University of Salento Lecce, Italy luigi.patrono@unisalento.it Abstract—In this paper, a Smart Parking System (SPS) based on the integration of Ultra-High Frequency (UHF) Radio Frequency Identification (RFID) and IEEE 802.15.4 Wireless Sensor Network (WSN) technologies is presented. The system is able to collect information about the occupancy state of parking spaces, and to direct drivers to the nearest vacant parking spot by using a customized software application. Such application also leverages an NFC-based e-wallet system to allow users to pay for the parking fee. Furthermore, a software application based on RESTful Java and Google Cloud Messaging (GCM) technologies has been installed on a Central Server in order to manage alert events (e.g. improper use of a reserved space or expiration of the purchased time). In such a case, it promptly informs the traffic cops through an Android mobile app, which has been designed ad hoc for the considered scenario. A proof-of-concept has demonstrated that the proposed solution can meet the real requirements of a SPS. Keywords—RFID; WSN;NFC; Integration; Smart Parking. I. INTRODUCTION Finding a vacant parking space during the rush hours is a common problem in most of the cities. It is estimated that 30% of the daily traffic congestion in an urban downtown area is caused by vehicles cruising for parking space, and that a driver spends on average 7.8 min to find a parking spot [1]. This not only causes waste of time and fuel for drivers looking for parking but also increases air pollution and drivers’ frustration. The recent achievements in the Internet of Things (IoT) enabling technologies [2] open up opportunities to develop innovative smart parking systems, able to significantly reduce the traffic congestion and improve the citizens’ quality of life. Among the emerging wireless technologies, the Radio Frequency Identification (RFID) and Wireless Sensor Networks (WSNs) represent two of the most promising candidate to implement a complete smart environment. In particular, RFID is a low-cost and low-power technology consisting of passive devices, called tags, which are able to transmit the stored data when powered by the electromagnetic field generated by an interrogator, called reader. Since passive RFID tags do not need a source of energy to operate, their lifetime can be measured in decades, thus making the RFID technology well suited for many application scenarios [3]-[5]. However, the main drawback of RFID technology stems from the fact that tags can operate solely under the reader coverage region, thus making the use of this solution limited to object identification in small areas. The integration of RFID and WSN technologies could be a well-suited approach to overcome this limit, thus enabling the development of complex, next- generation applications. Basically, WSNs consist of a large number of low-power embedded devices, called sensor nodes, which are able to self-configure and self-organize. These characteristics make them suitable to be deployed even in harsh environments in order to capture important parameters (e.g. temperature, light, humidity, etc.) without human intervention [6]-[8]. The collected data are usually delivered, in a multi-hop mode, to a central point for a proper utilization and processing. Although RFID and WSN were originally designed with different objectives, the benefits provided by both technologies suggest the development of an integrated solution, at physical layer, able to combine the identification capability of the RFID technology and the advanced communication features of the WSN solutions [9], [10]. This could significantly enhance the effectiveness of both technologies, giving new perspectives to a broad range of innovative applications, such as smart parking solutions. Over the last years, several works aiming at improving parking management have been proposed. Most of them are based on the use of intelligent parking guidance and information (PGI) systems able to provide the drivers with information on the location and the availability of spaces in car parks and direct them to vacant parking lots. The proper operation of these systems is based on the use of sensors able to detect the presence of vehicles placed in the vicinity of parking spaces. In [11], [12] video camera sensors are used to collect information of vehicle parking fields. However, such devices usually generate a large amount of data that are difficult to transmit in wireless networks. On the contrary, WSN technology represents the ideal choice for implementing smart parking services, since sensor nodes can be easily deployed in existing parking spaces without installing new components. Furthermore, the parking information retrieved by each node can be processed in a collaborative mode in order to evaluate important metrics, such as parking times, billing and payment. In, authors used WSN nodes equipped with a light sensor to detect the state of each parking lot in an indoor area and to report the retrieved information to a Web server via the