Wireless sensor network (WSN) technology provides the possibility to gather a wide range of environmental data, like temperature, humidity, acceleration, and transmit this data in real time to users via wireless communication. A WSN consists of several sensor nodes, also called motes, that are wirelessly interconnected. Depending on the platform, for the wireless communication different frequency bands and communication standards are used. A widespread communication technology in WSNs is 802.15.4 on an ISM frequency band, but also other frequencies and communication protocols are common.
While WSNs are already a large research topic for several years now, the available hardware in the past was mostly research-driven. Nowadays, a lot of new sensor node platforms are commercially available, mostly driven by governmental and industrial projects. Due to the better availability of hardware and the increasing need of real time information about the environment because of increasing population, inner city congestion and worse availability of resources, e.g., parking sites, several projects have started to equip inner cities and roads with sensing hardware.
In the SMART SANTANDER project (Libellium, 2013) the city of Santander, Spain, is equipped with more than 1100 Waspmote wireless sensor motes with a variety of sensors, e.g., temperature, luminosity, carbon and noise sensors. The city was divided into 22 separate WSNs with each zone having a Meshlium node as gateway that stores the data in a database and transmit the data via 3G or ethernet to web servers in the cloud. The sensor network provides information about air pollution, environmental noise and free parking slots. SmartSantander is a "city-scale experimental research facility in support of typical applications and services for future Smart Cities" (Libellium, 2013) and the project further envisions the deployment of a total amount of "20,000 sensors in the European cities of Belgrade, Guildford, Lübeck and Santander" (Libellium, 2013). Furthermore, sensors deployed in vehicles can be harnessed to monitor large areas automatically. Therefore, vehicular wireless sensor networks have been proposed, e.g., for monitoring the urban air quality (Hu et al. 2009) (Re et al. 2014). Other researchers already try to extend these technologies to gain a higher granularity of knowlege. Burgstahler et al. have already shown the detection of the position of parked cars within a single parking space by the use of magnetic field sensors and machine learning technologies (Burgstahler et al. 2014). This knowledge can be used to navigate drivers directly to parking spaces that are not only free but also fit to the size of the car.
Other projects like COmmunication Network VEhicle Road Global Extension (CONVERGE, 2013) are dealing with regularities and standards of Car2X communication, i.e. the communication of cars among each other and with the infrastructure, to increase security environmental friendliness and the avoidance of traffic jams.
All these new sensor and communication technologies can be seen as enabler for new sophisticated application scenarios. SIMPLI-CITY will be a platform of such new applications and thus participate from the recent development. Especially the information exchange between smart cities and the cars driving within these cities will further benefit.