# A Multi-Technology Communication Platform for Urban Mobile Sensing
## 2 Related Works  
### IoT Platforms for Smart Cities  
Various experimental platforms have been implemented and assessed in order to evaluate their behavior and sustainability for several IoT applications through the employment of different communication technologies. This subsection aims to provide general information about some of the currently available testbeds for Internet of Things (IoT) experimentation and development. [PERSON] et al. [11] presented a large deployed smart city real implementation in the city of Santander, Spain, known as the SmartSantander project ([[http://www.smartsantander.eu/](http://www.smartsantander.eu/)]([http://www.smartsantander.eu/](http://www.smartsantander.eu/))). SmartSantander proposes a city-scale experimental European research facility for the experimentation of architectures, key enabling technologies, services, and applications for the IoT context of a smart city by recurring to communication technologies such as Institute of Electrical and Electronics Engineers (IEEE) 802.15.4 as well as WiFi, 3G, Bluetooth, and Ethernet. Currently, it encompasses more than 10,000 diverse IoT devices (fixed and mobile sensor nodes, near-field communication (NFC) tags, gateway devices, citizens' smartphones, etc.) [12]. [PERSON] [13] present a large-scale deployment of IoT devices on vehicles that are continuously driving around the city. This was carried out under the SmartSantander testbed. Also, the authors introduce three mobile sensing network strategies used for distributing the data gathered, namely periodic reporting through mobile broadband network, opportunistic vehicle-to-infrastructure (V2I) networking on top of IEEE 802.15.4 links, and the delay-tolerant network (DTN) approach using IEEE 802.11. [PERSON] et al. [14] presented the City of Things testbed. It is a multi-technology testbed which allows for the testing of novel smart city experiments (e.g. evaluation of network protocols, data gathering mechanisms) with a real large-scale deployment. The testbed is built within the city of Antwerp in Belgium. A major distinguishing factor of this testbed is the fact that it allows a wide range of wireless technologies, including WiFi, DASH7 (a form of LPWAN technology), Bluetooth Low-Energy, IEEE 802.15.4, and LoRa, among others. It allows connections with high and low bit-rate sensors at close and long range, respectively. Furthermore, the authors employed a use case regarding air quality measurements in the city of Antwerp [15]. They developed a real time demo on the City of Things architecture, consisting of a set of air quality sensors mounted on the roofs of cars with wireless capabilities such as LoRa, Sigfox, and DASH7. These radios allow for real-time streaming of data on three separate communication channels. Moreover, WiFi is used to download all data gathered during the day in bulk. [PERSON] et al. [16] presented the UrbanSense platform deployed in the city of Porto in Portugal. Aiming to collect relevant sensory data for a smart city environmental monitoring, this platform has a data-collecting unit (DCU) as its fundamental element. Data gathered by DCUs can be carried to the UrbanSense server through different methods: metropolitan fiber ring backhaul, cellular network backhaul, or through a deployed vehicular delay-tolerant network provided by buses and municipality vehicles equipped with WiFi hotspots. The different forwarding data mechanisms provide a wide range of applications since both real-time and delay-tolerant communications are considered. [PERSON] et al. [17] described the LoRa Fabian as a network protocol stack and experimental network setup, which was deployed over the city of Rennes in France. Such experimental setup is able to generate traffic similar to a real IoT application such as sensor monitoring. This not only gives the possibility of extracting basic performance metrics like the packet error rate, but also metrics related to the LoRa physical layer.