# IoT-Enabled Smart Cities: Evolution and Outlook
## 3 Key Technologies Developed
### IoT Platforms  
Most existing commercial IoT platforms enable the user to connect devices to a vendor-operated cloud. Sensors send their data to the cloud for storage and analysis and actuators receive commands from there [68; 69; 70]. Some device vendors provide IoT clouds for a specific device technology or even a specific brand, whereas established general cloud providers typically support a wider range of technologies in particular based on the networking technologies described in the previous section. The tools provided by the vendor make it easy to integrate and manage the devices. In addition, there is support for some analytics and the visualization of the IoT information and the status of the deployment. The business model is targeted towards binding the user to the respective vendor, with the idea of selling more cloud resources, services and tools, possibly also additional devices. In the best case, a significant effort would be required to switch to a different platform. While such a business model may still be attractive for private users or for smaller scale commercial deployments, the resulting vendor lock-in poses a significant risk to a smart city. A smart city may need to integrate heterogeneous existing deployments, has to be able to scale up deployments over time and possibly integrate external stakeholders that may also have existing deployments. Another aspect is that there are technological developments moving IoT information processing to the edge, reducing bandwidth requirements, e.g., for processing video streams, and reducing latency and thus enabling control loops with hard real-time requirements. While some providers are in a position to provide edge computing facilities, e.g., a network provider that can extend existing deployments with edge computing resources, other providers are not in this position and may also not be able to easily integrate user-deployed edge resources. To reduce the risk of vendor lock-in and of being barred from technological developments as in the case of edge computing, smart cities are looking towards standards, for \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & **NFC** & **BLE** & **Z-Wave** & **Zigbee** & **LoRa** & **SigFox** & **LTE-M** & **NB-IoT** \\ \hline Coverage & 1–10 cm & 3–30 m & 30–100 m & 30–100 m & 3–15 km & 5–25 km & \textasci{}11 km & \textasci{}15 km & \textasci{}15 km \\ \hline Frequency & 13.56 MHz & 2.4 GHz & 2.4 GHz & 2.4 GHz & 868–915 MHz & 868–915 MHz & 868–915 MHz & LTE & LTE \\  & & & & & & MHz & in-band & in-band \\ \hline Data rate & 106 \textasci{} 424 kbps & 1–3 Mbps & 40–200 kbps & 20/40/250 & 300 bps \textasci{}50 & 100 bps & \textasci{}10 Mbps & \textasci{}200 kbps \\ \hline Payload size & & 358 bytes & 64 bytes & 127 bytes & 256 bytes & 12 bytes & - & - \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Key features of IoT network technologies. whole platforms or for specific functionalities and interfaces, e.g., for managing devices or requesting information. If complete deployments are based on standards, switching platform providers and integrating different deployments become feasible. In the following we look at some existing IoT standards and shortly describe what aspects they cover:  
* **oneM2M** standardizes an IoT service layer that constitutes software middleware between IoT hardware and communication technologies on one side and IoT applications on the other side. oneM2M [71] is a partnership project, whose partners are the regional telecommunication standardization organizations in Europe, Asia and North America, and whose respective member organizations drive the standardization process. The oneM2M service layer provides common service functions for data management, security, device management, connectivity and group management. A REST-style API provides standardized mechanisms for building REST resource structures and supports standardized interaction patterns. For the abstract API, different communication protocol bindings have been defined, including HTTP, CoAP and MQTT.