Smart City has become a broad term used to describe the use of the wireless communications devices & services deployed in the context of large-scale urban applications to improve public infrastructure and operations. The realization of Smart City networks involve a myriad wireless technologies, including Z-Wave, Zigbee, SIGFOX, LoRa, Thread, Bluetooth, WiFi and cellular. Smart city can separate to two, building (indoor) and environment (outdoor). Building (indoor) can extend to many other applications like energy management, water leakage/ gas detection and security. For the environment (outdoor), it has applications for flood detection, smart lighting, waste collection, parking lots and so on. With those IoT, smart city improves quality of life for citizens.