Radar-based motion detection systems are widely used in smart home, smart building, and smart city area for automatic control. In this invention, methods, subsystem, systems, computer program are disclosed to achieve power reduction of a radar sensor by operating the radar sensor in a sub-sampling manner in an illumination control system. By combining the information related to the detection area and the state of a lighting device, the sampling frequency of a radar sensor is configured according the user scenario. A balance between power reduction and motion detection performance is achieved therefrom.