An Energy Efficient Narrowband Internet of Things Radio Base Station

Abstract: NB-IoT was designed as an add-on to the LTE standard to enable wide area cellular connectivity to low-cost devices to facilitate the rapid growth of the Internet of Things. NB-IoT was found to increase the idle power consumption of the radio unit in an example LTE radio base station by almost 17%, costing the mobile network operator not only money, but also harming the environment through increased CO2 emissions. The objective of this thesis was to identify the reasons for NB-IoT increasing the power consumption in an LTE network, and discovering new methods aiming to mitigate this. The power consumption increase was identified to be due to the increased mandatory signaling in NB-IoT conflicting with existing power saving features. A major part of the thesis was spent implementing a new method in an Ericsson baseband unit, which was tested in a lab environment. The method reduced the power consumption increase by 50.2% by muting two antenna ports. A second method was investigated which would use multiple carriers and declaring subframes as invalid to retain capacity while reducing power consumption. It was found that a combination of the two methods could potentially lower the power consumption increase by NB-IoT by up to 74%, which would save an example network in the USA US$2.5 million a year, and lower emissions by 10.9 kilotons of CO2. Further work needs to be done in this area to investigate the impact these power saving features would have on connectivity in a live network.