Azure RTOS ThreadX Design for Low-End NB-IoT Device

As the Narrowband IoT (NB-IoT) technology becomes popular amongst constrained devices, the impact of secure communications and the use of a Real-Time Operating System (RTOS) needs to be considered. This paper presents an ultra-low-power low-end constrained monitoring end device capable of running on a battery for more than 10 years. It compares a bare-metal implementation and its redesign into an application supported by the Azure RTOS ThreadX, taking advantage of its low-power modes, and measuring the AES and RSA PKCS #1 v1.5 encryption impact on the battery lifetime and the RAM/FLASH memory. This study verified that even though the Azure RTOS ThreadX occupies more memory than the Bare-Metal design as expected, it is estimated to maintain the application running for more than 20 years (3000 mAh battery), based on the measured power consumption profile of the end device.