Internet of Things for smart homes: Lessons learned from the SPHERE case study

Building large-scale low-power Internet of Things (IoT) systems remains a challenge, as these systems have to meet the requirements of reliability, robustness, and energy-efficiency while running on resource-restricted microcontrollers without memory protection. In this paper we present the case study of IoT in SPHERE (Sensor Platform for HEalthcare in a Residential Environment), a project with the objective to develop a multipurpose, multi-modal sensor platform for monitoring people's health inside their homes. Atypically for academic projects, in 2017 the SPHERE software is going to be deployed in a 100-home study in volunteer homes, therefore it has to satisfy many real-world requirements. We discuss the requirements for IoT networking in this project, the IoT architecture (built on top of Contiki OS), software engineering challenges and lessons learned, as well as some of the general aspects that still make embedded low-power IoT software development difficult.