Free Spectrum for IoT: How Much Can It Take?

Vast numbers of IoT devices will soon be deployed in a ubiquitous manner connecting billions of small sensors to the Internet. The means of connectivity will be primarily provided by wireless networks. This paper presents the results of a spectrum occupancy experiment conducted in the ISM-band in Melbourne, Australia. The focus of this experiment is on the spectrum window of the already highly utilized 915-928~MHz as a potential candidate for some IoT technologies. The aim of this paper is to quantify the feasibility of using this free spectrum band for present and future IoT applications. We classify the spectrum measurements according to the population densities and we formulate a relation between the current spectrum occupancy and the underlaying population density. Based on the current occupancy figures and by using the pure ALOHA access model due to its similarity to the access models currently deployed in class-licensed bands, we draw future paradigms on the available spectral room for additional IoT services in this band.