Uncoordinated Access Schemes for the IoT: Approaches, Regulations, and Performance

Internet of Things devices communicate using a variety of protocols, differing in many aspects, with the channel access method being one of the most important. Most of the transmission technologies explicitly designed for IoT and machine-to-machine communication use either an ALOHA-based channel access or some type of Listen Before Talk strategy, based on carrier sensing. In this article, we provide a comparative overview of the uncoordinated channel access methods for Internet of Things technologies, namely ALOHA-based and Listen Before Talk schemes, in relation to the ETSI and FCC regulatory frameworks. Furthermore, we provide a performance comparison of these access schemes, in terms of both successful transmissions and energy efficiency, in a typical Internet of Things deployment. Results show that Listen Before Talk is effective in reducing inter-node interference even for long-range transmissions, although the energy efficiency can be lower than that provided by ALOHA methods. Furthermore, the adoption of rate adaptation schemes lowers the energy consumption while improving the fairness among nodes at different distances from the receiver. Coexistence issues are also investigated, showing that in massive deployments Listen Before Talk is severely affected by the presence of ALOHA devices in the same area.