Duty Cycle Challenges of IEEE 802.11ah Networks in M2M and IoT Applications

The IEEE 802.11ah technology, targeting vast amount of use cases within the Internet of Things (IoT) and Machine-to-Machine (M2M) expansion, is currently being finalized. This IoT/M2M connectivity technology is deployed at the sub-1 GHz ISM bands, that are subject to various coexistence regulations set by the authorities. In Europe, devices in the Sub-1 GHz ISM bands must comply with the maximum duty cycle limit of 2.8%, provided that they also support Listen Before Talk (LBT) and Adaptive Frequency Agility (AFA) features. In this article we investigate the challenges of such duty cycle limitation and its effect on the IEEE 802.11ah network performance from the uplink transmission perspective, considering typical use cases characterized by different traffic models. We first derive the theoretical maximum duty cycles of both an individual station and an individual AP assuming full-buffer or saturated traffic. Then, with emphasis on more practical uses cases, such as home/building automation and healthcare, where the traffic of an individual station or node is strongly unsaturated, we analyze the IEEE 802.11ah network performance without and with the 2.8% maximum duty cycle limitation. The obtained results show IEEE 802.11ah networks can provide efficient support for the most important use cases such as sensor networking, home automation and healthcare, despite the maximum duty cycle limit of 2.8%. This shows that IEEE 802.11ah is one of the most prominent and scalable IoT/M2M connectivity technology, that can enable different types of IoT applications, even in the presence of the tight coexistence requirements at the ISM band.