CAS-based Channel Access Protocol for IEEE 802.11ah WLANs

IEEE 802.11ah Task Group is currently working on the standardization of a new amendment with the focus placed on sensor and actuator networks. It will operate at sub-1GHz bands, ensure transmission ranges up to 1 Km, minimum network data rate of 100 kbps and very low power operation. This new amendment will extend IEEE 802.11 potential to applications such as smart metering, plan automation, eHealth or surveillance. In this paper we propose a novel channel access protocol for IEEE 802.11ah WLANs based on a smart use of the Channel Access Slots (CASs), in which the Restricted Access Windows (RAWs) can be divided. More concretely, our protocol optimizes the number of CASs, their length and their allocation to the stations (STAs). The presented scheme allows both the Access Point (AP) and the STAs to properly deliver data packets in densely populated scenarios, while maximizing the time they remain in sleep mode in order to keep the energy consumption low.