Energy-aware adaptive restricted access window for IEEE 802.11ah based smart grid networks

Restricted Access Window (RAW) has been introduced to IEEE 802.11ah MAC layer for application of smart grid networks to decrease collision probability. The number of devices involved and duration affect both transmission energy and overhead information. However, few work has been done on energy efficient RAW. In this paper, we investigate an energy efficient RAW optimization problem for IEEE 802.11ah based uplink communications. We first formulate the problem based on overall energy consumption and the data rate of each RAW by applying probability theory. Then, we derive the energy efficiency of the uplink transmission. Last but not the least, an access window algorithm to adapt the RAW size is proposed to optimise the energy efficiency by identifying the number of contending devices and the number of slots in each RAW. Simulation results show that our proposed algorithm outperforms existing RAW on uplink energy efficiency.