I. Introduction
IEEE 802.11 ah [1], marketed as WiFi Halow, provides network connectivity up to 8192 stations from 150 kbps to 78 Mbps over a transmission range up to 1 km. IEEE 802.11 ah operates in unlicensed sub-GHz frequency bands, i.e. 863–868 MHz in Europe, 755–787 MHz in China, and 902–928 MHz in North America (Fig. 1). It features fast association and authen-tication, restricted access window (RAW), traffic indication map (TIM), and target wakeup time (TWT) to provide access service to a large number of stations, energy efficiency, and extended network coverage.