MAC Protocols for IEEE 802.11ah-Based Internet of Things: A Survey

The IEEE 802.11ah, also known as WiFi HaLow, is a scalable solution for medium-range communication in Internet of Things (IoT). While provisioning support for the IoT and machine-to-machine (M2M) communication, IEEE 802.11ah leverages various innovative medium access control (MAC) layer concepts, such as restricted access window (RAW), hierarchical association identification (AID), traffic indication map (TIM) segmentation, etc. This article presents a survey on various MAC protocols for IEEE 802.11ah. While discussing the essential features of IEEE 802.11ah, this survey points out various issues and limitations of such MAC protocols. Although there are some surveys available for MAC protocols of IEEE 802.11ah, they do not include a large number of schemes that have been recently proposed to solve different standardization and implementation-based issues. This article individually surveys issues and challenges in the different problem domains of the IEEE 802.11ah MAC protocol and analyzes the recently proposed solutions. Moreover, this article identifies various factors for further improvement of these protocols. Compared to other relevant surveys, this article emphasizes the issues and challenges to enable researchers to easily identify the problem domain.