Design of MAC Layer Resource Allocation Schemes for IEEE 802.11ax: Future Directions

Wireless local area networks (WLANs) are widely deployed for internet-centric data applications. It is predicted that by 2018, about two-thirds of the world's internet traffic will be video, and more than half of the traffic will be offloaded to Wi-Fi networks. Consequently, WLANs need major improvements in both throughput and efficiency. New technologies continue to be introduced for WLAN applications for this purpose. The IEEE 802.11ac standard is the currently implemented amendment by the IEEE 802.11 standard working group that promises data rates at gigabits per second. The main features of the IEEE 802.11ac standard are adopting increased bandwidth and higher order modulation than the previous standard, and multiple-input multiple-output (MIMO) and multi-user MIMO transmission modes. These features are designed to improve the user experience. In addition to technologies that enhance the efficiency of the WLAN, the IEEE 802.11ax standard is also investigating and evaluating advanced wireless technologies to utilize the existing spectrum more efficiently. These modern communications technologies are steadily advancing physical layer data rates in WLANs, although data throughput efficiency of the WLAN may degrade rapidly as the physical layer data rate increases. The fundamental reason for the degradation is that the current medium access control (MAC) protocol allocates the entire channel to one user as a single source due to equally distributed time domain contention resolution. The challenges and difficulties have already been identified for designing efficient MAC layer resource allocation (MAC-RA) schemes for the upcoming IEEE 802.11ax high-efficiency WLAN. However, there is no profound investigation outcome for this kind of efficient resource allocation. Therefore, in this paper, we conduct an extensive survey of the expected features and challenges for IEEE 802.11ax in the design of fair and efficient MAC-RA. The associated previous research work is summarized as to future directions. Moreover, the need for each directed scheme is highlighted.