ACAC: An Airtime-Aware Centralized Association Control System in 802.11ac WLANs

In recent years, 802.11ac wireless local area networks (WLANs) have been popular in campus and enterprise environments, and a large number of access points (APs) are densely deployed to meet the rapidly increasing clients' demand. In such networks, it is challenging to promote the performance of AP-client association since numerous clients need to find their respective optimal APs under the conditions of multiple capability-limited APs and a small number of available channels. Thus, the conventional association mechanism that only utilizes local information on the client side, such as received signal strength indicator (RSSI), may lead to poor network performance. In this context, we propose and implement an airtime-aware centralized association control system that deals with client requests in a centralized manner and makes AP-client association decisions according to the global information, that is, AP airtime utilization and client requests' RSSI. In particular, we design an AP airtime measurement method to obtain AP airtime utilization from the ath10k driver, and present an airtime-aware AP selection algorithm to implement AP selection policy. Furthermore, we develop an experimental testbed, and conduct the experiments to evaluate the performance of our system. The results demonstrate that our system can significantly improve network throughput and effectively guarantee clients' fairness.