Joint rate adaptation, frame aggregation and MIMO mode selection for IEEE 802.11ac
Saeed Abdallah, Steven D. Blostein · 2016
The recently approved IEEE 802.11ac WLAN standard has dramatically boosted Wi-Fi capabilities through supporting more data streams, larger bandwidth and more efficient frame-aggregation, leading to significantly higher data rates. The multitude of data rates and MIMO configurations to choose from has made it crucial to develop efficient algorithms for rate adaptation and MIMO mode selection (spatial multiplexing versus spatial diversity) in order to realize the promised gains in data rate. At the MAC layer, the optimal level of frame aggregation needs to be chosen in order to maximize the throughput. The adaptation approach uses very limited feedback provided within the Wi-Fi packet acknowledgement protocol. In this paper, we develop a framework for jointly selecting the data rate, the MIMO mode and the frame aggregation configuration at the access point (AP) using subcarrier-level channel state information (CSI). We use approximate expressions for the BER based on the union bound for the first-event error probability in order to obtain approximate throughput expressions for the different rates and MIMO modes. Assuming A-MPDU aggregation, we also show that for each data rate and MIMO-mode pair, there is a corresponding optimal aggregation level, which we find analytically. Our numerical results reveal that the proposed joint selection scheme yields significant improvements in throughput.