Experimental investigation of link layer adaptation in IEEE 802.11n WLANs

Due to its low cost wireless communication methodology and improvements in both its physical (PHY) and MAC (Link) layers, the IEEE 802.11n wireless LAN (WLAN) technology has been adopted widely. However, fairness of current 802.11n rate adaptation (RA) mechanisms and analysis of practical user end-to-end throughput are among important issues still in their infancy. Thus in this paper, we conduct an experimental investigation of adapting 802.11n MAC and PHY layer parameters in an indoor 3 × 3 MIMO testbed. We detail the deployment of our infrastructure mode testbed and compare the performance of 802.11n RA mechanisms under various conditions, including simultaneous transmissions and Co-Channel Interference (CCI). We then examine a range of elements affecting application performance including the number of spatial streams, packet length, frame aggregation subframe number and length. Favorable results are observed across a set of configurations and parameters, such as the increase in A-MPDU subframe length and its impact on end-to-end throughput. We believe our results demonstrate how overall application performance may be influenced by the Link layer; some of which may also be applicable to the upcoming 802.11ac IEEE standard.