Modeling fast link adaptation-based 802.11n distributed coordination function

This paper presents a comprehensive performance study of closed-loop fast link adaptation (FLA) in the context of IEEE 802.11n, spanning the physical (PHY) and medium-access control (MAC) layers. In particular, a semi-analytical model is derived for Basic and request to send/clear to send (RTS/CTS) access schemes of the distributed coordination function (DCF), that applies to both, open- and closed-loop strategies. Numerical results serve to demonstrate the accuracy of the proposed model and the superiority of FLA, in terms of MAC goodput, in comparison to open-loop policies. Realistic operating conditions such as outdated feedback information and the use of statistical packet length distributions, issues not treated in previous studies, have also been considered. Moreover, it is shown that incorporating a time-out mechanism in the FLA scheme, weighing down the influence of channel information as this becomes outdated, is a useful strategy to counteract its deleterious effects.