Rate equilibria in WLANs with block ACKs

To achieve high system efficiency with increasing speeds, recent WiFi standards, such as IEEE 802.11e/n, allow burst transmissions with block acknowledgements, provided the initial packet is successfully received. Consequently, a user can sometimes improve its throughput by sending the initial packet at a lower rate than other users. We model such a system as a game. Our results show that the socially optimal strategy is to send the initial packet at a lower rate than the rest of the burst. Such a strategy results in a better Nash Equilibrium than using the same rate for the entire burst. Moreover, we show that using the rate that maximizes the per-packet throughput, as commonly done, can result in performance that is far from the social optimum.