Rate adaptation algorithms play a crucial role in IEEE 802.11 WLANs. While the network performance depends greatly on the rate adaptation algorithms, the detailed implementation is left to vendors. Due to its simplicity and practicality, the generic rate adaptation algorithm based on up/down thresholds is widely adopted in commercial IEEE 802.11 devices. Taking the popular ARF algorithm for example, the data rate is increased when ten consecutive transmissions are successful and a date rate downshift is triggered by two consecutive failed transmissions. Although widely deployed, disclosing the implicit objective function that the rate adaptation algorithm is dynamically maximizing, remains as an open problem in the literature. In this paper, we investigate the thresholds-based rate adaptation algorithm via a reverse engineering perspective where the implicit objective function is revealed. We consider this reverse engineering study of the thresholds-based rate adaptation algorithm as an important first step towards a comprehensive understanding on the rate adaptation mechanism designs and the complex interactions among multiple IEEE 802.11 stations.
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