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Most recent mobile multimedia devices, such as smart phones, laptops and tablet PCs, are equipped with IEEE 802.11 Wi-Fi interfaces for broadband wireless Internet access. The multimedia applications utilized by end users strongly require guaranteed QoS. Resource availability checking during initial connection establishment and seamless handover is essential under such conditions. Several analytical models of IEEE 802.11 WLAN have been proposed to estimate achievable throughput. However, they do not consider rate adaptations with multi-rate retry and individual channel conditions of each station. This paper proposes a realistic model to estimate achievable throughput considering Minstrel rate adaptation and multi-rate retry chain. The proposed model also considers each station individually, since stations may have different frame error rates in a real environment and thus, select different physical rates for frame delivery. Frame error rates are carefully read from the hardware registers of each station and applied to the model for enhanced accuracy. The correctness of the proposed model was verified through a series of experiments in a real testbed environment with up to 20 stations with MadWiFi interface cards. The proposed model shows accurate results in terms of aggregated and per-station throughput in various channel conditions.
Date of Publication: November 2011