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IEEE 802.lie proposed a new MAC protocol, hybrid coordination function (HCF), for achieving QoS with multiple classes of traffic for real-time multimedia services in wireless LANs (WLANs). HCF provides two modes of channel access - the contention free-based mode of HCF controlled channel access (HCCA) and the contention-based of enhanced distributed channel access (EDCA). Nevertheless, two issues in EDCA should be addressed for minimizing collision probability and maximizing throughput. First, EDCA supports the same minimum window for different classes traffic, which increases the collision probability from different classes of traffic. Second, the successful transmission traffic will transit to the minimum backoff stage, which causes unnecessary collisions from the same class traffic. Therefore, in this paper, we first propose a simple, efficient classification of traffic classes. Then, a high performance EDCA approach (H-EDCA), i.e., a distributed differentiated control of contention window, is proposed for suppressing unnecessary collisions from the same class traffic and different classes traffic. Moreover, collision probability and throughput are analyzed in detail based on the discrete-time Markov chain model. Numerical results demonstrate that the proposed H-EDCA approach outperforms significantly EDCA of IEEE 802.11e in both metrics.