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An analytical model is proposed to describe the enhanced distributed channel access (EDCA) mechanism of IEEE 802.11e, and to evaluate the performance of wireless local area network (WLAN) in practical conditions. Compared with the existing models, the proposed model takes several new factors into consideration: error-prone channel, wireless station supporting several access categories (ACs), different treatments of internal collision and external collision, retry limit, error-correction ability provided by channel coding. This makes the proposed model much more suitable for practical use than the existing models. The Markov chain model, state transfer and probabilities were presented; parameters and solution were derived; expressions of throughput and MAC delay were obtained. Simulation results validate the accuracy of the model. The proposed model has wide applicability, enabling evaluation of system performances and optimization of system parameter values.