Intelligent MAC model for traffic scheduling in IEEE 802.11e wireless LANs

IEEE 802.11e hybrid coordination function (HCF) medium access control (MAC) protocol aims to provide quality of service (QoS) in wireless local area networks (WLANs), which includes a new access mechanism, called enhanced distributed channel access (EDCA), and a polling-based scheme, called HCF controlled channel access (HCCA). In this paper, focusing on the problem of improving QoS in a mixed EDCA and HCCA scenario, an intelligent MAC model for traffic scheduling located at the QoS-enhanced access point (QAP) is proposed. The proposed MAC model includes two parts: two status estimators and an adaptive scheduler. The model not only takes into account the requirements of traffic streams (TSs) such as throughput, delay and priority, but also takes into account current system status. In order to evaluate current system status, decide call admission control and reserve resource accurately, the MAC model employs an unsaturation EDCA model in EDCA mode and a dynamic HCCA scheduling algorithm in HCCA mode. With the requirements information sent by TSs and the evaluated system status, the scheduler adaptively schedules TSs to transmit frames in the appropriate access mode. Simulation results prove the effectiveness of our approach and demonstrate that the proposed MAC model is effective and significantly improves QoS in terms of throughput and delay metrics. (C) 2008 Elsevier Inc. All rights reserved.