Timer based scheduling control algorithm in WLAN for real-time services

With the increasing demands on real-time services in WLAN systems, it is critical to determine whether the controls provided in WLAN are sufficient to ensure the required QoS. Besides the EDCF (enhanced distributed coordination function) and HCF (hybrid coordination function) defined by IEEE 802.11e, an enhanced timer-based scheduling control algorithm is proposed to manage the delay budget effectively. A simulation platform is developed to quantify the QoS performance and to provide a framework for developing new QoS control algorithms. Contention-based channel access and controlled channel access, which includes both the simple algorithm and the proposed algorithm, are compared and the results evaluated.