Wireless Personal Communications (2005) 34: 29–43 DOI: 10.1007/s11277-005-8725-y C  Springer 2005 Delay Performance Analysis and Evaluation of IEEE 802.11e EDCA in Finite Load Conditions DIMITRIS VASSIS and GEORGE KORMENTZAS Department of Information and Communication Systems Engineering, University of the Aegean, GR-83200, Karlovassi, Greece E-mail: divas@aegean.gr, gkorm@aegean.gr Abstract. The paper presents an analytical model for the performance evaluation of IEEE 802.11e EDCA scheme under finite load conditions on the basis of various instances of delay metric (i.e., media access delay, queuing delay and total delay). The simulation results show that the analytical estimated instances of the delay metric are almost accurate. The paper exhibits that concerning the delay of serving classes, EDCA compared to the conventional DCF, favors high priority classes against low priority ones, while almost does not affect the behavior of medium ones. Keywords: delay metric, EDCA, IEEE 802.11e, performance analysis, simulation 1. Introduction The IEEE 802.11 Wireless Local Area Networks (WLANs) gain an ongoing and continuous public acceptance as they combine the robustness of the wired IEEE 802.3 Ethernet networks with the flexibility and mobility of wireless systems [1]. The basic IEEE 802.11 WLAN standard [2] defines two mechanisms for accessing the medium: the mandatory Distributed Coordination Function (DCF) and the optional Point Coordination Function (PCF). DCF uses the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol to transmit data in a simple and robust way without providing transmission delay guarantees. PCF is located over DCF and its access protocol is a centralized polling-based one, which can guarantee transmission delay. However, PCF imposes overheads on the wireless system due to the transmission of the polling frames resulting in poor performance for distributed networking environments. As the acceptance of WLANs increases, so does the demand for provision of QoS guarantees especially for real-time delay sensitive video/voice data. Various works have been presented in the international literature for enhancing the basic DCF access method in the IEEE 802.11 MAC layer protocol for providing priorities and service differentiation mechanisms [3–5]. In the same context, the IEEE 802.11 Task Group E almost finalise the standardisation of a QoS-aware MAC protocol with appropriate service differentiation mechanisms. In the IEEE 802.11e MAC protocol [6], a Hybrid Coordination Function (HCF) is introduced to manage the access to the medium. Two different access methods are defined, namely the Enhanced Distributed Channel Access (EDCA), and the controlled based access procedure (HCF Controlled Channel Access – HCCA). The term EDCA replaced the originally one notated as EDCF (Enhanced DCF).