Most of the deployed IEEE 802.11e Wireless Local Area Networks (WLANs) use infrastructure Basic Service Set (BSS) in which an Access Point (AP) serves as a gateway between wired and wireless domains. We present the unfairness problem between the uplink and the downlink flows of any Access Category (AC) in the 802.11e Enhanced Distributed Channel Access (EDCA) when the default settings of the ED...

Wireless communication always attracts extensive research interest, as it is a core part of modern communication technology. During my PhD study, I have focused on two research areas of wireless communication: IEEE 802.11 network performance analysis, and wireless cooperative retransmission. The first part of this thesis focuses on IEEE 802.11 network performance analysis. Since IEEE 802.11 tec...

Despite of their very broad diffusion, IEEE 802.11 Wireless Local Area Networks are not able to provide service differentiation and to support real-time multimedia applications, due to their channel access methods. To overcome these limitations, the 802.11e working group has proposed the Enhanced Distributed Coordination Access (EDCA) scheme which achieves service differentiation on statistical...

The timing behavior of the EDCA mechanism defined in the IEEE 802.11e standard is analyzed. More specifically, the target of this paper is to evaluate the limitations of the highest priority level of the EDCA mechanism (voice category) when supporting real-time (RT) communication. By RT communication, we mean small-sized packets generated in periodic intervals that must be delivered before the ...

The paper aims at depicting certain limitations of EDCA queues related to the different traffic classes. Through simulation, we show main flaws of identical, medium size, Drop Tail queues used by default for each class, with reference to different traffic category’s requirements. We propose some substitutes such as differentiated, basically smaller buffer sizes and Active Queue Management mecha...

For use in vehicular networks, IEEE 802.11p has been standardized as the underlying wireless system. The 802.11 standard distinguishes two main methods of operation with respect to channel access, the Distributed Coordination Function (DCF) and the Enhanced Distributed Channel Access (EDCA), where the latter is the mandated method to be used in vehicular networks (in 802.11p). We present valida...

A flow-level simulator of EDCA-based WLANs to evaluate Call Admission Control (CAC) schemes and MAC parameters tuning algorithms is presented. A novel Admission Control scheme for infrastructure WLANs is evaluated. This Admission Control uses an adaptive MAC parameter tuning algorithm which decides the best instantaneous configuration of MAC parameters in order to: i) guarantee the QoS requirem...

We present a novel model of IEEE 802.11 EDCA with support for analysing networks with misbehaving nodes. In particular, we consider backoff misbehaviour. Firstly, we verify the model by extensive simulation analysis and by comparing it to three other IEEE 802.11 models. The results show that our model behaves satisfactorily and outperforms other widely acknowledged models. Secondly, a compariso...

Emergency department (ED) crowdedness is a global phenomenon that can lead to many adverse effects. The relationship of and emergency cardiac arrest (EDCA) occurrence still debated. COVID-19 pandemic precipitated change in the patient volume ED varied with epidemic continuous period. Different degrees provided us an opportunity study between EDCA occurrence. Our aim this was determine prognosis...