No abstract

We propose the Most-Emergent-First (MEF) scheduler which regard the emergency score obtained from the delay status and traffic specification (TSPEC) to determine transmit sequence of flows. Via cross-layer signaling, transmission opportunities (TXOPs) of flows are dynamically adjusted to meet the TSPEC while the bandwidth utilization in a IEEE 802.11e environment is maintained. The proposed prioritized and parameterized QoS mechanism at the MAC layer is a four-rule policy base where parameters such as TSPEC and TXOPs dynamically obtained and determined respectively according to instant network status. The experiment shows that optimal PSNR, fairness among flows of the video class, fairness between higher and lower priority classes and QoS differentiation are achieved even when the total bandwidth capacity is limited and the wireless network is with unpredictable traffic bursting and dynamics.