A Greedy Reclaiming Scheduler for IEEE 802.11e HCCA Real-Time Networks

The IEEE 802.11e standard introduces Quality of Service (QoS) support for wireless local area networks and suggests how to design a tailored HCF Controlled Channel Access (HCCA) scheduler. However the reference scheduling algorithm is suitable to assure service guarantees only for Constant Bit Rate traffic streams, whereas shows its limits for Variable Bit Rate traffic. Despite the numerous alternative schedulers proposed to improve the QoS support for multimedia applications, in the case of VBR traffic satisfactory real-time performance has not been yet achieved. This paper presents a new scheduling algorithm, Unused Time Shifting Scheduler (UTSS). It integrates a mechanism for bandwidth reclaiming into a HCCA real-time scheduler. UTSS assigns the unused portion of each transmission opportunity to the next scheduled traffic stream. Thanks to such feature, traffic variability is absorbed, reducing the waste of resources. The analytical evaluation, corroborated by the simulation results, shows that UTSS is suitable to reduce the delay experienced by VBR traffic streams and to increase the maximum burstiness sustainable by the network

Resource Control for the EDCA and HCCA Mechanisms in IEEE 802.11e Networks

Abstract — We investigate the problem of efficient resource control for elastic traffic over the EDCA (Enhanced Distributed Channel Access) and HCCA (Hybrid Coordination Function-HCF- Controlled Channel Access) mechanisms of IEEE 802.11e. Our approach considers an economic modelling framework based on congestion pricing that captures how various factors, such as the probability of attempting to transmit a frame, the transmission opportunity (TXOP), and the physical layer transmission rate, contribute to congestion. Additionally, we consider the joint control of the EDCA and HCCA mechanisms, which allows us to determine the optimal sharing of the wireless channel between the two access mechanisms. I