Modified HCCA mechanism for improving QoS support in IEEE 802.11e networks

Abstract

IEEE 802.11e Medium Access Control (MAC) standard proposes Hybrid Coordination Function (HCF), which is composed of HCCA (HCF Controlled Channel Access) and EDCA (Enhanced Distributed Channel Access) mechanisms for QoS support. HCCA performs a polling procedure with parameterized channel. However, a station may not always have pending data to transmit. That is, polling all the stations will waste time and therefore deteriorate the transmission performance. In this paper, we propose a modified HCCA mechanism using the beacon frame broadcasted by the AP to determine which station can transmit its pending data so as to improve the transmission performance. The simulation results show that the performance improvement of our proposed mechanism is significant for QoS support particularly under light load condition.

Enhancement of QoS support of HCCA schedulers using EDCA function in IEEE 802.11e networks

“…It misses on the necessary flexibility and applies stringent admission conditions with the acceptance of fewer TSs than possible, by wasting available resources. As a result, several alternative scheduling algorithms have been proposed to improve the QoS provisioning of IEEE 802.11e HCCA networks in the case of VBR traffic, [12][13][14][15][16][17] and few works have evaluated the realtime issues of the reference scheduler [6,7,12,[18][19][20][21], and proposed possible solutions.…”