Receiving-Opportunity Control-employed QoS guarantee scheme in DCF and EDCA stations coexisting WLAN

IEEE 802.11e Enhanced Distributed Channel Access (EDCA) is a MAC protocol for WLAN to realize Quality of Service (QoS) control. EDCA offers the possibility of defining four different classes of service at the MAC layer so that QoS requirements can be supported. Service between classes is differentiated by different sets of channel contention parameters. However, it is difficult to guarantee QoS of the high-priority stations in EDCA where both EDCA stations and Distributed Coordination Function (DCF) stations are connected to an access point (AP), because quality control is not considered in DCF. This paper proposes a novel scheme to guarantee the QoS requirement of the high-priority stations in EDCA in such a mixed environment. In this scheme, Receiving-Opportunity Control in MAC Frame (ROC) proposed by the authors is employed. ROC probabilistically refuses data frames from low-priority stations. This paper analyzes the appropriate probability which satisfies the requirement of high-priority stations in EDCA. The effectiveness of the proposed scheme is validated through simulation.