Contention-based QoS MAC mechanisms for VBR VoIP in IEEE 802.11e wireless LANs

We propose two contention-based medium access control (MAC) mechanisms to provide quality of service (QoS) for variable bit rate (VBR) voice over IP (VoIP) in IEEE 802.11e contention-based channel access (EDCA) wireless LANs (WLANs): Access time-based admission control (ATAC) and access point dynamic access (AP-DA). Simulation results indicate that the proposed mechanisms offer a satisfactory solution for QoS of VBR VoIP; the ATAC algorithm outperforms the EDCA and significantly improves QOS of VBR VoIP sessions in terms of average delay and delay distribution; and the AP-DA algorithm effectively balances downlink and uplink VoIP sessions.