QoS-Aware Adaptive A-MPDU Aggregation Scheduler for Voice Traffic in Aggregation-Enabled High Throughput WLANs

Currently available IEEE 802.11n implementations do not apply aggregate MAC protocol data unit (A-MPDU) aggregation to voice traffic because of its strict end-to-end delay requirements. When multiple nodes contend to send voice and other lower-priority traffic, 802.11n network faces serious performance degradation problems for two major reasons: i) due to the medium access control (MAC) and physical (PHY) layer overheads of individual short voice packet transmissions, the available network throughput for lower-priority traffic significantly decreases, and ii) increased contention results in high voice packet loss rate (PLR). This paper proposes a QoS-aware adaptive A-MPDU aggregation scheduler for voice traffic in 802.11n/ac WLANs that adaptively applies A-MPDU aggregation to voice traffic based on QoS requirements and periodically obtained average medium access delay and end-to-end delay statistics. Performance evaluations on 20 nodes sending uplink 64Kbps voice and saturated best-effort traffic at 150Mbps PHY rate showed that the proposed scheme achieved 160% throughput improvement compared to default implementations in driver. During the simulations with 50 nodes transmitting at 600Mbps PHY rate, the proposed scheme provided up to 275Mbps throughput against 0.13Mbps by default scheme; the proposed scheme delivered all voice packets (PLR = 0 percent) and over 99.9 percent of them had less than 150ms end-to-end delay.