Performance Analysis of Compressed Block Acknowledgment in IEEE 802.11ax

Abstract

IEEE 802.11ax utilizes frame aggregation and compressed block acknowledgements to reduce the MAC overhead and to increase the goodput. We analyze IEEE 802.11ax frame aggregation in error-prone environments and propose to adaptively limit the MPDU size. This results in MAC frames that are still small enough to have a high transmission success rate. A performance study using the discrete-event simulator ns-3 illustrates the benefits of the proposed approach. We find that a high retransmission rate results in a low utilization of the acknowledgment window and discuss its major negative impact on the goodput. Our delay-related studies further show that MAC mechanisms like strict ordering contribute disproportionally to increased latency due to head-of-line blocking, especially under high error rate conditions. We conclude that for decreased delays, smaller MPDUs are beneficial.