A Novel QoS-Aware ARQ Scheme for Multi-User Transmissions in IEEE802.11ax WLANs

The latest IEEE 802.11ax protocol has been launched to provide efficient services by adopting multi-user (MU) transmission technology. However, the MU transmissions in the aggregation-enabled wireless local area networks (WLANs) face two drawbacks when adopting the existing automatic repeat request (ARQ) schemes. (1) The failed packets caused by the channel noise can block the submission of subsequent packets and the transmission of queued ones. (2) When the lengths of aggregate media access control protocol data units (A-MPDU) transmitted by different users are varied, dummy bits should be added to the shorter frames to align the transmission duration. These drawbacks degrade the quality of service (QoS) performances, such as throughput, latency, and packet loss rate. In this paper, a novel QoS-aware backup padding ARQ (BP-ARQ) scheme for MU transmissions in the IEEE802.11ax WLANs is proposed to address these problems. The proposed scheme utilizes backups of selected packets instead of dummy bits to align the duration and to supress the influence of channel noise. An optimization problem that aims to improve the blocking problem of the failed packets is derived to determine the selection of packets. The promotion of the proposed scheme is well demonstrated by the simulations in NS-3.