CRUI: Collision Reduction and Utilization Improvement in OFDMA-based 802.11ax Networks

The number of IEEE 802.11 hotspots is increasing due to popularity and low price, resulting in a dense deployment of wireless local area networks (WLANs). To increase per station (STA) throughput in a densely deployed environment, a new amendment to the WLAN standard, namely, IEEE 802.11ax introduces orthogonal frequency-division multiple access (OFDMA). Especially, uplink OFDMA-based random access (UORA) enables multiple STAs to have simultaneous random access (RA) to an access point (AP) by using different subchannels. However, due to the nature of RA, UORA suffers from data collisions with the number of contending STAs. Moreover, the bandwidth underutilization problem degrades performance of UORA. In this paper, we propose a scheme, named CRUI, that substantially reduces data collisions and improves bandwidth utilization by using an extra backoff stage and opportunistic subchannel hopping. Through simulation, we demonstrate that our proposed scheme significantly improves UORA performance with lowered collision probability and improved bandwidth utilization while maintaining fairness.