Uplink Multi-user Beamforming for Contention-Based Wireless LAN

Abstract

To improve the throughput of the IEEE wireless local area network (WLAN) system, many uplink medium access control (MAC) protocols based on multi-user multiple-input multiple-output (MU-MIMO) technology have been proposed. However, a common problem of the methods is that the physical (PHY) layer operations are not considered. As a result, existing methods may find difficulties in real-world implementation. In this paper, we propose a simple but practical uplink scheme to solve the problem. The main idea is to perform multi-user beamforming (MUBF) at the access point. The advantage of the proposed method is that while the uplink throughput can be effectively improved, the MAC protocol of the original IEEE 802.11 standard remains unchanged. With the proposed method, simultaneous and asynchronous reception of signals from multiple users can be conducted, and the uplink channel collision probability can be reduced. A closed-form solution for the saturation throughput is also derived. Theoretical analysis and simulation results show that the performance of the proposed scheme is significantly better than the conventional WLAN system.