A WLAN Uplink Collision-Resolving Scheme Using Multi-User Beamforming Technique

To effectively improve the throughput of the IEEE contention-based wireless local area network (WLAN) system, many uplink medium access control layer (MAC) protocols based on multi-user multiple-input multiple-output (MU-MIMO) technology have been proposed. However, a common problem of these approaches is that many physical layer (PHY) operations, e.g., synchronization, are not considered. As a result, existing methods may find difficulties in real-world implementation. In this article, we propose a simple yet practical uplink scheme for systems with multiple antennas. The main idea is to conduct multi-user beamforming (MU-BF) at an access point such that it can resolve collided signals from multiple competitive users; the proposed scheme can effectively reduce the upstream collision probability and improve system throughput. The other distinct advantage of the proposed scheme is that the MAC protocol of the original IEEE 802.11 standard, i.e., distributed coordination function (DCF), can remain unchanged. The mathematical analysis of system performance is also presented and verified. Simulations show that the proposed scheme significantly outperforms conventional WLAN systems.