Exploiting Multiuser MIMO in the IEEE 802.11 Wireless LAN Systems

By adopting multiple-input-multiple-output (MIMO) antenna technologies, IEEE 802.11 wireless LANs are evolving into high speed systems. While only one user can transmit at a time in the conventional IEEE 802.11 systems, we investigate the possibility of multiuser transmission by using MIMO antennas, which is now known as multiuser MIMO. The multiuser MIMO technique enables multiple users to receive packets over the downlink simultaneously, but it should be carefully used in the IEEE 802.11 systems for interoperation with non-MIMO legacy terminals. Through analysis and simulation evaluation, we demonstrate that multiuser transmission with a scheduling algorithm and single-user transmission with enhanced spatial multiplexing achieve enhanced performance by exploiting multiuser diversity in the space and time domains. Especially, when the number of stations is large, multiuser transmission shows better performance than enhanced single-user transmission.