Study on MU-MIMO feature in 802.11ac using MATLAB

Multi-user Multiple-Input-Multiple-Output is a technique of MIMO technology added to 802.11ac WLANs which is expected to be the major innovative feature in improving performance. Objectives are to simulate basic scenarios to get an understanding of MU-MIMO and to identify functional blocks in the MAC/PHY layers to which modifications are made to support MU-MIMO. In this paper, MU-MIMO is studied extensively by examining the modifications which have been made to different functional blocks of both MAC and PHY layers to support MU MIMO. MATLAB R2016a version has incorporated a WLAN System Toolbox with provision to design, configure the physical layer in IEEE 802.11ac WLAN standard. Hence, simulations of some scenarios are performed in MATLAB. The MU-MIMO feature in 802.11ac introduces multiple spatial streams distributed between the clients. Multiple clients can be serviced simultaneously, hence congestion delay is not an issue. MU MIMO helps in distributing data to 4 users simultaneously using the space streams obtained through smart antennas. This is a major improvement over the limitation imposed by the MAC algorithm used in WLANs where stations can only gain access one following the other. Hence, latency and also throughput can be increased for multimedia applications. The following functional blocks have been identified to be key in MU MIMO performance. Sounding, Precoding and detection techniques in the PHY layer and Aggregation , TXOP and back off mechanisms in the MAC layer. These areas would then be the points of interest to future researchers who wish to enhance MU MIMO performance. Research is proposed in PHY(Algorithmic improvements in Precoding and detection) and in MAC Design a scheduler to optimise aggregation and TXOP/back off mechanisms to improve QoS for multiple users. Keyword 802.11ac, MU MIMO, Aggregation, Precoding, Access Point, QoS, TXOP