IEEE 802.11ax: Performance of OFDM Uplink Multi-User MIMO over Non-Ideal Scenarios

We first present the motivations, challenges and issues that have been driven intensive research and design activities toward the specification of IEEE 802.11ax amendment, the sixth generation of wireless local networks (WLANs). Next, we summarize the main medium access control (MAC) protocols and physical layer (PHY) techniques that have been researched and developed in the scope of the IEEE Task Group (TG) 802.11ax. In the following, we derive a mathematical model for both uplink multi-user multiple input multiple output (UL MUMIMO) transmission scheme and mean squared error (MMSE) MU-MIMO detector. After presenting a first order validation of an IEEE 802.11ax simulator, we show preliminary results on the performance of IEEE 802.11ax UL MU-MIMO transceivers. We conclude that reserving degrees of freedom at receiver side to allow diversity gains can mitigate the negative effects of imperfect channel state information (CSI), providing expressive power gains. We also have concluded that it is necessary to implement sophisticated channel estimation schemes and advance MIMO detectors to cope with the interference generated in uplink channels loaded with a large number of clients.