My report[1] tells you a simple viewpoint to understand the evolution of the wireless LAN from 1997 to the 2020s. You can also get basic knowledge on an uplink of Wi-Fi6, the latest IEEE 802.11ax standard. Data analysis results based on our experimental study in an indoor office environment using Cisco AP3802I operating in 5 GHz band will help you to understand the basic knowledge on the uplink of Wi-Fi6.
To operate uplink multi-user(UL-MU) transmission properly in Wi-Fi6, each signal power received from client terminals at one AP should be equal. Therefore, each client terminal performs Transmission Power Control (TPC) to reduce each transmission power.
I believe firmly that wireless terminal manufacturers will have a good collaboration with Cisco to have a good performance for UL-MU transmission in Wi-Fi6.
[1]My report has been opened to the public at <https://gblog.netone.co.jp/20200108-1/> since Jan.8, 2020.