Updated: May 6, 2020
Part 2 - What makes Wlan Wifi slow?
Too many active clients on a channel, this may very well be the number one problem on all wifi. 5G frequency radios have almost 10x as many channels for the access point to use. If you are having difficulties here, reduce the power on the 2.4 and increase the power on the 5G radios. Another choice that may help is to pick auto channel selection on your dashboard, enabling the access point to shift to a more clear channel. Some brands will shift while the radios have traffic users causing massive disconnect, be careful here.
If you are really focused and interested in speed, especially clients moving to servers on LAN, then a strong suggestion is to limit SSID or the access point to 20-25 maximum clients per access point, this is maximize your speed. If most of your clients are going to internet, then focus on 40-60 clients per access point, as your bottleneck speed will be at your gateway device or your security device.
Limit SSID to as few as possible, the more SSID's or VLAN the slower the network due to broadcasting by the access point. We will normally set up with four or five SSID coupled or uncoupled to VLANS to begin. Be careful here, some brands will only have 3 or 4 SSID's maximum, causing some serious problems as your network grows. You should have at least four staff, students, teachers, guests, workers, accounting, etc. But remember to limit to lowest level, more will slow your network.
Old, slow servers, such as your radius or DNS servers, you really may need fast or upgraded servers if most of your clients will sign on at the same time, such as students in class or users coming to work at 8AM.
Roaming, transferring the client from one access point to another, this is a real problem with lower cost systems, especially if the controller is set for "fast roaming". The fast roaming setting is a problem with most low cost and even some high cost networks as it will automatically cause disconnects and then force reconnections. Some of the less expensive brands only offer this option, mainly because it is free, but you really need to run away from this option and go to other choices , as this one will drive your clients truly crazy. You are better off with roaming choices that are not based in the controller function but are built into the access point itself.
Some WLAN brands have as many as four or five options to help you find the one that will most closely fit your needs.
Please remember that in order for the transfer of the client from one access point to another access point, they need to be close enough to each other to pass the information, normally in clear air, 30-40M with effective overlap.